1 menu "printk and dmesg options"
4 bool "Show timing information on printks"
7 Selecting this option causes time stamps of the printk()
8 messages to be added to the output of the syslog() system
9 call and at the console.
11 The timestamp is always recorded internally, and exported
12 to /dev/kmsg. This flag just specifies if the timestamp should
13 be included, not that the timestamp is recorded.
15 The behavior is also controlled by the kernel command line
16 parameter printk.time=1. See Documentation/kernel-parameters.txt
18 config MESSAGE_LOGLEVEL_DEFAULT
19 int "Default message log level (1-7)"
23 Default log level for printk statements with no specified priority.
25 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
26 that are auditing their logs closely may want to set it to a lower
29 config BOOT_PRINTK_DELAY
30 bool "Delay each boot printk message by N milliseconds"
31 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
33 This build option allows you to read kernel boot messages
34 by inserting a short delay after each one. The delay is
35 specified in milliseconds on the kernel command line,
38 It is likely that you would also need to use "lpj=M" to preset
39 the "loops per jiffie" value.
40 See a previous boot log for the "lpj" value to use for your
41 system, and then set "lpj=M" before setting "boot_delay=N".
42 NOTE: Using this option may adversely affect SMP systems.
43 I.e., processors other than the first one may not boot up.
44 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
45 what it believes to be lockup conditions.
48 bool "Enable dynamic printk() support"
54 Compiles debug level messages into the kernel, which would not
55 otherwise be available at runtime. These messages can then be
56 enabled/disabled based on various levels of scope - per source file,
57 function, module, format string, and line number. This mechanism
58 implicitly compiles in all pr_debug() and dev_dbg() calls, which
59 enlarges the kernel text size by about 2%.
61 If a source file is compiled with DEBUG flag set, any
62 pr_debug() calls in it are enabled by default, but can be
63 disabled at runtime as below. Note that DEBUG flag is
64 turned on by many CONFIG_*DEBUG* options.
68 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
69 which is contained in the 'debugfs' filesystem. Thus, the debugfs
70 filesystem must first be mounted before making use of this feature.
71 We refer the control file as: <debugfs>/dynamic_debug/control. This
72 file contains a list of the debug statements that can be enabled. The
73 format for each line of the file is:
75 filename:lineno [module]function flags format
77 filename : source file of the debug statement
78 lineno : line number of the debug statement
79 module : module that contains the debug statement
80 function : function that contains the debug statement
81 flags : '=p' means the line is turned 'on' for printing
82 format : the format used for the debug statement
86 nullarbor:~ # cat <debugfs>/dynamic_debug/control
87 # filename:lineno [module]function flags format
88 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
89 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
90 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
94 // enable the message at line 1603 of file svcsock.c
95 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
96 <debugfs>/dynamic_debug/control
98 // enable all the messages in file svcsock.c
99 nullarbor:~ # echo -n 'file svcsock.c +p' >
100 <debugfs>/dynamic_debug/control
102 // enable all the messages in the NFS server module
103 nullarbor:~ # echo -n 'module nfsd +p' >
104 <debugfs>/dynamic_debug/control
106 // enable all 12 messages in the function svc_process()
107 nullarbor:~ # echo -n 'func svc_process +p' >
108 <debugfs>/dynamic_debug/control
110 // disable all 12 messages in the function svc_process()
111 nullarbor:~ # echo -n 'func svc_process -p' >
112 <debugfs>/dynamic_debug/control
114 See Documentation/dynamic-debug-howto.txt for additional information.
116 endmenu # "printk and dmesg options"
118 menu "Compile-time checks and compiler options"
121 bool "Compile the kernel with debug info"
122 depends on DEBUG_KERNEL && !COMPILE_TEST
124 If you say Y here the resulting kernel image will include
125 debugging info resulting in a larger kernel image.
126 This adds debug symbols to the kernel and modules (gcc -g), and
127 is needed if you intend to use kernel crashdump or binary object
128 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
129 Say Y here only if you plan to debug the kernel.
133 config DEBUG_INFO_REDUCED
134 bool "Reduce debugging information"
135 depends on DEBUG_INFO
137 If you say Y here gcc is instructed to generate less debugging
138 information for structure types. This means that tools that
139 need full debugging information (like kgdb or systemtap) won't
140 be happy. But if you merely need debugging information to
141 resolve line numbers there is no loss. Advantage is that
142 build directory object sizes shrink dramatically over a full
143 DEBUG_INFO build and compile times are reduced too.
144 Only works with newer gcc versions.
146 config DEBUG_INFO_SPLIT
147 bool "Produce split debuginfo in .dwo files"
148 depends on DEBUG_INFO
150 Generate debug info into separate .dwo files. This significantly
151 reduces the build directory size for builds with DEBUG_INFO,
152 because it stores the information only once on disk in .dwo
153 files instead of multiple times in object files and executables.
154 In addition the debug information is also compressed.
156 Requires recent gcc (4.7+) and recent gdb/binutils.
157 Any tool that packages or reads debug information would need
158 to know about the .dwo files and include them.
159 Incompatible with older versions of ccache.
161 config DEBUG_INFO_DWARF4
162 bool "Generate dwarf4 debuginfo"
163 depends on DEBUG_INFO
165 Generate dwarf4 debug info. This requires recent versions
166 of gcc and gdb. It makes the debug information larger.
167 But it significantly improves the success of resolving
168 variables in gdb on optimized code.
171 bool "Provide GDB scripts for kernel debugging"
172 depends on DEBUG_INFO
174 This creates the required links to GDB helper scripts in the
175 build directory. If you load vmlinux into gdb, the helper
176 scripts will be automatically imported by gdb as well, and
177 additional functions are available to analyze a Linux kernel
178 instance. See Documentation/gdb-kernel-debugging.txt for further
181 config ENABLE_WARN_DEPRECATED
182 bool "Enable __deprecated logic"
185 Enable the __deprecated logic in the kernel build.
186 Disable this to suppress the "warning: 'foo' is deprecated
187 (declared at kernel/power/somefile.c:1234)" messages.
189 config ENABLE_MUST_CHECK
190 bool "Enable __must_check logic"
193 Enable the __must_check logic in the kernel build. Disable this to
194 suppress the "warning: ignoring return value of 'foo', declared with
195 attribute warn_unused_result" messages.
198 int "Warn for stack frames larger than (needs gcc 4.4)"
201 default 1024 if !64BIT
202 default 2048 if 64BIT
204 Tell gcc to warn at build time for stack frames larger than this.
205 Setting this too low will cause a lot of warnings.
206 Setting it to 0 disables the warning.
209 config STRIP_ASM_SYMS
210 bool "Strip assembler-generated symbols during link"
213 Strip internal assembler-generated symbols during a link (symbols
214 that look like '.Lxxx') so they don't pollute the output of
215 get_wchan() and suchlike.
218 bool "Generate readable assembler code"
219 depends on DEBUG_KERNEL
221 Disable some compiler optimizations that tend to generate human unreadable
222 assembler output. This may make the kernel slightly slower, but it helps
223 to keep kernel developers who have to stare a lot at assembler listings
226 config UNUSED_SYMBOLS
227 bool "Enable unused/obsolete exported symbols"
230 Unused but exported symbols make the kernel needlessly bigger. For
231 that reason most of these unused exports will soon be removed. This
232 option is provided temporarily to provide a transition period in case
233 some external kernel module needs one of these symbols anyway. If you
234 encounter such a case in your module, consider if you are actually
235 using the right API. (rationale: since nobody in the kernel is using
236 this in a module, there is a pretty good chance it's actually the
237 wrong interface to use). If you really need the symbol, please send a
238 mail to the linux kernel mailing list mentioning the symbol and why
239 you really need it, and what the merge plan to the mainline kernel for
243 bool "Track page owner"
244 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
247 select PAGE_EXTENSION
249 This keeps track of what call chain is the owner of a page, may
250 help to find bare alloc_page(s) leaks. Even if you include this
251 feature on your build, it is disabled in default. You should pass
252 "page_owner=on" to boot parameter in order to enable it. Eats
253 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
254 for user-space helper.
259 bool "Debug Filesystem"
261 debugfs is a virtual file system that kernel developers use to put
262 debugging files into. Enable this option to be able to read and
263 write to these files.
265 For detailed documentation on the debugfs API, see
266 Documentation/DocBook/filesystems.
271 bool "Run 'make headers_check' when building vmlinux"
274 This option will extract the user-visible kernel headers whenever
275 building the kernel, and will run basic sanity checks on them to
276 ensure that exported files do not attempt to include files which
277 were not exported, etc.
279 If you're making modifications to header files which are
280 relevant for userspace, say 'Y', and check the headers
281 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
282 your build tree), to make sure they're suitable.
284 config DEBUG_SECTION_MISMATCH
285 bool "Enable full Section mismatch analysis"
287 The section mismatch analysis checks if there are illegal
288 references from one section to another section.
289 During linktime or runtime, some sections are dropped;
290 any use of code/data previously in these sections would
291 most likely result in an oops.
292 In the code, functions and variables are annotated with
293 __init,, etc. (see the full list in include/linux/init.h),
294 which results in the code/data being placed in specific sections.
295 The section mismatch analysis is always performed after a full
296 kernel build, and enabling this option causes the following
297 additional steps to occur:
298 - Add the option -fno-inline-functions-called-once to gcc commands.
299 When inlining a function annotated with __init in a non-init
300 function, we would lose the section information and thus
301 the analysis would not catch the illegal reference.
302 This option tells gcc to inline less (but it does result in
304 - Run the section mismatch analysis for each module/built-in.o file.
305 When we run the section mismatch analysis on vmlinux.o, we
306 lose valueble information about where the mismatch was
308 Running the analysis for each module/built-in.o file
309 tells where the mismatch happens much closer to the
310 source. The drawback is that the same mismatch is
311 reported at least twice.
312 - Enable verbose reporting from modpost in order to help resolve
313 the section mismatches that are reported.
315 config SECTION_MISMATCH_WARN_ONLY
316 bool "Make section mismatch errors non-fatal"
319 If you say N here, the build process will fail if there are any
320 section mismatch, instead of just throwing warnings.
325 # Select this config option from the architecture Kconfig, if it
326 # is preferred to always offer frame pointers as a config
327 # option on the architecture (regardless of KERNEL_DEBUG):
329 config ARCH_WANT_FRAME_POINTERS
334 bool "Compile the kernel with frame pointers"
335 depends on DEBUG_KERNEL && \
336 (CRIS || M68K || FRV || UML || \
337 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \
338 ARCH_WANT_FRAME_POINTERS
339 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
341 If you say Y here the resulting kernel image will be slightly
342 larger and slower, but it gives very useful debugging information
343 in case of kernel bugs. (precise oopses/stacktraces/warnings)
345 config DEBUG_FORCE_WEAK_PER_CPU
346 bool "Force weak per-cpu definitions"
347 depends on DEBUG_KERNEL
349 s390 and alpha require percpu variables in modules to be
350 defined weak to work around addressing range issue which
351 puts the following two restrictions on percpu variable
354 1. percpu symbols must be unique whether static or not
355 2. percpu variables can't be defined inside a function
357 To ensure that generic code follows the above rules, this
358 option forces all percpu variables to be defined as weak.
360 endmenu # "Compiler options"
363 bool "Magic SysRq key"
366 If you say Y here, you will have some control over the system even
367 if the system crashes for example during kernel debugging (e.g., you
368 will be able to flush the buffer cache to disk, reboot the system
369 immediately or dump some status information). This is accomplished
370 by pressing various keys while holding SysRq (Alt+PrintScreen). It
371 also works on a serial console (on PC hardware at least), if you
372 send a BREAK and then within 5 seconds a command keypress. The
373 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
374 unless you really know what this hack does.
376 config MAGIC_SYSRQ_DEFAULT_ENABLE
377 hex "Enable magic SysRq key functions by default"
378 depends on MAGIC_SYSRQ
381 Specifies which SysRq key functions are enabled by default.
382 This may be set to 1 or 0 to enable or disable them all, or
383 to a bitmask as described in Documentation/sysrq.txt.
386 bool "Kernel debugging"
388 Say Y here if you are developing drivers or trying to debug and
389 identify kernel problems.
391 menu "Memory Debugging"
393 source mm/Kconfig.debug
396 bool "Debug object operations"
397 depends on DEBUG_KERNEL
399 If you say Y here, additional code will be inserted into the
400 kernel to track the life time of various objects and validate
401 the operations on those objects.
403 config DEBUG_OBJECTS_SELFTEST
404 bool "Debug objects selftest"
405 depends on DEBUG_OBJECTS
407 This enables the selftest of the object debug code.
409 config DEBUG_OBJECTS_FREE
410 bool "Debug objects in freed memory"
411 depends on DEBUG_OBJECTS
413 This enables checks whether a k/v free operation frees an area
414 which contains an object which has not been deactivated
415 properly. This can make kmalloc/kfree-intensive workloads
418 config DEBUG_OBJECTS_TIMERS
419 bool "Debug timer objects"
420 depends on DEBUG_OBJECTS
422 If you say Y here, additional code will be inserted into the
423 timer routines to track the life time of timer objects and
424 validate the timer operations.
426 config DEBUG_OBJECTS_WORK
427 bool "Debug work objects"
428 depends on DEBUG_OBJECTS
430 If you say Y here, additional code will be inserted into the
431 work queue routines to track the life time of work objects and
432 validate the work operations.
434 config DEBUG_OBJECTS_RCU_HEAD
435 bool "Debug RCU callbacks objects"
436 depends on DEBUG_OBJECTS
438 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
440 config DEBUG_OBJECTS_PERCPU_COUNTER
441 bool "Debug percpu counter objects"
442 depends on DEBUG_OBJECTS
444 If you say Y here, additional code will be inserted into the
445 percpu counter routines to track the life time of percpu counter
446 objects and validate the percpu counter operations.
448 config DEBUG_OBJECTS_ENABLE_DEFAULT
449 int "debug_objects bootup default value (0-1)"
452 depends on DEBUG_OBJECTS
454 Debug objects boot parameter default value
457 bool "Debug slab memory allocations"
458 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
460 Say Y here to have the kernel do limited verification on memory
461 allocation as well as poisoning memory on free to catch use of freed
462 memory. This can make kmalloc/kfree-intensive workloads much slower.
464 config DEBUG_SLAB_LEAK
465 bool "Memory leak debugging"
466 depends on DEBUG_SLAB
469 bool "SLUB debugging on by default"
470 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
473 Boot with debugging on by default. SLUB boots by default with
474 the runtime debug capabilities switched off. Enabling this is
475 equivalent to specifying the "slub_debug" parameter on boot.
476 There is no support for more fine grained debug control like
477 possible with slub_debug=xxx. SLUB debugging may be switched
478 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
483 bool "Enable SLUB performance statistics"
484 depends on SLUB && SYSFS
486 SLUB statistics are useful to debug SLUBs allocation behavior in
487 order find ways to optimize the allocator. This should never be
488 enabled for production use since keeping statistics slows down
489 the allocator by a few percentage points. The slabinfo command
490 supports the determination of the most active slabs to figure
491 out which slabs are relevant to a particular load.
492 Try running: slabinfo -DA
494 config HAVE_DEBUG_KMEMLEAK
497 config DEBUG_KMEMLEAK
498 bool "Kernel memory leak detector"
499 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
501 select STACKTRACE if STACKTRACE_SUPPORT
505 Say Y here if you want to enable the memory leak
506 detector. The memory allocation/freeing is traced in a way
507 similar to the Boehm's conservative garbage collector, the
508 difference being that the orphan objects are not freed but
509 only shown in /sys/kernel/debug/kmemleak. Enabling this
510 feature will introduce an overhead to memory
511 allocations. See Documentation/kmemleak.txt for more
514 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
515 of finding leaks due to the slab objects poisoning.
517 In order to access the kmemleak file, debugfs needs to be
518 mounted (usually at /sys/kernel/debug).
520 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
521 int "Maximum kmemleak early log entries"
522 depends on DEBUG_KMEMLEAK
526 Kmemleak must track all the memory allocations to avoid
527 reporting false positives. Since memory may be allocated or
528 freed before kmemleak is initialised, an early log buffer is
529 used to store these actions. If kmemleak reports "early log
530 buffer exceeded", please increase this value.
532 config DEBUG_KMEMLEAK_TEST
533 tristate "Simple test for the kernel memory leak detector"
534 depends on DEBUG_KMEMLEAK && m
536 This option enables a module that explicitly leaks memory.
540 config DEBUG_KMEMLEAK_DEFAULT_OFF
541 bool "Default kmemleak to off"
542 depends on DEBUG_KMEMLEAK
544 Say Y here to disable kmemleak by default. It can then be enabled
545 on the command line via kmemleak=on.
547 config DEBUG_STACK_USAGE
548 bool "Stack utilization instrumentation"
549 depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAG
551 Enables the display of the minimum amount of free stack which each
552 task has ever had available in the sysrq-T and sysrq-P debug output.
554 This option will slow down process creation somewhat.
558 depends on DEBUG_KERNEL
560 Enable this to turn on extended checks in the virtual-memory system
561 that may impact performance.
565 config DEBUG_VM_VMACACHE
566 bool "Debug VMA caching"
569 Enable this to turn on VMA caching debug information. Doing so
570 can cause significant overhead, so only enable it in non-production
576 bool "Debug VM red-black trees"
579 Enable VM red-black tree debugging information and extra validations.
583 config DEBUG_VM_PGFLAGS
584 bool "Debug page-flags operations"
587 Enables extra validation on page flags operations.
592 bool "Debug VM translations"
593 depends on DEBUG_KERNEL && X86
595 Enable some costly sanity checks in virtual to page code. This can
596 catch mistakes with virt_to_page() and friends.
600 config DEBUG_NOMMU_REGIONS
601 bool "Debug the global anon/private NOMMU mapping region tree"
602 depends on DEBUG_KERNEL && !MMU
604 This option causes the global tree of anonymous and private mapping
605 regions to be regularly checked for invalid topology.
607 config DEBUG_MEMORY_INIT
608 bool "Debug memory initialisation" if EXPERT
611 Enable this for additional checks during memory initialisation.
612 The sanity checks verify aspects of the VM such as the memory model
613 and other information provided by the architecture. Verbose
614 information will be printed at KERN_DEBUG loglevel depending
615 on the mminit_loglevel= command-line option.
619 config MEMORY_NOTIFIER_ERROR_INJECT
620 tristate "Memory hotplug notifier error injection module"
621 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
623 This option provides the ability to inject artificial errors to
624 memory hotplug notifier chain callbacks. It is controlled through
625 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
627 If the notifier call chain should be failed with some events
628 notified, write the error code to "actions/<notifier event>/error".
630 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
632 # cd /sys/kernel/debug/notifier-error-inject/memory
633 # echo -12 > actions/MEM_GOING_OFFLINE/error
634 # echo offline > /sys/devices/system/memory/memoryXXX/state
635 bash: echo: write error: Cannot allocate memory
637 To compile this code as a module, choose M here: the module will
638 be called memory-notifier-error-inject.
642 config DEBUG_PER_CPU_MAPS
643 bool "Debug access to per_cpu maps"
644 depends on DEBUG_KERNEL
647 Say Y to verify that the per_cpu map being accessed has
648 been set up. This adds a fair amount of code to kernel memory
649 and decreases performance.
654 bool "Highmem debugging"
655 depends on DEBUG_KERNEL && HIGHMEM
657 This option enables additional error checking for high memory
658 systems. Disable for production systems.
660 config HAVE_DEBUG_STACKOVERFLOW
663 config DEBUG_STACKOVERFLOW
664 bool "Check for stack overflows"
665 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
667 Say Y here if you want to check for overflows of kernel, IRQ
668 and exception stacks (if your architecture uses them). This
669 option will show detailed messages if free stack space drops
670 below a certain limit.
672 These kinds of bugs usually occur when call-chains in the
673 kernel get too deep, especially when interrupts are
676 Use this in cases where you see apparently random memory
677 corruption, especially if it appears in 'struct thread_info'
679 If in doubt, say "N".
681 source "lib/Kconfig.kmemcheck"
683 source "lib/Kconfig.kasan"
685 endmenu # "Memory Debugging"
688 bool "Debug shared IRQ handlers"
689 depends on DEBUG_KERNEL
691 Enable this to generate a spurious interrupt as soon as a shared
692 interrupt handler is registered, and just before one is deregistered.
693 Drivers ought to be able to handle interrupts coming in at those
694 points; some don't and need to be caught.
696 menu "Debug Lockups and Hangs"
698 config LOCKUP_DETECTOR
699 bool "Detect Hard and Soft Lockups"
700 depends on DEBUG_KERNEL && !S390
702 Say Y here to enable the kernel to act as a watchdog to detect
703 hard and soft lockups.
705 Softlockups are bugs that cause the kernel to loop in kernel
706 mode for more than 20 seconds, without giving other tasks a
707 chance to run. The current stack trace is displayed upon
708 detection and the system will stay locked up.
710 Hardlockups are bugs that cause the CPU to loop in kernel mode
711 for more than 10 seconds, without letting other interrupts have a
712 chance to run. The current stack trace is displayed upon detection
713 and the system will stay locked up.
715 The overhead should be minimal. A periodic hrtimer runs to
716 generate interrupts and kick the watchdog task every 4 seconds.
717 An NMI is generated every 10 seconds or so to check for hardlockups.
719 The frequency of hrtimer and NMI events and the soft and hard lockup
720 thresholds can be controlled through the sysctl watchdog_thresh.
722 config HARDLOCKUP_DETECTOR
724 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
725 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
727 config BOOTPARAM_HARDLOCKUP_PANIC
728 bool "Panic (Reboot) On Hard Lockups"
729 depends on HARDLOCKUP_DETECTOR
731 Say Y here to enable the kernel to panic on "hard lockups",
732 which are bugs that cause the kernel to loop in kernel
733 mode with interrupts disabled for more than 10 seconds (configurable
734 using the watchdog_thresh sysctl).
738 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
740 depends on HARDLOCKUP_DETECTOR
742 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
743 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
745 config BOOTPARAM_SOFTLOCKUP_PANIC
746 bool "Panic (Reboot) On Soft Lockups"
747 depends on LOCKUP_DETECTOR
749 Say Y here to enable the kernel to panic on "soft lockups",
750 which are bugs that cause the kernel to loop in kernel
751 mode for more than 20 seconds (configurable using the watchdog_thresh
752 sysctl), without giving other tasks a chance to run.
754 The panic can be used in combination with panic_timeout,
755 to cause the system to reboot automatically after a
756 lockup has been detected. This feature is useful for
757 high-availability systems that have uptime guarantees and
758 where a lockup must be resolved ASAP.
762 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
764 depends on LOCKUP_DETECTOR
766 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
767 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
769 config DETECT_HUNG_TASK
770 bool "Detect Hung Tasks"
771 depends on DEBUG_KERNEL
772 default LOCKUP_DETECTOR
774 Say Y here to enable the kernel to detect "hung tasks",
775 which are bugs that cause the task to be stuck in
776 uninterruptible "D" state indefinitiley.
778 When a hung task is detected, the kernel will print the
779 current stack trace (which you should report), but the
780 task will stay in uninterruptible state. If lockdep is
781 enabled then all held locks will also be reported. This
782 feature has negligible overhead.
784 config DEFAULT_HUNG_TASK_TIMEOUT
785 int "Default timeout for hung task detection (in seconds)"
786 depends on DETECT_HUNG_TASK
789 This option controls the default timeout (in seconds) used
790 to determine when a task has become non-responsive and should
793 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
794 sysctl or by writing a value to
795 /proc/sys/kernel/hung_task_timeout_secs.
797 A timeout of 0 disables the check. The default is two minutes.
798 Keeping the default should be fine in most cases.
800 config BOOTPARAM_HUNG_TASK_PANIC
801 bool "Panic (Reboot) On Hung Tasks"
802 depends on DETECT_HUNG_TASK
804 Say Y here to enable the kernel to panic on "hung tasks",
805 which are bugs that cause the kernel to leave a task stuck
806 in uninterruptible "D" state.
808 The panic can be used in combination with panic_timeout,
809 to cause the system to reboot automatically after a
810 hung task has been detected. This feature is useful for
811 high-availability systems that have uptime guarantees and
812 where a hung tasks must be resolved ASAP.
816 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
818 depends on DETECT_HUNG_TASK
820 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
821 default 1 if BOOTPARAM_HUNG_TASK_PANIC
824 bool "Detect Workqueue Stalls"
825 depends on DEBUG_KERNEL
827 Say Y here to enable stall detection on workqueues. If a
828 worker pool doesn't make forward progress on a pending work
829 item for over a given amount of time, 30s by default, a
830 warning message is printed along with dump of workqueue
831 state. This can be configured through kernel parameter
832 "workqueue.watchdog_thresh" and its sysfs counterpart.
834 endmenu # "Debug lockups and hangs"
839 Say Y here to enable the kernel to panic when it oopses. This
840 has the same effect as setting oops=panic on the kernel command
843 This feature is useful to ensure that the kernel does not do
844 anything erroneous after an oops which could result in data
845 corruption or other issues.
849 config PANIC_ON_OOPS_VALUE
852 default 0 if !PANIC_ON_OOPS
853 default 1 if PANIC_ON_OOPS
859 Set the timeout value (in seconds) until a reboot occurs when the
860 the kernel panics. If n = 0, then we wait forever. A timeout
861 value n > 0 will wait n seconds before rebooting, while a timeout
862 value n < 0 will reboot immediately.
865 bool "Collect scheduler debugging info"
866 depends on DEBUG_KERNEL && PROC_FS
869 If you say Y here, the /proc/sched_debug file will be provided
870 that can help debug the scheduler. The runtime overhead of this
878 bool "Collect scheduler statistics"
879 depends on DEBUG_KERNEL && PROC_FS
882 If you say Y here, additional code will be inserted into the
883 scheduler and related routines to collect statistics about
884 scheduler behavior and provide them in /proc/schedstat. These
885 stats may be useful for both tuning and debugging the scheduler
886 If you aren't debugging the scheduler or trying to tune a specific
887 application, you can say N to avoid the very slight overhead
890 config SCHED_STACK_END_CHECK
891 bool "Detect stack corruption on calls to schedule()"
892 depends on DEBUG_KERNEL
895 This option checks for a stack overrun on calls to schedule().
896 If the stack end location is found to be over written always panic as
897 the content of the corrupted region can no longer be trusted.
898 This is to ensure no erroneous behaviour occurs which could result in
899 data corruption or a sporadic crash at a later stage once the region
900 is examined. The runtime overhead introduced is minimal.
902 config DEBUG_TIMEKEEPING
903 bool "Enable extra timekeeping sanity checking"
905 This option will enable additional timekeeping sanity checks
906 which may be helpful when diagnosing issues where timekeeping
907 problems are suspected.
909 This may include checks in the timekeeping hotpaths, so this
910 option may have a (very small) performance impact to some
916 bool "Collect kernel timers statistics"
917 depends on DEBUG_KERNEL && PROC_FS
919 If you say Y here, additional code will be inserted into the
920 timer routines to collect statistics about kernel timers being
921 reprogrammed. The statistics can be read from /proc/timer_stats.
922 The statistics collection is started by writing 1 to /proc/timer_stats,
923 writing 0 stops it. This feature is useful to collect information
924 about timer usage patterns in kernel and userspace. This feature
925 is lightweight if enabled in the kernel config but not activated
926 (it defaults to deactivated on bootup and will only be activated
927 if some application like powertop activates it explicitly).
930 bool "Debug preemptible kernel"
931 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
934 If you say Y here then the kernel will use a debug variant of the
935 commonly used smp_processor_id() function and will print warnings
936 if kernel code uses it in a preemption-unsafe way. Also, the kernel
937 will detect preemption count underflows.
939 menu "Lock Debugging (spinlocks, mutexes, etc...)"
941 config DEBUG_RT_MUTEXES
942 bool "RT Mutex debugging, deadlock detection"
943 depends on DEBUG_KERNEL && RT_MUTEXES
945 This allows rt mutex semantics violations and rt mutex related
946 deadlocks (lockups) to be detected and reported automatically.
948 config DEBUG_SPINLOCK
949 bool "Spinlock and rw-lock debugging: basic checks"
950 depends on DEBUG_KERNEL
951 select UNINLINE_SPIN_UNLOCK
953 Say Y here and build SMP to catch missing spinlock initialization
954 and certain other kinds of spinlock errors commonly made. This is
955 best used in conjunction with the NMI watchdog so that spinlock
956 deadlocks are also debuggable.
959 bool "Mutex debugging: basic checks"
960 depends on DEBUG_KERNEL
962 This feature allows mutex semantics violations to be detected and
965 config DEBUG_WW_MUTEX_SLOWPATH
966 bool "Wait/wound mutex debugging: Slowpath testing"
967 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
968 select DEBUG_LOCK_ALLOC
969 select DEBUG_SPINLOCK
972 This feature enables slowpath testing for w/w mutex users by
973 injecting additional -EDEADLK wound/backoff cases. Together with
974 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
975 will test all possible w/w mutex interface abuse with the
976 exception of simply not acquiring all the required locks.
977 Note that this feature can introduce significant overhead, so
978 it really should not be enabled in a production or distro kernel,
979 even a debug kernel. If you are a driver writer, enable it. If
980 you are a distro, do not.
982 config DEBUG_LOCK_ALLOC
983 bool "Lock debugging: detect incorrect freeing of live locks"
984 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
985 select DEBUG_SPINLOCK
989 This feature will check whether any held lock (spinlock, rwlock,
990 mutex or rwsem) is incorrectly freed by the kernel, via any of the
991 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
992 vfree(), etc.), whether a live lock is incorrectly reinitialized via
993 spin_lock_init()/mutex_init()/etc., or whether there is any lock
994 held during task exit.
997 bool "Lock debugging: prove locking correctness"
998 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1000 select DEBUG_SPINLOCK
1001 select DEBUG_MUTEXES
1002 select DEBUG_LOCK_ALLOC
1003 select TRACE_IRQFLAGS
1006 This feature enables the kernel to prove that all locking
1007 that occurs in the kernel runtime is mathematically
1008 correct: that under no circumstance could an arbitrary (and
1009 not yet triggered) combination of observed locking
1010 sequences (on an arbitrary number of CPUs, running an
1011 arbitrary number of tasks and interrupt contexts) cause a
1014 In short, this feature enables the kernel to report locking
1015 related deadlocks before they actually occur.
1017 The proof does not depend on how hard and complex a
1018 deadlock scenario would be to trigger: how many
1019 participant CPUs, tasks and irq-contexts would be needed
1020 for it to trigger. The proof also does not depend on
1021 timing: if a race and a resulting deadlock is possible
1022 theoretically (no matter how unlikely the race scenario
1023 is), it will be proven so and will immediately be
1024 reported by the kernel (once the event is observed that
1025 makes the deadlock theoretically possible).
1027 If a deadlock is impossible (i.e. the locking rules, as
1028 observed by the kernel, are mathematically correct), the
1029 kernel reports nothing.
1031 NOTE: this feature can also be enabled for rwlocks, mutexes
1032 and rwsems - in which case all dependencies between these
1033 different locking variants are observed and mapped too, and
1034 the proof of observed correctness is also maintained for an
1035 arbitrary combination of these separate locking variants.
1037 For more details, see Documentation/locking/lockdep-design.txt.
1041 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1043 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
1048 bool "Lock usage statistics"
1049 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1051 select DEBUG_SPINLOCK
1052 select DEBUG_MUTEXES
1053 select DEBUG_LOCK_ALLOC
1056 This feature enables tracking lock contention points
1058 For more details, see Documentation/locking/lockstat.txt
1060 This also enables lock events required by "perf lock",
1062 If you want to use "perf lock", you also need to turn on
1063 CONFIG_EVENT_TRACING.
1065 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1066 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1068 config DEBUG_LOCKDEP
1069 bool "Lock dependency engine debugging"
1070 depends on DEBUG_KERNEL && LOCKDEP
1072 If you say Y here, the lock dependency engine will do
1073 additional runtime checks to debug itself, at the price
1074 of more runtime overhead.
1076 config DEBUG_ATOMIC_SLEEP
1077 bool "Sleep inside atomic section checking"
1078 select PREEMPT_COUNT
1079 depends on DEBUG_KERNEL
1081 If you say Y here, various routines which may sleep will become very
1082 noisy if they are called inside atomic sections: when a spinlock is
1083 held, inside an rcu read side critical section, inside preempt disabled
1084 sections, inside an interrupt, etc...
1086 config DEBUG_LOCKING_API_SELFTESTS
1087 bool "Locking API boot-time self-tests"
1088 depends on DEBUG_KERNEL
1090 Say Y here if you want the kernel to run a short self-test during
1091 bootup. The self-test checks whether common types of locking bugs
1092 are detected by debugging mechanisms or not. (if you disable
1093 lock debugging then those bugs wont be detected of course.)
1094 The following locking APIs are covered: spinlocks, rwlocks,
1097 config LOCK_TORTURE_TEST
1098 tristate "torture tests for locking"
1099 depends on DEBUG_KERNEL
1103 This option provides a kernel module that runs torture tests
1104 on kernel locking primitives. The kernel module may be built
1105 after the fact on the running kernel to be tested, if desired.
1107 Say Y here if you want kernel locking-primitive torture tests
1108 to be built into the kernel.
1109 Say M if you want these torture tests to build as a module.
1110 Say N if you are unsure.
1112 endmenu # lock debugging
1114 config TRACE_IRQFLAGS
1117 Enables hooks to interrupt enabling and disabling for
1118 either tracing or lock debugging.
1121 bool "Stack backtrace support"
1122 depends on STACKTRACE_SUPPORT
1124 This option causes the kernel to create a /proc/pid/stack for
1125 every process, showing its current stack trace.
1126 It is also used by various kernel debugging features that require
1127 stack trace generation.
1129 config DEBUG_KOBJECT
1130 bool "kobject debugging"
1131 depends on DEBUG_KERNEL
1133 If you say Y here, some extra kobject debugging messages will be sent
1136 config DEBUG_KOBJECT_RELEASE
1137 bool "kobject release debugging"
1138 depends on DEBUG_OBJECTS_TIMERS
1140 kobjects are reference counted objects. This means that their
1141 last reference count put is not predictable, and the kobject can
1142 live on past the point at which a driver decides to drop it's
1143 initial reference to the kobject gained on allocation. An
1144 example of this would be a struct device which has just been
1147 However, some buggy drivers assume that after such an operation,
1148 the memory backing the kobject can be immediately freed. This
1149 goes completely against the principles of a refcounted object.
1151 If you say Y here, the kernel will delay the release of kobjects
1152 on the last reference count to improve the visibility of this
1153 kind of kobject release bug.
1155 config HAVE_DEBUG_BUGVERBOSE
1158 config DEBUG_BUGVERBOSE
1159 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1160 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1163 Say Y here to make BUG() panics output the file name and line number
1164 of the BUG call as well as the EIP and oops trace. This aids
1165 debugging but costs about 70-100K of memory.
1168 bool "Debug linked list manipulation"
1169 depends on DEBUG_KERNEL
1171 Enable this to turn on extended checks in the linked-list
1176 config DEBUG_PI_LIST
1177 bool "Debug priority linked list manipulation"
1178 depends on DEBUG_KERNEL
1180 Enable this to turn on extended checks in the priority-ordered
1181 linked-list (plist) walking routines. This checks the entire
1182 list multiple times during each manipulation.
1187 bool "Debug SG table operations"
1188 depends on DEBUG_KERNEL
1190 Enable this to turn on checks on scatter-gather tables. This can
1191 help find problems with drivers that do not properly initialize
1196 config DEBUG_NOTIFIERS
1197 bool "Debug notifier call chains"
1198 depends on DEBUG_KERNEL
1200 Enable this to turn on sanity checking for notifier call chains.
1201 This is most useful for kernel developers to make sure that
1202 modules properly unregister themselves from notifier chains.
1203 This is a relatively cheap check but if you care about maximum
1206 config DEBUG_CREDENTIALS
1207 bool "Debug credential management"
1208 depends on DEBUG_KERNEL
1210 Enable this to turn on some debug checking for credential
1211 management. The additional code keeps track of the number of
1212 pointers from task_structs to any given cred struct, and checks to
1213 see that this number never exceeds the usage count of the cred
1216 Furthermore, if SELinux is enabled, this also checks that the
1217 security pointer in the cred struct is never seen to be invalid.
1221 menu "RCU Debugging"
1224 def_bool PROVE_LOCKING
1226 config PROVE_RCU_REPEATEDLY
1227 bool "RCU debugging: don't disable PROVE_RCU on first splat"
1228 depends on PROVE_RCU
1231 By itself, PROVE_RCU will disable checking upon issuing the
1232 first warning (or "splat"). This feature prevents such
1233 disabling, allowing multiple RCU-lockdep warnings to be printed
1236 Say Y to allow multiple RCU-lockdep warnings per boot.
1238 Say N if you are unsure.
1240 config SPARSE_RCU_POINTER
1241 bool "RCU debugging: sparse-based checks for pointer usage"
1244 This feature enables the __rcu sparse annotation for
1245 RCU-protected pointers. This annotation will cause sparse
1246 to flag any non-RCU used of annotated pointers. This can be
1247 helpful when debugging RCU usage. Please note that this feature
1248 is not intended to enforce code cleanliness; it is instead merely
1251 Say Y to make sparse flag questionable use of RCU-protected pointers
1253 Say N if you are unsure.
1259 config RCU_TORTURE_TEST
1260 tristate "torture tests for RCU"
1261 depends on DEBUG_KERNEL
1267 This option provides a kernel module that runs torture tests
1268 on the RCU infrastructure. The kernel module may be built
1269 after the fact on the running kernel to be tested, if desired.
1271 Say Y here if you want RCU torture tests to be built into
1273 Say M if you want the RCU torture tests to build as a module.
1274 Say N if you are unsure.
1276 config RCU_TORTURE_TEST_RUNNABLE
1277 bool "torture tests for RCU runnable by default"
1278 depends on RCU_TORTURE_TEST = y
1281 This option provides a way to build the RCU torture tests
1282 directly into the kernel without them starting up at boot
1283 time. You can use /proc/sys/kernel/rcutorture_runnable
1284 to manually override this setting. This /proc file is
1285 available only when the RCU torture tests have been built
1288 Say Y here if you want the RCU torture tests to start during
1289 boot (you probably don't).
1290 Say N here if you want the RCU torture tests to start only
1291 after being manually enabled via /proc.
1293 config RCU_TORTURE_TEST_SLOW_PREINIT
1294 bool "Slow down RCU grace-period pre-initialization to expose races"
1295 depends on RCU_TORTURE_TEST
1297 This option delays grace-period pre-initialization (the
1298 propagation of CPU-hotplug changes up the rcu_node combining
1299 tree) for a few jiffies between initializing each pair of
1300 consecutive rcu_node structures. This helps to expose races
1301 involving grace-period pre-initialization, in other words, it
1302 makes your kernel less stable. It can also greatly increase
1303 grace-period latency, especially on systems with large numbers
1304 of CPUs. This is useful when torture-testing RCU, but in
1305 almost no other circumstance.
1307 Say Y here if you want your system to crash and hang more often.
1308 Say N if you want a sane system.
1310 config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
1311 int "How much to slow down RCU grace-period pre-initialization"
1314 depends on RCU_TORTURE_TEST_SLOW_PREINIT
1316 This option specifies the number of jiffies to wait between
1317 each rcu_node structure pre-initialization step.
1319 config RCU_TORTURE_TEST_SLOW_INIT
1320 bool "Slow down RCU grace-period initialization to expose races"
1321 depends on RCU_TORTURE_TEST
1323 This option delays grace-period initialization for a few
1324 jiffies between initializing each pair of consecutive
1325 rcu_node structures. This helps to expose races involving
1326 grace-period initialization, in other words, it makes your
1327 kernel less stable. It can also greatly increase grace-period
1328 latency, especially on systems with large numbers of CPUs.
1329 This is useful when torture-testing RCU, but in almost no
1332 Say Y here if you want your system to crash and hang more often.
1333 Say N if you want a sane system.
1335 config RCU_TORTURE_TEST_SLOW_INIT_DELAY
1336 int "How much to slow down RCU grace-period initialization"
1339 depends on RCU_TORTURE_TEST_SLOW_INIT
1341 This option specifies the number of jiffies to wait between
1342 each rcu_node structure initialization.
1344 config RCU_TORTURE_TEST_SLOW_CLEANUP
1345 bool "Slow down RCU grace-period cleanup to expose races"
1346 depends on RCU_TORTURE_TEST
1348 This option delays grace-period cleanup for a few jiffies
1349 between cleaning up each pair of consecutive rcu_node
1350 structures. This helps to expose races involving grace-period
1351 cleanup, in other words, it makes your kernel less stable.
1352 It can also greatly increase grace-period latency, especially
1353 on systems with large numbers of CPUs. This is useful when
1354 torture-testing RCU, but in almost no other circumstance.
1356 Say Y here if you want your system to crash and hang more often.
1357 Say N if you want a sane system.
1359 config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
1360 int "How much to slow down RCU grace-period cleanup"
1363 depends on RCU_TORTURE_TEST_SLOW_CLEANUP
1365 This option specifies the number of jiffies to wait between
1366 each rcu_node structure cleanup operation.
1368 config RCU_CPU_STALL_TIMEOUT
1369 int "RCU CPU stall timeout in seconds"
1370 depends on RCU_STALL_COMMON
1374 If a given RCU grace period extends more than the specified
1375 number of seconds, a CPU stall warning is printed. If the
1376 RCU grace period persists, additional CPU stall warnings are
1377 printed at more widely spaced intervals.
1380 bool "Enable tracing for RCU"
1381 depends on DEBUG_KERNEL
1384 This option provides tracing in RCU which presents stats
1385 in debugfs for debugging RCU implementation.
1387 Say Y here if you want to enable RCU tracing
1388 Say N if you are unsure.
1390 config RCU_EQS_DEBUG
1391 bool "Provide debugging asserts for adding NO_HZ support to an arch"
1392 depends on DEBUG_KERNEL
1394 This option provides consistency checks in RCU's handling of
1395 NO_HZ. These checks have proven quite helpful in detecting
1396 bugs in arch-specific NO_HZ code.
1398 Say N here if you need ultimate kernel/user switch latencies
1399 Say Y if you are unsure
1401 endmenu # "RCU Debugging"
1403 config DEBUG_BLOCK_EXT_DEVT
1404 bool "Force extended block device numbers and spread them"
1405 depends on DEBUG_KERNEL
1409 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1410 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1411 YOU ARE DOING. Distros, please enable this and fix whatever
1414 Conventionally, block device numbers are allocated from
1415 predetermined contiguous area. However, extended block area
1416 may introduce non-contiguous block device numbers. This
1417 option forces most block device numbers to be allocated from
1418 the extended space and spreads them to discover kernel or
1419 userland code paths which assume predetermined contiguous
1420 device number allocation.
1422 Note that turning on this debug option shuffles all the
1423 device numbers for all IDE and SCSI devices including libata
1424 ones, so root partition specified using device number
1425 directly (via rdev or root=MAJ:MIN) won't work anymore.
1426 Textual device names (root=/dev/sdXn) will continue to work.
1428 Say N if you are unsure.
1430 config NOTIFIER_ERROR_INJECTION
1431 tristate "Notifier error injection"
1432 depends on DEBUG_KERNEL
1435 This option provides the ability to inject artificial errors to
1436 specified notifier chain callbacks. It is useful to test the error
1437 handling of notifier call chain failures.
1441 config CPU_NOTIFIER_ERROR_INJECT
1442 tristate "CPU notifier error injection module"
1443 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1445 This option provides a kernel module that can be used to test
1446 the error handling of the cpu notifiers by injecting artificial
1447 errors to CPU notifier chain callbacks. It is controlled through
1448 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
1450 If the notifier call chain should be failed with some events
1451 notified, write the error code to "actions/<notifier event>/error".
1453 Example: Inject CPU offline error (-1 == -EPERM)
1455 # cd /sys/kernel/debug/notifier-error-inject/cpu
1456 # echo -1 > actions/CPU_DOWN_PREPARE/error
1457 # echo 0 > /sys/devices/system/cpu/cpu1/online
1458 bash: echo: write error: Operation not permitted
1460 To compile this code as a module, choose M here: the module will
1461 be called cpu-notifier-error-inject.
1465 config PM_NOTIFIER_ERROR_INJECT
1466 tristate "PM notifier error injection module"
1467 depends on PM && NOTIFIER_ERROR_INJECTION
1468 default m if PM_DEBUG
1470 This option provides the ability to inject artificial errors to
1471 PM notifier chain callbacks. It is controlled through debugfs
1472 interface /sys/kernel/debug/notifier-error-inject/pm
1474 If the notifier call chain should be failed with some events
1475 notified, write the error code to "actions/<notifier event>/error".
1477 Example: Inject PM suspend error (-12 = -ENOMEM)
1479 # cd /sys/kernel/debug/notifier-error-inject/pm/
1480 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1481 # echo mem > /sys/power/state
1482 bash: echo: write error: Cannot allocate memory
1484 To compile this code as a module, choose M here: the module will
1485 be called pm-notifier-error-inject.
1489 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1490 tristate "OF reconfig notifier error injection module"
1491 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1493 This option provides the ability to inject artificial errors to
1494 OF reconfig notifier chain callbacks. It is controlled
1495 through debugfs interface under
1496 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1498 If the notifier call chain should be failed with some events
1499 notified, write the error code to "actions/<notifier event>/error".
1501 To compile this code as a module, choose M here: the module will
1502 be called of-reconfig-notifier-error-inject.
1506 config NETDEV_NOTIFIER_ERROR_INJECT
1507 tristate "Netdev notifier error injection module"
1508 depends on NET && NOTIFIER_ERROR_INJECTION
1510 This option provides the ability to inject artificial errors to
1511 netdevice notifier chain callbacks. It is controlled through debugfs
1512 interface /sys/kernel/debug/notifier-error-inject/netdev
1514 If the notifier call chain should be failed with some events
1515 notified, write the error code to "actions/<notifier event>/error".
1517 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1519 # cd /sys/kernel/debug/notifier-error-inject/netdev
1520 # echo -22 > actions/NETDEV_CHANGEMTU/error
1521 # ip link set eth0 mtu 1024
1522 RTNETLINK answers: Invalid argument
1524 To compile this code as a module, choose M here: the module will
1525 be called netdev-notifier-error-inject.
1529 config FAULT_INJECTION
1530 bool "Fault-injection framework"
1531 depends on DEBUG_KERNEL
1533 Provide fault-injection framework.
1534 For more details, see Documentation/fault-injection/.
1537 bool "Fault-injection capability for kmalloc"
1538 depends on FAULT_INJECTION
1539 depends on SLAB || SLUB
1541 Provide fault-injection capability for kmalloc.
1543 config FAIL_PAGE_ALLOC
1544 bool "Fault-injection capabilitiy for alloc_pages()"
1545 depends on FAULT_INJECTION
1547 Provide fault-injection capability for alloc_pages().
1549 config FAIL_MAKE_REQUEST
1550 bool "Fault-injection capability for disk IO"
1551 depends on FAULT_INJECTION && BLOCK
1553 Provide fault-injection capability for disk IO.
1555 config FAIL_IO_TIMEOUT
1556 bool "Fault-injection capability for faking disk interrupts"
1557 depends on FAULT_INJECTION && BLOCK
1559 Provide fault-injection capability on end IO handling. This
1560 will make the block layer "forget" an interrupt as configured,
1561 thus exercising the error handling.
1563 Only works with drivers that use the generic timeout handling,
1564 for others it wont do anything.
1566 config FAIL_MMC_REQUEST
1567 bool "Fault-injection capability for MMC IO"
1568 depends on FAULT_INJECTION_DEBUG_FS && MMC
1570 Provide fault-injection capability for MMC IO.
1571 This will make the mmc core return data errors. This is
1572 useful to test the error handling in the mmc block device
1573 and to test how the mmc host driver handles retries from
1577 bool "Fault-injection capability for futexes"
1579 depends on FAULT_INJECTION && FUTEX
1581 Provide fault-injection capability for futexes.
1583 config FAULT_INJECTION_DEBUG_FS
1584 bool "Debugfs entries for fault-injection capabilities"
1585 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1587 Enable configuration of fault-injection capabilities via debugfs.
1589 config FAULT_INJECTION_STACKTRACE_FILTER
1590 bool "stacktrace filter for fault-injection capabilities"
1591 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1594 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1596 Provide stacktrace filter for fault-injection capabilities
1599 bool "Latency measuring infrastructure"
1600 depends on DEBUG_KERNEL
1601 depends on STACKTRACE_SUPPORT
1603 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1610 Enable this option if you want to use the LatencyTOP tool
1611 to find out which userspace is blocking on what kernel operations.
1613 config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1616 config DEBUG_STRICT_USER_COPY_CHECKS
1617 bool "Strict user copy size checks"
1618 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1619 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
1621 Enabling this option turns a certain set of sanity checks for user
1622 copy operations into compile time failures.
1624 The copy_from_user() etc checks are there to help test if there
1625 are sufficient security checks on the length argument of
1626 the copy operation, by having gcc prove that the argument is
1631 source kernel/trace/Kconfig
1633 menu "Runtime Testing"
1636 tristate "Linux Kernel Dump Test Tool Module"
1641 This module enables testing of the different dumping mechanisms by
1642 inducing system failures at predefined crash points.
1643 If you don't need it: say N
1644 Choose M here to compile this code as a module. The module will be
1647 Documentation on how to use the module can be found in
1648 Documentation/fault-injection/provoke-crashes.txt
1650 config TEST_LIST_SORT
1651 bool "Linked list sorting test"
1652 depends on DEBUG_KERNEL
1654 Enable this to turn on 'list_sort()' function test. This test is
1655 executed only once during system boot, so affects only boot time.
1659 config KPROBES_SANITY_TEST
1660 bool "Kprobes sanity tests"
1661 depends on DEBUG_KERNEL
1665 This option provides for testing basic kprobes functionality on
1666 boot. A sample kprobe, jprobe and kretprobe are inserted and
1667 verified for functionality.
1669 Say N if you are unsure.
1671 config BACKTRACE_SELF_TEST
1672 tristate "Self test for the backtrace code"
1673 depends on DEBUG_KERNEL
1676 This option provides a kernel module that can be used to test
1677 the kernel stack backtrace code. This option is not useful
1678 for distributions or general kernels, but only for kernel
1679 developers working on architecture code.
1681 Note that if you want to also test saved backtraces, you will
1682 have to enable STACKTRACE as well.
1684 Say N if you are unsure.
1687 tristate "Red-Black tree test"
1688 depends on DEBUG_KERNEL
1690 A benchmark measuring the performance of the rbtree library.
1691 Also includes rbtree invariant checks.
1693 config INTERVAL_TREE_TEST
1694 tristate "Interval tree test"
1695 depends on m && DEBUG_KERNEL
1696 select INTERVAL_TREE
1698 A benchmark measuring the performance of the interval tree library
1701 tristate "Per cpu operations test"
1702 depends on m && DEBUG_KERNEL
1704 Enable this option to build test module which validates per-cpu
1709 config ATOMIC64_SELFTEST
1710 bool "Perform an atomic64_t self-test at boot"
1712 Enable this option to test the atomic64_t functions at boot.
1716 config ASYNC_RAID6_TEST
1717 tristate "Self test for hardware accelerated raid6 recovery"
1718 depends on ASYNC_RAID6_RECOV
1721 This is a one-shot self test that permutes through the
1722 recovery of all the possible two disk failure scenarios for a
1723 N-disk array. Recovery is performed with the asynchronous
1724 raid6 recovery routines, and will optionally use an offload
1725 engine if one is available.
1730 tristate "Test functions located in the hexdump module at runtime"
1732 config TEST_STRING_HELPERS
1733 tristate "Test functions located in the string_helpers module at runtime"
1736 tristate "Test kstrto*() family of functions at runtime"
1739 tristate "Test printf() family of functions at runtime"
1741 config TEST_RHASHTABLE
1742 tristate "Perform selftest on resizable hash table"
1745 Enable this option to test the rhashtable functions at boot.
1749 endmenu # runtime tests
1751 config PROVIDE_OHCI1394_DMA_INIT
1752 bool "Remote debugging over FireWire early on boot"
1753 depends on PCI && X86
1755 If you want to debug problems which hang or crash the kernel early
1756 on boot and the crashing machine has a FireWire port, you can use
1757 this feature to remotely access the memory of the crashed machine
1758 over FireWire. This employs remote DMA as part of the OHCI1394
1759 specification which is now the standard for FireWire controllers.
1761 With remote DMA, you can monitor the printk buffer remotely using
1762 firescope and access all memory below 4GB using fireproxy from gdb.
1763 Even controlling a kernel debugger is possible using remote DMA.
1767 If ohci1394_dma=early is used as boot parameter, it will initialize
1768 all OHCI1394 controllers which are found in the PCI config space.
1770 As all changes to the FireWire bus such as enabling and disabling
1771 devices cause a bus reset and thereby disable remote DMA for all
1772 devices, be sure to have the cable plugged and FireWire enabled on
1773 the debugging host before booting the debug target for debugging.
1775 This code (~1k) is freed after boot. By then, the firewire stack
1776 in charge of the OHCI-1394 controllers should be used instead.
1778 See Documentation/debugging-via-ohci1394.txt for more information.
1781 bool "Build targets in Documentation/ tree"
1782 depends on HEADERS_CHECK
1784 This option attempts to build objects from the source files in the
1785 kernel Documentation/ tree.
1787 Say N if you are unsure.
1789 config DMA_API_DEBUG
1790 bool "Enable debugging of DMA-API usage"
1791 depends on HAVE_DMA_API_DEBUG
1793 Enable this option to debug the use of the DMA API by device drivers.
1794 With this option you will be able to detect common bugs in device
1795 drivers like double-freeing of DMA mappings or freeing mappings that
1796 were never allocated.
1798 This also attempts to catch cases where a page owned by DMA is
1799 accessed by the cpu in a way that could cause data corruption. For
1800 example, this enables cow_user_page() to check that the source page is
1803 This option causes a performance degradation. Use only if you want to
1804 debug device drivers and dma interactions.
1809 tristate "Test module loading with 'hello world' module"
1813 This builds the "test_module" module that emits "Hello, world"
1814 on printk when loaded. It is designed to be used for basic
1815 evaluation of the module loading subsystem (for example when
1816 validating module verification). It lacks any extra dependencies,
1817 and will not normally be loaded by the system unless explicitly
1822 config TEST_USER_COPY
1823 tristate "Test user/kernel boundary protections"
1827 This builds the "test_user_copy" module that runs sanity checks
1828 on the copy_to/from_user infrastructure, making sure basic
1829 user/kernel boundary testing is working. If it fails to load,
1830 a regression has been detected in the user/kernel memory boundary
1836 tristate "Test BPF filter functionality"
1840 This builds the "test_bpf" module that runs various test vectors
1841 against the BPF interpreter or BPF JIT compiler depending on the
1842 current setting. This is in particular useful for BPF JIT compiler
1843 development, but also to run regression tests against changes in
1844 the interpreter code. It also enables test stubs for eBPF maps and
1845 verifier used by user space verifier testsuite.
1849 config TEST_FIRMWARE
1850 tristate "Test firmware loading via userspace interface"
1852 depends on FW_LOADER
1854 This builds the "test_firmware" module that creates a userspace
1855 interface for testing firmware loading. This can be used to
1856 control the triggering of firmware loading without needing an
1857 actual firmware-using device. The contents can be rechecked by
1863 tristate "udelay test driver"
1866 This builds the "udelay_test" module that helps to make sure
1867 that udelay() is working properly.
1873 depends on HAVE_MEMBLOCK
1875 This option adds a kernel parameter 'memtest', which allows memtest
1877 memtest=0, mean disabled; -- default
1878 memtest=1, mean do 1 test pattern;
1880 memtest=17, mean do 17 test patterns.
1881 If you are unsure how to answer this question, answer N.
1883 config TEST_STATIC_KEYS
1884 tristate "Test static keys"
1888 Test the static key interfaces.
1892 source "samples/Kconfig"
1894 source "lib/Kconfig.kgdb"
1896 source "lib/Kconfig.ubsan"
1898 config ARCH_HAS_DEVMEM_IS_ALLOWED
1901 config STRICT_DEVMEM
1902 bool "Filter access to /dev/mem"
1904 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
1905 default y if TILE || PPC
1907 If this option is disabled, you allow userspace (root) access to all
1908 of memory, including kernel and userspace memory. Accidental
1909 access to this is obviously disastrous, but specific access can
1910 be used by people debugging the kernel. Note that with PAT support
1911 enabled, even in this case there are restrictions on /dev/mem
1912 use due to the cache aliasing requirements.
1914 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
1915 file only allows userspace access to PCI space and the BIOS code and
1916 data regions. This is sufficient for dosemu and X and all common
1921 config IO_STRICT_DEVMEM
1922 bool "Filter I/O access to /dev/mem"
1923 depends on STRICT_DEVMEM
1925 If this option is disabled, you allow userspace (root) access to all
1926 io-memory regardless of whether a driver is actively using that
1927 range. Accidental access to this is obviously disastrous, but
1928 specific access can be used by people debugging kernel drivers.
1930 If this option is switched on, the /dev/mem file only allows
1931 userspace access to *idle* io-memory ranges (see /proc/iomem) This
1932 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
1933 if the driver using a given range cannot be disabled.
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