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0001 menu "printk and dmesg options"
0002 
0003 config PRINTK_TIME
0004         bool "Show timing information on printks"
0005         depends on PRINTK
0006         help
0007           Selecting this option causes time stamps of the printk()
0008           messages to be added to the output of the syslog() system
0009           call and at the console.
0010 
0011           The timestamp is always recorded internally, and exported
0012           to /dev/kmsg. This flag just specifies if the timestamp should
0013           be included, not that the timestamp is recorded.
0014 
0015           The behavior is also controlled by the kernel command line
0016           parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst
0017 
0018 config CONSOLE_LOGLEVEL_DEFAULT
0019         int "Default console loglevel (1-15)"
0020         range 1 15
0021         default "7"
0022         help
0023           Default loglevel to determine what will be printed on the console.
0024 
0025           Setting a default here is equivalent to passing in loglevel=<x> in
0026           the kernel bootargs. loglevel=<x> continues to override whatever
0027           value is specified here as well.
0028 
0029           Note: This does not affect the log level of un-prefixed printk()
0030           usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
0031           option.
0032 
0033 config MESSAGE_LOGLEVEL_DEFAULT
0034         int "Default message log level (1-7)"
0035         range 1 7
0036         default "4"
0037         help
0038           Default log level for printk statements with no specified priority.
0039 
0040           This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
0041           that are auditing their logs closely may want to set it to a lower
0042           priority.
0043 
0044           Note: This does not affect what message level gets printed on the console
0045           by default. To change that, use loglevel=<x> in the kernel bootargs,
0046           or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value.
0047 
0048 config BOOT_PRINTK_DELAY
0049         bool "Delay each boot printk message by N milliseconds"
0050         depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
0051         help
0052           This build option allows you to read kernel boot messages
0053           by inserting a short delay after each one.  The delay is
0054           specified in milliseconds on the kernel command line,
0055           using "boot_delay=N".
0056 
0057           It is likely that you would also need to use "lpj=M" to preset
0058           the "loops per jiffie" value.
0059           See a previous boot log for the "lpj" value to use for your
0060           system, and then set "lpj=M" before setting "boot_delay=N".
0061           NOTE:  Using this option may adversely affect SMP systems.
0062           I.e., processors other than the first one may not boot up.
0063           BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
0064           what it believes to be lockup conditions.
0065 
0066 config DYNAMIC_DEBUG
0067         bool "Enable dynamic printk() support"
0068         default n
0069         depends on PRINTK
0070         depends on DEBUG_FS
0071         help
0072 
0073           Compiles debug level messages into the kernel, which would not
0074           otherwise be available at runtime. These messages can then be
0075           enabled/disabled based on various levels of scope - per source file,
0076           function, module, format string, and line number. This mechanism
0077           implicitly compiles in all pr_debug() and dev_dbg() calls, which
0078           enlarges the kernel text size by about 2%.
0079 
0080           If a source file is compiled with DEBUG flag set, any
0081           pr_debug() calls in it are enabled by default, but can be
0082           disabled at runtime as below.  Note that DEBUG flag is
0083           turned on by many CONFIG_*DEBUG* options.
0084 
0085           Usage:
0086 
0087           Dynamic debugging is controlled via the 'dynamic_debug/control' file,
0088           which is contained in the 'debugfs' filesystem. Thus, the debugfs
0089           filesystem must first be mounted before making use of this feature.
0090           We refer the control file as: <debugfs>/dynamic_debug/control. This
0091           file contains a list of the debug statements that can be enabled. The
0092           format for each line of the file is:
0093 
0094                 filename:lineno [module]function flags format
0095 
0096           filename : source file of the debug statement
0097           lineno : line number of the debug statement
0098           module : module that contains the debug statement
0099           function : function that contains the debug statement
0100           flags : '=p' means the line is turned 'on' for printing
0101           format : the format used for the debug statement
0102 
0103           From a live system:
0104 
0105                 nullarbor:~ # cat <debugfs>/dynamic_debug/control
0106                 # filename:lineno [module]function flags format
0107                 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
0108                 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
0109                 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
0110 
0111           Example usage:
0112 
0113                 // enable the message at line 1603 of file svcsock.c
0114                 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
0115                                                 <debugfs>/dynamic_debug/control
0116 
0117                 // enable all the messages in file svcsock.c
0118                 nullarbor:~ # echo -n 'file svcsock.c +p' >
0119                                                 <debugfs>/dynamic_debug/control
0120 
0121                 // enable all the messages in the NFS server module
0122                 nullarbor:~ # echo -n 'module nfsd +p' >
0123                                                 <debugfs>/dynamic_debug/control
0124 
0125                 // enable all 12 messages in the function svc_process()
0126                 nullarbor:~ # echo -n 'func svc_process +p' >
0127                                                 <debugfs>/dynamic_debug/control
0128 
0129                 // disable all 12 messages in the function svc_process()
0130                 nullarbor:~ # echo -n 'func svc_process -p' >
0131                                                 <debugfs>/dynamic_debug/control
0132 
0133           See Documentation/dynamic-debug-howto.txt for additional information.
0134 
0135 endmenu # "printk and dmesg options"
0136 
0137 menu "Compile-time checks and compiler options"
0138 
0139 config DEBUG_INFO
0140         bool "Compile the kernel with debug info"
0141         depends on DEBUG_KERNEL && !COMPILE_TEST
0142         help
0143           If you say Y here the resulting kernel image will include
0144           debugging info resulting in a larger kernel image.
0145           This adds debug symbols to the kernel and modules (gcc -g), and
0146           is needed if you intend to use kernel crashdump or binary object
0147           tools like crash, kgdb, LKCD, gdb, etc on the kernel.
0148           Say Y here only if you plan to debug the kernel.
0149 
0150           If unsure, say N.
0151 
0152 config DEBUG_INFO_REDUCED
0153         bool "Reduce debugging information"
0154         depends on DEBUG_INFO
0155         help
0156           If you say Y here gcc is instructed to generate less debugging
0157           information for structure types. This means that tools that
0158           need full debugging information (like kgdb or systemtap) won't
0159           be happy. But if you merely need debugging information to
0160           resolve line numbers there is no loss. Advantage is that
0161           build directory object sizes shrink dramatically over a full
0162           DEBUG_INFO build and compile times are reduced too.
0163           Only works with newer gcc versions.
0164 
0165 config DEBUG_INFO_SPLIT
0166         bool "Produce split debuginfo in .dwo files"
0167         depends on DEBUG_INFO && !FRV
0168         help
0169           Generate debug info into separate .dwo files. This significantly
0170           reduces the build directory size for builds with DEBUG_INFO,
0171           because it stores the information only once on disk in .dwo
0172           files instead of multiple times in object files and executables.
0173           In addition the debug information is also compressed.
0174 
0175           Requires recent gcc (4.7+) and recent gdb/binutils.
0176           Any tool that packages or reads debug information would need
0177           to know about the .dwo files and include them.
0178           Incompatible with older versions of ccache.
0179 
0180 config DEBUG_INFO_DWARF4
0181         bool "Generate dwarf4 debuginfo"
0182         depends on DEBUG_INFO
0183         help
0184           Generate dwarf4 debug info. This requires recent versions
0185           of gcc and gdb. It makes the debug information larger.
0186           But it significantly improves the success of resolving
0187           variables in gdb on optimized code.
0188 
0189 config GDB_SCRIPTS
0190         bool "Provide GDB scripts for kernel debugging"
0191         depends on DEBUG_INFO
0192         help
0193           This creates the required links to GDB helper scripts in the
0194           build directory. If you load vmlinux into gdb, the helper
0195           scripts will be automatically imported by gdb as well, and
0196           additional functions are available to analyze a Linux kernel
0197           instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
0198           for further details.
0199 
0200 config ENABLE_WARN_DEPRECATED
0201         bool "Enable __deprecated logic"
0202         default y
0203         help
0204           Enable the __deprecated logic in the kernel build.
0205           Disable this to suppress the "warning: 'foo' is deprecated
0206           (declared at kernel/power/somefile.c:1234)" messages.
0207 
0208 config ENABLE_MUST_CHECK
0209         bool "Enable __must_check logic"
0210         default y
0211         help
0212           Enable the __must_check logic in the kernel build.  Disable this to
0213           suppress the "warning: ignoring return value of 'foo', declared with
0214           attribute warn_unused_result" messages.
0215 
0216 config FRAME_WARN
0217         int "Warn for stack frames larger than (needs gcc 4.4)"
0218         range 0 8192
0219         default 0 if KASAN
0220         default 2048 if GCC_PLUGIN_LATENT_ENTROPY
0221         default 1024 if !64BIT
0222         default 2048 if 64BIT
0223         help
0224           Tell gcc to warn at build time for stack frames larger than this.
0225           Setting this too low will cause a lot of warnings.
0226           Setting it to 0 disables the warning.
0227           Requires gcc 4.4
0228 
0229 config STRIP_ASM_SYMS
0230         bool "Strip assembler-generated symbols during link"
0231         default n
0232         help
0233           Strip internal assembler-generated symbols during a link (symbols
0234           that look like '.Lxxx') so they don't pollute the output of
0235           get_wchan() and suchlike.
0236 
0237 config READABLE_ASM
0238         bool "Generate readable assembler code"
0239         depends on DEBUG_KERNEL
0240         help
0241           Disable some compiler optimizations that tend to generate human unreadable
0242           assembler output. This may make the kernel slightly slower, but it helps
0243           to keep kernel developers who have to stare a lot at assembler listings
0244           sane.
0245 
0246 config UNUSED_SYMBOLS
0247         bool "Enable unused/obsolete exported symbols"
0248         default y if X86
0249         help
0250           Unused but exported symbols make the kernel needlessly bigger.  For
0251           that reason most of these unused exports will soon be removed.  This
0252           option is provided temporarily to provide a transition period in case
0253           some external kernel module needs one of these symbols anyway. If you
0254           encounter such a case in your module, consider if you are actually
0255           using the right API.  (rationale: since nobody in the kernel is using
0256           this in a module, there is a pretty good chance it's actually the
0257           wrong interface to use).  If you really need the symbol, please send a
0258           mail to the linux kernel mailing list mentioning the symbol and why
0259           you really need it, and what the merge plan to the mainline kernel for
0260           your module is.
0261 
0262 config PAGE_OWNER
0263         bool "Track page owner"
0264         depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
0265         select DEBUG_FS
0266         select STACKTRACE
0267         select STACKDEPOT
0268         select PAGE_EXTENSION
0269         help
0270           This keeps track of what call chain is the owner of a page, may
0271           help to find bare alloc_page(s) leaks. Even if you include this
0272           feature on your build, it is disabled in default. You should pass
0273           "page_owner=on" to boot parameter in order to enable it. Eats
0274           a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
0275           for user-space helper.
0276 
0277           If unsure, say N.
0278 
0279 config DEBUG_FS
0280         bool "Debug Filesystem"
0281         select SRCU
0282         help
0283           debugfs is a virtual file system that kernel developers use to put
0284           debugging files into.  Enable this option to be able to read and
0285           write to these files.
0286 
0287           For detailed documentation on the debugfs API, see
0288           Documentation/DocBook/filesystems.
0289 
0290           If unsure, say N.
0291 
0292 config HEADERS_CHECK
0293         bool "Run 'make headers_check' when building vmlinux"
0294         depends on !UML
0295         help
0296           This option will extract the user-visible kernel headers whenever
0297           building the kernel, and will run basic sanity checks on them to
0298           ensure that exported files do not attempt to include files which
0299           were not exported, etc.
0300 
0301           If you're making modifications to header files which are
0302           relevant for userspace, say 'Y', and check the headers
0303           exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
0304           your build tree), to make sure they're suitable.
0305 
0306 config DEBUG_SECTION_MISMATCH
0307         bool "Enable full Section mismatch analysis"
0308         help
0309           The section mismatch analysis checks if there are illegal
0310           references from one section to another section.
0311           During linktime or runtime, some sections are dropped;
0312           any use of code/data previously in these sections would
0313           most likely result in an oops.
0314           In the code, functions and variables are annotated with
0315           __init,, etc. (see the full list in include/linux/init.h),
0316           which results in the code/data being placed in specific sections.
0317           The section mismatch analysis is always performed after a full
0318           kernel build, and enabling this option causes the following
0319           additional steps to occur:
0320           - Add the option -fno-inline-functions-called-once to gcc commands.
0321             When inlining a function annotated with __init in a non-init
0322             function, we would lose the section information and thus
0323             the analysis would not catch the illegal reference.
0324             This option tells gcc to inline less (but it does result in
0325             a larger kernel).
0326           - Run the section mismatch analysis for each module/built-in.o file.
0327             When we run the section mismatch analysis on vmlinux.o, we
0328             lose valuable information about where the mismatch was
0329             introduced.
0330             Running the analysis for each module/built-in.o file
0331             tells where the mismatch happens much closer to the
0332             source. The drawback is that the same mismatch is
0333             reported at least twice.
0334           - Enable verbose reporting from modpost in order to help resolve
0335             the section mismatches that are reported.
0336 
0337 config SECTION_MISMATCH_WARN_ONLY
0338         bool "Make section mismatch errors non-fatal"
0339         default y
0340         help
0341           If you say N here, the build process will fail if there are any
0342           section mismatch, instead of just throwing warnings.
0343 
0344           If unsure, say Y.
0345 
0346 #
0347 # Select this config option from the architecture Kconfig, if it
0348 # is preferred to always offer frame pointers as a config
0349 # option on the architecture (regardless of KERNEL_DEBUG):
0350 #
0351 config ARCH_WANT_FRAME_POINTERS
0352         bool
0353         help
0354 
0355 config FRAME_POINTER
0356         bool "Compile the kernel with frame pointers"
0357         depends on DEBUG_KERNEL && \
0358                 (CRIS || M68K || FRV || UML || \
0359                  AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \
0360                 ARCH_WANT_FRAME_POINTERS
0361         default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
0362         help
0363           If you say Y here the resulting kernel image will be slightly
0364           larger and slower, but it gives very useful debugging information
0365           in case of kernel bugs. (precise oopses/stacktraces/warnings)
0366 
0367 config STACK_VALIDATION
0368         bool "Compile-time stack metadata validation"
0369         depends on HAVE_STACK_VALIDATION
0370         default n
0371         help
0372           Add compile-time checks to validate stack metadata, including frame
0373           pointers (if CONFIG_FRAME_POINTER is enabled).  This helps ensure
0374           that runtime stack traces are more reliable.
0375 
0376           For more information, see
0377           tools/objtool/Documentation/stack-validation.txt.
0378 
0379 config DEBUG_FORCE_WEAK_PER_CPU
0380         bool "Force weak per-cpu definitions"
0381         depends on DEBUG_KERNEL
0382         help
0383           s390 and alpha require percpu variables in modules to be
0384           defined weak to work around addressing range issue which
0385           puts the following two restrictions on percpu variable
0386           definitions.
0387 
0388           1. percpu symbols must be unique whether static or not
0389           2. percpu variables can't be defined inside a function
0390 
0391           To ensure that generic code follows the above rules, this
0392           option forces all percpu variables to be defined as weak.
0393 
0394 endmenu # "Compiler options"
0395 
0396 config MAGIC_SYSRQ
0397         bool "Magic SysRq key"
0398         depends on !UML
0399         help
0400           If you say Y here, you will have some control over the system even
0401           if the system crashes for example during kernel debugging (e.g., you
0402           will be able to flush the buffer cache to disk, reboot the system
0403           immediately or dump some status information). This is accomplished
0404           by pressing various keys while holding SysRq (Alt+PrintScreen). It
0405           also works on a serial console (on PC hardware at least), if you
0406           send a BREAK and then within 5 seconds a command keypress. The
0407           keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
0408           unless you really know what this hack does.
0409 
0410 config MAGIC_SYSRQ_DEFAULT_ENABLE
0411         hex "Enable magic SysRq key functions by default"
0412         depends on MAGIC_SYSRQ
0413         default 0x1
0414         help
0415           Specifies which SysRq key functions are enabled by default.
0416           This may be set to 1 or 0 to enable or disable them all, or
0417           to a bitmask as described in Documentation/sysrq.txt.
0418 
0419 config DEBUG_KERNEL
0420         bool "Kernel debugging"
0421         help
0422           Say Y here if you are developing drivers or trying to debug and
0423           identify kernel problems.
0424 
0425 menu "Memory Debugging"
0426 
0427 source mm/Kconfig.debug
0428 
0429 config DEBUG_OBJECTS
0430         bool "Debug object operations"
0431         depends on DEBUG_KERNEL
0432         help
0433           If you say Y here, additional code will be inserted into the
0434           kernel to track the life time of various objects and validate
0435           the operations on those objects.
0436 
0437 config DEBUG_OBJECTS_SELFTEST
0438         bool "Debug objects selftest"
0439         depends on DEBUG_OBJECTS
0440         help
0441           This enables the selftest of the object debug code.
0442 
0443 config DEBUG_OBJECTS_FREE
0444         bool "Debug objects in freed memory"
0445         depends on DEBUG_OBJECTS
0446         help
0447           This enables checks whether a k/v free operation frees an area
0448           which contains an object which has not been deactivated
0449           properly. This can make kmalloc/kfree-intensive workloads
0450           much slower.
0451 
0452 config DEBUG_OBJECTS_TIMERS
0453         bool "Debug timer objects"
0454         depends on DEBUG_OBJECTS
0455         help
0456           If you say Y here, additional code will be inserted into the
0457           timer routines to track the life time of timer objects and
0458           validate the timer operations.
0459 
0460 config DEBUG_OBJECTS_WORK
0461         bool "Debug work objects"
0462         depends on DEBUG_OBJECTS
0463         help
0464           If you say Y here, additional code will be inserted into the
0465           work queue routines to track the life time of work objects and
0466           validate the work operations.
0467 
0468 config DEBUG_OBJECTS_RCU_HEAD
0469         bool "Debug RCU callbacks objects"
0470         depends on DEBUG_OBJECTS
0471         help
0472           Enable this to turn on debugging of RCU list heads (call_rcu() usage).
0473 
0474 config DEBUG_OBJECTS_PERCPU_COUNTER
0475         bool "Debug percpu counter objects"
0476         depends on DEBUG_OBJECTS
0477         help
0478           If you say Y here, additional code will be inserted into the
0479           percpu counter routines to track the life time of percpu counter
0480           objects and validate the percpu counter operations.
0481 
0482 config DEBUG_OBJECTS_ENABLE_DEFAULT
0483         int "debug_objects bootup default value (0-1)"
0484         range 0 1
0485         default "1"
0486         depends on DEBUG_OBJECTS
0487         help
0488           Debug objects boot parameter default value
0489 
0490 config DEBUG_SLAB
0491         bool "Debug slab memory allocations"
0492         depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
0493         help
0494           Say Y here to have the kernel do limited verification on memory
0495           allocation as well as poisoning memory on free to catch use of freed
0496           memory. This can make kmalloc/kfree-intensive workloads much slower.
0497 
0498 config DEBUG_SLAB_LEAK
0499         bool "Memory leak debugging"
0500         depends on DEBUG_SLAB
0501 
0502 config SLUB_DEBUG_ON
0503         bool "SLUB debugging on by default"
0504         depends on SLUB && SLUB_DEBUG && !KMEMCHECK
0505         default n
0506         help
0507           Boot with debugging on by default. SLUB boots by default with
0508           the runtime debug capabilities switched off. Enabling this is
0509           equivalent to specifying the "slub_debug" parameter on boot.
0510           There is no support for more fine grained debug control like
0511           possible with slub_debug=xxx. SLUB debugging may be switched
0512           off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
0513           "slub_debug=-".
0514 
0515 config SLUB_STATS
0516         default n
0517         bool "Enable SLUB performance statistics"
0518         depends on SLUB && SYSFS
0519         help
0520           SLUB statistics are useful to debug SLUBs allocation behavior in
0521           order find ways to optimize the allocator. This should never be
0522           enabled for production use since keeping statistics slows down
0523           the allocator by a few percentage points. The slabinfo command
0524           supports the determination of the most active slabs to figure
0525           out which slabs are relevant to a particular load.
0526           Try running: slabinfo -DA
0527 
0528 config HAVE_DEBUG_KMEMLEAK
0529         bool
0530 
0531 config DEBUG_KMEMLEAK
0532         bool "Kernel memory leak detector"
0533         depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
0534         select DEBUG_FS
0535         select STACKTRACE if STACKTRACE_SUPPORT
0536         select KALLSYMS
0537         select CRC32
0538         help
0539           Say Y here if you want to enable the memory leak
0540           detector. The memory allocation/freeing is traced in a way
0541           similar to the Boehm's conservative garbage collector, the
0542           difference being that the orphan objects are not freed but
0543           only shown in /sys/kernel/debug/kmemleak. Enabling this
0544           feature will introduce an overhead to memory
0545           allocations. See Documentation/dev-tools/kmemleak.rst for more
0546           details.
0547 
0548           Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
0549           of finding leaks due to the slab objects poisoning.
0550 
0551           In order to access the kmemleak file, debugfs needs to be
0552           mounted (usually at /sys/kernel/debug).
0553 
0554 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
0555         int "Maximum kmemleak early log entries"
0556         depends on DEBUG_KMEMLEAK
0557         range 200 40000
0558         default 400
0559         help
0560           Kmemleak must track all the memory allocations to avoid
0561           reporting false positives. Since memory may be allocated or
0562           freed before kmemleak is initialised, an early log buffer is
0563           used to store these actions. If kmemleak reports "early log
0564           buffer exceeded", please increase this value.
0565 
0566 config DEBUG_KMEMLEAK_TEST
0567         tristate "Simple test for the kernel memory leak detector"
0568         depends on DEBUG_KMEMLEAK && m
0569         help
0570           This option enables a module that explicitly leaks memory.
0571 
0572           If unsure, say N.
0573 
0574 config DEBUG_KMEMLEAK_DEFAULT_OFF
0575         bool "Default kmemleak to off"
0576         depends on DEBUG_KMEMLEAK
0577         help
0578           Say Y here to disable kmemleak by default. It can then be enabled
0579           on the command line via kmemleak=on.
0580 
0581 config DEBUG_STACK_USAGE
0582         bool "Stack utilization instrumentation"
0583         depends on DEBUG_KERNEL && !IA64
0584         help
0585           Enables the display of the minimum amount of free stack which each
0586           task has ever had available in the sysrq-T and sysrq-P debug output.
0587 
0588           This option will slow down process creation somewhat.
0589 
0590 config DEBUG_VM
0591         bool "Debug VM"
0592         depends on DEBUG_KERNEL
0593         help
0594           Enable this to turn on extended checks in the virtual-memory system
0595           that may impact performance.
0596 
0597           If unsure, say N.
0598 
0599 config DEBUG_VM_VMACACHE
0600         bool "Debug VMA caching"
0601         depends on DEBUG_VM
0602         help
0603           Enable this to turn on VMA caching debug information. Doing so
0604           can cause significant overhead, so only enable it in non-production
0605           environments.
0606 
0607           If unsure, say N.
0608 
0609 config DEBUG_VM_RB
0610         bool "Debug VM red-black trees"
0611         depends on DEBUG_VM
0612         help
0613           Enable VM red-black tree debugging information and extra validations.
0614 
0615           If unsure, say N.
0616 
0617 config DEBUG_VM_PGFLAGS
0618         bool "Debug page-flags operations"
0619         depends on DEBUG_VM
0620         help
0621           Enables extra validation on page flags operations.
0622 
0623           If unsure, say N.
0624 
0625 config DEBUG_VIRTUAL
0626         bool "Debug VM translations"
0627         depends on DEBUG_KERNEL && X86
0628         help
0629           Enable some costly sanity checks in virtual to page code. This can
0630           catch mistakes with virt_to_page() and friends.
0631 
0632           If unsure, say N.
0633 
0634 config DEBUG_NOMMU_REGIONS
0635         bool "Debug the global anon/private NOMMU mapping region tree"
0636         depends on DEBUG_KERNEL && !MMU
0637         help
0638           This option causes the global tree of anonymous and private mapping
0639           regions to be regularly checked for invalid topology.
0640 
0641 config DEBUG_MEMORY_INIT
0642         bool "Debug memory initialisation" if EXPERT
0643         default !EXPERT
0644         help
0645           Enable this for additional checks during memory initialisation.
0646           The sanity checks verify aspects of the VM such as the memory model
0647           and other information provided by the architecture. Verbose
0648           information will be printed at KERN_DEBUG loglevel depending
0649           on the mminit_loglevel= command-line option.
0650 
0651           If unsure, say Y
0652 
0653 config MEMORY_NOTIFIER_ERROR_INJECT
0654         tristate "Memory hotplug notifier error injection module"
0655         depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
0656         help
0657           This option provides the ability to inject artificial errors to
0658           memory hotplug notifier chain callbacks.  It is controlled through
0659           debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
0660 
0661           If the notifier call chain should be failed with some events
0662           notified, write the error code to "actions/<notifier event>/error".
0663 
0664           Example: Inject memory hotplug offline error (-12 == -ENOMEM)
0665 
0666           # cd /sys/kernel/debug/notifier-error-inject/memory
0667           # echo -12 > actions/MEM_GOING_OFFLINE/error
0668           # echo offline > /sys/devices/system/memory/memoryXXX/state
0669           bash: echo: write error: Cannot allocate memory
0670 
0671           To compile this code as a module, choose M here: the module will
0672           be called memory-notifier-error-inject.
0673 
0674           If unsure, say N.
0675 
0676 config DEBUG_PER_CPU_MAPS
0677         bool "Debug access to per_cpu maps"
0678         depends on DEBUG_KERNEL
0679         depends on SMP
0680         help
0681           Say Y to verify that the per_cpu map being accessed has
0682           been set up. This adds a fair amount of code to kernel memory
0683           and decreases performance.
0684 
0685           Say N if unsure.
0686 
0687 config DEBUG_HIGHMEM
0688         bool "Highmem debugging"
0689         depends on DEBUG_KERNEL && HIGHMEM
0690         help
0691           This option enables additional error checking for high memory
0692           systems.  Disable for production systems.
0693 
0694 config HAVE_DEBUG_STACKOVERFLOW
0695         bool
0696 
0697 config DEBUG_STACKOVERFLOW
0698         bool "Check for stack overflows"
0699         depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
0700         ---help---
0701           Say Y here if you want to check for overflows of kernel, IRQ
0702           and exception stacks (if your architecture uses them). This
0703           option will show detailed messages if free stack space drops
0704           below a certain limit.
0705 
0706           These kinds of bugs usually occur when call-chains in the
0707           kernel get too deep, especially when interrupts are
0708           involved.
0709 
0710           Use this in cases where you see apparently random memory
0711           corruption, especially if it appears in 'struct thread_info'
0712 
0713           If in doubt, say "N".
0714 
0715 source "lib/Kconfig.kmemcheck"
0716 
0717 source "lib/Kconfig.kasan"
0718 
0719 endmenu # "Memory Debugging"
0720 
0721 config ARCH_HAS_KCOV
0722         bool
0723         help
0724           KCOV does not have any arch-specific code, but currently it is enabled
0725           only for x86_64. KCOV requires testing on other archs, and most likely
0726           disabling of instrumentation for some early boot code.
0727 
0728 config KCOV
0729         bool "Code coverage for fuzzing"
0730         depends on ARCH_HAS_KCOV
0731         select DEBUG_FS
0732         select GCC_PLUGINS if !COMPILE_TEST
0733         select GCC_PLUGIN_SANCOV if !COMPILE_TEST
0734         help
0735           KCOV exposes kernel code coverage information in a form suitable
0736           for coverage-guided fuzzing (randomized testing).
0737 
0738           If RANDOMIZE_BASE is enabled, PC values will not be stable across
0739           different machines and across reboots. If you need stable PC values,
0740           disable RANDOMIZE_BASE.
0741 
0742           For more details, see Documentation/dev-tools/kcov.rst.
0743 
0744 config KCOV_INSTRUMENT_ALL
0745         bool "Instrument all code by default"
0746         depends on KCOV
0747         default y if KCOV
0748         help
0749           If you are doing generic system call fuzzing (like e.g. syzkaller),
0750           then you will want to instrument the whole kernel and you should
0751           say y here. If you are doing more targeted fuzzing (like e.g.
0752           filesystem fuzzing with AFL) then you will want to enable coverage
0753           for more specific subsets of files, and should say n here.
0754 
0755 config DEBUG_SHIRQ
0756         bool "Debug shared IRQ handlers"
0757         depends on DEBUG_KERNEL
0758         help
0759           Enable this to generate a spurious interrupt as soon as a shared
0760           interrupt handler is registered, and just before one is deregistered.
0761           Drivers ought to be able to handle interrupts coming in at those
0762           points; some don't and need to be caught.
0763 
0764 menu "Debug Lockups and Hangs"
0765 
0766 config LOCKUP_DETECTOR
0767         bool "Detect Hard and Soft Lockups"
0768         depends on DEBUG_KERNEL && !S390
0769         help
0770           Say Y here to enable the kernel to act as a watchdog to detect
0771           hard and soft lockups.
0772 
0773           Softlockups are bugs that cause the kernel to loop in kernel
0774           mode for more than 20 seconds, without giving other tasks a
0775           chance to run.  The current stack trace is displayed upon
0776           detection and the system will stay locked up.
0777 
0778           Hardlockups are bugs that cause the CPU to loop in kernel mode
0779           for more than 10 seconds, without letting other interrupts have a
0780           chance to run.  The current stack trace is displayed upon detection
0781           and the system will stay locked up.
0782 
0783           The overhead should be minimal.  A periodic hrtimer runs to
0784           generate interrupts and kick the watchdog task every 4 seconds.
0785           An NMI is generated every 10 seconds or so to check for hardlockups.
0786 
0787           The frequency of hrtimer and NMI events and the soft and hard lockup
0788           thresholds can be controlled through the sysctl watchdog_thresh.
0789 
0790 config HARDLOCKUP_DETECTOR
0791         def_bool y
0792         depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
0793         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
0794 
0795 config BOOTPARAM_HARDLOCKUP_PANIC
0796         bool "Panic (Reboot) On Hard Lockups"
0797         depends on HARDLOCKUP_DETECTOR
0798         help
0799           Say Y here to enable the kernel to panic on "hard lockups",
0800           which are bugs that cause the kernel to loop in kernel
0801           mode with interrupts disabled for more than 10 seconds (configurable
0802           using the watchdog_thresh sysctl).
0803 
0804           Say N if unsure.
0805 
0806 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
0807         int
0808         depends on HARDLOCKUP_DETECTOR
0809         range 0 1
0810         default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
0811         default 1 if BOOTPARAM_HARDLOCKUP_PANIC
0812 
0813 config BOOTPARAM_SOFTLOCKUP_PANIC
0814         bool "Panic (Reboot) On Soft Lockups"
0815         depends on LOCKUP_DETECTOR
0816         help
0817           Say Y here to enable the kernel to panic on "soft lockups",
0818           which are bugs that cause the kernel to loop in kernel
0819           mode for more than 20 seconds (configurable using the watchdog_thresh
0820           sysctl), without giving other tasks a chance to run.
0821 
0822           The panic can be used in combination with panic_timeout,
0823           to cause the system to reboot automatically after a
0824           lockup has been detected. This feature is useful for
0825           high-availability systems that have uptime guarantees and
0826           where a lockup must be resolved ASAP.
0827 
0828           Say N if unsure.
0829 
0830 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
0831         int
0832         depends on LOCKUP_DETECTOR
0833         range 0 1
0834         default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
0835         default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
0836 
0837 config DETECT_HUNG_TASK
0838         bool "Detect Hung Tasks"
0839         depends on DEBUG_KERNEL
0840         default LOCKUP_DETECTOR
0841         help
0842           Say Y here to enable the kernel to detect "hung tasks",
0843           which are bugs that cause the task to be stuck in
0844           uninterruptible "D" state indefinitely.
0845 
0846           When a hung task is detected, the kernel will print the
0847           current stack trace (which you should report), but the
0848           task will stay in uninterruptible state. If lockdep is
0849           enabled then all held locks will also be reported. This
0850           feature has negligible overhead.
0851 
0852 config DEFAULT_HUNG_TASK_TIMEOUT
0853         int "Default timeout for hung task detection (in seconds)"
0854         depends on DETECT_HUNG_TASK
0855         default 120
0856         help
0857           This option controls the default timeout (in seconds) used
0858           to determine when a task has become non-responsive and should
0859           be considered hung.
0860 
0861           It can be adjusted at runtime via the kernel.hung_task_timeout_secs
0862           sysctl or by writing a value to
0863           /proc/sys/kernel/hung_task_timeout_secs.
0864 
0865           A timeout of 0 disables the check.  The default is two minutes.
0866           Keeping the default should be fine in most cases.
0867 
0868 config BOOTPARAM_HUNG_TASK_PANIC
0869         bool "Panic (Reboot) On Hung Tasks"
0870         depends on DETECT_HUNG_TASK
0871         help
0872           Say Y here to enable the kernel to panic on "hung tasks",
0873           which are bugs that cause the kernel to leave a task stuck
0874           in uninterruptible "D" state.
0875 
0876           The panic can be used in combination with panic_timeout,
0877           to cause the system to reboot automatically after a
0878           hung task has been detected. This feature is useful for
0879           high-availability systems that have uptime guarantees and
0880           where a hung tasks must be resolved ASAP.
0881 
0882           Say N if unsure.
0883 
0884 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
0885         int
0886         depends on DETECT_HUNG_TASK
0887         range 0 1
0888         default 0 if !BOOTPARAM_HUNG_TASK_PANIC
0889         default 1 if BOOTPARAM_HUNG_TASK_PANIC
0890 
0891 config WQ_WATCHDOG
0892         bool "Detect Workqueue Stalls"
0893         depends on DEBUG_KERNEL
0894         help
0895           Say Y here to enable stall detection on workqueues.  If a
0896           worker pool doesn't make forward progress on a pending work
0897           item for over a given amount of time, 30s by default, a
0898           warning message is printed along with dump of workqueue
0899           state.  This can be configured through kernel parameter
0900           "workqueue.watchdog_thresh" and its sysfs counterpart.
0901 
0902 endmenu # "Debug lockups and hangs"
0903 
0904 config PANIC_ON_OOPS
0905         bool "Panic on Oops"
0906         help
0907           Say Y here to enable the kernel to panic when it oopses. This
0908           has the same effect as setting oops=panic on the kernel command
0909           line.
0910 
0911           This feature is useful to ensure that the kernel does not do
0912           anything erroneous after an oops which could result in data
0913           corruption or other issues.
0914 
0915           Say N if unsure.
0916 
0917 config PANIC_ON_OOPS_VALUE
0918         int
0919         range 0 1
0920         default 0 if !PANIC_ON_OOPS
0921         default 1 if PANIC_ON_OOPS
0922 
0923 config PANIC_TIMEOUT
0924         int "panic timeout"
0925         default 0
0926         help
0927           Set the timeout value (in seconds) until a reboot occurs when the
0928           the kernel panics. If n = 0, then we wait forever. A timeout
0929           value n > 0 will wait n seconds before rebooting, while a timeout
0930           value n < 0 will reboot immediately.
0931 
0932 config SCHED_DEBUG
0933         bool "Collect scheduler debugging info"
0934         depends on DEBUG_KERNEL && PROC_FS
0935         default y
0936         help
0937           If you say Y here, the /proc/sched_debug file will be provided
0938           that can help debug the scheduler. The runtime overhead of this
0939           option is minimal.
0940 
0941 config SCHED_INFO
0942         bool
0943         default n
0944 
0945 config SCHEDSTATS
0946         bool "Collect scheduler statistics"
0947         depends on DEBUG_KERNEL && PROC_FS
0948         select SCHED_INFO
0949         help
0950           If you say Y here, additional code will be inserted into the
0951           scheduler and related routines to collect statistics about
0952           scheduler behavior and provide them in /proc/schedstat.  These
0953           stats may be useful for both tuning and debugging the scheduler
0954           If you aren't debugging the scheduler or trying to tune a specific
0955           application, you can say N to avoid the very slight overhead
0956           this adds.
0957 
0958 config SCHED_STACK_END_CHECK
0959         bool "Detect stack corruption on calls to schedule()"
0960         depends on DEBUG_KERNEL
0961         default n
0962         help
0963           This option checks for a stack overrun on calls to schedule().
0964           If the stack end location is found to be over written always panic as
0965           the content of the corrupted region can no longer be trusted.
0966           This is to ensure no erroneous behaviour occurs which could result in
0967           data corruption or a sporadic crash at a later stage once the region
0968           is examined. The runtime overhead introduced is minimal.
0969 
0970 config DEBUG_TIMEKEEPING
0971         bool "Enable extra timekeeping sanity checking"
0972         help
0973           This option will enable additional timekeeping sanity checks
0974           which may be helpful when diagnosing issues where timekeeping
0975           problems are suspected.
0976 
0977           This may include checks in the timekeeping hotpaths, so this
0978           option may have a (very small) performance impact to some
0979           workloads.
0980 
0981           If unsure, say N.
0982 
0983 config TIMER_STATS
0984         bool "Collect kernel timers statistics"
0985         depends on DEBUG_KERNEL && PROC_FS
0986         help
0987           If you say Y here, additional code will be inserted into the
0988           timer routines to collect statistics about kernel timers being
0989           reprogrammed. The statistics can be read from /proc/timer_stats.
0990           The statistics collection is started by writing 1 to /proc/timer_stats,
0991           writing 0 stops it. This feature is useful to collect information
0992           about timer usage patterns in kernel and userspace. This feature
0993           is lightweight if enabled in the kernel config but not activated
0994           (it defaults to deactivated on bootup and will only be activated
0995           if some application like powertop activates it explicitly).
0996 
0997 config DEBUG_PREEMPT
0998         bool "Debug preemptible kernel"
0999         depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
1000         default y
1001         help
1002           If you say Y here then the kernel will use a debug variant of the
1003           commonly used smp_processor_id() function and will print warnings
1004           if kernel code uses it in a preemption-unsafe way. Also, the kernel
1005           will detect preemption count underflows.
1006 
1007 menu "Lock Debugging (spinlocks, mutexes, etc...)"
1008 
1009 config DEBUG_RT_MUTEXES
1010         bool "RT Mutex debugging, deadlock detection"
1011         depends on DEBUG_KERNEL && RT_MUTEXES
1012         help
1013          This allows rt mutex semantics violations and rt mutex related
1014          deadlocks (lockups) to be detected and reported automatically.
1015 
1016 config DEBUG_SPINLOCK
1017         bool "Spinlock and rw-lock debugging: basic checks"
1018         depends on DEBUG_KERNEL
1019         select UNINLINE_SPIN_UNLOCK
1020         help
1021           Say Y here and build SMP to catch missing spinlock initialization
1022           and certain other kinds of spinlock errors commonly made.  This is
1023           best used in conjunction with the NMI watchdog so that spinlock
1024           deadlocks are also debuggable.
1025 
1026 config DEBUG_MUTEXES
1027         bool "Mutex debugging: basic checks"
1028         depends on DEBUG_KERNEL
1029         help
1030          This feature allows mutex semantics violations to be detected and
1031          reported.
1032 
1033 config DEBUG_WW_MUTEX_SLOWPATH
1034         bool "Wait/wound mutex debugging: Slowpath testing"
1035         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1036         select DEBUG_LOCK_ALLOC
1037         select DEBUG_SPINLOCK
1038         select DEBUG_MUTEXES
1039         help
1040          This feature enables slowpath testing for w/w mutex users by
1041          injecting additional -EDEADLK wound/backoff cases. Together with
1042          the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
1043          will test all possible w/w mutex interface abuse with the
1044          exception of simply not acquiring all the required locks.
1045          Note that this feature can introduce significant overhead, so
1046          it really should not be enabled in a production or distro kernel,
1047          even a debug kernel.  If you are a driver writer, enable it.  If
1048          you are a distro, do not.
1049 
1050 config DEBUG_LOCK_ALLOC
1051         bool "Lock debugging: detect incorrect freeing of live locks"
1052         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1053         select DEBUG_SPINLOCK
1054         select DEBUG_MUTEXES
1055         select LOCKDEP
1056         help
1057          This feature will check whether any held lock (spinlock, rwlock,
1058          mutex or rwsem) is incorrectly freed by the kernel, via any of the
1059          memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
1060          vfree(), etc.), whether a live lock is incorrectly reinitialized via
1061          spin_lock_init()/mutex_init()/etc., or whether there is any lock
1062          held during task exit.
1063 
1064 config PROVE_LOCKING
1065         bool "Lock debugging: prove locking correctness"
1066         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1067         select LOCKDEP
1068         select DEBUG_SPINLOCK
1069         select DEBUG_MUTEXES
1070         select DEBUG_LOCK_ALLOC
1071         select TRACE_IRQFLAGS
1072         default n
1073         help
1074          This feature enables the kernel to prove that all locking
1075          that occurs in the kernel runtime is mathematically
1076          correct: that under no circumstance could an arbitrary (and
1077          not yet triggered) combination of observed locking
1078          sequences (on an arbitrary number of CPUs, running an
1079          arbitrary number of tasks and interrupt contexts) cause a
1080          deadlock.
1081 
1082          In short, this feature enables the kernel to report locking
1083          related deadlocks before they actually occur.
1084 
1085          The proof does not depend on how hard and complex a
1086          deadlock scenario would be to trigger: how many
1087          participant CPUs, tasks and irq-contexts would be needed
1088          for it to trigger. The proof also does not depend on
1089          timing: if a race and a resulting deadlock is possible
1090          theoretically (no matter how unlikely the race scenario
1091          is), it will be proven so and will immediately be
1092          reported by the kernel (once the event is observed that
1093          makes the deadlock theoretically possible).
1094 
1095          If a deadlock is impossible (i.e. the locking rules, as
1096          observed by the kernel, are mathematically correct), the
1097          kernel reports nothing.
1098 
1099          NOTE: this feature can also be enabled for rwlocks, mutexes
1100          and rwsems - in which case all dependencies between these
1101          different locking variants are observed and mapped too, and
1102          the proof of observed correctness is also maintained for an
1103          arbitrary combination of these separate locking variants.
1104 
1105          For more details, see Documentation/locking/lockdep-design.txt.
1106 
1107 config PROVE_LOCKING_SMALL
1108         bool
1109 
1110 config LOCKDEP
1111         bool
1112         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1113         select STACKTRACE
1114         select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
1115         select KALLSYMS
1116         select KALLSYMS_ALL
1117 
1118 config LOCK_STAT
1119         bool "Lock usage statistics"
1120         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1121         select LOCKDEP
1122         select DEBUG_SPINLOCK
1123         select DEBUG_MUTEXES
1124         select DEBUG_LOCK_ALLOC
1125         default n
1126         help
1127          This feature enables tracking lock contention points
1128 
1129          For more details, see Documentation/locking/lockstat.txt
1130 
1131          This also enables lock events required by "perf lock",
1132          subcommand of perf.
1133          If you want to use "perf lock", you also need to turn on
1134          CONFIG_EVENT_TRACING.
1135 
1136          CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
1137          (CONFIG_LOCKDEP defines "acquire" and "release" events.)
1138 
1139 config DEBUG_LOCKDEP
1140         bool "Lock dependency engine debugging"
1141         depends on DEBUG_KERNEL && LOCKDEP
1142         help
1143           If you say Y here, the lock dependency engine will do
1144           additional runtime checks to debug itself, at the price
1145           of more runtime overhead.
1146 
1147 config DEBUG_ATOMIC_SLEEP
1148         bool "Sleep inside atomic section checking"
1149         select PREEMPT_COUNT
1150         depends on DEBUG_KERNEL
1151         help
1152           If you say Y here, various routines which may sleep will become very
1153           noisy if they are called inside atomic sections: when a spinlock is
1154           held, inside an rcu read side critical section, inside preempt disabled
1155           sections, inside an interrupt, etc...
1156 
1157 config DEBUG_LOCKING_API_SELFTESTS
1158         bool "Locking API boot-time self-tests"
1159         depends on DEBUG_KERNEL
1160         help
1161           Say Y here if you want the kernel to run a short self-test during
1162           bootup. The self-test checks whether common types of locking bugs
1163           are detected by debugging mechanisms or not. (if you disable
1164           lock debugging then those bugs wont be detected of course.)
1165           The following locking APIs are covered: spinlocks, rwlocks,
1166           mutexes and rwsems.
1167 
1168 config LOCK_TORTURE_TEST
1169         tristate "torture tests for locking"
1170         depends on DEBUG_KERNEL
1171         select TORTURE_TEST
1172         default n
1173         help
1174           This option provides a kernel module that runs torture tests
1175           on kernel locking primitives.  The kernel module may be built
1176           after the fact on the running kernel to be tested, if desired.
1177 
1178           Say Y here if you want kernel locking-primitive torture tests
1179           to be built into the kernel.
1180           Say M if you want these torture tests to build as a module.
1181           Say N if you are unsure.
1182 
1183 endmenu # lock debugging
1184 
1185 config TRACE_IRQFLAGS
1186         bool
1187         help
1188           Enables hooks to interrupt enabling and disabling for
1189           either tracing or lock debugging.
1190 
1191 config STACKTRACE
1192         bool "Stack backtrace support"
1193         depends on STACKTRACE_SUPPORT
1194         help
1195           This option causes the kernel to create a /proc/pid/stack for
1196           every process, showing its current stack trace.
1197           It is also used by various kernel debugging features that require
1198           stack trace generation.
1199 
1200 config DEBUG_KOBJECT
1201         bool "kobject debugging"
1202         depends on DEBUG_KERNEL
1203         help
1204           If you say Y here, some extra kobject debugging messages will be sent
1205           to the syslog. 
1206 
1207 config DEBUG_KOBJECT_RELEASE
1208         bool "kobject release debugging"
1209         depends on DEBUG_OBJECTS_TIMERS
1210         help
1211           kobjects are reference counted objects.  This means that their
1212           last reference count put is not predictable, and the kobject can
1213           live on past the point at which a driver decides to drop it's
1214           initial reference to the kobject gained on allocation.  An
1215           example of this would be a struct device which has just been
1216           unregistered.
1217 
1218           However, some buggy drivers assume that after such an operation,
1219           the memory backing the kobject can be immediately freed.  This
1220           goes completely against the principles of a refcounted object.
1221 
1222           If you say Y here, the kernel will delay the release of kobjects
1223           on the last reference count to improve the visibility of this
1224           kind of kobject release bug.
1225 
1226 config HAVE_DEBUG_BUGVERBOSE
1227         bool
1228 
1229 config DEBUG_BUGVERBOSE
1230         bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1231         depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1232         default y
1233         help
1234           Say Y here to make BUG() panics output the file name and line number
1235           of the BUG call as well as the EIP and oops trace.  This aids
1236           debugging but costs about 70-100K of memory.
1237 
1238 config DEBUG_LIST
1239         bool "Debug linked list manipulation"
1240         depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
1241         help
1242           Enable this to turn on extended checks in the linked-list
1243           walking routines.
1244 
1245           If unsure, say N.
1246 
1247 config DEBUG_PI_LIST
1248         bool "Debug priority linked list manipulation"
1249         depends on DEBUG_KERNEL
1250         help
1251           Enable this to turn on extended checks in the priority-ordered
1252           linked-list (plist) walking routines.  This checks the entire
1253           list multiple times during each manipulation.
1254 
1255           If unsure, say N.
1256 
1257 config DEBUG_SG
1258         bool "Debug SG table operations"
1259         depends on DEBUG_KERNEL
1260         help
1261           Enable this to turn on checks on scatter-gather tables. This can
1262           help find problems with drivers that do not properly initialize
1263           their sg tables.
1264 
1265           If unsure, say N.
1266 
1267 config DEBUG_NOTIFIERS
1268         bool "Debug notifier call chains"
1269         depends on DEBUG_KERNEL
1270         help
1271           Enable this to turn on sanity checking for notifier call chains.
1272           This is most useful for kernel developers to make sure that
1273           modules properly unregister themselves from notifier chains.
1274           This is a relatively cheap check but if you care about maximum
1275           performance, say N.
1276 
1277 config DEBUG_CREDENTIALS
1278         bool "Debug credential management"
1279         depends on DEBUG_KERNEL
1280         help
1281           Enable this to turn on some debug checking for credential
1282           management.  The additional code keeps track of the number of
1283           pointers from task_structs to any given cred struct, and checks to
1284           see that this number never exceeds the usage count of the cred
1285           struct.
1286 
1287           Furthermore, if SELinux is enabled, this also checks that the
1288           security pointer in the cred struct is never seen to be invalid.
1289 
1290           If unsure, say N.
1291 
1292 menu "RCU Debugging"
1293 
1294 config PROVE_RCU
1295         def_bool PROVE_LOCKING
1296 
1297 config PROVE_RCU_REPEATEDLY
1298         bool "RCU debugging: don't disable PROVE_RCU on first splat"
1299         depends on PROVE_RCU
1300         default n
1301         help
1302          By itself, PROVE_RCU will disable checking upon issuing the
1303          first warning (or "splat").  This feature prevents such
1304          disabling, allowing multiple RCU-lockdep warnings to be printed
1305          on a single reboot.
1306 
1307          Say Y to allow multiple RCU-lockdep warnings per boot.
1308 
1309          Say N if you are unsure.
1310 
1311 config SPARSE_RCU_POINTER
1312         bool "RCU debugging: sparse-based checks for pointer usage"
1313         default n
1314         help
1315          This feature enables the __rcu sparse annotation for
1316          RCU-protected pointers.  This annotation will cause sparse
1317          to flag any non-RCU used of annotated pointers.  This can be
1318          helpful when debugging RCU usage.  Please note that this feature
1319          is not intended to enforce code cleanliness; it is instead merely
1320          a debugging aid.
1321 
1322          Say Y to make sparse flag questionable use of RCU-protected pointers
1323 
1324          Say N if you are unsure.
1325 
1326 config TORTURE_TEST
1327         tristate
1328         default n
1329 
1330 config RCU_PERF_TEST
1331         tristate "performance tests for RCU"
1332         depends on DEBUG_KERNEL
1333         select TORTURE_TEST
1334         select SRCU
1335         select TASKS_RCU
1336         default n
1337         help
1338           This option provides a kernel module that runs performance
1339           tests on the RCU infrastructure.  The kernel module may be built
1340           after the fact on the running kernel to be tested, if desired.
1341 
1342           Say Y here if you want RCU performance tests to be built into
1343           the kernel.
1344           Say M if you want the RCU performance tests to build as a module.
1345           Say N if you are unsure.
1346 
1347 config RCU_TORTURE_TEST
1348         tristate "torture tests for RCU"
1349         depends on DEBUG_KERNEL
1350         select TORTURE_TEST
1351         select SRCU
1352         select TASKS_RCU
1353         default n
1354         help
1355           This option provides a kernel module that runs torture tests
1356           on the RCU infrastructure.  The kernel module may be built
1357           after the fact on the running kernel to be tested, if desired.
1358 
1359           Say Y here if you want RCU torture tests to be built into
1360           the kernel.
1361           Say M if you want the RCU torture tests to build as a module.
1362           Say N if you are unsure.
1363 
1364 config RCU_TORTURE_TEST_SLOW_PREINIT
1365         bool "Slow down RCU grace-period pre-initialization to expose races"
1366         depends on RCU_TORTURE_TEST
1367         help
1368           This option delays grace-period pre-initialization (the
1369           propagation of CPU-hotplug changes up the rcu_node combining
1370           tree) for a few jiffies between initializing each pair of
1371           consecutive rcu_node structures.  This helps to expose races
1372           involving grace-period pre-initialization, in other words, it
1373           makes your kernel less stable.  It can also greatly increase
1374           grace-period latency, especially on systems with large numbers
1375           of CPUs.  This is useful when torture-testing RCU, but in
1376           almost no other circumstance.
1377 
1378           Say Y here if you want your system to crash and hang more often.
1379           Say N if you want a sane system.
1380 
1381 config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
1382         int "How much to slow down RCU grace-period pre-initialization"
1383         range 0 5
1384         default 3
1385         depends on RCU_TORTURE_TEST_SLOW_PREINIT
1386         help
1387           This option specifies the number of jiffies to wait between
1388           each rcu_node structure pre-initialization step.
1389 
1390 config RCU_TORTURE_TEST_SLOW_INIT
1391         bool "Slow down RCU grace-period initialization to expose races"
1392         depends on RCU_TORTURE_TEST
1393         help
1394           This option delays grace-period initialization for a few
1395           jiffies between initializing each pair of consecutive
1396           rcu_node structures.  This helps to expose races involving
1397           grace-period initialization, in other words, it makes your
1398           kernel less stable.  It can also greatly increase grace-period
1399           latency, especially on systems with large numbers of CPUs.
1400           This is useful when torture-testing RCU, but in almost no
1401           other circumstance.
1402 
1403           Say Y here if you want your system to crash and hang more often.
1404           Say N if you want a sane system.
1405 
1406 config RCU_TORTURE_TEST_SLOW_INIT_DELAY
1407         int "How much to slow down RCU grace-period initialization"
1408         range 0 5
1409         default 3
1410         depends on RCU_TORTURE_TEST_SLOW_INIT
1411         help
1412           This option specifies the number of jiffies to wait between
1413           each rcu_node structure initialization.
1414 
1415 config RCU_TORTURE_TEST_SLOW_CLEANUP
1416         bool "Slow down RCU grace-period cleanup to expose races"
1417         depends on RCU_TORTURE_TEST
1418         help
1419           This option delays grace-period cleanup for a few jiffies
1420           between cleaning up each pair of consecutive rcu_node
1421           structures.  This helps to expose races involving grace-period
1422           cleanup, in other words, it makes your kernel less stable.
1423           It can also greatly increase grace-period latency, especially
1424           on systems with large numbers of CPUs.  This is useful when
1425           torture-testing RCU, but in almost no other circumstance.
1426 
1427           Say Y here if you want your system to crash and hang more often.
1428           Say N if you want a sane system.
1429 
1430 config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
1431         int "How much to slow down RCU grace-period cleanup"
1432         range 0 5
1433         default 3
1434         depends on RCU_TORTURE_TEST_SLOW_CLEANUP
1435         help
1436           This option specifies the number of jiffies to wait between
1437           each rcu_node structure cleanup operation.
1438 
1439 config RCU_CPU_STALL_TIMEOUT
1440         int "RCU CPU stall timeout in seconds"
1441         depends on RCU_STALL_COMMON
1442         range 3 300
1443         default 21
1444         help
1445           If a given RCU grace period extends more than the specified
1446           number of seconds, a CPU stall warning is printed.  If the
1447           RCU grace period persists, additional CPU stall warnings are
1448           printed at more widely spaced intervals.
1449 
1450 config RCU_TRACE
1451         bool "Enable tracing for RCU"
1452         depends on DEBUG_KERNEL
1453         select TRACE_CLOCK
1454         help
1455           This option provides tracing in RCU which presents stats
1456           in debugfs for debugging RCU implementation.  It also enables
1457           additional tracepoints for ftrace-style event tracing.
1458 
1459           Say Y here if you want to enable RCU tracing
1460           Say N if you are unsure.
1461 
1462 config RCU_EQS_DEBUG
1463         bool "Provide debugging asserts for adding NO_HZ support to an arch"
1464         depends on DEBUG_KERNEL
1465         help
1466           This option provides consistency checks in RCU's handling of
1467           NO_HZ.  These checks have proven quite helpful in detecting
1468           bugs in arch-specific NO_HZ code.
1469 
1470           Say N here if you need ultimate kernel/user switch latencies
1471           Say Y if you are unsure
1472 
1473 endmenu # "RCU Debugging"
1474 
1475 config DEBUG_WQ_FORCE_RR_CPU
1476         bool "Force round-robin CPU selection for unbound work items"
1477         depends on DEBUG_KERNEL
1478         default n
1479         help
1480           Workqueue used to implicitly guarantee that work items queued
1481           without explicit CPU specified are put on the local CPU.  This
1482           guarantee is no longer true and while local CPU is still
1483           preferred work items may be put on foreign CPUs.  Kernel
1484           parameter "workqueue.debug_force_rr_cpu" is added to force
1485           round-robin CPU selection to flush out usages which depend on the
1486           now broken guarantee.  This config option enables the debug
1487           feature by default.  When enabled, memory and cache locality will
1488           be impacted.
1489 
1490 config DEBUG_BLOCK_EXT_DEVT
1491         bool "Force extended block device numbers and spread them"
1492         depends on DEBUG_KERNEL
1493         depends on BLOCK
1494         default n
1495         help
1496           BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1497           SOME DISTRIBUTIONS.  DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1498           YOU ARE DOING.  Distros, please enable this and fix whatever
1499           is broken.
1500 
1501           Conventionally, block device numbers are allocated from
1502           predetermined contiguous area.  However, extended block area
1503           may introduce non-contiguous block device numbers.  This
1504           option forces most block device numbers to be allocated from
1505           the extended space and spreads them to discover kernel or
1506           userland code paths which assume predetermined contiguous
1507           device number allocation.
1508 
1509           Note that turning on this debug option shuffles all the
1510           device numbers for all IDE and SCSI devices including libata
1511           ones, so root partition specified using device number
1512           directly (via rdev or root=MAJ:MIN) won't work anymore.
1513           Textual device names (root=/dev/sdXn) will continue to work.
1514 
1515           Say N if you are unsure.
1516 
1517 config CPU_HOTPLUG_STATE_CONTROL
1518         bool "Enable CPU hotplug state control"
1519         depends on DEBUG_KERNEL
1520         depends on HOTPLUG_CPU
1521         default n
1522         help
1523           Allows to write steps between "offline" and "online" to the CPUs
1524           sysfs target file so states can be stepped granular. This is a debug
1525           option for now as the hotplug machinery cannot be stopped and
1526           restarted at arbitrary points yet.
1527 
1528           Say N if your are unsure.
1529 
1530 config NOTIFIER_ERROR_INJECTION
1531         tristate "Notifier error injection"
1532         depends on DEBUG_KERNEL
1533         select DEBUG_FS
1534         help
1535           This option provides the ability to inject artificial errors to
1536           specified notifier chain callbacks. It is useful to test the error
1537           handling of notifier call chain failures.
1538 
1539           Say N if unsure.
1540 
1541 config PM_NOTIFIER_ERROR_INJECT
1542         tristate "PM notifier error injection module"
1543         depends on PM && NOTIFIER_ERROR_INJECTION
1544         default m if PM_DEBUG
1545         help
1546           This option provides the ability to inject artificial errors to
1547           PM notifier chain callbacks.  It is controlled through debugfs
1548           interface /sys/kernel/debug/notifier-error-inject/pm
1549 
1550           If the notifier call chain should be failed with some events
1551           notified, write the error code to "actions/<notifier event>/error".
1552 
1553           Example: Inject PM suspend error (-12 = -ENOMEM)
1554 
1555           # cd /sys/kernel/debug/notifier-error-inject/pm/
1556           # echo -12 > actions/PM_SUSPEND_PREPARE/error
1557           # echo mem > /sys/power/state
1558           bash: echo: write error: Cannot allocate memory
1559 
1560           To compile this code as a module, choose M here: the module will
1561           be called pm-notifier-error-inject.
1562 
1563           If unsure, say N.
1564 
1565 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1566         tristate "OF reconfig notifier error injection module"
1567         depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1568         help
1569           This option provides the ability to inject artificial errors to
1570           OF reconfig notifier chain callbacks.  It is controlled
1571           through debugfs interface under
1572           /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1573 
1574           If the notifier call chain should be failed with some events
1575           notified, write the error code to "actions/<notifier event>/error".
1576 
1577           To compile this code as a module, choose M here: the module will
1578           be called of-reconfig-notifier-error-inject.
1579 
1580           If unsure, say N.
1581 
1582 config NETDEV_NOTIFIER_ERROR_INJECT
1583         tristate "Netdev notifier error injection module"
1584         depends on NET && NOTIFIER_ERROR_INJECTION
1585         help
1586           This option provides the ability to inject artificial errors to
1587           netdevice notifier chain callbacks.  It is controlled through debugfs
1588           interface /sys/kernel/debug/notifier-error-inject/netdev
1589 
1590           If the notifier call chain should be failed with some events
1591           notified, write the error code to "actions/<notifier event>/error".
1592 
1593           Example: Inject netdevice mtu change error (-22 = -EINVAL)
1594 
1595           # cd /sys/kernel/debug/notifier-error-inject/netdev
1596           # echo -22 > actions/NETDEV_CHANGEMTU/error
1597           # ip link set eth0 mtu 1024
1598           RTNETLINK answers: Invalid argument
1599 
1600           To compile this code as a module, choose M here: the module will
1601           be called netdev-notifier-error-inject.
1602 
1603           If unsure, say N.
1604 
1605 config FAULT_INJECTION
1606         bool "Fault-injection framework"
1607         depends on DEBUG_KERNEL
1608         help
1609           Provide fault-injection framework.
1610           For more details, see Documentation/fault-injection/.
1611 
1612 config FAILSLAB
1613         bool "Fault-injection capability for kmalloc"
1614         depends on FAULT_INJECTION
1615         depends on SLAB || SLUB
1616         help
1617           Provide fault-injection capability for kmalloc.
1618 
1619 config FAIL_PAGE_ALLOC
1620         bool "Fault-injection capabilitiy for alloc_pages()"
1621         depends on FAULT_INJECTION
1622         help
1623           Provide fault-injection capability for alloc_pages().
1624 
1625 config FAIL_MAKE_REQUEST
1626         bool "Fault-injection capability for disk IO"
1627         depends on FAULT_INJECTION && BLOCK
1628         help
1629           Provide fault-injection capability for disk IO.
1630 
1631 config FAIL_IO_TIMEOUT
1632         bool "Fault-injection capability for faking disk interrupts"
1633         depends on FAULT_INJECTION && BLOCK
1634         help
1635           Provide fault-injection capability on end IO handling. This
1636           will make the block layer "forget" an interrupt as configured,
1637           thus exercising the error handling.
1638 
1639           Only works with drivers that use the generic timeout handling,
1640           for others it wont do anything.
1641 
1642 config FAIL_MMC_REQUEST
1643         bool "Fault-injection capability for MMC IO"
1644         depends on FAULT_INJECTION_DEBUG_FS && MMC
1645         help
1646           Provide fault-injection capability for MMC IO.
1647           This will make the mmc core return data errors. This is
1648           useful to test the error handling in the mmc block device
1649           and to test how the mmc host driver handles retries from
1650           the block device.
1651 
1652 config FAIL_FUTEX
1653         bool "Fault-injection capability for futexes"
1654         select DEBUG_FS
1655         depends on FAULT_INJECTION && FUTEX
1656         help
1657           Provide fault-injection capability for futexes.
1658 
1659 config FAULT_INJECTION_DEBUG_FS
1660         bool "Debugfs entries for fault-injection capabilities"
1661         depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1662         help
1663           Enable configuration of fault-injection capabilities via debugfs.
1664 
1665 config FAULT_INJECTION_STACKTRACE_FILTER
1666         bool "stacktrace filter for fault-injection capabilities"
1667         depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1668         depends on !X86_64
1669         select STACKTRACE
1670         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1671         help
1672           Provide stacktrace filter for fault-injection capabilities
1673 
1674 config LATENCYTOP
1675         bool "Latency measuring infrastructure"
1676         depends on DEBUG_KERNEL
1677         depends on STACKTRACE_SUPPORT
1678         depends on PROC_FS
1679         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1680         select KALLSYMS
1681         select KALLSYMS_ALL
1682         select STACKTRACE
1683         select SCHEDSTATS
1684         select SCHED_DEBUG
1685         help
1686           Enable this option if you want to use the LatencyTOP tool
1687           to find out which userspace is blocking on what kernel operations.
1688 
1689 source kernel/trace/Kconfig
1690 
1691 menu "Runtime Testing"
1692 
1693 config LKDTM
1694         tristate "Linux Kernel Dump Test Tool Module"
1695         depends on DEBUG_FS
1696         depends on BLOCK
1697         default n
1698         help
1699         This module enables testing of the different dumping mechanisms by
1700         inducing system failures at predefined crash points.
1701         If you don't need it: say N
1702         Choose M here to compile this code as a module. The module will be
1703         called lkdtm.
1704 
1705         Documentation on how to use the module can be found in
1706         Documentation/fault-injection/provoke-crashes.txt
1707 
1708 config TEST_LIST_SORT
1709         bool "Linked list sorting test"
1710         depends on DEBUG_KERNEL
1711         help
1712           Enable this to turn on 'list_sort()' function test. This test is
1713           executed only once during system boot, so affects only boot time.
1714 
1715           If unsure, say N.
1716 
1717 config KPROBES_SANITY_TEST
1718         bool "Kprobes sanity tests"
1719         depends on DEBUG_KERNEL
1720         depends on KPROBES
1721         default n
1722         help
1723           This option provides for testing basic kprobes functionality on
1724           boot. A sample kprobe, jprobe and kretprobe are inserted and
1725           verified for functionality.
1726 
1727           Say N if you are unsure.
1728 
1729 config BACKTRACE_SELF_TEST
1730         tristate "Self test for the backtrace code"
1731         depends on DEBUG_KERNEL
1732         default n
1733         help
1734           This option provides a kernel module that can be used to test
1735           the kernel stack backtrace code. This option is not useful
1736           for distributions or general kernels, but only for kernel
1737           developers working on architecture code.
1738 
1739           Note that if you want to also test saved backtraces, you will
1740           have to enable STACKTRACE as well.
1741 
1742           Say N if you are unsure.
1743 
1744 config RBTREE_TEST
1745         tristate "Red-Black tree test"
1746         depends on DEBUG_KERNEL
1747         help
1748           A benchmark measuring the performance of the rbtree library.
1749           Also includes rbtree invariant checks.
1750 
1751 config INTERVAL_TREE_TEST
1752         tristate "Interval tree test"
1753         depends on m && DEBUG_KERNEL
1754         select INTERVAL_TREE
1755         help
1756           A benchmark measuring the performance of the interval tree library
1757 
1758 config PERCPU_TEST
1759         tristate "Per cpu operations test"
1760         depends on m && DEBUG_KERNEL
1761         help
1762           Enable this option to build test module which validates per-cpu
1763           operations.
1764 
1765           If unsure, say N.
1766 
1767 config ATOMIC64_SELFTEST
1768         bool "Perform an atomic64_t self-test at boot"
1769         help
1770           Enable this option to test the atomic64_t functions at boot.
1771 
1772           If unsure, say N.
1773 
1774 config ASYNC_RAID6_TEST
1775         tristate "Self test for hardware accelerated raid6 recovery"
1776         depends on ASYNC_RAID6_RECOV
1777         select ASYNC_MEMCPY
1778         ---help---
1779           This is a one-shot self test that permutes through the
1780           recovery of all the possible two disk failure scenarios for a
1781           N-disk array.  Recovery is performed with the asynchronous
1782           raid6 recovery routines, and will optionally use an offload
1783           engine if one is available.
1784 
1785           If unsure, say N.
1786 
1787 config TEST_HEXDUMP
1788         tristate "Test functions located in the hexdump module at runtime"
1789 
1790 config TEST_STRING_HELPERS
1791         tristate "Test functions located in the string_helpers module at runtime"
1792 
1793 config TEST_KSTRTOX
1794         tristate "Test kstrto*() family of functions at runtime"
1795 
1796 config TEST_PRINTF
1797         tristate "Test printf() family of functions at runtime"
1798 
1799 config TEST_BITMAP
1800         tristate "Test bitmap_*() family of functions at runtime"
1801         default n
1802         help
1803           Enable this option to test the bitmap functions at boot.
1804 
1805           If unsure, say N.
1806 
1807 config TEST_UUID
1808         tristate "Test functions located in the uuid module at runtime"
1809 
1810 config TEST_RHASHTABLE
1811         tristate "Perform selftest on resizable hash table"
1812         default n
1813         help
1814           Enable this option to test the rhashtable functions at boot.
1815 
1816           If unsure, say N.
1817 
1818 config TEST_HASH
1819         tristate "Perform selftest on hash functions"
1820         default n
1821         help
1822           Enable this option to test the kernel's integer (<linux/hash,h>)
1823           and string (<linux/stringhash.h>) hash functions on boot
1824           (or module load).
1825 
1826           This is intended to help people writing architecture-specific
1827           optimized versions.  If unsure, say N.
1828 
1829 endmenu # runtime tests
1830 
1831 config PROVIDE_OHCI1394_DMA_INIT
1832         bool "Remote debugging over FireWire early on boot"
1833         depends on PCI && X86
1834         help
1835           If you want to debug problems which hang or crash the kernel early
1836           on boot and the crashing machine has a FireWire port, you can use
1837           this feature to remotely access the memory of the crashed machine
1838           over FireWire. This employs remote DMA as part of the OHCI1394
1839           specification which is now the standard for FireWire controllers.
1840 
1841           With remote DMA, you can monitor the printk buffer remotely using
1842           firescope and access all memory below 4GB using fireproxy from gdb.
1843           Even controlling a kernel debugger is possible using remote DMA.
1844 
1845           Usage:
1846 
1847           If ohci1394_dma=early is used as boot parameter, it will initialize
1848           all OHCI1394 controllers which are found in the PCI config space.
1849 
1850           As all changes to the FireWire bus such as enabling and disabling
1851           devices cause a bus reset and thereby disable remote DMA for all
1852           devices, be sure to have the cable plugged and FireWire enabled on
1853           the debugging host before booting the debug target for debugging.
1854 
1855           This code (~1k) is freed after boot. By then, the firewire stack
1856           in charge of the OHCI-1394 controllers should be used instead.
1857 
1858           See Documentation/debugging-via-ohci1394.txt for more information.
1859 
1860 config DMA_API_DEBUG
1861         bool "Enable debugging of DMA-API usage"
1862         depends on HAVE_DMA_API_DEBUG
1863         help
1864           Enable this option to debug the use of the DMA API by device drivers.
1865           With this option you will be able to detect common bugs in device
1866           drivers like double-freeing of DMA mappings or freeing mappings that
1867           were never allocated.
1868 
1869           This also attempts to catch cases where a page owned by DMA is
1870           accessed by the cpu in a way that could cause data corruption.  For
1871           example, this enables cow_user_page() to check that the source page is
1872           not undergoing DMA.
1873 
1874           This option causes a performance degradation.  Use only if you want to
1875           debug device drivers and dma interactions.
1876 
1877           If unsure, say N.
1878 
1879 config TEST_LKM
1880         tristate "Test module loading with 'hello world' module"
1881         default n
1882         depends on m
1883         help
1884           This builds the "test_module" module that emits "Hello, world"
1885           on printk when loaded. It is designed to be used for basic
1886           evaluation of the module loading subsystem (for example when
1887           validating module verification). It lacks any extra dependencies,
1888           and will not normally be loaded by the system unless explicitly
1889           requested by name.
1890 
1891           If unsure, say N.
1892 
1893 config TEST_USER_COPY
1894         tristate "Test user/kernel boundary protections"
1895         default n
1896         depends on m
1897         help
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
1902           protections.
1903 
1904           If unsure, say N.
1905 
1906 config TEST_BPF
1907         tristate "Test BPF filter functionality"
1908         default n
1909         depends on m && NET
1910         help
1911           This builds the "test_bpf" module that runs various test vectors
1912           against the BPF interpreter or BPF JIT compiler depending on the
1913           current setting. This is in particular useful for BPF JIT compiler
1914           development, but also to run regression tests against changes in
1915           the interpreter code. It also enables test stubs for eBPF maps and
1916           verifier used by user space verifier testsuite.
1917 
1918           If unsure, say N.
1919 
1920 config TEST_FIRMWARE
1921         tristate "Test firmware loading via userspace interface"
1922         default n
1923         depends on FW_LOADER
1924         help
1925           This builds the "test_firmware" module that creates a userspace
1926           interface for testing firmware loading. This can be used to
1927           control the triggering of firmware loading without needing an
1928           actual firmware-using device. The contents can be rechecked by
1929           userspace.
1930 
1931           If unsure, say N.
1932 
1933 config TEST_UDELAY
1934         tristate "udelay test driver"
1935         default n
1936         help
1937           This builds the "udelay_test" module that helps to make sure
1938           that udelay() is working properly.
1939 
1940           If unsure, say N.
1941 
1942 config MEMTEST
1943         bool "Memtest"
1944         depends on HAVE_MEMBLOCK
1945         ---help---
1946           This option adds a kernel parameter 'memtest', which allows memtest
1947           to be set.
1948                 memtest=0, mean disabled; -- default
1949                 memtest=1, mean do 1 test pattern;
1950                 ...
1951                 memtest=17, mean do 17 test patterns.
1952           If you are unsure how to answer this question, answer N.
1953 
1954 config TEST_STATIC_KEYS
1955         tristate "Test static keys"
1956         default n
1957         depends on m
1958         help
1959           Test the static key interfaces.
1960 
1961           If unsure, say N.
1962 
1963 config BUG_ON_DATA_CORRUPTION
1964         bool "Trigger a BUG when data corruption is detected"
1965         select DEBUG_LIST
1966         help
1967           Select this option if the kernel should BUG when it encounters
1968           data corruption in kernel memory structures when they get checked
1969           for validity.
1970 
1971           If unsure, say N.
1972 
1973 source "samples/Kconfig"
1974 
1975 source "lib/Kconfig.kgdb"
1976 
1977 source "lib/Kconfig.ubsan"
1978 
1979 config ARCH_HAS_DEVMEM_IS_ALLOWED
1980         bool
1981 
1982 config STRICT_DEVMEM
1983         bool "Filter access to /dev/mem"
1984         depends on MMU && DEVMEM
1985         depends on ARCH_HAS_DEVMEM_IS_ALLOWED
1986         default y if TILE || PPC
1987         ---help---
1988           If this option is disabled, you allow userspace (root) access to all
1989           of memory, including kernel and userspace memory. Accidental
1990           access to this is obviously disastrous, but specific access can
1991           be used by people debugging the kernel. Note that with PAT support
1992           enabled, even in this case there are restrictions on /dev/mem
1993           use due to the cache aliasing requirements.
1994 
1995           If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
1996           file only allows userspace access to PCI space and the BIOS code and
1997           data regions.  This is sufficient for dosemu and X and all common
1998           users of /dev/mem.
1999 
2000           If in doubt, say Y.
2001 
2002 config IO_STRICT_DEVMEM
2003         bool "Filter I/O access to /dev/mem"
2004         depends on STRICT_DEVMEM
2005         ---help---
2006           If this option is disabled, you allow userspace (root) access to all
2007           io-memory regardless of whether a driver is actively using that
2008           range.  Accidental access to this is obviously disastrous, but
2009           specific access can be used by people debugging kernel drivers.
2010 
2011           If this option is switched on, the /dev/mem file only allows
2012           userspace access to *idle* io-memory ranges (see /proc/iomem) This
2013           may break traditional users of /dev/mem (dosemu, legacy X, etc...)
2014           if the driver using a given range cannot be disabled.
2015 
2016           If in doubt, say Y.