3 bool "Show timing information on printks"
6 Selecting this option causes time stamps of the printk()
7 messages to be added to the output of the syslog() system
8 call and at the console.
10 The timestamp is always recorded internally, and exported
11 to /dev/kmsg. This flag just specifies if the timestamp should
12 be included, not that the timestamp is recorded.
14 The behavior is also controlled by the kernel command line
15 parameter printk.time=1. See Documentation/kernel-parameters.txt
17 config DEFAULT_MESSAGE_LOGLEVEL
18 int "Default message log level (1-7)"
22 Default log level for printk statements with no specified priority.
24 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
25 that are auditing their logs closely may want to set it to a lower
28 config ENABLE_WARN_DEPRECATED
29 bool "Enable __deprecated logic"
32 Enable the __deprecated logic in the kernel build.
33 Disable this to suppress the "warning: 'foo' is deprecated
34 (declared at kernel/power/somefile.c:1234)" messages.
36 config ENABLE_MUST_CHECK
37 bool "Enable __must_check logic"
40 Enable the __must_check logic in the kernel build. Disable this to
41 suppress the "warning: ignoring return value of 'foo', declared with
42 attribute warn_unused_result" messages.
45 int "Warn for stack frames larger than (needs gcc 4.4)"
47 default 1024 if !64BIT
50 Tell gcc to warn at build time for stack frames larger than this.
51 Setting this too low will cause a lot of warnings.
52 Setting it to 0 disables the warning.
56 bool "Magic SysRq key"
59 If you say Y here, you will have some control over the system even
60 if the system crashes for example during kernel debugging (e.g., you
61 will be able to flush the buffer cache to disk, reboot the system
62 immediately or dump some status information). This is accomplished
63 by pressing various keys while holding SysRq (Alt+PrintScreen). It
64 also works on a serial console (on PC hardware at least), if you
65 send a BREAK and then within 5 seconds a command keypress. The
66 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
67 unless you really know what this hack does.
70 bool "Strip assembler-generated symbols during link"
73 Strip internal assembler-generated symbols during a link (symbols
74 that look like '.Lxxx') so they don't pollute the output of
75 get_wchan() and suchlike.
78 bool "Generate readable assembler code"
79 depends on DEBUG_KERNEL
81 Disable some compiler optimizations that tend to generate human unreadable
82 assembler output. This may make the kernel slightly slower, but it helps
83 to keep kernel developers who have to stare a lot at assembler listings
87 bool "Enable unused/obsolete exported symbols"
90 Unused but exported symbols make the kernel needlessly bigger. For
91 that reason most of these unused exports will soon be removed. This
92 option is provided temporarily to provide a transition period in case
93 some external kernel module needs one of these symbols anyway. If you
94 encounter such a case in your module, consider if you are actually
95 using the right API. (rationale: since nobody in the kernel is using
96 this in a module, there is a pretty good chance it's actually the
97 wrong interface to use). If you really need the symbol, please send a
98 mail to the linux kernel mailing list mentioning the symbol and why
99 you really need it, and what the merge plan to the mainline kernel for
103 bool "Debug Filesystem"
105 debugfs is a virtual file system that kernel developers use to put
106 debugging files into. Enable this option to be able to read and
107 write to these files.
109 For detailed documentation on the debugfs API, see
110 Documentation/DocBook/filesystems.
115 bool "Run 'make headers_check' when building vmlinux"
118 This option will extract the user-visible kernel headers whenever
119 building the kernel, and will run basic sanity checks on them to
120 ensure that exported files do not attempt to include files which
121 were not exported, etc.
123 If you're making modifications to header files which are
124 relevant for userspace, say 'Y', and check the headers
125 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
126 your build tree), to make sure they're suitable.
128 config DEBUG_SECTION_MISMATCH
129 bool "Enable full Section mismatch analysis"
131 The section mismatch analysis checks if there are illegal
132 references from one section to another section.
133 During linktime or runtime, some sections are dropped;
134 any use of code/data previously in these sections would
135 most likely result in an oops.
136 In the code, functions and variables are annotated with
137 __init, __devinit, etc. (see the full list in include/linux/init.h),
138 which results in the code/data being placed in specific sections.
139 The section mismatch analysis is always performed after a full
140 kernel build, and enabling this option causes the following
141 additional steps to occur:
142 - Add the option -fno-inline-functions-called-once to gcc commands.
143 When inlining a function annotated with __init in a non-init
144 function, we would lose the section information and thus
145 the analysis would not catch the illegal reference.
146 This option tells gcc to inline less (but it does result in
148 - Run the section mismatch analysis for each module/built-in.o file.
149 When we run the section mismatch analysis on vmlinux.o, we
150 lose valueble information about where the mismatch was
152 Running the analysis for each module/built-in.o file
153 tells where the mismatch happens much closer to the
154 source. The drawback is that the same mismatch is
155 reported at least twice.
156 - Enable verbose reporting from modpost in order to help resolve
157 the section mismatches that are reported.
160 bool "Kernel debugging"
162 Say Y here if you are developing drivers or trying to debug and
163 identify kernel problems.
166 bool "Debug shared IRQ handlers"
167 depends on DEBUG_KERNEL && GENERIC_HARDIRQS
169 Enable this to generate a spurious interrupt as soon as a shared
170 interrupt handler is registered, and just before one is deregistered.
171 Drivers ought to be able to handle interrupts coming in at those
172 points; some don't and need to be caught.
174 config LOCKUP_DETECTOR
175 bool "Detect Hard and Soft Lockups"
176 depends on DEBUG_KERNEL && !S390
178 Say Y here to enable the kernel to act as a watchdog to detect
179 hard and soft lockups.
181 Softlockups are bugs that cause the kernel to loop in kernel
182 mode for more than 20 seconds, without giving other tasks a
183 chance to run. The current stack trace is displayed upon
184 detection and the system will stay locked up.
186 Hardlockups are bugs that cause the CPU to loop in kernel mode
187 for more than 10 seconds, without letting other interrupts have a
188 chance to run. The current stack trace is displayed upon detection
189 and the system will stay locked up.
191 The overhead should be minimal. A periodic hrtimer runs to
192 generate interrupts and kick the watchdog task every 4 seconds.
193 An NMI is generated every 10 seconds or so to check for hardlockups.
195 The frequency of hrtimer and NMI events and the soft and hard lockup
196 thresholds can be controlled through the sysctl watchdog_thresh.
198 config HARDLOCKUP_DETECTOR
199 def_bool LOCKUP_DETECTOR && PERF_EVENTS && HAVE_PERF_EVENTS_NMI && \
202 config BOOTPARAM_HARDLOCKUP_PANIC
203 bool "Panic (Reboot) On Hard Lockups"
204 depends on LOCKUP_DETECTOR
206 Say Y here to enable the kernel to panic on "hard lockups",
207 which are bugs that cause the kernel to loop in kernel
208 mode with interrupts disabled for more than 10 seconds (configurable
209 using the watchdog_thresh sysctl).
213 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
215 depends on LOCKUP_DETECTOR
217 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
218 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
220 config BOOTPARAM_SOFTLOCKUP_PANIC
221 bool "Panic (Reboot) On Soft Lockups"
222 depends on LOCKUP_DETECTOR
224 Say Y here to enable the kernel to panic on "soft lockups",
225 which are bugs that cause the kernel to loop in kernel
226 mode for more than 20 seconds (configurable using the watchdog_thresh
227 sysctl), without giving other tasks a chance to run.
229 The panic can be used in combination with panic_timeout,
230 to cause the system to reboot automatically after a
231 lockup has been detected. This feature is useful for
232 high-availability systems that have uptime guarantees and
233 where a lockup must be resolved ASAP.
237 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
239 depends on LOCKUP_DETECTOR
241 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
242 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
245 bool "Panic on Oops" if EXPERT
248 Say Y here to enable the kernel to panic when it oopses. This
249 has the same effect as setting oops=panic on the kernel command
252 This feature is useful to ensure that the kernel does not do
253 anything erroneous after an oops which could result in data
254 corruption or other issues.
258 config PANIC_ON_OOPS_VALUE
261 default 0 if !PANIC_ON_OOPS
262 default 1 if PANIC_ON_OOPS
264 config DETECT_HUNG_TASK
265 bool "Detect Hung Tasks"
266 depends on DEBUG_KERNEL
267 default LOCKUP_DETECTOR
269 Say Y here to enable the kernel to detect "hung tasks",
270 which are bugs that cause the task to be stuck in
271 uninterruptible "D" state indefinitiley.
273 When a hung task is detected, the kernel will print the
274 current stack trace (which you should report), but the
275 task will stay in uninterruptible state. If lockdep is
276 enabled then all held locks will also be reported. This
277 feature has negligible overhead.
279 config DEFAULT_HUNG_TASK_TIMEOUT
280 int "Default timeout for hung task detection (in seconds)"
281 depends on DETECT_HUNG_TASK
284 This option controls the default timeout (in seconds) used
285 to determine when a task has become non-responsive and should
288 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
289 sysctl or by writing a value to
290 /proc/sys/kernel/hung_task_timeout_secs.
292 A timeout of 0 disables the check. The default is two minutes.
293 Keeping the default should be fine in most cases.
295 config BOOTPARAM_HUNG_TASK_PANIC
296 bool "Panic (Reboot) On Hung Tasks"
297 depends on DETECT_HUNG_TASK
299 Say Y here to enable the kernel to panic on "hung tasks",
300 which are bugs that cause the kernel to leave a task stuck
301 in uninterruptible "D" state.
303 The panic can be used in combination with panic_timeout,
304 to cause the system to reboot automatically after a
305 hung task has been detected. This feature is useful for
306 high-availability systems that have uptime guarantees and
307 where a hung tasks must be resolved ASAP.
311 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
313 depends on DETECT_HUNG_TASK
315 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
316 default 1 if BOOTPARAM_HUNG_TASK_PANIC
319 bool "Collect scheduler debugging info"
320 depends on DEBUG_KERNEL && PROC_FS
323 If you say Y here, the /proc/sched_debug file will be provided
324 that can help debug the scheduler. The runtime overhead of this
328 bool "Collect scheduler statistics"
329 depends on DEBUG_KERNEL && PROC_FS
331 If you say Y here, additional code will be inserted into the
332 scheduler and related routines to collect statistics about
333 scheduler behavior and provide them in /proc/schedstat. These
334 stats may be useful for both tuning and debugging the scheduler
335 If you aren't debugging the scheduler or trying to tune a specific
336 application, you can say N to avoid the very slight overhead
340 bool "Collect kernel timers statistics"
341 depends on DEBUG_KERNEL && PROC_FS
343 If you say Y here, additional code will be inserted into the
344 timer routines to collect statistics about kernel timers being
345 reprogrammed. The statistics can be read from /proc/timer_stats.
346 The statistics collection is started by writing 1 to /proc/timer_stats,
347 writing 0 stops it. This feature is useful to collect information
348 about timer usage patterns in kernel and userspace. This feature
349 is lightweight if enabled in the kernel config but not activated
350 (it defaults to deactivated on bootup and will only be activated
351 if some application like powertop activates it explicitly).
354 bool "Debug object operations"
355 depends on DEBUG_KERNEL
357 If you say Y here, additional code will be inserted into the
358 kernel to track the life time of various objects and validate
359 the operations on those objects.
361 config DEBUG_OBJECTS_SELFTEST
362 bool "Debug objects selftest"
363 depends on DEBUG_OBJECTS
365 This enables the selftest of the object debug code.
367 config DEBUG_OBJECTS_FREE
368 bool "Debug objects in freed memory"
369 depends on DEBUG_OBJECTS
371 This enables checks whether a k/v free operation frees an area
372 which contains an object which has not been deactivated
373 properly. This can make kmalloc/kfree-intensive workloads
376 config DEBUG_OBJECTS_TIMERS
377 bool "Debug timer objects"
378 depends on DEBUG_OBJECTS
380 If you say Y here, additional code will be inserted into the
381 timer routines to track the life time of timer objects and
382 validate the timer operations.
384 config DEBUG_OBJECTS_WORK
385 bool "Debug work objects"
386 depends on DEBUG_OBJECTS
388 If you say Y here, additional code will be inserted into the
389 work queue routines to track the life time of work objects and
390 validate the work operations.
392 config DEBUG_OBJECTS_RCU_HEAD
393 bool "Debug RCU callbacks objects"
394 depends on DEBUG_OBJECTS
396 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
398 config DEBUG_OBJECTS_PERCPU_COUNTER
399 bool "Debug percpu counter objects"
400 depends on DEBUG_OBJECTS
402 If you say Y here, additional code will be inserted into the
403 percpu counter routines to track the life time of percpu counter
404 objects and validate the percpu counter operations.
406 config DEBUG_OBJECTS_ENABLE_DEFAULT
407 int "debug_objects bootup default value (0-1)"
410 depends on DEBUG_OBJECTS
412 Debug objects boot parameter default value
415 bool "Debug slab memory allocations"
416 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
418 Say Y here to have the kernel do limited verification on memory
419 allocation as well as poisoning memory on free to catch use of freed
420 memory. This can make kmalloc/kfree-intensive workloads much slower.
422 config DEBUG_SLAB_LEAK
423 bool "Memory leak debugging"
424 depends on DEBUG_SLAB
427 bool "SLUB debugging on by default"
428 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
431 Boot with debugging on by default. SLUB boots by default with
432 the runtime debug capabilities switched off. Enabling this is
433 equivalent to specifying the "slub_debug" parameter on boot.
434 There is no support for more fine grained debug control like
435 possible with slub_debug=xxx. SLUB debugging may be switched
436 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
441 bool "Enable SLUB performance statistics"
442 depends on SLUB && SYSFS
444 SLUB statistics are useful to debug SLUBs allocation behavior in
445 order find ways to optimize the allocator. This should never be
446 enabled for production use since keeping statistics slows down
447 the allocator by a few percentage points. The slabinfo command
448 supports the determination of the most active slabs to figure
449 out which slabs are relevant to a particular load.
450 Try running: slabinfo -DA
452 config DEBUG_KMEMLEAK
453 bool "Kernel memory leak detector"
454 depends on DEBUG_KERNEL && EXPERIMENTAL && \
455 (X86 || ARM || PPC || MIPS || S390 || SPARC64 || SUPERH || MICROBLAZE || TILE)
458 select STACKTRACE if STACKTRACE_SUPPORT
462 Say Y here if you want to enable the memory leak
463 detector. The memory allocation/freeing is traced in a way
464 similar to the Boehm's conservative garbage collector, the
465 difference being that the orphan objects are not freed but
466 only shown in /sys/kernel/debug/kmemleak. Enabling this
467 feature will introduce an overhead to memory
468 allocations. See Documentation/kmemleak.txt for more
471 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
472 of finding leaks due to the slab objects poisoning.
474 In order to access the kmemleak file, debugfs needs to be
475 mounted (usually at /sys/kernel/debug).
477 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
478 int "Maximum kmemleak early log entries"
479 depends on DEBUG_KMEMLEAK
483 Kmemleak must track all the memory allocations to avoid
484 reporting false positives. Since memory may be allocated or
485 freed before kmemleak is initialised, an early log buffer is
486 used to store these actions. If kmemleak reports "early log
487 buffer exceeded", please increase this value.
489 config DEBUG_KMEMLEAK_TEST
490 tristate "Simple test for the kernel memory leak detector"
491 depends on DEBUG_KMEMLEAK && m
493 This option enables a module that explicitly leaks memory.
497 config DEBUG_KMEMLEAK_DEFAULT_OFF
498 bool "Default kmemleak to off"
499 depends on DEBUG_KMEMLEAK
501 Say Y here to disable kmemleak by default. It can then be enabled
502 on the command line via kmemleak=on.
505 bool "Debug preemptible kernel"
506 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
509 If you say Y here then the kernel will use a debug variant of the
510 commonly used smp_processor_id() function and will print warnings
511 if kernel code uses it in a preemption-unsafe way. Also, the kernel
512 will detect preemption count underflows.
514 config DEBUG_RT_MUTEXES
515 bool "RT Mutex debugging, deadlock detection"
516 depends on DEBUG_KERNEL && RT_MUTEXES
518 This allows rt mutex semantics violations and rt mutex related
519 deadlocks (lockups) to be detected and reported automatically.
524 depends on DEBUG_RT_MUTEXES
526 config RT_MUTEX_TESTER
527 bool "Built-in scriptable tester for rt-mutexes"
528 depends on DEBUG_KERNEL && RT_MUTEXES
530 This option enables a rt-mutex tester.
532 config DEBUG_SPINLOCK
533 bool "Spinlock and rw-lock debugging: basic checks"
534 depends on DEBUG_KERNEL
535 select UNINLINE_SPIN_UNLOCK
537 Say Y here and build SMP to catch missing spinlock initialization
538 and certain other kinds of spinlock errors commonly made. This is
539 best used in conjunction with the NMI watchdog so that spinlock
540 deadlocks are also debuggable.
543 bool "Mutex debugging: basic checks"
544 depends on DEBUG_KERNEL
546 This feature allows mutex semantics violations to be detected and
549 config DEBUG_LOCK_ALLOC
550 bool "Lock debugging: detect incorrect freeing of live locks"
551 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
552 select DEBUG_SPINLOCK
556 This feature will check whether any held lock (spinlock, rwlock,
557 mutex or rwsem) is incorrectly freed by the kernel, via any of the
558 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
559 vfree(), etc.), whether a live lock is incorrectly reinitialized via
560 spin_lock_init()/mutex_init()/etc., or whether there is any lock
561 held during task exit.
564 bool "Lock debugging: prove locking correctness"
565 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
567 select DEBUG_SPINLOCK
569 select DEBUG_LOCK_ALLOC
570 select TRACE_IRQFLAGS
573 This feature enables the kernel to prove that all locking
574 that occurs in the kernel runtime is mathematically
575 correct: that under no circumstance could an arbitrary (and
576 not yet triggered) combination of observed locking
577 sequences (on an arbitrary number of CPUs, running an
578 arbitrary number of tasks and interrupt contexts) cause a
581 In short, this feature enables the kernel to report locking
582 related deadlocks before they actually occur.
584 The proof does not depend on how hard and complex a
585 deadlock scenario would be to trigger: how many
586 participant CPUs, tasks and irq-contexts would be needed
587 for it to trigger. The proof also does not depend on
588 timing: if a race and a resulting deadlock is possible
589 theoretically (no matter how unlikely the race scenario
590 is), it will be proven so and will immediately be
591 reported by the kernel (once the event is observed that
592 makes the deadlock theoretically possible).
594 If a deadlock is impossible (i.e. the locking rules, as
595 observed by the kernel, are mathematically correct), the
596 kernel reports nothing.
598 NOTE: this feature can also be enabled for rwlocks, mutexes
599 and rwsems - in which case all dependencies between these
600 different locking variants are observed and mapped too, and
601 the proof of observed correctness is also maintained for an
602 arbitrary combination of these separate locking variants.
604 For more details, see Documentation/lockdep-design.txt.
607 bool "RCU debugging: prove RCU correctness"
608 depends on PROVE_LOCKING
611 This feature enables lockdep extensions that check for correct
612 use of RCU APIs. This is currently under development. Say Y
613 if you want to debug RCU usage or help work on the PROVE_RCU
616 Say N if you are unsure.
618 config PROVE_RCU_REPEATEDLY
619 bool "RCU debugging: don't disable PROVE_RCU on first splat"
623 By itself, PROVE_RCU will disable checking upon issuing the
624 first warning (or "splat"). This feature prevents such
625 disabling, allowing multiple RCU-lockdep warnings to be printed
628 Say Y to allow multiple RCU-lockdep warnings per boot.
630 Say N if you are unsure.
632 config SPARSE_RCU_POINTER
633 bool "RCU debugging: sparse-based checks for pointer usage"
636 This feature enables the __rcu sparse annotation for
637 RCU-protected pointers. This annotation will cause sparse
638 to flag any non-RCU used of annotated pointers. This can be
639 helpful when debugging RCU usage. Please note that this feature
640 is not intended to enforce code cleanliness; it is instead merely
643 Say Y to make sparse flag questionable use of RCU-protected pointers
645 Say N if you are unsure.
649 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
651 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE
656 bool "Lock usage statistics"
657 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
659 select DEBUG_SPINLOCK
661 select DEBUG_LOCK_ALLOC
664 This feature enables tracking lock contention points
666 For more details, see Documentation/lockstat.txt
668 This also enables lock events required by "perf lock",
670 If you want to use "perf lock", you also need to turn on
671 CONFIG_EVENT_TRACING.
673 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
674 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
677 bool "Lock dependency engine debugging"
678 depends on DEBUG_KERNEL && LOCKDEP
680 If you say Y here, the lock dependency engine will do
681 additional runtime checks to debug itself, at the price
682 of more runtime overhead.
684 config TRACE_IRQFLAGS
687 Enables hooks to interrupt enabling and disabling for
688 either tracing or lock debugging.
690 config DEBUG_ATOMIC_SLEEP
691 bool "Sleep inside atomic section checking"
693 depends on DEBUG_KERNEL
695 If you say Y here, various routines which may sleep will become very
696 noisy if they are called inside atomic sections: when a spinlock is
697 held, inside an rcu read side critical section, inside preempt disabled
698 sections, inside an interrupt, etc...
700 config DEBUG_LOCKING_API_SELFTESTS
701 bool "Locking API boot-time self-tests"
702 depends on DEBUG_KERNEL
704 Say Y here if you want the kernel to run a short self-test during
705 bootup. The self-test checks whether common types of locking bugs
706 are detected by debugging mechanisms or not. (if you disable
707 lock debugging then those bugs wont be detected of course.)
708 The following locking APIs are covered: spinlocks, rwlocks,
713 depends on STACKTRACE_SUPPORT
715 config DEBUG_STACK_USAGE
716 bool "Stack utilization instrumentation"
717 depends on DEBUG_KERNEL && !IA64 && !PARISC
719 Enables the display of the minimum amount of free stack which each
720 task has ever had available in the sysrq-T and sysrq-P debug output.
722 This option will slow down process creation somewhat.
725 bool "kobject debugging"
726 depends on DEBUG_KERNEL
728 If you say Y here, some extra kobject debugging messages will be sent
732 bool "Highmem debugging"
733 depends on DEBUG_KERNEL && HIGHMEM
735 This options enables addition error checking for high memory systems.
736 Disable for production systems.
738 config DEBUG_BUGVERBOSE
739 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
741 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \
742 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 || TILE
745 Say Y here to make BUG() panics output the file name and line number
746 of the BUG call as well as the EIP and oops trace. This aids
747 debugging but costs about 70-100K of memory.
750 bool "Compile the kernel with debug info"
751 depends on DEBUG_KERNEL
753 If you say Y here the resulting kernel image will include
754 debugging info resulting in a larger kernel image.
755 This adds debug symbols to the kernel and modules (gcc -g), and
756 is needed if you intend to use kernel crashdump or binary object
757 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
758 Say Y here only if you plan to debug the kernel.
762 config DEBUG_INFO_REDUCED
763 bool "Reduce debugging information"
764 depends on DEBUG_INFO
766 If you say Y here gcc is instructed to generate less debugging
767 information for structure types. This means that tools that
768 need full debugging information (like kgdb or systemtap) won't
769 be happy. But if you merely need debugging information to
770 resolve line numbers there is no loss. Advantage is that
771 build directory object sizes shrink dramatically over a full
772 DEBUG_INFO build and compile times are reduced too.
773 Only works with newer gcc versions.
777 depends on DEBUG_KERNEL
779 Enable this to turn on extended checks in the virtual-memory system
780 that may impact performance.
785 bool "Debug VM translations"
786 depends on DEBUG_KERNEL && X86
788 Enable some costly sanity checks in virtual to page code. This can
789 catch mistakes with virt_to_page() and friends.
793 config DEBUG_NOMMU_REGIONS
794 bool "Debug the global anon/private NOMMU mapping region tree"
795 depends on DEBUG_KERNEL && !MMU
797 This option causes the global tree of anonymous and private mapping
798 regions to be regularly checked for invalid topology.
800 config DEBUG_WRITECOUNT
801 bool "Debug filesystem writers count"
802 depends on DEBUG_KERNEL
804 Enable this to catch wrong use of the writers count in struct
805 vfsmount. This will increase the size of each file struct by
810 config DEBUG_MEMORY_INIT
811 bool "Debug memory initialisation" if EXPERT
814 Enable this for additional checks during memory initialisation.
815 The sanity checks verify aspects of the VM such as the memory model
816 and other information provided by the architecture. Verbose
817 information will be printed at KERN_DEBUG loglevel depending
818 on the mminit_loglevel= command-line option.
823 bool "Debug linked list manipulation"
824 depends on DEBUG_KERNEL
826 Enable this to turn on extended checks in the linked-list
831 config TEST_LIST_SORT
832 bool "Linked list sorting test"
833 depends on DEBUG_KERNEL
835 Enable this to turn on 'list_sort()' function test. This test is
836 executed only once during system boot, so affects only boot time.
841 bool "Debug SG table operations"
842 depends on DEBUG_KERNEL
844 Enable this to turn on checks on scatter-gather tables. This can
845 help find problems with drivers that do not properly initialize
850 config DEBUG_NOTIFIERS
851 bool "Debug notifier call chains"
852 depends on DEBUG_KERNEL
854 Enable this to turn on sanity checking for notifier call chains.
855 This is most useful for kernel developers to make sure that
856 modules properly unregister themselves from notifier chains.
857 This is a relatively cheap check but if you care about maximum
860 config DEBUG_CREDENTIALS
861 bool "Debug credential management"
862 depends on DEBUG_KERNEL
864 Enable this to turn on some debug checking for credential
865 management. The additional code keeps track of the number of
866 pointers from task_structs to any given cred struct, and checks to
867 see that this number never exceeds the usage count of the cred
870 Furthermore, if SELinux is enabled, this also checks that the
871 security pointer in the cred struct is never seen to be invalid.
876 # Select this config option from the architecture Kconfig, if it
877 # is preferred to always offer frame pointers as a config
878 # option on the architecture (regardless of KERNEL_DEBUG):
880 config ARCH_WANT_FRAME_POINTERS
885 bool "Compile the kernel with frame pointers"
886 depends on DEBUG_KERNEL && \
887 (CRIS || M68K || FRV || UML || \
888 AVR32 || SUPERH || BLACKFIN || MN10300) || \
889 ARCH_WANT_FRAME_POINTERS
890 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
892 If you say Y here the resulting kernel image will be slightly
893 larger and slower, but it gives very useful debugging information
894 in case of kernel bugs. (precise oopses/stacktraces/warnings)
896 config BOOT_PRINTK_DELAY
897 bool "Delay each boot printk message by N milliseconds"
898 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
900 This build option allows you to read kernel boot messages
901 by inserting a short delay after each one. The delay is
902 specified in milliseconds on the kernel command line,
903 using "boot_delay=N".
905 It is likely that you would also need to use "lpj=M" to preset
906 the "loops per jiffie" value.
907 See a previous boot log for the "lpj" value to use for your
908 system, and then set "lpj=M" before setting "boot_delay=N".
909 NOTE: Using this option may adversely affect SMP systems.
910 I.e., processors other than the first one may not boot up.
911 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
912 what it believes to be lockup conditions.
914 config RCU_TORTURE_TEST
915 tristate "torture tests for RCU"
916 depends on DEBUG_KERNEL
919 This option provides a kernel module that runs torture tests
920 on the RCU infrastructure. The kernel module may be built
921 after the fact on the running kernel to be tested, if desired.
923 Say Y here if you want RCU torture tests to be built into
925 Say M if you want the RCU torture tests to build as a module.
926 Say N if you are unsure.
928 config RCU_TORTURE_TEST_RUNNABLE
929 bool "torture tests for RCU runnable by default"
930 depends on RCU_TORTURE_TEST = y
933 This option provides a way to build the RCU torture tests
934 directly into the kernel without them starting up at boot
935 time. You can use /proc/sys/kernel/rcutorture_runnable
936 to manually override this setting. This /proc file is
937 available only when the RCU torture tests have been built
940 Say Y here if you want the RCU torture tests to start during
941 boot (you probably don't).
942 Say N here if you want the RCU torture tests to start only
943 after being manually enabled via /proc.
945 config RCU_CPU_STALL_TIMEOUT
946 int "RCU CPU stall timeout in seconds"
947 depends on TREE_RCU || TREE_PREEMPT_RCU
951 If a given RCU grace period extends more than the specified
952 number of seconds, a CPU stall warning is printed. If the
953 RCU grace period persists, additional CPU stall warnings are
954 printed at more widely spaced intervals.
956 config RCU_CPU_STALL_VERBOSE
957 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
958 depends on TREE_PREEMPT_RCU
961 This option causes RCU to printk detailed per-task information
962 for any tasks that are stalling the current RCU grace period.
964 Say N if you are unsure.
966 Say Y if you want to enable such checks.
968 config RCU_CPU_STALL_INFO
969 bool "Print additional diagnostics on RCU CPU stall"
970 depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL
973 For each stalled CPU that is aware of the current RCU grace
974 period, print out additional per-CPU diagnostic information
975 regarding scheduling-clock ticks, idle state, and,
976 for RCU_FAST_NO_HZ kernels, idle-entry state.
978 Say N if you are unsure.
980 Say Y if you want to enable such diagnostics.
983 bool "Enable tracing for RCU"
984 depends on DEBUG_KERNEL
986 This option provides tracing in RCU which presents stats
987 in debugfs for debugging RCU implementation.
989 Say Y here if you want to enable RCU tracing
990 Say N if you are unsure.
992 config KPROBES_SANITY_TEST
993 bool "Kprobes sanity tests"
994 depends on DEBUG_KERNEL
998 This option provides for testing basic kprobes functionality on
999 boot. A sample kprobe, jprobe and kretprobe are inserted and
1000 verified for functionality.
1002 Say N if you are unsure.
1004 config BACKTRACE_SELF_TEST
1005 tristate "Self test for the backtrace code"
1006 depends on DEBUG_KERNEL
1009 This option provides a kernel module that can be used to test
1010 the kernel stack backtrace code. This option is not useful
1011 for distributions or general kernels, but only for kernel
1012 developers working on architecture code.
1014 Note that if you want to also test saved backtraces, you will
1015 have to enable STACKTRACE as well.
1017 Say N if you are unsure.
1019 config DEBUG_BLOCK_EXT_DEVT
1020 bool "Force extended block device numbers and spread them"
1021 depends on DEBUG_KERNEL
1025 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1026 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1027 YOU ARE DOING. Distros, please enable this and fix whatever
1030 Conventionally, block device numbers are allocated from
1031 predetermined contiguous area. However, extended block area
1032 may introduce non-contiguous block device numbers. This
1033 option forces most block device numbers to be allocated from
1034 the extended space and spreads them to discover kernel or
1035 userland code paths which assume predetermined contiguous
1036 device number allocation.
1038 Note that turning on this debug option shuffles all the
1039 device numbers for all IDE and SCSI devices including libata
1040 ones, so root partition specified using device number
1041 directly (via rdev or root=MAJ:MIN) won't work anymore.
1042 Textual device names (root=/dev/sdXn) will continue to work.
1044 Say N if you are unsure.
1046 config DEBUG_FORCE_WEAK_PER_CPU
1047 bool "Force weak per-cpu definitions"
1048 depends on DEBUG_KERNEL
1050 s390 and alpha require percpu variables in modules to be
1051 defined weak to work around addressing range issue which
1052 puts the following two restrictions on percpu variable
1055 1. percpu symbols must be unique whether static or not
1056 2. percpu variables can't be defined inside a function
1058 To ensure that generic code follows the above rules, this
1059 option forces all percpu variables to be defined as weak.
1061 config DEBUG_PER_CPU_MAPS
1062 bool "Debug access to per_cpu maps"
1063 depends on DEBUG_KERNEL
1066 Say Y to verify that the per_cpu map being accessed has
1067 been set up. This adds a fair amount of code to kernel memory
1068 and decreases performance.
1073 tristate "Linux Kernel Dump Test Tool Module"
1078 This module enables testing of the different dumping mechanisms by
1079 inducing system failures at predefined crash points.
1080 If you don't need it: say N
1081 Choose M here to compile this code as a module. The module will be
1084 Documentation on how to use the module can be found in
1085 Documentation/fault-injection/provoke-crashes.txt
1087 config NOTIFIER_ERROR_INJECTION
1088 tristate "Notifier error injection"
1089 depends on DEBUG_KERNEL
1092 This option provides the ability to inject artifical errors to
1093 specified notifier chain callbacks. It is useful to test the error
1094 handling of notifier call chain failures.
1098 config CPU_NOTIFIER_ERROR_INJECT
1099 tristate "CPU notifier error injection module"
1100 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1102 This option provides a kernel module that can be used to test
1103 the error handling of the cpu notifiers by injecting artifical
1104 errors to CPU notifier chain callbacks. It is controlled through
1105 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
1107 If the notifier call chain should be failed with some events
1108 notified, write the error code to "actions/<notifier event>/error".
1110 Example: Inject CPU offline error (-1 == -EPERM)
1112 # cd /sys/kernel/debug/notifier-error-inject/cpu
1113 # echo -1 > actions/CPU_DOWN_PREPARE/error
1114 # echo 0 > /sys/devices/system/cpu/cpu1/online
1115 bash: echo: write error: Operation not permitted
1117 To compile this code as a module, choose M here: the module will
1118 be called cpu-notifier-error-inject.
1122 config FAULT_INJECTION
1123 bool "Fault-injection framework"
1124 depends on DEBUG_KERNEL
1126 Provide fault-injection framework.
1127 For more details, see Documentation/fault-injection/.
1130 bool "Fault-injection capability for kmalloc"
1131 depends on FAULT_INJECTION
1132 depends on SLAB || SLUB
1134 Provide fault-injection capability for kmalloc.
1136 config FAIL_PAGE_ALLOC
1137 bool "Fault-injection capabilitiy for alloc_pages()"
1138 depends on FAULT_INJECTION
1140 Provide fault-injection capability for alloc_pages().
1142 config FAIL_MAKE_REQUEST
1143 bool "Fault-injection capability for disk IO"
1144 depends on FAULT_INJECTION && BLOCK
1146 Provide fault-injection capability for disk IO.
1148 config FAIL_IO_TIMEOUT
1149 bool "Fault-injection capability for faking disk interrupts"
1150 depends on FAULT_INJECTION && BLOCK
1152 Provide fault-injection capability on end IO handling. This
1153 will make the block layer "forget" an interrupt as configured,
1154 thus exercising the error handling.
1156 Only works with drivers that use the generic timeout handling,
1157 for others it wont do anything.
1159 config FAIL_MMC_REQUEST
1160 bool "Fault-injection capability for MMC IO"
1162 depends on FAULT_INJECTION && MMC
1164 Provide fault-injection capability for MMC IO.
1165 This will make the mmc core return data errors. This is
1166 useful to test the error handling in the mmc block device
1167 and to test how the mmc host driver handles retries from
1170 config FAULT_INJECTION_DEBUG_FS
1171 bool "Debugfs entries for fault-injection capabilities"
1172 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1174 Enable configuration of fault-injection capabilities via debugfs.
1176 config FAULT_INJECTION_STACKTRACE_FILTER
1177 bool "stacktrace filter for fault-injection capabilities"
1178 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1181 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND
1183 Provide stacktrace filter for fault-injection capabilities
1186 bool "Latency measuring infrastructure"
1187 depends on HAVE_LATENCYTOP_SUPPORT
1188 depends on DEBUG_KERNEL
1189 depends on STACKTRACE_SUPPORT
1191 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND
1198 Enable this option if you want to use the LatencyTOP tool
1199 to find out which userspace is blocking on what kernel operations.
1201 source mm/Kconfig.debug
1202 source kernel/trace/Kconfig
1204 config PROVIDE_OHCI1394_DMA_INIT
1205 bool "Remote debugging over FireWire early on boot"
1206 depends on PCI && X86
1208 If you want to debug problems which hang or crash the kernel early
1209 on boot and the crashing machine has a FireWire port, you can use
1210 this feature to remotely access the memory of the crashed machine
1211 over FireWire. This employs remote DMA as part of the OHCI1394
1212 specification which is now the standard for FireWire controllers.
1214 With remote DMA, you can monitor the printk buffer remotely using
1215 firescope and access all memory below 4GB using fireproxy from gdb.
1216 Even controlling a kernel debugger is possible using remote DMA.
1220 If ohci1394_dma=early is used as boot parameter, it will initialize
1221 all OHCI1394 controllers which are found in the PCI config space.
1223 As all changes to the FireWire bus such as enabling and disabling
1224 devices cause a bus reset and thereby disable remote DMA for all
1225 devices, be sure to have the cable plugged and FireWire enabled on
1226 the debugging host before booting the debug target for debugging.
1228 This code (~1k) is freed after boot. By then, the firewire stack
1229 in charge of the OHCI-1394 controllers should be used instead.
1231 See Documentation/debugging-via-ohci1394.txt for more information.
1233 config FIREWIRE_OHCI_REMOTE_DMA
1234 bool "Remote debugging over FireWire with firewire-ohci"
1235 depends on FIREWIRE_OHCI
1237 This option lets you use the FireWire bus for remote debugging
1238 with help of the firewire-ohci driver. It enables unfiltered
1239 remote DMA in firewire-ohci.
1240 See Documentation/debugging-via-ohci1394.txt for more information.
1245 bool "Build targets in Documentation/ tree"
1246 depends on HEADERS_CHECK
1248 This option attempts to build objects from the source files in the
1249 kernel Documentation/ tree.
1251 Say N if you are unsure.
1253 config DYNAMIC_DEBUG
1254 bool "Enable dynamic printk() support"
1260 Compiles debug level messages into the kernel, which would not
1261 otherwise be available at runtime. These messages can then be
1262 enabled/disabled based on various levels of scope - per source file,
1263 function, module, format string, and line number. This mechanism
1264 implicitly compiles in all pr_debug() and dev_dbg() calls, which
1265 enlarges the kernel text size by about 2%.
1267 If a source file is compiled with DEBUG flag set, any
1268 pr_debug() calls in it are enabled by default, but can be
1269 disabled at runtime as below. Note that DEBUG flag is
1270 turned on by many CONFIG_*DEBUG* options.
1274 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
1275 which is contained in the 'debugfs' filesystem. Thus, the debugfs
1276 filesystem must first be mounted before making use of this feature.
1277 We refer the control file as: <debugfs>/dynamic_debug/control. This
1278 file contains a list of the debug statements that can be enabled. The
1279 format for each line of the file is:
1281 filename:lineno [module]function flags format
1283 filename : source file of the debug statement
1284 lineno : line number of the debug statement
1285 module : module that contains the debug statement
1286 function : function that contains the debug statement
1287 flags : '=p' means the line is turned 'on' for printing
1288 format : the format used for the debug statement
1292 nullarbor:~ # cat <debugfs>/dynamic_debug/control
1293 # filename:lineno [module]function flags format
1294 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
1295 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
1296 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
1300 // enable the message at line 1603 of file svcsock.c
1301 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
1302 <debugfs>/dynamic_debug/control
1304 // enable all the messages in file svcsock.c
1305 nullarbor:~ # echo -n 'file svcsock.c +p' >
1306 <debugfs>/dynamic_debug/control
1308 // enable all the messages in the NFS server module
1309 nullarbor:~ # echo -n 'module nfsd +p' >
1310 <debugfs>/dynamic_debug/control
1312 // enable all 12 messages in the function svc_process()
1313 nullarbor:~ # echo -n 'func svc_process +p' >
1314 <debugfs>/dynamic_debug/control
1316 // disable all 12 messages in the function svc_process()
1317 nullarbor:~ # echo -n 'func svc_process -p' >
1318 <debugfs>/dynamic_debug/control
1320 See Documentation/dynamic-debug-howto.txt for additional information.
1322 config DMA_API_DEBUG
1323 bool "Enable debugging of DMA-API usage"
1324 depends on HAVE_DMA_API_DEBUG
1326 Enable this option to debug the use of the DMA API by device drivers.
1327 With this option you will be able to detect common bugs in device
1328 drivers like double-freeing of DMA mappings or freeing mappings that
1329 were never allocated.
1330 This option causes a performance degredation. Use only if you want
1331 to debug device drivers. If unsure, say N.
1333 config ATOMIC64_SELFTEST
1334 bool "Perform an atomic64_t self-test at boot"
1336 Enable this option to test the atomic64_t functions at boot.
1340 config ASYNC_RAID6_TEST
1341 tristate "Self test for hardware accelerated raid6 recovery"
1342 depends on ASYNC_RAID6_RECOV
1345 This is a one-shot self test that permutes through the
1346 recovery of all the possible two disk failure scenarios for a
1347 N-disk array. Recovery is performed with the asynchronous
1348 raid6 recovery routines, and will optionally use an offload
1349 engine if one is available.
1353 source "samples/Kconfig"
1355 source "lib/Kconfig.kgdb"
1357 source "lib/Kconfig.kmemcheck"
1360 tristate "Test kstrto*() family of functions at runtime"