1 2config PRINTK_TIME 3 bool "Show timing information on printks" 4 depends on PRINTK 5 help 6 Selecting this option causes time stamps of the printk() 7 messages to be added to the output of the syslog() system 8 call and at the console. 9 10 The timestamp is always recorded internally, and exported 11 to /dev/kmsg. This flag just specifies if the timestamp should 12 be included, not that the timestamp is recorded. 13 14 The behavior is also controlled by the kernel command line 15 parameter printk.time=1. See Documentation/kernel-parameters.txt 16 17config DEFAULT_MESSAGE_LOGLEVEL 18 int "Default message log level (1-7)" 19 range 1 7 20 default "4" 21 help 22 Default log level for printk statements with no specified priority. 23 24 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks 25 that are auditing their logs closely may want to set it to a lower 26 priority. 27 28config ENABLE_WARN_DEPRECATED 29 bool "Enable __deprecated logic" 30 default y 31 help 32 Enable the __deprecated logic in the kernel build. 33 Disable this to suppress the "warning: 'foo' is deprecated 34 (declared at kernel/power/somefile.c:1234)" messages. 35 36config ENABLE_MUST_CHECK 37 bool "Enable __must_check logic" 38 default y 39 help 40 Enable the __must_check logic in the kernel build. Disable this to 41 suppress the "warning: ignoring return value of 'foo', declared with 42 attribute warn_unused_result" messages. 43 44config FRAME_WARN 45 int "Warn for stack frames larger than (needs gcc 4.4)" 46 range 0 8192 47 default 1024 if !64BIT 48 default 2048 if 64BIT 49 help 50 Tell gcc to warn at build time for stack frames larger than this. 51 Setting this too low will cause a lot of warnings. 52 Setting it to 0 disables the warning. 53 Requires gcc 4.4 54 55config MAGIC_SYSRQ 56 bool "Magic SysRq key" 57 depends on !UML 58 help 59 If you say Y here, you will have some control over the system even 60 if the system crashes for example during kernel debugging (e.g., you 61 will be able to flush the buffer cache to disk, reboot the system 62 immediately or dump some status information). This is accomplished 63 by pressing various keys while holding SysRq (Alt+PrintScreen). It 64 also works on a serial console (on PC hardware at least), if you 65 send a BREAK and then within 5 seconds a command keypress. The 66 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 67 unless you really know what this hack does. 68 69config STRIP_ASM_SYMS 70 bool "Strip assembler-generated symbols during link" 71 default n 72 help 73 Strip internal assembler-generated symbols during a link (symbols 74 that look like '.Lxxx') so they don't pollute the output of 75 get_wchan() and suchlike. 76 77config READABLE_ASM 78 bool "Generate readable assembler code" 79 depends on DEBUG_KERNEL 80 help 81 Disable some compiler optimizations that tend to generate human unreadable 82 assembler output. This may make the kernel slightly slower, but it helps 83 to keep kernel developers who have to stare a lot at assembler listings 84 sane. 85 86config UNUSED_SYMBOLS 87 bool "Enable unused/obsolete exported symbols" 88 default y if X86 89 help 90 Unused but exported symbols make the kernel needlessly bigger. For 91 that reason most of these unused exports will soon be removed. This 92 option is provided temporarily to provide a transition period in case 93 some external kernel module needs one of these symbols anyway. If you 94 encounter such a case in your module, consider if you are actually 95 using the right API. (rationale: since nobody in the kernel is using 96 this in a module, there is a pretty good chance it's actually the 97 wrong interface to use). If you really need the symbol, please send a 98 mail to the linux kernel mailing list mentioning the symbol and why 99 you really need it, and what the merge plan to the mainline kernel for 100 your module is. 101 102config DEBUG_FS 103 bool "Debug Filesystem" 104 help 105 debugfs is a virtual file system that kernel developers use to put 106 debugging files into. Enable this option to be able to read and 107 write to these files. 108 109 For detailed documentation on the debugfs API, see 110 Documentation/DocBook/filesystems. 111 112 If unsure, say N. 113 114config HEADERS_CHECK 115 bool "Run 'make headers_check' when building vmlinux" 116 depends on !UML 117 help 118 This option will extract the user-visible kernel headers whenever 119 building the kernel, and will run basic sanity checks on them to 120 ensure that exported files do not attempt to include files which 121 were not exported, etc. 122 123 If you're making modifications to header files which are 124 relevant for userspace, say 'Y', and check the headers 125 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 126 your build tree), to make sure they're suitable. 127 128config DEBUG_SECTION_MISMATCH 129 bool "Enable full Section mismatch analysis" 130 help 131 The section mismatch analysis checks if there are illegal 132 references from one section to another section. 133 During linktime or runtime, some sections are dropped; 134 any use of code/data previously in these sections would 135 most likely result in an oops. 136 In the code, functions and variables are annotated with 137 __init, __devinit, etc. (see the full list in include/linux/init.h), 138 which results in the code/data being placed in specific sections. 139 The section mismatch analysis is always performed after a full 140 kernel build, and enabling this option causes the following 141 additional steps to occur: 142 - Add the option -fno-inline-functions-called-once to gcc commands. 143 When inlining a function annotated with __init in a non-init 144 function, we would lose the section information and thus 145 the analysis would not catch the illegal reference. 146 This option tells gcc to inline less (but it does result in 147 a larger kernel). 148 - Run the section mismatch analysis for each module/built-in.o file. 149 When we run the section mismatch analysis on vmlinux.o, we 150 lose valueble information about where the mismatch was 151 introduced. 152 Running the analysis for each module/built-in.o file 153 tells where the mismatch happens much closer to the 154 source. The drawback is that the same mismatch is 155 reported at least twice. 156 - Enable verbose reporting from modpost in order to help resolve 157 the section mismatches that are reported. 158 159config DEBUG_KERNEL 160 bool "Kernel debugging" 161 help 162 Say Y here if you are developing drivers or trying to debug and 163 identify kernel problems. 164 165config DEBUG_SHIRQ 166 bool "Debug shared IRQ handlers" 167 depends on DEBUG_KERNEL && GENERIC_HARDIRQS 168 help 169 Enable this to generate a spurious interrupt as soon as a shared 170 interrupt handler is registered, and just before one is deregistered. 171 Drivers ought to be able to handle interrupts coming in at those 172 points; some don't and need to be caught. 173 174config LOCKUP_DETECTOR 175 bool "Detect Hard and Soft Lockups" 176 depends on DEBUG_KERNEL && !S390 177 help 178 Say Y here to enable the kernel to act as a watchdog to detect 179 hard and soft lockups. 180 181 Softlockups are bugs that cause the kernel to loop in kernel 182 mode for more than 20 seconds, without giving other tasks a 183 chance to run. The current stack trace is displayed upon 184 detection and the system will stay locked up. 185 186 Hardlockups are bugs that cause the CPU to loop in kernel mode 187 for more than 10 seconds, without letting other interrupts have a 188 chance to run. The current stack trace is displayed upon detection 189 and the system will stay locked up. 190 191 The overhead should be minimal. A periodic hrtimer runs to 192 generate interrupts and kick the watchdog task every 4 seconds. 193 An NMI is generated every 10 seconds or so to check for hardlockups. 194 195 The frequency of hrtimer and NMI events and the soft and hard lockup 196 thresholds can be controlled through the sysctl watchdog_thresh. 197 198config HARDLOCKUP_DETECTOR 199 def_bool y 200 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 201 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 202 203config BOOTPARAM_HARDLOCKUP_PANIC 204 bool "Panic (Reboot) On Hard Lockups" 205 depends on HARDLOCKUP_DETECTOR 206 help 207 Say Y here to enable the kernel to panic on "hard lockups", 208 which are bugs that cause the kernel to loop in kernel 209 mode with interrupts disabled for more than 10 seconds (configurable 210 using the watchdog_thresh sysctl). 211 212 Say N if unsure. 213 214config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 215 int 216 depends on HARDLOCKUP_DETECTOR 217 range 0 1 218 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 219 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 220 221config BOOTPARAM_SOFTLOCKUP_PANIC 222 bool "Panic (Reboot) On Soft Lockups" 223 depends on LOCKUP_DETECTOR 224 help 225 Say Y here to enable the kernel to panic on "soft lockups", 226 which are bugs that cause the kernel to loop in kernel 227 mode for more than 20 seconds (configurable using the watchdog_thresh 228 sysctl), without giving other tasks a chance to run. 229 230 The panic can be used in combination with panic_timeout, 231 to cause the system to reboot automatically after a 232 lockup has been detected. This feature is useful for 233 high-availability systems that have uptime guarantees and 234 where a lockup must be resolved ASAP. 235 236 Say N if unsure. 237 238config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 239 int 240 depends on LOCKUP_DETECTOR 241 range 0 1 242 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 243 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 244 245config PANIC_ON_OOPS 246 bool "Panic on Oops" if EXPERT 247 default n 248 help 249 Say Y here to enable the kernel to panic when it oopses. This 250 has the same effect as setting oops=panic on the kernel command 251 line. 252 253 This feature is useful to ensure that the kernel does not do 254 anything erroneous after an oops which could result in data 255 corruption or other issues. 256 257 Say N if unsure. 258 259config PANIC_ON_OOPS_VALUE 260 int 261 range 0 1 262 default 0 if !PANIC_ON_OOPS 263 default 1 if PANIC_ON_OOPS 264 265config DETECT_HUNG_TASK 266 bool "Detect Hung Tasks" 267 depends on DEBUG_KERNEL 268 default LOCKUP_DETECTOR 269 help 270 Say Y here to enable the kernel to detect "hung tasks", 271 which are bugs that cause the task to be stuck in 272 uninterruptible "D" state indefinitiley. 273 274 When a hung task is detected, the kernel will print the 275 current stack trace (which you should report), but the 276 task will stay in uninterruptible state. If lockdep is 277 enabled then all held locks will also be reported. This 278 feature has negligible overhead. 279 280config DEFAULT_HUNG_TASK_TIMEOUT 281 int "Default timeout for hung task detection (in seconds)" 282 depends on DETECT_HUNG_TASK 283 default 120 284 help 285 This option controls the default timeout (in seconds) used 286 to determine when a task has become non-responsive and should 287 be considered hung. 288 289 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 290 sysctl or by writing a value to 291 /proc/sys/kernel/hung_task_timeout_secs. 292 293 A timeout of 0 disables the check. The default is two minutes. 294 Keeping the default should be fine in most cases. 295 296config BOOTPARAM_HUNG_TASK_PANIC 297 bool "Panic (Reboot) On Hung Tasks" 298 depends on DETECT_HUNG_TASK 299 help 300 Say Y here to enable the kernel to panic on "hung tasks", 301 which are bugs that cause the kernel to leave a task stuck 302 in uninterruptible "D" state. 303 304 The panic can be used in combination with panic_timeout, 305 to cause the system to reboot automatically after a 306 hung task has been detected. This feature is useful for 307 high-availability systems that have uptime guarantees and 308 where a hung tasks must be resolved ASAP. 309 310 Say N if unsure. 311 312config BOOTPARAM_HUNG_TASK_PANIC_VALUE 313 int 314 depends on DETECT_HUNG_TASK 315 range 0 1 316 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 317 default 1 if BOOTPARAM_HUNG_TASK_PANIC 318 319config SCHED_DEBUG 320 bool "Collect scheduler debugging info" 321 depends on DEBUG_KERNEL && PROC_FS 322 default y 323 help 324 If you say Y here, the /proc/sched_debug file will be provided 325 that can help debug the scheduler. The runtime overhead of this 326 option is minimal. 327 328config SCHEDSTATS 329 bool "Collect scheduler statistics" 330 depends on DEBUG_KERNEL && PROC_FS 331 help 332 If you say Y here, additional code will be inserted into the 333 scheduler and related routines to collect statistics about 334 scheduler behavior and provide them in /proc/schedstat. These 335 stats may be useful for both tuning and debugging the scheduler 336 If you aren't debugging the scheduler or trying to tune a specific 337 application, you can say N to avoid the very slight overhead 338 this adds. 339 340config TIMER_STATS 341 bool "Collect kernel timers statistics" 342 depends on DEBUG_KERNEL && PROC_FS 343 help 344 If you say Y here, additional code will be inserted into the 345 timer routines to collect statistics about kernel timers being 346 reprogrammed. The statistics can be read from /proc/timer_stats. 347 The statistics collection is started by writing 1 to /proc/timer_stats, 348 writing 0 stops it. This feature is useful to collect information 349 about timer usage patterns in kernel and userspace. This feature 350 is lightweight if enabled in the kernel config but not activated 351 (it defaults to deactivated on bootup and will only be activated 352 if some application like powertop activates it explicitly). 353 354config DEBUG_OBJECTS 355 bool "Debug object operations" 356 depends on DEBUG_KERNEL 357 help 358 If you say Y here, additional code will be inserted into the 359 kernel to track the life time of various objects and validate 360 the operations on those objects. 361 362config DEBUG_OBJECTS_SELFTEST 363 bool "Debug objects selftest" 364 depends on DEBUG_OBJECTS 365 help 366 This enables the selftest of the object debug code. 367 368config DEBUG_OBJECTS_FREE 369 bool "Debug objects in freed memory" 370 depends on DEBUG_OBJECTS 371 help 372 This enables checks whether a k/v free operation frees an area 373 which contains an object which has not been deactivated 374 properly. This can make kmalloc/kfree-intensive workloads 375 much slower. 376 377config DEBUG_OBJECTS_TIMERS 378 bool "Debug timer objects" 379 depends on DEBUG_OBJECTS 380 help 381 If you say Y here, additional code will be inserted into the 382 timer routines to track the life time of timer objects and 383 validate the timer operations. 384 385config DEBUG_OBJECTS_WORK 386 bool "Debug work objects" 387 depends on DEBUG_OBJECTS 388 help 389 If you say Y here, additional code will be inserted into the 390 work queue routines to track the life time of work objects and 391 validate the work operations. 392 393config DEBUG_OBJECTS_RCU_HEAD 394 bool "Debug RCU callbacks objects" 395 depends on DEBUG_OBJECTS 396 help 397 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 398 399config DEBUG_OBJECTS_PERCPU_COUNTER 400 bool "Debug percpu counter objects" 401 depends on DEBUG_OBJECTS 402 help 403 If you say Y here, additional code will be inserted into the 404 percpu counter routines to track the life time of percpu counter 405 objects and validate the percpu counter operations. 406 407config DEBUG_OBJECTS_ENABLE_DEFAULT 408 int "debug_objects bootup default value (0-1)" 409 range 0 1 410 default "1" 411 depends on DEBUG_OBJECTS 412 help 413 Debug objects boot parameter default value 414 415config DEBUG_SLAB 416 bool "Debug slab memory allocations" 417 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 418 help 419 Say Y here to have the kernel do limited verification on memory 420 allocation as well as poisoning memory on free to catch use of freed 421 memory. This can make kmalloc/kfree-intensive workloads much slower. 422 423config DEBUG_SLAB_LEAK 424 bool "Memory leak debugging" 425 depends on DEBUG_SLAB 426 427config SLUB_DEBUG_ON 428 bool "SLUB debugging on by default" 429 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 430 default n 431 help 432 Boot with debugging on by default. SLUB boots by default with 433 the runtime debug capabilities switched off. Enabling this is 434 equivalent to specifying the "slub_debug" parameter on boot. 435 There is no support for more fine grained debug control like 436 possible with slub_debug=xxx. SLUB debugging may be switched 437 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 438 "slub_debug=-". 439 440config SLUB_STATS 441 default n 442 bool "Enable SLUB performance statistics" 443 depends on SLUB && SYSFS 444 help 445 SLUB statistics are useful to debug SLUBs allocation behavior in 446 order find ways to optimize the allocator. This should never be 447 enabled for production use since keeping statistics slows down 448 the allocator by a few percentage points. The slabinfo command 449 supports the determination of the most active slabs to figure 450 out which slabs are relevant to a particular load. 451 Try running: slabinfo -DA 452 453config HAVE_DEBUG_KMEMLEAK 454 bool 455 456config DEBUG_KMEMLEAK 457 bool "Kernel memory leak detector" 458 depends on DEBUG_KERNEL && EXPERIMENTAL && HAVE_DEBUG_KMEMLEAK 459 select DEBUG_FS 460 select STACKTRACE if STACKTRACE_SUPPORT 461 select KALLSYMS 462 select CRC32 463 help 464 Say Y here if you want to enable the memory leak 465 detector. The memory allocation/freeing is traced in a way 466 similar to the Boehm's conservative garbage collector, the 467 difference being that the orphan objects are not freed but 468 only shown in /sys/kernel/debug/kmemleak. Enabling this 469 feature will introduce an overhead to memory 470 allocations. See Documentation/kmemleak.txt for more 471 details. 472 473 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 474 of finding leaks due to the slab objects poisoning. 475 476 In order to access the kmemleak file, debugfs needs to be 477 mounted (usually at /sys/kernel/debug). 478 479config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 480 int "Maximum kmemleak early log entries" 481 depends on DEBUG_KMEMLEAK 482 range 200 40000 483 default 400 484 help 485 Kmemleak must track all the memory allocations to avoid 486 reporting false positives. Since memory may be allocated or 487 freed before kmemleak is initialised, an early log buffer is 488 used to store these actions. If kmemleak reports "early log 489 buffer exceeded", please increase this value. 490 491config DEBUG_KMEMLEAK_TEST 492 tristate "Simple test for the kernel memory leak detector" 493 depends on DEBUG_KMEMLEAK && m 494 help 495 This option enables a module that explicitly leaks memory. 496 497 If unsure, say N. 498 499config DEBUG_KMEMLEAK_DEFAULT_OFF 500 bool "Default kmemleak to off" 501 depends on DEBUG_KMEMLEAK 502 help 503 Say Y here to disable kmemleak by default. It can then be enabled 504 on the command line via kmemleak=on. 505 506config DEBUG_PREEMPT 507 bool "Debug preemptible kernel" 508 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 509 default y 510 help 511 If you say Y here then the kernel will use a debug variant of the 512 commonly used smp_processor_id() function and will print warnings 513 if kernel code uses it in a preemption-unsafe way. Also, the kernel 514 will detect preemption count underflows. 515 516config DEBUG_RT_MUTEXES 517 bool "RT Mutex debugging, deadlock detection" 518 depends on DEBUG_KERNEL && RT_MUTEXES 519 help 520 This allows rt mutex semantics violations and rt mutex related 521 deadlocks (lockups) to be detected and reported automatically. 522 523config DEBUG_PI_LIST 524 bool 525 default y 526 depends on DEBUG_RT_MUTEXES 527 528config RT_MUTEX_TESTER 529 bool "Built-in scriptable tester for rt-mutexes" 530 depends on DEBUG_KERNEL && RT_MUTEXES 531 help 532 This option enables a rt-mutex tester. 533 534config DEBUG_SPINLOCK 535 bool "Spinlock and rw-lock debugging: basic checks" 536 depends on DEBUG_KERNEL 537 select UNINLINE_SPIN_UNLOCK 538 help 539 Say Y here and build SMP to catch missing spinlock initialization 540 and certain other kinds of spinlock errors commonly made. This is 541 best used in conjunction with the NMI watchdog so that spinlock 542 deadlocks are also debuggable. 543 544config DEBUG_MUTEXES 545 bool "Mutex debugging: basic checks" 546 depends on DEBUG_KERNEL 547 help 548 This feature allows mutex semantics violations to be detected and 549 reported. 550 551config DEBUG_LOCK_ALLOC 552 bool "Lock debugging: detect incorrect freeing of live locks" 553 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 554 select DEBUG_SPINLOCK 555 select DEBUG_MUTEXES 556 select LOCKDEP 557 help 558 This feature will check whether any held lock (spinlock, rwlock, 559 mutex or rwsem) is incorrectly freed by the kernel, via any of the 560 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 561 vfree(), etc.), whether a live lock is incorrectly reinitialized via 562 spin_lock_init()/mutex_init()/etc., or whether there is any lock 563 held during task exit. 564 565config PROVE_LOCKING 566 bool "Lock debugging: prove locking correctness" 567 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 568 select LOCKDEP 569 select DEBUG_SPINLOCK 570 select DEBUG_MUTEXES 571 select DEBUG_LOCK_ALLOC 572 select TRACE_IRQFLAGS 573 default n 574 help 575 This feature enables the kernel to prove that all locking 576 that occurs in the kernel runtime is mathematically 577 correct: that under no circumstance could an arbitrary (and 578 not yet triggered) combination of observed locking 579 sequences (on an arbitrary number of CPUs, running an 580 arbitrary number of tasks and interrupt contexts) cause a 581 deadlock. 582 583 In short, this feature enables the kernel to report locking 584 related deadlocks before they actually occur. 585 586 The proof does not depend on how hard and complex a 587 deadlock scenario would be to trigger: how many 588 participant CPUs, tasks and irq-contexts would be needed 589 for it to trigger. The proof also does not depend on 590 timing: if a race and a resulting deadlock is possible 591 theoretically (no matter how unlikely the race scenario 592 is), it will be proven so and will immediately be 593 reported by the kernel (once the event is observed that 594 makes the deadlock theoretically possible). 595 596 If a deadlock is impossible (i.e. the locking rules, as 597 observed by the kernel, are mathematically correct), the 598 kernel reports nothing. 599 600 NOTE: this feature can also be enabled for rwlocks, mutexes 601 and rwsems - in which case all dependencies between these 602 different locking variants are observed and mapped too, and 603 the proof of observed correctness is also maintained for an 604 arbitrary combination of these separate locking variants. 605 606 For more details, see Documentation/lockdep-design.txt. 607 608config PROVE_RCU 609 bool "RCU debugging: prove RCU correctness" 610 depends on PROVE_LOCKING 611 default n 612 help 613 This feature enables lockdep extensions that check for correct 614 use of RCU APIs. This is currently under development. Say Y 615 if you want to debug RCU usage or help work on the PROVE_RCU 616 feature. 617 618 Say N if you are unsure. 619 620config PROVE_RCU_REPEATEDLY 621 bool "RCU debugging: don't disable PROVE_RCU on first splat" 622 depends on PROVE_RCU 623 default n 624 help 625 By itself, PROVE_RCU will disable checking upon issuing the 626 first warning (or "splat"). This feature prevents such 627 disabling, allowing multiple RCU-lockdep warnings to be printed 628 on a single reboot. 629 630 Say Y to allow multiple RCU-lockdep warnings per boot. 631 632 Say N if you are unsure. 633 634config PROVE_RCU_DELAY 635 bool "RCU debugging: preemptible RCU race provocation" 636 depends on DEBUG_KERNEL && PREEMPT_RCU 637 default n 638 help 639 There is a class of races that involve an unlikely preemption 640 of __rcu_read_unlock() just after ->rcu_read_lock_nesting has 641 been set to INT_MIN. This feature inserts a delay at that 642 point to increase the probability of these races. 643 644 Say Y to increase probability of preemption of __rcu_read_unlock(). 645 646 Say N if you are unsure. 647 648config SPARSE_RCU_POINTER 649 bool "RCU debugging: sparse-based checks for pointer usage" 650 default n 651 help 652 This feature enables the __rcu sparse annotation for 653 RCU-protected pointers. This annotation will cause sparse 654 to flag any non-RCU used of annotated pointers. This can be 655 helpful when debugging RCU usage. Please note that this feature 656 is not intended to enforce code cleanliness; it is instead merely 657 a debugging aid. 658 659 Say Y to make sparse flag questionable use of RCU-protected pointers 660 661 Say N if you are unsure. 662 663config LOCKDEP 664 bool 665 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 666 select STACKTRACE 667 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE 668 select KALLSYMS 669 select KALLSYMS_ALL 670 671config LOCK_STAT 672 bool "Lock usage statistics" 673 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 674 select LOCKDEP 675 select DEBUG_SPINLOCK 676 select DEBUG_MUTEXES 677 select DEBUG_LOCK_ALLOC 678 default n 679 help 680 This feature enables tracking lock contention points 681 682 For more details, see Documentation/lockstat.txt 683 684 This also enables lock events required by "perf lock", 685 subcommand of perf. 686 If you want to use "perf lock", you also need to turn on 687 CONFIG_EVENT_TRACING. 688 689 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 690 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 691 692config DEBUG_LOCKDEP 693 bool "Lock dependency engine debugging" 694 depends on DEBUG_KERNEL && LOCKDEP 695 help 696 If you say Y here, the lock dependency engine will do 697 additional runtime checks to debug itself, at the price 698 of more runtime overhead. 699 700config TRACE_IRQFLAGS 701 bool 702 help 703 Enables hooks to interrupt enabling and disabling for 704 either tracing or lock debugging. 705 706config DEBUG_ATOMIC_SLEEP 707 bool "Sleep inside atomic section checking" 708 select PREEMPT_COUNT 709 depends on DEBUG_KERNEL 710 help 711 If you say Y here, various routines which may sleep will become very 712 noisy if they are called inside atomic sections: when a spinlock is 713 held, inside an rcu read side critical section, inside preempt disabled 714 sections, inside an interrupt, etc... 715 716config DEBUG_LOCKING_API_SELFTESTS 717 bool "Locking API boot-time self-tests" 718 depends on DEBUG_KERNEL 719 help 720 Say Y here if you want the kernel to run a short self-test during 721 bootup. The self-test checks whether common types of locking bugs 722 are detected by debugging mechanisms or not. (if you disable 723 lock debugging then those bugs wont be detected of course.) 724 The following locking APIs are covered: spinlocks, rwlocks, 725 mutexes and rwsems. 726 727config STACKTRACE 728 bool 729 depends on STACKTRACE_SUPPORT 730 731config DEBUG_STACK_USAGE 732 bool "Stack utilization instrumentation" 733 depends on DEBUG_KERNEL && !IA64 && !PARISC 734 help 735 Enables the display of the minimum amount of free stack which each 736 task has ever had available in the sysrq-T and sysrq-P debug output. 737 738 This option will slow down process creation somewhat. 739 740config DEBUG_KOBJECT 741 bool "kobject debugging" 742 depends on DEBUG_KERNEL 743 help 744 If you say Y here, some extra kobject debugging messages will be sent 745 to the syslog. 746 747config DEBUG_HIGHMEM 748 bool "Highmem debugging" 749 depends on DEBUG_KERNEL && HIGHMEM 750 help 751 This options enables addition error checking for high memory systems. 752 Disable for production systems. 753 754config HAVE_DEBUG_BUGVERBOSE 755 bool 756 757config DEBUG_BUGVERBOSE 758 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 759 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 760 default y 761 help 762 Say Y here to make BUG() panics output the file name and line number 763 of the BUG call as well as the EIP and oops trace. This aids 764 debugging but costs about 70-100K of memory. 765 766config DEBUG_INFO 767 bool "Compile the kernel with debug info" 768 depends on DEBUG_KERNEL 769 help 770 If you say Y here the resulting kernel image will include 771 debugging info resulting in a larger kernel image. 772 This adds debug symbols to the kernel and modules (gcc -g), and 773 is needed if you intend to use kernel crashdump or binary object 774 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 775 Say Y here only if you plan to debug the kernel. 776 777 If unsure, say N. 778 779config DEBUG_INFO_REDUCED 780 bool "Reduce debugging information" 781 depends on DEBUG_INFO 782 help 783 If you say Y here gcc is instructed to generate less debugging 784 information for structure types. This means that tools that 785 need full debugging information (like kgdb or systemtap) won't 786 be happy. But if you merely need debugging information to 787 resolve line numbers there is no loss. Advantage is that 788 build directory object sizes shrink dramatically over a full 789 DEBUG_INFO build and compile times are reduced too. 790 Only works with newer gcc versions. 791 792config DEBUG_VM 793 bool "Debug VM" 794 depends on DEBUG_KERNEL 795 help 796 Enable this to turn on extended checks in the virtual-memory system 797 that may impact performance. 798 799 If unsure, say N. 800 801config DEBUG_VM_RB 802 bool "Debug VM red-black trees" 803 depends on DEBUG_VM 804 help 805 Enable this to turn on more extended checks in the virtual-memory 806 system that may impact performance. 807 808 If unsure, say N. 809 810config DEBUG_VIRTUAL 811 bool "Debug VM translations" 812 depends on DEBUG_KERNEL && X86 813 help 814 Enable some costly sanity checks in virtual to page code. This can 815 catch mistakes with virt_to_page() and friends. 816 817 If unsure, say N. 818 819config DEBUG_NOMMU_REGIONS 820 bool "Debug the global anon/private NOMMU mapping region tree" 821 depends on DEBUG_KERNEL && !MMU 822 help 823 This option causes the global tree of anonymous and private mapping 824 regions to be regularly checked for invalid topology. 825 826config DEBUG_WRITECOUNT 827 bool "Debug filesystem writers count" 828 depends on DEBUG_KERNEL 829 help 830 Enable this to catch wrong use of the writers count in struct 831 vfsmount. This will increase the size of each file struct by 832 32 bits. 833 834 If unsure, say N. 835 836config DEBUG_MEMORY_INIT 837 bool "Debug memory initialisation" if EXPERT 838 default !EXPERT 839 help 840 Enable this for additional checks during memory initialisation. 841 The sanity checks verify aspects of the VM such as the memory model 842 and other information provided by the architecture. Verbose 843 information will be printed at KERN_DEBUG loglevel depending 844 on the mminit_loglevel= command-line option. 845 846 If unsure, say Y 847 848config DEBUG_LIST 849 bool "Debug linked list manipulation" 850 depends on DEBUG_KERNEL 851 help 852 Enable this to turn on extended checks in the linked-list 853 walking routines. 854 855 If unsure, say N. 856 857config TEST_LIST_SORT 858 bool "Linked list sorting test" 859 depends on DEBUG_KERNEL 860 help 861 Enable this to turn on 'list_sort()' function test. This test is 862 executed only once during system boot, so affects only boot time. 863 864 If unsure, say N. 865 866config DEBUG_SG 867 bool "Debug SG table operations" 868 depends on DEBUG_KERNEL 869 help 870 Enable this to turn on checks on scatter-gather tables. This can 871 help find problems with drivers that do not properly initialize 872 their sg tables. 873 874 If unsure, say N. 875 876config DEBUG_NOTIFIERS 877 bool "Debug notifier call chains" 878 depends on DEBUG_KERNEL 879 help 880 Enable this to turn on sanity checking for notifier call chains. 881 This is most useful for kernel developers to make sure that 882 modules properly unregister themselves from notifier chains. 883 This is a relatively cheap check but if you care about maximum 884 performance, say N. 885 886config DEBUG_CREDENTIALS 887 bool "Debug credential management" 888 depends on DEBUG_KERNEL 889 help 890 Enable this to turn on some debug checking for credential 891 management. The additional code keeps track of the number of 892 pointers from task_structs to any given cred struct, and checks to 893 see that this number never exceeds the usage count of the cred 894 struct. 895 896 Furthermore, if SELinux is enabled, this also checks that the 897 security pointer in the cred struct is never seen to be invalid. 898 899 If unsure, say N. 900 901# 902# Select this config option from the architecture Kconfig, if it 903# is preferred to always offer frame pointers as a config 904# option on the architecture (regardless of KERNEL_DEBUG): 905# 906config ARCH_WANT_FRAME_POINTERS 907 bool 908 help 909 910config FRAME_POINTER 911 bool "Compile the kernel with frame pointers" 912 depends on DEBUG_KERNEL && \ 913 (CRIS || M68K || FRV || UML || \ 914 AVR32 || SUPERH || BLACKFIN || MN10300) || \ 915 ARCH_WANT_FRAME_POINTERS 916 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 917 help 918 If you say Y here the resulting kernel image will be slightly 919 larger and slower, but it gives very useful debugging information 920 in case of kernel bugs. (precise oopses/stacktraces/warnings) 921 922config BOOT_PRINTK_DELAY 923 bool "Delay each boot printk message by N milliseconds" 924 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 925 help 926 This build option allows you to read kernel boot messages 927 by inserting a short delay after each one. The delay is 928 specified in milliseconds on the kernel command line, 929 using "boot_delay=N". 930 931 It is likely that you would also need to use "lpj=M" to preset 932 the "loops per jiffie" value. 933 See a previous boot log for the "lpj" value to use for your 934 system, and then set "lpj=M" before setting "boot_delay=N". 935 NOTE: Using this option may adversely affect SMP systems. 936 I.e., processors other than the first one may not boot up. 937 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect 938 what it believes to be lockup conditions. 939 940config RCU_TORTURE_TEST 941 tristate "torture tests for RCU" 942 depends on DEBUG_KERNEL 943 default n 944 help 945 This option provides a kernel module that runs torture tests 946 on the RCU infrastructure. The kernel module may be built 947 after the fact on the running kernel to be tested, if desired. 948 949 Say Y here if you want RCU torture tests to be built into 950 the kernel. 951 Say M if you want the RCU torture tests to build as a module. 952 Say N if you are unsure. 953 954config RCU_TORTURE_TEST_RUNNABLE 955 bool "torture tests for RCU runnable by default" 956 depends on RCU_TORTURE_TEST = y 957 default n 958 help 959 This option provides a way to build the RCU torture tests 960 directly into the kernel without them starting up at boot 961 time. You can use /proc/sys/kernel/rcutorture_runnable 962 to manually override this setting. This /proc file is 963 available only when the RCU torture tests have been built 964 into the kernel. 965 966 Say Y here if you want the RCU torture tests to start during 967 boot (you probably don't). 968 Say N here if you want the RCU torture tests to start only 969 after being manually enabled via /proc. 970 971config RCU_CPU_STALL_TIMEOUT 972 int "RCU CPU stall timeout in seconds" 973 depends on TREE_RCU || TREE_PREEMPT_RCU 974 range 3 300 975 default 21 976 help 977 If a given RCU grace period extends more than the specified 978 number of seconds, a CPU stall warning is printed. If the 979 RCU grace period persists, additional CPU stall warnings are 980 printed at more widely spaced intervals. 981 982config RCU_CPU_STALL_VERBOSE 983 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" 984 depends on TREE_PREEMPT_RCU 985 default y 986 help 987 This option causes RCU to printk detailed per-task information 988 for any tasks that are stalling the current RCU grace period. 989 990 Say N if you are unsure. 991 992 Say Y if you want to enable such checks. 993 994config RCU_CPU_STALL_INFO 995 bool "Print additional diagnostics on RCU CPU stall" 996 depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL 997 default n 998 help 999 For each stalled CPU that is aware of the current RCU grace 1000 period, print out additional per-CPU diagnostic information 1001 regarding scheduling-clock ticks, idle state, and, 1002 for RCU_FAST_NO_HZ kernels, idle-entry state. 1003 1004 Say N if you are unsure. 1005 1006 Say Y if you want to enable such diagnostics. 1007 1008config RCU_TRACE 1009 bool "Enable tracing for RCU" 1010 depends on DEBUG_KERNEL 1011 help 1012 This option provides tracing in RCU which presents stats 1013 in debugfs for debugging RCU implementation. 1014 1015 Say Y here if you want to enable RCU tracing 1016 Say N if you are unsure. 1017 1018config KPROBES_SANITY_TEST 1019 bool "Kprobes sanity tests" 1020 depends on DEBUG_KERNEL 1021 depends on KPROBES 1022 default n 1023 help 1024 This option provides for testing basic kprobes functionality on 1025 boot. A sample kprobe, jprobe and kretprobe are inserted and 1026 verified for functionality. 1027 1028 Say N if you are unsure. 1029 1030config BACKTRACE_SELF_TEST 1031 tristate "Self test for the backtrace code" 1032 depends on DEBUG_KERNEL 1033 default n 1034 help 1035 This option provides a kernel module that can be used to test 1036 the kernel stack backtrace code. This option is not useful 1037 for distributions or general kernels, but only for kernel 1038 developers working on architecture code. 1039 1040 Note that if you want to also test saved backtraces, you will 1041 have to enable STACKTRACE as well. 1042 1043 Say N if you are unsure. 1044 1045config DEBUG_BLOCK_EXT_DEVT 1046 bool "Force extended block device numbers and spread them" 1047 depends on DEBUG_KERNEL 1048 depends on BLOCK 1049 default n 1050 help 1051 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1052 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1053 YOU ARE DOING. Distros, please enable this and fix whatever 1054 is broken. 1055 1056 Conventionally, block device numbers are allocated from 1057 predetermined contiguous area. However, extended block area 1058 may introduce non-contiguous block device numbers. This 1059 option forces most block device numbers to be allocated from 1060 the extended space and spreads them to discover kernel or 1061 userland code paths which assume predetermined contiguous 1062 device number allocation. 1063 1064 Note that turning on this debug option shuffles all the 1065 device numbers for all IDE and SCSI devices including libata 1066 ones, so root partition specified using device number 1067 directly (via rdev or root=MAJ:MIN) won't work anymore. 1068 Textual device names (root=/dev/sdXn) will continue to work. 1069 1070 Say N if you are unsure. 1071 1072config DEBUG_FORCE_WEAK_PER_CPU 1073 bool "Force weak per-cpu definitions" 1074 depends on DEBUG_KERNEL 1075 help 1076 s390 and alpha require percpu variables in modules to be 1077 defined weak to work around addressing range issue which 1078 puts the following two restrictions on percpu variable 1079 definitions. 1080 1081 1. percpu symbols must be unique whether static or not 1082 2. percpu variables can't be defined inside a function 1083 1084 To ensure that generic code follows the above rules, this 1085 option forces all percpu variables to be defined as weak. 1086 1087config DEBUG_PER_CPU_MAPS 1088 bool "Debug access to per_cpu maps" 1089 depends on DEBUG_KERNEL 1090 depends on SMP 1091 help 1092 Say Y to verify that the per_cpu map being accessed has 1093 been set up. This adds a fair amount of code to kernel memory 1094 and decreases performance. 1095 1096 Say N if unsure. 1097 1098config LKDTM 1099 tristate "Linux Kernel Dump Test Tool Module" 1100 depends on DEBUG_FS 1101 depends on BLOCK 1102 default n 1103 help 1104 This module enables testing of the different dumping mechanisms by 1105 inducing system failures at predefined crash points. 1106 If you don't need it: say N 1107 Choose M here to compile this code as a module. The module will be 1108 called lkdtm. 1109 1110 Documentation on how to use the module can be found in 1111 Documentation/fault-injection/provoke-crashes.txt 1112 1113config NOTIFIER_ERROR_INJECTION 1114 tristate "Notifier error injection" 1115 depends on DEBUG_KERNEL 1116 select DEBUG_FS 1117 help 1118 This option provides the ability to inject artificial errors to 1119 specified notifier chain callbacks. It is useful to test the error 1120 handling of notifier call chain failures. 1121 1122 Say N if unsure. 1123 1124config CPU_NOTIFIER_ERROR_INJECT 1125 tristate "CPU notifier error injection module" 1126 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1127 help 1128 This option provides a kernel module that can be used to test 1129 the error handling of the cpu notifiers by injecting artificial 1130 errors to CPU notifier chain callbacks. It is controlled through 1131 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1132 1133 If the notifier call chain should be failed with some events 1134 notified, write the error code to "actions/<notifier event>/error". 1135 1136 Example: Inject CPU offline error (-1 == -EPERM) 1137 1138 # cd /sys/kernel/debug/notifier-error-inject/cpu 1139 # echo -1 > actions/CPU_DOWN_PREPARE/error 1140 # echo 0 > /sys/devices/system/cpu/cpu1/online 1141 bash: echo: write error: Operation not permitted 1142 1143 To compile this code as a module, choose M here: the module will 1144 be called cpu-notifier-error-inject. 1145 1146 If unsure, say N. 1147 1148config PM_NOTIFIER_ERROR_INJECT 1149 tristate "PM notifier error injection module" 1150 depends on PM && NOTIFIER_ERROR_INJECTION 1151 default m if PM_DEBUG 1152 help 1153 This option provides the ability to inject artificial errors to 1154 PM notifier chain callbacks. It is controlled through debugfs 1155 interface /sys/kernel/debug/notifier-error-inject/pm 1156 1157 If the notifier call chain should be failed with some events 1158 notified, write the error code to "actions/<notifier event>/error". 1159 1160 Example: Inject PM suspend error (-12 = -ENOMEM) 1161 1162 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1163 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1164 # echo mem > /sys/power/state 1165 bash: echo: write error: Cannot allocate memory 1166 1167 To compile this code as a module, choose M here: the module will 1168 be called pm-notifier-error-inject. 1169 1170 If unsure, say N. 1171 1172config MEMORY_NOTIFIER_ERROR_INJECT 1173 tristate "Memory hotplug notifier error injection module" 1174 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 1175 help 1176 This option provides the ability to inject artificial errors to 1177 memory hotplug notifier chain callbacks. It is controlled through 1178 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 1179 1180 If the notifier call chain should be failed with some events 1181 notified, write the error code to "actions/<notifier event>/error". 1182 1183 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 1184 1185 # cd /sys/kernel/debug/notifier-error-inject/memory 1186 # echo -12 > actions/MEM_GOING_OFFLINE/error 1187 # echo offline > /sys/devices/system/memory/memoryXXX/state 1188 bash: echo: write error: Cannot allocate memory 1189 1190 To compile this code as a module, choose M here: the module will 1191 be called pSeries-reconfig-notifier-error-inject. 1192 1193 If unsure, say N. 1194 1195config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1196 tristate "OF reconfig notifier error injection module" 1197 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1198 help 1199 This option provides the ability to inject artificial errors to 1200 OF reconfig notifier chain callbacks. It is controlled 1201 through debugfs interface under 1202 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1203 1204 If the notifier call chain should be failed with some events 1205 notified, write the error code to "actions/<notifier event>/error". 1206 1207 To compile this code as a module, choose M here: the module will 1208 be called memory-notifier-error-inject. 1209 1210 If unsure, say N. 1211 1212config FAULT_INJECTION 1213 bool "Fault-injection framework" 1214 depends on DEBUG_KERNEL 1215 help 1216 Provide fault-injection framework. 1217 For more details, see Documentation/fault-injection/. 1218 1219config FAILSLAB 1220 bool "Fault-injection capability for kmalloc" 1221 depends on FAULT_INJECTION 1222 depends on SLAB || SLUB 1223 help 1224 Provide fault-injection capability for kmalloc. 1225 1226config FAIL_PAGE_ALLOC 1227 bool "Fault-injection capabilitiy for alloc_pages()" 1228 depends on FAULT_INJECTION 1229 help 1230 Provide fault-injection capability for alloc_pages(). 1231 1232config FAIL_MAKE_REQUEST 1233 bool "Fault-injection capability for disk IO" 1234 depends on FAULT_INJECTION && BLOCK 1235 help 1236 Provide fault-injection capability for disk IO. 1237 1238config FAIL_IO_TIMEOUT 1239 bool "Fault-injection capability for faking disk interrupts" 1240 depends on FAULT_INJECTION && BLOCK 1241 help 1242 Provide fault-injection capability on end IO handling. This 1243 will make the block layer "forget" an interrupt as configured, 1244 thus exercising the error handling. 1245 1246 Only works with drivers that use the generic timeout handling, 1247 for others it wont do anything. 1248 1249config FAIL_MMC_REQUEST 1250 bool "Fault-injection capability for MMC IO" 1251 select DEBUG_FS 1252 depends on FAULT_INJECTION && MMC 1253 help 1254 Provide fault-injection capability for MMC IO. 1255 This will make the mmc core return data errors. This is 1256 useful to test the error handling in the mmc block device 1257 and to test how the mmc host driver handles retries from 1258 the block device. 1259 1260config FAULT_INJECTION_DEBUG_FS 1261 bool "Debugfs entries for fault-injection capabilities" 1262 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1263 help 1264 Enable configuration of fault-injection capabilities via debugfs. 1265 1266config FAULT_INJECTION_STACKTRACE_FILTER 1267 bool "stacktrace filter for fault-injection capabilities" 1268 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1269 depends on !X86_64 1270 select STACKTRACE 1271 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND 1272 help 1273 Provide stacktrace filter for fault-injection capabilities 1274 1275config LATENCYTOP 1276 bool "Latency measuring infrastructure" 1277 depends on HAVE_LATENCYTOP_SUPPORT 1278 depends on DEBUG_KERNEL 1279 depends on STACKTRACE_SUPPORT 1280 depends on PROC_FS 1281 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND 1282 select KALLSYMS 1283 select KALLSYMS_ALL 1284 select STACKTRACE 1285 select SCHEDSTATS 1286 select SCHED_DEBUG 1287 help 1288 Enable this option if you want to use the LatencyTOP tool 1289 to find out which userspace is blocking on what kernel operations. 1290 1291source mm/Kconfig.debug 1292source kernel/trace/Kconfig 1293 1294config RBTREE_TEST 1295 tristate "Red-Black tree test" 1296 depends on m && DEBUG_KERNEL 1297 help 1298 A benchmark measuring the performance of the rbtree library. 1299 Also includes rbtree invariant checks. 1300 1301config INTERVAL_TREE_TEST 1302 tristate "Interval tree test" 1303 depends on m && DEBUG_KERNEL 1304 help 1305 A benchmark measuring the performance of the interval tree library 1306 1307config PROVIDE_OHCI1394_DMA_INIT 1308 bool "Remote debugging over FireWire early on boot" 1309 depends on PCI && X86 1310 help 1311 If you want to debug problems which hang or crash the kernel early 1312 on boot and the crashing machine has a FireWire port, you can use 1313 this feature to remotely access the memory of the crashed machine 1314 over FireWire. This employs remote DMA as part of the OHCI1394 1315 specification which is now the standard for FireWire controllers. 1316 1317 With remote DMA, you can monitor the printk buffer remotely using 1318 firescope and access all memory below 4GB using fireproxy from gdb. 1319 Even controlling a kernel debugger is possible using remote DMA. 1320 1321 Usage: 1322 1323 If ohci1394_dma=early is used as boot parameter, it will initialize 1324 all OHCI1394 controllers which are found in the PCI config space. 1325 1326 As all changes to the FireWire bus such as enabling and disabling 1327 devices cause a bus reset and thereby disable remote DMA for all 1328 devices, be sure to have the cable plugged and FireWire enabled on 1329 the debugging host before booting the debug target for debugging. 1330 1331 This code (~1k) is freed after boot. By then, the firewire stack 1332 in charge of the OHCI-1394 controllers should be used instead. 1333 1334 See Documentation/debugging-via-ohci1394.txt for more information. 1335 1336config FIREWIRE_OHCI_REMOTE_DMA 1337 bool "Remote debugging over FireWire with firewire-ohci" 1338 depends on FIREWIRE_OHCI 1339 help 1340 This option lets you use the FireWire bus for remote debugging 1341 with help of the firewire-ohci driver. It enables unfiltered 1342 remote DMA in firewire-ohci. 1343 See Documentation/debugging-via-ohci1394.txt for more information. 1344 1345 If unsure, say N. 1346 1347config BUILD_DOCSRC 1348 bool "Build targets in Documentation/ tree" 1349 depends on HEADERS_CHECK 1350 help 1351 This option attempts to build objects from the source files in the 1352 kernel Documentation/ tree. 1353 1354 Say N if you are unsure. 1355 1356config DYNAMIC_DEBUG 1357 bool "Enable dynamic printk() support" 1358 default n 1359 depends on PRINTK 1360 depends on DEBUG_FS 1361 help 1362 1363 Compiles debug level messages into the kernel, which would not 1364 otherwise be available at runtime. These messages can then be 1365 enabled/disabled based on various levels of scope - per source file, 1366 function, module, format string, and line number. This mechanism 1367 implicitly compiles in all pr_debug() and dev_dbg() calls, which 1368 enlarges the kernel text size by about 2%. 1369 1370 If a source file is compiled with DEBUG flag set, any 1371 pr_debug() calls in it are enabled by default, but can be 1372 disabled at runtime as below. Note that DEBUG flag is 1373 turned on by many CONFIG_*DEBUG* options. 1374 1375 Usage: 1376 1377 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 1378 which is contained in the 'debugfs' filesystem. Thus, the debugfs 1379 filesystem must first be mounted before making use of this feature. 1380 We refer the control file as: <debugfs>/dynamic_debug/control. This 1381 file contains a list of the debug statements that can be enabled. The 1382 format for each line of the file is: 1383 1384 filename:lineno [module]function flags format 1385 1386 filename : source file of the debug statement 1387 lineno : line number of the debug statement 1388 module : module that contains the debug statement 1389 function : function that contains the debug statement 1390 flags : '=p' means the line is turned 'on' for printing 1391 format : the format used for the debug statement 1392 1393 From a live system: 1394 1395 nullarbor:~ # cat <debugfs>/dynamic_debug/control 1396 # filename:lineno [module]function flags format 1397 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012" 1398 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012" 1399 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012" 1400 1401 Example usage: 1402 1403 // enable the message at line 1603 of file svcsock.c 1404 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 1405 <debugfs>/dynamic_debug/control 1406 1407 // enable all the messages in file svcsock.c 1408 nullarbor:~ # echo -n 'file svcsock.c +p' > 1409 <debugfs>/dynamic_debug/control 1410 1411 // enable all the messages in the NFS server module 1412 nullarbor:~ # echo -n 'module nfsd +p' > 1413 <debugfs>/dynamic_debug/control 1414 1415 // enable all 12 messages in the function svc_process() 1416 nullarbor:~ # echo -n 'func svc_process +p' > 1417 <debugfs>/dynamic_debug/control 1418 1419 // disable all 12 messages in the function svc_process() 1420 nullarbor:~ # echo -n 'func svc_process -p' > 1421 <debugfs>/dynamic_debug/control 1422 1423 See Documentation/dynamic-debug-howto.txt for additional information. 1424 1425config DMA_API_DEBUG 1426 bool "Enable debugging of DMA-API usage" 1427 depends on HAVE_DMA_API_DEBUG 1428 help 1429 Enable this option to debug the use of the DMA API by device drivers. 1430 With this option you will be able to detect common bugs in device 1431 drivers like double-freeing of DMA mappings or freeing mappings that 1432 were never allocated. 1433 This option causes a performance degredation. Use only if you want 1434 to debug device drivers. If unsure, say N. 1435 1436config ATOMIC64_SELFTEST 1437 bool "Perform an atomic64_t self-test at boot" 1438 help 1439 Enable this option to test the atomic64_t functions at boot. 1440 1441 If unsure, say N. 1442 1443config ASYNC_RAID6_TEST 1444 tristate "Self test for hardware accelerated raid6 recovery" 1445 depends on ASYNC_RAID6_RECOV 1446 select ASYNC_MEMCPY 1447 ---help--- 1448 This is a one-shot self test that permutes through the 1449 recovery of all the possible two disk failure scenarios for a 1450 N-disk array. Recovery is performed with the asynchronous 1451 raid6 recovery routines, and will optionally use an offload 1452 engine if one is available. 1453 1454 If unsure, say N. 1455 1456source "samples/Kconfig" 1457 1458source "lib/Kconfig.kgdb" 1459 1460source "lib/Kconfig.kmemcheck" 1461 1462config TEST_KSTRTOX 1463 tristate "Test kstrto*() family of functions at runtime" 1464