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)"
220 default 3072 if KASAN_EXTRA
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"
285 debugfs is a virtual file system that kernel developers use to put
286 debugging files into. Enable this option to be able to read and
287 write to these files.
289 For detailed documentation on the debugfs API, see
290 Documentation/filesystems/.
295 bool "Run 'make headers_check' when building vmlinux"
298 This option will extract the user-visible kernel headers whenever
299 building the kernel, and will run basic sanity checks on them to
300 ensure that exported files do not attempt to include files which
301 were not exported, etc.
303 If you're making modifications to header files which are
304 relevant for userspace, say 'Y', and check the headers
305 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
306 your build tree), to make sure they're suitable.
308 config DEBUG_SECTION_MISMATCH
309 bool "Enable full Section mismatch analysis"
311 The section mismatch analysis checks if there are illegal
312 references from one section to another section.
313 During linktime or runtime, some sections are dropped;
314 any use of code/data previously in these sections would
315 most likely result in an oops.
316 In the code, functions and variables are annotated with
317 __init,, etc. (see the full list in include/linux/init.h),
318 which results in the code/data being placed in specific sections.
319 The section mismatch analysis is always performed after a full
320 kernel build, and enabling this option causes the following
321 additional steps to occur:
322 - Add the option -fno-inline-functions-called-once to gcc commands.
323 When inlining a function annotated with __init in a non-init
324 function, we would lose the section information and thus
325 the analysis would not catch the illegal reference.
326 This option tells gcc to inline less (but it does result in
328 - Run the section mismatch analysis for each module/built-in.o file.
329 When we run the section mismatch analysis on vmlinux.o, we
330 lose valuable information about where the mismatch was
332 Running the analysis for each module/built-in.o file
333 tells where the mismatch happens much closer to the
334 source. The drawback is that the same mismatch is
335 reported at least twice.
336 - Enable verbose reporting from modpost in order to help resolve
337 the section mismatches that are reported.
339 config SECTION_MISMATCH_WARN_ONLY
340 bool "Make section mismatch errors non-fatal"
343 If you say N here, the build process will fail if there are any
344 section mismatch, instead of just throwing warnings.
349 # Select this config option from the architecture Kconfig, if it
350 # is preferred to always offer frame pointers as a config
351 # option on the architecture (regardless of KERNEL_DEBUG):
353 config ARCH_WANT_FRAME_POINTERS
358 bool "Compile the kernel with frame pointers"
359 depends on DEBUG_KERNEL && \
360 (CRIS || M68K || FRV || UML || \
361 SUPERH || BLACKFIN || MN10300 || METAG) || \
362 ARCH_WANT_FRAME_POINTERS
363 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
365 If you say Y here the resulting kernel image will be slightly
366 larger and slower, but it gives very useful debugging information
367 in case of kernel bugs. (precise oopses/stacktraces/warnings)
369 config STACK_VALIDATION
370 bool "Compile-time stack metadata validation"
371 depends on HAVE_STACK_VALIDATION
374 Add compile-time checks to validate stack metadata, including frame
375 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
376 that runtime stack traces are more reliable.
378 This is also a prerequisite for generation of ORC unwind data, which
379 is needed for CONFIG_UNWINDER_ORC.
381 For more information, see
382 tools/objtool/Documentation/stack-validation.txt.
384 config DEBUG_FORCE_WEAK_PER_CPU
385 bool "Force weak per-cpu definitions"
386 depends on DEBUG_KERNEL
388 s390 and alpha require percpu variables in modules to be
389 defined weak to work around addressing range issue which
390 puts the following two restrictions on percpu variable
393 1. percpu symbols must be unique whether static or not
394 2. percpu variables can't be defined inside a function
396 To ensure that generic code follows the above rules, this
397 option forces all percpu variables to be defined as weak.
399 endmenu # "Compiler options"
402 bool "Magic SysRq key"
405 If you say Y here, you will have some control over the system even
406 if the system crashes for example during kernel debugging (e.g., you
407 will be able to flush the buffer cache to disk, reboot the system
408 immediately or dump some status information). This is accomplished
409 by pressing various keys while holding SysRq (Alt+PrintScreen). It
410 also works on a serial console (on PC hardware at least), if you
411 send a BREAK and then within 5 seconds a command keypress. The
412 keys are documented in <file:Documentation/admin-guide/sysrq.rst>.
413 Don't say Y unless you really know what this hack does.
415 config MAGIC_SYSRQ_DEFAULT_ENABLE
416 hex "Enable magic SysRq key functions by default"
417 depends on MAGIC_SYSRQ
420 Specifies which SysRq key functions are enabled by default.
421 This may be set to 1 or 0 to enable or disable them all, or
422 to a bitmask as described in Documentation/admin-guide/sysrq.rst.
424 config MAGIC_SYSRQ_SERIAL
425 bool "Enable magic SysRq key over serial"
426 depends on MAGIC_SYSRQ
429 Many embedded boards have a disconnected TTL level serial which can
430 generate some garbage that can lead to spurious false sysrq detects.
431 This option allows you to decide whether you want to enable the
435 bool "Kernel debugging"
437 Say Y here if you are developing drivers or trying to debug and
438 identify kernel problems.
440 menu "Memory Debugging"
442 source mm/Kconfig.debug
445 bool "Debug object operations"
446 depends on DEBUG_KERNEL
448 If you say Y here, additional code will be inserted into the
449 kernel to track the life time of various objects and validate
450 the operations on those objects.
452 config DEBUG_OBJECTS_SELFTEST
453 bool "Debug objects selftest"
454 depends on DEBUG_OBJECTS
456 This enables the selftest of the object debug code.
458 config DEBUG_OBJECTS_FREE
459 bool "Debug objects in freed memory"
460 depends on DEBUG_OBJECTS
462 This enables checks whether a k/v free operation frees an area
463 which contains an object which has not been deactivated
464 properly. This can make kmalloc/kfree-intensive workloads
467 config DEBUG_OBJECTS_TIMERS
468 bool "Debug timer objects"
469 depends on DEBUG_OBJECTS
471 If you say Y here, additional code will be inserted into the
472 timer routines to track the life time of timer objects and
473 validate the timer operations.
475 config DEBUG_OBJECTS_WORK
476 bool "Debug work objects"
477 depends on DEBUG_OBJECTS
479 If you say Y here, additional code will be inserted into the
480 work queue routines to track the life time of work objects and
481 validate the work operations.
483 config DEBUG_OBJECTS_RCU_HEAD
484 bool "Debug RCU callbacks objects"
485 depends on DEBUG_OBJECTS
487 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
489 config DEBUG_OBJECTS_PERCPU_COUNTER
490 bool "Debug percpu counter objects"
491 depends on DEBUG_OBJECTS
493 If you say Y here, additional code will be inserted into the
494 percpu counter routines to track the life time of percpu counter
495 objects and validate the percpu counter operations.
497 config DEBUG_OBJECTS_ENABLE_DEFAULT
498 int "debug_objects bootup default value (0-1)"
501 depends on DEBUG_OBJECTS
503 Debug objects boot parameter default value
506 bool "Debug slab memory allocations"
507 depends on DEBUG_KERNEL && SLAB
509 Say Y here to have the kernel do limited verification on memory
510 allocation as well as poisoning memory on free to catch use of freed
511 memory. This can make kmalloc/kfree-intensive workloads much slower.
513 config DEBUG_SLAB_LEAK
514 bool "Memory leak debugging"
515 depends on DEBUG_SLAB
518 bool "SLUB debugging on by default"
519 depends on SLUB && SLUB_DEBUG
522 Boot with debugging on by default. SLUB boots by default with
523 the runtime debug capabilities switched off. Enabling this is
524 equivalent to specifying the "slub_debug" parameter on boot.
525 There is no support for more fine grained debug control like
526 possible with slub_debug=xxx. SLUB debugging may be switched
527 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
532 bool "Enable SLUB performance statistics"
533 depends on SLUB && SYSFS
535 SLUB statistics are useful to debug SLUBs allocation behavior in
536 order find ways to optimize the allocator. This should never be
537 enabled for production use since keeping statistics slows down
538 the allocator by a few percentage points. The slabinfo command
539 supports the determination of the most active slabs to figure
540 out which slabs are relevant to a particular load.
541 Try running: slabinfo -DA
543 config HAVE_DEBUG_KMEMLEAK
546 config DEBUG_KMEMLEAK
547 bool "Kernel memory leak detector"
548 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
550 select STACKTRACE if STACKTRACE_SUPPORT
554 Say Y here if you want to enable the memory leak
555 detector. The memory allocation/freeing is traced in a way
556 similar to the Boehm's conservative garbage collector, the
557 difference being that the orphan objects are not freed but
558 only shown in /sys/kernel/debug/kmemleak. Enabling this
559 feature will introduce an overhead to memory
560 allocations. See Documentation/dev-tools/kmemleak.rst for more
563 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
564 of finding leaks due to the slab objects poisoning.
566 In order to access the kmemleak file, debugfs needs to be
567 mounted (usually at /sys/kernel/debug).
569 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
570 int "Maximum kmemleak early log entries"
571 depends on DEBUG_KMEMLEAK
575 Kmemleak must track all the memory allocations to avoid
576 reporting false positives. Since memory may be allocated or
577 freed before kmemleak is initialised, an early log buffer is
578 used to store these actions. If kmemleak reports "early log
579 buffer exceeded", please increase this value.
581 config DEBUG_KMEMLEAK_TEST
582 tristate "Simple test for the kernel memory leak detector"
583 depends on DEBUG_KMEMLEAK && m
585 This option enables a module that explicitly leaks memory.
589 config DEBUG_KMEMLEAK_DEFAULT_OFF
590 bool "Default kmemleak to off"
591 depends on DEBUG_KMEMLEAK
593 Say Y here to disable kmemleak by default. It can then be enabled
594 on the command line via kmemleak=on.
596 config DEBUG_STACK_USAGE
597 bool "Stack utilization instrumentation"
598 depends on DEBUG_KERNEL && !IA64
600 Enables the display of the minimum amount of free stack which each
601 task has ever had available in the sysrq-T and sysrq-P debug output.
603 This option will slow down process creation somewhat.
607 depends on DEBUG_KERNEL
609 Enable this to turn on extended checks in the virtual-memory system
610 that may impact performance.
614 config DEBUG_VM_VMACACHE
615 bool "Debug VMA caching"
618 Enable this to turn on VMA caching debug information. Doing so
619 can cause significant overhead, so only enable it in non-production
625 bool "Debug VM red-black trees"
628 Enable VM red-black tree debugging information and extra validations.
632 config DEBUG_VM_PGFLAGS
633 bool "Debug page-flags operations"
636 Enables extra validation on page flags operations.
640 config ARCH_HAS_DEBUG_VIRTUAL
644 bool "Debug VM translations"
645 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
647 Enable some costly sanity checks in virtual to page code. This can
648 catch mistakes with virt_to_page() and friends.
652 config DEBUG_NOMMU_REGIONS
653 bool "Debug the global anon/private NOMMU mapping region tree"
654 depends on DEBUG_KERNEL && !MMU
656 This option causes the global tree of anonymous and private mapping
657 regions to be regularly checked for invalid topology.
659 config DEBUG_MEMORY_INIT
660 bool "Debug memory initialisation" if EXPERT
663 Enable this for additional checks during memory initialisation.
664 The sanity checks verify aspects of the VM such as the memory model
665 and other information provided by the architecture. Verbose
666 information will be printed at KERN_DEBUG loglevel depending
667 on the mminit_loglevel= command-line option.
671 config MEMORY_NOTIFIER_ERROR_INJECT
672 tristate "Memory hotplug notifier error injection module"
673 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
675 This option provides the ability to inject artificial errors to
676 memory hotplug notifier chain callbacks. It is controlled through
677 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
679 If the notifier call chain should be failed with some events
680 notified, write the error code to "actions/<notifier event>/error".
682 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
684 # cd /sys/kernel/debug/notifier-error-inject/memory
685 # echo -12 > actions/MEM_GOING_OFFLINE/error
686 # echo offline > /sys/devices/system/memory/memoryXXX/state
687 bash: echo: write error: Cannot allocate memory
689 To compile this code as a module, choose M here: the module will
690 be called memory-notifier-error-inject.
694 config DEBUG_PER_CPU_MAPS
695 bool "Debug access to per_cpu maps"
696 depends on DEBUG_KERNEL
699 Say Y to verify that the per_cpu map being accessed has
700 been set up. This adds a fair amount of code to kernel memory
701 and decreases performance.
706 bool "Highmem debugging"
707 depends on DEBUG_KERNEL && HIGHMEM
709 This option enables additional error checking for high memory
710 systems. Disable for production systems.
712 config HAVE_DEBUG_STACKOVERFLOW
715 config DEBUG_STACKOVERFLOW
716 bool "Check for stack overflows"
717 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
719 Say Y here if you want to check for overflows of kernel, IRQ
720 and exception stacks (if your architecture uses them). This
721 option will show detailed messages if free stack space drops
722 below a certain limit.
724 These kinds of bugs usually occur when call-chains in the
725 kernel get too deep, especially when interrupts are
728 Use this in cases where you see apparently random memory
729 corruption, especially if it appears in 'struct thread_info'
731 If in doubt, say "N".
733 source "lib/Kconfig.kasan"
735 endmenu # "Memory Debugging"
740 KCOV does not have any arch-specific code, but currently it is enabled
741 only for x86_64. KCOV requires testing on other archs, and most likely
742 disabling of instrumentation for some early boot code.
745 bool "Code coverage for fuzzing"
746 depends on ARCH_HAS_KCOV
748 select GCC_PLUGINS if !COMPILE_TEST
749 select GCC_PLUGIN_SANCOV if !COMPILE_TEST
751 KCOV exposes kernel code coverage information in a form suitable
752 for coverage-guided fuzzing (randomized testing).
754 If RANDOMIZE_BASE is enabled, PC values will not be stable across
755 different machines and across reboots. If you need stable PC values,
756 disable RANDOMIZE_BASE.
758 For more details, see Documentation/dev-tools/kcov.rst.
760 config KCOV_INSTRUMENT_ALL
761 bool "Instrument all code by default"
765 If you are doing generic system call fuzzing (like e.g. syzkaller),
766 then you will want to instrument the whole kernel and you should
767 say y here. If you are doing more targeted fuzzing (like e.g.
768 filesystem fuzzing with AFL) then you will want to enable coverage
769 for more specific subsets of files, and should say n here.
772 bool "Debug shared IRQ handlers"
773 depends on DEBUG_KERNEL
775 Enable this to generate a spurious interrupt as soon as a shared
776 interrupt handler is registered, and just before one is deregistered.
777 Drivers ought to be able to handle interrupts coming in at those
778 points; some don't and need to be caught.
780 menu "Debug Lockups and Hangs"
782 config LOCKUP_DETECTOR
785 config SOFTLOCKUP_DETECTOR
786 bool "Detect Soft Lockups"
787 depends on DEBUG_KERNEL && !S390
788 select LOCKUP_DETECTOR
790 Say Y here to enable the kernel to act as a watchdog to detect
793 Softlockups are bugs that cause the kernel to loop in kernel
794 mode for more than 20 seconds, without giving other tasks a
795 chance to run. The current stack trace is displayed upon
796 detection and the system will stay locked up.
798 config HARDLOCKUP_DETECTOR_PERF
800 select SOFTLOCKUP_DETECTOR
803 # Enables a timestamp based low pass filter to compensate for perf based
804 # hard lockup detection which runs too fast due to turbo modes.
806 config HARDLOCKUP_CHECK_TIMESTAMP
810 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
811 # lockup detector rather than the perf based detector.
813 config HARDLOCKUP_DETECTOR
814 bool "Detect Hard Lockups"
815 depends on DEBUG_KERNEL && !S390
816 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
817 select LOCKUP_DETECTOR
818 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
819 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
821 Say Y here to enable the kernel to act as a watchdog to detect
824 Hardlockups are bugs that cause the CPU to loop in kernel mode
825 for more than 10 seconds, without letting other interrupts have a
826 chance to run. The current stack trace is displayed upon detection
827 and the system will stay locked up.
829 config BOOTPARAM_HARDLOCKUP_PANIC
830 bool "Panic (Reboot) On Hard Lockups"
831 depends on HARDLOCKUP_DETECTOR
833 Say Y here to enable the kernel to panic on "hard lockups",
834 which are bugs that cause the kernel to loop in kernel
835 mode with interrupts disabled for more than 10 seconds (configurable
836 using the watchdog_thresh sysctl).
840 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
842 depends on HARDLOCKUP_DETECTOR
844 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
845 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
847 config BOOTPARAM_SOFTLOCKUP_PANIC
848 bool "Panic (Reboot) On Soft Lockups"
849 depends on SOFTLOCKUP_DETECTOR
851 Say Y here to enable the kernel to panic on "soft lockups",
852 which are bugs that cause the kernel to loop in kernel
853 mode for more than 20 seconds (configurable using the watchdog_thresh
854 sysctl), without giving other tasks a chance to run.
856 The panic can be used in combination with panic_timeout,
857 to cause the system to reboot automatically after a
858 lockup has been detected. This feature is useful for
859 high-availability systems that have uptime guarantees and
860 where a lockup must be resolved ASAP.
864 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
866 depends on SOFTLOCKUP_DETECTOR
868 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
869 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
871 config DETECT_HUNG_TASK
872 bool "Detect Hung Tasks"
873 depends on DEBUG_KERNEL
874 default SOFTLOCKUP_DETECTOR
876 Say Y here to enable the kernel to detect "hung tasks",
877 which are bugs that cause the task to be stuck in
878 uninterruptible "D" state indefinitely.
880 When a hung task is detected, the kernel will print the
881 current stack trace (which you should report), but the
882 task will stay in uninterruptible state. If lockdep is
883 enabled then all held locks will also be reported. This
884 feature has negligible overhead.
886 config DEFAULT_HUNG_TASK_TIMEOUT
887 int "Default timeout for hung task detection (in seconds)"
888 depends on DETECT_HUNG_TASK
891 This option controls the default timeout (in seconds) used
892 to determine when a task has become non-responsive and should
895 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
896 sysctl or by writing a value to
897 /proc/sys/kernel/hung_task_timeout_secs.
899 A timeout of 0 disables the check. The default is two minutes.
900 Keeping the default should be fine in most cases.
902 config BOOTPARAM_HUNG_TASK_PANIC
903 bool "Panic (Reboot) On Hung Tasks"
904 depends on DETECT_HUNG_TASK
906 Say Y here to enable the kernel to panic on "hung tasks",
907 which are bugs that cause the kernel to leave a task stuck
908 in uninterruptible "D" state.
910 The panic can be used in combination with panic_timeout,
911 to cause the system to reboot automatically after a
912 hung task has been detected. This feature is useful for
913 high-availability systems that have uptime guarantees and
914 where a hung tasks must be resolved ASAP.
918 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
920 depends on DETECT_HUNG_TASK
922 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
923 default 1 if BOOTPARAM_HUNG_TASK_PANIC
926 bool "Detect Workqueue Stalls"
927 depends on DEBUG_KERNEL
929 Say Y here to enable stall detection on workqueues. If a
930 worker pool doesn't make forward progress on a pending work
931 item for over a given amount of time, 30s by default, a
932 warning message is printed along with dump of workqueue
933 state. This can be configured through kernel parameter
934 "workqueue.watchdog_thresh" and its sysfs counterpart.
936 endmenu # "Debug lockups and hangs"
941 Say Y here to enable the kernel to panic when it oopses. This
942 has the same effect as setting oops=panic on the kernel command
945 This feature is useful to ensure that the kernel does not do
946 anything erroneous after an oops which could result in data
947 corruption or other issues.
951 config PANIC_ON_OOPS_VALUE
954 default 0 if !PANIC_ON_OOPS
955 default 1 if PANIC_ON_OOPS
961 Set the timeout value (in seconds) until a reboot occurs when the
962 the kernel panics. If n = 0, then we wait forever. A timeout
963 value n > 0 will wait n seconds before rebooting, while a timeout
964 value n < 0 will reboot immediately.
967 bool "Collect scheduler debugging info"
968 depends on DEBUG_KERNEL && PROC_FS
971 If you say Y here, the /proc/sched_debug file will be provided
972 that can help debug the scheduler. The runtime overhead of this
980 bool "Collect scheduler statistics"
981 depends on DEBUG_KERNEL && PROC_FS
984 If you say Y here, additional code will be inserted into the
985 scheduler and related routines to collect statistics about
986 scheduler behavior and provide them in /proc/schedstat. These
987 stats may be useful for both tuning and debugging the scheduler
988 If you aren't debugging the scheduler or trying to tune a specific
989 application, you can say N to avoid the very slight overhead
992 config SCHED_STACK_END_CHECK
993 bool "Detect stack corruption on calls to schedule()"
994 depends on DEBUG_KERNEL
997 This option checks for a stack overrun on calls to schedule().
998 If the stack end location is found to be over written always panic as
999 the content of the corrupted region can no longer be trusted.
1000 This is to ensure no erroneous behaviour occurs which could result in
1001 data corruption or a sporadic crash at a later stage once the region
1002 is examined. The runtime overhead introduced is minimal.
1004 config DEBUG_TIMEKEEPING
1005 bool "Enable extra timekeeping sanity checking"
1007 This option will enable additional timekeeping sanity checks
1008 which may be helpful when diagnosing issues where timekeeping
1009 problems are suspected.
1011 This may include checks in the timekeeping hotpaths, so this
1012 option may have a (very small) performance impact to some
1017 config DEBUG_PREEMPT
1018 bool "Debug preemptible kernel"
1019 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1022 If you say Y here then the kernel will use a debug variant of the
1023 commonly used smp_processor_id() function and will print warnings
1024 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1025 will detect preemption count underflows.
1027 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1029 config DEBUG_RT_MUTEXES
1030 bool "RT Mutex debugging, deadlock detection"
1031 depends on DEBUG_KERNEL && RT_MUTEXES
1033 This allows rt mutex semantics violations and rt mutex related
1034 deadlocks (lockups) to be detected and reported automatically.
1036 config DEBUG_SPINLOCK
1037 bool "Spinlock and rw-lock debugging: basic checks"
1038 depends on DEBUG_KERNEL
1039 select UNINLINE_SPIN_UNLOCK
1041 Say Y here and build SMP to catch missing spinlock initialization
1042 and certain other kinds of spinlock errors commonly made. This is
1043 best used in conjunction with the NMI watchdog so that spinlock
1044 deadlocks are also debuggable.
1046 config DEBUG_MUTEXES
1047 bool "Mutex debugging: basic checks"
1048 depends on DEBUG_KERNEL
1050 This feature allows mutex semantics violations to be detected and
1053 config DEBUG_WW_MUTEX_SLOWPATH
1054 bool "Wait/wound mutex debugging: Slowpath testing"
1055 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1056 select DEBUG_LOCK_ALLOC
1057 select DEBUG_SPINLOCK
1058 select DEBUG_MUTEXES
1060 This feature enables slowpath testing for w/w mutex users by
1061 injecting additional -EDEADLK wound/backoff cases. Together with
1062 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1063 will test all possible w/w mutex interface abuse with the
1064 exception of simply not acquiring all the required locks.
1065 Note that this feature can introduce significant overhead, so
1066 it really should not be enabled in a production or distro kernel,
1067 even a debug kernel. If you are a driver writer, enable it. If
1068 you are a distro, do not.
1070 config DEBUG_LOCK_ALLOC
1071 bool "Lock debugging: detect incorrect freeing of live locks"
1072 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1073 select DEBUG_SPINLOCK
1074 select DEBUG_MUTEXES
1075 select DEBUG_RT_MUTEXES if RT_MUTEXES
1078 This feature will check whether any held lock (spinlock, rwlock,
1079 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1080 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1081 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1082 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1083 held during task exit.
1085 config PROVE_LOCKING
1086 bool "Lock debugging: prove locking correctness"
1087 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1089 select DEBUG_SPINLOCK
1090 select DEBUG_MUTEXES
1091 select DEBUG_RT_MUTEXES if RT_MUTEXES
1092 select DEBUG_LOCK_ALLOC
1093 select LOCKDEP_CROSSRELEASE if BROKEN
1094 select LOCKDEP_COMPLETIONS if BROKEN
1095 select TRACE_IRQFLAGS
1098 This feature enables the kernel to prove that all locking
1099 that occurs in the kernel runtime is mathematically
1100 correct: that under no circumstance could an arbitrary (and
1101 not yet triggered) combination of observed locking
1102 sequences (on an arbitrary number of CPUs, running an
1103 arbitrary number of tasks and interrupt contexts) cause a
1106 In short, this feature enables the kernel to report locking
1107 related deadlocks before they actually occur.
1109 The proof does not depend on how hard and complex a
1110 deadlock scenario would be to trigger: how many
1111 participant CPUs, tasks and irq-contexts would be needed
1112 for it to trigger. The proof also does not depend on
1113 timing: if a race and a resulting deadlock is possible
1114 theoretically (no matter how unlikely the race scenario
1115 is), it will be proven so and will immediately be
1116 reported by the kernel (once the event is observed that
1117 makes the deadlock theoretically possible).
1119 If a deadlock is impossible (i.e. the locking rules, as
1120 observed by the kernel, are mathematically correct), the
1121 kernel reports nothing.
1123 NOTE: this feature can also be enabled for rwlocks, mutexes
1124 and rwsems - in which case all dependencies between these
1125 different locking variants are observed and mapped too, and
1126 the proof of observed correctness is also maintained for an
1127 arbitrary combination of these separate locking variants.
1129 For more details, see Documentation/locking/lockdep-design.txt.
1133 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1135 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE && !X86
1139 config LOCKDEP_SMALL
1143 bool "Lock usage statistics"
1144 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1146 select DEBUG_SPINLOCK
1147 select DEBUG_MUTEXES
1148 select DEBUG_RT_MUTEXES if RT_MUTEXES
1149 select DEBUG_LOCK_ALLOC
1152 This feature enables tracking lock contention points
1154 For more details, see Documentation/locking/lockstat.txt
1156 This also enables lock events required by "perf lock",
1158 If you want to use "perf lock", you also need to turn on
1159 CONFIG_EVENT_TRACING.
1161 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1162 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1164 config LOCKDEP_CROSSRELEASE
1167 This makes lockdep work for crosslock which is a lock allowed to
1168 be released in a different context from the acquisition context.
1169 Normally a lock must be released in the context acquiring the lock.
1170 However, relexing this constraint helps synchronization primitives
1171 such as page locks or completions can use the lock correctness
1174 config LOCKDEP_COMPLETIONS
1177 A deadlock caused by wait_for_completion() and complete() can be
1178 detected by lockdep using crossrelease feature.
1180 config DEBUG_LOCKDEP
1181 bool "Lock dependency engine debugging"
1182 depends on DEBUG_KERNEL && LOCKDEP
1184 If you say Y here, the lock dependency engine will do
1185 additional runtime checks to debug itself, at the price
1186 of more runtime overhead.
1188 config DEBUG_ATOMIC_SLEEP
1189 bool "Sleep inside atomic section checking"
1190 select PREEMPT_COUNT
1191 depends on DEBUG_KERNEL
1193 If you say Y here, various routines which may sleep will become very
1194 noisy if they are called inside atomic sections: when a spinlock is
1195 held, inside an rcu read side critical section, inside preempt disabled
1196 sections, inside an interrupt, etc...
1198 config DEBUG_LOCKING_API_SELFTESTS
1199 bool "Locking API boot-time self-tests"
1200 depends on DEBUG_KERNEL
1202 Say Y here if you want the kernel to run a short self-test during
1203 bootup. The self-test checks whether common types of locking bugs
1204 are detected by debugging mechanisms or not. (if you disable
1205 lock debugging then those bugs wont be detected of course.)
1206 The following locking APIs are covered: spinlocks, rwlocks,
1209 config LOCK_TORTURE_TEST
1210 tristate "torture tests for locking"
1211 depends on DEBUG_KERNEL
1215 This option provides a kernel module that runs torture tests
1216 on kernel locking primitives. The kernel module may be built
1217 after the fact on the running kernel to be tested, if desired.
1219 Say Y here if you want kernel locking-primitive torture tests
1220 to be built into the kernel.
1221 Say M if you want these torture tests to build as a module.
1222 Say N if you are unsure.
1224 config WW_MUTEX_SELFTEST
1225 tristate "Wait/wound mutex selftests"
1227 This option provides a kernel module that runs tests on the
1228 on the struct ww_mutex locking API.
1230 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1231 with this test harness.
1233 Say M if you want these self tests to build as a module.
1234 Say N if you are unsure.
1236 endmenu # lock debugging
1238 config TRACE_IRQFLAGS
1241 Enables hooks to interrupt enabling and disabling for
1242 either tracing or lock debugging.
1245 bool "Stack backtrace support"
1246 depends on STACKTRACE_SUPPORT
1248 This option causes the kernel to create a /proc/pid/stack for
1249 every process, showing its current stack trace.
1250 It is also used by various kernel debugging features that require
1251 stack trace generation.
1253 config WARN_ALL_UNSEEDED_RANDOM
1254 bool "Warn for all uses of unseeded randomness"
1257 Some parts of the kernel contain bugs relating to their use of
1258 cryptographically secure random numbers before it's actually possible
1259 to generate those numbers securely. This setting ensures that these
1260 flaws don't go unnoticed, by enabling a message, should this ever
1261 occur. This will allow people with obscure setups to know when things
1262 are going wrong, so that they might contact developers about fixing
1265 Unfortunately, on some models of some architectures getting
1266 a fully seeded CRNG is extremely difficult, and so this can
1267 result in dmesg getting spammed for a surprisingly long
1268 time. This is really bad from a security perspective, and
1269 so architecture maintainers really need to do what they can
1270 to get the CRNG seeded sooner after the system is booted.
1271 However, since users can not do anything actionble to
1272 address this, by default the kernel will issue only a single
1273 warning for the first use of unseeded randomness.
1275 Say Y here if you want to receive warnings for all uses of
1276 unseeded randomness. This will be of use primarily for
1277 those developers interersted in improving the security of
1278 Linux kernels running on their architecture (or
1281 config DEBUG_KOBJECT
1282 bool "kobject debugging"
1283 depends on DEBUG_KERNEL
1285 If you say Y here, some extra kobject debugging messages will be sent
1288 config DEBUG_KOBJECT_RELEASE
1289 bool "kobject release debugging"
1290 depends on DEBUG_OBJECTS_TIMERS
1292 kobjects are reference counted objects. This means that their
1293 last reference count put is not predictable, and the kobject can
1294 live on past the point at which a driver decides to drop it's
1295 initial reference to the kobject gained on allocation. An
1296 example of this would be a struct device which has just been
1299 However, some buggy drivers assume that after such an operation,
1300 the memory backing the kobject can be immediately freed. This
1301 goes completely against the principles of a refcounted object.
1303 If you say Y here, the kernel will delay the release of kobjects
1304 on the last reference count to improve the visibility of this
1305 kind of kobject release bug.
1307 config HAVE_DEBUG_BUGVERBOSE
1310 config DEBUG_BUGVERBOSE
1311 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1312 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1315 Say Y here to make BUG() panics output the file name and line number
1316 of the BUG call as well as the EIP and oops trace. This aids
1317 debugging but costs about 70-100K of memory.
1320 bool "Debug linked list manipulation"
1321 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1323 Enable this to turn on extended checks in the linked-list
1328 config DEBUG_PI_LIST
1329 bool "Debug priority linked list manipulation"
1330 depends on DEBUG_KERNEL
1332 Enable this to turn on extended checks in the priority-ordered
1333 linked-list (plist) walking routines. This checks the entire
1334 list multiple times during each manipulation.
1339 bool "Debug SG table operations"
1340 depends on DEBUG_KERNEL
1342 Enable this to turn on checks on scatter-gather tables. This can
1343 help find problems with drivers that do not properly initialize
1348 config DEBUG_NOTIFIERS
1349 bool "Debug notifier call chains"
1350 depends on DEBUG_KERNEL
1352 Enable this to turn on sanity checking for notifier call chains.
1353 This is most useful for kernel developers to make sure that
1354 modules properly unregister themselves from notifier chains.
1355 This is a relatively cheap check but if you care about maximum
1358 config DEBUG_CREDENTIALS
1359 bool "Debug credential management"
1360 depends on DEBUG_KERNEL
1362 Enable this to turn on some debug checking for credential
1363 management. The additional code keeps track of the number of
1364 pointers from task_structs to any given cred struct, and checks to
1365 see that this number never exceeds the usage count of the cred
1368 Furthermore, if SELinux is enabled, this also checks that the
1369 security pointer in the cred struct is never seen to be invalid.
1373 source "kernel/rcu/Kconfig.debug"
1375 config DEBUG_WQ_FORCE_RR_CPU
1376 bool "Force round-robin CPU selection for unbound work items"
1377 depends on DEBUG_KERNEL
1380 Workqueue used to implicitly guarantee that work items queued
1381 without explicit CPU specified are put on the local CPU. This
1382 guarantee is no longer true and while local CPU is still
1383 preferred work items may be put on foreign CPUs. Kernel
1384 parameter "workqueue.debug_force_rr_cpu" is added to force
1385 round-robin CPU selection to flush out usages which depend on the
1386 now broken guarantee. This config option enables the debug
1387 feature by default. When enabled, memory and cache locality will
1390 config DEBUG_BLOCK_EXT_DEVT
1391 bool "Force extended block device numbers and spread them"
1392 depends on DEBUG_KERNEL
1396 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1397 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1398 YOU ARE DOING. Distros, please enable this and fix whatever
1401 Conventionally, block device numbers are allocated from
1402 predetermined contiguous area. However, extended block area
1403 may introduce non-contiguous block device numbers. This
1404 option forces most block device numbers to be allocated from
1405 the extended space and spreads them to discover kernel or
1406 userland code paths which assume predetermined contiguous
1407 device number allocation.
1409 Note that turning on this debug option shuffles all the
1410 device numbers for all IDE and SCSI devices including libata
1411 ones, so root partition specified using device number
1412 directly (via rdev or root=MAJ:MIN) won't work anymore.
1413 Textual device names (root=/dev/sdXn) will continue to work.
1415 Say N if you are unsure.
1417 config CPU_HOTPLUG_STATE_CONTROL
1418 bool "Enable CPU hotplug state control"
1419 depends on DEBUG_KERNEL
1420 depends on HOTPLUG_CPU
1423 Allows to write steps between "offline" and "online" to the CPUs
1424 sysfs target file so states can be stepped granular. This is a debug
1425 option for now as the hotplug machinery cannot be stopped and
1426 restarted at arbitrary points yet.
1428 Say N if your are unsure.
1430 config NOTIFIER_ERROR_INJECTION
1431 tristate "Notifier error injection"
1432 depends on DEBUG_KERNEL
1435 This option provides the ability to inject artificial errors to
1436 specified notifier chain callbacks. It is useful to test the error
1437 handling of notifier call chain failures.
1441 config PM_NOTIFIER_ERROR_INJECT
1442 tristate "PM notifier error injection module"
1443 depends on PM && NOTIFIER_ERROR_INJECTION
1444 default m if PM_DEBUG
1446 This option provides the ability to inject artificial errors to
1447 PM notifier chain callbacks. It is controlled through debugfs
1448 interface /sys/kernel/debug/notifier-error-inject/pm
1450 If the notifier call chain should be failed with some events
1451 notified, write the error code to "actions/<notifier event>/error".
1453 Example: Inject PM suspend error (-12 = -ENOMEM)
1455 # cd /sys/kernel/debug/notifier-error-inject/pm/
1456 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1457 # echo mem > /sys/power/state
1458 bash: echo: write error: Cannot allocate memory
1460 To compile this code as a module, choose M here: the module will
1461 be called pm-notifier-error-inject.
1465 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1466 tristate "OF reconfig notifier error injection module"
1467 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1469 This option provides the ability to inject artificial errors to
1470 OF reconfig notifier chain callbacks. It is controlled
1471 through debugfs interface under
1472 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1474 If the notifier call chain should be failed with some events
1475 notified, write the error code to "actions/<notifier event>/error".
1477 To compile this code as a module, choose M here: the module will
1478 be called of-reconfig-notifier-error-inject.
1482 config NETDEV_NOTIFIER_ERROR_INJECT
1483 tristate "Netdev notifier error injection module"
1484 depends on NET && NOTIFIER_ERROR_INJECTION
1486 This option provides the ability to inject artificial errors to
1487 netdevice notifier chain callbacks. It is controlled through debugfs
1488 interface /sys/kernel/debug/notifier-error-inject/netdev
1490 If the notifier call chain should be failed with some events
1491 notified, write the error code to "actions/<notifier event>/error".
1493 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1495 # cd /sys/kernel/debug/notifier-error-inject/netdev
1496 # echo -22 > actions/NETDEV_CHANGEMTU/error
1497 # ip link set eth0 mtu 1024
1498 RTNETLINK answers: Invalid argument
1500 To compile this code as a module, choose M here: the module will
1501 be called netdev-notifier-error-inject.
1505 config FAULT_INJECTION
1506 bool "Fault-injection framework"
1507 depends on DEBUG_KERNEL
1509 Provide fault-injection framework.
1510 For more details, see Documentation/fault-injection/.
1513 bool "Fault-injection capability for kmalloc"
1514 depends on FAULT_INJECTION
1515 depends on SLAB || SLUB
1517 Provide fault-injection capability for kmalloc.
1519 config FAIL_PAGE_ALLOC
1520 bool "Fault-injection capabilitiy for alloc_pages()"
1521 depends on FAULT_INJECTION
1523 Provide fault-injection capability for alloc_pages().
1525 config FAIL_MAKE_REQUEST
1526 bool "Fault-injection capability for disk IO"
1527 depends on FAULT_INJECTION && BLOCK
1529 Provide fault-injection capability for disk IO.
1531 config FAIL_IO_TIMEOUT
1532 bool "Fault-injection capability for faking disk interrupts"
1533 depends on FAULT_INJECTION && BLOCK
1535 Provide fault-injection capability on end IO handling. This
1536 will make the block layer "forget" an interrupt as configured,
1537 thus exercising the error handling.
1539 Only works with drivers that use the generic timeout handling,
1540 for others it wont do anything.
1542 config FAIL_MMC_REQUEST
1543 bool "Fault-injection capability for MMC IO"
1544 depends on FAULT_INJECTION_DEBUG_FS && MMC
1546 Provide fault-injection capability for MMC IO.
1547 This will make the mmc core return data errors. This is
1548 useful to test the error handling in the mmc block device
1549 and to test how the mmc host driver handles retries from
1553 bool "Fault-injection capability for futexes"
1555 depends on FAULT_INJECTION && FUTEX
1557 Provide fault-injection capability for futexes.
1559 config FAULT_INJECTION_DEBUG_FS
1560 bool "Debugfs entries for fault-injection capabilities"
1561 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1563 Enable configuration of fault-injection capabilities via debugfs.
1565 config FAULT_INJECTION_STACKTRACE_FILTER
1566 bool "stacktrace filter for fault-injection capabilities"
1567 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1570 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE && !X86
1572 Provide stacktrace filter for fault-injection capabilities
1575 bool "Latency measuring infrastructure"
1576 depends on DEBUG_KERNEL
1577 depends on STACKTRACE_SUPPORT
1579 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !X86
1586 Enable this option if you want to use the LatencyTOP tool
1587 to find out which userspace is blocking on what kernel operations.
1589 source kernel/trace/Kconfig
1591 config PROVIDE_OHCI1394_DMA_INIT
1592 bool "Remote debugging over FireWire early on boot"
1593 depends on PCI && X86
1595 If you want to debug problems which hang or crash the kernel early
1596 on boot and the crashing machine has a FireWire port, you can use
1597 this feature to remotely access the memory of the crashed machine
1598 over FireWire. This employs remote DMA as part of the OHCI1394
1599 specification which is now the standard for FireWire controllers.
1601 With remote DMA, you can monitor the printk buffer remotely using
1602 firescope and access all memory below 4GB using fireproxy from gdb.
1603 Even controlling a kernel debugger is possible using remote DMA.
1607 If ohci1394_dma=early is used as boot parameter, it will initialize
1608 all OHCI1394 controllers which are found in the PCI config space.
1610 As all changes to the FireWire bus such as enabling and disabling
1611 devices cause a bus reset and thereby disable remote DMA for all
1612 devices, be sure to have the cable plugged and FireWire enabled on
1613 the debugging host before booting the debug target for debugging.
1615 This code (~1k) is freed after boot. By then, the firewire stack
1616 in charge of the OHCI-1394 controllers should be used instead.
1618 See Documentation/debugging-via-ohci1394.txt for more information.
1620 config DMA_API_DEBUG
1621 bool "Enable debugging of DMA-API usage"
1622 depends on HAVE_DMA_API_DEBUG
1624 Enable this option to debug the use of the DMA API by device drivers.
1625 With this option you will be able to detect common bugs in device
1626 drivers like double-freeing of DMA mappings or freeing mappings that
1627 were never allocated.
1629 This also attempts to catch cases where a page owned by DMA is
1630 accessed by the cpu in a way that could cause data corruption. For
1631 example, this enables cow_user_page() to check that the source page is
1634 This option causes a performance degradation. Use only if you want to
1635 debug device drivers and dma interactions.
1639 menu "Runtime Testing"
1642 tristate "Linux Kernel Dump Test Tool Module"
1647 This module enables testing of the different dumping mechanisms by
1648 inducing system failures at predefined crash points.
1649 If you don't need it: say N
1650 Choose M here to compile this code as a module. The module will be
1653 Documentation on how to use the module can be found in
1654 Documentation/fault-injection/provoke-crashes.txt
1656 config TEST_LIST_SORT
1657 tristate "Linked list sorting test"
1658 depends on DEBUG_KERNEL || m
1660 Enable this to turn on 'list_sort()' function test. This test is
1661 executed only once during system boot (so affects only boot time),
1662 or at module load time.
1667 tristate "Array-based sort test"
1668 depends on DEBUG_KERNEL || m
1670 This option enables the self-test function of 'sort()' at boot,
1671 or at module load time.
1675 config KPROBES_SANITY_TEST
1676 bool "Kprobes sanity tests"
1677 depends on DEBUG_KERNEL
1681 This option provides for testing basic kprobes functionality on
1682 boot. A sample kprobe, jprobe and kretprobe are inserted and
1683 verified for functionality.
1685 Say N if you are unsure.
1687 config BACKTRACE_SELF_TEST
1688 tristate "Self test for the backtrace code"
1689 depends on DEBUG_KERNEL
1692 This option provides a kernel module that can be used to test
1693 the kernel stack backtrace code. This option is not useful
1694 for distributions or general kernels, but only for kernel
1695 developers working on architecture code.
1697 Note that if you want to also test saved backtraces, you will
1698 have to enable STACKTRACE as well.
1700 Say N if you are unsure.
1703 tristate "Red-Black tree test"
1704 depends on DEBUG_KERNEL
1706 A benchmark measuring the performance of the rbtree library.
1707 Also includes rbtree invariant checks.
1709 config INTERVAL_TREE_TEST
1710 tristate "Interval tree test"
1711 depends on DEBUG_KERNEL
1712 select INTERVAL_TREE
1714 A benchmark measuring the performance of the interval tree library
1717 tristate "Per cpu operations test"
1718 depends on m && DEBUG_KERNEL
1720 Enable this option to build test module which validates per-cpu
1725 config ATOMIC64_SELFTEST
1726 tristate "Perform an atomic64_t self-test"
1728 Enable this option to test the atomic64_t functions at boot or
1729 at module load time.
1733 config ASYNC_RAID6_TEST
1734 tristate "Self test for hardware accelerated raid6 recovery"
1735 depends on ASYNC_RAID6_RECOV
1738 This is a one-shot self test that permutes through the
1739 recovery of all the possible two disk failure scenarios for a
1740 N-disk array. Recovery is performed with the asynchronous
1741 raid6 recovery routines, and will optionally use an offload
1742 engine if one is available.
1747 tristate "Test functions located in the hexdump module at runtime"
1749 config TEST_STRING_HELPERS
1750 tristate "Test functions located in the string_helpers module at runtime"
1753 tristate "Test kstrto*() family of functions at runtime"
1756 tristate "Test printf() family of functions at runtime"
1759 tristate "Test bitmap_*() family of functions at runtime"
1762 Enable this option to test the bitmap functions at boot.
1767 tristate "Test functions located in the uuid module at runtime"
1769 config TEST_RHASHTABLE
1770 tristate "Perform selftest on resizable hash table"
1773 Enable this option to test the rhashtable functions at boot.
1778 tristate "Perform selftest on hash functions"
1781 Enable this option to test the kernel's integer (<linux/hash.h>),
1782 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1783 hash functions on boot (or module load).
1785 This is intended to help people writing architecture-specific
1786 optimized versions. If unsure, say N.
1789 tristate "Perform selftest on priority array manager"
1793 Enable this option to test priority array manager on boot
1799 tristate "Test module loading with 'hello world' module"
1803 This builds the "test_module" module that emits "Hello, world"
1804 on printk when loaded. It is designed to be used for basic
1805 evaluation of the module loading subsystem (for example when
1806 validating module verification). It lacks any extra dependencies,
1807 and will not normally be loaded by the system unless explicitly
1812 config TEST_USER_COPY
1813 tristate "Test user/kernel boundary protections"
1817 This builds the "test_user_copy" module that runs sanity checks
1818 on the copy_to/from_user infrastructure, making sure basic
1819 user/kernel boundary testing is working. If it fails to load,
1820 a regression has been detected in the user/kernel memory boundary
1826 tristate "Test BPF filter functionality"
1830 This builds the "test_bpf" module that runs various test vectors
1831 against the BPF interpreter or BPF JIT compiler depending on the
1832 current setting. This is in particular useful for BPF JIT compiler
1833 development, but also to run regression tests against changes in
1834 the interpreter code. It also enables test stubs for eBPF maps and
1835 verifier used by user space verifier testsuite.
1839 config TEST_FIRMWARE
1840 tristate "Test firmware loading via userspace interface"
1842 depends on FW_LOADER
1844 This builds the "test_firmware" module that creates a userspace
1845 interface for testing firmware loading. This can be used to
1846 control the triggering of firmware loading without needing an
1847 actual firmware-using device. The contents can be rechecked by
1853 tristate "sysctl test driver"
1855 depends on PROC_SYSCTL
1857 This builds the "test_sysctl" module. This driver enables to test the
1858 proc sysctl interfaces available to drivers safely without affecting
1859 production knobs which might alter system functionality.
1864 tristate "udelay test driver"
1867 This builds the "udelay_test" module that helps to make sure
1868 that udelay() is working properly.
1872 config TEST_STATIC_KEYS
1873 tristate "Test static keys"
1877 Test the static key interfaces.
1882 tristate "kmod stress tester"
1885 depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS
1886 depends on NETDEVICES && NET_CORE && INET # for TUN
1892 Test the kernel's module loading mechanism: kmod. kmod implements
1893 support to load modules using the Linux kernel's usermode helper.
1894 This test provides a series of tests against kmod.
1896 Although technically you can either build test_kmod as a module or
1897 into the kernel we disallow building it into the kernel since
1898 it stress tests request_module() and this will very likely cause
1899 some issues by taking over precious threads available from other
1900 module load requests, ultimately this could be fatal.
1904 tools/testing/selftests/kmod/kmod.sh --help
1908 config TEST_DEBUG_VIRTUAL
1909 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
1910 depends on DEBUG_VIRTUAL
1912 Test the kernel's ability to detect incorrect calls to
1913 virt_to_phys() done against the non-linear part of the
1914 kernel's virtual address map.
1918 endmenu # runtime tests
1922 depends on HAVE_MEMBLOCK
1924 This option adds a kernel parameter 'memtest', which allows memtest
1926 memtest=0, mean disabled; -- default
1927 memtest=1, mean do 1 test pattern;
1929 memtest=17, mean do 17 test patterns.
1930 If you are unsure how to answer this question, answer N.
1932 config BUG_ON_DATA_CORRUPTION
1933 bool "Trigger a BUG when data corruption is detected"
1936 Select this option if the kernel should BUG when it encounters
1937 data corruption in kernel memory structures when they get checked
1942 source "samples/Kconfig"
1944 source "lib/Kconfig.kgdb"
1946 source "lib/Kconfig.ubsan"
1948 config ARCH_HAS_DEVMEM_IS_ALLOWED
1951 config STRICT_DEVMEM
1952 bool "Filter access to /dev/mem"
1953 depends on MMU && DEVMEM
1954 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
1955 default y if TILE || PPC
1957 If this option is disabled, you allow userspace (root) access to all
1958 of memory, including kernel and userspace memory. Accidental
1959 access to this is obviously disastrous, but specific access can
1960 be used by people debugging the kernel. Note that with PAT support
1961 enabled, even in this case there are restrictions on /dev/mem
1962 use due to the cache aliasing requirements.
1964 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
1965 file only allows userspace access to PCI space and the BIOS code and
1966 data regions. This is sufficient for dosemu and X and all common
1971 config IO_STRICT_DEVMEM
1972 bool "Filter I/O access to /dev/mem"
1973 depends on STRICT_DEVMEM
1975 If this option is disabled, you allow userspace (root) access to all
1976 io-memory regardless of whether a driver is actively using that
1977 range. Accidental access to this is obviously disastrous, but
1978 specific access can be used by people debugging kernel drivers.
1980 If this option is switched on, the /dev/mem file only allows
1981 userspace access to *idle* io-memory ranges (see /proc/iomem) This
1982 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
1983 if the driver using a given range cannot be disabled.
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