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