Version:  2.0.40 2.2.26 2.4.37 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16

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_VMACACHE
505         bool "Debug VMA caching"
506         depends on DEBUG_VM
507         help
508           Enable this to turn on VMA caching debug information. Doing so
509           can cause significant overhead, so only enable it in non-production
510           environments.
511 
512           If unsure, say N.
513 
514 config DEBUG_VM_RB
515         bool "Debug VM red-black trees"
516         depends on DEBUG_VM
517         help
518           Enable VM red-black tree debugging information and extra validations.
519 
520           If unsure, say N.
521 
522 config DEBUG_VIRTUAL
523         bool "Debug VM translations"
524         depends on DEBUG_KERNEL && X86
525         help
526           Enable some costly sanity checks in virtual to page code. This can
527           catch mistakes with virt_to_page() and friends.
528 
529           If unsure, say N.
530 
531 config DEBUG_NOMMU_REGIONS
532         bool "Debug the global anon/private NOMMU mapping region tree"
533         depends on DEBUG_KERNEL && !MMU
534         help
535           This option causes the global tree of anonymous and private mapping
536           regions to be regularly checked for invalid topology.
537 
538 config DEBUG_MEMORY_INIT
539         bool "Debug memory initialisation" if EXPERT
540         default !EXPERT
541         help
542           Enable this for additional checks during memory initialisation.
543           The sanity checks verify aspects of the VM such as the memory model
544           and other information provided by the architecture. Verbose
545           information will be printed at KERN_DEBUG loglevel depending
546           on the mminit_loglevel= command-line option.
547 
548           If unsure, say Y
549 
550 config MEMORY_NOTIFIER_ERROR_INJECT
551         tristate "Memory hotplug notifier error injection module"
552         depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
553         help
554           This option provides the ability to inject artificial errors to
555           memory hotplug notifier chain callbacks.  It is controlled through
556           debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
557 
558           If the notifier call chain should be failed with some events
559           notified, write the error code to "actions/<notifier event>/error".
560 
561           Example: Inject memory hotplug offline error (-12 == -ENOMEM)
562 
563           # cd /sys/kernel/debug/notifier-error-inject/memory
564           # echo -12 > actions/MEM_GOING_OFFLINE/error
565           # echo offline > /sys/devices/system/memory/memoryXXX/state
566           bash: echo: write error: Cannot allocate memory
567 
568           To compile this code as a module, choose M here: the module will
569           be called memory-notifier-error-inject.
570 
571           If unsure, say N.
572 
573 config DEBUG_PER_CPU_MAPS
574         bool "Debug access to per_cpu maps"
575         depends on DEBUG_KERNEL
576         depends on SMP
577         help
578           Say Y to verify that the per_cpu map being accessed has
579           been set up. This adds a fair amount of code to kernel memory
580           and decreases performance.
581 
582           Say N if unsure.
583 
584 config DEBUG_HIGHMEM
585         bool "Highmem debugging"
586         depends on DEBUG_KERNEL && HIGHMEM
587         help
588           This option enables additional error checking for high memory
589           systems.  Disable for production systems.
590 
591 config HAVE_DEBUG_STACKOVERFLOW
592         bool
593 
594 config DEBUG_STACKOVERFLOW
595         bool "Check for stack overflows"
596         depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
597         ---help---
598           Say Y here if you want to check for overflows of kernel, IRQ
599           and exception stacks (if your archicture uses them). This
600           option will show detailed messages if free stack space drops
601           below a certain limit.
602 
603           These kinds of bugs usually occur when call-chains in the
604           kernel get too deep, especially when interrupts are
605           involved.
606 
607           Use this in cases where you see apparently random memory
608           corruption, especially if it appears in 'struct thread_info'
609 
610           If in doubt, say "N".
611 
612 source "lib/Kconfig.kmemcheck"
613 
614 endmenu # "Memory Debugging"
615 
616 config DEBUG_SHIRQ
617         bool "Debug shared IRQ handlers"
618         depends on DEBUG_KERNEL
619         help
620           Enable this to generate a spurious interrupt as soon as a shared
621           interrupt handler is registered, and just before one is deregistered.
622           Drivers ought to be able to handle interrupts coming in at those
623           points; some don't and need to be caught.
624 
625 menu "Debug Lockups and Hangs"
626 
627 config LOCKUP_DETECTOR
628         bool "Detect Hard and Soft Lockups"
629         depends on DEBUG_KERNEL && !S390
630         help
631           Say Y here to enable the kernel to act as a watchdog to detect
632           hard and soft lockups.
633 
634           Softlockups are bugs that cause the kernel to loop in kernel
635           mode for more than 20 seconds, without giving other tasks a
636           chance to run.  The current stack trace is displayed upon
637           detection and the system will stay locked up.
638 
639           Hardlockups are bugs that cause the CPU to loop in kernel mode
640           for more than 10 seconds, without letting other interrupts have a
641           chance to run.  The current stack trace is displayed upon detection
642           and the system will stay locked up.
643 
644           The overhead should be minimal.  A periodic hrtimer runs to
645           generate interrupts and kick the watchdog task every 4 seconds.
646           An NMI is generated every 10 seconds or so to check for hardlockups.
647 
648           The frequency of hrtimer and NMI events and the soft and hard lockup
649           thresholds can be controlled through the sysctl watchdog_thresh.
650 
651 config HARDLOCKUP_DETECTOR
652         def_bool y
653         depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
654         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
655 
656 config BOOTPARAM_HARDLOCKUP_PANIC
657         bool "Panic (Reboot) On Hard Lockups"
658         depends on HARDLOCKUP_DETECTOR
659         help
660           Say Y here to enable the kernel to panic on "hard lockups",
661           which are bugs that cause the kernel to loop in kernel
662           mode with interrupts disabled for more than 10 seconds (configurable
663           using the watchdog_thresh sysctl).
664 
665           Say N if unsure.
666 
667 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
668         int
669         depends on HARDLOCKUP_DETECTOR
670         range 0 1
671         default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
672         default 1 if BOOTPARAM_HARDLOCKUP_PANIC
673 
674 config BOOTPARAM_SOFTLOCKUP_PANIC
675         bool "Panic (Reboot) On Soft Lockups"
676         depends on LOCKUP_DETECTOR
677         help
678           Say Y here to enable the kernel to panic on "soft lockups",
679           which are bugs that cause the kernel to loop in kernel
680           mode for more than 20 seconds (configurable using the watchdog_thresh
681           sysctl), without giving other tasks a chance to run.
682 
683           The panic can be used in combination with panic_timeout,
684           to cause the system to reboot automatically after a
685           lockup has been detected. This feature is useful for
686           high-availability systems that have uptime guarantees and
687           where a lockup must be resolved ASAP.
688 
689           Say N if unsure.
690 
691 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
692         int
693         depends on LOCKUP_DETECTOR
694         range 0 1
695         default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
696         default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
697 
698 config DETECT_HUNG_TASK
699         bool "Detect Hung Tasks"
700         depends on DEBUG_KERNEL
701         default LOCKUP_DETECTOR
702         help
703           Say Y here to enable the kernel to detect "hung tasks",
704           which are bugs that cause the task to be stuck in
705           uninterruptible "D" state indefinitiley.
706 
707           When a hung task is detected, the kernel will print the
708           current stack trace (which you should report), but the
709           task will stay in uninterruptible state. If lockdep is
710           enabled then all held locks will also be reported. This
711           feature has negligible overhead.
712 
713 config DEFAULT_HUNG_TASK_TIMEOUT
714         int "Default timeout for hung task detection (in seconds)"
715         depends on DETECT_HUNG_TASK
716         default 120
717         help
718           This option controls the default timeout (in seconds) used
719           to determine when a task has become non-responsive and should
720           be considered hung.
721 
722           It can be adjusted at runtime via the kernel.hung_task_timeout_secs
723           sysctl or by writing a value to
724           /proc/sys/kernel/hung_task_timeout_secs.
725 
726           A timeout of 0 disables the check.  The default is two minutes.
727           Keeping the default should be fine in most cases.
728 
729 config BOOTPARAM_HUNG_TASK_PANIC
730         bool "Panic (Reboot) On Hung Tasks"
731         depends on DETECT_HUNG_TASK
732         help
733           Say Y here to enable the kernel to panic on "hung tasks",
734           which are bugs that cause the kernel to leave a task stuck
735           in uninterruptible "D" state.
736 
737           The panic can be used in combination with panic_timeout,
738           to cause the system to reboot automatically after a
739           hung task has been detected. This feature is useful for
740           high-availability systems that have uptime guarantees and
741           where a hung tasks must be resolved ASAP.
742 
743           Say N if unsure.
744 
745 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
746         int
747         depends on DETECT_HUNG_TASK
748         range 0 1
749         default 0 if !BOOTPARAM_HUNG_TASK_PANIC
750         default 1 if BOOTPARAM_HUNG_TASK_PANIC
751 
752 endmenu # "Debug lockups and hangs"
753 
754 config PANIC_ON_OOPS
755         bool "Panic on Oops"
756         help
757           Say Y here to enable the kernel to panic when it oopses. This
758           has the same effect as setting oops=panic on the kernel command
759           line.
760 
761           This feature is useful to ensure that the kernel does not do
762           anything erroneous after an oops which could result in data
763           corruption or other issues.
764 
765           Say N if unsure.
766 
767 config PANIC_ON_OOPS_VALUE
768         int
769         range 0 1
770         default 0 if !PANIC_ON_OOPS
771         default 1 if PANIC_ON_OOPS
772 
773 config PANIC_TIMEOUT
774         int "panic timeout"
775         default 0
776         help
777           Set the timeout value (in seconds) until a reboot occurs when the
778           the kernel panics. If n = 0, then we wait forever. A timeout
779           value n > 0 will wait n seconds before rebooting, while a timeout
780           value n < 0 will reboot immediately.
781 
782 config SCHED_DEBUG
783         bool "Collect scheduler debugging info"
784         depends on DEBUG_KERNEL && PROC_FS
785         default y
786         help
787           If you say Y here, the /proc/sched_debug file will be provided
788           that can help debug the scheduler. The runtime overhead of this
789           option is minimal.
790 
791 config SCHEDSTATS
792         bool "Collect scheduler statistics"
793         depends on DEBUG_KERNEL && PROC_FS
794         help
795           If you say Y here, additional code will be inserted into the
796           scheduler and related routines to collect statistics about
797           scheduler behavior and provide them in /proc/schedstat.  These
798           stats may be useful for both tuning and debugging the scheduler
799           If you aren't debugging the scheduler or trying to tune a specific
800           application, you can say N to avoid the very slight overhead
801           this adds.
802 
803 config TIMER_STATS
804         bool "Collect kernel timers statistics"
805         depends on DEBUG_KERNEL && PROC_FS
806         help
807           If you say Y here, additional code will be inserted into the
808           timer routines to collect statistics about kernel timers being
809           reprogrammed. The statistics can be read from /proc/timer_stats.
810           The statistics collection is started by writing 1 to /proc/timer_stats,
811           writing 0 stops it. This feature is useful to collect information
812           about timer usage patterns in kernel and userspace. This feature
813           is lightweight if enabled in the kernel config but not activated
814           (it defaults to deactivated on bootup and will only be activated
815           if some application like powertop activates it explicitly).
816 
817 config DEBUG_PREEMPT
818         bool "Debug preemptible kernel"
819         depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
820         default y
821         help
822           If you say Y here then the kernel will use a debug variant of the
823           commonly used smp_processor_id() function and will print warnings
824           if kernel code uses it in a preemption-unsafe way. Also, the kernel
825           will detect preemption count underflows.
826 
827 menu "Lock Debugging (spinlocks, mutexes, etc...)"
828 
829 config DEBUG_RT_MUTEXES
830         bool "RT Mutex debugging, deadlock detection"
831         depends on DEBUG_KERNEL && RT_MUTEXES
832         help
833          This allows rt mutex semantics violations and rt mutex related
834          deadlocks (lockups) to be detected and reported automatically.
835 
836 config RT_MUTEX_TESTER
837         bool "Built-in scriptable tester for rt-mutexes"
838         depends on DEBUG_KERNEL && RT_MUTEXES
839         help
840           This option enables a rt-mutex tester.
841 
842 config DEBUG_SPINLOCK
843         bool "Spinlock and rw-lock debugging: basic checks"
844         depends on DEBUG_KERNEL
845         select UNINLINE_SPIN_UNLOCK
846         help
847           Say Y here and build SMP to catch missing spinlock initialization
848           and certain other kinds of spinlock errors commonly made.  This is
849           best used in conjunction with the NMI watchdog so that spinlock
850           deadlocks are also debuggable.
851 
852 config DEBUG_MUTEXES
853         bool "Mutex debugging: basic checks"
854         depends on DEBUG_KERNEL
855         help
856          This feature allows mutex semantics violations to be detected and
857          reported.
858 
859 config DEBUG_WW_MUTEX_SLOWPATH
860         bool "Wait/wound mutex debugging: Slowpath testing"
861         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
862         select DEBUG_LOCK_ALLOC
863         select DEBUG_SPINLOCK
864         select DEBUG_MUTEXES
865         help
866          This feature enables slowpath testing for w/w mutex users by
867          injecting additional -EDEADLK wound/backoff cases. Together with
868          the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
869          will test all possible w/w mutex interface abuse with the
870          exception of simply not acquiring all the required locks.
871 
872 config DEBUG_LOCK_ALLOC
873         bool "Lock debugging: detect incorrect freeing of live locks"
874         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
875         select DEBUG_SPINLOCK
876         select DEBUG_MUTEXES
877         select LOCKDEP
878         help
879          This feature will check whether any held lock (spinlock, rwlock,
880          mutex or rwsem) is incorrectly freed by the kernel, via any of the
881          memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
882          vfree(), etc.), whether a live lock is incorrectly reinitialized via
883          spin_lock_init()/mutex_init()/etc., or whether there is any lock
884          held during task exit.
885 
886 config PROVE_LOCKING
887         bool "Lock debugging: prove locking correctness"
888         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
889         select LOCKDEP
890         select DEBUG_SPINLOCK
891         select DEBUG_MUTEXES
892         select DEBUG_LOCK_ALLOC
893         select TRACE_IRQFLAGS
894         default n
895         help
896          This feature enables the kernel to prove that all locking
897          that occurs in the kernel runtime is mathematically
898          correct: that under no circumstance could an arbitrary (and
899          not yet triggered) combination of observed locking
900          sequences (on an arbitrary number of CPUs, running an
901          arbitrary number of tasks and interrupt contexts) cause a
902          deadlock.
903 
904          In short, this feature enables the kernel to report locking
905          related deadlocks before they actually occur.
906 
907          The proof does not depend on how hard and complex a
908          deadlock scenario would be to trigger: how many
909          participant CPUs, tasks and irq-contexts would be needed
910          for it to trigger. The proof also does not depend on
911          timing: if a race and a resulting deadlock is possible
912          theoretically (no matter how unlikely the race scenario
913          is), it will be proven so and will immediately be
914          reported by the kernel (once the event is observed that
915          makes the deadlock theoretically possible).
916 
917          If a deadlock is impossible (i.e. the locking rules, as
918          observed by the kernel, are mathematically correct), the
919          kernel reports nothing.
920 
921          NOTE: this feature can also be enabled for rwlocks, mutexes
922          and rwsems - in which case all dependencies between these
923          different locking variants are observed and mapped too, and
924          the proof of observed correctness is also maintained for an
925          arbitrary combination of these separate locking variants.
926 
927          For more details, see Documentation/lockdep-design.txt.
928 
929 config LOCKDEP
930         bool
931         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
932         select STACKTRACE
933         select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
934         select KALLSYMS
935         select KALLSYMS_ALL
936 
937 config LOCK_STAT
938         bool "Lock usage statistics"
939         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
940         select LOCKDEP
941         select DEBUG_SPINLOCK
942         select DEBUG_MUTEXES
943         select DEBUG_LOCK_ALLOC
944         default n
945         help
946          This feature enables tracking lock contention points
947 
948          For more details, see Documentation/lockstat.txt
949 
950          This also enables lock events required by "perf lock",
951          subcommand of perf.
952          If you want to use "perf lock", you also need to turn on
953          CONFIG_EVENT_TRACING.
954 
955          CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
956          (CONFIG_LOCKDEP defines "acquire" and "release" events.)
957 
958 config DEBUG_LOCKDEP
959         bool "Lock dependency engine debugging"
960         depends on DEBUG_KERNEL && LOCKDEP
961         help
962           If you say Y here, the lock dependency engine will do
963           additional runtime checks to debug itself, at the price
964           of more runtime overhead.
965 
966 config DEBUG_ATOMIC_SLEEP
967         bool "Sleep inside atomic section checking"
968         select PREEMPT_COUNT
969         depends on DEBUG_KERNEL
970         help
971           If you say Y here, various routines which may sleep will become very
972           noisy if they are called inside atomic sections: when a spinlock is
973           held, inside an rcu read side critical section, inside preempt disabled
974           sections, inside an interrupt, etc...
975 
976 config DEBUG_LOCKING_API_SELFTESTS
977         bool "Locking API boot-time self-tests"
978         depends on DEBUG_KERNEL
979         help
980           Say Y here if you want the kernel to run a short self-test during
981           bootup. The self-test checks whether common types of locking bugs
982           are detected by debugging mechanisms or not. (if you disable
983           lock debugging then those bugs wont be detected of course.)
984           The following locking APIs are covered: spinlocks, rwlocks,
985           mutexes and rwsems.
986 
987 config LOCK_TORTURE_TEST
988         tristate "torture tests for locking"
989         depends on DEBUG_KERNEL
990         select TORTURE_TEST
991         default n
992         help
993           This option provides a kernel module that runs torture tests
994           on kernel locking primitives.  The kernel module may be built
995           after the fact on the running kernel to be tested, if desired.
996 
997           Say Y here if you want kernel locking-primitive torture tests
998           to be built into the kernel.
999           Say M if you want these torture tests to build as a module.
1000           Say N if you are unsure.
1001 
1002 endmenu # lock debugging
1003 
1004 config TRACE_IRQFLAGS
1005         bool
1006         help
1007           Enables hooks to interrupt enabling and disabling for
1008           either tracing or lock debugging.
1009 
1010 config STACKTRACE
1011         bool
1012         depends on STACKTRACE_SUPPORT
1013 
1014 config DEBUG_KOBJECT
1015         bool "kobject debugging"
1016         depends on DEBUG_KERNEL
1017         help
1018           If you say Y here, some extra kobject debugging messages will be sent
1019           to the syslog. 
1020 
1021 config DEBUG_KOBJECT_RELEASE
1022         bool "kobject release debugging"
1023         depends on DEBUG_OBJECTS_TIMERS
1024         help
1025           kobjects are reference counted objects.  This means that their
1026           last reference count put is not predictable, and the kobject can
1027           live on past the point at which a driver decides to drop it's
1028           initial reference to the kobject gained on allocation.  An
1029           example of this would be a struct device which has just been
1030           unregistered.
1031 
1032           However, some buggy drivers assume that after such an operation,
1033           the memory backing the kobject can be immediately freed.  This
1034           goes completely against the principles of a refcounted object.
1035 
1036           If you say Y here, the kernel will delay the release of kobjects
1037           on the last reference count to improve the visibility of this
1038           kind of kobject release bug.
1039 
1040 config HAVE_DEBUG_BUGVERBOSE
1041         bool
1042 
1043 config DEBUG_BUGVERBOSE
1044         bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1045         depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1046         default y
1047         help
1048           Say Y here to make BUG() panics output the file name and line number
1049           of the BUG call as well as the EIP and oops trace.  This aids
1050           debugging but costs about 70-100K of memory.
1051 
1052 config DEBUG_LIST
1053         bool "Debug linked list manipulation"
1054         depends on DEBUG_KERNEL
1055         help
1056           Enable this to turn on extended checks in the linked-list
1057           walking routines.
1058 
1059           If unsure, say N.
1060 
1061 config DEBUG_PI_LIST
1062         bool "Debug priority linked list manipulation"
1063         depends on DEBUG_KERNEL
1064         help
1065           Enable this to turn on extended checks in the priority-ordered
1066           linked-list (plist) walking routines.  This checks the entire
1067           list multiple times during each manipulation.
1068 
1069           If unsure, say N.
1070 
1071 config DEBUG_SG
1072         bool "Debug SG table operations"
1073         depends on DEBUG_KERNEL
1074         help
1075           Enable this to turn on checks on scatter-gather tables. This can
1076           help find problems with drivers that do not properly initialize
1077           their sg tables.
1078 
1079           If unsure, say N.
1080 
1081 config DEBUG_NOTIFIERS
1082         bool "Debug notifier call chains"
1083         depends on DEBUG_KERNEL
1084         help
1085           Enable this to turn on sanity checking for notifier call chains.
1086           This is most useful for kernel developers to make sure that
1087           modules properly unregister themselves from notifier chains.
1088           This is a relatively cheap check but if you care about maximum
1089           performance, say N.
1090 
1091 config DEBUG_CREDENTIALS
1092         bool "Debug credential management"
1093         depends on DEBUG_KERNEL
1094         help
1095           Enable this to turn on some debug checking for credential
1096           management.  The additional code keeps track of the number of
1097           pointers from task_structs to any given cred struct, and checks to
1098           see that this number never exceeds the usage count of the cred
1099           struct.
1100 
1101           Furthermore, if SELinux is enabled, this also checks that the
1102           security pointer in the cred struct is never seen to be invalid.
1103 
1104           If unsure, say N.
1105 
1106 menu "RCU Debugging"
1107 
1108 config PROVE_RCU
1109         bool "RCU debugging: prove RCU correctness"
1110         depends on PROVE_LOCKING
1111         default n
1112         help
1113          This feature enables lockdep extensions that check for correct
1114          use of RCU APIs.  This is currently under development.  Say Y
1115          if you want to debug RCU usage or help work on the PROVE_RCU
1116          feature.
1117 
1118          Say N if you are unsure.
1119 
1120 config PROVE_RCU_REPEATEDLY
1121         bool "RCU debugging: don't disable PROVE_RCU on first splat"
1122         depends on PROVE_RCU
1123         default n
1124         help
1125          By itself, PROVE_RCU will disable checking upon issuing the
1126          first warning (or "splat").  This feature prevents such
1127          disabling, allowing multiple RCU-lockdep warnings to be printed
1128          on a single reboot.
1129 
1130          Say Y to allow multiple RCU-lockdep warnings per boot.
1131 
1132          Say N if you are unsure.
1133 
1134 config PROVE_RCU_DELAY
1135         bool "RCU debugging: preemptible RCU race provocation"
1136         depends on DEBUG_KERNEL && PREEMPT_RCU
1137         default n
1138         help
1139          There is a class of races that involve an unlikely preemption
1140          of __rcu_read_unlock() just after ->rcu_read_lock_nesting has
1141          been set to INT_MIN.  This feature inserts a delay at that
1142          point to increase the probability of these races.
1143 
1144          Say Y to increase probability of preemption of __rcu_read_unlock().
1145 
1146          Say N if you are unsure.
1147 
1148 config SPARSE_RCU_POINTER
1149         bool "RCU debugging: sparse-based checks for pointer usage"
1150         default n
1151         help
1152          This feature enables the __rcu sparse annotation for
1153          RCU-protected pointers.  This annotation will cause sparse
1154          to flag any non-RCU used of annotated pointers.  This can be
1155          helpful when debugging RCU usage.  Please note that this feature
1156          is not intended to enforce code cleanliness; it is instead merely
1157          a debugging aid.
1158 
1159          Say Y to make sparse flag questionable use of RCU-protected pointers
1160 
1161          Say N if you are unsure.
1162 
1163 config TORTURE_TEST
1164         tristate
1165         default n
1166 
1167 config RCU_TORTURE_TEST
1168         tristate "torture tests for RCU"
1169         depends on DEBUG_KERNEL
1170         select TORTURE_TEST
1171         default n
1172         help
1173           This option provides a kernel module that runs torture tests
1174           on the RCU infrastructure.  The kernel module may be built
1175           after the fact on the running kernel to be tested, if desired.
1176 
1177           Say Y here if you want RCU torture tests to be built into
1178           the kernel.
1179           Say M if you want the RCU torture tests to build as a module.
1180           Say N if you are unsure.
1181 
1182 config RCU_TORTURE_TEST_RUNNABLE
1183         bool "torture tests for RCU runnable by default"
1184         depends on RCU_TORTURE_TEST = y
1185         default n
1186         help
1187           This option provides a way to build the RCU torture tests
1188           directly into the kernel without them starting up at boot
1189           time.  You can use /proc/sys/kernel/rcutorture_runnable
1190           to manually override this setting.  This /proc file is
1191           available only when the RCU torture tests have been built
1192           into the kernel.
1193 
1194           Say Y here if you want the RCU torture tests to start during
1195           boot (you probably don't).
1196           Say N here if you want the RCU torture tests to start only
1197           after being manually enabled via /proc.
1198 
1199 config RCU_CPU_STALL_TIMEOUT
1200         int "RCU CPU stall timeout in seconds"
1201         depends on RCU_STALL_COMMON
1202         range 3 300
1203         default 21
1204         help
1205           If a given RCU grace period extends more than the specified
1206           number of seconds, a CPU stall warning is printed.  If the
1207           RCU grace period persists, additional CPU stall warnings are
1208           printed at more widely spaced intervals.
1209 
1210 config RCU_CPU_STALL_VERBOSE
1211         bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
1212         depends on TREE_PREEMPT_RCU
1213         default y
1214         help
1215           This option causes RCU to printk detailed per-task information
1216           for any tasks that are stalling the current RCU grace period.
1217 
1218           Say N if you are unsure.
1219 
1220           Say Y if you want to enable such checks.
1221 
1222 config RCU_CPU_STALL_INFO
1223         bool "Print additional diagnostics on RCU CPU stall"
1224         depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL
1225         default n
1226         help
1227           For each stalled CPU that is aware of the current RCU grace
1228           period, print out additional per-CPU diagnostic information
1229           regarding scheduling-clock ticks, idle state, and,
1230           for RCU_FAST_NO_HZ kernels, idle-entry state.
1231 
1232           Say N if you are unsure.
1233 
1234           Say Y if you want to enable such diagnostics.
1235 
1236 config RCU_TRACE
1237         bool "Enable tracing for RCU"
1238         depends on DEBUG_KERNEL
1239         select TRACE_CLOCK
1240         help
1241           This option provides tracing in RCU which presents stats
1242           in debugfs for debugging RCU implementation.
1243 
1244           Say Y here if you want to enable RCU tracing
1245           Say N if you are unsure.
1246 
1247 endmenu # "RCU Debugging"
1248 
1249 config DEBUG_BLOCK_EXT_DEVT
1250         bool "Force extended block device numbers and spread them"
1251         depends on DEBUG_KERNEL
1252         depends on BLOCK
1253         default n
1254         help
1255           BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1256           SOME DISTRIBUTIONS.  DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1257           YOU ARE DOING.  Distros, please enable this and fix whatever
1258           is broken.
1259 
1260           Conventionally, block device numbers are allocated from
1261           predetermined contiguous area.  However, extended block area
1262           may introduce non-contiguous block device numbers.  This
1263           option forces most block device numbers to be allocated from
1264           the extended space and spreads them to discover kernel or
1265           userland code paths which assume predetermined contiguous
1266           device number allocation.
1267 
1268           Note that turning on this debug option shuffles all the
1269           device numbers for all IDE and SCSI devices including libata
1270           ones, so root partition specified using device number
1271           directly (via rdev or root=MAJ:MIN) won't work anymore.
1272           Textual device names (root=/dev/sdXn) will continue to work.
1273 
1274           Say N if you are unsure.
1275 
1276 config NOTIFIER_ERROR_INJECTION
1277         tristate "Notifier error injection"
1278         depends on DEBUG_KERNEL
1279         select DEBUG_FS
1280         help
1281           This option provides the ability to inject artificial errors to
1282           specified notifier chain callbacks. It is useful to test the error
1283           handling of notifier call chain failures.
1284 
1285           Say N if unsure.
1286 
1287 config CPU_NOTIFIER_ERROR_INJECT
1288         tristate "CPU notifier error injection module"
1289         depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1290         help
1291           This option provides a kernel module that can be used to test
1292           the error handling of the cpu notifiers by injecting artificial
1293           errors to CPU notifier chain callbacks.  It is controlled through
1294           debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
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 CPU offline error (-1 == -EPERM)
1300 
1301           # cd /sys/kernel/debug/notifier-error-inject/cpu
1302           # echo -1 > actions/CPU_DOWN_PREPARE/error
1303           # echo 0 > /sys/devices/system/cpu/cpu1/online
1304           bash: echo: write error: Operation not permitted
1305 
1306           To compile this code as a module, choose M here: the module will
1307           be called cpu-notifier-error-inject.
1308 
1309           If unsure, say N.
1310 
1311 config PM_NOTIFIER_ERROR_INJECT
1312         tristate "PM notifier error injection module"
1313         depends on PM && NOTIFIER_ERROR_INJECTION
1314         default m if PM_DEBUG
1315         help
1316           This option provides the ability to inject artificial errors to
1317           PM notifier chain callbacks.  It is controlled through debugfs
1318           interface /sys/kernel/debug/notifier-error-inject/pm
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           Example: Inject PM suspend error (-12 = -ENOMEM)
1324 
1325           # cd /sys/kernel/debug/notifier-error-inject/pm/
1326           # echo -12 > actions/PM_SUSPEND_PREPARE/error
1327           # echo mem > /sys/power/state
1328           bash: echo: write error: Cannot allocate memory
1329 
1330           To compile this code as a module, choose M here: the module will
1331           be called pm-notifier-error-inject.
1332 
1333           If unsure, say N.
1334 
1335 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1336         tristate "OF reconfig notifier error injection module"
1337         depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1338         help
1339           This option provides the ability to inject artificial errors to
1340           OF reconfig notifier chain callbacks.  It is controlled
1341           through debugfs interface under
1342           /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1343 
1344           If the notifier call chain should be failed with some events
1345           notified, write the error code to "actions/<notifier event>/error".
1346 
1347           To compile this code as a module, choose M here: the module will
1348           be called of-reconfig-notifier-error-inject.
1349 
1350           If unsure, say N.
1351 
1352 config FAULT_INJECTION
1353         bool "Fault-injection framework"
1354         depends on DEBUG_KERNEL
1355         help
1356           Provide fault-injection framework.
1357           For more details, see Documentation/fault-injection/.
1358 
1359 config FAILSLAB
1360         bool "Fault-injection capability for kmalloc"
1361         depends on FAULT_INJECTION
1362         depends on SLAB || SLUB
1363         help
1364           Provide fault-injection capability for kmalloc.
1365 
1366 config FAIL_PAGE_ALLOC
1367         bool "Fault-injection capabilitiy for alloc_pages()"
1368         depends on FAULT_INJECTION
1369         help
1370           Provide fault-injection capability for alloc_pages().
1371 
1372 config FAIL_MAKE_REQUEST
1373         bool "Fault-injection capability for disk IO"
1374         depends on FAULT_INJECTION && BLOCK
1375         help
1376           Provide fault-injection capability for disk IO.
1377 
1378 config FAIL_IO_TIMEOUT
1379         bool "Fault-injection capability for faking disk interrupts"
1380         depends on FAULT_INJECTION && BLOCK
1381         help
1382           Provide fault-injection capability on end IO handling. This
1383           will make the block layer "forget" an interrupt as configured,
1384           thus exercising the error handling.
1385 
1386           Only works with drivers that use the generic timeout handling,
1387           for others it wont do anything.
1388 
1389 config FAIL_MMC_REQUEST
1390         bool "Fault-injection capability for MMC IO"
1391         select DEBUG_FS
1392         depends on FAULT_INJECTION && MMC
1393         help
1394           Provide fault-injection capability for MMC IO.
1395           This will make the mmc core return data errors. This is
1396           useful to test the error handling in the mmc block device
1397           and to test how the mmc host driver handles retries from
1398           the block device.
1399 
1400 config FAULT_INJECTION_DEBUG_FS
1401         bool "Debugfs entries for fault-injection capabilities"
1402         depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1403         help
1404           Enable configuration of fault-injection capabilities via debugfs.
1405 
1406 config FAULT_INJECTION_STACKTRACE_FILTER
1407         bool "stacktrace filter for fault-injection capabilities"
1408         depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1409         depends on !X86_64
1410         select STACKTRACE
1411         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1412         help
1413           Provide stacktrace filter for fault-injection capabilities
1414 
1415 config LATENCYTOP
1416         bool "Latency measuring infrastructure"
1417         depends on HAVE_LATENCYTOP_SUPPORT
1418         depends on DEBUG_KERNEL
1419         depends on STACKTRACE_SUPPORT
1420         depends on PROC_FS
1421         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1422         select KALLSYMS
1423         select KALLSYMS_ALL
1424         select STACKTRACE
1425         select SCHEDSTATS
1426         select SCHED_DEBUG
1427         help
1428           Enable this option if you want to use the LatencyTOP tool
1429           to find out which userspace is blocking on what kernel operations.
1430 
1431 config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1432         bool
1433 
1434 config DEBUG_STRICT_USER_COPY_CHECKS
1435         bool "Strict user copy size checks"
1436         depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1437         depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
1438         help
1439           Enabling this option turns a certain set of sanity checks for user
1440           copy operations into compile time failures.
1441 
1442           The copy_from_user() etc checks are there to help test if there
1443           are sufficient security checks on the length argument of
1444           the copy operation, by having gcc prove that the argument is
1445           within bounds.
1446 
1447           If unsure, say N.
1448 
1449 source kernel/trace/Kconfig
1450 
1451 menu "Runtime Testing"
1452 
1453 config LKDTM
1454         tristate "Linux Kernel Dump Test Tool Module"
1455         depends on DEBUG_FS
1456         depends on BLOCK
1457         default n
1458         help
1459         This module enables testing of the different dumping mechanisms by
1460         inducing system failures at predefined crash points.
1461         If you don't need it: say N
1462         Choose M here to compile this code as a module. The module will be
1463         called lkdtm.
1464 
1465         Documentation on how to use the module can be found in
1466         Documentation/fault-injection/provoke-crashes.txt
1467 
1468 config TEST_LIST_SORT
1469         bool "Linked list sorting test"
1470         depends on DEBUG_KERNEL
1471         help
1472           Enable this to turn on 'list_sort()' function test. This test is
1473           executed only once during system boot, so affects only boot time.
1474 
1475           If unsure, say N.
1476 
1477 config KPROBES_SANITY_TEST
1478         bool "Kprobes sanity tests"
1479         depends on DEBUG_KERNEL
1480         depends on KPROBES
1481         default n
1482         help
1483           This option provides for testing basic kprobes functionality on
1484           boot. A sample kprobe, jprobe and kretprobe are inserted and
1485           verified for functionality.
1486 
1487           Say N if you are unsure.
1488 
1489 config BACKTRACE_SELF_TEST
1490         tristate "Self test for the backtrace code"
1491         depends on DEBUG_KERNEL
1492         default n
1493         help
1494           This option provides a kernel module that can be used to test
1495           the kernel stack backtrace code. This option is not useful
1496           for distributions or general kernels, but only for kernel
1497           developers working on architecture code.
1498 
1499           Note that if you want to also test saved backtraces, you will
1500           have to enable STACKTRACE as well.
1501 
1502           Say N if you are unsure.
1503 
1504 config RBTREE_TEST
1505         tristate "Red-Black tree test"
1506         depends on DEBUG_KERNEL
1507         help
1508           A benchmark measuring the performance of the rbtree library.
1509           Also includes rbtree invariant checks.
1510 
1511 config INTERVAL_TREE_TEST
1512         tristate "Interval tree test"
1513         depends on m && DEBUG_KERNEL
1514         select INTERVAL_TREE
1515         help
1516           A benchmark measuring the performance of the interval tree library
1517 
1518 config PERCPU_TEST
1519         tristate "Per cpu operations test"
1520         depends on m && DEBUG_KERNEL
1521         help
1522           Enable this option to build test module which validates per-cpu
1523           operations.
1524 
1525           If unsure, say N.
1526 
1527 config ATOMIC64_SELFTEST
1528         bool "Perform an atomic64_t self-test at boot"
1529         help
1530           Enable this option to test the atomic64_t functions at boot.
1531 
1532           If unsure, say N.
1533 
1534 config ASYNC_RAID6_TEST
1535         tristate "Self test for hardware accelerated raid6 recovery"
1536         depends on ASYNC_RAID6_RECOV
1537         select ASYNC_MEMCPY
1538         ---help---
1539           This is a one-shot self test that permutes through the
1540           recovery of all the possible two disk failure scenarios for a
1541           N-disk array.  Recovery is performed with the asynchronous
1542           raid6 recovery routines, and will optionally use an offload
1543           engine if one is available.
1544 
1545           If unsure, say N.
1546 
1547 config TEST_STRING_HELPERS
1548         tristate "Test functions located in the string_helpers module at runtime"
1549 
1550 config TEST_KSTRTOX
1551         tristate "Test kstrto*() family of functions at runtime"
1552 
1553 endmenu # runtime tests
1554 
1555 config PROVIDE_OHCI1394_DMA_INIT
1556         bool "Remote debugging over FireWire early on boot"
1557         depends on PCI && X86
1558         help
1559           If you want to debug problems which hang or crash the kernel early
1560           on boot and the crashing machine has a FireWire port, you can use
1561           this feature to remotely access the memory of the crashed machine
1562           over FireWire. This employs remote DMA as part of the OHCI1394
1563           specification which is now the standard for FireWire controllers.
1564 
1565           With remote DMA, you can monitor the printk buffer remotely using
1566           firescope and access all memory below 4GB using fireproxy from gdb.
1567           Even controlling a kernel debugger is possible using remote DMA.
1568 
1569           Usage:
1570 
1571           If ohci1394_dma=early is used as boot parameter, it will initialize
1572           all OHCI1394 controllers which are found in the PCI config space.
1573 
1574           As all changes to the FireWire bus such as enabling and disabling
1575           devices cause a bus reset and thereby disable remote DMA for all
1576           devices, be sure to have the cable plugged and FireWire enabled on
1577           the debugging host before booting the debug target for debugging.
1578 
1579           This code (~1k) is freed after boot. By then, the firewire stack
1580           in charge of the OHCI-1394 controllers should be used instead.
1581 
1582           See Documentation/debugging-via-ohci1394.txt for more information.
1583 
1584 config BUILD_DOCSRC
1585         bool "Build targets in Documentation/ tree"
1586         depends on HEADERS_CHECK
1587         help
1588           This option attempts to build objects from the source files in the
1589           kernel Documentation/ tree.
1590 
1591           Say N if you are unsure.
1592 
1593 config DMA_API_DEBUG
1594         bool "Enable debugging of DMA-API usage"
1595         depends on HAVE_DMA_API_DEBUG
1596         help
1597           Enable this option to debug the use of the DMA API by device drivers.
1598           With this option you will be able to detect common bugs in device
1599           drivers like double-freeing of DMA mappings or freeing mappings that
1600           were never allocated.
1601 
1602           This also attempts to catch cases where a page owned by DMA is
1603           accessed by the cpu in a way that could cause data corruption.  For
1604           example, this enables cow_user_page() to check that the source page is
1605           not undergoing DMA.
1606 
1607           This option causes a performance degradation.  Use only if you want to
1608           debug device drivers and dma interactions.
1609 
1610           If unsure, say N.
1611 
1612 config TEST_MODULE
1613         tristate "Test module loading with 'hello world' module"
1614         default n
1615         depends on m
1616         help
1617           This builds the "test_module" module that emits "Hello, world"
1618           on printk when loaded. It is designed to be used for basic
1619           evaluation of the module loading subsystem (for example when
1620           validating module verification). It lacks any extra dependencies,
1621           and will not normally be loaded by the system unless explicitly
1622           requested by name.
1623 
1624           If unsure, say N.
1625 
1626 config TEST_USER_COPY
1627         tristate "Test user/kernel boundary protections"
1628         default n
1629         depends on m
1630         help
1631           This builds the "test_user_copy" module that runs sanity checks
1632           on the copy_to/from_user infrastructure, making sure basic
1633           user/kernel boundary testing is working. If it fails to load,
1634           a regression has been detected in the user/kernel memory boundary
1635           protections.
1636 
1637           If unsure, say N.
1638 
1639 config TEST_BPF
1640         tristate "Test BPF filter functionality"
1641         default n
1642         depends on m && NET
1643         help
1644           This builds the "test_bpf" module that runs various test vectors
1645           against the BPF interpreter or BPF JIT compiler depending on the
1646           current setting. This is in particular useful for BPF JIT compiler
1647           development, but also to run regression tests against changes in
1648           the interpreter code.
1649 
1650           If unsure, say N.
1651 
1652 source "samples/Kconfig"
1653 
1654 source "lib/Kconfig.kgdb"
1655 

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