[mirror_ubuntu-artful-kernel.git] / arch / x86 / Kconfig.debug

menu "Kernel hacking"

config TRACE_IRQFLAGS_SUPPORT
	def_bool y

source "lib/Kconfig.debug"

config NONPROMISC_DEVMEM
	bool "Disable promiscuous /dev/mem"
	help
	  The /dev/mem file by default only allows userspace access to PCI
	  space and the BIOS code and data regions. This is sufficient for
	  dosemu and X and all common users of /dev/mem. With this config
	  option, you allow userspace access to all of memory, including
	  kernel and userspace memory. Accidental access to this is
	  obviously disasterous, but specific access can be used by people
	  debugging the kernel.

config EARLY_PRINTK
	bool "Early printk" if EMBEDDED
	default y
	help
	  Write kernel log output directly into the VGA buffer or to a serial
	  port.

	  This is useful for kernel debugging when your machine crashes very
	  early before the console code is initialized. For normal operation
	  it is not recommended because it looks ugly and doesn't cooperate
	  with klogd/syslogd or the X server. You should normally N here,
	  unless you want to debug such a crash.

config DEBUG_STACKOVERFLOW
	bool "Check for stack overflows"
	depends on DEBUG_KERNEL
	help
	  This option will cause messages to be printed if free stack space
	  drops below a certain limit.

config DEBUG_STACK_USAGE
	bool "Stack utilization instrumentation"
	depends on DEBUG_KERNEL
	help
	  Enables the display of the minimum amount of free stack which each
	  task has ever had available in the sysrq-T and sysrq-P debug output.

	  This option will slow down process creation somewhat.

config DEBUG_PAGEALLOC
	bool "Debug page memory allocations"
	depends on DEBUG_KERNEL
	help
	  Unmap pages from the kernel linear mapping after free_pages().
	  This results in a large slowdown, but helps to find certain types
	  of memory corruptions.

config DEBUG_PER_CPU_MAPS
	bool "Debug access to per_cpu maps"
	depends on DEBUG_KERNEL
	depends on X86_64_SMP
	default n
	help
	  Say Y to verify that the per_cpu map being accessed has
	  been setup.  Adds a fair amount of code to kernel memory
	  and decreases performance.

	  Say N if unsure.

config X86_PTDUMP
	bool "Export kernel pagetable layout to userspace via debugfs"
	depends on DEBUG_KERNEL
	select DEBUG_FS
	help
	  Say Y here if you want to show the kernel pagetable layout in a
	  debugfs file. This information is only useful for kernel developers
	  who are working in architecture specific areas of the kernel.
	  It is probably not a good idea to enable this feature in a production
	  kernel.
	  If in doubt, say "N"

config DEBUG_RODATA
	bool "Write protect kernel read-only data structures"
	default y
	depends on DEBUG_KERNEL
	help
	  Mark the kernel read-only data as write-protected in the pagetables,
	  in order to catch accidental (and incorrect) writes to such const
	  data. This is recommended so that we can catch kernel bugs sooner.
	  If in doubt, say "Y".

config DIRECT_GBPAGES
	bool "Enable gbpages-mapped kernel pagetables"
	depends on DEBUG_KERNEL && EXPERIMENTAL && X86_64
	help
	  Enable gigabyte pages support (if the CPU supports it). This can
	  improve the kernel's performance a tiny bit by reducing TLB
	  pressure.

	  This is experimental code.

	  If in doubt, say "N".

config DEBUG_RODATA_TEST
	bool "Testcase for the DEBUG_RODATA feature"
	depends on DEBUG_RODATA
	help
	  This option enables a testcase for the DEBUG_RODATA
	  feature as well as for the change_page_attr() infrastructure.
	  If in doubt, say "N"

config DEBUG_NX_TEST
	tristate "Testcase for the NX non-executable stack feature"
	depends on DEBUG_KERNEL && m
	help
	  This option enables a testcase for the CPU NX capability
	  and the software setup of this feature.
	  If in doubt, say "N"

config 4KSTACKS
	bool "Use 4Kb for kernel stacks instead of 8Kb"
	depends on X86_32
	help
	  If you say Y here the kernel will use a 4Kb stacksize for the
	  kernel stack attached to each process/thread. This facilitates
	  running more threads on a system and also reduces the pressure
	  on the VM subsystem for higher order allocations. This option
	  will also use IRQ stacks to compensate for the reduced stackspace.

config X86_FIND_SMP_CONFIG
	def_bool y
	depends on X86_LOCAL_APIC || X86_VOYAGER
	depends on X86_32

config X86_MPPARSE
	def_bool y
	depends on (X86_32 && (X86_LOCAL_APIC && !X86_VISWS)) || X86_64

config DOUBLEFAULT
	default y
	bool "Enable doublefault exception handler" if EMBEDDED
	depends on X86_32
	help
	  This option allows trapping of rare doublefault exceptions that
	  would otherwise cause a system to silently reboot. Disabling this
	  option saves about 4k and might cause you much additional grey
	  hair.

config IOMMU_DEBUG
	bool "Enable IOMMU debugging"
	depends on GART_IOMMU && DEBUG_KERNEL
	depends on X86_64
	help
	  Force the IOMMU to on even when you have less than 4GB of
	  memory and add debugging code. On overflow always panic. And
	  allow to enable IOMMU leak tracing. Can be disabled at boot
	  time with iommu=noforce. This will also enable scatter gather
	  list merging.  Currently not recommended for production
	  code. When you use it make sure you have a big enough
	  IOMMU/AGP aperture.  Most of the options enabled by this can
	  be set more finegrained using the iommu= command line
	  options. See Documentation/x86_64/boot-options.txt for more
	  details.

config IOMMU_LEAK
	bool "IOMMU leak tracing"
	depends on DEBUG_KERNEL
	depends on IOMMU_DEBUG
	help
	  Add a simple leak tracer to the IOMMU code. This is useful when you
	  are debugging a buggy device driver that leaks IOMMU mappings.

config PAGE_FAULT_HANDLERS
	bool "Custom page fault handlers"
	depends on DEBUG_KERNEL
	help
	  Allow the use of custom page fault handlers. A kernel module may
	  register a function that is called on every page fault. Custom
	  handlers are used by some debugging and reverse engineering tools.

config MMIOTRACE
	tristate "Memory mapped IO tracing"
	depends on DEBUG_KERNEL && PAGE_FAULT_HANDLERS && RELAY && DEBUG_FS
	default n
	help
	  This will build a kernel module called mmiotrace.

	  Mmiotrace traces Memory Mapped I/O access and is meant for debugging
	  and reverse engineering. The kernel module offers wrapped
	  versions of the ioremap family of functions. The driver to be traced
	  must be modified to call these wrappers. A user space program is
	  required to collect the MMIO data.

	  See http://nouveau.freedesktop.org/wiki/MmioTrace
	  If you are not helping to develop drivers, say N.

config MMIOTRACE_TEST
	tristate "Test module for mmiotrace"
	depends on MMIOTRACE && m
	default n
	help
	  This is a dumb module for testing mmiotrace. It is very dangerous
	  as it will write garbage to IO memory starting at a given address.
	  However, it should be safe to use on e.g. unused portion of VRAM.

	  Say N, unless you absolutely know what you are doing.

#
# IO delay types:
#

config IO_DELAY_TYPE_0X80
	int
	default "0"

config IO_DELAY_TYPE_0XED
	int
	default "1"

config IO_DELAY_TYPE_UDELAY
	int
	default "2"

config IO_DELAY_TYPE_NONE
	int
	default "3"

choice
	prompt "IO delay type"
	default IO_DELAY_0X80

config IO_DELAY_0X80
	bool "port 0x80 based port-IO delay [recommended]"
	help
	  This is the traditional Linux IO delay used for in/out_p.
	  It is the most tested hence safest selection here.

config IO_DELAY_0XED
	bool "port 0xed based port-IO delay"
	help
	  Use port 0xed as the IO delay. This frees up port 0x80 which is
	  often used as a hardware-debug port.

config IO_DELAY_UDELAY
	bool "udelay based port-IO delay"
	help
	  Use udelay(2) as the IO delay method. This provides the delay
	  while not having any side-effect on the IO port space.

config IO_DELAY_NONE
	bool "no port-IO delay"
	help
	  No port-IO delay. Will break on old boxes that require port-IO
	  delay for certain operations. Should work on most new machines.

endchoice

if IO_DELAY_0X80
config DEFAULT_IO_DELAY_TYPE
	int
	default IO_DELAY_TYPE_0X80
endif

if IO_DELAY_0XED
config DEFAULT_IO_DELAY_TYPE
	int
	default IO_DELAY_TYPE_0XED
endif

if IO_DELAY_UDELAY
config DEFAULT_IO_DELAY_TYPE
	int
	default IO_DELAY_TYPE_UDELAY
endif

if IO_DELAY_NONE
config DEFAULT_IO_DELAY_TYPE
	int
	default IO_DELAY_TYPE_NONE
endif

config DEBUG_BOOT_PARAMS
	bool "Debug boot parameters"
	depends on DEBUG_KERNEL
	depends on DEBUG_FS
	help
	  This option will cause struct boot_params to be exported via debugfs.

config CPA_DEBUG
	bool "CPA self-test code"
	depends on DEBUG_KERNEL
	help
	  Do change_page_attr() self-tests every 30 seconds.

config OPTIMIZE_INLINING
	bool "Allow gcc to uninline functions marked 'inline'"
	depends on BROKEN
	help
	  This option determines if the kernel forces gcc to inline the functions
	  developers have marked 'inline'. Doing so takes away freedom from gcc to
	  do what it thinks is best, which is desirable for the gcc 3.x series of
	  compilers. The gcc 4.x series have a rewritten inlining algorithm and
	  disabling this option will generate a smaller kernel there. Hopefully
	  this algorithm is so good that allowing gcc4 to make the decision can
	  become the default in the future, until then this option is there to
	  test gcc for this.

endmenu
Commit	Line	Data
1da177e4 LT	1	menu "Kernel hacking"
1da177e4 LT	2
55f327fa	3	config TRACE_IRQFLAGS_SUPPORT
d013a27c	4	def_bool y
55f327fa	5
1da177e4 LT	6	source "lib/Kconfig.debug"
1da177e4 LT	7
ae531c26 AV	8	config NONPROMISC_DEVMEM
ae531c26 AV	9	bool "Disable promiscuous /dev/mem"
ae531c26 AV	10	help
	11	The /dev/mem file by default only allows userspace access to PCI
	12	space and the BIOS code and data regions. This is sufficient for
	13	dosemu and X and all common users of /dev/mem. With this config
	14	option, you allow userspace access to all of memory, including
	15	kernel and userspace memory. Accidental access to this is
	16	obviously disasterous, but specific access can be used by people
	17	debugging the kernel.
	18
1da177e4	19	config EARLY_PRINTK
076f9776	20	bool "Early printk" if EMBEDDED
1da177e4 LT	21	default y
	22	help
	23	Write kernel log output directly into the VGA buffer or to a serial
	24	port.
	25
	26	This is useful for kernel debugging when your machine crashes very
	27	early before the console code is initialized. For normal operation
	28	it is not recommended because it looks ugly and doesn't cooperate
	29	with klogd/syslogd or the X server. You should normally N here,
	30	unless you want to debug such a crash.
	31
	32	config DEBUG_STACKOVERFLOW
	33	bool "Check for stack overflows"
	34	depends on DEBUG_KERNEL
dab175f3 AB	35	help
	36	This option will cause messages to be printed if free stack space
	37	drops below a certain limit.
1da177e4	38
1da177e4 LT	39	config DEBUG_STACK_USAGE
	40	bool "Stack utilization instrumentation"
	41	depends on DEBUG_KERNEL
	42	help
	43	Enables the display of the minimum amount of free stack which each
	44	task has ever had available in the sysrq-T and sysrq-P debug output.
	45
	46	This option will slow down process creation somewhat.
	47
1da177e4	48	config DEBUG_PAGEALLOC
4a2f0acf	49	bool "Debug page memory allocations"
b1d95f4e	50	depends on DEBUG_KERNEL
1da177e4 LT	51	help
	52	Unmap pages from the kernel linear mapping after free_pages().
	53	This results in a large slowdown, but helps to find certain types
	54	of memory corruptions.
	55
c49a4955	56	config DEBUG_PER_CPU_MAPS
	57	bool "Debug access to per_cpu maps"
	58	depends on DEBUG_KERNEL
	59	depends on X86_64_SMP
	60	default n
	61	help
	62	Say Y to verify that the per_cpu map being accessed has
	63	been setup. Adds a fair amount of code to kernel memory
	64	and decreases performance.
	65
	66	Say N if unsure.
	67
926e5392 AV	68	config X86_PTDUMP
926e5392 AV	69	bool "Export kernel pagetable layout to userspace via debugfs"
fe770bf0	70	depends on DEBUG_KERNEL
926e5392 AV	71	select DEBUG_FS
	72	help
	73	Say Y here if you want to show the kernel pagetable layout in a
	74	debugfs file. This information is only useful for kernel developers
	75	who are working in architecture specific areas of the kernel.
	76	It is probably not a good idea to enable this feature in a production
	77	kernel.
	78	If in doubt, say "N"
	79
63aaf308 AV	80	config DEBUG_RODATA
63aaf308 AV	81	bool "Write protect kernel read-only data structures"
11201e60	82	default y
63aaf308 AV	83	depends on DEBUG_KERNEL
	84	help
	85	Mark the kernel read-only data as write-protected in the pagetables,
	86	in order to catch accidental (and incorrect) writes to such const
11201e60 IM	87	data. This is recommended so that we can catch kernel bugs sooner.
11201e60 IM	88	If in doubt, say "Y".
63aaf308	89
00d1c5e0 IM	90	config DIRECT_GBPAGES
	91	bool "Enable gbpages-mapped kernel pagetables"
	92	depends on DEBUG_KERNEL && EXPERIMENTAL && X86_64
	93	help
	94	Enable gigabyte pages support (if the CPU supports it). This can
	95	improve the kernel's performance a tiny bit by reducing TLB
	96	pressure.
	97
	98	This is experimental code.
	99
	100	If in doubt, say "N".
	101
aba8391f IM	102	config DEBUG_RODATA_TEST
	103	bool "Testcase for the DEBUG_RODATA feature"
	104	depends on DEBUG_RODATA
	105	help
	106	This option enables a testcase for the DEBUG_RODATA
	107	feature as well as for the change_page_attr() infrastructure.
	108	If in doubt, say "N"
	109
	110	config DEBUG_NX_TEST
	111	tristate "Testcase for the NX non-executable stack feature"
	112	depends on DEBUG_KERNEL && m
	113	help
	114	This option enables a testcase for the CPU NX capability
	115	and the software setup of this feature.
	116	If in doubt, say "N"
	117
1da177e4 LT	118	config 4KSTACKS
1da177e4 LT	119	bool "Use 4Kb for kernel stacks instead of 8Kb"
d013a27c	120	depends on X86_32
1da177e4 LT	121	help
	122	If you say Y here the kernel will use a 4Kb stacksize for the
	123	kernel stack attached to each process/thread. This facilitates
	124	running more threads on a system and also reduces the pressure
	125	on the VM subsystem for higher order allocations. This option
	126	will also use IRQ stacks to compensate for the reduced stackspace.
	127
	128	config X86_FIND_SMP_CONFIG
d013a27c	129	def_bool y
1da177e4	130	depends on X86_LOCAL_APIC \|\| X86_VOYAGER
d013a27c	131	depends on X86_32
1da177e4 LT	132
1da177e4 LT	133	config X86_MPPARSE
d013a27c	134	def_bool y
6b0c3d44	135	depends on (X86_32 && (X86_LOCAL_APIC && !X86_VISWS)) \|\| X86_64
1da177e4	136
102e41fd AK	137	config DOUBLEFAULT
	138	default y
	139	bool "Enable doublefault exception handler" if EMBEDDED
d013a27c RD	140	depends on X86_32
	141	help
	142	This option allows trapping of rare doublefault exceptions that
	143	would otherwise cause a system to silently reboot. Disabling this
	144	option saves about 4k and might cause you much additional grey
	145	hair.
	146
	147	config IOMMU_DEBUG
	148	bool "Enable IOMMU debugging"
966396d3	149	depends on GART_IOMMU && DEBUG_KERNEL
d013a27c	150	depends on X86_64
102e41fd	151	help
d013a27c RD	152	Force the IOMMU to on even when you have less than 4GB of
	153	memory and add debugging code. On overflow always panic. And
	154	allow to enable IOMMU leak tracing. Can be disabled at boot
	155	time with iommu=noforce. This will also enable scatter gather
	156	list merging. Currently not recommended for production
	157	code. When you use it make sure you have a big enough
	158	IOMMU/AGP aperture. Most of the options enabled by this can
	159	be set more finegrained using the iommu= command line
	160	options. See Documentation/x86_64/boot-options.txt for more
	161	details.
	162
	163	config IOMMU_LEAK
	164	bool "IOMMU leak tracing"
	165	depends on DEBUG_KERNEL
	166	depends on IOMMU_DEBUG
	167	help
	168	Add a simple leak tracer to the IOMMU code. This is useful when you
	169	are debugging a buggy device driver that leaks IOMMU mappings.
	170
86069782 PP	171	config PAGE_FAULT_HANDLERS
	172	bool "Custom page fault handlers"
	173	depends on DEBUG_KERNEL
	174	help
	175	Allow the use of custom page fault handlers. A kernel module may
	176	register a function that is called on every page fault. Custom
	177	handlers are used by some debugging and reverse engineering tools.
	178
8b7d89d0 PP	179	config MMIOTRACE
	180	tristate "Memory mapped IO tracing"
	181	depends on DEBUG_KERNEL && PAGE_FAULT_HANDLERS && RELAY && DEBUG_FS
	182	default n
	183	help
	184	This will build a kernel module called mmiotrace.
	185
	186	Mmiotrace traces Memory Mapped I/O access and is meant for debugging
	187	and reverse engineering. The kernel module offers wrapped
	188	versions of the ioremap family of functions. The driver to be traced
	189	must be modified to call these wrappers. A user space program is
	190	required to collect the MMIO data.
	191
	192	See http://nouveau.freedesktop.org/wiki/MmioTrace
	193	If you are not helping to develop drivers, say N.
	194
	195	config MMIOTRACE_TEST
	196	tristate "Test module for mmiotrace"
	197	depends on MMIOTRACE && m
	198	default n
	199	help
	200	This is a dumb module for testing mmiotrace. It is very dangerous
	201	as it will write garbage to IO memory starting at a given address.
	202	However, it should be safe to use on e.g. unused portion of VRAM.
	203
	204	Say N, unless you absolutely know what you are doing.
	205
6e7c4025 IM	206	#
	207	# IO delay types:
	208	#
	209
	210	config IO_DELAY_TYPE_0X80
	211	int
	212	default "0"
	213
	214	config IO_DELAY_TYPE_0XED
	215	int
	216	default "1"
	217
	218	config IO_DELAY_TYPE_UDELAY
	219	int
	220	default "2"
	221
	222	config IO_DELAY_TYPE_NONE
	223	int
	224	default "3"
	225
	226	choice
	227	prompt "IO delay type"
fd59e9e9	228	default IO_DELAY_0X80
6e7c4025 IM	229
	230	config IO_DELAY_0X80
	231	bool "port 0x80 based port-IO delay [recommended]"
	232	help
	233	This is the traditional Linux IO delay used for in/out_p.
	234	It is the most tested hence safest selection here.
	235
	236	config IO_DELAY_0XED
	237	bool "port 0xed based port-IO delay"
	238	help
	239	Use port 0xed as the IO delay. This frees up port 0x80 which is
	240	often used as a hardware-debug port.
	241
	242	config IO_DELAY_UDELAY
	243	bool "udelay based port-IO delay"
	244	help
	245	Use udelay(2) as the IO delay method. This provides the delay
	246	while not having any side-effect on the IO port space.
	247
	248	config IO_DELAY_NONE
	249	bool "no port-IO delay"
b02aae9c	250	help
6e7c4025 IM	251	No port-IO delay. Will break on old boxes that require port-IO
	252	delay for certain operations. Should work on most new machines.
	253
	254	endchoice
	255
	256	if IO_DELAY_0X80
	257	config DEFAULT_IO_DELAY_TYPE
	258	int
	259	default IO_DELAY_TYPE_0X80
	260	endif
	261
	262	if IO_DELAY_0XED
	263	config DEFAULT_IO_DELAY_TYPE
	264	int
	265	default IO_DELAY_TYPE_0XED
	266	endif
	267
	268	if IO_DELAY_UDELAY
	269	config DEFAULT_IO_DELAY_TYPE
	270	int
	271	default IO_DELAY_TYPE_UDELAY
	272	endif
	273
	274	if IO_DELAY_NONE
	275	config DEFAULT_IO_DELAY_TYPE
	276	int
	277	default IO_DELAY_TYPE_NONE
	278	endif
b02aae9c	279
6d7d7433 HY	280	config DEBUG_BOOT_PARAMS
	281	bool "Debug boot parameters"
	282	depends on DEBUG_KERNEL
	283	depends on DEBUG_FS
	284	help
	285	This option will cause struct boot_params to be exported via debugfs.
	286
0c42f392	287	config CPA_DEBUG
971a52d6	288	bool "CPA self-test code"
f316fe68	289	depends on DEBUG_KERNEL
0c42f392	290	help
971a52d6	291	Do change_page_attr() self-tests every 30 seconds.
0c42f392	292
60a3cdd0 IM	293	config OPTIMIZE_INLINING
60a3cdd0 IM	294	bool "Allow gcc to uninline functions marked 'inline'"
6d98ca73	295	depends on BROKEN
60a3cdd0 IM	296	help
	297	This option determines if the kernel forces gcc to inline the functions
	298	developers have marked 'inline'. Doing so takes away freedom from gcc to
	299	do what it thinks is best, which is desirable for the gcc 3.x series of
	300	compilers. The gcc 4.x series have a rewritten inlining algorithm and
	301	disabling this option will generate a smaller kernel there. Hopefully
	302	this algorithm is so good that allowing gcc4 to make the decision can
	303	become the default in the future, until then this option is there to
	304	test gcc for this.
c9af1e33 IM	305
	306	endmenu
	307