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
247 select PAGE_EXTENSION
249 This keeps track of what call chain is the owner of a page, may
250 help to find bare alloc_page(s) leaks. Even if you include this
251 feature on your build, it is disabled in default. You should pass
252 "page_owner=on" to boot parameter in order to enable it. Eats
253 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
254 for user-space helper.
259 bool "Debug Filesystem"
261 debugfs is a virtual file system that kernel developers use to put
262 debugging files into. Enable this option to be able to read and
263 write to these files.
265 For detailed documentation on the debugfs API, see
266 Documentation/DocBook/filesystems.
271 bool "Run 'make headers_check' when building vmlinux"
274 This option will extract the user-visible kernel headers whenever
275 building the kernel, and will run basic sanity checks on them to
276 ensure that exported files do not attempt to include files which
277 were not exported, etc.
279 If you're making modifications to header files which are
280 relevant for userspace, say 'Y', and check the headers
281 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
282 your build tree), to make sure they're suitable.
284 config DEBUG_SECTION_MISMATCH
285 bool "Enable full Section mismatch analysis"
287 The section mismatch analysis checks if there are illegal
288 references from one section to another section.
289 During linktime or runtime, some sections are dropped;
290 any use of code/data previously in these sections would
291 most likely result in an oops.
292 In the code, functions and variables are annotated with
293 __init,, etc. (see the full list in include/linux/init.h),
294 which results in the code/data being placed in specific sections.
295 The section mismatch analysis is always performed after a full
296 kernel build, and enabling this option causes the following
297 additional steps to occur:
298 - Add the option -fno-inline-functions-called-once to gcc commands.
299 When inlining a function annotated with __init in a non-init
300 function, we would lose the section information and thus
301 the analysis would not catch the illegal reference.
302 This option tells gcc to inline less (but it does result in
304 - Run the section mismatch analysis for each module/built-in.o file.
305 When we run the section mismatch analysis on vmlinux.o, we
306 lose valueble information about where the mismatch was
308 Running the analysis for each module/built-in.o file
309 tells where the mismatch happens much closer to the
310 source. The drawback is that the same mismatch is
311 reported at least twice.
312 - Enable verbose reporting from modpost in order to help resolve
313 the section mismatches that are reported.
315 config SECTION_MISMATCH_WARN_ONLY
316 bool "Make section mismatch errors non-fatal"
319 If you say N here, the build process will fail if there are any
320 section mismatch, instead of just throwing warnings.
325 # Select this config option from the architecture Kconfig, if it
326 # is preferred to always offer frame pointers as a config
327 # option on the architecture (regardless of KERNEL_DEBUG):
329 config ARCH_WANT_FRAME_POINTERS
334 bool "Compile the kernel with frame pointers"
335 depends on DEBUG_KERNEL && \
336 (CRIS || M68K || FRV || UML || \
337 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \
338 ARCH_WANT_FRAME_POINTERS
339 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
341 If you say Y here the resulting kernel image will be slightly
342 larger and slower, but it gives very useful debugging information
343 in case of kernel bugs. (precise oopses/stacktraces/warnings)
345 config STACK_VALIDATION
346 bool "Compile-time stack metadata validation"
347 depends on HAVE_STACK_VALIDATION
350 Add compile-time checks to validate stack metadata, including frame
351 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
352 that runtime stack traces are more reliable.
354 For more information, see
355 tools/objtool/Documentation/stack-validation.txt.
357 config DEBUG_FORCE_WEAK_PER_CPU
358 bool "Force weak per-cpu definitions"
359 depends on DEBUG_KERNEL
361 s390 and alpha require percpu variables in modules to be
362 defined weak to work around addressing range issue which
363 puts the following two restrictions on percpu variable
366 1. percpu symbols must be unique whether static or not
367 2. percpu variables can't be defined inside a function
369 To ensure that generic code follows the above rules, this
370 option forces all percpu variables to be defined as weak.
372 endmenu # "Compiler options"
375 bool "Magic SysRq key"
378 If you say Y here, you will have some control over the system even
379 if the system crashes for example during kernel debugging (e.g., you
380 will be able to flush the buffer cache to disk, reboot the system
381 immediately or dump some status information). This is accomplished
382 by pressing various keys while holding SysRq (Alt+PrintScreen). It
383 also works on a serial console (on PC hardware at least), if you
384 send a BREAK and then within 5 seconds a command keypress. The
385 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
386 unless you really know what this hack does.
388 config MAGIC_SYSRQ_DEFAULT_ENABLE
389 hex "Enable magic SysRq key functions by default"
390 depends on MAGIC_SYSRQ
393 Specifies which SysRq key functions are enabled by default.
394 This may be set to 1 or 0 to enable or disable them all, or
395 to a bitmask as described in Documentation/sysrq.txt.
398 bool "Kernel debugging"
400 Say Y here if you are developing drivers or trying to debug and
401 identify kernel problems.
403 menu "Memory Debugging"
405 source mm/Kconfig.debug
408 bool "Debug object operations"
409 depends on DEBUG_KERNEL
411 If you say Y here, additional code will be inserted into the
412 kernel to track the life time of various objects and validate
413 the operations on those objects.
415 config DEBUG_OBJECTS_SELFTEST
416 bool "Debug objects selftest"
417 depends on DEBUG_OBJECTS
419 This enables the selftest of the object debug code.
421 config DEBUG_OBJECTS_FREE
422 bool "Debug objects in freed memory"
423 depends on DEBUG_OBJECTS
425 This enables checks whether a k/v free operation frees an area
426 which contains an object which has not been deactivated
427 properly. This can make kmalloc/kfree-intensive workloads
430 config DEBUG_OBJECTS_TIMERS
431 bool "Debug timer objects"
432 depends on DEBUG_OBJECTS
434 If you say Y here, additional code will be inserted into the
435 timer routines to track the life time of timer objects and
436 validate the timer operations.
438 config DEBUG_OBJECTS_WORK
439 bool "Debug work objects"
440 depends on DEBUG_OBJECTS
442 If you say Y here, additional code will be inserted into the
443 work queue routines to track the life time of work objects and
444 validate the work operations.
446 config DEBUG_OBJECTS_RCU_HEAD
447 bool "Debug RCU callbacks objects"
448 depends on DEBUG_OBJECTS
450 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
452 config DEBUG_OBJECTS_PERCPU_COUNTER
453 bool "Debug percpu counter objects"
454 depends on DEBUG_OBJECTS
456 If you say Y here, additional code will be inserted into the
457 percpu counter routines to track the life time of percpu counter
458 objects and validate the percpu counter operations.
460 config DEBUG_OBJECTS_ENABLE_DEFAULT
461 int "debug_objects bootup default value (0-1)"
464 depends on DEBUG_OBJECTS
466 Debug objects boot parameter default value
469 bool "Debug slab memory allocations"
470 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
472 Say Y here to have the kernel do limited verification on memory
473 allocation as well as poisoning memory on free to catch use of freed
474 memory. This can make kmalloc/kfree-intensive workloads much slower.
476 config DEBUG_SLAB_LEAK
477 bool "Memory leak debugging"
478 depends on DEBUG_SLAB
481 bool "SLUB debugging on by default"
482 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
485 Boot with debugging on by default. SLUB boots by default with
486 the runtime debug capabilities switched off. Enabling this is
487 equivalent to specifying the "slub_debug" parameter on boot.
488 There is no support for more fine grained debug control like
489 possible with slub_debug=xxx. SLUB debugging may be switched
490 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
495 bool "Enable SLUB performance statistics"
496 depends on SLUB && SYSFS
498 SLUB statistics are useful to debug SLUBs allocation behavior in
499 order find ways to optimize the allocator. This should never be
500 enabled for production use since keeping statistics slows down
501 the allocator by a few percentage points. The slabinfo command
502 supports the determination of the most active slabs to figure
503 out which slabs are relevant to a particular load.
504 Try running: slabinfo -DA
506 config HAVE_DEBUG_KMEMLEAK
509 config DEBUG_KMEMLEAK
510 bool "Kernel memory leak detector"
511 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
513 select STACKTRACE if STACKTRACE_SUPPORT
517 Say Y here if you want to enable the memory leak
518 detector. The memory allocation/freeing is traced in a way
519 similar to the Boehm's conservative garbage collector, the
520 difference being that the orphan objects are not freed but
521 only shown in /sys/kernel/debug/kmemleak. Enabling this
522 feature will introduce an overhead to memory
523 allocations. See Documentation/kmemleak.txt for more
526 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
527 of finding leaks due to the slab objects poisoning.
529 In order to access the kmemleak file, debugfs needs to be
530 mounted (usually at /sys/kernel/debug).
532 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
533 int "Maximum kmemleak early log entries"
534 depends on DEBUG_KMEMLEAK
538 Kmemleak must track all the memory allocations to avoid
539 reporting false positives. Since memory may be allocated or
540 freed before kmemleak is initialised, an early log buffer is
541 used to store these actions. If kmemleak reports "early log
542 buffer exceeded", please increase this value.
544 config DEBUG_KMEMLEAK_TEST
545 tristate "Simple test for the kernel memory leak detector"
546 depends on DEBUG_KMEMLEAK && m
548 This option enables a module that explicitly leaks memory.
552 config DEBUG_KMEMLEAK_DEFAULT_OFF
553 bool "Default kmemleak to off"
554 depends on DEBUG_KMEMLEAK
556 Say Y here to disable kmemleak by default. It can then be enabled
557 on the command line via kmemleak=on.
559 config DEBUG_STACK_USAGE
560 bool "Stack utilization instrumentation"
561 depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAG
563 Enables the display of the minimum amount of free stack which each
564 task has ever had available in the sysrq-T and sysrq-P debug output.
566 This option will slow down process creation somewhat.
570 depends on DEBUG_KERNEL
572 Enable this to turn on extended checks in the virtual-memory system
573 that may impact performance.
577 config DEBUG_VM_VMACACHE
578 bool "Debug VMA caching"
581 Enable this to turn on VMA caching debug information. Doing so
582 can cause significant overhead, so only enable it in non-production
588 bool "Debug VM red-black trees"
591 Enable VM red-black tree debugging information and extra validations.
595 config DEBUG_VM_PGFLAGS
596 bool "Debug page-flags operations"
599 Enables extra validation on page flags operations.
604 bool "Debug VM translations"
605 depends on DEBUG_KERNEL && X86
607 Enable some costly sanity checks in virtual to page code. This can
608 catch mistakes with virt_to_page() and friends.
612 config DEBUG_NOMMU_REGIONS
613 bool "Debug the global anon/private NOMMU mapping region tree"
614 depends on DEBUG_KERNEL && !MMU
616 This option causes the global tree of anonymous and private mapping
617 regions to be regularly checked for invalid topology.
619 config DEBUG_MEMORY_INIT
620 bool "Debug memory initialisation" if EXPERT
623 Enable this for additional checks during memory initialisation.
624 The sanity checks verify aspects of the VM such as the memory model
625 and other information provided by the architecture. Verbose
626 information will be printed at KERN_DEBUG loglevel depending
627 on the mminit_loglevel= command-line option.
631 config MEMORY_NOTIFIER_ERROR_INJECT
632 tristate "Memory hotplug notifier error injection module"
633 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
635 This option provides the ability to inject artificial errors to
636 memory hotplug notifier chain callbacks. It is controlled through
637 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
639 If the notifier call chain should be failed with some events
640 notified, write the error code to "actions/<notifier event>/error".
642 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
644 # cd /sys/kernel/debug/notifier-error-inject/memory
645 # echo -12 > actions/MEM_GOING_OFFLINE/error
646 # echo offline > /sys/devices/system/memory/memoryXXX/state
647 bash: echo: write error: Cannot allocate memory
649 To compile this code as a module, choose M here: the module will
650 be called memory-notifier-error-inject.
654 config DEBUG_PER_CPU_MAPS
655 bool "Debug access to per_cpu maps"
656 depends on DEBUG_KERNEL
659 Say Y to verify that the per_cpu map being accessed has
660 been set up. This adds a fair amount of code to kernel memory
661 and decreases performance.
666 bool "Highmem debugging"
667 depends on DEBUG_KERNEL && HIGHMEM
669 This option enables additional error checking for high memory
670 systems. Disable for production systems.
672 config HAVE_DEBUG_STACKOVERFLOW
675 config DEBUG_STACKOVERFLOW
676 bool "Check for stack overflows"
677 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
679 Say Y here if you want to check for overflows of kernel, IRQ
680 and exception stacks (if your architecture uses them). This
681 option will show detailed messages if free stack space drops
682 below a certain limit.
684 These kinds of bugs usually occur when call-chains in the
685 kernel get too deep, especially when interrupts are
688 Use this in cases where you see apparently random memory
689 corruption, especially if it appears in 'struct thread_info'
691 If in doubt, say "N".
693 source "lib/Kconfig.kmemcheck"
695 source "lib/Kconfig.kasan"
697 endmenu # "Memory Debugging"
700 bool "Debug shared IRQ handlers"
701 depends on DEBUG_KERNEL
703 Enable this to generate a spurious interrupt as soon as a shared
704 interrupt handler is registered, and just before one is deregistered.
705 Drivers ought to be able to handle interrupts coming in at those
706 points; some don't and need to be caught.
708 menu "Debug Lockups and Hangs"
710 config LOCKUP_DETECTOR
711 bool "Detect Hard and Soft Lockups"
712 depends on DEBUG_KERNEL && !S390
714 Say Y here to enable the kernel to act as a watchdog to detect
715 hard and soft lockups.
717 Softlockups are bugs that cause the kernel to loop in kernel
718 mode for more than 20 seconds, without giving other tasks a
719 chance to run. The current stack trace is displayed upon
720 detection and the system will stay locked up.
722 Hardlockups are bugs that cause the CPU to loop in kernel mode
723 for more than 10 seconds, without letting other interrupts have a
724 chance to run. The current stack trace is displayed upon detection
725 and the system will stay locked up.
727 The overhead should be minimal. A periodic hrtimer runs to
728 generate interrupts and kick the watchdog task every 4 seconds.
729 An NMI is generated every 10 seconds or so to check for hardlockups.
731 The frequency of hrtimer and NMI events and the soft and hard lockup
732 thresholds can be controlled through the sysctl watchdog_thresh.
734 config HARDLOCKUP_DETECTOR
736 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
737 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
739 config BOOTPARAM_HARDLOCKUP_PANIC
740 bool "Panic (Reboot) On Hard Lockups"
741 depends on HARDLOCKUP_DETECTOR
743 Say Y here to enable the kernel to panic on "hard lockups",
744 which are bugs that cause the kernel to loop in kernel
745 mode with interrupts disabled for more than 10 seconds (configurable
746 using the watchdog_thresh sysctl).
750 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
752 depends on HARDLOCKUP_DETECTOR
754 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
755 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
757 config BOOTPARAM_SOFTLOCKUP_PANIC
758 bool "Panic (Reboot) On Soft Lockups"
759 depends on LOCKUP_DETECTOR
761 Say Y here to enable the kernel to panic on "soft lockups",
762 which are bugs that cause the kernel to loop in kernel
763 mode for more than 20 seconds (configurable using the watchdog_thresh
764 sysctl), without giving other tasks a chance to run.
766 The panic can be used in combination with panic_timeout,
767 to cause the system to reboot automatically after a
768 lockup has been detected. This feature is useful for
769 high-availability systems that have uptime guarantees and
770 where a lockup must be resolved ASAP.
774 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
776 depends on LOCKUP_DETECTOR
778 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
779 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
781 config DETECT_HUNG_TASK
782 bool "Detect Hung Tasks"
783 depends on DEBUG_KERNEL
784 default LOCKUP_DETECTOR
786 Say Y here to enable the kernel to detect "hung tasks",
787 which are bugs that cause the task to be stuck in
788 uninterruptible "D" state indefinitiley.
790 When a hung task is detected, the kernel will print the
791 current stack trace (which you should report), but the
792 task will stay in uninterruptible state. If lockdep is
793 enabled then all held locks will also be reported. This
794 feature has negligible overhead.
796 config DEFAULT_HUNG_TASK_TIMEOUT
797 int "Default timeout for hung task detection (in seconds)"
798 depends on DETECT_HUNG_TASK
801 This option controls the default timeout (in seconds) used
802 to determine when a task has become non-responsive and should
805 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
806 sysctl or by writing a value to
807 /proc/sys/kernel/hung_task_timeout_secs.
809 A timeout of 0 disables the check. The default is two minutes.
810 Keeping the default should be fine in most cases.
812 config BOOTPARAM_HUNG_TASK_PANIC
813 bool "Panic (Reboot) On Hung Tasks"
814 depends on DETECT_HUNG_TASK
816 Say Y here to enable the kernel to panic on "hung tasks",
817 which are bugs that cause the kernel to leave a task stuck
818 in uninterruptible "D" state.
820 The panic can be used in combination with panic_timeout,
821 to cause the system to reboot automatically after a
822 hung task has been detected. This feature is useful for
823 high-availability systems that have uptime guarantees and
824 where a hung tasks must be resolved ASAP.
828 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
830 depends on DETECT_HUNG_TASK
832 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
833 default 1 if BOOTPARAM_HUNG_TASK_PANIC
836 bool "Detect Workqueue Stalls"
837 depends on DEBUG_KERNEL
839 Say Y here to enable stall detection on workqueues. If a
840 worker pool doesn't make forward progress on a pending work
841 item for over a given amount of time, 30s by default, a
842 warning message is printed along with dump of workqueue
843 state. This can be configured through kernel parameter
844 "workqueue.watchdog_thresh" and its sysfs counterpart.
846 endmenu # "Debug lockups and hangs"
851 Say Y here to enable the kernel to panic when it oopses. This
852 has the same effect as setting oops=panic on the kernel command
855 This feature is useful to ensure that the kernel does not do
856 anything erroneous after an oops which could result in data
857 corruption or other issues.
861 config PANIC_ON_OOPS_VALUE
864 default 0 if !PANIC_ON_OOPS
865 default 1 if PANIC_ON_OOPS
871 Set the timeout value (in seconds) until a reboot occurs when the
872 the kernel panics. If n = 0, then we wait forever. A timeout
873 value n > 0 will wait n seconds before rebooting, while a timeout
874 value n < 0 will reboot immediately.
877 bool "Collect scheduler debugging info"
878 depends on DEBUG_KERNEL && PROC_FS
881 If you say Y here, the /proc/sched_debug file will be provided
882 that can help debug the scheduler. The runtime overhead of this
890 bool "Collect scheduler statistics"
891 depends on DEBUG_KERNEL && PROC_FS
894 If you say Y here, additional code will be inserted into the
895 scheduler and related routines to collect statistics about
896 scheduler behavior and provide them in /proc/schedstat. These
897 stats may be useful for both tuning and debugging the scheduler
898 If you aren't debugging the scheduler or trying to tune a specific
899 application, you can say N to avoid the very slight overhead
902 config SCHED_STACK_END_CHECK
903 bool "Detect stack corruption on calls to schedule()"
904 depends on DEBUG_KERNEL
907 This option checks for a stack overrun on calls to schedule().
908 If the stack end location is found to be over written always panic as
909 the content of the corrupted region can no longer be trusted.
910 This is to ensure no erroneous behaviour occurs which could result in
911 data corruption or a sporadic crash at a later stage once the region
912 is examined. The runtime overhead introduced is minimal.
914 config DEBUG_TIMEKEEPING
915 bool "Enable extra timekeeping sanity checking"
917 This option will enable additional timekeeping sanity checks
918 which may be helpful when diagnosing issues where timekeeping
919 problems are suspected.
921 This may include checks in the timekeeping hotpaths, so this
922 option may have a (very small) performance impact to some
928 bool "Collect kernel timers statistics"
929 depends on DEBUG_KERNEL && PROC_FS
931 If you say Y here, additional code will be inserted into the
932 timer routines to collect statistics about kernel timers being
933 reprogrammed. The statistics can be read from /proc/timer_stats.
934 The statistics collection is started by writing 1 to /proc/timer_stats,
935 writing 0 stops it. This feature is useful to collect information
936 about timer usage patterns in kernel and userspace. This feature
937 is lightweight if enabled in the kernel config but not activated
938 (it defaults to deactivated on bootup and will only be activated
939 if some application like powertop activates it explicitly).
942 bool "Debug preemptible kernel"
943 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
946 If you say Y here then the kernel will use a debug variant of the
947 commonly used smp_processor_id() function and will print warnings
948 if kernel code uses it in a preemption-unsafe way. Also, the kernel
949 will detect preemption count underflows.
951 menu "Lock Debugging (spinlocks, mutexes, etc...)"
953 config DEBUG_RT_MUTEXES
954 bool "RT Mutex debugging, deadlock detection"
955 depends on DEBUG_KERNEL && RT_MUTEXES
957 This allows rt mutex semantics violations and rt mutex related
958 deadlocks (lockups) to be detected and reported automatically.
960 config DEBUG_SPINLOCK
961 bool "Spinlock and rw-lock debugging: basic checks"
962 depends on DEBUG_KERNEL
963 select UNINLINE_SPIN_UNLOCK
965 Say Y here and build SMP to catch missing spinlock initialization
966 and certain other kinds of spinlock errors commonly made. This is
967 best used in conjunction with the NMI watchdog so that spinlock
968 deadlocks are also debuggable.
971 bool "Mutex debugging: basic checks"
972 depends on DEBUG_KERNEL
974 This feature allows mutex semantics violations to be detected and
977 config DEBUG_WW_MUTEX_SLOWPATH
978 bool "Wait/wound mutex debugging: Slowpath testing"
979 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
980 select DEBUG_LOCK_ALLOC
981 select DEBUG_SPINLOCK
984 This feature enables slowpath testing for w/w mutex users by
985 injecting additional -EDEADLK wound/backoff cases. Together with
986 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
987 will test all possible w/w mutex interface abuse with the
988 exception of simply not acquiring all the required locks.
989 Note that this feature can introduce significant overhead, so
990 it really should not be enabled in a production or distro kernel,
991 even a debug kernel. If you are a driver writer, enable it. If
992 you are a distro, do not.
994 config DEBUG_LOCK_ALLOC
995 bool "Lock debugging: detect incorrect freeing of live locks"
996 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
997 select DEBUG_SPINLOCK
1001 This feature will check whether any held lock (spinlock, rwlock,
1002 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1003 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1004 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1005 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1006 held during task exit.
1008 config PROVE_LOCKING
1009 bool "Lock debugging: prove locking correctness"
1010 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1012 select DEBUG_SPINLOCK
1013 select DEBUG_MUTEXES
1014 select DEBUG_LOCK_ALLOC
1015 select TRACE_IRQFLAGS
1018 This feature enables the kernel to prove that all locking
1019 that occurs in the kernel runtime is mathematically
1020 correct: that under no circumstance could an arbitrary (and
1021 not yet triggered) combination of observed locking
1022 sequences (on an arbitrary number of CPUs, running an
1023 arbitrary number of tasks and interrupt contexts) cause a
1026 In short, this feature enables the kernel to report locking
1027 related deadlocks before they actually occur.
1029 The proof does not depend on how hard and complex a
1030 deadlock scenario would be to trigger: how many
1031 participant CPUs, tasks and irq-contexts would be needed
1032 for it to trigger. The proof also does not depend on
1033 timing: if a race and a resulting deadlock is possible
1034 theoretically (no matter how unlikely the race scenario
1035 is), it will be proven so and will immediately be
1036 reported by the kernel (once the event is observed that
1037 makes the deadlock theoretically possible).
1039 If a deadlock is impossible (i.e. the locking rules, as
1040 observed by the kernel, are mathematically correct), the
1041 kernel reports nothing.
1043 NOTE: this feature can also be enabled for rwlocks, mutexes
1044 and rwsems - in which case all dependencies between these
1045 different locking variants are observed and mapped too, and
1046 the proof of observed correctness is also maintained for an
1047 arbitrary combination of these separate locking variants.
1049 For more details, see Documentation/locking/lockdep-design.txt.
1053 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1055 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
1060 bool "Lock usage statistics"
1061 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1063 select DEBUG_SPINLOCK
1064 select DEBUG_MUTEXES
1065 select DEBUG_LOCK_ALLOC
1068 This feature enables tracking lock contention points
1070 For more details, see Documentation/locking/lockstat.txt
1072 This also enables lock events required by "perf lock",
1074 If you want to use "perf lock", you also need to turn on
1075 CONFIG_EVENT_TRACING.
1077 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1078 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1080 config DEBUG_LOCKDEP
1081 bool "Lock dependency engine debugging"
1082 depends on DEBUG_KERNEL && LOCKDEP
1084 If you say Y here, the lock dependency engine will do
1085 additional runtime checks to debug itself, at the price
1086 of more runtime overhead.
1088 config DEBUG_ATOMIC_SLEEP
1089 bool "Sleep inside atomic section checking"
1090 select PREEMPT_COUNT
1091 depends on DEBUG_KERNEL
1093 If you say Y here, various routines which may sleep will become very
1094 noisy if they are called inside atomic sections: when a spinlock is
1095 held, inside an rcu read side critical section, inside preempt disabled
1096 sections, inside an interrupt, etc...
1098 config DEBUG_LOCKING_API_SELFTESTS
1099 bool "Locking API boot-time self-tests"
1100 depends on DEBUG_KERNEL
1102 Say Y here if you want the kernel to run a short self-test during
1103 bootup. The self-test checks whether common types of locking bugs
1104 are detected by debugging mechanisms or not. (if you disable
1105 lock debugging then those bugs wont be detected of course.)
1106 The following locking APIs are covered: spinlocks, rwlocks,
1109 config LOCK_TORTURE_TEST
1110 tristate "torture tests for locking"
1111 depends on DEBUG_KERNEL
1115 This option provides a kernel module that runs torture tests
1116 on kernel locking primitives. The kernel module may be built
1117 after the fact on the running kernel to be tested, if desired.
1119 Say Y here if you want kernel locking-primitive torture tests
1120 to be built into the kernel.
1121 Say M if you want these torture tests to build as a module.
1122 Say N if you are unsure.
1124 endmenu # lock debugging
1126 config TRACE_IRQFLAGS
1129 Enables hooks to interrupt enabling and disabling for
1130 either tracing or lock debugging.
1133 bool "Stack backtrace support"
1134 depends on STACKTRACE_SUPPORT
1136 This option causes the kernel to create a /proc/pid/stack for
1137 every process, showing its current stack trace.
1138 It is also used by various kernel debugging features that require
1139 stack trace generation.
1141 config DEBUG_KOBJECT
1142 bool "kobject debugging"
1143 depends on DEBUG_KERNEL
1145 If you say Y here, some extra kobject debugging messages will be sent
1148 config DEBUG_KOBJECT_RELEASE
1149 bool "kobject release debugging"
1150 depends on DEBUG_OBJECTS_TIMERS
1152 kobjects are reference counted objects. This means that their
1153 last reference count put is not predictable, and the kobject can
1154 live on past the point at which a driver decides to drop it's
1155 initial reference to the kobject gained on allocation. An
1156 example of this would be a struct device which has just been
1159 However, some buggy drivers assume that after such an operation,
1160 the memory backing the kobject can be immediately freed. This
1161 goes completely against the principles of a refcounted object.
1163 If you say Y here, the kernel will delay the release of kobjects
1164 on the last reference count to improve the visibility of this
1165 kind of kobject release bug.
1167 config HAVE_DEBUG_BUGVERBOSE
1170 config DEBUG_BUGVERBOSE
1171 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1172 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1175 Say Y here to make BUG() panics output the file name and line number
1176 of the BUG call as well as the EIP and oops trace. This aids
1177 debugging but costs about 70-100K of memory.
1180 bool "Debug linked list manipulation"
1181 depends on DEBUG_KERNEL
1183 Enable this to turn on extended checks in the linked-list
1188 config DEBUG_PI_LIST
1189 bool "Debug priority linked list manipulation"
1190 depends on DEBUG_KERNEL
1192 Enable this to turn on extended checks in the priority-ordered
1193 linked-list (plist) walking routines. This checks the entire
1194 list multiple times during each manipulation.
1199 bool "Debug SG table operations"
1200 depends on DEBUG_KERNEL
1202 Enable this to turn on checks on scatter-gather tables. This can
1203 help find problems with drivers that do not properly initialize
1208 config DEBUG_NOTIFIERS
1209 bool "Debug notifier call chains"
1210 depends on DEBUG_KERNEL
1212 Enable this to turn on sanity checking for notifier call chains.
1213 This is most useful for kernel developers to make sure that
1214 modules properly unregister themselves from notifier chains.
1215 This is a relatively cheap check but if you care about maximum
1218 config DEBUG_CREDENTIALS
1219 bool "Debug credential management"
1220 depends on DEBUG_KERNEL
1222 Enable this to turn on some debug checking for credential
1223 management. The additional code keeps track of the number of
1224 pointers from task_structs to any given cred struct, and checks to
1225 see that this number never exceeds the usage count of the cred
1228 Furthermore, if SELinux is enabled, this also checks that the
1229 security pointer in the cred struct is never seen to be invalid.
1233 menu "RCU Debugging"
1236 def_bool PROVE_LOCKING
1238 config PROVE_RCU_REPEATEDLY
1239 bool "RCU debugging: don't disable PROVE_RCU on first splat"
1240 depends on PROVE_RCU
1243 By itself, PROVE_RCU will disable checking upon issuing the
1244 first warning (or "splat"). This feature prevents such
1245 disabling, allowing multiple RCU-lockdep warnings to be printed
1248 Say Y to allow multiple RCU-lockdep warnings per boot.
1250 Say N if you are unsure.
1252 config SPARSE_RCU_POINTER
1253 bool "RCU debugging: sparse-based checks for pointer usage"
1256 This feature enables the __rcu sparse annotation for
1257 RCU-protected pointers. This annotation will cause sparse
1258 to flag any non-RCU used of annotated pointers. This can be
1259 helpful when debugging RCU usage. Please note that this feature
1260 is not intended to enforce code cleanliness; it is instead merely
1263 Say Y to make sparse flag questionable use of RCU-protected pointers
1265 Say N if you are unsure.
1271 config RCU_TORTURE_TEST
1272 tristate "torture tests for RCU"
1273 depends on DEBUG_KERNEL
1279 This option provides a kernel module that runs torture tests
1280 on the RCU infrastructure. The kernel module may be built
1281 after the fact on the running kernel to be tested, if desired.
1283 Say Y here if you want RCU torture tests to be built into
1285 Say M if you want the RCU torture tests to build as a module.
1286 Say N if you are unsure.
1288 config RCU_TORTURE_TEST_RUNNABLE
1289 bool "torture tests for RCU runnable by default"
1290 depends on RCU_TORTURE_TEST = y
1293 This option provides a way to build the RCU torture tests
1294 directly into the kernel without them starting up at boot
1295 time. You can use /proc/sys/kernel/rcutorture_runnable
1296 to manually override this setting. This /proc file is
1297 available only when the RCU torture tests have been built
1300 Say Y here if you want the RCU torture tests to start during
1301 boot (you probably don't).
1302 Say N here if you want the RCU torture tests to start only
1303 after being manually enabled via /proc.
1305 config RCU_TORTURE_TEST_SLOW_PREINIT
1306 bool "Slow down RCU grace-period pre-initialization to expose races"
1307 depends on RCU_TORTURE_TEST
1309 This option delays grace-period pre-initialization (the
1310 propagation of CPU-hotplug changes up the rcu_node combining
1311 tree) for a few jiffies between initializing each pair of
1312 consecutive rcu_node structures. This helps to expose races
1313 involving grace-period pre-initialization, in other words, it
1314 makes your kernel less stable. It can also greatly increase
1315 grace-period latency, especially on systems with large numbers
1316 of CPUs. This is useful when torture-testing RCU, but in
1317 almost no other circumstance.
1319 Say Y here if you want your system to crash and hang more often.
1320 Say N if you want a sane system.
1322 config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
1323 int "How much to slow down RCU grace-period pre-initialization"
1326 depends on RCU_TORTURE_TEST_SLOW_PREINIT
1328 This option specifies the number of jiffies to wait between
1329 each rcu_node structure pre-initialization step.
1331 config RCU_TORTURE_TEST_SLOW_INIT
1332 bool "Slow down RCU grace-period initialization to expose races"
1333 depends on RCU_TORTURE_TEST
1335 This option delays grace-period initialization for a few
1336 jiffies between initializing each pair of consecutive
1337 rcu_node structures. This helps to expose races involving
1338 grace-period initialization, in other words, it makes your
1339 kernel less stable. It can also greatly increase grace-period
1340 latency, especially on systems with large numbers of CPUs.
1341 This is useful when torture-testing RCU, but in almost no
1344 Say Y here if you want your system to crash and hang more often.
1345 Say N if you want a sane system.
1347 config RCU_TORTURE_TEST_SLOW_INIT_DELAY
1348 int "How much to slow down RCU grace-period initialization"
1351 depends on RCU_TORTURE_TEST_SLOW_INIT
1353 This option specifies the number of jiffies to wait between
1354 each rcu_node structure initialization.
1356 config RCU_TORTURE_TEST_SLOW_CLEANUP
1357 bool "Slow down RCU grace-period cleanup to expose races"
1358 depends on RCU_TORTURE_TEST
1360 This option delays grace-period cleanup for a few jiffies
1361 between cleaning up each pair of consecutive rcu_node
1362 structures. This helps to expose races involving grace-period
1363 cleanup, in other words, it makes your kernel less stable.
1364 It can also greatly increase grace-period latency, especially
1365 on systems with large numbers of CPUs. This is useful when
1366 torture-testing RCU, but in almost no other circumstance.
1368 Say Y here if you want your system to crash and hang more often.
1369 Say N if you want a sane system.
1371 config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
1372 int "How much to slow down RCU grace-period cleanup"
1375 depends on RCU_TORTURE_TEST_SLOW_CLEANUP
1377 This option specifies the number of jiffies to wait between
1378 each rcu_node structure cleanup operation.
1380 config RCU_CPU_STALL_TIMEOUT
1381 int "RCU CPU stall timeout in seconds"
1382 depends on RCU_STALL_COMMON
1386 If a given RCU grace period extends more than the specified
1387 number of seconds, a CPU stall warning is printed. If the
1388 RCU grace period persists, additional CPU stall warnings are
1389 printed at more widely spaced intervals.
1392 bool "Enable tracing for RCU"
1393 depends on DEBUG_KERNEL
1396 This option provides tracing in RCU which presents stats
1397 in debugfs for debugging RCU implementation.
1399 Say Y here if you want to enable RCU tracing
1400 Say N if you are unsure.
1402 config RCU_EQS_DEBUG
1403 bool "Provide debugging asserts for adding NO_HZ support to an arch"
1404 depends on DEBUG_KERNEL
1406 This option provides consistency checks in RCU's handling of
1407 NO_HZ. These checks have proven quite helpful in detecting
1408 bugs in arch-specific NO_HZ code.
1410 Say N here if you need ultimate kernel/user switch latencies
1411 Say Y if you are unsure
1413 endmenu # "RCU Debugging"
1415 config DEBUG_WQ_FORCE_RR_CPU
1416 bool "Force round-robin CPU selection for unbound work items"
1417 depends on DEBUG_KERNEL
1420 Workqueue used to implicitly guarantee that work items queued
1421 without explicit CPU specified are put on the local CPU. This
1422 guarantee is no longer true and while local CPU is still
1423 preferred work items may be put on foreign CPUs. Kernel
1424 parameter "workqueue.debug_force_rr_cpu" is added to force
1425 round-robin CPU selection to flush out usages which depend on the
1426 now broken guarantee. This config option enables the debug
1427 feature by default. When enabled, memory and cache locality will
1430 config DEBUG_BLOCK_EXT_DEVT
1431 bool "Force extended block device numbers and spread them"
1432 depends on DEBUG_KERNEL
1436 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1437 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1438 YOU ARE DOING. Distros, please enable this and fix whatever
1441 Conventionally, block device numbers are allocated from
1442 predetermined contiguous area. However, extended block area
1443 may introduce non-contiguous block device numbers. This
1444 option forces most block device numbers to be allocated from
1445 the extended space and spreads them to discover kernel or
1446 userland code paths which assume predetermined contiguous
1447 device number allocation.
1449 Note that turning on this debug option shuffles all the
1450 device numbers for all IDE and SCSI devices including libata
1451 ones, so root partition specified using device number
1452 directly (via rdev or root=MAJ:MIN) won't work anymore.
1453 Textual device names (root=/dev/sdXn) will continue to work.
1455 Say N if you are unsure.
1457 config CPU_HOTPLUG_STATE_CONTROL
1458 bool "Enable CPU hotplug state control"
1459 depends on DEBUG_KERNEL
1460 depends on HOTPLUG_CPU
1463 Allows to write steps between "offline" and "online" to the CPUs
1464 sysfs target file so states can be stepped granular. This is a debug
1465 option for now as the hotplug machinery cannot be stopped and
1466 restarted at arbitrary points yet.
1468 Say N if your are unsure.
1470 config NOTIFIER_ERROR_INJECTION
1471 tristate "Notifier error injection"
1472 depends on DEBUG_KERNEL
1475 This option provides the ability to inject artificial errors to
1476 specified notifier chain callbacks. It is useful to test the error
1477 handling of notifier call chain failures.
1481 config CPU_NOTIFIER_ERROR_INJECT
1482 tristate "CPU notifier error injection module"
1483 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1485 This option provides a kernel module that can be used to test
1486 the error handling of the cpu notifiers by injecting artificial
1487 errors to CPU notifier chain callbacks. It is controlled through
1488 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
1490 If the notifier call chain should be failed with some events
1491 notified, write the error code to "actions/<notifier event>/error".
1493 Example: Inject CPU offline error (-1 == -EPERM)
1495 # cd /sys/kernel/debug/notifier-error-inject/cpu
1496 # echo -1 > actions/CPU_DOWN_PREPARE/error
1497 # echo 0 > /sys/devices/system/cpu/cpu1/online
1498 bash: echo: write error: Operation not permitted
1500 To compile this code as a module, choose M here: the module will
1501 be called cpu-notifier-error-inject.
1505 config PM_NOTIFIER_ERROR_INJECT
1506 tristate "PM notifier error injection module"
1507 depends on PM && NOTIFIER_ERROR_INJECTION
1508 default m if PM_DEBUG
1510 This option provides the ability to inject artificial errors to
1511 PM notifier chain callbacks. It is controlled through debugfs
1512 interface /sys/kernel/debug/notifier-error-inject/pm
1514 If the notifier call chain should be failed with some events
1515 notified, write the error code to "actions/<notifier event>/error".
1517 Example: Inject PM suspend error (-12 = -ENOMEM)
1519 # cd /sys/kernel/debug/notifier-error-inject/pm/
1520 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1521 # echo mem > /sys/power/state
1522 bash: echo: write error: Cannot allocate memory
1524 To compile this code as a module, choose M here: the module will
1525 be called pm-notifier-error-inject.
1529 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1530 tristate "OF reconfig notifier error injection module"
1531 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1533 This option provides the ability to inject artificial errors to
1534 OF reconfig notifier chain callbacks. It is controlled
1535 through debugfs interface under
1536 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1538 If the notifier call chain should be failed with some events
1539 notified, write the error code to "actions/<notifier event>/error".
1541 To compile this code as a module, choose M here: the module will
1542 be called of-reconfig-notifier-error-inject.
1546 config NETDEV_NOTIFIER_ERROR_INJECT
1547 tristate "Netdev notifier error injection module"
1548 depends on NET && NOTIFIER_ERROR_INJECTION
1550 This option provides the ability to inject artificial errors to
1551 netdevice notifier chain callbacks. It is controlled through debugfs
1552 interface /sys/kernel/debug/notifier-error-inject/netdev
1554 If the notifier call chain should be failed with some events
1555 notified, write the error code to "actions/<notifier event>/error".
1557 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1559 # cd /sys/kernel/debug/notifier-error-inject/netdev
1560 # echo -22 > actions/NETDEV_CHANGEMTU/error
1561 # ip link set eth0 mtu 1024
1562 RTNETLINK answers: Invalid argument
1564 To compile this code as a module, choose M here: the module will
1565 be called netdev-notifier-error-inject.
1569 config FAULT_INJECTION
1570 bool "Fault-injection framework"
1571 depends on DEBUG_KERNEL
1573 Provide fault-injection framework.
1574 For more details, see Documentation/fault-injection/.
1577 bool "Fault-injection capability for kmalloc"
1578 depends on FAULT_INJECTION
1579 depends on SLAB || SLUB
1581 Provide fault-injection capability for kmalloc.
1583 config FAIL_PAGE_ALLOC
1584 bool "Fault-injection capabilitiy for alloc_pages()"
1585 depends on FAULT_INJECTION
1587 Provide fault-injection capability for alloc_pages().
1589 config FAIL_MAKE_REQUEST
1590 bool "Fault-injection capability for disk IO"
1591 depends on FAULT_INJECTION && BLOCK
1593 Provide fault-injection capability for disk IO.
1595 config FAIL_IO_TIMEOUT
1596 bool "Fault-injection capability for faking disk interrupts"
1597 depends on FAULT_INJECTION && BLOCK
1599 Provide fault-injection capability on end IO handling. This
1600 will make the block layer "forget" an interrupt as configured,
1601 thus exercising the error handling.
1603 Only works with drivers that use the generic timeout handling,
1604 for others it wont do anything.
1606 config FAIL_MMC_REQUEST
1607 bool "Fault-injection capability for MMC IO"
1608 depends on FAULT_INJECTION_DEBUG_FS && MMC
1610 Provide fault-injection capability for MMC IO.
1611 This will make the mmc core return data errors. This is
1612 useful to test the error handling in the mmc block device
1613 and to test how the mmc host driver handles retries from
1617 bool "Fault-injection capability for futexes"
1619 depends on FAULT_INJECTION && FUTEX
1621 Provide fault-injection capability for futexes.
1623 config FAULT_INJECTION_DEBUG_FS
1624 bool "Debugfs entries for fault-injection capabilities"
1625 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1627 Enable configuration of fault-injection capabilities via debugfs.
1629 config FAULT_INJECTION_STACKTRACE_FILTER
1630 bool "stacktrace filter for fault-injection capabilities"
1631 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1634 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1636 Provide stacktrace filter for fault-injection capabilities
1639 bool "Latency measuring infrastructure"
1640 depends on DEBUG_KERNEL
1641 depends on STACKTRACE_SUPPORT
1643 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1650 Enable this option if you want to use the LatencyTOP tool
1651 to find out which userspace is blocking on what kernel operations.
1653 config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1656 config DEBUG_STRICT_USER_COPY_CHECKS
1657 bool "Strict user copy size checks"
1658 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1659 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
1661 Enabling this option turns a certain set of sanity checks for user
1662 copy operations into compile time failures.
1664 The copy_from_user() etc checks are there to help test if there
1665 are sufficient security checks on the length argument of
1666 the copy operation, by having gcc prove that the argument is
1671 source kernel/trace/Kconfig
1673 menu "Runtime Testing"
1676 tristate "Linux Kernel Dump Test Tool Module"
1681 This module enables testing of the different dumping mechanisms by
1682 inducing system failures at predefined crash points.
1683 If you don't need it: say N
1684 Choose M here to compile this code as a module. The module will be
1687 Documentation on how to use the module can be found in
1688 Documentation/fault-injection/provoke-crashes.txt
1690 config TEST_LIST_SORT
1691 bool "Linked list sorting test"
1692 depends on DEBUG_KERNEL
1694 Enable this to turn on 'list_sort()' function test. This test is
1695 executed only once during system boot, so affects only boot time.
1699 config KPROBES_SANITY_TEST
1700 bool "Kprobes sanity tests"
1701 depends on DEBUG_KERNEL
1705 This option provides for testing basic kprobes functionality on
1706 boot. A sample kprobe, jprobe and kretprobe are inserted and
1707 verified for functionality.
1709 Say N if you are unsure.
1711 config BACKTRACE_SELF_TEST
1712 tristate "Self test for the backtrace code"
1713 depends on DEBUG_KERNEL
1716 This option provides a kernel module that can be used to test
1717 the kernel stack backtrace code. This option is not useful
1718 for distributions or general kernels, but only for kernel
1719 developers working on architecture code.
1721 Note that if you want to also test saved backtraces, you will
1722 have to enable STACKTRACE as well.
1724 Say N if you are unsure.
1727 tristate "Red-Black tree test"
1728 depends on DEBUG_KERNEL
1730 A benchmark measuring the performance of the rbtree library.
1731 Also includes rbtree invariant checks.
1733 config INTERVAL_TREE_TEST
1734 tristate "Interval tree test"
1735 depends on m && DEBUG_KERNEL
1736 select INTERVAL_TREE
1738 A benchmark measuring the performance of the interval tree library
1741 tristate "Per cpu operations test"
1742 depends on m && DEBUG_KERNEL
1744 Enable this option to build test module which validates per-cpu
1749 config ATOMIC64_SELFTEST
1750 bool "Perform an atomic64_t self-test at boot"
1752 Enable this option to test the atomic64_t functions at boot.
1756 config ASYNC_RAID6_TEST
1757 tristate "Self test for hardware accelerated raid6 recovery"
1758 depends on ASYNC_RAID6_RECOV
1761 This is a one-shot self test that permutes through the
1762 recovery of all the possible two disk failure scenarios for a
1763 N-disk array. Recovery is performed with the asynchronous
1764 raid6 recovery routines, and will optionally use an offload
1765 engine if one is available.
1770 tristate "Test functions located in the hexdump module at runtime"
1772 config TEST_STRING_HELPERS
1773 tristate "Test functions located in the string_helpers module at runtime"
1776 tristate "Test kstrto*() family of functions at runtime"
1779 tristate "Test printf() family of functions at runtime"
1782 tristate "Test bitmap_*() family of functions at runtime"
1785 Enable this option to test the bitmap functions at boot.
1789 config TEST_RHASHTABLE
1790 tristate "Perform selftest on resizable hash table"
1793 Enable this option to test the rhashtable functions at boot.
1797 endmenu # runtime tests
1799 config PROVIDE_OHCI1394_DMA_INIT
1800 bool "Remote debugging over FireWire early on boot"
1801 depends on PCI && X86
1803 If you want to debug problems which hang or crash the kernel early
1804 on boot and the crashing machine has a FireWire port, you can use
1805 this feature to remotely access the memory of the crashed machine
1806 over FireWire. This employs remote DMA as part of the OHCI1394
1807 specification which is now the standard for FireWire controllers.
1809 With remote DMA, you can monitor the printk buffer remotely using
1810 firescope and access all memory below 4GB using fireproxy from gdb.
1811 Even controlling a kernel debugger is possible using remote DMA.
1815 If ohci1394_dma=early is used as boot parameter, it will initialize
1816 all OHCI1394 controllers which are found in the PCI config space.
1818 As all changes to the FireWire bus such as enabling and disabling
1819 devices cause a bus reset and thereby disable remote DMA for all
1820 devices, be sure to have the cable plugged and FireWire enabled on
1821 the debugging host before booting the debug target for debugging.
1823 This code (~1k) is freed after boot. By then, the firewire stack
1824 in charge of the OHCI-1394 controllers should be used instead.
1826 See Documentation/debugging-via-ohci1394.txt for more information.
1829 bool "Build targets in Documentation/ tree"
1830 depends on HEADERS_CHECK
1832 This option attempts to build objects from the source files in the
1833 kernel Documentation/ tree.
1835 Say N if you are unsure.
1837 config DMA_API_DEBUG
1838 bool "Enable debugging of DMA-API usage"
1839 depends on HAVE_DMA_API_DEBUG
1841 Enable this option to debug the use of the DMA API by device drivers.
1842 With this option you will be able to detect common bugs in device
1843 drivers like double-freeing of DMA mappings or freeing mappings that
1844 were never allocated.
1846 This also attempts to catch cases where a page owned by DMA is
1847 accessed by the cpu in a way that could cause data corruption. For
1848 example, this enables cow_user_page() to check that the source page is
1851 This option causes a performance degradation. Use only if you want to
1852 debug device drivers and dma interactions.
1857 tristate "Test module loading with 'hello world' module"
1861 This builds the "test_module" module that emits "Hello, world"
1862 on printk when loaded. It is designed to be used for basic
1863 evaluation of the module loading subsystem (for example when
1864 validating module verification). It lacks any extra dependencies,
1865 and will not normally be loaded by the system unless explicitly
1870 config TEST_USER_COPY
1871 tristate "Test user/kernel boundary protections"
1875 This builds the "test_user_copy" module that runs sanity checks
1876 on the copy_to/from_user infrastructure, making sure basic
1877 user/kernel boundary testing is working. If it fails to load,
1878 a regression has been detected in the user/kernel memory boundary
1884 tristate "Test BPF filter functionality"
1888 This builds the "test_bpf" module that runs various test vectors
1889 against the BPF interpreter or BPF JIT compiler depending on the
1890 current setting. This is in particular useful for BPF JIT compiler
1891 development, but also to run regression tests against changes in
1892 the interpreter code. It also enables test stubs for eBPF maps and
1893 verifier used by user space verifier testsuite.
1897 config TEST_FIRMWARE
1898 tristate "Test firmware loading via userspace interface"
1900 depends on FW_LOADER
1902 This builds the "test_firmware" module that creates a userspace
1903 interface for testing firmware loading. This can be used to
1904 control the triggering of firmware loading without needing an
1905 actual firmware-using device. The contents can be rechecked by
1911 tristate "udelay test driver"
1914 This builds the "udelay_test" module that helps to make sure
1915 that udelay() is working properly.
1921 depends on HAVE_MEMBLOCK
1923 This option adds a kernel parameter 'memtest', which allows memtest
1925 memtest=0, mean disabled; -- default
1926 memtest=1, mean do 1 test pattern;
1928 memtest=17, mean do 17 test patterns.
1929 If you are unsure how to answer this question, answer N.
1931 config TEST_STATIC_KEYS
1932 tristate "Test static keys"
1936 Test the static key interfaces.
1940 source "samples/Kconfig"
1942 source "lib/Kconfig.kgdb"
1944 source "lib/Kconfig.ubsan"
1946 config ARCH_HAS_DEVMEM_IS_ALLOWED
1949 config STRICT_DEVMEM
1950 bool "Filter access to /dev/mem"
1952 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
1953 default y if TILE || PPC
1955 If this option is disabled, you allow userspace (root) access to all
1956 of memory, including kernel and userspace memory. Accidental
1957 access to this is obviously disastrous, but specific access can
1958 be used by people debugging the kernel. Note that with PAT support
1959 enabled, even in this case there are restrictions on /dev/mem
1960 use due to the cache aliasing requirements.
1962 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
1963 file only allows userspace access to PCI space and the BIOS code and
1964 data regions. This is sufficient for dosemu and X and all common
1969 config IO_STRICT_DEVMEM
1970 bool "Filter I/O access to /dev/mem"
1971 depends on STRICT_DEVMEM
1973 If this option is disabled, you allow userspace (root) access to all
1974 io-memory regardless of whether a driver is actively using that
1975 range. Accidental access to this is obviously disastrous, but
1976 specific access can be used by people debugging kernel drivers.
1978 If this option is switched on, the /dev/mem file only allows
1979 userspace access to *idle* io-memory ranges (see /proc/iomem) This
1980 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
1981 if the driver using a given range cannot be disabled.
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