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"
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. Thus, the debugfs
120 filesystem must first be mounted before making use of this feature.
121 We refer the control file as: <debugfs>/dynamic_debug/control. This
122 file contains a list of the debug statements that can be enabled. The
123 format for each line of the file is:
125 filename:lineno [module]function flags format
127 filename : source file of the debug statement
128 lineno : line number of the debug statement
129 module : module that contains the debug statement
130 function : function that contains the debug statement
131 flags : '=p' means the line is turned 'on' for printing
132 format : the format used for the debug statement
136 nullarbor:~ # cat <debugfs>/dynamic_debug/control
137 # filename:lineno [module]function flags format
138 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
139 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
140 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
144 // enable the message at line 1603 of file svcsock.c
145 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
146 <debugfs>/dynamic_debug/control
148 // enable all the messages in file svcsock.c
149 nullarbor:~ # echo -n 'file svcsock.c +p' >
150 <debugfs>/dynamic_debug/control
152 // enable all the messages in the NFS server module
153 nullarbor:~ # echo -n 'module nfsd +p' >
154 <debugfs>/dynamic_debug/control
156 // enable all 12 messages in the function svc_process()
157 nullarbor:~ # echo -n 'func svc_process +p' >
158 <debugfs>/dynamic_debug/control
160 // disable all 12 messages in the function svc_process()
161 nullarbor:~ # echo -n 'func svc_process -p' >
162 <debugfs>/dynamic_debug/control
164 See Documentation/admin-guide/dynamic-debug-howto.rst for additional
167 config SYMBOLIC_ERRNAME
168 bool "Support symbolic error names in printf"
171 If you say Y here, the kernel's printf implementation will
172 be able to print symbolic error names such as ENOSPC instead
173 of the number 28. It makes the kernel image slightly larger
174 (about 3KB), but can make the kernel logs easier to read.
176 config DEBUG_BUGVERBOSE
177 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
178 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
181 Say Y here to make BUG() panics output the file name and line number
182 of the BUG call as well as the EIP and oops trace. This aids
183 debugging but costs about 70-100K of memory.
185 endmenu # "printk and dmesg options"
187 menu "Compile-time checks and compiler options"
190 bool "Compile the kernel with debug info"
191 depends on DEBUG_KERNEL && !COMPILE_TEST
193 If you say Y here the resulting kernel image will include
194 debugging info resulting in a larger kernel image.
195 This adds debug symbols to the kernel and modules (gcc -g), and
196 is needed if you intend to use kernel crashdump or binary object
197 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
198 Say Y here only if you plan to debug the kernel.
202 config DEBUG_INFO_REDUCED
203 bool "Reduce debugging information"
204 depends on DEBUG_INFO
206 If you say Y here gcc is instructed to generate less debugging
207 information for structure types. This means that tools that
208 need full debugging information (like kgdb or systemtap) won't
209 be happy. But if you merely need debugging information to
210 resolve line numbers there is no loss. Advantage is that
211 build directory object sizes shrink dramatically over a full
212 DEBUG_INFO build and compile times are reduced too.
213 Only works with newer gcc versions.
215 config DEBUG_INFO_SPLIT
216 bool "Produce split debuginfo in .dwo files"
217 depends on DEBUG_INFO
218 depends on $(cc-option,-gsplit-dwarf)
220 Generate debug info into separate .dwo files. This significantly
221 reduces the build directory size for builds with DEBUG_INFO,
222 because it stores the information only once on disk in .dwo
223 files instead of multiple times in object files and executables.
224 In addition the debug information is also compressed.
226 Requires recent gcc (4.7+) and recent gdb/binutils.
227 Any tool that packages or reads debug information would need
228 to know about the .dwo files and include them.
229 Incompatible with older versions of ccache.
231 config DEBUG_INFO_DWARF4
232 bool "Generate dwarf4 debuginfo"
233 depends on DEBUG_INFO
234 depends on $(cc-option,-gdwarf-4)
236 Generate dwarf4 debug info. This requires recent versions
237 of gcc and gdb. It makes the debug information larger.
238 But it significantly improves the success of resolving
239 variables in gdb on optimized code.
241 config DEBUG_INFO_BTF
242 bool "Generate BTF typeinfo"
243 depends on DEBUG_INFO
245 Generate deduplicated BTF type information from DWARF debug info.
246 Turning this on expects presence of pahole tool, which will convert
247 DWARF type info into equivalent deduplicated BTF type info.
250 bool "Provide GDB scripts for kernel debugging"
251 depends on DEBUG_INFO
253 This creates the required links to GDB helper scripts in the
254 build directory. If you load vmlinux into gdb, the helper
255 scripts will be automatically imported by gdb as well, and
256 additional functions are available to analyze a Linux kernel
257 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
260 config ENABLE_MUST_CHECK
261 bool "Enable __must_check logic"
264 Enable the __must_check logic in the kernel build. Disable this to
265 suppress the "warning: ignoring return value of 'foo', declared with
266 attribute warn_unused_result" messages.
269 int "Warn for stack frames larger than"
271 default 2048 if GCC_PLUGIN_LATENT_ENTROPY
272 default 1280 if (!64BIT && PARISC)
273 default 1024 if (!64BIT && !PARISC)
274 default 2048 if 64BIT
276 Tell gcc to warn at build time for stack frames larger than this.
277 Setting this too low will cause a lot of warnings.
278 Setting it to 0 disables the warning.
280 config STRIP_ASM_SYMS
281 bool "Strip assembler-generated symbols during link"
284 Strip internal assembler-generated symbols during a link (symbols
285 that look like '.Lxxx') so they don't pollute the output of
286 get_wchan() and suchlike.
289 bool "Generate readable assembler code"
290 depends on DEBUG_KERNEL
292 Disable some compiler optimizations that tend to generate human unreadable
293 assembler output. This may make the kernel slightly slower, but it helps
294 to keep kernel developers who have to stare a lot at assembler listings
297 config HEADERS_INSTALL
298 bool "Install uapi headers to usr/include"
301 This option will install uapi headers (headers exported to user-space)
302 into the usr/include directory for use during the kernel build.
303 This is unneeded for building the kernel itself, but needed for some
304 user-space program samples. It is also needed by some features such
305 as uapi header sanity checks.
307 config OPTIMIZE_INLINING
310 This option determines if the kernel forces gcc to inline the functions
311 developers have marked 'inline'. Doing so takes away freedom from gcc to
312 do what it thinks is best, which is desirable for the gcc 3.x series of
313 compilers. The gcc 4.x series have a rewritten inlining algorithm and
314 enabling this option will generate a smaller kernel there. Hopefully
315 this algorithm is so good that allowing gcc 4.x and above to make the
316 decision will become the default in the future. Until then this option
317 is there to test gcc for this.
319 config DEBUG_SECTION_MISMATCH
320 bool "Enable full Section mismatch analysis"
322 The section mismatch analysis checks if there are illegal
323 references from one section to another section.
324 During linktime or runtime, some sections are dropped;
325 any use of code/data previously in these sections would
326 most likely result in an oops.
327 In the code, functions and variables are annotated with
328 __init,, etc. (see the full list in include/linux/init.h),
329 which results in the code/data being placed in specific sections.
330 The section mismatch analysis is always performed after a full
331 kernel build, and enabling this option causes the following
332 additional step to occur:
333 - Add the option -fno-inline-functions-called-once to gcc commands.
334 When inlining a function annotated with __init in a non-init
335 function, we would lose the section information and thus
336 the analysis would not catch the illegal reference.
337 This option tells gcc to inline less (but it does result in
340 config SECTION_MISMATCH_WARN_ONLY
341 bool "Make section mismatch errors non-fatal"
344 If you say N here, the build process will fail if there are any
345 section mismatch, instead of just throwing warnings.
350 # Select this config option from the architecture Kconfig, if it
351 # is preferred to always offer frame pointers as a config
352 # option on the architecture (regardless of KERNEL_DEBUG):
354 config ARCH_WANT_FRAME_POINTERS
358 bool "Compile the kernel with frame pointers"
359 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS
360 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
362 If you say Y here the resulting kernel image will be slightly
363 larger and slower, but it gives very useful debugging information
364 in case of kernel bugs. (precise oopses/stacktraces/warnings)
366 config STACK_VALIDATION
367 bool "Compile-time stack metadata validation"
368 depends on HAVE_STACK_VALIDATION
371 Add compile-time checks to validate stack metadata, including frame
372 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
373 that runtime stack traces are more reliable.
375 This is also a prerequisite for generation of ORC unwind data, which
376 is needed for CONFIG_UNWINDER_ORC.
378 For more information, see
379 tools/objtool/Documentation/stack-validation.txt.
381 config DEBUG_FORCE_WEAK_PER_CPU
382 bool "Force weak per-cpu definitions"
383 depends on DEBUG_KERNEL
385 s390 and alpha require percpu variables in modules to be
386 defined weak to work around addressing range issue which
387 puts the following two restrictions on percpu variable
390 1. percpu symbols must be unique whether static or not
391 2. percpu variables can't be defined inside a function
393 To ensure that generic code follows the above rules, this
394 option forces all percpu variables to be defined as weak.
396 endmenu # "Compiler options"
398 menu "Generic Kernel Debugging Instruments"
401 bool "Magic SysRq key"
404 If you say Y here, you will have some control over the system even
405 if the system crashes for example during kernel debugging (e.g., you
406 will be able to flush the buffer cache to disk, reboot the system
407 immediately or dump some status information). This is accomplished
408 by pressing various keys while holding SysRq (Alt+PrintScreen). It
409 also works on a serial console (on PC hardware at least), if you
410 send a BREAK and then within 5 seconds a command keypress. The
411 keys are documented in <file:Documentation/admin-guide/sysrq.rst>.
412 Don't say Y unless you really know what this hack does.
414 config MAGIC_SYSRQ_DEFAULT_ENABLE
415 hex "Enable magic SysRq key functions by default"
416 depends on MAGIC_SYSRQ
419 Specifies which SysRq key functions are enabled by default.
420 This may be set to 1 or 0 to enable or disable them all, or
421 to a bitmask as described in Documentation/admin-guide/sysrq.rst.
423 config MAGIC_SYSRQ_SERIAL
424 bool "Enable magic SysRq key over serial"
425 depends on MAGIC_SYSRQ
428 Many embedded boards have a disconnected TTL level serial which can
429 generate some garbage that can lead to spurious false sysrq detects.
430 This option allows you to decide whether you want to enable the
433 config MAGIC_SYSRQ_SERIAL_SEQUENCE
434 string "Char sequence that enables magic SysRq over serial"
435 depends on MAGIC_SYSRQ_SERIAL
438 Specifies a sequence of characters that can follow BREAK to enable
439 SysRq on a serial console.
441 If unsure, leave an empty string and the option will not be enabled.
444 bool "Debug Filesystem"
446 debugfs is a virtual file system that kernel developers use to put
447 debugging files into. Enable this option to be able to read and
448 write to these files.
450 For detailed documentation on the debugfs API, see
451 Documentation/filesystems/.
455 source "lib/Kconfig.kgdb"
457 source "lib/Kconfig.ubsan"
462 bool "Kernel debugging"
464 Say Y here if you are developing drivers or trying to debug and
465 identify kernel problems.
468 bool "Miscellaneous debug code"
470 depends on DEBUG_KERNEL
472 Say Y here if you need to enable miscellaneous debug code that should
473 be under a more specific debug option but isn't.
476 menu "Memory Debugging"
478 source "mm/Kconfig.debug"
481 bool "Debug object operations"
482 depends on DEBUG_KERNEL
484 If you say Y here, additional code will be inserted into the
485 kernel to track the life time of various objects and validate
486 the operations on those objects.
488 config DEBUG_OBJECTS_SELFTEST
489 bool "Debug objects selftest"
490 depends on DEBUG_OBJECTS
492 This enables the selftest of the object debug code.
494 config DEBUG_OBJECTS_FREE
495 bool "Debug objects in freed memory"
496 depends on DEBUG_OBJECTS
498 This enables checks whether a k/v free operation frees an area
499 which contains an object which has not been deactivated
500 properly. This can make kmalloc/kfree-intensive workloads
503 config DEBUG_OBJECTS_TIMERS
504 bool "Debug timer objects"
505 depends on DEBUG_OBJECTS
507 If you say Y here, additional code will be inserted into the
508 timer routines to track the life time of timer objects and
509 validate the timer operations.
511 config DEBUG_OBJECTS_WORK
512 bool "Debug work objects"
513 depends on DEBUG_OBJECTS
515 If you say Y here, additional code will be inserted into the
516 work queue routines to track the life time of work objects and
517 validate the work operations.
519 config DEBUG_OBJECTS_RCU_HEAD
520 bool "Debug RCU callbacks objects"
521 depends on DEBUG_OBJECTS
523 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
525 config DEBUG_OBJECTS_PERCPU_COUNTER
526 bool "Debug percpu counter objects"
527 depends on DEBUG_OBJECTS
529 If you say Y here, additional code will be inserted into the
530 percpu counter routines to track the life time of percpu counter
531 objects and validate the percpu counter operations.
533 config DEBUG_OBJECTS_ENABLE_DEFAULT
534 int "debug_objects bootup default value (0-1)"
537 depends on DEBUG_OBJECTS
539 Debug objects boot parameter default value
542 bool "Debug slab memory allocations"
543 depends on DEBUG_KERNEL && SLAB
545 Say Y here to have the kernel do limited verification on memory
546 allocation as well as poisoning memory on free to catch use of freed
547 memory. This can make kmalloc/kfree-intensive workloads much slower.
550 bool "SLUB debugging on by default"
551 depends on SLUB && SLUB_DEBUG
554 Boot with debugging on by default. SLUB boots by default with
555 the runtime debug capabilities switched off. Enabling this is
556 equivalent to specifying the "slub_debug" parameter on boot.
557 There is no support for more fine grained debug control like
558 possible with slub_debug=xxx. SLUB debugging may be switched
559 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
564 bool "Enable SLUB performance statistics"
565 depends on SLUB && SYSFS
567 SLUB statistics are useful to debug SLUBs allocation behavior in
568 order find ways to optimize the allocator. This should never be
569 enabled for production use since keeping statistics slows down
570 the allocator by a few percentage points. The slabinfo command
571 supports the determination of the most active slabs to figure
572 out which slabs are relevant to a particular load.
573 Try running: slabinfo -DA
575 config HAVE_DEBUG_KMEMLEAK
578 config DEBUG_KMEMLEAK
579 bool "Kernel memory leak detector"
580 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
582 select STACKTRACE if STACKTRACE_SUPPORT
586 Say Y here if you want to enable the memory leak
587 detector. The memory allocation/freeing is traced in a way
588 similar to the Boehm's conservative garbage collector, the
589 difference being that the orphan objects are not freed but
590 only shown in /sys/kernel/debug/kmemleak. Enabling this
591 feature will introduce an overhead to memory
592 allocations. See Documentation/dev-tools/kmemleak.rst for more
595 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
596 of finding leaks due to the slab objects poisoning.
598 In order to access the kmemleak file, debugfs needs to be
599 mounted (usually at /sys/kernel/debug).
601 config DEBUG_KMEMLEAK_MEM_POOL_SIZE
602 int "Kmemleak memory pool size"
603 depends on DEBUG_KMEMLEAK
607 Kmemleak must track all the memory allocations to avoid
608 reporting false positives. Since memory may be allocated or
609 freed before kmemleak is fully initialised, use a static pool
610 of metadata objects to track such callbacks. After kmemleak is
611 fully initialised, this memory pool acts as an emergency one
612 if slab allocations fail.
614 config DEBUG_KMEMLEAK_TEST
615 tristate "Simple test for the kernel memory leak detector"
616 depends on DEBUG_KMEMLEAK && m
618 This option enables a module that explicitly leaks memory.
622 config DEBUG_KMEMLEAK_DEFAULT_OFF
623 bool "Default kmemleak to off"
624 depends on DEBUG_KMEMLEAK
626 Say Y here to disable kmemleak by default. It can then be enabled
627 on the command line via kmemleak=on.
629 config DEBUG_KMEMLEAK_AUTO_SCAN
630 bool "Enable kmemleak auto scan thread on boot up"
632 depends on DEBUG_KMEMLEAK
634 Depending on the cpu, kmemleak scan may be cpu intensive and can
635 stall user tasks at times. This option enables/disables automatic
636 kmemleak scan at boot up.
638 Say N here to disable kmemleak auto scan thread to stop automatic
639 scanning. Disabling this option disables automatic reporting of
644 config DEBUG_STACK_USAGE
645 bool "Stack utilization instrumentation"
646 depends on DEBUG_KERNEL && !IA64
648 Enables the display of the minimum amount of free stack which each
649 task has ever had available in the sysrq-T and sysrq-P debug output.
651 This option will slow down process creation somewhat.
653 config SCHED_STACK_END_CHECK
654 bool "Detect stack corruption on calls to schedule()"
655 depends on DEBUG_KERNEL
658 This option checks for a stack overrun on calls to schedule().
659 If the stack end location is found to be over written always panic as
660 the content of the corrupted region can no longer be trusted.
661 This is to ensure no erroneous behaviour occurs which could result in
662 data corruption or a sporadic crash at a later stage once the region
663 is examined. The runtime overhead introduced is minimal.
667 depends on DEBUG_KERNEL
669 Enable this to turn on extended checks in the virtual-memory system
670 that may impact performance.
674 config DEBUG_VM_VMACACHE
675 bool "Debug VMA caching"
678 Enable this to turn on VMA caching debug information. Doing so
679 can cause significant overhead, so only enable it in non-production
685 bool "Debug VM red-black trees"
688 Enable VM red-black tree debugging information and extra validations.
692 config DEBUG_VM_PGFLAGS
693 bool "Debug page-flags operations"
696 Enables extra validation on page flags operations.
700 config ARCH_HAS_DEBUG_VIRTUAL
704 bool "Debug VM translations"
705 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
707 Enable some costly sanity checks in virtual to page code. This can
708 catch mistakes with virt_to_page() and friends.
712 config DEBUG_NOMMU_REGIONS
713 bool "Debug the global anon/private NOMMU mapping region tree"
714 depends on DEBUG_KERNEL && !MMU
716 This option causes the global tree of anonymous and private mapping
717 regions to be regularly checked for invalid topology.
719 config DEBUG_MEMORY_INIT
720 bool "Debug memory initialisation" if EXPERT
723 Enable this for additional checks during memory initialisation.
724 The sanity checks verify aspects of the VM such as the memory model
725 and other information provided by the architecture. Verbose
726 information will be printed at KERN_DEBUG loglevel depending
727 on the mminit_loglevel= command-line option.
731 config MEMORY_NOTIFIER_ERROR_INJECT
732 tristate "Memory hotplug notifier error injection module"
733 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
735 This option provides the ability to inject artificial errors to
736 memory hotplug notifier chain callbacks. It is controlled through
737 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
739 If the notifier call chain should be failed with some events
740 notified, write the error code to "actions/<notifier event>/error".
742 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
744 # cd /sys/kernel/debug/notifier-error-inject/memory
745 # echo -12 > actions/MEM_GOING_OFFLINE/error
746 # echo offline > /sys/devices/system/memory/memoryXXX/state
747 bash: echo: write error: Cannot allocate memory
749 To compile this code as a module, choose M here: the module will
750 be called memory-notifier-error-inject.
754 config DEBUG_PER_CPU_MAPS
755 bool "Debug access to per_cpu maps"
756 depends on DEBUG_KERNEL
759 Say Y to verify that the per_cpu map being accessed has
760 been set up. This adds a fair amount of code to kernel memory
761 and decreases performance.
766 bool "Highmem debugging"
767 depends on DEBUG_KERNEL && HIGHMEM
769 This option enables additional error checking for high memory
770 systems. Disable for production systems.
772 config HAVE_DEBUG_STACKOVERFLOW
775 config DEBUG_STACKOVERFLOW
776 bool "Check for stack overflows"
777 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
779 Say Y here if you want to check for overflows of kernel, IRQ
780 and exception stacks (if your architecture uses them). This
781 option will show detailed messages if free stack space drops
782 below a certain limit.
784 These kinds of bugs usually occur when call-chains in the
785 kernel get too deep, especially when interrupts are
788 Use this in cases where you see apparently random memory
789 corruption, especially if it appears in 'struct thread_info'
791 If in doubt, say "N".
793 source "lib/Kconfig.kasan"
795 endmenu # "Memory Debugging"
798 bool "Debug shared IRQ handlers"
799 depends on DEBUG_KERNEL
801 Enable this to generate a spurious interrupt as soon as a shared
802 interrupt handler is registered, and just before one is deregistered.
803 Drivers ought to be able to handle interrupts coming in at those
804 points; some don't and need to be caught.
806 menu "Debug Oops, Lockups and Hangs"
811 Say Y here to enable the kernel to panic when it oopses. This
812 has the same effect as setting oops=panic on the kernel command
815 This feature is useful to ensure that the kernel does not do
816 anything erroneous after an oops which could result in data
817 corruption or other issues.
821 config PANIC_ON_OOPS_VALUE
824 default 0 if !PANIC_ON_OOPS
825 default 1 if PANIC_ON_OOPS
831 Set the timeout value (in seconds) until a reboot occurs when the
832 the kernel panics. If n = 0, then we wait forever. A timeout
833 value n > 0 will wait n seconds before rebooting, while a timeout
834 value n < 0 will reboot immediately.
836 config LOCKUP_DETECTOR
839 config SOFTLOCKUP_DETECTOR
840 bool "Detect Soft Lockups"
841 depends on DEBUG_KERNEL && !S390
842 select LOCKUP_DETECTOR
844 Say Y here to enable the kernel to act as a watchdog to detect
847 Softlockups are bugs that cause the kernel to loop in kernel
848 mode for more than 20 seconds, without giving other tasks a
849 chance to run. The current stack trace is displayed upon
850 detection and the system will stay locked up.
852 config BOOTPARAM_SOFTLOCKUP_PANIC
853 bool "Panic (Reboot) On Soft Lockups"
854 depends on SOFTLOCKUP_DETECTOR
856 Say Y here to enable the kernel to panic on "soft lockups",
857 which are bugs that cause the kernel to loop in kernel
858 mode for more than 20 seconds (configurable using the watchdog_thresh
859 sysctl), without giving other tasks a chance to run.
861 The panic can be used in combination with panic_timeout,
862 to cause the system to reboot automatically after a
863 lockup has been detected. This feature is useful for
864 high-availability systems that have uptime guarantees and
865 where a lockup must be resolved ASAP.
869 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
871 depends on SOFTLOCKUP_DETECTOR
873 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
874 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
876 config HARDLOCKUP_DETECTOR_PERF
878 select SOFTLOCKUP_DETECTOR
881 # Enables a timestamp based low pass filter to compensate for perf based
882 # hard lockup detection which runs too fast due to turbo modes.
884 config HARDLOCKUP_CHECK_TIMESTAMP
888 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
889 # lockup detector rather than the perf based detector.
891 config HARDLOCKUP_DETECTOR
892 bool "Detect Hard Lockups"
893 depends on DEBUG_KERNEL && !S390
894 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
895 select LOCKUP_DETECTOR
896 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
897 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
899 Say Y here to enable the kernel to act as a watchdog to detect
902 Hardlockups are bugs that cause the CPU to loop in kernel mode
903 for more than 10 seconds, without letting other interrupts have a
904 chance to run. The current stack trace is displayed upon detection
905 and the system will stay locked up.
907 config BOOTPARAM_HARDLOCKUP_PANIC
908 bool "Panic (Reboot) On Hard Lockups"
909 depends on HARDLOCKUP_DETECTOR
911 Say Y here to enable the kernel to panic on "hard lockups",
912 which are bugs that cause the kernel to loop in kernel
913 mode with interrupts disabled for more than 10 seconds (configurable
914 using the watchdog_thresh sysctl).
918 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
920 depends on HARDLOCKUP_DETECTOR
922 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
923 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
925 config DETECT_HUNG_TASK
926 bool "Detect Hung Tasks"
927 depends on DEBUG_KERNEL
928 default SOFTLOCKUP_DETECTOR
930 Say Y here to enable the kernel to detect "hung tasks",
931 which are bugs that cause the task to be stuck in
932 uninterruptible "D" state indefinitely.
934 When a hung task is detected, the kernel will print the
935 current stack trace (which you should report), but the
936 task will stay in uninterruptible state. If lockdep is
937 enabled then all held locks will also be reported. This
938 feature has negligible overhead.
940 config DEFAULT_HUNG_TASK_TIMEOUT
941 int "Default timeout for hung task detection (in seconds)"
942 depends on DETECT_HUNG_TASK
945 This option controls the default timeout (in seconds) used
946 to determine when a task has become non-responsive and should
949 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
950 sysctl or by writing a value to
951 /proc/sys/kernel/hung_task_timeout_secs.
953 A timeout of 0 disables the check. The default is two minutes.
954 Keeping the default should be fine in most cases.
956 config BOOTPARAM_HUNG_TASK_PANIC
957 bool "Panic (Reboot) On Hung Tasks"
958 depends on DETECT_HUNG_TASK
960 Say Y here to enable the kernel to panic on "hung tasks",
961 which are bugs that cause the kernel to leave a task stuck
962 in uninterruptible "D" state.
964 The panic can be used in combination with panic_timeout,
965 to cause the system to reboot automatically after a
966 hung task has been detected. This feature is useful for
967 high-availability systems that have uptime guarantees and
968 where a hung tasks must be resolved ASAP.
972 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
974 depends on DETECT_HUNG_TASK
976 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
977 default 1 if BOOTPARAM_HUNG_TASK_PANIC
980 bool "Detect Workqueue Stalls"
981 depends on DEBUG_KERNEL
983 Say Y here to enable stall detection on workqueues. If a
984 worker pool doesn't make forward progress on a pending work
985 item for over a given amount of time, 30s by default, a
986 warning message is printed along with dump of workqueue
987 state. This can be configured through kernel parameter
988 "workqueue.watchdog_thresh" and its sysfs counterpart.
990 endmenu # "Debug lockups and hangs"
992 menu "Scheduler Debugging"
995 bool "Collect scheduler debugging info"
996 depends on DEBUG_KERNEL && PROC_FS
999 If you say Y here, the /proc/sched_debug file will be provided
1000 that can help debug the scheduler. The runtime overhead of this
1008 bool "Collect scheduler statistics"
1009 depends on DEBUG_KERNEL && PROC_FS
1012 If you say Y here, additional code will be inserted into the
1013 scheduler and related routines to collect statistics about
1014 scheduler behavior and provide them in /proc/schedstat. These
1015 stats may be useful for both tuning and debugging the scheduler
1016 If you aren't debugging the scheduler or trying to tune a specific
1017 application, you can say N to avoid the very slight overhead
1022 config DEBUG_TIMEKEEPING
1023 bool "Enable extra timekeeping sanity checking"
1025 This option will enable additional timekeeping sanity checks
1026 which may be helpful when diagnosing issues where timekeeping
1027 problems are suspected.
1029 This may include checks in the timekeeping hotpaths, so this
1030 option may have a (very small) performance impact to some
1035 config DEBUG_PREEMPT
1036 bool "Debug preemptible kernel"
1037 depends on DEBUG_KERNEL && PREEMPTION && TRACE_IRQFLAGS_SUPPORT
1040 If you say Y here then the kernel will use a debug variant of the
1041 commonly used smp_processor_id() function and will print warnings
1042 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1043 will detect preemption count underflows.
1045 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1047 config LOCK_DEBUGGING_SUPPORT
1049 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1052 config PROVE_LOCKING
1053 bool "Lock debugging: prove locking correctness"
1054 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1056 select DEBUG_SPINLOCK
1057 select DEBUG_MUTEXES
1058 select DEBUG_RT_MUTEXES if RT_MUTEXES
1060 select DEBUG_WW_MUTEX_SLOWPATH
1061 select DEBUG_LOCK_ALLOC
1062 select TRACE_IRQFLAGS
1065 This feature enables the kernel to prove that all locking
1066 that occurs in the kernel runtime is mathematically
1067 correct: that under no circumstance could an arbitrary (and
1068 not yet triggered) combination of observed locking
1069 sequences (on an arbitrary number of CPUs, running an
1070 arbitrary number of tasks and interrupt contexts) cause a
1073 In short, this feature enables the kernel to report locking
1074 related deadlocks before they actually occur.
1076 The proof does not depend on how hard and complex a
1077 deadlock scenario would be to trigger: how many
1078 participant CPUs, tasks and irq-contexts would be needed
1079 for it to trigger. The proof also does not depend on
1080 timing: if a race and a resulting deadlock is possible
1081 theoretically (no matter how unlikely the race scenario
1082 is), it will be proven so and will immediately be
1083 reported by the kernel (once the event is observed that
1084 makes the deadlock theoretically possible).
1086 If a deadlock is impossible (i.e. the locking rules, as
1087 observed by the kernel, are mathematically correct), the
1088 kernel reports nothing.
1090 NOTE: this feature can also be enabled for rwlocks, mutexes
1091 and rwsems - in which case all dependencies between these
1092 different locking variants are observed and mapped too, and
1093 the proof of observed correctness is also maintained for an
1094 arbitrary combination of these separate locking variants.
1096 For more details, see Documentation/locking/lockdep-design.rst.
1098 config PROVE_RAW_LOCK_NESTING
1099 bool "Enable raw_spinlock - spinlock nesting checks"
1100 depends on PROVE_LOCKING
1103 Enable the raw_spinlock vs. spinlock nesting checks which ensure
1104 that the lock nesting rules for PREEMPT_RT enabled kernels are
1107 NOTE: There are known nesting problems. So if you enable this
1108 option expect lockdep splats until these problems have been fully
1109 addressed which is work in progress. This config switch allows to
1110 identify and analyze these problems. It will be removed and the
1111 check permanentely enabled once the main issues have been fixed.
1113 If unsure, select N.
1116 bool "Lock usage statistics"
1117 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1119 select DEBUG_SPINLOCK
1120 select DEBUG_MUTEXES
1121 select DEBUG_RT_MUTEXES if RT_MUTEXES
1122 select DEBUG_LOCK_ALLOC
1125 This feature enables tracking lock contention points
1127 For more details, see Documentation/locking/lockstat.rst
1129 This also enables lock events required by "perf lock",
1131 If you want to use "perf lock", you also need to turn on
1132 CONFIG_EVENT_TRACING.
1134 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1135 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1137 config DEBUG_RT_MUTEXES
1138 bool "RT Mutex debugging, deadlock detection"
1139 depends on DEBUG_KERNEL && RT_MUTEXES
1141 This allows rt mutex semantics violations and rt mutex related
1142 deadlocks (lockups) to be detected and reported automatically.
1144 config DEBUG_SPINLOCK
1145 bool "Spinlock and rw-lock debugging: basic checks"
1146 depends on DEBUG_KERNEL
1147 select UNINLINE_SPIN_UNLOCK
1149 Say Y here and build SMP to catch missing spinlock initialization
1150 and certain other kinds of spinlock errors commonly made. This is
1151 best used in conjunction with the NMI watchdog so that spinlock
1152 deadlocks are also debuggable.
1154 config DEBUG_MUTEXES
1155 bool "Mutex debugging: basic checks"
1156 depends on DEBUG_KERNEL
1158 This feature allows mutex semantics violations to be detected and
1161 config DEBUG_WW_MUTEX_SLOWPATH
1162 bool "Wait/wound mutex debugging: Slowpath testing"
1163 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1164 select DEBUG_LOCK_ALLOC
1165 select DEBUG_SPINLOCK
1166 select DEBUG_MUTEXES
1168 This feature enables slowpath testing for w/w mutex users by
1169 injecting additional -EDEADLK wound/backoff cases. Together with
1170 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1171 will test all possible w/w mutex interface abuse with the
1172 exception of simply not acquiring all the required locks.
1173 Note that this feature can introduce significant overhead, so
1174 it really should not be enabled in a production or distro kernel,
1175 even a debug kernel. If you are a driver writer, enable it. If
1176 you are a distro, do not.
1179 bool "RW Semaphore debugging: basic checks"
1180 depends on DEBUG_KERNEL
1182 This debugging feature allows mismatched rw semaphore locks
1183 and unlocks to be detected and reported.
1185 config DEBUG_LOCK_ALLOC
1186 bool "Lock debugging: detect incorrect freeing of live locks"
1187 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1188 select DEBUG_SPINLOCK
1189 select DEBUG_MUTEXES
1190 select DEBUG_RT_MUTEXES if RT_MUTEXES
1193 This feature will check whether any held lock (spinlock, rwlock,
1194 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1195 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1196 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1197 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1198 held during task exit.
1202 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1204 select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86
1208 config LOCKDEP_SMALL
1211 config DEBUG_LOCKDEP
1212 bool "Lock dependency engine debugging"
1213 depends on DEBUG_KERNEL && LOCKDEP
1215 If you say Y here, the lock dependency engine will do
1216 additional runtime checks to debug itself, at the price
1217 of more runtime overhead.
1219 config DEBUG_ATOMIC_SLEEP
1220 bool "Sleep inside atomic section checking"
1221 select PREEMPT_COUNT
1222 depends on DEBUG_KERNEL
1223 depends on !ARCH_NO_PREEMPT
1225 If you say Y here, various routines which may sleep will become very
1226 noisy if they are called inside atomic sections: when a spinlock is
1227 held, inside an rcu read side critical section, inside preempt disabled
1228 sections, inside an interrupt, etc...
1230 config DEBUG_LOCKING_API_SELFTESTS
1231 bool "Locking API boot-time self-tests"
1232 depends on DEBUG_KERNEL
1234 Say Y here if you want the kernel to run a short self-test during
1235 bootup. The self-test checks whether common types of locking bugs
1236 are detected by debugging mechanisms or not. (if you disable
1237 lock debugging then those bugs wont be detected of course.)
1238 The following locking APIs are covered: spinlocks, rwlocks,
1241 config LOCK_TORTURE_TEST
1242 tristate "torture tests for locking"
1243 depends on DEBUG_KERNEL
1246 This option provides a kernel module that runs torture tests
1247 on kernel locking primitives. The kernel module may be built
1248 after the fact on the running kernel to be tested, if desired.
1250 Say Y here if you want kernel locking-primitive torture tests
1251 to be built into the kernel.
1252 Say M if you want these torture tests to build as a module.
1253 Say N if you are unsure.
1255 config WW_MUTEX_SELFTEST
1256 tristate "Wait/wound mutex selftests"
1258 This option provides a kernel module that runs tests on the
1259 on the struct ww_mutex locking API.
1261 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1262 with this test harness.
1264 Say M if you want these self tests to build as a module.
1265 Say N if you are unsure.
1267 endmenu # lock debugging
1269 config TRACE_IRQFLAGS
1272 Enables hooks to interrupt enabling and disabling for
1273 either tracing or lock debugging.
1276 bool "Stack backtrace support"
1277 depends on STACKTRACE_SUPPORT
1279 This option causes the kernel to create a /proc/pid/stack for
1280 every process, showing its current stack trace.
1281 It is also used by various kernel debugging features that require
1282 stack trace generation.
1284 config WARN_ALL_UNSEEDED_RANDOM
1285 bool "Warn for all uses of unseeded randomness"
1288 Some parts of the kernel contain bugs relating to their use of
1289 cryptographically secure random numbers before it's actually possible
1290 to generate those numbers securely. This setting ensures that these
1291 flaws don't go unnoticed, by enabling a message, should this ever
1292 occur. This will allow people with obscure setups to know when things
1293 are going wrong, so that they might contact developers about fixing
1296 Unfortunately, on some models of some architectures getting
1297 a fully seeded CRNG is extremely difficult, and so this can
1298 result in dmesg getting spammed for a surprisingly long
1299 time. This is really bad from a security perspective, and
1300 so architecture maintainers really need to do what they can
1301 to get the CRNG seeded sooner after the system is booted.
1302 However, since users cannot do anything actionable to
1303 address this, by default the kernel will issue only a single
1304 warning for the first use of unseeded randomness.
1306 Say Y here if you want to receive warnings for all uses of
1307 unseeded randomness. This will be of use primarily for
1308 those developers interested in improving the security of
1309 Linux kernels running on their architecture (or
1312 config DEBUG_KOBJECT
1313 bool "kobject debugging"
1314 depends on DEBUG_KERNEL
1316 If you say Y here, some extra kobject debugging messages will be sent
1319 config DEBUG_KOBJECT_RELEASE
1320 bool "kobject release debugging"
1321 depends on DEBUG_OBJECTS_TIMERS
1323 kobjects are reference counted objects. This means that their
1324 last reference count put is not predictable, and the kobject can
1325 live on past the point at which a driver decides to drop it's
1326 initial reference to the kobject gained on allocation. An
1327 example of this would be a struct device which has just been
1330 However, some buggy drivers assume that after such an operation,
1331 the memory backing the kobject can be immediately freed. This
1332 goes completely against the principles of a refcounted object.
1334 If you say Y here, the kernel will delay the release of kobjects
1335 on the last reference count to improve the visibility of this
1336 kind of kobject release bug.
1338 config HAVE_DEBUG_BUGVERBOSE
1341 menu "Debug kernel data structures"
1344 bool "Debug linked list manipulation"
1345 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1347 Enable this to turn on extended checks in the linked-list
1353 bool "Debug priority linked list manipulation"
1354 depends on DEBUG_KERNEL
1356 Enable this to turn on extended checks in the priority-ordered
1357 linked-list (plist) walking routines. This checks the entire
1358 list multiple times during each manipulation.
1363 bool "Debug SG table operations"
1364 depends on DEBUG_KERNEL
1366 Enable this to turn on checks on scatter-gather tables. This can
1367 help find problems with drivers that do not properly initialize
1372 config DEBUG_NOTIFIERS
1373 bool "Debug notifier call chains"
1374 depends on DEBUG_KERNEL
1376 Enable this to turn on sanity checking for notifier call chains.
1377 This is most useful for kernel developers to make sure that
1378 modules properly unregister themselves from notifier chains.
1379 This is a relatively cheap check but if you care about maximum
1382 config BUG_ON_DATA_CORRUPTION
1383 bool "Trigger a BUG when data corruption is detected"
1386 Select this option if the kernel should BUG when it encounters
1387 data corruption in kernel memory structures when they get checked
1394 config DEBUG_CREDENTIALS
1395 bool "Debug credential management"
1396 depends on DEBUG_KERNEL
1398 Enable this to turn on some debug checking for credential
1399 management. The additional code keeps track of the number of
1400 pointers from task_structs to any given cred struct, and checks to
1401 see that this number never exceeds the usage count of the cred
1404 Furthermore, if SELinux is enabled, this also checks that the
1405 security pointer in the cred struct is never seen to be invalid.
1409 source "kernel/rcu/Kconfig.debug"
1411 config DEBUG_WQ_FORCE_RR_CPU
1412 bool "Force round-robin CPU selection for unbound work items"
1413 depends on DEBUG_KERNEL
1416 Workqueue used to implicitly guarantee that work items queued
1417 without explicit CPU specified are put on the local CPU. This
1418 guarantee is no longer true and while local CPU is still
1419 preferred work items may be put on foreign CPUs. Kernel
1420 parameter "workqueue.debug_force_rr_cpu" is added to force
1421 round-robin CPU selection to flush out usages which depend on the
1422 now broken guarantee. This config option enables the debug
1423 feature by default. When enabled, memory and cache locality will
1426 config DEBUG_BLOCK_EXT_DEVT
1427 bool "Force extended block device numbers and spread them"
1428 depends on DEBUG_KERNEL
1432 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1433 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1434 YOU ARE DOING. Distros, please enable this and fix whatever
1437 Conventionally, block device numbers are allocated from
1438 predetermined contiguous area. However, extended block area
1439 may introduce non-contiguous block device numbers. This
1440 option forces most block device numbers to be allocated from
1441 the extended space and spreads them to discover kernel or
1442 userland code paths which assume predetermined contiguous
1443 device number allocation.
1445 Note that turning on this debug option shuffles all the
1446 device numbers for all IDE and SCSI devices including libata
1447 ones, so root partition specified using device number
1448 directly (via rdev or root=MAJ:MIN) won't work anymore.
1449 Textual device names (root=/dev/sdXn) will continue to work.
1451 Say N if you are unsure.
1453 config CPU_HOTPLUG_STATE_CONTROL
1454 bool "Enable CPU hotplug state control"
1455 depends on DEBUG_KERNEL
1456 depends on HOTPLUG_CPU
1459 Allows to write steps between "offline" and "online" to the CPUs
1460 sysfs target file so states can be stepped granular. This is a debug
1461 option for now as the hotplug machinery cannot be stopped and
1462 restarted at arbitrary points yet.
1464 Say N if your are unsure.
1467 bool "Latency measuring infrastructure"
1468 depends on DEBUG_KERNEL
1469 depends on STACKTRACE_SUPPORT
1471 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1478 Enable this option if you want to use the LatencyTOP tool
1479 to find out which userspace is blocking on what kernel operations.
1481 source "kernel/trace/Kconfig"
1483 config PROVIDE_OHCI1394_DMA_INIT
1484 bool "Remote debugging over FireWire early on boot"
1485 depends on PCI && X86
1487 If you want to debug problems which hang or crash the kernel early
1488 on boot and the crashing machine has a FireWire port, you can use
1489 this feature to remotely access the memory of the crashed machine
1490 over FireWire. This employs remote DMA as part of the OHCI1394
1491 specification which is now the standard for FireWire controllers.
1493 With remote DMA, you can monitor the printk buffer remotely using
1494 firescope and access all memory below 4GB using fireproxy from gdb.
1495 Even controlling a kernel debugger is possible using remote DMA.
1499 If ohci1394_dma=early is used as boot parameter, it will initialize
1500 all OHCI1394 controllers which are found in the PCI config space.
1502 As all changes to the FireWire bus such as enabling and disabling
1503 devices cause a bus reset and thereby disable remote DMA for all
1504 devices, be sure to have the cable plugged and FireWire enabled on
1505 the debugging host before booting the debug target for debugging.
1507 This code (~1k) is freed after boot. By then, the firewire stack
1508 in charge of the OHCI-1394 controllers should be used instead.
1510 See Documentation/debugging-via-ohci1394.txt for more information.
1512 source "samples/Kconfig"
1514 config ARCH_HAS_DEVMEM_IS_ALLOWED
1517 config STRICT_DEVMEM
1518 bool "Filter access to /dev/mem"
1519 depends on MMU && DEVMEM
1520 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
1521 default y if PPC || X86 || ARM64
1523 If this option is disabled, you allow userspace (root) access to all
1524 of memory, including kernel and userspace memory. Accidental
1525 access to this is obviously disastrous, but specific access can
1526 be used by people debugging the kernel. Note that with PAT support
1527 enabled, even in this case there are restrictions on /dev/mem
1528 use due to the cache aliasing requirements.
1530 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
1531 file only allows userspace access to PCI space and the BIOS code and
1532 data regions. This is sufficient for dosemu and X and all common
1537 config IO_STRICT_DEVMEM
1538 bool "Filter I/O access to /dev/mem"
1539 depends on STRICT_DEVMEM
1541 If this option is disabled, you allow userspace (root) access to all
1542 io-memory regardless of whether a driver is actively using that
1543 range. Accidental access to this is obviously disastrous, but
1544 specific access can be used by people debugging kernel drivers.
1546 If this option is switched on, the /dev/mem file only allows
1547 userspace access to *idle* io-memory ranges (see /proc/iomem) This
1548 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
1549 if the driver using a given range cannot be disabled.
1553 menu "$(SRCARCH) Debugging"
1555 source "arch/$(SRCARCH)/Kconfig.debug"
1559 menu "Kernel Testing and Coverage"
1561 source "lib/kunit/Kconfig"
1563 config NOTIFIER_ERROR_INJECTION
1564 tristate "Notifier error injection"
1565 depends on DEBUG_KERNEL
1568 This option provides the ability to inject artificial errors to
1569 specified notifier chain callbacks. It is useful to test the error
1570 handling of notifier call chain failures.
1574 config PM_NOTIFIER_ERROR_INJECT
1575 tristate "PM notifier error injection module"
1576 depends on PM && NOTIFIER_ERROR_INJECTION
1577 default m if PM_DEBUG
1579 This option provides the ability to inject artificial errors to
1580 PM notifier chain callbacks. It is controlled through debugfs
1581 interface /sys/kernel/debug/notifier-error-inject/pm
1583 If the notifier call chain should be failed with some events
1584 notified, write the error code to "actions/<notifier event>/error".
1586 Example: Inject PM suspend error (-12 = -ENOMEM)
1588 # cd /sys/kernel/debug/notifier-error-inject/pm/
1589 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1590 # echo mem > /sys/power/state
1591 bash: echo: write error: Cannot allocate memory
1593 To compile this code as a module, choose M here: the module will
1594 be called pm-notifier-error-inject.
1598 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1599 tristate "OF reconfig notifier error injection module"
1600 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1602 This option provides the ability to inject artificial errors to
1603 OF reconfig notifier chain callbacks. It is controlled
1604 through debugfs interface under
1605 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1607 If the notifier call chain should be failed with some events
1608 notified, write the error code to "actions/<notifier event>/error".
1610 To compile this code as a module, choose M here: the module will
1611 be called of-reconfig-notifier-error-inject.
1615 config NETDEV_NOTIFIER_ERROR_INJECT
1616 tristate "Netdev notifier error injection module"
1617 depends on NET && NOTIFIER_ERROR_INJECTION
1619 This option provides the ability to inject artificial errors to
1620 netdevice notifier chain callbacks. It is controlled through debugfs
1621 interface /sys/kernel/debug/notifier-error-inject/netdev
1623 If the notifier call chain should be failed with some events
1624 notified, write the error code to "actions/<notifier event>/error".
1626 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1628 # cd /sys/kernel/debug/notifier-error-inject/netdev
1629 # echo -22 > actions/NETDEV_CHANGEMTU/error
1630 # ip link set eth0 mtu 1024
1631 RTNETLINK answers: Invalid argument
1633 To compile this code as a module, choose M here: the module will
1634 be called netdev-notifier-error-inject.
1638 config FUNCTION_ERROR_INJECTION
1640 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
1642 config FAULT_INJECTION
1643 bool "Fault-injection framework"
1644 depends on DEBUG_KERNEL
1646 Provide fault-injection framework.
1647 For more details, see Documentation/fault-injection/.
1650 bool "Fault-injection capability for kmalloc"
1651 depends on FAULT_INJECTION
1652 depends on SLAB || SLUB
1654 Provide fault-injection capability for kmalloc.
1656 config FAIL_PAGE_ALLOC
1657 bool "Fault-injection capabilitiy for alloc_pages()"
1658 depends on FAULT_INJECTION
1660 Provide fault-injection capability for alloc_pages().
1662 config FAIL_MAKE_REQUEST
1663 bool "Fault-injection capability for disk IO"
1664 depends on FAULT_INJECTION && BLOCK
1666 Provide fault-injection capability for disk IO.
1668 config FAIL_IO_TIMEOUT
1669 bool "Fault-injection capability for faking disk interrupts"
1670 depends on FAULT_INJECTION && BLOCK
1672 Provide fault-injection capability on end IO handling. This
1673 will make the block layer "forget" an interrupt as configured,
1674 thus exercising the error handling.
1676 Only works with drivers that use the generic timeout handling,
1677 for others it wont do anything.
1680 bool "Fault-injection capability for futexes"
1682 depends on FAULT_INJECTION && FUTEX
1684 Provide fault-injection capability for futexes.
1686 config FAULT_INJECTION_DEBUG_FS
1687 bool "Debugfs entries for fault-injection capabilities"
1688 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1690 Enable configuration of fault-injection capabilities via debugfs.
1692 config FAIL_FUNCTION
1693 bool "Fault-injection capability for functions"
1694 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
1696 Provide function-based fault-injection capability.
1697 This will allow you to override a specific function with a return
1698 with given return value. As a result, function caller will see
1699 an error value and have to handle it. This is useful to test the
1700 error handling in various subsystems.
1702 config FAIL_MMC_REQUEST
1703 bool "Fault-injection capability for MMC IO"
1704 depends on FAULT_INJECTION_DEBUG_FS && MMC
1706 Provide fault-injection capability for MMC IO.
1707 This will make the mmc core return data errors. This is
1708 useful to test the error handling in the mmc block device
1709 and to test how the mmc host driver handles retries from
1712 config FAULT_INJECTION_STACKTRACE_FILTER
1713 bool "stacktrace filter for fault-injection capabilities"
1714 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1717 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1719 Provide stacktrace filter for fault-injection capabilities
1721 config ARCH_HAS_KCOV
1724 An architecture should select this when it can successfully
1725 build and run with CONFIG_KCOV. This typically requires
1726 disabling instrumentation for some early boot code.
1728 config CC_HAS_SANCOV_TRACE_PC
1729 def_bool $(cc-option,-fsanitize-coverage=trace-pc)
1733 bool "Code coverage for fuzzing"
1734 depends on ARCH_HAS_KCOV
1735 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
1737 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
1739 KCOV exposes kernel code coverage information in a form suitable
1740 for coverage-guided fuzzing (randomized testing).
1742 If RANDOMIZE_BASE is enabled, PC values will not be stable across
1743 different machines and across reboots. If you need stable PC values,
1744 disable RANDOMIZE_BASE.
1746 For more details, see Documentation/dev-tools/kcov.rst.
1748 config KCOV_ENABLE_COMPARISONS
1749 bool "Enable comparison operands collection by KCOV"
1751 depends on $(cc-option,-fsanitize-coverage=trace-cmp)
1753 KCOV also exposes operands of every comparison in the instrumented
1754 code along with operand sizes and PCs of the comparison instructions.
1755 These operands can be used by fuzzing engines to improve the quality
1756 of fuzzing coverage.
1758 config KCOV_INSTRUMENT_ALL
1759 bool "Instrument all code by default"
1763 If you are doing generic system call fuzzing (like e.g. syzkaller),
1764 then you will want to instrument the whole kernel and you should
1765 say y here. If you are doing more targeted fuzzing (like e.g.
1766 filesystem fuzzing with AFL) then you will want to enable coverage
1767 for more specific subsets of files, and should say n here.
1769 menuconfig RUNTIME_TESTING_MENU
1770 bool "Runtime Testing"
1773 if RUNTIME_TESTING_MENU
1776 tristate "Linux Kernel Dump Test Tool Module"
1779 This module enables testing of the different dumping mechanisms by
1780 inducing system failures at predefined crash points.
1781 If you don't need it: say N
1782 Choose M here to compile this code as a module. The module will be
1785 Documentation on how to use the module can be found in
1786 Documentation/fault-injection/provoke-crashes.rst
1788 config TEST_LIST_SORT
1789 tristate "Linked list sorting test"
1790 depends on DEBUG_KERNEL || m
1792 Enable this to turn on 'list_sort()' function test. This test is
1793 executed only once during system boot (so affects only boot time),
1794 or at module load time.
1798 config TEST_MIN_HEAP
1799 tristate "Min heap test"
1800 depends on DEBUG_KERNEL || m
1802 Enable this to turn on min heap function tests. This test is
1803 executed only once during system boot (so affects only boot time),
1804 or at module load time.
1809 tristate "Array-based sort test"
1810 depends on DEBUG_KERNEL || m
1812 This option enables the self-test function of 'sort()' at boot,
1813 or at module load time.
1817 config KPROBES_SANITY_TEST
1818 bool "Kprobes sanity tests"
1819 depends on DEBUG_KERNEL
1822 This option provides for testing basic kprobes functionality on
1823 boot. Samples of kprobe and kretprobe are inserted and
1824 verified for functionality.
1826 Say N if you are unsure.
1828 config BACKTRACE_SELF_TEST
1829 tristate "Self test for the backtrace code"
1830 depends on DEBUG_KERNEL
1832 This option provides a kernel module that can be used to test
1833 the kernel stack backtrace code. This option is not useful
1834 for distributions or general kernels, but only for kernel
1835 developers working on architecture code.
1837 Note that if you want to also test saved backtraces, you will
1838 have to enable STACKTRACE as well.
1840 Say N if you are unsure.
1843 tristate "Red-Black tree test"
1844 depends on DEBUG_KERNEL
1846 A benchmark measuring the performance of the rbtree library.
1847 Also includes rbtree invariant checks.
1849 config REED_SOLOMON_TEST
1850 tristate "Reed-Solomon library test"
1851 depends on DEBUG_KERNEL || m
1853 select REED_SOLOMON_ENC16
1854 select REED_SOLOMON_DEC16
1856 This option enables the self-test function of rslib at boot,
1857 or at module load time.
1861 config INTERVAL_TREE_TEST
1862 tristate "Interval tree test"
1863 depends on DEBUG_KERNEL
1864 select INTERVAL_TREE
1866 A benchmark measuring the performance of the interval tree library
1869 tristate "Per cpu operations test"
1870 depends on m && DEBUG_KERNEL
1872 Enable this option to build test module which validates per-cpu
1877 config ATOMIC64_SELFTEST
1878 tristate "Perform an atomic64_t self-test"
1880 Enable this option to test the atomic64_t functions at boot or
1881 at module load time.
1885 config ASYNC_RAID6_TEST
1886 tristate "Self test for hardware accelerated raid6 recovery"
1887 depends on ASYNC_RAID6_RECOV
1890 This is a one-shot self test that permutes through the
1891 recovery of all the possible two disk failure scenarios for a
1892 N-disk array. Recovery is performed with the asynchronous
1893 raid6 recovery routines, and will optionally use an offload
1894 engine if one is available.
1899 tristate "Test functions located in the hexdump module at runtime"
1901 config TEST_STRING_HELPERS
1902 tristate "Test functions located in the string_helpers module at runtime"
1905 tristate "Test strscpy*() family of functions at runtime"
1908 tristate "Test kstrto*() family of functions at runtime"
1911 tristate "Test printf() family of functions at runtime"
1914 tristate "Test bitmap_*() family of functions at runtime"
1916 Enable this option to test the bitmap functions at boot.
1920 config TEST_BITFIELD
1921 tristate "Test bitfield functions at runtime"
1923 Enable this option to test the bitfield functions at boot.
1928 tristate "Test functions located in the uuid module at runtime"
1931 tristate "Test the XArray code at runtime"
1933 config TEST_OVERFLOW
1934 tristate "Test check_*_overflow() functions at runtime"
1936 config TEST_RHASHTABLE
1937 tristate "Perform selftest on resizable hash table"
1939 Enable this option to test the rhashtable functions at boot.
1944 tristate "Perform selftest on hash functions"
1946 Enable this option to test the kernel's integer (<linux/hash.h>),
1947 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1948 hash functions on boot (or module load).
1950 This is intended to help people writing architecture-specific
1951 optimized versions. If unsure, say N.
1954 tristate "Perform selftest on IDA functions"
1957 tristate "Perform selftest on priority array manager"
1960 Enable this option to test priority array manager on boot
1965 config TEST_IRQ_TIMINGS
1966 bool "IRQ timings selftest"
1967 depends on IRQ_TIMINGS
1969 Enable this option to test the irq timings code on boot.
1974 tristate "Test module loading with 'hello world' module"
1977 This builds the "test_module" module that emits "Hello, world"
1978 on printk when loaded. It is designed to be used for basic
1979 evaluation of the module loading subsystem (for example when
1980 validating module verification). It lacks any extra dependencies,
1981 and will not normally be loaded by the system unless explicitly
1987 tristate "Test module for stress/performance analysis of vmalloc allocator"
1992 This builds the "test_vmalloc" module that should be used for
1993 stress and performance analysis. So, any new change for vmalloc
1994 subsystem can be evaluated from performance and stability point
1999 config TEST_USER_COPY
2000 tristate "Test user/kernel boundary protections"
2003 This builds the "test_user_copy" module that runs sanity checks
2004 on the copy_to/from_user infrastructure, making sure basic
2005 user/kernel boundary testing is working. If it fails to load,
2006 a regression has been detected in the user/kernel memory boundary
2012 tristate "Test BPF filter functionality"
2015 This builds the "test_bpf" module that runs various test vectors
2016 against the BPF interpreter or BPF JIT compiler depending on the
2017 current setting. This is in particular useful for BPF JIT compiler
2018 development, but also to run regression tests against changes in
2019 the interpreter code. It also enables test stubs for eBPF maps and
2020 verifier used by user space verifier testsuite.
2024 config TEST_BLACKHOLE_DEV
2025 tristate "Test blackhole netdev functionality"
2028 This builds the "test_blackhole_dev" module that validates the
2029 data path through this blackhole netdev.
2033 config FIND_BIT_BENCHMARK
2034 tristate "Test find_bit functions"
2036 This builds the "test_find_bit" module that measure find_*_bit()
2037 functions performance.
2041 config TEST_FIRMWARE
2042 tristate "Test firmware loading via userspace interface"
2043 depends on FW_LOADER
2045 This builds the "test_firmware" module that creates a userspace
2046 interface for testing firmware loading. This can be used to
2047 control the triggering of firmware loading without needing an
2048 actual firmware-using device. The contents can be rechecked by
2054 tristate "sysctl test driver"
2055 depends on PROC_SYSCTL
2057 This builds the "test_sysctl" module. This driver enables to test the
2058 proc sysctl interfaces available to drivers safely without affecting
2059 production knobs which might alter system functionality.
2063 config SYSCTL_KUNIT_TEST
2064 tristate "KUnit test for sysctl"
2067 This builds the proc sysctl unit test, which runs on boot.
2068 Tests the API contract and implementation correctness of sysctl.
2069 For more information on KUnit and unit tests in general please refer
2070 to the KUnit documentation in Documentation/dev-tools/kunit/.
2074 config LIST_KUNIT_TEST
2075 tristate "KUnit Test for Kernel Linked-list structures"
2078 This builds the linked list KUnit test suite.
2079 It tests that the API and basic functionality of the list_head type
2080 and associated macros.
2082 KUnit tests run during boot and output the results to the debug log
2083 in TAP format (http://testanything.org/). Only useful for kernel devs
2084 running the KUnit test harness, and not intended for inclusion into a
2087 For more information on KUnit and unit tests in general please refer
2088 to the KUnit documentation in Documentation/dev-tools/kunit/.
2093 tristate "udelay test driver"
2095 This builds the "udelay_test" module that helps to make sure
2096 that udelay() is working properly.
2100 config TEST_STATIC_KEYS
2101 tristate "Test static keys"
2104 Test the static key interfaces.
2109 tristate "kmod stress tester"
2111 depends on NETDEVICES && NET_CORE && INET # for TUN
2118 Test the kernel's module loading mechanism: kmod. kmod implements
2119 support to load modules using the Linux kernel's usermode helper.
2120 This test provides a series of tests against kmod.
2122 Although technically you can either build test_kmod as a module or
2123 into the kernel we disallow building it into the kernel since
2124 it stress tests request_module() and this will very likely cause
2125 some issues by taking over precious threads available from other
2126 module load requests, ultimately this could be fatal.
2130 tools/testing/selftests/kmod/kmod.sh --help
2134 config TEST_DEBUG_VIRTUAL
2135 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
2136 depends on DEBUG_VIRTUAL
2138 Test the kernel's ability to detect incorrect calls to
2139 virt_to_phys() done against the non-linear part of the
2140 kernel's virtual address map.
2144 config TEST_MEMCAT_P
2145 tristate "Test memcat_p() helper function"
2147 Test the memcat_p() helper for correctly merging two
2148 pointer arrays together.
2152 config TEST_LIVEPATCH
2153 tristate "Test livepatching"
2155 depends on DYNAMIC_DEBUG
2156 depends on LIVEPATCH
2159 Test kernel livepatching features for correctness. The tests will
2160 load test modules that will be livepatched in various scenarios.
2162 To run all the livepatching tests:
2164 make -C tools/testing/selftests TARGETS=livepatch run_tests
2166 Alternatively, individual tests may be invoked:
2168 tools/testing/selftests/livepatch/test-callbacks.sh
2169 tools/testing/selftests/livepatch/test-livepatch.sh
2170 tools/testing/selftests/livepatch/test-shadow-vars.sh
2175 tristate "Perform selftest on object aggreration manager"
2179 Enable this option to test object aggregation manager on boot
2183 config TEST_STACKINIT
2184 tristate "Test level of stack variable initialization"
2186 Test if the kernel is zero-initializing stack variables and
2187 padding. Coverage is controlled by compiler flags,
2188 CONFIG_GCC_PLUGIN_STRUCTLEAK, CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF,
2189 or CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL.
2194 tristate "Test heap/page initialization"
2196 Test if the kernel is zero-initializing heap and page allocations.
2197 This can be useful to test init_on_alloc and init_on_free features.
2201 endif # RUNTIME_TESTING_MENU
2206 This option adds a kernel parameter 'memtest', which allows memtest
2208 memtest=0, mean disabled; -- default
2209 memtest=1, mean do 1 test pattern;
2211 memtest=17, mean do 17 test patterns.
2212 If you are unsure how to answer this question, answer N.
2216 config HYPERV_TESTING
2217 bool "Microsoft Hyper-V driver testing"
2219 depends on HYPERV && DEBUG_FS
2221 Select this option to enable Hyper-V vmbus testing.
2223 endmenu # "Kernel Testing and Coverage"
2225 endmenu # Kernel hacking
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