1 # SPDX-License-Identifier: GPL-2.0-only
4 menu "printk and dmesg options"
7 bool "Show timing information on printks"
10 Selecting this option causes time stamps of the printk()
11 messages to be added to the output of the syslog() system
12 call and at the console.
14 The timestamp is always recorded internally, and exported
15 to /dev/kmsg. This flag just specifies if the timestamp should
16 be included, not that the timestamp is recorded.
18 The behavior is also controlled by the kernel command line
19 parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst
22 bool "Show caller information on printks"
25 Selecting this option causes printk() to add a caller "thread id" (if
26 in task context) or a caller "processor id" (if not in task context)
29 This option is intended for environments where multiple threads
30 concurrently call printk() for many times, for it is difficult to
31 interpret without knowing where these lines (or sometimes individual
32 line which was divided into multiple lines due to race) came from.
34 Since toggling after boot makes the code racy, currently there is
35 no option to enable/disable at the kernel command line parameter or
38 config CONSOLE_LOGLEVEL_DEFAULT
39 int "Default console loglevel (1-15)"
43 Default loglevel to determine what will be printed on the console.
45 Setting a default here is equivalent to passing in loglevel=<x> in
46 the kernel bootargs. loglevel=<x> continues to override whatever
47 value is specified here as well.
49 Note: This does not affect the log level of un-prefixed printk()
50 usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
53 config CONSOLE_LOGLEVEL_QUIET
54 int "quiet console loglevel (1-15)"
58 loglevel to use when "quiet" is passed on the kernel commandline.
60 When "quiet" is passed on the kernel commandline this loglevel
61 will be used as the loglevel. IOW passing "quiet" will be the
62 equivalent of passing "loglevel=<CONSOLE_LOGLEVEL_QUIET>"
64 config MESSAGE_LOGLEVEL_DEFAULT
65 int "Default message log level (1-7)"
69 Default log level for printk statements with no specified priority.
71 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
72 that are auditing their logs closely may want to set it to a lower
75 Note: This does not affect what message level gets printed on the console
76 by default. To change that, use loglevel=<x> in the kernel bootargs,
77 or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value.
79 config BOOT_PRINTK_DELAY
80 bool "Delay each boot printk message by N milliseconds"
81 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
83 This build option allows you to read kernel boot messages
84 by inserting a short delay after each one. The delay is
85 specified in milliseconds on the kernel command line,
88 It is likely that you would also need to use "lpj=M" to preset
89 the "loops per jiffie" value.
90 See a previous boot log for the "lpj" value to use for your
91 system, and then set "lpj=M" before setting "boot_delay=N".
92 NOTE: Using this option may adversely affect SMP systems.
93 I.e., processors other than the first one may not boot up.
94 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
95 what it believes to be lockup conditions.
98 bool "Enable dynamic printk() support"
104 Compiles debug level messages into the kernel, which would not
105 otherwise be available at runtime. These messages can then be
106 enabled/disabled based on various levels of scope - per source file,
107 function, module, format string, and line number. This mechanism
108 implicitly compiles in all pr_debug() and dev_dbg() calls, which
109 enlarges the kernel text size by about 2%.
111 If a source file is compiled with DEBUG flag set, any
112 pr_debug() calls in it are enabled by default, but can be
113 disabled at runtime as below. Note that DEBUG flag is
114 turned on by many CONFIG_*DEBUG* options.
118 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
119 which is contained in the 'debugfs' filesystem. Thus, the debugfs
120 filesystem must first be mounted before making use of this feature.
121 We refer the control file as: <debugfs>/dynamic_debug/control. This
122 file contains a list of the debug statements that can be enabled. The
123 format for each line of the file is:
125 filename:lineno [module]function flags format
127 filename : source file of the debug statement
128 lineno : line number of the debug statement
129 module : module that contains the debug statement
130 function : function that contains the debug statement
131 flags : '=p' means the line is turned 'on' for printing
132 format : the format used for the debug statement
136 nullarbor:~ # cat <debugfs>/dynamic_debug/control
137 # filename:lineno [module]function flags format
138 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
139 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
140 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
144 // enable the message at line 1603 of file svcsock.c
145 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
146 <debugfs>/dynamic_debug/control
148 // enable all the messages in file svcsock.c
149 nullarbor:~ # echo -n 'file svcsock.c +p' >
150 <debugfs>/dynamic_debug/control
152 // enable all the messages in the NFS server module
153 nullarbor:~ # echo -n 'module nfsd +p' >
154 <debugfs>/dynamic_debug/control
156 // enable all 12 messages in the function svc_process()
157 nullarbor:~ # echo -n 'func svc_process +p' >
158 <debugfs>/dynamic_debug/control
160 // disable all 12 messages in the function svc_process()
161 nullarbor:~ # echo -n 'func svc_process -p' >
162 <debugfs>/dynamic_debug/control
164 See Documentation/admin-guide/dynamic-debug-howto.rst for additional
167 endmenu # "printk and dmesg options"
169 menu "Compile-time checks and compiler options"
172 bool "Compile the kernel with debug info"
173 depends on DEBUG_KERNEL && !COMPILE_TEST
175 If you say Y here the resulting kernel image will include
176 debugging info resulting in a larger kernel image.
177 This adds debug symbols to the kernel and modules (gcc -g), and
178 is needed if you intend to use kernel crashdump or binary object
179 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
180 Say Y here only if you plan to debug the kernel.
184 config DEBUG_INFO_REDUCED
185 bool "Reduce debugging information"
186 depends on DEBUG_INFO
188 If you say Y here gcc is instructed to generate less debugging
189 information for structure types. This means that tools that
190 need full debugging information (like kgdb or systemtap) won't
191 be happy. But if you merely need debugging information to
192 resolve line numbers there is no loss. Advantage is that
193 build directory object sizes shrink dramatically over a full
194 DEBUG_INFO build and compile times are reduced too.
195 Only works with newer gcc versions.
197 config DEBUG_INFO_SPLIT
198 bool "Produce split debuginfo in .dwo files"
199 depends on DEBUG_INFO
200 depends on $(cc-option,-gsplit-dwarf)
202 Generate debug info into separate .dwo files. This significantly
203 reduces the build directory size for builds with DEBUG_INFO,
204 because it stores the information only once on disk in .dwo
205 files instead of multiple times in object files and executables.
206 In addition the debug information is also compressed.
208 Requires recent gcc (4.7+) and recent gdb/binutils.
209 Any tool that packages or reads debug information would need
210 to know about the .dwo files and include them.
211 Incompatible with older versions of ccache.
213 config DEBUG_INFO_DWARF4
214 bool "Generate dwarf4 debuginfo"
215 depends on DEBUG_INFO
216 depends on $(cc-option,-gdwarf-4)
218 Generate dwarf4 debug info. This requires recent versions
219 of gcc and gdb. It makes the debug information larger.
220 But it significantly improves the success of resolving
221 variables in gdb on optimized code.
223 config DEBUG_INFO_BTF
224 bool "Generate BTF typeinfo"
225 depends on DEBUG_INFO
227 Generate deduplicated BTF type information from DWARF debug info.
228 Turning this on expects presence of pahole tool, which will convert
229 DWARF type info into equivalent deduplicated BTF type info.
232 bool "Provide GDB scripts for kernel debugging"
233 depends on DEBUG_INFO
235 This creates the required links to GDB helper scripts in the
236 build directory. If you load vmlinux into gdb, the helper
237 scripts will be automatically imported by gdb as well, and
238 additional functions are available to analyze a Linux kernel
239 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
242 config ENABLE_MUST_CHECK
243 bool "Enable __must_check logic"
246 Enable the __must_check logic in the kernel build. Disable this to
247 suppress the "warning: ignoring return value of 'foo', declared with
248 attribute warn_unused_result" messages.
251 int "Warn for stack frames larger than (needs gcc 4.4)"
253 default 2048 if GCC_PLUGIN_LATENT_ENTROPY
254 default 1280 if (!64BIT && PARISC)
255 default 1024 if (!64BIT && !PARISC)
256 default 2048 if 64BIT
258 Tell gcc to warn at build time for stack frames larger than this.
259 Setting this too low will cause a lot of warnings.
260 Setting it to 0 disables the warning.
263 config STRIP_ASM_SYMS
264 bool "Strip assembler-generated symbols during link"
267 Strip internal assembler-generated symbols during a link (symbols
268 that look like '.Lxxx') so they don't pollute the output of
269 get_wchan() and suchlike.
272 bool "Generate readable assembler code"
273 depends on DEBUG_KERNEL
275 Disable some compiler optimizations that tend to generate human unreadable
276 assembler output. This may make the kernel slightly slower, but it helps
277 to keep kernel developers who have to stare a lot at assembler listings
281 bool "Debug Filesystem"
283 debugfs is a virtual file system that kernel developers use to put
284 debugging files into. Enable this option to be able to read and
285 write to these files.
287 For detailed documentation on the debugfs API, see
288 Documentation/filesystems/.
292 config HEADERS_INSTALL
293 bool "Install uapi headers to usr/include"
296 This option will install uapi headers (headers exported to user-space)
297 into the usr/include directory for use during the kernel build.
298 This is unneeded for building the kernel itself, but needed for some
299 user-space program samples. It is also needed by some features such
300 as uapi header sanity checks.
302 config OPTIMIZE_INLINING
305 This option determines if the kernel forces gcc to inline the functions
306 developers have marked 'inline'. Doing so takes away freedom from gcc to
307 do what it thinks is best, which is desirable for the gcc 3.x series of
308 compilers. The gcc 4.x series have a rewritten inlining algorithm and
309 enabling this option will generate a smaller kernel there. Hopefully
310 this algorithm is so good that allowing gcc 4.x and above to make the
311 decision will become the default in the future. Until then this option
312 is there to test gcc for this.
314 config DEBUG_SECTION_MISMATCH
315 bool "Enable full Section mismatch analysis"
317 The section mismatch analysis checks if there are illegal
318 references from one section to another section.
319 During linktime or runtime, some sections are dropped;
320 any use of code/data previously in these sections would
321 most likely result in an oops.
322 In the code, functions and variables are annotated with
323 __init,, etc. (see the full list in include/linux/init.h),
324 which results in the code/data being placed in specific sections.
325 The section mismatch analysis is always performed after a full
326 kernel build, and enabling this option causes the following
327 additional step to occur:
328 - Add the option -fno-inline-functions-called-once to gcc commands.
329 When inlining a function annotated with __init in a non-init
330 function, we would lose the section information and thus
331 the analysis would not catch the illegal reference.
332 This option tells gcc to inline less (but it does result in
335 config SECTION_MISMATCH_WARN_ONLY
336 bool "Make section mismatch errors non-fatal"
339 If you say N here, the build process will fail if there are any
340 section mismatch, instead of just throwing warnings.
345 # Select this config option from the architecture Kconfig, if it
346 # is preferred to always offer frame pointers as a config
347 # option on the architecture (regardless of KERNEL_DEBUG):
349 config ARCH_WANT_FRAME_POINTERS
353 bool "Compile the kernel with frame pointers"
354 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS
355 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
357 If you say Y here the resulting kernel image will be slightly
358 larger and slower, but it gives very useful debugging information
359 in case of kernel bugs. (precise oopses/stacktraces/warnings)
361 config STACK_VALIDATION
362 bool "Compile-time stack metadata validation"
363 depends on HAVE_STACK_VALIDATION
366 Add compile-time checks to validate stack metadata, including frame
367 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
368 that runtime stack traces are more reliable.
370 This is also a prerequisite for generation of ORC unwind data, which
371 is needed for CONFIG_UNWINDER_ORC.
373 For more information, see
374 tools/objtool/Documentation/stack-validation.txt.
376 config DEBUG_FORCE_WEAK_PER_CPU
377 bool "Force weak per-cpu definitions"
378 depends on DEBUG_KERNEL
380 s390 and alpha require percpu variables in modules to be
381 defined weak to work around addressing range issue which
382 puts the following two restrictions on percpu variable
385 1. percpu symbols must be unique whether static or not
386 2. percpu variables can't be defined inside a function
388 To ensure that generic code follows the above rules, this
389 option forces all percpu variables to be defined as weak.
391 endmenu # "Compiler options"
394 bool "Magic SysRq key"
397 If you say Y here, you will have some control over the system even
398 if the system crashes for example during kernel debugging (e.g., you
399 will be able to flush the buffer cache to disk, reboot the system
400 immediately or dump some status information). This is accomplished
401 by pressing various keys while holding SysRq (Alt+PrintScreen). It
402 also works on a serial console (on PC hardware at least), if you
403 send a BREAK and then within 5 seconds a command keypress. The
404 keys are documented in <file:Documentation/admin-guide/sysrq.rst>.
405 Don't say Y unless you really know what this hack does.
407 config MAGIC_SYSRQ_DEFAULT_ENABLE
408 hex "Enable magic SysRq key functions by default"
409 depends on MAGIC_SYSRQ
412 Specifies which SysRq key functions are enabled by default.
413 This may be set to 1 or 0 to enable or disable them all, or
414 to a bitmask as described in Documentation/admin-guide/sysrq.rst.
416 config MAGIC_SYSRQ_SERIAL
417 bool "Enable magic SysRq key over serial"
418 depends on MAGIC_SYSRQ
421 Many embedded boards have a disconnected TTL level serial which can
422 generate some garbage that can lead to spurious false sysrq detects.
423 This option allows you to decide whether you want to enable the
427 bool "Kernel debugging"
429 Say Y here if you are developing drivers or trying to debug and
430 identify kernel problems.
433 bool "Miscellaneous debug code"
435 depends on DEBUG_KERNEL
437 Say Y here if you need to enable miscellaneous debug code that should
438 be under a more specific debug option but isn't.
441 menu "Memory Debugging"
443 source "mm/Kconfig.debug"
446 bool "Debug object operations"
447 depends on DEBUG_KERNEL
449 If you say Y here, additional code will be inserted into the
450 kernel to track the life time of various objects and validate
451 the operations on those objects.
453 config DEBUG_OBJECTS_SELFTEST
454 bool "Debug objects selftest"
455 depends on DEBUG_OBJECTS
457 This enables the selftest of the object debug code.
459 config DEBUG_OBJECTS_FREE
460 bool "Debug objects in freed memory"
461 depends on DEBUG_OBJECTS
463 This enables checks whether a k/v free operation frees an area
464 which contains an object which has not been deactivated
465 properly. This can make kmalloc/kfree-intensive workloads
468 config DEBUG_OBJECTS_TIMERS
469 bool "Debug timer objects"
470 depends on DEBUG_OBJECTS
472 If you say Y here, additional code will be inserted into the
473 timer routines to track the life time of timer objects and
474 validate the timer operations.
476 config DEBUG_OBJECTS_WORK
477 bool "Debug work objects"
478 depends on DEBUG_OBJECTS
480 If you say Y here, additional code will be inserted into the
481 work queue routines to track the life time of work objects and
482 validate the work operations.
484 config DEBUG_OBJECTS_RCU_HEAD
485 bool "Debug RCU callbacks objects"
486 depends on DEBUG_OBJECTS
488 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
490 config DEBUG_OBJECTS_PERCPU_COUNTER
491 bool "Debug percpu counter objects"
492 depends on DEBUG_OBJECTS
494 If you say Y here, additional code will be inserted into the
495 percpu counter routines to track the life time of percpu counter
496 objects and validate the percpu counter operations.
498 config DEBUG_OBJECTS_ENABLE_DEFAULT
499 int "debug_objects bootup default value (0-1)"
502 depends on DEBUG_OBJECTS
504 Debug objects boot parameter default value
507 bool "Debug slab memory allocations"
508 depends on DEBUG_KERNEL && SLAB
510 Say Y here to have the kernel do limited verification on memory
511 allocation as well as poisoning memory on free to catch use of freed
512 memory. This can make kmalloc/kfree-intensive workloads much slower.
515 bool "SLUB debugging on by default"
516 depends on SLUB && SLUB_DEBUG
519 Boot with debugging on by default. SLUB boots by default with
520 the runtime debug capabilities switched off. Enabling this is
521 equivalent to specifying the "slub_debug" parameter on boot.
522 There is no support for more fine grained debug control like
523 possible with slub_debug=xxx. SLUB debugging may be switched
524 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
529 bool "Enable SLUB performance statistics"
530 depends on SLUB && SYSFS
532 SLUB statistics are useful to debug SLUBs allocation behavior in
533 order find ways to optimize the allocator. This should never be
534 enabled for production use since keeping statistics slows down
535 the allocator by a few percentage points. The slabinfo command
536 supports the determination of the most active slabs to figure
537 out which slabs are relevant to a particular load.
538 Try running: slabinfo -DA
540 config HAVE_DEBUG_KMEMLEAK
543 config DEBUG_KMEMLEAK
544 bool "Kernel memory leak detector"
545 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
547 select STACKTRACE if STACKTRACE_SUPPORT
551 Say Y here if you want to enable the memory leak
552 detector. The memory allocation/freeing is traced in a way
553 similar to the Boehm's conservative garbage collector, the
554 difference being that the orphan objects are not freed but
555 only shown in /sys/kernel/debug/kmemleak. Enabling this
556 feature will introduce an overhead to memory
557 allocations. See Documentation/dev-tools/kmemleak.rst for more
560 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
561 of finding leaks due to the slab objects poisoning.
563 In order to access the kmemleak file, debugfs needs to be
564 mounted (usually at /sys/kernel/debug).
566 config DEBUG_KMEMLEAK_MEM_POOL_SIZE
567 int "Kmemleak memory pool size"
568 depends on DEBUG_KMEMLEAK
572 Kmemleak must track all the memory allocations to avoid
573 reporting false positives. Since memory may be allocated or
574 freed before kmemleak is fully initialised, use a static pool
575 of metadata objects to track such callbacks. After kmemleak is
576 fully initialised, this memory pool acts as an emergency one
577 if slab allocations fail.
579 config DEBUG_KMEMLEAK_TEST
580 tristate "Simple test for the kernel memory leak detector"
581 depends on DEBUG_KMEMLEAK && m
583 This option enables a module that explicitly leaks memory.
587 config DEBUG_KMEMLEAK_DEFAULT_OFF
588 bool "Default kmemleak to off"
589 depends on DEBUG_KMEMLEAK
591 Say Y here to disable kmemleak by default. It can then be enabled
592 on the command line via kmemleak=on.
594 config DEBUG_KMEMLEAK_AUTO_SCAN
595 bool "Enable kmemleak auto scan thread on boot up"
597 depends on DEBUG_KMEMLEAK
599 Depending on the cpu, kmemleak scan may be cpu intensive and can
600 stall user tasks at times. This option enables/disables automatic
601 kmemleak scan at boot up.
603 Say N here to disable kmemleak auto scan thread to stop automatic
604 scanning. Disabling this option disables automatic reporting of
609 config DEBUG_STACK_USAGE
610 bool "Stack utilization instrumentation"
611 depends on DEBUG_KERNEL && !IA64
613 Enables the display of the minimum amount of free stack which each
614 task has ever had available in the sysrq-T and sysrq-P debug output.
616 This option will slow down process creation somewhat.
620 depends on DEBUG_KERNEL
622 Enable this to turn on extended checks in the virtual-memory system
623 that may impact performance.
627 config DEBUG_VM_VMACACHE
628 bool "Debug VMA caching"
631 Enable this to turn on VMA caching debug information. Doing so
632 can cause significant overhead, so only enable it in non-production
638 bool "Debug VM red-black trees"
641 Enable VM red-black tree debugging information and extra validations.
645 config DEBUG_VM_PGFLAGS
646 bool "Debug page-flags operations"
649 Enables extra validation on page flags operations.
653 config ARCH_HAS_DEBUG_VIRTUAL
657 bool "Debug VM translations"
658 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
660 Enable some costly sanity checks in virtual to page code. This can
661 catch mistakes with virt_to_page() and friends.
665 config DEBUG_NOMMU_REGIONS
666 bool "Debug the global anon/private NOMMU mapping region tree"
667 depends on DEBUG_KERNEL && !MMU
669 This option causes the global tree of anonymous and private mapping
670 regions to be regularly checked for invalid topology.
672 config DEBUG_MEMORY_INIT
673 bool "Debug memory initialisation" if EXPERT
676 Enable this for additional checks during memory initialisation.
677 The sanity checks verify aspects of the VM such as the memory model
678 and other information provided by the architecture. Verbose
679 information will be printed at KERN_DEBUG loglevel depending
680 on the mminit_loglevel= command-line option.
684 config MEMORY_NOTIFIER_ERROR_INJECT
685 tristate "Memory hotplug notifier error injection module"
686 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
688 This option provides the ability to inject artificial errors to
689 memory hotplug notifier chain callbacks. It is controlled through
690 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
692 If the notifier call chain should be failed with some events
693 notified, write the error code to "actions/<notifier event>/error".
695 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
697 # cd /sys/kernel/debug/notifier-error-inject/memory
698 # echo -12 > actions/MEM_GOING_OFFLINE/error
699 # echo offline > /sys/devices/system/memory/memoryXXX/state
700 bash: echo: write error: Cannot allocate memory
702 To compile this code as a module, choose M here: the module will
703 be called memory-notifier-error-inject.
707 config DEBUG_PER_CPU_MAPS
708 bool "Debug access to per_cpu maps"
709 depends on DEBUG_KERNEL
712 Say Y to verify that the per_cpu map being accessed has
713 been set up. This adds a fair amount of code to kernel memory
714 and decreases performance.
719 bool "Highmem debugging"
720 depends on DEBUG_KERNEL && HIGHMEM
722 This option enables additional error checking for high memory
723 systems. Disable for production systems.
725 config HAVE_DEBUG_STACKOVERFLOW
728 config DEBUG_STACKOVERFLOW
729 bool "Check for stack overflows"
730 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
732 Say Y here if you want to check for overflows of kernel, IRQ
733 and exception stacks (if your architecture uses them). This
734 option will show detailed messages if free stack space drops
735 below a certain limit.
737 These kinds of bugs usually occur when call-chains in the
738 kernel get too deep, especially when interrupts are
741 Use this in cases where you see apparently random memory
742 corruption, especially if it appears in 'struct thread_info'
744 If in doubt, say "N".
746 source "lib/Kconfig.kasan"
748 endmenu # "Memory Debugging"
753 An architecture should select this when it can successfully
754 build and run with CONFIG_KCOV. This typically requires
755 disabling instrumentation for some early boot code.
757 config CC_HAS_SANCOV_TRACE_PC
758 def_bool $(cc-option,-fsanitize-coverage=trace-pc)
761 bool "Code coverage for fuzzing"
762 depends on ARCH_HAS_KCOV
763 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
765 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
767 KCOV exposes kernel code coverage information in a form suitable
768 for coverage-guided fuzzing (randomized testing).
770 If RANDOMIZE_BASE is enabled, PC values will not be stable across
771 different machines and across reboots. If you need stable PC values,
772 disable RANDOMIZE_BASE.
774 For more details, see Documentation/dev-tools/kcov.rst.
776 config KCOV_ENABLE_COMPARISONS
777 bool "Enable comparison operands collection by KCOV"
779 depends on $(cc-option,-fsanitize-coverage=trace-cmp)
781 KCOV also exposes operands of every comparison in the instrumented
782 code along with operand sizes and PCs of the comparison instructions.
783 These operands can be used by fuzzing engines to improve the quality
786 config KCOV_INSTRUMENT_ALL
787 bool "Instrument all code by default"
791 If you are doing generic system call fuzzing (like e.g. syzkaller),
792 then you will want to instrument the whole kernel and you should
793 say y here. If you are doing more targeted fuzzing (like e.g.
794 filesystem fuzzing with AFL) then you will want to enable coverage
795 for more specific subsets of files, and should say n here.
798 bool "Debug shared IRQ handlers"
799 depends on DEBUG_KERNEL
801 Enable this to generate a spurious interrupt as soon as a shared
802 interrupt handler is registered, and just before one is deregistered.
803 Drivers ought to be able to handle interrupts coming in at those
804 points; some don't and need to be caught.
806 menu "Debug Lockups and Hangs"
808 config LOCKUP_DETECTOR
811 config SOFTLOCKUP_DETECTOR
812 bool "Detect Soft Lockups"
813 depends on DEBUG_KERNEL && !S390
814 select LOCKUP_DETECTOR
816 Say Y here to enable the kernel to act as a watchdog to detect
819 Softlockups are bugs that cause the kernel to loop in kernel
820 mode for more than 20 seconds, without giving other tasks a
821 chance to run. The current stack trace is displayed upon
822 detection and the system will stay locked up.
824 config BOOTPARAM_SOFTLOCKUP_PANIC
825 bool "Panic (Reboot) On Soft Lockups"
826 depends on SOFTLOCKUP_DETECTOR
828 Say Y here to enable the kernel to panic on "soft lockups",
829 which are bugs that cause the kernel to loop in kernel
830 mode for more than 20 seconds (configurable using the watchdog_thresh
831 sysctl), without giving other tasks a chance to run.
833 The panic can be used in combination with panic_timeout,
834 to cause the system to reboot automatically after a
835 lockup has been detected. This feature is useful for
836 high-availability systems that have uptime guarantees and
837 where a lockup must be resolved ASAP.
841 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
843 depends on SOFTLOCKUP_DETECTOR
845 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
846 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
848 config HARDLOCKUP_DETECTOR_PERF
850 select SOFTLOCKUP_DETECTOR
853 # Enables a timestamp based low pass filter to compensate for perf based
854 # hard lockup detection which runs too fast due to turbo modes.
856 config HARDLOCKUP_CHECK_TIMESTAMP
860 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
861 # lockup detector rather than the perf based detector.
863 config HARDLOCKUP_DETECTOR
864 bool "Detect Hard Lockups"
865 depends on DEBUG_KERNEL && !S390
866 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
867 select LOCKUP_DETECTOR
868 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
869 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
871 Say Y here to enable the kernel to act as a watchdog to detect
874 Hardlockups are bugs that cause the CPU to loop in kernel mode
875 for more than 10 seconds, without letting other interrupts have a
876 chance to run. The current stack trace is displayed upon detection
877 and the system will stay locked up.
879 config BOOTPARAM_HARDLOCKUP_PANIC
880 bool "Panic (Reboot) On Hard Lockups"
881 depends on HARDLOCKUP_DETECTOR
883 Say Y here to enable the kernel to panic on "hard lockups",
884 which are bugs that cause the kernel to loop in kernel
885 mode with interrupts disabled for more than 10 seconds (configurable
886 using the watchdog_thresh sysctl).
890 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
892 depends on HARDLOCKUP_DETECTOR
894 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
895 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
897 config DETECT_HUNG_TASK
898 bool "Detect Hung Tasks"
899 depends on DEBUG_KERNEL
900 default SOFTLOCKUP_DETECTOR
902 Say Y here to enable the kernel to detect "hung tasks",
903 which are bugs that cause the task to be stuck in
904 uninterruptible "D" state indefinitely.
906 When a hung task is detected, the kernel will print the
907 current stack trace (which you should report), but the
908 task will stay in uninterruptible state. If lockdep is
909 enabled then all held locks will also be reported. This
910 feature has negligible overhead.
912 config DEFAULT_HUNG_TASK_TIMEOUT
913 int "Default timeout for hung task detection (in seconds)"
914 depends on DETECT_HUNG_TASK
917 This option controls the default timeout (in seconds) used
918 to determine when a task has become non-responsive and should
921 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
922 sysctl or by writing a value to
923 /proc/sys/kernel/hung_task_timeout_secs.
925 A timeout of 0 disables the check. The default is two minutes.
926 Keeping the default should be fine in most cases.
928 config BOOTPARAM_HUNG_TASK_PANIC
929 bool "Panic (Reboot) On Hung Tasks"
930 depends on DETECT_HUNG_TASK
932 Say Y here to enable the kernel to panic on "hung tasks",
933 which are bugs that cause the kernel to leave a task stuck
934 in uninterruptible "D" state.
936 The panic can be used in combination with panic_timeout,
937 to cause the system to reboot automatically after a
938 hung task has been detected. This feature is useful for
939 high-availability systems that have uptime guarantees and
940 where a hung tasks must be resolved ASAP.
944 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
946 depends on DETECT_HUNG_TASK
948 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
949 default 1 if BOOTPARAM_HUNG_TASK_PANIC
952 bool "Detect Workqueue Stalls"
953 depends on DEBUG_KERNEL
955 Say Y here to enable stall detection on workqueues. If a
956 worker pool doesn't make forward progress on a pending work
957 item for over a given amount of time, 30s by default, a
958 warning message is printed along with dump of workqueue
959 state. This can be configured through kernel parameter
960 "workqueue.watchdog_thresh" and its sysfs counterpart.
962 endmenu # "Debug lockups and hangs"
967 Say Y here to enable the kernel to panic when it oopses. This
968 has the same effect as setting oops=panic on the kernel command
971 This feature is useful to ensure that the kernel does not do
972 anything erroneous after an oops which could result in data
973 corruption or other issues.
977 config PANIC_ON_OOPS_VALUE
980 default 0 if !PANIC_ON_OOPS
981 default 1 if PANIC_ON_OOPS
987 Set the timeout value (in seconds) until a reboot occurs when the
988 the kernel panics. If n = 0, then we wait forever. A timeout
989 value n > 0 will wait n seconds before rebooting, while a timeout
990 value n < 0 will reboot immediately.
993 bool "Collect scheduler debugging info"
994 depends on DEBUG_KERNEL && PROC_FS
997 If you say Y here, the /proc/sched_debug file will be provided
998 that can help debug the scheduler. The runtime overhead of this
1006 bool "Collect scheduler statistics"
1007 depends on DEBUG_KERNEL && PROC_FS
1010 If you say Y here, additional code will be inserted into the
1011 scheduler and related routines to collect statistics about
1012 scheduler behavior and provide them in /proc/schedstat. These
1013 stats may be useful for both tuning and debugging the scheduler
1014 If you aren't debugging the scheduler or trying to tune a specific
1015 application, you can say N to avoid the very slight overhead
1018 config SCHED_STACK_END_CHECK
1019 bool "Detect stack corruption on calls to schedule()"
1020 depends on DEBUG_KERNEL
1023 This option checks for a stack overrun on calls to schedule().
1024 If the stack end location is found to be over written always panic as
1025 the content of the corrupted region can no longer be trusted.
1026 This is to ensure no erroneous behaviour occurs which could result in
1027 data corruption or a sporadic crash at a later stage once the region
1028 is examined. The runtime overhead introduced is minimal.
1030 config DEBUG_TIMEKEEPING
1031 bool "Enable extra timekeeping sanity checking"
1033 This option will enable additional timekeeping sanity checks
1034 which may be helpful when diagnosing issues where timekeeping
1035 problems are suspected.
1037 This may include checks in the timekeeping hotpaths, so this
1038 option may have a (very small) performance impact to some
1043 config DEBUG_PREEMPT
1044 bool "Debug preemptible kernel"
1045 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1048 If you say Y here then the kernel will use a debug variant of the
1049 commonly used smp_processor_id() function and will print warnings
1050 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1051 will detect preemption count underflows.
1053 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1055 config LOCK_DEBUGGING_SUPPORT
1057 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1060 config PROVE_LOCKING
1061 bool "Lock debugging: prove locking correctness"
1062 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1064 select DEBUG_SPINLOCK
1065 select DEBUG_MUTEXES
1066 select DEBUG_RT_MUTEXES if RT_MUTEXES
1068 select DEBUG_WW_MUTEX_SLOWPATH
1069 select DEBUG_LOCK_ALLOC
1070 select TRACE_IRQFLAGS
1073 This feature enables the kernel to prove that all locking
1074 that occurs in the kernel runtime is mathematically
1075 correct: that under no circumstance could an arbitrary (and
1076 not yet triggered) combination of observed locking
1077 sequences (on an arbitrary number of CPUs, running an
1078 arbitrary number of tasks and interrupt contexts) cause a
1081 In short, this feature enables the kernel to report locking
1082 related deadlocks before they actually occur.
1084 The proof does not depend on how hard and complex a
1085 deadlock scenario would be to trigger: how many
1086 participant CPUs, tasks and irq-contexts would be needed
1087 for it to trigger. The proof also does not depend on
1088 timing: if a race and a resulting deadlock is possible
1089 theoretically (no matter how unlikely the race scenario
1090 is), it will be proven so and will immediately be
1091 reported by the kernel (once the event is observed that
1092 makes the deadlock theoretically possible).
1094 If a deadlock is impossible (i.e. the locking rules, as
1095 observed by the kernel, are mathematically correct), the
1096 kernel reports nothing.
1098 NOTE: this feature can also be enabled for rwlocks, mutexes
1099 and rwsems - in which case all dependencies between these
1100 different locking variants are observed and mapped too, and
1101 the proof of observed correctness is also maintained for an
1102 arbitrary combination of these separate locking variants.
1104 For more details, see Documentation/locking/lockdep-design.rst.
1107 bool "Lock usage statistics"
1108 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1110 select DEBUG_SPINLOCK
1111 select DEBUG_MUTEXES
1112 select DEBUG_RT_MUTEXES if RT_MUTEXES
1113 select DEBUG_LOCK_ALLOC
1116 This feature enables tracking lock contention points
1118 For more details, see Documentation/locking/lockstat.rst
1120 This also enables lock events required by "perf lock",
1122 If you want to use "perf lock", you also need to turn on
1123 CONFIG_EVENT_TRACING.
1125 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1126 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1128 config DEBUG_RT_MUTEXES
1129 bool "RT Mutex debugging, deadlock detection"
1130 depends on DEBUG_KERNEL && RT_MUTEXES
1132 This allows rt mutex semantics violations and rt mutex related
1133 deadlocks (lockups) to be detected and reported automatically.
1135 config DEBUG_SPINLOCK
1136 bool "Spinlock and rw-lock debugging: basic checks"
1137 depends on DEBUG_KERNEL
1138 select UNINLINE_SPIN_UNLOCK
1140 Say Y here and build SMP to catch missing spinlock initialization
1141 and certain other kinds of spinlock errors commonly made. This is
1142 best used in conjunction with the NMI watchdog so that spinlock
1143 deadlocks are also debuggable.
1145 config DEBUG_MUTEXES
1146 bool "Mutex debugging: basic checks"
1147 depends on DEBUG_KERNEL
1149 This feature allows mutex semantics violations to be detected and
1152 config DEBUG_WW_MUTEX_SLOWPATH
1153 bool "Wait/wound mutex debugging: Slowpath testing"
1154 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1155 select DEBUG_LOCK_ALLOC
1156 select DEBUG_SPINLOCK
1157 select DEBUG_MUTEXES
1159 This feature enables slowpath testing for w/w mutex users by
1160 injecting additional -EDEADLK wound/backoff cases. Together with
1161 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1162 will test all possible w/w mutex interface abuse with the
1163 exception of simply not acquiring all the required locks.
1164 Note that this feature can introduce significant overhead, so
1165 it really should not be enabled in a production or distro kernel,
1166 even a debug kernel. If you are a driver writer, enable it. If
1167 you are a distro, do not.
1170 bool "RW Semaphore debugging: basic checks"
1171 depends on DEBUG_KERNEL
1173 This debugging feature allows mismatched rw semaphore locks
1174 and unlocks to be detected and reported.
1176 config DEBUG_LOCK_ALLOC
1177 bool "Lock debugging: detect incorrect freeing of live locks"
1178 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1179 select DEBUG_SPINLOCK
1180 select DEBUG_MUTEXES
1181 select DEBUG_RT_MUTEXES if RT_MUTEXES
1184 This feature will check whether any held lock (spinlock, rwlock,
1185 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1186 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1187 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1188 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1189 held during task exit.
1193 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1195 select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86
1199 config LOCKDEP_SMALL
1202 config DEBUG_LOCKDEP
1203 bool "Lock dependency engine debugging"
1204 depends on DEBUG_KERNEL && LOCKDEP
1206 If you say Y here, the lock dependency engine will do
1207 additional runtime checks to debug itself, at the price
1208 of more runtime overhead.
1210 config DEBUG_ATOMIC_SLEEP
1211 bool "Sleep inside atomic section checking"
1212 select PREEMPT_COUNT
1213 depends on DEBUG_KERNEL
1214 depends on !ARCH_NO_PREEMPT
1216 If you say Y here, various routines which may sleep will become very
1217 noisy if they are called inside atomic sections: when a spinlock is
1218 held, inside an rcu read side critical section, inside preempt disabled
1219 sections, inside an interrupt, etc...
1221 config DEBUG_LOCKING_API_SELFTESTS
1222 bool "Locking API boot-time self-tests"
1223 depends on DEBUG_KERNEL
1225 Say Y here if you want the kernel to run a short self-test during
1226 bootup. The self-test checks whether common types of locking bugs
1227 are detected by debugging mechanisms or not. (if you disable
1228 lock debugging then those bugs wont be detected of course.)
1229 The following locking APIs are covered: spinlocks, rwlocks,
1232 config LOCK_TORTURE_TEST
1233 tristate "torture tests for locking"
1234 depends on DEBUG_KERNEL
1237 This option provides a kernel module that runs torture tests
1238 on kernel locking primitives. The kernel module may be built
1239 after the fact on the running kernel to be tested, if desired.
1241 Say Y here if you want kernel locking-primitive torture tests
1242 to be built into the kernel.
1243 Say M if you want these torture tests to build as a module.
1244 Say N if you are unsure.
1246 config WW_MUTEX_SELFTEST
1247 tristate "Wait/wound mutex selftests"
1249 This option provides a kernel module that runs tests on the
1250 on the struct ww_mutex locking API.
1252 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1253 with this test harness.
1255 Say M if you want these self tests to build as a module.
1256 Say N if you are unsure.
1258 endmenu # lock debugging
1260 config TRACE_IRQFLAGS
1263 Enables hooks to interrupt enabling and disabling for
1264 either tracing or lock debugging.
1267 bool "Stack backtrace support"
1268 depends on STACKTRACE_SUPPORT
1270 This option causes the kernel to create a /proc/pid/stack for
1271 every process, showing its current stack trace.
1272 It is also used by various kernel debugging features that require
1273 stack trace generation.
1275 config WARN_ALL_UNSEEDED_RANDOM
1276 bool "Warn for all uses of unseeded randomness"
1279 Some parts of the kernel contain bugs relating to their use of
1280 cryptographically secure random numbers before it's actually possible
1281 to generate those numbers securely. This setting ensures that these
1282 flaws don't go unnoticed, by enabling a message, should this ever
1283 occur. This will allow people with obscure setups to know when things
1284 are going wrong, so that they might contact developers about fixing
1287 Unfortunately, on some models of some architectures getting
1288 a fully seeded CRNG is extremely difficult, and so this can
1289 result in dmesg getting spammed for a surprisingly long
1290 time. This is really bad from a security perspective, and
1291 so architecture maintainers really need to do what they can
1292 to get the CRNG seeded sooner after the system is booted.
1293 However, since users cannot do anything actionable to
1294 address this, by default the kernel will issue only a single
1295 warning for the first use of unseeded randomness.
1297 Say Y here if you want to receive warnings for all uses of
1298 unseeded randomness. This will be of use primarily for
1299 those developers interested in improving the security of
1300 Linux kernels running on their architecture (or
1303 config DEBUG_KOBJECT
1304 bool "kobject debugging"
1305 depends on DEBUG_KERNEL
1307 If you say Y here, some extra kobject debugging messages will be sent
1310 config DEBUG_KOBJECT_RELEASE
1311 bool "kobject release debugging"
1312 depends on DEBUG_OBJECTS_TIMERS
1314 kobjects are reference counted objects. This means that their
1315 last reference count put is not predictable, and the kobject can
1316 live on past the point at which a driver decides to drop it's
1317 initial reference to the kobject gained on allocation. An
1318 example of this would be a struct device which has just been
1321 However, some buggy drivers assume that after such an operation,
1322 the memory backing the kobject can be immediately freed. This
1323 goes completely against the principles of a refcounted object.
1325 If you say Y here, the kernel will delay the release of kobjects
1326 on the last reference count to improve the visibility of this
1327 kind of kobject release bug.
1329 config HAVE_DEBUG_BUGVERBOSE
1332 config DEBUG_BUGVERBOSE
1333 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1334 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1337 Say Y here to make BUG() panics output the file name and line number
1338 of the BUG call as well as the EIP and oops trace. This aids
1339 debugging but costs about 70-100K of memory.
1342 bool "Debug linked list manipulation"
1343 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1345 Enable this to turn on extended checks in the linked-list
1351 bool "Debug priority linked list manipulation"
1352 depends on DEBUG_KERNEL
1354 Enable this to turn on extended checks in the priority-ordered
1355 linked-list (plist) walking routines. This checks the entire
1356 list multiple times during each manipulation.
1361 bool "Debug SG table operations"
1362 depends on DEBUG_KERNEL
1364 Enable this to turn on checks on scatter-gather tables. This can
1365 help find problems with drivers that do not properly initialize
1370 config DEBUG_NOTIFIERS
1371 bool "Debug notifier call chains"
1372 depends on DEBUG_KERNEL
1374 Enable this to turn on sanity checking for notifier call chains.
1375 This is most useful for kernel developers to make sure that
1376 modules properly unregister themselves from notifier chains.
1377 This is a relatively cheap check but if you care about maximum
1380 config DEBUG_CREDENTIALS
1381 bool "Debug credential management"
1382 depends on DEBUG_KERNEL
1384 Enable this to turn on some debug checking for credential
1385 management. The additional code keeps track of the number of
1386 pointers from task_structs to any given cred struct, and checks to
1387 see that this number never exceeds the usage count of the cred
1390 Furthermore, if SELinux is enabled, this also checks that the
1391 security pointer in the cred struct is never seen to be invalid.
1395 source "kernel/rcu/Kconfig.debug"
1397 config DEBUG_WQ_FORCE_RR_CPU
1398 bool "Force round-robin CPU selection for unbound work items"
1399 depends on DEBUG_KERNEL
1402 Workqueue used to implicitly guarantee that work items queued
1403 without explicit CPU specified are put on the local CPU. This
1404 guarantee is no longer true and while local CPU is still
1405 preferred work items may be put on foreign CPUs. Kernel
1406 parameter "workqueue.debug_force_rr_cpu" is added to force
1407 round-robin CPU selection to flush out usages which depend on the
1408 now broken guarantee. This config option enables the debug
1409 feature by default. When enabled, memory and cache locality will
1412 config DEBUG_BLOCK_EXT_DEVT
1413 bool "Force extended block device numbers and spread them"
1414 depends on DEBUG_KERNEL
1418 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1419 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1420 YOU ARE DOING. Distros, please enable this and fix whatever
1423 Conventionally, block device numbers are allocated from
1424 predetermined contiguous area. However, extended block area
1425 may introduce non-contiguous block device numbers. This
1426 option forces most block device numbers to be allocated from
1427 the extended space and spreads them to discover kernel or
1428 userland code paths which assume predetermined contiguous
1429 device number allocation.
1431 Note that turning on this debug option shuffles all the
1432 device numbers for all IDE and SCSI devices including libata
1433 ones, so root partition specified using device number
1434 directly (via rdev or root=MAJ:MIN) won't work anymore.
1435 Textual device names (root=/dev/sdXn) will continue to work.
1437 Say N if you are unsure.
1439 config CPU_HOTPLUG_STATE_CONTROL
1440 bool "Enable CPU hotplug state control"
1441 depends on DEBUG_KERNEL
1442 depends on HOTPLUG_CPU
1445 Allows to write steps between "offline" and "online" to the CPUs
1446 sysfs target file so states can be stepped granular. This is a debug
1447 option for now as the hotplug machinery cannot be stopped and
1448 restarted at arbitrary points yet.
1450 Say N if your are unsure.
1452 config NOTIFIER_ERROR_INJECTION
1453 tristate "Notifier error injection"
1454 depends on DEBUG_KERNEL
1457 This option provides the ability to inject artificial errors to
1458 specified notifier chain callbacks. It is useful to test the error
1459 handling of notifier call chain failures.
1463 config PM_NOTIFIER_ERROR_INJECT
1464 tristate "PM notifier error injection module"
1465 depends on PM && NOTIFIER_ERROR_INJECTION
1466 default m if PM_DEBUG
1468 This option provides the ability to inject artificial errors to
1469 PM notifier chain callbacks. It is controlled through debugfs
1470 interface /sys/kernel/debug/notifier-error-inject/pm
1472 If the notifier call chain should be failed with some events
1473 notified, write the error code to "actions/<notifier event>/error".
1475 Example: Inject PM suspend error (-12 = -ENOMEM)
1477 # cd /sys/kernel/debug/notifier-error-inject/pm/
1478 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1479 # echo mem > /sys/power/state
1480 bash: echo: write error: Cannot allocate memory
1482 To compile this code as a module, choose M here: the module will
1483 be called pm-notifier-error-inject.
1487 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1488 tristate "OF reconfig notifier error injection module"
1489 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1491 This option provides the ability to inject artificial errors to
1492 OF reconfig notifier chain callbacks. It is controlled
1493 through debugfs interface under
1494 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1496 If the notifier call chain should be failed with some events
1497 notified, write the error code to "actions/<notifier event>/error".
1499 To compile this code as a module, choose M here: the module will
1500 be called of-reconfig-notifier-error-inject.
1504 config NETDEV_NOTIFIER_ERROR_INJECT
1505 tristate "Netdev notifier error injection module"
1506 depends on NET && NOTIFIER_ERROR_INJECTION
1508 This option provides the ability to inject artificial errors to
1509 netdevice notifier chain callbacks. It is controlled through debugfs
1510 interface /sys/kernel/debug/notifier-error-inject/netdev
1512 If the notifier call chain should be failed with some events
1513 notified, write the error code to "actions/<notifier event>/error".
1515 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1517 # cd /sys/kernel/debug/notifier-error-inject/netdev
1518 # echo -22 > actions/NETDEV_CHANGEMTU/error
1519 # ip link set eth0 mtu 1024
1520 RTNETLINK answers: Invalid argument
1522 To compile this code as a module, choose M here: the module will
1523 be called netdev-notifier-error-inject.
1527 config FUNCTION_ERROR_INJECTION
1529 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
1531 config FAULT_INJECTION
1532 bool "Fault-injection framework"
1533 depends on DEBUG_KERNEL
1535 Provide fault-injection framework.
1536 For more details, see Documentation/fault-injection/.
1539 bool "Fault-injection capability for kmalloc"
1540 depends on FAULT_INJECTION
1541 depends on SLAB || SLUB
1543 Provide fault-injection capability for kmalloc.
1545 config FAIL_PAGE_ALLOC
1546 bool "Fault-injection capabilitiy for alloc_pages()"
1547 depends on FAULT_INJECTION
1549 Provide fault-injection capability for alloc_pages().
1551 config FAIL_MAKE_REQUEST
1552 bool "Fault-injection capability for disk IO"
1553 depends on FAULT_INJECTION && BLOCK
1555 Provide fault-injection capability for disk IO.
1557 config FAIL_IO_TIMEOUT
1558 bool "Fault-injection capability for faking disk interrupts"
1559 depends on FAULT_INJECTION && BLOCK
1561 Provide fault-injection capability on end IO handling. This
1562 will make the block layer "forget" an interrupt as configured,
1563 thus exercising the error handling.
1565 Only works with drivers that use the generic timeout handling,
1566 for others it wont do anything.
1569 bool "Fault-injection capability for futexes"
1571 depends on FAULT_INJECTION && FUTEX
1573 Provide fault-injection capability for futexes.
1575 config FAULT_INJECTION_DEBUG_FS
1576 bool "Debugfs entries for fault-injection capabilities"
1577 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1579 Enable configuration of fault-injection capabilities via debugfs.
1581 config FAIL_FUNCTION
1582 bool "Fault-injection capability for functions"
1583 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
1585 Provide function-based fault-injection capability.
1586 This will allow you to override a specific function with a return
1587 with given return value. As a result, function caller will see
1588 an error value and have to handle it. This is useful to test the
1589 error handling in various subsystems.
1591 config FAIL_MMC_REQUEST
1592 bool "Fault-injection capability for MMC IO"
1593 depends on FAULT_INJECTION_DEBUG_FS && MMC
1595 Provide fault-injection capability for MMC IO.
1596 This will make the mmc core return data errors. This is
1597 useful to test the error handling in the mmc block device
1598 and to test how the mmc host driver handles retries from
1601 config FAULT_INJECTION_STACKTRACE_FILTER
1602 bool "stacktrace filter for fault-injection capabilities"
1603 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1606 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1608 Provide stacktrace filter for fault-injection capabilities
1611 bool "Latency measuring infrastructure"
1612 depends on DEBUG_KERNEL
1613 depends on STACKTRACE_SUPPORT
1615 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1622 Enable this option if you want to use the LatencyTOP tool
1623 to find out which userspace is blocking on what kernel operations.
1625 source "kernel/trace/Kconfig"
1627 config PROVIDE_OHCI1394_DMA_INIT
1628 bool "Remote debugging over FireWire early on boot"
1629 depends on PCI && X86
1631 If you want to debug problems which hang or crash the kernel early
1632 on boot and the crashing machine has a FireWire port, you can use
1633 this feature to remotely access the memory of the crashed machine
1634 over FireWire. This employs remote DMA as part of the OHCI1394
1635 specification which is now the standard for FireWire controllers.
1637 With remote DMA, you can monitor the printk buffer remotely using
1638 firescope and access all memory below 4GB using fireproxy from gdb.
1639 Even controlling a kernel debugger is possible using remote DMA.
1643 If ohci1394_dma=early is used as boot parameter, it will initialize
1644 all OHCI1394 controllers which are found in the PCI config space.
1646 As all changes to the FireWire bus such as enabling and disabling
1647 devices cause a bus reset and thereby disable remote DMA for all
1648 devices, be sure to have the cable plugged and FireWire enabled on
1649 the debugging host before booting the debug target for debugging.
1651 This code (~1k) is freed after boot. By then, the firewire stack
1652 in charge of the OHCI-1394 controllers should be used instead.
1654 See Documentation/debugging-via-ohci1394.txt for more information.
1656 menuconfig RUNTIME_TESTING_MENU
1657 bool "Runtime Testing"
1660 if RUNTIME_TESTING_MENU
1663 tristate "Linux Kernel Dump Test Tool Module"
1666 This module enables testing of the different dumping mechanisms by
1667 inducing system failures at predefined crash points.
1668 If you don't need it: say N
1669 Choose M here to compile this code as a module. The module will be
1672 Documentation on how to use the module can be found in
1673 Documentation/fault-injection/provoke-crashes.rst
1675 config TEST_LIST_SORT
1676 tristate "Linked list sorting test"
1677 depends on DEBUG_KERNEL || m
1679 Enable this to turn on 'list_sort()' function test. This test is
1680 executed only once during system boot (so affects only boot time),
1681 or at module load time.
1686 tristate "Array-based sort test"
1687 depends on DEBUG_KERNEL || m
1689 This option enables the self-test function of 'sort()' at boot,
1690 or at module load time.
1694 config KPROBES_SANITY_TEST
1695 bool "Kprobes sanity tests"
1696 depends on DEBUG_KERNEL
1699 This option provides for testing basic kprobes functionality on
1700 boot. Samples of kprobe and kretprobe are inserted and
1701 verified for functionality.
1703 Say N if you are unsure.
1705 config BACKTRACE_SELF_TEST
1706 tristate "Self test for the backtrace code"
1707 depends on DEBUG_KERNEL
1709 This option provides a kernel module that can be used to test
1710 the kernel stack backtrace code. This option is not useful
1711 for distributions or general kernels, but only for kernel
1712 developers working on architecture code.
1714 Note that if you want to also test saved backtraces, you will
1715 have to enable STACKTRACE as well.
1717 Say N if you are unsure.
1720 tristate "Red-Black tree test"
1721 depends on DEBUG_KERNEL
1723 A benchmark measuring the performance of the rbtree library.
1724 Also includes rbtree invariant checks.
1726 config REED_SOLOMON_TEST
1727 tristate "Reed-Solomon library test"
1728 depends on DEBUG_KERNEL || m
1730 select REED_SOLOMON_ENC16
1731 select REED_SOLOMON_DEC16
1733 This option enables the self-test function of rslib at boot,
1734 or at module load time.
1738 config INTERVAL_TREE_TEST
1739 tristate "Interval tree test"
1740 depends on DEBUG_KERNEL
1741 select INTERVAL_TREE
1743 A benchmark measuring the performance of the interval tree library
1746 tristate "Per cpu operations test"
1747 depends on m && DEBUG_KERNEL
1749 Enable this option to build test module which validates per-cpu
1754 config ATOMIC64_SELFTEST
1755 tristate "Perform an atomic64_t self-test"
1757 Enable this option to test the atomic64_t functions at boot or
1758 at module load time.
1762 config ASYNC_RAID6_TEST
1763 tristate "Self test for hardware accelerated raid6 recovery"
1764 depends on ASYNC_RAID6_RECOV
1767 This is a one-shot self test that permutes through the
1768 recovery of all the possible two disk failure scenarios for a
1769 N-disk array. Recovery is performed with the asynchronous
1770 raid6 recovery routines, and will optionally use an offload
1771 engine if one is available.
1776 tristate "Test functions located in the hexdump module at runtime"
1778 config TEST_STRING_HELPERS
1779 tristate "Test functions located in the string_helpers module at runtime"
1782 tristate "Test strscpy*() family of functions at runtime"
1785 tristate "Test kstrto*() family of functions at runtime"
1788 tristate "Test printf() family of functions at runtime"
1791 tristate "Test bitmap_*() family of functions at runtime"
1793 Enable this option to test the bitmap functions at boot.
1797 config TEST_BITFIELD
1798 tristate "Test bitfield functions at runtime"
1800 Enable this option to test the bitfield functions at boot.
1805 tristate "Test functions located in the uuid module at runtime"
1808 tristate "Test the XArray code at runtime"
1810 config TEST_OVERFLOW
1811 tristate "Test check_*_overflow() functions at runtime"
1813 config TEST_RHASHTABLE
1814 tristate "Perform selftest on resizable hash table"
1816 Enable this option to test the rhashtable functions at boot.
1821 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 IDA functions"
1834 tristate "Perform selftest on priority array manager"
1837 Enable this option to test priority array manager on boot
1842 config TEST_IRQ_TIMINGS
1843 bool "IRQ timings selftest"
1844 depends on IRQ_TIMINGS
1846 Enable this option to test the irq timings code on boot.
1851 tristate "Test module loading with 'hello world' module"
1854 This builds the "test_module" module that emits "Hello, world"
1855 on printk when loaded. It is designed to be used for basic
1856 evaluation of the module loading subsystem (for example when
1857 validating module verification). It lacks any extra dependencies,
1858 and will not normally be loaded by the system unless explicitly
1864 tristate "Test module for stress/performance analysis of vmalloc allocator"
1869 This builds the "test_vmalloc" module that should be used for
1870 stress and performance analysis. So, any new change for vmalloc
1871 subsystem can be evaluated from performance and stability point
1876 config TEST_USER_COPY
1877 tristate "Test user/kernel boundary protections"
1880 This builds the "test_user_copy" module that runs sanity checks
1881 on the copy_to/from_user infrastructure, making sure basic
1882 user/kernel boundary testing is working. If it fails to load,
1883 a regression has been detected in the user/kernel memory boundary
1889 tristate "Test BPF filter functionality"
1892 This builds the "test_bpf" module that runs various test vectors
1893 against the BPF interpreter or BPF JIT compiler depending on the
1894 current setting. This is in particular useful for BPF JIT compiler
1895 development, but also to run regression tests against changes in
1896 the interpreter code. It also enables test stubs for eBPF maps and
1897 verifier used by user space verifier testsuite.
1901 config TEST_BLACKHOLE_DEV
1902 tristate "Test blackhole netdev functionality"
1905 This builds the "test_blackhole_dev" module that validates the
1906 data path through this blackhole netdev.
1910 config FIND_BIT_BENCHMARK
1911 tristate "Test find_bit functions"
1913 This builds the "test_find_bit" module that measure find_*_bit()
1914 functions performance.
1918 config TEST_FIRMWARE
1919 tristate "Test firmware loading via userspace interface"
1920 depends on FW_LOADER
1922 This builds the "test_firmware" module that creates a userspace
1923 interface for testing firmware loading. This can be used to
1924 control the triggering of firmware loading without needing an
1925 actual firmware-using device. The contents can be rechecked by
1931 tristate "sysctl test driver"
1932 depends on PROC_SYSCTL
1934 This builds the "test_sysctl" module. This driver enables to test the
1935 proc sysctl interfaces available to drivers safely without affecting
1936 production knobs which might alter system functionality.
1941 tristate "udelay test driver"
1943 This builds the "udelay_test" module that helps to make sure
1944 that udelay() is working properly.
1948 config TEST_STATIC_KEYS
1949 tristate "Test static keys"
1952 Test the static key interfaces.
1957 tristate "kmod stress tester"
1959 depends on NETDEVICES && NET_CORE && INET # for TUN
1966 Test the kernel's module loading mechanism: kmod. kmod implements
1967 support to load modules using the Linux kernel's usermode helper.
1968 This test provides a series of tests against kmod.
1970 Although technically you can either build test_kmod as a module or
1971 into the kernel we disallow building it into the kernel since
1972 it stress tests request_module() and this will very likely cause
1973 some issues by taking over precious threads available from other
1974 module load requests, ultimately this could be fatal.
1978 tools/testing/selftests/kmod/kmod.sh --help
1982 config TEST_DEBUG_VIRTUAL
1983 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
1984 depends on DEBUG_VIRTUAL
1986 Test the kernel's ability to detect incorrect calls to
1987 virt_to_phys() done against the non-linear part of the
1988 kernel's virtual address map.
1992 config TEST_MEMCAT_P
1993 tristate "Test memcat_p() helper function"
1995 Test the memcat_p() helper for correctly merging two
1996 pointer arrays together.
2000 config TEST_LIVEPATCH
2001 tristate "Test livepatching"
2003 depends on DYNAMIC_DEBUG
2004 depends on LIVEPATCH
2007 Test kernel livepatching features for correctness. The tests will
2008 load test modules that will be livepatched in various scenarios.
2010 To run all the livepatching tests:
2012 make -C tools/testing/selftests TARGETS=livepatch run_tests
2014 Alternatively, individual tests may be invoked:
2016 tools/testing/selftests/livepatch/test-callbacks.sh
2017 tools/testing/selftests/livepatch/test-livepatch.sh
2018 tools/testing/selftests/livepatch/test-shadow-vars.sh
2023 tristate "Perform selftest on object aggreration manager"
2027 Enable this option to test object aggregation manager on boot
2031 config TEST_STACKINIT
2032 tristate "Test level of stack variable initialization"
2034 Test if the kernel is zero-initializing stack variables and
2035 padding. Coverage is controlled by compiler flags,
2036 CONFIG_GCC_PLUGIN_STRUCTLEAK, CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF,
2037 or CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL.
2042 tristate "Test heap/page initialization"
2044 Test if the kernel is zero-initializing heap and page allocations.
2045 This can be useful to test init_on_alloc and init_on_free features.
2049 endif # RUNTIME_TESTING_MENU
2054 This option adds a kernel parameter 'memtest', which allows memtest
2056 memtest=0, mean disabled; -- default
2057 memtest=1, mean do 1 test pattern;
2059 memtest=17, mean do 17 test patterns.
2060 If you are unsure how to answer this question, answer N.
2062 config BUG_ON_DATA_CORRUPTION
2063 bool "Trigger a BUG when data corruption is detected"
2066 Select this option if the kernel should BUG when it encounters
2067 data corruption in kernel memory structures when they get checked
2072 source "samples/Kconfig"
2074 source "lib/Kconfig.kgdb"
2076 source "lib/Kconfig.ubsan"
2078 config ARCH_HAS_DEVMEM_IS_ALLOWED
2081 config STRICT_DEVMEM
2082 bool "Filter access to /dev/mem"
2083 depends on MMU && DEVMEM
2084 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
2085 default y if PPC || X86 || ARM64
2087 If this option is disabled, you allow userspace (root) access to all
2088 of memory, including kernel and userspace memory. Accidental
2089 access to this is obviously disastrous, but specific access can
2090 be used by people debugging the kernel. Note that with PAT support
2091 enabled, even in this case there are restrictions on /dev/mem
2092 use due to the cache aliasing requirements.
2094 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
2095 file only allows userspace access to PCI space and the BIOS code and
2096 data regions. This is sufficient for dosemu and X and all common
2101 config IO_STRICT_DEVMEM
2102 bool "Filter I/O access to /dev/mem"
2103 depends on STRICT_DEVMEM
2105 If this option is disabled, you allow userspace (root) access to all
2106 io-memory regardless of whether a driver is actively using that
2107 range. Accidental access to this is obviously disastrous, but
2108 specific access can be used by people debugging kernel drivers.
2110 If this option is switched on, the /dev/mem file only allows
2111 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2112 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2113 if the driver using a given range cannot be disabled.
2117 source "arch/$(SRCARCH)/Kconfig.debug"
2119 endmenu # Kernel hacking
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