lib/Kconfig.debug

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