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