Overview of Document:
=====================
This document is intended to give an good overview of how to debug
-Linux for s/390 & z/Architecture it isn't intended as a complete reference & not a
-tutorial on the fundamentals of C & assembly, it dosen't go into
+Linux for s/390 & z/Architecture. It isn't intended as a complete reference & 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.
0 0 Reserved ( must be 0 ) otherwise specification exception occurs.
1 1 Program Event Recording 1 PER enabled,
- PER is used to facilititate debugging e.g. single stepping.
+ PER is used to facilitate debugging e.g. single stepping.
2-4 2-4 Reserved ( must be 0 ).
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
+ compatibility), linux always runs with this bit set to 1
33-64 Instruction address.
33-63 Reserved must be 0
are used by the processor itself for holding such information as exception indications &
entry points for exceptions.
Bytes after 0xc00 hex are used by linux for per processor globals on s/390 & z/Architecture
-( there is a gap on z/Architecure too currently between 0xc00 & 1000 which linux uses ).
+( there is a gap on z/Architecture too currently between 0xc00 & 1000 which linux uses ).
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
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
+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
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).
+(which we use for per-processor globals).
-The kernel stack pointer is intimately tied with the task stucture for
+The kernel stack pointer is intimately tied with the task structure for
each processor as follows.
s/390
}
i.e. just anding the current kernel stack pointer with the mask -8192.
-Thankfully because Linux dosen't have support for nested IO interrupts
+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.
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 probalby
+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.
back-chain:
This is a pointer to the stack pointer before entering a
framed functions ( see frameless function ) prologue got by
-deferencing the address of the current stack pointer,
+dereferencing the address of the current stack pointer,
i.e. got by accessing the 32 bit value at the stack pointers
current location.
1) You can double check whether the files you expect to be included are the ones
that are being included ( e.g. double check that you aren't going to the i386 asm directory ).
2) Check that macro definitions aren't clashing with typedefs,
-3) Check that definitons aren't being used before they are being included.
+3) Check that definitions aren't being used before they are being included.
4) Helps put the line emitting the error under the microscope if it contains macros.
For convenience the Linux kernel's makefile will do preprocessing automatically for you
A source/assembly mixed dump of the kernel can be done with the line
objdump --source vmlinux > vmlinux.lst
-Also if the file isn't compiled -g this will output as much debugging information
-as it can ( e.g. function names ), however, this is very slow as it spends lots
-of time searching for debugging info, the following self explanitory line should be used
-instead if the code isn't compiled -g.
+Also, if the file isn't compiled -g, this will output as much debugging information
+as it can (e.g. function names). This is very slow as it spends lots
+of time searching for debugging info. The following self explanatory line should be used
+instead if the code isn't compiled -g, as it is much faster:
objdump --disassemble-all --syms vmlinux > vmlinux.lst
-as it is much faster
As hard drive space is valuble most of us use the following approach.
1) Look at the emitted psw on the console to find the crash address in the kernel.
6) rm /arch/s390/kernel/signal.o
7) make /arch/s390/kernel/signal.o
8) watch the gcc command line emitted
-9) type it in again or alernatively cut & paste it on the console adding the -g option.
+9) type it in again or alternatively cut & paste it on the console adding the -g option.
10) objdump --source arch/s390/kernel/signal.o > signal.lst
This will output the source & the assembly intermixed, as the snippet below shows
This will unfortunately output addresses which aren't the same
strace ping -c 1 127.0.0.1
& then look at the man pages for each of the syscalls below,
( In fact this is sometimes easier than looking at some spagetti
-source which conditionally compiles for several architectures )
-Not everything that it throws out needs to make sense immeadiately
+source which conditionally compiles for several architectures ).
+Not everything that it throws out needs to make sense immediately.
Just looking quickly you can see that it is making up a RAW socket
for the ICMP protocol.
Example 3
---------
-Getting sophistocated
-telnetd crashes on & I don't know why
+Getting sophisticated
+telnetd crashes & I don't know why
+
Steps
-----
1) Replace the following line in /etc/inetd.conf
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 convient if you aren't updating the kernel much &
+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 ).
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 & device end
status in the IRB without channel checks etc. your IO probably went okay. If you didn't you
-probably need a doctorto examine the IRB & extended status word etc.
-If an error occurs more sophistocated control units have a facitity known as
+probably need a doctor to examine the IRB & extended status word etc.
+If an error occurs, more sophistocated control units have a facitity 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.
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 Paralell IO interface.
+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 390 IO systems come in 2 flavours the current 390 machines support both
-The Older 360 & 370 Interface,sometimes called the paralell I/O interface,
+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 paralell channel path/bus has parity & data on the "Bus" cable
+This byte wide Parallel channel path/bus has parity & data on the "Bus" cable
& control lines on the "Tag" cable. These can operate in byte multiplex mode for
sharing between several slow devices or burst mode & monopolize the channel for the
whole burst. Upto 256 devices can be addressed on one of these cables. These cables are
DASD's direct access storage devices ( otherwise known as hard disks ).
Tape Drives.
CTC ( Channel to Channel Adapters ),
-ESCON or Paralell Cables used as a very high speed serial link
+ESCON or Parallel Cables used as a very high speed serial link
between 2 machines. We use 2 cables under linux to do a bi-directional serial link.
OSA 7C14 ON OSA 7C14 SUBCHANNEL = 0002
OSA 7C15 ON OSA 7C15 SUBCHANNEL = 0003
-If you have a guest with certain priviliges you may be able to see devices
-which don't belong to you to avoid this do add the option V.
+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
RECEIVE / LOG TXT A1 ( replace
8)
filel & press F11 to look at it
-You should see someting like.
+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
--------
info registers: displays registers other than floating point.
info all-registers: displays floating points as well.
-disassemble: dissassembles
+disassemble: disassembles
e.g.
disassemble without parameters will disassemble the current function
disassemble $pc $pc+10
info breakpoints: shows all current breakpoints
-info stack: shows stack back trace ( if this dosent work too well, I'll show you the
+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.
list:
e.g.
list lists current function source
-list 1,10 list first 10 lines of curret file.
+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 sensititive about slashes )
+(note it is a bit sensititive about slashes)
e.g. To add the root of the filesystem to the searchpath do
directory //
Disassembling instructions without debug info
---------------------------------------------
-gdb typically compains if there is a lack of debugging
-symbols in the disassemble command with
-"No function contains specified address." to get around
+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.
/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 inefficent ptrace interface for peeking at DATA.
+rather inefficient ptrace interface for peeking at DATA.
cat status
+ RELSTATUS=release
+ MACHTYPE=i586-pc-linux-gnu
-perl -d <scriptname> runs the perlscript in a fully intercative debugger
+perl -d <scriptname> runs the perlscript in a fully interactive debugger
<like gdb>.
Type 'h' in the debugger for help.
projects / mirror_ubuntu-artful-kernel.git / blobdiff