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