linux/lib/Kconfig.debug
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   1
   2config 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
  12config 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
  20config 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
  28config 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
  39config 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
  53config 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
  61config 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
  77config 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
  89config 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
 103config DEBUG_SECTION_MISMATCH
 104        bool "Enable full Section mismatch analysis"
 105        depends on UNDEFINED || (BLACKFIN)
 106        default y
 107        # This option is on purpose disabled for now.
 108        # It will be enabled when we are down to a reasonable number
 109        # of section mismatch warnings (< 10 for an allyesconfig build)
 110        help
 111          The section mismatch analysis checks if there are illegal
 112          references from one section to another section.
 113          Linux will during link or during runtime drop some sections
 114          and any use of code/data previously in these sections will
 115          most likely result in an oops.
 116          In the code functions and variables are annotated with
 117          __init, __devinit etc. (see full list in include/linux/init.h)
 118          which results in the code/data being placed in specific sections.
 119          The section mismatch analysis is always done after a full
 120          kernel build but enabling this option will in addition
 121          do the following:
 122          - Add the option -fno-inline-functions-called-once to gcc
 123            When inlining a function annotated __init in a non-init
 124            function we would lose the section information and thus
 125            the analysis would not catch the illegal reference.
 126            This option tells gcc to inline less but will also
 127            result in a larger kernel.
 128          - Run the section mismatch analysis for each module/built-in.o
 129            When we run the section mismatch analysis on vmlinux.o we
 130            lose valueble information about where the mismatch was
 131            introduced.
 132            Running the analysis for each module/built-in.o file
 133            will tell where the mismatch happens much closer to the
 134            source. The drawback is that we will report the same
 135            mismatch at least twice.
 136          - Enable verbose reporting from modpost to help solving
 137            the section mismatches reported.
 138
 139config DEBUG_KERNEL
 140        bool "Kernel debugging"
 141        help
 142          Say Y here if you are developing drivers or trying to debug and
 143          identify kernel problems.
 144
 145config DEBUG_SHIRQ
 146        bool "Debug shared IRQ handlers"
 147        depends on DEBUG_KERNEL && GENERIC_HARDIRQS
 148        help
 149          Enable this to generate a spurious interrupt as soon as a shared
 150          interrupt handler is registered, and just before one is deregistered.
 151          Drivers ought to be able to handle interrupts coming in at those
 152          points; some don't and need to be caught.
 153
 154config LOCKUP_DETECTOR
 155        bool "Detect Hard and Soft Lockups"
 156        depends on DEBUG_KERNEL && !S390
 157        help
 158          Say Y here to enable the kernel to act as a watchdog to detect
 159          hard and soft lockups.
 160
 161          Softlockups are bugs that cause the kernel to loop in kernel
 162          mode for more than 60 seconds, without giving other tasks a
 163          chance to run.  The current stack trace is displayed upon
 164          detection and the system will stay locked up.
 165
 166          Hardlockups are bugs that cause the CPU to loop in kernel mode
 167          for more than 60 seconds, without letting other interrupts have a
 168          chance to run.  The current stack trace is displayed upon detection
 169          and the system will stay locked up.
 170
 171          The overhead should be minimal.  A periodic hrtimer runs to
 172          generate interrupts and kick the watchdog task every 10-12 seconds.
 173          An NMI is generated every 60 seconds or so to check for hardlockups.
 174
 175config HARDLOCKUP_DETECTOR
 176        def_bool LOCKUP_DETECTOR && PERF_EVENTS && HAVE_PERF_EVENTS_NMI
 177
 178config BOOTPARAM_SOFTLOCKUP_PANIC
 179        bool "Panic (Reboot) On Soft Lockups"
 180        depends on LOCKUP_DETECTOR
 181        help
 182          Say Y here to enable the kernel to panic on "soft lockups",
 183          which are bugs that cause the kernel to loop in kernel
 184          mode for more than 60 seconds, without giving other tasks a
 185          chance to run.
 186
 187          The panic can be used in combination with panic_timeout,
 188          to cause the system to reboot automatically after a
 189          lockup has been detected. This feature is useful for
 190          high-availability systems that have uptime guarantees and
 191          where a lockup must be resolved ASAP.
 192
 193          Say N if unsure.
 194
 195config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
 196        int
 197        depends on LOCKUP_DETECTOR
 198        range 0 1
 199        default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
 200        default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
 201
 202config DETECT_HUNG_TASK
 203        bool "Detect Hung Tasks"
 204        depends on DEBUG_KERNEL
 205        default DETECT_SOFTLOCKUP
 206        help
 207          Say Y here to enable the kernel to detect "hung tasks",
 208          which are bugs that cause the task to be stuck in
 209          uninterruptible "D" state indefinitiley.
 210
 211          When a hung task is detected, the kernel will print the
 212          current stack trace (which you should report), but the
 213          task will stay in uninterruptible state. If lockdep is
 214          enabled then all held locks will also be reported. This
 215          feature has negligible overhead.
 216
 217config BOOTPARAM_HUNG_TASK_PANIC
 218        bool "Panic (Reboot) On Hung Tasks"
 219        depends on DETECT_HUNG_TASK
 220        help
 221          Say Y here to enable the kernel to panic on "hung tasks",
 222          which are bugs that cause the kernel to leave a task stuck
 223          in uninterruptible "D" state.
 224
 225          The panic can be used in combination with panic_timeout,
 226          to cause the system to reboot automatically after a
 227          hung task has been detected. This feature is useful for
 228          high-availability systems that have uptime guarantees and
 229          where a hung tasks must be resolved ASAP.
 230
 231          Say N if unsure.
 232
 233config BOOTPARAM_HUNG_TASK_PANIC_VALUE
 234        int
 235        depends on DETECT_HUNG_TASK
 236        range 0 1
 237        default 0 if !BOOTPARAM_HUNG_TASK_PANIC
 238        default 1 if BOOTPARAM_HUNG_TASK_PANIC
 239
 240config SCHED_DEBUG
 241        bool "Collect scheduler debugging info"
 242        depends on DEBUG_KERNEL && PROC_FS
 243        default y
 244        help
 245          If you say Y here, the /proc/sched_debug file will be provided
 246          that can help debug the scheduler. The runtime overhead of this
 247          option is minimal.
 248
 249config SCHEDSTATS
 250        bool "Collect scheduler statistics"
 251        depends on DEBUG_KERNEL && PROC_FS
 252        help
 253          If you say Y here, additional code will be inserted into the
 254          scheduler and related routines to collect statistics about
 255          scheduler behavior and provide them in /proc/schedstat.  These
 256          stats may be useful for both tuning and debugging the scheduler
 257          If you aren't debugging the scheduler or trying to tune a specific
 258          application, you can say N to avoid the very slight overhead
 259          this adds.
 260
 261config TIMER_STATS
 262        bool "Collect kernel timers statistics"
 263        depends on DEBUG_KERNEL && PROC_FS
 264        help
 265          If you say Y here, additional code will be inserted into the
 266          timer routines to collect statistics about kernel timers being
 267          reprogrammed. The statistics can be read from /proc/timer_stats.
 268          The statistics collection is started by writing 1 to /proc/timer_stats,
 269          writing 0 stops it. This feature is useful to collect information
 270          about timer usage patterns in kernel and userspace. This feature
 271          is lightweight if enabled in the kernel config but not activated
 272          (it defaults to deactivated on bootup and will only be activated
 273          if some application like powertop activates it explicitly).
 274
 275config DEBUG_OBJECTS
 276        bool "Debug object operations"
 277        depends on DEBUG_KERNEL
 278        help
 279          If you say Y here, additional code will be inserted into the
 280          kernel to track the life time of various objects and validate
 281          the operations on those objects.
 282
 283config DEBUG_OBJECTS_SELFTEST
 284        bool "Debug objects selftest"
 285        depends on DEBUG_OBJECTS
 286        help
 287          This enables the selftest of the object debug code.
 288
 289config DEBUG_OBJECTS_FREE
 290        bool "Debug objects in freed memory"
 291        depends on DEBUG_OBJECTS
 292        help
 293          This enables checks whether a k/v free operation frees an area
 294          which contains an object which has not been deactivated
 295          properly. This can make kmalloc/kfree-intensive workloads
 296          much slower.
 297
 298config DEBUG_OBJECTS_TIMERS
 299        bool "Debug timer objects"
 300        depends on DEBUG_OBJECTS
 301        help
 302          If you say Y here, additional code will be inserted into the
 303          timer routines to track the life time of timer objects and
 304          validate the timer operations.
 305
 306config DEBUG_OBJECTS_WORK
 307        bool "Debug work objects"
 308        depends on DEBUG_OBJECTS
 309        help
 310          If you say Y here, additional code will be inserted into the
 311          work queue routines to track the life time of work objects and
 312          validate the work operations.
 313
 314config DEBUG_OBJECTS_RCU_HEAD
 315        bool "Debug RCU callbacks objects"
 316        depends on DEBUG_OBJECTS && PREEMPT
 317        help
 318          Enable this to turn on debugging of RCU list heads (call_rcu() usage).
 319
 320config DEBUG_OBJECTS_PERCPU_COUNTER
 321        bool "Debug percpu counter objects"
 322        depends on DEBUG_OBJECTS
 323        help
 324          If you say Y here, additional code will be inserted into the
 325          percpu counter routines to track the life time of percpu counter
 326          objects and validate the percpu counter operations.
 327
 328config DEBUG_OBJECTS_ENABLE_DEFAULT
 329        int "debug_objects bootup default value (0-1)"
 330        range 0 1
 331        default "1"
 332        depends on DEBUG_OBJECTS
 333        help
 334          Debug objects boot parameter default value
 335
 336config DEBUG_SLAB
 337        bool "Debug slab memory allocations"
 338        depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
 339        help
 340          Say Y here to have the kernel do limited verification on memory
 341          allocation as well as poisoning memory on free to catch use of freed
 342          memory. This can make kmalloc/kfree-intensive workloads much slower.
 343
 344config DEBUG_SLAB_LEAK
 345        bool "Memory leak debugging"
 346        depends on DEBUG_SLAB
 347
 348config SLUB_DEBUG_ON
 349        bool "SLUB debugging on by default"
 350        depends on SLUB && SLUB_DEBUG && !KMEMCHECK
 351        default n
 352        help
 353          Boot with debugging on by default. SLUB boots by default with
 354          the runtime debug capabilities switched off. Enabling this is
 355          equivalent to specifying the "slub_debug" parameter on boot.
 356          There is no support for more fine grained debug control like
 357          possible with slub_debug=xxx. SLUB debugging may be switched
 358          off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
 359          "slub_debug=-".
 360
 361config SLUB_STATS
 362        default n
 363        bool "Enable SLUB performance statistics"
 364        depends on SLUB && SYSFS
 365        help
 366          SLUB statistics are useful to debug SLUBs allocation behavior in
 367          order find ways to optimize the allocator. This should never be
 368          enabled for production use since keeping statistics slows down
 369          the allocator by a few percentage points. The slabinfo command
 370          supports the determination of the most active slabs to figure
 371          out which slabs are relevant to a particular load.
 372          Try running: slabinfo -DA
 373
 374config DEBUG_KMEMLEAK
 375        bool "Kernel memory leak detector"
 376        depends on DEBUG_KERNEL && EXPERIMENTAL && !MEMORY_HOTPLUG && \
 377                (X86 || ARM || PPC || S390 || SPARC64 || SUPERH || MICROBLAZE || TILE)
 378
 379        select DEBUG_FS if SYSFS
 380        select STACKTRACE if STACKTRACE_SUPPORT
 381        select KALLSYMS
 382        select CRC32
 383        help
 384          Say Y here if you want to enable the memory leak
 385          detector. The memory allocation/freeing is traced in a way
 386          similar to the Boehm's conservative garbage collector, the
 387          difference being that the orphan objects are not freed but
 388          only shown in /sys/kernel/debug/kmemleak. Enabling this
 389          feature will introduce an overhead to memory
 390          allocations. See Documentation/kmemleak.txt for more
 391          details.
 392
 393          Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
 394          of finding leaks due to the slab objects poisoning.
 395
 396          In order to access the kmemleak file, debugfs needs to be
 397          mounted (usually at /sys/kernel/debug).
 398
 399config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
 400        int "Maximum kmemleak early log entries"
 401        depends on DEBUG_KMEMLEAK
 402        range 200 40000
 403        default 400
 404        help
 405          Kmemleak must track all the memory allocations to avoid
 406          reporting false positives. Since memory may be allocated or
 407          freed before kmemleak is initialised, an early log buffer is
 408          used to store these actions. If kmemleak reports "early log
 409          buffer exceeded", please increase this value.
 410
 411config DEBUG_KMEMLEAK_TEST
 412        tristate "Simple test for the kernel memory leak detector"
 413        depends on DEBUG_KMEMLEAK
 414        help
 415          Say Y or M here to build a test for the kernel memory leak
 416          detector. This option enables a module that explicitly leaks
 417          memory.
 418
 419          If unsure, say N.
 420
 421config DEBUG_KMEMLEAK_DEFAULT_OFF
 422        bool "Default kmemleak to off"
 423        depends on DEBUG_KMEMLEAK
 424        help
 425          Say Y here to disable kmemleak by default. It can then be enabled
 426          on the command line via kmemleak=on.
 427
 428config DEBUG_PREEMPT
 429        bool "Debug preemptible kernel"
 430        depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
 431        default y
 432        help
 433          If you say Y here then the kernel will use a debug variant of the
 434          commonly used smp_processor_id() function and will print warnings
 435          if kernel code uses it in a preemption-unsafe way. Also, the kernel
 436          will detect preemption count underflows.
 437
 438config DEBUG_RT_MUTEXES
 439        bool "RT Mutex debugging, deadlock detection"
 440        depends on DEBUG_KERNEL && RT_MUTEXES
 441        help
 442         This allows rt mutex semantics violations and rt mutex related
 443         deadlocks (lockups) to be detected and reported automatically.
 444
 445config DEBUG_PI_LIST
 446        bool
 447        default y
 448        depends on DEBUG_RT_MUTEXES
 449
 450config RT_MUTEX_TESTER
 451        bool "Built-in scriptable tester for rt-mutexes"
 452        depends on DEBUG_KERNEL && RT_MUTEXES
 453        help
 454          This option enables a rt-mutex tester.
 455
 456config DEBUG_SPINLOCK
 457        bool "Spinlock and rw-lock debugging: basic checks"
 458        depends on DEBUG_KERNEL
 459        help
 460          Say Y here and build SMP to catch missing spinlock initialization
 461          and certain other kinds of spinlock errors commonly made.  This is
 462          best used in conjunction with the NMI watchdog so that spinlock
 463          deadlocks are also debuggable.
 464
 465config DEBUG_MUTEXES
 466        bool "Mutex debugging: basic checks"
 467        depends on DEBUG_KERNEL
 468        help
 469         This feature allows mutex semantics violations to be detected and
 470         reported.
 471
 472config BKL
 473        bool "Big Kernel Lock" if (SMP || PREEMPT)
 474        default y
 475        help
 476          This is the traditional lock that is used in old code instead
 477          of proper locking. All drivers that use the BKL should depend
 478          on this symbol.
 479          Say Y here unless you are working on removing the BKL.
 480
 481config DEBUG_LOCK_ALLOC
 482        bool "Lock debugging: detect incorrect freeing of live locks"
 483        depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 484        select DEBUG_SPINLOCK
 485        select DEBUG_MUTEXES
 486        select LOCKDEP
 487        help
 488         This feature will check whether any held lock (spinlock, rwlock,
 489         mutex or rwsem) is incorrectly freed by the kernel, via any of the
 490         memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
 491         vfree(), etc.), whether a live lock is incorrectly reinitialized via
 492         spin_lock_init()/mutex_init()/etc., or whether there is any lock
 493         held during task exit.
 494
 495config PROVE_LOCKING
 496        bool "Lock debugging: prove locking correctness"
 497        depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 498        select LOCKDEP
 499        select DEBUG_SPINLOCK
 500        select DEBUG_MUTEXES
 501        select DEBUG_LOCK_ALLOC
 502        select TRACE_IRQFLAGS
 503        default n
 504        help
 505         This feature enables the kernel to prove that all locking
 506         that occurs in the kernel runtime is mathematically
 507         correct: that under no circumstance could an arbitrary (and
 508         not yet triggered) combination of observed locking
 509         sequences (on an arbitrary number of CPUs, running an
 510         arbitrary number of tasks and interrupt contexts) cause a
 511         deadlock.
 512
 513         In short, this feature enables the kernel to report locking
 514         related deadlocks before they actually occur.
 515
 516         The proof does not depend on how hard and complex a
 517         deadlock scenario would be to trigger: how many
 518         participant CPUs, tasks and irq-contexts would be needed
 519         for it to trigger. The proof also does not depend on
 520         timing: if a race and a resulting deadlock is possible
 521         theoretically (no matter how unlikely the race scenario
 522         is), it will be proven so and will immediately be
 523         reported by the kernel (once the event is observed that
 524         makes the deadlock theoretically possible).
 525
 526         If a deadlock is impossible (i.e. the locking rules, as
 527         observed by the kernel, are mathematically correct), the
 528         kernel reports nothing.
 529
 530         NOTE: this feature can also be enabled for rwlocks, mutexes
 531         and rwsems - in which case all dependencies between these
 532         different locking variants are observed and mapped too, and
 533         the proof of observed correctness is also maintained for an
 534         arbitrary combination of these separate locking variants.
 535
 536         For more details, see Documentation/lockdep-design.txt.
 537
 538config PROVE_RCU
 539        bool "RCU debugging: prove RCU correctness"
 540        depends on PROVE_LOCKING
 541        default n
 542        help
 543         This feature enables lockdep extensions that check for correct
 544         use of RCU APIs.  This is currently under development.  Say Y
 545         if you want to debug RCU usage or help work on the PROVE_RCU
 546         feature.
 547
 548         Say N if you are unsure.
 549
 550config PROVE_RCU_REPEATEDLY
 551        bool "RCU debugging: don't disable PROVE_RCU on first splat"
 552        depends on PROVE_RCU
 553        default n
 554        help
 555         By itself, PROVE_RCU will disable checking upon issuing the
 556         first warning (or "splat").  This feature prevents such
 557         disabling, allowing multiple RCU-lockdep warnings to be printed
 558         on a single reboot.
 559
 560         Say Y to allow multiple RCU-lockdep warnings per boot.
 561
 562         Say N if you are unsure.
 563
 564config SPARSE_RCU_POINTER
 565        bool "RCU debugging: sparse-based checks for pointer usage"
 566        default n
 567        help
 568         This feature enables the __rcu sparse annotation for
 569         RCU-protected pointers.  This annotation will cause sparse
 570         to flag any non-RCU used of annotated pointers.  This can be
 571         helpful when debugging RCU usage.  Please note that this feature
 572         is not intended to enforce code cleanliness; it is instead merely
 573         a debugging aid.
 574
 575         Say Y to make sparse flag questionable use of RCU-protected pointers
 576
 577         Say N if you are unsure.
 578
 579config LOCKDEP
 580        bool
 581        depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 582        select STACKTRACE
 583        select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE
 584        select KALLSYMS
 585        select KALLSYMS_ALL
 586
 587config LOCK_STAT
 588        bool "Lock usage statistics"
 589        depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 590        select LOCKDEP
 591        select DEBUG_SPINLOCK
 592        select DEBUG_MUTEXES
 593        select DEBUG_LOCK_ALLOC
 594        default n
 595        help
 596         This feature enables tracking lock contention points
 597
 598         For more details, see Documentation/lockstat.txt
 599
 600         This also enables lock events required by "perf lock",
 601         subcommand of perf.
 602         If you want to use "perf lock", you also need to turn on
 603         CONFIG_EVENT_TRACING.
 604
 605         CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
 606         (CONFIG_LOCKDEP defines "acquire" and "release" events.)
 607
 608config DEBUG_LOCKDEP
 609        bool "Lock dependency engine debugging"
 610        depends on DEBUG_KERNEL && LOCKDEP
 611        help
 612          If you say Y here, the lock dependency engine will do
 613          additional runtime checks to debug itself, at the price
 614          of more runtime overhead.
 615
 616config TRACE_IRQFLAGS
 617        bool
 618        help
 619          Enables hooks to interrupt enabling and disabling for
 620          either tracing or lock debugging.
 621
 622config DEBUG_SPINLOCK_SLEEP
 623        bool "Spinlock debugging: sleep-inside-spinlock checking"
 624        depends on DEBUG_KERNEL
 625        help
 626          If you say Y here, various routines which may sleep will become very
 627          noisy if they are called with a spinlock held.
 628
 629config DEBUG_LOCKING_API_SELFTESTS
 630        bool "Locking API boot-time self-tests"
 631        depends on DEBUG_KERNEL
 632        help
 633          Say Y here if you want the kernel to run a short self-test during
 634          bootup. The self-test checks whether common types of locking bugs
 635          are detected by debugging mechanisms or not. (if you disable
 636          lock debugging then those bugs wont be detected of course.)
 637          The following locking APIs are covered: spinlocks, rwlocks,
 638          mutexes and rwsems.
 639
 640config STACKTRACE
 641        bool
 642        depends on STACKTRACE_SUPPORT
 643
 644config DEBUG_KOBJECT
 645        bool "kobject debugging"
 646        depends on DEBUG_KERNEL
 647        help
 648          If you say Y here, some extra kobject debugging messages will be sent
 649          to the syslog. 
 650
 651config DEBUG_HIGHMEM
 652        bool "Highmem debugging"
 653        depends on DEBUG_KERNEL && HIGHMEM
 654        help
 655          This options enables addition error checking for high memory systems.
 656          Disable for production systems.
 657
 658config DEBUG_BUGVERBOSE
 659        bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED
 660        depends on BUG
 661        depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \
 662                   FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300
 663        default y
 664        help
 665          Say Y here to make BUG() panics output the file name and line number
 666          of the BUG call as well as the EIP and oops trace.  This aids
 667          debugging but costs about 70-100K of memory.
 668
 669config DEBUG_INFO
 670        bool "Compile the kernel with debug info"
 671        depends on DEBUG_KERNEL
 672        help
 673          If you say Y here the resulting kernel image will include
 674          debugging info resulting in a larger kernel image.
 675          This adds debug symbols to the kernel and modules (gcc -g), and
 676          is needed if you intend to use kernel crashdump or binary object
 677          tools like crash, kgdb, LKCD, gdb, etc on the kernel.
 678          Say Y here only if you plan to debug the kernel.
 679
 680          If unsure, say N.
 681
 682config DEBUG_INFO_REDUCED
 683        bool "Reduce debugging information"
 684        depends on DEBUG_INFO
 685        help
 686          If you say Y here gcc is instructed to generate less debugging
 687          information for structure types. This means that tools that
 688          need full debugging information (like kgdb or systemtap) won't
 689          be happy. But if you merely need debugging information to
 690          resolve line numbers there is no loss. Advantage is that
 691          build directory object sizes shrink dramatically over a full
 692          DEBUG_INFO build and compile times are reduced too.
 693          Only works with newer gcc versions.
 694
 695config DEBUG_VM
 696        bool "Debug VM"
 697        depends on DEBUG_KERNEL
 698        help
 699          Enable this to turn on extended checks in the virtual-memory system
 700          that may impact performance.
 701
 702          If unsure, say N.
 703
 704config DEBUG_VIRTUAL
 705        bool "Debug VM translations"
 706        depends on DEBUG_KERNEL && X86
 707        help
 708          Enable some costly sanity checks in virtual to page code. This can
 709          catch mistakes with virt_to_page() and friends.
 710
 711          If unsure, say N.
 712
 713config DEBUG_NOMMU_REGIONS
 714        bool "Debug the global anon/private NOMMU mapping region tree"
 715        depends on DEBUG_KERNEL && !MMU
 716        help
 717          This option causes the global tree of anonymous and private mapping
 718          regions to be regularly checked for invalid topology.
 719
 720config DEBUG_WRITECOUNT
 721        bool "Debug filesystem writers count"
 722        depends on DEBUG_KERNEL
 723        help
 724          Enable this to catch wrong use of the writers count in struct
 725          vfsmount.  This will increase the size of each file struct by
 726          32 bits.
 727
 728          If unsure, say N.
 729
 730config DEBUG_MEMORY_INIT
 731        bool "Debug memory initialisation" if EMBEDDED
 732        default !EMBEDDED
 733        help
 734          Enable this for additional checks during memory initialisation.
 735          The sanity checks verify aspects of the VM such as the memory model
 736          and other information provided by the architecture. Verbose
 737          information will be printed at KERN_DEBUG loglevel depending
 738          on the mminit_loglevel= command-line option.
 739
 740          If unsure, say Y
 741
 742config DEBUG_LIST
 743        bool "Debug linked list manipulation"
 744        depends on DEBUG_KERNEL
 745        help
 746          Enable this to turn on extended checks in the linked-list
 747          walking routines.
 748
 749          If unsure, say N.
 750
 751config TEST_LIST_SORT
 752        bool "Linked list sorting test"
 753        depends on DEBUG_KERNEL
 754        help
 755          Enable this to turn on 'list_sort()' function test. This test is
 756          executed only once during system boot, so affects only boot time.
 757
 758          If unsure, say N.
 759
 760config DEBUG_SG
 761        bool "Debug SG table operations"
 762        depends on DEBUG_KERNEL
 763        help
 764          Enable this to turn on checks on scatter-gather tables. This can
 765          help find problems with drivers that do not properly initialize
 766          their sg tables.
 767
 768          If unsure, say N.
 769
 770config DEBUG_NOTIFIERS
 771        bool "Debug notifier call chains"
 772        depends on DEBUG_KERNEL
 773        help
 774          Enable this to turn on sanity checking for notifier call chains.
 775          This is most useful for kernel developers to make sure that
 776          modules properly unregister themselves from notifier chains.
 777          This is a relatively cheap check but if you care about maximum
 778          performance, say N.
 779
 780config DEBUG_CREDENTIALS
 781        bool "Debug credential management"
 782        depends on DEBUG_KERNEL
 783        help
 784          Enable this to turn on some debug checking for credential
 785          management.  The additional code keeps track of the number of
 786          pointers from task_structs to any given cred struct, and checks to
 787          see that this number never exceeds the usage count of the cred
 788          struct.
 789
 790          Furthermore, if SELinux is enabled, this also checks that the
 791          security pointer in the cred struct is never seen to be invalid.
 792
 793          If unsure, say N.
 794
 795#
 796# Select this config option from the architecture Kconfig, if it
 797# it is preferred to always offer frame pointers as a config
 798# option on the architecture (regardless of KERNEL_DEBUG):
 799#
 800config ARCH_WANT_FRAME_POINTERS
 801        bool
 802        help
 803
 804config FRAME_POINTER
 805        bool "Compile the kernel with frame pointers"
 806        depends on DEBUG_KERNEL && \
 807                (CRIS || M68K || M68KNOMMU || FRV || UML || \
 808                 AVR32 || SUPERH || BLACKFIN || MN10300) || \
 809                ARCH_WANT_FRAME_POINTERS
 810        default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
 811        help
 812          If you say Y here the resulting kernel image will be slightly
 813          larger and slower, but it gives very useful debugging information
 814          in case of kernel bugs. (precise oopses/stacktraces/warnings)
 815
 816config BOOT_PRINTK_DELAY
 817        bool "Delay each boot printk message by N milliseconds"
 818        depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
 819        help
 820          This build option allows you to read kernel boot messages
 821          by inserting a short delay after each one.  The delay is
 822          specified in milliseconds on the kernel command line,
 823          using "boot_delay=N".
 824
 825          It is likely that you would also need to use "lpj=M" to preset
 826          the "loops per jiffie" value.
 827          See a previous boot log for the "lpj" value to use for your
 828          system, and then set "lpj=M" before setting "boot_delay=N".
 829          NOTE:  Using this option may adversely affect SMP systems.
 830          I.e., processors other than the first one may not boot up.
 831          BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect
 832          what it believes to be lockup conditions.
 833
 834config RCU_TORTURE_TEST
 835        tristate "torture tests for RCU"
 836        depends on DEBUG_KERNEL
 837        default n
 838        help
 839          This option provides a kernel module that runs torture tests
 840          on the RCU infrastructure.  The kernel module may be built
 841          after the fact on the running kernel to be tested, if desired.
 842
 843          Say Y here if you want RCU torture tests to be built into
 844          the kernel.
 845          Say M if you want the RCU torture tests to build as a module.
 846          Say N if you are unsure.
 847
 848config RCU_TORTURE_TEST_RUNNABLE
 849        bool "torture tests for RCU runnable by default"
 850        depends on RCU_TORTURE_TEST = y
 851        default n
 852        help
 853          This option provides a way to build the RCU torture tests
 854          directly into the kernel without them starting up at boot
 855          time.  You can use /proc/sys/kernel/rcutorture_runnable
 856          to manually override this setting.  This /proc file is
 857          available only when the RCU torture tests have been built
 858          into the kernel.
 859
 860          Say Y here if you want the RCU torture tests to start during
 861          boot (you probably don't).
 862          Say N here if you want the RCU torture tests to start only
 863          after being manually enabled via /proc.
 864
 865config RCU_CPU_STALL_DETECTOR
 866        bool "Check for stalled CPUs delaying RCU grace periods"
 867        depends on TREE_RCU || TREE_PREEMPT_RCU
 868        default y
 869        help
 870          This option causes RCU to printk information on which
 871          CPUs are delaying the current grace period, but only when
 872          the grace period extends for excessive time periods.
 873
 874          Say N if you want to disable such checks.
 875
 876          Say Y if you are unsure.
 877
 878config RCU_CPU_STALL_TIMEOUT
 879        int "RCU CPU stall timeout in seconds"
 880        depends on RCU_CPU_STALL_DETECTOR
 881        range 3 300
 882        default 60
 883        help
 884          If a given RCU grace period extends more than the specified
 885          number of seconds, a CPU stall warning is printed.  If the
 886          RCU grace period persists, additional CPU stall warnings are
 887          printed at more widely spaced intervals.
 888
 889config RCU_CPU_STALL_DETECTOR_RUNNABLE
 890        bool "RCU CPU stall checking starts automatically at boot"
 891        depends on RCU_CPU_STALL_DETECTOR
 892        default y
 893        help
 894          If set, start checking for RCU CPU stalls immediately on
 895          boot.  Otherwise, RCU CPU stall checking must be manually
 896          enabled.
 897
 898          Say Y if you are unsure.
 899
 900          Say N if you wish to suppress RCU CPU stall checking during boot.
 901
 902config RCU_CPU_STALL_VERBOSE
 903        bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
 904        depends on RCU_CPU_STALL_DETECTOR && TREE_PREEMPT_RCU
 905        default y
 906        help
 907          This option causes RCU to printk detailed per-task information
 908          for any tasks that are stalling the current RCU grace period.
 909
 910          Say N if you are unsure.
 911
 912          Say Y if you want to enable such checks.
 913
 914config KPROBES_SANITY_TEST
 915        bool "Kprobes sanity tests"
 916        depends on DEBUG_KERNEL
 917        depends on KPROBES
 918        default n
 919        help
 920          This option provides for testing basic kprobes functionality on
 921          boot. A sample kprobe, jprobe and kretprobe are inserted and
 922          verified for functionality.
 923
 924          Say N if you are unsure.
 925
 926config BACKTRACE_SELF_TEST
 927        tristate "Self test for the backtrace code"
 928        depends on DEBUG_KERNEL
 929        default n
 930        help
 931          This option provides a kernel module that can be used to test
 932          the kernel stack backtrace code. This option is not useful
 933          for distributions or general kernels, but only for kernel
 934          developers working on architecture code.
 935
 936          Note that if you want to also test saved backtraces, you will
 937          have to enable STACKTRACE as well.
 938
 939          Say N if you are unsure.
 940
 941config DEBUG_BLOCK_EXT_DEVT
 942        bool "Force extended block device numbers and spread them"
 943        depends on DEBUG_KERNEL
 944        depends on BLOCK
 945        default n
 946        help
 947          BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
 948          SOME DISTRIBUTIONS.  DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
 949          YOU ARE DOING.  Distros, please enable this and fix whatever
 950          is broken.
 951
 952          Conventionally, block device numbers are allocated from
 953          predetermined contiguous area.  However, extended block area
 954          may introduce non-contiguous block device numbers.  This
 955          option forces most block device numbers to be allocated from
 956          the extended space and spreads them to discover kernel or
 957          userland code paths which assume predetermined contiguous
 958          device number allocation.
 959
 960          Note that turning on this debug option shuffles all the
 961          device numbers for all IDE and SCSI devices including libata
 962          ones, so root partition specified using device number
 963          directly (via rdev or root=MAJ:MIN) won't work anymore.
 964          Textual device names (root=/dev/sdXn) will continue to work.
 965
 966          Say N if you are unsure.
 967
 968config DEBUG_FORCE_WEAK_PER_CPU
 969        bool "Force weak per-cpu definitions"
 970        depends on DEBUG_KERNEL
 971        help
 972          s390 and alpha require percpu variables in modules to be
 973          defined weak to work around addressing range issue which
 974          puts the following two restrictions on percpu variable
 975          definitions.
 976
 977          1. percpu symbols must be unique whether static or not
 978          2. percpu variables can't be defined inside a function
 979
 980          To ensure that generic code follows the above rules, this
 981          option forces all percpu variables to be defined as weak.
 982
 983config LKDTM
 984        tristate "Linux Kernel Dump Test Tool Module"
 985        depends on DEBUG_FS
 986        depends on BLOCK
 987        default n
 988        help
 989        This module enables testing of the different dumping mechanisms by
 990        inducing system failures at predefined crash points.
 991        If you don't need it: say N
 992        Choose M here to compile this code as a module. The module will be
 993        called lkdtm.
 994
 995        Documentation on how to use the module can be found in
 996        Documentation/fault-injection/provoke-crashes.txt
 997
 998config CPU_NOTIFIER_ERROR_INJECT
 999        tristate "CPU notifier error injection module"
1000        depends on HOTPLUG_CPU && DEBUG_KERNEL
1001        help
1002          This option provides a kernel module that can be used to test
1003          the error handling of the cpu notifiers
1004
1005          To compile this code as a module, choose M here: the module will
1006          be called cpu-notifier-error-inject.
1007
1008          If unsure, say N.
1009
1010config FAULT_INJECTION
1011        bool "Fault-injection framework"
1012        depends on DEBUG_KERNEL
1013        help
1014          Provide fault-injection framework.
1015          For more details, see Documentation/fault-injection/.
1016
1017config FAILSLAB
1018        bool "Fault-injection capability for kmalloc"
1019        depends on FAULT_INJECTION
1020        depends on SLAB || SLUB
1021        help
1022          Provide fault-injection capability for kmalloc.
1023
1024config FAIL_PAGE_ALLOC
1025        bool "Fault-injection capabilitiy for alloc_pages()"
1026        depends on FAULT_INJECTION
1027        help
1028          Provide fault-injection capability for alloc_pages().
1029
1030config FAIL_MAKE_REQUEST
1031        bool "Fault-injection capability for disk IO"
1032        depends on FAULT_INJECTION && BLOCK
1033        help
1034          Provide fault-injection capability for disk IO.
1035
1036config FAIL_IO_TIMEOUT
1037        bool "Fault-injection capability for faking disk interrupts"
1038        depends on FAULT_INJECTION && BLOCK
1039        help
1040          Provide fault-injection capability on end IO handling. This
1041          will make the block layer "forget" an interrupt as configured,
1042          thus exercising the error handling.
1043
1044          Only works with drivers that use the generic timeout handling,
1045          for others it wont do anything.
1046
1047config FAULT_INJECTION_DEBUG_FS
1048        bool "Debugfs entries for fault-injection capabilities"
1049        depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1050        help
1051          Enable configuration of fault-injection capabilities via debugfs.
1052
1053config FAULT_INJECTION_STACKTRACE_FILTER
1054        bool "stacktrace filter for fault-injection capabilities"
1055        depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1056        depends on !X86_64
1057        select STACKTRACE
1058        select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE
1059        help
1060          Provide stacktrace filter for fault-injection capabilities
1061
1062config LATENCYTOP
1063        bool "Latency measuring infrastructure"
1064        depends on HAVE_LATENCYTOP_SUPPORT
1065        depends on DEBUG_KERNEL
1066        depends on STACKTRACE_SUPPORT
1067        depends on PROC_FS
1068        select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE
1069        select KALLSYMS
1070        select KALLSYMS_ALL
1071        select STACKTRACE
1072        select SCHEDSTATS
1073        select SCHED_DEBUG
1074        help
1075          Enable this option if you want to use the LatencyTOP tool
1076          to find out which userspace is blocking on what kernel operations.
1077
1078config SYSCTL_SYSCALL_CHECK
1079        bool "Sysctl checks"
1080        depends on SYSCTL
1081        ---help---
1082          sys_sysctl uses binary paths that have been found challenging
1083          to properly maintain and use. This enables checks that help
1084          you to keep things correct.
1085
1086source mm/Kconfig.debug
1087source kernel/trace/Kconfig
1088
1089config PROVIDE_OHCI1394_DMA_INIT
1090        bool "Remote debugging over FireWire early on boot"
1091        depends on PCI && X86
1092        help
1093          If you want to debug problems which hang or crash the kernel early
1094          on boot and the crashing machine has a FireWire port, you can use
1095          this feature to remotely access the memory of the crashed machine
1096          over FireWire. This employs remote DMA as part of the OHCI1394
1097          specification which is now the standard for FireWire controllers.
1098
1099          With remote DMA, you can monitor the printk buffer remotely using
1100          firescope and access all memory below 4GB using fireproxy from gdb.
1101          Even controlling a kernel debugger is possible using remote DMA.
1102
1103          Usage:
1104
1105          If ohci1394_dma=early is used as boot parameter, it will initialize
1106          all OHCI1394 controllers which are found in the PCI config space.
1107
1108          As all changes to the FireWire bus such as enabling and disabling
1109          devices cause a bus reset and thereby disable remote DMA for all
1110          devices, be sure to have the cable plugged and FireWire enabled on
1111          the debugging host before booting the debug target for debugging.
1112
1113          This code (~1k) is freed after boot. By then, the firewire stack
1114          in charge of the OHCI-1394 controllers should be used instead.
1115
1116          See Documentation/debugging-via-ohci1394.txt for more information.
1117
1118config FIREWIRE_OHCI_REMOTE_DMA
1119        bool "Remote debugging over FireWire with firewire-ohci"
1120        depends on FIREWIRE_OHCI
1121        help
1122          This option lets you use the FireWire bus for remote debugging
1123          with help of the firewire-ohci driver. It enables unfiltered
1124          remote DMA in firewire-ohci.
1125          See Documentation/debugging-via-ohci1394.txt for more information.
1126
1127          If unsure, say N.
1128
1129config BUILD_DOCSRC
1130        bool "Build targets in Documentation/ tree"
1131        depends on HEADERS_CHECK
1132        help
1133          This option attempts to build objects from the source files in the
1134          kernel Documentation/ tree.
1135
1136          Say N if you are unsure.
1137
1138config DYNAMIC_DEBUG
1139        bool "Enable dynamic printk() support"
1140        default n
1141        depends on PRINTK
1142        depends on DEBUG_FS
1143        help
1144
1145          Compiles debug level messages into the kernel, which would not
1146          otherwise be available at runtime. These messages can then be
1147          enabled/disabled based on various levels of scope - per source file,
1148          function, module, format string, and line number. This mechanism
1149          implicitly enables all pr_debug() and dev_dbg() calls. The impact of
1150          this compile option is a larger kernel text size of about 2%.
1151
1152          Usage:
1153
1154          Dynamic debugging is controlled via the 'dynamic_debug/control' file,
1155          which is contained in the 'debugfs' filesystem. Thus, the debugfs
1156          filesystem must first be mounted before making use of this feature.
1157          We refer the control file as: <debugfs>/dynamic_debug/control. This
1158          file contains a list of the debug statements that can be enabled. The
1159          format for each line of the file is:
1160
1161                filename:lineno [module]function flags format
1162
1163          filename : source file of the debug statement
1164          lineno : line number of the debug statement
1165          module : module that contains the debug statement
1166          function : function that contains the debug statement
1167          flags : 'p' means the line is turned 'on' for printing
1168          format : the format used for the debug statement
1169
1170          From a live system:
1171
1172                nullarbor:~ # cat <debugfs>/dynamic_debug/control
1173                # filename:lineno [module]function flags format
1174                fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012"
1175                fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012"
1176                fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012"
1177
1178          Example usage:
1179
1180                // enable the message at line 1603 of file svcsock.c
1181                nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
1182                                                <debugfs>/dynamic_debug/control
1183
1184                // enable all the messages in file svcsock.c
1185                nullarbor:~ # echo -n 'file svcsock.c +p' >
1186                                                <debugfs>/dynamic_debug/control
1187
1188                // enable all the messages in the NFS server module
1189                nullarbor:~ # echo -n 'module nfsd +p' >
1190                                                <debugfs>/dynamic_debug/control
1191
1192                // enable all 12 messages in the function svc_process()
1193                nullarbor:~ # echo -n 'func svc_process +p' >
1194                                                <debugfs>/dynamic_debug/control
1195
1196                // disable all 12 messages in the function svc_process()
1197                nullarbor:~ # echo -n 'func svc_process -p' >
1198                                                <debugfs>/dynamic_debug/control
1199
1200          See Documentation/dynamic-debug-howto.txt for additional information.
1201
1202config DMA_API_DEBUG
1203        bool "Enable debugging of DMA-API usage"
1204        depends on HAVE_DMA_API_DEBUG
1205        help
1206          Enable this option to debug the use of the DMA API by device drivers.
1207          With this option you will be able to detect common bugs in device
1208          drivers like double-freeing of DMA mappings or freeing mappings that
1209          were never allocated.
1210          This option causes a performance degredation.  Use only if you want
1211          to debug device drivers. If unsure, say N.
1212
1213config ATOMIC64_SELFTEST
1214        bool "Perform an atomic64_t self-test at boot"
1215        help
1216          Enable this option to test the atomic64_t functions at boot.
1217
1218          If unsure, say N.
1219
1220config ASYNC_RAID6_TEST
1221        tristate "Self test for hardware accelerated raid6 recovery"
1222        depends on ASYNC_RAID6_RECOV
1223        select ASYNC_MEMCPY
1224        ---help---
1225          This is a one-shot self test that permutes through the
1226          recovery of all the possible two disk failure scenarios for a
1227          N-disk array.  Recovery is performed with the asynchronous
1228          raid6 recovery routines, and will optionally use an offload
1229          engine if one is available.
1230
1231          If unsure, say N.
1232
1233source "samples/Kconfig"
1234
1235source "lib/Kconfig.kgdb"
1236
1237source "lib/Kconfig.kmemcheck"
1238