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 && 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_WW_MUTEX_SLOWPATH 551 bool "Wait/wound mutex debugging: Slowpath testing" 552 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 553 select DEBUG_LOCK_ALLOC 554 select DEBUG_SPINLOCK 555 select DEBUG_MUTEXES 556 help 557 This feature enables slowpath testing for w/w mutex users by 558 injecting additional -EDEADLK wound/backoff cases. Together with 559 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 560 will test all possible w/w mutex interface abuse with the 561 exception of simply not acquiring all the required locks. 562 563config DEBUG_LOCK_ALLOC 564 bool "Lock debugging: detect incorrect freeing of live locks" 565 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 566 select DEBUG_SPINLOCK 567 select DEBUG_MUTEXES 568 select LOCKDEP 569 help 570 This feature will check whether any held lock (spinlock, rwlock, 571 mutex or rwsem) is incorrectly freed by the kernel, via any of the 572 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 573 vfree(), etc.), whether a live lock is incorrectly reinitialized via 574 spin_lock_init()/mutex_init()/etc., or whether there is any lock 575 held during task exit. 576 577config PROVE_LOCKING 578 bool "Lock debugging: prove locking correctness" 579 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 580 select LOCKDEP 581 select DEBUG_SPINLOCK 582 select DEBUG_MUTEXES 583 select DEBUG_LOCK_ALLOC 584 select TRACE_IRQFLAGS 585 default n 586 help 587 This feature enables the kernel to prove that all locking 588 that occurs in the kernel runtime is mathematically 589 correct: that under no circumstance could an arbitrary (and 590 not yet triggered) combination of observed locking 591 sequences (on an arbitrary number of CPUs, running an 592 arbitrary number of tasks and interrupt contexts) cause a 593 deadlock. 594 595 In short, this feature enables the kernel to report locking 596 related deadlocks before they actually occur. 597 598 The proof does not depend on how hard and complex a 599 deadlock scenario would be to trigger: how many 600 participant CPUs, tasks and irq-contexts would be needed 601 for it to trigger. The proof also does not depend on 602 timing: if a race and a resulting deadlock is possible 603 theoretically (no matter how unlikely the race scenario 604 is), it will be proven so and will immediately be 605 reported by the kernel (once the event is observed that 606 makes the deadlock theoretically possible). 607 608 If a deadlock is impossible (i.e. the locking rules, as 609 observed by the kernel, are mathematically correct), the 610 kernel reports nothing. 611 612 NOTE: this feature can also be enabled for rwlocks, mutexes 613 and rwsems - in which case all dependencies between these 614 different locking variants are observed and mapped too, and 615 the proof of observed correctness is also maintained for an 616 arbitrary combination of these separate locking variants. 617 618 For more details, see Documentation/lockdep-design.txt. 619 620config LOCKDEP 621 bool 622 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 623 select STACKTRACE 624 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE 625 select KALLSYMS 626 select KALLSYMS_ALL 627 628config LOCK_STAT 629 bool "Lock usage statistics" 630 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 631 select LOCKDEP 632 select DEBUG_SPINLOCK 633 select DEBUG_MUTEXES 634 select DEBUG_LOCK_ALLOC 635 default n 636 help 637 This feature enables tracking lock contention points 638 639 For more details, see Documentation/lockstat.txt 640 641 This also enables lock events required by "perf lock", 642 subcommand of perf. 643 If you want to use "perf lock", you also need to turn on 644 CONFIG_EVENT_TRACING. 645 646 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 647 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 648 649config DEBUG_LOCKDEP 650 bool "Lock dependency engine debugging" 651 depends on DEBUG_KERNEL && LOCKDEP 652 help 653 If you say Y here, the lock dependency engine will do 654 additional runtime checks to debug itself, at the price 655 of more runtime overhead. 656 657config TRACE_IRQFLAGS 658 bool 659 help 660 Enables hooks to interrupt enabling and disabling for 661 either tracing or lock debugging. 662 663config DEBUG_ATOMIC_SLEEP 664 bool "Sleep inside atomic section checking" 665 select PREEMPT_COUNT 666 depends on DEBUG_KERNEL 667 help 668 If you say Y here, various routines which may sleep will become very 669 noisy if they are called inside atomic sections: when a spinlock is 670 held, inside an rcu read side critical section, inside preempt disabled 671 sections, inside an interrupt, etc... 672 673config DEBUG_LOCKING_API_SELFTESTS 674 bool "Locking API boot-time self-tests" 675 depends on DEBUG_KERNEL 676 help 677 Say Y here if you want the kernel to run a short self-test during 678 bootup. The self-test checks whether common types of locking bugs 679 are detected by debugging mechanisms or not. (if you disable 680 lock debugging then those bugs wont be detected of course.) 681 The following locking APIs are covered: spinlocks, rwlocks, 682 mutexes and rwsems. 683 684config STACKTRACE 685 bool 686 depends on STACKTRACE_SUPPORT 687 688config DEBUG_STACK_USAGE 689 bool "Stack utilization instrumentation" 690 depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAG 691 help 692 Enables the display of the minimum amount of free stack which each 693 task has ever had available in the sysrq-T and sysrq-P debug output. 694 695 This option will slow down process creation somewhat. 696 697config DEBUG_KOBJECT 698 bool "kobject debugging" 699 depends on DEBUG_KERNEL 700 help 701 If you say Y here, some extra kobject debugging messages will be sent 702 to the syslog. 703 704config DEBUG_HIGHMEM 705 bool "Highmem debugging" 706 depends on DEBUG_KERNEL && HIGHMEM 707 help 708 This options enables addition error checking for high memory systems. 709 Disable for production systems. 710 711config HAVE_DEBUG_BUGVERBOSE 712 bool 713 714config DEBUG_BUGVERBOSE 715 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 716 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 717 default y 718 help 719 Say Y here to make BUG() panics output the file name and line number 720 of the BUG call as well as the EIP and oops trace. This aids 721 debugging but costs about 70-100K of memory. 722 723config DEBUG_INFO 724 bool "Compile the kernel with debug info" 725 depends on DEBUG_KERNEL 726 help 727 If you say Y here the resulting kernel image will include 728 debugging info resulting in a larger kernel image. 729 This adds debug symbols to the kernel and modules (gcc -g), and 730 is needed if you intend to use kernel crashdump or binary object 731 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 732 Say Y here only if you plan to debug the kernel. 733 734 If unsure, say N. 735 736config DEBUG_INFO_REDUCED 737 bool "Reduce debugging information" 738 depends on DEBUG_INFO 739 help 740 If you say Y here gcc is instructed to generate less debugging 741 information for structure types. This means that tools that 742 need full debugging information (like kgdb or systemtap) won't 743 be happy. But if you merely need debugging information to 744 resolve line numbers there is no loss. Advantage is that 745 build directory object sizes shrink dramatically over a full 746 DEBUG_INFO build and compile times are reduced too. 747 Only works with newer gcc versions. 748 749config DEBUG_VM 750 bool "Debug VM" 751 depends on DEBUG_KERNEL 752 help 753 Enable this to turn on extended checks in the virtual-memory system 754 that may impact performance. 755 756 If unsure, say N. 757 758config DEBUG_VM_RB 759 bool "Debug VM red-black trees" 760 depends on DEBUG_VM 761 help 762 Enable this to turn on more extended checks in the virtual-memory 763 system that may impact performance. 764 765 If unsure, say N. 766 767config DEBUG_VIRTUAL 768 bool "Debug VM translations" 769 depends on DEBUG_KERNEL && X86 770 help 771 Enable some costly sanity checks in virtual to page code. This can 772 catch mistakes with virt_to_page() and friends. 773 774 If unsure, say N. 775 776config DEBUG_NOMMU_REGIONS 777 bool "Debug the global anon/private NOMMU mapping region tree" 778 depends on DEBUG_KERNEL && !MMU 779 help 780 This option causes the global tree of anonymous and private mapping 781 regions to be regularly checked for invalid topology. 782 783config DEBUG_WRITECOUNT 784 bool "Debug filesystem writers count" 785 depends on DEBUG_KERNEL 786 help 787 Enable this to catch wrong use of the writers count in struct 788 vfsmount. This will increase the size of each file struct by 789 32 bits. 790 791 If unsure, say N. 792 793config DEBUG_MEMORY_INIT 794 bool "Debug memory initialisation" if EXPERT 795 default !EXPERT 796 help 797 Enable this for additional checks during memory initialisation. 798 The sanity checks verify aspects of the VM such as the memory model 799 and other information provided by the architecture. Verbose 800 information will be printed at KERN_DEBUG loglevel depending 801 on the mminit_loglevel= command-line option. 802 803 If unsure, say Y 804 805config DEBUG_LIST 806 bool "Debug linked list manipulation" 807 depends on DEBUG_KERNEL 808 help 809 Enable this to turn on extended checks in the linked-list 810 walking routines. 811 812 If unsure, say N. 813 814config TEST_LIST_SORT 815 bool "Linked list sorting test" 816 depends on DEBUG_KERNEL 817 help 818 Enable this to turn on 'list_sort()' function test. This test is 819 executed only once during system boot, so affects only boot time. 820 821 If unsure, say N. 822 823config DEBUG_SG 824 bool "Debug SG table operations" 825 depends on DEBUG_KERNEL 826 help 827 Enable this to turn on checks on scatter-gather tables. This can 828 help find problems with drivers that do not properly initialize 829 their sg tables. 830 831 If unsure, say N. 832 833config DEBUG_NOTIFIERS 834 bool "Debug notifier call chains" 835 depends on DEBUG_KERNEL 836 help 837 Enable this to turn on sanity checking for notifier call chains. 838 This is most useful for kernel developers to make sure that 839 modules properly unregister themselves from notifier chains. 840 This is a relatively cheap check but if you care about maximum 841 performance, say N. 842 843config DEBUG_CREDENTIALS 844 bool "Debug credential management" 845 depends on DEBUG_KERNEL 846 help 847 Enable this to turn on some debug checking for credential 848 management. The additional code keeps track of the number of 849 pointers from task_structs to any given cred struct, and checks to 850 see that this number never exceeds the usage count of the cred 851 struct. 852 853 Furthermore, if SELinux is enabled, this also checks that the 854 security pointer in the cred struct is never seen to be invalid. 855 856 If unsure, say N. 857 858# 859# Select this config option from the architecture Kconfig, if it 860# is preferred to always offer frame pointers as a config 861# option on the architecture (regardless of KERNEL_DEBUG): 862# 863config ARCH_WANT_FRAME_POINTERS 864 bool 865 help 866 867config FRAME_POINTER 868 bool "Compile the kernel with frame pointers" 869 depends on DEBUG_KERNEL && \ 870 (CRIS || M68K || FRV || UML || \ 871 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \ 872 ARCH_WANT_FRAME_POINTERS 873 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 874 help 875 If you say Y here the resulting kernel image will be slightly 876 larger and slower, but it gives very useful debugging information 877 in case of kernel bugs. (precise oopses/stacktraces/warnings) 878 879config BOOT_PRINTK_DELAY 880 bool "Delay each boot printk message by N milliseconds" 881 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 882 help 883 This build option allows you to read kernel boot messages 884 by inserting a short delay after each one. The delay is 885 specified in milliseconds on the kernel command line, 886 using "boot_delay=N". 887 888 It is likely that you would also need to use "lpj=M" to preset 889 the "loops per jiffie" value. 890 See a previous boot log for the "lpj" value to use for your 891 system, and then set "lpj=M" before setting "boot_delay=N". 892 NOTE: Using this option may adversely affect SMP systems. 893 I.e., processors other than the first one may not boot up. 894 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect 895 what it believes to be lockup conditions. 896 897menu "RCU Debugging" 898 899config PROVE_RCU 900 bool "RCU debugging: prove RCU correctness" 901 depends on PROVE_LOCKING 902 default n 903 help 904 This feature enables lockdep extensions that check for correct 905 use of RCU APIs. This is currently under development. Say Y 906 if you want to debug RCU usage or help work on the PROVE_RCU 907 feature. 908 909 Say N if you are unsure. 910 911config PROVE_RCU_REPEATEDLY 912 bool "RCU debugging: don't disable PROVE_RCU on first splat" 913 depends on PROVE_RCU 914 default n 915 help 916 By itself, PROVE_RCU will disable checking upon issuing the 917 first warning (or "splat"). This feature prevents such 918 disabling, allowing multiple RCU-lockdep warnings to be printed 919 on a single reboot. 920 921 Say Y to allow multiple RCU-lockdep warnings per boot. 922 923 Say N if you are unsure. 924 925config PROVE_RCU_DELAY 926 bool "RCU debugging: preemptible RCU race provocation" 927 depends on DEBUG_KERNEL && PREEMPT_RCU 928 default n 929 help 930 There is a class of races that involve an unlikely preemption 931 of __rcu_read_unlock() just after ->rcu_read_lock_nesting has 932 been set to INT_MIN. This feature inserts a delay at that 933 point to increase the probability of these races. 934 935 Say Y to increase probability of preemption of __rcu_read_unlock(). 936 937 Say N if you are unsure. 938 939config SPARSE_RCU_POINTER 940 bool "RCU debugging: sparse-based checks for pointer usage" 941 default n 942 help 943 This feature enables the __rcu sparse annotation for 944 RCU-protected pointers. This annotation will cause sparse 945 to flag any non-RCU used of annotated pointers. This can be 946 helpful when debugging RCU usage. Please note that this feature 947 is not intended to enforce code cleanliness; it is instead merely 948 a debugging aid. 949 950 Say Y to make sparse flag questionable use of RCU-protected pointers 951 952 Say N if you are unsure. 953 954config RCU_TORTURE_TEST 955 tristate "torture tests for RCU" 956 depends on DEBUG_KERNEL 957 default n 958 help 959 This option provides a kernel module that runs torture tests 960 on the RCU infrastructure. The kernel module may be built 961 after the fact on the running kernel to be tested, if desired. 962 963 Say Y here if you want RCU torture tests to be built into 964 the kernel. 965 Say M if you want the RCU torture tests to build as a module. 966 Say N if you are unsure. 967 968config RCU_TORTURE_TEST_RUNNABLE 969 bool "torture tests for RCU runnable by default" 970 depends on RCU_TORTURE_TEST = y 971 default n 972 help 973 This option provides a way to build the RCU torture tests 974 directly into the kernel without them starting up at boot 975 time. You can use /proc/sys/kernel/rcutorture_runnable 976 to manually override this setting. This /proc file is 977 available only when the RCU torture tests have been built 978 into the kernel. 979 980 Say Y here if you want the RCU torture tests to start during 981 boot (you probably don't). 982 Say N here if you want the RCU torture tests to start only 983 after being manually enabled via /proc. 984 985config RCU_CPU_STALL_TIMEOUT 986 int "RCU CPU stall timeout in seconds" 987 depends on RCU_STALL_COMMON 988 range 3 300 989 default 21 990 help 991 If a given RCU grace period extends more than the specified 992 number of seconds, a CPU stall warning is printed. If the 993 RCU grace period persists, additional CPU stall warnings are 994 printed at more widely spaced intervals. 995 996config RCU_CPU_STALL_VERBOSE 997 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" 998 depends on TREE_PREEMPT_RCU 999 default y 1000 help 1001 This option causes RCU to printk detailed per-task information 1002 for any tasks that are stalling the current RCU grace period. 1003 1004 Say N if you are unsure. 1005 1006 Say Y if you want to enable such checks. 1007 1008config RCU_CPU_STALL_INFO 1009 bool "Print additional diagnostics on RCU CPU stall" 1010 depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL 1011 default n 1012 help 1013 For each stalled CPU that is aware of the current RCU grace 1014 period, print out additional per-CPU diagnostic information 1015 regarding scheduling-clock ticks, idle state, and, 1016 for RCU_FAST_NO_HZ kernels, idle-entry state. 1017 1018 Say N if you are unsure. 1019 1020 Say Y if you want to enable such diagnostics. 1021 1022config RCU_TRACE 1023 bool "Enable tracing for RCU" 1024 depends on DEBUG_KERNEL 1025 select TRACE_CLOCK 1026 help 1027 This option provides tracing in RCU which presents stats 1028 in debugfs for debugging RCU implementation. 1029 1030 Say Y here if you want to enable RCU tracing 1031 Say N if you are unsure. 1032 1033endmenu # "RCU Debugging" 1034 1035config KPROBES_SANITY_TEST 1036 bool "Kprobes sanity tests" 1037 depends on DEBUG_KERNEL 1038 depends on KPROBES 1039 default n 1040 help 1041 This option provides for testing basic kprobes functionality on 1042 boot. A sample kprobe, jprobe and kretprobe are inserted and 1043 verified for functionality. 1044 1045 Say N if you are unsure. 1046 1047config BACKTRACE_SELF_TEST 1048 tristate "Self test for the backtrace code" 1049 depends on DEBUG_KERNEL 1050 default n 1051 help 1052 This option provides a kernel module that can be used to test 1053 the kernel stack backtrace code. This option is not useful 1054 for distributions or general kernels, but only for kernel 1055 developers working on architecture code. 1056 1057 Note that if you want to also test saved backtraces, you will 1058 have to enable STACKTRACE as well. 1059 1060 Say N if you are unsure. 1061 1062config DEBUG_BLOCK_EXT_DEVT 1063 bool "Force extended block device numbers and spread them" 1064 depends on DEBUG_KERNEL 1065 depends on BLOCK 1066 default n 1067 help 1068 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1069 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1070 YOU ARE DOING. Distros, please enable this and fix whatever 1071 is broken. 1072 1073 Conventionally, block device numbers are allocated from 1074 predetermined contiguous area. However, extended block area 1075 may introduce non-contiguous block device numbers. This 1076 option forces most block device numbers to be allocated from 1077 the extended space and spreads them to discover kernel or 1078 userland code paths which assume predetermined contiguous 1079 device number allocation. 1080 1081 Note that turning on this debug option shuffles all the 1082 device numbers for all IDE and SCSI devices including libata 1083 ones, so root partition specified using device number 1084 directly (via rdev or root=MAJ:MIN) won't work anymore. 1085 Textual device names (root=/dev/sdXn) will continue to work. 1086 1087 Say N if you are unsure. 1088 1089config DEBUG_FORCE_WEAK_PER_CPU 1090 bool "Force weak per-cpu definitions" 1091 depends on DEBUG_KERNEL 1092 help 1093 s390 and alpha require percpu variables in modules to be 1094 defined weak to work around addressing range issue which 1095 puts the following two restrictions on percpu variable 1096 definitions. 1097 1098 1. percpu symbols must be unique whether static or not 1099 2. percpu variables can't be defined inside a function 1100 1101 To ensure that generic code follows the above rules, this 1102 option forces all percpu variables to be defined as weak. 1103 1104config DEBUG_PER_CPU_MAPS 1105 bool "Debug access to per_cpu maps" 1106 depends on DEBUG_KERNEL 1107 depends on SMP 1108 help 1109 Say Y to verify that the per_cpu map being accessed has 1110 been set up. This adds a fair amount of code to kernel memory 1111 and decreases performance. 1112 1113 Say N if unsure. 1114 1115config LKDTM 1116 tristate "Linux Kernel Dump Test Tool Module" 1117 depends on DEBUG_FS 1118 depends on BLOCK 1119 default n 1120 help 1121 This module enables testing of the different dumping mechanisms by 1122 inducing system failures at predefined crash points. 1123 If you don't need it: say N 1124 Choose M here to compile this code as a module. The module will be 1125 called lkdtm. 1126 1127 Documentation on how to use the module can be found in 1128 Documentation/fault-injection/provoke-crashes.txt 1129 1130config NOTIFIER_ERROR_INJECTION 1131 tristate "Notifier error injection" 1132 depends on DEBUG_KERNEL 1133 select DEBUG_FS 1134 help 1135 This option provides the ability to inject artificial errors to 1136 specified notifier chain callbacks. It is useful to test the error 1137 handling of notifier call chain failures. 1138 1139 Say N if unsure. 1140 1141config CPU_NOTIFIER_ERROR_INJECT 1142 tristate "CPU notifier error injection module" 1143 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1144 help 1145 This option provides a kernel module that can be used to test 1146 the error handling of the cpu notifiers by injecting artificial 1147 errors to CPU notifier chain callbacks. It is controlled through 1148 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1149 1150 If the notifier call chain should be failed with some events 1151 notified, write the error code to "actions/<notifier event>/error". 1152 1153 Example: Inject CPU offline error (-1 == -EPERM) 1154 1155 # cd /sys/kernel/debug/notifier-error-inject/cpu 1156 # echo -1 > actions/CPU_DOWN_PREPARE/error 1157 # echo 0 > /sys/devices/system/cpu/cpu1/online 1158 bash: echo: write error: Operation not permitted 1159 1160 To compile this code as a module, choose M here: the module will 1161 be called cpu-notifier-error-inject. 1162 1163 If unsure, say N. 1164 1165config PM_NOTIFIER_ERROR_INJECT 1166 tristate "PM notifier error injection module" 1167 depends on PM && NOTIFIER_ERROR_INJECTION 1168 default m if PM_DEBUG 1169 help 1170 This option provides the ability to inject artificial errors to 1171 PM notifier chain callbacks. It is controlled through debugfs 1172 interface /sys/kernel/debug/notifier-error-inject/pm 1173 1174 If the notifier call chain should be failed with some events 1175 notified, write the error code to "actions/<notifier event>/error". 1176 1177 Example: Inject PM suspend error (-12 = -ENOMEM) 1178 1179 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1180 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1181 # echo mem > /sys/power/state 1182 bash: echo: write error: Cannot allocate memory 1183 1184 To compile this code as a module, choose M here: the module will 1185 be called pm-notifier-error-inject. 1186 1187 If unsure, say N. 1188 1189config MEMORY_NOTIFIER_ERROR_INJECT 1190 tristate "Memory hotplug notifier error injection module" 1191 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 1192 help 1193 This option provides the ability to inject artificial errors to 1194 memory hotplug notifier chain callbacks. It is controlled through 1195 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 1196 1197 If the notifier call chain should be failed with some events 1198 notified, write the error code to "actions/<notifier event>/error". 1199 1200 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 1201 1202 # cd /sys/kernel/debug/notifier-error-inject/memory 1203 # echo -12 > actions/MEM_GOING_OFFLINE/error 1204 # echo offline > /sys/devices/system/memory/memoryXXX/state 1205 bash: echo: write error: Cannot allocate memory 1206 1207 To compile this code as a module, choose M here: the module will 1208 be called memory-notifier-error-inject. 1209 1210 If unsure, say N. 1211 1212config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1213 tristate "OF reconfig notifier error injection module" 1214 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1215 help 1216 This option provides the ability to inject artificial errors to 1217 OF reconfig notifier chain callbacks. It is controlled 1218 through debugfs interface under 1219 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1220 1221 If the notifier call chain should be failed with some events 1222 notified, write the error code to "actions/<notifier event>/error". 1223 1224 To compile this code as a module, choose M here: the module will 1225 be called of-reconfig-notifier-error-inject. 1226 1227 If unsure, say N. 1228 1229config FAULT_INJECTION 1230 bool "Fault-injection framework" 1231 depends on DEBUG_KERNEL 1232 help 1233 Provide fault-injection framework. 1234 For more details, see Documentation/fault-injection/. 1235 1236config FAILSLAB 1237 bool "Fault-injection capability for kmalloc" 1238 depends on FAULT_INJECTION 1239 depends on SLAB || SLUB 1240 help 1241 Provide fault-injection capability for kmalloc. 1242 1243config FAIL_PAGE_ALLOC 1244 bool "Fault-injection capabilitiy for alloc_pages()" 1245 depends on FAULT_INJECTION 1246 help 1247 Provide fault-injection capability for alloc_pages(). 1248 1249config FAIL_MAKE_REQUEST 1250 bool "Fault-injection capability for disk IO" 1251 depends on FAULT_INJECTION && BLOCK 1252 help 1253 Provide fault-injection capability for disk IO. 1254 1255config FAIL_IO_TIMEOUT 1256 bool "Fault-injection capability for faking disk interrupts" 1257 depends on FAULT_INJECTION && BLOCK 1258 help 1259 Provide fault-injection capability on end IO handling. This 1260 will make the block layer "forget" an interrupt as configured, 1261 thus exercising the error handling. 1262 1263 Only works with drivers that use the generic timeout handling, 1264 for others it wont do anything. 1265 1266config FAIL_MMC_REQUEST 1267 bool "Fault-injection capability for MMC IO" 1268 select DEBUG_FS 1269 depends on FAULT_INJECTION && MMC 1270 help 1271 Provide fault-injection capability for MMC IO. 1272 This will make the mmc core return data errors. This is 1273 useful to test the error handling in the mmc block device 1274 and to test how the mmc host driver handles retries from 1275 the block device. 1276 1277config FAULT_INJECTION_DEBUG_FS 1278 bool "Debugfs entries for fault-injection capabilities" 1279 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1280 help 1281 Enable configuration of fault-injection capabilities via debugfs. 1282 1283config FAULT_INJECTION_STACKTRACE_FILTER 1284 bool "stacktrace filter for fault-injection capabilities" 1285 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1286 depends on !X86_64 1287 select STACKTRACE 1288 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND 1289 help 1290 Provide stacktrace filter for fault-injection capabilities 1291 1292config LATENCYTOP 1293 bool "Latency measuring infrastructure" 1294 depends on HAVE_LATENCYTOP_SUPPORT 1295 depends on DEBUG_KERNEL 1296 depends on STACKTRACE_SUPPORT 1297 depends on PROC_FS 1298 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND 1299 select KALLSYMS 1300 select KALLSYMS_ALL 1301 select STACKTRACE 1302 select SCHEDSTATS 1303 select SCHED_DEBUG 1304 help 1305 Enable this option if you want to use the LatencyTOP tool 1306 to find out which userspace is blocking on what kernel operations. 1307 1308config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1309 bool 1310 1311config DEBUG_STRICT_USER_COPY_CHECKS 1312 bool "Strict user copy size checks" 1313 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1314 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING 1315 help 1316 Enabling this option turns a certain set of sanity checks for user 1317 copy operations into compile time failures. 1318 1319 The copy_from_user() etc checks are there to help test if there 1320 are sufficient security checks on the length argument of 1321 the copy operation, by having gcc prove that the argument is 1322 within bounds. 1323 1324 If unsure, say N. 1325 1326source mm/Kconfig.debug 1327source kernel/trace/Kconfig 1328 1329config RBTREE_TEST 1330 tristate "Red-Black tree test" 1331 depends on m && DEBUG_KERNEL 1332 help 1333 A benchmark measuring the performance of the rbtree library. 1334 Also includes rbtree invariant checks. 1335 1336config INTERVAL_TREE_TEST 1337 tristate "Interval tree test" 1338 depends on m && DEBUG_KERNEL 1339 help 1340 A benchmark measuring the performance of the interval tree library 1341 1342config PROVIDE_OHCI1394_DMA_INIT 1343 bool "Remote debugging over FireWire early on boot" 1344 depends on PCI && X86 1345 help 1346 If you want to debug problems which hang or crash the kernel early 1347 on boot and the crashing machine has a FireWire port, you can use 1348 this feature to remotely access the memory of the crashed machine 1349 over FireWire. This employs remote DMA as part of the OHCI1394 1350 specification which is now the standard for FireWire controllers. 1351 1352 With remote DMA, you can monitor the printk buffer remotely using 1353 firescope and access all memory below 4GB using fireproxy from gdb. 1354 Even controlling a kernel debugger is possible using remote DMA. 1355 1356 Usage: 1357 1358 If ohci1394_dma=early is used as boot parameter, it will initialize 1359 all OHCI1394 controllers which are found in the PCI config space. 1360 1361 As all changes to the FireWire bus such as enabling and disabling 1362 devices cause a bus reset and thereby disable remote DMA for all 1363 devices, be sure to have the cable plugged and FireWire enabled on 1364 the debugging host before booting the debug target for debugging. 1365 1366 This code (~1k) is freed after boot. By then, the firewire stack 1367 in charge of the OHCI-1394 controllers should be used instead. 1368 1369 See Documentation/debugging-via-ohci1394.txt for more information. 1370 1371config FIREWIRE_OHCI_REMOTE_DMA 1372 bool "Remote debugging over FireWire with firewire-ohci" 1373 depends on FIREWIRE_OHCI 1374 help 1375 This option lets you use the FireWire bus for remote debugging 1376 with help of the firewire-ohci driver. It enables unfiltered 1377 remote DMA in firewire-ohci. 1378 See Documentation/debugging-via-ohci1394.txt for more information. 1379 1380 If unsure, say N. 1381 1382config BUILD_DOCSRC 1383 bool "Build targets in Documentation/ tree" 1384 depends on HEADERS_CHECK 1385 help 1386 This option attempts to build objects from the source files in the 1387 kernel Documentation/ tree. 1388 1389 Say N if you are unsure. 1390 1391config DYNAMIC_DEBUG 1392 bool "Enable dynamic printk() support" 1393 default n 1394 depends on PRINTK 1395 depends on DEBUG_FS 1396 help 1397 1398 Compiles debug level messages into the kernel, which would not 1399 otherwise be available at runtime. These messages can then be 1400 enabled/disabled based on various levels of scope - per source file, 1401 function, module, format string, and line number. This mechanism 1402 implicitly compiles in all pr_debug() and dev_dbg() calls, which 1403 enlarges the kernel text size by about 2%. 1404 1405 If a source file is compiled with DEBUG flag set, any 1406 pr_debug() calls in it are enabled by default, but can be 1407 disabled at runtime as below. Note that DEBUG flag is 1408 turned on by many CONFIG_*DEBUG* options. 1409 1410 Usage: 1411 1412 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 1413 which is contained in the 'debugfs' filesystem. Thus, the debugfs 1414 filesystem must first be mounted before making use of this feature. 1415 We refer the control file as: <debugfs>/dynamic_debug/control. This 1416 file contains a list of the debug statements that can be enabled. The 1417 format for each line of the file is: 1418 1419 filename:lineno [module]function flags format 1420 1421 filename : source file of the debug statement 1422 lineno : line number of the debug statement 1423 module : module that contains the debug statement 1424 function : function that contains the debug statement 1425 flags : '=p' means the line is turned 'on' for printing 1426 format : the format used for the debug statement 1427 1428 From a live system: 1429 1430 nullarbor:~ # cat <debugfs>/dynamic_debug/control 1431 # filename:lineno [module]function flags format 1432 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012" 1433 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012" 1434 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012" 1435 1436 Example usage: 1437 1438 // enable the message at line 1603 of file svcsock.c 1439 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 1440 <debugfs>/dynamic_debug/control 1441 1442 // enable all the messages in file svcsock.c 1443 nullarbor:~ # echo -n 'file svcsock.c +p' > 1444 <debugfs>/dynamic_debug/control 1445 1446 // enable all the messages in the NFS server module 1447 nullarbor:~ # echo -n 'module nfsd +p' > 1448 <debugfs>/dynamic_debug/control 1449 1450 // enable all 12 messages in the function svc_process() 1451 nullarbor:~ # echo -n 'func svc_process +p' > 1452 <debugfs>/dynamic_debug/control 1453 1454 // disable all 12 messages in the function svc_process() 1455 nullarbor:~ # echo -n 'func svc_process -p' > 1456 <debugfs>/dynamic_debug/control 1457 1458 See Documentation/dynamic-debug-howto.txt for additional information. 1459 1460config DMA_API_DEBUG 1461 bool "Enable debugging of DMA-API usage" 1462 depends on HAVE_DMA_API_DEBUG 1463 help 1464 Enable this option to debug the use of the DMA API by device drivers. 1465 With this option you will be able to detect common bugs in device 1466 drivers like double-freeing of DMA mappings or freeing mappings that 1467 were never allocated. 1468 This option causes a performance degredation. Use only if you want 1469 to debug device drivers. If unsure, say N. 1470 1471config ATOMIC64_SELFTEST 1472 bool "Perform an atomic64_t self-test at boot" 1473 help 1474 Enable this option to test the atomic64_t functions at boot. 1475 1476 If unsure, say N. 1477 1478config ASYNC_RAID6_TEST 1479 tristate "Self test for hardware accelerated raid6 recovery" 1480 depends on ASYNC_RAID6_RECOV 1481 select ASYNC_MEMCPY 1482 ---help--- 1483 This is a one-shot self test that permutes through the 1484 recovery of all the possible two disk failure scenarios for a 1485 N-disk array. Recovery is performed with the asynchronous 1486 raid6 recovery routines, and will optionally use an offload 1487 engine if one is available. 1488 1489 If unsure, say N. 1490 1491source "samples/Kconfig" 1492 1493source "lib/Kconfig.kgdb" 1494 1495source "lib/Kconfig.kmemcheck" 1496 1497config TEST_STRING_HELPERS 1498 tristate "Test functions located in the string_helpers module at runtime" 1499 1500config TEST_KSTRTOX 1501 tristate "Test kstrto*() family of functions at runtime" 1502