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
199 depends on $(cc-option,-gsplit-dwarf)
201 Generate debug info into separate .dwo files. This significantly
202 reduces the build directory size for builds with DEBUG_INFO,
203 because it stores the information only once on disk in .dwo
204 files instead of multiple times in object files and executables.
205 In addition the debug information is also compressed.
207 Requires recent gcc (4.7+) and recent gdb/binutils.
208 Any tool that packages or reads debug information would need
209 to know about the .dwo files and include them.
210 Incompatible with older versions of ccache.
212 config DEBUG_INFO_DWARF4
213 bool "Generate dwarf4 debuginfo"
214 depends on DEBUG_INFO
215 depends on $(cc-option,-gdwarf-4)
217 Generate dwarf4 debug info. This requires recent versions
218 of gcc and gdb. It makes the debug information larger.
219 But it significantly improves the success of resolving
220 variables in gdb on optimized code.
223 bool "Provide GDB scripts for kernel debugging"
224 depends on DEBUG_INFO
226 This creates the required links to GDB helper scripts in the
227 build directory. If you load vmlinux into gdb, the helper
228 scripts will be automatically imported by gdb as well, and
229 additional functions are available to analyze a Linux kernel
230 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
233 config ENABLE_MUST_CHECK
234 bool "Enable __must_check logic"
237 Enable the __must_check logic in the kernel build. Disable this to
238 suppress the "warning: ignoring return value of 'foo', declared with
239 attribute warn_unused_result" messages.
242 int "Warn for stack frames larger than (needs gcc 4.4)"
244 default 2048 if GCC_PLUGIN_LATENT_ENTROPY
245 default 1280 if (!64BIT && PARISC)
246 default 1024 if (!64BIT && !PARISC)
247 default 2048 if 64BIT
249 Tell gcc to warn at build time for stack frames larger than this.
250 Setting this too low will cause a lot of warnings.
251 Setting it to 0 disables the warning.
254 config STRIP_ASM_SYMS
255 bool "Strip assembler-generated symbols during link"
258 Strip internal assembler-generated symbols during a link (symbols
259 that look like '.Lxxx') so they don't pollute the output of
260 get_wchan() and suchlike.
263 bool "Generate readable assembler code"
264 depends on DEBUG_KERNEL
266 Disable some compiler optimizations that tend to generate human unreadable
267 assembler output. This may make the kernel slightly slower, but it helps
268 to keep kernel developers who have to stare a lot at assembler listings
271 config UNUSED_SYMBOLS
272 bool "Enable unused/obsolete exported symbols"
275 Unused but exported symbols make the kernel needlessly bigger. For
276 that reason most of these unused exports will soon be removed. This
277 option is provided temporarily to provide a transition period in case
278 some external kernel module needs one of these symbols anyway. If you
279 encounter such a case in your module, consider if you are actually
280 using the right API. (rationale: since nobody in the kernel is using
281 this in a module, there is a pretty good chance it's actually the
282 wrong interface to use). If you really need the symbol, please send a
283 mail to the linux kernel mailing list mentioning the symbol and why
284 you really need it, and what the merge plan to the mainline kernel for
288 bool "Debug Filesystem"
290 debugfs is a virtual file system that kernel developers use to put
291 debugging files into. Enable this option to be able to read and
292 write to these files.
294 For detailed documentation on the debugfs API, see
295 Documentation/filesystems/.
300 bool "Run 'make headers_check' when building vmlinux"
303 This option will extract the user-visible kernel headers whenever
304 building the kernel, and will run basic sanity checks on them to
305 ensure that exported files do not attempt to include files which
306 were not exported, etc.
308 If you're making modifications to header files which are
309 relevant for userspace, say 'Y', and check the headers
310 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
311 your build tree), to make sure they're suitable.
313 config DEBUG_SECTION_MISMATCH
314 bool "Enable full Section mismatch analysis"
316 The section mismatch analysis checks if there are illegal
317 references from one section to another section.
318 During linktime or runtime, some sections are dropped;
319 any use of code/data previously in these sections would
320 most likely result in an oops.
321 In the code, functions and variables are annotated with
322 __init,, etc. (see the full list in include/linux/init.h),
323 which results in the code/data being placed in specific sections.
324 The section mismatch analysis is always performed after a full
325 kernel build, and enabling this option causes the following
326 additional steps to occur:
327 - Add the option -fno-inline-functions-called-once to gcc commands.
328 When inlining a function annotated with __init in a non-init
329 function, we would lose the section information and thus
330 the analysis would not catch the illegal reference.
331 This option tells gcc to inline less (but it does result in
333 - Run the section mismatch analysis for each module/built-in.a file.
334 When we run the section mismatch analysis on vmlinux.o, we
335 lose valuable information about where the mismatch was
337 Running the analysis for each module/built-in.a file
338 tells where the mismatch happens much closer to the
339 source. The drawback is that the same mismatch is
340 reported at least twice.
341 - Enable verbose reporting from modpost in order to help resolve
342 the section mismatches that are reported.
344 config SECTION_MISMATCH_WARN_ONLY
345 bool "Make section mismatch errors non-fatal"
348 If you say N here, the build process will fail if there are any
349 section mismatch, instead of just throwing warnings.
354 # Select this config option from the architecture Kconfig, if it
355 # is preferred to always offer frame pointers as a config
356 # option on the architecture (regardless of KERNEL_DEBUG):
358 config ARCH_WANT_FRAME_POINTERS
362 bool "Compile the kernel with frame pointers"
363 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS
364 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
366 If you say Y here the resulting kernel image will be slightly
367 larger and slower, but it gives very useful debugging information
368 in case of kernel bugs. (precise oopses/stacktraces/warnings)
370 config STACK_VALIDATION
371 bool "Compile-time stack metadata validation"
372 depends on HAVE_STACK_VALIDATION
375 Add compile-time checks to validate stack metadata, including frame
376 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
377 that runtime stack traces are more reliable.
379 This is also a prerequisite for generation of ORC unwind data, which
380 is needed for CONFIG_UNWINDER_ORC.
382 For more information, see
383 tools/objtool/Documentation/stack-validation.txt.
385 config DEBUG_FORCE_WEAK_PER_CPU
386 bool "Force weak per-cpu definitions"
387 depends on DEBUG_KERNEL
389 s390 and alpha require percpu variables in modules to be
390 defined weak to work around addressing range issue which
391 puts the following two restrictions on percpu variable
394 1. percpu symbols must be unique whether static or not
395 2. percpu variables can't be defined inside a function
397 To ensure that generic code follows the above rules, this
398 option forces all percpu variables to be defined as weak.
400 endmenu # "Compiler options"
403 bool "Magic SysRq key"
406 If you say Y here, you will have some control over the system even
407 if the system crashes for example during kernel debugging (e.g., you
408 will be able to flush the buffer cache to disk, reboot the system
409 immediately or dump some status information). This is accomplished
410 by pressing various keys while holding SysRq (Alt+PrintScreen). It
411 also works on a serial console (on PC hardware at least), if you
412 send a BREAK and then within 5 seconds a command keypress. The
413 keys are documented in <file:Documentation/admin-guide/sysrq.rst>.
414 Don't say Y unless you really know what this hack does.
416 config MAGIC_SYSRQ_DEFAULT_ENABLE
417 hex "Enable magic SysRq key functions by default"
418 depends on MAGIC_SYSRQ
421 Specifies which SysRq key functions are enabled by default.
422 This may be set to 1 or 0 to enable or disable them all, or
423 to a bitmask as described in Documentation/admin-guide/sysrq.rst.
425 config MAGIC_SYSRQ_SERIAL
426 bool "Enable magic SysRq key over serial"
427 depends on MAGIC_SYSRQ
430 Many embedded boards have a disconnected TTL level serial which can
431 generate some garbage that can lead to spurious false sysrq detects.
432 This option allows you to decide whether you want to enable the
436 bool "Kernel debugging"
438 Say Y here if you are developing drivers or trying to debug and
439 identify kernel problems.
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.
514 config DEBUG_SLAB_LEAK
515 bool "Memory leak debugging"
516 depends on DEBUG_SLAB
519 bool "SLUB debugging on by default"
520 depends on SLUB && SLUB_DEBUG
523 Boot with debugging on by default. SLUB boots by default with
524 the runtime debug capabilities switched off. Enabling this is
525 equivalent to specifying the "slub_debug" parameter on boot.
526 There is no support for more fine grained debug control like
527 possible with slub_debug=xxx. SLUB debugging may be switched
528 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
533 bool "Enable SLUB performance statistics"
534 depends on SLUB && SYSFS
536 SLUB statistics are useful to debug SLUBs allocation behavior in
537 order find ways to optimize the allocator. This should never be
538 enabled for production use since keeping statistics slows down
539 the allocator by a few percentage points. The slabinfo command
540 supports the determination of the most active slabs to figure
541 out which slabs are relevant to a particular load.
542 Try running: slabinfo -DA
544 config HAVE_DEBUG_KMEMLEAK
547 config DEBUG_KMEMLEAK
548 bool "Kernel memory leak detector"
549 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
551 select STACKTRACE if STACKTRACE_SUPPORT
555 Say Y here if you want to enable the memory leak
556 detector. The memory allocation/freeing is traced in a way
557 similar to the Boehm's conservative garbage collector, the
558 difference being that the orphan objects are not freed but
559 only shown in /sys/kernel/debug/kmemleak. Enabling this
560 feature will introduce an overhead to memory
561 allocations. See Documentation/dev-tools/kmemleak.rst for more
564 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
565 of finding leaks due to the slab objects poisoning.
567 In order to access the kmemleak file, debugfs needs to be
568 mounted (usually at /sys/kernel/debug).
570 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
571 int "Maximum kmemleak early log entries"
572 depends on DEBUG_KMEMLEAK
576 Kmemleak must track all the memory allocations to avoid
577 reporting false positives. Since memory may be allocated or
578 freed before kmemleak is initialised, an early log buffer is
579 used to store these actions. If kmemleak reports "early log
580 buffer exceeded", please increase this value.
582 config DEBUG_KMEMLEAK_TEST
583 tristate "Simple test for the kernel memory leak detector"
584 depends on DEBUG_KMEMLEAK && m
586 This option enables a module that explicitly leaks memory.
590 config DEBUG_KMEMLEAK_DEFAULT_OFF
591 bool "Default kmemleak to off"
592 depends on DEBUG_KMEMLEAK
594 Say Y here to disable kmemleak by default. It can then be enabled
595 on the command line via kmemleak=on.
597 config DEBUG_KMEMLEAK_AUTO_SCAN
598 bool "Enable kmemleak auto scan thread on boot up"
600 depends on DEBUG_KMEMLEAK
602 Depending on the cpu, kmemleak scan may be cpu intensive and can
603 stall user tasks at times. This option enables/disables automatic
604 kmemleak scan at boot up.
606 Say N here to disable kmemleak auto scan thread to stop automatic
607 scanning. Disabling this option disables automatic reporting of
612 config DEBUG_STACK_USAGE
613 bool "Stack utilization instrumentation"
614 depends on DEBUG_KERNEL && !IA64
616 Enables the display of the minimum amount of free stack which each
617 task has ever had available in the sysrq-T and sysrq-P debug output.
619 This option will slow down process creation somewhat.
623 depends on DEBUG_KERNEL
625 Enable this to turn on extended checks in the virtual-memory system
626 that may impact performance.
630 config DEBUG_VM_VMACACHE
631 bool "Debug VMA caching"
634 Enable this to turn on VMA caching debug information. Doing so
635 can cause significant overhead, so only enable it in non-production
641 bool "Debug VM red-black trees"
644 Enable VM red-black tree debugging information and extra validations.
648 config DEBUG_VM_PGFLAGS
649 bool "Debug page-flags operations"
652 Enables extra validation on page flags operations.
656 config ARCH_HAS_DEBUG_VIRTUAL
660 bool "Debug VM translations"
661 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
663 Enable some costly sanity checks in virtual to page code. This can
664 catch mistakes with virt_to_page() and friends.
668 config DEBUG_NOMMU_REGIONS
669 bool "Debug the global anon/private NOMMU mapping region tree"
670 depends on DEBUG_KERNEL && !MMU
672 This option causes the global tree of anonymous and private mapping
673 regions to be regularly checked for invalid topology.
675 config DEBUG_MEMORY_INIT
676 bool "Debug memory initialisation" if EXPERT
679 Enable this for additional checks during memory initialisation.
680 The sanity checks verify aspects of the VM such as the memory model
681 and other information provided by the architecture. Verbose
682 information will be printed at KERN_DEBUG loglevel depending
683 on the mminit_loglevel= command-line option.
687 config MEMORY_NOTIFIER_ERROR_INJECT
688 tristate "Memory hotplug notifier error injection module"
689 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
691 This option provides the ability to inject artificial errors to
692 memory hotplug notifier chain callbacks. It is controlled through
693 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
695 If the notifier call chain should be failed with some events
696 notified, write the error code to "actions/<notifier event>/error".
698 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
700 # cd /sys/kernel/debug/notifier-error-inject/memory
701 # echo -12 > actions/MEM_GOING_OFFLINE/error
702 # echo offline > /sys/devices/system/memory/memoryXXX/state
703 bash: echo: write error: Cannot allocate memory
705 To compile this code as a module, choose M here: the module will
706 be called memory-notifier-error-inject.
710 config DEBUG_PER_CPU_MAPS
711 bool "Debug access to per_cpu maps"
712 depends on DEBUG_KERNEL
715 Say Y to verify that the per_cpu map being accessed has
716 been set up. This adds a fair amount of code to kernel memory
717 and decreases performance.
722 bool "Highmem debugging"
723 depends on DEBUG_KERNEL && HIGHMEM
725 This option enables additional error checking for high memory
726 systems. Disable for production systems.
728 config HAVE_DEBUG_STACKOVERFLOW
731 config DEBUG_STACKOVERFLOW
732 bool "Check for stack overflows"
733 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
735 Say Y here if you want to check for overflows of kernel, IRQ
736 and exception stacks (if your architecture uses them). This
737 option will show detailed messages if free stack space drops
738 below a certain limit.
740 These kinds of bugs usually occur when call-chains in the
741 kernel get too deep, especially when interrupts are
744 Use this in cases where you see apparently random memory
745 corruption, especially if it appears in 'struct thread_info'
747 If in doubt, say "N".
749 source "lib/Kconfig.kasan"
751 endmenu # "Memory Debugging"
756 An architecture should select this when it can successfully
757 build and run with CONFIG_KCOV. This typically requires
758 disabling instrumentation for some early boot code.
760 config CC_HAS_SANCOV_TRACE_PC
761 def_bool $(cc-option,-fsanitize-coverage=trace-pc)
764 bool "Code coverage for fuzzing"
765 depends on ARCH_HAS_KCOV
766 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
768 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
770 KCOV exposes kernel code coverage information in a form suitable
771 for coverage-guided fuzzing (randomized testing).
773 If RANDOMIZE_BASE is enabled, PC values will not be stable across
774 different machines and across reboots. If you need stable PC values,
775 disable RANDOMIZE_BASE.
777 For more details, see Documentation/dev-tools/kcov.rst.
779 config KCOV_ENABLE_COMPARISONS
780 bool "Enable comparison operands collection by KCOV"
782 depends on $(cc-option,-fsanitize-coverage=trace-cmp)
784 KCOV also exposes operands of every comparison in the instrumented
785 code along with operand sizes and PCs of the comparison instructions.
786 These operands can be used by fuzzing engines to improve the quality
789 config KCOV_INSTRUMENT_ALL
790 bool "Instrument all code by default"
794 If you are doing generic system call fuzzing (like e.g. syzkaller),
795 then you will want to instrument the whole kernel and you should
796 say y here. If you are doing more targeted fuzzing (like e.g.
797 filesystem fuzzing with AFL) then you will want to enable coverage
798 for more specific subsets of files, and should say n here.
801 bool "Debug shared IRQ handlers"
802 depends on DEBUG_KERNEL
804 Enable this to generate a spurious interrupt as soon as a shared
805 interrupt handler is registered, and just before one is deregistered.
806 Drivers ought to be able to handle interrupts coming in at those
807 points; some don't and need to be caught.
809 menu "Debug Lockups and Hangs"
811 config LOCKUP_DETECTOR
814 config SOFTLOCKUP_DETECTOR
815 bool "Detect Soft Lockups"
816 depends on DEBUG_KERNEL && !S390
817 select LOCKUP_DETECTOR
819 Say Y here to enable the kernel to act as a watchdog to detect
822 Softlockups are bugs that cause the kernel to loop in kernel
823 mode for more than 20 seconds, without giving other tasks a
824 chance to run. The current stack trace is displayed upon
825 detection and the system will stay locked up.
827 config BOOTPARAM_SOFTLOCKUP_PANIC
828 bool "Panic (Reboot) On Soft Lockups"
829 depends on SOFTLOCKUP_DETECTOR
831 Say Y here to enable the kernel to panic on "soft lockups",
832 which are bugs that cause the kernel to loop in kernel
833 mode for more than 20 seconds (configurable using the watchdog_thresh
834 sysctl), without giving other tasks a chance to run.
836 The panic can be used in combination with panic_timeout,
837 to cause the system to reboot automatically after a
838 lockup has been detected. This feature is useful for
839 high-availability systems that have uptime guarantees and
840 where a lockup must be resolved ASAP.
844 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
846 depends on SOFTLOCKUP_DETECTOR
848 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
849 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
851 config HARDLOCKUP_DETECTOR_PERF
853 select SOFTLOCKUP_DETECTOR
856 # Enables a timestamp based low pass filter to compensate for perf based
857 # hard lockup detection which runs too fast due to turbo modes.
859 config HARDLOCKUP_CHECK_TIMESTAMP
863 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
864 # lockup detector rather than the perf based detector.
866 config HARDLOCKUP_DETECTOR
867 bool "Detect Hard Lockups"
868 depends on DEBUG_KERNEL && !S390
869 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
870 select LOCKUP_DETECTOR
871 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
872 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
874 Say Y here to enable the kernel to act as a watchdog to detect
877 Hardlockups are bugs that cause the CPU to loop in kernel mode
878 for more than 10 seconds, without letting other interrupts have a
879 chance to run. The current stack trace is displayed upon detection
880 and the system will stay locked up.
882 config BOOTPARAM_HARDLOCKUP_PANIC
883 bool "Panic (Reboot) On Hard Lockups"
884 depends on HARDLOCKUP_DETECTOR
886 Say Y here to enable the kernel to panic on "hard lockups",
887 which are bugs that cause the kernel to loop in kernel
888 mode with interrupts disabled for more than 10 seconds (configurable
889 using the watchdog_thresh sysctl).
893 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
895 depends on HARDLOCKUP_DETECTOR
897 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
898 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
900 config DETECT_HUNG_TASK
901 bool "Detect Hung Tasks"
902 depends on DEBUG_KERNEL
903 default SOFTLOCKUP_DETECTOR
905 Say Y here to enable the kernel to detect "hung tasks",
906 which are bugs that cause the task to be stuck in
907 uninterruptible "D" state indefinitely.
909 When a hung task is detected, the kernel will print the
910 current stack trace (which you should report), but the
911 task will stay in uninterruptible state. If lockdep is
912 enabled then all held locks will also be reported. This
913 feature has negligible overhead.
915 config DEFAULT_HUNG_TASK_TIMEOUT
916 int "Default timeout for hung task detection (in seconds)"
917 depends on DETECT_HUNG_TASK
920 This option controls the default timeout (in seconds) used
921 to determine when a task has become non-responsive and should
924 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
925 sysctl or by writing a value to
926 /proc/sys/kernel/hung_task_timeout_secs.
928 A timeout of 0 disables the check. The default is two minutes.
929 Keeping the default should be fine in most cases.
931 config BOOTPARAM_HUNG_TASK_PANIC
932 bool "Panic (Reboot) On Hung Tasks"
933 depends on DETECT_HUNG_TASK
935 Say Y here to enable the kernel to panic on "hung tasks",
936 which are bugs that cause the kernel to leave a task stuck
937 in uninterruptible "D" state.
939 The panic can be used in combination with panic_timeout,
940 to cause the system to reboot automatically after a
941 hung task has been detected. This feature is useful for
942 high-availability systems that have uptime guarantees and
943 where a hung tasks must be resolved ASAP.
947 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
949 depends on DETECT_HUNG_TASK
951 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
952 default 1 if BOOTPARAM_HUNG_TASK_PANIC
955 bool "Detect Workqueue Stalls"
956 depends on DEBUG_KERNEL
958 Say Y here to enable stall detection on workqueues. If a
959 worker pool doesn't make forward progress on a pending work
960 item for over a given amount of time, 30s by default, a
961 warning message is printed along with dump of workqueue
962 state. This can be configured through kernel parameter
963 "workqueue.watchdog_thresh" and its sysfs counterpart.
965 endmenu # "Debug lockups and hangs"
970 Say Y here to enable the kernel to panic when it oopses. This
971 has the same effect as setting oops=panic on the kernel command
974 This feature is useful to ensure that the kernel does not do
975 anything erroneous after an oops which could result in data
976 corruption or other issues.
980 config PANIC_ON_OOPS_VALUE
983 default 0 if !PANIC_ON_OOPS
984 default 1 if PANIC_ON_OOPS
990 Set the timeout value (in seconds) until a reboot occurs when the
991 the kernel panics. If n = 0, then we wait forever. A timeout
992 value n > 0 will wait n seconds before rebooting, while a timeout
993 value n < 0 will reboot immediately.
996 bool "Collect scheduler debugging info"
997 depends on DEBUG_KERNEL && PROC_FS
1000 If you say Y here, the /proc/sched_debug file will be provided
1001 that can help debug the scheduler. The runtime overhead of this
1009 bool "Collect scheduler statistics"
1010 depends on DEBUG_KERNEL && PROC_FS
1013 If you say Y here, additional code will be inserted into the
1014 scheduler and related routines to collect statistics about
1015 scheduler behavior and provide them in /proc/schedstat. These
1016 stats may be useful for both tuning and debugging the scheduler
1017 If you aren't debugging the scheduler or trying to tune a specific
1018 application, you can say N to avoid the very slight overhead
1021 config SCHED_STACK_END_CHECK
1022 bool "Detect stack corruption on calls to schedule()"
1023 depends on DEBUG_KERNEL
1026 This option checks for a stack overrun on calls to schedule().
1027 If the stack end location is found to be over written always panic as
1028 the content of the corrupted region can no longer be trusted.
1029 This is to ensure no erroneous behaviour occurs which could result in
1030 data corruption or a sporadic crash at a later stage once the region
1031 is examined. The runtime overhead introduced is minimal.
1033 config DEBUG_TIMEKEEPING
1034 bool "Enable extra timekeeping sanity checking"
1036 This option will enable additional timekeeping sanity checks
1037 which may be helpful when diagnosing issues where timekeeping
1038 problems are suspected.
1040 This may include checks in the timekeeping hotpaths, so this
1041 option may have a (very small) performance impact to some
1046 config DEBUG_PREEMPT
1047 bool "Debug preemptible kernel"
1048 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1051 If you say Y here then the kernel will use a debug variant of the
1052 commonly used smp_processor_id() function and will print warnings
1053 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1054 will detect preemption count underflows.
1056 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1058 config LOCK_DEBUGGING_SUPPORT
1060 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1063 config PROVE_LOCKING
1064 bool "Lock debugging: prove locking correctness"
1065 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1067 select DEBUG_SPINLOCK
1068 select DEBUG_MUTEXES
1069 select DEBUG_RT_MUTEXES if RT_MUTEXES
1070 select DEBUG_RWSEMS if RWSEM_SPIN_ON_OWNER
1071 select DEBUG_WW_MUTEX_SLOWPATH
1072 select DEBUG_LOCK_ALLOC
1073 select TRACE_IRQFLAGS
1076 This feature enables the kernel to prove that all locking
1077 that occurs in the kernel runtime is mathematically
1078 correct: that under no circumstance could an arbitrary (and
1079 not yet triggered) combination of observed locking
1080 sequences (on an arbitrary number of CPUs, running an
1081 arbitrary number of tasks and interrupt contexts) cause a
1084 In short, this feature enables the kernel to report locking
1085 related deadlocks before they actually occur.
1087 The proof does not depend on how hard and complex a
1088 deadlock scenario would be to trigger: how many
1089 participant CPUs, tasks and irq-contexts would be needed
1090 for it to trigger. The proof also does not depend on
1091 timing: if a race and a resulting deadlock is possible
1092 theoretically (no matter how unlikely the race scenario
1093 is), it will be proven so and will immediately be
1094 reported by the kernel (once the event is observed that
1095 makes the deadlock theoretically possible).
1097 If a deadlock is impossible (i.e. the locking rules, as
1098 observed by the kernel, are mathematically correct), the
1099 kernel reports nothing.
1101 NOTE: this feature can also be enabled for rwlocks, mutexes
1102 and rwsems - in which case all dependencies between these
1103 different locking variants are observed and mapped too, and
1104 the proof of observed correctness is also maintained for an
1105 arbitrary combination of these separate locking variants.
1107 For more details, see Documentation/locking/lockdep-design.txt.
1110 bool "Lock usage statistics"
1111 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1113 select DEBUG_SPINLOCK
1114 select DEBUG_MUTEXES
1115 select DEBUG_RT_MUTEXES if RT_MUTEXES
1116 select DEBUG_LOCK_ALLOC
1119 This feature enables tracking lock contention points
1121 For more details, see Documentation/locking/lockstat.txt
1123 This also enables lock events required by "perf lock",
1125 If you want to use "perf lock", you also need to turn on
1126 CONFIG_EVENT_TRACING.
1128 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1129 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1131 config DEBUG_RT_MUTEXES
1132 bool "RT Mutex debugging, deadlock detection"
1133 depends on DEBUG_KERNEL && RT_MUTEXES
1135 This allows rt mutex semantics violations and rt mutex related
1136 deadlocks (lockups) to be detected and reported automatically.
1138 config DEBUG_SPINLOCK
1139 bool "Spinlock and rw-lock debugging: basic checks"
1140 depends on DEBUG_KERNEL
1141 select UNINLINE_SPIN_UNLOCK
1143 Say Y here and build SMP to catch missing spinlock initialization
1144 and certain other kinds of spinlock errors commonly made. This is
1145 best used in conjunction with the NMI watchdog so that spinlock
1146 deadlocks are also debuggable.
1148 config DEBUG_MUTEXES
1149 bool "Mutex debugging: basic checks"
1150 depends on DEBUG_KERNEL
1152 This feature allows mutex semantics violations to be detected and
1155 config DEBUG_WW_MUTEX_SLOWPATH
1156 bool "Wait/wound mutex debugging: Slowpath testing"
1157 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1158 select DEBUG_LOCK_ALLOC
1159 select DEBUG_SPINLOCK
1160 select DEBUG_MUTEXES
1162 This feature enables slowpath testing for w/w mutex users by
1163 injecting additional -EDEADLK wound/backoff cases. Together with
1164 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1165 will test all possible w/w mutex interface abuse with the
1166 exception of simply not acquiring all the required locks.
1167 Note that this feature can introduce significant overhead, so
1168 it really should not be enabled in a production or distro kernel,
1169 even a debug kernel. If you are a driver writer, enable it. If
1170 you are a distro, do not.
1173 bool "RW Semaphore debugging: basic checks"
1174 depends on DEBUG_KERNEL && RWSEM_SPIN_ON_OWNER
1176 This debugging feature allows mismatched rw semaphore locks and unlocks
1177 to be detected and reported.
1179 config DEBUG_LOCK_ALLOC
1180 bool "Lock debugging: detect incorrect freeing of live locks"
1181 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1182 select DEBUG_SPINLOCK
1183 select DEBUG_MUTEXES
1184 select DEBUG_RT_MUTEXES if RT_MUTEXES
1187 This feature will check whether any held lock (spinlock, rwlock,
1188 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1189 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1190 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1191 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1192 held during task exit.
1196 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1198 select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86
1202 config LOCKDEP_SMALL
1205 config DEBUG_LOCKDEP
1206 bool "Lock dependency engine debugging"
1207 depends on DEBUG_KERNEL && LOCKDEP
1209 If you say Y here, the lock dependency engine will do
1210 additional runtime checks to debug itself, at the price
1211 of more runtime overhead.
1213 config DEBUG_ATOMIC_SLEEP
1214 bool "Sleep inside atomic section checking"
1215 select PREEMPT_COUNT
1216 depends on DEBUG_KERNEL
1217 depends on !ARCH_NO_PREEMPT
1219 If you say Y here, various routines which may sleep will become very
1220 noisy if they are called inside atomic sections: when a spinlock is
1221 held, inside an rcu read side critical section, inside preempt disabled
1222 sections, inside an interrupt, etc...
1224 config DEBUG_LOCKING_API_SELFTESTS
1225 bool "Locking API boot-time self-tests"
1226 depends on DEBUG_KERNEL
1228 Say Y here if you want the kernel to run a short self-test during
1229 bootup. The self-test checks whether common types of locking bugs
1230 are detected by debugging mechanisms or not. (if you disable
1231 lock debugging then those bugs wont be detected of course.)
1232 The following locking APIs are covered: spinlocks, rwlocks,
1235 config LOCK_TORTURE_TEST
1236 tristate "torture tests for locking"
1237 depends on DEBUG_KERNEL
1240 This option provides a kernel module that runs torture tests
1241 on kernel locking primitives. The kernel module may be built
1242 after the fact on the running kernel to be tested, if desired.
1244 Say Y here if you want kernel locking-primitive torture tests
1245 to be built into the kernel.
1246 Say M if you want these torture tests to build as a module.
1247 Say N if you are unsure.
1249 config WW_MUTEX_SELFTEST
1250 tristate "Wait/wound mutex selftests"
1252 This option provides a kernel module that runs tests on the
1253 on the struct ww_mutex locking API.
1255 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1256 with this test harness.
1258 Say M if you want these self tests to build as a module.
1259 Say N if you are unsure.
1261 endmenu # lock debugging
1263 config TRACE_IRQFLAGS
1266 Enables hooks to interrupt enabling and disabling for
1267 either tracing or lock debugging.
1270 bool "Stack backtrace support"
1271 depends on STACKTRACE_SUPPORT
1273 This option causes the kernel to create a /proc/pid/stack for
1274 every process, showing its current stack trace.
1275 It is also used by various kernel debugging features that require
1276 stack trace generation.
1278 config WARN_ALL_UNSEEDED_RANDOM
1279 bool "Warn for all uses of unseeded randomness"
1282 Some parts of the kernel contain bugs relating to their use of
1283 cryptographically secure random numbers before it's actually possible
1284 to generate those numbers securely. This setting ensures that these
1285 flaws don't go unnoticed, by enabling a message, should this ever
1286 occur. This will allow people with obscure setups to know when things
1287 are going wrong, so that they might contact developers about fixing
1290 Unfortunately, on some models of some architectures getting
1291 a fully seeded CRNG is extremely difficult, and so this can
1292 result in dmesg getting spammed for a surprisingly long
1293 time. This is really bad from a security perspective, and
1294 so architecture maintainers really need to do what they can
1295 to get the CRNG seeded sooner after the system is booted.
1296 However, since users cannot do anything actionable to
1297 address this, by default the kernel will issue only a single
1298 warning for the first use of unseeded randomness.
1300 Say Y here if you want to receive warnings for all uses of
1301 unseeded randomness. This will be of use primarily for
1302 those developers interested in improving the security of
1303 Linux kernels running on their architecture (or
1306 config DEBUG_KOBJECT
1307 bool "kobject debugging"
1308 depends on DEBUG_KERNEL
1310 If you say Y here, some extra kobject debugging messages will be sent
1313 config DEBUG_KOBJECT_RELEASE
1314 bool "kobject release debugging"
1315 depends on DEBUG_OBJECTS_TIMERS
1317 kobjects are reference counted objects. This means that their
1318 last reference count put is not predictable, and the kobject can
1319 live on past the point at which a driver decides to drop it's
1320 initial reference to the kobject gained on allocation. An
1321 example of this would be a struct device which has just been
1324 However, some buggy drivers assume that after such an operation,
1325 the memory backing the kobject can be immediately freed. This
1326 goes completely against the principles of a refcounted object.
1328 If you say Y here, the kernel will delay the release of kobjects
1329 on the last reference count to improve the visibility of this
1330 kind of kobject release bug.
1332 config HAVE_DEBUG_BUGVERBOSE
1335 config DEBUG_BUGVERBOSE
1336 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1337 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1340 Say Y here to make BUG() panics output the file name and line number
1341 of the BUG call as well as the EIP and oops trace. This aids
1342 debugging but costs about 70-100K of memory.
1345 bool "Debug linked list manipulation"
1346 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1348 Enable this to turn on extended checks in the linked-list
1353 config DEBUG_PI_LIST
1354 bool "Debug priority linked list manipulation"
1355 depends on DEBUG_KERNEL
1357 Enable this to turn on extended checks in the priority-ordered
1358 linked-list (plist) walking routines. This checks the entire
1359 list multiple times during each manipulation.
1364 bool "Debug SG table operations"
1365 depends on DEBUG_KERNEL
1367 Enable this to turn on checks on scatter-gather tables. This can
1368 help find problems with drivers that do not properly initialize
1373 config DEBUG_NOTIFIERS
1374 bool "Debug notifier call chains"
1375 depends on DEBUG_KERNEL
1377 Enable this to turn on sanity checking for notifier call chains.
1378 This is most useful for kernel developers to make sure that
1379 modules properly unregister themselves from notifier chains.
1380 This is a relatively cheap check but if you care about maximum
1383 config DEBUG_CREDENTIALS
1384 bool "Debug credential management"
1385 depends on DEBUG_KERNEL
1387 Enable this to turn on some debug checking for credential
1388 management. The additional code keeps track of the number of
1389 pointers from task_structs to any given cred struct, and checks to
1390 see that this number never exceeds the usage count of the cred
1393 Furthermore, if SELinux is enabled, this also checks that the
1394 security pointer in the cred struct is never seen to be invalid.
1398 source "kernel/rcu/Kconfig.debug"
1400 config DEBUG_WQ_FORCE_RR_CPU
1401 bool "Force round-robin CPU selection for unbound work items"
1402 depends on DEBUG_KERNEL
1405 Workqueue used to implicitly guarantee that work items queued
1406 without explicit CPU specified are put on the local CPU. This
1407 guarantee is no longer true and while local CPU is still
1408 preferred work items may be put on foreign CPUs. Kernel
1409 parameter "workqueue.debug_force_rr_cpu" is added to force
1410 round-robin CPU selection to flush out usages which depend on the
1411 now broken guarantee. This config option enables the debug
1412 feature by default. When enabled, memory and cache locality will
1415 config DEBUG_BLOCK_EXT_DEVT
1416 bool "Force extended block device numbers and spread them"
1417 depends on DEBUG_KERNEL
1421 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1422 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1423 YOU ARE DOING. Distros, please enable this and fix whatever
1426 Conventionally, block device numbers are allocated from
1427 predetermined contiguous area. However, extended block area
1428 may introduce non-contiguous block device numbers. This
1429 option forces most block device numbers to be allocated from
1430 the extended space and spreads them to discover kernel or
1431 userland code paths which assume predetermined contiguous
1432 device number allocation.
1434 Note that turning on this debug option shuffles all the
1435 device numbers for all IDE and SCSI devices including libata
1436 ones, so root partition specified using device number
1437 directly (via rdev or root=MAJ:MIN) won't work anymore.
1438 Textual device names (root=/dev/sdXn) will continue to work.
1440 Say N if you are unsure.
1442 config CPU_HOTPLUG_STATE_CONTROL
1443 bool "Enable CPU hotplug state control"
1444 depends on DEBUG_KERNEL
1445 depends on HOTPLUG_CPU
1448 Allows to write steps between "offline" and "online" to the CPUs
1449 sysfs target file so states can be stepped granular. This is a debug
1450 option for now as the hotplug machinery cannot be stopped and
1451 restarted at arbitrary points yet.
1453 Say N if your are unsure.
1455 config NOTIFIER_ERROR_INJECTION
1456 tristate "Notifier error injection"
1457 depends on DEBUG_KERNEL
1460 This option provides the ability to inject artificial errors to
1461 specified notifier chain callbacks. It is useful to test the error
1462 handling of notifier call chain failures.
1466 config PM_NOTIFIER_ERROR_INJECT
1467 tristate "PM notifier error injection module"
1468 depends on PM && NOTIFIER_ERROR_INJECTION
1469 default m if PM_DEBUG
1471 This option provides the ability to inject artificial errors to
1472 PM notifier chain callbacks. It is controlled through debugfs
1473 interface /sys/kernel/debug/notifier-error-inject/pm
1475 If the notifier call chain should be failed with some events
1476 notified, write the error code to "actions/<notifier event>/error".
1478 Example: Inject PM suspend error (-12 = -ENOMEM)
1480 # cd /sys/kernel/debug/notifier-error-inject/pm/
1481 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1482 # echo mem > /sys/power/state
1483 bash: echo: write error: Cannot allocate memory
1485 To compile this code as a module, choose M here: the module will
1486 be called pm-notifier-error-inject.
1490 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1491 tristate "OF reconfig notifier error injection module"
1492 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1494 This option provides the ability to inject artificial errors to
1495 OF reconfig notifier chain callbacks. It is controlled
1496 through debugfs interface under
1497 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1499 If the notifier call chain should be failed with some events
1500 notified, write the error code to "actions/<notifier event>/error".
1502 To compile this code as a module, choose M here: the module will
1503 be called of-reconfig-notifier-error-inject.
1507 config NETDEV_NOTIFIER_ERROR_INJECT
1508 tristate "Netdev notifier error injection module"
1509 depends on NET && NOTIFIER_ERROR_INJECTION
1511 This option provides the ability to inject artificial errors to
1512 netdevice notifier chain callbacks. It is controlled through debugfs
1513 interface /sys/kernel/debug/notifier-error-inject/netdev
1515 If the notifier call chain should be failed with some events
1516 notified, write the error code to "actions/<notifier event>/error".
1518 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1520 # cd /sys/kernel/debug/notifier-error-inject/netdev
1521 # echo -22 > actions/NETDEV_CHANGEMTU/error
1522 # ip link set eth0 mtu 1024
1523 RTNETLINK answers: Invalid argument
1525 To compile this code as a module, choose M here: the module will
1526 be called netdev-notifier-error-inject.
1530 config FUNCTION_ERROR_INJECTION
1532 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
1534 config FAULT_INJECTION
1535 bool "Fault-injection framework"
1536 depends on DEBUG_KERNEL
1538 Provide fault-injection framework.
1539 For more details, see Documentation/fault-injection/.
1542 bool "Fault-injection capability for kmalloc"
1543 depends on FAULT_INJECTION
1544 depends on SLAB || SLUB
1546 Provide fault-injection capability for kmalloc.
1548 config FAIL_PAGE_ALLOC
1549 bool "Fault-injection capabilitiy for alloc_pages()"
1550 depends on FAULT_INJECTION
1552 Provide fault-injection capability for alloc_pages().
1554 config FAIL_MAKE_REQUEST
1555 bool "Fault-injection capability for disk IO"
1556 depends on FAULT_INJECTION && BLOCK
1558 Provide fault-injection capability for disk IO.
1560 config FAIL_IO_TIMEOUT
1561 bool "Fault-injection capability for faking disk interrupts"
1562 depends on FAULT_INJECTION && BLOCK
1564 Provide fault-injection capability on end IO handling. This
1565 will make the block layer "forget" an interrupt as configured,
1566 thus exercising the error handling.
1568 Only works with drivers that use the generic timeout handling,
1569 for others it wont do anything.
1572 bool "Fault-injection capability for futexes"
1574 depends on FAULT_INJECTION && FUTEX
1576 Provide fault-injection capability for futexes.
1578 config FAULT_INJECTION_DEBUG_FS
1579 bool "Debugfs entries for fault-injection capabilities"
1580 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1582 Enable configuration of fault-injection capabilities via debugfs.
1584 config FAIL_FUNCTION
1585 bool "Fault-injection capability for functions"
1586 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
1588 Provide function-based fault-injection capability.
1589 This will allow you to override a specific function with a return
1590 with given return value. As a result, function caller will see
1591 an error value and have to handle it. This is useful to test the
1592 error handling in various subsystems.
1594 config FAIL_MMC_REQUEST
1595 bool "Fault-injection capability for MMC IO"
1596 depends on FAULT_INJECTION_DEBUG_FS && MMC
1598 Provide fault-injection capability for MMC IO.
1599 This will make the mmc core return data errors. This is
1600 useful to test the error handling in the mmc block device
1601 and to test how the mmc host driver handles retries from
1604 config FAULT_INJECTION_STACKTRACE_FILTER
1605 bool "stacktrace filter for fault-injection capabilities"
1606 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1609 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1611 Provide stacktrace filter for fault-injection capabilities
1614 bool "Latency measuring infrastructure"
1615 depends on DEBUG_KERNEL
1616 depends on STACKTRACE_SUPPORT
1618 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1625 Enable this option if you want to use the LatencyTOP tool
1626 to find out which userspace is blocking on what kernel operations.
1628 source "kernel/trace/Kconfig"
1630 config PROVIDE_OHCI1394_DMA_INIT
1631 bool "Remote debugging over FireWire early on boot"
1632 depends on PCI && X86
1634 If you want to debug problems which hang or crash the kernel early
1635 on boot and the crashing machine has a FireWire port, you can use
1636 this feature to remotely access the memory of the crashed machine
1637 over FireWire. This employs remote DMA as part of the OHCI1394
1638 specification which is now the standard for FireWire controllers.
1640 With remote DMA, you can monitor the printk buffer remotely using
1641 firescope and access all memory below 4GB using fireproxy from gdb.
1642 Even controlling a kernel debugger is possible using remote DMA.
1646 If ohci1394_dma=early is used as boot parameter, it will initialize
1647 all OHCI1394 controllers which are found in the PCI config space.
1649 As all changes to the FireWire bus such as enabling and disabling
1650 devices cause a bus reset and thereby disable remote DMA for all
1651 devices, be sure to have the cable plugged and FireWire enabled on
1652 the debugging host before booting the debug target for debugging.
1654 This code (~1k) is freed after boot. By then, the firewire stack
1655 in charge of the OHCI-1394 controllers should be used instead.
1657 See Documentation/debugging-via-ohci1394.txt for more information.
1659 menuconfig RUNTIME_TESTING_MENU
1660 bool "Runtime Testing"
1663 if RUNTIME_TESTING_MENU
1666 tristate "Linux Kernel Dump Test Tool Module"
1669 This module enables testing of the different dumping mechanisms by
1670 inducing system failures at predefined crash points.
1671 If you don't need it: say N
1672 Choose M here to compile this code as a module. The module will be
1675 Documentation on how to use the module can be found in
1676 Documentation/fault-injection/provoke-crashes.txt
1678 config TEST_LIST_SORT
1679 tristate "Linked list sorting test"
1680 depends on DEBUG_KERNEL || m
1682 Enable this to turn on 'list_sort()' function test. This test is
1683 executed only once during system boot (so affects only boot time),
1684 or at module load time.
1689 tristate "Array-based sort test"
1690 depends on DEBUG_KERNEL || m
1692 This option enables the self-test function of 'sort()' at boot,
1693 or at module load time.
1697 config KPROBES_SANITY_TEST
1698 bool "Kprobes sanity tests"
1699 depends on DEBUG_KERNEL
1702 This option provides for testing basic kprobes functionality on
1703 boot. Samples of kprobe and kretprobe are inserted and
1704 verified for functionality.
1706 Say N if you are unsure.
1708 config BACKTRACE_SELF_TEST
1709 tristate "Self test for the backtrace code"
1710 depends on DEBUG_KERNEL
1712 This option provides a kernel module that can be used to test
1713 the kernel stack backtrace code. This option is not useful
1714 for distributions or general kernels, but only for kernel
1715 developers working on architecture code.
1717 Note that if you want to also test saved backtraces, you will
1718 have to enable STACKTRACE as well.
1720 Say N if you are unsure.
1723 tristate "Red-Black tree test"
1724 depends on DEBUG_KERNEL
1726 A benchmark measuring the performance of the rbtree library.
1727 Also includes rbtree invariant checks.
1729 config INTERVAL_TREE_TEST
1730 tristate "Interval tree test"
1731 depends on DEBUG_KERNEL
1732 select INTERVAL_TREE
1734 A benchmark measuring the performance of the interval tree library
1737 tristate "Per cpu operations test"
1738 depends on m && DEBUG_KERNEL
1740 Enable this option to build test module which validates per-cpu
1745 config ATOMIC64_SELFTEST
1746 tristate "Perform an atomic64_t self-test"
1748 Enable this option to test the atomic64_t functions at boot or
1749 at module load time.
1753 config ASYNC_RAID6_TEST
1754 tristate "Self test for hardware accelerated raid6 recovery"
1755 depends on ASYNC_RAID6_RECOV
1758 This is a one-shot self test that permutes through the
1759 recovery of all the possible two disk failure scenarios for a
1760 N-disk array. Recovery is performed with the asynchronous
1761 raid6 recovery routines, and will optionally use an offload
1762 engine if one is available.
1767 tristate "Test functions located in the hexdump module at runtime"
1769 config TEST_STRING_HELPERS
1770 tristate "Test functions located in the string_helpers module at runtime"
1773 tristate "Test kstrto*() family of functions at runtime"
1776 tristate "Test printf() family of functions at runtime"
1779 tristate "Test bitmap_*() family of functions at runtime"
1781 Enable this option to test the bitmap functions at boot.
1785 config TEST_BITFIELD
1786 tristate "Test bitfield functions at runtime"
1788 Enable this option to test the bitfield functions at boot.
1793 tristate "Test functions located in the uuid module at runtime"
1796 tristate "Test the XArray code at runtime"
1798 config TEST_OVERFLOW
1799 tristate "Test check_*_overflow() functions at runtime"
1801 config TEST_RHASHTABLE
1802 tristate "Perform selftest on resizable hash table"
1804 Enable this option to test the rhashtable functions at boot.
1809 tristate "Perform selftest on hash functions"
1811 Enable this option to test the kernel's integer (<linux/hash.h>),
1812 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1813 hash functions on boot (or module load).
1815 This is intended to help people writing architecture-specific
1816 optimized versions. If unsure, say N.
1819 tristate "Perform selftest on IDA functions"
1822 tristate "Perform selftest on priority array manager"
1825 Enable this option to test priority array manager on boot
1831 tristate "Test module loading with 'hello world' module"
1834 This builds the "test_module" module that emits "Hello, world"
1835 on printk when loaded. It is designed to be used for basic
1836 evaluation of the module loading subsystem (for example when
1837 validating module verification). It lacks any extra dependencies,
1838 and will not normally be loaded by the system unless explicitly
1844 tristate "Test module for stress/performance analysis of vmalloc allocator"
1849 This builds the "test_vmalloc" module that should be used for
1850 stress and performance analysis. So, any new change for vmalloc
1851 subsystem can be evaluated from performance and stability point
1856 config TEST_USER_COPY
1857 tristate "Test user/kernel boundary protections"
1860 This builds the "test_user_copy" module that runs sanity checks
1861 on the copy_to/from_user infrastructure, making sure basic
1862 user/kernel boundary testing is working. If it fails to load,
1863 a regression has been detected in the user/kernel memory boundary
1869 tristate "Test BPF filter functionality"
1872 This builds the "test_bpf" module that runs various test vectors
1873 against the BPF interpreter or BPF JIT compiler depending on the
1874 current setting. This is in particular useful for BPF JIT compiler
1875 development, but also to run regression tests against changes in
1876 the interpreter code. It also enables test stubs for eBPF maps and
1877 verifier used by user space verifier testsuite.
1881 config FIND_BIT_BENCHMARK
1882 tristate "Test find_bit functions"
1884 This builds the "test_find_bit" module that measure find_*_bit()
1885 functions performance.
1889 config TEST_FIRMWARE
1890 tristate "Test firmware loading via userspace interface"
1891 depends on FW_LOADER
1893 This builds the "test_firmware" module that creates a userspace
1894 interface for testing firmware loading. This can be used to
1895 control the triggering of firmware loading without needing an
1896 actual firmware-using device. The contents can be rechecked by
1902 tristate "sysctl test driver"
1903 depends on PROC_SYSCTL
1905 This builds the "test_sysctl" module. This driver enables to test the
1906 proc sysctl interfaces available to drivers safely without affecting
1907 production knobs which might alter system functionality.
1912 tristate "udelay test driver"
1914 This builds the "udelay_test" module that helps to make sure
1915 that udelay() is working properly.
1919 config TEST_STATIC_KEYS
1920 tristate "Test static keys"
1923 Test the static key interfaces.
1928 tristate "kmod stress tester"
1930 depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS
1931 depends on NETDEVICES && NET_CORE && INET # for TUN
1937 Test the kernel's module loading mechanism: kmod. kmod implements
1938 support to load modules using the Linux kernel's usermode helper.
1939 This test provides a series of tests against kmod.
1941 Although technically you can either build test_kmod as a module or
1942 into the kernel we disallow building it into the kernel since
1943 it stress tests request_module() and this will very likely cause
1944 some issues by taking over precious threads available from other
1945 module load requests, ultimately this could be fatal.
1949 tools/testing/selftests/kmod/kmod.sh --help
1953 config TEST_DEBUG_VIRTUAL
1954 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
1955 depends on DEBUG_VIRTUAL
1957 Test the kernel's ability to detect incorrect calls to
1958 virt_to_phys() done against the non-linear part of the
1959 kernel's virtual address map.
1963 config TEST_MEMCAT_P
1964 tristate "Test memcat_p() helper function"
1966 Test the memcat_p() helper for correctly merging two
1967 pointer arrays together.
1971 config TEST_LIVEPATCH
1972 tristate "Test livepatching"
1974 depends on DYNAMIC_DEBUG
1975 depends on LIVEPATCH
1978 Test kernel livepatching features for correctness. The tests will
1979 load test modules that will be livepatched in various scenarios.
1981 To run all the livepatching tests:
1983 make -C tools/testing/selftests TARGETS=livepatch run_tests
1985 Alternatively, individual tests may be invoked:
1987 tools/testing/selftests/livepatch/test-callbacks.sh
1988 tools/testing/selftests/livepatch/test-livepatch.sh
1989 tools/testing/selftests/livepatch/test-shadow-vars.sh
1994 tristate "Perform selftest on object aggreration manager"
1998 Enable this option to test object aggregation manager on boot
2002 config TEST_STACKINIT
2003 tristate "Test level of stack variable initialization"
2005 Test if the kernel is zero-initializing stack variables and
2006 padding. Coverage is controlled by compiler flags,
2007 CONFIG_GCC_PLUGIN_STRUCTLEAK, CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF,
2008 or CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL.
2012 endif # RUNTIME_TESTING_MENU
2017 This option adds a kernel parameter 'memtest', which allows memtest
2019 memtest=0, mean disabled; -- default
2020 memtest=1, mean do 1 test pattern;
2022 memtest=17, mean do 17 test patterns.
2023 If you are unsure how to answer this question, answer N.
2025 config BUG_ON_DATA_CORRUPTION
2026 bool "Trigger a BUG when data corruption is detected"
2029 Select this option if the kernel should BUG when it encounters
2030 data corruption in kernel memory structures when they get checked
2035 source "samples/Kconfig"
2037 source "lib/Kconfig.kgdb"
2039 source "lib/Kconfig.ubsan"
2041 config ARCH_HAS_DEVMEM_IS_ALLOWED
2044 config STRICT_DEVMEM
2045 bool "Filter access to /dev/mem"
2046 depends on MMU && DEVMEM
2047 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
2048 default y if PPC || X86 || ARM64
2050 If this option is disabled, you allow userspace (root) access to all
2051 of memory, including kernel and userspace memory. Accidental
2052 access to this is obviously disastrous, but specific access can
2053 be used by people debugging the kernel. Note that with PAT support
2054 enabled, even in this case there are restrictions on /dev/mem
2055 use due to the cache aliasing requirements.
2057 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
2058 file only allows userspace access to PCI space and the BIOS code and
2059 data regions. This is sufficient for dosemu and X and all common
2064 config IO_STRICT_DEVMEM
2065 bool "Filter I/O access to /dev/mem"
2066 depends on STRICT_DEVMEM
2068 If this option is disabled, you allow userspace (root) access to all
2069 io-memory regardless of whether a driver is actively using that
2070 range. Accidental access to this is obviously disastrous, but
2071 specific access can be used by people debugging kernel drivers.
2073 If this option is switched on, the /dev/mem file only allows
2074 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2075 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2076 if the driver using a given range cannot be disabled.
2080 source "arch/$(SRCARCH)/Kconfig.debug"
2082 endmenu # Kernel hacking
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