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 timing information to be
   7           included in printk output.  This allows you to measure
   8           the interval between kernel operations, including bootup
   9           operations.  This is useful for identifying long delays
  10           in kernel startup.
  11
  12 config ENABLE_WARN_DEPRECATED
  13         bool "Enable __deprecated logic"
  14         default y
  15         help
  16           Enable the __deprecated logic in the kernel build.
  17           Disable this to suppress the "warning: 'foo' is deprecated
  18           (declared at kernel/power/somefile.c:1234)" messages.
  19
  20 config ENABLE_MUST_CHECK
  21         bool "Enable __must_check logic"
  22         default y
  23         help
  24           Enable the __must_check logic in the kernel build.  Disable this to
  25           suppress the "warning: ignoring return value of 'foo', declared with
  26           attribute warn_unused_result" messages.
  27
  28 config FRAME_WARN
  29         int "Warn for stack frames larger than (needs gcc 4.4)"
  30         range 0 8192
  31         default 1024 if !64BIT
  32         default 2048 if 64BIT
  33         help
  34           Tell gcc to warn at build time for stack frames larger than this.
  35           Setting this too low will cause a lot of warnings.
  36           Setting it to 0 disables the warning.
  37           Requires gcc 4.4
  38
  39 config MAGIC_SYSRQ
  40         bool "Magic SysRq key"
  41         depends on !UML
  42         help
  43           If you say Y here, you will have some control over the system even
  44           if the system crashes for example during kernel debugging (e.g., you
  45           will be able to flush the buffer cache to disk, reboot the system
  46           immediately or dump some status information). This is accomplished
  47           by pressing various keys while holding SysRq (Alt+PrintScreen). It
  48           also works on a serial console (on PC hardware at least), if you
  49           send a BREAK and then within 5 seconds a command keypress. The
  50           keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
  51           unless you really know what this hack does.
  52
  53 config STRIP_ASM_SYMS
  54         bool "Strip assembler-generated symbols during link"
  55         default n
  56         help
  57           Strip internal assembler-generated symbols during a link (symbols
  58           that look like '.Lxxx') so they don't pollute the output of
  59           get_wchan() and suchlike.
  60
  61 config UNUSED_SYMBOLS
  62         bool "Enable unused/obsolete exported symbols"
  63         default y if X86
  64         help
  65           Unused but exported symbols make the kernel needlessly bigger.  For
  66           that reason most of these unused exports will soon be removed.  This
  67           option is provided temporarily to provide a transition period in case
  68           some external kernel module needs one of these symbols anyway. If you
  69           encounter such a case in your module, consider if you are actually
  70           using the right API.  (rationale: since nobody in the kernel is using
  71           this in a module, there is a pretty good chance it's actually the
  72           wrong interface to use).  If you really need the symbol, please send a
  73           mail to the linux kernel mailing list mentioning the symbol and why
  74           you really need it, and what the merge plan to the mainline kernel for
  75           your module is.
  76
  77 config DEBUG_FS
  78         bool "Debug Filesystem"
  79         help
  80           debugfs is a virtual file system that kernel developers use to put
  81           debugging files into.  Enable this option to be able to read and
  82           write to these files.
  83
  84           For detailed documentation on the debugfs API, see
  85           Documentation/DocBook/filesystems.
  86
  87           If unsure, say N.
  88
  89 config HEADERS_CHECK
  90         bool "Run 'make headers_check' when building vmlinux"
  91         depends on !UML
  92         help
  93           This option will extract the user-visible kernel headers whenever
  94           building the kernel, and will run basic sanity checks on them to
  95           ensure that exported files do not attempt to include files which
  96           were not exported, etc.
  97
  98           If you're making modifications to header files which are
  99           relevant for userspace, say 'Y', and check the headers
 100           exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
 101           your build tree), to make sure they're suitable.
 102
 103 config DEBUG_SECTION_MISMATCH
 104         bool "Enable full Section mismatch analysis"
 105         help
 106           The section mismatch analysis checks if there are illegal
 107           references from one section to another section.
 108           Linux will during link or during runtime drop some sections
 109           and any use of code/data previously in these sections will
 110           most likely result in an oops.
 111           In the code functions and variables are annotated with
 112           __init, __devinit etc. (see full list in include/linux/init.h)
 113           which results in the code/data being placed in specific sections.
 114           The section mismatch analysis is always done after a full
 115           kernel build but enabling this option will in addition
 116           do the following:
 117           - Add the option -fno-inline-functions-called-once to gcc
 118             When inlining a function annotated __init in a non-init
 119             function we would lose the section information and thus
 120             the analysis would not catch the illegal reference.
 121             This option tells gcc to inline less but will also
 122             result in a larger kernel.
 123           - Run the section mismatch analysis for each module/built-in.o
 124             When we run the section mismatch analysis on vmlinux.o we
 125             lose valueble information about where the mismatch was
 126             introduced.
 127             Running the analysis for each module/built-in.o file
 128             will tell where the mismatch happens much closer to the
 129             source. The drawback is that we will report the same
 130             mismatch at least twice.
 131           - Enable verbose reporting from modpost to help solving
 132             the section mismatches reported.
 133
 134 config DEBUG_KERNEL
 135         bool "Kernel debugging"
 136         help
 137           Say Y here if you are developing drivers or trying to debug and
 138           identify kernel problems.
 139
 140 config DEBUG_SHIRQ
 141         bool "Debug shared IRQ handlers"
 142         depends on DEBUG_KERNEL && GENERIC_HARDIRQS
 143         help
 144           Enable this to generate a spurious interrupt as soon as a shared
 145           interrupt handler is registered, and just before one is deregistered.
 146           Drivers ought to be able to handle interrupts coming in at those
 147           points; some don't and need to be caught.
 148
 149 config LOCKUP_DETECTOR
 150         bool "Detect Hard and Soft Lockups"
 151         depends on DEBUG_KERNEL && !S390
 152         help
 153           Say Y here to enable the kernel to act as a watchdog to detect
 154           hard and soft lockups.
 155
 156           Softlockups are bugs that cause the kernel to loop in kernel
 157           mode for more than 60 seconds, without giving other tasks a
 158           chance to run.  The current stack trace is displayed upon
 159           detection and the system will stay locked up.
 160
 161           Hardlockups are bugs that cause the CPU to loop in kernel mode
 162           for more than 60 seconds, without letting other interrupts have a
 163           chance to run.  The current stack trace is displayed upon detection
 164           and the system will stay locked up.
 165
 166           The overhead should be minimal.  A periodic hrtimer runs to
 167           generate interrupts and kick the watchdog task every 10-12 seconds.
 168           An NMI is generated every 60 seconds or so to check for hardlockups.
 169
 170 config HARDLOCKUP_DETECTOR
 171         def_bool LOCKUP_DETECTOR && PERF_EVENTS && HAVE_PERF_EVENTS_NMI && \
 172                  !ARCH_HAS_NMI_WATCHDOG
 173
 174 config BOOTPARAM_SOFTLOCKUP_PANIC
 175         bool "Panic (Reboot) On Soft Lockups"
 176         depends on LOCKUP_DETECTOR
 177         help
 178           Say Y here to enable the kernel to panic on "soft lockups",
 179           which are bugs that cause the kernel to loop in kernel
 180           mode for more than 60 seconds, without giving other tasks a
 181           chance to run.
 182
 183           The panic can be used in combination with panic_timeout,
 184           to cause the system to reboot automatically after a
 185           lockup has been detected. This feature is useful for
 186           high-availability systems that have uptime guarantees and
 187           where a lockup must be resolved ASAP.
 188
 189           Say N if unsure.
 190
 191 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
 192         int
 193         depends on LOCKUP_DETECTOR
 194         range 0 1
 195         default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
 196         default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
 197
 198 config DETECT_HUNG_TASK
 199         bool "Detect Hung Tasks"
 200         depends on DEBUG_KERNEL
 201         default DETECT_SOFTLOCKUP
 202         help
 203           Say Y here to enable the kernel to detect "hung tasks",
 204           which are bugs that cause the task to be stuck in
 205           uninterruptible "D" state indefinitiley.
 206
 207           When a hung task is detected, the kernel will print the
 208           current stack trace (which you should report), but the
 209           task will stay in uninterruptible state. If lockdep is
 210           enabled then all held locks will also be reported. This
 211           feature has negligible overhead.
 212
 213 config BOOTPARAM_HUNG_TASK_PANIC
 214         bool "Panic (Reboot) On Hung Tasks"
 215         depends on DETECT_HUNG_TASK
 216         help
 217           Say Y here to enable the kernel to panic on "hung tasks",
 218           which are bugs that cause the kernel to leave a task stuck
 219           in uninterruptible "D" state.
 220
 221           The panic can be used in combination with panic_timeout,
 222           to cause the system to reboot automatically after a
 223           hung task has been detected. This feature is useful for
 224           high-availability systems that have uptime guarantees and
 225           where a hung tasks must be resolved ASAP.
 226
 227           Say N if unsure.
 228
 229 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
 230         int
 231         depends on DETECT_HUNG_TASK
 232         range 0 1
 233         default 0 if !BOOTPARAM_HUNG_TASK_PANIC
 234         default 1 if BOOTPARAM_HUNG_TASK_PANIC
 235
 236 config SCHED_DEBUG
 237         bool "Collect scheduler debugging info"
 238         depends on DEBUG_KERNEL && PROC_FS
 239         default y
 240         help
 241           If you say Y here, the /proc/sched_debug file will be provided
 242           that can help debug the scheduler. The runtime overhead of this
 243           option is minimal.
 244
 245 config SCHEDSTATS
 246         bool "Collect scheduler statistics"
 247         depends on DEBUG_KERNEL && PROC_FS
 248         help
 249           If you say Y here, additional code will be inserted into the
 250           scheduler and related routines to collect statistics about
 251           scheduler behavior and provide them in /proc/schedstat.  These
 252           stats may be useful for both tuning and debugging the scheduler
 253           If you aren't debugging the scheduler or trying to tune a specific
 254           application, you can say N to avoid the very slight overhead
 255           this adds.
 256
 257 config TIMER_STATS
 258         bool "Collect kernel timers statistics"
 259         depends on DEBUG_KERNEL && PROC_FS
 260         help
 261           If you say Y here, additional code will be inserted into the
 262           timer routines to collect statistics about kernel timers being
 263           reprogrammed. The statistics can be read from /proc/timer_stats.
 264           The statistics collection is started by writing 1 to /proc/timer_stats,
 265           writing 0 stops it. This feature is useful to collect information
 266           about timer usage patterns in kernel and userspace. This feature
 267           is lightweight if enabled in the kernel config but not activated
 268           (it defaults to deactivated on bootup and will only be activated
 269           if some application like powertop activates it explicitly).
 270
 271 config DEBUG_OBJECTS
 272         bool "Debug object operations"
 273         depends on DEBUG_KERNEL
 274         help
 275           If you say Y here, additional code will be inserted into the
 276           kernel to track the life time of various objects and validate
 277           the operations on those objects.
 278
 279 config DEBUG_OBJECTS_SELFTEST
 280         bool "Debug objects selftest"
 281         depends on DEBUG_OBJECTS
 282         help
 283           This enables the selftest of the object debug code.
 284
 285 config DEBUG_OBJECTS_FREE
 286         bool "Debug objects in freed memory"
 287         depends on DEBUG_OBJECTS
 288         help
 289           This enables checks whether a k/v free operation frees an area
 290           which contains an object which has not been deactivated
 291           properly. This can make kmalloc/kfree-intensive workloads
 292           much slower.
 293
 294 config DEBUG_OBJECTS_TIMERS
 295         bool "Debug timer objects"
 296         depends on DEBUG_OBJECTS
 297         help
 298           If you say Y here, additional code will be inserted into the
 299           timer routines to track the life time of timer objects and
 300           validate the timer operations.
 301
 302 config DEBUG_OBJECTS_WORK
 303         bool "Debug work objects"
 304         depends on DEBUG_OBJECTS
 305         help
 306           If you say Y here, additional code will be inserted into the
 307           work queue routines to track the life time of work objects and
 308           validate the work operations.
 309
 310 config DEBUG_OBJECTS_RCU_HEAD
 311         bool "Debug RCU callbacks objects"
 312         depends on DEBUG_OBJECTS && PREEMPT
 313         help
 314           Enable this to turn on debugging of RCU list heads (call_rcu() usage).
 315
 316 config DEBUG_OBJECTS_PERCPU_COUNTER
 317         bool "Debug percpu counter objects"
 318         depends on DEBUG_OBJECTS
 319         help
 320           If you say Y here, additional code will be inserted into the
 321           percpu counter routines to track the life time of percpu counter
 322           objects and validate the percpu counter operations.
 323
 324 config DEBUG_OBJECTS_ENABLE_DEFAULT
 325         int "debug_objects bootup default value (0-1)"
 326         range 0 1
 327         default "1"
 328         depends on DEBUG_OBJECTS
 329         help
 330           Debug objects boot parameter default value
 331
 332 config DEBUG_SLAB
 333         bool "Debug slab memory allocations"
 334         depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
 335         help
 336           Say Y here to have the kernel do limited verification on memory
 337           allocation as well as poisoning memory on free to catch use of freed
 338           memory. This can make kmalloc/kfree-intensive workloads much slower.
 339
 340 config DEBUG_SLAB_LEAK
 341         bool "Memory leak debugging"
 342         depends on DEBUG_SLAB
 343
 344 config SLUB_DEBUG_ON
 345         bool "SLUB debugging on by default"
 346         depends on SLUB && SLUB_DEBUG && !KMEMCHECK
 347         default n
 348         help
 349           Boot with debugging on by default. SLUB boots by default with
 350           the runtime debug capabilities switched off. Enabling this is
 351           equivalent to specifying the "slub_debug" parameter on boot.
 352           There is no support for more fine grained debug control like
 353           possible with slub_debug=xxx. SLUB debugging may be switched
 354           off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
 355           "slub_debug=-".
 356
 357 config SLUB_STATS
 358         default n
 359         bool "Enable SLUB performance statistics"
 360         depends on SLUB && SYSFS
 361         help
 362           SLUB statistics are useful to debug SLUBs allocation behavior in
 363           order find ways to optimize the allocator. This should never be
 364           enabled for production use since keeping statistics slows down
 365           the allocator by a few percentage points. The slabinfo command
 366           supports the determination of the most active slabs to figure
 367           out which slabs are relevant to a particular load.
 368           Try running: slabinfo -DA
 369
 370 config DEBUG_KMEMLEAK
 371         bool "Kernel memory leak detector"
 372         depends on DEBUG_KERNEL && EXPERIMENTAL && !MEMORY_HOTPLUG && \
 373                 (X86 || ARM || PPC || S390 || SPARC64 || SUPERH || MICROBLAZE || TILE)
 374
 375         select DEBUG_FS if SYSFS
 376         select STACKTRACE if STACKTRACE_SUPPORT
 377         select KALLSYMS
 378         select CRC32
 379         help
 380           Say Y here if you want to enable the memory leak
 381           detector. The memory allocation/freeing is traced in a way
 382           similar to the Boehm's conservative garbage collector, the
 383           difference being that the orphan objects are not freed but
 384           only shown in /sys/kernel/debug/kmemleak. Enabling this
 385           feature will introduce an overhead to memory
 386           allocations. See Documentation/kmemleak.txt for more
 387           details.
 388
 389           Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
 390           of finding leaks due to the slab objects poisoning.
 391
 392           In order to access the kmemleak file, debugfs needs to be
 393           mounted (usually at /sys/kernel/debug).
 394
 395 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
 396         int "Maximum kmemleak early log entries"
 397         depends on DEBUG_KMEMLEAK
 398         range 200 40000
 399         default 400
 400         help
 401           Kmemleak must track all the memory allocations to avoid
 402           reporting false positives. Since memory may be allocated or
 403           freed before kmemleak is initialised, an early log buffer is
 404           used to store these actions. If kmemleak reports "early log
 405           buffer exceeded", please increase this value.
 406
 407 config DEBUG_KMEMLEAK_TEST
 408         tristate "Simple test for the kernel memory leak detector"
 409         depends on DEBUG_KMEMLEAK
 410         help
 411           Say Y or M here to build a test for the kernel memory leak
 412           detector. This option enables a module that explicitly leaks
 413           memory.
 414
 415           If unsure, say N.
 416
 417 config DEBUG_KMEMLEAK_DEFAULT_OFF
 418         bool "Default kmemleak to off"
 419         depends on DEBUG_KMEMLEAK
 420         help
 421           Say Y here to disable kmemleak by default. It can then be enabled
 422           on the command line via kmemleak=on.
 423
 424 config DEBUG_PREEMPT
 425         bool "Debug preemptible kernel"
 426         depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
 427         default y
 428         help
 429           If you say Y here then the kernel will use a debug variant of the
 430           commonly used smp_processor_id() function and will print warnings
 431           if kernel code uses it in a preemption-unsafe way. Also, the kernel
 432           will detect preemption count underflows.
 433
 434 config DEBUG_RT_MUTEXES
 435         bool "RT Mutex debugging, deadlock detection"
 436         depends on DEBUG_KERNEL && RT_MUTEXES
 437         help
 438          This allows rt mutex semantics violations and rt mutex related
 439          deadlocks (lockups) to be detected and reported automatically.
 440
 441 config DEBUG_PI_LIST
 442         bool
 443         default y
 444         depends on DEBUG_RT_MUTEXES
 445
 446 config RT_MUTEX_TESTER
 447         bool "Built-in scriptable tester for rt-mutexes"
 448         depends on DEBUG_KERNEL && RT_MUTEXES
 449         help
 450           This option enables a rt-mutex tester.
 451
 452 config DEBUG_SPINLOCK
 453         bool "Spinlock and rw-lock debugging: basic checks"
 454         depends on DEBUG_KERNEL
 455         help
 456           Say Y here and build SMP to catch missing spinlock initialization
 457           and certain other kinds of spinlock errors commonly made.  This is
 458           best used in conjunction with the NMI watchdog so that spinlock
 459           deadlocks are also debuggable.
 460
 461 config DEBUG_MUTEXES
 462         bool "Mutex debugging: basic checks"
 463         depends on DEBUG_KERNEL
 464         help
 465          This feature allows mutex semantics violations to be detected and
 466          reported.
 467
 468 config DEBUG_LOCK_ALLOC
 469         bool "Lock debugging: detect incorrect freeing of live locks"
 470         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 471         select DEBUG_SPINLOCK
 472         select DEBUG_MUTEXES
 473         select LOCKDEP
 474         help
 475          This feature will check whether any held lock (spinlock, rwlock,
 476          mutex or rwsem) is incorrectly freed by the kernel, via any of the
 477          memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
 478          vfree(), etc.), whether a live lock is incorrectly reinitialized via
 479          spin_lock_init()/mutex_init()/etc., or whether there is any lock
 480          held during task exit.
 481
 482 config PROVE_LOCKING
 483         bool "Lock debugging: prove locking correctness"
 484         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 485         select LOCKDEP
 486         select DEBUG_SPINLOCK
 487         select DEBUG_MUTEXES
 488         select DEBUG_LOCK_ALLOC
 489         select TRACE_IRQFLAGS
 490         default n
 491         help
 492          This feature enables the kernel to prove that all locking
 493          that occurs in the kernel runtime is mathematically
 494          correct: that under no circumstance could an arbitrary (and
 495          not yet triggered) combination of observed locking
 496          sequences (on an arbitrary number of CPUs, running an
 497          arbitrary number of tasks and interrupt contexts) cause a
 498          deadlock.
 499
 500          In short, this feature enables the kernel to report locking
 501          related deadlocks before they actually occur.
 502
 503          The proof does not depend on how hard and complex a
 504          deadlock scenario would be to trigger: how many
 505          participant CPUs, tasks and irq-contexts would be needed
 506          for it to trigger. The proof also does not depend on
 507          timing: if a race and a resulting deadlock is possible
 508          theoretically (no matter how unlikely the race scenario
 509          is), it will be proven so and will immediately be
 510          reported by the kernel (once the event is observed that
 511          makes the deadlock theoretically possible).
 512
 513          If a deadlock is impossible (i.e. the locking rules, as
 514          observed by the kernel, are mathematically correct), the
 515          kernel reports nothing.
 516
 517          NOTE: this feature can also be enabled for rwlocks, mutexes
 518          and rwsems - in which case all dependencies between these
 519          different locking variants are observed and mapped too, and
 520          the proof of observed correctness is also maintained for an
 521          arbitrary combination of these separate locking variants.
 522
 523          For more details, see Documentation/lockdep-design.txt.
 524
 525 config PROVE_RCU
 526         bool "RCU debugging: prove RCU correctness"
 527         depends on PROVE_LOCKING
 528         default n
 529         help
 530          This feature enables lockdep extensions that check for correct
 531          use of RCU APIs.  This is currently under development.  Say Y
 532          if you want to debug RCU usage or help work on the PROVE_RCU
 533          feature.
 534
 535          Say N if you are unsure.
 536
 537 config PROVE_RCU_REPEATEDLY
 538         bool "RCU debugging: don't disable PROVE_RCU on first splat"
 539         depends on PROVE_RCU
 540         default n
 541         help
 542          By itself, PROVE_RCU will disable checking upon issuing the
 543          first warning (or "splat").  This feature prevents such
 544          disabling, allowing multiple RCU-lockdep warnings to be printed
 545          on a single reboot.
 546
 547          Say Y to allow multiple RCU-lockdep warnings per boot.
 548
 549          Say N if you are unsure.
 550
 551 config SPARSE_RCU_POINTER
 552         bool "RCU debugging: sparse-based checks for pointer usage"
 553         default n
 554         help
 555          This feature enables the __rcu sparse annotation for
 556          RCU-protected pointers.  This annotation will cause sparse
 557          to flag any non-RCU used of annotated pointers.  This can be
 558          helpful when debugging RCU usage.  Please note that this feature
 559          is not intended to enforce code cleanliness; it is instead merely
 560          a debugging aid.
 561
 562          Say Y to make sparse flag questionable use of RCU-protected pointers
 563
 564          Say N if you are unsure.
 565
 566 config LOCKDEP
 567         bool
 568         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 569         select STACKTRACE
 570         select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE
 571         select KALLSYMS
 572         select KALLSYMS_ALL
 573
 574 config LOCK_STAT
 575         bool "Lock usage statistics"
 576         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 577         select LOCKDEP
 578         select DEBUG_SPINLOCK
 579         select DEBUG_MUTEXES
 580         select DEBUG_LOCK_ALLOC
 581         default n
 582         help
 583          This feature enables tracking lock contention points
 584
 585          For more details, see Documentation/lockstat.txt
 586
 587          This also enables lock events required by "perf lock",
 588          subcommand of perf.
 589          If you want to use "perf lock", you also need to turn on
 590          CONFIG_EVENT_TRACING.
 591
 592          CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
 593          (CONFIG_LOCKDEP defines "acquire" and "release" events.)
 594
 595 config DEBUG_LOCKDEP
 596         bool "Lock dependency engine debugging"
 597         depends on DEBUG_KERNEL && LOCKDEP
 598         help
 599           If you say Y here, the lock dependency engine will do
 600           additional runtime checks to debug itself, at the price
 601           of more runtime overhead.
 602
 603 config TRACE_IRQFLAGS
 604         bool
 605         help
 606           Enables hooks to interrupt enabling and disabling for
 607           either tracing or lock debugging.
 608
 609 config DEBUG_SPINLOCK_SLEEP
 610         bool "Spinlock debugging: sleep-inside-spinlock checking"
 611         depends on DEBUG_KERNEL
 612         help
 613           If you say Y here, various routines which may sleep will become very
 614           noisy if they are called with a spinlock held.
 615
 616 config DEBUG_LOCKING_API_SELFTESTS
 617         bool "Locking API boot-time self-tests"
 618         depends on DEBUG_KERNEL
 619         help
 620           Say Y here if you want the kernel to run a short self-test during
 621           bootup. The self-test checks whether common types of locking bugs
 622           are detected by debugging mechanisms or not. (if you disable
 623           lock debugging then those bugs wont be detected of course.)
 624           The following locking APIs are covered: spinlocks, rwlocks,
 625           mutexes and rwsems.
 626
 627 config STACKTRACE
 628         bool
 629         depends on STACKTRACE_SUPPORT
 630
 631 config DEBUG_KOBJECT
 632         bool "kobject debugging"
 633         depends on DEBUG_KERNEL
 634         help
 635           If you say Y here, some extra kobject debugging messages will be sent
 636           to the syslog.
 637
 638 config DEBUG_HIGHMEM
 639         bool "Highmem debugging"
 640         depends on DEBUG_KERNEL && HIGHMEM
 641         help
 642           This options enables addition error checking for high memory systems.
 643           Disable for production systems.
 644
 645 config DEBUG_BUGVERBOSE
 646         bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
 647         depends on BUG
 648         depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \
 649                    FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300
 650         default y
 651         help
 652           Say Y here to make BUG() panics output the file name and line number
 653           of the BUG call as well as the EIP and oops trace.  This aids
 654           debugging but costs about 70-100K of memory.
 655
 656 config DEBUG_INFO
 657         bool "Compile the kernel with debug info"
 658         depends on DEBUG_KERNEL
 659         help
 660           If you say Y here the resulting kernel image will include
 661           debugging info resulting in a larger kernel image.
 662           This adds debug symbols to the kernel and modules (gcc -g), and
 663           is needed if you intend to use kernel crashdump or binary object
 664           tools like crash, kgdb, LKCD, gdb, etc on the kernel.
 665           Say Y here only if you plan to debug the kernel.
 666
 667           If unsure, say N.
 668
 669 config DEBUG_INFO_REDUCED
 670         bool "Reduce debugging information"
 671         depends on DEBUG_INFO
 672         help
 673           If you say Y here gcc is instructed to generate less debugging
 674           information for structure types. This means that tools that
 675           need full debugging information (like kgdb or systemtap) won't
 676           be happy. But if you merely need debugging information to
 677           resolve line numbers there is no loss. Advantage is that
 678           build directory object sizes shrink dramatically over a full
 679           DEBUG_INFO build and compile times are reduced too.
 680           Only works with newer gcc versions.
 681
 682 config DEBUG_VM
 683         bool "Debug VM"
 684         depends on DEBUG_KERNEL
 685         help
 686           Enable this to turn on extended checks in the virtual-memory system
 687           that may impact performance.
 688
 689           If unsure, say N.
 690
 691 config DEBUG_VIRTUAL
 692         bool "Debug VM translations"
 693         depends on DEBUG_KERNEL && X86
 694         help
 695           Enable some costly sanity checks in virtual to page code. This can
 696           catch mistakes with virt_to_page() and friends.
 697
 698           If unsure, say N.
 699
 700 config DEBUG_NOMMU_REGIONS
 701         bool "Debug the global anon/private NOMMU mapping region tree"
 702         depends on DEBUG_KERNEL && !MMU
 703         help
 704           This option causes the global tree of anonymous and private mapping
 705           regions to be regularly checked for invalid topology.
 706
 707 config DEBUG_WRITECOUNT
 708         bool "Debug filesystem writers count"
 709         depends on DEBUG_KERNEL
 710         help
 711           Enable this to catch wrong use of the writers count in struct
 712           vfsmount.  This will increase the size of each file struct by
 713           32 bits.
 714
 715           If unsure, say N.
 716
 717 config DEBUG_MEMORY_INIT
 718         bool "Debug memory initialisation" if EXPERT
 719         default !EXPERT
 720         help
 721           Enable this for additional checks during memory initialisation.
 722           The sanity checks verify aspects of the VM such as the memory model
 723           and other information provided by the architecture. Verbose
 724           information will be printed at KERN_DEBUG loglevel depending
 725           on the mminit_loglevel= command-line option.
 726
 727           If unsure, say Y
 728
 729 config DEBUG_LIST
 730         bool "Debug linked list manipulation"
 731         depends on DEBUG_KERNEL
 732         help
 733           Enable this to turn on extended checks in the linked-list
 734           walking routines.
 735
 736           If unsure, say N.
 737
 738 config TEST_LIST_SORT
 739         bool "Linked list sorting test"
 740         depends on DEBUG_KERNEL
 741         help
 742           Enable this to turn on 'list_sort()' function test. This test is
 743           executed only once during system boot, so affects only boot time.
 744
 745           If unsure, say N.
 746
 747 config DEBUG_SG
 748         bool "Debug SG table operations"
 749         depends on DEBUG_KERNEL
 750         help
 751           Enable this to turn on checks on scatter-gather tables. This can
 752           help find problems with drivers that do not properly initialize
 753           their sg tables.
 754
 755           If unsure, say N.
 756
 757 config DEBUG_NOTIFIERS
 758         bool "Debug notifier call chains"
 759         depends on DEBUG_KERNEL
 760         help
 761           Enable this to turn on sanity checking for notifier call chains.
 762           This is most useful for kernel developers to make sure that
 763           modules properly unregister themselves from notifier chains.
 764           This is a relatively cheap check but if you care about maximum
 765           performance, say N.
 766
 767 config DEBUG_CREDENTIALS
 768         bool "Debug credential management"
 769         depends on DEBUG_KERNEL
 770         help
 771           Enable this to turn on some debug checking for credential
 772           management.  The additional code keeps track of the number of
 773           pointers from task_structs to any given cred struct, and checks to
 774           see that this number never exceeds the usage count of the cred
 775           struct.
 776
 777           Furthermore, if SELinux is enabled, this also checks that the
 778           security pointer in the cred struct is never seen to be invalid.
 779
 780           If unsure, say N.
 781
 782 #
 783 # Select this config option from the architecture Kconfig, if it
 784 # it is preferred to always offer frame pointers as a config
 785 # option on the architecture (regardless of KERNEL_DEBUG):
 786 #
 787 config ARCH_WANT_FRAME_POINTERS
 788         bool
 789         help
 790
 791 config FRAME_POINTER
 792         bool "Compile the kernel with frame pointers"
 793         depends on DEBUG_KERNEL && \
 794                 (CRIS || M68K || FRV || UML || \
 795                  AVR32 || SUPERH || BLACKFIN || MN10300) || \
 796                 ARCH_WANT_FRAME_POINTERS
 797         default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
 798         help
 799           If you say Y here the resulting kernel image will be slightly
 800           larger and slower, but it gives very useful debugging information
 801           in case of kernel bugs. (precise oopses/stacktraces/warnings)
 802
 803 config BOOT_PRINTK_DELAY
 804         bool "Delay each boot printk message by N milliseconds"
 805         depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
 806         help
 807           This build option allows you to read kernel boot messages
 808           by inserting a short delay after each one.  The delay is
 809           specified in milliseconds on the kernel command line,
 810           using "boot_delay=N".
 811
 812           It is likely that you would also need to use "lpj=M" to preset
 813           the "loops per jiffie" value.
 814           See a previous boot log for the "lpj" value to use for your
 815           system, and then set "lpj=M" before setting "boot_delay=N".
 816           NOTE:  Using this option may adversely affect SMP systems.
 817           I.e., processors other than the first one may not boot up.
 818           BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect
 819           what it believes to be lockup conditions.
 820
 821 config RCU_TORTURE_TEST
 822         tristate "torture tests for RCU"
 823         depends on DEBUG_KERNEL
 824         default n
 825         help
 826           This option provides a kernel module that runs torture tests
 827           on the RCU infrastructure.  The kernel module may be built
 828           after the fact on the running kernel to be tested, if desired.
 829
 830           Say Y here if you want RCU torture tests to be built into
 831           the kernel.
 832           Say M if you want the RCU torture tests to build as a module.
 833           Say N if you are unsure.
 834
 835 config RCU_TORTURE_TEST_RUNNABLE
 836         bool "torture tests for RCU runnable by default"
 837         depends on RCU_TORTURE_TEST = y
 838         default n
 839         help
 840           This option provides a way to build the RCU torture tests
 841           directly into the kernel without them starting up at boot
 842           time.  You can use /proc/sys/kernel/rcutorture_runnable
 843           to manually override this setting.  This /proc file is
 844           available only when the RCU torture tests have been built
 845           into the kernel.
 846
 847           Say Y here if you want the RCU torture tests to start during
 848           boot (you probably don't).
 849           Say N here if you want the RCU torture tests to start only
 850           after being manually enabled via /proc.
 851
 852 config RCU_CPU_STALL_DETECTOR
 853         bool "Check for stalled CPUs delaying RCU grace periods"
 854         depends on TREE_RCU || TREE_PREEMPT_RCU
 855         default y
 856         help
 857           This option causes RCU to printk information on which
 858           CPUs are delaying the current grace period, but only when
 859           the grace period extends for excessive time periods.
 860
 861           Say N if you want to disable such checks.
 862
 863           Say Y if you are unsure.
 864
 865 config RCU_CPU_STALL_TIMEOUT
 866         int "RCU CPU stall timeout in seconds"
 867         depends on RCU_CPU_STALL_DETECTOR
 868         range 3 300
 869         default 60
 870         help
 871           If a given RCU grace period extends more than the specified
 872           number of seconds, a CPU stall warning is printed.  If the
 873           RCU grace period persists, additional CPU stall warnings are
 874           printed at more widely spaced intervals.
 875
 876 config RCU_CPU_STALL_DETECTOR_RUNNABLE
 877         bool "RCU CPU stall checking starts automatically at boot"
 878         depends on RCU_CPU_STALL_DETECTOR
 879         default y
 880         help
 881           If set, start checking for RCU CPU stalls immediately on
 882           boot.  Otherwise, RCU CPU stall checking must be manually
 883           enabled.
 884
 885           Say Y if you are unsure.
 886
 887           Say N if you wish to suppress RCU CPU stall checking during boot.
 888
 889 config RCU_CPU_STALL_VERBOSE
 890         bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
 891         depends on RCU_CPU_STALL_DETECTOR && TREE_PREEMPT_RCU
 892         default y
 893         help
 894           This option causes RCU to printk detailed per-task information
 895           for any tasks that are stalling the current RCU grace period.
 896
 897           Say N if you are unsure.
 898
 899           Say Y if you want to enable such checks.
 900
 901 config KPROBES_SANITY_TEST
 902         bool "Kprobes sanity tests"
 903         depends on DEBUG_KERNEL
 904         depends on KPROBES
 905         default n
 906         help
 907           This option provides for testing basic kprobes functionality on
 908           boot. A sample kprobe, jprobe and kretprobe are inserted and
 909           verified for functionality.
 910
 911           Say N if you are unsure.
 912
 913 config BACKTRACE_SELF_TEST
 914         tristate "Self test for the backtrace code"
 915         depends on DEBUG_KERNEL
 916         default n
 917         help
 918           This option provides a kernel module that can be used to test
 919           the kernel stack backtrace code. This option is not useful
 920           for distributions or general kernels, but only for kernel
 921           developers working on architecture code.
 922
 923           Note that if you want to also test saved backtraces, you will
 924           have to enable STACKTRACE as well.
 925
 926           Say N if you are unsure.
 927
 928 config DEBUG_BLOCK_EXT_DEVT
 929         bool "Force extended block device numbers and spread them"
 930         depends on DEBUG_KERNEL
 931         depends on BLOCK
 932         default n
 933         help
 934           BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
 935           SOME DISTRIBUTIONS.  DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
 936           YOU ARE DOING.  Distros, please enable this and fix whatever
 937           is broken.
 938
 939           Conventionally, block device numbers are allocated from
 940           predetermined contiguous area.  However, extended block area
 941           may introduce non-contiguous block device numbers.  This
 942           option forces most block device numbers to be allocated from
 943           the extended space and spreads them to discover kernel or
 944           userland code paths which assume predetermined contiguous
 945           device number allocation.
 946
 947           Note that turning on this debug option shuffles all the
 948           device numbers for all IDE and SCSI devices including libata
 949           ones, so root partition specified using device number
 950           directly (via rdev or root=MAJ:MIN) won't work anymore.
 951           Textual device names (root=/dev/sdXn) will continue to work.
 952
 953           Say N if you are unsure.
 954
 955 config DEBUG_FORCE_WEAK_PER_CPU
 956         bool "Force weak per-cpu definitions"
 957         depends on DEBUG_KERNEL
 958         help
 959           s390 and alpha require percpu variables in modules to be
 960           defined weak to work around addressing range issue which
 961           puts the following two restrictions on percpu variable
 962           definitions.
 963
 964           1. percpu symbols must be unique whether static or not
 965           2. percpu variables can't be defined inside a function
 966
 967           To ensure that generic code follows the above rules, this
 968           option forces all percpu variables to be defined as weak.
 969
 970 config LKDTM
 971         tristate "Linux Kernel Dump Test Tool Module"
 972         depends on DEBUG_FS
 973         depends on BLOCK
 974         default n
 975         help
 976         This module enables testing of the different dumping mechanisms by
 977         inducing system failures at predefined crash points.
 978         If you don't need it: say N
 979         Choose M here to compile this code as a module. The module will be
 980         called lkdtm.
 981
 982         Documentation on how to use the module can be found in
 983         Documentation/fault-injection/provoke-crashes.txt
 984
 985 config CPU_NOTIFIER_ERROR_INJECT
 986         tristate "CPU notifier error injection module"
 987         depends on HOTPLUG_CPU && DEBUG_KERNEL
 988         help
 989           This option provides a kernel module that can be used to test
 990           the error handling of the cpu notifiers
 991
 992           To compile this code as a module, choose M here: the module will
 993           be called cpu-notifier-error-inject.
 994
 995           If unsure, say N.
 996
 997 config FAULT_INJECTION
 998         bool "Fault-injection framework"
 999         depends on DEBUG_KERNEL
1000         help
1001           Provide fault-injection framework.
1002           For more details, see Documentation/fault-injection/.
1003
1004 config FAILSLAB
1005         bool "Fault-injection capability for kmalloc"
1006         depends on FAULT_INJECTION
1007         depends on SLAB || SLUB
1008         help
1009           Provide fault-injection capability for kmalloc.
1010
1011 config FAIL_PAGE_ALLOC
1012         bool "Fault-injection capabilitiy for alloc_pages()"
1013         depends on FAULT_INJECTION
1014         help
1015           Provide fault-injection capability for alloc_pages().
1016
1017 config FAIL_MAKE_REQUEST
1018         bool "Fault-injection capability for disk IO"
1019         depends on FAULT_INJECTION && BLOCK
1020         help
1021           Provide fault-injection capability for disk IO.
1022
1023 config FAIL_IO_TIMEOUT
1024         bool "Fault-injection capability for faking disk interrupts"
1025         depends on FAULT_INJECTION && BLOCK
1026         help
1027           Provide fault-injection capability on end IO handling. This
1028           will make the block layer "forget" an interrupt as configured,
1029           thus exercising the error handling.
1030
1031           Only works with drivers that use the generic timeout handling,
1032           for others it wont do anything.
1033
1034 config FAULT_INJECTION_DEBUG_FS
1035         bool "Debugfs entries for fault-injection capabilities"
1036         depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1037         help
1038           Enable configuration of fault-injection capabilities via debugfs.
1039
1040 config FAULT_INJECTION_STACKTRACE_FILTER
1041         bool "stacktrace filter for fault-injection capabilities"
1042         depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1043         depends on !X86_64
1044         select STACKTRACE
1045         select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE
1046         help
1047           Provide stacktrace filter for fault-injection capabilities
1048
1049 config LATENCYTOP
1050         bool "Latency measuring infrastructure"
1051         depends on HAVE_LATENCYTOP_SUPPORT
1052         depends on DEBUG_KERNEL
1053         depends on STACKTRACE_SUPPORT
1054         depends on PROC_FS
1055         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE
1056         select KALLSYMS
1057         select KALLSYMS_ALL
1058         select STACKTRACE
1059         select SCHEDSTATS
1060         select SCHED_DEBUG
1061         help
1062           Enable this option if you want to use the LatencyTOP tool
1063           to find out which userspace is blocking on what kernel operations.
1064
1065 config SYSCTL_SYSCALL_CHECK
1066         bool "Sysctl checks"
1067         depends on SYSCTL
1068         ---help---
1069           sys_sysctl uses binary paths that have been found challenging
1070           to properly maintain and use. This enables checks that help
1071           you to keep things correct.
1072
1073 source mm/Kconfig.debug
1074 source kernel/trace/Kconfig
1075
1076 config PROVIDE_OHCI1394_DMA_INIT
1077         bool "Remote debugging over FireWire early on boot"
1078         depends on PCI && X86
1079         help
1080           If you want to debug problems which hang or crash the kernel early
1081           on boot and the crashing machine has a FireWire port, you can use
1082           this feature to remotely access the memory of the crashed machine
1083           over FireWire. This employs remote DMA as part of the OHCI1394
1084           specification which is now the standard for FireWire controllers.
1085
1086           With remote DMA, you can monitor the printk buffer remotely using
1087           firescope and access all memory below 4GB using fireproxy from gdb.
1088           Even controlling a kernel debugger is possible using remote DMA.
1089
1090           Usage:
1091
1092           If ohci1394_dma=early is used as boot parameter, it will initialize
1093           all OHCI1394 controllers which are found in the PCI config space.
1094
1095           As all changes to the FireWire bus such as enabling and disabling
1096           devices cause a bus reset and thereby disable remote DMA for all
1097           devices, be sure to have the cable plugged and FireWire enabled on
1098           the debugging host before booting the debug target for debugging.
1099
1100           This code (~1k) is freed after boot. By then, the firewire stack
1101           in charge of the OHCI-1394 controllers should be used instead.
1102
1103           See Documentation/debugging-via-ohci1394.txt for more information.
1104
1105 config FIREWIRE_OHCI_REMOTE_DMA
1106         bool "Remote debugging over FireWire with firewire-ohci"
1107         depends on FIREWIRE_OHCI
1108         help
1109           This option lets you use the FireWire bus for remote debugging
1110           with help of the firewire-ohci driver. It enables unfiltered
1111           remote DMA in firewire-ohci.
1112           See Documentation/debugging-via-ohci1394.txt for more information.
1113
1114           If unsure, say N.
1115
1116 config BUILD_DOCSRC
1117         bool "Build targets in Documentation/ tree"
1118         depends on HEADERS_CHECK
1119         help
1120           This option attempts to build objects from the source files in the
1121           kernel Documentation/ tree.
1122
1123           Say N if you are unsure.
1124
1125 config DYNAMIC_DEBUG
1126         bool "Enable dynamic printk() support"
1127         default n
1128         depends on PRINTK
1129         depends on DEBUG_FS
1130         help
1131
1132           Compiles debug level messages into the kernel, which would not
1133           otherwise be available at runtime. These messages can then be
1134           enabled/disabled based on various levels of scope - per source file,
1135           function, module, format string, and line number. This mechanism
1136           implicitly enables all pr_debug() and dev_dbg() calls. The impact of
1137           this compile option is a larger kernel text size of about 2%.
1138
1139           Usage:
1140
1141           Dynamic debugging is controlled via the 'dynamic_debug/control' file,
1142           which is contained in the 'debugfs' filesystem. Thus, the debugfs
1143           filesystem must first be mounted before making use of this feature.
1144           We refer the control file as: <debugfs>/dynamic_debug/control. This
1145           file contains a list of the debug statements that can be enabled. The
1146           format for each line of the file is:
1147
1148                 filename:lineno [module]function flags format
1149
1150           filename : source file of the debug statement
1151           lineno : line number of the debug statement
1152           module : module that contains the debug statement
1153           function : function that contains the debug statement
1154           flags : 'p' means the line is turned 'on' for printing
1155           format : the format used for the debug statement
1156
1157           From a live system:
1158
1159                 nullarbor:~ # cat <debugfs>/dynamic_debug/control
1160                 # filename:lineno [module]function flags format
1161                 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012"
1162                 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012"
1163                 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012"
1164
1165           Example usage:
1166
1167                 // enable the message at line 1603 of file svcsock.c
1168                 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
1169                                                 <debugfs>/dynamic_debug/control
1170
1171                 // enable all the messages in file svcsock.c
1172                 nullarbor:~ # echo -n 'file svcsock.c +p' >
1173                                                 <debugfs>/dynamic_debug/control
1174
1175                 // enable all the messages in the NFS server module
1176                 nullarbor:~ # echo -n 'module nfsd +p' >
1177                                                 <debugfs>/dynamic_debug/control
1178
1179                 // enable all 12 messages in the function svc_process()
1180                 nullarbor:~ # echo -n 'func svc_process +p' >
1181                                                 <debugfs>/dynamic_debug/control
1182
1183                 // disable all 12 messages in the function svc_process()
1184                 nullarbor:~ # echo -n 'func svc_process -p' >
1185                                                 <debugfs>/dynamic_debug/control
1186
1187           See Documentation/dynamic-debug-howto.txt for additional information.
1188
1189 config DMA_API_DEBUG
1190         bool "Enable debugging of DMA-API usage"
1191         depends on HAVE_DMA_API_DEBUG
1192         help
1193           Enable this option to debug the use of the DMA API by device drivers.
1194           With this option you will be able to detect common bugs in device
1195           drivers like double-freeing of DMA mappings or freeing mappings that
1196           were never allocated.
1197           This option causes a performance degredation.  Use only if you want
1198           to debug device drivers. If unsure, say N.
1199
1200 config ATOMIC64_SELFTEST
1201         bool "Perform an atomic64_t self-test at boot"
1202         help
1203           Enable this option to test the atomic64_t functions at boot.
1204
1205           If unsure, say N.
1206
1207 config ASYNC_RAID6_TEST
1208         tristate "Self test for hardware accelerated raid6 recovery"
1209         depends on ASYNC_RAID6_RECOV
1210         select ASYNC_MEMCPY
1211         ---help---
1212           This is a one-shot self test that permutes through the
1213           recovery of all the possible two disk failure scenarios for a
1214           N-disk array.  Recovery is performed with the asynchronous
1215           raid6 recovery routines, and will optionally use an offload
1216           engine if one is available.
1217
1218           If unsure, say N.
1219
1220 source "samples/Kconfig"
1221
1222 source "lib/Kconfig.kgdb"
1223
1224 source "lib/Kconfig.kmemcheck"