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 help 364 Say Y here if you want to enable the memory leak 365 detector. The memory allocation/freeing is traced in a way 366 similar to the Boehm's conservative garbage collector, the 367 difference being that the orphan objects are not freed but 368 only shown in /sys/kernel/debug/kmemleak. Enabling this 369 feature will introduce an overhead to memory 370 allocations. See Documentation/kmemleak.txt for more 371 details. 372 373 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 374 of finding leaks due to the slab objects poisoning. 375 376 In order to access the kmemleak file, debugfs needs to be 377 mounted (usually at /sys/kernel/debug). 378 379config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 380 int "Maximum kmemleak early log entries" 381 depends on DEBUG_KMEMLEAK 382 range 200 40000 383 default 400 384 help 385 Kmemleak must track all the memory allocations to avoid 386 reporting false positives. Since memory may be allocated or 387 freed before kmemleak is initialised, an early log buffer is 388 used to store these actions. If kmemleak reports "early log 389 buffer exceeded", please increase this value. 390 391config DEBUG_KMEMLEAK_TEST 392 tristate "Simple test for the kernel memory leak detector" 393 depends on DEBUG_KMEMLEAK 394 help 395 Say Y or M here to build a test for the kernel memory leak 396 detector. This option enables a module that explicitly leaks 397 memory. 398 399 If unsure, say N. 400 401config DEBUG_PREEMPT 402 bool "Debug preemptible kernel" 403 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 404 default y 405 help 406 If you say Y here then the kernel will use a debug variant of the 407 commonly used smp_processor_id() function and will print warnings 408 if kernel code uses it in a preemption-unsafe way. Also, the kernel 409 will detect preemption count underflows. 410 411config DEBUG_RT_MUTEXES 412 bool "RT Mutex debugging, deadlock detection" 413 depends on DEBUG_KERNEL && RT_MUTEXES 414 help 415 This allows rt mutex semantics violations and rt mutex related 416 deadlocks (lockups) to be detected and reported automatically. 417 418config DEBUG_PI_LIST 419 bool 420 default y 421 depends on DEBUG_RT_MUTEXES 422 423config RT_MUTEX_TESTER 424 bool "Built-in scriptable tester for rt-mutexes" 425 depends on DEBUG_KERNEL && RT_MUTEXES 426 help 427 This option enables a rt-mutex tester. 428 429config DEBUG_SPINLOCK 430 bool "Spinlock and rw-lock debugging: basic checks" 431 depends on DEBUG_KERNEL 432 help 433 Say Y here and build SMP to catch missing spinlock initialization 434 and certain other kinds of spinlock errors commonly made. This is 435 best used in conjunction with the NMI watchdog so that spinlock 436 deadlocks are also debuggable. 437 438config DEBUG_MUTEXES 439 bool "Mutex debugging: basic checks" 440 depends on DEBUG_KERNEL 441 help 442 This feature allows mutex semantics violations to be detected and 443 reported. 444 445config DEBUG_LOCK_ALLOC 446 bool "Lock debugging: detect incorrect freeing of live locks" 447 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 448 select DEBUG_SPINLOCK 449 select DEBUG_MUTEXES 450 select LOCKDEP 451 help 452 This feature will check whether any held lock (spinlock, rwlock, 453 mutex or rwsem) is incorrectly freed by the kernel, via any of the 454 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 455 vfree(), etc.), whether a live lock is incorrectly reinitialized via 456 spin_lock_init()/mutex_init()/etc., or whether there is any lock 457 held during task exit. 458 459config PROVE_LOCKING 460 bool "Lock debugging: prove locking correctness" 461 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 462 select LOCKDEP 463 select DEBUG_SPINLOCK 464 select DEBUG_MUTEXES 465 select DEBUG_LOCK_ALLOC 466 default n 467 help 468 This feature enables the kernel to prove that all locking 469 that occurs in the kernel runtime is mathematically 470 correct: that under no circumstance could an arbitrary (and 471 not yet triggered) combination of observed locking 472 sequences (on an arbitrary number of CPUs, running an 473 arbitrary number of tasks and interrupt contexts) cause a 474 deadlock. 475 476 In short, this feature enables the kernel to report locking 477 related deadlocks before they actually occur. 478 479 The proof does not depend on how hard and complex a 480 deadlock scenario would be to trigger: how many 481 participant CPUs, tasks and irq-contexts would be needed 482 for it to trigger. The proof also does not depend on 483 timing: if a race and a resulting deadlock is possible 484 theoretically (no matter how unlikely the race scenario 485 is), it will be proven so and will immediately be 486 reported by the kernel (once the event is observed that 487 makes the deadlock theoretically possible). 488 489 If a deadlock is impossible (i.e. the locking rules, as 490 observed by the kernel, are mathematically correct), the 491 kernel reports nothing. 492 493 NOTE: this feature can also be enabled for rwlocks, mutexes 494 and rwsems - in which case all dependencies between these 495 different locking variants are observed and mapped too, and 496 the proof of observed correctness is also maintained for an 497 arbitrary combination of these separate locking variants. 498 499 For more details, see Documentation/lockdep-design.txt. 500 501config LOCKDEP 502 bool 503 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 504 select STACKTRACE 505 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 506 select KALLSYMS 507 select KALLSYMS_ALL 508 509config LOCK_STAT 510 bool "Lock usage statistics" 511 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 512 select LOCKDEP 513 select DEBUG_SPINLOCK 514 select DEBUG_MUTEXES 515 select DEBUG_LOCK_ALLOC 516 default n 517 help 518 This feature enables tracking lock contention points 519 520 For more details, see Documentation/lockstat.txt 521 522config DEBUG_LOCKDEP 523 bool "Lock dependency engine debugging" 524 depends on DEBUG_KERNEL && LOCKDEP 525 help 526 If you say Y here, the lock dependency engine will do 527 additional runtime checks to debug itself, at the price 528 of more runtime overhead. 529 530config TRACE_IRQFLAGS 531 depends on DEBUG_KERNEL 532 bool 533 default y 534 depends on TRACE_IRQFLAGS_SUPPORT 535 depends on PROVE_LOCKING 536 537config DEBUG_SPINLOCK_SLEEP 538 bool "Spinlock debugging: sleep-inside-spinlock checking" 539 depends on DEBUG_KERNEL 540 help 541 If you say Y here, various routines which may sleep will become very 542 noisy if they are called with a spinlock held. 543 544config DEBUG_LOCKING_API_SELFTESTS 545 bool "Locking API boot-time self-tests" 546 depends on DEBUG_KERNEL 547 help 548 Say Y here if you want the kernel to run a short self-test during 549 bootup. The self-test checks whether common types of locking bugs 550 are detected by debugging mechanisms or not. (if you disable 551 lock debugging then those bugs wont be detected of course.) 552 The following locking APIs are covered: spinlocks, rwlocks, 553 mutexes and rwsems. 554 555config STACKTRACE 556 bool 557 depends on STACKTRACE_SUPPORT 558 559config DEBUG_KOBJECT 560 bool "kobject debugging" 561 depends on DEBUG_KERNEL 562 help 563 If you say Y here, some extra kobject debugging messages will be sent 564 to the syslog. 565 566config DEBUG_HIGHMEM 567 bool "Highmem debugging" 568 depends on DEBUG_KERNEL && HIGHMEM 569 help 570 This options enables addition error checking for high memory systems. 571 Disable for production systems. 572 573config DEBUG_BUGVERBOSE 574 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED 575 depends on BUG 576 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ 577 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 578 default !EMBEDDED 579 help 580 Say Y here to make BUG() panics output the file name and line number 581 of the BUG call as well as the EIP and oops trace. This aids 582 debugging but costs about 70-100K of memory. 583 584config DEBUG_INFO 585 bool "Compile the kernel with debug info" 586 depends on DEBUG_KERNEL 587 help 588 If you say Y here the resulting kernel image will include 589 debugging info resulting in a larger kernel image. 590 This adds debug symbols to the kernel and modules (gcc -g), and 591 is needed if you intend to use kernel crashdump or binary object 592 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 593 Say Y here only if you plan to debug the kernel. 594 595 If unsure, say N. 596 597config DEBUG_VM 598 bool "Debug VM" 599 depends on DEBUG_KERNEL 600 help 601 Enable this to turn on extended checks in the virtual-memory system 602 that may impact performance. 603 604 If unsure, say N. 605 606config DEBUG_VIRTUAL 607 bool "Debug VM translations" 608 depends on DEBUG_KERNEL && X86 609 help 610 Enable some costly sanity checks in virtual to page code. This can 611 catch mistakes with virt_to_page() and friends. 612 613 If unsure, say N. 614 615config DEBUG_NOMMU_REGIONS 616 bool "Debug the global anon/private NOMMU mapping region tree" 617 depends on DEBUG_KERNEL && !MMU 618 help 619 This option causes the global tree of anonymous and private mapping 620 regions to be regularly checked for invalid topology. 621 622config DEBUG_WRITECOUNT 623 bool "Debug filesystem writers count" 624 depends on DEBUG_KERNEL 625 help 626 Enable this to catch wrong use of the writers count in struct 627 vfsmount. This will increase the size of each file struct by 628 32 bits. 629 630 If unsure, say N. 631 632config DEBUG_MEMORY_INIT 633 bool "Debug memory initialisation" if EMBEDDED 634 default !EMBEDDED 635 help 636 Enable this for additional checks during memory initialisation. 637 The sanity checks verify aspects of the VM such as the memory model 638 and other information provided by the architecture. Verbose 639 information will be printed at KERN_DEBUG loglevel depending 640 on the mminit_loglevel= command-line option. 641 642 If unsure, say Y 643 644config DEBUG_LIST 645 bool "Debug linked list manipulation" 646 depends on DEBUG_KERNEL 647 help 648 Enable this to turn on extended checks in the linked-list 649 walking routines. 650 651 If unsure, say N. 652 653config DEBUG_SG 654 bool "Debug SG table operations" 655 depends on DEBUG_KERNEL 656 help 657 Enable this to turn on checks on scatter-gather tables. This can 658 help find problems with drivers that do not properly initialize 659 their sg tables. 660 661 If unsure, say N. 662 663config DEBUG_NOTIFIERS 664 bool "Debug notifier call chains" 665 depends on DEBUG_KERNEL 666 help 667 Enable this to turn on sanity checking for notifier call chains. 668 This is most useful for kernel developers to make sure that 669 modules properly unregister themselves from notifier chains. 670 This is a relatively cheap check but if you care about maximum 671 performance, say N. 672 673config DEBUG_CREDENTIALS 674 bool "Debug credential management" 675 depends on DEBUG_KERNEL 676 help 677 Enable this to turn on some debug checking for credential 678 management. The additional code keeps track of the number of 679 pointers from task_structs to any given cred struct, and checks to 680 see that this number never exceeds the usage count of the cred 681 struct. 682 683 Furthermore, if SELinux is enabled, this also checks that the 684 security pointer in the cred struct is never seen to be invalid. 685 686 If unsure, say N. 687 688# 689# Select this config option from the architecture Kconfig, if it 690# it is preferred to always offer frame pointers as a config 691# option on the architecture (regardless of KERNEL_DEBUG): 692# 693config ARCH_WANT_FRAME_POINTERS 694 bool 695 help 696 697config FRAME_POINTER 698 bool "Compile the kernel with frame pointers" 699 depends on DEBUG_KERNEL && \ 700 (CRIS || M68K || M68KNOMMU || FRV || UML || \ 701 AVR32 || SUPERH || BLACKFIN || MN10300) || \ 702 ARCH_WANT_FRAME_POINTERS 703 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 704 help 705 If you say Y here the resulting kernel image will be slightly 706 larger and slower, but it gives very useful debugging information 707 in case of kernel bugs. (precise oopses/stacktraces/warnings) 708 709config BOOT_PRINTK_DELAY 710 bool "Delay each boot printk message by N milliseconds" 711 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 712 help 713 This build option allows you to read kernel boot messages 714 by inserting a short delay after each one. The delay is 715 specified in milliseconds on the kernel command line, 716 using "boot_delay=N". 717 718 It is likely that you would also need to use "lpj=M" to preset 719 the "loops per jiffie" value. 720 See a previous boot log for the "lpj" value to use for your 721 system, and then set "lpj=M" before setting "boot_delay=N". 722 NOTE: Using this option may adversely affect SMP systems. 723 I.e., processors other than the first one may not boot up. 724 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect 725 what it believes to be lockup conditions. 726 727config RCU_TORTURE_TEST 728 tristate "torture tests for RCU" 729 depends on DEBUG_KERNEL 730 default n 731 help 732 This option provides a kernel module that runs torture tests 733 on the RCU infrastructure. The kernel module may be built 734 after the fact on the running kernel to be tested, if desired. 735 736 Say Y here if you want RCU torture tests to be built into 737 the kernel. 738 Say M if you want the RCU torture tests to build as a module. 739 Say N if you are unsure. 740 741config RCU_TORTURE_TEST_RUNNABLE 742 bool "torture tests for RCU runnable by default" 743 depends on RCU_TORTURE_TEST = y 744 default n 745 help 746 This option provides a way to build the RCU torture tests 747 directly into the kernel without them starting up at boot 748 time. You can use /proc/sys/kernel/rcutorture_runnable 749 to manually override this setting. This /proc file is 750 available only when the RCU torture tests have been built 751 into the kernel. 752 753 Say Y here if you want the RCU torture tests to start during 754 boot (you probably don't). 755 Say N here if you want the RCU torture tests to start only 756 after being manually enabled via /proc. 757 758config RCU_CPU_STALL_DETECTOR 759 bool "Check for stalled CPUs delaying RCU grace periods" 760 depends on TREE_RCU || TREE_PREEMPT_RCU 761 default y 762 help 763 This option causes RCU to printk information on which 764 CPUs are delaying the current grace period, but only when 765 the grace period extends for excessive time periods. 766 767 Say Y if you want RCU to perform such checks. 768 769 Say N if you are unsure. 770 771config KPROBES_SANITY_TEST 772 bool "Kprobes sanity tests" 773 depends on DEBUG_KERNEL 774 depends on KPROBES 775 default n 776 help 777 This option provides for testing basic kprobes functionality on 778 boot. A sample kprobe, jprobe and kretprobe are inserted and 779 verified for functionality. 780 781 Say N if you are unsure. 782 783config BACKTRACE_SELF_TEST 784 tristate "Self test for the backtrace code" 785 depends on DEBUG_KERNEL 786 default n 787 help 788 This option provides a kernel module that can be used to test 789 the kernel stack backtrace code. This option is not useful 790 for distributions or general kernels, but only for kernel 791 developers working on architecture code. 792 793 Note that if you want to also test saved backtraces, you will 794 have to enable STACKTRACE as well. 795 796 Say N if you are unsure. 797 798config DEBUG_BLOCK_EXT_DEVT 799 bool "Force extended block device numbers and spread them" 800 depends on DEBUG_KERNEL 801 depends on BLOCK 802 default n 803 help 804 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 805 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 806 YOU ARE DOING. Distros, please enable this and fix whatever 807 is broken. 808 809 Conventionally, block device numbers are allocated from 810 predetermined contiguous area. However, extended block area 811 may introduce non-contiguous block device numbers. This 812 option forces most block device numbers to be allocated from 813 the extended space and spreads them to discover kernel or 814 userland code paths which assume predetermined contiguous 815 device number allocation. 816 817 Note that turning on this debug option shuffles all the 818 device numbers for all IDE and SCSI devices including libata 819 ones, so root partition specified using device number 820 directly (via rdev or root=MAJ:MIN) won't work anymore. 821 Textual device names (root=/dev/sdXn) will continue to work. 822 823 Say N if you are unsure. 824 825config DEBUG_FORCE_WEAK_PER_CPU 826 bool "Force weak per-cpu definitions" 827 depends on DEBUG_KERNEL 828 help 829 s390 and alpha require percpu variables in modules to be 830 defined weak to work around addressing range issue which 831 puts the following two restrictions on percpu variable 832 definitions. 833 834 1. percpu symbols must be unique whether static or not 835 2. percpu variables can't be defined inside a function 836 837 To ensure that generic code follows the above rules, this 838 option forces all percpu variables to be defined as weak. 839 840config LKDTM 841 tristate "Linux Kernel Dump Test Tool Module" 842 depends on DEBUG_KERNEL 843 depends on KPROBES 844 depends on BLOCK 845 default n 846 help 847 This module enables testing of the different dumping mechanisms by 848 inducing system failures at predefined crash points. 849 If you don't need it: say N 850 Choose M here to compile this code as a module. The module will be 851 called lkdtm. 852 853 Documentation on how to use the module can be found in 854 drivers/misc/lkdtm.c 855 856config FAULT_INJECTION 857 bool "Fault-injection framework" 858 depends on DEBUG_KERNEL 859 help 860 Provide fault-injection framework. 861 For more details, see Documentation/fault-injection/. 862 863config FAILSLAB 864 bool "Fault-injection capability for kmalloc" 865 depends on FAULT_INJECTION 866 depends on SLAB || SLUB 867 help 868 Provide fault-injection capability for kmalloc. 869 870config FAIL_PAGE_ALLOC 871 bool "Fault-injection capabilitiy for alloc_pages()" 872 depends on FAULT_INJECTION 873 help 874 Provide fault-injection capability for alloc_pages(). 875 876config FAIL_MAKE_REQUEST 877 bool "Fault-injection capability for disk IO" 878 depends on FAULT_INJECTION && BLOCK 879 help 880 Provide fault-injection capability for disk IO. 881 882config FAIL_IO_TIMEOUT 883 bool "Faul-injection capability for faking disk interrupts" 884 depends on FAULT_INJECTION && BLOCK 885 help 886 Provide fault-injection capability on end IO handling. This 887 will make the block layer "forget" an interrupt as configured, 888 thus exercising the error handling. 889 890 Only works with drivers that use the generic timeout handling, 891 for others it wont do anything. 892 893config FAULT_INJECTION_DEBUG_FS 894 bool "Debugfs entries for fault-injection capabilities" 895 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 896 help 897 Enable configuration of fault-injection capabilities via debugfs. 898 899config FAULT_INJECTION_STACKTRACE_FILTER 900 bool "stacktrace filter for fault-injection capabilities" 901 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 902 depends on !X86_64 903 select STACKTRACE 904 select FRAME_POINTER if !PPC && !S390 905 help 906 Provide stacktrace filter for fault-injection capabilities 907 908config LATENCYTOP 909 bool "Latency measuring infrastructure" 910 select FRAME_POINTER if !MIPS && !PPC && !S390 911 select KALLSYMS 912 select KALLSYMS_ALL 913 select STACKTRACE 914 select SCHEDSTATS 915 select SCHED_DEBUG 916 depends on HAVE_LATENCYTOP_SUPPORT 917 help 918 Enable this option if you want to use the LatencyTOP tool 919 to find out which userspace is blocking on what kernel operations. 920 921config SYSCTL_SYSCALL_CHECK 922 bool "Sysctl checks" 923 depends on SYSCTL 924 ---help--- 925 sys_sysctl uses binary paths that have been found challenging 926 to properly maintain and use. This enables checks that help 927 you to keep things correct. 928 929source mm/Kconfig.debug 930source kernel/trace/Kconfig 931 932config PROVIDE_OHCI1394_DMA_INIT 933 bool "Remote debugging over FireWire early on boot" 934 depends on PCI && X86 935 help 936 If you want to debug problems which hang or crash the kernel early 937 on boot and the crashing machine has a FireWire port, you can use 938 this feature to remotely access the memory of the crashed machine 939 over FireWire. This employs remote DMA as part of the OHCI1394 940 specification which is now the standard for FireWire controllers. 941 942 With remote DMA, you can monitor the printk buffer remotely using 943 firescope and access all memory below 4GB using fireproxy from gdb. 944 Even controlling a kernel debugger is possible using remote DMA. 945 946 Usage: 947 948 If ohci1394_dma=early is used as boot parameter, it will initialize 949 all OHCI1394 controllers which are found in the PCI config space. 950 951 As all changes to the FireWire bus such as enabling and disabling 952 devices cause a bus reset and thereby disable remote DMA for all 953 devices, be sure to have the cable plugged and FireWire enabled on 954 the debugging host before booting the debug target for debugging. 955 956 This code (~1k) is freed after boot. By then, the firewire stack 957 in charge of the OHCI-1394 controllers should be used instead. 958 959 See Documentation/debugging-via-ohci1394.txt for more information. 960 961config FIREWIRE_OHCI_REMOTE_DMA 962 bool "Remote debugging over FireWire with firewire-ohci" 963 depends on FIREWIRE_OHCI 964 help 965 This option lets you use the FireWire bus for remote debugging 966 with help of the firewire-ohci driver. It enables unfiltered 967 remote DMA in firewire-ohci. 968 See Documentation/debugging-via-ohci1394.txt for more information. 969 970 If unsure, say N. 971 972config BUILD_DOCSRC 973 bool "Build targets in Documentation/ tree" 974 depends on HEADERS_CHECK 975 help 976 This option attempts to build objects from the source files in the 977 kernel Documentation/ tree. 978 979 Say N if you are unsure. 980 981config DYNAMIC_DEBUG 982 bool "Enable dynamic printk() support" 983 default n 984 depends on PRINTK 985 depends on DEBUG_FS 986 help 987 988 Compiles debug level messages into the kernel, which would not 989 otherwise be available at runtime. These messages can then be 990 enabled/disabled based on various levels of scope - per source file, 991 function, module, format string, and line number. This mechanism 992 implicitly enables all pr_debug() and dev_dbg() calls. The impact of 993 this compile option is a larger kernel text size of about 2%. 994 995 Usage: 996 997 Dynamic debugging is controlled via the 'dynamic_debug/ddebug' file, 998 which is contained in the 'debugfs' filesystem. Thus, the debugfs 999 filesystem must first be mounted before making use of this feature. 1000 We refer the control file as: <debugfs>/dynamic_debug/ddebug. This 1001 file contains a list of the debug statements that can be enabled. The 1002 format for each line of the file is: 1003 1004 filename:lineno [module]function flags format 1005 1006 filename : source file of the debug statement 1007 lineno : line number of the debug statement 1008 module : module that contains the debug statement 1009 function : function that contains the debug statement 1010 flags : 'p' means the line is turned 'on' for printing 1011 format : the format used for the debug statement 1012 1013 From a live system: 1014 1015 nullarbor:~ # cat <debugfs>/dynamic_debug/ddebug 1016 # filename:lineno [module]function flags format 1017 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012" 1018 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012" 1019 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012" 1020 1021 Example usage: 1022 1023 // enable the message at line 1603 of file svcsock.c 1024 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 1025 <debugfs>/dynamic_debug/ddebug 1026 1027 // enable all the messages in file svcsock.c 1028 nullarbor:~ # echo -n 'file svcsock.c +p' > 1029 <debugfs>/dynamic_debug/ddebug 1030 1031 // enable all the messages in the NFS server module 1032 nullarbor:~ # echo -n 'module nfsd +p' > 1033 <debugfs>/dynamic_debug/ddebug 1034 1035 // enable all 12 messages in the function svc_process() 1036 nullarbor:~ # echo -n 'func svc_process +p' > 1037 <debugfs>/dynamic_debug/ddebug 1038 1039 // disable all 12 messages in the function svc_process() 1040 nullarbor:~ # echo -n 'func svc_process -p' > 1041 <debugfs>/dynamic_debug/ddebug 1042 1043 See Documentation/dynamic-debug-howto.txt for additional information. 1044 1045config DMA_API_DEBUG 1046 bool "Enable debugging of DMA-API usage" 1047 depends on HAVE_DMA_API_DEBUG 1048 help 1049 Enable this option to debug the use of the DMA API by device drivers. 1050 With this option you will be able to detect common bugs in device 1051 drivers like double-freeing of DMA mappings or freeing mappings that 1052 were never allocated. 1053 This option causes a performance degredation. Use only if you want 1054 to debug device drivers. If unsure, say N. 1055 1056source "samples/Kconfig" 1057 1058source "lib/Kconfig.kgdb" 1059 1060source "lib/Kconfig.kmemcheck" 1061