Version:  2.0.40 2.2.26 2.4.37 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0

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 TIMER_STATS
869         bool "Collect kernel timers statistics"
870         depends on DEBUG_KERNEL && PROC_FS
871         help
872           If you say Y here, additional code will be inserted into the
873           timer routines to collect statistics about kernel timers being
874           reprogrammed. The statistics can be read from /proc/timer_stats.
875           The statistics collection is started by writing 1 to /proc/timer_stats,
876           writing 0 stops it. This feature is useful to collect information
877           about timer usage patterns in kernel and userspace. This feature
878           is lightweight if enabled in the kernel config but not activated
879           (it defaults to deactivated on bootup and will only be activated
880           if some application like powertop activates it explicitly).
881 
882 config DEBUG_PREEMPT
883         bool "Debug preemptible kernel"
884         depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
885         default y
886         help
887           If you say Y here then the kernel will use a debug variant of the
888           commonly used smp_processor_id() function and will print warnings
889           if kernel code uses it in a preemption-unsafe way. Also, the kernel
890           will detect preemption count underflows.
891 
892 menu "Lock Debugging (spinlocks, mutexes, etc...)"
893 
894 config DEBUG_RT_MUTEXES
895         bool "RT Mutex debugging, deadlock detection"
896         depends on DEBUG_KERNEL && RT_MUTEXES
897         help
898          This allows rt mutex semantics violations and rt mutex related
899          deadlocks (lockups) to be detected and reported automatically.
900 
901 config RT_MUTEX_TESTER
902         bool "Built-in scriptable tester for rt-mutexes"
903         depends on DEBUG_KERNEL && RT_MUTEXES && BROKEN
904         help
905           This option enables a rt-mutex tester.
906 
907 config DEBUG_SPINLOCK
908         bool "Spinlock and rw-lock debugging: basic checks"
909         depends on DEBUG_KERNEL
910         select UNINLINE_SPIN_UNLOCK
911         help
912           Say Y here and build SMP to catch missing spinlock initialization
913           and certain other kinds of spinlock errors commonly made.  This is
914           best used in conjunction with the NMI watchdog so that spinlock
915           deadlocks are also debuggable.
916 
917 config DEBUG_MUTEXES
918         bool "Mutex debugging: basic checks"
919         depends on DEBUG_KERNEL
920         help
921          This feature allows mutex semantics violations to be detected and
922          reported.
923 
924 config DEBUG_WW_MUTEX_SLOWPATH
925         bool "Wait/wound mutex debugging: Slowpath testing"
926         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
927         select DEBUG_LOCK_ALLOC
928         select DEBUG_SPINLOCK
929         select DEBUG_MUTEXES
930         help
931          This feature enables slowpath testing for w/w mutex users by
932          injecting additional -EDEADLK wound/backoff cases. Together with
933          the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
934          will test all possible w/w mutex interface abuse with the
935          exception of simply not acquiring all the required locks.
936          Note that this feature can introduce significant overhead, so
937          it really should not be enabled in a production or distro kernel,
938          even a debug kernel.  If you are a driver writer, enable it.  If
939          you are a distro, do not.
940 
941 config DEBUG_LOCK_ALLOC
942         bool "Lock debugging: detect incorrect freeing of live locks"
943         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
944         select DEBUG_SPINLOCK
945         select DEBUG_MUTEXES
946         select LOCKDEP
947         help
948          This feature will check whether any held lock (spinlock, rwlock,
949          mutex or rwsem) is incorrectly freed by the kernel, via any of the
950          memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
951          vfree(), etc.), whether a live lock is incorrectly reinitialized via
952          spin_lock_init()/mutex_init()/etc., or whether there is any lock
953          held during task exit.
954 
955 config PROVE_LOCKING
956         bool "Lock debugging: prove locking correctness"
957         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
958         select LOCKDEP
959         select DEBUG_SPINLOCK
960         select DEBUG_MUTEXES
961         select DEBUG_LOCK_ALLOC
962         select TRACE_IRQFLAGS
963         default n
964         help
965          This feature enables the kernel to prove that all locking
966          that occurs in the kernel runtime is mathematically
967          correct: that under no circumstance could an arbitrary (and
968          not yet triggered) combination of observed locking
969          sequences (on an arbitrary number of CPUs, running an
970          arbitrary number of tasks and interrupt contexts) cause a
971          deadlock.
972 
973          In short, this feature enables the kernel to report locking
974          related deadlocks before they actually occur.
975 
976          The proof does not depend on how hard and complex a
977          deadlock scenario would be to trigger: how many
978          participant CPUs, tasks and irq-contexts would be needed
979          for it to trigger. The proof also does not depend on
980          timing: if a race and a resulting deadlock is possible
981          theoretically (no matter how unlikely the race scenario
982          is), it will be proven so and will immediately be
983          reported by the kernel (once the event is observed that
984          makes the deadlock theoretically possible).
985 
986          If a deadlock is impossible (i.e. the locking rules, as
987          observed by the kernel, are mathematically correct), the
988          kernel reports nothing.
989 
990          NOTE: this feature can also be enabled for rwlocks, mutexes
991          and rwsems - in which case all dependencies between these
992          different locking variants are observed and mapped too, and
993          the proof of observed correctness is also maintained for an
994          arbitrary combination of these separate locking variants.
995 
996          For more details, see Documentation/locking/lockdep-design.txt.
997 
998 config LOCKDEP
999         bool
1000         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1001         select STACKTRACE
1002         select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
1003         select KALLSYMS
1004         select KALLSYMS_ALL
1005 
1006 config LOCK_STAT
1007         bool "Lock usage statistics"
1008         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1009         select LOCKDEP
1010         select DEBUG_SPINLOCK
1011         select DEBUG_MUTEXES
1012         select DEBUG_LOCK_ALLOC
1013         default n
1014         help
1015          This feature enables tracking lock contention points
1016 
1017          For more details, see Documentation/locking/lockstat.txt
1018 
1019          This also enables lock events required by "perf lock",
1020          subcommand of perf.
1021          If you want to use "perf lock", you also need to turn on
1022          CONFIG_EVENT_TRACING.
1023 
1024          CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1025          (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1026 
1027 config DEBUG_LOCKDEP
1028         bool "Lock dependency engine debugging"
1029         depends on DEBUG_KERNEL && LOCKDEP
1030         help
1031           If you say Y here, the lock dependency engine will do
1032           additional runtime checks to debug itself, at the price
1033           of more runtime overhead.
1034 
1035 config DEBUG_ATOMIC_SLEEP
1036         bool "Sleep inside atomic section checking"
1037         select PREEMPT_COUNT
1038         depends on DEBUG_KERNEL
1039         help
1040           If you say Y here, various routines which may sleep will become very
1041           noisy if they are called inside atomic sections: when a spinlock is
1042           held, inside an rcu read side critical section, inside preempt disabled
1043           sections, inside an interrupt, etc...
1044 
1045 config DEBUG_LOCKING_API_SELFTESTS
1046         bool "Locking API boot-time self-tests"
1047         depends on DEBUG_KERNEL
1048         help
1049           Say Y here if you want the kernel to run a short self-test during
1050           bootup. The self-test checks whether common types of locking bugs
1051           are detected by debugging mechanisms or not. (if you disable
1052           lock debugging then those bugs wont be detected of course.)
1053           The following locking APIs are covered: spinlocks, rwlocks,
1054           mutexes and rwsems.
1055 
1056 config LOCK_TORTURE_TEST
1057         tristate "torture tests for locking"
1058         depends on DEBUG_KERNEL
1059         select TORTURE_TEST
1060         default n
1061         help
1062           This option provides a kernel module that runs torture tests
1063           on kernel locking primitives.  The kernel module may be built
1064           after the fact on the running kernel to be tested, if desired.
1065 
1066           Say Y here if you want kernel locking-primitive torture tests
1067           to be built into the kernel.
1068           Say M if you want these torture tests to build as a module.
1069           Say N if you are unsure.
1070 
1071 endmenu # lock debugging
1072 
1073 config TRACE_IRQFLAGS
1074         bool
1075         help
1076           Enables hooks to interrupt enabling and disabling for
1077           either tracing or lock debugging.
1078 
1079 config STACKTRACE
1080         bool "Stack backtrace support"
1081         depends on STACKTRACE_SUPPORT
1082         help
1083           This option causes the kernel to create a /proc/pid/stack for
1084           every process, showing its current stack trace.
1085           It is also used by various kernel debugging features that require
1086           stack trace generation.
1087 
1088 config DEBUG_KOBJECT
1089         bool "kobject debugging"
1090         depends on DEBUG_KERNEL
1091         help
1092           If you say Y here, some extra kobject debugging messages will be sent
1093           to the syslog. 
1094 
1095 config DEBUG_KOBJECT_RELEASE
1096         bool "kobject release debugging"
1097         depends on DEBUG_OBJECTS_TIMERS
1098         help
1099           kobjects are reference counted objects.  This means that their
1100           last reference count put is not predictable, and the kobject can
1101           live on past the point at which a driver decides to drop it's
1102           initial reference to the kobject gained on allocation.  An
1103           example of this would be a struct device which has just been
1104           unregistered.
1105 
1106           However, some buggy drivers assume that after such an operation,
1107           the memory backing the kobject can be immediately freed.  This
1108           goes completely against the principles of a refcounted object.
1109 
1110           If you say Y here, the kernel will delay the release of kobjects
1111           on the last reference count to improve the visibility of this
1112           kind of kobject release bug.
1113 
1114 config HAVE_DEBUG_BUGVERBOSE
1115         bool
1116 
1117 config DEBUG_BUGVERBOSE
1118         bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1119         depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1120         default y
1121         help
1122           Say Y here to make BUG() panics output the file name and line number
1123           of the BUG call as well as the EIP and oops trace.  This aids
1124           debugging but costs about 70-100K of memory.
1125 
1126 config DEBUG_LIST
1127         bool "Debug linked list manipulation"
1128         depends on DEBUG_KERNEL
1129         help
1130           Enable this to turn on extended checks in the linked-list
1131           walking routines.
1132 
1133           If unsure, say N.
1134 
1135 config DEBUG_PI_LIST
1136         bool "Debug priority linked list manipulation"
1137         depends on DEBUG_KERNEL
1138         help
1139           Enable this to turn on extended checks in the priority-ordered
1140           linked-list (plist) walking routines.  This checks the entire
1141           list multiple times during each manipulation.
1142 
1143           If unsure, say N.
1144 
1145 config DEBUG_SG
1146         bool "Debug SG table operations"
1147         depends on DEBUG_KERNEL
1148         help
1149           Enable this to turn on checks on scatter-gather tables. This can
1150           help find problems with drivers that do not properly initialize
1151           their sg tables.
1152 
1153           If unsure, say N.
1154 
1155 config DEBUG_NOTIFIERS
1156         bool "Debug notifier call chains"
1157         depends on DEBUG_KERNEL
1158         help
1159           Enable this to turn on sanity checking for notifier call chains.
1160           This is most useful for kernel developers to make sure that
1161           modules properly unregister themselves from notifier chains.
1162           This is a relatively cheap check but if you care about maximum
1163           performance, say N.
1164 
1165 config DEBUG_CREDENTIALS
1166         bool "Debug credential management"
1167         depends on DEBUG_KERNEL
1168         help
1169           Enable this to turn on some debug checking for credential
1170           management.  The additional code keeps track of the number of
1171           pointers from task_structs to any given cred struct, and checks to
1172           see that this number never exceeds the usage count of the cred
1173           struct.
1174 
1175           Furthermore, if SELinux is enabled, this also checks that the
1176           security pointer in the cred struct is never seen to be invalid.
1177 
1178           If unsure, say N.
1179 
1180 menu "RCU Debugging"
1181 
1182 config PROVE_RCU
1183         bool "RCU debugging: prove RCU correctness"
1184         depends on PROVE_LOCKING
1185         default n
1186         help
1187          This feature enables lockdep extensions that check for correct
1188          use of RCU APIs.  This is currently under development.  Say Y
1189          if you want to debug RCU usage or help work on the PROVE_RCU
1190          feature.
1191 
1192          Say N if you are unsure.
1193 
1194 config PROVE_RCU_REPEATEDLY
1195         bool "RCU debugging: don't disable PROVE_RCU on first splat"
1196         depends on PROVE_RCU
1197         default n
1198         help
1199          By itself, PROVE_RCU will disable checking upon issuing the
1200          first warning (or "splat").  This feature prevents such
1201          disabling, allowing multiple RCU-lockdep warnings to be printed
1202          on a single reboot.
1203 
1204          Say Y to allow multiple RCU-lockdep warnings per boot.
1205 
1206          Say N if you are unsure.
1207 
1208 config SPARSE_RCU_POINTER
1209         bool "RCU debugging: sparse-based checks for pointer usage"
1210         default n
1211         help
1212          This feature enables the __rcu sparse annotation for
1213          RCU-protected pointers.  This annotation will cause sparse
1214          to flag any non-RCU used of annotated pointers.  This can be
1215          helpful when debugging RCU usage.  Please note that this feature
1216          is not intended to enforce code cleanliness; it is instead merely
1217          a debugging aid.
1218 
1219          Say Y to make sparse flag questionable use of RCU-protected pointers
1220 
1221          Say N if you are unsure.
1222 
1223 config TORTURE_TEST
1224         tristate
1225         default n
1226 
1227 config RCU_TORTURE_TEST
1228         tristate "torture tests for RCU"
1229         depends on DEBUG_KERNEL
1230         select TORTURE_TEST
1231         select SRCU
1232         default n
1233         help
1234           This option provides a kernel module that runs torture tests
1235           on the RCU infrastructure.  The kernel module may be built
1236           after the fact on the running kernel to be tested, if desired.
1237 
1238           Say Y here if you want RCU torture tests to be built into
1239           the kernel.
1240           Say M if you want the RCU torture tests to build as a module.
1241           Say N if you are unsure.
1242 
1243 config RCU_TORTURE_TEST_RUNNABLE
1244         bool "torture tests for RCU runnable by default"
1245         depends on RCU_TORTURE_TEST = y
1246         default n
1247         help
1248           This option provides a way to build the RCU torture tests
1249           directly into the kernel without them starting up at boot
1250           time.  You can use /proc/sys/kernel/rcutorture_runnable
1251           to manually override this setting.  This /proc file is
1252           available only when the RCU torture tests have been built
1253           into the kernel.
1254 
1255           Say Y here if you want the RCU torture tests to start during
1256           boot (you probably don't).
1257           Say N here if you want the RCU torture tests to start only
1258           after being manually enabled via /proc.
1259 
1260 config RCU_CPU_STALL_TIMEOUT
1261         int "RCU CPU stall timeout in seconds"
1262         depends on RCU_STALL_COMMON
1263         range 3 300
1264         default 21
1265         help
1266           If a given RCU grace period extends more than the specified
1267           number of seconds, a CPU stall warning is printed.  If the
1268           RCU grace period persists, additional CPU stall warnings are
1269           printed at more widely spaced intervals.
1270 
1271 config RCU_CPU_STALL_INFO
1272         bool "Print additional diagnostics on RCU CPU stall"
1273         depends on (TREE_RCU || PREEMPT_RCU) && DEBUG_KERNEL
1274         default y
1275         help
1276           For each stalled CPU that is aware of the current RCU grace
1277           period, print out additional per-CPU diagnostic information
1278           regarding scheduling-clock ticks, idle state, and,
1279           for RCU_FAST_NO_HZ kernels, idle-entry state.
1280 
1281           Say N if you are unsure.
1282 
1283           Say Y if you want to enable such diagnostics.
1284 
1285 config RCU_TRACE
1286         bool "Enable tracing for RCU"
1287         depends on DEBUG_KERNEL
1288         select TRACE_CLOCK
1289         help
1290           This option provides tracing in RCU which presents stats
1291           in debugfs for debugging RCU implementation.
1292 
1293           Say Y here if you want to enable RCU tracing
1294           Say N if you are unsure.
1295 
1296 endmenu # "RCU Debugging"
1297 
1298 config DEBUG_BLOCK_EXT_DEVT
1299         bool "Force extended block device numbers and spread them"
1300         depends on DEBUG_KERNEL
1301         depends on BLOCK
1302         default n
1303         help
1304           BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1305           SOME DISTRIBUTIONS.  DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1306           YOU ARE DOING.  Distros, please enable this and fix whatever
1307           is broken.
1308 
1309           Conventionally, block device numbers are allocated from
1310           predetermined contiguous area.  However, extended block area
1311           may introduce non-contiguous block device numbers.  This
1312           option forces most block device numbers to be allocated from
1313           the extended space and spreads them to discover kernel or
1314           userland code paths which assume predetermined contiguous
1315           device number allocation.
1316 
1317           Note that turning on this debug option shuffles all the
1318           device numbers for all IDE and SCSI devices including libata
1319           ones, so root partition specified using device number
1320           directly (via rdev or root=MAJ:MIN) won't work anymore.
1321           Textual device names (root=/dev/sdXn) will continue to work.
1322 
1323           Say N if you are unsure.
1324 
1325 config NOTIFIER_ERROR_INJECTION
1326         tristate "Notifier error injection"
1327         depends on DEBUG_KERNEL
1328         select DEBUG_FS
1329         help
1330           This option provides the ability to inject artificial errors to
1331           specified notifier chain callbacks. It is useful to test the error
1332           handling of notifier call chain failures.
1333 
1334           Say N if unsure.
1335 
1336 config CPU_NOTIFIER_ERROR_INJECT
1337         tristate "CPU notifier error injection module"
1338         depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1339         help
1340           This option provides a kernel module that can be used to test
1341           the error handling of the cpu notifiers by injecting artificial
1342           errors to CPU notifier chain callbacks.  It is controlled through
1343           debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
1344 
1345           If the notifier call chain should be failed with some events
1346           notified, write the error code to "actions/<notifier event>/error".
1347 
1348           Example: Inject CPU offline error (-1 == -EPERM)
1349 
1350           # cd /sys/kernel/debug/notifier-error-inject/cpu
1351           # echo -1 > actions/CPU_DOWN_PREPARE/error
1352           # echo 0 > /sys/devices/system/cpu/cpu1/online
1353           bash: echo: write error: Operation not permitted
1354 
1355           To compile this code as a module, choose M here: the module will
1356           be called cpu-notifier-error-inject.
1357 
1358           If unsure, say N.
1359 
1360 config PM_NOTIFIER_ERROR_INJECT
1361         tristate "PM notifier error injection module"
1362         depends on PM && NOTIFIER_ERROR_INJECTION
1363         default m if PM_DEBUG
1364         help
1365           This option provides the ability to inject artificial errors to
1366           PM notifier chain callbacks.  It is controlled through debugfs
1367           interface /sys/kernel/debug/notifier-error-inject/pm
1368 
1369           If the notifier call chain should be failed with some events
1370           notified, write the error code to "actions/<notifier event>/error".
1371 
1372           Example: Inject PM suspend error (-12 = -ENOMEM)
1373 
1374           # cd /sys/kernel/debug/notifier-error-inject/pm/
1375           # echo -12 > actions/PM_SUSPEND_PREPARE/error
1376           # echo mem > /sys/power/state
1377           bash: echo: write error: Cannot allocate memory
1378 
1379           To compile this code as a module, choose M here: the module will
1380           be called pm-notifier-error-inject.
1381 
1382           If unsure, say N.
1383 
1384 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1385         tristate "OF reconfig notifier error injection module"
1386         depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1387         help
1388           This option provides the ability to inject artificial errors to
1389           OF reconfig notifier chain callbacks.  It is controlled
1390           through debugfs interface under
1391           /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1392 
1393           If the notifier call chain should be failed with some events
1394           notified, write the error code to "actions/<notifier event>/error".
1395 
1396           To compile this code as a module, choose M here: the module will
1397           be called of-reconfig-notifier-error-inject.
1398 
1399           If unsure, say N.
1400 
1401 config FAULT_INJECTION
1402         bool "Fault-injection framework"
1403         depends on DEBUG_KERNEL
1404         help
1405           Provide fault-injection framework.
1406           For more details, see Documentation/fault-injection/.
1407 
1408 config FAILSLAB
1409         bool "Fault-injection capability for kmalloc"
1410         depends on FAULT_INJECTION
1411         depends on SLAB || SLUB
1412         help
1413           Provide fault-injection capability for kmalloc.
1414 
1415 config FAIL_PAGE_ALLOC
1416         bool "Fault-injection capabilitiy for alloc_pages()"
1417         depends on FAULT_INJECTION
1418         help
1419           Provide fault-injection capability for alloc_pages().
1420 
1421 config FAIL_MAKE_REQUEST
1422         bool "Fault-injection capability for disk IO"
1423         depends on FAULT_INJECTION && BLOCK
1424         help
1425           Provide fault-injection capability for disk IO.
1426 
1427 config FAIL_IO_TIMEOUT
1428         bool "Fault-injection capability for faking disk interrupts"
1429         depends on FAULT_INJECTION && BLOCK
1430         help
1431           Provide fault-injection capability on end IO handling. This
1432           will make the block layer "forget" an interrupt as configured,
1433           thus exercising the error handling.
1434 
1435           Only works with drivers that use the generic timeout handling,
1436           for others it wont do anything.
1437 
1438 config FAIL_MMC_REQUEST
1439         bool "Fault-injection capability for MMC IO"
1440         select DEBUG_FS
1441         depends on FAULT_INJECTION && MMC
1442         help
1443           Provide fault-injection capability for MMC IO.
1444           This will make the mmc core return data errors. This is
1445           useful to test the error handling in the mmc block device
1446           and to test how the mmc host driver handles retries from
1447           the block device.
1448 
1449 config FAULT_INJECTION_DEBUG_FS
1450         bool "Debugfs entries for fault-injection capabilities"
1451         depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1452         help
1453           Enable configuration of fault-injection capabilities via debugfs.
1454 
1455 config FAULT_INJECTION_STACKTRACE_FILTER
1456         bool "stacktrace filter for fault-injection capabilities"
1457         depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1458         depends on !X86_64
1459         select STACKTRACE
1460         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1461         help
1462           Provide stacktrace filter for fault-injection capabilities
1463 
1464 config LATENCYTOP
1465         bool "Latency measuring infrastructure"
1466         depends on HAVE_LATENCYTOP_SUPPORT
1467         depends on DEBUG_KERNEL
1468         depends on STACKTRACE_SUPPORT
1469         depends on PROC_FS
1470         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1471         select KALLSYMS
1472         select KALLSYMS_ALL
1473         select STACKTRACE
1474         select SCHEDSTATS
1475         select SCHED_DEBUG
1476         help
1477           Enable this option if you want to use the LatencyTOP tool
1478           to find out which userspace is blocking on what kernel operations.
1479 
1480 config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1481         bool
1482 
1483 config DEBUG_STRICT_USER_COPY_CHECKS
1484         bool "Strict user copy size checks"
1485         depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1486         depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
1487         help
1488           Enabling this option turns a certain set of sanity checks for user
1489           copy operations into compile time failures.
1490 
1491           The copy_from_user() etc checks are there to help test if there
1492           are sufficient security checks on the length argument of
1493           the copy operation, by having gcc prove that the argument is
1494           within bounds.
1495 
1496           If unsure, say N.
1497 
1498 source kernel/trace/Kconfig
1499 
1500 menu "Runtime Testing"
1501 
1502 config LKDTM
1503         tristate "Linux Kernel Dump Test Tool Module"
1504         depends on DEBUG_FS
1505         depends on BLOCK
1506         default n
1507         help
1508         This module enables testing of the different dumping mechanisms by
1509         inducing system failures at predefined crash points.
1510         If you don't need it: say N
1511         Choose M here to compile this code as a module. The module will be
1512         called lkdtm.
1513 
1514         Documentation on how to use the module can be found in
1515         Documentation/fault-injection/provoke-crashes.txt
1516 
1517 config TEST_LIST_SORT
1518         bool "Linked list sorting test"
1519         depends on DEBUG_KERNEL
1520         help
1521           Enable this to turn on 'list_sort()' function test. This test is
1522           executed only once during system boot, so affects only boot time.
1523 
1524           If unsure, say N.
1525 
1526 config KPROBES_SANITY_TEST
1527         bool "Kprobes sanity tests"
1528         depends on DEBUG_KERNEL
1529         depends on KPROBES
1530         default n
1531         help
1532           This option provides for testing basic kprobes functionality on
1533           boot. A sample kprobe, jprobe and kretprobe are inserted and
1534           verified for functionality.
1535 
1536           Say N if you are unsure.
1537 
1538 config BACKTRACE_SELF_TEST
1539         tristate "Self test for the backtrace code"
1540         depends on DEBUG_KERNEL
1541         default n
1542         help
1543           This option provides a kernel module that can be used to test
1544           the kernel stack backtrace code. This option is not useful
1545           for distributions or general kernels, but only for kernel
1546           developers working on architecture code.
1547 
1548           Note that if you want to also test saved backtraces, you will
1549           have to enable STACKTRACE as well.
1550 
1551           Say N if you are unsure.
1552 
1553 config RBTREE_TEST
1554         tristate "Red-Black tree test"
1555         depends on DEBUG_KERNEL
1556         help
1557           A benchmark measuring the performance of the rbtree library.
1558           Also includes rbtree invariant checks.
1559 
1560 config INTERVAL_TREE_TEST
1561         tristate "Interval tree test"
1562         depends on m && DEBUG_KERNEL
1563         select INTERVAL_TREE
1564         help
1565           A benchmark measuring the performance of the interval tree library
1566 
1567 config PERCPU_TEST
1568         tristate "Per cpu operations test"
1569         depends on m && DEBUG_KERNEL
1570         help
1571           Enable this option to build test module which validates per-cpu
1572           operations.
1573 
1574           If unsure, say N.
1575 
1576 config ATOMIC64_SELFTEST
1577         bool "Perform an atomic64_t self-test at boot"
1578         help
1579           Enable this option to test the atomic64_t functions at boot.
1580 
1581           If unsure, say N.
1582 
1583 config ASYNC_RAID6_TEST
1584         tristate "Self test for hardware accelerated raid6 recovery"
1585         depends on ASYNC_RAID6_RECOV
1586         select ASYNC_MEMCPY
1587         ---help---
1588           This is a one-shot self test that permutes through the
1589           recovery of all the possible two disk failure scenarios for a
1590           N-disk array.  Recovery is performed with the asynchronous
1591           raid6 recovery routines, and will optionally use an offload
1592           engine if one is available.
1593 
1594           If unsure, say N.
1595 
1596 config TEST_HEXDUMP
1597         tristate "Test functions located in the hexdump module at runtime"
1598 
1599 config TEST_STRING_HELPERS
1600         tristate "Test functions located in the string_helpers module at runtime"
1601 
1602 config TEST_KSTRTOX
1603         tristate "Test kstrto*() family of functions at runtime"
1604 
1605 config TEST_RHASHTABLE
1606         tristate "Perform selftest on resizable hash table"
1607         default n
1608         help
1609           Enable this option to test the rhashtable functions at boot.
1610 
1611           If unsure, say N.
1612 
1613 endmenu # runtime tests
1614 
1615 config PROVIDE_OHCI1394_DMA_INIT
1616         bool "Remote debugging over FireWire early on boot"
1617         depends on PCI && X86
1618         help
1619           If you want to debug problems which hang or crash the kernel early
1620           on boot and the crashing machine has a FireWire port, you can use
1621           this feature to remotely access the memory of the crashed machine
1622           over FireWire. This employs remote DMA as part of the OHCI1394
1623           specification which is now the standard for FireWire controllers.
1624 
1625           With remote DMA, you can monitor the printk buffer remotely using
1626           firescope and access all memory below 4GB using fireproxy from gdb.
1627           Even controlling a kernel debugger is possible using remote DMA.
1628 
1629           Usage:
1630 
1631           If ohci1394_dma=early is used as boot parameter, it will initialize
1632           all OHCI1394 controllers which are found in the PCI config space.
1633 
1634           As all changes to the FireWire bus such as enabling and disabling
1635           devices cause a bus reset and thereby disable remote DMA for all
1636           devices, be sure to have the cable plugged and FireWire enabled on
1637           the debugging host before booting the debug target for debugging.
1638 
1639           This code (~1k) is freed after boot. By then, the firewire stack
1640           in charge of the OHCI-1394 controllers should be used instead.
1641 
1642           See Documentation/debugging-via-ohci1394.txt for more information.
1643 
1644 config BUILD_DOCSRC
1645         bool "Build targets in Documentation/ tree"
1646         depends on HEADERS_CHECK
1647         help
1648           This option attempts to build objects from the source files in the
1649           kernel Documentation/ tree.
1650 
1651           Say N if you are unsure.
1652 
1653 config DMA_API_DEBUG
1654         bool "Enable debugging of DMA-API usage"
1655         depends on HAVE_DMA_API_DEBUG
1656         help
1657           Enable this option to debug the use of the DMA API by device drivers.
1658           With this option you will be able to detect common bugs in device
1659           drivers like double-freeing of DMA mappings or freeing mappings that
1660           were never allocated.
1661 
1662           This also attempts to catch cases where a page owned by DMA is
1663           accessed by the cpu in a way that could cause data corruption.  For
1664           example, this enables cow_user_page() to check that the source page is
1665           not undergoing DMA.
1666 
1667           This option causes a performance degradation.  Use only if you want to
1668           debug device drivers and dma interactions.
1669 
1670           If unsure, say N.
1671 
1672 config TEST_LKM
1673         tristate "Test module loading with 'hello world' module"
1674         default n
1675         depends on m
1676         help
1677           This builds the "test_module" module that emits "Hello, world"
1678           on printk when loaded. It is designed to be used for basic
1679           evaluation of the module loading subsystem (for example when
1680           validating module verification). It lacks any extra dependencies,
1681           and will not normally be loaded by the system unless explicitly
1682           requested by name.
1683 
1684           If unsure, say N.
1685 
1686 config TEST_USER_COPY
1687         tristate "Test user/kernel boundary protections"
1688         default n
1689         depends on m
1690         help
1691           This builds the "test_user_copy" module that runs sanity checks
1692           on the copy_to/from_user infrastructure, making sure basic
1693           user/kernel boundary testing is working. If it fails to load,
1694           a regression has been detected in the user/kernel memory boundary
1695           protections.
1696 
1697           If unsure, say N.
1698 
1699 config TEST_BPF
1700         tristate "Test BPF filter functionality"
1701         default n
1702         depends on m && NET
1703         help
1704           This builds the "test_bpf" module that runs various test vectors
1705           against the BPF interpreter or BPF JIT compiler depending on the
1706           current setting. This is in particular useful for BPF JIT compiler
1707           development, but also to run regression tests against changes in
1708           the interpreter code. It also enables test stubs for eBPF maps and
1709           verifier used by user space verifier testsuite.
1710 
1711           If unsure, say N.
1712 
1713 config TEST_FIRMWARE
1714         tristate "Test firmware loading via userspace interface"
1715         default n
1716         depends on FW_LOADER
1717         help
1718           This builds the "test_firmware" module that creates a userspace
1719           interface for testing firmware loading. This can be used to
1720           control the triggering of firmware loading without needing an
1721           actual firmware-using device. The contents can be rechecked by
1722           userspace.
1723 
1724           If unsure, say N.
1725 
1726 config TEST_UDELAY
1727         tristate "udelay test driver"
1728         default n
1729         help
1730           This builds the "udelay_test" module that helps to make sure
1731           that udelay() is working properly.
1732 
1733           If unsure, say N.
1734 
1735 source "samples/Kconfig"
1736 
1737 source "lib/Kconfig.kgdb"
1738 

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