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
227 Generate deduplicated BTF type information from DWARF debug info.
228 Turning this on expects presence of pahole tool, which will convert
229 DWARF type info into equivalent deduplicated BTF type info.
232 bool "Provide GDB scripts for kernel debugging"
233 depends on DEBUG_INFO
235 This creates the required links to GDB helper scripts in the
236 build directory. If you load vmlinux into gdb, the helper
237 scripts will be automatically imported by gdb as well, and
238 additional functions are available to analyze a Linux kernel
239 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
242 config ENABLE_MUST_CHECK
243 bool "Enable __must_check logic"
246 Enable the __must_check logic in the kernel build. Disable this to
247 suppress the "warning: ignoring return value of 'foo', declared with
248 attribute warn_unused_result" messages.
251 int "Warn for stack frames larger than (needs gcc 4.4)"
253 default 2048 if GCC_PLUGIN_LATENT_ENTROPY
254 default 1280 if (!64BIT && PARISC)
255 default 1024 if (!64BIT && !PARISC)
256 default 2048 if 64BIT
258 Tell gcc to warn at build time for stack frames larger than this.
259 Setting this too low will cause a lot of warnings.
260 Setting it to 0 disables the warning.
263 config STRIP_ASM_SYMS
264 bool "Strip assembler-generated symbols during link"
267 Strip internal assembler-generated symbols during a link (symbols
268 that look like '.Lxxx') so they don't pollute the output of
269 get_wchan() and suchlike.
272 bool "Generate readable assembler code"
273 depends on DEBUG_KERNEL
275 Disable some compiler optimizations that tend to generate human unreadable
276 assembler output. This may make the kernel slightly slower, but it helps
277 to keep kernel developers who have to stare a lot at assembler listings
280 config UNUSED_SYMBOLS
281 bool "Enable unused/obsolete exported symbols"
284 Unused but exported symbols make the kernel needlessly bigger. For
285 that reason most of these unused exports will soon be removed. This
286 option is provided temporarily to provide a transition period in case
287 some external kernel module needs one of these symbols anyway. If you
288 encounter such a case in your module, consider if you are actually
289 using the right API. (rationale: since nobody in the kernel is using
290 this in a module, there is a pretty good chance it's actually the
291 wrong interface to use). If you really need the symbol, please send a
292 mail to the linux kernel mailing list mentioning the symbol and why
293 you really need it, and what the merge plan to the mainline kernel for
297 bool "Debug Filesystem"
299 debugfs is a virtual file system that kernel developers use to put
300 debugging files into. Enable this option to be able to read and
301 write to these files.
303 For detailed documentation on the debugfs API, see
304 Documentation/filesystems/.
308 config HEADERS_INSTALL
309 bool "Install uapi headers to usr/include"
312 This option will install uapi headers (headers exported to user-space)
313 into the usr/include directory for use during the kernel build.
314 This is unneeded for building the kernel itself, but needed for some
315 user-space program samples. It is also needed by some features such
316 as uapi header sanity checks.
319 bool "Run sanity checks on uapi headers when building 'all'"
320 depends on HEADERS_INSTALL
322 This option will run basic sanity checks on uapi headers when
323 building the 'all' target, for example, ensure that they do not
324 attempt to include files which were not exported, etc.
326 If you're making modifications to header files which are
327 relevant for userspace, say 'Y'.
329 config OPTIMIZE_INLINING
330 bool "Allow compiler to uninline functions marked 'inline'"
332 This option determines if the kernel forces gcc to inline the functions
333 developers have marked 'inline'. Doing so takes away freedom from gcc to
334 do what it thinks is best, which is desirable for the gcc 3.x series of
335 compilers. The gcc 4.x series have a rewritten inlining algorithm and
336 enabling this option will generate a smaller kernel there. Hopefully
337 this algorithm is so good that allowing gcc 4.x and above to make the
338 decision will become the default in the future. Until then this option
339 is there to test gcc for this.
343 config DEBUG_SECTION_MISMATCH
344 bool "Enable full Section mismatch analysis"
346 The section mismatch analysis checks if there are illegal
347 references from one section to another section.
348 During linktime or runtime, some sections are dropped;
349 any use of code/data previously in these sections would
350 most likely result in an oops.
351 In the code, functions and variables are annotated with
352 __init,, etc. (see the full list in include/linux/init.h),
353 which results in the code/data being placed in specific sections.
354 The section mismatch analysis is always performed after a full
355 kernel build, and enabling this option causes the following
356 additional steps to occur:
357 - Add the option -fno-inline-functions-called-once to gcc commands.
358 When inlining a function annotated with __init in a non-init
359 function, we would lose the section information and thus
360 the analysis would not catch the illegal reference.
361 This option tells gcc to inline less (but it does result in
363 - Run the section mismatch analysis for each module/built-in.a file.
364 When we run the section mismatch analysis on vmlinux.o, we
365 lose valuable information about where the mismatch was
367 Running the analysis for each module/built-in.a file
368 tells where the mismatch happens much closer to the
369 source. The drawback is that the same mismatch is
370 reported at least twice.
371 - Enable verbose reporting from modpost in order to help resolve
372 the section mismatches that are reported.
374 config SECTION_MISMATCH_WARN_ONLY
375 bool "Make section mismatch errors non-fatal"
378 If you say N here, the build process will fail if there are any
379 section mismatch, instead of just throwing warnings.
384 # Select this config option from the architecture Kconfig, if it
385 # is preferred to always offer frame pointers as a config
386 # option on the architecture (regardless of KERNEL_DEBUG):
388 config ARCH_WANT_FRAME_POINTERS
392 bool "Compile the kernel with frame pointers"
393 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS
394 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
396 If you say Y here the resulting kernel image will be slightly
397 larger and slower, but it gives very useful debugging information
398 in case of kernel bugs. (precise oopses/stacktraces/warnings)
400 config STACK_VALIDATION
401 bool "Compile-time stack metadata validation"
402 depends on HAVE_STACK_VALIDATION
405 Add compile-time checks to validate stack metadata, including frame
406 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
407 that runtime stack traces are more reliable.
409 This is also a prerequisite for generation of ORC unwind data, which
410 is needed for CONFIG_UNWINDER_ORC.
412 For more information, see
413 tools/objtool/Documentation/stack-validation.txt.
415 config DEBUG_FORCE_WEAK_PER_CPU
416 bool "Force weak per-cpu definitions"
417 depends on DEBUG_KERNEL
419 s390 and alpha require percpu variables in modules to be
420 defined weak to work around addressing range issue which
421 puts the following two restrictions on percpu variable
424 1. percpu symbols must be unique whether static or not
425 2. percpu variables can't be defined inside a function
427 To ensure that generic code follows the above rules, this
428 option forces all percpu variables to be defined as weak.
430 endmenu # "Compiler options"
433 bool "Magic SysRq key"
436 If you say Y here, you will have some control over the system even
437 if the system crashes for example during kernel debugging (e.g., you
438 will be able to flush the buffer cache to disk, reboot the system
439 immediately or dump some status information). This is accomplished
440 by pressing various keys while holding SysRq (Alt+PrintScreen). It
441 also works on a serial console (on PC hardware at least), if you
442 send a BREAK and then within 5 seconds a command keypress. The
443 keys are documented in <file:Documentation/admin-guide/sysrq.rst>.
444 Don't say Y unless you really know what this hack does.
446 config MAGIC_SYSRQ_DEFAULT_ENABLE
447 hex "Enable magic SysRq key functions by default"
448 depends on MAGIC_SYSRQ
451 Specifies which SysRq key functions are enabled by default.
452 This may be set to 1 or 0 to enable or disable them all, or
453 to a bitmask as described in Documentation/admin-guide/sysrq.rst.
455 config MAGIC_SYSRQ_SERIAL
456 bool "Enable magic SysRq key over serial"
457 depends on MAGIC_SYSRQ
460 Many embedded boards have a disconnected TTL level serial which can
461 generate some garbage that can lead to spurious false sysrq detects.
462 This option allows you to decide whether you want to enable the
466 bool "Kernel debugging"
468 Say Y here if you are developing drivers or trying to debug and
469 identify kernel problems.
472 bool "Miscellaneous debug code"
474 depends on DEBUG_KERNEL
476 Say Y here if you need to enable miscellaneous debug code that should
477 be under a more specific debug option but isn't.
480 menu "Memory Debugging"
482 source "mm/Kconfig.debug"
485 bool "Debug object operations"
486 depends on DEBUG_KERNEL
488 If you say Y here, additional code will be inserted into the
489 kernel to track the life time of various objects and validate
490 the operations on those objects.
492 config DEBUG_OBJECTS_SELFTEST
493 bool "Debug objects selftest"
494 depends on DEBUG_OBJECTS
496 This enables the selftest of the object debug code.
498 config DEBUG_OBJECTS_FREE
499 bool "Debug objects in freed memory"
500 depends on DEBUG_OBJECTS
502 This enables checks whether a k/v free operation frees an area
503 which contains an object which has not been deactivated
504 properly. This can make kmalloc/kfree-intensive workloads
507 config DEBUG_OBJECTS_TIMERS
508 bool "Debug timer objects"
509 depends on DEBUG_OBJECTS
511 If you say Y here, additional code will be inserted into the
512 timer routines to track the life time of timer objects and
513 validate the timer operations.
515 config DEBUG_OBJECTS_WORK
516 bool "Debug work objects"
517 depends on DEBUG_OBJECTS
519 If you say Y here, additional code will be inserted into the
520 work queue routines to track the life time of work objects and
521 validate the work operations.
523 config DEBUG_OBJECTS_RCU_HEAD
524 bool "Debug RCU callbacks objects"
525 depends on DEBUG_OBJECTS
527 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
529 config DEBUG_OBJECTS_PERCPU_COUNTER
530 bool "Debug percpu counter objects"
531 depends on DEBUG_OBJECTS
533 If you say Y here, additional code will be inserted into the
534 percpu counter routines to track the life time of percpu counter
535 objects and validate the percpu counter operations.
537 config DEBUG_OBJECTS_ENABLE_DEFAULT
538 int "debug_objects bootup default value (0-1)"
541 depends on DEBUG_OBJECTS
543 Debug objects boot parameter default value
546 bool "Debug slab memory allocations"
547 depends on DEBUG_KERNEL && SLAB
549 Say Y here to have the kernel do limited verification on memory
550 allocation as well as poisoning memory on free to catch use of freed
551 memory. This can make kmalloc/kfree-intensive workloads much slower.
554 bool "SLUB debugging on by default"
555 depends on SLUB && SLUB_DEBUG
558 Boot with debugging on by default. SLUB boots by default with
559 the runtime debug capabilities switched off. Enabling this is
560 equivalent to specifying the "slub_debug" parameter on boot.
561 There is no support for more fine grained debug control like
562 possible with slub_debug=xxx. SLUB debugging may be switched
563 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
568 bool "Enable SLUB performance statistics"
569 depends on SLUB && SYSFS
571 SLUB statistics are useful to debug SLUBs allocation behavior in
572 order find ways to optimize the allocator. This should never be
573 enabled for production use since keeping statistics slows down
574 the allocator by a few percentage points. The slabinfo command
575 supports the determination of the most active slabs to figure
576 out which slabs are relevant to a particular load.
577 Try running: slabinfo -DA
579 config HAVE_DEBUG_KMEMLEAK
582 config DEBUG_KMEMLEAK
583 bool "Kernel memory leak detector"
584 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
586 select STACKTRACE if STACKTRACE_SUPPORT
590 Say Y here if you want to enable the memory leak
591 detector. The memory allocation/freeing is traced in a way
592 similar to the Boehm's conservative garbage collector, the
593 difference being that the orphan objects are not freed but
594 only shown in /sys/kernel/debug/kmemleak. Enabling this
595 feature will introduce an overhead to memory
596 allocations. See Documentation/dev-tools/kmemleak.rst for more
599 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
600 of finding leaks due to the slab objects poisoning.
602 In order to access the kmemleak file, debugfs needs to be
603 mounted (usually at /sys/kernel/debug).
605 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
606 int "Maximum kmemleak early log entries"
607 depends on DEBUG_KMEMLEAK
611 Kmemleak must track all the memory allocations to avoid
612 reporting false positives. Since memory may be allocated or
613 freed before kmemleak is initialised, an early log buffer is
614 used to store these actions. If kmemleak reports "early log
615 buffer exceeded", please increase this value.
617 config DEBUG_KMEMLEAK_TEST
618 tristate "Simple test for the kernel memory leak detector"
619 depends on DEBUG_KMEMLEAK && m
621 This option enables a module that explicitly leaks memory.
625 config DEBUG_KMEMLEAK_DEFAULT_OFF
626 bool "Default kmemleak to off"
627 depends on DEBUG_KMEMLEAK
629 Say Y here to disable kmemleak by default. It can then be enabled
630 on the command line via kmemleak=on.
632 config DEBUG_KMEMLEAK_AUTO_SCAN
633 bool "Enable kmemleak auto scan thread on boot up"
635 depends on DEBUG_KMEMLEAK
637 Depending on the cpu, kmemleak scan may be cpu intensive and can
638 stall user tasks at times. This option enables/disables automatic
639 kmemleak scan at boot up.
641 Say N here to disable kmemleak auto scan thread to stop automatic
642 scanning. Disabling this option disables automatic reporting of
647 config DEBUG_STACK_USAGE
648 bool "Stack utilization instrumentation"
649 depends on DEBUG_KERNEL && !IA64
651 Enables the display of the minimum amount of free stack which each
652 task has ever had available in the sysrq-T and sysrq-P debug output.
654 This option will slow down process creation somewhat.
658 depends on DEBUG_KERNEL
660 Enable this to turn on extended checks in the virtual-memory system
661 that may impact performance.
665 config DEBUG_VM_VMACACHE
666 bool "Debug VMA caching"
669 Enable this to turn on VMA caching debug information. Doing so
670 can cause significant overhead, so only enable it in non-production
676 bool "Debug VM red-black trees"
679 Enable VM red-black tree debugging information and extra validations.
683 config DEBUG_VM_PGFLAGS
684 bool "Debug page-flags operations"
687 Enables extra validation on page flags operations.
691 config ARCH_HAS_DEBUG_VIRTUAL
695 bool "Debug VM translations"
696 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
698 Enable some costly sanity checks in virtual to page code. This can
699 catch mistakes with virt_to_page() and friends.
703 config DEBUG_NOMMU_REGIONS
704 bool "Debug the global anon/private NOMMU mapping region tree"
705 depends on DEBUG_KERNEL && !MMU
707 This option causes the global tree of anonymous and private mapping
708 regions to be regularly checked for invalid topology.
710 config DEBUG_MEMORY_INIT
711 bool "Debug memory initialisation" if EXPERT
714 Enable this for additional checks during memory initialisation.
715 The sanity checks verify aspects of the VM such as the memory model
716 and other information provided by the architecture. Verbose
717 information will be printed at KERN_DEBUG loglevel depending
718 on the mminit_loglevel= command-line option.
722 config MEMORY_NOTIFIER_ERROR_INJECT
723 tristate "Memory hotplug notifier error injection module"
724 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
726 This option provides the ability to inject artificial errors to
727 memory hotplug notifier chain callbacks. It is controlled through
728 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
730 If the notifier call chain should be failed with some events
731 notified, write the error code to "actions/<notifier event>/error".
733 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
735 # cd /sys/kernel/debug/notifier-error-inject/memory
736 # echo -12 > actions/MEM_GOING_OFFLINE/error
737 # echo offline > /sys/devices/system/memory/memoryXXX/state
738 bash: echo: write error: Cannot allocate memory
740 To compile this code as a module, choose M here: the module will
741 be called memory-notifier-error-inject.
745 config DEBUG_PER_CPU_MAPS
746 bool "Debug access to per_cpu maps"
747 depends on DEBUG_KERNEL
750 Say Y to verify that the per_cpu map being accessed has
751 been set up. This adds a fair amount of code to kernel memory
752 and decreases performance.
757 bool "Highmem debugging"
758 depends on DEBUG_KERNEL && HIGHMEM
760 This option enables additional error checking for high memory
761 systems. Disable for production systems.
763 config HAVE_DEBUG_STACKOVERFLOW
766 config DEBUG_STACKOVERFLOW
767 bool "Check for stack overflows"
768 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
770 Say Y here if you want to check for overflows of kernel, IRQ
771 and exception stacks (if your architecture uses them). This
772 option will show detailed messages if free stack space drops
773 below a certain limit.
775 These kinds of bugs usually occur when call-chains in the
776 kernel get too deep, especially when interrupts are
779 Use this in cases where you see apparently random memory
780 corruption, especially if it appears in 'struct thread_info'
782 If in doubt, say "N".
784 source "lib/Kconfig.kasan"
786 endmenu # "Memory Debugging"
791 An architecture should select this when it can successfully
792 build and run with CONFIG_KCOV. This typically requires
793 disabling instrumentation for some early boot code.
795 config CC_HAS_SANCOV_TRACE_PC
796 def_bool $(cc-option,-fsanitize-coverage=trace-pc)
799 bool "Code coverage for fuzzing"
800 depends on ARCH_HAS_KCOV
801 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
803 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
805 KCOV exposes kernel code coverage information in a form suitable
806 for coverage-guided fuzzing (randomized testing).
808 If RANDOMIZE_BASE is enabled, PC values will not be stable across
809 different machines and across reboots. If you need stable PC values,
810 disable RANDOMIZE_BASE.
812 For more details, see Documentation/dev-tools/kcov.rst.
814 config KCOV_ENABLE_COMPARISONS
815 bool "Enable comparison operands collection by KCOV"
817 depends on $(cc-option,-fsanitize-coverage=trace-cmp)
819 KCOV also exposes operands of every comparison in the instrumented
820 code along with operand sizes and PCs of the comparison instructions.
821 These operands can be used by fuzzing engines to improve the quality
824 config KCOV_INSTRUMENT_ALL
825 bool "Instrument all code by default"
829 If you are doing generic system call fuzzing (like e.g. syzkaller),
830 then you will want to instrument the whole kernel and you should
831 say y here. If you are doing more targeted fuzzing (like e.g.
832 filesystem fuzzing with AFL) then you will want to enable coverage
833 for more specific subsets of files, and should say n here.
836 bool "Debug shared IRQ handlers"
837 depends on DEBUG_KERNEL
839 Enable this to generate a spurious interrupt as soon as a shared
840 interrupt handler is registered, and just before one is deregistered.
841 Drivers ought to be able to handle interrupts coming in at those
842 points; some don't and need to be caught.
844 menu "Debug Lockups and Hangs"
846 config LOCKUP_DETECTOR
849 config SOFTLOCKUP_DETECTOR
850 bool "Detect Soft Lockups"
851 depends on DEBUG_KERNEL && !S390
852 select LOCKUP_DETECTOR
854 Say Y here to enable the kernel to act as a watchdog to detect
857 Softlockups are bugs that cause the kernel to loop in kernel
858 mode for more than 20 seconds, without giving other tasks a
859 chance to run. The current stack trace is displayed upon
860 detection and the system will stay locked up.
862 config BOOTPARAM_SOFTLOCKUP_PANIC
863 bool "Panic (Reboot) On Soft Lockups"
864 depends on SOFTLOCKUP_DETECTOR
866 Say Y here to enable the kernel to panic on "soft lockups",
867 which are bugs that cause the kernel to loop in kernel
868 mode for more than 20 seconds (configurable using the watchdog_thresh
869 sysctl), without giving other tasks a chance to run.
871 The panic can be used in combination with panic_timeout,
872 to cause the system to reboot automatically after a
873 lockup has been detected. This feature is useful for
874 high-availability systems that have uptime guarantees and
875 where a lockup must be resolved ASAP.
879 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
881 depends on SOFTLOCKUP_DETECTOR
883 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
884 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
886 config HARDLOCKUP_DETECTOR_PERF
888 select SOFTLOCKUP_DETECTOR
891 # Enables a timestamp based low pass filter to compensate for perf based
892 # hard lockup detection which runs too fast due to turbo modes.
894 config HARDLOCKUP_CHECK_TIMESTAMP
898 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
899 # lockup detector rather than the perf based detector.
901 config HARDLOCKUP_DETECTOR
902 bool "Detect Hard Lockups"
903 depends on DEBUG_KERNEL && !S390
904 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
905 select LOCKUP_DETECTOR
906 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
907 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
909 Say Y here to enable the kernel to act as a watchdog to detect
912 Hardlockups are bugs that cause the CPU to loop in kernel mode
913 for more than 10 seconds, without letting other interrupts have a
914 chance to run. The current stack trace is displayed upon detection
915 and the system will stay locked up.
917 config BOOTPARAM_HARDLOCKUP_PANIC
918 bool "Panic (Reboot) On Hard Lockups"
919 depends on HARDLOCKUP_DETECTOR
921 Say Y here to enable the kernel to panic on "hard lockups",
922 which are bugs that cause the kernel to loop in kernel
923 mode with interrupts disabled for more than 10 seconds (configurable
924 using the watchdog_thresh sysctl).
928 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
930 depends on HARDLOCKUP_DETECTOR
932 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
933 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
935 config DETECT_HUNG_TASK
936 bool "Detect Hung Tasks"
937 depends on DEBUG_KERNEL
938 default SOFTLOCKUP_DETECTOR
940 Say Y here to enable the kernel to detect "hung tasks",
941 which are bugs that cause the task to be stuck in
942 uninterruptible "D" state indefinitely.
944 When a hung task is detected, the kernel will print the
945 current stack trace (which you should report), but the
946 task will stay in uninterruptible state. If lockdep is
947 enabled then all held locks will also be reported. This
948 feature has negligible overhead.
950 config DEFAULT_HUNG_TASK_TIMEOUT
951 int "Default timeout for hung task detection (in seconds)"
952 depends on DETECT_HUNG_TASK
955 This option controls the default timeout (in seconds) used
956 to determine when a task has become non-responsive and should
959 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
960 sysctl or by writing a value to
961 /proc/sys/kernel/hung_task_timeout_secs.
963 A timeout of 0 disables the check. The default is two minutes.
964 Keeping the default should be fine in most cases.
966 config BOOTPARAM_HUNG_TASK_PANIC
967 bool "Panic (Reboot) On Hung Tasks"
968 depends on DETECT_HUNG_TASK
970 Say Y here to enable the kernel to panic on "hung tasks",
971 which are bugs that cause the kernel to leave a task stuck
972 in uninterruptible "D" state.
974 The panic can be used in combination with panic_timeout,
975 to cause the system to reboot automatically after a
976 hung task has been detected. This feature is useful for
977 high-availability systems that have uptime guarantees and
978 where a hung tasks must be resolved ASAP.
982 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
984 depends on DETECT_HUNG_TASK
986 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
987 default 1 if BOOTPARAM_HUNG_TASK_PANIC
990 bool "Detect Workqueue Stalls"
991 depends on DEBUG_KERNEL
993 Say Y here to enable stall detection on workqueues. If a
994 worker pool doesn't make forward progress on a pending work
995 item for over a given amount of time, 30s by default, a
996 warning message is printed along with dump of workqueue
997 state. This can be configured through kernel parameter
998 "workqueue.watchdog_thresh" and its sysfs counterpart.
1000 endmenu # "Debug lockups and hangs"
1002 config PANIC_ON_OOPS
1003 bool "Panic on Oops"
1005 Say Y here to enable the kernel to panic when it oopses. This
1006 has the same effect as setting oops=panic on the kernel command
1009 This feature is useful to ensure that the kernel does not do
1010 anything erroneous after an oops which could result in data
1011 corruption or other issues.
1015 config PANIC_ON_OOPS_VALUE
1018 default 0 if !PANIC_ON_OOPS
1019 default 1 if PANIC_ON_OOPS
1021 config PANIC_TIMEOUT
1025 Set the timeout value (in seconds) until a reboot occurs when the
1026 the kernel panics. If n = 0, then we wait forever. A timeout
1027 value n > 0 will wait n seconds before rebooting, while a timeout
1028 value n < 0 will reboot immediately.
1031 bool "Collect scheduler debugging info"
1032 depends on DEBUG_KERNEL && PROC_FS
1035 If you say Y here, the /proc/sched_debug file will be provided
1036 that can help debug the scheduler. The runtime overhead of this
1044 bool "Collect scheduler statistics"
1045 depends on DEBUG_KERNEL && PROC_FS
1048 If you say Y here, additional code will be inserted into the
1049 scheduler and related routines to collect statistics about
1050 scheduler behavior and provide them in /proc/schedstat. These
1051 stats may be useful for both tuning and debugging the scheduler
1052 If you aren't debugging the scheduler or trying to tune a specific
1053 application, you can say N to avoid the very slight overhead
1056 config SCHED_STACK_END_CHECK
1057 bool "Detect stack corruption on calls to schedule()"
1058 depends on DEBUG_KERNEL
1061 This option checks for a stack overrun on calls to schedule().
1062 If the stack end location is found to be over written always panic as
1063 the content of the corrupted region can no longer be trusted.
1064 This is to ensure no erroneous behaviour occurs which could result in
1065 data corruption or a sporadic crash at a later stage once the region
1066 is examined. The runtime overhead introduced is minimal.
1068 config DEBUG_TIMEKEEPING
1069 bool "Enable extra timekeeping sanity checking"
1071 This option will enable additional timekeeping sanity checks
1072 which may be helpful when diagnosing issues where timekeeping
1073 problems are suspected.
1075 This may include checks in the timekeeping hotpaths, so this
1076 option may have a (very small) performance impact to some
1081 config DEBUG_PREEMPT
1082 bool "Debug preemptible kernel"
1083 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1086 If you say Y here then the kernel will use a debug variant of the
1087 commonly used smp_processor_id() function and will print warnings
1088 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1089 will detect preemption count underflows.
1091 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1093 config LOCK_DEBUGGING_SUPPORT
1095 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1098 config PROVE_LOCKING
1099 bool "Lock debugging: prove locking correctness"
1100 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1102 select DEBUG_SPINLOCK
1103 select DEBUG_MUTEXES
1104 select DEBUG_RT_MUTEXES if RT_MUTEXES
1105 select DEBUG_RWSEMS if RWSEM_SPIN_ON_OWNER
1106 select DEBUG_WW_MUTEX_SLOWPATH
1107 select DEBUG_LOCK_ALLOC
1108 select TRACE_IRQFLAGS
1111 This feature enables the kernel to prove that all locking
1112 that occurs in the kernel runtime is mathematically
1113 correct: that under no circumstance could an arbitrary (and
1114 not yet triggered) combination of observed locking
1115 sequences (on an arbitrary number of CPUs, running an
1116 arbitrary number of tasks and interrupt contexts) cause a
1119 In short, this feature enables the kernel to report locking
1120 related deadlocks before they actually occur.
1122 The proof does not depend on how hard and complex a
1123 deadlock scenario would be to trigger: how many
1124 participant CPUs, tasks and irq-contexts would be needed
1125 for it to trigger. The proof also does not depend on
1126 timing: if a race and a resulting deadlock is possible
1127 theoretically (no matter how unlikely the race scenario
1128 is), it will be proven so and will immediately be
1129 reported by the kernel (once the event is observed that
1130 makes the deadlock theoretically possible).
1132 If a deadlock is impossible (i.e. the locking rules, as
1133 observed by the kernel, are mathematically correct), the
1134 kernel reports nothing.
1136 NOTE: this feature can also be enabled for rwlocks, mutexes
1137 and rwsems - in which case all dependencies between these
1138 different locking variants are observed and mapped too, and
1139 the proof of observed correctness is also maintained for an
1140 arbitrary combination of these separate locking variants.
1142 For more details, see Documentation/locking/lockdep-design.txt.
1145 bool "Lock usage statistics"
1146 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1148 select DEBUG_SPINLOCK
1149 select DEBUG_MUTEXES
1150 select DEBUG_RT_MUTEXES if RT_MUTEXES
1151 select DEBUG_LOCK_ALLOC
1154 This feature enables tracking lock contention points
1156 For more details, see Documentation/locking/lockstat.txt
1158 This also enables lock events required by "perf lock",
1160 If you want to use "perf lock", you also need to turn on
1161 CONFIG_EVENT_TRACING.
1163 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1164 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1166 config DEBUG_RT_MUTEXES
1167 bool "RT Mutex debugging, deadlock detection"
1168 depends on DEBUG_KERNEL && RT_MUTEXES
1170 This allows rt mutex semantics violations and rt mutex related
1171 deadlocks (lockups) to be detected and reported automatically.
1173 config DEBUG_SPINLOCK
1174 bool "Spinlock and rw-lock debugging: basic checks"
1175 depends on DEBUG_KERNEL
1176 select UNINLINE_SPIN_UNLOCK
1178 Say Y here and build SMP to catch missing spinlock initialization
1179 and certain other kinds of spinlock errors commonly made. This is
1180 best used in conjunction with the NMI watchdog so that spinlock
1181 deadlocks are also debuggable.
1183 config DEBUG_MUTEXES
1184 bool "Mutex debugging: basic checks"
1185 depends on DEBUG_KERNEL
1187 This feature allows mutex semantics violations to be detected and
1190 config DEBUG_WW_MUTEX_SLOWPATH
1191 bool "Wait/wound mutex debugging: Slowpath testing"
1192 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1193 select DEBUG_LOCK_ALLOC
1194 select DEBUG_SPINLOCK
1195 select DEBUG_MUTEXES
1197 This feature enables slowpath testing for w/w mutex users by
1198 injecting additional -EDEADLK wound/backoff cases. Together with
1199 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1200 will test all possible w/w mutex interface abuse with the
1201 exception of simply not acquiring all the required locks.
1202 Note that this feature can introduce significant overhead, so
1203 it really should not be enabled in a production or distro kernel,
1204 even a debug kernel. If you are a driver writer, enable it. If
1205 you are a distro, do not.
1208 bool "RW Semaphore debugging: basic checks"
1209 depends on DEBUG_KERNEL && RWSEM_SPIN_ON_OWNER
1211 This debugging feature allows mismatched rw semaphore locks and unlocks
1212 to be detected and reported.
1214 config DEBUG_LOCK_ALLOC
1215 bool "Lock debugging: detect incorrect freeing of live locks"
1216 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1217 select DEBUG_SPINLOCK
1218 select DEBUG_MUTEXES
1219 select DEBUG_RT_MUTEXES if RT_MUTEXES
1222 This feature will check whether any held lock (spinlock, rwlock,
1223 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1224 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1225 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1226 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1227 held during task exit.
1231 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1233 select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86
1237 config LOCKDEP_SMALL
1240 config DEBUG_LOCKDEP
1241 bool "Lock dependency engine debugging"
1242 depends on DEBUG_KERNEL && LOCKDEP
1244 If you say Y here, the lock dependency engine will do
1245 additional runtime checks to debug itself, at the price
1246 of more runtime overhead.
1248 config DEBUG_ATOMIC_SLEEP
1249 bool "Sleep inside atomic section checking"
1250 select PREEMPT_COUNT
1251 depends on DEBUG_KERNEL
1252 depends on !ARCH_NO_PREEMPT
1254 If you say Y here, various routines which may sleep will become very
1255 noisy if they are called inside atomic sections: when a spinlock is
1256 held, inside an rcu read side critical section, inside preempt disabled
1257 sections, inside an interrupt, etc...
1259 config DEBUG_LOCKING_API_SELFTESTS
1260 bool "Locking API boot-time self-tests"
1261 depends on DEBUG_KERNEL
1263 Say Y here if you want the kernel to run a short self-test during
1264 bootup. The self-test checks whether common types of locking bugs
1265 are detected by debugging mechanisms or not. (if you disable
1266 lock debugging then those bugs wont be detected of course.)
1267 The following locking APIs are covered: spinlocks, rwlocks,
1270 config LOCK_TORTURE_TEST
1271 tristate "torture tests for locking"
1272 depends on DEBUG_KERNEL
1275 This option provides a kernel module that runs torture tests
1276 on kernel locking primitives. The kernel module may be built
1277 after the fact on the running kernel to be tested, if desired.
1279 Say Y here if you want kernel locking-primitive torture tests
1280 to be built into the kernel.
1281 Say M if you want these torture tests to build as a module.
1282 Say N if you are unsure.
1284 config WW_MUTEX_SELFTEST
1285 tristate "Wait/wound mutex selftests"
1287 This option provides a kernel module that runs tests on the
1288 on the struct ww_mutex locking API.
1290 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1291 with this test harness.
1293 Say M if you want these self tests to build as a module.
1294 Say N if you are unsure.
1296 endmenu # lock debugging
1298 config TRACE_IRQFLAGS
1301 Enables hooks to interrupt enabling and disabling for
1302 either tracing or lock debugging.
1305 bool "Stack backtrace support"
1306 depends on STACKTRACE_SUPPORT
1308 This option causes the kernel to create a /proc/pid/stack for
1309 every process, showing its current stack trace.
1310 It is also used by various kernel debugging features that require
1311 stack trace generation.
1313 config WARN_ALL_UNSEEDED_RANDOM
1314 bool "Warn for all uses of unseeded randomness"
1317 Some parts of the kernel contain bugs relating to their use of
1318 cryptographically secure random numbers before it's actually possible
1319 to generate those numbers securely. This setting ensures that these
1320 flaws don't go unnoticed, by enabling a message, should this ever
1321 occur. This will allow people with obscure setups to know when things
1322 are going wrong, so that they might contact developers about fixing
1325 Unfortunately, on some models of some architectures getting
1326 a fully seeded CRNG is extremely difficult, and so this can
1327 result in dmesg getting spammed for a surprisingly long
1328 time. This is really bad from a security perspective, and
1329 so architecture maintainers really need to do what they can
1330 to get the CRNG seeded sooner after the system is booted.
1331 However, since users cannot do anything actionable to
1332 address this, by default the kernel will issue only a single
1333 warning for the first use of unseeded randomness.
1335 Say Y here if you want to receive warnings for all uses of
1336 unseeded randomness. This will be of use primarily for
1337 those developers interested in improving the security of
1338 Linux kernels running on their architecture (or
1341 config DEBUG_KOBJECT
1342 bool "kobject debugging"
1343 depends on DEBUG_KERNEL
1345 If you say Y here, some extra kobject debugging messages will be sent
1348 config DEBUG_KOBJECT_RELEASE
1349 bool "kobject release debugging"
1350 depends on DEBUG_OBJECTS_TIMERS
1352 kobjects are reference counted objects. This means that their
1353 last reference count put is not predictable, and the kobject can
1354 live on past the point at which a driver decides to drop it's
1355 initial reference to the kobject gained on allocation. An
1356 example of this would be a struct device which has just been
1359 However, some buggy drivers assume that after such an operation,
1360 the memory backing the kobject can be immediately freed. This
1361 goes completely against the principles of a refcounted object.
1363 If you say Y here, the kernel will delay the release of kobjects
1364 on the last reference count to improve the visibility of this
1365 kind of kobject release bug.
1367 config HAVE_DEBUG_BUGVERBOSE
1370 config DEBUG_BUGVERBOSE
1371 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1372 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1375 Say Y here to make BUG() panics output the file name and line number
1376 of the BUG call as well as the EIP and oops trace. This aids
1377 debugging but costs about 70-100K of memory.
1380 bool "Debug linked list manipulation"
1381 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1383 Enable this to turn on extended checks in the linked-list
1389 bool "Debug priority linked list manipulation"
1390 depends on DEBUG_KERNEL
1392 Enable this to turn on extended checks in the priority-ordered
1393 linked-list (plist) walking routines. This checks the entire
1394 list multiple times during each manipulation.
1399 bool "Debug SG table operations"
1400 depends on DEBUG_KERNEL
1402 Enable this to turn on checks on scatter-gather tables. This can
1403 help find problems with drivers that do not properly initialize
1408 config DEBUG_NOTIFIERS
1409 bool "Debug notifier call chains"
1410 depends on DEBUG_KERNEL
1412 Enable this to turn on sanity checking for notifier call chains.
1413 This is most useful for kernel developers to make sure that
1414 modules properly unregister themselves from notifier chains.
1415 This is a relatively cheap check but if you care about maximum
1418 config DEBUG_CREDENTIALS
1419 bool "Debug credential management"
1420 depends on DEBUG_KERNEL
1422 Enable this to turn on some debug checking for credential
1423 management. The additional code keeps track of the number of
1424 pointers from task_structs to any given cred struct, and checks to
1425 see that this number never exceeds the usage count of the cred
1428 Furthermore, if SELinux is enabled, this also checks that the
1429 security pointer in the cred struct is never seen to be invalid.
1433 source "kernel/rcu/Kconfig.debug"
1435 config DEBUG_WQ_FORCE_RR_CPU
1436 bool "Force round-robin CPU selection for unbound work items"
1437 depends on DEBUG_KERNEL
1440 Workqueue used to implicitly guarantee that work items queued
1441 without explicit CPU specified are put on the local CPU. This
1442 guarantee is no longer true and while local CPU is still
1443 preferred work items may be put on foreign CPUs. Kernel
1444 parameter "workqueue.debug_force_rr_cpu" is added to force
1445 round-robin CPU selection to flush out usages which depend on the
1446 now broken guarantee. This config option enables the debug
1447 feature by default. When enabled, memory and cache locality will
1450 config DEBUG_BLOCK_EXT_DEVT
1451 bool "Force extended block device numbers and spread them"
1452 depends on DEBUG_KERNEL
1456 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1457 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1458 YOU ARE DOING. Distros, please enable this and fix whatever
1461 Conventionally, block device numbers are allocated from
1462 predetermined contiguous area. However, extended block area
1463 may introduce non-contiguous block device numbers. This
1464 option forces most block device numbers to be allocated from
1465 the extended space and spreads them to discover kernel or
1466 userland code paths which assume predetermined contiguous
1467 device number allocation.
1469 Note that turning on this debug option shuffles all the
1470 device numbers for all IDE and SCSI devices including libata
1471 ones, so root partition specified using device number
1472 directly (via rdev or root=MAJ:MIN) won't work anymore.
1473 Textual device names (root=/dev/sdXn) will continue to work.
1475 Say N if you are unsure.
1477 config CPU_HOTPLUG_STATE_CONTROL
1478 bool "Enable CPU hotplug state control"
1479 depends on DEBUG_KERNEL
1480 depends on HOTPLUG_CPU
1483 Allows to write steps between "offline" and "online" to the CPUs
1484 sysfs target file so states can be stepped granular. This is a debug
1485 option for now as the hotplug machinery cannot be stopped and
1486 restarted at arbitrary points yet.
1488 Say N if your are unsure.
1490 config NOTIFIER_ERROR_INJECTION
1491 tristate "Notifier error injection"
1492 depends on DEBUG_KERNEL
1495 This option provides the ability to inject artificial errors to
1496 specified notifier chain callbacks. It is useful to test the error
1497 handling of notifier call chain failures.
1501 config PM_NOTIFIER_ERROR_INJECT
1502 tristate "PM notifier error injection module"
1503 depends on PM && NOTIFIER_ERROR_INJECTION
1504 default m if PM_DEBUG
1506 This option provides the ability to inject artificial errors to
1507 PM notifier chain callbacks. It is controlled through debugfs
1508 interface /sys/kernel/debug/notifier-error-inject/pm
1510 If the notifier call chain should be failed with some events
1511 notified, write the error code to "actions/<notifier event>/error".
1513 Example: Inject PM suspend error (-12 = -ENOMEM)
1515 # cd /sys/kernel/debug/notifier-error-inject/pm/
1516 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1517 # echo mem > /sys/power/state
1518 bash: echo: write error: Cannot allocate memory
1520 To compile this code as a module, choose M here: the module will
1521 be called pm-notifier-error-inject.
1525 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1526 tristate "OF reconfig notifier error injection module"
1527 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1529 This option provides the ability to inject artificial errors to
1530 OF reconfig notifier chain callbacks. It is controlled
1531 through debugfs interface under
1532 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1534 If the notifier call chain should be failed with some events
1535 notified, write the error code to "actions/<notifier event>/error".
1537 To compile this code as a module, choose M here: the module will
1538 be called of-reconfig-notifier-error-inject.
1542 config NETDEV_NOTIFIER_ERROR_INJECT
1543 tristate "Netdev notifier error injection module"
1544 depends on NET && NOTIFIER_ERROR_INJECTION
1546 This option provides the ability to inject artificial errors to
1547 netdevice notifier chain callbacks. It is controlled through debugfs
1548 interface /sys/kernel/debug/notifier-error-inject/netdev
1550 If the notifier call chain should be failed with some events
1551 notified, write the error code to "actions/<notifier event>/error".
1553 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1555 # cd /sys/kernel/debug/notifier-error-inject/netdev
1556 # echo -22 > actions/NETDEV_CHANGEMTU/error
1557 # ip link set eth0 mtu 1024
1558 RTNETLINK answers: Invalid argument
1560 To compile this code as a module, choose M here: the module will
1561 be called netdev-notifier-error-inject.
1565 config FUNCTION_ERROR_INJECTION
1567 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
1569 config FAULT_INJECTION
1570 bool "Fault-injection framework"
1571 depends on DEBUG_KERNEL
1573 Provide fault-injection framework.
1574 For more details, see Documentation/fault-injection/.
1577 bool "Fault-injection capability for kmalloc"
1578 depends on FAULT_INJECTION
1579 depends on SLAB || SLUB
1581 Provide fault-injection capability for kmalloc.
1583 config FAIL_PAGE_ALLOC
1584 bool "Fault-injection capabilitiy for alloc_pages()"
1585 depends on FAULT_INJECTION
1587 Provide fault-injection capability for alloc_pages().
1589 config FAIL_MAKE_REQUEST
1590 bool "Fault-injection capability for disk IO"
1591 depends on FAULT_INJECTION && BLOCK
1593 Provide fault-injection capability for disk IO.
1595 config FAIL_IO_TIMEOUT
1596 bool "Fault-injection capability for faking disk interrupts"
1597 depends on FAULT_INJECTION && BLOCK
1599 Provide fault-injection capability on end IO handling. This
1600 will make the block layer "forget" an interrupt as configured,
1601 thus exercising the error handling.
1603 Only works with drivers that use the generic timeout handling,
1604 for others it wont do anything.
1607 bool "Fault-injection capability for futexes"
1609 depends on FAULT_INJECTION && FUTEX
1611 Provide fault-injection capability for futexes.
1613 config FAULT_INJECTION_DEBUG_FS
1614 bool "Debugfs entries for fault-injection capabilities"
1615 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1617 Enable configuration of fault-injection capabilities via debugfs.
1619 config FAIL_FUNCTION
1620 bool "Fault-injection capability for functions"
1621 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
1623 Provide function-based fault-injection capability.
1624 This will allow you to override a specific function with a return
1625 with given return value. As a result, function caller will see
1626 an error value and have to handle it. This is useful to test the
1627 error handling in various subsystems.
1629 config FAIL_MMC_REQUEST
1630 bool "Fault-injection capability for MMC IO"
1631 depends on FAULT_INJECTION_DEBUG_FS && MMC
1633 Provide fault-injection capability for MMC IO.
1634 This will make the mmc core return data errors. This is
1635 useful to test the error handling in the mmc block device
1636 and to test how the mmc host driver handles retries from
1639 config FAULT_INJECTION_STACKTRACE_FILTER
1640 bool "stacktrace filter for fault-injection capabilities"
1641 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1644 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1646 Provide stacktrace filter for fault-injection capabilities
1649 bool "Latency measuring infrastructure"
1650 depends on DEBUG_KERNEL
1651 depends on STACKTRACE_SUPPORT
1653 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1660 Enable this option if you want to use the LatencyTOP tool
1661 to find out which userspace is blocking on what kernel operations.
1663 source "kernel/trace/Kconfig"
1665 config PROVIDE_OHCI1394_DMA_INIT
1666 bool "Remote debugging over FireWire early on boot"
1667 depends on PCI && X86
1669 If you want to debug problems which hang or crash the kernel early
1670 on boot and the crashing machine has a FireWire port, you can use
1671 this feature to remotely access the memory of the crashed machine
1672 over FireWire. This employs remote DMA as part of the OHCI1394
1673 specification which is now the standard for FireWire controllers.
1675 With remote DMA, you can monitor the printk buffer remotely using
1676 firescope and access all memory below 4GB using fireproxy from gdb.
1677 Even controlling a kernel debugger is possible using remote DMA.
1681 If ohci1394_dma=early is used as boot parameter, it will initialize
1682 all OHCI1394 controllers which are found in the PCI config space.
1684 As all changes to the FireWire bus such as enabling and disabling
1685 devices cause a bus reset and thereby disable remote DMA for all
1686 devices, be sure to have the cable plugged and FireWire enabled on
1687 the debugging host before booting the debug target for debugging.
1689 This code (~1k) is freed after boot. By then, the firewire stack
1690 in charge of the OHCI-1394 controllers should be used instead.
1692 See Documentation/debugging-via-ohci1394.txt for more information.
1694 menuconfig RUNTIME_TESTING_MENU
1695 bool "Runtime Testing"
1698 if RUNTIME_TESTING_MENU
1701 tristate "Linux Kernel Dump Test Tool Module"
1704 This module enables testing of the different dumping mechanisms by
1705 inducing system failures at predefined crash points.
1706 If you don't need it: say N
1707 Choose M here to compile this code as a module. The module will be
1710 Documentation on how to use the module can be found in
1711 Documentation/fault-injection/provoke-crashes.txt
1713 config TEST_LIST_SORT
1714 tristate "Linked list sorting test"
1715 depends on DEBUG_KERNEL || m
1717 Enable this to turn on 'list_sort()' function test. This test is
1718 executed only once during system boot (so affects only boot time),
1719 or at module load time.
1724 tristate "Array-based sort test"
1725 depends on DEBUG_KERNEL || m
1727 This option enables the self-test function of 'sort()' at boot,
1728 or at module load time.
1732 config KPROBES_SANITY_TEST
1733 bool "Kprobes sanity tests"
1734 depends on DEBUG_KERNEL
1737 This option provides for testing basic kprobes functionality on
1738 boot. Samples of kprobe and kretprobe are inserted and
1739 verified for functionality.
1741 Say N if you are unsure.
1743 config BACKTRACE_SELF_TEST
1744 tristate "Self test for the backtrace code"
1745 depends on DEBUG_KERNEL
1747 This option provides a kernel module that can be used to test
1748 the kernel stack backtrace code. This option is not useful
1749 for distributions or general kernels, but only for kernel
1750 developers working on architecture code.
1752 Note that if you want to also test saved backtraces, you will
1753 have to enable STACKTRACE as well.
1755 Say N if you are unsure.
1758 tristate "Red-Black tree test"
1759 depends on DEBUG_KERNEL
1761 A benchmark measuring the performance of the rbtree library.
1762 Also includes rbtree invariant checks.
1764 config INTERVAL_TREE_TEST
1765 tristate "Interval tree test"
1766 depends on DEBUG_KERNEL
1767 select INTERVAL_TREE
1769 A benchmark measuring the performance of the interval tree library
1772 tristate "Per cpu operations test"
1773 depends on m && DEBUG_KERNEL
1775 Enable this option to build test module which validates per-cpu
1780 config ATOMIC64_SELFTEST
1781 tristate "Perform an atomic64_t self-test"
1783 Enable this option to test the atomic64_t functions at boot or
1784 at module load time.
1788 config ASYNC_RAID6_TEST
1789 tristate "Self test for hardware accelerated raid6 recovery"
1790 depends on ASYNC_RAID6_RECOV
1793 This is a one-shot self test that permutes through the
1794 recovery of all the possible two disk failure scenarios for a
1795 N-disk array. Recovery is performed with the asynchronous
1796 raid6 recovery routines, and will optionally use an offload
1797 engine if one is available.
1802 tristate "Test functions located in the hexdump module at runtime"
1804 config TEST_STRING_HELPERS
1805 tristate "Test functions located in the string_helpers module at runtime"
1808 tristate "Test strscpy*() family of functions at runtime"
1811 tristate "Test kstrto*() family of functions at runtime"
1814 tristate "Test printf() family of functions at runtime"
1817 tristate "Test bitmap_*() family of functions at runtime"
1819 Enable this option to test the bitmap functions at boot.
1823 config TEST_BITFIELD
1824 tristate "Test bitfield functions at runtime"
1826 Enable this option to test the bitfield functions at boot.
1831 tristate "Test functions located in the uuid module at runtime"
1834 tristate "Test the XArray code at runtime"
1836 config TEST_OVERFLOW
1837 tristate "Test check_*_overflow() functions at runtime"
1839 config TEST_RHASHTABLE
1840 tristate "Perform selftest on resizable hash table"
1842 Enable this option to test the rhashtable functions at boot.
1847 tristate "Perform selftest on hash functions"
1849 Enable this option to test the kernel's integer (<linux/hash.h>),
1850 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1851 hash functions on boot (or module load).
1853 This is intended to help people writing architecture-specific
1854 optimized versions. If unsure, say N.
1857 tristate "Perform selftest on IDA functions"
1860 tristate "Perform selftest on priority array manager"
1863 Enable this option to test priority array manager on boot
1869 tristate "Test module loading with 'hello world' module"
1872 This builds the "test_module" module that emits "Hello, world"
1873 on printk when loaded. It is designed to be used for basic
1874 evaluation of the module loading subsystem (for example when
1875 validating module verification). It lacks any extra dependencies,
1876 and will not normally be loaded by the system unless explicitly
1882 tristate "Test module for stress/performance analysis of vmalloc allocator"
1887 This builds the "test_vmalloc" module that should be used for
1888 stress and performance analysis. So, any new change for vmalloc
1889 subsystem can be evaluated from performance and stability point
1894 config TEST_USER_COPY
1895 tristate "Test user/kernel boundary protections"
1898 This builds the "test_user_copy" module that runs sanity checks
1899 on the copy_to/from_user infrastructure, making sure basic
1900 user/kernel boundary testing is working. If it fails to load,
1901 a regression has been detected in the user/kernel memory boundary
1907 tristate "Test BPF filter functionality"
1910 This builds the "test_bpf" module that runs various test vectors
1911 against the BPF interpreter or BPF JIT compiler depending on the
1912 current setting. This is in particular useful for BPF JIT compiler
1913 development, but also to run regression tests against changes in
1914 the interpreter code. It also enables test stubs for eBPF maps and
1915 verifier used by user space verifier testsuite.
1919 config FIND_BIT_BENCHMARK
1920 tristate "Test find_bit functions"
1922 This builds the "test_find_bit" module that measure find_*_bit()
1923 functions performance.
1927 config TEST_FIRMWARE
1928 tristate "Test firmware loading via userspace interface"
1929 depends on FW_LOADER
1931 This builds the "test_firmware" module that creates a userspace
1932 interface for testing firmware loading. This can be used to
1933 control the triggering of firmware loading without needing an
1934 actual firmware-using device. The contents can be rechecked by
1940 tristate "sysctl test driver"
1941 depends on PROC_SYSCTL
1943 This builds the "test_sysctl" module. This driver enables to test the
1944 proc sysctl interfaces available to drivers safely without affecting
1945 production knobs which might alter system functionality.
1950 tristate "udelay test driver"
1952 This builds the "udelay_test" module that helps to make sure
1953 that udelay() is working properly.
1957 config TEST_STATIC_KEYS
1958 tristate "Test static keys"
1961 Test the static key interfaces.
1966 tristate "kmod stress tester"
1968 depends on NETDEVICES && NET_CORE && INET # for TUN
1975 Test the kernel's module loading mechanism: kmod. kmod implements
1976 support to load modules using the Linux kernel's usermode helper.
1977 This test provides a series of tests against kmod.
1979 Although technically you can either build test_kmod as a module or
1980 into the kernel we disallow building it into the kernel since
1981 it stress tests request_module() and this will very likely cause
1982 some issues by taking over precious threads available from other
1983 module load requests, ultimately this could be fatal.
1987 tools/testing/selftests/kmod/kmod.sh --help
1991 config TEST_DEBUG_VIRTUAL
1992 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
1993 depends on DEBUG_VIRTUAL
1995 Test the kernel's ability to detect incorrect calls to
1996 virt_to_phys() done against the non-linear part of the
1997 kernel's virtual address map.
2001 config TEST_MEMCAT_P
2002 tristate "Test memcat_p() helper function"
2004 Test the memcat_p() helper for correctly merging two
2005 pointer arrays together.
2009 config TEST_LIVEPATCH
2010 tristate "Test livepatching"
2012 depends on DYNAMIC_DEBUG
2013 depends on LIVEPATCH
2016 Test kernel livepatching features for correctness. The tests will
2017 load test modules that will be livepatched in various scenarios.
2019 To run all the livepatching tests:
2021 make -C tools/testing/selftests TARGETS=livepatch run_tests
2023 Alternatively, individual tests may be invoked:
2025 tools/testing/selftests/livepatch/test-callbacks.sh
2026 tools/testing/selftests/livepatch/test-livepatch.sh
2027 tools/testing/selftests/livepatch/test-shadow-vars.sh
2032 tristate "Perform selftest on object aggreration manager"
2036 Enable this option to test object aggregation manager on boot
2040 config TEST_STACKINIT
2041 tristate "Test level of stack variable initialization"
2043 Test if the kernel is zero-initializing stack variables and
2044 padding. Coverage is controlled by compiler flags,
2045 CONFIG_GCC_PLUGIN_STRUCTLEAK, CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF,
2046 or CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL.
2050 endif # RUNTIME_TESTING_MENU
2055 This option adds a kernel parameter 'memtest', which allows memtest
2057 memtest=0, mean disabled; -- default
2058 memtest=1, mean do 1 test pattern;
2060 memtest=17, mean do 17 test patterns.
2061 If you are unsure how to answer this question, answer N.
2063 config BUG_ON_DATA_CORRUPTION
2064 bool "Trigger a BUG when data corruption is detected"
2067 Select this option if the kernel should BUG when it encounters
2068 data corruption in kernel memory structures when they get checked
2073 source "samples/Kconfig"
2075 source "lib/Kconfig.kgdb"
2077 source "lib/Kconfig.ubsan"
2079 config ARCH_HAS_DEVMEM_IS_ALLOWED
2082 config STRICT_DEVMEM
2083 bool "Filter access to /dev/mem"
2084 depends on MMU && DEVMEM
2085 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
2086 default y if PPC || X86 || ARM64
2088 If this option is disabled, you allow userspace (root) access to all
2089 of memory, including kernel and userspace memory. Accidental
2090 access to this is obviously disastrous, but specific access can
2091 be used by people debugging the kernel. Note that with PAT support
2092 enabled, even in this case there are restrictions on /dev/mem
2093 use due to the cache aliasing requirements.
2095 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
2096 file only allows userspace access to PCI space and the BIOS code and
2097 data regions. This is sufficient for dosemu and X and all common
2102 config IO_STRICT_DEVMEM
2103 bool "Filter I/O access to /dev/mem"
2104 depends on STRICT_DEVMEM
2106 If this option is disabled, you allow userspace (root) access to all
2107 io-memory regardless of whether a driver is actively using that
2108 range. Accidental access to this is obviously disastrous, but
2109 specific access can be used by people debugging kernel drivers.
2111 If this option is switched on, the /dev/mem file only allows
2112 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2113 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2114 if the driver using a given range cannot be disabled.
2118 source "arch/$(SRCARCH)/Kconfig.debug"
2120 endmenu # Kernel hacking
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