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 DEBUG_FORCE_WEAK_PER_CPU
346 bool "Force weak per-cpu definitions"
347 depends on DEBUG_KERNEL
349 s390 and alpha require percpu variables in modules to be
350 defined weak to work around addressing range issue which
351 puts the following two restrictions on percpu variable
354 1. percpu symbols must be unique whether static or not
355 2. percpu variables can't be defined inside a function
357 To ensure that generic code follows the above rules, this
358 option forces all percpu variables to be defined as weak.
360 endmenu # "Compiler options"
363 bool "Magic SysRq key"
366 If you say Y here, you will have some control over the system even
367 if the system crashes for example during kernel debugging (e.g., you
368 will be able to flush the buffer cache to disk, reboot the system
369 immediately or dump some status information). This is accomplished
370 by pressing various keys while holding SysRq (Alt+PrintScreen). It
371 also works on a serial console (on PC hardware at least), if you
372 send a BREAK and then within 5 seconds a command keypress. The
373 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
374 unless you really know what this hack does.
376 config MAGIC_SYSRQ_DEFAULT_ENABLE
377 hex "Enable magic SysRq key functions by default"
378 depends on MAGIC_SYSRQ
381 Specifies which SysRq key functions are enabled by default.
382 This may be set to 1 or 0 to enable or disable them all, or
383 to a bitmask as described in Documentation/sysrq.txt.
386 bool "Kernel debugging"
388 Say Y here if you are developing drivers or trying to debug and
389 identify kernel problems.
391 menu "Memory Debugging"
393 source mm/Kconfig.debug
396 bool "Debug object operations"
397 depends on DEBUG_KERNEL
399 If you say Y here, additional code will be inserted into the
400 kernel to track the life time of various objects and validate
401 the operations on those objects.
403 config DEBUG_OBJECTS_SELFTEST
404 bool "Debug objects selftest"
405 depends on DEBUG_OBJECTS
407 This enables the selftest of the object debug code.
409 config DEBUG_OBJECTS_FREE
410 bool "Debug objects in freed memory"
411 depends on DEBUG_OBJECTS
413 This enables checks whether a k/v free operation frees an area
414 which contains an object which has not been deactivated
415 properly. This can make kmalloc/kfree-intensive workloads
418 config DEBUG_OBJECTS_TIMERS
419 bool "Debug timer objects"
420 depends on DEBUG_OBJECTS
422 If you say Y here, additional code will be inserted into the
423 timer routines to track the life time of timer objects and
424 validate the timer operations.
426 config DEBUG_OBJECTS_WORK
427 bool "Debug work objects"
428 depends on DEBUG_OBJECTS
430 If you say Y here, additional code will be inserted into the
431 work queue routines to track the life time of work objects and
432 validate the work operations.
434 config DEBUG_OBJECTS_RCU_HEAD
435 bool "Debug RCU callbacks objects"
436 depends on DEBUG_OBJECTS
438 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
440 config DEBUG_OBJECTS_PERCPU_COUNTER
441 bool "Debug percpu counter objects"
442 depends on DEBUG_OBJECTS
444 If you say Y here, additional code will be inserted into the
445 percpu counter routines to track the life time of percpu counter
446 objects and validate the percpu counter operations.
448 config DEBUG_OBJECTS_ENABLE_DEFAULT
449 int "debug_objects bootup default value (0-1)"
452 depends on DEBUG_OBJECTS
454 Debug objects boot parameter default value
457 bool "Debug slab memory allocations"
458 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
460 Say Y here to have the kernel do limited verification on memory
461 allocation as well as poisoning memory on free to catch use of freed
462 memory. This can make kmalloc/kfree-intensive workloads much slower.
464 config DEBUG_SLAB_LEAK
465 bool "Memory leak debugging"
466 depends on DEBUG_SLAB
469 bool "SLUB debugging on by default"
470 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
473 Boot with debugging on by default. SLUB boots by default with
474 the runtime debug capabilities switched off. Enabling this is
475 equivalent to specifying the "slub_debug" parameter on boot.
476 There is no support for more fine grained debug control like
477 possible with slub_debug=xxx. SLUB debugging may be switched
478 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
483 bool "Enable SLUB performance statistics"
484 depends on SLUB && SYSFS
486 SLUB statistics are useful to debug SLUBs allocation behavior in
487 order find ways to optimize the allocator. This should never be
488 enabled for production use since keeping statistics slows down
489 the allocator by a few percentage points. The slabinfo command
490 supports the determination of the most active slabs to figure
491 out which slabs are relevant to a particular load.
492 Try running: slabinfo -DA
494 config HAVE_DEBUG_KMEMLEAK
497 config DEBUG_KMEMLEAK
498 bool "Kernel memory leak detector"
499 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
501 select STACKTRACE if STACKTRACE_SUPPORT
505 Say Y here if you want to enable the memory leak
506 detector. The memory allocation/freeing is traced in a way
507 similar to the Boehm's conservative garbage collector, the
508 difference being that the orphan objects are not freed but
509 only shown in /sys/kernel/debug/kmemleak. Enabling this
510 feature will introduce an overhead to memory
511 allocations. See Documentation/kmemleak.txt for more
514 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
515 of finding leaks due to the slab objects poisoning.
517 In order to access the kmemleak file, debugfs needs to be
518 mounted (usually at /sys/kernel/debug).
520 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
521 int "Maximum kmemleak early log entries"
522 depends on DEBUG_KMEMLEAK
526 Kmemleak must track all the memory allocations to avoid
527 reporting false positives. Since memory may be allocated or
528 freed before kmemleak is initialised, an early log buffer is
529 used to store these actions. If kmemleak reports "early log
530 buffer exceeded", please increase this value.
532 config DEBUG_KMEMLEAK_TEST
533 tristate "Simple test for the kernel memory leak detector"
534 depends on DEBUG_KMEMLEAK && m
536 This option enables a module that explicitly leaks memory.
540 config DEBUG_KMEMLEAK_DEFAULT_OFF
541 bool "Default kmemleak to off"
542 depends on DEBUG_KMEMLEAK
544 Say Y here to disable kmemleak by default. It can then be enabled
545 on the command line via kmemleak=on.
547 config DEBUG_STACK_USAGE
548 bool "Stack utilization instrumentation"
549 depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAG
551 Enables the display of the minimum amount of free stack which each
552 task has ever had available in the sysrq-T and sysrq-P debug output.
554 This option will slow down process creation somewhat.
558 depends on DEBUG_KERNEL
560 Enable this to turn on extended checks in the virtual-memory system
561 that may impact performance.
565 config DEBUG_VM_VMACACHE
566 bool "Debug VMA caching"
569 Enable this to turn on VMA caching debug information. Doing so
570 can cause significant overhead, so only enable it in non-production
576 bool "Debug VM red-black trees"
579 Enable VM red-black tree debugging information and extra validations.
583 config DEBUG_VM_PGFLAGS
584 bool "Debug page-flags operations"
587 Enables extra validation on page flags operations.
592 bool "Debug VM translations"
593 depends on DEBUG_KERNEL && X86
595 Enable some costly sanity checks in virtual to page code. This can
596 catch mistakes with virt_to_page() and friends.
600 config DEBUG_NOMMU_REGIONS
601 bool "Debug the global anon/private NOMMU mapping region tree"
602 depends on DEBUG_KERNEL && !MMU
604 This option causes the global tree of anonymous and private mapping
605 regions to be regularly checked for invalid topology.
607 config DEBUG_MEMORY_INIT
608 bool "Debug memory initialisation" if EXPERT
611 Enable this for additional checks during memory initialisation.
612 The sanity checks verify aspects of the VM such as the memory model
613 and other information provided by the architecture. Verbose
614 information will be printed at KERN_DEBUG loglevel depending
615 on the mminit_loglevel= command-line option.
619 config MEMORY_NOTIFIER_ERROR_INJECT
620 tristate "Memory hotplug notifier error injection module"
621 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
623 This option provides the ability to inject artificial errors to
624 memory hotplug notifier chain callbacks. It is controlled through
625 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
627 If the notifier call chain should be failed with some events
628 notified, write the error code to "actions/<notifier event>/error".
630 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
632 # cd /sys/kernel/debug/notifier-error-inject/memory
633 # echo -12 > actions/MEM_GOING_OFFLINE/error
634 # echo offline > /sys/devices/system/memory/memoryXXX/state
635 bash: echo: write error: Cannot allocate memory
637 To compile this code as a module, choose M here: the module will
638 be called memory-notifier-error-inject.
642 config DEBUG_PER_CPU_MAPS
643 bool "Debug access to per_cpu maps"
644 depends on DEBUG_KERNEL
647 Say Y to verify that the per_cpu map being accessed has
648 been set up. This adds a fair amount of code to kernel memory
649 and decreases performance.
654 bool "Highmem debugging"
655 depends on DEBUG_KERNEL && HIGHMEM
657 This option enables additional error checking for high memory
658 systems. Disable for production systems.
660 config HAVE_DEBUG_STACKOVERFLOW
663 config DEBUG_STACKOVERFLOW
664 bool "Check for stack overflows"
665 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
667 Say Y here if you want to check for overflows of kernel, IRQ
668 and exception stacks (if your architecture uses them). This
669 option will show detailed messages if free stack space drops
670 below a certain limit.
672 These kinds of bugs usually occur when call-chains in the
673 kernel get too deep, especially when interrupts are
676 Use this in cases where you see apparently random memory
677 corruption, especially if it appears in 'struct thread_info'
679 If in doubt, say "N".
681 source "lib/Kconfig.kmemcheck"
683 source "lib/Kconfig.kasan"
685 endmenu # "Memory Debugging"
690 KCOV does not have any arch-specific code, but currently it is enabled
691 only for x86_64. KCOV requires testing on other archs, and most likely
692 disabling of instrumentation for some early boot code.
695 bool "Code coverage for fuzzing"
696 depends on ARCH_HAS_KCOV
699 KCOV exposes kernel code coverage information in a form suitable
700 for coverage-guided fuzzing (randomized testing).
702 If RANDOMIZE_BASE is enabled, PC values will not be stable across
703 different machines and across reboots. If you need stable PC values,
704 disable RANDOMIZE_BASE.
706 For more details, see Documentation/kcov.txt.
709 bool "Debug shared IRQ handlers"
710 depends on DEBUG_KERNEL
712 Enable this to generate a spurious interrupt as soon as a shared
713 interrupt handler is registered, and just before one is deregistered.
714 Drivers ought to be able to handle interrupts coming in at those
715 points; some don't and need to be caught.
717 menu "Debug Lockups and Hangs"
719 config LOCKUP_DETECTOR
720 bool "Detect Hard and Soft Lockups"
721 depends on DEBUG_KERNEL && !S390
723 Say Y here to enable the kernel to act as a watchdog to detect
724 hard and soft lockups.
726 Softlockups are bugs that cause the kernel to loop in kernel
727 mode for more than 20 seconds, without giving other tasks a
728 chance to run. The current stack trace is displayed upon
729 detection and the system will stay locked up.
731 Hardlockups are bugs that cause the CPU to loop in kernel mode
732 for more than 10 seconds, without letting other interrupts have a
733 chance to run. The current stack trace is displayed upon detection
734 and the system will stay locked up.
736 The overhead should be minimal. A periodic hrtimer runs to
737 generate interrupts and kick the watchdog task every 4 seconds.
738 An NMI is generated every 10 seconds or so to check for hardlockups.
740 The frequency of hrtimer and NMI events and the soft and hard lockup
741 thresholds can be controlled through the sysctl watchdog_thresh.
743 config HARDLOCKUP_DETECTOR
745 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
746 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
748 config BOOTPARAM_HARDLOCKUP_PANIC
749 bool "Panic (Reboot) On Hard Lockups"
750 depends on HARDLOCKUP_DETECTOR
752 Say Y here to enable the kernel to panic on "hard lockups",
753 which are bugs that cause the kernel to loop in kernel
754 mode with interrupts disabled for more than 10 seconds (configurable
755 using the watchdog_thresh sysctl).
759 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
761 depends on HARDLOCKUP_DETECTOR
763 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
764 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
766 config BOOTPARAM_SOFTLOCKUP_PANIC
767 bool "Panic (Reboot) On Soft Lockups"
768 depends on LOCKUP_DETECTOR
770 Say Y here to enable the kernel to panic on "soft lockups",
771 which are bugs that cause the kernel to loop in kernel
772 mode for more than 20 seconds (configurable using the watchdog_thresh
773 sysctl), without giving other tasks a chance to run.
775 The panic can be used in combination with panic_timeout,
776 to cause the system to reboot automatically after a
777 lockup has been detected. This feature is useful for
778 high-availability systems that have uptime guarantees and
779 where a lockup must be resolved ASAP.
783 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
785 depends on LOCKUP_DETECTOR
787 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
788 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
790 config DETECT_HUNG_TASK
791 bool "Detect Hung Tasks"
792 depends on DEBUG_KERNEL
793 default LOCKUP_DETECTOR
795 Say Y here to enable the kernel to detect "hung tasks",
796 which are bugs that cause the task to be stuck in
797 uninterruptible "D" state indefinitiley.
799 When a hung task is detected, the kernel will print the
800 current stack trace (which you should report), but the
801 task will stay in uninterruptible state. If lockdep is
802 enabled then all held locks will also be reported. This
803 feature has negligible overhead.
805 config DEFAULT_HUNG_TASK_TIMEOUT
806 int "Default timeout for hung task detection (in seconds)"
807 depends on DETECT_HUNG_TASK
810 This option controls the default timeout (in seconds) used
811 to determine when a task has become non-responsive and should
814 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
815 sysctl or by writing a value to
816 /proc/sys/kernel/hung_task_timeout_secs.
818 A timeout of 0 disables the check. The default is two minutes.
819 Keeping the default should be fine in most cases.
821 config BOOTPARAM_HUNG_TASK_PANIC
822 bool "Panic (Reboot) On Hung Tasks"
823 depends on DETECT_HUNG_TASK
825 Say Y here to enable the kernel to panic on "hung tasks",
826 which are bugs that cause the kernel to leave a task stuck
827 in uninterruptible "D" state.
829 The panic can be used in combination with panic_timeout,
830 to cause the system to reboot automatically after a
831 hung task has been detected. This feature is useful for
832 high-availability systems that have uptime guarantees and
833 where a hung tasks must be resolved ASAP.
837 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
839 depends on DETECT_HUNG_TASK
841 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
842 default 1 if BOOTPARAM_HUNG_TASK_PANIC
845 bool "Detect Workqueue Stalls"
846 depends on DEBUG_KERNEL
848 Say Y here to enable stall detection on workqueues. If a
849 worker pool doesn't make forward progress on a pending work
850 item for over a given amount of time, 30s by default, a
851 warning message is printed along with dump of workqueue
852 state. This can be configured through kernel parameter
853 "workqueue.watchdog_thresh" and its sysfs counterpart.
855 endmenu # "Debug lockups and hangs"
860 Say Y here to enable the kernel to panic when it oopses. This
861 has the same effect as setting oops=panic on the kernel command
864 This feature is useful to ensure that the kernel does not do
865 anything erroneous after an oops which could result in data
866 corruption or other issues.
870 config PANIC_ON_OOPS_VALUE
873 default 0 if !PANIC_ON_OOPS
874 default 1 if PANIC_ON_OOPS
880 Set the timeout value (in seconds) until a reboot occurs when the
881 the kernel panics. If n = 0, then we wait forever. A timeout
882 value n > 0 will wait n seconds before rebooting, while a timeout
883 value n < 0 will reboot immediately.
886 bool "Collect scheduler debugging info"
887 depends on DEBUG_KERNEL && PROC_FS
890 If you say Y here, the /proc/sched_debug file will be provided
891 that can help debug the scheduler. The runtime overhead of this
899 bool "Collect scheduler statistics"
900 depends on DEBUG_KERNEL && PROC_FS
903 If you say Y here, additional code will be inserted into the
904 scheduler and related routines to collect statistics about
905 scheduler behavior and provide them in /proc/schedstat. These
906 stats may be useful for both tuning and debugging the scheduler
907 If you aren't debugging the scheduler or trying to tune a specific
908 application, you can say N to avoid the very slight overhead
911 config SCHED_STACK_END_CHECK
912 bool "Detect stack corruption on calls to schedule()"
913 depends on DEBUG_KERNEL
916 This option checks for a stack overrun on calls to schedule().
917 If the stack end location is found to be over written always panic as
918 the content of the corrupted region can no longer be trusted.
919 This is to ensure no erroneous behaviour occurs which could result in
920 data corruption or a sporadic crash at a later stage once the region
921 is examined. The runtime overhead introduced is minimal.
923 config DEBUG_TIMEKEEPING
924 bool "Enable extra timekeeping sanity checking"
926 This option will enable additional timekeeping sanity checks
927 which may be helpful when diagnosing issues where timekeeping
928 problems are suspected.
930 This may include checks in the timekeeping hotpaths, so this
931 option may have a (very small) performance impact to some
937 bool "Collect kernel timers statistics"
938 depends on DEBUG_KERNEL && PROC_FS
940 If you say Y here, additional code will be inserted into the
941 timer routines to collect statistics about kernel timers being
942 reprogrammed. The statistics can be read from /proc/timer_stats.
943 The statistics collection is started by writing 1 to /proc/timer_stats,
944 writing 0 stops it. This feature is useful to collect information
945 about timer usage patterns in kernel and userspace. This feature
946 is lightweight if enabled in the kernel config but not activated
947 (it defaults to deactivated on bootup and will only be activated
948 if some application like powertop activates it explicitly).
951 bool "Debug preemptible kernel"
952 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
955 If you say Y here then the kernel will use a debug variant of the
956 commonly used smp_processor_id() function and will print warnings
957 if kernel code uses it in a preemption-unsafe way. Also, the kernel
958 will detect preemption count underflows.
960 menu "Lock Debugging (spinlocks, mutexes, etc...)"
962 config DEBUG_RT_MUTEXES
963 bool "RT Mutex debugging, deadlock detection"
964 depends on DEBUG_KERNEL && RT_MUTEXES
966 This allows rt mutex semantics violations and rt mutex related
967 deadlocks (lockups) to be detected and reported automatically.
969 config DEBUG_SPINLOCK
970 bool "Spinlock and rw-lock debugging: basic checks"
971 depends on DEBUG_KERNEL
972 select UNINLINE_SPIN_UNLOCK
974 Say Y here and build SMP to catch missing spinlock initialization
975 and certain other kinds of spinlock errors commonly made. This is
976 best used in conjunction with the NMI watchdog so that spinlock
977 deadlocks are also debuggable.
980 bool "Mutex debugging: basic checks"
981 depends on DEBUG_KERNEL
983 This feature allows mutex semantics violations to be detected and
986 config DEBUG_WW_MUTEX_SLOWPATH
987 bool "Wait/wound mutex debugging: Slowpath testing"
988 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
989 select DEBUG_LOCK_ALLOC
990 select DEBUG_SPINLOCK
993 This feature enables slowpath testing for w/w mutex users by
994 injecting additional -EDEADLK wound/backoff cases. Together with
995 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
996 will test all possible w/w mutex interface abuse with the
997 exception of simply not acquiring all the required locks.
998 Note that this feature can introduce significant overhead, so
999 it really should not be enabled in a production or distro kernel,
1000 even a debug kernel. If you are a driver writer, enable it. If
1001 you are a distro, do not.
1003 config DEBUG_LOCK_ALLOC
1004 bool "Lock debugging: detect incorrect freeing of live locks"
1005 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1006 select DEBUG_SPINLOCK
1007 select DEBUG_MUTEXES
1010 This feature will check whether any held lock (spinlock, rwlock,
1011 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1012 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1013 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1014 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1015 held during task exit.
1017 config PROVE_LOCKING
1018 bool "Lock debugging: prove locking correctness"
1019 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1021 select DEBUG_SPINLOCK
1022 select DEBUG_MUTEXES
1023 select DEBUG_LOCK_ALLOC
1024 select TRACE_IRQFLAGS
1027 This feature enables the kernel to prove that all locking
1028 that occurs in the kernel runtime is mathematically
1029 correct: that under no circumstance could an arbitrary (and
1030 not yet triggered) combination of observed locking
1031 sequences (on an arbitrary number of CPUs, running an
1032 arbitrary number of tasks and interrupt contexts) cause a
1035 In short, this feature enables the kernel to report locking
1036 related deadlocks before they actually occur.
1038 The proof does not depend on how hard and complex a
1039 deadlock scenario would be to trigger: how many
1040 participant CPUs, tasks and irq-contexts would be needed
1041 for it to trigger. The proof also does not depend on
1042 timing: if a race and a resulting deadlock is possible
1043 theoretically (no matter how unlikely the race scenario
1044 is), it will be proven so and will immediately be
1045 reported by the kernel (once the event is observed that
1046 makes the deadlock theoretically possible).
1048 If a deadlock is impossible (i.e. the locking rules, as
1049 observed by the kernel, are mathematically correct), the
1050 kernel reports nothing.
1052 NOTE: this feature can also be enabled for rwlocks, mutexes
1053 and rwsems - in which case all dependencies between these
1054 different locking variants are observed and mapped too, and
1055 the proof of observed correctness is also maintained for an
1056 arbitrary combination of these separate locking variants.
1058 For more details, see Documentation/locking/lockdep-design.txt.
1062 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1064 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
1069 bool "Lock usage statistics"
1070 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1072 select DEBUG_SPINLOCK
1073 select DEBUG_MUTEXES
1074 select DEBUG_LOCK_ALLOC
1077 This feature enables tracking lock contention points
1079 For more details, see Documentation/locking/lockstat.txt
1081 This also enables lock events required by "perf lock",
1083 If you want to use "perf lock", you also need to turn on
1084 CONFIG_EVENT_TRACING.
1086 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1087 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1089 config DEBUG_LOCKDEP
1090 bool "Lock dependency engine debugging"
1091 depends on DEBUG_KERNEL && LOCKDEP
1093 If you say Y here, the lock dependency engine will do
1094 additional runtime checks to debug itself, at the price
1095 of more runtime overhead.
1097 config DEBUG_ATOMIC_SLEEP
1098 bool "Sleep inside atomic section checking"
1099 select PREEMPT_COUNT
1100 depends on DEBUG_KERNEL
1102 If you say Y here, various routines which may sleep will become very
1103 noisy if they are called inside atomic sections: when a spinlock is
1104 held, inside an rcu read side critical section, inside preempt disabled
1105 sections, inside an interrupt, etc...
1107 config DEBUG_LOCKING_API_SELFTESTS
1108 bool "Locking API boot-time self-tests"
1109 depends on DEBUG_KERNEL
1111 Say Y here if you want the kernel to run a short self-test during
1112 bootup. The self-test checks whether common types of locking bugs
1113 are detected by debugging mechanisms or not. (if you disable
1114 lock debugging then those bugs wont be detected of course.)
1115 The following locking APIs are covered: spinlocks, rwlocks,
1118 config LOCK_TORTURE_TEST
1119 tristate "torture tests for locking"
1120 depends on DEBUG_KERNEL
1124 This option provides a kernel module that runs torture tests
1125 on kernel locking primitives. The kernel module may be built
1126 after the fact on the running kernel to be tested, if desired.
1128 Say Y here if you want kernel locking-primitive torture tests
1129 to be built into the kernel.
1130 Say M if you want these torture tests to build as a module.
1131 Say N if you are unsure.
1133 endmenu # lock debugging
1135 config TRACE_IRQFLAGS
1138 Enables hooks to interrupt enabling and disabling for
1139 either tracing or lock debugging.
1142 bool "Stack backtrace support"
1143 depends on STACKTRACE_SUPPORT
1145 This option causes the kernel to create a /proc/pid/stack for
1146 every process, showing its current stack trace.
1147 It is also used by various kernel debugging features that require
1148 stack trace generation.
1150 config DEBUG_KOBJECT
1151 bool "kobject debugging"
1152 depends on DEBUG_KERNEL
1154 If you say Y here, some extra kobject debugging messages will be sent
1157 config DEBUG_KOBJECT_RELEASE
1158 bool "kobject release debugging"
1159 depends on DEBUG_OBJECTS_TIMERS
1161 kobjects are reference counted objects. This means that their
1162 last reference count put is not predictable, and the kobject can
1163 live on past the point at which a driver decides to drop it's
1164 initial reference to the kobject gained on allocation. An
1165 example of this would be a struct device which has just been
1168 However, some buggy drivers assume that after such an operation,
1169 the memory backing the kobject can be immediately freed. This
1170 goes completely against the principles of a refcounted object.
1172 If you say Y here, the kernel will delay the release of kobjects
1173 on the last reference count to improve the visibility of this
1174 kind of kobject release bug.
1176 config HAVE_DEBUG_BUGVERBOSE
1179 config DEBUG_BUGVERBOSE
1180 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1181 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1184 Say Y here to make BUG() panics output the file name and line number
1185 of the BUG call as well as the EIP and oops trace. This aids
1186 debugging but costs about 70-100K of memory.
1189 bool "Debug linked list manipulation"
1190 depends on DEBUG_KERNEL
1192 Enable this to turn on extended checks in the linked-list
1197 config DEBUG_PI_LIST
1198 bool "Debug priority linked list manipulation"
1199 depends on DEBUG_KERNEL
1201 Enable this to turn on extended checks in the priority-ordered
1202 linked-list (plist) walking routines. This checks the entire
1203 list multiple times during each manipulation.
1208 bool "Debug SG table operations"
1209 depends on DEBUG_KERNEL
1211 Enable this to turn on checks on scatter-gather tables. This can
1212 help find problems with drivers that do not properly initialize
1217 config DEBUG_NOTIFIERS
1218 bool "Debug notifier call chains"
1219 depends on DEBUG_KERNEL
1221 Enable this to turn on sanity checking for notifier call chains.
1222 This is most useful for kernel developers to make sure that
1223 modules properly unregister themselves from notifier chains.
1224 This is a relatively cheap check but if you care about maximum
1227 config DEBUG_CREDENTIALS
1228 bool "Debug credential management"
1229 depends on DEBUG_KERNEL
1231 Enable this to turn on some debug checking for credential
1232 management. The additional code keeps track of the number of
1233 pointers from task_structs to any given cred struct, and checks to
1234 see that this number never exceeds the usage count of the cred
1237 Furthermore, if SELinux is enabled, this also checks that the
1238 security pointer in the cred struct is never seen to be invalid.
1242 menu "RCU Debugging"
1245 def_bool PROVE_LOCKING
1247 config PROVE_RCU_REPEATEDLY
1248 bool "RCU debugging: don't disable PROVE_RCU on first splat"
1249 depends on PROVE_RCU
1252 By itself, PROVE_RCU will disable checking upon issuing the
1253 first warning (or "splat"). This feature prevents such
1254 disabling, allowing multiple RCU-lockdep warnings to be printed
1257 Say Y to allow multiple RCU-lockdep warnings per boot.
1259 Say N if you are unsure.
1261 config SPARSE_RCU_POINTER
1262 bool "RCU debugging: sparse-based checks for pointer usage"
1265 This feature enables the __rcu sparse annotation for
1266 RCU-protected pointers. This annotation will cause sparse
1267 to flag any non-RCU used of annotated pointers. This can be
1268 helpful when debugging RCU usage. Please note that this feature
1269 is not intended to enforce code cleanliness; it is instead merely
1272 Say Y to make sparse flag questionable use of RCU-protected pointers
1274 Say N if you are unsure.
1280 config RCU_PERF_TEST
1281 tristate "performance tests for RCU"
1282 depends on DEBUG_KERNEL
1288 This option provides a kernel module that runs performance
1289 tests on the RCU infrastructure. The kernel module may be built
1290 after the fact on the running kernel to be tested, if desired.
1292 Say Y here if you want RCU performance tests to be built into
1294 Say M if you want the RCU performance tests to build as a module.
1295 Say N if you are unsure.
1297 config RCU_PERF_TEST_RUNNABLE
1298 bool "performance tests for RCU runnable by default"
1299 depends on RCU_PERF_TEST = y
1302 This option provides a way to build the RCU performance tests
1303 directly into the kernel without them starting up at boot time.
1304 You can use /sys/module to manually override this setting.
1305 This /proc file is available only when the RCU performance
1306 tests have been built into the kernel.
1308 Say Y here if you want the RCU performance tests to start during
1309 boot (you probably don't).
1310 Say N here if you want the RCU performance tests to start only
1311 after being manually enabled via /sys/module.
1313 config RCU_TORTURE_TEST
1314 tristate "torture tests for RCU"
1315 depends on DEBUG_KERNEL
1321 This option provides a kernel module that runs torture tests
1322 on the RCU infrastructure. The kernel module may be built
1323 after the fact on the running kernel to be tested, if desired.
1325 Say Y here if you want RCU torture tests to be built into
1327 Say M if you want the RCU torture tests to build as a module.
1328 Say N if you are unsure.
1330 config RCU_TORTURE_TEST_RUNNABLE
1331 bool "torture tests for RCU runnable by default"
1332 depends on RCU_TORTURE_TEST = y
1335 This option provides a way to build the RCU torture tests
1336 directly into the kernel without them starting up at boot
1337 time. You can use /proc/sys/kernel/rcutorture_runnable
1338 to manually override this setting. This /proc file is
1339 available only when the RCU torture tests have been built
1342 Say Y here if you want the RCU torture tests to start during
1343 boot (you probably don't).
1344 Say N here if you want the RCU torture tests to start only
1345 after being manually enabled via /proc.
1347 config RCU_TORTURE_TEST_SLOW_PREINIT
1348 bool "Slow down RCU grace-period pre-initialization to expose races"
1349 depends on RCU_TORTURE_TEST
1351 This option delays grace-period pre-initialization (the
1352 propagation of CPU-hotplug changes up the rcu_node combining
1353 tree) for a few jiffies between initializing each pair of
1354 consecutive rcu_node structures. This helps to expose races
1355 involving grace-period pre-initialization, in other words, it
1356 makes your kernel less stable. It can also greatly increase
1357 grace-period latency, especially on systems with large numbers
1358 of CPUs. This is useful when torture-testing RCU, but in
1359 almost no other circumstance.
1361 Say Y here if you want your system to crash and hang more often.
1362 Say N if you want a sane system.
1364 config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
1365 int "How much to slow down RCU grace-period pre-initialization"
1368 depends on RCU_TORTURE_TEST_SLOW_PREINIT
1370 This option specifies the number of jiffies to wait between
1371 each rcu_node structure pre-initialization step.
1373 config RCU_TORTURE_TEST_SLOW_INIT
1374 bool "Slow down RCU grace-period initialization to expose races"
1375 depends on RCU_TORTURE_TEST
1377 This option delays grace-period initialization for a few
1378 jiffies between initializing each pair of consecutive
1379 rcu_node structures. This helps to expose races involving
1380 grace-period initialization, in other words, it makes your
1381 kernel less stable. It can also greatly increase grace-period
1382 latency, especially on systems with large numbers of CPUs.
1383 This is useful when torture-testing RCU, but in almost no
1386 Say Y here if you want your system to crash and hang more often.
1387 Say N if you want a sane system.
1389 config RCU_TORTURE_TEST_SLOW_INIT_DELAY
1390 int "How much to slow down RCU grace-period initialization"
1393 depends on RCU_TORTURE_TEST_SLOW_INIT
1395 This option specifies the number of jiffies to wait between
1396 each rcu_node structure initialization.
1398 config RCU_TORTURE_TEST_SLOW_CLEANUP
1399 bool "Slow down RCU grace-period cleanup to expose races"
1400 depends on RCU_TORTURE_TEST
1402 This option delays grace-period cleanup for a few jiffies
1403 between cleaning up each pair of consecutive rcu_node
1404 structures. This helps to expose races involving grace-period
1405 cleanup, in other words, it makes your kernel less stable.
1406 It can also greatly increase grace-period latency, especially
1407 on systems with large numbers of CPUs. This is useful when
1408 torture-testing RCU, but in almost no other circumstance.
1410 Say Y here if you want your system to crash and hang more often.
1411 Say N if you want a sane system.
1413 config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
1414 int "How much to slow down RCU grace-period cleanup"
1417 depends on RCU_TORTURE_TEST_SLOW_CLEANUP
1419 This option specifies the number of jiffies to wait between
1420 each rcu_node structure cleanup operation.
1422 config RCU_CPU_STALL_TIMEOUT
1423 int "RCU CPU stall timeout in seconds"
1424 depends on RCU_STALL_COMMON
1428 If a given RCU grace period extends more than the specified
1429 number of seconds, a CPU stall warning is printed. If the
1430 RCU grace period persists, additional CPU stall warnings are
1431 printed at more widely spaced intervals.
1434 bool "Enable tracing for RCU"
1435 depends on DEBUG_KERNEL
1438 This option provides tracing in RCU which presents stats
1439 in debugfs for debugging RCU implementation.
1441 Say Y here if you want to enable RCU tracing
1442 Say N if you are unsure.
1444 config RCU_EQS_DEBUG
1445 bool "Provide debugging asserts for adding NO_HZ support to an arch"
1446 depends on DEBUG_KERNEL
1448 This option provides consistency checks in RCU's handling of
1449 NO_HZ. These checks have proven quite helpful in detecting
1450 bugs in arch-specific NO_HZ code.
1452 Say N here if you need ultimate kernel/user switch latencies
1453 Say Y if you are unsure
1455 endmenu # "RCU Debugging"
1457 config DEBUG_WQ_FORCE_RR_CPU
1458 bool "Force round-robin CPU selection for unbound work items"
1459 depends on DEBUG_KERNEL
1462 Workqueue used to implicitly guarantee that work items queued
1463 without explicit CPU specified are put on the local CPU. This
1464 guarantee is no longer true and while local CPU is still
1465 preferred work items may be put on foreign CPUs. Kernel
1466 parameter "workqueue.debug_force_rr_cpu" is added to force
1467 round-robin CPU selection to flush out usages which depend on the
1468 now broken guarantee. This config option enables the debug
1469 feature by default. When enabled, memory and cache locality will
1472 config DEBUG_BLOCK_EXT_DEVT
1473 bool "Force extended block device numbers and spread them"
1474 depends on DEBUG_KERNEL
1478 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1479 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1480 YOU ARE DOING. Distros, please enable this and fix whatever
1483 Conventionally, block device numbers are allocated from
1484 predetermined contiguous area. However, extended block area
1485 may introduce non-contiguous block device numbers. This
1486 option forces most block device numbers to be allocated from
1487 the extended space and spreads them to discover kernel or
1488 userland code paths which assume predetermined contiguous
1489 device number allocation.
1491 Note that turning on this debug option shuffles all the
1492 device numbers for all IDE and SCSI devices including libata
1493 ones, so root partition specified using device number
1494 directly (via rdev or root=MAJ:MIN) won't work anymore.
1495 Textual device names (root=/dev/sdXn) will continue to work.
1497 Say N if you are unsure.
1499 config NOTIFIER_ERROR_INJECTION
1500 tristate "Notifier error injection"
1501 depends on DEBUG_KERNEL
1504 This option provides the ability to inject artificial errors to
1505 specified notifier chain callbacks. It is useful to test the error
1506 handling of notifier call chain failures.
1510 config CPU_NOTIFIER_ERROR_INJECT
1511 tristate "CPU notifier error injection module"
1512 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1514 This option provides a kernel module that can be used to test
1515 the error handling of the cpu notifiers by injecting artificial
1516 errors to CPU notifier chain callbacks. It is controlled through
1517 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
1519 If the notifier call chain should be failed with some events
1520 notified, write the error code to "actions/<notifier event>/error".
1522 Example: Inject CPU offline error (-1 == -EPERM)
1524 # cd /sys/kernel/debug/notifier-error-inject/cpu
1525 # echo -1 > actions/CPU_DOWN_PREPARE/error
1526 # echo 0 > /sys/devices/system/cpu/cpu1/online
1527 bash: echo: write error: Operation not permitted
1529 To compile this code as a module, choose M here: the module will
1530 be called cpu-notifier-error-inject.
1534 config PM_NOTIFIER_ERROR_INJECT
1535 tristate "PM notifier error injection module"
1536 depends on PM && NOTIFIER_ERROR_INJECTION
1537 default m if PM_DEBUG
1539 This option provides the ability to inject artificial errors to
1540 PM notifier chain callbacks. It is controlled through debugfs
1541 interface /sys/kernel/debug/notifier-error-inject/pm
1543 If the notifier call chain should be failed with some events
1544 notified, write the error code to "actions/<notifier event>/error".
1546 Example: Inject PM suspend error (-12 = -ENOMEM)
1548 # cd /sys/kernel/debug/notifier-error-inject/pm/
1549 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1550 # echo mem > /sys/power/state
1551 bash: echo: write error: Cannot allocate memory
1553 To compile this code as a module, choose M here: the module will
1554 be called pm-notifier-error-inject.
1558 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1559 tristate "OF reconfig notifier error injection module"
1560 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1562 This option provides the ability to inject artificial errors to
1563 OF reconfig notifier chain callbacks. It is controlled
1564 through debugfs interface under
1565 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1567 If the notifier call chain should be failed with some events
1568 notified, write the error code to "actions/<notifier event>/error".
1570 To compile this code as a module, choose M here: the module will
1571 be called of-reconfig-notifier-error-inject.
1575 config NETDEV_NOTIFIER_ERROR_INJECT
1576 tristate "Netdev notifier error injection module"
1577 depends on NET && NOTIFIER_ERROR_INJECTION
1579 This option provides the ability to inject artificial errors to
1580 netdevice notifier chain callbacks. It is controlled through debugfs
1581 interface /sys/kernel/debug/notifier-error-inject/netdev
1583 If the notifier call chain should be failed with some events
1584 notified, write the error code to "actions/<notifier event>/error".
1586 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1588 # cd /sys/kernel/debug/notifier-error-inject/netdev
1589 # echo -22 > actions/NETDEV_CHANGEMTU/error
1590 # ip link set eth0 mtu 1024
1591 RTNETLINK answers: Invalid argument
1593 To compile this code as a module, choose M here: the module will
1594 be called netdev-notifier-error-inject.
1598 config FAULT_INJECTION
1599 bool "Fault-injection framework"
1600 depends on DEBUG_KERNEL
1602 Provide fault-injection framework.
1603 For more details, see Documentation/fault-injection/.
1606 bool "Fault-injection capability for kmalloc"
1607 depends on FAULT_INJECTION
1608 depends on SLAB || SLUB
1610 Provide fault-injection capability for kmalloc.
1612 config FAIL_PAGE_ALLOC
1613 bool "Fault-injection capabilitiy for alloc_pages()"
1614 depends on FAULT_INJECTION
1616 Provide fault-injection capability for alloc_pages().
1618 config FAIL_MAKE_REQUEST
1619 bool "Fault-injection capability for disk IO"
1620 depends on FAULT_INJECTION && BLOCK
1622 Provide fault-injection capability for disk IO.
1624 config FAIL_IO_TIMEOUT
1625 bool "Fault-injection capability for faking disk interrupts"
1626 depends on FAULT_INJECTION && BLOCK
1628 Provide fault-injection capability on end IO handling. This
1629 will make the block layer "forget" an interrupt as configured,
1630 thus exercising the error handling.
1632 Only works with drivers that use the generic timeout handling,
1633 for others it wont do anything.
1635 config FAIL_MMC_REQUEST
1636 bool "Fault-injection capability for MMC IO"
1637 depends on FAULT_INJECTION_DEBUG_FS && MMC
1639 Provide fault-injection capability for MMC IO.
1640 This will make the mmc core return data errors. This is
1641 useful to test the error handling in the mmc block device
1642 and to test how the mmc host driver handles retries from
1646 bool "Fault-injection capability for futexes"
1648 depends on FAULT_INJECTION && FUTEX
1650 Provide fault-injection capability for futexes.
1652 config FAULT_INJECTION_DEBUG_FS
1653 bool "Debugfs entries for fault-injection capabilities"
1654 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1656 Enable configuration of fault-injection capabilities via debugfs.
1658 config FAULT_INJECTION_STACKTRACE_FILTER
1659 bool "stacktrace filter for fault-injection capabilities"
1660 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1663 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1665 Provide stacktrace filter for fault-injection capabilities
1668 bool "Latency measuring infrastructure"
1669 depends on DEBUG_KERNEL
1670 depends on STACKTRACE_SUPPORT
1672 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1679 Enable this option if you want to use the LatencyTOP tool
1680 to find out which userspace is blocking on what kernel operations.
1682 config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1685 config DEBUG_STRICT_USER_COPY_CHECKS
1686 bool "Strict user copy size checks"
1687 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1688 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
1690 Enabling this option turns a certain set of sanity checks for user
1691 copy operations into compile time failures.
1693 The copy_from_user() etc checks are there to help test if there
1694 are sufficient security checks on the length argument of
1695 the copy operation, by having gcc prove that the argument is
1700 source kernel/trace/Kconfig
1702 menu "Runtime Testing"
1705 tristate "Linux Kernel Dump Test Tool Module"
1710 This module enables testing of the different dumping mechanisms by
1711 inducing system failures at predefined crash points.
1712 If you don't need it: say N
1713 Choose M here to compile this code as a module. The module will be
1716 Documentation on how to use the module can be found in
1717 Documentation/fault-injection/provoke-crashes.txt
1719 config TEST_LIST_SORT
1720 bool "Linked list sorting test"
1721 depends on DEBUG_KERNEL
1723 Enable this to turn on 'list_sort()' function test. This test is
1724 executed only once during system boot, so affects only boot time.
1728 config KPROBES_SANITY_TEST
1729 bool "Kprobes sanity tests"
1730 depends on DEBUG_KERNEL
1734 This option provides for testing basic kprobes functionality on
1735 boot. A sample kprobe, jprobe and kretprobe are inserted and
1736 verified for functionality.
1738 Say N if you are unsure.
1740 config BACKTRACE_SELF_TEST
1741 tristate "Self test for the backtrace code"
1742 depends on DEBUG_KERNEL
1745 This option provides a kernel module that can be used to test
1746 the kernel stack backtrace code. This option is not useful
1747 for distributions or general kernels, but only for kernel
1748 developers working on architecture code.
1750 Note that if you want to also test saved backtraces, you will
1751 have to enable STACKTRACE as well.
1753 Say N if you are unsure.
1756 tristate "Red-Black tree test"
1757 depends on DEBUG_KERNEL
1759 A benchmark measuring the performance of the rbtree library.
1760 Also includes rbtree invariant checks.
1762 config INTERVAL_TREE_TEST
1763 tristate "Interval tree test"
1764 depends on m && DEBUG_KERNEL
1765 select INTERVAL_TREE
1767 A benchmark measuring the performance of the interval tree library
1770 tristate "Per cpu operations test"
1771 depends on m && DEBUG_KERNEL
1773 Enable this option to build test module which validates per-cpu
1778 config ATOMIC64_SELFTEST
1779 bool "Perform an atomic64_t self-test at boot"
1781 Enable this option to test the atomic64_t functions at boot.
1785 config ASYNC_RAID6_TEST
1786 tristate "Self test for hardware accelerated raid6 recovery"
1787 depends on ASYNC_RAID6_RECOV
1790 This is a one-shot self test that permutes through the
1791 recovery of all the possible two disk failure scenarios for a
1792 N-disk array. Recovery is performed with the asynchronous
1793 raid6 recovery routines, and will optionally use an offload
1794 engine if one is available.
1799 tristate "Test functions located in the hexdump module at runtime"
1801 config TEST_STRING_HELPERS
1802 tristate "Test functions located in the string_helpers module at runtime"
1805 tristate "Test kstrto*() family of functions at runtime"
1808 tristate "Test printf() family of functions at runtime"
1810 config TEST_RHASHTABLE
1811 tristate "Perform selftest on resizable hash table"
1814 Enable this option to test the rhashtable functions at boot.
1818 endmenu # runtime tests
1820 config PROVIDE_OHCI1394_DMA_INIT
1821 bool "Remote debugging over FireWire early on boot"
1822 depends on PCI && X86
1824 If you want to debug problems which hang or crash the kernel early
1825 on boot and the crashing machine has a FireWire port, you can use
1826 this feature to remotely access the memory of the crashed machine
1827 over FireWire. This employs remote DMA as part of the OHCI1394
1828 specification which is now the standard for FireWire controllers.
1830 With remote DMA, you can monitor the printk buffer remotely using
1831 firescope and access all memory below 4GB using fireproxy from gdb.
1832 Even controlling a kernel debugger is possible using remote DMA.
1836 If ohci1394_dma=early is used as boot parameter, it will initialize
1837 all OHCI1394 controllers which are found in the PCI config space.
1839 As all changes to the FireWire bus such as enabling and disabling
1840 devices cause a bus reset and thereby disable remote DMA for all
1841 devices, be sure to have the cable plugged and FireWire enabled on
1842 the debugging host before booting the debug target for debugging.
1844 This code (~1k) is freed after boot. By then, the firewire stack
1845 in charge of the OHCI-1394 controllers should be used instead.
1847 See Documentation/debugging-via-ohci1394.txt for more information.
1850 bool "Build targets in Documentation/ tree"
1851 depends on HEADERS_CHECK
1853 This option attempts to build objects from the source files in the
1854 kernel Documentation/ tree.
1856 Say N if you are unsure.
1858 config DMA_API_DEBUG
1859 bool "Enable debugging of DMA-API usage"
1860 depends on HAVE_DMA_API_DEBUG
1862 Enable this option to debug the use of the DMA API by device drivers.
1863 With this option you will be able to detect common bugs in device
1864 drivers like double-freeing of DMA mappings or freeing mappings that
1865 were never allocated.
1867 This also attempts to catch cases where a page owned by DMA is
1868 accessed by the cpu in a way that could cause data corruption. For
1869 example, this enables cow_user_page() to check that the source page is
1872 This option causes a performance degradation. Use only if you want to
1873 debug device drivers and dma interactions.
1878 tristate "Test module loading with 'hello world' module"
1882 This builds the "test_module" module that emits "Hello, world"
1883 on printk when loaded. It is designed to be used for basic
1884 evaluation of the module loading subsystem (for example when
1885 validating module verification). It lacks any extra dependencies,
1886 and will not normally be loaded by the system unless explicitly
1891 config TEST_USER_COPY
1892 tristate "Test user/kernel boundary protections"
1896 This builds the "test_user_copy" module that runs sanity checks
1897 on the copy_to/from_user infrastructure, making sure basic
1898 user/kernel boundary testing is working. If it fails to load,
1899 a regression has been detected in the user/kernel memory boundary
1905 tristate "Test BPF filter functionality"
1909 This builds the "test_bpf" module that runs various test vectors
1910 against the BPF interpreter or BPF JIT compiler depending on the
1911 current setting. This is in particular useful for BPF JIT compiler
1912 development, but also to run regression tests against changes in
1913 the interpreter code. It also enables test stubs for eBPF maps and
1914 verifier used by user space verifier testsuite.
1918 config TEST_FIRMWARE
1919 tristate "Test firmware loading via userspace interface"
1921 depends on FW_LOADER
1923 This builds the "test_firmware" module that creates a userspace
1924 interface for testing firmware loading. This can be used to
1925 control the triggering of firmware loading without needing an
1926 actual firmware-using device. The contents can be rechecked by
1932 tristate "udelay test driver"
1935 This builds the "udelay_test" module that helps to make sure
1936 that udelay() is working properly.
1942 depends on HAVE_MEMBLOCK
1944 This option adds a kernel parameter 'memtest', which allows memtest
1946 memtest=0, mean disabled; -- default
1947 memtest=1, mean do 1 test pattern;
1949 memtest=17, mean do 17 test patterns.
1950 If you are unsure how to answer this question, answer N.
1952 config TEST_STATIC_KEYS
1953 tristate "Test static keys"
1957 Test the static key interfaces.
1961 source "samples/Kconfig"
1963 source "lib/Kconfig.kgdb"
1965 source "lib/Kconfig.ubsan"
1967 config ARCH_HAS_DEVMEM_IS_ALLOWED
1970 config STRICT_DEVMEM
1971 bool "Filter access to /dev/mem"
1973 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
1974 default y if TILE || PPC
1976 If this option is disabled, you allow userspace (root) access to all
1977 of memory, including kernel and userspace memory. Accidental
1978 access to this is obviously disastrous, but specific access can
1979 be used by people debugging the kernel. Note that with PAT support
1980 enabled, even in this case there are restrictions on /dev/mem
1981 use due to the cache aliasing requirements.
1983 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
1984 file only allows userspace access to PCI space and the BIOS code and
1985 data regions. This is sufficient for dosemu and X and all common
1990 config IO_STRICT_DEVMEM
1991 bool "Filter I/O access to /dev/mem"
1992 depends on STRICT_DEVMEM
1994 If this option is disabled, you allow userspace (root) access to all
1995 io-memory regardless of whether a driver is actively using that
1996 range. Accidental access to this is obviously disastrous, but
1997 specific access can be used by people debugging kernel drivers.
1999 If this option is switched on, the /dev/mem file only allows
2000 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2001 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2002 if the driver using a given range cannot be disabled.
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