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
246 Generate deduplicated BTF type information from DWARF debug info.
247 Turning this on expects presence of pahole tool, which will convert
248 DWARF type info into equivalent deduplicated BTF type info.
251 bool "Provide GDB scripts for kernel debugging"
252 depends on DEBUG_INFO
254 This creates the required links to GDB helper scripts in the
255 build directory. If you load vmlinux into gdb, the helper
256 scripts will be automatically imported by gdb as well, and
257 additional functions are available to analyze a Linux kernel
258 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
261 config ENABLE_MUST_CHECK
262 bool "Enable __must_check logic"
265 Enable the __must_check logic in the kernel build. Disable this to
266 suppress the "warning: ignoring return value of 'foo', declared with
267 attribute warn_unused_result" messages.
270 int "Warn for stack frames larger than"
272 default 2048 if GCC_PLUGIN_LATENT_ENTROPY
273 default 1280 if (!64BIT && PARISC)
274 default 1024 if (!64BIT && !PARISC)
275 default 2048 if 64BIT
277 Tell gcc to warn at build time for stack frames larger than this.
278 Setting this too low will cause a lot of warnings.
279 Setting it to 0 disables the warning.
281 config STRIP_ASM_SYMS
282 bool "Strip assembler-generated symbols during link"
285 Strip internal assembler-generated symbols during a link (symbols
286 that look like '.Lxxx') so they don't pollute the output of
287 get_wchan() and suchlike.
290 bool "Generate readable assembler code"
291 depends on DEBUG_KERNEL
293 Disable some compiler optimizations that tend to generate human unreadable
294 assembler output. This may make the kernel slightly slower, but it helps
295 to keep kernel developers who have to stare a lot at assembler listings
298 config HEADERS_INSTALL
299 bool "Install uapi headers to usr/include"
302 This option will install uapi headers (headers exported to user-space)
303 into the usr/include directory for use during the kernel build.
304 This is unneeded for building the kernel itself, but needed for some
305 user-space program samples. It is also needed by some features such
306 as uapi header sanity checks.
308 config DEBUG_SECTION_MISMATCH
309 bool "Enable full Section mismatch analysis"
311 The section mismatch analysis checks if there are illegal
312 references from one section to another section.
313 During linktime or runtime, some sections are dropped;
314 any use of code/data previously in these sections would
315 most likely result in an oops.
316 In the code, functions and variables are annotated with
317 __init,, etc. (see the full list in include/linux/init.h),
318 which results in the code/data being placed in specific sections.
319 The section mismatch analysis is always performed after a full
320 kernel build, and enabling this option causes the following
321 additional step to occur:
322 - Add the option -fno-inline-functions-called-once to gcc commands.
323 When inlining a function annotated with __init in a non-init
324 function, we would lose the section information and thus
325 the analysis would not catch the illegal reference.
326 This option tells gcc to inline less (but it does result in
329 config SECTION_MISMATCH_WARN_ONLY
330 bool "Make section mismatch errors non-fatal"
333 If you say N here, the build process will fail if there are any
334 section mismatch, instead of just throwing warnings.
339 # Select this config option from the architecture Kconfig, if it
340 # is preferred to always offer frame pointers as a config
341 # option on the architecture (regardless of KERNEL_DEBUG):
343 config ARCH_WANT_FRAME_POINTERS
347 bool "Compile the kernel with frame pointers"
348 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS
349 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
351 If you say Y here the resulting kernel image will be slightly
352 larger and slower, but it gives very useful debugging information
353 in case of kernel bugs. (precise oopses/stacktraces/warnings)
355 config STACK_VALIDATION
356 bool "Compile-time stack metadata validation"
357 depends on HAVE_STACK_VALIDATION
360 Add compile-time checks to validate stack metadata, including frame
361 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
362 that runtime stack traces are more reliable.
364 This is also a prerequisite for generation of ORC unwind data, which
365 is needed for CONFIG_UNWINDER_ORC.
367 For more information, see
368 tools/objtool/Documentation/stack-validation.txt.
370 config DEBUG_FORCE_WEAK_PER_CPU
371 bool "Force weak per-cpu definitions"
372 depends on DEBUG_KERNEL
374 s390 and alpha require percpu variables in modules to be
375 defined weak to work around addressing range issue which
376 puts the following two restrictions on percpu variable
379 1. percpu symbols must be unique whether static or not
380 2. percpu variables can't be defined inside a function
382 To ensure that generic code follows the above rules, this
383 option forces all percpu variables to be defined as weak.
385 endmenu # "Compiler options"
387 menu "Generic Kernel Debugging Instruments"
390 bool "Magic SysRq key"
393 If you say Y here, you will have some control over the system even
394 if the system crashes for example during kernel debugging (e.g., you
395 will be able to flush the buffer cache to disk, reboot the system
396 immediately or dump some status information). This is accomplished
397 by pressing various keys while holding SysRq (Alt+PrintScreen). It
398 also works on a serial console (on PC hardware at least), if you
399 send a BREAK and then within 5 seconds a command keypress. The
400 keys are documented in <file:Documentation/admin-guide/sysrq.rst>.
401 Don't say Y unless you really know what this hack does.
403 config MAGIC_SYSRQ_DEFAULT_ENABLE
404 hex "Enable magic SysRq key functions by default"
405 depends on MAGIC_SYSRQ
408 Specifies which SysRq key functions are enabled by default.
409 This may be set to 1 or 0 to enable or disable them all, or
410 to a bitmask as described in Documentation/admin-guide/sysrq.rst.
412 config MAGIC_SYSRQ_SERIAL
413 bool "Enable magic SysRq key over serial"
414 depends on MAGIC_SYSRQ
417 Many embedded boards have a disconnected TTL level serial which can
418 generate some garbage that can lead to spurious false sysrq detects.
419 This option allows you to decide whether you want to enable the
422 config MAGIC_SYSRQ_SERIAL_SEQUENCE
423 string "Char sequence that enables magic SysRq over serial"
424 depends on MAGIC_SYSRQ_SERIAL
427 Specifies a sequence of characters that can follow BREAK to enable
428 SysRq on a serial console.
430 If unsure, leave an empty string and the option will not be enabled.
433 bool "Debug Filesystem"
435 debugfs is a virtual file system that kernel developers use to put
436 debugging files into. Enable this option to be able to read and
437 write to these files.
439 For detailed documentation on the debugfs API, see
440 Documentation/filesystems/.
444 source "lib/Kconfig.kgdb"
446 source "lib/Kconfig.ubsan"
451 bool "Kernel debugging"
453 Say Y here if you are developing drivers or trying to debug and
454 identify kernel problems.
457 bool "Miscellaneous debug code"
459 depends on DEBUG_KERNEL
461 Say Y here if you need to enable miscellaneous debug code that should
462 be under a more specific debug option but isn't.
465 menu "Memory Debugging"
467 source "mm/Kconfig.debug"
470 bool "Debug object operations"
471 depends on DEBUG_KERNEL
473 If you say Y here, additional code will be inserted into the
474 kernel to track the life time of various objects and validate
475 the operations on those objects.
477 config DEBUG_OBJECTS_SELFTEST
478 bool "Debug objects selftest"
479 depends on DEBUG_OBJECTS
481 This enables the selftest of the object debug code.
483 config DEBUG_OBJECTS_FREE
484 bool "Debug objects in freed memory"
485 depends on DEBUG_OBJECTS
487 This enables checks whether a k/v free operation frees an area
488 which contains an object which has not been deactivated
489 properly. This can make kmalloc/kfree-intensive workloads
492 config DEBUG_OBJECTS_TIMERS
493 bool "Debug timer objects"
494 depends on DEBUG_OBJECTS
496 If you say Y here, additional code will be inserted into the
497 timer routines to track the life time of timer objects and
498 validate the timer operations.
500 config DEBUG_OBJECTS_WORK
501 bool "Debug work objects"
502 depends on DEBUG_OBJECTS
504 If you say Y here, additional code will be inserted into the
505 work queue routines to track the life time of work objects and
506 validate the work operations.
508 config DEBUG_OBJECTS_RCU_HEAD
509 bool "Debug RCU callbacks objects"
510 depends on DEBUG_OBJECTS
512 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
514 config DEBUG_OBJECTS_PERCPU_COUNTER
515 bool "Debug percpu counter objects"
516 depends on DEBUG_OBJECTS
518 If you say Y here, additional code will be inserted into the
519 percpu counter routines to track the life time of percpu counter
520 objects and validate the percpu counter operations.
522 config DEBUG_OBJECTS_ENABLE_DEFAULT
523 int "debug_objects bootup default value (0-1)"
526 depends on DEBUG_OBJECTS
528 Debug objects boot parameter default value
531 bool "Debug slab memory allocations"
532 depends on DEBUG_KERNEL && SLAB
534 Say Y here to have the kernel do limited verification on memory
535 allocation as well as poisoning memory on free to catch use of freed
536 memory. This can make kmalloc/kfree-intensive workloads much slower.
539 bool "SLUB debugging on by default"
540 depends on SLUB && SLUB_DEBUG
543 Boot with debugging on by default. SLUB boots by default with
544 the runtime debug capabilities switched off. Enabling this is
545 equivalent to specifying the "slub_debug" parameter on boot.
546 There is no support for more fine grained debug control like
547 possible with slub_debug=xxx. SLUB debugging may be switched
548 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
553 bool "Enable SLUB performance statistics"
554 depends on SLUB && SYSFS
556 SLUB statistics are useful to debug SLUBs allocation behavior in
557 order find ways to optimize the allocator. This should never be
558 enabled for production use since keeping statistics slows down
559 the allocator by a few percentage points. The slabinfo command
560 supports the determination of the most active slabs to figure
561 out which slabs are relevant to a particular load.
562 Try running: slabinfo -DA
564 config HAVE_DEBUG_KMEMLEAK
567 config DEBUG_KMEMLEAK
568 bool "Kernel memory leak detector"
569 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
571 select STACKTRACE if STACKTRACE_SUPPORT
575 Say Y here if you want to enable the memory leak
576 detector. The memory allocation/freeing is traced in a way
577 similar to the Boehm's conservative garbage collector, the
578 difference being that the orphan objects are not freed but
579 only shown in /sys/kernel/debug/kmemleak. Enabling this
580 feature will introduce an overhead to memory
581 allocations. See Documentation/dev-tools/kmemleak.rst for more
584 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
585 of finding leaks due to the slab objects poisoning.
587 In order to access the kmemleak file, debugfs needs to be
588 mounted (usually at /sys/kernel/debug).
590 config DEBUG_KMEMLEAK_MEM_POOL_SIZE
591 int "Kmemleak memory pool size"
592 depends on DEBUG_KMEMLEAK
596 Kmemleak must track all the memory allocations to avoid
597 reporting false positives. Since memory may be allocated or
598 freed before kmemleak is fully initialised, use a static pool
599 of metadata objects to track such callbacks. After kmemleak is
600 fully initialised, this memory pool acts as an emergency one
601 if slab allocations fail.
603 config DEBUG_KMEMLEAK_TEST
604 tristate "Simple test for the kernel memory leak detector"
605 depends on DEBUG_KMEMLEAK && m
607 This option enables a module that explicitly leaks memory.
611 config DEBUG_KMEMLEAK_DEFAULT_OFF
612 bool "Default kmemleak to off"
613 depends on DEBUG_KMEMLEAK
615 Say Y here to disable kmemleak by default. It can then be enabled
616 on the command line via kmemleak=on.
618 config DEBUG_KMEMLEAK_AUTO_SCAN
619 bool "Enable kmemleak auto scan thread on boot up"
621 depends on DEBUG_KMEMLEAK
623 Depending on the cpu, kmemleak scan may be cpu intensive and can
624 stall user tasks at times. This option enables/disables automatic
625 kmemleak scan at boot up.
627 Say N here to disable kmemleak auto scan thread to stop automatic
628 scanning. Disabling this option disables automatic reporting of
633 config DEBUG_STACK_USAGE
634 bool "Stack utilization instrumentation"
635 depends on DEBUG_KERNEL && !IA64
637 Enables the display of the minimum amount of free stack which each
638 task has ever had available in the sysrq-T and sysrq-P debug output.
640 This option will slow down process creation somewhat.
642 config SCHED_STACK_END_CHECK
643 bool "Detect stack corruption on calls to schedule()"
644 depends on DEBUG_KERNEL
647 This option checks for a stack overrun on calls to schedule().
648 If the stack end location is found to be over written always panic as
649 the content of the corrupted region can no longer be trusted.
650 This is to ensure no erroneous behaviour occurs which could result in
651 data corruption or a sporadic crash at a later stage once the region
652 is examined. The runtime overhead introduced is minimal.
656 depends on DEBUG_KERNEL
658 Enable this to turn on extended checks in the virtual-memory system
659 that may impact performance.
663 config DEBUG_VM_VMACACHE
664 bool "Debug VMA caching"
667 Enable this to turn on VMA caching debug information. Doing so
668 can cause significant overhead, so only enable it in non-production
674 bool "Debug VM red-black trees"
677 Enable VM red-black tree debugging information and extra validations.
681 config DEBUG_VM_PGFLAGS
682 bool "Debug page-flags operations"
685 Enables extra validation on page flags operations.
689 config ARCH_HAS_DEBUG_VIRTUAL
693 bool "Debug VM translations"
694 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
696 Enable some costly sanity checks in virtual to page code. This can
697 catch mistakes with virt_to_page() and friends.
701 config DEBUG_NOMMU_REGIONS
702 bool "Debug the global anon/private NOMMU mapping region tree"
703 depends on DEBUG_KERNEL && !MMU
705 This option causes the global tree of anonymous and private mapping
706 regions to be regularly checked for invalid topology.
708 config DEBUG_MEMORY_INIT
709 bool "Debug memory initialisation" if EXPERT
712 Enable this for additional checks during memory initialisation.
713 The sanity checks verify aspects of the VM such as the memory model
714 and other information provided by the architecture. Verbose
715 information will be printed at KERN_DEBUG loglevel depending
716 on the mminit_loglevel= command-line option.
720 config MEMORY_NOTIFIER_ERROR_INJECT
721 tristate "Memory hotplug notifier error injection module"
722 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
724 This option provides the ability to inject artificial errors to
725 memory hotplug notifier chain callbacks. It is controlled through
726 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
728 If the notifier call chain should be failed with some events
729 notified, write the error code to "actions/<notifier event>/error".
731 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
733 # cd /sys/kernel/debug/notifier-error-inject/memory
734 # echo -12 > actions/MEM_GOING_OFFLINE/error
735 # echo offline > /sys/devices/system/memory/memoryXXX/state
736 bash: echo: write error: Cannot allocate memory
738 To compile this code as a module, choose M here: the module will
739 be called memory-notifier-error-inject.
743 config DEBUG_PER_CPU_MAPS
744 bool "Debug access to per_cpu maps"
745 depends on DEBUG_KERNEL
748 Say Y to verify that the per_cpu map being accessed has
749 been set up. This adds a fair amount of code to kernel memory
750 and decreases performance.
755 bool "Highmem debugging"
756 depends on DEBUG_KERNEL && HIGHMEM
758 This option enables additional error checking for high memory
759 systems. Disable for production systems.
761 config HAVE_DEBUG_STACKOVERFLOW
764 config DEBUG_STACKOVERFLOW
765 bool "Check for stack overflows"
766 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
768 Say Y here if you want to check for overflows of kernel, IRQ
769 and exception stacks (if your architecture uses them). This
770 option will show detailed messages if free stack space drops
771 below a certain limit.
773 These kinds of bugs usually occur when call-chains in the
774 kernel get too deep, especially when interrupts are
777 Use this in cases where you see apparently random memory
778 corruption, especially if it appears in 'struct thread_info'
780 If in doubt, say "N".
782 source "lib/Kconfig.kasan"
784 endmenu # "Memory Debugging"
787 bool "Debug shared IRQ handlers"
788 depends on DEBUG_KERNEL
790 Enable this to generate a spurious interrupt as soon as a shared
791 interrupt handler is registered, and just before one is deregistered.
792 Drivers ought to be able to handle interrupts coming in at those
793 points; some don't and need to be caught.
795 menu "Debug Oops, Lockups and Hangs"
800 Say Y here to enable the kernel to panic when it oopses. This
801 has the same effect as setting oops=panic on the kernel command
804 This feature is useful to ensure that the kernel does not do
805 anything erroneous after an oops which could result in data
806 corruption or other issues.
810 config PANIC_ON_OOPS_VALUE
813 default 0 if !PANIC_ON_OOPS
814 default 1 if PANIC_ON_OOPS
820 Set the timeout value (in seconds) until a reboot occurs when the
821 the kernel panics. If n = 0, then we wait forever. A timeout
822 value n > 0 will wait n seconds before rebooting, while a timeout
823 value n < 0 will reboot immediately.
825 config LOCKUP_DETECTOR
828 config SOFTLOCKUP_DETECTOR
829 bool "Detect Soft Lockups"
830 depends on DEBUG_KERNEL && !S390
831 select LOCKUP_DETECTOR
833 Say Y here to enable the kernel to act as a watchdog to detect
836 Softlockups are bugs that cause the kernel to loop in kernel
837 mode for more than 20 seconds, without giving other tasks a
838 chance to run. The current stack trace is displayed upon
839 detection and the system will stay locked up.
841 config BOOTPARAM_SOFTLOCKUP_PANIC
842 bool "Panic (Reboot) On Soft Lockups"
843 depends on SOFTLOCKUP_DETECTOR
845 Say Y here to enable the kernel to panic on "soft lockups",
846 which are bugs that cause the kernel to loop in kernel
847 mode for more than 20 seconds (configurable using the watchdog_thresh
848 sysctl), without giving other tasks a chance to run.
850 The panic can be used in combination with panic_timeout,
851 to cause the system to reboot automatically after a
852 lockup has been detected. This feature is useful for
853 high-availability systems that have uptime guarantees and
854 where a lockup must be resolved ASAP.
858 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
860 depends on SOFTLOCKUP_DETECTOR
862 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
863 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
865 config HARDLOCKUP_DETECTOR_PERF
867 select SOFTLOCKUP_DETECTOR
870 # Enables a timestamp based low pass filter to compensate for perf based
871 # hard lockup detection which runs too fast due to turbo modes.
873 config HARDLOCKUP_CHECK_TIMESTAMP
877 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
878 # lockup detector rather than the perf based detector.
880 config HARDLOCKUP_DETECTOR
881 bool "Detect Hard Lockups"
882 depends on DEBUG_KERNEL && !S390
883 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
884 select LOCKUP_DETECTOR
885 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
886 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
888 Say Y here to enable the kernel to act as a watchdog to detect
891 Hardlockups are bugs that cause the CPU to loop in kernel mode
892 for more than 10 seconds, without letting other interrupts have a
893 chance to run. The current stack trace is displayed upon detection
894 and the system will stay locked up.
896 config BOOTPARAM_HARDLOCKUP_PANIC
897 bool "Panic (Reboot) On Hard Lockups"
898 depends on HARDLOCKUP_DETECTOR
900 Say Y here to enable the kernel to panic on "hard lockups",
901 which are bugs that cause the kernel to loop in kernel
902 mode with interrupts disabled for more than 10 seconds (configurable
903 using the watchdog_thresh sysctl).
907 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
909 depends on HARDLOCKUP_DETECTOR
911 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
912 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
914 config DETECT_HUNG_TASK
915 bool "Detect Hung Tasks"
916 depends on DEBUG_KERNEL
917 default SOFTLOCKUP_DETECTOR
919 Say Y here to enable the kernel to detect "hung tasks",
920 which are bugs that cause the task to be stuck in
921 uninterruptible "D" state indefinitely.
923 When a hung task is detected, the kernel will print the
924 current stack trace (which you should report), but the
925 task will stay in uninterruptible state. If lockdep is
926 enabled then all held locks will also be reported. This
927 feature has negligible overhead.
929 config DEFAULT_HUNG_TASK_TIMEOUT
930 int "Default timeout for hung task detection (in seconds)"
931 depends on DETECT_HUNG_TASK
934 This option controls the default timeout (in seconds) used
935 to determine when a task has become non-responsive and should
938 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
939 sysctl or by writing a value to
940 /proc/sys/kernel/hung_task_timeout_secs.
942 A timeout of 0 disables the check. The default is two minutes.
943 Keeping the default should be fine in most cases.
945 config BOOTPARAM_HUNG_TASK_PANIC
946 bool "Panic (Reboot) On Hung Tasks"
947 depends on DETECT_HUNG_TASK
949 Say Y here to enable the kernel to panic on "hung tasks",
950 which are bugs that cause the kernel to leave a task stuck
951 in uninterruptible "D" state.
953 The panic can be used in combination with panic_timeout,
954 to cause the system to reboot automatically after a
955 hung task has been detected. This feature is useful for
956 high-availability systems that have uptime guarantees and
957 where a hung tasks must be resolved ASAP.
961 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
963 depends on DETECT_HUNG_TASK
965 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
966 default 1 if BOOTPARAM_HUNG_TASK_PANIC
969 bool "Detect Workqueue Stalls"
970 depends on DEBUG_KERNEL
972 Say Y here to enable stall detection on workqueues. If a
973 worker pool doesn't make forward progress on a pending work
974 item for over a given amount of time, 30s by default, a
975 warning message is printed along with dump of workqueue
976 state. This can be configured through kernel parameter
977 "workqueue.watchdog_thresh" and its sysfs counterpart.
980 tristate "Test module to generate lockups"
982 This builds the "test_lockup" module that helps to make sure
983 that watchdogs and lockup detectors are working properly.
985 Depending on module parameters it could emulate soft or hard
986 lockup, "hung task", or locking arbitrary lock for a long time.
987 Also it could generate series of lockups with cooling-down periods.
991 endmenu # "Debug lockups and hangs"
993 menu "Scheduler Debugging"
996 bool "Collect scheduler debugging info"
997 depends on DEBUG_KERNEL && PROC_FS
1000 If you say Y here, the /proc/sched_debug file will be provided
1001 that can help debug the scheduler. The runtime overhead of this
1009 bool "Collect scheduler statistics"
1010 depends on DEBUG_KERNEL && PROC_FS
1013 If you say Y here, additional code will be inserted into the
1014 scheduler and related routines to collect statistics about
1015 scheduler behavior and provide them in /proc/schedstat. These
1016 stats may be useful for both tuning and debugging the scheduler
1017 If you aren't debugging the scheduler or trying to tune a specific
1018 application, you can say N to avoid the very slight overhead
1023 config DEBUG_TIMEKEEPING
1024 bool "Enable extra timekeeping sanity checking"
1026 This option will enable additional timekeeping sanity checks
1027 which may be helpful when diagnosing issues where timekeeping
1028 problems are suspected.
1030 This may include checks in the timekeeping hotpaths, so this
1031 option may have a (very small) performance impact to some
1036 config DEBUG_PREEMPT
1037 bool "Debug preemptible kernel"
1038 depends on DEBUG_KERNEL && PREEMPTION && TRACE_IRQFLAGS_SUPPORT
1041 If you say Y here then the kernel will use a debug variant of the
1042 commonly used smp_processor_id() function and will print warnings
1043 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1044 will detect preemption count underflows.
1046 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1048 config LOCK_DEBUGGING_SUPPORT
1050 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1053 config PROVE_LOCKING
1054 bool "Lock debugging: prove locking correctness"
1055 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1057 select DEBUG_SPINLOCK
1058 select DEBUG_MUTEXES
1059 select DEBUG_RT_MUTEXES if RT_MUTEXES
1061 select DEBUG_WW_MUTEX_SLOWPATH
1062 select DEBUG_LOCK_ALLOC
1063 select TRACE_IRQFLAGS
1066 This feature enables the kernel to prove that all locking
1067 that occurs in the kernel runtime is mathematically
1068 correct: that under no circumstance could an arbitrary (and
1069 not yet triggered) combination of observed locking
1070 sequences (on an arbitrary number of CPUs, running an
1071 arbitrary number of tasks and interrupt contexts) cause a
1074 In short, this feature enables the kernel to report locking
1075 related deadlocks before they actually occur.
1077 The proof does not depend on how hard and complex a
1078 deadlock scenario would be to trigger: how many
1079 participant CPUs, tasks and irq-contexts would be needed
1080 for it to trigger. The proof also does not depend on
1081 timing: if a race and a resulting deadlock is possible
1082 theoretically (no matter how unlikely the race scenario
1083 is), it will be proven so and will immediately be
1084 reported by the kernel (once the event is observed that
1085 makes the deadlock theoretically possible).
1087 If a deadlock is impossible (i.e. the locking rules, as
1088 observed by the kernel, are mathematically correct), the
1089 kernel reports nothing.
1091 NOTE: this feature can also be enabled for rwlocks, mutexes
1092 and rwsems - in which case all dependencies between these
1093 different locking variants are observed and mapped too, and
1094 the proof of observed correctness is also maintained for an
1095 arbitrary combination of these separate locking variants.
1097 For more details, see Documentation/locking/lockdep-design.rst.
1099 config PROVE_RAW_LOCK_NESTING
1100 bool "Enable raw_spinlock - spinlock nesting checks"
1101 depends on PROVE_LOCKING
1104 Enable the raw_spinlock vs. spinlock nesting checks which ensure
1105 that the lock nesting rules for PREEMPT_RT enabled kernels are
1108 NOTE: There are known nesting problems. So if you enable this
1109 option expect lockdep splats until these problems have been fully
1110 addressed which is work in progress. This config switch allows to
1111 identify and analyze these problems. It will be removed and the
1112 check permanentely enabled once the main issues have been fixed.
1114 If unsure, select N.
1117 bool "Lock usage statistics"
1118 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1120 select DEBUG_SPINLOCK
1121 select DEBUG_MUTEXES
1122 select DEBUG_RT_MUTEXES if RT_MUTEXES
1123 select DEBUG_LOCK_ALLOC
1126 This feature enables tracking lock contention points
1128 For more details, see Documentation/locking/lockstat.rst
1130 This also enables lock events required by "perf lock",
1132 If you want to use "perf lock", you also need to turn on
1133 CONFIG_EVENT_TRACING.
1135 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1136 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1138 config DEBUG_RT_MUTEXES
1139 bool "RT Mutex debugging, deadlock detection"
1140 depends on DEBUG_KERNEL && RT_MUTEXES
1142 This allows rt mutex semantics violations and rt mutex related
1143 deadlocks (lockups) to be detected and reported automatically.
1145 config DEBUG_SPINLOCK
1146 bool "Spinlock and rw-lock debugging: basic checks"
1147 depends on DEBUG_KERNEL
1148 select UNINLINE_SPIN_UNLOCK
1150 Say Y here and build SMP to catch missing spinlock initialization
1151 and certain other kinds of spinlock errors commonly made. This is
1152 best used in conjunction with the NMI watchdog so that spinlock
1153 deadlocks are also debuggable.
1155 config DEBUG_MUTEXES
1156 bool "Mutex debugging: basic checks"
1157 depends on DEBUG_KERNEL
1159 This feature allows mutex semantics violations to be detected and
1162 config DEBUG_WW_MUTEX_SLOWPATH
1163 bool "Wait/wound mutex debugging: Slowpath testing"
1164 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1165 select DEBUG_LOCK_ALLOC
1166 select DEBUG_SPINLOCK
1167 select DEBUG_MUTEXES
1169 This feature enables slowpath testing for w/w mutex users by
1170 injecting additional -EDEADLK wound/backoff cases. Together with
1171 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1172 will test all possible w/w mutex interface abuse with the
1173 exception of simply not acquiring all the required locks.
1174 Note that this feature can introduce significant overhead, so
1175 it really should not be enabled in a production or distro kernel,
1176 even a debug kernel. If you are a driver writer, enable it. If
1177 you are a distro, do not.
1180 bool "RW Semaphore debugging: basic checks"
1181 depends on DEBUG_KERNEL
1183 This debugging feature allows mismatched rw semaphore locks
1184 and unlocks to be detected and reported.
1186 config DEBUG_LOCK_ALLOC
1187 bool "Lock debugging: detect incorrect freeing of live locks"
1188 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1189 select DEBUG_SPINLOCK
1190 select DEBUG_MUTEXES
1191 select DEBUG_RT_MUTEXES if RT_MUTEXES
1194 This feature will check whether any held lock (spinlock, rwlock,
1195 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1196 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1197 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1198 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1199 held during task exit.
1203 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1205 select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86
1209 config LOCKDEP_SMALL
1212 config DEBUG_LOCKDEP
1213 bool "Lock dependency engine debugging"
1214 depends on DEBUG_KERNEL && LOCKDEP
1216 If you say Y here, the lock dependency engine will do
1217 additional runtime checks to debug itself, at the price
1218 of more runtime overhead.
1220 config DEBUG_ATOMIC_SLEEP
1221 bool "Sleep inside atomic section checking"
1222 select PREEMPT_COUNT
1223 depends on DEBUG_KERNEL
1224 depends on !ARCH_NO_PREEMPT
1226 If you say Y here, various routines which may sleep will become very
1227 noisy if they are called inside atomic sections: when a spinlock is
1228 held, inside an rcu read side critical section, inside preempt disabled
1229 sections, inside an interrupt, etc...
1231 config DEBUG_LOCKING_API_SELFTESTS
1232 bool "Locking API boot-time self-tests"
1233 depends on DEBUG_KERNEL
1235 Say Y here if you want the kernel to run a short self-test during
1236 bootup. The self-test checks whether common types of locking bugs
1237 are detected by debugging mechanisms or not. (if you disable
1238 lock debugging then those bugs wont be detected of course.)
1239 The following locking APIs are covered: spinlocks, rwlocks,
1242 config LOCK_TORTURE_TEST
1243 tristate "torture tests for locking"
1244 depends on DEBUG_KERNEL
1247 This option provides a kernel module that runs torture tests
1248 on kernel locking primitives. The kernel module may be built
1249 after the fact on the running kernel to be tested, if desired.
1251 Say Y here if you want kernel locking-primitive torture tests
1252 to be built into the kernel.
1253 Say M if you want these torture tests to build as a module.
1254 Say N if you are unsure.
1256 config WW_MUTEX_SELFTEST
1257 tristate "Wait/wound mutex selftests"
1259 This option provides a kernel module that runs tests on the
1260 on the struct ww_mutex locking API.
1262 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1263 with this test harness.
1265 Say M if you want these self tests to build as a module.
1266 Say N if you are unsure.
1268 endmenu # lock debugging
1270 config TRACE_IRQFLAGS
1273 Enables hooks to interrupt enabling and disabling for
1274 either tracing or lock debugging.
1277 bool "Stack backtrace support"
1278 depends on STACKTRACE_SUPPORT
1280 This option causes the kernel to create a /proc/pid/stack for
1281 every process, showing its current stack trace.
1282 It is also used by various kernel debugging features that require
1283 stack trace generation.
1285 config WARN_ALL_UNSEEDED_RANDOM
1286 bool "Warn for all uses of unseeded randomness"
1289 Some parts of the kernel contain bugs relating to their use of
1290 cryptographically secure random numbers before it's actually possible
1291 to generate those numbers securely. This setting ensures that these
1292 flaws don't go unnoticed, by enabling a message, should this ever
1293 occur. This will allow people with obscure setups to know when things
1294 are going wrong, so that they might contact developers about fixing
1297 Unfortunately, on some models of some architectures getting
1298 a fully seeded CRNG is extremely difficult, and so this can
1299 result in dmesg getting spammed for a surprisingly long
1300 time. This is really bad from a security perspective, and
1301 so architecture maintainers really need to do what they can
1302 to get the CRNG seeded sooner after the system is booted.
1303 However, since users cannot do anything actionable to
1304 address this, by default the kernel will issue only a single
1305 warning for the first use of unseeded randomness.
1307 Say Y here if you want to receive warnings for all uses of
1308 unseeded randomness. This will be of use primarily for
1309 those developers interested in improving the security of
1310 Linux kernels running on their architecture (or
1313 config DEBUG_KOBJECT
1314 bool "kobject debugging"
1315 depends on DEBUG_KERNEL
1317 If you say Y here, some extra kobject debugging messages will be sent
1320 config DEBUG_KOBJECT_RELEASE
1321 bool "kobject release debugging"
1322 depends on DEBUG_OBJECTS_TIMERS
1324 kobjects are reference counted objects. This means that their
1325 last reference count put is not predictable, and the kobject can
1326 live on past the point at which a driver decides to drop it's
1327 initial reference to the kobject gained on allocation. An
1328 example of this would be a struct device which has just been
1331 However, some buggy drivers assume that after such an operation,
1332 the memory backing the kobject can be immediately freed. This
1333 goes completely against the principles of a refcounted object.
1335 If you say Y here, the kernel will delay the release of kobjects
1336 on the last reference count to improve the visibility of this
1337 kind of kobject release bug.
1339 config HAVE_DEBUG_BUGVERBOSE
1342 menu "Debug kernel data structures"
1345 bool "Debug linked list manipulation"
1346 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1348 Enable this to turn on extended checks in the linked-list
1354 bool "Debug priority linked list manipulation"
1355 depends on DEBUG_KERNEL
1357 Enable this to turn on extended checks in the priority-ordered
1358 linked-list (plist) walking routines. This checks the entire
1359 list multiple times during each manipulation.
1364 bool "Debug SG table operations"
1365 depends on DEBUG_KERNEL
1367 Enable this to turn on checks on scatter-gather tables. This can
1368 help find problems with drivers that do not properly initialize
1373 config DEBUG_NOTIFIERS
1374 bool "Debug notifier call chains"
1375 depends on DEBUG_KERNEL
1377 Enable this to turn on sanity checking for notifier call chains.
1378 This is most useful for kernel developers to make sure that
1379 modules properly unregister themselves from notifier chains.
1380 This is a relatively cheap check but if you care about maximum
1383 config BUG_ON_DATA_CORRUPTION
1384 bool "Trigger a BUG when data corruption is detected"
1387 Select this option if the kernel should BUG when it encounters
1388 data corruption in kernel memory structures when they get checked
1395 config DEBUG_CREDENTIALS
1396 bool "Debug credential management"
1397 depends on DEBUG_KERNEL
1399 Enable this to turn on some debug checking for credential
1400 management. The additional code keeps track of the number of
1401 pointers from task_structs to any given cred struct, and checks to
1402 see that this number never exceeds the usage count of the cred
1405 Furthermore, if SELinux is enabled, this also checks that the
1406 security pointer in the cred struct is never seen to be invalid.
1410 source "kernel/rcu/Kconfig.debug"
1412 config DEBUG_WQ_FORCE_RR_CPU
1413 bool "Force round-robin CPU selection for unbound work items"
1414 depends on DEBUG_KERNEL
1417 Workqueue used to implicitly guarantee that work items queued
1418 without explicit CPU specified are put on the local CPU. This
1419 guarantee is no longer true and while local CPU is still
1420 preferred work items may be put on foreign CPUs. Kernel
1421 parameter "workqueue.debug_force_rr_cpu" is added to force
1422 round-robin CPU selection to flush out usages which depend on the
1423 now broken guarantee. This config option enables the debug
1424 feature by default. When enabled, memory and cache locality will
1427 config DEBUG_BLOCK_EXT_DEVT
1428 bool "Force extended block device numbers and spread them"
1429 depends on DEBUG_KERNEL
1433 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1434 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1435 YOU ARE DOING. Distros, please enable this and fix whatever
1438 Conventionally, block device numbers are allocated from
1439 predetermined contiguous area. However, extended block area
1440 may introduce non-contiguous block device numbers. This
1441 option forces most block device numbers to be allocated from
1442 the extended space and spreads them to discover kernel or
1443 userland code paths which assume predetermined contiguous
1444 device number allocation.
1446 Note that turning on this debug option shuffles all the
1447 device numbers for all IDE and SCSI devices including libata
1448 ones, so root partition specified using device number
1449 directly (via rdev or root=MAJ:MIN) won't work anymore.
1450 Textual device names (root=/dev/sdXn) will continue to work.
1452 Say N if you are unsure.
1454 config CPU_HOTPLUG_STATE_CONTROL
1455 bool "Enable CPU hotplug state control"
1456 depends on DEBUG_KERNEL
1457 depends on HOTPLUG_CPU
1460 Allows to write steps between "offline" and "online" to the CPUs
1461 sysfs target file so states can be stepped granular. This is a debug
1462 option for now as the hotplug machinery cannot be stopped and
1463 restarted at arbitrary points yet.
1465 Say N if your are unsure.
1468 bool "Latency measuring infrastructure"
1469 depends on DEBUG_KERNEL
1470 depends on STACKTRACE_SUPPORT
1472 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1479 Enable this option if you want to use the LatencyTOP tool
1480 to find out which userspace is blocking on what kernel operations.
1482 source "kernel/trace/Kconfig"
1484 config PROVIDE_OHCI1394_DMA_INIT
1485 bool "Remote debugging over FireWire early on boot"
1486 depends on PCI && X86
1488 If you want to debug problems which hang or crash the kernel early
1489 on boot and the crashing machine has a FireWire port, you can use
1490 this feature to remotely access the memory of the crashed machine
1491 over FireWire. This employs remote DMA as part of the OHCI1394
1492 specification which is now the standard for FireWire controllers.
1494 With remote DMA, you can monitor the printk buffer remotely using
1495 firescope and access all memory below 4GB using fireproxy from gdb.
1496 Even controlling a kernel debugger is possible using remote DMA.
1500 If ohci1394_dma=early is used as boot parameter, it will initialize
1501 all OHCI1394 controllers which are found in the PCI config space.
1503 As all changes to the FireWire bus such as enabling and disabling
1504 devices cause a bus reset and thereby disable remote DMA for all
1505 devices, be sure to have the cable plugged and FireWire enabled on
1506 the debugging host before booting the debug target for debugging.
1508 This code (~1k) is freed after boot. By then, the firewire stack
1509 in charge of the OHCI-1394 controllers should be used instead.
1511 See Documentation/debugging-via-ohci1394.txt for more information.
1513 source "samples/Kconfig"
1515 config ARCH_HAS_DEVMEM_IS_ALLOWED
1518 config STRICT_DEVMEM
1519 bool "Filter access to /dev/mem"
1520 depends on MMU && DEVMEM
1521 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
1522 default y if PPC || X86 || ARM64
1524 If this option is disabled, you allow userspace (root) access to all
1525 of memory, including kernel and userspace memory. Accidental
1526 access to this is obviously disastrous, but specific access can
1527 be used by people debugging the kernel. Note that with PAT support
1528 enabled, even in this case there are restrictions on /dev/mem
1529 use due to the cache aliasing requirements.
1531 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
1532 file only allows userspace access to PCI space and the BIOS code and
1533 data regions. This is sufficient for dosemu and X and all common
1538 config IO_STRICT_DEVMEM
1539 bool "Filter I/O access to /dev/mem"
1540 depends on STRICT_DEVMEM
1542 If this option is disabled, you allow userspace (root) access to all
1543 io-memory regardless of whether a driver is actively using that
1544 range. Accidental access to this is obviously disastrous, but
1545 specific access can be used by people debugging kernel drivers.
1547 If this option is switched on, the /dev/mem file only allows
1548 userspace access to *idle* io-memory ranges (see /proc/iomem) This
1549 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
1550 if the driver using a given range cannot be disabled.
1554 menu "$(SRCARCH) Debugging"
1556 source "arch/$(SRCARCH)/Kconfig.debug"
1560 menu "Kernel Testing and Coverage"
1562 source "lib/kunit/Kconfig"
1564 config NOTIFIER_ERROR_INJECTION
1565 tristate "Notifier error injection"
1566 depends on DEBUG_KERNEL
1569 This option provides the ability to inject artificial errors to
1570 specified notifier chain callbacks. It is useful to test the error
1571 handling of notifier call chain failures.
1575 config PM_NOTIFIER_ERROR_INJECT
1576 tristate "PM notifier error injection module"
1577 depends on PM && NOTIFIER_ERROR_INJECTION
1578 default m if PM_DEBUG
1580 This option provides the ability to inject artificial errors to
1581 PM notifier chain callbacks. It is controlled through debugfs
1582 interface /sys/kernel/debug/notifier-error-inject/pm
1584 If the notifier call chain should be failed with some events
1585 notified, write the error code to "actions/<notifier event>/error".
1587 Example: Inject PM suspend error (-12 = -ENOMEM)
1589 # cd /sys/kernel/debug/notifier-error-inject/pm/
1590 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1591 # echo mem > /sys/power/state
1592 bash: echo: write error: Cannot allocate memory
1594 To compile this code as a module, choose M here: the module will
1595 be called pm-notifier-error-inject.
1599 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1600 tristate "OF reconfig notifier error injection module"
1601 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1603 This option provides the ability to inject artificial errors to
1604 OF reconfig notifier chain callbacks. It is controlled
1605 through debugfs interface under
1606 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1608 If the notifier call chain should be failed with some events
1609 notified, write the error code to "actions/<notifier event>/error".
1611 To compile this code as a module, choose M here: the module will
1612 be called of-reconfig-notifier-error-inject.
1616 config NETDEV_NOTIFIER_ERROR_INJECT
1617 tristate "Netdev notifier error injection module"
1618 depends on NET && NOTIFIER_ERROR_INJECTION
1620 This option provides the ability to inject artificial errors to
1621 netdevice notifier chain callbacks. It is controlled through debugfs
1622 interface /sys/kernel/debug/notifier-error-inject/netdev
1624 If the notifier call chain should be failed with some events
1625 notified, write the error code to "actions/<notifier event>/error".
1627 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1629 # cd /sys/kernel/debug/notifier-error-inject/netdev
1630 # echo -22 > actions/NETDEV_CHANGEMTU/error
1631 # ip link set eth0 mtu 1024
1632 RTNETLINK answers: Invalid argument
1634 To compile this code as a module, choose M here: the module will
1635 be called netdev-notifier-error-inject.
1639 config FUNCTION_ERROR_INJECTION
1641 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
1643 config FAULT_INJECTION
1644 bool "Fault-injection framework"
1645 depends on DEBUG_KERNEL
1647 Provide fault-injection framework.
1648 For more details, see Documentation/fault-injection/.
1651 bool "Fault-injection capability for kmalloc"
1652 depends on FAULT_INJECTION
1653 depends on SLAB || SLUB
1655 Provide fault-injection capability for kmalloc.
1657 config FAIL_PAGE_ALLOC
1658 bool "Fault-injection capability for alloc_pages()"
1659 depends on FAULT_INJECTION
1661 Provide fault-injection capability for alloc_pages().
1663 config FAIL_MAKE_REQUEST
1664 bool "Fault-injection capability for disk IO"
1665 depends on FAULT_INJECTION && BLOCK
1667 Provide fault-injection capability for disk IO.
1669 config FAIL_IO_TIMEOUT
1670 bool "Fault-injection capability for faking disk interrupts"
1671 depends on FAULT_INJECTION && BLOCK
1673 Provide fault-injection capability on end IO handling. This
1674 will make the block layer "forget" an interrupt as configured,
1675 thus exercising the error handling.
1677 Only works with drivers that use the generic timeout handling,
1678 for others it wont do anything.
1681 bool "Fault-injection capability for futexes"
1683 depends on FAULT_INJECTION && FUTEX
1685 Provide fault-injection capability for futexes.
1687 config FAULT_INJECTION_DEBUG_FS
1688 bool "Debugfs entries for fault-injection capabilities"
1689 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1691 Enable configuration of fault-injection capabilities via debugfs.
1693 config FAIL_FUNCTION
1694 bool "Fault-injection capability for functions"
1695 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
1697 Provide function-based fault-injection capability.
1698 This will allow you to override a specific function with a return
1699 with given return value. As a result, function caller will see
1700 an error value and have to handle it. This is useful to test the
1701 error handling in various subsystems.
1703 config FAIL_MMC_REQUEST
1704 bool "Fault-injection capability for MMC IO"
1705 depends on FAULT_INJECTION_DEBUG_FS && MMC
1707 Provide fault-injection capability for MMC IO.
1708 This will make the mmc core return data errors. This is
1709 useful to test the error handling in the mmc block device
1710 and to test how the mmc host driver handles retries from
1713 config FAULT_INJECTION_STACKTRACE_FILTER
1714 bool "stacktrace filter for fault-injection capabilities"
1715 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1718 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1720 Provide stacktrace filter for fault-injection capabilities
1722 config ARCH_HAS_KCOV
1725 An architecture should select this when it can successfully
1726 build and run with CONFIG_KCOV. This typically requires
1727 disabling instrumentation for some early boot code.
1729 config CC_HAS_SANCOV_TRACE_PC
1730 def_bool $(cc-option,-fsanitize-coverage=trace-pc)
1734 bool "Code coverage for fuzzing"
1735 depends on ARCH_HAS_KCOV
1736 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
1738 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
1740 KCOV exposes kernel code coverage information in a form suitable
1741 for coverage-guided fuzzing (randomized testing).
1743 If RANDOMIZE_BASE is enabled, PC values will not be stable across
1744 different machines and across reboots. If you need stable PC values,
1745 disable RANDOMIZE_BASE.
1747 For more details, see Documentation/dev-tools/kcov.rst.
1749 config KCOV_ENABLE_COMPARISONS
1750 bool "Enable comparison operands collection by KCOV"
1752 depends on $(cc-option,-fsanitize-coverage=trace-cmp)
1754 KCOV also exposes operands of every comparison in the instrumented
1755 code along with operand sizes and PCs of the comparison instructions.
1756 These operands can be used by fuzzing engines to improve the quality
1757 of fuzzing coverage.
1759 config KCOV_INSTRUMENT_ALL
1760 bool "Instrument all code by default"
1764 If you are doing generic system call fuzzing (like e.g. syzkaller),
1765 then you will want to instrument the whole kernel and you should
1766 say y here. If you are doing more targeted fuzzing (like e.g.
1767 filesystem fuzzing with AFL) then you will want to enable coverage
1768 for more specific subsets of files, and should say n here.
1770 menuconfig RUNTIME_TESTING_MENU
1771 bool "Runtime Testing"
1774 if RUNTIME_TESTING_MENU
1777 tristate "Linux Kernel Dump Test Tool Module"
1780 This module enables testing of the different dumping mechanisms by
1781 inducing system failures at predefined crash points.
1782 If you don't need it: say N
1783 Choose M here to compile this code as a module. The module will be
1786 Documentation on how to use the module can be found in
1787 Documentation/fault-injection/provoke-crashes.rst
1789 config TEST_LIST_SORT
1790 tristate "Linked list sorting test"
1791 depends on DEBUG_KERNEL || m
1793 Enable this to turn on 'list_sort()' function test. This test is
1794 executed only once during system boot (so affects only boot time),
1795 or at module load time.
1799 config TEST_MIN_HEAP
1800 tristate "Min heap test"
1801 depends on DEBUG_KERNEL || m
1803 Enable this to turn on min heap function tests. This test is
1804 executed only once during system boot (so affects only boot time),
1805 or at module load time.
1810 tristate "Array-based sort test"
1811 depends on DEBUG_KERNEL || m
1813 This option enables the self-test function of 'sort()' at boot,
1814 or at module load time.
1818 config KPROBES_SANITY_TEST
1819 bool "Kprobes sanity tests"
1820 depends on DEBUG_KERNEL
1823 This option provides for testing basic kprobes functionality on
1824 boot. Samples of kprobe and kretprobe are inserted and
1825 verified for functionality.
1827 Say N if you are unsure.
1829 config BACKTRACE_SELF_TEST
1830 tristate "Self test for the backtrace code"
1831 depends on DEBUG_KERNEL
1833 This option provides a kernel module that can be used to test
1834 the kernel stack backtrace code. This option is not useful
1835 for distributions or general kernels, but only for kernel
1836 developers working on architecture code.
1838 Note that if you want to also test saved backtraces, you will
1839 have to enable STACKTRACE as well.
1841 Say N if you are unsure.
1844 tristate "Red-Black tree test"
1845 depends on DEBUG_KERNEL
1847 A benchmark measuring the performance of the rbtree library.
1848 Also includes rbtree invariant checks.
1850 config REED_SOLOMON_TEST
1851 tristate "Reed-Solomon library test"
1852 depends on DEBUG_KERNEL || m
1854 select REED_SOLOMON_ENC16
1855 select REED_SOLOMON_DEC16
1857 This option enables the self-test function of rslib at boot,
1858 or at module load time.
1862 config INTERVAL_TREE_TEST
1863 tristate "Interval tree test"
1864 depends on DEBUG_KERNEL
1865 select INTERVAL_TREE
1867 A benchmark measuring the performance of the interval tree library
1870 tristate "Per cpu operations test"
1871 depends on m && DEBUG_KERNEL
1873 Enable this option to build test module which validates per-cpu
1878 config ATOMIC64_SELFTEST
1879 tristate "Perform an atomic64_t self-test"
1881 Enable this option to test the atomic64_t functions at boot or
1882 at module load time.
1886 config ASYNC_RAID6_TEST
1887 tristate "Self test for hardware accelerated raid6 recovery"
1888 depends on ASYNC_RAID6_RECOV
1891 This is a one-shot self test that permutes through the
1892 recovery of all the possible two disk failure scenarios for a
1893 N-disk array. Recovery is performed with the asynchronous
1894 raid6 recovery routines, and will optionally use an offload
1895 engine if one is available.
1900 tristate "Test functions located in the hexdump module at runtime"
1902 config TEST_STRING_HELPERS
1903 tristate "Test functions located in the string_helpers module at runtime"
1906 tristate "Test strscpy*() family of functions at runtime"
1909 tristate "Test kstrto*() family of functions at runtime"
1912 tristate "Test printf() family of functions at runtime"
1915 tristate "Test bitmap_*() family of functions at runtime"
1917 Enable this option to test the bitmap functions at boot.
1921 config TEST_BITFIELD
1922 tristate "Test bitfield functions at runtime"
1924 Enable this option to test the bitfield functions at boot.
1929 tristate "Test functions located in the uuid module at runtime"
1932 tristate "Test the XArray code at runtime"
1934 config TEST_OVERFLOW
1935 tristate "Test check_*_overflow() functions at runtime"
1937 config TEST_RHASHTABLE
1938 tristate "Perform selftest on resizable hash table"
1940 Enable this option to test the rhashtable functions at boot.
1945 tristate "Perform selftest on hash functions"
1947 Enable this option to test the kernel's integer (<linux/hash.h>),
1948 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1949 hash functions on boot (or module load).
1951 This is intended to help people writing architecture-specific
1952 optimized versions. If unsure, say N.
1955 tristate "Perform selftest on IDA functions"
1958 tristate "Perform selftest on priority array manager"
1961 Enable this option to test priority array manager on boot
1966 config TEST_IRQ_TIMINGS
1967 bool "IRQ timings selftest"
1968 depends on IRQ_TIMINGS
1970 Enable this option to test the irq timings code on boot.
1975 tristate "Test module loading with 'hello world' module"
1978 This builds the "test_module" module that emits "Hello, world"
1979 on printk when loaded. It is designed to be used for basic
1980 evaluation of the module loading subsystem (for example when
1981 validating module verification). It lacks any extra dependencies,
1982 and will not normally be loaded by the system unless explicitly
1988 tristate "Test module for stress/performance analysis of vmalloc allocator"
1993 This builds the "test_vmalloc" module that should be used for
1994 stress and performance analysis. So, any new change for vmalloc
1995 subsystem can be evaluated from performance and stability point
2000 config TEST_USER_COPY
2001 tristate "Test user/kernel boundary protections"
2004 This builds the "test_user_copy" module that runs sanity checks
2005 on the copy_to/from_user infrastructure, making sure basic
2006 user/kernel boundary testing is working. If it fails to load,
2007 a regression has been detected in the user/kernel memory boundary
2013 tristate "Test BPF filter functionality"
2016 This builds the "test_bpf" module that runs various test vectors
2017 against the BPF interpreter or BPF JIT compiler depending on the
2018 current setting. This is in particular useful for BPF JIT compiler
2019 development, but also to run regression tests against changes in
2020 the interpreter code. It also enables test stubs for eBPF maps and
2021 verifier used by user space verifier testsuite.
2025 config TEST_BLACKHOLE_DEV
2026 tristate "Test blackhole netdev functionality"
2029 This builds the "test_blackhole_dev" module that validates the
2030 data path through this blackhole netdev.
2034 config FIND_BIT_BENCHMARK
2035 tristate "Test find_bit functions"
2037 This builds the "test_find_bit" module that measure find_*_bit()
2038 functions performance.
2042 config TEST_FIRMWARE
2043 tristate "Test firmware loading via userspace interface"
2044 depends on FW_LOADER
2046 This builds the "test_firmware" module that creates a userspace
2047 interface for testing firmware loading. This can be used to
2048 control the triggering of firmware loading without needing an
2049 actual firmware-using device. The contents can be rechecked by
2055 tristate "sysctl test driver"
2056 depends on PROC_SYSCTL
2058 This builds the "test_sysctl" module. This driver enables to test the
2059 proc sysctl interfaces available to drivers safely without affecting
2060 production knobs which might alter system functionality.
2064 config SYSCTL_KUNIT_TEST
2065 tristate "KUnit test for sysctl"
2068 This builds the proc sysctl unit test, which runs on boot.
2069 Tests the API contract and implementation correctness of sysctl.
2070 For more information on KUnit and unit tests in general please refer
2071 to the KUnit documentation in Documentation/dev-tools/kunit/.
2075 config LIST_KUNIT_TEST
2076 tristate "KUnit Test for Kernel Linked-list structures"
2079 This builds the linked list KUnit test suite.
2080 It tests that the API and basic functionality of the list_head type
2081 and associated macros.
2083 KUnit tests run during boot and output the results to the debug log
2084 in TAP format (http://testanything.org/). Only useful for kernel devs
2085 running the KUnit test harness, and not intended for inclusion into a
2088 For more information on KUnit and unit tests in general please refer
2089 to the KUnit documentation in Documentation/dev-tools/kunit/.
2094 tristate "udelay test driver"
2096 This builds the "udelay_test" module that helps to make sure
2097 that udelay() is working properly.
2101 config TEST_STATIC_KEYS
2102 tristate "Test static keys"
2105 Test the static key interfaces.
2110 tristate "kmod stress tester"
2112 depends on NETDEVICES && NET_CORE && INET # for TUN
2119 Test the kernel's module loading mechanism: kmod. kmod implements
2120 support to load modules using the Linux kernel's usermode helper.
2121 This test provides a series of tests against kmod.
2123 Although technically you can either build test_kmod as a module or
2124 into the kernel we disallow building it into the kernel since
2125 it stress tests request_module() and this will very likely cause
2126 some issues by taking over precious threads available from other
2127 module load requests, ultimately this could be fatal.
2131 tools/testing/selftests/kmod/kmod.sh --help
2135 config TEST_DEBUG_VIRTUAL
2136 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
2137 depends on DEBUG_VIRTUAL
2139 Test the kernel's ability to detect incorrect calls to
2140 virt_to_phys() done against the non-linear part of the
2141 kernel's virtual address map.
2145 config TEST_MEMCAT_P
2146 tristate "Test memcat_p() helper function"
2148 Test the memcat_p() helper for correctly merging two
2149 pointer arrays together.
2153 config TEST_LIVEPATCH
2154 tristate "Test livepatching"
2156 depends on DYNAMIC_DEBUG
2157 depends on LIVEPATCH
2160 Test kernel livepatching features for correctness. The tests will
2161 load test modules that will be livepatched in various scenarios.
2163 To run all the livepatching tests:
2165 make -C tools/testing/selftests TARGETS=livepatch run_tests
2167 Alternatively, individual tests may be invoked:
2169 tools/testing/selftests/livepatch/test-callbacks.sh
2170 tools/testing/selftests/livepatch/test-livepatch.sh
2171 tools/testing/selftests/livepatch/test-shadow-vars.sh
2176 tristate "Perform selftest on object aggreration manager"
2180 Enable this option to test object aggregation manager on boot
2184 config TEST_STACKINIT
2185 tristate "Test level of stack variable initialization"
2187 Test if the kernel is zero-initializing stack variables and
2188 padding. Coverage is controlled by compiler flags,
2189 CONFIG_GCC_PLUGIN_STRUCTLEAK, CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF,
2190 or CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL.
2195 tristate "Test heap/page initialization"
2197 Test if the kernel is zero-initializing heap and page allocations.
2198 This can be useful to test init_on_alloc and init_on_free features.
2202 endif # RUNTIME_TESTING_MENU
2207 This option adds a kernel parameter 'memtest', which allows memtest
2209 memtest=0, mean disabled; -- default
2210 memtest=1, mean do 1 test pattern;
2212 memtest=17, mean do 17 test patterns.
2213 If you are unsure how to answer this question, answer N.
2217 config HYPERV_TESTING
2218 bool "Microsoft Hyper-V driver testing"
2220 depends on HYPERV && DEBUG_FS
2222 Select this option to enable Hyper-V vmbus testing.
2224 endmenu # "Kernel Testing and Coverage"
2226 endmenu # Kernel hacking