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.
663 depends on DEBUG_KERNEL
665 Enable this to turn on extended checks in the virtual-memory system
666 that may impact performance.
670 config DEBUG_VM_VMACACHE
671 bool "Debug VMA caching"
674 Enable this to turn on VMA caching debug information. Doing so
675 can cause significant overhead, so only enable it in non-production
681 bool "Debug VM red-black trees"
684 Enable VM red-black tree debugging information and extra validations.
688 config DEBUG_VM_PGFLAGS
689 bool "Debug page-flags operations"
692 Enables extra validation on page flags operations.
696 config ARCH_HAS_DEBUG_VIRTUAL
700 bool "Debug VM translations"
701 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
703 Enable some costly sanity checks in virtual to page code. This can
704 catch mistakes with virt_to_page() and friends.
708 config DEBUG_NOMMU_REGIONS
709 bool "Debug the global anon/private NOMMU mapping region tree"
710 depends on DEBUG_KERNEL && !MMU
712 This option causes the global tree of anonymous and private mapping
713 regions to be regularly checked for invalid topology.
715 config DEBUG_MEMORY_INIT
716 bool "Debug memory initialisation" if EXPERT
719 Enable this for additional checks during memory initialisation.
720 The sanity checks verify aspects of the VM such as the memory model
721 and other information provided by the architecture. Verbose
722 information will be printed at KERN_DEBUG loglevel depending
723 on the mminit_loglevel= command-line option.
727 config MEMORY_NOTIFIER_ERROR_INJECT
728 tristate "Memory hotplug notifier error injection module"
729 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
731 This option provides the ability to inject artificial errors to
732 memory hotplug notifier chain callbacks. It is controlled through
733 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
735 If the notifier call chain should be failed with some events
736 notified, write the error code to "actions/<notifier event>/error".
738 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
740 # cd /sys/kernel/debug/notifier-error-inject/memory
741 # echo -12 > actions/MEM_GOING_OFFLINE/error
742 # echo offline > /sys/devices/system/memory/memoryXXX/state
743 bash: echo: write error: Cannot allocate memory
745 To compile this code as a module, choose M here: the module will
746 be called memory-notifier-error-inject.
750 config DEBUG_PER_CPU_MAPS
751 bool "Debug access to per_cpu maps"
752 depends on DEBUG_KERNEL
755 Say Y to verify that the per_cpu map being accessed has
756 been set up. This adds a fair amount of code to kernel memory
757 and decreases performance.
762 bool "Highmem debugging"
763 depends on DEBUG_KERNEL && HIGHMEM
765 This option enables additional error checking for high memory
766 systems. Disable for production systems.
768 config HAVE_DEBUG_STACKOVERFLOW
771 config DEBUG_STACKOVERFLOW
772 bool "Check for stack overflows"
773 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
775 Say Y here if you want to check for overflows of kernel, IRQ
776 and exception stacks (if your architecture uses them). This
777 option will show detailed messages if free stack space drops
778 below a certain limit.
780 These kinds of bugs usually occur when call-chains in the
781 kernel get too deep, especially when interrupts are
784 Use this in cases where you see apparently random memory
785 corruption, especially if it appears in 'struct thread_info'
787 If in doubt, say "N".
789 source "lib/Kconfig.kasan"
791 endmenu # "Memory Debugging"
794 bool "Debug shared IRQ handlers"
795 depends on DEBUG_KERNEL
797 Enable this to generate a spurious interrupt as soon as a shared
798 interrupt handler is registered, and just before one is deregistered.
799 Drivers ought to be able to handle interrupts coming in at those
800 points; some don't and need to be caught.
802 menu "Debug Oops, Lockups and Hangs"
807 Say Y here to enable the kernel to panic when it oopses. This
808 has the same effect as setting oops=panic on the kernel command
811 This feature is useful to ensure that the kernel does not do
812 anything erroneous after an oops which could result in data
813 corruption or other issues.
817 config PANIC_ON_OOPS_VALUE
820 default 0 if !PANIC_ON_OOPS
821 default 1 if PANIC_ON_OOPS
827 Set the timeout value (in seconds) until a reboot occurs when the
828 the kernel panics. If n = 0, then we wait forever. A timeout
829 value n > 0 will wait n seconds before rebooting, while a timeout
830 value n < 0 will reboot immediately.
832 config LOCKUP_DETECTOR
835 config SOFTLOCKUP_DETECTOR
836 bool "Detect Soft Lockups"
837 depends on DEBUG_KERNEL && !S390
838 select LOCKUP_DETECTOR
840 Say Y here to enable the kernel to act as a watchdog to detect
843 Softlockups are bugs that cause the kernel to loop in kernel
844 mode for more than 20 seconds, without giving other tasks a
845 chance to run. The current stack trace is displayed upon
846 detection and the system will stay locked up.
848 config BOOTPARAM_SOFTLOCKUP_PANIC
849 bool "Panic (Reboot) On Soft Lockups"
850 depends on SOFTLOCKUP_DETECTOR
852 Say Y here to enable the kernel to panic on "soft lockups",
853 which are bugs that cause the kernel to loop in kernel
854 mode for more than 20 seconds (configurable using the watchdog_thresh
855 sysctl), without giving other tasks a chance to run.
857 The panic can be used in combination with panic_timeout,
858 to cause the system to reboot automatically after a
859 lockup has been detected. This feature is useful for
860 high-availability systems that have uptime guarantees and
861 where a lockup must be resolved ASAP.
865 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
867 depends on SOFTLOCKUP_DETECTOR
869 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
870 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
872 config HARDLOCKUP_DETECTOR_PERF
874 select SOFTLOCKUP_DETECTOR
877 # Enables a timestamp based low pass filter to compensate for perf based
878 # hard lockup detection which runs too fast due to turbo modes.
880 config HARDLOCKUP_CHECK_TIMESTAMP
884 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
885 # lockup detector rather than the perf based detector.
887 config HARDLOCKUP_DETECTOR
888 bool "Detect Hard Lockups"
889 depends on DEBUG_KERNEL && !S390
890 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
891 select LOCKUP_DETECTOR
892 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
893 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
895 Say Y here to enable the kernel to act as a watchdog to detect
898 Hardlockups are bugs that cause the CPU to loop in kernel mode
899 for more than 10 seconds, without letting other interrupts have a
900 chance to run. The current stack trace is displayed upon detection
901 and the system will stay locked up.
903 config BOOTPARAM_HARDLOCKUP_PANIC
904 bool "Panic (Reboot) On Hard Lockups"
905 depends on HARDLOCKUP_DETECTOR
907 Say Y here to enable the kernel to panic on "hard lockups",
908 which are bugs that cause the kernel to loop in kernel
909 mode with interrupts disabled for more than 10 seconds (configurable
910 using the watchdog_thresh sysctl).
914 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
916 depends on HARDLOCKUP_DETECTOR
918 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
919 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
921 config DETECT_HUNG_TASK
922 bool "Detect Hung Tasks"
923 depends on DEBUG_KERNEL
924 default SOFTLOCKUP_DETECTOR
926 Say Y here to enable the kernel to detect "hung tasks",
927 which are bugs that cause the task to be stuck in
928 uninterruptible "D" state indefinitely.
930 When a hung task is detected, the kernel will print the
931 current stack trace (which you should report), but the
932 task will stay in uninterruptible state. If lockdep is
933 enabled then all held locks will also be reported. This
934 feature has negligible overhead.
936 config DEFAULT_HUNG_TASK_TIMEOUT
937 int "Default timeout for hung task detection (in seconds)"
938 depends on DETECT_HUNG_TASK
941 This option controls the default timeout (in seconds) used
942 to determine when a task has become non-responsive and should
945 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
946 sysctl or by writing a value to
947 /proc/sys/kernel/hung_task_timeout_secs.
949 A timeout of 0 disables the check. The default is two minutes.
950 Keeping the default should be fine in most cases.
952 config BOOTPARAM_HUNG_TASK_PANIC
953 bool "Panic (Reboot) On Hung Tasks"
954 depends on DETECT_HUNG_TASK
956 Say Y here to enable the kernel to panic on "hung tasks",
957 which are bugs that cause the kernel to leave a task stuck
958 in uninterruptible "D" state.
960 The panic can be used in combination with panic_timeout,
961 to cause the system to reboot automatically after a
962 hung task has been detected. This feature is useful for
963 high-availability systems that have uptime guarantees and
964 where a hung tasks must be resolved ASAP.
968 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
970 depends on DETECT_HUNG_TASK
972 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
973 default 1 if BOOTPARAM_HUNG_TASK_PANIC
976 bool "Detect Workqueue Stalls"
977 depends on DEBUG_KERNEL
979 Say Y here to enable stall detection on workqueues. If a
980 worker pool doesn't make forward progress on a pending work
981 item for over a given amount of time, 30s by default, a
982 warning message is printed along with dump of workqueue
983 state. This can be configured through kernel parameter
984 "workqueue.watchdog_thresh" and its sysfs counterpart.
987 tristate "Test module to generate lockups"
989 This builds the "test_lockup" module that helps to make sure
990 that watchdogs and lockup detectors are working properly.
992 Depending on module parameters it could emulate soft or hard
993 lockup, "hung task", or locking arbitrary lock for a long time.
994 Also it could generate series of lockups with cooling-down periods.
998 endmenu # "Debug lockups and hangs"
1000 menu "Scheduler Debugging"
1003 bool "Collect scheduler debugging info"
1004 depends on DEBUG_KERNEL && PROC_FS
1007 If you say Y here, the /proc/sched_debug file will be provided
1008 that can help debug the scheduler. The runtime overhead of this
1016 bool "Collect scheduler statistics"
1017 depends on DEBUG_KERNEL && PROC_FS
1020 If you say Y here, additional code will be inserted into the
1021 scheduler and related routines to collect statistics about
1022 scheduler behavior and provide them in /proc/schedstat. These
1023 stats may be useful for both tuning and debugging the scheduler
1024 If you aren't debugging the scheduler or trying to tune a specific
1025 application, you can say N to avoid the very slight overhead
1030 config DEBUG_TIMEKEEPING
1031 bool "Enable extra timekeeping sanity checking"
1033 This option will enable additional timekeeping sanity checks
1034 which may be helpful when diagnosing issues where timekeeping
1035 problems are suspected.
1037 This may include checks in the timekeeping hotpaths, so this
1038 option may have a (very small) performance impact to some
1043 config DEBUG_PREEMPT
1044 bool "Debug preemptible kernel"
1045 depends on DEBUG_KERNEL && PREEMPTION && TRACE_IRQFLAGS_SUPPORT
1048 If you say Y here then the kernel will use a debug variant of the
1049 commonly used smp_processor_id() function and will print warnings
1050 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1051 will detect preemption count underflows.
1053 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1055 config LOCK_DEBUGGING_SUPPORT
1057 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1060 config PROVE_LOCKING
1061 bool "Lock debugging: prove locking correctness"
1062 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1064 select DEBUG_SPINLOCK
1065 select DEBUG_MUTEXES
1066 select DEBUG_RT_MUTEXES if RT_MUTEXES
1068 select DEBUG_WW_MUTEX_SLOWPATH
1069 select DEBUG_LOCK_ALLOC
1070 select TRACE_IRQFLAGS
1073 This feature enables the kernel to prove that all locking
1074 that occurs in the kernel runtime is mathematically
1075 correct: that under no circumstance could an arbitrary (and
1076 not yet triggered) combination of observed locking
1077 sequences (on an arbitrary number of CPUs, running an
1078 arbitrary number of tasks and interrupt contexts) cause a
1081 In short, this feature enables the kernel to report locking
1082 related deadlocks before they actually occur.
1084 The proof does not depend on how hard and complex a
1085 deadlock scenario would be to trigger: how many
1086 participant CPUs, tasks and irq-contexts would be needed
1087 for it to trigger. The proof also does not depend on
1088 timing: if a race and a resulting deadlock is possible
1089 theoretically (no matter how unlikely the race scenario
1090 is), it will be proven so and will immediately be
1091 reported by the kernel (once the event is observed that
1092 makes the deadlock theoretically possible).
1094 If a deadlock is impossible (i.e. the locking rules, as
1095 observed by the kernel, are mathematically correct), the
1096 kernel reports nothing.
1098 NOTE: this feature can also be enabled for rwlocks, mutexes
1099 and rwsems - in which case all dependencies between these
1100 different locking variants are observed and mapped too, and
1101 the proof of observed correctness is also maintained for an
1102 arbitrary combination of these separate locking variants.
1104 For more details, see Documentation/locking/lockdep-design.rst.
1106 config PROVE_RAW_LOCK_NESTING
1107 bool "Enable raw_spinlock - spinlock nesting checks"
1108 depends on PROVE_LOCKING
1111 Enable the raw_spinlock vs. spinlock nesting checks which ensure
1112 that the lock nesting rules for PREEMPT_RT enabled kernels are
1115 NOTE: There are known nesting problems. So if you enable this
1116 option expect lockdep splats until these problems have been fully
1117 addressed which is work in progress. This config switch allows to
1118 identify and analyze these problems. It will be removed and the
1119 check permanentely enabled once the main issues have been fixed.
1121 If unsure, select N.
1124 bool "Lock usage statistics"
1125 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1127 select DEBUG_SPINLOCK
1128 select DEBUG_MUTEXES
1129 select DEBUG_RT_MUTEXES if RT_MUTEXES
1130 select DEBUG_LOCK_ALLOC
1133 This feature enables tracking lock contention points
1135 For more details, see Documentation/locking/lockstat.rst
1137 This also enables lock events required by "perf lock",
1139 If you want to use "perf lock", you also need to turn on
1140 CONFIG_EVENT_TRACING.
1142 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1143 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1145 config DEBUG_RT_MUTEXES
1146 bool "RT Mutex debugging, deadlock detection"
1147 depends on DEBUG_KERNEL && RT_MUTEXES
1149 This allows rt mutex semantics violations and rt mutex related
1150 deadlocks (lockups) to be detected and reported automatically.
1152 config DEBUG_SPINLOCK
1153 bool "Spinlock and rw-lock debugging: basic checks"
1154 depends on DEBUG_KERNEL
1155 select UNINLINE_SPIN_UNLOCK
1157 Say Y here and build SMP to catch missing spinlock initialization
1158 and certain other kinds of spinlock errors commonly made. This is
1159 best used in conjunction with the NMI watchdog so that spinlock
1160 deadlocks are also debuggable.
1162 config DEBUG_MUTEXES
1163 bool "Mutex debugging: basic checks"
1164 depends on DEBUG_KERNEL
1166 This feature allows mutex semantics violations to be detected and
1169 config DEBUG_WW_MUTEX_SLOWPATH
1170 bool "Wait/wound mutex debugging: Slowpath testing"
1171 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1172 select DEBUG_LOCK_ALLOC
1173 select DEBUG_SPINLOCK
1174 select DEBUG_MUTEXES
1176 This feature enables slowpath testing for w/w mutex users by
1177 injecting additional -EDEADLK wound/backoff cases. Together with
1178 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1179 will test all possible w/w mutex interface abuse with the
1180 exception of simply not acquiring all the required locks.
1181 Note that this feature can introduce significant overhead, so
1182 it really should not be enabled in a production or distro kernel,
1183 even a debug kernel. If you are a driver writer, enable it. If
1184 you are a distro, do not.
1187 bool "RW Semaphore debugging: basic checks"
1188 depends on DEBUG_KERNEL
1190 This debugging feature allows mismatched rw semaphore locks
1191 and unlocks to be detected and reported.
1193 config DEBUG_LOCK_ALLOC
1194 bool "Lock debugging: detect incorrect freeing of live locks"
1195 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1196 select DEBUG_SPINLOCK
1197 select DEBUG_MUTEXES
1198 select DEBUG_RT_MUTEXES if RT_MUTEXES
1201 This feature will check whether any held lock (spinlock, rwlock,
1202 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1203 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1204 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1205 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1206 held during task exit.
1210 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1212 select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86
1216 config LOCKDEP_SMALL
1219 config DEBUG_LOCKDEP
1220 bool "Lock dependency engine debugging"
1221 depends on DEBUG_KERNEL && LOCKDEP
1223 If you say Y here, the lock dependency engine will do
1224 additional runtime checks to debug itself, at the price
1225 of more runtime overhead.
1227 config DEBUG_ATOMIC_SLEEP
1228 bool "Sleep inside atomic section checking"
1229 select PREEMPT_COUNT
1230 depends on DEBUG_KERNEL
1231 depends on !ARCH_NO_PREEMPT
1233 If you say Y here, various routines which may sleep will become very
1234 noisy if they are called inside atomic sections: when a spinlock is
1235 held, inside an rcu read side critical section, inside preempt disabled
1236 sections, inside an interrupt, etc...
1238 config DEBUG_LOCKING_API_SELFTESTS
1239 bool "Locking API boot-time self-tests"
1240 depends on DEBUG_KERNEL
1242 Say Y here if you want the kernel to run a short self-test during
1243 bootup. The self-test checks whether common types of locking bugs
1244 are detected by debugging mechanisms or not. (if you disable
1245 lock debugging then those bugs wont be detected of course.)
1246 The following locking APIs are covered: spinlocks, rwlocks,
1249 config LOCK_TORTURE_TEST
1250 tristate "torture tests for locking"
1251 depends on DEBUG_KERNEL
1254 This option provides a kernel module that runs torture tests
1255 on kernel locking primitives. The kernel module may be built
1256 after the fact on the running kernel to be tested, if desired.
1258 Say Y here if you want kernel locking-primitive torture tests
1259 to be built into the kernel.
1260 Say M if you want these torture tests to build as a module.
1261 Say N if you are unsure.
1263 config WW_MUTEX_SELFTEST
1264 tristate "Wait/wound mutex selftests"
1266 This option provides a kernel module that runs tests on the
1267 on the struct ww_mutex locking API.
1269 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1270 with this test harness.
1272 Say M if you want these self tests to build as a module.
1273 Say N if you are unsure.
1275 endmenu # lock debugging
1277 config TRACE_IRQFLAGS
1280 Enables hooks to interrupt enabling and disabling for
1281 either tracing or lock debugging.
1284 bool "Stack backtrace support"
1285 depends on STACKTRACE_SUPPORT
1287 This option causes the kernel to create a /proc/pid/stack for
1288 every process, showing its current stack trace.
1289 It is also used by various kernel debugging features that require
1290 stack trace generation.
1292 config WARN_ALL_UNSEEDED_RANDOM
1293 bool "Warn for all uses of unseeded randomness"
1296 Some parts of the kernel contain bugs relating to their use of
1297 cryptographically secure random numbers before it's actually possible
1298 to generate those numbers securely. This setting ensures that these
1299 flaws don't go unnoticed, by enabling a message, should this ever
1300 occur. This will allow people with obscure setups to know when things
1301 are going wrong, so that they might contact developers about fixing
1304 Unfortunately, on some models of some architectures getting
1305 a fully seeded CRNG is extremely difficult, and so this can
1306 result in dmesg getting spammed for a surprisingly long
1307 time. This is really bad from a security perspective, and
1308 so architecture maintainers really need to do what they can
1309 to get the CRNG seeded sooner after the system is booted.
1310 However, since users cannot do anything actionable to
1311 address this, by default the kernel will issue only a single
1312 warning for the first use of unseeded randomness.
1314 Say Y here if you want to receive warnings for all uses of
1315 unseeded randomness. This will be of use primarily for
1316 those developers interested in improving the security of
1317 Linux kernels running on their architecture (or
1320 config DEBUG_KOBJECT
1321 bool "kobject debugging"
1322 depends on DEBUG_KERNEL
1324 If you say Y here, some extra kobject debugging messages will be sent
1327 config DEBUG_KOBJECT_RELEASE
1328 bool "kobject release debugging"
1329 depends on DEBUG_OBJECTS_TIMERS
1331 kobjects are reference counted objects. This means that their
1332 last reference count put is not predictable, and the kobject can
1333 live on past the point at which a driver decides to drop it's
1334 initial reference to the kobject gained on allocation. An
1335 example of this would be a struct device which has just been
1338 However, some buggy drivers assume that after such an operation,
1339 the memory backing the kobject can be immediately freed. This
1340 goes completely against the principles of a refcounted object.
1342 If you say Y here, the kernel will delay the release of kobjects
1343 on the last reference count to improve the visibility of this
1344 kind of kobject release bug.
1346 config HAVE_DEBUG_BUGVERBOSE
1349 menu "Debug kernel data structures"
1352 bool "Debug linked list manipulation"
1353 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1355 Enable this to turn on extended checks in the linked-list
1361 bool "Debug priority linked list manipulation"
1362 depends on DEBUG_KERNEL
1364 Enable this to turn on extended checks in the priority-ordered
1365 linked-list (plist) walking routines. This checks the entire
1366 list multiple times during each manipulation.
1371 bool "Debug SG table operations"
1372 depends on DEBUG_KERNEL
1374 Enable this to turn on checks on scatter-gather tables. This can
1375 help find problems with drivers that do not properly initialize
1380 config DEBUG_NOTIFIERS
1381 bool "Debug notifier call chains"
1382 depends on DEBUG_KERNEL
1384 Enable this to turn on sanity checking for notifier call chains.
1385 This is most useful for kernel developers to make sure that
1386 modules properly unregister themselves from notifier chains.
1387 This is a relatively cheap check but if you care about maximum
1390 config BUG_ON_DATA_CORRUPTION
1391 bool "Trigger a BUG when data corruption is detected"
1394 Select this option if the kernel should BUG when it encounters
1395 data corruption in kernel memory structures when they get checked
1402 config DEBUG_CREDENTIALS
1403 bool "Debug credential management"
1404 depends on DEBUG_KERNEL
1406 Enable this to turn on some debug checking for credential
1407 management. The additional code keeps track of the number of
1408 pointers from task_structs to any given cred struct, and checks to
1409 see that this number never exceeds the usage count of the cred
1412 Furthermore, if SELinux is enabled, this also checks that the
1413 security pointer in the cred struct is never seen to be invalid.
1417 source "kernel/rcu/Kconfig.debug"
1419 config DEBUG_WQ_FORCE_RR_CPU
1420 bool "Force round-robin CPU selection for unbound work items"
1421 depends on DEBUG_KERNEL
1424 Workqueue used to implicitly guarantee that work items queued
1425 without explicit CPU specified are put on the local CPU. This
1426 guarantee is no longer true and while local CPU is still
1427 preferred work items may be put on foreign CPUs. Kernel
1428 parameter "workqueue.debug_force_rr_cpu" is added to force
1429 round-robin CPU selection to flush out usages which depend on the
1430 now broken guarantee. This config option enables the debug
1431 feature by default. When enabled, memory and cache locality will
1434 config DEBUG_BLOCK_EXT_DEVT
1435 bool "Force extended block device numbers and spread them"
1436 depends on DEBUG_KERNEL
1440 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1441 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1442 YOU ARE DOING. Distros, please enable this and fix whatever
1445 Conventionally, block device numbers are allocated from
1446 predetermined contiguous area. However, extended block area
1447 may introduce non-contiguous block device numbers. This
1448 option forces most block device numbers to be allocated from
1449 the extended space and spreads them to discover kernel or
1450 userland code paths which assume predetermined contiguous
1451 device number allocation.
1453 Note that turning on this debug option shuffles all the
1454 device numbers for all IDE and SCSI devices including libata
1455 ones, so root partition specified using device number
1456 directly (via rdev or root=MAJ:MIN) won't work anymore.
1457 Textual device names (root=/dev/sdXn) will continue to work.
1459 Say N if you are unsure.
1461 config CPU_HOTPLUG_STATE_CONTROL
1462 bool "Enable CPU hotplug state control"
1463 depends on DEBUG_KERNEL
1464 depends on HOTPLUG_CPU
1467 Allows to write steps between "offline" and "online" to the CPUs
1468 sysfs target file so states can be stepped granular. This is a debug
1469 option for now as the hotplug machinery cannot be stopped and
1470 restarted at arbitrary points yet.
1472 Say N if your are unsure.
1475 bool "Latency measuring infrastructure"
1476 depends on DEBUG_KERNEL
1477 depends on STACKTRACE_SUPPORT
1479 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1486 Enable this option if you want to use the LatencyTOP tool
1487 to find out which userspace is blocking on what kernel operations.
1489 source "kernel/trace/Kconfig"
1491 config PROVIDE_OHCI1394_DMA_INIT
1492 bool "Remote debugging over FireWire early on boot"
1493 depends on PCI && X86
1495 If you want to debug problems which hang or crash the kernel early
1496 on boot and the crashing machine has a FireWire port, you can use
1497 this feature to remotely access the memory of the crashed machine
1498 over FireWire. This employs remote DMA as part of the OHCI1394
1499 specification which is now the standard for FireWire controllers.
1501 With remote DMA, you can monitor the printk buffer remotely using
1502 firescope and access all memory below 4GB using fireproxy from gdb.
1503 Even controlling a kernel debugger is possible using remote DMA.
1507 If ohci1394_dma=early is used as boot parameter, it will initialize
1508 all OHCI1394 controllers which are found in the PCI config space.
1510 As all changes to the FireWire bus such as enabling and disabling
1511 devices cause a bus reset and thereby disable remote DMA for all
1512 devices, be sure to have the cable plugged and FireWire enabled on
1513 the debugging host before booting the debug target for debugging.
1515 This code (~1k) is freed after boot. By then, the firewire stack
1516 in charge of the OHCI-1394 controllers should be used instead.
1518 See Documentation/core-api/debugging-via-ohci1394.rst for more information.
1520 source "samples/Kconfig"
1522 config ARCH_HAS_DEVMEM_IS_ALLOWED
1525 config STRICT_DEVMEM
1526 bool "Filter access to /dev/mem"
1527 depends on MMU && DEVMEM
1528 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
1529 default y if PPC || X86 || ARM64
1531 If this option is disabled, you allow userspace (root) access to all
1532 of memory, including kernel and userspace memory. Accidental
1533 access to this is obviously disastrous, but specific access can
1534 be used by people debugging the kernel. Note that with PAT support
1535 enabled, even in this case there are restrictions on /dev/mem
1536 use due to the cache aliasing requirements.
1538 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
1539 file only allows userspace access to PCI space and the BIOS code and
1540 data regions. This is sufficient for dosemu and X and all common
1545 config IO_STRICT_DEVMEM
1546 bool "Filter I/O access to /dev/mem"
1547 depends on STRICT_DEVMEM
1549 If this option is disabled, you allow userspace (root) access to all
1550 io-memory regardless of whether a driver is actively using that
1551 range. Accidental access to this is obviously disastrous, but
1552 specific access can be used by people debugging kernel drivers.
1554 If this option is switched on, the /dev/mem file only allows
1555 userspace access to *idle* io-memory ranges (see /proc/iomem) This
1556 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
1557 if the driver using a given range cannot be disabled.
1561 menu "$(SRCARCH) Debugging"
1563 source "arch/$(SRCARCH)/Kconfig.debug"
1567 menu "Kernel Testing and Coverage"
1569 source "lib/kunit/Kconfig"
1571 config NOTIFIER_ERROR_INJECTION
1572 tristate "Notifier error injection"
1573 depends on DEBUG_KERNEL
1576 This option provides the ability to inject artificial errors to
1577 specified notifier chain callbacks. It is useful to test the error
1578 handling of notifier call chain failures.
1582 config PM_NOTIFIER_ERROR_INJECT
1583 tristate "PM notifier error injection module"
1584 depends on PM && NOTIFIER_ERROR_INJECTION
1585 default m if PM_DEBUG
1587 This option provides the ability to inject artificial errors to
1588 PM notifier chain callbacks. It is controlled through debugfs
1589 interface /sys/kernel/debug/notifier-error-inject/pm
1591 If the notifier call chain should be failed with some events
1592 notified, write the error code to "actions/<notifier event>/error".
1594 Example: Inject PM suspend error (-12 = -ENOMEM)
1596 # cd /sys/kernel/debug/notifier-error-inject/pm/
1597 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1598 # echo mem > /sys/power/state
1599 bash: echo: write error: Cannot allocate memory
1601 To compile this code as a module, choose M here: the module will
1602 be called pm-notifier-error-inject.
1606 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1607 tristate "OF reconfig notifier error injection module"
1608 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1610 This option provides the ability to inject artificial errors to
1611 OF reconfig notifier chain callbacks. It is controlled
1612 through debugfs interface under
1613 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1615 If the notifier call chain should be failed with some events
1616 notified, write the error code to "actions/<notifier event>/error".
1618 To compile this code as a module, choose M here: the module will
1619 be called of-reconfig-notifier-error-inject.
1623 config NETDEV_NOTIFIER_ERROR_INJECT
1624 tristate "Netdev notifier error injection module"
1625 depends on NET && NOTIFIER_ERROR_INJECTION
1627 This option provides the ability to inject artificial errors to
1628 netdevice notifier chain callbacks. It is controlled through debugfs
1629 interface /sys/kernel/debug/notifier-error-inject/netdev
1631 If the notifier call chain should be failed with some events
1632 notified, write the error code to "actions/<notifier event>/error".
1634 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1636 # cd /sys/kernel/debug/notifier-error-inject/netdev
1637 # echo -22 > actions/NETDEV_CHANGEMTU/error
1638 # ip link set eth0 mtu 1024
1639 RTNETLINK answers: Invalid argument
1641 To compile this code as a module, choose M here: the module will
1642 be called netdev-notifier-error-inject.
1646 config FUNCTION_ERROR_INJECTION
1648 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
1650 config FAULT_INJECTION
1651 bool "Fault-injection framework"
1652 depends on DEBUG_KERNEL
1654 Provide fault-injection framework.
1655 For more details, see Documentation/fault-injection/.
1658 bool "Fault-injection capability for kmalloc"
1659 depends on FAULT_INJECTION
1660 depends on SLAB || SLUB
1662 Provide fault-injection capability for kmalloc.
1664 config FAIL_PAGE_ALLOC
1665 bool "Fault-injection capability for alloc_pages()"
1666 depends on FAULT_INJECTION
1668 Provide fault-injection capability for alloc_pages().
1670 config FAIL_MAKE_REQUEST
1671 bool "Fault-injection capability for disk IO"
1672 depends on FAULT_INJECTION && BLOCK
1674 Provide fault-injection capability for disk IO.
1676 config FAIL_IO_TIMEOUT
1677 bool "Fault-injection capability for faking disk interrupts"
1678 depends on FAULT_INJECTION && BLOCK
1680 Provide fault-injection capability on end IO handling. This
1681 will make the block layer "forget" an interrupt as configured,
1682 thus exercising the error handling.
1684 Only works with drivers that use the generic timeout handling,
1685 for others it wont do anything.
1688 bool "Fault-injection capability for futexes"
1690 depends on FAULT_INJECTION && FUTEX
1692 Provide fault-injection capability for futexes.
1694 config FAULT_INJECTION_DEBUG_FS
1695 bool "Debugfs entries for fault-injection capabilities"
1696 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1698 Enable configuration of fault-injection capabilities via debugfs.
1700 config FAIL_FUNCTION
1701 bool "Fault-injection capability for functions"
1702 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
1704 Provide function-based fault-injection capability.
1705 This will allow you to override a specific function with a return
1706 with given return value. As a result, function caller will see
1707 an error value and have to handle it. This is useful to test the
1708 error handling in various subsystems.
1710 config FAIL_MMC_REQUEST
1711 bool "Fault-injection capability for MMC IO"
1712 depends on FAULT_INJECTION_DEBUG_FS && MMC
1714 Provide fault-injection capability for MMC IO.
1715 This will make the mmc core return data errors. This is
1716 useful to test the error handling in the mmc block device
1717 and to test how the mmc host driver handles retries from
1720 config FAULT_INJECTION_STACKTRACE_FILTER
1721 bool "stacktrace filter for fault-injection capabilities"
1722 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1725 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1727 Provide stacktrace filter for fault-injection capabilities
1729 config ARCH_HAS_KCOV
1732 An architecture should select this when it can successfully
1733 build and run with CONFIG_KCOV. This typically requires
1734 disabling instrumentation for some early boot code.
1736 config CC_HAS_SANCOV_TRACE_PC
1737 def_bool $(cc-option,-fsanitize-coverage=trace-pc)
1741 bool "Code coverage for fuzzing"
1742 depends on ARCH_HAS_KCOV
1743 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
1745 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
1747 KCOV exposes kernel code coverage information in a form suitable
1748 for coverage-guided fuzzing (randomized testing).
1750 If RANDOMIZE_BASE is enabled, PC values will not be stable across
1751 different machines and across reboots. If you need stable PC values,
1752 disable RANDOMIZE_BASE.
1754 For more details, see Documentation/dev-tools/kcov.rst.
1756 config KCOV_ENABLE_COMPARISONS
1757 bool "Enable comparison operands collection by KCOV"
1759 depends on $(cc-option,-fsanitize-coverage=trace-cmp)
1761 KCOV also exposes operands of every comparison in the instrumented
1762 code along with operand sizes and PCs of the comparison instructions.
1763 These operands can be used by fuzzing engines to improve the quality
1764 of fuzzing coverage.
1766 config KCOV_INSTRUMENT_ALL
1767 bool "Instrument all code by default"
1771 If you are doing generic system call fuzzing (like e.g. syzkaller),
1772 then you will want to instrument the whole kernel and you should
1773 say y here. If you are doing more targeted fuzzing (like e.g.
1774 filesystem fuzzing with AFL) then you will want to enable coverage
1775 for more specific subsets of files, and should say n here.
1777 menuconfig RUNTIME_TESTING_MENU
1778 bool "Runtime Testing"
1781 if RUNTIME_TESTING_MENU
1784 tristate "Linux Kernel Dump Test Tool Module"
1787 This module enables testing of the different dumping mechanisms by
1788 inducing system failures at predefined crash points.
1789 If you don't need it: say N
1790 Choose M here to compile this code as a module. The module will be
1793 Documentation on how to use the module can be found in
1794 Documentation/fault-injection/provoke-crashes.rst
1796 config TEST_LIST_SORT
1797 tristate "Linked list sorting test"
1798 depends on DEBUG_KERNEL || m
1800 Enable this to turn on 'list_sort()' function test. This test is
1801 executed only once during system boot (so affects only boot time),
1802 or at module load time.
1806 config TEST_MIN_HEAP
1807 tristate "Min heap test"
1808 depends on DEBUG_KERNEL || m
1810 Enable this to turn on min heap function tests. This test is
1811 executed only once during system boot (so affects only boot time),
1812 or at module load time.
1817 tristate "Array-based sort test"
1818 depends on DEBUG_KERNEL || m
1820 This option enables the self-test function of 'sort()' at boot,
1821 or at module load time.
1825 config KPROBES_SANITY_TEST
1826 bool "Kprobes sanity tests"
1827 depends on DEBUG_KERNEL
1830 This option provides for testing basic kprobes functionality on
1831 boot. Samples of kprobe and kretprobe are inserted and
1832 verified for functionality.
1834 Say N if you are unsure.
1836 config BACKTRACE_SELF_TEST
1837 tristate "Self test for the backtrace code"
1838 depends on DEBUG_KERNEL
1840 This option provides a kernel module that can be used to test
1841 the kernel stack backtrace code. This option is not useful
1842 for distributions or general kernels, but only for kernel
1843 developers working on architecture code.
1845 Note that if you want to also test saved backtraces, you will
1846 have to enable STACKTRACE as well.
1848 Say N if you are unsure.
1851 tristate "Red-Black tree test"
1852 depends on DEBUG_KERNEL
1854 A benchmark measuring the performance of the rbtree library.
1855 Also includes rbtree invariant checks.
1857 config REED_SOLOMON_TEST
1858 tristate "Reed-Solomon library test"
1859 depends on DEBUG_KERNEL || m
1861 select REED_SOLOMON_ENC16
1862 select REED_SOLOMON_DEC16
1864 This option enables the self-test function of rslib at boot,
1865 or at module load time.
1869 config INTERVAL_TREE_TEST
1870 tristate "Interval tree test"
1871 depends on DEBUG_KERNEL
1872 select INTERVAL_TREE
1874 A benchmark measuring the performance of the interval tree library
1877 tristate "Per cpu operations test"
1878 depends on m && DEBUG_KERNEL
1880 Enable this option to build test module which validates per-cpu
1885 config ATOMIC64_SELFTEST
1886 tristate "Perform an atomic64_t self-test"
1888 Enable this option to test the atomic64_t functions at boot or
1889 at module load time.
1893 config ASYNC_RAID6_TEST
1894 tristate "Self test for hardware accelerated raid6 recovery"
1895 depends on ASYNC_RAID6_RECOV
1898 This is a one-shot self test that permutes through the
1899 recovery of all the possible two disk failure scenarios for a
1900 N-disk array. Recovery is performed with the asynchronous
1901 raid6 recovery routines, and will optionally use an offload
1902 engine if one is available.
1907 tristate "Test functions located in the hexdump module at runtime"
1909 config TEST_STRING_HELPERS
1910 tristate "Test functions located in the string_helpers module at runtime"
1913 tristate "Test strscpy*() family of functions at runtime"
1916 tristate "Test kstrto*() family of functions at runtime"
1919 tristate "Test printf() family of functions at runtime"
1922 tristate "Test bitmap_*() family of functions at runtime"
1924 Enable this option to test the bitmap functions at boot.
1928 config TEST_BITFIELD
1929 tristate "Test bitfield functions at runtime"
1931 Enable this option to test the bitfield functions at boot.
1936 tristate "Test functions located in the uuid module at runtime"
1939 tristate "Test the XArray code at runtime"
1941 config TEST_OVERFLOW
1942 tristate "Test check_*_overflow() functions at runtime"
1944 config TEST_RHASHTABLE
1945 tristate "Perform selftest on resizable hash table"
1947 Enable this option to test the rhashtable functions at boot.
1952 tristate "Perform selftest on hash functions"
1954 Enable this option to test the kernel's integer (<linux/hash.h>),
1955 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1956 hash functions on boot (or module load).
1958 This is intended to help people writing architecture-specific
1959 optimized versions. If unsure, say N.
1962 tristate "Perform selftest on IDA functions"
1965 tristate "Perform selftest on priority array manager"
1968 Enable this option to test priority array manager on boot
1973 config TEST_IRQ_TIMINGS
1974 bool "IRQ timings selftest"
1975 depends on IRQ_TIMINGS
1977 Enable this option to test the irq timings code on boot.
1982 tristate "Test module loading with 'hello world' module"
1985 This builds the "test_module" module that emits "Hello, world"
1986 on printk when loaded. It is designed to be used for basic
1987 evaluation of the module loading subsystem (for example when
1988 validating module verification). It lacks any extra dependencies,
1989 and will not normally be loaded by the system unless explicitly
1995 tristate "Test module for stress/performance analysis of vmalloc allocator"
2000 This builds the "test_vmalloc" module that should be used for
2001 stress and performance analysis. So, any new change for vmalloc
2002 subsystem can be evaluated from performance and stability point
2007 config TEST_USER_COPY
2008 tristate "Test user/kernel boundary protections"
2011 This builds the "test_user_copy" module that runs sanity checks
2012 on the copy_to/from_user infrastructure, making sure basic
2013 user/kernel boundary testing is working. If it fails to load,
2014 a regression has been detected in the user/kernel memory boundary
2020 tristate "Test BPF filter functionality"
2023 This builds the "test_bpf" module that runs various test vectors
2024 against the BPF interpreter or BPF JIT compiler depending on the
2025 current setting. This is in particular useful for BPF JIT compiler
2026 development, but also to run regression tests against changes in
2027 the interpreter code. It also enables test stubs for eBPF maps and
2028 verifier used by user space verifier testsuite.
2032 config TEST_BLACKHOLE_DEV
2033 tristate "Test blackhole netdev functionality"
2036 This builds the "test_blackhole_dev" module that validates the
2037 data path through this blackhole netdev.
2041 config FIND_BIT_BENCHMARK
2042 tristate "Test find_bit functions"
2044 This builds the "test_find_bit" module that measure find_*_bit()
2045 functions performance.
2049 config TEST_FIRMWARE
2050 tristate "Test firmware loading via userspace interface"
2051 depends on FW_LOADER
2053 This builds the "test_firmware" module that creates a userspace
2054 interface for testing firmware loading. This can be used to
2055 control the triggering of firmware loading without needing an
2056 actual firmware-using device. The contents can be rechecked by
2062 tristate "sysctl test driver"
2063 depends on PROC_SYSCTL
2065 This builds the "test_sysctl" module. This driver enables to test the
2066 proc sysctl interfaces available to drivers safely without affecting
2067 production knobs which might alter system functionality.
2071 config SYSCTL_KUNIT_TEST
2072 tristate "KUnit test for sysctl"
2075 This builds the proc sysctl unit test, which runs on boot.
2076 Tests the API contract and implementation correctness of sysctl.
2077 For more information on KUnit and unit tests in general please refer
2078 to the KUnit documentation in Documentation/dev-tools/kunit/.
2082 config LIST_KUNIT_TEST
2083 tristate "KUnit Test for Kernel Linked-list structures"
2086 This builds the linked list KUnit test suite.
2087 It tests that the API and basic functionality of the list_head type
2088 and associated macros.
2090 KUnit tests run during boot and output the results to the debug log
2091 in TAP format (http://testanything.org/). Only useful for kernel devs
2092 running the KUnit test harness, and not intended for inclusion into a
2095 For more information on KUnit and unit tests in general please refer
2096 to the KUnit documentation in Documentation/dev-tools/kunit/.
2100 config LINEAR_RANGES_TEST
2101 tristate "KUnit test for linear_ranges"
2103 select LINEAR_RANGES
2105 This builds the linear_ranges unit test, which runs on boot.
2106 Tests the linear_ranges logic correctness.
2107 For more information on KUnit and unit tests in general please refer
2108 to the KUnit documentation in Documentation/dev-tools/kunit/.
2113 tristate "udelay test driver"
2115 This builds the "udelay_test" module that helps to make sure
2116 that udelay() is working properly.
2120 config TEST_STATIC_KEYS
2121 tristate "Test static keys"
2124 Test the static key interfaces.
2129 tristate "kmod stress tester"
2131 depends on NETDEVICES && NET_CORE && INET # for TUN
2138 Test the kernel's module loading mechanism: kmod. kmod implements
2139 support to load modules using the Linux kernel's usermode helper.
2140 This test provides a series of tests against kmod.
2142 Although technically you can either build test_kmod as a module or
2143 into the kernel we disallow building it into the kernel since
2144 it stress tests request_module() and this will very likely cause
2145 some issues by taking over precious threads available from other
2146 module load requests, ultimately this could be fatal.
2150 tools/testing/selftests/kmod/kmod.sh --help
2154 config TEST_DEBUG_VIRTUAL
2155 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
2156 depends on DEBUG_VIRTUAL
2158 Test the kernel's ability to detect incorrect calls to
2159 virt_to_phys() done against the non-linear part of the
2160 kernel's virtual address map.
2164 config TEST_MEMCAT_P
2165 tristate "Test memcat_p() helper function"
2167 Test the memcat_p() helper for correctly merging two
2168 pointer arrays together.
2172 config TEST_LIVEPATCH
2173 tristate "Test livepatching"
2175 depends on DYNAMIC_DEBUG
2176 depends on LIVEPATCH
2179 Test kernel livepatching features for correctness. The tests will
2180 load test modules that will be livepatched in various scenarios.
2182 To run all the livepatching tests:
2184 make -C tools/testing/selftests TARGETS=livepatch run_tests
2186 Alternatively, individual tests may be invoked:
2188 tools/testing/selftests/livepatch/test-callbacks.sh
2189 tools/testing/selftests/livepatch/test-livepatch.sh
2190 tools/testing/selftests/livepatch/test-shadow-vars.sh
2195 tristate "Perform selftest on object aggreration manager"
2199 Enable this option to test object aggregation manager on boot
2203 config TEST_STACKINIT
2204 tristate "Test level of stack variable initialization"
2206 Test if the kernel is zero-initializing stack variables and
2207 padding. Coverage is controlled by compiler flags,
2208 CONFIG_GCC_PLUGIN_STRUCTLEAK, CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF,
2209 or CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL.
2214 tristate "Test heap/page initialization"
2216 Test if the kernel is zero-initializing heap and page allocations.
2217 This can be useful to test init_on_alloc and init_on_free features.
2221 endif # RUNTIME_TESTING_MENU
2226 This option adds a kernel parameter 'memtest', which allows memtest
2228 memtest=0, mean disabled; -- default
2229 memtest=1, mean do 1 test pattern;
2231 memtest=17, mean do 17 test patterns.
2232 If you are unsure how to answer this question, answer N.
2236 config HYPERV_TESTING
2237 bool "Microsoft Hyper-V driver testing"
2239 depends on HYPERV && DEBUG_FS
2241 Select this option to enable Hyper-V vmbus testing.
2243 endmenu # "Kernel Testing and Coverage"
2245 endmenu # Kernel hacking