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, __devinit, 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 LOCKUP_DETECTOR && PERF_EVENTS && HAVE_PERF_EVENTS_NMI && \
 200                  !HAVE_NMI_WATCHDOG
 201
 202 config BOOTPARAM_HARDLOCKUP_PANIC
 203         bool "Panic (Reboot) On Hard Lockups"
 204         depends on LOCKUP_DETECTOR
 205         help
 206           Say Y here to enable the kernel to panic on "hard lockups",
 207           which are bugs that cause the kernel to loop in kernel
 208           mode with interrupts disabled for more than 10 seconds (configurable
 209           using the watchdog_thresh sysctl).
 210
 211           Say N if unsure.
 212
 213 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
 214         int
 215         depends on LOCKUP_DETECTOR
 216         range 0 1
 217         default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
 218         default 1 if BOOTPARAM_HARDLOCKUP_PANIC
 219
 220 config BOOTPARAM_SOFTLOCKUP_PANIC
 221         bool "Panic (Reboot) On Soft Lockups"
 222         depends on LOCKUP_DETECTOR
 223         help
 224           Say Y here to enable the kernel to panic on "soft lockups",
 225           which are bugs that cause the kernel to loop in kernel
 226           mode for more than 20 seconds (configurable using the watchdog_thresh
 227           sysctl), without giving other tasks a chance to run.
 228
 229           The panic can be used in combination with panic_timeout,
 230           to cause the system to reboot automatically after a
 231           lockup has been detected. This feature is useful for
 232           high-availability systems that have uptime guarantees and
 233           where a lockup must be resolved ASAP.
 234
 235           Say N if unsure.
 236
 237 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
 238         int
 239         depends on LOCKUP_DETECTOR
 240         range 0 1
 241         default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
 242         default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
 243
 244 config PANIC_ON_OOPS
 245         bool "Panic on Oops" if EXPERT
 246         default n
 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 DEBUG_KMEMLEAK
 453         bool "Kernel memory leak detector"
 454         depends on DEBUG_KERNEL && EXPERIMENTAL && \
 455                 (X86 || ARM || PPC || MIPS || S390 || SPARC64 || SUPERH || MICROBLAZE || TILE)
 456
 457         select DEBUG_FS
 458         select STACKTRACE if STACKTRACE_SUPPORT
 459         select KALLSYMS
 460         select CRC32
 461         help
 462           Say Y here if you want to enable the memory leak
 463           detector. The memory allocation/freeing is traced in a way
 464           similar to the Boehm's conservative garbage collector, the
 465           difference being that the orphan objects are not freed but
 466           only shown in /sys/kernel/debug/kmemleak. Enabling this
 467           feature will introduce an overhead to memory
 468           allocations. See Documentation/kmemleak.txt for more
 469           details.
 470
 471           Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
 472           of finding leaks due to the slab objects poisoning.
 473
 474           In order to access the kmemleak file, debugfs needs to be
 475           mounted (usually at /sys/kernel/debug).
 476
 477 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
 478         int "Maximum kmemleak early log entries"
 479         depends on DEBUG_KMEMLEAK
 480         range 200 40000
 481         default 400
 482         help
 483           Kmemleak must track all the memory allocations to avoid
 484           reporting false positives. Since memory may be allocated or
 485           freed before kmemleak is initialised, an early log buffer is
 486           used to store these actions. If kmemleak reports "early log
 487           buffer exceeded", please increase this value.
 488
 489 config DEBUG_KMEMLEAK_TEST
 490         tristate "Simple test for the kernel memory leak detector"
 491         depends on DEBUG_KMEMLEAK && m
 492         help
 493           This option enables a module that explicitly leaks memory.
 494
 495           If unsure, say N.
 496
 497 config DEBUG_KMEMLEAK_DEFAULT_OFF
 498         bool "Default kmemleak to off"
 499         depends on DEBUG_KMEMLEAK
 500         help
 501           Say Y here to disable kmemleak by default. It can then be enabled
 502           on the command line via kmemleak=on.
 503
 504 config DEBUG_PREEMPT
 505         bool "Debug preemptible kernel"
 506         depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
 507         default y
 508         help
 509           If you say Y here then the kernel will use a debug variant of the
 510           commonly used smp_processor_id() function and will print warnings
 511           if kernel code uses it in a preemption-unsafe way. Also, the kernel
 512           will detect preemption count underflows.
 513
 514 config DEBUG_RT_MUTEXES
 515         bool "RT Mutex debugging, deadlock detection"
 516         depends on DEBUG_KERNEL && RT_MUTEXES
 517         help
 518          This allows rt mutex semantics violations and rt mutex related
 519          deadlocks (lockups) to be detected and reported automatically.
 520
 521 config DEBUG_PI_LIST
 522         bool
 523         default y
 524         depends on DEBUG_RT_MUTEXES
 525
 526 config RT_MUTEX_TESTER
 527         bool "Built-in scriptable tester for rt-mutexes"
 528         depends on DEBUG_KERNEL && RT_MUTEXES
 529         help
 530           This option enables a rt-mutex tester.
 531
 532 config DEBUG_SPINLOCK
 533         bool "Spinlock and rw-lock debugging: basic checks"
 534         depends on DEBUG_KERNEL
 535         select UNINLINE_SPIN_UNLOCK
 536         help
 537           Say Y here and build SMP to catch missing spinlock initialization
 538           and certain other kinds of spinlock errors commonly made.  This is
 539           best used in conjunction with the NMI watchdog so that spinlock
 540           deadlocks are also debuggable.
 541
 542 config DEBUG_MUTEXES
 543         bool "Mutex debugging: basic checks"
 544         depends on DEBUG_KERNEL
 545         help
 546          This feature allows mutex semantics violations to be detected and
 547          reported.
 548
 549 config DEBUG_LOCK_ALLOC
 550         bool "Lock debugging: detect incorrect freeing of live locks"
 551         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 552         select DEBUG_SPINLOCK
 553         select DEBUG_MUTEXES
 554         select LOCKDEP
 555         help
 556          This feature will check whether any held lock (spinlock, rwlock,
 557          mutex or rwsem) is incorrectly freed by the kernel, via any of the
 558          memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
 559          vfree(), etc.), whether a live lock is incorrectly reinitialized via
 560          spin_lock_init()/mutex_init()/etc., or whether there is any lock
 561          held during task exit.
 562
 563 config PROVE_LOCKING
 564         bool "Lock debugging: prove locking correctness"
 565         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 566         select LOCKDEP
 567         select DEBUG_SPINLOCK
 568         select DEBUG_MUTEXES
 569         select DEBUG_LOCK_ALLOC
 570         select TRACE_IRQFLAGS
 571         default n
 572         help
 573          This feature enables the kernel to prove that all locking
 574          that occurs in the kernel runtime is mathematically
 575          correct: that under no circumstance could an arbitrary (and
 576          not yet triggered) combination of observed locking
 577          sequences (on an arbitrary number of CPUs, running an
 578          arbitrary number of tasks and interrupt contexts) cause a
 579          deadlock.
 580
 581          In short, this feature enables the kernel to report locking
 582          related deadlocks before they actually occur.
 583
 584          The proof does not depend on how hard and complex a
 585          deadlock scenario would be to trigger: how many
 586          participant CPUs, tasks and irq-contexts would be needed
 587          for it to trigger. The proof also does not depend on
 588          timing: if a race and a resulting deadlock is possible
 589          theoretically (no matter how unlikely the race scenario
 590          is), it will be proven so and will immediately be
 591          reported by the kernel (once the event is observed that
 592          makes the deadlock theoretically possible).
 593
 594          If a deadlock is impossible (i.e. the locking rules, as
 595          observed by the kernel, are mathematically correct), the
 596          kernel reports nothing.
 597
 598          NOTE: this feature can also be enabled for rwlocks, mutexes
 599          and rwsems - in which case all dependencies between these
 600          different locking variants are observed and mapped too, and
 601          the proof of observed correctness is also maintained for an
 602          arbitrary combination of these separate locking variants.
 603
 604          For more details, see Documentation/lockdep-design.txt.
 605
 606 config PROVE_RCU
 607         bool "RCU debugging: prove RCU correctness"
 608         depends on PROVE_LOCKING
 609         default n
 610         help
 611          This feature enables lockdep extensions that check for correct
 612          use of RCU APIs.  This is currently under development.  Say Y
 613          if you want to debug RCU usage or help work on the PROVE_RCU
 614          feature.
 615
 616          Say N if you are unsure.
 617
 618 config PROVE_RCU_REPEATEDLY
 619         bool "RCU debugging: don't disable PROVE_RCU on first splat"
 620         depends on PROVE_RCU
 621         default n
 622         help
 623          By itself, PROVE_RCU will disable checking upon issuing the
 624          first warning (or "splat").  This feature prevents such
 625          disabling, allowing multiple RCU-lockdep warnings to be printed
 626          on a single reboot.
 627
 628          Say Y to allow multiple RCU-lockdep warnings per boot.
 629
 630          Say N if you are unsure.
 631
 632 config SPARSE_RCU_POINTER
 633         bool "RCU debugging: sparse-based checks for pointer usage"
 634         default n
 635         help
 636          This feature enables the __rcu sparse annotation for
 637          RCU-protected pointers.  This annotation will cause sparse
 638          to flag any non-RCU used of annotated pointers.  This can be
 639          helpful when debugging RCU usage.  Please note that this feature
 640          is not intended to enforce code cleanliness; it is instead merely
 641          a debugging aid.
 642
 643          Say Y to make sparse flag questionable use of RCU-protected pointers
 644
 645          Say N if you are unsure.
 646
 647 config LOCKDEP
 648         bool
 649         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 650         select STACKTRACE
 651         select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE
 652         select KALLSYMS
 653         select KALLSYMS_ALL
 654
 655 config LOCK_STAT
 656         bool "Lock usage statistics"
 657         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 658         select LOCKDEP
 659         select DEBUG_SPINLOCK
 660         select DEBUG_MUTEXES
 661         select DEBUG_LOCK_ALLOC
 662         default n
 663         help
 664          This feature enables tracking lock contention points
 665
 666          For more details, see Documentation/lockstat.txt
 667
 668          This also enables lock events required by "perf lock",
 669          subcommand of perf.
 670          If you want to use "perf lock", you also need to turn on
 671          CONFIG_EVENT_TRACING.
 672
 673          CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
 674          (CONFIG_LOCKDEP defines "acquire" and "release" events.)
 675
 676 config DEBUG_LOCKDEP
 677         bool "Lock dependency engine debugging"
 678         depends on DEBUG_KERNEL && LOCKDEP
 679         help
 680           If you say Y here, the lock dependency engine will do
 681           additional runtime checks to debug itself, at the price
 682           of more runtime overhead.
 683
 684 config TRACE_IRQFLAGS
 685         bool
 686         help
 687           Enables hooks to interrupt enabling and disabling for
 688           either tracing or lock debugging.
 689
 690 config DEBUG_ATOMIC_SLEEP
 691         bool "Sleep inside atomic section checking"
 692         select PREEMPT_COUNT
 693         depends on DEBUG_KERNEL
 694         help
 695           If you say Y here, various routines which may sleep will become very
 696           noisy if they are called inside atomic sections: when a spinlock is
 697           held, inside an rcu read side critical section, inside preempt disabled
 698           sections, inside an interrupt, etc...
 699
 700 config DEBUG_LOCKING_API_SELFTESTS
 701         bool "Locking API boot-time self-tests"
 702         depends on DEBUG_KERNEL
 703         help
 704           Say Y here if you want the kernel to run a short self-test during
 705           bootup. The self-test checks whether common types of locking bugs
 706           are detected by debugging mechanisms or not. (if you disable
 707           lock debugging then those bugs wont be detected of course.)
 708           The following locking APIs are covered: spinlocks, rwlocks,
 709           mutexes and rwsems.
 710
 711 config STACKTRACE
 712         bool
 713         depends on STACKTRACE_SUPPORT
 714
 715 config DEBUG_STACK_USAGE
 716         bool "Stack utilization instrumentation"
 717         depends on DEBUG_KERNEL
 718         help
 719           Enables the display of the minimum amount of free stack which each
 720           task has ever had available in the sysrq-T and sysrq-P debug output.
 721
 722           This option will slow down process creation somewhat.
 723
 724 config DEBUG_KOBJECT
 725         bool "kobject debugging"
 726         depends on DEBUG_KERNEL
 727         help
 728           If you say Y here, some extra kobject debugging messages will be sent
 729           to the syslog.
 730
 731 config DEBUG_HIGHMEM
 732         bool "Highmem debugging"
 733         depends on DEBUG_KERNEL && HIGHMEM
 734         help
 735           This options enables addition error checking for high memory systems.
 736           Disable for production systems.
 737
 738 config DEBUG_BUGVERBOSE
 739         bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
 740         depends on BUG
 741         depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \
 742                    FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 || TILE
 743         default y
 744         help
 745           Say Y here to make BUG() panics output the file name and line number
 746           of the BUG call as well as the EIP and oops trace.  This aids
 747           debugging but costs about 70-100K of memory.
 748
 749 config DEBUG_INFO
 750         bool "Compile the kernel with debug info"
 751         depends on DEBUG_KERNEL
 752         help
 753           If you say Y here the resulting kernel image will include
 754           debugging info resulting in a larger kernel image.
 755           This adds debug symbols to the kernel and modules (gcc -g), and
 756           is needed if you intend to use kernel crashdump or binary object
 757           tools like crash, kgdb, LKCD, gdb, etc on the kernel.
 758           Say Y here only if you plan to debug the kernel.
 759
 760           If unsure, say N.
 761
 762 config DEBUG_INFO_REDUCED
 763         bool "Reduce debugging information"
 764         depends on DEBUG_INFO
 765         help
 766           If you say Y here gcc is instructed to generate less debugging
 767           information for structure types. This means that tools that
 768           need full debugging information (like kgdb or systemtap) won't
 769           be happy. But if you merely need debugging information to
 770           resolve line numbers there is no loss. Advantage is that
 771           build directory object sizes shrink dramatically over a full
 772           DEBUG_INFO build and compile times are reduced too.
 773           Only works with newer gcc versions.
 774
 775 config DEBUG_VM
 776         bool "Debug VM"
 777         depends on DEBUG_KERNEL
 778         help
 779           Enable this to turn on extended checks in the virtual-memory system
 780           that may impact performance.
 781
 782           If unsure, say N.
 783
 784 config DEBUG_VIRTUAL
 785         bool "Debug VM translations"
 786         depends on DEBUG_KERNEL && X86
 787         help
 788           Enable some costly sanity checks in virtual to page code. This can
 789           catch mistakes with virt_to_page() and friends.
 790
 791           If unsure, say N.
 792
 793 config DEBUG_NOMMU_REGIONS
 794         bool "Debug the global anon/private NOMMU mapping region tree"
 795         depends on DEBUG_KERNEL && !MMU
 796         help
 797           This option causes the global tree of anonymous and private mapping
 798           regions to be regularly checked for invalid topology.
 799
 800 config DEBUG_WRITECOUNT
 801         bool "Debug filesystem writers count"
 802         depends on DEBUG_KERNEL
 803         help
 804           Enable this to catch wrong use of the writers count in struct
 805           vfsmount.  This will increase the size of each file struct by
 806           32 bits.
 807
 808           If unsure, say N.
 809
 810 config DEBUG_MEMORY_INIT
 811         bool "Debug memory initialisation" if EXPERT
 812         default !EXPERT
 813         help
 814           Enable this for additional checks during memory initialisation.
 815           The sanity checks verify aspects of the VM such as the memory model
 816           and other information provided by the architecture. Verbose
 817           information will be printed at KERN_DEBUG loglevel depending
 818           on the mminit_loglevel= command-line option.
 819
 820           If unsure, say Y
 821
 822 config DEBUG_LIST
 823         bool "Debug linked list manipulation"
 824         depends on DEBUG_KERNEL
 825         help
 826           Enable this to turn on extended checks in the linked-list
 827           walking routines.
 828
 829           If unsure, say N.
 830
 831 config TEST_LIST_SORT
 832         bool "Linked list sorting test"
 833         depends on DEBUG_KERNEL
 834         help
 835           Enable this to turn on 'list_sort()' function test. This test is
 836           executed only once during system boot, so affects only boot time.
 837
 838           If unsure, say N.
 839
 840 config DEBUG_SG
 841         bool "Debug SG table operations"
 842         depends on DEBUG_KERNEL
 843         help
 844           Enable this to turn on checks on scatter-gather tables. This can
 845           help find problems with drivers that do not properly initialize
 846           their sg tables.
 847
 848           If unsure, say N.
 849
 850 config DEBUG_NOTIFIERS
 851         bool "Debug notifier call chains"
 852         depends on DEBUG_KERNEL
 853         help
 854           Enable this to turn on sanity checking for notifier call chains.
 855           This is most useful for kernel developers to make sure that
 856           modules properly unregister themselves from notifier chains.
 857           This is a relatively cheap check but if you care about maximum
 858           performance, say N.
 859
 860 config DEBUG_CREDENTIALS
 861         bool "Debug credential management"
 862         depends on DEBUG_KERNEL
 863         help
 864           Enable this to turn on some debug checking for credential
 865           management.  The additional code keeps track of the number of
 866           pointers from task_structs to any given cred struct, and checks to
 867           see that this number never exceeds the usage count of the cred
 868           struct.
 869
 870           Furthermore, if SELinux is enabled, this also checks that the
 871           security pointer in the cred struct is never seen to be invalid.
 872
 873           If unsure, say N.
 874
 875 #
 876 # Select this config option from the architecture Kconfig, if it
 877 # is preferred to always offer frame pointers as a config
 878 # option on the architecture (regardless of KERNEL_DEBUG):
 879 #
 880 config ARCH_WANT_FRAME_POINTERS
 881         bool
 882         help
 883
 884 config FRAME_POINTER
 885         bool "Compile the kernel with frame pointers"
 886         depends on DEBUG_KERNEL && \
 887                 (CRIS || M68K || FRV || UML || \
 888                  AVR32 || SUPERH || BLACKFIN || MN10300) || \
 889                 ARCH_WANT_FRAME_POINTERS
 890         default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
 891         help
 892           If you say Y here the resulting kernel image will be slightly
 893           larger and slower, but it gives very useful debugging information
 894           in case of kernel bugs. (precise oopses/stacktraces/warnings)
 895
 896 config BOOT_PRINTK_DELAY
 897         bool "Delay each boot printk message by N milliseconds"
 898         depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
 899         help
 900           This build option allows you to read kernel boot messages
 901           by inserting a short delay after each one.  The delay is
 902           specified in milliseconds on the kernel command line,
 903           using "boot_delay=N".
 904
 905           It is likely that you would also need to use "lpj=M" to preset
 906           the "loops per jiffie" value.
 907           See a previous boot log for the "lpj" value to use for your
 908           system, and then set "lpj=M" before setting "boot_delay=N".
 909           NOTE:  Using this option may adversely affect SMP systems.
 910           I.e., processors other than the first one may not boot up.
 911           BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
 912           what it believes to be lockup conditions.
 913
 914 config RCU_TORTURE_TEST
 915         tristate "torture tests for RCU"
 916         depends on DEBUG_KERNEL
 917         default n
 918         help
 919           This option provides a kernel module that runs torture tests
 920           on the RCU infrastructure.  The kernel module may be built
 921           after the fact on the running kernel to be tested, if desired.
 922
 923           Say Y here if you want RCU torture tests to be built into
 924           the kernel.
 925           Say M if you want the RCU torture tests to build as a module.
 926           Say N if you are unsure.
 927
 928 config RCU_TORTURE_TEST_RUNNABLE
 929         bool "torture tests for RCU runnable by default"
 930         depends on RCU_TORTURE_TEST = y
 931         default n
 932         help
 933           This option provides a way to build the RCU torture tests
 934           directly into the kernel without them starting up at boot
 935           time.  You can use /proc/sys/kernel/rcutorture_runnable
 936           to manually override this setting.  This /proc file is
 937           available only when the RCU torture tests have been built
 938           into the kernel.
 939
 940           Say Y here if you want the RCU torture tests to start during
 941           boot (you probably don't).
 942           Say N here if you want the RCU torture tests to start only
 943           after being manually enabled via /proc.
 944
 945 config RCU_CPU_STALL_TIMEOUT
 946         int "RCU CPU stall timeout in seconds"
 947         depends on TREE_RCU || TREE_PREEMPT_RCU
 948         range 3 300
 949         default 60
 950         help
 951           If a given RCU grace period extends more than the specified
 952           number of seconds, a CPU stall warning is printed.  If the
 953           RCU grace period persists, additional CPU stall warnings are
 954           printed at more widely spaced intervals.
 955
 956 config RCU_CPU_STALL_VERBOSE
 957         bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
 958         depends on TREE_PREEMPT_RCU
 959         default y
 960         help
 961           This option causes RCU to printk detailed per-task information
 962           for any tasks that are stalling the current RCU grace period.
 963
 964           Say N if you are unsure.
 965
 966           Say Y if you want to enable such checks.
 967
 968 config RCU_CPU_STALL_INFO
 969         bool "Print additional diagnostics on RCU CPU stall"
 970         depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL
 971         default n
 972         help
 973           For each stalled CPU that is aware of the current RCU grace
 974           period, print out additional per-CPU diagnostic information
 975           regarding scheduling-clock ticks, idle state, and,
 976           for RCU_FAST_NO_HZ kernels, idle-entry state.
 977
 978           Say N if you are unsure.
 979
 980           Say Y if you want to enable such diagnostics.
 981
 982 config RCU_TRACE
 983         bool "Enable tracing for RCU"
 984         depends on DEBUG_KERNEL
 985         help
 986           This option provides tracing in RCU which presents stats
 987           in debugfs for debugging RCU implementation.
 988
 989           Say Y here if you want to enable RCU tracing
 990           Say N if you are unsure.
 991
 992 config KPROBES_SANITY_TEST
 993         bool "Kprobes sanity tests"
 994         depends on DEBUG_KERNEL
 995         depends on KPROBES
 996         default n
 997         help
 998           This option provides for testing basic kprobes functionality on
 999           boot. A sample kprobe, jprobe and kretprobe are inserted and
1000           verified for functionality.
1001
1002           Say N if you are unsure.
1003
1004 config BACKTRACE_SELF_TEST
1005         tristate "Self test for the backtrace code"
1006         depends on DEBUG_KERNEL
1007         default n
1008         help
1009           This option provides a kernel module that can be used to test
1010           the kernel stack backtrace code. This option is not useful
1011           for distributions or general kernels, but only for kernel
1012           developers working on architecture code.
1013
1014           Note that if you want to also test saved backtraces, you will
1015           have to enable STACKTRACE as well.
1016
1017           Say N if you are unsure.
1018
1019 config DEBUG_BLOCK_EXT_DEVT
1020         bool "Force extended block device numbers and spread them"
1021         depends on DEBUG_KERNEL
1022         depends on BLOCK
1023         default n
1024         help
1025           BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1026           SOME DISTRIBUTIONS.  DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1027           YOU ARE DOING.  Distros, please enable this and fix whatever
1028           is broken.
1029
1030           Conventionally, block device numbers are allocated from
1031           predetermined contiguous area.  However, extended block area
1032           may introduce non-contiguous block device numbers.  This
1033           option forces most block device numbers to be allocated from
1034           the extended space and spreads them to discover kernel or
1035           userland code paths which assume predetermined contiguous
1036           device number allocation.
1037
1038           Note that turning on this debug option shuffles all the
1039           device numbers for all IDE and SCSI devices including libata
1040           ones, so root partition specified using device number
1041           directly (via rdev or root=MAJ:MIN) won't work anymore.
1042           Textual device names (root=/dev/sdXn) will continue to work.
1043
1044           Say N if you are unsure.
1045
1046 config DEBUG_FORCE_WEAK_PER_CPU
1047         bool "Force weak per-cpu definitions"
1048         depends on DEBUG_KERNEL
1049         help
1050           s390 and alpha require percpu variables in modules to be
1051           defined weak to work around addressing range issue which
1052           puts the following two restrictions on percpu variable
1053           definitions.
1054
1055           1. percpu symbols must be unique whether static or not
1056           2. percpu variables can't be defined inside a function
1057
1058           To ensure that generic code follows the above rules, this
1059           option forces all percpu variables to be defined as weak.
1060
1061 config DEBUG_PER_CPU_MAPS
1062         bool "Debug access to per_cpu maps"
1063         depends on DEBUG_KERNEL
1064         depends on SMP
1065         help
1066           Say Y to verify that the per_cpu map being accessed has
1067           been set up. This adds a fair amount of code to kernel memory
1068           and decreases performance.
1069
1070           Say N if unsure.
1071
1072 config LKDTM
1073         tristate "Linux Kernel Dump Test Tool Module"
1074         depends on DEBUG_FS
1075         depends on BLOCK
1076         default n
1077         help
1078         This module enables testing of the different dumping mechanisms by
1079         inducing system failures at predefined crash points.
1080         If you don't need it: say N
1081         Choose M here to compile this code as a module. The module will be
1082         called lkdtm.
1083
1084         Documentation on how to use the module can be found in
1085         Documentation/fault-injection/provoke-crashes.txt
1086
1087 config CPU_NOTIFIER_ERROR_INJECT
1088         tristate "CPU notifier error injection module"
1089         depends on HOTPLUG_CPU && DEBUG_KERNEL
1090         help
1091           This option provides a kernel module that can be used to test
1092           the error handling of the cpu notifiers
1093
1094           To compile this code as a module, choose M here: the module will
1095           be called cpu-notifier-error-inject.
1096
1097           If unsure, say N.
1098
1099 config FAULT_INJECTION
1100         bool "Fault-injection framework"
1101         depends on DEBUG_KERNEL
1102         help
1103           Provide fault-injection framework.
1104           For more details, see Documentation/fault-injection/.
1105
1106 config FAILSLAB
1107         bool "Fault-injection capability for kmalloc"
1108         depends on FAULT_INJECTION
1109         depends on SLAB || SLUB
1110         help
1111           Provide fault-injection capability for kmalloc.
1112
1113 config FAIL_PAGE_ALLOC
1114         bool "Fault-injection capabilitiy for alloc_pages()"
1115         depends on FAULT_INJECTION
1116         help
1117           Provide fault-injection capability for alloc_pages().
1118
1119 config FAIL_MAKE_REQUEST
1120         bool "Fault-injection capability for disk IO"
1121         depends on FAULT_INJECTION && BLOCK
1122         help
1123           Provide fault-injection capability for disk IO.
1124
1125 config FAIL_IO_TIMEOUT
1126         bool "Fault-injection capability for faking disk interrupts"
1127         depends on FAULT_INJECTION && BLOCK
1128         help
1129           Provide fault-injection capability on end IO handling. This
1130           will make the block layer "forget" an interrupt as configured,
1131           thus exercising the error handling.
1132
1133           Only works with drivers that use the generic timeout handling,
1134           for others it wont do anything.
1135
1136 config FAIL_MMC_REQUEST
1137         bool "Fault-injection capability for MMC IO"
1138         select DEBUG_FS
1139         depends on FAULT_INJECTION && MMC
1140         help
1141           Provide fault-injection capability for MMC IO.
1142           This will make the mmc core return data errors. This is
1143           useful to test the error handling in the mmc block device
1144           and to test how the mmc host driver handles retries from
1145           the block device.
1146
1147 config FAULT_INJECTION_DEBUG_FS
1148         bool "Debugfs entries for fault-injection capabilities"
1149         depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1150         help
1151           Enable configuration of fault-injection capabilities via debugfs.
1152
1153 config FAULT_INJECTION_STACKTRACE_FILTER
1154         bool "stacktrace filter for fault-injection capabilities"
1155         depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1156         depends on !X86_64
1157         select STACKTRACE
1158         select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND
1159         help
1160           Provide stacktrace filter for fault-injection capabilities
1161
1162 config LATENCYTOP
1163         bool "Latency measuring infrastructure"
1164         depends on HAVE_LATENCYTOP_SUPPORT
1165         depends on DEBUG_KERNEL
1166         depends on STACKTRACE_SUPPORT
1167         depends on PROC_FS
1168         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND
1169         select KALLSYMS
1170         select KALLSYMS_ALL
1171         select STACKTRACE
1172         select SCHEDSTATS
1173         select SCHED_DEBUG
1174         help
1175           Enable this option if you want to use the LatencyTOP tool
1176           to find out which userspace is blocking on what kernel operations.
1177
1178 source mm/Kconfig.debug
1179 source kernel/trace/Kconfig
1180
1181 config PROVIDE_OHCI1394_DMA_INIT
1182         bool "Remote debugging over FireWire early on boot"
1183         depends on PCI && X86
1184         help
1185           If you want to debug problems which hang or crash the kernel early
1186           on boot and the crashing machine has a FireWire port, you can use
1187           this feature to remotely access the memory of the crashed machine
1188           over FireWire. This employs remote DMA as part of the OHCI1394
1189           specification which is now the standard for FireWire controllers.
1190
1191           With remote DMA, you can monitor the printk buffer remotely using
1192           firescope and access all memory below 4GB using fireproxy from gdb.
1193           Even controlling a kernel debugger is possible using remote DMA.
1194
1195           Usage:
1196
1197           If ohci1394_dma=early is used as boot parameter, it will initialize
1198           all OHCI1394 controllers which are found in the PCI config space.
1199
1200           As all changes to the FireWire bus such as enabling and disabling
1201           devices cause a bus reset and thereby disable remote DMA for all
1202           devices, be sure to have the cable plugged and FireWire enabled on
1203           the debugging host before booting the debug target for debugging.
1204
1205           This code (~1k) is freed after boot. By then, the firewire stack
1206           in charge of the OHCI-1394 controllers should be used instead.
1207
1208           See Documentation/debugging-via-ohci1394.txt for more information.
1209
1210 config FIREWIRE_OHCI_REMOTE_DMA
1211         bool "Remote debugging over FireWire with firewire-ohci"
1212         depends on FIREWIRE_OHCI
1213         help
1214           This option lets you use the FireWire bus for remote debugging
1215           with help of the firewire-ohci driver. It enables unfiltered
1216           remote DMA in firewire-ohci.
1217           See Documentation/debugging-via-ohci1394.txt for more information.
1218
1219           If unsure, say N.
1220
1221 config BUILD_DOCSRC
1222         bool "Build targets in Documentation/ tree"
1223         depends on HEADERS_CHECK
1224         help
1225           This option attempts to build objects from the source files in the
1226           kernel Documentation/ tree.
1227
1228           Say N if you are unsure.
1229
1230 config DYNAMIC_DEBUG
1231         bool "Enable dynamic printk() support"
1232         default n
1233         depends on PRINTK
1234         depends on DEBUG_FS
1235         help
1236
1237           Compiles debug level messages into the kernel, which would not
1238           otherwise be available at runtime. These messages can then be
1239           enabled/disabled based on various levels of scope - per source file,
1240           function, module, format string, and line number. This mechanism
1241           implicitly compiles in all pr_debug() and dev_dbg() calls, which
1242           enlarges the kernel text size by about 2%.
1243
1244           If a source file is compiled with DEBUG flag set, any
1245           pr_debug() calls in it are enabled by default, but can be
1246           disabled at runtime as below.  Note that DEBUG flag is
1247           turned on by many CONFIG_*DEBUG* options.
1248
1249           Usage:
1250
1251           Dynamic debugging is controlled via the 'dynamic_debug/control' file,
1252           which is contained in the 'debugfs' filesystem. Thus, the debugfs
1253           filesystem must first be mounted before making use of this feature.
1254           We refer the control file as: <debugfs>/dynamic_debug/control. This
1255           file contains a list of the debug statements that can be enabled. The
1256           format for each line of the file is:
1257
1258                 filename:lineno [module]function flags format
1259
1260           filename : source file of the debug statement
1261           lineno : line number of the debug statement
1262           module : module that contains the debug statement
1263           function : function that contains the debug statement
1264           flags : '=p' means the line is turned 'on' for printing
1265           format : the format used for the debug statement
1266
1267           From a live system:
1268
1269                 nullarbor:~ # cat <debugfs>/dynamic_debug/control
1270                 # filename:lineno [module]function flags format
1271                 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
1272                 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
1273                 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
1274
1275           Example usage:
1276
1277                 // enable the message at line 1603 of file svcsock.c
1278                 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
1279                                                 <debugfs>/dynamic_debug/control
1280
1281                 // enable all the messages in file svcsock.c
1282                 nullarbor:~ # echo -n 'file svcsock.c +p' >
1283                                                 <debugfs>/dynamic_debug/control
1284
1285                 // enable all the messages in the NFS server module
1286                 nullarbor:~ # echo -n 'module nfsd +p' >
1287                                                 <debugfs>/dynamic_debug/control
1288
1289                 // enable all 12 messages in the function svc_process()
1290                 nullarbor:~ # echo -n 'func svc_process +p' >
1291                                                 <debugfs>/dynamic_debug/control
1292
1293                 // disable all 12 messages in the function svc_process()
1294                 nullarbor:~ # echo -n 'func svc_process -p' >
1295                                                 <debugfs>/dynamic_debug/control
1296
1297           See Documentation/dynamic-debug-howto.txt for additional information.
1298
1299 config DMA_API_DEBUG
1300         bool "Enable debugging of DMA-API usage"
1301         depends on HAVE_DMA_API_DEBUG
1302         help
1303           Enable this option to debug the use of the DMA API by device drivers.
1304           With this option you will be able to detect common bugs in device
1305           drivers like double-freeing of DMA mappings or freeing mappings that
1306           were never allocated.
1307           This option causes a performance degredation.  Use only if you want
1308           to debug device drivers. If unsure, say N.
1309
1310 config ATOMIC64_SELFTEST
1311         bool "Perform an atomic64_t self-test at boot"
1312         help
1313           Enable this option to test the atomic64_t functions at boot.
1314
1315           If unsure, say N.
1316
1317 config ASYNC_RAID6_TEST
1318         tristate "Self test for hardware accelerated raid6 recovery"
1319         depends on ASYNC_RAID6_RECOV
1320         select ASYNC_MEMCPY
1321         ---help---
1322           This is a one-shot self test that permutes through the
1323           recovery of all the possible two disk failure scenarios for a
1324           N-disk array.  Recovery is performed with the asynchronous
1325           raid6 recovery routines, and will optionally use an offload
1326           engine if one is available.
1327
1328           If unsure, say N.
1329
1330 source "samples/Kconfig"
1331
1332 source "lib/Kconfig.kgdb"
1333
1334 source "lib/Kconfig.kmemcheck"
1335
1336 config TEST_KSTRTOX
1337         tristate "Test kstrto*() family of functions at runtime"