1 2config PRINTK_TIME 3 bool "Show timing information on printks" 4 depends on PRINTK 5 help 6 Selecting this option causes timing information to be 7 included in printk output. This allows you to measure 8 the interval between kernel operations, including bootup 9 operations. This is useful for identifying long delays 10 in kernel startup. 11 12config ENABLE_WARN_DEPRECATED 13 bool "Enable __deprecated logic" 14 default y 15 help 16 Enable the __deprecated logic in the kernel build. 17 Disable this to suppress the "warning: 'foo' is deprecated 18 (declared at kernel/power/somefile.c:1234)" messages. 19 20config ENABLE_MUST_CHECK 21 bool "Enable __must_check logic" 22 default y 23 help 24 Enable the __must_check logic in the kernel build. Disable this to 25 suppress the "warning: ignoring return value of 'foo', declared with 26 attribute warn_unused_result" messages. 27 28config FRAME_WARN 29 int "Warn for stack frames larger than (needs gcc 4.4)" 30 range 0 8192 31 default 1024 if !64BIT 32 default 2048 if 64BIT 33 help 34 Tell gcc to warn at build time for stack frames larger than this. 35 Setting this too low will cause a lot of warnings. 36 Setting it to 0 disables the warning. 37 Requires gcc 4.4 38 39config MAGIC_SYSRQ 40 bool "Magic SysRq key" 41 depends on !UML 42 help 43 If you say Y here, you will have some control over the system even 44 if the system crashes for example during kernel debugging (e.g., you 45 will be able to flush the buffer cache to disk, reboot the system 46 immediately or dump some status information). This is accomplished 47 by pressing various keys while holding SysRq (Alt+PrintScreen). It 48 also works on a serial console (on PC hardware at least), if you 49 send a BREAK and then within 5 seconds a command keypress. The 50 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 51 unless you really know what this hack does. 52 53config STRIP_ASM_SYMS 54 bool "Strip assembler-generated symbols during link" 55 default n 56 help 57 Strip internal assembler-generated symbols during a link (symbols 58 that look like '.Lxxx') so they don't pollute the output of 59 get_wchan() and suchlike. 60 61config UNUSED_SYMBOLS 62 bool "Enable unused/obsolete exported symbols" 63 default y if X86 64 help 65 Unused but exported symbols make the kernel needlessly bigger. For 66 that reason most of these unused exports will soon be removed. This 67 option is provided temporarily to provide a transition period in case 68 some external kernel module needs one of these symbols anyway. If you 69 encounter such a case in your module, consider if you are actually 70 using the right API. (rationale: since nobody in the kernel is using 71 this in a module, there is a pretty good chance it's actually the 72 wrong interface to use). If you really need the symbol, please send a 73 mail to the linux kernel mailing list mentioning the symbol and why 74 you really need it, and what the merge plan to the mainline kernel for 75 your module is. 76 77config DEBUG_FS 78 bool "Debug Filesystem" 79 depends on SYSFS 80 help 81 debugfs is a virtual file system that kernel developers use to put 82 debugging files into. Enable this option to be able to read and 83 write to these files. 84 85 For detailed documentation on the debugfs API, see 86 Documentation/DocBook/filesystems. 87 88 If unsure, say N. 89 90config HEADERS_CHECK 91 bool "Run 'make headers_check' when building vmlinux" 92 depends on !UML 93 help 94 This option will extract the user-visible kernel headers whenever 95 building the kernel, and will run basic sanity checks on them to 96 ensure that exported files do not attempt to include files which 97 were not exported, etc. 98 99 If you're making modifications to header files which are 100 relevant for userspace, say 'Y', and check the headers 101 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 102 your build tree), to make sure they're suitable. 103 104config DEBUG_SECTION_MISMATCH 105 bool "Enable full Section mismatch analysis" 106 depends on UNDEFINED 107 # This option is on purpose disabled for now. 108 # It will be enabled when we are down to a resonable number 109 # of section mismatch warnings (< 10 for an allyesconfig build) 110 help 111 The section mismatch analysis checks if there are illegal 112 references from one section to another section. 113 Linux will during link or during runtime drop some sections 114 and any use of code/data previously in these sections will 115 most likely result in an oops. 116 In the code functions and variables are annotated with 117 __init, __devinit etc. (see full list in include/linux/init.h) 118 which results in the code/data being placed in specific sections. 119 The section mismatch analysis is always done after a full 120 kernel build but enabling this option will in addition 121 do the following: 122 - Add the option -fno-inline-functions-called-once to gcc 123 When inlining a function annotated __init in a non-init 124 function we would lose the section information and thus 125 the analysis would not catch the illegal reference. 126 This option tells gcc to inline less but will also 127 result in a larger kernel. 128 - Run the section mismatch analysis for each module/built-in.o 129 When we run the section mismatch analysis on vmlinux.o we 130 lose valueble information about where the mismatch was 131 introduced. 132 Running the analysis for each module/built-in.o file 133 will tell where the mismatch happens much closer to the 134 source. The drawback is that we will report the same 135 mismatch at least twice. 136 - Enable verbose reporting from modpost to help solving 137 the section mismatches reported. 138 139config DEBUG_KERNEL 140 bool "Kernel debugging" 141 help 142 Say Y here if you are developing drivers or trying to debug and 143 identify kernel problems. 144 145config DEBUG_SHIRQ 146 bool "Debug shared IRQ handlers" 147 depends on DEBUG_KERNEL && GENERIC_HARDIRQS 148 help 149 Enable this to generate a spurious interrupt as soon as a shared 150 interrupt handler is registered, and just before one is deregistered. 151 Drivers ought to be able to handle interrupts coming in at those 152 points; some don't and need to be caught. 153 154config DETECT_SOFTLOCKUP 155 bool "Detect Soft Lockups" 156 depends on DEBUG_KERNEL && !S390 157 default y 158 help 159 Say Y here to enable the kernel to detect "soft lockups", 160 which are bugs that cause the kernel to loop in kernel 161 mode for more than 60 seconds, without giving other tasks a 162 chance to run. 163 164 When a soft-lockup is detected, the kernel will print the 165 current stack trace (which you should report), but the 166 system will stay locked up. This feature has negligible 167 overhead. 168 169 (Note that "hard lockups" are separate type of bugs that 170 can be detected via the NMI-watchdog, on platforms that 171 support it.) 172 173config BOOTPARAM_SOFTLOCKUP_PANIC 174 bool "Panic (Reboot) On Soft Lockups" 175 depends on DETECT_SOFTLOCKUP 176 help 177 Say Y here to enable the kernel to panic on "soft lockups", 178 which are bugs that cause the kernel to loop in kernel 179 mode for more than 60 seconds, without giving other tasks a 180 chance to run. 181 182 The panic can be used in combination with panic_timeout, 183 to cause the system to reboot automatically after a 184 lockup has been detected. This feature is useful for 185 high-availability systems that have uptime guarantees and 186 where a lockup must be resolved ASAP. 187 188 Say N if unsure. 189 190config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 191 int 192 depends on DETECT_SOFTLOCKUP 193 range 0 1 194 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 195 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 196 197config DETECT_HUNG_TASK 198 bool "Detect Hung Tasks" 199 depends on DEBUG_KERNEL 200 default DETECT_SOFTLOCKUP 201 help 202 Say Y here to enable the kernel to detect "hung tasks", 203 which are bugs that cause the task to be stuck in 204 uninterruptible "D" state indefinitiley. 205 206 When a hung task is detected, the kernel will print the 207 current stack trace (which you should report), but the 208 task will stay in uninterruptible state. If lockdep is 209 enabled then all held locks will also be reported. This 210 feature has negligible overhead. 211 212config BOOTPARAM_HUNG_TASK_PANIC 213 bool "Panic (Reboot) On Hung Tasks" 214 depends on DETECT_HUNG_TASK 215 help 216 Say Y here to enable the kernel to panic on "hung tasks", 217 which are bugs that cause the kernel to leave a task stuck 218 in uninterruptible "D" state. 219 220 The panic can be used in combination with panic_timeout, 221 to cause the system to reboot automatically after a 222 hung task has been detected. This feature is useful for 223 high-availability systems that have uptime guarantees and 224 where a hung tasks must be resolved ASAP. 225 226 Say N if unsure. 227 228config BOOTPARAM_HUNG_TASK_PANIC_VALUE 229 int 230 depends on DETECT_HUNG_TASK 231 range 0 1 232 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 233 default 1 if BOOTPARAM_HUNG_TASK_PANIC 234 235config SCHED_DEBUG 236 bool "Collect scheduler debugging info" 237 depends on DEBUG_KERNEL && PROC_FS 238 default y 239 help 240 If you say Y here, the /proc/sched_debug file will be provided 241 that can help debug the scheduler. The runtime overhead of this 242 option is minimal. 243 244config SCHEDSTATS 245 bool "Collect scheduler statistics" 246 depends on DEBUG_KERNEL && PROC_FS 247 help 248 If you say Y here, additional code will be inserted into the 249 scheduler and related routines to collect statistics about 250 scheduler behavior and provide them in /proc/schedstat. These 251 stats may be useful for both tuning and debugging the scheduler 252 If you aren't debugging the scheduler or trying to tune a specific 253 application, you can say N to avoid the very slight overhead 254 this adds. 255 256config TIMER_STATS 257 bool "Collect kernel timers statistics" 258 depends on DEBUG_KERNEL && PROC_FS 259 help 260 If you say Y here, additional code will be inserted into the 261 timer routines to collect statistics about kernel timers being 262 reprogrammed. The statistics can be read from /proc/timer_stats. 263 The statistics collection is started by writing 1 to /proc/timer_stats, 264 writing 0 stops it. This feature is useful to collect information 265 about timer usage patterns in kernel and userspace. This feature 266 is lightweight if enabled in the kernel config but not activated 267 (it defaults to deactivated on bootup and will only be activated 268 if some application like powertop activates it explicitly). 269 270config DEBUG_OBJECTS 271 bool "Debug object operations" 272 depends on DEBUG_KERNEL 273 help 274 If you say Y here, additional code will be inserted into the 275 kernel to track the life time of various objects and validate 276 the operations on those objects. 277 278config DEBUG_OBJECTS_SELFTEST 279 bool "Debug objects selftest" 280 depends on DEBUG_OBJECTS 281 help 282 This enables the selftest of the object debug code. 283 284config DEBUG_OBJECTS_FREE 285 bool "Debug objects in freed memory" 286 depends on DEBUG_OBJECTS 287 help 288 This enables checks whether a k/v free operation frees an area 289 which contains an object which has not been deactivated 290 properly. This can make kmalloc/kfree-intensive workloads 291 much slower. 292 293config DEBUG_OBJECTS_TIMERS 294 bool "Debug timer objects" 295 depends on DEBUG_OBJECTS 296 help 297 If you say Y here, additional code will be inserted into the 298 timer routines to track the life time of timer objects and 299 validate the timer operations. 300 301config DEBUG_OBJECTS_ENABLE_DEFAULT 302 int "debug_objects bootup default value (0-1)" 303 range 0 1 304 default "1" 305 depends on DEBUG_OBJECTS 306 help 307 Debug objects boot parameter default value 308 309config DEBUG_SLAB 310 bool "Debug slab memory allocations" 311 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 312 help 313 Say Y here to have the kernel do limited verification on memory 314 allocation as well as poisoning memory on free to catch use of freed 315 memory. This can make kmalloc/kfree-intensive workloads much slower. 316 317config DEBUG_SLAB_LEAK 318 bool "Memory leak debugging" 319 depends on DEBUG_SLAB 320 321config SLUB_DEBUG_ON 322 bool "SLUB debugging on by default" 323 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 324 default n 325 help 326 Boot with debugging on by default. SLUB boots by default with 327 the runtime debug capabilities switched off. Enabling this is 328 equivalent to specifying the "slub_debug" parameter on boot. 329 There is no support for more fine grained debug control like 330 possible with slub_debug=xxx. SLUB debugging may be switched 331 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 332 "slub_debug=-". 333 334config SLUB_STATS 335 default n 336 bool "Enable SLUB performance statistics" 337 depends on SLUB && SLUB_DEBUG && SYSFS 338 help 339 SLUB statistics are useful to debug SLUBs allocation behavior in 340 order find ways to optimize the allocator. This should never be 341 enabled for production use since keeping statistics slows down 342 the allocator by a few percentage points. The slabinfo command 343 supports the determination of the most active slabs to figure 344 out which slabs are relevant to a particular load. 345 Try running: slabinfo -DA 346 347config DEBUG_KMEMLEAK 348 bool "Kernel memory leak detector" 349 depends on DEBUG_KERNEL && EXPERIMENTAL && !MEMORY_HOTPLUG && \ 350 (X86 || ARM || PPC || S390) 351 352 select DEBUG_FS if SYSFS 353 select STACKTRACE if STACKTRACE_SUPPORT 354 select KALLSYMS 355 help 356 Say Y here if you want to enable the memory leak 357 detector. The memory allocation/freeing is traced in a way 358 similar to the Boehm's conservative garbage collector, the 359 difference being that the orphan objects are not freed but 360 only shown in /sys/kernel/debug/kmemleak. Enabling this 361 feature will introduce an overhead to memory 362 allocations. See Documentation/kmemleak.txt for more 363 details. 364 365 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 366 of finding leaks due to the slab objects poisoning. 367 368 In order to access the kmemleak file, debugfs needs to be 369 mounted (usually at /sys/kernel/debug). 370 371config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 372 int "Maximum kmemleak early log entries" 373 depends on DEBUG_KMEMLEAK 374 range 200 40000 375 default 400 376 help 377 Kmemleak must track all the memory allocations to avoid 378 reporting false positives. Since memory may be allocated or 379 freed before kmemleak is initialised, an early log buffer is 380 used to store these actions. If kmemleak reports "early log 381 buffer exceeded", please increase this value. 382 383config DEBUG_KMEMLEAK_TEST 384 tristate "Simple test for the kernel memory leak detector" 385 depends on DEBUG_KMEMLEAK 386 help 387 Say Y or M here to build a test for the kernel memory leak 388 detector. This option enables a module that explicitly leaks 389 memory. 390 391 If unsure, say N. 392 393config DEBUG_PREEMPT 394 bool "Debug preemptible kernel" 395 depends on DEBUG_KERNEL && PREEMPT && (TRACE_IRQFLAGS_SUPPORT || PPC64) 396 default y 397 help 398 If you say Y here then the kernel will use a debug variant of the 399 commonly used smp_processor_id() function and will print warnings 400 if kernel code uses it in a preemption-unsafe way. Also, the kernel 401 will detect preemption count underflows. 402 403config DEBUG_RT_MUTEXES 404 bool "RT Mutex debugging, deadlock detection" 405 depends on DEBUG_KERNEL && RT_MUTEXES 406 help 407 This allows rt mutex semantics violations and rt mutex related 408 deadlocks (lockups) to be detected and reported automatically. 409 410config DEBUG_PI_LIST 411 bool 412 default y 413 depends on DEBUG_RT_MUTEXES 414 415config RT_MUTEX_TESTER 416 bool "Built-in scriptable tester for rt-mutexes" 417 depends on DEBUG_KERNEL && RT_MUTEXES 418 help 419 This option enables a rt-mutex tester. 420 421config DEBUG_SPINLOCK 422 bool "Spinlock and rw-lock debugging: basic checks" 423 depends on DEBUG_KERNEL 424 help 425 Say Y here and build SMP to catch missing spinlock initialization 426 and certain other kinds of spinlock errors commonly made. This is 427 best used in conjunction with the NMI watchdog so that spinlock 428 deadlocks are also debuggable. 429 430config DEBUG_MUTEXES 431 bool "Mutex debugging: basic checks" 432 depends on DEBUG_KERNEL 433 help 434 This feature allows mutex semantics violations to be detected and 435 reported. 436 437config DEBUG_LOCK_ALLOC 438 bool "Lock debugging: detect incorrect freeing of live locks" 439 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 440 select DEBUG_SPINLOCK 441 select DEBUG_MUTEXES 442 select LOCKDEP 443 help 444 This feature will check whether any held lock (spinlock, rwlock, 445 mutex or rwsem) is incorrectly freed by the kernel, via any of the 446 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 447 vfree(), etc.), whether a live lock is incorrectly reinitialized via 448 spin_lock_init()/mutex_init()/etc., or whether there is any lock 449 held during task exit. 450 451config PROVE_LOCKING 452 bool "Lock debugging: prove locking correctness" 453 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 454 select LOCKDEP 455 select DEBUG_SPINLOCK 456 select DEBUG_MUTEXES 457 select DEBUG_LOCK_ALLOC 458 default n 459 help 460 This feature enables the kernel to prove that all locking 461 that occurs in the kernel runtime is mathematically 462 correct: that under no circumstance could an arbitrary (and 463 not yet triggered) combination of observed locking 464 sequences (on an arbitrary number of CPUs, running an 465 arbitrary number of tasks and interrupt contexts) cause a 466 deadlock. 467 468 In short, this feature enables the kernel to report locking 469 related deadlocks before they actually occur. 470 471 The proof does not depend on how hard and complex a 472 deadlock scenario would be to trigger: how many 473 participant CPUs, tasks and irq-contexts would be needed 474 for it to trigger. The proof also does not depend on 475 timing: if a race and a resulting deadlock is possible 476 theoretically (no matter how unlikely the race scenario 477 is), it will be proven so and will immediately be 478 reported by the kernel (once the event is observed that 479 makes the deadlock theoretically possible). 480 481 If a deadlock is impossible (i.e. the locking rules, as 482 observed by the kernel, are mathematically correct), the 483 kernel reports nothing. 484 485 NOTE: this feature can also be enabled for rwlocks, mutexes 486 and rwsems - in which case all dependencies between these 487 different locking variants are observed and mapped too, and 488 the proof of observed correctness is also maintained for an 489 arbitrary combination of these separate locking variants. 490 491 For more details, see Documentation/lockdep-design.txt. 492 493config LOCKDEP 494 bool 495 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 496 select STACKTRACE 497 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 498 select KALLSYMS 499 select KALLSYMS_ALL 500 501config LOCK_STAT 502 bool "Lock usage statistics" 503 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 504 select LOCKDEP 505 select DEBUG_SPINLOCK 506 select DEBUG_MUTEXES 507 select DEBUG_LOCK_ALLOC 508 default n 509 help 510 This feature enables tracking lock contention points 511 512 For more details, see Documentation/lockstat.txt 513 514config DEBUG_LOCKDEP 515 bool "Lock dependency engine debugging" 516 depends on DEBUG_KERNEL && LOCKDEP 517 help 518 If you say Y here, the lock dependency engine will do 519 additional runtime checks to debug itself, at the price 520 of more runtime overhead. 521 522config TRACE_IRQFLAGS 523 depends on DEBUG_KERNEL 524 bool 525 default y 526 depends on TRACE_IRQFLAGS_SUPPORT 527 depends on PROVE_LOCKING 528 529config DEBUG_SPINLOCK_SLEEP 530 bool "Spinlock debugging: sleep-inside-spinlock checking" 531 depends on DEBUG_KERNEL 532 help 533 If you say Y here, various routines which may sleep will become very 534 noisy if they are called with a spinlock held. 535 536config DEBUG_LOCKING_API_SELFTESTS 537 bool "Locking API boot-time self-tests" 538 depends on DEBUG_KERNEL 539 help 540 Say Y here if you want the kernel to run a short self-test during 541 bootup. The self-test checks whether common types of locking bugs 542 are detected by debugging mechanisms or not. (if you disable 543 lock debugging then those bugs wont be detected of course.) 544 The following locking APIs are covered: spinlocks, rwlocks, 545 mutexes and rwsems. 546 547config STACKTRACE 548 bool 549 depends on STACKTRACE_SUPPORT 550 551config DEBUG_KOBJECT 552 bool "kobject debugging" 553 depends on DEBUG_KERNEL 554 help 555 If you say Y here, some extra kobject debugging messages will be sent 556 to the syslog. 557 558config DEBUG_HIGHMEM 559 bool "Highmem debugging" 560 depends on DEBUG_KERNEL && HIGHMEM 561 help 562 This options enables addition error checking for high memory systems. 563 Disable for production systems. 564 565config DEBUG_BUGVERBOSE 566 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED 567 depends on BUG 568 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ 569 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 570 default !EMBEDDED 571 help 572 Say Y here to make BUG() panics output the file name and line number 573 of the BUG call as well as the EIP and oops trace. This aids 574 debugging but costs about 70-100K of memory. 575 576config DEBUG_INFO 577 bool "Compile the kernel with debug info" 578 depends on DEBUG_KERNEL 579 help 580 If you say Y here the resulting kernel image will include 581 debugging info resulting in a larger kernel image. 582 This adds debug symbols to the kernel and modules (gcc -g), and 583 is needed if you intend to use kernel crashdump or binary object 584 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 585 Say Y here only if you plan to debug the kernel. 586 587 If unsure, say N. 588 589config DEBUG_VM 590 bool "Debug VM" 591 depends on DEBUG_KERNEL 592 help 593 Enable this to turn on extended checks in the virtual-memory system 594 that may impact performance. 595 596 If unsure, say N. 597 598config DEBUG_VIRTUAL 599 bool "Debug VM translations" 600 depends on DEBUG_KERNEL && X86 601 help 602 Enable some costly sanity checks in virtual to page code. This can 603 catch mistakes with virt_to_page() and friends. 604 605 If unsure, say N. 606 607config DEBUG_NOMMU_REGIONS 608 bool "Debug the global anon/private NOMMU mapping region tree" 609 depends on DEBUG_KERNEL && !MMU 610 help 611 This option causes the global tree of anonymous and private mapping 612 regions to be regularly checked for invalid topology. 613 614config DEBUG_WRITECOUNT 615 bool "Debug filesystem writers count" 616 depends on DEBUG_KERNEL 617 help 618 Enable this to catch wrong use of the writers count in struct 619 vfsmount. This will increase the size of each file struct by 620 32 bits. 621 622 If unsure, say N. 623 624config DEBUG_MEMORY_INIT 625 bool "Debug memory initialisation" if EMBEDDED 626 default !EMBEDDED 627 help 628 Enable this for additional checks during memory initialisation. 629 The sanity checks verify aspects of the VM such as the memory model 630 and other information provided by the architecture. Verbose 631 information will be printed at KERN_DEBUG loglevel depending 632 on the mminit_loglevel= command-line option. 633 634 If unsure, say Y 635 636config DEBUG_LIST 637 bool "Debug linked list manipulation" 638 depends on DEBUG_KERNEL 639 help 640 Enable this to turn on extended checks in the linked-list 641 walking routines. 642 643 If unsure, say N. 644 645config DEBUG_SG 646 bool "Debug SG table operations" 647 depends on DEBUG_KERNEL 648 help 649 Enable this to turn on checks on scatter-gather tables. This can 650 help find problems with drivers that do not properly initialize 651 their sg tables. 652 653 If unsure, say N. 654 655config DEBUG_NOTIFIERS 656 bool "Debug notifier call chains" 657 depends on DEBUG_KERNEL 658 help 659 Enable this to turn on sanity checking for notifier call chains. 660 This is most useful for kernel developers to make sure that 661 modules properly unregister themselves from notifier chains. 662 This is a relatively cheap check but if you care about maximum 663 performance, say N. 664 665config DEBUG_CREDENTIALS 666 bool "Debug credential management" 667 depends on DEBUG_KERNEL 668 help 669 Enable this to turn on some debug checking for credential 670 management. The additional code keeps track of the number of 671 pointers from task_structs to any given cred struct, and checks to 672 see that this number never exceeds the usage count of the cred 673 struct. 674 675 Furthermore, if SELinux is enabled, this also checks that the 676 security pointer in the cred struct is never seen to be invalid. 677 678 If unsure, say N. 679 680# 681# Select this config option from the architecture Kconfig, if it 682# it is preferred to always offer frame pointers as a config 683# option on the architecture (regardless of KERNEL_DEBUG): 684# 685config ARCH_WANT_FRAME_POINTERS 686 bool 687 help 688 689config FRAME_POINTER 690 bool "Compile the kernel with frame pointers" 691 depends on DEBUG_KERNEL && \ 692 (CRIS || M68K || M68KNOMMU || FRV || UML || \ 693 AVR32 || SUPERH || BLACKFIN || MN10300) || \ 694 ARCH_WANT_FRAME_POINTERS 695 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 696 help 697 If you say Y here the resulting kernel image will be slightly 698 larger and slower, but it gives very useful debugging information 699 in case of kernel bugs. (precise oopses/stacktraces/warnings) 700 701config BOOT_PRINTK_DELAY 702 bool "Delay each boot printk message by N milliseconds" 703 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 704 help 705 This build option allows you to read kernel boot messages 706 by inserting a short delay after each one. The delay is 707 specified in milliseconds on the kernel command line, 708 using "boot_delay=N". 709 710 It is likely that you would also need to use "lpj=M" to preset 711 the "loops per jiffie" value. 712 See a previous boot log for the "lpj" value to use for your 713 system, and then set "lpj=M" before setting "boot_delay=N". 714 NOTE: Using this option may adversely affect SMP systems. 715 I.e., processors other than the first one may not boot up. 716 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect 717 what it believes to be lockup conditions. 718 719config RCU_TORTURE_TEST 720 tristate "torture tests for RCU" 721 depends on DEBUG_KERNEL 722 default n 723 help 724 This option provides a kernel module that runs torture tests 725 on the RCU infrastructure. The kernel module may be built 726 after the fact on the running kernel to be tested, if desired. 727 728 Say Y here if you want RCU torture tests to be built into 729 the kernel. 730 Say M if you want the RCU torture tests to build as a module. 731 Say N if you are unsure. 732 733config RCU_TORTURE_TEST_RUNNABLE 734 bool "torture tests for RCU runnable by default" 735 depends on RCU_TORTURE_TEST = y 736 default n 737 help 738 This option provides a way to build the RCU torture tests 739 directly into the kernel without them starting up at boot 740 time. You can use /proc/sys/kernel/rcutorture_runnable 741 to manually override this setting. This /proc file is 742 available only when the RCU torture tests have been built 743 into the kernel. 744 745 Say Y here if you want the RCU torture tests to start during 746 boot (you probably don't). 747 Say N here if you want the RCU torture tests to start only 748 after being manually enabled via /proc. 749 750config RCU_CPU_STALL_DETECTOR 751 bool "Check for stalled CPUs delaying RCU grace periods" 752 depends on TREE_RCU || TREE_PREEMPT_RCU 753 default n 754 help 755 This option causes RCU to printk information on which 756 CPUs are delaying the current grace period, but only when 757 the grace period extends for excessive time periods. 758 759 Say Y if you want RCU to perform such checks. 760 761 Say N if you are unsure. 762 763config KPROBES_SANITY_TEST 764 bool "Kprobes sanity tests" 765 depends on DEBUG_KERNEL 766 depends on KPROBES 767 default n 768 help 769 This option provides for testing basic kprobes functionality on 770 boot. A sample kprobe, jprobe and kretprobe are inserted and 771 verified for functionality. 772 773 Say N if you are unsure. 774 775config BACKTRACE_SELF_TEST 776 tristate "Self test for the backtrace code" 777 depends on DEBUG_KERNEL 778 default n 779 help 780 This option provides a kernel module that can be used to test 781 the kernel stack backtrace code. This option is not useful 782 for distributions or general kernels, but only for kernel 783 developers working on architecture code. 784 785 Note that if you want to also test saved backtraces, you will 786 have to enable STACKTRACE as well. 787 788 Say N if you are unsure. 789 790config DEBUG_BLOCK_EXT_DEVT 791 bool "Force extended block device numbers and spread them" 792 depends on DEBUG_KERNEL 793 depends on BLOCK 794 default n 795 help 796 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 797 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 798 YOU ARE DOING. Distros, please enable this and fix whatever 799 is broken. 800 801 Conventionally, block device numbers are allocated from 802 predetermined contiguous area. However, extended block area 803 may introduce non-contiguous block device numbers. This 804 option forces most block device numbers to be allocated from 805 the extended space and spreads them to discover kernel or 806 userland code paths which assume predetermined contiguous 807 device number allocation. 808 809 Note that turning on this debug option shuffles all the 810 device numbers for all IDE and SCSI devices including libata 811 ones, so root partition specified using device number 812 directly (via rdev or root=MAJ:MIN) won't work anymore. 813 Textual device names (root=/dev/sdXn) will continue to work. 814 815 Say N if you are unsure. 816 817config DEBUG_FORCE_WEAK_PER_CPU 818 bool "Force weak per-cpu definitions" 819 depends on DEBUG_KERNEL 820 help 821 s390 and alpha require percpu variables in modules to be 822 defined weak to work around addressing range issue which 823 puts the following two restrictions on percpu variable 824 definitions. 825 826 1. percpu symbols must be unique whether static or not 827 2. percpu variables can't be defined inside a function 828 829 To ensure that generic code follows the above rules, this 830 option forces all percpu variables to be defined as weak. 831 832config LKDTM 833 tristate "Linux Kernel Dump Test Tool Module" 834 depends on DEBUG_KERNEL 835 depends on KPROBES 836 depends on BLOCK 837 default n 838 help 839 This module enables testing of the different dumping mechanisms by 840 inducing system failures at predefined crash points. 841 If you don't need it: say N 842 Choose M here to compile this code as a module. The module will be 843 called lkdtm. 844 845 Documentation on how to use the module can be found in 846 drivers/misc/lkdtm.c 847 848config FAULT_INJECTION 849 bool "Fault-injection framework" 850 depends on DEBUG_KERNEL 851 help 852 Provide fault-injection framework. 853 For more details, see Documentation/fault-injection/. 854 855config FAILSLAB 856 bool "Fault-injection capability for kmalloc" 857 depends on FAULT_INJECTION 858 depends on SLAB || SLUB 859 help 860 Provide fault-injection capability for kmalloc. 861 862config FAIL_PAGE_ALLOC 863 bool "Fault-injection capabilitiy for alloc_pages()" 864 depends on FAULT_INJECTION 865 help 866 Provide fault-injection capability for alloc_pages(). 867 868config FAIL_MAKE_REQUEST 869 bool "Fault-injection capability for disk IO" 870 depends on FAULT_INJECTION && BLOCK 871 help 872 Provide fault-injection capability for disk IO. 873 874config FAIL_IO_TIMEOUT 875 bool "Faul-injection capability for faking disk interrupts" 876 depends on FAULT_INJECTION && BLOCK 877 help 878 Provide fault-injection capability on end IO handling. This 879 will make the block layer "forget" an interrupt as configured, 880 thus exercising the error handling. 881 882 Only works with drivers that use the generic timeout handling, 883 for others it wont do anything. 884 885config FAULT_INJECTION_DEBUG_FS 886 bool "Debugfs entries for fault-injection capabilities" 887 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 888 help 889 Enable configuration of fault-injection capabilities via debugfs. 890 891config FAULT_INJECTION_STACKTRACE_FILTER 892 bool "stacktrace filter for fault-injection capabilities" 893 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 894 depends on !X86_64 895 select STACKTRACE 896 select FRAME_POINTER if !PPC && !S390 897 help 898 Provide stacktrace filter for fault-injection capabilities 899 900config LATENCYTOP 901 bool "Latency measuring infrastructure" 902 select FRAME_POINTER if !MIPS && !PPC && !S390 903 select KALLSYMS 904 select KALLSYMS_ALL 905 select STACKTRACE 906 select SCHEDSTATS 907 select SCHED_DEBUG 908 depends on HAVE_LATENCYTOP_SUPPORT 909 help 910 Enable this option if you want to use the LatencyTOP tool 911 to find out which userspace is blocking on what kernel operations. 912 913config SYSCTL_SYSCALL_CHECK 914 bool "Sysctl checks" 915 depends on SYSCTL_SYSCALL 916 ---help--- 917 sys_sysctl uses binary paths that have been found challenging 918 to properly maintain and use. This enables checks that help 919 you to keep things correct. 920 921source mm/Kconfig.debug 922source kernel/trace/Kconfig 923 924config PROVIDE_OHCI1394_DMA_INIT 925 bool "Remote debugging over FireWire early on boot" 926 depends on PCI && X86 927 help 928 If you want to debug problems which hang or crash the kernel early 929 on boot and the crashing machine has a FireWire port, you can use 930 this feature to remotely access the memory of the crashed machine 931 over FireWire. This employs remote DMA as part of the OHCI1394 932 specification which is now the standard for FireWire controllers. 933 934 With remote DMA, you can monitor the printk buffer remotely using 935 firescope and access all memory below 4GB using fireproxy from gdb. 936 Even controlling a kernel debugger is possible using remote DMA. 937 938 Usage: 939 940 If ohci1394_dma=early is used as boot parameter, it will initialize 941 all OHCI1394 controllers which are found in the PCI config space. 942 943 As all changes to the FireWire bus such as enabling and disabling 944 devices cause a bus reset and thereby disable remote DMA for all 945 devices, be sure to have the cable plugged and FireWire enabled on 946 the debugging host before booting the debug target for debugging. 947 948 This code (~1k) is freed after boot. By then, the firewire stack 949 in charge of the OHCI-1394 controllers should be used instead. 950 951 See Documentation/debugging-via-ohci1394.txt for more information. 952 953config FIREWIRE_OHCI_REMOTE_DMA 954 bool "Remote debugging over FireWire with firewire-ohci" 955 depends on FIREWIRE_OHCI 956 help 957 This option lets you use the FireWire bus for remote debugging 958 with help of the firewire-ohci driver. It enables unfiltered 959 remote DMA in firewire-ohci. 960 See Documentation/debugging-via-ohci1394.txt for more information. 961 962 If unsure, say N. 963 964config BUILD_DOCSRC 965 bool "Build targets in Documentation/ tree" 966 depends on HEADERS_CHECK 967 help 968 This option attempts to build objects from the source files in the 969 kernel Documentation/ tree. 970 971 Say N if you are unsure. 972 973config DYNAMIC_DEBUG 974 bool "Enable dynamic printk() support" 975 default n 976 depends on PRINTK 977 depends on DEBUG_FS 978 help 979 980 Compiles debug level messages into the kernel, which would not 981 otherwise be available at runtime. These messages can then be 982 enabled/disabled based on various levels of scope - per source file, 983 function, module, format string, and line number. This mechanism 984 implicitly enables all pr_debug() and dev_dbg() calls. The impact of 985 this compile option is a larger kernel text size of about 2%. 986 987 Usage: 988 989 Dynamic debugging is controlled via the 'dynamic_debug/ddebug' file, 990 which is contained in the 'debugfs' filesystem. Thus, the debugfs 991 filesystem must first be mounted before making use of this feature. 992 We refer the control file as: <debugfs>/dynamic_debug/ddebug. This 993 file contains a list of the debug statements that can be enabled. The 994 format for each line of the file is: 995 996 filename:lineno [module]function flags format 997 998 filename : source file of the debug statement 999 lineno : line number of the debug statement 1000 module : module that contains the debug statement 1001 function : function that contains the debug statement 1002 flags : 'p' means the line is turned 'on' for printing 1003 format : the format used for the debug statement 1004 1005 From a live system: 1006 1007 nullarbor:~ # cat <debugfs>/dynamic_debug/ddebug 1008 # filename:lineno [module]function flags format 1009 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012" 1010 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012" 1011 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012" 1012 1013 Example usage: 1014 1015 // enable the message at line 1603 of file svcsock.c 1016 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 1017 <debugfs>/dynamic_debug/ddebug 1018 1019 // enable all the messages in file svcsock.c 1020 nullarbor:~ # echo -n 'file svcsock.c +p' > 1021 <debugfs>/dynamic_debug/ddebug 1022 1023 // enable all the messages in the NFS server module 1024 nullarbor:~ # echo -n 'module nfsd +p' > 1025 <debugfs>/dynamic_debug/ddebug 1026 1027 // enable all 12 messages in the function svc_process() 1028 nullarbor:~ # echo -n 'func svc_process +p' > 1029 <debugfs>/dynamic_debug/ddebug 1030 1031 // disable all 12 messages in the function svc_process() 1032 nullarbor:~ # echo -n 'func svc_process -p' > 1033 <debugfs>/dynamic_debug/ddebug 1034 1035 See Documentation/dynamic-debug-howto.txt for additional information. 1036 1037config DMA_API_DEBUG 1038 bool "Enable debugging of DMA-API usage" 1039 depends on HAVE_DMA_API_DEBUG 1040 help 1041 Enable this option to debug the use of the DMA API by device drivers. 1042 With this option you will be able to detect common bugs in device 1043 drivers like double-freeing of DMA mappings or freeing mappings that 1044 were never allocated. 1045 This option causes a performance degredation. Use only if you want 1046 to debug device drivers. If unsure, say N. 1047 1048source "samples/Kconfig" 1049 1050source "lib/Kconfig.kgdb" 1051 1052source "lib/Kconfig.kmemcheck" 1053