1 menu "printk and dmesg options"
4 bool "Show timing information on printks"
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.
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.
15 The behavior is also controlled by the kernel command line
16 parameter printk.time=1. See Documentation/kernel-parameters.txt
18 config MESSAGE_LOGLEVEL_DEFAULT
19 int "Default message log level (1-7)"
23 Default log level for printk statements with no specified priority.
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
29 config BOOT_PRINTK_DELAY
30 bool "Delay each boot printk message by N milliseconds"
31 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
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,
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.
48 bool "Enable dynamic printk() support"
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%.
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.
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:
75 filename:lineno [module]function flags format
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
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"
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
98 // enable all the messages in file svcsock.c
99 nullarbor:~ # echo -n 'file svcsock.c +p' >
100 <debugfs>/dynamic_debug/control
102 // enable all the messages in the NFS server module
103 nullarbor:~ # echo -n 'module nfsd +p' >
104 <debugfs>/dynamic_debug/control
106 // enable all 12 messages in the function svc_process()
107 nullarbor:~ # echo -n 'func svc_process +p' >
108 <debugfs>/dynamic_debug/control
110 // disable all 12 messages in the function svc_process()
111 nullarbor:~ # echo -n 'func svc_process -p' >
112 <debugfs>/dynamic_debug/control
114 See Documentation/dynamic-debug-howto.txt for additional information.
116 endmenu # "printk and dmesg options"
118 menu "Compile-time checks and compiler options"
121 bool "Compile the kernel with debug info"
122 depends on DEBUG_KERNEL && !COMPILE_TEST
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.
133 config DEBUG_INFO_REDUCED
134 bool "Reduce debugging information"
135 depends on DEBUG_INFO
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.
146 config DEBUG_INFO_SPLIT
147 bool "Produce split debuginfo in .dwo files"
148 depends on DEBUG_INFO
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.
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.
161 config DEBUG_INFO_DWARF4
162 bool "Generate dwarf4 debuginfo"
163 depends on DEBUG_INFO
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.
171 bool "Provide GDB scripts for kernel debugging"
172 depends on DEBUG_INFO
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
181 config ENABLE_WARN_DEPRECATED
182 bool "Enable __deprecated logic"
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.
189 config ENABLE_MUST_CHECK
190 bool "Enable __must_check logic"
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.
198 int "Warn for stack frames larger than (needs gcc 4.4)"
201 default 1024 if !64BIT
202 default 2048 if 64BIT
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.
209 config STRIP_ASM_SYMS
210 bool "Strip assembler-generated symbols during link"
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.
218 bool "Generate readable assembler code"
219 depends on DEBUG_KERNEL
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
226 config UNUSED_SYMBOLS
227 bool "Enable unused/obsolete exported symbols"
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
243 bool "Track page owner"
244 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
248 select PAGE_EXTENSION
250 This keeps track of what call chain is the owner of a page, may
251 help to find bare alloc_page(s) leaks. Even if you include this
252 feature on your build, it is disabled in default. You should pass
253 "page_owner=on" to boot parameter in order to enable it. Eats
254 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
255 for user-space helper.
260 bool "Debug Filesystem"
263 debugfs is a virtual file system that kernel developers use to put
264 debugging files into. Enable this option to be able to read and
265 write to these files.
267 For detailed documentation on the debugfs API, see
268 Documentation/DocBook/filesystems.
273 bool "Run 'make headers_check' when building vmlinux"
276 This option will extract the user-visible kernel headers whenever
277 building the kernel, and will run basic sanity checks on them to
278 ensure that exported files do not attempt to include files which
279 were not exported, etc.
281 If you're making modifications to header files which are
282 relevant for userspace, say 'Y', and check the headers
283 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
284 your build tree), to make sure they're suitable.
286 config DEBUG_SECTION_MISMATCH
287 bool "Enable full Section mismatch analysis"
289 The section mismatch analysis checks if there are illegal
290 references from one section to another section.
291 During linktime or runtime, some sections are dropped;
292 any use of code/data previously in these sections would
293 most likely result in an oops.
294 In the code, functions and variables are annotated with
295 __init,, etc. (see the full list in include/linux/init.h),
296 which results in the code/data being placed in specific sections.
297 The section mismatch analysis is always performed after a full
298 kernel build, and enabling this option causes the following
299 additional steps to occur:
300 - Add the option -fno-inline-functions-called-once to gcc commands.
301 When inlining a function annotated with __init in a non-init
302 function, we would lose the section information and thus
303 the analysis would not catch the illegal reference.
304 This option tells gcc to inline less (but it does result in
306 - Run the section mismatch analysis for each module/built-in.o file.
307 When we run the section mismatch analysis on vmlinux.o, we
308 lose valueble information about where the mismatch was
310 Running the analysis for each module/built-in.o file
311 tells where the mismatch happens much closer to the
312 source. The drawback is that the same mismatch is
313 reported at least twice.
314 - Enable verbose reporting from modpost in order to help resolve
315 the section mismatches that are reported.
317 config SECTION_MISMATCH_WARN_ONLY
318 bool "Make section mismatch errors non-fatal"
321 If you say N here, the build process will fail if there are any
322 section mismatch, instead of just throwing warnings.
327 # Select this config option from the architecture Kconfig, if it
328 # is preferred to always offer frame pointers as a config
329 # option on the architecture (regardless of KERNEL_DEBUG):
331 config ARCH_WANT_FRAME_POINTERS
336 bool "Compile the kernel with frame pointers"
337 depends on DEBUG_KERNEL && \
338 (CRIS || M68K || FRV || UML || \
339 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \
340 ARCH_WANT_FRAME_POINTERS
341 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
343 If you say Y here the resulting kernel image will be slightly
344 larger and slower, but it gives very useful debugging information
345 in case of kernel bugs. (precise oopses/stacktraces/warnings)
347 config STACK_VALIDATION
348 bool "Compile-time stack metadata validation"
349 depends on HAVE_STACK_VALIDATION
352 Add compile-time checks to validate stack metadata, including frame
353 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
354 that runtime stack traces are more reliable.
356 For more information, see
357 tools/objtool/Documentation/stack-validation.txt.
359 config DEBUG_FORCE_WEAK_PER_CPU
360 bool "Force weak per-cpu definitions"
361 depends on DEBUG_KERNEL
363 s390 and alpha require percpu variables in modules to be
364 defined weak to work around addressing range issue which
365 puts the following two restrictions on percpu variable
368 1. percpu symbols must be unique whether static or not
369 2. percpu variables can't be defined inside a function
371 To ensure that generic code follows the above rules, this
372 option forces all percpu variables to be defined as weak.
374 endmenu # "Compiler options"
377 bool "Magic SysRq key"
380 If you say Y here, you will have some control over the system even
381 if the system crashes for example during kernel debugging (e.g., you
382 will be able to flush the buffer cache to disk, reboot the system
383 immediately or dump some status information). This is accomplished
384 by pressing various keys while holding SysRq (Alt+PrintScreen). It
385 also works on a serial console (on PC hardware at least), if you
386 send a BREAK and then within 5 seconds a command keypress. The
387 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
388 unless you really know what this hack does.
390 config MAGIC_SYSRQ_DEFAULT_ENABLE
391 hex "Enable magic SysRq key functions by default"
392 depends on MAGIC_SYSRQ
395 Specifies which SysRq key functions are enabled by default.
396 This may be set to 1 or 0 to enable or disable them all, or
397 to a bitmask as described in Documentation/sysrq.txt.
400 bool "Kernel debugging"
402 Say Y here if you are developing drivers or trying to debug and
403 identify kernel problems.
405 menu "Memory Debugging"
407 source mm/Kconfig.debug
410 bool "Debug object operations"
411 depends on DEBUG_KERNEL
413 If you say Y here, additional code will be inserted into the
414 kernel to track the life time of various objects and validate
415 the operations on those objects.
417 config DEBUG_OBJECTS_SELFTEST
418 bool "Debug objects selftest"
419 depends on DEBUG_OBJECTS
421 This enables the selftest of the object debug code.
423 config DEBUG_OBJECTS_FREE
424 bool "Debug objects in freed memory"
425 depends on DEBUG_OBJECTS
427 This enables checks whether a k/v free operation frees an area
428 which contains an object which has not been deactivated
429 properly. This can make kmalloc/kfree-intensive workloads
432 config DEBUG_OBJECTS_TIMERS
433 bool "Debug timer objects"
434 depends on DEBUG_OBJECTS
436 If you say Y here, additional code will be inserted into the
437 timer routines to track the life time of timer objects and
438 validate the timer operations.
440 config DEBUG_OBJECTS_WORK
441 bool "Debug work objects"
442 depends on DEBUG_OBJECTS
444 If you say Y here, additional code will be inserted into the
445 work queue routines to track the life time of work objects and
446 validate the work operations.
448 config DEBUG_OBJECTS_RCU_HEAD
449 bool "Debug RCU callbacks objects"
450 depends on DEBUG_OBJECTS
452 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
454 config DEBUG_OBJECTS_PERCPU_COUNTER
455 bool "Debug percpu counter objects"
456 depends on DEBUG_OBJECTS
458 If you say Y here, additional code will be inserted into the
459 percpu counter routines to track the life time of percpu counter
460 objects and validate the percpu counter operations.
462 config DEBUG_OBJECTS_ENABLE_DEFAULT
463 int "debug_objects bootup default value (0-1)"
466 depends on DEBUG_OBJECTS
468 Debug objects boot parameter default value
471 bool "Debug slab memory allocations"
472 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
474 Say Y here to have the kernel do limited verification on memory
475 allocation as well as poisoning memory on free to catch use of freed
476 memory. This can make kmalloc/kfree-intensive workloads much slower.
478 config DEBUG_SLAB_LEAK
479 bool "Memory leak debugging"
480 depends on DEBUG_SLAB
483 bool "SLUB debugging on by default"
484 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
487 Boot with debugging on by default. SLUB boots by default with
488 the runtime debug capabilities switched off. Enabling this is
489 equivalent to specifying the "slub_debug" parameter on boot.
490 There is no support for more fine grained debug control like
491 possible with slub_debug=xxx. SLUB debugging may be switched
492 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
497 bool "Enable SLUB performance statistics"
498 depends on SLUB && SYSFS
500 SLUB statistics are useful to debug SLUBs allocation behavior in
501 order find ways to optimize the allocator. This should never be
502 enabled for production use since keeping statistics slows down
503 the allocator by a few percentage points. The slabinfo command
504 supports the determination of the most active slabs to figure
505 out which slabs are relevant to a particular load.
506 Try running: slabinfo -DA
508 config HAVE_DEBUG_KMEMLEAK
511 config DEBUG_KMEMLEAK
512 bool "Kernel memory leak detector"
513 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
515 select STACKTRACE if STACKTRACE_SUPPORT
519 Say Y here if you want to enable the memory leak
520 detector. The memory allocation/freeing is traced in a way
521 similar to the Boehm's conservative garbage collector, the
522 difference being that the orphan objects are not freed but
523 only shown in /sys/kernel/debug/kmemleak. Enabling this
524 feature will introduce an overhead to memory
525 allocations. See Documentation/kmemleak.txt for more
528 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
529 of finding leaks due to the slab objects poisoning.
531 In order to access the kmemleak file, debugfs needs to be
532 mounted (usually at /sys/kernel/debug).
534 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
535 int "Maximum kmemleak early log entries"
536 depends on DEBUG_KMEMLEAK
540 Kmemleak must track all the memory allocations to avoid
541 reporting false positives. Since memory may be allocated or
542 freed before kmemleak is initialised, an early log buffer is
543 used to store these actions. If kmemleak reports "early log
544 buffer exceeded", please increase this value.
546 config DEBUG_KMEMLEAK_TEST
547 tristate "Simple test for the kernel memory leak detector"
548 depends on DEBUG_KMEMLEAK && m
550 This option enables a module that explicitly leaks memory.
554 config DEBUG_KMEMLEAK_DEFAULT_OFF
555 bool "Default kmemleak to off"
556 depends on DEBUG_KMEMLEAK
558 Say Y here to disable kmemleak by default. It can then be enabled
559 on the command line via kmemleak=on.
561 config DEBUG_STACK_USAGE
562 bool "Stack utilization instrumentation"
563 depends on DEBUG_KERNEL && !IA64
565 Enables the display of the minimum amount of free stack which each
566 task has ever had available in the sysrq-T and sysrq-P debug output.
568 This option will slow down process creation somewhat.
572 depends on DEBUG_KERNEL
574 Enable this to turn on extended checks in the virtual-memory system
575 that may impact performance.
579 config DEBUG_VM_VMACACHE
580 bool "Debug VMA caching"
583 Enable this to turn on VMA caching debug information. Doing so
584 can cause significant overhead, so only enable it in non-production
590 bool "Debug VM red-black trees"
593 Enable VM red-black tree debugging information and extra validations.
597 config DEBUG_VM_PGFLAGS
598 bool "Debug page-flags operations"
601 Enables extra validation on page flags operations.
606 bool "Debug VM translations"
607 depends on DEBUG_KERNEL && X86
609 Enable some costly sanity checks in virtual to page code. This can
610 catch mistakes with virt_to_page() and friends.
614 config DEBUG_NOMMU_REGIONS
615 bool "Debug the global anon/private NOMMU mapping region tree"
616 depends on DEBUG_KERNEL && !MMU
618 This option causes the global tree of anonymous and private mapping
619 regions to be regularly checked for invalid topology.
621 config DEBUG_MEMORY_INIT
622 bool "Debug memory initialisation" if EXPERT
625 Enable this for additional checks during memory initialisation.
626 The sanity checks verify aspects of the VM such as the memory model
627 and other information provided by the architecture. Verbose
628 information will be printed at KERN_DEBUG loglevel depending
629 on the mminit_loglevel= command-line option.
633 config MEMORY_NOTIFIER_ERROR_INJECT
634 tristate "Memory hotplug notifier error injection module"
635 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
637 This option provides the ability to inject artificial errors to
638 memory hotplug notifier chain callbacks. It is controlled through
639 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
641 If the notifier call chain should be failed with some events
642 notified, write the error code to "actions/<notifier event>/error".
644 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
646 # cd /sys/kernel/debug/notifier-error-inject/memory
647 # echo -12 > actions/MEM_GOING_OFFLINE/error
648 # echo offline > /sys/devices/system/memory/memoryXXX/state
649 bash: echo: write error: Cannot allocate memory
651 To compile this code as a module, choose M here: the module will
652 be called memory-notifier-error-inject.
656 config DEBUG_PER_CPU_MAPS
657 bool "Debug access to per_cpu maps"
658 depends on DEBUG_KERNEL
661 Say Y to verify that the per_cpu map being accessed has
662 been set up. This adds a fair amount of code to kernel memory
663 and decreases performance.
668 bool "Highmem debugging"
669 depends on DEBUG_KERNEL && HIGHMEM
671 This option enables additional error checking for high memory
672 systems. Disable for production systems.
674 config HAVE_DEBUG_STACKOVERFLOW
677 config DEBUG_STACKOVERFLOW
678 bool "Check for stack overflows"
679 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
681 Say Y here if you want to check for overflows of kernel, IRQ
682 and exception stacks (if your architecture uses them). This
683 option will show detailed messages if free stack space drops
684 below a certain limit.
686 These kinds of bugs usually occur when call-chains in the
687 kernel get too deep, especially when interrupts are
690 Use this in cases where you see apparently random memory
691 corruption, especially if it appears in 'struct thread_info'
693 If in doubt, say "N".
695 source "lib/Kconfig.kmemcheck"
697 source "lib/Kconfig.kasan"
699 endmenu # "Memory Debugging"
704 KCOV does not have any arch-specific code, but currently it is enabled
705 only for x86_64. KCOV requires testing on other archs, and most likely
706 disabling of instrumentation for some early boot code.
709 bool "Code coverage for fuzzing"
710 depends on ARCH_HAS_KCOV
712 select GCC_PLUGINS if !COMPILE_TEST
713 select GCC_PLUGIN_SANCOV if !COMPILE_TEST
715 KCOV exposes kernel code coverage information in a form suitable
716 for coverage-guided fuzzing (randomized testing).
718 If RANDOMIZE_BASE is enabled, PC values will not be stable across
719 different machines and across reboots. If you need stable PC values,
720 disable RANDOMIZE_BASE.
722 For more details, see Documentation/kcov.txt.
725 bool "Debug shared IRQ handlers"
726 depends on DEBUG_KERNEL
728 Enable this to generate a spurious interrupt as soon as a shared
729 interrupt handler is registered, and just before one is deregistered.
730 Drivers ought to be able to handle interrupts coming in at those
731 points; some don't and need to be caught.
733 menu "Debug Lockups and Hangs"
735 config LOCKUP_DETECTOR
736 bool "Detect Hard and Soft Lockups"
737 depends on DEBUG_KERNEL && !S390
739 Say Y here to enable the kernel to act as a watchdog to detect
740 hard and soft lockups.
742 Softlockups are bugs that cause the kernel to loop in kernel
743 mode for more than 20 seconds, without giving other tasks a
744 chance to run. The current stack trace is displayed upon
745 detection and the system will stay locked up.
747 Hardlockups are bugs that cause the CPU to loop in kernel mode
748 for more than 10 seconds, without letting other interrupts have a
749 chance to run. The current stack trace is displayed upon detection
750 and the system will stay locked up.
752 The overhead should be minimal. A periodic hrtimer runs to
753 generate interrupts and kick the watchdog task every 4 seconds.
754 An NMI is generated every 10 seconds or so to check for hardlockups.
756 The frequency of hrtimer and NMI events and the soft and hard lockup
757 thresholds can be controlled through the sysctl watchdog_thresh.
759 config HARDLOCKUP_DETECTOR
761 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
762 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
764 config BOOTPARAM_HARDLOCKUP_PANIC
765 bool "Panic (Reboot) On Hard Lockups"
766 depends on HARDLOCKUP_DETECTOR
768 Say Y here to enable the kernel to panic on "hard lockups",
769 which are bugs that cause the kernel to loop in kernel
770 mode with interrupts disabled for more than 10 seconds (configurable
771 using the watchdog_thresh sysctl).
775 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
777 depends on HARDLOCKUP_DETECTOR
779 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
780 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
782 config BOOTPARAM_SOFTLOCKUP_PANIC
783 bool "Panic (Reboot) On Soft Lockups"
784 depends on LOCKUP_DETECTOR
786 Say Y here to enable the kernel to panic on "soft lockups",
787 which are bugs that cause the kernel to loop in kernel
788 mode for more than 20 seconds (configurable using the watchdog_thresh
789 sysctl), without giving other tasks a chance to run.
791 The panic can be used in combination with panic_timeout,
792 to cause the system to reboot automatically after a
793 lockup has been detected. This feature is useful for
794 high-availability systems that have uptime guarantees and
795 where a lockup must be resolved ASAP.
799 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
801 depends on LOCKUP_DETECTOR
803 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
804 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
806 config DETECT_HUNG_TASK
807 bool "Detect Hung Tasks"
808 depends on DEBUG_KERNEL
809 default LOCKUP_DETECTOR
811 Say Y here to enable the kernel to detect "hung tasks",
812 which are bugs that cause the task to be stuck in
813 uninterruptible "D" state indefinitiley.
815 When a hung task is detected, the kernel will print the
816 current stack trace (which you should report), but the
817 task will stay in uninterruptible state. If lockdep is
818 enabled then all held locks will also be reported. This
819 feature has negligible overhead.
821 config DEFAULT_HUNG_TASK_TIMEOUT
822 int "Default timeout for hung task detection (in seconds)"
823 depends on DETECT_HUNG_TASK
826 This option controls the default timeout (in seconds) used
827 to determine when a task has become non-responsive and should
830 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
831 sysctl or by writing a value to
832 /proc/sys/kernel/hung_task_timeout_secs.
834 A timeout of 0 disables the check. The default is two minutes.
835 Keeping the default should be fine in most cases.
837 config BOOTPARAM_HUNG_TASK_PANIC
838 bool "Panic (Reboot) On Hung Tasks"
839 depends on DETECT_HUNG_TASK
841 Say Y here to enable the kernel to panic on "hung tasks",
842 which are bugs that cause the kernel to leave a task stuck
843 in uninterruptible "D" state.
845 The panic can be used in combination with panic_timeout,
846 to cause the system to reboot automatically after a
847 hung task has been detected. This feature is useful for
848 high-availability systems that have uptime guarantees and
849 where a hung tasks must be resolved ASAP.
853 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
855 depends on DETECT_HUNG_TASK
857 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
858 default 1 if BOOTPARAM_HUNG_TASK_PANIC
861 bool "Detect Workqueue Stalls"
862 depends on DEBUG_KERNEL
864 Say Y here to enable stall detection on workqueues. If a
865 worker pool doesn't make forward progress on a pending work
866 item for over a given amount of time, 30s by default, a
867 warning message is printed along with dump of workqueue
868 state. This can be configured through kernel parameter
869 "workqueue.watchdog_thresh" and its sysfs counterpart.
871 endmenu # "Debug lockups and hangs"
876 Say Y here to enable the kernel to panic when it oopses. This
877 has the same effect as setting oops=panic on the kernel command
880 This feature is useful to ensure that the kernel does not do
881 anything erroneous after an oops which could result in data
882 corruption or other issues.
886 config PANIC_ON_OOPS_VALUE
889 default 0 if !PANIC_ON_OOPS
890 default 1 if PANIC_ON_OOPS
896 Set the timeout value (in seconds) until a reboot occurs when the
897 the kernel panics. If n = 0, then we wait forever. A timeout
898 value n > 0 will wait n seconds before rebooting, while a timeout
899 value n < 0 will reboot immediately.
902 bool "Collect scheduler debugging info"
903 depends on DEBUG_KERNEL && PROC_FS
906 If you say Y here, the /proc/sched_debug file will be provided
907 that can help debug the scheduler. The runtime overhead of this
915 bool "Collect scheduler statistics"
916 depends on DEBUG_KERNEL && PROC_FS
919 If you say Y here, additional code will be inserted into the
920 scheduler and related routines to collect statistics about
921 scheduler behavior and provide them in /proc/schedstat. These
922 stats may be useful for both tuning and debugging the scheduler
923 If you aren't debugging the scheduler or trying to tune a specific
924 application, you can say N to avoid the very slight overhead
927 config SCHED_STACK_END_CHECK
928 bool "Detect stack corruption on calls to schedule()"
929 depends on DEBUG_KERNEL
932 This option checks for a stack overrun on calls to schedule().
933 If the stack end location is found to be over written always panic as
934 the content of the corrupted region can no longer be trusted.
935 This is to ensure no erroneous behaviour occurs which could result in
936 data corruption or a sporadic crash at a later stage once the region
937 is examined. The runtime overhead introduced is minimal.
939 config DEBUG_TIMEKEEPING
940 bool "Enable extra timekeeping sanity checking"
942 This option will enable additional timekeeping sanity checks
943 which may be helpful when diagnosing issues where timekeeping
944 problems are suspected.
946 This may include checks in the timekeeping hotpaths, so this
947 option may have a (very small) performance impact to some
953 bool "Collect kernel timers statistics"
954 depends on DEBUG_KERNEL && PROC_FS
956 If you say Y here, additional code will be inserted into the
957 timer routines to collect statistics about kernel timers being
958 reprogrammed. The statistics can be read from /proc/timer_stats.
959 The statistics collection is started by writing 1 to /proc/timer_stats,
960 writing 0 stops it. This feature is useful to collect information
961 about timer usage patterns in kernel and userspace. This feature
962 is lightweight if enabled in the kernel config but not activated
963 (it defaults to deactivated on bootup and will only be activated
964 if some application like powertop activates it explicitly).
967 bool "Debug preemptible kernel"
968 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
971 If you say Y here then the kernel will use a debug variant of the
972 commonly used smp_processor_id() function and will print warnings
973 if kernel code uses it in a preemption-unsafe way. Also, the kernel
974 will detect preemption count underflows.
976 menu "Lock Debugging (spinlocks, mutexes, etc...)"
978 config DEBUG_RT_MUTEXES
979 bool "RT Mutex debugging, deadlock detection"
980 depends on DEBUG_KERNEL && RT_MUTEXES
982 This allows rt mutex semantics violations and rt mutex related
983 deadlocks (lockups) to be detected and reported automatically.
985 config DEBUG_SPINLOCK
986 bool "Spinlock and rw-lock debugging: basic checks"
987 depends on DEBUG_KERNEL
988 select UNINLINE_SPIN_UNLOCK
990 Say Y here and build SMP to catch missing spinlock initialization
991 and certain other kinds of spinlock errors commonly made. This is
992 best used in conjunction with the NMI watchdog so that spinlock
993 deadlocks are also debuggable.
996 bool "Mutex debugging: basic checks"
997 depends on DEBUG_KERNEL
999 This feature allows mutex semantics violations to be detected and
1002 config DEBUG_WW_MUTEX_SLOWPATH
1003 bool "Wait/wound mutex debugging: Slowpath testing"
1004 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1005 select DEBUG_LOCK_ALLOC
1006 select DEBUG_SPINLOCK
1007 select DEBUG_MUTEXES
1009 This feature enables slowpath testing for w/w mutex users by
1010 injecting additional -EDEADLK wound/backoff cases. Together with
1011 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1012 will test all possible w/w mutex interface abuse with the
1013 exception of simply not acquiring all the required locks.
1014 Note that this feature can introduce significant overhead, so
1015 it really should not be enabled in a production or distro kernel,
1016 even a debug kernel. If you are a driver writer, enable it. If
1017 you are a distro, do not.
1019 config DEBUG_LOCK_ALLOC
1020 bool "Lock debugging: detect incorrect freeing of live locks"
1021 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1022 select DEBUG_SPINLOCK
1023 select DEBUG_MUTEXES
1026 This feature will check whether any held lock (spinlock, rwlock,
1027 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1028 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1029 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1030 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1031 held during task exit.
1033 config PROVE_LOCKING
1034 bool "Lock debugging: prove locking correctness"
1035 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1037 select DEBUG_SPINLOCK
1038 select DEBUG_MUTEXES
1039 select DEBUG_LOCK_ALLOC
1040 select TRACE_IRQFLAGS
1043 This feature enables the kernel to prove that all locking
1044 that occurs in the kernel runtime is mathematically
1045 correct: that under no circumstance could an arbitrary (and
1046 not yet triggered) combination of observed locking
1047 sequences (on an arbitrary number of CPUs, running an
1048 arbitrary number of tasks and interrupt contexts) cause a
1051 In short, this feature enables the kernel to report locking
1052 related deadlocks before they actually occur.
1054 The proof does not depend on how hard and complex a
1055 deadlock scenario would be to trigger: how many
1056 participant CPUs, tasks and irq-contexts would be needed
1057 for it to trigger. The proof also does not depend on
1058 timing: if a race and a resulting deadlock is possible
1059 theoretically (no matter how unlikely the race scenario
1060 is), it will be proven so and will immediately be
1061 reported by the kernel (once the event is observed that
1062 makes the deadlock theoretically possible).
1064 If a deadlock is impossible (i.e. the locking rules, as
1065 observed by the kernel, are mathematically correct), the
1066 kernel reports nothing.
1068 NOTE: this feature can also be enabled for rwlocks, mutexes
1069 and rwsems - in which case all dependencies between these
1070 different locking variants are observed and mapped too, and
1071 the proof of observed correctness is also maintained for an
1072 arbitrary combination of these separate locking variants.
1074 For more details, see Documentation/locking/lockdep-design.txt.
1078 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1080 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
1085 bool "Lock usage statistics"
1086 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1088 select DEBUG_SPINLOCK
1089 select DEBUG_MUTEXES
1090 select DEBUG_LOCK_ALLOC
1093 This feature enables tracking lock contention points
1095 For more details, see Documentation/locking/lockstat.txt
1097 This also enables lock events required by "perf lock",
1099 If you want to use "perf lock", you also need to turn on
1100 CONFIG_EVENT_TRACING.
1102 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1103 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1105 config DEBUG_LOCKDEP
1106 bool "Lock dependency engine debugging"
1107 depends on DEBUG_KERNEL && LOCKDEP
1109 If you say Y here, the lock dependency engine will do
1110 additional runtime checks to debug itself, at the price
1111 of more runtime overhead.
1113 config DEBUG_ATOMIC_SLEEP
1114 bool "Sleep inside atomic section checking"
1115 select PREEMPT_COUNT
1116 depends on DEBUG_KERNEL
1118 If you say Y here, various routines which may sleep will become very
1119 noisy if they are called inside atomic sections: when a spinlock is
1120 held, inside an rcu read side critical section, inside preempt disabled
1121 sections, inside an interrupt, etc...
1123 config DEBUG_LOCKING_API_SELFTESTS
1124 bool "Locking API boot-time self-tests"
1125 depends on DEBUG_KERNEL
1127 Say Y here if you want the kernel to run a short self-test during
1128 bootup. The self-test checks whether common types of locking bugs
1129 are detected by debugging mechanisms or not. (if you disable
1130 lock debugging then those bugs wont be detected of course.)
1131 The following locking APIs are covered: spinlocks, rwlocks,
1134 config LOCK_TORTURE_TEST
1135 tristate "torture tests for locking"
1136 depends on DEBUG_KERNEL
1140 This option provides a kernel module that runs torture tests
1141 on kernel locking primitives. The kernel module may be built
1142 after the fact on the running kernel to be tested, if desired.
1144 Say Y here if you want kernel locking-primitive torture tests
1145 to be built into the kernel.
1146 Say M if you want these torture tests to build as a module.
1147 Say N if you are unsure.
1149 endmenu # lock debugging
1151 config TRACE_IRQFLAGS
1154 Enables hooks to interrupt enabling and disabling for
1155 either tracing or lock debugging.
1158 bool "Stack backtrace support"
1159 depends on STACKTRACE_SUPPORT
1161 This option causes the kernel to create a /proc/pid/stack for
1162 every process, showing its current stack trace.
1163 It is also used by various kernel debugging features that require
1164 stack trace generation.
1166 config DEBUG_KOBJECT
1167 bool "kobject debugging"
1168 depends on DEBUG_KERNEL
1170 If you say Y here, some extra kobject debugging messages will be sent
1173 config DEBUG_KOBJECT_RELEASE
1174 bool "kobject release debugging"
1175 depends on DEBUG_OBJECTS_TIMERS
1177 kobjects are reference counted objects. This means that their
1178 last reference count put is not predictable, and the kobject can
1179 live on past the point at which a driver decides to drop it's
1180 initial reference to the kobject gained on allocation. An
1181 example of this would be a struct device which has just been
1184 However, some buggy drivers assume that after such an operation,
1185 the memory backing the kobject can be immediately freed. This
1186 goes completely against the principles of a refcounted object.
1188 If you say Y here, the kernel will delay the release of kobjects
1189 on the last reference count to improve the visibility of this
1190 kind of kobject release bug.
1192 config HAVE_DEBUG_BUGVERBOSE
1195 config DEBUG_BUGVERBOSE
1196 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1197 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1200 Say Y here to make BUG() panics output the file name and line number
1201 of the BUG call as well as the EIP and oops trace. This aids
1202 debugging but costs about 70-100K of memory.
1205 bool "Debug linked list manipulation"
1206 depends on DEBUG_KERNEL
1208 Enable this to turn on extended checks in the linked-list
1213 config DEBUG_PI_LIST
1214 bool "Debug priority linked list manipulation"
1215 depends on DEBUG_KERNEL
1217 Enable this to turn on extended checks in the priority-ordered
1218 linked-list (plist) walking routines. This checks the entire
1219 list multiple times during each manipulation.
1224 bool "Debug SG table operations"
1225 depends on DEBUG_KERNEL
1227 Enable this to turn on checks on scatter-gather tables. This can
1228 help find problems with drivers that do not properly initialize
1233 config DEBUG_NOTIFIERS
1234 bool "Debug notifier call chains"
1235 depends on DEBUG_KERNEL
1237 Enable this to turn on sanity checking for notifier call chains.
1238 This is most useful for kernel developers to make sure that
1239 modules properly unregister themselves from notifier chains.
1240 This is a relatively cheap check but if you care about maximum
1243 config DEBUG_CREDENTIALS
1244 bool "Debug credential management"
1245 depends on DEBUG_KERNEL
1247 Enable this to turn on some debug checking for credential
1248 management. The additional code keeps track of the number of
1249 pointers from task_structs to any given cred struct, and checks to
1250 see that this number never exceeds the usage count of the cred
1253 Furthermore, if SELinux is enabled, this also checks that the
1254 security pointer in the cred struct is never seen to be invalid.
1258 menu "RCU Debugging"
1261 def_bool PROVE_LOCKING
1263 config PROVE_RCU_REPEATEDLY
1264 bool "RCU debugging: don't disable PROVE_RCU on first splat"
1265 depends on PROVE_RCU
1268 By itself, PROVE_RCU will disable checking upon issuing the
1269 first warning (or "splat"). This feature prevents such
1270 disabling, allowing multiple RCU-lockdep warnings to be printed
1273 Say Y to allow multiple RCU-lockdep warnings per boot.
1275 Say N if you are unsure.
1277 config SPARSE_RCU_POINTER
1278 bool "RCU debugging: sparse-based checks for pointer usage"
1281 This feature enables the __rcu sparse annotation for
1282 RCU-protected pointers. This annotation will cause sparse
1283 to flag any non-RCU used of annotated pointers. This can be
1284 helpful when debugging RCU usage. Please note that this feature
1285 is not intended to enforce code cleanliness; it is instead merely
1288 Say Y to make sparse flag questionable use of RCU-protected pointers
1290 Say N if you are unsure.
1296 config RCU_PERF_TEST
1297 tristate "performance tests for RCU"
1298 depends on DEBUG_KERNEL
1304 This option provides a kernel module that runs performance
1305 tests on the RCU infrastructure. The kernel module may be built
1306 after the fact on the running kernel to be tested, if desired.
1308 Say Y here if you want RCU performance tests to be built into
1310 Say M if you want the RCU performance tests to build as a module.
1311 Say N if you are unsure.
1313 config RCU_TORTURE_TEST
1314 tristate "torture tests for RCU"
1315 depends on DEBUG_KERNEL
1321 This option provides a kernel module that runs torture tests
1322 on the RCU infrastructure. The kernel module may be built
1323 after the fact on the running kernel to be tested, if desired.
1325 Say Y here if you want RCU torture tests to be built into
1327 Say M if you want the RCU torture tests to build as a module.
1328 Say N if you are unsure.
1330 config RCU_TORTURE_TEST_SLOW_PREINIT
1331 bool "Slow down RCU grace-period pre-initialization to expose races"
1332 depends on RCU_TORTURE_TEST
1334 This option delays grace-period pre-initialization (the
1335 propagation of CPU-hotplug changes up the rcu_node combining
1336 tree) for a few jiffies between initializing each pair of
1337 consecutive rcu_node structures. This helps to expose races
1338 involving grace-period pre-initialization, in other words, it
1339 makes your kernel less stable. It can also greatly increase
1340 grace-period latency, especially on systems with large numbers
1341 of CPUs. This is useful when torture-testing RCU, but in
1342 almost no other circumstance.
1344 Say Y here if you want your system to crash and hang more often.
1345 Say N if you want a sane system.
1347 config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
1348 int "How much to slow down RCU grace-period pre-initialization"
1351 depends on RCU_TORTURE_TEST_SLOW_PREINIT
1353 This option specifies the number of jiffies to wait between
1354 each rcu_node structure pre-initialization step.
1356 config RCU_TORTURE_TEST_SLOW_INIT
1357 bool "Slow down RCU grace-period initialization to expose races"
1358 depends on RCU_TORTURE_TEST
1360 This option delays grace-period initialization for a few
1361 jiffies between initializing each pair of consecutive
1362 rcu_node structures. This helps to expose races involving
1363 grace-period initialization, in other words, it makes your
1364 kernel less stable. It can also greatly increase grace-period
1365 latency, especially on systems with large numbers of CPUs.
1366 This is useful when torture-testing RCU, but in almost no
1369 Say Y here if you want your system to crash and hang more often.
1370 Say N if you want a sane system.
1372 config RCU_TORTURE_TEST_SLOW_INIT_DELAY
1373 int "How much to slow down RCU grace-period initialization"
1376 depends on RCU_TORTURE_TEST_SLOW_INIT
1378 This option specifies the number of jiffies to wait between
1379 each rcu_node structure initialization.
1381 config RCU_TORTURE_TEST_SLOW_CLEANUP
1382 bool "Slow down RCU grace-period cleanup to expose races"
1383 depends on RCU_TORTURE_TEST
1385 This option delays grace-period cleanup for a few jiffies
1386 between cleaning up each pair of consecutive rcu_node
1387 structures. This helps to expose races involving grace-period
1388 cleanup, in other words, it makes your kernel less stable.
1389 It can also greatly increase grace-period latency, especially
1390 on systems with large numbers of CPUs. This is useful when
1391 torture-testing RCU, but in almost no other circumstance.
1393 Say Y here if you want your system to crash and hang more often.
1394 Say N if you want a sane system.
1396 config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
1397 int "How much to slow down RCU grace-period cleanup"
1400 depends on RCU_TORTURE_TEST_SLOW_CLEANUP
1402 This option specifies the number of jiffies to wait between
1403 each rcu_node structure cleanup operation.
1405 config RCU_CPU_STALL_TIMEOUT
1406 int "RCU CPU stall timeout in seconds"
1407 depends on RCU_STALL_COMMON
1411 If a given RCU grace period extends more than the specified
1412 number of seconds, a CPU stall warning is printed. If the
1413 RCU grace period persists, additional CPU stall warnings are
1414 printed at more widely spaced intervals.
1417 bool "Enable tracing for RCU"
1418 depends on DEBUG_KERNEL
1421 This option provides tracing in RCU which presents stats
1422 in debugfs for debugging RCU implementation.
1424 Say Y here if you want to enable RCU tracing
1425 Say N if you are unsure.
1427 config RCU_EQS_DEBUG
1428 bool "Provide debugging asserts for adding NO_HZ support to an arch"
1429 depends on DEBUG_KERNEL
1431 This option provides consistency checks in RCU's handling of
1432 NO_HZ. These checks have proven quite helpful in detecting
1433 bugs in arch-specific NO_HZ code.
1435 Say N here if you need ultimate kernel/user switch latencies
1436 Say Y if you are unsure
1438 endmenu # "RCU Debugging"
1440 config DEBUG_WQ_FORCE_RR_CPU
1441 bool "Force round-robin CPU selection for unbound work items"
1442 depends on DEBUG_KERNEL
1445 Workqueue used to implicitly guarantee that work items queued
1446 without explicit CPU specified are put on the local CPU. This
1447 guarantee is no longer true and while local CPU is still
1448 preferred work items may be put on foreign CPUs. Kernel
1449 parameter "workqueue.debug_force_rr_cpu" is added to force
1450 round-robin CPU selection to flush out usages which depend on the
1451 now broken guarantee. This config option enables the debug
1452 feature by default. When enabled, memory and cache locality will
1455 config DEBUG_BLOCK_EXT_DEVT
1456 bool "Force extended block device numbers and spread them"
1457 depends on DEBUG_KERNEL
1461 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1462 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1463 YOU ARE DOING. Distros, please enable this and fix whatever
1466 Conventionally, block device numbers are allocated from
1467 predetermined contiguous area. However, extended block area
1468 may introduce non-contiguous block device numbers. This
1469 option forces most block device numbers to be allocated from
1470 the extended space and spreads them to discover kernel or
1471 userland code paths which assume predetermined contiguous
1472 device number allocation.
1474 Note that turning on this debug option shuffles all the
1475 device numbers for all IDE and SCSI devices including libata
1476 ones, so root partition specified using device number
1477 directly (via rdev or root=MAJ:MIN) won't work anymore.
1478 Textual device names (root=/dev/sdXn) will continue to work.
1480 Say N if you are unsure.
1482 config CPU_HOTPLUG_STATE_CONTROL
1483 bool "Enable CPU hotplug state control"
1484 depends on DEBUG_KERNEL
1485 depends on HOTPLUG_CPU
1488 Allows to write steps between "offline" and "online" to the CPUs
1489 sysfs target file so states can be stepped granular. This is a debug
1490 option for now as the hotplug machinery cannot be stopped and
1491 restarted at arbitrary points yet.
1493 Say N if your are unsure.
1495 config NOTIFIER_ERROR_INJECTION
1496 tristate "Notifier error injection"
1497 depends on DEBUG_KERNEL
1500 This option provides the ability to inject artificial errors to
1501 specified notifier chain callbacks. It is useful to test the error
1502 handling of notifier call chain failures.
1506 config CPU_NOTIFIER_ERROR_INJECT
1507 tristate "CPU notifier error injection module"
1508 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1510 This option provides a kernel module that can be used to test
1511 the error handling of the cpu notifiers by injecting artificial
1512 errors to CPU notifier chain callbacks. It is controlled through
1513 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
1515 If the notifier call chain should be failed with some events
1516 notified, write the error code to "actions/<notifier event>/error".
1518 Example: Inject CPU offline error (-1 == -EPERM)
1520 # cd /sys/kernel/debug/notifier-error-inject/cpu
1521 # echo -1 > actions/CPU_DOWN_PREPARE/error
1522 # echo 0 > /sys/devices/system/cpu/cpu1/online
1523 bash: echo: write error: Operation not permitted
1525 To compile this code as a module, choose M here: the module will
1526 be called cpu-notifier-error-inject.
1530 config PM_NOTIFIER_ERROR_INJECT
1531 tristate "PM notifier error injection module"
1532 depends on PM && NOTIFIER_ERROR_INJECTION
1533 default m if PM_DEBUG
1535 This option provides the ability to inject artificial errors to
1536 PM notifier chain callbacks. It is controlled through debugfs
1537 interface /sys/kernel/debug/notifier-error-inject/pm
1539 If the notifier call chain should be failed with some events
1540 notified, write the error code to "actions/<notifier event>/error".
1542 Example: Inject PM suspend error (-12 = -ENOMEM)
1544 # cd /sys/kernel/debug/notifier-error-inject/pm/
1545 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1546 # echo mem > /sys/power/state
1547 bash: echo: write error: Cannot allocate memory
1549 To compile this code as a module, choose M here: the module will
1550 be called pm-notifier-error-inject.
1554 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1555 tristate "OF reconfig notifier error injection module"
1556 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1558 This option provides the ability to inject artificial errors to
1559 OF reconfig notifier chain callbacks. It is controlled
1560 through debugfs interface under
1561 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1563 If the notifier call chain should be failed with some events
1564 notified, write the error code to "actions/<notifier event>/error".
1566 To compile this code as a module, choose M here: the module will
1567 be called of-reconfig-notifier-error-inject.
1571 config NETDEV_NOTIFIER_ERROR_INJECT
1572 tristate "Netdev notifier error injection module"
1573 depends on NET && NOTIFIER_ERROR_INJECTION
1575 This option provides the ability to inject artificial errors to
1576 netdevice notifier chain callbacks. It is controlled through debugfs
1577 interface /sys/kernel/debug/notifier-error-inject/netdev
1579 If the notifier call chain should be failed with some events
1580 notified, write the error code to "actions/<notifier event>/error".
1582 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1584 # cd /sys/kernel/debug/notifier-error-inject/netdev
1585 # echo -22 > actions/NETDEV_CHANGEMTU/error
1586 # ip link set eth0 mtu 1024
1587 RTNETLINK answers: Invalid argument
1589 To compile this code as a module, choose M here: the module will
1590 be called netdev-notifier-error-inject.
1594 config FAULT_INJECTION
1595 bool "Fault-injection framework"
1596 depends on DEBUG_KERNEL
1598 Provide fault-injection framework.
1599 For more details, see Documentation/fault-injection/.
1602 bool "Fault-injection capability for kmalloc"
1603 depends on FAULT_INJECTION
1604 depends on SLAB || SLUB
1606 Provide fault-injection capability for kmalloc.
1608 config FAIL_PAGE_ALLOC
1609 bool "Fault-injection capabilitiy for alloc_pages()"
1610 depends on FAULT_INJECTION
1612 Provide fault-injection capability for alloc_pages().
1614 config FAIL_MAKE_REQUEST
1615 bool "Fault-injection capability for disk IO"
1616 depends on FAULT_INJECTION && BLOCK
1618 Provide fault-injection capability for disk IO.
1620 config FAIL_IO_TIMEOUT
1621 bool "Fault-injection capability for faking disk interrupts"
1622 depends on FAULT_INJECTION && BLOCK
1624 Provide fault-injection capability on end IO handling. This
1625 will make the block layer "forget" an interrupt as configured,
1626 thus exercising the error handling.
1628 Only works with drivers that use the generic timeout handling,
1629 for others it wont do anything.
1631 config FAIL_MMC_REQUEST
1632 bool "Fault-injection capability for MMC IO"
1633 depends on FAULT_INJECTION_DEBUG_FS && MMC
1635 Provide fault-injection capability for MMC IO.
1636 This will make the mmc core return data errors. This is
1637 useful to test the error handling in the mmc block device
1638 and to test how the mmc host driver handles retries from
1642 bool "Fault-injection capability for futexes"
1644 depends on FAULT_INJECTION && FUTEX
1646 Provide fault-injection capability for futexes.
1648 config FAULT_INJECTION_DEBUG_FS
1649 bool "Debugfs entries for fault-injection capabilities"
1650 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1652 Enable configuration of fault-injection capabilities via debugfs.
1654 config FAULT_INJECTION_STACKTRACE_FILTER
1655 bool "stacktrace filter for fault-injection capabilities"
1656 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1659 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1661 Provide stacktrace filter for fault-injection capabilities
1664 bool "Latency measuring infrastructure"
1665 depends on DEBUG_KERNEL
1666 depends on STACKTRACE_SUPPORT
1668 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1675 Enable this option if you want to use the LatencyTOP tool
1676 to find out which userspace is blocking on what kernel operations.
1678 config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1681 config DEBUG_STRICT_USER_COPY_CHECKS
1682 bool "Strict user copy size checks"
1683 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1684 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
1686 Enabling this option turns a certain set of sanity checks for user
1687 copy operations into compile time failures.
1689 The copy_from_user() etc checks are there to help test if there
1690 are sufficient security checks on the length argument of
1691 the copy operation, by having gcc prove that the argument is
1696 source kernel/trace/Kconfig
1698 menu "Runtime Testing"
1701 tristate "Linux Kernel Dump Test Tool Module"
1706 This module enables testing of the different dumping mechanisms by
1707 inducing system failures at predefined crash points.
1708 If you don't need it: say N
1709 Choose M here to compile this code as a module. The module will be
1712 Documentation on how to use the module can be found in
1713 Documentation/fault-injection/provoke-crashes.txt
1715 config TEST_LIST_SORT
1716 bool "Linked list sorting test"
1717 depends on DEBUG_KERNEL
1719 Enable this to turn on 'list_sort()' function test. This test is
1720 executed only once during system boot, so affects only boot time.
1724 config KPROBES_SANITY_TEST
1725 bool "Kprobes sanity tests"
1726 depends on DEBUG_KERNEL
1730 This option provides for testing basic kprobes functionality on
1731 boot. A sample kprobe, jprobe and kretprobe are inserted and
1732 verified for functionality.
1734 Say N if you are unsure.
1736 config BACKTRACE_SELF_TEST
1737 tristate "Self test for the backtrace code"
1738 depends on DEBUG_KERNEL
1741 This option provides a kernel module that can be used to test
1742 the kernel stack backtrace code. This option is not useful
1743 for distributions or general kernels, but only for kernel
1744 developers working on architecture code.
1746 Note that if you want to also test saved backtraces, you will
1747 have to enable STACKTRACE as well.
1749 Say N if you are unsure.
1752 tristate "Red-Black tree test"
1753 depends on DEBUG_KERNEL
1755 A benchmark measuring the performance of the rbtree library.
1756 Also includes rbtree invariant checks.
1758 config INTERVAL_TREE_TEST
1759 tristate "Interval tree test"
1760 depends on m && DEBUG_KERNEL
1761 select INTERVAL_TREE
1763 A benchmark measuring the performance of the interval tree library
1766 tristate "Per cpu operations test"
1767 depends on m && DEBUG_KERNEL
1769 Enable this option to build test module which validates per-cpu
1774 config ATOMIC64_SELFTEST
1775 bool "Perform an atomic64_t self-test at boot"
1777 Enable this option to test the atomic64_t functions at boot.
1781 config ASYNC_RAID6_TEST
1782 tristate "Self test for hardware accelerated raid6 recovery"
1783 depends on ASYNC_RAID6_RECOV
1786 This is a one-shot self test that permutes through the
1787 recovery of all the possible two disk failure scenarios for a
1788 N-disk array. Recovery is performed with the asynchronous
1789 raid6 recovery routines, and will optionally use an offload
1790 engine if one is available.
1795 tristate "Test functions located in the hexdump module at runtime"
1797 config TEST_STRING_HELPERS
1798 tristate "Test functions located in the string_helpers module at runtime"
1801 tristate "Test kstrto*() family of functions at runtime"
1804 tristate "Test printf() family of functions at runtime"
1807 tristate "Test bitmap_*() family of functions at runtime"
1810 Enable this option to test the bitmap functions at boot.
1815 tristate "Test functions located in the uuid module at runtime"
1817 config TEST_RHASHTABLE
1818 tristate "Perform selftest on resizable hash table"
1821 Enable this option to test the rhashtable functions at boot.
1826 tristate "Perform selftest on hash functions"
1829 Enable this option to test the kernel's integer (<linux/hash,h>)
1830 and string (<linux/stringhash.h>) hash functions on boot
1833 This is intended to help people writing architecture-specific
1834 optimized versions. If unsure, say N.
1836 endmenu # runtime tests
1838 config PROVIDE_OHCI1394_DMA_INIT
1839 bool "Remote debugging over FireWire early on boot"
1840 depends on PCI && X86
1842 If you want to debug problems which hang or crash the kernel early
1843 on boot and the crashing machine has a FireWire port, you can use
1844 this feature to remotely access the memory of the crashed machine
1845 over FireWire. This employs remote DMA as part of the OHCI1394
1846 specification which is now the standard for FireWire controllers.
1848 With remote DMA, you can monitor the printk buffer remotely using
1849 firescope and access all memory below 4GB using fireproxy from gdb.
1850 Even controlling a kernel debugger is possible using remote DMA.
1854 If ohci1394_dma=early is used as boot parameter, it will initialize
1855 all OHCI1394 controllers which are found in the PCI config space.
1857 As all changes to the FireWire bus such as enabling and disabling
1858 devices cause a bus reset and thereby disable remote DMA for all
1859 devices, be sure to have the cable plugged and FireWire enabled on
1860 the debugging host before booting the debug target for debugging.
1862 This code (~1k) is freed after boot. By then, the firewire stack
1863 in charge of the OHCI-1394 controllers should be used instead.
1865 See Documentation/debugging-via-ohci1394.txt for more information.
1868 bool "Build targets in Documentation/ tree"
1869 depends on HEADERS_CHECK
1871 This option attempts to build objects from the source files in the
1872 kernel Documentation/ tree.
1874 Say N if you are unsure.
1876 config DMA_API_DEBUG
1877 bool "Enable debugging of DMA-API usage"
1878 depends on HAVE_DMA_API_DEBUG
1880 Enable this option to debug the use of the DMA API by device drivers.
1881 With this option you will be able to detect common bugs in device
1882 drivers like double-freeing of DMA mappings or freeing mappings that
1883 were never allocated.
1885 This also attempts to catch cases where a page owned by DMA is
1886 accessed by the cpu in a way that could cause data corruption. For
1887 example, this enables cow_user_page() to check that the source page is
1890 This option causes a performance degradation. Use only if you want to
1891 debug device drivers and dma interactions.
1896 tristate "Test module loading with 'hello world' module"
1900 This builds the "test_module" module that emits "Hello, world"
1901 on printk when loaded. It is designed to be used for basic
1902 evaluation of the module loading subsystem (for example when
1903 validating module verification). It lacks any extra dependencies,
1904 and will not normally be loaded by the system unless explicitly
1909 config TEST_USER_COPY
1910 tristate "Test user/kernel boundary protections"
1914 This builds the "test_user_copy" module that runs sanity checks
1915 on the copy_to/from_user infrastructure, making sure basic
1916 user/kernel boundary testing is working. If it fails to load,
1917 a regression has been detected in the user/kernel memory boundary
1923 tristate "Test BPF filter functionality"
1927 This builds the "test_bpf" module that runs various test vectors
1928 against the BPF interpreter or BPF JIT compiler depending on the
1929 current setting. This is in particular useful for BPF JIT compiler
1930 development, but also to run regression tests against changes in
1931 the interpreter code. It also enables test stubs for eBPF maps and
1932 verifier used by user space verifier testsuite.
1936 config TEST_FIRMWARE
1937 tristate "Test firmware loading via userspace interface"
1939 depends on FW_LOADER
1941 This builds the "test_firmware" module that creates a userspace
1942 interface for testing firmware loading. This can be used to
1943 control the triggering of firmware loading without needing an
1944 actual firmware-using device. The contents can be rechecked by
1950 tristate "udelay test driver"
1953 This builds the "udelay_test" module that helps to make sure
1954 that udelay() is working properly.
1960 depends on HAVE_MEMBLOCK
1962 This option adds a kernel parameter 'memtest', which allows memtest
1964 memtest=0, mean disabled; -- default
1965 memtest=1, mean do 1 test pattern;
1967 memtest=17, mean do 17 test patterns.
1968 If you are unsure how to answer this question, answer N.
1970 config TEST_STATIC_KEYS
1971 tristate "Test static keys"
1975 Test the static key interfaces.
1979 source "samples/Kconfig"
1981 source "lib/Kconfig.kgdb"
1983 source "lib/Kconfig.ubsan"
1985 config ARCH_HAS_DEVMEM_IS_ALLOWED
1988 config STRICT_DEVMEM
1989 bool "Filter access to /dev/mem"
1991 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
1992 default y if TILE || PPC
1994 If this option is disabled, you allow userspace (root) access to all
1995 of memory, including kernel and userspace memory. Accidental
1996 access to this is obviously disastrous, but specific access can
1997 be used by people debugging the kernel. Note that with PAT support
1998 enabled, even in this case there are restrictions on /dev/mem
1999 use due to the cache aliasing requirements.
2001 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
2002 file only allows userspace access to PCI space and the BIOS code and
2003 data regions. This is sufficient for dosemu and X and all common
2008 config IO_STRICT_DEVMEM
2009 bool "Filter I/O access to /dev/mem"
2010 depends on STRICT_DEVMEM
2012 If this option is disabled, you allow userspace (root) access to all
2013 io-memory regardless of whether a driver is actively using that
2014 range. Accidental access to this is obviously disastrous, but
2015 specific access can be used by people debugging kernel drivers.
2017 If this option is switched on, the /dev/mem file only allows
2018 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2019 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2020 if the driver using a given range cannot be disabled.
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