lib/Kconfig.debug

   1 menu "printk and dmesg options"
   2
   3 config PRINTK_TIME
   4         bool "Show timing information on printks"
   5         depends on PRINTK
   6         help
   7           Selecting this option causes time stamps of the printk()
   8           messages to be added to the output of the syslog() system
   9           call and at the console.
  10
  11           The timestamp is always recorded internally, and exported
  12           to /dev/kmsg. This flag just specifies if the timestamp should
  13           be included, not that the timestamp is recorded.
  14
  15           The behavior is also controlled by the kernel command line
  16           parameter printk.time=1. See Documentation/kernel-parameters.txt
  17
  18 config MESSAGE_LOGLEVEL_DEFAULT
  19         int "Default message log level (1-7)"
  20         range 1 7
  21         default "4"
  22         help
  23           Default log level for printk statements with no specified priority.
  24
  25           This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
  26           that are auditing their logs closely may want to set it to a lower
  27           priority.
  28
  29 config BOOT_PRINTK_DELAY
  30         bool "Delay each boot printk message by N milliseconds"
  31         depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
  32         help
  33           This build option allows you to read kernel boot messages
  34           by inserting a short delay after each one.  The delay is
  35           specified in milliseconds on the kernel command line,
  36           using "boot_delay=N".
  37
  38           It is likely that you would also need to use "lpj=M" to preset
  39           the "loops per jiffie" value.
  40           See a previous boot log for the "lpj" value to use for your
  41           system, and then set "lpj=M" before setting "boot_delay=N".
  42           NOTE:  Using this option may adversely affect SMP systems.
  43           I.e., processors other than the first one may not boot up.
  44           BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
  45           what it believes to be lockup conditions.
  46
  47 config DYNAMIC_DEBUG
  48         bool "Enable dynamic printk() support"
  49         default n
  50         depends on PRINTK
  51         depends on DEBUG_FS
  52         help
  53
  54           Compiles debug level messages into the kernel, which would not
  55           otherwise be available at runtime. These messages can then be
  56           enabled/disabled based on various levels of scope - per source file,
  57           function, module, format string, and line number. This mechanism
  58           implicitly compiles in all pr_debug() and dev_dbg() calls, which
  59           enlarges the kernel text size by about 2%.
  60
  61           If a source file is compiled with DEBUG flag set, any
  62           pr_debug() calls in it are enabled by default, but can be
  63           disabled at runtime as below.  Note that DEBUG flag is
  64           turned on by many CONFIG_*DEBUG* options.
  65
  66           Usage:
  67
  68           Dynamic debugging is controlled via the 'dynamic_debug/control' file,
  69           which is contained in the 'debugfs' filesystem. Thus, the debugfs
  70           filesystem must first be mounted before making use of this feature.
  71           We refer the control file as: <debugfs>/dynamic_debug/control. This
  72           file contains a list of the debug statements that can be enabled. The
  73           format for each line of the file is:
  74
  75                 filename:lineno [module]function flags format
  76
  77           filename : source file of the debug statement
  78           lineno : line number of the debug statement
  79           module : module that contains the debug statement
  80           function : function that contains the debug statement
  81           flags : '=p' means the line is turned 'on' for printing
  82           format : the format used for the debug statement
  83
  84           From a live system:
  85
  86                 nullarbor:~ # cat <debugfs>/dynamic_debug/control
  87                 # filename:lineno [module]function flags format
  88                 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
  89                 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
  90                 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
  91
  92           Example usage:
  93
  94                 // enable the message at line 1603 of file svcsock.c
  95                 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
  96                                                 <debugfs>/dynamic_debug/control
  97
  98                 // enable all the messages in file svcsock.c
  99                 nullarbor:~ # echo -n 'file svcsock.c +p' >
 100                                                 <debugfs>/dynamic_debug/control
 101
 102                 // enable all the messages in the NFS server module
 103                 nullarbor:~ # echo -n 'module nfsd +p' >
 104                                                 <debugfs>/dynamic_debug/control
 105
 106                 // enable all 12 messages in the function svc_process()
 107                 nullarbor:~ # echo -n 'func svc_process +p' >
 108                                                 <debugfs>/dynamic_debug/control
 109
 110                 // disable all 12 messages in the function svc_process()
 111                 nullarbor:~ # echo -n 'func svc_process -p' >
 112                                                 <debugfs>/dynamic_debug/control
 113
 114           See Documentation/dynamic-debug-howto.txt for additional information.
 115
 116 endmenu # "printk and dmesg options"
 117
 118 menu "Compile-time checks and compiler options"
 119
 120 config DEBUG_INFO
 121         bool "Compile the kernel with debug info"
 122         depends on DEBUG_KERNEL && !COMPILE_TEST
 123         help
 124           If you say Y here the resulting kernel image will include
 125           debugging info resulting in a larger kernel image.
 126           This adds debug symbols to the kernel and modules (gcc -g), and
 127           is needed if you intend to use kernel crashdump or binary object
 128           tools like crash, kgdb, LKCD, gdb, etc on the kernel.
 129           Say Y here only if you plan to debug the kernel.
 130
 131           If unsure, say N.
 132
 133 config DEBUG_INFO_REDUCED
 134         bool "Reduce debugging information"
 135         depends on DEBUG_INFO
 136         help
 137           If you say Y here gcc is instructed to generate less debugging
 138           information for structure types. This means that tools that
 139           need full debugging information (like kgdb or systemtap) won't
 140           be happy. But if you merely need debugging information to
 141           resolve line numbers there is no loss. Advantage is that
 142           build directory object sizes shrink dramatically over a full
 143           DEBUG_INFO build and compile times are reduced too.
 144           Only works with newer gcc versions.
 145
 146 config DEBUG_INFO_SPLIT
 147         bool "Produce split debuginfo in .dwo files"
 148         depends on DEBUG_INFO
 149         help
 150           Generate debug info into separate .dwo files. This significantly
 151           reduces the build directory size for builds with DEBUG_INFO,
 152           because it stores the information only once on disk in .dwo
 153           files instead of multiple times in object files and executables.
 154           In addition the debug information is also compressed.
 155
 156           Requires recent gcc (4.7+) and recent gdb/binutils.
 157           Any tool that packages or reads debug information would need
 158           to know about the .dwo files and include them.
 159           Incompatible with older versions of ccache.
 160
 161 config DEBUG_INFO_DWARF4
 162         bool "Generate dwarf4 debuginfo"
 163         depends on DEBUG_INFO
 164         help
 165           Generate dwarf4 debug info. This requires recent versions
 166           of gcc and gdb. It makes the debug information larger.
 167           But it significantly improves the success of resolving
 168           variables in gdb on optimized code.
 169
 170 config ENABLE_WARN_DEPRECATED
 171         bool "Enable __deprecated logic"
 172         default y
 173         help
 174           Enable the __deprecated logic in the kernel build.
 175           Disable this to suppress the "warning: 'foo' is deprecated
 176           (declared at kernel/power/somefile.c:1234)" messages.
 177
 178 config ENABLE_MUST_CHECK
 179         bool "Enable __must_check logic"
 180         default y
 181         help
 182           Enable the __must_check logic in the kernel build.  Disable this to
 183           suppress the "warning: ignoring return value of 'foo', declared with
 184           attribute warn_unused_result" messages.
 185
 186 config FRAME_WARN
 187         int "Warn for stack frames larger than (needs gcc 4.4)"
 188         range 0 8192
 189         default 1024 if !64BIT
 190         default 2048 if 64BIT
 191         help
 192           Tell gcc to warn at build time for stack frames larger than this.
 193           Setting this too low will cause a lot of warnings.
 194           Setting it to 0 disables the warning.
 195           Requires gcc 4.4
 196
 197 config STRIP_ASM_SYMS
 198         bool "Strip assembler-generated symbols during link"
 199         default n
 200         help
 201           Strip internal assembler-generated symbols during a link (symbols
 202           that look like '.Lxxx') so they don't pollute the output of
 203           get_wchan() and suchlike.
 204
 205 config READABLE_ASM
 206         bool "Generate readable assembler code"
 207         depends on DEBUG_KERNEL
 208         help
 209           Disable some compiler optimizations that tend to generate human unreadable
 210           assembler output. This may make the kernel slightly slower, but it helps
 211           to keep kernel developers who have to stare a lot at assembler listings
 212           sane.
 213
 214 config UNUSED_SYMBOLS
 215         bool "Enable unused/obsolete exported symbols"
 216         default y if X86
 217         help
 218           Unused but exported symbols make the kernel needlessly bigger.  For
 219           that reason most of these unused exports will soon be removed.  This
 220           option is provided temporarily to provide a transition period in case
 221           some external kernel module needs one of these symbols anyway. If you
 222           encounter such a case in your module, consider if you are actually
 223           using the right API.  (rationale: since nobody in the kernel is using
 224           this in a module, there is a pretty good chance it's actually the
 225           wrong interface to use).  If you really need the symbol, please send a
 226           mail to the linux kernel mailing list mentioning the symbol and why
 227           you really need it, and what the merge plan to the mainline kernel for
 228           your module is.
 229
 230 config DEBUG_FS
 231         bool "Debug Filesystem"
 232         help
 233           debugfs is a virtual file system that kernel developers use to put
 234           debugging files into.  Enable this option to be able to read and
 235           write to these files.
 236
 237           For detailed documentation on the debugfs API, see
 238           Documentation/DocBook/filesystems.
 239
 240           If unsure, say N.
 241
 242 config HEADERS_CHECK
 243         bool "Run 'make headers_check' when building vmlinux"
 244         depends on !UML
 245         help
 246           This option will extract the user-visible kernel headers whenever
 247           building the kernel, and will run basic sanity checks on them to
 248           ensure that exported files do not attempt to include files which
 249           were not exported, etc.
 250
 251           If you're making modifications to header files which are
 252           relevant for userspace, say 'Y', and check the headers
 253           exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
 254           your build tree), to make sure they're suitable.
 255
 256 config DEBUG_SECTION_MISMATCH
 257         bool "Enable full Section mismatch analysis"
 258         help
 259           The section mismatch analysis checks if there are illegal
 260           references from one section to another section.
 261           During linktime or runtime, some sections are dropped;
 262           any use of code/data previously in these sections would
 263           most likely result in an oops.
 264           In the code, functions and variables are annotated with
 265           __init,, etc. (see the full list in include/linux/init.h),
 266           which results in the code/data being placed in specific sections.
 267           The section mismatch analysis is always performed after a full
 268           kernel build, and enabling this option causes the following
 269           additional steps to occur:
 270           - Add the option -fno-inline-functions-called-once to gcc commands.
 271             When inlining a function annotated with __init in a non-init
 272             function, we would lose the section information and thus
 273             the analysis would not catch the illegal reference.
 274             This option tells gcc to inline less (but it does result in
 275             a larger kernel).
 276           - Run the section mismatch analysis for each module/built-in.o file.
 277             When we run the section mismatch analysis on vmlinux.o, we
 278             lose valueble information about where the mismatch was
 279             introduced.
 280             Running the analysis for each module/built-in.o file
 281             tells where the mismatch happens much closer to the
 282             source. The drawback is that the same mismatch is
 283             reported at least twice.
 284           - Enable verbose reporting from modpost in order to help resolve
 285             the section mismatches that are reported.
 286
 287 #
 288 # Select this config option from the architecture Kconfig, if it
 289 # is preferred to always offer frame pointers as a config
 290 # option on the architecture (regardless of KERNEL_DEBUG):
 291 #
 292 config ARCH_WANT_FRAME_POINTERS
 293         bool
 294         help
 295
 296 config FRAME_POINTER
 297         bool "Compile the kernel with frame pointers"
 298         depends on DEBUG_KERNEL && \
 299                 (CRIS || M68K || FRV || UML || \
 300                  AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \
 301                 ARCH_WANT_FRAME_POINTERS
 302         default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
 303         help
 304           If you say Y here the resulting kernel image will be slightly
 305           larger and slower, but it gives very useful debugging information
 306           in case of kernel bugs. (precise oopses/stacktraces/warnings)
 307
 308 config DEBUG_FORCE_WEAK_PER_CPU
 309         bool "Force weak per-cpu definitions"
 310         depends on DEBUG_KERNEL
 311         help
 312           s390 and alpha require percpu variables in modules to be
 313           defined weak to work around addressing range issue which
 314           puts the following two restrictions on percpu variable
 315           definitions.
 316
 317           1. percpu symbols must be unique whether static or not
 318           2. percpu variables can't be defined inside a function
 319
 320           To ensure that generic code follows the above rules, this
 321           option forces all percpu variables to be defined as weak.
 322
 323 endmenu # "Compiler options"
 324
 325 config MAGIC_SYSRQ
 326         bool "Magic SysRq key"
 327         depends on !UML
 328         help
 329           If you say Y here, you will have some control over the system even
 330           if the system crashes for example during kernel debugging (e.g., you
 331           will be able to flush the buffer cache to disk, reboot the system
 332           immediately or dump some status information). This is accomplished
 333           by pressing various keys while holding SysRq (Alt+PrintScreen). It
 334           also works on a serial console (on PC hardware at least), if you
 335           send a BREAK and then within 5 seconds a command keypress. The
 336           keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
 337           unless you really know what this hack does.
 338
 339 config MAGIC_SYSRQ_DEFAULT_ENABLE
 340         hex "Enable magic SysRq key functions by default"
 341         depends on MAGIC_SYSRQ
 342         default 0x1
 343         help
 344           Specifies which SysRq key functions are enabled by default.
 345           This may be set to 1 or 0 to enable or disable them all, or
 346           to a bitmask as described in Documentation/sysrq.txt.
 347
 348 config DEBUG_KERNEL
 349         bool "Kernel debugging"
 350         help
 351           Say Y here if you are developing drivers or trying to debug and
 352           identify kernel problems.
 353
 354 menu "Memory Debugging"
 355
 356 source mm/Kconfig.debug
 357
 358 config DEBUG_OBJECTS
 359         bool "Debug object operations"
 360         depends on DEBUG_KERNEL
 361         help
 362           If you say Y here, additional code will be inserted into the
 363           kernel to track the life time of various objects and validate
 364           the operations on those objects.
 365
 366 config DEBUG_OBJECTS_SELFTEST
 367         bool "Debug objects selftest"
 368         depends on DEBUG_OBJECTS
 369         help
 370           This enables the selftest of the object debug code.
 371
 372 config DEBUG_OBJECTS_FREE
 373         bool "Debug objects in freed memory"
 374         depends on DEBUG_OBJECTS
 375         help
 376           This enables checks whether a k/v free operation frees an area
 377           which contains an object which has not been deactivated
 378           properly. This can make kmalloc/kfree-intensive workloads
 379           much slower.
 380
 381 config DEBUG_OBJECTS_TIMERS
 382         bool "Debug timer objects"
 383         depends on DEBUG_OBJECTS
 384         help
 385           If you say Y here, additional code will be inserted into the
 386           timer routines to track the life time of timer objects and
 387           validate the timer operations.
 388
 389 config DEBUG_OBJECTS_WORK
 390         bool "Debug work objects"
 391         depends on DEBUG_OBJECTS
 392         help
 393           If you say Y here, additional code will be inserted into the
 394           work queue routines to track the life time of work objects and
 395           validate the work operations.
 396
 397 config DEBUG_OBJECTS_RCU_HEAD
 398         bool "Debug RCU callbacks objects"
 399         depends on DEBUG_OBJECTS
 400         help
 401           Enable this to turn on debugging of RCU list heads (call_rcu() usage).
 402
 403 config DEBUG_OBJECTS_PERCPU_COUNTER
 404         bool "Debug percpu counter objects"
 405         depends on DEBUG_OBJECTS
 406         help
 407           If you say Y here, additional code will be inserted into the
 408           percpu counter routines to track the life time of percpu counter
 409           objects and validate the percpu counter operations.
 410
 411 config DEBUG_OBJECTS_ENABLE_DEFAULT
 412         int "debug_objects bootup default value (0-1)"
 413         range 0 1
 414         default "1"
 415         depends on DEBUG_OBJECTS
 416         help
 417           Debug objects boot parameter default value
 418
 419 config DEBUG_SLAB
 420         bool "Debug slab memory allocations"
 421         depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
 422         help
 423           Say Y here to have the kernel do limited verification on memory
 424           allocation as well as poisoning memory on free to catch use of freed
 425           memory. This can make kmalloc/kfree-intensive workloads much slower.
 426
 427 config DEBUG_SLAB_LEAK
 428         bool "Memory leak debugging"
 429         depends on DEBUG_SLAB
 430
 431 config SLUB_DEBUG_ON
 432         bool "SLUB debugging on by default"
 433         depends on SLUB && SLUB_DEBUG && !KMEMCHECK
 434         default n
 435         help
 436           Boot with debugging on by default. SLUB boots by default with
 437           the runtime debug capabilities switched off. Enabling this is
 438           equivalent to specifying the "slub_debug" parameter on boot.
 439           There is no support for more fine grained debug control like
 440           possible with slub_debug=xxx. SLUB debugging may be switched
 441           off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
 442           "slub_debug=-".
 443
 444 config SLUB_STATS
 445         default n
 446         bool "Enable SLUB performance statistics"
 447         depends on SLUB && SYSFS
 448         help
 449           SLUB statistics are useful to debug SLUBs allocation behavior in
 450           order find ways to optimize the allocator. This should never be
 451           enabled for production use since keeping statistics slows down
 452           the allocator by a few percentage points. The slabinfo command
 453           supports the determination of the most active slabs to figure
 454           out which slabs are relevant to a particular load.
 455           Try running: slabinfo -DA
 456
 457 config HAVE_DEBUG_KMEMLEAK
 458         bool
 459
 460 config DEBUG_KMEMLEAK
 461         bool "Kernel memory leak detector"
 462         depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
 463         select DEBUG_FS
 464         select STACKTRACE if STACKTRACE_SUPPORT
 465         select KALLSYMS
 466         select CRC32
 467         help
 468           Say Y here if you want to enable the memory leak
 469           detector. The memory allocation/freeing is traced in a way
 470           similar to the Boehm's conservative garbage collector, the
 471           difference being that the orphan objects are not freed but
 472           only shown in /sys/kernel/debug/kmemleak. Enabling this
 473           feature will introduce an overhead to memory
 474           allocations. See Documentation/kmemleak.txt for more
 475           details.
 476
 477           Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
 478           of finding leaks due to the slab objects poisoning.
 479
 480           In order to access the kmemleak file, debugfs needs to be
 481           mounted (usually at /sys/kernel/debug).
 482
 483 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
 484         int "Maximum kmemleak early log entries"
 485         depends on DEBUG_KMEMLEAK
 486         range 200 40000
 487         default 400
 488         help
 489           Kmemleak must track all the memory allocations to avoid
 490           reporting false positives. Since memory may be allocated or
 491           freed before kmemleak is initialised, an early log buffer is
 492           used to store these actions. If kmemleak reports "early log
 493           buffer exceeded", please increase this value.
 494
 495 config DEBUG_KMEMLEAK_TEST
 496         tristate "Simple test for the kernel memory leak detector"
 497         depends on DEBUG_KMEMLEAK && m
 498         help
 499           This option enables a module that explicitly leaks memory.
 500
 501           If unsure, say N.
 502
 503 config DEBUG_KMEMLEAK_DEFAULT_OFF
 504         bool "Default kmemleak to off"
 505         depends on DEBUG_KMEMLEAK
 506         help
 507           Say Y here to disable kmemleak by default. It can then be enabled
 508           on the command line via kmemleak=on.
 509
 510 config DEBUG_STACK_USAGE
 511         bool "Stack utilization instrumentation"
 512         depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAG
 513         help
 514           Enables the display of the minimum amount of free stack which each
 515           task has ever had available in the sysrq-T and sysrq-P debug output.
 516
 517           This option will slow down process creation somewhat.
 518
 519 config DEBUG_VM
 520         bool "Debug VM"
 521         depends on DEBUG_KERNEL
 522         help
 523           Enable this to turn on extended checks in the virtual-memory system
 524           that may impact performance.
 525
 526           If unsure, say N.
 527
 528 config DEBUG_VM_VMACACHE
 529         bool "Debug VMA caching"
 530         depends on DEBUG_VM
 531         help
 532           Enable this to turn on VMA caching debug information. Doing so
 533           can cause significant overhead, so only enable it in non-production
 534           environments.
 535
 536           If unsure, say N.
 537
 538 config DEBUG_VM_RB
 539         bool "Debug VM red-black trees"
 540         depends on DEBUG_VM
 541         help
 542           Enable VM red-black tree debugging information and extra validations.
 543
 544           If unsure, say N.
 545
 546 config DEBUG_VIRTUAL
 547         bool "Debug VM translations"
 548         depends on DEBUG_KERNEL && X86
 549         help
 550           Enable some costly sanity checks in virtual to page code. This can
 551           catch mistakes with virt_to_page() and friends.
 552
 553           If unsure, say N.
 554
 555 config DEBUG_NOMMU_REGIONS
 556         bool "Debug the global anon/private NOMMU mapping region tree"
 557         depends on DEBUG_KERNEL && !MMU
 558         help
 559           This option causes the global tree of anonymous and private mapping
 560           regions to be regularly checked for invalid topology.
 561
 562 config DEBUG_MEMORY_INIT
 563         bool "Debug memory initialisation" if EXPERT
 564         default !EXPERT
 565         help
 566           Enable this for additional checks during memory initialisation.
 567           The sanity checks verify aspects of the VM such as the memory model
 568           and other information provided by the architecture. Verbose
 569           information will be printed at KERN_DEBUG loglevel depending
 570           on the mminit_loglevel= command-line option.
 571
 572           If unsure, say Y
 573
 574 config MEMORY_NOTIFIER_ERROR_INJECT
 575         tristate "Memory hotplug notifier error injection module"
 576         depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
 577         help
 578           This option provides the ability to inject artificial errors to
 579           memory hotplug notifier chain callbacks.  It is controlled through
 580           debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
 581
 582           If the notifier call chain should be failed with some events
 583           notified, write the error code to "actions/<notifier event>/error".
 584
 585           Example: Inject memory hotplug offline error (-12 == -ENOMEM)
 586
 587           # cd /sys/kernel/debug/notifier-error-inject/memory
 588           # echo -12 > actions/MEM_GOING_OFFLINE/error
 589           # echo offline > /sys/devices/system/memory/memoryXXX/state
 590           bash: echo: write error: Cannot allocate memory
 591
 592           To compile this code as a module, choose M here: the module will
 593           be called memory-notifier-error-inject.
 594
 595           If unsure, say N.
 596
 597 config DEBUG_PER_CPU_MAPS
 598         bool "Debug access to per_cpu maps"
 599         depends on DEBUG_KERNEL
 600         depends on SMP
 601         help
 602           Say Y to verify that the per_cpu map being accessed has
 603           been set up. This adds a fair amount of code to kernel memory
 604           and decreases performance.
 605
 606           Say N if unsure.
 607
 608 config DEBUG_HIGHMEM
 609         bool "Highmem debugging"
 610         depends on DEBUG_KERNEL && HIGHMEM
 611         help
 612           This option enables additional error checking for high memory
 613           systems.  Disable for production systems.
 614
 615 config HAVE_DEBUG_STACKOVERFLOW
 616         bool
 617
 618 config DEBUG_STACKOVERFLOW
 619         bool "Check for stack overflows"
 620         depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
 621         ---help---
 622           Say Y here if you want to check for overflows of kernel, IRQ
 623           and exception stacks (if your archicture uses them). This
 624           option will show detailed messages if free stack space drops
 625           below a certain limit.
 626
 627           These kinds of bugs usually occur when call-chains in the
 628           kernel get too deep, especially when interrupts are
 629           involved.
 630
 631           Use this in cases where you see apparently random memory
 632           corruption, especially if it appears in 'struct thread_info'
 633
 634           If in doubt, say "N".
 635
 636 source "lib/Kconfig.kmemcheck"
 637
 638 endmenu # "Memory Debugging"
 639
 640 config DEBUG_SHIRQ
 641         bool "Debug shared IRQ handlers"
 642         depends on DEBUG_KERNEL
 643         help
 644           Enable this to generate a spurious interrupt as soon as a shared
 645           interrupt handler is registered, and just before one is deregistered.
 646           Drivers ought to be able to handle interrupts coming in at those
 647           points; some don't and need to be caught.
 648
 649 menu "Debug Lockups and Hangs"
 650
 651 config LOCKUP_DETECTOR
 652         bool "Detect Hard and Soft Lockups"
 653         depends on DEBUG_KERNEL && !S390
 654         help
 655           Say Y here to enable the kernel to act as a watchdog to detect
 656           hard and soft lockups.
 657
 658           Softlockups are bugs that cause the kernel to loop in kernel
 659           mode for more than 20 seconds, without giving other tasks a
 660           chance to run.  The current stack trace is displayed upon
 661           detection and the system will stay locked up.
 662
 663           Hardlockups are bugs that cause the CPU to loop in kernel mode
 664           for more than 10 seconds, without letting other interrupts have a
 665           chance to run.  The current stack trace is displayed upon detection
 666           and the system will stay locked up.
 667
 668           The overhead should be minimal.  A periodic hrtimer runs to
 669           generate interrupts and kick the watchdog task every 4 seconds.
 670           An NMI is generated every 10 seconds or so to check for hardlockups.
 671
 672           The frequency of hrtimer and NMI events and the soft and hard lockup
 673           thresholds can be controlled through the sysctl watchdog_thresh.
 674
 675 config HARDLOCKUP_DETECTOR
 676         def_bool y
 677         depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
 678         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
 679
 680 config BOOTPARAM_HARDLOCKUP_PANIC
 681         bool "Panic (Reboot) On Hard Lockups"
 682         depends on HARDLOCKUP_DETECTOR
 683         help
 684           Say Y here to enable the kernel to panic on "hard lockups",
 685           which are bugs that cause the kernel to loop in kernel
 686           mode with interrupts disabled for more than 10 seconds (configurable
 687           using the watchdog_thresh sysctl).
 688
 689           Say N if unsure.
 690
 691 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
 692         int
 693         depends on HARDLOCKUP_DETECTOR
 694         range 0 1
 695         default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
 696         default 1 if BOOTPARAM_HARDLOCKUP_PANIC
 697
 698 config BOOTPARAM_SOFTLOCKUP_PANIC
 699         bool "Panic (Reboot) On Soft Lockups"
 700         depends on LOCKUP_DETECTOR
 701         help
 702           Say Y here to enable the kernel to panic on "soft lockups",
 703           which are bugs that cause the kernel to loop in kernel
 704           mode for more than 20 seconds (configurable using the watchdog_thresh
 705           sysctl), without giving other tasks a chance to run.
 706
 707           The panic can be used in combination with panic_timeout,
 708           to cause the system to reboot automatically after a
 709           lockup has been detected. This feature is useful for
 710           high-availability systems that have uptime guarantees and
 711           where a lockup must be resolved ASAP.
 712
 713           Say N if unsure.
 714
 715 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
 716         int
 717         depends on LOCKUP_DETECTOR
 718         range 0 1
 719         default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
 720         default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
 721
 722 config DETECT_HUNG_TASK
 723         bool "Detect Hung Tasks"
 724         depends on DEBUG_KERNEL
 725         default LOCKUP_DETECTOR
 726         help
 727           Say Y here to enable the kernel to detect "hung tasks",
 728           which are bugs that cause the task to be stuck in
 729           uninterruptible "D" state indefinitiley.
 730
 731           When a hung task is detected, the kernel will print the
 732           current stack trace (which you should report), but the
 733           task will stay in uninterruptible state. If lockdep is
 734           enabled then all held locks will also be reported. This
 735           feature has negligible overhead.
 736
 737 config DEFAULT_HUNG_TASK_TIMEOUT
 738         int "Default timeout for hung task detection (in seconds)"
 739         depends on DETECT_HUNG_TASK
 740         default 120
 741         help
 742           This option controls the default timeout (in seconds) used
 743           to determine when a task has become non-responsive and should
 744           be considered hung.
 745
 746           It can be adjusted at runtime via the kernel.hung_task_timeout_secs
 747           sysctl or by writing a value to
 748           /proc/sys/kernel/hung_task_timeout_secs.
 749
 750           A timeout of 0 disables the check.  The default is two minutes.
 751           Keeping the default should be fine in most cases.
 752
 753 config BOOTPARAM_HUNG_TASK_PANIC
 754         bool "Panic (Reboot) On Hung Tasks"
 755         depends on DETECT_HUNG_TASK
 756         help
 757           Say Y here to enable the kernel to panic on "hung tasks",
 758           which are bugs that cause the kernel to leave a task stuck
 759           in uninterruptible "D" state.
 760
 761           The panic can be used in combination with panic_timeout,
 762           to cause the system to reboot automatically after a
 763           hung task has been detected. This feature is useful for
 764           high-availability systems that have uptime guarantees and
 765           where a hung tasks must be resolved ASAP.
 766
 767           Say N if unsure.
 768
 769 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
 770         int
 771         depends on DETECT_HUNG_TASK
 772         range 0 1
 773         default 0 if !BOOTPARAM_HUNG_TASK_PANIC
 774         default 1 if BOOTPARAM_HUNG_TASK_PANIC
 775
 776 endmenu # "Debug lockups and hangs"
 777
 778 config PANIC_ON_OOPS
 779         bool "Panic on Oops"
 780         help
 781           Say Y here to enable the kernel to panic when it oopses. This
 782           has the same effect as setting oops=panic on the kernel command
 783           line.
 784
 785           This feature is useful to ensure that the kernel does not do
 786           anything erroneous after an oops which could result in data
 787           corruption or other issues.
 788
 789           Say N if unsure.
 790
 791 config PANIC_ON_OOPS_VALUE
 792         int
 793         range 0 1
 794         default 0 if !PANIC_ON_OOPS
 795         default 1 if PANIC_ON_OOPS
 796
 797 config PANIC_TIMEOUT
 798         int "panic timeout"
 799         default 0
 800         help
 801           Set the timeout value (in seconds) until a reboot occurs when the
 802           the kernel panics. If n = 0, then we wait forever. A timeout
 803           value n > 0 will wait n seconds before rebooting, while a timeout
 804           value n < 0 will reboot immediately.
 805
 806 config SCHED_DEBUG
 807         bool "Collect scheduler debugging info"
 808         depends on DEBUG_KERNEL && PROC_FS
 809         default y
 810         help
 811           If you say Y here, the /proc/sched_debug file will be provided
 812           that can help debug the scheduler. The runtime overhead of this
 813           option is minimal.
 814
 815 config SCHEDSTATS
 816         bool "Collect scheduler statistics"
 817         depends on DEBUG_KERNEL && PROC_FS
 818         help
 819           If you say Y here, additional code will be inserted into the
 820           scheduler and related routines to collect statistics about
 821           scheduler behavior and provide them in /proc/schedstat.  These
 822           stats may be useful for both tuning and debugging the scheduler
 823           If you aren't debugging the scheduler or trying to tune a specific
 824           application, you can say N to avoid the very slight overhead
 825           this adds.
 826
 827 config TIMER_STATS
 828         bool "Collect kernel timers statistics"
 829         depends on DEBUG_KERNEL && PROC_FS
 830         help
 831           If you say Y here, additional code will be inserted into the
 832           timer routines to collect statistics about kernel timers being
 833           reprogrammed. The statistics can be read from /proc/timer_stats.
 834           The statistics collection is started by writing 1 to /proc/timer_stats,
 835           writing 0 stops it. This feature is useful to collect information
 836           about timer usage patterns in kernel and userspace. This feature
 837           is lightweight if enabled in the kernel config but not activated
 838           (it defaults to deactivated on bootup and will only be activated
 839           if some application like powertop activates it explicitly).
 840
 841 config DEBUG_PREEMPT
 842         bool "Debug preemptible kernel"
 843         depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
 844         default y
 845         help
 846           If you say Y here then the kernel will use a debug variant of the
 847           commonly used smp_processor_id() function and will print warnings
 848           if kernel code uses it in a preemption-unsafe way. Also, the kernel
 849           will detect preemption count underflows.
 850
 851 menu "Lock Debugging (spinlocks, mutexes, etc...)"
 852
 853 config DEBUG_RT_MUTEXES
 854         bool "RT Mutex debugging, deadlock detection"
 855         depends on DEBUG_KERNEL && RT_MUTEXES
 856         help
 857          This allows rt mutex semantics violations and rt mutex related
 858          deadlocks (lockups) to be detected and reported automatically.
 859
 860 config RT_MUTEX_TESTER
 861         bool "Built-in scriptable tester for rt-mutexes"
 862         depends on DEBUG_KERNEL && RT_MUTEXES && BROKEN
 863         help
 864           This option enables a rt-mutex tester.
 865
 866 config DEBUG_SPINLOCK
 867         bool "Spinlock and rw-lock debugging: basic checks"
 868         depends on DEBUG_KERNEL
 869         select UNINLINE_SPIN_UNLOCK
 870         help
 871           Say Y here and build SMP to catch missing spinlock initialization
 872           and certain other kinds of spinlock errors commonly made.  This is
 873           best used in conjunction with the NMI watchdog so that spinlock
 874           deadlocks are also debuggable.
 875
 876 config DEBUG_MUTEXES
 877         bool "Mutex debugging: basic checks"
 878         depends on DEBUG_KERNEL
 879         help
 880          This feature allows mutex semantics violations to be detected and
 881          reported.
 882
 883 config DEBUG_WW_MUTEX_SLOWPATH
 884         bool "Wait/wound mutex debugging: Slowpath testing"
 885         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 886         select DEBUG_LOCK_ALLOC
 887         select DEBUG_SPINLOCK
 888         select DEBUG_MUTEXES
 889         help
 890          This feature enables slowpath testing for w/w mutex users by
 891          injecting additional -EDEADLK wound/backoff cases. Together with
 892          the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
 893          will test all possible w/w mutex interface abuse with the
 894          exception of simply not acquiring all the required locks.
 895
 896 config DEBUG_LOCK_ALLOC
 897         bool "Lock debugging: detect incorrect freeing of live locks"
 898         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 899         select DEBUG_SPINLOCK
 900         select DEBUG_MUTEXES
 901         select LOCKDEP
 902         help
 903          This feature will check whether any held lock (spinlock, rwlock,
 904          mutex or rwsem) is incorrectly freed by the kernel, via any of the
 905          memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
 906          vfree(), etc.), whether a live lock is incorrectly reinitialized via
 907          spin_lock_init()/mutex_init()/etc., or whether there is any lock
 908          held during task exit.
 909
 910 config PROVE_LOCKING
 911         bool "Lock debugging: prove locking correctness"
 912         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 913         select LOCKDEP
 914         select DEBUG_SPINLOCK
 915         select DEBUG_MUTEXES
 916         select DEBUG_LOCK_ALLOC
 917         select TRACE_IRQFLAGS
 918         default n
 919         help
 920          This feature enables the kernel to prove that all locking
 921          that occurs in the kernel runtime is mathematically
 922          correct: that under no circumstance could an arbitrary (and
 923          not yet triggered) combination of observed locking
 924          sequences (on an arbitrary number of CPUs, running an
 925          arbitrary number of tasks and interrupt contexts) cause a
 926          deadlock.
 927
 928          In short, this feature enables the kernel to report locking
 929          related deadlocks before they actually occur.
 930
 931          The proof does not depend on how hard and complex a
 932          deadlock scenario would be to trigger: how many
 933          participant CPUs, tasks and irq-contexts would be needed
 934          for it to trigger. The proof also does not depend on
 935          timing: if a race and a resulting deadlock is possible
 936          theoretically (no matter how unlikely the race scenario
 937          is), it will be proven so and will immediately be
 938          reported by the kernel (once the event is observed that
 939          makes the deadlock theoretically possible).
 940
 941          If a deadlock is impossible (i.e. the locking rules, as
 942          observed by the kernel, are mathematically correct), the
 943          kernel reports nothing.
 944
 945          NOTE: this feature can also be enabled for rwlocks, mutexes
 946          and rwsems - in which case all dependencies between these
 947          different locking variants are observed and mapped too, and
 948          the proof of observed correctness is also maintained for an
 949          arbitrary combination of these separate locking variants.
 950
 951          For more details, see Documentation/lockdep-design.txt.
 952
 953 config LOCKDEP
 954         bool
 955         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 956         select STACKTRACE
 957         select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
 958         select KALLSYMS
 959         select KALLSYMS_ALL
 960
 961 config LOCK_STAT
 962         bool "Lock usage statistics"
 963         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 964         select LOCKDEP
 965         select DEBUG_SPINLOCK
 966         select DEBUG_MUTEXES
 967         select DEBUG_LOCK_ALLOC
 968         default n
 969         help
 970          This feature enables tracking lock contention points
 971
 972          For more details, see Documentation/lockstat.txt
 973
 974          This also enables lock events required by "perf lock",
 975          subcommand of perf.
 976          If you want to use "perf lock", you also need to turn on
 977          CONFIG_EVENT_TRACING.
 978
 979          CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
 980          (CONFIG_LOCKDEP defines "acquire" and "release" events.)
 981
 982 config DEBUG_LOCKDEP
 983         bool "Lock dependency engine debugging"
 984         depends on DEBUG_KERNEL && LOCKDEP
 985         help
 986           If you say Y here, the lock dependency engine will do
 987           additional runtime checks to debug itself, at the price
 988           of more runtime overhead.
 989
 990 config DEBUG_ATOMIC_SLEEP
 991         bool "Sleep inside atomic section checking"
 992         select PREEMPT_COUNT
 993         depends on DEBUG_KERNEL
 994         help
 995           If you say Y here, various routines which may sleep will become very
 996           noisy if they are called inside atomic sections: when a spinlock is
 997           held, inside an rcu read side critical section, inside preempt disabled
 998           sections, inside an interrupt, etc...
 999
1000 config DEBUG_LOCKING_API_SELFTESTS
1001         bool "Locking API boot-time self-tests"
1002         depends on DEBUG_KERNEL
1003         help
1004           Say Y here if you want the kernel to run a short self-test during
1005           bootup. The self-test checks whether common types of locking bugs
1006           are detected by debugging mechanisms or not. (if you disable
1007           lock debugging then those bugs wont be detected of course.)
1008           The following locking APIs are covered: spinlocks, rwlocks,
1009           mutexes and rwsems.
1010
1011 config LOCK_TORTURE_TEST
1012         tristate "torture tests for locking"
1013         depends on DEBUG_KERNEL
1014         select TORTURE_TEST
1015         default n
1016         help
1017           This option provides a kernel module that runs torture tests
1018           on kernel locking primitives.  The kernel module may be built
1019           after the fact on the running kernel to be tested, if desired.
1020
1021           Say Y here if you want kernel locking-primitive torture tests
1022           to be built into the kernel.
1023           Say M if you want these torture tests to build as a module.
1024           Say N if you are unsure.
1025
1026 endmenu # lock debugging
1027
1028 config TRACE_IRQFLAGS
1029         bool
1030         help
1031           Enables hooks to interrupt enabling and disabling for
1032           either tracing or lock debugging.
1033
1034 config STACKTRACE
1035         bool
1036         depends on STACKTRACE_SUPPORT
1037
1038 config DEBUG_KOBJECT
1039         bool "kobject debugging"
1040         depends on DEBUG_KERNEL
1041         help
1042           If you say Y here, some extra kobject debugging messages will be sent
1043           to the syslog.
1044
1045 config DEBUG_KOBJECT_RELEASE
1046         bool "kobject release debugging"
1047         depends on DEBUG_OBJECTS_TIMERS
1048         help
1049           kobjects are reference counted objects.  This means that their
1050           last reference count put is not predictable, and the kobject can
1051           live on past the point at which a driver decides to drop it's
1052           initial reference to the kobject gained on allocation.  An
1053           example of this would be a struct device which has just been
1054           unregistered.
1055
1056           However, some buggy drivers assume that after such an operation,
1057           the memory backing the kobject can be immediately freed.  This
1058           goes completely against the principles of a refcounted object.
1059
1060           If you say Y here, the kernel will delay the release of kobjects
1061           on the last reference count to improve the visibility of this
1062           kind of kobject release bug.
1063
1064 config HAVE_DEBUG_BUGVERBOSE
1065         bool
1066
1067 config DEBUG_BUGVERBOSE
1068         bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
1069         depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
1070         default y
1071         help
1072           Say Y here to make BUG() panics output the file name and line number
1073           of the BUG call as well as the EIP and oops trace.  This aids
1074           debugging but costs about 70-100K of memory.
1075
1076 config DEBUG_LIST
1077         bool "Debug linked list manipulation"
1078         depends on DEBUG_KERNEL
1079         help
1080           Enable this to turn on extended checks in the linked-list
1081           walking routines.
1082
1083           If unsure, say N.
1084
1085 config DEBUG_PI_LIST
1086         bool "Debug priority linked list manipulation"
1087         depends on DEBUG_KERNEL
1088         help
1089           Enable this to turn on extended checks in the priority-ordered
1090           linked-list (plist) walking routines.  This checks the entire
1091           list multiple times during each manipulation.
1092
1093           If unsure, say N.
1094
1095 config DEBUG_SG
1096         bool "Debug SG table operations"
1097         depends on DEBUG_KERNEL
1098         help
1099           Enable this to turn on checks on scatter-gather tables. This can
1100           help find problems with drivers that do not properly initialize
1101           their sg tables.
1102
1103           If unsure, say N.
1104
1105 config DEBUG_NOTIFIERS
1106         bool "Debug notifier call chains"
1107         depends on DEBUG_KERNEL
1108         help
1109           Enable this to turn on sanity checking for notifier call chains.
1110           This is most useful for kernel developers to make sure that
1111           modules properly unregister themselves from notifier chains.
1112           This is a relatively cheap check but if you care about maximum
1113           performance, say N.
1114
1115 config DEBUG_CREDENTIALS
1116         bool "Debug credential management"
1117         depends on DEBUG_KERNEL
1118         help
1119           Enable this to turn on some debug checking for credential
1120           management.  The additional code keeps track of the number of
1121           pointers from task_structs to any given cred struct, and checks to
1122           see that this number never exceeds the usage count of the cred
1123           struct.
1124
1125           Furthermore, if SELinux is enabled, this also checks that the
1126           security pointer in the cred struct is never seen to be invalid.
1127
1128           If unsure, say N.
1129
1130 menu "RCU Debugging"
1131
1132 config PROVE_RCU
1133         bool "RCU debugging: prove RCU correctness"
1134         depends on PROVE_LOCKING
1135         default n
1136         help
1137          This feature enables lockdep extensions that check for correct
1138          use of RCU APIs.  This is currently under development.  Say Y
1139          if you want to debug RCU usage or help work on the PROVE_RCU
1140          feature.
1141
1142          Say N if you are unsure.
1143
1144 config PROVE_RCU_REPEATEDLY
1145         bool "RCU debugging: don't disable PROVE_RCU on first splat"
1146         depends on PROVE_RCU
1147         default n
1148         help
1149          By itself, PROVE_RCU will disable checking upon issuing the
1150          first warning (or "splat").  This feature prevents such
1151          disabling, allowing multiple RCU-lockdep warnings to be printed
1152          on a single reboot.
1153
1154          Say Y to allow multiple RCU-lockdep warnings per boot.
1155
1156          Say N if you are unsure.
1157
1158 config SPARSE_RCU_POINTER
1159         bool "RCU debugging: sparse-based checks for pointer usage"
1160         default n
1161         help
1162          This feature enables the __rcu sparse annotation for
1163          RCU-protected pointers.  This annotation will cause sparse
1164          to flag any non-RCU used of annotated pointers.  This can be
1165          helpful when debugging RCU usage.  Please note that this feature
1166          is not intended to enforce code cleanliness; it is instead merely
1167          a debugging aid.
1168
1169          Say Y to make sparse flag questionable use of RCU-protected pointers
1170
1171          Say N if you are unsure.
1172
1173 config TORTURE_TEST
1174         tristate
1175         default n
1176
1177 config RCU_TORTURE_TEST
1178         tristate "torture tests for RCU"
1179         depends on DEBUG_KERNEL
1180         select TORTURE_TEST
1181         default n
1182         help
1183           This option provides a kernel module that runs torture tests
1184           on the RCU infrastructure.  The kernel module may be built
1185           after the fact on the running kernel to be tested, if desired.
1186
1187           Say Y here if you want RCU torture tests to be built into
1188           the kernel.
1189           Say M if you want the RCU torture tests to build as a module.
1190           Say N if you are unsure.
1191
1192 config RCU_TORTURE_TEST_RUNNABLE
1193         bool "torture tests for RCU runnable by default"
1194         depends on RCU_TORTURE_TEST = y
1195         default n
1196         help
1197           This option provides a way to build the RCU torture tests
1198           directly into the kernel without them starting up at boot
1199           time.  You can use /proc/sys/kernel/rcutorture_runnable
1200           to manually override this setting.  This /proc file is
1201           available only when the RCU torture tests have been built
1202           into the kernel.
1203
1204           Say Y here if you want the RCU torture tests to start during
1205           boot (you probably don't).
1206           Say N here if you want the RCU torture tests to start only
1207           after being manually enabled via /proc.
1208
1209 config RCU_CPU_STALL_TIMEOUT
1210         int "RCU CPU stall timeout in seconds"
1211         depends on RCU_STALL_COMMON
1212         range 3 300
1213         default 21
1214         help
1215           If a given RCU grace period extends more than the specified
1216           number of seconds, a CPU stall warning is printed.  If the
1217           RCU grace period persists, additional CPU stall warnings are
1218           printed at more widely spaced intervals.
1219
1220 config RCU_CPU_STALL_VERBOSE
1221         bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
1222         depends on TREE_PREEMPT_RCU
1223         default y
1224         help
1225           This option causes RCU to printk detailed per-task information
1226           for any tasks that are stalling the current RCU grace period.
1227
1228           Say N if you are unsure.
1229
1230           Say Y if you want to enable such checks.
1231
1232 config RCU_CPU_STALL_INFO
1233         bool "Print additional diagnostics on RCU CPU stall"
1234         depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL
1235         default n
1236         help
1237           For each stalled CPU that is aware of the current RCU grace
1238           period, print out additional per-CPU diagnostic information
1239           regarding scheduling-clock ticks, idle state, and,
1240           for RCU_FAST_NO_HZ kernels, idle-entry state.
1241
1242           Say N if you are unsure.
1243
1244           Say Y if you want to enable such diagnostics.
1245
1246 config RCU_TRACE
1247         bool "Enable tracing for RCU"
1248         depends on DEBUG_KERNEL
1249         select TRACE_CLOCK
1250         help
1251           This option provides tracing in RCU which presents stats
1252           in debugfs for debugging RCU implementation.
1253
1254           Say Y here if you want to enable RCU tracing
1255           Say N if you are unsure.
1256
1257 endmenu # "RCU Debugging"
1258
1259 config DEBUG_BLOCK_EXT_DEVT
1260         bool "Force extended block device numbers and spread them"
1261         depends on DEBUG_KERNEL
1262         depends on BLOCK
1263         default n
1264         help
1265           BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1266           SOME DISTRIBUTIONS.  DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1267           YOU ARE DOING.  Distros, please enable this and fix whatever
1268           is broken.
1269
1270           Conventionally, block device numbers are allocated from
1271           predetermined contiguous area.  However, extended block area
1272           may introduce non-contiguous block device numbers.  This
1273           option forces most block device numbers to be allocated from
1274           the extended space and spreads them to discover kernel or
1275           userland code paths which assume predetermined contiguous
1276           device number allocation.
1277
1278           Note that turning on this debug option shuffles all the
1279           device numbers for all IDE and SCSI devices including libata
1280           ones, so root partition specified using device number
1281           directly (via rdev or root=MAJ:MIN) won't work anymore.
1282           Textual device names (root=/dev/sdXn) will continue to work.
1283
1284           Say N if you are unsure.
1285
1286 config NOTIFIER_ERROR_INJECTION
1287         tristate "Notifier error injection"
1288         depends on DEBUG_KERNEL
1289         select DEBUG_FS
1290         help
1291           This option provides the ability to inject artificial errors to
1292           specified notifier chain callbacks. It is useful to test the error
1293           handling of notifier call chain failures.
1294
1295           Say N if unsure.
1296
1297 config CPU_NOTIFIER_ERROR_INJECT
1298         tristate "CPU notifier error injection module"
1299         depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
1300         help
1301           This option provides a kernel module that can be used to test
1302           the error handling of the cpu notifiers by injecting artificial
1303           errors to CPU notifier chain callbacks.  It is controlled through
1304           debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
1305
1306           If the notifier call chain should be failed with some events
1307           notified, write the error code to "actions/<notifier event>/error".
1308
1309           Example: Inject CPU offline error (-1 == -EPERM)
1310
1311           # cd /sys/kernel/debug/notifier-error-inject/cpu
1312           # echo -1 > actions/CPU_DOWN_PREPARE/error
1313           # echo 0 > /sys/devices/system/cpu/cpu1/online
1314           bash: echo: write error: Operation not permitted
1315
1316           To compile this code as a module, choose M here: the module will
1317           be called cpu-notifier-error-inject.
1318
1319           If unsure, say N.
1320
1321 config PM_NOTIFIER_ERROR_INJECT
1322         tristate "PM notifier error injection module"
1323         depends on PM && NOTIFIER_ERROR_INJECTION
1324         default m if PM_DEBUG
1325         help
1326           This option provides the ability to inject artificial errors to
1327           PM notifier chain callbacks.  It is controlled through debugfs
1328           interface /sys/kernel/debug/notifier-error-inject/pm
1329
1330           If the notifier call chain should be failed with some events
1331           notified, write the error code to "actions/<notifier event>/error".
1332
1333           Example: Inject PM suspend error (-12 = -ENOMEM)
1334
1335           # cd /sys/kernel/debug/notifier-error-inject/pm/
1336           # echo -12 > actions/PM_SUSPEND_PREPARE/error
1337           # echo mem > /sys/power/state
1338           bash: echo: write error: Cannot allocate memory
1339
1340           To compile this code as a module, choose M here: the module will
1341           be called pm-notifier-error-inject.
1342
1343           If unsure, say N.
1344
1345 config OF_RECONFIG_NOTIFIER_ERROR_INJECT
1346         tristate "OF reconfig notifier error injection module"
1347         depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
1348         help
1349           This option provides the ability to inject artificial errors to
1350           OF reconfig notifier chain callbacks.  It is controlled
1351           through debugfs interface under
1352           /sys/kernel/debug/notifier-error-inject/OF-reconfig/
1353
1354           If the notifier call chain should be failed with some events
1355           notified, write the error code to "actions/<notifier event>/error".
1356
1357           To compile this code as a module, choose M here: the module will
1358           be called of-reconfig-notifier-error-inject.
1359
1360           If unsure, say N.
1361
1362 config FAULT_INJECTION
1363         bool "Fault-injection framework"
1364         depends on DEBUG_KERNEL
1365         help
1366           Provide fault-injection framework.
1367           For more details, see Documentation/fault-injection/.
1368
1369 config FAILSLAB
1370         bool "Fault-injection capability for kmalloc"
1371         depends on FAULT_INJECTION
1372         depends on SLAB || SLUB
1373         help
1374           Provide fault-injection capability for kmalloc.
1375
1376 config FAIL_PAGE_ALLOC
1377         bool "Fault-injection capabilitiy for alloc_pages()"
1378         depends on FAULT_INJECTION
1379         help
1380           Provide fault-injection capability for alloc_pages().
1381
1382 config FAIL_MAKE_REQUEST
1383         bool "Fault-injection capability for disk IO"
1384         depends on FAULT_INJECTION && BLOCK
1385         help
1386           Provide fault-injection capability for disk IO.
1387
1388 config FAIL_IO_TIMEOUT
1389         bool "Fault-injection capability for faking disk interrupts"
1390         depends on FAULT_INJECTION && BLOCK
1391         help
1392           Provide fault-injection capability on end IO handling. This
1393           will make the block layer "forget" an interrupt as configured,
1394           thus exercising the error handling.
1395
1396           Only works with drivers that use the generic timeout handling,
1397           for others it wont do anything.
1398
1399 config FAIL_MMC_REQUEST
1400         bool "Fault-injection capability for MMC IO"
1401         select DEBUG_FS
1402         depends on FAULT_INJECTION && MMC
1403         help
1404           Provide fault-injection capability for MMC IO.
1405           This will make the mmc core return data errors. This is
1406           useful to test the error handling in the mmc block device
1407           and to test how the mmc host driver handles retries from
1408           the block device.
1409
1410 config FAULT_INJECTION_DEBUG_FS
1411         bool "Debugfs entries for fault-injection capabilities"
1412         depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1413         help
1414           Enable configuration of fault-injection capabilities via debugfs.
1415
1416 config FAULT_INJECTION_STACKTRACE_FILTER
1417         bool "stacktrace filter for fault-injection capabilities"
1418         depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1419         depends on !X86_64
1420         select STACKTRACE
1421         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
1422         help
1423           Provide stacktrace filter for fault-injection capabilities
1424
1425 config LATENCYTOP
1426         bool "Latency measuring infrastructure"
1427         depends on HAVE_LATENCYTOP_SUPPORT
1428         depends on DEBUG_KERNEL
1429         depends on STACKTRACE_SUPPORT
1430         depends on PROC_FS
1431         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
1432         select KALLSYMS
1433         select KALLSYMS_ALL
1434         select STACKTRACE
1435         select SCHEDSTATS
1436         select SCHED_DEBUG
1437         help
1438           Enable this option if you want to use the LatencyTOP tool
1439           to find out which userspace is blocking on what kernel operations.
1440
1441 config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1442         bool
1443
1444 config DEBUG_STRICT_USER_COPY_CHECKS
1445         bool "Strict user copy size checks"
1446         depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
1447         depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
1448         help
1449           Enabling this option turns a certain set of sanity checks for user
1450           copy operations into compile time failures.
1451
1452           The copy_from_user() etc checks are there to help test if there
1453           are sufficient security checks on the length argument of
1454           the copy operation, by having gcc prove that the argument is
1455           within bounds.
1456
1457           If unsure, say N.
1458
1459 source kernel/trace/Kconfig
1460
1461 menu "Runtime Testing"
1462
1463 config LKDTM
1464         tristate "Linux Kernel Dump Test Tool Module"
1465         depends on DEBUG_FS
1466         depends on BLOCK
1467         default n
1468         help
1469         This module enables testing of the different dumping mechanisms by
1470         inducing system failures at predefined crash points.
1471         If you don't need it: say N
1472         Choose M here to compile this code as a module. The module will be
1473         called lkdtm.
1474
1475         Documentation on how to use the module can be found in
1476         Documentation/fault-injection/provoke-crashes.txt
1477
1478 config TEST_LIST_SORT
1479         bool "Linked list sorting test"
1480         depends on DEBUG_KERNEL
1481         help
1482           Enable this to turn on 'list_sort()' function test. This test is
1483           executed only once during system boot, so affects only boot time.
1484
1485           If unsure, say N.
1486
1487 config KPROBES_SANITY_TEST
1488         bool "Kprobes sanity tests"
1489         depends on DEBUG_KERNEL
1490         depends on KPROBES
1491         default n
1492         help
1493           This option provides for testing basic kprobes functionality on
1494           boot. A sample kprobe, jprobe and kretprobe are inserted and
1495           verified for functionality.
1496
1497           Say N if you are unsure.
1498
1499 config BACKTRACE_SELF_TEST
1500         tristate "Self test for the backtrace code"
1501         depends on DEBUG_KERNEL
1502         default n
1503         help
1504           This option provides a kernel module that can be used to test
1505           the kernel stack backtrace code. This option is not useful
1506           for distributions or general kernels, but only for kernel
1507           developers working on architecture code.
1508
1509           Note that if you want to also test saved backtraces, you will
1510           have to enable STACKTRACE as well.
1511
1512           Say N if you are unsure.
1513
1514 config RBTREE_TEST
1515         tristate "Red-Black tree test"
1516         depends on DEBUG_KERNEL
1517         help
1518           A benchmark measuring the performance of the rbtree library.
1519           Also includes rbtree invariant checks.
1520
1521 config INTERVAL_TREE_TEST
1522         tristate "Interval tree test"
1523         depends on m && DEBUG_KERNEL
1524         select INTERVAL_TREE
1525         help
1526           A benchmark measuring the performance of the interval tree library
1527
1528 config PERCPU_TEST
1529         tristate "Per cpu operations test"
1530         depends on m && DEBUG_KERNEL
1531         help
1532           Enable this option to build test module which validates per-cpu
1533           operations.
1534
1535           If unsure, say N.
1536
1537 config ATOMIC64_SELFTEST
1538         bool "Perform an atomic64_t self-test at boot"
1539         help
1540           Enable this option to test the atomic64_t functions at boot.
1541
1542           If unsure, say N.
1543
1544 config ASYNC_RAID6_TEST
1545         tristate "Self test for hardware accelerated raid6 recovery"
1546         depends on ASYNC_RAID6_RECOV
1547         select ASYNC_MEMCPY
1548         ---help---
1549           This is a one-shot self test that permutes through the
1550           recovery of all the possible two disk failure scenarios for a
1551           N-disk array.  Recovery is performed with the asynchronous
1552           raid6 recovery routines, and will optionally use an offload
1553           engine if one is available.
1554
1555           If unsure, say N.
1556
1557 config TEST_STRING_HELPERS
1558         tristate "Test functions located in the string_helpers module at runtime"
1559
1560 config TEST_KSTRTOX
1561         tristate "Test kstrto*() family of functions at runtime"
1562
1563 config TEST_RHASHTABLE
1564         bool "Perform selftest on resizable hash table"
1565         default n
1566         help
1567           Enable this option to test the rhashtable functions at boot.
1568
1569           If unsure, say N.
1570
1571 endmenu # runtime tests
1572
1573 config PROVIDE_OHCI1394_DMA_INIT
1574         bool "Remote debugging over FireWire early on boot"
1575         depends on PCI && X86
1576         help
1577           If you want to debug problems which hang or crash the kernel early
1578           on boot and the crashing machine has a FireWire port, you can use
1579           this feature to remotely access the memory of the crashed machine
1580           over FireWire. This employs remote DMA as part of the OHCI1394
1581           specification which is now the standard for FireWire controllers.
1582
1583           With remote DMA, you can monitor the printk buffer remotely using
1584           firescope and access all memory below 4GB using fireproxy from gdb.
1585           Even controlling a kernel debugger is possible using remote DMA.
1586
1587           Usage:
1588
1589           If ohci1394_dma=early is used as boot parameter, it will initialize
1590           all OHCI1394 controllers which are found in the PCI config space.
1591
1592           As all changes to the FireWire bus such as enabling and disabling
1593           devices cause a bus reset and thereby disable remote DMA for all
1594           devices, be sure to have the cable plugged and FireWire enabled on
1595           the debugging host before booting the debug target for debugging.
1596
1597           This code (~1k) is freed after boot. By then, the firewire stack
1598           in charge of the OHCI-1394 controllers should be used instead.
1599
1600           See Documentation/debugging-via-ohci1394.txt for more information.
1601
1602 config BUILD_DOCSRC
1603         bool "Build targets in Documentation/ tree"
1604         depends on HEADERS_CHECK
1605         help
1606           This option attempts to build objects from the source files in the
1607           kernel Documentation/ tree.
1608
1609           Say N if you are unsure.
1610
1611 config DMA_API_DEBUG
1612         bool "Enable debugging of DMA-API usage"
1613         depends on HAVE_DMA_API_DEBUG
1614         help
1615           Enable this option to debug the use of the DMA API by device drivers.
1616           With this option you will be able to detect common bugs in device
1617           drivers like double-freeing of DMA mappings or freeing mappings that
1618           were never allocated.
1619
1620           This also attempts to catch cases where a page owned by DMA is
1621           accessed by the cpu in a way that could cause data corruption.  For
1622           example, this enables cow_user_page() to check that the source page is
1623           not undergoing DMA.
1624
1625           This option causes a performance degradation.  Use only if you want to
1626           debug device drivers and dma interactions.
1627
1628           If unsure, say N.
1629
1630 config TEST_MODULE
1631         tristate "Test module loading with 'hello world' module"
1632         default n
1633         depends on m
1634         help
1635           This builds the "test_module" module that emits "Hello, world"
1636           on printk when loaded. It is designed to be used for basic
1637           evaluation of the module loading subsystem (for example when
1638           validating module verification). It lacks any extra dependencies,
1639           and will not normally be loaded by the system unless explicitly
1640           requested by name.
1641
1642           If unsure, say N.
1643
1644 config TEST_USER_COPY
1645         tristate "Test user/kernel boundary protections"
1646         default n
1647         depends on m
1648         help
1649           This builds the "test_user_copy" module that runs sanity checks
1650           on the copy_to/from_user infrastructure, making sure basic
1651           user/kernel boundary testing is working. If it fails to load,
1652           a regression has been detected in the user/kernel memory boundary
1653           protections.
1654
1655           If unsure, say N.
1656
1657 config TEST_BPF
1658         tristate "Test BPF filter functionality"
1659         default n
1660         depends on m && NET
1661         help
1662           This builds the "test_bpf" module that runs various test vectors
1663           against the BPF interpreter or BPF JIT compiler depending on the
1664           current setting. This is in particular useful for BPF JIT compiler
1665           development, but also to run regression tests against changes in
1666           the interpreter code.
1667
1668           If unsure, say N.
1669
1670 config TEST_FIRMWARE
1671         tristate "Test firmware loading via userspace interface"
1672         default n
1673         depends on FW_LOADER
1674         help
1675           This builds the "test_firmware" module that creates a userspace
1676           interface for testing firmware loading. This can be used to
1677           control the triggering of firmware loading without needing an
1678           actual firmware-using device. The contents can be rechecked by
1679           userspace.
1680
1681           If unsure, say N.
1682
1683 config TEST_UDELAY
1684         tristate "udelay test driver"
1685         default n
1686         help
1687           This builds the "udelay_test" module that helps to make sure
1688           that udelay() is working properly.
1689
1690           If unsure, say N.
1691
1692 source "samples/Kconfig"
1693
1694 source "lib/Kconfig.kgdb"
1695