Version:  2.0.40 2.2.26 2.4.37 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4

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 GDB_SCRIPTS
171         bool "Provide GDB scripts for kernel debugging"
172         depends on DEBUG_INFO
173         help
174           This creates the required links to GDB helper scripts in the
175           build directory. If you load vmlinux into gdb, the helper
176           scripts will be automatically imported by gdb as well, and
177           additional functions are available to analyze a Linux kernel
178           instance. See Documentation/gdb-kernel-debugging.txt for further
179           details.
180 
181 config ENABLE_WARN_DEPRECATED
182         bool "Enable __deprecated logic"
183         default y
184         help
185           Enable the __deprecated logic in the kernel build.
186           Disable this to suppress the "warning: 'foo' is deprecated
187           (declared at kernel/power/somefile.c:1234)" messages.
188 
189 config ENABLE_MUST_CHECK
190         bool "Enable __must_check logic"
191         default y
192         help
193           Enable the __must_check logic in the kernel build.  Disable this to
194           suppress the "warning: ignoring return value of 'foo', declared with
195           attribute warn_unused_result" messages.
196 
197 config FRAME_WARN
198         int "Warn for stack frames larger than (needs gcc 4.4)"
199         range 0 8192
200         default 0 if KASAN
201         default 1024 if !64BIT
202         default 2048 if 64BIT
203         help
204           Tell gcc to warn at build time for stack frames larger than this.
205           Setting this too low will cause a lot of warnings.
206           Setting it to 0 disables the warning.
207           Requires gcc 4.4
208 
209 config STRIP_ASM_SYMS
210         bool "Strip assembler-generated symbols during link"
211         default n
212         help
213           Strip internal assembler-generated symbols during a link (symbols
214           that look like '.Lxxx') so they don't pollute the output of
215           get_wchan() and suchlike.
216 
217 config READABLE_ASM
218         bool "Generate readable assembler code"
219         depends on DEBUG_KERNEL
220         help
221           Disable some compiler optimizations that tend to generate human unreadable
222           assembler output. This may make the kernel slightly slower, but it helps
223           to keep kernel developers who have to stare a lot at assembler listings
224           sane.
225 
226 config UNUSED_SYMBOLS
227         bool "Enable unused/obsolete exported symbols"
228         default y if X86
229         help
230           Unused but exported symbols make the kernel needlessly bigger.  For
231           that reason most of these unused exports will soon be removed.  This
232           option is provided temporarily to provide a transition period in case
233           some external kernel module needs one of these symbols anyway. If you
234           encounter such a case in your module, consider if you are actually
235           using the right API.  (rationale: since nobody in the kernel is using
236           this in a module, there is a pretty good chance it's actually the
237           wrong interface to use).  If you really need the symbol, please send a
238           mail to the linux kernel mailing list mentioning the symbol and why
239           you really need it, and what the merge plan to the mainline kernel for
240           your module is.
241 
242 config PAGE_OWNER
243         bool "Track page owner"
244         depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
245         select DEBUG_FS
246         select STACKTRACE
247         select PAGE_EXTENSION
248         help
249           This keeps track of what call chain is the owner of a page, may
250           help to find bare alloc_page(s) leaks. Even if you include this
251           feature on your build, it is disabled in default. You should pass
252           "page_owner=on" to boot parameter in order to enable it. Eats
253           a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
254           for user-space helper.
255 
256           If unsure, say N.
257 
258 config DEBUG_FS
259         bool "Debug Filesystem"
260         help
261           debugfs is a virtual file system that kernel developers use to put
262           debugging files into.  Enable this option to be able to read and
263           write to these files.
264 
265           For detailed documentation on the debugfs API, see
266           Documentation/DocBook/filesystems.
267 
268           If unsure, say N.
269 
270 config HEADERS_CHECK
271         bool "Run 'make headers_check' when building vmlinux"
272         depends on !UML
273         help
274           This option will extract the user-visible kernel headers whenever
275           building the kernel, and will run basic sanity checks on them to
276           ensure that exported files do not attempt to include files which
277           were not exported, etc.
278 
279           If you're making modifications to header files which are
280           relevant for userspace, say 'Y', and check the headers
281           exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
282           your build tree), to make sure they're suitable.
283 
284 config DEBUG_SECTION_MISMATCH
285         bool "Enable full Section mismatch analysis"
286         help
287           The section mismatch analysis checks if there are illegal
288           references from one section to another section.
289           During linktime or runtime, some sections are dropped;
290           any use of code/data previously in these sections would
291           most likely result in an oops.
292           In the code, functions and variables are annotated with
293           __init,, etc. (see the full list in include/linux/init.h),
294           which results in the code/data being placed in specific sections.
295           The section mismatch analysis is always performed after a full
296           kernel build, and enabling this option causes the following
297           additional steps to occur:
298           - Add the option -fno-inline-functions-called-once to gcc commands.
299             When inlining a function annotated with __init in a non-init
300             function, we would lose the section information and thus
301             the analysis would not catch the illegal reference.
302             This option tells gcc to inline less (but it does result in
303             a larger kernel).
304           - Run the section mismatch analysis for each module/built-in.o file.
305             When we run the section mismatch analysis on vmlinux.o, we
306             lose valueble information about where the mismatch was
307             introduced.
308             Running the analysis for each module/built-in.o file
309             tells where the mismatch happens much closer to the
310             source. The drawback is that the same mismatch is
311             reported at least twice.
312           - Enable verbose reporting from modpost in order to help resolve
313             the section mismatches that are reported.
314 
315 config SECTION_MISMATCH_WARN_ONLY
316         bool "Make section mismatch errors non-fatal"
317         default y
318         help
319           If you say N here, the build process will fail if there are any
320           section mismatch, instead of just throwing warnings.
321 
322           If unsure, say Y.
323 
324 #
325 # Select this config option from the architecture Kconfig, if it
326 # is preferred to always offer frame pointers as a config
327 # option on the architecture (regardless of KERNEL_DEBUG):
328 #
329 config ARCH_WANT_FRAME_POINTERS
330         bool
331         help
332 
333 config FRAME_POINTER
334         bool "Compile the kernel with frame pointers"
335         depends on DEBUG_KERNEL && \
336                 (CRIS || M68K || FRV || UML || \
337                  AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \
338                 ARCH_WANT_FRAME_POINTERS
339         default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
340         help
341           If you say Y here the resulting kernel image will be slightly
342           larger and slower, but it gives very useful debugging information
343           in case of kernel bugs. (precise oopses/stacktraces/warnings)
344 
345 config DEBUG_FORCE_WEAK_PER_CPU
346         bool "Force weak per-cpu definitions"
347         depends on DEBUG_KERNEL
348         help
349           s390 and alpha require percpu variables in modules to be
350           defined weak to work around addressing range issue which
351           puts the following two restrictions on percpu variable
352           definitions.
353 
354           1. percpu symbols must be unique whether static or not
355           2. percpu variables can't be defined inside a function
356 
357           To ensure that generic code follows the above rules, this
358           option forces all percpu variables to be defined as weak.
359 
360 endmenu # "Compiler options"
361 
362 config MAGIC_SYSRQ
363         bool "Magic SysRq key"
364         depends on !UML
365         help
366           If you say Y here, you will have some control over the system even
367           if the system crashes for example during kernel debugging (e.g., you
368           will be able to flush the buffer cache to disk, reboot the system
369           immediately or dump some status information). This is accomplished
370           by pressing various keys while holding SysRq (Alt+PrintScreen). It
371           also works on a serial console (on PC hardware at least), if you
372           send a BREAK and then within 5 seconds a command keypress. The
373           keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
374           unless you really know what this hack does.
375 
376 config MAGIC_SYSRQ_DEFAULT_ENABLE
377         hex "Enable magic SysRq key functions by default"
378         depends on MAGIC_SYSRQ
379         default 0x1
380         help
381           Specifies which SysRq key functions are enabled by default.
382           This may be set to 1 or 0 to enable or disable them all, or
383           to a bitmask as described in Documentation/sysrq.txt.
384 
385 config DEBUG_KERNEL
386         bool "Kernel debugging"
387         help
388           Say Y here if you are developing drivers or trying to debug and
389           identify kernel problems.
390 
391 menu "Memory Debugging"
392 
393 source mm/Kconfig.debug
394 
395 config DEBUG_OBJECTS
396         bool "Debug object operations"
397         depends on DEBUG_KERNEL
398         help
399           If you say Y here, additional code will be inserted into the
400           kernel to track the life time of various objects and validate
401           the operations on those objects.
402 
403 config DEBUG_OBJECTS_SELFTEST
404         bool "Debug objects selftest"
405         depends on DEBUG_OBJECTS
406         help
407           This enables the selftest of the object debug code.
408 
409 config DEBUG_OBJECTS_FREE
410         bool "Debug objects in freed memory"
411         depends on DEBUG_OBJECTS
412         help
413           This enables checks whether a k/v free operation frees an area
414           which contains an object which has not been deactivated
415           properly. This can make kmalloc/kfree-intensive workloads
416           much slower.
417 
418 config DEBUG_OBJECTS_TIMERS
419         bool "Debug timer objects"
420         depends on DEBUG_OBJECTS
421         help
422           If you say Y here, additional code will be inserted into the
423           timer routines to track the life time of timer objects and
424           validate the timer operations.
425 
426 config DEBUG_OBJECTS_WORK
427         bool "Debug work objects"
428         depends on DEBUG_OBJECTS
429         help
430           If you say Y here, additional code will be inserted into the
431           work queue routines to track the life time of work objects and
432           validate the work operations.
433 
434 config DEBUG_OBJECTS_RCU_HEAD
435         bool "Debug RCU callbacks objects"
436         depends on DEBUG_OBJECTS
437         help
438           Enable this to turn on debugging of RCU list heads (call_rcu() usage).
439 
440 config DEBUG_OBJECTS_PERCPU_COUNTER
441         bool "Debug percpu counter objects"
442         depends on DEBUG_OBJECTS
443         help
444           If you say Y here, additional code will be inserted into the
445           percpu counter routines to track the life time of percpu counter
446           objects and validate the percpu counter operations.
447 
448 config DEBUG_OBJECTS_ENABLE_DEFAULT
449         int "debug_objects bootup default value (0-1)"
450         range 0 1
451         default "1"
452         depends on DEBUG_OBJECTS
453         help
454           Debug objects boot parameter default value
455 
456 config DEBUG_SLAB
457         bool "Debug slab memory allocations"
458         depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
459         help
460           Say Y here to have the kernel do limited verification on memory
461           allocation as well as poisoning memory on free to catch use of freed
462           memory. This can make kmalloc/kfree-intensive workloads much slower.
463 
464 config DEBUG_SLAB_LEAK
465         bool "Memory leak debugging"
466         depends on DEBUG_SLAB
467 
468 config SLUB_DEBUG_ON
469         bool "SLUB debugging on by default"
470         depends on SLUB && SLUB_DEBUG && !KMEMCHECK
471         default n
472         help
473           Boot with debugging on by default. SLUB boots by default with
474           the runtime debug capabilities switched off. Enabling this is
475           equivalent to specifying the "slub_debug" parameter on boot.
476           There is no support for more fine grained debug control like
477           possible with slub_debug=xxx. SLUB debugging may be switched
478           off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
479           "slub_debug=-".
480 
481 config SLUB_STATS
482         default n
483         bool "Enable SLUB performance statistics"
484         depends on SLUB && SYSFS
485         help
486           SLUB statistics are useful to debug SLUBs allocation behavior in
487           order find ways to optimize the allocator. This should never be
488           enabled for production use since keeping statistics slows down
489           the allocator by a few percentage points. The slabinfo command
490           supports the determination of the most active slabs to figure
491           out which slabs are relevant to a particular load.
492           Try running: slabinfo -DA
493 
494 config HAVE_DEBUG_KMEMLEAK
495         bool
496 
497 config DEBUG_KMEMLEAK
498         bool "Kernel memory leak detector"
499         depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
500         select DEBUG_FS
501         select STACKTRACE if STACKTRACE_SUPPORT
502         select KALLSYMS
503         select CRC32
504         help
505           Say Y here if you want to enable the memory leak
506           detector. The memory allocation/freeing is traced in a way
507           similar to the Boehm's conservative garbage collector, the
508           difference being that the orphan objects are not freed but
509           only shown in /sys/kernel/debug/kmemleak. Enabling this
510           feature will introduce an overhead to memory
511           allocations. See Documentation/kmemleak.txt for more
512           details.
513 
514           Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
515           of finding leaks due to the slab objects poisoning.
516 
517           In order to access the kmemleak file, debugfs needs to be
518           mounted (usually at /sys/kernel/debug).
519 
520 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
521         int "Maximum kmemleak early log entries"
522         depends on DEBUG_KMEMLEAK
523         range 200 40000
524         default 400
525         help
526           Kmemleak must track all the memory allocations to avoid
527           reporting false positives. Since memory may be allocated or
528           freed before kmemleak is initialised, an early log buffer is
529           used to store these actions. If kmemleak reports "early log
530           buffer exceeded", please increase this value.
531 
532 config DEBUG_KMEMLEAK_TEST
533         tristate "Simple test for the kernel memory leak detector"
534         depends on DEBUG_KMEMLEAK && m
535         help
536           This option enables a module that explicitly leaks memory.
537 
538           If unsure, say N.
539 
540 config DEBUG_KMEMLEAK_DEFAULT_OFF
541         bool "Default kmemleak to off"
542         depends on DEBUG_KMEMLEAK
543         help
544           Say Y here to disable kmemleak by default. It can then be enabled
545           on the command line via kmemleak=on.
546 
547 config DEBUG_STACK_USAGE
548         bool "Stack utilization instrumentation"
549         depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAG
550         help
551           Enables the display of the minimum amount of free stack which each
552           task has ever had available in the sysrq-T and sysrq-P debug output.
553 
554           This option will slow down process creation somewhat.
555 
556 config DEBUG_VM
557         bool "Debug VM"
558         depends on DEBUG_KERNEL
559         help
560           Enable this to turn on extended checks in the virtual-memory system
561           that may impact performance.
562 
563           If unsure, say N.
564 
565 config DEBUG_VM_VMACACHE
566         bool "Debug VMA caching"
567         depends on DEBUG_VM
568         help
569           Enable this to turn on VMA caching debug information. Doing so
570           can cause significant overhead, so only enable it in non-production
571           environments.
572 
573           If unsure, say N.
574 
575 config DEBUG_VM_RB
576         bool "Debug VM red-black trees"
577         depends on DEBUG_VM
578         help
579           Enable VM red-black tree debugging information and extra validations.
580 
581           If unsure, say N.
582 
583 config DEBUG_VIRTUAL
584         bool "Debug VM translations"
585         depends on DEBUG_KERNEL && X86
586         help
587           Enable some costly sanity checks in virtual to page code. This can
588           catch mistakes with virt_to_page() and friends.
589 
590           If unsure, say N.
591 
592 config DEBUG_NOMMU_REGIONS
593         bool "Debug the global anon/private NOMMU mapping region tree"
594         depends on DEBUG_KERNEL && !MMU
595         help
596           This option causes the global tree of anonymous and private mapping
597           regions to be regularly checked for invalid topology.
598 
599 config DEBUG_MEMORY_INIT
600         bool "Debug memory initialisation" if EXPERT
601         default !EXPERT
602         help
603           Enable this for additional checks during memory initialisation.
604           The sanity checks verify aspects of the VM such as the memory model
605           and other information provided by the architecture. Verbose
606           information will be printed at KERN_DEBUG loglevel depending
607           on the mminit_loglevel= command-line option.
608 
609           If unsure, say Y
610 
611 config MEMORY_NOTIFIER_ERROR_INJECT
612         tristate "Memory hotplug notifier error injection module"
613         depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
614         help
615           This option provides the ability to inject artificial errors to
616           memory hotplug notifier chain callbacks.  It is controlled through
617           debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
618 
619           If the notifier call chain should be failed with some events
620           notified, write the error code to "actions/<notifier event>/error".
621 
622           Example: Inject memory hotplug offline error (-12 == -ENOMEM)
623 
624           # cd /sys/kernel/debug/notifier-error-inject/memory
625           # echo -12 > actions/MEM_GOING_OFFLINE/error
626           # echo offline > /sys/devices/system/memory/memoryXXX/state
627           bash: echo: write error: Cannot allocate memory
628 
629           To compile this code as a module, choose M here: the module will
630           be called memory-notifier-error-inject.
631 
632           If unsure, say N.
633 
634 config DEBUG_PER_CPU_MAPS
635         bool "Debug access to per_cpu maps"
636         depends on DEBUG_KERNEL
637         depends on SMP
638         help
639           Say Y to verify that the per_cpu map being accessed has
640           been set up. This adds a fair amount of code to kernel memory
641           and decreases performance.
642 
643           Say N if unsure.
644 
645 config DEBUG_HIGHMEM
646         bool "Highmem debugging"
647         depends on DEBUG_KERNEL && HIGHMEM
648         help
649           This option enables additional error checking for high memory
650           systems.  Disable for production systems.
651 
652 config HAVE_DEBUG_STACKOVERFLOW
653         bool
654 
655 config DEBUG_STACKOVERFLOW
656         bool "Check for stack overflows"
657         depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
658         ---help---
659           Say Y here if you want to check for overflows of kernel, IRQ
660           and exception stacks (if your architecture uses them). This
661           option will show detailed messages if free stack space drops
662           below a certain limit.
663 
664           These kinds of bugs usually occur when call-chains in the
665           kernel get too deep, especially when interrupts are
666           involved.
667 
668           Use this in cases where you see apparently random memory
669           corruption, especially if it appears in 'struct thread_info'
670 
671           If in doubt, say "N".
672 
673 source "lib/Kconfig.kmemcheck"
674 
675 source "lib/Kconfig.kasan"
676 
677 endmenu # "Memory Debugging"
678 
679 config DEBUG_SHIRQ
680         bool "Debug shared IRQ handlers"
681         depends on DEBUG_KERNEL
682         help
683           Enable this to generate a spurious interrupt as soon as a shared
684           interrupt handler is registered, and just before one is deregistered.
685           Drivers ought to be able to handle interrupts coming in at those
686           points; some don't and need to be caught.
687 
688 menu "Debug Lockups and Hangs"
689 
690 config LOCKUP_DETECTOR
691         bool "Detect Hard and Soft Lockups"
692         depends on DEBUG_KERNEL && !S390
693         help
694           Say Y here to enable the kernel to act as a watchdog to detect
695           hard and soft lockups.
696 
697           Softlockups are bugs that cause the kernel to loop in kernel
698           mode for more than 20 seconds, without giving other tasks a
699           chance to run.  The current stack trace is displayed upon
700           detection and the system will stay locked up.
701 
702           Hardlockups are bugs that cause the CPU to loop in kernel mode
703           for more than 10 seconds, without letting other interrupts have a
704           chance to run.  The current stack trace is displayed upon detection
705           and the system will stay locked up.
706 
707           The overhead should be minimal.  A periodic hrtimer runs to
708           generate interrupts and kick the watchdog task every 4 seconds.
709           An NMI is generated every 10 seconds or so to check for hardlockups.
710 
711           The frequency of hrtimer and NMI events and the soft and hard lockup
712           thresholds can be controlled through the sysctl watchdog_thresh.
713 
714 config HARDLOCKUP_DETECTOR
715         def_bool y
716         depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
717         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
718 
719 config BOOTPARAM_HARDLOCKUP_PANIC
720         bool "Panic (Reboot) On Hard Lockups"
721         depends on HARDLOCKUP_DETECTOR
722         help
723           Say Y here to enable the kernel to panic on "hard lockups",
724           which are bugs that cause the kernel to loop in kernel
725           mode with interrupts disabled for more than 10 seconds (configurable
726           using the watchdog_thresh sysctl).
727 
728           Say N if unsure.
729 
730 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
731         int
732         depends on HARDLOCKUP_DETECTOR
733         range 0 1
734         default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
735         default 1 if BOOTPARAM_HARDLOCKUP_PANIC
736 
737 config BOOTPARAM_SOFTLOCKUP_PANIC
738         bool "Panic (Reboot) On Soft Lockups"
739         depends on LOCKUP_DETECTOR
740         help
741           Say Y here to enable the kernel to panic on "soft lockups",
742           which are bugs that cause the kernel to loop in kernel
743           mode for more than 20 seconds (configurable using the watchdog_thresh
744           sysctl), without giving other tasks a chance to run.
745 
746           The panic can be used in combination with panic_timeout,
747           to cause the system to reboot automatically after a
748           lockup has been detected. This feature is useful for
749           high-availability systems that have uptime guarantees and
750           where a lockup must be resolved ASAP.
751 
752           Say N if unsure.
753 
754 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
755         int
756         depends on LOCKUP_DETECTOR
757         range 0 1
758         default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
759         default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
760 
761 config DETECT_HUNG_TASK
762         bool "Detect Hung Tasks"
763         depends on DEBUG_KERNEL
764         default LOCKUP_DETECTOR
765         help
766           Say Y here to enable the kernel to detect "hung tasks",
767           which are bugs that cause the task to be stuck in
768           uninterruptible "D" state indefinitiley.
769 
770           When a hung task is detected, the kernel will print the
771           current stack trace (which you should report), but the
772           task will stay in uninterruptible state. If lockdep is
773           enabled then all held locks will also be reported. This
774           feature has negligible overhead.
775 
776 config DEFAULT_HUNG_TASK_TIMEOUT
777         int "Default timeout for hung task detection (in seconds)"
778         depends on DETECT_HUNG_TASK
779         default 120
780         help
781           This option controls the default timeout (in seconds) used
782           to determine when a task has become non-responsive and should
783           be considered hung.
784 
785           It can be adjusted at runtime via the kernel.hung_task_timeout_secs
786           sysctl or by writing a value to
787           /proc/sys/kernel/hung_task_timeout_secs.
788 
789           A timeout of 0 disables the check.  The default is two minutes.
790           Keeping the default should be fine in most cases.
791 
792 config BOOTPARAM_HUNG_TASK_PANIC
793         bool "Panic (Reboot) On Hung Tasks"
794         depends on DETECT_HUNG_TASK
795         help
796           Say Y here to enable the kernel to panic on "hung tasks",
797           which are bugs that cause the kernel to leave a task stuck
798           in uninterruptible "D" state.
799 
800           The panic can be used in combination with panic_timeout,
801           to cause the system to reboot automatically after a
802           hung task has been detected. This feature is useful for
803           high-availability systems that have uptime guarantees and
804           where a hung tasks must be resolved ASAP.
805 
806           Say N if unsure.
807 
808 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
809         int
810         depends on DETECT_HUNG_TASK
811         range 0 1
812         default 0 if !BOOTPARAM_HUNG_TASK_PANIC
813         default 1 if BOOTPARAM_HUNG_TASK_PANIC
814 
815 endmenu # "Debug lockups and hangs"
816 
817 config PANIC_ON_OOPS
818         bool "Panic on Oops"
819         help
820           Say Y here to enable the kernel to panic when it oopses. This
821           has the same effect as setting oops=panic on the kernel command
822           line.
823 
824           This feature is useful to ensure that the kernel does not do
825           anything erroneous after an oops which could result in data
826           corruption or other issues.
827 
828           Say N if unsure.
829 
830 config PANIC_ON_OOPS_VALUE
831         int
832         range 0 1
833         default 0 if !PANIC_ON_OOPS
834         default 1 if PANIC_ON_OOPS
835 
836 config PANIC_TIMEOUT
837         int "panic timeout"
838         default 0
839         help
840           Set the timeout value (in seconds) until a reboot occurs when the
841           the kernel panics. If n = 0, then we wait forever. A timeout
842           value n > 0 will wait n seconds before rebooting, while a timeout
843           value n < 0 will reboot immediately.
844 
845 config SCHED_DEBUG
846         bool "Collect scheduler debugging info"
847         depends on DEBUG_KERNEL && PROC_FS
848         default y
849         help
850           If you say Y here, the /proc/sched_debug file will be provided
851           that can help debug the scheduler. The runtime overhead of this
852           option is minimal.
853 
854 config SCHED_INFO
855         bool
856         default n
857 
858 config SCHEDSTATS
859         bool "Collect scheduler statistics"
860         depends on DEBUG_KERNEL && PROC_FS
861         select SCHED_INFO
862         help
863           If you say Y here, additional code will be inserted into the
864           scheduler and related routines to collect statistics about
865           scheduler behavior and provide them in /proc/schedstat.  These
866           stats may be useful for both tuning and debugging the scheduler
867           If you aren't debugging the scheduler or trying to tune a specific
868           application, you can say N to avoid the very slight overhead
869           this adds.
870 
871 config SCHED_STACK_END_CHECK
872         bool "Detect stack corruption on calls to schedule()"
873         depends on DEBUG_KERNEL
874         default n
875         help
876           This option checks for a stack overrun on calls to schedule().
877           If the stack end location is found to be over written always panic as
878           the content of the corrupted region can no longer be trusted.
879           This is to ensure no erroneous behaviour occurs which could result in
880           data corruption or a sporadic crash at a later stage once the region
881           is examined. The runtime overhead introduced is minimal.
882 
883 config DEBUG_TIMEKEEPING
884         bool "Enable extra timekeeping sanity checking"
885         help
886           This option will enable additional timekeeping sanity checks
887           which may be helpful when diagnosing issues where timekeeping
888           problems are suspected.
889 
890           This may include checks in the timekeeping hotpaths, so this
891           option may have a (very small) performance impact to some
892           workloads.
893 
894           If unsure, say N.
895 
896 config TIMER_STATS
897         bool "Collect kernel timers statistics"
898         depends on DEBUG_KERNEL && PROC_FS
899         help
900           If you say Y here, additional code will be inserted into the
901           timer routines to collect statistics about kernel timers being
902           reprogrammed. The statistics can be read from /proc/timer_stats.
903           The statistics collection is started by writing 1 to /proc/timer_stats,
904           writing 0 stops it. This feature is useful to collect information
905           about timer usage patterns in kernel and userspace. This feature
906           is lightweight if enabled in the kernel config but not activated
907           (it defaults to deactivated on bootup and will only be activated
908           if some application like powertop activates it explicitly).
909 
910 config DEBUG_PREEMPT
911         bool "Debug preemptible kernel"
912         depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
913         default y
914         help
915           If you say Y here then the kernel will use a debug variant of the
916           commonly used smp_processor_id() function and will print warnings
917           if kernel code uses it in a preemption-unsafe way. Also, the kernel
918           will detect preemption count underflows.
919 
920 menu "Lock Debugging (spinlocks, mutexes, etc...)"
921 
922 config DEBUG_RT_MUTEXES
923         bool "RT Mutex debugging, deadlock detection"
924         depends on DEBUG_KERNEL && RT_MUTEXES
925         help
926          This allows rt mutex semantics violations and rt mutex related
927          deadlocks (lockups) to be detected and reported automatically.
928 
929 config DEBUG_SPINLOCK
930         bool "Spinlock and rw-lock debugging: basic checks"
931         depends on DEBUG_KERNEL
932         select UNINLINE_SPIN_UNLOCK
933         help
934           Say Y here and build SMP to catch missing spinlock initialization
935           and certain other kinds of spinlock errors commonly made.  This is
936           best used in conjunction with the NMI watchdog so that spinlock
937           deadlocks are also debuggable.
938 
939 config DEBUG_MUTEXES
940         bool "Mutex debugging: basic checks"
941         depends on DEBUG_KERNEL
942         help
943          This feature allows mutex semantics violations to be detected and
944          reported.
945 
946 config DEBUG_WW_MUTEX_SLOWPATH
947         bool "Wait/wound mutex debugging: Slowpath testing"
948         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
949         select DEBUG_LOCK_ALLOC
950         select DEBUG_SPINLOCK
951         select DEBUG_MUTEXES
952         help
953          This feature enables slowpath testing for w/w mutex users by
954          injecting additional -EDEADLK wound/backoff cases. Together with
955          the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
956          will test all possible w/w mutex interface abuse with the
957          exception of simply not acquiring all the required locks.
958          Note that this feature can introduce significant overhead, so
959          it really should not be enabled in a production or distro kernel,
960          even a debug kernel.  If you are a driver writer, enable it.  If
961          you are a distro, do not.
962 
963 config DEBUG_LOCK_ALLOC
964         bool "Lock debugging: detect incorrect freeing of live locks"
965         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
966         select DEBUG_SPINLOCK
967         select DEBUG_MUTEXES
968         select LOCKDEP
969         help
970          This feature will check whether any held lock (spinlock, rwlock,
971          mutex or rwsem) is incorrectly freed by the kernel, via any of the
972          memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
973          vfree(), etc.), whether a live lock is incorrectly reinitialized via
974          spin_lock_init()/mutex_init()/etc., or whether there is any lock
975          held during task exit.
976 
977 config PROVE_LOCKING
978         bool "Lock debugging: prove locking correctness"
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         select TRACE_IRQFLAGS
985         default n
986         help
987          This feature enables the kernel to prove that all locking
988          that occurs in the kernel runtime is mathematically
989          correct: that under no circumstance could an arbitrary (and
990          not yet triggered) combination of observed locking
991          sequences (on an arbitrary number of CPUs, running an
992          arbitrary number of tasks and interrupt contexts) cause a
993          deadlock.
994 
995          In short, this feature enables the kernel to report locking
996          related deadlocks before they actually occur.
997 
998          The proof does not depend on how hard and complex a
999          deadlock scenario would be to trigger: how many
1000          participant CPUs, tasks and irq-contexts would be needed
1001          for it to trigger. The proof also does not depend on
1002          timing: if a race and a resulting deadlock is possible
1003          theoretically (no matter how unlikely the race scenario
1004          is), it will be proven so and will immediately be
1005          reported by the kernel (once the event is observed that
1006          makes the deadlock theoretically possible).
1007 
1008          If a deadlock is impossible (i.e. the locking rules, as
1009          observed by the kernel, are mathematically correct), the
1010          kernel reports nothing.
1011 
1012          NOTE: this feature can also be enabled for rwlocks, mutexes
1013          and rwsems - in which case all dependencies between these
1014          different locking variants are observed and mapped too, and
1015          the proof of observed correctness is also maintained for an
1016          arbitrary combination of these separate locking variants.
1017 
1018          For more details, see Documentation/locking/lockdep-design.txt.
1019 
1020 config LOCKDEP
1021         bool
1022         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1023         select STACKTRACE
1024         select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
1025         select KALLSYMS
1026         select KALLSYMS_ALL
1027 
1028 config LOCK_STAT
1029         bool "Lock usage statistics"
1030         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1031         select LOCKDEP
1032         select DEBUG_SPINLOCK
1033         select DEBUG_MUTEXES
1034         select DEBUG_LOCK_ALLOC
1035         default n
1036         help
1037          This feature enables tracking lock contention points
1038 
1039          For more details, see Documentation/locking/lockstat.txt
1040 
1041          This also enables lock events required by "perf lock",
1042          subcommand of perf.
1043          If you want to use "perf lock", you also need to turn on
1044          CONFIG_EVENT_TRACING.
1045 
1046          CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1047          (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1048 
1049 config DEBUG_LOCKDEP
1050         bool "Lock dependency engine debugging"
1051         depends on DEBUG_KERNEL && LOCKDEP
1052         help
1053           If you say Y here, the lock dependency engine will do
1054           additional runtime checks to debug itself, at the price
1055           of more runtime overhead.
1056 
1057 config DEBUG_ATOMIC_SLEEP
1058         bool "Sleep inside atomic section checking"
1059         select PREEMPT_COUNT
1060         depends on DEBUG_KERNEL
1061         help
1062           If you say Y here, various routines which may sleep will become very
1063           noisy if they are called inside atomic sections: when a spinlock is
1064           held, inside an rcu read side critical section, inside preempt disabled
1065           sections, inside an interrupt, etc...
1066 
1067 config DEBUG_LOCKING_API_SELFTESTS
1068         bool "Locking API boot-time self-tests"
1069         depends on DEBUG_KERNEL
1070         help
1071           Say Y here if you want the kernel to run a short self-test during
1072           bootup. The self-test checks whether common types of locking bugs
1073           are detected by debugging mechanisms or not. (if you disable
1074           lock debugging then those bugs wont be detected of course.)
1075           The following locking APIs are covered: spinlocks, rwlocks,
1076           mutexes and rwsems.
1077 
1078 config LOCK_TORTURE_TEST
1079         tristate "torture tests for locking"
1080         depends on DEBUG_KERNEL
1081         select TORTURE_TEST
1082         default n
1083         help
1084           This option provides a kernel module that runs torture tests
1085           on kernel locking primitives.  The kernel module may be built
1086           after the fact on the running kernel to be tested, if desired.
1087 
1088           Say Y here if you want kernel locking-primitive torture tests
1089           to be built into the kernel.
1090           Say M if you want these torture tests to build as a module.
1091           Say N if you are unsure.
1092 
1093 endmenu # lock debugging
1094 
1095 config TRACE_IRQFLAGS
1096         bool
1097         help
1098           Enables hooks to interrupt enabling and disabling for
1099           either tracing or lock debugging.
1100 
1101 config STACKTRACE
1102         bool "Stack backtrace support"
1103         depends on STACKTRACE_SUPPORT
1104         help
1105           This option causes the kernel to create a /proc/pid/stack for
1106           every process, showing its current stack trace.
1107           It is also used by various kernel debugging features that require
1108           stack trace generation.
1109 
1110 config DEBUG_KOBJECT
1111         bool "kobject debugging"
1112         depends on DEBUG_KERNEL
1113         help
1114           If you say Y here, some extra kobject debugging messages will be sent
1115           to the syslog. 
1116 
1117 config DEBUG_KOBJECT_RELEASE
1118         bool "kobject release debugging"
1119         depends on DEBUG_OBJECTS_TIMERS
1120         help
1121           kobjects are reference counted objects.  This means that their
1122           last reference count put is not predictable, and the kobject can
1123           live on past the point at which a driver decides to drop it's
1124           initial reference to the kobject gained on allocation.  An
1125           example of this would be a struct device which has just been
1126           unregistered.
1127 
1128           However, some buggy drivers assume that after such an operation,
1129           the memory backing the kobject can be immediately freed.  This
1130           goes completely against the principles of a refcounted object.
1131 
1132           If you say Y here, the kernel will delay the release of kobjects
1133           on the last reference count to improve the visibility of this
1134           kind of kobject release bug.
1135 
1136 config HAVE_DEBUG_BUGVERBOSE
1137         bool
1138 
1139 config DEBUG_BUGVERBOSE
1140         bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1141         depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1142         default y
1143         help
1144           Say Y here to make BUG() panics output the file name and line number
1145           of the BUG call as well as the EIP and oops trace.  This aids
1146           debugging but costs about 70-100K of memory.
1147 
1148 config DEBUG_LIST
1149         bool "Debug linked list manipulation"
1150         depends on DEBUG_KERNEL
1151         help
1152           Enable this to turn on extended checks in the linked-list
1153           walking routines.
1154 
1155           If unsure, say N.
1156 
1157 config DEBUG_PI_LIST
1158         bool "Debug priority linked list manipulation"
1159         depends on DEBUG_KERNEL
1160         help
1161           Enable this to turn on extended checks in the priority-ordered
1162           linked-list (plist) walking routines.  This checks the entire
1163           list multiple times during each manipulation.
1164 
1165           If unsure, say N.
1166 
1167 config DEBUG_SG
1168         bool "Debug SG table operations"
1169         depends on DEBUG_KERNEL
1170         help
1171           Enable this to turn on checks on scatter-gather tables. This can
1172           help find problems with drivers that do not properly initialize
1173           their sg tables.
1174 
1175           If unsure, say N.
1176 
1177 config DEBUG_NOTIFIERS
1178         bool "Debug notifier call chains"
1179         depends on DEBUG_KERNEL
1180         help
1181           Enable this to turn on sanity checking for notifier call chains.
1182           This is most useful for kernel developers to make sure that
1183           modules properly unregister themselves from notifier chains.
1184           This is a relatively cheap check but if you care about maximum
1185           performance, say N.
1186 
1187 config DEBUG_CREDENTIALS
1188         bool "Debug credential management"
1189         depends on DEBUG_KERNEL
1190         help
1191           Enable this to turn on some debug checking for credential
1192           management.  The additional code keeps track of the number of
1193           pointers from task_structs to any given cred struct, and checks to
1194           see that this number never exceeds the usage count of the cred
1195           struct.
1196 
1197           Furthermore, if SELinux is enabled, this also checks that the
1198           security pointer in the cred struct is never seen to be invalid.
1199 
1200           If unsure, say N.
1201 
1202 menu "RCU Debugging"
1203 
1204 config PROVE_RCU
1205         def_bool PROVE_LOCKING
1206 
1207 config PROVE_RCU_REPEATEDLY
1208         bool "RCU debugging: don't disable PROVE_RCU on first splat"
1209         depends on PROVE_RCU
1210         default n
1211         help
1212          By itself, PROVE_RCU will disable checking upon issuing the
1213          first warning (or "splat").  This feature prevents such
1214          disabling, allowing multiple RCU-lockdep warnings to be printed
1215          on a single reboot.
1216 
1217          Say Y to allow multiple RCU-lockdep warnings per boot.
1218 
1219          Say N if you are unsure.
1220 
1221 config SPARSE_RCU_POINTER
1222         bool "RCU debugging: sparse-based checks for pointer usage"
1223         default n
1224         help
1225          This feature enables the __rcu sparse annotation for
1226          RCU-protected pointers.  This annotation will cause sparse
1227          to flag any non-RCU used of annotated pointers.  This can be
1228          helpful when debugging RCU usage.  Please note that this feature
1229          is not intended to enforce code cleanliness; it is instead merely
1230          a debugging aid.
1231 
1232          Say Y to make sparse flag questionable use of RCU-protected pointers
1233 
1234          Say N if you are unsure.
1235 
1236 config TORTURE_TEST
1237         tristate
1238         default n
1239 
1240 config RCU_TORTURE_TEST
1241         tristate "torture tests for RCU"
1242         depends on DEBUG_KERNEL
1243         select TORTURE_TEST
1244         select SRCU
1245         select TASKS_RCU
1246         default n
1247         help
1248           This option provides a kernel module that runs torture tests
1249           on the RCU infrastructure.  The kernel module may be built
1250           after the fact on the running kernel to be tested, if desired.
1251 
1252           Say Y here if you want RCU torture tests to be built into
1253           the kernel.
1254           Say M if you want the RCU torture tests to build as a module.
1255           Say N if you are unsure.
1256 
1257 config RCU_TORTURE_TEST_RUNNABLE
1258         bool "torture tests for RCU runnable by default"
1259         depends on RCU_TORTURE_TEST = y
1260         default n
1261         help
1262           This option provides a way to build the RCU torture tests
1263           directly into the kernel without them starting up at boot
1264           time.  You can use /proc/sys/kernel/rcutorture_runnable
1265           to manually override this setting.  This /proc file is
1266           available only when the RCU torture tests have been built
1267           into the kernel.
1268 
1269           Say Y here if you want the RCU torture tests to start during
1270           boot (you probably don't).
1271           Say N here if you want the RCU torture tests to start only
1272           after being manually enabled via /proc.
1273 
1274 config RCU_TORTURE_TEST_SLOW_PREINIT
1275         bool "Slow down RCU grace-period pre-initialization to expose races"
1276         depends on RCU_TORTURE_TEST
1277         help
1278           This option delays grace-period pre-initialization (the
1279           propagation of CPU-hotplug changes up the rcu_node combining
1280           tree) for a few jiffies between initializing each pair of
1281           consecutive rcu_node structures.  This helps to expose races
1282           involving grace-period pre-initialization, in other words, it
1283           makes your kernel less stable.  It can also greatly increase
1284           grace-period latency, especially on systems with large numbers
1285           of CPUs.  This is useful when torture-testing RCU, but in
1286           almost no other circumstance.
1287 
1288           Say Y here if you want your system to crash and hang more often.
1289           Say N if you want a sane system.
1290 
1291 config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
1292         int "How much to slow down RCU grace-period pre-initialization"
1293         range 0 5
1294         default 3
1295         depends on RCU_TORTURE_TEST_SLOW_PREINIT
1296         help
1297           This option specifies the number of jiffies to wait between
1298           each rcu_node structure pre-initialization step.
1299 
1300 config RCU_TORTURE_TEST_SLOW_INIT
1301         bool "Slow down RCU grace-period initialization to expose races"
1302         depends on RCU_TORTURE_TEST
1303         help
1304           This option delays grace-period initialization for a few
1305           jiffies between initializing each pair of consecutive
1306           rcu_node structures.  This helps to expose races involving
1307           grace-period initialization, in other words, it makes your
1308           kernel less stable.  It can also greatly increase grace-period
1309           latency, especially on systems with large numbers of CPUs.
1310           This is useful when torture-testing RCU, but in almost no
1311           other circumstance.
1312 
1313           Say Y here if you want your system to crash and hang more often.
1314           Say N if you want a sane system.
1315 
1316 config RCU_TORTURE_TEST_SLOW_INIT_DELAY
1317         int "How much to slow down RCU grace-period initialization"
1318         range 0 5
1319         default 3
1320         depends on RCU_TORTURE_TEST_SLOW_INIT
1321         help
1322           This option specifies the number of jiffies to wait between
1323           each rcu_node structure initialization.
1324 
1325 config RCU_TORTURE_TEST_SLOW_CLEANUP
1326         bool "Slow down RCU grace-period cleanup to expose races"
1327         depends on RCU_TORTURE_TEST
1328         help
1329           This option delays grace-period cleanup for a few jiffies
1330           between cleaning up each pair of consecutive rcu_node
1331           structures.  This helps to expose races involving grace-period
1332           cleanup, in other words, it makes your kernel less stable.
1333           It can also greatly increase grace-period latency, especially
1334           on systems with large numbers of CPUs.  This is useful when
1335           torture-testing RCU, but in almost no other circumstance.
1336 
1337           Say Y here if you want your system to crash and hang more often.
1338           Say N if you want a sane system.
1339 
1340 config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
1341         int "How much to slow down RCU grace-period cleanup"
1342         range 0 5
1343         default 3
1344         depends on RCU_TORTURE_TEST_SLOW_CLEANUP
1345         help
1346           This option specifies the number of jiffies to wait between
1347           each rcu_node structure cleanup operation.
1348 
1349 config RCU_CPU_STALL_TIMEOUT
1350         int "RCU CPU stall timeout in seconds"
1351         depends on RCU_STALL_COMMON
1352         range 3 300
1353         default 21
1354         help
1355           If a given RCU grace period extends more than the specified
1356           number of seconds, a CPU stall warning is printed.  If the
1357           RCU grace period persists, additional CPU stall warnings are
1358           printed at more widely spaced intervals.
1359 
1360 config RCU_TRACE
1361         bool "Enable tracing for RCU"
1362         depends on DEBUG_KERNEL
1363         select TRACE_CLOCK
1364         help
1365           This option provides tracing in RCU which presents stats
1366           in debugfs for debugging RCU implementation.
1367 
1368           Say Y here if you want to enable RCU tracing
1369           Say N if you are unsure.
1370 
1371 config RCU_EQS_DEBUG
1372         bool "Provide debugging asserts for adding NO_HZ support to an arch"
1373         depends on DEBUG_KERNEL
1374         help
1375           This option provides consistency checks in RCU's handling of
1376           NO_HZ.  These checks have proven quite helpful in detecting
1377           bugs in arch-specific NO_HZ code.
1378 
1379           Say N here if you need ultimate kernel/user switch latencies
1380           Say Y if you are unsure
1381 
1382 endmenu # "RCU Debugging"
1383 
1384 config DEBUG_BLOCK_EXT_DEVT
1385         bool "Force extended block device numbers and spread them"
1386         depends on DEBUG_KERNEL
1387         depends on BLOCK
1388         default n
1389         help
1390           BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1391           SOME DISTRIBUTIONS.  DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1392           YOU ARE DOING.  Distros, please enable this and fix whatever
1393           is broken.
1394 
1395           Conventionally, block device numbers are allocated from
1396           predetermined contiguous area.  However, extended block area
1397           may introduce non-contiguous block device numbers.  This
1398           option forces most block device numbers to be allocated from
1399           the extended space and spreads them to discover kernel or
1400           userland code paths which assume predetermined contiguous
1401           device number allocation.
1402 
1403           Note that turning on this debug option shuffles all the
1404           device numbers for all IDE and SCSI devices including libata
1405           ones, so root partition specified using device number
1406           directly (via rdev or root=MAJ:MIN) won't work anymore.
1407           Textual device names (root=/dev/sdXn) will continue to work.
1408 
1409           Say N if you are unsure.
1410 
1411 config NOTIFIER_ERROR_INJECTION
1412         tristate "Notifier error injection"
1413         depends on DEBUG_KERNEL
1414         select DEBUG_FS
1415         help
1416           This option provides the ability to inject artificial errors to
1417           specified notifier chain callbacks. It is useful to test the error
1418           handling of notifier call chain failures.
1419 
1420           Say N if unsure.
1421 
1422 config CPU_NOTIFIER_ERROR_INJECT
1423         tristate "CPU notifier error injection module"
1424         depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1425         help
1426           This option provides a kernel module that can be used to test
1427           the error handling of the cpu notifiers by injecting artificial
1428           errors to CPU notifier chain callbacks.  It is controlled through
1429           debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
1430 
1431           If the notifier call chain should be failed with some events
1432           notified, write the error code to "actions/<notifier event>/error".
1433 
1434           Example: Inject CPU offline error (-1 == -EPERM)
1435 
1436           # cd /sys/kernel/debug/notifier-error-inject/cpu
1437           # echo -1 > actions/CPU_DOWN_PREPARE/error
1438           # echo 0 > /sys/devices/system/cpu/cpu1/online
1439           bash: echo: write error: Operation not permitted
1440 
1441           To compile this code as a module, choose M here: the module will
1442           be called cpu-notifier-error-inject.
1443 
1444           If unsure, say N.
1445 
1446 config PM_NOTIFIER_ERROR_INJECT
1447         tristate "PM notifier error injection module"
1448         depends on PM && NOTIFIER_ERROR_INJECTION
1449         default m if PM_DEBUG
1450         help
1451           This option provides the ability to inject artificial errors to
1452           PM notifier chain callbacks.  It is controlled through debugfs
1453           interface /sys/kernel/debug/notifier-error-inject/pm
1454 
1455           If the notifier call chain should be failed with some events
1456           notified, write the error code to "actions/<notifier event>/error".
1457 
1458           Example: Inject PM suspend error (-12 = -ENOMEM)
1459 
1460           # cd /sys/kernel/debug/notifier-error-inject/pm/
1461           # echo -12 > actions/PM_SUSPEND_PREPARE/error
1462           # echo mem > /sys/power/state
1463           bash: echo: write error: Cannot allocate memory
1464 
1465           To compile this code as a module, choose M here: the module will
1466           be called pm-notifier-error-inject.
1467 
1468           If unsure, say N.
1469 
1470 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1471         tristate "OF reconfig notifier error injection module"
1472         depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1473         help
1474           This option provides the ability to inject artificial errors to
1475           OF reconfig notifier chain callbacks.  It is controlled
1476           through debugfs interface under
1477           /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1478 
1479           If the notifier call chain should be failed with some events
1480           notified, write the error code to "actions/<notifier event>/error".
1481 
1482           To compile this code as a module, choose M here: the module will
1483           be called of-reconfig-notifier-error-inject.
1484 
1485           If unsure, say N.
1486 
1487 config FAULT_INJECTION
1488         bool "Fault-injection framework"
1489         depends on DEBUG_KERNEL
1490         help
1491           Provide fault-injection framework.
1492           For more details, see Documentation/fault-injection/.
1493 
1494 config FAILSLAB
1495         bool "Fault-injection capability for kmalloc"
1496         depends on FAULT_INJECTION
1497         depends on SLAB || SLUB
1498         help
1499           Provide fault-injection capability for kmalloc.
1500 
1501 config FAIL_PAGE_ALLOC
1502         bool "Fault-injection capabilitiy for alloc_pages()"
1503         depends on FAULT_INJECTION
1504         help
1505           Provide fault-injection capability for alloc_pages().
1506 
1507 config FAIL_MAKE_REQUEST
1508         bool "Fault-injection capability for disk IO"
1509         depends on FAULT_INJECTION && BLOCK
1510         help
1511           Provide fault-injection capability for disk IO.
1512 
1513 config FAIL_IO_TIMEOUT
1514         bool "Fault-injection capability for faking disk interrupts"
1515         depends on FAULT_INJECTION && BLOCK
1516         help
1517           Provide fault-injection capability on end IO handling. This
1518           will make the block layer "forget" an interrupt as configured,
1519           thus exercising the error handling.
1520 
1521           Only works with drivers that use the generic timeout handling,
1522           for others it wont do anything.
1523 
1524 config FAIL_MMC_REQUEST
1525         bool "Fault-injection capability for MMC IO"
1526         select DEBUG_FS
1527         depends on FAULT_INJECTION && MMC
1528         help
1529           Provide fault-injection capability for MMC IO.
1530           This will make the mmc core return data errors. This is
1531           useful to test the error handling in the mmc block device
1532           and to test how the mmc host driver handles retries from
1533           the block device.
1534 
1535 config FAIL_FUTEX
1536         bool "Fault-injection capability for futexes"
1537         select DEBUG_FS
1538         depends on FAULT_INJECTION && FUTEX
1539         help
1540           Provide fault-injection capability for futexes.
1541 
1542 config FAULT_INJECTION_DEBUG_FS
1543         bool "Debugfs entries for fault-injection capabilities"
1544         depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1545         help
1546           Enable configuration of fault-injection capabilities via debugfs.
1547 
1548 config FAULT_INJECTION_STACKTRACE_FILTER
1549         bool "stacktrace filter for fault-injection capabilities"
1550         depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1551         depends on !X86_64
1552         select STACKTRACE
1553         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1554         help
1555           Provide stacktrace filter for fault-injection capabilities
1556 
1557 config LATENCYTOP
1558         bool "Latency measuring infrastructure"
1559         depends on HAVE_LATENCYTOP_SUPPORT
1560         depends on DEBUG_KERNEL
1561         depends on STACKTRACE_SUPPORT
1562         depends on PROC_FS
1563         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1564         select KALLSYMS
1565         select KALLSYMS_ALL
1566         select STACKTRACE
1567         select SCHEDSTATS
1568         select SCHED_DEBUG
1569         help
1570           Enable this option if you want to use the LatencyTOP tool
1571           to find out which userspace is blocking on what kernel operations.
1572 
1573 config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1574         bool
1575 
1576 config DEBUG_STRICT_USER_COPY_CHECKS
1577         bool "Strict user copy size checks"
1578         depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1579         depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
1580         help
1581           Enabling this option turns a certain set of sanity checks for user
1582           copy operations into compile time failures.
1583 
1584           The copy_from_user() etc checks are there to help test if there
1585           are sufficient security checks on the length argument of
1586           the copy operation, by having gcc prove that the argument is
1587           within bounds.
1588 
1589           If unsure, say N.
1590 
1591 source kernel/trace/Kconfig
1592 
1593 menu "Runtime Testing"
1594 
1595 config LKDTM
1596         tristate "Linux Kernel Dump Test Tool Module"
1597         depends on DEBUG_FS
1598         depends on BLOCK
1599         default n
1600         help
1601         This module enables testing of the different dumping mechanisms by
1602         inducing system failures at predefined crash points.
1603         If you don't need it: say N
1604         Choose M here to compile this code as a module. The module will be
1605         called lkdtm.
1606 
1607         Documentation on how to use the module can be found in
1608         Documentation/fault-injection/provoke-crashes.txt
1609 
1610 config TEST_LIST_SORT
1611         bool "Linked list sorting test"
1612         depends on DEBUG_KERNEL
1613         help
1614           Enable this to turn on 'list_sort()' function test. This test is
1615           executed only once during system boot, so affects only boot time.
1616 
1617           If unsure, say N.
1618 
1619 config KPROBES_SANITY_TEST
1620         bool "Kprobes sanity tests"
1621         depends on DEBUG_KERNEL
1622         depends on KPROBES
1623         default n
1624         help
1625           This option provides for testing basic kprobes functionality on
1626           boot. A sample kprobe, jprobe and kretprobe are inserted and
1627           verified for functionality.
1628 
1629           Say N if you are unsure.
1630 
1631 config BACKTRACE_SELF_TEST
1632         tristate "Self test for the backtrace code"
1633         depends on DEBUG_KERNEL
1634         default n
1635         help
1636           This option provides a kernel module that can be used to test
1637           the kernel stack backtrace code. This option is not useful
1638           for distributions or general kernels, but only for kernel
1639           developers working on architecture code.
1640 
1641           Note that if you want to also test saved backtraces, you will
1642           have to enable STACKTRACE as well.
1643 
1644           Say N if you are unsure.
1645 
1646 config RBTREE_TEST
1647         tristate "Red-Black tree test"
1648         depends on DEBUG_KERNEL
1649         help
1650           A benchmark measuring the performance of the rbtree library.
1651           Also includes rbtree invariant checks.
1652 
1653 config INTERVAL_TREE_TEST
1654         tristate "Interval tree test"
1655         depends on m && DEBUG_KERNEL
1656         select INTERVAL_TREE
1657         help
1658           A benchmark measuring the performance of the interval tree library
1659 
1660 config PERCPU_TEST
1661         tristate "Per cpu operations test"
1662         depends on m && DEBUG_KERNEL
1663         help
1664           Enable this option to build test module which validates per-cpu
1665           operations.
1666 
1667           If unsure, say N.
1668 
1669 config ATOMIC64_SELFTEST
1670         bool "Perform an atomic64_t self-test at boot"
1671         help
1672           Enable this option to test the atomic64_t functions at boot.
1673 
1674           If unsure, say N.
1675 
1676 config ASYNC_RAID6_TEST
1677         tristate "Self test for hardware accelerated raid6 recovery"
1678         depends on ASYNC_RAID6_RECOV
1679         select ASYNC_MEMCPY
1680         ---help---
1681           This is a one-shot self test that permutes through the
1682           recovery of all the possible two disk failure scenarios for a
1683           N-disk array.  Recovery is performed with the asynchronous
1684           raid6 recovery routines, and will optionally use an offload
1685           engine if one is available.
1686 
1687           If unsure, say N.
1688 
1689 config TEST_HEXDUMP
1690         tristate "Test functions located in the hexdump module at runtime"
1691 
1692 config TEST_STRING_HELPERS
1693         tristate "Test functions located in the string_helpers module at runtime"
1694 
1695 config TEST_KSTRTOX
1696         tristate "Test kstrto*() family of functions at runtime"
1697 
1698 config TEST_PRINTF
1699         tristate "Test printf() family of functions at runtime"
1700 
1701 config TEST_RHASHTABLE
1702         tristate "Perform selftest on resizable hash table"
1703         default n
1704         help
1705           Enable this option to test the rhashtable functions at boot.
1706 
1707           If unsure, say N.
1708 
1709 endmenu # runtime tests
1710 
1711 config PROVIDE_OHCI1394_DMA_INIT
1712         bool "Remote debugging over FireWire early on boot"
1713         depends on PCI && X86
1714         help
1715           If you want to debug problems which hang or crash the kernel early
1716           on boot and the crashing machine has a FireWire port, you can use
1717           this feature to remotely access the memory of the crashed machine
1718           over FireWire. This employs remote DMA as part of the OHCI1394
1719           specification which is now the standard for FireWire controllers.
1720 
1721           With remote DMA, you can monitor the printk buffer remotely using
1722           firescope and access all memory below 4GB using fireproxy from gdb.
1723           Even controlling a kernel debugger is possible using remote DMA.
1724 
1725           Usage:
1726 
1727           If ohci1394_dma=early is used as boot parameter, it will initialize
1728           all OHCI1394 controllers which are found in the PCI config space.
1729 
1730           As all changes to the FireWire bus such as enabling and disabling
1731           devices cause a bus reset and thereby disable remote DMA for all
1732           devices, be sure to have the cable plugged and FireWire enabled on
1733           the debugging host before booting the debug target for debugging.
1734 
1735           This code (~1k) is freed after boot. By then, the firewire stack
1736           in charge of the OHCI-1394 controllers should be used instead.
1737 
1738           See Documentation/debugging-via-ohci1394.txt for more information.
1739 
1740 config BUILD_DOCSRC
1741         bool "Build targets in Documentation/ tree"
1742         depends on HEADERS_CHECK
1743         help
1744           This option attempts to build objects from the source files in the
1745           kernel Documentation/ tree.
1746 
1747           Say N if you are unsure.
1748 
1749 config DMA_API_DEBUG
1750         bool "Enable debugging of DMA-API usage"
1751         depends on HAVE_DMA_API_DEBUG
1752         help
1753           Enable this option to debug the use of the DMA API by device drivers.
1754           With this option you will be able to detect common bugs in device
1755           drivers like double-freeing of DMA mappings or freeing mappings that
1756           were never allocated.
1757 
1758           This also attempts to catch cases where a page owned by DMA is
1759           accessed by the cpu in a way that could cause data corruption.  For
1760           example, this enables cow_user_page() to check that the source page is
1761           not undergoing DMA.
1762 
1763           This option causes a performance degradation.  Use only if you want to
1764           debug device drivers and dma interactions.
1765 
1766           If unsure, say N.
1767 
1768 config TEST_LKM
1769         tristate "Test module loading with 'hello world' module"
1770         default n
1771         depends on m
1772         help
1773           This builds the "test_module" module that emits "Hello, world"
1774           on printk when loaded. It is designed to be used for basic
1775           evaluation of the module loading subsystem (for example when
1776           validating module verification). It lacks any extra dependencies,
1777           and will not normally be loaded by the system unless explicitly
1778           requested by name.
1779 
1780           If unsure, say N.
1781 
1782 config TEST_USER_COPY
1783         tristate "Test user/kernel boundary protections"
1784         default n
1785         depends on m
1786         help
1787           This builds the "test_user_copy" module that runs sanity checks
1788           on the copy_to/from_user infrastructure, making sure basic
1789           user/kernel boundary testing is working. If it fails to load,
1790           a regression has been detected in the user/kernel memory boundary
1791           protections.
1792 
1793           If unsure, say N.
1794 
1795 config TEST_BPF
1796         tristate "Test BPF filter functionality"
1797         default n
1798         depends on m && NET
1799         help
1800           This builds the "test_bpf" module that runs various test vectors
1801           against the BPF interpreter or BPF JIT compiler depending on the
1802           current setting. This is in particular useful for BPF JIT compiler
1803           development, but also to run regression tests against changes in
1804           the interpreter code. It also enables test stubs for eBPF maps and
1805           verifier used by user space verifier testsuite.
1806 
1807           If unsure, say N.
1808 
1809 config TEST_FIRMWARE
1810         tristate "Test firmware loading via userspace interface"
1811         default n
1812         depends on FW_LOADER
1813         help
1814           This builds the "test_firmware" module that creates a userspace
1815           interface for testing firmware loading. This can be used to
1816           control the triggering of firmware loading without needing an
1817           actual firmware-using device. The contents can be rechecked by
1818           userspace.
1819 
1820           If unsure, say N.
1821 
1822 config TEST_UDELAY
1823         tristate "udelay test driver"
1824         default n
1825         help
1826           This builds the "udelay_test" module that helps to make sure
1827           that udelay() is working properly.
1828 
1829           If unsure, say N.
1830 
1831 config MEMTEST
1832         bool "Memtest"
1833         depends on HAVE_MEMBLOCK
1834         ---help---
1835           This option adds a kernel parameter 'memtest', which allows memtest
1836           to be set.
1837                 memtest=0, mean disabled; -- default
1838                 memtest=1, mean do 1 test pattern;
1839                 ...
1840                 memtest=17, mean do 17 test patterns.
1841           If you are unsure how to answer this question, answer N.
1842 
1843 config TEST_STATIC_KEYS
1844         tristate "Test static keys"
1845         default n
1846         depends on m
1847         help
1848           Test the static key interfaces.
1849 
1850           If unsure, say N.
1851 
1852 source "samples/Kconfig"
1853 
1854 source "lib/Kconfig.kgdb"
1855 

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