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 resonable 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_ENABLE_DEFAULT 302 int "debug_objects bootup default value (0-1)" 303 range 0 1 304 default "1" 305 depends on DEBUG_OBJECTS 306 help 307 Debug objects boot parameter default value 308 309config DEBUG_SLAB 310 bool "Debug slab memory allocations" 311 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 312 help 313 Say Y here to have the kernel do limited verification on memory 314 allocation as well as poisoning memory on free to catch use of freed 315 memory. This can make kmalloc/kfree-intensive workloads much slower. 316 317config DEBUG_SLAB_LEAK 318 bool "Memory leak debugging" 319 depends on DEBUG_SLAB 320 321config SLUB_DEBUG_ON 322 bool "SLUB debugging on by default" 323 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 324 default n 325 help 326 Boot with debugging on by default. SLUB boots by default with 327 the runtime debug capabilities switched off. Enabling this is 328 equivalent to specifying the "slub_debug" parameter on boot. 329 There is no support for more fine grained debug control like 330 possible with slub_debug=xxx. SLUB debugging may be switched 331 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 332 "slub_debug=-". 333 334config SLUB_STATS 335 default n 336 bool "Enable SLUB performance statistics" 337 depends on SLUB && SLUB_DEBUG && SYSFS 338 help 339 SLUB statistics are useful to debug SLUBs allocation behavior in 340 order find ways to optimize the allocator. This should never be 341 enabled for production use since keeping statistics slows down 342 the allocator by a few percentage points. The slabinfo command 343 supports the determination of the most active slabs to figure 344 out which slabs are relevant to a particular load. 345 Try running: slabinfo -DA 346 347config DEBUG_KMEMLEAK 348 bool "Kernel memory leak detector" 349 depends on DEBUG_KERNEL && EXPERIMENTAL && (X86 || ARM || PPC) && \ 350 !MEMORY_HOTPLUG 351 select DEBUG_FS if SYSFS 352 select STACKTRACE if STACKTRACE_SUPPORT 353 select KALLSYMS 354 help 355 Say Y here if you want to enable the memory leak 356 detector. The memory allocation/freeing is traced in a way 357 similar to the Boehm's conservative garbage collector, the 358 difference being that the orphan objects are not freed but 359 only shown in /sys/kernel/debug/kmemleak. Enabling this 360 feature will introduce an overhead to memory 361 allocations. See Documentation/kmemleak.txt for more 362 details. 363 364 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 365 of finding leaks due to the slab objects poisoning. 366 367 In order to access the kmemleak file, debugfs needs to be 368 mounted (usually at /sys/kernel/debug). 369 370config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 371 int "Maximum kmemleak early log entries" 372 depends on DEBUG_KMEMLEAK 373 range 200 2000 374 default 400 375 help 376 Kmemleak must track all the memory allocations to avoid 377 reporting false positives. Since memory may be allocated or 378 freed before kmemleak is initialised, an early log buffer is 379 used to store these actions. If kmemleak reports "early log 380 buffer exceeded", please increase this value. 381 382config DEBUG_KMEMLEAK_TEST 383 tristate "Simple test for the kernel memory leak detector" 384 depends on DEBUG_KMEMLEAK 385 help 386 Say Y or M here to build a test for the kernel memory leak 387 detector. This option enables a module that explicitly leaks 388 memory. 389 390 If unsure, say N. 391 392config DEBUG_PREEMPT 393 bool "Debug preemptible kernel" 394 depends on DEBUG_KERNEL && PREEMPT && (TRACE_IRQFLAGS_SUPPORT || PPC64) 395 default y 396 help 397 If you say Y here then the kernel will use a debug variant of the 398 commonly used smp_processor_id() function and will print warnings 399 if kernel code uses it in a preemption-unsafe way. Also, the kernel 400 will detect preemption count underflows. 401 402config DEBUG_RT_MUTEXES 403 bool "RT Mutex debugging, deadlock detection" 404 depends on DEBUG_KERNEL && RT_MUTEXES 405 help 406 This allows rt mutex semantics violations and rt mutex related 407 deadlocks (lockups) to be detected and reported automatically. 408 409config DEBUG_PI_LIST 410 bool 411 default y 412 depends on DEBUG_RT_MUTEXES 413 414config RT_MUTEX_TESTER 415 bool "Built-in scriptable tester for rt-mutexes" 416 depends on DEBUG_KERNEL && RT_MUTEXES 417 help 418 This option enables a rt-mutex tester. 419 420config DEBUG_SPINLOCK 421 bool "Spinlock and rw-lock debugging: basic checks" 422 depends on DEBUG_KERNEL 423 help 424 Say Y here and build SMP to catch missing spinlock initialization 425 and certain other kinds of spinlock errors commonly made. This is 426 best used in conjunction with the NMI watchdog so that spinlock 427 deadlocks are also debuggable. 428 429config DEBUG_MUTEXES 430 bool "Mutex debugging: basic checks" 431 depends on DEBUG_KERNEL 432 help 433 This feature allows mutex semantics violations to be detected and 434 reported. 435 436config DEBUG_LOCK_ALLOC 437 bool "Lock debugging: detect incorrect freeing of live locks" 438 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 439 select DEBUG_SPINLOCK 440 select DEBUG_MUTEXES 441 select LOCKDEP 442 help 443 This feature will check whether any held lock (spinlock, rwlock, 444 mutex or rwsem) is incorrectly freed by the kernel, via any of the 445 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 446 vfree(), etc.), whether a live lock is incorrectly reinitialized via 447 spin_lock_init()/mutex_init()/etc., or whether there is any lock 448 held during task exit. 449 450config PROVE_LOCKING 451 bool "Lock debugging: prove locking correctness" 452 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 453 select LOCKDEP 454 select DEBUG_SPINLOCK 455 select DEBUG_MUTEXES 456 select DEBUG_LOCK_ALLOC 457 default n 458 help 459 This feature enables the kernel to prove that all locking 460 that occurs in the kernel runtime is mathematically 461 correct: that under no circumstance could an arbitrary (and 462 not yet triggered) combination of observed locking 463 sequences (on an arbitrary number of CPUs, running an 464 arbitrary number of tasks and interrupt contexts) cause a 465 deadlock. 466 467 In short, this feature enables the kernel to report locking 468 related deadlocks before they actually occur. 469 470 The proof does not depend on how hard and complex a 471 deadlock scenario would be to trigger: how many 472 participant CPUs, tasks and irq-contexts would be needed 473 for it to trigger. The proof also does not depend on 474 timing: if a race and a resulting deadlock is possible 475 theoretically (no matter how unlikely the race scenario 476 is), it will be proven so and will immediately be 477 reported by the kernel (once the event is observed that 478 makes the deadlock theoretically possible). 479 480 If a deadlock is impossible (i.e. the locking rules, as 481 observed by the kernel, are mathematically correct), the 482 kernel reports nothing. 483 484 NOTE: this feature can also be enabled for rwlocks, mutexes 485 and rwsems - in which case all dependencies between these 486 different locking variants are observed and mapped too, and 487 the proof of observed correctness is also maintained for an 488 arbitrary combination of these separate locking variants. 489 490 For more details, see Documentation/lockdep-design.txt. 491 492config LOCKDEP 493 bool 494 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 495 select STACKTRACE 496 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 497 select KALLSYMS 498 select KALLSYMS_ALL 499 500config LOCK_STAT 501 bool "Lock usage statistics" 502 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 503 select LOCKDEP 504 select DEBUG_SPINLOCK 505 select DEBUG_MUTEXES 506 select DEBUG_LOCK_ALLOC 507 default n 508 help 509 This feature enables tracking lock contention points 510 511 For more details, see Documentation/lockstat.txt 512 513config DEBUG_LOCKDEP 514 bool "Lock dependency engine debugging" 515 depends on DEBUG_KERNEL && LOCKDEP 516 help 517 If you say Y here, the lock dependency engine will do 518 additional runtime checks to debug itself, at the price 519 of more runtime overhead. 520 521config TRACE_IRQFLAGS 522 depends on DEBUG_KERNEL 523 bool 524 default y 525 depends on TRACE_IRQFLAGS_SUPPORT 526 depends on PROVE_LOCKING 527 528config DEBUG_SPINLOCK_SLEEP 529 bool "Spinlock debugging: sleep-inside-spinlock checking" 530 depends on DEBUG_KERNEL 531 help 532 If you say Y here, various routines which may sleep will become very 533 noisy if they are called with a spinlock held. 534 535config DEBUG_LOCKING_API_SELFTESTS 536 bool "Locking API boot-time self-tests" 537 depends on DEBUG_KERNEL 538 help 539 Say Y here if you want the kernel to run a short self-test during 540 bootup. The self-test checks whether common types of locking bugs 541 are detected by debugging mechanisms or not. (if you disable 542 lock debugging then those bugs wont be detected of course.) 543 The following locking APIs are covered: spinlocks, rwlocks, 544 mutexes and rwsems. 545 546config STACKTRACE 547 bool 548 depends on STACKTRACE_SUPPORT 549 550config DEBUG_KOBJECT 551 bool "kobject debugging" 552 depends on DEBUG_KERNEL 553 help 554 If you say Y here, some extra kobject debugging messages will be sent 555 to the syslog. 556 557config DEBUG_HIGHMEM 558 bool "Highmem debugging" 559 depends on DEBUG_KERNEL && HIGHMEM 560 help 561 This options enables addition error checking for high memory systems. 562 Disable for production systems. 563 564config DEBUG_BUGVERBOSE 565 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED 566 depends on BUG 567 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ 568 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 569 default !EMBEDDED 570 help 571 Say Y here to make BUG() panics output the file name and line number 572 of the BUG call as well as the EIP and oops trace. This aids 573 debugging but costs about 70-100K of memory. 574 575config DEBUG_INFO 576 bool "Compile the kernel with debug info" 577 depends on DEBUG_KERNEL 578 help 579 If you say Y here the resulting kernel image will include 580 debugging info resulting in a larger kernel image. 581 This adds debug symbols to the kernel and modules (gcc -g), and 582 is needed if you intend to use kernel crashdump or binary object 583 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 584 Say Y here only if you plan to debug the kernel. 585 586 If unsure, say N. 587 588config DEBUG_VM 589 bool "Debug VM" 590 depends on DEBUG_KERNEL 591 help 592 Enable this to turn on extended checks in the virtual-memory system 593 that may impact performance. 594 595 If unsure, say N. 596 597config DEBUG_VIRTUAL 598 bool "Debug VM translations" 599 depends on DEBUG_KERNEL && X86 600 help 601 Enable some costly sanity checks in virtual to page code. This can 602 catch mistakes with virt_to_page() and friends. 603 604 If unsure, say N. 605 606config DEBUG_NOMMU_REGIONS 607 bool "Debug the global anon/private NOMMU mapping region tree" 608 depends on DEBUG_KERNEL && !MMU 609 help 610 This option causes the global tree of anonymous and private mapping 611 regions to be regularly checked for invalid topology. 612 613config DEBUG_WRITECOUNT 614 bool "Debug filesystem writers count" 615 depends on DEBUG_KERNEL 616 help 617 Enable this to catch wrong use of the writers count in struct 618 vfsmount. This will increase the size of each file struct by 619 32 bits. 620 621 If unsure, say N. 622 623config DEBUG_MEMORY_INIT 624 bool "Debug memory initialisation" if EMBEDDED 625 default !EMBEDDED 626 help 627 Enable this for additional checks during memory initialisation. 628 The sanity checks verify aspects of the VM such as the memory model 629 and other information provided by the architecture. Verbose 630 information will be printed at KERN_DEBUG loglevel depending 631 on the mminit_loglevel= command-line option. 632 633 If unsure, say Y 634 635config DEBUG_LIST 636 bool "Debug linked list manipulation" 637 depends on DEBUG_KERNEL 638 help 639 Enable this to turn on extended checks in the linked-list 640 walking routines. 641 642 If unsure, say N. 643 644config DEBUG_SG 645 bool "Debug SG table operations" 646 depends on DEBUG_KERNEL 647 help 648 Enable this to turn on checks on scatter-gather tables. This can 649 help find problems with drivers that do not properly initialize 650 their sg tables. 651 652 If unsure, say N. 653 654config DEBUG_NOTIFIERS 655 bool "Debug notifier call chains" 656 depends on DEBUG_KERNEL 657 help 658 Enable this to turn on sanity checking for notifier call chains. 659 This is most useful for kernel developers to make sure that 660 modules properly unregister themselves from notifier chains. 661 This is a relatively cheap check but if you care about maximum 662 performance, say N. 663 664config DEBUG_CREDENTIALS 665 bool "Debug credential management" 666 depends on DEBUG_KERNEL 667 help 668 Enable this to turn on some debug checking for credential 669 management. The additional code keeps track of the number of 670 pointers from task_structs to any given cred struct, and checks to 671 see that this number never exceeds the usage count of the cred 672 struct. 673 674 Furthermore, if SELinux is enabled, this also checks that the 675 security pointer in the cred struct is never seen to be invalid. 676 677 If unsure, say N. 678 679# 680# Select this config option from the architecture Kconfig, if it 681# it is preferred to always offer frame pointers as a config 682# option on the architecture (regardless of KERNEL_DEBUG): 683# 684config ARCH_WANT_FRAME_POINTERS 685 bool 686 help 687 688config FRAME_POINTER 689 bool "Compile the kernel with frame pointers" 690 depends on DEBUG_KERNEL && \ 691 (CRIS || M68K || M68KNOMMU || FRV || UML || \ 692 AVR32 || SUPERH || BLACKFIN || MN10300) || \ 693 ARCH_WANT_FRAME_POINTERS 694 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 695 help 696 If you say Y here the resulting kernel image will be slightly 697 larger and slower, but it gives very useful debugging information 698 in case of kernel bugs. (precise oopses/stacktraces/warnings) 699 700config BOOT_PRINTK_DELAY 701 bool "Delay each boot printk message by N milliseconds" 702 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 703 help 704 This build option allows you to read kernel boot messages 705 by inserting a short delay after each one. The delay is 706 specified in milliseconds on the kernel command line, 707 using "boot_delay=N". 708 709 It is likely that you would also need to use "lpj=M" to preset 710 the "loops per jiffie" value. 711 See a previous boot log for the "lpj" value to use for your 712 system, and then set "lpj=M" before setting "boot_delay=N". 713 NOTE: Using this option may adversely affect SMP systems. 714 I.e., processors other than the first one may not boot up. 715 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect 716 what it believes to be lockup conditions. 717 718config RCU_TORTURE_TEST 719 tristate "torture tests for RCU" 720 depends on DEBUG_KERNEL 721 default n 722 help 723 This option provides a kernel module that runs torture tests 724 on the RCU infrastructure. The kernel module may be built 725 after the fact on the running kernel to be tested, if desired. 726 727 Say Y here if you want RCU torture tests to be built into 728 the kernel. 729 Say M if you want the RCU torture tests to build as a module. 730 Say N if you are unsure. 731 732config RCU_TORTURE_TEST_RUNNABLE 733 bool "torture tests for RCU runnable by default" 734 depends on RCU_TORTURE_TEST = y 735 default n 736 help 737 This option provides a way to build the RCU torture tests 738 directly into the kernel without them starting up at boot 739 time. You can use /proc/sys/kernel/rcutorture_runnable 740 to manually override this setting. This /proc file is 741 available only when the RCU torture tests have been built 742 into the kernel. 743 744 Say Y here if you want the RCU torture tests to start during 745 boot (you probably don't). 746 Say N here if you want the RCU torture tests to start only 747 after being manually enabled via /proc. 748 749config RCU_CPU_STALL_DETECTOR 750 bool "Check for stalled CPUs delaying RCU grace periods" 751 depends on TREE_RCU || TREE_PREEMPT_RCU 752 default n 753 help 754 This option causes RCU to printk information on which 755 CPUs are delaying the current grace period, but only when 756 the grace period extends for excessive time periods. 757 758 Say Y if you want RCU to perform such checks. 759 760 Say N if you are unsure. 761 762config KPROBES_SANITY_TEST 763 bool "Kprobes sanity tests" 764 depends on DEBUG_KERNEL 765 depends on KPROBES 766 default n 767 help 768 This option provides for testing basic kprobes functionality on 769 boot. A sample kprobe, jprobe and kretprobe are inserted and 770 verified for functionality. 771 772 Say N if you are unsure. 773 774config BACKTRACE_SELF_TEST 775 tristate "Self test for the backtrace code" 776 depends on DEBUG_KERNEL 777 default n 778 help 779 This option provides a kernel module that can be used to test 780 the kernel stack backtrace code. This option is not useful 781 for distributions or general kernels, but only for kernel 782 developers working on architecture code. 783 784 Note that if you want to also test saved backtraces, you will 785 have to enable STACKTRACE as well. 786 787 Say N if you are unsure. 788 789config DEBUG_BLOCK_EXT_DEVT 790 bool "Force extended block device numbers and spread them" 791 depends on DEBUG_KERNEL 792 depends on BLOCK 793 default n 794 help 795 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 796 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 797 YOU ARE DOING. Distros, please enable this and fix whatever 798 is broken. 799 800 Conventionally, block device numbers are allocated from 801 predetermined contiguous area. However, extended block area 802 may introduce non-contiguous block device numbers. This 803 option forces most block device numbers to be allocated from 804 the extended space and spreads them to discover kernel or 805 userland code paths which assume predetermined contiguous 806 device number allocation. 807 808 Note that turning on this debug option shuffles all the 809 device numbers for all IDE and SCSI devices including libata 810 ones, so root partition specified using device number 811 directly (via rdev or root=MAJ:MIN) won't work anymore. 812 Textual device names (root=/dev/sdXn) will continue to work. 813 814 Say N if you are unsure. 815 816config DEBUG_FORCE_WEAK_PER_CPU 817 bool "Force weak per-cpu definitions" 818 depends on DEBUG_KERNEL 819 help 820 s390 and alpha require percpu variables in modules to be 821 defined weak to work around addressing range issue which 822 puts the following two restrictions on percpu variable 823 definitions. 824 825 1. percpu symbols must be unique whether static or not 826 2. percpu variables can't be defined inside a function 827 828 To ensure that generic code follows the above rules, this 829 option forces all percpu variables to be defined as weak. 830 831config LKDTM 832 tristate "Linux Kernel Dump Test Tool Module" 833 depends on DEBUG_KERNEL 834 depends on KPROBES 835 depends on BLOCK 836 default n 837 help 838 This module enables testing of the different dumping mechanisms by 839 inducing system failures at predefined crash points. 840 If you don't need it: say N 841 Choose M here to compile this code as a module. The module will be 842 called lkdtm. 843 844 Documentation on how to use the module can be found in 845 drivers/misc/lkdtm.c 846 847config FAULT_INJECTION 848 bool "Fault-injection framework" 849 depends on DEBUG_KERNEL 850 help 851 Provide fault-injection framework. 852 For more details, see Documentation/fault-injection/. 853 854config FAILSLAB 855 bool "Fault-injection capability for kmalloc" 856 depends on FAULT_INJECTION 857 depends on SLAB || SLUB 858 help 859 Provide fault-injection capability for kmalloc. 860 861config FAIL_PAGE_ALLOC 862 bool "Fault-injection capabilitiy for alloc_pages()" 863 depends on FAULT_INJECTION 864 help 865 Provide fault-injection capability for alloc_pages(). 866 867config FAIL_MAKE_REQUEST 868 bool "Fault-injection capability for disk IO" 869 depends on FAULT_INJECTION && BLOCK 870 help 871 Provide fault-injection capability for disk IO. 872 873config FAIL_IO_TIMEOUT 874 bool "Faul-injection capability for faking disk interrupts" 875 depends on FAULT_INJECTION && BLOCK 876 help 877 Provide fault-injection capability on end IO handling. This 878 will make the block layer "forget" an interrupt as configured, 879 thus exercising the error handling. 880 881 Only works with drivers that use the generic timeout handling, 882 for others it wont do anything. 883 884config FAULT_INJECTION_DEBUG_FS 885 bool "Debugfs entries for fault-injection capabilities" 886 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 887 help 888 Enable configuration of fault-injection capabilities via debugfs. 889 890config FAULT_INJECTION_STACKTRACE_FILTER 891 bool "stacktrace filter for fault-injection capabilities" 892 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 893 depends on !X86_64 894 select STACKTRACE 895 select FRAME_POINTER if !PPC && !S390 896 help 897 Provide stacktrace filter for fault-injection capabilities 898 899config LATENCYTOP 900 bool "Latency measuring infrastructure" 901 select FRAME_POINTER if !MIPS && !PPC && !S390 902 select KALLSYMS 903 select KALLSYMS_ALL 904 select STACKTRACE 905 select SCHEDSTATS 906 select SCHED_DEBUG 907 depends on HAVE_LATENCYTOP_SUPPORT 908 help 909 Enable this option if you want to use the LatencyTOP tool 910 to find out which userspace is blocking on what kernel operations. 911 912config SYSCTL_SYSCALL_CHECK 913 bool "Sysctl checks" 914 depends on SYSCTL_SYSCALL 915 ---help--- 916 sys_sysctl uses binary paths that have been found challenging 917 to properly maintain and use. This enables checks that help 918 you to keep things correct. 919 920source mm/Kconfig.debug 921source kernel/trace/Kconfig 922 923config PROVIDE_OHCI1394_DMA_INIT 924 bool "Remote debugging over FireWire early on boot" 925 depends on PCI && X86 926 help 927 If you want to debug problems which hang or crash the kernel early 928 on boot and the crashing machine has a FireWire port, you can use 929 this feature to remotely access the memory of the crashed machine 930 over FireWire. This employs remote DMA as part of the OHCI1394 931 specification which is now the standard for FireWire controllers. 932 933 With remote DMA, you can monitor the printk buffer remotely using 934 firescope and access all memory below 4GB using fireproxy from gdb. 935 Even controlling a kernel debugger is possible using remote DMA. 936 937 Usage: 938 939 If ohci1394_dma=early is used as boot parameter, it will initialize 940 all OHCI1394 controllers which are found in the PCI config space. 941 942 As all changes to the FireWire bus such as enabling and disabling 943 devices cause a bus reset and thereby disable remote DMA for all 944 devices, be sure to have the cable plugged and FireWire enabled on 945 the debugging host before booting the debug target for debugging. 946 947 This code (~1k) is freed after boot. By then, the firewire stack 948 in charge of the OHCI-1394 controllers should be used instead. 949 950 See Documentation/debugging-via-ohci1394.txt for more information. 951 952config FIREWIRE_OHCI_REMOTE_DMA 953 bool "Remote debugging over FireWire with firewire-ohci" 954 depends on FIREWIRE_OHCI 955 help 956 This option lets you use the FireWire bus for remote debugging 957 with help of the firewire-ohci driver. It enables unfiltered 958 remote DMA in firewire-ohci. 959 See Documentation/debugging-via-ohci1394.txt for more information. 960 961 If unsure, say N. 962 963config BUILD_DOCSRC 964 bool "Build targets in Documentation/ tree" 965 depends on HEADERS_CHECK 966 help 967 This option attempts to build objects from the source files in the 968 kernel Documentation/ tree. 969 970 Say N if you are unsure. 971 972config DYNAMIC_DEBUG 973 bool "Enable dynamic printk() support" 974 default n 975 depends on PRINTK 976 depends on DEBUG_FS 977 help 978 979 Compiles debug level messages into the kernel, which would not 980 otherwise be available at runtime. These messages can then be 981 enabled/disabled based on various levels of scope - per source file, 982 function, module, format string, and line number. This mechanism 983 implicitly enables all pr_debug() and dev_dbg() calls. The impact of 984 this compile option is a larger kernel text size of about 2%. 985 986 Usage: 987 988 Dynamic debugging is controlled via the 'dynamic_debug/ddebug' file, 989 which is contained in the 'debugfs' filesystem. Thus, the debugfs 990 filesystem must first be mounted before making use of this feature. 991 We refer the control file as: <debugfs>/dynamic_debug/ddebug. This 992 file contains a list of the debug statements that can be enabled. The 993 format for each line of the file is: 994 995 filename:lineno [module]function flags format 996 997 filename : source file of the debug statement 998 lineno : line number of the debug statement 999 module : module that contains the debug statement 1000 function : function that contains the debug statement 1001 flags : 'p' means the line is turned 'on' for printing 1002 format : the format used for the debug statement 1003 1004 From a live system: 1005 1006 nullarbor:~ # cat <debugfs>/dynamic_debug/ddebug 1007 # filename:lineno [module]function flags format 1008 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012" 1009 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012" 1010 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012" 1011 1012 Example usage: 1013 1014 // enable the message at line 1603 of file svcsock.c 1015 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 1016 <debugfs>/dynamic_debug/ddebug 1017 1018 // enable all the messages in file svcsock.c 1019 nullarbor:~ # echo -n 'file svcsock.c +p' > 1020 <debugfs>/dynamic_debug/ddebug 1021 1022 // enable all the messages in the NFS server module 1023 nullarbor:~ # echo -n 'module nfsd +p' > 1024 <debugfs>/dynamic_debug/ddebug 1025 1026 // enable all 12 messages in the function svc_process() 1027 nullarbor:~ # echo -n 'func svc_process +p' > 1028 <debugfs>/dynamic_debug/ddebug 1029 1030 // disable all 12 messages in the function svc_process() 1031 nullarbor:~ # echo -n 'func svc_process -p' > 1032 <debugfs>/dynamic_debug/ddebug 1033 1034 See Documentation/dynamic-debug-howto.txt for additional information. 1035 1036config DMA_API_DEBUG 1037 bool "Enable debugging of DMA-API usage" 1038 depends on HAVE_DMA_API_DEBUG 1039 help 1040 Enable this option to debug the use of the DMA API by device drivers. 1041 With this option you will be able to detect common bugs in device 1042 drivers like double-freeing of DMA mappings or freeing mappings that 1043 were never allocated. 1044 This option causes a performance degredation. Use only if you want 1045 to debug device drivers. If unsure, say N. 1046 1047source "samples/Kconfig" 1048 1049source "lib/Kconfig.kgdb" 1050 1051source "lib/Kconfig.kmemcheck" 1052