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/admin-guide/dynamic-debug-howto.rst for additional
136 endmenu # "printk and dmesg options"
138 menu "Compile-time checks and compiler options"
141 bool "Compile the kernel with debug info"
142 depends on DEBUG_KERNEL && !COMPILE_TEST
144 If you say Y here the resulting kernel image will include
145 debugging info resulting in a larger kernel image.
146 This adds debug symbols to the kernel and modules (gcc -g), and
147 is needed if you intend to use kernel crashdump or binary object
148 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
149 Say Y here only if you plan to debug the kernel.
153 config DEBUG_INFO_REDUCED
154 bool "Reduce debugging information"
155 depends on DEBUG_INFO
157 If you say Y here gcc is instructed to generate less debugging
158 information for structure types. This means that tools that
159 need full debugging information (like kgdb or systemtap) won't
160 be happy. But if you merely need debugging information to
161 resolve line numbers there is no loss. Advantage is that
162 build directory object sizes shrink dramatically over a full
163 DEBUG_INFO build and compile times are reduced too.
164 Only works with newer gcc versions.
166 config DEBUG_INFO_SPLIT
167 bool "Produce split debuginfo in .dwo files"
168 depends on DEBUG_INFO
170 Generate debug info into separate .dwo files. This significantly
171 reduces the build directory size for builds with DEBUG_INFO,
172 because it stores the information only once on disk in .dwo
173 files instead of multiple times in object files and executables.
174 In addition the debug information is also compressed.
176 Requires recent gcc (4.7+) and recent gdb/binutils.
177 Any tool that packages or reads debug information would need
178 to know about the .dwo files and include them.
179 Incompatible with older versions of ccache.
181 config DEBUG_INFO_DWARF4
182 bool "Generate dwarf4 debuginfo"
183 depends on DEBUG_INFO
185 Generate dwarf4 debug info. This requires recent versions
186 of gcc and gdb. It makes the debug information larger.
187 But it significantly improves the success of resolving
188 variables in gdb on optimized code.
191 bool "Provide GDB scripts for kernel debugging"
192 depends on DEBUG_INFO
194 This creates the required links to GDB helper scripts in the
195 build directory. If you load vmlinux into gdb, the helper
196 scripts will be automatically imported by gdb as well, and
197 additional functions are available to analyze a Linux kernel
198 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
201 config ENABLE_WARN_DEPRECATED
202 bool "Enable __deprecated logic"
205 Enable the __deprecated logic in the kernel build.
206 Disable this to suppress the "warning: 'foo' is deprecated
207 (declared at kernel/power/somefile.c:1234)" messages.
209 config ENABLE_MUST_CHECK
210 bool "Enable __must_check logic"
213 Enable the __must_check logic in the kernel build. Disable this to
214 suppress the "warning: ignoring return value of 'foo', declared with
215 attribute warn_unused_result" messages.
218 int "Warn for stack frames larger than (needs gcc 4.4)"
220 default 3072 if KASAN_EXTRA
221 default 2048 if GCC_PLUGIN_LATENT_ENTROPY
222 default 1280 if (!64BIT && PARISC)
223 default 1024 if (!64BIT && !PARISC)
224 default 2048 if 64BIT
226 Tell gcc to warn at build time for stack frames larger than this.
227 Setting this too low will cause a lot of warnings.
228 Setting it to 0 disables the warning.
231 config STRIP_ASM_SYMS
232 bool "Strip assembler-generated symbols during link"
235 Strip internal assembler-generated symbols during a link (symbols
236 that look like '.Lxxx') so they don't pollute the output of
237 get_wchan() and suchlike.
240 bool "Generate readable assembler code"
241 depends on DEBUG_KERNEL
243 Disable some compiler optimizations that tend to generate human unreadable
244 assembler output. This may make the kernel slightly slower, but it helps
245 to keep kernel developers who have to stare a lot at assembler listings
248 config UNUSED_SYMBOLS
249 bool "Enable unused/obsolete exported symbols"
252 Unused but exported symbols make the kernel needlessly bigger. For
253 that reason most of these unused exports will soon be removed. This
254 option is provided temporarily to provide a transition period in case
255 some external kernel module needs one of these symbols anyway. If you
256 encounter such a case in your module, consider if you are actually
257 using the right API. (rationale: since nobody in the kernel is using
258 this in a module, there is a pretty good chance it's actually the
259 wrong interface to use). If you really need the symbol, please send a
260 mail to the linux kernel mailing list mentioning the symbol and why
261 you really need it, and what the merge plan to the mainline kernel for
265 bool "Track page owner"
266 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
270 select PAGE_EXTENSION
272 This keeps track of what call chain is the owner of a page, may
273 help to find bare alloc_page(s) leaks. Even if you include this
274 feature on your build, it is disabled in default. You should pass
275 "page_owner=on" to boot parameter in order to enable it. Eats
276 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
277 for user-space helper.
282 bool "Debug Filesystem"
284 debugfs is a virtual file system that kernel developers use to put
285 debugging files into. Enable this option to be able to read and
286 write to these files.
288 For detailed documentation on the debugfs API, see
289 Documentation/filesystems/.
294 bool "Run 'make headers_check' when building vmlinux"
297 This option will extract the user-visible kernel headers whenever
298 building the kernel, and will run basic sanity checks on them to
299 ensure that exported files do not attempt to include files which
300 were not exported, etc.
302 If you're making modifications to header files which are
303 relevant for userspace, say 'Y', and check the headers
304 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
305 your build tree), to make sure they're suitable.
307 config DEBUG_SECTION_MISMATCH
308 bool "Enable full Section mismatch analysis"
310 The section mismatch analysis checks if there are illegal
311 references from one section to another section.
312 During linktime or runtime, some sections are dropped;
313 any use of code/data previously in these sections would
314 most likely result in an oops.
315 In the code, functions and variables are annotated with
316 __init,, etc. (see the full list in include/linux/init.h),
317 which results in the code/data being placed in specific sections.
318 The section mismatch analysis is always performed after a full
319 kernel build, and enabling this option causes the following
320 additional steps to occur:
321 - Add the option -fno-inline-functions-called-once to gcc commands.
322 When inlining a function annotated with __init in a non-init
323 function, we would lose the section information and thus
324 the analysis would not catch the illegal reference.
325 This option tells gcc to inline less (but it does result in
327 - Run the section mismatch analysis for each module/built-in.a file.
328 When we run the section mismatch analysis on vmlinux.o, we
329 lose valuable information about where the mismatch was
331 Running the analysis for each module/built-in.a file
332 tells where the mismatch happens much closer to the
333 source. The drawback is that the same mismatch is
334 reported at least twice.
335 - Enable verbose reporting from modpost in order to help resolve
336 the section mismatches that are reported.
338 config SECTION_MISMATCH_WARN_ONLY
339 bool "Make section mismatch errors non-fatal"
342 If you say N here, the build process will fail if there are any
343 section mismatch, instead of just throwing warnings.
348 # Select this config option from the architecture Kconfig, if it
349 # is preferred to always offer frame pointers as a config
350 # option on the architecture (regardless of KERNEL_DEBUG):
352 config ARCH_WANT_FRAME_POINTERS
356 bool "Compile the kernel with frame pointers"
357 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS
358 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
360 If you say Y here the resulting kernel image will be slightly
361 larger and slower, but it gives very useful debugging information
362 in case of kernel bugs. (precise oopses/stacktraces/warnings)
364 config STACK_VALIDATION
365 bool "Compile-time stack metadata validation"
366 depends on HAVE_STACK_VALIDATION
369 Add compile-time checks to validate stack metadata, including frame
370 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
371 that runtime stack traces are more reliable.
373 This is also a prerequisite for generation of ORC unwind data, which
374 is needed for CONFIG_UNWINDER_ORC.
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/admin-guide/sysrq.rst>.
408 Don't say Y 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/admin-guide/sysrq.rst.
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
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
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.kasan"
730 endmenu # "Memory Debugging"
735 KCOV does not have any arch-specific code, but currently it is enabled
736 only for x86_64. KCOV requires testing on other archs, and most likely
737 disabling of instrumentation for some early boot code.
739 config CC_HAS_SANCOV_TRACE_PC
740 def_bool $(cc-option,-fsanitize-coverage=trace-pc)
743 bool "Code coverage for fuzzing"
744 depends on ARCH_HAS_KCOV
745 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
747 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
749 KCOV exposes kernel code coverage information in a form suitable
750 for coverage-guided fuzzing (randomized testing).
752 If RANDOMIZE_BASE is enabled, PC values will not be stable across
753 different machines and across reboots. If you need stable PC values,
754 disable RANDOMIZE_BASE.
756 For more details, see Documentation/dev-tools/kcov.rst.
758 config KCOV_ENABLE_COMPARISONS
759 bool "Enable comparison operands collection by KCOV"
761 depends on $(cc-option,-fsanitize-coverage=trace-cmp)
763 KCOV also exposes operands of every comparison in the instrumented
764 code along with operand sizes and PCs of the comparison instructions.
765 These operands can be used by fuzzing engines to improve the quality
768 config KCOV_INSTRUMENT_ALL
769 bool "Instrument all code by default"
773 If you are doing generic system call fuzzing (like e.g. syzkaller),
774 then you will want to instrument the whole kernel and you should
775 say y here. If you are doing more targeted fuzzing (like e.g.
776 filesystem fuzzing with AFL) then you will want to enable coverage
777 for more specific subsets of files, and should say n here.
780 bool "Debug shared IRQ handlers"
781 depends on DEBUG_KERNEL
783 Enable this to generate a spurious interrupt as soon as a shared
784 interrupt handler is registered, and just before one is deregistered.
785 Drivers ought to be able to handle interrupts coming in at those
786 points; some don't and need to be caught.
788 menu "Debug Lockups and Hangs"
790 config LOCKUP_DETECTOR
793 config SOFTLOCKUP_DETECTOR
794 bool "Detect Soft Lockups"
795 depends on DEBUG_KERNEL && !S390
796 select LOCKUP_DETECTOR
798 Say Y here to enable the kernel to act as a watchdog to detect
801 Softlockups are bugs that cause the kernel to loop in kernel
802 mode for more than 20 seconds, without giving other tasks a
803 chance to run. The current stack trace is displayed upon
804 detection and the system will stay locked up.
806 config BOOTPARAM_SOFTLOCKUP_PANIC
807 bool "Panic (Reboot) On Soft Lockups"
808 depends on SOFTLOCKUP_DETECTOR
810 Say Y here to enable the kernel to panic on "soft lockups",
811 which are bugs that cause the kernel to loop in kernel
812 mode for more than 20 seconds (configurable using the watchdog_thresh
813 sysctl), without giving other tasks a chance to run.
815 The panic can be used in combination with panic_timeout,
816 to cause the system to reboot automatically after a
817 lockup has been detected. This feature is useful for
818 high-availability systems that have uptime guarantees and
819 where a lockup must be resolved ASAP.
823 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
825 depends on SOFTLOCKUP_DETECTOR
827 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
828 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
830 config HARDLOCKUP_DETECTOR_PERF
832 select SOFTLOCKUP_DETECTOR
835 # Enables a timestamp based low pass filter to compensate for perf based
836 # hard lockup detection which runs too fast due to turbo modes.
838 config HARDLOCKUP_CHECK_TIMESTAMP
842 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
843 # lockup detector rather than the perf based detector.
845 config HARDLOCKUP_DETECTOR
846 bool "Detect Hard Lockups"
847 depends on DEBUG_KERNEL && !S390
848 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
849 select LOCKUP_DETECTOR
850 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
851 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
853 Say Y here to enable the kernel to act as a watchdog to detect
856 Hardlockups are bugs that cause the CPU to loop in kernel mode
857 for more than 10 seconds, without letting other interrupts have a
858 chance to run. The current stack trace is displayed upon detection
859 and the system will stay locked up.
861 config BOOTPARAM_HARDLOCKUP_PANIC
862 bool "Panic (Reboot) On Hard Lockups"
863 depends on HARDLOCKUP_DETECTOR
865 Say Y here to enable the kernel to panic on "hard lockups",
866 which are bugs that cause the kernel to loop in kernel
867 mode with interrupts disabled for more than 10 seconds (configurable
868 using the watchdog_thresh sysctl).
872 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
874 depends on HARDLOCKUP_DETECTOR
876 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
877 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
879 config DETECT_HUNG_TASK
880 bool "Detect Hung Tasks"
881 depends on DEBUG_KERNEL
882 default SOFTLOCKUP_DETECTOR
884 Say Y here to enable the kernel to detect "hung tasks",
885 which are bugs that cause the task to be stuck in
886 uninterruptible "D" state indefinitely.
888 When a hung task is detected, the kernel will print the
889 current stack trace (which you should report), but the
890 task will stay in uninterruptible state. If lockdep is
891 enabled then all held locks will also be reported. This
892 feature has negligible overhead.
894 config DEFAULT_HUNG_TASK_TIMEOUT
895 int "Default timeout for hung task detection (in seconds)"
896 depends on DETECT_HUNG_TASK
899 This option controls the default timeout (in seconds) used
900 to determine when a task has become non-responsive and should
903 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
904 sysctl or by writing a value to
905 /proc/sys/kernel/hung_task_timeout_secs.
907 A timeout of 0 disables the check. The default is two minutes.
908 Keeping the default should be fine in most cases.
910 config BOOTPARAM_HUNG_TASK_PANIC
911 bool "Panic (Reboot) On Hung Tasks"
912 depends on DETECT_HUNG_TASK
914 Say Y here to enable the kernel to panic on "hung tasks",
915 which are bugs that cause the kernel to leave a task stuck
916 in uninterruptible "D" state.
918 The panic can be used in combination with panic_timeout,
919 to cause the system to reboot automatically after a
920 hung task has been detected. This feature is useful for
921 high-availability systems that have uptime guarantees and
922 where a hung tasks must be resolved ASAP.
926 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
928 depends on DETECT_HUNG_TASK
930 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
931 default 1 if BOOTPARAM_HUNG_TASK_PANIC
934 bool "Detect Workqueue Stalls"
935 depends on DEBUG_KERNEL
937 Say Y here to enable stall detection on workqueues. If a
938 worker pool doesn't make forward progress on a pending work
939 item for over a given amount of time, 30s by default, a
940 warning message is printed along with dump of workqueue
941 state. This can be configured through kernel parameter
942 "workqueue.watchdog_thresh" and its sysfs counterpart.
944 endmenu # "Debug lockups and hangs"
949 Say Y here to enable the kernel to panic when it oopses. This
950 has the same effect as setting oops=panic on the kernel command
953 This feature is useful to ensure that the kernel does not do
954 anything erroneous after an oops which could result in data
955 corruption or other issues.
959 config PANIC_ON_OOPS_VALUE
962 default 0 if !PANIC_ON_OOPS
963 default 1 if PANIC_ON_OOPS
969 Set the timeout value (in seconds) until a reboot occurs when the
970 the kernel panics. If n = 0, then we wait forever. A timeout
971 value n > 0 will wait n seconds before rebooting, while a timeout
972 value n < 0 will reboot immediately.
975 bool "Collect scheduler debugging info"
976 depends on DEBUG_KERNEL && PROC_FS
979 If you say Y here, the /proc/sched_debug file will be provided
980 that can help debug the scheduler. The runtime overhead of this
988 bool "Collect scheduler statistics"
989 depends on DEBUG_KERNEL && PROC_FS
992 If you say Y here, additional code will be inserted into the
993 scheduler and related routines to collect statistics about
994 scheduler behavior and provide them in /proc/schedstat. These
995 stats may be useful for both tuning and debugging the scheduler
996 If you aren't debugging the scheduler or trying to tune a specific
997 application, you can say N to avoid the very slight overhead
1000 config SCHED_STACK_END_CHECK
1001 bool "Detect stack corruption on calls to schedule()"
1002 depends on DEBUG_KERNEL
1005 This option checks for a stack overrun on calls to schedule().
1006 If the stack end location is found to be over written always panic as
1007 the content of the corrupted region can no longer be trusted.
1008 This is to ensure no erroneous behaviour occurs which could result in
1009 data corruption or a sporadic crash at a later stage once the region
1010 is examined. The runtime overhead introduced is minimal.
1012 config DEBUG_TIMEKEEPING
1013 bool "Enable extra timekeeping sanity checking"
1015 This option will enable additional timekeeping sanity checks
1016 which may be helpful when diagnosing issues where timekeeping
1017 problems are suspected.
1019 This may include checks in the timekeeping hotpaths, so this
1020 option may have a (very small) performance impact to some
1025 config DEBUG_PREEMPT
1026 bool "Debug preemptible kernel"
1027 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1030 If you say Y here then the kernel will use a debug variant of the
1031 commonly used smp_processor_id() function and will print warnings
1032 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1033 will detect preemption count underflows.
1035 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1037 config LOCK_DEBUGGING_SUPPORT
1039 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1042 config PROVE_LOCKING
1043 bool "Lock debugging: prove locking correctness"
1044 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1046 select DEBUG_SPINLOCK
1047 select DEBUG_MUTEXES
1048 select DEBUG_RT_MUTEXES if RT_MUTEXES
1049 select DEBUG_RWSEMS if RWSEM_SPIN_ON_OWNER
1050 select DEBUG_WW_MUTEX_SLOWPATH
1051 select DEBUG_LOCK_ALLOC
1052 select TRACE_IRQFLAGS
1055 This feature enables the kernel to prove that all locking
1056 that occurs in the kernel runtime is mathematically
1057 correct: that under no circumstance could an arbitrary (and
1058 not yet triggered) combination of observed locking
1059 sequences (on an arbitrary number of CPUs, running an
1060 arbitrary number of tasks and interrupt contexts) cause a
1063 In short, this feature enables the kernel to report locking
1064 related deadlocks before they actually occur.
1066 The proof does not depend on how hard and complex a
1067 deadlock scenario would be to trigger: how many
1068 participant CPUs, tasks and irq-contexts would be needed
1069 for it to trigger. The proof also does not depend on
1070 timing: if a race and a resulting deadlock is possible
1071 theoretically (no matter how unlikely the race scenario
1072 is), it will be proven so and will immediately be
1073 reported by the kernel (once the event is observed that
1074 makes the deadlock theoretically possible).
1076 If a deadlock is impossible (i.e. the locking rules, as
1077 observed by the kernel, are mathematically correct), the
1078 kernel reports nothing.
1080 NOTE: this feature can also be enabled for rwlocks, mutexes
1081 and rwsems - in which case all dependencies between these
1082 different locking variants are observed and mapped too, and
1083 the proof of observed correctness is also maintained for an
1084 arbitrary combination of these separate locking variants.
1086 For more details, see Documentation/locking/lockdep-design.txt.
1089 bool "Lock usage statistics"
1090 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1092 select DEBUG_SPINLOCK
1093 select DEBUG_MUTEXES
1094 select DEBUG_RT_MUTEXES if RT_MUTEXES
1095 select DEBUG_LOCK_ALLOC
1098 This feature enables tracking lock contention points
1100 For more details, see Documentation/locking/lockstat.txt
1102 This also enables lock events required by "perf lock",
1104 If you want to use "perf lock", you also need to turn on
1105 CONFIG_EVENT_TRACING.
1107 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1108 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1110 config DEBUG_RT_MUTEXES
1111 bool "RT Mutex debugging, deadlock detection"
1112 depends on DEBUG_KERNEL && RT_MUTEXES
1114 This allows rt mutex semantics violations and rt mutex related
1115 deadlocks (lockups) to be detected and reported automatically.
1117 config DEBUG_SPINLOCK
1118 bool "Spinlock and rw-lock debugging: basic checks"
1119 depends on DEBUG_KERNEL
1120 select UNINLINE_SPIN_UNLOCK
1122 Say Y here and build SMP to catch missing spinlock initialization
1123 and certain other kinds of spinlock errors commonly made. This is
1124 best used in conjunction with the NMI watchdog so that spinlock
1125 deadlocks are also debuggable.
1127 config DEBUG_MUTEXES
1128 bool "Mutex debugging: basic checks"
1129 depends on DEBUG_KERNEL
1131 This feature allows mutex semantics violations to be detected and
1134 config DEBUG_WW_MUTEX_SLOWPATH
1135 bool "Wait/wound mutex debugging: Slowpath testing"
1136 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1137 select DEBUG_LOCK_ALLOC
1138 select DEBUG_SPINLOCK
1139 select DEBUG_MUTEXES
1141 This feature enables slowpath testing for w/w mutex users by
1142 injecting additional -EDEADLK wound/backoff cases. Together with
1143 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1144 will test all possible w/w mutex interface abuse with the
1145 exception of simply not acquiring all the required locks.
1146 Note that this feature can introduce significant overhead, so
1147 it really should not be enabled in a production or distro kernel,
1148 even a debug kernel. If you are a driver writer, enable it. If
1149 you are a distro, do not.
1152 bool "RW Semaphore debugging: basic checks"
1153 depends on DEBUG_KERNEL && RWSEM_SPIN_ON_OWNER
1155 This debugging feature allows mismatched rw semaphore locks and unlocks
1156 to be detected and reported.
1158 config DEBUG_LOCK_ALLOC
1159 bool "Lock debugging: detect incorrect freeing of live locks"
1160 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1161 select DEBUG_SPINLOCK
1162 select DEBUG_MUTEXES
1163 select DEBUG_RT_MUTEXES if RT_MUTEXES
1166 This feature will check whether any held lock (spinlock, rwlock,
1167 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1168 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1169 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1170 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1171 held during task exit.
1175 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1177 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !X86
1181 config LOCKDEP_SMALL
1184 config DEBUG_LOCKDEP
1185 bool "Lock dependency engine debugging"
1186 depends on DEBUG_KERNEL && LOCKDEP
1188 If you say Y here, the lock dependency engine will do
1189 additional runtime checks to debug itself, at the price
1190 of more runtime overhead.
1192 config DEBUG_ATOMIC_SLEEP
1193 bool "Sleep inside atomic section checking"
1194 select PREEMPT_COUNT
1195 depends on DEBUG_KERNEL
1197 If you say Y here, various routines which may sleep will become very
1198 noisy if they are called inside atomic sections: when a spinlock is
1199 held, inside an rcu read side critical section, inside preempt disabled
1200 sections, inside an interrupt, etc...
1202 config DEBUG_LOCKING_API_SELFTESTS
1203 bool "Locking API boot-time self-tests"
1204 depends on DEBUG_KERNEL
1206 Say Y here if you want the kernel to run a short self-test during
1207 bootup. The self-test checks whether common types of locking bugs
1208 are detected by debugging mechanisms or not. (if you disable
1209 lock debugging then those bugs wont be detected of course.)
1210 The following locking APIs are covered: spinlocks, rwlocks,
1213 config LOCK_TORTURE_TEST
1214 tristate "torture tests for locking"
1215 depends on DEBUG_KERNEL
1219 This option provides a kernel module that runs torture tests
1220 on kernel locking primitives. The kernel module may be built
1221 after the fact on the running kernel to be tested, if desired.
1223 Say Y here if you want kernel locking-primitive torture tests
1224 to be built into the kernel.
1225 Say M if you want these torture tests to build as a module.
1226 Say N if you are unsure.
1228 config WW_MUTEX_SELFTEST
1229 tristate "Wait/wound mutex selftests"
1231 This option provides a kernel module that runs tests on the
1232 on the struct ww_mutex locking API.
1234 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1235 with this test harness.
1237 Say M if you want these self tests to build as a module.
1238 Say N if you are unsure.
1240 endmenu # lock debugging
1242 config TRACE_IRQFLAGS
1245 Enables hooks to interrupt enabling and disabling for
1246 either tracing or lock debugging.
1249 bool "Stack backtrace support"
1250 depends on STACKTRACE_SUPPORT
1252 This option causes the kernel to create a /proc/pid/stack for
1253 every process, showing its current stack trace.
1254 It is also used by various kernel debugging features that require
1255 stack trace generation.
1257 config WARN_ALL_UNSEEDED_RANDOM
1258 bool "Warn for all uses of unseeded randomness"
1261 Some parts of the kernel contain bugs relating to their use of
1262 cryptographically secure random numbers before it's actually possible
1263 to generate those numbers securely. This setting ensures that these
1264 flaws don't go unnoticed, by enabling a message, should this ever
1265 occur. This will allow people with obscure setups to know when things
1266 are going wrong, so that they might contact developers about fixing
1269 Unfortunately, on some models of some architectures getting
1270 a fully seeded CRNG is extremely difficult, and so this can
1271 result in dmesg getting spammed for a surprisingly long
1272 time. This is really bad from a security perspective, and
1273 so architecture maintainers really need to do what they can
1274 to get the CRNG seeded sooner after the system is booted.
1275 However, since users can not do anything actionble to
1276 address this, by default the kernel will issue only a single
1277 warning for the first use of unseeded randomness.
1279 Say Y here if you want to receive warnings for all uses of
1280 unseeded randomness. This will be of use primarily for
1281 those developers interersted in improving the security of
1282 Linux kernels running on their architecture (or
1285 config DEBUG_KOBJECT
1286 bool "kobject debugging"
1287 depends on DEBUG_KERNEL
1289 If you say Y here, some extra kobject debugging messages will be sent
1292 config DEBUG_KOBJECT_RELEASE
1293 bool "kobject release debugging"
1294 depends on DEBUG_OBJECTS_TIMERS
1296 kobjects are reference counted objects. This means that their
1297 last reference count put is not predictable, and the kobject can
1298 live on past the point at which a driver decides to drop it's
1299 initial reference to the kobject gained on allocation. An
1300 example of this would be a struct device which has just been
1303 However, some buggy drivers assume that after such an operation,
1304 the memory backing the kobject can be immediately freed. This
1305 goes completely against the principles of a refcounted object.
1307 If you say Y here, the kernel will delay the release of kobjects
1308 on the last reference count to improve the visibility of this
1309 kind of kobject release bug.
1311 config HAVE_DEBUG_BUGVERBOSE
1314 config DEBUG_BUGVERBOSE
1315 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1316 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1319 Say Y here to make BUG() panics output the file name and line number
1320 of the BUG call as well as the EIP and oops trace. This aids
1321 debugging but costs about 70-100K of memory.
1324 bool "Debug linked list manipulation"
1325 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1327 Enable this to turn on extended checks in the linked-list
1332 config DEBUG_PI_LIST
1333 bool "Debug priority linked list manipulation"
1334 depends on DEBUG_KERNEL
1336 Enable this to turn on extended checks in the priority-ordered
1337 linked-list (plist) walking routines. This checks the entire
1338 list multiple times during each manipulation.
1343 bool "Debug SG table operations"
1344 depends on DEBUG_KERNEL
1346 Enable this to turn on checks on scatter-gather tables. This can
1347 help find problems with drivers that do not properly initialize
1352 config DEBUG_NOTIFIERS
1353 bool "Debug notifier call chains"
1354 depends on DEBUG_KERNEL
1356 Enable this to turn on sanity checking for notifier call chains.
1357 This is most useful for kernel developers to make sure that
1358 modules properly unregister themselves from notifier chains.
1359 This is a relatively cheap check but if you care about maximum
1362 config DEBUG_CREDENTIALS
1363 bool "Debug credential management"
1364 depends on DEBUG_KERNEL
1366 Enable this to turn on some debug checking for credential
1367 management. The additional code keeps track of the number of
1368 pointers from task_structs to any given cred struct, and checks to
1369 see that this number never exceeds the usage count of the cred
1372 Furthermore, if SELinux is enabled, this also checks that the
1373 security pointer in the cred struct is never seen to be invalid.
1377 source "kernel/rcu/Kconfig.debug"
1379 config DEBUG_WQ_FORCE_RR_CPU
1380 bool "Force round-robin CPU selection for unbound work items"
1381 depends on DEBUG_KERNEL
1384 Workqueue used to implicitly guarantee that work items queued
1385 without explicit CPU specified are put on the local CPU. This
1386 guarantee is no longer true and while local CPU is still
1387 preferred work items may be put on foreign CPUs. Kernel
1388 parameter "workqueue.debug_force_rr_cpu" is added to force
1389 round-robin CPU selection to flush out usages which depend on the
1390 now broken guarantee. This config option enables the debug
1391 feature by default. When enabled, memory and cache locality will
1394 config DEBUG_BLOCK_EXT_DEVT
1395 bool "Force extended block device numbers and spread them"
1396 depends on DEBUG_KERNEL
1400 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1401 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1402 YOU ARE DOING. Distros, please enable this and fix whatever
1405 Conventionally, block device numbers are allocated from
1406 predetermined contiguous area. However, extended block area
1407 may introduce non-contiguous block device numbers. This
1408 option forces most block device numbers to be allocated from
1409 the extended space and spreads them to discover kernel or
1410 userland code paths which assume predetermined contiguous
1411 device number allocation.
1413 Note that turning on this debug option shuffles all the
1414 device numbers for all IDE and SCSI devices including libata
1415 ones, so root partition specified using device number
1416 directly (via rdev or root=MAJ:MIN) won't work anymore.
1417 Textual device names (root=/dev/sdXn) will continue to work.
1419 Say N if you are unsure.
1421 config CPU_HOTPLUG_STATE_CONTROL
1422 bool "Enable CPU hotplug state control"
1423 depends on DEBUG_KERNEL
1424 depends on HOTPLUG_CPU
1427 Allows to write steps between "offline" and "online" to the CPUs
1428 sysfs target file so states can be stepped granular. This is a debug
1429 option for now as the hotplug machinery cannot be stopped and
1430 restarted at arbitrary points yet.
1432 Say N if your are unsure.
1434 config NOTIFIER_ERROR_INJECTION
1435 tristate "Notifier error injection"
1436 depends on DEBUG_KERNEL
1439 This option provides the ability to inject artificial errors to
1440 specified notifier chain callbacks. It is useful to test the error
1441 handling of notifier call chain failures.
1445 config PM_NOTIFIER_ERROR_INJECT
1446 tristate "PM notifier error injection module"
1447 depends on PM && NOTIFIER_ERROR_INJECTION
1448 default m if PM_DEBUG
1450 This option provides the ability to inject artificial errors to
1451 PM notifier chain callbacks. It is controlled through debugfs
1452 interface /sys/kernel/debug/notifier-error-inject/pm
1454 If the notifier call chain should be failed with some events
1455 notified, write the error code to "actions/<notifier event>/error".
1457 Example: Inject PM suspend error (-12 = -ENOMEM)
1459 # cd /sys/kernel/debug/notifier-error-inject/pm/
1460 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1461 # echo mem > /sys/power/state
1462 bash: echo: write error: Cannot allocate memory
1464 To compile this code as a module, choose M here: the module will
1465 be called pm-notifier-error-inject.
1469 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1470 tristate "OF reconfig notifier error injection module"
1471 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1473 This option provides the ability to inject artificial errors to
1474 OF reconfig notifier chain callbacks. It is controlled
1475 through debugfs interface under
1476 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1478 If the notifier call chain should be failed with some events
1479 notified, write the error code to "actions/<notifier event>/error".
1481 To compile this code as a module, choose M here: the module will
1482 be called of-reconfig-notifier-error-inject.
1486 config NETDEV_NOTIFIER_ERROR_INJECT
1487 tristate "Netdev notifier error injection module"
1488 depends on NET && NOTIFIER_ERROR_INJECTION
1490 This option provides the ability to inject artificial errors to
1491 netdevice notifier chain callbacks. It is controlled through debugfs
1492 interface /sys/kernel/debug/notifier-error-inject/netdev
1494 If the notifier call chain should be failed with some events
1495 notified, write the error code to "actions/<notifier event>/error".
1497 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1499 # cd /sys/kernel/debug/notifier-error-inject/netdev
1500 # echo -22 > actions/NETDEV_CHANGEMTU/error
1501 # ip link set eth0 mtu 1024
1502 RTNETLINK answers: Invalid argument
1504 To compile this code as a module, choose M here: the module will
1505 be called netdev-notifier-error-inject.
1509 config FAULT_INJECTION
1510 bool "Fault-injection framework"
1511 depends on DEBUG_KERNEL
1513 Provide fault-injection framework.
1514 For more details, see Documentation/fault-injection/.
1516 config FUNCTION_ERROR_INJECTION
1518 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
1521 bool "Fault-injection capability for kmalloc"
1522 depends on FAULT_INJECTION
1523 depends on SLAB || SLUB
1525 Provide fault-injection capability for kmalloc.
1527 config FAIL_PAGE_ALLOC
1528 bool "Fault-injection capabilitiy for alloc_pages()"
1529 depends on FAULT_INJECTION
1531 Provide fault-injection capability for alloc_pages().
1533 config FAIL_MAKE_REQUEST
1534 bool "Fault-injection capability for disk IO"
1535 depends on FAULT_INJECTION && BLOCK
1537 Provide fault-injection capability for disk IO.
1539 config FAIL_IO_TIMEOUT
1540 bool "Fault-injection capability for faking disk interrupts"
1541 depends on FAULT_INJECTION && BLOCK
1543 Provide fault-injection capability on end IO handling. This
1544 will make the block layer "forget" an interrupt as configured,
1545 thus exercising the error handling.
1547 Only works with drivers that use the generic timeout handling,
1548 for others it wont do anything.
1550 config FAIL_MMC_REQUEST
1551 bool "Fault-injection capability for MMC IO"
1552 depends on FAULT_INJECTION_DEBUG_FS && MMC
1554 Provide fault-injection capability for MMC IO.
1555 This will make the mmc core return data errors. This is
1556 useful to test the error handling in the mmc block device
1557 and to test how the mmc host driver handles retries from
1561 bool "Fault-injection capability for futexes"
1563 depends on FAULT_INJECTION && FUTEX
1565 Provide fault-injection capability for futexes.
1567 config FAIL_FUNCTION
1568 bool "Fault-injection capability for functions"
1569 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
1571 Provide function-based fault-injection capability.
1572 This will allow you to override a specific function with a return
1573 with given return value. As a result, function caller will see
1574 an error value and have to handle it. This is useful to test the
1575 error handling in various subsystems.
1577 config FAULT_INJECTION_DEBUG_FS
1578 bool "Debugfs entries for fault-injection capabilities"
1579 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1581 Enable configuration of fault-injection capabilities via debugfs.
1583 config FAULT_INJECTION_STACKTRACE_FILTER
1584 bool "stacktrace filter for fault-injection capabilities"
1585 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1588 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !X86
1590 Provide stacktrace filter for fault-injection capabilities
1593 bool "Latency measuring infrastructure"
1594 depends on DEBUG_KERNEL
1595 depends on STACKTRACE_SUPPORT
1597 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !X86
1604 Enable this option if you want to use the LatencyTOP tool
1605 to find out which userspace is blocking on what kernel operations.
1607 source kernel/trace/Kconfig
1609 config PROVIDE_OHCI1394_DMA_INIT
1610 bool "Remote debugging over FireWire early on boot"
1611 depends on PCI && X86
1613 If you want to debug problems which hang or crash the kernel early
1614 on boot and the crashing machine has a FireWire port, you can use
1615 this feature to remotely access the memory of the crashed machine
1616 over FireWire. This employs remote DMA as part of the OHCI1394
1617 specification which is now the standard for FireWire controllers.
1619 With remote DMA, you can monitor the printk buffer remotely using
1620 firescope and access all memory below 4GB using fireproxy from gdb.
1621 Even controlling a kernel debugger is possible using remote DMA.
1625 If ohci1394_dma=early is used as boot parameter, it will initialize
1626 all OHCI1394 controllers which are found in the PCI config space.
1628 As all changes to the FireWire bus such as enabling and disabling
1629 devices cause a bus reset and thereby disable remote DMA for all
1630 devices, be sure to have the cable plugged and FireWire enabled on
1631 the debugging host before booting the debug target for debugging.
1633 This code (~1k) is freed after boot. By then, the firewire stack
1634 in charge of the OHCI-1394 controllers should be used instead.
1636 See Documentation/debugging-via-ohci1394.txt for more information.
1638 config DMA_API_DEBUG
1639 bool "Enable debugging of DMA-API usage"
1640 select NEED_DMA_MAP_STATE
1642 Enable this option to debug the use of the DMA API by device drivers.
1643 With this option you will be able to detect common bugs in device
1644 drivers like double-freeing of DMA mappings or freeing mappings that
1645 were never allocated.
1647 This also attempts to catch cases where a page owned by DMA is
1648 accessed by the cpu in a way that could cause data corruption. For
1649 example, this enables cow_user_page() to check that the source page is
1652 This option causes a performance degradation. Use only if you want to
1653 debug device drivers and dma interactions.
1657 config DMA_API_DEBUG_SG
1658 bool "Debug DMA scatter-gather usage"
1660 depends on DMA_API_DEBUG
1662 Perform extra checking that callers of dma_map_sg() have respected the
1663 appropriate segment length/boundary limits for the given device when
1664 preparing DMA scatterlists.
1666 This is particularly likely to have been overlooked in cases where the
1667 dma_map_sg() API is used for general bulk mapping of pages rather than
1668 preparing literal scatter-gather descriptors, where there is a risk of
1669 unexpected behaviour from DMA API implementations if the scatterlist
1670 is technically out-of-spec.
1674 menuconfig RUNTIME_TESTING_MENU
1675 bool "Runtime Testing"
1678 if RUNTIME_TESTING_MENU
1681 tristate "Linux Kernel Dump Test Tool Module"
1686 This module enables testing of the different dumping mechanisms by
1687 inducing system failures at predefined crash points.
1688 If you don't need it: say N
1689 Choose M here to compile this code as a module. The module will be
1692 Documentation on how to use the module can be found in
1693 Documentation/fault-injection/provoke-crashes.txt
1695 config TEST_LIST_SORT
1696 tristate "Linked list sorting test"
1697 depends on DEBUG_KERNEL || m
1699 Enable this to turn on 'list_sort()' function test. This test is
1700 executed only once during system boot (so affects only boot time),
1701 or at module load time.
1706 tristate "Array-based sort test"
1707 depends on DEBUG_KERNEL || m
1709 This option enables the self-test function of 'sort()' at boot,
1710 or at module load time.
1714 config KPROBES_SANITY_TEST
1715 bool "Kprobes sanity tests"
1716 depends on DEBUG_KERNEL
1720 This option provides for testing basic kprobes functionality on
1721 boot. A sample kprobe, jprobe and kretprobe are inserted and
1722 verified for functionality.
1724 Say N if you are unsure.
1726 config BACKTRACE_SELF_TEST
1727 tristate "Self test for the backtrace code"
1728 depends on DEBUG_KERNEL
1731 This option provides a kernel module that can be used to test
1732 the kernel stack backtrace code. This option is not useful
1733 for distributions or general kernels, but only for kernel
1734 developers working on architecture code.
1736 Note that if you want to also test saved backtraces, you will
1737 have to enable STACKTRACE as well.
1739 Say N if you are unsure.
1742 tristate "Red-Black tree test"
1743 depends on DEBUG_KERNEL
1745 A benchmark measuring the performance of the rbtree library.
1746 Also includes rbtree invariant checks.
1748 config INTERVAL_TREE_TEST
1749 tristate "Interval tree test"
1750 depends on DEBUG_KERNEL
1751 select INTERVAL_TREE
1753 A benchmark measuring the performance of the interval tree library
1756 tristate "Per cpu operations test"
1757 depends on m && DEBUG_KERNEL
1759 Enable this option to build test module which validates per-cpu
1764 config ATOMIC64_SELFTEST
1765 tristate "Perform an atomic64_t self-test"
1767 Enable this option to test the atomic64_t functions at boot or
1768 at module load time.
1772 config ASYNC_RAID6_TEST
1773 tristate "Self test for hardware accelerated raid6 recovery"
1774 depends on ASYNC_RAID6_RECOV
1777 This is a one-shot self test that permutes through the
1778 recovery of all the possible two disk failure scenarios for a
1779 N-disk array. Recovery is performed with the asynchronous
1780 raid6 recovery routines, and will optionally use an offload
1781 engine if one is available.
1786 tristate "Test functions located in the hexdump module at runtime"
1788 config TEST_STRING_HELPERS
1789 tristate "Test functions located in the string_helpers module at runtime"
1792 tristate "Test kstrto*() family of functions at runtime"
1795 tristate "Test printf() family of functions at runtime"
1798 tristate "Test bitmap_*() family of functions at runtime"
1801 Enable this option to test the bitmap functions at boot.
1806 tristate "Test functions located in the uuid module at runtime"
1808 config TEST_OVERFLOW
1809 tristate "Test check_*_overflow() functions at runtime"
1811 config TEST_RHASHTABLE
1812 tristate "Perform selftest on resizable hash table"
1815 Enable this option to test the rhashtable functions at boot.
1820 tristate "Perform selftest on hash functions"
1823 Enable this option to test the kernel's integer (<linux/hash.h>),
1824 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1825 hash functions on boot (or module load).
1827 This is intended to help people writing architecture-specific
1828 optimized versions. If unsure, say N.
1831 tristate "Perform selftest on priority array manager"
1835 Enable this option to test priority array manager on boot
1841 tristate "Test module loading with 'hello world' module"
1845 This builds the "test_module" module that emits "Hello, world"
1846 on printk when loaded. It is designed to be used for basic
1847 evaluation of the module loading subsystem (for example when
1848 validating module verification). It lacks any extra dependencies,
1849 and will not normally be loaded by the system unless explicitly
1854 config TEST_USER_COPY
1855 tristate "Test user/kernel boundary protections"
1859 This builds the "test_user_copy" module that runs sanity checks
1860 on the copy_to/from_user infrastructure, making sure basic
1861 user/kernel boundary testing is working. If it fails to load,
1862 a regression has been detected in the user/kernel memory boundary
1868 tristate "Test BPF filter functionality"
1872 This builds the "test_bpf" module that runs various test vectors
1873 against the BPF interpreter or BPF JIT compiler depending on the
1874 current setting. This is in particular useful for BPF JIT compiler
1875 development, but also to run regression tests against changes in
1876 the interpreter code. It also enables test stubs for eBPF maps and
1877 verifier used by user space verifier testsuite.
1881 config FIND_BIT_BENCHMARK
1882 tristate "Test find_bit functions"
1885 This builds the "test_find_bit" module that measure find_*_bit()
1886 functions performance.
1890 config TEST_FIRMWARE
1891 tristate "Test firmware loading via userspace interface"
1893 depends on FW_LOADER
1895 This builds the "test_firmware" module that creates a userspace
1896 interface for testing firmware loading. This can be used to
1897 control the triggering of firmware loading without needing an
1898 actual firmware-using device. The contents can be rechecked by
1904 tristate "sysctl test driver"
1906 depends on PROC_SYSCTL
1908 This builds the "test_sysctl" module. This driver enables to test the
1909 proc sysctl interfaces available to drivers safely without affecting
1910 production knobs which might alter system functionality.
1915 tristate "udelay test driver"
1918 This builds the "udelay_test" module that helps to make sure
1919 that udelay() is working properly.
1923 config TEST_STATIC_KEYS
1924 tristate "Test static keys"
1928 Test the static key interfaces.
1933 tristate "kmod stress tester"
1936 depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS
1937 depends on NETDEVICES && NET_CORE && INET # for TUN
1943 Test the kernel's module loading mechanism: kmod. kmod implements
1944 support to load modules using the Linux kernel's usermode helper.
1945 This test provides a series of tests against kmod.
1947 Although technically you can either build test_kmod as a module or
1948 into the kernel we disallow building it into the kernel since
1949 it stress tests request_module() and this will very likely cause
1950 some issues by taking over precious threads available from other
1951 module load requests, ultimately this could be fatal.
1955 tools/testing/selftests/kmod/kmod.sh --help
1959 config TEST_DEBUG_VIRTUAL
1960 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
1961 depends on DEBUG_VIRTUAL
1963 Test the kernel's ability to detect incorrect calls to
1964 virt_to_phys() done against the non-linear part of the
1965 kernel's virtual address map.
1969 endif # RUNTIME_TESTING_MENU
1973 depends on HAVE_MEMBLOCK
1975 This option adds a kernel parameter 'memtest', which allows memtest
1977 memtest=0, mean disabled; -- default
1978 memtest=1, mean do 1 test pattern;
1980 memtest=17, mean do 17 test patterns.
1981 If you are unsure how to answer this question, answer N.
1983 config BUG_ON_DATA_CORRUPTION
1984 bool "Trigger a BUG when data corruption is detected"
1987 Select this option if the kernel should BUG when it encounters
1988 data corruption in kernel memory structures when they get checked
1993 source "samples/Kconfig"
1995 source "lib/Kconfig.kgdb"
1997 source "lib/Kconfig.ubsan"
1999 config ARCH_HAS_DEVMEM_IS_ALLOWED
2002 config STRICT_DEVMEM
2003 bool "Filter access to /dev/mem"
2004 depends on MMU && DEVMEM
2005 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
2006 default y if PPC || X86 || ARM64
2008 If this option is disabled, you allow userspace (root) access to all
2009 of memory, including kernel and userspace memory. Accidental
2010 access to this is obviously disastrous, but specific access can
2011 be used by people debugging the kernel. Note that with PAT support
2012 enabled, even in this case there are restrictions on /dev/mem
2013 use due to the cache aliasing requirements.
2015 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
2016 file only allows userspace access to PCI space and the BIOS code and
2017 data regions. This is sufficient for dosemu and X and all common
2022 config IO_STRICT_DEVMEM
2023 bool "Filter I/O access to /dev/mem"
2024 depends on STRICT_DEVMEM
2026 If this option is disabled, you allow userspace (root) access to all
2027 io-memory regardless of whether a driver is actively using that
2028 range. Accidental access to this is obviously disastrous, but
2029 specific access can be used by people debugging kernel drivers.
2031 If this option is switched on, the /dev/mem file only allows
2032 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2033 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2034 if the driver using a given range cannot be disabled.
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