3 menu "printk and dmesg options"
6 bool "Show timing information on printks"
9 Selecting this option causes time stamps of the printk()
10 messages to be added to the output of the syslog() system
11 call and at the console.
13 The timestamp is always recorded internally, and exported
14 to /dev/kmsg. This flag just specifies if the timestamp should
15 be included, not that the timestamp is recorded.
17 The behavior is also controlled by the kernel command line
18 parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst
20 config CONSOLE_LOGLEVEL_DEFAULT
21 int "Default console loglevel (1-15)"
25 Default loglevel to determine what will be printed on the console.
27 Setting a default here is equivalent to passing in loglevel=<x> in
28 the kernel bootargs. loglevel=<x> continues to override whatever
29 value is specified here as well.
31 Note: This does not affect the log level of un-prefixed printk()
32 usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
35 config CONSOLE_LOGLEVEL_QUIET
36 int "quiet console loglevel (1-15)"
40 loglevel to use when "quiet" is passed on the kernel commandline.
42 When "quiet" is passed on the kernel commandline this loglevel
43 will be used as the loglevel. IOW passing "quiet" will be the
44 equivalent of passing "loglevel=<CONSOLE_LOGLEVEL_QUIET>"
46 config MESSAGE_LOGLEVEL_DEFAULT
47 int "Default message log level (1-7)"
51 Default log level for printk statements with no specified priority.
53 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
54 that are auditing their logs closely may want to set it to a lower
57 Note: This does not affect what message level gets printed on the console
58 by default. To change that, use loglevel=<x> in the kernel bootargs,
59 or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value.
61 config BOOT_PRINTK_DELAY
62 bool "Delay each boot printk message by N milliseconds"
63 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
65 This build option allows you to read kernel boot messages
66 by inserting a short delay after each one. The delay is
67 specified in milliseconds on the kernel command line,
70 It is likely that you would also need to use "lpj=M" to preset
71 the "loops per jiffie" value.
72 See a previous boot log for the "lpj" value to use for your
73 system, and then set "lpj=M" before setting "boot_delay=N".
74 NOTE: Using this option may adversely affect SMP systems.
75 I.e., processors other than the first one may not boot up.
76 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
77 what it believes to be lockup conditions.
80 bool "Enable dynamic printk() support"
86 Compiles debug level messages into the kernel, which would not
87 otherwise be available at runtime. These messages can then be
88 enabled/disabled based on various levels of scope - per source file,
89 function, module, format string, and line number. This mechanism
90 implicitly compiles in all pr_debug() and dev_dbg() calls, which
91 enlarges the kernel text size by about 2%.
93 If a source file is compiled with DEBUG flag set, any
94 pr_debug() calls in it are enabled by default, but can be
95 disabled at runtime as below. Note that DEBUG flag is
96 turned on by many CONFIG_*DEBUG* options.
100 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
101 which is contained in the 'debugfs' filesystem. Thus, the debugfs
102 filesystem must first be mounted before making use of this feature.
103 We refer the control file as: <debugfs>/dynamic_debug/control. This
104 file contains a list of the debug statements that can be enabled. The
105 format for each line of the file is:
107 filename:lineno [module]function flags format
109 filename : source file of the debug statement
110 lineno : line number of the debug statement
111 module : module that contains the debug statement
112 function : function that contains the debug statement
113 flags : '=p' means the line is turned 'on' for printing
114 format : the format used for the debug statement
118 nullarbor:~ # cat <debugfs>/dynamic_debug/control
119 # filename:lineno [module]function flags format
120 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
121 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
122 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
126 // enable the message at line 1603 of file svcsock.c
127 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
128 <debugfs>/dynamic_debug/control
130 // enable all the messages in file svcsock.c
131 nullarbor:~ # echo -n 'file svcsock.c +p' >
132 <debugfs>/dynamic_debug/control
134 // enable all the messages in the NFS server module
135 nullarbor:~ # echo -n 'module nfsd +p' >
136 <debugfs>/dynamic_debug/control
138 // enable all 12 messages in the function svc_process()
139 nullarbor:~ # echo -n 'func svc_process +p' >
140 <debugfs>/dynamic_debug/control
142 // disable all 12 messages in the function svc_process()
143 nullarbor:~ # echo -n 'func svc_process -p' >
144 <debugfs>/dynamic_debug/control
146 See Documentation/admin-guide/dynamic-debug-howto.rst for additional
149 endmenu # "printk and dmesg options"
151 menu "Compile-time checks and compiler options"
154 bool "Compile the kernel with debug info"
155 depends on DEBUG_KERNEL && !COMPILE_TEST
157 If you say Y here the resulting kernel image will include
158 debugging info resulting in a larger kernel image.
159 This adds debug symbols to the kernel and modules (gcc -g), and
160 is needed if you intend to use kernel crashdump or binary object
161 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
162 Say Y here only if you plan to debug the kernel.
166 config DEBUG_INFO_REDUCED
167 bool "Reduce debugging information"
168 depends on DEBUG_INFO
170 If you say Y here gcc is instructed to generate less debugging
171 information for structure types. This means that tools that
172 need full debugging information (like kgdb or systemtap) won't
173 be happy. But if you merely need debugging information to
174 resolve line numbers there is no loss. Advantage is that
175 build directory object sizes shrink dramatically over a full
176 DEBUG_INFO build and compile times are reduced too.
177 Only works with newer gcc versions.
179 config DEBUG_INFO_SPLIT
180 bool "Produce split debuginfo in .dwo files"
181 depends on DEBUG_INFO
183 Generate debug info into separate .dwo files. This significantly
184 reduces the build directory size for builds with DEBUG_INFO,
185 because it stores the information only once on disk in .dwo
186 files instead of multiple times in object files and executables.
187 In addition the debug information is also compressed.
189 Requires recent gcc (4.7+) and recent gdb/binutils.
190 Any tool that packages or reads debug information would need
191 to know about the .dwo files and include them.
192 Incompatible with older versions of ccache.
194 config DEBUG_INFO_DWARF4
195 bool "Generate dwarf4 debuginfo"
196 depends on DEBUG_INFO
198 Generate dwarf4 debug info. This requires recent versions
199 of gcc and gdb. It makes the debug information larger.
200 But it significantly improves the success of resolving
201 variables in gdb on optimized code.
204 bool "Provide GDB scripts for kernel debugging"
205 depends on DEBUG_INFO
207 This creates the required links to GDB helper scripts in the
208 build directory. If you load vmlinux into gdb, the helper
209 scripts will be automatically imported by gdb as well, and
210 additional functions are available to analyze a Linux kernel
211 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
214 config ENABLE_MUST_CHECK
215 bool "Enable __must_check logic"
218 Enable the __must_check logic in the kernel build. Disable this to
219 suppress the "warning: ignoring return value of 'foo', declared with
220 attribute warn_unused_result" messages.
223 int "Warn for stack frames larger than (needs gcc 4.4)"
225 default 3072 if KASAN_EXTRA
226 default 2048 if GCC_PLUGIN_LATENT_ENTROPY
227 default 1280 if (!64BIT && PARISC)
228 default 1024 if (!64BIT && !PARISC)
229 default 2048 if 64BIT
231 Tell gcc to warn at build time for stack frames larger than this.
232 Setting this too low will cause a lot of warnings.
233 Setting it to 0 disables the warning.
236 config STRIP_ASM_SYMS
237 bool "Strip assembler-generated symbols during link"
240 Strip internal assembler-generated symbols during a link (symbols
241 that look like '.Lxxx') so they don't pollute the output of
242 get_wchan() and suchlike.
245 bool "Generate readable assembler code"
246 depends on DEBUG_KERNEL
248 Disable some compiler optimizations that tend to generate human unreadable
249 assembler output. This may make the kernel slightly slower, but it helps
250 to keep kernel developers who have to stare a lot at assembler listings
253 config UNUSED_SYMBOLS
254 bool "Enable unused/obsolete exported symbols"
257 Unused but exported symbols make the kernel needlessly bigger. For
258 that reason most of these unused exports will soon be removed. This
259 option is provided temporarily to provide a transition period in case
260 some external kernel module needs one of these symbols anyway. If you
261 encounter such a case in your module, consider if you are actually
262 using the right API. (rationale: since nobody in the kernel is using
263 this in a module, there is a pretty good chance it's actually the
264 wrong interface to use). If you really need the symbol, please send a
265 mail to the linux kernel mailing list mentioning the symbol and why
266 you really need it, and what the merge plan to the mainline kernel for
270 bool "Track page owner"
271 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
275 select PAGE_EXTENSION
277 This keeps track of what call chain is the owner of a page, may
278 help to find bare alloc_page(s) leaks. Even if you include this
279 feature on your build, it is disabled in default. You should pass
280 "page_owner=on" to boot parameter in order to enable it. Eats
281 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
282 for user-space helper.
287 bool "Debug Filesystem"
289 debugfs is a virtual file system that kernel developers use to put
290 debugging files into. Enable this option to be able to read and
291 write to these files.
293 For detailed documentation on the debugfs API, see
294 Documentation/filesystems/.
299 bool "Run 'make headers_check' when building vmlinux"
302 This option will extract the user-visible kernel headers whenever
303 building the kernel, and will run basic sanity checks on them to
304 ensure that exported files do not attempt to include files which
305 were not exported, etc.
307 If you're making modifications to header files which are
308 relevant for userspace, say 'Y', and check the headers
309 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
310 your build tree), to make sure they're suitable.
312 config DEBUG_SECTION_MISMATCH
313 bool "Enable full Section mismatch analysis"
315 The section mismatch analysis checks if there are illegal
316 references from one section to another section.
317 During linktime or runtime, some sections are dropped;
318 any use of code/data previously in these sections would
319 most likely result in an oops.
320 In the code, functions and variables are annotated with
321 __init,, etc. (see the full list in include/linux/init.h),
322 which results in the code/data being placed in specific sections.
323 The section mismatch analysis is always performed after a full
324 kernel build, and enabling this option causes the following
325 additional steps to occur:
326 - Add the option -fno-inline-functions-called-once to gcc commands.
327 When inlining a function annotated with __init in a non-init
328 function, we would lose the section information and thus
329 the analysis would not catch the illegal reference.
330 This option tells gcc to inline less (but it does result in
332 - Run the section mismatch analysis for each module/built-in.a file.
333 When we run the section mismatch analysis on vmlinux.o, we
334 lose valuable information about where the mismatch was
336 Running the analysis for each module/built-in.a file
337 tells where the mismatch happens much closer to the
338 source. The drawback is that the same mismatch is
339 reported at least twice.
340 - Enable verbose reporting from modpost in order to help resolve
341 the section mismatches that are reported.
343 config SECTION_MISMATCH_WARN_ONLY
344 bool "Make section mismatch errors non-fatal"
347 If you say N here, the build process will fail if there are any
348 section mismatch, instead of just throwing warnings.
353 # Select this config option from the architecture Kconfig, if it
354 # is preferred to always offer frame pointers as a config
355 # option on the architecture (regardless of KERNEL_DEBUG):
357 config ARCH_WANT_FRAME_POINTERS
361 bool "Compile the kernel with frame pointers"
362 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || 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.
744 config CC_HAS_SANCOV_TRACE_PC
745 def_bool $(cc-option,-fsanitize-coverage=trace-pc)
748 bool "Code coverage for fuzzing"
749 depends on ARCH_HAS_KCOV
750 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
752 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
754 KCOV exposes kernel code coverage information in a form suitable
755 for coverage-guided fuzzing (randomized testing).
757 If RANDOMIZE_BASE is enabled, PC values will not be stable across
758 different machines and across reboots. If you need stable PC values,
759 disable RANDOMIZE_BASE.
761 For more details, see Documentation/dev-tools/kcov.rst.
763 config KCOV_ENABLE_COMPARISONS
764 bool "Enable comparison operands collection by KCOV"
766 depends on $(cc-option,-fsanitize-coverage=trace-cmp)
768 KCOV also exposes operands of every comparison in the instrumented
769 code along with operand sizes and PCs of the comparison instructions.
770 These operands can be used by fuzzing engines to improve the quality
773 config KCOV_INSTRUMENT_ALL
774 bool "Instrument all code by default"
778 If you are doing generic system call fuzzing (like e.g. syzkaller),
779 then you will want to instrument the whole kernel and you should
780 say y here. If you are doing more targeted fuzzing (like e.g.
781 filesystem fuzzing with AFL) then you will want to enable coverage
782 for more specific subsets of files, and should say n here.
785 bool "Debug shared IRQ handlers"
786 depends on DEBUG_KERNEL
788 Enable this to generate a spurious interrupt as soon as a shared
789 interrupt handler is registered, and just before one is deregistered.
790 Drivers ought to be able to handle interrupts coming in at those
791 points; some don't and need to be caught.
793 menu "Debug Lockups and Hangs"
795 config LOCKUP_DETECTOR
798 config SOFTLOCKUP_DETECTOR
799 bool "Detect Soft Lockups"
800 depends on DEBUG_KERNEL && !S390
801 select LOCKUP_DETECTOR
803 Say Y here to enable the kernel to act as a watchdog to detect
806 Softlockups are bugs that cause the kernel to loop in kernel
807 mode for more than 20 seconds, without giving other tasks a
808 chance to run. The current stack trace is displayed upon
809 detection and the system will stay locked up.
811 config BOOTPARAM_SOFTLOCKUP_PANIC
812 bool "Panic (Reboot) On Soft Lockups"
813 depends on SOFTLOCKUP_DETECTOR
815 Say Y here to enable the kernel to panic on "soft lockups",
816 which are bugs that cause the kernel to loop in kernel
817 mode for more than 20 seconds (configurable using the watchdog_thresh
818 sysctl), without giving other tasks a chance to run.
820 The panic can be used in combination with panic_timeout,
821 to cause the system to reboot automatically after a
822 lockup has been detected. This feature is useful for
823 high-availability systems that have uptime guarantees and
824 where a lockup must be resolved ASAP.
828 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
830 depends on SOFTLOCKUP_DETECTOR
832 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
833 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
835 config HARDLOCKUP_DETECTOR_PERF
837 select SOFTLOCKUP_DETECTOR
840 # Enables a timestamp based low pass filter to compensate for perf based
841 # hard lockup detection which runs too fast due to turbo modes.
843 config HARDLOCKUP_CHECK_TIMESTAMP
847 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
848 # lockup detector rather than the perf based detector.
850 config HARDLOCKUP_DETECTOR
851 bool "Detect Hard Lockups"
852 depends on DEBUG_KERNEL && !S390
853 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
854 select LOCKUP_DETECTOR
855 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
857 Say Y here to enable the kernel to act as a watchdog to detect
860 Hardlockups are bugs that cause the CPU to loop in kernel mode
861 for more than 10 seconds, without letting other interrupts have a
862 chance to run. The current stack trace is displayed upon detection
863 and the system will stay locked up.
865 config BOOTPARAM_HARDLOCKUP_PANIC
866 bool "Panic (Reboot) On Hard Lockups"
867 depends on HARDLOCKUP_DETECTOR
869 Say Y here to enable the kernel to panic on "hard lockups",
870 which are bugs that cause the kernel to loop in kernel
871 mode with interrupts disabled for more than 10 seconds (configurable
872 using the watchdog_thresh sysctl).
876 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
878 depends on HARDLOCKUP_DETECTOR
880 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
881 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
883 config DETECT_HUNG_TASK
884 bool "Detect Hung Tasks"
885 depends on DEBUG_KERNEL
886 default SOFTLOCKUP_DETECTOR
888 Say Y here to enable the kernel to detect "hung tasks",
889 which are bugs that cause the task to be stuck in
890 uninterruptible "D" state indefinitely.
892 When a hung task is detected, the kernel will print the
893 current stack trace (which you should report), but the
894 task will stay in uninterruptible state. If lockdep is
895 enabled then all held locks will also be reported. This
896 feature has negligible overhead.
898 config DEFAULT_HUNG_TASK_TIMEOUT
899 int "Default timeout for hung task detection (in seconds)"
900 depends on DETECT_HUNG_TASK
903 This option controls the default timeout (in seconds) used
904 to determine when a task has become non-responsive and should
907 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
908 sysctl or by writing a value to
909 /proc/sys/kernel/hung_task_timeout_secs.
911 A timeout of 0 disables the check. The default is two minutes.
912 Keeping the default should be fine in most cases.
914 config BOOTPARAM_HUNG_TASK_PANIC
915 bool "Panic (Reboot) On Hung Tasks"
916 depends on DETECT_HUNG_TASK
918 Say Y here to enable the kernel to panic on "hung tasks",
919 which are bugs that cause the kernel to leave a task stuck
920 in uninterruptible "D" state.
922 The panic can be used in combination with panic_timeout,
923 to cause the system to reboot automatically after a
924 hung task has been detected. This feature is useful for
925 high-availability systems that have uptime guarantees and
926 where a hung tasks must be resolved ASAP.
930 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
932 depends on DETECT_HUNG_TASK
934 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
935 default 1 if BOOTPARAM_HUNG_TASK_PANIC
938 bool "Detect Workqueue Stalls"
939 depends on DEBUG_KERNEL
941 Say Y here to enable stall detection on workqueues. If a
942 worker pool doesn't make forward progress on a pending work
943 item for over a given amount of time, 30s by default, a
944 warning message is printed along with dump of workqueue
945 state. This can be configured through kernel parameter
946 "workqueue.watchdog_thresh" and its sysfs counterpart.
948 endmenu # "Debug lockups and hangs"
953 Say Y here to enable the kernel to panic when it oopses. This
954 has the same effect as setting oops=panic on the kernel command
957 This feature is useful to ensure that the kernel does not do
958 anything erroneous after an oops which could result in data
959 corruption or other issues.
963 config PANIC_ON_OOPS_VALUE
966 default 0 if !PANIC_ON_OOPS
967 default 1 if PANIC_ON_OOPS
973 Set the timeout value (in seconds) until a reboot occurs when the
974 the kernel panics. If n = 0, then we wait forever. A timeout
975 value n > 0 will wait n seconds before rebooting, while a timeout
976 value n < 0 will reboot immediately.
979 bool "Collect scheduler debugging info"
980 depends on DEBUG_KERNEL && PROC_FS
983 If you say Y here, the /proc/sched_debug file will be provided
984 that can help debug the scheduler. The runtime overhead of this
992 bool "Collect scheduler statistics"
993 depends on DEBUG_KERNEL && PROC_FS
996 If you say Y here, additional code will be inserted into the
997 scheduler and related routines to collect statistics about
998 scheduler behavior and provide them in /proc/schedstat. These
999 stats may be useful for both tuning and debugging the scheduler
1000 If you aren't debugging the scheduler or trying to tune a specific
1001 application, you can say N to avoid the very slight overhead
1004 config SCHED_STACK_END_CHECK
1005 bool "Detect stack corruption on calls to schedule()"
1006 depends on DEBUG_KERNEL
1009 This option checks for a stack overrun on calls to schedule().
1010 If the stack end location is found to be over written always panic as
1011 the content of the corrupted region can no longer be trusted.
1012 This is to ensure no erroneous behaviour occurs which could result in
1013 data corruption or a sporadic crash at a later stage once the region
1014 is examined. The runtime overhead introduced is minimal.
1016 config DEBUG_TIMEKEEPING
1017 bool "Enable extra timekeeping sanity checking"
1019 This option will enable additional timekeeping sanity checks
1020 which may be helpful when diagnosing issues where timekeeping
1021 problems are suspected.
1023 This may include checks in the timekeeping hotpaths, so this
1024 option may have a (very small) performance impact to some
1029 config DEBUG_PREEMPT
1030 bool "Debug preemptible kernel"
1031 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1034 If you say Y here then the kernel will use a debug variant of the
1035 commonly used smp_processor_id() function and will print warnings
1036 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1037 will detect preemption count underflows.
1039 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1041 config LOCK_DEBUGGING_SUPPORT
1043 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1046 config PROVE_LOCKING
1047 bool "Lock debugging: prove locking correctness"
1048 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1050 select DEBUG_SPINLOCK
1051 select DEBUG_MUTEXES
1052 select DEBUG_RT_MUTEXES if RT_MUTEXES
1053 select DEBUG_RWSEMS if RWSEM_SPIN_ON_OWNER
1054 select DEBUG_WW_MUTEX_SLOWPATH
1055 select DEBUG_LOCK_ALLOC
1056 select TRACE_IRQFLAGS
1059 This feature enables the kernel to prove that all locking
1060 that occurs in the kernel runtime is mathematically
1061 correct: that under no circumstance could an arbitrary (and
1062 not yet triggered) combination of observed locking
1063 sequences (on an arbitrary number of CPUs, running an
1064 arbitrary number of tasks and interrupt contexts) cause a
1067 In short, this feature enables the kernel to report locking
1068 related deadlocks before they actually occur.
1070 The proof does not depend on how hard and complex a
1071 deadlock scenario would be to trigger: how many
1072 participant CPUs, tasks and irq-contexts would be needed
1073 for it to trigger. The proof also does not depend on
1074 timing: if a race and a resulting deadlock is possible
1075 theoretically (no matter how unlikely the race scenario
1076 is), it will be proven so and will immediately be
1077 reported by the kernel (once the event is observed that
1078 makes the deadlock theoretically possible).
1080 If a deadlock is impossible (i.e. the locking rules, as
1081 observed by the kernel, are mathematically correct), the
1082 kernel reports nothing.
1084 NOTE: this feature can also be enabled for rwlocks, mutexes
1085 and rwsems - in which case all dependencies between these
1086 different locking variants are observed and mapped too, and
1087 the proof of observed correctness is also maintained for an
1088 arbitrary combination of these separate locking variants.
1090 For more details, see Documentation/locking/lockdep-design.txt.
1093 bool "Lock usage statistics"
1094 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1096 select DEBUG_SPINLOCK
1097 select DEBUG_MUTEXES
1098 select DEBUG_RT_MUTEXES if RT_MUTEXES
1099 select DEBUG_LOCK_ALLOC
1102 This feature enables tracking lock contention points
1104 For more details, see Documentation/locking/lockstat.txt
1106 This also enables lock events required by "perf lock",
1108 If you want to use "perf lock", you also need to turn on
1109 CONFIG_EVENT_TRACING.
1111 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1112 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1114 config DEBUG_RT_MUTEXES
1115 bool "RT Mutex debugging, deadlock detection"
1116 depends on DEBUG_KERNEL && RT_MUTEXES
1118 This allows rt mutex semantics violations and rt mutex related
1119 deadlocks (lockups) to be detected and reported automatically.
1121 config DEBUG_SPINLOCK
1122 bool "Spinlock and rw-lock debugging: basic checks"
1123 depends on DEBUG_KERNEL
1124 select UNINLINE_SPIN_UNLOCK
1126 Say Y here and build SMP to catch missing spinlock initialization
1127 and certain other kinds of spinlock errors commonly made. This is
1128 best used in conjunction with the NMI watchdog so that spinlock
1129 deadlocks are also debuggable.
1131 config DEBUG_MUTEXES
1132 bool "Mutex debugging: basic checks"
1133 depends on DEBUG_KERNEL
1135 This feature allows mutex semantics violations to be detected and
1138 config DEBUG_WW_MUTEX_SLOWPATH
1139 bool "Wait/wound mutex debugging: Slowpath testing"
1140 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1141 select DEBUG_LOCK_ALLOC
1142 select DEBUG_SPINLOCK
1143 select DEBUG_MUTEXES
1145 This feature enables slowpath testing for w/w mutex users by
1146 injecting additional -EDEADLK wound/backoff cases. Together with
1147 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1148 will test all possible w/w mutex interface abuse with the
1149 exception of simply not acquiring all the required locks.
1150 Note that this feature can introduce significant overhead, so
1151 it really should not be enabled in a production or distro kernel,
1152 even a debug kernel. If you are a driver writer, enable it. If
1153 you are a distro, do not.
1156 bool "RW Semaphore debugging: basic checks"
1157 depends on DEBUG_KERNEL && RWSEM_SPIN_ON_OWNER
1159 This debugging feature allows mismatched rw semaphore locks and unlocks
1160 to be detected and reported.
1162 config DEBUG_LOCK_ALLOC
1163 bool "Lock debugging: detect incorrect freeing of live locks"
1164 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1165 select DEBUG_SPINLOCK
1166 select DEBUG_MUTEXES
1167 select DEBUG_RT_MUTEXES if RT_MUTEXES
1170 This feature will check whether any held lock (spinlock, rwlock,
1171 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1172 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1173 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1174 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1175 held during task exit.
1179 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1181 select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86
1185 config LOCKDEP_SMALL
1188 config DEBUG_LOCKDEP
1189 bool "Lock dependency engine debugging"
1190 depends on DEBUG_KERNEL && LOCKDEP
1192 If you say Y here, the lock dependency engine will do
1193 additional runtime checks to debug itself, at the price
1194 of more runtime overhead.
1196 config DEBUG_ATOMIC_SLEEP
1197 bool "Sleep inside atomic section checking"
1198 select PREEMPT_COUNT
1199 depends on DEBUG_KERNEL
1200 depends on !ARCH_NO_PREEMPT
1202 If you say Y here, various routines which may sleep will become very
1203 noisy if they are called inside atomic sections: when a spinlock is
1204 held, inside an rcu read side critical section, inside preempt disabled
1205 sections, inside an interrupt, etc...
1207 config DEBUG_LOCKING_API_SELFTESTS
1208 bool "Locking API boot-time self-tests"
1209 depends on DEBUG_KERNEL
1211 Say Y here if you want the kernel to run a short self-test during
1212 bootup. The self-test checks whether common types of locking bugs
1213 are detected by debugging mechanisms or not. (if you disable
1214 lock debugging then those bugs wont be detected of course.)
1215 The following locking APIs are covered: spinlocks, rwlocks,
1218 config LOCK_TORTURE_TEST
1219 tristate "torture tests for locking"
1220 depends on DEBUG_KERNEL
1223 This option provides a kernel module that runs torture tests
1224 on kernel locking primitives. The kernel module may be built
1225 after the fact on the running kernel to be tested, if desired.
1227 Say Y here if you want kernel locking-primitive torture tests
1228 to be built into the kernel.
1229 Say M if you want these torture tests to build as a module.
1230 Say N if you are unsure.
1232 config WW_MUTEX_SELFTEST
1233 tristate "Wait/wound mutex selftests"
1235 This option provides a kernel module that runs tests on the
1236 on the struct ww_mutex locking API.
1238 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1239 with this test harness.
1241 Say M if you want these self tests to build as a module.
1242 Say N if you are unsure.
1244 endmenu # lock debugging
1246 config TRACE_IRQFLAGS
1249 Enables hooks to interrupt enabling and disabling for
1250 either tracing or lock debugging.
1253 bool "Stack backtrace support"
1254 depends on STACKTRACE_SUPPORT
1256 This option causes the kernel to create a /proc/pid/stack for
1257 every process, showing its current stack trace.
1258 It is also used by various kernel debugging features that require
1259 stack trace generation.
1261 config WARN_ALL_UNSEEDED_RANDOM
1262 bool "Warn for all uses of unseeded randomness"
1265 Some parts of the kernel contain bugs relating to their use of
1266 cryptographically secure random numbers before it's actually possible
1267 to generate those numbers securely. This setting ensures that these
1268 flaws don't go unnoticed, by enabling a message, should this ever
1269 occur. This will allow people with obscure setups to know when things
1270 are going wrong, so that they might contact developers about fixing
1273 Unfortunately, on some models of some architectures getting
1274 a fully seeded CRNG is extremely difficult, and so this can
1275 result in dmesg getting spammed for a surprisingly long
1276 time. This is really bad from a security perspective, and
1277 so architecture maintainers really need to do what they can
1278 to get the CRNG seeded sooner after the system is booted.
1279 However, since users cannot do anything actionable to
1280 address this, by default the kernel will issue only a single
1281 warning for the first use of unseeded randomness.
1283 Say Y here if you want to receive warnings for all uses of
1284 unseeded randomness. This will be of use primarily for
1285 those developers interested in improving the security of
1286 Linux kernels running on their architecture (or
1289 config DEBUG_KOBJECT
1290 bool "kobject debugging"
1291 depends on DEBUG_KERNEL
1293 If you say Y here, some extra kobject debugging messages will be sent
1296 config DEBUG_KOBJECT_RELEASE
1297 bool "kobject release debugging"
1298 depends on DEBUG_OBJECTS_TIMERS
1300 kobjects are reference counted objects. This means that their
1301 last reference count put is not predictable, and the kobject can
1302 live on past the point at which a driver decides to drop it's
1303 initial reference to the kobject gained on allocation. An
1304 example of this would be a struct device which has just been
1307 However, some buggy drivers assume that after such an operation,
1308 the memory backing the kobject can be immediately freed. This
1309 goes completely against the principles of a refcounted object.
1311 If you say Y here, the kernel will delay the release of kobjects
1312 on the last reference count to improve the visibility of this
1313 kind of kobject release bug.
1315 config HAVE_DEBUG_BUGVERBOSE
1318 config DEBUG_BUGVERBOSE
1319 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1320 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1323 Say Y here to make BUG() panics output the file name and line number
1324 of the BUG call as well as the EIP and oops trace. This aids
1325 debugging but costs about 70-100K of memory.
1328 bool "Debug linked list manipulation"
1329 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1331 Enable this to turn on extended checks in the linked-list
1336 config DEBUG_PI_LIST
1337 bool "Debug priority linked list manipulation"
1338 depends on DEBUG_KERNEL
1340 Enable this to turn on extended checks in the priority-ordered
1341 linked-list (plist) walking routines. This checks the entire
1342 list multiple times during each manipulation.
1347 bool "Debug SG table operations"
1348 depends on DEBUG_KERNEL
1350 Enable this to turn on checks on scatter-gather tables. This can
1351 help find problems with drivers that do not properly initialize
1356 config DEBUG_NOTIFIERS
1357 bool "Debug notifier call chains"
1358 depends on DEBUG_KERNEL
1360 Enable this to turn on sanity checking for notifier call chains.
1361 This is most useful for kernel developers to make sure that
1362 modules properly unregister themselves from notifier chains.
1363 This is a relatively cheap check but if you care about maximum
1366 config DEBUG_CREDENTIALS
1367 bool "Debug credential management"
1368 depends on DEBUG_KERNEL
1370 Enable this to turn on some debug checking for credential
1371 management. The additional code keeps track of the number of
1372 pointers from task_structs to any given cred struct, and checks to
1373 see that this number never exceeds the usage count of the cred
1376 Furthermore, if SELinux is enabled, this also checks that the
1377 security pointer in the cred struct is never seen to be invalid.
1381 source "kernel/rcu/Kconfig.debug"
1383 config DEBUG_WQ_FORCE_RR_CPU
1384 bool "Force round-robin CPU selection for unbound work items"
1385 depends on DEBUG_KERNEL
1388 Workqueue used to implicitly guarantee that work items queued
1389 without explicit CPU specified are put on the local CPU. This
1390 guarantee is no longer true and while local CPU is still
1391 preferred work items may be put on foreign CPUs. Kernel
1392 parameter "workqueue.debug_force_rr_cpu" is added to force
1393 round-robin CPU selection to flush out usages which depend on the
1394 now broken guarantee. This config option enables the debug
1395 feature by default. When enabled, memory and cache locality will
1398 config DEBUG_BLOCK_EXT_DEVT
1399 bool "Force extended block device numbers and spread them"
1400 depends on DEBUG_KERNEL
1404 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1405 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1406 YOU ARE DOING. Distros, please enable this and fix whatever
1409 Conventionally, block device numbers are allocated from
1410 predetermined contiguous area. However, extended block area
1411 may introduce non-contiguous block device numbers. This
1412 option forces most block device numbers to be allocated from
1413 the extended space and spreads them to discover kernel or
1414 userland code paths which assume predetermined contiguous
1415 device number allocation.
1417 Note that turning on this debug option shuffles all the
1418 device numbers for all IDE and SCSI devices including libata
1419 ones, so root partition specified using device number
1420 directly (via rdev or root=MAJ:MIN) won't work anymore.
1421 Textual device names (root=/dev/sdXn) will continue to work.
1423 Say N if you are unsure.
1425 config CPU_HOTPLUG_STATE_CONTROL
1426 bool "Enable CPU hotplug state control"
1427 depends on DEBUG_KERNEL
1428 depends on HOTPLUG_CPU
1431 Allows to write steps between "offline" and "online" to the CPUs
1432 sysfs target file so states can be stepped granular. This is a debug
1433 option for now as the hotplug machinery cannot be stopped and
1434 restarted at arbitrary points yet.
1436 Say N if your are unsure.
1438 config NOTIFIER_ERROR_INJECTION
1439 tristate "Notifier error injection"
1440 depends on DEBUG_KERNEL
1443 This option provides the ability to inject artificial errors to
1444 specified notifier chain callbacks. It is useful to test the error
1445 handling of notifier call chain failures.
1449 config PM_NOTIFIER_ERROR_INJECT
1450 tristate "PM notifier error injection module"
1451 depends on PM && NOTIFIER_ERROR_INJECTION
1452 default m if PM_DEBUG
1454 This option provides the ability to inject artificial errors to
1455 PM notifier chain callbacks. It is controlled through debugfs
1456 interface /sys/kernel/debug/notifier-error-inject/pm
1458 If the notifier call chain should be failed with some events
1459 notified, write the error code to "actions/<notifier event>/error".
1461 Example: Inject PM suspend error (-12 = -ENOMEM)
1463 # cd /sys/kernel/debug/notifier-error-inject/pm/
1464 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1465 # echo mem > /sys/power/state
1466 bash: echo: write error: Cannot allocate memory
1468 To compile this code as a module, choose M here: the module will
1469 be called pm-notifier-error-inject.
1473 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1474 tristate "OF reconfig notifier error injection module"
1475 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1477 This option provides the ability to inject artificial errors to
1478 OF reconfig notifier chain callbacks. It is controlled
1479 through debugfs interface under
1480 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1482 If the notifier call chain should be failed with some events
1483 notified, write the error code to "actions/<notifier event>/error".
1485 To compile this code as a module, choose M here: the module will
1486 be called of-reconfig-notifier-error-inject.
1490 config NETDEV_NOTIFIER_ERROR_INJECT
1491 tristate "Netdev notifier error injection module"
1492 depends on NET && NOTIFIER_ERROR_INJECTION
1494 This option provides the ability to inject artificial errors to
1495 netdevice notifier chain callbacks. It is controlled through debugfs
1496 interface /sys/kernel/debug/notifier-error-inject/netdev
1498 If the notifier call chain should be failed with some events
1499 notified, write the error code to "actions/<notifier event>/error".
1501 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1503 # cd /sys/kernel/debug/notifier-error-inject/netdev
1504 # echo -22 > actions/NETDEV_CHANGEMTU/error
1505 # ip link set eth0 mtu 1024
1506 RTNETLINK answers: Invalid argument
1508 To compile this code as a module, choose M here: the module will
1509 be called netdev-notifier-error-inject.
1513 config FUNCTION_ERROR_INJECTION
1515 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
1517 config FAULT_INJECTION
1518 bool "Fault-injection framework"
1519 depends on DEBUG_KERNEL
1521 Provide fault-injection framework.
1522 For more details, see Documentation/fault-injection/.
1525 bool "Fault-injection capability for kmalloc"
1526 depends on FAULT_INJECTION
1527 depends on SLAB || SLUB
1529 Provide fault-injection capability for kmalloc.
1531 config FAIL_PAGE_ALLOC
1532 bool "Fault-injection capabilitiy for alloc_pages()"
1533 depends on FAULT_INJECTION
1535 Provide fault-injection capability for alloc_pages().
1537 config FAIL_MAKE_REQUEST
1538 bool "Fault-injection capability for disk IO"
1539 depends on FAULT_INJECTION && BLOCK
1541 Provide fault-injection capability for disk IO.
1543 config FAIL_IO_TIMEOUT
1544 bool "Fault-injection capability for faking disk interrupts"
1545 depends on FAULT_INJECTION && BLOCK
1547 Provide fault-injection capability on end IO handling. This
1548 will make the block layer "forget" an interrupt as configured,
1549 thus exercising the error handling.
1551 Only works with drivers that use the generic timeout handling,
1552 for others it wont do anything.
1555 bool "Fault-injection capability for futexes"
1557 depends on FAULT_INJECTION && FUTEX
1559 Provide fault-injection capability for futexes.
1561 config FAULT_INJECTION_DEBUG_FS
1562 bool "Debugfs entries for fault-injection capabilities"
1563 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1565 Enable configuration of fault-injection capabilities via debugfs.
1567 config FAIL_FUNCTION
1568 bool "Fault-injection capability for functions"
1569 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
1571 Provide function-based fault-injection capability.
1572 This will allow you to override a specific function with a return
1573 with given return value. As a result, function caller will see
1574 an error value and have to handle it. This is useful to test the
1575 error handling in various subsystems.
1577 config FAIL_MMC_REQUEST
1578 bool "Fault-injection capability for MMC IO"
1579 depends on FAULT_INJECTION_DEBUG_FS && MMC
1581 Provide fault-injection capability for MMC IO.
1582 This will make the mmc core return data errors. This is
1583 useful to test the error handling in the mmc block device
1584 and to test how the mmc host driver handles retries from
1587 config FAULT_INJECTION_STACKTRACE_FILTER
1588 bool "stacktrace filter for fault-injection capabilities"
1589 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1592 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1594 Provide stacktrace filter for fault-injection capabilities
1597 bool "Latency measuring infrastructure"
1598 depends on DEBUG_KERNEL
1599 depends on STACKTRACE_SUPPORT
1601 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1608 Enable this option if you want to use the LatencyTOP tool
1609 to find out which userspace is blocking on what kernel operations.
1611 source kernel/trace/Kconfig
1613 config PROVIDE_OHCI1394_DMA_INIT
1614 bool "Remote debugging over FireWire early on boot"
1615 depends on PCI && X86
1617 If you want to debug problems which hang or crash the kernel early
1618 on boot and the crashing machine has a FireWire port, you can use
1619 this feature to remotely access the memory of the crashed machine
1620 over FireWire. This employs remote DMA as part of the OHCI1394
1621 specification which is now the standard for FireWire controllers.
1623 With remote DMA, you can monitor the printk buffer remotely using
1624 firescope and access all memory below 4GB using fireproxy from gdb.
1625 Even controlling a kernel debugger is possible using remote DMA.
1629 If ohci1394_dma=early is used as boot parameter, it will initialize
1630 all OHCI1394 controllers which are found in the PCI config space.
1632 As all changes to the FireWire bus such as enabling and disabling
1633 devices cause a bus reset and thereby disable remote DMA for all
1634 devices, be sure to have the cable plugged and FireWire enabled on
1635 the debugging host before booting the debug target for debugging.
1637 This code (~1k) is freed after boot. By then, the firewire stack
1638 in charge of the OHCI-1394 controllers should be used instead.
1640 See Documentation/debugging-via-ohci1394.txt for more information.
1642 config DMA_API_DEBUG
1643 bool "Enable debugging of DMA-API usage"
1644 select NEED_DMA_MAP_STATE
1646 Enable this option to debug the use of the DMA API by device drivers.
1647 With this option you will be able to detect common bugs in device
1648 drivers like double-freeing of DMA mappings or freeing mappings that
1649 were never allocated.
1651 This also attempts to catch cases where a page owned by DMA is
1652 accessed by the cpu in a way that could cause data corruption. For
1653 example, this enables cow_user_page() to check that the source page is
1656 This option causes a performance degradation. Use only if you want to
1657 debug device drivers and dma interactions.
1661 config DMA_API_DEBUG_SG
1662 bool "Debug DMA scatter-gather usage"
1664 depends on DMA_API_DEBUG
1666 Perform extra checking that callers of dma_map_sg() have respected the
1667 appropriate segment length/boundary limits for the given device when
1668 preparing DMA scatterlists.
1670 This is particularly likely to have been overlooked in cases where the
1671 dma_map_sg() API is used for general bulk mapping of pages rather than
1672 preparing literal scatter-gather descriptors, where there is a risk of
1673 unexpected behaviour from DMA API implementations if the scatterlist
1674 is technically out-of-spec.
1678 menuconfig RUNTIME_TESTING_MENU
1679 bool "Runtime Testing"
1682 if RUNTIME_TESTING_MENU
1685 tristate "Linux Kernel Dump Test Tool Module"
1689 This module enables testing of the different dumping mechanisms by
1690 inducing system failures at predefined crash points.
1691 If you don't need it: say N
1692 Choose M here to compile this code as a module. The module will be
1695 Documentation on how to use the module can be found in
1696 Documentation/fault-injection/provoke-crashes.txt
1698 config TEST_LIST_SORT
1699 tristate "Linked list sorting test"
1700 depends on DEBUG_KERNEL || m
1702 Enable this to turn on 'list_sort()' function test. This test is
1703 executed only once during system boot (so affects only boot time),
1704 or at module load time.
1709 tristate "Array-based sort test"
1710 depends on DEBUG_KERNEL || m
1712 This option enables the self-test function of 'sort()' at boot,
1713 or at module load time.
1717 config KPROBES_SANITY_TEST
1718 bool "Kprobes sanity tests"
1719 depends on DEBUG_KERNEL
1722 This option provides for testing basic kprobes functionality on
1723 boot. Samples of kprobe and kretprobe are inserted and
1724 verified for functionality.
1726 Say N if you are unsure.
1728 config BACKTRACE_SELF_TEST
1729 tristate "Self test for the backtrace code"
1730 depends on DEBUG_KERNEL
1732 This option provides a kernel module that can be used to test
1733 the kernel stack backtrace code. This option is not useful
1734 for distributions or general kernels, but only for kernel
1735 developers working on architecture code.
1737 Note that if you want to also test saved backtraces, you will
1738 have to enable STACKTRACE as well.
1740 Say N if you are unsure.
1743 tristate "Red-Black tree test"
1744 depends on DEBUG_KERNEL
1746 A benchmark measuring the performance of the rbtree library.
1747 Also includes rbtree invariant checks.
1749 config INTERVAL_TREE_TEST
1750 tristate "Interval tree test"
1751 depends on DEBUG_KERNEL
1752 select INTERVAL_TREE
1754 A benchmark measuring the performance of the interval tree library
1757 tristate "Per cpu operations test"
1758 depends on m && DEBUG_KERNEL
1760 Enable this option to build test module which validates per-cpu
1765 config ATOMIC64_SELFTEST
1766 tristate "Perform an atomic64_t self-test"
1768 Enable this option to test the atomic64_t functions at boot or
1769 at module load time.
1773 config ASYNC_RAID6_TEST
1774 tristate "Self test for hardware accelerated raid6 recovery"
1775 depends on ASYNC_RAID6_RECOV
1778 This is a one-shot self test that permutes through the
1779 recovery of all the possible two disk failure scenarios for a
1780 N-disk array. Recovery is performed with the asynchronous
1781 raid6 recovery routines, and will optionally use an offload
1782 engine if one is available.
1787 tristate "Test functions located in the hexdump module at runtime"
1789 config TEST_STRING_HELPERS
1790 tristate "Test functions located in the string_helpers module at runtime"
1793 tristate "Test kstrto*() family of functions at runtime"
1796 tristate "Test printf() family of functions at runtime"
1799 tristate "Test bitmap_*() family of functions at runtime"
1801 Enable this option to test the bitmap functions at boot.
1805 config TEST_BITFIELD
1806 tristate "Test bitfield functions at runtime"
1808 Enable this option to test the bitfield functions at boot.
1813 tristate "Test functions located in the uuid module at runtime"
1815 config TEST_OVERFLOW
1816 tristate "Test check_*_overflow() functions at runtime"
1818 config TEST_RHASHTABLE
1819 tristate "Perform selftest on resizable hash table"
1821 Enable this option to test the rhashtable functions at boot.
1826 tristate "Perform selftest on hash functions"
1828 Enable this option to test the kernel's integer (<linux/hash.h>),
1829 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1830 hash functions on boot (or module load).
1832 This is intended to help people writing architecture-specific
1833 optimized versions. If unsure, say N.
1836 tristate "Perform selftest on IDA functions"
1839 tristate "Perform selftest on priority array manager"
1842 Enable this option to test priority array manager on boot
1848 tristate "Test module loading with 'hello world' module"
1851 This builds the "test_module" module that emits "Hello, world"
1852 on printk when loaded. It is designed to be used for basic
1853 evaluation of the module loading subsystem (for example when
1854 validating module verification). It lacks any extra dependencies,
1855 and will not normally be loaded by the system unless explicitly
1860 config TEST_USER_COPY
1861 tristate "Test user/kernel boundary protections"
1864 This builds the "test_user_copy" module that runs sanity checks
1865 on the copy_to/from_user infrastructure, making sure basic
1866 user/kernel boundary testing is working. If it fails to load,
1867 a regression has been detected in the user/kernel memory boundary
1873 tristate "Test BPF filter functionality"
1876 This builds the "test_bpf" module that runs various test vectors
1877 against the BPF interpreter or BPF JIT compiler depending on the
1878 current setting. This is in particular useful for BPF JIT compiler
1879 development, but also to run regression tests against changes in
1880 the interpreter code. It also enables test stubs for eBPF maps and
1881 verifier used by user space verifier testsuite.
1885 config FIND_BIT_BENCHMARK
1886 tristate "Test find_bit functions"
1888 This builds the "test_find_bit" module that measure find_*_bit()
1889 functions performance.
1893 config TEST_FIRMWARE
1894 tristate "Test firmware loading via userspace interface"
1895 depends on FW_LOADER
1897 This builds the "test_firmware" module that creates a userspace
1898 interface for testing firmware loading. This can be used to
1899 control the triggering of firmware loading without needing an
1900 actual firmware-using device. The contents can be rechecked by
1906 tristate "sysctl test driver"
1907 depends on PROC_SYSCTL
1909 This builds the "test_sysctl" module. This driver enables to test the
1910 proc sysctl interfaces available to drivers safely without affecting
1911 production knobs which might alter system functionality.
1916 tristate "udelay test driver"
1918 This builds the "udelay_test" module that helps to make sure
1919 that udelay() is working properly.
1923 config TEST_STATIC_KEYS
1924 tristate "Test static keys"
1927 Test the static key interfaces.
1932 tristate "kmod stress tester"
1934 depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS
1935 depends on NETDEVICES && NET_CORE && INET # for TUN
1942 Test the kernel's module loading mechanism: kmod. kmod implements
1943 support to load modules using the Linux kernel's usermode helper.
1944 This test provides a series of tests against kmod.
1946 Although technically you can either build test_kmod as a module or
1947 into the kernel we disallow building it into the kernel since
1948 it stress tests request_module() and this will very likely cause
1949 some issues by taking over precious threads available from other
1950 module load requests, ultimately this could be fatal.
1954 tools/testing/selftests/kmod/kmod.sh --help
1958 config TEST_DEBUG_VIRTUAL
1959 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
1960 depends on DEBUG_VIRTUAL
1962 Test the kernel's ability to detect incorrect calls to
1963 virt_to_phys() done against the non-linear part of the
1964 kernel's virtual address map.
1968 endif # RUNTIME_TESTING_MENU
1972 depends on HAVE_MEMBLOCK
1974 This option adds a kernel parameter 'memtest', which allows memtest
1976 memtest=0, mean disabled; -- default
1977 memtest=1, mean do 1 test pattern;
1979 memtest=17, mean do 17 test patterns.
1980 If you are unsure how to answer this question, answer N.
1982 config BUG_ON_DATA_CORRUPTION
1983 bool "Trigger a BUG when data corruption is detected"
1986 Select this option if the kernel should BUG when it encounters
1987 data corruption in kernel memory structures when they get checked
1992 source "samples/Kconfig"
1994 source "lib/Kconfig.kgdb"
1996 source "lib/Kconfig.ubsan"
1998 config ARCH_HAS_DEVMEM_IS_ALLOWED
2001 config STRICT_DEVMEM
2002 bool "Filter access to /dev/mem"
2003 depends on MMU && DEVMEM
2004 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
2005 default y if PPC || X86 || ARM64
2007 If this option is disabled, you allow userspace (root) access to all
2008 of memory, including kernel and userspace memory. Accidental
2009 access to this is obviously disastrous, but specific access can
2010 be used by people debugging the kernel. Note that with PAT support
2011 enabled, even in this case there are restrictions on /dev/mem
2012 use due to the cache aliasing requirements.
2014 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
2015 file only allows userspace access to PCI space and the BIOS code and
2016 data regions. This is sufficient for dosemu and X and all common
2021 config IO_STRICT_DEVMEM
2022 bool "Filter I/O access to /dev/mem"
2023 depends on STRICT_DEVMEM
2025 If this option is disabled, you allow userspace (root) access to all
2026 io-memory regardless of whether a driver is actively using that
2027 range. Accidental access to this is obviously disastrous, but
2028 specific access can be used by people debugging kernel drivers.
2030 If this option is switched on, the /dev/mem file only allows
2031 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2032 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2033 if the driver using a given range cannot be disabled.
2037 source "arch/$(SRCARCH)/Kconfig.debug"
2039 endmenu # Kernel hacking