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