lib/Kconfig.debug

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