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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 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         select SRCU
261         help
262           debugfs is a virtual file system that kernel developers use to put
263           debugging files into.  Enable this option to be able to read and
264           write to these files.
265 
266           For detailed documentation on the debugfs API, see
267           Documentation/DocBook/filesystems.
268 
269           If unsure, say N.
270 
271 config HEADERS_CHECK
272         bool "Run 'make headers_check' when building vmlinux"
273         depends on !UML
274         help
275           This option will extract the user-visible kernel headers whenever
276           building the kernel, and will run basic sanity checks on them to
277           ensure that exported files do not attempt to include files which
278           were not exported, etc.
279 
280           If you're making modifications to header files which are
281           relevant for userspace, say 'Y', and check the headers
282           exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
283           your build tree), to make sure they're suitable.
284 
285 config DEBUG_SECTION_MISMATCH
286         bool "Enable full Section mismatch analysis"
287         help
288           The section mismatch analysis checks if there are illegal
289           references from one section to another section.
290           During linktime or runtime, some sections are dropped;
291           any use of code/data previously in these sections would
292           most likely result in an oops.
293           In the code, functions and variables are annotated with
294           __init,, etc. (see the full list in include/linux/init.h),
295           which results in the code/data being placed in specific sections.
296           The section mismatch analysis is always performed after a full
297           kernel build, and enabling this option causes the following
298           additional steps to occur:
299           - Add the option -fno-inline-functions-called-once to gcc commands.
300             When inlining a function annotated with __init in a non-init
301             function, we would lose the section information and thus
302             the analysis would not catch the illegal reference.
303             This option tells gcc to inline less (but it does result in
304             a larger kernel).
305           - Run the section mismatch analysis for each module/built-in.o file.
306             When we run the section mismatch analysis on vmlinux.o, we
307             lose valueble information about where the mismatch was
308             introduced.
309             Running the analysis for each module/built-in.o file
310             tells where the mismatch happens much closer to the
311             source. The drawback is that the same mismatch is
312             reported at least twice.
313           - Enable verbose reporting from modpost in order to help resolve
314             the section mismatches that are reported.
315 
316 config SECTION_MISMATCH_WARN_ONLY
317         bool "Make section mismatch errors non-fatal"
318         default y
319         help
320           If you say N here, the build process will fail if there are any
321           section mismatch, instead of just throwing warnings.
322 
323           If unsure, say Y.
324 
325 #
326 # Select this config option from the architecture Kconfig, if it
327 # is preferred to always offer frame pointers as a config
328 # option on the architecture (regardless of KERNEL_DEBUG):
329 #
330 config ARCH_WANT_FRAME_POINTERS
331         bool
332         help
333 
334 config FRAME_POINTER
335         bool "Compile the kernel with frame pointers"
336         depends on DEBUG_KERNEL && \
337                 (CRIS || M68K || FRV || UML || \
338                  AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \
339                 ARCH_WANT_FRAME_POINTERS
340         default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
341         help
342           If you say Y here the resulting kernel image will be slightly
343           larger and slower, but it gives very useful debugging information
344           in case of kernel bugs. (precise oopses/stacktraces/warnings)
345 
346 config STACK_VALIDATION
347         bool "Compile-time stack metadata validation"
348         depends on HAVE_STACK_VALIDATION
349         default n
350         help
351           Add compile-time checks to validate stack metadata, including frame
352           pointers (if CONFIG_FRAME_POINTER is enabled).  This helps ensure
353           that runtime stack traces are more reliable.
354 
355           For more information, see
356           tools/objtool/Documentation/stack-validation.txt.
357 
358 config DEBUG_FORCE_WEAK_PER_CPU
359         bool "Force weak per-cpu definitions"
360         depends on DEBUG_KERNEL
361         help
362           s390 and alpha require percpu variables in modules to be
363           defined weak to work around addressing range issue which
364           puts the following two restrictions on percpu variable
365           definitions.
366 
367           1. percpu symbols must be unique whether static or not
368           2. percpu variables can't be defined inside a function
369 
370           To ensure that generic code follows the above rules, this
371           option forces all percpu variables to be defined as weak.
372 
373 endmenu # "Compiler options"
374 
375 config MAGIC_SYSRQ
376         bool "Magic SysRq key"
377         depends on !UML
378         help
379           If you say Y here, you will have some control over the system even
380           if the system crashes for example during kernel debugging (e.g., you
381           will be able to flush the buffer cache to disk, reboot the system
382           immediately or dump some status information). This is accomplished
383           by pressing various keys while holding SysRq (Alt+PrintScreen). It
384           also works on a serial console (on PC hardware at least), if you
385           send a BREAK and then within 5 seconds a command keypress. The
386           keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
387           unless you really know what this hack does.
388 
389 config MAGIC_SYSRQ_DEFAULT_ENABLE
390         hex "Enable magic SysRq key functions by default"
391         depends on MAGIC_SYSRQ
392         default 0x1
393         help
394           Specifies which SysRq key functions are enabled by default.
395           This may be set to 1 or 0 to enable or disable them all, or
396           to a bitmask as described in Documentation/sysrq.txt.
397 
398 config DEBUG_KERNEL
399         bool "Kernel debugging"
400         help
401           Say Y here if you are developing drivers or trying to debug and
402           identify kernel problems.
403 
404 menu "Memory Debugging"
405 
406 source mm/Kconfig.debug
407 
408 config DEBUG_OBJECTS
409         bool "Debug object operations"
410         depends on DEBUG_KERNEL
411         help
412           If you say Y here, additional code will be inserted into the
413           kernel to track the life time of various objects and validate
414           the operations on those objects.
415 
416 config DEBUG_OBJECTS_SELFTEST
417         bool "Debug objects selftest"
418         depends on DEBUG_OBJECTS
419         help
420           This enables the selftest of the object debug code.
421 
422 config DEBUG_OBJECTS_FREE
423         bool "Debug objects in freed memory"
424         depends on DEBUG_OBJECTS
425         help
426           This enables checks whether a k/v free operation frees an area
427           which contains an object which has not been deactivated
428           properly. This can make kmalloc/kfree-intensive workloads
429           much slower.
430 
431 config DEBUG_OBJECTS_TIMERS
432         bool "Debug timer objects"
433         depends on DEBUG_OBJECTS
434         help
435           If you say Y here, additional code will be inserted into the
436           timer routines to track the life time of timer objects and
437           validate the timer operations.
438 
439 config DEBUG_OBJECTS_WORK
440         bool "Debug work objects"
441         depends on DEBUG_OBJECTS
442         help
443           If you say Y here, additional code will be inserted into the
444           work queue routines to track the life time of work objects and
445           validate the work operations.
446 
447 config DEBUG_OBJECTS_RCU_HEAD
448         bool "Debug RCU callbacks objects"
449         depends on DEBUG_OBJECTS
450         help
451           Enable this to turn on debugging of RCU list heads (call_rcu() usage).
452 
453 config DEBUG_OBJECTS_PERCPU_COUNTER
454         bool "Debug percpu counter objects"
455         depends on DEBUG_OBJECTS
456         help
457           If you say Y here, additional code will be inserted into the
458           percpu counter routines to track the life time of percpu counter
459           objects and validate the percpu counter operations.
460 
461 config DEBUG_OBJECTS_ENABLE_DEFAULT
462         int "debug_objects bootup default value (0-1)"
463         range 0 1
464         default "1"
465         depends on DEBUG_OBJECTS
466         help
467           Debug objects boot parameter default value
468 
469 config DEBUG_SLAB
470         bool "Debug slab memory allocations"
471         depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
472         help
473           Say Y here to have the kernel do limited verification on memory
474           allocation as well as poisoning memory on free to catch use of freed
475           memory. This can make kmalloc/kfree-intensive workloads much slower.
476 
477 config DEBUG_SLAB_LEAK
478         bool "Memory leak debugging"
479         depends on DEBUG_SLAB
480 
481 config SLUB_DEBUG_ON
482         bool "SLUB debugging on by default"
483         depends on SLUB && SLUB_DEBUG && !KMEMCHECK
484         default n
485         help
486           Boot with debugging on by default. SLUB boots by default with
487           the runtime debug capabilities switched off. Enabling this is
488           equivalent to specifying the "slub_debug" parameter on boot.
489           There is no support for more fine grained debug control like
490           possible with slub_debug=xxx. SLUB debugging may be switched
491           off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
492           "slub_debug=-".
493 
494 config SLUB_STATS
495         default n
496         bool "Enable SLUB performance statistics"
497         depends on SLUB && SYSFS
498         help
499           SLUB statistics are useful to debug SLUBs allocation behavior in
500           order find ways to optimize the allocator. This should never be
501           enabled for production use since keeping statistics slows down
502           the allocator by a few percentage points. The slabinfo command
503           supports the determination of the most active slabs to figure
504           out which slabs are relevant to a particular load.
505           Try running: slabinfo -DA
506 
507 config HAVE_DEBUG_KMEMLEAK
508         bool
509 
510 config DEBUG_KMEMLEAK
511         bool "Kernel memory leak detector"
512         depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
513         select DEBUG_FS
514         select STACKTRACE if STACKTRACE_SUPPORT
515         select KALLSYMS
516         select CRC32
517         help
518           Say Y here if you want to enable the memory leak
519           detector. The memory allocation/freeing is traced in a way
520           similar to the Boehm's conservative garbage collector, the
521           difference being that the orphan objects are not freed but
522           only shown in /sys/kernel/debug/kmemleak. Enabling this
523           feature will introduce an overhead to memory
524           allocations. See Documentation/kmemleak.txt for more
525           details.
526 
527           Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
528           of finding leaks due to the slab objects poisoning.
529 
530           In order to access the kmemleak file, debugfs needs to be
531           mounted (usually at /sys/kernel/debug).
532 
533 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
534         int "Maximum kmemleak early log entries"
535         depends on DEBUG_KMEMLEAK
536         range 200 40000
537         default 400
538         help
539           Kmemleak must track all the memory allocations to avoid
540           reporting false positives. Since memory may be allocated or
541           freed before kmemleak is initialised, an early log buffer is
542           used to store these actions. If kmemleak reports "early log
543           buffer exceeded", please increase this value.
544 
545 config DEBUG_KMEMLEAK_TEST
546         tristate "Simple test for the kernel memory leak detector"
547         depends on DEBUG_KMEMLEAK && m
548         help
549           This option enables a module that explicitly leaks memory.
550 
551           If unsure, say N.
552 
553 config DEBUG_KMEMLEAK_DEFAULT_OFF
554         bool "Default kmemleak to off"
555         depends on DEBUG_KMEMLEAK
556         help
557           Say Y here to disable kmemleak by default. It can then be enabled
558           on the command line via kmemleak=on.
559 
560 config DEBUG_STACK_USAGE
561         bool "Stack utilization instrumentation"
562         depends on DEBUG_KERNEL && !IA64
563         help
564           Enables the display of the minimum amount of free stack which each
565           task has ever had available in the sysrq-T and sysrq-P debug output.
566 
567           This option will slow down process creation somewhat.
568 
569 config DEBUG_VM
570         bool "Debug VM"
571         depends on DEBUG_KERNEL
572         help
573           Enable this to turn on extended checks in the virtual-memory system
574           that may impact performance.
575 
576           If unsure, say N.
577 
578 config DEBUG_VM_VMACACHE
579         bool "Debug VMA caching"
580         depends on DEBUG_VM
581         help
582           Enable this to turn on VMA caching debug information. Doing so
583           can cause significant overhead, so only enable it in non-production
584           environments.
585 
586           If unsure, say N.
587 
588 config DEBUG_VM_RB
589         bool "Debug VM red-black trees"
590         depends on DEBUG_VM
591         help
592           Enable VM red-black tree debugging information and extra validations.
593 
594           If unsure, say N.
595 
596 config DEBUG_VM_PGFLAGS
597         bool "Debug page-flags operations"
598         depends on DEBUG_VM
599         help
600           Enables extra validation on page flags operations.
601 
602           If unsure, say N.
603 
604 config DEBUG_VIRTUAL
605         bool "Debug VM translations"
606         depends on DEBUG_KERNEL && X86
607         help
608           Enable some costly sanity checks in virtual to page code. This can
609           catch mistakes with virt_to_page() and friends.
610 
611           If unsure, say N.
612 
613 config DEBUG_NOMMU_REGIONS
614         bool "Debug the global anon/private NOMMU mapping region tree"
615         depends on DEBUG_KERNEL && !MMU
616         help
617           This option causes the global tree of anonymous and private mapping
618           regions to be regularly checked for invalid topology.
619 
620 config DEBUG_MEMORY_INIT
621         bool "Debug memory initialisation" if EXPERT
622         default !EXPERT
623         help
624           Enable this for additional checks during memory initialisation.
625           The sanity checks verify aspects of the VM such as the memory model
626           and other information provided by the architecture. Verbose
627           information will be printed at KERN_DEBUG loglevel depending
628           on the mminit_loglevel= command-line option.
629 
630           If unsure, say Y
631 
632 config MEMORY_NOTIFIER_ERROR_INJECT
633         tristate "Memory hotplug notifier error injection module"
634         depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
635         help
636           This option provides the ability to inject artificial errors to
637           memory hotplug notifier chain callbacks.  It is controlled through
638           debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
639 
640           If the notifier call chain should be failed with some events
641           notified, write the error code to "actions/<notifier event>/error".
642 
643           Example: Inject memory hotplug offline error (-12 == -ENOMEM)
644 
645           # cd /sys/kernel/debug/notifier-error-inject/memory
646           # echo -12 > actions/MEM_GOING_OFFLINE/error
647           # echo offline > /sys/devices/system/memory/memoryXXX/state
648           bash: echo: write error: Cannot allocate memory
649 
650           To compile this code as a module, choose M here: the module will
651           be called memory-notifier-error-inject.
652 
653           If unsure, say N.
654 
655 config DEBUG_PER_CPU_MAPS
656         bool "Debug access to per_cpu maps"
657         depends on DEBUG_KERNEL
658         depends on SMP
659         help
660           Say Y to verify that the per_cpu map being accessed has
661           been set up. This adds a fair amount of code to kernel memory
662           and decreases performance.
663 
664           Say N if unsure.
665 
666 config DEBUG_HIGHMEM
667         bool "Highmem debugging"
668         depends on DEBUG_KERNEL && HIGHMEM
669         help
670           This option enables additional error checking for high memory
671           systems.  Disable for production systems.
672 
673 config HAVE_DEBUG_STACKOVERFLOW
674         bool
675 
676 config DEBUG_STACKOVERFLOW
677         bool "Check for stack overflows"
678         depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
679         ---help---
680           Say Y here if you want to check for overflows of kernel, IRQ
681           and exception stacks (if your architecture uses them). This
682           option will show detailed messages if free stack space drops
683           below a certain limit.
684 
685           These kinds of bugs usually occur when call-chains in the
686           kernel get too deep, especially when interrupts are
687           involved.
688 
689           Use this in cases where you see apparently random memory
690           corruption, especially if it appears in 'struct thread_info'
691 
692           If in doubt, say "N".
693 
694 source "lib/Kconfig.kmemcheck"
695 
696 source "lib/Kconfig.kasan"
697 
698 endmenu # "Memory Debugging"
699 
700 config ARCH_HAS_KCOV
701         bool
702         help
703           KCOV does not have any arch-specific code, but currently it is enabled
704           only for x86_64. KCOV requires testing on other archs, and most likely
705           disabling of instrumentation for some early boot code.
706 
707 config KCOV
708         bool "Code coverage for fuzzing"
709         depends on ARCH_HAS_KCOV
710         select DEBUG_FS
711         help
712           KCOV exposes kernel code coverage information in a form suitable
713           for coverage-guided fuzzing (randomized testing).
714 
715           If RANDOMIZE_BASE is enabled, PC values will not be stable across
716           different machines and across reboots. If you need stable PC values,
717           disable RANDOMIZE_BASE.
718 
719           For more details, see Documentation/kcov.txt.
720 
721 config DEBUG_SHIRQ
722         bool "Debug shared IRQ handlers"
723         depends on DEBUG_KERNEL
724         help
725           Enable this to generate a spurious interrupt as soon as a shared
726           interrupt handler is registered, and just before one is deregistered.
727           Drivers ought to be able to handle interrupts coming in at those
728           points; some don't and need to be caught.
729 
730 menu "Debug Lockups and Hangs"
731 
732 config LOCKUP_DETECTOR
733         bool "Detect Hard and Soft Lockups"
734         depends on DEBUG_KERNEL && !S390
735         help
736           Say Y here to enable the kernel to act as a watchdog to detect
737           hard and soft lockups.
738 
739           Softlockups are bugs that cause the kernel to loop in kernel
740           mode for more than 20 seconds, without giving other tasks a
741           chance to run.  The current stack trace is displayed upon
742           detection and the system will stay locked up.
743 
744           Hardlockups are bugs that cause the CPU to loop in kernel mode
745           for more than 10 seconds, without letting other interrupts have a
746           chance to run.  The current stack trace is displayed upon detection
747           and the system will stay locked up.
748 
749           The overhead should be minimal.  A periodic hrtimer runs to
750           generate interrupts and kick the watchdog task every 4 seconds.
751           An NMI is generated every 10 seconds or so to check for hardlockups.
752 
753           The frequency of hrtimer and NMI events and the soft and hard lockup
754           thresholds can be controlled through the sysctl watchdog_thresh.
755 
756 config HARDLOCKUP_DETECTOR
757         def_bool y
758         depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
759         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
760 
761 config BOOTPARAM_HARDLOCKUP_PANIC
762         bool "Panic (Reboot) On Hard Lockups"
763         depends on HARDLOCKUP_DETECTOR
764         help
765           Say Y here to enable the kernel to panic on "hard lockups",
766           which are bugs that cause the kernel to loop in kernel
767           mode with interrupts disabled for more than 10 seconds (configurable
768           using the watchdog_thresh sysctl).
769 
770           Say N if unsure.
771 
772 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
773         int
774         depends on HARDLOCKUP_DETECTOR
775         range 0 1
776         default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
777         default 1 if BOOTPARAM_HARDLOCKUP_PANIC
778 
779 config BOOTPARAM_SOFTLOCKUP_PANIC
780         bool "Panic (Reboot) On Soft Lockups"
781         depends on LOCKUP_DETECTOR
782         help
783           Say Y here to enable the kernel to panic on "soft lockups",
784           which are bugs that cause the kernel to loop in kernel
785           mode for more than 20 seconds (configurable using the watchdog_thresh
786           sysctl), without giving other tasks a chance to run.
787 
788           The panic can be used in combination with panic_timeout,
789           to cause the system to reboot automatically after a
790           lockup has been detected. This feature is useful for
791           high-availability systems that have uptime guarantees and
792           where a lockup must be resolved ASAP.
793 
794           Say N if unsure.
795 
796 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
797         int
798         depends on LOCKUP_DETECTOR
799         range 0 1
800         default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
801         default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
802 
803 config DETECT_HUNG_TASK
804         bool "Detect Hung Tasks"
805         depends on DEBUG_KERNEL
806         default LOCKUP_DETECTOR
807         help
808           Say Y here to enable the kernel to detect "hung tasks",
809           which are bugs that cause the task to be stuck in
810           uninterruptible "D" state indefinitiley.
811 
812           When a hung task is detected, the kernel will print the
813           current stack trace (which you should report), but the
814           task will stay in uninterruptible state. If lockdep is
815           enabled then all held locks will also be reported. This
816           feature has negligible overhead.
817 
818 config DEFAULT_HUNG_TASK_TIMEOUT
819         int "Default timeout for hung task detection (in seconds)"
820         depends on DETECT_HUNG_TASK
821         default 120
822         help
823           This option controls the default timeout (in seconds) used
824           to determine when a task has become non-responsive and should
825           be considered hung.
826 
827           It can be adjusted at runtime via the kernel.hung_task_timeout_secs
828           sysctl or by writing a value to
829           /proc/sys/kernel/hung_task_timeout_secs.
830 
831           A timeout of 0 disables the check.  The default is two minutes.
832           Keeping the default should be fine in most cases.
833 
834 config BOOTPARAM_HUNG_TASK_PANIC
835         bool "Panic (Reboot) On Hung Tasks"
836         depends on DETECT_HUNG_TASK
837         help
838           Say Y here to enable the kernel to panic on "hung tasks",
839           which are bugs that cause the kernel to leave a task stuck
840           in uninterruptible "D" state.
841 
842           The panic can be used in combination with panic_timeout,
843           to cause the system to reboot automatically after a
844           hung task has been detected. This feature is useful for
845           high-availability systems that have uptime guarantees and
846           where a hung tasks must be resolved ASAP.
847 
848           Say N if unsure.
849 
850 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
851         int
852         depends on DETECT_HUNG_TASK
853         range 0 1
854         default 0 if !BOOTPARAM_HUNG_TASK_PANIC
855         default 1 if BOOTPARAM_HUNG_TASK_PANIC
856 
857 config WQ_WATCHDOG
858         bool "Detect Workqueue Stalls"
859         depends on DEBUG_KERNEL
860         help
861           Say Y here to enable stall detection on workqueues.  If a
862           worker pool doesn't make forward progress on a pending work
863           item for over a given amount of time, 30s by default, a
864           warning message is printed along with dump of workqueue
865           state.  This can be configured through kernel parameter
866           "workqueue.watchdog_thresh" and its sysfs counterpart.
867 
868 endmenu # "Debug lockups and hangs"
869 
870 config PANIC_ON_OOPS
871         bool "Panic on Oops"
872         help
873           Say Y here to enable the kernel to panic when it oopses. This
874           has the same effect as setting oops=panic on the kernel command
875           line.
876 
877           This feature is useful to ensure that the kernel does not do
878           anything erroneous after an oops which could result in data
879           corruption or other issues.
880 
881           Say N if unsure.
882 
883 config PANIC_ON_OOPS_VALUE
884         int
885         range 0 1
886         default 0 if !PANIC_ON_OOPS
887         default 1 if PANIC_ON_OOPS
888 
889 config PANIC_TIMEOUT
890         int "panic timeout"
891         default 0
892         help
893           Set the timeout value (in seconds) until a reboot occurs when the
894           the kernel panics. If n = 0, then we wait forever. A timeout
895           value n > 0 will wait n seconds before rebooting, while a timeout
896           value n < 0 will reboot immediately.
897 
898 config SCHED_DEBUG
899         bool "Collect scheduler debugging info"
900         depends on DEBUG_KERNEL && PROC_FS
901         default y
902         help
903           If you say Y here, the /proc/sched_debug file will be provided
904           that can help debug the scheduler. The runtime overhead of this
905           option is minimal.
906 
907 config SCHED_INFO
908         bool
909         default n
910 
911 config SCHEDSTATS
912         bool "Collect scheduler statistics"
913         depends on DEBUG_KERNEL && PROC_FS
914         select SCHED_INFO
915         help
916           If you say Y here, additional code will be inserted into the
917           scheduler and related routines to collect statistics about
918           scheduler behavior and provide them in /proc/schedstat.  These
919           stats may be useful for both tuning and debugging the scheduler
920           If you aren't debugging the scheduler or trying to tune a specific
921           application, you can say N to avoid the very slight overhead
922           this adds.
923 
924 config SCHED_STACK_END_CHECK
925         bool "Detect stack corruption on calls to schedule()"
926         depends on DEBUG_KERNEL
927         default n
928         help
929           This option checks for a stack overrun on calls to schedule().
930           If the stack end location is found to be over written always panic as
931           the content of the corrupted region can no longer be trusted.
932           This is to ensure no erroneous behaviour occurs which could result in
933           data corruption or a sporadic crash at a later stage once the region
934           is examined. The runtime overhead introduced is minimal.
935 
936 config DEBUG_TIMEKEEPING
937         bool "Enable extra timekeeping sanity checking"
938         help
939           This option will enable additional timekeeping sanity checks
940           which may be helpful when diagnosing issues where timekeeping
941           problems are suspected.
942 
943           This may include checks in the timekeeping hotpaths, so this
944           option may have a (very small) performance impact to some
945           workloads.
946 
947           If unsure, say N.
948 
949 config TIMER_STATS
950         bool "Collect kernel timers statistics"
951         depends on DEBUG_KERNEL && PROC_FS
952         help
953           If you say Y here, additional code will be inserted into the
954           timer routines to collect statistics about kernel timers being
955           reprogrammed. The statistics can be read from /proc/timer_stats.
956           The statistics collection is started by writing 1 to /proc/timer_stats,
957           writing 0 stops it. This feature is useful to collect information
958           about timer usage patterns in kernel and userspace. This feature
959           is lightweight if enabled in the kernel config but not activated
960           (it defaults to deactivated on bootup and will only be activated
961           if some application like powertop activates it explicitly).
962 
963 config DEBUG_PREEMPT
964         bool "Debug preemptible kernel"
965         depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
966         default y
967         help
968           If you say Y here then the kernel will use a debug variant of the
969           commonly used smp_processor_id() function and will print warnings
970           if kernel code uses it in a preemption-unsafe way. Also, the kernel
971           will detect preemption count underflows.
972 
973 menu "Lock Debugging (spinlocks, mutexes, etc...)"
974 
975 config DEBUG_RT_MUTEXES
976         bool "RT Mutex debugging, deadlock detection"
977         depends on DEBUG_KERNEL && RT_MUTEXES
978         help
979          This allows rt mutex semantics violations and rt mutex related
980          deadlocks (lockups) to be detected and reported automatically.
981 
982 config DEBUG_SPINLOCK
983         bool "Spinlock and rw-lock debugging: basic checks"
984         depends on DEBUG_KERNEL
985         select UNINLINE_SPIN_UNLOCK
986         help
987           Say Y here and build SMP to catch missing spinlock initialization
988           and certain other kinds of spinlock errors commonly made.  This is
989           best used in conjunction with the NMI watchdog so that spinlock
990           deadlocks are also debuggable.
991 
992 config DEBUG_MUTEXES
993         bool "Mutex debugging: basic checks"
994         depends on DEBUG_KERNEL
995         help
996          This feature allows mutex semantics violations to be detected and
997          reported.
998 
999 config DEBUG_WW_MUTEX_SLOWPATH
1000         bool "Wait/wound mutex debugging: Slowpath testing"
1001         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1002         select DEBUG_LOCK_ALLOC
1003         select DEBUG_SPINLOCK
1004         select DEBUG_MUTEXES
1005         help
1006          This feature enables slowpath testing for w/w mutex users by
1007          injecting additional -EDEADLK wound/backoff cases. Together with
1008          the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1009          will test all possible w/w mutex interface abuse with the
1010          exception of simply not acquiring all the required locks.
1011          Note that this feature can introduce significant overhead, so
1012          it really should not be enabled in a production or distro kernel,
1013          even a debug kernel.  If you are a driver writer, enable it.  If
1014          you are a distro, do not.
1015 
1016 config DEBUG_LOCK_ALLOC
1017         bool "Lock debugging: detect incorrect freeing of live locks"
1018         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1019         select DEBUG_SPINLOCK
1020         select DEBUG_MUTEXES
1021         select LOCKDEP
1022         help
1023          This feature will check whether any held lock (spinlock, rwlock,
1024          mutex or rwsem) is incorrectly freed by the kernel, via any of the
1025          memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1026          vfree(), etc.), whether a live lock is incorrectly reinitialized via
1027          spin_lock_init()/mutex_init()/etc., or whether there is any lock
1028          held during task exit.
1029 
1030 config PROVE_LOCKING
1031         bool "Lock debugging: prove locking correctness"
1032         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1033         select LOCKDEP
1034         select DEBUG_SPINLOCK
1035         select DEBUG_MUTEXES
1036         select DEBUG_LOCK_ALLOC
1037         select TRACE_IRQFLAGS
1038         default n
1039         help
1040          This feature enables the kernel to prove that all locking
1041          that occurs in the kernel runtime is mathematically
1042          correct: that under no circumstance could an arbitrary (and
1043          not yet triggered) combination of observed locking
1044          sequences (on an arbitrary number of CPUs, running an
1045          arbitrary number of tasks and interrupt contexts) cause a
1046          deadlock.
1047 
1048          In short, this feature enables the kernel to report locking
1049          related deadlocks before they actually occur.
1050 
1051          The proof does not depend on how hard and complex a
1052          deadlock scenario would be to trigger: how many
1053          participant CPUs, tasks and irq-contexts would be needed
1054          for it to trigger. The proof also does not depend on
1055          timing: if a race and a resulting deadlock is possible
1056          theoretically (no matter how unlikely the race scenario
1057          is), it will be proven so and will immediately be
1058          reported by the kernel (once the event is observed that
1059          makes the deadlock theoretically possible).
1060 
1061          If a deadlock is impossible (i.e. the locking rules, as
1062          observed by the kernel, are mathematically correct), the
1063          kernel reports nothing.
1064 
1065          NOTE: this feature can also be enabled for rwlocks, mutexes
1066          and rwsems - in which case all dependencies between these
1067          different locking variants are observed and mapped too, and
1068          the proof of observed correctness is also maintained for an
1069          arbitrary combination of these separate locking variants.
1070 
1071          For more details, see Documentation/locking/lockdep-design.txt.
1072 
1073 config LOCKDEP
1074         bool
1075         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1076         select STACKTRACE
1077         select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
1078         select KALLSYMS
1079         select KALLSYMS_ALL
1080 
1081 config LOCK_STAT
1082         bool "Lock usage statistics"
1083         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1084         select LOCKDEP
1085         select DEBUG_SPINLOCK
1086         select DEBUG_MUTEXES
1087         select DEBUG_LOCK_ALLOC
1088         default n
1089         help
1090          This feature enables tracking lock contention points
1091 
1092          For more details, see Documentation/locking/lockstat.txt
1093 
1094          This also enables lock events required by "perf lock",
1095          subcommand of perf.
1096          If you want to use "perf lock", you also need to turn on
1097          CONFIG_EVENT_TRACING.
1098 
1099          CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1100          (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1101 
1102 config DEBUG_LOCKDEP
1103         bool "Lock dependency engine debugging"
1104         depends on DEBUG_KERNEL && LOCKDEP
1105         help
1106           If you say Y here, the lock dependency engine will do
1107           additional runtime checks to debug itself, at the price
1108           of more runtime overhead.
1109 
1110 config DEBUG_ATOMIC_SLEEP
1111         bool "Sleep inside atomic section checking"
1112         select PREEMPT_COUNT
1113         depends on DEBUG_KERNEL
1114         help
1115           If you say Y here, various routines which may sleep will become very
1116           noisy if they are called inside atomic sections: when a spinlock is
1117           held, inside an rcu read side critical section, inside preempt disabled
1118           sections, inside an interrupt, etc...
1119 
1120 config DEBUG_LOCKING_API_SELFTESTS
1121         bool "Locking API boot-time self-tests"
1122         depends on DEBUG_KERNEL
1123         help
1124           Say Y here if you want the kernel to run a short self-test during
1125           bootup. The self-test checks whether common types of locking bugs
1126           are detected by debugging mechanisms or not. (if you disable
1127           lock debugging then those bugs wont be detected of course.)
1128           The following locking APIs are covered: spinlocks, rwlocks,
1129           mutexes and rwsems.
1130 
1131 config LOCK_TORTURE_TEST
1132         tristate "torture tests for locking"
1133         depends on DEBUG_KERNEL
1134         select TORTURE_TEST
1135         default n
1136         help
1137           This option provides a kernel module that runs torture tests
1138           on kernel locking primitives.  The kernel module may be built
1139           after the fact on the running kernel to be tested, if desired.
1140 
1141           Say Y here if you want kernel locking-primitive torture tests
1142           to be built into the kernel.
1143           Say M if you want these torture tests to build as a module.
1144           Say N if you are unsure.
1145 
1146 endmenu # lock debugging
1147 
1148 config TRACE_IRQFLAGS
1149         bool
1150         help
1151           Enables hooks to interrupt enabling and disabling for
1152           either tracing or lock debugging.
1153 
1154 config STACKTRACE
1155         bool "Stack backtrace support"
1156         depends on STACKTRACE_SUPPORT
1157         help
1158           This option causes the kernel to create a /proc/pid/stack for
1159           every process, showing its current stack trace.
1160           It is also used by various kernel debugging features that require
1161           stack trace generation.
1162 
1163 config DEBUG_KOBJECT
1164         bool "kobject debugging"
1165         depends on DEBUG_KERNEL
1166         help
1167           If you say Y here, some extra kobject debugging messages will be sent
1168           to the syslog. 
1169 
1170 config DEBUG_KOBJECT_RELEASE
1171         bool "kobject release debugging"
1172         depends on DEBUG_OBJECTS_TIMERS
1173         help
1174           kobjects are reference counted objects.  This means that their
1175           last reference count put is not predictable, and the kobject can
1176           live on past the point at which a driver decides to drop it's
1177           initial reference to the kobject gained on allocation.  An
1178           example of this would be a struct device which has just been
1179           unregistered.
1180 
1181           However, some buggy drivers assume that after such an operation,
1182           the memory backing the kobject can be immediately freed.  This
1183           goes completely against the principles of a refcounted object.
1184 
1185           If you say Y here, the kernel will delay the release of kobjects
1186           on the last reference count to improve the visibility of this
1187           kind of kobject release bug.
1188 
1189 config HAVE_DEBUG_BUGVERBOSE
1190         bool
1191 
1192 config DEBUG_BUGVERBOSE
1193         bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1194         depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1195         default y
1196         help
1197           Say Y here to make BUG() panics output the file name and line number
1198           of the BUG call as well as the EIP and oops trace.  This aids
1199           debugging but costs about 70-100K of memory.
1200 
1201 config DEBUG_LIST
1202         bool "Debug linked list manipulation"
1203         depends on DEBUG_KERNEL
1204         help
1205           Enable this to turn on extended checks in the linked-list
1206           walking routines.
1207 
1208           If unsure, say N.
1209 
1210 config DEBUG_PI_LIST
1211         bool "Debug priority linked list manipulation"
1212         depends on DEBUG_KERNEL
1213         help
1214           Enable this to turn on extended checks in the priority-ordered
1215           linked-list (plist) walking routines.  This checks the entire
1216           list multiple times during each manipulation.
1217 
1218           If unsure, say N.
1219 
1220 config DEBUG_SG
1221         bool "Debug SG table operations"
1222         depends on DEBUG_KERNEL
1223         help
1224           Enable this to turn on checks on scatter-gather tables. This can
1225           help find problems with drivers that do not properly initialize
1226           their sg tables.
1227 
1228           If unsure, say N.
1229 
1230 config DEBUG_NOTIFIERS
1231         bool "Debug notifier call chains"
1232         depends on DEBUG_KERNEL
1233         help
1234           Enable this to turn on sanity checking for notifier call chains.
1235           This is most useful for kernel developers to make sure that
1236           modules properly unregister themselves from notifier chains.
1237           This is a relatively cheap check but if you care about maximum
1238           performance, say N.
1239 
1240 config DEBUG_CREDENTIALS
1241         bool "Debug credential management"
1242         depends on DEBUG_KERNEL
1243         help
1244           Enable this to turn on some debug checking for credential
1245           management.  The additional code keeps track of the number of
1246           pointers from task_structs to any given cred struct, and checks to
1247           see that this number never exceeds the usage count of the cred
1248           struct.
1249 
1250           Furthermore, if SELinux is enabled, this also checks that the
1251           security pointer in the cred struct is never seen to be invalid.
1252 
1253           If unsure, say N.
1254 
1255 menu "RCU Debugging"
1256 
1257 config PROVE_RCU
1258         def_bool PROVE_LOCKING
1259 
1260 config PROVE_RCU_REPEATEDLY
1261         bool "RCU debugging: don't disable PROVE_RCU on first splat"
1262         depends on PROVE_RCU
1263         default n
1264         help
1265          By itself, PROVE_RCU will disable checking upon issuing the
1266          first warning (or "splat").  This feature prevents such
1267          disabling, allowing multiple RCU-lockdep warnings to be printed
1268          on a single reboot.
1269 
1270          Say Y to allow multiple RCU-lockdep warnings per boot.
1271 
1272          Say N if you are unsure.
1273 
1274 config SPARSE_RCU_POINTER
1275         bool "RCU debugging: sparse-based checks for pointer usage"
1276         default n
1277         help
1278          This feature enables the __rcu sparse annotation for
1279          RCU-protected pointers.  This annotation will cause sparse
1280          to flag any non-RCU used of annotated pointers.  This can be
1281          helpful when debugging RCU usage.  Please note that this feature
1282          is not intended to enforce code cleanliness; it is instead merely
1283          a debugging aid.
1284 
1285          Say Y to make sparse flag questionable use of RCU-protected pointers
1286 
1287          Say N if you are unsure.
1288 
1289 config TORTURE_TEST
1290         tristate
1291         default n
1292 
1293 config RCU_PERF_TEST
1294         tristate "performance tests for RCU"
1295         depends on DEBUG_KERNEL
1296         select TORTURE_TEST
1297         select SRCU
1298         select TASKS_RCU
1299         default n
1300         help
1301           This option provides a kernel module that runs performance
1302           tests on the RCU infrastructure.  The kernel module may be built
1303           after the fact on the running kernel to be tested, if desired.
1304 
1305           Say Y here if you want RCU performance tests to be built into
1306           the kernel.
1307           Say M if you want the RCU performance tests to build as a module.
1308           Say N if you are unsure.
1309 
1310 config RCU_PERF_TEST_RUNNABLE
1311         bool "performance tests for RCU runnable by default"
1312         depends on RCU_PERF_TEST = y
1313         default n
1314         help
1315           This option provides a way to build the RCU performance tests
1316           directly into the kernel without them starting up at boot time.
1317           You can use /sys/module to manually override this setting.
1318           This /proc file is available only when the RCU performance
1319           tests have been built into the kernel.
1320 
1321           Say Y here if you want the RCU performance tests to start during
1322           boot (you probably don't).
1323           Say N here if you want the RCU performance tests to start only
1324           after being manually enabled via /sys/module.
1325 
1326 config RCU_TORTURE_TEST
1327         tristate "torture tests for RCU"
1328         depends on DEBUG_KERNEL
1329         select TORTURE_TEST
1330         select SRCU
1331         select TASKS_RCU
1332         default n
1333         help
1334           This option provides a kernel module that runs torture tests
1335           on the RCU infrastructure.  The kernel module may be built
1336           after the fact on the running kernel to be tested, if desired.
1337 
1338           Say Y here if you want RCU torture tests to be built into
1339           the kernel.
1340           Say M if you want the RCU torture tests to build as a module.
1341           Say N if you are unsure.
1342 
1343 config RCU_TORTURE_TEST_RUNNABLE
1344         bool "torture tests for RCU runnable by default"
1345         depends on RCU_TORTURE_TEST = y
1346         default n
1347         help
1348           This option provides a way to build the RCU torture tests
1349           directly into the kernel without them starting up at boot
1350           time.  You can use /proc/sys/kernel/rcutorture_runnable
1351           to manually override this setting.  This /proc file is
1352           available only when the RCU torture tests have been built
1353           into the kernel.
1354 
1355           Say Y here if you want the RCU torture tests to start during
1356           boot (you probably don't).
1357           Say N here if you want the RCU torture tests to start only
1358           after being manually enabled via /proc.
1359 
1360 config RCU_TORTURE_TEST_SLOW_PREINIT
1361         bool "Slow down RCU grace-period pre-initialization to expose races"
1362         depends on RCU_TORTURE_TEST
1363         help
1364           This option delays grace-period pre-initialization (the
1365           propagation of CPU-hotplug changes up the rcu_node combining
1366           tree) for a few jiffies between initializing each pair of
1367           consecutive rcu_node structures.  This helps to expose races
1368           involving grace-period pre-initialization, in other words, it
1369           makes your kernel less stable.  It can also greatly increase
1370           grace-period latency, especially on systems with large numbers
1371           of CPUs.  This is useful when torture-testing RCU, but in
1372           almost no other circumstance.
1373 
1374           Say Y here if you want your system to crash and hang more often.
1375           Say N if you want a sane system.
1376 
1377 config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
1378         int "How much to slow down RCU grace-period pre-initialization"
1379         range 0 5
1380         default 3
1381         depends on RCU_TORTURE_TEST_SLOW_PREINIT
1382         help
1383           This option specifies the number of jiffies to wait between
1384           each rcu_node structure pre-initialization step.
1385 
1386 config RCU_TORTURE_TEST_SLOW_INIT
1387         bool "Slow down RCU grace-period initialization to expose races"
1388         depends on RCU_TORTURE_TEST
1389         help
1390           This option delays grace-period initialization for a few
1391           jiffies between initializing each pair of consecutive
1392           rcu_node structures.  This helps to expose races involving
1393           grace-period initialization, in other words, it makes your
1394           kernel less stable.  It can also greatly increase grace-period
1395           latency, especially on systems with large numbers of CPUs.
1396           This is useful when torture-testing RCU, but in almost no
1397           other circumstance.
1398 
1399           Say Y here if you want your system to crash and hang more often.
1400           Say N if you want a sane system.
1401 
1402 config RCU_TORTURE_TEST_SLOW_INIT_DELAY
1403         int "How much to slow down RCU grace-period initialization"
1404         range 0 5
1405         default 3
1406         depends on RCU_TORTURE_TEST_SLOW_INIT
1407         help
1408           This option specifies the number of jiffies to wait between
1409           each rcu_node structure initialization.
1410 
1411 config RCU_TORTURE_TEST_SLOW_CLEANUP
1412         bool "Slow down RCU grace-period cleanup to expose races"
1413         depends on RCU_TORTURE_TEST
1414         help
1415           This option delays grace-period cleanup for a few jiffies
1416           between cleaning up each pair of consecutive rcu_node
1417           structures.  This helps to expose races involving grace-period
1418           cleanup, in other words, it makes your kernel less stable.
1419           It can also greatly increase grace-period latency, especially
1420           on systems with large numbers of CPUs.  This is useful when
1421           torture-testing RCU, but in almost no other circumstance.
1422 
1423           Say Y here if you want your system to crash and hang more often.
1424           Say N if you want a sane system.
1425 
1426 config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
1427         int "How much to slow down RCU grace-period cleanup"
1428         range 0 5
1429         default 3
1430         depends on RCU_TORTURE_TEST_SLOW_CLEANUP
1431         help
1432           This option specifies the number of jiffies to wait between
1433           each rcu_node structure cleanup operation.
1434 
1435 config RCU_CPU_STALL_TIMEOUT
1436         int "RCU CPU stall timeout in seconds"
1437         depends on RCU_STALL_COMMON
1438         range 3 300
1439         default 21
1440         help
1441           If a given RCU grace period extends more than the specified
1442           number of seconds, a CPU stall warning is printed.  If the
1443           RCU grace period persists, additional CPU stall warnings are
1444           printed at more widely spaced intervals.
1445 
1446 config RCU_TRACE
1447         bool "Enable tracing for RCU"
1448         depends on DEBUG_KERNEL
1449         select TRACE_CLOCK
1450         help
1451           This option provides tracing in RCU which presents stats
1452           in debugfs for debugging RCU implementation.
1453 
1454           Say Y here if you want to enable RCU tracing
1455           Say N if you are unsure.
1456 
1457 config RCU_EQS_DEBUG
1458         bool "Provide debugging asserts for adding NO_HZ support to an arch"
1459         depends on DEBUG_KERNEL
1460         help
1461           This option provides consistency checks in RCU's handling of
1462           NO_HZ.  These checks have proven quite helpful in detecting
1463           bugs in arch-specific NO_HZ code.
1464 
1465           Say N here if you need ultimate kernel/user switch latencies
1466           Say Y if you are unsure
1467 
1468 endmenu # "RCU Debugging"
1469 
1470 config DEBUG_WQ_FORCE_RR_CPU
1471         bool "Force round-robin CPU selection for unbound work items"
1472         depends on DEBUG_KERNEL
1473         default n
1474         help
1475           Workqueue used to implicitly guarantee that work items queued
1476           without explicit CPU specified are put on the local CPU.  This
1477           guarantee is no longer true and while local CPU is still
1478           preferred work items may be put on foreign CPUs.  Kernel
1479           parameter "workqueue.debug_force_rr_cpu" is added to force
1480           round-robin CPU selection to flush out usages which depend on the
1481           now broken guarantee.  This config option enables the debug
1482           feature by default.  When enabled, memory and cache locality will
1483           be impacted.
1484 
1485 config DEBUG_BLOCK_EXT_DEVT
1486         bool "Force extended block device numbers and spread them"
1487         depends on DEBUG_KERNEL
1488         depends on BLOCK
1489         default n
1490         help
1491           BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1492           SOME DISTRIBUTIONS.  DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1493           YOU ARE DOING.  Distros, please enable this and fix whatever
1494           is broken.
1495 
1496           Conventionally, block device numbers are allocated from
1497           predetermined contiguous area.  However, extended block area
1498           may introduce non-contiguous block device numbers.  This
1499           option forces most block device numbers to be allocated from
1500           the extended space and spreads them to discover kernel or
1501           userland code paths which assume predetermined contiguous
1502           device number allocation.
1503 
1504           Note that turning on this debug option shuffles all the
1505           device numbers for all IDE and SCSI devices including libata
1506           ones, so root partition specified using device number
1507           directly (via rdev or root=MAJ:MIN) won't work anymore.
1508           Textual device names (root=/dev/sdXn) will continue to work.
1509 
1510           Say N if you are unsure.
1511 
1512 config CPU_HOTPLUG_STATE_CONTROL
1513         bool "Enable CPU hotplug state control"
1514         depends on DEBUG_KERNEL
1515         depends on HOTPLUG_CPU
1516         default n
1517         help
1518           Allows to write steps between "offline" and "online" to the CPUs
1519           sysfs target file so states can be stepped granular. This is a debug
1520           option for now as the hotplug machinery cannot be stopped and
1521           restarted at arbitrary points yet.
1522 
1523           Say N if your are unsure.
1524 
1525 config NOTIFIER_ERROR_INJECTION
1526         tristate "Notifier error injection"
1527         depends on DEBUG_KERNEL
1528         select DEBUG_FS
1529         help
1530           This option provides the ability to inject artificial errors to
1531           specified notifier chain callbacks. It is useful to test the error
1532           handling of notifier call chain failures.
1533 
1534           Say N if unsure.
1535 
1536 config CPU_NOTIFIER_ERROR_INJECT
1537         tristate "CPU notifier error injection module"
1538         depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1539         help
1540           This option provides a kernel module that can be used to test
1541           the error handling of the cpu notifiers by injecting artificial
1542           errors to CPU notifier chain callbacks.  It is controlled through
1543           debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
1544 
1545           If the notifier call chain should be failed with some events
1546           notified, write the error code to "actions/<notifier event>/error".
1547 
1548           Example: Inject CPU offline error (-1 == -EPERM)
1549 
1550           # cd /sys/kernel/debug/notifier-error-inject/cpu
1551           # echo -1 > actions/CPU_DOWN_PREPARE/error
1552           # echo 0 > /sys/devices/system/cpu/cpu1/online
1553           bash: echo: write error: Operation not permitted
1554 
1555           To compile this code as a module, choose M here: the module will
1556           be called cpu-notifier-error-inject.
1557 
1558           If unsure, say N.
1559 
1560 config PM_NOTIFIER_ERROR_INJECT
1561         tristate "PM notifier error injection module"
1562         depends on PM && NOTIFIER_ERROR_INJECTION
1563         default m if PM_DEBUG
1564         help
1565           This option provides the ability to inject artificial errors to
1566           PM notifier chain callbacks.  It is controlled through debugfs
1567           interface /sys/kernel/debug/notifier-error-inject/pm
1568 
1569           If the notifier call chain should be failed with some events
1570           notified, write the error code to "actions/<notifier event>/error".
1571 
1572           Example: Inject PM suspend error (-12 = -ENOMEM)
1573 
1574           # cd /sys/kernel/debug/notifier-error-inject/pm/
1575           # echo -12 > actions/PM_SUSPEND_PREPARE/error
1576           # echo mem > /sys/power/state
1577           bash: echo: write error: Cannot allocate memory
1578 
1579           To compile this code as a module, choose M here: the module will
1580           be called pm-notifier-error-inject.
1581 
1582           If unsure, say N.
1583 
1584 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1585         tristate "OF reconfig notifier error injection module"
1586         depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1587         help
1588           This option provides the ability to inject artificial errors to
1589           OF reconfig notifier chain callbacks.  It is controlled
1590           through debugfs interface under
1591           /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1592 
1593           If the notifier call chain should be failed with some events
1594           notified, write the error code to "actions/<notifier event>/error".
1595 
1596           To compile this code as a module, choose M here: the module will
1597           be called of-reconfig-notifier-error-inject.
1598 
1599           If unsure, say N.
1600 
1601 config NETDEV_NOTIFIER_ERROR_INJECT
1602         tristate "Netdev notifier error injection module"
1603         depends on NET && NOTIFIER_ERROR_INJECTION
1604         help
1605           This option provides the ability to inject artificial errors to
1606           netdevice notifier chain callbacks.  It is controlled through debugfs
1607           interface /sys/kernel/debug/notifier-error-inject/netdev
1608 
1609           If the notifier call chain should be failed with some events
1610           notified, write the error code to "actions/<notifier event>/error".
1611 
1612           Example: Inject netdevice mtu change error (-22 = -EINVAL)
1613 
1614           # cd /sys/kernel/debug/notifier-error-inject/netdev
1615           # echo -22 > actions/NETDEV_CHANGEMTU/error
1616           # ip link set eth0 mtu 1024
1617           RTNETLINK answers: Invalid argument
1618 
1619           To compile this code as a module, choose M here: the module will
1620           be called netdev-notifier-error-inject.
1621 
1622           If unsure, say N.
1623 
1624 config FAULT_INJECTION
1625         bool "Fault-injection framework"
1626         depends on DEBUG_KERNEL
1627         help
1628           Provide fault-injection framework.
1629           For more details, see Documentation/fault-injection/.
1630 
1631 config FAILSLAB
1632         bool "Fault-injection capability for kmalloc"
1633         depends on FAULT_INJECTION
1634         depends on SLAB || SLUB
1635         help
1636           Provide fault-injection capability for kmalloc.
1637 
1638 config FAIL_PAGE_ALLOC
1639         bool "Fault-injection capabilitiy for alloc_pages()"
1640         depends on FAULT_INJECTION
1641         help
1642           Provide fault-injection capability for alloc_pages().
1643 
1644 config FAIL_MAKE_REQUEST
1645         bool "Fault-injection capability for disk IO"
1646         depends on FAULT_INJECTION && BLOCK
1647         help
1648           Provide fault-injection capability for disk IO.
1649 
1650 config FAIL_IO_TIMEOUT
1651         bool "Fault-injection capability for faking disk interrupts"
1652         depends on FAULT_INJECTION && BLOCK
1653         help
1654           Provide fault-injection capability on end IO handling. This
1655           will make the block layer "forget" an interrupt as configured,
1656           thus exercising the error handling.
1657 
1658           Only works with drivers that use the generic timeout handling,
1659           for others it wont do anything.
1660 
1661 config FAIL_MMC_REQUEST
1662         bool "Fault-injection capability for MMC IO"
1663         depends on FAULT_INJECTION_DEBUG_FS && MMC
1664         help
1665           Provide fault-injection capability for MMC IO.
1666           This will make the mmc core return data errors. This is
1667           useful to test the error handling in the mmc block device
1668           and to test how the mmc host driver handles retries from
1669           the block device.
1670 
1671 config FAIL_FUTEX
1672         bool "Fault-injection capability for futexes"
1673         select DEBUG_FS
1674         depends on FAULT_INJECTION && FUTEX
1675         help
1676           Provide fault-injection capability for futexes.
1677 
1678 config FAULT_INJECTION_DEBUG_FS
1679         bool "Debugfs entries for fault-injection capabilities"
1680         depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1681         help
1682           Enable configuration of fault-injection capabilities via debugfs.
1683 
1684 config FAULT_INJECTION_STACKTRACE_FILTER
1685         bool "stacktrace filter for fault-injection capabilities"
1686         depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1687         depends on !X86_64
1688         select STACKTRACE
1689         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1690         help
1691           Provide stacktrace filter for fault-injection capabilities
1692 
1693 config LATENCYTOP
1694         bool "Latency measuring infrastructure"
1695         depends on DEBUG_KERNEL
1696         depends on STACKTRACE_SUPPORT
1697         depends on PROC_FS
1698         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1699         select KALLSYMS
1700         select KALLSYMS_ALL
1701         select STACKTRACE
1702         select SCHEDSTATS
1703         select SCHED_DEBUG
1704         help
1705           Enable this option if you want to use the LatencyTOP tool
1706           to find out which userspace is blocking on what kernel operations.
1707 
1708 config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1709         bool
1710 
1711 config DEBUG_STRICT_USER_COPY_CHECKS
1712         bool "Strict user copy size checks"
1713         depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1714         depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
1715         help
1716           Enabling this option turns a certain set of sanity checks for user
1717           copy operations into compile time failures.
1718 
1719           The copy_from_user() etc checks are there to help test if there
1720           are sufficient security checks on the length argument of
1721           the copy operation, by having gcc prove that the argument is
1722           within bounds.
1723 
1724           If unsure, say N.
1725 
1726 source kernel/trace/Kconfig
1727 
1728 menu "Runtime Testing"
1729 
1730 config LKDTM
1731         tristate "Linux Kernel Dump Test Tool Module"
1732         depends on DEBUG_FS
1733         depends on BLOCK
1734         default n
1735         help
1736         This module enables testing of the different dumping mechanisms by
1737         inducing system failures at predefined crash points.
1738         If you don't need it: say N
1739         Choose M here to compile this code as a module. The module will be
1740         called lkdtm.
1741 
1742         Documentation on how to use the module can be found in
1743         Documentation/fault-injection/provoke-crashes.txt
1744 
1745 config TEST_LIST_SORT
1746         bool "Linked list sorting test"
1747         depends on DEBUG_KERNEL
1748         help
1749           Enable this to turn on 'list_sort()' function test. This test is
1750           executed only once during system boot, so affects only boot time.
1751 
1752           If unsure, say N.
1753 
1754 config KPROBES_SANITY_TEST
1755         bool "Kprobes sanity tests"
1756         depends on DEBUG_KERNEL
1757         depends on KPROBES
1758         default n
1759         help
1760           This option provides for testing basic kprobes functionality on
1761           boot. A sample kprobe, jprobe and kretprobe are inserted and
1762           verified for functionality.
1763 
1764           Say N if you are unsure.
1765 
1766 config BACKTRACE_SELF_TEST
1767         tristate "Self test for the backtrace code"
1768         depends on DEBUG_KERNEL
1769         default n
1770         help
1771           This option provides a kernel module that can be used to test
1772           the kernel stack backtrace code. This option is not useful
1773           for distributions or general kernels, but only for kernel
1774           developers working on architecture code.
1775 
1776           Note that if you want to also test saved backtraces, you will
1777           have to enable STACKTRACE as well.
1778 
1779           Say N if you are unsure.
1780 
1781 config RBTREE_TEST
1782         tristate "Red-Black tree test"
1783         depends on DEBUG_KERNEL
1784         help
1785           A benchmark measuring the performance of the rbtree library.
1786           Also includes rbtree invariant checks.
1787 
1788 config INTERVAL_TREE_TEST
1789         tristate "Interval tree test"
1790         depends on m && DEBUG_KERNEL
1791         select INTERVAL_TREE
1792         help
1793           A benchmark measuring the performance of the interval tree library
1794 
1795 config PERCPU_TEST
1796         tristate "Per cpu operations test"
1797         depends on m && DEBUG_KERNEL
1798         help
1799           Enable this option to build test module which validates per-cpu
1800           operations.
1801 
1802           If unsure, say N.
1803 
1804 config ATOMIC64_SELFTEST
1805         bool "Perform an atomic64_t self-test at boot"
1806         help
1807           Enable this option to test the atomic64_t functions at boot.
1808 
1809           If unsure, say N.
1810 
1811 config ASYNC_RAID6_TEST
1812         tristate "Self test for hardware accelerated raid6 recovery"
1813         depends on ASYNC_RAID6_RECOV
1814         select ASYNC_MEMCPY
1815         ---help---
1816           This is a one-shot self test that permutes through the
1817           recovery of all the possible two disk failure scenarios for a
1818           N-disk array.  Recovery is performed with the asynchronous
1819           raid6 recovery routines, and will optionally use an offload
1820           engine if one is available.
1821 
1822           If unsure, say N.
1823 
1824 config TEST_HEXDUMP
1825         tristate "Test functions located in the hexdump module at runtime"
1826 
1827 config TEST_STRING_HELPERS
1828         tristate "Test functions located in the string_helpers module at runtime"
1829 
1830 config TEST_KSTRTOX
1831         tristate "Test kstrto*() family of functions at runtime"
1832 
1833 config TEST_PRINTF
1834         tristate "Test printf() family of functions at runtime"
1835 
1836 config TEST_BITMAP
1837         tristate "Test bitmap_*() family of functions at runtime"
1838         default n
1839         help
1840           Enable this option to test the bitmap functions at boot.
1841 
1842           If unsure, say N.
1843 
1844 config TEST_UUID
1845         tristate "Test functions located in the uuid module at runtime"
1846 
1847 config TEST_RHASHTABLE
1848         tristate "Perform selftest on resizable hash table"
1849         default n
1850         help
1851           Enable this option to test the rhashtable functions at boot.
1852 
1853           If unsure, say N.
1854 
1855 config TEST_HASH
1856         tristate "Perform selftest on hash functions"
1857         default n
1858         help
1859           Enable this option to test the kernel's integer (<linux/hash,h>)
1860           and string (<linux/stringhash.h>) hash functions on boot
1861           (or module load).
1862 
1863           This is intended to help people writing architecture-specific
1864           optimized versions.  If unsure, say N.
1865 
1866 endmenu # runtime tests
1867 
1868 config PROVIDE_OHCI1394_DMA_INIT
1869         bool "Remote debugging over FireWire early on boot"
1870         depends on PCI && X86
1871         help
1872           If you want to debug problems which hang or crash the kernel early
1873           on boot and the crashing machine has a FireWire port, you can use
1874           this feature to remotely access the memory of the crashed machine
1875           over FireWire. This employs remote DMA as part of the OHCI1394
1876           specification which is now the standard for FireWire controllers.
1877 
1878           With remote DMA, you can monitor the printk buffer remotely using
1879           firescope and access all memory below 4GB using fireproxy from gdb.
1880           Even controlling a kernel debugger is possible using remote DMA.
1881 
1882           Usage:
1883 
1884           If ohci1394_dma=early is used as boot parameter, it will initialize
1885           all OHCI1394 controllers which are found in the PCI config space.
1886 
1887           As all changes to the FireWire bus such as enabling and disabling
1888           devices cause a bus reset and thereby disable remote DMA for all
1889           devices, be sure to have the cable plugged and FireWire enabled on
1890           the debugging host before booting the debug target for debugging.
1891 
1892           This code (~1k) is freed after boot. By then, the firewire stack
1893           in charge of the OHCI-1394 controllers should be used instead.
1894 
1895           See Documentation/debugging-via-ohci1394.txt for more information.
1896 
1897 config BUILD_DOCSRC
1898         bool "Build targets in Documentation/ tree"
1899         depends on HEADERS_CHECK
1900         help
1901           This option attempts to build objects from the source files in the
1902           kernel Documentation/ tree.
1903 
1904           Say N if you are unsure.
1905 
1906 config DMA_API_DEBUG
1907         bool "Enable debugging of DMA-API usage"
1908         depends on HAVE_DMA_API_DEBUG
1909         help
1910           Enable this option to debug the use of the DMA API by device drivers.
1911           With this option you will be able to detect common bugs in device
1912           drivers like double-freeing of DMA mappings or freeing mappings that
1913           were never allocated.
1914 
1915           This also attempts to catch cases where a page owned by DMA is
1916           accessed by the cpu in a way that could cause data corruption.  For
1917           example, this enables cow_user_page() to check that the source page is
1918           not undergoing DMA.
1919 
1920           This option causes a performance degradation.  Use only if you want to
1921           debug device drivers and dma interactions.
1922 
1923           If unsure, say N.
1924 
1925 config TEST_LKM
1926         tristate "Test module loading with 'hello world' module"
1927         default n
1928         depends on m
1929         help
1930           This builds the "test_module" module that emits "Hello, world"
1931           on printk when loaded. It is designed to be used for basic
1932           evaluation of the module loading subsystem (for example when
1933           validating module verification). It lacks any extra dependencies,
1934           and will not normally be loaded by the system unless explicitly
1935           requested by name.
1936 
1937           If unsure, say N.
1938 
1939 config TEST_USER_COPY
1940         tristate "Test user/kernel boundary protections"
1941         default n
1942         depends on m
1943         help
1944           This builds the "test_user_copy" module that runs sanity checks
1945           on the copy_to/from_user infrastructure, making sure basic
1946           user/kernel boundary testing is working. If it fails to load,
1947           a regression has been detected in the user/kernel memory boundary
1948           protections.
1949 
1950           If unsure, say N.
1951 
1952 config TEST_BPF
1953         tristate "Test BPF filter functionality"
1954         default n
1955         depends on m && NET
1956         help
1957           This builds the "test_bpf" module that runs various test vectors
1958           against the BPF interpreter or BPF JIT compiler depending on the
1959           current setting. This is in particular useful for BPF JIT compiler
1960           development, but also to run regression tests against changes in
1961           the interpreter code. It also enables test stubs for eBPF maps and
1962           verifier used by user space verifier testsuite.
1963 
1964           If unsure, say N.
1965 
1966 config TEST_FIRMWARE
1967         tristate "Test firmware loading via userspace interface"
1968         default n
1969         depends on FW_LOADER
1970         help
1971           This builds the "test_firmware" module that creates a userspace
1972           interface for testing firmware loading. This can be used to
1973           control the triggering of firmware loading without needing an
1974           actual firmware-using device. The contents can be rechecked by
1975           userspace.
1976 
1977           If unsure, say N.
1978 
1979 config TEST_UDELAY
1980         tristate "udelay test driver"
1981         default n
1982         help
1983           This builds the "udelay_test" module that helps to make sure
1984           that udelay() is working properly.
1985 
1986           If unsure, say N.
1987 
1988 config MEMTEST
1989         bool "Memtest"
1990         depends on HAVE_MEMBLOCK
1991         ---help---
1992           This option adds a kernel parameter 'memtest', which allows memtest
1993           to be set.
1994                 memtest=0, mean disabled; -- default
1995                 memtest=1, mean do 1 test pattern;
1996                 ...
1997                 memtest=17, mean do 17 test patterns.
1998           If you are unsure how to answer this question, answer N.
1999 
2000 config TEST_STATIC_KEYS
2001         tristate "Test static keys"
2002         default n
2003         depends on m
2004         help
2005           Test the static key interfaces.
2006 
2007           If unsure, say N.
2008 
2009 source "samples/Kconfig"
2010 
2011 source "lib/Kconfig.kgdb"
2012 
2013 source "lib/Kconfig.ubsan"
2014 
2015 config ARCH_HAS_DEVMEM_IS_ALLOWED
2016         bool
2017 
2018 config STRICT_DEVMEM
2019         bool "Filter access to /dev/mem"
2020         depends on MMU
2021         depends on ARCH_HAS_DEVMEM_IS_ALLOWED
2022         default y if TILE || PPC
2023         ---help---
2024           If this option is disabled, you allow userspace (root) access to all
2025           of memory, including kernel and userspace memory. Accidental
2026           access to this is obviously disastrous, but specific access can
2027           be used by people debugging the kernel. Note that with PAT support
2028           enabled, even in this case there are restrictions on /dev/mem
2029           use due to the cache aliasing requirements.
2030 
2031           If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
2032           file only allows userspace access to PCI space and the BIOS code and
2033           data regions.  This is sufficient for dosemu and X and all common
2034           users of /dev/mem.
2035 
2036           If in doubt, say Y.
2037 
2038 config IO_STRICT_DEVMEM
2039         bool "Filter I/O access to /dev/mem"
2040         depends on STRICT_DEVMEM
2041         ---help---
2042           If this option is disabled, you allow userspace (root) access to all
2043           io-memory regardless of whether a driver is actively using that
2044           range.  Accidental access to this is obviously disastrous, but
2045           specific access can be used by people debugging kernel drivers.
2046 
2047           If this option is switched on, the /dev/mem file only allows
2048           userspace access to *idle* io-memory ranges (see /proc/iomem) This
2049           may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2050           if the driver using a given range cannot be disabled.
2051 
2052           If in doubt, say Y.

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