3 bool "Show timing information on printks"
6 Selecting this option causes timing information to be
7 included in printk output. This allows you to measure
8 the interval between kernel operations, including bootup
9 operations. This is useful for identifying long delays
10 in kernel startup. Or add printk.time=1 at boot-time.
11 See Documentation/kernel-parameters.txt
13 config DEFAULT_MESSAGE_LOGLEVEL
14 int "Default message log level (1-7)"
18 Default log level for printk statements with no specified priority.
20 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
21 that are auditing their logs closely may want to set it to a lower
24 config ENABLE_WARN_DEPRECATED
25 bool "Enable __deprecated logic"
28 Enable the __deprecated logic in the kernel build.
29 Disable this to suppress the "warning: 'foo' is deprecated
30 (declared at kernel/power/somefile.c:1234)" messages.
32 config ENABLE_MUST_CHECK
33 bool "Enable __must_check logic"
36 Enable the __must_check logic in the kernel build. Disable this to
37 suppress the "warning: ignoring return value of 'foo', declared with
38 attribute warn_unused_result" messages.
41 int "Warn for stack frames larger than (needs gcc 4.4)"
43 default 1024 if !64BIT
46 Tell gcc to warn at build time for stack frames larger than this.
47 Setting this too low will cause a lot of warnings.
48 Setting it to 0 disables the warning.
52 bool "Magic SysRq key"
55 If you say Y here, you will have some control over the system even
56 if the system crashes for example during kernel debugging (e.g., you
57 will be able to flush the buffer cache to disk, reboot the system
58 immediately or dump some status information). This is accomplished
59 by pressing various keys while holding SysRq (Alt+PrintScreen). It
60 also works on a serial console (on PC hardware at least), if you
61 send a BREAK and then within 5 seconds a command keypress. The
62 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
63 unless you really know what this hack does.
66 bool "Strip assembler-generated symbols during link"
69 Strip internal assembler-generated symbols during a link (symbols
70 that look like '.Lxxx') so they don't pollute the output of
71 get_wchan() and suchlike.
74 bool "Enable unused/obsolete exported symbols"
77 Unused but exported symbols make the kernel needlessly bigger. For
78 that reason most of these unused exports will soon be removed. This
79 option is provided temporarily to provide a transition period in case
80 some external kernel module needs one of these symbols anyway. If you
81 encounter such a case in your module, consider if you are actually
82 using the right API. (rationale: since nobody in the kernel is using
83 this in a module, there is a pretty good chance it's actually the
84 wrong interface to use). If you really need the symbol, please send a
85 mail to the linux kernel mailing list mentioning the symbol and why
86 you really need it, and what the merge plan to the mainline kernel for
90 bool "Debug Filesystem"
92 debugfs is a virtual file system that kernel developers use to put
93 debugging files into. Enable this option to be able to read and
96 For detailed documentation on the debugfs API, see
97 Documentation/DocBook/filesystems.
102 bool "Run 'make headers_check' when building vmlinux"
105 This option will extract the user-visible kernel headers whenever
106 building the kernel, and will run basic sanity checks on them to
107 ensure that exported files do not attempt to include files which
108 were not exported, etc.
110 If you're making modifications to header files which are
111 relevant for userspace, say 'Y', and check the headers
112 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
113 your build tree), to make sure they're suitable.
115 config DEBUG_SECTION_MISMATCH
116 bool "Enable full Section mismatch analysis"
118 The section mismatch analysis checks if there are illegal
119 references from one section to another section.
120 Linux will during link or during runtime drop some sections
121 and any use of code/data previously in these sections will
122 most likely result in an oops.
123 In the code functions and variables are annotated with
124 __init, __devinit etc. (see full list in include/linux/init.h)
125 which results in the code/data being placed in specific sections.
126 The section mismatch analysis is always done after a full
127 kernel build but enabling this option will in addition
129 - Add the option -fno-inline-functions-called-once to gcc
130 When inlining a function annotated __init in a non-init
131 function we would lose the section information and thus
132 the analysis would not catch the illegal reference.
133 This option tells gcc to inline less but will also
134 result in a larger kernel.
135 - Run the section mismatch analysis for each module/built-in.o
136 When we run the section mismatch analysis on vmlinux.o we
137 lose valueble information about where the mismatch was
139 Running the analysis for each module/built-in.o file
140 will tell where the mismatch happens much closer to the
141 source. The drawback is that we will report the same
142 mismatch at least twice.
143 - Enable verbose reporting from modpost to help solving
144 the section mismatches reported.
147 bool "Kernel debugging"
149 Say Y here if you are developing drivers or trying to debug and
150 identify kernel problems.
153 bool "Debug shared IRQ handlers"
154 depends on DEBUG_KERNEL && GENERIC_HARDIRQS
156 Enable this to generate a spurious interrupt as soon as a shared
157 interrupt handler is registered, and just before one is deregistered.
158 Drivers ought to be able to handle interrupts coming in at those
159 points; some don't and need to be caught.
161 config LOCKUP_DETECTOR
162 bool "Detect Hard and Soft Lockups"
163 depends on DEBUG_KERNEL && !S390
165 Say Y here to enable the kernel to act as a watchdog to detect
166 hard and soft lockups.
168 Softlockups are bugs that cause the kernel to loop in kernel
169 mode for more than 60 seconds, without giving other tasks a
170 chance to run. The current stack trace is displayed upon
171 detection and the system will stay locked up.
173 Hardlockups are bugs that cause the CPU to loop in kernel mode
174 for more than 60 seconds, without letting other interrupts have a
175 chance to run. The current stack trace is displayed upon detection
176 and the system will stay locked up.
178 The overhead should be minimal. A periodic hrtimer runs to
179 generate interrupts and kick the watchdog task every 10-12 seconds.
180 An NMI is generated every 60 seconds or so to check for hardlockups.
182 config HARDLOCKUP_DETECTOR
183 def_bool LOCKUP_DETECTOR && PERF_EVENTS && HAVE_PERF_EVENTS_NMI && \
184 !ARCH_HAS_NMI_WATCHDOG
186 config BOOTPARAM_HARDLOCKUP_PANIC
187 bool "Panic (Reboot) On Hard Lockups"
188 depends on LOCKUP_DETECTOR
190 Say Y here to enable the kernel to panic on "hard lockups",
191 which are bugs that cause the kernel to loop in kernel
192 mode with interrupts disabled for more than 60 seconds.
196 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
198 depends on LOCKUP_DETECTOR
200 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
201 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
203 config BOOTPARAM_SOFTLOCKUP_PANIC
204 bool "Panic (Reboot) On Soft Lockups"
205 depends on LOCKUP_DETECTOR
207 Say Y here to enable the kernel to panic on "soft lockups",
208 which are bugs that cause the kernel to loop in kernel
209 mode for more than 60 seconds, without giving other tasks a
212 The panic can be used in combination with panic_timeout,
213 to cause the system to reboot automatically after a
214 lockup has been detected. This feature is useful for
215 high-availability systems that have uptime guarantees and
216 where a lockup must be resolved ASAP.
220 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
222 depends on LOCKUP_DETECTOR
224 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
225 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
227 config DETECT_HUNG_TASK
228 bool "Detect Hung Tasks"
229 depends on DEBUG_KERNEL
230 default DETECT_SOFTLOCKUP
232 Say Y here to enable the kernel to detect "hung tasks",
233 which are bugs that cause the task to be stuck in
234 uninterruptible "D" state indefinitiley.
236 When a hung task is detected, the kernel will print the
237 current stack trace (which you should report), but the
238 task will stay in uninterruptible state. If lockdep is
239 enabled then all held locks will also be reported. This
240 feature has negligible overhead.
242 config BOOTPARAM_HUNG_TASK_PANIC
243 bool "Panic (Reboot) On Hung Tasks"
244 depends on DETECT_HUNG_TASK
246 Say Y here to enable the kernel to panic on "hung tasks",
247 which are bugs that cause the kernel to leave a task stuck
248 in uninterruptible "D" state.
250 The panic can be used in combination with panic_timeout,
251 to cause the system to reboot automatically after a
252 hung task has been detected. This feature is useful for
253 high-availability systems that have uptime guarantees and
254 where a hung tasks must be resolved ASAP.
258 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
260 depends on DETECT_HUNG_TASK
262 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
263 default 1 if BOOTPARAM_HUNG_TASK_PANIC
266 bool "Collect scheduler debugging info"
267 depends on DEBUG_KERNEL && PROC_FS
270 If you say Y here, the /proc/sched_debug file will be provided
271 that can help debug the scheduler. The runtime overhead of this
275 bool "Collect scheduler statistics"
276 depends on DEBUG_KERNEL && PROC_FS
278 If you say Y here, additional code will be inserted into the
279 scheduler and related routines to collect statistics about
280 scheduler behavior and provide them in /proc/schedstat. These
281 stats may be useful for both tuning and debugging the scheduler
282 If you aren't debugging the scheduler or trying to tune a specific
283 application, you can say N to avoid the very slight overhead
287 bool "Collect kernel timers statistics"
288 depends on DEBUG_KERNEL && PROC_FS
290 If you say Y here, additional code will be inserted into the
291 timer routines to collect statistics about kernel timers being
292 reprogrammed. The statistics can be read from /proc/timer_stats.
293 The statistics collection is started by writing 1 to /proc/timer_stats,
294 writing 0 stops it. This feature is useful to collect information
295 about timer usage patterns in kernel and userspace. This feature
296 is lightweight if enabled in the kernel config but not activated
297 (it defaults to deactivated on bootup and will only be activated
298 if some application like powertop activates it explicitly).
301 bool "Debug object operations"
302 depends on DEBUG_KERNEL
304 If you say Y here, additional code will be inserted into the
305 kernel to track the life time of various objects and validate
306 the operations on those objects.
308 config DEBUG_OBJECTS_SELFTEST
309 bool "Debug objects selftest"
310 depends on DEBUG_OBJECTS
312 This enables the selftest of the object debug code.
314 config DEBUG_OBJECTS_FREE
315 bool "Debug objects in freed memory"
316 depends on DEBUG_OBJECTS
318 This enables checks whether a k/v free operation frees an area
319 which contains an object which has not been deactivated
320 properly. This can make kmalloc/kfree-intensive workloads
323 config DEBUG_OBJECTS_TIMERS
324 bool "Debug timer objects"
325 depends on DEBUG_OBJECTS
327 If you say Y here, additional code will be inserted into the
328 timer routines to track the life time of timer objects and
329 validate the timer operations.
331 config DEBUG_OBJECTS_WORK
332 bool "Debug work objects"
333 depends on DEBUG_OBJECTS
335 If you say Y here, additional code will be inserted into the
336 work queue routines to track the life time of work objects and
337 validate the work operations.
339 config DEBUG_OBJECTS_RCU_HEAD
340 bool "Debug RCU callbacks objects"
341 depends on DEBUG_OBJECTS && PREEMPT
343 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
345 config DEBUG_OBJECTS_PERCPU_COUNTER
346 bool "Debug percpu counter objects"
347 depends on DEBUG_OBJECTS
349 If you say Y here, additional code will be inserted into the
350 percpu counter routines to track the life time of percpu counter
351 objects and validate the percpu counter operations.
353 config DEBUG_OBJECTS_ENABLE_DEFAULT
354 int "debug_objects bootup default value (0-1)"
357 depends on DEBUG_OBJECTS
359 Debug objects boot parameter default value
362 bool "Debug slab memory allocations"
363 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
365 Say Y here to have the kernel do limited verification on memory
366 allocation as well as poisoning memory on free to catch use of freed
367 memory. This can make kmalloc/kfree-intensive workloads much slower.
369 config DEBUG_SLAB_LEAK
370 bool "Memory leak debugging"
371 depends on DEBUG_SLAB
374 bool "SLUB debugging on by default"
375 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
378 Boot with debugging on by default. SLUB boots by default with
379 the runtime debug capabilities switched off. Enabling this is
380 equivalent to specifying the "slub_debug" parameter on boot.
381 There is no support for more fine grained debug control like
382 possible with slub_debug=xxx. SLUB debugging may be switched
383 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
388 bool "Enable SLUB performance statistics"
389 depends on SLUB && SYSFS
391 SLUB statistics are useful to debug SLUBs allocation behavior in
392 order find ways to optimize the allocator. This should never be
393 enabled for production use since keeping statistics slows down
394 the allocator by a few percentage points. The slabinfo command
395 supports the determination of the most active slabs to figure
396 out which slabs are relevant to a particular load.
397 Try running: slabinfo -DA
399 config DEBUG_KMEMLEAK
400 bool "Kernel memory leak detector"
401 depends on DEBUG_KERNEL && EXPERIMENTAL && !MEMORY_HOTPLUG && \
402 (X86 || ARM || PPC || S390 || SPARC64 || SUPERH || MICROBLAZE || TILE)
404 select DEBUG_FS if SYSFS
405 select STACKTRACE if STACKTRACE_SUPPORT
409 Say Y here if you want to enable the memory leak
410 detector. The memory allocation/freeing is traced in a way
411 similar to the Boehm's conservative garbage collector, the
412 difference being that the orphan objects are not freed but
413 only shown in /sys/kernel/debug/kmemleak. Enabling this
414 feature will introduce an overhead to memory
415 allocations. See Documentation/kmemleak.txt for more
418 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
419 of finding leaks due to the slab objects poisoning.
421 In order to access the kmemleak file, debugfs needs to be
422 mounted (usually at /sys/kernel/debug).
424 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
425 int "Maximum kmemleak early log entries"
426 depends on DEBUG_KMEMLEAK
430 Kmemleak must track all the memory allocations to avoid
431 reporting false positives. Since memory may be allocated or
432 freed before kmemleak is initialised, an early log buffer is
433 used to store these actions. If kmemleak reports "early log
434 buffer exceeded", please increase this value.
436 config DEBUG_KMEMLEAK_TEST
437 tristate "Simple test for the kernel memory leak detector"
438 depends on DEBUG_KMEMLEAK && m
440 This option enables a module that explicitly leaks memory.
444 config DEBUG_KMEMLEAK_DEFAULT_OFF
445 bool "Default kmemleak to off"
446 depends on DEBUG_KMEMLEAK
448 Say Y here to disable kmemleak by default. It can then be enabled
449 on the command line via kmemleak=on.
452 bool "Debug preemptible kernel"
453 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
456 If you say Y here then the kernel will use a debug variant of the
457 commonly used smp_processor_id() function and will print warnings
458 if kernel code uses it in a preemption-unsafe way. Also, the kernel
459 will detect preemption count underflows.
461 config DEBUG_RT_MUTEXES
462 bool "RT Mutex debugging, deadlock detection"
463 depends on DEBUG_KERNEL && RT_MUTEXES
465 This allows rt mutex semantics violations and rt mutex related
466 deadlocks (lockups) to be detected and reported automatically.
471 depends on DEBUG_RT_MUTEXES
473 config RT_MUTEX_TESTER
474 bool "Built-in scriptable tester for rt-mutexes"
475 depends on DEBUG_KERNEL && RT_MUTEXES
477 This option enables a rt-mutex tester.
479 config DEBUG_SPINLOCK
480 bool "Spinlock and rw-lock debugging: basic checks"
481 depends on DEBUG_KERNEL
483 Say Y here and build SMP to catch missing spinlock initialization
484 and certain other kinds of spinlock errors commonly made. This is
485 best used in conjunction with the NMI watchdog so that spinlock
486 deadlocks are also debuggable.
489 bool "Mutex debugging: basic checks"
490 depends on DEBUG_KERNEL
492 This feature allows mutex semantics violations to be detected and
495 config DEBUG_LOCK_ALLOC
496 bool "Lock debugging: detect incorrect freeing of live locks"
497 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
498 select DEBUG_SPINLOCK
502 This feature will check whether any held lock (spinlock, rwlock,
503 mutex or rwsem) is incorrectly freed by the kernel, via any of the
504 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
505 vfree(), etc.), whether a live lock is incorrectly reinitialized via
506 spin_lock_init()/mutex_init()/etc., or whether there is any lock
507 held during task exit.
510 bool "Lock debugging: prove locking correctness"
511 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
513 select DEBUG_SPINLOCK
515 select DEBUG_LOCK_ALLOC
516 select TRACE_IRQFLAGS
519 This feature enables the kernel to prove that all locking
520 that occurs in the kernel runtime is mathematically
521 correct: that under no circumstance could an arbitrary (and
522 not yet triggered) combination of observed locking
523 sequences (on an arbitrary number of CPUs, running an
524 arbitrary number of tasks and interrupt contexts) cause a
527 In short, this feature enables the kernel to report locking
528 related deadlocks before they actually occur.
530 The proof does not depend on how hard and complex a
531 deadlock scenario would be to trigger: how many
532 participant CPUs, tasks and irq-contexts would be needed
533 for it to trigger. The proof also does not depend on
534 timing: if a race and a resulting deadlock is possible
535 theoretically (no matter how unlikely the race scenario
536 is), it will be proven so and will immediately be
537 reported by the kernel (once the event is observed that
538 makes the deadlock theoretically possible).
540 If a deadlock is impossible (i.e. the locking rules, as
541 observed by the kernel, are mathematically correct), the
542 kernel reports nothing.
544 NOTE: this feature can also be enabled for rwlocks, mutexes
545 and rwsems - in which case all dependencies between these
546 different locking variants are observed and mapped too, and
547 the proof of observed correctness is also maintained for an
548 arbitrary combination of these separate locking variants.
550 For more details, see Documentation/lockdep-design.txt.
553 bool "RCU debugging: prove RCU correctness"
554 depends on PROVE_LOCKING
557 This feature enables lockdep extensions that check for correct
558 use of RCU APIs. This is currently under development. Say Y
559 if you want to debug RCU usage or help work on the PROVE_RCU
562 Say N if you are unsure.
564 config PROVE_RCU_REPEATEDLY
565 bool "RCU debugging: don't disable PROVE_RCU on first splat"
569 By itself, PROVE_RCU will disable checking upon issuing the
570 first warning (or "splat"). This feature prevents such
571 disabling, allowing multiple RCU-lockdep warnings to be printed
574 Say Y to allow multiple RCU-lockdep warnings per boot.
576 Say N if you are unsure.
578 config SPARSE_RCU_POINTER
579 bool "RCU debugging: sparse-based checks for pointer usage"
582 This feature enables the __rcu sparse annotation for
583 RCU-protected pointers. This annotation will cause sparse
584 to flag any non-RCU used of annotated pointers. This can be
585 helpful when debugging RCU usage. Please note that this feature
586 is not intended to enforce code cleanliness; it is instead merely
589 Say Y to make sparse flag questionable use of RCU-protected pointers
591 Say N if you are unsure.
595 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
597 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE
602 bool "Lock usage statistics"
603 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
605 select DEBUG_SPINLOCK
607 select DEBUG_LOCK_ALLOC
610 This feature enables tracking lock contention points
612 For more details, see Documentation/lockstat.txt
614 This also enables lock events required by "perf lock",
616 If you want to use "perf lock", you also need to turn on
617 CONFIG_EVENT_TRACING.
619 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
620 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
623 bool "Lock dependency engine debugging"
624 depends on DEBUG_KERNEL && LOCKDEP
626 If you say Y here, the lock dependency engine will do
627 additional runtime checks to debug itself, at the price
628 of more runtime overhead.
630 config TRACE_IRQFLAGS
633 Enables hooks to interrupt enabling and disabling for
634 either tracing or lock debugging.
636 config DEBUG_SPINLOCK_SLEEP
637 bool "Spinlock debugging: sleep-inside-spinlock checking"
638 depends on DEBUG_KERNEL
640 If you say Y here, various routines which may sleep will become very
641 noisy if they are called with a spinlock held.
643 config DEBUG_LOCKING_API_SELFTESTS
644 bool "Locking API boot-time self-tests"
645 depends on DEBUG_KERNEL
647 Say Y here if you want the kernel to run a short self-test during
648 bootup. The self-test checks whether common types of locking bugs
649 are detected by debugging mechanisms or not. (if you disable
650 lock debugging then those bugs wont be detected of course.)
651 The following locking APIs are covered: spinlocks, rwlocks,
656 depends on STACKTRACE_SUPPORT
659 bool "kobject debugging"
660 depends on DEBUG_KERNEL
662 If you say Y here, some extra kobject debugging messages will be sent
666 bool "Highmem debugging"
667 depends on DEBUG_KERNEL && HIGHMEM
669 This options enables addition error checking for high memory systems.
670 Disable for production systems.
672 config DEBUG_BUGVERBOSE
673 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
675 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \
676 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300
679 Say Y here to make BUG() panics output the file name and line number
680 of the BUG call as well as the EIP and oops trace. This aids
681 debugging but costs about 70-100K of memory.
684 bool "Compile the kernel with debug info"
685 depends on DEBUG_KERNEL
687 If you say Y here the resulting kernel image will include
688 debugging info resulting in a larger kernel image.
689 This adds debug symbols to the kernel and modules (gcc -g), and
690 is needed if you intend to use kernel crashdump or binary object
691 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
692 Say Y here only if you plan to debug the kernel.
696 config DEBUG_INFO_REDUCED
697 bool "Reduce debugging information"
698 depends on DEBUG_INFO
700 If you say Y here gcc is instructed to generate less debugging
701 information for structure types. This means that tools that
702 need full debugging information (like kgdb or systemtap) won't
703 be happy. But if you merely need debugging information to
704 resolve line numbers there is no loss. Advantage is that
705 build directory object sizes shrink dramatically over a full
706 DEBUG_INFO build and compile times are reduced too.
707 Only works with newer gcc versions.
711 depends on DEBUG_KERNEL
713 Enable this to turn on extended checks in the virtual-memory system
714 that may impact performance.
719 bool "Debug VM translations"
720 depends on DEBUG_KERNEL && X86
722 Enable some costly sanity checks in virtual to page code. This can
723 catch mistakes with virt_to_page() and friends.
727 config DEBUG_NOMMU_REGIONS
728 bool "Debug the global anon/private NOMMU mapping region tree"
729 depends on DEBUG_KERNEL && !MMU
731 This option causes the global tree of anonymous and private mapping
732 regions to be regularly checked for invalid topology.
734 config DEBUG_WRITECOUNT
735 bool "Debug filesystem writers count"
736 depends on DEBUG_KERNEL
738 Enable this to catch wrong use of the writers count in struct
739 vfsmount. This will increase the size of each file struct by
744 config DEBUG_MEMORY_INIT
745 bool "Debug memory initialisation" if EXPERT
748 Enable this for additional checks during memory initialisation.
749 The sanity checks verify aspects of the VM such as the memory model
750 and other information provided by the architecture. Verbose
751 information will be printed at KERN_DEBUG loglevel depending
752 on the mminit_loglevel= command-line option.
757 bool "Debug linked list manipulation"
758 depends on DEBUG_KERNEL
760 Enable this to turn on extended checks in the linked-list
765 config TEST_LIST_SORT
766 bool "Linked list sorting test"
767 depends on DEBUG_KERNEL
769 Enable this to turn on 'list_sort()' function test. This test is
770 executed only once during system boot, so affects only boot time.
775 bool "Debug SG table operations"
776 depends on DEBUG_KERNEL
778 Enable this to turn on checks on scatter-gather tables. This can
779 help find problems with drivers that do not properly initialize
784 config DEBUG_NOTIFIERS
785 bool "Debug notifier call chains"
786 depends on DEBUG_KERNEL
788 Enable this to turn on sanity checking for notifier call chains.
789 This is most useful for kernel developers to make sure that
790 modules properly unregister themselves from notifier chains.
791 This is a relatively cheap check but if you care about maximum
794 config DEBUG_CREDENTIALS
795 bool "Debug credential management"
796 depends on DEBUG_KERNEL
798 Enable this to turn on some debug checking for credential
799 management. The additional code keeps track of the number of
800 pointers from task_structs to any given cred struct, and checks to
801 see that this number never exceeds the usage count of the cred
804 Furthermore, if SELinux is enabled, this also checks that the
805 security pointer in the cred struct is never seen to be invalid.
810 # Select this config option from the architecture Kconfig, if it
811 # it is preferred to always offer frame pointers as a config
812 # option on the architecture (regardless of KERNEL_DEBUG):
814 config ARCH_WANT_FRAME_POINTERS
819 bool "Compile the kernel with frame pointers"
820 depends on DEBUG_KERNEL && \
821 (CRIS || M68K || FRV || UML || \
822 AVR32 || SUPERH || BLACKFIN || MN10300) || \
823 ARCH_WANT_FRAME_POINTERS
824 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
826 If you say Y here the resulting kernel image will be slightly
827 larger and slower, but it gives very useful debugging information
828 in case of kernel bugs. (precise oopses/stacktraces/warnings)
830 config BOOT_PRINTK_DELAY
831 bool "Delay each boot printk message by N milliseconds"
832 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
834 This build option allows you to read kernel boot messages
835 by inserting a short delay after each one. The delay is
836 specified in milliseconds on the kernel command line,
837 using "boot_delay=N".
839 It is likely that you would also need to use "lpj=M" to preset
840 the "loops per jiffie" value.
841 See a previous boot log for the "lpj" value to use for your
842 system, and then set "lpj=M" before setting "boot_delay=N".
843 NOTE: Using this option may adversely affect SMP systems.
844 I.e., processors other than the first one may not boot up.
845 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect
846 what it believes to be lockup conditions.
848 config RCU_TORTURE_TEST
849 tristate "torture tests for RCU"
850 depends on DEBUG_KERNEL
853 This option provides a kernel module that runs torture tests
854 on the RCU infrastructure. The kernel module may be built
855 after the fact on the running kernel to be tested, if desired.
857 Say Y here if you want RCU torture tests to be built into
859 Say M if you want the RCU torture tests to build as a module.
860 Say N if you are unsure.
862 config RCU_TORTURE_TEST_RUNNABLE
863 bool "torture tests for RCU runnable by default"
864 depends on RCU_TORTURE_TEST = y
867 This option provides a way to build the RCU torture tests
868 directly into the kernel without them starting up at boot
869 time. You can use /proc/sys/kernel/rcutorture_runnable
870 to manually override this setting. This /proc file is
871 available only when the RCU torture tests have been built
874 Say Y here if you want the RCU torture tests to start during
875 boot (you probably don't).
876 Say N here if you want the RCU torture tests to start only
877 after being manually enabled via /proc.
879 config RCU_CPU_STALL_DETECTOR
880 bool "Check for stalled CPUs delaying RCU grace periods"
881 depends on TREE_RCU || TREE_PREEMPT_RCU
884 This option causes RCU to printk information on which
885 CPUs are delaying the current grace period, but only when
886 the grace period extends for excessive time periods.
888 Say N if you want to disable such checks.
890 Say Y if you are unsure.
892 config RCU_CPU_STALL_TIMEOUT
893 int "RCU CPU stall timeout in seconds"
894 depends on RCU_CPU_STALL_DETECTOR
898 If a given RCU grace period extends more than the specified
899 number of seconds, a CPU stall warning is printed. If the
900 RCU grace period persists, additional CPU stall warnings are
901 printed at more widely spaced intervals.
903 config RCU_CPU_STALL_DETECTOR_RUNNABLE
904 bool "RCU CPU stall checking starts automatically at boot"
905 depends on RCU_CPU_STALL_DETECTOR
908 If set, start checking for RCU CPU stalls immediately on
909 boot. Otherwise, RCU CPU stall checking must be manually
912 Say Y if you are unsure.
914 Say N if you wish to suppress RCU CPU stall checking during boot.
916 config RCU_CPU_STALL_VERBOSE
917 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
918 depends on RCU_CPU_STALL_DETECTOR && TREE_PREEMPT_RCU
921 This option causes RCU to printk detailed per-task information
922 for any tasks that are stalling the current RCU grace period.
924 Say N if you are unsure.
926 Say Y if you want to enable such checks.
928 config KPROBES_SANITY_TEST
929 bool "Kprobes sanity tests"
930 depends on DEBUG_KERNEL
934 This option provides for testing basic kprobes functionality on
935 boot. A sample kprobe, jprobe and kretprobe are inserted and
936 verified for functionality.
938 Say N if you are unsure.
940 config BACKTRACE_SELF_TEST
941 tristate "Self test for the backtrace code"
942 depends on DEBUG_KERNEL
945 This option provides a kernel module that can be used to test
946 the kernel stack backtrace code. This option is not useful
947 for distributions or general kernels, but only for kernel
948 developers working on architecture code.
950 Note that if you want to also test saved backtraces, you will
951 have to enable STACKTRACE as well.
953 Say N if you are unsure.
955 config DEBUG_BLOCK_EXT_DEVT
956 bool "Force extended block device numbers and spread them"
957 depends on DEBUG_KERNEL
961 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
962 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
963 YOU ARE DOING. Distros, please enable this and fix whatever
966 Conventionally, block device numbers are allocated from
967 predetermined contiguous area. However, extended block area
968 may introduce non-contiguous block device numbers. This
969 option forces most block device numbers to be allocated from
970 the extended space and spreads them to discover kernel or
971 userland code paths which assume predetermined contiguous
972 device number allocation.
974 Note that turning on this debug option shuffles all the
975 device numbers for all IDE and SCSI devices including libata
976 ones, so root partition specified using device number
977 directly (via rdev or root=MAJ:MIN) won't work anymore.
978 Textual device names (root=/dev/sdXn) will continue to work.
980 Say N if you are unsure.
982 config DEBUG_FORCE_WEAK_PER_CPU
983 bool "Force weak per-cpu definitions"
984 depends on DEBUG_KERNEL
986 s390 and alpha require percpu variables in modules to be
987 defined weak to work around addressing range issue which
988 puts the following two restrictions on percpu variable
991 1. percpu symbols must be unique whether static or not
992 2. percpu variables can't be defined inside a function
994 To ensure that generic code follows the above rules, this
995 option forces all percpu variables to be defined as weak.
998 tristate "Linux Kernel Dump Test Tool Module"
1003 This module enables testing of the different dumping mechanisms by
1004 inducing system failures at predefined crash points.
1005 If you don't need it: say N
1006 Choose M here to compile this code as a module. The module will be
1009 Documentation on how to use the module can be found in
1010 Documentation/fault-injection/provoke-crashes.txt
1012 config CPU_NOTIFIER_ERROR_INJECT
1013 tristate "CPU notifier error injection module"
1014 depends on HOTPLUG_CPU && DEBUG_KERNEL
1016 This option provides a kernel module that can be used to test
1017 the error handling of the cpu notifiers
1019 To compile this code as a module, choose M here: the module will
1020 be called cpu-notifier-error-inject.
1024 config FAULT_INJECTION
1025 bool "Fault-injection framework"
1026 depends on DEBUG_KERNEL
1028 Provide fault-injection framework.
1029 For more details, see Documentation/fault-injection/.
1032 bool "Fault-injection capability for kmalloc"
1033 depends on FAULT_INJECTION
1034 depends on SLAB || SLUB
1036 Provide fault-injection capability for kmalloc.
1038 config FAIL_PAGE_ALLOC
1039 bool "Fault-injection capabilitiy for alloc_pages()"
1040 depends on FAULT_INJECTION
1042 Provide fault-injection capability for alloc_pages().
1044 config FAIL_MAKE_REQUEST
1045 bool "Fault-injection capability for disk IO"
1046 depends on FAULT_INJECTION && BLOCK
1048 Provide fault-injection capability for disk IO.
1050 config FAIL_IO_TIMEOUT
1051 bool "Fault-injection capability for faking disk interrupts"
1052 depends on FAULT_INJECTION && BLOCK
1054 Provide fault-injection capability on end IO handling. This
1055 will make the block layer "forget" an interrupt as configured,
1056 thus exercising the error handling.
1058 Only works with drivers that use the generic timeout handling,
1059 for others it wont do anything.
1061 config FAULT_INJECTION_DEBUG_FS
1062 bool "Debugfs entries for fault-injection capabilities"
1063 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1065 Enable configuration of fault-injection capabilities via debugfs.
1067 config FAULT_INJECTION_STACKTRACE_FILTER
1068 bool "stacktrace filter for fault-injection capabilities"
1069 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1072 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE
1074 Provide stacktrace filter for fault-injection capabilities
1077 bool "Latency measuring infrastructure"
1078 depends on HAVE_LATENCYTOP_SUPPORT
1079 depends on DEBUG_KERNEL
1080 depends on STACKTRACE_SUPPORT
1082 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE
1089 Enable this option if you want to use the LatencyTOP tool
1090 to find out which userspace is blocking on what kernel operations.
1092 config SYSCTL_SYSCALL_CHECK
1093 bool "Sysctl checks"
1096 sys_sysctl uses binary paths that have been found challenging
1097 to properly maintain and use. This enables checks that help
1098 you to keep things correct.
1100 source mm/Kconfig.debug
1101 source kernel/trace/Kconfig
1103 config PROVIDE_OHCI1394_DMA_INIT
1104 bool "Remote debugging over FireWire early on boot"
1105 depends on PCI && X86
1107 If you want to debug problems which hang or crash the kernel early
1108 on boot and the crashing machine has a FireWire port, you can use
1109 this feature to remotely access the memory of the crashed machine
1110 over FireWire. This employs remote DMA as part of the OHCI1394
1111 specification which is now the standard for FireWire controllers.
1113 With remote DMA, you can monitor the printk buffer remotely using
1114 firescope and access all memory below 4GB using fireproxy from gdb.
1115 Even controlling a kernel debugger is possible using remote DMA.
1119 If ohci1394_dma=early is used as boot parameter, it will initialize
1120 all OHCI1394 controllers which are found in the PCI config space.
1122 As all changes to the FireWire bus such as enabling and disabling
1123 devices cause a bus reset and thereby disable remote DMA for all
1124 devices, be sure to have the cable plugged and FireWire enabled on
1125 the debugging host before booting the debug target for debugging.
1127 This code (~1k) is freed after boot. By then, the firewire stack
1128 in charge of the OHCI-1394 controllers should be used instead.
1130 See Documentation/debugging-via-ohci1394.txt for more information.
1132 config FIREWIRE_OHCI_REMOTE_DMA
1133 bool "Remote debugging over FireWire with firewire-ohci"
1134 depends on FIREWIRE_OHCI
1136 This option lets you use the FireWire bus for remote debugging
1137 with help of the firewire-ohci driver. It enables unfiltered
1138 remote DMA in firewire-ohci.
1139 See Documentation/debugging-via-ohci1394.txt for more information.
1144 bool "Build targets in Documentation/ tree"
1145 depends on HEADERS_CHECK
1147 This option attempts to build objects from the source files in the
1148 kernel Documentation/ tree.
1150 Say N if you are unsure.
1152 config DYNAMIC_DEBUG
1153 bool "Enable dynamic printk() support"
1159 Compiles debug level messages into the kernel, which would not
1160 otherwise be available at runtime. These messages can then be
1161 enabled/disabled based on various levels of scope - per source file,
1162 function, module, format string, and line number. This mechanism
1163 implicitly enables all pr_debug() and dev_dbg() calls. The impact of
1164 this compile option is a larger kernel text size of about 2%.
1168 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
1169 which is contained in the 'debugfs' filesystem. Thus, the debugfs
1170 filesystem must first be mounted before making use of this feature.
1171 We refer the control file as: <debugfs>/dynamic_debug/control. This
1172 file contains a list of the debug statements that can be enabled. The
1173 format for each line of the file is:
1175 filename:lineno [module]function flags format
1177 filename : source file of the debug statement
1178 lineno : line number of the debug statement
1179 module : module that contains the debug statement
1180 function : function that contains the debug statement
1181 flags : 'p' means the line is turned 'on' for printing
1182 format : the format used for the debug statement
1186 nullarbor:~ # cat <debugfs>/dynamic_debug/control
1187 # filename:lineno [module]function flags format
1188 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012"
1189 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012"
1190 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012"
1194 // enable the message at line 1603 of file svcsock.c
1195 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
1196 <debugfs>/dynamic_debug/control
1198 // enable all the messages in file svcsock.c
1199 nullarbor:~ # echo -n 'file svcsock.c +p' >
1200 <debugfs>/dynamic_debug/control
1202 // enable all the messages in the NFS server module
1203 nullarbor:~ # echo -n 'module nfsd +p' >
1204 <debugfs>/dynamic_debug/control
1206 // enable all 12 messages in the function svc_process()
1207 nullarbor:~ # echo -n 'func svc_process +p' >
1208 <debugfs>/dynamic_debug/control
1210 // disable all 12 messages in the function svc_process()
1211 nullarbor:~ # echo -n 'func svc_process -p' >
1212 <debugfs>/dynamic_debug/control
1214 See Documentation/dynamic-debug-howto.txt for additional information.
1216 config DMA_API_DEBUG
1217 bool "Enable debugging of DMA-API usage"
1218 depends on HAVE_DMA_API_DEBUG
1220 Enable this option to debug the use of the DMA API by device drivers.
1221 With this option you will be able to detect common bugs in device
1222 drivers like double-freeing of DMA mappings or freeing mappings that
1223 were never allocated.
1224 This option causes a performance degredation. Use only if you want
1225 to debug device drivers. If unsure, say N.
1227 config ATOMIC64_SELFTEST
1228 bool "Perform an atomic64_t self-test at boot"
1230 Enable this option to test the atomic64_t functions at boot.
1234 config ASYNC_RAID6_TEST
1235 tristate "Self test for hardware accelerated raid6 recovery"
1236 depends on ASYNC_RAID6_RECOV
1239 This is a one-shot self test that permutes through the
1240 recovery of all the possible two disk failure scenarios for a
1241 N-disk array. Recovery is performed with the asynchronous
1242 raid6 recovery routines, and will optionally use an offload
1243 engine if one is available.
1247 source "samples/Kconfig"
1249 source "lib/Kconfig.kgdb"
1251 source "lib/Kconfig.kmemcheck"
1254 tristate "Test kstrto*() family of functions at runtime"