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 UNUSED_SYMBOLS 54 bool "Enable unused/obsolete exported symbols" 55 default y if X86 56 help 57 Unused but exported symbols make the kernel needlessly bigger. For 58 that reason most of these unused exports will soon be removed. This 59 option is provided temporarily to provide a transition period in case 60 some external kernel module needs one of these symbols anyway. If you 61 encounter such a case in your module, consider if you are actually 62 using the right API. (rationale: since nobody in the kernel is using 63 this in a module, there is a pretty good chance it's actually the 64 wrong interface to use). If you really need the symbol, please send a 65 mail to the linux kernel mailing list mentioning the symbol and why 66 you really need it, and what the merge plan to the mainline kernel for 67 your module is. 68 69config DEBUG_FS 70 bool "Debug Filesystem" 71 depends on SYSFS 72 help 73 debugfs is a virtual file system that kernel developers use to put 74 debugging files into. Enable this option to be able to read and 75 write to these files. 76 77 For detailed documentation on the debugfs API, see 78 Documentation/DocBook/filesystems. 79 80 If unsure, say N. 81 82config HEADERS_CHECK 83 bool "Run 'make headers_check' when building vmlinux" 84 depends on !UML 85 help 86 This option will extract the user-visible kernel headers whenever 87 building the kernel, and will run basic sanity checks on them to 88 ensure that exported files do not attempt to include files which 89 were not exported, etc. 90 91 If you're making modifications to header files which are 92 relevant for userspace, say 'Y', and check the headers 93 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 94 your build tree), to make sure they're suitable. 95 96config DEBUG_SECTION_MISMATCH 97 bool "Enable full Section mismatch analysis" 98 depends on UNDEFINED 99 # This option is on purpose disabled for now. 100 # It will be enabled when we are down to a resonable number 101 # of section mismatch warnings (< 10 for an allyesconfig build) 102 help 103 The section mismatch analysis checks if there are illegal 104 references from one section to another section. 105 Linux will during link or during runtime drop some sections 106 and any use of code/data previously in these sections will 107 most likely result in an oops. 108 In the code functions and variables are annotated with 109 __init, __devinit etc. (see full list in include/linux/init.h) 110 which results in the code/data being placed in specific sections. 111 The section mismatch analysis is always done after a full 112 kernel build but enabling this option will in addition 113 do the following: 114 - Add the option -fno-inline-functions-called-once to gcc 115 When inlining a function annotated __init in a non-init 116 function we would lose the section information and thus 117 the analysis would not catch the illegal reference. 118 This option tells gcc to inline less but will also 119 result in a larger kernel. 120 - Run the section mismatch analysis for each module/built-in.o 121 When we run the section mismatch analysis on vmlinux.o we 122 lose valueble information about where the mismatch was 123 introduced. 124 Running the analysis for each module/built-in.o file 125 will tell where the mismatch happens much closer to the 126 source. The drawback is that we will report the same 127 mismatch at least twice. 128 - Enable verbose reporting from modpost to help solving 129 the section mismatches reported. 130 131config DEBUG_KERNEL 132 bool "Kernel debugging" 133 help 134 Say Y here if you are developing drivers or trying to debug and 135 identify kernel problems. 136 137config DEBUG_SHIRQ 138 bool "Debug shared IRQ handlers" 139 depends on DEBUG_KERNEL && GENERIC_HARDIRQS 140 help 141 Enable this to generate a spurious interrupt as soon as a shared 142 interrupt handler is registered, and just before one is deregistered. 143 Drivers ought to be able to handle interrupts coming in at those 144 points; some don't and need to be caught. 145 146config DETECT_SOFTLOCKUP 147 bool "Detect Soft Lockups" 148 depends on DEBUG_KERNEL && !S390 149 default y 150 help 151 Say Y here to enable the kernel to detect "soft lockups", 152 which are bugs that cause the kernel to loop in kernel 153 mode for more than 60 seconds, without giving other tasks a 154 chance to run. 155 156 When a soft-lockup is detected, the kernel will print the 157 current stack trace (which you should report), but the 158 system will stay locked up. This feature has negligible 159 overhead. 160 161 (Note that "hard lockups" are separate type of bugs that 162 can be detected via the NMI-watchdog, on platforms that 163 support it.) 164 165config BOOTPARAM_SOFTLOCKUP_PANIC 166 bool "Panic (Reboot) On Soft Lockups" 167 depends on DETECT_SOFTLOCKUP 168 help 169 Say Y here to enable the kernel to panic on "soft lockups", 170 which are bugs that cause the kernel to loop in kernel 171 mode for more than 60 seconds, without giving other tasks a 172 chance to run. 173 174 The panic can be used in combination with panic_timeout, 175 to cause the system to reboot automatically after a 176 lockup has been detected. This feature is useful for 177 high-availability systems that have uptime guarantees and 178 where a lockup must be resolved ASAP. 179 180 Say N if unsure. 181 182config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 183 int 184 depends on DETECT_SOFTLOCKUP 185 range 0 1 186 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 187 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 188 189config DETECT_HUNG_TASK 190 bool "Detect Hung Tasks" 191 depends on DEBUG_KERNEL 192 default DETECT_SOFTLOCKUP 193 help 194 Say Y here to enable the kernel to detect "hung tasks", 195 which are bugs that cause the task to be stuck in 196 uninterruptible "D" state indefinitiley. 197 198 When a hung task is detected, the kernel will print the 199 current stack trace (which you should report), but the 200 task will stay in uninterruptible state. If lockdep is 201 enabled then all held locks will also be reported. This 202 feature has negligible overhead. 203 204config BOOTPARAM_HUNG_TASK_PANIC 205 bool "Panic (Reboot) On Hung Tasks" 206 depends on DETECT_HUNG_TASK 207 help 208 Say Y here to enable the kernel to panic on "hung tasks", 209 which are bugs that cause the kernel to leave a task stuck 210 in uninterruptible "D" state. 211 212 The panic can be used in combination with panic_timeout, 213 to cause the system to reboot automatically after a 214 hung task has been detected. This feature is useful for 215 high-availability systems that have uptime guarantees and 216 where a hung tasks must be resolved ASAP. 217 218 Say N if unsure. 219 220config BOOTPARAM_HUNG_TASK_PANIC_VALUE 221 int 222 depends on DETECT_HUNG_TASK 223 range 0 1 224 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 225 default 1 if BOOTPARAM_HUNG_TASK_PANIC 226 227config SCHED_DEBUG 228 bool "Collect scheduler debugging info" 229 depends on DEBUG_KERNEL && PROC_FS 230 default y 231 help 232 If you say Y here, the /proc/sched_debug file will be provided 233 that can help debug the scheduler. The runtime overhead of this 234 option is minimal. 235 236config SCHEDSTATS 237 bool "Collect scheduler statistics" 238 depends on DEBUG_KERNEL && PROC_FS 239 help 240 If you say Y here, additional code will be inserted into the 241 scheduler and related routines to collect statistics about 242 scheduler behavior and provide them in /proc/schedstat. These 243 stats may be useful for both tuning and debugging the scheduler 244 If you aren't debugging the scheduler or trying to tune a specific 245 application, you can say N to avoid the very slight overhead 246 this adds. 247 248config TIMER_STATS 249 bool "Collect kernel timers statistics" 250 depends on DEBUG_KERNEL && PROC_FS 251 help 252 If you say Y here, additional code will be inserted into the 253 timer routines to collect statistics about kernel timers being 254 reprogrammed. The statistics can be read from /proc/timer_stats. 255 The statistics collection is started by writing 1 to /proc/timer_stats, 256 writing 0 stops it. This feature is useful to collect information 257 about timer usage patterns in kernel and userspace. This feature 258 is lightweight if enabled in the kernel config but not activated 259 (it defaults to deactivated on bootup and will only be activated 260 if some application like powertop activates it explicitly). 261 262config DEBUG_OBJECTS 263 bool "Debug object operations" 264 depends on DEBUG_KERNEL 265 help 266 If you say Y here, additional code will be inserted into the 267 kernel to track the life time of various objects and validate 268 the operations on those objects. 269 270config DEBUG_OBJECTS_SELFTEST 271 bool "Debug objects selftest" 272 depends on DEBUG_OBJECTS 273 help 274 This enables the selftest of the object debug code. 275 276config DEBUG_OBJECTS_FREE 277 bool "Debug objects in freed memory" 278 depends on DEBUG_OBJECTS 279 help 280 This enables checks whether a k/v free operation frees an area 281 which contains an object which has not been deactivated 282 properly. This can make kmalloc/kfree-intensive workloads 283 much slower. 284 285config DEBUG_OBJECTS_TIMERS 286 bool "Debug timer objects" 287 depends on DEBUG_OBJECTS 288 help 289 If you say Y here, additional code will be inserted into the 290 timer routines to track the life time of timer objects and 291 validate the timer operations. 292 293config DEBUG_OBJECTS_ENABLE_DEFAULT 294 int "debug_objects bootup default value (0-1)" 295 range 0 1 296 default "1" 297 depends on DEBUG_OBJECTS 298 help 299 Debug objects boot parameter default value 300 301config DEBUG_SLAB 302 bool "Debug slab memory allocations" 303 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 304 help 305 Say Y here to have the kernel do limited verification on memory 306 allocation as well as poisoning memory on free to catch use of freed 307 memory. This can make kmalloc/kfree-intensive workloads much slower. 308 309config DEBUG_SLAB_LEAK 310 bool "Memory leak debugging" 311 depends on DEBUG_SLAB 312 313config SLUB_DEBUG_ON 314 bool "SLUB debugging on by default" 315 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 316 default n 317 help 318 Boot with debugging on by default. SLUB boots by default with 319 the runtime debug capabilities switched off. Enabling this is 320 equivalent to specifying the "slub_debug" parameter on boot. 321 There is no support for more fine grained debug control like 322 possible with slub_debug=xxx. SLUB debugging may be switched 323 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 324 "slub_debug=-". 325 326config SLUB_STATS 327 default n 328 bool "Enable SLUB performance statistics" 329 depends on SLUB && SLUB_DEBUG && SYSFS 330 help 331 SLUB statistics are useful to debug SLUBs allocation behavior in 332 order find ways to optimize the allocator. This should never be 333 enabled for production use since keeping statistics slows down 334 the allocator by a few percentage points. The slabinfo command 335 supports the determination of the most active slabs to figure 336 out which slabs are relevant to a particular load. 337 Try running: slabinfo -DA 338 339config DEBUG_KMEMLEAK 340 bool "Kernel memory leak detector" 341 depends on DEBUG_KERNEL && EXPERIMENTAL && (X86 || ARM) && \ 342 !MEMORY_HOTPLUG 343 select DEBUG_FS if SYSFS 344 select STACKTRACE if STACKTRACE_SUPPORT 345 select KALLSYMS 346 help 347 Say Y here if you want to enable the memory leak 348 detector. The memory allocation/freeing is traced in a way 349 similar to the Boehm's conservative garbage collector, the 350 difference being that the orphan objects are not freed but 351 only shown in /sys/kernel/debug/kmemleak. Enabling this 352 feature will introduce an overhead to memory 353 allocations. See Documentation/kmemleak.txt for more 354 details. 355 356 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 357 of finding leaks due to the slab objects poisoning. 358 359 In order to access the kmemleak file, debugfs needs to be 360 mounted (usually at /sys/kernel/debug). 361 362config DEBUG_KMEMLEAK_TEST 363 tristate "Simple test for the kernel memory leak detector" 364 depends on DEBUG_KMEMLEAK 365 help 366 Say Y or M here to build a test for the kernel memory leak 367 detector. This option enables a module that explicitly leaks 368 memory. 369 370 If unsure, say N. 371 372config DEBUG_PREEMPT 373 bool "Debug preemptible kernel" 374 depends on DEBUG_KERNEL && PREEMPT && (TRACE_IRQFLAGS_SUPPORT || PPC64) 375 default y 376 help 377 If you say Y here then the kernel will use a debug variant of the 378 commonly used smp_processor_id() function and will print warnings 379 if kernel code uses it in a preemption-unsafe way. Also, the kernel 380 will detect preemption count underflows. 381 382config DEBUG_RT_MUTEXES 383 bool "RT Mutex debugging, deadlock detection" 384 depends on DEBUG_KERNEL && RT_MUTEXES 385 help 386 This allows rt mutex semantics violations and rt mutex related 387 deadlocks (lockups) to be detected and reported automatically. 388 389config DEBUG_PI_LIST 390 bool 391 default y 392 depends on DEBUG_RT_MUTEXES 393 394config RT_MUTEX_TESTER 395 bool "Built-in scriptable tester for rt-mutexes" 396 depends on DEBUG_KERNEL && RT_MUTEXES 397 help 398 This option enables a rt-mutex tester. 399 400config DEBUG_SPINLOCK 401 bool "Spinlock and rw-lock debugging: basic checks" 402 depends on DEBUG_KERNEL 403 help 404 Say Y here and build SMP to catch missing spinlock initialization 405 and certain other kinds of spinlock errors commonly made. This is 406 best used in conjunction with the NMI watchdog so that spinlock 407 deadlocks are also debuggable. 408 409config DEBUG_MUTEXES 410 bool "Mutex debugging: basic checks" 411 depends on DEBUG_KERNEL 412 help 413 This feature allows mutex semantics violations to be detected and 414 reported. 415 416config DEBUG_LOCK_ALLOC 417 bool "Lock debugging: detect incorrect freeing of live locks" 418 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 419 select DEBUG_SPINLOCK 420 select DEBUG_MUTEXES 421 select LOCKDEP 422 help 423 This feature will check whether any held lock (spinlock, rwlock, 424 mutex or rwsem) is incorrectly freed by the kernel, via any of the 425 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 426 vfree(), etc.), whether a live lock is incorrectly reinitialized via 427 spin_lock_init()/mutex_init()/etc., or whether there is any lock 428 held during task exit. 429 430config PROVE_LOCKING 431 bool "Lock debugging: prove locking correctness" 432 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 433 select LOCKDEP 434 select DEBUG_SPINLOCK 435 select DEBUG_MUTEXES 436 select DEBUG_LOCK_ALLOC 437 default n 438 help 439 This feature enables the kernel to prove that all locking 440 that occurs in the kernel runtime is mathematically 441 correct: that under no circumstance could an arbitrary (and 442 not yet triggered) combination of observed locking 443 sequences (on an arbitrary number of CPUs, running an 444 arbitrary number of tasks and interrupt contexts) cause a 445 deadlock. 446 447 In short, this feature enables the kernel to report locking 448 related deadlocks before they actually occur. 449 450 The proof does not depend on how hard and complex a 451 deadlock scenario would be to trigger: how many 452 participant CPUs, tasks and irq-contexts would be needed 453 for it to trigger. The proof also does not depend on 454 timing: if a race and a resulting deadlock is possible 455 theoretically (no matter how unlikely the race scenario 456 is), it will be proven so and will immediately be 457 reported by the kernel (once the event is observed that 458 makes the deadlock theoretically possible). 459 460 If a deadlock is impossible (i.e. the locking rules, as 461 observed by the kernel, are mathematically correct), the 462 kernel reports nothing. 463 464 NOTE: this feature can also be enabled for rwlocks, mutexes 465 and rwsems - in which case all dependencies between these 466 different locking variants are observed and mapped too, and 467 the proof of observed correctness is also maintained for an 468 arbitrary combination of these separate locking variants. 469 470 For more details, see Documentation/lockdep-design.txt. 471 472config LOCKDEP 473 bool 474 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 475 select STACKTRACE 476 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 477 select KALLSYMS 478 select KALLSYMS_ALL 479 480config LOCK_STAT 481 bool "Lock usage statistics" 482 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 483 select LOCKDEP 484 select DEBUG_SPINLOCK 485 select DEBUG_MUTEXES 486 select DEBUG_LOCK_ALLOC 487 default n 488 help 489 This feature enables tracking lock contention points 490 491 For more details, see Documentation/lockstat.txt 492 493config DEBUG_LOCKDEP 494 bool "Lock dependency engine debugging" 495 depends on DEBUG_KERNEL && LOCKDEP 496 help 497 If you say Y here, the lock dependency engine will do 498 additional runtime checks to debug itself, at the price 499 of more runtime overhead. 500 501config TRACE_IRQFLAGS 502 depends on DEBUG_KERNEL 503 bool 504 default y 505 depends on TRACE_IRQFLAGS_SUPPORT 506 depends on PROVE_LOCKING 507 508config DEBUG_SPINLOCK_SLEEP 509 bool "Spinlock debugging: sleep-inside-spinlock checking" 510 depends on DEBUG_KERNEL 511 help 512 If you say Y here, various routines which may sleep will become very 513 noisy if they are called with a spinlock held. 514 515config DEBUG_LOCKING_API_SELFTESTS 516 bool "Locking API boot-time self-tests" 517 depends on DEBUG_KERNEL 518 help 519 Say Y here if you want the kernel to run a short self-test during 520 bootup. The self-test checks whether common types of locking bugs 521 are detected by debugging mechanisms or not. (if you disable 522 lock debugging then those bugs wont be detected of course.) 523 The following locking APIs are covered: spinlocks, rwlocks, 524 mutexes and rwsems. 525 526config STACKTRACE 527 bool 528 depends on STACKTRACE_SUPPORT 529 530config DEBUG_KOBJECT 531 bool "kobject debugging" 532 depends on DEBUG_KERNEL 533 help 534 If you say Y here, some extra kobject debugging messages will be sent 535 to the syslog. 536 537config DEBUG_HIGHMEM 538 bool "Highmem debugging" 539 depends on DEBUG_KERNEL && HIGHMEM 540 help 541 This options enables addition error checking for high memory systems. 542 Disable for production systems. 543 544config DEBUG_BUGVERBOSE 545 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED 546 depends on BUG 547 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ 548 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 549 default !EMBEDDED 550 help 551 Say Y here to make BUG() panics output the file name and line number 552 of the BUG call as well as the EIP and oops trace. This aids 553 debugging but costs about 70-100K of memory. 554 555config DEBUG_INFO 556 bool "Compile the kernel with debug info" 557 depends on DEBUG_KERNEL 558 help 559 If you say Y here the resulting kernel image will include 560 debugging info resulting in a larger kernel image. 561 This adds debug symbols to the kernel and modules (gcc -g), and 562 is needed if you intend to use kernel crashdump or binary object 563 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 564 Say Y here only if you plan to debug the kernel. 565 566 If unsure, say N. 567 568config DEBUG_VM 569 bool "Debug VM" 570 depends on DEBUG_KERNEL 571 help 572 Enable this to turn on extended checks in the virtual-memory system 573 that may impact performance. 574 575 If unsure, say N. 576 577config DEBUG_VIRTUAL 578 bool "Debug VM translations" 579 depends on DEBUG_KERNEL && X86 580 help 581 Enable some costly sanity checks in virtual to page code. This can 582 catch mistakes with virt_to_page() and friends. 583 584 If unsure, say N. 585 586config DEBUG_NOMMU_REGIONS 587 bool "Debug the global anon/private NOMMU mapping region tree" 588 depends on DEBUG_KERNEL && !MMU 589 help 590 This option causes the global tree of anonymous and private mapping 591 regions to be regularly checked for invalid topology. 592 593config DEBUG_WRITECOUNT 594 bool "Debug filesystem writers count" 595 depends on DEBUG_KERNEL 596 help 597 Enable this to catch wrong use of the writers count in struct 598 vfsmount. This will increase the size of each file struct by 599 32 bits. 600 601 If unsure, say N. 602 603config DEBUG_MEMORY_INIT 604 bool "Debug memory initialisation" if EMBEDDED 605 default !EMBEDDED 606 help 607 Enable this for additional checks during memory initialisation. 608 The sanity checks verify aspects of the VM such as the memory model 609 and other information provided by the architecture. Verbose 610 information will be printed at KERN_DEBUG loglevel depending 611 on the mminit_loglevel= command-line option. 612 613 If unsure, say Y 614 615config DEBUG_LIST 616 bool "Debug linked list manipulation" 617 depends on DEBUG_KERNEL 618 help 619 Enable this to turn on extended checks in the linked-list 620 walking routines. 621 622 If unsure, say N. 623 624config DEBUG_SG 625 bool "Debug SG table operations" 626 depends on DEBUG_KERNEL 627 help 628 Enable this to turn on checks on scatter-gather tables. This can 629 help find problems with drivers that do not properly initialize 630 their sg tables. 631 632 If unsure, say N. 633 634config DEBUG_NOTIFIERS 635 bool "Debug notifier call chains" 636 depends on DEBUG_KERNEL 637 help 638 Enable this to turn on sanity checking for notifier call chains. 639 This is most useful for kernel developers to make sure that 640 modules properly unregister themselves from notifier chains. 641 This is a relatively cheap check but if you care about maximum 642 performance, say N. 643 644# 645# Select this config option from the architecture Kconfig, if it 646# it is preferred to always offer frame pointers as a config 647# option on the architecture (regardless of KERNEL_DEBUG): 648# 649config ARCH_WANT_FRAME_POINTERS 650 bool 651 help 652 653config FRAME_POINTER 654 bool "Compile the kernel with frame pointers" 655 depends on DEBUG_KERNEL && \ 656 (CRIS || M68K || M68KNOMMU || FRV || UML || \ 657 AVR32 || SUPERH || BLACKFIN || MN10300) || \ 658 ARCH_WANT_FRAME_POINTERS 659 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 660 help 661 If you say Y here the resulting kernel image will be slightly 662 larger and slower, but it gives very useful debugging information 663 in case of kernel bugs. (precise oopses/stacktraces/warnings) 664 665config BOOT_PRINTK_DELAY 666 bool "Delay each boot printk message by N milliseconds" 667 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 668 help 669 This build option allows you to read kernel boot messages 670 by inserting a short delay after each one. The delay is 671 specified in milliseconds on the kernel command line, 672 using "boot_delay=N". 673 674 It is likely that you would also need to use "lpj=M" to preset 675 the "loops per jiffie" value. 676 See a previous boot log for the "lpj" value to use for your 677 system, and then set "lpj=M" before setting "boot_delay=N". 678 NOTE: Using this option may adversely affect SMP systems. 679 I.e., processors other than the first one may not boot up. 680 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect 681 what it believes to be lockup conditions. 682 683config RCU_TORTURE_TEST 684 tristate "torture tests for RCU" 685 depends on DEBUG_KERNEL 686 default n 687 help 688 This option provides a kernel module that runs torture tests 689 on the RCU infrastructure. The kernel module may be built 690 after the fact on the running kernel to be tested, if desired. 691 692 Say Y here if you want RCU torture tests to be built into 693 the kernel. 694 Say M if you want the RCU torture tests to build as a module. 695 Say N if you are unsure. 696 697config RCU_TORTURE_TEST_RUNNABLE 698 bool "torture tests for RCU runnable by default" 699 depends on RCU_TORTURE_TEST = y 700 default n 701 help 702 This option provides a way to build the RCU torture tests 703 directly into the kernel without them starting up at boot 704 time. You can use /proc/sys/kernel/rcutorture_runnable 705 to manually override this setting. This /proc file is 706 available only when the RCU torture tests have been built 707 into the kernel. 708 709 Say Y here if you want the RCU torture tests to start during 710 boot (you probably don't). 711 Say N here if you want the RCU torture tests to start only 712 after being manually enabled via /proc. 713 714config RCU_CPU_STALL_DETECTOR 715 bool "Check for stalled CPUs delaying RCU grace periods" 716 depends on CLASSIC_RCU || TREE_RCU 717 default n 718 help 719 This option causes RCU to printk information on which 720 CPUs are delaying the current grace period, but only when 721 the grace period extends for excessive time periods. 722 723 Say Y if you want RCU to perform such checks. 724 725 Say N if you are unsure. 726 727config KPROBES_SANITY_TEST 728 bool "Kprobes sanity tests" 729 depends on DEBUG_KERNEL 730 depends on KPROBES 731 default n 732 help 733 This option provides for testing basic kprobes functionality on 734 boot. A sample kprobe, jprobe and kretprobe are inserted and 735 verified for functionality. 736 737 Say N if you are unsure. 738 739config BACKTRACE_SELF_TEST 740 tristate "Self test for the backtrace code" 741 depends on DEBUG_KERNEL 742 default n 743 help 744 This option provides a kernel module that can be used to test 745 the kernel stack backtrace code. This option is not useful 746 for distributions or general kernels, but only for kernel 747 developers working on architecture code. 748 749 Note that if you want to also test saved backtraces, you will 750 have to enable STACKTRACE as well. 751 752 Say N if you are unsure. 753 754config DEBUG_BLOCK_EXT_DEVT 755 bool "Force extended block device numbers and spread them" 756 depends on DEBUG_KERNEL 757 depends on BLOCK 758 default n 759 help 760 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 761 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 762 YOU ARE DOING. Distros, please enable this and fix whatever 763 is broken. 764 765 Conventionally, block device numbers are allocated from 766 predetermined contiguous area. However, extended block area 767 may introduce non-contiguous block device numbers. This 768 option forces most block device numbers to be allocated from 769 the extended space and spreads them to discover kernel or 770 userland code paths which assume predetermined contiguous 771 device number allocation. 772 773 Note that turning on this debug option shuffles all the 774 device numbers for all IDE and SCSI devices including libata 775 ones, so root partition specified using device number 776 directly (via rdev or root=MAJ:MIN) won't work anymore. 777 Textual device names (root=/dev/sdXn) will continue to work. 778 779 Say N if you are unsure. 780 781config LKDTM 782 tristate "Linux Kernel Dump Test Tool Module" 783 depends on DEBUG_KERNEL 784 depends on KPROBES 785 depends on BLOCK 786 default n 787 help 788 This module enables testing of the different dumping mechanisms by 789 inducing system failures at predefined crash points. 790 If you don't need it: say N 791 Choose M here to compile this code as a module. The module will be 792 called lkdtm. 793 794 Documentation on how to use the module can be found in 795 drivers/misc/lkdtm.c 796 797config FAULT_INJECTION 798 bool "Fault-injection framework" 799 depends on DEBUG_KERNEL 800 help 801 Provide fault-injection framework. 802 For more details, see Documentation/fault-injection/. 803 804config FAILSLAB 805 bool "Fault-injection capability for kmalloc" 806 depends on FAULT_INJECTION 807 depends on SLAB || SLUB 808 help 809 Provide fault-injection capability for kmalloc. 810 811config FAIL_PAGE_ALLOC 812 bool "Fault-injection capabilitiy for alloc_pages()" 813 depends on FAULT_INJECTION 814 help 815 Provide fault-injection capability for alloc_pages(). 816 817config FAIL_MAKE_REQUEST 818 bool "Fault-injection capability for disk IO" 819 depends on FAULT_INJECTION && BLOCK 820 help 821 Provide fault-injection capability for disk IO. 822 823config FAIL_IO_TIMEOUT 824 bool "Faul-injection capability for faking disk interrupts" 825 depends on FAULT_INJECTION && BLOCK 826 help 827 Provide fault-injection capability on end IO handling. This 828 will make the block layer "forget" an interrupt as configured, 829 thus exercising the error handling. 830 831 Only works with drivers that use the generic timeout handling, 832 for others it wont do anything. 833 834config FAULT_INJECTION_DEBUG_FS 835 bool "Debugfs entries for fault-injection capabilities" 836 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 837 help 838 Enable configuration of fault-injection capabilities via debugfs. 839 840config FAULT_INJECTION_STACKTRACE_FILTER 841 bool "stacktrace filter for fault-injection capabilities" 842 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 843 depends on !X86_64 844 select STACKTRACE 845 select FRAME_POINTER if !PPC && !S390 846 help 847 Provide stacktrace filter for fault-injection capabilities 848 849config LATENCYTOP 850 bool "Latency measuring infrastructure" 851 select FRAME_POINTER if !MIPS && !PPC && !S390 852 select KALLSYMS 853 select KALLSYMS_ALL 854 select STACKTRACE 855 select SCHEDSTATS 856 select SCHED_DEBUG 857 depends on HAVE_LATENCYTOP_SUPPORT 858 help 859 Enable this option if you want to use the LatencyTOP tool 860 to find out which userspace is blocking on what kernel operations. 861 862config SYSCTL_SYSCALL_CHECK 863 bool "Sysctl checks" 864 depends on SYSCTL_SYSCALL 865 ---help--- 866 sys_sysctl uses binary paths that have been found challenging 867 to properly maintain and use. This enables checks that help 868 you to keep things correct. 869 870source mm/Kconfig.debug 871source kernel/trace/Kconfig 872 873config PROVIDE_OHCI1394_DMA_INIT 874 bool "Remote debugging over FireWire early on boot" 875 depends on PCI && X86 876 help 877 If you want to debug problems which hang or crash the kernel early 878 on boot and the crashing machine has a FireWire port, you can use 879 this feature to remotely access the memory of the crashed machine 880 over FireWire. This employs remote DMA as part of the OHCI1394 881 specification which is now the standard for FireWire controllers. 882 883 With remote DMA, you can monitor the printk buffer remotely using 884 firescope and access all memory below 4GB using fireproxy from gdb. 885 Even controlling a kernel debugger is possible using remote DMA. 886 887 Usage: 888 889 If ohci1394_dma=early is used as boot parameter, it will initialize 890 all OHCI1394 controllers which are found in the PCI config space. 891 892 As all changes to the FireWire bus such as enabling and disabling 893 devices cause a bus reset and thereby disable remote DMA for all 894 devices, be sure to have the cable plugged and FireWire enabled on 895 the debugging host before booting the debug target for debugging. 896 897 This code (~1k) is freed after boot. By then, the firewire stack 898 in charge of the OHCI-1394 controllers should be used instead. 899 900 See Documentation/debugging-via-ohci1394.txt for more information. 901 902config FIREWIRE_OHCI_REMOTE_DMA 903 bool "Remote debugging over FireWire with firewire-ohci" 904 depends on FIREWIRE_OHCI 905 help 906 This option lets you use the FireWire bus for remote debugging 907 with help of the firewire-ohci driver. It enables unfiltered 908 remote DMA in firewire-ohci. 909 See Documentation/debugging-via-ohci1394.txt for more information. 910 911 If unsure, say N. 912 913config BUILD_DOCSRC 914 bool "Build targets in Documentation/ tree" 915 depends on HEADERS_CHECK 916 help 917 This option attempts to build objects from the source files in the 918 kernel Documentation/ tree. 919 920 Say N if you are unsure. 921 922config DYNAMIC_DEBUG 923 bool "Enable dynamic printk() support" 924 default n 925 depends on PRINTK 926 depends on DEBUG_FS 927 help 928 929 Compiles debug level messages into the kernel, which would not 930 otherwise be available at runtime. These messages can then be 931 enabled/disabled based on various levels of scope - per source file, 932 function, module, format string, and line number. This mechanism 933 implicitly enables all pr_debug() and dev_dbg() calls. The impact of 934 this compile option is a larger kernel text size of about 2%. 935 936 Usage: 937 938 Dynamic debugging is controlled via the 'dynamic_debug/ddebug' file, 939 which is contained in the 'debugfs' filesystem. Thus, the debugfs 940 filesystem must first be mounted before making use of this feature. 941 We refer the control file as: <debugfs>/dynamic_debug/ddebug. This 942 file contains a list of the debug statements that can be enabled. The 943 format for each line of the file is: 944 945 filename:lineno [module]function flags format 946 947 filename : source file of the debug statement 948 lineno : line number of the debug statement 949 module : module that contains the debug statement 950 function : function that contains the debug statement 951 flags : 'p' means the line is turned 'on' for printing 952 format : the format used for the debug statement 953 954 From a live system: 955 956 nullarbor:~ # cat <debugfs>/dynamic_debug/ddebug 957 # filename:lineno [module]function flags format 958 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012" 959 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012" 960 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012" 961 962 Example usage: 963 964 // enable the message at line 1603 of file svcsock.c 965 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 966 <debugfs>/dynamic_debug/ddebug 967 968 // enable all the messages in file svcsock.c 969 nullarbor:~ # echo -n 'file svcsock.c +p' > 970 <debugfs>/dynamic_debug/ddebug 971 972 // enable all the messages in the NFS server module 973 nullarbor:~ # echo -n 'module nfsd +p' > 974 <debugfs>/dynamic_debug/ddebug 975 976 // enable all 12 messages in the function svc_process() 977 nullarbor:~ # echo -n 'func svc_process +p' > 978 <debugfs>/dynamic_debug/ddebug 979 980 // disable all 12 messages in the function svc_process() 981 nullarbor:~ # echo -n 'func svc_process -p' > 982 <debugfs>/dynamic_debug/ddebug 983 984 See Documentation/dynamic-debug-howto.txt for additional information. 985 986config DMA_API_DEBUG 987 bool "Enable debugging of DMA-API usage" 988 depends on HAVE_DMA_API_DEBUG 989 help 990 Enable this option to debug the use of the DMA API by device drivers. 991 With this option you will be able to detect common bugs in device 992 drivers like double-freeing of DMA mappings or freeing mappings that 993 were never allocated. 994 This option causes a performance degredation. Use only if you want 995 to debug device drivers. If unsure, say N. 996 997source "samples/Kconfig" 998 999source "lib/Kconfig.kgdb" 1000 1001source "lib/Kconfig.kmemcheck" 1002