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. Or add printk.time=1 at boot-time. 11 See Documentation/kernel-parameters.txt 12 13config 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 24config 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 32config 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 40config 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 51config 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 65config 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 73config 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 89config 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 101config 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 115config 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 146config 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 152config 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 161config 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 182config HARDLOCKUP_DETECTOR 183 def_bool LOCKUP_DETECTOR && PERF_EVENTS && HAVE_PERF_EVENTS_NMI && \ 184 !ARCH_HAS_NMI_WATCHDOG 185 186config 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 196config 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 203config 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 220config 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 227config 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 242config 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 257config 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 273config 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 280config 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 289config 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 301config 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 315config 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 323config 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 329config 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 338config 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 346config 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 354config 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 360config 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 368config 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 376config 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 384config DEBUG_SLAB_LEAK 385 bool "Memory leak debugging" 386 depends on DEBUG_SLAB 387 388config 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 401config 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 414config 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 439config 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 451config 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 459config 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 466config 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 476config 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 483config DEBUG_PI_LIST 484 bool 485 default y 486 depends on DEBUG_RT_MUTEXES 487 488config 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 494config 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 503config 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 510config 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 524config 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 567config 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 579config 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 593config 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 608config 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 616config 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 637config 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 645config TRACE_IRQFLAGS 646 bool 647 help 648 Enables hooks to interrupt enabling and disabling for 649 either tracing or lock debugging. 650 651config 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 658config 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 669config STACKTRACE 670 bool 671 depends on STACKTRACE_SUPPORT 672 673config DEBUG_STACK_USAGE 674 bool "Stack utilization instrumentation" 675 depends on DEBUG_KERNEL 676 help 677 Enables the display of the minimum amount of free stack which each 678 task has ever had available in the sysrq-T and sysrq-P debug output. 679 680 This option will slow down process creation somewhat. 681 682config DEBUG_KOBJECT 683 bool "kobject debugging" 684 depends on DEBUG_KERNEL 685 help 686 If you say Y here, some extra kobject debugging messages will be sent 687 to the syslog. 688 689config DEBUG_HIGHMEM 690 bool "Highmem debugging" 691 depends on DEBUG_KERNEL && HIGHMEM 692 help 693 This options enables addition error checking for high memory systems. 694 Disable for production systems. 695 696config DEBUG_BUGVERBOSE 697 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 698 depends on BUG 699 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ 700 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 701 default y 702 help 703 Say Y here to make BUG() panics output the file name and line number 704 of the BUG call as well as the EIP and oops trace. This aids 705 debugging but costs about 70-100K of memory. 706 707config DEBUG_INFO 708 bool "Compile the kernel with debug info" 709 depends on DEBUG_KERNEL 710 help 711 If you say Y here the resulting kernel image will include 712 debugging info resulting in a larger kernel image. 713 This adds debug symbols to the kernel and modules (gcc -g), and 714 is needed if you intend to use kernel crashdump or binary object 715 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 716 Say Y here only if you plan to debug the kernel. 717 718 If unsure, say N. 719 720config DEBUG_INFO_REDUCED 721 bool "Reduce debugging information" 722 depends on DEBUG_INFO 723 help 724 If you say Y here gcc is instructed to generate less debugging 725 information for structure types. This means that tools that 726 need full debugging information (like kgdb or systemtap) won't 727 be happy. But if you merely need debugging information to 728 resolve line numbers there is no loss. Advantage is that 729 build directory object sizes shrink dramatically over a full 730 DEBUG_INFO build and compile times are reduced too. 731 Only works with newer gcc versions. 732 733config DEBUG_VM 734 bool "Debug VM" 735 depends on DEBUG_KERNEL 736 help 737 Enable this to turn on extended checks in the virtual-memory system 738 that may impact performance. 739 740 If unsure, say N. 741 742config DEBUG_VIRTUAL 743 bool "Debug VM translations" 744 depends on DEBUG_KERNEL && X86 745 help 746 Enable some costly sanity checks in virtual to page code. This can 747 catch mistakes with virt_to_page() and friends. 748 749 If unsure, say N. 750 751config DEBUG_NOMMU_REGIONS 752 bool "Debug the global anon/private NOMMU mapping region tree" 753 depends on DEBUG_KERNEL && !MMU 754 help 755 This option causes the global tree of anonymous and private mapping 756 regions to be regularly checked for invalid topology. 757 758config DEBUG_WRITECOUNT 759 bool "Debug filesystem writers count" 760 depends on DEBUG_KERNEL 761 help 762 Enable this to catch wrong use of the writers count in struct 763 vfsmount. This will increase the size of each file struct by 764 32 bits. 765 766 If unsure, say N. 767 768config DEBUG_MEMORY_INIT 769 bool "Debug memory initialisation" if EXPERT 770 default !EXPERT 771 help 772 Enable this for additional checks during memory initialisation. 773 The sanity checks verify aspects of the VM such as the memory model 774 and other information provided by the architecture. Verbose 775 information will be printed at KERN_DEBUG loglevel depending 776 on the mminit_loglevel= command-line option. 777 778 If unsure, say Y 779 780config DEBUG_LIST 781 bool "Debug linked list manipulation" 782 depends on DEBUG_KERNEL 783 help 784 Enable this to turn on extended checks in the linked-list 785 walking routines. 786 787 If unsure, say N. 788 789config TEST_LIST_SORT 790 bool "Linked list sorting test" 791 depends on DEBUG_KERNEL 792 help 793 Enable this to turn on 'list_sort()' function test. This test is 794 executed only once during system boot, so affects only boot time. 795 796 If unsure, say N. 797 798config DEBUG_SG 799 bool "Debug SG table operations" 800 depends on DEBUG_KERNEL 801 help 802 Enable this to turn on checks on scatter-gather tables. This can 803 help find problems with drivers that do not properly initialize 804 their sg tables. 805 806 If unsure, say N. 807 808config DEBUG_NOTIFIERS 809 bool "Debug notifier call chains" 810 depends on DEBUG_KERNEL 811 help 812 Enable this to turn on sanity checking for notifier call chains. 813 This is most useful for kernel developers to make sure that 814 modules properly unregister themselves from notifier chains. 815 This is a relatively cheap check but if you care about maximum 816 performance, say N. 817 818config DEBUG_CREDENTIALS 819 bool "Debug credential management" 820 depends on DEBUG_KERNEL 821 help 822 Enable this to turn on some debug checking for credential 823 management. The additional code keeps track of the number of 824 pointers from task_structs to any given cred struct, and checks to 825 see that this number never exceeds the usage count of the cred 826 struct. 827 828 Furthermore, if SELinux is enabled, this also checks that the 829 security pointer in the cred struct is never seen to be invalid. 830 831 If unsure, say N. 832 833# 834# Select this config option from the architecture Kconfig, if it 835# it is preferred to always offer frame pointers as a config 836# option on the architecture (regardless of KERNEL_DEBUG): 837# 838config ARCH_WANT_FRAME_POINTERS 839 bool 840 help 841 842config FRAME_POINTER 843 bool "Compile the kernel with frame pointers" 844 depends on DEBUG_KERNEL && \ 845 (CRIS || M68K || FRV || UML || \ 846 AVR32 || SUPERH || BLACKFIN || MN10300) || \ 847 ARCH_WANT_FRAME_POINTERS 848 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 849 help 850 If you say Y here the resulting kernel image will be slightly 851 larger and slower, but it gives very useful debugging information 852 in case of kernel bugs. (precise oopses/stacktraces/warnings) 853 854config BOOT_PRINTK_DELAY 855 bool "Delay each boot printk message by N milliseconds" 856 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 857 help 858 This build option allows you to read kernel boot messages 859 by inserting a short delay after each one. The delay is 860 specified in milliseconds on the kernel command line, 861 using "boot_delay=N". 862 863 It is likely that you would also need to use "lpj=M" to preset 864 the "loops per jiffie" value. 865 See a previous boot log for the "lpj" value to use for your 866 system, and then set "lpj=M" before setting "boot_delay=N". 867 NOTE: Using this option may adversely affect SMP systems. 868 I.e., processors other than the first one may not boot up. 869 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect 870 what it believes to be lockup conditions. 871 872config RCU_TORTURE_TEST 873 tristate "torture tests for RCU" 874 depends on DEBUG_KERNEL 875 default n 876 help 877 This option provides a kernel module that runs torture tests 878 on the RCU infrastructure. The kernel module may be built 879 after the fact on the running kernel to be tested, if desired. 880 881 Say Y here if you want RCU torture tests to be built into 882 the kernel. 883 Say M if you want the RCU torture tests to build as a module. 884 Say N if you are unsure. 885 886config RCU_TORTURE_TEST_RUNNABLE 887 bool "torture tests for RCU runnable by default" 888 depends on RCU_TORTURE_TEST = y 889 default n 890 help 891 This option provides a way to build the RCU torture tests 892 directly into the kernel without them starting up at boot 893 time. You can use /proc/sys/kernel/rcutorture_runnable 894 to manually override this setting. This /proc file is 895 available only when the RCU torture tests have been built 896 into the kernel. 897 898 Say Y here if you want the RCU torture tests to start during 899 boot (you probably don't). 900 Say N here if you want the RCU torture tests to start only 901 after being manually enabled via /proc. 902 903config RCU_CPU_STALL_TIMEOUT 904 int "RCU CPU stall timeout in seconds" 905 depends on TREE_RCU || TREE_PREEMPT_RCU 906 range 3 300 907 default 60 908 help 909 If a given RCU grace period extends more than the specified 910 number of seconds, a CPU stall warning is printed. If the 911 RCU grace period persists, additional CPU stall warnings are 912 printed at more widely spaced intervals. 913 914config RCU_CPU_STALL_VERBOSE 915 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" 916 depends on TREE_PREEMPT_RCU 917 default y 918 help 919 This option causes RCU to printk detailed per-task information 920 for any tasks that are stalling the current RCU grace period. 921 922 Say N if you are unsure. 923 924 Say Y if you want to enable such checks. 925 926config KPROBES_SANITY_TEST 927 bool "Kprobes sanity tests" 928 depends on DEBUG_KERNEL 929 depends on KPROBES 930 default n 931 help 932 This option provides for testing basic kprobes functionality on 933 boot. A sample kprobe, jprobe and kretprobe are inserted and 934 verified for functionality. 935 936 Say N if you are unsure. 937 938config BACKTRACE_SELF_TEST 939 tristate "Self test for the backtrace code" 940 depends on DEBUG_KERNEL 941 default n 942 help 943 This option provides a kernel module that can be used to test 944 the kernel stack backtrace code. This option is not useful 945 for distributions or general kernels, but only for kernel 946 developers working on architecture code. 947 948 Note that if you want to also test saved backtraces, you will 949 have to enable STACKTRACE as well. 950 951 Say N if you are unsure. 952 953config DEBUG_BLOCK_EXT_DEVT 954 bool "Force extended block device numbers and spread them" 955 depends on DEBUG_KERNEL 956 depends on BLOCK 957 default n 958 help 959 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 960 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 961 YOU ARE DOING. Distros, please enable this and fix whatever 962 is broken. 963 964 Conventionally, block device numbers are allocated from 965 predetermined contiguous area. However, extended block area 966 may introduce non-contiguous block device numbers. This 967 option forces most block device numbers to be allocated from 968 the extended space and spreads them to discover kernel or 969 userland code paths which assume predetermined contiguous 970 device number allocation. 971 972 Note that turning on this debug option shuffles all the 973 device numbers for all IDE and SCSI devices including libata 974 ones, so root partition specified using device number 975 directly (via rdev or root=MAJ:MIN) won't work anymore. 976 Textual device names (root=/dev/sdXn) will continue to work. 977 978 Say N if you are unsure. 979 980config DEBUG_FORCE_WEAK_PER_CPU 981 bool "Force weak per-cpu definitions" 982 depends on DEBUG_KERNEL 983 help 984 s390 and alpha require percpu variables in modules to be 985 defined weak to work around addressing range issue which 986 puts the following two restrictions on percpu variable 987 definitions. 988 989 1. percpu symbols must be unique whether static or not 990 2. percpu variables can't be defined inside a function 991 992 To ensure that generic code follows the above rules, this 993 option forces all percpu variables to be defined as weak. 994 995config DEBUG_PER_CPU_MAPS 996 bool "Debug access to per_cpu maps" 997 depends on DEBUG_KERNEL 998 depends on SMP 999 help 1000 Say Y to verify that the per_cpu map being accessed has 1001 been set up. This adds a fair amount of code to kernel memory 1002 and decreases performance. 1003 1004 Say N if unsure. 1005 1006config LKDTM 1007 tristate "Linux Kernel Dump Test Tool Module" 1008 depends on DEBUG_FS 1009 depends on BLOCK 1010 default n 1011 help 1012 This module enables testing of the different dumping mechanisms by 1013 inducing system failures at predefined crash points. 1014 If you don't need it: say N 1015 Choose M here to compile this code as a module. The module will be 1016 called lkdtm. 1017 1018 Documentation on how to use the module can be found in 1019 Documentation/fault-injection/provoke-crashes.txt 1020 1021config CPU_NOTIFIER_ERROR_INJECT 1022 tristate "CPU notifier error injection module" 1023 depends on HOTPLUG_CPU && DEBUG_KERNEL 1024 help 1025 This option provides a kernel module that can be used to test 1026 the error handling of the cpu notifiers 1027 1028 To compile this code as a module, choose M here: the module will 1029 be called cpu-notifier-error-inject. 1030 1031 If unsure, say N. 1032 1033config FAULT_INJECTION 1034 bool "Fault-injection framework" 1035 depends on DEBUG_KERNEL 1036 help 1037 Provide fault-injection framework. 1038 For more details, see Documentation/fault-injection/. 1039 1040config FAILSLAB 1041 bool "Fault-injection capability for kmalloc" 1042 depends on FAULT_INJECTION 1043 depends on SLAB || SLUB 1044 help 1045 Provide fault-injection capability for kmalloc. 1046 1047config FAIL_PAGE_ALLOC 1048 bool "Fault-injection capabilitiy for alloc_pages()" 1049 depends on FAULT_INJECTION 1050 help 1051 Provide fault-injection capability for alloc_pages(). 1052 1053config FAIL_MAKE_REQUEST 1054 bool "Fault-injection capability for disk IO" 1055 depends on FAULT_INJECTION && BLOCK 1056 help 1057 Provide fault-injection capability for disk IO. 1058 1059config FAIL_IO_TIMEOUT 1060 bool "Fault-injection capability for faking disk interrupts" 1061 depends on FAULT_INJECTION && BLOCK 1062 help 1063 Provide fault-injection capability on end IO handling. This 1064 will make the block layer "forget" an interrupt as configured, 1065 thus exercising the error handling. 1066 1067 Only works with drivers that use the generic timeout handling, 1068 for others it wont do anything. 1069 1070config FAULT_INJECTION_DEBUG_FS 1071 bool "Debugfs entries for fault-injection capabilities" 1072 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1073 help 1074 Enable configuration of fault-injection capabilities via debugfs. 1075 1076config FAULT_INJECTION_STACKTRACE_FILTER 1077 bool "stacktrace filter for fault-injection capabilities" 1078 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1079 depends on !X86_64 1080 select STACKTRACE 1081 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE 1082 help 1083 Provide stacktrace filter for fault-injection capabilities 1084 1085config LATENCYTOP 1086 bool "Latency measuring infrastructure" 1087 depends on HAVE_LATENCYTOP_SUPPORT 1088 depends on DEBUG_KERNEL 1089 depends on STACKTRACE_SUPPORT 1090 depends on PROC_FS 1091 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE 1092 select KALLSYMS 1093 select KALLSYMS_ALL 1094 select STACKTRACE 1095 select SCHEDSTATS 1096 select SCHED_DEBUG 1097 help 1098 Enable this option if you want to use the LatencyTOP tool 1099 to find out which userspace is blocking on what kernel operations. 1100 1101config SYSCTL_SYSCALL_CHECK 1102 bool "Sysctl checks" 1103 depends on SYSCTL 1104 ---help--- 1105 sys_sysctl uses binary paths that have been found challenging 1106 to properly maintain and use. This enables checks that help 1107 you to keep things correct. 1108 1109source mm/Kconfig.debug 1110source kernel/trace/Kconfig 1111 1112config PROVIDE_OHCI1394_DMA_INIT 1113 bool "Remote debugging over FireWire early on boot" 1114 depends on PCI && X86 1115 help 1116 If you want to debug problems which hang or crash the kernel early 1117 on boot and the crashing machine has a FireWire port, you can use 1118 this feature to remotely access the memory of the crashed machine 1119 over FireWire. This employs remote DMA as part of the OHCI1394 1120 specification which is now the standard for FireWire controllers. 1121 1122 With remote DMA, you can monitor the printk buffer remotely using 1123 firescope and access all memory below 4GB using fireproxy from gdb. 1124 Even controlling a kernel debugger is possible using remote DMA. 1125 1126 Usage: 1127 1128 If ohci1394_dma=early is used as boot parameter, it will initialize 1129 all OHCI1394 controllers which are found in the PCI config space. 1130 1131 As all changes to the FireWire bus such as enabling and disabling 1132 devices cause a bus reset and thereby disable remote DMA for all 1133 devices, be sure to have the cable plugged and FireWire enabled on 1134 the debugging host before booting the debug target for debugging. 1135 1136 This code (~1k) is freed after boot. By then, the firewire stack 1137 in charge of the OHCI-1394 controllers should be used instead. 1138 1139 See Documentation/debugging-via-ohci1394.txt for more information. 1140 1141config FIREWIRE_OHCI_REMOTE_DMA 1142 bool "Remote debugging over FireWire with firewire-ohci" 1143 depends on FIREWIRE_OHCI 1144 help 1145 This option lets you use the FireWire bus for remote debugging 1146 with help of the firewire-ohci driver. It enables unfiltered 1147 remote DMA in firewire-ohci. 1148 See Documentation/debugging-via-ohci1394.txt for more information. 1149 1150 If unsure, say N. 1151 1152config BUILD_DOCSRC 1153 bool "Build targets in Documentation/ tree" 1154 depends on HEADERS_CHECK 1155 help 1156 This option attempts to build objects from the source files in the 1157 kernel Documentation/ tree. 1158 1159 Say N if you are unsure. 1160 1161config DYNAMIC_DEBUG 1162 bool "Enable dynamic printk() support" 1163 default n 1164 depends on PRINTK 1165 depends on DEBUG_FS 1166 help 1167 1168 Compiles debug level messages into the kernel, which would not 1169 otherwise be available at runtime. These messages can then be 1170 enabled/disabled based on various levels of scope - per source file, 1171 function, module, format string, and line number. This mechanism 1172 implicitly enables all pr_debug() and dev_dbg() calls. The impact of 1173 this compile option is a larger kernel text size of about 2%. 1174 1175 Usage: 1176 1177 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 1178 which is contained in the 'debugfs' filesystem. Thus, the debugfs 1179 filesystem must first be mounted before making use of this feature. 1180 We refer the control file as: <debugfs>/dynamic_debug/control. This 1181 file contains a list of the debug statements that can be enabled. The 1182 format for each line of the file is: 1183 1184 filename:lineno [module]function flags format 1185 1186 filename : source file of the debug statement 1187 lineno : line number of the debug statement 1188 module : module that contains the debug statement 1189 function : function that contains the debug statement 1190 flags : 'p' means the line is turned 'on' for printing 1191 format : the format used for the debug statement 1192 1193 From a live system: 1194 1195 nullarbor:~ # cat <debugfs>/dynamic_debug/control 1196 # filename:lineno [module]function flags format 1197 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012" 1198 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012" 1199 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012" 1200 1201 Example usage: 1202 1203 // enable the message at line 1603 of file svcsock.c 1204 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 1205 <debugfs>/dynamic_debug/control 1206 1207 // enable all the messages in file svcsock.c 1208 nullarbor:~ # echo -n 'file svcsock.c +p' > 1209 <debugfs>/dynamic_debug/control 1210 1211 // enable all the messages in the NFS server module 1212 nullarbor:~ # echo -n 'module nfsd +p' > 1213 <debugfs>/dynamic_debug/control 1214 1215 // enable all 12 messages in the function svc_process() 1216 nullarbor:~ # echo -n 'func svc_process +p' > 1217 <debugfs>/dynamic_debug/control 1218 1219 // disable all 12 messages in the function svc_process() 1220 nullarbor:~ # echo -n 'func svc_process -p' > 1221 <debugfs>/dynamic_debug/control 1222 1223 See Documentation/dynamic-debug-howto.txt for additional information. 1224 1225config DMA_API_DEBUG 1226 bool "Enable debugging of DMA-API usage" 1227 depends on HAVE_DMA_API_DEBUG 1228 help 1229 Enable this option to debug the use of the DMA API by device drivers. 1230 With this option you will be able to detect common bugs in device 1231 drivers like double-freeing of DMA mappings or freeing mappings that 1232 were never allocated. 1233 This option causes a performance degredation. Use only if you want 1234 to debug device drivers. If unsure, say N. 1235 1236config ATOMIC64_SELFTEST 1237 bool "Perform an atomic64_t self-test at boot" 1238 help 1239 Enable this option to test the atomic64_t functions at boot. 1240 1241 If unsure, say N. 1242 1243config ASYNC_RAID6_TEST 1244 tristate "Self test for hardware accelerated raid6 recovery" 1245 depends on ASYNC_RAID6_RECOV 1246 select ASYNC_MEMCPY 1247 ---help--- 1248 This is a one-shot self test that permutes through the 1249 recovery of all the possible two disk failure scenarios for a 1250 N-disk array. Recovery is performed with the asynchronous 1251 raid6 recovery routines, and will optionally use an offload 1252 engine if one is available. 1253 1254 If unsure, say N. 1255 1256source "samples/Kconfig" 1257 1258source "lib/Kconfig.kgdb" 1259 1260source "lib/Kconfig.kmemcheck" 1261 1262config TEST_KSTRTOX 1263 tristate "Test kstrto*() family of functions at runtime" 1264