Version:  2.0.40 2.2.26 2.4.37 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6

Linux/lib/Kconfig.debug

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

This page was automatically generated by LXR 0.3.1 (source).  •  Linux is a registered trademark of Linus Torvalds  •  Contact us