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