1 # SPDX-License-Identifier: GPL-2.0-only
4 menu "printk and dmesg options"
7 bool "Show timing information on printks"
10 Selecting this option causes time stamps of the printk()
11 messages to be added to the output of the syslog() system
12 call and at the console.
14 The timestamp is always recorded internally, and exported
15 to /dev/kmsg. This flag just specifies if the timestamp should
16 be included, not that the timestamp is recorded.
18 The behavior is also controlled by the kernel command line
19 parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst
22 bool "Show caller information on printks"
25 Selecting this option causes printk() to add a caller "thread id" (if
26 in task context) or a caller "processor id" (if not in task context)
29 This option is intended for environments where multiple threads
30 concurrently call printk() for many times, for it is difficult to
31 interpret without knowing where these lines (or sometimes individual
32 line which was divided into multiple lines due to race) came from.
34 Since toggling after boot makes the code racy, currently there is
35 no option to enable/disable at the kernel command line parameter or
38 config CONSOLE_LOGLEVEL_DEFAULT
39 int "Default console loglevel (1-15)"
43 Default loglevel to determine what will be printed on the console.
45 Setting a default here is equivalent to passing in loglevel=<x> in
46 the kernel bootargs. loglevel=<x> continues to override whatever
47 value is specified here as well.
49 Note: This does not affect the log level of un-prefixed printk()
50 usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
53 config CONSOLE_LOGLEVEL_QUIET
54 int "quiet console loglevel (1-15)"
58 loglevel to use when "quiet" is passed on the kernel commandline.
60 When "quiet" is passed on the kernel commandline this loglevel
61 will be used as the loglevel. IOW passing "quiet" will be the
62 equivalent of passing "loglevel=<CONSOLE_LOGLEVEL_QUIET>"
64 config MESSAGE_LOGLEVEL_DEFAULT
65 int "Default message log level (1-7)"
69 Default log level for printk statements with no specified priority.
71 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
72 that are auditing their logs closely may want to set it to a lower
75 Note: This does not affect what message level gets printed on the console
76 by default. To change that, use loglevel=<x> in the kernel bootargs,
77 or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value.
79 config BOOT_PRINTK_DELAY
80 bool "Delay each boot printk message by N milliseconds"
81 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
83 This build option allows you to read kernel boot messages
84 by inserting a short delay after each one. The delay is
85 specified in milliseconds on the kernel command line,
88 It is likely that you would also need to use "lpj=M" to preset
89 the "loops per jiffie" value.
90 See a previous boot log for the "lpj" value to use for your
91 system, and then set "lpj=M" before setting "boot_delay=N".
92 NOTE: Using this option may adversely affect SMP systems.
93 I.e., processors other than the first one may not boot up.
94 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
95 what it believes to be lockup conditions.
98 bool "Enable dynamic printk() support"
104 Compiles debug level messages into the kernel, which would not
105 otherwise be available at runtime. These messages can then be
106 enabled/disabled based on various levels of scope - per source file,
107 function, module, format string, and line number. This mechanism
108 implicitly compiles in all pr_debug() and dev_dbg() calls, which
109 enlarges the kernel text size by about 2%.
111 If a source file is compiled with DEBUG flag set, any
112 pr_debug() calls in it are enabled by default, but can be
113 disabled at runtime as below. Note that DEBUG flag is
114 turned on by many CONFIG_*DEBUG* options.
118 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
119 which is contained in the 'debugfs' filesystem. Thus, the debugfs
120 filesystem must first be mounted before making use of this feature.
121 We refer the control file as: <debugfs>/dynamic_debug/control. This
122 file contains a list of the debug statements that can be enabled. The
123 format for each line of the file is:
125 filename:lineno [module]function flags format
127 filename : source file of the debug statement
128 lineno : line number of the debug statement
129 module : module that contains the debug statement
130 function : function that contains the debug statement
131 flags : '=p' means the line is turned 'on' for printing
132 format : the format used for the debug statement
136 nullarbor:~ # cat <debugfs>/dynamic_debug/control
137 # filename:lineno [module]function flags format
138 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
139 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
140 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
144 // enable the message at line 1603 of file svcsock.c
145 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
146 <debugfs>/dynamic_debug/control
148 // enable all the messages in file svcsock.c
149 nullarbor:~ # echo -n 'file svcsock.c +p' >
150 <debugfs>/dynamic_debug/control
152 // enable all the messages in the NFS server module
153 nullarbor:~ # echo -n 'module nfsd +p' >
154 <debugfs>/dynamic_debug/control
156 // enable all 12 messages in the function svc_process()
157 nullarbor:~ # echo -n 'func svc_process +p' >
158 <debugfs>/dynamic_debug/control
160 // disable all 12 messages in the function svc_process()
161 nullarbor:~ # echo -n 'func svc_process -p' >
162 <debugfs>/dynamic_debug/control
164 See Documentation/admin-guide/dynamic-debug-howto.rst for additional
167 endmenu # "printk and dmesg options"
169 menu "Compile-time checks and compiler options"
172 bool "Compile the kernel with debug info"
173 depends on DEBUG_KERNEL && !COMPILE_TEST
175 If you say Y here the resulting kernel image will include
176 debugging info resulting in a larger kernel image.
177 This adds debug symbols to the kernel and modules (gcc -g), and
178 is needed if you intend to use kernel crashdump or binary object
179 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
180 Say Y here only if you plan to debug the kernel.
184 config DEBUG_INFO_REDUCED
185 bool "Reduce debugging information"
186 depends on DEBUG_INFO
188 If you say Y here gcc is instructed to generate less debugging
189 information for structure types. This means that tools that
190 need full debugging information (like kgdb or systemtap) won't
191 be happy. But if you merely need debugging information to
192 resolve line numbers there is no loss. Advantage is that
193 build directory object sizes shrink dramatically over a full
194 DEBUG_INFO build and compile times are reduced too.
195 Only works with newer gcc versions.
197 config DEBUG_INFO_SPLIT
198 bool "Produce split debuginfo in .dwo files"
199 depends on DEBUG_INFO
200 depends on $(cc-option,-gsplit-dwarf)
202 Generate debug info into separate .dwo files. This significantly
203 reduces the build directory size for builds with DEBUG_INFO,
204 because it stores the information only once on disk in .dwo
205 files instead of multiple times in object files and executables.
206 In addition the debug information is also compressed.
208 Requires recent gcc (4.7+) and recent gdb/binutils.
209 Any tool that packages or reads debug information would need
210 to know about the .dwo files and include them.
211 Incompatible with older versions of ccache.
213 config DEBUG_INFO_DWARF4
214 bool "Generate dwarf4 debuginfo"
215 depends on DEBUG_INFO
216 depends on $(cc-option,-gdwarf-4)
218 Generate dwarf4 debug info. This requires recent versions
219 of gcc and gdb. It makes the debug information larger.
220 But it significantly improves the success of resolving
221 variables in gdb on optimized code.
223 config DEBUG_INFO_BTF
224 bool "Generate BTF typeinfo"
225 depends on DEBUG_INFO
226 depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED
227 depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST
229 Generate deduplicated BTF type information from DWARF debug info.
230 Turning this on expects presence of pahole tool, which will convert
231 DWARF type info into equivalent deduplicated BTF type info.
234 bool "Provide GDB scripts for kernel debugging"
235 depends on DEBUG_INFO
237 This creates the required links to GDB helper scripts in the
238 build directory. If you load vmlinux into gdb, the helper
239 scripts will be automatically imported by gdb as well, and
240 additional functions are available to analyze a Linux kernel
241 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
244 config ENABLE_MUST_CHECK
245 bool "Enable __must_check logic"
248 Enable the __must_check logic in the kernel build. Disable this to
249 suppress the "warning: ignoring return value of 'foo', declared with
250 attribute warn_unused_result" messages.
253 int "Warn for stack frames larger than (needs gcc 4.4)"
255 default 2048 if GCC_PLUGIN_LATENT_ENTROPY
256 default 1280 if (!64BIT && PARISC)
257 default 1024 if (!64BIT && !PARISC)
258 default 2048 if 64BIT
260 Tell gcc to warn at build time for stack frames larger than this.
261 Setting this too low will cause a lot of warnings.
262 Setting it to 0 disables the warning.
265 config STRIP_ASM_SYMS
266 bool "Strip assembler-generated symbols during link"
269 Strip internal assembler-generated symbols during a link (symbols
270 that look like '.Lxxx') so they don't pollute the output of
271 get_wchan() and suchlike.
274 bool "Generate readable assembler code"
275 depends on DEBUG_KERNEL
277 Disable some compiler optimizations that tend to generate human unreadable
278 assembler output. This may make the kernel slightly slower, but it helps
279 to keep kernel developers who have to stare a lot at assembler listings
283 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/.
294 config HEADERS_INSTALL
295 bool "Install uapi headers to usr/include"
298 This option will install uapi headers (headers exported to user-space)
299 into the usr/include directory for use during the kernel build.
300 This is unneeded for building the kernel itself, but needed for some
301 user-space program samples. It is also needed by some features such
302 as uapi header sanity checks.
304 config OPTIMIZE_INLINING
307 This option determines if the kernel forces gcc to inline the functions
308 developers have marked 'inline'. Doing so takes away freedom from gcc to
309 do what it thinks is best, which is desirable for the gcc 3.x series of
310 compilers. The gcc 4.x series have a rewritten inlining algorithm and
311 enabling this option will generate a smaller kernel there. Hopefully
312 this algorithm is so good that allowing gcc 4.x and above to make the
313 decision will become the default in the future. Until then this option
314 is there to test gcc for this.
316 config DEBUG_SECTION_MISMATCH
317 bool "Enable full Section mismatch analysis"
319 The section mismatch analysis checks if there are illegal
320 references from one section to another section.
321 During linktime or runtime, some sections are dropped;
322 any use of code/data previously in these sections would
323 most likely result in an oops.
324 In the code, functions and variables are annotated with
325 __init,, etc. (see the full list in include/linux/init.h),
326 which results in the code/data being placed in specific sections.
327 The section mismatch analysis is always performed after a full
328 kernel build, and enabling this option causes the following
329 additional step to occur:
330 - Add the option -fno-inline-functions-called-once to gcc commands.
331 When inlining a function annotated with __init in a non-init
332 function, we would lose the section information and thus
333 the analysis would not catch the illegal reference.
334 This option tells gcc to inline less (but it does result in
337 config SECTION_MISMATCH_WARN_ONLY
338 bool "Make section mismatch errors non-fatal"
341 If you say N here, the build process will fail if there are any
342 section mismatch, instead of just throwing warnings.
347 # Select this config option from the architecture Kconfig, if it
348 # is preferred to always offer frame pointers as a config
349 # option on the architecture (regardless of KERNEL_DEBUG):
351 config ARCH_WANT_FRAME_POINTERS
355 bool "Compile the kernel with frame pointers"
356 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS
357 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
359 If you say Y here the resulting kernel image will be slightly
360 larger and slower, but it gives very useful debugging information
361 in case of kernel bugs. (precise oopses/stacktraces/warnings)
363 config STACK_VALIDATION
364 bool "Compile-time stack metadata validation"
365 depends on HAVE_STACK_VALIDATION
368 Add compile-time checks to validate stack metadata, including frame
369 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
370 that runtime stack traces are more reliable.
372 This is also a prerequisite for generation of ORC unwind data, which
373 is needed for CONFIG_UNWINDER_ORC.
375 For more information, see
376 tools/objtool/Documentation/stack-validation.txt.
378 config DEBUG_FORCE_WEAK_PER_CPU
379 bool "Force weak per-cpu definitions"
380 depends on DEBUG_KERNEL
382 s390 and alpha require percpu variables in modules to be
383 defined weak to work around addressing range issue which
384 puts the following two restrictions on percpu variable
387 1. percpu symbols must be unique whether static or not
388 2. percpu variables can't be defined inside a function
390 To ensure that generic code follows the above rules, this
391 option forces all percpu variables to be defined as weak.
393 endmenu # "Compiler options"
396 bool "Magic SysRq key"
399 If you say Y here, you will have some control over the system even
400 if the system crashes for example during kernel debugging (e.g., you
401 will be able to flush the buffer cache to disk, reboot the system
402 immediately or dump some status information). This is accomplished
403 by pressing various keys while holding SysRq (Alt+PrintScreen). It
404 also works on a serial console (on PC hardware at least), if you
405 send a BREAK and then within 5 seconds a command keypress. The
406 keys are documented in <file:Documentation/admin-guide/sysrq.rst>.
407 Don't say Y unless you really know what this hack does.
409 config MAGIC_SYSRQ_DEFAULT_ENABLE
410 hex "Enable magic SysRq key functions by default"
411 depends on MAGIC_SYSRQ
414 Specifies which SysRq key functions are enabled by default.
415 This may be set to 1 or 0 to enable or disable them all, or
416 to a bitmask as described in Documentation/admin-guide/sysrq.rst.
418 config MAGIC_SYSRQ_SERIAL
419 bool "Enable magic SysRq key over serial"
420 depends on MAGIC_SYSRQ
423 Many embedded boards have a disconnected TTL level serial which can
424 generate some garbage that can lead to spurious false sysrq detects.
425 This option allows you to decide whether you want to enable the
429 bool "Kernel debugging"
431 Say Y here if you are developing drivers or trying to debug and
432 identify kernel problems.
435 bool "Miscellaneous debug code"
437 depends on DEBUG_KERNEL
439 Say Y here if you need to enable miscellaneous debug code that should
440 be under a more specific debug option but isn't.
443 menu "Memory Debugging"
445 source "mm/Kconfig.debug"
448 bool "Debug object operations"
449 depends on DEBUG_KERNEL
451 If you say Y here, additional code will be inserted into the
452 kernel to track the life time of various objects and validate
453 the operations on those objects.
455 config DEBUG_OBJECTS_SELFTEST
456 bool "Debug objects selftest"
457 depends on DEBUG_OBJECTS
459 This enables the selftest of the object debug code.
461 config DEBUG_OBJECTS_FREE
462 bool "Debug objects in freed memory"
463 depends on DEBUG_OBJECTS
465 This enables checks whether a k/v free operation frees an area
466 which contains an object which has not been deactivated
467 properly. This can make kmalloc/kfree-intensive workloads
470 config DEBUG_OBJECTS_TIMERS
471 bool "Debug timer objects"
472 depends on DEBUG_OBJECTS
474 If you say Y here, additional code will be inserted into the
475 timer routines to track the life time of timer objects and
476 validate the timer operations.
478 config DEBUG_OBJECTS_WORK
479 bool "Debug work objects"
480 depends on DEBUG_OBJECTS
482 If you say Y here, additional code will be inserted into the
483 work queue routines to track the life time of work objects and
484 validate the work operations.
486 config DEBUG_OBJECTS_RCU_HEAD
487 bool "Debug RCU callbacks objects"
488 depends on DEBUG_OBJECTS
490 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
492 config DEBUG_OBJECTS_PERCPU_COUNTER
493 bool "Debug percpu counter objects"
494 depends on DEBUG_OBJECTS
496 If you say Y here, additional code will be inserted into the
497 percpu counter routines to track the life time of percpu counter
498 objects and validate the percpu counter operations.
500 config DEBUG_OBJECTS_ENABLE_DEFAULT
501 int "debug_objects bootup default value (0-1)"
504 depends on DEBUG_OBJECTS
506 Debug objects boot parameter default value
509 bool "Debug slab memory allocations"
510 depends on DEBUG_KERNEL && SLAB
512 Say Y here to have the kernel do limited verification on memory
513 allocation as well as poisoning memory on free to catch use of freed
514 memory. This can make kmalloc/kfree-intensive workloads much slower.
517 bool "SLUB debugging on by default"
518 depends on SLUB && SLUB_DEBUG
521 Boot with debugging on by default. SLUB boots by default with
522 the runtime debug capabilities switched off. Enabling this is
523 equivalent to specifying the "slub_debug" parameter on boot.
524 There is no support for more fine grained debug control like
525 possible with slub_debug=xxx. SLUB debugging may be switched
526 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
531 bool "Enable SLUB performance statistics"
532 depends on SLUB && SYSFS
534 SLUB statistics are useful to debug SLUBs allocation behavior in
535 order find ways to optimize the allocator. This should never be
536 enabled for production use since keeping statistics slows down
537 the allocator by a few percentage points. The slabinfo command
538 supports the determination of the most active slabs to figure
539 out which slabs are relevant to a particular load.
540 Try running: slabinfo -DA
542 config HAVE_DEBUG_KMEMLEAK
545 config DEBUG_KMEMLEAK
546 bool "Kernel memory leak detector"
547 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
549 select STACKTRACE if STACKTRACE_SUPPORT
553 Say Y here if you want to enable the memory leak
554 detector. The memory allocation/freeing is traced in a way
555 similar to the Boehm's conservative garbage collector, the
556 difference being that the orphan objects are not freed but
557 only shown in /sys/kernel/debug/kmemleak. Enabling this
558 feature will introduce an overhead to memory
559 allocations. See Documentation/dev-tools/kmemleak.rst for more
562 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
563 of finding leaks due to the slab objects poisoning.
565 In order to access the kmemleak file, debugfs needs to be
566 mounted (usually at /sys/kernel/debug).
568 config DEBUG_KMEMLEAK_MEM_POOL_SIZE
569 int "Kmemleak memory pool size"
570 depends on DEBUG_KMEMLEAK
574 Kmemleak must track all the memory allocations to avoid
575 reporting false positives. Since memory may be allocated or
576 freed before kmemleak is fully initialised, use a static pool
577 of metadata objects to track such callbacks. After kmemleak is
578 fully initialised, this memory pool acts as an emergency one
579 if slab allocations fail.
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_KMEMLEAK_AUTO_SCAN
597 bool "Enable kmemleak auto scan thread on boot up"
599 depends on DEBUG_KMEMLEAK
601 Depending on the cpu, kmemleak scan may be cpu intensive and can
602 stall user tasks at times. This option enables/disables automatic
603 kmemleak scan at boot up.
605 Say N here to disable kmemleak auto scan thread to stop automatic
606 scanning. Disabling this option disables automatic reporting of
611 config DEBUG_STACK_USAGE
612 bool "Stack utilization instrumentation"
613 depends on DEBUG_KERNEL && !IA64
615 Enables the display of the minimum amount of free stack which each
616 task has ever had available in the sysrq-T and sysrq-P debug output.
618 This option will slow down process creation somewhat.
622 depends on DEBUG_KERNEL
624 Enable this to turn on extended checks in the virtual-memory system
625 that may impact performance.
629 config DEBUG_VM_VMACACHE
630 bool "Debug VMA caching"
633 Enable this to turn on VMA caching debug information. Doing so
634 can cause significant overhead, so only enable it in non-production
640 bool "Debug VM red-black trees"
643 Enable VM red-black tree debugging information and extra validations.
647 config DEBUG_VM_PGFLAGS
648 bool "Debug page-flags operations"
651 Enables extra validation on page flags operations.
655 config ARCH_HAS_DEBUG_VIRTUAL
659 bool "Debug VM translations"
660 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
662 Enable some costly sanity checks in virtual to page code. This can
663 catch mistakes with virt_to_page() and friends.
667 config DEBUG_NOMMU_REGIONS
668 bool "Debug the global anon/private NOMMU mapping region tree"
669 depends on DEBUG_KERNEL && !MMU
671 This option causes the global tree of anonymous and private mapping
672 regions to be regularly checked for invalid topology.
674 config DEBUG_MEMORY_INIT
675 bool "Debug memory initialisation" if EXPERT
678 Enable this for additional checks during memory initialisation.
679 The sanity checks verify aspects of the VM such as the memory model
680 and other information provided by the architecture. Verbose
681 information will be printed at KERN_DEBUG loglevel depending
682 on the mminit_loglevel= command-line option.
686 config MEMORY_NOTIFIER_ERROR_INJECT
687 tristate "Memory hotplug notifier error injection module"
688 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
690 This option provides the ability to inject artificial errors to
691 memory hotplug notifier chain callbacks. It is controlled through
692 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
694 If the notifier call chain should be failed with some events
695 notified, write the error code to "actions/<notifier event>/error".
697 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
699 # cd /sys/kernel/debug/notifier-error-inject/memory
700 # echo -12 > actions/MEM_GOING_OFFLINE/error
701 # echo offline > /sys/devices/system/memory/memoryXXX/state
702 bash: echo: write error: Cannot allocate memory
704 To compile this code as a module, choose M here: the module will
705 be called memory-notifier-error-inject.
709 config DEBUG_PER_CPU_MAPS
710 bool "Debug access to per_cpu maps"
711 depends on DEBUG_KERNEL
714 Say Y to verify that the per_cpu map being accessed has
715 been set up. This adds a fair amount of code to kernel memory
716 and decreases performance.
721 bool "Highmem debugging"
722 depends on DEBUG_KERNEL && HIGHMEM
724 This option enables additional error checking for high memory
725 systems. Disable for production systems.
727 config HAVE_DEBUG_STACKOVERFLOW
730 config DEBUG_STACKOVERFLOW
731 bool "Check for stack overflows"
732 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
734 Say Y here if you want to check for overflows of kernel, IRQ
735 and exception stacks (if your architecture uses them). This
736 option will show detailed messages if free stack space drops
737 below a certain limit.
739 These kinds of bugs usually occur when call-chains in the
740 kernel get too deep, especially when interrupts are
743 Use this in cases where you see apparently random memory
744 corruption, especially if it appears in 'struct thread_info'
746 If in doubt, say "N".
748 source "lib/Kconfig.kasan"
750 endmenu # "Memory Debugging"
755 An architecture should select this when it can successfully
756 build and run with CONFIG_KCOV. This typically requires
757 disabling instrumentation for some early boot code.
759 config CC_HAS_SANCOV_TRACE_PC
760 def_bool $(cc-option,-fsanitize-coverage=trace-pc)
763 bool "Code coverage for fuzzing"
764 depends on ARCH_HAS_KCOV
765 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
767 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
769 KCOV exposes kernel code coverage information in a form suitable
770 for coverage-guided fuzzing (randomized testing).
772 If RANDOMIZE_BASE is enabled, PC values will not be stable across
773 different machines and across reboots. If you need stable PC values,
774 disable RANDOMIZE_BASE.
776 For more details, see Documentation/dev-tools/kcov.rst.
778 config KCOV_ENABLE_COMPARISONS
779 bool "Enable comparison operands collection by KCOV"
781 depends on $(cc-option,-fsanitize-coverage=trace-cmp)
783 KCOV also exposes operands of every comparison in the instrumented
784 code along with operand sizes and PCs of the comparison instructions.
785 These operands can be used by fuzzing engines to improve the quality
788 config KCOV_INSTRUMENT_ALL
789 bool "Instrument all code by default"
793 If you are doing generic system call fuzzing (like e.g. syzkaller),
794 then you will want to instrument the whole kernel and you should
795 say y here. If you are doing more targeted fuzzing (like e.g.
796 filesystem fuzzing with AFL) then you will want to enable coverage
797 for more specific subsets of files, and should say n here.
800 bool "Debug shared IRQ handlers"
801 depends on DEBUG_KERNEL
803 Enable this to generate a spurious interrupt as soon as a shared
804 interrupt handler is registered, and just before one is deregistered.
805 Drivers ought to be able to handle interrupts coming in at those
806 points; some don't and need to be caught.
808 menu "Debug Lockups and Hangs"
810 config LOCKUP_DETECTOR
813 config SOFTLOCKUP_DETECTOR
814 bool "Detect Soft Lockups"
815 depends on DEBUG_KERNEL && !S390
816 select LOCKUP_DETECTOR
818 Say Y here to enable the kernel to act as a watchdog to detect
821 Softlockups are bugs that cause the kernel to loop in kernel
822 mode for more than 20 seconds, without giving other tasks a
823 chance to run. The current stack trace is displayed upon
824 detection and the system will stay locked up.
826 config BOOTPARAM_SOFTLOCKUP_PANIC
827 bool "Panic (Reboot) On Soft Lockups"
828 depends on SOFTLOCKUP_DETECTOR
830 Say Y here to enable the kernel to panic on "soft lockups",
831 which are bugs that cause the kernel to loop in kernel
832 mode for more than 20 seconds (configurable using the watchdog_thresh
833 sysctl), without giving other tasks a chance to run.
835 The panic can be used in combination with panic_timeout,
836 to cause the system to reboot automatically after a
837 lockup has been detected. This feature is useful for
838 high-availability systems that have uptime guarantees and
839 where a lockup must be resolved ASAP.
843 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
845 depends on SOFTLOCKUP_DETECTOR
847 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
848 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
850 config HARDLOCKUP_DETECTOR_PERF
852 select SOFTLOCKUP_DETECTOR
855 # Enables a timestamp based low pass filter to compensate for perf based
856 # hard lockup detection which runs too fast due to turbo modes.
858 config HARDLOCKUP_CHECK_TIMESTAMP
862 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
863 # lockup detector rather than the perf based detector.
865 config HARDLOCKUP_DETECTOR
866 bool "Detect Hard Lockups"
867 depends on DEBUG_KERNEL && !S390
868 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
869 select LOCKUP_DETECTOR
870 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
871 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
873 Say Y here to enable the kernel to act as a watchdog to detect
876 Hardlockups are bugs that cause the CPU to loop in kernel mode
877 for more than 10 seconds, without letting other interrupts have a
878 chance to run. The current stack trace is displayed upon detection
879 and the system will stay locked up.
881 config BOOTPARAM_HARDLOCKUP_PANIC
882 bool "Panic (Reboot) On Hard Lockups"
883 depends on HARDLOCKUP_DETECTOR
885 Say Y here to enable the kernel to panic on "hard lockups",
886 which are bugs that cause the kernel to loop in kernel
887 mode with interrupts disabled for more than 10 seconds (configurable
888 using the watchdog_thresh sysctl).
892 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
894 depends on HARDLOCKUP_DETECTOR
896 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
897 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
899 config DETECT_HUNG_TASK
900 bool "Detect Hung Tasks"
901 depends on DEBUG_KERNEL
902 default SOFTLOCKUP_DETECTOR
904 Say Y here to enable the kernel to detect "hung tasks",
905 which are bugs that cause the task to be stuck in
906 uninterruptible "D" state indefinitely.
908 When a hung task is detected, the kernel will print the
909 current stack trace (which you should report), but the
910 task will stay in uninterruptible state. If lockdep is
911 enabled then all held locks will also be reported. This
912 feature has negligible overhead.
914 config DEFAULT_HUNG_TASK_TIMEOUT
915 int "Default timeout for hung task detection (in seconds)"
916 depends on DETECT_HUNG_TASK
919 This option controls the default timeout (in seconds) used
920 to determine when a task has become non-responsive and should
923 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
924 sysctl or by writing a value to
925 /proc/sys/kernel/hung_task_timeout_secs.
927 A timeout of 0 disables the check. The default is two minutes.
928 Keeping the default should be fine in most cases.
930 config BOOTPARAM_HUNG_TASK_PANIC
931 bool "Panic (Reboot) On Hung Tasks"
932 depends on DETECT_HUNG_TASK
934 Say Y here to enable the kernel to panic on "hung tasks",
935 which are bugs that cause the kernel to leave a task stuck
936 in uninterruptible "D" state.
938 The panic can be used in combination with panic_timeout,
939 to cause the system to reboot automatically after a
940 hung task has been detected. This feature is useful for
941 high-availability systems that have uptime guarantees and
942 where a hung tasks must be resolved ASAP.
946 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
948 depends on DETECT_HUNG_TASK
950 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
951 default 1 if BOOTPARAM_HUNG_TASK_PANIC
954 bool "Detect Workqueue Stalls"
955 depends on DEBUG_KERNEL
957 Say Y here to enable stall detection on workqueues. If a
958 worker pool doesn't make forward progress on a pending work
959 item for over a given amount of time, 30s by default, a
960 warning message is printed along with dump of workqueue
961 state. This can be configured through kernel parameter
962 "workqueue.watchdog_thresh" and its sysfs counterpart.
964 endmenu # "Debug lockups and hangs"
969 Say Y here to enable the kernel to panic when it oopses. This
970 has the same effect as setting oops=panic on the kernel command
973 This feature is useful to ensure that the kernel does not do
974 anything erroneous after an oops which could result in data
975 corruption or other issues.
979 config PANIC_ON_OOPS_VALUE
982 default 0 if !PANIC_ON_OOPS
983 default 1 if PANIC_ON_OOPS
989 Set the timeout value (in seconds) until a reboot occurs when the
990 the kernel panics. If n = 0, then we wait forever. A timeout
991 value n > 0 will wait n seconds before rebooting, while a timeout
992 value n < 0 will reboot immediately.
995 bool "Collect scheduler debugging info"
996 depends on DEBUG_KERNEL && PROC_FS
999 If you say Y here, the /proc/sched_debug file will be provided
1000 that can help debug the scheduler. The runtime overhead of this
1008 bool "Collect scheduler statistics"
1009 depends on DEBUG_KERNEL && PROC_FS
1012 If you say Y here, additional code will be inserted into the
1013 scheduler and related routines to collect statistics about
1014 scheduler behavior and provide them in /proc/schedstat. These
1015 stats may be useful for both tuning and debugging the scheduler
1016 If you aren't debugging the scheduler or trying to tune a specific
1017 application, you can say N to avoid the very slight overhead
1020 config SCHED_STACK_END_CHECK
1021 bool "Detect stack corruption on calls to schedule()"
1022 depends on DEBUG_KERNEL
1025 This option checks for a stack overrun on calls to schedule().
1026 If the stack end location is found to be over written always panic as
1027 the content of the corrupted region can no longer be trusted.
1028 This is to ensure no erroneous behaviour occurs which could result in
1029 data corruption or a sporadic crash at a later stage once the region
1030 is examined. The runtime overhead introduced is minimal.
1032 config DEBUG_TIMEKEEPING
1033 bool "Enable extra timekeeping sanity checking"
1035 This option will enable additional timekeeping sanity checks
1036 which may be helpful when diagnosing issues where timekeeping
1037 problems are suspected.
1039 This may include checks in the timekeeping hotpaths, so this
1040 option may have a (very small) performance impact to some
1045 config DEBUG_PREEMPT
1046 bool "Debug preemptible kernel"
1047 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1050 If you say Y here then the kernel will use a debug variant of the
1051 commonly used smp_processor_id() function and will print warnings
1052 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1053 will detect preemption count underflows.
1055 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1057 config LOCK_DEBUGGING_SUPPORT
1059 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1062 config PROVE_LOCKING
1063 bool "Lock debugging: prove locking correctness"
1064 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1066 select DEBUG_SPINLOCK
1067 select DEBUG_MUTEXES
1068 select DEBUG_RT_MUTEXES if RT_MUTEXES
1070 select DEBUG_WW_MUTEX_SLOWPATH
1071 select DEBUG_LOCK_ALLOC
1072 select TRACE_IRQFLAGS
1075 This feature enables the kernel to prove that all locking
1076 that occurs in the kernel runtime is mathematically
1077 correct: that under no circumstance could an arbitrary (and
1078 not yet triggered) combination of observed locking
1079 sequences (on an arbitrary number of CPUs, running an
1080 arbitrary number of tasks and interrupt contexts) cause a
1083 In short, this feature enables the kernel to report locking
1084 related deadlocks before they actually occur.
1086 The proof does not depend on how hard and complex a
1087 deadlock scenario would be to trigger: how many
1088 participant CPUs, tasks and irq-contexts would be needed
1089 for it to trigger. The proof also does not depend on
1090 timing: if a race and a resulting deadlock is possible
1091 theoretically (no matter how unlikely the race scenario
1092 is), it will be proven so and will immediately be
1093 reported by the kernel (once the event is observed that
1094 makes the deadlock theoretically possible).
1096 If a deadlock is impossible (i.e. the locking rules, as
1097 observed by the kernel, are mathematically correct), the
1098 kernel reports nothing.
1100 NOTE: this feature can also be enabled for rwlocks, mutexes
1101 and rwsems - in which case all dependencies between these
1102 different locking variants are observed and mapped too, and
1103 the proof of observed correctness is also maintained for an
1104 arbitrary combination of these separate locking variants.
1106 For more details, see Documentation/locking/lockdep-design.rst.
1109 bool "Lock usage statistics"
1110 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1112 select DEBUG_SPINLOCK
1113 select DEBUG_MUTEXES
1114 select DEBUG_RT_MUTEXES if RT_MUTEXES
1115 select DEBUG_LOCK_ALLOC
1118 This feature enables tracking lock contention points
1120 For more details, see Documentation/locking/lockstat.rst
1122 This also enables lock events required by "perf lock",
1124 If you want to use "perf lock", you also need to turn on
1125 CONFIG_EVENT_TRACING.
1127 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1128 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1130 config DEBUG_RT_MUTEXES
1131 bool "RT Mutex debugging, deadlock detection"
1132 depends on DEBUG_KERNEL && RT_MUTEXES
1134 This allows rt mutex semantics violations and rt mutex related
1135 deadlocks (lockups) to be detected and reported automatically.
1137 config DEBUG_SPINLOCK
1138 bool "Spinlock and rw-lock debugging: basic checks"
1139 depends on DEBUG_KERNEL
1140 select UNINLINE_SPIN_UNLOCK
1142 Say Y here and build SMP to catch missing spinlock initialization
1143 and certain other kinds of spinlock errors commonly made. This is
1144 best used in conjunction with the NMI watchdog so that spinlock
1145 deadlocks are also debuggable.
1147 config DEBUG_MUTEXES
1148 bool "Mutex debugging: basic checks"
1149 depends on DEBUG_KERNEL
1151 This feature allows mutex semantics violations to be detected and
1154 config DEBUG_WW_MUTEX_SLOWPATH
1155 bool "Wait/wound mutex debugging: Slowpath testing"
1156 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1157 select DEBUG_LOCK_ALLOC
1158 select DEBUG_SPINLOCK
1159 select DEBUG_MUTEXES
1161 This feature enables slowpath testing for w/w mutex users by
1162 injecting additional -EDEADLK wound/backoff cases. Together with
1163 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1164 will test all possible w/w mutex interface abuse with the
1165 exception of simply not acquiring all the required locks.
1166 Note that this feature can introduce significant overhead, so
1167 it really should not be enabled in a production or distro kernel,
1168 even a debug kernel. If you are a driver writer, enable it. If
1169 you are a distro, do not.
1172 bool "RW Semaphore debugging: basic checks"
1173 depends on DEBUG_KERNEL
1175 This debugging feature allows mismatched rw semaphore locks
1176 and unlocks to be detected and reported.
1178 config DEBUG_LOCK_ALLOC
1179 bool "Lock debugging: detect incorrect freeing of live locks"
1180 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1181 select DEBUG_SPINLOCK
1182 select DEBUG_MUTEXES
1183 select DEBUG_RT_MUTEXES if RT_MUTEXES
1186 This feature will check whether any held lock (spinlock, rwlock,
1187 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1188 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1189 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1190 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1191 held during task exit.
1195 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1197 select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86
1201 config LOCKDEP_SMALL
1204 config DEBUG_LOCKDEP
1205 bool "Lock dependency engine debugging"
1206 depends on DEBUG_KERNEL && LOCKDEP
1208 If you say Y here, the lock dependency engine will do
1209 additional runtime checks to debug itself, at the price
1210 of more runtime overhead.
1212 config DEBUG_ATOMIC_SLEEP
1213 bool "Sleep inside atomic section checking"
1214 select PREEMPT_COUNT
1215 depends on DEBUG_KERNEL
1216 depends on !ARCH_NO_PREEMPT
1218 If you say Y here, various routines which may sleep will become very
1219 noisy if they are called inside atomic sections: when a spinlock is
1220 held, inside an rcu read side critical section, inside preempt disabled
1221 sections, inside an interrupt, etc...
1223 config DEBUG_LOCKING_API_SELFTESTS
1224 bool "Locking API boot-time self-tests"
1225 depends on DEBUG_KERNEL
1227 Say Y here if you want the kernel to run a short self-test during
1228 bootup. The self-test checks whether common types of locking bugs
1229 are detected by debugging mechanisms or not. (if you disable
1230 lock debugging then those bugs wont be detected of course.)
1231 The following locking APIs are covered: spinlocks, rwlocks,
1234 config LOCK_TORTURE_TEST
1235 tristate "torture tests for locking"
1236 depends on DEBUG_KERNEL
1239 This option provides a kernel module that runs torture tests
1240 on kernel locking primitives. The kernel module may be built
1241 after the fact on the running kernel to be tested, if desired.
1243 Say Y here if you want kernel locking-primitive torture tests
1244 to be built into the kernel.
1245 Say M if you want these torture tests to build as a module.
1246 Say N if you are unsure.
1248 config WW_MUTEX_SELFTEST
1249 tristate "Wait/wound mutex selftests"
1251 This option provides a kernel module that runs tests on the
1252 on the struct ww_mutex locking API.
1254 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1255 with this test harness.
1257 Say M if you want these self tests to build as a module.
1258 Say N if you are unsure.
1260 endmenu # lock debugging
1262 config TRACE_IRQFLAGS
1265 Enables hooks to interrupt enabling and disabling for
1266 either tracing or lock debugging.
1269 bool "Stack backtrace support"
1270 depends on STACKTRACE_SUPPORT
1272 This option causes the kernel to create a /proc/pid/stack for
1273 every process, showing its current stack trace.
1274 It is also used by various kernel debugging features that require
1275 stack trace generation.
1277 config WARN_ALL_UNSEEDED_RANDOM
1278 bool "Warn for all uses of unseeded randomness"
1281 Some parts of the kernel contain bugs relating to their use of
1282 cryptographically secure random numbers before it's actually possible
1283 to generate those numbers securely. This setting ensures that these
1284 flaws don't go unnoticed, by enabling a message, should this ever
1285 occur. This will allow people with obscure setups to know when things
1286 are going wrong, so that they might contact developers about fixing
1289 Unfortunately, on some models of some architectures getting
1290 a fully seeded CRNG is extremely difficult, and so this can
1291 result in dmesg getting spammed for a surprisingly long
1292 time. This is really bad from a security perspective, and
1293 so architecture maintainers really need to do what they can
1294 to get the CRNG seeded sooner after the system is booted.
1295 However, since users cannot do anything actionable to
1296 address this, by default the kernel will issue only a single
1297 warning for the first use of unseeded randomness.
1299 Say Y here if you want to receive warnings for all uses of
1300 unseeded randomness. This will be of use primarily for
1301 those developers interested in improving the security of
1302 Linux kernels running on their architecture (or
1305 config DEBUG_KOBJECT
1306 bool "kobject debugging"
1307 depends on DEBUG_KERNEL
1309 If you say Y here, some extra kobject debugging messages will be sent
1312 config DEBUG_KOBJECT_RELEASE
1313 bool "kobject release debugging"
1314 depends on DEBUG_OBJECTS_TIMERS
1316 kobjects are reference counted objects. This means that their
1317 last reference count put is not predictable, and the kobject can
1318 live on past the point at which a driver decides to drop it's
1319 initial reference to the kobject gained on allocation. An
1320 example of this would be a struct device which has just been
1323 However, some buggy drivers assume that after such an operation,
1324 the memory backing the kobject can be immediately freed. This
1325 goes completely against the principles of a refcounted object.
1327 If you say Y here, the kernel will delay the release of kobjects
1328 on the last reference count to improve the visibility of this
1329 kind of kobject release bug.
1331 config HAVE_DEBUG_BUGVERBOSE
1334 config DEBUG_BUGVERBOSE
1335 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1336 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1339 Say Y here to make BUG() panics output the file name and line number
1340 of the BUG call as well as the EIP and oops trace. This aids
1341 debugging but costs about 70-100K of memory.
1344 bool "Debug linked list manipulation"
1345 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1347 Enable this to turn on extended checks in the linked-list
1353 bool "Debug priority linked list manipulation"
1354 depends on DEBUG_KERNEL
1356 Enable this to turn on extended checks in the priority-ordered
1357 linked-list (plist) walking routines. This checks the entire
1358 list multiple times during each manipulation.
1363 bool "Debug SG table operations"
1364 depends on DEBUG_KERNEL
1366 Enable this to turn on checks on scatter-gather tables. This can
1367 help find problems with drivers that do not properly initialize
1372 config DEBUG_NOTIFIERS
1373 bool "Debug notifier call chains"
1374 depends on DEBUG_KERNEL
1376 Enable this to turn on sanity checking for notifier call chains.
1377 This is most useful for kernel developers to make sure that
1378 modules properly unregister themselves from notifier chains.
1379 This is a relatively cheap check but if you care about maximum
1382 config DEBUG_CREDENTIALS
1383 bool "Debug credential management"
1384 depends on DEBUG_KERNEL
1386 Enable this to turn on some debug checking for credential
1387 management. The additional code keeps track of the number of
1388 pointers from task_structs to any given cred struct, and checks to
1389 see that this number never exceeds the usage count of the cred
1392 Furthermore, if SELinux is enabled, this also checks that the
1393 security pointer in the cred struct is never seen to be invalid.
1397 source "kernel/rcu/Kconfig.debug"
1399 config DEBUG_WQ_FORCE_RR_CPU
1400 bool "Force round-robin CPU selection for unbound work items"
1401 depends on DEBUG_KERNEL
1404 Workqueue used to implicitly guarantee that work items queued
1405 without explicit CPU specified are put on the local CPU. This
1406 guarantee is no longer true and while local CPU is still
1407 preferred work items may be put on foreign CPUs. Kernel
1408 parameter "workqueue.debug_force_rr_cpu" is added to force
1409 round-robin CPU selection to flush out usages which depend on the
1410 now broken guarantee. This config option enables the debug
1411 feature by default. When enabled, memory and cache locality will
1414 config DEBUG_BLOCK_EXT_DEVT
1415 bool "Force extended block device numbers and spread them"
1416 depends on DEBUG_KERNEL
1420 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1421 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1422 YOU ARE DOING. Distros, please enable this and fix whatever
1425 Conventionally, block device numbers are allocated from
1426 predetermined contiguous area. However, extended block area
1427 may introduce non-contiguous block device numbers. This
1428 option forces most block device numbers to be allocated from
1429 the extended space and spreads them to discover kernel or
1430 userland code paths which assume predetermined contiguous
1431 device number allocation.
1433 Note that turning on this debug option shuffles all the
1434 device numbers for all IDE and SCSI devices including libata
1435 ones, so root partition specified using device number
1436 directly (via rdev or root=MAJ:MIN) won't work anymore.
1437 Textual device names (root=/dev/sdXn) will continue to work.
1439 Say N if you are unsure.
1441 config CPU_HOTPLUG_STATE_CONTROL
1442 bool "Enable CPU hotplug state control"
1443 depends on DEBUG_KERNEL
1444 depends on HOTPLUG_CPU
1447 Allows to write steps between "offline" and "online" to the CPUs
1448 sysfs target file so states can be stepped granular. This is a debug
1449 option for now as the hotplug machinery cannot be stopped and
1450 restarted at arbitrary points yet.
1452 Say N if your are unsure.
1454 config NOTIFIER_ERROR_INJECTION
1455 tristate "Notifier error injection"
1456 depends on DEBUG_KERNEL
1459 This option provides the ability to inject artificial errors to
1460 specified notifier chain callbacks. It is useful to test the error
1461 handling of notifier call chain failures.
1465 config PM_NOTIFIER_ERROR_INJECT
1466 tristate "PM notifier error injection module"
1467 depends on PM && NOTIFIER_ERROR_INJECTION
1468 default m if PM_DEBUG
1470 This option provides the ability to inject artificial errors to
1471 PM notifier chain callbacks. It is controlled through debugfs
1472 interface /sys/kernel/debug/notifier-error-inject/pm
1474 If the notifier call chain should be failed with some events
1475 notified, write the error code to "actions/<notifier event>/error".
1477 Example: Inject PM suspend error (-12 = -ENOMEM)
1479 # cd /sys/kernel/debug/notifier-error-inject/pm/
1480 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1481 # echo mem > /sys/power/state
1482 bash: echo: write error: Cannot allocate memory
1484 To compile this code as a module, choose M here: the module will
1485 be called pm-notifier-error-inject.
1489 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1490 tristate "OF reconfig notifier error injection module"
1491 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1493 This option provides the ability to inject artificial errors to
1494 OF reconfig notifier chain callbacks. It is controlled
1495 through debugfs interface under
1496 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1498 If the notifier call chain should be failed with some events
1499 notified, write the error code to "actions/<notifier event>/error".
1501 To compile this code as a module, choose M here: the module will
1502 be called of-reconfig-notifier-error-inject.
1506 config NETDEV_NOTIFIER_ERROR_INJECT
1507 tristate "Netdev notifier error injection module"
1508 depends on NET && NOTIFIER_ERROR_INJECTION
1510 This option provides the ability to inject artificial errors to
1511 netdevice notifier chain callbacks. It is controlled through debugfs
1512 interface /sys/kernel/debug/notifier-error-inject/netdev
1514 If the notifier call chain should be failed with some events
1515 notified, write the error code to "actions/<notifier event>/error".
1517 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1519 # cd /sys/kernel/debug/notifier-error-inject/netdev
1520 # echo -22 > actions/NETDEV_CHANGEMTU/error
1521 # ip link set eth0 mtu 1024
1522 RTNETLINK answers: Invalid argument
1524 To compile this code as a module, choose M here: the module will
1525 be called netdev-notifier-error-inject.
1529 config FUNCTION_ERROR_INJECTION
1531 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
1533 config FAULT_INJECTION
1534 bool "Fault-injection framework"
1535 depends on DEBUG_KERNEL
1537 Provide fault-injection framework.
1538 For more details, see Documentation/fault-injection/.
1541 bool "Fault-injection capability for kmalloc"
1542 depends on FAULT_INJECTION
1543 depends on SLAB || SLUB
1545 Provide fault-injection capability for kmalloc.
1547 config FAIL_PAGE_ALLOC
1548 bool "Fault-injection capabilitiy for alloc_pages()"
1549 depends on FAULT_INJECTION
1551 Provide fault-injection capability for alloc_pages().
1553 config FAIL_MAKE_REQUEST
1554 bool "Fault-injection capability for disk IO"
1555 depends on FAULT_INJECTION && BLOCK
1557 Provide fault-injection capability for disk IO.
1559 config FAIL_IO_TIMEOUT
1560 bool "Fault-injection capability for faking disk interrupts"
1561 depends on FAULT_INJECTION && BLOCK
1563 Provide fault-injection capability on end IO handling. This
1564 will make the block layer "forget" an interrupt as configured,
1565 thus exercising the error handling.
1567 Only works with drivers that use the generic timeout handling,
1568 for others it wont do anything.
1571 bool "Fault-injection capability for futexes"
1573 depends on FAULT_INJECTION && FUTEX
1575 Provide fault-injection capability for futexes.
1577 config FAULT_INJECTION_DEBUG_FS
1578 bool "Debugfs entries for fault-injection capabilities"
1579 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1581 Enable configuration of fault-injection capabilities via debugfs.
1583 config FAIL_FUNCTION
1584 bool "Fault-injection capability for functions"
1585 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
1587 Provide function-based fault-injection capability.
1588 This will allow you to override a specific function with a return
1589 with given return value. As a result, function caller will see
1590 an error value and have to handle it. This is useful to test the
1591 error handling in various subsystems.
1593 config FAIL_MMC_REQUEST
1594 bool "Fault-injection capability for MMC IO"
1595 depends on FAULT_INJECTION_DEBUG_FS && MMC
1597 Provide fault-injection capability for MMC IO.
1598 This will make the mmc core return data errors. This is
1599 useful to test the error handling in the mmc block device
1600 and to test how the mmc host driver handles retries from
1603 config FAULT_INJECTION_STACKTRACE_FILTER
1604 bool "stacktrace filter for fault-injection capabilities"
1605 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1608 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1610 Provide stacktrace filter for fault-injection capabilities
1613 bool "Latency measuring infrastructure"
1614 depends on DEBUG_KERNEL
1615 depends on STACKTRACE_SUPPORT
1617 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1624 Enable this option if you want to use the LatencyTOP tool
1625 to find out which userspace is blocking on what kernel operations.
1627 source "kernel/trace/Kconfig"
1629 config PROVIDE_OHCI1394_DMA_INIT
1630 bool "Remote debugging over FireWire early on boot"
1631 depends on PCI && X86
1633 If you want to debug problems which hang or crash the kernel early
1634 on boot and the crashing machine has a FireWire port, you can use
1635 this feature to remotely access the memory of the crashed machine
1636 over FireWire. This employs remote DMA as part of the OHCI1394
1637 specification which is now the standard for FireWire controllers.
1639 With remote DMA, you can monitor the printk buffer remotely using
1640 firescope and access all memory below 4GB using fireproxy from gdb.
1641 Even controlling a kernel debugger is possible using remote DMA.
1645 If ohci1394_dma=early is used as boot parameter, it will initialize
1646 all OHCI1394 controllers which are found in the PCI config space.
1648 As all changes to the FireWire bus such as enabling and disabling
1649 devices cause a bus reset and thereby disable remote DMA for all
1650 devices, be sure to have the cable plugged and FireWire enabled on
1651 the debugging host before booting the debug target for debugging.
1653 This code (~1k) is freed after boot. By then, the firewire stack
1654 in charge of the OHCI-1394 controllers should be used instead.
1656 See Documentation/debugging-via-ohci1394.txt for more information.
1658 menuconfig RUNTIME_TESTING_MENU
1659 bool "Runtime Testing"
1662 if RUNTIME_TESTING_MENU
1665 tristate "Linux Kernel Dump Test Tool Module"
1668 This module enables testing of the different dumping mechanisms by
1669 inducing system failures at predefined crash points.
1670 If you don't need it: say N
1671 Choose M here to compile this code as a module. The module will be
1674 Documentation on how to use the module can be found in
1675 Documentation/fault-injection/provoke-crashes.rst
1677 config TEST_LIST_SORT
1678 tristate "Linked list sorting test"
1679 depends on DEBUG_KERNEL || m
1681 Enable this to turn on 'list_sort()' function test. This test is
1682 executed only once during system boot (so affects only boot time),
1683 or at module load time.
1688 tristate "Array-based sort test"
1689 depends on DEBUG_KERNEL || m
1691 This option enables the self-test function of 'sort()' at boot,
1692 or at module load time.
1696 config KPROBES_SANITY_TEST
1697 bool "Kprobes sanity tests"
1698 depends on DEBUG_KERNEL
1701 This option provides for testing basic kprobes functionality on
1702 boot. Samples of kprobe and kretprobe are inserted and
1703 verified for functionality.
1705 Say N if you are unsure.
1707 config BACKTRACE_SELF_TEST
1708 tristate "Self test for the backtrace code"
1709 depends on DEBUG_KERNEL
1711 This option provides a kernel module that can be used to test
1712 the kernel stack backtrace code. This option is not useful
1713 for distributions or general kernels, but only for kernel
1714 developers working on architecture code.
1716 Note that if you want to also test saved backtraces, you will
1717 have to enable STACKTRACE as well.
1719 Say N if you are unsure.
1722 tristate "Red-Black tree test"
1723 depends on DEBUG_KERNEL
1725 A benchmark measuring the performance of the rbtree library.
1726 Also includes rbtree invariant checks.
1728 config REED_SOLOMON_TEST
1729 tristate "Reed-Solomon library test"
1730 depends on DEBUG_KERNEL || m
1732 select REED_SOLOMON_ENC16
1733 select REED_SOLOMON_DEC16
1735 This option enables the self-test function of rslib at boot,
1736 or at module load time.
1740 config INTERVAL_TREE_TEST
1741 tristate "Interval tree test"
1742 depends on DEBUG_KERNEL
1743 select INTERVAL_TREE
1745 A benchmark measuring the performance of the interval tree library
1748 tristate "Per cpu operations test"
1749 depends on m && DEBUG_KERNEL
1751 Enable this option to build test module which validates per-cpu
1756 config ATOMIC64_SELFTEST
1757 tristate "Perform an atomic64_t self-test"
1759 Enable this option to test the atomic64_t functions at boot or
1760 at module load time.
1764 config ASYNC_RAID6_TEST
1765 tristate "Self test for hardware accelerated raid6 recovery"
1766 depends on ASYNC_RAID6_RECOV
1769 This is a one-shot self test that permutes through the
1770 recovery of all the possible two disk failure scenarios for a
1771 N-disk array. Recovery is performed with the asynchronous
1772 raid6 recovery routines, and will optionally use an offload
1773 engine if one is available.
1778 tristate "Test functions located in the hexdump module at runtime"
1780 config TEST_STRING_HELPERS
1781 tristate "Test functions located in the string_helpers module at runtime"
1784 tristate "Test strscpy*() family of functions at runtime"
1787 tristate "Test kstrto*() family of functions at runtime"
1790 tristate "Test printf() family of functions at runtime"
1793 tristate "Test bitmap_*() family of functions at runtime"
1795 Enable this option to test the bitmap functions at boot.
1799 config TEST_BITFIELD
1800 tristate "Test bitfield functions at runtime"
1802 Enable this option to test the bitfield functions at boot.
1807 tristate "Test functions located in the uuid module at runtime"
1810 tristate "Test the XArray code at runtime"
1812 config TEST_OVERFLOW
1813 tristate "Test check_*_overflow() functions at runtime"
1815 config TEST_RHASHTABLE
1816 tristate "Perform selftest on resizable hash table"
1818 Enable this option to test the rhashtable functions at boot.
1823 tristate "Perform selftest on hash functions"
1825 Enable this option to test the kernel's integer (<linux/hash.h>),
1826 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1827 hash functions on boot (or module load).
1829 This is intended to help people writing architecture-specific
1830 optimized versions. If unsure, say N.
1833 tristate "Perform selftest on IDA functions"
1836 tristate "Perform selftest on priority array manager"
1839 Enable this option to test priority array manager on boot
1844 config TEST_IRQ_TIMINGS
1845 bool "IRQ timings selftest"
1846 depends on IRQ_TIMINGS
1848 Enable this option to test the irq timings code on boot.
1853 tristate "Test module loading with 'hello world' module"
1856 This builds the "test_module" module that emits "Hello, world"
1857 on printk when loaded. It is designed to be used for basic
1858 evaluation of the module loading subsystem (for example when
1859 validating module verification). It lacks any extra dependencies,
1860 and will not normally be loaded by the system unless explicitly
1866 tristate "Test module for stress/performance analysis of vmalloc allocator"
1871 This builds the "test_vmalloc" module that should be used for
1872 stress and performance analysis. So, any new change for vmalloc
1873 subsystem can be evaluated from performance and stability point
1878 config TEST_USER_COPY
1879 tristate "Test user/kernel boundary protections"
1882 This builds the "test_user_copy" module that runs sanity checks
1883 on the copy_to/from_user infrastructure, making sure basic
1884 user/kernel boundary testing is working. If it fails to load,
1885 a regression has been detected in the user/kernel memory boundary
1891 tristate "Test BPF filter functionality"
1894 This builds the "test_bpf" module that runs various test vectors
1895 against the BPF interpreter or BPF JIT compiler depending on the
1896 current setting. This is in particular useful for BPF JIT compiler
1897 development, but also to run regression tests against changes in
1898 the interpreter code. It also enables test stubs for eBPF maps and
1899 verifier used by user space verifier testsuite.
1903 config TEST_BLACKHOLE_DEV
1904 tristate "Test blackhole netdev functionality"
1907 This builds the "test_blackhole_dev" module that validates the
1908 data path through this blackhole netdev.
1912 config FIND_BIT_BENCHMARK
1913 tristate "Test find_bit functions"
1915 This builds the "test_find_bit" module that measure find_*_bit()
1916 functions performance.
1920 config TEST_FIRMWARE
1921 tristate "Test firmware loading via userspace interface"
1922 depends on FW_LOADER
1924 This builds the "test_firmware" module that creates a userspace
1925 interface for testing firmware loading. This can be used to
1926 control the triggering of firmware loading without needing an
1927 actual firmware-using device. The contents can be rechecked by
1933 tristate "sysctl test driver"
1934 depends on PROC_SYSCTL
1936 This builds the "test_sysctl" module. This driver enables to test the
1937 proc sysctl interfaces available to drivers safely without affecting
1938 production knobs which might alter system functionality.
1943 tristate "udelay test driver"
1945 This builds the "udelay_test" module that helps to make sure
1946 that udelay() is working properly.
1950 config TEST_STATIC_KEYS
1951 tristate "Test static keys"
1954 Test the static key interfaces.
1959 tristate "kmod stress tester"
1961 depends on NETDEVICES && NET_CORE && INET # for TUN
1968 Test the kernel's module loading mechanism: kmod. kmod implements
1969 support to load modules using the Linux kernel's usermode helper.
1970 This test provides a series of tests against kmod.
1972 Although technically you can either build test_kmod as a module or
1973 into the kernel we disallow building it into the kernel since
1974 it stress tests request_module() and this will very likely cause
1975 some issues by taking over precious threads available from other
1976 module load requests, ultimately this could be fatal.
1980 tools/testing/selftests/kmod/kmod.sh --help
1984 config TEST_DEBUG_VIRTUAL
1985 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
1986 depends on DEBUG_VIRTUAL
1988 Test the kernel's ability to detect incorrect calls to
1989 virt_to_phys() done against the non-linear part of the
1990 kernel's virtual address map.
1994 config TEST_MEMCAT_P
1995 tristate "Test memcat_p() helper function"
1997 Test the memcat_p() helper for correctly merging two
1998 pointer arrays together.
2002 config TEST_LIVEPATCH
2003 tristate "Test livepatching"
2005 depends on DYNAMIC_DEBUG
2006 depends on LIVEPATCH
2009 Test kernel livepatching features for correctness. The tests will
2010 load test modules that will be livepatched in various scenarios.
2012 To run all the livepatching tests:
2014 make -C tools/testing/selftests TARGETS=livepatch run_tests
2016 Alternatively, individual tests may be invoked:
2018 tools/testing/selftests/livepatch/test-callbacks.sh
2019 tools/testing/selftests/livepatch/test-livepatch.sh
2020 tools/testing/selftests/livepatch/test-shadow-vars.sh
2025 tristate "Perform selftest on object aggreration manager"
2029 Enable this option to test object aggregation manager on boot
2033 config TEST_STACKINIT
2034 tristate "Test level of stack variable initialization"
2036 Test if the kernel is zero-initializing stack variables and
2037 padding. Coverage is controlled by compiler flags,
2038 CONFIG_GCC_PLUGIN_STRUCTLEAK, CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF,
2039 or CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL.
2044 tristate "Test heap/page initialization"
2046 Test if the kernel is zero-initializing heap and page allocations.
2047 This can be useful to test init_on_alloc and init_on_free features.
2051 endif # RUNTIME_TESTING_MENU
2056 This option adds a kernel parameter 'memtest', which allows memtest
2058 memtest=0, mean disabled; -- default
2059 memtest=1, mean do 1 test pattern;
2061 memtest=17, mean do 17 test patterns.
2062 If you are unsure how to answer this question, answer N.
2064 config BUG_ON_DATA_CORRUPTION
2065 bool "Trigger a BUG when data corruption is detected"
2068 Select this option if the kernel should BUG when it encounters
2069 data corruption in kernel memory structures when they get checked
2074 source "samples/Kconfig"
2076 source "lib/Kconfig.kgdb"
2078 source "lib/Kconfig.ubsan"
2080 config ARCH_HAS_DEVMEM_IS_ALLOWED
2083 config STRICT_DEVMEM
2084 bool "Filter access to /dev/mem"
2085 depends on MMU && DEVMEM
2086 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
2087 default y if PPC || X86 || ARM64
2089 If this option is disabled, you allow userspace (root) access to all
2090 of memory, including kernel and userspace memory. Accidental
2091 access to this is obviously disastrous, but specific access can
2092 be used by people debugging the kernel. Note that with PAT support
2093 enabled, even in this case there are restrictions on /dev/mem
2094 use due to the cache aliasing requirements.
2096 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
2097 file only allows userspace access to PCI space and the BIOS code and
2098 data regions. This is sufficient for dosemu and X and all common
2103 config IO_STRICT_DEVMEM
2104 bool "Filter I/O access to /dev/mem"
2105 depends on STRICT_DEVMEM
2107 If this option is disabled, you allow userspace (root) access to all
2108 io-memory regardless of whether a driver is actively using that
2109 range. Accidental access to this is obviously disastrous, but
2110 specific access can be used by people debugging kernel drivers.
2112 If this option is switched on, the /dev/mem file only allows
2113 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2114 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2115 if the driver using a given range cannot be disabled.
2119 source "arch/$(SRCARCH)/Kconfig.debug"
2121 endmenu # Kernel hacking
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