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
12 config ENABLE_WARN_DEPRECATED
13 bool "Enable __deprecated logic"
16 Enable the __deprecated logic in the kernel build.
17 Disable this to suppress the "warning: 'foo' is deprecated
18 (declared at kernel/power/somefile.c:1234)" messages.
20 config ENABLE_MUST_CHECK
21 bool "Enable __must_check logic"
24 Enable the __must_check logic in the kernel build. Disable this to
25 suppress the "warning: ignoring return value of 'foo', declared with
26 attribute warn_unused_result" messages.
29 int "Warn for stack frames larger than (needs gcc 4.4)"
31 default 1024 if !64BIT
34 Tell gcc to warn at build time for stack frames larger than this.
35 Setting this too low will cause a lot of warnings.
36 Setting it to 0 disables the warning.
40 bool "Magic SysRq key"
43 If you say Y here, you will have some control over the system even
44 if the system crashes for example during kernel debugging (e.g., you
45 will be able to flush the buffer cache to disk, reboot the system
46 immediately or dump some status information). This is accomplished
47 by pressing various keys while holding SysRq (Alt+PrintScreen). It
48 also works on a serial console (on PC hardware at least), if you
49 send a BREAK and then within 5 seconds a command keypress. The
50 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
51 unless you really know what this hack does.
54 bool "Strip assembler-generated symbols during link"
57 Strip internal assembler-generated symbols during a link (symbols
58 that look like '.Lxxx') so they don't pollute the output of
59 get_wchan() and suchlike.
62 bool "Enable unused/obsolete exported symbols"
65 Unused but exported symbols make the kernel needlessly bigger. For
66 that reason most of these unused exports will soon be removed. This
67 option is provided temporarily to provide a transition period in case
68 some external kernel module needs one of these symbols anyway. If you
69 encounter such a case in your module, consider if you are actually
70 using the right API. (rationale: since nobody in the kernel is using
71 this in a module, there is a pretty good chance it's actually the
72 wrong interface to use). If you really need the symbol, please send a
73 mail to the linux kernel mailing list mentioning the symbol and why
74 you really need it, and what the merge plan to the mainline kernel for
78 bool "Debug Filesystem"
81 debugfs is a virtual file system that kernel developers use to put
82 debugging files into. Enable this option to be able to read and
85 For detailed documentation on the debugfs API, see
86 Documentation/DocBook/filesystems.
91 bool "Run 'make headers_check' when building vmlinux"
94 This option will extract the user-visible kernel headers whenever
95 building the kernel, and will run basic sanity checks on them to
96 ensure that exported files do not attempt to include files which
97 were not exported, etc.
99 If you're making modifications to header files which are
100 relevant for userspace, say 'Y', and check the headers
101 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
102 your build tree), to make sure they're suitable.
104 config DEBUG_SECTION_MISMATCH
105 bool "Enable full Section mismatch analysis"
106 depends on UNDEFINED || (BLACKFIN)
108 # This option is on purpose disabled for now.
109 # It will be enabled when we are down to a reasonable number
110 # of section mismatch warnings (< 10 for an allyesconfig build)
112 The section mismatch analysis checks if there are illegal
113 references from one section to another section.
114 Linux will during link or during runtime drop some sections
115 and any use of code/data previously in these sections will
116 most likely result in an oops.
117 In the code functions and variables are annotated with
118 __init, __devinit etc. (see full list in include/linux/init.h)
119 which results in the code/data being placed in specific sections.
120 The section mismatch analysis is always done after a full
121 kernel build but enabling this option will in addition
123 - Add the option -fno-inline-functions-called-once to gcc
124 When inlining a function annotated __init in a non-init
125 function we would lose the section information and thus
126 the analysis would not catch the illegal reference.
127 This option tells gcc to inline less but will also
128 result in a larger kernel.
129 - Run the section mismatch analysis for each module/built-in.o
130 When we run the section mismatch analysis on vmlinux.o we
131 lose valueble information about where the mismatch was
133 Running the analysis for each module/built-in.o file
134 will tell where the mismatch happens much closer to the
135 source. The drawback is that we will report the same
136 mismatch at least twice.
137 - Enable verbose reporting from modpost to help solving
138 the section mismatches reported.
141 bool "Kernel debugging"
143 Say Y here if you are developing drivers or trying to debug and
144 identify kernel problems.
147 bool "Debug shared IRQ handlers"
148 depends on DEBUG_KERNEL && GENERIC_HARDIRQS
150 Enable this to generate a spurious interrupt as soon as a shared
151 interrupt handler is registered, and just before one is deregistered.
152 Drivers ought to be able to handle interrupts coming in at those
153 points; some don't and need to be caught.
155 config LOCKUP_DETECTOR
156 bool "Detect Hard and Soft Lockups"
157 depends on DEBUG_KERNEL && !S390
159 Say Y here to enable the kernel to act as a watchdog to detect
160 hard and soft lockups.
162 Softlockups are bugs that cause the kernel to loop in kernel
163 mode for more than 60 seconds, without giving other tasks a
164 chance to run. The current stack trace is displayed upon
165 detection and the system will stay locked up.
167 Hardlockups are bugs that cause the CPU to loop in kernel mode
168 for more than 60 seconds, without letting other interrupts have a
169 chance to run. The current stack trace is displayed upon detection
170 and the system will stay locked up.
172 The overhead should be minimal. A periodic hrtimer runs to
173 generate interrupts and kick the watchdog task every 10-12 seconds.
174 An NMI is generated every 60 seconds or so to check for hardlockups.
176 config HARDLOCKUP_DETECTOR
177 def_bool LOCKUP_DETECTOR && PERF_EVENTS && HAVE_PERF_EVENTS_NMI
179 config BOOTPARAM_SOFTLOCKUP_PANIC
180 bool "Panic (Reboot) On Soft Lockups"
181 depends on LOCKUP_DETECTOR
183 Say Y here to enable the kernel to panic on "soft lockups",
184 which are bugs that cause the kernel to loop in kernel
185 mode for more than 60 seconds, without giving other tasks a
188 The panic can be used in combination with panic_timeout,
189 to cause the system to reboot automatically after a
190 lockup has been detected. This feature is useful for
191 high-availability systems that have uptime guarantees and
192 where a lockup must be resolved ASAP.
196 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
198 depends on LOCKUP_DETECTOR
200 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
201 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
203 config DETECT_HUNG_TASK
204 bool "Detect Hung Tasks"
205 depends on DEBUG_KERNEL
206 default DETECT_SOFTLOCKUP
208 Say Y here to enable the kernel to detect "hung tasks",
209 which are bugs that cause the task to be stuck in
210 uninterruptible "D" state indefinitiley.
212 When a hung task is detected, the kernel will print the
213 current stack trace (which you should report), but the
214 task will stay in uninterruptible state. If lockdep is
215 enabled then all held locks will also be reported. This
216 feature has negligible overhead.
218 config BOOTPARAM_HUNG_TASK_PANIC
219 bool "Panic (Reboot) On Hung Tasks"
220 depends on DETECT_HUNG_TASK
222 Say Y here to enable the kernel to panic on "hung tasks",
223 which are bugs that cause the kernel to leave a task stuck
224 in uninterruptible "D" state.
226 The panic can be used in combination with panic_timeout,
227 to cause the system to reboot automatically after a
228 hung task has been detected. This feature is useful for
229 high-availability systems that have uptime guarantees and
230 where a hung tasks must be resolved ASAP.
234 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
236 depends on DETECT_HUNG_TASK
238 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
239 default 1 if BOOTPARAM_HUNG_TASK_PANIC
242 bool "Collect scheduler debugging info"
243 depends on DEBUG_KERNEL && PROC_FS
246 If you say Y here, the /proc/sched_debug file will be provided
247 that can help debug the scheduler. The runtime overhead of this
251 bool "Collect scheduler statistics"
252 depends on DEBUG_KERNEL && PROC_FS
254 If you say Y here, additional code will be inserted into the
255 scheduler and related routines to collect statistics about
256 scheduler behavior and provide them in /proc/schedstat. These
257 stats may be useful for both tuning and debugging the scheduler
258 If you aren't debugging the scheduler or trying to tune a specific
259 application, you can say N to avoid the very slight overhead
263 bool "Collect kernel timers statistics"
264 depends on DEBUG_KERNEL && PROC_FS
266 If you say Y here, additional code will be inserted into the
267 timer routines to collect statistics about kernel timers being
268 reprogrammed. The statistics can be read from /proc/timer_stats.
269 The statistics collection is started by writing 1 to /proc/timer_stats,
270 writing 0 stops it. This feature is useful to collect information
271 about timer usage patterns in kernel and userspace. This feature
272 is lightweight if enabled in the kernel config but not activated
273 (it defaults to deactivated on bootup and will only be activated
274 if some application like powertop activates it explicitly).
277 bool "Debug object operations"
278 depends on DEBUG_KERNEL
280 If you say Y here, additional code will be inserted into the
281 kernel to track the life time of various objects and validate
282 the operations on those objects.
284 config DEBUG_OBJECTS_SELFTEST
285 bool "Debug objects selftest"
286 depends on DEBUG_OBJECTS
288 This enables the selftest of the object debug code.
290 config DEBUG_OBJECTS_FREE
291 bool "Debug objects in freed memory"
292 depends on DEBUG_OBJECTS
294 This enables checks whether a k/v free operation frees an area
295 which contains an object which has not been deactivated
296 properly. This can make kmalloc/kfree-intensive workloads
299 config DEBUG_OBJECTS_TIMERS
300 bool "Debug timer objects"
301 depends on DEBUG_OBJECTS
303 If you say Y here, additional code will be inserted into the
304 timer routines to track the life time of timer objects and
305 validate the timer operations.
307 config DEBUG_OBJECTS_WORK
308 bool "Debug work objects"
309 depends on DEBUG_OBJECTS
311 If you say Y here, additional code will be inserted into the
312 work queue routines to track the life time of work objects and
313 validate the work operations.
315 config DEBUG_OBJECTS_RCU_HEAD
316 bool "Debug RCU callbacks objects"
317 depends on DEBUG_OBJECTS && PREEMPT
319 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
321 config DEBUG_OBJECTS_ENABLE_DEFAULT
322 int "debug_objects bootup default value (0-1)"
325 depends on DEBUG_OBJECTS
327 Debug objects boot parameter default value
330 bool "Debug slab memory allocations"
331 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
333 Say Y here to have the kernel do limited verification on memory
334 allocation as well as poisoning memory on free to catch use of freed
335 memory. This can make kmalloc/kfree-intensive workloads much slower.
337 config DEBUG_SLAB_LEAK
338 bool "Memory leak debugging"
339 depends on DEBUG_SLAB
342 bool "SLUB debugging on by default"
343 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
346 Boot with debugging on by default. SLUB boots by default with
347 the runtime debug capabilities switched off. Enabling this is
348 equivalent to specifying the "slub_debug" parameter on boot.
349 There is no support for more fine grained debug control like
350 possible with slub_debug=xxx. SLUB debugging may be switched
351 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
356 bool "Enable SLUB performance statistics"
357 depends on SLUB && SLUB_DEBUG && SYSFS
359 SLUB statistics are useful to debug SLUBs allocation behavior in
360 order find ways to optimize the allocator. This should never be
361 enabled for production use since keeping statistics slows down
362 the allocator by a few percentage points. The slabinfo command
363 supports the determination of the most active slabs to figure
364 out which slabs are relevant to a particular load.
365 Try running: slabinfo -DA
367 config DEBUG_KMEMLEAK
368 bool "Kernel memory leak detector"
369 depends on DEBUG_KERNEL && EXPERIMENTAL && !MEMORY_HOTPLUG && \
370 (X86 || ARM || PPC || S390 || SPARC64 || SUPERH || MICROBLAZE)
372 select DEBUG_FS if SYSFS
373 select STACKTRACE if STACKTRACE_SUPPORT
377 Say Y here if you want to enable the memory leak
378 detector. The memory allocation/freeing is traced in a way
379 similar to the Boehm's conservative garbage collector, the
380 difference being that the orphan objects are not freed but
381 only shown in /sys/kernel/debug/kmemleak. Enabling this
382 feature will introduce an overhead to memory
383 allocations. See Documentation/kmemleak.txt for more
386 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
387 of finding leaks due to the slab objects poisoning.
389 In order to access the kmemleak file, debugfs needs to be
390 mounted (usually at /sys/kernel/debug).
392 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
393 int "Maximum kmemleak early log entries"
394 depends on DEBUG_KMEMLEAK
398 Kmemleak must track all the memory allocations to avoid
399 reporting false positives. Since memory may be allocated or
400 freed before kmemleak is initialised, an early log buffer is
401 used to store these actions. If kmemleak reports "early log
402 buffer exceeded", please increase this value.
404 config DEBUG_KMEMLEAK_TEST
405 tristate "Simple test for the kernel memory leak detector"
406 depends on DEBUG_KMEMLEAK
408 Say Y or M here to build a test for the kernel memory leak
409 detector. This option enables a module that explicitly leaks
415 bool "Debug preemptible kernel"
416 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
419 If you say Y here then the kernel will use a debug variant of the
420 commonly used smp_processor_id() function and will print warnings
421 if kernel code uses it in a preemption-unsafe way. Also, the kernel
422 will detect preemption count underflows.
424 config DEBUG_RT_MUTEXES
425 bool "RT Mutex debugging, deadlock detection"
426 depends on DEBUG_KERNEL && RT_MUTEXES
428 This allows rt mutex semantics violations and rt mutex related
429 deadlocks (lockups) to be detected and reported automatically.
434 depends on DEBUG_RT_MUTEXES
436 config RT_MUTEX_TESTER
437 bool "Built-in scriptable tester for rt-mutexes"
438 depends on DEBUG_KERNEL && RT_MUTEXES
440 This option enables a rt-mutex tester.
442 config DEBUG_SPINLOCK
443 bool "Spinlock and rw-lock debugging: basic checks"
444 depends on DEBUG_KERNEL
446 Say Y here and build SMP to catch missing spinlock initialization
447 and certain other kinds of spinlock errors commonly made. This is
448 best used in conjunction with the NMI watchdog so that spinlock
449 deadlocks are also debuggable.
452 bool "Mutex debugging: basic checks"
453 depends on DEBUG_KERNEL
455 This feature allows mutex semantics violations to be detected and
458 config DEBUG_LOCK_ALLOC
459 bool "Lock debugging: detect incorrect freeing of live locks"
460 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
461 select DEBUG_SPINLOCK
465 This feature will check whether any held lock (spinlock, rwlock,
466 mutex or rwsem) is incorrectly freed by the kernel, via any of the
467 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
468 vfree(), etc.), whether a live lock is incorrectly reinitialized via
469 spin_lock_init()/mutex_init()/etc., or whether there is any lock
470 held during task exit.
473 bool "Lock debugging: prove locking correctness"
474 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
476 select DEBUG_SPINLOCK
478 select DEBUG_LOCK_ALLOC
481 This feature enables the kernel to prove that all locking
482 that occurs in the kernel runtime is mathematically
483 correct: that under no circumstance could an arbitrary (and
484 not yet triggered) combination of observed locking
485 sequences (on an arbitrary number of CPUs, running an
486 arbitrary number of tasks and interrupt contexts) cause a
489 In short, this feature enables the kernel to report locking
490 related deadlocks before they actually occur.
492 The proof does not depend on how hard and complex a
493 deadlock scenario would be to trigger: how many
494 participant CPUs, tasks and irq-contexts would be needed
495 for it to trigger. The proof also does not depend on
496 timing: if a race and a resulting deadlock is possible
497 theoretically (no matter how unlikely the race scenario
498 is), it will be proven so and will immediately be
499 reported by the kernel (once the event is observed that
500 makes the deadlock theoretically possible).
502 If a deadlock is impossible (i.e. the locking rules, as
503 observed by the kernel, are mathematically correct), the
504 kernel reports nothing.
506 NOTE: this feature can also be enabled for rwlocks, mutexes
507 and rwsems - in which case all dependencies between these
508 different locking variants are observed and mapped too, and
509 the proof of observed correctness is also maintained for an
510 arbitrary combination of these separate locking variants.
512 For more details, see Documentation/lockdep-design.txt.
515 bool "RCU debugging: prove RCU correctness"
516 depends on PROVE_LOCKING
519 This feature enables lockdep extensions that check for correct
520 use of RCU APIs. This is currently under development. Say Y
521 if you want to debug RCU usage or help work on the PROVE_RCU
524 Say N if you are unsure.
526 config PROVE_RCU_REPEATEDLY
527 bool "RCU debugging: don't disable PROVE_RCU on first splat"
531 By itself, PROVE_RCU will disable checking upon issuing the
532 first warning (or "splat"). This feature prevents such
533 disabling, allowing multiple RCU-lockdep warnings to be printed
536 Say N if you are unsure.
540 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
542 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE
547 bool "Lock usage statistics"
548 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
550 select DEBUG_SPINLOCK
552 select DEBUG_LOCK_ALLOC
555 This feature enables tracking lock contention points
557 For more details, see Documentation/lockstat.txt
559 This also enables lock events required by "perf lock",
561 If you want to use "perf lock", you also need to turn on
562 CONFIG_EVENT_TRACING.
564 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
565 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
568 bool "Lock dependency engine debugging"
569 depends on DEBUG_KERNEL && LOCKDEP
571 If you say Y here, the lock dependency engine will do
572 additional runtime checks to debug itself, at the price
573 of more runtime overhead.
575 config TRACE_IRQFLAGS
576 depends on DEBUG_KERNEL
579 depends on TRACE_IRQFLAGS_SUPPORT
580 depends on PROVE_LOCKING
582 config DEBUG_SPINLOCK_SLEEP
583 bool "Spinlock debugging: sleep-inside-spinlock checking"
584 depends on DEBUG_KERNEL
586 If you say Y here, various routines which may sleep will become very
587 noisy if they are called with a spinlock held.
589 config DEBUG_LOCKING_API_SELFTESTS
590 bool "Locking API boot-time self-tests"
591 depends on DEBUG_KERNEL
593 Say Y here if you want the kernel to run a short self-test during
594 bootup. The self-test checks whether common types of locking bugs
595 are detected by debugging mechanisms or not. (if you disable
596 lock debugging then those bugs wont be detected of course.)
597 The following locking APIs are covered: spinlocks, rwlocks,
602 depends on STACKTRACE_SUPPORT
605 bool "kobject debugging"
606 depends on DEBUG_KERNEL
608 If you say Y here, some extra kobject debugging messages will be sent
612 bool "Highmem debugging"
613 depends on DEBUG_KERNEL && HIGHMEM
615 This options enables addition error checking for high memory systems.
616 Disable for production systems.
618 config DEBUG_BUGVERBOSE
619 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED
621 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \
622 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300
625 Say Y here to make BUG() panics output the file name and line number
626 of the BUG call as well as the EIP and oops trace. This aids
627 debugging but costs about 70-100K of memory.
630 bool "Compile the kernel with debug info"
631 depends on DEBUG_KERNEL
633 If you say Y here the resulting kernel image will include
634 debugging info resulting in a larger kernel image.
635 This adds debug symbols to the kernel and modules (gcc -g), and
636 is needed if you intend to use kernel crashdump or binary object
637 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
638 Say Y here only if you plan to debug the kernel.
642 config DEBUG_INFO_REDUCED
643 bool "Reduce debugging information"
644 depends on DEBUG_INFO
646 If you say Y here gcc is instructed to generate less debugging
647 information for structure types. This means that tools that
648 need full debugging information (like kgdb or systemtap) won't
649 be happy. But if you merely need debugging information to
650 resolve line numbers there is no loss. Advantage is that
651 build directory object sizes shrink dramatically over a full
652 DEBUG_INFO build and compile times are reduced too.
653 Only works with newer gcc versions.
657 depends on DEBUG_KERNEL
659 Enable this to turn on extended checks in the virtual-memory system
660 that may impact performance.
665 bool "Debug VM translations"
666 depends on DEBUG_KERNEL && X86
668 Enable some costly sanity checks in virtual to page code. This can
669 catch mistakes with virt_to_page() and friends.
673 config DEBUG_NOMMU_REGIONS
674 bool "Debug the global anon/private NOMMU mapping region tree"
675 depends on DEBUG_KERNEL && !MMU
677 This option causes the global tree of anonymous and private mapping
678 regions to be regularly checked for invalid topology.
680 config DEBUG_WRITECOUNT
681 bool "Debug filesystem writers count"
682 depends on DEBUG_KERNEL
684 Enable this to catch wrong use of the writers count in struct
685 vfsmount. This will increase the size of each file struct by
690 config DEBUG_MEMORY_INIT
691 bool "Debug memory initialisation" if EMBEDDED
694 Enable this for additional checks during memory initialisation.
695 The sanity checks verify aspects of the VM such as the memory model
696 and other information provided by the architecture. Verbose
697 information will be printed at KERN_DEBUG loglevel depending
698 on the mminit_loglevel= command-line option.
703 bool "Debug linked list manipulation"
704 depends on DEBUG_KERNEL
706 Enable this to turn on extended checks in the linked-list
712 bool "Debug SG table operations"
713 depends on DEBUG_KERNEL
715 Enable this to turn on checks on scatter-gather tables. This can
716 help find problems with drivers that do not properly initialize
721 config DEBUG_NOTIFIERS
722 bool "Debug notifier call chains"
723 depends on DEBUG_KERNEL
725 Enable this to turn on sanity checking for notifier call chains.
726 This is most useful for kernel developers to make sure that
727 modules properly unregister themselves from notifier chains.
728 This is a relatively cheap check but if you care about maximum
731 config DEBUG_CREDENTIALS
732 bool "Debug credential management"
733 depends on DEBUG_KERNEL
735 Enable this to turn on some debug checking for credential
736 management. The additional code keeps track of the number of
737 pointers from task_structs to any given cred struct, and checks to
738 see that this number never exceeds the usage count of the cred
741 Furthermore, if SELinux is enabled, this also checks that the
742 security pointer in the cred struct is never seen to be invalid.
747 # Select this config option from the architecture Kconfig, if it
748 # it is preferred to always offer frame pointers as a config
749 # option on the architecture (regardless of KERNEL_DEBUG):
751 config ARCH_WANT_FRAME_POINTERS
756 bool "Compile the kernel with frame pointers"
757 depends on DEBUG_KERNEL && \
758 (CRIS || M68K || M68KNOMMU || FRV || UML || \
759 AVR32 || SUPERH || BLACKFIN || MN10300) || \
760 ARCH_WANT_FRAME_POINTERS
761 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
763 If you say Y here the resulting kernel image will be slightly
764 larger and slower, but it gives very useful debugging information
765 in case of kernel bugs. (precise oopses/stacktraces/warnings)
767 config BOOT_PRINTK_DELAY
768 bool "Delay each boot printk message by N milliseconds"
769 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
771 This build option allows you to read kernel boot messages
772 by inserting a short delay after each one. The delay is
773 specified in milliseconds on the kernel command line,
774 using "boot_delay=N".
776 It is likely that you would also need to use "lpj=M" to preset
777 the "loops per jiffie" value.
778 See a previous boot log for the "lpj" value to use for your
779 system, and then set "lpj=M" before setting "boot_delay=N".
780 NOTE: Using this option may adversely affect SMP systems.
781 I.e., processors other than the first one may not boot up.
782 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect
783 what it believes to be lockup conditions.
785 config RCU_TORTURE_TEST
786 tristate "torture tests for RCU"
787 depends on DEBUG_KERNEL
790 This option provides a kernel module that runs torture tests
791 on the RCU infrastructure. The kernel module may be built
792 after the fact on the running kernel to be tested, if desired.
794 Say Y here if you want RCU torture tests to be built into
796 Say M if you want the RCU torture tests to build as a module.
797 Say N if you are unsure.
799 config RCU_TORTURE_TEST_RUNNABLE
800 bool "torture tests for RCU runnable by default"
801 depends on RCU_TORTURE_TEST = y
804 This option provides a way to build the RCU torture tests
805 directly into the kernel without them starting up at boot
806 time. You can use /proc/sys/kernel/rcutorture_runnable
807 to manually override this setting. This /proc file is
808 available only when the RCU torture tests have been built
811 Say Y here if you want the RCU torture tests to start during
812 boot (you probably don't).
813 Say N here if you want the RCU torture tests to start only
814 after being manually enabled via /proc.
816 config RCU_CPU_STALL_DETECTOR
817 bool "Check for stalled CPUs delaying RCU grace periods"
818 depends on TREE_RCU || TREE_PREEMPT_RCU
821 This option causes RCU to printk information on which
822 CPUs are delaying the current grace period, but only when
823 the grace period extends for excessive time periods.
825 Say N if you want to disable such checks.
827 Say Y if you are unsure.
829 config RCU_CPU_STALL_VERBOSE
830 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
831 depends on RCU_CPU_STALL_DETECTOR && TREE_PREEMPT_RCU
834 This option causes RCU to printk detailed per-task information
835 for any tasks that are stalling the current RCU grace period.
837 Say N if you are unsure.
839 Say Y if you want to enable such checks.
841 config KPROBES_SANITY_TEST
842 bool "Kprobes sanity tests"
843 depends on DEBUG_KERNEL
847 This option provides for testing basic kprobes functionality on
848 boot. A sample kprobe, jprobe and kretprobe are inserted and
849 verified for functionality.
851 Say N if you are unsure.
853 config BACKTRACE_SELF_TEST
854 tristate "Self test for the backtrace code"
855 depends on DEBUG_KERNEL
858 This option provides a kernel module that can be used to test
859 the kernel stack backtrace code. This option is not useful
860 for distributions or general kernels, but only for kernel
861 developers working on architecture code.
863 Note that if you want to also test saved backtraces, you will
864 have to enable STACKTRACE as well.
866 Say N if you are unsure.
868 config DEBUG_BLOCK_EXT_DEVT
869 bool "Force extended block device numbers and spread them"
870 depends on DEBUG_KERNEL
874 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
875 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
876 YOU ARE DOING. Distros, please enable this and fix whatever
879 Conventionally, block device numbers are allocated from
880 predetermined contiguous area. However, extended block area
881 may introduce non-contiguous block device numbers. This
882 option forces most block device numbers to be allocated from
883 the extended space and spreads them to discover kernel or
884 userland code paths which assume predetermined contiguous
885 device number allocation.
887 Note that turning on this debug option shuffles all the
888 device numbers for all IDE and SCSI devices including libata
889 ones, so root partition specified using device number
890 directly (via rdev or root=MAJ:MIN) won't work anymore.
891 Textual device names (root=/dev/sdXn) will continue to work.
893 Say N if you are unsure.
895 config DEBUG_FORCE_WEAK_PER_CPU
896 bool "Force weak per-cpu definitions"
897 depends on DEBUG_KERNEL
899 s390 and alpha require percpu variables in modules to be
900 defined weak to work around addressing range issue which
901 puts the following two restrictions on percpu variable
904 1. percpu symbols must be unique whether static or not
905 2. percpu variables can't be defined inside a function
907 To ensure that generic code follows the above rules, this
908 option forces all percpu variables to be defined as weak.
911 tristate "Linux Kernel Dump Test Tool Module"
916 This module enables testing of the different dumping mechanisms by
917 inducing system failures at predefined crash points.
918 If you don't need it: say N
919 Choose M here to compile this code as a module. The module will be
922 Documentation on how to use the module can be found in
923 Documentation/fault-injection/provoke-crashes.txt
925 config CPU_NOTIFIER_ERROR_INJECT
926 tristate "CPU notifier error injection module"
927 depends on HOTPLUG_CPU && DEBUG_KERNEL
929 This option provides a kernel module that can be used to test
930 the error handling of the cpu notifiers
932 To compile this code as a module, choose M here: the module will
933 be called cpu-notifier-error-inject.
937 config FAULT_INJECTION
938 bool "Fault-injection framework"
939 depends on DEBUG_KERNEL
941 Provide fault-injection framework.
942 For more details, see Documentation/fault-injection/.
945 bool "Fault-injection capability for kmalloc"
946 depends on FAULT_INJECTION
947 depends on SLAB || SLUB
949 Provide fault-injection capability for kmalloc.
951 config FAIL_PAGE_ALLOC
952 bool "Fault-injection capabilitiy for alloc_pages()"
953 depends on FAULT_INJECTION
955 Provide fault-injection capability for alloc_pages().
957 config FAIL_MAKE_REQUEST
958 bool "Fault-injection capability for disk IO"
959 depends on FAULT_INJECTION && BLOCK
961 Provide fault-injection capability for disk IO.
963 config FAIL_IO_TIMEOUT
964 bool "Fault-injection capability for faking disk interrupts"
965 depends on FAULT_INJECTION && BLOCK
967 Provide fault-injection capability on end IO handling. This
968 will make the block layer "forget" an interrupt as configured,
969 thus exercising the error handling.
971 Only works with drivers that use the generic timeout handling,
972 for others it wont do anything.
974 config FAULT_INJECTION_DEBUG_FS
975 bool "Debugfs entries for fault-injection capabilities"
976 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
978 Enable configuration of fault-injection capabilities via debugfs.
980 config FAULT_INJECTION_STACKTRACE_FILTER
981 bool "stacktrace filter for fault-injection capabilities"
982 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
985 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE
987 Provide stacktrace filter for fault-injection capabilities
990 bool "Latency measuring infrastructure"
991 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE
997 depends on HAVE_LATENCYTOP_SUPPORT
999 Enable this option if you want to use the LatencyTOP tool
1000 to find out which userspace is blocking on what kernel operations.
1002 config SYSCTL_SYSCALL_CHECK
1003 bool "Sysctl checks"
1006 sys_sysctl uses binary paths that have been found challenging
1007 to properly maintain and use. This enables checks that help
1008 you to keep things correct.
1010 source mm/Kconfig.debug
1011 source kernel/trace/Kconfig
1013 config PROVIDE_OHCI1394_DMA_INIT
1014 bool "Remote debugging over FireWire early on boot"
1015 depends on PCI && X86
1017 If you want to debug problems which hang or crash the kernel early
1018 on boot and the crashing machine has a FireWire port, you can use
1019 this feature to remotely access the memory of the crashed machine
1020 over FireWire. This employs remote DMA as part of the OHCI1394
1021 specification which is now the standard for FireWire controllers.
1023 With remote DMA, you can monitor the printk buffer remotely using
1024 firescope and access all memory below 4GB using fireproxy from gdb.
1025 Even controlling a kernel debugger is possible using remote DMA.
1029 If ohci1394_dma=early is used as boot parameter, it will initialize
1030 all OHCI1394 controllers which are found in the PCI config space.
1032 As all changes to the FireWire bus such as enabling and disabling
1033 devices cause a bus reset and thereby disable remote DMA for all
1034 devices, be sure to have the cable plugged and FireWire enabled on
1035 the debugging host before booting the debug target for debugging.
1037 This code (~1k) is freed after boot. By then, the firewire stack
1038 in charge of the OHCI-1394 controllers should be used instead.
1040 See Documentation/debugging-via-ohci1394.txt for more information.
1042 config FIREWIRE_OHCI_REMOTE_DMA
1043 bool "Remote debugging over FireWire with firewire-ohci"
1044 depends on FIREWIRE_OHCI
1046 This option lets you use the FireWire bus for remote debugging
1047 with help of the firewire-ohci driver. It enables unfiltered
1048 remote DMA in firewire-ohci.
1049 See Documentation/debugging-via-ohci1394.txt for more information.
1054 bool "Build targets in Documentation/ tree"
1055 depends on HEADERS_CHECK
1057 This option attempts to build objects from the source files in the
1058 kernel Documentation/ tree.
1060 Say N if you are unsure.
1062 config DYNAMIC_DEBUG
1063 bool "Enable dynamic printk() support"
1069 Compiles debug level messages into the kernel, which would not
1070 otherwise be available at runtime. These messages can then be
1071 enabled/disabled based on various levels of scope - per source file,
1072 function, module, format string, and line number. This mechanism
1073 implicitly enables all pr_debug() and dev_dbg() calls. The impact of
1074 this compile option is a larger kernel text size of about 2%.
1078 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
1079 which is contained in the 'debugfs' filesystem. Thus, the debugfs
1080 filesystem must first be mounted before making use of this feature.
1081 We refer the control file as: <debugfs>/dynamic_debug/control. This
1082 file contains a list of the debug statements that can be enabled. The
1083 format for each line of the file is:
1085 filename:lineno [module]function flags format
1087 filename : source file of the debug statement
1088 lineno : line number of the debug statement
1089 module : module that contains the debug statement
1090 function : function that contains the debug statement
1091 flags : 'p' means the line is turned 'on' for printing
1092 format : the format used for the debug statement
1096 nullarbor:~ # cat <debugfs>/dynamic_debug/control
1097 # filename:lineno [module]function flags format
1098 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012"
1099 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012"
1100 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012"
1104 // enable the message at line 1603 of file svcsock.c
1105 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
1106 <debugfs>/dynamic_debug/control
1108 // enable all the messages in file svcsock.c
1109 nullarbor:~ # echo -n 'file svcsock.c +p' >
1110 <debugfs>/dynamic_debug/control
1112 // enable all the messages in the NFS server module
1113 nullarbor:~ # echo -n 'module nfsd +p' >
1114 <debugfs>/dynamic_debug/control
1116 // enable all 12 messages in the function svc_process()
1117 nullarbor:~ # echo -n 'func svc_process +p' >
1118 <debugfs>/dynamic_debug/control
1120 // disable all 12 messages in the function svc_process()
1121 nullarbor:~ # echo -n 'func svc_process -p' >
1122 <debugfs>/dynamic_debug/control
1124 See Documentation/dynamic-debug-howto.txt for additional information.
1126 config DMA_API_DEBUG
1127 bool "Enable debugging of DMA-API usage"
1128 depends on HAVE_DMA_API_DEBUG
1130 Enable this option to debug the use of the DMA API by device drivers.
1131 With this option you will be able to detect common bugs in device
1132 drivers like double-freeing of DMA mappings or freeing mappings that
1133 were never allocated.
1134 This option causes a performance degredation. Use only if you want
1135 to debug device drivers. If unsure, say N.
1137 config ATOMIC64_SELFTEST
1138 bool "Perform an atomic64_t self-test at boot"
1140 Enable this option to test the atomic64_t functions at boot.
1144 source "samples/Kconfig"
1146 source "lib/Kconfig.kgdb"
1148 source "lib/Kconfig.kmemcheck"