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.
419 config MAGIC_SYSRQ_SERIAL
420 bool "Enable magic SysRq key over serial"
421 depends on MAGIC_SYSRQ
424 Many embedded boards have a disconnected TTL level serial which can
425 generate some garbage that can lead to spurious false sysrq detects.
426 This option allows you to decide whether you want to enable the
430 bool "Kernel debugging"
432 Say Y here if you are developing drivers or trying to debug and
433 identify kernel problems.
435 menu "Memory Debugging"
437 source mm/Kconfig.debug
440 bool "Debug object operations"
441 depends on DEBUG_KERNEL
443 If you say Y here, additional code will be inserted into the
444 kernel to track the life time of various objects and validate
445 the operations on those objects.
447 config DEBUG_OBJECTS_SELFTEST
448 bool "Debug objects selftest"
449 depends on DEBUG_OBJECTS
451 This enables the selftest of the object debug code.
453 config DEBUG_OBJECTS_FREE
454 bool "Debug objects in freed memory"
455 depends on DEBUG_OBJECTS
457 This enables checks whether a k/v free operation frees an area
458 which contains an object which has not been deactivated
459 properly. This can make kmalloc/kfree-intensive workloads
462 config DEBUG_OBJECTS_TIMERS
463 bool "Debug timer objects"
464 depends on DEBUG_OBJECTS
466 If you say Y here, additional code will be inserted into the
467 timer routines to track the life time of timer objects and
468 validate the timer operations.
470 config DEBUG_OBJECTS_WORK
471 bool "Debug work objects"
472 depends on DEBUG_OBJECTS
474 If you say Y here, additional code will be inserted into the
475 work queue routines to track the life time of work objects and
476 validate the work operations.
478 config DEBUG_OBJECTS_RCU_HEAD
479 bool "Debug RCU callbacks objects"
480 depends on DEBUG_OBJECTS
482 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
484 config DEBUG_OBJECTS_PERCPU_COUNTER
485 bool "Debug percpu counter objects"
486 depends on DEBUG_OBJECTS
488 If you say Y here, additional code will be inserted into the
489 percpu counter routines to track the life time of percpu counter
490 objects and validate the percpu counter operations.
492 config DEBUG_OBJECTS_ENABLE_DEFAULT
493 int "debug_objects bootup default value (0-1)"
496 depends on DEBUG_OBJECTS
498 Debug objects boot parameter default value
501 bool "Debug slab memory allocations"
502 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
504 Say Y here to have the kernel do limited verification on memory
505 allocation as well as poisoning memory on free to catch use of freed
506 memory. This can make kmalloc/kfree-intensive workloads much slower.
508 config DEBUG_SLAB_LEAK
509 bool "Memory leak debugging"
510 depends on DEBUG_SLAB
513 bool "SLUB debugging on by default"
514 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
517 Boot with debugging on by default. SLUB boots by default with
518 the runtime debug capabilities switched off. Enabling this is
519 equivalent to specifying the "slub_debug" parameter on boot.
520 There is no support for more fine grained debug control like
521 possible with slub_debug=xxx. SLUB debugging may be switched
522 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
527 bool "Enable SLUB performance statistics"
528 depends on SLUB && SYSFS
530 SLUB statistics are useful to debug SLUBs allocation behavior in
531 order find ways to optimize the allocator. This should never be
532 enabled for production use since keeping statistics slows down
533 the allocator by a few percentage points. The slabinfo command
534 supports the determination of the most active slabs to figure
535 out which slabs are relevant to a particular load.
536 Try running: slabinfo -DA
538 config HAVE_DEBUG_KMEMLEAK
541 config DEBUG_KMEMLEAK
542 bool "Kernel memory leak detector"
543 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
545 select STACKTRACE if STACKTRACE_SUPPORT
549 Say Y here if you want to enable the memory leak
550 detector. The memory allocation/freeing is traced in a way
551 similar to the Boehm's conservative garbage collector, the
552 difference being that the orphan objects are not freed but
553 only shown in /sys/kernel/debug/kmemleak. Enabling this
554 feature will introduce an overhead to memory
555 allocations. See Documentation/dev-tools/kmemleak.rst for more
558 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
559 of finding leaks due to the slab objects poisoning.
561 In order to access the kmemleak file, debugfs needs to be
562 mounted (usually at /sys/kernel/debug).
564 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
565 int "Maximum kmemleak early log entries"
566 depends on DEBUG_KMEMLEAK
570 Kmemleak must track all the memory allocations to avoid
571 reporting false positives. Since memory may be allocated or
572 freed before kmemleak is initialised, an early log buffer is
573 used to store these actions. If kmemleak reports "early log
574 buffer exceeded", please increase this value.
576 config DEBUG_KMEMLEAK_TEST
577 tristate "Simple test for the kernel memory leak detector"
578 depends on DEBUG_KMEMLEAK && m
580 This option enables a module that explicitly leaks memory.
584 config DEBUG_KMEMLEAK_DEFAULT_OFF
585 bool "Default kmemleak to off"
586 depends on DEBUG_KMEMLEAK
588 Say Y here to disable kmemleak by default. It can then be enabled
589 on the command line via kmemleak=on.
591 config DEBUG_STACK_USAGE
592 bool "Stack utilization instrumentation"
593 depends on DEBUG_KERNEL && !IA64
595 Enables the display of the minimum amount of free stack which each
596 task has ever had available in the sysrq-T and sysrq-P debug output.
598 This option will slow down process creation somewhat.
602 depends on DEBUG_KERNEL
604 Enable this to turn on extended checks in the virtual-memory system
605 that may impact performance.
609 config DEBUG_VM_VMACACHE
610 bool "Debug VMA caching"
613 Enable this to turn on VMA caching debug information. Doing so
614 can cause significant overhead, so only enable it in non-production
620 bool "Debug VM red-black trees"
623 Enable VM red-black tree debugging information and extra validations.
627 config DEBUG_VM_PGFLAGS
628 bool "Debug page-flags operations"
631 Enables extra validation on page flags operations.
635 config ARCH_HAS_DEBUG_VIRTUAL
639 bool "Debug VM translations"
640 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
642 Enable some costly sanity checks in virtual to page code. This can
643 catch mistakes with virt_to_page() and friends.
647 config DEBUG_NOMMU_REGIONS
648 bool "Debug the global anon/private NOMMU mapping region tree"
649 depends on DEBUG_KERNEL && !MMU
651 This option causes the global tree of anonymous and private mapping
652 regions to be regularly checked for invalid topology.
654 config DEBUG_MEMORY_INIT
655 bool "Debug memory initialisation" if EXPERT
658 Enable this for additional checks during memory initialisation.
659 The sanity checks verify aspects of the VM such as the memory model
660 and other information provided by the architecture. Verbose
661 information will be printed at KERN_DEBUG loglevel depending
662 on the mminit_loglevel= command-line option.
666 config MEMORY_NOTIFIER_ERROR_INJECT
667 tristate "Memory hotplug notifier error injection module"
668 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
670 This option provides the ability to inject artificial errors to
671 memory hotplug notifier chain callbacks. It is controlled through
672 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
674 If the notifier call chain should be failed with some events
675 notified, write the error code to "actions/<notifier event>/error".
677 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
679 # cd /sys/kernel/debug/notifier-error-inject/memory
680 # echo -12 > actions/MEM_GOING_OFFLINE/error
681 # echo offline > /sys/devices/system/memory/memoryXXX/state
682 bash: echo: write error: Cannot allocate memory
684 To compile this code as a module, choose M here: the module will
685 be called memory-notifier-error-inject.
689 config DEBUG_PER_CPU_MAPS
690 bool "Debug access to per_cpu maps"
691 depends on DEBUG_KERNEL
694 Say Y to verify that the per_cpu map being accessed has
695 been set up. This adds a fair amount of code to kernel memory
696 and decreases performance.
701 bool "Highmem debugging"
702 depends on DEBUG_KERNEL && HIGHMEM
704 This option enables additional error checking for high memory
705 systems. Disable for production systems.
707 config HAVE_DEBUG_STACKOVERFLOW
710 config DEBUG_STACKOVERFLOW
711 bool "Check for stack overflows"
712 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
714 Say Y here if you want to check for overflows of kernel, IRQ
715 and exception stacks (if your architecture uses them). This
716 option will show detailed messages if free stack space drops
717 below a certain limit.
719 These kinds of bugs usually occur when call-chains in the
720 kernel get too deep, especially when interrupts are
723 Use this in cases where you see apparently random memory
724 corruption, especially if it appears in 'struct thread_info'
726 If in doubt, say "N".
728 source "lib/Kconfig.kmemcheck"
730 source "lib/Kconfig.kasan"
732 config DEBUG_REFCOUNT
733 bool "Verbose refcount checks"
735 Say Y here if you want reference counters (refcount_t and kref) to
736 generate WARNs on dubious usage. Without this refcount_t will still
737 be a saturating counter and avoid Use-After-Free by turning it into
738 a resource leak Denial-Of-Service.
740 Use of this option will increase kernel text size but will alert the
741 admin of potential abuse.
743 If in doubt, say "N".
745 endmenu # "Memory Debugging"
750 KCOV does not have any arch-specific code, but currently it is enabled
751 only for x86_64. KCOV requires testing on other archs, and most likely
752 disabling of instrumentation for some early boot code.
755 bool "Code coverage for fuzzing"
756 depends on ARCH_HAS_KCOV
758 select GCC_PLUGINS if !COMPILE_TEST
759 select GCC_PLUGIN_SANCOV if !COMPILE_TEST
761 KCOV exposes kernel code coverage information in a form suitable
762 for coverage-guided fuzzing (randomized testing).
764 If RANDOMIZE_BASE is enabled, PC values will not be stable across
765 different machines and across reboots. If you need stable PC values,
766 disable RANDOMIZE_BASE.
768 For more details, see Documentation/dev-tools/kcov.rst.
770 config KCOV_INSTRUMENT_ALL
771 bool "Instrument all code by default"
775 If you are doing generic system call fuzzing (like e.g. syzkaller),
776 then you will want to instrument the whole kernel and you should
777 say y here. If you are doing more targeted fuzzing (like e.g.
778 filesystem fuzzing with AFL) then you will want to enable coverage
779 for more specific subsets of files, and should say n here.
782 bool "Debug shared IRQ handlers"
783 depends on DEBUG_KERNEL
785 Enable this to generate a spurious interrupt as soon as a shared
786 interrupt handler is registered, and just before one is deregistered.
787 Drivers ought to be able to handle interrupts coming in at those
788 points; some don't and need to be caught.
790 menu "Debug Lockups and Hangs"
792 config LOCKUP_DETECTOR
793 bool "Detect Hard and Soft Lockups"
794 depends on DEBUG_KERNEL && !S390
796 Say Y here to enable the kernel to act as a watchdog to detect
797 hard and soft lockups.
799 Softlockups are bugs that cause the kernel to loop in kernel
800 mode for more than 20 seconds, without giving other tasks a
801 chance to run. The current stack trace is displayed upon
802 detection and the system will stay locked up.
804 Hardlockups are bugs that cause the CPU to loop in kernel mode
805 for more than 10 seconds, without letting other interrupts have a
806 chance to run. The current stack trace is displayed upon detection
807 and the system will stay locked up.
809 The overhead should be minimal. A periodic hrtimer runs to
810 generate interrupts and kick the watchdog task every 4 seconds.
811 An NMI is generated every 10 seconds or so to check for hardlockups.
813 The frequency of hrtimer and NMI events and the soft and hard lockup
814 thresholds can be controlled through the sysctl watchdog_thresh.
816 config HARDLOCKUP_DETECTOR
818 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
819 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
821 config BOOTPARAM_HARDLOCKUP_PANIC
822 bool "Panic (Reboot) On Hard Lockups"
823 depends on HARDLOCKUP_DETECTOR
825 Say Y here to enable the kernel to panic on "hard lockups",
826 which are bugs that cause the kernel to loop in kernel
827 mode with interrupts disabled for more than 10 seconds (configurable
828 using the watchdog_thresh sysctl).
832 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
834 depends on HARDLOCKUP_DETECTOR
836 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
837 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
839 config BOOTPARAM_SOFTLOCKUP_PANIC
840 bool "Panic (Reboot) On Soft Lockups"
841 depends on LOCKUP_DETECTOR
843 Say Y here to enable the kernel to panic on "soft lockups",
844 which are bugs that cause the kernel to loop in kernel
845 mode for more than 20 seconds (configurable using the watchdog_thresh
846 sysctl), without giving other tasks a chance to run.
848 The panic can be used in combination with panic_timeout,
849 to cause the system to reboot automatically after a
850 lockup has been detected. This feature is useful for
851 high-availability systems that have uptime guarantees and
852 where a lockup must be resolved ASAP.
856 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
858 depends on LOCKUP_DETECTOR
860 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
861 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
863 config DETECT_HUNG_TASK
864 bool "Detect Hung Tasks"
865 depends on DEBUG_KERNEL
866 default LOCKUP_DETECTOR
868 Say Y here to enable the kernel to detect "hung tasks",
869 which are bugs that cause the task to be stuck in
870 uninterruptible "D" state indefinitely.
872 When a hung task is detected, the kernel will print the
873 current stack trace (which you should report), but the
874 task will stay in uninterruptible state. If lockdep is
875 enabled then all held locks will also be reported. This
876 feature has negligible overhead.
878 config DEFAULT_HUNG_TASK_TIMEOUT
879 int "Default timeout for hung task detection (in seconds)"
880 depends on DETECT_HUNG_TASK
883 This option controls the default timeout (in seconds) used
884 to determine when a task has become non-responsive and should
887 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
888 sysctl or by writing a value to
889 /proc/sys/kernel/hung_task_timeout_secs.
891 A timeout of 0 disables the check. The default is two minutes.
892 Keeping the default should be fine in most cases.
894 config BOOTPARAM_HUNG_TASK_PANIC
895 bool "Panic (Reboot) On Hung Tasks"
896 depends on DETECT_HUNG_TASK
898 Say Y here to enable the kernel to panic on "hung tasks",
899 which are bugs that cause the kernel to leave a task stuck
900 in uninterruptible "D" state.
902 The panic can be used in combination with panic_timeout,
903 to cause the system to reboot automatically after a
904 hung task has been detected. This feature is useful for
905 high-availability systems that have uptime guarantees and
906 where a hung tasks must be resolved ASAP.
910 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
912 depends on DETECT_HUNG_TASK
914 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
915 default 1 if BOOTPARAM_HUNG_TASK_PANIC
918 bool "Detect Workqueue Stalls"
919 depends on DEBUG_KERNEL
921 Say Y here to enable stall detection on workqueues. If a
922 worker pool doesn't make forward progress on a pending work
923 item for over a given amount of time, 30s by default, a
924 warning message is printed along with dump of workqueue
925 state. This can be configured through kernel parameter
926 "workqueue.watchdog_thresh" and its sysfs counterpart.
928 endmenu # "Debug lockups and hangs"
933 Say Y here to enable the kernel to panic when it oopses. This
934 has the same effect as setting oops=panic on the kernel command
937 This feature is useful to ensure that the kernel does not do
938 anything erroneous after an oops which could result in data
939 corruption or other issues.
943 config PANIC_ON_OOPS_VALUE
946 default 0 if !PANIC_ON_OOPS
947 default 1 if PANIC_ON_OOPS
953 Set the timeout value (in seconds) until a reboot occurs when the
954 the kernel panics. If n = 0, then we wait forever. A timeout
955 value n > 0 will wait n seconds before rebooting, while a timeout
956 value n < 0 will reboot immediately.
959 bool "Collect scheduler debugging info"
960 depends on DEBUG_KERNEL && PROC_FS
963 If you say Y here, the /proc/sched_debug file will be provided
964 that can help debug the scheduler. The runtime overhead of this
972 bool "Collect scheduler statistics"
973 depends on DEBUG_KERNEL && PROC_FS
976 If you say Y here, additional code will be inserted into the
977 scheduler and related routines to collect statistics about
978 scheduler behavior and provide them in /proc/schedstat. These
979 stats may be useful for both tuning and debugging the scheduler
980 If you aren't debugging the scheduler or trying to tune a specific
981 application, you can say N to avoid the very slight overhead
984 config SCHED_STACK_END_CHECK
985 bool "Detect stack corruption on calls to schedule()"
986 depends on DEBUG_KERNEL
989 This option checks for a stack overrun on calls to schedule().
990 If the stack end location is found to be over written always panic as
991 the content of the corrupted region can no longer be trusted.
992 This is to ensure no erroneous behaviour occurs which could result in
993 data corruption or a sporadic crash at a later stage once the region
994 is examined. The runtime overhead introduced is minimal.
996 config DEBUG_TIMEKEEPING
997 bool "Enable extra timekeeping sanity checking"
999 This option will enable additional timekeeping sanity checks
1000 which may be helpful when diagnosing issues where timekeeping
1001 problems are suspected.
1003 This may include checks in the timekeeping hotpaths, so this
1004 option may have a (very small) performance impact to some
1009 config DEBUG_PREEMPT
1010 bool "Debug preemptible kernel"
1011 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1014 If you say Y here then the kernel will use a debug variant of the
1015 commonly used smp_processor_id() function and will print warnings
1016 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1017 will detect preemption count underflows.
1019 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1021 config DEBUG_RT_MUTEXES
1022 bool "RT Mutex debugging, deadlock detection"
1023 depends on DEBUG_KERNEL && RT_MUTEXES
1025 This allows rt mutex semantics violations and rt mutex related
1026 deadlocks (lockups) to be detected and reported automatically.
1028 config DEBUG_SPINLOCK
1029 bool "Spinlock and rw-lock debugging: basic checks"
1030 depends on DEBUG_KERNEL
1031 select UNINLINE_SPIN_UNLOCK
1033 Say Y here and build SMP to catch missing spinlock initialization
1034 and certain other kinds of spinlock errors commonly made. This is
1035 best used in conjunction with the NMI watchdog so that spinlock
1036 deadlocks are also debuggable.
1038 config DEBUG_MUTEXES
1039 bool "Mutex debugging: basic checks"
1040 depends on DEBUG_KERNEL
1042 This feature allows mutex semantics violations to be detected and
1045 config DEBUG_WW_MUTEX_SLOWPATH
1046 bool "Wait/wound mutex debugging: Slowpath testing"
1047 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1048 select DEBUG_LOCK_ALLOC
1049 select DEBUG_SPINLOCK
1050 select DEBUG_MUTEXES
1052 This feature enables slowpath testing for w/w mutex users by
1053 injecting additional -EDEADLK wound/backoff cases. Together with
1054 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1055 will test all possible w/w mutex interface abuse with the
1056 exception of simply not acquiring all the required locks.
1057 Note that this feature can introduce significant overhead, so
1058 it really should not be enabled in a production or distro kernel,
1059 even a debug kernel. If you are a driver writer, enable it. If
1060 you are a distro, do not.
1062 config DEBUG_LOCK_ALLOC
1063 bool "Lock debugging: detect incorrect freeing of live locks"
1064 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1065 select DEBUG_SPINLOCK
1066 select DEBUG_MUTEXES
1069 This feature will check whether any held lock (spinlock, rwlock,
1070 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1071 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1072 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1073 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1074 held during task exit.
1076 config PROVE_LOCKING
1077 bool "Lock debugging: prove locking correctness"
1078 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1080 select DEBUG_SPINLOCK
1081 select DEBUG_MUTEXES
1082 select DEBUG_LOCK_ALLOC
1083 select TRACE_IRQFLAGS
1086 This feature enables the kernel to prove that all locking
1087 that occurs in the kernel runtime is mathematically
1088 correct: that under no circumstance could an arbitrary (and
1089 not yet triggered) combination of observed locking
1090 sequences (on an arbitrary number of CPUs, running an
1091 arbitrary number of tasks and interrupt contexts) cause a
1094 In short, this feature enables the kernel to report locking
1095 related deadlocks before they actually occur.
1097 The proof does not depend on how hard and complex a
1098 deadlock scenario would be to trigger: how many
1099 participant CPUs, tasks and irq-contexts would be needed
1100 for it to trigger. The proof also does not depend on
1101 timing: if a race and a resulting deadlock is possible
1102 theoretically (no matter how unlikely the race scenario
1103 is), it will be proven so and will immediately be
1104 reported by the kernel (once the event is observed that
1105 makes the deadlock theoretically possible).
1107 If a deadlock is impossible (i.e. the locking rules, as
1108 observed by the kernel, are mathematically correct), the
1109 kernel reports nothing.
1111 NOTE: this feature can also be enabled for rwlocks, mutexes
1112 and rwsems - in which case all dependencies between these
1113 different locking variants are observed and mapped too, and
1114 the proof of observed correctness is also maintained for an
1115 arbitrary combination of these separate locking variants.
1117 For more details, see Documentation/locking/lockdep-design.txt.
1119 config PROVE_LOCKING_SMALL
1124 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1126 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
1131 bool "Lock usage statistics"
1132 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1134 select DEBUG_SPINLOCK
1135 select DEBUG_MUTEXES
1136 select DEBUG_LOCK_ALLOC
1139 This feature enables tracking lock contention points
1141 For more details, see Documentation/locking/lockstat.txt
1143 This also enables lock events required by "perf lock",
1145 If you want to use "perf lock", you also need to turn on
1146 CONFIG_EVENT_TRACING.
1148 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1149 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1151 config DEBUG_LOCKDEP
1152 bool "Lock dependency engine debugging"
1153 depends on DEBUG_KERNEL && LOCKDEP
1155 If you say Y here, the lock dependency engine will do
1156 additional runtime checks to debug itself, at the price
1157 of more runtime overhead.
1159 config DEBUG_ATOMIC_SLEEP
1160 bool "Sleep inside atomic section checking"
1161 select PREEMPT_COUNT
1162 depends on DEBUG_KERNEL
1164 If you say Y here, various routines which may sleep will become very
1165 noisy if they are called inside atomic sections: when a spinlock is
1166 held, inside an rcu read side critical section, inside preempt disabled
1167 sections, inside an interrupt, etc...
1169 config DEBUG_LOCKING_API_SELFTESTS
1170 bool "Locking API boot-time self-tests"
1171 depends on DEBUG_KERNEL
1173 Say Y here if you want the kernel to run a short self-test during
1174 bootup. The self-test checks whether common types of locking bugs
1175 are detected by debugging mechanisms or not. (if you disable
1176 lock debugging then those bugs wont be detected of course.)
1177 The following locking APIs are covered: spinlocks, rwlocks,
1180 config LOCK_TORTURE_TEST
1181 tristate "torture tests for locking"
1182 depends on DEBUG_KERNEL
1186 This option provides a kernel module that runs torture tests
1187 on kernel locking primitives. The kernel module may be built
1188 after the fact on the running kernel to be tested, if desired.
1190 Say Y here if you want kernel locking-primitive torture tests
1191 to be built into the kernel.
1192 Say M if you want these torture tests to build as a module.
1193 Say N if you are unsure.
1195 config WW_MUTEX_SELFTEST
1196 tristate "Wait/wound mutex selftests"
1198 This option provides a kernel module that runs tests on the
1199 on the struct ww_mutex locking API.
1201 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1202 with this test harness.
1204 Say M if you want these self tests to build as a module.
1205 Say N if you are unsure.
1207 endmenu # lock debugging
1209 config TRACE_IRQFLAGS
1212 Enables hooks to interrupt enabling and disabling for
1213 either tracing or lock debugging.
1216 bool "Stack backtrace support"
1217 depends on STACKTRACE_SUPPORT
1219 This option causes the kernel to create a /proc/pid/stack for
1220 every process, showing its current stack trace.
1221 It is also used by various kernel debugging features that require
1222 stack trace generation.
1224 config DEBUG_KOBJECT
1225 bool "kobject debugging"
1226 depends on DEBUG_KERNEL
1228 If you say Y here, some extra kobject debugging messages will be sent
1231 config DEBUG_KOBJECT_RELEASE
1232 bool "kobject release debugging"
1233 depends on DEBUG_OBJECTS_TIMERS
1235 kobjects are reference counted objects. This means that their
1236 last reference count put is not predictable, and the kobject can
1237 live on past the point at which a driver decides to drop it's
1238 initial reference to the kobject gained on allocation. An
1239 example of this would be a struct device which has just been
1242 However, some buggy drivers assume that after such an operation,
1243 the memory backing the kobject can be immediately freed. This
1244 goes completely against the principles of a refcounted object.
1246 If you say Y here, the kernel will delay the release of kobjects
1247 on the last reference count to improve the visibility of this
1248 kind of kobject release bug.
1250 config HAVE_DEBUG_BUGVERBOSE
1253 config DEBUG_BUGVERBOSE
1254 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1255 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1258 Say Y here to make BUG() panics output the file name and line number
1259 of the BUG call as well as the EIP and oops trace. This aids
1260 debugging but costs about 70-100K of memory.
1263 bool "Debug linked list manipulation"
1264 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1266 Enable this to turn on extended checks in the linked-list
1271 config DEBUG_PI_LIST
1272 bool "Debug priority linked list manipulation"
1273 depends on DEBUG_KERNEL
1275 Enable this to turn on extended checks in the priority-ordered
1276 linked-list (plist) walking routines. This checks the entire
1277 list multiple times during each manipulation.
1282 bool "Debug SG table operations"
1283 depends on DEBUG_KERNEL
1285 Enable this to turn on checks on scatter-gather tables. This can
1286 help find problems with drivers that do not properly initialize
1291 config DEBUG_NOTIFIERS
1292 bool "Debug notifier call chains"
1293 depends on DEBUG_KERNEL
1295 Enable this to turn on sanity checking for notifier call chains.
1296 This is most useful for kernel developers to make sure that
1297 modules properly unregister themselves from notifier chains.
1298 This is a relatively cheap check but if you care about maximum
1301 config DEBUG_CREDENTIALS
1302 bool "Debug credential management"
1303 depends on DEBUG_KERNEL
1305 Enable this to turn on some debug checking for credential
1306 management. The additional code keeps track of the number of
1307 pointers from task_structs to any given cred struct, and checks to
1308 see that this number never exceeds the usage count of the cred
1311 Furthermore, if SELinux is enabled, this also checks that the
1312 security pointer in the cred struct is never seen to be invalid.
1316 menu "RCU Debugging"
1319 def_bool PROVE_LOCKING
1321 config PROVE_RCU_REPEATEDLY
1322 bool "RCU debugging: don't disable PROVE_RCU on first splat"
1323 depends on PROVE_RCU
1326 By itself, PROVE_RCU will disable checking upon issuing the
1327 first warning (or "splat"). This feature prevents such
1328 disabling, allowing multiple RCU-lockdep warnings to be printed
1331 Say Y to allow multiple RCU-lockdep warnings per boot.
1333 Say N if you are unsure.
1335 config SPARSE_RCU_POINTER
1336 bool "RCU debugging: sparse-based checks for pointer usage"
1339 This feature enables the __rcu sparse annotation for
1340 RCU-protected pointers. This annotation will cause sparse
1341 to flag any non-RCU used of annotated pointers. This can be
1342 helpful when debugging RCU usage. Please note that this feature
1343 is not intended to enforce code cleanliness; it is instead merely
1346 Say Y to make sparse flag questionable use of RCU-protected pointers
1348 Say N if you are unsure.
1354 config RCU_PERF_TEST
1355 tristate "performance tests for RCU"
1356 depends on DEBUG_KERNEL
1362 This option provides a kernel module that runs performance
1363 tests on the RCU infrastructure. The kernel module may be built
1364 after the fact on the running kernel to be tested, if desired.
1366 Say Y here if you want RCU performance tests to be built into
1368 Say M if you want the RCU performance tests to build as a module.
1369 Say N if you are unsure.
1371 config RCU_TORTURE_TEST
1372 tristate "torture tests for RCU"
1373 depends on DEBUG_KERNEL
1379 This option provides a kernel module that runs torture tests
1380 on the RCU infrastructure. The kernel module may be built
1381 after the fact on the running kernel to be tested, if desired.
1383 Say Y here if you want RCU torture tests to be built into
1385 Say M if you want the RCU torture tests to build as a module.
1386 Say N if you are unsure.
1388 config RCU_TORTURE_TEST_SLOW_PREINIT
1389 bool "Slow down RCU grace-period pre-initialization to expose races"
1390 depends on RCU_TORTURE_TEST
1392 This option delays grace-period pre-initialization (the
1393 propagation of CPU-hotplug changes up the rcu_node combining
1394 tree) for a few jiffies between initializing each pair of
1395 consecutive rcu_node structures. This helps to expose races
1396 involving grace-period pre-initialization, in other words, it
1397 makes your kernel less stable. It can also greatly increase
1398 grace-period latency, especially on systems with large numbers
1399 of CPUs. This is useful when torture-testing RCU, but in
1400 almost no other circumstance.
1402 Say Y here if you want your system to crash and hang more often.
1403 Say N if you want a sane system.
1405 config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
1406 int "How much to slow down RCU grace-period pre-initialization"
1409 depends on RCU_TORTURE_TEST_SLOW_PREINIT
1411 This option specifies the number of jiffies to wait between
1412 each rcu_node structure pre-initialization step.
1414 config RCU_TORTURE_TEST_SLOW_INIT
1415 bool "Slow down RCU grace-period initialization to expose races"
1416 depends on RCU_TORTURE_TEST
1418 This option delays grace-period initialization for a few
1419 jiffies between initializing each pair of consecutive
1420 rcu_node structures. This helps to expose races involving
1421 grace-period initialization, in other words, it makes your
1422 kernel less stable. It can also greatly increase grace-period
1423 latency, especially on systems with large numbers of CPUs.
1424 This is useful when torture-testing RCU, but in almost no
1427 Say Y here if you want your system to crash and hang more often.
1428 Say N if you want a sane system.
1430 config RCU_TORTURE_TEST_SLOW_INIT_DELAY
1431 int "How much to slow down RCU grace-period initialization"
1434 depends on RCU_TORTURE_TEST_SLOW_INIT
1436 This option specifies the number of jiffies to wait between
1437 each rcu_node structure initialization.
1439 config RCU_TORTURE_TEST_SLOW_CLEANUP
1440 bool "Slow down RCU grace-period cleanup to expose races"
1441 depends on RCU_TORTURE_TEST
1443 This option delays grace-period cleanup for a few jiffies
1444 between cleaning up each pair of consecutive rcu_node
1445 structures. This helps to expose races involving grace-period
1446 cleanup, in other words, it makes your kernel less stable.
1447 It can also greatly increase grace-period latency, especially
1448 on systems with large numbers of CPUs. This is useful when
1449 torture-testing RCU, but in almost no other circumstance.
1451 Say Y here if you want your system to crash and hang more often.
1452 Say N if you want a sane system.
1454 config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
1455 int "How much to slow down RCU grace-period cleanup"
1458 depends on RCU_TORTURE_TEST_SLOW_CLEANUP
1460 This option specifies the number of jiffies to wait between
1461 each rcu_node structure cleanup operation.
1463 config RCU_CPU_STALL_TIMEOUT
1464 int "RCU CPU stall timeout in seconds"
1465 depends on RCU_STALL_COMMON
1469 If a given RCU grace period extends more than the specified
1470 number of seconds, a CPU stall warning is printed. If the
1471 RCU grace period persists, additional CPU stall warnings are
1472 printed at more widely spaced intervals.
1475 bool "Enable tracing for RCU"
1476 depends on DEBUG_KERNEL
1477 default y if TREE_RCU
1480 This option provides tracing in RCU which presents stats
1481 in debugfs for debugging RCU implementation. It also enables
1482 additional tracepoints for ftrace-style event tracing.
1484 Say Y here if you want to enable RCU tracing
1485 Say N if you are unsure.
1487 config RCU_EQS_DEBUG
1488 bool "Provide debugging asserts for adding NO_HZ support to an arch"
1489 depends on DEBUG_KERNEL
1491 This option provides consistency checks in RCU's handling of
1492 NO_HZ. These checks have proven quite helpful in detecting
1493 bugs in arch-specific NO_HZ code.
1495 Say N here if you need ultimate kernel/user switch latencies
1496 Say Y if you are unsure
1498 endmenu # "RCU Debugging"
1500 config DEBUG_WQ_FORCE_RR_CPU
1501 bool "Force round-robin CPU selection for unbound work items"
1502 depends on DEBUG_KERNEL
1505 Workqueue used to implicitly guarantee that work items queued
1506 without explicit CPU specified are put on the local CPU. This
1507 guarantee is no longer true and while local CPU is still
1508 preferred work items may be put on foreign CPUs. Kernel
1509 parameter "workqueue.debug_force_rr_cpu" is added to force
1510 round-robin CPU selection to flush out usages which depend on the
1511 now broken guarantee. This config option enables the debug
1512 feature by default. When enabled, memory and cache locality will
1515 config DEBUG_BLOCK_EXT_DEVT
1516 bool "Force extended block device numbers and spread them"
1517 depends on DEBUG_KERNEL
1521 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1522 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1523 YOU ARE DOING. Distros, please enable this and fix whatever
1526 Conventionally, block device numbers are allocated from
1527 predetermined contiguous area. However, extended block area
1528 may introduce non-contiguous block device numbers. This
1529 option forces most block device numbers to be allocated from
1530 the extended space and spreads them to discover kernel or
1531 userland code paths which assume predetermined contiguous
1532 device number allocation.
1534 Note that turning on this debug option shuffles all the
1535 device numbers for all IDE and SCSI devices including libata
1536 ones, so root partition specified using device number
1537 directly (via rdev or root=MAJ:MIN) won't work anymore.
1538 Textual device names (root=/dev/sdXn) will continue to work.
1540 Say N if you are unsure.
1542 config CPU_HOTPLUG_STATE_CONTROL
1543 bool "Enable CPU hotplug state control"
1544 depends on DEBUG_KERNEL
1545 depends on HOTPLUG_CPU
1548 Allows to write steps between "offline" and "online" to the CPUs
1549 sysfs target file so states can be stepped granular. This is a debug
1550 option for now as the hotplug machinery cannot be stopped and
1551 restarted at arbitrary points yet.
1553 Say N if your are unsure.
1555 config NOTIFIER_ERROR_INJECTION
1556 tristate "Notifier error injection"
1557 depends on DEBUG_KERNEL
1560 This option provides the ability to inject artificial errors to
1561 specified notifier chain callbacks. It is useful to test the error
1562 handling of notifier call chain failures.
1566 config PM_NOTIFIER_ERROR_INJECT
1567 tristate "PM notifier error injection module"
1568 depends on PM && NOTIFIER_ERROR_INJECTION
1569 default m if PM_DEBUG
1571 This option provides the ability to inject artificial errors to
1572 PM notifier chain callbacks. It is controlled through debugfs
1573 interface /sys/kernel/debug/notifier-error-inject/pm
1575 If the notifier call chain should be failed with some events
1576 notified, write the error code to "actions/<notifier event>/error".
1578 Example: Inject PM suspend error (-12 = -ENOMEM)
1580 # cd /sys/kernel/debug/notifier-error-inject/pm/
1581 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1582 # echo mem > /sys/power/state
1583 bash: echo: write error: Cannot allocate memory
1585 To compile this code as a module, choose M here: the module will
1586 be called pm-notifier-error-inject.
1590 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1591 tristate "OF reconfig notifier error injection module"
1592 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1594 This option provides the ability to inject artificial errors to
1595 OF reconfig notifier chain callbacks. It is controlled
1596 through debugfs interface under
1597 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1599 If the notifier call chain should be failed with some events
1600 notified, write the error code to "actions/<notifier event>/error".
1602 To compile this code as a module, choose M here: the module will
1603 be called of-reconfig-notifier-error-inject.
1607 config NETDEV_NOTIFIER_ERROR_INJECT
1608 tristate "Netdev notifier error injection module"
1609 depends on NET && NOTIFIER_ERROR_INJECTION
1611 This option provides the ability to inject artificial errors to
1612 netdevice notifier chain callbacks. It is controlled through debugfs
1613 interface /sys/kernel/debug/notifier-error-inject/netdev
1615 If the notifier call chain should be failed with some events
1616 notified, write the error code to "actions/<notifier event>/error".
1618 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1620 # cd /sys/kernel/debug/notifier-error-inject/netdev
1621 # echo -22 > actions/NETDEV_CHANGEMTU/error
1622 # ip link set eth0 mtu 1024
1623 RTNETLINK answers: Invalid argument
1625 To compile this code as a module, choose M here: the module will
1626 be called netdev-notifier-error-inject.
1630 config FAULT_INJECTION
1631 bool "Fault-injection framework"
1632 depends on DEBUG_KERNEL
1634 Provide fault-injection framework.
1635 For more details, see Documentation/fault-injection/.
1638 bool "Fault-injection capability for kmalloc"
1639 depends on FAULT_INJECTION
1640 depends on SLAB || SLUB
1642 Provide fault-injection capability for kmalloc.
1644 config FAIL_PAGE_ALLOC
1645 bool "Fault-injection capabilitiy for alloc_pages()"
1646 depends on FAULT_INJECTION
1648 Provide fault-injection capability for alloc_pages().
1650 config FAIL_MAKE_REQUEST
1651 bool "Fault-injection capability for disk IO"
1652 depends on FAULT_INJECTION && BLOCK
1654 Provide fault-injection capability for disk IO.
1656 config FAIL_IO_TIMEOUT
1657 bool "Fault-injection capability for faking disk interrupts"
1658 depends on FAULT_INJECTION && BLOCK
1660 Provide fault-injection capability on end IO handling. This
1661 will make the block layer "forget" an interrupt as configured,
1662 thus exercising the error handling.
1664 Only works with drivers that use the generic timeout handling,
1665 for others it wont do anything.
1667 config FAIL_MMC_REQUEST
1668 bool "Fault-injection capability for MMC IO"
1669 depends on FAULT_INJECTION_DEBUG_FS && MMC
1671 Provide fault-injection capability for MMC IO.
1672 This will make the mmc core return data errors. This is
1673 useful to test the error handling in the mmc block device
1674 and to test how the mmc host driver handles retries from
1678 bool "Fault-injection capability for futexes"
1680 depends on FAULT_INJECTION && FUTEX
1682 Provide fault-injection capability for futexes.
1684 config FAULT_INJECTION_DEBUG_FS
1685 bool "Debugfs entries for fault-injection capabilities"
1686 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1688 Enable configuration of fault-injection capabilities via debugfs.
1690 config FAULT_INJECTION_STACKTRACE_FILTER
1691 bool "stacktrace filter for fault-injection capabilities"
1692 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1695 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1697 Provide stacktrace filter for fault-injection capabilities
1700 bool "Latency measuring infrastructure"
1701 depends on DEBUG_KERNEL
1702 depends on STACKTRACE_SUPPORT
1704 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1711 Enable this option if you want to use the LatencyTOP tool
1712 to find out which userspace is blocking on what kernel operations.
1714 source kernel/trace/Kconfig
1716 menu "Runtime Testing"
1719 tristate "Linux Kernel Dump Test Tool Module"
1724 This module enables testing of the different dumping mechanisms by
1725 inducing system failures at predefined crash points.
1726 If you don't need it: say N
1727 Choose M here to compile this code as a module. The module will be
1730 Documentation on how to use the module can be found in
1731 Documentation/fault-injection/provoke-crashes.txt
1733 config TEST_LIST_SORT
1734 bool "Linked list sorting test"
1735 depends on DEBUG_KERNEL
1737 Enable this to turn on 'list_sort()' function test. This test is
1738 executed only once during system boot, so affects only boot time.
1742 config KPROBES_SANITY_TEST
1743 bool "Kprobes sanity tests"
1744 depends on DEBUG_KERNEL
1748 This option provides for testing basic kprobes functionality on
1749 boot. A sample kprobe, jprobe and kretprobe are inserted and
1750 verified for functionality.
1752 Say N if you are unsure.
1754 config BACKTRACE_SELF_TEST
1755 tristate "Self test for the backtrace code"
1756 depends on DEBUG_KERNEL
1759 This option provides a kernel module that can be used to test
1760 the kernel stack backtrace code. This option is not useful
1761 for distributions or general kernels, but only for kernel
1762 developers working on architecture code.
1764 Note that if you want to also test saved backtraces, you will
1765 have to enable STACKTRACE as well.
1767 Say N if you are unsure.
1770 tristate "Red-Black tree test"
1771 depends on DEBUG_KERNEL
1773 A benchmark measuring the performance of the rbtree library.
1774 Also includes rbtree invariant checks.
1776 config INTERVAL_TREE_TEST
1777 tristate "Interval tree test"
1778 depends on m && DEBUG_KERNEL
1779 select INTERVAL_TREE
1781 A benchmark measuring the performance of the interval tree library
1784 tristate "Per cpu operations test"
1785 depends on m && DEBUG_KERNEL
1787 Enable this option to build test module which validates per-cpu
1792 config ATOMIC64_SELFTEST
1793 bool "Perform an atomic64_t self-test at boot"
1795 Enable this option to test the atomic64_t functions at boot.
1799 config ASYNC_RAID6_TEST
1800 tristate "Self test for hardware accelerated raid6 recovery"
1801 depends on ASYNC_RAID6_RECOV
1804 This is a one-shot self test that permutes through the
1805 recovery of all the possible two disk failure scenarios for a
1806 N-disk array. Recovery is performed with the asynchronous
1807 raid6 recovery routines, and will optionally use an offload
1808 engine if one is available.
1813 tristate "Test functions located in the hexdump module at runtime"
1815 config TEST_STRING_HELPERS
1816 tristate "Test functions located in the string_helpers module at runtime"
1819 tristate "Test kstrto*() family of functions at runtime"
1822 tristate "Test printf() family of functions at runtime"
1825 tristate "Test bitmap_*() family of functions at runtime"
1828 Enable this option to test the bitmap functions at boot.
1833 tristate "Test functions located in the uuid module at runtime"
1835 config TEST_RHASHTABLE
1836 tristate "Perform selftest on resizable hash table"
1839 Enable this option to test the rhashtable functions at boot.
1844 tristate "Perform selftest on hash functions"
1847 Enable this option to test the kernel's integer (<linux/hash.h>),
1848 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1849 hash functions on boot (or module load).
1851 This is intended to help people writing architecture-specific
1852 optimized versions. If unsure, say N.
1855 tristate "Perform selftest on priority array manager"
1859 Enable this option to test priority array manager on boot
1864 endmenu # runtime tests
1866 config PROVIDE_OHCI1394_DMA_INIT
1867 bool "Remote debugging over FireWire early on boot"
1868 depends on PCI && X86
1870 If you want to debug problems which hang or crash the kernel early
1871 on boot and the crashing machine has a FireWire port, you can use
1872 this feature to remotely access the memory of the crashed machine
1873 over FireWire. This employs remote DMA as part of the OHCI1394
1874 specification which is now the standard for FireWire controllers.
1876 With remote DMA, you can monitor the printk buffer remotely using
1877 firescope and access all memory below 4GB using fireproxy from gdb.
1878 Even controlling a kernel debugger is possible using remote DMA.
1882 If ohci1394_dma=early is used as boot parameter, it will initialize
1883 all OHCI1394 controllers which are found in the PCI config space.
1885 As all changes to the FireWire bus such as enabling and disabling
1886 devices cause a bus reset and thereby disable remote DMA for all
1887 devices, be sure to have the cable plugged and FireWire enabled on
1888 the debugging host before booting the debug target for debugging.
1890 This code (~1k) is freed after boot. By then, the firewire stack
1891 in charge of the OHCI-1394 controllers should be used instead.
1893 See Documentation/debugging-via-ohci1394.txt for more information.
1895 config DMA_API_DEBUG
1896 bool "Enable debugging of DMA-API usage"
1897 depends on HAVE_DMA_API_DEBUG
1899 Enable this option to debug the use of the DMA API by device drivers.
1900 With this option you will be able to detect common bugs in device
1901 drivers like double-freeing of DMA mappings or freeing mappings that
1902 were never allocated.
1904 This also attempts to catch cases where a page owned by DMA is
1905 accessed by the cpu in a way that could cause data corruption. For
1906 example, this enables cow_user_page() to check that the source page is
1909 This option causes a performance degradation. Use only if you want to
1910 debug device drivers and dma interactions.
1915 tristate "Test module loading with 'hello world' module"
1919 This builds the "test_module" module that emits "Hello, world"
1920 on printk when loaded. It is designed to be used for basic
1921 evaluation of the module loading subsystem (for example when
1922 validating module verification). It lacks any extra dependencies,
1923 and will not normally be loaded by the system unless explicitly
1928 config TEST_USER_COPY
1929 tristate "Test user/kernel boundary protections"
1933 This builds the "test_user_copy" module that runs sanity checks
1934 on the copy_to/from_user infrastructure, making sure basic
1935 user/kernel boundary testing is working. If it fails to load,
1936 a regression has been detected in the user/kernel memory boundary
1942 tristate "Test BPF filter functionality"
1946 This builds the "test_bpf" module that runs various test vectors
1947 against the BPF interpreter or BPF JIT compiler depending on the
1948 current setting. This is in particular useful for BPF JIT compiler
1949 development, but also to run regression tests against changes in
1950 the interpreter code. It also enables test stubs for eBPF maps and
1951 verifier used by user space verifier testsuite.
1955 config TEST_FIRMWARE
1956 tristate "Test firmware loading via userspace interface"
1958 depends on FW_LOADER
1960 This builds the "test_firmware" module that creates a userspace
1961 interface for testing firmware loading. This can be used to
1962 control the triggering of firmware loading without needing an
1963 actual firmware-using device. The contents can be rechecked by
1969 tristate "udelay test driver"
1972 This builds the "udelay_test" module that helps to make sure
1973 that udelay() is working properly.
1979 depends on HAVE_MEMBLOCK
1981 This option adds a kernel parameter 'memtest', which allows memtest
1983 memtest=0, mean disabled; -- default
1984 memtest=1, mean do 1 test pattern;
1986 memtest=17, mean do 17 test patterns.
1987 If you are unsure how to answer this question, answer N.
1989 config TEST_STATIC_KEYS
1990 tristate "Test static keys"
1994 Test the static key interfaces.
1998 config BUG_ON_DATA_CORRUPTION
1999 bool "Trigger a BUG when data corruption is detected"
2002 Select this option if the kernel should BUG when it encounters
2003 data corruption in kernel memory structures when they get checked
2008 source "samples/Kconfig"
2010 source "lib/Kconfig.kgdb"
2012 source "lib/Kconfig.ubsan"
2014 config ARCH_HAS_DEVMEM_IS_ALLOWED
2017 config STRICT_DEVMEM
2018 bool "Filter access to /dev/mem"
2019 depends on MMU && DEVMEM
2020 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
2021 default y if TILE || PPC
2023 If this option is disabled, you allow userspace (root) access to all
2024 of memory, including kernel and userspace memory. Accidental
2025 access to this is obviously disastrous, but specific access can
2026 be used by people debugging the kernel. Note that with PAT support
2027 enabled, even in this case there are restrictions on /dev/mem
2028 use due to the cache aliasing requirements.
2030 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
2031 file only allows userspace access to PCI space and the BIOS code and
2032 data regions. This is sufficient for dosemu and X and all common
2037 config IO_STRICT_DEVMEM
2038 bool "Filter I/O access to /dev/mem"
2039 depends on STRICT_DEVMEM
2041 If this option is disabled, you allow userspace (root) access to all
2042 io-memory regardless of whether a driver is actively using that
2043 range. Accidental access to this is obviously disastrous, but
2044 specific access can be used by people debugging kernel drivers.
2046 If this option is switched on, the /dev/mem file only allows
2047 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2048 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2049 if the driver using a given range cannot be disabled.
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