3 menu "printk and dmesg options"
6 bool "Show timing information on printks"
9 Selecting this option causes time stamps of the printk()
10 messages to be added to the output of the syslog() system
11 call and at the console.
13 The timestamp is always recorded internally, and exported
14 to /dev/kmsg. This flag just specifies if the timestamp should
15 be included, not that the timestamp is recorded.
17 The behavior is also controlled by the kernel command line
18 parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst
21 bool "Show caller information on printks"
24 Selecting this option causes printk() to add a caller "thread id" (if
25 in task context) or a caller "processor id" (if not in task context)
28 This option is intended for environments where multiple threads
29 concurrently call printk() for many times, for it is difficult to
30 interpret without knowing where these lines (or sometimes individual
31 line which was divided into multiple lines due to race) came from.
33 Since toggling after boot makes the code racy, currently there is
34 no option to enable/disable at the kernel command line parameter or
37 config CONSOLE_LOGLEVEL_DEFAULT
38 int "Default console loglevel (1-15)"
42 Default loglevel to determine what will be printed on the console.
44 Setting a default here is equivalent to passing in loglevel=<x> in
45 the kernel bootargs. loglevel=<x> continues to override whatever
46 value is specified here as well.
48 Note: This does not affect the log level of un-prefixed printk()
49 usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
52 config CONSOLE_LOGLEVEL_QUIET
53 int "quiet console loglevel (1-15)"
57 loglevel to use when "quiet" is passed on the kernel commandline.
59 When "quiet" is passed on the kernel commandline this loglevel
60 will be used as the loglevel. IOW passing "quiet" will be the
61 equivalent of passing "loglevel=<CONSOLE_LOGLEVEL_QUIET>"
63 config MESSAGE_LOGLEVEL_DEFAULT
64 int "Default message log level (1-7)"
68 Default log level for printk statements with no specified priority.
70 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
71 that are auditing their logs closely may want to set it to a lower
74 Note: This does not affect what message level gets printed on the console
75 by default. To change that, use loglevel=<x> in the kernel bootargs,
76 or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value.
78 config BOOT_PRINTK_DELAY
79 bool "Delay each boot printk message by N milliseconds"
80 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
82 This build option allows you to read kernel boot messages
83 by inserting a short delay after each one. The delay is
84 specified in milliseconds on the kernel command line,
87 It is likely that you would also need to use "lpj=M" to preset
88 the "loops per jiffie" value.
89 See a previous boot log for the "lpj" value to use for your
90 system, and then set "lpj=M" before setting "boot_delay=N".
91 NOTE: Using this option may adversely affect SMP systems.
92 I.e., processors other than the first one may not boot up.
93 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
94 what it believes to be lockup conditions.
97 bool "Enable dynamic printk() support"
103 Compiles debug level messages into the kernel, which would not
104 otherwise be available at runtime. These messages can then be
105 enabled/disabled based on various levels of scope - per source file,
106 function, module, format string, and line number. This mechanism
107 implicitly compiles in all pr_debug() and dev_dbg() calls, which
108 enlarges the kernel text size by about 2%.
110 If a source file is compiled with DEBUG flag set, any
111 pr_debug() calls in it are enabled by default, but can be
112 disabled at runtime as below. Note that DEBUG flag is
113 turned on by many CONFIG_*DEBUG* options.
117 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
118 which is contained in the 'debugfs' filesystem. Thus, the debugfs
119 filesystem must first be mounted before making use of this feature.
120 We refer the control file as: <debugfs>/dynamic_debug/control. This
121 file contains a list of the debug statements that can be enabled. The
122 format for each line of the file is:
124 filename:lineno [module]function flags format
126 filename : source file of the debug statement
127 lineno : line number of the debug statement
128 module : module that contains the debug statement
129 function : function that contains the debug statement
130 flags : '=p' means the line is turned 'on' for printing
131 format : the format used for the debug statement
135 nullarbor:~ # cat <debugfs>/dynamic_debug/control
136 # filename:lineno [module]function flags format
137 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
138 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
139 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
143 // enable the message at line 1603 of file svcsock.c
144 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
145 <debugfs>/dynamic_debug/control
147 // enable all the messages in file svcsock.c
148 nullarbor:~ # echo -n 'file svcsock.c +p' >
149 <debugfs>/dynamic_debug/control
151 // enable all the messages in the NFS server module
152 nullarbor:~ # echo -n 'module nfsd +p' >
153 <debugfs>/dynamic_debug/control
155 // enable all 12 messages in the function svc_process()
156 nullarbor:~ # echo -n 'func svc_process +p' >
157 <debugfs>/dynamic_debug/control
159 // disable all 12 messages in the function svc_process()
160 nullarbor:~ # echo -n 'func svc_process -p' >
161 <debugfs>/dynamic_debug/control
163 See Documentation/admin-guide/dynamic-debug-howto.rst for additional
166 endmenu # "printk and dmesg options"
168 menu "Compile-time checks and compiler options"
171 bool "Compile the kernel with debug info"
172 depends on DEBUG_KERNEL && !COMPILE_TEST
174 If you say Y here the resulting kernel image will include
175 debugging info resulting in a larger kernel image.
176 This adds debug symbols to the kernel and modules (gcc -g), and
177 is needed if you intend to use kernel crashdump or binary object
178 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
179 Say Y here only if you plan to debug the kernel.
183 config DEBUG_INFO_REDUCED
184 bool "Reduce debugging information"
185 depends on DEBUG_INFO
187 If you say Y here gcc is instructed to generate less debugging
188 information for structure types. This means that tools that
189 need full debugging information (like kgdb or systemtap) won't
190 be happy. But if you merely need debugging information to
191 resolve line numbers there is no loss. Advantage is that
192 build directory object sizes shrink dramatically over a full
193 DEBUG_INFO build and compile times are reduced too.
194 Only works with newer gcc versions.
196 config DEBUG_INFO_SPLIT
197 bool "Produce split debuginfo in .dwo files"
198 depends on DEBUG_INFO
200 Generate debug info into separate .dwo files. This significantly
201 reduces the build directory size for builds with DEBUG_INFO,
202 because it stores the information only once on disk in .dwo
203 files instead of multiple times in object files and executables.
204 In addition the debug information is also compressed.
206 Requires recent gcc (4.7+) and recent gdb/binutils.
207 Any tool that packages or reads debug information would need
208 to know about the .dwo files and include them.
209 Incompatible with older versions of ccache.
211 config DEBUG_INFO_DWARF4
212 bool "Generate dwarf4 debuginfo"
213 depends on DEBUG_INFO
215 Generate dwarf4 debug info. This requires recent versions
216 of gcc and gdb. It makes the debug information larger.
217 But it significantly improves the success of resolving
218 variables in gdb on optimized code.
221 bool "Provide GDB scripts for kernel debugging"
222 depends on DEBUG_INFO
224 This creates the required links to GDB helper scripts in the
225 build directory. If you load vmlinux into gdb, the helper
226 scripts will be automatically imported by gdb as well, and
227 additional functions are available to analyze a Linux kernel
228 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
231 config ENABLE_MUST_CHECK
232 bool "Enable __must_check logic"
235 Enable the __must_check logic in the kernel build. Disable this to
236 suppress the "warning: ignoring return value of 'foo', declared with
237 attribute warn_unused_result" messages.
240 int "Warn for stack frames larger than (needs gcc 4.4)"
242 default 2048 if GCC_PLUGIN_LATENT_ENTROPY
243 default 1280 if (!64BIT && PARISC)
244 default 1024 if (!64BIT && !PARISC)
245 default 2048 if 64BIT
247 Tell gcc to warn at build time for stack frames larger than this.
248 Setting this too low will cause a lot of warnings.
249 Setting it to 0 disables the warning.
252 config STRIP_ASM_SYMS
253 bool "Strip assembler-generated symbols during link"
256 Strip internal assembler-generated symbols during a link (symbols
257 that look like '.Lxxx') so they don't pollute the output of
258 get_wchan() and suchlike.
261 bool "Generate readable assembler code"
262 depends on DEBUG_KERNEL
264 Disable some compiler optimizations that tend to generate human unreadable
265 assembler output. This may make the kernel slightly slower, but it helps
266 to keep kernel developers who have to stare a lot at assembler listings
269 config UNUSED_SYMBOLS
270 bool "Enable unused/obsolete exported symbols"
273 Unused but exported symbols make the kernel needlessly bigger. For
274 that reason most of these unused exports will soon be removed. This
275 option is provided temporarily to provide a transition period in case
276 some external kernel module needs one of these symbols anyway. If you
277 encounter such a case in your module, consider if you are actually
278 using the right API. (rationale: since nobody in the kernel is using
279 this in a module, there is a pretty good chance it's actually the
280 wrong interface to use). If you really need the symbol, please send a
281 mail to the linux kernel mailing list mentioning the symbol and why
282 you really need it, and what the merge plan to the mainline kernel for
286 bool "Debug Filesystem"
288 debugfs is a virtual file system that kernel developers use to put
289 debugging files into. Enable this option to be able to read and
290 write to these files.
292 For detailed documentation on the debugfs API, see
293 Documentation/filesystems/.
298 bool "Run 'make headers_check' when building vmlinux"
301 This option will extract the user-visible kernel headers whenever
302 building the kernel, and will run basic sanity checks on them to
303 ensure that exported files do not attempt to include files which
304 were not exported, etc.
306 If you're making modifications to header files which are
307 relevant for userspace, say 'Y', and check the headers
308 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
309 your build tree), to make sure they're suitable.
311 config DEBUG_SECTION_MISMATCH
312 bool "Enable full Section mismatch analysis"
314 The section mismatch analysis checks if there are illegal
315 references from one section to another section.
316 During linktime or runtime, some sections are dropped;
317 any use of code/data previously in these sections would
318 most likely result in an oops.
319 In the code, functions and variables are annotated with
320 __init,, etc. (see the full list in include/linux/init.h),
321 which results in the code/data being placed in specific sections.
322 The section mismatch analysis is always performed after a full
323 kernel build, and enabling this option causes the following
324 additional steps to occur:
325 - Add the option -fno-inline-functions-called-once to gcc commands.
326 When inlining a function annotated with __init in a non-init
327 function, we would lose the section information and thus
328 the analysis would not catch the illegal reference.
329 This option tells gcc to inline less (but it does result in
331 - Run the section mismatch analysis for each module/built-in.a file.
332 When we run the section mismatch analysis on vmlinux.o, we
333 lose valuable information about where the mismatch was
335 Running the analysis for each module/built-in.a file
336 tells where the mismatch happens much closer to the
337 source. The drawback is that the same mismatch is
338 reported at least twice.
339 - Enable verbose reporting from modpost in order to help resolve
340 the section mismatches that are reported.
342 config SECTION_MISMATCH_WARN_ONLY
343 bool "Make section mismatch errors non-fatal"
346 If you say N here, the build process will fail if there are any
347 section mismatch, instead of just throwing warnings.
352 # Select this config option from the architecture Kconfig, if it
353 # is preferred to always offer frame pointers as a config
354 # option on the architecture (regardless of KERNEL_DEBUG):
356 config ARCH_WANT_FRAME_POINTERS
360 bool "Compile the kernel with frame pointers"
361 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS
362 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
364 If you say Y here the resulting kernel image will be slightly
365 larger and slower, but it gives very useful debugging information
366 in case of kernel bugs. (precise oopses/stacktraces/warnings)
368 config STACK_VALIDATION
369 bool "Compile-time stack metadata validation"
370 depends on HAVE_STACK_VALIDATION
373 Add compile-time checks to validate stack metadata, including frame
374 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
375 that runtime stack traces are more reliable.
377 This is also a prerequisite for generation of ORC unwind data, which
378 is needed for CONFIG_UNWINDER_ORC.
380 For more information, see
381 tools/objtool/Documentation/stack-validation.txt.
383 config DEBUG_FORCE_WEAK_PER_CPU
384 bool "Force weak per-cpu definitions"
385 depends on DEBUG_KERNEL
387 s390 and alpha require percpu variables in modules to be
388 defined weak to work around addressing range issue which
389 puts the following two restrictions on percpu variable
392 1. percpu symbols must be unique whether static or not
393 2. percpu variables can't be defined inside a function
395 To ensure that generic code follows the above rules, this
396 option forces all percpu variables to be defined as weak.
398 endmenu # "Compiler options"
401 bool "Magic SysRq key"
404 If you say Y here, you will have some control over the system even
405 if the system crashes for example during kernel debugging (e.g., you
406 will be able to flush the buffer cache to disk, reboot the system
407 immediately or dump some status information). This is accomplished
408 by pressing various keys while holding SysRq (Alt+PrintScreen). It
409 also works on a serial console (on PC hardware at least), if you
410 send a BREAK and then within 5 seconds a command keypress. The
411 keys are documented in <file:Documentation/admin-guide/sysrq.rst>.
412 Don't say Y unless you really know what this hack does.
414 config MAGIC_SYSRQ_DEFAULT_ENABLE
415 hex "Enable magic SysRq key functions by default"
416 depends on MAGIC_SYSRQ
419 Specifies which SysRq key functions are enabled by default.
420 This may be set to 1 or 0 to enable or disable them all, or
421 to a bitmask as described in Documentation/admin-guide/sysrq.rst.
423 config MAGIC_SYSRQ_SERIAL
424 bool "Enable magic SysRq key over serial"
425 depends on MAGIC_SYSRQ
428 Many embedded boards have a disconnected TTL level serial which can
429 generate some garbage that can lead to spurious false sysrq detects.
430 This option allows you to decide whether you want to enable the
434 bool "Kernel debugging"
436 Say Y here if you are developing drivers or trying to debug and
437 identify kernel problems.
439 menu "Memory Debugging"
441 source "mm/Kconfig.debug"
444 bool "Debug object operations"
445 depends on DEBUG_KERNEL
447 If you say Y here, additional code will be inserted into the
448 kernel to track the life time of various objects and validate
449 the operations on those objects.
451 config DEBUG_OBJECTS_SELFTEST
452 bool "Debug objects selftest"
453 depends on DEBUG_OBJECTS
455 This enables the selftest of the object debug code.
457 config DEBUG_OBJECTS_FREE
458 bool "Debug objects in freed memory"
459 depends on DEBUG_OBJECTS
461 This enables checks whether a k/v free operation frees an area
462 which contains an object which has not been deactivated
463 properly. This can make kmalloc/kfree-intensive workloads
466 config DEBUG_OBJECTS_TIMERS
467 bool "Debug timer objects"
468 depends on DEBUG_OBJECTS
470 If you say Y here, additional code will be inserted into the
471 timer routines to track the life time of timer objects and
472 validate the timer operations.
474 config DEBUG_OBJECTS_WORK
475 bool "Debug work objects"
476 depends on DEBUG_OBJECTS
478 If you say Y here, additional code will be inserted into the
479 work queue routines to track the life time of work objects and
480 validate the work operations.
482 config DEBUG_OBJECTS_RCU_HEAD
483 bool "Debug RCU callbacks objects"
484 depends on DEBUG_OBJECTS
486 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
488 config DEBUG_OBJECTS_PERCPU_COUNTER
489 bool "Debug percpu counter objects"
490 depends on DEBUG_OBJECTS
492 If you say Y here, additional code will be inserted into the
493 percpu counter routines to track the life time of percpu counter
494 objects and validate the percpu counter operations.
496 config DEBUG_OBJECTS_ENABLE_DEFAULT
497 int "debug_objects bootup default value (0-1)"
500 depends on DEBUG_OBJECTS
502 Debug objects boot parameter default value
505 bool "Debug slab memory allocations"
506 depends on DEBUG_KERNEL && SLAB
508 Say Y here to have the kernel do limited verification on memory
509 allocation as well as poisoning memory on free to catch use of freed
510 memory. This can make kmalloc/kfree-intensive workloads much slower.
512 config DEBUG_SLAB_LEAK
513 bool "Memory leak debugging"
514 depends on DEBUG_SLAB
517 bool "SLUB debugging on by default"
518 depends on SLUB && SLUB_DEBUG
521 Boot with debugging on by default. SLUB boots by default with
522 the runtime debug capabilities switched off. Enabling this is
523 equivalent to specifying the "slub_debug" parameter on boot.
524 There is no support for more fine grained debug control like
525 possible with slub_debug=xxx. SLUB debugging may be switched
526 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
531 bool "Enable SLUB performance statistics"
532 depends on SLUB && SYSFS
534 SLUB statistics are useful to debug SLUBs allocation behavior in
535 order find ways to optimize the allocator. This should never be
536 enabled for production use since keeping statistics slows down
537 the allocator by a few percentage points. The slabinfo command
538 supports the determination of the most active slabs to figure
539 out which slabs are relevant to a particular load.
540 Try running: slabinfo -DA
542 config HAVE_DEBUG_KMEMLEAK
545 config DEBUG_KMEMLEAK
546 bool "Kernel memory leak detector"
547 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
549 select STACKTRACE if STACKTRACE_SUPPORT
553 Say Y here if you want to enable the memory leak
554 detector. The memory allocation/freeing is traced in a way
555 similar to the Boehm's conservative garbage collector, the
556 difference being that the orphan objects are not freed but
557 only shown in /sys/kernel/debug/kmemleak. Enabling this
558 feature will introduce an overhead to memory
559 allocations. See Documentation/dev-tools/kmemleak.rst for more
562 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
563 of finding leaks due to the slab objects poisoning.
565 In order to access the kmemleak file, debugfs needs to be
566 mounted (usually at /sys/kernel/debug).
568 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
569 int "Maximum kmemleak early log entries"
570 depends on DEBUG_KMEMLEAK
574 Kmemleak must track all the memory allocations to avoid
575 reporting false positives. Since memory may be allocated or
576 freed before kmemleak is initialised, an early log buffer is
577 used to store these actions. If kmemleak reports "early log
578 buffer exceeded", please increase this value.
580 config DEBUG_KMEMLEAK_TEST
581 tristate "Simple test for the kernel memory leak detector"
582 depends on DEBUG_KMEMLEAK && m
584 This option enables a module that explicitly leaks memory.
588 config DEBUG_KMEMLEAK_DEFAULT_OFF
589 bool "Default kmemleak to off"
590 depends on DEBUG_KMEMLEAK
592 Say Y here to disable kmemleak by default. It can then be enabled
593 on the command line via kmemleak=on.
595 config DEBUG_KMEMLEAK_AUTO_SCAN
596 bool "Enable kmemleak auto scan thread on boot up"
598 depends on DEBUG_KMEMLEAK
600 Depending on the cpu, kmemleak scan may be cpu intensive and can
601 stall user tasks at times. This option enables/disables automatic
602 kmemleak scan at boot up.
604 Say N here to disable kmemleak auto scan thread to stop automatic
605 scanning. Disabling this option disables automatic reporting of
610 config DEBUG_STACK_USAGE
611 bool "Stack utilization instrumentation"
612 depends on DEBUG_KERNEL && !IA64
614 Enables the display of the minimum amount of free stack which each
615 task has ever had available in the sysrq-T and sysrq-P debug output.
617 This option will slow down process creation somewhat.
621 depends on DEBUG_KERNEL
623 Enable this to turn on extended checks in the virtual-memory system
624 that may impact performance.
628 config DEBUG_VM_VMACACHE
629 bool "Debug VMA caching"
632 Enable this to turn on VMA caching debug information. Doing so
633 can cause significant overhead, so only enable it in non-production
639 bool "Debug VM red-black trees"
642 Enable VM red-black tree debugging information and extra validations.
646 config DEBUG_VM_PGFLAGS
647 bool "Debug page-flags operations"
650 Enables extra validation on page flags operations.
654 config ARCH_HAS_DEBUG_VIRTUAL
658 bool "Debug VM translations"
659 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
661 Enable some costly sanity checks in virtual to page code. This can
662 catch mistakes with virt_to_page() and friends.
666 config DEBUG_NOMMU_REGIONS
667 bool "Debug the global anon/private NOMMU mapping region tree"
668 depends on DEBUG_KERNEL && !MMU
670 This option causes the global tree of anonymous and private mapping
671 regions to be regularly checked for invalid topology.
673 config DEBUG_MEMORY_INIT
674 bool "Debug memory initialisation" if EXPERT
677 Enable this for additional checks during memory initialisation.
678 The sanity checks verify aspects of the VM such as the memory model
679 and other information provided by the architecture. Verbose
680 information will be printed at KERN_DEBUG loglevel depending
681 on the mminit_loglevel= command-line option.
685 config MEMORY_NOTIFIER_ERROR_INJECT
686 tristate "Memory hotplug notifier error injection module"
687 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
689 This option provides the ability to inject artificial errors to
690 memory hotplug notifier chain callbacks. It is controlled through
691 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
693 If the notifier call chain should be failed with some events
694 notified, write the error code to "actions/<notifier event>/error".
696 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
698 # cd /sys/kernel/debug/notifier-error-inject/memory
699 # echo -12 > actions/MEM_GOING_OFFLINE/error
700 # echo offline > /sys/devices/system/memory/memoryXXX/state
701 bash: echo: write error: Cannot allocate memory
703 To compile this code as a module, choose M here: the module will
704 be called memory-notifier-error-inject.
708 config DEBUG_PER_CPU_MAPS
709 bool "Debug access to per_cpu maps"
710 depends on DEBUG_KERNEL
713 Say Y to verify that the per_cpu map being accessed has
714 been set up. This adds a fair amount of code to kernel memory
715 and decreases performance.
720 bool "Highmem debugging"
721 depends on DEBUG_KERNEL && HIGHMEM
723 This option enables additional error checking for high memory
724 systems. Disable for production systems.
726 config HAVE_DEBUG_STACKOVERFLOW
729 config DEBUG_STACKOVERFLOW
730 bool "Check for stack overflows"
731 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
733 Say Y here if you want to check for overflows of kernel, IRQ
734 and exception stacks (if your architecture uses them). This
735 option will show detailed messages if free stack space drops
736 below a certain limit.
738 These kinds of bugs usually occur when call-chains in the
739 kernel get too deep, especially when interrupts are
742 Use this in cases where you see apparently random memory
743 corruption, especially if it appears in 'struct thread_info'
745 If in doubt, say "N".
747 source "lib/Kconfig.kasan"
749 endmenu # "Memory Debugging"
754 KCOV does not have any arch-specific code, but currently it is enabled
755 only for x86_64. KCOV requires testing on other archs, and most likely
756 disabling of instrumentation for some early boot code.
758 config CC_HAS_SANCOV_TRACE_PC
759 def_bool $(cc-option,-fsanitize-coverage=trace-pc)
762 bool "Code coverage for fuzzing"
763 depends on ARCH_HAS_KCOV
764 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
766 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
768 KCOV exposes kernel code coverage information in a form suitable
769 for coverage-guided fuzzing (randomized testing).
771 If RANDOMIZE_BASE is enabled, PC values will not be stable across
772 different machines and across reboots. If you need stable PC values,
773 disable RANDOMIZE_BASE.
775 For more details, see Documentation/dev-tools/kcov.rst.
777 config KCOV_ENABLE_COMPARISONS
778 bool "Enable comparison operands collection by KCOV"
780 depends on $(cc-option,-fsanitize-coverage=trace-cmp)
782 KCOV also exposes operands of every comparison in the instrumented
783 code along with operand sizes and PCs of the comparison instructions.
784 These operands can be used by fuzzing engines to improve the quality
787 config KCOV_INSTRUMENT_ALL
788 bool "Instrument all code by default"
792 If you are doing generic system call fuzzing (like e.g. syzkaller),
793 then you will want to instrument the whole kernel and you should
794 say y here. If you are doing more targeted fuzzing (like e.g.
795 filesystem fuzzing with AFL) then you will want to enable coverage
796 for more specific subsets of files, and should say n here.
799 bool "Debug shared IRQ handlers"
800 depends on DEBUG_KERNEL
802 Enable this to generate a spurious interrupt as soon as a shared
803 interrupt handler is registered, and just before one is deregistered.
804 Drivers ought to be able to handle interrupts coming in at those
805 points; some don't and need to be caught.
807 menu "Debug Lockups and Hangs"
809 config LOCKUP_DETECTOR
812 config SOFTLOCKUP_DETECTOR
813 bool "Detect Soft Lockups"
814 depends on DEBUG_KERNEL && !S390
815 select LOCKUP_DETECTOR
817 Say Y here to enable the kernel to act as a watchdog to detect
820 Softlockups are bugs that cause the kernel to loop in kernel
821 mode for more than 20 seconds, without giving other tasks a
822 chance to run. The current stack trace is displayed upon
823 detection and the system will stay locked up.
825 config BOOTPARAM_SOFTLOCKUP_PANIC
826 bool "Panic (Reboot) On Soft Lockups"
827 depends on SOFTLOCKUP_DETECTOR
829 Say Y here to enable the kernel to panic on "soft lockups",
830 which are bugs that cause the kernel to loop in kernel
831 mode for more than 20 seconds (configurable using the watchdog_thresh
832 sysctl), without giving other tasks a chance to run.
834 The panic can be used in combination with panic_timeout,
835 to cause the system to reboot automatically after a
836 lockup has been detected. This feature is useful for
837 high-availability systems that have uptime guarantees and
838 where a lockup must be resolved ASAP.
842 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
844 depends on SOFTLOCKUP_DETECTOR
846 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
847 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
849 config HARDLOCKUP_DETECTOR_PERF
851 select SOFTLOCKUP_DETECTOR
854 # Enables a timestamp based low pass filter to compensate for perf based
855 # hard lockup detection which runs too fast due to turbo modes.
857 config HARDLOCKUP_CHECK_TIMESTAMP
861 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
862 # lockup detector rather than the perf based detector.
864 config HARDLOCKUP_DETECTOR
865 bool "Detect Hard Lockups"
866 depends on DEBUG_KERNEL && !S390
867 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
868 select LOCKUP_DETECTOR
869 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
870 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
872 Say Y here to enable the kernel to act as a watchdog to detect
875 Hardlockups are bugs that cause the CPU to loop in kernel mode
876 for more than 10 seconds, without letting other interrupts have a
877 chance to run. The current stack trace is displayed upon detection
878 and the system will stay locked up.
880 config BOOTPARAM_HARDLOCKUP_PANIC
881 bool "Panic (Reboot) On Hard Lockups"
882 depends on HARDLOCKUP_DETECTOR
884 Say Y here to enable the kernel to panic on "hard lockups",
885 which are bugs that cause the kernel to loop in kernel
886 mode with interrupts disabled for more than 10 seconds (configurable
887 using the watchdog_thresh sysctl).
891 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
893 depends on HARDLOCKUP_DETECTOR
895 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
896 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
898 config DETECT_HUNG_TASK
899 bool "Detect Hung Tasks"
900 depends on DEBUG_KERNEL
901 default SOFTLOCKUP_DETECTOR
903 Say Y here to enable the kernel to detect "hung tasks",
904 which are bugs that cause the task to be stuck in
905 uninterruptible "D" state indefinitely.
907 When a hung task is detected, the kernel will print the
908 current stack trace (which you should report), but the
909 task will stay in uninterruptible state. If lockdep is
910 enabled then all held locks will also be reported. This
911 feature has negligible overhead.
913 config DEFAULT_HUNG_TASK_TIMEOUT
914 int "Default timeout for hung task detection (in seconds)"
915 depends on DETECT_HUNG_TASK
918 This option controls the default timeout (in seconds) used
919 to determine when a task has become non-responsive and should
922 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
923 sysctl or by writing a value to
924 /proc/sys/kernel/hung_task_timeout_secs.
926 A timeout of 0 disables the check. The default is two minutes.
927 Keeping the default should be fine in most cases.
929 config BOOTPARAM_HUNG_TASK_PANIC
930 bool "Panic (Reboot) On Hung Tasks"
931 depends on DETECT_HUNG_TASK
933 Say Y here to enable the kernel to panic on "hung tasks",
934 which are bugs that cause the kernel to leave a task stuck
935 in uninterruptible "D" state.
937 The panic can be used in combination with panic_timeout,
938 to cause the system to reboot automatically after a
939 hung task has been detected. This feature is useful for
940 high-availability systems that have uptime guarantees and
941 where a hung tasks must be resolved ASAP.
945 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
947 depends on DETECT_HUNG_TASK
949 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
950 default 1 if BOOTPARAM_HUNG_TASK_PANIC
953 bool "Detect Workqueue Stalls"
954 depends on DEBUG_KERNEL
956 Say Y here to enable stall detection on workqueues. If a
957 worker pool doesn't make forward progress on a pending work
958 item for over a given amount of time, 30s by default, a
959 warning message is printed along with dump of workqueue
960 state. This can be configured through kernel parameter
961 "workqueue.watchdog_thresh" and its sysfs counterpart.
963 endmenu # "Debug lockups and hangs"
968 Say Y here to enable the kernel to panic when it oopses. This
969 has the same effect as setting oops=panic on the kernel command
972 This feature is useful to ensure that the kernel does not do
973 anything erroneous after an oops which could result in data
974 corruption or other issues.
978 config PANIC_ON_OOPS_VALUE
981 default 0 if !PANIC_ON_OOPS
982 default 1 if PANIC_ON_OOPS
988 Set the timeout value (in seconds) until a reboot occurs when the
989 the kernel panics. If n = 0, then we wait forever. A timeout
990 value n > 0 will wait n seconds before rebooting, while a timeout
991 value n < 0 will reboot immediately.
994 bool "Collect scheduler debugging info"
995 depends on DEBUG_KERNEL && PROC_FS
998 If you say Y here, the /proc/sched_debug file will be provided
999 that can help debug the scheduler. The runtime overhead of this
1007 bool "Collect scheduler statistics"
1008 depends on DEBUG_KERNEL && PROC_FS
1011 If you say Y here, additional code will be inserted into the
1012 scheduler and related routines to collect statistics about
1013 scheduler behavior and provide them in /proc/schedstat. These
1014 stats may be useful for both tuning and debugging the scheduler
1015 If you aren't debugging the scheduler or trying to tune a specific
1016 application, you can say N to avoid the very slight overhead
1019 config SCHED_STACK_END_CHECK
1020 bool "Detect stack corruption on calls to schedule()"
1021 depends on DEBUG_KERNEL
1024 This option checks for a stack overrun on calls to schedule().
1025 If the stack end location is found to be over written always panic as
1026 the content of the corrupted region can no longer be trusted.
1027 This is to ensure no erroneous behaviour occurs which could result in
1028 data corruption or a sporadic crash at a later stage once the region
1029 is examined. The runtime overhead introduced is minimal.
1031 config DEBUG_TIMEKEEPING
1032 bool "Enable extra timekeeping sanity checking"
1034 This option will enable additional timekeeping sanity checks
1035 which may be helpful when diagnosing issues where timekeeping
1036 problems are suspected.
1038 This may include checks in the timekeeping hotpaths, so this
1039 option may have a (very small) performance impact to some
1044 config DEBUG_PREEMPT
1045 bool "Debug preemptible kernel"
1046 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1049 If you say Y here then the kernel will use a debug variant of the
1050 commonly used smp_processor_id() function and will print warnings
1051 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1052 will detect preemption count underflows.
1054 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1056 config LOCK_DEBUGGING_SUPPORT
1058 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1061 config PROVE_LOCKING
1062 bool "Lock debugging: prove locking correctness"
1063 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1065 select DEBUG_SPINLOCK
1066 select DEBUG_MUTEXES
1067 select DEBUG_RT_MUTEXES if RT_MUTEXES
1068 select DEBUG_RWSEMS if RWSEM_SPIN_ON_OWNER
1069 select DEBUG_WW_MUTEX_SLOWPATH
1070 select DEBUG_LOCK_ALLOC
1071 select TRACE_IRQFLAGS
1074 This feature enables the kernel to prove that all locking
1075 that occurs in the kernel runtime is mathematically
1076 correct: that under no circumstance could an arbitrary (and
1077 not yet triggered) combination of observed locking
1078 sequences (on an arbitrary number of CPUs, running an
1079 arbitrary number of tasks and interrupt contexts) cause a
1082 In short, this feature enables the kernel to report locking
1083 related deadlocks before they actually occur.
1085 The proof does not depend on how hard and complex a
1086 deadlock scenario would be to trigger: how many
1087 participant CPUs, tasks and irq-contexts would be needed
1088 for it to trigger. The proof also does not depend on
1089 timing: if a race and a resulting deadlock is possible
1090 theoretically (no matter how unlikely the race scenario
1091 is), it will be proven so and will immediately be
1092 reported by the kernel (once the event is observed that
1093 makes the deadlock theoretically possible).
1095 If a deadlock is impossible (i.e. the locking rules, as
1096 observed by the kernel, are mathematically correct), the
1097 kernel reports nothing.
1099 NOTE: this feature can also be enabled for rwlocks, mutexes
1100 and rwsems - in which case all dependencies between these
1101 different locking variants are observed and mapped too, and
1102 the proof of observed correctness is also maintained for an
1103 arbitrary combination of these separate locking variants.
1105 For more details, see Documentation/locking/lockdep-design.txt.
1108 bool "Lock usage statistics"
1109 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1111 select DEBUG_SPINLOCK
1112 select DEBUG_MUTEXES
1113 select DEBUG_RT_MUTEXES if RT_MUTEXES
1114 select DEBUG_LOCK_ALLOC
1117 This feature enables tracking lock contention points
1119 For more details, see Documentation/locking/lockstat.txt
1121 This also enables lock events required by "perf lock",
1123 If you want to use "perf lock", you also need to turn on
1124 CONFIG_EVENT_TRACING.
1126 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1127 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1129 config DEBUG_RT_MUTEXES
1130 bool "RT Mutex debugging, deadlock detection"
1131 depends on DEBUG_KERNEL && RT_MUTEXES
1133 This allows rt mutex semantics violations and rt mutex related
1134 deadlocks (lockups) to be detected and reported automatically.
1136 config DEBUG_SPINLOCK
1137 bool "Spinlock and rw-lock debugging: basic checks"
1138 depends on DEBUG_KERNEL
1139 select UNINLINE_SPIN_UNLOCK
1141 Say Y here and build SMP to catch missing spinlock initialization
1142 and certain other kinds of spinlock errors commonly made. This is
1143 best used in conjunction with the NMI watchdog so that spinlock
1144 deadlocks are also debuggable.
1146 config DEBUG_MUTEXES
1147 bool "Mutex debugging: basic checks"
1148 depends on DEBUG_KERNEL
1150 This feature allows mutex semantics violations to be detected and
1153 config DEBUG_WW_MUTEX_SLOWPATH
1154 bool "Wait/wound mutex debugging: Slowpath testing"
1155 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1156 select DEBUG_LOCK_ALLOC
1157 select DEBUG_SPINLOCK
1158 select DEBUG_MUTEXES
1160 This feature enables slowpath testing for w/w mutex users by
1161 injecting additional -EDEADLK wound/backoff cases. Together with
1162 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1163 will test all possible w/w mutex interface abuse with the
1164 exception of simply not acquiring all the required locks.
1165 Note that this feature can introduce significant overhead, so
1166 it really should not be enabled in a production or distro kernel,
1167 even a debug kernel. If you are a driver writer, enable it. If
1168 you are a distro, do not.
1171 bool "RW Semaphore debugging: basic checks"
1172 depends on DEBUG_KERNEL && RWSEM_SPIN_ON_OWNER
1174 This debugging feature allows mismatched rw semaphore locks and unlocks
1175 to be detected and reported.
1177 config DEBUG_LOCK_ALLOC
1178 bool "Lock debugging: detect incorrect freeing of live locks"
1179 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1180 select DEBUG_SPINLOCK
1181 select DEBUG_MUTEXES
1182 select DEBUG_RT_MUTEXES if RT_MUTEXES
1185 This feature will check whether any held lock (spinlock, rwlock,
1186 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1187 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1188 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1189 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1190 held during task exit.
1194 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1196 select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86
1200 config LOCKDEP_SMALL
1203 config DEBUG_LOCKDEP
1204 bool "Lock dependency engine debugging"
1205 depends on DEBUG_KERNEL && LOCKDEP
1207 If you say Y here, the lock dependency engine will do
1208 additional runtime checks to debug itself, at the price
1209 of more runtime overhead.
1211 config DEBUG_ATOMIC_SLEEP
1212 bool "Sleep inside atomic section checking"
1213 select PREEMPT_COUNT
1214 depends on DEBUG_KERNEL
1215 depends on !ARCH_NO_PREEMPT
1217 If you say Y here, various routines which may sleep will become very
1218 noisy if they are called inside atomic sections: when a spinlock is
1219 held, inside an rcu read side critical section, inside preempt disabled
1220 sections, inside an interrupt, etc...
1222 config DEBUG_LOCKING_API_SELFTESTS
1223 bool "Locking API boot-time self-tests"
1224 depends on DEBUG_KERNEL
1226 Say Y here if you want the kernel to run a short self-test during
1227 bootup. The self-test checks whether common types of locking bugs
1228 are detected by debugging mechanisms or not. (if you disable
1229 lock debugging then those bugs wont be detected of course.)
1230 The following locking APIs are covered: spinlocks, rwlocks,
1233 config LOCK_TORTURE_TEST
1234 tristate "torture tests for locking"
1235 depends on DEBUG_KERNEL
1238 This option provides a kernel module that runs torture tests
1239 on kernel locking primitives. The kernel module may be built
1240 after the fact on the running kernel to be tested, if desired.
1242 Say Y here if you want kernel locking-primitive torture tests
1243 to be built into the kernel.
1244 Say M if you want these torture tests to build as a module.
1245 Say N if you are unsure.
1247 config WW_MUTEX_SELFTEST
1248 tristate "Wait/wound mutex selftests"
1250 This option provides a kernel module that runs tests on the
1251 on the struct ww_mutex locking API.
1253 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1254 with this test harness.
1256 Say M if you want these self tests to build as a module.
1257 Say N if you are unsure.
1259 endmenu # lock debugging
1261 config TRACE_IRQFLAGS
1264 Enables hooks to interrupt enabling and disabling for
1265 either tracing or lock debugging.
1268 bool "Stack backtrace support"
1269 depends on STACKTRACE_SUPPORT
1271 This option causes the kernel to create a /proc/pid/stack for
1272 every process, showing its current stack trace.
1273 It is also used by various kernel debugging features that require
1274 stack trace generation.
1276 config WARN_ALL_UNSEEDED_RANDOM
1277 bool "Warn for all uses of unseeded randomness"
1280 Some parts of the kernel contain bugs relating to their use of
1281 cryptographically secure random numbers before it's actually possible
1282 to generate those numbers securely. This setting ensures that these
1283 flaws don't go unnoticed, by enabling a message, should this ever
1284 occur. This will allow people with obscure setups to know when things
1285 are going wrong, so that they might contact developers about fixing
1288 Unfortunately, on some models of some architectures getting
1289 a fully seeded CRNG is extremely difficult, and so this can
1290 result in dmesg getting spammed for a surprisingly long
1291 time. This is really bad from a security perspective, and
1292 so architecture maintainers really need to do what they can
1293 to get the CRNG seeded sooner after the system is booted.
1294 However, since users cannot do anything actionable to
1295 address this, by default the kernel will issue only a single
1296 warning for the first use of unseeded randomness.
1298 Say Y here if you want to receive warnings for all uses of
1299 unseeded randomness. This will be of use primarily for
1300 those developers interested in improving the security of
1301 Linux kernels running on their architecture (or
1304 config DEBUG_KOBJECT
1305 bool "kobject debugging"
1306 depends on DEBUG_KERNEL
1308 If you say Y here, some extra kobject debugging messages will be sent
1311 config DEBUG_KOBJECT_RELEASE
1312 bool "kobject release debugging"
1313 depends on DEBUG_OBJECTS_TIMERS
1315 kobjects are reference counted objects. This means that their
1316 last reference count put is not predictable, and the kobject can
1317 live on past the point at which a driver decides to drop it's
1318 initial reference to the kobject gained on allocation. An
1319 example of this would be a struct device which has just been
1322 However, some buggy drivers assume that after such an operation,
1323 the memory backing the kobject can be immediately freed. This
1324 goes completely against the principles of a refcounted object.
1326 If you say Y here, the kernel will delay the release of kobjects
1327 on the last reference count to improve the visibility of this
1328 kind of kobject release bug.
1330 config HAVE_DEBUG_BUGVERBOSE
1333 config DEBUG_BUGVERBOSE
1334 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1335 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1338 Say Y here to make BUG() panics output the file name and line number
1339 of the BUG call as well as the EIP and oops trace. This aids
1340 debugging but costs about 70-100K of memory.
1343 bool "Debug linked list manipulation"
1344 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1346 Enable this to turn on extended checks in the linked-list
1351 config DEBUG_PI_LIST
1352 bool "Debug priority linked list manipulation"
1353 depends on DEBUG_KERNEL
1355 Enable this to turn on extended checks in the priority-ordered
1356 linked-list (plist) walking routines. This checks the entire
1357 list multiple times during each manipulation.
1362 bool "Debug SG table operations"
1363 depends on DEBUG_KERNEL
1365 Enable this to turn on checks on scatter-gather tables. This can
1366 help find problems with drivers that do not properly initialize
1371 config DEBUG_NOTIFIERS
1372 bool "Debug notifier call chains"
1373 depends on DEBUG_KERNEL
1375 Enable this to turn on sanity checking for notifier call chains.
1376 This is most useful for kernel developers to make sure that
1377 modules properly unregister themselves from notifier chains.
1378 This is a relatively cheap check but if you care about maximum
1381 config DEBUG_CREDENTIALS
1382 bool "Debug credential management"
1383 depends on DEBUG_KERNEL
1385 Enable this to turn on some debug checking for credential
1386 management. The additional code keeps track of the number of
1387 pointers from task_structs to any given cred struct, and checks to
1388 see that this number never exceeds the usage count of the cred
1391 Furthermore, if SELinux is enabled, this also checks that the
1392 security pointer in the cred struct is never seen to be invalid.
1396 source "kernel/rcu/Kconfig.debug"
1398 config DEBUG_WQ_FORCE_RR_CPU
1399 bool "Force round-robin CPU selection for unbound work items"
1400 depends on DEBUG_KERNEL
1403 Workqueue used to implicitly guarantee that work items queued
1404 without explicit CPU specified are put on the local CPU. This
1405 guarantee is no longer true and while local CPU is still
1406 preferred work items may be put on foreign CPUs. Kernel
1407 parameter "workqueue.debug_force_rr_cpu" is added to force
1408 round-robin CPU selection to flush out usages which depend on the
1409 now broken guarantee. This config option enables the debug
1410 feature by default. When enabled, memory and cache locality will
1413 config DEBUG_BLOCK_EXT_DEVT
1414 bool "Force extended block device numbers and spread them"
1415 depends on DEBUG_KERNEL
1419 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1420 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1421 YOU ARE DOING. Distros, please enable this and fix whatever
1424 Conventionally, block device numbers are allocated from
1425 predetermined contiguous area. However, extended block area
1426 may introduce non-contiguous block device numbers. This
1427 option forces most block device numbers to be allocated from
1428 the extended space and spreads them to discover kernel or
1429 userland code paths which assume predetermined contiguous
1430 device number allocation.
1432 Note that turning on this debug option shuffles all the
1433 device numbers for all IDE and SCSI devices including libata
1434 ones, so root partition specified using device number
1435 directly (via rdev or root=MAJ:MIN) won't work anymore.
1436 Textual device names (root=/dev/sdXn) will continue to work.
1438 Say N if you are unsure.
1440 config CPU_HOTPLUG_STATE_CONTROL
1441 bool "Enable CPU hotplug state control"
1442 depends on DEBUG_KERNEL
1443 depends on HOTPLUG_CPU
1446 Allows to write steps between "offline" and "online" to the CPUs
1447 sysfs target file so states can be stepped granular. This is a debug
1448 option for now as the hotplug machinery cannot be stopped and
1449 restarted at arbitrary points yet.
1451 Say N if your are unsure.
1453 config NOTIFIER_ERROR_INJECTION
1454 tristate "Notifier error injection"
1455 depends on DEBUG_KERNEL
1458 This option provides the ability to inject artificial errors to
1459 specified notifier chain callbacks. It is useful to test the error
1460 handling of notifier call chain failures.
1464 config PM_NOTIFIER_ERROR_INJECT
1465 tristate "PM notifier error injection module"
1466 depends on PM && NOTIFIER_ERROR_INJECTION
1467 default m if PM_DEBUG
1469 This option provides the ability to inject artificial errors to
1470 PM notifier chain callbacks. It is controlled through debugfs
1471 interface /sys/kernel/debug/notifier-error-inject/pm
1473 If the notifier call chain should be failed with some events
1474 notified, write the error code to "actions/<notifier event>/error".
1476 Example: Inject PM suspend error (-12 = -ENOMEM)
1478 # cd /sys/kernel/debug/notifier-error-inject/pm/
1479 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1480 # echo mem > /sys/power/state
1481 bash: echo: write error: Cannot allocate memory
1483 To compile this code as a module, choose M here: the module will
1484 be called pm-notifier-error-inject.
1488 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1489 tristate "OF reconfig notifier error injection module"
1490 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1492 This option provides the ability to inject artificial errors to
1493 OF reconfig notifier chain callbacks. It is controlled
1494 through debugfs interface under
1495 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1497 If the notifier call chain should be failed with some events
1498 notified, write the error code to "actions/<notifier event>/error".
1500 To compile this code as a module, choose M here: the module will
1501 be called of-reconfig-notifier-error-inject.
1505 config NETDEV_NOTIFIER_ERROR_INJECT
1506 tristate "Netdev notifier error injection module"
1507 depends on NET && NOTIFIER_ERROR_INJECTION
1509 This option provides the ability to inject artificial errors to
1510 netdevice notifier chain callbacks. It is controlled through debugfs
1511 interface /sys/kernel/debug/notifier-error-inject/netdev
1513 If the notifier call chain should be failed with some events
1514 notified, write the error code to "actions/<notifier event>/error".
1516 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1518 # cd /sys/kernel/debug/notifier-error-inject/netdev
1519 # echo -22 > actions/NETDEV_CHANGEMTU/error
1520 # ip link set eth0 mtu 1024
1521 RTNETLINK answers: Invalid argument
1523 To compile this code as a module, choose M here: the module will
1524 be called netdev-notifier-error-inject.
1528 config FUNCTION_ERROR_INJECTION
1530 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
1532 config FAULT_INJECTION
1533 bool "Fault-injection framework"
1534 depends on DEBUG_KERNEL
1536 Provide fault-injection framework.
1537 For more details, see Documentation/fault-injection/.
1540 bool "Fault-injection capability for kmalloc"
1541 depends on FAULT_INJECTION
1542 depends on SLAB || SLUB
1544 Provide fault-injection capability for kmalloc.
1546 config FAIL_PAGE_ALLOC
1547 bool "Fault-injection capabilitiy for alloc_pages()"
1548 depends on FAULT_INJECTION
1550 Provide fault-injection capability for alloc_pages().
1552 config FAIL_MAKE_REQUEST
1553 bool "Fault-injection capability for disk IO"
1554 depends on FAULT_INJECTION && BLOCK
1556 Provide fault-injection capability for disk IO.
1558 config FAIL_IO_TIMEOUT
1559 bool "Fault-injection capability for faking disk interrupts"
1560 depends on FAULT_INJECTION && BLOCK
1562 Provide fault-injection capability on end IO handling. This
1563 will make the block layer "forget" an interrupt as configured,
1564 thus exercising the error handling.
1566 Only works with drivers that use the generic timeout handling,
1567 for others it wont do anything.
1570 bool "Fault-injection capability for futexes"
1572 depends on FAULT_INJECTION && FUTEX
1574 Provide fault-injection capability for futexes.
1576 config FAULT_INJECTION_DEBUG_FS
1577 bool "Debugfs entries for fault-injection capabilities"
1578 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1580 Enable configuration of fault-injection capabilities via debugfs.
1582 config FAIL_FUNCTION
1583 bool "Fault-injection capability for functions"
1584 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
1586 Provide function-based fault-injection capability.
1587 This will allow you to override a specific function with a return
1588 with given return value. As a result, function caller will see
1589 an error value and have to handle it. This is useful to test the
1590 error handling in various subsystems.
1592 config FAIL_MMC_REQUEST
1593 bool "Fault-injection capability for MMC IO"
1594 depends on FAULT_INJECTION_DEBUG_FS && MMC
1596 Provide fault-injection capability for MMC IO.
1597 This will make the mmc core return data errors. This is
1598 useful to test the error handling in the mmc block device
1599 and to test how the mmc host driver handles retries from
1602 config FAULT_INJECTION_STACKTRACE_FILTER
1603 bool "stacktrace filter for fault-injection capabilities"
1604 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1607 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1609 Provide stacktrace filter for fault-injection capabilities
1612 bool "Latency measuring infrastructure"
1613 depends on DEBUG_KERNEL
1614 depends on STACKTRACE_SUPPORT
1616 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1623 Enable this option if you want to use the LatencyTOP tool
1624 to find out which userspace is blocking on what kernel operations.
1626 source "kernel/trace/Kconfig"
1628 config PROVIDE_OHCI1394_DMA_INIT
1629 bool "Remote debugging over FireWire early on boot"
1630 depends on PCI && X86
1632 If you want to debug problems which hang or crash the kernel early
1633 on boot and the crashing machine has a FireWire port, you can use
1634 this feature to remotely access the memory of the crashed machine
1635 over FireWire. This employs remote DMA as part of the OHCI1394
1636 specification which is now the standard for FireWire controllers.
1638 With remote DMA, you can monitor the printk buffer remotely using
1639 firescope and access all memory below 4GB using fireproxy from gdb.
1640 Even controlling a kernel debugger is possible using remote DMA.
1644 If ohci1394_dma=early is used as boot parameter, it will initialize
1645 all OHCI1394 controllers which are found in the PCI config space.
1647 As all changes to the FireWire bus such as enabling and disabling
1648 devices cause a bus reset and thereby disable remote DMA for all
1649 devices, be sure to have the cable plugged and FireWire enabled on
1650 the debugging host before booting the debug target for debugging.
1652 This code (~1k) is freed after boot. By then, the firewire stack
1653 in charge of the OHCI-1394 controllers should be used instead.
1655 See Documentation/debugging-via-ohci1394.txt for more information.
1657 config DMA_API_DEBUG
1658 bool "Enable debugging of DMA-API usage"
1659 select NEED_DMA_MAP_STATE
1661 Enable this option to debug the use of the DMA API by device drivers.
1662 With this option you will be able to detect common bugs in device
1663 drivers like double-freeing of DMA mappings or freeing mappings that
1664 were never allocated.
1666 This also attempts to catch cases where a page owned by DMA is
1667 accessed by the cpu in a way that could cause data corruption. For
1668 example, this enables cow_user_page() to check that the source page is
1671 This option causes a performance degradation. Use only if you want to
1672 debug device drivers and dma interactions.
1676 config DMA_API_DEBUG_SG
1677 bool "Debug DMA scatter-gather usage"
1679 depends on DMA_API_DEBUG
1681 Perform extra checking that callers of dma_map_sg() have respected the
1682 appropriate segment length/boundary limits for the given device when
1683 preparing DMA scatterlists.
1685 This is particularly likely to have been overlooked in cases where the
1686 dma_map_sg() API is used for general bulk mapping of pages rather than
1687 preparing literal scatter-gather descriptors, where there is a risk of
1688 unexpected behaviour from DMA API implementations if the scatterlist
1689 is technically out-of-spec.
1693 menuconfig RUNTIME_TESTING_MENU
1694 bool "Runtime Testing"
1697 if RUNTIME_TESTING_MENU
1700 tristate "Linux Kernel Dump Test Tool Module"
1703 This module enables testing of the different dumping mechanisms by
1704 inducing system failures at predefined crash points.
1705 If you don't need it: say N
1706 Choose M here to compile this code as a module. The module will be
1709 Documentation on how to use the module can be found in
1710 Documentation/fault-injection/provoke-crashes.txt
1712 config TEST_LIST_SORT
1713 tristate "Linked list sorting test"
1714 depends on DEBUG_KERNEL || m
1716 Enable this to turn on 'list_sort()' function test. This test is
1717 executed only once during system boot (so affects only boot time),
1718 or at module load time.
1723 tristate "Array-based sort test"
1724 depends on DEBUG_KERNEL || m
1726 This option enables the self-test function of 'sort()' at boot,
1727 or at module load time.
1731 config KPROBES_SANITY_TEST
1732 bool "Kprobes sanity tests"
1733 depends on DEBUG_KERNEL
1736 This option provides for testing basic kprobes functionality on
1737 boot. Samples of kprobe and kretprobe are inserted and
1738 verified for functionality.
1740 Say N if you are unsure.
1742 config BACKTRACE_SELF_TEST
1743 tristate "Self test for the backtrace code"
1744 depends on DEBUG_KERNEL
1746 This option provides a kernel module that can be used to test
1747 the kernel stack backtrace code. This option is not useful
1748 for distributions or general kernels, but only for kernel
1749 developers working on architecture code.
1751 Note that if you want to also test saved backtraces, you will
1752 have to enable STACKTRACE as well.
1754 Say N if you are unsure.
1757 tristate "Red-Black tree test"
1758 depends on DEBUG_KERNEL
1760 A benchmark measuring the performance of the rbtree library.
1761 Also includes rbtree invariant checks.
1763 config INTERVAL_TREE_TEST
1764 tristate "Interval tree test"
1765 depends on DEBUG_KERNEL
1766 select INTERVAL_TREE
1768 A benchmark measuring the performance of the interval tree library
1771 tristate "Per cpu operations test"
1772 depends on m && DEBUG_KERNEL
1774 Enable this option to build test module which validates per-cpu
1779 config ATOMIC64_SELFTEST
1780 tristate "Perform an atomic64_t self-test"
1782 Enable this option to test the atomic64_t functions at boot or
1783 at module load time.
1787 config ASYNC_RAID6_TEST
1788 tristate "Self test for hardware accelerated raid6 recovery"
1789 depends on ASYNC_RAID6_RECOV
1792 This is a one-shot self test that permutes through the
1793 recovery of all the possible two disk failure scenarios for a
1794 N-disk array. Recovery is performed with the asynchronous
1795 raid6 recovery routines, and will optionally use an offload
1796 engine if one is available.
1801 tristate "Test functions located in the hexdump module at runtime"
1803 config TEST_STRING_HELPERS
1804 tristate "Test functions located in the string_helpers module at runtime"
1807 tristate "Test kstrto*() family of functions at runtime"
1810 tristate "Test printf() family of functions at runtime"
1813 tristate "Test bitmap_*() family of functions at runtime"
1815 Enable this option to test the bitmap functions at boot.
1819 config TEST_BITFIELD
1820 tristate "Test bitfield functions at runtime"
1822 Enable this option to test the bitfield functions at boot.
1827 tristate "Test functions located in the uuid module at runtime"
1830 tristate "Test the XArray code at runtime"
1832 config TEST_OVERFLOW
1833 tristate "Test check_*_overflow() functions at runtime"
1835 config TEST_RHASHTABLE
1836 tristate "Perform selftest on resizable hash table"
1838 Enable this option to test the rhashtable functions at boot.
1843 tristate "Perform selftest on hash functions"
1845 Enable this option to test the kernel's integer (<linux/hash.h>),
1846 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1847 hash functions on boot (or module load).
1849 This is intended to help people writing architecture-specific
1850 optimized versions. If unsure, say N.
1853 tristate "Perform selftest on IDA functions"
1856 tristate "Perform selftest on priority array manager"
1859 Enable this option to test priority array manager on boot
1865 tristate "Test module loading with 'hello world' module"
1868 This builds the "test_module" module that emits "Hello, world"
1869 on printk when loaded. It is designed to be used for basic
1870 evaluation of the module loading subsystem (for example when
1871 validating module verification). It lacks any extra dependencies,
1872 and will not normally be loaded by the system unless explicitly
1878 tristate "Test module for stress/performance analysis of vmalloc allocator"
1882 This builds the "test_vmalloc" module that should be used for
1883 stress and performance analysis. So, any new change for vmalloc
1884 subsystem can be evaluated from performance and stability point
1889 config TEST_USER_COPY
1890 tristate "Test user/kernel boundary protections"
1893 This builds the "test_user_copy" module that runs sanity checks
1894 on the copy_to/from_user infrastructure, making sure basic
1895 user/kernel boundary testing is working. If it fails to load,
1896 a regression has been detected in the user/kernel memory boundary
1902 tristate "Test BPF filter functionality"
1905 This builds the "test_bpf" module that runs various test vectors
1906 against the BPF interpreter or BPF JIT compiler depending on the
1907 current setting. This is in particular useful for BPF JIT compiler
1908 development, but also to run regression tests against changes in
1909 the interpreter code. It also enables test stubs for eBPF maps and
1910 verifier used by user space verifier testsuite.
1914 config FIND_BIT_BENCHMARK
1915 tristate "Test find_bit functions"
1917 This builds the "test_find_bit" module that measure find_*_bit()
1918 functions performance.
1922 config TEST_FIRMWARE
1923 tristate "Test firmware loading via userspace interface"
1924 depends on FW_LOADER
1926 This builds the "test_firmware" module that creates a userspace
1927 interface for testing firmware loading. This can be used to
1928 control the triggering of firmware loading without needing an
1929 actual firmware-using device. The contents can be rechecked by
1935 tristate "sysctl test driver"
1936 depends on PROC_SYSCTL
1938 This builds the "test_sysctl" module. This driver enables to test the
1939 proc sysctl interfaces available to drivers safely without affecting
1940 production knobs which might alter system functionality.
1945 tristate "udelay test driver"
1947 This builds the "udelay_test" module that helps to make sure
1948 that udelay() is working properly.
1952 config TEST_STATIC_KEYS
1953 tristate "Test static keys"
1956 Test the static key interfaces.
1961 tristate "kmod stress tester"
1963 depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS
1964 depends on NETDEVICES && NET_CORE && INET # for TUN
1970 Test the kernel's module loading mechanism: kmod. kmod implements
1971 support to load modules using the Linux kernel's usermode helper.
1972 This test provides a series of tests against kmod.
1974 Although technically you can either build test_kmod as a module or
1975 into the kernel we disallow building it into the kernel since
1976 it stress tests request_module() and this will very likely cause
1977 some issues by taking over precious threads available from other
1978 module load requests, ultimately this could be fatal.
1982 tools/testing/selftests/kmod/kmod.sh --help
1986 config TEST_DEBUG_VIRTUAL
1987 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
1988 depends on DEBUG_VIRTUAL
1990 Test the kernel's ability to detect incorrect calls to
1991 virt_to_phys() done against the non-linear part of the
1992 kernel's virtual address map.
1996 config TEST_MEMCAT_P
1997 tristate "Test memcat_p() helper function"
1999 Test the memcat_p() helper for correctly merging two
2000 pointer arrays together.
2004 config TEST_LIVEPATCH
2005 tristate "Test livepatching"
2007 depends on DYNAMIC_DEBUG
2008 depends on LIVEPATCH
2011 Test kernel livepatching features for correctness. The tests will
2012 load test modules that will be livepatched in various scenarios.
2014 To run all the livepatching tests:
2016 make -C tools/testing/selftests TARGETS=livepatch run_tests
2018 Alternatively, individual tests may be invoked:
2020 tools/testing/selftests/livepatch/test-callbacks.sh
2021 tools/testing/selftests/livepatch/test-livepatch.sh
2022 tools/testing/selftests/livepatch/test-shadow-vars.sh
2027 tristate "Perform selftest on object aggreration manager"
2031 Enable this option to test object aggregation manager on boot
2035 endif # RUNTIME_TESTING_MENU
2040 This option adds a kernel parameter 'memtest', which allows memtest
2042 memtest=0, mean disabled; -- default
2043 memtest=1, mean do 1 test pattern;
2045 memtest=17, mean do 17 test patterns.
2046 If you are unsure how to answer this question, answer N.
2048 config BUG_ON_DATA_CORRUPTION
2049 bool "Trigger a BUG when data corruption is detected"
2052 Select this option if the kernel should BUG when it encounters
2053 data corruption in kernel memory structures when they get checked
2058 source "samples/Kconfig"
2060 source "lib/Kconfig.kgdb"
2062 source "lib/Kconfig.ubsan"
2064 config ARCH_HAS_DEVMEM_IS_ALLOWED
2067 config STRICT_DEVMEM
2068 bool "Filter access to /dev/mem"
2069 depends on MMU && DEVMEM
2070 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
2071 default y if PPC || X86 || ARM64
2073 If this option is disabled, you allow userspace (root) access to all
2074 of memory, including kernel and userspace memory. Accidental
2075 access to this is obviously disastrous, but specific access can
2076 be used by people debugging the kernel. Note that with PAT support
2077 enabled, even in this case there are restrictions on /dev/mem
2078 use due to the cache aliasing requirements.
2080 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
2081 file only allows userspace access to PCI space and the BIOS code and
2082 data regions. This is sufficient for dosemu and X and all common
2087 config IO_STRICT_DEVMEM
2088 bool "Filter I/O access to /dev/mem"
2089 depends on STRICT_DEVMEM
2091 If this option is disabled, you allow userspace (root) access to all
2092 io-memory regardless of whether a driver is actively using that
2093 range. Accidental access to this is obviously disastrous, but
2094 specific access can be used by people debugging kernel drivers.
2096 If this option is switched on, the /dev/mem file only allows
2097 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2098 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2099 if the driver using a given range cannot be disabled.
2103 config DEBUG_AID_FOR_SYZBOT
2104 bool "Additional debug code for syzbot"
2107 This option is intended for testing by syzbot.
2109 source "arch/$(SRCARCH)/Kconfig.debug"
2111 endmenu # Kernel hacking
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