Convert all text files with s390 documentation to ReST format.
Tried to preserve as much as possible the original document
format. Still, some of the files required some work in order
for it to be visible on both plain text and after converted
to html.
The conversion is actually:
- add blank lines and identation in order to identify paragraphs;
- fix tables markups;
- add some lists markups;
- mark literal blocks;
- adjust title markups.
At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
others).
ccw_timeout_log [S390]
- See Documentation/s390/CommonIO for details.
+ See Documentation/s390/common_io.rst for details.
cgroup_disable= [KNL] Disable a particular controller
Format: {name of the controller(s) to disable}
/selinux/checkreqprot.
cio_ignore= [S390]
- See Documentation/s390/CommonIO for details.
+ See Documentation/s390/common_io.rst for details.
clk_ignore_unused
[CLK]
Prevents the clock framework from automatically gating
although they are not the focus of this document.
Some additional information can also be found in the kernel source under
-Documentation/s390/driver-model.txt.
+Documentation/s390/driver-model.rst.
The css bus
===========
* Standard I/O subchannels, for use by the system. They have a child
device on the ccw bus and are described below.
* I/O subchannels bound to the vfio-ccw driver. See
- Documentation/s390/vfio-ccw.txt.
+ Documentation/s390/vfio-ccw.rst.
* Message subchannels. No Linux driver currently exists.
* CHSC subchannels (at most one). The chsc subchannel driver can be used
to send asynchronous chsc commands.
--- /dev/null
+===============================
+IBM 3270 Display System support
+===============================
+
+This file describes the driver that supports local channel attachment
+of IBM 3270 devices. It consists of three sections:
+
+ * Introduction
+ * Installation
+ * Operation
+
+
+Introduction
+============
+
+This paper describes installing and operating 3270 devices under
+Linux/390. A 3270 device is a block-mode rows-and-columns terminal of
+which I'm sure hundreds of millions were sold by IBM and clonemakers
+twenty and thirty years ago.
+
+You may have 3270s in-house and not know it. If you're using the
+VM-ESA operating system, define a 3270 to your virtual machine by using
+the command "DEF GRAF <hex-address>" This paper presumes you will be
+defining four 3270s with the CP/CMS commands:
+
+ - DEF GRAF 620
+ - DEF GRAF 621
+ - DEF GRAF 622
+ - DEF GRAF 623
+
+Your network connection from VM-ESA allows you to use x3270, tn3270, or
+another 3270 emulator, started from an xterm window on your PC or
+workstation. With the DEF GRAF command, an application such as xterm,
+and this Linux-390 3270 driver, you have another way of talking to your
+Linux box.
+
+This paper covers installation of the driver and operation of a
+dialed-in x3270.
+
+
+Installation
+============
+
+You install the driver by installing a patch, doing a kernel build, and
+running the configuration script (config3270.sh, in this directory).
+
+WARNING: If you are using 3270 console support, you must rerun the
+configuration script every time you change the console's address (perhaps
+by using the condev= parameter in silo's /boot/parmfile). More precisely,
+you should rerun the configuration script every time your set of 3270s,
+including the console 3270, changes subchannel identifier relative to
+one another. ReIPL as soon as possible after running the configuration
+script and the resulting /tmp/mkdev3270.
+
+If you have chosen to make tub3270 a module, you add a line to a
+configuration file under /etc/modprobe.d/. If you are working on a VM
+virtual machine, you can use DEF GRAF to define virtual 3270 devices.
+
+You may generate both 3270 and 3215 console support, or one or the
+other, or neither. If you generate both, the console type under VM is
+not changed. Use #CP Q TERM to see what the current console type is.
+Use #CP TERM CONMODE 3270 to change it to 3270. If you generate only
+3270 console support, then the driver automatically converts your console
+at boot time to a 3270 if it is a 3215.
+
+In brief, these are the steps:
+
+ 1. Install the tub3270 patch
+ 2. (If a module) add a line to a file in `/etc/modprobe.d/*.conf`
+ 3. (If VM) define devices with DEF GRAF
+ 4. Reboot
+ 5. Configure
+
+To test that everything works, assuming VM and x3270,
+
+ 1. Bring up an x3270 window.
+ 2. Use the DIAL command in that window.
+ 3. You should immediately see a Linux login screen.
+
+Here are the installation steps in detail:
+
+ 1. The 3270 driver is a part of the official Linux kernel
+ source. Build a tree with the kernel source and any necessary
+ patches. Then do::
+
+ make oldconfig
+ (If you wish to disable 3215 console support, edit
+ .config; change CONFIG_TN3215's value to "n";
+ and rerun "make oldconfig".)
+ make image
+ make modules
+ make modules_install
+
+ 2. (Perform this step only if you have configured tub3270 as a
+ module.) Add a line to a file `/etc/modprobe.d/*.conf` to automatically
+ load the driver when it's needed. With this line added, you will see
+ login prompts appear on your 3270s as soon as boot is complete (or
+ with emulated 3270s, as soon as you dial into your vm guest using the
+ command "DIAL <vmguestname>"). Since the line-mode major number is
+ 227, the line to add should be::
+
+ alias char-major-227 tub3270
+
+ 3. Define graphic devices to your vm guest machine, if you
+ haven't already. Define them before you reboot (reipl):
+
+ - DEFINE GRAF 620
+ - DEFINE GRAF 621
+ - DEFINE GRAF 622
+ - DEFINE GRAF 623
+
+ 4. Reboot. The reboot process scans hardware devices, including
+ 3270s, and this enables the tub3270 driver once loaded to respond
+ correctly to the configuration requests of the next step. If
+ you have chosen 3270 console support, your console now behaves
+ as a 3270, not a 3215.
+
+ 5. Run the 3270 configuration script config3270. It is
+ distributed in this same directory, Documentation/s390, as
+ config3270.sh. Inspect the output script it produces,
+ /tmp/mkdev3270, and then run that script. This will create the
+ necessary character special device files and make the necessary
+ changes to /etc/inittab.
+
+ Then notify /sbin/init that /etc/inittab has changed, by issuing
+ the telinit command with the q operand::
+
+ cd Documentation/s390
+ sh config3270.sh
+ sh /tmp/mkdev3270
+ telinit q
+
+ This should be sufficient for your first time. If your 3270
+ configuration has changed and you're reusing config3270, you
+ should follow these steps::
+
+ Change 3270 configuration
+ Reboot
+ Run config3270 and /tmp/mkdev3270
+ Reboot
+
+Here are the testing steps in detail:
+
+ 1. Bring up an x3270 window, or use an actual hardware 3278 or
+ 3279, or use the 3270 emulator of your choice. You would be
+ running the emulator on your PC or workstation. You would use
+ the command, for example::
+
+ x3270 vm-esa-domain-name &
+
+ if you wanted a 3278 Model 4 with 43 rows of 80 columns, the
+ default model number. The driver does not take advantage of
+ extended attributes.
+
+ The screen you should now see contains a VM logo with input
+ lines near the bottom. Use TAB to move to the bottom line,
+ probably labeled "COMMAND ===>".
+
+ 2. Use the DIAL command instead of the LOGIN command to connect
+ to one of the virtual 3270s you defined with the DEF GRAF
+ commands::
+
+ dial my-vm-guest-name
+
+ 3. You should immediately see a login prompt from your
+ Linux-390 operating system. If that does not happen, you would
+ see instead the line "DIALED TO my-vm-guest-name 0620".
+
+ To troubleshoot: do these things.
+
+ A. Is the driver loaded? Use the lsmod command (no operands)
+ to find out. Probably it isn't. Try loading it manually, with
+ the command "insmod tub3270". Does that command give error
+ messages? Ha! There's your problem.
+
+ B. Is the /etc/inittab file modified as in installation step 3
+ above? Use the grep command to find out; for instance, issue
+ "grep 3270 /etc/inittab". Nothing found? There's your
+ problem!
+
+ C. Are the device special files created, as in installation
+ step 2 above? Use the ls -l command to find out; for instance,
+ issue "ls -l /dev/3270/tty620". The output should start with the
+ letter "c" meaning character device and should contain "227, 1"
+ just to the left of the device name. No such file? no "c"?
+ Wrong major number? Wrong minor number? There's your
+ problem!
+
+ D. Do you get the message::
+
+ "HCPDIA047E my-vm-guest-name 0620 does not exist"?
+
+ If so, you must issue the command "DEF GRAF 620" from your VM
+ 3215 console and then reboot the system.
+
+
+
+OPERATION.
+==========
+
+The driver defines three areas on the 3270 screen: the log area, the
+input area, and the status area.
+
+The log area takes up all but the bottom two lines of the screen. The
+driver writes terminal output to it, starting at the top line and going
+down. When it fills, the status area changes from "Linux Running" to
+"Linux More...". After a scrolling timeout of (default) 5 sec, the
+screen clears and more output is written, from the top down.
+
+The input area extends from the beginning of the second-to-last screen
+line to the start of the status area. You type commands in this area
+and hit ENTER to execute them.
+
+The status area initializes to "Linux Running" to give you a warm
+fuzzy feeling. When the log area fills up and output awaits, it
+changes to "Linux More...". At this time you can do several things or
+nothing. If you do nothing, the screen will clear in (default) 5 sec
+and more output will appear. You may hit ENTER with nothing typed in
+the input area to toggle between "Linux More..." and "Linux Holding",
+which indicates no scrolling will occur. (If you hit ENTER with "Linux
+Running" and nothing typed, the application receives a newline.)
+
+You may change the scrolling timeout value. For example, the following
+command line::
+
+ echo scrolltime=60 > /proc/tty/driver/tty3270
+
+changes the scrolling timeout value to 60 sec. Set scrolltime to 0 if
+you wish to prevent scrolling entirely.
+
+Other things you may do when the log area fills up are: hit PA2 to
+clear the log area and write more output to it, or hit CLEAR to clear
+the log area and the input area and write more output to the log area.
+
+Some of the Program Function (PF) and Program Attention (PA) keys are
+preassigned special functions. The ones that are not yield an alarm
+when pressed.
+
+PA1 causes a SIGINT to the currently running application. You may do
+the same thing from the input area, by typing "^C" and hitting ENTER.
+
+PA2 causes the log area to be cleared. If output awaits, it is then
+written to the log area.
+
+PF3 causes an EOF to be received as input by the application. You may
+cause an EOF also by typing "^D" and hitting ENTER.
+
+No PF key is preassigned to cause a job suspension, but you may cause a
+job suspension by typing "^Z" and hitting ENTER. You may wish to
+assign this function to a PF key. To make PF7 cause job suspension,
+execute the command::
+
+ echo pf7=^z > /proc/tty/driver/tty3270
+
+If the input you type does not end with the two characters "^n", the
+driver appends a newline character and sends it to the tty driver;
+otherwise the driver strips the "^n" and does not append a newline.
+The IBM 3215 driver behaves similarly.
+
+Pf10 causes the most recent command to be retrieved from the tube's
+command stack (default depth 20) and displayed in the input area. You
+may hit PF10 again for the next-most-recent command, and so on. A
+command is entered into the stack only when the input area is not made
+invisible (such as for password entry) and it is not identical to the
+current top entry. PF10 rotates backward through the command stack;
+PF11 rotates forward. You may assign the backward function to any PF
+key (or PA key, for that matter), say, PA3, with the command::
+
+ echo -e pa3=\\033k > /proc/tty/driver/tty3270
+
+This assigns the string ESC-k to PA3. Similarly, the string ESC-j
+performs the forward function. (Rationale: In bash with vi-mode line
+editing, ESC-k and ESC-j retrieve backward and forward history.
+Suggestions welcome.)
+
+Is a stack size of twenty commands not to your liking? Change it on
+the fly. To change to saving the last 100 commands, execute the
+command::
+
+ echo recallsize=100 > /proc/tty/driver/tty3270
+
+Have a command you issue frequently? Assign it to a PF or PA key! Use
+the command::
+
+ echo pf24="mkdir foobar; cd foobar" > /proc/tty/driver/tty3270
+
+to execute the commands mkdir foobar and cd foobar immediately when you
+hit PF24. Want to see the command line first, before you execute it?
+Use the -n option of the echo command::
+
+ echo -n pf24="mkdir foo; cd foo" > /proc/tty/driver/tty3270
+
+
+
+Happy testing! I welcome any and all comments about this document, the
+driver, etc etc.
+
+Dick Hitt <rbh00@utsglobal.com>
+++ /dev/null
-IBM 3270 Display System support
-
-This file describes the driver that supports local channel attachment
-of IBM 3270 devices. It consists of three sections:
- * Introduction
- * Installation
- * Operation
-
-
-INTRODUCTION.
-
-This paper describes installing and operating 3270 devices under
-Linux/390. A 3270 device is a block-mode rows-and-columns terminal of
-which I'm sure hundreds of millions were sold by IBM and clonemakers
-twenty and thirty years ago.
-
-You may have 3270s in-house and not know it. If you're using the
-VM-ESA operating system, define a 3270 to your virtual machine by using
-the command "DEF GRAF <hex-address>" This paper presumes you will be
-defining four 3270s with the CP/CMS commands
-
- DEF GRAF 620
- DEF GRAF 621
- DEF GRAF 622
- DEF GRAF 623
-
-Your network connection from VM-ESA allows you to use x3270, tn3270, or
-another 3270 emulator, started from an xterm window on your PC or
-workstation. With the DEF GRAF command, an application such as xterm,
-and this Linux-390 3270 driver, you have another way of talking to your
-Linux box.
-
-This paper covers installation of the driver and operation of a
-dialed-in x3270.
-
-
-INSTALLATION.
-
-You install the driver by installing a patch, doing a kernel build, and
-running the configuration script (config3270.sh, in this directory).
-
-WARNING: If you are using 3270 console support, you must rerun the
-configuration script every time you change the console's address (perhaps
-by using the condev= parameter in silo's /boot/parmfile). More precisely,
-you should rerun the configuration script every time your set of 3270s,
-including the console 3270, changes subchannel identifier relative to
-one another. ReIPL as soon as possible after running the configuration
-script and the resulting /tmp/mkdev3270.
-
-If you have chosen to make tub3270 a module, you add a line to a
-configuration file under /etc/modprobe.d/. If you are working on a VM
-virtual machine, you can use DEF GRAF to define virtual 3270 devices.
-
-You may generate both 3270 and 3215 console support, or one or the
-other, or neither. If you generate both, the console type under VM is
-not changed. Use #CP Q TERM to see what the current console type is.
-Use #CP TERM CONMODE 3270 to change it to 3270. If you generate only
-3270 console support, then the driver automatically converts your console
-at boot time to a 3270 if it is a 3215.
-
-In brief, these are the steps:
- 1. Install the tub3270 patch
- 2. (If a module) add a line to a file in /etc/modprobe.d/*.conf
- 3. (If VM) define devices with DEF GRAF
- 4. Reboot
- 5. Configure
-
-To test that everything works, assuming VM and x3270,
- 1. Bring up an x3270 window.
- 2. Use the DIAL command in that window.
- 3. You should immediately see a Linux login screen.
-
-Here are the installation steps in detail:
-
- 1. The 3270 driver is a part of the official Linux kernel
- source. Build a tree with the kernel source and any necessary
- patches. Then do
- make oldconfig
- (If you wish to disable 3215 console support, edit
- .config; change CONFIG_TN3215's value to "n";
- and rerun "make oldconfig".)
- make image
- make modules
- make modules_install
-
- 2. (Perform this step only if you have configured tub3270 as a
- module.) Add a line to a file /etc/modprobe.d/*.conf to automatically
- load the driver when it's needed. With this line added, you will see
- login prompts appear on your 3270s as soon as boot is complete (or
- with emulated 3270s, as soon as you dial into your vm guest using the
- command "DIAL <vmguestname>"). Since the line-mode major number is
- 227, the line to add should be:
- alias char-major-227 tub3270
-
- 3. Define graphic devices to your vm guest machine, if you
- haven't already. Define them before you reboot (reipl):
- DEFINE GRAF 620
- DEFINE GRAF 621
- DEFINE GRAF 622
- DEFINE GRAF 623
-
- 4. Reboot. The reboot process scans hardware devices, including
- 3270s, and this enables the tub3270 driver once loaded to respond
- correctly to the configuration requests of the next step. If
- you have chosen 3270 console support, your console now behaves
- as a 3270, not a 3215.
-
- 5. Run the 3270 configuration script config3270. It is
- distributed in this same directory, Documentation/s390, as
- config3270.sh. Inspect the output script it produces,
- /tmp/mkdev3270, and then run that script. This will create the
- necessary character special device files and make the necessary
- changes to /etc/inittab.
-
- Then notify /sbin/init that /etc/inittab has changed, by issuing
- the telinit command with the q operand:
- cd Documentation/s390
- sh config3270.sh
- sh /tmp/mkdev3270
- telinit q
-
- This should be sufficient for your first time. If your 3270
- configuration has changed and you're reusing config3270, you
- should follow these steps:
- Change 3270 configuration
- Reboot
- Run config3270 and /tmp/mkdev3270
- Reboot
-
-Here are the testing steps in detail:
-
- 1. Bring up an x3270 window, or use an actual hardware 3278 or
- 3279, or use the 3270 emulator of your choice. You would be
- running the emulator on your PC or workstation. You would use
- the command, for example,
- x3270 vm-esa-domain-name &
- if you wanted a 3278 Model 4 with 43 rows of 80 columns, the
- default model number. The driver does not take advantage of
- extended attributes.
-
- The screen you should now see contains a VM logo with input
- lines near the bottom. Use TAB to move to the bottom line,
- probably labeled "COMMAND ===>".
-
- 2. Use the DIAL command instead of the LOGIN command to connect
- to one of the virtual 3270s you defined with the DEF GRAF
- commands:
- dial my-vm-guest-name
-
- 3. You should immediately see a login prompt from your
- Linux-390 operating system. If that does not happen, you would
- see instead the line "DIALED TO my-vm-guest-name 0620".
-
- To troubleshoot: do these things.
-
- A. Is the driver loaded? Use the lsmod command (no operands)
- to find out. Probably it isn't. Try loading it manually, with
- the command "insmod tub3270". Does that command give error
- messages? Ha! There's your problem.
-
- B. Is the /etc/inittab file modified as in installation step 3
- above? Use the grep command to find out; for instance, issue
- "grep 3270 /etc/inittab". Nothing found? There's your
- problem!
-
- C. Are the device special files created, as in installation
- step 2 above? Use the ls -l command to find out; for instance,
- issue "ls -l /dev/3270/tty620". The output should start with the
- letter "c" meaning character device and should contain "227, 1"
- just to the left of the device name. No such file? no "c"?
- Wrong major number? Wrong minor number? There's your
- problem!
-
- D. Do you get the message
- "HCPDIA047E my-vm-guest-name 0620 does not exist"?
- If so, you must issue the command "DEF GRAF 620" from your VM
- 3215 console and then reboot the system.
-
-
-
-OPERATION.
-
-The driver defines three areas on the 3270 screen: the log area, the
-input area, and the status area.
-
-The log area takes up all but the bottom two lines of the screen. The
-driver writes terminal output to it, starting at the top line and going
-down. When it fills, the status area changes from "Linux Running" to
-"Linux More...". After a scrolling timeout of (default) 5 sec, the
-screen clears and more output is written, from the top down.
-
-The input area extends from the beginning of the second-to-last screen
-line to the start of the status area. You type commands in this area
-and hit ENTER to execute them.
-
-The status area initializes to "Linux Running" to give you a warm
-fuzzy feeling. When the log area fills up and output awaits, it
-changes to "Linux More...". At this time you can do several things or
-nothing. If you do nothing, the screen will clear in (default) 5 sec
-and more output will appear. You may hit ENTER with nothing typed in
-the input area to toggle between "Linux More..." and "Linux Holding",
-which indicates no scrolling will occur. (If you hit ENTER with "Linux
-Running" and nothing typed, the application receives a newline.)
-
-You may change the scrolling timeout value. For example, the following
-command line:
- echo scrolltime=60 > /proc/tty/driver/tty3270
-changes the scrolling timeout value to 60 sec. Set scrolltime to 0 if
-you wish to prevent scrolling entirely.
-
-Other things you may do when the log area fills up are: hit PA2 to
-clear the log area and write more output to it, or hit CLEAR to clear
-the log area and the input area and write more output to the log area.
-
-Some of the Program Function (PF) and Program Attention (PA) keys are
-preassigned special functions. The ones that are not yield an alarm
-when pressed.
-
-PA1 causes a SIGINT to the currently running application. You may do
-the same thing from the input area, by typing "^C" and hitting ENTER.
-
-PA2 causes the log area to be cleared. If output awaits, it is then
-written to the log area.
-
-PF3 causes an EOF to be received as input by the application. You may
-cause an EOF also by typing "^D" and hitting ENTER.
-
-No PF key is preassigned to cause a job suspension, but you may cause a
-job suspension by typing "^Z" and hitting ENTER. You may wish to
-assign this function to a PF key. To make PF7 cause job suspension,
-execute the command:
- echo pf7=^z > /proc/tty/driver/tty3270
-
-If the input you type does not end with the two characters "^n", the
-driver appends a newline character and sends it to the tty driver;
-otherwise the driver strips the "^n" and does not append a newline.
-The IBM 3215 driver behaves similarly.
-
-Pf10 causes the most recent command to be retrieved from the tube's
-command stack (default depth 20) and displayed in the input area. You
-may hit PF10 again for the next-most-recent command, and so on. A
-command is entered into the stack only when the input area is not made
-invisible (such as for password entry) and it is not identical to the
-current top entry. PF10 rotates backward through the command stack;
-PF11 rotates forward. You may assign the backward function to any PF
-key (or PA key, for that matter), say, PA3, with the command:
- echo -e pa3=\\033k > /proc/tty/driver/tty3270
-This assigns the string ESC-k to PA3. Similarly, the string ESC-j
-performs the forward function. (Rationale: In bash with vi-mode line
-editing, ESC-k and ESC-j retrieve backward and forward history.
-Suggestions welcome.)
-
-Is a stack size of twenty commands not to your liking? Change it on
-the fly. To change to saving the last 100 commands, execute the
-command:
- echo recallsize=100 > /proc/tty/driver/tty3270
-
-Have a command you issue frequently? Assign it to a PF or PA key! Use
-the command
- echo pf24="mkdir foobar; cd foobar" > /proc/tty/driver/tty3270
-to execute the commands mkdir foobar and cd foobar immediately when you
-hit PF24. Want to see the command line first, before you execute it?
-Use the -n option of the echo command:
- echo -n pf24="mkdir foo; cd foo" > /proc/tty/driver/tty3270
-
-
-
-Happy testing! I welcome any and all comments about this document, the
-driver, etc etc.
-
-Dick Hitt <rbh00@utsglobal.com>
+++ /dev/null
-S/390 common I/O-Layer - command line parameters, procfs and debugfs entries
-============================================================================
-
-Command line parameters
------------------------
-
-* ccw_timeout_log
-
- Enable logging of debug information in case of ccw device timeouts.
-
-* cio_ignore = device[,device[,..]]
-
- device := {all | [!]ipldev | [!]condev | [!]<devno> | [!]<devno>-<devno>}
-
- The given devices will be ignored by the common I/O-layer; no detection
- and device sensing will be done on any of those devices. The subchannel to
- which the device in question is attached will be treated as if no device was
- attached.
-
- An ignored device can be un-ignored later; see the "/proc entries"-section for
- details.
-
- The devices must be given either as bus ids (0.x.abcd) or as hexadecimal
- device numbers (0xabcd or abcd, for 2.4 backward compatibility). If you
- give a device number 0xabcd, it will be interpreted as 0.0.abcd.
-
- You can use the 'all' keyword to ignore all devices. The 'ipldev' and 'condev'
- keywords can be used to refer to the CCW based boot device and CCW console
- device respectively (these are probably useful only when combined with the '!'
- operator). The '!' operator will cause the I/O-layer to _not_ ignore a device.
- The command line is parsed from left to right.
-
- For example,
- cio_ignore=0.0.0023-0.0.0042,0.0.4711
- will ignore all devices ranging from 0.0.0023 to 0.0.0042 and the device
- 0.0.4711, if detected.
- As another example,
- cio_ignore=all,!0.0.4711,!0.0.fd00-0.0.fd02
- will ignore all devices but 0.0.4711, 0.0.fd00, 0.0.fd01, 0.0.fd02.
-
- By default, no devices are ignored.
-
-
-/proc entries
--------------
-
-* /proc/cio_ignore
-
- Lists the ranges of devices (by bus id) which are ignored by common I/O.
-
- You can un-ignore certain or all devices by piping to /proc/cio_ignore.
- "free all" will un-ignore all ignored devices,
- "free <device range>, <device range>, ..." will un-ignore the specified
- devices.
-
- For example, if devices 0.0.0023 to 0.0.0042 and 0.0.4711 are ignored,
- - echo free 0.0.0030-0.0.0032 > /proc/cio_ignore
- will un-ignore devices 0.0.0030 to 0.0.0032 and will leave devices 0.0.0023
- to 0.0.002f, 0.0.0033 to 0.0.0042 and 0.0.4711 ignored;
- - echo free 0.0.0041 > /proc/cio_ignore will furthermore un-ignore device
- 0.0.0041;
- - echo free all > /proc/cio_ignore will un-ignore all remaining ignored
- devices.
-
- When a device is un-ignored, device recognition and sensing is performed and
- the device driver will be notified if possible, so the device will become
- available to the system. Note that un-ignoring is performed asynchronously.
-
- You can also add ranges of devices to be ignored by piping to
- /proc/cio_ignore; "add <device range>, <device range>, ..." will ignore the
- specified devices.
-
- Note: While already known devices can be added to the list of devices to be
- ignored, there will be no effect on then. However, if such a device
- disappears and then reappears, it will then be ignored. To make
- known devices go away, you need the "purge" command (see below).
-
- For example,
- "echo add 0.0.a000-0.0.accc, 0.0.af00-0.0.afff > /proc/cio_ignore"
- will add 0.0.a000-0.0.accc and 0.0.af00-0.0.afff to the list of ignored
- devices.
-
- You can remove already known but now ignored devices via
- "echo purge > /proc/cio_ignore"
- All devices ignored but still registered and not online (= not in use)
- will be deregistered and thus removed from the system.
-
- The devices can be specified either by bus id (0.x.abcd) or, for 2.4 backward
- compatibility, by the device number in hexadecimal (0xabcd or abcd). Device
- numbers given as 0xabcd will be interpreted as 0.0.abcd.
-
-* /proc/cio_settle
-
- A write request to this file is blocked until all queued cio actions are
- handled. This will allow userspace to wait for pending work affecting
- device availability after changing cio_ignore or the hardware configuration.
-
-* For some of the information present in the /proc filesystem in 2.4 (namely,
- /proc/subchannels and /proc/chpids), see driver-model.txt.
- Information formerly in /proc/irq_count is now in /proc/interrupts.
-
-
-debugfs entries
----------------
-
-* /sys/kernel/debug/s390dbf/cio_*/ (S/390 debug feature)
-
- Some views generated by the debug feature to hold various debug outputs.
-
- - /sys/kernel/debug/s390dbf/cio_crw/sprintf
- Messages from the processing of pending channel report words (machine check
- handling).
-
- - /sys/kernel/debug/s390dbf/cio_msg/sprintf
- Various debug messages from the common I/O-layer.
-
- - /sys/kernel/debug/s390dbf/cio_trace/hex_ascii
- Logs the calling of functions in the common I/O-layer and, if applicable,
- which subchannel they were called for, as well as dumps of some data
- structures (like irb in an error case).
-
- The level of logging can be changed to be more or less verbose by piping to
- /sys/kernel/debug/s390dbf/cio_*/level a number between 0 and 6; see the
- documentation on the S/390 debug feature (Documentation/s390/s390dbf.txt)
- for details.
+++ /dev/null
-DASD device driver
-
-S/390's disk devices (DASDs) are managed by Linux via the DASD device
-driver. It is valid for all types of DASDs and represents them to
-Linux as block devices, namely "dd". Currently the DASD driver uses a
-single major number (254) and 4 minor numbers per volume (1 for the
-physical volume and 3 for partitions). With respect to partitions see
-below. Thus you may have up to 64 DASD devices in your system.
-
-The kernel parameter 'dasd=from-to,...' may be issued arbitrary times
-in the kernel's parameter line or not at all. The 'from' and 'to'
-parameters are to be given in hexadecimal notation without a leading
-0x.
-If you supply kernel parameters the different instances are processed
-in order of appearance and a minor number is reserved for any device
-covered by the supplied range up to 64 volumes. Additional DASDs are
-ignored. If you do not supply the 'dasd=' kernel parameter at all, the
-DASD driver registers all supported DASDs of your system to a minor
-number in ascending order of the subchannel number.
-
-The driver currently supports ECKD-devices and there are stubs for
-support of the FBA and CKD architectures. For the FBA architecture
-only some smart data structures are missing to make the support
-complete.
-We performed our testing on 3380 and 3390 type disks of different
-sizes, under VM and on the bare hardware (LPAR), using internal disks
-of the multiprise as well as a RAMAC virtual array. Disks exported by
-an Enterprise Storage Server (Seascape) should work fine as well.
-
-We currently implement one partition per volume, which is the whole
-volume, skipping the first blocks up to the volume label. These are
-reserved for IPL records and IBM's volume label to assure
-accessibility of the DASD from other OSs. In a later stage we will
-provide support of partitions, maybe VTOC oriented or using a kind of
-partition table in the label record.
-
-USAGE
-
--Low-level format (?CKD only)
-For using an ECKD-DASD as a Linux harddisk you have to low-level
-format the tracks by issuing the BLKDASDFORMAT-ioctl on that
-device. This will erase any data on that volume including IBM volume
-labels, VTOCs etc. The ioctl may take a 'struct format_data *' or
-'NULL' as an argument.
-typedef struct {
- int start_unit;
- int stop_unit;
- int blksize;
-} format_data_t;
-When a NULL argument is passed to the BLKDASDFORMAT ioctl the whole
-disk is formatted to a blocksize of 1024 bytes. Otherwise start_unit
-and stop_unit are the first and last track to be formatted. If
-stop_unit is -1 it implies that the DASD is formatted from start_unit
-up to the last track. blksize can be any power of two between 512 and
-4096. We recommend no blksize lower than 1024 because the ext2fs uses
-1kB blocks anyway and you gain approx. 50% of capacity increasing your
-blksize from 512 byte to 1kB.
-
--Make a filesystem
-Then you can mk??fs the filesystem of your choice on that volume or
-partition. For reasons of sanity you should build your filesystem on
-the partition /dev/dd?1 instead of the whole volume. You only lose 3kB
-but may be sure that you can reuse your data after introduction of a
-real partition table.
-
-BUGS:
-- Performance sometimes is rather low because we don't fully exploit clustering
-
-TODO-List:
-- Add IBM'S Disk layout to genhd
-- Enhance driver to use more than one major number
-- Enable usage as a module
-- Support Cache fast write and DASD fast write (ECKD)
+++ /dev/null
-
- Debugging on Linux for s/390 & z/Architecture
- by
- Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com)
- Copyright (C) 2000-2001 IBM Deutschland Entwicklung GmbH, IBM Corporation
- Best viewed with fixed width fonts
-
-Overview of Document:
-=====================
-This document is intended to give a good overview of how to debug Linux for
-s/390 and z/Architecture. It is not intended as a complete reference and not a
-tutorial on the fundamentals of C & assembly. It doesn't go into
-390 IO in any detail. It is intended to complement the documents in the
-reference section below & any other worthwhile references you get.
-
-It is intended like the Enterprise Systems Architecture/390 Reference Summary
-to be printed out & used as a quick cheat sheet self help style reference when
-problems occur.
-
-Contents
-========
-Register Set
-Address Spaces on Intel Linux
-Address Spaces on Linux for s/390 & z/Architecture
-The Linux for s/390 & z/Architecture Kernel Task Structure
-Register Usage & Stackframes on Linux for s/390 & z/Architecture
-A sample program with comments
-Compiling programs for debugging on Linux for s/390 & z/Architecture
-Debugging under VM
-s/390 & z/Architecture IO Overview
-Debugging IO on s/390 & z/Architecture under VM
-GDB on s/390 & z/Architecture
-Stack chaining in gdb by hand
-Examining core dumps
-ldd
-Debugging modules
-The proc file system
-SysRq
-References
-Special Thanks
-
-Register Set
-============
-The current architectures have the following registers.
-
-16 General propose registers, 32 bit on s/390 and 64 bit on z/Architecture,
-r0-r15 (or gpr0-gpr15), used for arithmetic and addressing.
-
-16 Control registers, 32 bit on s/390 and 64 bit on z/Architecture, cr0-cr15,
-kernel usage only, used for memory management, interrupt control, debugging
-control etc.
-
-16 Access registers (ar0-ar15), 32 bit on both s/390 and z/Architecture,
-normally not used by normal programs but potentially could be used as
-temporary storage. These registers have a 1:1 association with general
-purpose registers and are designed to be used in the so-called access
-register mode to select different address spaces.
-Access register 0 (and access register 1 on z/Architecture, which needs a
-64 bit pointer) is currently used by the pthread library as a pointer to
-the current running threads private area.
-
-16 64 bit floating point registers (fp0-fp15 ) IEEE & HFP floating
-point format compliant on G5 upwards & a Floating point control reg (FPC)
-4 64 bit registers (fp0,fp2,fp4 & fp6) HFP only on older machines.
-Note:
-Linux (currently) always uses IEEE & emulates G5 IEEE format on older machines,
-( provided the kernel is configured for this ).
-
-
-The PSW is the most important register on the machine it
-is 64 bit on s/390 & 128 bit on z/Architecture & serves the roles of
-a program counter (pc), condition code register,memory space designator.
-In IBM standard notation I am counting bit 0 as the MSB.
-It has several advantages over a normal program counter
-in that you can change address translation & program counter
-in a single instruction. To change address translation,
-e.g. switching address translation off requires that you
-have a logical=physical mapping for the address you are
-currently running at.
-
-+-------------------------+-------------------------------------------------+
-| Bit | |
-+--------+----------------+ Value |
-| s/390 | z/Architecture | |
-+========+================+=================================================+
-| 0 | 0 | Reserved (must be 0) otherwise specification |
-| | | exception occurs. |
-+--------+----------------+-------------------------------------------------+
-| 1 | 1 | Program Event Recording 1 PER enabled, |
-| | | PER is used to facilitate debugging e.g. |
-| | | single stepping. |
-+--------+----------------+-------------------------------------------------+
-| 2-4 | 2-4 | Reserved (must be 0). |
-+--------+----------------+-------------------------------------------------+
-| 5 | 5 | Dynamic address translation 1=DAT on. |
-+--------+----------------+-------------------------------------------------+
-| 6 | 6 | Input/Output interrupt Mask |
-+--------+----------------+-------------------------------------------------+
-| 7 | 7 | External interrupt Mask used primarily for |
-| | | interprocessor signalling and clock interrupts. |
-+--------+----------------+-------------------------------------------------+
-| 8-11 | 8-11 | PSW Key used for complex memory protection |
-| | | mechanism (not used under linux) |
-+--------+----------------+-------------------------------------------------+
-| 12 | 12 | 1 on s/390 0 on z/Architecture |
-+--------+----------------+-------------------------------------------------+
-| 13 | 13 | Machine Check Mask 1=enable machine check |
-| | | interrupts |
-+--------+----------------+-------------------------------------------------+
-| 14 | 14 | Wait State. Set this to 1 to stop the processor |
-| | | except for interrupts and give time to other |
-| | | LPARS. Used in CPU idle in the kernel to |
-| | | increase overall usage of processor resources. |
-+--------+----------------+-------------------------------------------------+
-| 15 | 15 | Problem state (if set to 1 certain instructions |
-| | | are disabled). All linux user programs run with |
-| | | this bit 1 (useful info for debugging under VM).|
-+--------+----------------+-------------------------------------------------+
-| 16-17 | 16-17 | Address Space Control |
-| | | |
-| | | 00 Primary Space Mode: |
-| | | |
-| | | The register CR1 contains the primary |
-| | | address-space control element (PASCE), which |
-| | | points to the primary space region/segment |
-| | | table origin. |
-| | | |
-| | | 01 Access register mode |
-| | | |
-| | | 10 Secondary Space Mode: |
-| | | |
-| | | The register CR7 contains the secondary |
-| | | address-space control element (SASCE), which |
-| | | points to the secondary space region or |
-| | | segment table origin. |
-| | | |
-| | | 11 Home Space Mode: |
-| | | |
-| | | The register CR13 contains the home space |
-| | | address-space control element (HASCE), which |
-| | | points to the home space region/segment |
-| | | table origin. |
-| | | |
-| | | See "Address Spaces on Linux for s/390 & |
-| | | z/Architecture" below for more information |
-| | | about address space usage in Linux. |
-+--------+----------------+-------------------------------------------------+
-| 18-19 | 18-19 | Condition codes (CC) |
-+--------+----------------+-------------------------------------------------+
-| 20 | 20 | Fixed point overflow mask if 1=FPU exceptions |
-| | | for this event occur (normally 0) |
-+--------+----------------+-------------------------------------------------+
-| 21 | 21 | Decimal overflow mask if 1=FPU exceptions for |
-| | | this event occur (normally 0) |
-+--------+----------------+-------------------------------------------------+
-| 22 | 22 | Exponent underflow mask if 1=FPU exceptions |
-| | | for this event occur (normally 0) |
-+--------+----------------+-------------------------------------------------+
-| 23 | 23 | Significance Mask if 1=FPU exceptions for this |
-| | | event occur (normally 0) |
-+--------+----------------+-------------------------------------------------+
-| 24-31 | 24-30 | Reserved Must be 0. |
-| +----------------+-------------------------------------------------+
-| | 31 | Extended Addressing Mode |
-| +----------------+-------------------------------------------------+
-| | 32 | Basic Addressing Mode |
-| | | |
-| | | Used to set addressing mode |
-| | | |
-| | | +---------+----------+----------+ |
-| | | | PSW 31 | PSW 32 | | |
-| | | +---------+----------+----------+ |
-| | | | 0 | 0 | 24 bit | |
-| | | +---------+----------+----------+ |
-| | | | 0 | 1 | 31 bit | |
-| | | +---------+----------+----------+ |
-| | | | 1 | 1 | 64 bit | |
-| | | +---------+----------+----------+ |
-+--------+----------------+-------------------------------------------------+
-| 32 | | 1=31 bit addressing mode 0=24 bit addressing |
-| | | mode (for backward compatibility), linux |
-| | | always runs with this bit set to 1 |
-+--------+----------------+-------------------------------------------------+
-| 33-64 | | Instruction address. |
-| +----------------+-------------------------------------------------+
-| | 33-63 | Reserved must be 0 |
-| +----------------+-------------------------------------------------+
-| | 64-127 | Address |
-| | | |
-| | | - In 24 bits mode bits 64-103=0 bits 104-127 |
-| | | Address |
-| | | - In 31 bits mode bits 64-96=0 bits 97-127 |
-| | | Address |
-| | | |
-| | | Note: |
-| | | unlike 31 bit mode on s/390 bit 96 must be |
-| | | zero when loading the address with LPSWE |
-| | | otherwise a specification exception occurs, |
-| | | LPSW is fully backward compatible. |
-+--------+----------------+-------------------------------------------------+
-
-Prefix Page(s)
---------------
-This per cpu memory area is too intimately tied to the processor not to mention.
-It exists between the real addresses 0-4096 on s/390 and between 0-8192 on
-z/Architecture and is exchanged with one page on s/390 or two pages on
-z/Architecture in absolute storage by the set prefix instruction during Linux
-startup.
-This page is mapped to a different prefix for each processor in an SMP
-configuration (assuming the OS designer is sane of course).
-Bytes 0-512 (200 hex) on s/390 and 0-512, 4096-4544, 4604-5119 currently on
-z/Architecture are used by the processor itself for holding such information
-as exception indications and entry points for exceptions.
-Bytes after 0xc00 hex are used by linux for per processor globals on s/390 and
-z/Architecture (there is a gap on z/Architecture currently between 0xc00 and
-0x1000, too, which is used by Linux).
-The closest thing to this on traditional architectures is the interrupt
-vector table. This is a good thing & does simplify some of the kernel coding
-however it means that we now cannot catch stray NULL pointers in the
-kernel without hard coded checks.
-
-
-
-Address Spaces on Intel Linux
-=============================
-
-The traditional Intel Linux is approximately mapped as follows forgive
-the ascii art.
-0xFFFFFFFF 4GB Himem *****************
- * *
- * Kernel Space *
- * *
- ***************** ****************
-User Space Himem * User Stack * * *
-(typically 0xC0000000 3GB ) ***************** * *
- * Shared Libs * * Next Process *
- ***************** * to *
- * * <== * Run * <==
- * User Program * * *
- * Data BSS * * *
- * Text * * *
- * Sections * * *
-0x00000000 ***************** ****************
-
-Now it is easy to see that on Intel it is quite easy to recognise a kernel
-address as being one greater than user space himem (in this case 0xC0000000),
-and addresses of less than this are the ones in the current running program on
-this processor (if an smp box).
-If using the virtual machine ( VM ) as a debugger it is quite difficult to
-know which user process is running as the address space you are looking at
-could be from any process in the run queue.
-
-The limitation of Intels addressing technique is that the linux
-kernel uses a very simple real address to virtual addressing technique
-of Real Address=Virtual Address-User Space Himem.
-This means that on Intel the kernel linux can typically only address
-Himem=0xFFFFFFFF-0xC0000000=1GB & this is all the RAM these machines
-can typically use.
-They can lower User Himem to 2GB or lower & thus be
-able to use 2GB of RAM however this shrinks the maximum size
-of User Space from 3GB to 2GB they have a no win limit of 4GB unless
-they go to 64 Bit.
-
-
-On 390 our limitations & strengths make us slightly different.
-For backward compatibility we are only allowed use 31 bits (2GB)
-of our 32 bit addresses, however, we use entirely separate address
-spaces for the user & kernel.
-
-This means we can support 2GB of non Extended RAM on s/390, & more
-with the Extended memory management swap device &
-currently 4TB of physical memory currently on z/Architecture.
-
-
-Address Spaces on Linux for s/390 & z/Architecture
-==================================================
-
-Our addressing scheme is basically as follows:
-
- Primary Space Home Space
-Himem 0x7fffffff 2GB on s/390 ***************** ****************
-currently 0x3ffffffffff (2^42)-1 * User Stack * * *
-on z/Architecture. ***************** * *
- * Shared Libs * * *
- ***************** * *
- * * * Kernel *
- * User Program * * *
- * Data BSS * * *
- * Text * * *
- * Sections * * *
-0x00000000 ***************** ****************
-
-This also means that we need to look at the PSW problem state bit and the
-addressing mode to decide whether we are looking at user or kernel space.
-
-User space runs in primary address mode (or access register mode within
-the vdso code).
-
-The kernel usually also runs in home space mode, however when accessing
-user space the kernel switches to primary or secondary address mode if
-the mvcos instruction is not available or if a compare-and-swap (futex)
-instruction on a user space address is performed.
-
-When also looking at the ASCE control registers, this means:
-
-User space:
-- runs in primary or access register mode
-- cr1 contains the user asce
-- cr7 contains the user asce
-- cr13 contains the kernel asce
-
-Kernel space:
-- runs in home space mode
-- cr1 contains the user or kernel asce
- -> the kernel asce is loaded when a uaccess requires primary or
- secondary address mode
-- cr7 contains the user or kernel asce, (changed with set_fs())
-- cr13 contains the kernel asce
-
-In case of uaccess the kernel changes to:
-- primary space mode in case of a uaccess (copy_to_user) and uses
- e.g. the mvcp instruction to access user space. However the kernel
- will stay in home space mode if the mvcos instruction is available
-- secondary space mode in case of futex atomic operations, so that the
- instructions come from primary address space and data from secondary
- space
-
-In case of KVM, the kernel runs in home space mode, but cr1 gets switched
-to contain the gmap asce before the SIE instruction gets executed. When
-the SIE instruction is finished, cr1 will be switched back to contain the
-user asce.
-
-
-Virtual Addresses on s/390 & z/Architecture
-===========================================
-
-A virtual address on s/390 is made up of 3 parts
-The SX (segment index, roughly corresponding to the PGD & PMD in Linux
-terminology) being bits 1-11.
-The PX (page index, corresponding to the page table entry (pte) in Linux
-terminology) being bits 12-19.
-The remaining bits BX (the byte index are the offset in the page )
-i.e. bits 20 to 31.
-
-On z/Architecture in linux we currently make up an address from 4 parts.
-The region index bits (RX) 0-32 we currently use bits 22-32
-The segment index (SX) being bits 33-43
-The page index (PX) being bits 44-51
-The byte index (BX) being bits 52-63
-
-Notes:
-1) s/390 has no PMD so the PMD is really the PGD also.
-A lot of this stuff is defined in pgtable.h.
-
-2) Also seeing as s/390's page indexes are only 1k in size
-(bits 12-19 x 4 bytes per pte ) we use 1 ( page 4k )
-to make the best use of memory by updating 4 segment indices
-entries each time we mess with a PMD & use offsets
-0,1024,2048 & 3072 in this page as for our segment indexes.
-On z/Architecture our page indexes are now 2k in size
-( bits 12-19 x 8 bytes per pte ) we do a similar trick
-but only mess with 2 segment indices each time we mess with
-a PMD.
-
-3) As z/Architecture supports up to a massive 5-level page table lookup we
-can only use 3 currently on Linux ( as this is all the generic kernel
-currently supports ) however this may change in future
-this allows us to access ( according to my sums )
-4TB of virtual storage per process i.e.
-4096*512(PTES)*1024(PMDS)*2048(PGD) = 4398046511104 bytes,
-enough for another 2 or 3 of years I think :-).
-to do this we use a region-third-table designation type in
-our address space control registers.
-
-
-The Linux for s/390 & z/Architecture Kernel Task Structure
-==========================================================
-Each process/thread under Linux for S390 has its own kernel task_struct
-defined in linux/include/linux/sched.h
-The S390 on initialisation & resuming of a process on a cpu sets
-the __LC_KERNEL_STACK variable in the spare prefix area for this cpu
-(which we use for per-processor globals).
-
-The kernel stack pointer is intimately tied with the task structure for
-each processor as follows.
-
- s/390
- ************************
- * 1 page kernel stack *
- * ( 4K ) *
- ************************
- * 1 page task_struct *
- * ( 4K ) *
-8K aligned ************************
-
- z/Architecture
- ************************
- * 2 page kernel stack *
- * ( 8K ) *
- ************************
- * 2 page task_struct *
- * ( 8K ) *
-16K aligned ************************
-
-What this means is that we don't need to dedicate any register or global
-variable to point to the current running process & can retrieve it with the
-following very simple construct for s/390 & one very similar for z/Architecture.
-
-static inline struct task_struct * get_current(void)
-{
- struct task_struct *current;
- __asm__("lhi %0,-8192\n\t"
- "nr %0,15"
- : "=r" (current) );
- return current;
-}
-
-i.e. just anding the current kernel stack pointer with the mask -8192.
-Thankfully because Linux doesn't have support for nested IO interrupts
-& our devices have large buffers can survive interrupts being shut for
-short amounts of time we don't need a separate stack for interrupts.
-
-
-
-
-Register Usage & Stackframes on Linux for s/390 & z/Architecture
-=================================================================
-Overview:
----------
-This is the code that gcc produces at the top & the bottom of
-each function. It usually is fairly consistent & similar from
-function to function & if you know its layout you can probably
-make some headway in finding the ultimate cause of a problem
-after a crash without a source level debugger.
-
-Note: To follow stackframes requires a knowledge of C or Pascal &
-limited knowledge of one assembly language.
-
-It should be noted that there are some differences between the
-s/390 and z/Architecture stack layouts as the z/Architecture stack layout
-didn't have to maintain compatibility with older linkage formats.
-
-Glossary:
----------
-alloca:
-This is a built in compiler function for runtime allocation
-of extra space on the callers stack which is obviously freed
-up on function exit ( e.g. the caller may choose to allocate nothing
-of a buffer of 4k if required for temporary purposes ), it generates
-very efficient code ( a few cycles ) when compared to alternatives
-like malloc.
-
-automatics: These are local variables on the stack,
-i.e they aren't in registers & they aren't static.
-
-back-chain:
-This is a pointer to the stack pointer before entering a
-framed functions ( see frameless function ) prologue got by
-dereferencing the address of the current stack pointer,
- i.e. got by accessing the 32 bit value at the stack pointers
-current location.
-
-base-pointer:
-This is a pointer to the back of the literal pool which
-is an area just behind each procedure used to store constants
-in each function.
-
-call-clobbered: The caller probably needs to save these registers if there
-is something of value in them, on the stack or elsewhere before making a
-call to another procedure so that it can restore it later.
-
-epilogue:
-The code generated by the compiler to return to the caller.
-
-frameless-function
-A frameless function in Linux for s390 & z/Architecture is one which doesn't
-need more than the register save area (96 bytes on s/390, 160 on z/Architecture)
-given to it by the caller.
-A frameless function never:
-1) Sets up a back chain.
-2) Calls alloca.
-3) Calls other normal functions
-4) Has automatics.
-
-GOT-pointer:
-This is a pointer to the global-offset-table in ELF
-( Executable Linkable Format, Linux'es most common executable format ),
-all globals & shared library objects are found using this pointer.
-
-lazy-binding
-ELF shared libraries are typically only loaded when routines in the shared
-library are actually first called at runtime. This is lazy binding.
-
-procedure-linkage-table
-This is a table found from the GOT which contains pointers to routines
-in other shared libraries which can't be called to by easier means.
-
-prologue:
-The code generated by the compiler to set up the stack frame.
-
-outgoing-args:
-This is extra area allocated on the stack of the calling function if the
-parameters for the callee's cannot all be put in registers, the same
-area can be reused by each function the caller calls.
-
-routine-descriptor:
-A COFF executable format based concept of a procedure reference
-actually being 8 bytes or more as opposed to a simple pointer to the routine.
-This is typically defined as follows
-Routine Descriptor offset 0=Pointer to Function
-Routine Descriptor offset 4=Pointer to Table of Contents
-The table of contents/TOC is roughly equivalent to a GOT pointer.
-& it means that shared libraries etc. can be shared between several
-environments each with their own TOC.
-
-
-static-chain: This is used in nested functions a concept adopted from pascal
-by gcc not used in ansi C or C++ ( although quite useful ), basically it
-is a pointer used to reference local variables of enclosing functions.
-You might come across this stuff once or twice in your lifetime.
-
-e.g.
-The function below should return 11 though gcc may get upset & toss warnings
-about unused variables.
-int FunctionA(int a)
-{
- int b;
- FunctionC(int c)
- {
- b=c+1;
- }
- FunctionC(10);
- return(b);
-}
-
-
-s/390 & z/Architecture Register usage
-=====================================
-r0 used by syscalls/assembly call-clobbered
-r1 used by syscalls/assembly call-clobbered
-r2 argument 0 / return value 0 call-clobbered
-r3 argument 1 / return value 1 (if long long) call-clobbered
-r4 argument 2 call-clobbered
-r5 argument 3 call-clobbered
-r6 argument 4 saved
-r7 pointer-to arguments 5 to ... saved
-r8 this & that saved
-r9 this & that saved
-r10 static-chain ( if nested function ) saved
-r11 frame-pointer ( if function used alloca ) saved
-r12 got-pointer saved
-r13 base-pointer saved
-r14 return-address saved
-r15 stack-pointer saved
-
-f0 argument 0 / return value ( float/double ) call-clobbered
-f2 argument 1 call-clobbered
-f4 z/Architecture argument 2 saved
-f6 z/Architecture argument 3 saved
-The remaining floating points
-f1,f3,f5 f7-f15 are call-clobbered.
-
-Notes:
-------
-1) The only requirement is that registers which are used
-by the callee are saved, e.g. the compiler is perfectly
-capable of using r11 for purposes other than a frame a
-frame pointer if a frame pointer is not needed.
-2) In functions with variable arguments e.g. printf the calling procedure
-is identical to one without variable arguments & the same number of
-parameters. However, the prologue of this function is somewhat more
-hairy owing to it having to move these parameters to the stack to
-get va_start, va_arg & va_end to work.
-3) Access registers are currently unused by gcc but are used in
-the kernel. Possibilities exist to use them at the moment for
-temporary storage but it isn't recommended.
-4) Only 4 of the floating point registers are used for
-parameter passing as older machines such as G3 only have only 4
-& it keeps the stack frame compatible with other compilers.
-However with IEEE floating point emulation under linux on the
-older machines you are free to use the other 12.
-5) A long long or double parameter cannot be have the
-first 4 bytes in a register & the second four bytes in the
-outgoing args area. It must be purely in the outgoing args
-area if crossing this boundary.
-6) Floating point parameters are mixed with outgoing args
-on the outgoing args area in the order the are passed in as parameters.
-7) Floating point arguments 2 & 3 are saved in the outgoing args area for
-z/Architecture
-
-
-Stack Frame Layout
-------------------
-s/390 z/Architecture
-0 0 back chain ( a 0 here signifies end of back chain )
-4 8 eos ( end of stack, not used on Linux for S390 used in other linkage formats )
-8 16 glue used in other s/390 linkage formats for saved routine descriptors etc.
-12 24 glue used in other s/390 linkage formats for saved routine descriptors etc.
-16 32 scratch area
-20 40 scratch area
-24 48 saved r6 of caller function
-28 56 saved r7 of caller function
-32 64 saved r8 of caller function
-36 72 saved r9 of caller function
-40 80 saved r10 of caller function
-44 88 saved r11 of caller function
-48 96 saved r12 of caller function
-52 104 saved r13 of caller function
-56 112 saved r14 of caller function
-60 120 saved r15 of caller function
-64 128 saved f4 of caller function
-72 132 saved f6 of caller function
-80 undefined
-96 160 outgoing args passed from caller to callee
-96+x 160+x possible stack alignment ( 8 bytes desirable )
-96+x+y 160+x+y alloca space of caller ( if used )
-96+x+y+z 160+x+y+z automatics of caller ( if used )
-0 back-chain
-
-A sample program with comments.
-===============================
-
-Comments on the function test
------------------------------
-1) It didn't need to set up a pointer to the constant pool gpr13 as it is not
-used ( :-( ).
-2) This is a frameless function & no stack is bought.
-3) The compiler was clever enough to recognise that it could return the
-value in r2 as well as use it for the passed in parameter ( :-) ).
-4) The basr ( branch relative & save ) trick works as follows the instruction
-has a special case with r0,r0 with some instruction operands is understood as
-the literal value 0, some risc architectures also do this ). So now
-we are branching to the next address & the address new program counter is
-in r13,so now we subtract the size of the function prologue we have executed
-+ the size of the literal pool to get to the top of the literal pool
-0040037c int test(int b)
-{ # Function prologue below
- 40037c: 90 de f0 34 stm %r13,%r14,52(%r15) # Save registers r13 & r14
- 400380: 0d d0 basr %r13,%r0 # Set up pointer to constant pool using
- 400382: a7 da ff fa ahi %r13,-6 # basr trick
- return(5+b);
- # Huge main program
- 400386: a7 2a 00 05 ahi %r2,5 # add 5 to r2
-
- # Function epilogue below
- 40038a: 98 de f0 34 lm %r13,%r14,52(%r15) # restore registers r13 & 14
- 40038e: 07 fe br %r14 # return
-}
-
-Comments on the function main
------------------------------
-1) The compiler did this function optimally ( 8-) )
-
-Literal pool for main.
-400390: ff ff ff ec .long 0xffffffec
-main(int argc,char *argv[])
-{ # Function prologue below
- 400394: 90 bf f0 2c stm %r11,%r15,44(%r15) # Save necessary registers
- 400398: 18 0f lr %r0,%r15 # copy stack pointer to r0
- 40039a: a7 fa ff a0 ahi %r15,-96 # Make area for callee saving
- 40039e: 0d d0 basr %r13,%r0 # Set up r13 to point to
- 4003a0: a7 da ff f0 ahi %r13,-16 # literal pool
- 4003a4: 50 00 f0 00 st %r0,0(%r15) # Save backchain
-
- return(test(5)); # Main Program Below
- 4003a8: 58 e0 d0 00 l %r14,0(%r13) # load relative address of test from
- # literal pool
- 4003ac: a7 28 00 05 lhi %r2,5 # Set first parameter to 5
- 4003b0: 4d ee d0 00 bas %r14,0(%r14,%r13) # jump to test setting r14 as return
- # address using branch & save instruction.
-
- # Function Epilogue below
- 4003b4: 98 bf f0 8c lm %r11,%r15,140(%r15)# Restore necessary registers.
- 4003b8: 07 fe br %r14 # return to do program exit
-}
-
-
-Compiler updates
-----------------
-
-main(int argc,char *argv[])
-{
- 4004fc: 90 7f f0 1c stm %r7,%r15,28(%r15)
- 400500: a7 d5 00 04 bras %r13,400508 <main+0xc>
- 400504: 00 40 04 f4 .long 0x004004f4
- # compiler now puts constant pool in code to so it saves an instruction
- 400508: 18 0f lr %r0,%r15
- 40050a: a7 fa ff a0 ahi %r15,-96
- 40050e: 50 00 f0 00 st %r0,0(%r15)
- return(test(5));
- 400512: 58 10 d0 00 l %r1,0(%r13)
- 400516: a7 28 00 05 lhi %r2,5
- 40051a: 0d e1 basr %r14,%r1
- # compiler adds 1 extra instruction to epilogue this is done to
- # avoid processor pipeline stalls owing to data dependencies on g5 &
- # above as register 14 in the old code was needed directly after being loaded
- # by the lm %r11,%r15,140(%r15) for the br %14.
- 40051c: 58 40 f0 98 l %r4,152(%r15)
- 400520: 98 7f f0 7c lm %r7,%r15,124(%r15)
- 400524: 07 f4 br %r4
-}
-
-
-Hartmut ( our compiler developer ) also has been threatening to take out the
-stack backchain in optimised code as this also causes pipeline stalls, you
-have been warned.
-
-64 bit z/Architecture code disassembly
---------------------------------------
-
-If you understand the stuff above you'll understand the stuff
-below too so I'll avoid repeating myself & just say that
-some of the instructions have g's on the end of them to indicate
-they are 64 bit & the stack offsets are a bigger,
-the only other difference you'll find between 32 & 64 bit is that
-we now use f4 & f6 for floating point arguments on 64 bit.
-00000000800005b0 <test>:
-int test(int b)
-{
- return(5+b);
- 800005b0: a7 2a 00 05 ahi %r2,5
- 800005b4: b9 14 00 22 lgfr %r2,%r2 # downcast to integer
- 800005b8: 07 fe br %r14
- 800005ba: 07 07 bcr 0,%r7
-
-
-}
-
-00000000800005bc <main>:
-main(int argc,char *argv[])
-{
- 800005bc: eb bf f0 58 00 24 stmg %r11,%r15,88(%r15)
- 800005c2: b9 04 00 1f lgr %r1,%r15
- 800005c6: a7 fb ff 60 aghi %r15,-160
- 800005ca: e3 10 f0 00 00 24 stg %r1,0(%r15)
- return(test(5));
- 800005d0: a7 29 00 05 lghi %r2,5
- # brasl allows jumps > 64k & is overkill here bras would do fune
- 800005d4: c0 e5 ff ff ff ee brasl %r14,800005b0 <test>
- 800005da: e3 40 f1 10 00 04 lg %r4,272(%r15)
- 800005e0: eb bf f0 f8 00 04 lmg %r11,%r15,248(%r15)
- 800005e6: 07 f4 br %r4
-}
-
-
-
-Compiling programs for debugging on Linux for s/390 & z/Architecture
-====================================================================
--gdwarf-2 now works it should be considered the default debugging
-format for s/390 & z/Architecture as it is more reliable for debugging
-shared libraries, normal -g debugging works much better now
-Thanks to the IBM java compiler developers bug reports.
-
-This is typically done adding/appending the flags -g or -gdwarf-2 to the
-CFLAGS & LDFLAGS variables Makefile of the program concerned.
-
-If using gdb & you would like accurate displays of registers &
- stack traces compile without optimisation i.e make sure
-that there is no -O2 or similar on the CFLAGS line of the Makefile &
-the emitted gcc commands, obviously this will produce worse code
-( not advisable for shipment ) but it is an aid to the debugging process.
-
-This aids debugging because the compiler will copy parameters passed in
-in registers onto the stack so backtracing & looking at passed in
-parameters will work, however some larger programs which use inline functions
-will not compile without optimisation.
-
-Debugging with optimisation has since much improved after fixing
-some bugs, please make sure you are using gdb-5.0 or later developed
-after Nov'2000.
-
-
-
-Debugging under VM
-==================
-
-Notes
------
-Addresses & values in the VM debugger are always hex never decimal
-Address ranges are of the format <HexValue1>-<HexValue2> or
-<HexValue1>.<HexValue2>
-For example, the address range 0x2000 to 0x3000 can be described as 2000-3000
-or 2000.1000
-
-The VM Debugger is case insensitive.
-
-VM's strengths are usually other debuggers weaknesses you can get at any
-resource no matter how sensitive e.g. memory management resources, change
-address translation in the PSW. For kernel hacking you will reap dividends if
-you get good at it.
-
-The VM Debugger displays operators but not operands, and also the debugger
-displays useful information on the same line as the author of the code probably
-felt that it was a good idea not to go over the 80 columns on the screen.
-This isn't as unintuitive as it may seem as the s/390 instructions are easy to
-decode mentally and you can make a good guess at a lot of them as all the
-operands are nibble (half byte aligned).
-So if you have an objdump listing by hand, it is quite easy to follow, and if
-you don't have an objdump listing keep a copy of the s/390 Reference Summary
-or alternatively the s/390 principles of operation next to you.
-e.g. even I can guess that
-0001AFF8' LR 180F CC 0
-is a ( load register ) lr r0,r15
-
-Also it is very easy to tell the length of a 390 instruction from the 2 most
-significant bits in the instruction (not that this info is really useful except
-if you are trying to make sense of a hexdump of code).
-Here is a table
-Bits Instruction Length
-------------------------------------------
-00 2 Bytes
-01 4 Bytes
-10 4 Bytes
-11 6 Bytes
-
-The debugger also displays other useful info on the same line such as the
-addresses being operated on destination addresses of branches & condition codes.
-e.g.
-00019736' AHI A7DAFF0E CC 1
-000198BA' BRC A7840004 -> 000198C2' CC 0
-000198CE' STM 900EF068 >> 0FA95E78 CC 2
-
-
-
-Useful VM debugger commands
----------------------------
-
-I suppose I'd better mention this before I start
-to list the current active traces do
-Q TR
-there can be a maximum of 255 of these per set
-( more about trace sets later ).
-To stop traces issue a
-TR END.
-To delete a particular breakpoint issue
-TR DEL <breakpoint number>
-
-The PA1 key drops to CP mode so you can issue debugger commands,
-Doing alt c (on my 3270 console at least ) clears the screen.
-hitting b <enter> comes back to the running operating system
-from cp mode ( in our case linux ).
-It is typically useful to add shortcuts to your profile.exec file
-if you have one ( this is roughly equivalent to autoexec.bat in DOS ).
-file here are a few from mine.
-/* this gives me command history on issuing f12 */
-set pf12 retrieve
-/* this continues */
-set pf8 imm b
-/* goes to trace set a */
-set pf1 imm tr goto a
-/* goes to trace set b */
-set pf2 imm tr goto b
-/* goes to trace set c */
-set pf3 imm tr goto c
-
-
-
-Instruction Tracing
--------------------
-Setting a simple breakpoint
-TR I PSWA <address>
-To debug a particular function try
-TR I R <function address range>
-TR I on its own will single step.
-TR I DATA <MNEMONIC> <OPTIONAL RANGE> will trace for particular mnemonics
-e.g.
-TR I DATA 4D R 0197BC.4000
-will trace for BAS'es ( opcode 4D ) in the range 0197BC.4000
-if you were inclined you could add traces for all branch instructions &
-suffix them with the run prefix so you would have a backtrace on screen
-when a program crashes.
-TR BR <INTO OR FROM> will trace branches into or out of an address.
-e.g.
-TR BR INTO 0 is often quite useful if a program is getting awkward & deciding
-to branch to 0 & crashing as this will stop at the address before in jumps to 0.
-TR I R <address range> RUN cmd d g
-single steps a range of addresses but stays running &
-displays the gprs on each step.
-
-
-
-Displaying & modifying Registers
---------------------------------
-D G will display all the gprs
-Adding a extra G to all the commands is necessary to access the full 64 bit
-content in VM on z/Architecture. Obviously this isn't required for access
-registers as these are still 32 bit.
-e.g. DGG instead of DG
-D X will display all the control registers
-D AR will display all the access registers
-D AR4-7 will display access registers 4 to 7
-CPU ALL D G will display the GRPS of all CPUS in the configuration
-D PSW will display the current PSW
-st PSW 2000 will put the value 2000 into the PSW &
-cause crash your machine.
-D PREFIX displays the prefix offset
-
-
-Displaying Memory
------------------
-To display memory mapped using the current PSW's mapping try
-D <range>
-To make VM display a message each time it hits a particular address and
-continue try
-D I<range> will disassemble/display a range of instructions.
-ST addr 32 bit word will store a 32 bit aligned address
-D T<range> will display the EBCDIC in an address (if you are that way inclined)
-D R<range> will display real addresses ( without DAT ) but with prefixing.
-There are other complex options to display if you need to get at say home space
-but are in primary space the easiest thing to do is to temporarily
-modify the PSW to the other addressing mode, display the stuff & then
-restore it.
-
-
-
-Hints
------
-If you want to issue a debugger command without halting your virtual machine
-with the PA1 key try prefixing the command with #CP e.g.
-#cp tr i pswa 2000
-also suffixing most debugger commands with RUN will cause them not
-to stop just display the mnemonic at the current instruction on the console.
-If you have several breakpoints you want to put into your program &
-you get fed up of cross referencing with System.map
-you can do the following trick for several symbols.
-grep do_signal System.map
-which emits the following among other things
-0001f4e0 T do_signal
-now you can do
-
-TR I PSWA 0001f4e0 cmd msg * do_signal
-This sends a message to your own console each time do_signal is entered.
-( As an aside I wrote a perl script once which automatically generated a REXX
-script with breakpoints on every kernel procedure, this isn't a good idea
-because there are thousands of these routines & VM can only set 255 breakpoints
-at a time so you nearly had to spend as long pruning the file down as you would
-entering the msgs by hand), however, the trick might be useful for a single
-object file. In the 3270 terminal emulator x3270 there is a very useful option
-in the file menu called "Save Screen In File" - this is very good for keeping a
-copy of traces.
-
-From CMS help <command name> will give you online help on a particular command.
-e.g.
-HELP DISPLAY
-
-Also CP has a file called profile.exec which automatically gets called
-on startup of CMS ( like autoexec.bat ), keeping on a DOS analogy session
-CP has a feature similar to doskey, it may be useful for you to
-use profile.exec to define some keystrokes.
-e.g.
-SET PF9 IMM B
-This does a single step in VM on pressing F8.
-SET PF10 ^
-This sets up the ^ key.
-which can be used for ^c (ctrl-c),^z (ctrl-z) which can't be typed directly
-into some 3270 consoles.
-SET PF11 ^-
-This types the starting keystrokes for a sysrq see SysRq below.
-SET PF12 RETRIEVE
-This retrieves command history on pressing F12.
-
-
-Sometimes in VM the display is set up to scroll automatically this
-can be very annoying if there are messages you wish to look at
-to stop this do
-TERM MORE 255 255
-This will nearly stop automatic screen updates, however it will
-cause a denial of service if lots of messages go to the 3270 console,
-so it would be foolish to use this as the default on a production machine.
-
-
-Tracing particular processes
-----------------------------
-The kernel's text segment is intentionally at an address in memory that it will
-very seldom collide with text segments of user programs ( thanks Martin ),
-this simplifies debugging the kernel.
-However it is quite common for user processes to have addresses which collide
-this can make debugging a particular process under VM painful under normal
-circumstances as the process may change when doing a
-TR I R <address range>.
-Thankfully after reading VM's online help I figured out how to debug
-I particular process.
-
-Your first problem is to find the STD ( segment table designation )
-of the program you wish to debug.
-There are several ways you can do this here are a few
-1) objdump --syms <program to be debugged> | grep main
-To get the address of main in the program.
-tr i pswa <address of main>
-Start the program, if VM drops to CP on what looks like the entry
-point of the main function this is most likely the process you wish to debug.
-Now do a D X13 or D XG13 on z/Architecture.
-On 31 bit the STD is bits 1-19 ( the STO segment table origin )
-& 25-31 ( the STL segment table length ) of CR13.
-now type
-TR I R STD <CR13's value> 0.7fffffff
-e.g.
-TR I R STD 8F32E1FF 0.7fffffff
-Another very useful variation is
-TR STORE INTO STD <CR13's value> <address range>
-for finding out when a particular variable changes.
-
-An alternative way of finding the STD of a currently running process
-is to do the following, ( this method is more complex but
-could be quite convenient if you aren't updating the kernel much &
-so your kernel structures will stay constant for a reasonable period of
-time ).
-
-grep task /proc/<pid>/status
-from this you should see something like
-task: 0f160000 ksp: 0f161de8 pt_regs: 0f161f68
-This now gives you a pointer to the task structure.
-Now make CC:="s390-gcc -g" kernel/sched.s
-To get the task_struct stabinfo.
-( task_struct is defined in include/linux/sched.h ).
-Now we want to look at
-task->active_mm->pgd
-on my machine the active_mm in the task structure stab is
-active_mm:(4,12),672,32
-its offset is 672/8=84=0x54
-the pgd member in the mm_struct stab is
-pgd:(4,6)=*(29,5),96,32
-so its offset is 96/8=12=0xc
-
-so we'll
-hexdump -s 0xf160054 /dev/mem | more
-i.e. task_struct+active_mm offset
-to look at the active_mm member
-f160054 0fee cc60 0019 e334 0000 0000 0000 0011
-hexdump -s 0x0feecc6c /dev/mem | more
-i.e. active_mm+pgd offset
-feecc6c 0f2c 0000 0000 0001 0000 0001 0000 0010
-we get something like
-now do
-TR I R STD <pgd|0x7f> 0.7fffffff
-i.e. the 0x7f is added because the pgd only
-gives the page table origin & we need to set the low bits
-to the maximum possible segment table length.
-TR I R STD 0f2c007f 0.7fffffff
-on z/Architecture you'll probably need to do
-TR I R STD <pgd|0x7> 0.ffffffffffffffff
-to set the TableType to 0x1 & the Table length to 3.
-
-
-
-Tracing Program Exceptions
---------------------------
-If you get a crash which says something like
-illegal operation or specification exception followed by a register dump
-You can restart linux & trace these using the tr prog <range or value> trace
-option.
-
-
-The most common ones you will normally be tracing for is
-1=operation exception
-2=privileged operation exception
-4=protection exception
-5=addressing exception
-6=specification exception
-10=segment translation exception
-11=page translation exception
-
-The full list of these is on page 22 of the current s/390 Reference Summary.
-e.g.
-tr prog 10 will trace segment translation exceptions.
-tr prog on its own will trace all program interruption codes.
-
-Trace Sets
-----------
-On starting VM you are initially in the INITIAL trace set.
-You can do a Q TR to verify this.
-If you have a complex tracing situation where you wish to wait for instance
-till a driver is open before you start tracing IO, but know in your
-heart that you are going to have to make several runs through the code till you
-have a clue whats going on.
-
-What you can do is
-TR I PSWA <Driver open address>
-hit b to continue till breakpoint
-reach the breakpoint
-now do your
-TR GOTO B
-TR IO 7c08-7c09 inst int run
-or whatever the IO channels you wish to trace are & hit b
-
-To got back to the initial trace set do
-TR GOTO INITIAL
-& the TR I PSWA <Driver open address> will be the only active breakpoint again.
-
-
-Tracing linux syscalls under VM
--------------------------------
-Syscalls are implemented on Linux for S390 by the Supervisor call instruction
-(SVC). There 256 possibilities of these as the instruction is made up of a 0xA
-opcode and the second byte being the syscall number. They are traced using the
-simple command:
-TR SVC <Optional value or range>
-the syscalls are defined in linux/arch/s390/include/asm/unistd.h
-e.g. to trace all file opens just do
-TR SVC 5 ( as this is the syscall number of open )
-
-
-SMP Specific commands
----------------------
-To find out how many cpus you have
-Q CPUS displays all the CPU's available to your virtual machine
-To find the cpu that the current cpu VM debugger commands are being directed at
-do Q CPU to change the current cpu VM debugger commands are being directed at do
-CPU <desired cpu no>
-
-On a SMP guest issue a command to all CPUs try prefixing the command with cpu
-all. To issue a command to a particular cpu try cpu <cpu number> e.g.
-CPU 01 TR I R 2000.3000
-If you are running on a guest with several cpus & you have a IO related problem
-& cannot follow the flow of code but you know it isn't smp related.
-from the bash prompt issue
-shutdown -h now or halt.
-do a Q CPUS to find out how many cpus you have
-detach each one of them from cp except cpu 0
-by issuing a
-DETACH CPU 01-(number of cpus in configuration)
-& boot linux again.
-TR SIGP will trace inter processor signal processor instructions.
-DEFINE CPU 01-(number in configuration)
-will get your guests cpus back.
-
-
-Help for displaying ascii textstrings
--------------------------------------
-On the very latest VM Nucleus'es VM can now display ascii
-( thanks Neale for the hint ) by doing
-D TX<lowaddr>.<len>
-e.g.
-D TX0.100
-
-Alternatively
-=============
-Under older VM debuggers (I love EBDIC too) you can use following little
-program which converts a command line of hex digits to ascii text. It can be
-compiled under linux and you can copy the hex digits from your x3270 terminal
-to your xterm if you are debugging from a linuxbox.
-
-This is quite useful when looking at a parameter passed in as a text string
-under VM ( unless you are good at decoding ASCII in your head ).
-
-e.g. consider tracing an open syscall
-TR SVC 5
-We have stopped at a breakpoint
-000151B0' SVC 0A05 -> 0001909A' CC 0
-
-D 20.8 to check the SVC old psw in the prefix area and see was it from userspace
-(for the layout of the prefix area consult the "Fixed Storage Locations"
-chapter of the s/390 Reference Summary if you have it available).
-V00000020 070C2000 800151B2
-The problem state bit wasn't set & it's also too early in the boot sequence
-for it to be a userspace SVC if it was we would have to temporarily switch the
-psw to user space addressing so we could get at the first parameter of the open
-in gpr2.
-Next do a
-D G2
-GPR 2 = 00014CB4
-Now display what gpr2 is pointing to
-D 00014CB4.20
-V00014CB4 2F646576 2F636F6E 736F6C65 00001BF5
-V00014CC4 FC00014C B4001001 E0001000 B8070707
-Now copy the text till the first 00 hex ( which is the end of the string
-to an xterm & do hex2ascii on it.
-hex2ascii 2F646576 2F636F6E 736F6C65 00
-outputs
-Decoded Hex:=/ d e v / c o n s o l e 0x00
-We were opening the console device,
-
-You can compile the code below yourself for practice :-),
-/*
- * hex2ascii.c
- * a useful little tool for converting a hexadecimal command line to ascii
- *
- * Author(s): Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com)
- * (C) 2000 IBM Deutschland Entwicklung GmbH, IBM Corporation.
- */
-#include <stdio.h>
-
-int main(int argc,char *argv[])
-{
- int cnt1,cnt2,len,toggle=0;
- int startcnt=1;
- unsigned char c,hex;
-
- if(argc>1&&(strcmp(argv[1],"-a")==0))
- startcnt=2;
- printf("Decoded Hex:=");
- for(cnt1=startcnt;cnt1<argc;cnt1++)
- {
- len=strlen(argv[cnt1]);
- for(cnt2=0;cnt2<len;cnt2++)
- {
- c=argv[cnt1][cnt2];
- if(c>='0'&&c<='9')
- c=c-'0';
- if(c>='A'&&c<='F')
- c=c-'A'+10;
- if(c>='a'&&c<='f')
- c=c-'a'+10;
- switch(toggle)
- {
- case 0:
- hex=c<<4;
- toggle=1;
- break;
- case 1:
- hex+=c;
- if(hex<32||hex>127)
- {
- if(startcnt==1)
- printf("0x%02X ",(int)hex);
- else
- printf(".");
- }
- else
- {
- printf("%c",hex);
- if(startcnt==1)
- printf(" ");
- }
- toggle=0;
- break;
- }
- }
- }
- printf("\n");
-}
-
-
-
-
-Stack tracing under VM
-----------------------
-A basic backtrace
------------------
-
-Here are the tricks I use 9 out of 10 times it works pretty well,
-
-When your backchain reaches a dead end
---------------------------------------
-This can happen when an exception happens in the kernel and the kernel is
-entered twice. If you reach the NULL pointer at the end of the back chain you
-should be able to sniff further back if you follow the following tricks.
-1) A kernel address should be easy to recognise since it is in
-primary space & the problem state bit isn't set & also
-The Hi bit of the address is set.
-2) Another backchain should also be easy to recognise since it is an
-address pointing to another address approximately 100 bytes or 0x70 hex
-behind the current stackpointer.
-
-
-Here is some practice.
-boot the kernel & hit PA1 at some random time
-d g to display the gprs, this should display something like
-GPR 0 = 00000001 00156018 0014359C 00000000
-GPR 4 = 00000001 001B8888 000003E0 00000000
-GPR 8 = 00100080 00100084 00000000 000FE000
-GPR 12 = 00010400 8001B2DC 8001B36A 000FFED8
-Note that GPR14 is a return address but as we are real men we are going to
-trace the stack.
-display 0x40 bytes after the stack pointer.
-
-V000FFED8 000FFF38 8001B838 80014C8E 000FFF38
-V000FFEE8 00000000 00000000 000003E0 00000000
-V000FFEF8 00100080 00100084 00000000 000FE000
-V000FFF08 00010400 8001B2DC 8001B36A 000FFED8
-
-
-Ah now look at whats in sp+56 (sp+0x38) this is 8001B36A our saved r14 if
-you look above at our stackframe & also agrees with GPR14.
-
-now backchain
-d 000FFF38.40
-we now are taking the contents of SP to get our first backchain.
-
-V000FFF38 000FFFA0 00000000 00014995 00147094
-V000FFF48 00147090 001470A0 000003E0 00000000
-V000FFF58 00100080 00100084 00000000 001BF1D0
-V000FFF68 00010400 800149BA 80014CA6 000FFF38
-
-This displays a 2nd return address of 80014CA6
-
-now do d 000FFFA0.40 for our 3rd backchain
-
-V000FFFA0 04B52002 0001107F 00000000 00000000
-V000FFFB0 00000000 00000000 FF000000 0001107F
-V000FFFC0 00000000 00000000 00000000 00000000
-V000FFFD0 00010400 80010802 8001085A 000FFFA0
-
-
-our 3rd return address is 8001085A
-
-as the 04B52002 looks suspiciously like rubbish it is fair to assume that the
-kernel entry routines for the sake of optimisation don't set up a backchain.
-
-now look at System.map to see if the addresses make any sense.
-
-grep -i 0001b3 System.map
-outputs among other things
-0001b304 T cpu_idle
-so 8001B36A
-is cpu_idle+0x66 ( quiet the cpu is asleep, don't wake it )
-
-
-grep -i 00014 System.map
-produces among other things
-00014a78 T start_kernel
-so 0014CA6 is start_kernel+some hex number I can't add in my head.
-
-grep -i 00108 System.map
-this produces
-00010800 T _stext
-so 8001085A is _stext+0x5a
-
-Congrats you've done your first backchain.
-
-
-
-s/390 & z/Architecture IO Overview
-==================================
-
-I am not going to give a course in 390 IO architecture as this would take me
-quite a while and I'm no expert. Instead I'll give a 390 IO architecture
-summary for Dummies. If you have the s/390 principles of operation available
-read this instead. If nothing else you may find a few useful keywords in here
-and be able to use them on a web search engine to find more useful information.
-
-Unlike other bus architectures modern 390 systems do their IO using mostly
-fibre optics and devices such as tapes and disks can be shared between several
-mainframes. Also S390 can support up to 65536 devices while a high end PC based
-system might be choking with around 64.
-
-Here is some of the common IO terminology:
-
-Subchannel:
-This is the logical number most IO commands use to talk to an IO device. There
-can be up to 0x10000 (65536) of these in a configuration, typically there are a
-few hundred. Under VM for simplicity they are allocated contiguously, however
-on the native hardware they are not. They typically stay consistent between
-boots provided no new hardware is inserted or removed.
-Under Linux for s390 we use these as IRQ's and also when issuing an IO command
-(CLEAR SUBCHANNEL, HALT SUBCHANNEL, MODIFY SUBCHANNEL, RESUME SUBCHANNEL,
-START SUBCHANNEL, STORE SUBCHANNEL and TEST SUBCHANNEL). We use this as the ID
-of the device we wish to talk to. The most important of these instructions are
-START SUBCHANNEL (to start IO), TEST SUBCHANNEL (to check whether the IO
-completed successfully) and HALT SUBCHANNEL (to kill IO). A subchannel can have
-up to 8 channel paths to a device, this offers redundancy if one is not
-available.
-
-Device Number:
-This number remains static and is closely tied to the hardware. There are 65536
-of these, made up of a CHPID (Channel Path ID, the most significant 8 bits) and
-another lsb 8 bits. These remain static even if more devices are inserted or
-removed from the hardware. There is a 1 to 1 mapping between subchannels and
-device numbers, provided devices aren't inserted or removed.
-
-Channel Control Words:
-CCWs are linked lists of instructions initially pointed to by an operation
-request block (ORB), which is initially given to Start Subchannel (SSCH)
-command along with the subchannel number for the IO subsystem to process
-while the CPU continues executing normal code.
-CCWs come in two flavours, Format 0 (24 bit for backward compatibility) and
-Format 1 (31 bit). These are typically used to issue read and write (and many
-other) instructions. They consist of a length field and an absolute address
-field.
-Each IO typically gets 1 or 2 interrupts, one for channel end (primary status)
-when the channel is idle, and the second for device end (secondary status).
-Sometimes you get both concurrently. You check how the IO went on by issuing a
-TEST SUBCHANNEL at each interrupt, from which you receive an Interruption
-response block (IRB). If you get channel and device end status in the IRB
-without channel checks etc. your IO probably went okay. If you didn't you
-probably need to examine the IRB, extended status word etc.
-If an error occurs, more sophisticated control units have a facility known as
-concurrent sense. This means that if an error occurs Extended sense information
-will be presented in the Extended status word in the IRB. If not you have to
-issue a subsequent SENSE CCW command after the test subchannel.
-
-
-TPI (Test pending interrupt) can also be used for polled IO, but in
-multitasking multiprocessor systems it isn't recommended except for
-checking special cases (i.e. non looping checks for pending IO etc.).
-
-Store Subchannel and Modify Subchannel can be used to examine and modify
-operating characteristics of a subchannel (e.g. channel paths).
-
-Other IO related Terms:
-Sysplex: S390's Clustering Technology
-QDIO: S390's new high speed IO architecture to support devices such as gigabit
-ethernet, this architecture is also designed to be forward compatible with
-upcoming 64 bit machines.
-
-
-General Concepts
-
-Input Output Processors (IOP's) are responsible for communicating between
-the mainframe CPU's & the channel & relieve the mainframe CPU's from the
-burden of communicating with IO devices directly, this allows the CPU's to
-concentrate on data processing.
-
-IOP's can use one or more links ( known as channel paths ) to talk to each
-IO device. It first checks for path availability & chooses an available one,
-then starts ( & sometimes terminates IO ).
-There are two types of channel path: ESCON & the Parallel IO interface.
-
-IO devices are attached to control units, control units provide the
-logic to interface the channel paths & channel path IO protocols to
-the IO devices, they can be integrated with the devices or housed separately
-& often talk to several similar devices ( typical examples would be raid
-controllers or a control unit which connects to 1000 3270 terminals ).
-
-
- +---------------------------------------------------------------+
- | +-----+ +-----+ +-----+ +-----+ +----------+ +----------+ |
- | | CPU | | CPU | | CPU | | CPU | | Main | | Expanded | |
- | | | | | | | | | | Memory | | Storage | |
- | +-----+ +-----+ +-----+ +-----+ +----------+ +----------+ |
- |---------------------------------------------------------------+
- | IOP | IOP | IOP |
- |---------------------------------------------------------------
- | C | C | C | C | C | C | C | C | C | C | C | C | C | C | C | C |
- ----------------------------------------------------------------
- || ||
- || Bus & Tag Channel Path || ESCON
- || ====================== || Channel
- || || || || Path
- +----------+ +----------+ +----------+
- | | | | | |
- | CU | | CU | | CU |
- | | | | | |
- +----------+ +----------+ +----------+
- | | | | |
-+----------+ +----------+ +----------+ +----------+ +----------+
-|I/O Device| |I/O Device| |I/O Device| |I/O Device| |I/O Device|
-+----------+ +----------+ +----------+ +----------+ +----------+
- CPU = Central Processing Unit
- C = Channel
- IOP = IP Processor
- CU = Control Unit
-
-The 390 IO systems come in 2 flavours the current 390 machines support both
-
-The Older 360 & 370 Interface,sometimes called the Parallel I/O interface,
-sometimes called Bus-and Tag & sometimes Original Equipment Manufacturers
-Interface (OEMI).
-
-This byte wide Parallel channel path/bus has parity & data on the "Bus" cable
-and control lines on the "Tag" cable. These can operate in byte multiplex mode
-for sharing between several slow devices or burst mode and monopolize the
-channel for the whole burst. Up to 256 devices can be addressed on one of these
-cables. These cables are about one inch in diameter. The maximum unextended
-length supported by these cables is 125 Meters but this can be extended up to
-2km with a fibre optic channel extended such as a 3044. The maximum burst speed
-supported is 4.5 megabytes per second. However, some really old processors
-support only transfer rates of 3.0, 2.0 & 1.0 MB/sec.
-One of these paths can be daisy chained to up to 8 control units.
-
-
-ESCON if fibre optic it is also called FICON
-Was introduced by IBM in 1990. Has 2 fibre optic cables and uses either leds or
-lasers for communication at a signaling rate of up to 200 megabits/sec. As
-10bits are transferred for every 8 bits info this drops to 160 megabits/sec
-and to 18.6 Megabytes/sec once control info and CRC are added. ESCON only
-operates in burst mode.
-
-ESCONs typical max cable length is 3km for the led version and 20km for the
-laser version known as XDF (extended distance facility). This can be further
-extended by using an ESCON director which triples the above mentioned ranges.
-Unlike Bus & Tag as ESCON is serial it uses a packet switching architecture,
-the standard Bus & Tag control protocol is however present within the packets.
-Up to 256 devices can be attached to each control unit that uses one of these
-interfaces.
-
-Common 390 Devices include:
-Network adapters typically OSA2,3172's,2116's & OSA-E gigabit ethernet adapters,
-Consoles 3270 & 3215 (a teletype emulated under linux for a line mode console).
-DASD's direct access storage devices ( otherwise known as hard disks ).
-Tape Drives.
-CTC ( Channel to Channel Adapters ),
-ESCON or Parallel Cables used as a very high speed serial link
-between 2 machines.
-
-
-Debugging IO on s/390 & z/Architecture under VM
-===============================================
-
-Now we are ready to go on with IO tracing commands under VM
-
-A few self explanatory queries:
-Q OSA
-Q CTC
-Q DISK ( This command is CMS specific )
-Q DASD
-
-
-
-
-
-
-Q OSA on my machine returns
-OSA 7C08 ON OSA 7C08 SUBCHANNEL = 0000
-OSA 7C09 ON OSA 7C09 SUBCHANNEL = 0001
-OSA 7C14 ON OSA 7C14 SUBCHANNEL = 0002
-OSA 7C15 ON OSA 7C15 SUBCHANNEL = 0003
-
-If you have a guest with certain privileges you may be able to see devices
-which don't belong to you. To avoid this, add the option V.
-e.g.
-Q V OSA
-
-Now using the device numbers returned by this command we will
-Trace the io starting up on the first device 7c08 & 7c09
-In our simplest case we can trace the
-start subchannels
-like TR SSCH 7C08-7C09
-or the halt subchannels
-or TR HSCH 7C08-7C09
-MSCH's ,STSCH's I think you can guess the rest
-
-A good trick is tracing all the IO's and CCWS and spooling them into the reader
-of another VM guest so he can ftp the logfile back to his own machine. I'll do
-a small bit of this and give you a look at the output.
-
-1) Spool stdout to VM reader
-SP PRT TO (another vm guest ) or * for the local vm guest
-2) Fill the reader with the trace
-TR IO 7c08-7c09 INST INT CCW PRT RUN
-3) Start up linux
-i 00c
-4) Finish the trace
-TR END
-5) close the reader
-C PRT
-6) list reader contents
-RDRLIST
-7) copy it to linux4's minidisk
-RECEIVE / LOG TXT A1 ( replace
-8)
-filel & press F11 to look at it
-You should see something like:
-
-00020942' SSCH B2334000 0048813C CC 0 SCH 0000 DEV 7C08
- CPA 000FFDF0 PARM 00E2C9C4 KEY 0 FPI C0 LPM 80
- CCW 000FFDF0 E4200100 00487FE8 0000 E4240100 ........
- IDAL 43D8AFE8
- IDAL 0FB76000
-00020B0A' I/O DEV 7C08 -> 000197BC' SCH 0000 PARM 00E2C9C4
-00021628' TSCH B2354000 >> 00488164 CC 0 SCH 0000 DEV 7C08
- CCWA 000FFDF8 DEV STS 0C SCH STS 00 CNT 00EC
- KEY 0 FPI C0 CC 0 CTLS 4007
-00022238' STSCH B2344000 >> 00488108 CC 0 SCH 0000 DEV 7C08
-
-If you don't like messing up your readed ( because you possibly booted from it )
-you can alternatively spool it to another readers guest.
-
-
-Other common VM device related commands
----------------------------------------------
-These commands are listed only because they have
-been of use to me in the past & may be of use to
-you too. For more complete info on each of the commands
-use type HELP <command> from CMS.
-detaching devices
-DET <devno range>
-ATT <devno range> <guest>
-attach a device to guest * for your own guest
-READY <devno> cause VM to issue a fake interrupt.
-
-The VARY command is normally only available to VM administrators.
-VARY ON PATH <path> TO <devno range>
-VARY OFF PATH <PATH> FROM <devno range>
-This is used to switch on or off channel paths to devices.
-
-Q CHPID <channel path ID>
-This displays state of devices using this channel path
-D SCHIB <subchannel>
-This displays the subchannel information SCHIB block for the device.
-this I believe is also only available to administrators.
-DEFINE CTC <devno>
-defines a virtual CTC channel to channel connection
-2 need to be defined on each guest for the CTC driver to use.
-COUPLE devno userid remote devno
-Joins a local virtual device to a remote virtual device
-( commonly used for the CTC driver ).
-
-Building a VM ramdisk under CMS which linux can use
-def vfb-<blocksize> <subchannel> <number blocks>
-blocksize is commonly 4096 for linux.
-Formatting it
-format <subchannel> <driver letter e.g. x> (blksize <blocksize>
-
-Sharing a disk between multiple guests
-LINK userid devno1 devno2 mode password
-
-
-
-GDB on S390
-===========
-N.B. if compiling for debugging gdb works better without optimisation
-( see Compiling programs for debugging )
-
-invocation
-----------
-gdb <victim program> <optional corefile>
-
-Online help
------------
-help: gives help on commands
-e.g.
-help
-help display
-Note gdb's online help is very good use it.
-
-
-Assembly
---------
-info registers: displays registers other than floating point.
-info all-registers: displays floating points as well.
-disassemble: disassembles
-e.g.
-disassemble without parameters will disassemble the current function
-disassemble $pc $pc+10
-
-Viewing & modifying variables
------------------------------
-print or p: displays variable or register
-e.g. p/x $sp will display the stack pointer
-
-display: prints variable or register each time program stops
-e.g.
-display/x $pc will display the program counter
-display argc
-
-undisplay : undo's display's
-
-info breakpoints: shows all current breakpoints
-
-info stack: shows stack back trace (if this doesn't work too well, I'll show
-you the stacktrace by hand below).
-
-info locals: displays local variables.
-
-info args: display current procedure arguments.
-
-set args: will set argc & argv each time the victim program is invoked.
-
-set <variable>=value
-set argc=100
-set $pc=0
-
-
-
-Modifying execution
--------------------
-step: steps n lines of sourcecode
-step steps 1 line.
-step 100 steps 100 lines of code.
-
-next: like step except this will not step into subroutines
-
-stepi: steps a single machine code instruction.
-e.g. stepi 100
-
-nexti: steps a single machine code instruction but will not step into
-subroutines.
-
-finish: will run until exit of the current routine
-
-run: (re)starts a program
-
-cont: continues a program
-
-quit: exits gdb.
-
-
-breakpoints
-------------
-
-break
-sets a breakpoint
-e.g.
-
-break main
-
-break *$pc
-
-break *0x400618
-
-Here's a really useful one for large programs
-rbr
-Set a breakpoint for all functions matching REGEXP
-e.g.
-rbr 390
-will set a breakpoint with all functions with 390 in their name.
-
-info breakpoints
-lists all breakpoints
-
-delete: delete breakpoint by number or delete them all
-e.g.
-delete 1 will delete the first breakpoint
-delete will delete them all
-
-watch: This will set a watchpoint ( usually hardware assisted ),
-This will watch a variable till it changes
-e.g.
-watch cnt, will watch the variable cnt till it changes.
-As an aside unfortunately gdb's, architecture independent watchpoint code
-is inconsistent & not very good, watchpoints usually work but not always.
-
-info watchpoints: Display currently active watchpoints
-
-condition: ( another useful one )
-Specify breakpoint number N to break only if COND is true.
-Usage is `condition N COND', where N is an integer and COND is an
-expression to be evaluated whenever breakpoint N is reached.
-
-
-
-User defined functions/macros
------------------------------
-define: ( Note this is very very useful,simple & powerful )
-usage define <name> <list of commands> end
-
-examples which you should consider putting into .gdbinit in your home directory
-define d
-stepi
-disassemble $pc $pc+10
-end
-
-define e
-nexti
-disassemble $pc $pc+10
-end
-
-
-Other hard to classify stuff
-----------------------------
-signal n:
-sends the victim program a signal.
-e.g. signal 3 will send a SIGQUIT.
-
-info signals:
-what gdb does when the victim receives certain signals.
-
-list:
-e.g.
-list lists current function source
-list 1,10 list first 10 lines of current file.
-list test.c:1,10
-
-
-directory:
-Adds directories to be searched for source if gdb cannot find the source.
-(note it is a bit sensitive about slashes)
-e.g. To add the root of the filesystem to the searchpath do
-directory //
-
-
-call <function>
-This calls a function in the victim program, this is pretty powerful
-e.g.
-(gdb) call printf("hello world")
-outputs:
-$1 = 11
-
-You might now be thinking that the line above didn't work, something extra had
-to be done.
-(gdb) call fflush(stdout)
-hello world$2 = 0
-As an aside the debugger also calls malloc & free under the hood
-to make space for the "hello world" string.
-
-
-
-hints
------
-1) command completion works just like bash
-( if you are a bad typist like me this really helps )
-e.g. hit br <TAB> & cursor up & down :-).
-
-2) if you have a debugging problem that takes a few steps to recreate
-put the steps into a file called .gdbinit in your current working directory
-if you have defined a few extra useful user defined commands put these in
-your home directory & they will be read each time gdb is launched.
-
-A typical .gdbinit file might be.
-break main
-run
-break runtime_exception
-cont
-
-
-stack chaining in gdb by hand
------------------------------
-This is done using a the same trick described for VM
-p/x (*($sp+56))&0x7fffffff get the first backchain.
-
-For z/Architecture
-Replace 56 with 112 & ignore the &0x7fffffff
-in the macros below & do nasty casts to longs like the following
-as gdb unfortunately deals with printed arguments as ints which
-messes up everything.
-i.e. here is a 3rd backchain dereference
-p/x *(long *)(***(long ***)$sp+112)
-
-
-this outputs
-$5 = 0x528f18
-on my machine.
-Now you can use
-info symbol (*($sp+56))&0x7fffffff
-you might see something like.
-rl_getc + 36 in section .text telling you what is located at address 0x528f18
-Now do.
-p/x (*(*$sp+56))&0x7fffffff
-This outputs
-$6 = 0x528ed0
-Now do.
-info symbol (*(*$sp+56))&0x7fffffff
-rl_read_key + 180 in section .text
-now do
-p/x (*(**$sp+56))&0x7fffffff
-& so on.
-
-Disassembling instructions without debug info
----------------------------------------------
-gdb typically complains if there is a lack of debugging
-symbols in the disassemble command with
-"No function contains specified address." To get around
-this do
-x/<number lines to disassemble>xi <address>
-e.g.
-x/20xi 0x400730
-
-
-
-Note: Remember gdb has history just like bash you don't need to retype the
-whole line just use the up & down arrows.
-
-
-
-For more info
--------------
-From your linuxbox do
-man gdb or info gdb.
-
-core dumps
-----------
-What a core dump ?,
-A core dump is a file generated by the kernel (if allowed) which contains the
-registers and all active pages of the program which has crashed.
-From this file gdb will allow you to look at the registers, stack trace and
-memory of the program as if it just crashed on your system. It is usually
-called core and created in the current working directory.
-This is very useful in that a customer can mail a core dump to a technical
-support department and the technical support department can reconstruct what
-happened. Provided they have an identical copy of this program with debugging
-symbols compiled in and the source base of this build is available.
-In short it is far more useful than something like a crash log could ever hope
-to be.
-
-Why have I never seen one ?.
-Probably because you haven't used the command
-ulimit -c unlimited in bash
-to allow core dumps, now do
-ulimit -a
-to verify that the limit was accepted.
-
-A sample core dump
-To create this I'm going to do
-ulimit -c unlimited
-gdb
-to launch gdb (my victim app. ) now be bad & do the following from another
-telnet/xterm session to the same machine
-ps -aux | grep gdb
-kill -SIGSEGV <gdb's pid>
-or alternatively use killall -SIGSEGV gdb if you have the killall command.
-Now look at the core dump.
-./gdb core
-Displays the following
-GNU gdb 4.18
-Copyright 1998 Free Software Foundation, Inc.
-GDB is free software, covered by the GNU General Public License, and you are
-welcome to change it and/or distribute copies of it under certain conditions.
-Type "show copying" to see the conditions.
-There is absolutely no warranty for GDB. Type "show warranty" for details.
-This GDB was configured as "s390-ibm-linux"...
-Core was generated by `./gdb'.
-Program terminated with signal 11, Segmentation fault.
-Reading symbols from /usr/lib/libncurses.so.4...done.
-Reading symbols from /lib/libm.so.6...done.
-Reading symbols from /lib/libc.so.6...done.
-Reading symbols from /lib/ld-linux.so.2...done.
-#0 0x40126d1a in read () from /lib/libc.so.6
-Setting up the environment for debugging gdb.
-Breakpoint 1 at 0x4dc6f8: file utils.c, line 471.
-Breakpoint 2 at 0x4d87a4: file top.c, line 2609.
-(top-gdb) info stack
-#0 0x40126d1a in read () from /lib/libc.so.6
-#1 0x528f26 in rl_getc (stream=0x7ffffde8) at input.c:402
-#2 0x528ed0 in rl_read_key () at input.c:381
-#3 0x5167e6 in readline_internal_char () at readline.c:454
-#4 0x5168ee in readline_internal_charloop () at readline.c:507
-#5 0x51692c in readline_internal () at readline.c:521
-#6 0x5164fe in readline (prompt=0x7ffff810)
- at readline.c:349
-#7 0x4d7a8a in command_line_input (prompt=0x564420 "(gdb) ", repeat=1,
- annotation_suffix=0x4d6b44 "prompt") at top.c:2091
-#8 0x4d6cf0 in command_loop () at top.c:1345
-#9 0x4e25bc in main (argc=1, argv=0x7ffffdf4) at main.c:635
-
-
-LDD
-===
-This is a program which lists the shared libraries which a library needs,
-Note you also get the relocations of the shared library text segments which
-help when using objdump --source.
-e.g.
- ldd ./gdb
-outputs
-libncurses.so.4 => /usr/lib/libncurses.so.4 (0x40018000)
-libm.so.6 => /lib/libm.so.6 (0x4005e000)
-libc.so.6 => /lib/libc.so.6 (0x40084000)
-/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
-
-
-Debugging shared libraries
-==========================
-Most programs use shared libraries, however it can be very painful
-when you single step instruction into a function like printf for the
-first time & you end up in functions like _dl_runtime_resolve this is
-the ld.so doing lazy binding, lazy binding is a concept in ELF where
-shared library functions are not loaded into memory unless they are
-actually used, great for saving memory but a pain to debug.
-To get around this either relink the program -static or exit gdb type
-export LD_BIND_NOW=true this will stop lazy binding & restart the gdb'ing
-the program in question.
-
-
-
-Debugging modules
-=================
-As modules are dynamically loaded into the kernel their address can be
-anywhere to get around this use the -m option with insmod to emit a load
-map which can be piped into a file if required.
-
-The proc file system
-====================
-What is it ?.
-It is a filesystem created by the kernel with files which are created on demand
-by the kernel if read, or can be used to modify kernel parameters,
-it is a powerful concept.
-
-e.g.
-
-cat /proc/sys/net/ipv4/ip_forward
-On my machine outputs
-0
-telling me ip_forwarding is not on to switch it on I can do
-echo 1 > /proc/sys/net/ipv4/ip_forward
-cat it again
-cat /proc/sys/net/ipv4/ip_forward
-On my machine now outputs
-1
-IP forwarding is on.
-There is a lot of useful info in here best found by going in and having a look
-around, so I'll take you through some entries I consider important.
-
-All the processes running on the machine have their own entry defined by
-/proc/<pid>
-So lets have a look at the init process
-cd /proc/1
-
-cat cmdline
-emits
-init [2]
-
-cd /proc/1/fd
-This contains numerical entries of all the open files,
-some of these you can cat e.g. stdout (2)
-
-cat /proc/29/maps
-on my machine emits
-
-00400000-00478000 r-xp 00000000 5f:00 4103 /bin/bash
-00478000-0047e000 rw-p 00077000 5f:00 4103 /bin/bash
-0047e000-00492000 rwxp 00000000 00:00 0
-40000000-40015000 r-xp 00000000 5f:00 14382 /lib/ld-2.1.2.so
-40015000-40016000 rw-p 00014000 5f:00 14382 /lib/ld-2.1.2.so
-40016000-40017000 rwxp 00000000 00:00 0
-40017000-40018000 rw-p 00000000 00:00 0
-40018000-4001b000 r-xp 00000000 5f:00 14435 /lib/libtermcap.so.2.0.8
-4001b000-4001c000 rw-p 00002000 5f:00 14435 /lib/libtermcap.so.2.0.8
-4001c000-4010d000 r-xp 00000000 5f:00 14387 /lib/libc-2.1.2.so
-4010d000-40111000 rw-p 000f0000 5f:00 14387 /lib/libc-2.1.2.so
-40111000-40114000 rw-p 00000000 00:00 0
-40114000-4011e000 r-xp 00000000 5f:00 14408 /lib/libnss_files-2.1.2.so
-4011e000-4011f000 rw-p 00009000 5f:00 14408 /lib/libnss_files-2.1.2.so
-7fffd000-80000000 rwxp ffffe000 00:00 0
-
-
-Showing us the shared libraries init uses where they are in memory
-& memory access permissions for each virtual memory area.
-
-/proc/1/cwd is a softlink to the current working directory.
-/proc/1/root is the root of the filesystem for this process.
-
-/proc/1/mem is the current running processes memory which you
-can read & write to like a file.
-strace uses this sometimes as it is a bit faster than the
-rather inefficient ptrace interface for peeking at DATA.
-
-
-cat status
-
-Name: init
-State: S (sleeping)
-Pid: 1
-PPid: 0
-Uid: 0 0 0 0
-Gid: 0 0 0 0
-Groups:
-VmSize: 408 kB
-VmLck: 0 kB
-VmRSS: 208 kB
-VmData: 24 kB
-VmStk: 8 kB
-VmExe: 368 kB
-VmLib: 0 kB
-SigPnd: 0000000000000000
-SigBlk: 0000000000000000
-SigIgn: 7fffffffd7f0d8fc
-SigCgt: 00000000280b2603
-CapInh: 00000000fffffeff
-CapPrm: 00000000ffffffff
-CapEff: 00000000fffffeff
-
-User PSW: 070de000 80414146
-task: 004b6000 tss: 004b62d8 ksp: 004b7ca8 pt_regs: 004b7f68
-User GPRS:
-00000400 00000000 0000000b 7ffffa90
-00000000 00000000 00000000 0045d9f4
-0045cafc 7ffffa90 7fffff18 0045cb08
-00010400 804039e8 80403af8 7ffff8b0
-User ACRS:
-00000000 00000000 00000000 00000000
-00000001 00000000 00000000 00000000
-00000000 00000000 00000000 00000000
-00000000 00000000 00000000 00000000
-Kernel BackChain CallChain BackChain CallChain
- 004b7ca8 8002bd0c 004b7d18 8002b92c
- 004b7db8 8005cd50 004b7e38 8005d12a
- 004b7f08 80019114
-Showing among other things memory usage & status of some signals &
-the processes'es registers from the kernel task_structure
-as well as a backchain which may be useful if a process crashes
-in the kernel for some unknown reason.
-
-Some driver debugging techniques
-================================
-debug feature
--------------
-Some of our drivers now support a "debug feature" in
-/proc/s390dbf see s390dbf.txt in the linux/Documentation directory
-for more info.
-e.g.
-to switch on the lcs "debug feature"
-echo 5 > /proc/s390dbf/lcs/level
-& then after the error occurred.
-cat /proc/s390dbf/lcs/sprintf >/logfile
-the logfile now contains some information which may help
-tech support resolve a problem in the field.
-
-
-
-high level debugging network drivers
-------------------------------------
-ifconfig is a quite useful command
-it gives the current state of network drivers.
-
-If you suspect your network device driver is dead
-one way to check is type
-ifconfig <network device>
-e.g. tr0
-You should see something like
-tr0 Link encap:16/4 Mbps Token Ring (New) HWaddr 00:04:AC:20:8E:48
- inet addr:9.164.185.132 Bcast:9.164.191.255 Mask:255.255.224.0
- UP BROADCAST RUNNING MULTICAST MTU:2000 Metric:1
- RX packets:246134 errors:0 dropped:0 overruns:0 frame:0
- TX packets:5 errors:0 dropped:0 overruns:0 carrier:0
- collisions:0 txqueuelen:100
-
-if the device doesn't say up
-try
-/etc/rc.d/init.d/network start
-( this starts the network stack & hopefully calls ifconfig tr0 up ).
-ifconfig looks at the output of /proc/net/dev and presents it in a more
-presentable form.
-Now ping the device from a machine in the same subnet.
-if the RX packets count & TX packets counts don't increment you probably
-have problems.
-next
-cat /proc/net/arp
-Do you see any hardware addresses in the cache if not you may have problems.
-Next try
-ping -c 5 <broadcast_addr> i.e. the Bcast field above in the output of
-ifconfig. Do you see any replies from machines other than the local machine
-if not you may have problems. also if the TX packets count in ifconfig
-hasn't incremented either you have serious problems in your driver
-(e.g. the txbusy field of the network device being stuck on )
-or you may have multiple network devices connected.
-
-
-chandev
--------
-There is a new device layer for channel devices, some
-drivers e.g. lcs are registered with this layer.
-If the device uses the channel device layer you'll be
-able to find what interrupts it uses & the current state
-of the device.
-See the manpage chandev.8 &type cat /proc/chandev for more info.
-
-
-SysRq
-=====
-This is now supported by linux for s/390 & z/Architecture.
-To enable it do compile the kernel with
-Kernel Hacking -> Magic SysRq Key Enabled
-echo "1" > /proc/sys/kernel/sysrq
-also type
-echo "8" >/proc/sys/kernel/printk
-To make printk output go to console.
-On 390 all commands are prefixed with
-^-
-e.g.
-^-t will show tasks.
-^-? or some unknown command will display help.
-The sysrq key reading is very picky ( I have to type the keys in an
- xterm session & paste them into the x3270 console )
-& it may be wise to predefine the keys as described in the VM hints above
-
-This is particularly useful for syncing disks unmounting & rebooting
-if the machine gets partially hung.
-
-Read Documentation/admin-guide/sysrq.rst for more info
-
-References:
-===========
-Enterprise Systems Architecture Reference Summary
-Enterprise Systems Architecture Principles of Operation
-Hartmut Penners s390 stack frame sheet.
-IBM Mainframe Channel Attachment a technology brief from a CISCO webpage
-Various bits of man & info pages of Linux.
-Linux & GDB source.
-Various info & man pages.
-CMS Help on tracing commands.
-Linux for s/390 Elf Application Binary Interface
-Linux for z/Series Elf Application Binary Interface ( Both Highly Recommended )
-z/Architecture Principles of Operation SA22-7832-00
-Enterprise Systems Architecture/390 Reference Summary SA22-7209-01 & the
-Enterprise Systems Architecture/390 Principles of Operation SA22-7201-05
-
-Special Thanks
-==============
-Special thanks to Neale Ferguson who maintains a much
-prettier HTML version of this page at
-http://linuxvm.org/penguinvm/
-Bob Grainger Stefan Bader & others for reporting bugs
--- /dev/null
+===========================
+Linux for S/390 and zSeries
+===========================
+
+Common Device Support (CDS)
+Device Driver I/O Support Routines
+
+Authors:
+ - Ingo Adlung
+ - Cornelia Huck
+
+Copyright, IBM Corp. 1999-2002
+
+Introduction
+============
+
+This document describes the common device support routines for Linux/390.
+Different than other hardware architectures, ESA/390 has defined a unified
+I/O access method. This gives relief to the device drivers as they don't
+have to deal with different bus types, polling versus interrupt
+processing, shared versus non-shared interrupt processing, DMA versus port
+I/O (PIO), and other hardware features more. However, this implies that
+either every single device driver needs to implement the hardware I/O
+attachment functionality itself, or the operating system provides for a
+unified method to access the hardware, providing all the functionality that
+every single device driver would have to provide itself.
+
+The document does not intend to explain the ESA/390 hardware architecture in
+every detail.This information can be obtained from the ESA/390 Principles of
+Operation manual (IBM Form. No. SA22-7201).
+
+In order to build common device support for ESA/390 I/O interfaces, a
+functional layer was introduced that provides generic I/O access methods to
+the hardware.
+
+The common device support layer comprises the I/O support routines defined
+below. Some of them implement common Linux device driver interfaces, while
+some of them are ESA/390 platform specific.
+
+Note:
+ In order to write a driver for S/390, you also need to look into the interface
+ described in Documentation/s390/driver-model.rst.
+
+Note for porting drivers from 2.4:
+
+The major changes are:
+
+* The functions use a ccw_device instead of an irq (subchannel).
+* All drivers must define a ccw_driver (see driver-model.txt) and the associated
+ functions.
+* request_irq() and free_irq() are no longer done by the driver.
+* The oper_handler is (kindof) replaced by the probe() and set_online() functions
+ of the ccw_driver.
+* The not_oper_handler is (kindof) replaced by the remove() and set_offline()
+ functions of the ccw_driver.
+* The channel device layer is gone.
+* The interrupt handlers must be adapted to use a ccw_device as argument.
+ Moreover, they don't return a devstat, but an irb.
+* Before initiating an io, the options must be set via ccw_device_set_options().
+* Instead of calling read_dev_chars()/read_conf_data(), the driver issues
+ the channel program and handles the interrupt itself.
+
+ccw_device_get_ciw()
+ get commands from extended sense data.
+
+ccw_device_start(), ccw_device_start_timeout(), ccw_device_start_key(), ccw_device_start_key_timeout()
+ initiate an I/O request.
+
+ccw_device_resume()
+ resume channel program execution.
+
+ccw_device_halt()
+ terminate the current I/O request processed on the device.
+
+do_IRQ()
+ generic interrupt routine. This function is called by the interrupt entry
+ routine whenever an I/O interrupt is presented to the system. The do_IRQ()
+ routine determines the interrupt status and calls the device specific
+ interrupt handler according to the rules (flags) defined during I/O request
+ initiation with do_IO().
+
+The next chapters describe the functions other than do_IRQ() in more details.
+The do_IRQ() interface is not described, as it is called from the Linux/390
+first level interrupt handler only and does not comprise a device driver
+callable interface. Instead, the functional description of do_IO() also
+describes the input to the device specific interrupt handler.
+
+Note:
+ All explanations apply also to the 64 bit architecture s390x.
+
+
+Common Device Support (CDS) for Linux/390 Device Drivers
+========================================================
+
+General Information
+-------------------
+
+The following chapters describe the I/O related interface routines the
+Linux/390 common device support (CDS) provides to allow for device specific
+driver implementations on the IBM ESA/390 hardware platform. Those interfaces
+intend to provide the functionality required by every device driver
+implementation to allow to drive a specific hardware device on the ESA/390
+platform. Some of the interface routines are specific to Linux/390 and some
+of them can be found on other Linux platforms implementations too.
+Miscellaneous function prototypes, data declarations, and macro definitions
+can be found in the architecture specific C header file
+linux/arch/s390/include/asm/irq.h.
+
+Overview of CDS interface concepts
+----------------------------------
+
+Different to other hardware platforms, the ESA/390 architecture doesn't define
+interrupt lines managed by a specific interrupt controller and bus systems
+that may or may not allow for shared interrupts, DMA processing, etc.. Instead,
+the ESA/390 architecture has implemented a so called channel subsystem, that
+provides a unified view of the devices physically attached to the systems.
+Though the ESA/390 hardware platform knows about a huge variety of different
+peripheral attachments like disk devices (aka. DASDs), tapes, communication
+controllers, etc. they can all be accessed by a well defined access method and
+they are presenting I/O completion a unified way : I/O interruptions. Every
+single device is uniquely identified to the system by a so called subchannel,
+where the ESA/390 architecture allows for 64k devices be attached.
+
+Linux, however, was first built on the Intel PC architecture, with its two
+cascaded 8259 programmable interrupt controllers (PICs), that allow for a
+maximum of 15 different interrupt lines. All devices attached to such a system
+share those 15 interrupt levels. Devices attached to the ISA bus system must
+not share interrupt levels (aka. IRQs), as the ISA bus bases on edge triggered
+interrupts. MCA, EISA, PCI and other bus systems base on level triggered
+interrupts, and therewith allow for shared IRQs. However, if multiple devices
+present their hardware status by the same (shared) IRQ, the operating system
+has to call every single device driver registered on this IRQ in order to
+determine the device driver owning the device that raised the interrupt.
+
+Up to kernel 2.4, Linux/390 used to provide interfaces via the IRQ (subchannel).
+For internal use of the common I/O layer, these are still there. However,
+device drivers should use the new calling interface via the ccw_device only.
+
+During its startup the Linux/390 system checks for peripheral devices. Each
+of those devices is uniquely defined by a so called subchannel by the ESA/390
+channel subsystem. While the subchannel numbers are system generated, each
+subchannel also takes a user defined attribute, the so called device number.
+Both subchannel number and device number cannot exceed 65535. During sysfs
+initialisation, the information about control unit type and device types that
+imply specific I/O commands (channel command words - CCWs) in order to operate
+the device are gathered. Device drivers can retrieve this set of hardware
+information during their initialization step to recognize the devices they
+support using the information saved in the struct ccw_device given to them.
+This methods implies that Linux/390 doesn't require to probe for free (not
+armed) interrupt request lines (IRQs) to drive its devices with. Where
+applicable, the device drivers can use issue the READ DEVICE CHARACTERISTICS
+ccw to retrieve device characteristics in its online routine.
+
+In order to allow for easy I/O initiation the CDS layer provides a
+ccw_device_start() interface that takes a device specific channel program (one
+or more CCWs) as input sets up the required architecture specific control blocks
+and initiates an I/O request on behalf of the device driver. The
+ccw_device_start() routine allows to specify whether it expects the CDS layer
+to notify the device driver for every interrupt it observes, or with final status
+only. See ccw_device_start() for more details. A device driver must never issue
+ESA/390 I/O commands itself, but must use the Linux/390 CDS interfaces instead.
+
+For long running I/O request to be canceled, the CDS layer provides the
+ccw_device_halt() function. Some devices require to initially issue a HALT
+SUBCHANNEL (HSCH) command without having pending I/O requests. This function is
+also covered by ccw_device_halt().
+
+
+get_ciw() - get command information word
+
+This call enables a device driver to get information about supported commands
+from the extended SenseID data.
+
+::
+
+ struct ciw *
+ ccw_device_get_ciw(struct ccw_device *cdev, __u32 cmd);
+
+==== ========================================================
+cdev The ccw_device for which the command is to be retrieved.
+cmd The command type to be retrieved.
+==== ========================================================
+
+ccw_device_get_ciw() returns:
+
+===== ================================================================
+ NULL No extended data available, invalid device or command not found.
+!NULL The command requested.
+===== ================================================================
+
+::
+
+ ccw_device_start() - Initiate I/O Request
+
+The ccw_device_start() routines is the I/O request front-end processor. All
+device driver I/O requests must be issued using this routine. A device driver
+must not issue ESA/390 I/O commands itself. Instead the ccw_device_start()
+routine provides all interfaces required to drive arbitrary devices.
+
+This description also covers the status information passed to the device
+driver's interrupt handler as this is related to the rules (flags) defined
+with the associated I/O request when calling ccw_device_start().
+
+::
+
+ int ccw_device_start(struct ccw_device *cdev,
+ struct ccw1 *cpa,
+ unsigned long intparm,
+ __u8 lpm,
+ unsigned long flags);
+ int ccw_device_start_timeout(struct ccw_device *cdev,
+ struct ccw1 *cpa,
+ unsigned long intparm,
+ __u8 lpm,
+ unsigned long flags,
+ int expires);
+ int ccw_device_start_key(struct ccw_device *cdev,
+ struct ccw1 *cpa,
+ unsigned long intparm,
+ __u8 lpm,
+ __u8 key,
+ unsigned long flags);
+ int ccw_device_start_key_timeout(struct ccw_device *cdev,
+ struct ccw1 *cpa,
+ unsigned long intparm,
+ __u8 lpm,
+ __u8 key,
+ unsigned long flags,
+ int expires);
+
+============= =============================================================
+cdev ccw_device the I/O is destined for
+cpa logical start address of channel program
+user_intparm user specific interrupt information; will be presented
+ back to the device driver's interrupt handler. Allows a
+ device driver to associate the interrupt with a
+ particular I/O request.
+lpm defines the channel path to be used for a specific I/O
+ request. A value of 0 will make cio use the opm.
+key the storage key to use for the I/O (useful for operating on a
+ storage with a storage key != default key)
+flag defines the action to be performed for I/O processing
+expires timeout value in jiffies. The common I/O layer will terminate
+ the running program after this and call the interrupt handler
+ with ERR_PTR(-ETIMEDOUT) as irb.
+============= =============================================================
+
+Possible flag values are:
+
+========================= =============================================
+DOIO_ALLOW_SUSPEND channel program may become suspended
+DOIO_DENY_PREFETCH don't allow for CCW prefetch; usually
+ this implies the channel program might
+ become modified
+DOIO_SUPPRESS_INTER don't call the handler on intermediate status
+========================= =============================================
+
+The cpa parameter points to the first format 1 CCW of a channel program::
+
+ struct ccw1 {
+ __u8 cmd_code;/* command code */
+ __u8 flags; /* flags, like IDA addressing, etc. */
+ __u16 count; /* byte count */
+ __u32 cda; /* data address */
+ } __attribute__ ((packed,aligned(8)));
+
+with the following CCW flags values defined:
+
+=================== =========================
+CCW_FLAG_DC data chaining
+CCW_FLAG_CC command chaining
+CCW_FLAG_SLI suppress incorrect length
+CCW_FLAG_SKIP skip
+CCW_FLAG_PCI PCI
+CCW_FLAG_IDA indirect addressing
+CCW_FLAG_SUSPEND suspend
+=================== =========================
+
+
+Via ccw_device_set_options(), the device driver may specify the following
+options for the device:
+
+========================= ======================================
+DOIO_EARLY_NOTIFICATION allow for early interrupt notification
+DOIO_REPORT_ALL report all interrupt conditions
+========================= ======================================
+
+
+The ccw_device_start() function returns:
+
+======== ======================================================================
+ 0 successful completion or request successfully initiated
+ -EBUSY The device is currently processing a previous I/O request, or there is
+ a status pending at the device.
+-ENODEV cdev is invalid, the device is not operational or the ccw_device is
+ not online.
+======== ======================================================================
+
+When the I/O request completes, the CDS first level interrupt handler will
+accumulate the status in a struct irb and then call the device interrupt handler.
+The intparm field will contain the value the device driver has associated with a
+particular I/O request. If a pending device status was recognized,
+intparm will be set to 0 (zero). This may happen during I/O initiation or delayed
+by an alert status notification. In any case this status is not related to the
+current (last) I/O request. In case of a delayed status notification no special
+interrupt will be presented to indicate I/O completion as the I/O request was
+never started, even though ccw_device_start() returned with successful completion.
+
+The irb may contain an error value, and the device driver should check for this
+first:
+
+========== =================================================================
+-ETIMEDOUT the common I/O layer terminated the request after the specified
+ timeout value
+-EIO the common I/O layer terminated the request due to an error state
+========== =================================================================
+
+If the concurrent sense flag in the extended status word (esw) in the irb is
+set, the field erw.scnt in the esw describes the number of device specific
+sense bytes available in the extended control word irb->scsw.ecw[]. No device
+sensing by the device driver itself is required.
+
+The device interrupt handler can use the following definitions to investigate
+the primary unit check source coded in sense byte 0 :
+
+======================= ====
+SNS0_CMD_REJECT 0x80
+SNS0_INTERVENTION_REQ 0x40
+SNS0_BUS_OUT_CHECK 0x20
+SNS0_EQUIPMENT_CHECK 0x10
+SNS0_DATA_CHECK 0x08
+SNS0_OVERRUN 0x04
+SNS0_INCOMPL_DOMAIN 0x01
+======================= ====
+
+Depending on the device status, multiple of those values may be set together.
+Please refer to the device specific documentation for details.
+
+The irb->scsw.cstat field provides the (accumulated) subchannel status :
+
+========================= ============================
+SCHN_STAT_PCI program controlled interrupt
+SCHN_STAT_INCORR_LEN incorrect length
+SCHN_STAT_PROG_CHECK program check
+SCHN_STAT_PROT_CHECK protection check
+SCHN_STAT_CHN_DATA_CHK channel data check
+SCHN_STAT_CHN_CTRL_CHK channel control check
+SCHN_STAT_INTF_CTRL_CHK interface control check
+SCHN_STAT_CHAIN_CHECK chaining check
+========================= ============================
+
+The irb->scsw.dstat field provides the (accumulated) device status :
+
+===================== =================
+DEV_STAT_ATTENTION attention
+DEV_STAT_STAT_MOD status modifier
+DEV_STAT_CU_END control unit end
+DEV_STAT_BUSY busy
+DEV_STAT_CHN_END channel end
+DEV_STAT_DEV_END device end
+DEV_STAT_UNIT_CHECK unit check
+DEV_STAT_UNIT_EXCEP unit exception
+===================== =================
+
+Please see the ESA/390 Principles of Operation manual for details on the
+individual flag meanings.
+
+Usage Notes:
+
+ccw_device_start() must be called disabled and with the ccw device lock held.
+
+The device driver is allowed to issue the next ccw_device_start() call from
+within its interrupt handler already. It is not required to schedule a
+bottom-half, unless a non deterministically long running error recovery procedure
+or similar needs to be scheduled. During I/O processing the Linux/390 generic
+I/O device driver support has already obtained the IRQ lock, i.e. the handler
+must not try to obtain it again when calling ccw_device_start() or we end in a
+deadlock situation!
+
+If a device driver relies on an I/O request to be completed prior to start the
+next it can reduce I/O processing overhead by chaining a NoOp I/O command
+CCW_CMD_NOOP to the end of the submitted CCW chain. This will force Channel-End
+and Device-End status to be presented together, with a single interrupt.
+However, this should be used with care as it implies the channel will remain
+busy, not being able to process I/O requests for other devices on the same
+channel. Therefore e.g. read commands should never use this technique, as the
+result will be presented by a single interrupt anyway.
+
+In order to minimize I/O overhead, a device driver should use the
+DOIO_REPORT_ALL only if the device can report intermediate interrupt
+information prior to device-end the device driver urgently relies on. In this
+case all I/O interruptions are presented to the device driver until final
+status is recognized.
+
+If a device is able to recover from asynchronously presented I/O errors, it can
+perform overlapping I/O using the DOIO_EARLY_NOTIFICATION flag. While some
+devices always report channel-end and device-end together, with a single
+interrupt, others present primary status (channel-end) when the channel is
+ready for the next I/O request and secondary status (device-end) when the data
+transmission has been completed at the device.
+
+Above flag allows to exploit this feature, e.g. for communication devices that
+can handle lost data on the network to allow for enhanced I/O processing.
+
+Unless the channel subsystem at any time presents a secondary status interrupt,
+exploiting this feature will cause only primary status interrupts to be
+presented to the device driver while overlapping I/O is performed. When a
+secondary status without error (alert status) is presented, this indicates
+successful completion for all overlapping ccw_device_start() requests that have
+been issued since the last secondary (final) status.
+
+Channel programs that intend to set the suspend flag on a channel command word
+(CCW) must start the I/O operation with the DOIO_ALLOW_SUSPEND option or the
+suspend flag will cause a channel program check. At the time the channel program
+becomes suspended an intermediate interrupt will be generated by the channel
+subsystem.
+
+ccw_device_resume() - Resume Channel Program Execution
+
+If a device driver chooses to suspend the current channel program execution by
+setting the CCW suspend flag on a particular CCW, the channel program execution
+is suspended. In order to resume channel program execution the CIO layer
+provides the ccw_device_resume() routine.
+
+::
+
+ int ccw_device_resume(struct ccw_device *cdev);
+
+==== ================================================
+cdev ccw_device the resume operation is requested for
+==== ================================================
+
+The ccw_device_resume() function returns:
+
+========= ==============================================
+ 0 suspended channel program is resumed
+ -EBUSY status pending
+ -ENODEV cdev invalid or not-operational subchannel
+ -EINVAL resume function not applicable
+-ENOTCONN there is no I/O request pending for completion
+========= ==============================================
+
+Usage Notes:
+
+Please have a look at the ccw_device_start() usage notes for more details on
+suspended channel programs.
+
+ccw_device_halt() - Halt I/O Request Processing
+
+Sometimes a device driver might need a possibility to stop the processing of
+a long-running channel program or the device might require to initially issue
+a halt subchannel (HSCH) I/O command. For those purposes the ccw_device_halt()
+command is provided.
+
+ccw_device_halt() must be called disabled and with the ccw device lock held.
+
+::
+
+ int ccw_device_halt(struct ccw_device *cdev,
+ unsigned long intparm);
+
+======= =====================================================
+cdev ccw_device the halt operation is requested for
+intparm interruption parameter; value is only used if no I/O
+ is outstanding, otherwise the intparm associated with
+ the I/O request is returned
+======= =====================================================
+
+The ccw_device_halt() function returns:
+
+======= ==============================================================
+ 0 request successfully initiated
+-EBUSY the device is currently busy, or status pending.
+-ENODEV cdev invalid.
+-EINVAL The device is not operational or the ccw device is not online.
+======= ==============================================================
+
+Usage Notes:
+
+A device driver may write a never-ending channel program by writing a channel
+program that at its end loops back to its beginning by means of a transfer in
+channel (TIC) command (CCW_CMD_TIC). Usually this is performed by network
+device drivers by setting the PCI CCW flag (CCW_FLAG_PCI). Once this CCW is
+executed a program controlled interrupt (PCI) is generated. The device driver
+can then perform an appropriate action. Prior to interrupt of an outstanding
+read to a network device (with or without PCI flag) a ccw_device_halt()
+is required to end the pending operation.
+
+::
+
+ ccw_device_clear() - Terminage I/O Request Processing
+
+In order to terminate all I/O processing at the subchannel, the clear subchannel
+(CSCH) command is used. It can be issued via ccw_device_clear().
+
+ccw_device_clear() must be called disabled and with the ccw device lock held.
+
+::
+
+ int ccw_device_clear(struct ccw_device *cdev, unsigned long intparm);
+
+======= ===============================================
+cdev ccw_device the clear operation is requested for
+intparm interruption parameter (see ccw_device_halt())
+======= ===============================================
+
+The ccw_device_clear() function returns:
+
+======= ==============================================================
+ 0 request successfully initiated
+-ENODEV cdev invalid
+-EINVAL The device is not operational or the ccw device is not online.
+======= ==============================================================
+
+Miscellaneous Support Routines
+------------------------------
+
+This chapter describes various routines to be used in a Linux/390 device
+driver programming environment.
+
+get_ccwdev_lock()
+
+Get the address of the device specific lock. This is then used in
+spin_lock() / spin_unlock() calls.
+
+::
+
+ __u8 ccw_device_get_path_mask(struct ccw_device *cdev);
+
+Get the mask of the path currently available for cdev.
+++ /dev/null
-Linux for S/390 and zSeries
-
-Common Device Support (CDS)
-Device Driver I/O Support Routines
-
-Authors : Ingo Adlung
- Cornelia Huck
-
-Copyright, IBM Corp. 1999-2002
-
-Introduction
-
-This document describes the common device support routines for Linux/390.
-Different than other hardware architectures, ESA/390 has defined a unified
-I/O access method. This gives relief to the device drivers as they don't
-have to deal with different bus types, polling versus interrupt
-processing, shared versus non-shared interrupt processing, DMA versus port
-I/O (PIO), and other hardware features more. However, this implies that
-either every single device driver needs to implement the hardware I/O
-attachment functionality itself, or the operating system provides for a
-unified method to access the hardware, providing all the functionality that
-every single device driver would have to provide itself.
-
-The document does not intend to explain the ESA/390 hardware architecture in
-every detail.This information can be obtained from the ESA/390 Principles of
-Operation manual (IBM Form. No. SA22-7201).
-
-In order to build common device support for ESA/390 I/O interfaces, a
-functional layer was introduced that provides generic I/O access methods to
-the hardware.
-
-The common device support layer comprises the I/O support routines defined
-below. Some of them implement common Linux device driver interfaces, while
-some of them are ESA/390 platform specific.
-
-Note:
-In order to write a driver for S/390, you also need to look into the interface
-described in Documentation/s390/driver-model.txt.
-
-Note for porting drivers from 2.4:
-The major changes are:
-* The functions use a ccw_device instead of an irq (subchannel).
-* All drivers must define a ccw_driver (see driver-model.txt) and the associated
- functions.
-* request_irq() and free_irq() are no longer done by the driver.
-* The oper_handler is (kindof) replaced by the probe() and set_online() functions
- of the ccw_driver.
-* The not_oper_handler is (kindof) replaced by the remove() and set_offline()
- functions of the ccw_driver.
-* The channel device layer is gone.
-* The interrupt handlers must be adapted to use a ccw_device as argument.
- Moreover, they don't return a devstat, but an irb.
-* Before initiating an io, the options must be set via ccw_device_set_options().
-* Instead of calling read_dev_chars()/read_conf_data(), the driver issues
- the channel program and handles the interrupt itself.
-
-ccw_device_get_ciw()
- get commands from extended sense data.
-
-ccw_device_start()
-ccw_device_start_timeout()
-ccw_device_start_key()
-ccw_device_start_key_timeout()
- initiate an I/O request.
-
-ccw_device_resume()
- resume channel program execution.
-
-ccw_device_halt()
- terminate the current I/O request processed on the device.
-
-do_IRQ()
- generic interrupt routine. This function is called by the interrupt entry
- routine whenever an I/O interrupt is presented to the system. The do_IRQ()
- routine determines the interrupt status and calls the device specific
- interrupt handler according to the rules (flags) defined during I/O request
- initiation with do_IO().
-
-The next chapters describe the functions other than do_IRQ() in more details.
-The do_IRQ() interface is not described, as it is called from the Linux/390
-first level interrupt handler only and does not comprise a device driver
-callable interface. Instead, the functional description of do_IO() also
-describes the input to the device specific interrupt handler.
-
-Note: All explanations apply also to the 64 bit architecture s390x.
-
-
-Common Device Support (CDS) for Linux/390 Device Drivers
-
-General Information
-
-The following chapters describe the I/O related interface routines the
-Linux/390 common device support (CDS) provides to allow for device specific
-driver implementations on the IBM ESA/390 hardware platform. Those interfaces
-intend to provide the functionality required by every device driver
-implementation to allow to drive a specific hardware device on the ESA/390
-platform. Some of the interface routines are specific to Linux/390 and some
-of them can be found on other Linux platforms implementations too.
-Miscellaneous function prototypes, data declarations, and macro definitions
-can be found in the architecture specific C header file
-linux/arch/s390/include/asm/irq.h.
-
-Overview of CDS interface concepts
-
-Different to other hardware platforms, the ESA/390 architecture doesn't define
-interrupt lines managed by a specific interrupt controller and bus systems
-that may or may not allow for shared interrupts, DMA processing, etc.. Instead,
-the ESA/390 architecture has implemented a so called channel subsystem, that
-provides a unified view of the devices physically attached to the systems.
-Though the ESA/390 hardware platform knows about a huge variety of different
-peripheral attachments like disk devices (aka. DASDs), tapes, communication
-controllers, etc. they can all be accessed by a well defined access method and
-they are presenting I/O completion a unified way : I/O interruptions. Every
-single device is uniquely identified to the system by a so called subchannel,
-where the ESA/390 architecture allows for 64k devices be attached.
-
-Linux, however, was first built on the Intel PC architecture, with its two
-cascaded 8259 programmable interrupt controllers (PICs), that allow for a
-maximum of 15 different interrupt lines. All devices attached to such a system
-share those 15 interrupt levels. Devices attached to the ISA bus system must
-not share interrupt levels (aka. IRQs), as the ISA bus bases on edge triggered
-interrupts. MCA, EISA, PCI and other bus systems base on level triggered
-interrupts, and therewith allow for shared IRQs. However, if multiple devices
-present their hardware status by the same (shared) IRQ, the operating system
-has to call every single device driver registered on this IRQ in order to
-determine the device driver owning the device that raised the interrupt.
-
-Up to kernel 2.4, Linux/390 used to provide interfaces via the IRQ (subchannel).
-For internal use of the common I/O layer, these are still there. However,
-device drivers should use the new calling interface via the ccw_device only.
-
-During its startup the Linux/390 system checks for peripheral devices. Each
-of those devices is uniquely defined by a so called subchannel by the ESA/390
-channel subsystem. While the subchannel numbers are system generated, each
-subchannel also takes a user defined attribute, the so called device number.
-Both subchannel number and device number cannot exceed 65535. During sysfs
-initialisation, the information about control unit type and device types that
-imply specific I/O commands (channel command words - CCWs) in order to operate
-the device are gathered. Device drivers can retrieve this set of hardware
-information during their initialization step to recognize the devices they
-support using the information saved in the struct ccw_device given to them.
-This methods implies that Linux/390 doesn't require to probe for free (not
-armed) interrupt request lines (IRQs) to drive its devices with. Where
-applicable, the device drivers can use issue the READ DEVICE CHARACTERISTICS
-ccw to retrieve device characteristics in its online routine.
-
-In order to allow for easy I/O initiation the CDS layer provides a
-ccw_device_start() interface that takes a device specific channel program (one
-or more CCWs) as input sets up the required architecture specific control blocks
-and initiates an I/O request on behalf of the device driver. The
-ccw_device_start() routine allows to specify whether it expects the CDS layer
-to notify the device driver for every interrupt it observes, or with final status
-only. See ccw_device_start() for more details. A device driver must never issue
-ESA/390 I/O commands itself, but must use the Linux/390 CDS interfaces instead.
-
-For long running I/O request to be canceled, the CDS layer provides the
-ccw_device_halt() function. Some devices require to initially issue a HALT
-SUBCHANNEL (HSCH) command without having pending I/O requests. This function is
-also covered by ccw_device_halt().
-
-
-get_ciw() - get command information word
-
-This call enables a device driver to get information about supported commands
-from the extended SenseID data.
-
-struct ciw *
-ccw_device_get_ciw(struct ccw_device *cdev, __u32 cmd);
-
-cdev - The ccw_device for which the command is to be retrieved.
-cmd - The command type to be retrieved.
-
-ccw_device_get_ciw() returns:
-NULL - No extended data available, invalid device or command not found.
-!NULL - The command requested.
-
-
-ccw_device_start() - Initiate I/O Request
-
-The ccw_device_start() routines is the I/O request front-end processor. All
-device driver I/O requests must be issued using this routine. A device driver
-must not issue ESA/390 I/O commands itself. Instead the ccw_device_start()
-routine provides all interfaces required to drive arbitrary devices.
-
-This description also covers the status information passed to the device
-driver's interrupt handler as this is related to the rules (flags) defined
-with the associated I/O request when calling ccw_device_start().
-
-int ccw_device_start(struct ccw_device *cdev,
- struct ccw1 *cpa,
- unsigned long intparm,
- __u8 lpm,
- unsigned long flags);
-int ccw_device_start_timeout(struct ccw_device *cdev,
- struct ccw1 *cpa,
- unsigned long intparm,
- __u8 lpm,
- unsigned long flags,
- int expires);
-int ccw_device_start_key(struct ccw_device *cdev,
- struct ccw1 *cpa,
- unsigned long intparm,
- __u8 lpm,
- __u8 key,
- unsigned long flags);
-int ccw_device_start_key_timeout(struct ccw_device *cdev,
- struct ccw1 *cpa,
- unsigned long intparm,
- __u8 lpm,
- __u8 key,
- unsigned long flags,
- int expires);
-
-cdev : ccw_device the I/O is destined for
-cpa : logical start address of channel program
-user_intparm : user specific interrupt information; will be presented
- back to the device driver's interrupt handler. Allows a
- device driver to associate the interrupt with a
- particular I/O request.
-lpm : defines the channel path to be used for a specific I/O
- request. A value of 0 will make cio use the opm.
-key : the storage key to use for the I/O (useful for operating on a
- storage with a storage key != default key)
-flag : defines the action to be performed for I/O processing
-expires : timeout value in jiffies. The common I/O layer will terminate
- the running program after this and call the interrupt handler
- with ERR_PTR(-ETIMEDOUT) as irb.
-
-Possible flag values are :
-
-DOIO_ALLOW_SUSPEND - channel program may become suspended
-DOIO_DENY_PREFETCH - don't allow for CCW prefetch; usually
- this implies the channel program might
- become modified
-DOIO_SUPPRESS_INTER - don't call the handler on intermediate status
-
-The cpa parameter points to the first format 1 CCW of a channel program :
-
-struct ccw1 {
- __u8 cmd_code;/* command code */
- __u8 flags; /* flags, like IDA addressing, etc. */
- __u16 count; /* byte count */
- __u32 cda; /* data address */
-} __attribute__ ((packed,aligned(8)));
-
-with the following CCW flags values defined :
-
-CCW_FLAG_DC - data chaining
-CCW_FLAG_CC - command chaining
-CCW_FLAG_SLI - suppress incorrect length
-CCW_FLAG_SKIP - skip
-CCW_FLAG_PCI - PCI
-CCW_FLAG_IDA - indirect addressing
-CCW_FLAG_SUSPEND - suspend
-
-
-Via ccw_device_set_options(), the device driver may specify the following
-options for the device:
-
-DOIO_EARLY_NOTIFICATION - allow for early interrupt notification
-DOIO_REPORT_ALL - report all interrupt conditions
-
-
-The ccw_device_start() function returns :
-
- 0 - successful completion or request successfully initiated
--EBUSY - The device is currently processing a previous I/O request, or there is
- a status pending at the device.
--ENODEV - cdev is invalid, the device is not operational or the ccw_device is
- not online.
-
-When the I/O request completes, the CDS first level interrupt handler will
-accumulate the status in a struct irb and then call the device interrupt handler.
-The intparm field will contain the value the device driver has associated with a
-particular I/O request. If a pending device status was recognized,
-intparm will be set to 0 (zero). This may happen during I/O initiation or delayed
-by an alert status notification. In any case this status is not related to the
-current (last) I/O request. In case of a delayed status notification no special
-interrupt will be presented to indicate I/O completion as the I/O request was
-never started, even though ccw_device_start() returned with successful completion.
-
-The irb may contain an error value, and the device driver should check for this
-first:
-
--ETIMEDOUT: the common I/O layer terminated the request after the specified
- timeout value
--EIO: the common I/O layer terminated the request due to an error state
-
-If the concurrent sense flag in the extended status word (esw) in the irb is
-set, the field erw.scnt in the esw describes the number of device specific
-sense bytes available in the extended control word irb->scsw.ecw[]. No device
-sensing by the device driver itself is required.
-
-The device interrupt handler can use the following definitions to investigate
-the primary unit check source coded in sense byte 0 :
-
-SNS0_CMD_REJECT 0x80
-SNS0_INTERVENTION_REQ 0x40
-SNS0_BUS_OUT_CHECK 0x20
-SNS0_EQUIPMENT_CHECK 0x10
-SNS0_DATA_CHECK 0x08
-SNS0_OVERRUN 0x04
-SNS0_INCOMPL_DOMAIN 0x01
-
-Depending on the device status, multiple of those values may be set together.
-Please refer to the device specific documentation for details.
-
-The irb->scsw.cstat field provides the (accumulated) subchannel status :
-
-SCHN_STAT_PCI - program controlled interrupt
-SCHN_STAT_INCORR_LEN - incorrect length
-SCHN_STAT_PROG_CHECK - program check
-SCHN_STAT_PROT_CHECK - protection check
-SCHN_STAT_CHN_DATA_CHK - channel data check
-SCHN_STAT_CHN_CTRL_CHK - channel control check
-SCHN_STAT_INTF_CTRL_CHK - interface control check
-SCHN_STAT_CHAIN_CHECK - chaining check
-
-The irb->scsw.dstat field provides the (accumulated) device status :
-
-DEV_STAT_ATTENTION - attention
-DEV_STAT_STAT_MOD - status modifier
-DEV_STAT_CU_END - control unit end
-DEV_STAT_BUSY - busy
-DEV_STAT_CHN_END - channel end
-DEV_STAT_DEV_END - device end
-DEV_STAT_UNIT_CHECK - unit check
-DEV_STAT_UNIT_EXCEP - unit exception
-
-Please see the ESA/390 Principles of Operation manual for details on the
-individual flag meanings.
-
-Usage Notes :
-
-ccw_device_start() must be called disabled and with the ccw device lock held.
-
-The device driver is allowed to issue the next ccw_device_start() call from
-within its interrupt handler already. It is not required to schedule a
-bottom-half, unless a non deterministically long running error recovery procedure
-or similar needs to be scheduled. During I/O processing the Linux/390 generic
-I/O device driver support has already obtained the IRQ lock, i.e. the handler
-must not try to obtain it again when calling ccw_device_start() or we end in a
-deadlock situation!
-
-If a device driver relies on an I/O request to be completed prior to start the
-next it can reduce I/O processing overhead by chaining a NoOp I/O command
-CCW_CMD_NOOP to the end of the submitted CCW chain. This will force Channel-End
-and Device-End status to be presented together, with a single interrupt.
-However, this should be used with care as it implies the channel will remain
-busy, not being able to process I/O requests for other devices on the same
-channel. Therefore e.g. read commands should never use this technique, as the
-result will be presented by a single interrupt anyway.
-
-In order to minimize I/O overhead, a device driver should use the
-DOIO_REPORT_ALL only if the device can report intermediate interrupt
-information prior to device-end the device driver urgently relies on. In this
-case all I/O interruptions are presented to the device driver until final
-status is recognized.
-
-If a device is able to recover from asynchronously presented I/O errors, it can
-perform overlapping I/O using the DOIO_EARLY_NOTIFICATION flag. While some
-devices always report channel-end and device-end together, with a single
-interrupt, others present primary status (channel-end) when the channel is
-ready for the next I/O request and secondary status (device-end) when the data
-transmission has been completed at the device.
-
-Above flag allows to exploit this feature, e.g. for communication devices that
-can handle lost data on the network to allow for enhanced I/O processing.
-
-Unless the channel subsystem at any time presents a secondary status interrupt,
-exploiting this feature will cause only primary status interrupts to be
-presented to the device driver while overlapping I/O is performed. When a
-secondary status without error (alert status) is presented, this indicates
-successful completion for all overlapping ccw_device_start() requests that have
-been issued since the last secondary (final) status.
-
-Channel programs that intend to set the suspend flag on a channel command word
-(CCW) must start the I/O operation with the DOIO_ALLOW_SUSPEND option or the
-suspend flag will cause a channel program check. At the time the channel program
-becomes suspended an intermediate interrupt will be generated by the channel
-subsystem.
-
-ccw_device_resume() - Resume Channel Program Execution
-
-If a device driver chooses to suspend the current channel program execution by
-setting the CCW suspend flag on a particular CCW, the channel program execution
-is suspended. In order to resume channel program execution the CIO layer
-provides the ccw_device_resume() routine.
-
-int ccw_device_resume(struct ccw_device *cdev);
-
-cdev - ccw_device the resume operation is requested for
-
-The ccw_device_resume() function returns:
-
- 0 - suspended channel program is resumed
--EBUSY - status pending
--ENODEV - cdev invalid or not-operational subchannel
--EINVAL - resume function not applicable
--ENOTCONN - there is no I/O request pending for completion
-
-Usage Notes:
-Please have a look at the ccw_device_start() usage notes for more details on
-suspended channel programs.
-
-ccw_device_halt() - Halt I/O Request Processing
-
-Sometimes a device driver might need a possibility to stop the processing of
-a long-running channel program or the device might require to initially issue
-a halt subchannel (HSCH) I/O command. For those purposes the ccw_device_halt()
-command is provided.
-
-ccw_device_halt() must be called disabled and with the ccw device lock held.
-
-int ccw_device_halt(struct ccw_device *cdev,
- unsigned long intparm);
-
-cdev : ccw_device the halt operation is requested for
-intparm : interruption parameter; value is only used if no I/O
- is outstanding, otherwise the intparm associated with
- the I/O request is returned
-
-The ccw_device_halt() function returns :
-
- 0 - request successfully initiated
--EBUSY - the device is currently busy, or status pending.
--ENODEV - cdev invalid.
--EINVAL - The device is not operational or the ccw device is not online.
-
-Usage Notes :
-
-A device driver may write a never-ending channel program by writing a channel
-program that at its end loops back to its beginning by means of a transfer in
-channel (TIC) command (CCW_CMD_TIC). Usually this is performed by network
-device drivers by setting the PCI CCW flag (CCW_FLAG_PCI). Once this CCW is
-executed a program controlled interrupt (PCI) is generated. The device driver
-can then perform an appropriate action. Prior to interrupt of an outstanding
-read to a network device (with or without PCI flag) a ccw_device_halt()
-is required to end the pending operation.
-
-ccw_device_clear() - Terminage I/O Request Processing
-
-In order to terminate all I/O processing at the subchannel, the clear subchannel
-(CSCH) command is used. It can be issued via ccw_device_clear().
-
-ccw_device_clear() must be called disabled and with the ccw device lock held.
-
-int ccw_device_clear(struct ccw_device *cdev, unsigned long intparm);
-
-cdev: ccw_device the clear operation is requested for
-intparm: interruption parameter (see ccw_device_halt())
-
-The ccw_device_clear() function returns:
-
- 0 - request successfully initiated
--ENODEV - cdev invalid
--EINVAL - The device is not operational or the ccw device is not online.
-
-Miscellaneous Support Routines
-
-This chapter describes various routines to be used in a Linux/390 device
-driver programming environment.
-
-get_ccwdev_lock()
-
-Get the address of the device specific lock. This is then used in
-spin_lock() / spin_unlock() calls.
-
-
-__u8 ccw_device_get_path_mask(struct ccw_device *cdev);
-
-Get the mask of the path currently available for cdev.
--- /dev/null
+======================
+S/390 common I/O-Layer
+======================
+
+command line parameters, procfs and debugfs entries
+===================================================
+
+Command line parameters
+-----------------------
+
+* ccw_timeout_log
+
+ Enable logging of debug information in case of ccw device timeouts.
+
+* cio_ignore = device[,device[,..]]
+
+ device := {all | [!]ipldev | [!]condev | [!]<devno> | [!]<devno>-<devno>}
+
+ The given devices will be ignored by the common I/O-layer; no detection
+ and device sensing will be done on any of those devices. The subchannel to
+ which the device in question is attached will be treated as if no device was
+ attached.
+
+ An ignored device can be un-ignored later; see the "/proc entries"-section for
+ details.
+
+ The devices must be given either as bus ids (0.x.abcd) or as hexadecimal
+ device numbers (0xabcd or abcd, for 2.4 backward compatibility). If you
+ give a device number 0xabcd, it will be interpreted as 0.0.abcd.
+
+ You can use the 'all' keyword to ignore all devices. The 'ipldev' and 'condev'
+ keywords can be used to refer to the CCW based boot device and CCW console
+ device respectively (these are probably useful only when combined with the '!'
+ operator). The '!' operator will cause the I/O-layer to _not_ ignore a device.
+ The command line
+ is parsed from left to right.
+
+ For example::
+
+ cio_ignore=0.0.0023-0.0.0042,0.0.4711
+
+ will ignore all devices ranging from 0.0.0023 to 0.0.0042 and the device
+ 0.0.4711, if detected.
+
+ As another example::
+
+ cio_ignore=all,!0.0.4711,!0.0.fd00-0.0.fd02
+
+ will ignore all devices but 0.0.4711, 0.0.fd00, 0.0.fd01, 0.0.fd02.
+
+ By default, no devices are ignored.
+
+
+/proc entries
+-------------
+
+* /proc/cio_ignore
+
+ Lists the ranges of devices (by bus id) which are ignored by common I/O.
+
+ You can un-ignore certain or all devices by piping to /proc/cio_ignore.
+ "free all" will un-ignore all ignored devices,
+ "free <device range>, <device range>, ..." will un-ignore the specified
+ devices.
+
+ For example, if devices 0.0.0023 to 0.0.0042 and 0.0.4711 are ignored,
+
+ - echo free 0.0.0030-0.0.0032 > /proc/cio_ignore
+ will un-ignore devices 0.0.0030 to 0.0.0032 and will leave devices 0.0.0023
+ to 0.0.002f, 0.0.0033 to 0.0.0042 and 0.0.4711 ignored;
+ - echo free 0.0.0041 > /proc/cio_ignore will furthermore un-ignore device
+ 0.0.0041;
+ - echo free all > /proc/cio_ignore will un-ignore all remaining ignored
+ devices.
+
+ When a device is un-ignored, device recognition and sensing is performed and
+ the device driver will be notified if possible, so the device will become
+ available to the system. Note that un-ignoring is performed asynchronously.
+
+ You can also add ranges of devices to be ignored by piping to
+ /proc/cio_ignore; "add <device range>, <device range>, ..." will ignore the
+ specified devices.
+
+ Note: While already known devices can be added to the list of devices to be
+ ignored, there will be no effect on then. However, if such a device
+ disappears and then reappears, it will then be ignored. To make
+ known devices go away, you need the "purge" command (see below).
+
+ For example::
+
+ "echo add 0.0.a000-0.0.accc, 0.0.af00-0.0.afff > /proc/cio_ignore"
+
+ will add 0.0.a000-0.0.accc and 0.0.af00-0.0.afff to the list of ignored
+ devices.
+
+ You can remove already known but now ignored devices via::
+
+ "echo purge > /proc/cio_ignore"
+
+ All devices ignored but still registered and not online (= not in use)
+ will be deregistered and thus removed from the system.
+
+ The devices can be specified either by bus id (0.x.abcd) or, for 2.4 backward
+ compatibility, by the device number in hexadecimal (0xabcd or abcd). Device
+ numbers given as 0xabcd will be interpreted as 0.0.abcd.
+
+* /proc/cio_settle
+
+ A write request to this file is blocked until all queued cio actions are
+ handled. This will allow userspace to wait for pending work affecting
+ device availability after changing cio_ignore or the hardware configuration.
+
+* For some of the information present in the /proc filesystem in 2.4 (namely,
+ /proc/subchannels and /proc/chpids), see driver-model.txt.
+ Information formerly in /proc/irq_count is now in /proc/interrupts.
+
+
+debugfs entries
+---------------
+
+* /sys/kernel/debug/s390dbf/cio_*/ (S/390 debug feature)
+
+ Some views generated by the debug feature to hold various debug outputs.
+
+ - /sys/kernel/debug/s390dbf/cio_crw/sprintf
+ Messages from the processing of pending channel report words (machine check
+ handling).
+
+ - /sys/kernel/debug/s390dbf/cio_msg/sprintf
+ Various debug messages from the common I/O-layer.
+
+ - /sys/kernel/debug/s390dbf/cio_trace/hex_ascii
+ Logs the calling of functions in the common I/O-layer and, if applicable,
+ which subchannel they were called for, as well as dumps of some data
+ structures (like irb in an error case).
+
+ The level of logging can be changed to be more or less verbose by piping to
+ /sys/kernel/debug/s390dbf/cio_*/level a number between 0 and 6; see the
+ documentation on the S/390 debug feature (Documentation/s390/s390dbf.rst)
+ for details.
--- /dev/null
+==================
+DASD device driver
+==================
+
+S/390's disk devices (DASDs) are managed by Linux via the DASD device
+driver. It is valid for all types of DASDs and represents them to
+Linux as block devices, namely "dd". Currently the DASD driver uses a
+single major number (254) and 4 minor numbers per volume (1 for the
+physical volume and 3 for partitions). With respect to partitions see
+below. Thus you may have up to 64 DASD devices in your system.
+
+The kernel parameter 'dasd=from-to,...' may be issued arbitrary times
+in the kernel's parameter line or not at all. The 'from' and 'to'
+parameters are to be given in hexadecimal notation without a leading
+0x.
+If you supply kernel parameters the different instances are processed
+in order of appearance and a minor number is reserved for any device
+covered by the supplied range up to 64 volumes. Additional DASDs are
+ignored. If you do not supply the 'dasd=' kernel parameter at all, the
+DASD driver registers all supported DASDs of your system to a minor
+number in ascending order of the subchannel number.
+
+The driver currently supports ECKD-devices and there are stubs for
+support of the FBA and CKD architectures. For the FBA architecture
+only some smart data structures are missing to make the support
+complete.
+We performed our testing on 3380 and 3390 type disks of different
+sizes, under VM and on the bare hardware (LPAR), using internal disks
+of the multiprise as well as a RAMAC virtual array. Disks exported by
+an Enterprise Storage Server (Seascape) should work fine as well.
+
+We currently implement one partition per volume, which is the whole
+volume, skipping the first blocks up to the volume label. These are
+reserved for IPL records and IBM's volume label to assure
+accessibility of the DASD from other OSs. In a later stage we will
+provide support of partitions, maybe VTOC oriented or using a kind of
+partition table in the label record.
+
+Usage
+=====
+
+-Low-level format (?CKD only)
+For using an ECKD-DASD as a Linux harddisk you have to low-level
+format the tracks by issuing the BLKDASDFORMAT-ioctl on that
+device. This will erase any data on that volume including IBM volume
+labels, VTOCs etc. The ioctl may take a `struct format_data *` or
+'NULL' as an argument::
+
+ typedef struct {
+ int start_unit;
+ int stop_unit;
+ int blksize;
+ } format_data_t;
+
+When a NULL argument is passed to the BLKDASDFORMAT ioctl the whole
+disk is formatted to a blocksize of 1024 bytes. Otherwise start_unit
+and stop_unit are the first and last track to be formatted. If
+stop_unit is -1 it implies that the DASD is formatted from start_unit
+up to the last track. blksize can be any power of two between 512 and
+4096. We recommend no blksize lower than 1024 because the ext2fs uses
+1kB blocks anyway and you gain approx. 50% of capacity increasing your
+blksize from 512 byte to 1kB.
+
+Make a filesystem
+=================
+
+Then you can mk??fs the filesystem of your choice on that volume or
+partition. For reasons of sanity you should build your filesystem on
+the partition /dev/dd?1 instead of the whole volume. You only lose 3kB
+but may be sure that you can reuse your data after introduction of a
+real partition table.
+
+Bugs
+====
+
+- Performance sometimes is rather low because we don't fully exploit clustering
+
+TODO-List
+=========
+
+- Add IBM'S Disk layout to genhd
+- Enhance driver to use more than one major number
+- Enable usage as a module
+- Support Cache fast write and DASD fast write (ECKD)
--- /dev/null
+=============================================
+Debugging on Linux for s/390 & z/Architecture
+=============================================
+
+Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com)
+
+Copyright (C) 2000-2001 IBM Deutschland Entwicklung GmbH, IBM Corporation
+
+.. Best viewed with fixed width fonts
+
+Overview of Document:
+=====================
+This document is intended to give a good overview of how to debug Linux for
+s/390 and z/Architecture. It is not intended as a complete reference and not a
+tutorial on the fundamentals of C & assembly. It doesn't go into
+390 IO in any detail. It is intended to complement the documents in the
+reference section below & any other worthwhile references you get.
+
+It is intended like the Enterprise Systems Architecture/390 Reference Summary
+to be printed out & used as a quick cheat sheet self help style reference when
+problems occur.
+
+.. Contents
+ ========
+ Register Set
+ Address Spaces on Intel Linux
+ Address Spaces on Linux for s/390 & z/Architecture
+ The Linux for s/390 & z/Architecture Kernel Task Structure
+ Register Usage & Stackframes on Linux for s/390 & z/Architecture
+ A sample program with comments
+ Compiling programs for debugging on Linux for s/390 & z/Architecture
+ Debugging under VM
+ s/390 & z/Architecture IO Overview
+ Debugging IO on s/390 & z/Architecture under VM
+ GDB on s/390 & z/Architecture
+ Stack chaining in gdb by hand
+ Examining core dumps
+ ldd
+ Debugging modules
+ The proc file system
+ SysRq
+ References
+ Special Thanks
+
+Register Set
+============
+The current architectures have the following registers.
+
+16 General propose registers, 32 bit on s/390 and 64 bit on z/Architecture,
+r0-r15 (or gpr0-gpr15), used for arithmetic and addressing.
+
+16 Control registers, 32 bit on s/390 and 64 bit on z/Architecture, cr0-cr15,
+kernel usage only, used for memory management, interrupt control, debugging
+control etc.
+
+16 Access registers (ar0-ar15), 32 bit on both s/390 and z/Architecture,
+normally not used by normal programs but potentially could be used as
+temporary storage. These registers have a 1:1 association with general
+purpose registers and are designed to be used in the so-called access
+register mode to select different address spaces.
+Access register 0 (and access register 1 on z/Architecture, which needs a
+64 bit pointer) is currently used by the pthread library as a pointer to
+the current running threads private area.
+
+16 64-bit floating point registers (fp0-fp15 ) IEEE & HFP floating
+point format compliant on G5 upwards & a Floating point control reg (FPC)
+
+4 64-bit registers (fp0,fp2,fp4 & fp6) HFP only on older machines.
+
+Note:
+ Linux (currently) always uses IEEE & emulates G5 IEEE format on older
+ machines, ( provided the kernel is configured for this ).
+
+
+The PSW is the most important register on the machine it
+is 64 bit on s/390 & 128 bit on z/Architecture & serves the roles of
+a program counter (pc), condition code register,memory space designator.
+In IBM standard notation I am counting bit 0 as the MSB.
+It has several advantages over a normal program counter
+in that you can change address translation & program counter
+in a single instruction. To change address translation,
+e.g. switching address translation off requires that you
+have a logical=physical mapping for the address you are
+currently running at.
+
++-------------------------+-------------------------------------------------+
+| Bit | |
++--------+----------------+ Value |
+| s/390 | z/Architecture | |
++========+================+=================================================+
+| 0 | 0 | Reserved (must be 0) otherwise specification |
+| | | exception occurs. |
++--------+----------------+-------------------------------------------------+
+| 1 | 1 | Program Event Recording 1 PER enabled, |
+| | | PER is used to facilitate debugging e.g. |
+| | | single stepping. |
++--------+----------------+-------------------------------------------------+
+| 2-4 | 2-4 | Reserved (must be 0). |
++--------+----------------+-------------------------------------------------+
+| 5 | 5 | Dynamic address translation 1=DAT on. |
++--------+----------------+-------------------------------------------------+
+| 6 | 6 | Input/Output interrupt Mask |
++--------+----------------+-------------------------------------------------+
+| 7 | 7 | External interrupt Mask used primarily for |
+| | | interprocessor signalling and clock interrupts. |
++--------+----------------+-------------------------------------------------+
+| 8-11 | 8-11 | PSW Key used for complex memory protection |
+| | | mechanism (not used under linux) |
++--------+----------------+-------------------------------------------------+
+| 12 | 12 | 1 on s/390 0 on z/Architecture |
++--------+----------------+-------------------------------------------------+
+| 13 | 13 | Machine Check Mask 1=enable machine check |
+| | | interrupts |
++--------+----------------+-------------------------------------------------+
+| 14 | 14 | Wait State. Set this to 1 to stop the processor |
+| | | except for interrupts and give time to other |
+| | | LPARS. Used in CPU idle in the kernel to |
+| | | increase overall usage of processor resources. |
++--------+----------------+-------------------------------------------------+
+| 15 | 15 | Problem state (if set to 1 certain instructions |
+| | | are disabled). All linux user programs run with |
+| | | this bit 1 (useful info for debugging under VM).|
++--------+----------------+-------------------------------------------------+
+| 16-17 | 16-17 | Address Space Control |
+| | | |
+| | | 00 Primary Space Mode: |
+| | | |
+| | | The register CR1 contains the primary |
+| | | address-space control element (PASCE), which |
+| | | points to the primary space region/segment |
+| | | table origin. |
+| | | |
+| | | 01 Access register mode |
+| | | |
+| | | 10 Secondary Space Mode: |
+| | | |
+| | | The register CR7 contains the secondary |
+| | | address-space control element (SASCE), which |
+| | | points to the secondary space region or |
+| | | segment table origin. |
+| | | |
+| | | 11 Home Space Mode: |
+| | | |
+| | | The register CR13 contains the home space |
+| | | address-space control element (HASCE), which |
+| | | points to the home space region/segment |
+| | | table origin. |
+| | | |
+| | | See "Address Spaces on Linux for s/390 & |
+| | | z/Architecture" below for more information |
+| | | about address space usage in Linux. |
++--------+----------------+-------------------------------------------------+
+| 18-19 | 18-19 | Condition codes (CC) |
++--------+----------------+-------------------------------------------------+
+| 20 | 20 | Fixed point overflow mask if 1=FPU exceptions |
+| | | for this event occur (normally 0) |
++--------+----------------+-------------------------------------------------+
+| 21 | 21 | Decimal overflow mask if 1=FPU exceptions for |
+| | | this event occur (normally 0) |
++--------+----------------+-------------------------------------------------+
+| 22 | 22 | Exponent underflow mask if 1=FPU exceptions |
+| | | for this event occur (normally 0) |
++--------+----------------+-------------------------------------------------+
+| 23 | 23 | Significance Mask if 1=FPU exceptions for this |
+| | | event occur (normally 0) |
++--------+----------------+-------------------------------------------------+
+| 24-31 | 24-30 | Reserved Must be 0. |
+| +----------------+-------------------------------------------------+
+| | 31 | Extended Addressing Mode |
+| +----------------+-------------------------------------------------+
+| | 32 | Basic Addressing Mode |
+| | | |
+| | | Used to set addressing mode |
+| | | |
+| | | +---------+----------+----------+ |
+| | | | PSW 31 | PSW 32 | | |
+| | | +---------+----------+----------+ |
+| | | | 0 | 0 | 24 bit | |
+| | | +---------+----------+----------+ |
+| | | | 0 | 1 | 31 bit | |
+| | | +---------+----------+----------+ |
+| | | | 1 | 1 | 64 bit | |
+| | | +---------+----------+----------+ |
++--------+----------------+-------------------------------------------------+
+| 32 | | 1=31 bit addressing mode 0=24 bit addressing |
+| | | mode (for backward compatibility), linux |
+| | | always runs with this bit set to 1 |
++--------+----------------+-------------------------------------------------+
+| 33-64 | | Instruction address. |
+| +----------------+-------------------------------------------------+
+| | 33-63 | Reserved must be 0 |
+| +----------------+-------------------------------------------------+
+| | 64-127 | Address |
+| | | |
+| | | - In 24 bits mode bits 64-103=0 bits 104-127 |
+| | | Address |
+| | | - In 31 bits mode bits 64-96=0 bits 97-127 |
+| | | Address |
+| | | |
+| | | Note: |
+| | | unlike 31 bit mode on s/390 bit 96 must be |
+| | | zero when loading the address with LPSWE |
+| | | otherwise a specification exception occurs, |
+| | | LPSW is fully backward compatible. |
++--------+----------------+-------------------------------------------------+
+
+Prefix Page(s)
+--------------
+This per cpu memory area is too intimately tied to the processor not to mention.
+It exists between the real addresses 0-4096 on s/390 and between 0-8192 on
+z/Architecture and is exchanged with one page on s/390 or two pages on
+z/Architecture in absolute storage by the set prefix instruction during Linux
+startup.
+
+This page is mapped to a different prefix for each processor in an SMP
+configuration (assuming the OS designer is sane of course).
+
+Bytes 0-512 (200 hex) on s/390 and 0-512, 4096-4544, 4604-5119 currently on
+z/Architecture are used by the processor itself for holding such information
+as exception indications and entry points for exceptions.
+
+Bytes after 0xc00 hex are used by linux for per processor globals on s/390 and
+z/Architecture (there is a gap on z/Architecture currently between 0xc00 and
+0x1000, too, which is used by Linux).
+
+The closest thing to this on traditional architectures is the interrupt
+vector table. This is a good thing & does simplify some of the kernel coding
+however it means that we now cannot catch stray NULL pointers in the
+kernel without hard coded checks.
+
+
+
+Address Spaces on Intel Linux
+=============================
+
+The traditional Intel Linux is approximately mapped as follows forgive
+the ascii art::
+
+ 0xFFFFFFFF 4GB Himem *****************
+ * *
+ * Kernel Space *
+ * *
+ ***************** ****************
+ User Space Himem * User Stack * * *
+ (typically 0xC0000000 3GB ) ***************** * *
+ * Shared Libs * * Next Process *
+ ***************** * to *
+ * * <== * Run * <==
+ * User Program * * *
+ * Data BSS * * *
+ * Text * * *
+ * Sections * * *
+ 0x00000000 ***************** ****************
+
+Now it is easy to see that on Intel it is quite easy to recognise a kernel
+address as being one greater than user space himem (in this case 0xC0000000),
+and addresses of less than this are the ones in the current running program on
+this processor (if an smp box).
+
+If using the virtual machine ( VM ) as a debugger it is quite difficult to
+know which user process is running as the address space you are looking at
+could be from any process in the run queue.
+
+The limitation of Intels addressing technique is that the linux
+kernel uses a very simple real address to virtual addressing technique
+of Real Address=Virtual Address-User Space Himem.
+This means that on Intel the kernel linux can typically only address
+Himem=0xFFFFFFFF-0xC0000000=1GB & this is all the RAM these machines
+can typically use.
+
+They can lower User Himem to 2GB or lower & thus be
+able to use 2GB of RAM however this shrinks the maximum size
+of User Space from 3GB to 2GB they have a no win limit of 4GB unless
+they go to 64 Bit.
+
+
+On 390 our limitations & strengths make us slightly different.
+For backward compatibility we are only allowed use 31 bits (2GB)
+of our 32 bit addresses, however, we use entirely separate address
+spaces for the user & kernel.
+
+This means we can support 2GB of non Extended RAM on s/390, & more
+with the Extended memory management swap device &
+currently 4TB of physical memory currently on z/Architecture.
+
+
+Address Spaces on Linux for s/390 & z/Architecture
+==================================================
+
+Our addressing scheme is basically as follows::
+
+ Primary Space Home Space
+ Himem 0x7fffffff 2GB on s/390 ***************** ****************
+ currently 0x3ffffffffff (2^42)-1 * User Stack * * *
+ on z/Architecture. ***************** * *
+ * Shared Libs * * *
+ ***************** * *
+ * * * Kernel *
+ * User Program * * *
+ * Data BSS * * *
+ * Text * * *
+ * Sections * * *
+ 0x00000000 ***************** ****************
+
+This also means that we need to look at the PSW problem state bit and the
+addressing mode to decide whether we are looking at user or kernel space.
+
+User space runs in primary address mode (or access register mode within
+the vdso code).
+
+The kernel usually also runs in home space mode, however when accessing
+user space the kernel switches to primary or secondary address mode if
+the mvcos instruction is not available or if a compare-and-swap (futex)
+instruction on a user space address is performed.
+
+When also looking at the ASCE control registers, this means:
+
+User space:
+
+- runs in primary or access register mode
+- cr1 contains the user asce
+- cr7 contains the user asce
+- cr13 contains the kernel asce
+
+Kernel space:
+
+- runs in home space mode
+- cr1 contains the user or kernel asce
+
+ - the kernel asce is loaded when a uaccess requires primary or
+ secondary address mode
+
+- cr7 contains the user or kernel asce, (changed with set_fs())
+- cr13 contains the kernel asce
+
+In case of uaccess the kernel changes to:
+
+- primary space mode in case of a uaccess (copy_to_user) and uses
+ e.g. the mvcp instruction to access user space. However the kernel
+ will stay in home space mode if the mvcos instruction is available
+- secondary space mode in case of futex atomic operations, so that the
+ instructions come from primary address space and data from secondary
+ space
+
+In case of KVM, the kernel runs in home space mode, but cr1 gets switched
+to contain the gmap asce before the SIE instruction gets executed. When
+the SIE instruction is finished, cr1 will be switched back to contain the
+user asce.
+
+
+Virtual Addresses on s/390 & z/Architecture
+===========================================
+
+A virtual address on s/390 is made up of 3 parts
+The SX (segment index, roughly corresponding to the PGD & PMD in Linux
+terminology) being bits 1-11.
+
+The PX (page index, corresponding to the page table entry (pte) in Linux
+terminology) being bits 12-19.
+
+The remaining bits BX (the byte index are the offset in the page )
+i.e. bits 20 to 31.
+
+On z/Architecture in linux we currently make up an address from 4 parts.
+
+- The region index bits (RX) 0-32 we currently use bits 22-32
+- The segment index (SX) being bits 33-43
+- The page index (PX) being bits 44-51
+- The byte index (BX) being bits 52-63
+
+Notes:
+ 1) s/390 has no PMD so the PMD is really the PGD also.
+ A lot of this stuff is defined in pgtable.h.
+
+ 2) Also seeing as s/390's page indexes are only 1k in size
+ (bits 12-19 x 4 bytes per pte ) we use 1 ( page 4k )
+ to make the best use of memory by updating 4 segment indices
+ entries each time we mess with a PMD & use offsets
+ 0,1024,2048 & 3072 in this page as for our segment indexes.
+ On z/Architecture our page indexes are now 2k in size
+ ( bits 12-19 x 8 bytes per pte ) we do a similar trick
+ but only mess with 2 segment indices each time we mess with
+ a PMD.
+
+ 3) As z/Architecture supports up to a massive 5-level page table lookup we
+ can only use 3 currently on Linux ( as this is all the generic kernel
+ currently supports ) however this may change in future
+ this allows us to access ( according to my sums )
+ 4TB of virtual storage per process i.e.
+ 4096*512(PTES)*1024(PMDS)*2048(PGD) = 4398046511104 bytes,
+ enough for another 2 or 3 of years I think :-).
+ to do this we use a region-third-table designation type in
+ our address space control registers.
+
+
+The Linux for s/390 & z/Architecture Kernel Task Structure
+==========================================================
+Each process/thread under Linux for S390 has its own kernel task_struct
+defined in linux/include/linux/sched.h
+The S390 on initialisation & resuming of a process on a cpu sets
+the __LC_KERNEL_STACK variable in the spare prefix area for this cpu
+(which we use for per-processor globals).
+
+The kernel stack pointer is intimately tied with the task structure for
+each processor as follows::
+
+ s/390
+ ************************
+ * 1 page kernel stack *
+ * ( 4K ) *
+ ************************
+ * 1 page task_struct *
+ * ( 4K ) *
+ 8K aligned ************************
+
+ z/Architecture
+ ************************
+ * 2 page kernel stack *
+ * ( 8K ) *
+ ************************
+ * 2 page task_struct *
+ * ( 8K ) *
+ 16K aligned ************************
+
+What this means is that we don't need to dedicate any register or global
+variable to point to the current running process & can retrieve it with the
+following very simple construct for s/390 & one very similar for
+z/Architecture::
+
+ static inline struct task_struct * get_current(void)
+ {
+ struct task_struct *current;
+ __asm__("lhi %0,-8192\n\t"
+ "nr %0,15"
+ : "=r" (current) );
+ return current;
+ }
+
+i.e. just anding the current kernel stack pointer with the mask -8192.
+Thankfully because Linux doesn't have support for nested IO interrupts
+& our devices have large buffers can survive interrupts being shut for
+short amounts of time we don't need a separate stack for interrupts.
+
+
+
+
+Register Usage & Stackframes on Linux for s/390 & z/Architecture
+=================================================================
+Overview:
+---------
+This is the code that gcc produces at the top & the bottom of
+each function. It usually is fairly consistent & similar from
+function to function & if you know its layout you can probably
+make some headway in finding the ultimate cause of a problem
+after a crash without a source level debugger.
+
+Note: To follow stackframes requires a knowledge of C or Pascal &
+limited knowledge of one assembly language.
+
+It should be noted that there are some differences between the
+s/390 and z/Architecture stack layouts as the z/Architecture stack layout
+didn't have to maintain compatibility with older linkage formats.
+
+Glossary:
+---------
+alloca:
+ This is a built in compiler function for runtime allocation
+ of extra space on the callers stack which is obviously freed
+ up on function exit ( e.g. the caller may choose to allocate nothing
+ of a buffer of 4k if required for temporary purposes ), it generates
+ very efficient code ( a few cycles ) when compared to alternatives
+ like malloc.
+
+automatics:
+ These are local variables on the stack, i.e they aren't in registers &
+ they aren't static.
+
+back-chain:
+ This is a pointer to the stack pointer before entering a
+ framed functions ( see frameless function ) prologue got by
+ dereferencing the address of the current stack pointer,
+ i.e. got by accessing the 32 bit value at the stack pointers
+ current location.
+
+base-pointer:
+ This is a pointer to the back of the literal pool which
+ is an area just behind each procedure used to store constants
+ in each function.
+
+call-clobbered:
+ The caller probably needs to save these registers if there
+ is something of value in them, on the stack or elsewhere before making a
+ call to another procedure so that it can restore it later.
+
+epilogue:
+ The code generated by the compiler to return to the caller.
+
+frameless-function:
+ A frameless function in Linux for s390 & z/Architecture is one which doesn't
+ need more than the register save area (96 bytes on s/390, 160 on z/Architecture)
+ given to it by the caller.
+
+ A frameless function never:
+
+ 1) Sets up a back chain.
+ 2) Calls alloca.
+ 3) Calls other normal functions
+ 4) Has automatics.
+
+GOT-pointer:
+ This is a pointer to the global-offset-table in ELF
+ ( Executable Linkable Format, Linux'es most common executable format ),
+ all globals & shared library objects are found using this pointer.
+
+lazy-binding
+ ELF shared libraries are typically only loaded when routines in the shared
+ library are actually first called at runtime. This is lazy binding.
+
+procedure-linkage-table
+ This is a table found from the GOT which contains pointers to routines
+ in other shared libraries which can't be called to by easier means.
+
+prologue:
+ The code generated by the compiler to set up the stack frame.
+
+outgoing-args:
+ This is extra area allocated on the stack of the calling function if the
+ parameters for the callee's cannot all be put in registers, the same
+ area can be reused by each function the caller calls.
+
+routine-descriptor:
+ A COFF executable format based concept of a procedure reference
+ actually being 8 bytes or more as opposed to a simple pointer to the routine.
+ This is typically defined as follows:
+
+ - Routine Descriptor offset 0=Pointer to Function
+ - Routine Descriptor offset 4=Pointer to Table of Contents
+
+ The table of contents/TOC is roughly equivalent to a GOT pointer.
+ & it means that shared libraries etc. can be shared between several
+ environments each with their own TOC.
+
+static-chain:
+ This is used in nested functions a concept adopted from pascal
+ by gcc not used in ansi C or C++ ( although quite useful ), basically it
+ is a pointer used to reference local variables of enclosing functions.
+ You might come across this stuff once or twice in your lifetime.
+
+ e.g.
+
+ The function below should return 11 though gcc may get upset & toss warnings
+ about unused variables::
+
+ int FunctionA(int a)
+ {
+ int b;
+ FunctionC(int c)
+ {
+ b=c+1;
+ }
+ FunctionC(10);
+ return(b);
+ }
+
+
+s/390 & z/Architecture Register usage
+=====================================
+
+======== ========================================== ===============
+r0 used by syscalls/assembly call-clobbered
+r1 used by syscalls/assembly call-clobbered
+r2 argument 0 / return value 0 call-clobbered
+r3 argument 1 / return value 1 (if long long) call-clobbered
+r4 argument 2 call-clobbered
+r5 argument 3 call-clobbered
+r6 argument 4 saved
+r7 pointer-to arguments 5 to ... saved
+r8 this & that saved
+r9 this & that saved
+r10 static-chain ( if nested function ) saved
+r11 frame-pointer ( if function used alloca ) saved
+r12 got-pointer saved
+r13 base-pointer saved
+r14 return-address saved
+r15 stack-pointer saved
+
+f0 argument 0 / return value ( float/double ) call-clobbered
+f2 argument 1 call-clobbered
+f4 z/Architecture argument 2 saved
+f6 z/Architecture argument 3 saved
+======== ========================================== ===============
+
+The remaining floating points
+f1,f3,f5 f7-f15 are call-clobbered.
+
+Notes:
+------
+1) The only requirement is that registers which are used
+ by the callee are saved, e.g. the compiler is perfectly
+ capable of using r11 for purposes other than a frame a
+ frame pointer if a frame pointer is not needed.
+2) In functions with variable arguments e.g. printf the calling procedure
+ is identical to one without variable arguments & the same number of
+ parameters. However, the prologue of this function is somewhat more
+ hairy owing to it having to move these parameters to the stack to
+ get va_start, va_arg & va_end to work.
+3) Access registers are currently unused by gcc but are used in
+ the kernel. Possibilities exist to use them at the moment for
+ temporary storage but it isn't recommended.
+4) Only 4 of the floating point registers are used for
+ parameter passing as older machines such as G3 only have only 4
+ & it keeps the stack frame compatible with other compilers.
+ However with IEEE floating point emulation under linux on the
+ older machines you are free to use the other 12.
+5) A long long or double parameter cannot be have the
+ first 4 bytes in a register & the second four bytes in the
+ outgoing args area. It must be purely in the outgoing args
+ area if crossing this boundary.
+6) Floating point parameters are mixed with outgoing args
+ on the outgoing args area in the order the are passed in as parameters.
+7) Floating point arguments 2 & 3 are saved in the outgoing args area for
+ z/Architecture
+
+
+Stack Frame Layout
+------------------
+
+========= ============== ======================================================
+s/390 z/Architecture
+========= ============== ======================================================
+0 0 back chain ( a 0 here signifies end of back chain )
+4 8 eos ( end of stack, not used on Linux for S390 used
+ in other linkage formats )
+8 16 glue used in other s/390 linkage formats for saved
+ routine descriptors etc.
+12 24 glue used in other s/390 linkage formats for saved
+ routine descriptors etc.
+16 32 scratch area
+20 40 scratch area
+24 48 saved r6 of caller function
+28 56 saved r7 of caller function
+32 64 saved r8 of caller function
+36 72 saved r9 of caller function
+40 80 saved r10 of caller function
+44 88 saved r11 of caller function
+48 96 saved r12 of caller function
+52 104 saved r13 of caller function
+56 112 saved r14 of caller function
+60 120 saved r15 of caller function
+64 128 saved f4 of caller function
+72 132 saved f6 of caller function
+80 undefined
+96 160 outgoing args passed from caller to callee
+96+x 160+x possible stack alignment ( 8 bytes desirable )
+96+x+y 160+x+y alloca space of caller ( if used )
+96+x+y+z 160+x+y+z automatics of caller ( if used )
+0 back-chain
+========= ============== ======================================================
+
+A sample program with comments.
+===============================
+
+Comments on the function test
+-----------------------------
+1) It didn't need to set up a pointer to the constant pool gpr13 as it is not
+ used ( :-( ).
+2) This is a frameless function & no stack is bought.
+3) The compiler was clever enough to recognise that it could return the
+ value in r2 as well as use it for the passed in parameter ( :-) ).
+4) The basr ( branch relative & save ) trick works as follows the instruction
+ has a special case with r0,r0 with some instruction operands is understood as
+ the literal value 0, some risc architectures also do this ). So now
+ we are branching to the next address & the address new program counter is
+ in r13,so now we subtract the size of the function prologue we have executed
+ the size of the literal pool to get to the top of the literal pool::
+
+
+ 0040037c int test(int b)
+ { # Function prologue below
+ 40037c: 90 de f0 34 stm %r13,%r14,52(%r15) # Save registers r13 & r14
+ 400380: 0d d0 basr %r13,%r0 # Set up pointer to constant pool using
+ 400382: a7 da ff fa ahi %r13,-6 # basr trick
+ return(5+b);
+ # Huge main program
+ 400386: a7 2a 00 05 ahi %r2,5 # add 5 to r2
+
+ # Function epilogue below
+ 40038a: 98 de f0 34 lm %r13,%r14,52(%r15) # restore registers r13 & 14
+ 40038e: 07 fe br %r14 # return
+ }
+
+Comments on the function main
+-----------------------------
+1) The compiler did this function optimally ( 8-) )::
+
+ Literal pool for main.
+ 400390: ff ff ff ec .long 0xffffffec
+ main(int argc,char *argv[])
+ { # Function prologue below
+ 400394: 90 bf f0 2c stm %r11,%r15,44(%r15) # Save necessary registers
+ 400398: 18 0f lr %r0,%r15 # copy stack pointer to r0
+ 40039a: a7 fa ff a0 ahi %r15,-96 # Make area for callee saving
+ 40039e: 0d d0 basr %r13,%r0 # Set up r13 to point to
+ 4003a0: a7 da ff f0 ahi %r13,-16 # literal pool
+ 4003a4: 50 00 f0 00 st %r0,0(%r15) # Save backchain
+
+ return(test(5)); # Main Program Below
+ 4003a8: 58 e0 d0 00 l %r14,0(%r13) # load relative address of test from
+ # literal pool
+ 4003ac: a7 28 00 05 lhi %r2,5 # Set first parameter to 5
+ 4003b0: 4d ee d0 00 bas %r14,0(%r14,%r13) # jump to test setting r14 as return
+ # address using branch & save instruction.
+
+ # Function Epilogue below
+ 4003b4: 98 bf f0 8c lm %r11,%r15,140(%r15)# Restore necessary registers.
+ 4003b8: 07 fe br %r14 # return to do program exit
+ }
+
+
+Compiler updates
+----------------
+
+::
+
+ main(int argc,char *argv[])
+ {
+ 4004fc: 90 7f f0 1c stm %r7,%r15,28(%r15)
+ 400500: a7 d5 00 04 bras %r13,400508 <main+0xc>
+ 400504: 00 40 04 f4 .long 0x004004f4
+ # compiler now puts constant pool in code to so it saves an instruction
+ 400508: 18 0f lr %r0,%r15
+ 40050a: a7 fa ff a0 ahi %r15,-96
+ 40050e: 50 00 f0 00 st %r0,0(%r15)
+ return(test(5));
+ 400512: 58 10 d0 00 l %r1,0(%r13)
+ 400516: a7 28 00 05 lhi %r2,5
+ 40051a: 0d e1 basr %r14,%r1
+ # compiler adds 1 extra instruction to epilogue this is done to
+ # avoid processor pipeline stalls owing to data dependencies on g5 &
+ # above as register 14 in the old code was needed directly after being loaded
+ # by the lm %r11,%r15,140(%r15) for the br %14.
+ 40051c: 58 40 f0 98 l %r4,152(%r15)
+ 400520: 98 7f f0 7c lm %r7,%r15,124(%r15)
+ 400524: 07 f4 br %r4
+ }
+
+
+Hartmut ( our compiler developer ) also has been threatening to take out the
+stack backchain in optimised code as this also causes pipeline stalls, you
+have been warned.
+
+64 bit z/Architecture code disassembly
+--------------------------------------
+
+If you understand the stuff above you'll understand the stuff
+below too so I'll avoid repeating myself & just say that
+some of the instructions have g's on the end of them to indicate
+they are 64 bit & the stack offsets are a bigger,
+the only other difference you'll find between 32 & 64 bit is that
+we now use f4 & f6 for floating point arguments on 64 bit::
+
+ 00000000800005b0 <test>:
+ int test(int b)
+ {
+ return(5+b);
+ 800005b0: a7 2a 00 05 ahi %r2,5
+ 800005b4: b9 14 00 22 lgfr %r2,%r2 # downcast to integer
+ 800005b8: 07 fe br %r14
+ 800005ba: 07 07 bcr 0,%r7
+
+
+ }
+
+ 00000000800005bc <main>:
+ main(int argc,char *argv[])
+ {
+ 800005bc: eb bf f0 58 00 24 stmg %r11,%r15,88(%r15)
+ 800005c2: b9 04 00 1f lgr %r1,%r15
+ 800005c6: a7 fb ff 60 aghi %r15,-160
+ 800005ca: e3 10 f0 00 00 24 stg %r1,0(%r15)
+ return(test(5));
+ 800005d0: a7 29 00 05 lghi %r2,5
+ # brasl allows jumps > 64k & is overkill here bras would do fune
+ 800005d4: c0 e5 ff ff ff ee brasl %r14,800005b0 <test>
+ 800005da: e3 40 f1 10 00 04 lg %r4,272(%r15)
+ 800005e0: eb bf f0 f8 00 04 lmg %r11,%r15,248(%r15)
+ 800005e6: 07 f4 br %r4
+ }
+
+
+
+Compiling programs for debugging on Linux for s/390 & z/Architecture
+====================================================================
+-gdwarf-2 now works it should be considered the default debugging
+format for s/390 & z/Architecture as it is more reliable for debugging
+shared libraries, normal -g debugging works much better now
+Thanks to the IBM java compiler developers bug reports.
+
+This is typically done adding/appending the flags -g or -gdwarf-2 to the
+CFLAGS & LDFLAGS variables Makefile of the program concerned.
+
+If using gdb & you would like accurate displays of registers &
+stack traces compile without optimisation i.e make sure
+that there is no -O2 or similar on the CFLAGS line of the Makefile &
+the emitted gcc commands, obviously this will produce worse code
+( not advisable for shipment ) but it is an aid to the debugging process.
+
+This aids debugging because the compiler will copy parameters passed in
+in registers onto the stack so backtracing & looking at passed in
+parameters will work, however some larger programs which use inline functions
+will not compile without optimisation.
+
+Debugging with optimisation has since much improved after fixing
+some bugs, please make sure you are using gdb-5.0 or later developed
+after Nov'2000.
+
+
+
+Debugging under VM
+==================
+
+Notes
+-----
+Addresses & values in the VM debugger are always hex never decimal
+Address ranges are of the format <HexValue1>-<HexValue2> or
+<HexValue1>.<HexValue2>
+For example, the address range 0x2000 to 0x3000 can be described as 2000-3000
+or 2000.1000
+
+The VM Debugger is case insensitive.
+
+VM's strengths are usually other debuggers weaknesses you can get at any
+resource no matter how sensitive e.g. memory management resources, change
+address translation in the PSW. For kernel hacking you will reap dividends if
+you get good at it.
+
+The VM Debugger displays operators but not operands, and also the debugger
+displays useful information on the same line as the author of the code probably
+felt that it was a good idea not to go over the 80 columns on the screen.
+This isn't as unintuitive as it may seem as the s/390 instructions are easy to
+decode mentally and you can make a good guess at a lot of them as all the
+operands are nibble (half byte aligned).
+So if you have an objdump listing by hand, it is quite easy to follow, and if
+you don't have an objdump listing keep a copy of the s/390 Reference Summary
+or alternatively the s/390 principles of operation next to you.
+e.g. even I can guess that
+0001AFF8' LR 180F CC 0
+is a ( load register ) lr r0,r15
+
+Also it is very easy to tell the length of a 390 instruction from the 2 most
+significant bits in the instruction (not that this info is really useful except
+if you are trying to make sense of a hexdump of code).
+Here is a table
+
+======================= ==================
+Bits Instruction Length
+======================= ==================
+00 2 Bytes
+01 4 Bytes
+10 4 Bytes
+11 6 Bytes
+======================= ==================
+
+The debugger also displays other useful info on the same line such as the
+addresses being operated on destination addresses of branches & condition codes.
+e.g.::
+
+ 00019736' AHI A7DAFF0E CC 1
+ 000198BA' BRC A7840004 -> 000198C2' CC 0
+ 000198CE' STM 900EF068 >> 0FA95E78 CC 2
+
+
+
+Useful VM debugger commands
+---------------------------
+
+I suppose I'd better mention this before I start
+to list the current active traces do::
+
+ Q TR
+
+there can be a maximum of 255 of these per set
+( more about trace sets later ).
+
+To stop traces issue a::
+
+ TR END.
+
+To delete a particular breakpoint issue::
+
+ TR DEL <breakpoint number>
+
+The PA1 key drops to CP mode so you can issue debugger commands,
+Doing alt c (on my 3270 console at least ) clears the screen.
+
+hitting b <enter> comes back to the running operating system
+from cp mode ( in our case linux ).
+
+It is typically useful to add shortcuts to your profile.exec file
+if you have one ( this is roughly equivalent to autoexec.bat in DOS ).
+file here are a few from mine::
+
+ /* this gives me command history on issuing f12 */
+ set pf12 retrieve
+ /* this continues */
+ set pf8 imm b
+ /* goes to trace set a */
+ set pf1 imm tr goto a
+ /* goes to trace set b */
+ set pf2 imm tr goto b
+ /* goes to trace set c */
+ set pf3 imm tr goto c
+
+
+
+Instruction Tracing
+-------------------
+Setting a simple breakpoint::
+
+ TR I PSWA <address>
+
+To debug a particular function try::
+
+ TR I R <function address range>
+ TR I on its own will single step.
+ TR I DATA <MNEMONIC> <OPTIONAL RANGE> will trace for particular mnemonics
+
+e.g.::
+
+ TR I DATA 4D R 0197BC.4000
+
+will trace for BAS'es ( opcode 4D ) in the range 0197BC.4000
+
+if you were inclined you could add traces for all branch instructions &
+suffix them with the run prefix so you would have a backtrace on screen
+when a program crashes::
+
+ TR BR <INTO OR FROM> will trace branches into or out of an address.
+
+e.g.::
+
+ TR BR INTO 0
+
+is often quite useful if a program is getting awkward & deciding
+to branch to 0 & crashing as this will stop at the address before in jumps to 0.
+
+::
+
+ TR I R <address range> RUN cmd d g
+
+single steps a range of addresses but stays running &
+displays the gprs on each step.
+
+
+
+Displaying & modifying Registers
+--------------------------------
+D G
+ will display all the gprs
+
+Adding a extra G to all the commands is necessary to access the full 64 bit
+content in VM on z/Architecture. Obviously this isn't required for access
+registers as these are still 32 bit.
+
+e.g.
+
+DGG
+ instead of DG
+
+D X
+ will display all the control registers
+D AR
+ will display all the access registers
+D AR4-7
+ will display access registers 4 to 7
+CPU ALL D G
+ will display the GRPS of all CPUS in the configuration
+D PSW
+ will display the current PSW
+st PSW 2000
+ will put the value 2000 into the PSW & cause crash your machine.
+D PREFIX
+ displays the prefix offset
+
+
+Displaying Memory
+-----------------
+To display memory mapped using the current PSW's mapping try::
+
+ D <range>
+
+To make VM display a message each time it hits a particular address and
+continue try:
+
+D I<range>
+ will disassemble/display a range of instructions.
+
+ST addr 32 bit word
+ will store a 32 bit aligned address
+D T<range>
+ will display the EBCDIC in an address (if you are that way inclined)
+D R<range>
+ will display real addresses ( without DAT ) but with prefixing.
+
+There are other complex options to display if you need to get at say home space
+but are in primary space the easiest thing to do is to temporarily
+modify the PSW to the other addressing mode, display the stuff & then
+restore it.
+
+
+
+Hints
+-----
+If you want to issue a debugger command without halting your virtual machine
+with the PA1 key try prefixing the command with #CP e.g.::
+
+ #cp tr i pswa 2000
+
+also suffixing most debugger commands with RUN will cause them not
+to stop just display the mnemonic at the current instruction on the console.
+
+If you have several breakpoints you want to put into your program &
+you get fed up of cross referencing with System.map
+you can do the following trick for several symbols.
+
+::
+
+ grep do_signal System.map
+
+which emits the following among other things::
+
+ 0001f4e0 T do_signal
+
+now you can do::
+
+ TR I PSWA 0001f4e0 cmd msg * do_signal
+
+This sends a message to your own console each time do_signal is entered.
+( As an aside I wrote a perl script once which automatically generated a REXX
+script with breakpoints on every kernel procedure, this isn't a good idea
+because there are thousands of these routines & VM can only set 255 breakpoints
+at a time so you nearly had to spend as long pruning the file down as you would
+entering the msgs by hand), however, the trick might be useful for a single
+object file. In the 3270 terminal emulator x3270 there is a very useful option
+in the file menu called "Save Screen In File" - this is very good for keeping a
+copy of traces.
+
+From CMS help <command name> will give you online help on a particular command.
+e.g.::
+
+ HELP DISPLAY
+
+Also CP has a file called profile.exec which automatically gets called
+on startup of CMS ( like autoexec.bat ), keeping on a DOS analogy session
+CP has a feature similar to doskey, it may be useful for you to
+use profile.exec to define some keystrokes.
+
+SET PF9 IMM B
+ This does a single step in VM on pressing F8.
+
+SET PF10 ^
+ This sets up the ^ key.
+ which can be used for ^c (ctrl-c),^z (ctrl-z) which can't be typed
+ directly into some 3270 consoles.
+
+SET PF11 ^-
+ This types the starting keystrokes for a sysrq see SysRq below.
+SET PF12 RETRIEVE
+ This retrieves command history on pressing F12.
+
+
+Sometimes in VM the display is set up to scroll automatically this
+can be very annoying if there are messages you wish to look at
+to stop this do
+
+TERM MORE 255 255
+ This will nearly stop automatic screen updates, however it will
+ cause a denial of service if lots of messages go to the 3270 console,
+ so it would be foolish to use this as the default on a production machine.
+
+
+Tracing particular processes
+----------------------------
+The kernel's text segment is intentionally at an address in memory that it will
+very seldom collide with text segments of user programs ( thanks Martin ),
+this simplifies debugging the kernel.
+However it is quite common for user processes to have addresses which collide
+this can make debugging a particular process under VM painful under normal
+circumstances as the process may change when doing a::
+
+ TR I R <address range>.
+
+Thankfully after reading VM's online help I figured out how to debug
+I particular process.
+
+Your first problem is to find the STD ( segment table designation )
+of the program you wish to debug.
+There are several ways you can do this here are a few
+
+Run::
+
+ objdump --syms <program to be debugged> | grep main
+
+To get the address of main in the program. Then::
+
+ tr i pswa <address of main>
+
+Start the program, if VM drops to CP on what looks like the entry
+point of the main function this is most likely the process you wish to debug.
+Now do a D X13 or D XG13 on z/Architecture.
+
+On 31 bit the STD is bits 1-19 ( the STO segment table origin )
+& 25-31 ( the STL segment table length ) of CR13.
+
+now type::
+
+ TR I R STD <CR13's value> 0.7fffffff
+
+e.g.::
+
+ TR I R STD 8F32E1FF 0.7fffffff
+
+Another very useful variation is::
+
+ TR STORE INTO STD <CR13's value> <address range>
+
+for finding out when a particular variable changes.
+
+An alternative way of finding the STD of a currently running process
+is to do the following, ( this method is more complex but
+could be quite convenient if you aren't updating the kernel much &
+so your kernel structures will stay constant for a reasonable period of
+time ).
+
+::
+
+ grep task /proc/<pid>/status
+
+from this you should see something like::
+
+ task: 0f160000 ksp: 0f161de8 pt_regs: 0f161f68
+
+This now gives you a pointer to the task structure.
+
+Now make::
+
+ CC:="s390-gcc -g" kernel/sched.s
+
+To get the task_struct stabinfo.
+
+( task_struct is defined in include/linux/sched.h ).
+
+Now we want to look at
+task->active_mm->pgd
+
+on my machine the active_mm in the task structure stab is
+active_mm:(4,12),672,32
+
+its offset is 672/8=84=0x54
+
+the pgd member in the mm_struct stab is
+pgd:(4,6)=*(29,5),96,32
+so its offset is 96/8=12=0xc
+
+so we'll::
+
+ hexdump -s 0xf160054 /dev/mem | more
+
+i.e. task_struct+active_mm offset
+to look at the active_mm member::
+
+ f160054 0fee cc60 0019 e334 0000 0000 0000 0011
+
+::
+
+ hexdump -s 0x0feecc6c /dev/mem | more
+
+i.e. active_mm+pgd offset::
+
+ feecc6c 0f2c 0000 0000 0001 0000 0001 0000 0010
+
+we get something like
+now do::
+
+ TR I R STD <pgd|0x7f> 0.7fffffff
+
+i.e. the 0x7f is added because the pgd only
+gives the page table origin & we need to set the low bits
+to the maximum possible segment table length.
+
+::
+
+ TR I R STD 0f2c007f 0.7fffffff
+
+on z/Architecture you'll probably need to do::
+
+ TR I R STD <pgd|0x7> 0.ffffffffffffffff
+
+to set the TableType to 0x1 & the Table length to 3.
+
+
+
+Tracing Program Exceptions
+--------------------------
+If you get a crash which says something like
+illegal operation or specification exception followed by a register dump
+You can restart linux & trace these using the tr prog <range or value> trace
+option.
+
+
+The most common ones you will normally be tracing for is:
+
+- 1=operation exception
+- 2=privileged operation exception
+- 4=protection exception
+- 5=addressing exception
+- 6=specification exception
+- 10=segment translation exception
+- 11=page translation exception
+
+The full list of these is on page 22 of the current s/390 Reference Summary.
+e.g.
+
+tr prog 10 will trace segment translation exceptions.
+
+tr prog on its own will trace all program interruption codes.
+
+Trace Sets
+----------
+On starting VM you are initially in the INITIAL trace set.
+You can do a Q TR to verify this.
+If you have a complex tracing situation where you wish to wait for instance
+till a driver is open before you start tracing IO, but know in your
+heart that you are going to have to make several runs through the code till you
+have a clue whats going on.
+
+What you can do is::
+
+ TR I PSWA <Driver open address>
+
+hit b to continue till breakpoint
+
+reach the breakpoint
+
+now do your::
+
+ TR GOTO B
+ TR IO 7c08-7c09 inst int run
+
+or whatever the IO channels you wish to trace are & hit b
+
+To got back to the initial trace set do::
+
+ TR GOTO INITIAL
+
+& the TR I PSWA <Driver open address> will be the only active breakpoint again.
+
+
+Tracing linux syscalls under VM
+-------------------------------
+Syscalls are implemented on Linux for S390 by the Supervisor call instruction
+(SVC). There 256 possibilities of these as the instruction is made up of a 0xA
+opcode and the second byte being the syscall number. They are traced using the
+simple command::
+
+ TR SVC <Optional value or range>
+
+the syscalls are defined in linux/arch/s390/include/asm/unistd.h
+e.g. to trace all file opens just do::
+
+ TR SVC 5 ( as this is the syscall number of open )
+
+
+SMP Specific commands
+---------------------
+To find out how many cpus you have
+Q CPUS displays all the CPU's available to your virtual machine
+To find the cpu that the current cpu VM debugger commands are being directed at
+do Q CPU to change the current cpu VM debugger commands are being directed at
+do::
+
+ CPU <desired cpu no>
+
+On a SMP guest issue a command to all CPUs try prefixing the command with cpu
+all. To issue a command to a particular cpu try cpu <cpu number> e.g.::
+
+ CPU 01 TR I R 2000.3000
+
+If you are running on a guest with several cpus & you have a IO related problem
+& cannot follow the flow of code but you know it isn't smp related.
+
+from the bash prompt issue::
+
+ shutdown -h now or halt.
+
+do a::
+
+ Q CPUS
+
+to find out how many cpus you have detach each one of them from cp except
+cpu 0 by issuing a::
+
+ DETACH CPU 01-(number of cpus in configuration)
+
+& boot linux again.
+
+TR SIGP
+ will trace inter processor signal processor instructions.
+
+DEFINE CPU 01-(number in configuration)
+ will get your guests cpus back.
+
+
+Help for displaying ascii textstrings
+-------------------------------------
+On the very latest VM Nucleus'es VM can now display ascii
+( thanks Neale for the hint ) by doing::
+
+ D TX<lowaddr>.<len>
+
+e.g.::
+
+ D TX0.100
+
+Alternatively
+=============
+Under older VM debuggers (I love EBDIC too) you can use following little
+program which converts a command line of hex digits to ascii text. It can be
+compiled under linux and you can copy the hex digits from your x3270 terminal
+to your xterm if you are debugging from a linuxbox.
+
+This is quite useful when looking at a parameter passed in as a text string
+under VM ( unless you are good at decoding ASCII in your head ).
+
+e.g. consider tracing an open syscall::
+
+ TR SVC 5
+
+We have stopped at a breakpoint::
+
+ 000151B0' SVC 0A05 -> 0001909A' CC 0
+
+D 20.8 to check the SVC old psw in the prefix area and see was it from userspace
+(for the layout of the prefix area consult the "Fixed Storage Locations"
+chapter of the s/390 Reference Summary if you have it available).
+
+::
+
+ V00000020 070C2000 800151B2
+
+The problem state bit wasn't set & it's also too early in the boot sequence
+for it to be a userspace SVC if it was we would have to temporarily switch the
+psw to user space addressing so we could get at the first parameter of the open
+in gpr2.
+
+Next do a::
+
+ D G2
+ GPR 2 = 00014CB4
+
+Now display what gpr2 is pointing to::
+
+ D 00014CB4.20
+ V00014CB4 2F646576 2F636F6E 736F6C65 00001BF5
+ V00014CC4 FC00014C B4001001 E0001000 B8070707
+
+Now copy the text till the first 00 hex ( which is the end of the string
+to an xterm & do hex2ascii on it::
+
+ hex2ascii 2F646576 2F636F6E 736F6C65 00
+
+outputs::
+
+ Decoded Hex:=/ d e v / c o n s o l e 0x00
+
+We were opening the console device,
+
+You can compile the code below yourself for practice :-),
+
+::
+
+ /*
+ * hex2ascii.c
+ * a useful little tool for converting a hexadecimal command line to ascii
+ *
+ * Author(s): Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com)
+ * (C) 2000 IBM Deutschland Entwicklung GmbH, IBM Corporation.
+ */
+ #include <stdio.h>
+
+ int main(int argc,char *argv[])
+ {
+ int cnt1,cnt2,len,toggle=0;
+ int startcnt=1;
+ unsigned char c,hex;
+
+ if(argc>1&&(strcmp(argv[1],"-a")==0))
+ startcnt=2;
+ printf("Decoded Hex:=");
+ for(cnt1=startcnt;cnt1<argc;cnt1++)
+ {
+ len=strlen(argv[cnt1]);
+ for(cnt2=0;cnt2<len;cnt2++)
+ {
+ c=argv[cnt1][cnt2];
+ if(c>='0'&&c<='9')
+ c=c-'0';
+ if(c>='A'&&c<='F')
+ c=c-'A'+10;
+ if(c>='a'&&c<='f')
+ c=c-'a'+10;
+ switch(toggle)
+ {
+ case 0:
+ hex=c<<4;
+ toggle=1;
+ break;
+ case 1:
+ hex+=c;
+ if(hex<32||hex>127)
+ {
+ if(startcnt==1)
+ printf("0x%02X ",(int)hex);
+ else
+ printf(".");
+ }
+ else
+ {
+ printf("%c",hex);
+ if(startcnt==1)
+ printf(" ");
+ }
+ toggle=0;
+ break;
+ }
+ }
+ }
+ printf("\n");
+ }
+
+
+
+
+Stack tracing under VM
+----------------------
+A basic backtrace
+-----------------
+
+Here are the tricks I use 9 out of 10 times it works pretty well,
+
+When your backchain reaches a dead end
+--------------------------------------
+This can happen when an exception happens in the kernel and the kernel is
+entered twice. If you reach the NULL pointer at the end of the back chain you
+should be able to sniff further back if you follow the following tricks.
+1) A kernel address should be easy to recognise since it is in
+primary space & the problem state bit isn't set & also
+The Hi bit of the address is set.
+2) Another backchain should also be easy to recognise since it is an
+address pointing to another address approximately 100 bytes or 0x70 hex
+behind the current stackpointer.
+
+
+Here is some practice.
+
+boot the kernel & hit PA1 at some random time
+
+d g to display the gprs, this should display something like::
+
+ GPR 0 = 00000001 00156018 0014359C 00000000
+ GPR 4 = 00000001 001B8888 000003E0 00000000
+ GPR 8 = 00100080 00100084 00000000 000FE000
+ GPR 12 = 00010400 8001B2DC 8001B36A 000FFED8
+
+Note that GPR14 is a return address but as we are real men we are going to
+trace the stack.
+display 0x40 bytes after the stack pointer::
+
+ V000FFED8 000FFF38 8001B838 80014C8E 000FFF38
+ V000FFEE8 00000000 00000000 000003E0 00000000
+ V000FFEF8 00100080 00100084 00000000 000FE000
+ V000FFF08 00010400 8001B2DC 8001B36A 000FFED8
+
+
+Ah now look at whats in sp+56 (sp+0x38) this is 8001B36A our saved r14 if
+you look above at our stackframe & also agrees with GPR14.
+
+now backchain::
+
+ d 000FFF38.40
+
+we now are taking the contents of SP to get our first backchain::
+
+ V000FFF38 000FFFA0 00000000 00014995 00147094
+ V000FFF48 00147090 001470A0 000003E0 00000000
+ V000FFF58 00100080 00100084 00000000 001BF1D0
+ V000FFF68 00010400 800149BA 80014CA6 000FFF38
+
+This displays a 2nd return address of 80014CA6
+
+now do::
+
+ d 000FFFA0.40
+
+for our 3rd backchain::
+
+ V000FFFA0 04B52002 0001107F 00000000 00000000
+ V000FFFB0 00000000 00000000 FF000000 0001107F
+ V000FFFC0 00000000 00000000 00000000 00000000
+ V000FFFD0 00010400 80010802 8001085A 000FFFA0
+
+
+our 3rd return address is 8001085A
+
+as the 04B52002 looks suspiciously like rubbish it is fair to assume that the
+kernel entry routines for the sake of optimisation don't set up a backchain.
+
+now look at System.map to see if the addresses make any sense::
+
+ grep -i 0001b3 System.map
+
+outputs among other things::
+
+ 0001b304 T cpu_idle
+
+so 8001B36A
+is cpu_idle+0x66 ( quiet the cpu is asleep, don't wake it )
+
+::
+
+ grep -i 00014 System.map
+
+produces among other things::
+
+ 00014a78 T start_kernel
+
+so 0014CA6 is start_kernel+some hex number I can't add in my head.
+
+::
+
+ grep -i 00108 System.map
+
+this produces::
+
+ 00010800 T _stext
+
+so 8001085A is _stext+0x5a
+
+Congrats you've done your first backchain.
+
+
+
+s/390 & z/Architecture IO Overview
+==================================
+
+I am not going to give a course in 390 IO architecture as this would take me
+quite a while and I'm no expert. Instead I'll give a 390 IO architecture
+summary for Dummies. If you have the s/390 principles of operation available
+read this instead. If nothing else you may find a few useful keywords in here
+and be able to use them on a web search engine to find more useful information.
+
+Unlike other bus architectures modern 390 systems do their IO using mostly
+fibre optics and devices such as tapes and disks can be shared between several
+mainframes. Also S390 can support up to 65536 devices while a high end PC based
+system might be choking with around 64.
+
+Here is some of the common IO terminology:
+
+Subchannel:
+ This is the logical number most IO commands use to talk to an IO device. There
+ can be up to 0x10000 (65536) of these in a configuration, typically there are a
+ few hundred. Under VM for simplicity they are allocated contiguously, however
+ on the native hardware they are not. They typically stay consistent between
+ boots provided no new hardware is inserted or removed.
+
+ Under Linux for s390 we use these as IRQ's and also when issuing an IO command
+ (CLEAR SUBCHANNEL, HALT SUBCHANNEL, MODIFY SUBCHANNEL, RESUME SUBCHANNEL,
+ START SUBCHANNEL, STORE SUBCHANNEL and TEST SUBCHANNEL). We use this as the ID
+ of the device we wish to talk to. The most important of these instructions are
+ START SUBCHANNEL (to start IO), TEST SUBCHANNEL (to check whether the IO
+ completed successfully) and HALT SUBCHANNEL (to kill IO). A subchannel can have
+ up to 8 channel paths to a device, this offers redundancy if one is not
+ available.
+
+Device Number:
+ This number remains static and is closely tied to the hardware. There are 65536
+ of these, made up of a CHPID (Channel Path ID, the most significant 8 bits) and
+ another lsb 8 bits. These remain static even if more devices are inserted or
+ removed from the hardware. There is a 1 to 1 mapping between subchannels and
+ device numbers, provided devices aren't inserted or removed.
+
+Channel Control Words:
+ CCWs are linked lists of instructions initially pointed to by an operation
+ request block (ORB), which is initially given to Start Subchannel (SSCH)
+ command along with the subchannel number for the IO subsystem to process
+ while the CPU continues executing normal code.
+ CCWs come in two flavours, Format 0 (24 bit for backward compatibility) and
+ Format 1 (31 bit). These are typically used to issue read and write (and many
+ other) instructions. They consist of a length field and an absolute address
+ field.
+
+ Each IO typically gets 1 or 2 interrupts, one for channel end (primary status)
+ when the channel is idle, and the second for device end (secondary status).
+ Sometimes you get both concurrently. You check how the IO went on by issuing a
+ TEST SUBCHANNEL at each interrupt, from which you receive an Interruption
+ response block (IRB). If you get channel and device end status in the IRB
+ without channel checks etc. your IO probably went okay. If you didn't you
+ probably need to examine the IRB, extended status word etc.
+ If an error occurs, more sophisticated control units have a facility known as
+ concurrent sense. This means that if an error occurs Extended sense information
+ will be presented in the Extended status word in the IRB. If not you have to
+ issue a subsequent SENSE CCW command after the test subchannel.
+
+
+TPI (Test pending interrupt) can also be used for polled IO, but in
+multitasking multiprocessor systems it isn't recommended except for
+checking special cases (i.e. non looping checks for pending IO etc.).
+
+Store Subchannel and Modify Subchannel can be used to examine and modify
+operating characteristics of a subchannel (e.g. channel paths).
+
+Other IO related Terms:
+
+Sysplex:
+ S390's Clustering Technology
+QDIO:
+ S390's new high speed IO architecture to support devices such as gigabit
+ ethernet, this architecture is also designed to be forward compatible with
+ upcoming 64 bit machines.
+
+
+General Concepts
+----------------
+
+Input Output Processors (IOP's) are responsible for communicating between
+the mainframe CPU's & the channel & relieve the mainframe CPU's from the
+burden of communicating with IO devices directly, this allows the CPU's to
+concentrate on data processing.
+
+IOP's can use one or more links ( known as channel paths ) to talk to each
+IO device. It first checks for path availability & chooses an available one,
+then starts ( & sometimes terminates IO ).
+There are two types of channel path: ESCON & the Parallel IO interface.
+
+IO devices are attached to control units, control units provide the
+logic to interface the channel paths & channel path IO protocols to
+the IO devices, they can be integrated with the devices or housed separately
+& often talk to several similar devices ( typical examples would be raid
+controllers or a control unit which connects to 1000 3270 terminals )::
+
+
+ +---------------------------------------------------------------+
+ | +-----+ +-----+ +-----+ +-----+ +----------+ +----------+ |
+ | | CPU | | CPU | | CPU | | CPU | | Main | | Expanded | |
+ | | | | | | | | | | Memory | | Storage | |
+ | +-----+ +-----+ +-----+ +-----+ +----------+ +----------+ |
+ |---------------------------------------------------------------+
+ | IOP | IOP | IOP |
+ |---------------------------------------------------------------
+ | C | C | C | C | C | C | C | C | C | C | C | C | C | C | C | C |
+ ----------------------------------------------------------------
+ || ||
+ || Bus & Tag Channel Path || ESCON
+ || ====================== || Channel
+ || || || || Path
+ +----------+ +----------+ +----------+
+ | | | | | |
+ | CU | | CU | | CU |
+ | | | | | |
+ +----------+ +----------+ +----------+
+ | | | | |
+ +----------+ +----------+ +----------+ +----------+ +----------+
+ |I/O Device| |I/O Device| |I/O Device| |I/O Device| |I/O Device|
+ +----------+ +----------+ +----------+ +----------+ +----------+
+ CPU = Central Processing Unit
+ C = Channel
+ IOP = IP Processor
+ CU = Control Unit
+
+The 390 IO systems come in 2 flavours the current 390 machines support both
+
+The Older 360 & 370 Interface,sometimes called the Parallel I/O interface,
+sometimes called Bus-and Tag & sometimes Original Equipment Manufacturers
+Interface (OEMI).
+
+This byte wide Parallel channel path/bus has parity & data on the "Bus" cable
+and control lines on the "Tag" cable. These can operate in byte multiplex mode
+for sharing between several slow devices or burst mode and monopolize the
+channel for the whole burst. Up to 256 devices can be addressed on one of these
+cables. These cables are about one inch in diameter. The maximum unextended
+length supported by these cables is 125 Meters but this can be extended up to
+2km with a fibre optic channel extended such as a 3044. The maximum burst speed
+supported is 4.5 megabytes per second. However, some really old processors
+support only transfer rates of 3.0, 2.0 & 1.0 MB/sec.
+One of these paths can be daisy chained to up to 8 control units.
+
+
+ESCON if fibre optic it is also called FICON
+Was introduced by IBM in 1990. Has 2 fibre optic cables and uses either leds or
+lasers for communication at a signaling rate of up to 200 megabits/sec. As
+10bits are transferred for every 8 bits info this drops to 160 megabits/sec
+and to 18.6 Megabytes/sec once control info and CRC are added. ESCON only
+operates in burst mode.
+
+ESCONs typical max cable length is 3km for the led version and 20km for the
+laser version known as XDF (extended distance facility). This can be further
+extended by using an ESCON director which triples the above mentioned ranges.
+Unlike Bus & Tag as ESCON is serial it uses a packet switching architecture,
+the standard Bus & Tag control protocol is however present within the packets.
+Up to 256 devices can be attached to each control unit that uses one of these
+interfaces.
+
+Common 390 Devices include:
+Network adapters typically OSA2,3172's,2116's & OSA-E gigabit ethernet adapters,
+Consoles 3270 & 3215 (a teletype emulated under linux for a line mode console).
+DASD's direct access storage devices ( otherwise known as hard disks ).
+Tape Drives.
+CTC ( Channel to Channel Adapters ),
+ESCON or Parallel Cables used as a very high speed serial link
+between 2 machines.
+
+
+Debugging IO on s/390 & z/Architecture under VM
+===============================================
+
+Now we are ready to go on with IO tracing commands under VM
+
+A few self explanatory queries::
+
+ Q OSA
+ Q CTC
+ Q DISK ( This command is CMS specific )
+ Q DASD
+
+Q OSA on my machine returns::
+
+ OSA 7C08 ON OSA 7C08 SUBCHANNEL = 0000
+ OSA 7C09 ON OSA 7C09 SUBCHANNEL = 0001
+ OSA 7C14 ON OSA 7C14 SUBCHANNEL = 0002
+ OSA 7C15 ON OSA 7C15 SUBCHANNEL = 0003
+
+If you have a guest with certain privileges you may be able to see devices
+which don't belong to you. To avoid this, add the option V.
+e.g.::
+
+ Q V OSA
+
+Now using the device numbers returned by this command we will
+Trace the io starting up on the first device 7c08 & 7c09
+In our simplest case we can trace the
+start subchannels
+like TR SSCH 7C08-7C09
+or the halt subchannels
+or TR HSCH 7C08-7C09
+MSCH's ,STSCH's I think you can guess the rest
+
+A good trick is tracing all the IO's and CCWS and spooling them into the reader
+of another VM guest so he can ftp the logfile back to his own machine. I'll do
+a small bit of this and give you a look at the output.
+
+1) Spool stdout to VM reader::
+
+ SP PRT TO (another vm guest ) or * for the local vm guest
+
+2) Fill the reader with the trace::
+
+ TR IO 7c08-7c09 INST INT CCW PRT RUN
+
+3) Start up linux::
+
+ i 00c
+4) Finish the trace::
+
+ TR END
+
+5) close the reader::
+
+ C PRT
+
+6) list reader contents::
+
+ RDRLIST
+
+7) copy it to linux4's minidisk::
+
+ RECEIVE / LOG TXT A1 ( replace
+
+8)
+filel & press F11 to look at it
+You should see something like::
+
+ 00020942' SSCH B2334000 0048813C CC 0 SCH 0000 DEV 7C08
+ CPA 000FFDF0 PARM 00E2C9C4 KEY 0 FPI C0 LPM 80
+ CCW 000FFDF0 E4200100 00487FE8 0000 E4240100 ........
+ IDAL 43D8AFE8
+ IDAL 0FB76000
+ 00020B0A' I/O DEV 7C08 -> 000197BC' SCH 0000 PARM 00E2C9C4
+ 00021628' TSCH B2354000 >> 00488164 CC 0 SCH 0000 DEV 7C08
+ CCWA 000FFDF8 DEV STS 0C SCH STS 00 CNT 00EC
+ KEY 0 FPI C0 CC 0 CTLS 4007
+ 00022238' STSCH B2344000 >> 00488108 CC 0 SCH 0000 DEV 7C08
+
+If you don't like messing up your readed ( because you possibly booted from it )
+you can alternatively spool it to another readers guest.
+
+
+Other common VM device related commands
+---------------------------------------------
+These commands are listed only because they have
+been of use to me in the past & may be of use to
+you too. For more complete info on each of the commands
+use type HELP <command> from CMS.
+
+detaching devices::
+
+ DET <devno range>
+ ATT <devno range> <guest>
+
+attach a device to guest * for your own guest
+
+READY <devno>
+ cause VM to issue a fake interrupt.
+
+The VARY command is normally only available to VM administrators::
+
+ VARY ON PATH <path> TO <devno range>
+ VARY OFF PATH <PATH> FROM <devno range>
+
+This is used to switch on or off channel paths to devices.
+
+Q CHPID <channel path ID>
+ This displays state of devices using this channel path
+
+D SCHIB <subchannel>
+ This displays the subchannel information SCHIB block for the device.
+ this I believe is also only available to administrators.
+
+DEFINE CTC <devno>
+ defines a virtual CTC channel to channel connection
+ 2 need to be defined on each guest for the CTC driver to use.
+
+COUPLE devno userid remote devno
+ Joins a local virtual device to a remote virtual device
+ ( commonly used for the CTC driver ).
+
+Building a VM ramdisk under CMS which linux can use::
+
+ def vfb-<blocksize> <subchannel> <number blocks>
+
+blocksize is commonly 4096 for linux.
+
+Formatting it::
+
+ format <subchannel> <driver letter e.g. x> (blksize <blocksize>
+
+Sharing a disk between multiple guests::
+
+ LINK userid devno1 devno2 mode password
+
+
+
+GDB on S390
+===========
+N.B. if compiling for debugging gdb works better without optimisation
+( see Compiling programs for debugging )
+
+invocation
+----------
+gdb <victim program> <optional corefile>
+
+Online help
+-----------
+help: gives help on commands
+
+e.g.::
+
+ help
+ help display
+
+Note gdb's online help is very good use it.
+
+
+Assembly
+--------
+info registers:
+ displays registers other than floating point.
+
+info all-registers:
+ displays floating points as well.
+
+disassemble:
+ disassembles
+
+e.g.::
+
+ disassemble without parameters will disassemble the current function
+ disassemble $pc $pc+10
+
+Viewing & modifying variables
+-----------------------------
+print or p:
+ displays variable or register
+
+e.g. p/x $sp will display the stack pointer
+
+display:
+ prints variable or register each time program stops
+
+e.g.::
+
+ display/x $pc will display the program counter
+ display argc
+
+undisplay:
+ undo's display's
+
+info breakpoints:
+ shows all current breakpoints
+
+info stack:
+ shows stack back trace (if this doesn't work too well, I'll show
+ you the stacktrace by hand below).
+
+info locals:
+ displays local variables.
+
+info args:
+ display current procedure arguments.
+
+set args:
+ will set argc & argv each time the victim program is invoked
+
+e.g.::
+
+ set <variable>=value
+ set argc=100
+ set $pc=0
+
+
+
+Modifying execution
+-------------------
+step:
+ steps n lines of sourcecode
+
+step
+ steps 1 line.
+
+step 100
+ steps 100 lines of code.
+
+next:
+ like step except this will not step into subroutines
+
+stepi:
+ steps a single machine code instruction.
+
+e.g.::
+
+ stepi 100
+
+nexti:
+ steps a single machine code instruction but will not step into
+ subroutines.
+
+finish:
+ will run until exit of the current routine
+
+run:
+ (re)starts a program
+
+cont:
+ continues a program
+
+quit:
+ exits gdb.
+
+
+breakpoints
+------------
+
+break
+ sets a breakpoint
+
+e.g.::
+
+ break main
+ break *$pc
+ break *0x400618
+
+Here's a really useful one for large programs
+
+rbr
+ Set a breakpoint for all functions matching REGEXP
+
+e.g.::
+
+ rbr 390
+
+will set a breakpoint with all functions with 390 in their name.
+
+info breakpoints
+ lists all breakpoints
+
+delete:
+ delete breakpoint by number or delete them all
+
+e.g.
+
+delete 1
+ will delete the first breakpoint
+
+
+delete
+ will delete them all
+
+watch:
+ This will set a watchpoint ( usually hardware assisted ),
+
+This will watch a variable till it changes
+
+e.g.
+
+watch cnt
+ will watch the variable cnt till it changes.
+
+As an aside unfortunately gdb's, architecture independent watchpoint code
+is inconsistent & not very good, watchpoints usually work but not always.
+
+info watchpoints:
+ Display currently active watchpoints
+
+condition: ( another useful one )
+ Specify breakpoint number N to break only if COND is true.
+
+Usage is `condition N COND`, where N is an integer and COND is an
+expression to be evaluated whenever breakpoint N is reached.
+
+
+
+User defined functions/macros
+-----------------------------
+define: ( Note this is very very useful,simple & powerful )
+
+usage define <name> <list of commands> end
+
+examples which you should consider putting into .gdbinit in your home
+directory::
+
+ define d
+ stepi
+ disassemble $pc $pc+10
+ end
+ define e
+ nexti
+ disassemble $pc $pc+10
+ end
+
+
+Other hard to classify stuff
+----------------------------
+signal n:
+ sends the victim program a signal.
+
+e.g. `signal 3` will send a SIGQUIT.
+
+info signals:
+ what gdb does when the victim receives certain signals.
+
+list:
+
+e.g.:
+
+list
+ lists current function source
+list 1,10
+ list first 10 lines of current file.
+
+list test.c:1,10
+
+
+directory:
+ Adds directories to be searched for source if gdb cannot find the source.
+ (note it is a bit sensitive about slashes)
+
+e.g. To add the root of the filesystem to the searchpath do::
+
+ directory //
+
+
+call <function>
+This calls a function in the victim program, this is pretty powerful
+e.g.
+(gdb) call printf("hello world")
+outputs:
+$1 = 11
+
+You might now be thinking that the line above didn't work, something extra had
+to be done.
+(gdb) call fflush(stdout)
+hello world$2 = 0
+As an aside the debugger also calls malloc & free under the hood
+to make space for the "hello world" string.
+
+
+
+hints
+-----
+1) command completion works just like bash
+ ( if you are a bad typist like me this really helps )
+
+e.g. hit br <TAB> & cursor up & down :-).
+
+2) if you have a debugging problem that takes a few steps to recreate
+put the steps into a file called .gdbinit in your current working directory
+if you have defined a few extra useful user defined commands put these in
+your home directory & they will be read each time gdb is launched.
+
+A typical .gdbinit file might be.::
+
+ break main
+ run
+ break runtime_exception
+ cont
+
+
+stack chaining in gdb by hand
+-----------------------------
+This is done using a the same trick described for VM::
+
+ p/x (*($sp+56))&0x7fffffff
+
+get the first backchain.
+
+For z/Architecture
+Replace 56 with 112 & ignore the &0x7fffffff
+in the macros below & do nasty casts to longs like the following
+as gdb unfortunately deals with printed arguments as ints which
+messes up everything.
+
+i.e. here is a 3rd backchain dereference::
+
+ p/x *(long *)(***(long ***)$sp+112)
+
+
+this outputs::
+
+ $5 = 0x528f18
+
+on my machine.
+
+Now you can use::
+
+ info symbol (*($sp+56))&0x7fffffff
+
+you might see something like::
+
+ rl_getc + 36 in section .text
+
+telling you what is located at address 0x528f18
+Now do::
+
+ p/x (*(*$sp+56))&0x7fffffff
+
+This outputs::
+
+ $6 = 0x528ed0
+
+Now do::
+
+ info symbol (*(*$sp+56))&0x7fffffff
+ rl_read_key + 180 in section .text
+
+now do::
+
+ p/x (*(**$sp+56))&0x7fffffff
+
+& so on.
+
+Disassembling instructions without debug info
+---------------------------------------------
+gdb typically complains if there is a lack of debugging
+symbols in the disassemble command with
+"No function contains specified address." To get around
+this do::
+
+ x/<number lines to disassemble>xi <address>
+
+e.g.::
+
+ x/20xi 0x400730
+
+
+
+Note:
+ Remember gdb has history just like bash you don't need to retype the
+ whole line just use the up & down arrows.
+
+
+
+For more info
+-------------
+From your linuxbox do::
+
+ man gdb
+
+or::
+
+ info gdb.
+
+core dumps
+----------
+
+What a core dump ?
+^^^^^^^^^^^^^^^^^^
+
+A core dump is a file generated by the kernel (if allowed) which contains the
+registers and all active pages of the program which has crashed.
+
+From this file gdb will allow you to look at the registers, stack trace and
+memory of the program as if it just crashed on your system. It is usually
+called core and created in the current working directory.
+
+This is very useful in that a customer can mail a core dump to a technical
+support department and the technical support department can reconstruct what
+happened. Provided they have an identical copy of this program with debugging
+symbols compiled in and the source base of this build is available.
+
+In short it is far more useful than something like a crash log could ever hope
+to be.
+
+Why have I never seen one ?
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Probably because you haven't used the command::
+
+ ulimit -c unlimited in bash
+
+to allow core dumps, now do::
+
+ ulimit -a
+
+to verify that the limit was accepted.
+
+A sample core dump
+ To create this I'm going to do::
+
+ ulimit -c unlimited
+ gdb
+
+to launch gdb (my victim app. ) now be bad & do the following from another
+telnet/xterm session to the same machine::
+
+ ps -aux | grep gdb
+ kill -SIGSEGV <gdb's pid>
+
+or alternatively use `killall -SIGSEGV gdb` if you have the killall command.
+
+Now look at the core dump::
+
+ ./gdb core
+
+Displays the following::
+
+ GNU gdb 4.18
+ Copyright 1998 Free Software Foundation, Inc.
+ GDB is free software, covered by the GNU General Public License, and you are
+ welcome to change it and/or distribute copies of it under certain conditions.
+ Type "show copying" to see the conditions.
+ There is absolutely no warranty for GDB. Type "show warranty" for details.
+ This GDB was configured as "s390-ibm-linux"...
+ Core was generated by `./gdb'.
+ Program terminated with signal 11, Segmentation fault.
+ Reading symbols from /usr/lib/libncurses.so.4...done.
+ Reading symbols from /lib/libm.so.6...done.
+ Reading symbols from /lib/libc.so.6...done.
+ Reading symbols from /lib/ld-linux.so.2...done.
+ #0 0x40126d1a in read () from /lib/libc.so.6
+ Setting up the environment for debugging gdb.
+ Breakpoint 1 at 0x4dc6f8: file utils.c, line 471.
+ Breakpoint 2 at 0x4d87a4: file top.c, line 2609.
+ (top-gdb) info stack
+ #0 0x40126d1a in read () from /lib/libc.so.6
+ #1 0x528f26 in rl_getc (stream=0x7ffffde8) at input.c:402
+ #2 0x528ed0 in rl_read_key () at input.c:381
+ #3 0x5167e6 in readline_internal_char () at readline.c:454
+ #4 0x5168ee in readline_internal_charloop () at readline.c:507
+ #5 0x51692c in readline_internal () at readline.c:521
+ #6 0x5164fe in readline (prompt=0x7ffff810)
+ at readline.c:349
+ #7 0x4d7a8a in command_line_input (prompt=0x564420 "(gdb) ", repeat=1,
+ annotation_suffix=0x4d6b44 "prompt") at top.c:2091
+ #8 0x4d6cf0 in command_loop () at top.c:1345
+ #9 0x4e25bc in main (argc=1, argv=0x7ffffdf4) at main.c:635
+
+
+LDD
+===
+This is a program which lists the shared libraries which a library needs,
+Note you also get the relocations of the shared library text segments which
+help when using objdump --source.
+
+e.g.::
+
+ ldd ./gdb
+
+outputs::
+
+ libncurses.so.4 => /usr/lib/libncurses.so.4 (0x40018000)
+ libm.so.6 => /lib/libm.so.6 (0x4005e000)
+ libc.so.6 => /lib/libc.so.6 (0x40084000)
+ /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
+
+
+Debugging shared libraries
+==========================
+Most programs use shared libraries, however it can be very painful
+when you single step instruction into a function like printf for the
+first time & you end up in functions like _dl_runtime_resolve this is
+the ld.so doing lazy binding, lazy binding is a concept in ELF where
+shared library functions are not loaded into memory unless they are
+actually used, great for saving memory but a pain to debug.
+
+To get around this either relink the program -static or exit gdb type
+export LD_BIND_NOW=true this will stop lazy binding & restart the gdb'ing
+the program in question.
+
+
+
+Debugging modules
+=================
+As modules are dynamically loaded into the kernel their address can be
+anywhere to get around this use the -m option with insmod to emit a load
+map which can be piped into a file if required.
+
+The proc file system
+====================
+What is it ?.
+It is a filesystem created by the kernel with files which are created on demand
+by the kernel if read, or can be used to modify kernel parameters,
+it is a powerful concept.
+
+e.g.::
+
+ cat /proc/sys/net/ipv4/ip_forward
+
+On my machine outputs::
+
+ 0
+
+telling me ip_forwarding is not on to switch it on I can do::
+
+ echo 1 > /proc/sys/net/ipv4/ip_forward
+
+cat it again::
+
+ cat /proc/sys/net/ipv4/ip_forward
+
+On my machine now outputs::
+
+ 1
+
+IP forwarding is on.
+
+There is a lot of useful info in here best found by going in and having a look
+around, so I'll take you through some entries I consider important.
+
+All the processes running on the machine have their own entry defined by
+/proc/<pid>
+
+So lets have a look at the init process::
+
+ cd /proc/1
+ cat cmdline
+
+emits::
+
+ init [2]
+
+::
+
+ cd /proc/1/fd
+
+This contains numerical entries of all the open files,
+some of these you can cat e.g. stdout (2)::
+
+ cat /proc/29/maps
+
+on my machine emits::
+
+ 00400000-00478000 r-xp 00000000 5f:00 4103 /bin/bash
+ 00478000-0047e000 rw-p 00077000 5f:00 4103 /bin/bash
+ 0047e000-00492000 rwxp 00000000 00:00 0
+ 40000000-40015000 r-xp 00000000 5f:00 14382 /lib/ld-2.1.2.so
+ 40015000-40016000 rw-p 00014000 5f:00 14382 /lib/ld-2.1.2.so
+ 40016000-40017000 rwxp 00000000 00:00 0
+ 40017000-40018000 rw-p 00000000 00:00 0
+ 40018000-4001b000 r-xp 00000000 5f:00 14435 /lib/libtermcap.so.2.0.8
+ 4001b000-4001c000 rw-p 00002000 5f:00 14435 /lib/libtermcap.so.2.0.8
+ 4001c000-4010d000 r-xp 00000000 5f:00 14387 /lib/libc-2.1.2.so
+ 4010d000-40111000 rw-p 000f0000 5f:00 14387 /lib/libc-2.1.2.so
+ 40111000-40114000 rw-p 00000000 00:00 0
+ 40114000-4011e000 r-xp 00000000 5f:00 14408 /lib/libnss_files-2.1.2.so
+ 4011e000-4011f000 rw-p 00009000 5f:00 14408 /lib/libnss_files-2.1.2.so
+ 7fffd000-80000000 rwxp ffffe000 00:00 0
+
+
+Showing us the shared libraries init uses where they are in memory
+& memory access permissions for each virtual memory area.
+
+/proc/1/cwd is a softlink to the current working directory.
+
+/proc/1/root is the root of the filesystem for this process.
+
+/proc/1/mem is the current running processes memory which you
+can read & write to like a file.
+
+strace uses this sometimes as it is a bit faster than the
+rather inefficient ptrace interface for peeking at DATA.
+
+::
+
+ cat status
+
+ Name: init
+ State: S (sleeping)
+ Pid: 1
+ PPid: 0
+ Uid: 0 0 0 0
+ Gid: 0 0 0 0
+ Groups:
+ VmSize: 408 kB
+ VmLck: 0 kB
+ VmRSS: 208 kB
+ VmData: 24 kB
+ VmStk: 8 kB
+ VmExe: 368 kB
+ VmLib: 0 kB
+ SigPnd: 0000000000000000
+ SigBlk: 0000000000000000
+ SigIgn: 7fffffffd7f0d8fc
+ SigCgt: 00000000280b2603
+ CapInh: 00000000fffffeff
+ CapPrm: 00000000ffffffff
+ CapEff: 00000000fffffeff
+
+ User PSW: 070de000 80414146
+ task: 004b6000 tss: 004b62d8 ksp: 004b7ca8 pt_regs: 004b7f68
+ User GPRS:
+ 00000400 00000000 0000000b 7ffffa90
+ 00000000 00000000 00000000 0045d9f4
+ 0045cafc 7ffffa90 7fffff18 0045cb08
+ 00010400 804039e8 80403af8 7ffff8b0
+ User ACRS:
+ 00000000 00000000 00000000 00000000
+ 00000001 00000000 00000000 00000000
+ 00000000 00000000 00000000 00000000
+ 00000000 00000000 00000000 00000000
+ Kernel BackChain CallChain BackChain CallChain
+ 004b7ca8 8002bd0c 004b7d18 8002b92c
+ 004b7db8 8005cd50 004b7e38 8005d12a
+ 004b7f08 80019114
+
+Showing among other things memory usage & status of some signals &
+the processes'es registers from the kernel task_structure
+as well as a backchain which may be useful if a process crashes
+in the kernel for some unknown reason.
+
+Some driver debugging techniques
+================================
+debug feature
+-------------
+Some of our drivers now support a "debug feature" in
+/proc/s390dbf see s390dbf.txt in the linux/Documentation directory
+for more info.
+
+e.g.
+to switch on the lcs "debug feature"::
+
+ echo 5 > /proc/s390dbf/lcs/level
+
+& then after the error occurred::
+
+ cat /proc/s390dbf/lcs/sprintf >/logfile
+
+the logfile now contains some information which may help
+tech support resolve a problem in the field.
+
+
+
+high level debugging network drivers
+------------------------------------
+ifconfig is a quite useful command
+it gives the current state of network drivers.
+
+If you suspect your network device driver is dead
+one way to check is type::
+
+ ifconfig <network device>
+
+e.g. tr0
+
+You should see something like::
+
+ ifconfig tr0
+ tr0 Link encap:16/4 Mbps Token Ring (New) HWaddr 00:04:AC:20:8E:48
+ inet addr:9.164.185.132 Bcast:9.164.191.255 Mask:255.255.224.0
+ UP BROADCAST RUNNING MULTICAST MTU:2000 Metric:1
+ RX packets:246134 errors:0 dropped:0 overruns:0 frame:0
+ TX packets:5 errors:0 dropped:0 overruns:0 carrier:0
+ collisions:0 txqueuelen:100
+
+if the device doesn't say up
+try::
+
+ /etc/rc.d/init.d/network start
+
+( this starts the network stack & hopefully calls ifconfig tr0 up ).
+ifconfig looks at the output of /proc/net/dev and presents it in a more
+presentable form.
+
+Now ping the device from a machine in the same subnet.
+
+if the RX packets count & TX packets counts don't increment you probably
+have problems.
+
+next::
+
+ cat /proc/net/arp
+
+Do you see any hardware addresses in the cache if not you may have problems.
+Next try::
+
+ ping -c 5 <broadcast_addr>
+
+i.e. the Bcast field above in the output of
+ifconfig. Do you see any replies from machines other than the local machine
+if not you may have problems. also if the TX packets count in ifconfig
+hasn't incremented either you have serious problems in your driver
+(e.g. the txbusy field of the network device being stuck on )
+or you may have multiple network devices connected.
+
+
+chandev
+-------
+There is a new device layer for channel devices, some
+drivers e.g. lcs are registered with this layer.
+
+If the device uses the channel device layer you'll be
+able to find what interrupts it uses & the current state
+of the device.
+
+See the manpage chandev.8 &type cat /proc/chandev for more info.
+
+
+SysRq
+=====
+This is now supported by linux for s/390 & z/Architecture.
+
+To enable it do compile the kernel with::
+
+ Kernel Hacking -> Magic SysRq Key Enabled
+
+Then::
+
+ echo "1" > /proc/sys/kernel/sysrq
+
+also type::
+
+ echo "8" >/proc/sys/kernel/printk
+
+To make printk output go to console.
+
+On 390 all commands are prefixed with::
+
+ ^-
+
+e.g.::
+
+ ^-t will show tasks.
+ ^-? or some unknown command will display help.
+
+The sysrq key reading is very picky ( I have to type the keys in an
+xterm session & paste them into the x3270 console )
+& it may be wise to predefine the keys as described in the VM hints above
+
+This is particularly useful for syncing disks unmounting & rebooting
+if the machine gets partially hung.
+
+Read Documentation/admin-guide/sysrq.rst for more info
+
+References:
+===========
+- Enterprise Systems Architecture Reference Summary
+- Enterprise Systems Architecture Principles of Operation
+- Hartmut Penners s390 stack frame sheet.
+- IBM Mainframe Channel Attachment a technology brief from a CISCO webpage
+- Various bits of man & info pages of Linux.
+- Linux & GDB source.
+- Various info & man pages.
+- CMS Help on tracing commands.
+- Linux for s/390 Elf Application Binary Interface
+- Linux for z/Series Elf Application Binary Interface ( Both Highly Recommended )
+- z/Architecture Principles of Operation SA22-7832-00
+- Enterprise Systems Architecture/390 Reference Summary SA22-7209-01 & the
+- Enterprise Systems Architecture/390 Principles of Operation SA22-7201-05
+
+Special Thanks
+==============
+Special thanks to Neale Ferguson who maintains a much
+prettier HTML version of this page at
+http://linuxvm.org/penguinvm/
+Bob Grainger Stefan Bader & others for reporting bugs
--- /dev/null
+=============================
+S/390 driver model interfaces
+=============================
+
+1. CCW devices
+--------------
+
+All devices which can be addressed by means of ccws are called 'CCW devices' -
+even if they aren't actually driven by ccws.
+
+All ccw devices are accessed via a subchannel, this is reflected in the
+structures under devices/::
+
+ devices/
+ - system/
+ - css0/
+ - 0.0.0000/0.0.0815/
+ - 0.0.0001/0.0.4711/
+ - 0.0.0002/
+ - 0.1.0000/0.1.1234/
+ ...
+ - defunct/
+
+In this example, device 0815 is accessed via subchannel 0 in subchannel set 0,
+device 4711 via subchannel 1 in subchannel set 0, and subchannel 2 is a non-I/O
+subchannel. Device 1234 is accessed via subchannel 0 in subchannel set 1.
+
+The subchannel named 'defunct' does not represent any real subchannel on the
+system; it is a pseudo subchannel where disconnected ccw devices are moved to
+if they are displaced by another ccw device becoming operational on their
+former subchannel. The ccw devices will be moved again to a proper subchannel
+if they become operational again on that subchannel.
+
+You should address a ccw device via its bus id (e.g. 0.0.4711); the device can
+be found under bus/ccw/devices/.
+
+All ccw devices export some data via sysfs.
+
+cutype:
+ The control unit type / model.
+
+devtype:
+ The device type / model, if applicable.
+
+availability:
+ Can be 'good' or 'boxed'; 'no path' or 'no device' for
+ disconnected devices.
+
+online:
+ An interface to set the device online and offline.
+ In the special case of the device being disconnected (see the
+ notify function under 1.2), piping 0 to online will forcibly delete
+ the device.
+
+The device drivers can add entries to export per-device data and interfaces.
+
+There is also some data exported on a per-subchannel basis (see under
+bus/css/devices/):
+
+chpids:
+ Via which chpids the device is connected.
+
+pimpampom:
+ The path installed, path available and path operational masks.
+
+There also might be additional data, for example for block devices.
+
+
+1.1 Bringing up a ccw device
+----------------------------
+
+This is done in several steps.
+
+a. Each driver can provide one or more parameter interfaces where parameters can
+ be specified. These interfaces are also in the driver's responsibility.
+b. After a. has been performed, if necessary, the device is finally brought up
+ via the 'online' interface.
+
+
+1.2 Writing a driver for ccw devices
+------------------------------------
+
+The basic struct ccw_device and struct ccw_driver data structures can be found
+under include/asm/ccwdev.h::
+
+ struct ccw_device {
+ spinlock_t *ccwlock;
+ struct ccw_device_private *private;
+ struct ccw_device_id id;
+
+ struct ccw_driver *drv;
+ struct device dev;
+ int online;
+
+ void (*handler) (struct ccw_device *dev, unsigned long intparm,
+ struct irb *irb);
+ };
+
+ struct ccw_driver {
+ struct module *owner;
+ struct ccw_device_id *ids;
+ int (*probe) (struct ccw_device *);
+ int (*remove) (struct ccw_device *);
+ int (*set_online) (struct ccw_device *);
+ int (*set_offline) (struct ccw_device *);
+ int (*notify) (struct ccw_device *, int);
+ struct device_driver driver;
+ char *name;
+ };
+
+The 'private' field contains data needed for internal i/o operation only, and
+is not available to the device driver.
+
+Each driver should declare in a MODULE_DEVICE_TABLE into which CU types/models
+and/or device types/models it is interested. This information can later be found
+in the struct ccw_device_id fields::
+
+ struct ccw_device_id {
+ __u16 match_flags;
+
+ __u16 cu_type;
+ __u16 dev_type;
+ __u8 cu_model;
+ __u8 dev_model;
+
+ unsigned long driver_info;
+ };
+
+The functions in ccw_driver should be used in the following way:
+
+probe:
+ This function is called by the device layer for each device the driver
+ is interested in. The driver should only allocate private structures
+ to put in dev->driver_data and create attributes (if needed). Also,
+ the interrupt handler (see below) should be set here.
+
+::
+
+ int (*probe) (struct ccw_device *cdev);
+
+Parameters:
+ cdev
+ - the device to be probed.
+
+
+remove:
+ This function is called by the device layer upon removal of the driver,
+ the device or the module. The driver should perform cleanups here.
+
+::
+
+ int (*remove) (struct ccw_device *cdev);
+
+Parameters:
+ cdev
+ - the device to be removed.
+
+
+set_online:
+ This function is called by the common I/O layer when the device is
+ activated via the 'online' attribute. The driver should finally
+ setup and activate the device here.
+
+::
+
+ int (*set_online) (struct ccw_device *);
+
+Parameters:
+ cdev
+ - the device to be activated. The common layer has
+ verified that the device is not already online.
+
+
+set_offline: This function is called by the common I/O layer when the device is
+ de-activated via the 'online' attribute. The driver should shut
+ down the device, but not de-allocate its private data.
+
+::
+
+ int (*set_offline) (struct ccw_device *);
+
+Parameters:
+ cdev
+ - the device to be deactivated. The common layer has
+ verified that the device is online.
+
+
+notify:
+ This function is called by the common I/O layer for some state changes
+ of the device.
+
+ Signalled to the driver are:
+
+ * In online state, device detached (CIO_GONE) or last path gone
+ (CIO_NO_PATH). The driver must return !0 to keep the device; for
+ return code 0, the device will be deleted as usual (also when no
+ notify function is registered). If the driver wants to keep the
+ device, it is moved into disconnected state.
+ * In disconnected state, device operational again (CIO_OPER). The
+ common I/O layer performs some sanity checks on device number and
+ Device / CU to be reasonably sure if it is still the same device.
+ If not, the old device is removed and a new one registered. By the
+ return code of the notify function the device driver signals if it
+ wants the device back: !0 for keeping, 0 to make the device being
+ removed and re-registered.
+
+::
+
+ int (*notify) (struct ccw_device *, int);
+
+Parameters:
+ cdev
+ - the device whose state changed.
+
+ event
+ - the event that happened. This can be one of CIO_GONE,
+ CIO_NO_PATH or CIO_OPER.
+
+The handler field of the struct ccw_device is meant to be set to the interrupt
+handler for the device. In order to accommodate drivers which use several
+distinct handlers (e.g. multi subchannel devices), this is a member of ccw_device
+instead of ccw_driver.
+The handler is registered with the common layer during set_online() processing
+before the driver is called, and is deregistered during set_offline() after the
+driver has been called. Also, after registering / before deregistering, path
+grouping resp. disbanding of the path group (if applicable) are performed.
+
+::
+
+ void (*handler) (struct ccw_device *dev, unsigned long intparm, struct irb *irb);
+
+Parameters: dev - the device the handler is called for
+ intparm - the intparm which allows the device driver to identify
+ the i/o the interrupt is associated with, or to recognize
+ the interrupt as unsolicited.
+ irb - interruption response block which contains the accumulated
+ status.
+
+The device driver is called from the common ccw_device layer and can retrieve
+information about the interrupt from the irb parameter.
+
+
+1.3 ccwgroup devices
+--------------------
+
+The ccwgroup mechanism is designed to handle devices consisting of multiple ccw
+devices, like lcs or ctc.
+
+The ccw driver provides a 'group' attribute. Piping bus ids of ccw devices to
+this attributes creates a ccwgroup device consisting of these ccw devices (if
+possible). This ccwgroup device can be set online or offline just like a normal
+ccw device.
+
+Each ccwgroup device also provides an 'ungroup' attribute to destroy the device
+again (only when offline). This is a generic ccwgroup mechanism (the driver does
+not need to implement anything beyond normal removal routines).
+
+A ccw device which is a member of a ccwgroup device carries a pointer to the
+ccwgroup device in the driver_data of its device struct. This field must not be
+touched by the driver - it should use the ccwgroup device's driver_data for its
+private data.
+
+To implement a ccwgroup driver, please refer to include/asm/ccwgroup.h. Keep in
+mind that most drivers will need to implement both a ccwgroup and a ccw
+driver.
+
+
+2. Channel paths
+-----------------
+
+Channel paths show up, like subchannels, under the channel subsystem root (css0)
+and are called 'chp0.<chpid>'. They have no driver and do not belong to any bus.
+Please note, that unlike /proc/chpids in 2.4, the channel path objects reflect
+only the logical state and not the physical state, since we cannot track the
+latter consistently due to lacking machine support (we don't need to be aware
+of it anyway).
+
+status
+ - Can be 'online' or 'offline'.
+ Piping 'on' or 'off' sets the chpid logically online/offline.
+ Piping 'on' to an online chpid triggers path reprobing for all devices
+ the chpid connects to. This can be used to force the kernel to re-use
+ a channel path the user knows to be online, but the machine hasn't
+ created a machine check for.
+
+type
+ - The physical type of the channel path.
+
+shared
+ - Whether the channel path is shared.
+
+cmg
+ - The channel measurement group.
+
+3. System devices
+-----------------
+
+3.1 xpram
+---------
+
+xpram shows up under devices/system/ as 'xpram'.
+
+3.2 cpus
+--------
+
+For each cpu, a directory is created under devices/system/cpu/. Each cpu has an
+attribute 'online' which can be 0 or 1.
+
+
+4. Other devices
+----------------
+
+4.1 Netiucv
+-----------
+
+The netiucv driver creates an attribute 'connection' under
+bus/iucv/drivers/netiucv. Piping to this attribute creates a new netiucv
+connection to the specified host.
+
+Netiucv connections show up under devices/iucv/ as "netiucv<ifnum>". The interface
+number is assigned sequentially to the connections defined via the 'connection'
+attribute.
+
+user
+ - shows the connection partner.
+
+buffer
+ - maximum buffer size. Pipe to it to change buffer size.
+++ /dev/null
-S/390 driver model interfaces
------------------------------
-
-1. CCW devices
---------------
-
-All devices which can be addressed by means of ccws are called 'CCW devices' -
-even if they aren't actually driven by ccws.
-
-All ccw devices are accessed via a subchannel, this is reflected in the
-structures under devices/:
-
-devices/
- - system/
- - css0/
- - 0.0.0000/0.0.0815/
- - 0.0.0001/0.0.4711/
- - 0.0.0002/
- - 0.1.0000/0.1.1234/
- ...
- - defunct/
-
-In this example, device 0815 is accessed via subchannel 0 in subchannel set 0,
-device 4711 via subchannel 1 in subchannel set 0, and subchannel 2 is a non-I/O
-subchannel. Device 1234 is accessed via subchannel 0 in subchannel set 1.
-
-The subchannel named 'defunct' does not represent any real subchannel on the
-system; it is a pseudo subchannel where disconnected ccw devices are moved to
-if they are displaced by another ccw device becoming operational on their
-former subchannel. The ccw devices will be moved again to a proper subchannel
-if they become operational again on that subchannel.
-
-You should address a ccw device via its bus id (e.g. 0.0.4711); the device can
-be found under bus/ccw/devices/.
-
-All ccw devices export some data via sysfs.
-
-cutype: The control unit type / model.
-
-devtype: The device type / model, if applicable.
-
-availability: Can be 'good' or 'boxed'; 'no path' or 'no device' for
- disconnected devices.
-
-online: An interface to set the device online and offline.
- In the special case of the device being disconnected (see the
- notify function under 1.2), piping 0 to online will forcibly delete
- the device.
-
-The device drivers can add entries to export per-device data and interfaces.
-
-There is also some data exported on a per-subchannel basis (see under
-bus/css/devices/):
-
-chpids: Via which chpids the device is connected.
-
-pimpampom: The path installed, path available and path operational masks.
-
-There also might be additional data, for example for block devices.
-
-
-1.1 Bringing up a ccw device
-----------------------------
-
-This is done in several steps.
-
-a. Each driver can provide one or more parameter interfaces where parameters can
- be specified. These interfaces are also in the driver's responsibility.
-b. After a. has been performed, if necessary, the device is finally brought up
- via the 'online' interface.
-
-
-1.2 Writing a driver for ccw devices
-------------------------------------
-
-The basic struct ccw_device and struct ccw_driver data structures can be found
-under include/asm/ccwdev.h.
-
-struct ccw_device {
- spinlock_t *ccwlock;
- struct ccw_device_private *private;
- struct ccw_device_id id;
-
- struct ccw_driver *drv;
- struct device dev;
- int online;
-
- void (*handler) (struct ccw_device *dev, unsigned long intparm,
- struct irb *irb);
-};
-
-struct ccw_driver {
- struct module *owner;
- struct ccw_device_id *ids;
- int (*probe) (struct ccw_device *);
- int (*remove) (struct ccw_device *);
- int (*set_online) (struct ccw_device *);
- int (*set_offline) (struct ccw_device *);
- int (*notify) (struct ccw_device *, int);
- struct device_driver driver;
- char *name;
-};
-
-The 'private' field contains data needed for internal i/o operation only, and
-is not available to the device driver.
-
-Each driver should declare in a MODULE_DEVICE_TABLE into which CU types/models
-and/or device types/models it is interested. This information can later be found
-in the struct ccw_device_id fields:
-
-struct ccw_device_id {
- __u16 match_flags;
-
- __u16 cu_type;
- __u16 dev_type;
- __u8 cu_model;
- __u8 dev_model;
-
- unsigned long driver_info;
-};
-
-The functions in ccw_driver should be used in the following way:
-probe: This function is called by the device layer for each device the driver
- is interested in. The driver should only allocate private structures
- to put in dev->driver_data and create attributes (if needed). Also,
- the interrupt handler (see below) should be set here.
-
-int (*probe) (struct ccw_device *cdev);
-
-Parameters: cdev - the device to be probed.
-
-
-remove: This function is called by the device layer upon removal of the driver,
- the device or the module. The driver should perform cleanups here.
-
-int (*remove) (struct ccw_device *cdev);
-
-Parameters: cdev - the device to be removed.
-
-
-set_online: This function is called by the common I/O layer when the device is
- activated via the 'online' attribute. The driver should finally
- setup and activate the device here.
-
-int (*set_online) (struct ccw_device *);
-
-Parameters: cdev - the device to be activated. The common layer has
- verified that the device is not already online.
-
-
-set_offline: This function is called by the common I/O layer when the device is
- de-activated via the 'online' attribute. The driver should shut
- down the device, but not de-allocate its private data.
-
-int (*set_offline) (struct ccw_device *);
-
-Parameters: cdev - the device to be deactivated. The common layer has
- verified that the device is online.
-
-
-notify: This function is called by the common I/O layer for some state changes
- of the device.
- Signalled to the driver are:
- * In online state, device detached (CIO_GONE) or last path gone
- (CIO_NO_PATH). The driver must return !0 to keep the device; for
- return code 0, the device will be deleted as usual (also when no
- notify function is registered). If the driver wants to keep the
- device, it is moved into disconnected state.
- * In disconnected state, device operational again (CIO_OPER). The
- common I/O layer performs some sanity checks on device number and
- Device / CU to be reasonably sure if it is still the same device.
- If not, the old device is removed and a new one registered. By the
- return code of the notify function the device driver signals if it
- wants the device back: !0 for keeping, 0 to make the device being
- removed and re-registered.
-
-int (*notify) (struct ccw_device *, int);
-
-Parameters: cdev - the device whose state changed.
- event - the event that happened. This can be one of CIO_GONE,
- CIO_NO_PATH or CIO_OPER.
-
-The handler field of the struct ccw_device is meant to be set to the interrupt
-handler for the device. In order to accommodate drivers which use several
-distinct handlers (e.g. multi subchannel devices), this is a member of ccw_device
-instead of ccw_driver.
-The handler is registered with the common layer during set_online() processing
-before the driver is called, and is deregistered during set_offline() after the
-driver has been called. Also, after registering / before deregistering, path
-grouping resp. disbanding of the path group (if applicable) are performed.
-
-void (*handler) (struct ccw_device *dev, unsigned long intparm, struct irb *irb);
-
-Parameters: dev - the device the handler is called for
- intparm - the intparm which allows the device driver to identify
- the i/o the interrupt is associated with, or to recognize
- the interrupt as unsolicited.
- irb - interruption response block which contains the accumulated
- status.
-
-The device driver is called from the common ccw_device layer and can retrieve
-information about the interrupt from the irb parameter.
-
-
-1.3 ccwgroup devices
---------------------
-
-The ccwgroup mechanism is designed to handle devices consisting of multiple ccw
-devices, like lcs or ctc.
-
-The ccw driver provides a 'group' attribute. Piping bus ids of ccw devices to
-this attributes creates a ccwgroup device consisting of these ccw devices (if
-possible). This ccwgroup device can be set online or offline just like a normal
-ccw device.
-
-Each ccwgroup device also provides an 'ungroup' attribute to destroy the device
-again (only when offline). This is a generic ccwgroup mechanism (the driver does
-not need to implement anything beyond normal removal routines).
-
-A ccw device which is a member of a ccwgroup device carries a pointer to the
-ccwgroup device in the driver_data of its device struct. This field must not be
-touched by the driver - it should use the ccwgroup device's driver_data for its
-private data.
-
-To implement a ccwgroup driver, please refer to include/asm/ccwgroup.h. Keep in
-mind that most drivers will need to implement both a ccwgroup and a ccw
-driver.
-
-
-2. Channel paths
------------------
-
-Channel paths show up, like subchannels, under the channel subsystem root (css0)
-and are called 'chp0.<chpid>'. They have no driver and do not belong to any bus.
-Please note, that unlike /proc/chpids in 2.4, the channel path objects reflect
-only the logical state and not the physical state, since we cannot track the
-latter consistently due to lacking machine support (we don't need to be aware
-of it anyway).
-
-status - Can be 'online' or 'offline'.
- Piping 'on' or 'off' sets the chpid logically online/offline.
- Piping 'on' to an online chpid triggers path reprobing for all devices
- the chpid connects to. This can be used to force the kernel to re-use
- a channel path the user knows to be online, but the machine hasn't
- created a machine check for.
-
-type - The physical type of the channel path.
-
-shared - Whether the channel path is shared.
-
-cmg - The channel measurement group.
-
-3. System devices
------------------
-
-3.1 xpram
----------
-
-xpram shows up under devices/system/ as 'xpram'.
-
-3.2 cpus
---------
-
-For each cpu, a directory is created under devices/system/cpu/. Each cpu has an
-attribute 'online' which can be 0 or 1.
-
-
-4. Other devices
-----------------
-
-4.1 Netiucv
------------
-
-The netiucv driver creates an attribute 'connection' under
-bus/iucv/drivers/netiucv. Piping to this attribute creates a new netiucv
-connection to the specified host.
-
-Netiucv connections show up under devices/iucv/ as "netiucv<ifnum>". The interface
-number is assigned sequentially to the connections defined via the 'connection'
-attribute.
-
-user - shows the connection partner.
-
-buffer - maximum buffer size.
- Pipe to it to change buffer size.
-
-
--- /dev/null
+:orphan:
+
+=================
+s390 Architecture
+=================
+
+.. toctree::
+ :maxdepth: 1
+
+ cds
+ 3270
+ debugging390
+ driver-model
+ monreader
+ qeth
+ s390dbf
+ vfio-ap
+ vfio-ccw
+ zfcpdump
+ dasd
+ common_io
+
+ text_files
+
+.. only:: subproject and html
+
+ Indices
+ =======
+
+ * :ref:`genindex`
--- /dev/null
+=================================================
+Linux API for read access to z/VM Monitor Records
+=================================================
+
+Date : 2004-Nov-26
+
+Author: Gerald Schaefer (geraldsc@de.ibm.com)
+
+
+
+
+Description
+===========
+This item delivers a new Linux API in the form of a misc char device that is
+usable from user space and allows read access to the z/VM Monitor Records
+collected by the `*MONITOR` System Service of z/VM.
+
+
+User Requirements
+=================
+The z/VM guest on which you want to access this API needs to be configured in
+order to allow IUCV connections to the `*MONITOR` service, i.e. it needs the
+IUCV `*MONITOR` statement in its user entry. If the monitor DCSS to be used is
+restricted (likely), you also need the NAMESAVE <DCSS NAME> statement.
+This item will use the IUCV device driver to access the z/VM services, so you
+need a kernel with IUCV support. You also need z/VM version 4.4 or 5.1.
+
+There are two options for being able to load the monitor DCSS (examples assume
+that the monitor DCSS begins at 144 MB and ends at 152 MB). You can query the
+location of the monitor DCSS with the Class E privileged CP command Q NSS MAP
+(the values BEGPAG and ENDPAG are given in units of 4K pages).
+
+See also "CP Command and Utility Reference" (SC24-6081-00) for more information
+on the DEF STOR and Q NSS MAP commands, as well as "Saved Segments Planning
+and Administration" (SC24-6116-00) for more information on DCSSes.
+
+1st option:
+-----------
+You can use the CP command DEF STOR CONFIG to define a "memory hole" in your
+guest virtual storage around the address range of the DCSS.
+
+Example: DEF STOR CONFIG 0.140M 200M.200M
+
+This defines two blocks of storage, the first is 140MB in size an begins at
+address 0MB, the second is 200MB in size and begins at address 200MB,
+resulting in a total storage of 340MB. Note that the first block should
+always start at 0 and be at least 64MB in size.
+
+2nd option:
+-----------
+Your guest virtual storage has to end below the starting address of the DCSS
+and you have to specify the "mem=" kernel parameter in your parmfile with a
+value greater than the ending address of the DCSS.
+
+Example::
+
+ DEF STOR 140M
+
+This defines 140MB storage size for your guest, the parameter "mem=160M" is
+added to the parmfile.
+
+
+User Interface
+==============
+The char device is implemented as a kernel module named "monreader",
+which can be loaded via the modprobe command, or it can be compiled into the
+kernel instead. There is one optional module (or kernel) parameter, "mondcss",
+to specify the name of the monitor DCSS. If the module is compiled into the
+kernel, the kernel parameter "monreader.mondcss=<DCSS NAME>" can be specified
+in the parmfile.
+
+The default name for the DCSS is "MONDCSS" if none is specified. In case that
+there are other users already connected to the `*MONITOR` service (e.g.
+Performance Toolkit), the monitor DCSS is already defined and you have to use
+the same DCSS. The CP command Q MONITOR (Class E privileged) shows the name
+of the monitor DCSS, if already defined, and the users connected to the
+`*MONITOR` service.
+Refer to the "z/VM Performance" book (SC24-6109-00) on how to create a monitor
+DCSS if your z/VM doesn't have one already, you need Class E privileges to
+define and save a DCSS.
+
+Example:
+--------
+
+::
+
+ modprobe monreader mondcss=MYDCSS
+
+This loads the module and sets the DCSS name to "MYDCSS".
+
+NOTE:
+-----
+This API provides no interface to control the `*MONITOR` service, e.g. specify
+which data should be collected. This can be done by the CP command MONITOR
+(Class E privileged), see "CP Command and Utility Reference".
+
+Device nodes with udev:
+-----------------------
+After loading the module, a char device will be created along with the device
+node /<udev directory>/monreader.
+
+Device nodes without udev:
+--------------------------
+If your distribution does not support udev, a device node will not be created
+automatically and you have to create it manually after loading the module.
+Therefore you need to know the major and minor numbers of the device. These
+numbers can be found in /sys/class/misc/monreader/dev.
+
+Typing cat /sys/class/misc/monreader/dev will give an output of the form
+<major>:<minor>. The device node can be created via the mknod command, enter
+mknod <name> c <major> <minor>, where <name> is the name of the device node
+to be created.
+
+Example:
+--------
+
+::
+
+ # modprobe monreader
+ # cat /sys/class/misc/monreader/dev
+ 10:63
+ # mknod /dev/monreader c 10 63
+
+This loads the module with the default monitor DCSS (MONDCSS) and creates a
+device node.
+
+File operations:
+----------------
+The following file operations are supported: open, release, read, poll.
+There are two alternative methods for reading: either non-blocking read in
+conjunction with polling, or blocking read without polling. IOCTLs are not
+supported.
+
+Read:
+-----
+Reading from the device provides a 12 Byte monitor control element (MCE),
+followed by a set of one or more contiguous monitor records (similar to the
+output of the CMS utility MONWRITE without the 4K control blocks). The MCE
+contains information on the type of the following record set (sample/event
+data), the monitor domains contained within it and the start and end address
+of the record set in the monitor DCSS. The start and end address can be used
+to determine the size of the record set, the end address is the address of the
+last byte of data. The start address is needed to handle "end-of-frame" records
+correctly (domain 1, record 13), i.e. it can be used to determine the record
+start offset relative to a 4K page (frame) boundary.
+
+See "Appendix A: `*MONITOR`" in the "z/VM Performance" document for a description
+of the monitor control element layout. The layout of the monitor records can
+be found here (z/VM 5.1): http://www.vm.ibm.com/pubs/mon510/index.html
+
+The layout of the data stream provided by the monreader device is as follows::
+
+ ...
+ <0 byte read>
+ <first MCE> \
+ <first set of records> |
+ ... |- data set
+ <last MCE> |
+ <last set of records> /
+ <0 byte read>
+ ...
+
+There may be more than one combination of MCE and corresponding record set
+within one data set and the end of each data set is indicated by a successful
+read with a return value of 0 (0 byte read).
+Any received data must be considered invalid until a complete set was
+read successfully, including the closing 0 byte read. Therefore you should
+always read the complete set into a buffer before processing the data.
+
+The maximum size of a data set can be as large as the size of the
+monitor DCSS, so design the buffer adequately or use dynamic memory allocation.
+The size of the monitor DCSS will be printed into syslog after loading the
+module. You can also use the (Class E privileged) CP command Q NSS MAP to
+list all available segments and information about them.
+
+As with most char devices, error conditions are indicated by returning a
+negative value for the number of bytes read. In this case, the errno variable
+indicates the error condition:
+
+EIO:
+ reply failed, read data is invalid and the application
+ should discard the data read since the last successful read with 0 size.
+EFAULT:
+ copy_to_user failed, read data is invalid and the application should
+ discard the data read since the last successful read with 0 size.
+EAGAIN:
+ occurs on a non-blocking read if there is no data available at the
+ moment. There is no data missing or corrupted, just try again or rather
+ use polling for non-blocking reads.
+EOVERFLOW:
+ message limit reached, the data read since the last successful
+ read with 0 size is valid but subsequent records may be missing.
+
+In the last case (EOVERFLOW) there may be missing data, in the first two cases
+(EIO, EFAULT) there will be missing data. It's up to the application if it will
+continue reading subsequent data or rather exit.
+
+Open:
+-----
+Only one user is allowed to open the char device. If it is already in use, the
+open function will fail (return a negative value) and set errno to EBUSY.
+The open function may also fail if an IUCV connection to the `*MONITOR` service
+cannot be established. In this case errno will be set to EIO and an error
+message with an IPUSER SEVER code will be printed into syslog. The IPUSER SEVER
+codes are described in the "z/VM Performance" book, Appendix A.
+
+NOTE:
+-----
+As soon as the device is opened, incoming messages will be accepted and they
+will account for the message limit, i.e. opening the device without reading
+from it will provoke the "message limit reached" error (EOVERFLOW error code)
+eventually.
+++ /dev/null
-
-Date : 2004-Nov-26
-Author: Gerald Schaefer (geraldsc@de.ibm.com)
-
-
- Linux API for read access to z/VM Monitor Records
- =================================================
-
-
-Description
-===========
-This item delivers a new Linux API in the form of a misc char device that is
-usable from user space and allows read access to the z/VM Monitor Records
-collected by the *MONITOR System Service of z/VM.
-
-
-User Requirements
-=================
-The z/VM guest on which you want to access this API needs to be configured in
-order to allow IUCV connections to the *MONITOR service, i.e. it needs the
-IUCV *MONITOR statement in its user entry. If the monitor DCSS to be used is
-restricted (likely), you also need the NAMESAVE <DCSS NAME> statement.
-This item will use the IUCV device driver to access the z/VM services, so you
-need a kernel with IUCV support. You also need z/VM version 4.4 or 5.1.
-
-There are two options for being able to load the monitor DCSS (examples assume
-that the monitor DCSS begins at 144 MB and ends at 152 MB). You can query the
-location of the monitor DCSS with the Class E privileged CP command Q NSS MAP
-(the values BEGPAG and ENDPAG are given in units of 4K pages).
-
-See also "CP Command and Utility Reference" (SC24-6081-00) for more information
-on the DEF STOR and Q NSS MAP commands, as well as "Saved Segments Planning
-and Administration" (SC24-6116-00) for more information on DCSSes.
-
-1st option:
------------
-You can use the CP command DEF STOR CONFIG to define a "memory hole" in your
-guest virtual storage around the address range of the DCSS.
-
-Example: DEF STOR CONFIG 0.140M 200M.200M
-
-This defines two blocks of storage, the first is 140MB in size an begins at
-address 0MB, the second is 200MB in size and begins at address 200MB,
-resulting in a total storage of 340MB. Note that the first block should
-always start at 0 and be at least 64MB in size.
-
-2nd option:
------------
-Your guest virtual storage has to end below the starting address of the DCSS
-and you have to specify the "mem=" kernel parameter in your parmfile with a
-value greater than the ending address of the DCSS.
-
-Example: DEF STOR 140M
-
-This defines 140MB storage size for your guest, the parameter "mem=160M" is
-added to the parmfile.
-
-
-User Interface
-==============
-The char device is implemented as a kernel module named "monreader",
-which can be loaded via the modprobe command, or it can be compiled into the
-kernel instead. There is one optional module (or kernel) parameter, "mondcss",
-to specify the name of the monitor DCSS. If the module is compiled into the
-kernel, the kernel parameter "monreader.mondcss=<DCSS NAME>" can be specified
-in the parmfile.
-
-The default name for the DCSS is "MONDCSS" if none is specified. In case that
-there are other users already connected to the *MONITOR service (e.g.
-Performance Toolkit), the monitor DCSS is already defined and you have to use
-the same DCSS. The CP command Q MONITOR (Class E privileged) shows the name
-of the monitor DCSS, if already defined, and the users connected to the
-*MONITOR service.
-Refer to the "z/VM Performance" book (SC24-6109-00) on how to create a monitor
-DCSS if your z/VM doesn't have one already, you need Class E privileges to
-define and save a DCSS.
-
-Example:
---------
-modprobe monreader mondcss=MYDCSS
-
-This loads the module and sets the DCSS name to "MYDCSS".
-
-NOTE:
------
-This API provides no interface to control the *MONITOR service, e.g. specify
-which data should be collected. This can be done by the CP command MONITOR
-(Class E privileged), see "CP Command and Utility Reference".
-
-Device nodes with udev:
------------------------
-After loading the module, a char device will be created along with the device
-node /<udev directory>/monreader.
-
-Device nodes without udev:
---------------------------
-If your distribution does not support udev, a device node will not be created
-automatically and you have to create it manually after loading the module.
-Therefore you need to know the major and minor numbers of the device. These
-numbers can be found in /sys/class/misc/monreader/dev.
-Typing cat /sys/class/misc/monreader/dev will give an output of the form
-<major>:<minor>. The device node can be created via the mknod command, enter
-mknod <name> c <major> <minor>, where <name> is the name of the device node
-to be created.
-
-Example:
---------
-# modprobe monreader
-# cat /sys/class/misc/monreader/dev
-10:63
-# mknod /dev/monreader c 10 63
-
-This loads the module with the default monitor DCSS (MONDCSS) and creates a
-device node.
-
-File operations:
-----------------
-The following file operations are supported: open, release, read, poll.
-There are two alternative methods for reading: either non-blocking read in
-conjunction with polling, or blocking read without polling. IOCTLs are not
-supported.
-
-Read:
------
-Reading from the device provides a 12 Byte monitor control element (MCE),
-followed by a set of one or more contiguous monitor records (similar to the
-output of the CMS utility MONWRITE without the 4K control blocks). The MCE
-contains information on the type of the following record set (sample/event
-data), the monitor domains contained within it and the start and end address
-of the record set in the monitor DCSS. The start and end address can be used
-to determine the size of the record set, the end address is the address of the
-last byte of data. The start address is needed to handle "end-of-frame" records
-correctly (domain 1, record 13), i.e. it can be used to determine the record
-start offset relative to a 4K page (frame) boundary.
-
-See "Appendix A: *MONITOR" in the "z/VM Performance" document for a description
-of the monitor control element layout. The layout of the monitor records can
-be found here (z/VM 5.1): http://www.vm.ibm.com/pubs/mon510/index.html
-
-The layout of the data stream provided by the monreader device is as follows:
-...
-<0 byte read>
-<first MCE> \
-<first set of records> |
-... |- data set
-<last MCE> |
-<last set of records> /
-<0 byte read>
-...
-
-There may be more than one combination of MCE and corresponding record set
-within one data set and the end of each data set is indicated by a successful
-read with a return value of 0 (0 byte read).
-Any received data must be considered invalid until a complete set was
-read successfully, including the closing 0 byte read. Therefore you should
-always read the complete set into a buffer before processing the data.
-
-The maximum size of a data set can be as large as the size of the
-monitor DCSS, so design the buffer adequately or use dynamic memory allocation.
-The size of the monitor DCSS will be printed into syslog after loading the
-module. You can also use the (Class E privileged) CP command Q NSS MAP to
-list all available segments and information about them.
-
-As with most char devices, error conditions are indicated by returning a
-negative value for the number of bytes read. In this case, the errno variable
-indicates the error condition:
-
-EIO: reply failed, read data is invalid and the application
- should discard the data read since the last successful read with 0 size.
-EFAULT: copy_to_user failed, read data is invalid and the application should
- discard the data read since the last successful read with 0 size.
-EAGAIN: occurs on a non-blocking read if there is no data available at the
- moment. There is no data missing or corrupted, just try again or rather
- use polling for non-blocking reads.
-EOVERFLOW: message limit reached, the data read since the last successful
- read with 0 size is valid but subsequent records may be missing.
-
-In the last case (EOVERFLOW) there may be missing data, in the first two cases
-(EIO, EFAULT) there will be missing data. It's up to the application if it will
-continue reading subsequent data or rather exit.
-
-Open:
------
-Only one user is allowed to open the char device. If it is already in use, the
-open function will fail (return a negative value) and set errno to EBUSY.
-The open function may also fail if an IUCV connection to the *MONITOR service
-cannot be established. In this case errno will be set to EIO and an error
-message with an IPUSER SEVER code will be printed into syslog. The IPUSER SEVER
-codes are described in the "z/VM Performance" book, Appendix A.
-
-NOTE:
------
-As soon as the device is opened, incoming messages will be accepted and they
-will account for the message limit, i.e. opening the device without reading
-from it will provoke the "message limit reached" error (EOVERFLOW error code)
-eventually.
-
--- /dev/null
+=============================
+IBM s390 QDIO Ethernet Driver
+=============================
+
+OSA and HiperSockets Bridge Port Support
+========================================
+
+Uevents
+-------
+
+To generate the events the device must be assigned a role of either
+a primary or a secondary Bridge Port. For more information, see
+"z/VM Connectivity, SC24-6174".
+
+When run on an OSA or HiperSockets Bridge Capable Port hardware, and the state
+of some configured Bridge Port device on the channel changes, a udev
+event with ACTION=CHANGE is emitted on behalf of the corresponding
+ccwgroup device. The event has the following attributes:
+
+BRIDGEPORT=statechange
+ indicates that the Bridge Port device changed
+ its state.
+
+ROLE={primary|secondary|none}
+ the role assigned to the port.
+
+STATE={active|standby|inactive}
+ the newly assumed state of the port.
+
+When run on HiperSockets Bridge Capable Port hardware with host address
+notifications enabled, a udev event with ACTION=CHANGE is emitted.
+It is emitted on behalf of the corresponding ccwgroup device when a host
+or a VLAN is registered or unregistered on the network served by the device.
+The event has the following attributes:
+
+BRIDGEDHOST={reset|register|deregister|abort}
+ host address
+ notifications are started afresh, a new host or VLAN is registered or
+ deregistered on the Bridge Port HiperSockets channel, or address
+ notifications are aborted.
+
+VLAN=numeric-vlan-id
+ VLAN ID on which the event occurred. Not included
+ if no VLAN is involved in the event.
+
+MAC=xx:xx:xx:xx:xx:xx
+ MAC address of the host that is being registered
+ or deregistered from the HiperSockets channel. Not reported if the
+ event reports the creation or destruction of a VLAN.
+
+NTOK_BUSID=x.y.zzzz
+ device bus ID (CSSID, SSID and device number).
+
+NTOK_IID=xx
+ device IID.
+
+NTOK_CHPID=xx
+ device CHPID.
+
+NTOK_CHID=xxxx
+ device channel ID.
+
+Note that the `NTOK_*` attributes refer to devices other than the one
+connected to the system on which the OS is running.
+++ /dev/null
-IBM s390 QDIO Ethernet Driver
-
-OSA and HiperSockets Bridge Port Support
-
-Uevents
-
-To generate the events the device must be assigned a role of either
-a primary or a secondary Bridge Port. For more information, see
-"z/VM Connectivity, SC24-6174".
-
-When run on an OSA or HiperSockets Bridge Capable Port hardware, and the state
-of some configured Bridge Port device on the channel changes, a udev
-event with ACTION=CHANGE is emitted on behalf of the corresponding
-ccwgroup device. The event has the following attributes:
-
-BRIDGEPORT=statechange - indicates that the Bridge Port device changed
- its state.
-
-ROLE={primary|secondary|none} - the role assigned to the port.
-
-STATE={active|standby|inactive} - the newly assumed state of the port.
-
-When run on HiperSockets Bridge Capable Port hardware with host address
-notifications enabled, a udev event with ACTION=CHANGE is emitted.
-It is emitted on behalf of the corresponding ccwgroup device when a host
-or a VLAN is registered or unregistered on the network served by the device.
-The event has the following attributes:
-
-BRIDGEDHOST={reset|register|deregister|abort} - host address
- notifications are started afresh, a new host or VLAN is registered or
- deregistered on the Bridge Port HiperSockets channel, or address
- notifications are aborted.
-
-VLAN=numeric-vlan-id - VLAN ID on which the event occurred. Not included
- if no VLAN is involved in the event.
-
-MAC=xx:xx:xx:xx:xx:xx - MAC address of the host that is being registered
- or deregistered from the HiperSockets channel. Not reported if the
- event reports the creation or destruction of a VLAN.
-
-NTOK_BUSID=x.y.zzzz - device bus ID (CSSID, SSID and device number).
-
-NTOK_IID=xx - device IID.
-
-NTOK_CHPID=xx - device CHPID.
-
-NTOK_CHID=xxxx - device channel ID.
-
-Note that the NTOK_* attributes refer to devices other than the one
-connected to the system on which the OS is running.
--- /dev/null
+==================
+S390 Debug Feature
+==================
+
+files:
+ - arch/s390/kernel/debug.c
+ - arch/s390/include/asm/debug.h
+
+Description:
+------------
+The goal of this feature is to provide a kernel debug logging API
+where log records can be stored efficiently in memory, where each component
+(e.g. device drivers) can have one separate debug log.
+One purpose of this is to inspect the debug logs after a production system crash
+in order to analyze the reason for the crash.
+
+If the system still runs but only a subcomponent which uses dbf fails,
+it is possible to look at the debug logs on a live system via the Linux
+debugfs filesystem.
+
+The debug feature may also very useful for kernel and driver development.
+
+Design:
+-------
+Kernel components (e.g. device drivers) can register themselves at the debug
+feature with the function call debug_register(). This function initializes a
+debug log for the caller. For each debug log exists a number of debug areas
+where exactly one is active at one time. Each debug area consists of contiguous
+pages in memory. In the debug areas there are stored debug entries (log records)
+which are written by event- and exception-calls.
+
+An event-call writes the specified debug entry to the active debug
+area and updates the log pointer for the active area. If the end
+of the active debug area is reached, a wrap around is done (ring buffer)
+and the next debug entry will be written at the beginning of the active
+debug area.
+
+An exception-call writes the specified debug entry to the log and
+switches to the next debug area. This is done in order to be sure
+that the records which describe the origin of the exception are not
+overwritten when a wrap around for the current area occurs.
+
+The debug areas themselves are also ordered in form of a ring buffer.
+When an exception is thrown in the last debug area, the following debug
+entries are then written again in the very first area.
+
+There are three versions for the event- and exception-calls: One for
+logging raw data, one for text and one for numbers.
+
+Each debug entry contains the following data:
+
+- Timestamp
+- Cpu-Number of calling task
+- Level of debug entry (0...6)
+- Return Address to caller
+- Flag, if entry is an exception or not
+
+The debug logs can be inspected in a live system through entries in
+the debugfs-filesystem. Under the toplevel directory "s390dbf" there is
+a directory for each registered component, which is named like the
+corresponding component. The debugfs normally should be mounted to
+/sys/kernel/debug therefore the debug feature can be accessed under
+/sys/kernel/debug/s390dbf.
+
+The content of the directories are files which represent different views
+to the debug log. Each component can decide which views should be
+used through registering them with the function debug_register_view().
+Predefined views for hex/ascii, sprintf and raw binary data are provided.
+It is also possible to define other views. The content of
+a view can be inspected simply by reading the corresponding debugfs file.
+
+All debug logs have an actual debug level (range from 0 to 6).
+The default level is 3. Event and Exception functions have a 'level'
+parameter. Only debug entries with a level that is lower or equal
+than the actual level are written to the log. This means, when
+writing events, high priority log entries should have a low level
+value whereas low priority entries should have a high one.
+The actual debug level can be changed with the help of the debugfs-filesystem
+through writing a number string "x" to the 'level' debugfs file which is
+provided for every debug log. Debugging can be switched off completely
+by using "-" on the 'level' debugfs file.
+
+Example::
+
+ > echo "-" > /sys/kernel/debug/s390dbf/dasd/level
+
+It is also possible to deactivate the debug feature globally for every
+debug log. You can change the behavior using 2 sysctl parameters in
+/proc/sys/s390dbf:
+
+There are currently 2 possible triggers, which stop the debug feature
+globally. The first possibility is to use the "debug_active" sysctl. If
+set to 1 the debug feature is running. If "debug_active" is set to 0 the
+debug feature is turned off.
+
+The second trigger which stops the debug feature is a kernel oops.
+That prevents the debug feature from overwriting debug information that
+happened before the oops. After an oops you can reactivate the debug feature
+by piping 1 to /proc/sys/s390dbf/debug_active. Nevertheless, its not
+suggested to use an oopsed kernel in a production environment.
+
+If you want to disallow the deactivation of the debug feature, you can use
+the "debug_stoppable" sysctl. If you set "debug_stoppable" to 0 the debug
+feature cannot be stopped. If the debug feature is already stopped, it
+will stay deactivated.
+
+----------------------------------------------------------------------------
+
+Kernel Interfaces:
+------------------
+
+::
+
+ debug_info_t *debug_register(char *name, int pages, int nr_areas,
+ int buf_size);
+
+Parameter:
+ name:
+ Name of debug log (e.g. used for debugfs entry)
+ pages:
+ Number of pages, which will be allocated per area
+ nr_areas:
+ Number of debug areas
+ buf_size:
+ Size of data area in each debug entry
+
+Return Value:
+ Handle for generated debug area
+
+ NULL if register failed
+
+Description: Allocates memory for a debug log
+ Must not be called within an interrupt handler
+
+----------------------------------------------------------------------------
+
+::
+
+ debug_info_t *debug_register_mode(char *name, int pages, int nr_areas,
+ int buf_size, mode_t mode, uid_t uid,
+ gid_t gid);
+
+Parameter:
+ name:
+ Name of debug log (e.g. used for debugfs entry)
+ pages:
+ Number of pages, which will be allocated per area
+ nr_areas:
+ Number of debug areas
+ buf_size:
+ Size of data area in each debug entry
+ mode:
+ File mode for debugfs files. E.g. S_IRWXUGO
+ uid:
+ User ID for debugfs files. Currently only 0 is
+ supported.
+ gid:
+ Group ID for debugfs files. Currently only 0 is
+ supported.
+
+Return Value:
+ Handle for generated debug area
+
+ NULL if register failed
+
+Description:
+ Allocates memory for a debug log
+ Must not be called within an interrupt handler
+
+---------------------------------------------------------------------------
+
+::
+
+ void debug_unregister (debug_info_t * id);
+
+Parameter:
+ id:
+ handle for debug log
+
+Return Value:
+ none
+
+Description:
+ frees memory for a debug log and removes all registered debug
+ views.
+
+ Must not be called within an interrupt handler
+
+---------------------------------------------------------------------------
+
+::
+
+ void debug_set_level (debug_info_t * id, int new_level);
+
+Parameter: id: handle for debug log
+ new_level: new debug level
+
+Return Value:
+ none
+
+Description:
+ Sets new actual debug level if new_level is valid.
+
+---------------------------------------------------------------------------
+
+::
+
+ bool debug_level_enabled (debug_info_t * id, int level);
+
+Parameter:
+ id:
+ handle for debug log
+ level:
+ debug level
+
+Return Value:
+ True if level is less or equal to the current debug level.
+
+Description:
+ Returns true if debug events for the specified level would be
+ logged. Otherwise returns false.
+
+---------------------------------------------------------------------------
+
+::
+
+ void debug_stop_all(void);
+
+Parameter:
+ none
+
+Return Value:
+ none
+
+Description:
+ stops the debug feature if stopping is allowed. Currently
+ used in case of a kernel oops.
+
+---------------------------------------------------------------------------
+
+::
+
+ debug_entry_t* debug_event (debug_info_t* id, int level, void* data,
+ int length);
+
+Parameter:
+ id:
+ handle for debug log
+ level:
+ debug level
+ data:
+ pointer to data for debug entry
+ length:
+ length of data in bytes
+
+Return Value:
+ Address of written debug entry
+
+Description:
+ writes debug entry to active debug area (if level <= actual
+ debug level)
+
+---------------------------------------------------------------------------
+
+::
+
+ debug_entry_t* debug_int_event (debug_info_t * id, int level,
+ unsigned int data);
+ debug_entry_t* debug_long_event(debug_info_t * id, int level,
+ unsigned long data);
+
+Parameter:
+ id:
+ handle for debug log
+ level:
+ debug level
+ data:
+ integer value for debug entry
+
+Return Value:
+ Address of written debug entry
+
+Description:
+ writes debug entry to active debug area (if level <= actual
+ debug level)
+
+---------------------------------------------------------------------------
+
+::
+
+ debug_entry_t* debug_text_event (debug_info_t * id, int level,
+ const char* data);
+
+Parameter:
+ id:
+ handle for debug log
+ level:
+ debug level
+ data:
+ string for debug entry
+
+Return Value:
+ Address of written debug entry
+
+Description:
+ writes debug entry in ascii format to active debug area
+ (if level <= actual debug level)
+
+---------------------------------------------------------------------------
+
+::
+
+ debug_entry_t* debug_sprintf_event (debug_info_t * id, int level,
+ char* string,...);
+
+Parameter:
+ id:
+ handle for debug log
+ level:
+ debug level
+ string:
+ format string for debug entry
+ ...:
+ varargs used as in sprintf()
+
+Return Value: Address of written debug entry
+
+Description:
+ writes debug entry with format string and varargs (longs) to
+ active debug area (if level $<=$ actual debug level).
+ floats and long long datatypes cannot be used as varargs.
+
+---------------------------------------------------------------------------
+
+::
+
+ debug_entry_t* debug_exception (debug_info_t* id, int level, void* data,
+ int length);
+
+Parameter:
+ id:
+ handle for debug log
+ level:
+ debug level
+ data:
+ pointer to data for debug entry
+ length:
+ length of data in bytes
+
+Return Value:
+ Address of written debug entry
+
+Description:
+ writes debug entry to active debug area (if level <= actual
+ debug level) and switches to next debug area
+
+---------------------------------------------------------------------------
+
+::
+
+ debug_entry_t* debug_int_exception (debug_info_t * id, int level,
+ unsigned int data);
+ debug_entry_t* debug_long_exception(debug_info_t * id, int level,
+ unsigned long data);
+
+Parameter: id: handle for debug log
+ level: debug level
+ data: integer value for debug entry
+
+Return Value: Address of written debug entry
+
+Description: writes debug entry to active debug area (if level <= actual
+ debug level) and switches to next debug area
+
+---------------------------------------------------------------------------
+
+::
+
+ debug_entry_t* debug_text_exception (debug_info_t * id, int level,
+ const char* data);
+
+Parameter: id: handle for debug log
+ level: debug level
+ data: string for debug entry
+
+Return Value: Address of written debug entry
+
+Description: writes debug entry in ascii format to active debug area
+ (if level <= actual debug level) and switches to next debug
+ area
+
+---------------------------------------------------------------------------
+
+::
+
+ debug_entry_t* debug_sprintf_exception (debug_info_t * id, int level,
+ char* string,...);
+
+Parameter: id: handle for debug log
+ level: debug level
+ string: format string for debug entry
+ ...: varargs used as in sprintf()
+
+Return Value: Address of written debug entry
+
+Description: writes debug entry with format string and varargs (longs) to
+ active debug area (if level $<=$ actual debug level) and
+ switches to next debug area.
+ floats and long long datatypes cannot be used as varargs.
+
+---------------------------------------------------------------------------
+
+::
+
+ int debug_register_view (debug_info_t * id, struct debug_view *view);
+
+Parameter: id: handle for debug log
+ view: pointer to debug view struct
+
+Return Value: 0 : ok
+ < 0: Error
+
+Description: registers new debug view and creates debugfs dir entry
+
+---------------------------------------------------------------------------
+
+::
+
+ int debug_unregister_view (debug_info_t * id, struct debug_view *view);
+
+Parameter: id: handle for debug log
+ view: pointer to debug view struct
+
+Return Value: 0 : ok
+ < 0: Error
+
+Description: unregisters debug view and removes debugfs dir entry
+
+
+
+Predefined views:
+-----------------
+
+extern struct debug_view debug_hex_ascii_view;
+
+extern struct debug_view debug_raw_view;
+
+extern struct debug_view debug_sprintf_view;
+
+Examples
+--------
+
+::
+
+ /*
+ * hex_ascii- + raw-view Example
+ */
+
+ #include <linux/init.h>
+ #include <asm/debug.h>
+
+ static debug_info_t* debug_info;
+
+ static int init(void)
+ {
+ /* register 4 debug areas with one page each and 4 byte data field */
+
+ debug_info = debug_register ("test", 1, 4, 4 );
+ debug_register_view(debug_info,&debug_hex_ascii_view);
+ debug_register_view(debug_info,&debug_raw_view);
+
+ debug_text_event(debug_info, 4 , "one ");
+ debug_int_exception(debug_info, 4, 4711);
+ debug_event(debug_info, 3, &debug_info, 4);
+
+ return 0;
+ }
+
+ static void cleanup(void)
+ {
+ debug_unregister (debug_info);
+ }
+
+ module_init(init);
+ module_exit(cleanup);
+
+---------------------------------------------------------------------------
+
+::
+
+ /*
+ * sprintf-view Example
+ */
+
+ #include <linux/init.h>
+ #include <asm/debug.h>
+
+ static debug_info_t* debug_info;
+
+ static int init(void)
+ {
+ /* register 4 debug areas with one page each and data field for */
+ /* format string pointer + 2 varargs (= 3 * sizeof(long)) */
+
+ debug_info = debug_register ("test", 1, 4, sizeof(long) * 3);
+ debug_register_view(debug_info,&debug_sprintf_view);
+
+ debug_sprintf_event(debug_info, 2 , "first event in %s:%i\n",__FILE__,__LINE__);
+ debug_sprintf_exception(debug_info, 1, "pointer to debug info: %p\n",&debug_info);
+
+ return 0;
+ }
+
+ static void cleanup(void)
+ {
+ debug_unregister (debug_info);
+ }
+
+ module_init(init);
+ module_exit(cleanup);
+
+Debugfs Interface
+-----------------
+Views to the debug logs can be investigated through reading the corresponding
+debugfs-files:
+
+Example::
+
+ > ls /sys/kernel/debug/s390dbf/dasd
+ flush hex_ascii level pages raw
+ > cat /sys/kernel/debug/s390dbf/dasd/hex_ascii | sort -k2,2 -s
+ 00 00974733272:680099 2 - 02 0006ad7e 07 ea 4a 90 | ....
+ 00 00974733272:682210 2 - 02 0006ade6 46 52 45 45 | FREE
+ 00 00974733272:682213 2 - 02 0006adf6 07 ea 4a 90 | ....
+ 00 00974733272:682281 1 * 02 0006ab08 41 4c 4c 43 | EXCP
+ 01 00974733272:682284 2 - 02 0006ab16 45 43 4b 44 | ECKD
+ 01 00974733272:682287 2 - 02 0006ab28 00 00 00 04 | ....
+ 01 00974733272:682289 2 - 02 0006ab3e 00 00 00 20 | ...
+ 01 00974733272:682297 2 - 02 0006ad7e 07 ea 4a 90 | ....
+ 01 00974733272:684384 2 - 00 0006ade6 46 52 45 45 | FREE
+ 01 00974733272:684388 2 - 00 0006adf6 07 ea 4a 90 | ....
+
+See section about predefined views for explanation of the above output!
+
+Changing the debug level
+------------------------
+
+Example::
+
+
+ > cat /sys/kernel/debug/s390dbf/dasd/level
+ 3
+ > echo "5" > /sys/kernel/debug/s390dbf/dasd/level
+ > cat /sys/kernel/debug/s390dbf/dasd/level
+ 5
+
+Flushing debug areas
+--------------------
+Debug areas can be flushed with piping the number of the desired
+area (0...n) to the debugfs file "flush". When using "-" all debug areas
+are flushed.
+
+Examples:
+
+1. Flush debug area 0::
+
+ > echo "0" > /sys/kernel/debug/s390dbf/dasd/flush
+
+2. Flush all debug areas::
+
+ > echo "-" > /sys/kernel/debug/s390dbf/dasd/flush
+
+Changing the size of debug areas
+------------------------------------
+It is possible the change the size of debug areas through piping
+the number of pages to the debugfs file "pages". The resize request will
+also flush the debug areas.
+
+Example:
+
+Define 4 pages for the debug areas of debug feature "dasd"::
+
+ > echo "4" > /sys/kernel/debug/s390dbf/dasd/pages
+
+Stooping the debug feature
+--------------------------
+Example:
+
+1. Check if stopping is allowed::
+
+ > cat /proc/sys/s390dbf/debug_stoppable
+
+2. Stop debug feature::
+
+ > echo 0 > /proc/sys/s390dbf/debug_active
+
+lcrash Interface
+----------------
+It is planned that the dump analysis tool lcrash gets an additional command
+'s390dbf' to display all the debug logs. With this tool it will be possible
+to investigate the debug logs on a live system and with a memory dump after
+a system crash.
+
+Investigating raw memory
+------------------------
+One last possibility to investigate the debug logs at a live
+system and after a system crash is to look at the raw memory
+under VM or at the Service Element.
+It is possible to find the anker of the debug-logs through
+the 'debug_area_first' symbol in the System map. Then one has
+to follow the correct pointers of the data-structures defined
+in debug.h and find the debug-areas in memory.
+Normally modules which use the debug feature will also have
+a global variable with the pointer to the debug-logs. Following
+this pointer it will also be possible to find the debug logs in
+memory.
+
+For this method it is recommended to use '16 * x + 4' byte (x = 0..n)
+for the length of the data field in debug_register() in
+order to see the debug entries well formatted.
+
+
+Predefined Views
+----------------
+
+There are three predefined views: hex_ascii, raw and sprintf.
+The hex_ascii view shows the data field in hex and ascii representation
+(e.g. '45 43 4b 44 | ECKD').
+The raw view returns a bytestream as the debug areas are stored in memory.
+
+The sprintf view formats the debug entries in the same way as the sprintf
+function would do. The sprintf event/exception functions write to the
+debug entry a pointer to the format string (size = sizeof(long))
+and for each vararg a long value. So e.g. for a debug entry with a format
+string plus two varargs one would need to allocate a (3 * sizeof(long))
+byte data area in the debug_register() function.
+
+IMPORTANT:
+ Using "%s" in sprintf event functions is dangerous. You can only
+ use "%s" in the sprintf event functions, if the memory for the passed string
+ is available as long as the debug feature exists. The reason behind this is
+ that due to performance considerations only a pointer to the string is stored
+ in the debug feature. If you log a string that is freed afterwards, you will
+ get an OOPS when inspecting the debug feature, because then the debug feature
+ will access the already freed memory.
+
+NOTE:
+ If using the sprintf view do NOT use other event/exception functions
+ than the sprintf-event and -exception functions.
+
+The format of the hex_ascii and sprintf view is as follows:
+
+- Number of area
+- Timestamp (formatted as seconds and microseconds since 00:00:00 Coordinated
+ Universal Time (UTC), January 1, 1970)
+- level of debug entry
+- Exception flag (* = Exception)
+- Cpu-Number of calling task
+- Return Address to caller
+- data field
+
+The format of the raw view is:
+
+- Header as described in debug.h
+- datafield
+
+A typical line of the hex_ascii view will look like the following (first line
+is only for explanation and will not be displayed when 'cating' the view):
+
+area time level exception cpu caller data (hex + ascii)
+--------------------------------------------------------------------------
+00 00964419409:440690 1 - 00 88023fe
+
+
+Defining views
+--------------
+
+Views are specified with the 'debug_view' structure. There are defined
+callback functions which are used for reading and writing the debugfs files::
+
+ struct debug_view {
+ char name[DEBUG_MAX_PROCF_LEN];
+ debug_prolog_proc_t* prolog_proc;
+ debug_header_proc_t* header_proc;
+ debug_format_proc_t* format_proc;
+ debug_input_proc_t* input_proc;
+ void* private_data;
+ };
+
+where::
+
+ typedef int (debug_header_proc_t) (debug_info_t* id,
+ struct debug_view* view,
+ int area,
+ debug_entry_t* entry,
+ char* out_buf);
+
+ typedef int (debug_format_proc_t) (debug_info_t* id,
+ struct debug_view* view, char* out_buf,
+ const char* in_buf);
+ typedef int (debug_prolog_proc_t) (debug_info_t* id,
+ struct debug_view* view,
+ char* out_buf);
+ typedef int (debug_input_proc_t) (debug_info_t* id,
+ struct debug_view* view,
+ struct file* file, const char* user_buf,
+ size_t in_buf_size, loff_t* offset);
+
+
+The "private_data" member can be used as pointer to view specific data.
+It is not used by the debug feature itself.
+
+The output when reading a debugfs file is structured like this::
+
+ "prolog_proc output"
+
+ "header_proc output 1" "format_proc output 1"
+ "header_proc output 2" "format_proc output 2"
+ "header_proc output 3" "format_proc output 3"
+ ...
+
+When a view is read from the debugfs, the Debug Feature calls the
+'prolog_proc' once for writing the prolog.
+Then 'header_proc' and 'format_proc' are called for each
+existing debug entry.
+
+The input_proc can be used to implement functionality when it is written to
+the view (e.g. like with 'echo "0" > /sys/kernel/debug/s390dbf/dasd/level).
+
+For header_proc there can be used the default function
+debug_dflt_header_fn() which is defined in debug.h.
+and which produces the same header output as the predefined views.
+E.g::
+
+ 00 00964419409:440761 2 - 00 88023ec
+
+In order to see how to use the callback functions check the implementation
+of the default views!
+
+Example::
+
+ #include <asm/debug.h>
+
+ #define UNKNOWNSTR "data: %08x"
+
+ const char* messages[] =
+ {"This error...........\n",
+ "That error...........\n",
+ "Problem..............\n",
+ "Something went wrong.\n",
+ "Everything ok........\n",
+ NULL
+ };
+
+ static int debug_test_format_fn(
+ debug_info_t * id, struct debug_view *view,
+ char *out_buf, const char *in_buf
+ )
+ {
+ int i, rc = 0;
+
+ if(id->buf_size >= 4) {
+ int msg_nr = *((int*)in_buf);
+ if(msg_nr < sizeof(messages)/sizeof(char*) - 1)
+ rc += sprintf(out_buf, "%s", messages[msg_nr]);
+ else
+ rc += sprintf(out_buf, UNKNOWNSTR, msg_nr);
+ }
+ out:
+ return rc;
+ }
+
+ struct debug_view debug_test_view = {
+ "myview", /* name of view */
+ NULL, /* no prolog */
+ &debug_dflt_header_fn, /* default header for each entry */
+ &debug_test_format_fn, /* our own format function */
+ NULL, /* no input function */
+ NULL /* no private data */
+ };
+
+test:
+=====
+
+::
+
+ debug_info_t *debug_info;
+ ...
+ debug_info = debug_register ("test", 0, 4, 4 ));
+ debug_register_view(debug_info, &debug_test_view);
+ for(i = 0; i < 10; i ++) debug_int_event(debug_info, 1, i);
+
+ > cat /sys/kernel/debug/s390dbf/test/myview
+ 00 00964419734:611402 1 - 00 88042ca This error...........
+ 00 00964419734:611405 1 - 00 88042ca That error...........
+ 00 00964419734:611408 1 - 00 88042ca Problem..............
+ 00 00964419734:611411 1 - 00 88042ca Something went wrong.
+ 00 00964419734:611414 1 - 00 88042ca Everything ok........
+ 00 00964419734:611417 1 - 00 88042ca data: 00000005
+ 00 00964419734:611419 1 - 00 88042ca data: 00000006
+ 00 00964419734:611422 1 - 00 88042ca data: 00000007
+ 00 00964419734:611425 1 - 00 88042ca data: 00000008
+ 00 00964419734:611428 1 - 00 88042ca data: 00000009
+++ /dev/null
-S390 Debug Feature
-==================
-
-files: arch/s390/kernel/debug.c
- arch/s390/include/asm/debug.h
-
-Description:
-------------
-The goal of this feature is to provide a kernel debug logging API
-where log records can be stored efficiently in memory, where each component
-(e.g. device drivers) can have one separate debug log.
-One purpose of this is to inspect the debug logs after a production system crash
-in order to analyze the reason for the crash.
-If the system still runs but only a subcomponent which uses dbf fails,
-it is possible to look at the debug logs on a live system via the Linux
-debugfs filesystem.
-The debug feature may also very useful for kernel and driver development.
-
-Design:
--------
-Kernel components (e.g. device drivers) can register themselves at the debug
-feature with the function call debug_register(). This function initializes a
-debug log for the caller. For each debug log exists a number of debug areas
-where exactly one is active at one time. Each debug area consists of contiguous
-pages in memory. In the debug areas there are stored debug entries (log records)
-which are written by event- and exception-calls.
-
-An event-call writes the specified debug entry to the active debug
-area and updates the log pointer for the active area. If the end
-of the active debug area is reached, a wrap around is done (ring buffer)
-and the next debug entry will be written at the beginning of the active
-debug area.
-
-An exception-call writes the specified debug entry to the log and
-switches to the next debug area. This is done in order to be sure
-that the records which describe the origin of the exception are not
-overwritten when a wrap around for the current area occurs.
-
-The debug areas themselves are also ordered in form of a ring buffer.
-When an exception is thrown in the last debug area, the following debug
-entries are then written again in the very first area.
-
-There are three versions for the event- and exception-calls: One for
-logging raw data, one for text and one for numbers.
-
-Each debug entry contains the following data:
-
-- Timestamp
-- Cpu-Number of calling task
-- Level of debug entry (0...6)
-- Return Address to caller
-- Flag, if entry is an exception or not
-
-The debug logs can be inspected in a live system through entries in
-the debugfs-filesystem. Under the toplevel directory "s390dbf" there is
-a directory for each registered component, which is named like the
-corresponding component. The debugfs normally should be mounted to
-/sys/kernel/debug therefore the debug feature can be accessed under
-/sys/kernel/debug/s390dbf.
-
-The content of the directories are files which represent different views
-to the debug log. Each component can decide which views should be
-used through registering them with the function debug_register_view().
-Predefined views for hex/ascii, sprintf and raw binary data are provided.
-It is also possible to define other views. The content of
-a view can be inspected simply by reading the corresponding debugfs file.
-
-All debug logs have an actual debug level (range from 0 to 6).
-The default level is 3. Event and Exception functions have a 'level'
-parameter. Only debug entries with a level that is lower or equal
-than the actual level are written to the log. This means, when
-writing events, high priority log entries should have a low level
-value whereas low priority entries should have a high one.
-The actual debug level can be changed with the help of the debugfs-filesystem
-through writing a number string "x" to the 'level' debugfs file which is
-provided for every debug log. Debugging can be switched off completely
-by using "-" on the 'level' debugfs file.
-
-Example:
-
-> echo "-" > /sys/kernel/debug/s390dbf/dasd/level
-
-It is also possible to deactivate the debug feature globally for every
-debug log. You can change the behavior using 2 sysctl parameters in
-/proc/sys/s390dbf:
-There are currently 2 possible triggers, which stop the debug feature
-globally. The first possibility is to use the "debug_active" sysctl. If
-set to 1 the debug feature is running. If "debug_active" is set to 0 the
-debug feature is turned off.
-The second trigger which stops the debug feature is a kernel oops.
-That prevents the debug feature from overwriting debug information that
-happened before the oops. After an oops you can reactivate the debug feature
-by piping 1 to /proc/sys/s390dbf/debug_active. Nevertheless, its not
-suggested to use an oopsed kernel in a production environment.
-If you want to disallow the deactivation of the debug feature, you can use
-the "debug_stoppable" sysctl. If you set "debug_stoppable" to 0 the debug
-feature cannot be stopped. If the debug feature is already stopped, it
-will stay deactivated.
-
-Kernel Interfaces:
-------------------
-
-----------------------------------------------------------------------------
-debug_info_t *debug_register(char *name, int pages, int nr_areas,
- int buf_size);
-
-Parameter: name: Name of debug log (e.g. used for debugfs entry)
- pages: number of pages, which will be allocated per area
- nr_areas: number of debug areas
- buf_size: size of data area in each debug entry
-
-Return Value: Handle for generated debug area
- NULL if register failed
-
-Description: Allocates memory for a debug log
- Must not be called within an interrupt handler
-
-----------------------------------------------------------------------------
-debug_info_t *debug_register_mode(char *name, int pages, int nr_areas,
- int buf_size, mode_t mode, uid_t uid,
- gid_t gid);
-
-Parameter: name: Name of debug log (e.g. used for debugfs entry)
- pages: Number of pages, which will be allocated per area
- nr_areas: Number of debug areas
- buf_size: Size of data area in each debug entry
- mode: File mode for debugfs files. E.g. S_IRWXUGO
- uid: User ID for debugfs files. Currently only 0 is
- supported.
- gid: Group ID for debugfs files. Currently only 0 is
- supported.
-
-Return Value: Handle for generated debug area
- NULL if register failed
-
-Description: Allocates memory for a debug log
- Must not be called within an interrupt handler
-
----------------------------------------------------------------------------
-void debug_unregister (debug_info_t * id);
-
-Parameter: id: handle for debug log
-
-Return Value: none
-
-Description: frees memory for a debug log and removes all registered debug
- views.
- Must not be called within an interrupt handler
-
----------------------------------------------------------------------------
-void debug_set_level (debug_info_t * id, int new_level);
-
-Parameter: id: handle for debug log
- new_level: new debug level
-
-Return Value: none
-
-Description: Sets new actual debug level if new_level is valid.
-
----------------------------------------------------------------------------
-bool debug_level_enabled (debug_info_t * id, int level);
-
-Parameter: id: handle for debug log
- level: debug level
-
-Return Value: True if level is less or equal to the current debug level.
-
-Description: Returns true if debug events for the specified level would be
- logged. Otherwise returns false.
----------------------------------------------------------------------------
-void debug_stop_all(void);
-
-Parameter: none
-
-Return Value: none
-
-Description: stops the debug feature if stopping is allowed. Currently
- used in case of a kernel oops.
-
----------------------------------------------------------------------------
-debug_entry_t* debug_event (debug_info_t* id, int level, void* data,
- int length);
-
-Parameter: id: handle for debug log
- level: debug level
- data: pointer to data for debug entry
- length: length of data in bytes
-
-Return Value: Address of written debug entry
-
-Description: writes debug entry to active debug area (if level <= actual
- debug level)
-
----------------------------------------------------------------------------
-debug_entry_t* debug_int_event (debug_info_t * id, int level,
- unsigned int data);
-debug_entry_t* debug_long_event(debug_info_t * id, int level,
- unsigned long data);
-
-Parameter: id: handle for debug log
- level: debug level
- data: integer value for debug entry
-
-Return Value: Address of written debug entry
-
-Description: writes debug entry to active debug area (if level <= actual
- debug level)
-
----------------------------------------------------------------------------
-debug_entry_t* debug_text_event (debug_info_t * id, int level,
- const char* data);
-
-Parameter: id: handle for debug log
- level: debug level
- data: string for debug entry
-
-Return Value: Address of written debug entry
-
-Description: writes debug entry in ascii format to active debug area
- (if level <= actual debug level)
-
----------------------------------------------------------------------------
-debug_entry_t* debug_sprintf_event (debug_info_t * id, int level,
- char* string,...);
-
-Parameter: id: handle for debug log
- level: debug level
- string: format string for debug entry
- ...: varargs used as in sprintf()
-
-Return Value: Address of written debug entry
-
-Description: writes debug entry with format string and varargs (longs) to
- active debug area (if level $<=$ actual debug level).
- floats and long long datatypes cannot be used as varargs.
-
----------------------------------------------------------------------------
-
-debug_entry_t* debug_exception (debug_info_t* id, int level, void* data,
- int length);
-
-Parameter: id: handle for debug log
- level: debug level
- data: pointer to data for debug entry
- length: length of data in bytes
-
-Return Value: Address of written debug entry
-
-Description: writes debug entry to active debug area (if level <= actual
- debug level) and switches to next debug area
-
----------------------------------------------------------------------------
-debug_entry_t* debug_int_exception (debug_info_t * id, int level,
- unsigned int data);
-debug_entry_t* debug_long_exception(debug_info_t * id, int level,
- unsigned long data);
-
-Parameter: id: handle for debug log
- level: debug level
- data: integer value for debug entry
-
-Return Value: Address of written debug entry
-
-Description: writes debug entry to active debug area (if level <= actual
- debug level) and switches to next debug area
-
----------------------------------------------------------------------------
-debug_entry_t* debug_text_exception (debug_info_t * id, int level,
- const char* data);
-
-Parameter: id: handle for debug log
- level: debug level
- data: string for debug entry
-
-Return Value: Address of written debug entry
-
-Description: writes debug entry in ascii format to active debug area
- (if level <= actual debug level) and switches to next debug
- area
-
----------------------------------------------------------------------------
-debug_entry_t* debug_sprintf_exception (debug_info_t * id, int level,
- char* string,...);
-
-Parameter: id: handle for debug log
- level: debug level
- string: format string for debug entry
- ...: varargs used as in sprintf()
-
-Return Value: Address of written debug entry
-
-Description: writes debug entry with format string and varargs (longs) to
- active debug area (if level $<=$ actual debug level) and
- switches to next debug area.
- floats and long long datatypes cannot be used as varargs.
-
----------------------------------------------------------------------------
-
-int debug_register_view (debug_info_t * id, struct debug_view *view);
-
-Parameter: id: handle for debug log
- view: pointer to debug view struct
-
-Return Value: 0 : ok
- < 0: Error
-
-Description: registers new debug view and creates debugfs dir entry
-
----------------------------------------------------------------------------
-int debug_unregister_view (debug_info_t * id, struct debug_view *view);
-
-Parameter: id: handle for debug log
- view: pointer to debug view struct
-
-Return Value: 0 : ok
- < 0: Error
-
-Description: unregisters debug view and removes debugfs dir entry
-
-
-
-Predefined views:
------------------
-
-extern struct debug_view debug_hex_ascii_view;
-extern struct debug_view debug_raw_view;
-extern struct debug_view debug_sprintf_view;
-
-Examples
---------
-
-/*
- * hex_ascii- + raw-view Example
- */
-
-#include <linux/init.h>
-#include <asm/debug.h>
-
-static debug_info_t* debug_info;
-
-static int init(void)
-{
- /* register 4 debug areas with one page each and 4 byte data field */
-
- debug_info = debug_register ("test", 1, 4, 4 );
- debug_register_view(debug_info,&debug_hex_ascii_view);
- debug_register_view(debug_info,&debug_raw_view);
-
- debug_text_event(debug_info, 4 , "one ");
- debug_int_exception(debug_info, 4, 4711);
- debug_event(debug_info, 3, &debug_info, 4);
-
- return 0;
-}
-
-static void cleanup(void)
-{
- debug_unregister (debug_info);
-}
-
-module_init(init);
-module_exit(cleanup);
-
----------------------------------------------------------------------------
-
-/*
- * sprintf-view Example
- */
-
-#include <linux/init.h>
-#include <asm/debug.h>
-
-static debug_info_t* debug_info;
-
-static int init(void)
-{
- /* register 4 debug areas with one page each and data field for */
- /* format string pointer + 2 varargs (= 3 * sizeof(long)) */
-
- debug_info = debug_register ("test", 1, 4, sizeof(long) * 3);
- debug_register_view(debug_info,&debug_sprintf_view);
-
- debug_sprintf_event(debug_info, 2 , "first event in %s:%i\n",__FILE__,__LINE__);
- debug_sprintf_exception(debug_info, 1, "pointer to debug info: %p\n",&debug_info);
-
- return 0;
-}
-
-static void cleanup(void)
-{
- debug_unregister (debug_info);
-}
-
-module_init(init);
-module_exit(cleanup);
-
-
-
-Debugfs Interface
-----------------
-Views to the debug logs can be investigated through reading the corresponding
-debugfs-files:
-
-Example:
-
-> ls /sys/kernel/debug/s390dbf/dasd
-flush hex_ascii level pages raw
-> cat /sys/kernel/debug/s390dbf/dasd/hex_ascii | sort -k2,2 -s
-00 00974733272:680099 2 - 02 0006ad7e 07 ea 4a 90 | ....
-00 00974733272:682210 2 - 02 0006ade6 46 52 45 45 | FREE
-00 00974733272:682213 2 - 02 0006adf6 07 ea 4a 90 | ....
-00 00974733272:682281 1 * 02 0006ab08 41 4c 4c 43 | EXCP
-01 00974733272:682284 2 - 02 0006ab16 45 43 4b 44 | ECKD
-01 00974733272:682287 2 - 02 0006ab28 00 00 00 04 | ....
-01 00974733272:682289 2 - 02 0006ab3e 00 00 00 20 | ...
-01 00974733272:682297 2 - 02 0006ad7e 07 ea 4a 90 | ....
-01 00974733272:684384 2 - 00 0006ade6 46 52 45 45 | FREE
-01 00974733272:684388 2 - 00 0006adf6 07 ea 4a 90 | ....
-
-See section about predefined views for explanation of the above output!
-
-Changing the debug level
-------------------------
-
-Example:
-
-
-> cat /sys/kernel/debug/s390dbf/dasd/level
-3
-> echo "5" > /sys/kernel/debug/s390dbf/dasd/level
-> cat /sys/kernel/debug/s390dbf/dasd/level
-5
-
-Flushing debug areas
---------------------
-Debug areas can be flushed with piping the number of the desired
-area (0...n) to the debugfs file "flush". When using "-" all debug areas
-are flushed.
-
-Examples:
-
-1. Flush debug area 0:
-> echo "0" > /sys/kernel/debug/s390dbf/dasd/flush
-
-2. Flush all debug areas:
-> echo "-" > /sys/kernel/debug/s390dbf/dasd/flush
-
-Changing the size of debug areas
-------------------------------------
-It is possible the change the size of debug areas through piping
-the number of pages to the debugfs file "pages". The resize request will
-also flush the debug areas.
-
-Example:
-
-Define 4 pages for the debug areas of debug feature "dasd":
-> echo "4" > /sys/kernel/debug/s390dbf/dasd/pages
-
-Stooping the debug feature
---------------------------
-Example:
-
-1. Check if stopping is allowed
-> cat /proc/sys/s390dbf/debug_stoppable
-2. Stop debug feature
-> echo 0 > /proc/sys/s390dbf/debug_active
-
-lcrash Interface
-----------------
-It is planned that the dump analysis tool lcrash gets an additional command
-'s390dbf' to display all the debug logs. With this tool it will be possible
-to investigate the debug logs on a live system and with a memory dump after
-a system crash.
-
-Investigating raw memory
-------------------------
-One last possibility to investigate the debug logs at a live
-system and after a system crash is to look at the raw memory
-under VM or at the Service Element.
-It is possible to find the anker of the debug-logs through
-the 'debug_area_first' symbol in the System map. Then one has
-to follow the correct pointers of the data-structures defined
-in debug.h and find the debug-areas in memory.
-Normally modules which use the debug feature will also have
-a global variable with the pointer to the debug-logs. Following
-this pointer it will also be possible to find the debug logs in
-memory.
-
-For this method it is recommended to use '16 * x + 4' byte (x = 0..n)
-for the length of the data field in debug_register() in
-order to see the debug entries well formatted.
-
-
-Predefined Views
-----------------
-
-There are three predefined views: hex_ascii, raw and sprintf.
-The hex_ascii view shows the data field in hex and ascii representation
-(e.g. '45 43 4b 44 | ECKD').
-The raw view returns a bytestream as the debug areas are stored in memory.
-
-The sprintf view formats the debug entries in the same way as the sprintf
-function would do. The sprintf event/exception functions write to the
-debug entry a pointer to the format string (size = sizeof(long))
-and for each vararg a long value. So e.g. for a debug entry with a format
-string plus two varargs one would need to allocate a (3 * sizeof(long))
-byte data area in the debug_register() function.
-
-IMPORTANT: Using "%s" in sprintf event functions is dangerous. You can only
-use "%s" in the sprintf event functions, if the memory for the passed string is
-available as long as the debug feature exists. The reason behind this is that
-due to performance considerations only a pointer to the string is stored in
-the debug feature. If you log a string that is freed afterwards, you will get
-an OOPS when inspecting the debug feature, because then the debug feature will
-access the already freed memory.
-
-NOTE: If using the sprintf view do NOT use other event/exception functions
-than the sprintf-event and -exception functions.
-
-The format of the hex_ascii and sprintf view is as follows:
-- Number of area
-- Timestamp (formatted as seconds and microseconds since 00:00:00 Coordinated
- Universal Time (UTC), January 1, 1970)
-- level of debug entry
-- Exception flag (* = Exception)
-- Cpu-Number of calling task
-- Return Address to caller
-- data field
-
-The format of the raw view is:
-- Header as described in debug.h
-- datafield
-
-A typical line of the hex_ascii view will look like the following (first line
-is only for explanation and will not be displayed when 'cating' the view):
-
-area time level exception cpu caller data (hex + ascii)
---------------------------------------------------------------------------
-00 00964419409:440690 1 - 00 88023fe
-
-
-Defining views
---------------
-
-Views are specified with the 'debug_view' structure. There are defined
-callback functions which are used for reading and writing the debugfs files:
-
-struct debug_view {
- char name[DEBUG_MAX_PROCF_LEN];
- debug_prolog_proc_t* prolog_proc;
- debug_header_proc_t* header_proc;
- debug_format_proc_t* format_proc;
- debug_input_proc_t* input_proc;
- void* private_data;
-};
-
-where
-
-typedef int (debug_header_proc_t) (debug_info_t* id,
- struct debug_view* view,
- int area,
- debug_entry_t* entry,
- char* out_buf);
-
-typedef int (debug_format_proc_t) (debug_info_t* id,
- struct debug_view* view, char* out_buf,
- const char* in_buf);
-typedef int (debug_prolog_proc_t) (debug_info_t* id,
- struct debug_view* view,
- char* out_buf);
-typedef int (debug_input_proc_t) (debug_info_t* id,
- struct debug_view* view,
- struct file* file, const char* user_buf,
- size_t in_buf_size, loff_t* offset);
-
-
-The "private_data" member can be used as pointer to view specific data.
-It is not used by the debug feature itself.
-
-The output when reading a debugfs file is structured like this:
-
-"prolog_proc output"
-
-"header_proc output 1" "format_proc output 1"
-"header_proc output 2" "format_proc output 2"
-"header_proc output 3" "format_proc output 3"
-...
-
-When a view is read from the debugfs, the Debug Feature calls the
-'prolog_proc' once for writing the prolog.
-Then 'header_proc' and 'format_proc' are called for each
-existing debug entry.
-
-The input_proc can be used to implement functionality when it is written to
-the view (e.g. like with 'echo "0" > /sys/kernel/debug/s390dbf/dasd/level).
-
-For header_proc there can be used the default function
-debug_dflt_header_fn() which is defined in debug.h.
-and which produces the same header output as the predefined views.
-E.g:
-00 00964419409:440761 2 - 00 88023ec
-
-In order to see how to use the callback functions check the implementation
-of the default views!
-
-Example
-
-#include <asm/debug.h>
-
-#define UNKNOWNSTR "data: %08x"
-
-const char* messages[] =
-{"This error...........\n",
- "That error...........\n",
- "Problem..............\n",
- "Something went wrong.\n",
- "Everything ok........\n",
- NULL
-};
-
-static int debug_test_format_fn(
- debug_info_t * id, struct debug_view *view,
- char *out_buf, const char *in_buf
-)
-{
- int i, rc = 0;
-
- if(id->buf_size >= 4) {
- int msg_nr = *((int*)in_buf);
- if(msg_nr < sizeof(messages)/sizeof(char*) - 1)
- rc += sprintf(out_buf, "%s", messages[msg_nr]);
- else
- rc += sprintf(out_buf, UNKNOWNSTR, msg_nr);
- }
- out:
- return rc;
-}
-
-struct debug_view debug_test_view = {
- "myview", /* name of view */
- NULL, /* no prolog */
- &debug_dflt_header_fn, /* default header for each entry */
- &debug_test_format_fn, /* our own format function */
- NULL, /* no input function */
- NULL /* no private data */
-};
-
-=====
-test:
-=====
-debug_info_t *debug_info;
-...
-debug_info = debug_register ("test", 0, 4, 4 ));
-debug_register_view(debug_info, &debug_test_view);
-for(i = 0; i < 10; i ++) debug_int_event(debug_info, 1, i);
-
-> cat /sys/kernel/debug/s390dbf/test/myview
-00 00964419734:611402 1 - 00 88042ca This error...........
-00 00964419734:611405 1 - 00 88042ca That error...........
-00 00964419734:611408 1 - 00 88042ca Problem..............
-00 00964419734:611411 1 - 00 88042ca Something went wrong.
-00 00964419734:611414 1 - 00 88042ca Everything ok........
-00 00964419734:611417 1 - 00 88042ca data: 00000005
-00 00964419734:611419 1 - 00 88042ca data: 00000006
-00 00964419734:611422 1 - 00 88042ca data: 00000007
-00 00964419734:611425 1 - 00 88042ca data: 00000008
-00 00964419734:611428 1 - 00 88042ca data: 00000009
--- /dev/null
+ibm 3270 changelog
+------------------
+
+.. include:: 3270.ChangeLog
+ :literal:
+
+ibm 3270 config3270.sh
+----------------------
+
+.. literalinclude:: config3270.sh
+ :language: shell
--- /dev/null
+===============================
+Adjunct Processor (AP) facility
+===============================
+
+
+Introduction
+============
+The Adjunct Processor (AP) facility is an IBM Z cryptographic facility comprised
+of three AP instructions and from 1 up to 256 PCIe cryptographic adapter cards.
+The AP devices provide cryptographic functions to all CPUs assigned to a
+linux system running in an IBM Z system LPAR.
+
+The AP adapter cards are exposed via the AP bus. The motivation for vfio-ap
+is to make AP cards available to KVM guests using the VFIO mediated device
+framework. This implementation relies considerably on the s390 virtualization
+facilities which do most of the hard work of providing direct access to AP
+devices.
+
+AP Architectural Overview
+=========================
+To facilitate the comprehension of the design, let's start with some
+definitions:
+
+* AP adapter
+
+ An AP adapter is an IBM Z adapter card that can perform cryptographic
+ functions. There can be from 0 to 256 adapters assigned to an LPAR. Adapters
+ assigned to the LPAR in which a linux host is running will be available to
+ the linux host. Each adapter is identified by a number from 0 to 255; however,
+ the maximum adapter number is determined by machine model and/or adapter type.
+ When installed, an AP adapter is accessed by AP instructions executed by any
+ CPU.
+
+ The AP adapter cards are assigned to a given LPAR via the system's Activation
+ Profile which can be edited via the HMC. When the linux host system is IPL'd
+ in the LPAR, the AP bus detects the AP adapter cards assigned to the LPAR and
+ creates a sysfs device for each assigned adapter. For example, if AP adapters
+ 4 and 10 (0x0a) are assigned to the LPAR, the AP bus will create the following
+ sysfs device entries::
+
+ /sys/devices/ap/card04
+ /sys/devices/ap/card0a
+
+ Symbolic links to these devices will also be created in the AP bus devices
+ sub-directory::
+
+ /sys/bus/ap/devices/[card04]
+ /sys/bus/ap/devices/[card04]
+
+* AP domain
+
+ An adapter is partitioned into domains. An adapter can hold up to 256 domains
+ depending upon the adapter type and hardware configuration. A domain is
+ identified by a number from 0 to 255; however, the maximum domain number is
+ determined by machine model and/or adapter type.. A domain can be thought of
+ as a set of hardware registers and memory used for processing AP commands. A
+ domain can be configured with a secure private key used for clear key
+ encryption. A domain is classified in one of two ways depending upon how it
+ may be accessed:
+
+ * Usage domains are domains that are targeted by an AP instruction to
+ process an AP command.
+
+ * Control domains are domains that are changed by an AP command sent to a
+ usage domain; for example, to set the secure private key for the control
+ domain.
+
+ The AP usage and control domains are assigned to a given LPAR via the system's
+ Activation Profile which can be edited via the HMC. When a linux host system
+ is IPL'd in the LPAR, the AP bus module detects the AP usage and control
+ domains assigned to the LPAR. The domain number of each usage domain and
+ adapter number of each AP adapter are combined to create AP queue devices
+ (see AP Queue section below). The domain number of each control domain will be
+ represented in a bitmask and stored in a sysfs file
+ /sys/bus/ap/ap_control_domain_mask. The bits in the mask, from most to least
+ significant bit, correspond to domains 0-255.
+
+* AP Queue
+
+ An AP queue is the means by which an AP command is sent to a usage domain
+ inside a specific adapter. An AP queue is identified by a tuple
+ comprised of an AP adapter ID (APID) and an AP queue index (APQI). The
+ APQI corresponds to a given usage domain number within the adapter. This tuple
+ forms an AP Queue Number (APQN) uniquely identifying an AP queue. AP
+ instructions include a field containing the APQN to identify the AP queue to
+ which the AP command is to be sent for processing.
+
+ The AP bus will create a sysfs device for each APQN that can be derived from
+ the cross product of the AP adapter and usage domain numbers detected when the
+ AP bus module is loaded. For example, if adapters 4 and 10 (0x0a) and usage
+ domains 6 and 71 (0x47) are assigned to the LPAR, the AP bus will create the
+ following sysfs entries::
+
+ /sys/devices/ap/card04/04.0006
+ /sys/devices/ap/card04/04.0047
+ /sys/devices/ap/card0a/0a.0006
+ /sys/devices/ap/card0a/0a.0047
+
+ The following symbolic links to these devices will be created in the AP bus
+ devices subdirectory::
+
+ /sys/bus/ap/devices/[04.0006]
+ /sys/bus/ap/devices/[04.0047]
+ /sys/bus/ap/devices/[0a.0006]
+ /sys/bus/ap/devices/[0a.0047]
+
+* AP Instructions:
+
+ There are three AP instructions:
+
+ * NQAP: to enqueue an AP command-request message to a queue
+ * DQAP: to dequeue an AP command-reply message from a queue
+ * PQAP: to administer the queues
+
+ AP instructions identify the domain that is targeted to process the AP
+ command; this must be one of the usage domains. An AP command may modify a
+ domain that is not one of the usage domains, but the modified domain
+ must be one of the control domains.
+
+AP and SIE
+==========
+Let's now take a look at how AP instructions executed on a guest are interpreted
+by the hardware.
+
+A satellite control block called the Crypto Control Block (CRYCB) is attached to
+our main hardware virtualization control block. The CRYCB contains three fields
+to identify the adapters, usage domains and control domains assigned to the KVM
+guest:
+
+* The AP Mask (APM) field is a bit mask that identifies the AP adapters assigned
+ to the KVM guest. Each bit in the mask, from left to right (i.e. from most
+ significant to least significant bit in big endian order), corresponds to
+ an APID from 0-255. If a bit is set, the corresponding adapter is valid for
+ use by the KVM guest.
+
+* The AP Queue Mask (AQM) field is a bit mask identifying the AP usage domains
+ assigned to the KVM guest. Each bit in the mask, from left to right (i.e. from
+ most significant to least significant bit in big endian order), corresponds to
+ an AP queue index (APQI) from 0-255. If a bit is set, the corresponding queue
+ is valid for use by the KVM guest.
+
+* The AP Domain Mask field is a bit mask that identifies the AP control domains
+ assigned to the KVM guest. The ADM bit mask controls which domains can be
+ changed by an AP command-request message sent to a usage domain from the
+ guest. Each bit in the mask, from left to right (i.e. from most significant to
+ least significant bit in big endian order), corresponds to a domain from
+ 0-255. If a bit is set, the corresponding domain can be modified by an AP
+ command-request message sent to a usage domain.
+
+If you recall from the description of an AP Queue, AP instructions include
+an APQN to identify the AP queue to which an AP command-request message is to be
+sent (NQAP and PQAP instructions), or from which a command-reply message is to
+be received (DQAP instruction). The validity of an APQN is defined by the matrix
+calculated from the APM and AQM; it is the cross product of all assigned adapter
+numbers (APM) with all assigned queue indexes (AQM). For example, if adapters 1
+and 2 and usage domains 5 and 6 are assigned to a guest, the APQNs (1,5), (1,6),
+(2,5) and (2,6) will be valid for the guest.
+
+The APQNs can provide secure key functionality - i.e., a private key is stored
+on the adapter card for each of its domains - so each APQN must be assigned to
+at most one guest or to the linux host::
+
+ Example 1: Valid configuration:
+ ------------------------------
+ Guest1: adapters 1,2 domains 5,6
+ Guest2: adapter 1,2 domain 7
+
+ This is valid because both guests have a unique set of APQNs:
+ Guest1 has APQNs (1,5), (1,6), (2,5), (2,6);
+ Guest2 has APQNs (1,7), (2,7)
+
+ Example 2: Valid configuration:
+ ------------------------------
+ Guest1: adapters 1,2 domains 5,6
+ Guest2: adapters 3,4 domains 5,6
+
+ This is also valid because both guests have a unique set of APQNs:
+ Guest1 has APQNs (1,5), (1,6), (2,5), (2,6);
+ Guest2 has APQNs (3,5), (3,6), (4,5), (4,6)
+
+ Example 3: Invalid configuration:
+ --------------------------------
+ Guest1: adapters 1,2 domains 5,6
+ Guest2: adapter 1 domains 6,7
+
+ This is an invalid configuration because both guests have access to
+ APQN (1,6).
+
+The Design
+==========
+The design introduces three new objects:
+
+1. AP matrix device
+2. VFIO AP device driver (vfio_ap.ko)
+3. VFIO AP mediated matrix pass-through device
+
+The VFIO AP device driver
+-------------------------
+The VFIO AP (vfio_ap) device driver serves the following purposes:
+
+1. Provides the interfaces to secure APQNs for exclusive use of KVM guests.
+
+2. Sets up the VFIO mediated device interfaces to manage a mediated matrix
+ device and creates the sysfs interfaces for assigning adapters, usage
+ domains, and control domains comprising the matrix for a KVM guest.
+
+3. Configures the APM, AQM and ADM in the CRYCB referenced by a KVM guest's
+ SIE state description to grant the guest access to a matrix of AP devices
+
+Reserve APQNs for exclusive use of KVM guests
+---------------------------------------------
+The following block diagram illustrates the mechanism by which APQNs are
+reserved::
+
+ +------------------+
+ 7 remove | |
+ +--------------------> cex4queue driver |
+ | | |
+ | +------------------+
+ |
+ |
+ | +------------------+ +----------------+
+ | 5 register driver | | 3 create | |
+ | +----------------> Device core +----------> matrix device |
+ | | | | | |
+ | | +--------^---------+ +----------------+
+ | | |
+ | | +-------------------+
+ | | +-----------------------------------+ |
+ | | | 4 register AP driver | | 2 register device
+ | | | | |
+ +--------+---+-v---+ +--------+-------+-+
+ | | | |
+ | ap_bus +--------------------- > vfio_ap driver |
+ | | 8 probe | |
+ +--------^---------+ +--^--^------------+
+ 6 edit | | |
+ apmask | +-----------------------------+ | 9 mdev create
+ aqmask | | 1 modprobe |
+ +--------+-----+---+ +----------------+-+ +----------------+
+ | | | |8 create | mediated |
+ | admin | | VFIO device core |---------> matrix |
+ | + | | | device |
+ +------+-+---------+ +--------^---------+ +--------^-------+
+ | | | |
+ | | 9 create vfio_ap-passthrough | |
+ | +------------------------------+ |
+ +-------------------------------------------------------------+
+ 10 assign adapter/domain/control domain
+
+The process for reserving an AP queue for use by a KVM guest is:
+
+1. The administrator loads the vfio_ap device driver
+2. The vfio-ap driver during its initialization will register a single 'matrix'
+ device with the device core. This will serve as the parent device for
+ all mediated matrix devices used to configure an AP matrix for a guest.
+3. The /sys/devices/vfio_ap/matrix device is created by the device core
+4. The vfio_ap device driver will register with the AP bus for AP queue devices
+ of type 10 and higher (CEX4 and newer). The driver will provide the vfio_ap
+ driver's probe and remove callback interfaces. Devices older than CEX4 queues
+ are not supported to simplify the implementation by not needlessly
+ complicating the design by supporting older devices that will go out of
+ service in the relatively near future, and for which there are few older
+ systems around on which to test.
+5. The AP bus registers the vfio_ap device driver with the device core
+6. The administrator edits the AP adapter and queue masks to reserve AP queues
+ for use by the vfio_ap device driver.
+7. The AP bus removes the AP queues reserved for the vfio_ap driver from the
+ default zcrypt cex4queue driver.
+8. The AP bus probes the vfio_ap device driver to bind the queues reserved for
+ it.
+9. The administrator creates a passthrough type mediated matrix device to be
+ used by a guest
+10. The administrator assigns the adapters, usage domains and control domains
+ to be exclusively used by a guest.
+
+Set up the VFIO mediated device interfaces
+------------------------------------------
+The VFIO AP device driver utilizes the common interface of the VFIO mediated
+device core driver to:
+
+* Register an AP mediated bus driver to add a mediated matrix device to and
+ remove it from a VFIO group.
+* Create and destroy a mediated matrix device
+* Add a mediated matrix device to and remove it from the AP mediated bus driver
+* Add a mediated matrix device to and remove it from an IOMMU group
+
+The following high-level block diagram shows the main components and interfaces
+of the VFIO AP mediated matrix device driver::
+
+ +-------------+
+ | |
+ | +---------+ | mdev_register_driver() +--------------+
+ | | Mdev | +<-----------------------+ |
+ | | bus | | | vfio_mdev.ko |
+ | | driver | +----------------------->+ |<-> VFIO user
+ | +---------+ | probe()/remove() +--------------+ APIs
+ | |
+ | MDEV CORE |
+ | MODULE |
+ | mdev.ko |
+ | +---------+ | mdev_register_device() +--------------+
+ | |Physical | +<-----------------------+ |
+ | | device | | | vfio_ap.ko |<-> matrix
+ | |interface| +----------------------->+ | device
+ | +---------+ | callback +--------------+
+ +-------------+
+
+During initialization of the vfio_ap module, the matrix device is registered
+with an 'mdev_parent_ops' structure that provides the sysfs attribute
+structures, mdev functions and callback interfaces for managing the mediated
+matrix device.
+
+* sysfs attribute structures:
+
+ supported_type_groups
+ The VFIO mediated device framework supports creation of user-defined
+ mediated device types. These mediated device types are specified
+ via the 'supported_type_groups' structure when a device is registered
+ with the mediated device framework. The registration process creates the
+ sysfs structures for each mediated device type specified in the
+ 'mdev_supported_types' sub-directory of the device being registered. Along
+ with the device type, the sysfs attributes of the mediated device type are
+ provided.
+
+ The VFIO AP device driver will register one mediated device type for
+ passthrough devices:
+
+ /sys/devices/vfio_ap/matrix/mdev_supported_types/vfio_ap-passthrough
+
+ Only the read-only attributes required by the VFIO mdev framework will
+ be provided::
+
+ ... name
+ ... device_api
+ ... available_instances
+ ... device_api
+
+ Where:
+
+ * name:
+ specifies the name of the mediated device type
+ * device_api:
+ the mediated device type's API
+ * available_instances:
+ the number of mediated matrix passthrough devices
+ that can be created
+ * device_api:
+ specifies the VFIO API
+ mdev_attr_groups
+ This attribute group identifies the user-defined sysfs attributes of the
+ mediated device. When a device is registered with the VFIO mediated device
+ framework, the sysfs attribute files identified in the 'mdev_attr_groups'
+ structure will be created in the mediated matrix device's directory. The
+ sysfs attributes for a mediated matrix device are:
+
+ assign_adapter / unassign_adapter:
+ Write-only attributes for assigning/unassigning an AP adapter to/from the
+ mediated matrix device. To assign/unassign an adapter, the APID of the
+ adapter is echoed to the respective attribute file.
+ assign_domain / unassign_domain:
+ Write-only attributes for assigning/unassigning an AP usage domain to/from
+ the mediated matrix device. To assign/unassign a domain, the domain
+ number of the the usage domain is echoed to the respective attribute
+ file.
+ matrix:
+ A read-only file for displaying the APQNs derived from the cross product
+ of the adapter and domain numbers assigned to the mediated matrix device.
+ assign_control_domain / unassign_control_domain:
+ Write-only attributes for assigning/unassigning an AP control domain
+ to/from the mediated matrix device. To assign/unassign a control domain,
+ the ID of the domain to be assigned/unassigned is echoed to the respective
+ attribute file.
+ control_domains:
+ A read-only file for displaying the control domain numbers assigned to the
+ mediated matrix device.
+
+* functions:
+
+ create:
+ allocates the ap_matrix_mdev structure used by the vfio_ap driver to:
+
+ * Store the reference to the KVM structure for the guest using the mdev
+ * Store the AP matrix configuration for the adapters, domains, and control
+ domains assigned via the corresponding sysfs attributes files
+
+ remove:
+ deallocates the mediated matrix device's ap_matrix_mdev structure. This will
+ be allowed only if a running guest is not using the mdev.
+
+* callback interfaces
+
+ open:
+ The vfio_ap driver uses this callback to register a
+ VFIO_GROUP_NOTIFY_SET_KVM notifier callback function for the mdev matrix
+ device. The open is invoked when QEMU connects the VFIO iommu group
+ for the mdev matrix device to the MDEV bus. Access to the KVM structure used
+ to configure the KVM guest is provided via this callback. The KVM structure,
+ is used to configure the guest's access to the AP matrix defined via the
+ mediated matrix device's sysfs attribute files.
+ release:
+ unregisters the VFIO_GROUP_NOTIFY_SET_KVM notifier callback function for the
+ mdev matrix device and deconfigures the guest's AP matrix.
+
+Configure the APM, AQM and ADM in the CRYCB
+-------------------------------------------
+Configuring the AP matrix for a KVM guest will be performed when the
+VFIO_GROUP_NOTIFY_SET_KVM notifier callback is invoked. The notifier
+function is called when QEMU connects to KVM. The guest's AP matrix is
+configured via it's CRYCB by:
+
+* Setting the bits in the APM corresponding to the APIDs assigned to the
+ mediated matrix device via its 'assign_adapter' interface.
+* Setting the bits in the AQM corresponding to the domains assigned to the
+ mediated matrix device via its 'assign_domain' interface.
+* Setting the bits in the ADM corresponding to the domain dIDs assigned to the
+ mediated matrix device via its 'assign_control_domains' interface.
+
+The CPU model features for AP
+-----------------------------
+The AP stack relies on the presence of the AP instructions as well as two
+facilities: The AP Facilities Test (APFT) facility; and the AP Query
+Configuration Information (QCI) facility. These features/facilities are made
+available to a KVM guest via the following CPU model features:
+
+1. ap: Indicates whether the AP instructions are installed on the guest. This
+ feature will be enabled by KVM only if the AP instructions are installed
+ on the host.
+
+2. apft: Indicates the APFT facility is available on the guest. This facility
+ can be made available to the guest only if it is available on the host (i.e.,
+ facility bit 15 is set).
+
+3. apqci: Indicates the AP QCI facility is available on the guest. This facility
+ can be made available to the guest only if it is available on the host (i.e.,
+ facility bit 12 is set).
+
+Note: If the user chooses to specify a CPU model different than the 'host'
+model to QEMU, the CPU model features and facilities need to be turned on
+explicitly; for example::
+
+ /usr/bin/qemu-system-s390x ... -cpu z13,ap=on,apqci=on,apft=on
+
+A guest can be precluded from using AP features/facilities by turning them off
+explicitly; for example::
+
+ /usr/bin/qemu-system-s390x ... -cpu host,ap=off,apqci=off,apft=off
+
+Note: If the APFT facility is turned off (apft=off) for the guest, the guest
+will not see any AP devices. The zcrypt device drivers that register for type 10
+and newer AP devices - i.e., the cex4card and cex4queue device drivers - need
+the APFT facility to ascertain the facilities installed on a given AP device. If
+the APFT facility is not installed on the guest, then the probe of device
+drivers will fail since only type 10 and newer devices can be configured for
+guest use.
+
+Example
+=======
+Let's now provide an example to illustrate how KVM guests may be given
+access to AP facilities. For this example, we will show how to configure
+three guests such that executing the lszcrypt command on the guests would
+look like this:
+
+Guest1
+------
+=========== ===== ============
+CARD.DOMAIN TYPE MODE
+=========== ===== ============
+05 CEX5C CCA-Coproc
+05.0004 CEX5C CCA-Coproc
+05.00ab CEX5C CCA-Coproc
+06 CEX5A Accelerator
+06.0004 CEX5A Accelerator
+06.00ab CEX5C CCA-Coproc
+=========== ===== ============
+
+Guest2
+------
+=========== ===== ============
+CARD.DOMAIN TYPE MODE
+=========== ===== ============
+05 CEX5A Accelerator
+05.0047 CEX5A Accelerator
+05.00ff CEX5A Accelerator
+=========== ===== ============
+
+Guest2
+------
+=========== ===== ============
+CARD.DOMAIN TYPE MODE
+=========== ===== ============
+06 CEX5A Accelerator
+06.0047 CEX5A Accelerator
+06.00ff CEX5A Accelerator
+=========== ===== ============
+
+These are the steps:
+
+1. Install the vfio_ap module on the linux host. The dependency chain for the
+ vfio_ap module is:
+ * iommu
+ * s390
+ * zcrypt
+ * vfio
+ * vfio_mdev
+ * vfio_mdev_device
+ * KVM
+
+ To build the vfio_ap module, the kernel build must be configured with the
+ following Kconfig elements selected:
+ * IOMMU_SUPPORT
+ * S390
+ * ZCRYPT
+ * S390_AP_IOMMU
+ * VFIO
+ * VFIO_MDEV
+ * VFIO_MDEV_DEVICE
+ * KVM
+
+ If using make menuconfig select the following to build the vfio_ap module::
+
+ -> Device Drivers
+ -> IOMMU Hardware Support
+ select S390 AP IOMMU Support
+ -> VFIO Non-Privileged userspace driver framework
+ -> Mediated device driver frramework
+ -> VFIO driver for Mediated devices
+ -> I/O subsystem
+ -> VFIO support for AP devices
+
+2. Secure the AP queues to be used by the three guests so that the host can not
+ access them. To secure them, there are two sysfs files that specify
+ bitmasks marking a subset of the APQN range as 'usable by the default AP
+ queue device drivers' or 'not usable by the default device drivers' and thus
+ available for use by the vfio_ap device driver'. The location of the sysfs
+ files containing the masks are::
+
+ /sys/bus/ap/apmask
+ /sys/bus/ap/aqmask
+
+ The 'apmask' is a 256-bit mask that identifies a set of AP adapter IDs
+ (APID). Each bit in the mask, from left to right (i.e., from most significant
+ to least significant bit in big endian order), corresponds to an APID from
+ 0-255. If a bit is set, the APID is marked as usable only by the default AP
+ queue device drivers; otherwise, the APID is usable by the vfio_ap
+ device driver.
+
+ The 'aqmask' is a 256-bit mask that identifies a set of AP queue indexes
+ (APQI). Each bit in the mask, from left to right (i.e., from most significant
+ to least significant bit in big endian order), corresponds to an APQI from
+ 0-255. If a bit is set, the APQI is marked as usable only by the default AP
+ queue device drivers; otherwise, the APQI is usable by the vfio_ap device
+ driver.
+
+ Take, for example, the following mask::
+
+ 0x7dffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+
+ It indicates:
+
+ 1, 2, 3, 4, 5, and 7-255 belong to the default drivers' pool, and 0 and 6
+ belong to the vfio_ap device driver's pool.
+
+ The APQN of each AP queue device assigned to the linux host is checked by the
+ AP bus against the set of APQNs derived from the cross product of APIDs
+ and APQIs marked as usable only by the default AP queue device drivers. If a
+ match is detected, only the default AP queue device drivers will be probed;
+ otherwise, the vfio_ap device driver will be probed.
+
+ By default, the two masks are set to reserve all APQNs for use by the default
+ AP queue device drivers. There are two ways the default masks can be changed:
+
+ 1. The sysfs mask files can be edited by echoing a string into the
+ respective sysfs mask file in one of two formats:
+
+ * An absolute hex string starting with 0x - like "0x12345678" - sets
+ the mask. If the given string is shorter than the mask, it is padded
+ with 0s on the right; for example, specifying a mask value of 0x41 is
+ the same as specifying::
+
+ 0x4100000000000000000000000000000000000000000000000000000000000000
+
+ Keep in mind that the mask reads from left to right (i.e., most
+ significant to least significant bit in big endian order), so the mask
+ above identifies device numbers 1 and 7 (01000001).
+
+ If the string is longer than the mask, the operation is terminated with
+ an error (EINVAL).
+
+ * Individual bits in the mask can be switched on and off by specifying
+ each bit number to be switched in a comma separated list. Each bit
+ number string must be prepended with a ('+') or minus ('-') to indicate
+ the corresponding bit is to be switched on ('+') or off ('-'). Some
+ valid values are:
+
+ - "+0" switches bit 0 on
+ - "-13" switches bit 13 off
+ - "+0x41" switches bit 65 on
+ - "-0xff" switches bit 255 off
+
+ The following example:
+
+ +0,-6,+0x47,-0xf0
+
+ Switches bits 0 and 71 (0x47) on
+
+ Switches bits 6 and 240 (0xf0) off
+
+ Note that the bits not specified in the list remain as they were before
+ the operation.
+
+ 2. The masks can also be changed at boot time via parameters on the kernel
+ command line like this:
+
+ ap.apmask=0xffff ap.aqmask=0x40
+
+ This would create the following masks::
+
+ apmask:
+ 0xffff000000000000000000000000000000000000000000000000000000000000
+
+ aqmask:
+ 0x4000000000000000000000000000000000000000000000000000000000000000
+
+ Resulting in these two pools::
+
+ default drivers pool: adapter 0-15, domain 1
+ alternate drivers pool: adapter 16-255, domains 0, 2-255
+
+Securing the APQNs for our example
+----------------------------------
+ To secure the AP queues 05.0004, 05.0047, 05.00ab, 05.00ff, 06.0004, 06.0047,
+ 06.00ab, and 06.00ff for use by the vfio_ap device driver, the corresponding
+ APQNs can either be removed from the default masks::
+
+ echo -5,-6 > /sys/bus/ap/apmask
+
+ echo -4,-0x47,-0xab,-0xff > /sys/bus/ap/aqmask
+
+ Or the masks can be set as follows::
+
+ echo 0xf9ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff \
+ > apmask
+
+ echo 0xf7fffffffffffffffeffffffffffffffffffffffffeffffffffffffffffffffe \
+ > aqmask
+
+ This will result in AP queues 05.0004, 05.0047, 05.00ab, 05.00ff, 06.0004,
+ 06.0047, 06.00ab, and 06.00ff getting bound to the vfio_ap device driver. The
+ sysfs directory for the vfio_ap device driver will now contain symbolic links
+ to the AP queue devices bound to it::
+
+ /sys/bus/ap
+ ... [drivers]
+ ...... [vfio_ap]
+ ......... [05.0004]
+ ......... [05.0047]
+ ......... [05.00ab]
+ ......... [05.00ff]
+ ......... [06.0004]
+ ......... [06.0047]
+ ......... [06.00ab]
+ ......... [06.00ff]
+
+ Keep in mind that only type 10 and newer adapters (i.e., CEX4 and later)
+ can be bound to the vfio_ap device driver. The reason for this is to
+ simplify the implementation by not needlessly complicating the design by
+ supporting older devices that will go out of service in the relatively near
+ future and for which there are few older systems on which to test.
+
+ The administrator, therefore, must take care to secure only AP queues that
+ can be bound to the vfio_ap device driver. The device type for a given AP
+ queue device can be read from the parent card's sysfs directory. For example,
+ to see the hardware type of the queue 05.0004:
+
+ cat /sys/bus/ap/devices/card05/hwtype
+
+ The hwtype must be 10 or higher (CEX4 or newer) in order to be bound to the
+ vfio_ap device driver.
+
+3. Create the mediated devices needed to configure the AP matrixes for the
+ three guests and to provide an interface to the vfio_ap driver for
+ use by the guests::
+
+ /sys/devices/vfio_ap/matrix/
+ --- [mdev_supported_types]
+ ------ [vfio_ap-passthrough] (passthrough mediated matrix device type)
+ --------- create
+ --------- [devices]
+
+ To create the mediated devices for the three guests::
+
+ uuidgen > create
+ uuidgen > create
+ uuidgen > create
+
+ or
+
+ echo $uuid1 > create
+ echo $uuid2 > create
+ echo $uuid3 > create
+
+ This will create three mediated devices in the [devices] subdirectory named
+ after the UUID written to the create attribute file. We call them $uuid1,
+ $uuid2 and $uuid3 and this is the sysfs directory structure after creation::
+
+ /sys/devices/vfio_ap/matrix/
+ --- [mdev_supported_types]
+ ------ [vfio_ap-passthrough]
+ --------- [devices]
+ ------------ [$uuid1]
+ --------------- assign_adapter
+ --------------- assign_control_domain
+ --------------- assign_domain
+ --------------- matrix
+ --------------- unassign_adapter
+ --------------- unassign_control_domain
+ --------------- unassign_domain
+
+ ------------ [$uuid2]
+ --------------- assign_adapter
+ --------------- assign_control_domain
+ --------------- assign_domain
+ --------------- matrix
+ --------------- unassign_adapter
+ ----------------unassign_control_domain
+ ----------------unassign_domain
+
+ ------------ [$uuid3]
+ --------------- assign_adapter
+ --------------- assign_control_domain
+ --------------- assign_domain
+ --------------- matrix
+ --------------- unassign_adapter
+ ----------------unassign_control_domain
+ ----------------unassign_domain
+
+4. The administrator now needs to configure the matrixes for the mediated
+ devices $uuid1 (for Guest1), $uuid2 (for Guest2) and $uuid3 (for Guest3).
+
+ This is how the matrix is configured for Guest1::
+
+ echo 5 > assign_adapter
+ echo 6 > assign_adapter
+ echo 4 > assign_domain
+ echo 0xab > assign_domain
+
+ Control domains can similarly be assigned using the assign_control_domain
+ sysfs file.
+
+ If a mistake is made configuring an adapter, domain or control domain,
+ you can use the unassign_xxx files to unassign the adapter, domain or
+ control domain.
+
+ To display the matrix configuration for Guest1::
+
+ cat matrix
+
+ This is how the matrix is configured for Guest2::
+
+ echo 5 > assign_adapter
+ echo 0x47 > assign_domain
+ echo 0xff > assign_domain
+
+ This is how the matrix is configured for Guest3::
+
+ echo 6 > assign_adapter
+ echo 0x47 > assign_domain
+ echo 0xff > assign_domain
+
+ In order to successfully assign an adapter:
+
+ * The adapter number specified must represent a value from 0 up to the
+ maximum adapter number configured for the system. If an adapter number
+ higher than the maximum is specified, the operation will terminate with
+ an error (ENODEV).
+
+ * All APQNs that can be derived from the adapter ID and the IDs of
+ the previously assigned domains must be bound to the vfio_ap device
+ driver. If no domains have yet been assigned, then there must be at least
+ one APQN with the specified APID bound to the vfio_ap driver. If no such
+ APQNs are bound to the driver, the operation will terminate with an
+ error (EADDRNOTAVAIL).
+
+ No APQN that can be derived from the adapter ID and the IDs of the
+ previously assigned domains can be assigned to another mediated matrix
+ device. If an APQN is assigned to another mediated matrix device, the
+ operation will terminate with an error (EADDRINUSE).
+
+ In order to successfully assign a domain:
+
+ * The domain number specified must represent a value from 0 up to the
+ maximum domain number configured for the system. If a domain number
+ higher than the maximum is specified, the operation will terminate with
+ an error (ENODEV).
+
+ * All APQNs that can be derived from the domain ID and the IDs of
+ the previously assigned adapters must be bound to the vfio_ap device
+ driver. If no domains have yet been assigned, then there must be at least
+ one APQN with the specified APQI bound to the vfio_ap driver. If no such
+ APQNs are bound to the driver, the operation will terminate with an
+ error (EADDRNOTAVAIL).
+
+ No APQN that can be derived from the domain ID and the IDs of the
+ previously assigned adapters can be assigned to another mediated matrix
+ device. If an APQN is assigned to another mediated matrix device, the
+ operation will terminate with an error (EADDRINUSE).
+
+ In order to successfully assign a control domain, the domain number
+ specified must represent a value from 0 up to the maximum domain number
+ configured for the system. If a control domain number higher than the maximum
+ is specified, the operation will terminate with an error (ENODEV).
+
+5. Start Guest1::
+
+ /usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on \
+ -device vfio-ap,sysfsdev=/sys/devices/vfio_ap/matrix/$uuid1 ...
+
+7. Start Guest2::
+
+ /usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on \
+ -device vfio-ap,sysfsdev=/sys/devices/vfio_ap/matrix/$uuid2 ...
+
+7. Start Guest3::
+
+ /usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on \
+ -device vfio-ap,sysfsdev=/sys/devices/vfio_ap/matrix/$uuid3 ...
+
+When the guest is shut down, the mediated matrix devices may be removed.
+
+Using our example again, to remove the mediated matrix device $uuid1::
+
+ /sys/devices/vfio_ap/matrix/
+ --- [mdev_supported_types]
+ ------ [vfio_ap-passthrough]
+ --------- [devices]
+ ------------ [$uuid1]
+ --------------- remove
+
+::
+
+ echo 1 > remove
+
+This will remove all of the mdev matrix device's sysfs structures including
+the mdev device itself. To recreate and reconfigure the mdev matrix device,
+all of the steps starting with step 3 will have to be performed again. Note
+that the remove will fail if a guest using the mdev is still running.
+
+It is not necessary to remove an mdev matrix device, but one may want to
+remove it if no guest will use it during the remaining lifetime of the linux
+host. If the mdev matrix device is removed, one may want to also reconfigure
+the pool of adapters and queues reserved for use by the default drivers.
+
+Limitations
+===========
+* The KVM/kernel interfaces do not provide a way to prevent restoring an APQN
+ to the default drivers pool of a queue that is still assigned to a mediated
+ device in use by a guest. It is incumbent upon the administrator to
+ ensure there is no mediated device in use by a guest to which the APQN is
+ assigned lest the host be given access to the private data of the AP queue
+ device such as a private key configured specifically for the guest.
+
+* Dynamically modifying the AP matrix for a running guest (which would amount to
+ hot(un)plug of AP devices for the guest) is currently not supported
+
+* Live guest migration is not supported for guests using AP devices.
+++ /dev/null
-Introduction:
-============
-The Adjunct Processor (AP) facility is an IBM Z cryptographic facility comprised
-of three AP instructions and from 1 up to 256 PCIe cryptographic adapter cards.
-The AP devices provide cryptographic functions to all CPUs assigned to a
-linux system running in an IBM Z system LPAR.
-
-The AP adapter cards are exposed via the AP bus. The motivation for vfio-ap
-is to make AP cards available to KVM guests using the VFIO mediated device
-framework. This implementation relies considerably on the s390 virtualization
-facilities which do most of the hard work of providing direct access to AP
-devices.
-
-AP Architectural Overview:
-=========================
-To facilitate the comprehension of the design, let's start with some
-definitions:
-
-* AP adapter
-
- An AP adapter is an IBM Z adapter card that can perform cryptographic
- functions. There can be from 0 to 256 adapters assigned to an LPAR. Adapters
- assigned to the LPAR in which a linux host is running will be available to
- the linux host. Each adapter is identified by a number from 0 to 255; however,
- the maximum adapter number is determined by machine model and/or adapter type.
- When installed, an AP adapter is accessed by AP instructions executed by any
- CPU.
-
- The AP adapter cards are assigned to a given LPAR via the system's Activation
- Profile which can be edited via the HMC. When the linux host system is IPL'd
- in the LPAR, the AP bus detects the AP adapter cards assigned to the LPAR and
- creates a sysfs device for each assigned adapter. For example, if AP adapters
- 4 and 10 (0x0a) are assigned to the LPAR, the AP bus will create the following
- sysfs device entries:
-
- /sys/devices/ap/card04
- /sys/devices/ap/card0a
-
- Symbolic links to these devices will also be created in the AP bus devices
- sub-directory:
-
- /sys/bus/ap/devices/[card04]
- /sys/bus/ap/devices/[card04]
-
-* AP domain
-
- An adapter is partitioned into domains. An adapter can hold up to 256 domains
- depending upon the adapter type and hardware configuration. A domain is
- identified by a number from 0 to 255; however, the maximum domain number is
- determined by machine model and/or adapter type.. A domain can be thought of
- as a set of hardware registers and memory used for processing AP commands. A
- domain can be configured with a secure private key used for clear key
- encryption. A domain is classified in one of two ways depending upon how it
- may be accessed:
-
- * Usage domains are domains that are targeted by an AP instruction to
- process an AP command.
-
- * Control domains are domains that are changed by an AP command sent to a
- usage domain; for example, to set the secure private key for the control
- domain.
-
- The AP usage and control domains are assigned to a given LPAR via the system's
- Activation Profile which can be edited via the HMC. When a linux host system
- is IPL'd in the LPAR, the AP bus module detects the AP usage and control
- domains assigned to the LPAR. The domain number of each usage domain and
- adapter number of each AP adapter are combined to create AP queue devices
- (see AP Queue section below). The domain number of each control domain will be
- represented in a bitmask and stored in a sysfs file
- /sys/bus/ap/ap_control_domain_mask. The bits in the mask, from most to least
- significant bit, correspond to domains 0-255.
-
-* AP Queue
-
- An AP queue is the means by which an AP command is sent to a usage domain
- inside a specific adapter. An AP queue is identified by a tuple
- comprised of an AP adapter ID (APID) and an AP queue index (APQI). The
- APQI corresponds to a given usage domain number within the adapter. This tuple
- forms an AP Queue Number (APQN) uniquely identifying an AP queue. AP
- instructions include a field containing the APQN to identify the AP queue to
- which the AP command is to be sent for processing.
-
- The AP bus will create a sysfs device for each APQN that can be derived from
- the cross product of the AP adapter and usage domain numbers detected when the
- AP bus module is loaded. For example, if adapters 4 and 10 (0x0a) and usage
- domains 6 and 71 (0x47) are assigned to the LPAR, the AP bus will create the
- following sysfs entries:
-
- /sys/devices/ap/card04/04.0006
- /sys/devices/ap/card04/04.0047
- /sys/devices/ap/card0a/0a.0006
- /sys/devices/ap/card0a/0a.0047
-
- The following symbolic links to these devices will be created in the AP bus
- devices subdirectory:
-
- /sys/bus/ap/devices/[04.0006]
- /sys/bus/ap/devices/[04.0047]
- /sys/bus/ap/devices/[0a.0006]
- /sys/bus/ap/devices/[0a.0047]
-
-* AP Instructions:
-
- There are three AP instructions:
-
- * NQAP: to enqueue an AP command-request message to a queue
- * DQAP: to dequeue an AP command-reply message from a queue
- * PQAP: to administer the queues
-
- AP instructions identify the domain that is targeted to process the AP
- command; this must be one of the usage domains. An AP command may modify a
- domain that is not one of the usage domains, but the modified domain
- must be one of the control domains.
-
-AP and SIE:
-==========
-Let's now take a look at how AP instructions executed on a guest are interpreted
-by the hardware.
-
-A satellite control block called the Crypto Control Block (CRYCB) is attached to
-our main hardware virtualization control block. The CRYCB contains three fields
-to identify the adapters, usage domains and control domains assigned to the KVM
-guest:
-
-* The AP Mask (APM) field is a bit mask that identifies the AP adapters assigned
- to the KVM guest. Each bit in the mask, from left to right (i.e. from most
- significant to least significant bit in big endian order), corresponds to
- an APID from 0-255. If a bit is set, the corresponding adapter is valid for
- use by the KVM guest.
-
-* The AP Queue Mask (AQM) field is a bit mask identifying the AP usage domains
- assigned to the KVM guest. Each bit in the mask, from left to right (i.e. from
- most significant to least significant bit in big endian order), corresponds to
- an AP queue index (APQI) from 0-255. If a bit is set, the corresponding queue
- is valid for use by the KVM guest.
-
-* The AP Domain Mask field is a bit mask that identifies the AP control domains
- assigned to the KVM guest. The ADM bit mask controls which domains can be
- changed by an AP command-request message sent to a usage domain from the
- guest. Each bit in the mask, from left to right (i.e. from most significant to
- least significant bit in big endian order), corresponds to a domain from
- 0-255. If a bit is set, the corresponding domain can be modified by an AP
- command-request message sent to a usage domain.
-
-If you recall from the description of an AP Queue, AP instructions include
-an APQN to identify the AP queue to which an AP command-request message is to be
-sent (NQAP and PQAP instructions), or from which a command-reply message is to
-be received (DQAP instruction). The validity of an APQN is defined by the matrix
-calculated from the APM and AQM; it is the cross product of all assigned adapter
-numbers (APM) with all assigned queue indexes (AQM). For example, if adapters 1
-and 2 and usage domains 5 and 6 are assigned to a guest, the APQNs (1,5), (1,6),
-(2,5) and (2,6) will be valid for the guest.
-
-The APQNs can provide secure key functionality - i.e., a private key is stored
-on the adapter card for each of its domains - so each APQN must be assigned to
-at most one guest or to the linux host.
-
- Example 1: Valid configuration:
- ------------------------------
- Guest1: adapters 1,2 domains 5,6
- Guest2: adapter 1,2 domain 7
-
- This is valid because both guests have a unique set of APQNs:
- Guest1 has APQNs (1,5), (1,6), (2,5), (2,6);
- Guest2 has APQNs (1,7), (2,7)
-
- Example 2: Valid configuration:
- ------------------------------
- Guest1: adapters 1,2 domains 5,6
- Guest2: adapters 3,4 domains 5,6
-
- This is also valid because both guests have a unique set of APQNs:
- Guest1 has APQNs (1,5), (1,6), (2,5), (2,6);
- Guest2 has APQNs (3,5), (3,6), (4,5), (4,6)
-
- Example 3: Invalid configuration:
- --------------------------------
- Guest1: adapters 1,2 domains 5,6
- Guest2: adapter 1 domains 6,7
-
- This is an invalid configuration because both guests have access to
- APQN (1,6).
-
-The Design:
-===========
-The design introduces three new objects:
-
-1. AP matrix device
-2. VFIO AP device driver (vfio_ap.ko)
-3. VFIO AP mediated matrix pass-through device
-
-The VFIO AP device driver
--------------------------
-The VFIO AP (vfio_ap) device driver serves the following purposes:
-
-1. Provides the interfaces to secure APQNs for exclusive use of KVM guests.
-
-2. Sets up the VFIO mediated device interfaces to manage a mediated matrix
- device and creates the sysfs interfaces for assigning adapters, usage
- domains, and control domains comprising the matrix for a KVM guest.
-
-3. Configures the APM, AQM and ADM in the CRYCB referenced by a KVM guest's
- SIE state description to grant the guest access to a matrix of AP devices
-
-Reserve APQNs for exclusive use of KVM guests
----------------------------------------------
-The following block diagram illustrates the mechanism by which APQNs are
-reserved:
-
- +------------------+
- 7 remove | |
- +--------------------> cex4queue driver |
- | | |
- | +------------------+
- |
- |
- | +------------------+ +-----------------+
- | 5 register driver | | 3 create | |
- | +----------------> Device core +----------> matrix device |
- | | | | | |
- | | +--------^---------+ +-----------------+
- | | |
- | | +-------------------+
- | | +-----------------------------------+ |
- | | | 4 register AP driver | | 2 register device
- | | | | |
-+--------+---+-v---+ +--------+-------+-+
-| | | |
-| ap_bus +--------------------- > vfio_ap driver |
-| | 8 probe | |
-+--------^---------+ +--^--^------------+
-6 edit | | |
- apmask | +-----------------------------+ | 9 mdev create
- aqmask | | 1 modprobe |
-+--------+-----+---+ +----------------+-+ +------------------+
-| | | |8 create | mediated |
-| admin | | VFIO device core |---------> matrix |
-| + | | | device |
-+------+-+---------+ +--------^---------+ +--------^---------+
- | | | |
- | | 9 create vfio_ap-passthrough | |
- | +------------------------------+ |
- +-------------------------------------------------------------+
- 10 assign adapter/domain/control domain
-
-The process for reserving an AP queue for use by a KVM guest is:
-
-1. The administrator loads the vfio_ap device driver
-2. The vfio-ap driver during its initialization will register a single 'matrix'
- device with the device core. This will serve as the parent device for
- all mediated matrix devices used to configure an AP matrix for a guest.
-3. The /sys/devices/vfio_ap/matrix device is created by the device core
-4 The vfio_ap device driver will register with the AP bus for AP queue devices
- of type 10 and higher (CEX4 and newer). The driver will provide the vfio_ap
- driver's probe and remove callback interfaces. Devices older than CEX4 queues
- are not supported to simplify the implementation by not needlessly
- complicating the design by supporting older devices that will go out of
- service in the relatively near future, and for which there are few older
- systems around on which to test.
-5. The AP bus registers the vfio_ap device driver with the device core
-6. The administrator edits the AP adapter and queue masks to reserve AP queues
- for use by the vfio_ap device driver.
-7. The AP bus removes the AP queues reserved for the vfio_ap driver from the
- default zcrypt cex4queue driver.
-8. The AP bus probes the vfio_ap device driver to bind the queues reserved for
- it.
-9. The administrator creates a passthrough type mediated matrix device to be
- used by a guest
-10 The administrator assigns the adapters, usage domains and control domains
- to be exclusively used by a guest.
-
-Set up the VFIO mediated device interfaces
-------------------------------------------
-The VFIO AP device driver utilizes the common interface of the VFIO mediated
-device core driver to:
-* Register an AP mediated bus driver to add a mediated matrix device to and
- remove it from a VFIO group.
-* Create and destroy a mediated matrix device
-* Add a mediated matrix device to and remove it from the AP mediated bus driver
-* Add a mediated matrix device to and remove it from an IOMMU group
-
-The following high-level block diagram shows the main components and interfaces
-of the VFIO AP mediated matrix device driver:
-
- +-------------+
- | |
- | +---------+ | mdev_register_driver() +--------------+
- | | Mdev | +<-----------------------+ |
- | | bus | | | vfio_mdev.ko |
- | | driver | +----------------------->+ |<-> VFIO user
- | +---------+ | probe()/remove() +--------------+ APIs
- | |
- | MDEV CORE |
- | MODULE |
- | mdev.ko |
- | +---------+ | mdev_register_device() +--------------+
- | |Physical | +<-----------------------+ |
- | | device | | | vfio_ap.ko |<-> matrix
- | |interface| +----------------------->+ | device
- | +---------+ | callback +--------------+
- +-------------+
-
-During initialization of the vfio_ap module, the matrix device is registered
-with an 'mdev_parent_ops' structure that provides the sysfs attribute
-structures, mdev functions and callback interfaces for managing the mediated
-matrix device.
-
-* sysfs attribute structures:
- * supported_type_groups
- The VFIO mediated device framework supports creation of user-defined
- mediated device types. These mediated device types are specified
- via the 'supported_type_groups' structure when a device is registered
- with the mediated device framework. The registration process creates the
- sysfs structures for each mediated device type specified in the
- 'mdev_supported_types' sub-directory of the device being registered. Along
- with the device type, the sysfs attributes of the mediated device type are
- provided.
-
- The VFIO AP device driver will register one mediated device type for
- passthrough devices:
- /sys/devices/vfio_ap/matrix/mdev_supported_types/vfio_ap-passthrough
- Only the read-only attributes required by the VFIO mdev framework will
- be provided:
- ... name
- ... device_api
- ... available_instances
- ... device_api
- Where:
- * name: specifies the name of the mediated device type
- * device_api: the mediated device type's API
- * available_instances: the number of mediated matrix passthrough devices
- that can be created
- * device_api: specifies the VFIO API
- * mdev_attr_groups
- This attribute group identifies the user-defined sysfs attributes of the
- mediated device. When a device is registered with the VFIO mediated device
- framework, the sysfs attribute files identified in the 'mdev_attr_groups'
- structure will be created in the mediated matrix device's directory. The
- sysfs attributes for a mediated matrix device are:
- * assign_adapter:
- * unassign_adapter:
- Write-only attributes for assigning/unassigning an AP adapter to/from the
- mediated matrix device. To assign/unassign an adapter, the APID of the
- adapter is echoed to the respective attribute file.
- * assign_domain:
- * unassign_domain:
- Write-only attributes for assigning/unassigning an AP usage domain to/from
- the mediated matrix device. To assign/unassign a domain, the domain
- number of the the usage domain is echoed to the respective attribute
- file.
- * matrix:
- A read-only file for displaying the APQNs derived from the cross product
- of the adapter and domain numbers assigned to the mediated matrix device.
- * assign_control_domain:
- * unassign_control_domain:
- Write-only attributes for assigning/unassigning an AP control domain
- to/from the mediated matrix device. To assign/unassign a control domain,
- the ID of the domain to be assigned/unassigned is echoed to the respective
- attribute file.
- * control_domains:
- A read-only file for displaying the control domain numbers assigned to the
- mediated matrix device.
-
-* functions:
- * create:
- allocates the ap_matrix_mdev structure used by the vfio_ap driver to:
- * Store the reference to the KVM structure for the guest using the mdev
- * Store the AP matrix configuration for the adapters, domains, and control
- domains assigned via the corresponding sysfs attributes files
- * remove:
- deallocates the mediated matrix device's ap_matrix_mdev structure. This will
- be allowed only if a running guest is not using the mdev.
-
-* callback interfaces
- * open:
- The vfio_ap driver uses this callback to register a
- VFIO_GROUP_NOTIFY_SET_KVM notifier callback function for the mdev matrix
- device. The open is invoked when QEMU connects the VFIO iommu group
- for the mdev matrix device to the MDEV bus. Access to the KVM structure used
- to configure the KVM guest is provided via this callback. The KVM structure,
- is used to configure the guest's access to the AP matrix defined via the
- mediated matrix device's sysfs attribute files.
- * release:
- unregisters the VFIO_GROUP_NOTIFY_SET_KVM notifier callback function for the
- mdev matrix device and deconfigures the guest's AP matrix.
-
-Configure the APM, AQM and ADM in the CRYCB:
--------------------------------------------
-Configuring the AP matrix for a KVM guest will be performed when the
-VFIO_GROUP_NOTIFY_SET_KVM notifier callback is invoked. The notifier
-function is called when QEMU connects to KVM. The guest's AP matrix is
-configured via it's CRYCB by:
-* Setting the bits in the APM corresponding to the APIDs assigned to the
- mediated matrix device via its 'assign_adapter' interface.
-* Setting the bits in the AQM corresponding to the domains assigned to the
- mediated matrix device via its 'assign_domain' interface.
-* Setting the bits in the ADM corresponding to the domain dIDs assigned to the
- mediated matrix device via its 'assign_control_domains' interface.
-
-The CPU model features for AP
------------------------------
-The AP stack relies on the presence of the AP instructions as well as two
-facilities: The AP Facilities Test (APFT) facility; and the AP Query
-Configuration Information (QCI) facility. These features/facilities are made
-available to a KVM guest via the following CPU model features:
-
-1. ap: Indicates whether the AP instructions are installed on the guest. This
- feature will be enabled by KVM only if the AP instructions are installed
- on the host.
-
-2. apft: Indicates the APFT facility is available on the guest. This facility
- can be made available to the guest only if it is available on the host (i.e.,
- facility bit 15 is set).
-
-3. apqci: Indicates the AP QCI facility is available on the guest. This facility
- can be made available to the guest only if it is available on the host (i.e.,
- facility bit 12 is set).
-
-Note: If the user chooses to specify a CPU model different than the 'host'
-model to QEMU, the CPU model features and facilities need to be turned on
-explicitly; for example:
-
- /usr/bin/qemu-system-s390x ... -cpu z13,ap=on,apqci=on,apft=on
-
-A guest can be precluded from using AP features/facilities by turning them off
-explicitly; for example:
-
- /usr/bin/qemu-system-s390x ... -cpu host,ap=off,apqci=off,apft=off
-
-Note: If the APFT facility is turned off (apft=off) for the guest, the guest
-will not see any AP devices. The zcrypt device drivers that register for type 10
-and newer AP devices - i.e., the cex4card and cex4queue device drivers - need
-the APFT facility to ascertain the facilities installed on a given AP device. If
-the APFT facility is not installed on the guest, then the probe of device
-drivers will fail since only type 10 and newer devices can be configured for
-guest use.
-
-Example:
-=======
-Let's now provide an example to illustrate how KVM guests may be given
-access to AP facilities. For this example, we will show how to configure
-three guests such that executing the lszcrypt command on the guests would
-look like this:
-
-Guest1
-------
-CARD.DOMAIN TYPE MODE
-------------------------------
-05 CEX5C CCA-Coproc
-05.0004 CEX5C CCA-Coproc
-05.00ab CEX5C CCA-Coproc
-06 CEX5A Accelerator
-06.0004 CEX5A Accelerator
-06.00ab CEX5C CCA-Coproc
-
-Guest2
-------
-CARD.DOMAIN TYPE MODE
-------------------------------
-05 CEX5A Accelerator
-05.0047 CEX5A Accelerator
-05.00ff CEX5A Accelerator
-
-Guest2
-------
-CARD.DOMAIN TYPE MODE
-------------------------------
-06 CEX5A Accelerator
-06.0047 CEX5A Accelerator
-06.00ff CEX5A Accelerator
-
-These are the steps:
-
-1. Install the vfio_ap module on the linux host. The dependency chain for the
- vfio_ap module is:
- * iommu
- * s390
- * zcrypt
- * vfio
- * vfio_mdev
- * vfio_mdev_device
- * KVM
-
- To build the vfio_ap module, the kernel build must be configured with the
- following Kconfig elements selected:
- * IOMMU_SUPPORT
- * S390
- * ZCRYPT
- * S390_AP_IOMMU
- * VFIO
- * VFIO_MDEV
- * VFIO_MDEV_DEVICE
- * KVM
-
- If using make menuconfig select the following to build the vfio_ap module:
- -> Device Drivers
- -> IOMMU Hardware Support
- select S390 AP IOMMU Support
- -> VFIO Non-Privileged userspace driver framework
- -> Mediated device driver frramework
- -> VFIO driver for Mediated devices
- -> I/O subsystem
- -> VFIO support for AP devices
-
-2. Secure the AP queues to be used by the three guests so that the host can not
- access them. To secure them, there are two sysfs files that specify
- bitmasks marking a subset of the APQN range as 'usable by the default AP
- queue device drivers' or 'not usable by the default device drivers' and thus
- available for use by the vfio_ap device driver'. The location of the sysfs
- files containing the masks are:
-
- /sys/bus/ap/apmask
- /sys/bus/ap/aqmask
-
- The 'apmask' is a 256-bit mask that identifies a set of AP adapter IDs
- (APID). Each bit in the mask, from left to right (i.e., from most significant
- to least significant bit in big endian order), corresponds to an APID from
- 0-255. If a bit is set, the APID is marked as usable only by the default AP
- queue device drivers; otherwise, the APID is usable by the vfio_ap
- device driver.
-
- The 'aqmask' is a 256-bit mask that identifies a set of AP queue indexes
- (APQI). Each bit in the mask, from left to right (i.e., from most significant
- to least significant bit in big endian order), corresponds to an APQI from
- 0-255. If a bit is set, the APQI is marked as usable only by the default AP
- queue device drivers; otherwise, the APQI is usable by the vfio_ap device
- driver.
-
- Take, for example, the following mask:
-
- 0x7dffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
-
- It indicates:
-
- 1, 2, 3, 4, 5, and 7-255 belong to the default drivers' pool, and 0 and 6
- belong to the vfio_ap device driver's pool.
-
- The APQN of each AP queue device assigned to the linux host is checked by the
- AP bus against the set of APQNs derived from the cross product of APIDs
- and APQIs marked as usable only by the default AP queue device drivers. If a
- match is detected, only the default AP queue device drivers will be probed;
- otherwise, the vfio_ap device driver will be probed.
-
- By default, the two masks are set to reserve all APQNs for use by the default
- AP queue device drivers. There are two ways the default masks can be changed:
-
- 1. The sysfs mask files can be edited by echoing a string into the
- respective sysfs mask file in one of two formats:
-
- * An absolute hex string starting with 0x - like "0x12345678" - sets
- the mask. If the given string is shorter than the mask, it is padded
- with 0s on the right; for example, specifying a mask value of 0x41 is
- the same as specifying:
-
- 0x4100000000000000000000000000000000000000000000000000000000000000
-
- Keep in mind that the mask reads from left to right (i.e., most
- significant to least significant bit in big endian order), so the mask
- above identifies device numbers 1 and 7 (01000001).
-
- If the string is longer than the mask, the operation is terminated with
- an error (EINVAL).
-
- * Individual bits in the mask can be switched on and off by specifying
- each bit number to be switched in a comma separated list. Each bit
- number string must be prepended with a ('+') or minus ('-') to indicate
- the corresponding bit is to be switched on ('+') or off ('-'). Some
- valid values are:
-
- "+0" switches bit 0 on
- "-13" switches bit 13 off
- "+0x41" switches bit 65 on
- "-0xff" switches bit 255 off
-
- The following example:
- +0,-6,+0x47,-0xf0
-
- Switches bits 0 and 71 (0x47) on
- Switches bits 6 and 240 (0xf0) off
-
- Note that the bits not specified in the list remain as they were before
- the operation.
-
- 2. The masks can also be changed at boot time via parameters on the kernel
- command line like this:
-
- ap.apmask=0xffff ap.aqmask=0x40
-
- This would create the following masks:
-
- apmask:
- 0xffff000000000000000000000000000000000000000000000000000000000000
-
- aqmask:
- 0x4000000000000000000000000000000000000000000000000000000000000000
-
- Resulting in these two pools:
-
- default drivers pool: adapter 0-15, domain 1
- alternate drivers pool: adapter 16-255, domains 0, 2-255
-
- Securing the APQNs for our example:
- ----------------------------------
- To secure the AP queues 05.0004, 05.0047, 05.00ab, 05.00ff, 06.0004, 06.0047,
- 06.00ab, and 06.00ff for use by the vfio_ap device driver, the corresponding
- APQNs can either be removed from the default masks:
-
- echo -5,-6 > /sys/bus/ap/apmask
-
- echo -4,-0x47,-0xab,-0xff > /sys/bus/ap/aqmask
-
- Or the masks can be set as follows:
-
- echo 0xf9ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff \
- > apmask
-
- echo 0xf7fffffffffffffffeffffffffffffffffffffffffeffffffffffffffffffffe \
- > aqmask
-
- This will result in AP queues 05.0004, 05.0047, 05.00ab, 05.00ff, 06.0004,
- 06.0047, 06.00ab, and 06.00ff getting bound to the vfio_ap device driver. The
- sysfs directory for the vfio_ap device driver will now contain symbolic links
- to the AP queue devices bound to it:
-
- /sys/bus/ap
- ... [drivers]
- ...... [vfio_ap]
- ......... [05.0004]
- ......... [05.0047]
- ......... [05.00ab]
- ......... [05.00ff]
- ......... [06.0004]
- ......... [06.0047]
- ......... [06.00ab]
- ......... [06.00ff]
-
- Keep in mind that only type 10 and newer adapters (i.e., CEX4 and later)
- can be bound to the vfio_ap device driver. The reason for this is to
- simplify the implementation by not needlessly complicating the design by
- supporting older devices that will go out of service in the relatively near
- future and for which there are few older systems on which to test.
-
- The administrator, therefore, must take care to secure only AP queues that
- can be bound to the vfio_ap device driver. The device type for a given AP
- queue device can be read from the parent card's sysfs directory. For example,
- to see the hardware type of the queue 05.0004:
-
- cat /sys/bus/ap/devices/card05/hwtype
-
- The hwtype must be 10 or higher (CEX4 or newer) in order to be bound to the
- vfio_ap device driver.
-
-3. Create the mediated devices needed to configure the AP matrixes for the
- three guests and to provide an interface to the vfio_ap driver for
- use by the guests:
-
- /sys/devices/vfio_ap/matrix/
- --- [mdev_supported_types]
- ------ [vfio_ap-passthrough] (passthrough mediated matrix device type)
- --------- create
- --------- [devices]
-
- To create the mediated devices for the three guests:
-
- uuidgen > create
- uuidgen > create
- uuidgen > create
-
- or
-
- echo $uuid1 > create
- echo $uuid2 > create
- echo $uuid3 > create
-
- This will create three mediated devices in the [devices] subdirectory named
- after the UUID written to the create attribute file. We call them $uuid1,
- $uuid2 and $uuid3 and this is the sysfs directory structure after creation:
-
- /sys/devices/vfio_ap/matrix/
- --- [mdev_supported_types]
- ------ [vfio_ap-passthrough]
- --------- [devices]
- ------------ [$uuid1]
- --------------- assign_adapter
- --------------- assign_control_domain
- --------------- assign_domain
- --------------- matrix
- --------------- unassign_adapter
- --------------- unassign_control_domain
- --------------- unassign_domain
-
- ------------ [$uuid2]
- --------------- assign_adapter
- --------------- assign_control_domain
- --------------- assign_domain
- --------------- matrix
- --------------- unassign_adapter
- ----------------unassign_control_domain
- ----------------unassign_domain
-
- ------------ [$uuid3]
- --------------- assign_adapter
- --------------- assign_control_domain
- --------------- assign_domain
- --------------- matrix
- --------------- unassign_adapter
- ----------------unassign_control_domain
- ----------------unassign_domain
-
-4. The administrator now needs to configure the matrixes for the mediated
- devices $uuid1 (for Guest1), $uuid2 (for Guest2) and $uuid3 (for Guest3).
-
- This is how the matrix is configured for Guest1:
-
- echo 5 > assign_adapter
- echo 6 > assign_adapter
- echo 4 > assign_domain
- echo 0xab > assign_domain
-
- Control domains can similarly be assigned using the assign_control_domain
- sysfs file.
-
- If a mistake is made configuring an adapter, domain or control domain,
- you can use the unassign_xxx files to unassign the adapter, domain or
- control domain.
-
- To display the matrix configuration for Guest1:
-
- cat matrix
-
- This is how the matrix is configured for Guest2:
-
- echo 5 > assign_adapter
- echo 0x47 > assign_domain
- echo 0xff > assign_domain
-
- This is how the matrix is configured for Guest3:
-
- echo 6 > assign_adapter
- echo 0x47 > assign_domain
- echo 0xff > assign_domain
-
- In order to successfully assign an adapter:
-
- * The adapter number specified must represent a value from 0 up to the
- maximum adapter number configured for the system. If an adapter number
- higher than the maximum is specified, the operation will terminate with
- an error (ENODEV).
-
- * All APQNs that can be derived from the adapter ID and the IDs of
- the previously assigned domains must be bound to the vfio_ap device
- driver. If no domains have yet been assigned, then there must be at least
- one APQN with the specified APID bound to the vfio_ap driver. If no such
- APQNs are bound to the driver, the operation will terminate with an
- error (EADDRNOTAVAIL).
-
- No APQN that can be derived from the adapter ID and the IDs of the
- previously assigned domains can be assigned to another mediated matrix
- device. If an APQN is assigned to another mediated matrix device, the
- operation will terminate with an error (EADDRINUSE).
-
- In order to successfully assign a domain:
-
- * The domain number specified must represent a value from 0 up to the
- maximum domain number configured for the system. If a domain number
- higher than the maximum is specified, the operation will terminate with
- an error (ENODEV).
-
- * All APQNs that can be derived from the domain ID and the IDs of
- the previously assigned adapters must be bound to the vfio_ap device
- driver. If no domains have yet been assigned, then there must be at least
- one APQN with the specified APQI bound to the vfio_ap driver. If no such
- APQNs are bound to the driver, the operation will terminate with an
- error (EADDRNOTAVAIL).
-
- No APQN that can be derived from the domain ID and the IDs of the
- previously assigned adapters can be assigned to another mediated matrix
- device. If an APQN is assigned to another mediated matrix device, the
- operation will terminate with an error (EADDRINUSE).
-
- In order to successfully assign a control domain, the domain number
- specified must represent a value from 0 up to the maximum domain number
- configured for the system. If a control domain number higher than the maximum
- is specified, the operation will terminate with an error (ENODEV).
-
-5. Start Guest1:
-
- /usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on \
- -device vfio-ap,sysfsdev=/sys/devices/vfio_ap/matrix/$uuid1 ...
-
-7. Start Guest2:
-
- /usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on \
- -device vfio-ap,sysfsdev=/sys/devices/vfio_ap/matrix/$uuid2 ...
-
-7. Start Guest3:
-
- /usr/bin/qemu-system-s390x ... -cpu host,ap=on,apqci=on,apft=on \
- -device vfio-ap,sysfsdev=/sys/devices/vfio_ap/matrix/$uuid3 ...
-
-When the guest is shut down, the mediated matrix devices may be removed.
-
-Using our example again, to remove the mediated matrix device $uuid1:
-
- /sys/devices/vfio_ap/matrix/
- --- [mdev_supported_types]
- ------ [vfio_ap-passthrough]
- --------- [devices]
- ------------ [$uuid1]
- --------------- remove
-
-
- echo 1 > remove
-
- This will remove all of the mdev matrix device's sysfs structures including
- the mdev device itself. To recreate and reconfigure the mdev matrix device,
- all of the steps starting with step 3 will have to be performed again. Note
- that the remove will fail if a guest using the mdev is still running.
-
- It is not necessary to remove an mdev matrix device, but one may want to
- remove it if no guest will use it during the remaining lifetime of the linux
- host. If the mdev matrix device is removed, one may want to also reconfigure
- the pool of adapters and queues reserved for use by the default drivers.
-
-Limitations
-===========
-* The KVM/kernel interfaces do not provide a way to prevent restoring an APQN
- to the default drivers pool of a queue that is still assigned to a mediated
- device in use by a guest. It is incumbent upon the administrator to
- ensure there is no mediated device in use by a guest to which the APQN is
- assigned lest the host be given access to the private data of the AP queue
- device such as a private key configured specifically for the guest.
-
-* Dynamically modifying the AP matrix for a running guest (which would amount to
- hot(un)plug of AP devices for the guest) is currently not supported
-
-* Live guest migration is not supported for guests using AP devices.
--- /dev/null
+==================================
+vfio-ccw: the basic infrastructure
+==================================
+
+Introduction
+------------
+
+Here we describe the vfio support for I/O subchannel devices for
+Linux/s390. Motivation for vfio-ccw is to passthrough subchannels to a
+virtual machine, while vfio is the means.
+
+Different than other hardware architectures, s390 has defined a unified
+I/O access method, which is so called Channel I/O. It has its own access
+patterns:
+
+- Channel programs run asynchronously on a separate (co)processor.
+- The channel subsystem will access any memory designated by the caller
+ in the channel program directly, i.e. there is no iommu involved.
+
+Thus when we introduce vfio support for these devices, we realize it
+with a mediated device (mdev) implementation. The vfio mdev will be
+added to an iommu group, so as to make itself able to be managed by the
+vfio framework. And we add read/write callbacks for special vfio I/O
+regions to pass the channel programs from the mdev to its parent device
+(the real I/O subchannel device) to do further address translation and
+to perform I/O instructions.
+
+This document does not intend to explain the s390 I/O architecture in
+every detail. More information/reference could be found here:
+
+- A good start to know Channel I/O in general:
+ https://en.wikipedia.org/wiki/Channel_I/O
+- s390 architecture:
+ s390 Principles of Operation manual (IBM Form. No. SA22-7832)
+- The existing QEMU code which implements a simple emulated channel
+ subsystem could also be a good reference. It makes it easier to follow
+ the flow.
+ qemu/hw/s390x/css.c
+
+For vfio mediated device framework:
+- Documentation/vfio-mediated-device.txt
+
+Motivation of vfio-ccw
+----------------------
+
+Typically, a guest virtualized via QEMU/KVM on s390 only sees
+paravirtualized virtio devices via the "Virtio Over Channel I/O
+(virtio-ccw)" transport. This makes virtio devices discoverable via
+standard operating system algorithms for handling channel devices.
+
+However this is not enough. On s390 for the majority of devices, which
+use the standard Channel I/O based mechanism, we also need to provide
+the functionality of passing through them to a QEMU virtual machine.
+This includes devices that don't have a virtio counterpart (e.g. tape
+drives) or that have specific characteristics which guests want to
+exploit.
+
+For passing a device to a guest, we want to use the same interface as
+everybody else, namely vfio. We implement this vfio support for channel
+devices via the vfio mediated device framework and the subchannel device
+driver "vfio_ccw".
+
+Access patterns of CCW devices
+------------------------------
+
+s390 architecture has implemented a so called channel subsystem, that
+provides a unified view of the devices physically attached to the
+systems. Though the s390 hardware platform knows about a huge variety of
+different peripheral attachments like disk devices (aka. DASDs), tapes,
+communication controllers, etc. They can all be accessed by a well
+defined access method and they are presenting I/O completion a unified
+way: I/O interruptions.
+
+All I/O requires the use of channel command words (CCWs). A CCW is an
+instruction to a specialized I/O channel processor. A channel program is
+a sequence of CCWs which are executed by the I/O channel subsystem. To
+issue a channel program to the channel subsystem, it is required to
+build an operation request block (ORB), which can be used to point out
+the format of the CCW and other control information to the system. The
+operating system signals the I/O channel subsystem to begin executing
+the channel program with a SSCH (start sub-channel) instruction. The
+central processor is then free to proceed with non-I/O instructions
+until interrupted. The I/O completion result is received by the
+interrupt handler in the form of interrupt response block (IRB).
+
+Back to vfio-ccw, in short:
+
+- ORBs and channel programs are built in guest kernel (with guest
+ physical addresses).
+- ORBs and channel programs are passed to the host kernel.
+- Host kernel translates the guest physical addresses to real addresses
+ and starts the I/O with issuing a privileged Channel I/O instruction
+ (e.g SSCH).
+- channel programs run asynchronously on a separate processor.
+- I/O completion will be signaled to the host with I/O interruptions.
+ And it will be copied as IRB to user space to pass it back to the
+ guest.
+
+Physical vfio ccw device and its child mdev
+-------------------------------------------
+
+As mentioned above, we realize vfio-ccw with a mdev implementation.
+
+Channel I/O does not have IOMMU hardware support, so the physical
+vfio-ccw device does not have an IOMMU level translation or isolation.
+
+Subchannel I/O instructions are all privileged instructions. When
+handling the I/O instruction interception, vfio-ccw has the software
+policing and translation how the channel program is programmed before
+it gets sent to hardware.
+
+Within this implementation, we have two drivers for two types of
+devices:
+
+- The vfio_ccw driver for the physical subchannel device.
+ This is an I/O subchannel driver for the real subchannel device. It
+ realizes a group of callbacks and registers to the mdev framework as a
+ parent (physical) device. As a consequence, mdev provides vfio_ccw a
+ generic interface (sysfs) to create mdev devices. A vfio mdev could be
+ created by vfio_ccw then and added to the mediated bus. It is the vfio
+ device that added to an IOMMU group and a vfio group.
+ vfio_ccw also provides an I/O region to accept channel program
+ request from user space and store I/O interrupt result for user
+ space to retrieve. To notify user space an I/O completion, it offers
+ an interface to setup an eventfd fd for asynchronous signaling.
+
+- The vfio_mdev driver for the mediated vfio ccw device.
+ This is provided by the mdev framework. It is a vfio device driver for
+ the mdev that created by vfio_ccw.
+ It realizes a group of vfio device driver callbacks, adds itself to a
+ vfio group, and registers itself to the mdev framework as a mdev
+ driver.
+ It uses a vfio iommu backend that uses the existing map and unmap
+ ioctls, but rather than programming them into an IOMMU for a device,
+ it simply stores the translations for use by later requests. This
+ means that a device programmed in a VM with guest physical addresses
+ can have the vfio kernel convert that address to process virtual
+ address, pin the page and program the hardware with the host physical
+ address in one step.
+ For a mdev, the vfio iommu backend will not pin the pages during the
+ VFIO_IOMMU_MAP_DMA ioctl. Mdev framework will only maintain a database
+ of the iova<->vaddr mappings in this operation. And they export a
+ vfio_pin_pages and a vfio_unpin_pages interfaces from the vfio iommu
+ backend for the physical devices to pin and unpin pages by demand.
+
+Below is a high Level block diagram::
+
+ +-------------+
+ | |
+ | +---------+ | mdev_register_driver() +--------------+
+ | | Mdev | +<-----------------------+ |
+ | | bus | | | vfio_mdev.ko |
+ | | driver | +----------------------->+ |<-> VFIO user
+ | +---------+ | probe()/remove() +--------------+ APIs
+ | |
+ | MDEV CORE |
+ | MODULE |
+ | mdev.ko |
+ | +---------+ | mdev_register_device() +--------------+
+ | |Physical | +<-----------------------+ |
+ | | device | | | vfio_ccw.ko |<-> subchannel
+ | |interface| +----------------------->+ | device
+ | +---------+ | callback +--------------+
+ +-------------+
+
+The process of how these work together.
+
+1. vfio_ccw.ko drives the physical I/O subchannel, and registers the
+ physical device (with callbacks) to mdev framework.
+ When vfio_ccw probing the subchannel device, it registers device
+ pointer and callbacks to the mdev framework. Mdev related file nodes
+ under the device node in sysfs would be created for the subchannel
+ device, namely 'mdev_create', 'mdev_destroy' and
+ 'mdev_supported_types'.
+2. Create a mediated vfio ccw device.
+ Use the 'mdev_create' sysfs file, we need to manually create one (and
+ only one for our case) mediated device.
+3. vfio_mdev.ko drives the mediated ccw device.
+ vfio_mdev is also the vfio device drvier. It will probe the mdev and
+ add it to an iommu_group and a vfio_group. Then we could pass through
+ the mdev to a guest.
+
+vfio-ccw I/O region
+-------------------
+
+An I/O region is used to accept channel program request from user
+space and store I/O interrupt result for user space to retrieve. The
+definition of the region is::
+
+ struct ccw_io_region {
+ #define ORB_AREA_SIZE 12
+ __u8 orb_area[ORB_AREA_SIZE];
+ #define SCSW_AREA_SIZE 12
+ __u8 scsw_area[SCSW_AREA_SIZE];
+ #define IRB_AREA_SIZE 96
+ __u8 irb_area[IRB_AREA_SIZE];
+ __u32 ret_code;
+ } __packed;
+
+While starting an I/O request, orb_area should be filled with the
+guest ORB, and scsw_area should be filled with the SCSW of the Virtual
+Subchannel.
+
+irb_area stores the I/O result.
+
+ret_code stores a return code for each access of the region.
+
+vfio-ccw operation details
+--------------------------
+
+vfio-ccw follows what vfio-pci did on the s390 platform and uses
+vfio-iommu-type1 as the vfio iommu backend.
+
+* CCW translation APIs
+ A group of APIs (start with `cp_`) to do CCW translation. The CCWs
+ passed in by a user space program are organized with their guest
+ physical memory addresses. These APIs will copy the CCWs into kernel
+ space, and assemble a runnable kernel channel program by updating the
+ guest physical addresses with their corresponding host physical addresses.
+ Note that we have to use IDALs even for direct-access CCWs, as the
+ referenced memory can be located anywhere, including above 2G.
+
+* vfio_ccw device driver
+ This driver utilizes the CCW translation APIs and introduces
+ vfio_ccw, which is the driver for the I/O subchannel devices you want
+ to pass through.
+ vfio_ccw implements the following vfio ioctls::
+
+ VFIO_DEVICE_GET_INFO
+ VFIO_DEVICE_GET_IRQ_INFO
+ VFIO_DEVICE_GET_REGION_INFO
+ VFIO_DEVICE_RESET
+ VFIO_DEVICE_SET_IRQS
+
+ This provides an I/O region, so that the user space program can pass a
+ channel program to the kernel, to do further CCW translation before
+ issuing them to a real device.
+ This also provides the SET_IRQ ioctl to setup an event notifier to
+ notify the user space program the I/O completion in an asynchronous
+ way.
+
+The use of vfio-ccw is not limited to QEMU, while QEMU is definitely a
+good example to get understand how these patches work. Here is a little
+bit more detail how an I/O request triggered by the QEMU guest will be
+handled (without error handling).
+
+Explanation:
+
+- Q1-Q7: QEMU side process.
+- K1-K5: Kernel side process.
+
+Q1.
+ Get I/O region info during initialization.
+
+Q2.
+ Setup event notifier and handler to handle I/O completion.
+
+... ...
+
+Q3.
+ Intercept a ssch instruction.
+Q4.
+ Write the guest channel program and ORB to the I/O region.
+
+ K1.
+ Copy from guest to kernel.
+ K2.
+ Translate the guest channel program to a host kernel space
+ channel program, which becomes runnable for a real device.
+ K3.
+ With the necessary information contained in the orb passed in
+ by QEMU, issue the ccwchain to the device.
+ K4.
+ Return the ssch CC code.
+Q5.
+ Return the CC code to the guest.
+
+... ...
+
+ K5.
+ Interrupt handler gets the I/O result and write the result to
+ the I/O region.
+ K6.
+ Signal QEMU to retrieve the result.
+
+Q6.
+ Get the signal and event handler reads out the result from the I/O
+ region.
+Q7.
+ Update the irb for the guest.
+
+Limitations
+-----------
+
+The current vfio-ccw implementation focuses on supporting basic commands
+needed to implement block device functionality (read/write) of DASD/ECKD
+device only. Some commands may need special handling in the future, for
+example, anything related to path grouping.
+
+DASD is a kind of storage device. While ECKD is a data recording format.
+More information for DASD and ECKD could be found here:
+https://en.wikipedia.org/wiki/Direct-access_storage_device
+https://en.wikipedia.org/wiki/Count_key_data
+
+Together with the corresponding work in QEMU, we can bring the passed
+through DASD/ECKD device online in a guest now and use it as a block
+device.
+
+While the current code allows the guest to start channel programs via
+START SUBCHANNEL, support for HALT SUBCHANNEL or CLEAR SUBCHANNEL is
+not yet implemented.
+
+vfio-ccw supports classic (command mode) channel I/O only. Transport
+mode (HPF) is not supported.
+
+QDIO subchannels are currently not supported. Classic devices other than
+DASD/ECKD might work, but have not been tested.
+
+Reference
+---------
+1. ESA/s390 Principles of Operation manual (IBM Form. No. SA22-7832)
+2. ESA/390 Common I/O Device Commands manual (IBM Form. No. SA22-7204)
+3. https://en.wikipedia.org/wiki/Channel_I/O
+4. Documentation/s390/cds.rst
+5. Documentation/vfio.txt
+6. Documentation/vfio-mediated-device.txt
+++ /dev/null
-vfio-ccw: the basic infrastructure
-==================================
-
-Introduction
-------------
-
-Here we describe the vfio support for I/O subchannel devices for
-Linux/s390. Motivation for vfio-ccw is to passthrough subchannels to a
-virtual machine, while vfio is the means.
-
-Different than other hardware architectures, s390 has defined a unified
-I/O access method, which is so called Channel I/O. It has its own access
-patterns:
-- Channel programs run asynchronously on a separate (co)processor.
-- The channel subsystem will access any memory designated by the caller
- in the channel program directly, i.e. there is no iommu involved.
-Thus when we introduce vfio support for these devices, we realize it
-with a mediated device (mdev) implementation. The vfio mdev will be
-added to an iommu group, so as to make itself able to be managed by the
-vfio framework. And we add read/write callbacks for special vfio I/O
-regions to pass the channel programs from the mdev to its parent device
-(the real I/O subchannel device) to do further address translation and
-to perform I/O instructions.
-
-This document does not intend to explain the s390 I/O architecture in
-every detail. More information/reference could be found here:
-- A good start to know Channel I/O in general:
- https://en.wikipedia.org/wiki/Channel_I/O
-- s390 architecture:
- s390 Principles of Operation manual (IBM Form. No. SA22-7832)
-- The existing QEMU code which implements a simple emulated channel
- subsystem could also be a good reference. It makes it easier to follow
- the flow.
- qemu/hw/s390x/css.c
-
-For vfio mediated device framework:
-- Documentation/vfio-mediated-device.txt
-
-Motivation of vfio-ccw
-----------------------
-
-Typically, a guest virtualized via QEMU/KVM on s390 only sees
-paravirtualized virtio devices via the "Virtio Over Channel I/O
-(virtio-ccw)" transport. This makes virtio devices discoverable via
-standard operating system algorithms for handling channel devices.
-
-However this is not enough. On s390 for the majority of devices, which
-use the standard Channel I/O based mechanism, we also need to provide
-the functionality of passing through them to a QEMU virtual machine.
-This includes devices that don't have a virtio counterpart (e.g. tape
-drives) or that have specific characteristics which guests want to
-exploit.
-
-For passing a device to a guest, we want to use the same interface as
-everybody else, namely vfio. We implement this vfio support for channel
-devices via the vfio mediated device framework and the subchannel device
-driver "vfio_ccw".
-
-Access patterns of CCW devices
-------------------------------
-
-s390 architecture has implemented a so called channel subsystem, that
-provides a unified view of the devices physically attached to the
-systems. Though the s390 hardware platform knows about a huge variety of
-different peripheral attachments like disk devices (aka. DASDs), tapes,
-communication controllers, etc. They can all be accessed by a well
-defined access method and they are presenting I/O completion a unified
-way: I/O interruptions.
-
-All I/O requires the use of channel command words (CCWs). A CCW is an
-instruction to a specialized I/O channel processor. A channel program is
-a sequence of CCWs which are executed by the I/O channel subsystem. To
-issue a channel program to the channel subsystem, it is required to
-build an operation request block (ORB), which can be used to point out
-the format of the CCW and other control information to the system. The
-operating system signals the I/O channel subsystem to begin executing
-the channel program with a SSCH (start sub-channel) instruction. The
-central processor is then free to proceed with non-I/O instructions
-until interrupted. The I/O completion result is received by the
-interrupt handler in the form of interrupt response block (IRB).
-
-Back to vfio-ccw, in short:
-- ORBs and channel programs are built in guest kernel (with guest
- physical addresses).
-- ORBs and channel programs are passed to the host kernel.
-- Host kernel translates the guest physical addresses to real addresses
- and starts the I/O with issuing a privileged Channel I/O instruction
- (e.g SSCH).
-- channel programs run asynchronously on a separate processor.
-- I/O completion will be signaled to the host with I/O interruptions.
- And it will be copied as IRB to user space to pass it back to the
- guest.
-
-Physical vfio ccw device and its child mdev
--------------------------------------------
-
-As mentioned above, we realize vfio-ccw with a mdev implementation.
-
-Channel I/O does not have IOMMU hardware support, so the physical
-vfio-ccw device does not have an IOMMU level translation or isolation.
-
-Subchannel I/O instructions are all privileged instructions. When
-handling the I/O instruction interception, vfio-ccw has the software
-policing and translation how the channel program is programmed before
-it gets sent to hardware.
-
-Within this implementation, we have two drivers for two types of
-devices:
-- The vfio_ccw driver for the physical subchannel device.
- This is an I/O subchannel driver for the real subchannel device. It
- realizes a group of callbacks and registers to the mdev framework as a
- parent (physical) device. As a consequence, mdev provides vfio_ccw a
- generic interface (sysfs) to create mdev devices. A vfio mdev could be
- created by vfio_ccw then and added to the mediated bus. It is the vfio
- device that added to an IOMMU group and a vfio group.
- vfio_ccw also provides an I/O region to accept channel program
- request from user space and store I/O interrupt result for user
- space to retrieve. To notify user space an I/O completion, it offers
- an interface to setup an eventfd fd for asynchronous signaling.
-
-- The vfio_mdev driver for the mediated vfio ccw device.
- This is provided by the mdev framework. It is a vfio device driver for
- the mdev that created by vfio_ccw.
- It realizes a group of vfio device driver callbacks, adds itself to a
- vfio group, and registers itself to the mdev framework as a mdev
- driver.
- It uses a vfio iommu backend that uses the existing map and unmap
- ioctls, but rather than programming them into an IOMMU for a device,
- it simply stores the translations for use by later requests. This
- means that a device programmed in a VM with guest physical addresses
- can have the vfio kernel convert that address to process virtual
- address, pin the page and program the hardware with the host physical
- address in one step.
- For a mdev, the vfio iommu backend will not pin the pages during the
- VFIO_IOMMU_MAP_DMA ioctl. Mdev framework will only maintain a database
- of the iova<->vaddr mappings in this operation. And they export a
- vfio_pin_pages and a vfio_unpin_pages interfaces from the vfio iommu
- backend for the physical devices to pin and unpin pages by demand.
-
-Below is a high Level block diagram.
-
- +-------------+
- | |
- | +---------+ | mdev_register_driver() +--------------+
- | | Mdev | +<-----------------------+ |
- | | bus | | | vfio_mdev.ko |
- | | driver | +----------------------->+ |<-> VFIO user
- | +---------+ | probe()/remove() +--------------+ APIs
- | |
- | MDEV CORE |
- | MODULE |
- | mdev.ko |
- | +---------+ | mdev_register_device() +--------------+
- | |Physical | +<-----------------------+ |
- | | device | | | vfio_ccw.ko |<-> subchannel
- | |interface| +----------------------->+ | device
- | +---------+ | callback +--------------+
- +-------------+
-
-The process of how these work together.
-1. vfio_ccw.ko drives the physical I/O subchannel, and registers the
- physical device (with callbacks) to mdev framework.
- When vfio_ccw probing the subchannel device, it registers device
- pointer and callbacks to the mdev framework. Mdev related file nodes
- under the device node in sysfs would be created for the subchannel
- device, namely 'mdev_create', 'mdev_destroy' and
- 'mdev_supported_types'.
-2. Create a mediated vfio ccw device.
- Use the 'mdev_create' sysfs file, we need to manually create one (and
- only one for our case) mediated device.
-3. vfio_mdev.ko drives the mediated ccw device.
- vfio_mdev is also the vfio device drvier. It will probe the mdev and
- add it to an iommu_group and a vfio_group. Then we could pass through
- the mdev to a guest.
-
-vfio-ccw I/O region
--------------------
-
-An I/O region is used to accept channel program request from user
-space and store I/O interrupt result for user space to retrieve. The
-definition of the region is:
-
-struct ccw_io_region {
-#define ORB_AREA_SIZE 12
- __u8 orb_area[ORB_AREA_SIZE];
-#define SCSW_AREA_SIZE 12
- __u8 scsw_area[SCSW_AREA_SIZE];
-#define IRB_AREA_SIZE 96
- __u8 irb_area[IRB_AREA_SIZE];
- __u32 ret_code;
-} __packed;
-
-While starting an I/O request, orb_area should be filled with the
-guest ORB, and scsw_area should be filled with the SCSW of the Virtual
-Subchannel.
-
-irb_area stores the I/O result.
-
-ret_code stores a return code for each access of the region.
-
-vfio-ccw operation details
---------------------------
-
-vfio-ccw follows what vfio-pci did on the s390 platform and uses
-vfio-iommu-type1 as the vfio iommu backend.
-
-* CCW translation APIs
- A group of APIs (start with 'cp_') to do CCW translation. The CCWs
- passed in by a user space program are organized with their guest
- physical memory addresses. These APIs will copy the CCWs into kernel
- space, and assemble a runnable kernel channel program by updating the
- guest physical addresses with their corresponding host physical addresses.
- Note that we have to use IDALs even for direct-access CCWs, as the
- referenced memory can be located anywhere, including above 2G.
-
-* vfio_ccw device driver
- This driver utilizes the CCW translation APIs and introduces
- vfio_ccw, which is the driver for the I/O subchannel devices you want
- to pass through.
- vfio_ccw implements the following vfio ioctls:
- VFIO_DEVICE_GET_INFO
- VFIO_DEVICE_GET_IRQ_INFO
- VFIO_DEVICE_GET_REGION_INFO
- VFIO_DEVICE_RESET
- VFIO_DEVICE_SET_IRQS
- This provides an I/O region, so that the user space program can pass a
- channel program to the kernel, to do further CCW translation before
- issuing them to a real device.
- This also provides the SET_IRQ ioctl to setup an event notifier to
- notify the user space program the I/O completion in an asynchronous
- way.
-
-The use of vfio-ccw is not limited to QEMU, while QEMU is definitely a
-good example to get understand how these patches work. Here is a little
-bit more detail how an I/O request triggered by the QEMU guest will be
-handled (without error handling).
-
-Explanation:
-Q1-Q7: QEMU side process.
-K1-K5: Kernel side process.
-
-Q1. Get I/O region info during initialization.
-Q2. Setup event notifier and handler to handle I/O completion.
-
-... ...
-
-Q3. Intercept a ssch instruction.
-Q4. Write the guest channel program and ORB to the I/O region.
- K1. Copy from guest to kernel.
- K2. Translate the guest channel program to a host kernel space
- channel program, which becomes runnable for a real device.
- K3. With the necessary information contained in the orb passed in
- by QEMU, issue the ccwchain to the device.
- K4. Return the ssch CC code.
-Q5. Return the CC code to the guest.
-
-... ...
-
- K5. Interrupt handler gets the I/O result and write the result to
- the I/O region.
- K6. Signal QEMU to retrieve the result.
-Q6. Get the signal and event handler reads out the result from the I/O
- region.
-Q7. Update the irb for the guest.
-
-Limitations
------------
-
-The current vfio-ccw implementation focuses on supporting basic commands
-needed to implement block device functionality (read/write) of DASD/ECKD
-device only. Some commands may need special handling in the future, for
-example, anything related to path grouping.
-
-DASD is a kind of storage device. While ECKD is a data recording format.
-More information for DASD and ECKD could be found here:
-https://en.wikipedia.org/wiki/Direct-access_storage_device
-https://en.wikipedia.org/wiki/Count_key_data
-
-Together with the corresponding work in QEMU, we can bring the passed
-through DASD/ECKD device online in a guest now and use it as a block
-device.
-
-While the current code allows the guest to start channel programs via
-START SUBCHANNEL, support for HALT SUBCHANNEL or CLEAR SUBCHANNEL is
-not yet implemented.
-
-vfio-ccw supports classic (command mode) channel I/O only. Transport
-mode (HPF) is not supported.
-
-QDIO subchannels are currently not supported. Classic devices other than
-DASD/ECKD might work, but have not been tested.
-
-Reference
----------
-1. ESA/s390 Principles of Operation manual (IBM Form. No. SA22-7832)
-2. ESA/390 Common I/O Device Commands manual (IBM Form. No. SA22-7204)
-3. https://en.wikipedia.org/wiki/Channel_I/O
-4. Documentation/s390/cds.txt
-5. Documentation/vfio.txt
-6. Documentation/vfio-mediated-device.txt
--- /dev/null
+==================================
+The s390 SCSI dump tool (zfcpdump)
+==================================
+
+System z machines (z900 or higher) provide hardware support for creating system
+dumps on SCSI disks. The dump process is initiated by booting a dump tool, which
+has to create a dump of the current (probably crashed) Linux image. In order to
+not overwrite memory of the crashed Linux with data of the dump tool, the
+hardware saves some memory plus the register sets of the boot CPU before the
+dump tool is loaded. There exists an SCLP hardware interface to obtain the saved
+memory afterwards. Currently 32 MB are saved.
+
+This zfcpdump implementation consists of a Linux dump kernel together with
+a user space dump tool, which are loaded together into the saved memory region
+below 32 MB. zfcpdump is installed on a SCSI disk using zipl (as contained in
+the s390-tools package) to make the device bootable. The operator of a Linux
+system can then trigger a SCSI dump by booting the SCSI disk, where zfcpdump
+resides on.
+
+The user space dump tool accesses the memory of the crashed system by means
+of the /proc/vmcore interface. This interface exports the crashed system's
+memory and registers in ELF core dump format. To access the memory which has
+been saved by the hardware SCLP requests will be created at the time the data
+is needed by /proc/vmcore. The tail part of the crashed systems memory which
+has not been stashed by hardware can just be copied from real memory.
+
+To build a dump enabled kernel the kernel config option CONFIG_CRASH_DUMP
+has to be set.
+
+To get a valid zfcpdump kernel configuration use "make zfcpdump_defconfig".
+
+The s390 zipl tool looks for the zfcpdump kernel and optional initrd/initramfs
+under the following locations:
+
+* kernel: <zfcpdump directory>/zfcpdump.image
+* ramdisk: <zfcpdump directory>/zfcpdump.rd
+
+The zfcpdump directory is defined in the s390-tools package.
+
+The user space application of zfcpdump can reside in an intitramfs or an
+initrd. It can also be included in a built-in kernel initramfs. The application
+reads from /proc/vmcore or zcore/mem and writes the system dump to a SCSI disk.
+
+The s390-tools package version 1.24.0 and above builds an external zfcpdump
+initramfs with a user space application that writes the dump to a SCSI
+partition.
+
+For more information on how to use zfcpdump refer to the s390 'Using the Dump
+Tools book', which is available from
+http://www.ibm.com/developerworks/linux/linux390.
+++ /dev/null
-The s390 SCSI dump tool (zfcpdump)
-
-System z machines (z900 or higher) provide hardware support for creating system
-dumps on SCSI disks. The dump process is initiated by booting a dump tool, which
-has to create a dump of the current (probably crashed) Linux image. In order to
-not overwrite memory of the crashed Linux with data of the dump tool, the
-hardware saves some memory plus the register sets of the boot CPU before the
-dump tool is loaded. There exists an SCLP hardware interface to obtain the saved
-memory afterwards. Currently 32 MB are saved.
-
-This zfcpdump implementation consists of a Linux dump kernel together with
-a user space dump tool, which are loaded together into the saved memory region
-below 32 MB. zfcpdump is installed on a SCSI disk using zipl (as contained in
-the s390-tools package) to make the device bootable. The operator of a Linux
-system can then trigger a SCSI dump by booting the SCSI disk, where zfcpdump
-resides on.
-
-The user space dump tool accesses the memory of the crashed system by means
-of the /proc/vmcore interface. This interface exports the crashed system's
-memory and registers in ELF core dump format. To access the memory which has
-been saved by the hardware SCLP requests will be created at the time the data
-is needed by /proc/vmcore. The tail part of the crashed systems memory which
-has not been stashed by hardware can just be copied from real memory.
-
-To build a dump enabled kernel the kernel config option CONFIG_CRASH_DUMP
-has to be set.
-
-To get a valid zfcpdump kernel configuration use "make zfcpdump_defconfig".
-
-The s390 zipl tool looks for the zfcpdump kernel and optional initrd/initramfs
-under the following locations:
-
-* kernel: <zfcpdump directory>/zfcpdump.image
-* ramdisk: <zfcpdump directory>/zfcpdump.rd
-
-The zfcpdump directory is defined in the s390-tools package.
-
-The user space application of zfcpdump can reside in an intitramfs or an
-initrd. It can also be included in a built-in kernel initramfs. The application
-reads from /proc/vmcore or zcore/mem and writes the system dump to a SCSI disk.
-
-The s390-tools package version 1.24.0 and above builds an external zfcpdump
-initramfs with a user space application that writes the dump to a SCSI
-partition.
-
-For more information on how to use zfcpdump refer to the s390 'Using the Dump
-Tools book', which is available from
-http://www.ibm.com/developerworks/linux/linux390.
L: kvm@vger.kernel.org
S: Supported
F: drivers/s390/cio/vfio_ccw*
-F: Documentation/s390/vfio-ccw.txt
+F: Documentation/s390/vfio-ccw.rst
F: include/uapi/linux/vfio_ccw.h
S390 ZCRYPT DRIVER
F: drivers/s390/crypto/vfio_ap_drv.c
F: drivers/s390/crypto/vfio_ap_private.h
F: drivers/s390/crypto/vfio_ap_ops.c
-F: Documentation/s390/vfio-ap.txt
+F: Documentation/s390/vfio-ap.rst
S390 ZFCP DRIVER
M: Steffen Maier <maier@linux.ibm.com>
Crash dump kernels are loaded in the main kernel with kexec-tools
into a specially reserved region and then later executed after
a crash by kdump/kexec.
- Refer to <file:Documentation/s390/zfcpdump.txt> for more details on this.
+ Refer to <file:Documentation/s390/zfcpdump.rst> for more details on this.
This option also enables s390 zfcpdump.
- See also <file:Documentation/s390/zfcpdump.txt>
+ See also <file:Documentation/s390/zfcpdump.rst>
endmenu
/*
* IMPORTANT: Use "%s" in sprintf format strings with care! Only pointers are
- * stored in the s390dbf. See Documentation/s390/s390dbf.txt for more details!
+ * stored in the s390dbf. See Documentation/s390/s390dbf.rst for more details!
*/
extern debug_entry_t *
__debug_sprintf_event(debug_info_t *id, int level, char *string, ...)
/*
* IMPORTANT: Use "%s" in sprintf format strings with care! Only pointers are
- * stored in the s390dbf. See Documentation/s390/s390dbf.txt for more details!
+ * stored in the s390dbf. See Documentation/s390/s390dbf.rst for more details!
*/
extern debug_entry_t *
__debug_sprintf_exception(debug_info_t *id, int level, char *string, ...)
* dumps on SCSI disks (zfcpdump). The "zcore/mem" debugfs file shows the same
* dump format as s390 standalone dumps.
*
- * For more information please refer to Documentation/s390/zfcpdump.txt
+ * For more information please refer to Documentation/s390/zfcpdump.rst
*
* Copyright IBM Corp. 2003, 2008
* Author(s): Michael Holzheu
projects / mirror_ubuntu-eoan-kernel.git / commitdiff