1 menu "printk and dmesg options"
4 bool "Show timing information on printks"
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/admin-guide/kernel-parameters.rst
18 config CONSOLE_LOGLEVEL_DEFAULT
19 int "Default console loglevel (1-15)"
23 Default loglevel to determine what will be printed on the console.
25 Setting a default here is equivalent to passing in loglevel=<x> in
26 the kernel bootargs. loglevel=<x> continues to override whatever
27 value is specified here as well.
29 Note: This does not affect the log level of un-prefixed printk()
30 usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
33 config MESSAGE_LOGLEVEL_DEFAULT
34 int "Default message log level (1-7)"
38 Default log level for printk statements with no specified priority.
40 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
41 that are auditing their logs closely may want to set it to a lower
44 Note: This does not affect what message level gets printed on the console
45 by default. To change that, use loglevel=<x> in the kernel bootargs,
46 or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value.
48 config BOOT_PRINTK_DELAY
49 bool "Delay each boot printk message by N milliseconds"
50 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
52 This build option allows you to read kernel boot messages
53 by inserting a short delay after each one. The delay is
54 specified in milliseconds on the kernel command line,
57 It is likely that you would also need to use "lpj=M" to preset
58 the "loops per jiffie" value.
59 See a previous boot log for the "lpj" value to use for your
60 system, and then set "lpj=M" before setting "boot_delay=N".
61 NOTE: Using this option may adversely affect SMP systems.
62 I.e., processors other than the first one may not boot up.
63 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
64 what it believes to be lockup conditions.
67 bool "Enable dynamic printk() support"
73 Compiles debug level messages into the kernel, which would not
74 otherwise be available at runtime. These messages can then be
75 enabled/disabled based on various levels of scope - per source file,
76 function, module, format string, and line number. This mechanism
77 implicitly compiles in all pr_debug() and dev_dbg() calls, which
78 enlarges the kernel text size by about 2%.
80 If a source file is compiled with DEBUG flag set, any
81 pr_debug() calls in it are enabled by default, but can be
82 disabled at runtime as below. Note that DEBUG flag is
83 turned on by many CONFIG_*DEBUG* options.
87 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
88 which is contained in the 'debugfs' filesystem. Thus, the debugfs
89 filesystem must first be mounted before making use of this feature.
90 We refer the control file as: <debugfs>/dynamic_debug/control. This
91 file contains a list of the debug statements that can be enabled. The
92 format for each line of the file is:
94 filename:lineno [module]function flags format
96 filename : source file of the debug statement
97 lineno : line number of the debug statement
98 module : module that contains the debug statement
99 function : function that contains the debug statement
100 flags : '=p' means the line is turned 'on' for printing
101 format : the format used for the debug statement
105 nullarbor:~ # cat <debugfs>/dynamic_debug/control
106 # filename:lineno [module]function flags format
107 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
108 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
109 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
113 // enable the message at line 1603 of file svcsock.c
114 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
115 <debugfs>/dynamic_debug/control
117 // enable all the messages in file svcsock.c
118 nullarbor:~ # echo -n 'file svcsock.c +p' >
119 <debugfs>/dynamic_debug/control
121 // enable all the messages in the NFS server module
122 nullarbor:~ # echo -n 'module nfsd +p' >
123 <debugfs>/dynamic_debug/control
125 // enable all 12 messages in the function svc_process()
126 nullarbor:~ # echo -n 'func svc_process +p' >
127 <debugfs>/dynamic_debug/control
129 // disable all 12 messages in the function svc_process()
130 nullarbor:~ # echo -n 'func svc_process -p' >
131 <debugfs>/dynamic_debug/control
133 See Documentation/admin-guide/dynamic-debug-howto.rst for additional
136 endmenu # "printk and dmesg options"
138 menu "Compile-time checks and compiler options"
141 bool "Compile the kernel with debug info"
142 depends on DEBUG_KERNEL && !COMPILE_TEST
144 If you say Y here the resulting kernel image will include
145 debugging info resulting in a larger kernel image.
146 This adds debug symbols to the kernel and modules (gcc -g), and
147 is needed if you intend to use kernel crashdump or binary object
148 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
149 Say Y here only if you plan to debug the kernel.
153 config DEBUG_INFO_REDUCED
154 bool "Reduce debugging information"
155 depends on DEBUG_INFO
157 If you say Y here gcc is instructed to generate less debugging
158 information for structure types. This means that tools that
159 need full debugging information (like kgdb or systemtap) won't
160 be happy. But if you merely need debugging information to
161 resolve line numbers there is no loss. Advantage is that
162 build directory object sizes shrink dramatically over a full
163 DEBUG_INFO build and compile times are reduced too.
164 Only works with newer gcc versions.
166 config DEBUG_INFO_SPLIT
167 bool "Produce split debuginfo in .dwo files"
168 depends on DEBUG_INFO && !FRV
170 Generate debug info into separate .dwo files. This significantly
171 reduces the build directory size for builds with DEBUG_INFO,
172 because it stores the information only once on disk in .dwo
173 files instead of multiple times in object files and executables.
174 In addition the debug information is also compressed.
176 Requires recent gcc (4.7+) and recent gdb/binutils.
177 Any tool that packages or reads debug information would need
178 to know about the .dwo files and include them.
179 Incompatible with older versions of ccache.
181 config DEBUG_INFO_DWARF4
182 bool "Generate dwarf4 debuginfo"
183 depends on DEBUG_INFO
185 Generate dwarf4 debug info. This requires recent versions
186 of gcc and gdb. It makes the debug information larger.
187 But it significantly improves the success of resolving
188 variables in gdb on optimized code.
191 bool "Provide GDB scripts for kernel debugging"
192 depends on DEBUG_INFO
194 This creates the required links to GDB helper scripts in the
195 build directory. If you load vmlinux into gdb, the helper
196 scripts will be automatically imported by gdb as well, and
197 additional functions are available to analyze a Linux kernel
198 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
201 config ENABLE_WARN_DEPRECATED
202 bool "Enable __deprecated logic"
205 Enable the __deprecated logic in the kernel build.
206 Disable this to suppress the "warning: 'foo' is deprecated
207 (declared at kernel/power/somefile.c:1234)" messages.
209 config ENABLE_MUST_CHECK
210 bool "Enable __must_check logic"
213 Enable the __must_check logic in the kernel build. Disable this to
214 suppress the "warning: ignoring return value of 'foo', declared with
215 attribute warn_unused_result" messages.
218 int "Warn for stack frames larger than (needs gcc 4.4)"
221 default 2048 if GCC_PLUGIN_LATENT_ENTROPY
222 default 1280 if (!64BIT && PARISC)
223 default 1024 if (!64BIT && !PARISC)
224 default 2048 if 64BIT
226 Tell gcc to warn at build time for stack frames larger than this.
227 Setting this too low will cause a lot of warnings.
228 Setting it to 0 disables the warning.
231 config STRIP_ASM_SYMS
232 bool "Strip assembler-generated symbols during link"
235 Strip internal assembler-generated symbols during a link (symbols
236 that look like '.Lxxx') so they don't pollute the output of
237 get_wchan() and suchlike.
240 bool "Generate readable assembler code"
241 depends on DEBUG_KERNEL
243 Disable some compiler optimizations that tend to generate human unreadable
244 assembler output. This may make the kernel slightly slower, but it helps
245 to keep kernel developers who have to stare a lot at assembler listings
248 config UNUSED_SYMBOLS
249 bool "Enable unused/obsolete exported symbols"
252 Unused but exported symbols make the kernel needlessly bigger. For
253 that reason most of these unused exports will soon be removed. This
254 option is provided temporarily to provide a transition period in case
255 some external kernel module needs one of these symbols anyway. If you
256 encounter such a case in your module, consider if you are actually
257 using the right API. (rationale: since nobody in the kernel is using
258 this in a module, there is a pretty good chance it's actually the
259 wrong interface to use). If you really need the symbol, please send a
260 mail to the linux kernel mailing list mentioning the symbol and why
261 you really need it, and what the merge plan to the mainline kernel for
265 bool "Track page owner"
266 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
270 select PAGE_EXTENSION
272 This keeps track of what call chain is the owner of a page, may
273 help to find bare alloc_page(s) leaks. Even if you include this
274 feature on your build, it is disabled in default. You should pass
275 "page_owner=on" to boot parameter in order to enable it. Eats
276 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
277 for user-space helper.
282 bool "Debug Filesystem"
284 debugfs is a virtual file system that kernel developers use to put
285 debugging files into. Enable this option to be able to read and
286 write to these files.
288 For detailed documentation on the debugfs API, see
289 Documentation/filesystems/.
294 bool "Run 'make headers_check' when building vmlinux"
297 This option will extract the user-visible kernel headers whenever
298 building the kernel, and will run basic sanity checks on them to
299 ensure that exported files do not attempt to include files which
300 were not exported, etc.
302 If you're making modifications to header files which are
303 relevant for userspace, say 'Y', and check the headers
304 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
305 your build tree), to make sure they're suitable.
307 config DEBUG_SECTION_MISMATCH
308 bool "Enable full Section mismatch analysis"
310 The section mismatch analysis checks if there are illegal
311 references from one section to another section.
312 During linktime or runtime, some sections are dropped;
313 any use of code/data previously in these sections would
314 most likely result in an oops.
315 In the code, functions and variables are annotated with
316 __init,, etc. (see the full list in include/linux/init.h),
317 which results in the code/data being placed in specific sections.
318 The section mismatch analysis is always performed after a full
319 kernel build, and enabling this option causes the following
320 additional steps to occur:
321 - Add the option -fno-inline-functions-called-once to gcc commands.
322 When inlining a function annotated with __init in a non-init
323 function, we would lose the section information and thus
324 the analysis would not catch the illegal reference.
325 This option tells gcc to inline less (but it does result in
327 - Run the section mismatch analysis for each module/built-in.o file.
328 When we run the section mismatch analysis on vmlinux.o, we
329 lose valuable information about where the mismatch was
331 Running the analysis for each module/built-in.o file
332 tells where the mismatch happens much closer to the
333 source. The drawback is that the same mismatch is
334 reported at least twice.
335 - Enable verbose reporting from modpost in order to help resolve
336 the section mismatches that are reported.
338 config SECTION_MISMATCH_WARN_ONLY
339 bool "Make section mismatch errors non-fatal"
342 If you say N here, the build process will fail if there are any
343 section mismatch, instead of just throwing warnings.
348 # Select this config option from the architecture Kconfig, if it
349 # is preferred to always offer frame pointers as a config
350 # option on the architecture (regardless of KERNEL_DEBUG):
352 config ARCH_WANT_FRAME_POINTERS
357 bool "Compile the kernel with frame pointers"
358 depends on DEBUG_KERNEL && \
359 (CRIS || M68K || FRV || UML || \
360 SUPERH || BLACKFIN || MN10300 || METAG) || \
361 ARCH_WANT_FRAME_POINTERS
362 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
364 If you say Y here the resulting kernel image will be slightly
365 larger and slower, but it gives very useful debugging information
366 in case of kernel bugs. (precise oopses/stacktraces/warnings)
368 config STACK_VALIDATION
369 bool "Compile-time stack metadata validation"
370 depends on HAVE_STACK_VALIDATION
373 Add compile-time checks to validate stack metadata, including frame
374 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
375 that runtime stack traces are more reliable.
377 This is also a prerequisite for generation of ORC unwind data, which
378 is needed for CONFIG_UNWINDER_ORC.
380 For more information, see
381 tools/objtool/Documentation/stack-validation.txt.
383 config DEBUG_FORCE_WEAK_PER_CPU
384 bool "Force weak per-cpu definitions"
385 depends on DEBUG_KERNEL
387 s390 and alpha require percpu variables in modules to be
388 defined weak to work around addressing range issue which
389 puts the following two restrictions on percpu variable
392 1. percpu symbols must be unique whether static or not
393 2. percpu variables can't be defined inside a function
395 To ensure that generic code follows the above rules, this
396 option forces all percpu variables to be defined as weak.
398 endmenu # "Compiler options"
401 bool "Magic SysRq key"
404 If you say Y here, you will have some control over the system even
405 if the system crashes for example during kernel debugging (e.g., you
406 will be able to flush the buffer cache to disk, reboot the system
407 immediately or dump some status information). This is accomplished
408 by pressing various keys while holding SysRq (Alt+PrintScreen). It
409 also works on a serial console (on PC hardware at least), if you
410 send a BREAK and then within 5 seconds a command keypress. The
411 keys are documented in <file:Documentation/admin-guide/sysrq.rst>.
412 Don't say Y unless you really know what this hack does.
414 config MAGIC_SYSRQ_DEFAULT_ENABLE
415 hex "Enable magic SysRq key functions by default"
416 depends on MAGIC_SYSRQ
419 Specifies which SysRq key functions are enabled by default.
420 This may be set to 1 or 0 to enable or disable them all, or
421 to a bitmask as described in Documentation/admin-guide/sysrq.rst.
423 config MAGIC_SYSRQ_SERIAL
424 bool "Enable magic SysRq key over serial"
425 depends on MAGIC_SYSRQ
428 Many embedded boards have a disconnected TTL level serial which can
429 generate some garbage that can lead to spurious false sysrq detects.
430 This option allows you to decide whether you want to enable the
434 bool "Kernel debugging"
436 Say Y here if you are developing drivers or trying to debug and
437 identify kernel problems.
439 menu "Memory Debugging"
441 source mm/Kconfig.debug
444 bool "Debug object operations"
445 depends on DEBUG_KERNEL
447 If you say Y here, additional code will be inserted into the
448 kernel to track the life time of various objects and validate
449 the operations on those objects.
451 config DEBUG_OBJECTS_SELFTEST
452 bool "Debug objects selftest"
453 depends on DEBUG_OBJECTS
455 This enables the selftest of the object debug code.
457 config DEBUG_OBJECTS_FREE
458 bool "Debug objects in freed memory"
459 depends on DEBUG_OBJECTS
461 This enables checks whether a k/v free operation frees an area
462 which contains an object which has not been deactivated
463 properly. This can make kmalloc/kfree-intensive workloads
466 config DEBUG_OBJECTS_TIMERS
467 bool "Debug timer objects"
468 depends on DEBUG_OBJECTS
470 If you say Y here, additional code will be inserted into the
471 timer routines to track the life time of timer objects and
472 validate the timer operations.
474 config DEBUG_OBJECTS_WORK
475 bool "Debug work objects"
476 depends on DEBUG_OBJECTS
478 If you say Y here, additional code will be inserted into the
479 work queue routines to track the life time of work objects and
480 validate the work operations.
482 config DEBUG_OBJECTS_RCU_HEAD
483 bool "Debug RCU callbacks objects"
484 depends on DEBUG_OBJECTS
486 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
488 config DEBUG_OBJECTS_PERCPU_COUNTER
489 bool "Debug percpu counter objects"
490 depends on DEBUG_OBJECTS
492 If you say Y here, additional code will be inserted into the
493 percpu counter routines to track the life time of percpu counter
494 objects and validate the percpu counter operations.
496 config DEBUG_OBJECTS_ENABLE_DEFAULT
497 int "debug_objects bootup default value (0-1)"
500 depends on DEBUG_OBJECTS
502 Debug objects boot parameter default value
505 bool "Debug slab memory allocations"
506 depends on DEBUG_KERNEL && SLAB
508 Say Y here to have the kernel do limited verification on memory
509 allocation as well as poisoning memory on free to catch use of freed
510 memory. This can make kmalloc/kfree-intensive workloads much slower.
512 config DEBUG_SLAB_LEAK
513 bool "Memory leak debugging"
514 depends on DEBUG_SLAB
517 bool "SLUB debugging on by default"
518 depends on SLUB && SLUB_DEBUG
521 Boot with debugging on by default. SLUB boots by default with
522 the runtime debug capabilities switched off. Enabling this is
523 equivalent to specifying the "slub_debug" parameter on boot.
524 There is no support for more fine grained debug control like
525 possible with slub_debug=xxx. SLUB debugging may be switched
526 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
531 bool "Enable SLUB performance statistics"
532 depends on SLUB && SYSFS
534 SLUB statistics are useful to debug SLUBs allocation behavior in
535 order find ways to optimize the allocator. This should never be
536 enabled for production use since keeping statistics slows down
537 the allocator by a few percentage points. The slabinfo command
538 supports the determination of the most active slabs to figure
539 out which slabs are relevant to a particular load.
540 Try running: slabinfo -DA
542 config HAVE_DEBUG_KMEMLEAK
545 config DEBUG_KMEMLEAK
546 bool "Kernel memory leak detector"
547 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
549 select STACKTRACE if STACKTRACE_SUPPORT
553 Say Y here if you want to enable the memory leak
554 detector. The memory allocation/freeing is traced in a way
555 similar to the Boehm's conservative garbage collector, the
556 difference being that the orphan objects are not freed but
557 only shown in /sys/kernel/debug/kmemleak. Enabling this
558 feature will introduce an overhead to memory
559 allocations. See Documentation/dev-tools/kmemleak.rst for more
562 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
563 of finding leaks due to the slab objects poisoning.
565 In order to access the kmemleak file, debugfs needs to be
566 mounted (usually at /sys/kernel/debug).
568 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
569 int "Maximum kmemleak early log entries"
570 depends on DEBUG_KMEMLEAK
574 Kmemleak must track all the memory allocations to avoid
575 reporting false positives. Since memory may be allocated or
576 freed before kmemleak is initialised, an early log buffer is
577 used to store these actions. If kmemleak reports "early log
578 buffer exceeded", please increase this value.
580 config DEBUG_KMEMLEAK_TEST
581 tristate "Simple test for the kernel memory leak detector"
582 depends on DEBUG_KMEMLEAK && m
584 This option enables a module that explicitly leaks memory.
588 config DEBUG_KMEMLEAK_DEFAULT_OFF
589 bool "Default kmemleak to off"
590 depends on DEBUG_KMEMLEAK
592 Say Y here to disable kmemleak by default. It can then be enabled
593 on the command line via kmemleak=on.
595 config DEBUG_STACK_USAGE
596 bool "Stack utilization instrumentation"
597 depends on DEBUG_KERNEL && !IA64
599 Enables the display of the minimum amount of free stack which each
600 task has ever had available in the sysrq-T and sysrq-P debug output.
602 This option will slow down process creation somewhat.
606 depends on DEBUG_KERNEL
608 Enable this to turn on extended checks in the virtual-memory system
609 that may impact performance.
613 config DEBUG_VM_VMACACHE
614 bool "Debug VMA caching"
617 Enable this to turn on VMA caching debug information. Doing so
618 can cause significant overhead, so only enable it in non-production
624 bool "Debug VM red-black trees"
627 Enable VM red-black tree debugging information and extra validations.
631 config DEBUG_VM_PGFLAGS
632 bool "Debug page-flags operations"
635 Enables extra validation on page flags operations.
639 config ARCH_HAS_DEBUG_VIRTUAL
643 bool "Debug VM translations"
644 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
646 Enable some costly sanity checks in virtual to page code. This can
647 catch mistakes with virt_to_page() and friends.
651 config DEBUG_NOMMU_REGIONS
652 bool "Debug the global anon/private NOMMU mapping region tree"
653 depends on DEBUG_KERNEL && !MMU
655 This option causes the global tree of anonymous and private mapping
656 regions to be regularly checked for invalid topology.
658 config DEBUG_MEMORY_INIT
659 bool "Debug memory initialisation" if EXPERT
662 Enable this for additional checks during memory initialisation.
663 The sanity checks verify aspects of the VM such as the memory model
664 and other information provided by the architecture. Verbose
665 information will be printed at KERN_DEBUG loglevel depending
666 on the mminit_loglevel= command-line option.
670 config MEMORY_NOTIFIER_ERROR_INJECT
671 tristate "Memory hotplug notifier error injection module"
672 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
674 This option provides the ability to inject artificial errors to
675 memory hotplug notifier chain callbacks. It is controlled through
676 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
678 If the notifier call chain should be failed with some events
679 notified, write the error code to "actions/<notifier event>/error".
681 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
683 # cd /sys/kernel/debug/notifier-error-inject/memory
684 # echo -12 > actions/MEM_GOING_OFFLINE/error
685 # echo offline > /sys/devices/system/memory/memoryXXX/state
686 bash: echo: write error: Cannot allocate memory
688 To compile this code as a module, choose M here: the module will
689 be called memory-notifier-error-inject.
693 config DEBUG_PER_CPU_MAPS
694 bool "Debug access to per_cpu maps"
695 depends on DEBUG_KERNEL
698 Say Y to verify that the per_cpu map being accessed has
699 been set up. This adds a fair amount of code to kernel memory
700 and decreases performance.
705 bool "Highmem debugging"
706 depends on DEBUG_KERNEL && HIGHMEM
708 This option enables additional error checking for high memory
709 systems. Disable for production systems.
711 config HAVE_DEBUG_STACKOVERFLOW
714 config DEBUG_STACKOVERFLOW
715 bool "Check for stack overflows"
716 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
718 Say Y here if you want to check for overflows of kernel, IRQ
719 and exception stacks (if your architecture uses them). This
720 option will show detailed messages if free stack space drops
721 below a certain limit.
723 These kinds of bugs usually occur when call-chains in the
724 kernel get too deep, especially when interrupts are
727 Use this in cases where you see apparently random memory
728 corruption, especially if it appears in 'struct thread_info'
730 If in doubt, say "N".
732 source "lib/Kconfig.kasan"
734 endmenu # "Memory Debugging"
739 KCOV does not have any arch-specific code, but currently it is enabled
740 only for x86_64. KCOV requires testing on other archs, and most likely
741 disabling of instrumentation for some early boot code.
744 bool "Code coverage for fuzzing"
745 depends on ARCH_HAS_KCOV
747 select GCC_PLUGINS if !COMPILE_TEST
748 select GCC_PLUGIN_SANCOV if !COMPILE_TEST
750 KCOV exposes kernel code coverage information in a form suitable
751 for coverage-guided fuzzing (randomized testing).
753 If RANDOMIZE_BASE is enabled, PC values will not be stable across
754 different machines and across reboots. If you need stable PC values,
755 disable RANDOMIZE_BASE.
757 For more details, see Documentation/dev-tools/kcov.rst.
759 config KCOV_INSTRUMENT_ALL
760 bool "Instrument all code by default"
764 If you are doing generic system call fuzzing (like e.g. syzkaller),
765 then you will want to instrument the whole kernel and you should
766 say y here. If you are doing more targeted fuzzing (like e.g.
767 filesystem fuzzing with AFL) then you will want to enable coverage
768 for more specific subsets of files, and should say n here.
771 bool "Debug shared IRQ handlers"
772 depends on DEBUG_KERNEL
774 Enable this to generate a spurious interrupt as soon as a shared
775 interrupt handler is registered, and just before one is deregistered.
776 Drivers ought to be able to handle interrupts coming in at those
777 points; some don't and need to be caught.
779 menu "Debug Lockups and Hangs"
781 config LOCKUP_DETECTOR
784 config SOFTLOCKUP_DETECTOR
785 bool "Detect Soft Lockups"
786 depends on DEBUG_KERNEL && !S390
787 select LOCKUP_DETECTOR
789 Say Y here to enable the kernel to act as a watchdog to detect
792 Softlockups are bugs that cause the kernel to loop in kernel
793 mode for more than 20 seconds, without giving other tasks a
794 chance to run. The current stack trace is displayed upon
795 detection and the system will stay locked up.
797 config HARDLOCKUP_DETECTOR_PERF
799 select SOFTLOCKUP_DETECTOR
802 # Enables a timestamp based low pass filter to compensate for perf based
803 # hard lockup detection which runs too fast due to turbo modes.
805 config HARDLOCKUP_CHECK_TIMESTAMP
809 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
810 # lockup detector rather than the perf based detector.
812 config HARDLOCKUP_DETECTOR
813 bool "Detect Hard Lockups"
814 depends on DEBUG_KERNEL && !S390
815 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
816 select LOCKUP_DETECTOR
817 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
818 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
820 Say Y here to enable the kernel to act as a watchdog to detect
823 Hardlockups are bugs that cause the CPU to loop in kernel mode
824 for more than 10 seconds, without letting other interrupts have a
825 chance to run. The current stack trace is displayed upon detection
826 and the system will stay locked up.
828 config BOOTPARAM_HARDLOCKUP_PANIC
829 bool "Panic (Reboot) On Hard Lockups"
830 depends on HARDLOCKUP_DETECTOR
832 Say Y here to enable the kernel to panic on "hard lockups",
833 which are bugs that cause the kernel to loop in kernel
834 mode with interrupts disabled for more than 10 seconds (configurable
835 using the watchdog_thresh sysctl).
839 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
841 depends on HARDLOCKUP_DETECTOR
843 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
844 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
846 config BOOTPARAM_SOFTLOCKUP_PANIC
847 bool "Panic (Reboot) On Soft Lockups"
848 depends on SOFTLOCKUP_DETECTOR
850 Say Y here to enable the kernel to panic on "soft lockups",
851 which are bugs that cause the kernel to loop in kernel
852 mode for more than 20 seconds (configurable using the watchdog_thresh
853 sysctl), without giving other tasks a chance to run.
855 The panic can be used in combination with panic_timeout,
856 to cause the system to reboot automatically after a
857 lockup has been detected. This feature is useful for
858 high-availability systems that have uptime guarantees and
859 where a lockup must be resolved ASAP.
863 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
865 depends on SOFTLOCKUP_DETECTOR
867 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
868 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
870 config DETECT_HUNG_TASK
871 bool "Detect Hung Tasks"
872 depends on DEBUG_KERNEL
873 default SOFTLOCKUP_DETECTOR
875 Say Y here to enable the kernel to detect "hung tasks",
876 which are bugs that cause the task to be stuck in
877 uninterruptible "D" state indefinitely.
879 When a hung task is detected, the kernel will print the
880 current stack trace (which you should report), but the
881 task will stay in uninterruptible state. If lockdep is
882 enabled then all held locks will also be reported. This
883 feature has negligible overhead.
885 config DEFAULT_HUNG_TASK_TIMEOUT
886 int "Default timeout for hung task detection (in seconds)"
887 depends on DETECT_HUNG_TASK
890 This option controls the default timeout (in seconds) used
891 to determine when a task has become non-responsive and should
894 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
895 sysctl or by writing a value to
896 /proc/sys/kernel/hung_task_timeout_secs.
898 A timeout of 0 disables the check. The default is two minutes.
899 Keeping the default should be fine in most cases.
901 config BOOTPARAM_HUNG_TASK_PANIC
902 bool "Panic (Reboot) On Hung Tasks"
903 depends on DETECT_HUNG_TASK
905 Say Y here to enable the kernel to panic on "hung tasks",
906 which are bugs that cause the kernel to leave a task stuck
907 in uninterruptible "D" state.
909 The panic can be used in combination with panic_timeout,
910 to cause the system to reboot automatically after a
911 hung task has been detected. This feature is useful for
912 high-availability systems that have uptime guarantees and
913 where a hung tasks must be resolved ASAP.
917 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
919 depends on DETECT_HUNG_TASK
921 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
922 default 1 if BOOTPARAM_HUNG_TASK_PANIC
925 bool "Detect Workqueue Stalls"
926 depends on DEBUG_KERNEL
928 Say Y here to enable stall detection on workqueues. If a
929 worker pool doesn't make forward progress on a pending work
930 item for over a given amount of time, 30s by default, a
931 warning message is printed along with dump of workqueue
932 state. This can be configured through kernel parameter
933 "workqueue.watchdog_thresh" and its sysfs counterpart.
935 endmenu # "Debug lockups and hangs"
940 Say Y here to enable the kernel to panic when it oopses. This
941 has the same effect as setting oops=panic on the kernel command
944 This feature is useful to ensure that the kernel does not do
945 anything erroneous after an oops which could result in data
946 corruption or other issues.
950 config PANIC_ON_OOPS_VALUE
953 default 0 if !PANIC_ON_OOPS
954 default 1 if PANIC_ON_OOPS
960 Set the timeout value (in seconds) until a reboot occurs when the
961 the kernel panics. If n = 0, then we wait forever. A timeout
962 value n > 0 will wait n seconds before rebooting, while a timeout
963 value n < 0 will reboot immediately.
966 bool "Collect scheduler debugging info"
967 depends on DEBUG_KERNEL && PROC_FS
970 If you say Y here, the /proc/sched_debug file will be provided
971 that can help debug the scheduler. The runtime overhead of this
979 bool "Collect scheduler statistics"
980 depends on DEBUG_KERNEL && PROC_FS
983 If you say Y here, additional code will be inserted into the
984 scheduler and related routines to collect statistics about
985 scheduler behavior and provide them in /proc/schedstat. These
986 stats may be useful for both tuning and debugging the scheduler
987 If you aren't debugging the scheduler or trying to tune a specific
988 application, you can say N to avoid the very slight overhead
991 config SCHED_STACK_END_CHECK
992 bool "Detect stack corruption on calls to schedule()"
993 depends on DEBUG_KERNEL
996 This option checks for a stack overrun on calls to schedule().
997 If the stack end location is found to be over written always panic as
998 the content of the corrupted region can no longer be trusted.
999 This is to ensure no erroneous behaviour occurs which could result in
1000 data corruption or a sporadic crash at a later stage once the region
1001 is examined. The runtime overhead introduced is minimal.
1003 config DEBUG_TIMEKEEPING
1004 bool "Enable extra timekeeping sanity checking"
1006 This option will enable additional timekeeping sanity checks
1007 which may be helpful when diagnosing issues where timekeeping
1008 problems are suspected.
1010 This may include checks in the timekeeping hotpaths, so this
1011 option may have a (very small) performance impact to some
1016 config DEBUG_PREEMPT
1017 bool "Debug preemptible kernel"
1018 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1021 If you say Y here then the kernel will use a debug variant of the
1022 commonly used smp_processor_id() function and will print warnings
1023 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1024 will detect preemption count underflows.
1026 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1028 config DEBUG_RT_MUTEXES
1029 bool "RT Mutex debugging, deadlock detection"
1030 depends on DEBUG_KERNEL && RT_MUTEXES
1032 This allows rt mutex semantics violations and rt mutex related
1033 deadlocks (lockups) to be detected and reported automatically.
1035 config DEBUG_SPINLOCK
1036 bool "Spinlock and rw-lock debugging: basic checks"
1037 depends on DEBUG_KERNEL
1038 select UNINLINE_SPIN_UNLOCK
1040 Say Y here and build SMP to catch missing spinlock initialization
1041 and certain other kinds of spinlock errors commonly made. This is
1042 best used in conjunction with the NMI watchdog so that spinlock
1043 deadlocks are also debuggable.
1045 config DEBUG_MUTEXES
1046 bool "Mutex debugging: basic checks"
1047 depends on DEBUG_KERNEL
1049 This feature allows mutex semantics violations to be detected and
1052 config DEBUG_WW_MUTEX_SLOWPATH
1053 bool "Wait/wound mutex debugging: Slowpath testing"
1054 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1055 select DEBUG_LOCK_ALLOC
1056 select DEBUG_SPINLOCK
1057 select DEBUG_MUTEXES
1059 This feature enables slowpath testing for w/w mutex users by
1060 injecting additional -EDEADLK wound/backoff cases. Together with
1061 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1062 will test all possible w/w mutex interface abuse with the
1063 exception of simply not acquiring all the required locks.
1064 Note that this feature can introduce significant overhead, so
1065 it really should not be enabled in a production or distro kernel,
1066 even a debug kernel. If you are a driver writer, enable it. If
1067 you are a distro, do not.
1069 config DEBUG_LOCK_ALLOC
1070 bool "Lock debugging: detect incorrect freeing of live locks"
1071 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1072 select DEBUG_SPINLOCK
1073 select DEBUG_MUTEXES
1074 select DEBUG_RT_MUTEXES if RT_MUTEXES
1077 This feature will check whether any held lock (spinlock, rwlock,
1078 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1079 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1080 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1081 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1082 held during task exit.
1084 config PROVE_LOCKING
1085 bool "Lock debugging: prove locking correctness"
1086 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1088 select DEBUG_SPINLOCK
1089 select DEBUG_MUTEXES
1090 select DEBUG_RT_MUTEXES if RT_MUTEXES
1091 select DEBUG_LOCK_ALLOC
1092 select LOCKDEP_CROSSRELEASE
1093 select LOCKDEP_COMPLETIONS
1094 select TRACE_IRQFLAGS
1097 This feature enables the kernel to prove that all locking
1098 that occurs in the kernel runtime is mathematically
1099 correct: that under no circumstance could an arbitrary (and
1100 not yet triggered) combination of observed locking
1101 sequences (on an arbitrary number of CPUs, running an
1102 arbitrary number of tasks and interrupt contexts) cause a
1105 In short, this feature enables the kernel to report locking
1106 related deadlocks before they actually occur.
1108 The proof does not depend on how hard and complex a
1109 deadlock scenario would be to trigger: how many
1110 participant CPUs, tasks and irq-contexts would be needed
1111 for it to trigger. The proof also does not depend on
1112 timing: if a race and a resulting deadlock is possible
1113 theoretically (no matter how unlikely the race scenario
1114 is), it will be proven so and will immediately be
1115 reported by the kernel (once the event is observed that
1116 makes the deadlock theoretically possible).
1118 If a deadlock is impossible (i.e. the locking rules, as
1119 observed by the kernel, are mathematically correct), the
1120 kernel reports nothing.
1122 NOTE: this feature can also be enabled for rwlocks, mutexes
1123 and rwsems - in which case all dependencies between these
1124 different locking variants are observed and mapped too, and
1125 the proof of observed correctness is also maintained for an
1126 arbitrary combination of these separate locking variants.
1128 For more details, see Documentation/locking/lockdep-design.txt.
1132 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1134 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE && !X86
1138 config LOCKDEP_SMALL
1142 bool "Lock usage statistics"
1143 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1145 select DEBUG_SPINLOCK
1146 select DEBUG_MUTEXES
1147 select DEBUG_RT_MUTEXES if RT_MUTEXES
1148 select DEBUG_LOCK_ALLOC
1151 This feature enables tracking lock contention points
1153 For more details, see Documentation/locking/lockstat.txt
1155 This also enables lock events required by "perf lock",
1157 If you want to use "perf lock", you also need to turn on
1158 CONFIG_EVENT_TRACING.
1160 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1161 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1163 config LOCKDEP_CROSSRELEASE
1166 This makes lockdep work for crosslock which is a lock allowed to
1167 be released in a different context from the acquisition context.
1168 Normally a lock must be released in the context acquiring the lock.
1169 However, relexing this constraint helps synchronization primitives
1170 such as page locks or completions can use the lock correctness
1173 config LOCKDEP_COMPLETIONS
1176 A deadlock caused by wait_for_completion() and complete() can be
1177 detected by lockdep using crossrelease feature.
1179 config BOOTPARAM_LOCKDEP_CROSSRELEASE_FULLSTACK
1180 bool "Enable the boot parameter, crossrelease_fullstack"
1181 depends on LOCKDEP_CROSSRELEASE
1184 The lockdep "cross-release" feature needs to record stack traces
1185 (of calling functions) for all acquisitions, for eventual later
1186 use during analysis. By default only a single caller is recorded,
1187 because the unwind operation can be very expensive with deeper
1190 However a boot parameter, crossrelease_fullstack, was
1191 introduced since sometimes deeper traces are required for full
1192 analysis. This option turns on the boot parameter.
1194 config DEBUG_LOCKDEP
1195 bool "Lock dependency engine debugging"
1196 depends on DEBUG_KERNEL && LOCKDEP
1198 If you say Y here, the lock dependency engine will do
1199 additional runtime checks to debug itself, at the price
1200 of more runtime overhead.
1202 config DEBUG_ATOMIC_SLEEP
1203 bool "Sleep inside atomic section checking"
1204 select PREEMPT_COUNT
1205 depends on DEBUG_KERNEL
1207 If you say Y here, various routines which may sleep will become very
1208 noisy if they are called inside atomic sections: when a spinlock is
1209 held, inside an rcu read side critical section, inside preempt disabled
1210 sections, inside an interrupt, etc...
1212 config DEBUG_LOCKING_API_SELFTESTS
1213 bool "Locking API boot-time self-tests"
1214 depends on DEBUG_KERNEL
1216 Say Y here if you want the kernel to run a short self-test during
1217 bootup. The self-test checks whether common types of locking bugs
1218 are detected by debugging mechanisms or not. (if you disable
1219 lock debugging then those bugs wont be detected of course.)
1220 The following locking APIs are covered: spinlocks, rwlocks,
1223 config LOCK_TORTURE_TEST
1224 tristate "torture tests for locking"
1225 depends on DEBUG_KERNEL
1229 This option provides a kernel module that runs torture tests
1230 on kernel locking primitives. The kernel module may be built
1231 after the fact on the running kernel to be tested, if desired.
1233 Say Y here if you want kernel locking-primitive torture tests
1234 to be built into the kernel.
1235 Say M if you want these torture tests to build as a module.
1236 Say N if you are unsure.
1238 config WW_MUTEX_SELFTEST
1239 tristate "Wait/wound mutex selftests"
1241 This option provides a kernel module that runs tests on the
1242 on the struct ww_mutex locking API.
1244 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1245 with this test harness.
1247 Say M if you want these self tests to build as a module.
1248 Say N if you are unsure.
1250 endmenu # lock debugging
1252 config TRACE_IRQFLAGS
1255 Enables hooks to interrupt enabling and disabling for
1256 either tracing or lock debugging.
1259 bool "Stack backtrace support"
1260 depends on STACKTRACE_SUPPORT
1262 This option causes the kernel to create a /proc/pid/stack for
1263 every process, showing its current stack trace.
1264 It is also used by various kernel debugging features that require
1265 stack trace generation.
1267 config WARN_ALL_UNSEEDED_RANDOM
1268 bool "Warn for all uses of unseeded randomness"
1271 Some parts of the kernel contain bugs relating to their use of
1272 cryptographically secure random numbers before it's actually possible
1273 to generate those numbers securely. This setting ensures that these
1274 flaws don't go unnoticed, by enabling a message, should this ever
1275 occur. This will allow people with obscure setups to know when things
1276 are going wrong, so that they might contact developers about fixing
1279 Unfortunately, on some models of some architectures getting
1280 a fully seeded CRNG is extremely difficult, and so this can
1281 result in dmesg getting spammed for a surprisingly long
1282 time. This is really bad from a security perspective, and
1283 so architecture maintainers really need to do what they can
1284 to get the CRNG seeded sooner after the system is booted.
1285 However, since users can not do anything actionble to
1286 address this, by default the kernel will issue only a single
1287 warning for the first use of unseeded randomness.
1289 Say Y here if you want to receive warnings for all uses of
1290 unseeded randomness. This will be of use primarily for
1291 those developers interersted in improving the security of
1292 Linux kernels running on their architecture (or
1295 config DEBUG_KOBJECT
1296 bool "kobject debugging"
1297 depends on DEBUG_KERNEL
1299 If you say Y here, some extra kobject debugging messages will be sent
1302 config DEBUG_KOBJECT_RELEASE
1303 bool "kobject release debugging"
1304 depends on DEBUG_OBJECTS_TIMERS
1306 kobjects are reference counted objects. This means that their
1307 last reference count put is not predictable, and the kobject can
1308 live on past the point at which a driver decides to drop it's
1309 initial reference to the kobject gained on allocation. An
1310 example of this would be a struct device which has just been
1313 However, some buggy drivers assume that after such an operation,
1314 the memory backing the kobject can be immediately freed. This
1315 goes completely against the principles of a refcounted object.
1317 If you say Y here, the kernel will delay the release of kobjects
1318 on the last reference count to improve the visibility of this
1319 kind of kobject release bug.
1321 config HAVE_DEBUG_BUGVERBOSE
1324 config DEBUG_BUGVERBOSE
1325 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1326 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1329 Say Y here to make BUG() panics output the file name and line number
1330 of the BUG call as well as the EIP and oops trace. This aids
1331 debugging but costs about 70-100K of memory.
1334 bool "Debug linked list manipulation"
1335 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1337 Enable this to turn on extended checks in the linked-list
1342 config DEBUG_PI_LIST
1343 bool "Debug priority linked list manipulation"
1344 depends on DEBUG_KERNEL
1346 Enable this to turn on extended checks in the priority-ordered
1347 linked-list (plist) walking routines. This checks the entire
1348 list multiple times during each manipulation.
1353 bool "Debug SG table operations"
1354 depends on DEBUG_KERNEL
1356 Enable this to turn on checks on scatter-gather tables. This can
1357 help find problems with drivers that do not properly initialize
1362 config DEBUG_NOTIFIERS
1363 bool "Debug notifier call chains"
1364 depends on DEBUG_KERNEL
1366 Enable this to turn on sanity checking for notifier call chains.
1367 This is most useful for kernel developers to make sure that
1368 modules properly unregister themselves from notifier chains.
1369 This is a relatively cheap check but if you care about maximum
1372 config DEBUG_CREDENTIALS
1373 bool "Debug credential management"
1374 depends on DEBUG_KERNEL
1376 Enable this to turn on some debug checking for credential
1377 management. The additional code keeps track of the number of
1378 pointers from task_structs to any given cred struct, and checks to
1379 see that this number never exceeds the usage count of the cred
1382 Furthermore, if SELinux is enabled, this also checks that the
1383 security pointer in the cred struct is never seen to be invalid.
1387 source "kernel/rcu/Kconfig.debug"
1389 config DEBUG_WQ_FORCE_RR_CPU
1390 bool "Force round-robin CPU selection for unbound work items"
1391 depends on DEBUG_KERNEL
1394 Workqueue used to implicitly guarantee that work items queued
1395 without explicit CPU specified are put on the local CPU. This
1396 guarantee is no longer true and while local CPU is still
1397 preferred work items may be put on foreign CPUs. Kernel
1398 parameter "workqueue.debug_force_rr_cpu" is added to force
1399 round-robin CPU selection to flush out usages which depend on the
1400 now broken guarantee. This config option enables the debug
1401 feature by default. When enabled, memory and cache locality will
1404 config DEBUG_BLOCK_EXT_DEVT
1405 bool "Force extended block device numbers and spread them"
1406 depends on DEBUG_KERNEL
1410 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1411 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1412 YOU ARE DOING. Distros, please enable this and fix whatever
1415 Conventionally, block device numbers are allocated from
1416 predetermined contiguous area. However, extended block area
1417 may introduce non-contiguous block device numbers. This
1418 option forces most block device numbers to be allocated from
1419 the extended space and spreads them to discover kernel or
1420 userland code paths which assume predetermined contiguous
1421 device number allocation.
1423 Note that turning on this debug option shuffles all the
1424 device numbers for all IDE and SCSI devices including libata
1425 ones, so root partition specified using device number
1426 directly (via rdev or root=MAJ:MIN) won't work anymore.
1427 Textual device names (root=/dev/sdXn) will continue to work.
1429 Say N if you are unsure.
1431 config CPU_HOTPLUG_STATE_CONTROL
1432 bool "Enable CPU hotplug state control"
1433 depends on DEBUG_KERNEL
1434 depends on HOTPLUG_CPU
1437 Allows to write steps between "offline" and "online" to the CPUs
1438 sysfs target file so states can be stepped granular. This is a debug
1439 option for now as the hotplug machinery cannot be stopped and
1440 restarted at arbitrary points yet.
1442 Say N if your are unsure.
1444 config NOTIFIER_ERROR_INJECTION
1445 tristate "Notifier error injection"
1446 depends on DEBUG_KERNEL
1449 This option provides the ability to inject artificial errors to
1450 specified notifier chain callbacks. It is useful to test the error
1451 handling of notifier call chain failures.
1455 config PM_NOTIFIER_ERROR_INJECT
1456 tristate "PM notifier error injection module"
1457 depends on PM && NOTIFIER_ERROR_INJECTION
1458 default m if PM_DEBUG
1460 This option provides the ability to inject artificial errors to
1461 PM notifier chain callbacks. It is controlled through debugfs
1462 interface /sys/kernel/debug/notifier-error-inject/pm
1464 If the notifier call chain should be failed with some events
1465 notified, write the error code to "actions/<notifier event>/error".
1467 Example: Inject PM suspend error (-12 = -ENOMEM)
1469 # cd /sys/kernel/debug/notifier-error-inject/pm/
1470 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1471 # echo mem > /sys/power/state
1472 bash: echo: write error: Cannot allocate memory
1474 To compile this code as a module, choose M here: the module will
1475 be called pm-notifier-error-inject.
1479 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1480 tristate "OF reconfig notifier error injection module"
1481 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1483 This option provides the ability to inject artificial errors to
1484 OF reconfig notifier chain callbacks. It is controlled
1485 through debugfs interface under
1486 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1488 If the notifier call chain should be failed with some events
1489 notified, write the error code to "actions/<notifier event>/error".
1491 To compile this code as a module, choose M here: the module will
1492 be called of-reconfig-notifier-error-inject.
1496 config NETDEV_NOTIFIER_ERROR_INJECT
1497 tristate "Netdev notifier error injection module"
1498 depends on NET && NOTIFIER_ERROR_INJECTION
1500 This option provides the ability to inject artificial errors to
1501 netdevice notifier chain callbacks. It is controlled through debugfs
1502 interface /sys/kernel/debug/notifier-error-inject/netdev
1504 If the notifier call chain should be failed with some events
1505 notified, write the error code to "actions/<notifier event>/error".
1507 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1509 # cd /sys/kernel/debug/notifier-error-inject/netdev
1510 # echo -22 > actions/NETDEV_CHANGEMTU/error
1511 # ip link set eth0 mtu 1024
1512 RTNETLINK answers: Invalid argument
1514 To compile this code as a module, choose M here: the module will
1515 be called netdev-notifier-error-inject.
1519 config FAULT_INJECTION
1520 bool "Fault-injection framework"
1521 depends on DEBUG_KERNEL
1523 Provide fault-injection framework.
1524 For more details, see Documentation/fault-injection/.
1527 bool "Fault-injection capability for kmalloc"
1528 depends on FAULT_INJECTION
1529 depends on SLAB || SLUB
1531 Provide fault-injection capability for kmalloc.
1533 config FAIL_PAGE_ALLOC
1534 bool "Fault-injection capabilitiy for alloc_pages()"
1535 depends on FAULT_INJECTION
1537 Provide fault-injection capability for alloc_pages().
1539 config FAIL_MAKE_REQUEST
1540 bool "Fault-injection capability for disk IO"
1541 depends on FAULT_INJECTION && BLOCK
1543 Provide fault-injection capability for disk IO.
1545 config FAIL_IO_TIMEOUT
1546 bool "Fault-injection capability for faking disk interrupts"
1547 depends on FAULT_INJECTION && BLOCK
1549 Provide fault-injection capability on end IO handling. This
1550 will make the block layer "forget" an interrupt as configured,
1551 thus exercising the error handling.
1553 Only works with drivers that use the generic timeout handling,
1554 for others it wont do anything.
1556 config FAIL_MMC_REQUEST
1557 bool "Fault-injection capability for MMC IO"
1558 depends on FAULT_INJECTION_DEBUG_FS && MMC
1560 Provide fault-injection capability for MMC IO.
1561 This will make the mmc core return data errors. This is
1562 useful to test the error handling in the mmc block device
1563 and to test how the mmc host driver handles retries from
1567 bool "Fault-injection capability for futexes"
1569 depends on FAULT_INJECTION && FUTEX
1571 Provide fault-injection capability for futexes.
1573 config FAULT_INJECTION_DEBUG_FS
1574 bool "Debugfs entries for fault-injection capabilities"
1575 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1577 Enable configuration of fault-injection capabilities via debugfs.
1579 config FAULT_INJECTION_STACKTRACE_FILTER
1580 bool "stacktrace filter for fault-injection capabilities"
1581 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1584 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE && !X86
1586 Provide stacktrace filter for fault-injection capabilities
1589 bool "Latency measuring infrastructure"
1590 depends on DEBUG_KERNEL
1591 depends on STACKTRACE_SUPPORT
1593 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !X86
1600 Enable this option if you want to use the LatencyTOP tool
1601 to find out which userspace is blocking on what kernel operations.
1603 source kernel/trace/Kconfig
1605 config PROVIDE_OHCI1394_DMA_INIT
1606 bool "Remote debugging over FireWire early on boot"
1607 depends on PCI && X86
1609 If you want to debug problems which hang or crash the kernel early
1610 on boot and the crashing machine has a FireWire port, you can use
1611 this feature to remotely access the memory of the crashed machine
1612 over FireWire. This employs remote DMA as part of the OHCI1394
1613 specification which is now the standard for FireWire controllers.
1615 With remote DMA, you can monitor the printk buffer remotely using
1616 firescope and access all memory below 4GB using fireproxy from gdb.
1617 Even controlling a kernel debugger is possible using remote DMA.
1621 If ohci1394_dma=early is used as boot parameter, it will initialize
1622 all OHCI1394 controllers which are found in the PCI config space.
1624 As all changes to the FireWire bus such as enabling and disabling
1625 devices cause a bus reset and thereby disable remote DMA for all
1626 devices, be sure to have the cable plugged and FireWire enabled on
1627 the debugging host before booting the debug target for debugging.
1629 This code (~1k) is freed after boot. By then, the firewire stack
1630 in charge of the OHCI-1394 controllers should be used instead.
1632 See Documentation/debugging-via-ohci1394.txt for more information.
1634 config DMA_API_DEBUG
1635 bool "Enable debugging of DMA-API usage"
1636 depends on HAVE_DMA_API_DEBUG
1638 Enable this option to debug the use of the DMA API by device drivers.
1639 With this option you will be able to detect common bugs in device
1640 drivers like double-freeing of DMA mappings or freeing mappings that
1641 were never allocated.
1643 This also attempts to catch cases where a page owned by DMA is
1644 accessed by the cpu in a way that could cause data corruption. For
1645 example, this enables cow_user_page() to check that the source page is
1648 This option causes a performance degradation. Use only if you want to
1649 debug device drivers and dma interactions.
1653 menu "Runtime Testing"
1656 tristate "Linux Kernel Dump Test Tool Module"
1661 This module enables testing of the different dumping mechanisms by
1662 inducing system failures at predefined crash points.
1663 If you don't need it: say N
1664 Choose M here to compile this code as a module. The module will be
1667 Documentation on how to use the module can be found in
1668 Documentation/fault-injection/provoke-crashes.txt
1670 config TEST_LIST_SORT
1671 tristate "Linked list sorting test"
1672 depends on DEBUG_KERNEL || m
1674 Enable this to turn on 'list_sort()' function test. This test is
1675 executed only once during system boot (so affects only boot time),
1676 or at module load time.
1681 tristate "Array-based sort test"
1682 depends on DEBUG_KERNEL || m
1684 This option enables the self-test function of 'sort()' at boot,
1685 or at module load time.
1689 config KPROBES_SANITY_TEST
1690 bool "Kprobes sanity tests"
1691 depends on DEBUG_KERNEL
1695 This option provides for testing basic kprobes functionality on
1696 boot. A sample kprobe, jprobe and kretprobe are inserted and
1697 verified for functionality.
1699 Say N if you are unsure.
1701 config BACKTRACE_SELF_TEST
1702 tristate "Self test for the backtrace code"
1703 depends on DEBUG_KERNEL
1706 This option provides a kernel module that can be used to test
1707 the kernel stack backtrace code. This option is not useful
1708 for distributions or general kernels, but only for kernel
1709 developers working on architecture code.
1711 Note that if you want to also test saved backtraces, you will
1712 have to enable STACKTRACE as well.
1714 Say N if you are unsure.
1717 tristate "Red-Black tree test"
1718 depends on DEBUG_KERNEL
1720 A benchmark measuring the performance of the rbtree library.
1721 Also includes rbtree invariant checks.
1723 config INTERVAL_TREE_TEST
1724 tristate "Interval tree test"
1725 depends on DEBUG_KERNEL
1726 select INTERVAL_TREE
1728 A benchmark measuring the performance of the interval tree library
1731 tristate "Per cpu operations test"
1732 depends on m && DEBUG_KERNEL
1734 Enable this option to build test module which validates per-cpu
1739 config ATOMIC64_SELFTEST
1740 tristate "Perform an atomic64_t self-test"
1742 Enable this option to test the atomic64_t functions at boot or
1743 at module load time.
1747 config ASYNC_RAID6_TEST
1748 tristate "Self test for hardware accelerated raid6 recovery"
1749 depends on ASYNC_RAID6_RECOV
1752 This is a one-shot self test that permutes through the
1753 recovery of all the possible two disk failure scenarios for a
1754 N-disk array. Recovery is performed with the asynchronous
1755 raid6 recovery routines, and will optionally use an offload
1756 engine if one is available.
1761 tristate "Test functions located in the hexdump module at runtime"
1763 config TEST_STRING_HELPERS
1764 tristate "Test functions located in the string_helpers module at runtime"
1767 tristate "Test kstrto*() family of functions at runtime"
1770 tristate "Test printf() family of functions at runtime"
1773 tristate "Test bitmap_*() family of functions at runtime"
1776 Enable this option to test the bitmap functions at boot.
1781 tristate "Test functions located in the uuid module at runtime"
1783 config TEST_RHASHTABLE
1784 tristate "Perform selftest on resizable hash table"
1787 Enable this option to test the rhashtable functions at boot.
1792 tristate "Perform selftest on hash functions"
1795 Enable this option to test the kernel's integer (<linux/hash.h>),
1796 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1797 hash functions on boot (or module load).
1799 This is intended to help people writing architecture-specific
1800 optimized versions. If unsure, say N.
1803 tristate "Perform selftest on priority array manager"
1807 Enable this option to test priority array manager on boot
1813 tristate "Test module loading with 'hello world' module"
1817 This builds the "test_module" module that emits "Hello, world"
1818 on printk when loaded. It is designed to be used for basic
1819 evaluation of the module loading subsystem (for example when
1820 validating module verification). It lacks any extra dependencies,
1821 and will not normally be loaded by the system unless explicitly
1826 config TEST_USER_COPY
1827 tristate "Test user/kernel boundary protections"
1831 This builds the "test_user_copy" module that runs sanity checks
1832 on the copy_to/from_user infrastructure, making sure basic
1833 user/kernel boundary testing is working. If it fails to load,
1834 a regression has been detected in the user/kernel memory boundary
1840 tristate "Test BPF filter functionality"
1844 This builds the "test_bpf" module that runs various test vectors
1845 against the BPF interpreter or BPF JIT compiler depending on the
1846 current setting. This is in particular useful for BPF JIT compiler
1847 development, but also to run regression tests against changes in
1848 the interpreter code. It also enables test stubs for eBPF maps and
1849 verifier used by user space verifier testsuite.
1853 config TEST_FIND_BIT
1854 tristate "Test find_bit functions"
1857 This builds the "test_find_bit" module that measure find_*_bit()
1858 functions performance.
1862 config TEST_FIRMWARE
1863 tristate "Test firmware loading via userspace interface"
1865 depends on FW_LOADER
1867 This builds the "test_firmware" module that creates a userspace
1868 interface for testing firmware loading. This can be used to
1869 control the triggering of firmware loading without needing an
1870 actual firmware-using device. The contents can be rechecked by
1876 tristate "sysctl test driver"
1878 depends on PROC_SYSCTL
1880 This builds the "test_sysctl" module. This driver enables to test the
1881 proc sysctl interfaces available to drivers safely without affecting
1882 production knobs which might alter system functionality.
1887 tristate "udelay test driver"
1890 This builds the "udelay_test" module that helps to make sure
1891 that udelay() is working properly.
1895 config TEST_STATIC_KEYS
1896 tristate "Test static keys"
1900 Test the static key interfaces.
1905 tristate "kmod stress tester"
1908 depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS
1909 depends on NETDEVICES && NET_CORE && INET # for TUN
1915 Test the kernel's module loading mechanism: kmod. kmod implements
1916 support to load modules using the Linux kernel's usermode helper.
1917 This test provides a series of tests against kmod.
1919 Although technically you can either build test_kmod as a module or
1920 into the kernel we disallow building it into the kernel since
1921 it stress tests request_module() and this will very likely cause
1922 some issues by taking over precious threads available from other
1923 module load requests, ultimately this could be fatal.
1927 tools/testing/selftests/kmod/kmod.sh --help
1931 config TEST_DEBUG_VIRTUAL
1932 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
1933 depends on DEBUG_VIRTUAL
1935 Test the kernel's ability to detect incorrect calls to
1936 virt_to_phys() done against the non-linear part of the
1937 kernel's virtual address map.
1941 endmenu # runtime tests
1945 depends on HAVE_MEMBLOCK
1947 This option adds a kernel parameter 'memtest', which allows memtest
1949 memtest=0, mean disabled; -- default
1950 memtest=1, mean do 1 test pattern;
1952 memtest=17, mean do 17 test patterns.
1953 If you are unsure how to answer this question, answer N.
1955 config BUG_ON_DATA_CORRUPTION
1956 bool "Trigger a BUG when data corruption is detected"
1959 Select this option if the kernel should BUG when it encounters
1960 data corruption in kernel memory structures when they get checked
1965 source "samples/Kconfig"
1967 source "lib/Kconfig.kgdb"
1969 source "lib/Kconfig.ubsan"
1971 config ARCH_HAS_DEVMEM_IS_ALLOWED
1974 config STRICT_DEVMEM
1975 bool "Filter access to /dev/mem"
1976 depends on MMU && DEVMEM
1977 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
1978 default y if TILE || PPC
1980 If this option is disabled, you allow userspace (root) access to all
1981 of memory, including kernel and userspace memory. Accidental
1982 access to this is obviously disastrous, but specific access can
1983 be used by people debugging the kernel. Note that with PAT support
1984 enabled, even in this case there are restrictions on /dev/mem
1985 use due to the cache aliasing requirements.
1987 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
1988 file only allows userspace access to PCI space and the BIOS code and
1989 data regions. This is sufficient for dosemu and X and all common
1994 config IO_STRICT_DEVMEM
1995 bool "Filter I/O access to /dev/mem"
1996 depends on STRICT_DEVMEM
1998 If this option is disabled, you allow userspace (root) access to all
1999 io-memory regardless of whether a driver is actively using that
2000 range. Accidental access to this is obviously disastrous, but
2001 specific access can be used by people debugging kernel drivers.
2003 If this option is switched on, the /dev/mem file only allows
2004 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2005 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2006 if the driver using a given range cannot be disabled.
projects / mirror_ubuntu-bionic-kernel.git / blob