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
20 config CONSOLE_LOGLEVEL_DEFAULT
21 int "Default console loglevel (1-15)"
25 Default loglevel to determine what will be printed on the console.
27 Setting a default here is equivalent to passing in loglevel=<x> in
28 the kernel bootargs. loglevel=<x> continues to override whatever
29 value is specified here as well.
31 Note: This does not affect the log level of un-prefixed printk()
32 usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
35 config CONSOLE_LOGLEVEL_QUIET
36 int "quiet console loglevel (1-15)"
40 loglevel to use when "quiet" is passed on the kernel commandline.
42 When "quiet" is passed on the kernel commandline this loglevel
43 will be used as the loglevel. IOW passing "quiet" will be the
44 equivalent of passing "loglevel=<CONSOLE_LOGLEVEL_QUIET>"
46 config MESSAGE_LOGLEVEL_DEFAULT
47 int "Default message log level (1-7)"
51 Default log level for printk statements with no specified priority.
53 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
54 that are auditing their logs closely may want to set it to a lower
57 Note: This does not affect what message level gets printed on the console
58 by default. To change that, use loglevel=<x> in the kernel bootargs,
59 or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value.
61 config BOOT_PRINTK_DELAY
62 bool "Delay each boot printk message by N milliseconds"
63 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
65 This build option allows you to read kernel boot messages
66 by inserting a short delay after each one. The delay is
67 specified in milliseconds on the kernel command line,
70 It is likely that you would also need to use "lpj=M" to preset
71 the "loops per jiffie" value.
72 See a previous boot log for the "lpj" value to use for your
73 system, and then set "lpj=M" before setting "boot_delay=N".
74 NOTE: Using this option may adversely affect SMP systems.
75 I.e., processors other than the first one may not boot up.
76 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
77 what it believes to be lockup conditions.
80 bool "Enable dynamic printk() support"
86 Compiles debug level messages into the kernel, which would not
87 otherwise be available at runtime. These messages can then be
88 enabled/disabled based on various levels of scope - per source file,
89 function, module, format string, and line number. This mechanism
90 implicitly compiles in all pr_debug() and dev_dbg() calls, which
91 enlarges the kernel text size by about 2%.
93 If a source file is compiled with DEBUG flag set, any
94 pr_debug() calls in it are enabled by default, but can be
95 disabled at runtime as below. Note that DEBUG flag is
96 turned on by many CONFIG_*DEBUG* options.
100 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
101 which is contained in the 'debugfs' filesystem. Thus, the debugfs
102 filesystem must first be mounted before making use of this feature.
103 We refer the control file as: <debugfs>/dynamic_debug/control. This
104 file contains a list of the debug statements that can be enabled. The
105 format for each line of the file is:
107 filename:lineno [module]function flags format
109 filename : source file of the debug statement
110 lineno : line number of the debug statement
111 module : module that contains the debug statement
112 function : function that contains the debug statement
113 flags : '=p' means the line is turned 'on' for printing
114 format : the format used for the debug statement
118 nullarbor:~ # cat <debugfs>/dynamic_debug/control
119 # filename:lineno [module]function flags format
120 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
121 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
122 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
126 // enable the message at line 1603 of file svcsock.c
127 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
128 <debugfs>/dynamic_debug/control
130 // enable all the messages in file svcsock.c
131 nullarbor:~ # echo -n 'file svcsock.c +p' >
132 <debugfs>/dynamic_debug/control
134 // enable all the messages in the NFS server module
135 nullarbor:~ # echo -n 'module nfsd +p' >
136 <debugfs>/dynamic_debug/control
138 // enable all 12 messages in the function svc_process()
139 nullarbor:~ # echo -n 'func svc_process +p' >
140 <debugfs>/dynamic_debug/control
142 // disable all 12 messages in the function svc_process()
143 nullarbor:~ # echo -n 'func svc_process -p' >
144 <debugfs>/dynamic_debug/control
146 See Documentation/admin-guide/dynamic-debug-howto.rst for additional
149 endmenu # "printk and dmesg options"
151 menu "Compile-time checks and compiler options"
154 bool "Compile the kernel with debug info"
155 depends on DEBUG_KERNEL && !COMPILE_TEST
157 If you say Y here the resulting kernel image will include
158 debugging info resulting in a larger kernel image.
159 This adds debug symbols to the kernel and modules (gcc -g), and
160 is needed if you intend to use kernel crashdump or binary object
161 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
162 Say Y here only if you plan to debug the kernel.
166 config DEBUG_INFO_REDUCED
167 bool "Reduce debugging information"
168 depends on DEBUG_INFO
170 If you say Y here gcc is instructed to generate less debugging
171 information for structure types. This means that tools that
172 need full debugging information (like kgdb or systemtap) won't
173 be happy. But if you merely need debugging information to
174 resolve line numbers there is no loss. Advantage is that
175 build directory object sizes shrink dramatically over a full
176 DEBUG_INFO build and compile times are reduced too.
177 Only works with newer gcc versions.
179 config DEBUG_INFO_SPLIT
180 bool "Produce split debuginfo in .dwo files"
181 depends on DEBUG_INFO
183 Generate debug info into separate .dwo files. This significantly
184 reduces the build directory size for builds with DEBUG_INFO,
185 because it stores the information only once on disk in .dwo
186 files instead of multiple times in object files and executables.
187 In addition the debug information is also compressed.
189 Requires recent gcc (4.7+) and recent gdb/binutils.
190 Any tool that packages or reads debug information would need
191 to know about the .dwo files and include them.
192 Incompatible with older versions of ccache.
194 config DEBUG_INFO_DWARF4
195 bool "Generate dwarf4 debuginfo"
196 depends on DEBUG_INFO
198 Generate dwarf4 debug info. This requires recent versions
199 of gcc and gdb. It makes the debug information larger.
200 But it significantly improves the success of resolving
201 variables in gdb on optimized code.
204 bool "Provide GDB scripts for kernel debugging"
205 depends on DEBUG_INFO
207 This creates the required links to GDB helper scripts in the
208 build directory. If you load vmlinux into gdb, the helper
209 scripts will be automatically imported by gdb as well, and
210 additional functions are available to analyze a Linux kernel
211 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
214 config ENABLE_MUST_CHECK
215 bool "Enable __must_check logic"
218 Enable the __must_check logic in the kernel build. Disable this to
219 suppress the "warning: ignoring return value of 'foo', declared with
220 attribute warn_unused_result" messages.
223 int "Warn for stack frames larger than (needs gcc 4.4)"
225 default 3072 if KASAN_EXTRA
226 default 2048 if GCC_PLUGIN_LATENT_ENTROPY
227 default 2048 if PARISC
228 default 1536 if (!64BIT && XTENSA)
229 default 1280 if KASAN && !64BIT
230 default 1024 if !64BIT
231 default 2048 if 64BIT
233 Tell gcc to warn at build time for stack frames larger than this.
234 Setting this too low will cause a lot of warnings.
235 Setting it to 0 disables the warning.
238 config STRIP_ASM_SYMS
239 bool "Strip assembler-generated symbols during link"
242 Strip internal assembler-generated symbols during a link (symbols
243 that look like '.Lxxx') so they don't pollute the output of
244 get_wchan() and suchlike.
247 bool "Generate readable assembler code"
248 depends on DEBUG_KERNEL
250 Disable some compiler optimizations that tend to generate human unreadable
251 assembler output. This may make the kernel slightly slower, but it helps
252 to keep kernel developers who have to stare a lot at assembler listings
255 config UNUSED_SYMBOLS
256 bool "Enable unused/obsolete exported symbols"
259 Unused but exported symbols make the kernel needlessly bigger. For
260 that reason most of these unused exports will soon be removed. This
261 option is provided temporarily to provide a transition period in case
262 some external kernel module needs one of these symbols anyway. If you
263 encounter such a case in your module, consider if you are actually
264 using the right API. (rationale: since nobody in the kernel is using
265 this in a module, there is a pretty good chance it's actually the
266 wrong interface to use). If you really need the symbol, please send a
267 mail to the linux kernel mailing list mentioning the symbol and why
268 you really need it, and what the merge plan to the mainline kernel for
272 bool "Track page owner"
273 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
277 select PAGE_EXTENSION
279 This keeps track of what call chain is the owner of a page, may
280 help to find bare alloc_page(s) leaks. Even if you include this
281 feature on your build, it is disabled in default. You should pass
282 "page_owner=on" to boot parameter in order to enable it. Eats
283 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
284 for user-space helper.
289 bool "Debug Filesystem"
291 debugfs is a virtual file system that kernel developers use to put
292 debugging files into. Enable this option to be able to read and
293 write to these files.
295 For detailed documentation on the debugfs API, see
296 Documentation/filesystems/.
301 bool "Run 'make headers_check' when building vmlinux"
304 This option will extract the user-visible kernel headers whenever
305 building the kernel, and will run basic sanity checks on them to
306 ensure that exported files do not attempt to include files which
307 were not exported, etc.
309 If you're making modifications to header files which are
310 relevant for userspace, say 'Y', and check the headers
311 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
312 your build tree), to make sure they're suitable.
314 config DEBUG_SECTION_MISMATCH
315 bool "Enable full Section mismatch analysis"
317 The section mismatch analysis checks if there are illegal
318 references from one section to another section.
319 During linktime or runtime, some sections are dropped;
320 any use of code/data previously in these sections would
321 most likely result in an oops.
322 In the code, functions and variables are annotated with
323 __init,, etc. (see the full list in include/linux/init.h),
324 which results in the code/data being placed in specific sections.
325 The section mismatch analysis is always performed after a full
326 kernel build, and enabling this option causes the following
327 additional steps to occur:
328 - Add the option -fno-inline-functions-called-once to gcc commands.
329 When inlining a function annotated with __init in a non-init
330 function, we would lose the section information and thus
331 the analysis would not catch the illegal reference.
332 This option tells gcc to inline less (but it does result in
334 - Run the section mismatch analysis for each module/built-in.a file.
335 When we run the section mismatch analysis on vmlinux.o, we
336 lose valuable information about where the mismatch was
338 Running the analysis for each module/built-in.a file
339 tells where the mismatch happens much closer to the
340 source. The drawback is that the same mismatch is
341 reported at least twice.
342 - Enable verbose reporting from modpost in order to help resolve
343 the section mismatches that are reported.
345 config SECTION_MISMATCH_WARN_ONLY
346 bool "Make section mismatch errors non-fatal"
349 If you say N here, the build process will fail if there are any
350 section mismatch, instead of just throwing warnings.
355 # Select this config option from the architecture Kconfig, if it
356 # is preferred to always offer frame pointers as a config
357 # option on the architecture (regardless of KERNEL_DEBUG):
359 config ARCH_WANT_FRAME_POINTERS
363 bool "Compile the kernel with frame pointers"
364 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS
365 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
367 If you say Y here the resulting kernel image will be slightly
368 larger and slower, but it gives very useful debugging information
369 in case of kernel bugs. (precise oopses/stacktraces/warnings)
371 config STACK_VALIDATION
372 bool "Compile-time stack metadata validation"
373 depends on HAVE_STACK_VALIDATION
376 Add compile-time checks to validate stack metadata, including frame
377 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
378 that runtime stack traces are more reliable.
380 This is also a prerequisite for generation of ORC unwind data, which
381 is needed for CONFIG_UNWINDER_ORC.
383 For more information, see
384 tools/objtool/Documentation/stack-validation.txt.
386 config DEBUG_FORCE_WEAK_PER_CPU
387 bool "Force weak per-cpu definitions"
388 depends on DEBUG_KERNEL
390 s390 and alpha require percpu variables in modules to be
391 defined weak to work around addressing range issue which
392 puts the following two restrictions on percpu variable
395 1. percpu symbols must be unique whether static or not
396 2. percpu variables can't be defined inside a function
398 To ensure that generic code follows the above rules, this
399 option forces all percpu variables to be defined as weak.
401 endmenu # "Compiler options"
404 bool "Magic SysRq key"
407 If you say Y here, you will have some control over the system even
408 if the system crashes for example during kernel debugging (e.g., you
409 will be able to flush the buffer cache to disk, reboot the system
410 immediately or dump some status information). This is accomplished
411 by pressing various keys while holding SysRq (Alt+PrintScreen). It
412 also works on a serial console (on PC hardware at least), if you
413 send a BREAK and then within 5 seconds a command keypress. The
414 keys are documented in <file:Documentation/admin-guide/sysrq.rst>.
415 Don't say Y unless you really know what this hack does.
417 config MAGIC_SYSRQ_DEFAULT_ENABLE
418 hex "Enable magic SysRq key functions by default"
419 depends on MAGIC_SYSRQ
422 Specifies which SysRq key functions are enabled by default.
423 This may be set to 1 or 0 to enable or disable them all, or
424 to a bitmask as described in Documentation/admin-guide/sysrq.rst.
426 config MAGIC_SYSRQ_SERIAL
427 bool "Enable magic SysRq key over serial"
428 depends on MAGIC_SYSRQ
431 Many embedded boards have a disconnected TTL level serial which can
432 generate some garbage that can lead to spurious false sysrq detects.
433 This option allows you to decide whether you want to enable the
437 bool "Kernel debugging"
439 Say Y here if you are developing drivers or trying to debug and
440 identify kernel problems.
442 menu "Memory Debugging"
444 source mm/Kconfig.debug
447 bool "Debug object operations"
448 depends on DEBUG_KERNEL
450 If you say Y here, additional code will be inserted into the
451 kernel to track the life time of various objects and validate
452 the operations on those objects.
454 config DEBUG_OBJECTS_SELFTEST
455 bool "Debug objects selftest"
456 depends on DEBUG_OBJECTS
458 This enables the selftest of the object debug code.
460 config DEBUG_OBJECTS_FREE
461 bool "Debug objects in freed memory"
462 depends on DEBUG_OBJECTS
464 This enables checks whether a k/v free operation frees an area
465 which contains an object which has not been deactivated
466 properly. This can make kmalloc/kfree-intensive workloads
469 config DEBUG_OBJECTS_TIMERS
470 bool "Debug timer objects"
471 depends on DEBUG_OBJECTS
473 If you say Y here, additional code will be inserted into the
474 timer routines to track the life time of timer objects and
475 validate the timer operations.
477 config DEBUG_OBJECTS_WORK
478 bool "Debug work objects"
479 depends on DEBUG_OBJECTS
481 If you say Y here, additional code will be inserted into the
482 work queue routines to track the life time of work objects and
483 validate the work operations.
485 config DEBUG_OBJECTS_RCU_HEAD
486 bool "Debug RCU callbacks objects"
487 depends on DEBUG_OBJECTS
489 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
491 config DEBUG_OBJECTS_PERCPU_COUNTER
492 bool "Debug percpu counter objects"
493 depends on DEBUG_OBJECTS
495 If you say Y here, additional code will be inserted into the
496 percpu counter routines to track the life time of percpu counter
497 objects and validate the percpu counter operations.
499 config DEBUG_OBJECTS_ENABLE_DEFAULT
500 int "debug_objects bootup default value (0-1)"
503 depends on DEBUG_OBJECTS
505 Debug objects boot parameter default value
508 bool "Debug slab memory allocations"
509 depends on DEBUG_KERNEL && SLAB
511 Say Y here to have the kernel do limited verification on memory
512 allocation as well as poisoning memory on free to catch use of freed
513 memory. This can make kmalloc/kfree-intensive workloads much slower.
515 config DEBUG_SLAB_LEAK
516 bool "Memory leak debugging"
517 depends on DEBUG_SLAB
520 bool "SLUB debugging on by default"
521 depends on SLUB && SLUB_DEBUG
524 Boot with debugging on by default. SLUB boots by default with
525 the runtime debug capabilities switched off. Enabling this is
526 equivalent to specifying the "slub_debug" parameter on boot.
527 There is no support for more fine grained debug control like
528 possible with slub_debug=xxx. SLUB debugging may be switched
529 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
534 bool "Enable SLUB performance statistics"
535 depends on SLUB && SYSFS
537 SLUB statistics are useful to debug SLUBs allocation behavior in
538 order find ways to optimize the allocator. This should never be
539 enabled for production use since keeping statistics slows down
540 the allocator by a few percentage points. The slabinfo command
541 supports the determination of the most active slabs to figure
542 out which slabs are relevant to a particular load.
543 Try running: slabinfo -DA
545 config HAVE_DEBUG_KMEMLEAK
548 config DEBUG_KMEMLEAK
549 bool "Kernel memory leak detector"
550 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
552 select STACKTRACE if STACKTRACE_SUPPORT
556 Say Y here if you want to enable the memory leak
557 detector. The memory allocation/freeing is traced in a way
558 similar to the Boehm's conservative garbage collector, the
559 difference being that the orphan objects are not freed but
560 only shown in /sys/kernel/debug/kmemleak. Enabling this
561 feature will introduce an overhead to memory
562 allocations. See Documentation/dev-tools/kmemleak.rst for more
565 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
566 of finding leaks due to the slab objects poisoning.
568 In order to access the kmemleak file, debugfs needs to be
569 mounted (usually at /sys/kernel/debug).
571 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
572 int "Maximum kmemleak early log entries"
573 depends on DEBUG_KMEMLEAK
577 Kmemleak must track all the memory allocations to avoid
578 reporting false positives. Since memory may be allocated or
579 freed before kmemleak is initialised, an early log buffer is
580 used to store these actions. If kmemleak reports "early log
581 buffer exceeded", please increase this value.
583 config DEBUG_KMEMLEAK_TEST
584 tristate "Simple test for the kernel memory leak detector"
585 depends on DEBUG_KMEMLEAK && m
587 This option enables a module that explicitly leaks memory.
591 config DEBUG_KMEMLEAK_DEFAULT_OFF
592 bool "Default kmemleak to off"
593 depends on DEBUG_KMEMLEAK
595 Say Y here to disable kmemleak by default. It can then be enabled
596 on the command line via kmemleak=on.
598 config DEBUG_STACK_USAGE
599 bool "Stack utilization instrumentation"
600 depends on DEBUG_KERNEL && !IA64
602 Enables the display of the minimum amount of free stack which each
603 task has ever had available in the sysrq-T and sysrq-P debug output.
605 This option will slow down process creation somewhat.
609 depends on DEBUG_KERNEL
611 Enable this to turn on extended checks in the virtual-memory system
612 that may impact performance.
616 config DEBUG_VM_VMACACHE
617 bool "Debug VMA caching"
620 Enable this to turn on VMA caching debug information. Doing so
621 can cause significant overhead, so only enable it in non-production
627 bool "Debug VM red-black trees"
630 Enable VM red-black tree debugging information and extra validations.
634 config DEBUG_VM_PGFLAGS
635 bool "Debug page-flags operations"
638 Enables extra validation on page flags operations.
642 config ARCH_HAS_DEBUG_VIRTUAL
646 bool "Debug VM translations"
647 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
649 Enable some costly sanity checks in virtual to page code. This can
650 catch mistakes with virt_to_page() and friends.
654 config DEBUG_NOMMU_REGIONS
655 bool "Debug the global anon/private NOMMU mapping region tree"
656 depends on DEBUG_KERNEL && !MMU
658 This option causes the global tree of anonymous and private mapping
659 regions to be regularly checked for invalid topology.
661 config DEBUG_MEMORY_INIT
662 bool "Debug memory initialisation" if EXPERT
665 Enable this for additional checks during memory initialisation.
666 The sanity checks verify aspects of the VM such as the memory model
667 and other information provided by the architecture. Verbose
668 information will be printed at KERN_DEBUG loglevel depending
669 on the mminit_loglevel= command-line option.
673 config MEMORY_NOTIFIER_ERROR_INJECT
674 tristate "Memory hotplug notifier error injection module"
675 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
677 This option provides the ability to inject artificial errors to
678 memory hotplug notifier chain callbacks. It is controlled through
679 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
681 If the notifier call chain should be failed with some events
682 notified, write the error code to "actions/<notifier event>/error".
684 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
686 # cd /sys/kernel/debug/notifier-error-inject/memory
687 # echo -12 > actions/MEM_GOING_OFFLINE/error
688 # echo offline > /sys/devices/system/memory/memoryXXX/state
689 bash: echo: write error: Cannot allocate memory
691 To compile this code as a module, choose M here: the module will
692 be called memory-notifier-error-inject.
696 config DEBUG_PER_CPU_MAPS
697 bool "Debug access to per_cpu maps"
698 depends on DEBUG_KERNEL
701 Say Y to verify that the per_cpu map being accessed has
702 been set up. This adds a fair amount of code to kernel memory
703 and decreases performance.
708 bool "Highmem debugging"
709 depends on DEBUG_KERNEL && HIGHMEM
711 This option enables additional error checking for high memory
712 systems. Disable for production systems.
714 config HAVE_DEBUG_STACKOVERFLOW
717 config DEBUG_STACKOVERFLOW
718 bool "Check for stack overflows"
719 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
721 Say Y here if you want to check for overflows of kernel, IRQ
722 and exception stacks (if your architecture uses them). This
723 option will show detailed messages if free stack space drops
724 below a certain limit.
726 These kinds of bugs usually occur when call-chains in the
727 kernel get too deep, especially when interrupts are
730 Use this in cases where you see apparently random memory
731 corruption, especially if it appears in 'struct thread_info'
733 If in doubt, say "N".
735 source "lib/Kconfig.kasan"
737 endmenu # "Memory Debugging"
742 KCOV does not have any arch-specific code, but currently it is enabled
743 only for x86_64. KCOV requires testing on other archs, and most likely
744 disabling of instrumentation for some early boot code.
746 config CC_HAS_SANCOV_TRACE_PC
747 def_bool $(cc-option,-fsanitize-coverage=trace-pc)
750 bool "Code coverage for fuzzing"
751 depends on ARCH_HAS_KCOV
752 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
754 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
756 KCOV exposes kernel code coverage information in a form suitable
757 for coverage-guided fuzzing (randomized testing).
759 If RANDOMIZE_BASE is enabled, PC values will not be stable across
760 different machines and across reboots. If you need stable PC values,
761 disable RANDOMIZE_BASE.
763 For more details, see Documentation/dev-tools/kcov.rst.
765 config KCOV_ENABLE_COMPARISONS
766 bool "Enable comparison operands collection by KCOV"
768 depends on $(cc-option,-fsanitize-coverage=trace-cmp)
770 KCOV also exposes operands of every comparison in the instrumented
771 code along with operand sizes and PCs of the comparison instructions.
772 These operands can be used by fuzzing engines to improve the quality
775 config KCOV_INSTRUMENT_ALL
776 bool "Instrument all code by default"
780 If you are doing generic system call fuzzing (like e.g. syzkaller),
781 then you will want to instrument the whole kernel and you should
782 say y here. If you are doing more targeted fuzzing (like e.g.
783 filesystem fuzzing with AFL) then you will want to enable coverage
784 for more specific subsets of files, and should say n here.
787 bool "Debug shared IRQ handlers"
788 depends on DEBUG_KERNEL
790 Enable this to generate a spurious interrupt as soon as a shared
791 interrupt handler is registered, and just before one is deregistered.
792 Drivers ought to be able to handle interrupts coming in at those
793 points; some don't and need to be caught.
795 menu "Debug Lockups and Hangs"
797 config LOCKUP_DETECTOR
800 config SOFTLOCKUP_DETECTOR
801 bool "Detect Soft Lockups"
802 depends on DEBUG_KERNEL && !S390
803 select LOCKUP_DETECTOR
805 Say Y here to enable the kernel to act as a watchdog to detect
808 Softlockups are bugs that cause the kernel to loop in kernel
809 mode for more than 20 seconds, without giving other tasks a
810 chance to run. The current stack trace is displayed upon
811 detection and the system will stay locked up.
813 config BOOTPARAM_SOFTLOCKUP_PANIC
814 bool "Panic (Reboot) On Soft Lockups"
815 depends on SOFTLOCKUP_DETECTOR
817 Say Y here to enable the kernel to panic on "soft lockups",
818 which are bugs that cause the kernel to loop in kernel
819 mode for more than 20 seconds (configurable using the watchdog_thresh
820 sysctl), without giving other tasks a chance to run.
822 The panic can be used in combination with panic_timeout,
823 to cause the system to reboot automatically after a
824 lockup has been detected. This feature is useful for
825 high-availability systems that have uptime guarantees and
826 where a lockup must be resolved ASAP.
830 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
832 depends on SOFTLOCKUP_DETECTOR
834 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
835 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
837 config HARDLOCKUP_DETECTOR_PERF
839 select SOFTLOCKUP_DETECTOR
842 # Enables a timestamp based low pass filter to compensate for perf based
843 # hard lockup detection which runs too fast due to turbo modes.
845 config HARDLOCKUP_CHECK_TIMESTAMP
849 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
850 # lockup detector rather than the perf based detector.
852 config HARDLOCKUP_DETECTOR
853 bool "Detect Hard Lockups"
854 depends on DEBUG_KERNEL && !S390
855 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
856 select LOCKUP_DETECTOR
857 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
859 Say Y here to enable the kernel to act as a watchdog to detect
862 Hardlockups are bugs that cause the CPU to loop in kernel mode
863 for more than 10 seconds, without letting other interrupts have a
864 chance to run. The current stack trace is displayed upon detection
865 and the system will stay locked up.
867 config BOOTPARAM_HARDLOCKUP_PANIC
868 bool "Panic (Reboot) On Hard Lockups"
869 depends on HARDLOCKUP_DETECTOR
871 Say Y here to enable the kernel to panic on "hard lockups",
872 which are bugs that cause the kernel to loop in kernel
873 mode with interrupts disabled for more than 10 seconds (configurable
874 using the watchdog_thresh sysctl).
878 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
880 depends on HARDLOCKUP_DETECTOR
882 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
883 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
885 config DETECT_HUNG_TASK
886 bool "Detect Hung Tasks"
887 depends on DEBUG_KERNEL
888 default SOFTLOCKUP_DETECTOR
890 Say Y here to enable the kernel to detect "hung tasks",
891 which are bugs that cause the task to be stuck in
892 uninterruptible "D" state indefinitely.
894 When a hung task is detected, the kernel will print the
895 current stack trace (which you should report), but the
896 task will stay in uninterruptible state. If lockdep is
897 enabled then all held locks will also be reported. This
898 feature has negligible overhead.
900 config DEFAULT_HUNG_TASK_TIMEOUT
901 int "Default timeout for hung task detection (in seconds)"
902 depends on DETECT_HUNG_TASK
905 This option controls the default timeout (in seconds) used
906 to determine when a task has become non-responsive and should
909 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
910 sysctl or by writing a value to
911 /proc/sys/kernel/hung_task_timeout_secs.
913 A timeout of 0 disables the check. The default is two minutes.
914 Keeping the default should be fine in most cases.
916 config BOOTPARAM_HUNG_TASK_PANIC
917 bool "Panic (Reboot) On Hung Tasks"
918 depends on DETECT_HUNG_TASK
920 Say Y here to enable the kernel to panic on "hung tasks",
921 which are bugs that cause the kernel to leave a task stuck
922 in uninterruptible "D" state.
924 The panic can be used in combination with panic_timeout,
925 to cause the system to reboot automatically after a
926 hung task has been detected. This feature is useful for
927 high-availability systems that have uptime guarantees and
928 where a hung tasks must be resolved ASAP.
932 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
934 depends on DETECT_HUNG_TASK
936 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
937 default 1 if BOOTPARAM_HUNG_TASK_PANIC
940 bool "Detect Workqueue Stalls"
941 depends on DEBUG_KERNEL
943 Say Y here to enable stall detection on workqueues. If a
944 worker pool doesn't make forward progress on a pending work
945 item for over a given amount of time, 30s by default, a
946 warning message is printed along with dump of workqueue
947 state. This can be configured through kernel parameter
948 "workqueue.watchdog_thresh" and its sysfs counterpart.
950 endmenu # "Debug lockups and hangs"
955 Say Y here to enable the kernel to panic when it oopses. This
956 has the same effect as setting oops=panic on the kernel command
959 This feature is useful to ensure that the kernel does not do
960 anything erroneous after an oops which could result in data
961 corruption or other issues.
965 config PANIC_ON_OOPS_VALUE
968 default 0 if !PANIC_ON_OOPS
969 default 1 if PANIC_ON_OOPS
975 Set the timeout value (in seconds) until a reboot occurs when the
976 the kernel panics. If n = 0, then we wait forever. A timeout
977 value n > 0 will wait n seconds before rebooting, while a timeout
978 value n < 0 will reboot immediately.
981 bool "Collect scheduler debugging info"
982 depends on DEBUG_KERNEL && PROC_FS
985 If you say Y here, the /proc/sched_debug file will be provided
986 that can help debug the scheduler. The runtime overhead of this
994 bool "Collect scheduler statistics"
995 depends on DEBUG_KERNEL && PROC_FS
998 If you say Y here, additional code will be inserted into the
999 scheduler and related routines to collect statistics about
1000 scheduler behavior and provide them in /proc/schedstat. These
1001 stats may be useful for both tuning and debugging the scheduler
1002 If you aren't debugging the scheduler or trying to tune a specific
1003 application, you can say N to avoid the very slight overhead
1006 config SCHED_STACK_END_CHECK
1007 bool "Detect stack corruption on calls to schedule()"
1008 depends on DEBUG_KERNEL
1011 This option checks for a stack overrun on calls to schedule().
1012 If the stack end location is found to be over written always panic as
1013 the content of the corrupted region can no longer be trusted.
1014 This is to ensure no erroneous behaviour occurs which could result in
1015 data corruption or a sporadic crash at a later stage once the region
1016 is examined. The runtime overhead introduced is minimal.
1018 config DEBUG_TIMEKEEPING
1019 bool "Enable extra timekeeping sanity checking"
1021 This option will enable additional timekeeping sanity checks
1022 which may be helpful when diagnosing issues where timekeeping
1023 problems are suspected.
1025 This may include checks in the timekeeping hotpaths, so this
1026 option may have a (very small) performance impact to some
1031 config DEBUG_PREEMPT
1032 bool "Debug preemptible kernel"
1033 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1036 If you say Y here then the kernel will use a debug variant of the
1037 commonly used smp_processor_id() function and will print warnings
1038 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1039 will detect preemption count underflows.
1041 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1043 config LOCK_DEBUGGING_SUPPORT
1045 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1048 config PROVE_LOCKING
1049 bool "Lock debugging: prove locking correctness"
1050 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1052 select DEBUG_SPINLOCK
1053 select DEBUG_MUTEXES
1054 select DEBUG_RT_MUTEXES if RT_MUTEXES
1055 select DEBUG_RWSEMS if RWSEM_SPIN_ON_OWNER
1056 select DEBUG_WW_MUTEX_SLOWPATH
1057 select DEBUG_LOCK_ALLOC
1058 select TRACE_IRQFLAGS
1061 This feature enables the kernel to prove that all locking
1062 that occurs in the kernel runtime is mathematically
1063 correct: that under no circumstance could an arbitrary (and
1064 not yet triggered) combination of observed locking
1065 sequences (on an arbitrary number of CPUs, running an
1066 arbitrary number of tasks and interrupt contexts) cause a
1069 In short, this feature enables the kernel to report locking
1070 related deadlocks before they actually occur.
1072 The proof does not depend on how hard and complex a
1073 deadlock scenario would be to trigger: how many
1074 participant CPUs, tasks and irq-contexts would be needed
1075 for it to trigger. The proof also does not depend on
1076 timing: if a race and a resulting deadlock is possible
1077 theoretically (no matter how unlikely the race scenario
1078 is), it will be proven so and will immediately be
1079 reported by the kernel (once the event is observed that
1080 makes the deadlock theoretically possible).
1082 If a deadlock is impossible (i.e. the locking rules, as
1083 observed by the kernel, are mathematically correct), the
1084 kernel reports nothing.
1086 NOTE: this feature can also be enabled for rwlocks, mutexes
1087 and rwsems - in which case all dependencies between these
1088 different locking variants are observed and mapped too, and
1089 the proof of observed correctness is also maintained for an
1090 arbitrary combination of these separate locking variants.
1092 For more details, see Documentation/locking/lockdep-design.txt.
1095 bool "Lock usage statistics"
1096 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1098 select DEBUG_SPINLOCK
1099 select DEBUG_MUTEXES
1100 select DEBUG_RT_MUTEXES if RT_MUTEXES
1101 select DEBUG_LOCK_ALLOC
1104 This feature enables tracking lock contention points
1106 For more details, see Documentation/locking/lockstat.txt
1108 This also enables lock events required by "perf lock",
1110 If you want to use "perf lock", you also need to turn on
1111 CONFIG_EVENT_TRACING.
1113 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1114 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1116 config DEBUG_RT_MUTEXES
1117 bool "RT Mutex debugging, deadlock detection"
1118 depends on DEBUG_KERNEL && RT_MUTEXES
1120 This allows rt mutex semantics violations and rt mutex related
1121 deadlocks (lockups) to be detected and reported automatically.
1123 config DEBUG_SPINLOCK
1124 bool "Spinlock and rw-lock debugging: basic checks"
1125 depends on DEBUG_KERNEL
1126 select UNINLINE_SPIN_UNLOCK
1128 Say Y here and build SMP to catch missing spinlock initialization
1129 and certain other kinds of spinlock errors commonly made. This is
1130 best used in conjunction with the NMI watchdog so that spinlock
1131 deadlocks are also debuggable.
1133 config DEBUG_MUTEXES
1134 bool "Mutex debugging: basic checks"
1135 depends on DEBUG_KERNEL
1137 This feature allows mutex semantics violations to be detected and
1140 config DEBUG_WW_MUTEX_SLOWPATH
1141 bool "Wait/wound mutex debugging: Slowpath testing"
1142 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1143 select DEBUG_LOCK_ALLOC
1144 select DEBUG_SPINLOCK
1145 select DEBUG_MUTEXES
1147 This feature enables slowpath testing for w/w mutex users by
1148 injecting additional -EDEADLK wound/backoff cases. Together with
1149 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1150 will test all possible w/w mutex interface abuse with the
1151 exception of simply not acquiring all the required locks.
1152 Note that this feature can introduce significant overhead, so
1153 it really should not be enabled in a production or distro kernel,
1154 even a debug kernel. If you are a driver writer, enable it. If
1155 you are a distro, do not.
1158 bool "RW Semaphore debugging: basic checks"
1159 depends on DEBUG_KERNEL && RWSEM_SPIN_ON_OWNER
1161 This debugging feature allows mismatched rw semaphore locks and unlocks
1162 to be detected and reported.
1164 config DEBUG_LOCK_ALLOC
1165 bool "Lock debugging: detect incorrect freeing of live locks"
1166 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1167 select DEBUG_SPINLOCK
1168 select DEBUG_MUTEXES
1169 select DEBUG_RT_MUTEXES if RT_MUTEXES
1172 This feature will check whether any held lock (spinlock, rwlock,
1173 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1174 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1175 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1176 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1177 held during task exit.
1181 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1183 select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86
1187 config LOCKDEP_SMALL
1190 config DEBUG_LOCKDEP
1191 bool "Lock dependency engine debugging"
1192 depends on DEBUG_KERNEL && LOCKDEP
1194 If you say Y here, the lock dependency engine will do
1195 additional runtime checks to debug itself, at the price
1196 of more runtime overhead.
1198 config DEBUG_ATOMIC_SLEEP
1199 bool "Sleep inside atomic section checking"
1200 select PREEMPT_COUNT
1201 depends on DEBUG_KERNEL
1202 depends on !ARCH_NO_PREEMPT
1204 If you say Y here, various routines which may sleep will become very
1205 noisy if they are called inside atomic sections: when a spinlock is
1206 held, inside an rcu read side critical section, inside preempt disabled
1207 sections, inside an interrupt, etc...
1209 config DEBUG_LOCKING_API_SELFTESTS
1210 bool "Locking API boot-time self-tests"
1211 depends on DEBUG_KERNEL
1213 Say Y here if you want the kernel to run a short self-test during
1214 bootup. The self-test checks whether common types of locking bugs
1215 are detected by debugging mechanisms or not. (if you disable
1216 lock debugging then those bugs wont be detected of course.)
1217 The following locking APIs are covered: spinlocks, rwlocks,
1220 config LOCK_TORTURE_TEST
1221 tristate "torture tests for locking"
1222 depends on DEBUG_KERNEL
1225 This option provides a kernel module that runs torture tests
1226 on kernel locking primitives. The kernel module may be built
1227 after the fact on the running kernel to be tested, if desired.
1229 Say Y here if you want kernel locking-primitive torture tests
1230 to be built into the kernel.
1231 Say M if you want these torture tests to build as a module.
1232 Say N if you are unsure.
1234 config WW_MUTEX_SELFTEST
1235 tristate "Wait/wound mutex selftests"
1237 This option provides a kernel module that runs tests on the
1238 on the struct ww_mutex locking API.
1240 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1241 with this test harness.
1243 Say M if you want these self tests to build as a module.
1244 Say N if you are unsure.
1246 endmenu # lock debugging
1248 config TRACE_IRQFLAGS
1251 Enables hooks to interrupt enabling and disabling for
1252 either tracing or lock debugging.
1255 bool "Stack backtrace support"
1256 depends on STACKTRACE_SUPPORT
1258 This option causes the kernel to create a /proc/pid/stack for
1259 every process, showing its current stack trace.
1260 It is also used by various kernel debugging features that require
1261 stack trace generation.
1263 config WARN_ALL_UNSEEDED_RANDOM
1264 bool "Warn for all uses of unseeded randomness"
1267 Some parts of the kernel contain bugs relating to their use of
1268 cryptographically secure random numbers before it's actually possible
1269 to generate those numbers securely. This setting ensures that these
1270 flaws don't go unnoticed, by enabling a message, should this ever
1271 occur. This will allow people with obscure setups to know when things
1272 are going wrong, so that they might contact developers about fixing
1275 Unfortunately, on some models of some architectures getting
1276 a fully seeded CRNG is extremely difficult, and so this can
1277 result in dmesg getting spammed for a surprisingly long
1278 time. This is really bad from a security perspective, and
1279 so architecture maintainers really need to do what they can
1280 to get the CRNG seeded sooner after the system is booted.
1281 However, since users cannot do anything actionable to
1282 address this, by default this option is disabled.
1284 Say Y here if you want to receive warnings for all uses of
1285 unseeded randomness. This will be of use primarily for
1286 those developers interested in improving the security of
1287 Linux kernels running on their architecture (or
1290 config DEBUG_KOBJECT
1291 bool "kobject debugging"
1292 depends on DEBUG_KERNEL
1294 If you say Y here, some extra kobject debugging messages will be sent
1297 config DEBUG_KOBJECT_RELEASE
1298 bool "kobject release debugging"
1299 depends on DEBUG_OBJECTS_TIMERS
1301 kobjects are reference counted objects. This means that their
1302 last reference count put is not predictable, and the kobject can
1303 live on past the point at which a driver decides to drop it's
1304 initial reference to the kobject gained on allocation. An
1305 example of this would be a struct device which has just been
1308 However, some buggy drivers assume that after such an operation,
1309 the memory backing the kobject can be immediately freed. This
1310 goes completely against the principles of a refcounted object.
1312 If you say Y here, the kernel will delay the release of kobjects
1313 on the last reference count to improve the visibility of this
1314 kind of kobject release bug.
1316 config HAVE_DEBUG_BUGVERBOSE
1319 config DEBUG_BUGVERBOSE
1320 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1321 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1324 Say Y here to make BUG() panics output the file name and line number
1325 of the BUG call as well as the EIP and oops trace. This aids
1326 debugging but costs about 70-100K of memory.
1329 bool "Debug linked list manipulation"
1330 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1332 Enable this to turn on extended checks in the linked-list
1337 config DEBUG_PI_LIST
1338 bool "Debug priority linked list manipulation"
1339 depends on DEBUG_KERNEL
1341 Enable this to turn on extended checks in the priority-ordered
1342 linked-list (plist) walking routines. This checks the entire
1343 list multiple times during each manipulation.
1348 bool "Debug SG table operations"
1349 depends on DEBUG_KERNEL
1351 Enable this to turn on checks on scatter-gather tables. This can
1352 help find problems with drivers that do not properly initialize
1357 config DEBUG_NOTIFIERS
1358 bool "Debug notifier call chains"
1359 depends on DEBUG_KERNEL
1361 Enable this to turn on sanity checking for notifier call chains.
1362 This is most useful for kernel developers to make sure that
1363 modules properly unregister themselves from notifier chains.
1364 This is a relatively cheap check but if you care about maximum
1367 config DEBUG_CREDENTIALS
1368 bool "Debug credential management"
1369 depends on DEBUG_KERNEL
1371 Enable this to turn on some debug checking for credential
1372 management. The additional code keeps track of the number of
1373 pointers from task_structs to any given cred struct, and checks to
1374 see that this number never exceeds the usage count of the cred
1377 Furthermore, if SELinux is enabled, this also checks that the
1378 security pointer in the cred struct is never seen to be invalid.
1382 source "kernel/rcu/Kconfig.debug"
1384 config DEBUG_WQ_FORCE_RR_CPU
1385 bool "Force round-robin CPU selection for unbound work items"
1386 depends on DEBUG_KERNEL
1389 Workqueue used to implicitly guarantee that work items queued
1390 without explicit CPU specified are put on the local CPU. This
1391 guarantee is no longer true and while local CPU is still
1392 preferred work items may be put on foreign CPUs. Kernel
1393 parameter "workqueue.debug_force_rr_cpu" is added to force
1394 round-robin CPU selection to flush out usages which depend on the
1395 now broken guarantee. This config option enables the debug
1396 feature by default. When enabled, memory and cache locality will
1399 config DEBUG_BLOCK_EXT_DEVT
1400 bool "Force extended block device numbers and spread them"
1401 depends on DEBUG_KERNEL
1405 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1406 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1407 YOU ARE DOING. Distros, please enable this and fix whatever
1410 Conventionally, block device numbers are allocated from
1411 predetermined contiguous area. However, extended block area
1412 may introduce non-contiguous block device numbers. This
1413 option forces most block device numbers to be allocated from
1414 the extended space and spreads them to discover kernel or
1415 userland code paths which assume predetermined contiguous
1416 device number allocation.
1418 Note that turning on this debug option shuffles all the
1419 device numbers for all IDE and SCSI devices including libata
1420 ones, so root partition specified using device number
1421 directly (via rdev or root=MAJ:MIN) won't work anymore.
1422 Textual device names (root=/dev/sdXn) will continue to work.
1424 Say N if you are unsure.
1426 config CPU_HOTPLUG_STATE_CONTROL
1427 bool "Enable CPU hotplug state control"
1428 depends on DEBUG_KERNEL
1429 depends on HOTPLUG_CPU
1432 Allows to write steps between "offline" and "online" to the CPUs
1433 sysfs target file so states can be stepped granular. This is a debug
1434 option for now as the hotplug machinery cannot be stopped and
1435 restarted at arbitrary points yet.
1437 Say N if your are unsure.
1439 config NOTIFIER_ERROR_INJECTION
1440 tristate "Notifier error injection"
1441 depends on DEBUG_KERNEL
1444 This option provides the ability to inject artificial errors to
1445 specified notifier chain callbacks. It is useful to test the error
1446 handling of notifier call chain failures.
1450 config PM_NOTIFIER_ERROR_INJECT
1451 tristate "PM notifier error injection module"
1452 depends on PM && NOTIFIER_ERROR_INJECTION
1453 default m if PM_DEBUG
1455 This option provides the ability to inject artificial errors to
1456 PM notifier chain callbacks. It is controlled through debugfs
1457 interface /sys/kernel/debug/notifier-error-inject/pm
1459 If the notifier call chain should be failed with some events
1460 notified, write the error code to "actions/<notifier event>/error".
1462 Example: Inject PM suspend error (-12 = -ENOMEM)
1464 # cd /sys/kernel/debug/notifier-error-inject/pm/
1465 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1466 # echo mem > /sys/power/state
1467 bash: echo: write error: Cannot allocate memory
1469 To compile this code as a module, choose M here: the module will
1470 be called pm-notifier-error-inject.
1474 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1475 tristate "OF reconfig notifier error injection module"
1476 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1478 This option provides the ability to inject artificial errors to
1479 OF reconfig notifier chain callbacks. It is controlled
1480 through debugfs interface under
1481 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1483 If the notifier call chain should be failed with some events
1484 notified, write the error code to "actions/<notifier event>/error".
1486 To compile this code as a module, choose M here: the module will
1487 be called of-reconfig-notifier-error-inject.
1491 config NETDEV_NOTIFIER_ERROR_INJECT
1492 tristate "Netdev notifier error injection module"
1493 depends on NET && NOTIFIER_ERROR_INJECTION
1495 This option provides the ability to inject artificial errors to
1496 netdevice notifier chain callbacks. It is controlled through debugfs
1497 interface /sys/kernel/debug/notifier-error-inject/netdev
1499 If the notifier call chain should be failed with some events
1500 notified, write the error code to "actions/<notifier event>/error".
1502 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1504 # cd /sys/kernel/debug/notifier-error-inject/netdev
1505 # echo -22 > actions/NETDEV_CHANGEMTU/error
1506 # ip link set eth0 mtu 1024
1507 RTNETLINK answers: Invalid argument
1509 To compile this code as a module, choose M here: the module will
1510 be called netdev-notifier-error-inject.
1514 config FUNCTION_ERROR_INJECTION
1515 bool "Fault-injections of functions"
1516 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
1518 Add fault injections into various functions that are annotated with
1519 ALLOW_ERROR_INJECTION() in the kernel. BPF may also modify the return
1520 value of theses functions. This is useful to test error paths of code.
1524 config FAULT_INJECTION
1525 bool "Fault-injection framework"
1526 depends on DEBUG_KERNEL
1528 Provide fault-injection framework.
1529 For more details, see Documentation/fault-injection/.
1532 bool "Fault-injection capability for kmalloc"
1533 depends on FAULT_INJECTION
1534 depends on SLAB || SLUB
1536 Provide fault-injection capability for kmalloc.
1538 config FAIL_PAGE_ALLOC
1539 bool "Fault-injection capabilitiy for alloc_pages()"
1540 depends on FAULT_INJECTION
1542 Provide fault-injection capability for alloc_pages().
1544 config FAIL_MAKE_REQUEST
1545 bool "Fault-injection capability for disk IO"
1546 depends on FAULT_INJECTION && BLOCK
1548 Provide fault-injection capability for disk IO.
1550 config FAIL_IO_TIMEOUT
1551 bool "Fault-injection capability for faking disk interrupts"
1552 depends on FAULT_INJECTION && BLOCK
1554 Provide fault-injection capability on end IO handling. This
1555 will make the block layer "forget" an interrupt as configured,
1556 thus exercising the error handling.
1558 Only works with drivers that use the generic timeout handling,
1559 for others it wont do anything.
1562 bool "Fault-injection capability for futexes"
1564 depends on FAULT_INJECTION && FUTEX
1566 Provide fault-injection capability for futexes.
1568 config FAULT_INJECTION_DEBUG_FS
1569 bool "Debugfs entries for fault-injection capabilities"
1570 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1572 Enable configuration of fault-injection capabilities via debugfs.
1574 config FAIL_FUNCTION
1575 bool "Fault-injection capability for functions"
1576 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
1578 Provide function-based fault-injection capability.
1579 This will allow you to override a specific function with a return
1580 with given return value. As a result, function caller will see
1581 an error value and have to handle it. This is useful to test the
1582 error handling in various subsystems.
1584 config FAIL_MMC_REQUEST
1585 bool "Fault-injection capability for MMC IO"
1586 depends on FAULT_INJECTION_DEBUG_FS && MMC
1588 Provide fault-injection capability for MMC IO.
1589 This will make the mmc core return data errors. This is
1590 useful to test the error handling in the mmc block device
1591 and to test how the mmc host driver handles retries from
1594 config FAULT_INJECTION_STACKTRACE_FILTER
1595 bool "stacktrace filter for fault-injection capabilities"
1596 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1599 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1601 Provide stacktrace filter for fault-injection capabilities
1604 bool "Latency measuring infrastructure"
1605 depends on DEBUG_KERNEL
1606 depends on STACKTRACE_SUPPORT
1608 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1615 Enable this option if you want to use the LatencyTOP tool
1616 to find out which userspace is blocking on what kernel operations.
1618 source kernel/trace/Kconfig
1620 config PROVIDE_OHCI1394_DMA_INIT
1621 bool "Remote debugging over FireWire early on boot"
1622 depends on PCI && X86
1624 If you want to debug problems which hang or crash the kernel early
1625 on boot and the crashing machine has a FireWire port, you can use
1626 this feature to remotely access the memory of the crashed machine
1627 over FireWire. This employs remote DMA as part of the OHCI1394
1628 specification which is now the standard for FireWire controllers.
1630 With remote DMA, you can monitor the printk buffer remotely using
1631 firescope and access all memory below 4GB using fireproxy from gdb.
1632 Even controlling a kernel debugger is possible using remote DMA.
1636 If ohci1394_dma=early is used as boot parameter, it will initialize
1637 all OHCI1394 controllers which are found in the PCI config space.
1639 As all changes to the FireWire bus such as enabling and disabling
1640 devices cause a bus reset and thereby disable remote DMA for all
1641 devices, be sure to have the cable plugged and FireWire enabled on
1642 the debugging host before booting the debug target for debugging.
1644 This code (~1k) is freed after boot. By then, the firewire stack
1645 in charge of the OHCI-1394 controllers should be used instead.
1647 See Documentation/debugging-via-ohci1394.txt for more information.
1649 config DMA_API_DEBUG
1650 bool "Enable debugging of DMA-API usage"
1651 select NEED_DMA_MAP_STATE
1653 Enable this option to debug the use of the DMA API by device drivers.
1654 With this option you will be able to detect common bugs in device
1655 drivers like double-freeing of DMA mappings or freeing mappings that
1656 were never allocated.
1658 This also attempts to catch cases where a page owned by DMA is
1659 accessed by the cpu in a way that could cause data corruption. For
1660 example, this enables cow_user_page() to check that the source page is
1663 This option causes a performance degradation. Use only if you want to
1664 debug device drivers and dma interactions.
1668 config DMA_API_DEBUG_SG
1669 bool "Debug DMA scatter-gather usage"
1671 depends on DMA_API_DEBUG
1673 Perform extra checking that callers of dma_map_sg() have respected the
1674 appropriate segment length/boundary limits for the given device when
1675 preparing DMA scatterlists.
1677 This is particularly likely to have been overlooked in cases where the
1678 dma_map_sg() API is used for general bulk mapping of pages rather than
1679 preparing literal scatter-gather descriptors, where there is a risk of
1680 unexpected behaviour from DMA API implementations if the scatterlist
1681 is technically out-of-spec.
1685 menuconfig RUNTIME_TESTING_MENU
1686 bool "Runtime Testing"
1689 if RUNTIME_TESTING_MENU
1692 tristate "Linux Kernel Dump Test Tool Module"
1696 This module enables testing of the different dumping mechanisms by
1697 inducing system failures at predefined crash points.
1698 If you don't need it: say N
1699 Choose M here to compile this code as a module. The module will be
1702 Documentation on how to use the module can be found in
1703 Documentation/fault-injection/provoke-crashes.txt
1705 config TEST_LIST_SORT
1706 tristate "Linked list sorting test"
1707 depends on DEBUG_KERNEL || m
1709 Enable this to turn on 'list_sort()' function test. This test is
1710 executed only once during system boot (so affects only boot time),
1711 or at module load time.
1716 tristate "Array-based sort test"
1717 depends on DEBUG_KERNEL || m
1719 This option enables the self-test function of 'sort()' at boot,
1720 or at module load time.
1724 config KPROBES_SANITY_TEST
1725 bool "Kprobes sanity tests"
1726 depends on DEBUG_KERNEL
1729 This option provides for testing basic kprobes functionality on
1730 boot. Samples of kprobe and kretprobe are inserted and
1731 verified for functionality.
1733 Say N if you are unsure.
1735 config BACKTRACE_SELF_TEST
1736 tristate "Self test for the backtrace code"
1737 depends on DEBUG_KERNEL
1739 This option provides a kernel module that can be used to test
1740 the kernel stack backtrace code. This option is not useful
1741 for distributions or general kernels, but only for kernel
1742 developers working on architecture code.
1744 Note that if you want to also test saved backtraces, you will
1745 have to enable STACKTRACE as well.
1747 Say N if you are unsure.
1750 tristate "Red-Black tree test"
1751 depends on DEBUG_KERNEL
1753 A benchmark measuring the performance of the rbtree library.
1754 Also includes rbtree invariant checks.
1756 config INTERVAL_TREE_TEST
1757 tristate "Interval tree test"
1758 depends on DEBUG_KERNEL
1759 select INTERVAL_TREE
1761 A benchmark measuring the performance of the interval tree library
1764 tristate "Per cpu operations test"
1765 depends on m && DEBUG_KERNEL
1767 Enable this option to build test module which validates per-cpu
1772 config ATOMIC64_SELFTEST
1773 tristate "Perform an atomic64_t self-test"
1775 Enable this option to test the atomic64_t functions at boot or
1776 at module load time.
1780 config ASYNC_RAID6_TEST
1781 tristate "Self test for hardware accelerated raid6 recovery"
1782 depends on ASYNC_RAID6_RECOV
1785 This is a one-shot self test that permutes through the
1786 recovery of all the possible two disk failure scenarios for a
1787 N-disk array. Recovery is performed with the asynchronous
1788 raid6 recovery routines, and will optionally use an offload
1789 engine if one is available.
1794 tristate "Test functions located in the hexdump module at runtime"
1796 config TEST_STRING_HELPERS
1797 tristate "Test functions located in the string_helpers module at runtime"
1800 tristate "Test kstrto*() family of functions at runtime"
1803 tristate "Test printf() family of functions at runtime"
1806 tristate "Test bitmap_*() family of functions at runtime"
1808 Enable this option to test the bitmap functions at boot.
1812 config TEST_BITFIELD
1813 tristate "Test bitfield functions at runtime"
1815 Enable this option to test the bitfield functions at boot.
1820 tristate "Test functions located in the uuid module at runtime"
1822 config TEST_OVERFLOW
1823 tristate "Test check_*_overflow() functions at runtime"
1825 config TEST_RHASHTABLE
1826 tristate "Perform selftest on resizable hash table"
1828 Enable this option to test the rhashtable functions at boot.
1833 tristate "Perform selftest on hash functions"
1835 Enable this option to test the kernel's integer (<linux/hash.h>),
1836 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1837 hash functions on boot (or module load).
1839 This is intended to help people writing architecture-specific
1840 optimized versions. If unsure, say N.
1843 tristate "Perform selftest on IDA functions"
1846 tristate "Perform selftest on priority array manager"
1849 Enable this option to test priority array manager on boot
1855 tristate "Test module loading with 'hello world' module"
1858 This builds the "test_module" module that emits "Hello, world"
1859 on printk when loaded. It is designed to be used for basic
1860 evaluation of the module loading subsystem (for example when
1861 validating module verification). It lacks any extra dependencies,
1862 and will not normally be loaded by the system unless explicitly
1867 config TEST_USER_COPY
1868 tristate "Test user/kernel boundary protections"
1871 This builds the "test_user_copy" module that runs sanity checks
1872 on the copy_to/from_user infrastructure, making sure basic
1873 user/kernel boundary testing is working. If it fails to load,
1874 a regression has been detected in the user/kernel memory boundary
1880 tristate "Test BPF filter functionality"
1883 This builds the "test_bpf" module that runs various test vectors
1884 against the BPF interpreter or BPF JIT compiler depending on the
1885 current setting. This is in particular useful for BPF JIT compiler
1886 development, but also to run regression tests against changes in
1887 the interpreter code. It also enables test stubs for eBPF maps and
1888 verifier used by user space verifier testsuite.
1892 config FIND_BIT_BENCHMARK
1893 tristate "Test find_bit functions"
1895 This builds the "test_find_bit" module that measure find_*_bit()
1896 functions performance.
1900 config TEST_FIRMWARE
1901 tristate "Test firmware loading via userspace interface"
1902 depends on FW_LOADER
1904 This builds the "test_firmware" module that creates a userspace
1905 interface for testing firmware loading. This can be used to
1906 control the triggering of firmware loading without needing an
1907 actual firmware-using device. The contents can be rechecked by
1913 tristate "sysctl test driver"
1914 depends on PROC_SYSCTL
1916 This builds the "test_sysctl" module. This driver enables to test the
1917 proc sysctl interfaces available to drivers safely without affecting
1918 production knobs which might alter system functionality.
1923 tristate "udelay test driver"
1925 This builds the "udelay_test" module that helps to make sure
1926 that udelay() is working properly.
1930 config TEST_STATIC_KEYS
1931 tristate "Test static keys"
1934 Test the static key interfaces.
1939 tristate "kmod stress tester"
1941 depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS
1942 depends on NETDEVICES && NET_CORE && INET # for TUN
1949 Test the kernel's module loading mechanism: kmod. kmod implements
1950 support to load modules using the Linux kernel's usermode helper.
1951 This test provides a series of tests against kmod.
1953 Although technically you can either build test_kmod as a module or
1954 into the kernel we disallow building it into the kernel since
1955 it stress tests request_module() and this will very likely cause
1956 some issues by taking over precious threads available from other
1957 module load requests, ultimately this could be fatal.
1961 tools/testing/selftests/kmod/kmod.sh --help
1965 config TEST_DEBUG_VIRTUAL
1966 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
1967 depends on DEBUG_VIRTUAL
1969 Test the kernel's ability to detect incorrect calls to
1970 virt_to_phys() done against the non-linear part of the
1971 kernel's virtual address map.
1975 endif # RUNTIME_TESTING_MENU
1979 depends on HAVE_MEMBLOCK
1981 This option adds a kernel parameter 'memtest', which allows memtest
1983 memtest=0, mean disabled; -- default
1984 memtest=1, mean do 1 test pattern;
1986 memtest=17, mean do 17 test patterns.
1987 If you are unsure how to answer this question, answer N.
1989 config BUG_ON_DATA_CORRUPTION
1990 bool "Trigger a BUG when data corruption is detected"
1993 Select this option if the kernel should BUG when it encounters
1994 data corruption in kernel memory structures when they get checked
1999 source "samples/Kconfig"
2001 source "lib/Kconfig.kgdb"
2003 source "lib/Kconfig.ubsan"
2005 config ARCH_HAS_DEVMEM_IS_ALLOWED
2008 config STRICT_DEVMEM
2009 bool "Filter access to /dev/mem"
2010 depends on MMU && DEVMEM
2011 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
2012 default y if PPC || X86 || ARM64
2014 If this option is disabled, you allow userspace (root) access to all
2015 of memory, including kernel and userspace memory. Accidental
2016 access to this is obviously disastrous, but specific access can
2017 be used by people debugging the kernel. Note that with PAT support
2018 enabled, even in this case there are restrictions on /dev/mem
2019 use due to the cache aliasing requirements.
2021 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
2022 file only allows userspace access to PCI space and the BIOS code and
2023 data regions. This is sufficient for dosemu and X and all common
2028 config IO_STRICT_DEVMEM
2029 bool "Filter I/O access to /dev/mem"
2030 depends on STRICT_DEVMEM
2032 If this option is disabled, you allow userspace (root) access to all
2033 io-memory regardless of whether a driver is actively using that
2034 range. Accidental access to this is obviously disastrous, but
2035 specific access can be used by people debugging kernel drivers.
2037 If this option is switched on, the /dev/mem file only allows
2038 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2039 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2040 if the driver using a given range cannot be disabled.
2044 source "arch/$(SRCARCH)/Kconfig.debug"
2046 endmenu # Kernel hacking