3 menu "printk and dmesg options"
6 bool "Show timing information on printks"
9 Selecting this option causes time stamps of the printk()
10 messages to be added to the output of the syslog() system
11 call and at the console.
13 The timestamp is always recorded internally, and exported
14 to /dev/kmsg. This flag just specifies if the timestamp should
15 be included, not that the timestamp is recorded.
17 The behavior is also controlled by the kernel command line
18 parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst
21 bool "Show caller information on printks"
24 Selecting this option causes printk() to add a caller "thread id" (if
25 in task context) or a caller "processor id" (if not in task context)
28 This option is intended for environments where multiple threads
29 concurrently call printk() for many times, for it is difficult to
30 interpret without knowing where these lines (or sometimes individual
31 line which was divided into multiple lines due to race) came from.
33 Since toggling after boot makes the code racy, currently there is
34 no option to enable/disable at the kernel command line parameter or
37 config CONSOLE_LOGLEVEL_DEFAULT
38 int "Default console loglevel (1-15)"
42 Default loglevel to determine what will be printed on the console.
44 Setting a default here is equivalent to passing in loglevel=<x> in
45 the kernel bootargs. loglevel=<x> continues to override whatever
46 value is specified here as well.
48 Note: This does not affect the log level of un-prefixed printk()
49 usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
52 config CONSOLE_LOGLEVEL_QUIET
53 int "quiet console loglevel (1-15)"
57 loglevel to use when "quiet" is passed on the kernel commandline.
59 When "quiet" is passed on the kernel commandline this loglevel
60 will be used as the loglevel. IOW passing "quiet" will be the
61 equivalent of passing "loglevel=<CONSOLE_LOGLEVEL_QUIET>"
63 config MESSAGE_LOGLEVEL_DEFAULT
64 int "Default message log level (1-7)"
68 Default log level for printk statements with no specified priority.
70 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
71 that are auditing their logs closely may want to set it to a lower
74 Note: This does not affect what message level gets printed on the console
75 by default. To change that, use loglevel=<x> in the kernel bootargs,
76 or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value.
78 config BOOT_PRINTK_DELAY
79 bool "Delay each boot printk message by N milliseconds"
80 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
82 This build option allows you to read kernel boot messages
83 by inserting a short delay after each one. The delay is
84 specified in milliseconds on the kernel command line,
87 It is likely that you would also need to use "lpj=M" to preset
88 the "loops per jiffie" value.
89 See a previous boot log for the "lpj" value to use for your
90 system, and then set "lpj=M" before setting "boot_delay=N".
91 NOTE: Using this option may adversely affect SMP systems.
92 I.e., processors other than the first one may not boot up.
93 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
94 what it believes to be lockup conditions.
97 bool "Enable dynamic printk() support"
103 Compiles debug level messages into the kernel, which would not
104 otherwise be available at runtime. These messages can then be
105 enabled/disabled based on various levels of scope - per source file,
106 function, module, format string, and line number. This mechanism
107 implicitly compiles in all pr_debug() and dev_dbg() calls, which
108 enlarges the kernel text size by about 2%.
110 If a source file is compiled with DEBUG flag set, any
111 pr_debug() calls in it are enabled by default, but can be
112 disabled at runtime as below. Note that DEBUG flag is
113 turned on by many CONFIG_*DEBUG* options.
117 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
118 which is contained in the 'debugfs' filesystem. Thus, the debugfs
119 filesystem must first be mounted before making use of this feature.
120 We refer the control file as: <debugfs>/dynamic_debug/control. This
121 file contains a list of the debug statements that can be enabled. The
122 format for each line of the file is:
124 filename:lineno [module]function flags format
126 filename : source file of the debug statement
127 lineno : line number of the debug statement
128 module : module that contains the debug statement
129 function : function that contains the debug statement
130 flags : '=p' means the line is turned 'on' for printing
131 format : the format used for the debug statement
135 nullarbor:~ # cat <debugfs>/dynamic_debug/control
136 # filename:lineno [module]function flags format
137 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
138 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
139 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
143 // enable the message at line 1603 of file svcsock.c
144 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
145 <debugfs>/dynamic_debug/control
147 // enable all the messages in file svcsock.c
148 nullarbor:~ # echo -n 'file svcsock.c +p' >
149 <debugfs>/dynamic_debug/control
151 // enable all the messages in the NFS server module
152 nullarbor:~ # echo -n 'module nfsd +p' >
153 <debugfs>/dynamic_debug/control
155 // enable all 12 messages in the function svc_process()
156 nullarbor:~ # echo -n 'func svc_process +p' >
157 <debugfs>/dynamic_debug/control
159 // disable all 12 messages in the function svc_process()
160 nullarbor:~ # echo -n 'func svc_process -p' >
161 <debugfs>/dynamic_debug/control
163 See Documentation/admin-guide/dynamic-debug-howto.rst for additional
166 endmenu # "printk and dmesg options"
168 menu "Compile-time checks and compiler options"
171 bool "Compile the kernel with debug info"
172 depends on DEBUG_KERNEL && !COMPILE_TEST
174 If you say Y here the resulting kernel image will include
175 debugging info resulting in a larger kernel image.
176 This adds debug symbols to the kernel and modules (gcc -g), and
177 is needed if you intend to use kernel crashdump or binary object
178 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
179 Say Y here only if you plan to debug the kernel.
183 config DEBUG_INFO_REDUCED
184 bool "Reduce debugging information"
185 depends on DEBUG_INFO
187 If you say Y here gcc is instructed to generate less debugging
188 information for structure types. This means that tools that
189 need full debugging information (like kgdb or systemtap) won't
190 be happy. But if you merely need debugging information to
191 resolve line numbers there is no loss. Advantage is that
192 build directory object sizes shrink dramatically over a full
193 DEBUG_INFO build and compile times are reduced too.
194 Only works with newer gcc versions.
196 config DEBUG_INFO_SPLIT
197 bool "Produce split debuginfo in .dwo files"
198 depends on DEBUG_INFO
199 depends on $(cc-option,-gsplit-dwarf)
201 Generate debug info into separate .dwo files. This significantly
202 reduces the build directory size for builds with DEBUG_INFO,
203 because it stores the information only once on disk in .dwo
204 files instead of multiple times in object files and executables.
205 In addition the debug information is also compressed.
207 Requires recent gcc (4.7+) and recent gdb/binutils.
208 Any tool that packages or reads debug information would need
209 to know about the .dwo files and include them.
210 Incompatible with older versions of ccache.
212 config DEBUG_INFO_DWARF4
213 bool "Generate dwarf4 debuginfo"
214 depends on DEBUG_INFO
215 depends on $(cc-option,-gdwarf-4)
217 Generate dwarf4 debug info. This requires recent versions
218 of gcc and gdb. It makes the debug information larger.
219 But it significantly improves the success of resolving
220 variables in gdb on optimized code.
222 config DEBUG_INFO_BTF
223 bool "Generate BTF typeinfo"
224 depends on DEBUG_INFO
226 Generate deduplicated BTF type information from DWARF debug info.
227 Turning this on expects presence of pahole tool, which will convert
228 DWARF type info into equivalent deduplicated BTF type info.
231 bool "Provide GDB scripts for kernel debugging"
232 depends on DEBUG_INFO
234 This creates the required links to GDB helper scripts in the
235 build directory. If you load vmlinux into gdb, the helper
236 scripts will be automatically imported by gdb as well, and
237 additional functions are available to analyze a Linux kernel
238 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
241 config ENABLE_MUST_CHECK
242 bool "Enable __must_check logic"
245 Enable the __must_check logic in the kernel build. Disable this to
246 suppress the "warning: ignoring return value of 'foo', declared with
247 attribute warn_unused_result" messages.
250 int "Warn for stack frames larger than (needs gcc 4.4)"
252 default 2048 if GCC_PLUGIN_LATENT_ENTROPY
253 default 1280 if (!64BIT && PARISC)
254 default 1024 if (!64BIT && !PARISC)
255 default 2048 if 64BIT
257 Tell gcc to warn at build time for stack frames larger than this.
258 Setting this too low will cause a lot of warnings.
259 Setting it to 0 disables the warning.
262 config STRIP_ASM_SYMS
263 bool "Strip assembler-generated symbols during link"
266 Strip internal assembler-generated symbols during a link (symbols
267 that look like '.Lxxx') so they don't pollute the output of
268 get_wchan() and suchlike.
271 bool "Generate readable assembler code"
272 depends on DEBUG_KERNEL
274 Disable some compiler optimizations that tend to generate human unreadable
275 assembler output. This may make the kernel slightly slower, but it helps
276 to keep kernel developers who have to stare a lot at assembler listings
279 config UNUSED_SYMBOLS
280 bool "Enable unused/obsolete exported symbols"
283 Unused but exported symbols make the kernel needlessly bigger. For
284 that reason most of these unused exports will soon be removed. This
285 option is provided temporarily to provide a transition period in case
286 some external kernel module needs one of these symbols anyway. If you
287 encounter such a case in your module, consider if you are actually
288 using the right API. (rationale: since nobody in the kernel is using
289 this in a module, there is a pretty good chance it's actually the
290 wrong interface to use). If you really need the symbol, please send a
291 mail to the linux kernel mailing list mentioning the symbol and why
292 you really need it, and what the merge plan to the mainline kernel for
296 bool "Debug Filesystem"
298 debugfs is a virtual file system that kernel developers use to put
299 debugging files into. Enable this option to be able to read and
300 write to these files.
302 For detailed documentation on the debugfs API, see
303 Documentation/filesystems/.
308 bool "Run 'make headers_check' when building vmlinux"
311 This option will extract the user-visible kernel headers whenever
312 building the kernel, and will run basic sanity checks on them to
313 ensure that exported files do not attempt to include files which
314 were not exported, etc.
316 If you're making modifications to header files which are
317 relevant for userspace, say 'Y', and check the headers
318 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
319 your build tree), to make sure they're suitable.
321 config OPTIMIZE_INLINING
322 bool "Allow compiler to uninline functions marked 'inline'"
324 This option determines if the kernel forces gcc to inline the functions
325 developers have marked 'inline'. Doing so takes away freedom from gcc to
326 do what it thinks is best, which is desirable for the gcc 3.x series of
327 compilers. The gcc 4.x series have a rewritten inlining algorithm and
328 enabling this option will generate a smaller kernel there. Hopefully
329 this algorithm is so good that allowing gcc 4.x and above to make the
330 decision will become the default in the future. Until then this option
331 is there to test gcc for this.
335 config DEBUG_SECTION_MISMATCH
336 bool "Enable full Section mismatch analysis"
338 The section mismatch analysis checks if there are illegal
339 references from one section to another section.
340 During linktime or runtime, some sections are dropped;
341 any use of code/data previously in these sections would
342 most likely result in an oops.
343 In the code, functions and variables are annotated with
344 __init,, etc. (see the full list in include/linux/init.h),
345 which results in the code/data being placed in specific sections.
346 The section mismatch analysis is always performed after a full
347 kernel build, and enabling this option causes the following
348 additional steps to occur:
349 - Add the option -fno-inline-functions-called-once to gcc commands.
350 When inlining a function annotated with __init in a non-init
351 function, we would lose the section information and thus
352 the analysis would not catch the illegal reference.
353 This option tells gcc to inline less (but it does result in
355 - Run the section mismatch analysis for each module/built-in.a file.
356 When we run the section mismatch analysis on vmlinux.o, we
357 lose valuable information about where the mismatch was
359 Running the analysis for each module/built-in.a file
360 tells where the mismatch happens much closer to the
361 source. The drawback is that the same mismatch is
362 reported at least twice.
363 - Enable verbose reporting from modpost in order to help resolve
364 the section mismatches that are reported.
366 config SECTION_MISMATCH_WARN_ONLY
367 bool "Make section mismatch errors non-fatal"
370 If you say N here, the build process will fail if there are any
371 section mismatch, instead of just throwing warnings.
376 # Select this config option from the architecture Kconfig, if it
377 # is preferred to always offer frame pointers as a config
378 # option on the architecture (regardless of KERNEL_DEBUG):
380 config ARCH_WANT_FRAME_POINTERS
384 bool "Compile the kernel with frame pointers"
385 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS
386 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
388 If you say Y here the resulting kernel image will be slightly
389 larger and slower, but it gives very useful debugging information
390 in case of kernel bugs. (precise oopses/stacktraces/warnings)
392 config STACK_VALIDATION
393 bool "Compile-time stack metadata validation"
394 depends on HAVE_STACK_VALIDATION
397 Add compile-time checks to validate stack metadata, including frame
398 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
399 that runtime stack traces are more reliable.
401 This is also a prerequisite for generation of ORC unwind data, which
402 is needed for CONFIG_UNWINDER_ORC.
404 For more information, see
405 tools/objtool/Documentation/stack-validation.txt.
407 config DEBUG_FORCE_WEAK_PER_CPU
408 bool "Force weak per-cpu definitions"
409 depends on DEBUG_KERNEL
411 s390 and alpha require percpu variables in modules to be
412 defined weak to work around addressing range issue which
413 puts the following two restrictions on percpu variable
416 1. percpu symbols must be unique whether static or not
417 2. percpu variables can't be defined inside a function
419 To ensure that generic code follows the above rules, this
420 option forces all percpu variables to be defined as weak.
422 endmenu # "Compiler options"
425 bool "Magic SysRq key"
428 If you say Y here, you will have some control over the system even
429 if the system crashes for example during kernel debugging (e.g., you
430 will be able to flush the buffer cache to disk, reboot the system
431 immediately or dump some status information). This is accomplished
432 by pressing various keys while holding SysRq (Alt+PrintScreen). It
433 also works on a serial console (on PC hardware at least), if you
434 send a BREAK and then within 5 seconds a command keypress. The
435 keys are documented in <file:Documentation/admin-guide/sysrq.rst>.
436 Don't say Y unless you really know what this hack does.
438 config MAGIC_SYSRQ_DEFAULT_ENABLE
439 hex "Enable magic SysRq key functions by default"
440 depends on MAGIC_SYSRQ
443 Specifies which SysRq key functions are enabled by default.
444 This may be set to 1 or 0 to enable or disable them all, or
445 to a bitmask as described in Documentation/admin-guide/sysrq.rst.
447 config MAGIC_SYSRQ_SERIAL
448 bool "Enable magic SysRq key over serial"
449 depends on MAGIC_SYSRQ
452 Many embedded boards have a disconnected TTL level serial which can
453 generate some garbage that can lead to spurious false sysrq detects.
454 This option allows you to decide whether you want to enable the
458 bool "Kernel debugging"
460 Say Y here if you are developing drivers or trying to debug and
461 identify kernel problems.
464 bool "Miscellaneous debug code"
466 depends on DEBUG_KERNEL
468 Say Y here if you need to enable miscellaneous debug code that should
469 be under a more specific debug option but isn't.
472 menu "Memory Debugging"
474 source "mm/Kconfig.debug"
477 bool "Debug object operations"
478 depends on DEBUG_KERNEL
480 If you say Y here, additional code will be inserted into the
481 kernel to track the life time of various objects and validate
482 the operations on those objects.
484 config DEBUG_OBJECTS_SELFTEST
485 bool "Debug objects selftest"
486 depends on DEBUG_OBJECTS
488 This enables the selftest of the object debug code.
490 config DEBUG_OBJECTS_FREE
491 bool "Debug objects in freed memory"
492 depends on DEBUG_OBJECTS
494 This enables checks whether a k/v free operation frees an area
495 which contains an object which has not been deactivated
496 properly. This can make kmalloc/kfree-intensive workloads
499 config DEBUG_OBJECTS_TIMERS
500 bool "Debug timer objects"
501 depends on DEBUG_OBJECTS
503 If you say Y here, additional code will be inserted into the
504 timer routines to track the life time of timer objects and
505 validate the timer operations.
507 config DEBUG_OBJECTS_WORK
508 bool "Debug work objects"
509 depends on DEBUG_OBJECTS
511 If you say Y here, additional code will be inserted into the
512 work queue routines to track the life time of work objects and
513 validate the work operations.
515 config DEBUG_OBJECTS_RCU_HEAD
516 bool "Debug RCU callbacks objects"
517 depends on DEBUG_OBJECTS
519 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
521 config DEBUG_OBJECTS_PERCPU_COUNTER
522 bool "Debug percpu counter objects"
523 depends on DEBUG_OBJECTS
525 If you say Y here, additional code will be inserted into the
526 percpu counter routines to track the life time of percpu counter
527 objects and validate the percpu counter operations.
529 config DEBUG_OBJECTS_ENABLE_DEFAULT
530 int "debug_objects bootup default value (0-1)"
533 depends on DEBUG_OBJECTS
535 Debug objects boot parameter default value
538 bool "Debug slab memory allocations"
539 depends on DEBUG_KERNEL && SLAB
541 Say Y here to have the kernel do limited verification on memory
542 allocation as well as poisoning memory on free to catch use of freed
543 memory. This can make kmalloc/kfree-intensive workloads much slower.
545 config DEBUG_SLAB_LEAK
546 bool "Memory leak debugging"
547 depends on DEBUG_SLAB
550 bool "SLUB debugging on by default"
551 depends on SLUB && SLUB_DEBUG
554 Boot with debugging on by default. SLUB boots by default with
555 the runtime debug capabilities switched off. Enabling this is
556 equivalent to specifying the "slub_debug" parameter on boot.
557 There is no support for more fine grained debug control like
558 possible with slub_debug=xxx. SLUB debugging may be switched
559 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
564 bool "Enable SLUB performance statistics"
565 depends on SLUB && SYSFS
567 SLUB statistics are useful to debug SLUBs allocation behavior in
568 order find ways to optimize the allocator. This should never be
569 enabled for production use since keeping statistics slows down
570 the allocator by a few percentage points. The slabinfo command
571 supports the determination of the most active slabs to figure
572 out which slabs are relevant to a particular load.
573 Try running: slabinfo -DA
575 config HAVE_DEBUG_KMEMLEAK
578 config DEBUG_KMEMLEAK
579 bool "Kernel memory leak detector"
580 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
582 select STACKTRACE if STACKTRACE_SUPPORT
586 Say Y here if you want to enable the memory leak
587 detector. The memory allocation/freeing is traced in a way
588 similar to the Boehm's conservative garbage collector, the
589 difference being that the orphan objects are not freed but
590 only shown in /sys/kernel/debug/kmemleak. Enabling this
591 feature will introduce an overhead to memory
592 allocations. See Documentation/dev-tools/kmemleak.rst for more
595 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
596 of finding leaks due to the slab objects poisoning.
598 In order to access the kmemleak file, debugfs needs to be
599 mounted (usually at /sys/kernel/debug).
601 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
602 int "Maximum kmemleak early log entries"
603 depends on DEBUG_KMEMLEAK
607 Kmemleak must track all the memory allocations to avoid
608 reporting false positives. Since memory may be allocated or
609 freed before kmemleak is initialised, an early log buffer is
610 used to store these actions. If kmemleak reports "early log
611 buffer exceeded", please increase this value.
613 config DEBUG_KMEMLEAK_TEST
614 tristate "Simple test for the kernel memory leak detector"
615 depends on DEBUG_KMEMLEAK && m
617 This option enables a module that explicitly leaks memory.
621 config DEBUG_KMEMLEAK_DEFAULT_OFF
622 bool "Default kmemleak to off"
623 depends on DEBUG_KMEMLEAK
625 Say Y here to disable kmemleak by default. It can then be enabled
626 on the command line via kmemleak=on.
628 config DEBUG_KMEMLEAK_AUTO_SCAN
629 bool "Enable kmemleak auto scan thread on boot up"
631 depends on DEBUG_KMEMLEAK
633 Depending on the cpu, kmemleak scan may be cpu intensive and can
634 stall user tasks at times. This option enables/disables automatic
635 kmemleak scan at boot up.
637 Say N here to disable kmemleak auto scan thread to stop automatic
638 scanning. Disabling this option disables automatic reporting of
643 config DEBUG_STACK_USAGE
644 bool "Stack utilization instrumentation"
645 depends on DEBUG_KERNEL && !IA64
647 Enables the display of the minimum amount of free stack which each
648 task has ever had available in the sysrq-T and sysrq-P debug output.
650 This option will slow down process creation somewhat.
654 depends on DEBUG_KERNEL
656 Enable this to turn on extended checks in the virtual-memory system
657 that may impact performance.
661 config DEBUG_VM_VMACACHE
662 bool "Debug VMA caching"
665 Enable this to turn on VMA caching debug information. Doing so
666 can cause significant overhead, so only enable it in non-production
672 bool "Debug VM red-black trees"
675 Enable VM red-black tree debugging information and extra validations.
679 config DEBUG_VM_PGFLAGS
680 bool "Debug page-flags operations"
683 Enables extra validation on page flags operations.
687 config ARCH_HAS_DEBUG_VIRTUAL
691 bool "Debug VM translations"
692 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
694 Enable some costly sanity checks in virtual to page code. This can
695 catch mistakes with virt_to_page() and friends.
699 config DEBUG_NOMMU_REGIONS
700 bool "Debug the global anon/private NOMMU mapping region tree"
701 depends on DEBUG_KERNEL && !MMU
703 This option causes the global tree of anonymous and private mapping
704 regions to be regularly checked for invalid topology.
706 config DEBUG_MEMORY_INIT
707 bool "Debug memory initialisation" if EXPERT
710 Enable this for additional checks during memory initialisation.
711 The sanity checks verify aspects of the VM such as the memory model
712 and other information provided by the architecture. Verbose
713 information will be printed at KERN_DEBUG loglevel depending
714 on the mminit_loglevel= command-line option.
718 config MEMORY_NOTIFIER_ERROR_INJECT
719 tristate "Memory hotplug notifier error injection module"
720 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
722 This option provides the ability to inject artificial errors to
723 memory hotplug notifier chain callbacks. It is controlled through
724 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
726 If the notifier call chain should be failed with some events
727 notified, write the error code to "actions/<notifier event>/error".
729 Example: Inject memory hotplug offline error (-12 == -ENOMEM)
731 # cd /sys/kernel/debug/notifier-error-inject/memory
732 # echo -12 > actions/MEM_GOING_OFFLINE/error
733 # echo offline > /sys/devices/system/memory/memoryXXX/state
734 bash: echo: write error: Cannot allocate memory
736 To compile this code as a module, choose M here: the module will
737 be called memory-notifier-error-inject.
741 config DEBUG_PER_CPU_MAPS
742 bool "Debug access to per_cpu maps"
743 depends on DEBUG_KERNEL
746 Say Y to verify that the per_cpu map being accessed has
747 been set up. This adds a fair amount of code to kernel memory
748 and decreases performance.
753 bool "Highmem debugging"
754 depends on DEBUG_KERNEL && HIGHMEM
756 This option enables additional error checking for high memory
757 systems. Disable for production systems.
759 config HAVE_DEBUG_STACKOVERFLOW
762 config DEBUG_STACKOVERFLOW
763 bool "Check for stack overflows"
764 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
766 Say Y here if you want to check for overflows of kernel, IRQ
767 and exception stacks (if your architecture uses them). This
768 option will show detailed messages if free stack space drops
769 below a certain limit.
771 These kinds of bugs usually occur when call-chains in the
772 kernel get too deep, especially when interrupts are
775 Use this in cases where you see apparently random memory
776 corruption, especially if it appears in 'struct thread_info'
778 If in doubt, say "N".
780 source "lib/Kconfig.kasan"
782 endmenu # "Memory Debugging"
787 An architecture should select this when it can successfully
788 build and run with CONFIG_KCOV. This typically requires
789 disabling instrumentation for some early boot code.
791 config CC_HAS_SANCOV_TRACE_PC
792 def_bool $(cc-option,-fsanitize-coverage=trace-pc)
795 bool "Code coverage for fuzzing"
796 depends on ARCH_HAS_KCOV
797 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
799 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
801 KCOV exposes kernel code coverage information in a form suitable
802 for coverage-guided fuzzing (randomized testing).
804 If RANDOMIZE_BASE is enabled, PC values will not be stable across
805 different machines and across reboots. If you need stable PC values,
806 disable RANDOMIZE_BASE.
808 For more details, see Documentation/dev-tools/kcov.rst.
810 config KCOV_ENABLE_COMPARISONS
811 bool "Enable comparison operands collection by KCOV"
813 depends on $(cc-option,-fsanitize-coverage=trace-cmp)
815 KCOV also exposes operands of every comparison in the instrumented
816 code along with operand sizes and PCs of the comparison instructions.
817 These operands can be used by fuzzing engines to improve the quality
820 config KCOV_INSTRUMENT_ALL
821 bool "Instrument all code by default"
825 If you are doing generic system call fuzzing (like e.g. syzkaller),
826 then you will want to instrument the whole kernel and you should
827 say y here. If you are doing more targeted fuzzing (like e.g.
828 filesystem fuzzing with AFL) then you will want to enable coverage
829 for more specific subsets of files, and should say n here.
832 bool "Debug shared IRQ handlers"
833 depends on DEBUG_KERNEL
835 Enable this to generate a spurious interrupt as soon as a shared
836 interrupt handler is registered, and just before one is deregistered.
837 Drivers ought to be able to handle interrupts coming in at those
838 points; some don't and need to be caught.
840 menu "Debug Lockups and Hangs"
842 config LOCKUP_DETECTOR
845 config SOFTLOCKUP_DETECTOR
846 bool "Detect Soft Lockups"
847 depends on DEBUG_KERNEL && !S390
848 select LOCKUP_DETECTOR
850 Say Y here to enable the kernel to act as a watchdog to detect
853 Softlockups are bugs that cause the kernel to loop in kernel
854 mode for more than 20 seconds, without giving other tasks a
855 chance to run. The current stack trace is displayed upon
856 detection and the system will stay locked up.
858 config BOOTPARAM_SOFTLOCKUP_PANIC
859 bool "Panic (Reboot) On Soft Lockups"
860 depends on SOFTLOCKUP_DETECTOR
862 Say Y here to enable the kernel to panic on "soft lockups",
863 which are bugs that cause the kernel to loop in kernel
864 mode for more than 20 seconds (configurable using the watchdog_thresh
865 sysctl), without giving other tasks a chance to run.
867 The panic can be used in combination with panic_timeout,
868 to cause the system to reboot automatically after a
869 lockup has been detected. This feature is useful for
870 high-availability systems that have uptime guarantees and
871 where a lockup must be resolved ASAP.
875 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
877 depends on SOFTLOCKUP_DETECTOR
879 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
880 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
882 config HARDLOCKUP_DETECTOR_PERF
884 select SOFTLOCKUP_DETECTOR
887 # Enables a timestamp based low pass filter to compensate for perf based
888 # hard lockup detection which runs too fast due to turbo modes.
890 config HARDLOCKUP_CHECK_TIMESTAMP
894 # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
895 # lockup detector rather than the perf based detector.
897 config HARDLOCKUP_DETECTOR
898 bool "Detect Hard Lockups"
899 depends on DEBUG_KERNEL && !S390
900 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
901 select LOCKUP_DETECTOR
902 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
903 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
905 Say Y here to enable the kernel to act as a watchdog to detect
908 Hardlockups are bugs that cause the CPU to loop in kernel mode
909 for more than 10 seconds, without letting other interrupts have a
910 chance to run. The current stack trace is displayed upon detection
911 and the system will stay locked up.
913 config BOOTPARAM_HARDLOCKUP_PANIC
914 bool "Panic (Reboot) On Hard Lockups"
915 depends on HARDLOCKUP_DETECTOR
917 Say Y here to enable the kernel to panic on "hard lockups",
918 which are bugs that cause the kernel to loop in kernel
919 mode with interrupts disabled for more than 10 seconds (configurable
920 using the watchdog_thresh sysctl).
924 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
926 depends on HARDLOCKUP_DETECTOR
928 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
929 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
931 config DETECT_HUNG_TASK
932 bool "Detect Hung Tasks"
933 depends on DEBUG_KERNEL
934 default SOFTLOCKUP_DETECTOR
936 Say Y here to enable the kernel to detect "hung tasks",
937 which are bugs that cause the task to be stuck in
938 uninterruptible "D" state indefinitely.
940 When a hung task is detected, the kernel will print the
941 current stack trace (which you should report), but the
942 task will stay in uninterruptible state. If lockdep is
943 enabled then all held locks will also be reported. This
944 feature has negligible overhead.
946 config DEFAULT_HUNG_TASK_TIMEOUT
947 int "Default timeout for hung task detection (in seconds)"
948 depends on DETECT_HUNG_TASK
951 This option controls the default timeout (in seconds) used
952 to determine when a task has become non-responsive and should
955 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
956 sysctl or by writing a value to
957 /proc/sys/kernel/hung_task_timeout_secs.
959 A timeout of 0 disables the check. The default is two minutes.
960 Keeping the default should be fine in most cases.
962 config BOOTPARAM_HUNG_TASK_PANIC
963 bool "Panic (Reboot) On Hung Tasks"
964 depends on DETECT_HUNG_TASK
966 Say Y here to enable the kernel to panic on "hung tasks",
967 which are bugs that cause the kernel to leave a task stuck
968 in uninterruptible "D" state.
970 The panic can be used in combination with panic_timeout,
971 to cause the system to reboot automatically after a
972 hung task has been detected. This feature is useful for
973 high-availability systems that have uptime guarantees and
974 where a hung tasks must be resolved ASAP.
978 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
980 depends on DETECT_HUNG_TASK
982 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
983 default 1 if BOOTPARAM_HUNG_TASK_PANIC
986 bool "Detect Workqueue Stalls"
987 depends on DEBUG_KERNEL
989 Say Y here to enable stall detection on workqueues. If a
990 worker pool doesn't make forward progress on a pending work
991 item for over a given amount of time, 30s by default, a
992 warning message is printed along with dump of workqueue
993 state. This can be configured through kernel parameter
994 "workqueue.watchdog_thresh" and its sysfs counterpart.
996 endmenu # "Debug lockups and hangs"
1001 Say Y here to enable the kernel to panic when it oopses. This
1002 has the same effect as setting oops=panic on the kernel command
1005 This feature is useful to ensure that the kernel does not do
1006 anything erroneous after an oops which could result in data
1007 corruption or other issues.
1011 config PANIC_ON_OOPS_VALUE
1014 default 0 if !PANIC_ON_OOPS
1015 default 1 if PANIC_ON_OOPS
1017 config PANIC_TIMEOUT
1021 Set the timeout value (in seconds) until a reboot occurs when the
1022 the kernel panics. If n = 0, then we wait forever. A timeout
1023 value n > 0 will wait n seconds before rebooting, while a timeout
1024 value n < 0 will reboot immediately.
1027 bool "Collect scheduler debugging info"
1028 depends on DEBUG_KERNEL && PROC_FS
1031 If you say Y here, the /proc/sched_debug file will be provided
1032 that can help debug the scheduler. The runtime overhead of this
1040 bool "Collect scheduler statistics"
1041 depends on DEBUG_KERNEL && PROC_FS
1044 If you say Y here, additional code will be inserted into the
1045 scheduler and related routines to collect statistics about
1046 scheduler behavior and provide them in /proc/schedstat. These
1047 stats may be useful for both tuning and debugging the scheduler
1048 If you aren't debugging the scheduler or trying to tune a specific
1049 application, you can say N to avoid the very slight overhead
1052 config SCHED_STACK_END_CHECK
1053 bool "Detect stack corruption on calls to schedule()"
1054 depends on DEBUG_KERNEL
1057 This option checks for a stack overrun on calls to schedule().
1058 If the stack end location is found to be over written always panic as
1059 the content of the corrupted region can no longer be trusted.
1060 This is to ensure no erroneous behaviour occurs which could result in
1061 data corruption or a sporadic crash at a later stage once the region
1062 is examined. The runtime overhead introduced is minimal.
1064 config DEBUG_TIMEKEEPING
1065 bool "Enable extra timekeeping sanity checking"
1067 This option will enable additional timekeeping sanity checks
1068 which may be helpful when diagnosing issues where timekeeping
1069 problems are suspected.
1071 This may include checks in the timekeeping hotpaths, so this
1072 option may have a (very small) performance impact to some
1077 config DEBUG_PREEMPT
1078 bool "Debug preemptible kernel"
1079 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1082 If you say Y here then the kernel will use a debug variant of the
1083 commonly used smp_processor_id() function and will print warnings
1084 if kernel code uses it in a preemption-unsafe way. Also, the kernel
1085 will detect preemption count underflows.
1087 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1089 config LOCK_DEBUGGING_SUPPORT
1091 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1094 config PROVE_LOCKING
1095 bool "Lock debugging: prove locking correctness"
1096 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1098 select DEBUG_SPINLOCK
1099 select DEBUG_MUTEXES
1100 select DEBUG_RT_MUTEXES if RT_MUTEXES
1101 select DEBUG_RWSEMS if RWSEM_SPIN_ON_OWNER
1102 select DEBUG_WW_MUTEX_SLOWPATH
1103 select DEBUG_LOCK_ALLOC
1104 select TRACE_IRQFLAGS
1107 This feature enables the kernel to prove that all locking
1108 that occurs in the kernel runtime is mathematically
1109 correct: that under no circumstance could an arbitrary (and
1110 not yet triggered) combination of observed locking
1111 sequences (on an arbitrary number of CPUs, running an
1112 arbitrary number of tasks and interrupt contexts) cause a
1115 In short, this feature enables the kernel to report locking
1116 related deadlocks before they actually occur.
1118 The proof does not depend on how hard and complex a
1119 deadlock scenario would be to trigger: how many
1120 participant CPUs, tasks and irq-contexts would be needed
1121 for it to trigger. The proof also does not depend on
1122 timing: if a race and a resulting deadlock is possible
1123 theoretically (no matter how unlikely the race scenario
1124 is), it will be proven so and will immediately be
1125 reported by the kernel (once the event is observed that
1126 makes the deadlock theoretically possible).
1128 If a deadlock is impossible (i.e. the locking rules, as
1129 observed by the kernel, are mathematically correct), the
1130 kernel reports nothing.
1132 NOTE: this feature can also be enabled for rwlocks, mutexes
1133 and rwsems - in which case all dependencies between these
1134 different locking variants are observed and mapped too, and
1135 the proof of observed correctness is also maintained for an
1136 arbitrary combination of these separate locking variants.
1138 For more details, see Documentation/locking/lockdep-design.txt.
1141 bool "Lock usage statistics"
1142 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1144 select DEBUG_SPINLOCK
1145 select DEBUG_MUTEXES
1146 select DEBUG_RT_MUTEXES if RT_MUTEXES
1147 select DEBUG_LOCK_ALLOC
1150 This feature enables tracking lock contention points
1152 For more details, see Documentation/locking/lockstat.txt
1154 This also enables lock events required by "perf lock",
1156 If you want to use "perf lock", you also need to turn on
1157 CONFIG_EVENT_TRACING.
1159 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1160 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1162 config DEBUG_RT_MUTEXES
1163 bool "RT Mutex debugging, deadlock detection"
1164 depends on DEBUG_KERNEL && RT_MUTEXES
1166 This allows rt mutex semantics violations and rt mutex related
1167 deadlocks (lockups) to be detected and reported automatically.
1169 config DEBUG_SPINLOCK
1170 bool "Spinlock and rw-lock debugging: basic checks"
1171 depends on DEBUG_KERNEL
1172 select UNINLINE_SPIN_UNLOCK
1174 Say Y here and build SMP to catch missing spinlock initialization
1175 and certain other kinds of spinlock errors commonly made. This is
1176 best used in conjunction with the NMI watchdog so that spinlock
1177 deadlocks are also debuggable.
1179 config DEBUG_MUTEXES
1180 bool "Mutex debugging: basic checks"
1181 depends on DEBUG_KERNEL
1183 This feature allows mutex semantics violations to be detected and
1186 config DEBUG_WW_MUTEX_SLOWPATH
1187 bool "Wait/wound mutex debugging: Slowpath testing"
1188 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1189 select DEBUG_LOCK_ALLOC
1190 select DEBUG_SPINLOCK
1191 select DEBUG_MUTEXES
1193 This feature enables slowpath testing for w/w mutex users by
1194 injecting additional -EDEADLK wound/backoff cases. Together with
1195 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1196 will test all possible w/w mutex interface abuse with the
1197 exception of simply not acquiring all the required locks.
1198 Note that this feature can introduce significant overhead, so
1199 it really should not be enabled in a production or distro kernel,
1200 even a debug kernel. If you are a driver writer, enable it. If
1201 you are a distro, do not.
1204 bool "RW Semaphore debugging: basic checks"
1205 depends on DEBUG_KERNEL && RWSEM_SPIN_ON_OWNER
1207 This debugging feature allows mismatched rw semaphore locks and unlocks
1208 to be detected and reported.
1210 config DEBUG_LOCK_ALLOC
1211 bool "Lock debugging: detect incorrect freeing of live locks"
1212 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1213 select DEBUG_SPINLOCK
1214 select DEBUG_MUTEXES
1215 select DEBUG_RT_MUTEXES if RT_MUTEXES
1218 This feature will check whether any held lock (spinlock, rwlock,
1219 mutex or rwsem) is incorrectly freed by the kernel, via any of the
1220 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1221 vfree(), etc.), whether a live lock is incorrectly reinitialized via
1222 spin_lock_init()/mutex_init()/etc., or whether there is any lock
1223 held during task exit.
1227 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
1229 select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86
1233 config LOCKDEP_SMALL
1236 config DEBUG_LOCKDEP
1237 bool "Lock dependency engine debugging"
1238 depends on DEBUG_KERNEL && LOCKDEP
1240 If you say Y here, the lock dependency engine will do
1241 additional runtime checks to debug itself, at the price
1242 of more runtime overhead.
1244 config DEBUG_ATOMIC_SLEEP
1245 bool "Sleep inside atomic section checking"
1246 select PREEMPT_COUNT
1247 depends on DEBUG_KERNEL
1248 depends on !ARCH_NO_PREEMPT
1250 If you say Y here, various routines which may sleep will become very
1251 noisy if they are called inside atomic sections: when a spinlock is
1252 held, inside an rcu read side critical section, inside preempt disabled
1253 sections, inside an interrupt, etc...
1255 config DEBUG_LOCKING_API_SELFTESTS
1256 bool "Locking API boot-time self-tests"
1257 depends on DEBUG_KERNEL
1259 Say Y here if you want the kernel to run a short self-test during
1260 bootup. The self-test checks whether common types of locking bugs
1261 are detected by debugging mechanisms or not. (if you disable
1262 lock debugging then those bugs wont be detected of course.)
1263 The following locking APIs are covered: spinlocks, rwlocks,
1266 config LOCK_TORTURE_TEST
1267 tristate "torture tests for locking"
1268 depends on DEBUG_KERNEL
1271 This option provides a kernel module that runs torture tests
1272 on kernel locking primitives. The kernel module may be built
1273 after the fact on the running kernel to be tested, if desired.
1275 Say Y here if you want kernel locking-primitive torture tests
1276 to be built into the kernel.
1277 Say M if you want these torture tests to build as a module.
1278 Say N if you are unsure.
1280 config WW_MUTEX_SELFTEST
1281 tristate "Wait/wound mutex selftests"
1283 This option provides a kernel module that runs tests on the
1284 on the struct ww_mutex locking API.
1286 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
1287 with this test harness.
1289 Say M if you want these self tests to build as a module.
1290 Say N if you are unsure.
1292 endmenu # lock debugging
1294 config TRACE_IRQFLAGS
1297 Enables hooks to interrupt enabling and disabling for
1298 either tracing or lock debugging.
1301 bool "Stack backtrace support"
1302 depends on STACKTRACE_SUPPORT
1304 This option causes the kernel to create a /proc/pid/stack for
1305 every process, showing its current stack trace.
1306 It is also used by various kernel debugging features that require
1307 stack trace generation.
1309 config WARN_ALL_UNSEEDED_RANDOM
1310 bool "Warn for all uses of unseeded randomness"
1313 Some parts of the kernel contain bugs relating to their use of
1314 cryptographically secure random numbers before it's actually possible
1315 to generate those numbers securely. This setting ensures that these
1316 flaws don't go unnoticed, by enabling a message, should this ever
1317 occur. This will allow people with obscure setups to know when things
1318 are going wrong, so that they might contact developers about fixing
1321 Unfortunately, on some models of some architectures getting
1322 a fully seeded CRNG is extremely difficult, and so this can
1323 result in dmesg getting spammed for a surprisingly long
1324 time. This is really bad from a security perspective, and
1325 so architecture maintainers really need to do what they can
1326 to get the CRNG seeded sooner after the system is booted.
1327 However, since users cannot do anything actionable to
1328 address this, by default the kernel will issue only a single
1329 warning for the first use of unseeded randomness.
1331 Say Y here if you want to receive warnings for all uses of
1332 unseeded randomness. This will be of use primarily for
1333 those developers interested in improving the security of
1334 Linux kernels running on their architecture (or
1337 config DEBUG_KOBJECT
1338 bool "kobject debugging"
1339 depends on DEBUG_KERNEL
1341 If you say Y here, some extra kobject debugging messages will be sent
1344 config DEBUG_KOBJECT_RELEASE
1345 bool "kobject release debugging"
1346 depends on DEBUG_OBJECTS_TIMERS
1348 kobjects are reference counted objects. This means that their
1349 last reference count put is not predictable, and the kobject can
1350 live on past the point at which a driver decides to drop it's
1351 initial reference to the kobject gained on allocation. An
1352 example of this would be a struct device which has just been
1355 However, some buggy drivers assume that after such an operation,
1356 the memory backing the kobject can be immediately freed. This
1357 goes completely against the principles of a refcounted object.
1359 If you say Y here, the kernel will delay the release of kobjects
1360 on the last reference count to improve the visibility of this
1361 kind of kobject release bug.
1363 config HAVE_DEBUG_BUGVERBOSE
1366 config DEBUG_BUGVERBOSE
1367 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1368 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1371 Say Y here to make BUG() panics output the file name and line number
1372 of the BUG call as well as the EIP and oops trace. This aids
1373 debugging but costs about 70-100K of memory.
1376 bool "Debug linked list manipulation"
1377 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1379 Enable this to turn on extended checks in the linked-list
1385 bool "Debug priority linked list manipulation"
1386 depends on DEBUG_KERNEL
1388 Enable this to turn on extended checks in the priority-ordered
1389 linked-list (plist) walking routines. This checks the entire
1390 list multiple times during each manipulation.
1395 bool "Debug SG table operations"
1396 depends on DEBUG_KERNEL
1398 Enable this to turn on checks on scatter-gather tables. This can
1399 help find problems with drivers that do not properly initialize
1404 config DEBUG_NOTIFIERS
1405 bool "Debug notifier call chains"
1406 depends on DEBUG_KERNEL
1408 Enable this to turn on sanity checking for notifier call chains.
1409 This is most useful for kernel developers to make sure that
1410 modules properly unregister themselves from notifier chains.
1411 This is a relatively cheap check but if you care about maximum
1414 config DEBUG_CREDENTIALS
1415 bool "Debug credential management"
1416 depends on DEBUG_KERNEL
1418 Enable this to turn on some debug checking for credential
1419 management. The additional code keeps track of the number of
1420 pointers from task_structs to any given cred struct, and checks to
1421 see that this number never exceeds the usage count of the cred
1424 Furthermore, if SELinux is enabled, this also checks that the
1425 security pointer in the cred struct is never seen to be invalid.
1429 source "kernel/rcu/Kconfig.debug"
1431 config DEBUG_WQ_FORCE_RR_CPU
1432 bool "Force round-robin CPU selection for unbound work items"
1433 depends on DEBUG_KERNEL
1436 Workqueue used to implicitly guarantee that work items queued
1437 without explicit CPU specified are put on the local CPU. This
1438 guarantee is no longer true and while local CPU is still
1439 preferred work items may be put on foreign CPUs. Kernel
1440 parameter "workqueue.debug_force_rr_cpu" is added to force
1441 round-robin CPU selection to flush out usages which depend on the
1442 now broken guarantee. This config option enables the debug
1443 feature by default. When enabled, memory and cache locality will
1446 config DEBUG_BLOCK_EXT_DEVT
1447 bool "Force extended block device numbers and spread them"
1448 depends on DEBUG_KERNEL
1452 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1453 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1454 YOU ARE DOING. Distros, please enable this and fix whatever
1457 Conventionally, block device numbers are allocated from
1458 predetermined contiguous area. However, extended block area
1459 may introduce non-contiguous block device numbers. This
1460 option forces most block device numbers to be allocated from
1461 the extended space and spreads them to discover kernel or
1462 userland code paths which assume predetermined contiguous
1463 device number allocation.
1465 Note that turning on this debug option shuffles all the
1466 device numbers for all IDE and SCSI devices including libata
1467 ones, so root partition specified using device number
1468 directly (via rdev or root=MAJ:MIN) won't work anymore.
1469 Textual device names (root=/dev/sdXn) will continue to work.
1471 Say N if you are unsure.
1473 config CPU_HOTPLUG_STATE_CONTROL
1474 bool "Enable CPU hotplug state control"
1475 depends on DEBUG_KERNEL
1476 depends on HOTPLUG_CPU
1479 Allows to write steps between "offline" and "online" to the CPUs
1480 sysfs target file so states can be stepped granular. This is a debug
1481 option for now as the hotplug machinery cannot be stopped and
1482 restarted at arbitrary points yet.
1484 Say N if your are unsure.
1486 config NOTIFIER_ERROR_INJECTION
1487 tristate "Notifier error injection"
1488 depends on DEBUG_KERNEL
1491 This option provides the ability to inject artificial errors to
1492 specified notifier chain callbacks. It is useful to test the error
1493 handling of notifier call chain failures.
1497 config PM_NOTIFIER_ERROR_INJECT
1498 tristate "PM notifier error injection module"
1499 depends on PM && NOTIFIER_ERROR_INJECTION
1500 default m if PM_DEBUG
1502 This option provides the ability to inject artificial errors to
1503 PM notifier chain callbacks. It is controlled through debugfs
1504 interface /sys/kernel/debug/notifier-error-inject/pm
1506 If the notifier call chain should be failed with some events
1507 notified, write the error code to "actions/<notifier event>/error".
1509 Example: Inject PM suspend error (-12 = -ENOMEM)
1511 # cd /sys/kernel/debug/notifier-error-inject/pm/
1512 # echo -12 > actions/PM_SUSPEND_PREPARE/error
1513 # echo mem > /sys/power/state
1514 bash: echo: write error: Cannot allocate memory
1516 To compile this code as a module, choose M here: the module will
1517 be called pm-notifier-error-inject.
1521 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1522 tristate "OF reconfig notifier error injection module"
1523 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1525 This option provides the ability to inject artificial errors to
1526 OF reconfig notifier chain callbacks. It is controlled
1527 through debugfs interface under
1528 /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1530 If the notifier call chain should be failed with some events
1531 notified, write the error code to "actions/<notifier event>/error".
1533 To compile this code as a module, choose M here: the module will
1534 be called of-reconfig-notifier-error-inject.
1538 config NETDEV_NOTIFIER_ERROR_INJECT
1539 tristate "Netdev notifier error injection module"
1540 depends on NET && NOTIFIER_ERROR_INJECTION
1542 This option provides the ability to inject artificial errors to
1543 netdevice notifier chain callbacks. It is controlled through debugfs
1544 interface /sys/kernel/debug/notifier-error-inject/netdev
1546 If the notifier call chain should be failed with some events
1547 notified, write the error code to "actions/<notifier event>/error".
1549 Example: Inject netdevice mtu change error (-22 = -EINVAL)
1551 # cd /sys/kernel/debug/notifier-error-inject/netdev
1552 # echo -22 > actions/NETDEV_CHANGEMTU/error
1553 # ip link set eth0 mtu 1024
1554 RTNETLINK answers: Invalid argument
1556 To compile this code as a module, choose M here: the module will
1557 be called netdev-notifier-error-inject.
1561 config FUNCTION_ERROR_INJECTION
1563 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
1565 config FAULT_INJECTION
1566 bool "Fault-injection framework"
1567 depends on DEBUG_KERNEL
1569 Provide fault-injection framework.
1570 For more details, see Documentation/fault-injection/.
1573 bool "Fault-injection capability for kmalloc"
1574 depends on FAULT_INJECTION
1575 depends on SLAB || SLUB
1577 Provide fault-injection capability for kmalloc.
1579 config FAIL_PAGE_ALLOC
1580 bool "Fault-injection capabilitiy for alloc_pages()"
1581 depends on FAULT_INJECTION
1583 Provide fault-injection capability for alloc_pages().
1585 config FAIL_MAKE_REQUEST
1586 bool "Fault-injection capability for disk IO"
1587 depends on FAULT_INJECTION && BLOCK
1589 Provide fault-injection capability for disk IO.
1591 config FAIL_IO_TIMEOUT
1592 bool "Fault-injection capability for faking disk interrupts"
1593 depends on FAULT_INJECTION && BLOCK
1595 Provide fault-injection capability on end IO handling. This
1596 will make the block layer "forget" an interrupt as configured,
1597 thus exercising the error handling.
1599 Only works with drivers that use the generic timeout handling,
1600 for others it wont do anything.
1603 bool "Fault-injection capability for futexes"
1605 depends on FAULT_INJECTION && FUTEX
1607 Provide fault-injection capability for futexes.
1609 config FAULT_INJECTION_DEBUG_FS
1610 bool "Debugfs entries for fault-injection capabilities"
1611 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1613 Enable configuration of fault-injection capabilities via debugfs.
1615 config FAIL_FUNCTION
1616 bool "Fault-injection capability for functions"
1617 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
1619 Provide function-based fault-injection capability.
1620 This will allow you to override a specific function with a return
1621 with given return value. As a result, function caller will see
1622 an error value and have to handle it. This is useful to test the
1623 error handling in various subsystems.
1625 config FAIL_MMC_REQUEST
1626 bool "Fault-injection capability for MMC IO"
1627 depends on FAULT_INJECTION_DEBUG_FS && MMC
1629 Provide fault-injection capability for MMC IO.
1630 This will make the mmc core return data errors. This is
1631 useful to test the error handling in the mmc block device
1632 and to test how the mmc host driver handles retries from
1635 config FAULT_INJECTION_STACKTRACE_FILTER
1636 bool "stacktrace filter for fault-injection capabilities"
1637 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1640 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1642 Provide stacktrace filter for fault-injection capabilities
1645 bool "Latency measuring infrastructure"
1646 depends on DEBUG_KERNEL
1647 depends on STACKTRACE_SUPPORT
1649 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
1656 Enable this option if you want to use the LatencyTOP tool
1657 to find out which userspace is blocking on what kernel operations.
1659 source "kernel/trace/Kconfig"
1661 config PROVIDE_OHCI1394_DMA_INIT
1662 bool "Remote debugging over FireWire early on boot"
1663 depends on PCI && X86
1665 If you want to debug problems which hang or crash the kernel early
1666 on boot and the crashing machine has a FireWire port, you can use
1667 this feature to remotely access the memory of the crashed machine
1668 over FireWire. This employs remote DMA as part of the OHCI1394
1669 specification which is now the standard for FireWire controllers.
1671 With remote DMA, you can monitor the printk buffer remotely using
1672 firescope and access all memory below 4GB using fireproxy from gdb.
1673 Even controlling a kernel debugger is possible using remote DMA.
1677 If ohci1394_dma=early is used as boot parameter, it will initialize
1678 all OHCI1394 controllers which are found in the PCI config space.
1680 As all changes to the FireWire bus such as enabling and disabling
1681 devices cause a bus reset and thereby disable remote DMA for all
1682 devices, be sure to have the cable plugged and FireWire enabled on
1683 the debugging host before booting the debug target for debugging.
1685 This code (~1k) is freed after boot. By then, the firewire stack
1686 in charge of the OHCI-1394 controllers should be used instead.
1688 See Documentation/debugging-via-ohci1394.txt for more information.
1690 menuconfig RUNTIME_TESTING_MENU
1691 bool "Runtime Testing"
1694 if RUNTIME_TESTING_MENU
1697 tristate "Linux Kernel Dump Test Tool Module"
1700 This module enables testing of the different dumping mechanisms by
1701 inducing system failures at predefined crash points.
1702 If you don't need it: say N
1703 Choose M here to compile this code as a module. The module will be
1706 Documentation on how to use the module can be found in
1707 Documentation/fault-injection/provoke-crashes.txt
1709 config TEST_LIST_SORT
1710 tristate "Linked list sorting test"
1711 depends on DEBUG_KERNEL || m
1713 Enable this to turn on 'list_sort()' function test. This test is
1714 executed only once during system boot (so affects only boot time),
1715 or at module load time.
1720 tristate "Array-based sort test"
1721 depends on DEBUG_KERNEL || m
1723 This option enables the self-test function of 'sort()' at boot,
1724 or at module load time.
1728 config KPROBES_SANITY_TEST
1729 bool "Kprobes sanity tests"
1730 depends on DEBUG_KERNEL
1733 This option provides for testing basic kprobes functionality on
1734 boot. Samples of kprobe and kretprobe are inserted and
1735 verified for functionality.
1737 Say N if you are unsure.
1739 config BACKTRACE_SELF_TEST
1740 tristate "Self test for the backtrace code"
1741 depends on DEBUG_KERNEL
1743 This option provides a kernel module that can be used to test
1744 the kernel stack backtrace code. This option is not useful
1745 for distributions or general kernels, but only for kernel
1746 developers working on architecture code.
1748 Note that if you want to also test saved backtraces, you will
1749 have to enable STACKTRACE as well.
1751 Say N if you are unsure.
1754 tristate "Red-Black tree test"
1755 depends on DEBUG_KERNEL
1757 A benchmark measuring the performance of the rbtree library.
1758 Also includes rbtree invariant checks.
1760 config INTERVAL_TREE_TEST
1761 tristate "Interval tree test"
1762 depends on DEBUG_KERNEL
1763 select INTERVAL_TREE
1765 A benchmark measuring the performance of the interval tree library
1768 tristate "Per cpu operations test"
1769 depends on m && DEBUG_KERNEL
1771 Enable this option to build test module which validates per-cpu
1776 config ATOMIC64_SELFTEST
1777 tristate "Perform an atomic64_t self-test"
1779 Enable this option to test the atomic64_t functions at boot or
1780 at module load time.
1784 config ASYNC_RAID6_TEST
1785 tristate "Self test for hardware accelerated raid6 recovery"
1786 depends on ASYNC_RAID6_RECOV
1789 This is a one-shot self test that permutes through the
1790 recovery of all the possible two disk failure scenarios for a
1791 N-disk array. Recovery is performed with the asynchronous
1792 raid6 recovery routines, and will optionally use an offload
1793 engine if one is available.
1798 tristate "Test functions located in the hexdump module at runtime"
1800 config TEST_STRING_HELPERS
1801 tristate "Test functions located in the string_helpers module at runtime"
1804 tristate "Test strscpy*() family of functions at runtime"
1807 tristate "Test kstrto*() family of functions at runtime"
1810 tristate "Test printf() family of functions at runtime"
1813 tristate "Test bitmap_*() family of functions at runtime"
1815 Enable this option to test the bitmap functions at boot.
1819 config TEST_BITFIELD
1820 tristate "Test bitfield functions at runtime"
1822 Enable this option to test the bitfield functions at boot.
1827 tristate "Test functions located in the uuid module at runtime"
1830 tristate "Test the XArray code at runtime"
1832 config TEST_OVERFLOW
1833 tristate "Test check_*_overflow() functions at runtime"
1835 config TEST_RHASHTABLE
1836 tristate "Perform selftest on resizable hash table"
1838 Enable this option to test the rhashtable functions at boot.
1843 tristate "Perform selftest on hash functions"
1845 Enable this option to test the kernel's integer (<linux/hash.h>),
1846 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
1847 hash functions on boot (or module load).
1849 This is intended to help people writing architecture-specific
1850 optimized versions. If unsure, say N.
1853 tristate "Perform selftest on IDA functions"
1856 tristate "Perform selftest on priority array manager"
1859 Enable this option to test priority array manager on boot
1865 tristate "Test module loading with 'hello world' module"
1868 This builds the "test_module" module that emits "Hello, world"
1869 on printk when loaded. It is designed to be used for basic
1870 evaluation of the module loading subsystem (for example when
1871 validating module verification). It lacks any extra dependencies,
1872 and will not normally be loaded by the system unless explicitly
1878 tristate "Test module for stress/performance analysis of vmalloc allocator"
1883 This builds the "test_vmalloc" module that should be used for
1884 stress and performance analysis. So, any new change for vmalloc
1885 subsystem can be evaluated from performance and stability point
1890 config TEST_USER_COPY
1891 tristate "Test user/kernel boundary protections"
1894 This builds the "test_user_copy" module that runs sanity checks
1895 on the copy_to/from_user infrastructure, making sure basic
1896 user/kernel boundary testing is working. If it fails to load,
1897 a regression has been detected in the user/kernel memory boundary
1903 tristate "Test BPF filter functionality"
1906 This builds the "test_bpf" module that runs various test vectors
1907 against the BPF interpreter or BPF JIT compiler depending on the
1908 current setting. This is in particular useful for BPF JIT compiler
1909 development, but also to run regression tests against changes in
1910 the interpreter code. It also enables test stubs for eBPF maps and
1911 verifier used by user space verifier testsuite.
1915 config FIND_BIT_BENCHMARK
1916 tristate "Test find_bit functions"
1918 This builds the "test_find_bit" module that measure find_*_bit()
1919 functions performance.
1923 config TEST_FIRMWARE
1924 tristate "Test firmware loading via userspace interface"
1925 depends on FW_LOADER
1927 This builds the "test_firmware" module that creates a userspace
1928 interface for testing firmware loading. This can be used to
1929 control the triggering of firmware loading without needing an
1930 actual firmware-using device. The contents can be rechecked by
1936 tristate "sysctl test driver"
1937 depends on PROC_SYSCTL
1939 This builds the "test_sysctl" module. This driver enables to test the
1940 proc sysctl interfaces available to drivers safely without affecting
1941 production knobs which might alter system functionality.
1946 tristate "udelay test driver"
1948 This builds the "udelay_test" module that helps to make sure
1949 that udelay() is working properly.
1953 config TEST_STATIC_KEYS
1954 tristate "Test static keys"
1957 Test the static key interfaces.
1962 tristate "kmod stress tester"
1964 depends on NETDEVICES && NET_CORE && INET # for TUN
1971 Test the kernel's module loading mechanism: kmod. kmod implements
1972 support to load modules using the Linux kernel's usermode helper.
1973 This test provides a series of tests against kmod.
1975 Although technically you can either build test_kmod as a module or
1976 into the kernel we disallow building it into the kernel since
1977 it stress tests request_module() and this will very likely cause
1978 some issues by taking over precious threads available from other
1979 module load requests, ultimately this could be fatal.
1983 tools/testing/selftests/kmod/kmod.sh --help
1987 config TEST_DEBUG_VIRTUAL
1988 tristate "Test CONFIG_DEBUG_VIRTUAL feature"
1989 depends on DEBUG_VIRTUAL
1991 Test the kernel's ability to detect incorrect calls to
1992 virt_to_phys() done against the non-linear part of the
1993 kernel's virtual address map.
1997 config TEST_MEMCAT_P
1998 tristate "Test memcat_p() helper function"
2000 Test the memcat_p() helper for correctly merging two
2001 pointer arrays together.
2005 config TEST_LIVEPATCH
2006 tristate "Test livepatching"
2008 depends on DYNAMIC_DEBUG
2009 depends on LIVEPATCH
2012 Test kernel livepatching features for correctness. The tests will
2013 load test modules that will be livepatched in various scenarios.
2015 To run all the livepatching tests:
2017 make -C tools/testing/selftests TARGETS=livepatch run_tests
2019 Alternatively, individual tests may be invoked:
2021 tools/testing/selftests/livepatch/test-callbacks.sh
2022 tools/testing/selftests/livepatch/test-livepatch.sh
2023 tools/testing/selftests/livepatch/test-shadow-vars.sh
2028 tristate "Perform selftest on object aggreration manager"
2032 Enable this option to test object aggregation manager on boot
2036 config TEST_STACKINIT
2037 tristate "Test level of stack variable initialization"
2039 Test if the kernel is zero-initializing stack variables and
2040 padding. Coverage is controlled by compiler flags,
2041 CONFIG_GCC_PLUGIN_STRUCTLEAK, CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF,
2042 or CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL.
2046 endif # RUNTIME_TESTING_MENU
2051 This option adds a kernel parameter 'memtest', which allows memtest
2053 memtest=0, mean disabled; -- default
2054 memtest=1, mean do 1 test pattern;
2056 memtest=17, mean do 17 test patterns.
2057 If you are unsure how to answer this question, answer N.
2059 config BUG_ON_DATA_CORRUPTION
2060 bool "Trigger a BUG when data corruption is detected"
2063 Select this option if the kernel should BUG when it encounters
2064 data corruption in kernel memory structures when they get checked
2069 source "samples/Kconfig"
2071 source "lib/Kconfig.kgdb"
2073 source "lib/Kconfig.ubsan"
2075 config ARCH_HAS_DEVMEM_IS_ALLOWED
2078 config STRICT_DEVMEM
2079 bool "Filter access to /dev/mem"
2080 depends on MMU && DEVMEM
2081 depends on ARCH_HAS_DEVMEM_IS_ALLOWED
2082 default y if PPC || X86 || ARM64
2084 If this option is disabled, you allow userspace (root) access to all
2085 of memory, including kernel and userspace memory. Accidental
2086 access to this is obviously disastrous, but specific access can
2087 be used by people debugging the kernel. Note that with PAT support
2088 enabled, even in this case there are restrictions on /dev/mem
2089 use due to the cache aliasing requirements.
2091 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
2092 file only allows userspace access to PCI space and the BIOS code and
2093 data regions. This is sufficient for dosemu and X and all common
2098 config IO_STRICT_DEVMEM
2099 bool "Filter I/O access to /dev/mem"
2100 depends on STRICT_DEVMEM
2102 If this option is disabled, you allow userspace (root) access to all
2103 io-memory regardless of whether a driver is actively using that
2104 range. Accidental access to this is obviously disastrous, but
2105 specific access can be used by people debugging kernel drivers.
2107 If this option is switched on, the /dev/mem file only allows
2108 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2109 may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2110 if the driver using a given range cannot be disabled.
2114 source "arch/$(SRCARCH)/Kconfig.debug"
2116 endmenu # Kernel hacking
projects / linux-2.6-microblaze.git / blob