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1 menu "printk and dmesg options"
3 config PRINTK_TIME
4 bool "Show timing information on printks"
5 depends on PRINTK
6 help
7 Selecting this option causes time stamps of the printk()
8 messages to be added to the output of the syslog() system
9 call and at the console.
11 The timestamp is always recorded internally, and exported
12 to /dev/kmsg. This flag just specifies if the timestamp should
13 be included, not that the timestamp is recorded.
15 The behavior is also controlled by the kernel command line
16 parameter printk.time=1. See Documentation/kernel-parameters.txt
18 config MESSAGE_LOGLEVEL_DEFAULT
19 int "Default message log level (1-7)"
20 range 1 7
21 default "4"
22 help
23 Default log level for printk statements with no specified priority.
25 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
26 that are auditing their logs closely may want to set it to a lower
27 priority.
29 config BOOT_PRINTK_DELAY
30 bool "Delay each boot printk message by N milliseconds"
31 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
32 help
33 This build option allows you to read kernel boot messages
34 by inserting a short delay after each one. The delay is
35 specified in milliseconds on the kernel command line,
36 using "boot_delay=N".
38 It is likely that you would also need to use "lpj=M" to preset
39 the "loops per jiffie" value.
40 See a previous boot log for the "lpj" value to use for your
41 system, and then set "lpj=M" before setting "boot_delay=N".
42 NOTE: Using this option may adversely affect SMP systems.
43 I.e., processors other than the first one may not boot up.
44 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
45 what it believes to be lockup conditions.
47 config DYNAMIC_DEBUG
48 bool "Enable dynamic printk() support"
49 default n
50 depends on PRINTK
51 depends on DEBUG_FS
52 help
54 Compiles debug level messages into the kernel, which would not
55 otherwise be available at runtime. These messages can then be
56 enabled/disabled based on various levels of scope - per source file,
57 function, module, format string, and line number. This mechanism
58 implicitly compiles in all pr_debug() and dev_dbg() calls, which
59 enlarges the kernel text size by about 2%.
61 If a source file is compiled with DEBUG flag set, any
62 pr_debug() calls in it are enabled by default, but can be
63 disabled at runtime as below. Note that DEBUG flag is
64 turned on by many CONFIG_*DEBUG* options.
66 Usage:
68 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
69 which is contained in the 'debugfs' filesystem. Thus, the debugfs
70 filesystem must first be mounted before making use of this feature.
71 We refer the control file as: <debugfs>/dynamic_debug/control. This
72 file contains a list of the debug statements that can be enabled. The
73 format for each line of the file is:
75 filename:lineno [module]function flags format
77 filename : source file of the debug statement
78 lineno : line number of the debug statement
79 module : module that contains the debug statement
80 function : function that contains the debug statement
81 flags : '=p' means the line is turned 'on' for printing
82 format : the format used for the debug statement
84 From a live system:
86 nullarbor:~ # cat <debugfs>/dynamic_debug/control
87 # filename:lineno [module]function flags format
88 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
89 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
90 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
92 Example usage:
94 // enable the message at line 1603 of file svcsock.c
95 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
96 <debugfs>/dynamic_debug/control
98 // enable all the messages in file svcsock.c
99 nullarbor:~ # echo -n 'file svcsock.c +p' >
100 <debugfs>/dynamic_debug/control
102 // enable all the messages in the NFS server module
103 nullarbor:~ # echo -n 'module nfsd +p' >
104 <debugfs>/dynamic_debug/control
106 // enable all 12 messages in the function svc_process()
107 nullarbor:~ # echo -n 'func svc_process +p' >
108 <debugfs>/dynamic_debug/control
110 // disable all 12 messages in the function svc_process()
111 nullarbor:~ # echo -n 'func svc_process -p' >
112 <debugfs>/dynamic_debug/control
114 See Documentation/dynamic-debug-howto.txt for additional information.
116 endmenu # "printk and dmesg options"
118 menu "Compile-time checks and compiler options"
120 config DEBUG_INFO
121 bool "Compile the kernel with debug info"
122 depends on DEBUG_KERNEL && !COMPILE_TEST
123 help
124 If you say Y here the resulting kernel image will include
125 debugging info resulting in a larger kernel image.
126 This adds debug symbols to the kernel and modules (gcc -g), and
127 is needed if you intend to use kernel crashdump or binary object
128 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
129 Say Y here only if you plan to debug the kernel.
131 If unsure, say N.
133 config DEBUG_INFO_REDUCED
134 bool "Reduce debugging information"
135 depends on DEBUG_INFO
136 help
137 If you say Y here gcc is instructed to generate less debugging
138 information for structure types. This means that tools that
139 need full debugging information (like kgdb or systemtap) won't
140 be happy. But if you merely need debugging information to
141 resolve line numbers there is no loss. Advantage is that
142 build directory object sizes shrink dramatically over a full
143 DEBUG_INFO build and compile times are reduced too.
144 Only works with newer gcc versions.
146 config DEBUG_INFO_SPLIT
147 bool "Produce split debuginfo in .dwo files"
148 depends on DEBUG_INFO
149 help
150 Generate debug info into separate .dwo files. This significantly
151 reduces the build directory size for builds with DEBUG_INFO,
152 because it stores the information only once on disk in .dwo
153 files instead of multiple times in object files and executables.
154 In addition the debug information is also compressed.
156 Requires recent gcc (4.7+) and recent gdb/binutils.
157 Any tool that packages or reads debug information would need
158 to know about the .dwo files and include them.
159 Incompatible with older versions of ccache.
161 config DEBUG_INFO_DWARF4
162 bool "Generate dwarf4 debuginfo"
163 depends on DEBUG_INFO
164 help
165 Generate dwarf4 debug info. This requires recent versions
166 of gcc and gdb. It makes the debug information larger.
167 But it significantly improves the success of resolving
168 variables in gdb on optimized code.
170 config GDB_SCRIPTS
171 bool "Provide GDB scripts for kernel debugging"
172 depends on DEBUG_INFO
173 help
174 This creates the required links to GDB helper scripts in the
175 build directory. If you load vmlinux into gdb, the helper
176 scripts will be automatically imported by gdb as well, and
177 additional functions are available to analyze a Linux kernel
178 instance. See Documentation/gdb-kernel-debugging.txt for further
179 details.
181 config ENABLE_WARN_DEPRECATED
182 bool "Enable __deprecated logic"
183 default y
184 help
185 Enable the __deprecated logic in the kernel build.
186 Disable this to suppress the "warning: 'foo' is deprecated
187 (declared at kernel/power/somefile.c:1234)" messages.
189 config ENABLE_MUST_CHECK
190 bool "Enable __must_check logic"
191 default y
192 help
193 Enable the __must_check logic in the kernel build. Disable this to
194 suppress the "warning: ignoring return value of 'foo', declared with
195 attribute warn_unused_result" messages.
197 config FRAME_WARN
198 int "Warn for stack frames larger than (needs gcc 4.4)"
199 range 0 8192
200 default 1024 if !64BIT
201 default 2048 if 64BIT
202 help
203 Tell gcc to warn at build time for stack frames larger than this.
204 Setting this too low will cause a lot of warnings.
205 Setting it to 0 disables the warning.
206 Requires gcc 4.4
208 config STRIP_ASM_SYMS
209 bool "Strip assembler-generated symbols during link"
210 default n
211 help
212 Strip internal assembler-generated symbols during a link (symbols
213 that look like '.Lxxx') so they don't pollute the output of
214 get_wchan() and suchlike.
216 config READABLE_ASM
217 bool "Generate readable assembler code"
218 depends on DEBUG_KERNEL
219 help
220 Disable some compiler optimizations that tend to generate human unreadable
221 assembler output. This may make the kernel slightly slower, but it helps
222 to keep kernel developers who have to stare a lot at assembler listings
223 sane.
225 config UNUSED_SYMBOLS
226 bool "Enable unused/obsolete exported symbols"
227 default y if X86
228 help
229 Unused but exported symbols make the kernel needlessly bigger. For
230 that reason most of these unused exports will soon be removed. This
231 option is provided temporarily to provide a transition period in case
232 some external kernel module needs one of these symbols anyway. If you
233 encounter such a case in your module, consider if you are actually
234 using the right API. (rationale: since nobody in the kernel is using
235 this in a module, there is a pretty good chance it's actually the
236 wrong interface to use). If you really need the symbol, please send a
237 mail to the linux kernel mailing list mentioning the symbol and why
238 you really need it, and what the merge plan to the mainline kernel for
239 your module is.
241 config PAGE_OWNER
242 bool "Track page owner"
243 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
244 select DEBUG_FS
245 select STACKTRACE
246 select PAGE_EXTENSION
247 help
248 This keeps track of what call chain is the owner of a page, may
249 help to find bare alloc_page(s) leaks. Even if you include this
250 feature on your build, it is disabled in default. You should pass
251 "page_owner=on" to boot parameter in order to enable it. Eats
252 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
253 for user-space helper.
255 If unsure, say N.
257 config DEBUG_FS
258 bool "Debug Filesystem"
259 help
260 debugfs is a virtual file system that kernel developers use to put
261 debugging files into. Enable this option to be able to read and
262 write to these files.
264 For detailed documentation on the debugfs API, see
265 Documentation/DocBook/filesystems.
267 If unsure, say N.
269 config HEADERS_CHECK
270 bool "Run 'make headers_check' when building vmlinux"
271 depends on !UML
272 help
273 This option will extract the user-visible kernel headers whenever
274 building the kernel, and will run basic sanity checks on them to
275 ensure that exported files do not attempt to include files which
276 were not exported, etc.
278 If you're making modifications to header files which are
279 relevant for userspace, say 'Y', and check the headers
280 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
281 your build tree), to make sure they're suitable.
283 config DEBUG_SECTION_MISMATCH
284 bool "Enable full Section mismatch analysis"
285 help
286 The section mismatch analysis checks if there are illegal
287 references from one section to another section.
288 During linktime or runtime, some sections are dropped;
289 any use of code/data previously in these sections would
290 most likely result in an oops.
291 In the code, functions and variables are annotated with
292 __init,, etc. (see the full list in include/linux/init.h),
293 which results in the code/data being placed in specific sections.
294 The section mismatch analysis is always performed after a full
295 kernel build, and enabling this option causes the following
296 additional steps to occur:
297 - Add the option -fno-inline-functions-called-once to gcc commands.
298 When inlining a function annotated with __init in a non-init
299 function, we would lose the section information and thus
300 the analysis would not catch the illegal reference.
301 This option tells gcc to inline less (but it does result in
302 a larger kernel).
303 - Run the section mismatch analysis for each module/built-in.o file.
304 When we run the section mismatch analysis on vmlinux.o, we
305 lose valueble information about where the mismatch was
306 introduced.
307 Running the analysis for each module/built-in.o file
308 tells where the mismatch happens much closer to the
309 source. The drawback is that the same mismatch is
310 reported at least twice.
311 - Enable verbose reporting from modpost in order to help resolve
312 the section mismatches that are reported.
314 #
315 # Select this config option from the architecture Kconfig, if it
316 # is preferred to always offer frame pointers as a config
317 # option on the architecture (regardless of KERNEL_DEBUG):
318 #
319 config ARCH_WANT_FRAME_POINTERS
320 bool
321 help
323 config FRAME_POINTER
324 bool "Compile the kernel with frame pointers"
325 depends on DEBUG_KERNEL && \
326 (CRIS || M68K || FRV || UML || \
327 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \
328 ARCH_WANT_FRAME_POINTERS
329 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
330 help
331 If you say Y here the resulting kernel image will be slightly
332 larger and slower, but it gives very useful debugging information
333 in case of kernel bugs. (precise oopses/stacktraces/warnings)
335 config DEBUG_FORCE_WEAK_PER_CPU
336 bool "Force weak per-cpu definitions"
337 depends on DEBUG_KERNEL
338 help
339 s390 and alpha require percpu variables in modules to be
340 defined weak to work around addressing range issue which
341 puts the following two restrictions on percpu variable
342 definitions.
344 1. percpu symbols must be unique whether static or not
345 2. percpu variables can't be defined inside a function
347 To ensure that generic code follows the above rules, this
348 option forces all percpu variables to be defined as weak.
350 endmenu # "Compiler options"
352 config MAGIC_SYSRQ
353 bool "Magic SysRq key"
354 depends on !UML
355 help
356 If you say Y here, you will have some control over the system even
357 if the system crashes for example during kernel debugging (e.g., you
358 will be able to flush the buffer cache to disk, reboot the system
359 immediately or dump some status information). This is accomplished
360 by pressing various keys while holding SysRq (Alt+PrintScreen). It
361 also works on a serial console (on PC hardware at least), if you
362 send a BREAK and then within 5 seconds a command keypress. The
363 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
364 unless you really know what this hack does.
366 config MAGIC_SYSRQ_DEFAULT_ENABLE
367 hex "Enable magic SysRq key functions by default"
368 depends on MAGIC_SYSRQ
369 default 0x1
370 help
371 Specifies which SysRq key functions are enabled by default.
372 This may be set to 1 or 0 to enable or disable them all, or
373 to a bitmask as described in Documentation/sysrq.txt.
375 config DEBUG_KERNEL
376 bool "Kernel debugging"
377 help
378 Say Y here if you are developing drivers or trying to debug and
379 identify kernel problems.
381 menu "Memory Debugging"
383 source mm/Kconfig.debug
385 config DEBUG_OBJECTS
386 bool "Debug object operations"
387 depends on DEBUG_KERNEL
388 help
389 If you say Y here, additional code will be inserted into the
390 kernel to track the life time of various objects and validate
391 the operations on those objects.
393 config DEBUG_OBJECTS_SELFTEST
394 bool "Debug objects selftest"
395 depends on DEBUG_OBJECTS
396 help
397 This enables the selftest of the object debug code.
399 config DEBUG_OBJECTS_FREE
400 bool "Debug objects in freed memory"
401 depends on DEBUG_OBJECTS
402 help
403 This enables checks whether a k/v free operation frees an area
404 which contains an object which has not been deactivated
405 properly. This can make kmalloc/kfree-intensive workloads
406 much slower.
408 config DEBUG_OBJECTS_TIMERS
409 bool "Debug timer objects"
410 depends on DEBUG_OBJECTS
411 help
412 If you say Y here, additional code will be inserted into the
413 timer routines to track the life time of timer objects and
414 validate the timer operations.
416 config DEBUG_OBJECTS_WORK
417 bool "Debug work objects"
418 depends on DEBUG_OBJECTS
419 help
420 If you say Y here, additional code will be inserted into the
421 work queue routines to track the life time of work objects and
422 validate the work operations.
424 config DEBUG_OBJECTS_RCU_HEAD
425 bool "Debug RCU callbacks objects"
426 depends on DEBUG_OBJECTS
427 help
428 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
430 config DEBUG_OBJECTS_PERCPU_COUNTER
431 bool "Debug percpu counter objects"
432 depends on DEBUG_OBJECTS
433 help
434 If you say Y here, additional code will be inserted into the
435 percpu counter routines to track the life time of percpu counter
436 objects and validate the percpu counter operations.
438 config DEBUG_OBJECTS_ENABLE_DEFAULT
439 int "debug_objects bootup default value (0-1)"
440 range 0 1
441 default "1"
442 depends on DEBUG_OBJECTS
443 help
444 Debug objects boot parameter default value
446 config DEBUG_SLAB
447 bool "Debug slab memory allocations"
448 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
449 help
450 Say Y here to have the kernel do limited verification on memory
451 allocation as well as poisoning memory on free to catch use of freed
452 memory. This can make kmalloc/kfree-intensive workloads much slower.
454 config DEBUG_SLAB_LEAK
455 bool "Memory leak debugging"
456 depends on DEBUG_SLAB
458 config SLUB_DEBUG_ON
459 bool "SLUB debugging on by default"
460 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
461 default n
462 help
463 Boot with debugging on by default. SLUB boots by default with
464 the runtime debug capabilities switched off. Enabling this is
465 equivalent to specifying the "slub_debug" parameter on boot.
466 There is no support for more fine grained debug control like
467 possible with slub_debug=xxx. SLUB debugging may be switched
468 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
469 "slub_debug=-".
471 config SLUB_STATS
472 default n
473 bool "Enable SLUB performance statistics"
474 depends on SLUB && SYSFS
475 help
476 SLUB statistics are useful to debug SLUBs allocation behavior in
477 order find ways to optimize the allocator. This should never be
478 enabled for production use since keeping statistics slows down
479 the allocator by a few percentage points. The slabinfo command
480 supports the determination of the most active slabs to figure
481 out which slabs are relevant to a particular load.
482 Try running: slabinfo -DA
484 config HAVE_DEBUG_KMEMLEAK
485 bool
487 config DEBUG_KMEMLEAK
488 bool "Kernel memory leak detector"
489 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
490 select DEBUG_FS
491 select STACKTRACE if STACKTRACE_SUPPORT
492 select KALLSYMS
493 select CRC32
494 help
495 Say Y here if you want to enable the memory leak
496 detector. The memory allocation/freeing is traced in a way
497 similar to the Boehm's conservative garbage collector, the
498 difference being that the orphan objects are not freed but
499 only shown in /sys/kernel/debug/kmemleak. Enabling this
500 feature will introduce an overhead to memory
501 allocations. See Documentation/kmemleak.txt for more
502 details.
504 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
505 of finding leaks due to the slab objects poisoning.
507 In order to access the kmemleak file, debugfs needs to be
508 mounted (usually at /sys/kernel/debug).
510 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
511 int "Maximum kmemleak early log entries"
512 depends on DEBUG_KMEMLEAK
513 range 200 40000
514 default 400
515 help
516 Kmemleak must track all the memory allocations to avoid
517 reporting false positives. Since memory may be allocated or
518 freed before kmemleak is initialised, an early log buffer is
519 used to store these actions. If kmemleak reports "early log
520 buffer exceeded", please increase this value.
522 config DEBUG_KMEMLEAK_TEST
523 tristate "Simple test for the kernel memory leak detector"
524 depends on DEBUG_KMEMLEAK && m
525 help
526 This option enables a module that explicitly leaks memory.
528 If unsure, say N.
530 config DEBUG_KMEMLEAK_DEFAULT_OFF
531 bool "Default kmemleak to off"
532 depends on DEBUG_KMEMLEAK
533 help
534 Say Y here to disable kmemleak by default. It can then be enabled
535 on the command line via kmemleak=on.
537 config DEBUG_STACK_USAGE
538 bool "Stack utilization instrumentation"
539 depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAG
540 help
541 Enables the display of the minimum amount of free stack which each
542 task has ever had available in the sysrq-T and sysrq-P debug output.
544 This option will slow down process creation somewhat.
546 config DEBUG_VM
547 bool "Debug VM"
548 depends on DEBUG_KERNEL
549 help
550 Enable this to turn on extended checks in the virtual-memory system
551 that may impact performance.
553 If unsure, say N.
555 config DEBUG_VM_VMACACHE
556 bool "Debug VMA caching"
557 depends on DEBUG_VM
558 help
559 Enable this to turn on VMA caching debug information. Doing so
560 can cause significant overhead, so only enable it in non-production
561 environments.
563 If unsure, say N.
565 config DEBUG_VM_RB
566 bool "Debug VM red-black trees"
567 depends on DEBUG_VM
568 help
569 Enable VM red-black tree debugging information and extra validations.
571 If unsure, say N.
573 config DEBUG_VIRTUAL
574 bool "Debug VM translations"
575 depends on DEBUG_KERNEL && X86
576 help
577 Enable some costly sanity checks in virtual to page code. This can
578 catch mistakes with virt_to_page() and friends.
580 If unsure, say N.
582 config DEBUG_NOMMU_REGIONS
583 bool "Debug the global anon/private NOMMU mapping region tree"
584 depends on DEBUG_KERNEL && !MMU
585 help
586 This option causes the global tree of anonymous and private mapping
587 regions to be regularly checked for invalid topology.
589 config DEBUG_MEMORY_INIT
590 bool "Debug memory initialisation" if EXPERT
591 default !EXPERT
592 help
593 Enable this for additional checks during memory initialisation.
594 The sanity checks verify aspects of the VM such as the memory model
595 and other information provided by the architecture. Verbose
596 information will be printed at KERN_DEBUG loglevel depending
597 on the mminit_loglevel= command-line option.
599 If unsure, say Y
601 config MEMORY_NOTIFIER_ERROR_INJECT
602 tristate "Memory hotplug notifier error injection module"
603 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
604 help
605 This option provides the ability to inject artificial errors to
606 memory hotplug notifier chain callbacks. It is controlled through
607 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
609 If the notifier call chain should be failed with some events
610 notified, write the error code to "actions/<notifier event>/error".
612 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
614 # cd /sys/kernel/debug/notifier-error-inject/memory
615 # echo -12 > actions/MEM_GOING_OFFLINE/error
616 # echo offline > /sys/devices/system/memory/memoryXXX/state
617 bash: echo: write error: Cannot allocate memory
619 To compile this code as a module, choose M here: the module will
620 be called memory-notifier-error-inject.
622 If unsure, say N.
624 config DEBUG_PER_CPU_MAPS
625 bool "Debug access to per_cpu maps"
626 depends on DEBUG_KERNEL
627 depends on SMP
628 help
629 Say Y to verify that the per_cpu map being accessed has
630 been set up. This adds a fair amount of code to kernel memory
631 and decreases performance.
633 Say N if unsure.
635 config DEBUG_HIGHMEM
636 bool "Highmem debugging"
637 depends on DEBUG_KERNEL && HIGHMEM
638 help
639 This option enables additional error checking for high memory
640 systems. Disable for production systems.
642 config HAVE_DEBUG_STACKOVERFLOW
643 bool
645 config DEBUG_STACKOVERFLOW
646 bool "Check for stack overflows"
647 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
648 ---help---
649 Say Y here if you want to check for overflows of kernel, IRQ
650 and exception stacks (if your architecture uses them). This
651 option will show detailed messages if free stack space drops
652 below a certain limit.
654 These kinds of bugs usually occur when call-chains in the
655 kernel get too deep, especially when interrupts are
656 involved.
658 Use this in cases where you see apparently random memory
659 corruption, especially if it appears in 'struct thread_info'
661 If in doubt, say "N".
663 source "lib/Kconfig.kmemcheck"
665 source "lib/Kconfig.kasan"
667 endmenu # "Memory Debugging"
669 config DEBUG_SHIRQ
670 bool "Debug shared IRQ handlers"
671 depends on DEBUG_KERNEL
672 help
673 Enable this to generate a spurious interrupt as soon as a shared
674 interrupt handler is registered, and just before one is deregistered.
675 Drivers ought to be able to handle interrupts coming in at those
676 points; some don't and need to be caught.
678 menu "Debug Lockups and Hangs"
680 config LOCKUP_DETECTOR
681 bool "Detect Hard and Soft Lockups"
682 depends on DEBUG_KERNEL && !S390
683 help
684 Say Y here to enable the kernel to act as a watchdog to detect
685 hard and soft lockups.
687 Softlockups are bugs that cause the kernel to loop in kernel
688 mode for more than 20 seconds, without giving other tasks a
689 chance to run. The current stack trace is displayed upon
690 detection and the system will stay locked up.
692 Hardlockups are bugs that cause the CPU to loop in kernel mode
693 for more than 10 seconds, without letting other interrupts have a
694 chance to run. The current stack trace is displayed upon detection
695 and the system will stay locked up.
697 The overhead should be minimal. A periodic hrtimer runs to
698 generate interrupts and kick the watchdog task every 4 seconds.
699 An NMI is generated every 10 seconds or so to check for hardlockups.
701 The frequency of hrtimer and NMI events and the soft and hard lockup
702 thresholds can be controlled through the sysctl watchdog_thresh.
704 config HARDLOCKUP_DETECTOR
705 def_bool y
706 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
707 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
709 config BOOTPARAM_HARDLOCKUP_PANIC
710 bool "Panic (Reboot) On Hard Lockups"
711 depends on HARDLOCKUP_DETECTOR
712 help
713 Say Y here to enable the kernel to panic on "hard lockups",
714 which are bugs that cause the kernel to loop in kernel
715 mode with interrupts disabled for more than 10 seconds (configurable
716 using the watchdog_thresh sysctl).
718 Say N if unsure.
720 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
721 int
722 depends on HARDLOCKUP_DETECTOR
723 range 0 1
724 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
725 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
727 config BOOTPARAM_SOFTLOCKUP_PANIC
728 bool "Panic (Reboot) On Soft Lockups"
729 depends on LOCKUP_DETECTOR
730 help
731 Say Y here to enable the kernel to panic on "soft lockups",
732 which are bugs that cause the kernel to loop in kernel
733 mode for more than 20 seconds (configurable using the watchdog_thresh
734 sysctl), without giving other tasks a chance to run.
736 The panic can be used in combination with panic_timeout,
737 to cause the system to reboot automatically after a
738 lockup has been detected. This feature is useful for
739 high-availability systems that have uptime guarantees and
740 where a lockup must be resolved ASAP.
742 Say N if unsure.
744 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
745 int
746 depends on LOCKUP_DETECTOR
747 range 0 1
748 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
749 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
751 config DETECT_HUNG_TASK
752 bool "Detect Hung Tasks"
753 depends on DEBUG_KERNEL
754 default LOCKUP_DETECTOR
755 help
756 Say Y here to enable the kernel to detect "hung tasks",
757 which are bugs that cause the task to be stuck in
758 uninterruptible "D" state indefinitiley.
760 When a hung task is detected, the kernel will print the
761 current stack trace (which you should report), but the
762 task will stay in uninterruptible state. If lockdep is
763 enabled then all held locks will also be reported. This
764 feature has negligible overhead.
766 config DEFAULT_HUNG_TASK_TIMEOUT
767 int "Default timeout for hung task detection (in seconds)"
768 depends on DETECT_HUNG_TASK
769 default 120
770 help
771 This option controls the default timeout (in seconds) used
772 to determine when a task has become non-responsive and should
773 be considered hung.
775 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
776 sysctl or by writing a value to
777 /proc/sys/kernel/hung_task_timeout_secs.
779 A timeout of 0 disables the check. The default is two minutes.
780 Keeping the default should be fine in most cases.
782 config BOOTPARAM_HUNG_TASK_PANIC
783 bool "Panic (Reboot) On Hung Tasks"
784 depends on DETECT_HUNG_TASK
785 help
786 Say Y here to enable the kernel to panic on "hung tasks",
787 which are bugs that cause the kernel to leave a task stuck
788 in uninterruptible "D" state.
790 The panic can be used in combination with panic_timeout,
791 to cause the system to reboot automatically after a
792 hung task has been detected. This feature is useful for
793 high-availability systems that have uptime guarantees and
794 where a hung tasks must be resolved ASAP.
796 Say N if unsure.
798 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
799 int
800 depends on DETECT_HUNG_TASK
801 range 0 1
802 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
803 default 1 if BOOTPARAM_HUNG_TASK_PANIC
805 endmenu # "Debug lockups and hangs"
807 config PANIC_ON_OOPS
808 bool "Panic on Oops"
809 help
810 Say Y here to enable the kernel to panic when it oopses. This
811 has the same effect as setting oops=panic on the kernel command
812 line.
814 This feature is useful to ensure that the kernel does not do
815 anything erroneous after an oops which could result in data
816 corruption or other issues.
818 Say N if unsure.
820 config PANIC_ON_OOPS_VALUE
821 int
822 range 0 1
823 default 0 if !PANIC_ON_OOPS
824 default 1 if PANIC_ON_OOPS
826 config PANIC_TIMEOUT
827 int "panic timeout"
828 default 0
829 help
830 Set the timeout value (in seconds) until a reboot occurs when the
831 the kernel panics. If n = 0, then we wait forever. A timeout
832 value n > 0 will wait n seconds before rebooting, while a timeout
833 value n < 0 will reboot immediately.
835 config SCHED_DEBUG
836 bool "Collect scheduler debugging info"
837 depends on DEBUG_KERNEL && PROC_FS
838 default y
839 help
840 If you say Y here, the /proc/sched_debug file will be provided
841 that can help debug the scheduler. The runtime overhead of this
842 option is minimal.
844 config SCHEDSTATS
845 bool "Collect scheduler statistics"
846 depends on DEBUG_KERNEL && PROC_FS
847 help
848 If you say Y here, additional code will be inserted into the
849 scheduler and related routines to collect statistics about
850 scheduler behavior and provide them in /proc/schedstat. These
851 stats may be useful for both tuning and debugging the scheduler
852 If you aren't debugging the scheduler or trying to tune a specific
853 application, you can say N to avoid the very slight overhead
854 this adds.
856 config SCHED_STACK_END_CHECK
857 bool "Detect stack corruption on calls to schedule()"
858 depends on DEBUG_KERNEL
859 default n
860 help
861 This option checks for a stack overrun on calls to schedule().
862 If the stack end location is found to be over written always panic as
863 the content of the corrupted region can no longer be trusted.
864 This is to ensure no erroneous behaviour occurs which could result in
865 data corruption or a sporadic crash at a later stage once the region
866 is examined. The runtime overhead introduced is minimal.
868 config DEBUG_TIMEKEEPING
869 bool "Enable extra timekeeping sanity checking"
870 help
871 This option will enable additional timekeeping sanity checks
872 which may be helpful when diagnosing issues where timekeeping
873 problems are suspected.
875 This may include checks in the timekeeping hotpaths, so this
876 option may have a (very small) performance impact to some
877 workloads.
879 If unsure, say N.
881 config TIMER_STATS
882 bool "Collect kernel timers statistics"
883 depends on DEBUG_KERNEL && PROC_FS
884 help
885 If you say Y here, additional code will be inserted into the
886 timer routines to collect statistics about kernel timers being
887 reprogrammed. The statistics can be read from /proc/timer_stats.
888 The statistics collection is started by writing 1 to /proc/timer_stats,
889 writing 0 stops it. This feature is useful to collect information
890 about timer usage patterns in kernel and userspace. This feature
891 is lightweight if enabled in the kernel config but not activated
892 (it defaults to deactivated on bootup and will only be activated
893 if some application like powertop activates it explicitly).
895 config DEBUG_PREEMPT
896 bool "Debug preemptible kernel"
897 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
898 default y
899 help
900 If you say Y here then the kernel will use a debug variant of the
901 commonly used smp_processor_id() function and will print warnings
902 if kernel code uses it in a preemption-unsafe way. Also, the kernel
903 will detect preemption count underflows.
905 menu "Lock Debugging (spinlocks, mutexes, etc...)"
907 config DEBUG_RT_MUTEXES
908 bool "RT Mutex debugging, deadlock detection"
909 depends on DEBUG_KERNEL && RT_MUTEXES
910 help
911 This allows rt mutex semantics violations and rt mutex related
912 deadlocks (lockups) to be detected and reported automatically.
914 config RT_MUTEX_TESTER
915 bool "Built-in scriptable tester for rt-mutexes"
916 depends on DEBUG_KERNEL && RT_MUTEXES && BROKEN
917 help
918 This option enables a rt-mutex tester.
920 config DEBUG_SPINLOCK
921 bool "Spinlock and rw-lock debugging: basic checks"
922 depends on DEBUG_KERNEL
923 select UNINLINE_SPIN_UNLOCK
924 help
925 Say Y here and build SMP to catch missing spinlock initialization
926 and certain other kinds of spinlock errors commonly made. This is
927 best used in conjunction with the NMI watchdog so that spinlock
928 deadlocks are also debuggable.
930 config DEBUG_MUTEXES
931 bool "Mutex debugging: basic checks"
932 depends on DEBUG_KERNEL
933 help
934 This feature allows mutex semantics violations to be detected and
935 reported.
937 config DEBUG_WW_MUTEX_SLOWPATH
938 bool "Wait/wound mutex debugging: Slowpath testing"
939 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
940 select DEBUG_LOCK_ALLOC
941 select DEBUG_SPINLOCK
942 select DEBUG_MUTEXES
943 help
944 This feature enables slowpath testing for w/w mutex users by
945 injecting additional -EDEADLK wound/backoff cases. Together with
946 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
947 will test all possible w/w mutex interface abuse with the
948 exception of simply not acquiring all the required locks.
949 Note that this feature can introduce significant overhead, so
950 it really should not be enabled in a production or distro kernel,
951 even a debug kernel. If you are a driver writer, enable it. If
952 you are a distro, do not.
954 config DEBUG_LOCK_ALLOC
955 bool "Lock debugging: detect incorrect freeing of live locks"
956 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
957 select DEBUG_SPINLOCK
958 select DEBUG_MUTEXES
959 select LOCKDEP
960 help
961 This feature will check whether any held lock (spinlock, rwlock,
962 mutex or rwsem) is incorrectly freed by the kernel, via any of the
963 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
964 vfree(), etc.), whether a live lock is incorrectly reinitialized via
965 spin_lock_init()/mutex_init()/etc., or whether there is any lock
966 held during task exit.
968 config PROVE_LOCKING
969 bool "Lock debugging: prove locking correctness"
970 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
971 select LOCKDEP
972 select DEBUG_SPINLOCK
973 select DEBUG_MUTEXES
974 select DEBUG_LOCK_ALLOC
975 select TRACE_IRQFLAGS
976 default n
977 help
978 This feature enables the kernel to prove that all locking
979 that occurs in the kernel runtime is mathematically
980 correct: that under no circumstance could an arbitrary (and
981 not yet triggered) combination of observed locking
982 sequences (on an arbitrary number of CPUs, running an
983 arbitrary number of tasks and interrupt contexts) cause a
984 deadlock.
986 In short, this feature enables the kernel to report locking
987 related deadlocks before they actually occur.
989 The proof does not depend on how hard and complex a
990 deadlock scenario would be to trigger: how many
991 participant CPUs, tasks and irq-contexts would be needed
992 for it to trigger. The proof also does not depend on
993 timing: if a race and a resulting deadlock is possible
994 theoretically (no matter how unlikely the race scenario
995 is), it will be proven so and will immediately be
996 reported by the kernel (once the event is observed that
997 makes the deadlock theoretically possible).
999 If a deadlock is impossible (i.e. the locking rules, as
1000 observed by the kernel, are mathematically correct), the
1001 kernel reports nothing.
1003 NOTE: this feature can also be enabled for rwlocks, mutexes
1004 and rwsems - in which case all dependencies between these
1005 different locking variants are observed and mapped too, and
1006 the proof of observed correctness is also maintained for an
1007 arbitrary combination of these separate locking variants.
1009 For more details, see Documentation/locking/lockdep-design.txt.
1011 config LOCKDEP
1012 bool
1013 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1014 select STACKTRACE
1015 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
1016 select KALLSYMS
1017 select KALLSYMS_ALL
1019 config LOCK_STAT
1020 bool "Lock usage statistics"
1021 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1022 select LOCKDEP
1023 select DEBUG_SPINLOCK
1024 select DEBUG_MUTEXES
1025 select DEBUG_LOCK_ALLOC
1026 default n
1027 help
1028 This feature enables tracking lock contention points
1030 For more details, see Documentation/locking/lockstat.txt
1032 This also enables lock events required by "perf lock",
1033 subcommand of perf.
1034 If you want to use "perf lock", you also need to turn on
1035 CONFIG_EVENT_TRACING.
1037 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1038 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1040 config DEBUG_LOCKDEP
1041 bool "Lock dependency engine debugging"
1042 depends on DEBUG_KERNEL && LOCKDEP
1043 help
1044 If you say Y here, the lock dependency engine will do
1045 additional runtime checks to debug itself, at the price
1046 of more runtime overhead.
1048 config DEBUG_ATOMIC_SLEEP
1049 bool "Sleep inside atomic section checking"
1050 select PREEMPT_COUNT
1051 depends on DEBUG_KERNEL
1052 help
1053 If you say Y here, various routines which may sleep will become very
1054 noisy if they are called inside atomic sections: when a spinlock is
1055 held, inside an rcu read side critical section, inside preempt disabled
1056 sections, inside an interrupt, etc...
1058 config DEBUG_LOCKING_API_SELFTESTS
1059 bool "Locking API boot-time self-tests"
1060 depends on DEBUG_KERNEL
1061 help
1062 Say Y here if you want the kernel to run a short self-test during
1063 bootup. The self-test checks whether common types of locking bugs
1064 are detected by debugging mechanisms or not. (if you disable
1065 lock debugging then those bugs wont be detected of course.)
1066 The following locking APIs are covered: spinlocks, rwlocks,
1067 mutexes and rwsems.
1069 config LOCK_TORTURE_TEST
1070 tristate "torture tests for locking"
1071 depends on DEBUG_KERNEL
1072 select TORTURE_TEST
1073 default n
1074 help
1075 This option provides a kernel module that runs torture tests
1076 on kernel locking primitives. The kernel module may be built
1077 after the fact on the running kernel to be tested, if desired.
1079 Say Y here if you want kernel locking-primitive torture tests
1080 to be built into the kernel.
1081 Say M if you want these torture tests to build as a module.
1082 Say N if you are unsure.
1084 endmenu # lock debugging
1086 config TRACE_IRQFLAGS
1087 bool
1088 help
1089 Enables hooks to interrupt enabling and disabling for
1090 either tracing or lock debugging.
1092 config STACKTRACE
1093 bool "Stack backtrace support"
1094 depends on STACKTRACE_SUPPORT
1095 help
1096 This option causes the kernel to create a /proc/pid/stack for
1097 every process, showing its current stack trace.
1098 It is also used by various kernel debugging features that require
1099 stack trace generation.
1101 config DEBUG_KOBJECT
1102 bool "kobject debugging"
1103 depends on DEBUG_KERNEL
1104 help
1105 If you say Y here, some extra kobject debugging messages will be sent
1106 to the syslog.
1108 config DEBUG_KOBJECT_RELEASE
1109 bool "kobject release debugging"
1110 depends on DEBUG_OBJECTS_TIMERS
1111 help
1112 kobjects are reference counted objects. This means that their
1113 last reference count put is not predictable, and the kobject can
1114 live on past the point at which a driver decides to drop it's
1115 initial reference to the kobject gained on allocation. An
1116 example of this would be a struct device which has just been
1117 unregistered.
1119 However, some buggy drivers assume that after such an operation,
1120 the memory backing the kobject can be immediately freed. This
1121 goes completely against the principles of a refcounted object.
1123 If you say Y here, the kernel will delay the release of kobjects
1124 on the last reference count to improve the visibility of this
1125 kind of kobject release bug.
1127 config HAVE_DEBUG_BUGVERBOSE
1128 bool
1130 config DEBUG_BUGVERBOSE
1131 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1132 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1133 default y
1134 help
1135 Say Y here to make BUG() panics output the file name and line number
1136 of the BUG call as well as the EIP and oops trace. This aids
1137 debugging but costs about 70-100K of memory.
1139 config DEBUG_LIST
1140 bool "Debug linked list manipulation"
1141 depends on DEBUG_KERNEL
1142 help
1143 Enable this to turn on extended checks in the linked-list
1144 walking routines.
1146 If unsure, say N.
1148 config DEBUG_PI_LIST
1149 bool "Debug priority linked list manipulation"
1150 depends on DEBUG_KERNEL
1151 help
1152 Enable this to turn on extended checks in the priority-ordered
1153 linked-list (plist) walking routines. This checks the entire
1154 list multiple times during each manipulation.
1156 If unsure, say N.
1158 config DEBUG_SG
1159 bool "Debug SG table operations"
1160 depends on DEBUG_KERNEL
1161 help
1162 Enable this to turn on checks on scatter-gather tables. This can
1163 help find problems with drivers that do not properly initialize
1164 their sg tables.
1166 If unsure, say N.
1168 config DEBUG_NOTIFIERS
1169 bool "Debug notifier call chains"
1170 depends on DEBUG_KERNEL
1171 help
1172 Enable this to turn on sanity checking for notifier call chains.
1173 This is most useful for kernel developers to make sure that
1174 modules properly unregister themselves from notifier chains.
1175 This is a relatively cheap check but if you care about maximum
1176 performance, say N.
1178 config DEBUG_CREDENTIALS
1179 bool "Debug credential management"
1180 depends on DEBUG_KERNEL
1181 help
1182 Enable this to turn on some debug checking for credential
1183 management. The additional code keeps track of the number of
1184 pointers from task_structs to any given cred struct, and checks to
1185 see that this number never exceeds the usage count of the cred
1186 struct.
1188 Furthermore, if SELinux is enabled, this also checks that the
1189 security pointer in the cred struct is never seen to be invalid.
1191 If unsure, say N.
1193 menu "RCU Debugging"
1195 config PROVE_RCU
1196 def_bool PROVE_LOCKING
1198 config PROVE_RCU_REPEATEDLY
1199 bool "RCU debugging: don't disable PROVE_RCU on first splat"
1200 depends on PROVE_RCU
1201 default n
1202 help
1203 By itself, PROVE_RCU will disable checking upon issuing the
1204 first warning (or "splat"). This feature prevents such
1205 disabling, allowing multiple RCU-lockdep warnings to be printed
1206 on a single reboot.
1208 Say Y to allow multiple RCU-lockdep warnings per boot.
1210 Say N if you are unsure.
1212 config SPARSE_RCU_POINTER
1213 bool "RCU debugging: sparse-based checks for pointer usage"
1214 default n
1215 help
1216 This feature enables the __rcu sparse annotation for
1217 RCU-protected pointers. This annotation will cause sparse
1218 to flag any non-RCU used of annotated pointers. This can be
1219 helpful when debugging RCU usage. Please note that this feature
1220 is not intended to enforce code cleanliness; it is instead merely
1221 a debugging aid.
1223 Say Y to make sparse flag questionable use of RCU-protected pointers
1225 Say N if you are unsure.
1227 config TORTURE_TEST
1228 tristate
1229 default n
1231 config RCU_TORTURE_TEST
1232 tristate "torture tests for RCU"
1233 depends on DEBUG_KERNEL
1234 select TORTURE_TEST
1235 select SRCU
1236 default n
1237 help
1238 This option provides a kernel module that runs torture tests
1239 on the RCU infrastructure. The kernel module may be built
1240 after the fact on the running kernel to be tested, if desired.
1242 Say Y here if you want RCU torture tests to be built into
1243 the kernel.
1244 Say M if you want the RCU torture tests to build as a module.
1245 Say N if you are unsure.
1247 config RCU_TORTURE_TEST_RUNNABLE
1248 bool "torture tests for RCU runnable by default"
1249 depends on RCU_TORTURE_TEST = y
1250 default n
1251 help
1252 This option provides a way to build the RCU torture tests
1253 directly into the kernel without them starting up at boot
1254 time. You can use /proc/sys/kernel/rcutorture_runnable
1255 to manually override this setting. This /proc file is
1256 available only when the RCU torture tests have been built
1257 into the kernel.
1259 Say Y here if you want the RCU torture tests to start during
1260 boot (you probably don't).
1261 Say N here if you want the RCU torture tests to start only
1262 after being manually enabled via /proc.
1264 config RCU_TORTURE_TEST_SLOW_INIT
1265 bool "Slow down RCU grace-period initialization to expose races"
1266 depends on RCU_TORTURE_TEST
1267 help
1268 This option makes grace-period initialization block for a
1269 few jiffies between initializing each pair of consecutive
1270 rcu_node structures. This helps to expose races involving
1271 grace-period initialization, in other words, it makes your
1272 kernel less stable. It can also greatly increase grace-period
1273 latency, especially on systems with large numbers of CPUs.
1274 This is useful when torture-testing RCU, but in almost no
1275 other circumstance.
1277 Say Y here if you want your system to crash and hang more often.
1278 Say N if you want a sane system.
1280 config RCU_TORTURE_TEST_SLOW_INIT_DELAY
1281 int "How much to slow down RCU grace-period initialization"
1282 range 0 5
1283 default 3
1284 help
1285 This option specifies the number of jiffies to wait between
1286 each rcu_node structure initialization.
1288 config RCU_CPU_STALL_TIMEOUT
1289 int "RCU CPU stall timeout in seconds"
1290 depends on RCU_STALL_COMMON
1291 range 3 300
1292 default 21
1293 help
1294 If a given RCU grace period extends more than the specified
1295 number of seconds, a CPU stall warning is printed. If the
1296 RCU grace period persists, additional CPU stall warnings are
1297 printed at more widely spaced intervals.
1299 config RCU_CPU_STALL_INFO
1300 bool "Print additional diagnostics on RCU CPU stall"
1301 depends on (TREE_RCU || PREEMPT_RCU) && DEBUG_KERNEL
1302 default y
1303 help
1304 For each stalled CPU that is aware of the current RCU grace
1305 period, print out additional per-CPU diagnostic information
1306 regarding scheduling-clock ticks, idle state, and,
1307 for RCU_FAST_NO_HZ kernels, idle-entry state.
1309 Say N if you are unsure.
1311 Say Y if you want to enable such diagnostics.
1313 config RCU_TRACE
1314 bool "Enable tracing for RCU"
1315 depends on DEBUG_KERNEL
1316 select TRACE_CLOCK
1317 help
1318 This option provides tracing in RCU which presents stats
1319 in debugfs for debugging RCU implementation.
1321 Say Y here if you want to enable RCU tracing
1322 Say N if you are unsure.
1324 endmenu # "RCU Debugging"
1326 config DEBUG_BLOCK_EXT_DEVT
1327 bool "Force extended block device numbers and spread them"
1328 depends on DEBUG_KERNEL
1329 depends on BLOCK
1330 default n
1331 help
1332 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1333 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1334 YOU ARE DOING. Distros, please enable this and fix whatever
1335 is broken.
1337 Conventionally, block device numbers are allocated from
1338 predetermined contiguous area. However, extended block area
1339 may introduce non-contiguous block device numbers. This
1340 option forces most block device numbers to be allocated from
1341 the extended space and spreads them to discover kernel or
1342 userland code paths which assume predetermined contiguous
1343 device number allocation.
1345 Note that turning on this debug option shuffles all the
1346 device numbers for all IDE and SCSI devices including libata
1347 ones, so root partition specified using device number
1348 directly (via rdev or root=MAJ:MIN) won't work anymore.
1349 Textual device names (root=/dev/sdXn) will continue to work.
1351 Say N if you are unsure.
1353 config NOTIFIER_ERROR_INJECTION
1354 tristate "Notifier error injection"
1355 depends on DEBUG_KERNEL
1356 select DEBUG_FS
1357 help
1358 This option provides the ability to inject artificial errors to
1359 specified notifier chain callbacks. It is useful to test the error
1360 handling of notifier call chain failures.
1362 Say N if unsure.
1364 config CPU_NOTIFIER_ERROR_INJECT
1365 tristate "CPU notifier error injection module"
1366 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1367 help
1368 This option provides a kernel module that can be used to test
1369 the error handling of the cpu notifiers by injecting artificial
1370 errors to CPU notifier chain callbacks. It is controlled through
1371 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
1373 If the notifier call chain should be failed with some events
1374 notified, write the error code to "actions/<notifier event>/error".
1376 Example: Inject CPU offline error (-1 == -EPERM)
1378 # cd /sys/kernel/debug/notifier-error-inject/cpu
1379 # echo -1 > actions/CPU_DOWN_PREPARE/error
1380 # echo 0 > /sys/devices/system/cpu/cpu1/online
1381 bash: echo: write error: Operation not permitted
1383 To compile this code as a module, choose M here: the module will
1384 be called cpu-notifier-error-inject.
1386 If unsure, say N.
1388 config PM_NOTIFIER_ERROR_INJECT
1389 tristate "PM notifier error injection module"
1390 depends on PM && NOTIFIER_ERROR_INJECTION
1391 default m if PM_DEBUG
1392 help
1393 This option provides the ability to inject artificial errors to
1394 PM notifier chain callbacks. It is controlled through debugfs
1395 interface /sys/kernel/debug/notifier-error-inject/pm
1397 If the notifier call chain should be failed with some events
1398 notified, write the error code to "actions/<notifier event>/error".
1400 Example: Inject PM suspend error (-12 = -ENOMEM)
1402 # cd /sys/kernel/debug/notifier-error-inject/pm/
1403 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1404 # echo mem > /sys/power/state
1405 bash: echo: write error: Cannot allocate memory
1407 To compile this code as a module, choose M here: the module will
1408 be called pm-notifier-error-inject.
1410 If unsure, say N.
1412 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1413 tristate "OF reconfig notifier error injection module"
1414 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1415 help
1416 This option provides the ability to inject artificial errors to
1417 OF reconfig notifier chain callbacks. It is controlled
1418 through debugfs interface under
1419 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1421 If the notifier call chain should be failed with some events
1422 notified, write the error code to "actions/<notifier event>/error".
1424 To compile this code as a module, choose M here: the module will
1425 be called of-reconfig-notifier-error-inject.
1427 If unsure, say N.
1429 config FAULT_INJECTION
1430 bool "Fault-injection framework"
1431 depends on DEBUG_KERNEL
1432 help
1433 Provide fault-injection framework.
1434 For more details, see Documentation/fault-injection/.
1436 config FAILSLAB
1437 bool "Fault-injection capability for kmalloc"
1438 depends on FAULT_INJECTION
1439 depends on SLAB || SLUB
1440 help
1441 Provide fault-injection capability for kmalloc.
1443 config FAIL_PAGE_ALLOC
1444 bool "Fault-injection capabilitiy for alloc_pages()"
1445 depends on FAULT_INJECTION
1446 help
1447 Provide fault-injection capability for alloc_pages().
1449 config FAIL_MAKE_REQUEST
1450 bool "Fault-injection capability for disk IO"
1451 depends on FAULT_INJECTION && BLOCK
1452 help
1453 Provide fault-injection capability for disk IO.
1455 config FAIL_IO_TIMEOUT
1456 bool "Fault-injection capability for faking disk interrupts"
1457 depends on FAULT_INJECTION && BLOCK
1458 help
1459 Provide fault-injection capability on end IO handling. This
1460 will make the block layer "forget" an interrupt as configured,
1461 thus exercising the error handling.
1463 Only works with drivers that use the generic timeout handling,
1464 for others it wont do anything.
1466 config FAIL_MMC_REQUEST
1467 bool "Fault-injection capability for MMC IO"
1468 select DEBUG_FS
1469 depends on FAULT_INJECTION && MMC
1470 help
1471 Provide fault-injection capability for MMC IO.
1472 This will make the mmc core return data errors. This is
1473 useful to test the error handling in the mmc block device
1474 and to test how the mmc host driver handles retries from
1475 the block device.
1477 config FAULT_INJECTION_DEBUG_FS
1478 bool "Debugfs entries for fault-injection capabilities"
1479 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1480 help
1481 Enable configuration of fault-injection capabilities via debugfs.
1483 config FAULT_INJECTION_STACKTRACE_FILTER
1484 bool "stacktrace filter for fault-injection capabilities"
1485 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1486 depends on !X86_64
1487 select STACKTRACE
1488 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1489 help
1490 Provide stacktrace filter for fault-injection capabilities
1492 config LATENCYTOP
1493 bool "Latency measuring infrastructure"
1494 depends on HAVE_LATENCYTOP_SUPPORT
1495 depends on DEBUG_KERNEL
1496 depends on STACKTRACE_SUPPORT
1497 depends on PROC_FS
1498 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1499 select KALLSYMS
1500 select KALLSYMS_ALL
1501 select STACKTRACE
1502 select SCHEDSTATS
1503 select SCHED_DEBUG
1504 help
1505 Enable this option if you want to use the LatencyTOP tool
1506 to find out which userspace is blocking on what kernel operations.
1508 config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1509 bool
1511 config DEBUG_STRICT_USER_COPY_CHECKS
1512 bool "Strict user copy size checks"
1513 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1514 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
1515 help
1516 Enabling this option turns a certain set of sanity checks for user
1517 copy operations into compile time failures.
1519 The copy_from_user() etc checks are there to help test if there
1520 are sufficient security checks on the length argument of
1521 the copy operation, by having gcc prove that the argument is
1522 within bounds.
1524 If unsure, say N.
1526 source kernel/trace/Kconfig
1528 menu "Runtime Testing"
1530 config LKDTM
1531 tristate "Linux Kernel Dump Test Tool Module"
1532 depends on DEBUG_FS
1533 depends on BLOCK
1534 default n
1535 help
1536 This module enables testing of the different dumping mechanisms by
1537 inducing system failures at predefined crash points.
1538 If you don't need it: say N
1539 Choose M here to compile this code as a module. The module will be
1540 called lkdtm.
1542 Documentation on how to use the module can be found in
1543 Documentation/fault-injection/provoke-crashes.txt
1545 config TEST_LIST_SORT
1546 bool "Linked list sorting test"
1547 depends on DEBUG_KERNEL
1548 help
1549 Enable this to turn on 'list_sort()' function test. This test is
1550 executed only once during system boot, so affects only boot time.
1552 If unsure, say N.
1554 config KPROBES_SANITY_TEST
1555 bool "Kprobes sanity tests"
1556 depends on DEBUG_KERNEL
1557 depends on KPROBES
1558 default n
1559 help
1560 This option provides for testing basic kprobes functionality on
1561 boot. A sample kprobe, jprobe and kretprobe are inserted and
1562 verified for functionality.
1564 Say N if you are unsure.
1566 config BACKTRACE_SELF_TEST
1567 tristate "Self test for the backtrace code"
1568 depends on DEBUG_KERNEL
1569 default n
1570 help
1571 This option provides a kernel module that can be used to test
1572 the kernel stack backtrace code. This option is not useful
1573 for distributions or general kernels, but only for kernel
1574 developers working on architecture code.
1576 Note that if you want to also test saved backtraces, you will
1577 have to enable STACKTRACE as well.
1579 Say N if you are unsure.
1581 config RBTREE_TEST
1582 tristate "Red-Black tree test"
1583 depends on DEBUG_KERNEL
1584 help
1585 A benchmark measuring the performance of the rbtree library.
1586 Also includes rbtree invariant checks.
1588 config INTERVAL_TREE_TEST
1589 tristate "Interval tree test"
1590 depends on m && DEBUG_KERNEL
1591 select INTERVAL_TREE
1592 help
1593 A benchmark measuring the performance of the interval tree library
1595 config PERCPU_TEST
1596 tristate "Per cpu operations test"
1597 depends on m && DEBUG_KERNEL
1598 help
1599 Enable this option to build test module which validates per-cpu
1600 operations.
1602 If unsure, say N.
1604 config ATOMIC64_SELFTEST
1605 bool "Perform an atomic64_t self-test at boot"
1606 help
1607 Enable this option to test the atomic64_t functions at boot.
1609 If unsure, say N.
1611 config ASYNC_RAID6_TEST
1612 tristate "Self test for hardware accelerated raid6 recovery"
1613 depends on ASYNC_RAID6_RECOV
1614 select ASYNC_MEMCPY
1615 ---help---
1616 This is a one-shot self test that permutes through the
1617 recovery of all the possible two disk failure scenarios for a
1618 N-disk array. Recovery is performed with the asynchronous
1619 raid6 recovery routines, and will optionally use an offload
1620 engine if one is available.
1622 If unsure, say N.
1624 config TEST_HEXDUMP
1625 tristate "Test functions located in the hexdump module at runtime"
1627 config TEST_STRING_HELPERS
1628 tristate "Test functions located in the string_helpers module at runtime"
1630 config TEST_KSTRTOX
1631 tristate "Test kstrto*() family of functions at runtime"
1633 config TEST_RHASHTABLE
1634 tristate "Perform selftest on resizable hash table"
1635 default n
1636 help
1637 Enable this option to test the rhashtable functions at boot.
1639 If unsure, say N.
1641 endmenu # runtime tests
1643 config PROVIDE_OHCI1394_DMA_INIT
1644 bool "Remote debugging over FireWire early on boot"
1645 depends on PCI && X86
1646 help
1647 If you want to debug problems which hang or crash the kernel early
1648 on boot and the crashing machine has a FireWire port, you can use
1649 this feature to remotely access the memory of the crashed machine
1650 over FireWire. This employs remote DMA as part of the OHCI1394
1651 specification which is now the standard for FireWire controllers.
1653 With remote DMA, you can monitor the printk buffer remotely using
1654 firescope and access all memory below 4GB using fireproxy from gdb.
1655 Even controlling a kernel debugger is possible using remote DMA.
1657 Usage:
1659 If ohci1394_dma=early is used as boot parameter, it will initialize
1660 all OHCI1394 controllers which are found in the PCI config space.
1662 As all changes to the FireWire bus such as enabling and disabling
1663 devices cause a bus reset and thereby disable remote DMA for all
1664 devices, be sure to have the cable plugged and FireWire enabled on
1665 the debugging host before booting the debug target for debugging.
1667 This code (~1k) is freed after boot. By then, the firewire stack
1668 in charge of the OHCI-1394 controllers should be used instead.
1670 See Documentation/debugging-via-ohci1394.txt for more information.
1672 config BUILD_DOCSRC
1673 bool "Build targets in Documentation/ tree"
1674 depends on HEADERS_CHECK
1675 help
1676 This option attempts to build objects from the source files in the
1677 kernel Documentation/ tree.
1679 Say N if you are unsure.
1681 config DMA_API_DEBUG
1682 bool "Enable debugging of DMA-API usage"
1683 depends on HAVE_DMA_API_DEBUG
1684 help
1685 Enable this option to debug the use of the DMA API by device drivers.
1686 With this option you will be able to detect common bugs in device
1687 drivers like double-freeing of DMA mappings or freeing mappings that
1688 were never allocated.
1690 This also attempts to catch cases where a page owned by DMA is
1691 accessed by the cpu in a way that could cause data corruption. For
1692 example, this enables cow_user_page() to check that the source page is
1693 not undergoing DMA.
1695 This option causes a performance degradation. Use only if you want to
1696 debug device drivers and dma interactions.
1698 If unsure, say N.
1700 config TEST_LKM
1701 tristate "Test module loading with 'hello world' module"
1702 default n
1703 depends on m
1704 help
1705 This builds the "test_module" module that emits "Hello, world"
1706 on printk when loaded. It is designed to be used for basic
1707 evaluation of the module loading subsystem (for example when
1708 validating module verification). It lacks any extra dependencies,
1709 and will not normally be loaded by the system unless explicitly
1710 requested by name.
1712 If unsure, say N.
1714 config TEST_USER_COPY
1715 tristate "Test user/kernel boundary protections"
1716 default n
1717 depends on m
1718 help
1719 This builds the "test_user_copy" module that runs sanity checks
1720 on the copy_to/from_user infrastructure, making sure basic
1721 user/kernel boundary testing is working. If it fails to load,
1722 a regression has been detected in the user/kernel memory boundary
1723 protections.
1725 If unsure, say N.
1727 config TEST_BPF
1728 tristate "Test BPF filter functionality"
1729 default n
1730 depends on m && NET
1731 help
1732 This builds the "test_bpf" module that runs various test vectors
1733 against the BPF interpreter or BPF JIT compiler depending on the
1734 current setting. This is in particular useful for BPF JIT compiler
1735 development, but also to run regression tests against changes in
1736 the interpreter code. It also enables test stubs for eBPF maps and
1737 verifier used by user space verifier testsuite.
1739 If unsure, say N.
1741 config TEST_FIRMWARE
1742 tristate "Test firmware loading via userspace interface"
1743 default n
1744 depends on FW_LOADER
1745 help
1746 This builds the "test_firmware" module that creates a userspace
1747 interface for testing firmware loading. This can be used to
1748 control the triggering of firmware loading without needing an
1749 actual firmware-using device. The contents can be rechecked by
1750 userspace.
1752 If unsure, say N.
1754 config TEST_UDELAY
1755 tristate "udelay test driver"
1756 default n
1757 help
1758 This builds the "udelay_test" module that helps to make sure
1759 that udelay() is working properly.
1761 If unsure, say N.
1763 config MEMTEST
1764 bool "Memtest"
1765 depends on HAVE_MEMBLOCK
1766 ---help---
1767 This option adds a kernel parameter 'memtest', which allows memtest
1768 to be set.
1769 memtest=0, mean disabled; -- default
1770 memtest=1, mean do 1 test pattern;
1771 ...
1772 memtest=17, mean do 17 test patterns.
1773 If you are unsure how to answer this question, answer N.
1775 source "samples/Kconfig"
1777 source "lib/Kconfig.kgdb"