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" 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 LOCKDEP 609 bool 610 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 611 select STACKTRACE 612 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE 613 select KALLSYMS 614 select KALLSYMS_ALL 615 616config LOCK_STAT 617 bool "Lock usage statistics" 618 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 619 select LOCKDEP 620 select DEBUG_SPINLOCK 621 select DEBUG_MUTEXES 622 select DEBUG_LOCK_ALLOC 623 default n 624 help 625 This feature enables tracking lock contention points 626 627 For more details, see Documentation/lockstat.txt 628 629 This also enables lock events required by "perf lock", 630 subcommand of perf. 631 If you want to use "perf lock", you also need to turn on 632 CONFIG_EVENT_TRACING. 633 634 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 635 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 636 637config DEBUG_LOCKDEP 638 bool "Lock dependency engine debugging" 639 depends on DEBUG_KERNEL && LOCKDEP 640 help 641 If you say Y here, the lock dependency engine will do 642 additional runtime checks to debug itself, at the price 643 of more runtime overhead. 644 645config TRACE_IRQFLAGS 646 bool 647 help 648 Enables hooks to interrupt enabling and disabling for 649 either tracing or lock debugging. 650 651config DEBUG_ATOMIC_SLEEP 652 bool "Sleep inside atomic section checking" 653 select PREEMPT_COUNT 654 depends on DEBUG_KERNEL 655 help 656 If you say Y here, various routines which may sleep will become very 657 noisy if they are called inside atomic sections: when a spinlock is 658 held, inside an rcu read side critical section, inside preempt disabled 659 sections, inside an interrupt, etc... 660 661config DEBUG_LOCKING_API_SELFTESTS 662 bool "Locking API boot-time self-tests" 663 depends on DEBUG_KERNEL 664 help 665 Say Y here if you want the kernel to run a short self-test during 666 bootup. The self-test checks whether common types of locking bugs 667 are detected by debugging mechanisms or not. (if you disable 668 lock debugging then those bugs wont be detected of course.) 669 The following locking APIs are covered: spinlocks, rwlocks, 670 mutexes and rwsems. 671 672config STACKTRACE 673 bool 674 depends on STACKTRACE_SUPPORT 675 676config DEBUG_STACK_USAGE 677 bool "Stack utilization instrumentation" 678 depends on DEBUG_KERNEL && !IA64 && !PARISC 679 help 680 Enables the display of the minimum amount of free stack which each 681 task has ever had available in the sysrq-T and sysrq-P debug output. 682 683 This option will slow down process creation somewhat. 684 685config DEBUG_KOBJECT 686 bool "kobject debugging" 687 depends on DEBUG_KERNEL 688 help 689 If you say Y here, some extra kobject debugging messages will be sent 690 to the syslog. 691 692config DEBUG_HIGHMEM 693 bool "Highmem debugging" 694 depends on DEBUG_KERNEL && HIGHMEM 695 help 696 This options enables addition error checking for high memory systems. 697 Disable for production systems. 698 699config HAVE_DEBUG_BUGVERBOSE 700 bool 701 702config DEBUG_BUGVERBOSE 703 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 704 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 705 default y 706 help 707 Say Y here to make BUG() panics output the file name and line number 708 of the BUG call as well as the EIP and oops trace. This aids 709 debugging but costs about 70-100K of memory. 710 711config DEBUG_INFO 712 bool "Compile the kernel with debug info" 713 depends on DEBUG_KERNEL 714 help 715 If you say Y here the resulting kernel image will include 716 debugging info resulting in a larger kernel image. 717 This adds debug symbols to the kernel and modules (gcc -g), and 718 is needed if you intend to use kernel crashdump or binary object 719 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 720 Say Y here only if you plan to debug the kernel. 721 722 If unsure, say N. 723 724config DEBUG_INFO_REDUCED 725 bool "Reduce debugging information" 726 depends on DEBUG_INFO 727 help 728 If you say Y here gcc is instructed to generate less debugging 729 information for structure types. This means that tools that 730 need full debugging information (like kgdb or systemtap) won't 731 be happy. But if you merely need debugging information to 732 resolve line numbers there is no loss. Advantage is that 733 build directory object sizes shrink dramatically over a full 734 DEBUG_INFO build and compile times are reduced too. 735 Only works with newer gcc versions. 736 737config DEBUG_VM 738 bool "Debug VM" 739 depends on DEBUG_KERNEL 740 help 741 Enable this to turn on extended checks in the virtual-memory system 742 that may impact performance. 743 744 If unsure, say N. 745 746config DEBUG_VM_RB 747 bool "Debug VM red-black trees" 748 depends on DEBUG_VM 749 help 750 Enable this to turn on more extended checks in the virtual-memory 751 system that may impact performance. 752 753 If unsure, say N. 754 755config DEBUG_VIRTUAL 756 bool "Debug VM translations" 757 depends on DEBUG_KERNEL && X86 758 help 759 Enable some costly sanity checks in virtual to page code. This can 760 catch mistakes with virt_to_page() and friends. 761 762 If unsure, say N. 763 764config DEBUG_NOMMU_REGIONS 765 bool "Debug the global anon/private NOMMU mapping region tree" 766 depends on DEBUG_KERNEL && !MMU 767 help 768 This option causes the global tree of anonymous and private mapping 769 regions to be regularly checked for invalid topology. 770 771config DEBUG_WRITECOUNT 772 bool "Debug filesystem writers count" 773 depends on DEBUG_KERNEL 774 help 775 Enable this to catch wrong use of the writers count in struct 776 vfsmount. This will increase the size of each file struct by 777 32 bits. 778 779 If unsure, say N. 780 781config DEBUG_MEMORY_INIT 782 bool "Debug memory initialisation" if EXPERT 783 default !EXPERT 784 help 785 Enable this for additional checks during memory initialisation. 786 The sanity checks verify aspects of the VM such as the memory model 787 and other information provided by the architecture. Verbose 788 information will be printed at KERN_DEBUG loglevel depending 789 on the mminit_loglevel= command-line option. 790 791 If unsure, say Y 792 793config DEBUG_LIST 794 bool "Debug linked list manipulation" 795 depends on DEBUG_KERNEL 796 help 797 Enable this to turn on extended checks in the linked-list 798 walking routines. 799 800 If unsure, say N. 801 802config TEST_LIST_SORT 803 bool "Linked list sorting test" 804 depends on DEBUG_KERNEL 805 help 806 Enable this to turn on 'list_sort()' function test. This test is 807 executed only once during system boot, so affects only boot time. 808 809 If unsure, say N. 810 811config DEBUG_SG 812 bool "Debug SG table operations" 813 depends on DEBUG_KERNEL 814 help 815 Enable this to turn on checks on scatter-gather tables. This can 816 help find problems with drivers that do not properly initialize 817 their sg tables. 818 819 If unsure, say N. 820 821config DEBUG_NOTIFIERS 822 bool "Debug notifier call chains" 823 depends on DEBUG_KERNEL 824 help 825 Enable this to turn on sanity checking for notifier call chains. 826 This is most useful for kernel developers to make sure that 827 modules properly unregister themselves from notifier chains. 828 This is a relatively cheap check but if you care about maximum 829 performance, say N. 830 831config DEBUG_CREDENTIALS 832 bool "Debug credential management" 833 depends on DEBUG_KERNEL 834 help 835 Enable this to turn on some debug checking for credential 836 management. The additional code keeps track of the number of 837 pointers from task_structs to any given cred struct, and checks to 838 see that this number never exceeds the usage count of the cred 839 struct. 840 841 Furthermore, if SELinux is enabled, this also checks that the 842 security pointer in the cred struct is never seen to be invalid. 843 844 If unsure, say N. 845 846# 847# Select this config option from the architecture Kconfig, if it 848# is preferred to always offer frame pointers as a config 849# option on the architecture (regardless of KERNEL_DEBUG): 850# 851config ARCH_WANT_FRAME_POINTERS 852 bool 853 help 854 855config FRAME_POINTER 856 bool "Compile the kernel with frame pointers" 857 depends on DEBUG_KERNEL && \ 858 (CRIS || M68K || FRV || UML || \ 859 AVR32 || SUPERH || BLACKFIN || MN10300) || \ 860 ARCH_WANT_FRAME_POINTERS 861 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 862 help 863 If you say Y here the resulting kernel image will be slightly 864 larger and slower, but it gives very useful debugging information 865 in case of kernel bugs. (precise oopses/stacktraces/warnings) 866 867config BOOT_PRINTK_DELAY 868 bool "Delay each boot printk message by N milliseconds" 869 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 870 help 871 This build option allows you to read kernel boot messages 872 by inserting a short delay after each one. The delay is 873 specified in milliseconds on the kernel command line, 874 using "boot_delay=N". 875 876 It is likely that you would also need to use "lpj=M" to preset 877 the "loops per jiffie" value. 878 See a previous boot log for the "lpj" value to use for your 879 system, and then set "lpj=M" before setting "boot_delay=N". 880 NOTE: Using this option may adversely affect SMP systems. 881 I.e., processors other than the first one may not boot up. 882 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect 883 what it believes to be lockup conditions. 884 885menu "RCU Debugging" 886 887config PROVE_RCU 888 bool "RCU debugging: prove RCU correctness" 889 depends on PROVE_LOCKING 890 default n 891 help 892 This feature enables lockdep extensions that check for correct 893 use of RCU APIs. This is currently under development. Say Y 894 if you want to debug RCU usage or help work on the PROVE_RCU 895 feature. 896 897 Say N if you are unsure. 898 899config PROVE_RCU_REPEATEDLY 900 bool "RCU debugging: don't disable PROVE_RCU on first splat" 901 depends on PROVE_RCU 902 default n 903 help 904 By itself, PROVE_RCU will disable checking upon issuing the 905 first warning (or "splat"). This feature prevents such 906 disabling, allowing multiple RCU-lockdep warnings to be printed 907 on a single reboot. 908 909 Say Y to allow multiple RCU-lockdep warnings per boot. 910 911 Say N if you are unsure. 912 913config PROVE_RCU_DELAY 914 bool "RCU debugging: preemptible RCU race provocation" 915 depends on DEBUG_KERNEL && PREEMPT_RCU 916 default n 917 help 918 There is a class of races that involve an unlikely preemption 919 of __rcu_read_unlock() just after ->rcu_read_lock_nesting has 920 been set to INT_MIN. This feature inserts a delay at that 921 point to increase the probability of these races. 922 923 Say Y to increase probability of preemption of __rcu_read_unlock(). 924 925 Say N if you are unsure. 926 927config SPARSE_RCU_POINTER 928 bool "RCU debugging: sparse-based checks for pointer usage" 929 default n 930 help 931 This feature enables the __rcu sparse annotation for 932 RCU-protected pointers. This annotation will cause sparse 933 to flag any non-RCU used of annotated pointers. This can be 934 helpful when debugging RCU usage. Please note that this feature 935 is not intended to enforce code cleanliness; it is instead merely 936 a debugging aid. 937 938 Say Y to make sparse flag questionable use of RCU-protected pointers 939 940 Say N if you are unsure. 941 942config RCU_TORTURE_TEST 943 tristate "torture tests for RCU" 944 depends on DEBUG_KERNEL 945 default n 946 help 947 This option provides a kernel module that runs torture tests 948 on the RCU infrastructure. The kernel module may be built 949 after the fact on the running kernel to be tested, if desired. 950 951 Say Y here if you want RCU torture tests to be built into 952 the kernel. 953 Say M if you want the RCU torture tests to build as a module. 954 Say N if you are unsure. 955 956config RCU_TORTURE_TEST_RUNNABLE 957 bool "torture tests for RCU runnable by default" 958 depends on RCU_TORTURE_TEST = y 959 default n 960 help 961 This option provides a way to build the RCU torture tests 962 directly into the kernel without them starting up at boot 963 time. You can use /proc/sys/kernel/rcutorture_runnable 964 to manually override this setting. This /proc file is 965 available only when the RCU torture tests have been built 966 into the kernel. 967 968 Say Y here if you want the RCU torture tests to start during 969 boot (you probably don't). 970 Say N here if you want the RCU torture tests to start only 971 after being manually enabled via /proc. 972 973config RCU_CPU_STALL_TIMEOUT 974 int "RCU CPU stall timeout in seconds" 975 depends on RCU_STALL_COMMON 976 range 3 300 977 default 21 978 help 979 If a given RCU grace period extends more than the specified 980 number of seconds, a CPU stall warning is printed. If the 981 RCU grace period persists, additional CPU stall warnings are 982 printed at more widely spaced intervals. 983 984config RCU_CPU_STALL_VERBOSE 985 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" 986 depends on TREE_PREEMPT_RCU 987 default y 988 help 989 This option causes RCU to printk detailed per-task information 990 for any tasks that are stalling the current RCU grace period. 991 992 Say N if you are unsure. 993 994 Say Y if you want to enable such checks. 995 996config RCU_CPU_STALL_INFO 997 bool "Print additional diagnostics on RCU CPU stall" 998 depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL 999 default n 1000 help 1001 For each stalled CPU that is aware of the current RCU grace 1002 period, print out additional per-CPU diagnostic information 1003 regarding scheduling-clock ticks, idle state, and, 1004 for RCU_FAST_NO_HZ kernels, idle-entry state. 1005 1006 Say N if you are unsure. 1007 1008 Say Y if you want to enable such diagnostics. 1009 1010config RCU_TRACE 1011 bool "Enable tracing for RCU" 1012 depends on DEBUG_KERNEL 1013 select TRACE_CLOCK 1014 help 1015 This option provides tracing in RCU which presents stats 1016 in debugfs for debugging RCU implementation. 1017 1018 Say Y here if you want to enable RCU tracing 1019 Say N if you are unsure. 1020 1021endmenu # "RCU Debugging" 1022 1023config KPROBES_SANITY_TEST 1024 bool "Kprobes sanity tests" 1025 depends on DEBUG_KERNEL 1026 depends on KPROBES 1027 default n 1028 help 1029 This option provides for testing basic kprobes functionality on 1030 boot. A sample kprobe, jprobe and kretprobe are inserted and 1031 verified for functionality. 1032 1033 Say N if you are unsure. 1034 1035config BACKTRACE_SELF_TEST 1036 tristate "Self test for the backtrace code" 1037 depends on DEBUG_KERNEL 1038 default n 1039 help 1040 This option provides a kernel module that can be used to test 1041 the kernel stack backtrace code. This option is not useful 1042 for distributions or general kernels, but only for kernel 1043 developers working on architecture code. 1044 1045 Note that if you want to also test saved backtraces, you will 1046 have to enable STACKTRACE as well. 1047 1048 Say N if you are unsure. 1049 1050config DEBUG_BLOCK_EXT_DEVT 1051 bool "Force extended block device numbers and spread them" 1052 depends on DEBUG_KERNEL 1053 depends on BLOCK 1054 default n 1055 help 1056 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1057 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1058 YOU ARE DOING. Distros, please enable this and fix whatever 1059 is broken. 1060 1061 Conventionally, block device numbers are allocated from 1062 predetermined contiguous area. However, extended block area 1063 may introduce non-contiguous block device numbers. This 1064 option forces most block device numbers to be allocated from 1065 the extended space and spreads them to discover kernel or 1066 userland code paths which assume predetermined contiguous 1067 device number allocation. 1068 1069 Note that turning on this debug option shuffles all the 1070 device numbers for all IDE and SCSI devices including libata 1071 ones, so root partition specified using device number 1072 directly (via rdev or root=MAJ:MIN) won't work anymore. 1073 Textual device names (root=/dev/sdXn) will continue to work. 1074 1075 Say N if you are unsure. 1076 1077config DEBUG_FORCE_WEAK_PER_CPU 1078 bool "Force weak per-cpu definitions" 1079 depends on DEBUG_KERNEL 1080 help 1081 s390 and alpha require percpu variables in modules to be 1082 defined weak to work around addressing range issue which 1083 puts the following two restrictions on percpu variable 1084 definitions. 1085 1086 1. percpu symbols must be unique whether static or not 1087 2. percpu variables can't be defined inside a function 1088 1089 To ensure that generic code follows the above rules, this 1090 option forces all percpu variables to be defined as weak. 1091 1092config DEBUG_PER_CPU_MAPS 1093 bool "Debug access to per_cpu maps" 1094 depends on DEBUG_KERNEL 1095 depends on SMP 1096 help 1097 Say Y to verify that the per_cpu map being accessed has 1098 been set up. This adds a fair amount of code to kernel memory 1099 and decreases performance. 1100 1101 Say N if unsure. 1102 1103config LKDTM 1104 tristate "Linux Kernel Dump Test Tool Module" 1105 depends on DEBUG_FS 1106 depends on BLOCK 1107 default n 1108 help 1109 This module enables testing of the different dumping mechanisms by 1110 inducing system failures at predefined crash points. 1111 If you don't need it: say N 1112 Choose M here to compile this code as a module. The module will be 1113 called lkdtm. 1114 1115 Documentation on how to use the module can be found in 1116 Documentation/fault-injection/provoke-crashes.txt 1117 1118config NOTIFIER_ERROR_INJECTION 1119 tristate "Notifier error injection" 1120 depends on DEBUG_KERNEL 1121 select DEBUG_FS 1122 help 1123 This option provides the ability to inject artificial errors to 1124 specified notifier chain callbacks. It is useful to test the error 1125 handling of notifier call chain failures. 1126 1127 Say N if unsure. 1128 1129config CPU_NOTIFIER_ERROR_INJECT 1130 tristate "CPU notifier error injection module" 1131 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1132 help 1133 This option provides a kernel module that can be used to test 1134 the error handling of the cpu notifiers by injecting artificial 1135 errors to CPU notifier chain callbacks. It is controlled through 1136 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1137 1138 If the notifier call chain should be failed with some events 1139 notified, write the error code to "actions/<notifier event>/error". 1140 1141 Example: Inject CPU offline error (-1 == -EPERM) 1142 1143 # cd /sys/kernel/debug/notifier-error-inject/cpu 1144 # echo -1 > actions/CPU_DOWN_PREPARE/error 1145 # echo 0 > /sys/devices/system/cpu/cpu1/online 1146 bash: echo: write error: Operation not permitted 1147 1148 To compile this code as a module, choose M here: the module will 1149 be called cpu-notifier-error-inject. 1150 1151 If unsure, say N. 1152 1153config PM_NOTIFIER_ERROR_INJECT 1154 tristate "PM notifier error injection module" 1155 depends on PM && NOTIFIER_ERROR_INJECTION 1156 default m if PM_DEBUG 1157 help 1158 This option provides the ability to inject artificial errors to 1159 PM notifier chain callbacks. It is controlled through debugfs 1160 interface /sys/kernel/debug/notifier-error-inject/pm 1161 1162 If the notifier call chain should be failed with some events 1163 notified, write the error code to "actions/<notifier event>/error". 1164 1165 Example: Inject PM suspend error (-12 = -ENOMEM) 1166 1167 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1168 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1169 # echo mem > /sys/power/state 1170 bash: echo: write error: Cannot allocate memory 1171 1172 To compile this code as a module, choose M here: the module will 1173 be called pm-notifier-error-inject. 1174 1175 If unsure, say N. 1176 1177config MEMORY_NOTIFIER_ERROR_INJECT 1178 tristate "Memory hotplug notifier error injection module" 1179 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 1180 help 1181 This option provides the ability to inject artificial errors to 1182 memory hotplug notifier chain callbacks. It is controlled through 1183 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 1184 1185 If the notifier call chain should be failed with some events 1186 notified, write the error code to "actions/<notifier event>/error". 1187 1188 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 1189 1190 # cd /sys/kernel/debug/notifier-error-inject/memory 1191 # echo -12 > actions/MEM_GOING_OFFLINE/error 1192 # echo offline > /sys/devices/system/memory/memoryXXX/state 1193 bash: echo: write error: Cannot allocate memory 1194 1195 To compile this code as a module, choose M here: the module will 1196 be called pSeries-reconfig-notifier-error-inject. 1197 1198 If unsure, say N. 1199 1200config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1201 tristate "OF reconfig notifier error injection module" 1202 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1203 help 1204 This option provides the ability to inject artificial errors to 1205 OF reconfig notifier chain callbacks. It is controlled 1206 through debugfs interface under 1207 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1208 1209 If the notifier call chain should be failed with some events 1210 notified, write the error code to "actions/<notifier event>/error". 1211 1212 To compile this code as a module, choose M here: the module will 1213 be called memory-notifier-error-inject. 1214 1215 If unsure, say N. 1216 1217config FAULT_INJECTION 1218 bool "Fault-injection framework" 1219 depends on DEBUG_KERNEL 1220 help 1221 Provide fault-injection framework. 1222 For more details, see Documentation/fault-injection/. 1223 1224config FAILSLAB 1225 bool "Fault-injection capability for kmalloc" 1226 depends on FAULT_INJECTION 1227 depends on SLAB || SLUB 1228 help 1229 Provide fault-injection capability for kmalloc. 1230 1231config FAIL_PAGE_ALLOC 1232 bool "Fault-injection capabilitiy for alloc_pages()" 1233 depends on FAULT_INJECTION 1234 help 1235 Provide fault-injection capability for alloc_pages(). 1236 1237config FAIL_MAKE_REQUEST 1238 bool "Fault-injection capability for disk IO" 1239 depends on FAULT_INJECTION && BLOCK 1240 help 1241 Provide fault-injection capability for disk IO. 1242 1243config FAIL_IO_TIMEOUT 1244 bool "Fault-injection capability for faking disk interrupts" 1245 depends on FAULT_INJECTION && BLOCK 1246 help 1247 Provide fault-injection capability on end IO handling. This 1248 will make the block layer "forget" an interrupt as configured, 1249 thus exercising the error handling. 1250 1251 Only works with drivers that use the generic timeout handling, 1252 for others it wont do anything. 1253 1254config FAIL_MMC_REQUEST 1255 bool "Fault-injection capability for MMC IO" 1256 select DEBUG_FS 1257 depends on FAULT_INJECTION && MMC 1258 help 1259 Provide fault-injection capability for MMC IO. 1260 This will make the mmc core return data errors. This is 1261 useful to test the error handling in the mmc block device 1262 and to test how the mmc host driver handles retries from 1263 the block device. 1264 1265config FAULT_INJECTION_DEBUG_FS 1266 bool "Debugfs entries for fault-injection capabilities" 1267 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1268 help 1269 Enable configuration of fault-injection capabilities via debugfs. 1270 1271config FAULT_INJECTION_STACKTRACE_FILTER 1272 bool "stacktrace filter for fault-injection capabilities" 1273 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1274 depends on !X86_64 1275 select STACKTRACE 1276 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND 1277 help 1278 Provide stacktrace filter for fault-injection capabilities 1279 1280config LATENCYTOP 1281 bool "Latency measuring infrastructure" 1282 depends on HAVE_LATENCYTOP_SUPPORT 1283 depends on DEBUG_KERNEL 1284 depends on STACKTRACE_SUPPORT 1285 depends on PROC_FS 1286 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND 1287 select KALLSYMS 1288 select KALLSYMS_ALL 1289 select STACKTRACE 1290 select SCHEDSTATS 1291 select SCHED_DEBUG 1292 help 1293 Enable this option if you want to use the LatencyTOP tool 1294 to find out which userspace is blocking on what kernel operations. 1295 1296source mm/Kconfig.debug 1297source kernel/trace/Kconfig 1298 1299config RBTREE_TEST 1300 tristate "Red-Black tree test" 1301 depends on m && DEBUG_KERNEL 1302 help 1303 A benchmark measuring the performance of the rbtree library. 1304 Also includes rbtree invariant checks. 1305 1306config INTERVAL_TREE_TEST 1307 tristate "Interval tree test" 1308 depends on m && DEBUG_KERNEL 1309 help 1310 A benchmark measuring the performance of the interval tree library 1311 1312config PROVIDE_OHCI1394_DMA_INIT 1313 bool "Remote debugging over FireWire early on boot" 1314 depends on PCI && X86 1315 help 1316 If you want to debug problems which hang or crash the kernel early 1317 on boot and the crashing machine has a FireWire port, you can use 1318 this feature to remotely access the memory of the crashed machine 1319 over FireWire. This employs remote DMA as part of the OHCI1394 1320 specification which is now the standard for FireWire controllers. 1321 1322 With remote DMA, you can monitor the printk buffer remotely using 1323 firescope and access all memory below 4GB using fireproxy from gdb. 1324 Even controlling a kernel debugger is possible using remote DMA. 1325 1326 Usage: 1327 1328 If ohci1394_dma=early is used as boot parameter, it will initialize 1329 all OHCI1394 controllers which are found in the PCI config space. 1330 1331 As all changes to the FireWire bus such as enabling and disabling 1332 devices cause a bus reset and thereby disable remote DMA for all 1333 devices, be sure to have the cable plugged and FireWire enabled on 1334 the debugging host before booting the debug target for debugging. 1335 1336 This code (~1k) is freed after boot. By then, the firewire stack 1337 in charge of the OHCI-1394 controllers should be used instead. 1338 1339 See Documentation/debugging-via-ohci1394.txt for more information. 1340 1341config FIREWIRE_OHCI_REMOTE_DMA 1342 bool "Remote debugging over FireWire with firewire-ohci" 1343 depends on FIREWIRE_OHCI 1344 help 1345 This option lets you use the FireWire bus for remote debugging 1346 with help of the firewire-ohci driver. It enables unfiltered 1347 remote DMA in firewire-ohci. 1348 See Documentation/debugging-via-ohci1394.txt for more information. 1349 1350 If unsure, say N. 1351 1352config BUILD_DOCSRC 1353 bool "Build targets in Documentation/ tree" 1354 depends on HEADERS_CHECK 1355 help 1356 This option attempts to build objects from the source files in the 1357 kernel Documentation/ tree. 1358 1359 Say N if you are unsure. 1360 1361config DYNAMIC_DEBUG 1362 bool "Enable dynamic printk() support" 1363 default n 1364 depends on PRINTK 1365 depends on DEBUG_FS 1366 help 1367 1368 Compiles debug level messages into the kernel, which would not 1369 otherwise be available at runtime. These messages can then be 1370 enabled/disabled based on various levels of scope - per source file, 1371 function, module, format string, and line number. This mechanism 1372 implicitly compiles in all pr_debug() and dev_dbg() calls, which 1373 enlarges the kernel text size by about 2%. 1374 1375 If a source file is compiled with DEBUG flag set, any 1376 pr_debug() calls in it are enabled by default, but can be 1377 disabled at runtime as below. Note that DEBUG flag is 1378 turned on by many CONFIG_*DEBUG* options. 1379 1380 Usage: 1381 1382 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 1383 which is contained in the 'debugfs' filesystem. Thus, the debugfs 1384 filesystem must first be mounted before making use of this feature. 1385 We refer the control file as: <debugfs>/dynamic_debug/control. This 1386 file contains a list of the debug statements that can be enabled. The 1387 format for each line of the file is: 1388 1389 filename:lineno [module]function flags format 1390 1391 filename : source file of the debug statement 1392 lineno : line number of the debug statement 1393 module : module that contains the debug statement 1394 function : function that contains the debug statement 1395 flags : '=p' means the line is turned 'on' for printing 1396 format : the format used for the debug statement 1397 1398 From a live system: 1399 1400 nullarbor:~ # cat <debugfs>/dynamic_debug/control 1401 # filename:lineno [module]function flags format 1402 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012" 1403 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012" 1404 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012" 1405 1406 Example usage: 1407 1408 // enable the message at line 1603 of file svcsock.c 1409 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 1410 <debugfs>/dynamic_debug/control 1411 1412 // enable all the messages in file svcsock.c 1413 nullarbor:~ # echo -n 'file svcsock.c +p' > 1414 <debugfs>/dynamic_debug/control 1415 1416 // enable all the messages in the NFS server module 1417 nullarbor:~ # echo -n 'module nfsd +p' > 1418 <debugfs>/dynamic_debug/control 1419 1420 // enable all 12 messages in the function svc_process() 1421 nullarbor:~ # echo -n 'func svc_process +p' > 1422 <debugfs>/dynamic_debug/control 1423 1424 // disable all 12 messages in the function svc_process() 1425 nullarbor:~ # echo -n 'func svc_process -p' > 1426 <debugfs>/dynamic_debug/control 1427 1428 See Documentation/dynamic-debug-howto.txt for additional information. 1429 1430config DMA_API_DEBUG 1431 bool "Enable debugging of DMA-API usage" 1432 depends on HAVE_DMA_API_DEBUG 1433 help 1434 Enable this option to debug the use of the DMA API by device drivers. 1435 With this option you will be able to detect common bugs in device 1436 drivers like double-freeing of DMA mappings or freeing mappings that 1437 were never allocated. 1438 This option causes a performance degredation. Use only if you want 1439 to debug device drivers. If unsure, say N. 1440 1441config ATOMIC64_SELFTEST 1442 bool "Perform an atomic64_t self-test at boot" 1443 help 1444 Enable this option to test the atomic64_t functions at boot. 1445 1446 If unsure, say N. 1447 1448config ASYNC_RAID6_TEST 1449 tristate "Self test for hardware accelerated raid6 recovery" 1450 depends on ASYNC_RAID6_RECOV 1451 select ASYNC_MEMCPY 1452 ---help--- 1453 This is a one-shot self test that permutes through the 1454 recovery of all the possible two disk failure scenarios for a 1455 N-disk array. Recovery is performed with the asynchronous 1456 raid6 recovery routines, and will optionally use an offload 1457 engine if one is available. 1458 1459 If unsure, say N. 1460 1461source "samples/Kconfig" 1462 1463source "lib/Kconfig.kgdb" 1464 1465source "lib/Kconfig.kmemcheck" 1466 1467config TEST_KSTRTOX 1468 tristate "Test kstrto*() family of functions at runtime" 1469