Version:  2.0.40 2.2.26 2.4.37 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 3.17 3.18

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

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