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