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 BOOTPARAM_HUNG_TASK_PANIC 242 bool "Panic (Reboot) On Hung Tasks" 243 depends on DETECT_HUNG_TASK 244 help 245 Say Y here to enable the kernel to panic on "hung tasks", 246 which are bugs that cause the kernel to leave a task stuck 247 in uninterruptible "D" state. 248 249 The panic can be used in combination with panic_timeout, 250 to cause the system to reboot automatically after a 251 hung task has been detected. This feature is useful for 252 high-availability systems that have uptime guarantees and 253 where a hung tasks must be resolved ASAP. 254 255 Say N if unsure. 256 257config BOOTPARAM_HUNG_TASK_PANIC_VALUE 258 int 259 depends on DETECT_HUNG_TASK 260 range 0 1 261 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 262 default 1 if BOOTPARAM_HUNG_TASK_PANIC 263 264config SCHED_DEBUG 265 bool "Collect scheduler debugging info" 266 depends on DEBUG_KERNEL && PROC_FS 267 default y 268 help 269 If you say Y here, the /proc/sched_debug file will be provided 270 that can help debug the scheduler. The runtime overhead of this 271 option is minimal. 272 273config SCHEDSTATS 274 bool "Collect scheduler statistics" 275 depends on DEBUG_KERNEL && PROC_FS 276 help 277 If you say Y here, additional code will be inserted into the 278 scheduler and related routines to collect statistics about 279 scheduler behavior and provide them in /proc/schedstat. These 280 stats may be useful for both tuning and debugging the scheduler 281 If you aren't debugging the scheduler or trying to tune a specific 282 application, you can say N to avoid the very slight overhead 283 this adds. 284 285config TIMER_STATS 286 bool "Collect kernel timers statistics" 287 depends on DEBUG_KERNEL && PROC_FS 288 help 289 If you say Y here, additional code will be inserted into the 290 timer routines to collect statistics about kernel timers being 291 reprogrammed. The statistics can be read from /proc/timer_stats. 292 The statistics collection is started by writing 1 to /proc/timer_stats, 293 writing 0 stops it. This feature is useful to collect information 294 about timer usage patterns in kernel and userspace. This feature 295 is lightweight if enabled in the kernel config but not activated 296 (it defaults to deactivated on bootup and will only be activated 297 if some application like powertop activates it explicitly). 298 299config DEBUG_OBJECTS 300 bool "Debug object operations" 301 depends on DEBUG_KERNEL 302 help 303 If you say Y here, additional code will be inserted into the 304 kernel to track the life time of various objects and validate 305 the operations on those objects. 306 307config DEBUG_OBJECTS_SELFTEST 308 bool "Debug objects selftest" 309 depends on DEBUG_OBJECTS 310 help 311 This enables the selftest of the object debug code. 312 313config DEBUG_OBJECTS_FREE 314 bool "Debug objects in freed memory" 315 depends on DEBUG_OBJECTS 316 help 317 This enables checks whether a k/v free operation frees an area 318 which contains an object which has not been deactivated 319 properly. This can make kmalloc/kfree-intensive workloads 320 much slower. 321 322config DEBUG_OBJECTS_TIMERS 323 bool "Debug timer objects" 324 depends on DEBUG_OBJECTS 325 help 326 If you say Y here, additional code will be inserted into the 327 timer routines to track the life time of timer objects and 328 validate the timer operations. 329 330config DEBUG_OBJECTS_WORK 331 bool "Debug work objects" 332 depends on DEBUG_OBJECTS 333 help 334 If you say Y here, additional code will be inserted into the 335 work queue routines to track the life time of work objects and 336 validate the work operations. 337 338config DEBUG_OBJECTS_RCU_HEAD 339 bool "Debug RCU callbacks objects" 340 depends on DEBUG_OBJECTS && PREEMPT 341 help 342 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 343 344config DEBUG_OBJECTS_PERCPU_COUNTER 345 bool "Debug percpu counter objects" 346 depends on DEBUG_OBJECTS 347 help 348 If you say Y here, additional code will be inserted into the 349 percpu counter routines to track the life time of percpu counter 350 objects and validate the percpu counter operations. 351 352config DEBUG_OBJECTS_ENABLE_DEFAULT 353 int "debug_objects bootup default value (0-1)" 354 range 0 1 355 default "1" 356 depends on DEBUG_OBJECTS 357 help 358 Debug objects boot parameter default value 359 360config DEBUG_SLAB 361 bool "Debug slab memory allocations" 362 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 363 help 364 Say Y here to have the kernel do limited verification on memory 365 allocation as well as poisoning memory on free to catch use of freed 366 memory. This can make kmalloc/kfree-intensive workloads much slower. 367 368config DEBUG_SLAB_LEAK 369 bool "Memory leak debugging" 370 depends on DEBUG_SLAB 371 372config SLUB_DEBUG_ON 373 bool "SLUB debugging on by default" 374 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 375 default n 376 help 377 Boot with debugging on by default. SLUB boots by default with 378 the runtime debug capabilities switched off. Enabling this is 379 equivalent to specifying the "slub_debug" parameter on boot. 380 There is no support for more fine grained debug control like 381 possible with slub_debug=xxx. SLUB debugging may be switched 382 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 383 "slub_debug=-". 384 385config SLUB_STATS 386 default n 387 bool "Enable SLUB performance statistics" 388 depends on SLUB && SYSFS 389 help 390 SLUB statistics are useful to debug SLUBs allocation behavior in 391 order find ways to optimize the allocator. This should never be 392 enabled for production use since keeping statistics slows down 393 the allocator by a few percentage points. The slabinfo command 394 supports the determination of the most active slabs to figure 395 out which slabs are relevant to a particular load. 396 Try running: slabinfo -DA 397 398config DEBUG_KMEMLEAK 399 bool "Kernel memory leak detector" 400 depends on DEBUG_KERNEL && EXPERIMENTAL && !MEMORY_HOTPLUG && \ 401 (X86 || ARM || PPC || S390 || SPARC64 || SUPERH || MICROBLAZE || TILE) 402 403 select DEBUG_FS if SYSFS 404 select STACKTRACE if STACKTRACE_SUPPORT 405 select KALLSYMS 406 select CRC32 407 help 408 Say Y here if you want to enable the memory leak 409 detector. The memory allocation/freeing is traced in a way 410 similar to the Boehm's conservative garbage collector, the 411 difference being that the orphan objects are not freed but 412 only shown in /sys/kernel/debug/kmemleak. Enabling this 413 feature will introduce an overhead to memory 414 allocations. See Documentation/kmemleak.txt for more 415 details. 416 417 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 418 of finding leaks due to the slab objects poisoning. 419 420 In order to access the kmemleak file, debugfs needs to be 421 mounted (usually at /sys/kernel/debug). 422 423config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 424 int "Maximum kmemleak early log entries" 425 depends on DEBUG_KMEMLEAK 426 range 200 40000 427 default 400 428 help 429 Kmemleak must track all the memory allocations to avoid 430 reporting false positives. Since memory may be allocated or 431 freed before kmemleak is initialised, an early log buffer is 432 used to store these actions. If kmemleak reports "early log 433 buffer exceeded", please increase this value. 434 435config DEBUG_KMEMLEAK_TEST 436 tristate "Simple test for the kernel memory leak detector" 437 depends on DEBUG_KMEMLEAK && m 438 help 439 This option enables a module that explicitly leaks memory. 440 441 If unsure, say N. 442 443config DEBUG_KMEMLEAK_DEFAULT_OFF 444 bool "Default kmemleak to off" 445 depends on DEBUG_KMEMLEAK 446 help 447 Say Y here to disable kmemleak by default. It can then be enabled 448 on the command line via kmemleak=on. 449 450config DEBUG_PREEMPT 451 bool "Debug preemptible kernel" 452 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 453 default y 454 help 455 If you say Y here then the kernel will use a debug variant of the 456 commonly used smp_processor_id() function and will print warnings 457 if kernel code uses it in a preemption-unsafe way. Also, the kernel 458 will detect preemption count underflows. 459 460config DEBUG_RT_MUTEXES 461 bool "RT Mutex debugging, deadlock detection" 462 depends on DEBUG_KERNEL && RT_MUTEXES 463 help 464 This allows rt mutex semantics violations and rt mutex related 465 deadlocks (lockups) to be detected and reported automatically. 466 467config DEBUG_PI_LIST 468 bool 469 default y 470 depends on DEBUG_RT_MUTEXES 471 472config RT_MUTEX_TESTER 473 bool "Built-in scriptable tester for rt-mutexes" 474 depends on DEBUG_KERNEL && RT_MUTEXES 475 help 476 This option enables a rt-mutex tester. 477 478config DEBUG_SPINLOCK 479 bool "Spinlock and rw-lock debugging: basic checks" 480 depends on DEBUG_KERNEL 481 help 482 Say Y here and build SMP to catch missing spinlock initialization 483 and certain other kinds of spinlock errors commonly made. This is 484 best used in conjunction with the NMI watchdog so that spinlock 485 deadlocks are also debuggable. 486 487config DEBUG_MUTEXES 488 bool "Mutex debugging: basic checks" 489 depends on DEBUG_KERNEL 490 help 491 This feature allows mutex semantics violations to be detected and 492 reported. 493 494config DEBUG_LOCK_ALLOC 495 bool "Lock debugging: detect incorrect freeing of live locks" 496 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 497 select DEBUG_SPINLOCK 498 select DEBUG_MUTEXES 499 select LOCKDEP 500 help 501 This feature will check whether any held lock (spinlock, rwlock, 502 mutex or rwsem) is incorrectly freed by the kernel, via any of the 503 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 504 vfree(), etc.), whether a live lock is incorrectly reinitialized via 505 spin_lock_init()/mutex_init()/etc., or whether there is any lock 506 held during task exit. 507 508config PROVE_LOCKING 509 bool "Lock debugging: prove locking correctness" 510 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 511 select LOCKDEP 512 select DEBUG_SPINLOCK 513 select DEBUG_MUTEXES 514 select DEBUG_LOCK_ALLOC 515 select TRACE_IRQFLAGS 516 default n 517 help 518 This feature enables the kernel to prove that all locking 519 that occurs in the kernel runtime is mathematically 520 correct: that under no circumstance could an arbitrary (and 521 not yet triggered) combination of observed locking 522 sequences (on an arbitrary number of CPUs, running an 523 arbitrary number of tasks and interrupt contexts) cause a 524 deadlock. 525 526 In short, this feature enables the kernel to report locking 527 related deadlocks before they actually occur. 528 529 The proof does not depend on how hard and complex a 530 deadlock scenario would be to trigger: how many 531 participant CPUs, tasks and irq-contexts would be needed 532 for it to trigger. The proof also does not depend on 533 timing: if a race and a resulting deadlock is possible 534 theoretically (no matter how unlikely the race scenario 535 is), it will be proven so and will immediately be 536 reported by the kernel (once the event is observed that 537 makes the deadlock theoretically possible). 538 539 If a deadlock is impossible (i.e. the locking rules, as 540 observed by the kernel, are mathematically correct), the 541 kernel reports nothing. 542 543 NOTE: this feature can also be enabled for rwlocks, mutexes 544 and rwsems - in which case all dependencies between these 545 different locking variants are observed and mapped too, and 546 the proof of observed correctness is also maintained for an 547 arbitrary combination of these separate locking variants. 548 549 For more details, see Documentation/lockdep-design.txt. 550 551config PROVE_RCU 552 bool "RCU debugging: prove RCU correctness" 553 depends on PROVE_LOCKING 554 default n 555 help 556 This feature enables lockdep extensions that check for correct 557 use of RCU APIs. This is currently under development. Say Y 558 if you want to debug RCU usage or help work on the PROVE_RCU 559 feature. 560 561 Say N if you are unsure. 562 563config PROVE_RCU_REPEATEDLY 564 bool "RCU debugging: don't disable PROVE_RCU on first splat" 565 depends on PROVE_RCU 566 default n 567 help 568 By itself, PROVE_RCU will disable checking upon issuing the 569 first warning (or "splat"). This feature prevents such 570 disabling, allowing multiple RCU-lockdep warnings to be printed 571 on a single reboot. 572 573 Say Y to allow multiple RCU-lockdep warnings per boot. 574 575 Say N if you are unsure. 576 577config SPARSE_RCU_POINTER 578 bool "RCU debugging: sparse-based checks for pointer usage" 579 default n 580 help 581 This feature enables the __rcu sparse annotation for 582 RCU-protected pointers. This annotation will cause sparse 583 to flag any non-RCU used of annotated pointers. This can be 584 helpful when debugging RCU usage. Please note that this feature 585 is not intended to enforce code cleanliness; it is instead merely 586 a debugging aid. 587 588 Say Y to make sparse flag questionable use of RCU-protected pointers 589 590 Say N if you are unsure. 591 592config LOCKDEP 593 bool 594 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 595 select STACKTRACE 596 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE 597 select KALLSYMS 598 select KALLSYMS_ALL 599 600config LOCK_STAT 601 bool "Lock usage statistics" 602 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 603 select LOCKDEP 604 select DEBUG_SPINLOCK 605 select DEBUG_MUTEXES 606 select DEBUG_LOCK_ALLOC 607 default n 608 help 609 This feature enables tracking lock contention points 610 611 For more details, see Documentation/lockstat.txt 612 613 This also enables lock events required by "perf lock", 614 subcommand of perf. 615 If you want to use "perf lock", you also need to turn on 616 CONFIG_EVENT_TRACING. 617 618 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 619 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 620 621config DEBUG_LOCKDEP 622 bool "Lock dependency engine debugging" 623 depends on DEBUG_KERNEL && LOCKDEP 624 help 625 If you say Y here, the lock dependency engine will do 626 additional runtime checks to debug itself, at the price 627 of more runtime overhead. 628 629config TRACE_IRQFLAGS 630 bool 631 help 632 Enables hooks to interrupt enabling and disabling for 633 either tracing or lock debugging. 634 635config DEBUG_SPINLOCK_SLEEP 636 bool "Spinlock debugging: sleep-inside-spinlock checking" 637 depends on DEBUG_KERNEL 638 help 639 If you say Y here, various routines which may sleep will become very 640 noisy if they are called with a spinlock held. 641 642config DEBUG_LOCKING_API_SELFTESTS 643 bool "Locking API boot-time self-tests" 644 depends on DEBUG_KERNEL 645 help 646 Say Y here if you want the kernel to run a short self-test during 647 bootup. The self-test checks whether common types of locking bugs 648 are detected by debugging mechanisms or not. (if you disable 649 lock debugging then those bugs wont be detected of course.) 650 The following locking APIs are covered: spinlocks, rwlocks, 651 mutexes and rwsems. 652 653config STACKTRACE 654 bool 655 depends on STACKTRACE_SUPPORT 656 657config DEBUG_KOBJECT 658 bool "kobject debugging" 659 depends on DEBUG_KERNEL 660 help 661 If you say Y here, some extra kobject debugging messages will be sent 662 to the syslog. 663 664config DEBUG_HIGHMEM 665 bool "Highmem debugging" 666 depends on DEBUG_KERNEL && HIGHMEM 667 help 668 This options enables addition error checking for high memory systems. 669 Disable for production systems. 670 671config DEBUG_BUGVERBOSE 672 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 673 depends on BUG 674 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ 675 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 676 default y 677 help 678 Say Y here to make BUG() panics output the file name and line number 679 of the BUG call as well as the EIP and oops trace. This aids 680 debugging but costs about 70-100K of memory. 681 682config DEBUG_INFO 683 bool "Compile the kernel with debug info" 684 depends on DEBUG_KERNEL 685 help 686 If you say Y here the resulting kernel image will include 687 debugging info resulting in a larger kernel image. 688 This adds debug symbols to the kernel and modules (gcc -g), and 689 is needed if you intend to use kernel crashdump or binary object 690 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 691 Say Y here only if you plan to debug the kernel. 692 693 If unsure, say N. 694 695config DEBUG_INFO_REDUCED 696 bool "Reduce debugging information" 697 depends on DEBUG_INFO 698 help 699 If you say Y here gcc is instructed to generate less debugging 700 information for structure types. This means that tools that 701 need full debugging information (like kgdb or systemtap) won't 702 be happy. But if you merely need debugging information to 703 resolve line numbers there is no loss. Advantage is that 704 build directory object sizes shrink dramatically over a full 705 DEBUG_INFO build and compile times are reduced too. 706 Only works with newer gcc versions. 707 708config DEBUG_VM 709 bool "Debug VM" 710 depends on DEBUG_KERNEL 711 help 712 Enable this to turn on extended checks in the virtual-memory system 713 that may impact performance. 714 715 If unsure, say N. 716 717config DEBUG_VIRTUAL 718 bool "Debug VM translations" 719 depends on DEBUG_KERNEL && X86 720 help 721 Enable some costly sanity checks in virtual to page code. This can 722 catch mistakes with virt_to_page() and friends. 723 724 If unsure, say N. 725 726config DEBUG_NOMMU_REGIONS 727 bool "Debug the global anon/private NOMMU mapping region tree" 728 depends on DEBUG_KERNEL && !MMU 729 help 730 This option causes the global tree of anonymous and private mapping 731 regions to be regularly checked for invalid topology. 732 733config DEBUG_WRITECOUNT 734 bool "Debug filesystem writers count" 735 depends on DEBUG_KERNEL 736 help 737 Enable this to catch wrong use of the writers count in struct 738 vfsmount. This will increase the size of each file struct by 739 32 bits. 740 741 If unsure, say N. 742 743config DEBUG_MEMORY_INIT 744 bool "Debug memory initialisation" if EXPERT 745 default !EXPERT 746 help 747 Enable this for additional checks during memory initialisation. 748 The sanity checks verify aspects of the VM such as the memory model 749 and other information provided by the architecture. Verbose 750 information will be printed at KERN_DEBUG loglevel depending 751 on the mminit_loglevel= command-line option. 752 753 If unsure, say Y 754 755config DEBUG_LIST 756 bool "Debug linked list manipulation" 757 depends on DEBUG_KERNEL 758 help 759 Enable this to turn on extended checks in the linked-list 760 walking routines. 761 762 If unsure, say N. 763 764config TEST_LIST_SORT 765 bool "Linked list sorting test" 766 depends on DEBUG_KERNEL 767 help 768 Enable this to turn on 'list_sort()' function test. This test is 769 executed only once during system boot, so affects only boot time. 770 771 If unsure, say N. 772 773config DEBUG_SG 774 bool "Debug SG table operations" 775 depends on DEBUG_KERNEL 776 help 777 Enable this to turn on checks on scatter-gather tables. This can 778 help find problems with drivers that do not properly initialize 779 their sg tables. 780 781 If unsure, say N. 782 783config DEBUG_NOTIFIERS 784 bool "Debug notifier call chains" 785 depends on DEBUG_KERNEL 786 help 787 Enable this to turn on sanity checking for notifier call chains. 788 This is most useful for kernel developers to make sure that 789 modules properly unregister themselves from notifier chains. 790 This is a relatively cheap check but if you care about maximum 791 performance, say N. 792 793config DEBUG_CREDENTIALS 794 bool "Debug credential management" 795 depends on DEBUG_KERNEL 796 help 797 Enable this to turn on some debug checking for credential 798 management. The additional code keeps track of the number of 799 pointers from task_structs to any given cred struct, and checks to 800 see that this number never exceeds the usage count of the cred 801 struct. 802 803 Furthermore, if SELinux is enabled, this also checks that the 804 security pointer in the cred struct is never seen to be invalid. 805 806 If unsure, say N. 807 808# 809# Select this config option from the architecture Kconfig, if it 810# it is preferred to always offer frame pointers as a config 811# option on the architecture (regardless of KERNEL_DEBUG): 812# 813config ARCH_WANT_FRAME_POINTERS 814 bool 815 help 816 817config FRAME_POINTER 818 bool "Compile the kernel with frame pointers" 819 depends on DEBUG_KERNEL && \ 820 (CRIS || M68K || FRV || UML || \ 821 AVR32 || SUPERH || BLACKFIN || MN10300) || \ 822 ARCH_WANT_FRAME_POINTERS 823 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 824 help 825 If you say Y here the resulting kernel image will be slightly 826 larger and slower, but it gives very useful debugging information 827 in case of kernel bugs. (precise oopses/stacktraces/warnings) 828 829config BOOT_PRINTK_DELAY 830 bool "Delay each boot printk message by N milliseconds" 831 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 832 help 833 This build option allows you to read kernel boot messages 834 by inserting a short delay after each one. The delay is 835 specified in milliseconds on the kernel command line, 836 using "boot_delay=N". 837 838 It is likely that you would also need to use "lpj=M" to preset 839 the "loops per jiffie" value. 840 See a previous boot log for the "lpj" value to use for your 841 system, and then set "lpj=M" before setting "boot_delay=N". 842 NOTE: Using this option may adversely affect SMP systems. 843 I.e., processors other than the first one may not boot up. 844 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect 845 what it believes to be lockup conditions. 846 847config RCU_TORTURE_TEST 848 tristate "torture tests for RCU" 849 depends on DEBUG_KERNEL 850 default n 851 help 852 This option provides a kernel module that runs torture tests 853 on the RCU infrastructure. The kernel module may be built 854 after the fact on the running kernel to be tested, if desired. 855 856 Say Y here if you want RCU torture tests to be built into 857 the kernel. 858 Say M if you want the RCU torture tests to build as a module. 859 Say N if you are unsure. 860 861config RCU_TORTURE_TEST_RUNNABLE 862 bool "torture tests for RCU runnable by default" 863 depends on RCU_TORTURE_TEST = y 864 default n 865 help 866 This option provides a way to build the RCU torture tests 867 directly into the kernel without them starting up at boot 868 time. You can use /proc/sys/kernel/rcutorture_runnable 869 to manually override this setting. This /proc file is 870 available only when the RCU torture tests have been built 871 into the kernel. 872 873 Say Y here if you want the RCU torture tests to start during 874 boot (you probably don't). 875 Say N here if you want the RCU torture tests to start only 876 after being manually enabled via /proc. 877 878config RCU_CPU_STALL_DETECTOR 879 bool "Check for stalled CPUs delaying RCU grace periods" 880 depends on TREE_RCU || TREE_PREEMPT_RCU 881 default y 882 help 883 This option causes RCU to printk information on which 884 CPUs are delaying the current grace period, but only when 885 the grace period extends for excessive time periods. 886 887 Say N if you want to disable such checks. 888 889 Say Y if you are unsure. 890 891config RCU_CPU_STALL_TIMEOUT 892 int "RCU CPU stall timeout in seconds" 893 depends on RCU_CPU_STALL_DETECTOR 894 range 3 300 895 default 60 896 help 897 If a given RCU grace period extends more than the specified 898 number of seconds, a CPU stall warning is printed. If the 899 RCU grace period persists, additional CPU stall warnings are 900 printed at more widely spaced intervals. 901 902config RCU_CPU_STALL_DETECTOR_RUNNABLE 903 bool "RCU CPU stall checking starts automatically at boot" 904 depends on RCU_CPU_STALL_DETECTOR 905 default y 906 help 907 If set, start checking for RCU CPU stalls immediately on 908 boot. Otherwise, RCU CPU stall checking must be manually 909 enabled. 910 911 Say Y if you are unsure. 912 913 Say N if you wish to suppress RCU CPU stall checking during boot. 914 915config RCU_CPU_STALL_VERBOSE 916 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" 917 depends on RCU_CPU_STALL_DETECTOR && TREE_PREEMPT_RCU 918 default y 919 help 920 This option causes RCU to printk detailed per-task information 921 for any tasks that are stalling the current RCU grace period. 922 923 Say N if you are unsure. 924 925 Say Y if you want to enable such checks. 926 927config KPROBES_SANITY_TEST 928 bool "Kprobes sanity tests" 929 depends on DEBUG_KERNEL 930 depends on KPROBES 931 default n 932 help 933 This option provides for testing basic kprobes functionality on 934 boot. A sample kprobe, jprobe and kretprobe are inserted and 935 verified for functionality. 936 937 Say N if you are unsure. 938 939config BACKTRACE_SELF_TEST 940 tristate "Self test for the backtrace code" 941 depends on DEBUG_KERNEL 942 default n 943 help 944 This option provides a kernel module that can be used to test 945 the kernel stack backtrace code. This option is not useful 946 for distributions or general kernels, but only for kernel 947 developers working on architecture code. 948 949 Note that if you want to also test saved backtraces, you will 950 have to enable STACKTRACE as well. 951 952 Say N if you are unsure. 953 954config DEBUG_BLOCK_EXT_DEVT 955 bool "Force extended block device numbers and spread them" 956 depends on DEBUG_KERNEL 957 depends on BLOCK 958 default n 959 help 960 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 961 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 962 YOU ARE DOING. Distros, please enable this and fix whatever 963 is broken. 964 965 Conventionally, block device numbers are allocated from 966 predetermined contiguous area. However, extended block area 967 may introduce non-contiguous block device numbers. This 968 option forces most block device numbers to be allocated from 969 the extended space and spreads them to discover kernel or 970 userland code paths which assume predetermined contiguous 971 device number allocation. 972 973 Note that turning on this debug option shuffles all the 974 device numbers for all IDE and SCSI devices including libata 975 ones, so root partition specified using device number 976 directly (via rdev or root=MAJ:MIN) won't work anymore. 977 Textual device names (root=/dev/sdXn) will continue to work. 978 979 Say N if you are unsure. 980 981config DEBUG_FORCE_WEAK_PER_CPU 982 bool "Force weak per-cpu definitions" 983 depends on DEBUG_KERNEL 984 help 985 s390 and alpha require percpu variables in modules to be 986 defined weak to work around addressing range issue which 987 puts the following two restrictions on percpu variable 988 definitions. 989 990 1. percpu symbols must be unique whether static or not 991 2. percpu variables can't be defined inside a function 992 993 To ensure that generic code follows the above rules, this 994 option forces all percpu variables to be defined as weak. 995 996config LKDTM 997 tristate "Linux Kernel Dump Test Tool Module" 998 depends on DEBUG_FS 999 depends on BLOCK 1000 default n
1001 help 1002 This module enables testing of the different dumping mechanisms by 1003 inducing system failures at predefined crash points. 1004 If you don't need it: say N 1005 Choose M here to compile this code as a module. The module will be 1006 called lkdtm. 1007 1008 Documentation on how to use the module can be found in 1009 Documentation/fault-injection/provoke-crashes.txt 1010 1011config CPU_NOTIFIER_ERROR_INJECT 1012 tristate "CPU notifier error injection module" 1013 depends on HOTPLUG_CPU && DEBUG_KERNEL 1014 help 1015 This option provides a kernel module that can be used to test 1016 the error handling of the cpu notifiers 1017 1018 To compile this code as a module, choose M here: the module will 1019 be called cpu-notifier-error-inject. 1020 1021 If unsure, say N. 1022 1023config FAULT_INJECTION 1024 bool "Fault-injection framework" 1025 depends on DEBUG_KERNEL 1026 help 1027 Provide fault-injection framework. 1028 For more details, see Documentation/fault-injection/. 1029 1030config FAILSLAB 1031 bool "Fault-injection capability for kmalloc" 1032 depends on FAULT_INJECTION 1033 depends on SLAB || SLUB 1034 help 1035 Provide fault-injection capability for kmalloc. 1036 1037config FAIL_PAGE_ALLOC 1038 bool "Fault-injection capabilitiy for alloc_pages()" 1039 depends on FAULT_INJECTION 1040 help 1041 Provide fault-injection capability for alloc_pages(). 1042 1043config FAIL_MAKE_REQUEST 1044 bool "Fault-injection capability for disk IO" 1045 depends on FAULT_INJECTION && BLOCK 1046 help 1047 Provide fault-injection capability for disk IO. 1048 1049config FAIL_IO_TIMEOUT 1050 bool "Fault-injection capability for faking disk interrupts" 1051 depends on FAULT_INJECTION && BLOCK 1052 help 1053 Provide fault-injection capability on end IO handling. This 1054 will make the block layer "forget" an interrupt as configured, 1055 thus exercising the error handling. 1056 1057 Only works with drivers that use the generic timeout handling, 1058 for others it wont do anything. 1059 1060config FAULT_INJECTION_DEBUG_FS 1061 bool "Debugfs entries for fault-injection capabilities" 1062 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1063 help 1064 Enable configuration of fault-injection capabilities via debugfs. 1065 1066config FAULT_INJECTION_STACKTRACE_FILTER 1067 bool "stacktrace filter for fault-injection capabilities" 1068 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1069 depends on !X86_64 1070 select STACKTRACE 1071 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE 1072 help 1073 Provide stacktrace filter for fault-injection capabilities 1074 1075config LATENCYTOP 1076 bool "Latency measuring infrastructure" 1077 depends on HAVE_LATENCYTOP_SUPPORT 1078 depends on DEBUG_KERNEL 1079 depends on STACKTRACE_SUPPORT 1080 depends on PROC_FS 1081 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE 1082 select KALLSYMS 1083 select KALLSYMS_ALL 1084 select STACKTRACE 1085 select SCHEDSTATS 1086 select SCHED_DEBUG 1087 help 1088 Enable this option if you want to use the LatencyTOP tool 1089 to find out which userspace is blocking on what kernel operations. 1090 1091config SYSCTL_SYSCALL_CHECK 1092 bool "Sysctl checks" 1093 depends on SYSCTL 1094 ---help--- 1095 sys_sysctl uses binary paths that have been found challenging 1096 to properly maintain and use. This enables checks that help 1097 you to keep things correct. 1098 1099source mm/Kconfig.debug 1100source kernel/trace/Kconfig 1101 1102config PROVIDE_OHCI1394_DMA_INIT 1103 bool "Remote debugging over FireWire early on boot" 1104 depends on PCI && X86 1105 help 1106 If you want to debug problems which hang or crash the kernel early 1107 on boot and the crashing machine has a FireWire port, you can use 1108 this feature to remotely access the memory of the crashed machine 1109 over FireWire. This employs remote DMA as part of the OHCI1394 1110 specification which is now the standard for FireWire controllers. 1111 1112 With remote DMA, you can monitor the printk buffer remotely using 1113 firescope and access all memory below 4GB using fireproxy from gdb. 1114 Even controlling a kernel debugger is possible using remote DMA. 1115 1116 Usage: 1117 1118 If ohci1394_dma=early is used as boot parameter, it will initialize 1119 all OHCI1394 controllers which are found in the PCI config space. 1120 1121 As all changes to the FireWire bus such as enabling and disabling 1122 devices cause a bus reset and thereby disable remote DMA for all 1123 devices, be sure to have the cable plugged and FireWire enabled on 1124 the debugging host before booting the debug target for debugging. 1125 1126 This code (~1k) is freed after boot. By then, the firewire stack 1127 in charge of the OHCI-1394 controllers should be used instead. 1128 1129 See Documentation/debugging-via-ohci1394.txt for more information. 1130 1131config FIREWIRE_OHCI_REMOTE_DMA 1132 bool "Remote debugging over FireWire with firewire-ohci" 1133 depends on FIREWIRE_OHCI 1134 help 1135 This option lets you use the FireWire bus for remote debugging 1136 with help of the firewire-ohci driver. It enables unfiltered 1137 remote DMA in firewire-ohci. 1138 See Documentation/debugging-via-ohci1394.txt for more information. 1139 1140 If unsure, say N. 1141 1142config BUILD_DOCSRC 1143 bool "Build targets in Documentation/ tree" 1144 depends on HEADERS_CHECK 1145 help 1146 This option attempts to build objects from the source files in the 1147 kernel Documentation/ tree. 1148 1149 Say N if you are unsure. 1150 1151config DYNAMIC_DEBUG 1152 bool "Enable dynamic printk() support" 1153 default n 1154 depends on PRINTK 1155 depends on DEBUG_FS 1156 help 1157 1158 Compiles debug level messages into the kernel, which would not 1159 otherwise be available at runtime. These messages can then be 1160 enabled/disabled based on various levels of scope - per source file, 1161 function, module, format string, and line number. This mechanism 1162 implicitly enables all pr_debug() and dev_dbg() calls. The impact of 1163 this compile option is a larger kernel text size of about 2%. 1164 1165 Usage: 1166 1167 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 1168 which is contained in the 'debugfs' filesystem. Thus, the debugfs 1169 filesystem must first be mounted before making use of this feature. 1170 We refer the control file as: <debugfs>/dynamic_debug/control. This 1171 file contains a list of the debug statements that can be enabled. The 1172 format for each line of the file is: 1173 1174 filename:lineno [module]function flags format 1175 1176 filename : source file of the debug statement 1177 lineno : line number of the debug statement 1178 module : module that contains the debug statement 1179 function : function that contains the debug statement 1180 flags : 'p' means the line is turned 'on' for printing 1181 format : the format used for the debug statement 1182 1183 From a live system: 1184 1185 nullarbor:~ # cat <debugfs>/dynamic_debug/control 1186 # filename:lineno [module]function flags format 1187 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012" 1188 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012" 1189 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012" 1190 1191 Example usage: 1192 1193 // enable the message at line 1603 of file svcsock.c 1194 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 1195 <debugfs>/dynamic_debug/control 1196 1197 // enable all the messages in file svcsock.c 1198 nullarbor:~ # echo -n 'file svcsock.c +p' > 1199 <debugfs>/dynamic_debug/control 1200 1201 // enable all the messages in the NFS server module 1202 nullarbor:~ # echo -n 'module nfsd +p' > 1203 <debugfs>/dynamic_debug/control 1204 1205 // enable all 12 messages in the function svc_process() 1206 nullarbor:~ # echo -n 'func svc_process +p' > 1207 <debugfs>/dynamic_debug/control 1208 1209 // disable all 12 messages in the function svc_process() 1210 nullarbor:~ # echo -n 'func svc_process -p' > 1211 <debugfs>/dynamic_debug/control 1212 1213 See Documentation/dynamic-debug-howto.txt for additional information. 1214 1215config DMA_API_DEBUG 1216 bool "Enable debugging of DMA-API usage" 1217 depends on HAVE_DMA_API_DEBUG 1218 help 1219 Enable this option to debug the use of the DMA API by device drivers. 1220 With this option you will be able to detect common bugs in device 1221 drivers like double-freeing of DMA mappings or freeing mappings that 1222 were never allocated. 1223 This option causes a performance degredation. Use only if you want 1224 to debug device drivers. If unsure, say N. 1225 1226config ATOMIC64_SELFTEST 1227 bool "Perform an atomic64_t self-test at boot" 1228 help 1229 Enable this option to test the atomic64_t functions at boot. 1230 1231 If unsure, say N. 1232 1233config ASYNC_RAID6_TEST 1234 tristate "Self test for hardware accelerated raid6 recovery" 1235 depends on ASYNC_RAID6_RECOV 1236 select ASYNC_MEMCPY 1237 ---help--- 1238 This is a one-shot self test that permutes through the 1239 recovery of all the possible two disk failure scenarios for a 1240 N-disk array. Recovery is performed with the asynchronous 1241 raid6 recovery routines, and will optionally use an offload 1242 engine if one is available. 1243 1244 If unsure, say N. 1245 1246source "samples/Kconfig" 1247 1248source "lib/Kconfig.kgdb" 1249 1250source "lib/Kconfig.kmemcheck" 1251 1252config TEST_KSTRTOX 1253 tristate "Test kstrto*() family of functions at runtime" 1254