1menu "printk and dmesg options" 2 3config PRINTK_TIME 4 bool "Show timing information on printks" 5 depends on PRINTK 6 help 7 Selecting this option causes time stamps of the printk() 8 messages to be added to the output of the syslog() system 9 call and at the console. 10 11 The timestamp is always recorded internally, and exported 12 to /dev/kmsg. This flag just specifies if the timestamp should 13 be included, not that the timestamp is recorded. 14 15 The behavior is also controlled by the kernel command line 16 parameter printk.time=1. See Documentation/kernel-parameters.txt 17 18config DEFAULT_MESSAGE_LOGLEVEL 19 int "Default message log level (1-7)" 20 range 1 7 21 default "4" 22 help 23 Default log level for printk statements with no specified priority. 24 25 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks 26 that are auditing their logs closely may want to set it to a lower 27 priority. 28 29config BOOT_PRINTK_DELAY 30 bool "Delay each boot printk message by N milliseconds" 31 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 32 help 33 This build option allows you to read kernel boot messages 34 by inserting a short delay after each one. The delay is 35 specified in milliseconds on the kernel command line, 36 using "boot_delay=N". 37 38 It is likely that you would also need to use "lpj=M" to preset 39 the "loops per jiffie" value. 40 See a previous boot log for the "lpj" value to use for your 41 system, and then set "lpj=M" before setting "boot_delay=N". 42 NOTE: Using this option may adversely affect SMP systems. 43 I.e., processors other than the first one may not boot up. 44 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect 45 what it believes to be lockup conditions. 46 47config DYNAMIC_DEBUG 48 bool "Enable dynamic printk() support" 49 default n 50 depends on PRINTK 51 depends on DEBUG_FS 52 help 53 54 Compiles debug level messages into the kernel, which would not 55 otherwise be available at runtime. These messages can then be 56 enabled/disabled based on various levels of scope - per source file, 57 function, module, format string, and line number. This mechanism 58 implicitly compiles in all pr_debug() and dev_dbg() calls, which 59 enlarges the kernel text size by about 2%. 60 61 If a source file is compiled with DEBUG flag set, any 62 pr_debug() calls in it are enabled by default, but can be 63 disabled at runtime as below. Note that DEBUG flag is 64 turned on by many CONFIG_*DEBUG* options. 65 66 Usage: 67 68 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 69 which is contained in the 'debugfs' filesystem. Thus, the debugfs 70 filesystem must first be mounted before making use of this feature. 71 We refer the control file as: <debugfs>/dynamic_debug/control. This 72 file contains a list of the debug statements that can be enabled. The 73 format for each line of the file is: 74 75 filename:lineno [module]function flags format 76 77 filename : source file of the debug statement 78 lineno : line number of the debug statement 79 module : module that contains the debug statement 80 function : function that contains the debug statement 81 flags : '=p' means the line is turned 'on' for printing 82 format : the format used for the debug statement 83 84 From a live system: 85 86 nullarbor:~ # cat <debugfs>/dynamic_debug/control 87 # filename:lineno [module]function flags format 88 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012" 89 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012" 90 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012" 91 92 Example usage: 93 94 // enable the message at line 1603 of file svcsock.c 95 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 96 <debugfs>/dynamic_debug/control 97 98 // enable all the messages in file svcsock.c 99 nullarbor:~ # echo -n 'file svcsock.c +p' > 100 <debugfs>/dynamic_debug/control 101 102 // enable all the messages in the NFS server module 103 nullarbor:~ # echo -n 'module nfsd +p' > 104 <debugfs>/dynamic_debug/control 105 106 // enable all 12 messages in the function svc_process() 107 nullarbor:~ # echo -n 'func svc_process +p' > 108 <debugfs>/dynamic_debug/control 109 110 // disable all 12 messages in the function svc_process() 111 nullarbor:~ # echo -n 'func svc_process -p' > 112 <debugfs>/dynamic_debug/control 113 114 See Documentation/dynamic-debug-howto.txt for additional information. 115 116endmenu # "printk and dmesg options" 117 118menu "Compile-time checks and compiler options" 119 120config DEBUG_INFO 121 bool "Compile the kernel with debug info" 122 depends on DEBUG_KERNEL && !COMPILE_TEST 123 help 124 If you say Y here the resulting kernel image will include 125 debugging info resulting in a larger kernel image. 126 This adds debug symbols to the kernel and modules (gcc -g), and 127 is needed if you intend to use kernel crashdump or binary object 128 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 129 Say Y here only if you plan to debug the kernel. 130 131 If unsure, say N. 132 133config DEBUG_INFO_REDUCED 134 bool "Reduce debugging information" 135 depends on DEBUG_INFO 136 help 137 If you say Y here gcc is instructed to generate less debugging 138 information for structure types. This means that tools that 139 need full debugging information (like kgdb or systemtap) won't 140 be happy. But if you merely need debugging information to 141 resolve line numbers there is no loss. Advantage is that 142 build directory object sizes shrink dramatically over a full 143 DEBUG_INFO build and compile times are reduced too. 144 Only works with newer gcc versions. 145 146config ENABLE_WARN_DEPRECATED 147 bool "Enable __deprecated logic" 148 default y 149 help 150 Enable the __deprecated logic in the kernel build. 151 Disable this to suppress the "warning: 'foo' is deprecated 152 (declared at kernel/power/somefile.c:1234)" messages. 153 154config ENABLE_MUST_CHECK 155 bool "Enable __must_check logic" 156 default y 157 help 158 Enable the __must_check logic in the kernel build. Disable this to 159 suppress the "warning: ignoring return value of 'foo', declared with 160 attribute warn_unused_result" messages. 161 162config FRAME_WARN 163 int "Warn for stack frames larger than (needs gcc 4.4)" 164 range 0 8192 165 default 1024 if !64BIT 166 default 2048 if 64BIT 167 help 168 Tell gcc to warn at build time for stack frames larger than this. 169 Setting this too low will cause a lot of warnings. 170 Setting it to 0 disables the warning. 171 Requires gcc 4.4 172 173config STRIP_ASM_SYMS 174 bool "Strip assembler-generated symbols during link" 175 default n 176 help 177 Strip internal assembler-generated symbols during a link (symbols 178 that look like '.Lxxx') so they don't pollute the output of 179 get_wchan() and suchlike. 180 181config READABLE_ASM 182 bool "Generate readable assembler code" 183 depends on DEBUG_KERNEL 184 help 185 Disable some compiler optimizations that tend to generate human unreadable 186 assembler output. This may make the kernel slightly slower, but it helps 187 to keep kernel developers who have to stare a lot at assembler listings 188 sane. 189 190config UNUSED_SYMBOLS 191 bool "Enable unused/obsolete exported symbols" 192 default y if X86 193 help 194 Unused but exported symbols make the kernel needlessly bigger. For 195 that reason most of these unused exports will soon be removed. This 196 option is provided temporarily to provide a transition period in case 197 some external kernel module needs one of these symbols anyway. If you 198 encounter such a case in your module, consider if you are actually 199 using the right API. (rationale: since nobody in the kernel is using 200 this in a module, there is a pretty good chance it's actually the 201 wrong interface to use). If you really need the symbol, please send a 202 mail to the linux kernel mailing list mentioning the symbol and why 203 you really need it, and what the merge plan to the mainline kernel for 204 your module is. 205 206config DEBUG_FS 207 bool "Debug Filesystem" 208 help 209 debugfs is a virtual file system that kernel developers use to put 210 debugging files into. Enable this option to be able to read and 211 write to these files. 212 213 For detailed documentation on the debugfs API, see 214 Documentation/DocBook/filesystems. 215 216 If unsure, say N. 217 218config HEADERS_CHECK 219 bool "Run 'make headers_check' when building vmlinux" 220 depends on !UML 221 help 222 This option will extract the user-visible kernel headers whenever 223 building the kernel, and will run basic sanity checks on them to 224 ensure that exported files do not attempt to include files which 225 were not exported, etc. 226 227 If you're making modifications to header files which are 228 relevant for userspace, say 'Y', and check the headers 229 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 230 your build tree), to make sure they're suitable. 231 232config DEBUG_SECTION_MISMATCH 233 bool "Enable full Section mismatch analysis" 234 help 235 The section mismatch analysis checks if there are illegal 236 references from one section to another section. 237 During linktime or runtime, some sections are dropped; 238 any use of code/data previously in these sections would 239 most likely result in an oops. 240 In the code, functions and variables are annotated with 241 __init,, etc. (see the full list in include/linux/init.h), 242 which results in the code/data being placed in specific sections. 243 The section mismatch analysis is always performed after a full 244 kernel build, and enabling this option causes the following 245 additional steps to occur: 246 - Add the option -fno-inline-functions-called-once to gcc commands. 247 When inlining a function annotated with __init in a non-init 248 function, we would lose the section information and thus 249 the analysis would not catch the illegal reference. 250 This option tells gcc to inline less (but it does result in 251 a larger kernel). 252 - Run the section mismatch analysis for each module/built-in.o file. 253 When we run the section mismatch analysis on vmlinux.o, we 254 lose valueble information about where the mismatch was 255 introduced. 256 Running the analysis for each module/built-in.o file 257 tells where the mismatch happens much closer to the 258 source. The drawback is that the same mismatch is 259 reported at least twice. 260 - Enable verbose reporting from modpost in order to help resolve 261 the section mismatches that are reported. 262 263# 264# Select this config option from the architecture Kconfig, if it 265# is preferred to always offer frame pointers as a config 266# option on the architecture (regardless of KERNEL_DEBUG): 267# 268config ARCH_WANT_FRAME_POINTERS 269 bool 270 help 271 272config FRAME_POINTER 273 bool "Compile the kernel with frame pointers" 274 depends on DEBUG_KERNEL && \ 275 (CRIS || M68K || FRV || UML || \ 276 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \ 277 ARCH_WANT_FRAME_POINTERS 278 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 279 help 280 If you say Y here the resulting kernel image will be slightly 281 larger and slower, but it gives very useful debugging information 282 in case of kernel bugs. (precise oopses/stacktraces/warnings) 283 284config DEBUG_FORCE_WEAK_PER_CPU 285 bool "Force weak per-cpu definitions" 286 depends on DEBUG_KERNEL 287 help 288 s390 and alpha require percpu variables in modules to be 289 defined weak to work around addressing range issue which 290 puts the following two restrictions on percpu variable 291 definitions. 292 293 1. percpu symbols must be unique whether static or not 294 2. percpu variables can't be defined inside a function 295 296 To ensure that generic code follows the above rules, this 297 option forces all percpu variables to be defined as weak. 298 299endmenu # "Compiler options" 300 301config MAGIC_SYSRQ 302 bool "Magic SysRq key" 303 depends on !UML 304 help 305 If you say Y here, you will have some control over the system even 306 if the system crashes for example during kernel debugging (e.g., you 307 will be able to flush the buffer cache to disk, reboot the system 308 immediately or dump some status information). This is accomplished 309 by pressing various keys while holding SysRq (Alt+PrintScreen). It 310 also works on a serial console (on PC hardware at least), if you 311 send a BREAK and then within 5 seconds a command keypress. The 312 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 313 unless you really know what this hack does. 314 315config MAGIC_SYSRQ_DEFAULT_ENABLE 316 hex "Enable magic SysRq key functions by default" 317 depends on MAGIC_SYSRQ 318 default 0x1 319 help 320 Specifies which SysRq key functions are enabled by default. 321 This may be set to 1 or 0 to enable or disable them all, or 322 to a bitmask as described in Documentation/sysrq.txt. 323 324config DEBUG_KERNEL 325 bool "Kernel debugging" 326 help 327 Say Y here if you are developing drivers or trying to debug and 328 identify kernel problems. 329 330menu "Memory Debugging" 331 332source mm/Kconfig.debug 333 334config DEBUG_OBJECTS 335 bool "Debug object operations" 336 depends on DEBUG_KERNEL 337 help 338 If you say Y here, additional code will be inserted into the 339 kernel to track the life time of various objects and validate 340 the operations on those objects. 341 342config DEBUG_OBJECTS_SELFTEST 343 bool "Debug objects selftest" 344 depends on DEBUG_OBJECTS 345 help 346 This enables the selftest of the object debug code. 347 348config DEBUG_OBJECTS_FREE 349 bool "Debug objects in freed memory" 350 depends on DEBUG_OBJECTS 351 help 352 This enables checks whether a k/v free operation frees an area 353 which contains an object which has not been deactivated 354 properly. This can make kmalloc/kfree-intensive workloads 355 much slower. 356 357config DEBUG_OBJECTS_TIMERS 358 bool "Debug timer objects" 359 depends on DEBUG_OBJECTS 360 help 361 If you say Y here, additional code will be inserted into the 362 timer routines to track the life time of timer objects and 363 validate the timer operations. 364 365config DEBUG_OBJECTS_WORK 366 bool "Debug work objects" 367 depends on DEBUG_OBJECTS 368 help 369 If you say Y here, additional code will be inserted into the 370 work queue routines to track the life time of work objects and 371 validate the work operations. 372 373config DEBUG_OBJECTS_RCU_HEAD 374 bool "Debug RCU callbacks objects" 375 depends on DEBUG_OBJECTS 376 help 377 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 378 379config DEBUG_OBJECTS_PERCPU_COUNTER 380 bool "Debug percpu counter objects" 381 depends on DEBUG_OBJECTS 382 help 383 If you say Y here, additional code will be inserted into the 384 percpu counter routines to track the life time of percpu counter 385 objects and validate the percpu counter operations. 386 387config DEBUG_OBJECTS_ENABLE_DEFAULT 388 int "debug_objects bootup default value (0-1)" 389 range 0 1 390 default "1" 391 depends on DEBUG_OBJECTS 392 help 393 Debug objects boot parameter default value 394 395config DEBUG_SLAB 396 bool "Debug slab memory allocations" 397 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 398 help 399 Say Y here to have the kernel do limited verification on memory 400 allocation as well as poisoning memory on free to catch use of freed 401 memory. This can make kmalloc/kfree-intensive workloads much slower. 402 403config DEBUG_SLAB_LEAK 404 bool "Memory leak debugging" 405 depends on DEBUG_SLAB 406 407config SLUB_DEBUG_ON 408 bool "SLUB debugging on by default" 409 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 410 default n 411 help 412 Boot with debugging on by default. SLUB boots by default with 413 the runtime debug capabilities switched off. Enabling this is 414 equivalent to specifying the "slub_debug" parameter on boot. 415 There is no support for more fine grained debug control like 416 possible with slub_debug=xxx. SLUB debugging may be switched 417 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 418 "slub_debug=-". 419 420config SLUB_STATS 421 default n 422 bool "Enable SLUB performance statistics" 423 depends on SLUB && SYSFS 424 help 425 SLUB statistics are useful to debug SLUBs allocation behavior in 426 order find ways to optimize the allocator. This should never be 427 enabled for production use since keeping statistics slows down 428 the allocator by a few percentage points. The slabinfo command 429 supports the determination of the most active slabs to figure 430 out which slabs are relevant to a particular load. 431 Try running: slabinfo -DA 432 433config HAVE_DEBUG_KMEMLEAK 434 bool 435 436config DEBUG_KMEMLEAK 437 bool "Kernel memory leak detector" 438 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 439 select DEBUG_FS 440 select STACKTRACE if STACKTRACE_SUPPORT 441 select KALLSYMS 442 select CRC32 443 help 444 Say Y here if you want to enable the memory leak 445 detector. The memory allocation/freeing is traced in a way 446 similar to the Boehm's conservative garbage collector, the 447 difference being that the orphan objects are not freed but 448 only shown in /sys/kernel/debug/kmemleak. Enabling this 449 feature will introduce an overhead to memory 450 allocations. See Documentation/kmemleak.txt for more 451 details. 452 453 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 454 of finding leaks due to the slab objects poisoning. 455 456 In order to access the kmemleak file, debugfs needs to be 457 mounted (usually at /sys/kernel/debug). 458 459config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 460 int "Maximum kmemleak early log entries" 461 depends on DEBUG_KMEMLEAK 462 range 200 40000 463 default 400 464 help 465 Kmemleak must track all the memory allocations to avoid 466 reporting false positives. Since memory may be allocated or 467 freed before kmemleak is initialised, an early log buffer is 468 used to store these actions. If kmemleak reports "early log 469 buffer exceeded", please increase this value. 470 471config DEBUG_KMEMLEAK_TEST 472 tristate "Simple test for the kernel memory leak detector" 473 depends on DEBUG_KMEMLEAK && m 474 help 475 This option enables a module that explicitly leaks memory. 476 477 If unsure, say N. 478 479config DEBUG_KMEMLEAK_DEFAULT_OFF 480 bool "Default kmemleak to off" 481 depends on DEBUG_KMEMLEAK 482 help 483 Say Y here to disable kmemleak by default. It can then be enabled 484 on the command line via kmemleak=on. 485 486config DEBUG_STACK_USAGE 487 bool "Stack utilization instrumentation" 488 depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAG 489 help 490 Enables the display of the minimum amount of free stack which each 491 task has ever had available in the sysrq-T and sysrq-P debug output. 492 493 This option will slow down process creation somewhat. 494 495config DEBUG_VM 496 bool "Debug VM" 497 depends on DEBUG_KERNEL 498 help 499 Enable this to turn on extended checks in the virtual-memory system 500 that may impact performance. 501 502 If unsure, say N. 503 504config DEBUG_VM_RB 505 bool "Debug VM red-black trees" 506 depends on DEBUG_VM 507 help 508 Enable VM red-black tree debugging information and extra validations. 509 510 If unsure, say N. 511 512config DEBUG_VIRTUAL 513 bool "Debug VM translations" 514 depends on DEBUG_KERNEL && X86 515 help 516 Enable some costly sanity checks in virtual to page code. This can 517 catch mistakes with virt_to_page() and friends. 518 519 If unsure, say N. 520 521config DEBUG_NOMMU_REGIONS 522 bool "Debug the global anon/private NOMMU mapping region tree" 523 depends on DEBUG_KERNEL && !MMU 524 help 525 This option causes the global tree of anonymous and private mapping 526 regions to be regularly checked for invalid topology. 527 528config DEBUG_MEMORY_INIT 529 bool "Debug memory initialisation" if EXPERT 530 default !EXPERT 531 help 532 Enable this for additional checks during memory initialisation. 533 The sanity checks verify aspects of the VM such as the memory model 534 and other information provided by the architecture. Verbose 535 information will be printed at KERN_DEBUG loglevel depending 536 on the mminit_loglevel= command-line option. 537 538 If unsure, say Y 539 540config MEMORY_NOTIFIER_ERROR_INJECT 541 tristate "Memory hotplug notifier error injection module" 542 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 543 help 544 This option provides the ability to inject artificial errors to 545 memory hotplug notifier chain callbacks. It is controlled through 546 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 547 548 If the notifier call chain should be failed with some events 549 notified, write the error code to "actions/<notifier event>/error". 550 551 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 552 553 # cd /sys/kernel/debug/notifier-error-inject/memory 554 # echo -12 > actions/MEM_GOING_OFFLINE/error 555 # echo offline > /sys/devices/system/memory/memoryXXX/state 556 bash: echo: write error: Cannot allocate memory 557 558 To compile this code as a module, choose M here: the module will 559 be called memory-notifier-error-inject. 560 561 If unsure, say N. 562 563config DEBUG_PER_CPU_MAPS 564 bool "Debug access to per_cpu maps" 565 depends on DEBUG_KERNEL 566 depends on SMP 567 help 568 Say Y to verify that the per_cpu map being accessed has 569 been set up. This adds a fair amount of code to kernel memory 570 and decreases performance. 571 572 Say N if unsure. 573 574config DEBUG_HIGHMEM 575 bool "Highmem debugging" 576 depends on DEBUG_KERNEL && HIGHMEM 577 help 578 This options enables addition error checking for high memory systems. 579 Disable for production systems. 580 581config HAVE_DEBUG_STACKOVERFLOW 582 bool 583 584config DEBUG_STACKOVERFLOW 585 bool "Check for stack overflows" 586 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 587 ---help--- 588 Say Y here if you want to check for overflows of kernel, IRQ 589 and exception stacks (if your archicture uses them). This 590 option will show detailed messages if free stack space drops 591 below a certain limit. 592 593 These kinds of bugs usually occur when call-chains in the 594 kernel get too deep, especially when interrupts are 595 involved. 596 597 Use this in cases where you see apparently random memory 598 corruption, especially if it appears in 'struct thread_info' 599 600 If in doubt, say "N". 601 602source "lib/Kconfig.kmemcheck" 603 604endmenu # "Memory Debugging" 605 606config DEBUG_SHIRQ 607 bool "Debug shared IRQ handlers" 608 depends on DEBUG_KERNEL 609 help 610 Enable this to generate a spurious interrupt as soon as a shared 611 interrupt handler is registered, and just before one is deregistered. 612 Drivers ought to be able to handle interrupts coming in at those 613 points; some don't and need to be caught. 614 615menu "Debug Lockups and Hangs" 616 617config LOCKUP_DETECTOR 618 bool "Detect Hard and Soft Lockups" 619 depends on DEBUG_KERNEL && !S390 620 help 621 Say Y here to enable the kernel to act as a watchdog to detect 622 hard and soft lockups. 623 624 Softlockups are bugs that cause the kernel to loop in kernel 625 mode for more than 20 seconds, without giving other tasks a 626 chance to run. The current stack trace is displayed upon 627 detection and the system will stay locked up. 628 629 Hardlockups are bugs that cause the CPU to loop in kernel mode 630 for more than 10 seconds, without letting other interrupts have a 631 chance to run. The current stack trace is displayed upon detection 632 and the system will stay locked up. 633 634 The overhead should be minimal. A periodic hrtimer runs to 635 generate interrupts and kick the watchdog task every 4 seconds. 636 An NMI is generated every 10 seconds or so to check for hardlockups. 637 638 The frequency of hrtimer and NMI events and the soft and hard lockup 639 thresholds can be controlled through the sysctl watchdog_thresh. 640 641config HARDLOCKUP_DETECTOR 642 def_bool y 643 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 644 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 645 646config BOOTPARAM_HARDLOCKUP_PANIC 647 bool "Panic (Reboot) On Hard Lockups" 648 depends on HARDLOCKUP_DETECTOR 649 help 650 Say Y here to enable the kernel to panic on "hard lockups", 651 which are bugs that cause the kernel to loop in kernel 652 mode with interrupts disabled for more than 10 seconds (configurable 653 using the watchdog_thresh sysctl). 654 655 Say N if unsure. 656 657config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 658 int 659 depends on HARDLOCKUP_DETECTOR 660 range 0 1 661 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 662 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 663 664config BOOTPARAM_SOFTLOCKUP_PANIC 665 bool "Panic (Reboot) On Soft Lockups" 666 depends on LOCKUP_DETECTOR 667 help 668 Say Y here to enable the kernel to panic on "soft lockups", 669 which are bugs that cause the kernel to loop in kernel 670 mode for more than 20 seconds (configurable using the watchdog_thresh 671 sysctl), without giving other tasks a chance to run. 672 673 The panic can be used in combination with panic_timeout, 674 to cause the system to reboot automatically after a 675 lockup has been detected. This feature is useful for 676 high-availability systems that have uptime guarantees and 677 where a lockup must be resolved ASAP. 678 679 Say N if unsure. 680 681config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 682 int 683 depends on LOCKUP_DETECTOR 684 range 0 1 685 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 686 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 687 688config DETECT_HUNG_TASK 689 bool "Detect Hung Tasks" 690 depends on DEBUG_KERNEL 691 default LOCKUP_DETECTOR 692 help 693 Say Y here to enable the kernel to detect "hung tasks", 694 which are bugs that cause the task to be stuck in 695 uninterruptible "D" state indefinitiley. 696 697 When a hung task is detected, the kernel will print the 698 current stack trace (which you should report), but the 699 task will stay in uninterruptible state. If lockdep is 700 enabled then all held locks will also be reported. This 701 feature has negligible overhead. 702 703config DEFAULT_HUNG_TASK_TIMEOUT 704 int "Default timeout for hung task detection (in seconds)" 705 depends on DETECT_HUNG_TASK 706 default 120 707 help 708 This option controls the default timeout (in seconds) used 709 to determine when a task has become non-responsive and should 710 be considered hung. 711 712 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 713 sysctl or by writing a value to 714 /proc/sys/kernel/hung_task_timeout_secs. 715 716 A timeout of 0 disables the check. The default is two minutes. 717 Keeping the default should be fine in most cases. 718 719config BOOTPARAM_HUNG_TASK_PANIC 720 bool "Panic (Reboot) On Hung Tasks" 721 depends on DETECT_HUNG_TASK 722 help 723 Say Y here to enable the kernel to panic on "hung tasks", 724 which are bugs that cause the kernel to leave a task stuck 725 in uninterruptible "D" state. 726 727 The panic can be used in combination with panic_timeout, 728 to cause the system to reboot automatically after a 729 hung task has been detected. This feature is useful for 730 high-availability systems that have uptime guarantees and 731 where a hung tasks must be resolved ASAP. 732 733 Say N if unsure. 734 735config BOOTPARAM_HUNG_TASK_PANIC_VALUE 736 int 737 depends on DETECT_HUNG_TASK 738 range 0 1 739 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 740 default 1 if BOOTPARAM_HUNG_TASK_PANIC 741 742endmenu # "Debug lockups and hangs" 743 744config PANIC_ON_OOPS 745 bool "Panic on Oops" 746 help 747 Say Y here to enable the kernel to panic when it oopses. This 748 has the same effect as setting oops=panic on the kernel command 749 line. 750 751 This feature is useful to ensure that the kernel does not do 752 anything erroneous after an oops which could result in data 753 corruption or other issues. 754 755 Say N if unsure. 756 757config PANIC_ON_OOPS_VALUE 758 int 759 range 0 1 760 default 0 if !PANIC_ON_OOPS 761 default 1 if PANIC_ON_OOPS 762 763config PANIC_TIMEOUT 764 int "panic timeout" 765 default 0 766 help 767 Set the timeout value (in seconds) until a reboot occurs when the 768 the kernel panics. If n = 0, then we wait forever. A timeout 769 value n > 0 will wait n seconds before rebooting, while a timeout 770 value n < 0 will reboot immediately. 771 772config SCHED_DEBUG 773 bool "Collect scheduler debugging info" 774 depends on DEBUG_KERNEL && PROC_FS 775 default y 776 help 777 If you say Y here, the /proc/sched_debug file will be provided 778 that can help debug the scheduler. The runtime overhead of this 779 option is minimal. 780 781config SCHEDSTATS 782 bool "Collect scheduler statistics" 783 depends on DEBUG_KERNEL && PROC_FS 784 help 785 If you say Y here, additional code will be inserted into the 786 scheduler and related routines to collect statistics about 787 scheduler behavior and provide them in /proc/schedstat. These 788 stats may be useful for both tuning and debugging the scheduler 789 If you aren't debugging the scheduler or trying to tune a specific 790 application, you can say N to avoid the very slight overhead 791 this adds. 792 793config TIMER_STATS 794 bool "Collect kernel timers statistics" 795 depends on DEBUG_KERNEL && PROC_FS 796 help 797 If you say Y here, additional code will be inserted into the 798 timer routines to collect statistics about kernel timers being 799 reprogrammed. The statistics can be read from /proc/timer_stats. 800 The statistics collection is started by writing 1 to /proc/timer_stats, 801 writing 0 stops it. This feature is useful to collect information 802 about timer usage patterns in kernel and userspace. This feature 803 is lightweight if enabled in the kernel config but not activated 804 (it defaults to deactivated on bootup and will only be activated 805 if some application like powertop activates it explicitly). 806 807config DEBUG_PREEMPT 808 bool "Debug preemptible kernel" 809 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 810 default y 811 help 812 If you say Y here then the kernel will use a debug variant of the 813 commonly used smp_processor_id() function and will print warnings 814 if kernel code uses it in a preemption-unsafe way. Also, the kernel 815 will detect preemption count underflows. 816 817menu "Lock Debugging (spinlocks, mutexes, etc...)" 818 819config DEBUG_RT_MUTEXES 820 bool "RT Mutex debugging, deadlock detection" 821 depends on DEBUG_KERNEL && RT_MUTEXES 822 help 823 This allows rt mutex semantics violations and rt mutex related 824 deadlocks (lockups) to be detected and reported automatically. 825 826config DEBUG_PI_LIST 827 bool 828 default y 829 depends on DEBUG_RT_MUTEXES 830 831config RT_MUTEX_TESTER 832 bool "Built-in scriptable tester for rt-mutexes" 833 depends on DEBUG_KERNEL && RT_MUTEXES 834 help 835 This option enables a rt-mutex tester. 836 837config DEBUG_SPINLOCK 838 bool "Spinlock and rw-lock debugging: basic checks" 839 depends on DEBUG_KERNEL 840 select UNINLINE_SPIN_UNLOCK 841 help 842 Say Y here and build SMP to catch missing spinlock initialization 843 and certain other kinds of spinlock errors commonly made. This is 844 best used in conjunction with the NMI watchdog so that spinlock 845 deadlocks are also debuggable. 846 847config DEBUG_MUTEXES 848 bool "Mutex debugging: basic checks" 849 depends on DEBUG_KERNEL 850 help 851 This feature allows mutex semantics violations to be detected and 852 reported. 853 854config DEBUG_WW_MUTEX_SLOWPATH 855 bool "Wait/wound mutex debugging: Slowpath testing" 856 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 857 select DEBUG_LOCK_ALLOC 858 select DEBUG_SPINLOCK 859 select DEBUG_MUTEXES 860 help 861 This feature enables slowpath testing for w/w mutex users by 862 injecting additional -EDEADLK wound/backoff cases. Together with 863 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 864 will test all possible w/w mutex interface abuse with the 865 exception of simply not acquiring all the required locks. 866 867config DEBUG_LOCK_ALLOC 868 bool "Lock debugging: detect incorrect freeing of live locks" 869 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 870 select DEBUG_SPINLOCK 871 select DEBUG_MUTEXES 872 select LOCKDEP 873 help 874 This feature will check whether any held lock (spinlock, rwlock, 875 mutex or rwsem) is incorrectly freed by the kernel, via any of the 876 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 877 vfree(), etc.), whether a live lock is incorrectly reinitialized via 878 spin_lock_init()/mutex_init()/etc., or whether there is any lock 879 held during task exit. 880 881config PROVE_LOCKING 882 bool "Lock debugging: prove locking correctness" 883 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 884 select LOCKDEP 885 select DEBUG_SPINLOCK 886 select DEBUG_MUTEXES 887 select DEBUG_LOCK_ALLOC 888 select TRACE_IRQFLAGS 889 default n 890 help 891 This feature enables the kernel to prove that all locking 892 that occurs in the kernel runtime is mathematically 893 correct: that under no circumstance could an arbitrary (and 894 not yet triggered) combination of observed locking 895 sequences (on an arbitrary number of CPUs, running an 896 arbitrary number of tasks and interrupt contexts) cause a 897 deadlock. 898 899 In short, this feature enables the kernel to report locking 900 related deadlocks before they actually occur. 901 902 The proof does not depend on how hard and complex a 903 deadlock scenario would be to trigger: how many 904 participant CPUs, tasks and irq-contexts would be needed 905 for it to trigger. The proof also does not depend on 906 timing: if a race and a resulting deadlock is possible 907 theoretically (no matter how unlikely the race scenario 908 is), it will be proven so and will immediately be 909 reported by the kernel (once the event is observed that 910 makes the deadlock theoretically possible). 911 912 If a deadlock is impossible (i.e. the locking rules, as 913 observed by the kernel, are mathematically correct), the 914 kernel reports nothing. 915 916 NOTE: this feature can also be enabled for rwlocks, mutexes 917 and rwsems - in which case all dependencies between these 918 different locking variants are observed and mapped too, and 919 the proof of observed correctness is also maintained for an 920 arbitrary combination of these separate locking variants. 921 922 For more details, see Documentation/lockdep-design.txt. 923 924config LOCKDEP 925 bool 926 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 927 select STACKTRACE 928 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC 929 select KALLSYMS 930 select KALLSYMS_ALL 931 932config LOCK_STAT 933 bool "Lock usage statistics" 934 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 935 select LOCKDEP 936 select DEBUG_SPINLOCK 937 select DEBUG_MUTEXES 938 select DEBUG_LOCK_ALLOC 939 default n 940 help 941 This feature enables tracking lock contention points 942 943 For more details, see Documentation/lockstat.txt 944 945 This also enables lock events required by "perf lock", 946 subcommand of perf. 947 If you want to use "perf lock", you also need to turn on 948 CONFIG_EVENT_TRACING. 949 950 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 951 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 952 953config DEBUG_LOCKDEP 954 bool "Lock dependency engine debugging" 955 depends on DEBUG_KERNEL && LOCKDEP 956 help 957 If you say Y here, the lock dependency engine will do 958 additional runtime checks to debug itself, at the price 959 of more runtime overhead. 960 961config DEBUG_ATOMIC_SLEEP 962 bool "Sleep inside atomic section checking" 963 select PREEMPT_COUNT 964 depends on DEBUG_KERNEL 965 help 966 If you say Y here, various routines which may sleep will become very 967 noisy if they are called inside atomic sections: when a spinlock is 968 held, inside an rcu read side critical section, inside preempt disabled 969 sections, inside an interrupt, etc... 970 971config DEBUG_LOCKING_API_SELFTESTS 972 bool "Locking API boot-time self-tests" 973 depends on DEBUG_KERNEL 974 help 975 Say Y here if you want the kernel to run a short self-test during 976 bootup. The self-test checks whether common types of locking bugs 977 are detected by debugging mechanisms or not. (if you disable 978 lock debugging then those bugs wont be detected of course.) 979 The following locking APIs are covered: spinlocks, rwlocks, 980 mutexes and rwsems. 981 982config LOCK_TORTURE_TEST 983 tristate "torture tests for locking" 984 depends on DEBUG_KERNEL 985 select TORTURE_TEST 986 default n 987 help 988 This option provides a kernel module that runs torture tests 989 on kernel locking primitives. The kernel module may be built 990 after the fact on the running kernel to be tested, if desired. 991 992 Say Y here if you want kernel locking-primitive torture tests 993 to be built into the kernel. 994 Say M if you want these torture tests to build as a module. 995 Say N if you are unsure. 996 997endmenu # lock debugging 998 999config TRACE_IRQFLAGS 1000 bool 1001 help 1002 Enables hooks to interrupt enabling and disabling for 1003 either tracing or lock debugging. 1004 1005config STACKTRACE 1006 bool 1007 depends on STACKTRACE_SUPPORT 1008 1009config DEBUG_KOBJECT 1010 bool "kobject debugging" 1011 depends on DEBUG_KERNEL 1012 help 1013 If you say Y here, some extra kobject debugging messages will be sent 1014 to the syslog. 1015 1016config DEBUG_KOBJECT_RELEASE 1017 bool "kobject release debugging" 1018 depends on DEBUG_OBJECTS_TIMERS 1019 help 1020 kobjects are reference counted objects. This means that their 1021 last reference count put is not predictable, and the kobject can 1022 live on past the point at which a driver decides to drop it's 1023 initial reference to the kobject gained on allocation. An 1024 example of this would be a struct device which has just been 1025 unregistered. 1026 1027 However, some buggy drivers assume that after such an operation, 1028 the memory backing the kobject can be immediately freed. This 1029 goes completely against the principles of a refcounted object. 1030 1031 If you say Y here, the kernel will delay the release of kobjects 1032 on the last reference count to improve the visibility of this 1033 kind of kobject release bug. 1034 1035config HAVE_DEBUG_BUGVERBOSE 1036 bool 1037 1038config DEBUG_BUGVERBOSE 1039 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1040 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1041 default y 1042 help 1043 Say Y here to make BUG() panics output the file name and line number 1044 of the BUG call as well as the EIP and oops trace. This aids 1045 debugging but costs about 70-100K of memory. 1046 1047config DEBUG_LIST 1048 bool "Debug linked list manipulation" 1049 depends on DEBUG_KERNEL 1050 help 1051 Enable this to turn on extended checks in the linked-list 1052 walking routines. 1053 1054 If unsure, say N. 1055 1056config DEBUG_SG 1057 bool "Debug SG table operations" 1058 depends on DEBUG_KERNEL 1059 help 1060 Enable this to turn on checks on scatter-gather tables. This can 1061 help find problems with drivers that do not properly initialize 1062 their sg tables. 1063 1064 If unsure, say N. 1065 1066config DEBUG_NOTIFIERS 1067 bool "Debug notifier call chains" 1068 depends on DEBUG_KERNEL 1069 help 1070 Enable this to turn on sanity checking for notifier call chains. 1071 This is most useful for kernel developers to make sure that 1072 modules properly unregister themselves from notifier chains. 1073 This is a relatively cheap check but if you care about maximum 1074 performance, say N. 1075 1076config DEBUG_CREDENTIALS 1077 bool "Debug credential management" 1078 depends on DEBUG_KERNEL 1079 help 1080 Enable this to turn on some debug checking for credential 1081 management. The additional code keeps track of the number of 1082 pointers from task_structs to any given cred struct, and checks to 1083 see that this number never exceeds the usage count of the cred 1084 struct. 1085 1086 Furthermore, if SELinux is enabled, this also checks that the 1087 security pointer in the cred struct is never seen to be invalid. 1088 1089 If unsure, say N. 1090 1091menu "RCU Debugging" 1092 1093config PROVE_RCU 1094 bool "RCU debugging: prove RCU correctness" 1095 depends on PROVE_LOCKING 1096 default n 1097 help 1098 This feature enables lockdep extensions that check for correct 1099 use of RCU APIs. This is currently under development. Say Y 1100 if you want to debug RCU usage or help work on the PROVE_RCU 1101 feature. 1102 1103 Say N if you are unsure. 1104 1105config PROVE_RCU_REPEATEDLY 1106 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1107 depends on PROVE_RCU 1108 default n 1109 help 1110 By itself, PROVE_RCU will disable checking upon issuing the 1111 first warning (or "splat"). This feature prevents such 1112 disabling, allowing multiple RCU-lockdep warnings to be printed 1113 on a single reboot. 1114 1115 Say Y to allow multiple RCU-lockdep warnings per boot. 1116 1117 Say N if you are unsure. 1118 1119config PROVE_RCU_DELAY 1120 bool "RCU debugging: preemptible RCU race provocation" 1121 depends on DEBUG_KERNEL && PREEMPT_RCU 1122 default n 1123 help 1124 There is a class of races that involve an unlikely preemption 1125 of __rcu_read_unlock() just after ->rcu_read_lock_nesting has 1126 been set to INT_MIN. This feature inserts a delay at that 1127 point to increase the probability of these races. 1128 1129 Say Y to increase probability of preemption of __rcu_read_unlock(). 1130 1131 Say N if you are unsure. 1132 1133config SPARSE_RCU_POINTER 1134 bool "RCU debugging: sparse-based checks for pointer usage" 1135 default n 1136 help 1137 This feature enables the __rcu sparse annotation for 1138 RCU-protected pointers. This annotation will cause sparse 1139 to flag any non-RCU used of annotated pointers. This can be 1140 helpful when debugging RCU usage. Please note that this feature 1141 is not intended to enforce code cleanliness; it is instead merely 1142 a debugging aid. 1143 1144 Say Y to make sparse flag questionable use of RCU-protected pointers 1145 1146 Say N if you are unsure. 1147 1148config TORTURE_TEST 1149 tristate 1150 default n 1151 1152config RCU_TORTURE_TEST 1153 tristate "torture tests for RCU" 1154 depends on DEBUG_KERNEL 1155 select TORTURE_TEST 1156 default n 1157 help 1158 This option provides a kernel module that runs torture tests 1159 on the RCU infrastructure. The kernel module may be built 1160 after the fact on the running kernel to be tested, if desired. 1161 1162 Say Y here if you want RCU torture tests to be built into 1163 the kernel. 1164 Say M if you want the RCU torture tests to build as a module. 1165 Say N if you are unsure. 1166 1167config RCU_TORTURE_TEST_RUNNABLE 1168 bool "torture tests for RCU runnable by default" 1169 depends on RCU_TORTURE_TEST = y 1170 default n 1171 help 1172 This option provides a way to build the RCU torture tests 1173 directly into the kernel without them starting up at boot 1174 time. You can use /proc/sys/kernel/rcutorture_runnable 1175 to manually override this setting. This /proc file is 1176 available only when the RCU torture tests have been built 1177 into the kernel. 1178 1179 Say Y here if you want the RCU torture tests to start during 1180 boot (you probably don't). 1181 Say N here if you want the RCU torture tests to start only 1182 after being manually enabled via /proc. 1183 1184config RCU_CPU_STALL_TIMEOUT 1185 int "RCU CPU stall timeout in seconds" 1186 depends on RCU_STALL_COMMON 1187 range 3 300 1188 default 21 1189 help 1190 If a given RCU grace period extends more than the specified 1191 number of seconds, a CPU stall warning is printed. If the 1192 RCU grace period persists, additional CPU stall warnings are 1193 printed at more widely spaced intervals. 1194 1195config RCU_CPU_STALL_VERBOSE 1196 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" 1197 depends on TREE_PREEMPT_RCU 1198 default y 1199 help 1200 This option causes RCU to printk detailed per-task information 1201 for any tasks that are stalling the current RCU grace period. 1202 1203 Say N if you are unsure. 1204 1205 Say Y if you want to enable such checks. 1206 1207config RCU_CPU_STALL_INFO 1208 bool "Print additional diagnostics on RCU CPU stall" 1209 depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL 1210 default n 1211 help 1212 For each stalled CPU that is aware of the current RCU grace 1213 period, print out additional per-CPU diagnostic information 1214 regarding scheduling-clock ticks, idle state, and, 1215 for RCU_FAST_NO_HZ kernels, idle-entry state. 1216 1217 Say N if you are unsure. 1218 1219 Say Y if you want to enable such diagnostics. 1220 1221config RCU_TRACE 1222 bool "Enable tracing for RCU" 1223 depends on DEBUG_KERNEL 1224 select TRACE_CLOCK 1225 help 1226 This option provides tracing in RCU which presents stats 1227 in debugfs for debugging RCU implementation. 1228 1229 Say Y here if you want to enable RCU tracing 1230 Say N if you are unsure. 1231 1232endmenu # "RCU Debugging" 1233 1234config DEBUG_BLOCK_EXT_DEVT 1235 bool "Force extended block device numbers and spread them" 1236 depends on DEBUG_KERNEL 1237 depends on BLOCK 1238 default n 1239 help 1240 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1241 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1242 YOU ARE DOING. Distros, please enable this and fix whatever 1243 is broken. 1244 1245 Conventionally, block device numbers are allocated from 1246 predetermined contiguous area. However, extended block area 1247 may introduce non-contiguous block device numbers. This 1248 option forces most block device numbers to be allocated from 1249 the extended space and spreads them to discover kernel or 1250 userland code paths which assume predetermined contiguous 1251 device number allocation. 1252 1253 Note that turning on this debug option shuffles all the 1254 device numbers for all IDE and SCSI devices including libata 1255 ones, so root partition specified using device number 1256 directly (via rdev or root=MAJ:MIN) won't work anymore. 1257 Textual device names (root=/dev/sdXn) will continue to work. 1258 1259 Say N if you are unsure. 1260 1261config NOTIFIER_ERROR_INJECTION 1262 tristate "Notifier error injection" 1263 depends on DEBUG_KERNEL 1264 select DEBUG_FS 1265 help 1266 This option provides the ability to inject artificial errors to 1267 specified notifier chain callbacks. It is useful to test the error 1268 handling of notifier call chain failures. 1269 1270 Say N if unsure. 1271 1272config CPU_NOTIFIER_ERROR_INJECT 1273 tristate "CPU notifier error injection module" 1274 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1275 help 1276 This option provides a kernel module that can be used to test 1277 the error handling of the cpu notifiers by injecting artificial 1278 errors to CPU notifier chain callbacks. It is controlled through 1279 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1280 1281 If the notifier call chain should be failed with some events 1282 notified, write the error code to "actions/<notifier event>/error". 1283 1284 Example: Inject CPU offline error (-1 == -EPERM) 1285 1286 # cd /sys/kernel/debug/notifier-error-inject/cpu 1287 # echo -1 > actions/CPU_DOWN_PREPARE/error 1288 # echo 0 > /sys/devices/system/cpu/cpu1/online 1289 bash: echo: write error: Operation not permitted 1290 1291 To compile this code as a module, choose M here: the module will 1292 be called cpu-notifier-error-inject. 1293 1294 If unsure, say N. 1295 1296config PM_NOTIFIER_ERROR_INJECT 1297 tristate "PM notifier error injection module" 1298 depends on PM && NOTIFIER_ERROR_INJECTION 1299 default m if PM_DEBUG 1300 help 1301 This option provides the ability to inject artificial errors to 1302 PM notifier chain callbacks. It is controlled through debugfs 1303 interface /sys/kernel/debug/notifier-error-inject/pm 1304 1305 If the notifier call chain should be failed with some events 1306 notified, write the error code to "actions/<notifier event>/error". 1307 1308 Example: Inject PM suspend error (-12 = -ENOMEM) 1309 1310 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1311 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1312 # echo mem > /sys/power/state 1313 bash: echo: write error: Cannot allocate memory 1314 1315 To compile this code as a module, choose M here: the module will 1316 be called pm-notifier-error-inject. 1317 1318 If unsure, say N. 1319 1320config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1321 tristate "OF reconfig notifier error injection module" 1322 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1323 help 1324 This option provides the ability to inject artificial errors to 1325 OF reconfig notifier chain callbacks. It is controlled 1326 through debugfs interface under 1327 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1328 1329 If the notifier call chain should be failed with some events 1330 notified, write the error code to "actions/<notifier event>/error". 1331 1332 To compile this code as a module, choose M here: the module will 1333 be called of-reconfig-notifier-error-inject. 1334 1335 If unsure, say N. 1336 1337config FAULT_INJECTION 1338 bool "Fault-injection framework" 1339 depends on DEBUG_KERNEL 1340 help 1341 Provide fault-injection framework. 1342 For more details, see Documentation/fault-injection/. 1343 1344config FAILSLAB 1345 bool "Fault-injection capability for kmalloc" 1346 depends on FAULT_INJECTION 1347 depends on SLAB || SLUB 1348 help 1349 Provide fault-injection capability for kmalloc. 1350 1351config FAIL_PAGE_ALLOC 1352 bool "Fault-injection capabilitiy for alloc_pages()" 1353 depends on FAULT_INJECTION 1354 help 1355 Provide fault-injection capability for alloc_pages(). 1356 1357config FAIL_MAKE_REQUEST 1358 bool "Fault-injection capability for disk IO" 1359 depends on FAULT_INJECTION && BLOCK 1360 help 1361 Provide fault-injection capability for disk IO. 1362 1363config FAIL_IO_TIMEOUT 1364 bool "Fault-injection capability for faking disk interrupts" 1365 depends on FAULT_INJECTION && BLOCK 1366 help 1367 Provide fault-injection capability on end IO handling. This 1368 will make the block layer "forget" an interrupt as configured, 1369 thus exercising the error handling. 1370 1371 Only works with drivers that use the generic timeout handling, 1372 for others it wont do anything. 1373 1374config FAIL_MMC_REQUEST 1375 bool "Fault-injection capability for MMC IO" 1376 select DEBUG_FS 1377 depends on FAULT_INJECTION && MMC 1378 help 1379 Provide fault-injection capability for MMC IO. 1380 This will make the mmc core return data errors. This is 1381 useful to test the error handling in the mmc block device 1382 and to test how the mmc host driver handles retries from 1383 the block device. 1384 1385config FAULT_INJECTION_DEBUG_FS 1386 bool "Debugfs entries for fault-injection capabilities" 1387 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1388 help 1389 Enable configuration of fault-injection capabilities via debugfs. 1390 1391config FAULT_INJECTION_STACKTRACE_FILTER 1392 bool "stacktrace filter for fault-injection capabilities" 1393 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1394 depends on !X86_64 1395 select STACKTRACE 1396 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1397 help 1398 Provide stacktrace filter for fault-injection capabilities 1399 1400config LATENCYTOP 1401 bool "Latency measuring infrastructure" 1402 depends on HAVE_LATENCYTOP_SUPPORT 1403 depends on DEBUG_KERNEL 1404 depends on STACKTRACE_SUPPORT 1405 depends on PROC_FS 1406 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1407 select KALLSYMS 1408 select KALLSYMS_ALL 1409 select STACKTRACE 1410 select SCHEDSTATS 1411 select SCHED_DEBUG 1412 help 1413 Enable this option if you want to use the LatencyTOP tool 1414 to find out which userspace is blocking on what kernel operations. 1415 1416config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1417 bool 1418 1419config DEBUG_STRICT_USER_COPY_CHECKS 1420 bool "Strict user copy size checks" 1421 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1422 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING 1423 help 1424 Enabling this option turns a certain set of sanity checks for user 1425 copy operations into compile time failures. 1426 1427 The copy_from_user() etc checks are there to help test if there 1428 are sufficient security checks on the length argument of 1429 the copy operation, by having gcc prove that the argument is 1430 within bounds. 1431 1432 If unsure, say N. 1433 1434source kernel/trace/Kconfig 1435 1436menu "Runtime Testing" 1437 1438config LKDTM 1439 tristate "Linux Kernel Dump Test Tool Module" 1440 depends on DEBUG_FS 1441 depends on BLOCK 1442 default n 1443 help 1444 This module enables testing of the different dumping mechanisms by 1445 inducing system failures at predefined crash points. 1446 If you don't need it: say N 1447 Choose M here to compile this code as a module. The module will be 1448 called lkdtm. 1449 1450 Documentation on how to use the module can be found in 1451 Documentation/fault-injection/provoke-crashes.txt 1452 1453config TEST_LIST_SORT 1454 bool "Linked list sorting test" 1455 depends on DEBUG_KERNEL 1456 help 1457 Enable this to turn on 'list_sort()' function test. This test is 1458 executed only once during system boot, so affects only boot time. 1459 1460 If unsure, say N. 1461 1462config KPROBES_SANITY_TEST 1463 bool "Kprobes sanity tests" 1464 depends on DEBUG_KERNEL 1465 depends on KPROBES 1466 default n 1467 help 1468 This option provides for testing basic kprobes functionality on 1469 boot. A sample kprobe, jprobe and kretprobe are inserted and 1470 verified for functionality. 1471 1472 Say N if you are unsure. 1473 1474config BACKTRACE_SELF_TEST 1475 tristate "Self test for the backtrace code" 1476 depends on DEBUG_KERNEL 1477 default n 1478 help 1479 This option provides a kernel module that can be used to test 1480 the kernel stack backtrace code. This option is not useful 1481 for distributions or general kernels, but only for kernel 1482 developers working on architecture code. 1483 1484 Note that if you want to also test saved backtraces, you will 1485 have to enable STACKTRACE as well. 1486 1487 Say N if you are unsure. 1488 1489config RBTREE_TEST 1490 tristate "Red-Black tree test" 1491 depends on DEBUG_KERNEL 1492 help 1493 A benchmark measuring the performance of the rbtree library. 1494 Also includes rbtree invariant checks. 1495 1496config INTERVAL_TREE_TEST 1497 tristate "Interval tree test" 1498 depends on m && DEBUG_KERNEL 1499 help 1500 A benchmark measuring the performance of the interval tree library 1501 1502config PERCPU_TEST 1503 tristate "Per cpu operations test" 1504 depends on m && DEBUG_KERNEL 1505 help 1506 Enable this option to build test module which validates per-cpu 1507 operations. 1508 1509 If unsure, say N. 1510 1511config ATOMIC64_SELFTEST 1512 bool "Perform an atomic64_t self-test at boot" 1513 help 1514 Enable this option to test the atomic64_t functions at boot. 1515 1516 If unsure, say N. 1517 1518config ASYNC_RAID6_TEST 1519 tristate "Self test for hardware accelerated raid6 recovery" 1520 depends on ASYNC_RAID6_RECOV 1521 select ASYNC_MEMCPY 1522 ---help--- 1523 This is a one-shot self test that permutes through the 1524 recovery of all the possible two disk failure scenarios for a 1525 N-disk array. Recovery is performed with the asynchronous 1526 raid6 recovery routines, and will optionally use an offload 1527 engine if one is available. 1528 1529 If unsure, say N. 1530 1531config TEST_STRING_HELPERS 1532 tristate "Test functions located in the string_helpers module at runtime" 1533 1534config TEST_KSTRTOX 1535 tristate "Test kstrto*() family of functions at runtime" 1536 1537endmenu # runtime tests 1538 1539config PROVIDE_OHCI1394_DMA_INIT 1540 bool "Remote debugging over FireWire early on boot" 1541 depends on PCI && X86 1542 help 1543 If you want to debug problems which hang or crash the kernel early 1544 on boot and the crashing machine has a FireWire port, you can use 1545 this feature to remotely access the memory of the crashed machine 1546 over FireWire. This employs remote DMA as part of the OHCI1394 1547 specification which is now the standard for FireWire controllers. 1548 1549 With remote DMA, you can monitor the printk buffer remotely using 1550 firescope and access all memory below 4GB using fireproxy from gdb. 1551 Even controlling a kernel debugger is possible using remote DMA. 1552 1553 Usage: 1554 1555 If ohci1394_dma=early is used as boot parameter, it will initialize 1556 all OHCI1394 controllers which are found in the PCI config space. 1557 1558 As all changes to the FireWire bus such as enabling and disabling 1559 devices cause a bus reset and thereby disable remote DMA for all 1560 devices, be sure to have the cable plugged and FireWire enabled on 1561 the debugging host before booting the debug target for debugging. 1562 1563 This code (~1k) is freed after boot. By then, the firewire stack 1564 in charge of the OHCI-1394 controllers should be used instead. 1565 1566 See Documentation/debugging-via-ohci1394.txt for more information. 1567 1568config BUILD_DOCSRC 1569 bool "Build targets in Documentation/ tree" 1570 depends on HEADERS_CHECK 1571 help 1572 This option attempts to build objects from the source files in the 1573 kernel Documentation/ tree. 1574 1575 Say N if you are unsure. 1576 1577config DMA_API_DEBUG 1578 bool "Enable debugging of DMA-API usage" 1579 depends on HAVE_DMA_API_DEBUG 1580 help 1581 Enable this option to debug the use of the DMA API by device drivers. 1582 With this option you will be able to detect common bugs in device 1583 drivers like double-freeing of DMA mappings or freeing mappings that 1584 were never allocated. 1585 1586 This also attempts to catch cases where a page owned by DMA is 1587 accessed by the cpu in a way that could cause data corruption. For 1588 example, this enables cow_user_page() to check that the source page is 1589 not undergoing DMA. 1590 1591 This option causes a performance degradation. Use only if you want to 1592 debug device drivers and dma interactions. 1593 1594 If unsure, say N. 1595 1596config TEST_MODULE 1597 tristate "Test module loading with 'hello world' module" 1598 default n 1599 depends on m 1600 help 1601 This builds the "test_module" module that emits "Hello, world" 1602 on printk when loaded. It is designed to be used for basic 1603 evaluation of the module loading subsystem (for example when 1604 validating module verification). It lacks any extra dependencies, 1605 and will not normally be loaded by the system unless explicitly 1606 requested by name. 1607 1608 If unsure, say N. 1609 1610config TEST_USER_COPY 1611 tristate "Test user/kernel boundary protections" 1612 default n 1613 depends on m 1614 help 1615 This builds the "test_user_copy" module that runs sanity checks 1616 on the copy_to/from_user infrastructure, making sure basic 1617 user/kernel boundary testing is working. If it fails to load, 1618 a regression has been detected in the user/kernel memory boundary 1619 protections. 1620 1621 If unsure, say N. 1622 1623source "samples/Kconfig" 1624 1625source "lib/Kconfig.kgdb" 1626 1627