1 menu "printk and dmesg options"
4 bool "Show timing information on printks"
7 Selecting this option causes time stamps of the printk()
8 messages to be added to the output of the syslog() system
9 call and at the console.
11 The timestamp is always recorded internally, and exported
12 to /dev/kmsg. This flag just specifies if the timestamp should
13 be included, not that the timestamp is recorded.
15 The behavior is also controlled by the kernel command line
16 parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst
18 config CONSOLE_LOGLEVEL_DEFAULT
19 int "Default console loglevel (1-15)"
23 Default loglevel to determine what will be printed on the console.
25 Setting a default here is equivalent to passing in loglevel=<x> in
26 the kernel bootargs. loglevel=<x> continues to override whatever
27 value is specified here as well.
29 Note: This does not affect the log level of un-prefixed printk()
30 usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
33 config MESSAGE_LOGLEVEL_DEFAULT
34 int "Default message log level (1-7)"
38 Default log level for printk statements with no specified priority.
40 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
41 that are auditing their logs closely may want to set it to a lower
44 Note: This does not affect what message level gets printed on the console
45 by default. To change that, use loglevel=<x> in the kernel bootargs,
46 or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value.
48 config BOOT_PRINTK_DELAY
49 bool "Delay each boot printk message by N milliseconds"
50 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
52 This build option allows you to read kernel boot messages
53 by inserting a short delay after each one. The delay is
54 specified in milliseconds on the kernel command line,
57 It is likely that you would also need to use "lpj=M" to preset
58 the "loops per jiffie" value.
59 See a previous boot log for the "lpj" value to use for your
60 system, and then set "lpj=M" before setting "boot_delay=N".
61 NOTE: Using this option may adversely affect SMP systems.
62 I.e., processors other than the first one may not boot up.
63 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
64 what it believes to be lockup conditions.
67 bool "Enable dynamic printk() support"
73 Compiles debug level messages into the kernel, which would not
74 otherwise be available at runtime. These messages can then be
75 enabled/disabled based on various levels of scope - per source file,
76 function, module, format string, and line number. This mechanism
77 implicitly compiles in all pr_debug() and dev_dbg() calls, which
78 enlarges the kernel text size by about 2%.
80 If a source file is compiled with DEBUG flag set, any
81 pr_debug() calls in it are enabled by default, but can be
82 disabled at runtime as below. Note that DEBUG flag is
83 turned on by many CONFIG_*DEBUG* options.
87 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
88 which is contained in the 'debugfs' filesystem. Thus, the debugfs
89 filesystem must first be mounted before making use of this feature.
90 We refer the control file as: <debugfs>/dynamic_debug/control. This
91 file contains a list of the debug statements that can be enabled. The
92 format for each line of the file is:
94 filename:lineno [module]function flags format
96 filename : source file of the debug statement
97 lineno : line number of the debug statement
98 module : module that contains the debug statement
99 function : function that contains the debug statement
100 flags : '=p' means the line is turned 'on' for printing
101 format : the format used for the debug statement
105 nullarbor:~ # cat <debugfs>/dynamic_debug/control
106 # filename:lineno [module]function flags format
107 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
108 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
109 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
113 // enable the message at line 1603 of file svcsock.c
114 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
115 <debugfs>/dynamic_debug/control
117 // enable all the messages in file svcsock.c
118 nullarbor:~ # echo -n 'file svcsock.c +p' >
119 <debugfs>/dynamic_debug/control
121 // enable all the messages in the NFS server module
122 nullarbor:~ # echo -n 'module nfsd +p' >
123 <debugfs>/dynamic_debug/control
125 // enable all 12 messages in the function svc_process()
126 nullarbor:~ # echo -n 'func svc_process +p' >
127 <debugfs>/dynamic_debug/control
129 // disable all 12 messages in the function svc_process()
130 nullarbor:~ # echo -n 'func svc_process -p' >
131 <debugfs>/dynamic_debug/control
133 See Documentation/admin-guide/dynamic-debug-howto.rst for additional
136 endmenu # "printk and dmesg options"
138 menu "Compile-time checks and compiler options"
141 bool "Compile the kernel with debug info"
142 depends on DEBUG_KERNEL && !COMPILE_TEST
144 If you say Y here the resulting kernel image will include
145 debugging info resulting in a larger kernel image.
146 This adds debug symbols to the kernel and modules (gcc -g), and
147 is needed if you intend to use kernel crashdump or binary object
148 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
149 Say Y here only if you plan to debug the kernel.
153 config DEBUG_INFO_REDUCED
154 bool "Reduce debugging information"
155 depends on DEBUG_INFO
157 If you say Y here gcc is instructed to generate less debugging
158 information for structure types. This means that tools that
159 need full debugging information (like kgdb or systemtap) won't
160 be happy. But if you merely need debugging information to
161 resolve line numbers there is no loss. Advantage is that
162 build directory object sizes shrink dramatically over a full
163 DEBUG_INFO build and compile times are reduced too.
164 Only works with newer gcc versions.
166 config DEBUG_INFO_SPLIT
167 bool "Produce split debuginfo in .dwo files"
168 depends on DEBUG_INFO && !FRV
170 Generate debug info into separate .dwo files. This significantly
171 reduces the build directory size for builds with DEBUG_INFO,
172 because it stores the information only once on disk in .dwo
173 files instead of multiple times in object files and executables.
174 In addition the debug information is also compressed.
176 Requires recent gcc (4.7+) and recent gdb/binutils.
177 Any tool that packages or reads debug information would need
178 to know about the .dwo files and include them.
179 Incompatible with older versions of ccache.
181 config DEBUG_INFO_DWARF4
182 bool "Generate dwarf4 debuginfo"
183 depends on DEBUG_INFO
185 Generate dwarf4 debug info. This requires recent versions
186 of gcc and gdb. It makes the debug information larger.
187 But it significantly improves the success of resolving
188 variables in gdb on optimized code.
191 bool "Provide GDB scripts for kernel debugging"
192 depends on DEBUG_INFO
194 This creates the required links to GDB helper scripts in the
195 build directory. If you load vmlinux into gdb, the helper
196 scripts will be automatically imported by gdb as well, and
197 additional functions are available to analyze a Linux kernel
198 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
201 config ENABLE_WARN_DEPRECATED
202 bool "Enable __deprecated logic"
205 Enable the __deprecated logic in the kernel build.
206 Disable this to suppress the "warning: 'foo' is deprecated
207 (declared at kernel/power/somefile.c:1234)" messages.
209 config ENABLE_MUST_CHECK
210 bool "Enable __must_check logic"
213 Enable the __must_check logic in the kernel build. Disable this to
214 suppress the "warning: ignoring return value of 'foo', declared with
215 attribute warn_unused_result" messages.
218 int "Warn for stack frames larger than (needs gcc 4.4)"
221 default 2048 if GCC_PLUGIN_LATENT_ENTROPY
222 default 1024 if !64BIT
223 default 2048 if 64BIT
225 Tell gcc to warn at build time for stack frames larger than this.
226 Setting this too low will cause a lot of warnings.
227 Setting it to 0 disables the warning.
230 config STRIP_ASM_SYMS
231 bool "Strip assembler-generated symbols during link"
234 Strip internal assembler-generated symbols during a link (symbols
235 that look like '.Lxxx') so they don't pollute the output of
236 get_wchan() and suchlike.
239 bool "Generate readable assembler code"
240 depends on DEBUG_KERNEL
242 Disable some compiler optimizations that tend to generate human unreadable
243 assembler output. This may make the kernel slightly slower, but it helps
244 to keep kernel developers who have to stare a lot at assembler listings
247 config UNUSED_SYMBOLS
248 bool "Enable unused/obsolete exported symbols"
251 Unused but exported symbols make the kernel needlessly bigger. For
252 that reason most of these unused exports will soon be removed. This
253 option is provided temporarily to provide a transition period in case
254 some external kernel module needs one of these symbols anyway. If you
255 encounter such a case in your module, consider if you are actually
256 using the right API. (rationale: since nobody in the kernel is using
257 this in a module, there is a pretty good chance it's actually the
258 wrong interface to use). If you really need the symbol, please send a
259 mail to the linux kernel mailing list mentioning the symbol and why
260 you really need it, and what the merge plan to the mainline kernel for
264 bool "Track page owner"
265 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
269 select PAGE_EXTENSION
271 This keeps track of what call chain is the owner of a page, may
272 help to find bare alloc_page(s) leaks. Even if you include this
273 feature on your build, it is disabled in default. You should pass
274 "page_owner=on" to boot parameter in order to enable it. Eats
275 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
276 for user-space helper.
281 bool "Debug Filesystem"
284 debugfs is a virtual file system that kernel developers use to put
285 debugging files into. Enable this option to be able to read and
286 write to these files.
288 For detailed documentation on the debugfs API, see
289 Documentation/filesystems/.
294 bool "Run 'make headers_check' when building vmlinux"
297 This option will extract the user-visible kernel headers whenever
298 building the kernel, and will run basic sanity checks on them to
299 ensure that exported files do not attempt to include files which
300 were not exported, etc.
302 If you're making modifications to header files which are
303 relevant for userspace, say 'Y', and check the headers
304 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
305 your build tree), to make sure they're suitable.
307 config DEBUG_SECTION_MISMATCH
308 bool "Enable full Section mismatch analysis"
310 The section mismatch analysis checks if there are illegal
311 references from one section to another section.
312 During linktime or runtime, some sections are dropped;
313 any use of code/data previously in these sections would
314 most likely result in an oops.
315 In the code, functions and variables are annotated with
316 __init,, etc. (see the full list in include/linux/init.h),
317 which results in the code/data being placed in specific sections.
318 The section mismatch analysis is always performed after a full
319 kernel build, and enabling this option causes the following
320 additional steps to occur:
321 - Add the option -fno-inline-functions-called-once to gcc commands.
322 When inlining a function annotated with __init in a non-init
323 function, we would lose the section information and thus
324 the analysis would not catch the illegal reference.
325 This option tells gcc to inline less (but it does result in
327 - Run the section mismatch analysis for each module/built-in.o file.
328 When we run the section mismatch analysis on vmlinux.o, we
329 lose valuable information about where the mismatch was
331 Running the analysis for each module/built-in.o file
332 tells where the mismatch happens much closer to the
333 source. The drawback is that the same mismatch is
334 reported at least twice.
335 - Enable verbose reporting from modpost in order to help resolve
336 the section mismatches that are reported.
338 config SECTION_MISMATCH_WARN_ONLY
339 bool "Make section mismatch errors non-fatal"
342 If you say N here, the build process will fail if there are any
343 section mismatch, instead of just throwing warnings.
348 # Select this config option from the architecture Kconfig, if it
349 # is preferred to always offer frame pointers as a config
350 # option on the architecture (regardless of KERNEL_DEBUG):
352 config ARCH_WANT_FRAME_POINTERS
357 bool "Compile the kernel with frame pointers"
358 depends on DEBUG_KERNEL && \
359 (CRIS || M68K || FRV || UML || \
360 SUPERH || BLACKFIN || MN10300 || METAG) || \
361 ARCH_WANT_FRAME_POINTERS
362 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
364 If you say Y here the resulting kernel image will be slightly
365 larger and slower, but it gives very useful debugging information
366 in case of kernel bugs. (precise oopses/stacktraces/warnings)
368 config STACK_VALIDATION
369 bool "Compile-time stack metadata validation"
370 depends on HAVE_STACK_VALIDATION
373 Add compile-time checks to validate stack metadata, including frame
374 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
375 that runtime stack traces are more reliable.
377 For more information, see
378 tools/objtool/Documentation/stack-validation.txt.
380 config DEBUG_FORCE_WEAK_PER_CPU
381 bool "Force weak per-cpu definitions"
382 depends on DEBUG_KERNEL
384 s390 and alpha require percpu variables in modules to be
385 defined weak to work around addressing range issue which
386 puts the following two restrictions on percpu variable
389 1. percpu symbols must be unique whether static or not
390 2. percpu variables can't be defined inside a function
392 To ensure that generic code follows the above rules, this
393 option forces all percpu variables to be defined as weak.
395 endmenu # "Compiler options"
398 bool "Magic SysRq key"
401 If you say Y here, you will have some control over the system even
402 if the system crashes for example during kernel debugging (e.g., you
403 will be able to flush the buffer cache to disk, reboot the system
404 immediately or dump some status information). This is accomplished
405 by pressing various keys while holding SysRq (Alt+PrintScreen). It
406 also works on a serial console (on PC hardware at least), if you
407 send a BREAK and then within 5 seconds a command keypress. The
408 keys are documented in <file:Documentation/admin-guide/sysrq.rst>.
409 Don't say Y unless you really know what this hack does.
411 config MAGIC_SYSRQ_DEFAULT_ENABLE
412 hex "Enable magic SysRq key functions by default"
413 depends on MAGIC_SYSRQ
416 Specifies which SysRq key functions are enabled by default.
417 This may be set to 1 or 0 to enable or disable them all, or
418 to a bitmask as described in Documentation/admin-guide/sysrq.rst.
420 config MAGIC_SYSRQ_SERIAL
421 bool "Enable magic SysRq key over serial"
422 depends on MAGIC_SYSRQ
425 Many embedded boards have a disconnected TTL level serial which can
426 generate some garbage that can lead to spurious false sysrq detects.
427 This option allows you to decide whether you want to enable the
431 bool "Kernel debugging"
433 Say Y here if you are developing drivers or trying to debug and
434 identify kernel problems.
436 menu "Memory Debugging"
438 source mm/Kconfig.debug
441 bool "Debug object operations"
442 depends on DEBUG_KERNEL
444 If you say Y here, additional code will be inserted into the
445 kernel to track the life time of various objects and validate
446 the operations on those objects.
448 config DEBUG_OBJECTS_SELFTEST
449 bool "Debug objects selftest"
450 depends on DEBUG_OBJECTS
452 This enables the selftest of the object debug code.
454 config DEBUG_OBJECTS_FREE
455 bool "Debug objects in freed memory"
456 depends on DEBUG_OBJECTS
458 This enables checks whether a k/v free operation frees an area
459 which contains an object which has not been deactivated
460 properly. This can make kmalloc/kfree-intensive workloads
463 config DEBUG_OBJECTS_TIMERS
464 bool "Debug timer objects"
465 depends on DEBUG_OBJECTS
467 If you say Y here, additional code will be inserted into the
468 timer routines to track the life time of timer objects and
469 validate the timer operations.
471 config DEBUG_OBJECTS_WORK
472 bool "Debug work objects"
473 depends on DEBUG_OBJECTS
475 If you say Y here, additional code will be inserted into the
476 work queue routines to track the life time of work objects and
477 validate the work operations.
479 config DEBUG_OBJECTS_RCU_HEAD
480 bool "Debug RCU callbacks objects"
481 depends on DEBUG_OBJECTS
483 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
485 config DEBUG_OBJECTS_PERCPU_COUNTER
486 bool "Debug percpu counter objects"
487 depends on DEBUG_OBJECTS
489 If you say Y here, additional code will be inserted into the
490 percpu counter routines to track the life time of percpu counter
491 objects and validate the percpu counter operations.
493 config DEBUG_OBJECTS_ENABLE_DEFAULT
494 int "debug_objects bootup default value (0-1)"
497 depends on DEBUG_OBJECTS
499 Debug objects boot parameter default value
502 bool "Debug slab memory allocations"
503 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
505 Say Y here to have the kernel do limited verification on memory
506 allocation as well as poisoning memory on free to catch use of freed
507 memory. This can make kmalloc/kfree-intensive workloads much slower.
509 config DEBUG_SLAB_LEAK
510 bool "Memory leak debugging"
511 depends on DEBUG_SLAB
514 bool "SLUB debugging on by default"
515 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
518 Boot with debugging on by default. SLUB boots by default with
519 the runtime debug capabilities switched off. Enabling this is
520 equivalent to specifying the "slub_debug" parameter on boot.
521 There is no support for more fine grained debug control like
522 possible with slub_debug=xxx. SLUB debugging may be switched
523 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
528 bool "Enable SLUB performance statistics"
529 depends on SLUB && SYSFS
531 SLUB statistics are useful to debug SLUBs allocation behavior in
532 order find ways to optimize the allocator. This should never be
533 enabled for production use since keeping statistics slows down
534 the allocator by a few percentage points. The slabinfo command
535 supports the determination of the most active slabs to figure
536 out which slabs are relevant to a particular load.
537 Try running: slabinfo -DA
539 config HAVE_DEBUG_KMEMLEAK
542 config DEBUG_KMEMLEAK
543 bool "Kernel memory leak detector"
544 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
546 select STACKTRACE if STACKTRACE_SUPPORT
550 Say Y here if you want to enable the memory leak
551 detector. The memory allocation/freeing is traced in a way
552 similar to the Boehm's conservative garbage collector, the
553 difference being that the orphan objects are not freed but
554 only shown in /sys/kernel/debug/kmemleak. Enabling this
555 feature will introduce an overhead to memory
556 allocations. See Documentation/dev-tools/kmemleak.rst for more
559 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
560 of finding leaks due to the slab objects poisoning.
562 In order to access the kmemleak file, debugfs needs to be
563 mounted (usually at /sys/kernel/debug).
565 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
566 int "Maximum kmemleak early log entries"
567 depends on DEBUG_KMEMLEAK
571 Kmemleak must track all the memory allocations to avoid
572 reporting false positives. Since memory may be allocated or
573 freed before kmemleak is initialised, an early log buffer is
574 used to store these actions. If kmemleak reports "early log
575 buffer exceeded", please increase this value.
577 config DEBUG_KMEMLEAK_TEST
578 tristate "Simple test for the kernel memory leak detector"
579 depends on DEBUG_KMEMLEAK && m
581 This option enables a module that explicitly leaks memory.
585 config DEBUG_KMEMLEAK_DEFAULT_OFF
586 bool "Default kmemleak to off"
587 depends on DEBUG_KMEMLEAK
589 Say Y here to disable kmemleak by default. It can then be enabled
590 on the command line via kmemleak=on.
592 config DEBUG_STACK_USAGE
593 bool "Stack utilization instrumentation"
594 depends on DEBUG_KERNEL && !IA64
596 Enables the display of the minimum amount of free stack which each
597 task has ever had available in the sysrq-T and sysrq-P debug output.
599 This option will slow down process creation somewhat.
603 depends on DEBUG_KERNEL
605 Enable this to turn on extended checks in the virtual-memory system
606 that may impact performance.
610 config DEBUG_VM_VMACACHE
611 bool "Debug VMA caching"
614 Enable this to turn on VMA caching debug information. Doing so
615 can cause significant overhead, so only enable it in non-production
621 bool "Debug VM red-black trees"
624 Enable VM red-black tree debugging information and extra validations.
628 config DEBUG_VM_PGFLAGS
629 bool "Debug page-flags operations"
632 Enables extra validation on page flags operations.
636 config ARCH_HAS_DEBUG_VIRTUAL
640 bool "Debug VM translations"
641 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
643 Enable some costly sanity checks in virtual to page code. This can
644 catch mistakes with virt_to_page() and friends.
648 config DEBUG_NOMMU_REGIONS
649 bool "Debug the global anon/private NOMMU mapping region tree"
650 depends on DEBUG_KERNEL && !MMU
652 This option causes the global tree of anonymous and private mapping
653 regions to be regularly checked for invalid topology.
655 config DEBUG_MEMORY_INIT
656 bool "Debug memory initialisation" if EXPERT
659 Enable this for additional checks during memory initialisation.
660 The sanity checks verify aspects of the VM such as the memory model
661 and other information provided by the architecture. Verbose
662 information will be printed at KERN_DEBUG loglevel depending
663 on the mminit_loglevel= command-line option.
667 config MEMORY_NOTIFIER_ERROR_INJECT
668 tristate "Memory hotplug notifier error injection module"
669 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
671 This option provides the ability to inject artificial errors to
672 memory hotplug notifier chain callbacks. It is controlled through
673 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
675 If the notifier call chain should be failed with some events
676 notified, write the error code to "actions/<notifier event>/error".
678 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
680 # cd /sys/kernel/debug/notifier-error-inject/memory
681 # echo -12 > actions/MEM_GOING_OFFLINE/error
682 # echo offline > /sys/devices/system/memory/memoryXXX/state
683 bash: echo: write error: Cannot allocate memory
685 To compile this code as a module, choose M here: the module will
686 be called memory-notifier-error-inject.
690 config DEBUG_PER_CPU_MAPS
691 bool "Debug access to per_cpu maps"
692 depends on DEBUG_KERNEL
695 Say Y to verify that the per_cpu map being accessed has
696 been set up. This adds a fair amount of code to kernel memory
697 and decreases performance.
702 bool "Highmem debugging"
703 depends on DEBUG_KERNEL && HIGHMEM
705 This option enables additional error checking for high memory
706 systems. Disable for production systems.
708 config HAVE_DEBUG_STACKOVERFLOW
711 config DEBUG_STACKOVERFLOW
712 bool "Check for stack overflows"
713 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
715 Say Y here if you want to check for overflows of kernel, IRQ
716 and exception stacks (if your architecture uses them). This
717 option will show detailed messages if free stack space drops
718 below a certain limit.
720 These kinds of bugs usually occur when call-chains in the
721 kernel get too deep, especially when interrupts are
724 Use this in cases where you see apparently random memory
725 corruption, especially if it appears in 'struct thread_info'
727 If in doubt, say "N".
729 source "lib/Kconfig.kmemcheck"
731 source "lib/Kconfig.kasan"
733 endmenu # "Memory Debugging"
738 KCOV does not have any arch-specific code, but currently it is enabled
739 only for x86_64. KCOV requires testing on other archs, and most likely
740 disabling of instrumentation for some early boot code.
743 bool "Code coverage for fuzzing"
744 depends on ARCH_HAS_KCOV
746 select GCC_PLUGINS if !COMPILE_TEST
747 select GCC_PLUGIN_SANCOV if !COMPILE_TEST
749 KCOV exposes kernel code coverage information in a form suitable
750 for coverage-guided fuzzing (randomized testing).
752 If RANDOMIZE_BASE is enabled, PC values will not be stable across
753 different machines and across reboots. If you need stable PC values,
754 disable RANDOMIZE_BASE.
756 For more details, see Documentation/dev-tools/kcov.rst.
758 config KCOV_INSTRUMENT_ALL
759 bool "Instrument all code by default"
763 If you are doing generic system call fuzzing (like e.g. syzkaller),
764 then you will want to instrument the whole kernel and you should
765 say y here. If you are doing more targeted fuzzing (like e.g.
766 filesystem fuzzing with AFL) then you will want to enable coverage
767 for more specific subsets of files, and should say n here.
770 bool "Debug shared IRQ handlers"
771 depends on DEBUG_KERNEL
773 Enable this to generate a spurious interrupt as soon as a shared
774 interrupt handler is registered, and just before one is deregistered.
775 Drivers ought to be able to handle interrupts coming in at those
776 points; some don't and need to be caught.
778 menu "Debug Lockups and Hangs"
780 config LOCKUP_DETECTOR
783 config SOFTLOCKUP_DETECTOR
784 bool "Detect Soft Lockups"
785 depends on DEBUG_KERNEL && !S390
786 select LOCKUP_DETECTOR
788 Say Y here to enable the kernel to act as a watchdog to detect
791 Softlockups are bugs that cause the kernel to loop in kernel
792 mode for more than 20 seconds, without giving other tasks a
793 chance to run. The current stack trace is displayed upon
794 detection and the system will stay locked up.
796 config HARDLOCKUP_DETECTOR_PERF
798 select SOFTLOCKUP_DETECTOR
801 # Enables a timestamp based low pass filter to compensate for perf based
802 # hard lockup detection which runs too fast due to turbo modes.
804 config HARDLOCKUP_CHECK_TIMESTAMP
808 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
809 # lockup detector rather than the perf based detector.
811 config HARDLOCKUP_DETECTOR
812 bool "Detect Hard Lockups"
813 depends on DEBUG_KERNEL && !S390
814 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
815 select LOCKUP_DETECTOR
816 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
817 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
819 Say Y here to enable the kernel to act as a watchdog to detect
822 Hardlockups are bugs that cause the CPU to loop in kernel mode
823 for more than 10 seconds, without letting other interrupts have a
824 chance to run. The current stack trace is displayed upon detection
825 and the system will stay locked up.
827 config BOOTPARAM_HARDLOCKUP_PANIC
828 bool "Panic (Reboot) On Hard Lockups"
829 depends on HARDLOCKUP_DETECTOR
831 Say Y here to enable the kernel to panic on "hard lockups",
832 which are bugs that cause the kernel to loop in kernel
833 mode with interrupts disabled for more than 10 seconds (configurable
834 using the watchdog_thresh sysctl).
838 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
840 depends on HARDLOCKUP_DETECTOR
842 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
843 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
845 config BOOTPARAM_SOFTLOCKUP_PANIC
846 bool "Panic (Reboot) On Soft Lockups"
847 depends on SOFTLOCKUP_DETECTOR
849 Say Y here to enable the kernel to panic on "soft lockups",
850 which are bugs that cause the kernel to loop in kernel
851 mode for more than 20 seconds (configurable using the watchdog_thresh
852 sysctl), without giving other tasks a chance to run.
854 The panic can be used in combination with panic_timeout,
855 to cause the system to reboot automatically after a
856 lockup has been detected. This feature is useful for
857 high-availability systems that have uptime guarantees and
858 where a lockup must be resolved ASAP.
862 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
864 depends on SOFTLOCKUP_DETECTOR
866 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
867 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
869 config DETECT_HUNG_TASK
870 bool "Detect Hung Tasks"
871 depends on DEBUG_KERNEL
872 default SOFTLOCKUP_DETECTOR
874 Say Y here to enable the kernel to detect "hung tasks",
875 which are bugs that cause the task to be stuck in
876 uninterruptible "D" state indefinitely.
878 When a hung task is detected, the kernel will print the
879 current stack trace (which you should report), but the
880 task will stay in uninterruptible state. If lockdep is
881 enabled then all held locks will also be reported. This
882 feature has negligible overhead.
884 config DEFAULT_HUNG_TASK_TIMEOUT
885 int "Default timeout for hung task detection (in seconds)"
886 depends on DETECT_HUNG_TASK
889 This option controls the default timeout (in seconds) used
890 to determine when a task has become non-responsive and should
893 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
894 sysctl or by writing a value to
895 /proc/sys/kernel/hung_task_timeout_secs.
897 A timeout of 0 disables the check. The default is two minutes.
898 Keeping the default should be fine in most cases.
900 config BOOTPARAM_HUNG_TASK_PANIC
901 bool "Panic (Reboot) On Hung Tasks"
902 depends on DETECT_HUNG_TASK
904 Say Y here to enable the kernel to panic on "hung tasks",
905 which are bugs that cause the kernel to leave a task stuck
906 in uninterruptible "D" state.
908 The panic can be used in combination with panic_timeout,
909 to cause the system to reboot automatically after a
910 hung task has been detected. This feature is useful for
911 high-availability systems that have uptime guarantees and
912 where a hung tasks must be resolved ASAP.
916 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
918 depends on DETECT_HUNG_TASK
920 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
921 default 1 if BOOTPARAM_HUNG_TASK_PANIC
924 bool "Detect Workqueue Stalls"
925 depends on DEBUG_KERNEL
927 Say Y here to enable stall detection on workqueues. If a
928 worker pool doesn't make forward progress on a pending work
929 item for over a given amount of time, 30s by default, a
930 warning message is printed along with dump of workqueue
931 state. This can be configured through kernel parameter
932 "workqueue.watchdog_thresh" and its sysfs counterpart.
934 endmenu # "Debug lockups and hangs"
939 Say Y here to enable the kernel to panic when it oopses. This
940 has the same effect as setting oops=panic on the kernel command
943 This feature is useful to ensure that the kernel does not do
944 anything erroneous after an oops which could result in data
945 corruption or other issues.
949 config PANIC_ON_OOPS_VALUE
952 default 0 if !PANIC_ON_OOPS
953 default 1 if PANIC_ON_OOPS
959 Set the timeout value (in seconds) until a reboot occurs when the
960 the kernel panics. If n = 0, then we wait forever. A timeout
961 value n > 0 will wait n seconds before rebooting, while a timeout
962 value n < 0 will reboot immediately.
965 bool "Collect scheduler debugging info"
966 depends on DEBUG_KERNEL && PROC_FS
969 If you say Y here, the /proc/sched_debug file will be provided
970 that can help debug the scheduler. The runtime overhead of this
978 bool "Collect scheduler statistics"
979 depends on DEBUG_KERNEL && PROC_FS
982 If you say Y here, additional code will be inserted into the
983 scheduler and related routines to collect statistics about
984 scheduler behavior and provide them in /proc/schedstat. These
985 stats may be useful for both tuning and debugging the scheduler
986 If you aren't debugging the scheduler or trying to tune a specific
987 application, you can say N to avoid the very slight overhead
990 config SCHED_STACK_END_CHECK
991 bool "Detect stack corruption on calls to schedule()"
992 depends on DEBUG_KERNEL
995 This option checks for a stack overrun on calls to schedule().
996 If the stack end location is found to be over written always panic as
997 the content of the corrupted region can no longer be trusted.
998 This is to ensure no erroneous behaviour occurs which could result in
999 data corruption or a sporadic crash at a later stage once the region
1000 is examined. The runtime overhead introduced is minimal.
1002 config DEBUG_TIMEKEEPING
1003 bool "Enable extra timekeeping sanity checking"
1005 This option will enable additional timekeeping sanity checks
1006 which may be helpful when diagnosing issues where timekeeping
1007 problems are suspected.
1009 This may include checks in the timekeeping hotpaths, so this
1010 option may have a (very small) performance impact to some
1015 config DEBUG_PREEMPT
1016 bool "Debug preemptible kernel"
1017 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1020 If you say Y here then the kernel will use a debug variant of the
1021 commonly used smp_processor_id() function and will print warnings
1022 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1023 will detect preemption count underflows.
1025 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1027 config DEBUG_RT_MUTEXES
1028 bool "RT Mutex debugging, deadlock detection"
1029 depends on DEBUG_KERNEL && RT_MUTEXES
1031 This allows rt mutex semantics violations and rt mutex related
1032 deadlocks (lockups) to be detected and reported automatically.
1034 config DEBUG_SPINLOCK
1035 bool "Spinlock and rw-lock debugging: basic checks"
1036 depends on DEBUG_KERNEL
1037 select UNINLINE_SPIN_UNLOCK
1039 Say Y here and build SMP to catch missing spinlock initialization
1040 and certain other kinds of spinlock errors commonly made. This is
1041 best used in conjunction with the NMI watchdog so that spinlock
1042 deadlocks are also debuggable.
1044 config DEBUG_MUTEXES
1045 bool "Mutex debugging: basic checks"
1046 depends on DEBUG_KERNEL
1048 This feature allows mutex semantics violations to be detected and
1051 config DEBUG_WW_MUTEX_SLOWPATH
1052 bool "Wait/wound mutex debugging: Slowpath testing"
1053 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1054 select DEBUG_LOCK_ALLOC
1055 select DEBUG_SPINLOCK
1056 select DEBUG_MUTEXES
1058 This feature enables slowpath testing for w/w mutex users by
1059 injecting additional -EDEADLK wound/backoff cases. Together with
1060 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1061 will test all possible w/w mutex interface abuse with the
1062 exception of simply not acquiring all the required locks.
1063 Note that this feature can introduce significant overhead, so
1064 it really should not be enabled in a production or distro kernel,
1065 even a debug kernel. If you are a driver writer, enable it. If
1066 you are a distro, do not.
1068 config DEBUG_LOCK_ALLOC
1069 bool "Lock debugging: detect incorrect freeing of live locks"
1070 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1071 select DEBUG_SPINLOCK
1072 select DEBUG_MUTEXES
1073 select DEBUG_RT_MUTEXES if RT_MUTEXES
1076 This feature will check whether any held lock (spinlock, rwlock,
1077 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1078 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1079 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1080 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1081 held during task exit.
1083 config PROVE_LOCKING
1084 bool "Lock debugging: prove locking correctness"
1085 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1087 select DEBUG_SPINLOCK
1088 select DEBUG_MUTEXES
1089 select DEBUG_RT_MUTEXES if RT_MUTEXES
1090 select DEBUG_LOCK_ALLOC
1091 select TRACE_IRQFLAGS
1094 This feature enables the kernel to prove that all locking
1095 that occurs in the kernel runtime is mathematically
1096 correct: that under no circumstance could an arbitrary (and
1097 not yet triggered) combination of observed locking
1098 sequences (on an arbitrary number of CPUs, running an
1099 arbitrary number of tasks and interrupt contexts) cause a
1102 In short, this feature enables the kernel to report locking
1103 related deadlocks before they actually occur.
1105 The proof does not depend on how hard and complex a
1106 deadlock scenario would be to trigger: how many
1107 participant CPUs, tasks and irq-contexts would be needed
1108 for it to trigger. The proof also does not depend on
1109 timing: if a race and a resulting deadlock is possible
1110 theoretically (no matter how unlikely the race scenario
1111 is), it will be proven so and will immediately be
1112 reported by the kernel (once the event is observed that
1113 makes the deadlock theoretically possible).
1115 If a deadlock is impossible (i.e. the locking rules, as
1116 observed by the kernel, are mathematically correct), the
1117 kernel reports nothing.
1119 NOTE: this feature can also be enabled for rwlocks, mutexes
1120 and rwsems - in which case all dependencies between these
1121 different locking variants are observed and mapped too, and
1122 the proof of observed correctness is also maintained for an
1123 arbitrary combination of these separate locking variants.
1125 For more details, see Documentation/locking/lockdep-design.txt.
1129 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1131 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
1135 config LOCKDEP_SMALL
1139 bool "Lock usage statistics"
1140 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1142 select DEBUG_SPINLOCK
1143 select DEBUG_MUTEXES
1144 select DEBUG_RT_MUTEXES if RT_MUTEXES
1145 select DEBUG_LOCK_ALLOC
1148 This feature enables tracking lock contention points
1150 For more details, see Documentation/locking/lockstat.txt
1152 This also enables lock events required by "perf lock",
1154 If you want to use "perf lock", you also need to turn on
1155 CONFIG_EVENT_TRACING.
1157 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1158 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1160 config DEBUG_LOCKDEP
1161 bool "Lock dependency engine debugging"
1162 depends on DEBUG_KERNEL && LOCKDEP
1164 If you say Y here, the lock dependency engine will do
1165 additional runtime checks to debug itself, at the price
1166 of more runtime overhead.
1168 config DEBUG_ATOMIC_SLEEP
1169 bool "Sleep inside atomic section checking"
1170 select PREEMPT_COUNT
1171 depends on DEBUG_KERNEL
1173 If you say Y here, various routines which may sleep will become very
1174 noisy if they are called inside atomic sections: when a spinlock is
1175 held, inside an rcu read side critical section, inside preempt disabled
1176 sections, inside an interrupt, etc...
1178 config DEBUG_LOCKING_API_SELFTESTS
1179 bool "Locking API boot-time self-tests"
1180 depends on DEBUG_KERNEL
1182 Say Y here if you want the kernel to run a short self-test during
1183 bootup. The self-test checks whether common types of locking bugs
1184 are detected by debugging mechanisms or not. (if you disable
1185 lock debugging then those bugs wont be detected of course.)
1186 The following locking APIs are covered: spinlocks, rwlocks,
1189 config LOCK_TORTURE_TEST
1190 tristate "torture tests for locking"
1191 depends on DEBUG_KERNEL
1195 This option provides a kernel module that runs torture tests
1196 on kernel locking primitives. The kernel module may be built
1197 after the fact on the running kernel to be tested, if desired.
1199 Say Y here if you want kernel locking-primitive torture tests
1200 to be built into the kernel.
1201 Say M if you want these torture tests to build as a module.
1202 Say N if you are unsure.
1204 config WW_MUTEX_SELFTEST
1205 tristate "Wait/wound mutex selftests"
1207 This option provides a kernel module that runs tests on the
1208 on the struct ww_mutex locking API.
1210 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1211 with this test harness.
1213 Say M if you want these self tests to build as a module.
1214 Say N if you are unsure.
1216 endmenu # lock debugging
1218 config TRACE_IRQFLAGS
1221 Enables hooks to interrupt enabling and disabling for
1222 either tracing or lock debugging.
1225 bool "Stack backtrace support"
1226 depends on STACKTRACE_SUPPORT
1228 This option causes the kernel to create a /proc/pid/stack for
1229 every process, showing its current stack trace.
1230 It is also used by various kernel debugging features that require
1231 stack trace generation.
1233 config WARN_ALL_UNSEEDED_RANDOM
1234 bool "Warn for all uses of unseeded randomness"
1237 Some parts of the kernel contain bugs relating to their use of
1238 cryptographically secure random numbers before it's actually possible
1239 to generate those numbers securely. This setting ensures that these
1240 flaws don't go unnoticed, by enabling a message, should this ever
1241 occur. This will allow people with obscure setups to know when things
1242 are going wrong, so that they might contact developers about fixing
1245 Unfortunately, on some models of some architectures getting
1246 a fully seeded CRNG is extremely difficult, and so this can
1247 result in dmesg getting spammed for a surprisingly long
1248 time. This is really bad from a security perspective, and
1249 so architecture maintainers really need to do what they can
1250 to get the CRNG seeded sooner after the system is booted.
1251 However, since users can not do anything actionble to
1252 address this, by default the kernel will issue only a single
1253 warning for the first use of unseeded randomness.
1255 Say Y here if you want to receive warnings for all uses of
1256 unseeded randomness. This will be of use primarily for
1257 those developers interersted in improving the security of
1258 Linux kernels running on their architecture (or
1261 config DEBUG_KOBJECT
1262 bool "kobject debugging"
1263 depends on DEBUG_KERNEL
1265 If you say Y here, some extra kobject debugging messages will be sent
1268 config DEBUG_KOBJECT_RELEASE
1269 bool "kobject release debugging"
1270 depends on DEBUG_OBJECTS_TIMERS
1272 kobjects are reference counted objects. This means that their
1273 last reference count put is not predictable, and the kobject can
1274 live on past the point at which a driver decides to drop it's
1275 initial reference to the kobject gained on allocation. An
1276 example of this would be a struct device which has just been
1279 However, some buggy drivers assume that after such an operation,
1280 the memory backing the kobject can be immediately freed. This
1281 goes completely against the principles of a refcounted object.
1283 If you say Y here, the kernel will delay the release of kobjects
1284 on the last reference count to improve the visibility of this
1285 kind of kobject release bug.
1287 config HAVE_DEBUG_BUGVERBOSE
1290 config DEBUG_BUGVERBOSE
1291 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1292 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1295 Say Y here to make BUG() panics output the file name and line number
1296 of the BUG call as well as the EIP and oops trace. This aids
1297 debugging but costs about 70-100K of memory.
1300 bool "Debug linked list manipulation"
1301 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1303 Enable this to turn on extended checks in the linked-list
1308 config DEBUG_PI_LIST
1309 bool "Debug priority linked list manipulation"
1310 depends on DEBUG_KERNEL
1312 Enable this to turn on extended checks in the priority-ordered
1313 linked-list (plist) walking routines. This checks the entire
1314 list multiple times during each manipulation.
1319 bool "Debug SG table operations"
1320 depends on DEBUG_KERNEL
1322 Enable this to turn on checks on scatter-gather tables. This can
1323 help find problems with drivers that do not properly initialize
1328 config DEBUG_NOTIFIERS
1329 bool "Debug notifier call chains"
1330 depends on DEBUG_KERNEL
1332 Enable this to turn on sanity checking for notifier call chains.
1333 This is most useful for kernel developers to make sure that
1334 modules properly unregister themselves from notifier chains.
1335 This is a relatively cheap check but if you care about maximum
1338 config DEBUG_CREDENTIALS
1339 bool "Debug credential management"
1340 depends on DEBUG_KERNEL
1342 Enable this to turn on some debug checking for credential
1343 management. The additional code keeps track of the number of
1344 pointers from task_structs to any given cred struct, and checks to
1345 see that this number never exceeds the usage count of the cred
1348 Furthermore, if SELinux is enabled, this also checks that the
1349 security pointer in the cred struct is never seen to be invalid.
1353 source "kernel/rcu/Kconfig.debug"
1355 config DEBUG_WQ_FORCE_RR_CPU
1356 bool "Force round-robin CPU selection for unbound work items"
1357 depends on DEBUG_KERNEL
1360 Workqueue used to implicitly guarantee that work items queued
1361 without explicit CPU specified are put on the local CPU. This
1362 guarantee is no longer true and while local CPU is still
1363 preferred work items may be put on foreign CPUs. Kernel
1364 parameter "workqueue.debug_force_rr_cpu" is added to force
1365 round-robin CPU selection to flush out usages which depend on the
1366 now broken guarantee. This config option enables the debug
1367 feature by default. When enabled, memory and cache locality will
1370 config DEBUG_BLOCK_EXT_DEVT
1371 bool "Force extended block device numbers and spread them"
1372 depends on DEBUG_KERNEL
1376 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1377 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1378 YOU ARE DOING. Distros, please enable this and fix whatever
1381 Conventionally, block device numbers are allocated from
1382 predetermined contiguous area. However, extended block area
1383 may introduce non-contiguous block device numbers. This
1384 option forces most block device numbers to be allocated from
1385 the extended space and spreads them to discover kernel or
1386 userland code paths which assume predetermined contiguous
1387 device number allocation.
1389 Note that turning on this debug option shuffles all the
1390 device numbers for all IDE and SCSI devices including libata
1391 ones, so root partition specified using device number
1392 directly (via rdev or root=MAJ:MIN) won't work anymore.
1393 Textual device names (root=/dev/sdXn) will continue to work.
1395 Say N if you are unsure.
1397 config CPU_HOTPLUG_STATE_CONTROL
1398 bool "Enable CPU hotplug state control"
1399 depends on DEBUG_KERNEL
1400 depends on HOTPLUG_CPU
1403 Allows to write steps between "offline" and "online" to the CPUs
1404 sysfs target file so states can be stepped granular. This is a debug
1405 option for now as the hotplug machinery cannot be stopped and
1406 restarted at arbitrary points yet.
1408 Say N if your are unsure.
1410 config NOTIFIER_ERROR_INJECTION
1411 tristate "Notifier error injection"
1412 depends on DEBUG_KERNEL
1415 This option provides the ability to inject artificial errors to
1416 specified notifier chain callbacks. It is useful to test the error
1417 handling of notifier call chain failures.
1421 config PM_NOTIFIER_ERROR_INJECT
1422 tristate "PM notifier error injection module"
1423 depends on PM && NOTIFIER_ERROR_INJECTION
1424 default m if PM_DEBUG
1426 This option provides the ability to inject artificial errors to
1427 PM notifier chain callbacks. It is controlled through debugfs
1428 interface /sys/kernel/debug/notifier-error-inject/pm
1430 If the notifier call chain should be failed with some events
1431 notified, write the error code to "actions/<notifier event>/error".
1433 Example: Inject PM suspend error (-12 = -ENOMEM)
1435 # cd /sys/kernel/debug/notifier-error-inject/pm/
1436 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1437 # echo mem > /sys/power/state
1438 bash: echo: write error: Cannot allocate memory
1440 To compile this code as a module, choose M here: the module will
1441 be called pm-notifier-error-inject.
1445 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1446 tristate "OF reconfig notifier error injection module"
1447 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1449 This option provides the ability to inject artificial errors to
1450 OF reconfig notifier chain callbacks. It is controlled
1451 through debugfs interface under
1452 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1454 If the notifier call chain should be failed with some events
1455 notified, write the error code to "actions/<notifier event>/error".
1457 To compile this code as a module, choose M here: the module will
1458 be called of-reconfig-notifier-error-inject.
1462 config NETDEV_NOTIFIER_ERROR_INJECT
1463 tristate "Netdev notifier error injection module"
1464 depends on NET && NOTIFIER_ERROR_INJECTION
1466 This option provides the ability to inject artificial errors to
1467 netdevice notifier chain callbacks. It is controlled through debugfs
1468 interface /sys/kernel/debug/notifier-error-inject/netdev
1470 If the notifier call chain should be failed with some events
1471 notified, write the error code to "actions/<notifier event>/error".
1473 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1475 # cd /sys/kernel/debug/notifier-error-inject/netdev
1476 # echo -22 > actions/NETDEV_CHANGEMTU/error
1477 # ip link set eth0 mtu 1024
1478 RTNETLINK answers: Invalid argument
1480 To compile this code as a module, choose M here: the module will
1481 be called netdev-notifier-error-inject.
1485 config FAULT_INJECTION
1486 bool "Fault-injection framework"
1487 depends on DEBUG_KERNEL
1489 Provide fault-injection framework.
1490 For more details, see Documentation/fault-injection/.
1493 bool "Fault-injection capability for kmalloc"
1494 depends on FAULT_INJECTION
1495 depends on SLAB || SLUB
1497 Provide fault-injection capability for kmalloc.
1499 config FAIL_PAGE_ALLOC
1500 bool "Fault-injection capabilitiy for alloc_pages()"
1501 depends on FAULT_INJECTION
1503 Provide fault-injection capability for alloc_pages().
1505 config FAIL_MAKE_REQUEST
1506 bool "Fault-injection capability for disk IO"
1507 depends on FAULT_INJECTION && BLOCK
1509 Provide fault-injection capability for disk IO.
1511 config FAIL_IO_TIMEOUT
1512 bool "Fault-injection capability for faking disk interrupts"
1513 depends on FAULT_INJECTION && BLOCK
1515 Provide fault-injection capability on end IO handling. This
1516 will make the block layer "forget" an interrupt as configured,
1517 thus exercising the error handling.
1519 Only works with drivers that use the generic timeout handling,
1520 for others it wont do anything.
1522 config FAIL_MMC_REQUEST
1523 bool "Fault-injection capability for MMC IO"
1524 depends on FAULT_INJECTION_DEBUG_FS && MMC
1526 Provide fault-injection capability for MMC IO.
1527 This will make the mmc core return data errors. This is
1528 useful to test the error handling in the mmc block device
1529 and to test how the mmc host driver handles retries from
1533 bool "Fault-injection capability for futexes"
1535 depends on FAULT_INJECTION && FUTEX
1537 Provide fault-injection capability for futexes.
1539 config FAULT_INJECTION_DEBUG_FS
1540 bool "Debugfs entries for fault-injection capabilities"
1541 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1543 Enable configuration of fault-injection capabilities via debugfs.
1545 config FAULT_INJECTION_STACKTRACE_FILTER
1546 bool "stacktrace filter for fault-injection capabilities"
1547 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1550 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1552 Provide stacktrace filter for fault-injection capabilities
1555 bool "Latency measuring infrastructure"
1556 depends on DEBUG_KERNEL
1557 depends on STACKTRACE_SUPPORT
1559 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1566 Enable this option if you want to use the LatencyTOP tool
1567 to find out which userspace is blocking on what kernel operations.
1569 source kernel/trace/Kconfig
1571 menu "Runtime Testing"
1574 tristate "Linux Kernel Dump Test Tool Module"
1579 This module enables testing of the different dumping mechanisms by
1580 inducing system failures at predefined crash points.
1581 If you don't need it: say N
1582 Choose M here to compile this code as a module. The module will be
1585 Documentation on how to use the module can be found in
1586 Documentation/fault-injection/provoke-crashes.txt
1588 config TEST_LIST_SORT
1589 tristate "Linked list sorting test"
1590 depends on DEBUG_KERNEL || m
1592 Enable this to turn on 'list_sort()' function test. This test is
1593 executed only once during system boot (so affects only boot time),
1594 or at module load time.
1599 tristate "Array-based sort test"
1600 depends on DEBUG_KERNEL || m
1602 This option enables the self-test function of 'sort()' at boot,
1603 or at module load time.
1607 config KPROBES_SANITY_TEST
1608 bool "Kprobes sanity tests"
1609 depends on DEBUG_KERNEL
1613 This option provides for testing basic kprobes functionality on
1614 boot. A sample kprobe, jprobe and kretprobe are inserted and
1615 verified for functionality.
1617 Say N if you are unsure.
1619 config BACKTRACE_SELF_TEST
1620 tristate "Self test for the backtrace code"
1621 depends on DEBUG_KERNEL
1624 This option provides a kernel module that can be used to test
1625 the kernel stack backtrace code. This option is not useful
1626 for distributions or general kernels, but only for kernel
1627 developers working on architecture code.
1629 Note that if you want to also test saved backtraces, you will
1630 have to enable STACKTRACE as well.
1632 Say N if you are unsure.
1635 tristate "Red-Black tree test"
1636 depends on DEBUG_KERNEL
1638 A benchmark measuring the performance of the rbtree library.
1639 Also includes rbtree invariant checks.
1641 config INTERVAL_TREE_TEST
1642 tristate "Interval tree test"
1643 depends on DEBUG_KERNEL
1644 select INTERVAL_TREE
1646 A benchmark measuring the performance of the interval tree library
1649 tristate "Per cpu operations test"
1650 depends on m && DEBUG_KERNEL
1652 Enable this option to build test module which validates per-cpu
1657 config ATOMIC64_SELFTEST
1658 tristate "Perform an atomic64_t self-test"
1660 Enable this option to test the atomic64_t functions at boot or
1661 at module load time.
1665 config ASYNC_RAID6_TEST
1666 tristate "Self test for hardware accelerated raid6 recovery"
1667 depends on ASYNC_RAID6_RECOV
1670 This is a one-shot self test that permutes through the
1671 recovery of all the possible two disk failure scenarios for a
1672 N-disk array. Recovery is performed with the asynchronous
1673 raid6 recovery routines, and will optionally use an offload
1674 engine if one is available.
1679 tristate "Test functions located in the hexdump module at runtime"
1681 config TEST_STRING_HELPERS
1682 tristate "Test functions located in the string_helpers module at runtime"
1685 tristate "Test kstrto*() family of functions at runtime"
1688 tristate "Test printf() family of functions at runtime"
1691 tristate "Test bitmap_*() family of functions at runtime"
1694 Enable this option to test the bitmap functions at boot.
1699 tristate "Test functions located in the uuid module at runtime"
1701 config TEST_RHASHTABLE
1702 tristate "Perform selftest on resizable hash table"
1705 Enable this option to test the rhashtable functions at boot.
1710 tristate "Perform selftest on hash functions"
1713 Enable this option to test the kernel's integer (<linux/hash.h>),
1714 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1715 hash functions on boot (or module load).
1717 This is intended to help people writing architecture-specific
1718 optimized versions. If unsure, say N.
1721 tristate "Perform selftest on priority array manager"
1725 Enable this option to test priority array manager on boot
1730 endmenu # runtime tests
1732 config PROVIDE_OHCI1394_DMA_INIT
1733 bool "Remote debugging over FireWire early on boot"
1734 depends on PCI && X86
1736 If you want to debug problems which hang or crash the kernel early
1737 on boot and the crashing machine has a FireWire port, you can use
1738 this feature to remotely access the memory of the crashed machine
1739 over FireWire. This employs remote DMA as part of the OHCI1394
1740 specification which is now the standard for FireWire controllers.
1742 With remote DMA, you can monitor the printk buffer remotely using
1743 firescope and access all memory below 4GB using fireproxy from gdb.
1744 Even controlling a kernel debugger is possible using remote DMA.
1748 If ohci1394_dma=early is used as boot parameter, it will initialize
1749 all OHCI1394 controllers which are found in the PCI config space.
1751 As all changes to the FireWire bus such as enabling and disabling
1752 devices cause a bus reset and thereby disable remote DMA for all
1753 devices, be sure to have the cable plugged and FireWire enabled on
1754 the debugging host before booting the debug target for debugging.
1756 This code (~1k) is freed after boot. By then, the firewire stack
1757 in charge of the OHCI-1394 controllers should be used instead.
1759 See Documentation/debugging-via-ohci1394.txt for more information.
1761 config DMA_API_DEBUG
1762 bool "Enable debugging of DMA-API usage"
1763 depends on HAVE_DMA_API_DEBUG
1765 Enable this option to debug the use of the DMA API by device drivers.
1766 With this option you will be able to detect common bugs in device
1767 drivers like double-freeing of DMA mappings or freeing mappings that
1768 were never allocated.
1770 This also attempts to catch cases where a page owned by DMA is
1771 accessed by the cpu in a way that could cause data corruption. For
1772 example, this enables cow_user_page() to check that the source page is
1775 This option causes a performance degradation. Use only if you want to
1776 debug device drivers and dma interactions.
1781 tristate "Test module loading with 'hello world' module"
1785 This builds the "test_module" module that emits "Hello, world"
1786 on printk when loaded. It is designed to be used for basic
1787 evaluation of the module loading subsystem (for example when
1788 validating module verification). It lacks any extra dependencies,
1789 and will not normally be loaded by the system unless explicitly
1794 config TEST_USER_COPY
1795 tristate "Test user/kernel boundary protections"
1799 This builds the "test_user_copy" module that runs sanity checks
1800 on the copy_to/from_user infrastructure, making sure basic
1801 user/kernel boundary testing is working. If it fails to load,
1802 a regression has been detected in the user/kernel memory boundary
1808 tristate "Test BPF filter functionality"
1812 This builds the "test_bpf" module that runs various test vectors
1813 against the BPF interpreter or BPF JIT compiler depending on the
1814 current setting. This is in particular useful for BPF JIT compiler
1815 development, but also to run regression tests against changes in
1816 the interpreter code. It also enables test stubs for eBPF maps and
1817 verifier used by user space verifier testsuite.
1821 config TEST_FIRMWARE
1822 tristate "Test firmware loading via userspace interface"
1824 depends on FW_LOADER
1826 This builds the "test_firmware" module that creates a userspace
1827 interface for testing firmware loading. This can be used to
1828 control the triggering of firmware loading without needing an
1829 actual firmware-using device. The contents can be rechecked by
1835 tristate "sysctl test driver"
1837 depends on PROC_SYSCTL
1839 This builds the "test_sysctl" module. This driver enables to test the
1840 proc sysctl interfaces available to drivers safely without affecting
1841 production knobs which might alter system functionality.
1846 tristate "udelay test driver"
1849 This builds the "udelay_test" module that helps to make sure
1850 that udelay() is working properly.
1856 depends on HAVE_MEMBLOCK
1858 This option adds a kernel parameter 'memtest', which allows memtest
1860 memtest=0, mean disabled; -- default
1861 memtest=1, mean do 1 test pattern;
1863 memtest=17, mean do 17 test patterns.
1864 If you are unsure how to answer this question, answer N.
1866 config TEST_STATIC_KEYS
1867 tristate "Test static keys"
1871 Test the static key interfaces.
1875 config BUG_ON_DATA_CORRUPTION
1876 bool "Trigger a BUG when data corruption is detected"
1879 Select this option if the kernel should BUG when it encounters
1880 data corruption in kernel memory structures when they get checked
1886 tristate "kmod stress tester"
1889 depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS
1890 depends on NETDEVICES && NET_CORE && INET # for TUN
1896 Test the kernel's module loading mechanism: kmod. kmod implements
1897 support to load modules using the Linux kernel's usermode helper.
1898 This test provides a series of tests against kmod.
1900 Although technically you can either build test_kmod as a module or
1901 into the kernel we disallow building it into the kernel since
1902 it stress tests request_module() and this will very likely cause
1903 some issues by taking over precious threads available from other
1904 module load requests, ultimately this could be fatal.
1908 tools/testing/selftests/kmod/kmod.sh --help
1912 source "samples/Kconfig"
1914 source "lib/Kconfig.kgdb"
1916 source "lib/Kconfig.ubsan"
1918 config ARCH_HAS_DEVMEM_IS_ALLOWED
1921 config STRICT_DEVMEM
1922 bool "Filter access to /dev/mem"
1923 depends on MMU && DEVMEM
1924 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
1925 default y if TILE || PPC
1927 If this option is disabled, you allow userspace (root) access to all
1928 of memory, including kernel and userspace memory. Accidental
1929 access to this is obviously disastrous, but specific access can
1930 be used by people debugging the kernel. Note that with PAT support
1931 enabled, even in this case there are restrictions on /dev/mem
1932 use due to the cache aliasing requirements.
1934 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
1935 file only allows userspace access to PCI space and the BIOS code and
1936 data regions. This is sufficient for dosemu and X and all common
1941 config IO_STRICT_DEVMEM
1942 bool "Filter I/O access to /dev/mem"
1943 depends on STRICT_DEVMEM
1945 If this option is disabled, you allow userspace (root) access to all
1946 io-memory regardless of whether a driver is actively using that
1947 range. Accidental access to this is obviously disastrous, but
1948 specific access can be used by people debugging kernel drivers.
1950 If this option is switched on, the /dev/mem file only allows
1951 userspace access to *idle* io-memory ranges (see /proc/iomem) This
1952 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
1953 if the driver using a given range cannot be disabled.
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