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, __cpuinit, 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" 247 help 248 Say Y here to enable the kernel to panic when it oopses. This 249 has the same effect as setting oops=panic on the kernel command 250 line. 251 252 This feature is useful to ensure that the kernel does not do 253 anything erroneous after an oops which could result in data 254 corruption or other issues. 255 256 Say N if unsure. 257 258config PANIC_ON_OOPS_VALUE 259 int 260 range 0 1 261 default 0 if !PANIC_ON_OOPS 262 default 1 if PANIC_ON_OOPS 263 264config DETECT_HUNG_TASK 265 bool "Detect Hung Tasks" 266 depends on DEBUG_KERNEL 267 default LOCKUP_DETECTOR 268 help 269 Say Y here to enable the kernel to detect "hung tasks", 270 which are bugs that cause the task to be stuck in 271 uninterruptible "D" state indefinitiley. 272 273 When a hung task is detected, the kernel will print the 274 current stack trace (which you should report), but the 275 task will stay in uninterruptible state. If lockdep is 276 enabled then all held locks will also be reported. This 277 feature has negligible overhead. 278 279config DEFAULT_HUNG_TASK_TIMEOUT 280 int "Default timeout for hung task detection (in seconds)" 281 depends on DETECT_HUNG_TASK 282 default 120 283 help 284 This option controls the default timeout (in seconds) used 285 to determine when a task has become non-responsive and should 286 be considered hung. 287 288 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 289 sysctl or by writing a value to 290 /proc/sys/kernel/hung_task_timeout_secs. 291 292 A timeout of 0 disables the check. The default is two minutes. 293 Keeping the default should be fine in most cases. 294 295config BOOTPARAM_HUNG_TASK_PANIC 296 bool "Panic (Reboot) On Hung Tasks" 297 depends on DETECT_HUNG_TASK 298 help 299 Say Y here to enable the kernel to panic on "hung tasks", 300 which are bugs that cause the kernel to leave a task stuck 301 in uninterruptible "D" state. 302 303 The panic can be used in combination with panic_timeout, 304 to cause the system to reboot automatically after a 305 hung task has been detected. This feature is useful for 306 high-availability systems that have uptime guarantees and 307 where a hung tasks must be resolved ASAP. 308 309 Say N if unsure. 310 311config BOOTPARAM_HUNG_TASK_PANIC_VALUE 312 int 313 depends on DETECT_HUNG_TASK 314 range 0 1 315 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 316 default 1 if BOOTPARAM_HUNG_TASK_PANIC 317 318config SCHED_DEBUG 319 bool "Collect scheduler debugging info" 320 depends on DEBUG_KERNEL && PROC_FS 321 default y 322 help 323 If you say Y here, the /proc/sched_debug file will be provided 324 that can help debug the scheduler. The runtime overhead of this 325 option is minimal. 326 327config SCHEDSTATS 328 bool "Collect scheduler statistics" 329 depends on DEBUG_KERNEL && PROC_FS 330 help 331 If you say Y here, additional code will be inserted into the 332 scheduler and related routines to collect statistics about 333 scheduler behavior and provide them in /proc/schedstat. These 334 stats may be useful for both tuning and debugging the scheduler 335 If you aren't debugging the scheduler or trying to tune a specific 336 application, you can say N to avoid the very slight overhead 337 this adds. 338 339config TIMER_STATS 340 bool "Collect kernel timers statistics" 341 depends on DEBUG_KERNEL && PROC_FS 342 help 343 If you say Y here, additional code will be inserted into the 344 timer routines to collect statistics about kernel timers being 345 reprogrammed. The statistics can be read from /proc/timer_stats. 346 The statistics collection is started by writing 1 to /proc/timer_stats, 347 writing 0 stops it. This feature is useful to collect information 348 about timer usage patterns in kernel and userspace. This feature 349 is lightweight if enabled in the kernel config but not activated 350 (it defaults to deactivated on bootup and will only be activated 351 if some application like powertop activates it explicitly). 352 353config DEBUG_OBJECTS 354 bool "Debug object operations" 355 depends on DEBUG_KERNEL 356 help 357 If you say Y here, additional code will be inserted into the 358 kernel to track the life time of various objects and validate 359 the operations on those objects. 360 361config DEBUG_OBJECTS_SELFTEST 362 bool "Debug objects selftest" 363 depends on DEBUG_OBJECTS 364 help 365 This enables the selftest of the object debug code. 366 367config DEBUG_OBJECTS_FREE 368 bool "Debug objects in freed memory" 369 depends on DEBUG_OBJECTS 370 help 371 This enables checks whether a k/v free operation frees an area 372 which contains an object which has not been deactivated 373 properly. This can make kmalloc/kfree-intensive workloads 374 much slower. 375 376config DEBUG_OBJECTS_TIMERS 377 bool "Debug timer objects" 378 depends on DEBUG_OBJECTS 379 help 380 If you say Y here, additional code will be inserted into the 381 timer routines to track the life time of timer objects and 382 validate the timer operations. 383 384config DEBUG_OBJECTS_WORK 385 bool "Debug work objects" 386 depends on DEBUG_OBJECTS 387 help 388 If you say Y here, additional code will be inserted into the 389 work queue routines to track the life time of work objects and 390 validate the work operations. 391 392config DEBUG_OBJECTS_RCU_HEAD 393 bool "Debug RCU callbacks objects" 394 depends on DEBUG_OBJECTS 395 help 396 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 397 398config DEBUG_OBJECTS_PERCPU_COUNTER 399 bool "Debug percpu counter objects" 400 depends on DEBUG_OBJECTS 401 help 402 If you say Y here, additional code will be inserted into the 403 percpu counter routines to track the life time of percpu counter 404 objects and validate the percpu counter operations. 405 406config DEBUG_OBJECTS_ENABLE_DEFAULT 407 int "debug_objects bootup default value (0-1)" 408 range 0 1 409 default "1" 410 depends on DEBUG_OBJECTS 411 help 412 Debug objects boot parameter default value 413 414config DEBUG_SLAB 415 bool "Debug slab memory allocations" 416 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 417 help 418 Say Y here to have the kernel do limited verification on memory 419 allocation as well as poisoning memory on free to catch use of freed 420 memory. This can make kmalloc/kfree-intensive workloads much slower. 421 422config DEBUG_SLAB_LEAK 423 bool "Memory leak debugging" 424 depends on DEBUG_SLAB 425 426config SLUB_DEBUG_ON 427 bool "SLUB debugging on by default" 428 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 429 default n 430 help 431 Boot with debugging on by default. SLUB boots by default with 432 the runtime debug capabilities switched off. Enabling this is 433 equivalent to specifying the "slub_debug" parameter on boot. 434 There is no support for more fine grained debug control like 435 possible with slub_debug=xxx. SLUB debugging may be switched 436 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 437 "slub_debug=-". 438 439config SLUB_STATS 440 default n 441 bool "Enable SLUB performance statistics" 442 depends on SLUB && SYSFS 443 help 444 SLUB statistics are useful to debug SLUBs allocation behavior in 445 order find ways to optimize the allocator. This should never be 446 enabled for production use since keeping statistics slows down 447 the allocator by a few percentage points. The slabinfo command 448 supports the determination of the most active slabs to figure 449 out which slabs are relevant to a particular load. 450 Try running: slabinfo -DA 451 452config HAVE_DEBUG_KMEMLEAK 453 bool 454 455config DEBUG_KMEMLEAK 456 bool "Kernel memory leak detector" 457 depends on DEBUG_KERNEL && EXPERIMENTAL && HAVE_DEBUG_KMEMLEAK 458 select DEBUG_FS 459 select STACKTRACE if STACKTRACE_SUPPORT 460 select KALLSYMS 461 select CRC32 462 help 463 Say Y here if you want to enable the memory leak 464 detector. The memory allocation/freeing is traced in a way 465 similar to the Boehm's conservative garbage collector, the 466 difference being that the orphan objects are not freed but 467 only shown in /sys/kernel/debug/kmemleak. Enabling this 468 feature will introduce an overhead to memory 469 allocations. See Documentation/kmemleak.txt for more 470 details. 471 472 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 473 of finding leaks due to the slab objects poisoning. 474 475 In order to access the kmemleak file, debugfs needs to be 476 mounted (usually at /sys/kernel/debug). 477 478config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 479 int "Maximum kmemleak early log entries" 480 depends on DEBUG_KMEMLEAK 481 range 200 40000 482 default 400 483 help 484 Kmemleak must track all the memory allocations to avoid 485 reporting false positives. Since memory may be allocated or 486 freed before kmemleak is initialised, an early log buffer is 487 used to store these actions. If kmemleak reports "early log 488 buffer exceeded", please increase this value. 489 490config DEBUG_KMEMLEAK_TEST 491 tristate "Simple test for the kernel memory leak detector" 492 depends on DEBUG_KMEMLEAK && m 493 help 494 This option enables a module that explicitly leaks memory. 495 496 If unsure, say N. 497 498config DEBUG_KMEMLEAK_DEFAULT_OFF 499 bool "Default kmemleak to off" 500 depends on DEBUG_KMEMLEAK 501 help 502 Say Y here to disable kmemleak by default. It can then be enabled 503 on the command line via kmemleak=on. 504 505config DEBUG_PREEMPT 506 bool "Debug preemptible kernel" 507 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 508 default y 509 help 510 If you say Y here then the kernel will use a debug variant of the 511 commonly used smp_processor_id() function and will print warnings 512 if kernel code uses it in a preemption-unsafe way. Also, the kernel 513 will detect preemption count underflows. 514 515config DEBUG_RT_MUTEXES 516 bool "RT Mutex debugging, deadlock detection" 517 depends on DEBUG_KERNEL && RT_MUTEXES 518 help 519 This allows rt mutex semantics violations and rt mutex related 520 deadlocks (lockups) to be detected and reported automatically. 521 522config DEBUG_PI_LIST 523 bool 524 default y 525 depends on DEBUG_RT_MUTEXES 526 527config RT_MUTEX_TESTER 528 bool "Built-in scriptable tester for rt-mutexes" 529 depends on DEBUG_KERNEL && RT_MUTEXES 530 help 531 This option enables a rt-mutex tester. 532 533config DEBUG_SPINLOCK 534 bool "Spinlock and rw-lock debugging: basic checks" 535 depends on DEBUG_KERNEL 536 select UNINLINE_SPIN_UNLOCK 537 help 538 Say Y here and build SMP to catch missing spinlock initialization 539 and certain other kinds of spinlock errors commonly made. This is 540 best used in conjunction with the NMI watchdog so that spinlock 541 deadlocks are also debuggable. 542 543config DEBUG_MUTEXES 544 bool "Mutex debugging: basic checks" 545 depends on DEBUG_KERNEL 546 help 547 This feature allows mutex semantics violations to be detected and 548 reported. 549 550config DEBUG_LOCK_ALLOC 551 bool "Lock debugging: detect incorrect freeing of live locks" 552 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 553 select DEBUG_SPINLOCK 554 select DEBUG_MUTEXES 555 select LOCKDEP 556 help 557 This feature will check whether any held lock (spinlock, rwlock, 558 mutex or rwsem) is incorrectly freed by the kernel, via any of the 559 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 560 vfree(), etc.), whether a live lock is incorrectly reinitialized via 561 spin_lock_init()/mutex_init()/etc., or whether there is any lock 562 held during task exit. 563 564config PROVE_LOCKING 565 bool "Lock debugging: prove locking correctness" 566 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 567 select LOCKDEP 568 select DEBUG_SPINLOCK 569 select DEBUG_MUTEXES 570 select DEBUG_LOCK_ALLOC 571 select TRACE_IRQFLAGS 572 default n 573 help 574 This feature enables the kernel to prove that all locking 575 that occurs in the kernel runtime is mathematically 576 correct: that under no circumstance could an arbitrary (and 577 not yet triggered) combination of observed locking 578 sequences (on an arbitrary number of CPUs, running an 579 arbitrary number of tasks and interrupt contexts) cause a 580 deadlock. 581 582 In short, this feature enables the kernel to report locking 583 related deadlocks before they actually occur. 584 585 The proof does not depend on how hard and complex a 586 deadlock scenario would be to trigger: how many 587 participant CPUs, tasks and irq-contexts would be needed 588 for it to trigger. The proof also does not depend on 589 timing: if a race and a resulting deadlock is possible 590 theoretically (no matter how unlikely the race scenario 591 is), it will be proven so and will immediately be 592 reported by the kernel (once the event is observed that 593 makes the deadlock theoretically possible). 594 595 If a deadlock is impossible (i.e. the locking rules, as 596 observed by the kernel, are mathematically correct), the 597 kernel reports nothing. 598 599 NOTE: this feature can also be enabled for rwlocks, mutexes 600 and rwsems - in which case all dependencies between these 601 different locking variants are observed and mapped too, and 602 the proof of observed correctness is also maintained for an 603 arbitrary combination of these separate locking variants. 604 605 For more details, see Documentation/lockdep-design.txt. 606 607config LOCKDEP 608 bool 609 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 610 select STACKTRACE 611 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE 612 select KALLSYMS 613 select KALLSYMS_ALL 614 615config LOCK_STAT 616 bool "Lock usage statistics" 617 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 618 select LOCKDEP 619 select DEBUG_SPINLOCK 620 select DEBUG_MUTEXES 621 select DEBUG_LOCK_ALLOC 622 default n 623 help 624 This feature enables tracking lock contention points 625 626 For more details, see Documentation/lockstat.txt 627 628 This also enables lock events required by "perf lock", 629 subcommand of perf. 630 If you want to use "perf lock", you also need to turn on 631 CONFIG_EVENT_TRACING. 632 633 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 634 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 635 636config DEBUG_LOCKDEP 637 bool "Lock dependency engine debugging" 638 depends on DEBUG_KERNEL && LOCKDEP 639 help 640 If you say Y here, the lock dependency engine will do 641 additional runtime checks to debug itself, at the price 642 of more runtime overhead. 643 644config TRACE_IRQFLAGS 645 bool 646 help 647 Enables hooks to interrupt enabling and disabling for 648 either tracing or lock debugging. 649 650config DEBUG_ATOMIC_SLEEP 651 bool "Sleep inside atomic section checking" 652 select PREEMPT_COUNT 653 depends on DEBUG_KERNEL 654 help 655 If you say Y here, various routines which may sleep will become very 656 noisy if they are called inside atomic sections: when a spinlock is 657 held, inside an rcu read side critical section, inside preempt disabled 658 sections, inside an interrupt, etc... 659 660config DEBUG_LOCKING_API_SELFTESTS 661 bool "Locking API boot-time self-tests" 662 depends on DEBUG_KERNEL 663 help 664 Say Y here if you want the kernel to run a short self-test during 665 bootup. The self-test checks whether common types of locking bugs 666 are detected by debugging mechanisms or not. (if you disable 667 lock debugging then those bugs wont be detected of course.) 668 The following locking APIs are covered: spinlocks, rwlocks, 669 mutexes and rwsems. 670 671config STACKTRACE 672 bool 673 depends on STACKTRACE_SUPPORT 674 675config DEBUG_STACK_USAGE 676 bool "Stack utilization instrumentation" 677 depends on DEBUG_KERNEL && !IA64 && !PARISC 678 help 679 Enables the display of the minimum amount of free stack which each 680 task has ever had available in the sysrq-T and sysrq-P debug output. 681 682 This option will slow down process creation somewhat. 683 684config DEBUG_KOBJECT 685 bool "kobject debugging" 686 depends on DEBUG_KERNEL 687 help 688 If you say Y here, some extra kobject debugging messages will be sent 689 to the syslog. 690 691config DEBUG_HIGHMEM 692 bool "Highmem debugging" 693 depends on DEBUG_KERNEL && HIGHMEM 694 help 695 This options enables addition error checking for high memory systems. 696 Disable for production systems. 697 698config HAVE_DEBUG_BUGVERBOSE 699 bool 700 701config DEBUG_BUGVERBOSE 702 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 703 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 704 default y 705 help 706 Say Y here to make BUG() panics output the file name and line number 707 of the BUG call as well as the EIP and oops trace. This aids 708 debugging but costs about 70-100K of memory. 709 710config DEBUG_INFO 711 bool "Compile the kernel with debug info" 712 depends on DEBUG_KERNEL 713 help 714 If you say Y here the resulting kernel image will include 715 debugging info resulting in a larger kernel image. 716 This adds debug symbols to the kernel and modules (gcc -g), and 717 is needed if you intend to use kernel crashdump or binary object 718 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 719 Say Y here only if you plan to debug the kernel. 720 721 If unsure, say N. 722 723config DEBUG_INFO_REDUCED 724 bool "Reduce debugging information" 725 depends on DEBUG_INFO 726 help 727 If you say Y here gcc is instructed to generate less debugging 728 information for structure types. This means that tools that 729 need full debugging information (like kgdb or systemtap) won't 730 be happy. But if you merely need debugging information to 731 resolve line numbers there is no loss. Advantage is that 732 build directory object sizes shrink dramatically over a full 733 DEBUG_INFO build and compile times are reduced too. 734 Only works with newer gcc versions. 735 736config DEBUG_VM 737 bool "Debug VM" 738 depends on DEBUG_KERNEL 739 help 740 Enable this to turn on extended checks in the virtual-memory system 741 that may impact performance. 742 743 If unsure, say N. 744 745config DEBUG_VM_RB 746 bool "Debug VM red-black trees" 747 depends on DEBUG_VM 748 help 749 Enable this to turn on more extended checks in the virtual-memory 750 system that may impact performance. 751 752 If unsure, say N. 753 754config DEBUG_VIRTUAL 755 bool "Debug VM translations" 756 depends on DEBUG_KERNEL && X86 757 help 758 Enable some costly sanity checks in virtual to page code. This can 759 catch mistakes with virt_to_page() and friends. 760 761 If unsure, say N. 762 763config DEBUG_NOMMU_REGIONS 764 bool "Debug the global anon/private NOMMU mapping region tree" 765 depends on DEBUG_KERNEL && !MMU 766 help 767 This option causes the global tree of anonymous and private mapping 768 regions to be regularly checked for invalid topology. 769 770config DEBUG_WRITECOUNT 771 bool "Debug filesystem writers count" 772 depends on DEBUG_KERNEL 773 help 774 Enable this to catch wrong use of the writers count in struct 775 vfsmount. This will increase the size of each file struct by 776 32 bits. 777 778 If unsure, say N. 779 780config DEBUG_MEMORY_INIT 781 bool "Debug memory initialisation" if EXPERT 782 default !EXPERT 783 help 784 Enable this for additional checks during memory initialisation. 785 The sanity checks verify aspects of the VM such as the memory model 786 and other information provided by the architecture. Verbose 787 information will be printed at KERN_DEBUG loglevel depending 788 on the mminit_loglevel= command-line option. 789 790 If unsure, say Y 791 792config DEBUG_LIST 793 bool "Debug linked list manipulation" 794 depends on DEBUG_KERNEL 795 help 796 Enable this to turn on extended checks in the linked-list 797 walking routines. 798 799 If unsure, say N. 800 801config TEST_LIST_SORT 802 bool "Linked list sorting test" 803 depends on DEBUG_KERNEL 804 help 805 Enable this to turn on 'list_sort()' function test. This test is 806 executed only once during system boot, so affects only boot time. 807 808 If unsure, say N. 809 810config DEBUG_SG 811 bool "Debug SG table operations" 812 depends on DEBUG_KERNEL 813 help 814 Enable this to turn on checks on scatter-gather tables. This can 815 help find problems with drivers that do not properly initialize 816 their sg tables. 817 818 If unsure, say N. 819 820config DEBUG_NOTIFIERS 821 bool "Debug notifier call chains" 822 depends on DEBUG_KERNEL 823 help 824 Enable this to turn on sanity checking for notifier call chains. 825 This is most useful for kernel developers to make sure that 826 modules properly unregister themselves from notifier chains. 827 This is a relatively cheap check but if you care about maximum 828 performance, say N. 829 830config DEBUG_CREDENTIALS 831 bool "Debug credential management" 832 depends on DEBUG_KERNEL 833 help 834 Enable this to turn on some debug checking for credential 835 management. The additional code keeps track of the number of 836 pointers from task_structs to any given cred struct, and checks to 837 see that this number never exceeds the usage count of the cred 838 struct. 839 840 Furthermore, if SELinux is enabled, this also checks that the 841 security pointer in the cred struct is never seen to be invalid. 842 843 If unsure, say N. 844 845# 846# Select this config option from the architecture Kconfig, if it 847# is preferred to always offer frame pointers as a config 848# option on the architecture (regardless of KERNEL_DEBUG): 849# 850config ARCH_WANT_FRAME_POINTERS 851 bool 852 help 853 854config FRAME_POINTER 855 bool "Compile the kernel with frame pointers" 856 depends on DEBUG_KERNEL && \ 857 (CRIS || M68K || FRV || UML || \ 858 AVR32 || SUPERH || BLACKFIN || MN10300) || \ 859 ARCH_WANT_FRAME_POINTERS 860 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 861 help 862 If you say Y here the resulting kernel image will be slightly 863 larger and slower, but it gives very useful debugging information 864 in case of kernel bugs. (precise oopses/stacktraces/warnings) 865 866config BOOT_PRINTK_DELAY 867 bool "Delay each boot printk message by N milliseconds" 868 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 869 help 870 This build option allows you to read kernel boot messages 871 by inserting a short delay after each one. The delay is 872 specified in milliseconds on the kernel command line, 873 using "boot_delay=N". 874 875 It is likely that you would also need to use "lpj=M" to preset 876 the "loops per jiffie" value. 877 See a previous boot log for the "lpj" value to use for your 878 system, and then set "lpj=M" before setting "boot_delay=N". 879 NOTE: Using this option may adversely affect SMP systems. 880 I.e., processors other than the first one may not boot up. 881 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect 882 what it believes to be lockup conditions. 883 884menu "RCU Debugging" 885 886config PROVE_RCU 887 bool "RCU debugging: prove RCU correctness" 888 depends on PROVE_LOCKING 889 default n 890 help 891 This feature enables lockdep extensions that check for correct 892 use of RCU APIs. This is currently under development. Say Y 893 if you want to debug RCU usage or help work on the PROVE_RCU 894 feature. 895 896 Say N if you are unsure. 897 898config PROVE_RCU_REPEATEDLY 899 bool "RCU debugging: don't disable PROVE_RCU on first splat" 900 depends on PROVE_RCU 901 default n 902 help 903 By itself, PROVE_RCU will disable checking upon issuing the 904 first warning (or "splat"). This feature prevents such 905 disabling, allowing multiple RCU-lockdep warnings to be printed 906 on a single reboot. 907 908 Say Y to allow multiple RCU-lockdep warnings per boot. 909 910 Say N if you are unsure. 911 912config PROVE_RCU_DELAY 913 bool "RCU debugging: preemptible RCU race provocation" 914 depends on DEBUG_KERNEL && PREEMPT_RCU 915 default n 916 help 917 There is a class of races that involve an unlikely preemption 918 of __rcu_read_unlock() just after ->rcu_read_lock_nesting has 919 been set to INT_MIN. This feature inserts a delay at that 920 point to increase the probability of these races. 921 922 Say Y to increase probability of preemption of __rcu_read_unlock(). 923 924 Say N if you are unsure. 925 926config SPARSE_RCU_POINTER 927 bool "RCU debugging: sparse-based checks for pointer usage" 928 default n 929 help 930 This feature enables the __rcu sparse annotation for 931 RCU-protected pointers. This annotation will cause sparse 932 to flag any non-RCU used of annotated pointers. This can be 933 helpful when debugging RCU usage. Please note that this feature 934 is not intended to enforce code cleanliness; it is instead merely 935 a debugging aid. 936 937 Say Y to make sparse flag questionable use of RCU-protected pointers 938 939 Say N if you are unsure. 940 941config RCU_TORTURE_TEST 942 tristate "torture tests for RCU" 943 depends on DEBUG_KERNEL 944 default n 945 help 946 This option provides a kernel module that runs torture tests 947 on the RCU infrastructure. The kernel module may be built 948 after the fact on the running kernel to be tested, if desired. 949 950 Say Y here if you want RCU torture tests to be built into 951 the kernel. 952 Say M if you want the RCU torture tests to build as a module. 953 Say N if you are unsure. 954 955config RCU_TORTURE_TEST_RUNNABLE 956 bool "torture tests for RCU runnable by default" 957 depends on RCU_TORTURE_TEST = y 958 default n 959 help 960 This option provides a way to build the RCU torture tests 961 directly into the kernel without them starting up at boot 962 time. You can use /proc/sys/kernel/rcutorture_runnable 963 to manually override this setting. This /proc file is 964 available only when the RCU torture tests have been built 965 into the kernel. 966 967 Say Y here if you want the RCU torture tests to start during 968 boot (you probably don't). 969 Say N here if you want the RCU torture tests to start only 970 after being manually enabled via /proc. 971 972config RCU_CPU_STALL_TIMEOUT 973 int "RCU CPU stall timeout in seconds" 974 depends on RCU_STALL_COMMON 975 range 3 300 976 default 21 977 help 978 If a given RCU grace period extends more than the specified 979 number of seconds, a CPU stall warning is printed. If the 980 RCU grace period persists, additional CPU stall warnings are 981 printed at more widely spaced intervals. 982 983config RCU_CPU_STALL_VERBOSE 984 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" 985 depends on TREE_PREEMPT_RCU 986 default y 987 help 988 This option causes RCU to printk detailed per-task information 989 for any tasks that are stalling the current RCU grace period. 990 991 Say N if you are unsure. 992 993 Say Y if you want to enable such checks. 994 995config RCU_CPU_STALL_INFO 996 bool "Print additional diagnostics on RCU CPU stall" 997 depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL 998 default n 999 help 1000 For each stalled CPU that is aware of the current RCU grace 1001 period, print out additional per-CPU diagnostic information 1002 regarding scheduling-clock ticks, idle state, and, 1003 for RCU_FAST_NO_HZ kernels, idle-entry state. 1004 1005 Say N if you are unsure. 1006 1007 Say Y if you want to enable such diagnostics. 1008 1009config RCU_TRACE 1010 bool "Enable tracing for RCU" 1011 depends on DEBUG_KERNEL 1012 select TRACE_CLOCK 1013 help 1014 This option provides tracing in RCU which presents stats 1015 in debugfs for debugging RCU implementation. 1016 1017 Say Y here if you want to enable RCU tracing 1018 Say N if you are unsure. 1019 1020endmenu # "RCU Debugging" 1021 1022config KPROBES_SANITY_TEST 1023 bool "Kprobes sanity tests" 1024 depends on DEBUG_KERNEL 1025 depends on KPROBES 1026 default n 1027 help 1028 This option provides for testing basic kprobes functionality on 1029 boot. A sample kprobe, jprobe and kretprobe are inserted and 1030 verified for functionality. 1031 1032 Say N if you are unsure. 1033 1034config BACKTRACE_SELF_TEST 1035 tristate "Self test for the backtrace code" 1036 depends on DEBUG_KERNEL 1037 default n 1038 help 1039 This option provides a kernel module that can be used to test 1040 the kernel stack backtrace code. This option is not useful 1041 for distributions or general kernels, but only for kernel 1042 developers working on architecture code. 1043 1044 Note that if you want to also test saved backtraces, you will 1045 have to enable STACKTRACE as well. 1046 1047 Say N if you are unsure. 1048 1049config DEBUG_BLOCK_EXT_DEVT 1050 bool "Force extended block device numbers and spread them" 1051 depends on DEBUG_KERNEL 1052 depends on BLOCK 1053 default n 1054 help 1055 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1056 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1057 YOU ARE DOING. Distros, please enable this and fix whatever 1058 is broken. 1059 1060 Conventionally, block device numbers are allocated from 1061 predetermined contiguous area. However, extended block area 1062 may introduce non-contiguous block device numbers. This 1063 option forces most block device numbers to be allocated from 1064 the extended space and spreads them to discover kernel or 1065 userland code paths which assume predetermined contiguous 1066 device number allocation. 1067 1068 Note that turning on this debug option shuffles all the 1069 device numbers for all IDE and SCSI devices including libata 1070 ones, so root partition specified using device number 1071 directly (via rdev or root=MAJ:MIN) won't work anymore. 1072 Textual device names (root=/dev/sdXn) will continue to work. 1073 1074 Say N if you are unsure. 1075 1076config DEBUG_FORCE_WEAK_PER_CPU 1077 bool "Force weak per-cpu definitions" 1078 depends on DEBUG_KERNEL 1079 help 1080 s390 and alpha require percpu variables in modules to be 1081 defined weak to work around addressing range issue which 1082 puts the following two restrictions on percpu variable 1083 definitions. 1084 1085 1. percpu symbols must be unique whether static or not 1086 2. percpu variables can't be defined inside a function 1087 1088 To ensure that generic code follows the above rules, this 1089 option forces all percpu variables to be defined as weak. 1090 1091config DEBUG_PER_CPU_MAPS 1092 bool "Debug access to per_cpu maps" 1093 depends on DEBUG_KERNEL 1094 depends on SMP 1095 help 1096 Say Y to verify that the per_cpu map being accessed has 1097 been set up. This adds a fair amount of code to kernel memory 1098 and decreases performance. 1099 1100 Say N if unsure. 1101 1102config LKDTM 1103 tristate "Linux Kernel Dump Test Tool Module" 1104 depends on DEBUG_FS 1105 depends on BLOCK 1106 default n 1107 help 1108 This module enables testing of the different dumping mechanisms by 1109 inducing system failures at predefined crash points. 1110 If you don't need it: say N 1111 Choose M here to compile this code as a module. The module will be 1112 called lkdtm. 1113 1114 Documentation on how to use the module can be found in 1115 Documentation/fault-injection/provoke-crashes.txt 1116 1117config NOTIFIER_ERROR_INJECTION 1118 tristate "Notifier error injection" 1119 depends on DEBUG_KERNEL 1120 select DEBUG_FS 1121 help 1122 This option provides the ability to inject artificial errors to 1123 specified notifier chain callbacks. It is useful to test the error 1124 handling of notifier call chain failures. 1125 1126 Say N if unsure. 1127 1128config CPU_NOTIFIER_ERROR_INJECT 1129 tristate "CPU notifier error injection module" 1130 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1131 help 1132 This option provides a kernel module that can be used to test 1133 the error handling of the cpu notifiers by injecting artificial 1134 errors to CPU notifier chain callbacks. It is controlled through 1135 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1136 1137 If the notifier call chain should be failed with some events 1138 notified, write the error code to "actions/<notifier event>/error". 1139 1140 Example: Inject CPU offline error (-1 == -EPERM) 1141 1142 # cd /sys/kernel/debug/notifier-error-inject/cpu 1143 # echo -1 > actions/CPU_DOWN_PREPARE/error 1144 # echo 0 > /sys/devices/system/cpu/cpu1/online 1145 bash: echo: write error: Operation not permitted 1146 1147 To compile this code as a module, choose M here: the module will 1148 be called cpu-notifier-error-inject. 1149 1150 If unsure, say N. 1151 1152config PM_NOTIFIER_ERROR_INJECT 1153 tristate "PM notifier error injection module" 1154 depends on PM && NOTIFIER_ERROR_INJECTION 1155 default m if PM_DEBUG 1156 help 1157 This option provides the ability to inject artificial errors to 1158 PM notifier chain callbacks. It is controlled through debugfs 1159 interface /sys/kernel/debug/notifier-error-inject/pm 1160 1161 If the notifier call chain should be failed with some events 1162 notified, write the error code to "actions/<notifier event>/error". 1163 1164 Example: Inject PM suspend error (-12 = -ENOMEM) 1165 1166 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1167 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1168 # echo mem > /sys/power/state 1169 bash: echo: write error: Cannot allocate memory 1170 1171 To compile this code as a module, choose M here: the module will 1172 be called pm-notifier-error-inject. 1173 1174 If unsure, say N. 1175 1176config MEMORY_NOTIFIER_ERROR_INJECT 1177 tristate "Memory hotplug notifier error injection module" 1178 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 1179 help 1180 This option provides the ability to inject artificial errors to 1181 memory hotplug notifier chain callbacks. It is controlled through 1182 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 1183 1184 If the notifier call chain should be failed with some events 1185 notified, write the error code to "actions/<notifier event>/error". 1186 1187 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 1188 1189 # cd /sys/kernel/debug/notifier-error-inject/memory 1190 # echo -12 > actions/MEM_GOING_OFFLINE/error 1191 # echo offline > /sys/devices/system/memory/memoryXXX/state 1192 bash: echo: write error: Cannot allocate memory 1193 1194 To compile this code as a module, choose M here: the module will 1195 be called pSeries-reconfig-notifier-error-inject. 1196 1197 If unsure, say N. 1198 1199config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1200 tristate "OF reconfig notifier error injection module" 1201 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1202 help 1203 This option provides the ability to inject artificial errors to 1204 OF reconfig notifier chain callbacks. It is controlled 1205 through debugfs interface under 1206 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1207 1208 If the notifier call chain should be failed with some events 1209 notified, write the error code to "actions/<notifier event>/error". 1210 1211 To compile this code as a module, choose M here: the module will 1212 be called memory-notifier-error-inject. 1213 1214 If unsure, say N. 1215 1216config FAULT_INJECTION 1217 bool "Fault-injection framework" 1218 depends on DEBUG_KERNEL 1219 help 1220 Provide fault-injection framework. 1221 For more details, see Documentation/fault-injection/. 1222 1223config FAILSLAB 1224 bool "Fault-injection capability for kmalloc" 1225 depends on FAULT_INJECTION 1226 depends on SLAB || SLUB 1227 help 1228 Provide fault-injection capability for kmalloc. 1229 1230config FAIL_PAGE_ALLOC 1231 bool "Fault-injection capabilitiy for alloc_pages()" 1232 depends on FAULT_INJECTION 1233 help 1234 Provide fault-injection capability for alloc_pages(). 1235 1236config FAIL_MAKE_REQUEST 1237 bool "Fault-injection capability for disk IO" 1238 depends on FAULT_INJECTION && BLOCK 1239 help 1240 Provide fault-injection capability for disk IO. 1241 1242config FAIL_IO_TIMEOUT 1243 bool "Fault-injection capability for faking disk interrupts" 1244 depends on FAULT_INJECTION && BLOCK 1245 help 1246 Provide fault-injection capability on end IO handling. This 1247 will make the block layer "forget" an interrupt as configured, 1248 thus exercising the error handling. 1249 1250 Only works with drivers that use the generic timeout handling, 1251 for others it wont do anything. 1252 1253config FAIL_MMC_REQUEST 1254 bool "Fault-injection capability for MMC IO" 1255 select DEBUG_FS 1256 depends on FAULT_INJECTION && MMC 1257 help 1258 Provide fault-injection capability for MMC IO. 1259 This will make the mmc core return data errors. This is 1260 useful to test the error handling in the mmc block device 1261 and to test how the mmc host driver handles retries from 1262 the block device. 1263 1264config FAULT_INJECTION_DEBUG_FS 1265 bool "Debugfs entries for fault-injection capabilities" 1266 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1267 help 1268 Enable configuration of fault-injection capabilities via debugfs. 1269 1270config FAULT_INJECTION_STACKTRACE_FILTER 1271 bool "stacktrace filter for fault-injection capabilities" 1272 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1273 depends on !X86_64 1274 select STACKTRACE 1275 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND 1276 help 1277 Provide stacktrace filter for fault-injection capabilities 1278 1279config LATENCYTOP 1280 bool "Latency measuring infrastructure" 1281 depends on HAVE_LATENCYTOP_SUPPORT 1282 depends on DEBUG_KERNEL 1283 depends on STACKTRACE_SUPPORT 1284 depends on PROC_FS 1285 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND 1286 select KALLSYMS 1287 select KALLSYMS_ALL 1288 select STACKTRACE 1289 select SCHEDSTATS 1290 select SCHED_DEBUG 1291 help 1292 Enable this option if you want to use the LatencyTOP tool 1293 to find out which userspace is blocking on what kernel operations. 1294 1295source mm/Kconfig.debug 1296source kernel/trace/Kconfig 1297 1298config RBTREE_TEST 1299 tristate "Red-Black tree test" 1300 depends on m && DEBUG_KERNEL 1301 help 1302 A benchmark measuring the performance of the rbtree library. 1303 Also includes rbtree invariant checks. 1304 1305config INTERVAL_TREE_TEST 1306 tristate "Interval tree test" 1307 depends on m && DEBUG_KERNEL 1308 help 1309 A benchmark measuring the performance of the interval tree library 1310 1311config PROVIDE_OHCI1394_DMA_INIT 1312 bool "Remote debugging over FireWire early on boot" 1313 depends on PCI && X86 1314 help 1315 If you want to debug problems which hang or crash the kernel early 1316 on boot and the crashing machine has a FireWire port, you can use 1317 this feature to remotely access the memory of the crashed machine 1318 over FireWire. This employs remote DMA as part of the OHCI1394 1319 specification which is now the standard for FireWire controllers. 1320 1321 With remote DMA, you can monitor the printk buffer remotely using 1322 firescope and access all memory below 4GB using fireproxy from gdb. 1323 Even controlling a kernel debugger is possible using remote DMA. 1324 1325 Usage: 1326 1327 If ohci1394_dma=early is used as boot parameter, it will initialize 1328 all OHCI1394 controllers which are found in the PCI config space. 1329 1330 As all changes to the FireWire bus such as enabling and disabling 1331 devices cause a bus reset and thereby disable remote DMA for all 1332 devices, be sure to have the cable plugged and FireWire enabled on 1333 the debugging host before booting the debug target for debugging. 1334 1335 This code (~1k) is freed after boot. By then, the firewire stack 1336 in charge of the OHCI-1394 controllers should be used instead. 1337 1338 See Documentation/debugging-via-ohci1394.txt for more information. 1339 1340config FIREWIRE_OHCI_REMOTE_DMA 1341 bool "Remote debugging over FireWire with firewire-ohci" 1342 depends on FIREWIRE_OHCI 1343 help 1344 This option lets you use the FireWire bus for remote debugging 1345 with help of the firewire-ohci driver. It enables unfiltered 1346 remote DMA in firewire-ohci. 1347 See Documentation/debugging-via-ohci1394.txt for more information. 1348 1349 If unsure, say N. 1350 1351config BUILD_DOCSRC 1352 bool "Build targets in Documentation/ tree" 1353 depends on HEADERS_CHECK 1354 help 1355 This option attempts to build objects from the source files in the 1356 kernel Documentation/ tree. 1357 1358 Say N if you are unsure. 1359 1360config DYNAMIC_DEBUG 1361 bool "Enable dynamic printk() support" 1362 default n 1363 depends on PRINTK 1364 depends on DEBUG_FS 1365 help 1366 1367 Compiles debug level messages into the kernel, which would not 1368 otherwise be available at runtime. These messages can then be 1369 enabled/disabled based on various levels of scope - per source file, 1370 function, module, format string, and line number. This mechanism 1371 implicitly compiles in all pr_debug() and dev_dbg() calls, which 1372 enlarges the kernel text size by about 2%. 1373 1374 If a source file is compiled with DEBUG flag set, any 1375 pr_debug() calls in it are enabled by default, but can be 1376 disabled at runtime as below. Note that DEBUG flag is 1377 turned on by many CONFIG_*DEBUG* options. 1378 1379 Usage: 1380 1381 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 1382 which is contained in the 'debugfs' filesystem. Thus, the debugfs 1383 filesystem must first be mounted before making use of this feature. 1384 We refer the control file as: <debugfs>/dynamic_debug/control. This 1385 file contains a list of the debug statements that can be enabled. The 1386 format for each line of the file is: 1387 1388 filename:lineno [module]function flags format 1389 1390 filename : source file of the debug statement 1391 lineno : line number of the debug statement 1392 module : module that contains the debug statement 1393 function : function that contains the debug statement 1394 flags : '=p' means the line is turned 'on' for printing 1395 format : the format used for the debug statement 1396 1397 From a live system: 1398 1399 nullarbor:~ # cat <debugfs>/dynamic_debug/control 1400 # filename:lineno [module]function flags format 1401 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012" 1402 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012" 1403 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012" 1404 1405 Example usage: 1406 1407 // enable the message at line 1603 of file svcsock.c 1408 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 1409 <debugfs>/dynamic_debug/control 1410 1411 // enable all the messages in file svcsock.c 1412 nullarbor:~ # echo -n 'file svcsock.c +p' > 1413 <debugfs>/dynamic_debug/control 1414 1415 // enable all the messages in the NFS server module 1416 nullarbor:~ # echo -n 'module nfsd +p' > 1417 <debugfs>/dynamic_debug/control 1418 1419 // enable all 12 messages in the function svc_process() 1420 nullarbor:~ # echo -n 'func svc_process +p' > 1421 <debugfs>/dynamic_debug/control 1422 1423 // disable all 12 messages in the function svc_process() 1424 nullarbor:~ # echo -n 'func svc_process -p' > 1425 <debugfs>/dynamic_debug/control 1426 1427 See Documentation/dynamic-debug-howto.txt for additional information. 1428 1429config DMA_API_DEBUG 1430 bool "Enable debugging of DMA-API usage" 1431 depends on HAVE_DMA_API_DEBUG 1432 help 1433 Enable this option to debug the use of the DMA API by device drivers. 1434 With this option you will be able to detect common bugs in device 1435 drivers like double-freeing of DMA mappings or freeing mappings that 1436 were never allocated. 1437 This option causes a performance degredation. Use only if you want 1438 to debug device drivers. If unsure, say N. 1439 1440config ATOMIC64_SELFTEST 1441 bool "Perform an atomic64_t self-test at boot" 1442 help 1443 Enable this option to test the atomic64_t functions at boot. 1444 1445 If unsure, say N. 1446 1447config ASYNC_RAID6_TEST 1448 tristate "Self test for hardware accelerated raid6 recovery" 1449 depends on ASYNC_RAID6_RECOV 1450 select ASYNC_MEMCPY 1451 ---help--- 1452 This is a one-shot self test that permutes through the 1453 recovery of all the possible two disk failure scenarios for a 1454 N-disk array. Recovery is performed with the asynchronous 1455 raid6 recovery routines, and will optionally use an offload 1456 engine if one is available. 1457 1458 If unsure, say N. 1459 1460source "samples/Kconfig" 1461 1462source "lib/Kconfig.kgdb" 1463 1464source "lib/Kconfig.kmemcheck" 1465 1466config TEST_KSTRTOX 1467 tristate "Test kstrto*() family of functions at runtime" 1468