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 LOCKUP_DETECTOR
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 DEFAULT_HUNG_TASK_TIMEOUT
243 int "Default timeout for hung task detection (in seconds)"
244 depends on DETECT_HUNG_TASK
247 This option controls the default timeout (in seconds) used
248 to determine when a task has become non-responsive and should
251 It can be adjusted at runtime via the kernel.hung_task_timeout
252 sysctl or by writing a value to /proc/sys/kernel/hung_task_timeout.
254 A timeout of 0 disables the check. The default is two minutes.
255 Keeping the default should be fine in most cases.
257 config BOOTPARAM_HUNG_TASK_PANIC
258 bool "Panic (Reboot) On Hung Tasks"
259 depends on DETECT_HUNG_TASK
261 Say Y here to enable the kernel to panic on "hung tasks",
262 which are bugs that cause the kernel to leave a task stuck
263 in uninterruptible "D" state.
265 The panic can be used in combination with panic_timeout,
266 to cause the system to reboot automatically after a
267 hung task has been detected. This feature is useful for
268 high-availability systems that have uptime guarantees and
269 where a hung tasks must be resolved ASAP.
273 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
275 depends on DETECT_HUNG_TASK
277 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
278 default 1 if BOOTPARAM_HUNG_TASK_PANIC
281 bool "Collect scheduler debugging info"
282 depends on DEBUG_KERNEL && PROC_FS
285 If you say Y here, the /proc/sched_debug file will be provided
286 that can help debug the scheduler. The runtime overhead of this
290 bool "Collect scheduler statistics"
291 depends on DEBUG_KERNEL && PROC_FS
293 If you say Y here, additional code will be inserted into the
294 scheduler and related routines to collect statistics about
295 scheduler behavior and provide them in /proc/schedstat. These
296 stats may be useful for both tuning and debugging the scheduler
297 If you aren't debugging the scheduler or trying to tune a specific
298 application, you can say N to avoid the very slight overhead
302 bool "Collect kernel timers statistics"
303 depends on DEBUG_KERNEL && PROC_FS
305 If you say Y here, additional code will be inserted into the
306 timer routines to collect statistics about kernel timers being
307 reprogrammed. The statistics can be read from /proc/timer_stats.
308 The statistics collection is started by writing 1 to /proc/timer_stats,
309 writing 0 stops it. This feature is useful to collect information
310 about timer usage patterns in kernel and userspace. This feature
311 is lightweight if enabled in the kernel config but not activated
312 (it defaults to deactivated on bootup and will only be activated
313 if some application like powertop activates it explicitly).
316 bool "Debug object operations"
317 depends on DEBUG_KERNEL
319 If you say Y here, additional code will be inserted into the
320 kernel to track the life time of various objects and validate
321 the operations on those objects.
323 config DEBUG_OBJECTS_SELFTEST
324 bool "Debug objects selftest"
325 depends on DEBUG_OBJECTS
327 This enables the selftest of the object debug code.
329 config DEBUG_OBJECTS_FREE
330 bool "Debug objects in freed memory"
331 depends on DEBUG_OBJECTS
333 This enables checks whether a k/v free operation frees an area
334 which contains an object which has not been deactivated
335 properly. This can make kmalloc/kfree-intensive workloads
338 config DEBUG_OBJECTS_TIMERS
339 bool "Debug timer objects"
340 depends on DEBUG_OBJECTS
342 If you say Y here, additional code will be inserted into the
343 timer routines to track the life time of timer objects and
344 validate the timer operations.
346 config DEBUG_OBJECTS_WORK
347 bool "Debug work objects"
348 depends on DEBUG_OBJECTS
350 If you say Y here, additional code will be inserted into the
351 work queue routines to track the life time of work objects and
352 validate the work operations.
354 config DEBUG_OBJECTS_RCU_HEAD
355 bool "Debug RCU callbacks objects"
356 depends on DEBUG_OBJECTS
358 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
360 config DEBUG_OBJECTS_PERCPU_COUNTER
361 bool "Debug percpu counter objects"
362 depends on DEBUG_OBJECTS
364 If you say Y here, additional code will be inserted into the
365 percpu counter routines to track the life time of percpu counter
366 objects and validate the percpu counter operations.
368 config DEBUG_OBJECTS_ENABLE_DEFAULT
369 int "debug_objects bootup default value (0-1)"
372 depends on DEBUG_OBJECTS
374 Debug objects boot parameter default value
377 bool "Debug slab memory allocations"
378 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
380 Say Y here to have the kernel do limited verification on memory
381 allocation as well as poisoning memory on free to catch use of freed
382 memory. This can make kmalloc/kfree-intensive workloads much slower.
384 config DEBUG_SLAB_LEAK
385 bool "Memory leak debugging"
386 depends on DEBUG_SLAB
389 bool "SLUB debugging on by default"
390 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
393 Boot with debugging on by default. SLUB boots by default with
394 the runtime debug capabilities switched off. Enabling this is
395 equivalent to specifying the "slub_debug" parameter on boot.
396 There is no support for more fine grained debug control like
397 possible with slub_debug=xxx. SLUB debugging may be switched
398 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
403 bool "Enable SLUB performance statistics"
404 depends on SLUB && SYSFS
406 SLUB statistics are useful to debug SLUBs allocation behavior in
407 order find ways to optimize the allocator. This should never be
408 enabled for production use since keeping statistics slows down
409 the allocator by a few percentage points. The slabinfo command
410 supports the determination of the most active slabs to figure
411 out which slabs are relevant to a particular load.
412 Try running: slabinfo -DA
414 config DEBUG_KMEMLEAK
415 bool "Kernel memory leak detector"
416 depends on DEBUG_KERNEL && EXPERIMENTAL && !MEMORY_HOTPLUG && \
417 (X86 || ARM || PPC || MIPS || S390 || SPARC64 || SUPERH || MICROBLAZE || TILE)
420 select STACKTRACE if STACKTRACE_SUPPORT
425 Say Y here if you want to enable the memory leak
426 detector. The memory allocation/freeing is traced in a way
427 similar to the Boehm's conservative garbage collector, the
428 difference being that the orphan objects are not freed but
429 only shown in /sys/kernel/debug/kmemleak. Enabling this
430 feature will introduce an overhead to memory
431 allocations. See Documentation/kmemleak.txt for more
434 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
435 of finding leaks due to the slab objects poisoning.
437 In order to access the kmemleak file, debugfs needs to be
438 mounted (usually at /sys/kernel/debug).
440 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
441 int "Maximum kmemleak early log entries"
442 depends on DEBUG_KMEMLEAK
446 Kmemleak must track all the memory allocations to avoid
447 reporting false positives. Since memory may be allocated or
448 freed before kmemleak is initialised, an early log buffer is
449 used to store these actions. If kmemleak reports "early log
450 buffer exceeded", please increase this value.
452 config DEBUG_KMEMLEAK_TEST
453 tristate "Simple test for the kernel memory leak detector"
454 depends on DEBUG_KMEMLEAK && m
456 This option enables a module that explicitly leaks memory.
460 config DEBUG_KMEMLEAK_DEFAULT_OFF
461 bool "Default kmemleak to off"
462 depends on DEBUG_KMEMLEAK
464 Say Y here to disable kmemleak by default. It can then be enabled
465 on the command line via kmemleak=on.
468 bool "Debug preemptible kernel"
469 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
472 If you say Y here then the kernel will use a debug variant of the
473 commonly used smp_processor_id() function and will print warnings
474 if kernel code uses it in a preemption-unsafe way. Also, the kernel
475 will detect preemption count underflows.
477 config DEBUG_RT_MUTEXES
478 bool "RT Mutex debugging, deadlock detection"
479 depends on DEBUG_KERNEL && RT_MUTEXES
481 This allows rt mutex semantics violations and rt mutex related
482 deadlocks (lockups) to be detected and reported automatically.
487 depends on DEBUG_RT_MUTEXES
489 config RT_MUTEX_TESTER
490 bool "Built-in scriptable tester for rt-mutexes"
491 depends on DEBUG_KERNEL && RT_MUTEXES
493 This option enables a rt-mutex tester.
495 config DEBUG_SPINLOCK
496 bool "Spinlock and rw-lock debugging: basic checks"
497 depends on DEBUG_KERNEL
499 Say Y here and build SMP to catch missing spinlock initialization
500 and certain other kinds of spinlock errors commonly made. This is
501 best used in conjunction with the NMI watchdog so that spinlock
502 deadlocks are also debuggable.
505 bool "Mutex debugging: basic checks"
506 depends on DEBUG_KERNEL
508 This feature allows mutex semantics violations to be detected and
511 config DEBUG_LOCK_ALLOC
512 bool "Lock debugging: detect incorrect freeing of live locks"
513 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
514 select DEBUG_SPINLOCK
518 This feature will check whether any held lock (spinlock, rwlock,
519 mutex or rwsem) is incorrectly freed by the kernel, via any of the
520 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
521 vfree(), etc.), whether a live lock is incorrectly reinitialized via
522 spin_lock_init()/mutex_init()/etc., or whether there is any lock
523 held during task exit.
526 bool "Lock debugging: prove locking correctness"
527 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
529 select DEBUG_SPINLOCK
531 select DEBUG_LOCK_ALLOC
532 select TRACE_IRQFLAGS
535 This feature enables the kernel to prove that all locking
536 that occurs in the kernel runtime is mathematically
537 correct: that under no circumstance could an arbitrary (and
538 not yet triggered) combination of observed locking
539 sequences (on an arbitrary number of CPUs, running an
540 arbitrary number of tasks and interrupt contexts) cause a
543 In short, this feature enables the kernel to report locking
544 related deadlocks before they actually occur.
546 The proof does not depend on how hard and complex a
547 deadlock scenario would be to trigger: how many
548 participant CPUs, tasks and irq-contexts would be needed
549 for it to trigger. The proof also does not depend on
550 timing: if a race and a resulting deadlock is possible
551 theoretically (no matter how unlikely the race scenario
552 is), it will be proven so and will immediately be
553 reported by the kernel (once the event is observed that
554 makes the deadlock theoretically possible).
556 If a deadlock is impossible (i.e. the locking rules, as
557 observed by the kernel, are mathematically correct), the
558 kernel reports nothing.
560 NOTE: this feature can also be enabled for rwlocks, mutexes
561 and rwsems - in which case all dependencies between these
562 different locking variants are observed and mapped too, and
563 the proof of observed correctness is also maintained for an
564 arbitrary combination of these separate locking variants.
566 For more details, see Documentation/lockdep-design.txt.
569 bool "RCU debugging: prove RCU correctness"
570 depends on PROVE_LOCKING
573 This feature enables lockdep extensions that check for correct
574 use of RCU APIs. This is currently under development. Say Y
575 if you want to debug RCU usage or help work on the PROVE_RCU
578 Say N if you are unsure.
580 config PROVE_RCU_REPEATEDLY
581 bool "RCU debugging: don't disable PROVE_RCU on first splat"
585 By itself, PROVE_RCU will disable checking upon issuing the
586 first warning (or "splat"). This feature prevents such
587 disabling, allowing multiple RCU-lockdep warnings to be printed
590 Say Y to allow multiple RCU-lockdep warnings per boot.
592 Say N if you are unsure.
594 config SPARSE_RCU_POINTER
595 bool "RCU debugging: sparse-based checks for pointer usage"
598 This feature enables the __rcu sparse annotation for
599 RCU-protected pointers. This annotation will cause sparse
600 to flag any non-RCU used of annotated pointers. This can be
601 helpful when debugging RCU usage. Please note that this feature
602 is not intended to enforce code cleanliness; it is instead merely
605 Say Y to make sparse flag questionable use of RCU-protected pointers
607 Say N if you are unsure.
611 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
613 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE
618 bool "Lock usage statistics"
619 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
621 select DEBUG_SPINLOCK
623 select DEBUG_LOCK_ALLOC
626 This feature enables tracking lock contention points
628 For more details, see Documentation/lockstat.txt
630 This also enables lock events required by "perf lock",
632 If you want to use "perf lock", you also need to turn on
633 CONFIG_EVENT_TRACING.
635 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
636 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
639 bool "Lock dependency engine debugging"
640 depends on DEBUG_KERNEL && LOCKDEP
642 If you say Y here, the lock dependency engine will do
643 additional runtime checks to debug itself, at the price
644 of more runtime overhead.
646 config TRACE_IRQFLAGS
649 Enables hooks to interrupt enabling and disabling for
650 either tracing or lock debugging.
652 config DEBUG_ATOMIC_SLEEP
653 bool "Sleep inside atomic section checking"
655 depends on DEBUG_KERNEL
657 If you say Y here, various routines which may sleep will become very
658 noisy if they are called inside atomic sections: when a spinlock is
659 held, inside an rcu read side critical section, inside preempt disabled
660 sections, inside an interrupt, etc...
662 config DEBUG_LOCKING_API_SELFTESTS
663 bool "Locking API boot-time self-tests"
664 depends on DEBUG_KERNEL
666 Say Y here if you want the kernel to run a short self-test during
667 bootup. The self-test checks whether common types of locking bugs
668 are detected by debugging mechanisms or not. (if you disable
669 lock debugging then those bugs wont be detected of course.)
670 The following locking APIs are covered: spinlocks, rwlocks,
675 depends on STACKTRACE_SUPPORT
677 config DEBUG_STACK_USAGE
678 bool "Stack utilization instrumentation"
679 depends on DEBUG_KERNEL
681 Enables the display of the minimum amount of free stack which each
682 task has ever had available in the sysrq-T and sysrq-P debug output.
684 This option will slow down process creation somewhat.
687 bool "kobject debugging"
688 depends on DEBUG_KERNEL
690 If you say Y here, some extra kobject debugging messages will be sent
694 bool "Highmem debugging"
695 depends on DEBUG_KERNEL && HIGHMEM
697 This options enables addition error checking for high memory systems.
698 Disable for production systems.
700 config DEBUG_BUGVERBOSE
701 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
703 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \
704 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 || TILE
707 Say Y here to make BUG() panics output the file name and line number
708 of the BUG call as well as the EIP and oops trace. This aids
709 debugging but costs about 70-100K of memory.
712 bool "Compile the kernel with debug info"
713 depends on DEBUG_KERNEL
715 If you say Y here the resulting kernel image will include
716 debugging info resulting in a larger kernel image.
717 This adds debug symbols to the kernel and modules (gcc -g), and
718 is needed if you intend to use kernel crashdump or binary object
719 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
720 Say Y here only if you plan to debug the kernel.
724 config DEBUG_INFO_REDUCED
725 bool "Reduce debugging information"
726 depends on DEBUG_INFO
728 If you say Y here gcc is instructed to generate less debugging
729 information for structure types. This means that tools that
730 need full debugging information (like kgdb or systemtap) won't
731 be happy. But if you merely need debugging information to
732 resolve line numbers there is no loss. Advantage is that
733 build directory object sizes shrink dramatically over a full
734 DEBUG_INFO build and compile times are reduced too.
735 Only works with newer gcc versions.
739 depends on DEBUG_KERNEL
741 Enable this to turn on extended checks in the virtual-memory system
742 that may impact performance.
747 bool "Debug VM translations"
748 depends on DEBUG_KERNEL && X86
750 Enable some costly sanity checks in virtual to page code. This can
751 catch mistakes with virt_to_page() and friends.
755 config DEBUG_NOMMU_REGIONS
756 bool "Debug the global anon/private NOMMU mapping region tree"
757 depends on DEBUG_KERNEL && !MMU
759 This option causes the global tree of anonymous and private mapping
760 regions to be regularly checked for invalid topology.
762 config DEBUG_WRITECOUNT
763 bool "Debug filesystem writers count"
764 depends on DEBUG_KERNEL
766 Enable this to catch wrong use of the writers count in struct
767 vfsmount. This will increase the size of each file struct by
772 config DEBUG_MEMORY_INIT
773 bool "Debug memory initialisation" if EXPERT
776 Enable this for additional checks during memory initialisation.
777 The sanity checks verify aspects of the VM such as the memory model
778 and other information provided by the architecture. Verbose
779 information will be printed at KERN_DEBUG loglevel depending
780 on the mminit_loglevel= command-line option.
785 bool "Debug linked list manipulation"
786 depends on DEBUG_KERNEL
788 Enable this to turn on extended checks in the linked-list
793 config TEST_LIST_SORT
794 bool "Linked list sorting test"
795 depends on DEBUG_KERNEL
797 Enable this to turn on 'list_sort()' function test. This test is
798 executed only once during system boot, so affects only boot time.
803 bool "Debug SG table operations"
804 depends on DEBUG_KERNEL
806 Enable this to turn on checks on scatter-gather tables. This can
807 help find problems with drivers that do not properly initialize
812 config DEBUG_NOTIFIERS
813 bool "Debug notifier call chains"
814 depends on DEBUG_KERNEL
816 Enable this to turn on sanity checking for notifier call chains.
817 This is most useful for kernel developers to make sure that
818 modules properly unregister themselves from notifier chains.
819 This is a relatively cheap check but if you care about maximum
822 config DEBUG_CREDENTIALS
823 bool "Debug credential management"
824 depends on DEBUG_KERNEL
826 Enable this to turn on some debug checking for credential
827 management. The additional code keeps track of the number of
828 pointers from task_structs to any given cred struct, and checks to
829 see that this number never exceeds the usage count of the cred
832 Furthermore, if SELinux is enabled, this also checks that the
833 security pointer in the cred struct is never seen to be invalid.
838 # Select this config option from the architecture Kconfig, if it
839 # it is preferred to always offer frame pointers as a config
840 # option on the architecture (regardless of KERNEL_DEBUG):
842 config ARCH_WANT_FRAME_POINTERS
847 bool "Compile the kernel with frame pointers"
848 depends on DEBUG_KERNEL && \
849 (CRIS || M68K || FRV || UML || \
850 AVR32 || SUPERH || BLACKFIN || MN10300) || \
851 ARCH_WANT_FRAME_POINTERS
852 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
854 If you say Y here the resulting kernel image will be slightly
855 larger and slower, but it gives very useful debugging information
856 in case of kernel bugs. (precise oopses/stacktraces/warnings)
858 config BOOT_PRINTK_DELAY
859 bool "Delay each boot printk message by N milliseconds"
860 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
862 This build option allows you to read kernel boot messages
863 by inserting a short delay after each one. The delay is
864 specified in milliseconds on the kernel command line,
865 using "boot_delay=N".
867 It is likely that you would also need to use "lpj=M" to preset
868 the "loops per jiffie" value.
869 See a previous boot log for the "lpj" value to use for your
870 system, and then set "lpj=M" before setting "boot_delay=N".
871 NOTE: Using this option may adversely affect SMP systems.
872 I.e., processors other than the first one may not boot up.
873 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
874 what it believes to be lockup conditions.
876 config RCU_TORTURE_TEST
877 tristate "torture tests for RCU"
878 depends on DEBUG_KERNEL
881 This option provides a kernel module that runs torture tests
882 on the RCU infrastructure. The kernel module may be built
883 after the fact on the running kernel to be tested, if desired.
885 Say Y here if you want RCU torture tests to be built into
887 Say M if you want the RCU torture tests to build as a module.
888 Say N if you are unsure.
890 config RCU_TORTURE_TEST_RUNNABLE
891 bool "torture tests for RCU runnable by default"
892 depends on RCU_TORTURE_TEST = y
895 This option provides a way to build the RCU torture tests
896 directly into the kernel without them starting up at boot
897 time. You can use /proc/sys/kernel/rcutorture_runnable
898 to manually override this setting. This /proc file is
899 available only when the RCU torture tests have been built
902 Say Y here if you want the RCU torture tests to start during
903 boot (you probably don't).
904 Say N here if you want the RCU torture tests to start only
905 after being manually enabled via /proc.
907 config RCU_CPU_STALL_TIMEOUT
908 int "RCU CPU stall timeout in seconds"
909 depends on TREE_RCU || TREE_PREEMPT_RCU
913 If a given RCU grace period extends more than the specified
914 number of seconds, a CPU stall warning is printed. If the
915 RCU grace period persists, additional CPU stall warnings are
916 printed at more widely spaced intervals.
918 config RCU_CPU_STALL_VERBOSE
919 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
920 depends on TREE_PREEMPT_RCU
923 This option causes RCU to printk detailed per-task information
924 for any tasks that are stalling the current RCU grace period.
926 Say N if you are unsure.
928 Say Y if you want to enable such checks.
930 config KPROBES_SANITY_TEST
931 bool "Kprobes sanity tests"
932 depends on DEBUG_KERNEL
936 This option provides for testing basic kprobes functionality on
937 boot. A sample kprobe, jprobe and kretprobe are inserted and
938 verified for functionality.
940 Say N if you are unsure.
942 config BACKTRACE_SELF_TEST
943 tristate "Self test for the backtrace code"
944 depends on DEBUG_KERNEL
947 This option provides a kernel module that can be used to test
948 the kernel stack backtrace code. This option is not useful
949 for distributions or general kernels, but only for kernel
950 developers working on architecture code.
952 Note that if you want to also test saved backtraces, you will
953 have to enable STACKTRACE as well.
955 Say N if you are unsure.
957 config DEBUG_BLOCK_EXT_DEVT
958 bool "Force extended block device numbers and spread them"
959 depends on DEBUG_KERNEL
963 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
964 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
965 YOU ARE DOING. Distros, please enable this and fix whatever
968 Conventionally, block device numbers are allocated from
969 predetermined contiguous area. However, extended block area
970 may introduce non-contiguous block device numbers. This
971 option forces most block device numbers to be allocated from
972 the extended space and spreads them to discover kernel or
973 userland code paths which assume predetermined contiguous
974 device number allocation.
976 Note that turning on this debug option shuffles all the
977 device numbers for all IDE and SCSI devices including libata
978 ones, so root partition specified using device number
979 directly (via rdev or root=MAJ:MIN) won't work anymore.
980 Textual device names (root=/dev/sdXn) will continue to work.
982 Say N if you are unsure.
984 config DEBUG_FORCE_WEAK_PER_CPU
985 bool "Force weak per-cpu definitions"
986 depends on DEBUG_KERNEL
988 s390 and alpha require percpu variables in modules to be
989 defined weak to work around addressing range issue which
990 puts the following two restrictions on percpu variable
993 1. percpu symbols must be unique whether static or not
994 2. percpu variables can't be defined inside a function
996 To ensure that generic code follows the above rules, this
997 option forces all percpu variables to be defined as weak.
999 config DEBUG_PER_CPU_MAPS
1000 bool "Debug access to per_cpu maps"
1001 depends on DEBUG_KERNEL
1004 Say Y to verify that the per_cpu map being accessed has
1005 been set up. This adds a fair amount of code to kernel memory
1006 and decreases performance.
1011 tristate "Linux Kernel Dump Test Tool Module"
1016 This module enables testing of the different dumping mechanisms by
1017 inducing system failures at predefined crash points.
1018 If you don't need it: say N
1019 Choose M here to compile this code as a module. The module will be
1022 Documentation on how to use the module can be found in
1023 Documentation/fault-injection/provoke-crashes.txt
1025 config CPU_NOTIFIER_ERROR_INJECT
1026 tristate "CPU notifier error injection module"
1027 depends on HOTPLUG_CPU && DEBUG_KERNEL
1029 This option provides a kernel module that can be used to test
1030 the error handling of the cpu notifiers
1032 To compile this code as a module, choose M here: the module will
1033 be called cpu-notifier-error-inject.
1037 config FAULT_INJECTION
1038 bool "Fault-injection framework"
1039 depends on DEBUG_KERNEL
1041 Provide fault-injection framework.
1042 For more details, see Documentation/fault-injection/.
1045 bool "Fault-injection capability for kmalloc"
1046 depends on FAULT_INJECTION
1047 depends on SLAB || SLUB
1049 Provide fault-injection capability for kmalloc.
1051 config FAIL_PAGE_ALLOC
1052 bool "Fault-injection capabilitiy for alloc_pages()"
1053 depends on FAULT_INJECTION
1055 Provide fault-injection capability for alloc_pages().
1057 config FAIL_MAKE_REQUEST
1058 bool "Fault-injection capability for disk IO"
1059 depends on FAULT_INJECTION && BLOCK
1061 Provide fault-injection capability for disk IO.
1063 config FAIL_IO_TIMEOUT
1064 bool "Fault-injection capability for faking disk interrupts"
1065 depends on FAULT_INJECTION && BLOCK
1067 Provide fault-injection capability on end IO handling. This
1068 will make the block layer "forget" an interrupt as configured,
1069 thus exercising the error handling.
1071 Only works with drivers that use the generic timeout handling,
1072 for others it wont do anything.
1074 config FAULT_INJECTION_DEBUG_FS
1075 bool "Debugfs entries for fault-injection capabilities"
1076 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1078 Enable configuration of fault-injection capabilities via debugfs.
1080 config FAULT_INJECTION_STACKTRACE_FILTER
1081 bool "stacktrace filter for fault-injection capabilities"
1082 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1085 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE
1087 Provide stacktrace filter for fault-injection capabilities
1090 bool "Latency measuring infrastructure"
1091 depends on HAVE_LATENCYTOP_SUPPORT
1092 depends on DEBUG_KERNEL
1093 depends on STACKTRACE_SUPPORT
1095 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE
1102 Enable this option if you want to use the LatencyTOP tool
1103 to find out which userspace is blocking on what kernel operations.
1105 config SYSCTL_SYSCALL_CHECK
1106 bool "Sysctl checks"
1109 sys_sysctl uses binary paths that have been found challenging
1110 to properly maintain and use. This enables checks that help
1111 you to keep things correct.
1113 source mm/Kconfig.debug
1114 source kernel/trace/Kconfig
1116 config PROVIDE_OHCI1394_DMA_INIT
1117 bool "Remote debugging over FireWire early on boot"
1118 depends on PCI && X86
1120 If you want to debug problems which hang or crash the kernel early
1121 on boot and the crashing machine has a FireWire port, you can use
1122 this feature to remotely access the memory of the crashed machine
1123 over FireWire. This employs remote DMA as part of the OHCI1394
1124 specification which is now the standard for FireWire controllers.
1126 With remote DMA, you can monitor the printk buffer remotely using
1127 firescope and access all memory below 4GB using fireproxy from gdb.
1128 Even controlling a kernel debugger is possible using remote DMA.
1132 If ohci1394_dma=early is used as boot parameter, it will initialize
1133 all OHCI1394 controllers which are found in the PCI config space.
1135 As all changes to the FireWire bus such as enabling and disabling
1136 devices cause a bus reset and thereby disable remote DMA for all
1137 devices, be sure to have the cable plugged and FireWire enabled on
1138 the debugging host before booting the debug target for debugging.
1140 This code (~1k) is freed after boot. By then, the firewire stack
1141 in charge of the OHCI-1394 controllers should be used instead.
1143 See Documentation/debugging-via-ohci1394.txt for more information.
1145 config FIREWIRE_OHCI_REMOTE_DMA
1146 bool "Remote debugging over FireWire with firewire-ohci"
1147 depends on FIREWIRE_OHCI
1149 This option lets you use the FireWire bus for remote debugging
1150 with help of the firewire-ohci driver. It enables unfiltered
1151 remote DMA in firewire-ohci.
1152 See Documentation/debugging-via-ohci1394.txt for more information.
1157 bool "Build targets in Documentation/ tree"
1158 depends on HEADERS_CHECK
1160 This option attempts to build objects from the source files in the
1161 kernel Documentation/ tree.
1163 Say N if you are unsure.
1165 config DYNAMIC_DEBUG
1166 bool "Enable dynamic printk() support"
1172 Compiles debug level messages into the kernel, which would not
1173 otherwise be available at runtime. These messages can then be
1174 enabled/disabled based on various levels of scope - per source file,
1175 function, module, format string, and line number. This mechanism
1176 implicitly enables all pr_debug() and dev_dbg() calls. The impact of
1177 this compile option is a larger kernel text size of about 2%.
1181 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
1182 which is contained in the 'debugfs' filesystem. Thus, the debugfs
1183 filesystem must first be mounted before making use of this feature.
1184 We refer the control file as: <debugfs>/dynamic_debug/control. This
1185 file contains a list of the debug statements that can be enabled. The
1186 format for each line of the file is:
1188 filename:lineno [module]function flags format
1190 filename : source file of the debug statement
1191 lineno : line number of the debug statement
1192 module : module that contains the debug statement
1193 function : function that contains the debug statement
1194 flags : 'p' means the line is turned 'on' for printing
1195 format : the format used for the debug statement
1199 nullarbor:~ # cat <debugfs>/dynamic_debug/control
1200 # filename:lineno [module]function flags format
1201 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012"
1202 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012"
1203 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012"
1207 // enable the message at line 1603 of file svcsock.c
1208 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
1209 <debugfs>/dynamic_debug/control
1211 // enable all the messages in file svcsock.c
1212 nullarbor:~ # echo -n 'file svcsock.c +p' >
1213 <debugfs>/dynamic_debug/control
1215 // enable all the messages in the NFS server module
1216 nullarbor:~ # echo -n 'module nfsd +p' >
1217 <debugfs>/dynamic_debug/control
1219 // enable all 12 messages in the function svc_process()
1220 nullarbor:~ # echo -n 'func svc_process +p' >
1221 <debugfs>/dynamic_debug/control
1223 // disable all 12 messages in the function svc_process()
1224 nullarbor:~ # echo -n 'func svc_process -p' >
1225 <debugfs>/dynamic_debug/control
1227 See Documentation/dynamic-debug-howto.txt for additional information.
1229 config DMA_API_DEBUG
1230 bool "Enable debugging of DMA-API usage"
1231 depends on HAVE_DMA_API_DEBUG
1233 Enable this option to debug the use of the DMA API by device drivers.
1234 With this option you will be able to detect common bugs in device
1235 drivers like double-freeing of DMA mappings or freeing mappings that
1236 were never allocated.
1237 This option causes a performance degredation. Use only if you want
1238 to debug device drivers. If unsure, say N.
1240 config ATOMIC64_SELFTEST
1241 bool "Perform an atomic64_t self-test at boot"
1243 Enable this option to test the atomic64_t functions at boot.
1247 config ASYNC_RAID6_TEST
1248 tristate "Self test for hardware accelerated raid6 recovery"
1249 depends on ASYNC_RAID6_RECOV
1252 This is a one-shot self test that permutes through the
1253 recovery of all the possible two disk failure scenarios for a
1254 N-disk array. Recovery is performed with the asynchronous
1255 raid6 recovery routines, and will optionally use an offload
1256 engine if one is available.
1260 source "samples/Kconfig"
1262 source "lib/Kconfig.kgdb"
1264 source "lib/Kconfig.kmemcheck"
1267 tristate "Test kstrto*() family of functions at runtime"