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1 menu "printk and dmesg options"
2
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.
10
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.
14
15 The behavior is also controlled by the kernel command line
16 parameter printk.time=1. See Documentation/kernel-parameters.txt
17
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.
24
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.
28
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".
37
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.
46
47 config DYNAMIC_DEBUG
48 bool "Enable dynamic printk() support"
49 default n
50 depends on PRINTK
51 depends on DEBUG_FS
52 help
53
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%.
60
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.
65
66 Usage:
67
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:
74
75 filename:lineno [module]function flags format
76
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
83
84 From a live system:
85
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"
91
92 Example usage:
93
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
97
98 // enable all the messages in file svcsock.c
99 nullarbor:~ # echo -n 'file svcsock.c +p' >
100 <debugfs>/dynamic_debug/control
101
102 // enable all the messages in the NFS server module
103 nullarbor:~ # echo -n 'module nfsd +p' >
104 <debugfs>/dynamic_debug/control
105
106 // enable all 12 messages in the function svc_process()
107 nullarbor:~ # echo -n 'func svc_process +p' >
108 <debugfs>/dynamic_debug/control
109
110 // disable all 12 messages in the function svc_process()
111 nullarbor:~ # echo -n 'func svc_process -p' >
112 <debugfs>/dynamic_debug/control
113
114 See Documentation/dynamic-debug-howto.txt for additional information.
115
116 endmenu # "printk and dmesg options"
117
118 menu "Compile-time checks and compiler options"
119
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.
130
131 If unsure, say N.
132
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.
145
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.
155
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.
160
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.
169
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.
180
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.
188
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.
196
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
207
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.
215
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.
224
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.
240
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.
254
255 If unsure, say N.
256
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.
263
264 For detailed documentation on the debugfs API, see
265 Documentation/DocBook/filesystems.
266
267 If unsure, say N.
268
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.
277
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.
282
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.
313
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
322
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)
334
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.
343
344 1. percpu symbols must be unique whether static or not
345 2. percpu variables can't be defined inside a function
346
347 To ensure that generic code follows the above rules, this
348 option forces all percpu variables to be defined as weak.
349
350 endmenu # "Compiler options"
351
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.
365
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.
374
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.
380
381 menu "Memory Debugging"
382
383 source mm/Kconfig.debug
384
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.
392
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.
398
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.
407
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.
415
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.
423
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).
429
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.
437
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
445
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.
453
454 config DEBUG_SLAB_LEAK
455 bool "Memory leak debugging"
456 depends on DEBUG_SLAB
457
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=-".
470
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
483
484 config HAVE_DEBUG_KMEMLEAK
485 bool
486
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.
503
504 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
505 of finding leaks due to the slab objects poisoning.
506
507 In order to access the kmemleak file, debugfs needs to be
508 mounted (usually at /sys/kernel/debug).
509
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.
521
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.
527
528 If unsure, say N.
529
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.
536
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.
543
544 This option will slow down process creation somewhat.
545
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.
552
553 If unsure, say N.
554
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.
562
563 If unsure, say N.
564
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.
570
571 If unsure, say N.
572
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.
579
580 If unsure, say N.
581
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.
588
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.
598
599 If unsure, say Y
600
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
608
609 If the notifier call chain should be failed with some events
610 notified, write the error code to "actions/<notifier event>/error".
611
612 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
613
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
618
619 To compile this code as a module, choose M here: the module will
620 be called memory-notifier-error-inject.
621
622 If unsure, say N.
623
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.
632
633 Say N if unsure.
634
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.
641
642 config HAVE_DEBUG_STACKOVERFLOW
643 bool
644
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.
653
654 These kinds of bugs usually occur when call-chains in the
655 kernel get too deep, especially when interrupts are
656 involved.
657
658 Use this in cases where you see apparently random memory
659 corruption, especially if it appears in 'struct thread_info'
660
661 If in doubt, say "N".
662
663 source "lib/Kconfig.kmemcheck"
664
665 source "lib/Kconfig.kasan"
666
667 endmenu # "Memory Debugging"
668
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.
677
678 menu "Debug Lockups and Hangs"
679
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.
686
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.
691
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.
696
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.
700
701 The frequency of hrtimer and NMI events and the soft and hard lockup
702 thresholds can be controlled through the sysctl watchdog_thresh.
703
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
708
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).
717
718 Say N if unsure.
719
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
726
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.
735
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.
741
742 Say N if unsure.
743
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
750
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.
759
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.
765
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.
774
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.
778
779 A timeout of 0 disables the check. The default is two minutes.
780 Keeping the default should be fine in most cases.
781
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.
789
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.
795
796 Say N if unsure.
797
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
804
805 endmenu # "Debug lockups and hangs"
806
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.
813
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.
817
818 Say N if unsure.
819
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
825
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.
834
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.
843
844 config SCHED_INFO
845 bool
846 default n
847
848 config SCHEDSTATS
849 bool "Collect scheduler statistics"
850 depends on DEBUG_KERNEL && PROC_FS
851 select SCHED_INFO
852 help
853 If you say Y here, additional code will be inserted into the
854 scheduler and related routines to collect statistics about
855 scheduler behavior and provide them in /proc/schedstat. These
856 stats may be useful for both tuning and debugging the scheduler
857 If you aren't debugging the scheduler or trying to tune a specific
858 application, you can say N to avoid the very slight overhead
859 this adds.
860
861 config SCHED_STACK_END_CHECK
862 bool "Detect stack corruption on calls to schedule()"
863 depends on DEBUG_KERNEL
864 default n
865 help
866 This option checks for a stack overrun on calls to schedule().
867 If the stack end location is found to be over written always panic as
868 the content of the corrupted region can no longer be trusted.
869 This is to ensure no erroneous behaviour occurs which could result in
870 data corruption or a sporadic crash at a later stage once the region
871 is examined. The runtime overhead introduced is minimal.
872
873 config DEBUG_TIMEKEEPING
874 bool "Enable extra timekeeping sanity checking"
875 help
876 This option will enable additional timekeeping sanity checks
877 which may be helpful when diagnosing issues where timekeeping
878 problems are suspected.
879
880 This may include checks in the timekeeping hotpaths, so this
881 option may have a (very small) performance impact to some
882 workloads.
883
884 If unsure, say N.
885
886 config TIMER_STATS
887 bool "Collect kernel timers statistics"
888 depends on DEBUG_KERNEL && PROC_FS
889 help
890 If you say Y here, additional code will be inserted into the
891 timer routines to collect statistics about kernel timers being
892 reprogrammed. The statistics can be read from /proc/timer_stats.
893 The statistics collection is started by writing 1 to /proc/timer_stats,
894 writing 0 stops it. This feature is useful to collect information
895 about timer usage patterns in kernel and userspace. This feature
896 is lightweight if enabled in the kernel config but not activated
897 (it defaults to deactivated on bootup and will only be activated
898 if some application like powertop activates it explicitly).
899
900 config DEBUG_PREEMPT
901 bool "Debug preemptible kernel"
902 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
903 default y
904 help
905 If you say Y here then the kernel will use a debug variant of the
906 commonly used smp_processor_id() function and will print warnings
907 if kernel code uses it in a preemption-unsafe way. Also, the kernel
908 will detect preemption count underflows.
909
910 menu "Lock Debugging (spinlocks, mutexes, etc...)"
911
912 config DEBUG_RT_MUTEXES
913 bool "RT Mutex debugging, deadlock detection"
914 depends on DEBUG_KERNEL && RT_MUTEXES
915 help
916 This allows rt mutex semantics violations and rt mutex related
917 deadlocks (lockups) to be detected and reported automatically.
918
919 config DEBUG_SPINLOCK
920 bool "Spinlock and rw-lock debugging: basic checks"
921 depends on DEBUG_KERNEL
922 select UNINLINE_SPIN_UNLOCK
923 help
924 Say Y here and build SMP to catch missing spinlock initialization
925 and certain other kinds of spinlock errors commonly made. This is
926 best used in conjunction with the NMI watchdog so that spinlock
927 deadlocks are also debuggable.
928
929 config DEBUG_MUTEXES
930 bool "Mutex debugging: basic checks"
931 depends on DEBUG_KERNEL
932 help
933 This feature allows mutex semantics violations to be detected and
934 reported.
935
936 config DEBUG_WW_MUTEX_SLOWPATH
937 bool "Wait/wound mutex debugging: Slowpath testing"
938 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
939 select DEBUG_LOCK_ALLOC
940 select DEBUG_SPINLOCK
941 select DEBUG_MUTEXES
942 help
943 This feature enables slowpath testing for w/w mutex users by
944 injecting additional -EDEADLK wound/backoff cases. Together with
945 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
946 will test all possible w/w mutex interface abuse with the
947 exception of simply not acquiring all the required locks.
948 Note that this feature can introduce significant overhead, so
949 it really should not be enabled in a production or distro kernel,
950 even a debug kernel. If you are a driver writer, enable it. If
951 you are a distro, do not.
952
953 config DEBUG_LOCK_ALLOC
954 bool "Lock debugging: detect incorrect freeing of live locks"
955 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
956 select DEBUG_SPINLOCK
957 select DEBUG_MUTEXES
958 select LOCKDEP
959 help
960 This feature will check whether any held lock (spinlock, rwlock,
961 mutex or rwsem) is incorrectly freed by the kernel, via any of the
962 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
963 vfree(), etc.), whether a live lock is incorrectly reinitialized via
964 spin_lock_init()/mutex_init()/etc., or whether there is any lock
965 held during task exit.
966
967 config PROVE_LOCKING
968 bool "Lock debugging: prove locking correctness"
969 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
970 select LOCKDEP
971 select DEBUG_SPINLOCK
972 select DEBUG_MUTEXES
973 select DEBUG_LOCK_ALLOC
974 select TRACE_IRQFLAGS
975 default n
976 help
977 This feature enables the kernel to prove that all locking
978 that occurs in the kernel runtime is mathematically
979 correct: that under no circumstance could an arbitrary (and
980 not yet triggered) combination of observed locking
981 sequences (on an arbitrary number of CPUs, running an
982 arbitrary number of tasks and interrupt contexts) cause a
983 deadlock.
984
985 In short, this feature enables the kernel to report locking
986 related deadlocks before they actually occur.
987
988 The proof does not depend on how hard and complex a
989 deadlock scenario would be to trigger: how many
990 participant CPUs, tasks and irq-contexts would be needed
991 for it to trigger. The proof also does not depend on
992 timing: if a race and a resulting deadlock is possible
993 theoretically (no matter how unlikely the race scenario
994 is), it will be proven so and will immediately be
995 reported by the kernel (once the event is observed that
996 makes the deadlock theoretically possible).
997
998 If a deadlock is impossible (i.e. the locking rules, as
999 observed by the kernel, are mathematically correct), the
1000 kernel reports nothing.
1001
1002 NOTE: this feature can also be enabled for rwlocks, mutexes
1003 and rwsems - in which case all dependencies between these
1004 different locking variants are observed and mapped too, and
1005 the proof of observed correctness is also maintained for an
1006 arbitrary combination of these separate locking variants.
1007
1008 For more details, see Documentation/locking/lockdep-design.txt.
1009
1010 config LOCKDEP
1011 bool
1012 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1013 select STACKTRACE
1014 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
1015 select KALLSYMS
1016 select KALLSYMS_ALL
1017
1018 config LOCK_STAT
1019 bool "Lock usage statistics"
1020 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1021 select LOCKDEP
1022 select DEBUG_SPINLOCK
1023 select DEBUG_MUTEXES
1024 select DEBUG_LOCK_ALLOC
1025 default n
1026 help
1027 This feature enables tracking lock contention points
1028
1029 For more details, see Documentation/locking/lockstat.txt
1030
1031 This also enables lock events required by "perf lock",
1032 subcommand of perf.
1033 If you want to use "perf lock", you also need to turn on
1034 CONFIG_EVENT_TRACING.
1035
1036 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1037 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1038
1039 config DEBUG_LOCKDEP
1040 bool "Lock dependency engine debugging"
1041 depends on DEBUG_KERNEL && LOCKDEP
1042 help
1043 If you say Y here, the lock dependency engine will do
1044 additional runtime checks to debug itself, at the price
1045 of more runtime overhead.
1046
1047 config DEBUG_ATOMIC_SLEEP
1048 bool "Sleep inside atomic section checking"
1049 select PREEMPT_COUNT
1050 depends on DEBUG_KERNEL
1051 help
1052 If you say Y here, various routines which may sleep will become very
1053 noisy if they are called inside atomic sections: when a spinlock is
1054 held, inside an rcu read side critical section, inside preempt disabled
1055 sections, inside an interrupt, etc...
1056
1057 config DEBUG_LOCKING_API_SELFTESTS
1058 bool "Locking API boot-time self-tests"
1059 depends on DEBUG_KERNEL
1060 help
1061 Say Y here if you want the kernel to run a short self-test during
1062 bootup. The self-test checks whether common types of locking bugs
1063 are detected by debugging mechanisms or not. (if you disable
1064 lock debugging then those bugs wont be detected of course.)
1065 The following locking APIs are covered: spinlocks, rwlocks,
1066 mutexes and rwsems.
1067
1068 config LOCK_TORTURE_TEST
1069 tristate "torture tests for locking"
1070 depends on DEBUG_KERNEL
1071 select TORTURE_TEST
1072 default n
1073 help
1074 This option provides a kernel module that runs torture tests
1075 on kernel locking primitives. The kernel module may be built
1076 after the fact on the running kernel to be tested, if desired.
1077
1078 Say Y here if you want kernel locking-primitive torture tests
1079 to be built into the kernel.
1080 Say M if you want these torture tests to build as a module.
1081 Say N if you are unsure.
1082
1083 endmenu # lock debugging
1084
1085 config TRACE_IRQFLAGS
1086 bool
1087 help
1088 Enables hooks to interrupt enabling and disabling for
1089 either tracing or lock debugging.
1090
1091 config STACKTRACE
1092 bool "Stack backtrace support"
1093 depends on STACKTRACE_SUPPORT
1094 help
1095 This option causes the kernel to create a /proc/pid/stack for
1096 every process, showing its current stack trace.
1097 It is also used by various kernel debugging features that require
1098 stack trace generation.
1099
1100 config DEBUG_KOBJECT
1101 bool "kobject debugging"
1102 depends on DEBUG_KERNEL
1103 help
1104 If you say Y here, some extra kobject debugging messages will be sent
1105 to the syslog.
1106
1107 config DEBUG_KOBJECT_RELEASE
1108 bool "kobject release debugging"
1109 depends on DEBUG_OBJECTS_TIMERS
1110 help
1111 kobjects are reference counted objects. This means that their
1112 last reference count put is not predictable, and the kobject can
1113 live on past the point at which a driver decides to drop it's
1114 initial reference to the kobject gained on allocation. An
1115 example of this would be a struct device which has just been
1116 unregistered.
1117
1118 However, some buggy drivers assume that after such an operation,
1119 the memory backing the kobject can be immediately freed. This
1120 goes completely against the principles of a refcounted object.
1121
1122 If you say Y here, the kernel will delay the release of kobjects
1123 on the last reference count to improve the visibility of this
1124 kind of kobject release bug.
1125
1126 config HAVE_DEBUG_BUGVERBOSE
1127 bool
1128
1129 config DEBUG_BUGVERBOSE
1130 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1131 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1132 default y
1133 help
1134 Say Y here to make BUG() panics output the file name and line number
1135 of the BUG call as well as the EIP and oops trace. This aids
1136 debugging but costs about 70-100K of memory.
1137
1138 config DEBUG_LIST
1139 bool "Debug linked list manipulation"
1140 depends on DEBUG_KERNEL
1141 help
1142 Enable this to turn on extended checks in the linked-list
1143 walking routines.
1144
1145 If unsure, say N.
1146
1147 config DEBUG_PI_LIST
1148 bool "Debug priority linked list manipulation"
1149 depends on DEBUG_KERNEL
1150 help
1151 Enable this to turn on extended checks in the priority-ordered
1152 linked-list (plist) walking routines. This checks the entire
1153 list multiple times during each manipulation.
1154
1155 If unsure, say N.
1156
1157 config DEBUG_SG
1158 bool "Debug SG table operations"
1159 depends on DEBUG_KERNEL
1160 help
1161 Enable this to turn on checks on scatter-gather tables. This can
1162 help find problems with drivers that do not properly initialize
1163 their sg tables.
1164
1165 If unsure, say N.
1166
1167 config DEBUG_NOTIFIERS
1168 bool "Debug notifier call chains"
1169 depends on DEBUG_KERNEL
1170 help
1171 Enable this to turn on sanity checking for notifier call chains.
1172 This is most useful for kernel developers to make sure that
1173 modules properly unregister themselves from notifier chains.
1174 This is a relatively cheap check but if you care about maximum
1175 performance, say N.
1176
1177 config DEBUG_CREDENTIALS
1178 bool "Debug credential management"
1179 depends on DEBUG_KERNEL
1180 help
1181 Enable this to turn on some debug checking for credential
1182 management. The additional code keeps track of the number of
1183 pointers from task_structs to any given cred struct, and checks to
1184 see that this number never exceeds the usage count of the cred
1185 struct.
1186
1187 Furthermore, if SELinux is enabled, this also checks that the
1188 security pointer in the cred struct is never seen to be invalid.
1189
1190 If unsure, say N.
1191
1192 menu "RCU Debugging"
1193
1194 config PROVE_RCU
1195 def_bool PROVE_LOCKING
1196
1197 config PROVE_RCU_REPEATEDLY
1198 bool "RCU debugging: don't disable PROVE_RCU on first splat"
1199 depends on PROVE_RCU
1200 default n
1201 help
1202 By itself, PROVE_RCU will disable checking upon issuing the
1203 first warning (or "splat"). This feature prevents such
1204 disabling, allowing multiple RCU-lockdep warnings to be printed
1205 on a single reboot.
1206
1207 Say Y to allow multiple RCU-lockdep warnings per boot.
1208
1209 Say N if you are unsure.
1210
1211 config SPARSE_RCU_POINTER
1212 bool "RCU debugging: sparse-based checks for pointer usage"
1213 default n
1214 help
1215 This feature enables the __rcu sparse annotation for
1216 RCU-protected pointers. This annotation will cause sparse
1217 to flag any non-RCU used of annotated pointers. This can be
1218 helpful when debugging RCU usage. Please note that this feature
1219 is not intended to enforce code cleanliness; it is instead merely
1220 a debugging aid.
1221
1222 Say Y to make sparse flag questionable use of RCU-protected pointers
1223
1224 Say N if you are unsure.
1225
1226 config TORTURE_TEST
1227 tristate
1228 default n
1229
1230 config RCU_TORTURE_TEST
1231 tristate "torture tests for RCU"
1232 depends on DEBUG_KERNEL
1233 select TORTURE_TEST
1234 select SRCU
1235 select TASKS_RCU
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.
1241
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.
1246
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.
1258
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.
1263
1264 config RCU_TORTURE_TEST_SLOW_PREINIT
1265 bool "Slow down RCU grace-period pre-initialization to expose races"
1266 depends on RCU_TORTURE_TEST
1267 help
1268 This option delays grace-period pre-initialization (the
1269 propagation of CPU-hotplug changes up the rcu_node combining
1270 tree) for a few jiffies between initializing each pair of
1271 consecutive rcu_node structures. This helps to expose races
1272 involving grace-period pre-initialization, in other words, it
1273 makes your kernel less stable. It can also greatly increase
1274 grace-period latency, especially on systems with large numbers
1275 of CPUs. This is useful when torture-testing RCU, but in
1276 almost no other circumstance.
1277
1278 Say Y here if you want your system to crash and hang more often.
1279 Say N if you want a sane system.
1280
1281 config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
1282 int "How much to slow down RCU grace-period pre-initialization"
1283 range 0 5
1284 default 3
1285 depends on RCU_TORTURE_TEST_SLOW_PREINIT
1286 help
1287 This option specifies the number of jiffies to wait between
1288 each rcu_node structure pre-initialization step.
1289
1290 config RCU_TORTURE_TEST_SLOW_INIT
1291 bool "Slow down RCU grace-period initialization to expose races"
1292 depends on RCU_TORTURE_TEST
1293 help
1294 This option delays grace-period initialization for a few
1295 jiffies between initializing each pair of consecutive
1296 rcu_node structures. This helps to expose races involving
1297 grace-period initialization, in other words, it makes your
1298 kernel less stable. It can also greatly increase grace-period
1299 latency, especially on systems with large numbers of CPUs.
1300 This is useful when torture-testing RCU, but in almost no
1301 other circumstance.
1302
1303 Say Y here if you want your system to crash and hang more often.
1304 Say N if you want a sane system.
1305
1306 config RCU_TORTURE_TEST_SLOW_INIT_DELAY
1307 int "How much to slow down RCU grace-period initialization"
1308 range 0 5
1309 default 3
1310 depends on RCU_TORTURE_TEST_SLOW_INIT
1311 help
1312 This option specifies the number of jiffies to wait between
1313 each rcu_node structure initialization.
1314
1315 config RCU_TORTURE_TEST_SLOW_CLEANUP
1316 bool "Slow down RCU grace-period cleanup to expose races"
1317 depends on RCU_TORTURE_TEST
1318 help
1319 This option delays grace-period cleanup for a few jiffies
1320 between cleaning up each pair of consecutive rcu_node
1321 structures. This helps to expose races involving grace-period
1322 cleanup, in other words, it makes your kernel less stable.
1323 It can also greatly increase grace-period latency, especially
1324 on systems with large numbers of CPUs. This is useful when
1325 torture-testing RCU, but in almost no other circumstance.
1326
1327 Say Y here if you want your system to crash and hang more often.
1328 Say N if you want a sane system.
1329
1330 config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
1331 int "How much to slow down RCU grace-period cleanup"
1332 range 0 5
1333 default 3
1334 depends on RCU_TORTURE_TEST_SLOW_CLEANUP
1335 help
1336 This option specifies the number of jiffies to wait between
1337 each rcu_node structure cleanup operation.
1338
1339 config RCU_CPU_STALL_TIMEOUT
1340 int "RCU CPU stall timeout in seconds"
1341 depends on RCU_STALL_COMMON
1342 range 3 300
1343 default 21
1344 help
1345 If a given RCU grace period extends more than the specified
1346 number of seconds, a CPU stall warning is printed. If the
1347 RCU grace period persists, additional CPU stall warnings are
1348 printed at more widely spaced intervals.
1349
1350 config RCU_TRACE
1351 bool "Enable tracing for RCU"
1352 depends on DEBUG_KERNEL
1353 select TRACE_CLOCK
1354 help
1355 This option provides tracing in RCU which presents stats
1356 in debugfs for debugging RCU implementation.
1357
1358 Say Y here if you want to enable RCU tracing
1359 Say N if you are unsure.
1360
1361 config RCU_EQS_DEBUG
1362 bool "Provide debugging asserts for adding NO_HZ support to an arch"
1363 depends on DEBUG_KERNEL
1364 help
1365 This option provides consistency checks in RCU's handling of
1366 NO_HZ. These checks have proven quite helpful in detecting
1367 bugs in arch-specific NO_HZ code.
1368
1369 Say N here if you need ultimate kernel/user switch latencies
1370 Say Y if you are unsure
1371
1372 endmenu # "RCU Debugging"
1373
1374 config DEBUG_BLOCK_EXT_DEVT
1375 bool "Force extended block device numbers and spread them"
1376 depends on DEBUG_KERNEL
1377 depends on BLOCK
1378 default n
1379 help
1380 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1381 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1382 YOU ARE DOING. Distros, please enable this and fix whatever
1383 is broken.
1384
1385 Conventionally, block device numbers are allocated from
1386 predetermined contiguous area. However, extended block area
1387 may introduce non-contiguous block device numbers. This
1388 option forces most block device numbers to be allocated from
1389 the extended space and spreads them to discover kernel or
1390 userland code paths which assume predetermined contiguous
1391 device number allocation.
1392
1393 Note that turning on this debug option shuffles all the
1394 device numbers for all IDE and SCSI devices including libata
1395 ones, so root partition specified using device number
1396 directly (via rdev or root=MAJ:MIN) won't work anymore.
1397 Textual device names (root=/dev/sdXn) will continue to work.
1398
1399 Say N if you are unsure.
1400
1401 config NOTIFIER_ERROR_INJECTION
1402 tristate "Notifier error injection"
1403 depends on DEBUG_KERNEL
1404 select DEBUG_FS
1405 help
1406 This option provides the ability to inject artificial errors to
1407 specified notifier chain callbacks. It is useful to test the error
1408 handling of notifier call chain failures.
1409
1410 Say N if unsure.
1411
1412 config CPU_NOTIFIER_ERROR_INJECT
1413 tristate "CPU notifier error injection module"
1414 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1415 help
1416 This option provides a kernel module that can be used to test
1417 the error handling of the cpu notifiers by injecting artificial
1418 errors to CPU notifier chain callbacks. It is controlled through
1419 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
1420
1421 If the notifier call chain should be failed with some events
1422 notified, write the error code to "actions/<notifier event>/error".
1423
1424 Example: Inject CPU offline error (-1 == -EPERM)
1425
1426 # cd /sys/kernel/debug/notifier-error-inject/cpu
1427 # echo -1 > actions/CPU_DOWN_PREPARE/error
1428 # echo 0 > /sys/devices/system/cpu/cpu1/online
1429 bash: echo: write error: Operation not permitted
1430
1431 To compile this code as a module, choose M here: the module will
1432 be called cpu-notifier-error-inject.
1433
1434 If unsure, say N.
1435
1436 config PM_NOTIFIER_ERROR_INJECT
1437 tristate "PM notifier error injection module"
1438 depends on PM && NOTIFIER_ERROR_INJECTION
1439 default m if PM_DEBUG
1440 help
1441 This option provides the ability to inject artificial errors to
1442 PM notifier chain callbacks. It is controlled through debugfs
1443 interface /sys/kernel/debug/notifier-error-inject/pm
1444
1445 If the notifier call chain should be failed with some events
1446 notified, write the error code to "actions/<notifier event>/error".
1447
1448 Example: Inject PM suspend error (-12 = -ENOMEM)
1449
1450 # cd /sys/kernel/debug/notifier-error-inject/pm/
1451 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1452 # echo mem > /sys/power/state
1453 bash: echo: write error: Cannot allocate memory
1454
1455 To compile this code as a module, choose M here: the module will
1456 be called pm-notifier-error-inject.
1457
1458 If unsure, say N.
1459
1460 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1461 tristate "OF reconfig notifier error injection module"
1462 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1463 help
1464 This option provides the ability to inject artificial errors to
1465 OF reconfig notifier chain callbacks. It is controlled
1466 through debugfs interface under
1467 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1468
1469 If the notifier call chain should be failed with some events
1470 notified, write the error code to "actions/<notifier event>/error".
1471
1472 To compile this code as a module, choose M here: the module will
1473 be called of-reconfig-notifier-error-inject.
1474
1475 If unsure, say N.
1476
1477 config FAULT_INJECTION
1478 bool "Fault-injection framework"
1479 depends on DEBUG_KERNEL
1480 help
1481 Provide fault-injection framework.
1482 For more details, see Documentation/fault-injection/.
1483
1484 config FAILSLAB
1485 bool "Fault-injection capability for kmalloc"
1486 depends on FAULT_INJECTION
1487 depends on SLAB || SLUB
1488 help
1489 Provide fault-injection capability for kmalloc.
1490
1491 config FAIL_PAGE_ALLOC
1492 bool "Fault-injection capabilitiy for alloc_pages()"
1493 depends on FAULT_INJECTION
1494 help
1495 Provide fault-injection capability for alloc_pages().
1496
1497 config FAIL_MAKE_REQUEST
1498 bool "Fault-injection capability for disk IO"
1499 depends on FAULT_INJECTION && BLOCK
1500 help
1501 Provide fault-injection capability for disk IO.
1502
1503 config FAIL_IO_TIMEOUT
1504 bool "Fault-injection capability for faking disk interrupts"
1505 depends on FAULT_INJECTION && BLOCK
1506 help
1507 Provide fault-injection capability on end IO handling. This
1508 will make the block layer "forget" an interrupt as configured,
1509 thus exercising the error handling.
1510
1511 Only works with drivers that use the generic timeout handling,
1512 for others it wont do anything.
1513
1514 config FAIL_MMC_REQUEST
1515 bool "Fault-injection capability for MMC IO"
1516 select DEBUG_FS
1517 depends on FAULT_INJECTION && MMC
1518 help
1519 Provide fault-injection capability for MMC IO.
1520 This will make the mmc core return data errors. This is
1521 useful to test the error handling in the mmc block device
1522 and to test how the mmc host driver handles retries from
1523 the block device.
1524
1525 config FAIL_FUTEX
1526 bool "Fault-injection capability for futexes"
1527 select DEBUG_FS
1528 depends on FAULT_INJECTION && FUTEX
1529 help
1530 Provide fault-injection capability for futexes.
1531
1532 config FAULT_INJECTION_DEBUG_FS
1533 bool "Debugfs entries for fault-injection capabilities"
1534 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1535 help
1536 Enable configuration of fault-injection capabilities via debugfs.
1537
1538 config FAULT_INJECTION_STACKTRACE_FILTER
1539 bool "stacktrace filter for fault-injection capabilities"
1540 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1541 depends on !X86_64
1542 select STACKTRACE
1543 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1544 help
1545 Provide stacktrace filter for fault-injection capabilities
1546
1547 config LATENCYTOP
1548 bool "Latency measuring infrastructure"
1549 depends on HAVE_LATENCYTOP_SUPPORT
1550 depends on DEBUG_KERNEL
1551 depends on STACKTRACE_SUPPORT
1552 depends on PROC_FS
1553 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1554 select KALLSYMS
1555 select KALLSYMS_ALL
1556 select STACKTRACE
1557 select SCHEDSTATS
1558 select SCHED_DEBUG
1559 help
1560 Enable this option if you want to use the LatencyTOP tool
1561 to find out which userspace is blocking on what kernel operations.
1562
1563 config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1564 bool
1565
1566 config DEBUG_STRICT_USER_COPY_CHECKS
1567 bool "Strict user copy size checks"
1568 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1569 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
1570 help
1571 Enabling this option turns a certain set of sanity checks for user
1572 copy operations into compile time failures.
1573
1574 The copy_from_user() etc checks are there to help test if there
1575 are sufficient security checks on the length argument of
1576 the copy operation, by having gcc prove that the argument is
1577 within bounds.
1578
1579 If unsure, say N.
1580
1581 source kernel/trace/Kconfig
1582
1583 menu "Runtime Testing"
1584
1585 config LKDTM
1586 tristate "Linux Kernel Dump Test Tool Module"
1587 depends on DEBUG_FS
1588 depends on BLOCK
1589 default n
1590 help
1591 This module enables testing of the different dumping mechanisms by
1592 inducing system failures at predefined crash points.
1593 If you don't need it: say N
1594 Choose M here to compile this code as a module. The module will be
1595 called lkdtm.
1596
1597 Documentation on how to use the module can be found in
1598 Documentation/fault-injection/provoke-crashes.txt
1599
1600 config TEST_LIST_SORT
1601 bool "Linked list sorting test"
1602 depends on DEBUG_KERNEL
1603 help
1604 Enable this to turn on 'list_sort()' function test. This test is
1605 executed only once during system boot, so affects only boot time.
1606
1607 If unsure, say N.
1608
1609 config KPROBES_SANITY_TEST
1610 bool "Kprobes sanity tests"
1611 depends on DEBUG_KERNEL
1612 depends on KPROBES
1613 default n
1614 help
1615 This option provides for testing basic kprobes functionality on
1616 boot. A sample kprobe, jprobe and kretprobe are inserted and
1617 verified for functionality.
1618
1619 Say N if you are unsure.
1620
1621 config BACKTRACE_SELF_TEST
1622 tristate "Self test for the backtrace code"
1623 depends on DEBUG_KERNEL
1624 default n
1625 help
1626 This option provides a kernel module that can be used to test
1627 the kernel stack backtrace code. This option is not useful
1628 for distributions or general kernels, but only for kernel
1629 developers working on architecture code.
1630
1631 Note that if you want to also test saved backtraces, you will
1632 have to enable STACKTRACE as well.
1633
1634 Say N if you are unsure.
1635
1636 config RBTREE_TEST
1637 tristate "Red-Black tree test"
1638 depends on DEBUG_KERNEL
1639 help
1640 A benchmark measuring the performance of the rbtree library.
1641 Also includes rbtree invariant checks.
1642
1643 config INTERVAL_TREE_TEST
1644 tristate "Interval tree test"
1645 depends on m && DEBUG_KERNEL
1646 select INTERVAL_TREE
1647 help
1648 A benchmark measuring the performance of the interval tree library
1649
1650 config PERCPU_TEST
1651 tristate "Per cpu operations test"
1652 depends on m && DEBUG_KERNEL
1653 help
1654 Enable this option to build test module which validates per-cpu
1655 operations.
1656
1657 If unsure, say N.
1658
1659 config ATOMIC64_SELFTEST
1660 bool "Perform an atomic64_t self-test at boot"
1661 help
1662 Enable this option to test the atomic64_t functions at boot.
1663
1664 If unsure, say N.
1665
1666 config ASYNC_RAID6_TEST
1667 tristate "Self test for hardware accelerated raid6 recovery"
1668 depends on ASYNC_RAID6_RECOV
1669 select ASYNC_MEMCPY
1670 ---help---
1671 This is a one-shot self test that permutes through the
1672 recovery of all the possible two disk failure scenarios for a
1673 N-disk array. Recovery is performed with the asynchronous
1674 raid6 recovery routines, and will optionally use an offload
1675 engine if one is available.
1676
1677 If unsure, say N.
1678
1679 config TEST_HEXDUMP
1680 tristate "Test functions located in the hexdump module at runtime"
1681
1682 config TEST_STRING_HELPERS
1683 tristate "Test functions located in the string_helpers module at runtime"
1684
1685 config TEST_KSTRTOX
1686 tristate "Test kstrto*() family of functions at runtime"
1687
1688 config TEST_RHASHTABLE
1689 tristate "Perform selftest on resizable hash table"
1690 default n
1691 help
1692 Enable this option to test the rhashtable functions at boot.
1693
1694 If unsure, say N.
1695
1696 endmenu # runtime tests
1697
1698 config PROVIDE_OHCI1394_DMA_INIT
1699 bool "Remote debugging over FireWire early on boot"
1700 depends on PCI && X86
1701 help
1702 If you want to debug problems which hang or crash the kernel early
1703 on boot and the crashing machine has a FireWire port, you can use
1704 this feature to remotely access the memory of the crashed machine
1705 over FireWire. This employs remote DMA as part of the OHCI1394
1706 specification which is now the standard for FireWire controllers.
1707
1708 With remote DMA, you can monitor the printk buffer remotely using
1709 firescope and access all memory below 4GB using fireproxy from gdb.
1710 Even controlling a kernel debugger is possible using remote DMA.
1711
1712 Usage:
1713
1714 If ohci1394_dma=early is used as boot parameter, it will initialize
1715 all OHCI1394 controllers which are found in the PCI config space.
1716
1717 As all changes to the FireWire bus such as enabling and disabling
1718 devices cause a bus reset and thereby disable remote DMA for all
1719 devices, be sure to have the cable plugged and FireWire enabled on
1720 the debugging host before booting the debug target for debugging.
1721
1722 This code (~1k) is freed after boot. By then, the firewire stack
1723 in charge of the OHCI-1394 controllers should be used instead.
1724
1725 See Documentation/debugging-via-ohci1394.txt for more information.
1726
1727 config BUILD_DOCSRC
1728 bool "Build targets in Documentation/ tree"
1729 depends on HEADERS_CHECK
1730 help
1731 This option attempts to build objects from the source files in the
1732 kernel Documentation/ tree.
1733
1734 Say N if you are unsure.
1735
1736 config DMA_API_DEBUG
1737 bool "Enable debugging of DMA-API usage"
1738 depends on HAVE_DMA_API_DEBUG
1739 help
1740 Enable this option to debug the use of the DMA API by device drivers.
1741 With this option you will be able to detect common bugs in device
1742 drivers like double-freeing of DMA mappings or freeing mappings that
1743 were never allocated.
1744
1745 This also attempts to catch cases where a page owned by DMA is
1746 accessed by the cpu in a way that could cause data corruption. For
1747 example, this enables cow_user_page() to check that the source page is
1748 not undergoing DMA.
1749
1750 This option causes a performance degradation. Use only if you want to
1751 debug device drivers and dma interactions.
1752
1753 If unsure, say N.
1754
1755 config TEST_LKM
1756 tristate "Test module loading with 'hello world' module"
1757 default n
1758 depends on m
1759 help
1760 This builds the "test_module" module that emits "Hello, world"
1761 on printk when loaded. It is designed to be used for basic
1762 evaluation of the module loading subsystem (for example when
1763 validating module verification). It lacks any extra dependencies,
1764 and will not normally be loaded by the system unless explicitly
1765 requested by name.
1766
1767 If unsure, say N.
1768
1769 config TEST_USER_COPY
1770 tristate "Test user/kernel boundary protections"
1771 default n
1772 depends on m
1773 help
1774 This builds the "test_user_copy" module that runs sanity checks
1775 on the copy_to/from_user infrastructure, making sure basic
1776 user/kernel boundary testing is working. If it fails to load,
1777 a regression has been detected in the user/kernel memory boundary
1778 protections.
1779
1780 If unsure, say N.
1781
1782 config TEST_BPF
1783 tristate "Test BPF filter functionality"
1784 default n
1785 depends on m && NET
1786 help
1787 This builds the "test_bpf" module that runs various test vectors
1788 against the BPF interpreter or BPF JIT compiler depending on the
1789 current setting. This is in particular useful for BPF JIT compiler
1790 development, but also to run regression tests against changes in
1791 the interpreter code. It also enables test stubs for eBPF maps and
1792 verifier used by user space verifier testsuite.
1793
1794 If unsure, say N.
1795
1796 config TEST_FIRMWARE
1797 tristate "Test firmware loading via userspace interface"
1798 default n
1799 depends on FW_LOADER
1800 help
1801 This builds the "test_firmware" module that creates a userspace
1802 interface for testing firmware loading. This can be used to
1803 control the triggering of firmware loading without needing an
1804 actual firmware-using device. The contents can be rechecked by
1805 userspace.
1806
1807 If unsure, say N.
1808
1809 config TEST_UDELAY
1810 tristate "udelay test driver"
1811 default n
1812 help
1813 This builds the "udelay_test" module that helps to make sure
1814 that udelay() is working properly.
1815
1816 If unsure, say N.
1817
1818 config MEMTEST
1819 bool "Memtest"
1820 depends on HAVE_MEMBLOCK
1821 ---help---
1822 This option adds a kernel parameter 'memtest', which allows memtest
1823 to be set.
1824 memtest=0, mean disabled; -- default
1825 memtest=1, mean do 1 test pattern;
1826 ...
1827 memtest=17, mean do 17 test patterns.
1828 If you are unsure how to answer this question, answer N.
1829
1830 config TEST_STATIC_KEYS
1831 tristate "Test static keys"
1832 default n
1833 depends on m
1834 help
1835 Test the static key interfaces.
1836
1837 If unsure, say N.
1838
1839 source "samples/Kconfig"
1840
1841 source "lib/Kconfig.kgdb"
1842