Version:  2.0.40 2.2.26 2.4.37 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1

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

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