1 # SPDX-License-Identifier: GPL-2.0-only
4 menu "printk and dmesg options"
7 bool "Show timing information on printks"
10 Selecting this option causes time stamps of the printk()
11 messages to be added to the output of the syslog() system
12 call and at the console.
14 The timestamp is always recorded internally, and exported
15 to /dev/kmsg. This flag just specifies if the timestamp should
16 be included, not that the timestamp is recorded.
18 The behavior is also controlled by the kernel command line
19 parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst
22 bool "Show caller information on printks"
25 Selecting this option causes printk() to add a caller "thread id" (if
26 in task context) or a caller "processor id" (if not in task context)
29 This option is intended for environments where multiple threads
30 concurrently call printk() for many times, for it is difficult to
31 interpret without knowing where these lines (or sometimes individual
32 line which was divided into multiple lines due to race) came from.
34 Since toggling after boot makes the code racy, currently there is
35 no option to enable/disable at the kernel command line parameter or
38 config CONSOLE_LOGLEVEL_DEFAULT
39 int "Default console loglevel (1-15)"
43 Default loglevel to determine what will be printed on the console.
45 Setting a default here is equivalent to passing in loglevel=<x> in
46 the kernel bootargs. loglevel=<x> continues to override whatever
47 value is specified here as well.
49 Note: This does not affect the log level of un-prefixed printk()
50 usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
53 config CONSOLE_LOGLEVEL_QUIET
54 int "quiet console loglevel (1-15)"
58 loglevel to use when "quiet" is passed on the kernel commandline.
60 When "quiet" is passed on the kernel commandline this loglevel
61 will be used as the loglevel. IOW passing "quiet" will be the
62 equivalent of passing "loglevel=<CONSOLE_LOGLEVEL_QUIET>"
64 config MESSAGE_LOGLEVEL_DEFAULT
65 int "Default message log level (1-7)"
69 Default log level for printk statements with no specified priority.
71 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
72 that are auditing their logs closely may want to set it to a lower
75 Note: This does not affect what message level gets printed on the console
76 by default. To change that, use loglevel=<x> in the kernel bootargs,
77 or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value.
79 config BOOT_PRINTK_DELAY
80 bool "Delay each boot printk message by N milliseconds"
81 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
83 This build option allows you to read kernel boot messages
84 by inserting a short delay after each one. The delay is
85 specified in milliseconds on the kernel command line,
88 It is likely that you would also need to use "lpj=M" to preset
89 the "loops per jiffie" value.
90 See a previous boot log for the "lpj" value to use for your
91 system, and then set "lpj=M" before setting "boot_delay=N".
92 NOTE: Using this option may adversely affect SMP systems.
93 I.e., processors other than the first one may not boot up.
94 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
95 what it believes to be lockup conditions.
98 bool "Enable dynamic printk() support"
101 depends on (DEBUG_FS || PROC_FS)
104 Compiles debug level messages into the kernel, which would not
105 otherwise be available at runtime. These messages can then be
106 enabled/disabled based on various levels of scope - per source file,
107 function, module, format string, and line number. This mechanism
108 implicitly compiles in all pr_debug() and dev_dbg() calls, which
109 enlarges the kernel text size by about 2%.
111 If a source file is compiled with DEBUG flag set, any
112 pr_debug() calls in it are enabled by default, but can be
113 disabled at runtime as below. Note that DEBUG flag is
114 turned on by many CONFIG_*DEBUG* options.
118 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
119 which is contained in the 'debugfs' filesystem or procfs.
120 Thus, the debugfs or procfs filesystem must first be mounted before
121 making use of this feature.
122 We refer the control file as: <debugfs>/dynamic_debug/control. This
123 file contains a list of the debug statements that can be enabled. The
124 format for each line of the file is:
126 filename:lineno [module]function flags format
128 filename : source file of the debug statement
129 lineno : line number of the debug statement
130 module : module that contains the debug statement
131 function : function that contains the debug statement
132 flags : '=p' means the line is turned 'on' for printing
133 format : the format used for the debug statement
137 nullarbor:~ # cat <debugfs>/dynamic_debug/control
138 # filename:lineno [module]function flags format
139 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
140 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
141 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
145 // enable the message at line 1603 of file svcsock.c
146 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
147 <debugfs>/dynamic_debug/control
149 // enable all the messages in file svcsock.c
150 nullarbor:~ # echo -n 'file svcsock.c +p' >
151 <debugfs>/dynamic_debug/control
153 // enable all the messages in the NFS server module
154 nullarbor:~ # echo -n 'module nfsd +p' >
155 <debugfs>/dynamic_debug/control
157 // enable all 12 messages in the function svc_process()
158 nullarbor:~ # echo -n 'func svc_process +p' >
159 <debugfs>/dynamic_debug/control
161 // disable all 12 messages in the function svc_process()
162 nullarbor:~ # echo -n 'func svc_process -p' >
163 <debugfs>/dynamic_debug/control
165 See Documentation/admin-guide/dynamic-debug-howto.rst for additional
168 config SYMBOLIC_ERRNAME
169 bool "Support symbolic error names in printf"
172 If you say Y here, the kernel's printf implementation will
173 be able to print symbolic error names such as ENOSPC instead
174 of the number 28. It makes the kernel image slightly larger
175 (about 3KB), but can make the kernel logs easier to read.
177 config DEBUG_BUGVERBOSE
178 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
179 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
182 Say Y here to make BUG() panics output the file name and line number
183 of the BUG call as well as the EIP and oops trace. This aids
184 debugging but costs about 70-100K of memory.
186 endmenu # "printk and dmesg options"
188 menu "Compile-time checks and compiler options"
191 bool "Compile the kernel with debug info"
192 depends on DEBUG_KERNEL && !COMPILE_TEST
194 If you say Y here the resulting kernel image will include
195 debugging info resulting in a larger kernel image.
196 This adds debug symbols to the kernel and modules (gcc -g), and
197 is needed if you intend to use kernel crashdump or binary object
198 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
199 Say Y here only if you plan to debug the kernel.
203 config DEBUG_INFO_REDUCED
204 bool "Reduce debugging information"
205 depends on DEBUG_INFO
207 If you say Y here gcc is instructed to generate less debugging
208 information for structure types. This means that tools that
209 need full debugging information (like kgdb or systemtap) won't
210 be happy. But if you merely need debugging information to
211 resolve line numbers there is no loss. Advantage is that
212 build directory object sizes shrink dramatically over a full
213 DEBUG_INFO build and compile times are reduced too.
214 Only works with newer gcc versions.
216 config DEBUG_INFO_SPLIT
217 bool "Produce split debuginfo in .dwo files"
218 depends on DEBUG_INFO
219 depends on $(cc-option,-gsplit-dwarf)
221 Generate debug info into separate .dwo files. This significantly
222 reduces the build directory size for builds with DEBUG_INFO,
223 because it stores the information only once on disk in .dwo
224 files instead of multiple times in object files and executables.
225 In addition the debug information is also compressed.
227 Requires recent gcc (4.7+) and recent gdb/binutils.
228 Any tool that packages or reads debug information would need
229 to know about the .dwo files and include them.
230 Incompatible with older versions of ccache.
232 config DEBUG_INFO_DWARF4
233 bool "Generate dwarf4 debuginfo"
234 depends on DEBUG_INFO
235 depends on $(cc-option,-gdwarf-4)
237 Generate dwarf4 debug info. This requires recent versions
238 of gcc and gdb. It makes the debug information larger.
239 But it significantly improves the success of resolving
240 variables in gdb on optimized code.
242 config DEBUG_INFO_BTF
243 bool "Generate BTF typeinfo"
244 depends on DEBUG_INFO
245 depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED
246 depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST
248 Generate deduplicated BTF type information from DWARF debug info.
249 Turning this on expects presence of pahole tool, which will convert
250 DWARF type info into equivalent deduplicated BTF type info.
253 bool "Provide GDB scripts for kernel debugging"
254 depends on DEBUG_INFO
256 This creates the required links to GDB helper scripts in the
257 build directory. If you load vmlinux into gdb, the helper
258 scripts will be automatically imported by gdb as well, and
259 additional functions are available to analyze a Linux kernel
260 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
263 config ENABLE_MUST_CHECK
264 bool "Enable __must_check logic"
267 Enable the __must_check logic in the kernel build. Disable this to
268 suppress the "warning: ignoring return value of 'foo', declared with
269 attribute warn_unused_result" messages.
272 int "Warn for stack frames larger than"
274 default 2048 if GCC_PLUGIN_LATENT_ENTROPY
275 default 1280 if (!64BIT && PARISC)
276 default 1024 if (!64BIT && !PARISC)
277 default 2048 if 64BIT
279 Tell gcc to warn at build time for stack frames larger than this.
280 Setting this too low will cause a lot of warnings.
281 Setting it to 0 disables the warning.
283 config STRIP_ASM_SYMS
284 bool "Strip assembler-generated symbols during link"
287 Strip internal assembler-generated symbols during a link (symbols
288 that look like '.Lxxx') so they don't pollute the output of
289 get_wchan() and suchlike.
292 bool "Generate readable assembler code"
293 depends on DEBUG_KERNEL
295 Disable some compiler optimizations that tend to generate human unreadable
296 assembler output. This may make the kernel slightly slower, but it helps
297 to keep kernel developers who have to stare a lot at assembler listings
300 config HEADERS_INSTALL
301 bool "Install uapi headers to usr/include"
304 This option will install uapi headers (headers exported to user-space)
305 into the usr/include directory for use during the kernel build.
306 This is unneeded for building the kernel itself, but needed for some
307 user-space program samples. It is also needed by some features such
308 as uapi header sanity checks.
310 config DEBUG_SECTION_MISMATCH
311 bool "Enable full Section mismatch analysis"
313 The section mismatch analysis checks if there are illegal
314 references from one section to another section.
315 During linktime or runtime, some sections are dropped;
316 any use of code/data previously in these sections would
317 most likely result in an oops.
318 In the code, functions and variables are annotated with
319 __init,, etc. (see the full list in include/linux/init.h),
320 which results in the code/data being placed in specific sections.
321 The section mismatch analysis is always performed after a full
322 kernel build, and enabling this option causes the following
323 additional step to occur:
324 - Add the option -fno-inline-functions-called-once to gcc commands.
325 When inlining a function annotated with __init in a non-init
326 function, we would lose the section information and thus
327 the analysis would not catch the illegal reference.
328 This option tells gcc to inline less (but it does result in
331 config SECTION_MISMATCH_WARN_ONLY
332 bool "Make section mismatch errors non-fatal"
335 If you say N here, the build process will fail if there are any
336 section mismatch, instead of just throwing warnings.
341 # Select this config option from the architecture Kconfig, if it
342 # is preferred to always offer frame pointers as a config
343 # option on the architecture (regardless of KERNEL_DEBUG):
345 config ARCH_WANT_FRAME_POINTERS
349 bool "Compile the kernel with frame pointers"
350 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS
351 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
353 If you say Y here the resulting kernel image will be slightly
354 larger and slower, but it gives very useful debugging information
355 in case of kernel bugs. (precise oopses/stacktraces/warnings)
357 config STACK_VALIDATION
358 bool "Compile-time stack metadata validation"
359 depends on HAVE_STACK_VALIDATION
362 Add compile-time checks to validate stack metadata, including frame
363 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
364 that runtime stack traces are more reliable.
366 This is also a prerequisite for generation of ORC unwind data, which
367 is needed for CONFIG_UNWINDER_ORC.
369 For more information, see
370 tools/objtool/Documentation/stack-validation.txt.
372 config VMLINUX_VALIDATION
374 depends on STACK_VALIDATION && DEBUG_ENTRY && !PARAVIRT
377 config DEBUG_FORCE_WEAK_PER_CPU
378 bool "Force weak per-cpu definitions"
379 depends on DEBUG_KERNEL
381 s390 and alpha require percpu variables in modules to be
382 defined weak to work around addressing range issue which
383 puts the following two restrictions on percpu variable
386 1. percpu symbols must be unique whether static or not
387 2. percpu variables can't be defined inside a function
389 To ensure that generic code follows the above rules, this
390 option forces all percpu variables to be defined as weak.
392 endmenu # "Compiler options"
394 menu "Generic Kernel Debugging Instruments"
397 bool "Magic SysRq key"
400 If you say Y here, you will have some control over the system even
401 if the system crashes for example during kernel debugging (e.g., you
402 will be able to flush the buffer cache to disk, reboot the system
403 immediately or dump some status information). This is accomplished
404 by pressing various keys while holding SysRq (Alt+PrintScreen). It
405 also works on a serial console (on PC hardware at least), if you
406 send a BREAK and then within 5 seconds a command keypress. The
407 keys are documented in <file:Documentation/admin-guide/sysrq.rst>.
408 Don't say Y unless you really know what this hack does.
410 config MAGIC_SYSRQ_DEFAULT_ENABLE
411 hex "Enable magic SysRq key functions by default"
412 depends on MAGIC_SYSRQ
415 Specifies which SysRq key functions are enabled by default.
416 This may be set to 1 or 0 to enable or disable them all, or
417 to a bitmask as described in Documentation/admin-guide/sysrq.rst.
419 config MAGIC_SYSRQ_SERIAL
420 bool "Enable magic SysRq key over serial"
421 depends on MAGIC_SYSRQ
424 Many embedded boards have a disconnected TTL level serial which can
425 generate some garbage that can lead to spurious false sysrq detects.
426 This option allows you to decide whether you want to enable the
429 config MAGIC_SYSRQ_SERIAL_SEQUENCE
430 string "Char sequence that enables magic SysRq over serial"
431 depends on MAGIC_SYSRQ_SERIAL
434 Specifies a sequence of characters that can follow BREAK to enable
435 SysRq on a serial console.
437 If unsure, leave an empty string and the option will not be enabled.
440 bool "Debug Filesystem"
442 debugfs is a virtual file system that kernel developers use to put
443 debugging files into. Enable this option to be able to read and
444 write to these files.
446 For detailed documentation on the debugfs API, see
447 Documentation/filesystems/.
451 source "lib/Kconfig.kgdb"
453 source "lib/Kconfig.ubsan"
458 bool "Kernel debugging"
460 Say Y here if you are developing drivers or trying to debug and
461 identify kernel problems.
464 bool "Miscellaneous debug code"
466 depends on DEBUG_KERNEL
468 Say Y here if you need to enable miscellaneous debug code that should
469 be under a more specific debug option but isn't.
472 menu "Memory Debugging"
474 source "mm/Kconfig.debug"
477 bool "Debug object operations"
478 depends on DEBUG_KERNEL
480 If you say Y here, additional code will be inserted into the
481 kernel to track the life time of various objects and validate
482 the operations on those objects.
484 config DEBUG_OBJECTS_SELFTEST
485 bool "Debug objects selftest"
486 depends on DEBUG_OBJECTS
488 This enables the selftest of the object debug code.
490 config DEBUG_OBJECTS_FREE
491 bool "Debug objects in freed memory"
492 depends on DEBUG_OBJECTS
494 This enables checks whether a k/v free operation frees an area
495 which contains an object which has not been deactivated
496 properly. This can make kmalloc/kfree-intensive workloads
499 config DEBUG_OBJECTS_TIMERS
500 bool "Debug timer objects"
501 depends on DEBUG_OBJECTS
503 If you say Y here, additional code will be inserted into the
504 timer routines to track the life time of timer objects and
505 validate the timer operations.
507 config DEBUG_OBJECTS_WORK
508 bool "Debug work objects"
509 depends on DEBUG_OBJECTS
511 If you say Y here, additional code will be inserted into the
512 work queue routines to track the life time of work objects and
513 validate the work operations.
515 config DEBUG_OBJECTS_RCU_HEAD
516 bool "Debug RCU callbacks objects"
517 depends on DEBUG_OBJECTS
519 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
521 config DEBUG_OBJECTS_PERCPU_COUNTER
522 bool "Debug percpu counter objects"
523 depends on DEBUG_OBJECTS
525 If you say Y here, additional code will be inserted into the
526 percpu counter routines to track the life time of percpu counter
527 objects and validate the percpu counter operations.
529 config DEBUG_OBJECTS_ENABLE_DEFAULT
530 int "debug_objects bootup default value (0-1)"
533 depends on DEBUG_OBJECTS
535 Debug objects boot parameter default value
538 bool "Debug slab memory allocations"
539 depends on DEBUG_KERNEL && SLAB
541 Say Y here to have the kernel do limited verification on memory
542 allocation as well as poisoning memory on free to catch use of freed
543 memory. This can make kmalloc/kfree-intensive workloads much slower.
546 bool "SLUB debugging on by default"
547 depends on SLUB && SLUB_DEBUG
550 Boot with debugging on by default. SLUB boots by default with
551 the runtime debug capabilities switched off. Enabling this is
552 equivalent to specifying the "slub_debug" parameter on boot.
553 There is no support for more fine grained debug control like
554 possible with slub_debug=xxx. SLUB debugging may be switched
555 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
560 bool "Enable SLUB performance statistics"
561 depends on SLUB && SYSFS
563 SLUB statistics are useful to debug SLUBs allocation behavior in
564 order find ways to optimize the allocator. This should never be
565 enabled for production use since keeping statistics slows down
566 the allocator by a few percentage points. The slabinfo command
567 supports the determination of the most active slabs to figure
568 out which slabs are relevant to a particular load.
569 Try running: slabinfo -DA
571 config HAVE_DEBUG_KMEMLEAK
574 config DEBUG_KMEMLEAK
575 bool "Kernel memory leak detector"
576 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
578 select STACKTRACE if STACKTRACE_SUPPORT
582 Say Y here if you want to enable the memory leak
583 detector. The memory allocation/freeing is traced in a way
584 similar to the Boehm's conservative garbage collector, the
585 difference being that the orphan objects are not freed but
586 only shown in /sys/kernel/debug/kmemleak. Enabling this
587 feature will introduce an overhead to memory
588 allocations. See Documentation/dev-tools/kmemleak.rst for more
591 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
592 of finding leaks due to the slab objects poisoning.
594 In order to access the kmemleak file, debugfs needs to be
595 mounted (usually at /sys/kernel/debug).
597 config DEBUG_KMEMLEAK_MEM_POOL_SIZE
598 int "Kmemleak memory pool size"
599 depends on DEBUG_KMEMLEAK
603 Kmemleak must track all the memory allocations to avoid
604 reporting false positives. Since memory may be allocated or
605 freed before kmemleak is fully initialised, use a static pool
606 of metadata objects to track such callbacks. After kmemleak is
607 fully initialised, this memory pool acts as an emergency one
608 if slab allocations fail.
610 config DEBUG_KMEMLEAK_TEST
611 tristate "Simple test for the kernel memory leak detector"
612 depends on DEBUG_KMEMLEAK && m
614 This option enables a module that explicitly leaks memory.
618 config DEBUG_KMEMLEAK_DEFAULT_OFF
619 bool "Default kmemleak to off"
620 depends on DEBUG_KMEMLEAK
622 Say Y here to disable kmemleak by default. It can then be enabled
623 on the command line via kmemleak=on.
625 config DEBUG_KMEMLEAK_AUTO_SCAN
626 bool "Enable kmemleak auto scan thread on boot up"
628 depends on DEBUG_KMEMLEAK
630 Depending on the cpu, kmemleak scan may be cpu intensive and can
631 stall user tasks at times. This option enables/disables automatic
632 kmemleak scan at boot up.
634 Say N here to disable kmemleak auto scan thread to stop automatic
635 scanning. Disabling this option disables automatic reporting of
640 config DEBUG_STACK_USAGE
641 bool "Stack utilization instrumentation"
642 depends on DEBUG_KERNEL && !IA64
644 Enables the display of the minimum amount of free stack which each
645 task has ever had available in the sysrq-T and sysrq-P debug output.
647 This option will slow down process creation somewhat.
649 config SCHED_STACK_END_CHECK
650 bool "Detect stack corruption on calls to schedule()"
651 depends on DEBUG_KERNEL
654 This option checks for a stack overrun on calls to schedule().
655 If the stack end location is found to be over written always panic as
656 the content of the corrupted region can no longer be trusted.
657 This is to ensure no erroneous behaviour occurs which could result in
658 data corruption or a sporadic crash at a later stage once the region
659 is examined. The runtime overhead introduced is minimal.
661 config ARCH_HAS_DEBUG_VM_PGTABLE
664 An architecture should select this when it can successfully
665 build and run DEBUG_VM_PGTABLE.
669 depends on DEBUG_KERNEL
671 Enable this to turn on extended checks in the virtual-memory system
672 that may impact performance.
676 config DEBUG_VM_VMACACHE
677 bool "Debug VMA caching"
680 Enable this to turn on VMA caching debug information. Doing so
681 can cause significant overhead, so only enable it in non-production
687 bool "Debug VM red-black trees"
690 Enable VM red-black tree debugging information and extra validations.
694 config DEBUG_VM_PGFLAGS
695 bool "Debug page-flags operations"
698 Enables extra validation on page flags operations.
702 config DEBUG_VM_PGTABLE
703 bool "Debug arch page table for semantics compliance"
705 depends on ARCH_HAS_DEBUG_VM_PGTABLE
706 default y if DEBUG_VM
708 This option provides a debug method which can be used to test
709 architecture page table helper functions on various platforms in
710 verifying if they comply with expected generic MM semantics. This
711 will help architecture code in making sure that any changes or
712 new additions of these helpers still conform to expected
713 semantics of the generic MM. Platforms will have to opt in for
714 this through ARCH_HAS_DEBUG_VM_PGTABLE.
718 config ARCH_HAS_DEBUG_VIRTUAL
722 bool "Debug VM translations"
723 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
725 Enable some costly sanity checks in virtual to page code. This can
726 catch mistakes with virt_to_page() and friends.
730 config DEBUG_NOMMU_REGIONS
731 bool "Debug the global anon/private NOMMU mapping region tree"
732 depends on DEBUG_KERNEL && !MMU
734 This option causes the global tree of anonymous and private mapping
735 regions to be regularly checked for invalid topology.
737 config DEBUG_MEMORY_INIT
738 bool "Debug memory initialisation" if EXPERT
741 Enable this for additional checks during memory initialisation.
742 The sanity checks verify aspects of the VM such as the memory model
743 and other information provided by the architecture. Verbose
744 information will be printed at KERN_DEBUG loglevel depending
745 on the mminit_loglevel= command-line option.
749 config MEMORY_NOTIFIER_ERROR_INJECT
750 tristate "Memory hotplug notifier error injection module"
751 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
753 This option provides the ability to inject artificial errors to
754 memory hotplug notifier chain callbacks. It is controlled through
755 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
757 If the notifier call chain should be failed with some events
758 notified, write the error code to "actions/<notifier event>/error".
760 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
762 # cd /sys/kernel/debug/notifier-error-inject/memory
763 # echo -12 > actions/MEM_GOING_OFFLINE/error
764 # echo offline > /sys/devices/system/memory/memoryXXX/state
765 bash: echo: write error: Cannot allocate memory
767 To compile this code as a module, choose M here: the module will
768 be called memory-notifier-error-inject.
772 config DEBUG_PER_CPU_MAPS
773 bool "Debug access to per_cpu maps"
774 depends on DEBUG_KERNEL
777 Say Y to verify that the per_cpu map being accessed has
778 been set up. This adds a fair amount of code to kernel memory
779 and decreases performance.
784 bool "Highmem debugging"
785 depends on DEBUG_KERNEL && HIGHMEM
787 This option enables additional error checking for high memory
788 systems. Disable for production systems.
790 config HAVE_DEBUG_STACKOVERFLOW
793 config DEBUG_STACKOVERFLOW
794 bool "Check for stack overflows"
795 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
797 Say Y here if you want to check for overflows of kernel, IRQ
798 and exception stacks (if your architecture uses them). This
799 option will show detailed messages if free stack space drops
800 below a certain limit.
802 These kinds of bugs usually occur when call-chains in the
803 kernel get too deep, especially when interrupts are
806 Use this in cases where you see apparently random memory
807 corruption, especially if it appears in 'struct thread_info'
809 If in doubt, say "N".
811 source "lib/Kconfig.kasan"
813 endmenu # "Memory Debugging"
816 bool "Debug shared IRQ handlers"
817 depends on DEBUG_KERNEL
819 Enable this to generate a spurious interrupt as soon as a shared
820 interrupt handler is registered, and just before one is deregistered.
821 Drivers ought to be able to handle interrupts coming in at those
822 points; some don't and need to be caught.
824 menu "Debug Oops, Lockups and Hangs"
829 Say Y here to enable the kernel to panic when it oopses. This
830 has the same effect as setting oops=panic on the kernel command
833 This feature is useful to ensure that the kernel does not do
834 anything erroneous after an oops which could result in data
835 corruption or other issues.
839 config PANIC_ON_OOPS_VALUE
842 default 0 if !PANIC_ON_OOPS
843 default 1 if PANIC_ON_OOPS
849 Set the timeout value (in seconds) until a reboot occurs when the
850 the kernel panics. If n = 0, then we wait forever. A timeout
851 value n > 0 will wait n seconds before rebooting, while a timeout
852 value n < 0 will reboot immediately.
854 config LOCKUP_DETECTOR
857 config SOFTLOCKUP_DETECTOR
858 bool "Detect Soft Lockups"
859 depends on DEBUG_KERNEL && !S390
860 select LOCKUP_DETECTOR
862 Say Y here to enable the kernel to act as a watchdog to detect
865 Softlockups are bugs that cause the kernel to loop in kernel
866 mode for more than 20 seconds, without giving other tasks a
867 chance to run. The current stack trace is displayed upon
868 detection and the system will stay locked up.
870 config BOOTPARAM_SOFTLOCKUP_PANIC
871 bool "Panic (Reboot) On Soft Lockups"
872 depends on SOFTLOCKUP_DETECTOR
874 Say Y here to enable the kernel to panic on "soft lockups",
875 which are bugs that cause the kernel to loop in kernel
876 mode for more than 20 seconds (configurable using the watchdog_thresh
877 sysctl), without giving other tasks a chance to run.
879 The panic can be used in combination with panic_timeout,
880 to cause the system to reboot automatically after a
881 lockup has been detected. This feature is useful for
882 high-availability systems that have uptime guarantees and
883 where a lockup must be resolved ASAP.
887 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
889 depends on SOFTLOCKUP_DETECTOR
891 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
892 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
894 config HARDLOCKUP_DETECTOR_PERF
896 select SOFTLOCKUP_DETECTOR
899 # Enables a timestamp based low pass filter to compensate for perf based
900 # hard lockup detection which runs too fast due to turbo modes.
902 config HARDLOCKUP_CHECK_TIMESTAMP
906 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
907 # lockup detector rather than the perf based detector.
909 config HARDLOCKUP_DETECTOR
910 bool "Detect Hard Lockups"
911 depends on DEBUG_KERNEL && !S390
912 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
913 select LOCKUP_DETECTOR
914 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
915 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
917 Say Y here to enable the kernel to act as a watchdog to detect
920 Hardlockups are bugs that cause the CPU to loop in kernel mode
921 for more than 10 seconds, without letting other interrupts have a
922 chance to run. The current stack trace is displayed upon detection
923 and the system will stay locked up.
925 config BOOTPARAM_HARDLOCKUP_PANIC
926 bool "Panic (Reboot) On Hard Lockups"
927 depends on HARDLOCKUP_DETECTOR
929 Say Y here to enable the kernel to panic on "hard lockups",
930 which are bugs that cause the kernel to loop in kernel
931 mode with interrupts disabled for more than 10 seconds (configurable
932 using the watchdog_thresh sysctl).
936 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
938 depends on HARDLOCKUP_DETECTOR
940 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
941 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
943 config DETECT_HUNG_TASK
944 bool "Detect Hung Tasks"
945 depends on DEBUG_KERNEL
946 default SOFTLOCKUP_DETECTOR
948 Say Y here to enable the kernel to detect "hung tasks",
949 which are bugs that cause the task to be stuck in
950 uninterruptible "D" state indefinitely.
952 When a hung task is detected, the kernel will print the
953 current stack trace (which you should report), but the
954 task will stay in uninterruptible state. If lockdep is
955 enabled then all held locks will also be reported. This
956 feature has negligible overhead.
958 config DEFAULT_HUNG_TASK_TIMEOUT
959 int "Default timeout for hung task detection (in seconds)"
960 depends on DETECT_HUNG_TASK
963 This option controls the default timeout (in seconds) used
964 to determine when a task has become non-responsive and should
967 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
968 sysctl or by writing a value to
969 /proc/sys/kernel/hung_task_timeout_secs.
971 A timeout of 0 disables the check. The default is two minutes.
972 Keeping the default should be fine in most cases.
974 config BOOTPARAM_HUNG_TASK_PANIC
975 bool "Panic (Reboot) On Hung Tasks"
976 depends on DETECT_HUNG_TASK
978 Say Y here to enable the kernel to panic on "hung tasks",
979 which are bugs that cause the kernel to leave a task stuck
980 in uninterruptible "D" state.
982 The panic can be used in combination with panic_timeout,
983 to cause the system to reboot automatically after a
984 hung task has been detected. This feature is useful for
985 high-availability systems that have uptime guarantees and
986 where a hung tasks must be resolved ASAP.
990 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
992 depends on DETECT_HUNG_TASK
994 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
995 default 1 if BOOTPARAM_HUNG_TASK_PANIC
998 bool "Detect Workqueue Stalls"
999 depends on DEBUG_KERNEL
1001 Say Y here to enable stall detection on workqueues. If a
1002 worker pool doesn't make forward progress on a pending work
1003 item for over a given amount of time, 30s by default, a
1004 warning message is printed along with dump of workqueue
1005 state. This can be configured through kernel parameter
1006 "workqueue.watchdog_thresh" and its sysfs counterpart.
1009 tristate "Test module to generate lockups"
1011 This builds the "test_lockup" module that helps to make sure
1012 that watchdogs and lockup detectors are working properly.
1014 Depending on module parameters it could emulate soft or hard
1015 lockup, "hung task", or locking arbitrary lock for a long time.
1016 Also it could generate series of lockups with cooling-down periods.
1020 endmenu # "Debug lockups and hangs"
1022 menu "Scheduler Debugging"
1025 bool "Collect scheduler debugging info"
1026 depends on DEBUG_KERNEL && PROC_FS
1029 If you say Y here, the /proc/sched_debug file will be provided
1030 that can help debug the scheduler. The runtime overhead of this
1038 bool "Collect scheduler statistics"
1039 depends on DEBUG_KERNEL && PROC_FS
1042 If you say Y here, additional code will be inserted into the
1043 scheduler and related routines to collect statistics about
1044 scheduler behavior and provide them in /proc/schedstat. These
1045 stats may be useful for both tuning and debugging the scheduler
1046 If you aren't debugging the scheduler or trying to tune a specific
1047 application, you can say N to avoid the very slight overhead
1052 config DEBUG_TIMEKEEPING
1053 bool "Enable extra timekeeping sanity checking"
1055 This option will enable additional timekeeping sanity checks
1056 which may be helpful when diagnosing issues where timekeeping
1057 problems are suspected.
1059 This may include checks in the timekeeping hotpaths, so this
1060 option may have a (very small) performance impact to some
1065 config DEBUG_PREEMPT
1066 bool "Debug preemptible kernel"
1067 depends on DEBUG_KERNEL && PREEMPTION && TRACE_IRQFLAGS_SUPPORT
1070 If you say Y here then the kernel will use a debug variant of the
1071 commonly used smp_processor_id() function and will print warnings
1072 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1073 will detect preemption count underflows.
1075 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1077 config LOCK_DEBUGGING_SUPPORT
1079 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1082 config PROVE_LOCKING
1083 bool "Lock debugging: prove locking correctness"
1084 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1086 select DEBUG_SPINLOCK
1087 select DEBUG_MUTEXES
1088 select DEBUG_RT_MUTEXES if RT_MUTEXES
1090 select DEBUG_WW_MUTEX_SLOWPATH
1091 select DEBUG_LOCK_ALLOC
1092 select TRACE_IRQFLAGS
1095 This feature enables the kernel to prove that all locking
1096 that occurs in the kernel runtime is mathematically
1097 correct: that under no circumstance could an arbitrary (and
1098 not yet triggered) combination of observed locking
1099 sequences (on an arbitrary number of CPUs, running an
1100 arbitrary number of tasks and interrupt contexts) cause a
1103 In short, this feature enables the kernel to report locking
1104 related deadlocks before they actually occur.
1106 The proof does not depend on how hard and complex a
1107 deadlock scenario would be to trigger: how many
1108 participant CPUs, tasks and irq-contexts would be needed
1109 for it to trigger. The proof also does not depend on
1110 timing: if a race and a resulting deadlock is possible
1111 theoretically (no matter how unlikely the race scenario
1112 is), it will be proven so and will immediately be
1113 reported by the kernel (once the event is observed that
1114 makes the deadlock theoretically possible).
1116 If a deadlock is impossible (i.e. the locking rules, as
1117 observed by the kernel, are mathematically correct), the
1118 kernel reports nothing.
1120 NOTE: this feature can also be enabled for rwlocks, mutexes
1121 and rwsems - in which case all dependencies between these
1122 different locking variants are observed and mapped too, and
1123 the proof of observed correctness is also maintained for an
1124 arbitrary combination of these separate locking variants.
1126 For more details, see Documentation/locking/lockdep-design.rst.
1128 config PROVE_RAW_LOCK_NESTING
1129 bool "Enable raw_spinlock - spinlock nesting checks"
1130 depends on PROVE_LOCKING
1133 Enable the raw_spinlock vs. spinlock nesting checks which ensure
1134 that the lock nesting rules for PREEMPT_RT enabled kernels are
1137 NOTE: There are known nesting problems. So if you enable this
1138 option expect lockdep splats until these problems have been fully
1139 addressed which is work in progress. This config switch allows to
1140 identify and analyze these problems. It will be removed and the
1141 check permanentely enabled once the main issues have been fixed.
1143 If unsure, select N.
1146 bool "Lock usage statistics"
1147 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1149 select DEBUG_SPINLOCK
1150 select DEBUG_MUTEXES
1151 select DEBUG_RT_MUTEXES if RT_MUTEXES
1152 select DEBUG_LOCK_ALLOC
1155 This feature enables tracking lock contention points
1157 For more details, see Documentation/locking/lockstat.rst
1159 This also enables lock events required by "perf lock",
1161 If you want to use "perf lock", you also need to turn on
1162 CONFIG_EVENT_TRACING.
1164 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1165 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1167 config DEBUG_RT_MUTEXES
1168 bool "RT Mutex debugging, deadlock detection"
1169 depends on DEBUG_KERNEL && RT_MUTEXES
1171 This allows rt mutex semantics violations and rt mutex related
1172 deadlocks (lockups) to be detected and reported automatically.
1174 config DEBUG_SPINLOCK
1175 bool "Spinlock and rw-lock debugging: basic checks"
1176 depends on DEBUG_KERNEL
1177 select UNINLINE_SPIN_UNLOCK
1179 Say Y here and build SMP to catch missing spinlock initialization
1180 and certain other kinds of spinlock errors commonly made. This is
1181 best used in conjunction with the NMI watchdog so that spinlock
1182 deadlocks are also debuggable.
1184 config DEBUG_MUTEXES
1185 bool "Mutex debugging: basic checks"
1186 depends on DEBUG_KERNEL
1188 This feature allows mutex semantics violations to be detected and
1191 config DEBUG_WW_MUTEX_SLOWPATH
1192 bool "Wait/wound mutex debugging: Slowpath testing"
1193 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1194 select DEBUG_LOCK_ALLOC
1195 select DEBUG_SPINLOCK
1196 select DEBUG_MUTEXES
1198 This feature enables slowpath testing for w/w mutex users by
1199 injecting additional -EDEADLK wound/backoff cases. Together with
1200 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1201 will test all possible w/w mutex interface abuse with the
1202 exception of simply not acquiring all the required locks.
1203 Note that this feature can introduce significant overhead, so
1204 it really should not be enabled in a production or distro kernel,
1205 even a debug kernel. If you are a driver writer, enable it. If
1206 you are a distro, do not.
1209 bool "RW Semaphore debugging: basic checks"
1210 depends on DEBUG_KERNEL
1212 This debugging feature allows mismatched rw semaphore locks
1213 and unlocks to be detected and reported.
1215 config DEBUG_LOCK_ALLOC
1216 bool "Lock debugging: detect incorrect freeing of live locks"
1217 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1218 select DEBUG_SPINLOCK
1219 select DEBUG_MUTEXES
1220 select DEBUG_RT_MUTEXES if RT_MUTEXES
1223 This feature will check whether any held lock (spinlock, rwlock,
1224 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1225 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1226 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1227 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1228 held during task exit.
1232 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1234 select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86
1238 config LOCKDEP_SMALL
1241 config DEBUG_LOCKDEP
1242 bool "Lock dependency engine debugging"
1243 depends on DEBUG_KERNEL && LOCKDEP
1245 If you say Y here, the lock dependency engine will do
1246 additional runtime checks to debug itself, at the price
1247 of more runtime overhead.
1249 config DEBUG_ATOMIC_SLEEP
1250 bool "Sleep inside atomic section checking"
1251 select PREEMPT_COUNT
1252 depends on DEBUG_KERNEL
1253 depends on !ARCH_NO_PREEMPT
1255 If you say Y here, various routines which may sleep will become very
1256 noisy if they are called inside atomic sections: when a spinlock is
1257 held, inside an rcu read side critical section, inside preempt disabled
1258 sections, inside an interrupt, etc...
1260 config DEBUG_LOCKING_API_SELFTESTS
1261 bool "Locking API boot-time self-tests"
1262 depends on DEBUG_KERNEL
1264 Say Y here if you want the kernel to run a short self-test during
1265 bootup. The self-test checks whether common types of locking bugs
1266 are detected by debugging mechanisms or not. (if you disable
1267 lock debugging then those bugs wont be detected of course.)
1268 The following locking APIs are covered: spinlocks, rwlocks,
1271 config LOCK_TORTURE_TEST
1272 tristate "torture tests for locking"
1273 depends on DEBUG_KERNEL
1276 This option provides a kernel module that runs torture tests
1277 on kernel locking primitives. The kernel module may be built
1278 after the fact on the running kernel to be tested, if desired.
1280 Say Y here if you want kernel locking-primitive torture tests
1281 to be built into the kernel.
1282 Say M if you want these torture tests to build as a module.
1283 Say N if you are unsure.
1285 config WW_MUTEX_SELFTEST
1286 tristate "Wait/wound mutex selftests"
1288 This option provides a kernel module that runs tests on the
1289 on the struct ww_mutex locking API.
1291 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1292 with this test harness.
1294 Say M if you want these self tests to build as a module.
1295 Say N if you are unsure.
1297 endmenu # lock debugging
1299 config TRACE_IRQFLAGS
1302 Enables hooks to interrupt enabling and disabling for
1303 either tracing or lock debugging.
1306 bool "Stack backtrace support"
1307 depends on STACKTRACE_SUPPORT
1309 This option causes the kernel to create a /proc/pid/stack for
1310 every process, showing its current stack trace.
1311 It is also used by various kernel debugging features that require
1312 stack trace generation.
1314 config WARN_ALL_UNSEEDED_RANDOM
1315 bool "Warn for all uses of unseeded randomness"
1318 Some parts of the kernel contain bugs relating to their use of
1319 cryptographically secure random numbers before it's actually possible
1320 to generate those numbers securely. This setting ensures that these
1321 flaws don't go unnoticed, by enabling a message, should this ever
1322 occur. This will allow people with obscure setups to know when things
1323 are going wrong, so that they might contact developers about fixing
1326 Unfortunately, on some models of some architectures getting
1327 a fully seeded CRNG is extremely difficult, and so this can
1328 result in dmesg getting spammed for a surprisingly long
1329 time. This is really bad from a security perspective, and
1330 so architecture maintainers really need to do what they can
1331 to get the CRNG seeded sooner after the system is booted.
1332 However, since users cannot do anything actionable to
1333 address this, by default the kernel will issue only a single
1334 warning for the first use of unseeded randomness.
1336 Say Y here if you want to receive warnings for all uses of
1337 unseeded randomness. This will be of use primarily for
1338 those developers interested in improving the security of
1339 Linux kernels running on their architecture (or
1342 config DEBUG_KOBJECT
1343 bool "kobject debugging"
1344 depends on DEBUG_KERNEL
1346 If you say Y here, some extra kobject debugging messages will be sent
1349 config DEBUG_KOBJECT_RELEASE
1350 bool "kobject release debugging"
1351 depends on DEBUG_OBJECTS_TIMERS
1353 kobjects are reference counted objects. This means that their
1354 last reference count put is not predictable, and the kobject can
1355 live on past the point at which a driver decides to drop it's
1356 initial reference to the kobject gained on allocation. An
1357 example of this would be a struct device which has just been
1360 However, some buggy drivers assume that after such an operation,
1361 the memory backing the kobject can be immediately freed. This
1362 goes completely against the principles of a refcounted object.
1364 If you say Y here, the kernel will delay the release of kobjects
1365 on the last reference count to improve the visibility of this
1366 kind of kobject release bug.
1368 config HAVE_DEBUG_BUGVERBOSE
1371 menu "Debug kernel data structures"
1374 bool "Debug linked list manipulation"
1375 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1377 Enable this to turn on extended checks in the linked-list
1383 bool "Debug priority linked list manipulation"
1384 depends on DEBUG_KERNEL
1386 Enable this to turn on extended checks in the priority-ordered
1387 linked-list (plist) walking routines. This checks the entire
1388 list multiple times during each manipulation.
1393 bool "Debug SG table operations"
1394 depends on DEBUG_KERNEL
1396 Enable this to turn on checks on scatter-gather tables. This can
1397 help find problems with drivers that do not properly initialize
1402 config DEBUG_NOTIFIERS
1403 bool "Debug notifier call chains"
1404 depends on DEBUG_KERNEL
1406 Enable this to turn on sanity checking for notifier call chains.
1407 This is most useful for kernel developers to make sure that
1408 modules properly unregister themselves from notifier chains.
1409 This is a relatively cheap check but if you care about maximum
1412 config BUG_ON_DATA_CORRUPTION
1413 bool "Trigger a BUG when data corruption is detected"
1416 Select this option if the kernel should BUG when it encounters
1417 data corruption in kernel memory structures when they get checked
1424 config DEBUG_CREDENTIALS
1425 bool "Debug credential management"
1426 depends on DEBUG_KERNEL
1428 Enable this to turn on some debug checking for credential
1429 management. The additional code keeps track of the number of
1430 pointers from task_structs to any given cred struct, and checks to
1431 see that this number never exceeds the usage count of the cred
1434 Furthermore, if SELinux is enabled, this also checks that the
1435 security pointer in the cred struct is never seen to be invalid.
1439 source "kernel/rcu/Kconfig.debug"
1441 config DEBUG_WQ_FORCE_RR_CPU
1442 bool "Force round-robin CPU selection for unbound work items"
1443 depends on DEBUG_KERNEL
1446 Workqueue used to implicitly guarantee that work items queued
1447 without explicit CPU specified are put on the local CPU. This
1448 guarantee is no longer true and while local CPU is still
1449 preferred work items may be put on foreign CPUs. Kernel
1450 parameter "workqueue.debug_force_rr_cpu" is added to force
1451 round-robin CPU selection to flush out usages which depend on the
1452 now broken guarantee. This config option enables the debug
1453 feature by default. When enabled, memory and cache locality will
1456 config DEBUG_BLOCK_EXT_DEVT
1457 bool "Force extended block device numbers and spread them"
1458 depends on DEBUG_KERNEL
1462 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1463 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1464 YOU ARE DOING. Distros, please enable this and fix whatever
1467 Conventionally, block device numbers are allocated from
1468 predetermined contiguous area. However, extended block area
1469 may introduce non-contiguous block device numbers. This
1470 option forces most block device numbers to be allocated from
1471 the extended space and spreads them to discover kernel or
1472 userland code paths which assume predetermined contiguous
1473 device number allocation.
1475 Note that turning on this debug option shuffles all the
1476 device numbers for all IDE and SCSI devices including libata
1477 ones, so root partition specified using device number
1478 directly (via rdev or root=MAJ:MIN) won't work anymore.
1479 Textual device names (root=/dev/sdXn) will continue to work.
1481 Say N if you are unsure.
1483 config CPU_HOTPLUG_STATE_CONTROL
1484 bool "Enable CPU hotplug state control"
1485 depends on DEBUG_KERNEL
1486 depends on HOTPLUG_CPU
1489 Allows to write steps between "offline" and "online" to the CPUs
1490 sysfs target file so states can be stepped granular. This is a debug
1491 option for now as the hotplug machinery cannot be stopped and
1492 restarted at arbitrary points yet.
1494 Say N if your are unsure.
1497 bool "Latency measuring infrastructure"
1498 depends on DEBUG_KERNEL
1499 depends on STACKTRACE_SUPPORT
1501 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1508 Enable this option if you want to use the LatencyTOP tool
1509 to find out which userspace is blocking on what kernel operations.
1511 source "kernel/trace/Kconfig"
1513 config PROVIDE_OHCI1394_DMA_INIT
1514 bool "Remote debugging over FireWire early on boot"
1515 depends on PCI && X86
1517 If you want to debug problems which hang or crash the kernel early
1518 on boot and the crashing machine has a FireWire port, you can use
1519 this feature to remotely access the memory of the crashed machine
1520 over FireWire. This employs remote DMA as part of the OHCI1394
1521 specification which is now the standard for FireWire controllers.
1523 With remote DMA, you can monitor the printk buffer remotely using
1524 firescope and access all memory below 4GB using fireproxy from gdb.
1525 Even controlling a kernel debugger is possible using remote DMA.
1529 If ohci1394_dma=early is used as boot parameter, it will initialize
1530 all OHCI1394 controllers which are found in the PCI config space.
1532 As all changes to the FireWire bus such as enabling and disabling
1533 devices cause a bus reset and thereby disable remote DMA for all
1534 devices, be sure to have the cable plugged and FireWire enabled on
1535 the debugging host before booting the debug target for debugging.
1537 This code (~1k) is freed after boot. By then, the firewire stack
1538 in charge of the OHCI-1394 controllers should be used instead.
1540 See Documentation/core-api/debugging-via-ohci1394.rst for more information.
1542 source "samples/Kconfig"
1544 config ARCH_HAS_DEVMEM_IS_ALLOWED
1547 config STRICT_DEVMEM
1548 bool "Filter access to /dev/mem"
1549 depends on MMU && DEVMEM
1550 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
1551 default y if PPC || X86 || ARM64
1553 If this option is disabled, you allow userspace (root) access to all
1554 of memory, including kernel and userspace memory. Accidental
1555 access to this is obviously disastrous, but specific access can
1556 be used by people debugging the kernel. Note that with PAT support
1557 enabled, even in this case there are restrictions on /dev/mem
1558 use due to the cache aliasing requirements.
1560 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
1561 file only allows userspace access to PCI space and the BIOS code and
1562 data regions. This is sufficient for dosemu and X and all common
1567 config IO_STRICT_DEVMEM
1568 bool "Filter I/O access to /dev/mem"
1569 depends on STRICT_DEVMEM
1571 If this option is disabled, you allow userspace (root) access to all
1572 io-memory regardless of whether a driver is actively using that
1573 range. Accidental access to this is obviously disastrous, but
1574 specific access can be used by people debugging kernel drivers.
1576 If this option is switched on, the /dev/mem file only allows
1577 userspace access to *idle* io-memory ranges (see /proc/iomem) This
1578 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
1579 if the driver using a given range cannot be disabled.
1583 menu "$(SRCARCH) Debugging"
1585 source "arch/$(SRCARCH)/Kconfig.debug"
1589 menu "Kernel Testing and Coverage"
1591 source "lib/kunit/Kconfig"
1593 config NOTIFIER_ERROR_INJECTION
1594 tristate "Notifier error injection"
1595 depends on DEBUG_KERNEL
1598 This option provides the ability to inject artificial errors to
1599 specified notifier chain callbacks. It is useful to test the error
1600 handling of notifier call chain failures.
1604 config PM_NOTIFIER_ERROR_INJECT
1605 tristate "PM notifier error injection module"
1606 depends on PM && NOTIFIER_ERROR_INJECTION
1607 default m if PM_DEBUG
1609 This option provides the ability to inject artificial errors to
1610 PM notifier chain callbacks. It is controlled through debugfs
1611 interface /sys/kernel/debug/notifier-error-inject/pm
1613 If the notifier call chain should be failed with some events
1614 notified, write the error code to "actions/<notifier event>/error".
1616 Example: Inject PM suspend error (-12 = -ENOMEM)
1618 # cd /sys/kernel/debug/notifier-error-inject/pm/
1619 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1620 # echo mem > /sys/power/state
1621 bash: echo: write error: Cannot allocate memory
1623 To compile this code as a module, choose M here: the module will
1624 be called pm-notifier-error-inject.
1628 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1629 tristate "OF reconfig notifier error injection module"
1630 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1632 This option provides the ability to inject artificial errors to
1633 OF reconfig notifier chain callbacks. It is controlled
1634 through debugfs interface under
1635 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1637 If the notifier call chain should be failed with some events
1638 notified, write the error code to "actions/<notifier event>/error".
1640 To compile this code as a module, choose M here: the module will
1641 be called of-reconfig-notifier-error-inject.
1645 config NETDEV_NOTIFIER_ERROR_INJECT
1646 tristate "Netdev notifier error injection module"
1647 depends on NET && NOTIFIER_ERROR_INJECTION
1649 This option provides the ability to inject artificial errors to
1650 netdevice notifier chain callbacks. It is controlled through debugfs
1651 interface /sys/kernel/debug/notifier-error-inject/netdev
1653 If the notifier call chain should be failed with some events
1654 notified, write the error code to "actions/<notifier event>/error".
1656 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1658 # cd /sys/kernel/debug/notifier-error-inject/netdev
1659 # echo -22 > actions/NETDEV_CHANGEMTU/error
1660 # ip link set eth0 mtu 1024
1661 RTNETLINK answers: Invalid argument
1663 To compile this code as a module, choose M here: the module will
1664 be called netdev-notifier-error-inject.
1668 config FUNCTION_ERROR_INJECTION
1670 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
1672 config FAULT_INJECTION
1673 bool "Fault-injection framework"
1674 depends on DEBUG_KERNEL
1676 Provide fault-injection framework.
1677 For more details, see Documentation/fault-injection/.
1680 bool "Fault-injection capability for kmalloc"
1681 depends on FAULT_INJECTION
1682 depends on SLAB || SLUB
1684 Provide fault-injection capability for kmalloc.
1686 config FAIL_PAGE_ALLOC
1687 bool "Fault-injection capability for alloc_pages()"
1688 depends on FAULT_INJECTION
1690 Provide fault-injection capability for alloc_pages().
1692 config FAIL_MAKE_REQUEST
1693 bool "Fault-injection capability for disk IO"
1694 depends on FAULT_INJECTION && BLOCK
1696 Provide fault-injection capability for disk IO.
1698 config FAIL_IO_TIMEOUT
1699 bool "Fault-injection capability for faking disk interrupts"
1700 depends on FAULT_INJECTION && BLOCK
1702 Provide fault-injection capability on end IO handling. This
1703 will make the block layer "forget" an interrupt as configured,
1704 thus exercising the error handling.
1706 Only works with drivers that use the generic timeout handling,
1707 for others it wont do anything.
1710 bool "Fault-injection capability for futexes"
1712 depends on FAULT_INJECTION && FUTEX
1714 Provide fault-injection capability for futexes.
1716 config FAULT_INJECTION_DEBUG_FS
1717 bool "Debugfs entries for fault-injection capabilities"
1718 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1720 Enable configuration of fault-injection capabilities via debugfs.
1722 config FAIL_FUNCTION
1723 bool "Fault-injection capability for functions"
1724 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
1726 Provide function-based fault-injection capability.
1727 This will allow you to override a specific function with a return
1728 with given return value. As a result, function caller will see
1729 an error value and have to handle it. This is useful to test the
1730 error handling in various subsystems.
1732 config FAIL_MMC_REQUEST
1733 bool "Fault-injection capability for MMC IO"
1734 depends on FAULT_INJECTION_DEBUG_FS && MMC
1736 Provide fault-injection capability for MMC IO.
1737 This will make the mmc core return data errors. This is
1738 useful to test the error handling in the mmc block device
1739 and to test how the mmc host driver handles retries from
1742 config FAULT_INJECTION_STACKTRACE_FILTER
1743 bool "stacktrace filter for fault-injection capabilities"
1744 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1747 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1749 Provide stacktrace filter for fault-injection capabilities
1751 config ARCH_HAS_KCOV
1754 An architecture should select this when it can successfully
1755 build and run with CONFIG_KCOV. This typically requires
1756 disabling instrumentation for some early boot code.
1758 config CC_HAS_SANCOV_TRACE_PC
1759 def_bool $(cc-option,-fsanitize-coverage=trace-pc)
1763 bool "Code coverage for fuzzing"
1764 depends on ARCH_HAS_KCOV
1765 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
1767 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
1769 KCOV exposes kernel code coverage information in a form suitable
1770 for coverage-guided fuzzing (randomized testing).
1772 If RANDOMIZE_BASE is enabled, PC values will not be stable across
1773 different machines and across reboots. If you need stable PC values,
1774 disable RANDOMIZE_BASE.
1776 For more details, see Documentation/dev-tools/kcov.rst.
1778 config KCOV_ENABLE_COMPARISONS
1779 bool "Enable comparison operands collection by KCOV"
1781 depends on $(cc-option,-fsanitize-coverage=trace-cmp)
1783 KCOV also exposes operands of every comparison in the instrumented
1784 code along with operand sizes and PCs of the comparison instructions.
1785 These operands can be used by fuzzing engines to improve the quality
1786 of fuzzing coverage.
1788 config KCOV_INSTRUMENT_ALL
1789 bool "Instrument all code by default"
1793 If you are doing generic system call fuzzing (like e.g. syzkaller),
1794 then you will want to instrument the whole kernel and you should
1795 say y here. If you are doing more targeted fuzzing (like e.g.
1796 filesystem fuzzing with AFL) then you will want to enable coverage
1797 for more specific subsets of files, and should say n here.
1799 config KCOV_IRQ_AREA_SIZE
1800 hex "Size of interrupt coverage collection area in words"
1804 KCOV uses preallocated per-cpu areas to collect coverage from
1805 soft interrupts. This specifies the size of those areas in the
1806 number of unsigned long words.
1808 menuconfig RUNTIME_TESTING_MENU
1809 bool "Runtime Testing"
1812 if RUNTIME_TESTING_MENU
1815 tristate "Linux Kernel Dump Test Tool Module"
1818 This module enables testing of the different dumping mechanisms by
1819 inducing system failures at predefined crash points.
1820 If you don't need it: say N
1821 Choose M here to compile this code as a module. The module will be
1824 Documentation on how to use the module can be found in
1825 Documentation/fault-injection/provoke-crashes.rst
1827 config TEST_LIST_SORT
1828 tristate "Linked list sorting test"
1829 depends on DEBUG_KERNEL || m
1831 Enable this to turn on 'list_sort()' function test. This test is
1832 executed only once during system boot (so affects only boot time),
1833 or at module load time.
1837 config TEST_MIN_HEAP
1838 tristate "Min heap test"
1839 depends on DEBUG_KERNEL || m
1841 Enable this to turn on min heap function tests. This test is
1842 executed only once during system boot (so affects only boot time),
1843 or at module load time.
1848 tristate "Array-based sort test"
1849 depends on DEBUG_KERNEL || m
1851 This option enables the self-test function of 'sort()' at boot,
1852 or at module load time.
1856 config KPROBES_SANITY_TEST
1857 bool "Kprobes sanity tests"
1858 depends on DEBUG_KERNEL
1861 This option provides for testing basic kprobes functionality on
1862 boot. Samples of kprobe and kretprobe are inserted and
1863 verified for functionality.
1865 Say N if you are unsure.
1867 config BACKTRACE_SELF_TEST
1868 tristate "Self test for the backtrace code"
1869 depends on DEBUG_KERNEL
1871 This option provides a kernel module that can be used to test
1872 the kernel stack backtrace code. This option is not useful
1873 for distributions or general kernels, but only for kernel
1874 developers working on architecture code.
1876 Note that if you want to also test saved backtraces, you will
1877 have to enable STACKTRACE as well.
1879 Say N if you are unsure.
1882 tristate "Red-Black tree test"
1883 depends on DEBUG_KERNEL
1885 A benchmark measuring the performance of the rbtree library.
1886 Also includes rbtree invariant checks.
1888 config REED_SOLOMON_TEST
1889 tristate "Reed-Solomon library test"
1890 depends on DEBUG_KERNEL || m
1892 select REED_SOLOMON_ENC16
1893 select REED_SOLOMON_DEC16
1895 This option enables the self-test function of rslib at boot,
1896 or at module load time.
1900 config INTERVAL_TREE_TEST
1901 tristate "Interval tree test"
1902 depends on DEBUG_KERNEL
1903 select INTERVAL_TREE
1905 A benchmark measuring the performance of the interval tree library
1908 tristate "Per cpu operations test"
1909 depends on m && DEBUG_KERNEL
1911 Enable this option to build test module which validates per-cpu
1916 config ATOMIC64_SELFTEST
1917 tristate "Perform an atomic64_t self-test"
1919 Enable this option to test the atomic64_t functions at boot or
1920 at module load time.
1924 config ASYNC_RAID6_TEST
1925 tristate "Self test for hardware accelerated raid6 recovery"
1926 depends on ASYNC_RAID6_RECOV
1929 This is a one-shot self test that permutes through the
1930 recovery of all the possible two disk failure scenarios for a
1931 N-disk array. Recovery is performed with the asynchronous
1932 raid6 recovery routines, and will optionally use an offload
1933 engine if one is available.
1938 tristate "Test functions located in the hexdump module at runtime"
1940 config TEST_STRING_HELPERS
1941 tristate "Test functions located in the string_helpers module at runtime"
1944 tristate "Test strscpy*() family of functions at runtime"
1947 tristate "Test kstrto*() family of functions at runtime"
1950 tristate "Test printf() family of functions at runtime"
1953 tristate "Test bitmap_*() family of functions at runtime"
1955 Enable this option to test the bitmap functions at boot.
1959 config TEST_BITFIELD
1960 tristate "Test bitfield functions at runtime"
1962 Enable this option to test the bitfield functions at boot.
1967 tristate "Test functions located in the uuid module at runtime"
1970 tristate "Test the XArray code at runtime"
1972 config TEST_OVERFLOW
1973 tristate "Test check_*_overflow() functions at runtime"
1975 config TEST_RHASHTABLE
1976 tristate "Perform selftest on resizable hash table"
1978 Enable this option to test the rhashtable functions at boot.
1983 tristate "Perform selftest on hash functions"
1985 Enable this option to test the kernel's integer (<linux/hash.h>),
1986 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1987 hash functions on boot (or module load).
1989 This is intended to help people writing architecture-specific
1990 optimized versions. If unsure, say N.
1993 tristate "Perform selftest on IDA functions"
1996 tristate "Perform selftest on priority array manager"
1999 Enable this option to test priority array manager on boot
2004 config TEST_IRQ_TIMINGS
2005 bool "IRQ timings selftest"
2006 depends on IRQ_TIMINGS
2008 Enable this option to test the irq timings code on boot.
2013 tristate "Test module loading with 'hello world' module"
2016 This builds the "test_module" module that emits "Hello, world"
2017 on printk when loaded. It is designed to be used for basic
2018 evaluation of the module loading subsystem (for example when
2019 validating module verification). It lacks any extra dependencies,
2020 and will not normally be loaded by the system unless explicitly
2026 tristate "Test module for compilation of clear_bit/set_bit operations"
2029 This builds the "test_bitops" module that is much like the
2030 TEST_LKM module except that it does a basic exercise of the
2031 clear_bit and set_bit macros to make sure there are no compiler
2032 warnings from C=1 sparse checker or -Wextra compilations. It has
2033 no dependencies and doesn't run or load unless explicitly requested
2034 by name. for example: modprobe test_bitops.
2039 tristate "Test module for stress/performance analysis of vmalloc allocator"
2044 This builds the "test_vmalloc" module that should be used for
2045 stress and performance analysis. So, any new change for vmalloc
2046 subsystem can be evaluated from performance and stability point
2051 config TEST_USER_COPY
2052 tristate "Test user/kernel boundary protections"
2055 This builds the "test_user_copy" module that runs sanity checks
2056 on the copy_to/from_user infrastructure, making sure basic
2057 user/kernel boundary testing is working. If it fails to load,
2058 a regression has been detected in the user/kernel memory boundary
2064 tristate "Test BPF filter functionality"
2067 This builds the "test_bpf" module that runs various test vectors
2068 against the BPF interpreter or BPF JIT compiler depending on the
2069 current setting. This is in particular useful for BPF JIT compiler
2070 development, but also to run regression tests against changes in
2071 the interpreter code. It also enables test stubs for eBPF maps and
2072 verifier used by user space verifier testsuite.
2076 config TEST_BLACKHOLE_DEV
2077 tristate "Test blackhole netdev functionality"
2080 This builds the "test_blackhole_dev" module that validates the
2081 data path through this blackhole netdev.
2085 config FIND_BIT_BENCHMARK
2086 tristate "Test find_bit functions"
2088 This builds the "test_find_bit" module that measure find_*_bit()
2089 functions performance.
2093 config TEST_FIRMWARE
2094 tristate "Test firmware loading via userspace interface"
2095 depends on FW_LOADER
2097 This builds the "test_firmware" module that creates a userspace
2098 interface for testing firmware loading. This can be used to
2099 control the triggering of firmware loading without needing an
2100 actual firmware-using device. The contents can be rechecked by
2106 tristate "sysctl test driver"
2107 depends on PROC_SYSCTL
2109 This builds the "test_sysctl" module. This driver enables to test the
2110 proc sysctl interfaces available to drivers safely without affecting
2111 production knobs which might alter system functionality.
2115 config SYSCTL_KUNIT_TEST
2116 tristate "KUnit test for sysctl"
2119 This builds the proc sysctl unit test, which runs on boot.
2120 Tests the API contract and implementation correctness of sysctl.
2121 For more information on KUnit and unit tests in general please refer
2122 to the KUnit documentation in Documentation/dev-tools/kunit/.
2126 config LIST_KUNIT_TEST
2127 tristate "KUnit Test for Kernel Linked-list structures"
2130 This builds the linked list KUnit test suite.
2131 It tests that the API and basic functionality of the list_head type
2132 and associated macros.
2134 KUnit tests run during boot and output the results to the debug log
2135 in TAP format (http://testanything.org/). Only useful for kernel devs
2136 running the KUnit test harness, and not intended for inclusion into a
2139 For more information on KUnit and unit tests in general please refer
2140 to the KUnit documentation in Documentation/dev-tools/kunit/.
2144 config LINEAR_RANGES_TEST
2145 tristate "KUnit test for linear_ranges"
2147 select LINEAR_RANGES
2149 This builds the linear_ranges unit test, which runs on boot.
2150 Tests the linear_ranges logic correctness.
2151 For more information on KUnit and unit tests in general please refer
2152 to the KUnit documentation in Documentation/dev-tools/kunit/.
2157 tristate "udelay test driver"
2159 This builds the "udelay_test" module that helps to make sure
2160 that udelay() is working properly.
2164 config TEST_STATIC_KEYS
2165 tristate "Test static keys"
2168 Test the static key interfaces.
2173 tristate "kmod stress tester"
2175 depends on NETDEVICES && NET_CORE && INET # for TUN
2182 Test the kernel's module loading mechanism: kmod. kmod implements
2183 support to load modules using the Linux kernel's usermode helper.
2184 This test provides a series of tests against kmod.
2186 Although technically you can either build test_kmod as a module or
2187 into the kernel we disallow building it into the kernel since
2188 it stress tests request_module() and this will very likely cause
2189 some issues by taking over precious threads available from other
2190 module load requests, ultimately this could be fatal.
2194 tools/testing/selftests/kmod/kmod.sh --help
2198 config TEST_DEBUG_VIRTUAL
2199 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
2200 depends on DEBUG_VIRTUAL
2202 Test the kernel's ability to detect incorrect calls to
2203 virt_to_phys() done against the non-linear part of the
2204 kernel's virtual address map.
2208 config TEST_MEMCAT_P
2209 tristate "Test memcat_p() helper function"
2211 Test the memcat_p() helper for correctly merging two
2212 pointer arrays together.
2216 config TEST_LIVEPATCH
2217 tristate "Test livepatching"
2219 depends on DYNAMIC_DEBUG
2220 depends on LIVEPATCH
2223 Test kernel livepatching features for correctness. The tests will
2224 load test modules that will be livepatched in various scenarios.
2226 To run all the livepatching tests:
2228 make -C tools/testing/selftests TARGETS=livepatch run_tests
2230 Alternatively, individual tests may be invoked:
2232 tools/testing/selftests/livepatch/test-callbacks.sh
2233 tools/testing/selftests/livepatch/test-livepatch.sh
2234 tools/testing/selftests/livepatch/test-shadow-vars.sh
2239 tristate "Perform selftest on object aggreration manager"
2243 Enable this option to test object aggregation manager on boot
2247 config TEST_STACKINIT
2248 tristate "Test level of stack variable initialization"
2250 Test if the kernel is zero-initializing stack variables and
2251 padding. Coverage is controlled by compiler flags,
2252 CONFIG_GCC_PLUGIN_STRUCTLEAK, CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF,
2253 or CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL.
2258 tristate "Test heap/page initialization"
2260 Test if the kernel is zero-initializing heap and page allocations.
2261 This can be useful to test init_on_alloc and init_on_free features.
2266 tristate "Test HMM (Heterogeneous Memory Management)"
2267 depends on TRANSPARENT_HUGEPAGE
2268 depends on DEVICE_PRIVATE
2272 This is a pseudo device driver solely for testing HMM.
2273 Say M here if you want to build the HMM test module.
2274 Doing so will allow you to run tools/testing/selftest/vm/hmm-tests.
2278 endif # RUNTIME_TESTING_MENU
2283 This option adds a kernel parameter 'memtest', which allows memtest
2285 memtest=0, mean disabled; -- default
2286 memtest=1, mean do 1 test pattern;
2288 memtest=17, mean do 17 test patterns.
2289 If you are unsure how to answer this question, answer N.
2293 config HYPERV_TESTING
2294 bool "Microsoft Hyper-V driver testing"
2296 depends on HYPERV && DEBUG_FS
2298 Select this option to enable Hyper-V vmbus testing.
2300 endmenu # "Kernel Testing and Coverage"
2302 endmenu # Kernel hacking