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/admin-guide/kernel-parameters.rst
18 config CONSOLE_LOGLEVEL_DEFAULT
19 int "Default console loglevel (1-15)"
23 Default loglevel to determine what will be printed on the console.
25 Setting a default here is equivalent to passing in loglevel=<x> in
26 the kernel bootargs. loglevel=<x> continues to override whatever
27 value is specified here as well.
29 Note: This does not affect the log level of un-prefixed printk()
30 usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
33 config MESSAGE_LOGLEVEL_DEFAULT
34 int "Default message log level (1-7)"
38 Default log level for printk statements with no specified priority.
40 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
41 that are auditing their logs closely may want to set it to a lower
44 Note: This does not affect what message level gets printed on the console
45 by default. To change that, use loglevel=<x> in the kernel bootargs,
46 or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value.
48 config BOOT_PRINTK_DELAY
49 bool "Delay each boot printk message by N milliseconds"
50 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
52 This build option allows you to read kernel boot messages
53 by inserting a short delay after each one. The delay is
54 specified in milliseconds on the kernel command line,
57 It is likely that you would also need to use "lpj=M" to preset
58 the "loops per jiffie" value.
59 See a previous boot log for the "lpj" value to use for your
60 system, and then set "lpj=M" before setting "boot_delay=N".
61 NOTE: Using this option may adversely affect SMP systems.
62 I.e., processors other than the first one may not boot up.
63 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
64 what it believes to be lockup conditions.
67 bool "Enable dynamic printk() support"
73 Compiles debug level messages into the kernel, which would not
74 otherwise be available at runtime. These messages can then be
75 enabled/disabled based on various levels of scope - per source file,
76 function, module, format string, and line number. This mechanism
77 implicitly compiles in all pr_debug() and dev_dbg() calls, which
78 enlarges the kernel text size by about 2%.
80 If a source file is compiled with DEBUG flag set, any
81 pr_debug() calls in it are enabled by default, but can be
82 disabled at runtime as below. Note that DEBUG flag is
83 turned on by many CONFIG_*DEBUG* options.
87 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
88 which is contained in the 'debugfs' filesystem. Thus, the debugfs
89 filesystem must first be mounted before making use of this feature.
90 We refer the control file as: <debugfs>/dynamic_debug/control. This
91 file contains a list of the debug statements that can be enabled. The
92 format for each line of the file is:
94 filename:lineno [module]function flags format
96 filename : source file of the debug statement
97 lineno : line number of the debug statement
98 module : module that contains the debug statement
99 function : function that contains the debug statement
100 flags : '=p' means the line is turned 'on' for printing
101 format : the format used for the debug statement
105 nullarbor:~ # cat <debugfs>/dynamic_debug/control
106 # filename:lineno [module]function flags format
107 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
108 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
109 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
113 // enable the message at line 1603 of file svcsock.c
114 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
115 <debugfs>/dynamic_debug/control
117 // enable all the messages in file svcsock.c
118 nullarbor:~ # echo -n 'file svcsock.c +p' >
119 <debugfs>/dynamic_debug/control
121 // enable all the messages in the NFS server module
122 nullarbor:~ # echo -n 'module nfsd +p' >
123 <debugfs>/dynamic_debug/control
125 // enable all 12 messages in the function svc_process()
126 nullarbor:~ # echo -n 'func svc_process +p' >
127 <debugfs>/dynamic_debug/control
129 // disable all 12 messages in the function svc_process()
130 nullarbor:~ # echo -n 'func svc_process -p' >
131 <debugfs>/dynamic_debug/control
133 See Documentation/dynamic-debug-howto.txt for additional information.
135 endmenu # "printk and dmesg options"
137 menu "Compile-time checks and compiler options"
140 bool "Compile the kernel with debug info"
141 depends on DEBUG_KERNEL && !COMPILE_TEST
143 If you say Y here the resulting kernel image will include
144 debugging info resulting in a larger kernel image.
145 This adds debug symbols to the kernel and modules (gcc -g), and
146 is needed if you intend to use kernel crashdump or binary object
147 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
148 Say Y here only if you plan to debug the kernel.
152 config DEBUG_INFO_REDUCED
153 bool "Reduce debugging information"
154 depends on DEBUG_INFO
156 If you say Y here gcc is instructed to generate less debugging
157 information for structure types. This means that tools that
158 need full debugging information (like kgdb or systemtap) won't
159 be happy. But if you merely need debugging information to
160 resolve line numbers there is no loss. Advantage is that
161 build directory object sizes shrink dramatically over a full
162 DEBUG_INFO build and compile times are reduced too.
163 Only works with newer gcc versions.
165 config DEBUG_INFO_SPLIT
166 bool "Produce split debuginfo in .dwo files"
167 depends on DEBUG_INFO && !FRV
169 Generate debug info into separate .dwo files. This significantly
170 reduces the build directory size for builds with DEBUG_INFO,
171 because it stores the information only once on disk in .dwo
172 files instead of multiple times in object files and executables.
173 In addition the debug information is also compressed.
175 Requires recent gcc (4.7+) and recent gdb/binutils.
176 Any tool that packages or reads debug information would need
177 to know about the .dwo files and include them.
178 Incompatible with older versions of ccache.
180 config DEBUG_INFO_DWARF4
181 bool "Generate dwarf4 debuginfo"
182 depends on DEBUG_INFO
184 Generate dwarf4 debug info. This requires recent versions
185 of gcc and gdb. It makes the debug information larger.
186 But it significantly improves the success of resolving
187 variables in gdb on optimized code.
190 bool "Provide GDB scripts for kernel debugging"
191 depends on DEBUG_INFO
193 This creates the required links to GDB helper scripts in the
194 build directory. If you load vmlinux into gdb, the helper
195 scripts will be automatically imported by gdb as well, and
196 additional functions are available to analyze a Linux kernel
197 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
200 config ENABLE_WARN_DEPRECATED
201 bool "Enable __deprecated logic"
204 Enable the __deprecated logic in the kernel build.
205 Disable this to suppress the "warning: 'foo' is deprecated
206 (declared at kernel/power/somefile.c:1234)" messages.
208 config ENABLE_MUST_CHECK
209 bool "Enable __must_check logic"
212 Enable the __must_check logic in the kernel build. Disable this to
213 suppress the "warning: ignoring return value of 'foo', declared with
214 attribute warn_unused_result" messages.
217 int "Warn for stack frames larger than (needs gcc 4.4)"
220 default 2048 if GCC_PLUGIN_LATENT_ENTROPY
221 default 1024 if !64BIT
222 default 2048 if 64BIT
224 Tell gcc to warn at build time for stack frames larger than this.
225 Setting this too low will cause a lot of warnings.
226 Setting it to 0 disables the warning.
229 config STRIP_ASM_SYMS
230 bool "Strip assembler-generated symbols during link"
233 Strip internal assembler-generated symbols during a link (symbols
234 that look like '.Lxxx') so they don't pollute the output of
235 get_wchan() and suchlike.
238 bool "Generate readable assembler code"
239 depends on DEBUG_KERNEL
241 Disable some compiler optimizations that tend to generate human unreadable
242 assembler output. This may make the kernel slightly slower, but it helps
243 to keep kernel developers who have to stare a lot at assembler listings
246 config UNUSED_SYMBOLS
247 bool "Enable unused/obsolete exported symbols"
250 Unused but exported symbols make the kernel needlessly bigger. For
251 that reason most of these unused exports will soon be removed. This
252 option is provided temporarily to provide a transition period in case
253 some external kernel module needs one of these symbols anyway. If you
254 encounter such a case in your module, consider if you are actually
255 using the right API. (rationale: since nobody in the kernel is using
256 this in a module, there is a pretty good chance it's actually the
257 wrong interface to use). If you really need the symbol, please send a
258 mail to the linux kernel mailing list mentioning the symbol and why
259 you really need it, and what the merge plan to the mainline kernel for
263 bool "Track page owner"
264 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
268 select PAGE_EXTENSION
270 This keeps track of what call chain is the owner of a page, may
271 help to find bare alloc_page(s) leaks. Even if you include this
272 feature on your build, it is disabled in default. You should pass
273 "page_owner=on" to boot parameter in order to enable it. Eats
274 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
275 for user-space helper.
280 bool "Debug Filesystem"
283 debugfs is a virtual file system that kernel developers use to put
284 debugging files into. Enable this option to be able to read and
285 write to these files.
287 For detailed documentation on the debugfs API, see
288 Documentation/DocBook/filesystems.
293 bool "Run 'make headers_check' when building vmlinux"
296 This option will extract the user-visible kernel headers whenever
297 building the kernel, and will run basic sanity checks on them to
298 ensure that exported files do not attempt to include files which
299 were not exported, etc.
301 If you're making modifications to header files which are
302 relevant for userspace, say 'Y', and check the headers
303 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
304 your build tree), to make sure they're suitable.
306 config DEBUG_SECTION_MISMATCH
307 bool "Enable full Section mismatch analysis"
309 The section mismatch analysis checks if there are illegal
310 references from one section to another section.
311 During linktime or runtime, some sections are dropped;
312 any use of code/data previously in these sections would
313 most likely result in an oops.
314 In the code, functions and variables are annotated with
315 __init,, etc. (see the full list in include/linux/init.h),
316 which results in the code/data being placed in specific sections.
317 The section mismatch analysis is always performed after a full
318 kernel build, and enabling this option causes the following
319 additional steps to occur:
320 - Add the option -fno-inline-functions-called-once to gcc commands.
321 When inlining a function annotated with __init in a non-init
322 function, we would lose the section information and thus
323 the analysis would not catch the illegal reference.
324 This option tells gcc to inline less (but it does result in
326 - Run the section mismatch analysis for each module/built-in.o file.
327 When we run the section mismatch analysis on vmlinux.o, we
328 lose valuable information about where the mismatch was
330 Running the analysis for each module/built-in.o file
331 tells where the mismatch happens much closer to the
332 source. The drawback is that the same mismatch is
333 reported at least twice.
334 - Enable verbose reporting from modpost in order to help resolve
335 the section mismatches that are reported.
337 config SECTION_MISMATCH_WARN_ONLY
338 bool "Make section mismatch errors non-fatal"
341 If you say N here, the build process will fail if there are any
342 section mismatch, instead of just throwing warnings.
347 # Select this config option from the architecture Kconfig, if it
348 # is preferred to always offer frame pointers as a config
349 # option on the architecture (regardless of KERNEL_DEBUG):
351 config ARCH_WANT_FRAME_POINTERS
356 bool "Compile the kernel with frame pointers"
357 depends on DEBUG_KERNEL && \
358 (CRIS || M68K || FRV || UML || \
359 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \
360 ARCH_WANT_FRAME_POINTERS
361 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
363 If you say Y here the resulting kernel image will be slightly
364 larger and slower, but it gives very useful debugging information
365 in case of kernel bugs. (precise oopses/stacktraces/warnings)
367 config STACK_VALIDATION
368 bool "Compile-time stack metadata validation"
369 depends on HAVE_STACK_VALIDATION
372 Add compile-time checks to validate stack metadata, including frame
373 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
374 that runtime stack traces are more reliable.
376 For more information, see
377 tools/objtool/Documentation/stack-validation.txt.
379 config DEBUG_FORCE_WEAK_PER_CPU
380 bool "Force weak per-cpu definitions"
381 depends on DEBUG_KERNEL
383 s390 and alpha require percpu variables in modules to be
384 defined weak to work around addressing range issue which
385 puts the following two restrictions on percpu variable
388 1. percpu symbols must be unique whether static or not
389 2. percpu variables can't be defined inside a function
391 To ensure that generic code follows the above rules, this
392 option forces all percpu variables to be defined as weak.
394 endmenu # "Compiler options"
397 bool "Magic SysRq key"
400 If you say Y here, you will have some control over the system even
401 if the system crashes for example during kernel debugging (e.g., you
402 will be able to flush the buffer cache to disk, reboot the system
403 immediately or dump some status information). This is accomplished
404 by pressing various keys while holding SysRq (Alt+PrintScreen). It
405 also works on a serial console (on PC hardware at least), if you
406 send a BREAK and then within 5 seconds a command keypress. The
407 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
408 unless you really know what this hack does.
410 config MAGIC_SYSRQ_DEFAULT_ENABLE
411 hex "Enable magic SysRq key functions by default"
412 depends on MAGIC_SYSRQ
415 Specifies which SysRq key functions are enabled by default.
416 This may be set to 1 or 0 to enable or disable them all, or
417 to a bitmask as described in Documentation/sysrq.txt.
420 bool "Kernel debugging"
422 Say Y here if you are developing drivers or trying to debug and
423 identify kernel problems.
425 menu "Memory Debugging"
427 source mm/Kconfig.debug
430 bool "Debug object operations"
431 depends on DEBUG_KERNEL
433 If you say Y here, additional code will be inserted into the
434 kernel to track the life time of various objects and validate
435 the operations on those objects.
437 config DEBUG_OBJECTS_SELFTEST
438 bool "Debug objects selftest"
439 depends on DEBUG_OBJECTS
441 This enables the selftest of the object debug code.
443 config DEBUG_OBJECTS_FREE
444 bool "Debug objects in freed memory"
445 depends on DEBUG_OBJECTS
447 This enables checks whether a k/v free operation frees an area
448 which contains an object which has not been deactivated
449 properly. This can make kmalloc/kfree-intensive workloads
452 config DEBUG_OBJECTS_TIMERS
453 bool "Debug timer objects"
454 depends on DEBUG_OBJECTS
456 If you say Y here, additional code will be inserted into the
457 timer routines to track the life time of timer objects and
458 validate the timer operations.
460 config DEBUG_OBJECTS_WORK
461 bool "Debug work objects"
462 depends on DEBUG_OBJECTS
464 If you say Y here, additional code will be inserted into the
465 work queue routines to track the life time of work objects and
466 validate the work operations.
468 config DEBUG_OBJECTS_RCU_HEAD
469 bool "Debug RCU callbacks objects"
470 depends on DEBUG_OBJECTS
472 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
474 config DEBUG_OBJECTS_PERCPU_COUNTER
475 bool "Debug percpu counter objects"
476 depends on DEBUG_OBJECTS
478 If you say Y here, additional code will be inserted into the
479 percpu counter routines to track the life time of percpu counter
480 objects and validate the percpu counter operations.
482 config DEBUG_OBJECTS_ENABLE_DEFAULT
483 int "debug_objects bootup default value (0-1)"
486 depends on DEBUG_OBJECTS
488 Debug objects boot parameter default value
491 bool "Debug slab memory allocations"
492 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
494 Say Y here to have the kernel do limited verification on memory
495 allocation as well as poisoning memory on free to catch use of freed
496 memory. This can make kmalloc/kfree-intensive workloads much slower.
498 config DEBUG_SLAB_LEAK
499 bool "Memory leak debugging"
500 depends on DEBUG_SLAB
503 bool "SLUB debugging on by default"
504 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
507 Boot with debugging on by default. SLUB boots by default with
508 the runtime debug capabilities switched off. Enabling this is
509 equivalent to specifying the "slub_debug" parameter on boot.
510 There is no support for more fine grained debug control like
511 possible with slub_debug=xxx. SLUB debugging may be switched
512 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
517 bool "Enable SLUB performance statistics"
518 depends on SLUB && SYSFS
520 SLUB statistics are useful to debug SLUBs allocation behavior in
521 order find ways to optimize the allocator. This should never be
522 enabled for production use since keeping statistics slows down
523 the allocator by a few percentage points. The slabinfo command
524 supports the determination of the most active slabs to figure
525 out which slabs are relevant to a particular load.
526 Try running: slabinfo -DA
528 config HAVE_DEBUG_KMEMLEAK
531 config DEBUG_KMEMLEAK
532 bool "Kernel memory leak detector"
533 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
535 select STACKTRACE if STACKTRACE_SUPPORT
539 Say Y here if you want to enable the memory leak
540 detector. The memory allocation/freeing is traced in a way
541 similar to the Boehm's conservative garbage collector, the
542 difference being that the orphan objects are not freed but
543 only shown in /sys/kernel/debug/kmemleak. Enabling this
544 feature will introduce an overhead to memory
545 allocations. See Documentation/dev-tools/kmemleak.rst for more
548 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
549 of finding leaks due to the slab objects poisoning.
551 In order to access the kmemleak file, debugfs needs to be
552 mounted (usually at /sys/kernel/debug).
554 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
555 int "Maximum kmemleak early log entries"
556 depends on DEBUG_KMEMLEAK
560 Kmemleak must track all the memory allocations to avoid
561 reporting false positives. Since memory may be allocated or
562 freed before kmemleak is initialised, an early log buffer is
563 used to store these actions. If kmemleak reports "early log
564 buffer exceeded", please increase this value.
566 config DEBUG_KMEMLEAK_TEST
567 tristate "Simple test for the kernel memory leak detector"
568 depends on DEBUG_KMEMLEAK && m
570 This option enables a module that explicitly leaks memory.
574 config DEBUG_KMEMLEAK_DEFAULT_OFF
575 bool "Default kmemleak to off"
576 depends on DEBUG_KMEMLEAK
578 Say Y here to disable kmemleak by default. It can then be enabled
579 on the command line via kmemleak=on.
581 config DEBUG_STACK_USAGE
582 bool "Stack utilization instrumentation"
583 depends on DEBUG_KERNEL && !IA64
585 Enables the display of the minimum amount of free stack which each
586 task has ever had available in the sysrq-T and sysrq-P debug output.
588 This option will slow down process creation somewhat.
592 depends on DEBUG_KERNEL
594 Enable this to turn on extended checks in the virtual-memory system
595 that may impact performance.
599 config DEBUG_VM_VMACACHE
600 bool "Debug VMA caching"
603 Enable this to turn on VMA caching debug information. Doing so
604 can cause significant overhead, so only enable it in non-production
610 bool "Debug VM red-black trees"
613 Enable VM red-black tree debugging information and extra validations.
617 config DEBUG_VM_PGFLAGS
618 bool "Debug page-flags operations"
621 Enables extra validation on page flags operations.
626 bool "Debug VM translations"
627 depends on DEBUG_KERNEL && X86
629 Enable some costly sanity checks in virtual to page code. This can
630 catch mistakes with virt_to_page() and friends.
634 config DEBUG_NOMMU_REGIONS
635 bool "Debug the global anon/private NOMMU mapping region tree"
636 depends on DEBUG_KERNEL && !MMU
638 This option causes the global tree of anonymous and private mapping
639 regions to be regularly checked for invalid topology.
641 config DEBUG_MEMORY_INIT
642 bool "Debug memory initialisation" if EXPERT
645 Enable this for additional checks during memory initialisation.
646 The sanity checks verify aspects of the VM such as the memory model
647 and other information provided by the architecture. Verbose
648 information will be printed at KERN_DEBUG loglevel depending
649 on the mminit_loglevel= command-line option.
653 config MEMORY_NOTIFIER_ERROR_INJECT
654 tristate "Memory hotplug notifier error injection module"
655 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
657 This option provides the ability to inject artificial errors to
658 memory hotplug notifier chain callbacks. It is controlled through
659 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
661 If the notifier call chain should be failed with some events
662 notified, write the error code to "actions/<notifier event>/error".
664 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
666 # cd /sys/kernel/debug/notifier-error-inject/memory
667 # echo -12 > actions/MEM_GOING_OFFLINE/error
668 # echo offline > /sys/devices/system/memory/memoryXXX/state
669 bash: echo: write error: Cannot allocate memory
671 To compile this code as a module, choose M here: the module will
672 be called memory-notifier-error-inject.
676 config DEBUG_PER_CPU_MAPS
677 bool "Debug access to per_cpu maps"
678 depends on DEBUG_KERNEL
681 Say Y to verify that the per_cpu map being accessed has
682 been set up. This adds a fair amount of code to kernel memory
683 and decreases performance.
688 bool "Highmem debugging"
689 depends on DEBUG_KERNEL && HIGHMEM
691 This option enables additional error checking for high memory
692 systems. Disable for production systems.
694 config HAVE_DEBUG_STACKOVERFLOW
697 config DEBUG_STACKOVERFLOW
698 bool "Check for stack overflows"
699 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
701 Say Y here if you want to check for overflows of kernel, IRQ
702 and exception stacks (if your architecture uses them). This
703 option will show detailed messages if free stack space drops
704 below a certain limit.
706 These kinds of bugs usually occur when call-chains in the
707 kernel get too deep, especially when interrupts are
710 Use this in cases where you see apparently random memory
711 corruption, especially if it appears in 'struct thread_info'
713 If in doubt, say "N".
715 source "lib/Kconfig.kmemcheck"
717 source "lib/Kconfig.kasan"
719 config DEBUG_REFCOUNT
720 bool "Verbose refcount checks"
722 Say Y here if you want reference counters (refcount_t and kref) to
723 generate WARNs on dubious usage. Without this refcount_t will still
724 be a saturating counter and avoid Use-After-Free by turning it into
725 a resource leak Denial-Of-Service.
727 Use of this option will increase kernel text size but will alert the
728 admin of potential abuse.
730 If in doubt, say "N".
732 endmenu # "Memory Debugging"
737 KCOV does not have any arch-specific code, but currently it is enabled
738 only for x86_64. KCOV requires testing on other archs, and most likely
739 disabling of instrumentation for some early boot code.
742 bool "Code coverage for fuzzing"
743 depends on ARCH_HAS_KCOV
745 select GCC_PLUGINS if !COMPILE_TEST
746 select GCC_PLUGIN_SANCOV if !COMPILE_TEST
748 KCOV exposes kernel code coverage information in a form suitable
749 for coverage-guided fuzzing (randomized testing).
751 If RANDOMIZE_BASE is enabled, PC values will not be stable across
752 different machines and across reboots. If you need stable PC values,
753 disable RANDOMIZE_BASE.
755 For more details, see Documentation/dev-tools/kcov.rst.
757 config KCOV_INSTRUMENT_ALL
758 bool "Instrument all code by default"
762 If you are doing generic system call fuzzing (like e.g. syzkaller),
763 then you will want to instrument the whole kernel and you should
764 say y here. If you are doing more targeted fuzzing (like e.g.
765 filesystem fuzzing with AFL) then you will want to enable coverage
766 for more specific subsets of files, and should say n here.
769 bool "Debug shared IRQ handlers"
770 depends on DEBUG_KERNEL
772 Enable this to generate a spurious interrupt as soon as a shared
773 interrupt handler is registered, and just before one is deregistered.
774 Drivers ought to be able to handle interrupts coming in at those
775 points; some don't and need to be caught.
777 menu "Debug Lockups and Hangs"
779 config LOCKUP_DETECTOR
780 bool "Detect Hard and Soft Lockups"
781 depends on DEBUG_KERNEL && !S390
783 Say Y here to enable the kernel to act as a watchdog to detect
784 hard and soft lockups.
786 Softlockups are bugs that cause the kernel to loop in kernel
787 mode for more than 20 seconds, without giving other tasks a
788 chance to run. The current stack trace is displayed upon
789 detection and the system will stay locked up.
791 Hardlockups are bugs that cause the CPU to loop in kernel mode
792 for more than 10 seconds, without letting other interrupts have a
793 chance to run. The current stack trace is displayed upon detection
794 and the system will stay locked up.
796 The overhead should be minimal. A periodic hrtimer runs to
797 generate interrupts and kick the watchdog task every 4 seconds.
798 An NMI is generated every 10 seconds or so to check for hardlockups.
800 The frequency of hrtimer and NMI events and the soft and hard lockup
801 thresholds can be controlled through the sysctl watchdog_thresh.
803 config HARDLOCKUP_DETECTOR
805 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
806 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
808 config BOOTPARAM_HARDLOCKUP_PANIC
809 bool "Panic (Reboot) On Hard Lockups"
810 depends on HARDLOCKUP_DETECTOR
812 Say Y here to enable the kernel to panic on "hard lockups",
813 which are bugs that cause the kernel to loop in kernel
814 mode with interrupts disabled for more than 10 seconds (configurable
815 using the watchdog_thresh sysctl).
819 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
821 depends on HARDLOCKUP_DETECTOR
823 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
824 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
826 config BOOTPARAM_SOFTLOCKUP_PANIC
827 bool "Panic (Reboot) On Soft Lockups"
828 depends on LOCKUP_DETECTOR
830 Say Y here to enable the kernel to panic on "soft lockups",
831 which are bugs that cause the kernel to loop in kernel
832 mode for more than 20 seconds (configurable using the watchdog_thresh
833 sysctl), without giving other tasks a chance to run.
835 The panic can be used in combination with panic_timeout,
836 to cause the system to reboot automatically after a
837 lockup has been detected. This feature is useful for
838 high-availability systems that have uptime guarantees and
839 where a lockup must be resolved ASAP.
843 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
845 depends on LOCKUP_DETECTOR
847 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
848 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
850 config DETECT_HUNG_TASK
851 bool "Detect Hung Tasks"
852 depends on DEBUG_KERNEL
853 default LOCKUP_DETECTOR
855 Say Y here to enable the kernel to detect "hung tasks",
856 which are bugs that cause the task to be stuck in
857 uninterruptible "D" state indefinitely.
859 When a hung task is detected, the kernel will print the
860 current stack trace (which you should report), but the
861 task will stay in uninterruptible state. If lockdep is
862 enabled then all held locks will also be reported. This
863 feature has negligible overhead.
865 config DEFAULT_HUNG_TASK_TIMEOUT
866 int "Default timeout for hung task detection (in seconds)"
867 depends on DETECT_HUNG_TASK
870 This option controls the default timeout (in seconds) used
871 to determine when a task has become non-responsive and should
874 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
875 sysctl or by writing a value to
876 /proc/sys/kernel/hung_task_timeout_secs.
878 A timeout of 0 disables the check. The default is two minutes.
879 Keeping the default should be fine in most cases.
881 config BOOTPARAM_HUNG_TASK_PANIC
882 bool "Panic (Reboot) On Hung Tasks"
883 depends on DETECT_HUNG_TASK
885 Say Y here to enable the kernel to panic on "hung tasks",
886 which are bugs that cause the kernel to leave a task stuck
887 in uninterruptible "D" state.
889 The panic can be used in combination with panic_timeout,
890 to cause the system to reboot automatically after a
891 hung task has been detected. This feature is useful for
892 high-availability systems that have uptime guarantees and
893 where a hung tasks must be resolved ASAP.
897 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
899 depends on DETECT_HUNG_TASK
901 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
902 default 1 if BOOTPARAM_HUNG_TASK_PANIC
905 bool "Detect Workqueue Stalls"
906 depends on DEBUG_KERNEL
908 Say Y here to enable stall detection on workqueues. If a
909 worker pool doesn't make forward progress on a pending work
910 item for over a given amount of time, 30s by default, a
911 warning message is printed along with dump of workqueue
912 state. This can be configured through kernel parameter
913 "workqueue.watchdog_thresh" and its sysfs counterpart.
915 endmenu # "Debug lockups and hangs"
920 Say Y here to enable the kernel to panic when it oopses. This
921 has the same effect as setting oops=panic on the kernel command
924 This feature is useful to ensure that the kernel does not do
925 anything erroneous after an oops which could result in data
926 corruption or other issues.
930 config PANIC_ON_OOPS_VALUE
933 default 0 if !PANIC_ON_OOPS
934 default 1 if PANIC_ON_OOPS
940 Set the timeout value (in seconds) until a reboot occurs when the
941 the kernel panics. If n = 0, then we wait forever. A timeout
942 value n > 0 will wait n seconds before rebooting, while a timeout
943 value n < 0 will reboot immediately.
946 bool "Collect scheduler debugging info"
947 depends on DEBUG_KERNEL && PROC_FS
950 If you say Y here, the /proc/sched_debug file will be provided
951 that can help debug the scheduler. The runtime overhead of this
959 bool "Collect scheduler statistics"
960 depends on DEBUG_KERNEL && PROC_FS
963 If you say Y here, additional code will be inserted into the
964 scheduler and related routines to collect statistics about
965 scheduler behavior and provide them in /proc/schedstat. These
966 stats may be useful for both tuning and debugging the scheduler
967 If you aren't debugging the scheduler or trying to tune a specific
968 application, you can say N to avoid the very slight overhead
971 config SCHED_STACK_END_CHECK
972 bool "Detect stack corruption on calls to schedule()"
973 depends on DEBUG_KERNEL
976 This option checks for a stack overrun on calls to schedule().
977 If the stack end location is found to be over written always panic as
978 the content of the corrupted region can no longer be trusted.
979 This is to ensure no erroneous behaviour occurs which could result in
980 data corruption or a sporadic crash at a later stage once the region
981 is examined. The runtime overhead introduced is minimal.
983 config DEBUG_TIMEKEEPING
984 bool "Enable extra timekeeping sanity checking"
986 This option will enable additional timekeeping sanity checks
987 which may be helpful when diagnosing issues where timekeeping
988 problems are suspected.
990 This may include checks in the timekeeping hotpaths, so this
991 option may have a (very small) performance impact to some
997 bool "Debug preemptible kernel"
998 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1001 If you say Y here then the kernel will use a debug variant of the
1002 commonly used smp_processor_id() function and will print warnings
1003 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1004 will detect preemption count underflows.
1006 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1008 config DEBUG_RT_MUTEXES
1009 bool "RT Mutex debugging, deadlock detection"
1010 depends on DEBUG_KERNEL && RT_MUTEXES
1012 This allows rt mutex semantics violations and rt mutex related
1013 deadlocks (lockups) to be detected and reported automatically.
1015 config DEBUG_SPINLOCK
1016 bool "Spinlock and rw-lock debugging: basic checks"
1017 depends on DEBUG_KERNEL
1018 select UNINLINE_SPIN_UNLOCK
1020 Say Y here and build SMP to catch missing spinlock initialization
1021 and certain other kinds of spinlock errors commonly made. This is
1022 best used in conjunction with the NMI watchdog so that spinlock
1023 deadlocks are also debuggable.
1025 config DEBUG_MUTEXES
1026 bool "Mutex debugging: basic checks"
1027 depends on DEBUG_KERNEL
1029 This feature allows mutex semantics violations to be detected and
1032 config DEBUG_WW_MUTEX_SLOWPATH
1033 bool "Wait/wound mutex debugging: Slowpath testing"
1034 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1035 select DEBUG_LOCK_ALLOC
1036 select DEBUG_SPINLOCK
1037 select DEBUG_MUTEXES
1039 This feature enables slowpath testing for w/w mutex users by
1040 injecting additional -EDEADLK wound/backoff cases. Together with
1041 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1042 will test all possible w/w mutex interface abuse with the
1043 exception of simply not acquiring all the required locks.
1044 Note that this feature can introduce significant overhead, so
1045 it really should not be enabled in a production or distro kernel,
1046 even a debug kernel. If you are a driver writer, enable it. If
1047 you are a distro, do not.
1049 config DEBUG_LOCK_ALLOC
1050 bool "Lock debugging: detect incorrect freeing of live locks"
1051 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1052 select DEBUG_SPINLOCK
1053 select DEBUG_MUTEXES
1056 This feature will check whether any held lock (spinlock, rwlock,
1057 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1058 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1059 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1060 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1061 held during task exit.
1063 config PROVE_LOCKING
1064 bool "Lock debugging: prove locking correctness"
1065 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1067 select DEBUG_SPINLOCK
1068 select DEBUG_MUTEXES
1069 select DEBUG_LOCK_ALLOC
1070 select TRACE_IRQFLAGS
1073 This feature enables the kernel to prove that all locking
1074 that occurs in the kernel runtime is mathematically
1075 correct: that under no circumstance could an arbitrary (and
1076 not yet triggered) combination of observed locking
1077 sequences (on an arbitrary number of CPUs, running an
1078 arbitrary number of tasks and interrupt contexts) cause a
1081 In short, this feature enables the kernel to report locking
1082 related deadlocks before they actually occur.
1084 The proof does not depend on how hard and complex a
1085 deadlock scenario would be to trigger: how many
1086 participant CPUs, tasks and irq-contexts would be needed
1087 for it to trigger. The proof also does not depend on
1088 timing: if a race and a resulting deadlock is possible
1089 theoretically (no matter how unlikely the race scenario
1090 is), it will be proven so and will immediately be
1091 reported by the kernel (once the event is observed that
1092 makes the deadlock theoretically possible).
1094 If a deadlock is impossible (i.e. the locking rules, as
1095 observed by the kernel, are mathematically correct), the
1096 kernel reports nothing.
1098 NOTE: this feature can also be enabled for rwlocks, mutexes
1099 and rwsems - in which case all dependencies between these
1100 different locking variants are observed and mapped too, and
1101 the proof of observed correctness is also maintained for an
1102 arbitrary combination of these separate locking variants.
1104 For more details, see Documentation/locking/lockdep-design.txt.
1106 config PROVE_LOCKING_SMALL
1111 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1113 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
1118 bool "Lock usage statistics"
1119 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1121 select DEBUG_SPINLOCK
1122 select DEBUG_MUTEXES
1123 select DEBUG_LOCK_ALLOC
1126 This feature enables tracking lock contention points
1128 For more details, see Documentation/locking/lockstat.txt
1130 This also enables lock events required by "perf lock",
1132 If you want to use "perf lock", you also need to turn on
1133 CONFIG_EVENT_TRACING.
1135 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1136 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1138 config DEBUG_LOCKDEP
1139 bool "Lock dependency engine debugging"
1140 depends on DEBUG_KERNEL && LOCKDEP
1142 If you say Y here, the lock dependency engine will do
1143 additional runtime checks to debug itself, at the price
1144 of more runtime overhead.
1146 config DEBUG_ATOMIC_SLEEP
1147 bool "Sleep inside atomic section checking"
1148 select PREEMPT_COUNT
1149 depends on DEBUG_KERNEL
1151 If you say Y here, various routines which may sleep will become very
1152 noisy if they are called inside atomic sections: when a spinlock is
1153 held, inside an rcu read side critical section, inside preempt disabled
1154 sections, inside an interrupt, etc...
1156 config DEBUG_LOCKING_API_SELFTESTS
1157 bool "Locking API boot-time self-tests"
1158 depends on DEBUG_KERNEL
1160 Say Y here if you want the kernel to run a short self-test during
1161 bootup. The self-test checks whether common types of locking bugs
1162 are detected by debugging mechanisms or not. (if you disable
1163 lock debugging then those bugs wont be detected of course.)
1164 The following locking APIs are covered: spinlocks, rwlocks,
1167 config LOCK_TORTURE_TEST
1168 tristate "torture tests for locking"
1169 depends on DEBUG_KERNEL
1173 This option provides a kernel module that runs torture tests
1174 on kernel locking primitives. The kernel module may be built
1175 after the fact on the running kernel to be tested, if desired.
1177 Say Y here if you want kernel locking-primitive torture tests
1178 to be built into the kernel.
1179 Say M if you want these torture tests to build as a module.
1180 Say N if you are unsure.
1182 config WW_MUTEX_SELFTEST
1183 tristate "Wait/wound mutex selftests"
1185 This option provides a kernel module that runs tests on the
1186 on the struct ww_mutex locking API.
1188 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1189 with this test harness.
1191 Say M if you want these self tests to build as a module.
1192 Say N if you are unsure.
1194 endmenu # lock debugging
1196 config TRACE_IRQFLAGS
1199 Enables hooks to interrupt enabling and disabling for
1200 either tracing or lock debugging.
1203 bool "Stack backtrace support"
1204 depends on STACKTRACE_SUPPORT
1206 This option causes the kernel to create a /proc/pid/stack for
1207 every process, showing its current stack trace.
1208 It is also used by various kernel debugging features that require
1209 stack trace generation.
1211 config DEBUG_KOBJECT
1212 bool "kobject debugging"
1213 depends on DEBUG_KERNEL
1215 If you say Y here, some extra kobject debugging messages will be sent
1218 config DEBUG_KOBJECT_RELEASE
1219 bool "kobject release debugging"
1220 depends on DEBUG_OBJECTS_TIMERS
1222 kobjects are reference counted objects. This means that their
1223 last reference count put is not predictable, and the kobject can
1224 live on past the point at which a driver decides to drop it's
1225 initial reference to the kobject gained on allocation. An
1226 example of this would be a struct device which has just been
1229 However, some buggy drivers assume that after such an operation,
1230 the memory backing the kobject can be immediately freed. This
1231 goes completely against the principles of a refcounted object.
1233 If you say Y here, the kernel will delay the release of kobjects
1234 on the last reference count to improve the visibility of this
1235 kind of kobject release bug.
1237 config HAVE_DEBUG_BUGVERBOSE
1240 config DEBUG_BUGVERBOSE
1241 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1242 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1245 Say Y here to make BUG() panics output the file name and line number
1246 of the BUG call as well as the EIP and oops trace. This aids
1247 debugging but costs about 70-100K of memory.
1250 bool "Debug linked list manipulation"
1251 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1253 Enable this to turn on extended checks in the linked-list
1258 config DEBUG_PI_LIST
1259 bool "Debug priority linked list manipulation"
1260 depends on DEBUG_KERNEL
1262 Enable this to turn on extended checks in the priority-ordered
1263 linked-list (plist) walking routines. This checks the entire
1264 list multiple times during each manipulation.
1269 bool "Debug SG table operations"
1270 depends on DEBUG_KERNEL
1272 Enable this to turn on checks on scatter-gather tables. This can
1273 help find problems with drivers that do not properly initialize
1278 config DEBUG_NOTIFIERS
1279 bool "Debug notifier call chains"
1280 depends on DEBUG_KERNEL
1282 Enable this to turn on sanity checking for notifier call chains.
1283 This is most useful for kernel developers to make sure that
1284 modules properly unregister themselves from notifier chains.
1285 This is a relatively cheap check but if you care about maximum
1288 config DEBUG_CREDENTIALS
1289 bool "Debug credential management"
1290 depends on DEBUG_KERNEL
1292 Enable this to turn on some debug checking for credential
1293 management. The additional code keeps track of the number of
1294 pointers from task_structs to any given cred struct, and checks to
1295 see that this number never exceeds the usage count of the cred
1298 Furthermore, if SELinux is enabled, this also checks that the
1299 security pointer in the cred struct is never seen to be invalid.
1303 menu "RCU Debugging"
1306 def_bool PROVE_LOCKING
1308 config PROVE_RCU_REPEATEDLY
1309 bool "RCU debugging: don't disable PROVE_RCU on first splat"
1310 depends on PROVE_RCU
1313 By itself, PROVE_RCU will disable checking upon issuing the
1314 first warning (or "splat"). This feature prevents such
1315 disabling, allowing multiple RCU-lockdep warnings to be printed
1318 Say Y to allow multiple RCU-lockdep warnings per boot.
1320 Say N if you are unsure.
1322 config SPARSE_RCU_POINTER
1323 bool "RCU debugging: sparse-based checks for pointer usage"
1326 This feature enables the __rcu sparse annotation for
1327 RCU-protected pointers. This annotation will cause sparse
1328 to flag any non-RCU used of annotated pointers. This can be
1329 helpful when debugging RCU usage. Please note that this feature
1330 is not intended to enforce code cleanliness; it is instead merely
1333 Say Y to make sparse flag questionable use of RCU-protected pointers
1335 Say N if you are unsure.
1341 config RCU_PERF_TEST
1342 tristate "performance tests for RCU"
1343 depends on DEBUG_KERNEL
1349 This option provides a kernel module that runs performance
1350 tests on the RCU infrastructure. The kernel module may be built
1351 after the fact on the running kernel to be tested, if desired.
1353 Say Y here if you want RCU performance tests to be built into
1355 Say M if you want the RCU performance tests to build as a module.
1356 Say N if you are unsure.
1358 config RCU_TORTURE_TEST
1359 tristate "torture tests for RCU"
1360 depends on DEBUG_KERNEL
1366 This option provides a kernel module that runs torture tests
1367 on the RCU infrastructure. The kernel module may be built
1368 after the fact on the running kernel to be tested, if desired.
1370 Say Y here if you want RCU torture tests to be built into
1372 Say M if you want the RCU torture tests to build as a module.
1373 Say N if you are unsure.
1375 config RCU_TORTURE_TEST_SLOW_PREINIT
1376 bool "Slow down RCU grace-period pre-initialization to expose races"
1377 depends on RCU_TORTURE_TEST
1379 This option delays grace-period pre-initialization (the
1380 propagation of CPU-hotplug changes up the rcu_node combining
1381 tree) for a few jiffies between initializing each pair of
1382 consecutive rcu_node structures. This helps to expose races
1383 involving grace-period pre-initialization, in other words, it
1384 makes your kernel less stable. It can also greatly increase
1385 grace-period latency, especially on systems with large numbers
1386 of CPUs. This is useful when torture-testing RCU, but in
1387 almost no other circumstance.
1389 Say Y here if you want your system to crash and hang more often.
1390 Say N if you want a sane system.
1392 config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
1393 int "How much to slow down RCU grace-period pre-initialization"
1396 depends on RCU_TORTURE_TEST_SLOW_PREINIT
1398 This option specifies the number of jiffies to wait between
1399 each rcu_node structure pre-initialization step.
1401 config RCU_TORTURE_TEST_SLOW_INIT
1402 bool "Slow down RCU grace-period initialization to expose races"
1403 depends on RCU_TORTURE_TEST
1405 This option delays grace-period initialization for a few
1406 jiffies between initializing each pair of consecutive
1407 rcu_node structures. This helps to expose races involving
1408 grace-period initialization, in other words, it makes your
1409 kernel less stable. It can also greatly increase grace-period
1410 latency, especially on systems with large numbers of CPUs.
1411 This is useful when torture-testing RCU, but in almost no
1414 Say Y here if you want your system to crash and hang more often.
1415 Say N if you want a sane system.
1417 config RCU_TORTURE_TEST_SLOW_INIT_DELAY
1418 int "How much to slow down RCU grace-period initialization"
1421 depends on RCU_TORTURE_TEST_SLOW_INIT
1423 This option specifies the number of jiffies to wait between
1424 each rcu_node structure initialization.
1426 config RCU_TORTURE_TEST_SLOW_CLEANUP
1427 bool "Slow down RCU grace-period cleanup to expose races"
1428 depends on RCU_TORTURE_TEST
1430 This option delays grace-period cleanup for a few jiffies
1431 between cleaning up each pair of consecutive rcu_node
1432 structures. This helps to expose races involving grace-period
1433 cleanup, in other words, it makes your kernel less stable.
1434 It can also greatly increase grace-period latency, especially
1435 on systems with large numbers of CPUs. This is useful when
1436 torture-testing RCU, but in almost no other circumstance.
1438 Say Y here if you want your system to crash and hang more often.
1439 Say N if you want a sane system.
1441 config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
1442 int "How much to slow down RCU grace-period cleanup"
1445 depends on RCU_TORTURE_TEST_SLOW_CLEANUP
1447 This option specifies the number of jiffies to wait between
1448 each rcu_node structure cleanup operation.
1450 config RCU_CPU_STALL_TIMEOUT
1451 int "RCU CPU stall timeout in seconds"
1452 depends on RCU_STALL_COMMON
1456 If a given RCU grace period extends more than the specified
1457 number of seconds, a CPU stall warning is printed. If the
1458 RCU grace period persists, additional CPU stall warnings are
1459 printed at more widely spaced intervals.
1462 bool "Enable tracing for RCU"
1463 depends on DEBUG_KERNEL
1464 default y if TREE_RCU
1467 This option provides tracing in RCU which presents stats
1468 in debugfs for debugging RCU implementation. It also enables
1469 additional tracepoints for ftrace-style event tracing.
1471 Say Y here if you want to enable RCU tracing
1472 Say N if you are unsure.
1474 config RCU_EQS_DEBUG
1475 bool "Provide debugging asserts for adding NO_HZ support to an arch"
1476 depends on DEBUG_KERNEL
1478 This option provides consistency checks in RCU's handling of
1479 NO_HZ. These checks have proven quite helpful in detecting
1480 bugs in arch-specific NO_HZ code.
1482 Say N here if you need ultimate kernel/user switch latencies
1483 Say Y if you are unsure
1485 endmenu # "RCU Debugging"
1487 config DEBUG_WQ_FORCE_RR_CPU
1488 bool "Force round-robin CPU selection for unbound work items"
1489 depends on DEBUG_KERNEL
1492 Workqueue used to implicitly guarantee that work items queued
1493 without explicit CPU specified are put on the local CPU. This
1494 guarantee is no longer true and while local CPU is still
1495 preferred work items may be put on foreign CPUs. Kernel
1496 parameter "workqueue.debug_force_rr_cpu" is added to force
1497 round-robin CPU selection to flush out usages which depend on the
1498 now broken guarantee. This config option enables the debug
1499 feature by default. When enabled, memory and cache locality will
1502 config DEBUG_BLOCK_EXT_DEVT
1503 bool "Force extended block device numbers and spread them"
1504 depends on DEBUG_KERNEL
1508 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1509 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1510 YOU ARE DOING. Distros, please enable this and fix whatever
1513 Conventionally, block device numbers are allocated from
1514 predetermined contiguous area. However, extended block area
1515 may introduce non-contiguous block device numbers. This
1516 option forces most block device numbers to be allocated from
1517 the extended space and spreads them to discover kernel or
1518 userland code paths which assume predetermined contiguous
1519 device number allocation.
1521 Note that turning on this debug option shuffles all the
1522 device numbers for all IDE and SCSI devices including libata
1523 ones, so root partition specified using device number
1524 directly (via rdev or root=MAJ:MIN) won't work anymore.
1525 Textual device names (root=/dev/sdXn) will continue to work.
1527 Say N if you are unsure.
1529 config CPU_HOTPLUG_STATE_CONTROL
1530 bool "Enable CPU hotplug state control"
1531 depends on DEBUG_KERNEL
1532 depends on HOTPLUG_CPU
1535 Allows to write steps between "offline" and "online" to the CPUs
1536 sysfs target file so states can be stepped granular. This is a debug
1537 option for now as the hotplug machinery cannot be stopped and
1538 restarted at arbitrary points yet.
1540 Say N if your are unsure.
1542 config NOTIFIER_ERROR_INJECTION
1543 tristate "Notifier error injection"
1544 depends on DEBUG_KERNEL
1547 This option provides the ability to inject artificial errors to
1548 specified notifier chain callbacks. It is useful to test the error
1549 handling of notifier call chain failures.
1553 config PM_NOTIFIER_ERROR_INJECT
1554 tristate "PM notifier error injection module"
1555 depends on PM && NOTIFIER_ERROR_INJECTION
1556 default m if PM_DEBUG
1558 This option provides the ability to inject artificial errors to
1559 PM notifier chain callbacks. It is controlled through debugfs
1560 interface /sys/kernel/debug/notifier-error-inject/pm
1562 If the notifier call chain should be failed with some events
1563 notified, write the error code to "actions/<notifier event>/error".
1565 Example: Inject PM suspend error (-12 = -ENOMEM)
1567 # cd /sys/kernel/debug/notifier-error-inject/pm/
1568 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1569 # echo mem > /sys/power/state
1570 bash: echo: write error: Cannot allocate memory
1572 To compile this code as a module, choose M here: the module will
1573 be called pm-notifier-error-inject.
1577 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1578 tristate "OF reconfig notifier error injection module"
1579 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1581 This option provides the ability to inject artificial errors to
1582 OF reconfig notifier chain callbacks. It is controlled
1583 through debugfs interface under
1584 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1586 If the notifier call chain should be failed with some events
1587 notified, write the error code to "actions/<notifier event>/error".
1589 To compile this code as a module, choose M here: the module will
1590 be called of-reconfig-notifier-error-inject.
1594 config NETDEV_NOTIFIER_ERROR_INJECT
1595 tristate "Netdev notifier error injection module"
1596 depends on NET && NOTIFIER_ERROR_INJECTION
1598 This option provides the ability to inject artificial errors to
1599 netdevice notifier chain callbacks. It is controlled through debugfs
1600 interface /sys/kernel/debug/notifier-error-inject/netdev
1602 If the notifier call chain should be failed with some events
1603 notified, write the error code to "actions/<notifier event>/error".
1605 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1607 # cd /sys/kernel/debug/notifier-error-inject/netdev
1608 # echo -22 > actions/NETDEV_CHANGEMTU/error
1609 # ip link set eth0 mtu 1024
1610 RTNETLINK answers: Invalid argument
1612 To compile this code as a module, choose M here: the module will
1613 be called netdev-notifier-error-inject.
1617 config FAULT_INJECTION
1618 bool "Fault-injection framework"
1619 depends on DEBUG_KERNEL
1621 Provide fault-injection framework.
1622 For more details, see Documentation/fault-injection/.
1625 bool "Fault-injection capability for kmalloc"
1626 depends on FAULT_INJECTION
1627 depends on SLAB || SLUB
1629 Provide fault-injection capability for kmalloc.
1631 config FAIL_PAGE_ALLOC
1632 bool "Fault-injection capabilitiy for alloc_pages()"
1633 depends on FAULT_INJECTION
1635 Provide fault-injection capability for alloc_pages().
1637 config FAIL_MAKE_REQUEST
1638 bool "Fault-injection capability for disk IO"
1639 depends on FAULT_INJECTION && BLOCK
1641 Provide fault-injection capability for disk IO.
1643 config FAIL_IO_TIMEOUT
1644 bool "Fault-injection capability for faking disk interrupts"
1645 depends on FAULT_INJECTION && BLOCK
1647 Provide fault-injection capability on end IO handling. This
1648 will make the block layer "forget" an interrupt as configured,
1649 thus exercising the error handling.
1651 Only works with drivers that use the generic timeout handling,
1652 for others it wont do anything.
1654 config FAIL_MMC_REQUEST
1655 bool "Fault-injection capability for MMC IO"
1656 depends on FAULT_INJECTION_DEBUG_FS && MMC
1658 Provide fault-injection capability for MMC IO.
1659 This will make the mmc core return data errors. This is
1660 useful to test the error handling in the mmc block device
1661 and to test how the mmc host driver handles retries from
1665 bool "Fault-injection capability for futexes"
1667 depends on FAULT_INJECTION && FUTEX
1669 Provide fault-injection capability for futexes.
1671 config FAULT_INJECTION_DEBUG_FS
1672 bool "Debugfs entries for fault-injection capabilities"
1673 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1675 Enable configuration of fault-injection capabilities via debugfs.
1677 config FAULT_INJECTION_STACKTRACE_FILTER
1678 bool "stacktrace filter for fault-injection capabilities"
1679 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1682 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1684 Provide stacktrace filter for fault-injection capabilities
1687 bool "Latency measuring infrastructure"
1688 depends on DEBUG_KERNEL
1689 depends on STACKTRACE_SUPPORT
1691 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1698 Enable this option if you want to use the LatencyTOP tool
1699 to find out which userspace is blocking on what kernel operations.
1701 source kernel/trace/Kconfig
1703 menu "Runtime Testing"
1706 tristate "Linux Kernel Dump Test Tool Module"
1711 This module enables testing of the different dumping mechanisms by
1712 inducing system failures at predefined crash points.
1713 If you don't need it: say N
1714 Choose M here to compile this code as a module. The module will be
1717 Documentation on how to use the module can be found in
1718 Documentation/fault-injection/provoke-crashes.txt
1720 config TEST_LIST_SORT
1721 bool "Linked list sorting test"
1722 depends on DEBUG_KERNEL
1724 Enable this to turn on 'list_sort()' function test. This test is
1725 executed only once during system boot, so affects only boot time.
1729 config KPROBES_SANITY_TEST
1730 bool "Kprobes sanity tests"
1731 depends on DEBUG_KERNEL
1735 This option provides for testing basic kprobes functionality on
1736 boot. A sample kprobe, jprobe and kretprobe are inserted and
1737 verified for functionality.
1739 Say N if you are unsure.
1741 config BACKTRACE_SELF_TEST
1742 tristate "Self test for the backtrace code"
1743 depends on DEBUG_KERNEL
1746 This option provides a kernel module that can be used to test
1747 the kernel stack backtrace code. This option is not useful
1748 for distributions or general kernels, but only for kernel
1749 developers working on architecture code.
1751 Note that if you want to also test saved backtraces, you will
1752 have to enable STACKTRACE as well.
1754 Say N if you are unsure.
1757 tristate "Red-Black tree test"
1758 depends on DEBUG_KERNEL
1760 A benchmark measuring the performance of the rbtree library.
1761 Also includes rbtree invariant checks.
1763 config INTERVAL_TREE_TEST
1764 tristate "Interval tree test"
1765 depends on m && DEBUG_KERNEL
1766 select INTERVAL_TREE
1768 A benchmark measuring the performance of the interval tree library
1771 tristate "Per cpu operations test"
1772 depends on m && DEBUG_KERNEL
1774 Enable this option to build test module which validates per-cpu
1779 config ATOMIC64_SELFTEST
1780 bool "Perform an atomic64_t self-test at boot"
1782 Enable this option to test the atomic64_t functions at boot.
1786 config ASYNC_RAID6_TEST
1787 tristate "Self test for hardware accelerated raid6 recovery"
1788 depends on ASYNC_RAID6_RECOV
1791 This is a one-shot self test that permutes through the
1792 recovery of all the possible two disk failure scenarios for a
1793 N-disk array. Recovery is performed with the asynchronous
1794 raid6 recovery routines, and will optionally use an offload
1795 engine if one is available.
1800 tristate "Test functions located in the hexdump module at runtime"
1802 config TEST_STRING_HELPERS
1803 tristate "Test functions located in the string_helpers module at runtime"
1806 tristate "Test kstrto*() family of functions at runtime"
1809 tristate "Test printf() family of functions at runtime"
1812 tristate "Test bitmap_*() family of functions at runtime"
1815 Enable this option to test the bitmap functions at boot.
1820 tristate "Test functions located in the uuid module at runtime"
1822 config TEST_RHASHTABLE
1823 tristate "Perform selftest on resizable hash table"
1826 Enable this option to test the rhashtable functions at boot.
1831 tristate "Perform selftest on hash functions"
1834 Enable this option to test the kernel's integer (<linux/hash,h>)
1835 and string (<linux/stringhash.h>) hash functions on boot
1838 This is intended to help people writing architecture-specific
1839 optimized versions. If unsure, say N.
1841 endmenu # runtime tests
1843 config PROVIDE_OHCI1394_DMA_INIT
1844 bool "Remote debugging over FireWire early on boot"
1845 depends on PCI && X86
1847 If you want to debug problems which hang or crash the kernel early
1848 on boot and the crashing machine has a FireWire port, you can use
1849 this feature to remotely access the memory of the crashed machine
1850 over FireWire. This employs remote DMA as part of the OHCI1394
1851 specification which is now the standard for FireWire controllers.
1853 With remote DMA, you can monitor the printk buffer remotely using
1854 firescope and access all memory below 4GB using fireproxy from gdb.
1855 Even controlling a kernel debugger is possible using remote DMA.
1859 If ohci1394_dma=early is used as boot parameter, it will initialize
1860 all OHCI1394 controllers which are found in the PCI config space.
1862 As all changes to the FireWire bus such as enabling and disabling
1863 devices cause a bus reset and thereby disable remote DMA for all
1864 devices, be sure to have the cable plugged and FireWire enabled on
1865 the debugging host before booting the debug target for debugging.
1867 This code (~1k) is freed after boot. By then, the firewire stack
1868 in charge of the OHCI-1394 controllers should be used instead.
1870 See Documentation/debugging-via-ohci1394.txt for more information.
1872 config DMA_API_DEBUG
1873 bool "Enable debugging of DMA-API usage"
1874 depends on HAVE_DMA_API_DEBUG
1876 Enable this option to debug the use of the DMA API by device drivers.
1877 With this option you will be able to detect common bugs in device
1878 drivers like double-freeing of DMA mappings or freeing mappings that
1879 were never allocated.
1881 This also attempts to catch cases where a page owned by DMA is
1882 accessed by the cpu in a way that could cause data corruption. For
1883 example, this enables cow_user_page() to check that the source page is
1886 This option causes a performance degradation. Use only if you want to
1887 debug device drivers and dma interactions.
1892 tristate "Test module loading with 'hello world' module"
1896 This builds the "test_module" module that emits "Hello, world"
1897 on printk when loaded. It is designed to be used for basic
1898 evaluation of the module loading subsystem (for example when
1899 validating module verification). It lacks any extra dependencies,
1900 and will not normally be loaded by the system unless explicitly
1905 config TEST_USER_COPY
1906 tristate "Test user/kernel boundary protections"
1910 This builds the "test_user_copy" module that runs sanity checks
1911 on the copy_to/from_user infrastructure, making sure basic
1912 user/kernel boundary testing is working. If it fails to load,
1913 a regression has been detected in the user/kernel memory boundary
1919 tristate "Test BPF filter functionality"
1923 This builds the "test_bpf" module that runs various test vectors
1924 against the BPF interpreter or BPF JIT compiler depending on the
1925 current setting. This is in particular useful for BPF JIT compiler
1926 development, but also to run regression tests against changes in
1927 the interpreter code. It also enables test stubs for eBPF maps and
1928 verifier used by user space verifier testsuite.
1932 config TEST_FIRMWARE
1933 tristate "Test firmware loading via userspace interface"
1935 depends on FW_LOADER
1937 This builds the "test_firmware" module that creates a userspace
1938 interface for testing firmware loading. This can be used to
1939 control the triggering of firmware loading without needing an
1940 actual firmware-using device. The contents can be rechecked by
1946 tristate "udelay test driver"
1949 This builds the "udelay_test" module that helps to make sure
1950 that udelay() is working properly.
1956 depends on HAVE_MEMBLOCK
1958 This option adds a kernel parameter 'memtest', which allows memtest
1960 memtest=0, mean disabled; -- default
1961 memtest=1, mean do 1 test pattern;
1963 memtest=17, mean do 17 test patterns.
1964 If you are unsure how to answer this question, answer N.
1966 config TEST_STATIC_KEYS
1967 tristate "Test static keys"
1971 Test the static key interfaces.
1975 config BUG_ON_DATA_CORRUPTION
1976 bool "Trigger a BUG when data corruption is detected"
1979 Select this option if the kernel should BUG when it encounters
1980 data corruption in kernel memory structures when they get checked
1985 source "samples/Kconfig"
1987 source "lib/Kconfig.kgdb"
1989 source "lib/Kconfig.ubsan"
1991 config ARCH_HAS_DEVMEM_IS_ALLOWED
1994 config STRICT_DEVMEM
1995 bool "Filter access to /dev/mem"
1996 depends on MMU && DEVMEM
1997 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
1998 default y if TILE || PPC
2000 If this option is disabled, you allow userspace (root) access to all
2001 of memory, including kernel and userspace memory. Accidental
2002 access to this is obviously disastrous, but specific access can
2003 be used by people debugging the kernel. Note that with PAT support
2004 enabled, even in this case there are restrictions on /dev/mem
2005 use due to the cache aliasing requirements.
2007 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
2008 file only allows userspace access to PCI space and the BIOS code and
2009 data regions. This is sufficient for dosemu and X and all common
2014 config IO_STRICT_DEVMEM
2015 bool "Filter I/O access to /dev/mem"
2016 depends on STRICT_DEVMEM
2018 If this option is disabled, you allow userspace (root) access to all
2019 io-memory regardless of whether a driver is actively using that
2020 range. Accidental access to this is obviously disastrous, but
2021 specific access can be used by people debugging kernel drivers.
2023 If this option is switched on, the /dev/mem file only allows
2024 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2025 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2026 if the driver using a given range cannot be disabled.
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