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 ENABLE_WARN_DEPRECATED 13 bool "Enable __deprecated logic" 14 default y 15 help 16 Enable the __deprecated logic in the kernel build. 17 Disable this to suppress the "warning: 'foo' is deprecated 18 (declared at kernel/power/somefile.c:1234)" messages. 19 20config ENABLE_MUST_CHECK 21 bool "Enable __must_check logic" 22 default y 23 help 24 Enable the __must_check logic in the kernel build. Disable this to 25 suppress the "warning: ignoring return value of 'foo', declared with 26 attribute warn_unused_result" messages. 27 28config FRAME_WARN 29 int "Warn for stack frames larger than (needs gcc 4.4)" 30 range 0 8192 31 default 1024 if !64BIT 32 default 2048 if 64BIT 33 help 34 Tell gcc to warn at build time for stack frames larger than this. 35 Setting this too low will cause a lot of warnings. 36 Setting it to 0 disables the warning. 37 Requires gcc 4.4 38 39config MAGIC_SYSRQ 40 bool "Magic SysRq key" 41 depends on !UML 42 help 43 If you say Y here, you will have some control over the system even 44 if the system crashes for example during kernel debugging (e.g., you 45 will be able to flush the buffer cache to disk, reboot the system 46 immediately or dump some status information). This is accomplished 47 by pressing various keys while holding SysRq (Alt+PrintScreen). It 48 also works on a serial console (on PC hardware at least), if you 49 send a BREAK and then within 5 seconds a command keypress. The 50 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 51 unless you really know what this hack does. 52 53config STRIP_ASM_SYMS 54 bool "Strip assembler-generated symbols during link" 55 default n 56 help 57 Strip internal assembler-generated symbols during a link (symbols 58 that look like '.Lxxx') so they don't pollute the output of 59 get_wchan() and suchlike. 60 61config UNUSED_SYMBOLS 62 bool "Enable unused/obsolete exported symbols" 63 default y if X86 64 help 65 Unused but exported symbols make the kernel needlessly bigger. For 66 that reason most of these unused exports will soon be removed. This 67 option is provided temporarily to provide a transition period in case 68 some external kernel module needs one of these symbols anyway. If you 69 encounter such a case in your module, consider if you are actually 70 using the right API. (rationale: since nobody in the kernel is using 71 this in a module, there is a pretty good chance it's actually the 72 wrong interface to use). If you really need the symbol, please send a 73 mail to the linux kernel mailing list mentioning the symbol and why 74 you really need it, and what the merge plan to the mainline kernel for 75 your module is. 76 77config DEBUG_FS 78 bool "Debug Filesystem" 79 help 80 debugfs is a virtual file system that kernel developers use to put 81 debugging files into. Enable this option to be able to read and 82 write to these files. 83 84 For detailed documentation on the debugfs API, see 85 Documentation/DocBook/filesystems. 86 87 If unsure, say N. 88 89config HEADERS_CHECK 90 bool "Run 'make headers_check' when building vmlinux" 91 depends on !UML 92 help 93 This option will extract the user-visible kernel headers whenever 94 building the kernel, and will run basic sanity checks on them to 95 ensure that exported files do not attempt to include files which 96 were not exported, etc. 97 98 If you're making modifications to header files which are 99 relevant for userspace, say 'Y', and check the headers 100 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 101 your build tree), to make sure they're suitable. 102 103config DEBUG_SECTION_MISMATCH 104 bool "Enable full Section mismatch analysis" 105 depends on UNDEFINED || (BLACKFIN) 106 default y 107 # This option is on purpose disabled for now. 108 # It will be enabled when we are down to a reasonable number 109 # of section mismatch warnings (< 10 for an allyesconfig build) 110 help 111 The section mismatch analysis checks if there are illegal 112 references from one section to another section. 113 Linux will during link or during runtime drop some sections 114 and any use of code/data previously in these sections will 115 most likely result in an oops. 116 In the code functions and variables are annotated with 117 __init, __devinit etc. (see full list in include/linux/init.h) 118 which results in the code/data being placed in specific sections. 119 The section mismatch analysis is always done after a full 120 kernel build but enabling this option will in addition 121 do the following: 122 - Add the option -fno-inline-functions-called-once to gcc 123 When inlining a function annotated __init in a non-init 124 function we would lose the section information and thus 125 the analysis would not catch the illegal reference. 126 This option tells gcc to inline less but will also 127 result in a larger kernel. 128 - Run the section mismatch analysis for each module/built-in.o 129 When we run the section mismatch analysis on vmlinux.o we 130 lose valueble information about where the mismatch was 131 introduced. 132 Running the analysis for each module/built-in.o file 133 will tell where the mismatch happens much closer to the 134 source. The drawback is that we will report the same 135 mismatch at least twice. 136 - Enable verbose reporting from modpost to help solving 137 the section mismatches reported. 138 139config DEBUG_KERNEL 140 bool "Kernel debugging" 141 help 142 Say Y here if you are developing drivers or trying to debug and 143 identify kernel problems. 144 145config DEBUG_SHIRQ 146 bool "Debug shared IRQ handlers" 147 depends on DEBUG_KERNEL && GENERIC_HARDIRQS 148 help 149 Enable this to generate a spurious interrupt as soon as a shared 150 interrupt handler is registered, and just before one is deregistered. 151 Drivers ought to be able to handle interrupts coming in at those 152 points; some don't and need to be caught. 153 154config LOCKUP_DETECTOR 155 bool "Detect Hard and Soft Lockups" 156 depends on DEBUG_KERNEL && !S390 157 help 158 Say Y here to enable the kernel to act as a watchdog to detect 159 hard and soft lockups. 160 161 Softlockups are bugs that cause the kernel to loop in kernel 162 mode for more than 60 seconds, without giving other tasks a 163 chance to run. The current stack trace is displayed upon 164 detection and the system will stay locked up. 165 166 Hardlockups are bugs that cause the CPU to loop in kernel mode 167 for more than 60 seconds, without letting other interrupts have a 168 chance to run. The current stack trace is displayed upon detection 169 and the system will stay locked up. 170 171 The overhead should be minimal. A periodic hrtimer runs to 172 generate interrupts and kick the watchdog task every 10-12 seconds. 173 An NMI is generated every 60 seconds or so to check for hardlockups. 174 175config HARDLOCKUP_DETECTOR 176 def_bool LOCKUP_DETECTOR && PERF_EVENTS && HAVE_PERF_EVENTS_NMI && \ 177 !ARCH_HAS_NMI_WATCHDOG 178 179config BOOTPARAM_SOFTLOCKUP_PANIC 180 bool "Panic (Reboot) On Soft Lockups" 181 depends on LOCKUP_DETECTOR 182 help 183 Say Y here to enable the kernel to panic on "soft lockups", 184 which are bugs that cause the kernel to loop in kernel 185 mode for more than 60 seconds, without giving other tasks a 186 chance to run. 187 188 The panic can be used in combination with panic_timeout, 189 to cause the system to reboot automatically after a 190 lockup has been detected. This feature is useful for 191 high-availability systems that have uptime guarantees and 192 where a lockup must be resolved ASAP. 193 194 Say N if unsure. 195 196config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 197 int 198 depends on LOCKUP_DETECTOR 199 range 0 1 200 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 201 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 202 203config DETECT_HUNG_TASK 204 bool "Detect Hung Tasks" 205 depends on DEBUG_KERNEL 206 default DETECT_SOFTLOCKUP 207 help 208 Say Y here to enable the kernel to detect "hung tasks", 209 which are bugs that cause the task to be stuck in 210 uninterruptible "D" state indefinitiley. 211 212 When a hung task is detected, the kernel will print the 213 current stack trace (which you should report), but the 214 task will stay in uninterruptible state. If lockdep is 215 enabled then all held locks will also be reported. This 216 feature has negligible overhead. 217 218config BOOTPARAM_HUNG_TASK_PANIC 219 bool "Panic (Reboot) On Hung Tasks" 220 depends on DETECT_HUNG_TASK 221 help 222 Say Y here to enable the kernel to panic on "hung tasks", 223 which are bugs that cause the kernel to leave a task stuck 224 in uninterruptible "D" state. 225 226 The panic can be used in combination with panic_timeout, 227 to cause the system to reboot automatically after a 228 hung task has been detected. This feature is useful for 229 high-availability systems that have uptime guarantees and 230 where a hung tasks must be resolved ASAP. 231 232 Say N if unsure. 233 234config BOOTPARAM_HUNG_TASK_PANIC_VALUE 235 int 236 depends on DETECT_HUNG_TASK 237 range 0 1 238 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 239 default 1 if BOOTPARAM_HUNG_TASK_PANIC 240 241config SCHED_DEBUG 242 bool "Collect scheduler debugging info" 243 depends on DEBUG_KERNEL && PROC_FS 244 default y 245 help 246 If you say Y here, the /proc/sched_debug file will be provided 247 that can help debug the scheduler. The runtime overhead of this 248 option is minimal. 249 250config SCHEDSTATS 251 bool "Collect scheduler statistics" 252 depends on DEBUG_KERNEL && PROC_FS 253 help 254 If you say Y here, additional code will be inserted into the 255 scheduler and related routines to collect statistics about 256 scheduler behavior and provide them in /proc/schedstat. These 257 stats may be useful for both tuning and debugging the scheduler 258 If you aren't debugging the scheduler or trying to tune a specific 259 application, you can say N to avoid the very slight overhead 260 this adds. 261 262config TIMER_STATS 263 bool "Collect kernel timers statistics" 264 depends on DEBUG_KERNEL && PROC_FS 265 help 266 If you say Y here, additional code will be inserted into the 267 timer routines to collect statistics about kernel timers being 268 reprogrammed. The statistics can be read from /proc/timer_stats. 269 The statistics collection is started by writing 1 to /proc/timer_stats, 270 writing 0 stops it. This feature is useful to collect information 271 about timer usage patterns in kernel and userspace. This feature 272 is lightweight if enabled in the kernel config but not activated 273 (it defaults to deactivated on bootup and will only be activated 274 if some application like powertop activates it explicitly). 275 276config DEBUG_OBJECTS 277 bool "Debug object operations" 278 depends on DEBUG_KERNEL 279 help 280 If you say Y here, additional code will be inserted into the 281 kernel to track the life time of various objects and validate 282 the operations on those objects. 283 284config DEBUG_OBJECTS_SELFTEST 285 bool "Debug objects selftest" 286 depends on DEBUG_OBJECTS 287 help 288 This enables the selftest of the object debug code. 289 290config DEBUG_OBJECTS_FREE 291 bool "Debug objects in freed memory" 292 depends on DEBUG_OBJECTS 293 help 294 This enables checks whether a k/v free operation frees an area 295 which contains an object which has not been deactivated 296 properly. This can make kmalloc/kfree-intensive workloads 297 much slower. 298 299config DEBUG_OBJECTS_TIMERS 300 bool "Debug timer objects" 301 depends on DEBUG_OBJECTS 302 help 303 If you say Y here, additional code will be inserted into the 304 timer routines to track the life time of timer objects and 305 validate the timer operations. 306 307config DEBUG_OBJECTS_WORK 308 bool "Debug work objects" 309 depends on DEBUG_OBJECTS 310 help 311 If you say Y here, additional code will be inserted into the 312 work queue routines to track the life time of work objects and 313 validate the work operations. 314 315config DEBUG_OBJECTS_RCU_HEAD 316 bool "Debug RCU callbacks objects" 317 depends on DEBUG_OBJECTS && PREEMPT 318 help 319 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 320 321config DEBUG_OBJECTS_PERCPU_COUNTER 322 bool "Debug percpu counter objects" 323 depends on DEBUG_OBJECTS 324 help 325 If you say Y here, additional code will be inserted into the 326 percpu counter routines to track the life time of percpu counter 327 objects and validate the percpu counter operations. 328 329config DEBUG_OBJECTS_ENABLE_DEFAULT 330 int "debug_objects bootup default value (0-1)" 331 range 0 1 332 default "1" 333 depends on DEBUG_OBJECTS 334 help 335 Debug objects boot parameter default value 336 337config DEBUG_SLAB 338 bool "Debug slab memory allocations" 339 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 340 help 341 Say Y here to have the kernel do limited verification on memory 342 allocation as well as poisoning memory on free to catch use of freed 343 memory. This can make kmalloc/kfree-intensive workloads much slower. 344 345config DEBUG_SLAB_LEAK 346 bool "Memory leak debugging" 347 depends on DEBUG_SLAB 348 349config SLUB_DEBUG_ON 350 bool "SLUB debugging on by default" 351 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 352 default n 353 help 354 Boot with debugging on by default. SLUB boots by default with 355 the runtime debug capabilities switched off. Enabling this is 356 equivalent to specifying the "slub_debug" parameter on boot. 357 There is no support for more fine grained debug control like 358 possible with slub_debug=xxx. SLUB debugging may be switched 359 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 360 "slub_debug=-". 361 362config SLUB_STATS 363 default n 364 bool "Enable SLUB performance statistics" 365 depends on SLUB && SYSFS 366 help 367 SLUB statistics are useful to debug SLUBs allocation behavior in 368 order find ways to optimize the allocator. This should never be 369 enabled for production use since keeping statistics slows down 370 the allocator by a few percentage points. The slabinfo command 371 supports the determination of the most active slabs to figure 372 out which slabs are relevant to a particular load. 373 Try running: slabinfo -DA 374 375config DEBUG_KMEMLEAK 376 bool "Kernel memory leak detector" 377 depends on DEBUG_KERNEL && EXPERIMENTAL && !MEMORY_HOTPLUG && \ 378 (X86 || ARM || PPC || S390 || SPARC64 || SUPERH || MICROBLAZE || TILE) 379 380 select DEBUG_FS if SYSFS 381 select STACKTRACE if STACKTRACE_SUPPORT 382 select KALLSYMS 383 select CRC32 384 help 385 Say Y here if you want to enable the memory leak 386 detector. The memory allocation/freeing is traced in a way 387 similar to the Boehm's conservative garbage collector, the 388 difference being that the orphan objects are not freed but 389 only shown in /sys/kernel/debug/kmemleak. Enabling this 390 feature will introduce an overhead to memory 391 allocations. See Documentation/kmemleak.txt for more 392 details. 393 394 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 395 of finding leaks due to the slab objects poisoning. 396 397 In order to access the kmemleak file, debugfs needs to be 398 mounted (usually at /sys/kernel/debug). 399 400config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 401 int "Maximum kmemleak early log entries" 402 depends on DEBUG_KMEMLEAK 403 range 200 40000 404 default 400 405 help 406 Kmemleak must track all the memory allocations to avoid 407 reporting false positives. Since memory may be allocated or 408 freed before kmemleak is initialised, an early log buffer is 409 used to store these actions. If kmemleak reports "early log 410 buffer exceeded", please increase this value. 411 412config DEBUG_KMEMLEAK_TEST 413 tristate "Simple test for the kernel memory leak detector" 414 depends on DEBUG_KMEMLEAK 415 help 416 Say Y or M here to build a test for the kernel memory leak 417 detector. This option enables a module that explicitly leaks 418 memory. 419 420 If unsure, say N. 421 422config DEBUG_KMEMLEAK_DEFAULT_OFF 423 bool "Default kmemleak to off" 424 depends on DEBUG_KMEMLEAK 425 help 426 Say Y here to disable kmemleak by default. It can then be enabled 427 on the command line via kmemleak=on. 428 429config DEBUG_PREEMPT 430 bool "Debug preemptible kernel" 431 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 432 default y 433 help 434 If you say Y here then the kernel will use a debug variant of the 435 commonly used smp_processor_id() function and will print warnings 436 if kernel code uses it in a preemption-unsafe way. Also, the kernel 437 will detect preemption count underflows. 438 439config DEBUG_RT_MUTEXES 440 bool "RT Mutex debugging, deadlock detection" 441 depends on DEBUG_KERNEL && RT_MUTEXES 442 help 443 This allows rt mutex semantics violations and rt mutex related 444 deadlocks (lockups) to be detected and reported automatically. 445 446config DEBUG_PI_LIST 447 bool 448 default y 449 depends on DEBUG_RT_MUTEXES 450 451config RT_MUTEX_TESTER 452 bool "Built-in scriptable tester for rt-mutexes" 453 depends on DEBUG_KERNEL && RT_MUTEXES 454 help 455 This option enables a rt-mutex tester. 456 457config DEBUG_SPINLOCK 458 bool "Spinlock and rw-lock debugging: basic checks" 459 depends on DEBUG_KERNEL 460 help 461 Say Y here and build SMP to catch missing spinlock initialization 462 and certain other kinds of spinlock errors commonly made. This is 463 best used in conjunction with the NMI watchdog so that spinlock 464 deadlocks are also debuggable. 465 466config DEBUG_MUTEXES 467 bool "Mutex debugging: basic checks" 468 depends on DEBUG_KERNEL 469 help 470 This feature allows mutex semantics violations to be detected and 471 reported. 472 473config BKL 474 bool "Big Kernel Lock" if (SMP || PREEMPT) 475 default y 476 help 477 This is the traditional lock that is used in old code instead 478 of proper locking. All drivers that use the BKL should depend 479 on this symbol. 480 Say Y here unless you are working on removing the BKL. 481 482config DEBUG_LOCK_ALLOC 483 bool "Lock debugging: detect incorrect freeing of live locks" 484 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 485 select DEBUG_SPINLOCK 486 select DEBUG_MUTEXES 487 select LOCKDEP 488 help 489 This feature will check whether any held lock (spinlock, rwlock, 490 mutex or rwsem) is incorrectly freed by the kernel, via any of the 491 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 492 vfree(), etc.), whether a live lock is incorrectly reinitialized via 493 spin_lock_init()/mutex_init()/etc., or whether there is any lock 494 held during task exit. 495 496config PROVE_LOCKING 497 bool "Lock debugging: prove locking correctness" 498 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 499 select LOCKDEP 500 select DEBUG_SPINLOCK 501 select DEBUG_MUTEXES 502 select DEBUG_LOCK_ALLOC 503 select TRACE_IRQFLAGS 504 default n 505 help 506 This feature enables the kernel to prove that all locking 507 that occurs in the kernel runtime is mathematically 508 correct: that under no circumstance could an arbitrary (and 509 not yet triggered) combination of observed locking 510 sequences (on an arbitrary number of CPUs, running an 511 arbitrary number of tasks and interrupt contexts) cause a 512 deadlock. 513 514 In short, this feature enables the kernel to report locking 515 related deadlocks before they actually occur. 516 517 The proof does not depend on how hard and complex a 518 deadlock scenario would be to trigger: how many 519 participant CPUs, tasks and irq-contexts would be needed 520 for it to trigger. The proof also does not depend on 521 timing: if a race and a resulting deadlock is possible 522 theoretically (no matter how unlikely the race scenario 523 is), it will be proven so and will immediately be 524 reported by the kernel (once the event is observed that 525 makes the deadlock theoretically possible). 526 527 If a deadlock is impossible (i.e. the locking rules, as 528 observed by the kernel, are mathematically correct), the 529 kernel reports nothing. 530 531 NOTE: this feature can also be enabled for rwlocks, mutexes 532 and rwsems - in which case all dependencies between these 533 different locking variants are observed and mapped too, and 534 the proof of observed correctness is also maintained for an 535 arbitrary combination of these separate locking variants. 536 537 For more details, see Documentation/lockdep-design.txt. 538 539config PROVE_RCU 540 bool "RCU debugging: prove RCU correctness" 541 depends on PROVE_LOCKING 542 default n 543 help 544 This feature enables lockdep extensions that check for correct 545 use of RCU APIs. This is currently under development. Say Y 546 if you want to debug RCU usage or help work on the PROVE_RCU 547 feature. 548 549 Say N if you are unsure. 550 551config PROVE_RCU_REPEATEDLY 552 bool "RCU debugging: don't disable PROVE_RCU on first splat" 553 depends on PROVE_RCU 554 default n 555 help 556 By itself, PROVE_RCU will disable checking upon issuing the 557 first warning (or "splat"). This feature prevents such 558 disabling, allowing multiple RCU-lockdep warnings to be printed 559 on a single reboot. 560 561 Say Y to allow multiple RCU-lockdep warnings per boot. 562 563 Say N if you are unsure. 564 565config SPARSE_RCU_POINTER 566 bool "RCU debugging: sparse-based checks for pointer usage" 567 default n 568 help 569 This feature enables the __rcu sparse annotation for 570 RCU-protected pointers. This annotation will cause sparse 571 to flag any non-RCU used of annotated pointers. This can be 572 helpful when debugging RCU usage. Please note that this feature 573 is not intended to enforce code cleanliness; it is instead merely 574 a debugging aid. 575 576 Say Y to make sparse flag questionable use of RCU-protected pointers 577 578 Say N if you are unsure. 579 580config LOCKDEP 581 bool 582 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 583 select STACKTRACE 584 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE 585 select KALLSYMS 586 select KALLSYMS_ALL 587 588config LOCK_STAT 589 bool "Lock usage statistics" 590 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 591 select LOCKDEP 592 select DEBUG_SPINLOCK 593 select DEBUG_MUTEXES 594 select DEBUG_LOCK_ALLOC 595 default n 596 help 597 This feature enables tracking lock contention points 598 599 For more details, see Documentation/lockstat.txt 600 601 This also enables lock events required by "perf lock", 602 subcommand of perf. 603 If you want to use "perf lock", you also need to turn on 604 CONFIG_EVENT_TRACING. 605 606 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 607 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 608 609config DEBUG_LOCKDEP 610 bool "Lock dependency engine debugging" 611 depends on DEBUG_KERNEL && LOCKDEP 612 help 613 If you say Y here, the lock dependency engine will do 614 additional runtime checks to debug itself, at the price 615 of more runtime overhead. 616 617config TRACE_IRQFLAGS 618 bool 619 help 620 Enables hooks to interrupt enabling and disabling for 621 either tracing or lock debugging. 622 623config DEBUG_SPINLOCK_SLEEP 624 bool "Spinlock debugging: sleep-inside-spinlock checking" 625 depends on DEBUG_KERNEL 626 help 627 If you say Y here, various routines which may sleep will become very 628 noisy if they are called with a spinlock held. 629 630config DEBUG_LOCKING_API_SELFTESTS 631 bool "Locking API boot-time self-tests" 632 depends on DEBUG_KERNEL 633 help 634 Say Y here if you want the kernel to run a short self-test during 635 bootup. The self-test checks whether common types of locking bugs 636 are detected by debugging mechanisms or not. (if you disable 637 lock debugging then those bugs wont be detected of course.) 638 The following locking APIs are covered: spinlocks, rwlocks, 639 mutexes and rwsems. 640 641config STACKTRACE 642 bool 643 depends on STACKTRACE_SUPPORT 644 645config DEBUG_KOBJECT 646 bool "kobject debugging" 647 depends on DEBUG_KERNEL 648 help 649 If you say Y here, some extra kobject debugging messages will be sent 650 to the syslog. 651 652config DEBUG_HIGHMEM 653 bool "Highmem debugging" 654 depends on DEBUG_KERNEL && HIGHMEM 655 help 656 This options enables addition error checking for high memory systems. 657 Disable for production systems. 658 659config DEBUG_BUGVERBOSE 660 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 661 depends on BUG 662 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ 663 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 664 default y 665 help 666 Say Y here to make BUG() panics output the file name and line number 667 of the BUG call as well as the EIP and oops trace. This aids 668 debugging but costs about 70-100K of memory. 669 670config DEBUG_INFO 671 bool "Compile the kernel with debug info" 672 depends on DEBUG_KERNEL 673 help 674 If you say Y here the resulting kernel image will include 675 debugging info resulting in a larger kernel image. 676 This adds debug symbols to the kernel and modules (gcc -g), and 677 is needed if you intend to use kernel crashdump or binary object 678 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 679 Say Y here only if you plan to debug the kernel. 680 681 If unsure, say N. 682 683config DEBUG_INFO_REDUCED 684 bool "Reduce debugging information" 685 depends on DEBUG_INFO 686 help 687 If you say Y here gcc is instructed to generate less debugging 688 information for structure types. This means that tools that 689 need full debugging information (like kgdb or systemtap) won't 690 be happy. But if you merely need debugging information to 691 resolve line numbers there is no loss. Advantage is that 692 build directory object sizes shrink dramatically over a full 693 DEBUG_INFO build and compile times are reduced too. 694 Only works with newer gcc versions. 695 696config DEBUG_VM 697 bool "Debug VM" 698 depends on DEBUG_KERNEL 699 help 700 Enable this to turn on extended checks in the virtual-memory system 701 that may impact performance. 702 703 If unsure, say N. 704 705config DEBUG_VIRTUAL 706 bool "Debug VM translations" 707 depends on DEBUG_KERNEL && X86 708 help 709 Enable some costly sanity checks in virtual to page code. This can 710 catch mistakes with virt_to_page() and friends. 711 712 If unsure, say N. 713 714config DEBUG_NOMMU_REGIONS 715 bool "Debug the global anon/private NOMMU mapping region tree" 716 depends on DEBUG_KERNEL && !MMU 717 help 718 This option causes the global tree of anonymous and private mapping 719 regions to be regularly checked for invalid topology. 720 721config DEBUG_WRITECOUNT 722 bool "Debug filesystem writers count" 723 depends on DEBUG_KERNEL 724 help 725 Enable this to catch wrong use of the writers count in struct 726 vfsmount. This will increase the size of each file struct by 727 32 bits. 728 729 If unsure, say N. 730 731config DEBUG_MEMORY_INIT 732 bool "Debug memory initialisation" if EXPERT 733 default !EXPERT 734 help 735 Enable this for additional checks during memory initialisation. 736 The sanity checks verify aspects of the VM such as the memory model 737 and other information provided by the architecture. Verbose 738 information will be printed at KERN_DEBUG loglevel depending 739 on the mminit_loglevel= command-line option. 740 741 If unsure, say Y 742 743config DEBUG_LIST 744 bool "Debug linked list manipulation" 745 depends on DEBUG_KERNEL 746 help 747 Enable this to turn on extended checks in the linked-list 748 walking routines. 749 750 If unsure, say N. 751 752config TEST_LIST_SORT 753 bool "Linked list sorting test" 754 depends on DEBUG_KERNEL 755 help 756 Enable this to turn on 'list_sort()' function test. This test is 757 executed only once during system boot, so affects only boot time. 758 759 If unsure, say N. 760 761config DEBUG_SG 762 bool "Debug SG table operations" 763 depends on DEBUG_KERNEL 764 help 765 Enable this to turn on checks on scatter-gather tables. This can 766 help find problems with drivers that do not properly initialize 767 their sg tables. 768 769 If unsure, say N. 770 771config DEBUG_NOTIFIERS 772 bool "Debug notifier call chains" 773 depends on DEBUG_KERNEL 774 help 775 Enable this to turn on sanity checking for notifier call chains. 776 This is most useful for kernel developers to make sure that 777 modules properly unregister themselves from notifier chains. 778 This is a relatively cheap check but if you care about maximum 779 performance, say N. 780 781config DEBUG_CREDENTIALS 782 bool "Debug credential management" 783 depends on DEBUG_KERNEL 784 help 785 Enable this to turn on some debug checking for credential 786 management. The additional code keeps track of the number of 787 pointers from task_structs to any given cred struct, and checks to 788 see that this number never exceeds the usage count of the cred 789 struct. 790 791 Furthermore, if SELinux is enabled, this also checks that the 792 security pointer in the cred struct is never seen to be invalid. 793 794 If unsure, say N. 795 796# 797# Select this config option from the architecture Kconfig, if it 798# it is preferred to always offer frame pointers as a config 799# option on the architecture (regardless of KERNEL_DEBUG): 800# 801config ARCH_WANT_FRAME_POINTERS 802 bool 803 help 804 805config FRAME_POINTER 806 bool "Compile the kernel with frame pointers" 807 depends on DEBUG_KERNEL && \ 808 (CRIS || M68K || M68KNOMMU || FRV || UML || \ 809 AVR32 || SUPERH || BLACKFIN || MN10300) || \ 810 ARCH_WANT_FRAME_POINTERS 811 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 812 help 813 If you say Y here the resulting kernel image will be slightly 814 larger and slower, but it gives very useful debugging information 815 in case of kernel bugs. (precise oopses/stacktraces/warnings) 816 817config BOOT_PRINTK_DELAY 818 bool "Delay each boot printk message by N milliseconds" 819 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 820 help 821 This build option allows you to read kernel boot messages 822 by inserting a short delay after each one. The delay is 823 specified in milliseconds on the kernel command line, 824 using "boot_delay=N". 825 826 It is likely that you would also need to use "lpj=M" to preset 827 the "loops per jiffie" value. 828 See a previous boot log for the "lpj" value to use for your 829 system, and then set "lpj=M" before setting "boot_delay=N". 830 NOTE: Using this option may adversely affect SMP systems. 831 I.e., processors other than the first one may not boot up. 832 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect 833 what it believes to be lockup conditions. 834 835config RCU_TORTURE_TEST 836 tristate "torture tests for RCU" 837 depends on DEBUG_KERNEL 838 default n 839 help 840 This option provides a kernel module that runs torture tests 841 on the RCU infrastructure. The kernel module may be built 842 after the fact on the running kernel to be tested, if desired. 843 844 Say Y here if you want RCU torture tests to be built into 845 the kernel. 846 Say M if you want the RCU torture tests to build as a module. 847 Say N if you are unsure. 848 849config RCU_TORTURE_TEST_RUNNABLE 850 bool "torture tests for RCU runnable by default" 851 depends on RCU_TORTURE_TEST = y 852 default n 853 help 854 This option provides a way to build the RCU torture tests 855 directly into the kernel without them starting up at boot 856 time. You can use /proc/sys/kernel/rcutorture_runnable 857 to manually override this setting. This /proc file is 858 available only when the RCU torture tests have been built 859 into the kernel. 860 861 Say Y here if you want the RCU torture tests to start during 862 boot (you probably don't). 863 Say N here if you want the RCU torture tests to start only 864 after being manually enabled via /proc. 865 866config RCU_CPU_STALL_DETECTOR 867 bool "Check for stalled CPUs delaying RCU grace periods" 868 depends on TREE_RCU || TREE_PREEMPT_RCU 869 default y 870 help 871 This option causes RCU to printk information on which 872 CPUs are delaying the current grace period, but only when 873 the grace period extends for excessive time periods. 874 875 Say N if you want to disable such checks. 876 877 Say Y if you are unsure. 878 879config RCU_CPU_STALL_TIMEOUT 880 int "RCU CPU stall timeout in seconds" 881 depends on RCU_CPU_STALL_DETECTOR 882 range 3 300 883 default 60 884 help 885 If a given RCU grace period extends more than the specified 886 number of seconds, a CPU stall warning is printed. If the 887 RCU grace period persists, additional CPU stall warnings are 888 printed at more widely spaced intervals. 889 890config RCU_CPU_STALL_DETECTOR_RUNNABLE 891 bool "RCU CPU stall checking starts automatically at boot" 892 depends on RCU_CPU_STALL_DETECTOR 893 default y 894 help 895 If set, start checking for RCU CPU stalls immediately on 896 boot. Otherwise, RCU CPU stall checking must be manually 897 enabled. 898 899 Say Y if you are unsure. 900 901 Say N if you wish to suppress RCU CPU stall checking during boot. 902 903config RCU_CPU_STALL_VERBOSE 904 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" 905 depends on RCU_CPU_STALL_DETECTOR && TREE_PREEMPT_RCU 906 default y 907 help 908 This option causes RCU to printk detailed per-task information 909 for any tasks that are stalling the current RCU grace period. 910 911 Say N if you are unsure. 912 913 Say Y if you want to enable such checks. 914 915config KPROBES_SANITY_TEST 916 bool "Kprobes sanity tests" 917 depends on DEBUG_KERNEL 918 depends on KPROBES 919 default n 920 help 921 This option provides for testing basic kprobes functionality on 922 boot. A sample kprobe, jprobe and kretprobe are inserted and 923 verified for functionality. 924 925 Say N if you are unsure. 926 927config BACKTRACE_SELF_TEST 928 tristate "Self test for the backtrace code" 929 depends on DEBUG_KERNEL 930 default n 931 help 932 This option provides a kernel module that can be used to test 933 the kernel stack backtrace code. This option is not useful 934 for distributions or general kernels, but only for kernel 935 developers working on architecture code. 936 937 Note that if you want to also test saved backtraces, you will 938 have to enable STACKTRACE as well. 939 940 Say N if you are unsure. 941 942config DEBUG_BLOCK_EXT_DEVT 943 bool "Force extended block device numbers and spread them" 944 depends on DEBUG_KERNEL 945 depends on BLOCK 946 default n 947 help 948 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 949 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 950 YOU ARE DOING. Distros, please enable this and fix whatever 951 is broken. 952 953 Conventionally, block device numbers are allocated from 954 predetermined contiguous area. However, extended block area 955 may introduce non-contiguous block device numbers. This 956 option forces most block device numbers to be allocated from 957 the extended space and spreads them to discover kernel or 958 userland code paths which assume predetermined contiguous 959 device number allocation. 960 961 Note that turning on this debug option shuffles all the 962 device numbers for all IDE and SCSI devices including libata 963 ones, so root partition specified using device number 964 directly (via rdev or root=MAJ:MIN) won't work anymore. 965 Textual device names (root=/dev/sdXn) will continue to work. 966 967 Say N if you are unsure. 968 969config DEBUG_FORCE_WEAK_PER_CPU 970 bool "Force weak per-cpu definitions" 971 depends on DEBUG_KERNEL 972 help 973 s390 and alpha require percpu variables in modules to be 974 defined weak to work around addressing range issue which 975 puts the following two restrictions on percpu variable 976 definitions. 977 978 1. percpu symbols must be unique whether static or not 979 2. percpu variables can't be defined inside a function 980 981 To ensure that generic code follows the above rules, this 982 option forces all percpu variables to be defined as weak. 983 984config LKDTM 985 tristate "Linux Kernel Dump Test Tool Module" 986 depends on DEBUG_FS 987 depends on BLOCK 988 default n 989 help 990 This module enables testing of the different dumping mechanisms by 991 inducing system failures at predefined crash points. 992 If you don't need it: say N 993 Choose M here to compile this code as a module. The module will be 994 called lkdtm. 995 996 Documentation on how to use the module can be found in 997 Documentation/fault-injection/provoke-crashes.txt 998 999config CPU_NOTIFIER_ERROR_INJECT 1000 tristate "CPU notifier error injection module" 1001 depends on HOTPLUG_CPU && DEBUG_KERNEL 1002 help 1003 This option provides a kernel module that can be used to test 1004 the error handling of the cpu notifiers 1005 1006 To compile this code as a module, choose M here: the module will 1007 be called cpu-notifier-error-inject. 1008 1009 If unsure, say N. 1010 1011config FAULT_INJECTION 1012 bool "Fault-injection framework" 1013 depends on DEBUG_KERNEL 1014 help 1015 Provide fault-injection framework. 1016 For more details, see Documentation/fault-injection/. 1017 1018config FAILSLAB 1019 bool "Fault-injection capability for kmalloc" 1020 depends on FAULT_INJECTION 1021 depends on SLAB || SLUB 1022 help 1023 Provide fault-injection capability for kmalloc. 1024 1025config FAIL_PAGE_ALLOC 1026 bool "Fault-injection capabilitiy for alloc_pages()" 1027 depends on FAULT_INJECTION 1028 help 1029 Provide fault-injection capability for alloc_pages(). 1030 1031config FAIL_MAKE_REQUEST 1032 bool "Fault-injection capability for disk IO" 1033 depends on FAULT_INJECTION && BLOCK 1034 help 1035 Provide fault-injection capability for disk IO. 1036 1037config FAIL_IO_TIMEOUT 1038 bool "Fault-injection capability for faking disk interrupts" 1039 depends on FAULT_INJECTION && BLOCK 1040 help 1041 Provide fault-injection capability on end IO handling. This 1042 will make the block layer "forget" an interrupt as configured, 1043 thus exercising the error handling. 1044 1045 Only works with drivers that use the generic timeout handling, 1046 for others it wont do anything. 1047 1048config FAULT_INJECTION_DEBUG_FS 1049 bool "Debugfs entries for fault-injection capabilities" 1050 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1051 help 1052 Enable configuration of fault-injection capabilities via debugfs. 1053 1054config FAULT_INJECTION_STACKTRACE_FILTER 1055 bool "stacktrace filter for fault-injection capabilities" 1056 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1057 depends on !X86_64 1058 select STACKTRACE 1059 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE 1060 help 1061 Provide stacktrace filter for fault-injection capabilities 1062 1063config LATENCYTOP 1064 bool "Latency measuring infrastructure" 1065 depends on HAVE_LATENCYTOP_SUPPORT 1066 depends on DEBUG_KERNEL 1067 depends on STACKTRACE_SUPPORT 1068 depends on PROC_FS 1069 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE 1070 select KALLSYMS 1071 select KALLSYMS_ALL 1072 select STACKTRACE 1073 select SCHEDSTATS 1074 select SCHED_DEBUG 1075 help 1076 Enable this option if you want to use the LatencyTOP tool 1077 to find out which userspace is blocking on what kernel operations. 1078 1079config SYSCTL_SYSCALL_CHECK 1080 bool "Sysctl checks" 1081 depends on SYSCTL 1082 ---help--- 1083 sys_sysctl uses binary paths that have been found challenging 1084 to properly maintain and use. This enables checks that help 1085 you to keep things correct. 1086 1087source mm/Kconfig.debug 1088source kernel/trace/Kconfig 1089 1090config PROVIDE_OHCI1394_DMA_INIT 1091 bool "Remote debugging over FireWire early on boot" 1092 depends on PCI && X86 1093 help 1094 If you want to debug problems which hang or crash the kernel early 1095 on boot and the crashing machine has a FireWire port, you can use 1096 this feature to remotely access the memory of the crashed machine 1097 over FireWire. This employs remote DMA as part of the OHCI1394 1098 specification which is now the standard for FireWire controllers. 1099 1100 With remote DMA, you can monitor the printk buffer remotely using 1101 firescope and access all memory below 4GB using fireproxy from gdb. 1102 Even controlling a kernel debugger is possible using remote DMA. 1103 1104 Usage: 1105 1106 If ohci1394_dma=early is used as boot parameter, it will initialize 1107 all OHCI1394 controllers which are found in the PCI config space. 1108 1109 As all changes to the FireWire bus such as enabling and disabling 1110 devices cause a bus reset and thereby disable remote DMA for all 1111 devices, be sure to have the cable plugged and FireWire enabled on 1112 the debugging host before booting the debug target for debugging. 1113 1114 This code (~1k) is freed after boot. By then, the firewire stack 1115 in charge of the OHCI-1394 controllers should be used instead. 1116 1117 See Documentation/debugging-via-ohci1394.txt for more information. 1118 1119config FIREWIRE_OHCI_REMOTE_DMA 1120 bool "Remote debugging over FireWire with firewire-ohci" 1121 depends on FIREWIRE_OHCI 1122 help 1123 This option lets you use the FireWire bus for remote debugging 1124 with help of the firewire-ohci driver. It enables unfiltered 1125 remote DMA in firewire-ohci. 1126 See Documentation/debugging-via-ohci1394.txt for more information. 1127 1128 If unsure, say N. 1129 1130config BUILD_DOCSRC 1131 bool "Build targets in Documentation/ tree" 1132 depends on HEADERS_CHECK 1133 help 1134 This option attempts to build objects from the source files in the 1135 kernel Documentation/ tree. 1136 1137 Say N if you are unsure. 1138 1139config DYNAMIC_DEBUG 1140 bool "Enable dynamic printk() support" 1141 default n 1142 depends on PRINTK 1143 depends on DEBUG_FS 1144 help 1145 1146 Compiles debug level messages into the kernel, which would not 1147 otherwise be available at runtime. These messages can then be 1148 enabled/disabled based on various levels of scope - per source file, 1149 function, module, format string, and line number. This mechanism 1150 implicitly enables all pr_debug() and dev_dbg() calls. The impact of 1151 this compile option is a larger kernel text size of about 2%. 1152 1153 Usage: 1154 1155 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 1156 which is contained in the 'debugfs' filesystem. Thus, the debugfs 1157 filesystem must first be mounted before making use of this feature. 1158 We refer the control file as: <debugfs>/dynamic_debug/control. This 1159 file contains a list of the debug statements that can be enabled. The 1160 format for each line of the file is: 1161 1162 filename:lineno [module]function flags format 1163 1164 filename : source file of the debug statement 1165 lineno : line number of the debug statement 1166 module : module that contains the debug statement 1167 function : function that contains the debug statement 1168 flags : 'p' means the line is turned 'on' for printing 1169 format : the format used for the debug statement 1170 1171 From a live system: 1172 1173 nullarbor:~ # cat <debugfs>/dynamic_debug/control 1174 # filename:lineno [module]function flags format 1175 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012" 1176 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012" 1177 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012" 1178 1179 Example usage: 1180 1181 // enable the message at line 1603 of file svcsock.c 1182 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 1183 <debugfs>/dynamic_debug/control 1184 1185 // enable all the messages in file svcsock.c 1186 nullarbor:~ # echo -n 'file svcsock.c +p' > 1187 <debugfs>/dynamic_debug/control 1188 1189 // enable all the messages in the NFS server module 1190 nullarbor:~ # echo -n 'module nfsd +p' > 1191 <debugfs>/dynamic_debug/control 1192 1193 // enable all 12 messages in the function svc_process() 1194 nullarbor:~ # echo -n 'func svc_process +p' > 1195 <debugfs>/dynamic_debug/control 1196 1197 // disable all 12 messages in the function svc_process() 1198 nullarbor:~ # echo -n 'func svc_process -p' > 1199 <debugfs>/dynamic_debug/control 1200 1201 See Documentation/dynamic-debug-howto.txt for additional information. 1202 1203config DMA_API_DEBUG 1204 bool "Enable debugging of DMA-API usage" 1205 depends on HAVE_DMA_API_DEBUG 1206 help 1207 Enable this option to debug the use of the DMA API by device drivers. 1208 With this option you will be able to detect common bugs in device 1209 drivers like double-freeing of DMA mappings or freeing mappings that 1210 were never allocated. 1211 This option causes a performance degredation. Use only if you want 1212 to debug device drivers. If unsure, say N. 1213 1214config ATOMIC64_SELFTEST 1215 bool "Perform an atomic64_t self-test at boot" 1216 help 1217 Enable this option to test the atomic64_t functions at boot. 1218 1219 If unsure, say N. 1220 1221config ASYNC_RAID6_TEST 1222 tristate "Self test for hardware accelerated raid6 recovery" 1223 depends on ASYNC_RAID6_RECOV 1224 select ASYNC_MEMCPY 1225 ---help--- 1226 This is a one-shot self test that permutes through the 1227 recovery of all the possible two disk failure scenarios for a 1228 N-disk array. Recovery is performed with the asynchronous 1229 raid6 recovery routines, and will optionally use an offload 1230 engine if one is available. 1231 1232 If unsure, say N. 1233 1234source "samples/Kconfig" 1235 1236source "lib/Kconfig.kgdb" 1237 1238source "lib/Kconfig.kmemcheck" 1239