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.
584 bool "Debug VM translations"
585 depends on DEBUG_KERNEL && X86
587 Enable some costly sanity checks in virtual to page code. This can
588 catch mistakes with virt_to_page() and friends.
592 config DEBUG_NOMMU_REGIONS
593 bool "Debug the global anon/private NOMMU mapping region tree"
594 depends on DEBUG_KERNEL && !MMU
596 This option causes the global tree of anonymous and private mapping
597 regions to be regularly checked for invalid topology.
599 config DEBUG_MEMORY_INIT
600 bool "Debug memory initialisation" if EXPERT
603 Enable this for additional checks during memory initialisation.
604 The sanity checks verify aspects of the VM such as the memory model
605 and other information provided by the architecture. Verbose
606 information will be printed at KERN_DEBUG loglevel depending
607 on the mminit_loglevel= command-line option.
611 config MEMORY_NOTIFIER_ERROR_INJECT
612 tristate "Memory hotplug notifier error injection module"
613 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
615 This option provides the ability to inject artificial errors to
616 memory hotplug notifier chain callbacks. It is controlled through
617 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
619 If the notifier call chain should be failed with some events
620 notified, write the error code to "actions/<notifier event>/error".
622 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
624 # cd /sys/kernel/debug/notifier-error-inject/memory
625 # echo -12 > actions/MEM_GOING_OFFLINE/error
626 # echo offline > /sys/devices/system/memory/memoryXXX/state
627 bash: echo: write error: Cannot allocate memory
629 To compile this code as a module, choose M here: the module will
630 be called memory-notifier-error-inject.
634 config DEBUG_PER_CPU_MAPS
635 bool "Debug access to per_cpu maps"
636 depends on DEBUG_KERNEL
639 Say Y to verify that the per_cpu map being accessed has
640 been set up. This adds a fair amount of code to kernel memory
641 and decreases performance.
646 bool "Highmem debugging"
647 depends on DEBUG_KERNEL && HIGHMEM
649 This option enables additional error checking for high memory
650 systems. Disable for production systems.
652 config HAVE_DEBUG_STACKOVERFLOW
655 config DEBUG_STACKOVERFLOW
656 bool "Check for stack overflows"
657 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
659 Say Y here if you want to check for overflows of kernel, IRQ
660 and exception stacks (if your architecture uses them). This
661 option will show detailed messages if free stack space drops
662 below a certain limit.
664 These kinds of bugs usually occur when call-chains in the
665 kernel get too deep, especially when interrupts are
668 Use this in cases where you see apparently random memory
669 corruption, especially if it appears in 'struct thread_info'
671 If in doubt, say "N".
673 source "lib/Kconfig.kmemcheck"
675 source "lib/Kconfig.kasan"
677 endmenu # "Memory Debugging"
680 bool "Debug shared IRQ handlers"
681 depends on DEBUG_KERNEL
683 Enable this to generate a spurious interrupt as soon as a shared
684 interrupt handler is registered, and just before one is deregistered.
685 Drivers ought to be able to handle interrupts coming in at those
686 points; some don't and need to be caught.
688 menu "Debug Lockups and Hangs"
690 config LOCKUP_DETECTOR
691 bool "Detect Hard and Soft Lockups"
692 depends on DEBUG_KERNEL && !S390
694 Say Y here to enable the kernel to act as a watchdog to detect
695 hard and soft lockups.
697 Softlockups are bugs that cause the kernel to loop in kernel
698 mode for more than 20 seconds, without giving other tasks a
699 chance to run. The current stack trace is displayed upon
700 detection and the system will stay locked up.
702 Hardlockups are bugs that cause the CPU to loop in kernel mode
703 for more than 10 seconds, without letting other interrupts have a
704 chance to run. The current stack trace is displayed upon detection
705 and the system will stay locked up.
707 The overhead should be minimal. A periodic hrtimer runs to
708 generate interrupts and kick the watchdog task every 4 seconds.
709 An NMI is generated every 10 seconds or so to check for hardlockups.
710 If NMIs are not available on the platform, every 12 seconds the
711 hrtimer interrupt on one cpu will be used to check for hardlockups
714 The frequency of hrtimer and NMI events and the soft and hard lockup
715 thresholds can be controlled through the sysctl watchdog_thresh.
717 config HARDLOCKUP_DETECTOR_NMI
719 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
720 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
722 config HARDLOCKUP_DETECTOR_OTHER_CPU
724 depends on LOCKUP_DETECTOR && SMP
725 depends on !HARDLOCKUP_DETECTOR_NMI && !HAVE_NMI_WATCHDOG
727 config HARDLOCKUP_DETECTOR
729 depends on HARDLOCKUP_DETECTOR_NMI || HARDLOCKUP_DETECTOR_OTHER_CPU
731 config BOOTPARAM_HARDLOCKUP_PANIC
732 bool "Panic (Reboot) On Hard Lockups"
733 depends on HARDLOCKUP_DETECTOR
735 Say Y here to enable the kernel to panic on "hard lockups",
736 which are bugs that cause the kernel to loop in kernel
737 mode with interrupts disabled for more than 10 seconds (configurable
738 using the watchdog_thresh sysctl).
742 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
744 depends on HARDLOCKUP_DETECTOR
746 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
747 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
749 config BOOTPARAM_SOFTLOCKUP_PANIC
750 bool "Panic (Reboot) On Soft Lockups"
751 depends on LOCKUP_DETECTOR
753 Say Y here to enable the kernel to panic on "soft lockups",
754 which are bugs that cause the kernel to loop in kernel
755 mode for more than 20 seconds (configurable using the watchdog_thresh
756 sysctl), without giving other tasks a chance to run.
758 The panic can be used in combination with panic_timeout,
759 to cause the system to reboot automatically after a
760 lockup has been detected. This feature is useful for
761 high-availability systems that have uptime guarantees and
762 where a lockup must be resolved ASAP.
766 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
768 depends on LOCKUP_DETECTOR
770 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
771 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
773 config DETECT_HUNG_TASK
774 bool "Detect Hung Tasks"
775 depends on DEBUG_KERNEL
776 default LOCKUP_DETECTOR
778 Say Y here to enable the kernel to detect "hung tasks",
779 which are bugs that cause the task to be stuck in
780 uninterruptible "D" state indefinitiley.
782 When a hung task is detected, the kernel will print the
783 current stack trace (which you should report), but the
784 task will stay in uninterruptible state. If lockdep is
785 enabled then all held locks will also be reported. This
786 feature has negligible overhead.
788 config DEFAULT_HUNG_TASK_TIMEOUT
789 int "Default timeout for hung task detection (in seconds)"
790 depends on DETECT_HUNG_TASK
793 This option controls the default timeout (in seconds) used
794 to determine when a task has become non-responsive and should
797 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
798 sysctl or by writing a value to
799 /proc/sys/kernel/hung_task_timeout_secs.
801 A timeout of 0 disables the check. The default is two minutes.
802 Keeping the default should be fine in most cases.
804 config BOOTPARAM_HUNG_TASK_PANIC
805 bool "Panic (Reboot) On Hung Tasks"
806 depends on DETECT_HUNG_TASK
808 Say Y here to enable the kernel to panic on "hung tasks",
809 which are bugs that cause the kernel to leave a task stuck
810 in uninterruptible "D" state.
812 The panic can be used in combination with panic_timeout,
813 to cause the system to reboot automatically after a
814 hung task has been detected. This feature is useful for
815 high-availability systems that have uptime guarantees and
816 where a hung tasks must be resolved ASAP.
820 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
822 depends on DETECT_HUNG_TASK
824 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
825 default 1 if BOOTPARAM_HUNG_TASK_PANIC
827 endmenu # "Debug lockups and hangs"
832 Say Y here to enable the kernel to panic when it oopses. This
833 has the same effect as setting oops=panic on the kernel command
836 This feature is useful to ensure that the kernel does not do
837 anything erroneous after an oops which could result in data
838 corruption or other issues.
842 config PANIC_ON_OOPS_VALUE
845 default 0 if !PANIC_ON_OOPS
846 default 1 if PANIC_ON_OOPS
852 Set the timeout value (in seconds) until a reboot occurs when the
853 the kernel panics. If n = 0, then we wait forever. A timeout
854 value n > 0 will wait n seconds before rebooting, while a timeout
855 value n < 0 will reboot immediately.
858 bool "Collect scheduler debugging info"
859 depends on DEBUG_KERNEL && PROC_FS
862 If you say Y here, the /proc/sched_debug file will be provided
863 that can help debug the scheduler. The runtime overhead of this
870 config PANIC_ON_RT_THROTTLING
871 bool "Panic on RT throttling"
873 Say Y here to enable the kernel to panic when a realtime
874 runqueue is throttled. This may be useful for detecting
875 and debugging RT throttling issues.
880 bool "Collect scheduler statistics"
881 depends on DEBUG_KERNEL && PROC_FS
884 If you say Y here, additional code will be inserted into the
885 scheduler and related routines to collect statistics about
886 scheduler behavior and provide them in /proc/schedstat. These
887 stats may be useful for both tuning and debugging the scheduler
888 If you aren't debugging the scheduler or trying to tune a specific
889 application, you can say N to avoid the very slight overhead
892 config SCHED_STACK_END_CHECK
893 bool "Detect stack corruption on calls to schedule()"
894 depends on DEBUG_KERNEL
897 This option checks for a stack overrun on calls to schedule().
898 If the stack end location is found to be over written always panic as
899 the content of the corrupted region can no longer be trusted.
900 This is to ensure no erroneous behaviour occurs which could result in
901 data corruption or a sporadic crash at a later stage once the region
902 is examined. The runtime overhead introduced is minimal.
904 config DEBUG_TIMEKEEPING
905 bool "Enable extra timekeeping sanity checking"
907 This option will enable additional timekeeping sanity checks
908 which may be helpful when diagnosing issues where timekeeping
909 problems are suspected.
911 This may include checks in the timekeeping hotpaths, so this
912 option may have a (very small) performance impact to some
918 bool "Collect kernel timers statistics"
919 depends on DEBUG_KERNEL && PROC_FS
921 If you say Y here, additional code will be inserted into the
922 timer routines to collect statistics about kernel timers being
923 reprogrammed. The statistics can be read from /proc/timer_stats.
924 The statistics collection is started by writing 1 to /proc/timer_stats,
925 writing 0 stops it. This feature is useful to collect information
926 about timer usage patterns in kernel and userspace. This feature
927 is lightweight if enabled in the kernel config but not activated
928 (it defaults to deactivated on bootup and will only be activated
929 if some application like powertop activates it explicitly).
932 bool "Debug preemptible kernel"
933 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
936 If you say Y here then the kernel will use a debug variant of the
937 commonly used smp_processor_id() function and will print warnings
938 if kernel code uses it in a preemption-unsafe way. Also, the kernel
939 will detect preemption count underflows.
941 menu "Lock Debugging (spinlocks, mutexes, etc...)"
943 config DEBUG_RT_MUTEXES
944 bool "RT Mutex debugging, deadlock detection"
945 depends on DEBUG_KERNEL && RT_MUTEXES
947 This allows rt mutex semantics violations and rt mutex related
948 deadlocks (lockups) to be detected and reported automatically.
950 config DEBUG_SPINLOCK
951 bool "Spinlock and rw-lock debugging: basic checks"
952 depends on DEBUG_KERNEL
953 select UNINLINE_SPIN_UNLOCK
955 Say Y here and build SMP to catch missing spinlock initialization
956 and certain other kinds of spinlock errors commonly made. This is
957 best used in conjunction with the NMI watchdog so that spinlock
958 deadlocks are also debuggable.
961 bool "Mutex debugging: basic checks"
962 depends on DEBUG_KERNEL
964 This feature allows mutex semantics violations to be detected and
967 config DEBUG_WW_MUTEX_SLOWPATH
968 bool "Wait/wound mutex debugging: Slowpath testing"
969 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
970 select DEBUG_LOCK_ALLOC
971 select DEBUG_SPINLOCK
974 This feature enables slowpath testing for w/w mutex users by
975 injecting additional -EDEADLK wound/backoff cases. Together with
976 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
977 will test all possible w/w mutex interface abuse with the
978 exception of simply not acquiring all the required locks.
979 Note that this feature can introduce significant overhead, so
980 it really should not be enabled in a production or distro kernel,
981 even a debug kernel. If you are a driver writer, enable it. If
982 you are a distro, do not.
984 config DEBUG_LOCK_ALLOC
985 bool "Lock debugging: detect incorrect freeing of live locks"
986 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
987 select DEBUG_SPINLOCK
991 This feature will check whether any held lock (spinlock, rwlock,
992 mutex or rwsem) is incorrectly freed by the kernel, via any of the
993 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
994 vfree(), etc.), whether a live lock is incorrectly reinitialized via
995 spin_lock_init()/mutex_init()/etc., or whether there is any lock
996 held during task exit.
999 bool "Lock debugging: prove locking correctness"
1000 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1002 select DEBUG_SPINLOCK
1003 select DEBUG_MUTEXES
1004 select DEBUG_LOCK_ALLOC
1005 select TRACE_IRQFLAGS
1008 This feature enables the kernel to prove that all locking
1009 that occurs in the kernel runtime is mathematically
1010 correct: that under no circumstance could an arbitrary (and
1011 not yet triggered) combination of observed locking
1012 sequences (on an arbitrary number of CPUs, running an
1013 arbitrary number of tasks and interrupt contexts) cause a
1016 In short, this feature enables the kernel to report locking
1017 related deadlocks before they actually occur.
1019 The proof does not depend on how hard and complex a
1020 deadlock scenario would be to trigger: how many
1021 participant CPUs, tasks and irq-contexts would be needed
1022 for it to trigger. The proof also does not depend on
1023 timing: if a race and a resulting deadlock is possible
1024 theoretically (no matter how unlikely the race scenario
1025 is), it will be proven so and will immediately be
1026 reported by the kernel (once the event is observed that
1027 makes the deadlock theoretically possible).
1029 If a deadlock is impossible (i.e. the locking rules, as
1030 observed by the kernel, are mathematically correct), the
1031 kernel reports nothing.
1033 NOTE: this feature can also be enabled for rwlocks, mutexes
1034 and rwsems - in which case all dependencies between these
1035 different locking variants are observed and mapped too, and
1036 the proof of observed correctness is also maintained for an
1037 arbitrary combination of these separate locking variants.
1039 For more details, see Documentation/locking/lockdep-design.txt.
1043 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1045 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
1050 bool "Lock usage statistics"
1051 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1053 select DEBUG_SPINLOCK
1054 select DEBUG_MUTEXES
1055 select DEBUG_LOCK_ALLOC
1058 This feature enables tracking lock contention points
1060 For more details, see Documentation/locking/lockstat.txt
1062 This also enables lock events required by "perf lock",
1064 If you want to use "perf lock", you also need to turn on
1065 CONFIG_EVENT_TRACING.
1067 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1068 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1070 config DEBUG_LOCKDEP
1071 bool "Lock dependency engine debugging"
1072 depends on DEBUG_KERNEL && LOCKDEP
1074 If you say Y here, the lock dependency engine will do
1075 additional runtime checks to debug itself, at the price
1076 of more runtime overhead.
1078 config DEBUG_ATOMIC_SLEEP
1079 bool "Sleep inside atomic section checking"
1080 select PREEMPT_COUNT
1081 depends on DEBUG_KERNEL
1083 If you say Y here, various routines which may sleep will become very
1084 noisy if they are called inside atomic sections: when a spinlock is
1085 held, inside an rcu read side critical section, inside preempt disabled
1086 sections, inside an interrupt, etc...
1088 config DEBUG_LOCKING_API_SELFTESTS
1089 bool "Locking API boot-time self-tests"
1090 depends on DEBUG_KERNEL
1092 Say Y here if you want the kernel to run a short self-test during
1093 bootup. The self-test checks whether common types of locking bugs
1094 are detected by debugging mechanisms or not. (if you disable
1095 lock debugging then those bugs wont be detected of course.)
1096 The following locking APIs are covered: spinlocks, rwlocks,
1099 config LOCK_TORTURE_TEST
1100 tristate "torture tests for locking"
1101 depends on DEBUG_KERNEL
1105 This option provides a kernel module that runs torture tests
1106 on kernel locking primitives. The kernel module may be built
1107 after the fact on the running kernel to be tested, if desired.
1109 Say Y here if you want kernel locking-primitive torture tests
1110 to be built into the kernel.
1111 Say M if you want these torture tests to build as a module.
1112 Say N if you are unsure.
1114 endmenu # lock debugging
1116 config TRACE_IRQFLAGS
1119 Enables hooks to interrupt enabling and disabling for
1120 either tracing or lock debugging.
1123 bool "Stack backtrace support"
1124 depends on STACKTRACE_SUPPORT
1126 This option causes the kernel to create a /proc/pid/stack for
1127 every process, showing its current stack trace.
1128 It is also used by various kernel debugging features that require
1129 stack trace generation.
1131 config DEBUG_KOBJECT
1132 bool "kobject debugging"
1133 depends on DEBUG_KERNEL
1135 If you say Y here, some extra kobject debugging messages will be sent
1138 config DEBUG_KOBJECT_RELEASE
1139 bool "kobject release debugging"
1140 depends on DEBUG_OBJECTS_TIMERS
1142 kobjects are reference counted objects. This means that their
1143 last reference count put is not predictable, and the kobject can
1144 live on past the point at which a driver decides to drop it's
1145 initial reference to the kobject gained on allocation. An
1146 example of this would be a struct device which has just been
1149 However, some buggy drivers assume that after such an operation,
1150 the memory backing the kobject can be immediately freed. This
1151 goes completely against the principles of a refcounted object.
1153 If you say Y here, the kernel will delay the release of kobjects
1154 on the last reference count to improve the visibility of this
1155 kind of kobject release bug.
1157 config HAVE_DEBUG_BUGVERBOSE
1160 config DEBUG_BUGVERBOSE
1161 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1162 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1165 Say Y here to make BUG() panics output the file name and line number
1166 of the BUG call as well as the EIP and oops trace. This aids
1167 debugging but costs about 70-100K of memory.
1170 bool "Debug linked list manipulation"
1171 depends on DEBUG_KERNEL
1173 Enable this to turn on extended checks in the linked-list
1178 config DEBUG_PI_LIST
1179 bool "Debug priority linked list manipulation"
1180 depends on DEBUG_KERNEL
1182 Enable this to turn on extended checks in the priority-ordered
1183 linked-list (plist) walking routines. This checks the entire
1184 list multiple times during each manipulation.
1189 bool "Debug SG table operations"
1190 depends on DEBUG_KERNEL
1192 Enable this to turn on checks on scatter-gather tables. This can
1193 help find problems with drivers that do not properly initialize
1198 config DEBUG_NOTIFIERS
1199 bool "Debug notifier call chains"
1200 depends on DEBUG_KERNEL
1202 Enable this to turn on sanity checking for notifier call chains.
1203 This is most useful for kernel developers to make sure that
1204 modules properly unregister themselves from notifier chains.
1205 This is a relatively cheap check but if you care about maximum
1208 config DEBUG_CREDENTIALS
1209 bool "Debug credential management"
1210 depends on DEBUG_KERNEL
1212 Enable this to turn on some debug checking for credential
1213 management. The additional code keeps track of the number of
1214 pointers from task_structs to any given cred struct, and checks to
1215 see that this number never exceeds the usage count of the cred
1218 Furthermore, if SELinux is enabled, this also checks that the
1219 security pointer in the cred struct is never seen to be invalid.
1223 menu "RCU Debugging"
1226 def_bool PROVE_LOCKING
1228 config PROVE_RCU_REPEATEDLY
1229 bool "RCU debugging: don't disable PROVE_RCU on first splat"
1230 depends on PROVE_RCU
1233 By itself, PROVE_RCU will disable checking upon issuing the
1234 first warning (or "splat"). This feature prevents such
1235 disabling, allowing multiple RCU-lockdep warnings to be printed
1238 Say Y to allow multiple RCU-lockdep warnings per boot.
1240 Say N if you are unsure.
1242 config SPARSE_RCU_POINTER
1243 bool "RCU debugging: sparse-based checks for pointer usage"
1246 This feature enables the __rcu sparse annotation for
1247 RCU-protected pointers. This annotation will cause sparse
1248 to flag any non-RCU used of annotated pointers. This can be
1249 helpful when debugging RCU usage. Please note that this feature
1250 is not intended to enforce code cleanliness; it is instead merely
1253 Say Y to make sparse flag questionable use of RCU-protected pointers
1255 Say N if you are unsure.
1261 config RCU_TORTURE_TEST
1262 tristate "torture tests for RCU"
1263 depends on DEBUG_KERNEL
1269 This option provides a kernel module that runs torture tests
1270 on the RCU infrastructure. The kernel module may be built
1271 after the fact on the running kernel to be tested, if desired.
1273 Say Y here if you want RCU torture tests to be built into
1275 Say M if you want the RCU torture tests to build as a module.
1276 Say N if you are unsure.
1278 config RCU_TORTURE_TEST_RUNNABLE
1279 bool "torture tests for RCU runnable by default"
1280 depends on RCU_TORTURE_TEST = y
1283 This option provides a way to build the RCU torture tests
1284 directly into the kernel without them starting up at boot
1285 time. You can use /proc/sys/kernel/rcutorture_runnable
1286 to manually override this setting. This /proc file is
1287 available only when the RCU torture tests have been built
1290 Say Y here if you want the RCU torture tests to start during
1291 boot (you probably don't).
1292 Say N here if you want the RCU torture tests to start only
1293 after being manually enabled via /proc.
1295 config RCU_TORTURE_TEST_SLOW_PREINIT
1296 bool "Slow down RCU grace-period pre-initialization to expose races"
1297 depends on RCU_TORTURE_TEST
1299 This option delays grace-period pre-initialization (the
1300 propagation of CPU-hotplug changes up the rcu_node combining
1301 tree) for a few jiffies between initializing each pair of
1302 consecutive rcu_node structures. This helps to expose races
1303 involving grace-period pre-initialization, in other words, it
1304 makes your kernel less stable. It can also greatly increase
1305 grace-period latency, especially on systems with large numbers
1306 of CPUs. This is useful when torture-testing RCU, but in
1307 almost no other circumstance.
1309 Say Y here if you want your system to crash and hang more often.
1310 Say N if you want a sane system.
1312 config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
1313 int "How much to slow down RCU grace-period pre-initialization"
1316 depends on RCU_TORTURE_TEST_SLOW_PREINIT
1318 This option specifies the number of jiffies to wait between
1319 each rcu_node structure pre-initialization step.
1321 config RCU_TORTURE_TEST_SLOW_INIT
1322 bool "Slow down RCU grace-period initialization to expose races"
1323 depends on RCU_TORTURE_TEST
1325 This option delays grace-period initialization for a few
1326 jiffies between initializing each pair of consecutive
1327 rcu_node structures. This helps to expose races involving
1328 grace-period initialization, in other words, it makes your
1329 kernel less stable. It can also greatly increase grace-period
1330 latency, especially on systems with large numbers of CPUs.
1331 This is useful when torture-testing RCU, but in almost no
1334 Say Y here if you want your system to crash and hang more often.
1335 Say N if you want a sane system.
1337 config RCU_TORTURE_TEST_SLOW_INIT_DELAY
1338 int "How much to slow down RCU grace-period initialization"
1341 depends on RCU_TORTURE_TEST_SLOW_INIT
1343 This option specifies the number of jiffies to wait between
1344 each rcu_node structure initialization.
1346 config RCU_TORTURE_TEST_SLOW_CLEANUP
1347 bool "Slow down RCU grace-period cleanup to expose races"
1348 depends on RCU_TORTURE_TEST
1350 This option delays grace-period cleanup for a few jiffies
1351 between cleaning up each pair of consecutive rcu_node
1352 structures. This helps to expose races involving grace-period
1353 cleanup, in other words, it makes your kernel less stable.
1354 It can also greatly increase grace-period latency, especially
1355 on systems with large numbers of CPUs. This is useful when
1356 torture-testing RCU, but in almost no other circumstance.
1358 Say Y here if you want your system to crash and hang more often.
1359 Say N if you want a sane system.
1361 config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
1362 int "How much to slow down RCU grace-period cleanup"
1365 depends on RCU_TORTURE_TEST_SLOW_CLEANUP
1367 This option specifies the number of jiffies to wait between
1368 each rcu_node structure cleanup operation.
1370 config RCU_CPU_STALL_TIMEOUT
1371 int "RCU CPU stall timeout in seconds"
1372 depends on RCU_STALL_COMMON
1376 If a given RCU grace period extends more than the specified
1377 number of seconds, a CPU stall warning is printed. If the
1378 RCU grace period persists, additional CPU stall warnings are
1379 printed at more widely spaced intervals.
1382 bool "Enable tracing for RCU"
1383 depends on DEBUG_KERNEL
1386 This option provides tracing in RCU which presents stats
1387 in debugfs for debugging RCU implementation.
1389 Say Y here if you want to enable RCU tracing
1390 Say N if you are unsure.
1392 config RCU_EQS_DEBUG
1393 bool "Provide debugging asserts for adding NO_HZ support to an arch"
1394 depends on DEBUG_KERNEL
1396 This option provides consistency checks in RCU's handling of
1397 NO_HZ. These checks have proven quite helpful in detecting
1398 bugs in arch-specific NO_HZ code.
1400 Say N here if you need ultimate kernel/user switch latencies
1401 Say Y if you are unsure
1403 endmenu # "RCU Debugging"
1405 config DEBUG_BLOCK_EXT_DEVT
1406 bool "Force extended block device numbers and spread them"
1407 depends on DEBUG_KERNEL
1411 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1412 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1413 YOU ARE DOING. Distros, please enable this and fix whatever
1416 Conventionally, block device numbers are allocated from
1417 predetermined contiguous area. However, extended block area
1418 may introduce non-contiguous block device numbers. This
1419 option forces most block device numbers to be allocated from
1420 the extended space and spreads them to discover kernel or
1421 userland code paths which assume predetermined contiguous
1422 device number allocation.
1424 Note that turning on this debug option shuffles all the
1425 device numbers for all IDE and SCSI devices including libata
1426 ones, so root partition specified using device number
1427 directly (via rdev or root=MAJ:MIN) won't work anymore.
1428 Textual device names (root=/dev/sdXn) will continue to work.
1430 Say N if you are unsure.
1432 config NOTIFIER_ERROR_INJECTION
1433 tristate "Notifier error injection"
1434 depends on DEBUG_KERNEL
1437 This option provides the ability to inject artificial errors to
1438 specified notifier chain callbacks. It is useful to test the error
1439 handling of notifier call chain failures.
1443 config CPU_NOTIFIER_ERROR_INJECT
1444 tristate "CPU notifier error injection module"
1445 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1447 This option provides a kernel module that can be used to test
1448 the error handling of the cpu notifiers by injecting artificial
1449 errors to CPU notifier chain callbacks. It is controlled through
1450 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
1452 If the notifier call chain should be failed with some events
1453 notified, write the error code to "actions/<notifier event>/error".
1455 Example: Inject CPU offline error (-1 == -EPERM)
1457 # cd /sys/kernel/debug/notifier-error-inject/cpu
1458 # echo -1 > actions/CPU_DOWN_PREPARE/error
1459 # echo 0 > /sys/devices/system/cpu/cpu1/online
1460 bash: echo: write error: Operation not permitted
1462 To compile this code as a module, choose M here: the module will
1463 be called cpu-notifier-error-inject.
1467 config PM_NOTIFIER_ERROR_INJECT
1468 tristate "PM notifier error injection module"
1469 depends on PM && NOTIFIER_ERROR_INJECTION
1470 default m if PM_DEBUG
1472 This option provides the ability to inject artificial errors to
1473 PM notifier chain callbacks. It is controlled through debugfs
1474 interface /sys/kernel/debug/notifier-error-inject/pm
1476 If the notifier call chain should be failed with some events
1477 notified, write the error code to "actions/<notifier event>/error".
1479 Example: Inject PM suspend error (-12 = -ENOMEM)
1481 # cd /sys/kernel/debug/notifier-error-inject/pm/
1482 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1483 # echo mem > /sys/power/state
1484 bash: echo: write error: Cannot allocate memory
1486 To compile this code as a module, choose M here: the module will
1487 be called pm-notifier-error-inject.
1491 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1492 tristate "OF reconfig notifier error injection module"
1493 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1495 This option provides the ability to inject artificial errors to
1496 OF reconfig notifier chain callbacks. It is controlled
1497 through debugfs interface under
1498 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1500 If the notifier call chain should be failed with some events
1501 notified, write the error code to "actions/<notifier event>/error".
1503 To compile this code as a module, choose M here: the module will
1504 be called of-reconfig-notifier-error-inject.
1508 config FAULT_INJECTION
1509 bool "Fault-injection framework"
1510 depends on DEBUG_KERNEL
1512 Provide fault-injection framework.
1513 For more details, see Documentation/fault-injection/.
1516 bool "Fault-injection capability for kmalloc"
1517 depends on FAULT_INJECTION
1518 depends on SLAB || SLUB
1520 Provide fault-injection capability for kmalloc.
1522 config FAIL_PAGE_ALLOC
1523 bool "Fault-injection capabilitiy for alloc_pages()"
1524 depends on FAULT_INJECTION
1526 Provide fault-injection capability for alloc_pages().
1528 config FAIL_MAKE_REQUEST
1529 bool "Fault-injection capability for disk IO"
1530 depends on FAULT_INJECTION && BLOCK
1532 Provide fault-injection capability for disk IO.
1534 config FAIL_IO_TIMEOUT
1535 bool "Fault-injection capability for faking disk interrupts"
1536 depends on FAULT_INJECTION && BLOCK
1538 Provide fault-injection capability on end IO handling. This
1539 will make the block layer "forget" an interrupt as configured,
1540 thus exercising the error handling.
1542 Only works with drivers that use the generic timeout handling,
1543 for others it wont do anything.
1545 config FAIL_MMC_REQUEST
1546 bool "Fault-injection capability for MMC IO"
1548 depends on FAULT_INJECTION && MMC
1550 Provide fault-injection capability for MMC IO.
1551 This will make the mmc core return data errors. This is
1552 useful to test the error handling in the mmc block device
1553 and to test how the mmc host driver handles retries from
1557 bool "Fault-injection capability for futexes"
1559 depends on FAULT_INJECTION && FUTEX
1561 Provide fault-injection capability for futexes.
1563 config FAULT_INJECTION_DEBUG_FS
1564 bool "Debugfs entries for fault-injection capabilities"
1565 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1567 Enable configuration of fault-injection capabilities via debugfs.
1569 config FAULT_INJECTION_STACKTRACE_FILTER
1570 bool "stacktrace filter for fault-injection capabilities"
1571 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1574 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1576 Provide stacktrace filter for fault-injection capabilities
1579 bool "Latency measuring infrastructure"
1580 depends on HAVE_LATENCYTOP_SUPPORT
1581 depends on DEBUG_KERNEL
1582 depends on STACKTRACE_SUPPORT
1584 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1591 Enable this option if you want to use the LatencyTOP tool
1592 to find out which userspace is blocking on what kernel operations.
1594 config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1597 config DEBUG_STRICT_USER_COPY_CHECKS
1598 bool "Strict user copy size checks"
1599 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1600 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
1602 Enabling this option turns a certain set of sanity checks for user
1603 copy operations into compile time failures.
1605 The copy_from_user() etc checks are there to help test if there
1606 are sufficient security checks on the length argument of
1607 the copy operation, by having gcc prove that the argument is
1612 source kernel/trace/Kconfig
1614 menu "Runtime Testing"
1617 tristate "Linux Kernel Dump Test Tool Module"
1622 This module enables testing of the different dumping mechanisms by
1623 inducing system failures at predefined crash points.
1624 If you don't need it: say N
1625 Choose M here to compile this code as a module. The module will be
1628 Documentation on how to use the module can be found in
1629 Documentation/fault-injection/provoke-crashes.txt
1631 config TEST_LIST_SORT
1632 bool "Linked list sorting test"
1633 depends on DEBUG_KERNEL
1635 Enable this to turn on 'list_sort()' function test. This test is
1636 executed only once during system boot, so affects only boot time.
1640 config KPROBES_SANITY_TEST
1641 bool "Kprobes sanity tests"
1642 depends on DEBUG_KERNEL
1646 This option provides for testing basic kprobes functionality on
1647 boot. A sample kprobe, jprobe and kretprobe are inserted and
1648 verified for functionality.
1650 Say N if you are unsure.
1652 config BACKTRACE_SELF_TEST
1653 tristate "Self test for the backtrace code"
1654 depends on DEBUG_KERNEL
1657 This option provides a kernel module that can be used to test
1658 the kernel stack backtrace code. This option is not useful
1659 for distributions or general kernels, but only for kernel
1660 developers working on architecture code.
1662 Note that if you want to also test saved backtraces, you will
1663 have to enable STACKTRACE as well.
1665 Say N if you are unsure.
1668 tristate "Red-Black tree test"
1669 depends on DEBUG_KERNEL
1671 A benchmark measuring the performance of the rbtree library.
1672 Also includes rbtree invariant checks.
1674 config INTERVAL_TREE_TEST
1675 tristate "Interval tree test"
1676 depends on m && DEBUG_KERNEL
1677 select INTERVAL_TREE
1679 A benchmark measuring the performance of the interval tree library
1682 tristate "Per cpu operations test"
1683 depends on m && DEBUG_KERNEL
1685 Enable this option to build test module which validates per-cpu
1690 config ATOMIC64_SELFTEST
1691 bool "Perform an atomic64_t self-test at boot"
1693 Enable this option to test the atomic64_t functions at boot.
1697 config ASYNC_RAID6_TEST
1698 tristate "Self test for hardware accelerated raid6 recovery"
1699 depends on ASYNC_RAID6_RECOV
1702 This is a one-shot self test that permutes through the
1703 recovery of all the possible two disk failure scenarios for a
1704 N-disk array. Recovery is performed with the asynchronous
1705 raid6 recovery routines, and will optionally use an offload
1706 engine if one is available.
1711 tristate "Test functions located in the hexdump module at runtime"
1713 config TEST_STRING_HELPERS
1714 tristate "Test functions located in the string_helpers module at runtime"
1717 tristate "Test kstrto*() family of functions at runtime"
1720 tristate "Test printf() family of functions at runtime"
1722 config TEST_RHASHTABLE
1723 tristate "Perform selftest on resizable hash table"
1726 Enable this option to test the rhashtable functions at boot.
1730 endmenu # runtime tests
1732 config PROVIDE_OHCI1394_DMA_INIT
1733 bool "Remote debugging over FireWire early on boot"
1734 depends on PCI && X86
1736 If you want to debug problems which hang or crash the kernel early
1737 on boot and the crashing machine has a FireWire port, you can use
1738 this feature to remotely access the memory of the crashed machine
1739 over FireWire. This employs remote DMA as part of the OHCI1394
1740 specification which is now the standard for FireWire controllers.
1742 With remote DMA, you can monitor the printk buffer remotely using
1743 firescope and access all memory below 4GB using fireproxy from gdb.
1744 Even controlling a kernel debugger is possible using remote DMA.
1748 If ohci1394_dma=early is used as boot parameter, it will initialize
1749 all OHCI1394 controllers which are found in the PCI config space.
1751 As all changes to the FireWire bus such as enabling and disabling
1752 devices cause a bus reset and thereby disable remote DMA for all
1753 devices, be sure to have the cable plugged and FireWire enabled on
1754 the debugging host before booting the debug target for debugging.
1756 This code (~1k) is freed after boot. By then, the firewire stack
1757 in charge of the OHCI-1394 controllers should be used instead.
1759 See Documentation/debugging-via-ohci1394.txt for more information.
1762 bool "Build targets in Documentation/ tree"
1763 depends on HEADERS_CHECK
1765 This option attempts to build objects from the source files in the
1766 kernel Documentation/ tree.
1768 Say N if you are unsure.
1770 config DMA_API_DEBUG
1771 bool "Enable debugging of DMA-API usage"
1772 depends on HAVE_DMA_API_DEBUG
1774 Enable this option to debug the use of the DMA API by device drivers.
1775 With this option you will be able to detect common bugs in device
1776 drivers like double-freeing of DMA mappings or freeing mappings that
1777 were never allocated.
1779 This also attempts to catch cases where a page owned by DMA is
1780 accessed by the cpu in a way that could cause data corruption. For
1781 example, this enables cow_user_page() to check that the source page is
1784 This option causes a performance degradation. Use only if you want to
1785 debug device drivers and dma interactions.
1790 tristate "Test module loading with 'hello world' module"
1794 This builds the "test_module" module that emits "Hello, world"
1795 on printk when loaded. It is designed to be used for basic
1796 evaluation of the module loading subsystem (for example when
1797 validating module verification). It lacks any extra dependencies,
1798 and will not normally be loaded by the system unless explicitly
1803 config TEST_USER_COPY
1804 tristate "Test user/kernel boundary protections"
1808 This builds the "test_user_copy" module that runs sanity checks
1809 on the copy_to/from_user infrastructure, making sure basic
1810 user/kernel boundary testing is working. If it fails to load,
1811 a regression has been detected in the user/kernel memory boundary
1817 tristate "Test BPF filter functionality"
1821 This builds the "test_bpf" module that runs various test vectors
1822 against the BPF interpreter or BPF JIT compiler depending on the
1823 current setting. This is in particular useful for BPF JIT compiler
1824 development, but also to run regression tests against changes in
1825 the interpreter code. It also enables test stubs for eBPF maps and
1826 verifier used by user space verifier testsuite.
1830 config TEST_FIRMWARE
1831 tristate "Test firmware loading via userspace interface"
1833 depends on FW_LOADER
1835 This builds the "test_firmware" module that creates a userspace
1836 interface for testing firmware loading. This can be used to
1837 control the triggering of firmware loading without needing an
1838 actual firmware-using device. The contents can be rechecked by
1844 tristate "udelay test driver"
1847 This builds the "udelay_test" module that helps to make sure
1848 that udelay() is working properly.
1854 depends on HAVE_MEMBLOCK
1856 This option adds a kernel parameter 'memtest', which allows memtest
1858 memtest=0, mean disabled; -- default
1859 memtest=1, mean do 1 test pattern;
1861 memtest=17, mean do 17 test patterns.
1862 If you are unsure how to answer this question, answer N.
1864 config TEST_STATIC_KEYS
1865 tristate "Test static keys"
1869 Test the static key interfaces.
1873 source "samples/Kconfig"
1875 source "lib/Kconfig.kgdb"
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