lib/Kconfig.debug

   1
   2 config PRINTK_TIME
   3         bool "Show timing information on printks"
   4         depends on PRINTK
   5         help
   6           Selecting this option causes time stamps of the printk()
   7           messages to be added to the output of the syslog() system
   8           call and at the console.
   9
  10           The timestamp is always recorded internally, and exported
  11           to /dev/kmsg. This flag just specifies if the timestamp should
  12           be included, not that the timestamp is recorded.
  13
  14           The behavior is also controlled by the kernel command line
  15           parameter printk.time=1. See Documentation/kernel-parameters.txt
  16
  17 config DEFAULT_MESSAGE_LOGLEVEL
  18         int "Default message log level (1-7)"
  19         range 1 7
  20         default "4"
  21         help
  22           Default log level for printk statements with no specified priority.
  23
  24           This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
  25           that are auditing their logs closely may want to set it to a lower
  26           priority.
  27
  28 config ENABLE_WARN_DEPRECATED
  29         bool "Enable __deprecated logic"
  30         default y
  31         help
  32           Enable the __deprecated logic in the kernel build.
  33           Disable this to suppress the "warning: 'foo' is deprecated
  34           (declared at kernel/power/somefile.c:1234)" messages.
  35
  36 config ENABLE_MUST_CHECK
  37         bool "Enable __must_check logic"
  38         default y
  39         help
  40           Enable the __must_check logic in the kernel build.  Disable this to
  41           suppress the "warning: ignoring return value of 'foo', declared with
  42           attribute warn_unused_result" messages.
  43
  44 config FRAME_WARN
  45         int "Warn for stack frames larger than (needs gcc 4.4)"
  46         range 0 8192
  47         default 1024 if !64BIT
  48         default 2048 if 64BIT
  49         help
  50           Tell gcc to warn at build time for stack frames larger than this.
  51           Setting this too low will cause a lot of warnings.
  52           Setting it to 0 disables the warning.
  53           Requires gcc 4.4
  54
  55 config MAGIC_SYSRQ
  56         bool "Magic SysRq key"
  57         depends on !UML
  58         help
  59           If you say Y here, you will have some control over the system even
  60           if the system crashes for example during kernel debugging (e.g., you
  61           will be able to flush the buffer cache to disk, reboot the system
  62           immediately or dump some status information). This is accomplished
  63           by pressing various keys while holding SysRq (Alt+PrintScreen). It
  64           also works on a serial console (on PC hardware at least), if you
  65           send a BREAK and then within 5 seconds a command keypress. The
  66           keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
  67           unless you really know what this hack does.
  68
  69 config STRIP_ASM_SYMS
  70         bool "Strip assembler-generated symbols during link"
  71         default n
  72         help
  73           Strip internal assembler-generated symbols during a link (symbols
  74           that look like '.Lxxx') so they don't pollute the output of
  75           get_wchan() and suchlike.
  76
  77 config READABLE_ASM
  78         bool "Generate readable assembler code"
  79         depends on DEBUG_KERNEL
  80         help
  81           Disable some compiler optimizations that tend to generate human unreadable
  82           assembler output. This may make the kernel slightly slower, but it helps
  83           to keep kernel developers who have to stare a lot at assembler listings
  84           sane.
  85
  86 config UNUSED_SYMBOLS
  87         bool "Enable unused/obsolete exported symbols"
  88         default y if X86
  89         help
  90           Unused but exported symbols make the kernel needlessly bigger.  For
  91           that reason most of these unused exports will soon be removed.  This
  92           option is provided temporarily to provide a transition period in case
  93           some external kernel module needs one of these symbols anyway. If you
  94           encounter such a case in your module, consider if you are actually
  95           using the right API.  (rationale: since nobody in the kernel is using
  96           this in a module, there is a pretty good chance it's actually the
  97           wrong interface to use).  If you really need the symbol, please send a
  98           mail to the linux kernel mailing list mentioning the symbol and why
  99           you really need it, and what the merge plan to the mainline kernel for
 100           your module is.
 101
 102 config DEBUG_FS
 103         bool "Debug Filesystem"
 104         help
 105           debugfs is a virtual file system that kernel developers use to put
 106           debugging files into.  Enable this option to be able to read and
 107           write to these files.
 108
 109           For detailed documentation on the debugfs API, see
 110           Documentation/DocBook/filesystems.
 111
 112           If unsure, say N.
 113
 114 config HEADERS_CHECK
 115         bool "Run 'make headers_check' when building vmlinux"
 116         depends on !UML
 117         help
 118           This option will extract the user-visible kernel headers whenever
 119           building the kernel, and will run basic sanity checks on them to
 120           ensure that exported files do not attempt to include files which
 121           were not exported, etc.
 122
 123           If you're making modifications to header files which are
 124           relevant for userspace, say 'Y', and check the headers
 125           exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
 126           your build tree), to make sure they're suitable.
 127
 128 config DEBUG_SECTION_MISMATCH
 129         bool "Enable full Section mismatch analysis"
 130         help
 131           The section mismatch analysis checks if there are illegal
 132           references from one section to another section.
 133           During linktime or runtime, some sections are dropped;
 134           any use of code/data previously in these sections would
 135           most likely result in an oops.
 136           In the code, functions and variables are annotated with
 137           __init, __devinit, etc. (see the full list in include/linux/init.h),
 138           which results in the code/data being placed in specific sections.
 139           The section mismatch analysis is always performed after a full
 140           kernel build, and enabling this option causes the following
 141           additional steps to occur:
 142           - Add the option -fno-inline-functions-called-once to gcc commands.
 143             When inlining a function annotated with __init in a non-init
 144             function, we would lose the section information and thus
 145             the analysis would not catch the illegal reference.
 146             This option tells gcc to inline less (but it does result in
 147             a larger kernel).
 148           - Run the section mismatch analysis for each module/built-in.o file.
 149             When we run the section mismatch analysis on vmlinux.o, we
 150             lose valueble information about where the mismatch was
 151             introduced.
 152             Running the analysis for each module/built-in.o file
 153             tells where the mismatch happens much closer to the
 154             source. The drawback is that the same mismatch is
 155             reported at least twice.
 156           - Enable verbose reporting from modpost in order to help resolve
 157             the section mismatches that are reported.
 158
 159 config DEBUG_KERNEL
 160         bool "Kernel debugging"
 161         help
 162           Say Y here if you are developing drivers or trying to debug and
 163           identify kernel problems.
 164
 165 config DEBUG_SHIRQ
 166         bool "Debug shared IRQ handlers"
 167         depends on DEBUG_KERNEL && GENERIC_HARDIRQS
 168         help
 169           Enable this to generate a spurious interrupt as soon as a shared
 170           interrupt handler is registered, and just before one is deregistered.
 171           Drivers ought to be able to handle interrupts coming in at those
 172           points; some don't and need to be caught.
 173
 174 config LOCKUP_DETECTOR
 175         bool "Detect Hard and Soft Lockups"
 176         depends on DEBUG_KERNEL && !S390
 177         help
 178           Say Y here to enable the kernel to act as a watchdog to detect
 179           hard and soft lockups.
 180
 181           Softlockups are bugs that cause the kernel to loop in kernel
 182           mode for more than 20 seconds, without giving other tasks a
 183           chance to run.  The current stack trace is displayed upon
 184           detection and the system will stay locked up.
 185
 186           Hardlockups are bugs that cause the CPU to loop in kernel mode
 187           for more than 10 seconds, without letting other interrupts have a
 188           chance to run.  The current stack trace is displayed upon detection
 189           and the system will stay locked up.
 190
 191           The overhead should be minimal.  A periodic hrtimer runs to
 192           generate interrupts and kick the watchdog task every 4 seconds.
 193           An NMI is generated every 10 seconds or so to check for hardlockups.
 194
 195           The frequency of hrtimer and NMI events and the soft and hard lockup
 196           thresholds can be controlled through the sysctl watchdog_thresh.
 197
 198 config HARDLOCKUP_DETECTOR
 199         def_bool LOCKUP_DETECTOR && PERF_EVENTS && HAVE_PERF_EVENTS_NMI && \
 200                  !HAVE_NMI_WATCHDOG
 201
 202 config BOOTPARAM_HARDLOCKUP_PANIC
 203         bool "Panic (Reboot) On Hard Lockups"
 204         depends on LOCKUP_DETECTOR
 205         help
 206           Say Y here to enable the kernel to panic on "hard lockups",
 207           which are bugs that cause the kernel to loop in kernel
 208           mode with interrupts disabled for more than 10 seconds (configurable
 209           using the watchdog_thresh sysctl).
 210
 211           Say N if unsure.
 212
 213 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
 214         int
 215         depends on LOCKUP_DETECTOR
 216         range 0 1
 217         default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
 218         default 1 if BOOTPARAM_HARDLOCKUP_PANIC
 219
 220 config BOOTPARAM_SOFTLOCKUP_PANIC
 221         bool "Panic (Reboot) On Soft Lockups"
 222         depends on LOCKUP_DETECTOR
 223         help
 224           Say Y here to enable the kernel to panic on "soft lockups",
 225           which are bugs that cause the kernel to loop in kernel
 226           mode for more than 20 seconds (configurable using the watchdog_thresh
 227           sysctl), without giving other tasks a chance to run.
 228
 229           The panic can be used in combination with panic_timeout,
 230           to cause the system to reboot automatically after a
 231           lockup has been detected. This feature is useful for
 232           high-availability systems that have uptime guarantees and
 233           where a lockup must be resolved ASAP.
 234
 235           Say N if unsure.
 236
 237 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
 238         int
 239         depends on LOCKUP_DETECTOR
 240         range 0 1
 241         default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
 242         default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
 243
 244 config DETECT_HUNG_TASK
 245         bool "Detect Hung Tasks"
 246         depends on DEBUG_KERNEL
 247         default LOCKUP_DETECTOR
 248         help
 249           Say Y here to enable the kernel to detect "hung tasks",
 250           which are bugs that cause the task to be stuck in
 251           uninterruptible "D" state indefinitiley.
 252
 253           When a hung task is detected, the kernel will print the
 254           current stack trace (which you should report), but the
 255           task will stay in uninterruptible state. If lockdep is
 256           enabled then all held locks will also be reported. This
 257           feature has negligible overhead.
 258
 259 config DEFAULT_HUNG_TASK_TIMEOUT
 260         int "Default timeout for hung task detection (in seconds)"
 261         depends on DETECT_HUNG_TASK
 262         default 120
 263         help
 264           This option controls the default timeout (in seconds) used
 265           to determine when a task has become non-responsive and should
 266           be considered hung.
 267
 268           It can be adjusted at runtime via the kernel.hung_task_timeout_secs
 269           sysctl or by writing a value to
 270           /proc/sys/kernel/hung_task_timeout_secs.
 271
 272           A timeout of 0 disables the check.  The default is two minutes.
 273           Keeping the default should be fine in most cases.
 274
 275 config BOOTPARAM_HUNG_TASK_PANIC
 276         bool "Panic (Reboot) On Hung Tasks"
 277         depends on DETECT_HUNG_TASK
 278         help
 279           Say Y here to enable the kernel to panic on "hung tasks",
 280           which are bugs that cause the kernel to leave a task stuck
 281           in uninterruptible "D" state.
 282
 283           The panic can be used in combination with panic_timeout,
 284           to cause the system to reboot automatically after a
 285           hung task has been detected. This feature is useful for
 286           high-availability systems that have uptime guarantees and
 287           where a hung tasks must be resolved ASAP.
 288
 289           Say N if unsure.
 290
 291 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
 292         int
 293         depends on DETECT_HUNG_TASK
 294         range 0 1
 295         default 0 if !BOOTPARAM_HUNG_TASK_PANIC
 296         default 1 if BOOTPARAM_HUNG_TASK_PANIC
 297
 298 config SCHED_DEBUG
 299         bool "Collect scheduler debugging info"
 300         depends on DEBUG_KERNEL && PROC_FS
 301         default y
 302         help
 303           If you say Y here, the /proc/sched_debug file will be provided
 304           that can help debug the scheduler. The runtime overhead of this
 305           option is minimal.
 306
 307 config SCHEDSTATS
 308         bool "Collect scheduler statistics"
 309         depends on DEBUG_KERNEL && PROC_FS
 310         help
 311           If you say Y here, additional code will be inserted into the
 312           scheduler and related routines to collect statistics about
 313           scheduler behavior and provide them in /proc/schedstat.  These
 314           stats may be useful for both tuning and debugging the scheduler
 315           If you aren't debugging the scheduler or trying to tune a specific
 316           application, you can say N to avoid the very slight overhead
 317           this adds.
 318
 319 config TIMER_STATS
 320         bool "Collect kernel timers statistics"
 321         depends on DEBUG_KERNEL && PROC_FS
 322         help
 323           If you say Y here, additional code will be inserted into the
 324           timer routines to collect statistics about kernel timers being
 325           reprogrammed. The statistics can be read from /proc/timer_stats.
 326           The statistics collection is started by writing 1 to /proc/timer_stats,
 327           writing 0 stops it. This feature is useful to collect information
 328           about timer usage patterns in kernel and userspace. This feature
 329           is lightweight if enabled in the kernel config but not activated
 330           (it defaults to deactivated on bootup and will only be activated
 331           if some application like powertop activates it explicitly).
 332
 333 config DEBUG_OBJECTS
 334         bool "Debug object operations"
 335         depends on DEBUG_KERNEL
 336         help
 337           If you say Y here, additional code will be inserted into the
 338           kernel to track the life time of various objects and validate
 339           the operations on those objects.
 340
 341 config DEBUG_OBJECTS_SELFTEST
 342         bool "Debug objects selftest"
 343         depends on DEBUG_OBJECTS
 344         help
 345           This enables the selftest of the object debug code.
 346
 347 config DEBUG_OBJECTS_FREE
 348         bool "Debug objects in freed memory"
 349         depends on DEBUG_OBJECTS
 350         help
 351           This enables checks whether a k/v free operation frees an area
 352           which contains an object which has not been deactivated
 353           properly. This can make kmalloc/kfree-intensive workloads
 354           much slower.
 355
 356 config DEBUG_OBJECTS_TIMERS
 357         bool "Debug timer objects"
 358         depends on DEBUG_OBJECTS
 359         help
 360           If you say Y here, additional code will be inserted into the
 361           timer routines to track the life time of timer objects and
 362           validate the timer operations.
 363
 364 config DEBUG_OBJECTS_WORK
 365         bool "Debug work objects"
 366         depends on DEBUG_OBJECTS
 367         help
 368           If you say Y here, additional code will be inserted into the
 369           work queue routines to track the life time of work objects and
 370           validate the work operations.
 371
 372 config DEBUG_OBJECTS_RCU_HEAD
 373         bool "Debug RCU callbacks objects"
 374         depends on DEBUG_OBJECTS
 375         help
 376           Enable this to turn on debugging of RCU list heads (call_rcu() usage).
 377
 378 config DEBUG_OBJECTS_PERCPU_COUNTER
 379         bool "Debug percpu counter objects"
 380         depends on DEBUG_OBJECTS
 381         help
 382           If you say Y here, additional code will be inserted into the
 383           percpu counter routines to track the life time of percpu counter
 384           objects and validate the percpu counter operations.
 385
 386 config DEBUG_OBJECTS_ENABLE_DEFAULT
 387         int "debug_objects bootup default value (0-1)"
 388         range 0 1
 389         default "1"
 390         depends on DEBUG_OBJECTS
 391         help
 392           Debug objects boot parameter default value
 393
 394 config DEBUG_SLAB
 395         bool "Debug slab memory allocations"
 396         depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
 397         help
 398           Say Y here to have the kernel do limited verification on memory
 399           allocation as well as poisoning memory on free to catch use of freed
 400           memory. This can make kmalloc/kfree-intensive workloads much slower.
 401
 402 config DEBUG_SLAB_LEAK
 403         bool "Memory leak debugging"
 404         depends on DEBUG_SLAB
 405
 406 config SLUB_DEBUG_ON
 407         bool "SLUB debugging on by default"
 408         depends on SLUB && SLUB_DEBUG && !KMEMCHECK
 409         default n
 410         help
 411           Boot with debugging on by default. SLUB boots by default with
 412           the runtime debug capabilities switched off. Enabling this is
 413           equivalent to specifying the "slub_debug" parameter on boot.
 414           There is no support for more fine grained debug control like
 415           possible with slub_debug=xxx. SLUB debugging may be switched
 416           off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
 417           "slub_debug=-".
 418
 419 config SLUB_STATS
 420         default n
 421         bool "Enable SLUB performance statistics"
 422         depends on SLUB && SYSFS
 423         help
 424           SLUB statistics are useful to debug SLUBs allocation behavior in
 425           order find ways to optimize the allocator. This should never be
 426           enabled for production use since keeping statistics slows down
 427           the allocator by a few percentage points. The slabinfo command
 428           supports the determination of the most active slabs to figure
 429           out which slabs are relevant to a particular load.
 430           Try running: slabinfo -DA
 431
 432 config DEBUG_KMEMLEAK
 433         bool "Kernel memory leak detector"
 434         depends on DEBUG_KERNEL && EXPERIMENTAL && \
 435                 (X86 || ARM || PPC || MIPS || S390 || SPARC64 || SUPERH || MICROBLAZE || TILE)
 436
 437         select DEBUG_FS
 438         select STACKTRACE if STACKTRACE_SUPPORT
 439         select KALLSYMS
 440         select CRC32
 441         help
 442           Say Y here if you want to enable the memory leak
 443           detector. The memory allocation/freeing is traced in a way
 444           similar to the Boehm's conservative garbage collector, the
 445           difference being that the orphan objects are not freed but
 446           only shown in /sys/kernel/debug/kmemleak. Enabling this
 447           feature will introduce an overhead to memory
 448           allocations. See Documentation/kmemleak.txt for more
 449           details.
 450
 451           Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
 452           of finding leaks due to the slab objects poisoning.
 453
 454           In order to access the kmemleak file, debugfs needs to be
 455           mounted (usually at /sys/kernel/debug).
 456
 457 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
 458         int "Maximum kmemleak early log entries"
 459         depends on DEBUG_KMEMLEAK
 460         range 200 40000
 461         default 400
 462         help
 463           Kmemleak must track all the memory allocations to avoid
 464           reporting false positives. Since memory may be allocated or
 465           freed before kmemleak is initialised, an early log buffer is
 466           used to store these actions. If kmemleak reports "early log
 467           buffer exceeded", please increase this value.
 468
 469 config DEBUG_KMEMLEAK_TEST
 470         tristate "Simple test for the kernel memory leak detector"
 471         depends on DEBUG_KMEMLEAK && m
 472         help
 473           This option enables a module that explicitly leaks memory.
 474
 475           If unsure, say N.
 476
 477 config DEBUG_KMEMLEAK_DEFAULT_OFF
 478         bool "Default kmemleak to off"
 479         depends on DEBUG_KMEMLEAK
 480         help
 481           Say Y here to disable kmemleak by default. It can then be enabled
 482           on the command line via kmemleak=on.
 483
 484 config DEBUG_PREEMPT
 485         bool "Debug preemptible kernel"
 486         depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
 487         default y
 488         help
 489           If you say Y here then the kernel will use a debug variant of the
 490           commonly used smp_processor_id() function and will print warnings
 491           if kernel code uses it in a preemption-unsafe way. Also, the kernel
 492           will detect preemption count underflows.
 493
 494 config DEBUG_RT_MUTEXES
 495         bool "RT Mutex debugging, deadlock detection"
 496         depends on DEBUG_KERNEL && RT_MUTEXES
 497         help
 498          This allows rt mutex semantics violations and rt mutex related
 499          deadlocks (lockups) to be detected and reported automatically.
 500
 501 config DEBUG_PI_LIST
 502         bool
 503         default y
 504         depends on DEBUG_RT_MUTEXES
 505
 506 config RT_MUTEX_TESTER
 507         bool "Built-in scriptable tester for rt-mutexes"
 508         depends on DEBUG_KERNEL && RT_MUTEXES
 509         help
 510           This option enables a rt-mutex tester.
 511
 512 config DEBUG_SPINLOCK
 513         bool "Spinlock and rw-lock debugging: basic checks"
 514         depends on DEBUG_KERNEL
 515         select UNINLINE_SPIN_UNLOCK
 516         help
 517           Say Y here and build SMP to catch missing spinlock initialization
 518           and certain other kinds of spinlock errors commonly made.  This is
 519           best used in conjunction with the NMI watchdog so that spinlock
 520           deadlocks are also debuggable.
 521
 522 config DEBUG_MUTEXES
 523         bool "Mutex debugging: basic checks"
 524         depends on DEBUG_KERNEL
 525         help
 526          This feature allows mutex semantics violations to be detected and
 527          reported.
 528
 529 config DEBUG_LOCK_ALLOC
 530         bool "Lock debugging: detect incorrect freeing of live locks"
 531         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 532         select DEBUG_SPINLOCK
 533         select DEBUG_MUTEXES
 534         select LOCKDEP
 535         help
 536          This feature will check whether any held lock (spinlock, rwlock,
 537          mutex or rwsem) is incorrectly freed by the kernel, via any of the
 538          memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
 539          vfree(), etc.), whether a live lock is incorrectly reinitialized via
 540          spin_lock_init()/mutex_init()/etc., or whether there is any lock
 541          held during task exit.
 542
 543 config PROVE_LOCKING
 544         bool "Lock debugging: prove locking correctness"
 545         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 546         select LOCKDEP
 547         select DEBUG_SPINLOCK
 548         select DEBUG_MUTEXES
 549         select DEBUG_LOCK_ALLOC
 550         select TRACE_IRQFLAGS
 551         default n
 552         help
 553          This feature enables the kernel to prove that all locking
 554          that occurs in the kernel runtime is mathematically
 555          correct: that under no circumstance could an arbitrary (and
 556          not yet triggered) combination of observed locking
 557          sequences (on an arbitrary number of CPUs, running an
 558          arbitrary number of tasks and interrupt contexts) cause a
 559          deadlock.
 560
 561          In short, this feature enables the kernel to report locking
 562          related deadlocks before they actually occur.
 563
 564          The proof does not depend on how hard and complex a
 565          deadlock scenario would be to trigger: how many
 566          participant CPUs, tasks and irq-contexts would be needed
 567          for it to trigger. The proof also does not depend on
 568          timing: if a race and a resulting deadlock is possible
 569          theoretically (no matter how unlikely the race scenario
 570          is), it will be proven so and will immediately be
 571          reported by the kernel (once the event is observed that
 572          makes the deadlock theoretically possible).
 573
 574          If a deadlock is impossible (i.e. the locking rules, as
 575          observed by the kernel, are mathematically correct), the
 576          kernel reports nothing.
 577
 578          NOTE: this feature can also be enabled for rwlocks, mutexes
 579          and rwsems - in which case all dependencies between these
 580          different locking variants are observed and mapped too, and
 581          the proof of observed correctness is also maintained for an
 582          arbitrary combination of these separate locking variants.
 583
 584          For more details, see Documentation/lockdep-design.txt.
 585
 586 config PROVE_RCU
 587         bool "RCU debugging: prove RCU correctness"
 588         depends on PROVE_LOCKING
 589         default n
 590         help
 591          This feature enables lockdep extensions that check for correct
 592          use of RCU APIs.  This is currently under development.  Say Y
 593          if you want to debug RCU usage or help work on the PROVE_RCU
 594          feature.
 595
 596          Say N if you are unsure.
 597
 598 config PROVE_RCU_REPEATEDLY
 599         bool "RCU debugging: don't disable PROVE_RCU on first splat"
 600         depends on PROVE_RCU
 601         default n
 602         help
 603          By itself, PROVE_RCU will disable checking upon issuing the
 604          first warning (or "splat").  This feature prevents such
 605          disabling, allowing multiple RCU-lockdep warnings to be printed
 606          on a single reboot.
 607
 608          Say Y to allow multiple RCU-lockdep warnings per boot.
 609
 610          Say N if you are unsure.
 611
 612 config SPARSE_RCU_POINTER
 613         bool "RCU debugging: sparse-based checks for pointer usage"
 614         default n
 615         help
 616          This feature enables the __rcu sparse annotation for
 617          RCU-protected pointers.  This annotation will cause sparse
 618          to flag any non-RCU used of annotated pointers.  This can be
 619          helpful when debugging RCU usage.  Please note that this feature
 620          is not intended to enforce code cleanliness; it is instead merely
 621          a debugging aid.
 622
 623          Say Y to make sparse flag questionable use of RCU-protected pointers
 624
 625          Say N if you are unsure.
 626
 627 config LOCKDEP
 628         bool
 629         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 630         select STACKTRACE
 631         select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE
 632         select KALLSYMS
 633         select KALLSYMS_ALL
 634
 635 config LOCK_STAT
 636         bool "Lock usage statistics"
 637         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 638         select LOCKDEP
 639         select DEBUG_SPINLOCK
 640         select DEBUG_MUTEXES
 641         select DEBUG_LOCK_ALLOC
 642         default n
 643         help
 644          This feature enables tracking lock contention points
 645
 646          For more details, see Documentation/lockstat.txt
 647
 648          This also enables lock events required by "perf lock",
 649          subcommand of perf.
 650          If you want to use "perf lock", you also need to turn on
 651          CONFIG_EVENT_TRACING.
 652
 653          CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
 654          (CONFIG_LOCKDEP defines "acquire" and "release" events.)
 655
 656 config DEBUG_LOCKDEP
 657         bool "Lock dependency engine debugging"
 658         depends on DEBUG_KERNEL && LOCKDEP
 659         help
 660           If you say Y here, the lock dependency engine will do
 661           additional runtime checks to debug itself, at the price
 662           of more runtime overhead.
 663
 664 config TRACE_IRQFLAGS
 665         bool
 666         help
 667           Enables hooks to interrupt enabling and disabling for
 668           either tracing or lock debugging.
 669
 670 config DEBUG_ATOMIC_SLEEP
 671         bool "Sleep inside atomic section checking"
 672         select PREEMPT_COUNT
 673         depends on DEBUG_KERNEL
 674         help
 675           If you say Y here, various routines which may sleep will become very
 676           noisy if they are called inside atomic sections: when a spinlock is
 677           held, inside an rcu read side critical section, inside preempt disabled
 678           sections, inside an interrupt, etc...
 679
 680 config DEBUG_LOCKING_API_SELFTESTS
 681         bool "Locking API boot-time self-tests"
 682         depends on DEBUG_KERNEL
 683         help
 684           Say Y here if you want the kernel to run a short self-test during
 685           bootup. The self-test checks whether common types of locking bugs
 686           are detected by debugging mechanisms or not. (if you disable
 687           lock debugging then those bugs wont be detected of course.)
 688           The following locking APIs are covered: spinlocks, rwlocks,
 689           mutexes and rwsems.
 690
 691 config STACKTRACE
 692         bool
 693         depends on STACKTRACE_SUPPORT
 694
 695 config DEBUG_STACK_USAGE
 696         bool "Stack utilization instrumentation"
 697         depends on DEBUG_KERNEL
 698         help
 699           Enables the display of the minimum amount of free stack which each
 700           task has ever had available in the sysrq-T and sysrq-P debug output.
 701
 702           This option will slow down process creation somewhat.
 703
 704 config DEBUG_KOBJECT
 705         bool "kobject debugging"
 706         depends on DEBUG_KERNEL
 707         help
 708           If you say Y here, some extra kobject debugging messages will be sent
 709           to the syslog.
 710
 711 config DEBUG_HIGHMEM
 712         bool "Highmem debugging"
 713         depends on DEBUG_KERNEL && HIGHMEM
 714         help
 715           This options enables addition error checking for high memory systems.
 716           Disable for production systems.
 717
 718 config DEBUG_BUGVERBOSE
 719         bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
 720         depends on BUG
 721         depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \
 722                    FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 || TILE
 723         default y
 724         help
 725           Say Y here to make BUG() panics output the file name and line number
 726           of the BUG call as well as the EIP and oops trace.  This aids
 727           debugging but costs about 70-100K of memory.
 728
 729 config DEBUG_INFO
 730         bool "Compile the kernel with debug info"
 731         depends on DEBUG_KERNEL
 732         help
 733           If you say Y here the resulting kernel image will include
 734           debugging info resulting in a larger kernel image.
 735           This adds debug symbols to the kernel and modules (gcc -g), and
 736           is needed if you intend to use kernel crashdump or binary object
 737           tools like crash, kgdb, LKCD, gdb, etc on the kernel.
 738           Say Y here only if you plan to debug the kernel.
 739
 740           If unsure, say N.
 741
 742 config DEBUG_INFO_REDUCED
 743         bool "Reduce debugging information"
 744         depends on DEBUG_INFO
 745         help
 746           If you say Y here gcc is instructed to generate less debugging
 747           information for structure types. This means that tools that
 748           need full debugging information (like kgdb or systemtap) won't
 749           be happy. But if you merely need debugging information to
 750           resolve line numbers there is no loss. Advantage is that
 751           build directory object sizes shrink dramatically over a full
 752           DEBUG_INFO build and compile times are reduced too.
 753           Only works with newer gcc versions.
 754
 755 config DEBUG_VM
 756         bool "Debug VM"
 757         depends on DEBUG_KERNEL
 758         help
 759           Enable this to turn on extended checks in the virtual-memory system
 760           that may impact performance.
 761
 762           If unsure, say N.
 763
 764 config DEBUG_VIRTUAL
 765         bool "Debug VM translations"
 766         depends on DEBUG_KERNEL && X86
 767         help
 768           Enable some costly sanity checks in virtual to page code. This can
 769           catch mistakes with virt_to_page() and friends.
 770
 771           If unsure, say N.
 772
 773 config DEBUG_NOMMU_REGIONS
 774         bool "Debug the global anon/private NOMMU mapping region tree"
 775         depends on DEBUG_KERNEL && !MMU
 776         help
 777           This option causes the global tree of anonymous and private mapping
 778           regions to be regularly checked for invalid topology.
 779
 780 config DEBUG_WRITECOUNT
 781         bool "Debug filesystem writers count"
 782         depends on DEBUG_KERNEL
 783         help
 784           Enable this to catch wrong use of the writers count in struct
 785           vfsmount.  This will increase the size of each file struct by
 786           32 bits.
 787
 788           If unsure, say N.
 789
 790 config DEBUG_MEMORY_INIT
 791         bool "Debug memory initialisation" if EXPERT
 792         default !EXPERT
 793         help
 794           Enable this for additional checks during memory initialisation.
 795           The sanity checks verify aspects of the VM such as the memory model
 796           and other information provided by the architecture. Verbose
 797           information will be printed at KERN_DEBUG loglevel depending
 798           on the mminit_loglevel= command-line option.
 799
 800           If unsure, say Y
 801
 802 config DEBUG_LIST
 803         bool "Debug linked list manipulation"
 804         depends on DEBUG_KERNEL
 805         help
 806           Enable this to turn on extended checks in the linked-list
 807           walking routines.
 808
 809           If unsure, say N.
 810
 811 config TEST_LIST_SORT
 812         bool "Linked list sorting test"
 813         depends on DEBUG_KERNEL
 814         help
 815           Enable this to turn on 'list_sort()' function test. This test is
 816           executed only once during system boot, so affects only boot time.
 817
 818           If unsure, say N.
 819
 820 config DEBUG_SG
 821         bool "Debug SG table operations"
 822         depends on DEBUG_KERNEL
 823         help
 824           Enable this to turn on checks on scatter-gather tables. This can
 825           help find problems with drivers that do not properly initialize
 826           their sg tables.
 827
 828           If unsure, say N.
 829
 830 config DEBUG_NOTIFIERS
 831         bool "Debug notifier call chains"
 832         depends on DEBUG_KERNEL
 833         help
 834           Enable this to turn on sanity checking for notifier call chains.
 835           This is most useful for kernel developers to make sure that
 836           modules properly unregister themselves from notifier chains.
 837           This is a relatively cheap check but if you care about maximum
 838           performance, say N.
 839
 840 config DEBUG_CREDENTIALS
 841         bool "Debug credential management"
 842         depends on DEBUG_KERNEL
 843         help
 844           Enable this to turn on some debug checking for credential
 845           management.  The additional code keeps track of the number of
 846           pointers from task_structs to any given cred struct, and checks to
 847           see that this number never exceeds the usage count of the cred
 848           struct.
 849
 850           Furthermore, if SELinux is enabled, this also checks that the
 851           security pointer in the cred struct is never seen to be invalid.
 852
 853           If unsure, say N.
 854
 855 #
 856 # Select this config option from the architecture Kconfig, if it
 857 # is preferred to always offer frame pointers as a config
 858 # option on the architecture (regardless of KERNEL_DEBUG):
 859 #
 860 config ARCH_WANT_FRAME_POINTERS
 861         bool
 862         help
 863
 864 config FRAME_POINTER
 865         bool "Compile the kernel with frame pointers"
 866         depends on DEBUG_KERNEL && \
 867                 (CRIS || M68K || FRV || UML || \
 868                  AVR32 || SUPERH || BLACKFIN || MN10300) || \
 869                 ARCH_WANT_FRAME_POINTERS
 870         default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
 871         help
 872           If you say Y here the resulting kernel image will be slightly
 873           larger and slower, but it gives very useful debugging information
 874           in case of kernel bugs. (precise oopses/stacktraces/warnings)
 875
 876 config BOOT_PRINTK_DELAY
 877         bool "Delay each boot printk message by N milliseconds"
 878         depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
 879         help
 880           This build option allows you to read kernel boot messages
 881           by inserting a short delay after each one.  The delay is
 882           specified in milliseconds on the kernel command line,
 883           using "boot_delay=N".
 884
 885           It is likely that you would also need to use "lpj=M" to preset
 886           the "loops per jiffie" value.
 887           See a previous boot log for the "lpj" value to use for your
 888           system, and then set "lpj=M" before setting "boot_delay=N".
 889           NOTE:  Using this option may adversely affect SMP systems.
 890           I.e., processors other than the first one may not boot up.
 891           BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
 892           what it believes to be lockup conditions.
 893
 894 config RCU_TORTURE_TEST
 895         tristate "torture tests for RCU"
 896         depends on DEBUG_KERNEL
 897         default n
 898         help
 899           This option provides a kernel module that runs torture tests
 900           on the RCU infrastructure.  The kernel module may be built
 901           after the fact on the running kernel to be tested, if desired.
 902
 903           Say Y here if you want RCU torture tests to be built into
 904           the kernel.
 905           Say M if you want the RCU torture tests to build as a module.
 906           Say N if you are unsure.
 907
 908 config RCU_TORTURE_TEST_RUNNABLE
 909         bool "torture tests for RCU runnable by default"
 910         depends on RCU_TORTURE_TEST = y
 911         default n
 912         help
 913           This option provides a way to build the RCU torture tests
 914           directly into the kernel without them starting up at boot
 915           time.  You can use /proc/sys/kernel/rcutorture_runnable
 916           to manually override this setting.  This /proc file is
 917           available only when the RCU torture tests have been built
 918           into the kernel.
 919
 920           Say Y here if you want the RCU torture tests to start during
 921           boot (you probably don't).
 922           Say N here if you want the RCU torture tests to start only
 923           after being manually enabled via /proc.
 924
 925 config RCU_CPU_STALL_TIMEOUT
 926         int "RCU CPU stall timeout in seconds"
 927         depends on TREE_RCU || TREE_PREEMPT_RCU
 928         range 3 300
 929         default 60
 930         help
 931           If a given RCU grace period extends more than the specified
 932           number of seconds, a CPU stall warning is printed.  If the
 933           RCU grace period persists, additional CPU stall warnings are
 934           printed at more widely spaced intervals.
 935
 936 config RCU_CPU_STALL_VERBOSE
 937         bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
 938         depends on TREE_PREEMPT_RCU
 939         default y
 940         help
 941           This option causes RCU to printk detailed per-task information
 942           for any tasks that are stalling the current RCU grace period.
 943
 944           Say N if you are unsure.
 945
 946           Say Y if you want to enable such checks.
 947
 948 config RCU_CPU_STALL_INFO
 949         bool "Print additional diagnostics on RCU CPU stall"
 950         depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL
 951         default n
 952         help
 953           For each stalled CPU that is aware of the current RCU grace
 954           period, print out additional per-CPU diagnostic information
 955           regarding scheduling-clock ticks, idle state, and,
 956           for RCU_FAST_NO_HZ kernels, idle-entry state.
 957
 958           Say N if you are unsure.
 959
 960           Say Y if you want to enable such diagnostics.
 961
 962 config RCU_TRACE
 963         bool "Enable tracing for RCU"
 964         depends on DEBUG_KERNEL
 965         help
 966           This option provides tracing in RCU which presents stats
 967           in debugfs for debugging RCU implementation.
 968
 969           Say Y here if you want to enable RCU tracing
 970           Say N if you are unsure.
 971
 972 config KPROBES_SANITY_TEST
 973         bool "Kprobes sanity tests"
 974         depends on DEBUG_KERNEL
 975         depends on KPROBES
 976         default n
 977         help
 978           This option provides for testing basic kprobes functionality on
 979           boot. A sample kprobe, jprobe and kretprobe are inserted and
 980           verified for functionality.
 981
 982           Say N if you are unsure.
 983
 984 config BACKTRACE_SELF_TEST
 985         tristate "Self test for the backtrace code"
 986         depends on DEBUG_KERNEL
 987         default n
 988         help
 989           This option provides a kernel module that can be used to test
 990           the kernel stack backtrace code. This option is not useful
 991           for distributions or general kernels, but only for kernel
 992           developers working on architecture code.
 993
 994           Note that if you want to also test saved backtraces, you will
 995           have to enable STACKTRACE as well.
 996
 997           Say N if you are unsure.
 998
 999 config DEBUG_BLOCK_EXT_DEVT
1000         bool "Force extended block device numbers and spread them"
1001         depends on DEBUG_KERNEL
1002         depends on BLOCK
1003         default n
1004         help
1005           BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1006           SOME DISTRIBUTIONS.  DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1007           YOU ARE DOING.  Distros, please enable this and fix whatever
1008           is broken.
1009
1010           Conventionally, block device numbers are allocated from
1011           predetermined contiguous area.  However, extended block area
1012           may introduce non-contiguous block device numbers.  This
1013           option forces most block device numbers to be allocated from
1014           the extended space and spreads them to discover kernel or
1015           userland code paths which assume predetermined contiguous
1016           device number allocation.
1017
1018           Note that turning on this debug option shuffles all the
1019           device numbers for all IDE and SCSI devices including libata
1020           ones, so root partition specified using device number
1021           directly (via rdev or root=MAJ:MIN) won't work anymore.
1022           Textual device names (root=/dev/sdXn) will continue to work.
1023
1024           Say N if you are unsure.
1025
1026 config DEBUG_FORCE_WEAK_PER_CPU
1027         bool "Force weak per-cpu definitions"
1028         depends on DEBUG_KERNEL
1029         help
1030           s390 and alpha require percpu variables in modules to be
1031           defined weak to work around addressing range issue which
1032           puts the following two restrictions on percpu variable
1033           definitions.
1034
1035           1. percpu symbols must be unique whether static or not
1036           2. percpu variables can't be defined inside a function
1037
1038           To ensure that generic code follows the above rules, this
1039           option forces all percpu variables to be defined as weak.
1040
1041 config DEBUG_PER_CPU_MAPS
1042         bool "Debug access to per_cpu maps"
1043         depends on DEBUG_KERNEL
1044         depends on SMP
1045         help
1046           Say Y to verify that the per_cpu map being accessed has
1047           been set up. This adds a fair amount of code to kernel memory
1048           and decreases performance.
1049
1050           Say N if unsure.
1051
1052 config LKDTM
1053         tristate "Linux Kernel Dump Test Tool Module"
1054         depends on DEBUG_FS
1055         depends on BLOCK
1056         default n
1057         help
1058         This module enables testing of the different dumping mechanisms by
1059         inducing system failures at predefined crash points.
1060         If you don't need it: say N
1061         Choose M here to compile this code as a module. The module will be
1062         called lkdtm.
1063
1064         Documentation on how to use the module can be found in
1065         Documentation/fault-injection/provoke-crashes.txt
1066
1067 config CPU_NOTIFIER_ERROR_INJECT
1068         tristate "CPU notifier error injection module"
1069         depends on HOTPLUG_CPU && DEBUG_KERNEL
1070         help
1071           This option provides a kernel module that can be used to test
1072           the error handling of the cpu notifiers
1073
1074           To compile this code as a module, choose M here: the module will
1075           be called cpu-notifier-error-inject.
1076
1077           If unsure, say N.
1078
1079 config FAULT_INJECTION
1080         bool "Fault-injection framework"
1081         depends on DEBUG_KERNEL
1082         help
1083           Provide fault-injection framework.
1084           For more details, see Documentation/fault-injection/.
1085
1086 config FAILSLAB
1087         bool "Fault-injection capability for kmalloc"
1088         depends on FAULT_INJECTION
1089         depends on SLAB || SLUB
1090         help
1091           Provide fault-injection capability for kmalloc.
1092
1093 config FAIL_PAGE_ALLOC
1094         bool "Fault-injection capabilitiy for alloc_pages()"
1095         depends on FAULT_INJECTION
1096         help
1097           Provide fault-injection capability for alloc_pages().
1098
1099 config FAIL_MAKE_REQUEST
1100         bool "Fault-injection capability for disk IO"
1101         depends on FAULT_INJECTION && BLOCK
1102         help
1103           Provide fault-injection capability for disk IO.
1104
1105 config FAIL_IO_TIMEOUT
1106         bool "Fault-injection capability for faking disk interrupts"
1107         depends on FAULT_INJECTION && BLOCK
1108         help
1109           Provide fault-injection capability on end IO handling. This
1110           will make the block layer "forget" an interrupt as configured,
1111           thus exercising the error handling.
1112
1113           Only works with drivers that use the generic timeout handling,
1114           for others it wont do anything.
1115
1116 config FAIL_MMC_REQUEST
1117         bool "Fault-injection capability for MMC IO"
1118         select DEBUG_FS
1119         depends on FAULT_INJECTION && MMC
1120         help
1121           Provide fault-injection capability for MMC IO.
1122           This will make the mmc core return data errors. This is
1123           useful to test the error handling in the mmc block device
1124           and to test how the mmc host driver handles retries from
1125           the block device.
1126
1127 config FAULT_INJECTION_DEBUG_FS
1128         bool "Debugfs entries for fault-injection capabilities"
1129         depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1130         help
1131           Enable configuration of fault-injection capabilities via debugfs.
1132
1133 config FAULT_INJECTION_STACKTRACE_FILTER
1134         bool "stacktrace filter for fault-injection capabilities"
1135         depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1136         depends on !X86_64
1137         select STACKTRACE
1138         select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND
1139         help
1140           Provide stacktrace filter for fault-injection capabilities
1141
1142 config LATENCYTOP
1143         bool "Latency measuring infrastructure"
1144         depends on HAVE_LATENCYTOP_SUPPORT
1145         depends on DEBUG_KERNEL
1146         depends on STACKTRACE_SUPPORT
1147         depends on PROC_FS
1148         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND
1149         select KALLSYMS
1150         select KALLSYMS_ALL
1151         select STACKTRACE
1152         select SCHEDSTATS
1153         select SCHED_DEBUG
1154         help
1155           Enable this option if you want to use the LatencyTOP tool
1156           to find out which userspace is blocking on what kernel operations.
1157
1158 source mm/Kconfig.debug
1159 source kernel/trace/Kconfig
1160
1161 config PROVIDE_OHCI1394_DMA_INIT
1162         bool "Remote debugging over FireWire early on boot"
1163         depends on PCI && X86
1164         help
1165           If you want to debug problems which hang or crash the kernel early
1166           on boot and the crashing machine has a FireWire port, you can use
1167           this feature to remotely access the memory of the crashed machine
1168           over FireWire. This employs remote DMA as part of the OHCI1394
1169           specification which is now the standard for FireWire controllers.
1170
1171           With remote DMA, you can monitor the printk buffer remotely using
1172           firescope and access all memory below 4GB using fireproxy from gdb.
1173           Even controlling a kernel debugger is possible using remote DMA.
1174
1175           Usage:
1176
1177           If ohci1394_dma=early is used as boot parameter, it will initialize
1178           all OHCI1394 controllers which are found in the PCI config space.
1179
1180           As all changes to the FireWire bus such as enabling and disabling
1181           devices cause a bus reset and thereby disable remote DMA for all
1182           devices, be sure to have the cable plugged and FireWire enabled on
1183           the debugging host before booting the debug target for debugging.
1184
1185           This code (~1k) is freed after boot. By then, the firewire stack
1186           in charge of the OHCI-1394 controllers should be used instead.
1187
1188           See Documentation/debugging-via-ohci1394.txt for more information.
1189
1190 config FIREWIRE_OHCI_REMOTE_DMA
1191         bool "Remote debugging over FireWire with firewire-ohci"
1192         depends on FIREWIRE_OHCI
1193         help
1194           This option lets you use the FireWire bus for remote debugging
1195           with help of the firewire-ohci driver. It enables unfiltered
1196           remote DMA in firewire-ohci.
1197           See Documentation/debugging-via-ohci1394.txt for more information.
1198
1199           If unsure, say N.
1200
1201 config BUILD_DOCSRC
1202         bool "Build targets in Documentation/ tree"
1203         depends on HEADERS_CHECK
1204         help
1205           This option attempts to build objects from the source files in the
1206           kernel Documentation/ tree.
1207
1208           Say N if you are unsure.
1209
1210 config DYNAMIC_DEBUG
1211         bool "Enable dynamic printk() support"
1212         default n
1213         depends on PRINTK
1214         depends on DEBUG_FS
1215         help
1216
1217           Compiles debug level messages into the kernel, which would not
1218           otherwise be available at runtime. These messages can then be
1219           enabled/disabled based on various levels of scope - per source file,
1220           function, module, format string, and line number. This mechanism
1221           implicitly compiles in all pr_debug() and dev_dbg() calls, which
1222           enlarges the kernel text size by about 2%.
1223
1224           If a source file is compiled with DEBUG flag set, any
1225           pr_debug() calls in it are enabled by default, but can be
1226           disabled at runtime as below.  Note that DEBUG flag is
1227           turned on by many CONFIG_*DEBUG* options.
1228
1229           Usage:
1230
1231           Dynamic debugging is controlled via the 'dynamic_debug/control' file,
1232           which is contained in the 'debugfs' filesystem. Thus, the debugfs
1233           filesystem must first be mounted before making use of this feature.
1234           We refer the control file as: <debugfs>/dynamic_debug/control. This
1235           file contains a list of the debug statements that can be enabled. The
1236           format for each line of the file is:
1237
1238                 filename:lineno [module]function flags format
1239
1240           filename : source file of the debug statement
1241           lineno : line number of the debug statement
1242           module : module that contains the debug statement
1243           function : function that contains the debug statement
1244           flags : '=p' means the line is turned 'on' for printing
1245           format : the format used for the debug statement
1246
1247           From a live system:
1248
1249                 nullarbor:~ # cat <debugfs>/dynamic_debug/control
1250                 # filename:lineno [module]function flags format
1251                 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
1252                 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
1253                 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
1254
1255           Example usage:
1256
1257                 // enable the message at line 1603 of file svcsock.c
1258                 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
1259                                                 <debugfs>/dynamic_debug/control
1260
1261                 // enable all the messages in file svcsock.c
1262                 nullarbor:~ # echo -n 'file svcsock.c +p' >
1263                                                 <debugfs>/dynamic_debug/control
1264
1265                 // enable all the messages in the NFS server module
1266                 nullarbor:~ # echo -n 'module nfsd +p' >
1267                                                 <debugfs>/dynamic_debug/control
1268
1269                 // enable all 12 messages in the function svc_process()
1270                 nullarbor:~ # echo -n 'func svc_process +p' >
1271                                                 <debugfs>/dynamic_debug/control
1272
1273                 // disable all 12 messages in the function svc_process()
1274                 nullarbor:~ # echo -n 'func svc_process -p' >
1275                                                 <debugfs>/dynamic_debug/control
1276
1277           See Documentation/dynamic-debug-howto.txt for additional information.
1278
1279 config DMA_API_DEBUG
1280         bool "Enable debugging of DMA-API usage"
1281         depends on HAVE_DMA_API_DEBUG
1282         help
1283           Enable this option to debug the use of the DMA API by device drivers.
1284           With this option you will be able to detect common bugs in device
1285           drivers like double-freeing of DMA mappings or freeing mappings that
1286           were never allocated.
1287           This option causes a performance degredation.  Use only if you want
1288           to debug device drivers. If unsure, say N.
1289
1290 config ATOMIC64_SELFTEST
1291         bool "Perform an atomic64_t self-test at boot"
1292         help
1293           Enable this option to test the atomic64_t functions at boot.
1294
1295           If unsure, say N.
1296
1297 config ASYNC_RAID6_TEST
1298         tristate "Self test for hardware accelerated raid6 recovery"
1299         depends on ASYNC_RAID6_RECOV
1300         select ASYNC_MEMCPY
1301         ---help---
1302           This is a one-shot self test that permutes through the
1303           recovery of all the possible two disk failure scenarios for a
1304           N-disk array.  Recovery is performed with the asynchronous
1305           raid6 recovery routines, and will optionally use an offload
1306           engine if one is available.
1307
1308           If unsure, say N.
1309
1310 source "samples/Kconfig"
1311
1312 source "lib/Kconfig.kgdb"
1313
1314 source "lib/Kconfig.kmemcheck"
1315
1316 config TEST_KSTRTOX
1317         tristate "Test kstrto*() family of functions at runtime"