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Linux/lib/Kconfig.debug

  1 menu "printk and dmesg options"
  2 
  3 config PRINTK_TIME
  4         bool "Show timing information on printks"
  5         depends on PRINTK
  6         help
  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.
 10 
 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.
 14 
 15           The behavior is also controlled by the kernel command line
 16           parameter printk.time=1. See Documentation/kernel-parameters.txt
 17 
 18 config DEFAULT_MESSAGE_LOGLEVEL
 19         int "Default message log level (1-7)"
 20         range 1 7
 21         default "4"
 22         help
 23           Default log level for printk statements with no specified priority.
 24 
 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
 27           priority.
 28 
 29 config BOOT_PRINTK_DELAY
 30         bool "Delay each boot printk message by N milliseconds"
 31         depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
 32         help
 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,
 36           using "boot_delay=N".
 37 
 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.
 46 
 47 config DYNAMIC_DEBUG
 48         bool "Enable dynamic printk() support"
 49         default n
 50         depends on PRINTK
 51         depends on DEBUG_FS
 52         help
 53 
 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%.
 60 
 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.
 65 
 66           Usage:
 67 
 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:
 74 
 75                 filename:lineno [module]function flags format
 76 
 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
 83 
 84           From a live system:
 85 
 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"
 91 
 92           Example usage:
 93 
 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
 97 
 98                 // enable all the messages in file svcsock.c
 99                 nullarbor:~ # echo -n 'file svcsock.c +p' >
100                                                 <debugfs>/dynamic_debug/control
101 
102                 // enable all the messages in the NFS server module
103                 nullarbor:~ # echo -n 'module nfsd +p' >
104                                                 <debugfs>/dynamic_debug/control
105 
106                 // enable all 12 messages in the function svc_process()
107                 nullarbor:~ # echo -n 'func svc_process +p' >
108                                                 <debugfs>/dynamic_debug/control
109 
110                 // disable all 12 messages in the function svc_process()
111                 nullarbor:~ # echo -n 'func svc_process -p' >
112                                                 <debugfs>/dynamic_debug/control
113 
114           See Documentation/dynamic-debug-howto.txt for additional information.
115 
116 endmenu # "printk and dmesg options"
117 
118 menu "Compile-time checks and compiler options"
119 
120 config DEBUG_INFO
121         bool "Compile the kernel with debug info"
122         depends on DEBUG_KERNEL && !COMPILE_TEST
123         help
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.
130 
131           If unsure, say N.
132 
133 config DEBUG_INFO_REDUCED
134         bool "Reduce debugging information"
135         depends on DEBUG_INFO
136         help
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.
145 
146 config ENABLE_WARN_DEPRECATED
147         bool "Enable __deprecated logic"
148         default y
149         help
150           Enable the __deprecated logic in the kernel build.
151           Disable this to suppress the "warning: 'foo' is deprecated
152           (declared at kernel/power/somefile.c:1234)" messages.
153 
154 config ENABLE_MUST_CHECK
155         bool "Enable __must_check logic"
156         default y
157         help
158           Enable the __must_check logic in the kernel build.  Disable this to
159           suppress the "warning: ignoring return value of 'foo', declared with
160           attribute warn_unused_result" messages.
161 
162 config FRAME_WARN
163         int "Warn for stack frames larger than (needs gcc 4.4)"
164         range 0 8192
165         default 1024 if !64BIT
166         default 2048 if 64BIT
167         help
168           Tell gcc to warn at build time for stack frames larger than this.
169           Setting this too low will cause a lot of warnings.
170           Setting it to 0 disables the warning.
171           Requires gcc 4.4
172 
173 config STRIP_ASM_SYMS
174         bool "Strip assembler-generated symbols during link"
175         default n
176         help
177           Strip internal assembler-generated symbols during a link (symbols
178           that look like '.Lxxx') so they don't pollute the output of
179           get_wchan() and suchlike.
180 
181 config READABLE_ASM
182         bool "Generate readable assembler code"
183         depends on DEBUG_KERNEL
184         help
185           Disable some compiler optimizations that tend to generate human unreadable
186           assembler output. This may make the kernel slightly slower, but it helps
187           to keep kernel developers who have to stare a lot at assembler listings
188           sane.
189 
190 config UNUSED_SYMBOLS
191         bool "Enable unused/obsolete exported symbols"
192         default y if X86
193         help
194           Unused but exported symbols make the kernel needlessly bigger.  For
195           that reason most of these unused exports will soon be removed.  This
196           option is provided temporarily to provide a transition period in case
197           some external kernel module needs one of these symbols anyway. If you
198           encounter such a case in your module, consider if you are actually
199           using the right API.  (rationale: since nobody in the kernel is using
200           this in a module, there is a pretty good chance it's actually the
201           wrong interface to use).  If you really need the symbol, please send a
202           mail to the linux kernel mailing list mentioning the symbol and why
203           you really need it, and what the merge plan to the mainline kernel for
204           your module is.
205 
206 config DEBUG_FS
207         bool "Debug Filesystem"
208         help
209           debugfs is a virtual file system that kernel developers use to put
210           debugging files into.  Enable this option to be able to read and
211           write to these files.
212 
213           For detailed documentation on the debugfs API, see
214           Documentation/DocBook/filesystems.
215 
216           If unsure, say N.
217 
218 config HEADERS_CHECK
219         bool "Run 'make headers_check' when building vmlinux"
220         depends on !UML
221         help
222           This option will extract the user-visible kernel headers whenever
223           building the kernel, and will run basic sanity checks on them to
224           ensure that exported files do not attempt to include files which
225           were not exported, etc.
226 
227           If you're making modifications to header files which are
228           relevant for userspace, say 'Y', and check the headers
229           exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
230           your build tree), to make sure they're suitable.
231 
232 config DEBUG_SECTION_MISMATCH
233         bool "Enable full Section mismatch analysis"
234         help
235           The section mismatch analysis checks if there are illegal
236           references from one section to another section.
237           During linktime or runtime, some sections are dropped;
238           any use of code/data previously in these sections would
239           most likely result in an oops.
240           In the code, functions and variables are annotated with
241           __init,, etc. (see the full list in include/linux/init.h),
242           which results in the code/data being placed in specific sections.
243           The section mismatch analysis is always performed after a full
244           kernel build, and enabling this option causes the following
245           additional steps to occur:
246           - Add the option -fno-inline-functions-called-once to gcc commands.
247             When inlining a function annotated with __init in a non-init
248             function, we would lose the section information and thus
249             the analysis would not catch the illegal reference.
250             This option tells gcc to inline less (but it does result in
251             a larger kernel).
252           - Run the section mismatch analysis for each module/built-in.o file.
253             When we run the section mismatch analysis on vmlinux.o, we
254             lose valueble information about where the mismatch was
255             introduced.
256             Running the analysis for each module/built-in.o file
257             tells where the mismatch happens much closer to the
258             source. The drawback is that the same mismatch is
259             reported at least twice.
260           - Enable verbose reporting from modpost in order to help resolve
261             the section mismatches that are reported.
262 
263 #
264 # Select this config option from the architecture Kconfig, if it
265 # is preferred to always offer frame pointers as a config
266 # option on the architecture (regardless of KERNEL_DEBUG):
267 #
268 config ARCH_WANT_FRAME_POINTERS
269         bool
270         help
271 
272 config FRAME_POINTER
273         bool "Compile the kernel with frame pointers"
274         depends on DEBUG_KERNEL && \
275                 (CRIS || M68K || FRV || UML || \
276                  AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \
277                 ARCH_WANT_FRAME_POINTERS
278         default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
279         help
280           If you say Y here the resulting kernel image will be slightly
281           larger and slower, but it gives very useful debugging information
282           in case of kernel bugs. (precise oopses/stacktraces/warnings)
283 
284 config DEBUG_FORCE_WEAK_PER_CPU
285         bool "Force weak per-cpu definitions"
286         depends on DEBUG_KERNEL
287         help
288           s390 and alpha require percpu variables in modules to be
289           defined weak to work around addressing range issue which
290           puts the following two restrictions on percpu variable
291           definitions.
292 
293           1. percpu symbols must be unique whether static or not
294           2. percpu variables can't be defined inside a function
295 
296           To ensure that generic code follows the above rules, this
297           option forces all percpu variables to be defined as weak.
298 
299 endmenu # "Compiler options"
300 
301 config MAGIC_SYSRQ
302         bool "Magic SysRq key"
303         depends on !UML
304         help
305           If you say Y here, you will have some control over the system even
306           if the system crashes for example during kernel debugging (e.g., you
307           will be able to flush the buffer cache to disk, reboot the system
308           immediately or dump some status information). This is accomplished
309           by pressing various keys while holding SysRq (Alt+PrintScreen). It
310           also works on a serial console (on PC hardware at least), if you
311           send a BREAK and then within 5 seconds a command keypress. The
312           keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
313           unless you really know what this hack does.
314 
315 config MAGIC_SYSRQ_DEFAULT_ENABLE
316         hex "Enable magic SysRq key functions by default"
317         depends on MAGIC_SYSRQ
318         default 0x1
319         help
320           Specifies which SysRq key functions are enabled by default.
321           This may be set to 1 or 0 to enable or disable them all, or
322           to a bitmask as described in Documentation/sysrq.txt.
323 
324 config DEBUG_KERNEL
325         bool "Kernel debugging"
326         help
327           Say Y here if you are developing drivers or trying to debug and
328           identify kernel problems.
329 
330 menu "Memory Debugging"
331 
332 source mm/Kconfig.debug
333 
334 config DEBUG_OBJECTS
335         bool "Debug object operations"
336         depends on DEBUG_KERNEL
337         help
338           If you say Y here, additional code will be inserted into the
339           kernel to track the life time of various objects and validate
340           the operations on those objects.
341 
342 config DEBUG_OBJECTS_SELFTEST
343         bool "Debug objects selftest"
344         depends on DEBUG_OBJECTS
345         help
346           This enables the selftest of the object debug code.
347 
348 config DEBUG_OBJECTS_FREE
349         bool "Debug objects in freed memory"
350         depends on DEBUG_OBJECTS
351         help
352           This enables checks whether a k/v free operation frees an area
353           which contains an object which has not been deactivated
354           properly. This can make kmalloc/kfree-intensive workloads
355           much slower.
356 
357 config DEBUG_OBJECTS_TIMERS
358         bool "Debug timer objects"
359         depends on DEBUG_OBJECTS
360         help
361           If you say Y here, additional code will be inserted into the
362           timer routines to track the life time of timer objects and
363           validate the timer operations.
364 
365 config DEBUG_OBJECTS_WORK
366         bool "Debug work objects"
367         depends on DEBUG_OBJECTS
368         help
369           If you say Y here, additional code will be inserted into the
370           work queue routines to track the life time of work objects and
371           validate the work operations.
372 
373 config DEBUG_OBJECTS_RCU_HEAD
374         bool "Debug RCU callbacks objects"
375         depends on DEBUG_OBJECTS
376         help
377           Enable this to turn on debugging of RCU list heads (call_rcu() usage).
378 
379 config DEBUG_OBJECTS_PERCPU_COUNTER
380         bool "Debug percpu counter objects"
381         depends on DEBUG_OBJECTS
382         help
383           If you say Y here, additional code will be inserted into the
384           percpu counter routines to track the life time of percpu counter
385           objects and validate the percpu counter operations.
386 
387 config DEBUG_OBJECTS_ENABLE_DEFAULT
388         int "debug_objects bootup default value (0-1)"
389         range 0 1
390         default "1"
391         depends on DEBUG_OBJECTS
392         help
393           Debug objects boot parameter default value
394 
395 config DEBUG_SLAB
396         bool "Debug slab memory allocations"
397         depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
398         help
399           Say Y here to have the kernel do limited verification on memory
400           allocation as well as poisoning memory on free to catch use of freed
401           memory. This can make kmalloc/kfree-intensive workloads much slower.
402 
403 config DEBUG_SLAB_LEAK
404         bool "Memory leak debugging"
405         depends on DEBUG_SLAB
406 
407 config SLUB_DEBUG_ON
408         bool "SLUB debugging on by default"
409         depends on SLUB && SLUB_DEBUG && !KMEMCHECK
410         default n
411         help
412           Boot with debugging on by default. SLUB boots by default with
413           the runtime debug capabilities switched off. Enabling this is
414           equivalent to specifying the "slub_debug" parameter on boot.
415           There is no support for more fine grained debug control like
416           possible with slub_debug=xxx. SLUB debugging may be switched
417           off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
418           "slub_debug=-".
419 
420 config SLUB_STATS
421         default n
422         bool "Enable SLUB performance statistics"
423         depends on SLUB && SYSFS
424         help
425           SLUB statistics are useful to debug SLUBs allocation behavior in
426           order find ways to optimize the allocator. This should never be
427           enabled for production use since keeping statistics slows down
428           the allocator by a few percentage points. The slabinfo command
429           supports the determination of the most active slabs to figure
430           out which slabs are relevant to a particular load.
431           Try running: slabinfo -DA
432 
433 config HAVE_DEBUG_KMEMLEAK
434         bool
435 
436 config DEBUG_KMEMLEAK
437         bool "Kernel memory leak detector"
438         depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
439         select DEBUG_FS
440         select STACKTRACE if STACKTRACE_SUPPORT
441         select KALLSYMS
442         select CRC32
443         help
444           Say Y here if you want to enable the memory leak
445           detector. The memory allocation/freeing is traced in a way
446           similar to the Boehm's conservative garbage collector, the
447           difference being that the orphan objects are not freed but
448           only shown in /sys/kernel/debug/kmemleak. Enabling this
449           feature will introduce an overhead to memory
450           allocations. See Documentation/kmemleak.txt for more
451           details.
452 
453           Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
454           of finding leaks due to the slab objects poisoning.
455 
456           In order to access the kmemleak file, debugfs needs to be
457           mounted (usually at /sys/kernel/debug).
458 
459 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
460         int "Maximum kmemleak early log entries"
461         depends on DEBUG_KMEMLEAK
462         range 200 40000
463         default 400
464         help
465           Kmemleak must track all the memory allocations to avoid
466           reporting false positives. Since memory may be allocated or
467           freed before kmemleak is initialised, an early log buffer is
468           used to store these actions. If kmemleak reports "early log
469           buffer exceeded", please increase this value.
470 
471 config DEBUG_KMEMLEAK_TEST
472         tristate "Simple test for the kernel memory leak detector"
473         depends on DEBUG_KMEMLEAK && m
474         help
475           This option enables a module that explicitly leaks memory.
476 
477           If unsure, say N.
478 
479 config DEBUG_KMEMLEAK_DEFAULT_OFF
480         bool "Default kmemleak to off"
481         depends on DEBUG_KMEMLEAK
482         help
483           Say Y here to disable kmemleak by default. It can then be enabled
484           on the command line via kmemleak=on.
485 
486 config DEBUG_STACK_USAGE
487         bool "Stack utilization instrumentation"
488         depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAG
489         help
490           Enables the display of the minimum amount of free stack which each
491           task has ever had available in the sysrq-T and sysrq-P debug output.
492 
493           This option will slow down process creation somewhat.
494 
495 config DEBUG_VM
496         bool "Debug VM"
497         depends on DEBUG_KERNEL
498         help
499           Enable this to turn on extended checks in the virtual-memory system
500           that may impact performance.
501 
502           If unsure, say N.
503 
504 config DEBUG_VM_RB
505         bool "Debug VM red-black trees"
506         depends on DEBUG_VM
507         help
508           Enable this to turn on more extended checks in the virtual-memory
509           system that may impact performance.
510 
511           If unsure, say N.
512 
513 config DEBUG_VIRTUAL
514         bool "Debug VM translations"
515         depends on DEBUG_KERNEL && X86
516         help
517           Enable some costly sanity checks in virtual to page code. This can
518           catch mistakes with virt_to_page() and friends.
519 
520           If unsure, say N.
521 
522 config DEBUG_NOMMU_REGIONS
523         bool "Debug the global anon/private NOMMU mapping region tree"
524         depends on DEBUG_KERNEL && !MMU
525         help
526           This option causes the global tree of anonymous and private mapping
527           regions to be regularly checked for invalid topology.
528 
529 config DEBUG_MEMORY_INIT
530         bool "Debug memory initialisation" if EXPERT
531         default !EXPERT
532         help
533           Enable this for additional checks during memory initialisation.
534           The sanity checks verify aspects of the VM such as the memory model
535           and other information provided by the architecture. Verbose
536           information will be printed at KERN_DEBUG loglevel depending
537           on the mminit_loglevel= command-line option.
538 
539           If unsure, say Y
540 
541 config MEMORY_NOTIFIER_ERROR_INJECT
542         tristate "Memory hotplug notifier error injection module"
543         depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
544         help
545           This option provides the ability to inject artificial errors to
546           memory hotplug notifier chain callbacks.  It is controlled through
547           debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
548 
549           If the notifier call chain should be failed with some events
550           notified, write the error code to "actions/<notifier event>/error".
551 
552           Example: Inject memory hotplug offline error (-12 == -ENOMEM)
553 
554           # cd /sys/kernel/debug/notifier-error-inject/memory
555           # echo -12 > actions/MEM_GOING_OFFLINE/error
556           # echo offline > /sys/devices/system/memory/memoryXXX/state
557           bash: echo: write error: Cannot allocate memory
558 
559           To compile this code as a module, choose M here: the module will
560           be called memory-notifier-error-inject.
561 
562           If unsure, say N.
563 
564 config DEBUG_PER_CPU_MAPS
565         bool "Debug access to per_cpu maps"
566         depends on DEBUG_KERNEL
567         depends on SMP
568         help
569           Say Y to verify that the per_cpu map being accessed has
570           been set up. This adds a fair amount of code to kernel memory
571           and decreases performance.
572 
573           Say N if unsure.
574 
575 config DEBUG_HIGHMEM
576         bool "Highmem debugging"
577         depends on DEBUG_KERNEL && HIGHMEM
578         help
579           This options enables addition error checking for high memory systems.
580           Disable for production systems.
581 
582 config HAVE_DEBUG_STACKOVERFLOW
583         bool
584 
585 config DEBUG_STACKOVERFLOW
586         bool "Check for stack overflows"
587         depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
588         ---help---
589           Say Y here if you want to check for overflows of kernel, IRQ
590           and exception stacks (if your archicture uses them). This
591           option will show detailed messages if free stack space drops
592           below a certain limit.
593 
594           These kinds of bugs usually occur when call-chains in the
595           kernel get too deep, especially when interrupts are
596           involved.
597 
598           Use this in cases where you see apparently random memory
599           corruption, especially if it appears in 'struct thread_info'
600 
601           If in doubt, say "N".
602 
603 source "lib/Kconfig.kmemcheck"
604 
605 endmenu # "Memory Debugging"
606 
607 config DEBUG_SHIRQ
608         bool "Debug shared IRQ handlers"
609         depends on DEBUG_KERNEL
610         help
611           Enable this to generate a spurious interrupt as soon as a shared
612           interrupt handler is registered, and just before one is deregistered.
613           Drivers ought to be able to handle interrupts coming in at those
614           points; some don't and need to be caught.
615 
616 menu "Debug Lockups and Hangs"
617 
618 config LOCKUP_DETECTOR
619         bool "Detect Hard and Soft Lockups"
620         depends on DEBUG_KERNEL && !S390
621         help
622           Say Y here to enable the kernel to act as a watchdog to detect
623           hard and soft lockups.
624 
625           Softlockups are bugs that cause the kernel to loop in kernel
626           mode for more than 20 seconds, without giving other tasks a
627           chance to run.  The current stack trace is displayed upon
628           detection and the system will stay locked up.
629 
630           Hardlockups are bugs that cause the CPU to loop in kernel mode
631           for more than 10 seconds, without letting other interrupts have a
632           chance to run.  The current stack trace is displayed upon detection
633           and the system will stay locked up.
634 
635           The overhead should be minimal.  A periodic hrtimer runs to
636           generate interrupts and kick the watchdog task every 4 seconds.
637           An NMI is generated every 10 seconds or so to check for hardlockups.
638 
639           The frequency of hrtimer and NMI events and the soft and hard lockup
640           thresholds can be controlled through the sysctl watchdog_thresh.
641 
642 config HARDLOCKUP_DETECTOR
643         def_bool y
644         depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
645         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
646 
647 config BOOTPARAM_HARDLOCKUP_PANIC
648         bool "Panic (Reboot) On Hard Lockups"
649         depends on HARDLOCKUP_DETECTOR
650         help
651           Say Y here to enable the kernel to panic on "hard lockups",
652           which are bugs that cause the kernel to loop in kernel
653           mode with interrupts disabled for more than 10 seconds (configurable
654           using the watchdog_thresh sysctl).
655 
656           Say N if unsure.
657 
658 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
659         int
660         depends on HARDLOCKUP_DETECTOR
661         range 0 1
662         default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
663         default 1 if BOOTPARAM_HARDLOCKUP_PANIC
664 
665 config BOOTPARAM_SOFTLOCKUP_PANIC
666         bool "Panic (Reboot) On Soft Lockups"
667         depends on LOCKUP_DETECTOR
668         help
669           Say Y here to enable the kernel to panic on "soft lockups",
670           which are bugs that cause the kernel to loop in kernel
671           mode for more than 20 seconds (configurable using the watchdog_thresh
672           sysctl), without giving other tasks a chance to run.
673 
674           The panic can be used in combination with panic_timeout,
675           to cause the system to reboot automatically after a
676           lockup has been detected. This feature is useful for
677           high-availability systems that have uptime guarantees and
678           where a lockup must be resolved ASAP.
679 
680           Say N if unsure.
681 
682 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
683         int
684         depends on LOCKUP_DETECTOR
685         range 0 1
686         default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
687         default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
688 
689 config DETECT_HUNG_TASK
690         bool "Detect Hung Tasks"
691         depends on DEBUG_KERNEL
692         default LOCKUP_DETECTOR
693         help
694           Say Y here to enable the kernel to detect "hung tasks",
695           which are bugs that cause the task to be stuck in
696           uninterruptible "D" state indefinitiley.
697 
698           When a hung task is detected, the kernel will print the
699           current stack trace (which you should report), but the
700           task will stay in uninterruptible state. If lockdep is
701           enabled then all held locks will also be reported. This
702           feature has negligible overhead.
703 
704 config DEFAULT_HUNG_TASK_TIMEOUT
705         int "Default timeout for hung task detection (in seconds)"
706         depends on DETECT_HUNG_TASK
707         default 120
708         help
709           This option controls the default timeout (in seconds) used
710           to determine when a task has become non-responsive and should
711           be considered hung.
712 
713           It can be adjusted at runtime via the kernel.hung_task_timeout_secs
714           sysctl or by writing a value to
715           /proc/sys/kernel/hung_task_timeout_secs.
716 
717           A timeout of 0 disables the check.  The default is two minutes.
718           Keeping the default should be fine in most cases.
719 
720 config BOOTPARAM_HUNG_TASK_PANIC
721         bool "Panic (Reboot) On Hung Tasks"
722         depends on DETECT_HUNG_TASK
723         help
724           Say Y here to enable the kernel to panic on "hung tasks",
725           which are bugs that cause the kernel to leave a task stuck
726           in uninterruptible "D" state.
727 
728           The panic can be used in combination with panic_timeout,
729           to cause the system to reboot automatically after a
730           hung task has been detected. This feature is useful for
731           high-availability systems that have uptime guarantees and
732           where a hung tasks must be resolved ASAP.
733 
734           Say N if unsure.
735 
736 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
737         int
738         depends on DETECT_HUNG_TASK
739         range 0 1
740         default 0 if !BOOTPARAM_HUNG_TASK_PANIC
741         default 1 if BOOTPARAM_HUNG_TASK_PANIC
742 
743 endmenu # "Debug lockups and hangs"
744 
745 config PANIC_ON_OOPS
746         bool "Panic on Oops"
747         help
748           Say Y here to enable the kernel to panic when it oopses. This
749           has the same effect as setting oops=panic on the kernel command
750           line.
751 
752           This feature is useful to ensure that the kernel does not do
753           anything erroneous after an oops which could result in data
754           corruption or other issues.
755 
756           Say N if unsure.
757 
758 config PANIC_ON_OOPS_VALUE
759         int
760         range 0 1
761         default 0 if !PANIC_ON_OOPS
762         default 1 if PANIC_ON_OOPS
763 
764 config PANIC_TIMEOUT
765         int "panic timeout"
766         default 0
767         help
768           Set the timeout value (in seconds) until a reboot occurs when the
769           the kernel panics. If n = 0, then we wait forever. A timeout
770           value n > 0 will wait n seconds before rebooting, while a timeout
771           value n < 0 will reboot immediately.
772 
773 config SCHED_DEBUG
774         bool "Collect scheduler debugging info"
775         depends on DEBUG_KERNEL && PROC_FS
776         default y
777         help
778           If you say Y here, the /proc/sched_debug file will be provided
779           that can help debug the scheduler. The runtime overhead of this
780           option is minimal.
781 
782 config SCHEDSTATS
783         bool "Collect scheduler statistics"
784         depends on DEBUG_KERNEL && PROC_FS
785         help
786           If you say Y here, additional code will be inserted into the
787           scheduler and related routines to collect statistics about
788           scheduler behavior and provide them in /proc/schedstat.  These
789           stats may be useful for both tuning and debugging the scheduler
790           If you aren't debugging the scheduler or trying to tune a specific
791           application, you can say N to avoid the very slight overhead
792           this adds.
793 
794 config TIMER_STATS
795         bool "Collect kernel timers statistics"
796         depends on DEBUG_KERNEL && PROC_FS
797         help
798           If you say Y here, additional code will be inserted into the
799           timer routines to collect statistics about kernel timers being
800           reprogrammed. The statistics can be read from /proc/timer_stats.
801           The statistics collection is started by writing 1 to /proc/timer_stats,
802           writing 0 stops it. This feature is useful to collect information
803           about timer usage patterns in kernel and userspace. This feature
804           is lightweight if enabled in the kernel config but not activated
805           (it defaults to deactivated on bootup and will only be activated
806           if some application like powertop activates it explicitly).
807 
808 config DEBUG_PREEMPT
809         bool "Debug preemptible kernel"
810         depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
811         default y
812         help
813           If you say Y here then the kernel will use a debug variant of the
814           commonly used smp_processor_id() function and will print warnings
815           if kernel code uses it in a preemption-unsafe way. Also, the kernel
816           will detect preemption count underflows.
817 
818 menu "Lock Debugging (spinlocks, mutexes, etc...)"
819 
820 config DEBUG_RT_MUTEXES
821         bool "RT Mutex debugging, deadlock detection"
822         depends on DEBUG_KERNEL && RT_MUTEXES
823         help
824          This allows rt mutex semantics violations and rt mutex related
825          deadlocks (lockups) to be detected and reported automatically.
826 
827 config DEBUG_PI_LIST
828         bool
829         default y
830         depends on DEBUG_RT_MUTEXES
831 
832 config RT_MUTEX_TESTER
833         bool "Built-in scriptable tester for rt-mutexes"
834         depends on DEBUG_KERNEL && RT_MUTEXES
835         help
836           This option enables a rt-mutex tester.
837 
838 config DEBUG_SPINLOCK
839         bool "Spinlock and rw-lock debugging: basic checks"
840         depends on DEBUG_KERNEL
841         select UNINLINE_SPIN_UNLOCK
842         help
843           Say Y here and build SMP to catch missing spinlock initialization
844           and certain other kinds of spinlock errors commonly made.  This is
845           best used in conjunction with the NMI watchdog so that spinlock
846           deadlocks are also debuggable.
847 
848 config DEBUG_MUTEXES
849         bool "Mutex debugging: basic checks"
850         depends on DEBUG_KERNEL
851         help
852          This feature allows mutex semantics violations to be detected and
853          reported.
854 
855 config DEBUG_WW_MUTEX_SLOWPATH
856         bool "Wait/wound mutex debugging: Slowpath testing"
857         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
858         select DEBUG_LOCK_ALLOC
859         select DEBUG_SPINLOCK
860         select DEBUG_MUTEXES
861         help
862          This feature enables slowpath testing for w/w mutex users by
863          injecting additional -EDEADLK wound/backoff cases. Together with
864          the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
865          will test all possible w/w mutex interface abuse with the
866          exception of simply not acquiring all the required locks.
867 
868 config DEBUG_LOCK_ALLOC
869         bool "Lock debugging: detect incorrect freeing of live locks"
870         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
871         select DEBUG_SPINLOCK
872         select DEBUG_MUTEXES
873         select LOCKDEP
874         help
875          This feature will check whether any held lock (spinlock, rwlock,
876          mutex or rwsem) is incorrectly freed by the kernel, via any of the
877          memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
878          vfree(), etc.), whether a live lock is incorrectly reinitialized via
879          spin_lock_init()/mutex_init()/etc., or whether there is any lock
880          held during task exit.
881 
882 config PROVE_LOCKING
883         bool "Lock debugging: prove locking correctness"
884         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
885         select LOCKDEP
886         select DEBUG_SPINLOCK
887         select DEBUG_MUTEXES
888         select DEBUG_LOCK_ALLOC
889         select TRACE_IRQFLAGS
890         default n
891         help
892          This feature enables the kernel to prove that all locking
893          that occurs in the kernel runtime is mathematically
894          correct: that under no circumstance could an arbitrary (and
895          not yet triggered) combination of observed locking
896          sequences (on an arbitrary number of CPUs, running an
897          arbitrary number of tasks and interrupt contexts) cause a
898          deadlock.
899 
900          In short, this feature enables the kernel to report locking
901          related deadlocks before they actually occur.
902 
903          The proof does not depend on how hard and complex a
904          deadlock scenario would be to trigger: how many
905          participant CPUs, tasks and irq-contexts would be needed
906          for it to trigger. The proof also does not depend on
907          timing: if a race and a resulting deadlock is possible
908          theoretically (no matter how unlikely the race scenario
909          is), it will be proven so and will immediately be
910          reported by the kernel (once the event is observed that
911          makes the deadlock theoretically possible).
912 
913          If a deadlock is impossible (i.e. the locking rules, as
914          observed by the kernel, are mathematically correct), the
915          kernel reports nothing.
916 
917          NOTE: this feature can also be enabled for rwlocks, mutexes
918          and rwsems - in which case all dependencies between these
919          different locking variants are observed and mapped too, and
920          the proof of observed correctness is also maintained for an
921          arbitrary combination of these separate locking variants.
922 
923          For more details, see Documentation/lockdep-design.txt.
924 
925 config LOCKDEP
926         bool
927         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
928         select STACKTRACE
929         select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC
930         select KALLSYMS
931         select KALLSYMS_ALL
932 
933 config LOCK_STAT
934         bool "Lock usage statistics"
935         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
936         select LOCKDEP
937         select DEBUG_SPINLOCK
938         select DEBUG_MUTEXES
939         select DEBUG_LOCK_ALLOC
940         default n
941         help
942          This feature enables tracking lock contention points
943 
944          For more details, see Documentation/lockstat.txt
945 
946          This also enables lock events required by "perf lock",
947          subcommand of perf.
948          If you want to use "perf lock", you also need to turn on
949          CONFIG_EVENT_TRACING.
950 
951          CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
952          (CONFIG_LOCKDEP defines "acquire" and "release" events.)
953 
954 config DEBUG_LOCKDEP
955         bool "Lock dependency engine debugging"
956         depends on DEBUG_KERNEL && LOCKDEP
957         help
958           If you say Y here, the lock dependency engine will do
959           additional runtime checks to debug itself, at the price
960           of more runtime overhead.
961 
962 config DEBUG_ATOMIC_SLEEP
963         bool "Sleep inside atomic section checking"
964         select PREEMPT_COUNT
965         depends on DEBUG_KERNEL
966         help
967           If you say Y here, various routines which may sleep will become very
968           noisy if they are called inside atomic sections: when a spinlock is
969           held, inside an rcu read side critical section, inside preempt disabled
970           sections, inside an interrupt, etc...
971 
972 config DEBUG_LOCKING_API_SELFTESTS
973         bool "Locking API boot-time self-tests"
974         depends on DEBUG_KERNEL
975         help
976           Say Y here if you want the kernel to run a short self-test during
977           bootup. The self-test checks whether common types of locking bugs
978           are detected by debugging mechanisms or not. (if you disable
979           lock debugging then those bugs wont be detected of course.)
980           The following locking APIs are covered: spinlocks, rwlocks,
981           mutexes and rwsems.
982 
983 endmenu # lock debugging
984 
985 config TRACE_IRQFLAGS
986         bool
987         help
988           Enables hooks to interrupt enabling and disabling for
989           either tracing or lock debugging.
990 
991 config STACKTRACE
992         bool
993         depends on STACKTRACE_SUPPORT
994 
995 config DEBUG_KOBJECT
996         bool "kobject debugging"
997         depends on DEBUG_KERNEL
998         help
999           If you say Y here, some extra kobject debugging messages will be sent
1000           to the syslog. 
1001 
1002 config DEBUG_KOBJECT_RELEASE
1003         bool "kobject release debugging"
1004         depends on DEBUG_OBJECTS_TIMERS
1005         help
1006           kobjects are reference counted objects.  This means that their
1007           last reference count put is not predictable, and the kobject can
1008           live on past the point at which a driver decides to drop it's
1009           initial reference to the kobject gained on allocation.  An
1010           example of this would be a struct device which has just been
1011           unregistered.
1012 
1013           However, some buggy drivers assume that after such an operation,
1014           the memory backing the kobject can be immediately freed.  This
1015           goes completely against the principles of a refcounted object.
1016 
1017           If you say Y here, the kernel will delay the release of kobjects
1018           on the last reference count to improve the visibility of this
1019           kind of kobject release bug.
1020 
1021 config HAVE_DEBUG_BUGVERBOSE
1022         bool
1023 
1024 config DEBUG_BUGVERBOSE
1025         bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1026         depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1027         default y
1028         help
1029           Say Y here to make BUG() panics output the file name and line number
1030           of the BUG call as well as the EIP and oops trace.  This aids
1031           debugging but costs about 70-100K of memory.
1032 
1033 config DEBUG_WRITECOUNT
1034         bool "Debug filesystem writers count"
1035         depends on DEBUG_KERNEL
1036         help
1037           Enable this to catch wrong use of the writers count in struct
1038           vfsmount.  This will increase the size of each file struct by
1039           32 bits.
1040 
1041           If unsure, say N.
1042 
1043 config DEBUG_LIST
1044         bool "Debug linked list manipulation"
1045         depends on DEBUG_KERNEL
1046         help
1047           Enable this to turn on extended checks in the linked-list
1048           walking routines.
1049 
1050           If unsure, say N.
1051 
1052 config DEBUG_SG
1053         bool "Debug SG table operations"
1054         depends on DEBUG_KERNEL
1055         help
1056           Enable this to turn on checks on scatter-gather tables. This can
1057           help find problems with drivers that do not properly initialize
1058           their sg tables.
1059 
1060           If unsure, say N.
1061 
1062 config DEBUG_NOTIFIERS
1063         bool "Debug notifier call chains"
1064         depends on DEBUG_KERNEL
1065         help
1066           Enable this to turn on sanity checking for notifier call chains.
1067           This is most useful for kernel developers to make sure that
1068           modules properly unregister themselves from notifier chains.
1069           This is a relatively cheap check but if you care about maximum
1070           performance, say N.
1071 
1072 config DEBUG_CREDENTIALS
1073         bool "Debug credential management"
1074         depends on DEBUG_KERNEL
1075         help
1076           Enable this to turn on some debug checking for credential
1077           management.  The additional code keeps track of the number of
1078           pointers from task_structs to any given cred struct, and checks to
1079           see that this number never exceeds the usage count of the cred
1080           struct.
1081 
1082           Furthermore, if SELinux is enabled, this also checks that the
1083           security pointer in the cred struct is never seen to be invalid.
1084 
1085           If unsure, say N.
1086 
1087 menu "RCU Debugging"
1088 
1089 config PROVE_RCU
1090         bool "RCU debugging: prove RCU correctness"
1091         depends on PROVE_LOCKING
1092         default n
1093         help
1094          This feature enables lockdep extensions that check for correct
1095          use of RCU APIs.  This is currently under development.  Say Y
1096          if you want to debug RCU usage or help work on the PROVE_RCU
1097          feature.
1098 
1099          Say N if you are unsure.
1100 
1101 config PROVE_RCU_REPEATEDLY
1102         bool "RCU debugging: don't disable PROVE_RCU on first splat"
1103         depends on PROVE_RCU
1104         default n
1105         help
1106          By itself, PROVE_RCU will disable checking upon issuing the
1107          first warning (or "splat").  This feature prevents such
1108          disabling, allowing multiple RCU-lockdep warnings to be printed
1109          on a single reboot.
1110 
1111          Say Y to allow multiple RCU-lockdep warnings per boot.
1112 
1113          Say N if you are unsure.
1114 
1115 config PROVE_RCU_DELAY
1116         bool "RCU debugging: preemptible RCU race provocation"
1117         depends on DEBUG_KERNEL && PREEMPT_RCU
1118         default n
1119         help
1120          There is a class of races that involve an unlikely preemption
1121          of __rcu_read_unlock() just after ->rcu_read_lock_nesting has
1122          been set to INT_MIN.  This feature inserts a delay at that
1123          point to increase the probability of these races.
1124 
1125          Say Y to increase probability of preemption of __rcu_read_unlock().
1126 
1127          Say N if you are unsure.
1128 
1129 config SPARSE_RCU_POINTER
1130         bool "RCU debugging: sparse-based checks for pointer usage"
1131         default n
1132         help
1133          This feature enables the __rcu sparse annotation for
1134          RCU-protected pointers.  This annotation will cause sparse
1135          to flag any non-RCU used of annotated pointers.  This can be
1136          helpful when debugging RCU usage.  Please note that this feature
1137          is not intended to enforce code cleanliness; it is instead merely
1138          a debugging aid.
1139 
1140          Say Y to make sparse flag questionable use of RCU-protected pointers
1141 
1142          Say N if you are unsure.
1143 
1144 config RCU_TORTURE_TEST
1145         tristate "torture tests for RCU"
1146         depends on DEBUG_KERNEL
1147         default n
1148         help
1149           This option provides a kernel module that runs torture tests
1150           on the RCU infrastructure.  The kernel module may be built
1151           after the fact on the running kernel to be tested, if desired.
1152 
1153           Say Y here if you want RCU torture tests to be built into
1154           the kernel.
1155           Say M if you want the RCU torture tests to build as a module.
1156           Say N if you are unsure.
1157 
1158 config RCU_TORTURE_TEST_RUNNABLE
1159         bool "torture tests for RCU runnable by default"
1160         depends on RCU_TORTURE_TEST = y
1161         default n
1162         help
1163           This option provides a way to build the RCU torture tests
1164           directly into the kernel without them starting up at boot
1165           time.  You can use /proc/sys/kernel/rcutorture_runnable
1166           to manually override this setting.  This /proc file is
1167           available only when the RCU torture tests have been built
1168           into the kernel.
1169 
1170           Say Y here if you want the RCU torture tests to start during
1171           boot (you probably don't).
1172           Say N here if you want the RCU torture tests to start only
1173           after being manually enabled via /proc.
1174 
1175 config RCU_CPU_STALL_TIMEOUT
1176         int "RCU CPU stall timeout in seconds"
1177         depends on RCU_STALL_COMMON
1178         range 3 300
1179         default 21
1180         help
1181           If a given RCU grace period extends more than the specified
1182           number of seconds, a CPU stall warning is printed.  If the
1183           RCU grace period persists, additional CPU stall warnings are
1184           printed at more widely spaced intervals.
1185 
1186 config RCU_CPU_STALL_VERBOSE
1187         bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
1188         depends on TREE_PREEMPT_RCU
1189         default y
1190         help
1191           This option causes RCU to printk detailed per-task information
1192           for any tasks that are stalling the current RCU grace period.
1193 
1194           Say N if you are unsure.
1195 
1196           Say Y if you want to enable such checks.
1197 
1198 config RCU_CPU_STALL_INFO
1199         bool "Print additional diagnostics on RCU CPU stall"
1200         depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL
1201         default n
1202         help
1203           For each stalled CPU that is aware of the current RCU grace
1204           period, print out additional per-CPU diagnostic information
1205           regarding scheduling-clock ticks, idle state, and,
1206           for RCU_FAST_NO_HZ kernels, idle-entry state.
1207 
1208           Say N if you are unsure.
1209 
1210           Say Y if you want to enable such diagnostics.
1211 
1212 config RCU_TRACE
1213         bool "Enable tracing for RCU"
1214         depends on DEBUG_KERNEL
1215         select TRACE_CLOCK
1216         help
1217           This option provides tracing in RCU which presents stats
1218           in debugfs for debugging RCU implementation.
1219 
1220           Say Y here if you want to enable RCU tracing
1221           Say N if you are unsure.
1222 
1223 endmenu # "RCU Debugging"
1224 
1225 config DEBUG_BLOCK_EXT_DEVT
1226         bool "Force extended block device numbers and spread them"
1227         depends on DEBUG_KERNEL
1228         depends on BLOCK
1229         default n
1230         help
1231           BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1232           SOME DISTRIBUTIONS.  DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1233           YOU ARE DOING.  Distros, please enable this and fix whatever
1234           is broken.
1235 
1236           Conventionally, block device numbers are allocated from
1237           predetermined contiguous area.  However, extended block area
1238           may introduce non-contiguous block device numbers.  This
1239           option forces most block device numbers to be allocated from
1240           the extended space and spreads them to discover kernel or
1241           userland code paths which assume predetermined contiguous
1242           device number allocation.
1243 
1244           Note that turning on this debug option shuffles all the
1245           device numbers for all IDE and SCSI devices including libata
1246           ones, so root partition specified using device number
1247           directly (via rdev or root=MAJ:MIN) won't work anymore.
1248           Textual device names (root=/dev/sdXn) will continue to work.
1249 
1250           Say N if you are unsure.
1251 
1252 config NOTIFIER_ERROR_INJECTION
1253         tristate "Notifier error injection"
1254         depends on DEBUG_KERNEL
1255         select DEBUG_FS
1256         help
1257           This option provides the ability to inject artificial errors to
1258           specified notifier chain callbacks. It is useful to test the error
1259           handling of notifier call chain failures.
1260 
1261           Say N if unsure.
1262 
1263 config CPU_NOTIFIER_ERROR_INJECT
1264         tristate "CPU notifier error injection module"
1265         depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1266         help
1267           This option provides a kernel module that can be used to test
1268           the error handling of the cpu notifiers by injecting artificial
1269           errors to CPU notifier chain callbacks.  It is controlled through
1270           debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
1271 
1272           If the notifier call chain should be failed with some events
1273           notified, write the error code to "actions/<notifier event>/error".
1274 
1275           Example: Inject CPU offline error (-1 == -EPERM)
1276 
1277           # cd /sys/kernel/debug/notifier-error-inject/cpu
1278           # echo -1 > actions/CPU_DOWN_PREPARE/error
1279           # echo 0 > /sys/devices/system/cpu/cpu1/online
1280           bash: echo: write error: Operation not permitted
1281 
1282           To compile this code as a module, choose M here: the module will
1283           be called cpu-notifier-error-inject.
1284 
1285           If unsure, say N.
1286 
1287 config PM_NOTIFIER_ERROR_INJECT
1288         tristate "PM notifier error injection module"
1289         depends on PM && NOTIFIER_ERROR_INJECTION
1290         default m if PM_DEBUG
1291         help
1292           This option provides the ability to inject artificial errors to
1293           PM notifier chain callbacks.  It is controlled through debugfs
1294           interface /sys/kernel/debug/notifier-error-inject/pm
1295 
1296           If the notifier call chain should be failed with some events
1297           notified, write the error code to "actions/<notifier event>/error".
1298 
1299           Example: Inject PM suspend error (-12 = -ENOMEM)
1300 
1301           # cd /sys/kernel/debug/notifier-error-inject/pm/
1302           # echo -12 > actions/PM_SUSPEND_PREPARE/error
1303           # echo mem > /sys/power/state
1304           bash: echo: write error: Cannot allocate memory
1305 
1306           To compile this code as a module, choose M here: the module will
1307           be called pm-notifier-error-inject.
1308 
1309           If unsure, say N.
1310 
1311 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1312         tristate "OF reconfig notifier error injection module"
1313         depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1314         help
1315           This option provides the ability to inject artificial errors to
1316           OF reconfig notifier chain callbacks.  It is controlled
1317           through debugfs interface under
1318           /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1319 
1320           If the notifier call chain should be failed with some events
1321           notified, write the error code to "actions/<notifier event>/error".
1322 
1323           To compile this code as a module, choose M here: the module will
1324           be called of-reconfig-notifier-error-inject.
1325 
1326           If unsure, say N.
1327 
1328 config FAULT_INJECTION
1329         bool "Fault-injection framework"
1330         depends on DEBUG_KERNEL
1331         help
1332           Provide fault-injection framework.
1333           For more details, see Documentation/fault-injection/.
1334 
1335 config FAILSLAB
1336         bool "Fault-injection capability for kmalloc"
1337         depends on FAULT_INJECTION
1338         depends on SLAB || SLUB
1339         help
1340           Provide fault-injection capability for kmalloc.
1341 
1342 config FAIL_PAGE_ALLOC
1343         bool "Fault-injection capabilitiy for alloc_pages()"
1344         depends on FAULT_INJECTION
1345         help
1346           Provide fault-injection capability for alloc_pages().
1347 
1348 config FAIL_MAKE_REQUEST
1349         bool "Fault-injection capability for disk IO"
1350         depends on FAULT_INJECTION && BLOCK
1351         help
1352           Provide fault-injection capability for disk IO.
1353 
1354 config FAIL_IO_TIMEOUT
1355         bool "Fault-injection capability for faking disk interrupts"
1356         depends on FAULT_INJECTION && BLOCK
1357         help
1358           Provide fault-injection capability on end IO handling. This
1359           will make the block layer "forget" an interrupt as configured,
1360           thus exercising the error handling.
1361 
1362           Only works with drivers that use the generic timeout handling,
1363           for others it wont do anything.
1364 
1365 config FAIL_MMC_REQUEST
1366         bool "Fault-injection capability for MMC IO"
1367         select DEBUG_FS
1368         depends on FAULT_INJECTION && MMC
1369         help
1370           Provide fault-injection capability for MMC IO.
1371           This will make the mmc core return data errors. This is
1372           useful to test the error handling in the mmc block device
1373           and to test how the mmc host driver handles retries from
1374           the block device.
1375 
1376 config FAULT_INJECTION_DEBUG_FS
1377         bool "Debugfs entries for fault-injection capabilities"
1378         depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1379         help
1380           Enable configuration of fault-injection capabilities via debugfs.
1381 
1382 config FAULT_INJECTION_STACKTRACE_FILTER
1383         bool "stacktrace filter for fault-injection capabilities"
1384         depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1385         depends on !X86_64
1386         select STACKTRACE
1387         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1388         help
1389           Provide stacktrace filter for fault-injection capabilities
1390 
1391 config LATENCYTOP
1392         bool "Latency measuring infrastructure"
1393         depends on HAVE_LATENCYTOP_SUPPORT
1394         depends on DEBUG_KERNEL
1395         depends on STACKTRACE_SUPPORT
1396         depends on PROC_FS
1397         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1398         select KALLSYMS
1399         select KALLSYMS_ALL
1400         select STACKTRACE
1401         select SCHEDSTATS
1402         select SCHED_DEBUG
1403         help
1404           Enable this option if you want to use the LatencyTOP tool
1405           to find out which userspace is blocking on what kernel operations.
1406 
1407 config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1408         bool
1409 
1410 config DEBUG_STRICT_USER_COPY_CHECKS
1411         bool "Strict user copy size checks"
1412         depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1413         depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
1414         help
1415           Enabling this option turns a certain set of sanity checks for user
1416           copy operations into compile time failures.
1417 
1418           The copy_from_user() etc checks are there to help test if there
1419           are sufficient security checks on the length argument of
1420           the copy operation, by having gcc prove that the argument is
1421           within bounds.
1422 
1423           If unsure, say N.
1424 
1425 source kernel/trace/Kconfig
1426 
1427 menu "Runtime Testing"
1428 
1429 config LKDTM
1430         tristate "Linux Kernel Dump Test Tool Module"
1431         depends on DEBUG_FS
1432         depends on BLOCK
1433         default n
1434         help
1435         This module enables testing of the different dumping mechanisms by
1436         inducing system failures at predefined crash points.
1437         If you don't need it: say N
1438         Choose M here to compile this code as a module. The module will be
1439         called lkdtm.
1440 
1441         Documentation on how to use the module can be found in
1442         Documentation/fault-injection/provoke-crashes.txt
1443 
1444 config TEST_LIST_SORT
1445         bool "Linked list sorting test"
1446         depends on DEBUG_KERNEL
1447         help
1448           Enable this to turn on 'list_sort()' function test. This test is
1449           executed only once during system boot, so affects only boot time.
1450 
1451           If unsure, say N.
1452 
1453 config KPROBES_SANITY_TEST
1454         bool "Kprobes sanity tests"
1455         depends on DEBUG_KERNEL
1456         depends on KPROBES
1457         default n
1458         help
1459           This option provides for testing basic kprobes functionality on
1460           boot. A sample kprobe, jprobe and kretprobe are inserted and
1461           verified for functionality.
1462 
1463           Say N if you are unsure.
1464 
1465 config BACKTRACE_SELF_TEST
1466         tristate "Self test for the backtrace code"
1467         depends on DEBUG_KERNEL
1468         default n
1469         help
1470           This option provides a kernel module that can be used to test
1471           the kernel stack backtrace code. This option is not useful
1472           for distributions or general kernels, but only for kernel
1473           developers working on architecture code.
1474 
1475           Note that if you want to also test saved backtraces, you will
1476           have to enable STACKTRACE as well.
1477 
1478           Say N if you are unsure.
1479 
1480 config RBTREE_TEST
1481         tristate "Red-Black tree test"
1482         depends on DEBUG_KERNEL
1483         help
1484           A benchmark measuring the performance of the rbtree library.
1485           Also includes rbtree invariant checks.
1486 
1487 config INTERVAL_TREE_TEST
1488         tristate "Interval tree test"
1489         depends on m && DEBUG_KERNEL
1490         help
1491           A benchmark measuring the performance of the interval tree library
1492 
1493 config PERCPU_TEST
1494         tristate "Per cpu operations test"
1495         depends on m && DEBUG_KERNEL
1496         help
1497           Enable this option to build test module which validates per-cpu
1498           operations.
1499 
1500           If unsure, say N.
1501 
1502 config ATOMIC64_SELFTEST
1503         bool "Perform an atomic64_t self-test at boot"
1504         help
1505           Enable this option to test the atomic64_t functions at boot.
1506 
1507           If unsure, say N.
1508 
1509 config ASYNC_RAID6_TEST
1510         tristate "Self test for hardware accelerated raid6 recovery"
1511         depends on ASYNC_RAID6_RECOV
1512         select ASYNC_MEMCPY
1513         ---help---
1514           This is a one-shot self test that permutes through the
1515           recovery of all the possible two disk failure scenarios for a
1516           N-disk array.  Recovery is performed with the asynchronous
1517           raid6 recovery routines, and will optionally use an offload
1518           engine if one is available.
1519 
1520           If unsure, say N.
1521 
1522 config TEST_STRING_HELPERS
1523         tristate "Test functions located in the string_helpers module at runtime"
1524 
1525 config TEST_KSTRTOX
1526         tristate "Test kstrto*() family of functions at runtime"
1527 
1528 endmenu # runtime tests
1529 
1530 config PROVIDE_OHCI1394_DMA_INIT
1531         bool "Remote debugging over FireWire early on boot"
1532         depends on PCI && X86
1533         help
1534           If you want to debug problems which hang or crash the kernel early
1535           on boot and the crashing machine has a FireWire port, you can use
1536           this feature to remotely access the memory of the crashed machine
1537           over FireWire. This employs remote DMA as part of the OHCI1394
1538           specification which is now the standard for FireWire controllers.
1539 
1540           With remote DMA, you can monitor the printk buffer remotely using
1541           firescope and access all memory below 4GB using fireproxy from gdb.
1542           Even controlling a kernel debugger is possible using remote DMA.
1543 
1544           Usage:
1545 
1546           If ohci1394_dma=early is used as boot parameter, it will initialize
1547           all OHCI1394 controllers which are found in the PCI config space.
1548 
1549           As all changes to the FireWire bus such as enabling and disabling
1550           devices cause a bus reset and thereby disable remote DMA for all
1551           devices, be sure to have the cable plugged and FireWire enabled on
1552           the debugging host before booting the debug target for debugging.
1553 
1554           This code (~1k) is freed after boot. By then, the firewire stack
1555           in charge of the OHCI-1394 controllers should be used instead.
1556 
1557           See Documentation/debugging-via-ohci1394.txt for more information.
1558 
1559 config BUILD_DOCSRC
1560         bool "Build targets in Documentation/ tree"
1561         depends on HEADERS_CHECK
1562         help
1563           This option attempts to build objects from the source files in the
1564           kernel Documentation/ tree.
1565 
1566           Say N if you are unsure.
1567 
1568 config DMA_API_DEBUG
1569         bool "Enable debugging of DMA-API usage"
1570         depends on HAVE_DMA_API_DEBUG
1571         help
1572           Enable this option to debug the use of the DMA API by device drivers.
1573           With this option you will be able to detect common bugs in device
1574           drivers like double-freeing of DMA mappings or freeing mappings that
1575           were never allocated.
1576 
1577           This also attempts to catch cases where a page owned by DMA is
1578           accessed by the cpu in a way that could cause data corruption.  For
1579           example, this enables cow_user_page() to check that the source page is
1580           not undergoing DMA.
1581 
1582           This option causes a performance degradation.  Use only if you want to
1583           debug device drivers and dma interactions.
1584 
1585           If unsure, say N.
1586 
1587 config TEST_MODULE
1588         tristate "Test module loading with 'hello world' module"
1589         default n
1590         depends on m
1591         help
1592           This builds the "test_module" module that emits "Hello, world"
1593           on printk when loaded. It is designed to be used for basic
1594           evaluation of the module loading subsystem (for example when
1595           validating module verification). It lacks any extra dependencies,
1596           and will not normally be loaded by the system unless explicitly
1597           requested by name.
1598 
1599           If unsure, say N.
1600 
1601 config TEST_USER_COPY
1602         tristate "Test user/kernel boundary protections"
1603         default n
1604         depends on m
1605         help
1606           This builds the "test_user_copy" module that runs sanity checks
1607           on the copy_to/from_user infrastructure, making sure basic
1608           user/kernel boundary testing is working. If it fails to load,
1609           a regression has been detected in the user/kernel memory boundary
1610           protections.
1611 
1612           If unsure, say N.
1613 
1614 source "samples/Kconfig"
1615 
1616 source "lib/Kconfig.kgdb"
1617 

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