Version:  2.0.40 2.2.26 2.4.37 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 3.17 3.18 3.19

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 MESSAGE_LOGLEVEL_DEFAULT
 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 DEBUG_INFO_SPLIT
147         bool "Produce split debuginfo in .dwo files"
148         depends on DEBUG_INFO
149         help
150           Generate debug info into separate .dwo files. This significantly
151           reduces the build directory size for builds with DEBUG_INFO,
152           because it stores the information only once on disk in .dwo
153           files instead of multiple times in object files and executables.
154           In addition the debug information is also compressed.
155 
156           Requires recent gcc (4.7+) and recent gdb/binutils.
157           Any tool that packages or reads debug information would need
158           to know about the .dwo files and include them.
159           Incompatible with older versions of ccache.
160 
161 config DEBUG_INFO_DWARF4
162         bool "Generate dwarf4 debuginfo"
163         depends on DEBUG_INFO
164         help
165           Generate dwarf4 debug info. This requires recent versions
166           of gcc and gdb. It makes the debug information larger.
167           But it significantly improves the success of resolving
168           variables in gdb on optimized code.
169 
170 config ENABLE_WARN_DEPRECATED
171         bool "Enable __deprecated logic"
172         default y
173         help
174           Enable the __deprecated logic in the kernel build.
175           Disable this to suppress the "warning: 'foo' is deprecated
176           (declared at kernel/power/somefile.c:1234)" messages.
177 
178 config ENABLE_MUST_CHECK
179         bool "Enable __must_check logic"
180         default y
181         help
182           Enable the __must_check logic in the kernel build.  Disable this to
183           suppress the "warning: ignoring return value of 'foo', declared with
184           attribute warn_unused_result" messages.
185 
186 config FRAME_WARN
187         int "Warn for stack frames larger than (needs gcc 4.4)"
188         range 0 8192
189         default 1024 if !64BIT
190         default 2048 if 64BIT
191         help
192           Tell gcc to warn at build time for stack frames larger than this.
193           Setting this too low will cause a lot of warnings.
194           Setting it to 0 disables the warning.
195           Requires gcc 4.4
196 
197 config STRIP_ASM_SYMS
198         bool "Strip assembler-generated symbols during link"
199         default n
200         help
201           Strip internal assembler-generated symbols during a link (symbols
202           that look like '.Lxxx') so they don't pollute the output of
203           get_wchan() and suchlike.
204 
205 config READABLE_ASM
206         bool "Generate readable assembler code"
207         depends on DEBUG_KERNEL
208         help
209           Disable some compiler optimizations that tend to generate human unreadable
210           assembler output. This may make the kernel slightly slower, but it helps
211           to keep kernel developers who have to stare a lot at assembler listings
212           sane.
213 
214 config UNUSED_SYMBOLS
215         bool "Enable unused/obsolete exported symbols"
216         default y if X86
217         help
218           Unused but exported symbols make the kernel needlessly bigger.  For
219           that reason most of these unused exports will soon be removed.  This
220           option is provided temporarily to provide a transition period in case
221           some external kernel module needs one of these symbols anyway. If you
222           encounter such a case in your module, consider if you are actually
223           using the right API.  (rationale: since nobody in the kernel is using
224           this in a module, there is a pretty good chance it's actually the
225           wrong interface to use).  If you really need the symbol, please send a
226           mail to the linux kernel mailing list mentioning the symbol and why
227           you really need it, and what the merge plan to the mainline kernel for
228           your module is.
229 
230 config PAGE_OWNER
231         bool "Track page owner"
232         depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
233         select DEBUG_FS
234         select STACKTRACE
235         select PAGE_EXTENSION
236         help
237           This keeps track of what call chain is the owner of a page, may
238           help to find bare alloc_page(s) leaks. Even if you include this
239           feature on your build, it is disabled in default. You should pass
240           "page_owner=on" to boot parameter in order to enable it. Eats
241           a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
242           for user-space helper.
243 
244           If unsure, say N.
245 
246 config DEBUG_FS
247         bool "Debug Filesystem"
248         help
249           debugfs is a virtual file system that kernel developers use to put
250           debugging files into.  Enable this option to be able to read and
251           write to these files.
252 
253           For detailed documentation on the debugfs API, see
254           Documentation/DocBook/filesystems.
255 
256           If unsure, say N.
257 
258 config HEADERS_CHECK
259         bool "Run 'make headers_check' when building vmlinux"
260         depends on !UML
261         help
262           This option will extract the user-visible kernel headers whenever
263           building the kernel, and will run basic sanity checks on them to
264           ensure that exported files do not attempt to include files which
265           were not exported, etc.
266 
267           If you're making modifications to header files which are
268           relevant for userspace, say 'Y', and check the headers
269           exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
270           your build tree), to make sure they're suitable.
271 
272 config DEBUG_SECTION_MISMATCH
273         bool "Enable full Section mismatch analysis"
274         help
275           The section mismatch analysis checks if there are illegal
276           references from one section to another section.
277           During linktime or runtime, some sections are dropped;
278           any use of code/data previously in these sections would
279           most likely result in an oops.
280           In the code, functions and variables are annotated with
281           __init,, etc. (see the full list in include/linux/init.h),
282           which results in the code/data being placed in specific sections.
283           The section mismatch analysis is always performed after a full
284           kernel build, and enabling this option causes the following
285           additional steps to occur:
286           - Add the option -fno-inline-functions-called-once to gcc commands.
287             When inlining a function annotated with __init in a non-init
288             function, we would lose the section information and thus
289             the analysis would not catch the illegal reference.
290             This option tells gcc to inline less (but it does result in
291             a larger kernel).
292           - Run the section mismatch analysis for each module/built-in.o file.
293             When we run the section mismatch analysis on vmlinux.o, we
294             lose valueble information about where the mismatch was
295             introduced.
296             Running the analysis for each module/built-in.o file
297             tells where the mismatch happens much closer to the
298             source. The drawback is that the same mismatch is
299             reported at least twice.
300           - Enable verbose reporting from modpost in order to help resolve
301             the section mismatches that are reported.
302 
303 #
304 # Select this config option from the architecture Kconfig, if it
305 # is preferred to always offer frame pointers as a config
306 # option on the architecture (regardless of KERNEL_DEBUG):
307 #
308 config ARCH_WANT_FRAME_POINTERS
309         bool
310         help
311 
312 config FRAME_POINTER
313         bool "Compile the kernel with frame pointers"
314         depends on DEBUG_KERNEL && \
315                 (CRIS || M68K || FRV || UML || \
316                  AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \
317                 ARCH_WANT_FRAME_POINTERS
318         default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
319         help
320           If you say Y here the resulting kernel image will be slightly
321           larger and slower, but it gives very useful debugging information
322           in case of kernel bugs. (precise oopses/stacktraces/warnings)
323 
324 config DEBUG_FORCE_WEAK_PER_CPU
325         bool "Force weak per-cpu definitions"
326         depends on DEBUG_KERNEL
327         help
328           s390 and alpha require percpu variables in modules to be
329           defined weak to work around addressing range issue which
330           puts the following two restrictions on percpu variable
331           definitions.
332 
333           1. percpu symbols must be unique whether static or not
334           2. percpu variables can't be defined inside a function
335 
336           To ensure that generic code follows the above rules, this
337           option forces all percpu variables to be defined as weak.
338 
339 endmenu # "Compiler options"
340 
341 config MAGIC_SYSRQ
342         bool "Magic SysRq key"
343         depends on !UML
344         help
345           If you say Y here, you will have some control over the system even
346           if the system crashes for example during kernel debugging (e.g., you
347           will be able to flush the buffer cache to disk, reboot the system
348           immediately or dump some status information). This is accomplished
349           by pressing various keys while holding SysRq (Alt+PrintScreen). It
350           also works on a serial console (on PC hardware at least), if you
351           send a BREAK and then within 5 seconds a command keypress. The
352           keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
353           unless you really know what this hack does.
354 
355 config MAGIC_SYSRQ_DEFAULT_ENABLE
356         hex "Enable magic SysRq key functions by default"
357         depends on MAGIC_SYSRQ
358         default 0x1
359         help
360           Specifies which SysRq key functions are enabled by default.
361           This may be set to 1 or 0 to enable or disable them all, or
362           to a bitmask as described in Documentation/sysrq.txt.
363 
364 config DEBUG_KERNEL
365         bool "Kernel debugging"
366         help
367           Say Y here if you are developing drivers or trying to debug and
368           identify kernel problems.
369 
370 menu "Memory Debugging"
371 
372 source mm/Kconfig.debug
373 
374 config DEBUG_OBJECTS
375         bool "Debug object operations"
376         depends on DEBUG_KERNEL
377         help
378           If you say Y here, additional code will be inserted into the
379           kernel to track the life time of various objects and validate
380           the operations on those objects.
381 
382 config DEBUG_OBJECTS_SELFTEST
383         bool "Debug objects selftest"
384         depends on DEBUG_OBJECTS
385         help
386           This enables the selftest of the object debug code.
387 
388 config DEBUG_OBJECTS_FREE
389         bool "Debug objects in freed memory"
390         depends on DEBUG_OBJECTS
391         help
392           This enables checks whether a k/v free operation frees an area
393           which contains an object which has not been deactivated
394           properly. This can make kmalloc/kfree-intensive workloads
395           much slower.
396 
397 config DEBUG_OBJECTS_TIMERS
398         bool "Debug timer objects"
399         depends on DEBUG_OBJECTS
400         help
401           If you say Y here, additional code will be inserted into the
402           timer routines to track the life time of timer objects and
403           validate the timer operations.
404 
405 config DEBUG_OBJECTS_WORK
406         bool "Debug work objects"
407         depends on DEBUG_OBJECTS
408         help
409           If you say Y here, additional code will be inserted into the
410           work queue routines to track the life time of work objects and
411           validate the work operations.
412 
413 config DEBUG_OBJECTS_RCU_HEAD
414         bool "Debug RCU callbacks objects"
415         depends on DEBUG_OBJECTS
416         help
417           Enable this to turn on debugging of RCU list heads (call_rcu() usage).
418 
419 config DEBUG_OBJECTS_PERCPU_COUNTER
420         bool "Debug percpu counter objects"
421         depends on DEBUG_OBJECTS
422         help
423           If you say Y here, additional code will be inserted into the
424           percpu counter routines to track the life time of percpu counter
425           objects and validate the percpu counter operations.
426 
427 config DEBUG_OBJECTS_ENABLE_DEFAULT
428         int "debug_objects bootup default value (0-1)"
429         range 0 1
430         default "1"
431         depends on DEBUG_OBJECTS
432         help
433           Debug objects boot parameter default value
434 
435 config DEBUG_SLAB
436         bool "Debug slab memory allocations"
437         depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
438         help
439           Say Y here to have the kernel do limited verification on memory
440           allocation as well as poisoning memory on free to catch use of freed
441           memory. This can make kmalloc/kfree-intensive workloads much slower.
442 
443 config DEBUG_SLAB_LEAK
444         bool "Memory leak debugging"
445         depends on DEBUG_SLAB
446 
447 config SLUB_DEBUG_ON
448         bool "SLUB debugging on by default"
449         depends on SLUB && SLUB_DEBUG && !KMEMCHECK
450         default n
451         help
452           Boot with debugging on by default. SLUB boots by default with
453           the runtime debug capabilities switched off. Enabling this is
454           equivalent to specifying the "slub_debug" parameter on boot.
455           There is no support for more fine grained debug control like
456           possible with slub_debug=xxx. SLUB debugging may be switched
457           off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
458           "slub_debug=-".
459 
460 config SLUB_STATS
461         default n
462         bool "Enable SLUB performance statistics"
463         depends on SLUB && SYSFS
464         help
465           SLUB statistics are useful to debug SLUBs allocation behavior in
466           order find ways to optimize the allocator. This should never be
467           enabled for production use since keeping statistics slows down
468           the allocator by a few percentage points. The slabinfo command
469           supports the determination of the most active slabs to figure
470           out which slabs are relevant to a particular load.
471           Try running: slabinfo -DA
472 
473 config HAVE_DEBUG_KMEMLEAK
474         bool
475 
476 config DEBUG_KMEMLEAK
477         bool "Kernel memory leak detector"
478         depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
479         select DEBUG_FS
480         select STACKTRACE if STACKTRACE_SUPPORT
481         select KALLSYMS
482         select CRC32
483         help
484           Say Y here if you want to enable the memory leak
485           detector. The memory allocation/freeing is traced in a way
486           similar to the Boehm's conservative garbage collector, the
487           difference being that the orphan objects are not freed but
488           only shown in /sys/kernel/debug/kmemleak. Enabling this
489           feature will introduce an overhead to memory
490           allocations. See Documentation/kmemleak.txt for more
491           details.
492 
493           Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
494           of finding leaks due to the slab objects poisoning.
495 
496           In order to access the kmemleak file, debugfs needs to be
497           mounted (usually at /sys/kernel/debug).
498 
499 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
500         int "Maximum kmemleak early log entries"
501         depends on DEBUG_KMEMLEAK
502         range 200 40000
503         default 400
504         help
505           Kmemleak must track all the memory allocations to avoid
506           reporting false positives. Since memory may be allocated or
507           freed before kmemleak is initialised, an early log buffer is
508           used to store these actions. If kmemleak reports "early log
509           buffer exceeded", please increase this value.
510 
511 config DEBUG_KMEMLEAK_TEST
512         tristate "Simple test for the kernel memory leak detector"
513         depends on DEBUG_KMEMLEAK && m
514         help
515           This option enables a module that explicitly leaks memory.
516 
517           If unsure, say N.
518 
519 config DEBUG_KMEMLEAK_DEFAULT_OFF
520         bool "Default kmemleak to off"
521         depends on DEBUG_KMEMLEAK
522         help
523           Say Y here to disable kmemleak by default. It can then be enabled
524           on the command line via kmemleak=on.
525 
526 config DEBUG_STACK_USAGE
527         bool "Stack utilization instrumentation"
528         depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAG
529         help
530           Enables the display of the minimum amount of free stack which each
531           task has ever had available in the sysrq-T and sysrq-P debug output.
532 
533           This option will slow down process creation somewhat.
534 
535 config DEBUG_VM
536         bool "Debug VM"
537         depends on DEBUG_KERNEL
538         help
539           Enable this to turn on extended checks in the virtual-memory system
540           that may impact performance.
541 
542           If unsure, say N.
543 
544 config DEBUG_VM_VMACACHE
545         bool "Debug VMA caching"
546         depends on DEBUG_VM
547         help
548           Enable this to turn on VMA caching debug information. Doing so
549           can cause significant overhead, so only enable it in non-production
550           environments.
551 
552           If unsure, say N.
553 
554 config DEBUG_VM_RB
555         bool "Debug VM red-black trees"
556         depends on DEBUG_VM
557         help
558           Enable VM red-black tree debugging information and extra validations.
559 
560           If unsure, say N.
561 
562 config DEBUG_VIRTUAL
563         bool "Debug VM translations"
564         depends on DEBUG_KERNEL && X86
565         help
566           Enable some costly sanity checks in virtual to page code. This can
567           catch mistakes with virt_to_page() and friends.
568 
569           If unsure, say N.
570 
571 config DEBUG_NOMMU_REGIONS
572         bool "Debug the global anon/private NOMMU mapping region tree"
573         depends on DEBUG_KERNEL && !MMU
574         help
575           This option causes the global tree of anonymous and private mapping
576           regions to be regularly checked for invalid topology.
577 
578 config DEBUG_MEMORY_INIT
579         bool "Debug memory initialisation" if EXPERT
580         default !EXPERT
581         help
582           Enable this for additional checks during memory initialisation.
583           The sanity checks verify aspects of the VM such as the memory model
584           and other information provided by the architecture. Verbose
585           information will be printed at KERN_DEBUG loglevel depending
586           on the mminit_loglevel= command-line option.
587 
588           If unsure, say Y
589 
590 config MEMORY_NOTIFIER_ERROR_INJECT
591         tristate "Memory hotplug notifier error injection module"
592         depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
593         help
594           This option provides the ability to inject artificial errors to
595           memory hotplug notifier chain callbacks.  It is controlled through
596           debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
597 
598           If the notifier call chain should be failed with some events
599           notified, write the error code to "actions/<notifier event>/error".
600 
601           Example: Inject memory hotplug offline error (-12 == -ENOMEM)
602 
603           # cd /sys/kernel/debug/notifier-error-inject/memory
604           # echo -12 > actions/MEM_GOING_OFFLINE/error
605           # echo offline > /sys/devices/system/memory/memoryXXX/state
606           bash: echo: write error: Cannot allocate memory
607 
608           To compile this code as a module, choose M here: the module will
609           be called memory-notifier-error-inject.
610 
611           If unsure, say N.
612 
613 config DEBUG_PER_CPU_MAPS
614         bool "Debug access to per_cpu maps"
615         depends on DEBUG_KERNEL
616         depends on SMP
617         help
618           Say Y to verify that the per_cpu map being accessed has
619           been set up. This adds a fair amount of code to kernel memory
620           and decreases performance.
621 
622           Say N if unsure.
623 
624 config DEBUG_HIGHMEM
625         bool "Highmem debugging"
626         depends on DEBUG_KERNEL && HIGHMEM
627         help
628           This option enables additional error checking for high memory
629           systems.  Disable for production systems.
630 
631 config HAVE_DEBUG_STACKOVERFLOW
632         bool
633 
634 config DEBUG_STACKOVERFLOW
635         bool "Check for stack overflows"
636         depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
637         ---help---
638           Say Y here if you want to check for overflows of kernel, IRQ
639           and exception stacks (if your archicture uses them). This
640           option will show detailed messages if free stack space drops
641           below a certain limit.
642 
643           These kinds of bugs usually occur when call-chains in the
644           kernel get too deep, especially when interrupts are
645           involved.
646 
647           Use this in cases where you see apparently random memory
648           corruption, especially if it appears in 'struct thread_info'
649 
650           If in doubt, say "N".
651 
652 source "lib/Kconfig.kmemcheck"
653 
654 endmenu # "Memory Debugging"
655 
656 config DEBUG_SHIRQ
657         bool "Debug shared IRQ handlers"
658         depends on DEBUG_KERNEL
659         help
660           Enable this to generate a spurious interrupt as soon as a shared
661           interrupt handler is registered, and just before one is deregistered.
662           Drivers ought to be able to handle interrupts coming in at those
663           points; some don't and need to be caught.
664 
665 menu "Debug Lockups and Hangs"
666 
667 config LOCKUP_DETECTOR
668         bool "Detect Hard and Soft Lockups"
669         depends on DEBUG_KERNEL && !S390
670         help
671           Say Y here to enable the kernel to act as a watchdog to detect
672           hard and soft lockups.
673 
674           Softlockups are bugs that cause the kernel to loop in kernel
675           mode for more than 20 seconds, without giving other tasks a
676           chance to run.  The current stack trace is displayed upon
677           detection and the system will stay locked up.
678 
679           Hardlockups are bugs that cause the CPU to loop in kernel mode
680           for more than 10 seconds, without letting other interrupts have a
681           chance to run.  The current stack trace is displayed upon detection
682           and the system will stay locked up.
683 
684           The overhead should be minimal.  A periodic hrtimer runs to
685           generate interrupts and kick the watchdog task every 4 seconds.
686           An NMI is generated every 10 seconds or so to check for hardlockups.
687 
688           The frequency of hrtimer and NMI events and the soft and hard lockup
689           thresholds can be controlled through the sysctl watchdog_thresh.
690 
691 config HARDLOCKUP_DETECTOR
692         def_bool y
693         depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
694         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
695 
696 config BOOTPARAM_HARDLOCKUP_PANIC
697         bool "Panic (Reboot) On Hard Lockups"
698         depends on HARDLOCKUP_DETECTOR
699         help
700           Say Y here to enable the kernel to panic on "hard lockups",
701           which are bugs that cause the kernel to loop in kernel
702           mode with interrupts disabled for more than 10 seconds (configurable
703           using the watchdog_thresh sysctl).
704 
705           Say N if unsure.
706 
707 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
708         int
709         depends on HARDLOCKUP_DETECTOR
710         range 0 1
711         default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
712         default 1 if BOOTPARAM_HARDLOCKUP_PANIC
713 
714 config BOOTPARAM_SOFTLOCKUP_PANIC
715         bool "Panic (Reboot) On Soft Lockups"
716         depends on LOCKUP_DETECTOR
717         help
718           Say Y here to enable the kernel to panic on "soft lockups",
719           which are bugs that cause the kernel to loop in kernel
720           mode for more than 20 seconds (configurable using the watchdog_thresh
721           sysctl), without giving other tasks a chance to run.
722 
723           The panic can be used in combination with panic_timeout,
724           to cause the system to reboot automatically after a
725           lockup has been detected. This feature is useful for
726           high-availability systems that have uptime guarantees and
727           where a lockup must be resolved ASAP.
728 
729           Say N if unsure.
730 
731 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
732         int
733         depends on LOCKUP_DETECTOR
734         range 0 1
735         default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
736         default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
737 
738 config DETECT_HUNG_TASK
739         bool "Detect Hung Tasks"
740         depends on DEBUG_KERNEL
741         default LOCKUP_DETECTOR
742         help
743           Say Y here to enable the kernel to detect "hung tasks",
744           which are bugs that cause the task to be stuck in
745           uninterruptible "D" state indefinitiley.
746 
747           When a hung task is detected, the kernel will print the
748           current stack trace (which you should report), but the
749           task will stay in uninterruptible state. If lockdep is
750           enabled then all held locks will also be reported. This
751           feature has negligible overhead.
752 
753 config DEFAULT_HUNG_TASK_TIMEOUT
754         int "Default timeout for hung task detection (in seconds)"
755         depends on DETECT_HUNG_TASK
756         default 120
757         help
758           This option controls the default timeout (in seconds) used
759           to determine when a task has become non-responsive and should
760           be considered hung.
761 
762           It can be adjusted at runtime via the kernel.hung_task_timeout_secs
763           sysctl or by writing a value to
764           /proc/sys/kernel/hung_task_timeout_secs.
765 
766           A timeout of 0 disables the check.  The default is two minutes.
767           Keeping the default should be fine in most cases.
768 
769 config BOOTPARAM_HUNG_TASK_PANIC
770         bool "Panic (Reboot) On Hung Tasks"
771         depends on DETECT_HUNG_TASK
772         help
773           Say Y here to enable the kernel to panic on "hung tasks",
774           which are bugs that cause the kernel to leave a task stuck
775           in uninterruptible "D" state.
776 
777           The panic can be used in combination with panic_timeout,
778           to cause the system to reboot automatically after a
779           hung task has been detected. This feature is useful for
780           high-availability systems that have uptime guarantees and
781           where a hung tasks must be resolved ASAP.
782 
783           Say N if unsure.
784 
785 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
786         int
787         depends on DETECT_HUNG_TASK
788         range 0 1
789         default 0 if !BOOTPARAM_HUNG_TASK_PANIC
790         default 1 if BOOTPARAM_HUNG_TASK_PANIC
791 
792 endmenu # "Debug lockups and hangs"
793 
794 config PANIC_ON_OOPS
795         bool "Panic on Oops"
796         help
797           Say Y here to enable the kernel to panic when it oopses. This
798           has the same effect as setting oops=panic on the kernel command
799           line.
800 
801           This feature is useful to ensure that the kernel does not do
802           anything erroneous after an oops which could result in data
803           corruption or other issues.
804 
805           Say N if unsure.
806 
807 config PANIC_ON_OOPS_VALUE
808         int
809         range 0 1
810         default 0 if !PANIC_ON_OOPS
811         default 1 if PANIC_ON_OOPS
812 
813 config PANIC_TIMEOUT
814         int "panic timeout"
815         default 0
816         help
817           Set the timeout value (in seconds) until a reboot occurs when the
818           the kernel panics. If n = 0, then we wait forever. A timeout
819           value n > 0 will wait n seconds before rebooting, while a timeout
820           value n < 0 will reboot immediately.
821 
822 config SCHED_DEBUG
823         bool "Collect scheduler debugging info"
824         depends on DEBUG_KERNEL && PROC_FS
825         default y
826         help
827           If you say Y here, the /proc/sched_debug file will be provided
828           that can help debug the scheduler. The runtime overhead of this
829           option is minimal.
830 
831 config SCHEDSTATS
832         bool "Collect scheduler statistics"
833         depends on DEBUG_KERNEL && PROC_FS
834         help
835           If you say Y here, additional code will be inserted into the
836           scheduler and related routines to collect statistics about
837           scheduler behavior and provide them in /proc/schedstat.  These
838           stats may be useful for both tuning and debugging the scheduler
839           If you aren't debugging the scheduler or trying to tune a specific
840           application, you can say N to avoid the very slight overhead
841           this adds.
842 
843 config SCHED_STACK_END_CHECK
844         bool "Detect stack corruption on calls to schedule()"
845         depends on DEBUG_KERNEL
846         default n
847         help
848           This option checks for a stack overrun on calls to schedule().
849           If the stack end location is found to be over written always panic as
850           the content of the corrupted region can no longer be trusted.
851           This is to ensure no erroneous behaviour occurs which could result in
852           data corruption or a sporadic crash at a later stage once the region
853           is examined. The runtime overhead introduced is minimal.
854 
855 config TIMER_STATS
856         bool "Collect kernel timers statistics"
857         depends on DEBUG_KERNEL && PROC_FS
858         help
859           If you say Y here, additional code will be inserted into the
860           timer routines to collect statistics about kernel timers being
861           reprogrammed. The statistics can be read from /proc/timer_stats.
862           The statistics collection is started by writing 1 to /proc/timer_stats,
863           writing 0 stops it. This feature is useful to collect information
864           about timer usage patterns in kernel and userspace. This feature
865           is lightweight if enabled in the kernel config but not activated
866           (it defaults to deactivated on bootup and will only be activated
867           if some application like powertop activates it explicitly).
868 
869 config DEBUG_PREEMPT
870         bool "Debug preemptible kernel"
871         depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
872         default y
873         help
874           If you say Y here then the kernel will use a debug variant of the
875           commonly used smp_processor_id() function and will print warnings
876           if kernel code uses it in a preemption-unsafe way. Also, the kernel
877           will detect preemption count underflows.
878 
879 menu "Lock Debugging (spinlocks, mutexes, etc...)"
880 
881 config DEBUG_RT_MUTEXES
882         bool "RT Mutex debugging, deadlock detection"
883         depends on DEBUG_KERNEL && RT_MUTEXES
884         help
885          This allows rt mutex semantics violations and rt mutex related
886          deadlocks (lockups) to be detected and reported automatically.
887 
888 config RT_MUTEX_TESTER
889         bool "Built-in scriptable tester for rt-mutexes"
890         depends on DEBUG_KERNEL && RT_MUTEXES && BROKEN
891         help
892           This option enables a rt-mutex tester.
893 
894 config DEBUG_SPINLOCK
895         bool "Spinlock and rw-lock debugging: basic checks"
896         depends on DEBUG_KERNEL
897         select UNINLINE_SPIN_UNLOCK
898         help
899           Say Y here and build SMP to catch missing spinlock initialization
900           and certain other kinds of spinlock errors commonly made.  This is
901           best used in conjunction with the NMI watchdog so that spinlock
902           deadlocks are also debuggable.
903 
904 config DEBUG_MUTEXES
905         bool "Mutex debugging: basic checks"
906         depends on DEBUG_KERNEL
907         help
908          This feature allows mutex semantics violations to be detected and
909          reported.
910 
911 config DEBUG_WW_MUTEX_SLOWPATH
912         bool "Wait/wound mutex debugging: Slowpath testing"
913         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
914         select DEBUG_LOCK_ALLOC
915         select DEBUG_SPINLOCK
916         select DEBUG_MUTEXES
917         help
918          This feature enables slowpath testing for w/w mutex users by
919          injecting additional -EDEADLK wound/backoff cases. Together with
920          the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
921          will test all possible w/w mutex interface abuse with the
922          exception of simply not acquiring all the required locks.
923          Note that this feature can introduce significant overhead, so
924          it really should not be enabled in a production or distro kernel,
925          even a debug kernel.  If you are a driver writer, enable it.  If
926          you are a distro, do not.
927 
928 config DEBUG_LOCK_ALLOC
929         bool "Lock debugging: detect incorrect freeing of live locks"
930         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
931         select DEBUG_SPINLOCK
932         select DEBUG_MUTEXES
933         select LOCKDEP
934         help
935          This feature will check whether any held lock (spinlock, rwlock,
936          mutex or rwsem) is incorrectly freed by the kernel, via any of the
937          memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
938          vfree(), etc.), whether a live lock is incorrectly reinitialized via
939          spin_lock_init()/mutex_init()/etc., or whether there is any lock
940          held during task exit.
941 
942 config PROVE_LOCKING
943         bool "Lock debugging: prove locking correctness"
944         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
945         select LOCKDEP
946         select DEBUG_SPINLOCK
947         select DEBUG_MUTEXES
948         select DEBUG_LOCK_ALLOC
949         select TRACE_IRQFLAGS
950         default n
951         help
952          This feature enables the kernel to prove that all locking
953          that occurs in the kernel runtime is mathematically
954          correct: that under no circumstance could an arbitrary (and
955          not yet triggered) combination of observed locking
956          sequences (on an arbitrary number of CPUs, running an
957          arbitrary number of tasks and interrupt contexts) cause a
958          deadlock.
959 
960          In short, this feature enables the kernel to report locking
961          related deadlocks before they actually occur.
962 
963          The proof does not depend on how hard and complex a
964          deadlock scenario would be to trigger: how many
965          participant CPUs, tasks and irq-contexts would be needed
966          for it to trigger. The proof also does not depend on
967          timing: if a race and a resulting deadlock is possible
968          theoretically (no matter how unlikely the race scenario
969          is), it will be proven so and will immediately be
970          reported by the kernel (once the event is observed that
971          makes the deadlock theoretically possible).
972 
973          If a deadlock is impossible (i.e. the locking rules, as
974          observed by the kernel, are mathematically correct), the
975          kernel reports nothing.
976 
977          NOTE: this feature can also be enabled for rwlocks, mutexes
978          and rwsems - in which case all dependencies between these
979          different locking variants are observed and mapped too, and
980          the proof of observed correctness is also maintained for an
981          arbitrary combination of these separate locking variants.
982 
983          For more details, see Documentation/locking/lockdep-design.txt.
984 
985 config LOCKDEP
986         bool
987         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
988         select STACKTRACE
989         select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
990         select KALLSYMS
991         select KALLSYMS_ALL
992 
993 config LOCK_STAT
994         bool "Lock usage statistics"
995         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
996         select LOCKDEP
997         select DEBUG_SPINLOCK
998         select DEBUG_MUTEXES
999         select DEBUG_LOCK_ALLOC
1000         default n
1001         help
1002          This feature enables tracking lock contention points
1003 
1004          For more details, see Documentation/locking/lockstat.txt
1005 
1006          This also enables lock events required by "perf lock",
1007          subcommand of perf.
1008          If you want to use "perf lock", you also need to turn on
1009          CONFIG_EVENT_TRACING.
1010 
1011          CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1012          (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1013 
1014 config DEBUG_LOCKDEP
1015         bool "Lock dependency engine debugging"
1016         depends on DEBUG_KERNEL && LOCKDEP
1017         help
1018           If you say Y here, the lock dependency engine will do
1019           additional runtime checks to debug itself, at the price
1020           of more runtime overhead.
1021 
1022 config DEBUG_ATOMIC_SLEEP
1023         bool "Sleep inside atomic section checking"
1024         select PREEMPT_COUNT
1025         depends on DEBUG_KERNEL
1026         help
1027           If you say Y here, various routines which may sleep will become very
1028           noisy if they are called inside atomic sections: when a spinlock is
1029           held, inside an rcu read side critical section, inside preempt disabled
1030           sections, inside an interrupt, etc...
1031 
1032 config DEBUG_LOCKING_API_SELFTESTS
1033         bool "Locking API boot-time self-tests"
1034         depends on DEBUG_KERNEL
1035         help
1036           Say Y here if you want the kernel to run a short self-test during
1037           bootup. The self-test checks whether common types of locking bugs
1038           are detected by debugging mechanisms or not. (if you disable
1039           lock debugging then those bugs wont be detected of course.)
1040           The following locking APIs are covered: spinlocks, rwlocks,
1041           mutexes and rwsems.
1042 
1043 config LOCK_TORTURE_TEST
1044         tristate "torture tests for locking"
1045         depends on DEBUG_KERNEL
1046         select TORTURE_TEST
1047         default n
1048         help
1049           This option provides a kernel module that runs torture tests
1050           on kernel locking primitives.  The kernel module may be built
1051           after the fact on the running kernel to be tested, if desired.
1052 
1053           Say Y here if you want kernel locking-primitive torture tests
1054           to be built into the kernel.
1055           Say M if you want these torture tests to build as a module.
1056           Say N if you are unsure.
1057 
1058 endmenu # lock debugging
1059 
1060 config TRACE_IRQFLAGS
1061         bool
1062         help
1063           Enables hooks to interrupt enabling and disabling for
1064           either tracing or lock debugging.
1065 
1066 config STACKTRACE
1067         bool "Stack backtrace support"
1068         depends on STACKTRACE_SUPPORT
1069         help
1070           This option causes the kernel to create a /proc/pid/stack for
1071           every process, showing its current stack trace.
1072           It is also used by various kernel debugging features that require
1073           stack trace generation.
1074 
1075 config DEBUG_KOBJECT
1076         bool "kobject debugging"
1077         depends on DEBUG_KERNEL
1078         help
1079           If you say Y here, some extra kobject debugging messages will be sent
1080           to the syslog. 
1081 
1082 config DEBUG_KOBJECT_RELEASE
1083         bool "kobject release debugging"
1084         depends on DEBUG_OBJECTS_TIMERS
1085         help
1086           kobjects are reference counted objects.  This means that their
1087           last reference count put is not predictable, and the kobject can
1088           live on past the point at which a driver decides to drop it's
1089           initial reference to the kobject gained on allocation.  An
1090           example of this would be a struct device which has just been
1091           unregistered.
1092 
1093           However, some buggy drivers assume that after such an operation,
1094           the memory backing the kobject can be immediately freed.  This
1095           goes completely against the principles of a refcounted object.
1096 
1097           If you say Y here, the kernel will delay the release of kobjects
1098           on the last reference count to improve the visibility of this
1099           kind of kobject release bug.
1100 
1101 config HAVE_DEBUG_BUGVERBOSE
1102         bool
1103 
1104 config DEBUG_BUGVERBOSE
1105         bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1106         depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1107         default y
1108         help
1109           Say Y here to make BUG() panics output the file name and line number
1110           of the BUG call as well as the EIP and oops trace.  This aids
1111           debugging but costs about 70-100K of memory.
1112 
1113 config DEBUG_LIST
1114         bool "Debug linked list manipulation"
1115         depends on DEBUG_KERNEL
1116         help
1117           Enable this to turn on extended checks in the linked-list
1118           walking routines.
1119 
1120           If unsure, say N.
1121 
1122 config DEBUG_PI_LIST
1123         bool "Debug priority linked list manipulation"
1124         depends on DEBUG_KERNEL
1125         help
1126           Enable this to turn on extended checks in the priority-ordered
1127           linked-list (plist) walking routines.  This checks the entire
1128           list multiple times during each manipulation.
1129 
1130           If unsure, say N.
1131 
1132 config DEBUG_SG
1133         bool "Debug SG table operations"
1134         depends on DEBUG_KERNEL
1135         help
1136           Enable this to turn on checks on scatter-gather tables. This can
1137           help find problems with drivers that do not properly initialize
1138           their sg tables.
1139 
1140           If unsure, say N.
1141 
1142 config DEBUG_NOTIFIERS
1143         bool "Debug notifier call chains"
1144         depends on DEBUG_KERNEL
1145         help
1146           Enable this to turn on sanity checking for notifier call chains.
1147           This is most useful for kernel developers to make sure that
1148           modules properly unregister themselves from notifier chains.
1149           This is a relatively cheap check but if you care about maximum
1150           performance, say N.
1151 
1152 config DEBUG_CREDENTIALS
1153         bool "Debug credential management"
1154         depends on DEBUG_KERNEL
1155         help
1156           Enable this to turn on some debug checking for credential
1157           management.  The additional code keeps track of the number of
1158           pointers from task_structs to any given cred struct, and checks to
1159           see that this number never exceeds the usage count of the cred
1160           struct.
1161 
1162           Furthermore, if SELinux is enabled, this also checks that the
1163           security pointer in the cred struct is never seen to be invalid.
1164 
1165           If unsure, say N.
1166 
1167 menu "RCU Debugging"
1168 
1169 config PROVE_RCU
1170         bool "RCU debugging: prove RCU correctness"
1171         depends on PROVE_LOCKING
1172         default n
1173         help
1174          This feature enables lockdep extensions that check for correct
1175          use of RCU APIs.  This is currently under development.  Say Y
1176          if you want to debug RCU usage or help work on the PROVE_RCU
1177          feature.
1178 
1179          Say N if you are unsure.
1180 
1181 config PROVE_RCU_REPEATEDLY
1182         bool "RCU debugging: don't disable PROVE_RCU on first splat"
1183         depends on PROVE_RCU
1184         default n
1185         help
1186          By itself, PROVE_RCU will disable checking upon issuing the
1187          first warning (or "splat").  This feature prevents such
1188          disabling, allowing multiple RCU-lockdep warnings to be printed
1189          on a single reboot.
1190 
1191          Say Y to allow multiple RCU-lockdep warnings per boot.
1192 
1193          Say N if you are unsure.
1194 
1195 config SPARSE_RCU_POINTER
1196         bool "RCU debugging: sparse-based checks for pointer usage"
1197         default n
1198         help
1199          This feature enables the __rcu sparse annotation for
1200          RCU-protected pointers.  This annotation will cause sparse
1201          to flag any non-RCU used of annotated pointers.  This can be
1202          helpful when debugging RCU usage.  Please note that this feature
1203          is not intended to enforce code cleanliness; it is instead merely
1204          a debugging aid.
1205 
1206          Say Y to make sparse flag questionable use of RCU-protected pointers
1207 
1208          Say N if you are unsure.
1209 
1210 config TORTURE_TEST
1211         tristate
1212         default n
1213 
1214 config RCU_TORTURE_TEST
1215         tristate "torture tests for RCU"
1216         depends on DEBUG_KERNEL
1217         select TORTURE_TEST
1218         default n
1219         help
1220           This option provides a kernel module that runs torture tests
1221           on the RCU infrastructure.  The kernel module may be built
1222           after the fact on the running kernel to be tested, if desired.
1223 
1224           Say Y here if you want RCU torture tests to be built into
1225           the kernel.
1226           Say M if you want the RCU torture tests to build as a module.
1227           Say N if you are unsure.
1228 
1229 config RCU_TORTURE_TEST_RUNNABLE
1230         bool "torture tests for RCU runnable by default"
1231         depends on RCU_TORTURE_TEST = y
1232         default n
1233         help
1234           This option provides a way to build the RCU torture tests
1235           directly into the kernel without them starting up at boot
1236           time.  You can use /proc/sys/kernel/rcutorture_runnable
1237           to manually override this setting.  This /proc file is
1238           available only when the RCU torture tests have been built
1239           into the kernel.
1240 
1241           Say Y here if you want the RCU torture tests to start during
1242           boot (you probably don't).
1243           Say N here if you want the RCU torture tests to start only
1244           after being manually enabled via /proc.
1245 
1246 config RCU_CPU_STALL_TIMEOUT
1247         int "RCU CPU stall timeout in seconds"
1248         depends on RCU_STALL_COMMON
1249         range 3 300
1250         default 21
1251         help
1252           If a given RCU grace period extends more than the specified
1253           number of seconds, a CPU stall warning is printed.  If the
1254           RCU grace period persists, additional CPU stall warnings are
1255           printed at more widely spaced intervals.
1256 
1257 config RCU_CPU_STALL_INFO
1258         bool "Print additional diagnostics on RCU CPU stall"
1259         depends on (TREE_RCU || PREEMPT_RCU) && DEBUG_KERNEL
1260         default n
1261         help
1262           For each stalled CPU that is aware of the current RCU grace
1263           period, print out additional per-CPU diagnostic information
1264           regarding scheduling-clock ticks, idle state, and,
1265           for RCU_FAST_NO_HZ kernels, idle-entry state.
1266 
1267           Say N if you are unsure.
1268 
1269           Say Y if you want to enable such diagnostics.
1270 
1271 config RCU_TRACE
1272         bool "Enable tracing for RCU"
1273         depends on DEBUG_KERNEL
1274         select TRACE_CLOCK
1275         help
1276           This option provides tracing in RCU which presents stats
1277           in debugfs for debugging RCU implementation.
1278 
1279           Say Y here if you want to enable RCU tracing
1280           Say N if you are unsure.
1281 
1282 endmenu # "RCU Debugging"
1283 
1284 config DEBUG_BLOCK_EXT_DEVT
1285         bool "Force extended block device numbers and spread them"
1286         depends on DEBUG_KERNEL
1287         depends on BLOCK
1288         default n
1289         help
1290           BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1291           SOME DISTRIBUTIONS.  DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1292           YOU ARE DOING.  Distros, please enable this and fix whatever
1293           is broken.
1294 
1295           Conventionally, block device numbers are allocated from
1296           predetermined contiguous area.  However, extended block area
1297           may introduce non-contiguous block device numbers.  This
1298           option forces most block device numbers to be allocated from
1299           the extended space and spreads them to discover kernel or
1300           userland code paths which assume predetermined contiguous
1301           device number allocation.
1302 
1303           Note that turning on this debug option shuffles all the
1304           device numbers for all IDE and SCSI devices including libata
1305           ones, so root partition specified using device number
1306           directly (via rdev or root=MAJ:MIN) won't work anymore.
1307           Textual device names (root=/dev/sdXn) will continue to work.
1308 
1309           Say N if you are unsure.
1310 
1311 config NOTIFIER_ERROR_INJECTION
1312         tristate "Notifier error injection"
1313         depends on DEBUG_KERNEL
1314         select DEBUG_FS
1315         help
1316           This option provides the ability to inject artificial errors to
1317           specified notifier chain callbacks. It is useful to test the error
1318           handling of notifier call chain failures.
1319 
1320           Say N if unsure.
1321 
1322 config CPU_NOTIFIER_ERROR_INJECT
1323         tristate "CPU notifier error injection module"
1324         depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1325         help
1326           This option provides a kernel module that can be used to test
1327           the error handling of the cpu notifiers by injecting artificial
1328           errors to CPU notifier chain callbacks.  It is controlled through
1329           debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
1330 
1331           If the notifier call chain should be failed with some events
1332           notified, write the error code to "actions/<notifier event>/error".
1333 
1334           Example: Inject CPU offline error (-1 == -EPERM)
1335 
1336           # cd /sys/kernel/debug/notifier-error-inject/cpu
1337           # echo -1 > actions/CPU_DOWN_PREPARE/error
1338           # echo 0 > /sys/devices/system/cpu/cpu1/online
1339           bash: echo: write error: Operation not permitted
1340 
1341           To compile this code as a module, choose M here: the module will
1342           be called cpu-notifier-error-inject.
1343 
1344           If unsure, say N.
1345 
1346 config PM_NOTIFIER_ERROR_INJECT
1347         tristate "PM notifier error injection module"
1348         depends on PM && NOTIFIER_ERROR_INJECTION
1349         default m if PM_DEBUG
1350         help
1351           This option provides the ability to inject artificial errors to
1352           PM notifier chain callbacks.  It is controlled through debugfs
1353           interface /sys/kernel/debug/notifier-error-inject/pm
1354 
1355           If the notifier call chain should be failed with some events
1356           notified, write the error code to "actions/<notifier event>/error".
1357 
1358           Example: Inject PM suspend error (-12 = -ENOMEM)
1359 
1360           # cd /sys/kernel/debug/notifier-error-inject/pm/
1361           # echo -12 > actions/PM_SUSPEND_PREPARE/error
1362           # echo mem > /sys/power/state
1363           bash: echo: write error: Cannot allocate memory
1364 
1365           To compile this code as a module, choose M here: the module will
1366           be called pm-notifier-error-inject.
1367 
1368           If unsure, say N.
1369 
1370 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1371         tristate "OF reconfig notifier error injection module"
1372         depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1373         help
1374           This option provides the ability to inject artificial errors to
1375           OF reconfig notifier chain callbacks.  It is controlled
1376           through debugfs interface under
1377           /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1378 
1379           If the notifier call chain should be failed with some events
1380           notified, write the error code to "actions/<notifier event>/error".
1381 
1382           To compile this code as a module, choose M here: the module will
1383           be called of-reconfig-notifier-error-inject.
1384 
1385           If unsure, say N.
1386 
1387 config FAULT_INJECTION
1388         bool "Fault-injection framework"
1389         depends on DEBUG_KERNEL
1390         help
1391           Provide fault-injection framework.
1392           For more details, see Documentation/fault-injection/.
1393 
1394 config FAILSLAB
1395         bool "Fault-injection capability for kmalloc"
1396         depends on FAULT_INJECTION
1397         depends on SLAB || SLUB
1398         help
1399           Provide fault-injection capability for kmalloc.
1400 
1401 config FAIL_PAGE_ALLOC
1402         bool "Fault-injection capabilitiy for alloc_pages()"
1403         depends on FAULT_INJECTION
1404         help
1405           Provide fault-injection capability for alloc_pages().
1406 
1407 config FAIL_MAKE_REQUEST
1408         bool "Fault-injection capability for disk IO"
1409         depends on FAULT_INJECTION && BLOCK
1410         help
1411           Provide fault-injection capability for disk IO.
1412 
1413 config FAIL_IO_TIMEOUT
1414         bool "Fault-injection capability for faking disk interrupts"
1415         depends on FAULT_INJECTION && BLOCK
1416         help
1417           Provide fault-injection capability on end IO handling. This
1418           will make the block layer "forget" an interrupt as configured,
1419           thus exercising the error handling.
1420 
1421           Only works with drivers that use the generic timeout handling,
1422           for others it wont do anything.
1423 
1424 config FAIL_MMC_REQUEST
1425         bool "Fault-injection capability for MMC IO"
1426         select DEBUG_FS
1427         depends on FAULT_INJECTION && MMC
1428         help
1429           Provide fault-injection capability for MMC IO.
1430           This will make the mmc core return data errors. This is
1431           useful to test the error handling in the mmc block device
1432           and to test how the mmc host driver handles retries from
1433           the block device.
1434 
1435 config FAULT_INJECTION_DEBUG_FS
1436         bool "Debugfs entries for fault-injection capabilities"
1437         depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1438         help
1439           Enable configuration of fault-injection capabilities via debugfs.
1440 
1441 config FAULT_INJECTION_STACKTRACE_FILTER
1442         bool "stacktrace filter for fault-injection capabilities"
1443         depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1444         depends on !X86_64
1445         select STACKTRACE
1446         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1447         help
1448           Provide stacktrace filter for fault-injection capabilities
1449 
1450 config LATENCYTOP
1451         bool "Latency measuring infrastructure"
1452         depends on HAVE_LATENCYTOP_SUPPORT
1453         depends on DEBUG_KERNEL
1454         depends on STACKTRACE_SUPPORT
1455         depends on PROC_FS
1456         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1457         select KALLSYMS
1458         select KALLSYMS_ALL
1459         select STACKTRACE
1460         select SCHEDSTATS
1461         select SCHED_DEBUG
1462         help
1463           Enable this option if you want to use the LatencyTOP tool
1464           to find out which userspace is blocking on what kernel operations.
1465 
1466 config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1467         bool
1468 
1469 config DEBUG_STRICT_USER_COPY_CHECKS
1470         bool "Strict user copy size checks"
1471         depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1472         depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
1473         help
1474           Enabling this option turns a certain set of sanity checks for user
1475           copy operations into compile time failures.
1476 
1477           The copy_from_user() etc checks are there to help test if there
1478           are sufficient security checks on the length argument of
1479           the copy operation, by having gcc prove that the argument is
1480           within bounds.
1481 
1482           If unsure, say N.
1483 
1484 source kernel/trace/Kconfig
1485 
1486 menu "Runtime Testing"
1487 
1488 config LKDTM
1489         tristate "Linux Kernel Dump Test Tool Module"
1490         depends on DEBUG_FS
1491         depends on BLOCK
1492         default n
1493         help
1494         This module enables testing of the different dumping mechanisms by
1495         inducing system failures at predefined crash points.
1496         If you don't need it: say N
1497         Choose M here to compile this code as a module. The module will be
1498         called lkdtm.
1499 
1500         Documentation on how to use the module can be found in
1501         Documentation/fault-injection/provoke-crashes.txt
1502 
1503 config TEST_LIST_SORT
1504         bool "Linked list sorting test"
1505         depends on DEBUG_KERNEL
1506         help
1507           Enable this to turn on 'list_sort()' function test. This test is
1508           executed only once during system boot, so affects only boot time.
1509 
1510           If unsure, say N.
1511 
1512 config KPROBES_SANITY_TEST
1513         bool "Kprobes sanity tests"
1514         depends on DEBUG_KERNEL
1515         depends on KPROBES
1516         default n
1517         help
1518           This option provides for testing basic kprobes functionality on
1519           boot. A sample kprobe, jprobe and kretprobe are inserted and
1520           verified for functionality.
1521 
1522           Say N if you are unsure.
1523 
1524 config BACKTRACE_SELF_TEST
1525         tristate "Self test for the backtrace code"
1526         depends on DEBUG_KERNEL
1527         default n
1528         help
1529           This option provides a kernel module that can be used to test
1530           the kernel stack backtrace code. This option is not useful
1531           for distributions or general kernels, but only for kernel
1532           developers working on architecture code.
1533 
1534           Note that if you want to also test saved backtraces, you will
1535           have to enable STACKTRACE as well.
1536 
1537           Say N if you are unsure.
1538 
1539 config RBTREE_TEST
1540         tristate "Red-Black tree test"
1541         depends on DEBUG_KERNEL
1542         help
1543           A benchmark measuring the performance of the rbtree library.
1544           Also includes rbtree invariant checks.
1545 
1546 config INTERVAL_TREE_TEST
1547         tristate "Interval tree test"
1548         depends on m && DEBUG_KERNEL
1549         select INTERVAL_TREE
1550         help
1551           A benchmark measuring the performance of the interval tree library
1552 
1553 config PERCPU_TEST
1554         tristate "Per cpu operations test"
1555         depends on m && DEBUG_KERNEL
1556         help
1557           Enable this option to build test module which validates per-cpu
1558           operations.
1559 
1560           If unsure, say N.
1561 
1562 config ATOMIC64_SELFTEST
1563         bool "Perform an atomic64_t self-test at boot"
1564         help
1565           Enable this option to test the atomic64_t functions at boot.
1566 
1567           If unsure, say N.
1568 
1569 config ASYNC_RAID6_TEST
1570         tristate "Self test for hardware accelerated raid6 recovery"
1571         depends on ASYNC_RAID6_RECOV
1572         select ASYNC_MEMCPY
1573         ---help---
1574           This is a one-shot self test that permutes through the
1575           recovery of all the possible two disk failure scenarios for a
1576           N-disk array.  Recovery is performed with the asynchronous
1577           raid6 recovery routines, and will optionally use an offload
1578           engine if one is available.
1579 
1580           If unsure, say N.
1581 
1582 config TEST_STRING_HELPERS
1583         tristate "Test functions located in the string_helpers module at runtime"
1584 
1585 config TEST_KSTRTOX
1586         tristate "Test kstrto*() family of functions at runtime"
1587 
1588 config TEST_RHASHTABLE
1589         bool "Perform selftest on resizable hash table"
1590         default n
1591         help
1592           Enable this option to test the rhashtable functions at boot.
1593 
1594           If unsure, say N.
1595 
1596 endmenu # runtime tests
1597 
1598 config PROVIDE_OHCI1394_DMA_INIT
1599         bool "Remote debugging over FireWire early on boot"
1600         depends on PCI && X86
1601         help
1602           If you want to debug problems which hang or crash the kernel early
1603           on boot and the crashing machine has a FireWire port, you can use
1604           this feature to remotely access the memory of the crashed machine
1605           over FireWire. This employs remote DMA as part of the OHCI1394
1606           specification which is now the standard for FireWire controllers.
1607 
1608           With remote DMA, you can monitor the printk buffer remotely using
1609           firescope and access all memory below 4GB using fireproxy from gdb.
1610           Even controlling a kernel debugger is possible using remote DMA.
1611 
1612           Usage:
1613 
1614           If ohci1394_dma=early is used as boot parameter, it will initialize
1615           all OHCI1394 controllers which are found in the PCI config space.
1616 
1617           As all changes to the FireWire bus such as enabling and disabling
1618           devices cause a bus reset and thereby disable remote DMA for all
1619           devices, be sure to have the cable plugged and FireWire enabled on
1620           the debugging host before booting the debug target for debugging.
1621 
1622           This code (~1k) is freed after boot. By then, the firewire stack
1623           in charge of the OHCI-1394 controllers should be used instead.
1624 
1625           See Documentation/debugging-via-ohci1394.txt for more information.
1626 
1627 config BUILD_DOCSRC
1628         bool "Build targets in Documentation/ tree"
1629         depends on HEADERS_CHECK
1630         help
1631           This option attempts to build objects from the source files in the
1632           kernel Documentation/ tree.
1633 
1634           Say N if you are unsure.
1635 
1636 config DMA_API_DEBUG
1637         bool "Enable debugging of DMA-API usage"
1638         depends on HAVE_DMA_API_DEBUG
1639         help
1640           Enable this option to debug the use of the DMA API by device drivers.
1641           With this option you will be able to detect common bugs in device
1642           drivers like double-freeing of DMA mappings or freeing mappings that
1643           were never allocated.
1644 
1645           This also attempts to catch cases where a page owned by DMA is
1646           accessed by the cpu in a way that could cause data corruption.  For
1647           example, this enables cow_user_page() to check that the source page is
1648           not undergoing DMA.
1649 
1650           This option causes a performance degradation.  Use only if you want to
1651           debug device drivers and dma interactions.
1652 
1653           If unsure, say N.
1654 
1655 config TEST_LKM
1656         tristate "Test module loading with 'hello world' module"
1657         default n
1658         depends on m
1659         help
1660           This builds the "test_module" module that emits "Hello, world"
1661           on printk when loaded. It is designed to be used for basic
1662           evaluation of the module loading subsystem (for example when
1663           validating module verification). It lacks any extra dependencies,
1664           and will not normally be loaded by the system unless explicitly
1665           requested by name.
1666 
1667           If unsure, say N.
1668 
1669 config TEST_USER_COPY
1670         tristate "Test user/kernel boundary protections"
1671         default n
1672         depends on m
1673         help
1674           This builds the "test_user_copy" module that runs sanity checks
1675           on the copy_to/from_user infrastructure, making sure basic
1676           user/kernel boundary testing is working. If it fails to load,
1677           a regression has been detected in the user/kernel memory boundary
1678           protections.
1679 
1680           If unsure, say N.
1681 
1682 config TEST_BPF
1683         tristate "Test BPF filter functionality"
1684         default n
1685         depends on m && NET
1686         help
1687           This builds the "test_bpf" module that runs various test vectors
1688           against the BPF interpreter or BPF JIT compiler depending on the
1689           current setting. This is in particular useful for BPF JIT compiler
1690           development, but also to run regression tests against changes in
1691           the interpreter code. It also enables test stubs for eBPF maps and
1692           verifier used by user space verifier testsuite.
1693 
1694           If unsure, say N.
1695 
1696 config TEST_FIRMWARE
1697         tristate "Test firmware loading via userspace interface"
1698         default n
1699         depends on FW_LOADER
1700         help
1701           This builds the "test_firmware" module that creates a userspace
1702           interface for testing firmware loading. This can be used to
1703           control the triggering of firmware loading without needing an
1704           actual firmware-using device. The contents can be rechecked by
1705           userspace.
1706 
1707           If unsure, say N.
1708 
1709 config TEST_UDELAY
1710         tristate "udelay test driver"
1711         default n
1712         help
1713           This builds the "udelay_test" module that helps to make sure
1714           that udelay() is working properly.
1715 
1716           If unsure, say N.
1717 
1718 source "samples/Kconfig"
1719 
1720 source "lib/Kconfig.kgdb"
1721 

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