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 438 help 439 Say Y or M here to build a test for the kernel memory leak 440 detector. This option enables a module that explicitly leaks 441 memory. 442 443 If unsure, say N. 444 445config DEBUG_KMEMLEAK_DEFAULT_OFF 446 bool "Default kmemleak to off" 447 depends on DEBUG_KMEMLEAK 448 help 449 Say Y here to disable kmemleak by default. It can then be enabled 450 on the command line via kmemleak=on. 451 452config DEBUG_PREEMPT 453 bool "Debug preemptible kernel" 454 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 455 default y 456 help 457 If you say Y here then the kernel will use a debug variant of the 458 commonly used smp_processor_id() function and will print warnings 459 if kernel code uses it in a preemption-unsafe way. Also, the kernel 460 will detect preemption count underflows. 461 462config DEBUG_RT_MUTEXES 463 bool "RT Mutex debugging, deadlock detection" 464 depends on DEBUG_KERNEL && RT_MUTEXES 465 help 466 This allows rt mutex semantics violations and rt mutex related 467 deadlocks (lockups) to be detected and reported automatically. 468 469config DEBUG_PI_LIST 470 bool 471 default y 472 depends on DEBUG_RT_MUTEXES 473 474config RT_MUTEX_TESTER 475 bool "Built-in scriptable tester for rt-mutexes" 476 depends on DEBUG_KERNEL && RT_MUTEXES 477 help 478 This option enables a rt-mutex tester. 479 480config DEBUG_SPINLOCK 481 bool "Spinlock and rw-lock debugging: basic checks" 482 depends on DEBUG_KERNEL 483 help 484 Say Y here and build SMP to catch missing spinlock initialization 485 and certain other kinds of spinlock errors commonly made. This is 486 best used in conjunction with the NMI watchdog so that spinlock 487 deadlocks are also debuggable. 488 489config DEBUG_MUTEXES 490 bool "Mutex debugging: basic checks" 491 depends on DEBUG_KERNEL 492 help 493 This feature allows mutex semantics violations to be detected and 494 reported. 495 496config DEBUG_LOCK_ALLOC 497 bool "Lock debugging: detect incorrect freeing of live locks" 498 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 499 select DEBUG_SPINLOCK 500 select DEBUG_MUTEXES 501 select LOCKDEP 502 help 503 This feature will check whether any held lock (spinlock, rwlock, 504 mutex or rwsem) is incorrectly freed by the kernel, via any of the 505 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 506 vfree(), etc.), whether a live lock is incorrectly reinitialized via 507 spin_lock_init()/mutex_init()/etc., or whether there is any lock 508 held during task exit. 509 510config PROVE_LOCKING 511 bool "Lock debugging: prove locking correctness" 512 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 513 select LOCKDEP 514 select DEBUG_SPINLOCK 515 select DEBUG_MUTEXES 516 select DEBUG_LOCK_ALLOC 517 select TRACE_IRQFLAGS 518 default n 519 help 520 This feature enables the kernel to prove that all locking 521 that occurs in the kernel runtime is mathematically 522 correct: that under no circumstance could an arbitrary (and 523 not yet triggered) combination of observed locking 524 sequences (on an arbitrary number of CPUs, running an 525 arbitrary number of tasks and interrupt contexts) cause a 526 deadlock. 527 528 In short, this feature enables the kernel to report locking 529 related deadlocks before they actually occur. 530 531 The proof does not depend on how hard and complex a 532 deadlock scenario would be to trigger: how many 533 participant CPUs, tasks and irq-contexts would be needed 534 for it to trigger. The proof also does not depend on 535 timing: if a race and a resulting deadlock is possible 536 theoretically (no matter how unlikely the race scenario 537 is), it will be proven so and will immediately be 538 reported by the kernel (once the event is observed that 539 makes the deadlock theoretically possible). 540 541 If a deadlock is impossible (i.e. the locking rules, as 542 observed by the kernel, are mathematically correct), the 543 kernel reports nothing. 544 545 NOTE: this feature can also be enabled for rwlocks, mutexes 546 and rwsems - in which case all dependencies between these 547 different locking variants are observed and mapped too, and 548 the proof of observed correctness is also maintained for an 549 arbitrary combination of these separate locking variants. 550 551 For more details, see Documentation/lockdep-design.txt. 552 553config PROVE_RCU 554 bool "RCU debugging: prove RCU correctness" 555 depends on PROVE_LOCKING 556 default n 557 help 558 This feature enables lockdep extensions that check for correct 559 use of RCU APIs. This is currently under development. Say Y 560 if you want to debug RCU usage or help work on the PROVE_RCU 561 feature. 562 563 Say N if you are unsure. 564 565config PROVE_RCU_REPEATEDLY 566 bool "RCU debugging: don't disable PROVE_RCU on first splat" 567 depends on PROVE_RCU 568 default n 569 help 570 By itself, PROVE_RCU will disable checking upon issuing the 571 first warning (or "splat"). This feature prevents such 572 disabling, allowing multiple RCU-lockdep warnings to be printed 573 on a single reboot. 574 575 Say Y to allow multiple RCU-lockdep warnings per boot. 576 577 Say N if you are unsure. 578 579config SPARSE_RCU_POINTER 580 bool "RCU debugging: sparse-based checks for pointer usage" 581 default n 582 help 583 This feature enables the __rcu sparse annotation for 584 RCU-protected pointers. This annotation will cause sparse 585 to flag any non-RCU used of annotated pointers. This can be 586 helpful when debugging RCU usage. Please note that this feature 587 is not intended to enforce code cleanliness; it is instead merely 588 a debugging aid. 589 590 Say Y to make sparse flag questionable use of RCU-protected pointers 591 592 Say N if you are unsure. 593 594config LOCKDEP 595 bool 596 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 597 select STACKTRACE 598 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE 599 select KALLSYMS 600 select KALLSYMS_ALL 601 602config LOCK_STAT 603 bool "Lock usage statistics" 604 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 605 select LOCKDEP 606 select DEBUG_SPINLOCK 607 select DEBUG_MUTEXES 608 select DEBUG_LOCK_ALLOC 609 default n 610 help 611 This feature enables tracking lock contention points 612 613 For more details, see Documentation/lockstat.txt 614 615 This also enables lock events required by "perf lock", 616 subcommand of perf. 617 If you want to use "perf lock", you also need to turn on 618 CONFIG_EVENT_TRACING. 619 620 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 621 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 622 623config DEBUG_LOCKDEP 624 bool "Lock dependency engine debugging" 625 depends on DEBUG_KERNEL && LOCKDEP 626 help 627 If you say Y here, the lock dependency engine will do 628 additional runtime checks to debug itself, at the price 629 of more runtime overhead. 630 631config TRACE_IRQFLAGS 632 bool 633 help 634 Enables hooks to interrupt enabling and disabling for 635 either tracing or lock debugging. 636 637config DEBUG_SPINLOCK_SLEEP 638 bool "Spinlock debugging: sleep-inside-spinlock checking" 639 depends on DEBUG_KERNEL 640 help 641 If you say Y here, various routines which may sleep will become very 642 noisy if they are called with a spinlock held. 643 644config DEBUG_LOCKING_API_SELFTESTS 645 bool "Locking API boot-time self-tests" 646 depends on DEBUG_KERNEL 647 help 648 Say Y here if you want the kernel to run a short self-test during 649 bootup. The self-test checks whether common types of locking bugs 650 are detected by debugging mechanisms or not. (if you disable 651 lock debugging then those bugs wont be detected of course.) 652 The following locking APIs are covered: spinlocks, rwlocks, 653 mutexes and rwsems. 654 655config STACKTRACE 656 bool 657 depends on STACKTRACE_SUPPORT 658 659config DEBUG_KOBJECT 660 bool "kobject debugging" 661 depends on DEBUG_KERNEL 662 help 663 If you say Y here, some extra kobject debugging messages will be sent 664 to the syslog. 665 666config DEBUG_HIGHMEM 667 bool "Highmem debugging" 668 depends on DEBUG_KERNEL && HIGHMEM 669 help 670 This options enables addition error checking for high memory systems. 671 Disable for production systems. 672 673config DEBUG_BUGVERBOSE 674 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 675 depends on BUG 676 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ 677 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 678 default y 679 help 680 Say Y here to make BUG() panics output the file name and line number 681 of the BUG call as well as the EIP and oops trace. This aids 682 debugging but costs about 70-100K of memory. 683 684config DEBUG_INFO 685 bool "Compile the kernel with debug info" 686 depends on DEBUG_KERNEL 687 help 688 If you say Y here the resulting kernel image will include 689 debugging info resulting in a larger kernel image. 690 This adds debug symbols to the kernel and modules (gcc -g), and 691 is needed if you intend to use kernel crashdump or binary object 692 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 693 Say Y here only if you plan to debug the kernel. 694 695 If unsure, say N. 696 697config DEBUG_INFO_REDUCED 698 bool "Reduce debugging information" 699 depends on DEBUG_INFO 700 help 701 If you say Y here gcc is instructed to generate less debugging 702 information for structure types. This means that tools that 703 need full debugging information (like kgdb or systemtap) won't 704 be happy. But if you merely need debugging information to 705 resolve line numbers there is no loss. Advantage is that 706 build directory object sizes shrink dramatically over a full 707 DEBUG_INFO build and compile times are reduced too. 708 Only works with newer gcc versions. 709 710config DEBUG_VM 711 bool "Debug VM" 712 depends on DEBUG_KERNEL 713 help 714 Enable this to turn on extended checks in the virtual-memory system 715 that may impact performance. 716 717 If unsure, say N. 718 719config DEBUG_VIRTUAL 720 bool "Debug VM translations" 721 depends on DEBUG_KERNEL && X86 722 help 723 Enable some costly sanity checks in virtual to page code. This can 724 catch mistakes with virt_to_page() and friends. 725 726 If unsure, say N. 727 728config DEBUG_NOMMU_REGIONS 729 bool "Debug the global anon/private NOMMU mapping region tree" 730 depends on DEBUG_KERNEL && !MMU 731 help 732 This option causes the global tree of anonymous and private mapping 733 regions to be regularly checked for invalid topology. 734 735config DEBUG_WRITECOUNT 736 bool "Debug filesystem writers count" 737 depends on DEBUG_KERNEL 738 help 739 Enable this to catch wrong use of the writers count in struct 740 vfsmount. This will increase the size of each file struct by 741 32 bits. 742 743 If unsure, say N. 744 745config DEBUG_MEMORY_INIT 746 bool "Debug memory initialisation" if EXPERT 747 default !EXPERT 748 help 749 Enable this for additional checks during memory initialisation. 750 The sanity checks verify aspects of the VM such as the memory model 751 and other information provided by the architecture. Verbose 752 information will be printed at KERN_DEBUG loglevel depending 753 on the mminit_loglevel= command-line option. 754 755 If unsure, say Y 756 757config DEBUG_LIST 758 bool "Debug linked list manipulation" 759 depends on DEBUG_KERNEL 760 help 761 Enable this to turn on extended checks in the linked-list 762 walking routines. 763 764 If unsure, say N. 765 766config TEST_LIST_SORT 767 bool "Linked list sorting test" 768 depends on DEBUG_KERNEL 769 help 770 Enable this to turn on 'list_sort()' function test. This test is 771 executed only once during system boot, so affects only boot time. 772 773 If unsure, say N. 774 775config DEBUG_SG 776 bool "Debug SG table operations" 777 depends on DEBUG_KERNEL 778 help 779 Enable this to turn on checks on scatter-gather tables. This can 780 help find problems with drivers that do not properly initialize 781 their sg tables. 782 783 If unsure, say N. 784 785config DEBUG_NOTIFIERS 786 bool "Debug notifier call chains" 787 depends on DEBUG_KERNEL 788 help 789 Enable this to turn on sanity checking for notifier call chains. 790 This is most useful for kernel developers to make sure that 791 modules properly unregister themselves from notifier chains. 792 This is a relatively cheap check but if you care about maximum 793 performance, say N. 794 795config DEBUG_CREDENTIALS 796 bool "Debug credential management" 797 depends on DEBUG_KERNEL 798 help 799 Enable this to turn on some debug checking for credential 800 management. The additional code keeps track of the number of 801 pointers from task_structs to any given cred struct, and checks to 802 see that this number never exceeds the usage count of the cred 803 struct. 804 805 Furthermore, if SELinux is enabled, this also checks that the 806 security pointer in the cred struct is never seen to be invalid. 807 808 If unsure, say N. 809 810# 811# Select this config option from the architecture Kconfig, if it 812# it is preferred to always offer frame pointers as a config 813# option on the architecture (regardless of KERNEL_DEBUG): 814# 815config ARCH_WANT_FRAME_POINTERS 816 bool 817 help 818 819config FRAME_POINTER 820 bool "Compile the kernel with frame pointers" 821 depends on DEBUG_KERNEL && \ 822 (CRIS || M68K || FRV || UML || \ 823 AVR32 || SUPERH || BLACKFIN || MN10300) || \ 824 ARCH_WANT_FRAME_POINTERS 825 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 826 help 827 If you say Y here the resulting kernel image will be slightly 828 larger and slower, but it gives very useful debugging information 829 in case of kernel bugs. (precise oopses/stacktraces/warnings) 830 831config BOOT_PRINTK_DELAY 832 bool "Delay each boot printk message by N milliseconds" 833 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 834 help 835 This build option allows you to read kernel boot messages 836 by inserting a short delay after each one. The delay is 837 specified in milliseconds on the kernel command line, 838 using "boot_delay=N". 839 840 It is likely that you would also need to use "lpj=M" to preset 841 the "loops per jiffie" value. 842 See a previous boot log for the "lpj" value to use for your 843 system, and then set "lpj=M" before setting "boot_delay=N". 844 NOTE: Using this option may adversely affect SMP systems. 845 I.e., processors other than the first one may not boot up. 846 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect 847 what it believes to be lockup conditions. 848 849config RCU_TORTURE_TEST 850 tristate "torture tests for RCU" 851 depends on DEBUG_KERNEL 852 default n 853 help 854 This option provides a kernel module that runs torture tests 855 on the RCU infrastructure. The kernel module may be built 856 after the fact on the running kernel to be tested, if desired. 857 858 Say Y here if you want RCU torture tests to be built into 859 the kernel. 860 Say M if you want the RCU torture tests to build as a module. 861 Say N if you are unsure. 862 863config RCU_TORTURE_TEST_RUNNABLE 864 bool "torture tests for RCU runnable by default" 865 depends on RCU_TORTURE_TEST = y 866 default n 867 help 868 This option provides a way to build the RCU torture tests 869 directly into the kernel without them starting up at boot 870 time. You can use /proc/sys/kernel/rcutorture_runnable 871 to manually override this setting. This /proc file is 872 available only when the RCU torture tests have been built 873 into the kernel. 874 875 Say Y here if you want the RCU torture tests to start during 876 boot (you probably don't). 877 Say N here if you want the RCU torture tests to start only 878 after being manually enabled via /proc. 879 880config RCU_CPU_STALL_DETECTOR 881 bool "Check for stalled CPUs delaying RCU grace periods" 882 depends on TREE_RCU || TREE_PREEMPT_RCU 883 default y 884 help 885 This option causes RCU to printk information on which 886 CPUs are delaying the current grace period, but only when 887 the grace period extends for excessive time periods. 888 889 Say N if you want to disable such checks. 890 891 Say Y if you are unsure. 892 893config RCU_CPU_STALL_TIMEOUT 894 int "RCU CPU stall timeout in seconds" 895 depends on RCU_CPU_STALL_DETECTOR 896 range 3 300 897 default 60 898 help 899 If a given RCU grace period extends more than the specified 900 number of seconds, a CPU stall warning is printed. If the 901 RCU grace period persists, additional CPU stall warnings are 902 printed at more widely spaced intervals. 903 904config RCU_CPU_STALL_DETECTOR_RUNNABLE 905 bool "RCU CPU stall checking starts automatically at boot" 906 depends on RCU_CPU_STALL_DETECTOR 907 default y 908 help 909 If set, start checking for RCU CPU stalls immediately on 910 boot. Otherwise, RCU CPU stall checking must be manually 911 enabled. 912 913 Say Y if you are unsure. 914 915 Say N if you wish to suppress RCU CPU stall checking during boot. 916 917config RCU_CPU_STALL_VERBOSE 918 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" 919 depends on RCU_CPU_STALL_DETECTOR && TREE_PREEMPT_RCU 920 default y 921 help 922 This option causes RCU to printk detailed per-task information 923 for any tasks that are stalling the current RCU grace period. 924 925 Say N if you are unsure. 926 927 Say Y if you want to enable such checks. 928 929config KPROBES_SANITY_TEST 930 bool "Kprobes sanity tests" 931 depends on DEBUG_KERNEL 932 depends on KPROBES 933 default n 934 help 935 This option provides for testing basic kprobes functionality on 936 boot. A sample kprobe, jprobe and kretprobe are inserted and 937 verified for functionality. 938 939 Say N if you are unsure. 940 941config BACKTRACE_SELF_TEST 942 tristate "Self test for the backtrace code" 943 depends on DEBUG_KERNEL 944 default n 945 help 946 This option provides a kernel module that can be used to test 947 the kernel stack backtrace code. This option is not useful 948 for distributions or general kernels, but only for kernel 949 developers working on architecture code. 950 951 Note that if you want to also test saved backtraces, you will 952 have to enable STACKTRACE as well. 953 954 Say N if you are unsure. 955 956config DEBUG_BLOCK_EXT_DEVT 957 bool "Force extended block device numbers and spread them" 958 depends on DEBUG_KERNEL 959 depends on BLOCK 960 default n 961 help 962 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 963 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 964 YOU ARE DOING. Distros, please enable this and fix whatever 965 is broken. 966 967 Conventionally, block device numbers are allocated from 968 predetermined contiguous area. However, extended block area 969 may introduce non-contiguous block device numbers. This 970 option forces most block device numbers to be allocated from 971 the extended space and spreads them to discover kernel or 972 userland code paths which assume predetermined contiguous 973 device number allocation. 974 975 Note that turning on this debug option shuffles all the 976 device numbers for all IDE and SCSI devices including libata 977 ones, so root partition specified using device number 978 directly (via rdev or root=MAJ:MIN) won't work anymore. 979 Textual device names (root=/dev/sdXn) will continue to work. 980 981 Say N if you are unsure. 982 983config DEBUG_FORCE_WEAK_PER_CPU 984 bool "Force weak per-cpu definitions" 985 depends on DEBUG_KERNEL 986 help 987 s390 and alpha require percpu variables in modules to be 988 defined weak to work around addressing range issue which 989 puts the following two restrictions on percpu variable 990 definitions. 991 992 1. percpu symbols must be unique whether static or not 993 2. percpu variables can't be defined inside a function 994 995 To ensure that generic code follows the above rules, this 996 option forces all percpu variables to be defined as weak. 997 998config LKDTM 999 tristate "Linux Kernel Dump Test Tool Module" 1000 depends on DEBUG_FS 1001 depends on BLOCK 1002 default n 1003 help 1004 This module enables testing of the different dumping mechanisms by 1005 inducing system failures at predefined crash points. 1006 If you don't need it: say N 1007 Choose M here to compile this code as a module. The module will be 1008 called lkdtm. 1009 1010 Documentation on how to use the module can be found in 1011 Documentation/fault-injection/provoke-crashes.txt 1012 1013config CPU_NOTIFIER_ERROR_INJECT 1014 tristate "CPU notifier error injection module" 1015 depends on HOTPLUG_CPU && DEBUG_KERNEL 1016 help 1017 This option provides a kernel module that can be used to test 1018 the error handling of the cpu notifiers 1019 1020 To compile this code as a module, choose M here: the module will 1021 be called cpu-notifier-error-inject. 1022 1023 If unsure, say N. 1024 1025config FAULT_INJECTION 1026 bool "Fault-injection framework" 1027 depends on DEBUG_KERNEL 1028 help 1029 Provide fault-injection framework. 1030 For more details, see Documentation/fault-injection/. 1031 1032config FAILSLAB 1033 bool "Fault-injection capability for kmalloc" 1034 depends on FAULT_INJECTION 1035 depends on SLAB || SLUB 1036 help 1037 Provide fault-injection capability for kmalloc. 1038 1039config FAIL_PAGE_ALLOC 1040 bool "Fault-injection capabilitiy for alloc_pages()" 1041 depends on FAULT_INJECTION 1042 help 1043 Provide fault-injection capability for alloc_pages(). 1044 1045config FAIL_MAKE_REQUEST 1046 bool "Fault-injection capability for disk IO" 1047 depends on FAULT_INJECTION && BLOCK 1048 help 1049 Provide fault-injection capability for disk IO. 1050 1051config FAIL_IO_TIMEOUT 1052 bool "Fault-injection capability for faking disk interrupts" 1053 depends on FAULT_INJECTION && BLOCK 1054 help 1055 Provide fault-injection capability on end IO handling. This 1056 will make the block layer "forget" an interrupt as configured, 1057 thus exercising the error handling. 1058 1059 Only works with drivers that use the generic timeout handling, 1060 for others it wont do anything. 1061 1062config FAULT_INJECTION_DEBUG_FS 1063 bool "Debugfs entries for fault-injection capabilities" 1064 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1065 help 1066 Enable configuration of fault-injection capabilities via debugfs. 1067 1068config FAULT_INJECTION_STACKTRACE_FILTER 1069 bool "stacktrace filter for fault-injection capabilities" 1070 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1071 depends on !X86_64 1072 select STACKTRACE 1073 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE 1074 help 1075 Provide stacktrace filter for fault-injection capabilities 1076 1077config LATENCYTOP 1078 bool "Latency measuring infrastructure" 1079 depends on HAVE_LATENCYTOP_SUPPORT 1080 depends on DEBUG_KERNEL 1081 depends on STACKTRACE_SUPPORT 1082 depends on PROC_FS 1083 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE 1084 select KALLSYMS 1085 select KALLSYMS_ALL 1086 select STACKTRACE 1087 select SCHEDSTATS 1088 select SCHED_DEBUG 1089 help 1090 Enable this option if you want to use the LatencyTOP tool 1091 to find out which userspace is blocking on what kernel operations. 1092 1093config SYSCTL_SYSCALL_CHECK 1094 bool "Sysctl checks" 1095 depends on SYSCTL 1096 ---help--- 1097 sys_sysctl uses binary paths that have been found challenging 1098 to properly maintain and use. This enables checks that help 1099 you to keep things correct. 1100 1101source mm/Kconfig.debug 1102source kernel/trace/Kconfig 1103 1104config PROVIDE_OHCI1394_DMA_INIT 1105 bool "Remote debugging over FireWire early on boot" 1106 depends on PCI && X86 1107 help 1108 If you want to debug problems which hang or crash the kernel early 1109 on boot and the crashing machine has a FireWire port, you can use 1110 this feature to remotely access the memory of the crashed machine 1111 over FireWire. This employs remote DMA as part of the OHCI1394 1112 specification which is now the standard for FireWire controllers. 1113 1114 With remote DMA, you can monitor the printk buffer remotely using 1115 firescope and access all memory below 4GB using fireproxy from gdb. 1116 Even controlling a kernel debugger is possible using remote DMA. 1117 1118 Usage: 1119 1120 If ohci1394_dma=early is used as boot parameter, it will initialize 1121 all OHCI1394 controllers which are found in the PCI config space. 1122 1123 As all changes to the FireWire bus such as enabling and disabling 1124 devices cause a bus reset and thereby disable remote DMA for all 1125 devices, be sure to have the cable plugged and FireWire enabled on 1126 the debugging host before booting the debug target for debugging. 1127 1128 This code (~1k) is freed after boot. By then, the firewire stack 1129 in charge of the OHCI-1394 controllers should be used instead. 1130 1131 See Documentation/debugging-via-ohci1394.txt for more information. 1132 1133config FIREWIRE_OHCI_REMOTE_DMA 1134 bool "Remote debugging over FireWire with firewire-ohci" 1135 depends on FIREWIRE_OHCI 1136 help 1137 This option lets you use the FireWire bus for remote debugging 1138 with help of the firewire-ohci driver. It enables unfiltered 1139 remote DMA in firewire-ohci. 1140 See Documentation/debugging-via-ohci1394.txt for more information. 1141 1142 If unsure, say N. 1143 1144config BUILD_DOCSRC 1145 bool "Build targets in Documentation/ tree" 1146 depends on HEADERS_CHECK 1147 help 1148 This option attempts to build objects from the source files in the 1149 kernel Documentation/ tree. 1150 1151 Say N if you are unsure. 1152 1153config DYNAMIC_DEBUG 1154 bool "Enable dynamic printk() support" 1155 default n 1156 depends on PRINTK 1157 depends on DEBUG_FS 1158 help 1159 1160 Compiles debug level messages into the kernel, which would not 1161 otherwise be available at runtime. These messages can then be 1162 enabled/disabled based on various levels of scope - per source file, 1163 function, module, format string, and line number. This mechanism 1164 implicitly enables all pr_debug() and dev_dbg() calls. The impact of 1165 this compile option is a larger kernel text size of about 2%. 1166 1167 Usage: 1168 1169 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 1170 which is contained in the 'debugfs' filesystem. Thus, the debugfs 1171 filesystem must first be mounted before making use of this feature. 1172 We refer the control file as: <debugfs>/dynamic_debug/control. This 1173 file contains a list of the debug statements that can be enabled. The 1174 format for each line of the file is: 1175 1176 filename:lineno [module]function flags format 1177 1178 filename : source file of the debug statement 1179 lineno : line number of the debug statement 1180 module : module that contains the debug statement 1181 function : function that contains the debug statement 1182 flags : 'p' means the line is turned 'on' for printing 1183 format : the format used for the debug statement 1184 1185 From a live system: 1186 1187 nullarbor:~ # cat <debugfs>/dynamic_debug/control 1188 # filename:lineno [module]function flags format 1189 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012" 1190 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012" 1191 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012" 1192 1193 Example usage: 1194 1195 // enable the message at line 1603 of file svcsock.c 1196 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 1197 <debugfs>/dynamic_debug/control 1198 1199 // enable all the messages in file svcsock.c 1200 nullarbor:~ # echo -n 'file svcsock.c +p' > 1201 <debugfs>/dynamic_debug/control 1202 1203 // enable all the messages in the NFS server module 1204 nullarbor:~ # echo -n 'module nfsd +p' > 1205 <debugfs>/dynamic_debug/control 1206 1207 // enable all 12 messages in the function svc_process() 1208 nullarbor:~ # echo -n 'func svc_process +p' > 1209 <debugfs>/dynamic_debug/control 1210 1211 // disable all 12 messages in the function svc_process() 1212 nullarbor:~ # echo -n 'func svc_process -p' > 1213 <debugfs>/dynamic_debug/control 1214 1215 See Documentation/dynamic-debug-howto.txt for additional information. 1216 1217config DMA_API_DEBUG 1218 bool "Enable debugging of DMA-API usage" 1219 depends on HAVE_DMA_API_DEBUG 1220 help 1221 Enable this option to debug the use of the DMA API by device drivers. 1222 With this option you will be able to detect common bugs in device 1223 drivers like double-freeing of DMA mappings or freeing mappings that 1224 were never allocated. 1225 This option causes a performance degredation. Use only if you want 1226 to debug device drivers. If unsure, say N. 1227 1228config ATOMIC64_SELFTEST 1229 bool "Perform an atomic64_t self-test at boot" 1230 help 1231 Enable this option to test the atomic64_t functions at boot. 1232 1233 If unsure, say N. 1234 1235config ASYNC_RAID6_TEST 1236 tristate "Self test for hardware accelerated raid6 recovery" 1237 depends on ASYNC_RAID6_RECOV 1238 select ASYNC_MEMCPY 1239 ---help--- 1240 This is a one-shot self test that permutes through the 1241 recovery of all the possible two disk failure scenarios for a 1242 N-disk array. Recovery is performed with the asynchronous 1243 raid6 recovery routines, and will optionally use an offload 1244 engine if one is available. 1245 1246 If unsure, say N. 1247 1248source "samples/Kconfig" 1249 1250source "lib/Kconfig.kgdb" 1251 1252source "lib/Kconfig.kmemcheck" 1253 1254config TEST_KSTRTOX 1255 tristate "Test kstrto*() family of functions at runtime" 1256