1 2config PRINTK_TIME 3 bool "Show timing information on printks" 4 depends on PRINTK 5 help 6 Selecting this option causes timing information to be 7 included in printk output. This allows you to measure 8 the interval between kernel operations, including bootup 9 operations. This is useful for identifying long delays 10 in kernel startup. 11 12config ENABLE_WARN_DEPRECATED 13 bool "Enable __deprecated logic" 14 default y 15 help 16 Enable the __deprecated logic in the kernel build. 17 Disable this to suppress the "warning: 'foo' is deprecated 18 (declared at kernel/power/somefile.c:1234)" messages. 19 20config ENABLE_MUST_CHECK 21 bool "Enable __must_check logic" 22 default y 23 help 24 Enable the __must_check logic in the kernel build. Disable this to 25 suppress the "warning: ignoring return value of 'foo', declared with 26 attribute warn_unused_result" messages. 27 28config FRAME_WARN 29 int "Warn for stack frames larger than (needs gcc 4.4)" 30 range 0 8192 31 default 1024 if !64BIT 32 default 2048 if 64BIT 33 help 34 Tell gcc to warn at build time for stack frames larger than this. 35 Setting this too low will cause a lot of warnings. 36 Setting it to 0 disables the warning. 37 Requires gcc 4.4 38 39config MAGIC_SYSRQ 40 bool "Magic SysRq key" 41 depends on !UML 42 help 43 If you say Y here, you will have some control over the system even 44 if the system crashes for example during kernel debugging (e.g., you 45 will be able to flush the buffer cache to disk, reboot the system 46 immediately or dump some status information). This is accomplished 47 by pressing various keys while holding SysRq (Alt+PrintScreen). It 48 also works on a serial console (on PC hardware at least), if you 49 send a BREAK and then within 5 seconds a command keypress. The 50 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 51 unless you really know what this hack does. 52 53config STRIP_ASM_SYMS 54 bool "Strip assembler-generated symbols during link" 55 default n 56 help 57 Strip internal assembler-generated symbols during a link (symbols 58 that look like '.Lxxx') so they don't pollute the output of 59 get_wchan() and suchlike. 60 61config UNUSED_SYMBOLS 62 bool "Enable unused/obsolete exported symbols" 63 default y if X86 64 help 65 Unused but exported symbols make the kernel needlessly bigger. For 66 that reason most of these unused exports will soon be removed. This 67 option is provided temporarily to provide a transition period in case 68 some external kernel module needs one of these symbols anyway. If you 69 encounter such a case in your module, consider if you are actually 70 using the right API. (rationale: since nobody in the kernel is using 71 this in a module, there is a pretty good chance it's actually the 72 wrong interface to use). If you really need the symbol, please send a 73 mail to the linux kernel mailing list mentioning the symbol and why 74 you really need it, and what the merge plan to the mainline kernel for 75 your module is. 76 77config DEBUG_FS 78 bool "Debug Filesystem" 79 depends on SYSFS 80 help 81 debugfs is a virtual file system that kernel developers use to put 82 debugging files into. Enable this option to be able to read and 83 write to these files. 84 85 For detailed documentation on the debugfs API, see 86 Documentation/DocBook/filesystems. 87 88 If unsure, say N. 89 90config HEADERS_CHECK 91 bool "Run 'make headers_check' when building vmlinux" 92 depends on !UML 93 help 94 This option will extract the user-visible kernel headers whenever 95 building the kernel, and will run basic sanity checks on them to 96 ensure that exported files do not attempt to include files which 97 were not exported, etc. 98 99 If you're making modifications to header files which are 100 relevant for userspace, say 'Y', and check the headers 101 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 102 your build tree), to make sure they're suitable. 103 104config DEBUG_SECTION_MISMATCH 105 bool "Enable full Section mismatch analysis" 106 depends on UNDEFINED 107 # This option is on purpose disabled for now. 108 # It will be enabled when we are down to a reasonable number 109 # of section mismatch warnings (< 10 for an allyesconfig build) 110 help 111 The section mismatch analysis checks if there are illegal 112 references from one section to another section. 113 Linux will during link or during runtime drop some sections 114 and any use of code/data previously in these sections will 115 most likely result in an oops. 116 In the code functions and variables are annotated with 117 __init, __devinit etc. (see full list in include/linux/init.h) 118 which results in the code/data being placed in specific sections. 119 The section mismatch analysis is always done after a full 120 kernel build but enabling this option will in addition 121 do the following: 122 - Add the option -fno-inline-functions-called-once to gcc 123 When inlining a function annotated __init in a non-init 124 function we would lose the section information and thus 125 the analysis would not catch the illegal reference. 126 This option tells gcc to inline less but will also 127 result in a larger kernel. 128 - Run the section mismatch analysis for each module/built-in.o 129 When we run the section mismatch analysis on vmlinux.o we 130 lose valueble information about where the mismatch was 131 introduced. 132 Running the analysis for each module/built-in.o file 133 will tell where the mismatch happens much closer to the 134 source. The drawback is that we will report the same 135 mismatch at least twice. 136 - Enable verbose reporting from modpost to help solving 137 the section mismatches reported. 138 139config DEBUG_KERNEL 140 bool "Kernel debugging" 141 help 142 Say Y here if you are developing drivers or trying to debug and 143 identify kernel problems. 144 145config DEBUG_SHIRQ 146 bool "Debug shared IRQ handlers" 147 depends on DEBUG_KERNEL && GENERIC_HARDIRQS 148 help 149 Enable this to generate a spurious interrupt as soon as a shared 150 interrupt handler is registered, and just before one is deregistered. 151 Drivers ought to be able to handle interrupts coming in at those 152 points; some don't and need to be caught. 153 154config DETECT_SOFTLOCKUP 155 bool "Detect Soft Lockups" 156 depends on DEBUG_KERNEL && !S390 157 default y 158 help 159 Say Y here to enable the kernel to detect "soft lockups", 160 which are bugs that cause the kernel to loop in kernel 161 mode for more than 60 seconds, without giving other tasks a 162 chance to run. 163 164 When a soft-lockup is detected, the kernel will print the 165 current stack trace (which you should report), but the 166 system will stay locked up. This feature has negligible 167 overhead. 168 169 (Note that "hard lockups" are separate type of bugs that 170 can be detected via the NMI-watchdog, on platforms that 171 support it.) 172 173config BOOTPARAM_SOFTLOCKUP_PANIC 174 bool "Panic (Reboot) On Soft Lockups" 175 depends on DETECT_SOFTLOCKUP 176 help 177 Say Y here to enable the kernel to panic on "soft lockups", 178 which are bugs that cause the kernel to loop in kernel 179 mode for more than 60 seconds, without giving other tasks a 180 chance to run. 181 182 The panic can be used in combination with panic_timeout, 183 to cause the system to reboot automatically after a 184 lockup has been detected. This feature is useful for 185 high-availability systems that have uptime guarantees and 186 where a lockup must be resolved ASAP. 187 188 Say N if unsure. 189 190config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 191 int 192 depends on DETECT_SOFTLOCKUP 193 range 0 1 194 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 195 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 196 197config DETECT_HUNG_TASK 198 bool "Detect Hung Tasks" 199 depends on DEBUG_KERNEL 200 default DETECT_SOFTLOCKUP 201 help 202 Say Y here to enable the kernel to detect "hung tasks", 203 which are bugs that cause the task to be stuck in 204 uninterruptible "D" state indefinitiley. 205 206 When a hung task is detected, the kernel will print the 207 current stack trace (which you should report), but the 208 task will stay in uninterruptible state. If lockdep is 209 enabled then all held locks will also be reported. This 210 feature has negligible overhead. 211 212config BOOTPARAM_HUNG_TASK_PANIC 213 bool "Panic (Reboot) On Hung Tasks" 214 depends on DETECT_HUNG_TASK 215 help 216 Say Y here to enable the kernel to panic on "hung tasks", 217 which are bugs that cause the kernel to leave a task stuck 218 in uninterruptible "D" state. 219 220 The panic can be used in combination with panic_timeout, 221 to cause the system to reboot automatically after a 222 hung task has been detected. This feature is useful for 223 high-availability systems that have uptime guarantees and 224 where a hung tasks must be resolved ASAP. 225 226 Say N if unsure. 227 228config BOOTPARAM_HUNG_TASK_PANIC_VALUE 229 int 230 depends on DETECT_HUNG_TASK 231 range 0 1 232 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 233 default 1 if BOOTPARAM_HUNG_TASK_PANIC 234 235config SCHED_DEBUG 236 bool "Collect scheduler debugging info" 237 depends on DEBUG_KERNEL && PROC_FS 238 default y 239 help 240 If you say Y here, the /proc/sched_debug file will be provided 241 that can help debug the scheduler. The runtime overhead of this 242 option is minimal. 243 244config SCHEDSTATS 245 bool "Collect scheduler statistics" 246 depends on DEBUG_KERNEL && PROC_FS 247 help 248 If you say Y here, additional code will be inserted into the 249 scheduler and related routines to collect statistics about 250 scheduler behavior and provide them in /proc/schedstat. These 251 stats may be useful for both tuning and debugging the scheduler 252 If you aren't debugging the scheduler or trying to tune a specific 253 application, you can say N to avoid the very slight overhead 254 this adds. 255 256config TIMER_STATS 257 bool "Collect kernel timers statistics" 258 depends on DEBUG_KERNEL && PROC_FS 259 help 260 If you say Y here, additional code will be inserted into the 261 timer routines to collect statistics about kernel timers being 262 reprogrammed. The statistics can be read from /proc/timer_stats. 263 The statistics collection is started by writing 1 to /proc/timer_stats, 264 writing 0 stops it. This feature is useful to collect information 265 about timer usage patterns in kernel and userspace. This feature 266 is lightweight if enabled in the kernel config but not activated 267 (it defaults to deactivated on bootup and will only be activated 268 if some application like powertop activates it explicitly). 269 270config DEBUG_OBJECTS 271 bool "Debug object operations" 272 depends on DEBUG_KERNEL 273 help 274 If you say Y here, additional code will be inserted into the 275 kernel to track the life time of various objects and validate 276 the operations on those objects. 277 278config DEBUG_OBJECTS_SELFTEST 279 bool "Debug objects selftest" 280 depends on DEBUG_OBJECTS 281 help 282 This enables the selftest of the object debug code. 283 284config DEBUG_OBJECTS_FREE 285 bool "Debug objects in freed memory" 286 depends on DEBUG_OBJECTS 287 help 288 This enables checks whether a k/v free operation frees an area 289 which contains an object which has not been deactivated 290 properly. This can make kmalloc/kfree-intensive workloads 291 much slower. 292 293config DEBUG_OBJECTS_TIMERS 294 bool "Debug timer objects" 295 depends on DEBUG_OBJECTS 296 help 297 If you say Y here, additional code will be inserted into the 298 timer routines to track the life time of timer objects and 299 validate the timer operations. 300 301config DEBUG_OBJECTS_WORK 302 bool "Debug work objects" 303 depends on DEBUG_OBJECTS 304 help 305 If you say Y here, additional code will be inserted into the 306 work queue routines to track the life time of work objects and 307 validate the work operations. 308 309config DEBUG_OBJECTS_ENABLE_DEFAULT 310 int "debug_objects bootup default value (0-1)" 311 range 0 1 312 default "1" 313 depends on DEBUG_OBJECTS 314 help 315 Debug objects boot parameter default value 316 317config DEBUG_SLAB 318 bool "Debug slab memory allocations" 319 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 320 help 321 Say Y here to have the kernel do limited verification on memory 322 allocation as well as poisoning memory on free to catch use of freed 323 memory. This can make kmalloc/kfree-intensive workloads much slower. 324 325config DEBUG_SLAB_LEAK 326 bool "Memory leak debugging" 327 depends on DEBUG_SLAB 328 329config SLUB_DEBUG_ON 330 bool "SLUB debugging on by default" 331 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 332 default n 333 help 334 Boot with debugging on by default. SLUB boots by default with 335 the runtime debug capabilities switched off. Enabling this is 336 equivalent to specifying the "slub_debug" parameter on boot. 337 There is no support for more fine grained debug control like 338 possible with slub_debug=xxx. SLUB debugging may be switched 339 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 340 "slub_debug=-". 341 342config SLUB_STATS 343 default n 344 bool "Enable SLUB performance statistics" 345 depends on SLUB && SLUB_DEBUG && SYSFS 346 help 347 SLUB statistics are useful to debug SLUBs allocation behavior in 348 order find ways to optimize the allocator. This should never be 349 enabled for production use since keeping statistics slows down 350 the allocator by a few percentage points. The slabinfo command 351 supports the determination of the most active slabs to figure 352 out which slabs are relevant to a particular load. 353 Try running: slabinfo -DA 354 355config DEBUG_KMEMLEAK 356 bool "Kernel memory leak detector" 357 depends on DEBUG_KERNEL && EXPERIMENTAL && !MEMORY_HOTPLUG && \ 358 (X86 || ARM || PPC || S390 || SUPERH) 359 360 select DEBUG_FS if SYSFS 361 select STACKTRACE if STACKTRACE_SUPPORT 362 select KALLSYMS 363 select CRC32 364 help 365 Say Y here if you want to enable the memory leak 366 detector. The memory allocation/freeing is traced in a way 367 similar to the Boehm's conservative garbage collector, the 368 difference being that the orphan objects are not freed but 369 only shown in /sys/kernel/debug/kmemleak. Enabling this 370 feature will introduce an overhead to memory 371 allocations. See Documentation/kmemleak.txt for more 372 details. 373 374 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 375 of finding leaks due to the slab objects poisoning. 376 377 In order to access the kmemleak file, debugfs needs to be 378 mounted (usually at /sys/kernel/debug). 379 380config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 381 int "Maximum kmemleak early log entries" 382 depends on DEBUG_KMEMLEAK 383 range 200 40000 384 default 400 385 help 386 Kmemleak must track all the memory allocations to avoid 387 reporting false positives. Since memory may be allocated or 388 freed before kmemleak is initialised, an early log buffer is 389 used to store these actions. If kmemleak reports "early log 390 buffer exceeded", please increase this value. 391 392config DEBUG_KMEMLEAK_TEST 393 tristate "Simple test for the kernel memory leak detector" 394 depends on DEBUG_KMEMLEAK 395 help 396 Say Y or M here to build a test for the kernel memory leak 397 detector. This option enables a module that explicitly leaks 398 memory. 399 400 If unsure, say N. 401 402config DEBUG_PREEMPT 403 bool "Debug preemptible kernel" 404 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 405 default y 406 help 407 If you say Y here then the kernel will use a debug variant of the 408 commonly used smp_processor_id() function and will print warnings 409 if kernel code uses it in a preemption-unsafe way. Also, the kernel 410 will detect preemption count underflows. 411 412config DEBUG_RT_MUTEXES 413 bool "RT Mutex debugging, deadlock detection" 414 depends on DEBUG_KERNEL && RT_MUTEXES 415 help 416 This allows rt mutex semantics violations and rt mutex related 417 deadlocks (lockups) to be detected and reported automatically. 418 419config DEBUG_PI_LIST 420 bool 421 default y 422 depends on DEBUG_RT_MUTEXES 423 424config RT_MUTEX_TESTER 425 bool "Built-in scriptable tester for rt-mutexes" 426 depends on DEBUG_KERNEL && RT_MUTEXES 427 help 428 This option enables a rt-mutex tester. 429 430config DEBUG_SPINLOCK 431 bool "Spinlock and rw-lock debugging: basic checks" 432 depends on DEBUG_KERNEL 433 help 434 Say Y here and build SMP to catch missing spinlock initialization 435 and certain other kinds of spinlock errors commonly made. This is 436 best used in conjunction with the NMI watchdog so that spinlock 437 deadlocks are also debuggable. 438 439config DEBUG_MUTEXES 440 bool "Mutex debugging: basic checks" 441 depends on DEBUG_KERNEL 442 help 443 This feature allows mutex semantics violations to be detected and 444 reported. 445 446config DEBUG_LOCK_ALLOC 447 bool "Lock debugging: detect incorrect freeing of live locks" 448 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 449 select DEBUG_SPINLOCK 450 select DEBUG_MUTEXES 451 select LOCKDEP 452 help 453 This feature will check whether any held lock (spinlock, rwlock, 454 mutex or rwsem) is incorrectly freed by the kernel, via any of the 455 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 456 vfree(), etc.), whether a live lock is incorrectly reinitialized via 457 spin_lock_init()/mutex_init()/etc., or whether there is any lock 458 held during task exit. 459 460config PROVE_LOCKING 461 bool "Lock debugging: prove locking correctness" 462 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 463 select LOCKDEP 464 select DEBUG_SPINLOCK 465 select DEBUG_MUTEXES 466 select DEBUG_LOCK_ALLOC 467 default n 468 help 469 This feature enables the kernel to prove that all locking 470 that occurs in the kernel runtime is mathematically 471 correct: that under no circumstance could an arbitrary (and 472 not yet triggered) combination of observed locking 473 sequences (on an arbitrary number of CPUs, running an 474 arbitrary number of tasks and interrupt contexts) cause a 475 deadlock. 476 477 In short, this feature enables the kernel to report locking 478 related deadlocks before they actually occur. 479 480 The proof does not depend on how hard and complex a 481 deadlock scenario would be to trigger: how many 482 participant CPUs, tasks and irq-contexts would be needed 483 for it to trigger. The proof also does not depend on 484 timing: if a race and a resulting deadlock is possible 485 theoretically (no matter how unlikely the race scenario 486 is), it will be proven so and will immediately be 487 reported by the kernel (once the event is observed that 488 makes the deadlock theoretically possible). 489 490 If a deadlock is impossible (i.e. the locking rules, as 491 observed by the kernel, are mathematically correct), the 492 kernel reports nothing. 493 494 NOTE: this feature can also be enabled for rwlocks, mutexes 495 and rwsems - in which case all dependencies between these 496 different locking variants are observed and mapped too, and 497 the proof of observed correctness is also maintained for an 498 arbitrary combination of these separate locking variants. 499 500 For more details, see Documentation/lockdep-design.txt. 501 502config PROVE_RCU 503 bool "RCU debugging: prove RCU correctness" 504 depends on PROVE_LOCKING 505 default n 506 help 507 This feature enables lockdep extensions that check for correct 508 use of RCU APIs. This is currently under development. Say Y 509 if you want to debug RCU usage or help work on the PROVE_RCU 510 feature. 511 512 Say N if you are unsure. 513 514config LOCKDEP 515 bool 516 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 517 select STACKTRACE 518 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 519 select KALLSYMS 520 select KALLSYMS_ALL 521 522config LOCK_STAT 523 bool "Lock usage statistics" 524 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 525 select LOCKDEP 526 select DEBUG_SPINLOCK 527 select DEBUG_MUTEXES 528 select DEBUG_LOCK_ALLOC 529 default n 530 help 531 This feature enables tracking lock contention points 532 533 For more details, see Documentation/lockstat.txt 534 535 This also enables lock events required by "perf lock", 536 subcommand of perf. 537 If you want to use "perf lock", you also need to turn on 538 CONFIG_EVENT_TRACING. 539 540 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 541 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 542 543config DEBUG_LOCKDEP 544 bool "Lock dependency engine debugging" 545 depends on DEBUG_KERNEL && LOCKDEP 546 help 547 If you say Y here, the lock dependency engine will do 548 additional runtime checks to debug itself, at the price 549 of more runtime overhead. 550 551config TRACE_IRQFLAGS 552 depends on DEBUG_KERNEL 553 bool 554 default y 555 depends on TRACE_IRQFLAGS_SUPPORT 556 depends on PROVE_LOCKING 557 558config DEBUG_SPINLOCK_SLEEP 559 bool "Spinlock debugging: sleep-inside-spinlock checking" 560 depends on DEBUG_KERNEL 561 help 562 If you say Y here, various routines which may sleep will become very 563 noisy if they are called with a spinlock held. 564 565config DEBUG_LOCKING_API_SELFTESTS 566 bool "Locking API boot-time self-tests" 567 depends on DEBUG_KERNEL 568 help 569 Say Y here if you want the kernel to run a short self-test during 570 bootup. The self-test checks whether common types of locking bugs 571 are detected by debugging mechanisms or not. (if you disable 572 lock debugging then those bugs wont be detected of course.) 573 The following locking APIs are covered: spinlocks, rwlocks, 574 mutexes and rwsems. 575 576config STACKTRACE 577 bool 578 depends on STACKTRACE_SUPPORT 579 580config DEBUG_KOBJECT 581 bool "kobject debugging" 582 depends on DEBUG_KERNEL 583 help 584 If you say Y here, some extra kobject debugging messages will be sent 585 to the syslog. 586 587config DEBUG_HIGHMEM 588 bool "Highmem debugging" 589 depends on DEBUG_KERNEL && HIGHMEM 590 help 591 This options enables addition error checking for high memory systems. 592 Disable for production systems. 593 594config DEBUG_BUGVERBOSE 595 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED 596 depends on BUG 597 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ 598 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 599 default y 600 help 601 Say Y here to make BUG() panics output the file name and line number 602 of the BUG call as well as the EIP and oops trace. This aids 603 debugging but costs about 70-100K of memory. 604 605config DEBUG_INFO 606 bool "Compile the kernel with debug info" 607 depends on DEBUG_KERNEL 608 help 609 If you say Y here the resulting kernel image will include 610 debugging info resulting in a larger kernel image. 611 This adds debug symbols to the kernel and modules (gcc -g), and 612 is needed if you intend to use kernel crashdump or binary object 613 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 614 Say Y here only if you plan to debug the kernel. 615 616 If unsure, say N. 617 618config DEBUG_VM 619 bool "Debug VM" 620 depends on DEBUG_KERNEL 621 help 622 Enable this to turn on extended checks in the virtual-memory system 623 that may impact performance. 624 625 If unsure, say N. 626 627config DEBUG_VIRTUAL 628 bool "Debug VM translations" 629 depends on DEBUG_KERNEL && X86 630 help 631 Enable some costly sanity checks in virtual to page code. This can 632 catch mistakes with virt_to_page() and friends. 633 634 If unsure, say N. 635 636config DEBUG_NOMMU_REGIONS 637 bool "Debug the global anon/private NOMMU mapping region tree" 638 depends on DEBUG_KERNEL && !MMU 639 help 640 This option causes the global tree of anonymous and private mapping 641 regions to be regularly checked for invalid topology. 642 643config DEBUG_WRITECOUNT 644 bool "Debug filesystem writers count" 645 depends on DEBUG_KERNEL 646 help 647 Enable this to catch wrong use of the writers count in struct 648 vfsmount. This will increase the size of each file struct by 649 32 bits. 650 651 If unsure, say N. 652 653config DEBUG_MEMORY_INIT 654 bool "Debug memory initialisation" if EMBEDDED 655 default !EMBEDDED 656 help 657 Enable this for additional checks during memory initialisation. 658 The sanity checks verify aspects of the VM such as the memory model 659 and other information provided by the architecture. Verbose 660 information will be printed at KERN_DEBUG loglevel depending 661 on the mminit_loglevel= command-line option. 662 663 If unsure, say Y 664 665config DEBUG_LIST 666 bool "Debug linked list manipulation" 667 depends on DEBUG_KERNEL 668 help 669 Enable this to turn on extended checks in the linked-list 670 walking routines. 671 672 If unsure, say N. 673 674config DEBUG_SG 675 bool "Debug SG table operations" 676 depends on DEBUG_KERNEL 677 help 678 Enable this to turn on checks on scatter-gather tables. This can 679 help find problems with drivers that do not properly initialize 680 their sg tables. 681 682 If unsure, say N. 683 684config DEBUG_NOTIFIERS 685 bool "Debug notifier call chains" 686 depends on DEBUG_KERNEL 687 help 688 Enable this to turn on sanity checking for notifier call chains. 689 This is most useful for kernel developers to make sure that 690 modules properly unregister themselves from notifier chains. 691 This is a relatively cheap check but if you care about maximum 692 performance, say N. 693 694config DEBUG_CREDENTIALS 695 bool "Debug credential management" 696 depends on DEBUG_KERNEL 697 help 698 Enable this to turn on some debug checking for credential 699 management. The additional code keeps track of the number of 700 pointers from task_structs to any given cred struct, and checks to 701 see that this number never exceeds the usage count of the cred 702 struct. 703 704 Furthermore, if SELinux is enabled, this also checks that the 705 security pointer in the cred struct is never seen to be invalid. 706 707 If unsure, say N. 708 709# 710# Select this config option from the architecture Kconfig, if it 711# it is preferred to always offer frame pointers as a config 712# option on the architecture (regardless of KERNEL_DEBUG): 713# 714config ARCH_WANT_FRAME_POINTERS 715 bool 716 help 717 718config FRAME_POINTER 719 bool "Compile the kernel with frame pointers" 720 depends on DEBUG_KERNEL && \ 721 (CRIS || M68K || M68KNOMMU || FRV || UML || \ 722 AVR32 || SUPERH || BLACKFIN || MN10300) || \ 723 ARCH_WANT_FRAME_POINTERS 724 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 725 help 726 If you say Y here the resulting kernel image will be slightly 727 larger and slower, but it gives very useful debugging information 728 in case of kernel bugs. (precise oopses/stacktraces/warnings) 729 730config BOOT_PRINTK_DELAY 731 bool "Delay each boot printk message by N milliseconds" 732 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 733 help 734 This build option allows you to read kernel boot messages 735 by inserting a short delay after each one. The delay is 736 specified in milliseconds on the kernel command line, 737 using "boot_delay=N". 738 739 It is likely that you would also need to use "lpj=M" to preset 740 the "loops per jiffie" value. 741 See a previous boot log for the "lpj" value to use for your 742 system, and then set "lpj=M" before setting "boot_delay=N". 743 NOTE: Using this option may adversely affect SMP systems. 744 I.e., processors other than the first one may not boot up. 745 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect 746 what it believes to be lockup conditions. 747 748config RCU_TORTURE_TEST 749 tristate "torture tests for RCU" 750 depends on DEBUG_KERNEL 751 default n 752 help 753 This option provides a kernel module that runs torture tests 754 on the RCU infrastructure. The kernel module may be built 755 after the fact on the running kernel to be tested, if desired. 756 757 Say Y here if you want RCU torture tests to be built into 758 the kernel. 759 Say M if you want the RCU torture tests to build as a module. 760 Say N if you are unsure. 761 762config RCU_TORTURE_TEST_RUNNABLE 763 bool "torture tests for RCU runnable by default" 764 depends on RCU_TORTURE_TEST = y 765 default n 766 help 767 This option provides a way to build the RCU torture tests 768 directly into the kernel without them starting up at boot 769 time. You can use /proc/sys/kernel/rcutorture_runnable 770 to manually override this setting. This /proc file is 771 available only when the RCU torture tests have been built 772 into the kernel. 773 774 Say Y here if you want the RCU torture tests to start during 775 boot (you probably don't). 776 Say N here if you want the RCU torture tests to start only 777 after being manually enabled via /proc. 778 779config RCU_CPU_STALL_DETECTOR 780 bool "Check for stalled CPUs delaying RCU grace periods" 781 depends on TREE_RCU || TREE_PREEMPT_RCU 782 default y 783 help 784 This option causes RCU to printk information on which 785 CPUs are delaying the current grace period, but only when 786 the grace period extends for excessive time periods. 787 788 Say N if you want to disable such checks. 789 790 Say Y if you are unsure. 791 792config RCU_CPU_STALL_VERBOSE 793 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" 794 depends on RCU_CPU_STALL_DETECTOR && TREE_PREEMPT_RCU 795 default n 796 help 797 This option causes RCU to printk detailed per-task information 798 for any tasks that are stalling the current RCU grace period. 799 800 Say N if you are unsure. 801 802 Say Y if you want to enable such checks. 803 804config KPROBES_SANITY_TEST 805 bool "Kprobes sanity tests" 806 depends on DEBUG_KERNEL 807 depends on KPROBES 808 default n 809 help 810 This option provides for testing basic kprobes functionality on 811 boot. A sample kprobe, jprobe and kretprobe are inserted and 812 verified for functionality. 813 814 Say N if you are unsure. 815 816config BACKTRACE_SELF_TEST 817 tristate "Self test for the backtrace code" 818 depends on DEBUG_KERNEL 819 default n 820 help 821 This option provides a kernel module that can be used to test 822 the kernel stack backtrace code. This option is not useful 823 for distributions or general kernels, but only for kernel 824 developers working on architecture code. 825 826 Note that if you want to also test saved backtraces, you will 827 have to enable STACKTRACE as well. 828 829 Say N if you are unsure. 830 831config DEBUG_BLOCK_EXT_DEVT 832 bool "Force extended block device numbers and spread them" 833 depends on DEBUG_KERNEL 834 depends on BLOCK 835 default n 836 help 837 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 838 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 839 YOU ARE DOING. Distros, please enable this and fix whatever 840 is broken. 841 842 Conventionally, block device numbers are allocated from 843 predetermined contiguous area. However, extended block area 844 may introduce non-contiguous block device numbers. This 845 option forces most block device numbers to be allocated from 846 the extended space and spreads them to discover kernel or 847 userland code paths which assume predetermined contiguous 848 device number allocation. 849 850 Note that turning on this debug option shuffles all the 851 device numbers for all IDE and SCSI devices including libata 852 ones, so root partition specified using device number 853 directly (via rdev or root=MAJ:MIN) won't work anymore. 854 Textual device names (root=/dev/sdXn) will continue to work. 855 856 Say N if you are unsure. 857 858config DEBUG_FORCE_WEAK_PER_CPU 859 bool "Force weak per-cpu definitions" 860 depends on DEBUG_KERNEL 861 help 862 s390 and alpha require percpu variables in modules to be 863 defined weak to work around addressing range issue which 864 puts the following two restrictions on percpu variable 865 definitions. 866 867 1. percpu symbols must be unique whether static or not 868 2. percpu variables can't be defined inside a function 869 870 To ensure that generic code follows the above rules, this 871 option forces all percpu variables to be defined as weak. 872 873config LKDTM 874 tristate "Linux Kernel Dump Test Tool Module" 875 depends on DEBUG_FS 876 depends on BLOCK 877 default n 878 help 879 This module enables testing of the different dumping mechanisms by 880 inducing system failures at predefined crash points. 881 If you don't need it: say N 882 Choose M here to compile this code as a module. The module will be 883 called lkdtm. 884 885 Documentation on how to use the module can be found in 886 Documentation/fault-injection/provoke-crashes.txt 887 888config FAULT_INJECTION 889 bool "Fault-injection framework" 890 depends on DEBUG_KERNEL 891 help 892 Provide fault-injection framework. 893 For more details, see Documentation/fault-injection/. 894 895config FAILSLAB 896 bool "Fault-injection capability for kmalloc" 897 depends on FAULT_INJECTION 898 depends on SLAB || SLUB 899 help 900 Provide fault-injection capability for kmalloc. 901 902config FAIL_PAGE_ALLOC 903 bool "Fault-injection capabilitiy for alloc_pages()" 904 depends on FAULT_INJECTION 905 help 906 Provide fault-injection capability for alloc_pages(). 907 908config FAIL_MAKE_REQUEST 909 bool "Fault-injection capability for disk IO" 910 depends on FAULT_INJECTION && BLOCK 911 help 912 Provide fault-injection capability for disk IO. 913 914config FAIL_IO_TIMEOUT 915 bool "Faul-injection capability for faking disk interrupts" 916 depends on FAULT_INJECTION && BLOCK 917 help 918 Provide fault-injection capability on end IO handling. This 919 will make the block layer "forget" an interrupt as configured, 920 thus exercising the error handling. 921 922 Only works with drivers that use the generic timeout handling, 923 for others it wont do anything. 924 925config FAULT_INJECTION_DEBUG_FS 926 bool "Debugfs entries for fault-injection capabilities" 927 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 928 help 929 Enable configuration of fault-injection capabilities via debugfs. 930 931config FAULT_INJECTION_STACKTRACE_FILTER 932 bool "stacktrace filter for fault-injection capabilities" 933 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 934 depends on !X86_64 935 select STACKTRACE 936 select FRAME_POINTER if !PPC && !S390 937 help 938 Provide stacktrace filter for fault-injection capabilities 939 940config LATENCYTOP 941 bool "Latency measuring infrastructure" 942 select FRAME_POINTER if !MIPS && !PPC && !S390 943 select KALLSYMS 944 select KALLSYMS_ALL 945 select STACKTRACE 946 select SCHEDSTATS 947 select SCHED_DEBUG 948 depends on HAVE_LATENCYTOP_SUPPORT 949 help 950 Enable this option if you want to use the LatencyTOP tool 951 to find out which userspace is blocking on what kernel operations. 952 953config SYSCTL_SYSCALL_CHECK 954 bool "Sysctl checks" 955 depends on SYSCTL 956 ---help--- 957 sys_sysctl uses binary paths that have been found challenging 958 to properly maintain and use. This enables checks that help 959 you to keep things correct. 960 961source mm/Kconfig.debug 962source kernel/trace/Kconfig 963 964config PROVIDE_OHCI1394_DMA_INIT 965 bool "Remote debugging over FireWire early on boot" 966 depends on PCI && X86 967 help 968 If you want to debug problems which hang or crash the kernel early 969 on boot and the crashing machine has a FireWire port, you can use 970 this feature to remotely access the memory of the crashed machine 971 over FireWire. This employs remote DMA as part of the OHCI1394 972 specification which is now the standard for FireWire controllers. 973 974 With remote DMA, you can monitor the printk buffer remotely using 975 firescope and access all memory below 4GB using fireproxy from gdb. 976 Even controlling a kernel debugger is possible using remote DMA. 977 978 Usage: 979 980 If ohci1394_dma=early is used as boot parameter, it will initialize 981 all OHCI1394 controllers which are found in the PCI config space. 982 983 As all changes to the FireWire bus such as enabling and disabling 984 devices cause a bus reset and thereby disable remote DMA for all 985 devices, be sure to have the cable plugged and FireWire enabled on 986 the debugging host before booting the debug target for debugging. 987 988 This code (~1k) is freed after boot. By then, the firewire stack 989 in charge of the OHCI-1394 controllers should be used instead. 990 991 See Documentation/debugging-via-ohci1394.txt for more information. 992 993config FIREWIRE_OHCI_REMOTE_DMA 994 bool "Remote debugging over FireWire with firewire-ohci" 995 depends on FIREWIRE_OHCI 996 help 997 This option lets you use the FireWire bus for remote debugging 998 with help of the firewire-ohci driver. It enables unfiltered 999 remote DMA in firewire-ohci. 1000 See Documentation/debugging-via-ohci1394.txt for more information. 1001 1002 If unsure, say N. 1003 1004config BUILD_DOCSRC 1005 bool "Build targets in Documentation/ tree" 1006 depends on HEADERS_CHECK 1007 help 1008 This option attempts to build objects from the source files in the 1009 kernel Documentation/ tree. 1010 1011 Say N if you are unsure. 1012 1013config DYNAMIC_DEBUG 1014 bool "Enable dynamic printk() support" 1015 default n 1016 depends on PRINTK 1017 depends on DEBUG_FS 1018 help 1019 1020 Compiles debug level messages into the kernel, which would not 1021 otherwise be available at runtime. These messages can then be 1022 enabled/disabled based on various levels of scope - per source file, 1023 function, module, format string, and line number. This mechanism 1024 implicitly enables all pr_debug() and dev_dbg() calls. The impact of 1025 this compile option is a larger kernel text size of about 2%. 1026 1027 Usage: 1028 1029 Dynamic debugging is controlled via the 'dynamic_debug/ddebug' file, 1030 which is contained in the 'debugfs' filesystem. Thus, the debugfs 1031 filesystem must first be mounted before making use of this feature. 1032 We refer the control file as: <debugfs>/dynamic_debug/ddebug. This 1033 file contains a list of the debug statements that can be enabled. The 1034 format for each line of the file is: 1035 1036 filename:lineno [module]function flags format 1037 1038 filename : source file of the debug statement 1039 lineno : line number of the debug statement 1040 module : module that contains the debug statement 1041 function : function that contains the debug statement 1042 flags : 'p' means the line is turned 'on' for printing 1043 format : the format used for the debug statement 1044 1045 From a live system: 1046 1047 nullarbor:~ # cat <debugfs>/dynamic_debug/ddebug 1048 # filename:lineno [module]function flags format 1049 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012" 1050 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012" 1051 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012" 1052 1053 Example usage: 1054 1055 // enable the message at line 1603 of file svcsock.c 1056 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 1057 <debugfs>/dynamic_debug/ddebug 1058 1059 // enable all the messages in file svcsock.c 1060 nullarbor:~ # echo -n 'file svcsock.c +p' > 1061 <debugfs>/dynamic_debug/ddebug 1062 1063 // enable all the messages in the NFS server module 1064 nullarbor:~ # echo -n 'module nfsd +p' > 1065 <debugfs>/dynamic_debug/ddebug 1066 1067 // enable all 12 messages in the function svc_process() 1068 nullarbor:~ # echo -n 'func svc_process +p' > 1069 <debugfs>/dynamic_debug/ddebug 1070 1071 // disable all 12 messages in the function svc_process() 1072 nullarbor:~ # echo -n 'func svc_process -p' > 1073 <debugfs>/dynamic_debug/ddebug 1074 1075 See Documentation/dynamic-debug-howto.txt for additional information. 1076 1077config DMA_API_DEBUG 1078 bool "Enable debugging of DMA-API usage" 1079 depends on HAVE_DMA_API_DEBUG 1080 help 1081 Enable this option to debug the use of the DMA API by device drivers. 1082 With this option you will be able to detect common bugs in device 1083 drivers like double-freeing of DMA mappings or freeing mappings that 1084 were never allocated. 1085 This option causes a performance degredation. Use only if you want 1086 to debug device drivers. If unsure, say N. 1087 1088source "samples/Kconfig" 1089 1090source "lib/Kconfig.kgdb" 1091 1092source "lib/Kconfig.kmemcheck" 1093