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/kernel-parameters.txt
18 config MESSAGE_LOGLEVEL_DEFAULT
19 int "Default message log level (1-7)"
23 Default log level for printk statements with no specified priority.
25 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
26 that are auditing their logs closely may want to set it to a lower
29 config BOOT_PRINTK_DELAY
30 bool "Delay each boot printk message by N milliseconds"
31 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
33 This build option allows you to read kernel boot messages
34 by inserting a short delay after each one. The delay is
35 specified in milliseconds on the kernel command line,
38 It is likely that you would also need to use "lpj=M" to preset
39 the "loops per jiffie" value.
40 See a previous boot log for the "lpj" value to use for your
41 system, and then set "lpj=M" before setting "boot_delay=N".
42 NOTE: Using this option may adversely affect SMP systems.
43 I.e., processors other than the first one may not boot up.
44 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
45 what it believes to be lockup conditions.
48 bool "Enable dynamic printk() support"
54 Compiles debug level messages into the kernel, which would not
55 otherwise be available at runtime. These messages can then be
56 enabled/disabled based on various levels of scope - per source file,
57 function, module, format string, and line number. This mechanism
58 implicitly compiles in all pr_debug() and dev_dbg() calls, which
59 enlarges the kernel text size by about 2%.
61 If a source file is compiled with DEBUG flag set, any
62 pr_debug() calls in it are enabled by default, but can be
63 disabled at runtime as below. Note that DEBUG flag is
64 turned on by many CONFIG_*DEBUG* options.
68 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
69 which is contained in the 'debugfs' filesystem. Thus, the debugfs
70 filesystem must first be mounted before making use of this feature.
71 We refer the control file as: <debugfs>/dynamic_debug/control. This
72 file contains a list of the debug statements that can be enabled. The
73 format for each line of the file is:
75 filename:lineno [module]function flags format
77 filename : source file of the debug statement
78 lineno : line number of the debug statement
79 module : module that contains the debug statement
80 function : function that contains the debug statement
81 flags : '=p' means the line is turned 'on' for printing
82 format : the format used for the debug statement
86 nullarbor:~ # cat <debugfs>/dynamic_debug/control
87 # filename:lineno [module]function flags format
88 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
89 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
90 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
94 // enable the message at line 1603 of file svcsock.c
95 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
96 <debugfs>/dynamic_debug/control
98 // enable all the messages in file svcsock.c
99 nullarbor:~ # echo -n 'file svcsock.c +p' >
100 <debugfs>/dynamic_debug/control
102 // enable all the messages in the NFS server module
103 nullarbor:~ # echo -n 'module nfsd +p' >
104 <debugfs>/dynamic_debug/control
106 // enable all 12 messages in the function svc_process()
107 nullarbor:~ # echo -n 'func svc_process +p' >
108 <debugfs>/dynamic_debug/control
110 // disable all 12 messages in the function svc_process()
111 nullarbor:~ # echo -n 'func svc_process -p' >
112 <debugfs>/dynamic_debug/control
114 See Documentation/dynamic-debug-howto.txt for additional information.
116 endmenu # "printk and dmesg options"
118 menu "Compile-time checks and compiler options"
121 bool "Compile the kernel with debug info"
122 depends on DEBUG_KERNEL && !COMPILE_TEST
124 If you say Y here the resulting kernel image will include
125 debugging info resulting in a larger kernel image.
126 This adds debug symbols to the kernel and modules (gcc -g), and
127 is needed if you intend to use kernel crashdump or binary object
128 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
129 Say Y here only if you plan to debug the kernel.
133 config DEBUG_INFO_REDUCED
134 bool "Reduce debugging information"
135 depends on DEBUG_INFO
137 If you say Y here gcc is instructed to generate less debugging
138 information for structure types. This means that tools that
139 need full debugging information (like kgdb or systemtap) won't
140 be happy. But if you merely need debugging information to
141 resolve line numbers there is no loss. Advantage is that
142 build directory object sizes shrink dramatically over a full
143 DEBUG_INFO build and compile times are reduced too.
144 Only works with newer gcc versions.
146 config DEBUG_INFO_SPLIT
147 bool "Produce split debuginfo in .dwo files"
148 depends on DEBUG_INFO
150 Generate debug info into separate .dwo files. This significantly
151 reduces the build directory size for builds with DEBUG_INFO,
152 because it stores the information only once on disk in .dwo
153 files instead of multiple times in object files and executables.
154 In addition the debug information is also compressed.
156 Requires recent gcc (4.7+) and recent gdb/binutils.
157 Any tool that packages or reads debug information would need
158 to know about the .dwo files and include them.
159 Incompatible with older versions of ccache.
161 config DEBUG_INFO_DWARF4
162 bool "Generate dwarf4 debuginfo"
163 depends on DEBUG_INFO
165 Generate dwarf4 debug info. This requires recent versions
166 of gcc and gdb. It makes the debug information larger.
167 But it significantly improves the success of resolving
168 variables in gdb on optimized code.
171 bool "Provide GDB scripts for kernel debugging"
172 depends on DEBUG_INFO
174 This creates the required links to GDB helper scripts in the
175 build directory. If you load vmlinux into gdb, the helper
176 scripts will be automatically imported by gdb as well, and
177 additional functions are available to analyze a Linux kernel
178 instance. See Documentation/gdb-kernel-debugging.txt for further
181 config ENABLE_WARN_DEPRECATED
182 bool "Enable __deprecated logic"
185 Enable the __deprecated logic in the kernel build.
186 Disable this to suppress the "warning: 'foo' is deprecated
187 (declared at kernel/power/somefile.c:1234)" messages.
189 config ENABLE_MUST_CHECK
190 bool "Enable __must_check logic"
193 Enable the __must_check logic in the kernel build. Disable this to
194 suppress the "warning: ignoring return value of 'foo', declared with
195 attribute warn_unused_result" messages.
198 int "Warn for stack frames larger than (needs gcc 4.4)"
201 default 1024 if !64BIT
202 default 2048 if 64BIT
204 Tell gcc to warn at build time for stack frames larger than this.
205 Setting this too low will cause a lot of warnings.
206 Setting it to 0 disables the warning.
209 config STRIP_ASM_SYMS
210 bool "Strip assembler-generated symbols during link"
213 Strip internal assembler-generated symbols during a link (symbols
214 that look like '.Lxxx') so they don't pollute the output of
215 get_wchan() and suchlike.
218 bool "Generate readable assembler code"
219 depends on DEBUG_KERNEL
221 Disable some compiler optimizations that tend to generate human unreadable
222 assembler output. This may make the kernel slightly slower, but it helps
223 to keep kernel developers who have to stare a lot at assembler listings
226 config UNUSED_SYMBOLS
227 bool "Enable unused/obsolete exported symbols"
230 Unused but exported symbols make the kernel needlessly bigger. For
231 that reason most of these unused exports will soon be removed. This
232 option is provided temporarily to provide a transition period in case
233 some external kernel module needs one of these symbols anyway. If you
234 encounter such a case in your module, consider if you are actually
235 using the right API. (rationale: since nobody in the kernel is using
236 this in a module, there is a pretty good chance it's actually the
237 wrong interface to use). If you really need the symbol, please send a
238 mail to the linux kernel mailing list mentioning the symbol and why
239 you really need it, and what the merge plan to the mainline kernel for
243 bool "Track page owner"
244 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
248 select PAGE_EXTENSION
250 This keeps track of what call chain is the owner of a page, may
251 help to find bare alloc_page(s) leaks. Even if you include this
252 feature on your build, it is disabled in default. You should pass
253 "page_owner=on" to boot parameter in order to enable it. Eats
254 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
255 for user-space helper.
260 bool "Debug Filesystem"
263 debugfs is a virtual file system that kernel developers use to put
264 debugging files into. Enable this option to be able to read and
265 write to these files.
267 For detailed documentation on the debugfs API, see
268 Documentation/DocBook/filesystems.
273 bool "Run 'make headers_check' when building vmlinux"
276 This option will extract the user-visible kernel headers whenever
277 building the kernel, and will run basic sanity checks on them to
278 ensure that exported files do not attempt to include files which
279 were not exported, etc.
281 If you're making modifications to header files which are
282 relevant for userspace, say 'Y', and check the headers
283 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
284 your build tree), to make sure they're suitable.
286 config DEBUG_SECTION_MISMATCH
287 bool "Enable full Section mismatch analysis"
289 The section mismatch analysis checks if there are illegal
290 references from one section to another section.
291 During linktime or runtime, some sections are dropped;
292 any use of code/data previously in these sections would
293 most likely result in an oops.
294 In the code, functions and variables are annotated with
295 __init,, etc. (see the full list in include/linux/init.h),
296 which results in the code/data being placed in specific sections.
297 The section mismatch analysis is always performed after a full
298 kernel build, and enabling this option causes the following
299 additional steps to occur:
300 - Add the option -fno-inline-functions-called-once to gcc commands.
301 When inlining a function annotated with __init in a non-init
302 function, we would lose the section information and thus
303 the analysis would not catch the illegal reference.
304 This option tells gcc to inline less (but it does result in
306 - Run the section mismatch analysis for each module/built-in.o file.
307 When we run the section mismatch analysis on vmlinux.o, we
308 lose valueble information about where the mismatch was
310 Running the analysis for each module/built-in.o file
311 tells where the mismatch happens much closer to the
312 source. The drawback is that the same mismatch is
313 reported at least twice.
314 - Enable verbose reporting from modpost in order to help resolve
315 the section mismatches that are reported.
317 config SECTION_MISMATCH_WARN_ONLY
318 bool "Make section mismatch errors non-fatal"
321 If you say N here, the build process will fail if there are any
322 section mismatch, instead of just throwing warnings.
327 # Select this config option from the architecture Kconfig, if it
328 # is preferred to always offer frame pointers as a config
329 # option on the architecture (regardless of KERNEL_DEBUG):
331 config ARCH_WANT_FRAME_POINTERS
336 bool "Compile the kernel with frame pointers"
337 depends on DEBUG_KERNEL && \
338 (CRIS || M68K || FRV || UML || \
339 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \
340 ARCH_WANT_FRAME_POINTERS
341 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
343 If you say Y here the resulting kernel image will be slightly
344 larger and slower, but it gives very useful debugging information
345 in case of kernel bugs. (precise oopses/stacktraces/warnings)
347 config STACK_VALIDATION
348 bool "Compile-time stack metadata validation"
349 depends on HAVE_STACK_VALIDATION
352 Add compile-time checks to validate stack metadata, including frame
353 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
354 that runtime stack traces are more reliable.
356 For more information, see
357 tools/objtool/Documentation/stack-validation.txt.
359 config DEBUG_FORCE_WEAK_PER_CPU
360 bool "Force weak per-cpu definitions"
361 depends on DEBUG_KERNEL
363 s390 and alpha require percpu variables in modules to be
364 defined weak to work around addressing range issue which
365 puts the following two restrictions on percpu variable
368 1. percpu symbols must be unique whether static or not
369 2. percpu variables can't be defined inside a function
371 To ensure that generic code follows the above rules, this
372 option forces all percpu variables to be defined as weak.
374 endmenu # "Compiler options"
377 bool "Magic SysRq key"
380 If you say Y here, you will have some control over the system even
381 if the system crashes for example during kernel debugging (e.g., you
382 will be able to flush the buffer cache to disk, reboot the system
383 immediately or dump some status information). This is accomplished
384 by pressing various keys while holding SysRq (Alt+PrintScreen). It
385 also works on a serial console (on PC hardware at least), if you
386 send a BREAK and then within 5 seconds a command keypress. The
387 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
388 unless you really know what this hack does.
390 config MAGIC_SYSRQ_DEFAULT_ENABLE
391 hex "Enable magic SysRq key functions by default"
392 depends on MAGIC_SYSRQ
395 Specifies which SysRq key functions are enabled by default.
396 This may be set to 1 or 0 to enable or disable them all, or
397 to a bitmask as described in Documentation/sysrq.txt.
400 bool "Kernel debugging"
402 Say Y here if you are developing drivers or trying to debug and
403 identify kernel problems.
405 menu "Memory Debugging"
407 source mm/Kconfig.debug
410 bool "Debug object operations"
411 depends on DEBUG_KERNEL
413 If you say Y here, additional code will be inserted into the
414 kernel to track the life time of various objects and validate
415 the operations on those objects.
417 config DEBUG_OBJECTS_SELFTEST
418 bool "Debug objects selftest"
419 depends on DEBUG_OBJECTS
421 This enables the selftest of the object debug code.
423 config DEBUG_OBJECTS_FREE
424 bool "Debug objects in freed memory"
425 depends on DEBUG_OBJECTS
427 This enables checks whether a k/v free operation frees an area
428 which contains an object which has not been deactivated
429 properly. This can make kmalloc/kfree-intensive workloads
432 config DEBUG_OBJECTS_TIMERS
433 bool "Debug timer objects"
434 depends on DEBUG_OBJECTS
436 If you say Y here, additional code will be inserted into the
437 timer routines to track the life time of timer objects and
438 validate the timer operations.
440 config DEBUG_OBJECTS_WORK
441 bool "Debug work objects"
442 depends on DEBUG_OBJECTS
444 If you say Y here, additional code will be inserted into the
445 work queue routines to track the life time of work objects and
446 validate the work operations.
448 config DEBUG_OBJECTS_RCU_HEAD
449 bool "Debug RCU callbacks objects"
450 depends on DEBUG_OBJECTS
452 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
454 config DEBUG_OBJECTS_PERCPU_COUNTER
455 bool "Debug percpu counter objects"
456 depends on DEBUG_OBJECTS
458 If you say Y here, additional code will be inserted into the
459 percpu counter routines to track the life time of percpu counter
460 objects and validate the percpu counter operations.
462 config DEBUG_OBJECTS_ENABLE_DEFAULT
463 int "debug_objects bootup default value (0-1)"
466 depends on DEBUG_OBJECTS
468 Debug objects boot parameter default value
471 bool "Debug slab memory allocations"
472 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
474 Say Y here to have the kernel do limited verification on memory
475 allocation as well as poisoning memory on free to catch use of freed
476 memory. This can make kmalloc/kfree-intensive workloads much slower.
478 config DEBUG_SLAB_LEAK
479 bool "Memory leak debugging"
480 depends on DEBUG_SLAB
483 bool "SLUB debugging on by default"
484 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
487 Boot with debugging on by default. SLUB boots by default with
488 the runtime debug capabilities switched off. Enabling this is
489 equivalent to specifying the "slub_debug" parameter on boot.
490 There is no support for more fine grained debug control like
491 possible with slub_debug=xxx. SLUB debugging may be switched
492 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
497 bool "Enable SLUB performance statistics"
498 depends on SLUB && SYSFS
500 SLUB statistics are useful to debug SLUBs allocation behavior in
501 order find ways to optimize the allocator. This should never be
502 enabled for production use since keeping statistics slows down
503 the allocator by a few percentage points. The slabinfo command
504 supports the determination of the most active slabs to figure
505 out which slabs are relevant to a particular load.
506 Try running: slabinfo -DA
508 config HAVE_DEBUG_KMEMLEAK
511 config DEBUG_KMEMLEAK
512 bool "Kernel memory leak detector"
513 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
515 select STACKTRACE if STACKTRACE_SUPPORT
519 Say Y here if you want to enable the memory leak
520 detector. The memory allocation/freeing is traced in a way
521 similar to the Boehm's conservative garbage collector, the
522 difference being that the orphan objects are not freed but
523 only shown in /sys/kernel/debug/kmemleak. Enabling this
524 feature will introduce an overhead to memory
525 allocations. See Documentation/kmemleak.txt for more
528 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
529 of finding leaks due to the slab objects poisoning.
531 In order to access the kmemleak file, debugfs needs to be
532 mounted (usually at /sys/kernel/debug).
534 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
535 int "Maximum kmemleak early log entries"
536 depends on DEBUG_KMEMLEAK
540 Kmemleak must track all the memory allocations to avoid
541 reporting false positives. Since memory may be allocated or
542 freed before kmemleak is initialised, an early log buffer is
543 used to store these actions. If kmemleak reports "early log
544 buffer exceeded", please increase this value.
546 config DEBUG_KMEMLEAK_TEST
547 tristate "Simple test for the kernel memory leak detector"
548 depends on DEBUG_KMEMLEAK && m
550 This option enables a module that explicitly leaks memory.
554 config DEBUG_KMEMLEAK_DEFAULT_OFF
555 bool "Default kmemleak to off"
556 depends on DEBUG_KMEMLEAK
558 Say Y here to disable kmemleak by default. It can then be enabled
559 on the command line via kmemleak=on.
561 config DEBUG_STACK_USAGE
562 bool "Stack utilization instrumentation"
563 depends on DEBUG_KERNEL && !IA64
565 Enables the display of the minimum amount of free stack which each
566 task has ever had available in the sysrq-T and sysrq-P debug output.
568 This option will slow down process creation somewhat.
572 depends on DEBUG_KERNEL
574 Enable this to turn on extended checks in the virtual-memory system
575 that may impact performance.
579 config DEBUG_VM_VMACACHE
580 bool "Debug VMA caching"
583 Enable this to turn on VMA caching debug information. Doing so
584 can cause significant overhead, so only enable it in non-production
590 bool "Debug VM red-black trees"
593 Enable VM red-black tree debugging information and extra validations.
597 config DEBUG_VM_PGFLAGS
598 bool "Debug page-flags operations"
601 Enables extra validation on page flags operations.
606 bool "Debug VM translations"
607 depends on DEBUG_KERNEL && X86
609 Enable some costly sanity checks in virtual to page code. This can
610 catch mistakes with virt_to_page() and friends.
614 config DEBUG_NOMMU_REGIONS
615 bool "Debug the global anon/private NOMMU mapping region tree"
616 depends on DEBUG_KERNEL && !MMU
618 This option causes the global tree of anonymous and private mapping
619 regions to be regularly checked for invalid topology.
621 config DEBUG_MEMORY_INIT
622 bool "Debug memory initialisation" if EXPERT
625 Enable this for additional checks during memory initialisation.
626 The sanity checks verify aspects of the VM such as the memory model
627 and other information provided by the architecture. Verbose
628 information will be printed at KERN_DEBUG loglevel depending
629 on the mminit_loglevel= command-line option.
633 config MEMORY_NOTIFIER_ERROR_INJECT
634 tristate "Memory hotplug notifier error injection module"
635 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
637 This option provides the ability to inject artificial errors to
638 memory hotplug notifier chain callbacks. It is controlled through
639 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
641 If the notifier call chain should be failed with some events
642 notified, write the error code to "actions/<notifier event>/error".
644 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
646 # cd /sys/kernel/debug/notifier-error-inject/memory
647 # echo -12 > actions/MEM_GOING_OFFLINE/error
648 # echo offline > /sys/devices/system/memory/memoryXXX/state
649 bash: echo: write error: Cannot allocate memory
651 To compile this code as a module, choose M here: the module will
652 be called memory-notifier-error-inject.
656 config DEBUG_PER_CPU_MAPS
657 bool "Debug access to per_cpu maps"
658 depends on DEBUG_KERNEL
661 Say Y to verify that the per_cpu map being accessed has
662 been set up. This adds a fair amount of code to kernel memory
663 and decreases performance.
668 bool "Highmem debugging"
669 depends on DEBUG_KERNEL && HIGHMEM
671 This option enables additional error checking for high memory
672 systems. Disable for production systems.
674 config HAVE_DEBUG_STACKOVERFLOW
677 config DEBUG_STACKOVERFLOW
678 bool "Check for stack overflows"
679 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
681 Say Y here if you want to check for overflows of kernel, IRQ
682 and exception stacks (if your architecture uses them). This
683 option will show detailed messages if free stack space drops
684 below a certain limit.
686 These kinds of bugs usually occur when call-chains in the
687 kernel get too deep, especially when interrupts are
690 Use this in cases where you see apparently random memory
691 corruption, especially if it appears in 'struct thread_info'
693 If in doubt, say "N".
695 source "lib/Kconfig.kmemcheck"
697 source "lib/Kconfig.kasan"
699 endmenu # "Memory Debugging"
704 KCOV does not have any arch-specific code, but currently it is enabled
705 only for x86_64. KCOV requires testing on other archs, and most likely
706 disabling of instrumentation for some early boot code.
709 bool "Code coverage for fuzzing"
710 depends on ARCH_HAS_KCOV
713 KCOV exposes kernel code coverage information in a form suitable
714 for coverage-guided fuzzing (randomized testing).
716 If RANDOMIZE_BASE is enabled, PC values will not be stable across
717 different machines and across reboots. If you need stable PC values,
718 disable RANDOMIZE_BASE.
720 For more details, see Documentation/kcov.txt.
723 bool "Debug shared IRQ handlers"
724 depends on DEBUG_KERNEL
726 Enable this to generate a spurious interrupt as soon as a shared
727 interrupt handler is registered, and just before one is deregistered.
728 Drivers ought to be able to handle interrupts coming in at those
729 points; some don't and need to be caught.
731 menu "Debug Lockups and Hangs"
733 config LOCKUP_DETECTOR
734 bool "Detect Hard and Soft Lockups"
735 depends on DEBUG_KERNEL && !S390
737 Say Y here to enable the kernel to act as a watchdog to detect
738 hard and soft lockups.
740 Softlockups are bugs that cause the kernel to loop in kernel
741 mode for more than 20 seconds, without giving other tasks a
742 chance to run. The current stack trace is displayed upon
743 detection and the system will stay locked up.
745 Hardlockups are bugs that cause the CPU to loop in kernel mode
746 for more than 10 seconds, without letting other interrupts have a
747 chance to run. The current stack trace is displayed upon detection
748 and the system will stay locked up.
750 The overhead should be minimal. A periodic hrtimer runs to
751 generate interrupts and kick the watchdog task every 4 seconds.
752 An NMI is generated every 10 seconds or so to check for hardlockups.
754 The frequency of hrtimer and NMI events and the soft and hard lockup
755 thresholds can be controlled through the sysctl watchdog_thresh.
757 config HARDLOCKUP_DETECTOR
759 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
760 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
762 config BOOTPARAM_HARDLOCKUP_PANIC
763 bool "Panic (Reboot) On Hard Lockups"
764 depends on HARDLOCKUP_DETECTOR
766 Say Y here to enable the kernel to panic on "hard lockups",
767 which are bugs that cause the kernel to loop in kernel
768 mode with interrupts disabled for more than 10 seconds (configurable
769 using the watchdog_thresh sysctl).
773 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
775 depends on HARDLOCKUP_DETECTOR
777 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
778 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
780 config BOOTPARAM_SOFTLOCKUP_PANIC
781 bool "Panic (Reboot) On Soft Lockups"
782 depends on LOCKUP_DETECTOR
784 Say Y here to enable the kernel to panic on "soft lockups",
785 which are bugs that cause the kernel to loop in kernel
786 mode for more than 20 seconds (configurable using the watchdog_thresh
787 sysctl), without giving other tasks a chance to run.
789 The panic can be used in combination with panic_timeout,
790 to cause the system to reboot automatically after a
791 lockup has been detected. This feature is useful for
792 high-availability systems that have uptime guarantees and
793 where a lockup must be resolved ASAP.
797 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
799 depends on LOCKUP_DETECTOR
801 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
802 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
804 config DETECT_HUNG_TASK
805 bool "Detect Hung Tasks"
806 depends on DEBUG_KERNEL
807 default LOCKUP_DETECTOR
809 Say Y here to enable the kernel to detect "hung tasks",
810 which are bugs that cause the task to be stuck in
811 uninterruptible "D" state indefinitiley.
813 When a hung task is detected, the kernel will print the
814 current stack trace (which you should report), but the
815 task will stay in uninterruptible state. If lockdep is
816 enabled then all held locks will also be reported. This
817 feature has negligible overhead.
819 config DEFAULT_HUNG_TASK_TIMEOUT
820 int "Default timeout for hung task detection (in seconds)"
821 depends on DETECT_HUNG_TASK
824 This option controls the default timeout (in seconds) used
825 to determine when a task has become non-responsive and should
828 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
829 sysctl or by writing a value to
830 /proc/sys/kernel/hung_task_timeout_secs.
832 A timeout of 0 disables the check. The default is two minutes.
833 Keeping the default should be fine in most cases.
835 config BOOTPARAM_HUNG_TASK_PANIC
836 bool "Panic (Reboot) On Hung Tasks"
837 depends on DETECT_HUNG_TASK
839 Say Y here to enable the kernel to panic on "hung tasks",
840 which are bugs that cause the kernel to leave a task stuck
841 in uninterruptible "D" state.
843 The panic can be used in combination with panic_timeout,
844 to cause the system to reboot automatically after a
845 hung task has been detected. This feature is useful for
846 high-availability systems that have uptime guarantees and
847 where a hung tasks must be resolved ASAP.
851 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
853 depends on DETECT_HUNG_TASK
855 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
856 default 1 if BOOTPARAM_HUNG_TASK_PANIC
859 bool "Detect Workqueue Stalls"
860 depends on DEBUG_KERNEL
862 Say Y here to enable stall detection on workqueues. If a
863 worker pool doesn't make forward progress on a pending work
864 item for over a given amount of time, 30s by default, a
865 warning message is printed along with dump of workqueue
866 state. This can be configured through kernel parameter
867 "workqueue.watchdog_thresh" and its sysfs counterpart.
869 endmenu # "Debug lockups and hangs"
874 Say Y here to enable the kernel to panic when it oopses. This
875 has the same effect as setting oops=panic on the kernel command
878 This feature is useful to ensure that the kernel does not do
879 anything erroneous after an oops which could result in data
880 corruption or other issues.
884 config PANIC_ON_OOPS_VALUE
887 default 0 if !PANIC_ON_OOPS
888 default 1 if PANIC_ON_OOPS
894 Set the timeout value (in seconds) until a reboot occurs when the
895 the kernel panics. If n = 0, then we wait forever. A timeout
896 value n > 0 will wait n seconds before rebooting, while a timeout
897 value n < 0 will reboot immediately.
900 bool "Collect scheduler debugging info"
901 depends on DEBUG_KERNEL && PROC_FS
904 If you say Y here, the /proc/sched_debug file will be provided
905 that can help debug the scheduler. The runtime overhead of this
913 bool "Collect scheduler statistics"
914 depends on DEBUG_KERNEL && PROC_FS
917 If you say Y here, additional code will be inserted into the
918 scheduler and related routines to collect statistics about
919 scheduler behavior and provide them in /proc/schedstat. These
920 stats may be useful for both tuning and debugging the scheduler
921 If you aren't debugging the scheduler or trying to tune a specific
922 application, you can say N to avoid the very slight overhead
925 config SCHED_STACK_END_CHECK
926 bool "Detect stack corruption on calls to schedule()"
927 depends on DEBUG_KERNEL
930 This option checks for a stack overrun on calls to schedule().
931 If the stack end location is found to be over written always panic as
932 the content of the corrupted region can no longer be trusted.
933 This is to ensure no erroneous behaviour occurs which could result in
934 data corruption or a sporadic crash at a later stage once the region
935 is examined. The runtime overhead introduced is minimal.
937 config DEBUG_TIMEKEEPING
938 bool "Enable extra timekeeping sanity checking"
940 This option will enable additional timekeeping sanity checks
941 which may be helpful when diagnosing issues where timekeeping
942 problems are suspected.
944 This may include checks in the timekeeping hotpaths, so this
945 option may have a (very small) performance impact to some
951 bool "Collect kernel timers statistics"
952 depends on DEBUG_KERNEL && PROC_FS
954 If you say Y here, additional code will be inserted into the
955 timer routines to collect statistics about kernel timers being
956 reprogrammed. The statistics can be read from /proc/timer_stats.
957 The statistics collection is started by writing 1 to /proc/timer_stats,
958 writing 0 stops it. This feature is useful to collect information
959 about timer usage patterns in kernel and userspace. This feature
960 is lightweight if enabled in the kernel config but not activated
961 (it defaults to deactivated on bootup and will only be activated
962 if some application like powertop activates it explicitly).
965 bool "Debug preemptible kernel"
966 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
969 If you say Y here then the kernel will use a debug variant of the
970 commonly used smp_processor_id() function and will print warnings
971 if kernel code uses it in a preemption-unsafe way. Also, the kernel
972 will detect preemption count underflows.
974 menu "Lock Debugging (spinlocks, mutexes, etc...)"
976 config DEBUG_RT_MUTEXES
977 bool "RT Mutex debugging, deadlock detection"
978 depends on DEBUG_KERNEL && RT_MUTEXES
980 This allows rt mutex semantics violations and rt mutex related
981 deadlocks (lockups) to be detected and reported automatically.
983 config DEBUG_SPINLOCK
984 bool "Spinlock and rw-lock debugging: basic checks"
985 depends on DEBUG_KERNEL
986 select UNINLINE_SPIN_UNLOCK
988 Say Y here and build SMP to catch missing spinlock initialization
989 and certain other kinds of spinlock errors commonly made. This is
990 best used in conjunction with the NMI watchdog so that spinlock
991 deadlocks are also debuggable.
994 bool "Mutex debugging: basic checks"
995 depends on DEBUG_KERNEL
997 This feature allows mutex semantics violations to be detected and
1000 config DEBUG_WW_MUTEX_SLOWPATH
1001 bool "Wait/wound mutex debugging: Slowpath testing"
1002 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1003 select DEBUG_LOCK_ALLOC
1004 select DEBUG_SPINLOCK
1005 select DEBUG_MUTEXES
1007 This feature enables slowpath testing for w/w mutex users by
1008 injecting additional -EDEADLK wound/backoff cases. Together with
1009 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1010 will test all possible w/w mutex interface abuse with the
1011 exception of simply not acquiring all the required locks.
1012 Note that this feature can introduce significant overhead, so
1013 it really should not be enabled in a production or distro kernel,
1014 even a debug kernel. If you are a driver writer, enable it. If
1015 you are a distro, do not.
1017 config DEBUG_LOCK_ALLOC
1018 bool "Lock debugging: detect incorrect freeing of live locks"
1019 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1020 select DEBUG_SPINLOCK
1021 select DEBUG_MUTEXES
1024 This feature will check whether any held lock (spinlock, rwlock,
1025 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1026 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1027 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1028 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1029 held during task exit.
1031 config PROVE_LOCKING
1032 bool "Lock debugging: prove locking correctness"
1033 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1035 select DEBUG_SPINLOCK
1036 select DEBUG_MUTEXES
1037 select DEBUG_LOCK_ALLOC
1038 select TRACE_IRQFLAGS
1041 This feature enables the kernel to prove that all locking
1042 that occurs in the kernel runtime is mathematically
1043 correct: that under no circumstance could an arbitrary (and
1044 not yet triggered) combination of observed locking
1045 sequences (on an arbitrary number of CPUs, running an
1046 arbitrary number of tasks and interrupt contexts) cause a
1049 In short, this feature enables the kernel to report locking
1050 related deadlocks before they actually occur.
1052 The proof does not depend on how hard and complex a
1053 deadlock scenario would be to trigger: how many
1054 participant CPUs, tasks and irq-contexts would be needed
1055 for it to trigger. The proof also does not depend on
1056 timing: if a race and a resulting deadlock is possible
1057 theoretically (no matter how unlikely the race scenario
1058 is), it will be proven so and will immediately be
1059 reported by the kernel (once the event is observed that
1060 makes the deadlock theoretically possible).
1062 If a deadlock is impossible (i.e. the locking rules, as
1063 observed by the kernel, are mathematically correct), the
1064 kernel reports nothing.
1066 NOTE: this feature can also be enabled for rwlocks, mutexes
1067 and rwsems - in which case all dependencies between these
1068 different locking variants are observed and mapped too, and
1069 the proof of observed correctness is also maintained for an
1070 arbitrary combination of these separate locking variants.
1072 For more details, see Documentation/locking/lockdep-design.txt.
1076 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1078 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
1083 bool "Lock usage statistics"
1084 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1086 select DEBUG_SPINLOCK
1087 select DEBUG_MUTEXES
1088 select DEBUG_LOCK_ALLOC
1091 This feature enables tracking lock contention points
1093 For more details, see Documentation/locking/lockstat.txt
1095 This also enables lock events required by "perf lock",
1097 If you want to use "perf lock", you also need to turn on
1098 CONFIG_EVENT_TRACING.
1100 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1101 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1103 config DEBUG_LOCKDEP
1104 bool "Lock dependency engine debugging"
1105 depends on DEBUG_KERNEL && LOCKDEP
1107 If you say Y here, the lock dependency engine will do
1108 additional runtime checks to debug itself, at the price
1109 of more runtime overhead.
1111 config DEBUG_ATOMIC_SLEEP
1112 bool "Sleep inside atomic section checking"
1113 select PREEMPT_COUNT
1114 depends on DEBUG_KERNEL
1116 If you say Y here, various routines which may sleep will become very
1117 noisy if they are called inside atomic sections: when a spinlock is
1118 held, inside an rcu read side critical section, inside preempt disabled
1119 sections, inside an interrupt, etc...
1121 config DEBUG_LOCKING_API_SELFTESTS
1122 bool "Locking API boot-time self-tests"
1123 depends on DEBUG_KERNEL
1125 Say Y here if you want the kernel to run a short self-test during
1126 bootup. The self-test checks whether common types of locking bugs
1127 are detected by debugging mechanisms or not. (if you disable
1128 lock debugging then those bugs wont be detected of course.)
1129 The following locking APIs are covered: spinlocks, rwlocks,
1132 config LOCK_TORTURE_TEST
1133 tristate "torture tests for locking"
1134 depends on DEBUG_KERNEL
1138 This option provides a kernel module that runs torture tests
1139 on kernel locking primitives. The kernel module may be built
1140 after the fact on the running kernel to be tested, if desired.
1142 Say Y here if you want kernel locking-primitive torture tests
1143 to be built into the kernel.
1144 Say M if you want these torture tests to build as a module.
1145 Say N if you are unsure.
1147 endmenu # lock debugging
1149 config TRACE_IRQFLAGS
1152 Enables hooks to interrupt enabling and disabling for
1153 either tracing or lock debugging.
1156 bool "Stack backtrace support"
1157 depends on STACKTRACE_SUPPORT
1159 This option causes the kernel to create a /proc/pid/stack for
1160 every process, showing its current stack trace.
1161 It is also used by various kernel debugging features that require
1162 stack trace generation.
1164 config DEBUG_KOBJECT
1165 bool "kobject debugging"
1166 depends on DEBUG_KERNEL
1168 If you say Y here, some extra kobject debugging messages will be sent
1171 config DEBUG_KOBJECT_RELEASE
1172 bool "kobject release debugging"
1173 depends on DEBUG_OBJECTS_TIMERS
1175 kobjects are reference counted objects. This means that their
1176 last reference count put is not predictable, and the kobject can
1177 live on past the point at which a driver decides to drop it's
1178 initial reference to the kobject gained on allocation. An
1179 example of this would be a struct device which has just been
1182 However, some buggy drivers assume that after such an operation,
1183 the memory backing the kobject can be immediately freed. This
1184 goes completely against the principles of a refcounted object.
1186 If you say Y here, the kernel will delay the release of kobjects
1187 on the last reference count to improve the visibility of this
1188 kind of kobject release bug.
1190 config HAVE_DEBUG_BUGVERBOSE
1193 config DEBUG_BUGVERBOSE
1194 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1195 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1198 Say Y here to make BUG() panics output the file name and line number
1199 of the BUG call as well as the EIP and oops trace. This aids
1200 debugging but costs about 70-100K of memory.
1203 bool "Debug linked list manipulation"
1204 depends on DEBUG_KERNEL
1206 Enable this to turn on extended checks in the linked-list
1211 config DEBUG_PI_LIST
1212 bool "Debug priority linked list manipulation"
1213 depends on DEBUG_KERNEL
1215 Enable this to turn on extended checks in the priority-ordered
1216 linked-list (plist) walking routines. This checks the entire
1217 list multiple times during each manipulation.
1222 bool "Debug SG table operations"
1223 depends on DEBUG_KERNEL
1225 Enable this to turn on checks on scatter-gather tables. This can
1226 help find problems with drivers that do not properly initialize
1231 config DEBUG_NOTIFIERS
1232 bool "Debug notifier call chains"
1233 depends on DEBUG_KERNEL
1235 Enable this to turn on sanity checking for notifier call chains.
1236 This is most useful for kernel developers to make sure that
1237 modules properly unregister themselves from notifier chains.
1238 This is a relatively cheap check but if you care about maximum
1241 config DEBUG_CREDENTIALS
1242 bool "Debug credential management"
1243 depends on DEBUG_KERNEL
1245 Enable this to turn on some debug checking for credential
1246 management. The additional code keeps track of the number of
1247 pointers from task_structs to any given cred struct, and checks to
1248 see that this number never exceeds the usage count of the cred
1251 Furthermore, if SELinux is enabled, this also checks that the
1252 security pointer in the cred struct is never seen to be invalid.
1256 menu "RCU Debugging"
1259 def_bool PROVE_LOCKING
1261 config PROVE_RCU_REPEATEDLY
1262 bool "RCU debugging: don't disable PROVE_RCU on first splat"
1263 depends on PROVE_RCU
1266 By itself, PROVE_RCU will disable checking upon issuing the
1267 first warning (or "splat"). This feature prevents such
1268 disabling, allowing multiple RCU-lockdep warnings to be printed
1271 Say Y to allow multiple RCU-lockdep warnings per boot.
1273 Say N if you are unsure.
1275 config SPARSE_RCU_POINTER
1276 bool "RCU debugging: sparse-based checks for pointer usage"
1279 This feature enables the __rcu sparse annotation for
1280 RCU-protected pointers. This annotation will cause sparse
1281 to flag any non-RCU used of annotated pointers. This can be
1282 helpful when debugging RCU usage. Please note that this feature
1283 is not intended to enforce code cleanliness; it is instead merely
1286 Say Y to make sparse flag questionable use of RCU-protected pointers
1288 Say N if you are unsure.
1294 config RCU_PERF_TEST
1295 tristate "performance tests for RCU"
1296 depends on DEBUG_KERNEL
1302 This option provides a kernel module that runs performance
1303 tests on the RCU infrastructure. The kernel module may be built
1304 after the fact on the running kernel to be tested, if desired.
1306 Say Y here if you want RCU performance tests to be built into
1308 Say M if you want the RCU performance tests to build as a module.
1309 Say N if you are unsure.
1311 config RCU_TORTURE_TEST
1312 tristate "torture tests for RCU"
1313 depends on DEBUG_KERNEL
1319 This option provides a kernel module that runs torture tests
1320 on the RCU infrastructure. The kernel module may be built
1321 after the fact on the running kernel to be tested, if desired.
1323 Say Y here if you want RCU torture tests to be built into
1325 Say M if you want the RCU torture tests to build as a module.
1326 Say N if you are unsure.
1328 config RCU_TORTURE_TEST_SLOW_PREINIT
1329 bool "Slow down RCU grace-period pre-initialization to expose races"
1330 depends on RCU_TORTURE_TEST
1332 This option delays grace-period pre-initialization (the
1333 propagation of CPU-hotplug changes up the rcu_node combining
1334 tree) for a few jiffies between initializing each pair of
1335 consecutive rcu_node structures. This helps to expose races
1336 involving grace-period pre-initialization, in other words, it
1337 makes your kernel less stable. It can also greatly increase
1338 grace-period latency, especially on systems with large numbers
1339 of CPUs. This is useful when torture-testing RCU, but in
1340 almost no other circumstance.
1342 Say Y here if you want your system to crash and hang more often.
1343 Say N if you want a sane system.
1345 config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
1346 int "How much to slow down RCU grace-period pre-initialization"
1349 depends on RCU_TORTURE_TEST_SLOW_PREINIT
1351 This option specifies the number of jiffies to wait between
1352 each rcu_node structure pre-initialization step.
1354 config RCU_TORTURE_TEST_SLOW_INIT
1355 bool "Slow down RCU grace-period initialization to expose races"
1356 depends on RCU_TORTURE_TEST
1358 This option delays grace-period initialization for a few
1359 jiffies between initializing each pair of consecutive
1360 rcu_node structures. This helps to expose races involving
1361 grace-period initialization, in other words, it makes your
1362 kernel less stable. It can also greatly increase grace-period
1363 latency, especially on systems with large numbers of CPUs.
1364 This is useful when torture-testing RCU, but in almost no
1367 Say Y here if you want your system to crash and hang more often.
1368 Say N if you want a sane system.
1370 config RCU_TORTURE_TEST_SLOW_INIT_DELAY
1371 int "How much to slow down RCU grace-period initialization"
1374 depends on RCU_TORTURE_TEST_SLOW_INIT
1376 This option specifies the number of jiffies to wait between
1377 each rcu_node structure initialization.
1379 config RCU_TORTURE_TEST_SLOW_CLEANUP
1380 bool "Slow down RCU grace-period cleanup to expose races"
1381 depends on RCU_TORTURE_TEST
1383 This option delays grace-period cleanup for a few jiffies
1384 between cleaning up each pair of consecutive rcu_node
1385 structures. This helps to expose races involving grace-period
1386 cleanup, in other words, it makes your kernel less stable.
1387 It can also greatly increase grace-period latency, especially
1388 on systems with large numbers of CPUs. This is useful when
1389 torture-testing RCU, but in almost no other circumstance.
1391 Say Y here if you want your system to crash and hang more often.
1392 Say N if you want a sane system.
1394 config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
1395 int "How much to slow down RCU grace-period cleanup"
1398 depends on RCU_TORTURE_TEST_SLOW_CLEANUP
1400 This option specifies the number of jiffies to wait between
1401 each rcu_node structure cleanup operation.
1403 config RCU_CPU_STALL_TIMEOUT
1404 int "RCU CPU stall timeout in seconds"
1405 depends on RCU_STALL_COMMON
1409 If a given RCU grace period extends more than the specified
1410 number of seconds, a CPU stall warning is printed. If the
1411 RCU grace period persists, additional CPU stall warnings are
1412 printed at more widely spaced intervals.
1415 bool "Enable tracing for RCU"
1416 depends on DEBUG_KERNEL
1419 This option provides tracing in RCU which presents stats
1420 in debugfs for debugging RCU implementation.
1422 Say Y here if you want to enable RCU tracing
1423 Say N if you are unsure.
1425 config RCU_EQS_DEBUG
1426 bool "Provide debugging asserts for adding NO_HZ support to an arch"
1427 depends on DEBUG_KERNEL
1429 This option provides consistency checks in RCU's handling of
1430 NO_HZ. These checks have proven quite helpful in detecting
1431 bugs in arch-specific NO_HZ code.
1433 Say N here if you need ultimate kernel/user switch latencies
1434 Say Y if you are unsure
1436 endmenu # "RCU Debugging"
1438 config DEBUG_WQ_FORCE_RR_CPU
1439 bool "Force round-robin CPU selection for unbound work items"
1440 depends on DEBUG_KERNEL
1443 Workqueue used to implicitly guarantee that work items queued
1444 without explicit CPU specified are put on the local CPU. This
1445 guarantee is no longer true and while local CPU is still
1446 preferred work items may be put on foreign CPUs. Kernel
1447 parameter "workqueue.debug_force_rr_cpu" is added to force
1448 round-robin CPU selection to flush out usages which depend on the
1449 now broken guarantee. This config option enables the debug
1450 feature by default. When enabled, memory and cache locality will
1453 config DEBUG_BLOCK_EXT_DEVT
1454 bool "Force extended block device numbers and spread them"
1455 depends on DEBUG_KERNEL
1459 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1460 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1461 YOU ARE DOING. Distros, please enable this and fix whatever
1464 Conventionally, block device numbers are allocated from
1465 predetermined contiguous area. However, extended block area
1466 may introduce non-contiguous block device numbers. This
1467 option forces most block device numbers to be allocated from
1468 the extended space and spreads them to discover kernel or
1469 userland code paths which assume predetermined contiguous
1470 device number allocation.
1472 Note that turning on this debug option shuffles all the
1473 device numbers for all IDE and SCSI devices including libata
1474 ones, so root partition specified using device number
1475 directly (via rdev or root=MAJ:MIN) won't work anymore.
1476 Textual device names (root=/dev/sdXn) will continue to work.
1478 Say N if you are unsure.
1480 config CPU_HOTPLUG_STATE_CONTROL
1481 bool "Enable CPU hotplug state control"
1482 depends on DEBUG_KERNEL
1483 depends on HOTPLUG_CPU
1486 Allows to write steps between "offline" and "online" to the CPUs
1487 sysfs target file so states can be stepped granular. This is a debug
1488 option for now as the hotplug machinery cannot be stopped and
1489 restarted at arbitrary points yet.
1491 Say N if your are unsure.
1493 config NOTIFIER_ERROR_INJECTION
1494 tristate "Notifier error injection"
1495 depends on DEBUG_KERNEL
1498 This option provides the ability to inject artificial errors to
1499 specified notifier chain callbacks. It is useful to test the error
1500 handling of notifier call chain failures.
1504 config CPU_NOTIFIER_ERROR_INJECT
1505 tristate "CPU notifier error injection module"
1506 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1508 This option provides a kernel module that can be used to test
1509 the error handling of the cpu notifiers by injecting artificial
1510 errors to CPU notifier chain callbacks. It is controlled through
1511 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
1513 If the notifier call chain should be failed with some events
1514 notified, write the error code to "actions/<notifier event>/error".
1516 Example: Inject CPU offline error (-1 == -EPERM)
1518 # cd /sys/kernel/debug/notifier-error-inject/cpu
1519 # echo -1 > actions/CPU_DOWN_PREPARE/error
1520 # echo 0 > /sys/devices/system/cpu/cpu1/online
1521 bash: echo: write error: Operation not permitted
1523 To compile this code as a module, choose M here: the module will
1524 be called cpu-notifier-error-inject.
1528 config PM_NOTIFIER_ERROR_INJECT
1529 tristate "PM notifier error injection module"
1530 depends on PM && NOTIFIER_ERROR_INJECTION
1531 default m if PM_DEBUG
1533 This option provides the ability to inject artificial errors to
1534 PM notifier chain callbacks. It is controlled through debugfs
1535 interface /sys/kernel/debug/notifier-error-inject/pm
1537 If the notifier call chain should be failed with some events
1538 notified, write the error code to "actions/<notifier event>/error".
1540 Example: Inject PM suspend error (-12 = -ENOMEM)
1542 # cd /sys/kernel/debug/notifier-error-inject/pm/
1543 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1544 # echo mem > /sys/power/state
1545 bash: echo: write error: Cannot allocate memory
1547 To compile this code as a module, choose M here: the module will
1548 be called pm-notifier-error-inject.
1552 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1553 tristate "OF reconfig notifier error injection module"
1554 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1556 This option provides the ability to inject artificial errors to
1557 OF reconfig notifier chain callbacks. It is controlled
1558 through debugfs interface under
1559 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1561 If the notifier call chain should be failed with some events
1562 notified, write the error code to "actions/<notifier event>/error".
1564 To compile this code as a module, choose M here: the module will
1565 be called of-reconfig-notifier-error-inject.
1569 config NETDEV_NOTIFIER_ERROR_INJECT
1570 tristate "Netdev notifier error injection module"
1571 depends on NET && NOTIFIER_ERROR_INJECTION
1573 This option provides the ability to inject artificial errors to
1574 netdevice notifier chain callbacks. It is controlled through debugfs
1575 interface /sys/kernel/debug/notifier-error-inject/netdev
1577 If the notifier call chain should be failed with some events
1578 notified, write the error code to "actions/<notifier event>/error".
1580 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1582 # cd /sys/kernel/debug/notifier-error-inject/netdev
1583 # echo -22 > actions/NETDEV_CHANGEMTU/error
1584 # ip link set eth0 mtu 1024
1585 RTNETLINK answers: Invalid argument
1587 To compile this code as a module, choose M here: the module will
1588 be called netdev-notifier-error-inject.
1592 config FAULT_INJECTION
1593 bool "Fault-injection framework"
1594 depends on DEBUG_KERNEL
1596 Provide fault-injection framework.
1597 For more details, see Documentation/fault-injection/.
1600 bool "Fault-injection capability for kmalloc"
1601 depends on FAULT_INJECTION
1602 depends on SLAB || SLUB
1604 Provide fault-injection capability for kmalloc.
1606 config FAIL_PAGE_ALLOC
1607 bool "Fault-injection capabilitiy for alloc_pages()"
1608 depends on FAULT_INJECTION
1610 Provide fault-injection capability for alloc_pages().
1612 config FAIL_MAKE_REQUEST
1613 bool "Fault-injection capability for disk IO"
1614 depends on FAULT_INJECTION && BLOCK
1616 Provide fault-injection capability for disk IO.
1618 config FAIL_IO_TIMEOUT
1619 bool "Fault-injection capability for faking disk interrupts"
1620 depends on FAULT_INJECTION && BLOCK
1622 Provide fault-injection capability on end IO handling. This
1623 will make the block layer "forget" an interrupt as configured,
1624 thus exercising the error handling.
1626 Only works with drivers that use the generic timeout handling,
1627 for others it wont do anything.
1629 config FAIL_MMC_REQUEST
1630 bool "Fault-injection capability for MMC IO"
1631 depends on FAULT_INJECTION_DEBUG_FS && MMC
1633 Provide fault-injection capability for MMC IO.
1634 This will make the mmc core return data errors. This is
1635 useful to test the error handling in the mmc block device
1636 and to test how the mmc host driver handles retries from
1640 bool "Fault-injection capability for futexes"
1642 depends on FAULT_INJECTION && FUTEX
1644 Provide fault-injection capability for futexes.
1646 config FAULT_INJECTION_DEBUG_FS
1647 bool "Debugfs entries for fault-injection capabilities"
1648 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1650 Enable configuration of fault-injection capabilities via debugfs.
1652 config FAULT_INJECTION_STACKTRACE_FILTER
1653 bool "stacktrace filter for fault-injection capabilities"
1654 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1657 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1659 Provide stacktrace filter for fault-injection capabilities
1662 bool "Latency measuring infrastructure"
1663 depends on DEBUG_KERNEL
1664 depends on STACKTRACE_SUPPORT
1666 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1673 Enable this option if you want to use the LatencyTOP tool
1674 to find out which userspace is blocking on what kernel operations.
1676 config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1679 config DEBUG_STRICT_USER_COPY_CHECKS
1680 bool "Strict user copy size checks"
1681 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1682 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
1684 Enabling this option turns a certain set of sanity checks for user
1685 copy operations into compile time failures.
1687 The copy_from_user() etc checks are there to help test if there
1688 are sufficient security checks on the length argument of
1689 the copy operation, by having gcc prove that the argument is
1694 source kernel/trace/Kconfig
1696 menu "Runtime Testing"
1699 tristate "Linux Kernel Dump Test Tool Module"
1704 This module enables testing of the different dumping mechanisms by
1705 inducing system failures at predefined crash points.
1706 If you don't need it: say N
1707 Choose M here to compile this code as a module. The module will be
1710 Documentation on how to use the module can be found in
1711 Documentation/fault-injection/provoke-crashes.txt
1713 config TEST_LIST_SORT
1714 bool "Linked list sorting test"
1715 depends on DEBUG_KERNEL
1717 Enable this to turn on 'list_sort()' function test. This test is
1718 executed only once during system boot, so affects only boot time.
1722 config KPROBES_SANITY_TEST
1723 bool "Kprobes sanity tests"
1724 depends on DEBUG_KERNEL
1728 This option provides for testing basic kprobes functionality on
1729 boot. A sample kprobe, jprobe and kretprobe are inserted and
1730 verified for functionality.
1732 Say N if you are unsure.
1734 config BACKTRACE_SELF_TEST
1735 tristate "Self test for the backtrace code"
1736 depends on DEBUG_KERNEL
1739 This option provides a kernel module that can be used to test
1740 the kernel stack backtrace code. This option is not useful
1741 for distributions or general kernels, but only for kernel
1742 developers working on architecture code.
1744 Note that if you want to also test saved backtraces, you will
1745 have to enable STACKTRACE as well.
1747 Say N if you are unsure.
1750 tristate "Red-Black tree test"
1751 depends on DEBUG_KERNEL
1753 A benchmark measuring the performance of the rbtree library.
1754 Also includes rbtree invariant checks.
1756 config INTERVAL_TREE_TEST
1757 tristate "Interval tree test"
1758 depends on m && DEBUG_KERNEL
1759 select INTERVAL_TREE
1761 A benchmark measuring the performance of the interval tree library
1764 tristate "Per cpu operations test"
1765 depends on m && DEBUG_KERNEL
1767 Enable this option to build test module which validates per-cpu
1772 config ATOMIC64_SELFTEST
1773 bool "Perform an atomic64_t self-test at boot"
1775 Enable this option to test the atomic64_t functions at boot.
1779 config ASYNC_RAID6_TEST
1780 tristate "Self test for hardware accelerated raid6 recovery"
1781 depends on ASYNC_RAID6_RECOV
1784 This is a one-shot self test that permutes through the
1785 recovery of all the possible two disk failure scenarios for a
1786 N-disk array. Recovery is performed with the asynchronous
1787 raid6 recovery routines, and will optionally use an offload
1788 engine if one is available.
1793 tristate "Test functions located in the hexdump module at runtime"
1795 config TEST_STRING_HELPERS
1796 tristate "Test functions located in the string_helpers module at runtime"
1799 tristate "Test kstrto*() family of functions at runtime"
1802 tristate "Test printf() family of functions at runtime"
1805 tristate "Test bitmap_*() family of functions at runtime"
1808 Enable this option to test the bitmap functions at boot.
1813 tristate "Test functions located in the uuid module at runtime"
1815 config TEST_RHASHTABLE
1816 tristate "Perform selftest on resizable hash table"
1819 Enable this option to test the rhashtable functions at boot.
1824 tristate "Perform selftest on hash functions"
1827 Enable this option to test the kernel's integer (<linux/hash,h>)
1828 and string (<linux/stringhash.h>) hash functions on boot
1831 This is intended to help people writing architecture-specific
1832 optimized versions. If unsure, say N.
1834 endmenu # runtime tests
1836 config PROVIDE_OHCI1394_DMA_INIT
1837 bool "Remote debugging over FireWire early on boot"
1838 depends on PCI && X86
1840 If you want to debug problems which hang or crash the kernel early
1841 on boot and the crashing machine has a FireWire port, you can use
1842 this feature to remotely access the memory of the crashed machine
1843 over FireWire. This employs remote DMA as part of the OHCI1394
1844 specification which is now the standard for FireWire controllers.
1846 With remote DMA, you can monitor the printk buffer remotely using
1847 firescope and access all memory below 4GB using fireproxy from gdb.
1848 Even controlling a kernel debugger is possible using remote DMA.
1852 If ohci1394_dma=early is used as boot parameter, it will initialize
1853 all OHCI1394 controllers which are found in the PCI config space.
1855 As all changes to the FireWire bus such as enabling and disabling
1856 devices cause a bus reset and thereby disable remote DMA for all
1857 devices, be sure to have the cable plugged and FireWire enabled on
1858 the debugging host before booting the debug target for debugging.
1860 This code (~1k) is freed after boot. By then, the firewire stack
1861 in charge of the OHCI-1394 controllers should be used instead.
1863 See Documentation/debugging-via-ohci1394.txt for more information.
1866 bool "Build targets in Documentation/ tree"
1867 depends on HEADERS_CHECK
1869 This option attempts to build objects from the source files in the
1870 kernel Documentation/ tree.
1872 Say N if you are unsure.
1874 config DMA_API_DEBUG
1875 bool "Enable debugging of DMA-API usage"
1876 depends on HAVE_DMA_API_DEBUG
1878 Enable this option to debug the use of the DMA API by device drivers.
1879 With this option you will be able to detect common bugs in device
1880 drivers like double-freeing of DMA mappings or freeing mappings that
1881 were never allocated.
1883 This also attempts to catch cases where a page owned by DMA is
1884 accessed by the cpu in a way that could cause data corruption. For
1885 example, this enables cow_user_page() to check that the source page is
1888 This option causes a performance degradation. Use only if you want to
1889 debug device drivers and dma interactions.
1894 tristate "Test module loading with 'hello world' module"
1898 This builds the "test_module" module that emits "Hello, world"
1899 on printk when loaded. It is designed to be used for basic
1900 evaluation of the module loading subsystem (for example when
1901 validating module verification). It lacks any extra dependencies,
1902 and will not normally be loaded by the system unless explicitly
1907 config TEST_USER_COPY
1908 tristate "Test user/kernel boundary protections"
1912 This builds the "test_user_copy" module that runs sanity checks
1913 on the copy_to/from_user infrastructure, making sure basic
1914 user/kernel boundary testing is working. If it fails to load,
1915 a regression has been detected in the user/kernel memory boundary
1921 tristate "Test BPF filter functionality"
1925 This builds the "test_bpf" module that runs various test vectors
1926 against the BPF interpreter or BPF JIT compiler depending on the
1927 current setting. This is in particular useful for BPF JIT compiler
1928 development, but also to run regression tests against changes in
1929 the interpreter code. It also enables test stubs for eBPF maps and
1930 verifier used by user space verifier testsuite.
1934 config TEST_FIRMWARE
1935 tristate "Test firmware loading via userspace interface"
1937 depends on FW_LOADER
1939 This builds the "test_firmware" module that creates a userspace
1940 interface for testing firmware loading. This can be used to
1941 control the triggering of firmware loading without needing an
1942 actual firmware-using device. The contents can be rechecked by
1948 tristate "udelay test driver"
1951 This builds the "udelay_test" module that helps to make sure
1952 that udelay() is working properly.
1958 depends on HAVE_MEMBLOCK
1960 This option adds a kernel parameter 'memtest', which allows memtest
1962 memtest=0, mean disabled; -- default
1963 memtest=1, mean do 1 test pattern;
1965 memtest=17, mean do 17 test patterns.
1966 If you are unsure how to answer this question, answer N.
1968 config TEST_STATIC_KEYS
1969 tristate "Test static keys"
1973 Test the static key interfaces.
1977 source "samples/Kconfig"
1979 source "lib/Kconfig.kgdb"
1981 source "lib/Kconfig.ubsan"
1983 config ARCH_HAS_DEVMEM_IS_ALLOWED
1986 config STRICT_DEVMEM
1987 bool "Filter access to /dev/mem"
1989 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
1990 default y if TILE || PPC
1992 If this option is disabled, you allow userspace (root) access to all
1993 of memory, including kernel and userspace memory. Accidental
1994 access to this is obviously disastrous, but specific access can
1995 be used by people debugging the kernel. Note that with PAT support
1996 enabled, even in this case there are restrictions on /dev/mem
1997 use due to the cache aliasing requirements.
1999 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
2000 file only allows userspace access to PCI space and the BIOS code and
2001 data regions. This is sufficient for dosemu and X and all common
2006 config IO_STRICT_DEVMEM
2007 bool "Filter I/O access to /dev/mem"
2008 depends on STRICT_DEVMEM
2010 If this option is disabled, you allow userspace (root) access to all
2011 io-memory regardless of whether a driver is actively using that
2012 range. Accidental access to this is obviously disastrous, but
2013 specific access can be used by people debugging kernel drivers.
2015 If this option is switched on, the /dev/mem file only allows
2016 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2017 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2018 if the driver using a given range cannot be disabled.
projects / mirror_ubuntu-jammy-kernel.git / blob