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.
740 bool "Code coverage for fuzzing"
741 depends on ARCH_HAS_KCOV
743 select GCC_PLUGINS if !COMPILE_TEST
744 select GCC_PLUGIN_SANCOV if !COMPILE_TEST
746 KCOV exposes kernel code coverage information in a form suitable
747 for coverage-guided fuzzing (randomized testing).
749 If RANDOMIZE_BASE is enabled, PC values will not be stable across
750 different machines and across reboots. If you need stable PC values,
751 disable RANDOMIZE_BASE.
753 For more details, see Documentation/dev-tools/kcov.rst.
755 config KCOV_ENABLE_COMPARISONS
756 bool "Enable comparison operands collection by KCOV"
760 KCOV also exposes operands of every comparison in the instrumented
761 code along with operand sizes and PCs of the comparison instructions.
762 These operands can be used by fuzzing engines to improve the quality
765 config KCOV_INSTRUMENT_ALL
766 bool "Instrument all code by default"
770 If you are doing generic system call fuzzing (like e.g. syzkaller),
771 then you will want to instrument the whole kernel and you should
772 say y here. If you are doing more targeted fuzzing (like e.g.
773 filesystem fuzzing with AFL) then you will want to enable coverage
774 for more specific subsets of files, and should say n here.
777 bool "Debug shared IRQ handlers"
778 depends on DEBUG_KERNEL
780 Enable this to generate a spurious interrupt as soon as a shared
781 interrupt handler is registered, and just before one is deregistered.
782 Drivers ought to be able to handle interrupts coming in at those
783 points; some don't and need to be caught.
785 menu "Debug Lockups and Hangs"
787 config LOCKUP_DETECTOR
790 config SOFTLOCKUP_DETECTOR
791 bool "Detect Soft Lockups"
792 depends on DEBUG_KERNEL && !S390
793 select LOCKUP_DETECTOR
795 Say Y here to enable the kernel to act as a watchdog to detect
798 Softlockups are bugs that cause the kernel to loop in kernel
799 mode for more than 20 seconds, without giving other tasks a
800 chance to run. The current stack trace is displayed upon
801 detection and the system will stay locked up.
803 config BOOTPARAM_SOFTLOCKUP_PANIC
804 bool "Panic (Reboot) On Soft Lockups"
805 depends on SOFTLOCKUP_DETECTOR
807 Say Y here to enable the kernel to panic on "soft lockups",
808 which are bugs that cause the kernel to loop in kernel
809 mode for more than 20 seconds (configurable using the watchdog_thresh
810 sysctl), without giving other tasks a chance to run.
812 The panic can be used in combination with panic_timeout,
813 to cause the system to reboot automatically after a
814 lockup has been detected. This feature is useful for
815 high-availability systems that have uptime guarantees and
816 where a lockup must be resolved ASAP.
820 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
822 depends on SOFTLOCKUP_DETECTOR
824 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
825 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
827 config HARDLOCKUP_DETECTOR_PERF
829 select SOFTLOCKUP_DETECTOR
832 # Enables a timestamp based low pass filter to compensate for perf based
833 # hard lockup detection which runs too fast due to turbo modes.
835 config HARDLOCKUP_CHECK_TIMESTAMP
839 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
840 # lockup detector rather than the perf based detector.
842 config HARDLOCKUP_DETECTOR
843 bool "Detect Hard Lockups"
844 depends on DEBUG_KERNEL && !S390
845 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
846 select LOCKUP_DETECTOR
847 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
848 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
850 Say Y here to enable the kernel to act as a watchdog to detect
853 Hardlockups are bugs that cause the CPU to loop in kernel mode
854 for more than 10 seconds, without letting other interrupts have a
855 chance to run. The current stack trace is displayed upon detection
856 and the system will stay locked up.
858 config BOOTPARAM_HARDLOCKUP_PANIC
859 bool "Panic (Reboot) On Hard Lockups"
860 depends on HARDLOCKUP_DETECTOR
862 Say Y here to enable the kernel to panic on "hard lockups",
863 which are bugs that cause the kernel to loop in kernel
864 mode with interrupts disabled for more than 10 seconds (configurable
865 using the watchdog_thresh sysctl).
869 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
871 depends on HARDLOCKUP_DETECTOR
873 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
874 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
876 config DETECT_HUNG_TASK
877 bool "Detect Hung Tasks"
878 depends on DEBUG_KERNEL
879 default SOFTLOCKUP_DETECTOR
881 Say Y here to enable the kernel to detect "hung tasks",
882 which are bugs that cause the task to be stuck in
883 uninterruptible "D" state indefinitely.
885 When a hung task is detected, the kernel will print the
886 current stack trace (which you should report), but the
887 task will stay in uninterruptible state. If lockdep is
888 enabled then all held locks will also be reported. This
889 feature has negligible overhead.
891 config DEFAULT_HUNG_TASK_TIMEOUT
892 int "Default timeout for hung task detection (in seconds)"
893 depends on DETECT_HUNG_TASK
896 This option controls the default timeout (in seconds) used
897 to determine when a task has become non-responsive and should
900 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
901 sysctl or by writing a value to
902 /proc/sys/kernel/hung_task_timeout_secs.
904 A timeout of 0 disables the check. The default is two minutes.
905 Keeping the default should be fine in most cases.
907 config BOOTPARAM_HUNG_TASK_PANIC
908 bool "Panic (Reboot) On Hung Tasks"
909 depends on DETECT_HUNG_TASK
911 Say Y here to enable the kernel to panic on "hung tasks",
912 which are bugs that cause the kernel to leave a task stuck
913 in uninterruptible "D" state.
915 The panic can be used in combination with panic_timeout,
916 to cause the system to reboot automatically after a
917 hung task has been detected. This feature is useful for
918 high-availability systems that have uptime guarantees and
919 where a hung tasks must be resolved ASAP.
923 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
925 depends on DETECT_HUNG_TASK
927 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
928 default 1 if BOOTPARAM_HUNG_TASK_PANIC
931 bool "Detect Workqueue Stalls"
932 depends on DEBUG_KERNEL
934 Say Y here to enable stall detection on workqueues. If a
935 worker pool doesn't make forward progress on a pending work
936 item for over a given amount of time, 30s by default, a
937 warning message is printed along with dump of workqueue
938 state. This can be configured through kernel parameter
939 "workqueue.watchdog_thresh" and its sysfs counterpart.
941 endmenu # "Debug lockups and hangs"
946 Say Y here to enable the kernel to panic when it oopses. This
947 has the same effect as setting oops=panic on the kernel command
950 This feature is useful to ensure that the kernel does not do
951 anything erroneous after an oops which could result in data
952 corruption or other issues.
956 config PANIC_ON_OOPS_VALUE
959 default 0 if !PANIC_ON_OOPS
960 default 1 if PANIC_ON_OOPS
966 Set the timeout value (in seconds) until a reboot occurs when the
967 the kernel panics. If n = 0, then we wait forever. A timeout
968 value n > 0 will wait n seconds before rebooting, while a timeout
969 value n < 0 will reboot immediately.
972 bool "Collect scheduler debugging info"
973 depends on DEBUG_KERNEL && PROC_FS
976 If you say Y here, the /proc/sched_debug file will be provided
977 that can help debug the scheduler. The runtime overhead of this
985 bool "Collect scheduler statistics"
986 depends on DEBUG_KERNEL && PROC_FS
989 If you say Y here, additional code will be inserted into the
990 scheduler and related routines to collect statistics about
991 scheduler behavior and provide them in /proc/schedstat. These
992 stats may be useful for both tuning and debugging the scheduler
993 If you aren't debugging the scheduler or trying to tune a specific
994 application, you can say N to avoid the very slight overhead
997 config SCHED_STACK_END_CHECK
998 bool "Detect stack corruption on calls to schedule()"
999 depends on DEBUG_KERNEL
1002 This option checks for a stack overrun on calls to schedule().
1003 If the stack end location is found to be over written always panic as
1004 the content of the corrupted region can no longer be trusted.
1005 This is to ensure no erroneous behaviour occurs which could result in
1006 data corruption or a sporadic crash at a later stage once the region
1007 is examined. The runtime overhead introduced is minimal.
1009 config DEBUG_TIMEKEEPING
1010 bool "Enable extra timekeeping sanity checking"
1012 This option will enable additional timekeeping sanity checks
1013 which may be helpful when diagnosing issues where timekeeping
1014 problems are suspected.
1016 This may include checks in the timekeeping hotpaths, so this
1017 option may have a (very small) performance impact to some
1022 config DEBUG_PREEMPT
1023 bool "Debug preemptible kernel"
1024 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1027 If you say Y here then the kernel will use a debug variant of the
1028 commonly used smp_processor_id() function and will print warnings
1029 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1030 will detect preemption count underflows.
1032 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1034 config LOCK_DEBUGGING_SUPPORT
1036 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1039 config PROVE_LOCKING
1040 bool "Lock debugging: prove locking correctness"
1041 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1043 select DEBUG_SPINLOCK
1044 select DEBUG_MUTEXES
1045 select DEBUG_RT_MUTEXES if RT_MUTEXES
1046 select DEBUG_RWSEMS if RWSEM_SPIN_ON_OWNER
1047 select DEBUG_WW_MUTEX_SLOWPATH
1048 select DEBUG_LOCK_ALLOC
1049 select TRACE_IRQFLAGS
1052 This feature enables the kernel to prove that all locking
1053 that occurs in the kernel runtime is mathematically
1054 correct: that under no circumstance could an arbitrary (and
1055 not yet triggered) combination of observed locking
1056 sequences (on an arbitrary number of CPUs, running an
1057 arbitrary number of tasks and interrupt contexts) cause a
1060 In short, this feature enables the kernel to report locking
1061 related deadlocks before they actually occur.
1063 The proof does not depend on how hard and complex a
1064 deadlock scenario would be to trigger: how many
1065 participant CPUs, tasks and irq-contexts would be needed
1066 for it to trigger. The proof also does not depend on
1067 timing: if a race and a resulting deadlock is possible
1068 theoretically (no matter how unlikely the race scenario
1069 is), it will be proven so and will immediately be
1070 reported by the kernel (once the event is observed that
1071 makes the deadlock theoretically possible).
1073 If a deadlock is impossible (i.e. the locking rules, as
1074 observed by the kernel, are mathematically correct), the
1075 kernel reports nothing.
1077 NOTE: this feature can also be enabled for rwlocks, mutexes
1078 and rwsems - in which case all dependencies between these
1079 different locking variants are observed and mapped too, and
1080 the proof of observed correctness is also maintained for an
1081 arbitrary combination of these separate locking variants.
1083 For more details, see Documentation/locking/lockdep-design.txt.
1086 bool "Lock usage statistics"
1087 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1089 select DEBUG_SPINLOCK
1090 select DEBUG_MUTEXES
1091 select DEBUG_RT_MUTEXES if RT_MUTEXES
1092 select DEBUG_LOCK_ALLOC
1095 This feature enables tracking lock contention points
1097 For more details, see Documentation/locking/lockstat.txt
1099 This also enables lock events required by "perf lock",
1101 If you want to use "perf lock", you also need to turn on
1102 CONFIG_EVENT_TRACING.
1104 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1105 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1107 config DEBUG_RT_MUTEXES
1108 bool "RT Mutex debugging, deadlock detection"
1109 depends on DEBUG_KERNEL && RT_MUTEXES
1111 This allows rt mutex semantics violations and rt mutex related
1112 deadlocks (lockups) to be detected and reported automatically.
1114 config DEBUG_SPINLOCK
1115 bool "Spinlock and rw-lock debugging: basic checks"
1116 depends on DEBUG_KERNEL
1117 select UNINLINE_SPIN_UNLOCK
1119 Say Y here and build SMP to catch missing spinlock initialization
1120 and certain other kinds of spinlock errors commonly made. This is
1121 best used in conjunction with the NMI watchdog so that spinlock
1122 deadlocks are also debuggable.
1124 config DEBUG_MUTEXES
1125 bool "Mutex debugging: basic checks"
1126 depends on DEBUG_KERNEL
1128 This feature allows mutex semantics violations to be detected and
1131 config DEBUG_WW_MUTEX_SLOWPATH
1132 bool "Wait/wound mutex debugging: Slowpath testing"
1133 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1134 select DEBUG_LOCK_ALLOC
1135 select DEBUG_SPINLOCK
1136 select DEBUG_MUTEXES
1138 This feature enables slowpath testing for w/w mutex users by
1139 injecting additional -EDEADLK wound/backoff cases. Together with
1140 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1141 will test all possible w/w mutex interface abuse with the
1142 exception of simply not acquiring all the required locks.
1143 Note that this feature can introduce significant overhead, so
1144 it really should not be enabled in a production or distro kernel,
1145 even a debug kernel. If you are a driver writer, enable it. If
1146 you are a distro, do not.
1149 bool "RW Semaphore debugging: basic checks"
1150 depends on DEBUG_KERNEL && RWSEM_SPIN_ON_OWNER
1152 This debugging feature allows mismatched rw semaphore locks and unlocks
1153 to be detected and reported.
1155 config DEBUG_LOCK_ALLOC
1156 bool "Lock debugging: detect incorrect freeing of live locks"
1157 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1158 select DEBUG_SPINLOCK
1159 select DEBUG_MUTEXES
1160 select DEBUG_RT_MUTEXES if RT_MUTEXES
1163 This feature will check whether any held lock (spinlock, rwlock,
1164 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1165 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1166 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1167 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1168 held during task exit.
1172 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1174 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !X86
1178 config LOCKDEP_SMALL
1181 config DEBUG_LOCKDEP
1182 bool "Lock dependency engine debugging"
1183 depends on DEBUG_KERNEL && LOCKDEP
1185 If you say Y here, the lock dependency engine will do
1186 additional runtime checks to debug itself, at the price
1187 of more runtime overhead.
1189 config DEBUG_ATOMIC_SLEEP
1190 bool "Sleep inside atomic section checking"
1191 select PREEMPT_COUNT
1192 depends on DEBUG_KERNEL
1194 If you say Y here, various routines which may sleep will become very
1195 noisy if they are called inside atomic sections: when a spinlock is
1196 held, inside an rcu read side critical section, inside preempt disabled
1197 sections, inside an interrupt, etc...
1199 config DEBUG_LOCKING_API_SELFTESTS
1200 bool "Locking API boot-time self-tests"
1201 depends on DEBUG_KERNEL
1203 Say Y here if you want the kernel to run a short self-test during
1204 bootup. The self-test checks whether common types of locking bugs
1205 are detected by debugging mechanisms or not. (if you disable
1206 lock debugging then those bugs wont be detected of course.)
1207 The following locking APIs are covered: spinlocks, rwlocks,
1210 config LOCK_TORTURE_TEST
1211 tristate "torture tests for locking"
1212 depends on DEBUG_KERNEL
1216 This option provides a kernel module that runs torture tests
1217 on kernel locking primitives. The kernel module may be built
1218 after the fact on the running kernel to be tested, if desired.
1220 Say Y here if you want kernel locking-primitive torture tests
1221 to be built into the kernel.
1222 Say M if you want these torture tests to build as a module.
1223 Say N if you are unsure.
1225 config WW_MUTEX_SELFTEST
1226 tristate "Wait/wound mutex selftests"
1228 This option provides a kernel module that runs tests on the
1229 on the struct ww_mutex locking API.
1231 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1232 with this test harness.
1234 Say M if you want these self tests to build as a module.
1235 Say N if you are unsure.
1237 endmenu # lock debugging
1239 config TRACE_IRQFLAGS
1242 Enables hooks to interrupt enabling and disabling for
1243 either tracing or lock debugging.
1246 bool "Stack backtrace support"
1247 depends on STACKTRACE_SUPPORT
1249 This option causes the kernel to create a /proc/pid/stack for
1250 every process, showing its current stack trace.
1251 It is also used by various kernel debugging features that require
1252 stack trace generation.
1254 config WARN_ALL_UNSEEDED_RANDOM
1255 bool "Warn for all uses of unseeded randomness"
1258 Some parts of the kernel contain bugs relating to their use of
1259 cryptographically secure random numbers before it's actually possible
1260 to generate those numbers securely. This setting ensures that these
1261 flaws don't go unnoticed, by enabling a message, should this ever
1262 occur. This will allow people with obscure setups to know when things
1263 are going wrong, so that they might contact developers about fixing
1266 Unfortunately, on some models of some architectures getting
1267 a fully seeded CRNG is extremely difficult, and so this can
1268 result in dmesg getting spammed for a surprisingly long
1269 time. This is really bad from a security perspective, and
1270 so architecture maintainers really need to do what they can
1271 to get the CRNG seeded sooner after the system is booted.
1272 However, since users can not do anything actionble to
1273 address this, by default the kernel will issue only a single
1274 warning for the first use of unseeded randomness.
1276 Say Y here if you want to receive warnings for all uses of
1277 unseeded randomness. This will be of use primarily for
1278 those developers interersted in improving the security of
1279 Linux kernels running on their architecture (or
1282 config DEBUG_KOBJECT
1283 bool "kobject debugging"
1284 depends on DEBUG_KERNEL
1286 If you say Y here, some extra kobject debugging messages will be sent
1289 config DEBUG_KOBJECT_RELEASE
1290 bool "kobject release debugging"
1291 depends on DEBUG_OBJECTS_TIMERS
1293 kobjects are reference counted objects. This means that their
1294 last reference count put is not predictable, and the kobject can
1295 live on past the point at which a driver decides to drop it's
1296 initial reference to the kobject gained on allocation. An
1297 example of this would be a struct device which has just been
1300 However, some buggy drivers assume that after such an operation,
1301 the memory backing the kobject can be immediately freed. This
1302 goes completely against the principles of a refcounted object.
1304 If you say Y here, the kernel will delay the release of kobjects
1305 on the last reference count to improve the visibility of this
1306 kind of kobject release bug.
1308 config HAVE_DEBUG_BUGVERBOSE
1311 config DEBUG_BUGVERBOSE
1312 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1313 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1316 Say Y here to make BUG() panics output the file name and line number
1317 of the BUG call as well as the EIP and oops trace. This aids
1318 debugging but costs about 70-100K of memory.
1321 bool "Debug linked list manipulation"
1322 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1324 Enable this to turn on extended checks in the linked-list
1329 config DEBUG_PI_LIST
1330 bool "Debug priority linked list manipulation"
1331 depends on DEBUG_KERNEL
1333 Enable this to turn on extended checks in the priority-ordered
1334 linked-list (plist) walking routines. This checks the entire
1335 list multiple times during each manipulation.
1340 bool "Debug SG table operations"
1341 depends on DEBUG_KERNEL
1343 Enable this to turn on checks on scatter-gather tables. This can
1344 help find problems with drivers that do not properly initialize
1349 config DEBUG_NOTIFIERS
1350 bool "Debug notifier call chains"
1351 depends on DEBUG_KERNEL
1353 Enable this to turn on sanity checking for notifier call chains.
1354 This is most useful for kernel developers to make sure that
1355 modules properly unregister themselves from notifier chains.
1356 This is a relatively cheap check but if you care about maximum
1359 config DEBUG_CREDENTIALS
1360 bool "Debug credential management"
1361 depends on DEBUG_KERNEL
1363 Enable this to turn on some debug checking for credential
1364 management. The additional code keeps track of the number of
1365 pointers from task_structs to any given cred struct, and checks to
1366 see that this number never exceeds the usage count of the cred
1369 Furthermore, if SELinux is enabled, this also checks that the
1370 security pointer in the cred struct is never seen to be invalid.
1374 source "kernel/rcu/Kconfig.debug"
1376 config DEBUG_WQ_FORCE_RR_CPU
1377 bool "Force round-robin CPU selection for unbound work items"
1378 depends on DEBUG_KERNEL
1381 Workqueue used to implicitly guarantee that work items queued
1382 without explicit CPU specified are put on the local CPU. This
1383 guarantee is no longer true and while local CPU is still
1384 preferred work items may be put on foreign CPUs. Kernel
1385 parameter "workqueue.debug_force_rr_cpu" is added to force
1386 round-robin CPU selection to flush out usages which depend on the
1387 now broken guarantee. This config option enables the debug
1388 feature by default. When enabled, memory and cache locality will
1391 config DEBUG_BLOCK_EXT_DEVT
1392 bool "Force extended block device numbers and spread them"
1393 depends on DEBUG_KERNEL
1397 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1398 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1399 YOU ARE DOING. Distros, please enable this and fix whatever
1402 Conventionally, block device numbers are allocated from
1403 predetermined contiguous area. However, extended block area
1404 may introduce non-contiguous block device numbers. This
1405 option forces most block device numbers to be allocated from
1406 the extended space and spreads them to discover kernel or
1407 userland code paths which assume predetermined contiguous
1408 device number allocation.
1410 Note that turning on this debug option shuffles all the
1411 device numbers for all IDE and SCSI devices including libata
1412 ones, so root partition specified using device number
1413 directly (via rdev or root=MAJ:MIN) won't work anymore.
1414 Textual device names (root=/dev/sdXn) will continue to work.
1416 Say N if you are unsure.
1418 config CPU_HOTPLUG_STATE_CONTROL
1419 bool "Enable CPU hotplug state control"
1420 depends on DEBUG_KERNEL
1421 depends on HOTPLUG_CPU
1424 Allows to write steps between "offline" and "online" to the CPUs
1425 sysfs target file so states can be stepped granular. This is a debug
1426 option for now as the hotplug machinery cannot be stopped and
1427 restarted at arbitrary points yet.
1429 Say N if your are unsure.
1431 config NOTIFIER_ERROR_INJECTION
1432 tristate "Notifier error injection"
1433 depends on DEBUG_KERNEL
1436 This option provides the ability to inject artificial errors to
1437 specified notifier chain callbacks. It is useful to test the error
1438 handling of notifier call chain failures.
1442 config PM_NOTIFIER_ERROR_INJECT
1443 tristate "PM notifier error injection module"
1444 depends on PM && NOTIFIER_ERROR_INJECTION
1445 default m if PM_DEBUG
1447 This option provides the ability to inject artificial errors to
1448 PM notifier chain callbacks. It is controlled through debugfs
1449 interface /sys/kernel/debug/notifier-error-inject/pm
1451 If the notifier call chain should be failed with some events
1452 notified, write the error code to "actions/<notifier event>/error".
1454 Example: Inject PM suspend error (-12 = -ENOMEM)
1456 # cd /sys/kernel/debug/notifier-error-inject/pm/
1457 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1458 # echo mem > /sys/power/state
1459 bash: echo: write error: Cannot allocate memory
1461 To compile this code as a module, choose M here: the module will
1462 be called pm-notifier-error-inject.
1466 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1467 tristate "OF reconfig notifier error injection module"
1468 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1470 This option provides the ability to inject artificial errors to
1471 OF reconfig notifier chain callbacks. It is controlled
1472 through debugfs interface under
1473 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1475 If the notifier call chain should be failed with some events
1476 notified, write the error code to "actions/<notifier event>/error".
1478 To compile this code as a module, choose M here: the module will
1479 be called of-reconfig-notifier-error-inject.
1483 config NETDEV_NOTIFIER_ERROR_INJECT
1484 tristate "Netdev notifier error injection module"
1485 depends on NET && NOTIFIER_ERROR_INJECTION
1487 This option provides the ability to inject artificial errors to
1488 netdevice notifier chain callbacks. It is controlled through debugfs
1489 interface /sys/kernel/debug/notifier-error-inject/netdev
1491 If the notifier call chain should be failed with some events
1492 notified, write the error code to "actions/<notifier event>/error".
1494 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1496 # cd /sys/kernel/debug/notifier-error-inject/netdev
1497 # echo -22 > actions/NETDEV_CHANGEMTU/error
1498 # ip link set eth0 mtu 1024
1499 RTNETLINK answers: Invalid argument
1501 To compile this code as a module, choose M here: the module will
1502 be called netdev-notifier-error-inject.
1506 config FAULT_INJECTION
1507 bool "Fault-injection framework"
1508 depends on DEBUG_KERNEL
1510 Provide fault-injection framework.
1511 For more details, see Documentation/fault-injection/.
1513 config FUNCTION_ERROR_INJECTION
1515 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
1518 bool "Fault-injection capability for kmalloc"
1519 depends on FAULT_INJECTION
1520 depends on SLAB || SLUB
1522 Provide fault-injection capability for kmalloc.
1524 config FAIL_PAGE_ALLOC
1525 bool "Fault-injection capabilitiy for alloc_pages()"
1526 depends on FAULT_INJECTION
1528 Provide fault-injection capability for alloc_pages().
1530 config FAIL_MAKE_REQUEST
1531 bool "Fault-injection capability for disk IO"
1532 depends on FAULT_INJECTION && BLOCK
1534 Provide fault-injection capability for disk IO.
1536 config FAIL_IO_TIMEOUT
1537 bool "Fault-injection capability for faking disk interrupts"
1538 depends on FAULT_INJECTION && BLOCK
1540 Provide fault-injection capability on end IO handling. This
1541 will make the block layer "forget" an interrupt as configured,
1542 thus exercising the error handling.
1544 Only works with drivers that use the generic timeout handling,
1545 for others it wont do anything.
1547 config FAIL_MMC_REQUEST
1548 bool "Fault-injection capability for MMC IO"
1549 depends on FAULT_INJECTION_DEBUG_FS && MMC
1551 Provide fault-injection capability for MMC IO.
1552 This will make the mmc core return data errors. This is
1553 useful to test the error handling in the mmc block device
1554 and to test how the mmc host driver handles retries from
1558 bool "Fault-injection capability for futexes"
1560 depends on FAULT_INJECTION && FUTEX
1562 Provide fault-injection capability for futexes.
1564 config FAIL_FUNCTION
1565 bool "Fault-injection capability for functions"
1566 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
1568 Provide function-based fault-injection capability.
1569 This will allow you to override a specific function with a return
1570 with given return value. As a result, function caller will see
1571 an error value and have to handle it. This is useful to test the
1572 error handling in various subsystems.
1574 config FAULT_INJECTION_DEBUG_FS
1575 bool "Debugfs entries for fault-injection capabilities"
1576 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1578 Enable configuration of fault-injection capabilities via debugfs.
1580 config FAULT_INJECTION_STACKTRACE_FILTER
1581 bool "stacktrace filter for fault-injection capabilities"
1582 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1585 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !X86
1587 Provide stacktrace filter for fault-injection capabilities
1590 bool "Latency measuring infrastructure"
1591 depends on DEBUG_KERNEL
1592 depends on STACKTRACE_SUPPORT
1594 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !X86
1601 Enable this option if you want to use the LatencyTOP tool
1602 to find out which userspace is blocking on what kernel operations.
1604 source kernel/trace/Kconfig
1606 config PROVIDE_OHCI1394_DMA_INIT
1607 bool "Remote debugging over FireWire early on boot"
1608 depends on PCI && X86
1610 If you want to debug problems which hang or crash the kernel early
1611 on boot and the crashing machine has a FireWire port, you can use
1612 this feature to remotely access the memory of the crashed machine
1613 over FireWire. This employs remote DMA as part of the OHCI1394
1614 specification which is now the standard for FireWire controllers.
1616 With remote DMA, you can monitor the printk buffer remotely using
1617 firescope and access all memory below 4GB using fireproxy from gdb.
1618 Even controlling a kernel debugger is possible using remote DMA.
1622 If ohci1394_dma=early is used as boot parameter, it will initialize
1623 all OHCI1394 controllers which are found in the PCI config space.
1625 As all changes to the FireWire bus such as enabling and disabling
1626 devices cause a bus reset and thereby disable remote DMA for all
1627 devices, be sure to have the cable plugged and FireWire enabled on
1628 the debugging host before booting the debug target for debugging.
1630 This code (~1k) is freed after boot. By then, the firewire stack
1631 in charge of the OHCI-1394 controllers should be used instead.
1633 See Documentation/debugging-via-ohci1394.txt for more information.
1635 config DMA_API_DEBUG
1636 bool "Enable debugging of DMA-API usage"
1637 select NEED_DMA_MAP_STATE
1639 Enable this option to debug the use of the DMA API by device drivers.
1640 With this option you will be able to detect common bugs in device
1641 drivers like double-freeing of DMA mappings or freeing mappings that
1642 were never allocated.
1644 This also attempts to catch cases where a page owned by DMA is
1645 accessed by the cpu in a way that could cause data corruption. For
1646 example, this enables cow_user_page() to check that the source page is
1649 This option causes a performance degradation. Use only if you want to
1650 debug device drivers and dma interactions.
1654 config DMA_API_DEBUG_SG
1655 bool "Debug DMA scatter-gather usage"
1657 depends on DMA_API_DEBUG
1659 Perform extra checking that callers of dma_map_sg() have respected the
1660 appropriate segment length/boundary limits for the given device when
1661 preparing DMA scatterlists.
1663 This is particularly likely to have been overlooked in cases where the
1664 dma_map_sg() API is used for general bulk mapping of pages rather than
1665 preparing literal scatter-gather descriptors, where there is a risk of
1666 unexpected behaviour from DMA API implementations if the scatterlist
1667 is technically out-of-spec.
1671 menuconfig RUNTIME_TESTING_MENU
1672 bool "Runtime Testing"
1675 if RUNTIME_TESTING_MENU
1678 tristate "Linux Kernel Dump Test Tool Module"
1683 This module enables testing of the different dumping mechanisms by
1684 inducing system failures at predefined crash points.
1685 If you don't need it: say N
1686 Choose M here to compile this code as a module. The module will be
1689 Documentation on how to use the module can be found in
1690 Documentation/fault-injection/provoke-crashes.txt
1692 config TEST_LIST_SORT
1693 tristate "Linked list sorting test"
1694 depends on DEBUG_KERNEL || m
1696 Enable this to turn on 'list_sort()' function test. This test is
1697 executed only once during system boot (so affects only boot time),
1698 or at module load time.
1703 tristate "Array-based sort test"
1704 depends on DEBUG_KERNEL || m
1706 This option enables the self-test function of 'sort()' at boot,
1707 or at module load time.
1711 config KPROBES_SANITY_TEST
1712 bool "Kprobes sanity tests"
1713 depends on DEBUG_KERNEL
1717 This option provides for testing basic kprobes functionality on
1718 boot. A sample kprobe, jprobe and kretprobe are inserted and
1719 verified for functionality.
1721 Say N if you are unsure.
1723 config BACKTRACE_SELF_TEST
1724 tristate "Self test for the backtrace code"
1725 depends on DEBUG_KERNEL
1728 This option provides a kernel module that can be used to test
1729 the kernel stack backtrace code. This option is not useful
1730 for distributions or general kernels, but only for kernel
1731 developers working on architecture code.
1733 Note that if you want to also test saved backtraces, you will
1734 have to enable STACKTRACE as well.
1736 Say N if you are unsure.
1739 tristate "Red-Black tree test"
1740 depends on DEBUG_KERNEL
1742 A benchmark measuring the performance of the rbtree library.
1743 Also includes rbtree invariant checks.
1745 config INTERVAL_TREE_TEST
1746 tristate "Interval tree test"
1747 depends on DEBUG_KERNEL
1748 select INTERVAL_TREE
1750 A benchmark measuring the performance of the interval tree library
1753 tristate "Per cpu operations test"
1754 depends on m && DEBUG_KERNEL
1756 Enable this option to build test module which validates per-cpu
1761 config ATOMIC64_SELFTEST
1762 tristate "Perform an atomic64_t self-test"
1764 Enable this option to test the atomic64_t functions at boot or
1765 at module load time.
1769 config ASYNC_RAID6_TEST
1770 tristate "Self test for hardware accelerated raid6 recovery"
1771 depends on ASYNC_RAID6_RECOV
1774 This is a one-shot self test that permutes through the
1775 recovery of all the possible two disk failure scenarios for a
1776 N-disk array. Recovery is performed with the asynchronous
1777 raid6 recovery routines, and will optionally use an offload
1778 engine if one is available.
1783 tristate "Test functions located in the hexdump module at runtime"
1785 config TEST_STRING_HELPERS
1786 tristate "Test functions located in the string_helpers module at runtime"
1789 tristate "Test kstrto*() family of functions at runtime"
1792 tristate "Test printf() family of functions at runtime"
1795 tristate "Test bitmap_*() family of functions at runtime"
1798 Enable this option to test the bitmap functions at boot.
1803 tristate "Test functions located in the uuid module at runtime"
1805 config TEST_OVERFLOW
1806 tristate "Test check_*_overflow() functions at runtime"
1808 config TEST_RHASHTABLE
1809 tristate "Perform selftest on resizable hash table"
1812 Enable this option to test the rhashtable functions at boot.
1817 tristate "Perform selftest on hash functions"
1820 Enable this option to test the kernel's integer (<linux/hash.h>),
1821 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1822 hash functions on boot (or module load).
1824 This is intended to help people writing architecture-specific
1825 optimized versions. If unsure, say N.
1828 tristate "Perform selftest on priority array manager"
1832 Enable this option to test priority array manager on boot
1838 tristate "Test module loading with 'hello world' module"
1842 This builds the "test_module" module that emits "Hello, world"
1843 on printk when loaded. It is designed to be used for basic
1844 evaluation of the module loading subsystem (for example when
1845 validating module verification). It lacks any extra dependencies,
1846 and will not normally be loaded by the system unless explicitly
1851 config TEST_USER_COPY
1852 tristate "Test user/kernel boundary protections"
1856 This builds the "test_user_copy" module that runs sanity checks
1857 on the copy_to/from_user infrastructure, making sure basic
1858 user/kernel boundary testing is working. If it fails to load,
1859 a regression has been detected in the user/kernel memory boundary
1865 tristate "Test BPF filter functionality"
1869 This builds the "test_bpf" module that runs various test vectors
1870 against the BPF interpreter or BPF JIT compiler depending on the
1871 current setting. This is in particular useful for BPF JIT compiler
1872 development, but also to run regression tests against changes in
1873 the interpreter code. It also enables test stubs for eBPF maps and
1874 verifier used by user space verifier testsuite.
1878 config FIND_BIT_BENCHMARK
1879 tristate "Test find_bit functions"
1882 This builds the "test_find_bit" module that measure find_*_bit()
1883 functions performance.
1887 config TEST_FIRMWARE
1888 tristate "Test firmware loading via userspace interface"
1890 depends on FW_LOADER
1892 This builds the "test_firmware" module that creates a userspace
1893 interface for testing firmware loading. This can be used to
1894 control the triggering of firmware loading without needing an
1895 actual firmware-using device. The contents can be rechecked by
1901 tristate "sysctl test driver"
1903 depends on PROC_SYSCTL
1905 This builds the "test_sysctl" module. This driver enables to test the
1906 proc sysctl interfaces available to drivers safely without affecting
1907 production knobs which might alter system functionality.
1912 tristate "udelay test driver"
1915 This builds the "udelay_test" module that helps to make sure
1916 that udelay() is working properly.
1920 config TEST_STATIC_KEYS
1921 tristate "Test static keys"
1925 Test the static key interfaces.
1930 tristate "kmod stress tester"
1933 depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS
1934 depends on NETDEVICES && NET_CORE && INET # for TUN
1940 Test the kernel's module loading mechanism: kmod. kmod implements
1941 support to load modules using the Linux kernel's usermode helper.
1942 This test provides a series of tests against kmod.
1944 Although technically you can either build test_kmod as a module or
1945 into the kernel we disallow building it into the kernel since
1946 it stress tests request_module() and this will very likely cause
1947 some issues by taking over precious threads available from other
1948 module load requests, ultimately this could be fatal.
1952 tools/testing/selftests/kmod/kmod.sh --help
1956 config TEST_DEBUG_VIRTUAL
1957 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
1958 depends on DEBUG_VIRTUAL
1960 Test the kernel's ability to detect incorrect calls to
1961 virt_to_phys() done against the non-linear part of the
1962 kernel's virtual address map.
1966 endif # RUNTIME_TESTING_MENU
1970 depends on HAVE_MEMBLOCK
1972 This option adds a kernel parameter 'memtest', which allows memtest
1974 memtest=0, mean disabled; -- default
1975 memtest=1, mean do 1 test pattern;
1977 memtest=17, mean do 17 test patterns.
1978 If you are unsure how to answer this question, answer N.
1980 config BUG_ON_DATA_CORRUPTION
1981 bool "Trigger a BUG when data corruption is detected"
1984 Select this option if the kernel should BUG when it encounters
1985 data corruption in kernel memory structures when they get checked
1990 source "samples/Kconfig"
1992 source "lib/Kconfig.kgdb"
1994 source "lib/Kconfig.ubsan"
1996 config ARCH_HAS_DEVMEM_IS_ALLOWED
1999 config STRICT_DEVMEM
2000 bool "Filter access to /dev/mem"
2001 depends on MMU && DEVMEM
2002 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
2003 default y if PPC || X86 || ARM64
2005 If this option is disabled, you allow userspace (root) access to all
2006 of memory, including kernel and userspace memory. Accidental
2007 access to this is obviously disastrous, but specific access can
2008 be used by people debugging the kernel. Note that with PAT support
2009 enabled, even in this case there are restrictions on /dev/mem
2010 use due to the cache aliasing requirements.
2012 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
2013 file only allows userspace access to PCI space and the BIOS code and
2014 data regions. This is sufficient for dosemu and X and all common
2019 config IO_STRICT_DEVMEM
2020 bool "Filter I/O access to /dev/mem"
2021 depends on STRICT_DEVMEM
2023 If this option is disabled, you allow userspace (root) access to all
2024 io-memory regardless of whether a driver is actively using that
2025 range. Accidental access to this is obviously disastrous, but
2026 specific access can be used by people debugging kernel drivers.
2028 If this option is switched on, the /dev/mem file only allows
2029 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2030 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2031 if the driver using a given range cannot be disabled.
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