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Linux/lib/Kconfig.debug

  1 menu "printk and dmesg options"
  2 
  3 config PRINTK_TIME
  4         bool "Show timing information on printks"
  5         depends on PRINTK
  6         help
  7           Selecting this option causes time stamps of the printk()
  8           messages to be added to the output of the syslog() system
  9           call and at the console.
 10 
 11           The timestamp is always recorded internally, and exported
 12           to /dev/kmsg. This flag just specifies if the timestamp should
 13           be included, not that the timestamp is recorded.
 14 
 15           The behavior is also controlled by the kernel command line
 16           parameter printk.time=1. See Documentation/kernel-parameters.txt
 17 
 18 config MESSAGE_LOGLEVEL_DEFAULT
 19         int "Default message log level (1-7)"
 20         range 1 7
 21         default "4"
 22         help
 23           Default log level for printk statements with no specified priority.
 24 
 25           This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
 26           that are auditing their logs closely may want to set it to a lower
 27           priority.
 28 
 29 config BOOT_PRINTK_DELAY
 30         bool "Delay each boot printk message by N milliseconds"
 31         depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
 32         help
 33           This build option allows you to read kernel boot messages
 34           by inserting a short delay after each one.  The delay is
 35           specified in milliseconds on the kernel command line,
 36           using "boot_delay=N".
 37 
 38           It is likely that you would also need to use "lpj=M" to preset
 39           the "loops per jiffie" value.
 40           See a previous boot log for the "lpj" value to use for your
 41           system, and then set "lpj=M" before setting "boot_delay=N".
 42           NOTE:  Using this option may adversely affect SMP systems.
 43           I.e., processors other than the first one may not boot up.
 44           BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
 45           what it believes to be lockup conditions.
 46 
 47 config DYNAMIC_DEBUG
 48         bool "Enable dynamic printk() support"
 49         default n
 50         depends on PRINTK
 51         depends on DEBUG_FS
 52         help
 53 
 54           Compiles debug level messages into the kernel, which would not
 55           otherwise be available at runtime. These messages can then be
 56           enabled/disabled based on various levels of scope - per source file,
 57           function, module, format string, and line number. This mechanism
 58           implicitly compiles in all pr_debug() and dev_dbg() calls, which
 59           enlarges the kernel text size by about 2%.
 60 
 61           If a source file is compiled with DEBUG flag set, any
 62           pr_debug() calls in it are enabled by default, but can be
 63           disabled at runtime as below.  Note that DEBUG flag is
 64           turned on by many CONFIG_*DEBUG* options.
 65 
 66           Usage:
 67 
 68           Dynamic debugging is controlled via the 'dynamic_debug/control' file,
 69           which is contained in the 'debugfs' filesystem. Thus, the debugfs
 70           filesystem must first be mounted before making use of this feature.
 71           We refer the control file as: <debugfs>/dynamic_debug/control. This
 72           file contains a list of the debug statements that can be enabled. The
 73           format for each line of the file is:
 74 
 75                 filename:lineno [module]function flags format
 76 
 77           filename : source file of the debug statement
 78           lineno : line number of the debug statement
 79           module : module that contains the debug statement
 80           function : function that contains the debug statement
 81           flags : '=p' means the line is turned 'on' for printing
 82           format : the format used for the debug statement
 83 
 84           From a live system:
 85 
 86                 nullarbor:~ # cat <debugfs>/dynamic_debug/control
 87                 # filename:lineno [module]function flags format
 88                 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
 89                 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
 90                 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
 91 
 92           Example usage:
 93 
 94                 // enable the message at line 1603 of file svcsock.c
 95                 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
 96                                                 <debugfs>/dynamic_debug/control
 97 
 98                 // enable all the messages in file svcsock.c
 99                 nullarbor:~ # echo -n 'file svcsock.c +p' >
100                                                 <debugfs>/dynamic_debug/control
101 
102                 // enable all the messages in the NFS server module
103                 nullarbor:~ # echo -n 'module nfsd +p' >
104                                                 <debugfs>/dynamic_debug/control
105 
106                 // enable all 12 messages in the function svc_process()
107                 nullarbor:~ # echo -n 'func svc_process +p' >
108                                                 <debugfs>/dynamic_debug/control
109 
110                 // disable all 12 messages in the function svc_process()
111                 nullarbor:~ # echo -n 'func svc_process -p' >
112                                                 <debugfs>/dynamic_debug/control
113 
114           See Documentation/dynamic-debug-howto.txt for additional information.
115 
116 endmenu # "printk and dmesg options"
117 
118 menu "Compile-time checks and compiler options"
119 
120 config DEBUG_INFO
121         bool "Compile the kernel with debug info"
122         depends on DEBUG_KERNEL && !COMPILE_TEST
123         help
124           If you say Y here the resulting kernel image will include
125           debugging info resulting in a larger kernel image.
126           This adds debug symbols to the kernel and modules (gcc -g), and
127           is needed if you intend to use kernel crashdump or binary object
128           tools like crash, kgdb, LKCD, gdb, etc on the kernel.
129           Say Y here only if you plan to debug the kernel.
130 
131           If unsure, say N.
132 
133 config DEBUG_INFO_REDUCED
134         bool "Reduce debugging information"
135         depends on DEBUG_INFO
136         help
137           If you say Y here gcc is instructed to generate less debugging
138           information for structure types. This means that tools that
139           need full debugging information (like kgdb or systemtap) won't
140           be happy. But if you merely need debugging information to
141           resolve line numbers there is no loss. Advantage is that
142           build directory object sizes shrink dramatically over a full
143           DEBUG_INFO build and compile times are reduced too.
144           Only works with newer gcc versions.
145 
146 config DEBUG_INFO_SPLIT
147         bool "Produce split debuginfo in .dwo files"
148         depends on DEBUG_INFO
149         help
150           Generate debug info into separate .dwo files. This significantly
151           reduces the build directory size for builds with DEBUG_INFO,
152           because it stores the information only once on disk in .dwo
153           files instead of multiple times in object files and executables.
154           In addition the debug information is also compressed.
155 
156           Requires recent gcc (4.7+) and recent gdb/binutils.
157           Any tool that packages or reads debug information would need
158           to know about the .dwo files and include them.
159           Incompatible with older versions of ccache.
160 
161 config DEBUG_INFO_DWARF4
162         bool "Generate dwarf4 debuginfo"
163         depends on DEBUG_INFO
164         help
165           Generate dwarf4 debug info. This requires recent versions
166           of gcc and gdb. It makes the debug information larger.
167           But it significantly improves the success of resolving
168           variables in gdb on optimized code.
169 
170 config GDB_SCRIPTS
171         bool "Provide GDB scripts for kernel debugging"
172         depends on DEBUG_INFO
173         help
174           This creates the required links to GDB helper scripts in the
175           build directory. If you load vmlinux into gdb, the helper
176           scripts will be automatically imported by gdb as well, and
177           additional functions are available to analyze a Linux kernel
178           instance. See Documentation/gdb-kernel-debugging.txt for further
179           details.
180 
181 config ENABLE_WARN_DEPRECATED
182         bool "Enable __deprecated logic"
183         default y
184         help
185           Enable the __deprecated logic in the kernel build.
186           Disable this to suppress the "warning: 'foo' is deprecated
187           (declared at kernel/power/somefile.c:1234)" messages.
188 
189 config ENABLE_MUST_CHECK
190         bool "Enable __must_check logic"
191         default y
192         help
193           Enable the __must_check logic in the kernel build.  Disable this to
194           suppress the "warning: ignoring return value of 'foo', declared with
195           attribute warn_unused_result" messages.
196 
197 config FRAME_WARN
198         int "Warn for stack frames larger than (needs gcc 4.4)"
199         range 0 8192
200         default 0 if KASAN
201         default 2048 if GCC_PLUGIN_LATENT_ENTROPY
202         default 1024 if !64BIT
203         default 2048 if 64BIT
204         help
205           Tell gcc to warn at build time for stack frames larger than this.
206           Setting this too low will cause a lot of warnings.
207           Setting it to 0 disables the warning.
208           Requires gcc 4.4
209 
210 config STRIP_ASM_SYMS
211         bool "Strip assembler-generated symbols during link"
212         default n
213         help
214           Strip internal assembler-generated symbols during a link (symbols
215           that look like '.Lxxx') so they don't pollute the output of
216           get_wchan() and suchlike.
217 
218 config READABLE_ASM
219         bool "Generate readable assembler code"
220         depends on DEBUG_KERNEL
221         help
222           Disable some compiler optimizations that tend to generate human unreadable
223           assembler output. This may make the kernel slightly slower, but it helps
224           to keep kernel developers who have to stare a lot at assembler listings
225           sane.
226 
227 config UNUSED_SYMBOLS
228         bool "Enable unused/obsolete exported symbols"
229         default y if X86
230         help
231           Unused but exported symbols make the kernel needlessly bigger.  For
232           that reason most of these unused exports will soon be removed.  This
233           option is provided temporarily to provide a transition period in case
234           some external kernel module needs one of these symbols anyway. If you
235           encounter such a case in your module, consider if you are actually
236           using the right API.  (rationale: since nobody in the kernel is using
237           this in a module, there is a pretty good chance it's actually the
238           wrong interface to use).  If you really need the symbol, please send a
239           mail to the linux kernel mailing list mentioning the symbol and why
240           you really need it, and what the merge plan to the mainline kernel for
241           your module is.
242 
243 config PAGE_OWNER
244         bool "Track page owner"
245         depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
246         select DEBUG_FS
247         select STACKTRACE
248         select STACKDEPOT
249         select PAGE_EXTENSION
250         help
251           This keeps track of what call chain is the owner of a page, may
252           help to find bare alloc_page(s) leaks. Even if you include this
253           feature on your build, it is disabled in default. You should pass
254           "page_owner=on" to boot parameter in order to enable it. Eats
255           a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
256           for user-space helper.
257 
258           If unsure, say N.
259 
260 config DEBUG_FS
261         bool "Debug Filesystem"
262         select SRCU
263         help
264           debugfs is a virtual file system that kernel developers use to put
265           debugging files into.  Enable this option to be able to read and
266           write to these files.
267 
268           For detailed documentation on the debugfs API, see
269           Documentation/DocBook/filesystems.
270 
271           If unsure, say N.
272 
273 config HEADERS_CHECK
274         bool "Run 'make headers_check' when building vmlinux"
275         depends on !UML
276         help
277           This option will extract the user-visible kernel headers whenever
278           building the kernel, and will run basic sanity checks on them to
279           ensure that exported files do not attempt to include files which
280           were not exported, etc.
281 
282           If you're making modifications to header files which are
283           relevant for userspace, say 'Y', and check the headers
284           exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
285           your build tree), to make sure they're suitable.
286 
287 config DEBUG_SECTION_MISMATCH
288         bool "Enable full Section mismatch analysis"
289         help
290           The section mismatch analysis checks if there are illegal
291           references from one section to another section.
292           During linktime or runtime, some sections are dropped;
293           any use of code/data previously in these sections would
294           most likely result in an oops.
295           In the code, functions and variables are annotated with
296           __init,, etc. (see the full list in include/linux/init.h),
297           which results in the code/data being placed in specific sections.
298           The section mismatch analysis is always performed after a full
299           kernel build, and enabling this option causes the following
300           additional steps to occur:
301           - Add the option -fno-inline-functions-called-once to gcc commands.
302             When inlining a function annotated with __init in a non-init
303             function, we would lose the section information and thus
304             the analysis would not catch the illegal reference.
305             This option tells gcc to inline less (but it does result in
306             a larger kernel).
307           - Run the section mismatch analysis for each module/built-in.o file.
308             When we run the section mismatch analysis on vmlinux.o, we
309             lose valuable information about where the mismatch was
310             introduced.
311             Running the analysis for each module/built-in.o file
312             tells where the mismatch happens much closer to the
313             source. The drawback is that the same mismatch is
314             reported at least twice.
315           - Enable verbose reporting from modpost in order to help resolve
316             the section mismatches that are reported.
317 
318 config SECTION_MISMATCH_WARN_ONLY
319         bool "Make section mismatch errors non-fatal"
320         default y
321         help
322           If you say N here, the build process will fail if there are any
323           section mismatch, instead of just throwing warnings.
324 
325           If unsure, say Y.
326 
327 #
328 # Select this config option from the architecture Kconfig, if it
329 # is preferred to always offer frame pointers as a config
330 # option on the architecture (regardless of KERNEL_DEBUG):
331 #
332 config ARCH_WANT_FRAME_POINTERS
333         bool
334         help
335 
336 config FRAME_POINTER
337         bool "Compile the kernel with frame pointers"
338         depends on DEBUG_KERNEL && \
339                 (CRIS || M68K || FRV || UML || \
340                  AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \
341                 ARCH_WANT_FRAME_POINTERS
342         default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
343         help
344           If you say Y here the resulting kernel image will be slightly
345           larger and slower, but it gives very useful debugging information
346           in case of kernel bugs. (precise oopses/stacktraces/warnings)
347 
348 config STACK_VALIDATION
349         bool "Compile-time stack metadata validation"
350         depends on HAVE_STACK_VALIDATION
351         default n
352         help
353           Add compile-time checks to validate stack metadata, including frame
354           pointers (if CONFIG_FRAME_POINTER is enabled).  This helps ensure
355           that runtime stack traces are more reliable.
356 
357           For more information, see
358           tools/objtool/Documentation/stack-validation.txt.
359 
360 config DEBUG_FORCE_WEAK_PER_CPU
361         bool "Force weak per-cpu definitions"
362         depends on DEBUG_KERNEL
363         help
364           s390 and alpha require percpu variables in modules to be
365           defined weak to work around addressing range issue which
366           puts the following two restrictions on percpu variable
367           definitions.
368 
369           1. percpu symbols must be unique whether static or not
370           2. percpu variables can't be defined inside a function
371 
372           To ensure that generic code follows the above rules, this
373           option forces all percpu variables to be defined as weak.
374 
375 endmenu # "Compiler options"
376 
377 config MAGIC_SYSRQ
378         bool "Magic SysRq key"
379         depends on !UML
380         help
381           If you say Y here, you will have some control over the system even
382           if the system crashes for example during kernel debugging (e.g., you
383           will be able to flush the buffer cache to disk, reboot the system
384           immediately or dump some status information). This is accomplished
385           by pressing various keys while holding SysRq (Alt+PrintScreen). It
386           also works on a serial console (on PC hardware at least), if you
387           send a BREAK and then within 5 seconds a command keypress. The
388           keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
389           unless you really know what this hack does.
390 
391 config MAGIC_SYSRQ_DEFAULT_ENABLE
392         hex "Enable magic SysRq key functions by default"
393         depends on MAGIC_SYSRQ
394         default 0x1
395         help
396           Specifies which SysRq key functions are enabled by default.
397           This may be set to 1 or 0 to enable or disable them all, or
398           to a bitmask as described in Documentation/sysrq.txt.
399 
400 config DEBUG_KERNEL
401         bool "Kernel debugging"
402         help
403           Say Y here if you are developing drivers or trying to debug and
404           identify kernel problems.
405 
406 menu "Memory Debugging"
407 
408 source mm/Kconfig.debug
409 
410 config DEBUG_OBJECTS
411         bool "Debug object operations"
412         depends on DEBUG_KERNEL
413         help
414           If you say Y here, additional code will be inserted into the
415           kernel to track the life time of various objects and validate
416           the operations on those objects.
417 
418 config DEBUG_OBJECTS_SELFTEST
419         bool "Debug objects selftest"
420         depends on DEBUG_OBJECTS
421         help
422           This enables the selftest of the object debug code.
423 
424 config DEBUG_OBJECTS_FREE
425         bool "Debug objects in freed memory"
426         depends on DEBUG_OBJECTS
427         help
428           This enables checks whether a k/v free operation frees an area
429           which contains an object which has not been deactivated
430           properly. This can make kmalloc/kfree-intensive workloads
431           much slower.
432 
433 config DEBUG_OBJECTS_TIMERS
434         bool "Debug timer objects"
435         depends on DEBUG_OBJECTS
436         help
437           If you say Y here, additional code will be inserted into the
438           timer routines to track the life time of timer objects and
439           validate the timer operations.
440 
441 config DEBUG_OBJECTS_WORK
442         bool "Debug work objects"
443         depends on DEBUG_OBJECTS
444         help
445           If you say Y here, additional code will be inserted into the
446           work queue routines to track the life time of work objects and
447           validate the work operations.
448 
449 config DEBUG_OBJECTS_RCU_HEAD
450         bool "Debug RCU callbacks objects"
451         depends on DEBUG_OBJECTS
452         help
453           Enable this to turn on debugging of RCU list heads (call_rcu() usage).
454 
455 config DEBUG_OBJECTS_PERCPU_COUNTER
456         bool "Debug percpu counter objects"
457         depends on DEBUG_OBJECTS
458         help
459           If you say Y here, additional code will be inserted into the
460           percpu counter routines to track the life time of percpu counter
461           objects and validate the percpu counter operations.
462 
463 config DEBUG_OBJECTS_ENABLE_DEFAULT
464         int "debug_objects bootup default value (0-1)"
465         range 0 1
466         default "1"
467         depends on DEBUG_OBJECTS
468         help
469           Debug objects boot parameter default value
470 
471 config DEBUG_SLAB
472         bool "Debug slab memory allocations"
473         depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
474         help
475           Say Y here to have the kernel do limited verification on memory
476           allocation as well as poisoning memory on free to catch use of freed
477           memory. This can make kmalloc/kfree-intensive workloads much slower.
478 
479 config DEBUG_SLAB_LEAK
480         bool "Memory leak debugging"
481         depends on DEBUG_SLAB
482 
483 config SLUB_DEBUG_ON
484         bool "SLUB debugging on by default"
485         depends on SLUB && SLUB_DEBUG && !KMEMCHECK
486         default n
487         help
488           Boot with debugging on by default. SLUB boots by default with
489           the runtime debug capabilities switched off. Enabling this is
490           equivalent to specifying the "slub_debug" parameter on boot.
491           There is no support for more fine grained debug control like
492           possible with slub_debug=xxx. SLUB debugging may be switched
493           off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
494           "slub_debug=-".
495 
496 config SLUB_STATS
497         default n
498         bool "Enable SLUB performance statistics"
499         depends on SLUB && SYSFS
500         help
501           SLUB statistics are useful to debug SLUBs allocation behavior in
502           order find ways to optimize the allocator. This should never be
503           enabled for production use since keeping statistics slows down
504           the allocator by a few percentage points. The slabinfo command
505           supports the determination of the most active slabs to figure
506           out which slabs are relevant to a particular load.
507           Try running: slabinfo -DA
508 
509 config HAVE_DEBUG_KMEMLEAK
510         bool
511 
512 config DEBUG_KMEMLEAK
513         bool "Kernel memory leak detector"
514         depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
515         select DEBUG_FS
516         select STACKTRACE if STACKTRACE_SUPPORT
517         select KALLSYMS
518         select CRC32
519         help
520           Say Y here if you want to enable the memory leak
521           detector. The memory allocation/freeing is traced in a way
522           similar to the Boehm's conservative garbage collector, the
523           difference being that the orphan objects are not freed but
524           only shown in /sys/kernel/debug/kmemleak. Enabling this
525           feature will introduce an overhead to memory
526           allocations. See Documentation/kmemleak.txt for more
527           details.
528 
529           Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
530           of finding leaks due to the slab objects poisoning.
531 
532           In order to access the kmemleak file, debugfs needs to be
533           mounted (usually at /sys/kernel/debug).
534 
535 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
536         int "Maximum kmemleak early log entries"
537         depends on DEBUG_KMEMLEAK
538         range 200 40000
539         default 400
540         help
541           Kmemleak must track all the memory allocations to avoid
542           reporting false positives. Since memory may be allocated or
543           freed before kmemleak is initialised, an early log buffer is
544           used to store these actions. If kmemleak reports "early log
545           buffer exceeded", please increase this value.
546 
547 config DEBUG_KMEMLEAK_TEST
548         tristate "Simple test for the kernel memory leak detector"
549         depends on DEBUG_KMEMLEAK && m
550         help
551           This option enables a module that explicitly leaks memory.
552 
553           If unsure, say N.
554 
555 config DEBUG_KMEMLEAK_DEFAULT_OFF
556         bool "Default kmemleak to off"
557         depends on DEBUG_KMEMLEAK
558         help
559           Say Y here to disable kmemleak by default. It can then be enabled
560           on the command line via kmemleak=on.
561 
562 config DEBUG_STACK_USAGE
563         bool "Stack utilization instrumentation"
564         depends on DEBUG_KERNEL && !IA64
565         help
566           Enables the display of the minimum amount of free stack which each
567           task has ever had available in the sysrq-T and sysrq-P debug output.
568 
569           This option will slow down process creation somewhat.
570 
571 config DEBUG_VM
572         bool "Debug VM"
573         depends on DEBUG_KERNEL
574         help
575           Enable this to turn on extended checks in the virtual-memory system
576           that may impact performance.
577 
578           If unsure, say N.
579 
580 config DEBUG_VM_VMACACHE
581         bool "Debug VMA caching"
582         depends on DEBUG_VM
583         help
584           Enable this to turn on VMA caching debug information. Doing so
585           can cause significant overhead, so only enable it in non-production
586           environments.
587 
588           If unsure, say N.
589 
590 config DEBUG_VM_RB
591         bool "Debug VM red-black trees"
592         depends on DEBUG_VM
593         help
594           Enable VM red-black tree debugging information and extra validations.
595 
596           If unsure, say N.
597 
598 config DEBUG_VM_PGFLAGS
599         bool "Debug page-flags operations"
600         depends on DEBUG_VM
601         help
602           Enables extra validation on page flags operations.
603 
604           If unsure, say N.
605 
606 config DEBUG_VIRTUAL
607         bool "Debug VM translations"
608         depends on DEBUG_KERNEL && X86
609         help
610           Enable some costly sanity checks in virtual to page code. This can
611           catch mistakes with virt_to_page() and friends.
612 
613           If unsure, say N.
614 
615 config DEBUG_NOMMU_REGIONS
616         bool "Debug the global anon/private NOMMU mapping region tree"
617         depends on DEBUG_KERNEL && !MMU
618         help
619           This option causes the global tree of anonymous and private mapping
620           regions to be regularly checked for invalid topology.
621 
622 config DEBUG_MEMORY_INIT
623         bool "Debug memory initialisation" if EXPERT
624         default !EXPERT
625         help
626           Enable this for additional checks during memory initialisation.
627           The sanity checks verify aspects of the VM such as the memory model
628           and other information provided by the architecture. Verbose
629           information will be printed at KERN_DEBUG loglevel depending
630           on the mminit_loglevel= command-line option.
631 
632           If unsure, say Y
633 
634 config MEMORY_NOTIFIER_ERROR_INJECT
635         tristate "Memory hotplug notifier error injection module"
636         depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
637         help
638           This option provides the ability to inject artificial errors to
639           memory hotplug notifier chain callbacks.  It is controlled through
640           debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
641 
642           If the notifier call chain should be failed with some events
643           notified, write the error code to "actions/<notifier event>/error".
644 
645           Example: Inject memory hotplug offline error (-12 == -ENOMEM)
646 
647           # cd /sys/kernel/debug/notifier-error-inject/memory
648           # echo -12 > actions/MEM_GOING_OFFLINE/error
649           # echo offline > /sys/devices/system/memory/memoryXXX/state
650           bash: echo: write error: Cannot allocate memory
651 
652           To compile this code as a module, choose M here: the module will
653           be called memory-notifier-error-inject.
654 
655           If unsure, say N.
656 
657 config DEBUG_PER_CPU_MAPS
658         bool "Debug access to per_cpu maps"
659         depends on DEBUG_KERNEL
660         depends on SMP
661         help
662           Say Y to verify that the per_cpu map being accessed has
663           been set up. This adds a fair amount of code to kernel memory
664           and decreases performance.
665 
666           Say N if unsure.
667 
668 config DEBUG_HIGHMEM
669         bool "Highmem debugging"
670         depends on DEBUG_KERNEL && HIGHMEM
671         help
672           This option enables additional error checking for high memory
673           systems.  Disable for production systems.
674 
675 config HAVE_DEBUG_STACKOVERFLOW
676         bool
677 
678 config DEBUG_STACKOVERFLOW
679         bool "Check for stack overflows"
680         depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
681         ---help---
682           Say Y here if you want to check for overflows of kernel, IRQ
683           and exception stacks (if your architecture uses them). This
684           option will show detailed messages if free stack space drops
685           below a certain limit.
686 
687           These kinds of bugs usually occur when call-chains in the
688           kernel get too deep, especially when interrupts are
689           involved.
690 
691           Use this in cases where you see apparently random memory
692           corruption, especially if it appears in 'struct thread_info'
693 
694           If in doubt, say "N".
695 
696 source "lib/Kconfig.kmemcheck"
697 
698 source "lib/Kconfig.kasan"
699 
700 endmenu # "Memory Debugging"
701 
702 config ARCH_HAS_KCOV
703         bool
704         help
705           KCOV does not have any arch-specific code, but currently it is enabled
706           only for x86_64. KCOV requires testing on other archs, and most likely
707           disabling of instrumentation for some early boot code.
708 
709 config KCOV
710         bool "Code coverage for fuzzing"
711         depends on ARCH_HAS_KCOV
712         select DEBUG_FS
713         select GCC_PLUGINS if !COMPILE_TEST
714         select GCC_PLUGIN_SANCOV if !COMPILE_TEST
715         help
716           KCOV exposes kernel code coverage information in a form suitable
717           for coverage-guided fuzzing (randomized testing).
718 
719           If RANDOMIZE_BASE is enabled, PC values will not be stable across
720           different machines and across reboots. If you need stable PC values,
721           disable RANDOMIZE_BASE.
722 
723           For more details, see Documentation/kcov.txt.
724 
725 config KCOV_INSTRUMENT_ALL
726         bool "Instrument all code by default"
727         depends on KCOV
728         default y if KCOV
729         help
730           If you are doing generic system call fuzzing (like e.g. syzkaller),
731           then you will want to instrument the whole kernel and you should
732           say y here. If you are doing more targeted fuzzing (like e.g.
733           filesystem fuzzing with AFL) then you will want to enable coverage
734           for more specific subsets of files, and should say n here.
735 
736 config DEBUG_SHIRQ
737         bool "Debug shared IRQ handlers"
738         depends on DEBUG_KERNEL
739         help
740           Enable this to generate a spurious interrupt as soon as a shared
741           interrupt handler is registered, and just before one is deregistered.
742           Drivers ought to be able to handle interrupts coming in at those
743           points; some don't and need to be caught.
744 
745 menu "Debug Lockups and Hangs"
746 
747 config LOCKUP_DETECTOR
748         bool "Detect Hard and Soft Lockups"
749         depends on DEBUG_KERNEL && !S390
750         help
751           Say Y here to enable the kernel to act as a watchdog to detect
752           hard and soft lockups.
753 
754           Softlockups are bugs that cause the kernel to loop in kernel
755           mode for more than 20 seconds, without giving other tasks a
756           chance to run.  The current stack trace is displayed upon
757           detection and the system will stay locked up.
758 
759           Hardlockups are bugs that cause the CPU to loop in kernel mode
760           for more than 10 seconds, without letting other interrupts have a
761           chance to run.  The current stack trace is displayed upon detection
762           and the system will stay locked up.
763 
764           The overhead should be minimal.  A periodic hrtimer runs to
765           generate interrupts and kick the watchdog task every 4 seconds.
766           An NMI is generated every 10 seconds or so to check for hardlockups.
767 
768           The frequency of hrtimer and NMI events and the soft and hard lockup
769           thresholds can be controlled through the sysctl watchdog_thresh.
770 
771 config HARDLOCKUP_DETECTOR
772         def_bool y
773         depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
774         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
775 
776 config BOOTPARAM_HARDLOCKUP_PANIC
777         bool "Panic (Reboot) On Hard Lockups"
778         depends on HARDLOCKUP_DETECTOR
779         help
780           Say Y here to enable the kernel to panic on "hard lockups",
781           which are bugs that cause the kernel to loop in kernel
782           mode with interrupts disabled for more than 10 seconds (configurable
783           using the watchdog_thresh sysctl).
784 
785           Say N if unsure.
786 
787 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
788         int
789         depends on HARDLOCKUP_DETECTOR
790         range 0 1
791         default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
792         default 1 if BOOTPARAM_HARDLOCKUP_PANIC
793 
794 config BOOTPARAM_SOFTLOCKUP_PANIC
795         bool "Panic (Reboot) On Soft Lockups"
796         depends on LOCKUP_DETECTOR
797         help
798           Say Y here to enable the kernel to panic on "soft lockups",
799           which are bugs that cause the kernel to loop in kernel
800           mode for more than 20 seconds (configurable using the watchdog_thresh
801           sysctl), without giving other tasks a chance to run.
802 
803           The panic can be used in combination with panic_timeout,
804           to cause the system to reboot automatically after a
805           lockup has been detected. This feature is useful for
806           high-availability systems that have uptime guarantees and
807           where a lockup must be resolved ASAP.
808 
809           Say N if unsure.
810 
811 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
812         int
813         depends on LOCKUP_DETECTOR
814         range 0 1
815         default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
816         default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
817 
818 config DETECT_HUNG_TASK
819         bool "Detect Hung Tasks"
820         depends on DEBUG_KERNEL
821         default LOCKUP_DETECTOR
822         help
823           Say Y here to enable the kernel to detect "hung tasks",
824           which are bugs that cause the task to be stuck in
825           uninterruptible "D" state indefinitely.
826 
827           When a hung task is detected, the kernel will print the
828           current stack trace (which you should report), but the
829           task will stay in uninterruptible state. If lockdep is
830           enabled then all held locks will also be reported. This
831           feature has negligible overhead.
832 
833 config DEFAULT_HUNG_TASK_TIMEOUT
834         int "Default timeout for hung task detection (in seconds)"
835         depends on DETECT_HUNG_TASK
836         default 120
837         help
838           This option controls the default timeout (in seconds) used
839           to determine when a task has become non-responsive and should
840           be considered hung.
841 
842           It can be adjusted at runtime via the kernel.hung_task_timeout_secs
843           sysctl or by writing a value to
844           /proc/sys/kernel/hung_task_timeout_secs.
845 
846           A timeout of 0 disables the check.  The default is two minutes.
847           Keeping the default should be fine in most cases.
848 
849 config BOOTPARAM_HUNG_TASK_PANIC
850         bool "Panic (Reboot) On Hung Tasks"
851         depends on DETECT_HUNG_TASK
852         help
853           Say Y here to enable the kernel to panic on "hung tasks",
854           which are bugs that cause the kernel to leave a task stuck
855           in uninterruptible "D" state.
856 
857           The panic can be used in combination with panic_timeout,
858           to cause the system to reboot automatically after a
859           hung task has been detected. This feature is useful for
860           high-availability systems that have uptime guarantees and
861           where a hung tasks must be resolved ASAP.
862 
863           Say N if unsure.
864 
865 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
866         int
867         depends on DETECT_HUNG_TASK
868         range 0 1
869         default 0 if !BOOTPARAM_HUNG_TASK_PANIC
870         default 1 if BOOTPARAM_HUNG_TASK_PANIC
871 
872 config WQ_WATCHDOG
873         bool "Detect Workqueue Stalls"
874         depends on DEBUG_KERNEL
875         help
876           Say Y here to enable stall detection on workqueues.  If a
877           worker pool doesn't make forward progress on a pending work
878           item for over a given amount of time, 30s by default, a
879           warning message is printed along with dump of workqueue
880           state.  This can be configured through kernel parameter
881           "workqueue.watchdog_thresh" and its sysfs counterpart.
882 
883 endmenu # "Debug lockups and hangs"
884 
885 config PANIC_ON_OOPS
886         bool "Panic on Oops"
887         help
888           Say Y here to enable the kernel to panic when it oopses. This
889           has the same effect as setting oops=panic on the kernel command
890           line.
891 
892           This feature is useful to ensure that the kernel does not do
893           anything erroneous after an oops which could result in data
894           corruption or other issues.
895 
896           Say N if unsure.
897 
898 config PANIC_ON_OOPS_VALUE
899         int
900         range 0 1
901         default 0 if !PANIC_ON_OOPS
902         default 1 if PANIC_ON_OOPS
903 
904 config PANIC_TIMEOUT
905         int "panic timeout"
906         default 0
907         help
908           Set the timeout value (in seconds) until a reboot occurs when the
909           the kernel panics. If n = 0, then we wait forever. A timeout
910           value n > 0 will wait n seconds before rebooting, while a timeout
911           value n < 0 will reboot immediately.
912 
913 config SCHED_DEBUG
914         bool "Collect scheduler debugging info"
915         depends on DEBUG_KERNEL && PROC_FS
916         default y
917         help
918           If you say Y here, the /proc/sched_debug file will be provided
919           that can help debug the scheduler. The runtime overhead of this
920           option is minimal.
921 
922 config SCHED_INFO
923         bool
924         default n
925 
926 config SCHEDSTATS
927         bool "Collect scheduler statistics"
928         depends on DEBUG_KERNEL && PROC_FS
929         select SCHED_INFO
930         help
931           If you say Y here, additional code will be inserted into the
932           scheduler and related routines to collect statistics about
933           scheduler behavior and provide them in /proc/schedstat.  These
934           stats may be useful for both tuning and debugging the scheduler
935           If you aren't debugging the scheduler or trying to tune a specific
936           application, you can say N to avoid the very slight overhead
937           this adds.
938 
939 config SCHED_STACK_END_CHECK
940         bool "Detect stack corruption on calls to schedule()"
941         depends on DEBUG_KERNEL
942         default n
943         help
944           This option checks for a stack overrun on calls to schedule().
945           If the stack end location is found to be over written always panic as
946           the content of the corrupted region can no longer be trusted.
947           This is to ensure no erroneous behaviour occurs which could result in
948           data corruption or a sporadic crash at a later stage once the region
949           is examined. The runtime overhead introduced is minimal.
950 
951 config DEBUG_TIMEKEEPING
952         bool "Enable extra timekeeping sanity checking"
953         help
954           This option will enable additional timekeeping sanity checks
955           which may be helpful when diagnosing issues where timekeeping
956           problems are suspected.
957 
958           This may include checks in the timekeeping hotpaths, so this
959           option may have a (very small) performance impact to some
960           workloads.
961 
962           If unsure, say N.
963 
964 config TIMER_STATS
965         bool "Collect kernel timers statistics"
966         depends on DEBUG_KERNEL && PROC_FS
967         help
968           If you say Y here, additional code will be inserted into the
969           timer routines to collect statistics about kernel timers being
970           reprogrammed. The statistics can be read from /proc/timer_stats.
971           The statistics collection is started by writing 1 to /proc/timer_stats,
972           writing 0 stops it. This feature is useful to collect information
973           about timer usage patterns in kernel and userspace. This feature
974           is lightweight if enabled in the kernel config but not activated
975           (it defaults to deactivated on bootup and will only be activated
976           if some application like powertop activates it explicitly).
977 
978 config DEBUG_PREEMPT
979         bool "Debug preemptible kernel"
980         depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
981         default y
982         help
983           If you say Y here then the kernel will use a debug variant of the
984           commonly used smp_processor_id() function and will print warnings
985           if kernel code uses it in a preemption-unsafe way. Also, the kernel
986           will detect preemption count underflows.
987 
988 menu "Lock Debugging (spinlocks, mutexes, etc...)"
989 
990 config DEBUG_RT_MUTEXES
991         bool "RT Mutex debugging, deadlock detection"
992         depends on DEBUG_KERNEL && RT_MUTEXES
993         help
994          This allows rt mutex semantics violations and rt mutex related
995          deadlocks (lockups) to be detected and reported automatically.
996 
997 config DEBUG_SPINLOCK
998         bool "Spinlock and rw-lock debugging: basic checks"
999         depends on DEBUG_KERNEL
1000         select UNINLINE_SPIN_UNLOCK
1001         help
1002           Say Y here and build SMP to catch missing spinlock initialization
1003           and certain other kinds of spinlock errors commonly made.  This is
1004           best used in conjunction with the NMI watchdog so that spinlock
1005           deadlocks are also debuggable.
1006 
1007 config DEBUG_MUTEXES
1008         bool "Mutex debugging: basic checks"
1009         depends on DEBUG_KERNEL
1010         help
1011          This feature allows mutex semantics violations to be detected and
1012          reported.
1013 
1014 config DEBUG_WW_MUTEX_SLOWPATH
1015         bool "Wait/wound mutex debugging: Slowpath testing"
1016         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1017         select DEBUG_LOCK_ALLOC
1018         select DEBUG_SPINLOCK
1019         select DEBUG_MUTEXES
1020         help
1021          This feature enables slowpath testing for w/w mutex users by
1022          injecting additional -EDEADLK wound/backoff cases. Together with
1023          the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1024          will test all possible w/w mutex interface abuse with the
1025          exception of simply not acquiring all the required locks.
1026          Note that this feature can introduce significant overhead, so
1027          it really should not be enabled in a production or distro kernel,
1028          even a debug kernel.  If you are a driver writer, enable it.  If
1029          you are a distro, do not.
1030 
1031 config DEBUG_LOCK_ALLOC
1032         bool "Lock debugging: detect incorrect freeing of live locks"
1033         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1034         select DEBUG_SPINLOCK
1035         select DEBUG_MUTEXES
1036         select LOCKDEP
1037         help
1038          This feature will check whether any held lock (spinlock, rwlock,
1039          mutex or rwsem) is incorrectly freed by the kernel, via any of the
1040          memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1041          vfree(), etc.), whether a live lock is incorrectly reinitialized via
1042          spin_lock_init()/mutex_init()/etc., or whether there is any lock
1043          held during task exit.
1044 
1045 config PROVE_LOCKING
1046         bool "Lock debugging: prove locking correctness"
1047         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1048         select LOCKDEP
1049         select DEBUG_SPINLOCK
1050         select DEBUG_MUTEXES
1051         select DEBUG_LOCK_ALLOC
1052         select TRACE_IRQFLAGS
1053         default n
1054         help
1055          This feature enables the kernel to prove that all locking
1056          that occurs in the kernel runtime is mathematically
1057          correct: that under no circumstance could an arbitrary (and
1058          not yet triggered) combination of observed locking
1059          sequences (on an arbitrary number of CPUs, running an
1060          arbitrary number of tasks and interrupt contexts) cause a
1061          deadlock.
1062 
1063          In short, this feature enables the kernel to report locking
1064          related deadlocks before they actually occur.
1065 
1066          The proof does not depend on how hard and complex a
1067          deadlock scenario would be to trigger: how many
1068          participant CPUs, tasks and irq-contexts would be needed
1069          for it to trigger. The proof also does not depend on
1070          timing: if a race and a resulting deadlock is possible
1071          theoretically (no matter how unlikely the race scenario
1072          is), it will be proven so and will immediately be
1073          reported by the kernel (once the event is observed that
1074          makes the deadlock theoretically possible).
1075 
1076          If a deadlock is impossible (i.e. the locking rules, as
1077          observed by the kernel, are mathematically correct), the
1078          kernel reports nothing.
1079 
1080          NOTE: this feature can also be enabled for rwlocks, mutexes
1081          and rwsems - in which case all dependencies between these
1082          different locking variants are observed and mapped too, and
1083          the proof of observed correctness is also maintained for an
1084          arbitrary combination of these separate locking variants.
1085 
1086          For more details, see Documentation/locking/lockdep-design.txt.
1087 
1088 config PROVE_LOCKING_SMALL
1089         bool
1090 
1091 config LOCKDEP
1092         bool
1093         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1094         select STACKTRACE
1095         select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
1096         select KALLSYMS
1097         select KALLSYMS_ALL
1098 
1099 config LOCK_STAT
1100         bool "Lock usage statistics"
1101         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1102         select LOCKDEP
1103         select DEBUG_SPINLOCK
1104         select DEBUG_MUTEXES
1105         select DEBUG_LOCK_ALLOC
1106         default n
1107         help
1108          This feature enables tracking lock contention points
1109 
1110          For more details, see Documentation/locking/lockstat.txt
1111 
1112          This also enables lock events required by "perf lock",
1113          subcommand of perf.
1114          If you want to use "perf lock", you also need to turn on
1115          CONFIG_EVENT_TRACING.
1116 
1117          CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1118          (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1119 
1120 config DEBUG_LOCKDEP
1121         bool "Lock dependency engine debugging"
1122         depends on DEBUG_KERNEL && LOCKDEP
1123         help
1124           If you say Y here, the lock dependency engine will do
1125           additional runtime checks to debug itself, at the price
1126           of more runtime overhead.
1127 
1128 config DEBUG_ATOMIC_SLEEP
1129         bool "Sleep inside atomic section checking"
1130         select PREEMPT_COUNT
1131         depends on DEBUG_KERNEL
1132         help
1133           If you say Y here, various routines which may sleep will become very
1134           noisy if they are called inside atomic sections: when a spinlock is
1135           held, inside an rcu read side critical section, inside preempt disabled
1136           sections, inside an interrupt, etc...
1137 
1138 config DEBUG_LOCKING_API_SELFTESTS
1139         bool "Locking API boot-time self-tests"
1140         depends on DEBUG_KERNEL
1141         help
1142           Say Y here if you want the kernel to run a short self-test during
1143           bootup. The self-test checks whether common types of locking bugs
1144           are detected by debugging mechanisms or not. (if you disable
1145           lock debugging then those bugs wont be detected of course.)
1146           The following locking APIs are covered: spinlocks, rwlocks,
1147           mutexes and rwsems.
1148 
1149 config LOCK_TORTURE_TEST
1150         tristate "torture tests for locking"
1151         depends on DEBUG_KERNEL
1152         select TORTURE_TEST
1153         default n
1154         help
1155           This option provides a kernel module that runs torture tests
1156           on kernel locking primitives.  The kernel module may be built
1157           after the fact on the running kernel to be tested, if desired.
1158 
1159           Say Y here if you want kernel locking-primitive torture tests
1160           to be built into the kernel.
1161           Say M if you want these torture tests to build as a module.
1162           Say N if you are unsure.
1163 
1164 endmenu # lock debugging
1165 
1166 config TRACE_IRQFLAGS
1167         bool
1168         help
1169           Enables hooks to interrupt enabling and disabling for
1170           either tracing or lock debugging.
1171 
1172 config STACKTRACE
1173         bool "Stack backtrace support"
1174         depends on STACKTRACE_SUPPORT
1175         help
1176           This option causes the kernel to create a /proc/pid/stack for
1177           every process, showing its current stack trace.
1178           It is also used by various kernel debugging features that require
1179           stack trace generation.
1180 
1181 config DEBUG_KOBJECT
1182         bool "kobject debugging"
1183         depends on DEBUG_KERNEL
1184         help
1185           If you say Y here, some extra kobject debugging messages will be sent
1186           to the syslog. 
1187 
1188 config DEBUG_KOBJECT_RELEASE
1189         bool "kobject release debugging"
1190         depends on DEBUG_OBJECTS_TIMERS
1191         help
1192           kobjects are reference counted objects.  This means that their
1193           last reference count put is not predictable, and the kobject can
1194           live on past the point at which a driver decides to drop it's
1195           initial reference to the kobject gained on allocation.  An
1196           example of this would be a struct device which has just been
1197           unregistered.
1198 
1199           However, some buggy drivers assume that after such an operation,
1200           the memory backing the kobject can be immediately freed.  This
1201           goes completely against the principles of a refcounted object.
1202 
1203           If you say Y here, the kernel will delay the release of kobjects
1204           on the last reference count to improve the visibility of this
1205           kind of kobject release bug.
1206 
1207 config HAVE_DEBUG_BUGVERBOSE
1208         bool
1209 
1210 config DEBUG_BUGVERBOSE
1211         bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1212         depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1213         default y
1214         help
1215           Say Y here to make BUG() panics output the file name and line number
1216           of the BUG call as well as the EIP and oops trace.  This aids
1217           debugging but costs about 70-100K of memory.
1218 
1219 config DEBUG_LIST
1220         bool "Debug linked list manipulation"
1221         depends on DEBUG_KERNEL
1222         help
1223           Enable this to turn on extended checks in the linked-list
1224           walking routines.
1225 
1226           If unsure, say N.
1227 
1228 config DEBUG_PI_LIST
1229         bool "Debug priority linked list manipulation"
1230         depends on DEBUG_KERNEL
1231         help
1232           Enable this to turn on extended checks in the priority-ordered
1233           linked-list (plist) walking routines.  This checks the entire
1234           list multiple times during each manipulation.
1235 
1236           If unsure, say N.
1237 
1238 config DEBUG_SG
1239         bool "Debug SG table operations"
1240         depends on DEBUG_KERNEL
1241         help
1242           Enable this to turn on checks on scatter-gather tables. This can
1243           help find problems with drivers that do not properly initialize
1244           their sg tables.
1245 
1246           If unsure, say N.
1247 
1248 config DEBUG_NOTIFIERS
1249         bool "Debug notifier call chains"
1250         depends on DEBUG_KERNEL
1251         help
1252           Enable this to turn on sanity checking for notifier call chains.
1253           This is most useful for kernel developers to make sure that
1254           modules properly unregister themselves from notifier chains.
1255           This is a relatively cheap check but if you care about maximum
1256           performance, say N.
1257 
1258 config DEBUG_CREDENTIALS
1259         bool "Debug credential management"
1260         depends on DEBUG_KERNEL
1261         help
1262           Enable this to turn on some debug checking for credential
1263           management.  The additional code keeps track of the number of
1264           pointers from task_structs to any given cred struct, and checks to
1265           see that this number never exceeds the usage count of the cred
1266           struct.
1267 
1268           Furthermore, if SELinux is enabled, this also checks that the
1269           security pointer in the cred struct is never seen to be invalid.
1270 
1271           If unsure, say N.
1272 
1273 menu "RCU Debugging"
1274 
1275 config PROVE_RCU
1276         def_bool PROVE_LOCKING
1277 
1278 config PROVE_RCU_REPEATEDLY
1279         bool "RCU debugging: don't disable PROVE_RCU on first splat"
1280         depends on PROVE_RCU
1281         default n
1282         help
1283          By itself, PROVE_RCU will disable checking upon issuing the
1284          first warning (or "splat").  This feature prevents such
1285          disabling, allowing multiple RCU-lockdep warnings to be printed
1286          on a single reboot.
1287 
1288          Say Y to allow multiple RCU-lockdep warnings per boot.
1289 
1290          Say N if you are unsure.
1291 
1292 config SPARSE_RCU_POINTER
1293         bool "RCU debugging: sparse-based checks for pointer usage"
1294         default n
1295         help
1296          This feature enables the __rcu sparse annotation for
1297          RCU-protected pointers.  This annotation will cause sparse
1298          to flag any non-RCU used of annotated pointers.  This can be
1299          helpful when debugging RCU usage.  Please note that this feature
1300          is not intended to enforce code cleanliness; it is instead merely
1301          a debugging aid.
1302 
1303          Say Y to make sparse flag questionable use of RCU-protected pointers
1304 
1305          Say N if you are unsure.
1306 
1307 config TORTURE_TEST
1308         tristate
1309         default n
1310 
1311 config RCU_PERF_TEST
1312         tristate "performance tests for RCU"
1313         depends on DEBUG_KERNEL
1314         select TORTURE_TEST
1315         select SRCU
1316         select TASKS_RCU
1317         default n
1318         help
1319           This option provides a kernel module that runs performance
1320           tests on the RCU infrastructure.  The kernel module may be built
1321           after the fact on the running kernel to be tested, if desired.
1322 
1323           Say Y here if you want RCU performance tests to be built into
1324           the kernel.
1325           Say M if you want the RCU performance tests to build as a module.
1326           Say N if you are unsure.
1327 
1328 config RCU_TORTURE_TEST
1329         tristate "torture tests for RCU"
1330         depends on DEBUG_KERNEL
1331         select TORTURE_TEST
1332         select SRCU
1333         select TASKS_RCU
1334         default n
1335         help
1336           This option provides a kernel module that runs torture tests
1337           on the RCU infrastructure.  The kernel module may be built
1338           after the fact on the running kernel to be tested, if desired.
1339 
1340           Say Y here if you want RCU torture tests to be built into
1341           the kernel.
1342           Say M if you want the RCU torture tests to build as a module.
1343           Say N if you are unsure.
1344 
1345 config RCU_TORTURE_TEST_SLOW_PREINIT
1346         bool "Slow down RCU grace-period pre-initialization to expose races"
1347         depends on RCU_TORTURE_TEST
1348         help
1349           This option delays grace-period pre-initialization (the
1350           propagation of CPU-hotplug changes up the rcu_node combining
1351           tree) for a few jiffies between initializing each pair of
1352           consecutive rcu_node structures.  This helps to expose races
1353           involving grace-period pre-initialization, in other words, it
1354           makes your kernel less stable.  It can also greatly increase
1355           grace-period latency, especially on systems with large numbers
1356           of CPUs.  This is useful when torture-testing RCU, but in
1357           almost no other circumstance.
1358 
1359           Say Y here if you want your system to crash and hang more often.
1360           Say N if you want a sane system.
1361 
1362 config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
1363         int "How much to slow down RCU grace-period pre-initialization"
1364         range 0 5
1365         default 3
1366         depends on RCU_TORTURE_TEST_SLOW_PREINIT
1367         help
1368           This option specifies the number of jiffies to wait between
1369           each rcu_node structure pre-initialization step.
1370 
1371 config RCU_TORTURE_TEST_SLOW_INIT
1372         bool "Slow down RCU grace-period initialization to expose races"
1373         depends on RCU_TORTURE_TEST
1374         help
1375           This option delays grace-period initialization for a few
1376           jiffies between initializing each pair of consecutive
1377           rcu_node structures.  This helps to expose races involving
1378           grace-period initialization, in other words, it makes your
1379           kernel less stable.  It can also greatly increase grace-period
1380           latency, especially on systems with large numbers of CPUs.
1381           This is useful when torture-testing RCU, but in almost no
1382           other circumstance.
1383 
1384           Say Y here if you want your system to crash and hang more often.
1385           Say N if you want a sane system.
1386 
1387 config RCU_TORTURE_TEST_SLOW_INIT_DELAY
1388         int "How much to slow down RCU grace-period initialization"
1389         range 0 5
1390         default 3
1391         depends on RCU_TORTURE_TEST_SLOW_INIT
1392         help
1393           This option specifies the number of jiffies to wait between
1394           each rcu_node structure initialization.
1395 
1396 config RCU_TORTURE_TEST_SLOW_CLEANUP
1397         bool "Slow down RCU grace-period cleanup to expose races"
1398         depends on RCU_TORTURE_TEST
1399         help
1400           This option delays grace-period cleanup for a few jiffies
1401           between cleaning up each pair of consecutive rcu_node
1402           structures.  This helps to expose races involving grace-period
1403           cleanup, in other words, it makes your kernel less stable.
1404           It can also greatly increase grace-period latency, especially
1405           on systems with large numbers of CPUs.  This is useful when
1406           torture-testing RCU, but in almost no other circumstance.
1407 
1408           Say Y here if you want your system to crash and hang more often.
1409           Say N if you want a sane system.
1410 
1411 config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
1412         int "How much to slow down RCU grace-period cleanup"
1413         range 0 5
1414         default 3
1415         depends on RCU_TORTURE_TEST_SLOW_CLEANUP
1416         help
1417           This option specifies the number of jiffies to wait between
1418           each rcu_node structure cleanup operation.
1419 
1420 config RCU_CPU_STALL_TIMEOUT
1421         int "RCU CPU stall timeout in seconds"
1422         depends on RCU_STALL_COMMON
1423         range 3 300
1424         default 21
1425         help
1426           If a given RCU grace period extends more than the specified
1427           number of seconds, a CPU stall warning is printed.  If the
1428           RCU grace period persists, additional CPU stall warnings are
1429           printed at more widely spaced intervals.
1430 
1431 config RCU_TRACE
1432         bool "Enable tracing for RCU"
1433         depends on DEBUG_KERNEL
1434         select TRACE_CLOCK
1435         help
1436           This option provides tracing in RCU which presents stats
1437           in debugfs for debugging RCU implementation.
1438 
1439           Say Y here if you want to enable RCU tracing
1440           Say N if you are unsure.
1441 
1442 config RCU_EQS_DEBUG
1443         bool "Provide debugging asserts for adding NO_HZ support to an arch"
1444         depends on DEBUG_KERNEL
1445         help
1446           This option provides consistency checks in RCU's handling of
1447           NO_HZ.  These checks have proven quite helpful in detecting
1448           bugs in arch-specific NO_HZ code.
1449 
1450           Say N here if you need ultimate kernel/user switch latencies
1451           Say Y if you are unsure
1452 
1453 endmenu # "RCU Debugging"
1454 
1455 config DEBUG_WQ_FORCE_RR_CPU
1456         bool "Force round-robin CPU selection for unbound work items"
1457         depends on DEBUG_KERNEL
1458         default n
1459         help
1460           Workqueue used to implicitly guarantee that work items queued
1461           without explicit CPU specified are put on the local CPU.  This
1462           guarantee is no longer true and while local CPU is still
1463           preferred work items may be put on foreign CPUs.  Kernel
1464           parameter "workqueue.debug_force_rr_cpu" is added to force
1465           round-robin CPU selection to flush out usages which depend on the
1466           now broken guarantee.  This config option enables the debug
1467           feature by default.  When enabled, memory and cache locality will
1468           be impacted.
1469 
1470 config DEBUG_BLOCK_EXT_DEVT
1471         bool "Force extended block device numbers and spread them"
1472         depends on DEBUG_KERNEL
1473         depends on BLOCK
1474         default n
1475         help
1476           BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1477           SOME DISTRIBUTIONS.  DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1478           YOU ARE DOING.  Distros, please enable this and fix whatever
1479           is broken.
1480 
1481           Conventionally, block device numbers are allocated from
1482           predetermined contiguous area.  However, extended block area
1483           may introduce non-contiguous block device numbers.  This
1484           option forces most block device numbers to be allocated from
1485           the extended space and spreads them to discover kernel or
1486           userland code paths which assume predetermined contiguous
1487           device number allocation.
1488 
1489           Note that turning on this debug option shuffles all the
1490           device numbers for all IDE and SCSI devices including libata
1491           ones, so root partition specified using device number
1492           directly (via rdev or root=MAJ:MIN) won't work anymore.
1493           Textual device names (root=/dev/sdXn) will continue to work.
1494 
1495           Say N if you are unsure.
1496 
1497 config CPU_HOTPLUG_STATE_CONTROL
1498         bool "Enable CPU hotplug state control"
1499         depends on DEBUG_KERNEL
1500         depends on HOTPLUG_CPU
1501         default n
1502         help
1503           Allows to write steps between "offline" and "online" to the CPUs
1504           sysfs target file so states can be stepped granular. This is a debug
1505           option for now as the hotplug machinery cannot be stopped and
1506           restarted at arbitrary points yet.
1507 
1508           Say N if your are unsure.
1509 
1510 config NOTIFIER_ERROR_INJECTION
1511         tristate "Notifier error injection"
1512         depends on DEBUG_KERNEL
1513         select DEBUG_FS
1514         help
1515           This option provides the ability to inject artificial errors to
1516           specified notifier chain callbacks. It is useful to test the error
1517           handling of notifier call chain failures.
1518 
1519           Say N if unsure.
1520 
1521 config CPU_NOTIFIER_ERROR_INJECT
1522         tristate "CPU notifier error injection module"
1523         depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1524         help
1525           This option provides a kernel module that can be used to test
1526           the error handling of the cpu notifiers by injecting artificial
1527           errors to CPU notifier chain callbacks.  It is controlled through
1528           debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
1529 
1530           If the notifier call chain should be failed with some events
1531           notified, write the error code to "actions/<notifier event>/error".
1532 
1533           Example: Inject CPU offline error (-1 == -EPERM)
1534 
1535           # cd /sys/kernel/debug/notifier-error-inject/cpu
1536           # echo -1 > actions/CPU_DOWN_PREPARE/error
1537           # echo 0 > /sys/devices/system/cpu/cpu1/online
1538           bash: echo: write error: Operation not permitted
1539 
1540           To compile this code as a module, choose M here: the module will
1541           be called cpu-notifier-error-inject.
1542 
1543           If unsure, say N.
1544 
1545 config PM_NOTIFIER_ERROR_INJECT
1546         tristate "PM notifier error injection module"
1547         depends on PM && NOTIFIER_ERROR_INJECTION
1548         default m if PM_DEBUG
1549         help
1550           This option provides the ability to inject artificial errors to
1551           PM notifier chain callbacks.  It is controlled through debugfs
1552           interface /sys/kernel/debug/notifier-error-inject/pm
1553 
1554           If the notifier call chain should be failed with some events
1555           notified, write the error code to "actions/<notifier event>/error".
1556 
1557           Example: Inject PM suspend error (-12 = -ENOMEM)
1558 
1559           # cd /sys/kernel/debug/notifier-error-inject/pm/
1560           # echo -12 > actions/PM_SUSPEND_PREPARE/error
1561           # echo mem > /sys/power/state
1562           bash: echo: write error: Cannot allocate memory
1563 
1564           To compile this code as a module, choose M here: the module will
1565           be called pm-notifier-error-inject.
1566 
1567           If unsure, say N.
1568 
1569 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1570         tristate "OF reconfig notifier error injection module"
1571         depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1572         help
1573           This option provides the ability to inject artificial errors to
1574           OF reconfig notifier chain callbacks.  It is controlled
1575           through debugfs interface under
1576           /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1577 
1578           If the notifier call chain should be failed with some events
1579           notified, write the error code to "actions/<notifier event>/error".
1580 
1581           To compile this code as a module, choose M here: the module will
1582           be called of-reconfig-notifier-error-inject.
1583 
1584           If unsure, say N.
1585 
1586 config NETDEV_NOTIFIER_ERROR_INJECT
1587         tristate "Netdev notifier error injection module"
1588         depends on NET && NOTIFIER_ERROR_INJECTION
1589         help
1590           This option provides the ability to inject artificial errors to
1591           netdevice notifier chain callbacks.  It is controlled through debugfs
1592           interface /sys/kernel/debug/notifier-error-inject/netdev
1593 
1594           If the notifier call chain should be failed with some events
1595           notified, write the error code to "actions/<notifier event>/error".
1596 
1597           Example: Inject netdevice mtu change error (-22 = -EINVAL)
1598 
1599           # cd /sys/kernel/debug/notifier-error-inject/netdev
1600           # echo -22 > actions/NETDEV_CHANGEMTU/error
1601           # ip link set eth0 mtu 1024
1602           RTNETLINK answers: Invalid argument
1603 
1604           To compile this code as a module, choose M here: the module will
1605           be called netdev-notifier-error-inject.
1606 
1607           If unsure, say N.
1608 
1609 config FAULT_INJECTION
1610         bool "Fault-injection framework"
1611         depends on DEBUG_KERNEL
1612         help
1613           Provide fault-injection framework.
1614           For more details, see Documentation/fault-injection/.
1615 
1616 config FAILSLAB
1617         bool "Fault-injection capability for kmalloc"
1618         depends on FAULT_INJECTION
1619         depends on SLAB || SLUB
1620         help
1621           Provide fault-injection capability for kmalloc.
1622 
1623 config FAIL_PAGE_ALLOC
1624         bool "Fault-injection capabilitiy for alloc_pages()"
1625         depends on FAULT_INJECTION
1626         help
1627           Provide fault-injection capability for alloc_pages().
1628 
1629 config FAIL_MAKE_REQUEST
1630         bool "Fault-injection capability for disk IO"
1631         depends on FAULT_INJECTION && BLOCK
1632         help
1633           Provide fault-injection capability for disk IO.
1634 
1635 config FAIL_IO_TIMEOUT
1636         bool "Fault-injection capability for faking disk interrupts"
1637         depends on FAULT_INJECTION && BLOCK
1638         help
1639           Provide fault-injection capability on end IO handling. This
1640           will make the block layer "forget" an interrupt as configured,
1641           thus exercising the error handling.
1642 
1643           Only works with drivers that use the generic timeout handling,
1644           for others it wont do anything.
1645 
1646 config FAIL_MMC_REQUEST
1647         bool "Fault-injection capability for MMC IO"
1648         depends on FAULT_INJECTION_DEBUG_FS && MMC
1649         help
1650           Provide fault-injection capability for MMC IO.
1651           This will make the mmc core return data errors. This is
1652           useful to test the error handling in the mmc block device
1653           and to test how the mmc host driver handles retries from
1654           the block device.
1655 
1656 config FAIL_FUTEX
1657         bool "Fault-injection capability for futexes"
1658         select DEBUG_FS
1659         depends on FAULT_INJECTION && FUTEX
1660         help
1661           Provide fault-injection capability for futexes.
1662 
1663 config FAULT_INJECTION_DEBUG_FS
1664         bool "Debugfs entries for fault-injection capabilities"
1665         depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1666         help
1667           Enable configuration of fault-injection capabilities via debugfs.
1668 
1669 config FAULT_INJECTION_STACKTRACE_FILTER
1670         bool "stacktrace filter for fault-injection capabilities"
1671         depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1672         depends on !X86_64
1673         select STACKTRACE
1674         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1675         help
1676           Provide stacktrace filter for fault-injection capabilities
1677 
1678 config LATENCYTOP
1679         bool "Latency measuring infrastructure"
1680         depends on DEBUG_KERNEL
1681         depends on STACKTRACE_SUPPORT
1682         depends on PROC_FS
1683         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1684         select KALLSYMS
1685         select KALLSYMS_ALL
1686         select STACKTRACE
1687         select SCHEDSTATS
1688         select SCHED_DEBUG
1689         help
1690           Enable this option if you want to use the LatencyTOP tool
1691           to find out which userspace is blocking on what kernel operations.
1692 
1693 source kernel/trace/Kconfig
1694 
1695 menu "Runtime Testing"
1696 
1697 config LKDTM
1698         tristate "Linux Kernel Dump Test Tool Module"
1699         depends on DEBUG_FS
1700         depends on BLOCK
1701         default n
1702         help
1703         This module enables testing of the different dumping mechanisms by
1704         inducing system failures at predefined crash points.
1705         If you don't need it: say N
1706         Choose M here to compile this code as a module. The module will be
1707         called lkdtm.
1708 
1709         Documentation on how to use the module can be found in
1710         Documentation/fault-injection/provoke-crashes.txt
1711 
1712 config TEST_LIST_SORT
1713         bool "Linked list sorting test"
1714         depends on DEBUG_KERNEL
1715         help
1716           Enable this to turn on 'list_sort()' function test. This test is
1717           executed only once during system boot, so affects only boot time.
1718 
1719           If unsure, say N.
1720 
1721 config KPROBES_SANITY_TEST
1722         bool "Kprobes sanity tests"
1723         depends on DEBUG_KERNEL
1724         depends on KPROBES
1725         default n
1726         help
1727           This option provides for testing basic kprobes functionality on
1728           boot. A sample kprobe, jprobe and kretprobe are inserted and
1729           verified for functionality.
1730 
1731           Say N if you are unsure.
1732 
1733 config BACKTRACE_SELF_TEST
1734         tristate "Self test for the backtrace code"
1735         depends on DEBUG_KERNEL
1736         default n
1737         help
1738           This option provides a kernel module that can be used to test
1739           the kernel stack backtrace code. This option is not useful
1740           for distributions or general kernels, but only for kernel
1741           developers working on architecture code.
1742 
1743           Note that if you want to also test saved backtraces, you will
1744           have to enable STACKTRACE as well.
1745 
1746           Say N if you are unsure.
1747 
1748 config RBTREE_TEST
1749         tristate "Red-Black tree test"
1750         depends on DEBUG_KERNEL
1751         help
1752           A benchmark measuring the performance of the rbtree library.
1753           Also includes rbtree invariant checks.
1754 
1755 config INTERVAL_TREE_TEST
1756         tristate "Interval tree test"
1757         depends on m && DEBUG_KERNEL
1758         select INTERVAL_TREE
1759         help
1760           A benchmark measuring the performance of the interval tree library
1761 
1762 config PERCPU_TEST
1763         tristate "Per cpu operations test"
1764         depends on m && DEBUG_KERNEL
1765         help
1766           Enable this option to build test module which validates per-cpu
1767           operations.
1768 
1769           If unsure, say N.
1770 
1771 config ATOMIC64_SELFTEST
1772         bool "Perform an atomic64_t self-test at boot"
1773         help
1774           Enable this option to test the atomic64_t functions at boot.
1775 
1776           If unsure, say N.
1777 
1778 config ASYNC_RAID6_TEST
1779         tristate "Self test for hardware accelerated raid6 recovery"
1780         depends on ASYNC_RAID6_RECOV
1781         select ASYNC_MEMCPY
1782         ---help---
1783           This is a one-shot self test that permutes through the
1784           recovery of all the possible two disk failure scenarios for a
1785           N-disk array.  Recovery is performed with the asynchronous
1786           raid6 recovery routines, and will optionally use an offload
1787           engine if one is available.
1788 
1789           If unsure, say N.
1790 
1791 config TEST_HEXDUMP
1792         tristate "Test functions located in the hexdump module at runtime"
1793 
1794 config TEST_STRING_HELPERS
1795         tristate "Test functions located in the string_helpers module at runtime"
1796 
1797 config TEST_KSTRTOX
1798         tristate "Test kstrto*() family of functions at runtime"
1799 
1800 config TEST_PRINTF
1801         tristate "Test printf() family of functions at runtime"
1802 
1803 config TEST_BITMAP
1804         tristate "Test bitmap_*() family of functions at runtime"
1805         default n
1806         help
1807           Enable this option to test the bitmap functions at boot.
1808 
1809           If unsure, say N.
1810 
1811 config TEST_UUID
1812         tristate "Test functions located in the uuid module at runtime"
1813 
1814 config TEST_RHASHTABLE
1815         tristate "Perform selftest on resizable hash table"
1816         default n
1817         help
1818           Enable this option to test the rhashtable functions at boot.
1819 
1820           If unsure, say N.
1821 
1822 config TEST_HASH
1823         tristate "Perform selftest on hash functions"
1824         default n
1825         help
1826           Enable this option to test the kernel's integer (<linux/hash,h>)
1827           and string (<linux/stringhash.h>) hash functions on boot
1828           (or module load).
1829 
1830           This is intended to help people writing architecture-specific
1831           optimized versions.  If unsure, say N.
1832 
1833 endmenu # runtime tests
1834 
1835 config PROVIDE_OHCI1394_DMA_INIT
1836         bool "Remote debugging over FireWire early on boot"
1837         depends on PCI && X86
1838         help
1839           If you want to debug problems which hang or crash the kernel early
1840           on boot and the crashing machine has a FireWire port, you can use
1841           this feature to remotely access the memory of the crashed machine
1842           over FireWire. This employs remote DMA as part of the OHCI1394
1843           specification which is now the standard for FireWire controllers.
1844 
1845           With remote DMA, you can monitor the printk buffer remotely using
1846           firescope and access all memory below 4GB using fireproxy from gdb.
1847           Even controlling a kernel debugger is possible using remote DMA.
1848 
1849           Usage:
1850 
1851           If ohci1394_dma=early is used as boot parameter, it will initialize
1852           all OHCI1394 controllers which are found in the PCI config space.
1853 
1854           As all changes to the FireWire bus such as enabling and disabling
1855           devices cause a bus reset and thereby disable remote DMA for all
1856           devices, be sure to have the cable plugged and FireWire enabled on
1857           the debugging host before booting the debug target for debugging.
1858 
1859           This code (~1k) is freed after boot. By then, the firewire stack
1860           in charge of the OHCI-1394 controllers should be used instead.
1861 
1862           See Documentation/debugging-via-ohci1394.txt for more information.
1863 
1864 config DMA_API_DEBUG
1865         bool "Enable debugging of DMA-API usage"
1866         depends on HAVE_DMA_API_DEBUG
1867         help
1868           Enable this option to debug the use of the DMA API by device drivers.
1869           With this option you will be able to detect common bugs in device
1870           drivers like double-freeing of DMA mappings or freeing mappings that
1871           were never allocated.
1872 
1873           This also attempts to catch cases where a page owned by DMA is
1874           accessed by the cpu in a way that could cause data corruption.  For
1875           example, this enables cow_user_page() to check that the source page is
1876           not undergoing DMA.
1877 
1878           This option causes a performance degradation.  Use only if you want to
1879           debug device drivers and dma interactions.
1880 
1881           If unsure, say N.
1882 
1883 config TEST_LKM
1884         tristate "Test module loading with 'hello world' module"
1885         default n
1886         depends on m
1887         help
1888           This builds the "test_module" module that emits "Hello, world"
1889           on printk when loaded. It is designed to be used for basic
1890           evaluation of the module loading subsystem (for example when
1891           validating module verification). It lacks any extra dependencies,
1892           and will not normally be loaded by the system unless explicitly
1893           requested by name.
1894 
1895           If unsure, say N.
1896 
1897 config TEST_USER_COPY
1898         tristate "Test user/kernel boundary protections"
1899         default n
1900         depends on m
1901         help
1902           This builds the "test_user_copy" module that runs sanity checks
1903           on the copy_to/from_user infrastructure, making sure basic
1904           user/kernel boundary testing is working. If it fails to load,
1905           a regression has been detected in the user/kernel memory boundary
1906           protections.
1907 
1908           If unsure, say N.
1909 
1910 config TEST_BPF
1911         tristate "Test BPF filter functionality"
1912         default n
1913         depends on m && NET
1914         help
1915           This builds the "test_bpf" module that runs various test vectors
1916           against the BPF interpreter or BPF JIT compiler depending on the
1917           current setting. This is in particular useful for BPF JIT compiler
1918           development, but also to run regression tests against changes in
1919           the interpreter code. It also enables test stubs for eBPF maps and
1920           verifier used by user space verifier testsuite.
1921 
1922           If unsure, say N.
1923 
1924 config TEST_FIRMWARE
1925         tristate "Test firmware loading via userspace interface"
1926         default n
1927         depends on FW_LOADER
1928         help
1929           This builds the "test_firmware" module that creates a userspace
1930           interface for testing firmware loading. This can be used to
1931           control the triggering of firmware loading without needing an
1932           actual firmware-using device. The contents can be rechecked by
1933           userspace.
1934 
1935           If unsure, say N.
1936 
1937 config TEST_UDELAY
1938         tristate "udelay test driver"
1939         default n
1940         help
1941           This builds the "udelay_test" module that helps to make sure
1942           that udelay() is working properly.
1943 
1944           If unsure, say N.
1945 
1946 config MEMTEST
1947         bool "Memtest"
1948         depends on HAVE_MEMBLOCK
1949         ---help---
1950           This option adds a kernel parameter 'memtest', which allows memtest
1951           to be set.
1952                 memtest=0, mean disabled; -- default
1953                 memtest=1, mean do 1 test pattern;
1954                 ...
1955                 memtest=17, mean do 17 test patterns.
1956           If you are unsure how to answer this question, answer N.
1957 
1958 config TEST_STATIC_KEYS
1959         tristate "Test static keys"
1960         default n
1961         depends on m
1962         help
1963           Test the static key interfaces.
1964 
1965           If unsure, say N.
1966 
1967 source "samples/Kconfig"
1968 
1969 source "lib/Kconfig.kgdb"
1970 
1971 source "lib/Kconfig.ubsan"
1972 
1973 config ARCH_HAS_DEVMEM_IS_ALLOWED
1974         bool
1975 
1976 config STRICT_DEVMEM
1977         bool "Filter access to /dev/mem"
1978         depends on MMU
1979         depends on ARCH_HAS_DEVMEM_IS_ALLOWED
1980         default y if TILE || PPC
1981         ---help---
1982           If this option is disabled, you allow userspace (root) access to all
1983           of memory, including kernel and userspace memory. Accidental
1984           access to this is obviously disastrous, but specific access can
1985           be used by people debugging the kernel. Note that with PAT support
1986           enabled, even in this case there are restrictions on /dev/mem
1987           use due to the cache aliasing requirements.
1988 
1989           If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
1990           file only allows userspace access to PCI space and the BIOS code and
1991           data regions.  This is sufficient for dosemu and X and all common
1992           users of /dev/mem.
1993 
1994           If in doubt, say Y.
1995 
1996 config IO_STRICT_DEVMEM
1997         bool "Filter I/O access to /dev/mem"
1998         depends on STRICT_DEVMEM
1999         ---help---
2000           If this option is disabled, you allow userspace (root) access to all
2001           io-memory regardless of whether a driver is actively using that
2002           range.  Accidental access to this is obviously disastrous, but
2003           specific access can be used by people debugging kernel drivers.
2004 
2005           If this option is switched on, the /dev/mem file only allows
2006           userspace access to *idle* io-memory ranges (see /proc/iomem) This
2007           may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2008           if the driver using a given range cannot be disabled.
2009 
2010           If in doubt, say Y.

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