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 MESSAGE_LOGLEVEL_DEFAULT 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 DEBUG_INFO_SPLIT 147 bool "Produce split debuginfo in .dwo files" 148 depends on DEBUG_INFO 149 help 150 Generate debug info into separate .dwo files. This significantly 151 reduces the build directory size for builds with DEBUG_INFO, 152 because it stores the information only once on disk in .dwo 153 files instead of multiple times in object files and executables. 154 In addition the debug information is also compressed. 155 156 Requires recent gcc (4.7+) and recent gdb/binutils. 157 Any tool that packages or reads debug information would need 158 to know about the .dwo files and include them. 159 Incompatible with older versions of ccache. 160 161config DEBUG_INFO_DWARF4 162 bool "Generate dwarf4 debuginfo" 163 depends on DEBUG_INFO 164 help 165 Generate dwarf4 debug info. This requires recent versions 166 of gcc and gdb. It makes the debug information larger. 167 But it significantly improves the success of resolving 168 variables in gdb on optimized code. 169 170config ENABLE_WARN_DEPRECATED 171 bool "Enable __deprecated logic" 172 default y 173 help 174 Enable the __deprecated logic in the kernel build. 175 Disable this to suppress the "warning: 'foo' is deprecated 176 (declared at kernel/power/somefile.c:1234)" messages. 177 178config ENABLE_MUST_CHECK 179 bool "Enable __must_check logic" 180 default y 181 help 182 Enable the __must_check logic in the kernel build. Disable this to 183 suppress the "warning: ignoring return value of 'foo', declared with 184 attribute warn_unused_result" messages. 185 186config FRAME_WARN 187 int "Warn for stack frames larger than (needs gcc 4.4)" 188 range 0 8192 189 default 1024 if !64BIT 190 default 2048 if 64BIT 191 help 192 Tell gcc to warn at build time for stack frames larger than this. 193 Setting this too low will cause a lot of warnings. 194 Setting it to 0 disables the warning. 195 Requires gcc 4.4 196 197config STRIP_ASM_SYMS 198 bool "Strip assembler-generated symbols during link" 199 default n 200 help 201 Strip internal assembler-generated symbols during a link (symbols 202 that look like '.Lxxx') so they don't pollute the output of 203 get_wchan() and suchlike. 204 205config READABLE_ASM 206 bool "Generate readable assembler code" 207 depends on DEBUG_KERNEL 208 help 209 Disable some compiler optimizations that tend to generate human unreadable 210 assembler output. This may make the kernel slightly slower, but it helps 211 to keep kernel developers who have to stare a lot at assembler listings 212 sane. 213 214config UNUSED_SYMBOLS 215 bool "Enable unused/obsolete exported symbols" 216 default y if X86 217 help 218 Unused but exported symbols make the kernel needlessly bigger. For 219 that reason most of these unused exports will soon be removed. This 220 option is provided temporarily to provide a transition period in case 221 some external kernel module needs one of these symbols anyway. If you 222 encounter such a case in your module, consider if you are actually 223 using the right API. (rationale: since nobody in the kernel is using 224 this in a module, there is a pretty good chance it's actually the 225 wrong interface to use). If you really need the symbol, please send a 226 mail to the linux kernel mailing list mentioning the symbol and why 227 you really need it, and what the merge plan to the mainline kernel for 228 your module is. 229 230config DEBUG_FS 231 bool "Debug Filesystem" 232 help 233 debugfs is a virtual file system that kernel developers use to put 234 debugging files into. Enable this option to be able to read and 235 write to these files. 236 237 For detailed documentation on the debugfs API, see 238 Documentation/DocBook/filesystems. 239 240 If unsure, say N. 241 242config HEADERS_CHECK 243 bool "Run 'make headers_check' when building vmlinux" 244 depends on !UML 245 help 246 This option will extract the user-visible kernel headers whenever 247 building the kernel, and will run basic sanity checks on them to 248 ensure that exported files do not attempt to include files which 249 were not exported, etc. 250 251 If you're making modifications to header files which are 252 relevant for userspace, say 'Y', and check the headers 253 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 254 your build tree), to make sure they're suitable. 255 256config DEBUG_SECTION_MISMATCH 257 bool "Enable full Section mismatch analysis" 258 help 259 The section mismatch analysis checks if there are illegal 260 references from one section to another section. 261 During linktime or runtime, some sections are dropped; 262 any use of code/data previously in these sections would 263 most likely result in an oops. 264 In the code, functions and variables are annotated with 265 __init,, etc. (see the full list in include/linux/init.h), 266 which results in the code/data being placed in specific sections. 267 The section mismatch analysis is always performed after a full 268 kernel build, and enabling this option causes the following 269 additional steps to occur: 270 - Add the option -fno-inline-functions-called-once to gcc commands. 271 When inlining a function annotated with __init in a non-init 272 function, we would lose the section information and thus 273 the analysis would not catch the illegal reference. 274 This option tells gcc to inline less (but it does result in 275 a larger kernel). 276 - Run the section mismatch analysis for each module/built-in.o file. 277 When we run the section mismatch analysis on vmlinux.o, we 278 lose valueble information about where the mismatch was 279 introduced. 280 Running the analysis for each module/built-in.o file 281 tells where the mismatch happens much closer to the 282 source. The drawback is that the same mismatch is 283 reported at least twice. 284 - Enable verbose reporting from modpost in order to help resolve 285 the section mismatches that are reported. 286 287# 288# Select this config option from the architecture Kconfig, if it 289# is preferred to always offer frame pointers as a config 290# option on the architecture (regardless of KERNEL_DEBUG): 291# 292config ARCH_WANT_FRAME_POINTERS 293 bool 294 help 295 296config FRAME_POINTER 297 bool "Compile the kernel with frame pointers" 298 depends on DEBUG_KERNEL && \ 299 (CRIS || M68K || FRV || UML || \ 300 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \ 301 ARCH_WANT_FRAME_POINTERS 302 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 303 help 304 If you say Y here the resulting kernel image will be slightly 305 larger and slower, but it gives very useful debugging information 306 in case of kernel bugs. (precise oopses/stacktraces/warnings) 307 308config DEBUG_FORCE_WEAK_PER_CPU 309 bool "Force weak per-cpu definitions" 310 depends on DEBUG_KERNEL 311 help 312 s390 and alpha require percpu variables in modules to be 313 defined weak to work around addressing range issue which 314 puts the following two restrictions on percpu variable 315 definitions. 316 317 1. percpu symbols must be unique whether static or not 318 2. percpu variables can't be defined inside a function 319 320 To ensure that generic code follows the above rules, this 321 option forces all percpu variables to be defined as weak. 322 323endmenu # "Compiler options" 324 325config MAGIC_SYSRQ 326 bool "Magic SysRq key" 327 depends on !UML 328 help 329 If you say Y here, you will have some control over the system even 330 if the system crashes for example during kernel debugging (e.g., you 331 will be able to flush the buffer cache to disk, reboot the system 332 immediately or dump some status information). This is accomplished 333 by pressing various keys while holding SysRq (Alt+PrintScreen). It 334 also works on a serial console (on PC hardware at least), if you 335 send a BREAK and then within 5 seconds a command keypress. The 336 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 337 unless you really know what this hack does. 338 339config MAGIC_SYSRQ_DEFAULT_ENABLE 340 hex "Enable magic SysRq key functions by default" 341 depends on MAGIC_SYSRQ 342 default 0x1 343 help 344 Specifies which SysRq key functions are enabled by default. 345 This may be set to 1 or 0 to enable or disable them all, or 346 to a bitmask as described in Documentation/sysrq.txt. 347 348config DEBUG_KERNEL 349 bool "Kernel debugging" 350 help 351 Say Y here if you are developing drivers or trying to debug and 352 identify kernel problems. 353 354menu "Memory Debugging" 355 356source mm/Kconfig.debug 357 358config DEBUG_OBJECTS 359 bool "Debug object operations" 360 depends on DEBUG_KERNEL 361 help 362 If you say Y here, additional code will be inserted into the 363 kernel to track the life time of various objects and validate 364 the operations on those objects. 365 366config DEBUG_OBJECTS_SELFTEST 367 bool "Debug objects selftest" 368 depends on DEBUG_OBJECTS 369 help 370 This enables the selftest of the object debug code. 371 372config DEBUG_OBJECTS_FREE 373 bool "Debug objects in freed memory" 374 depends on DEBUG_OBJECTS 375 help 376 This enables checks whether a k/v free operation frees an area 377 which contains an object which has not been deactivated 378 properly. This can make kmalloc/kfree-intensive workloads 379 much slower. 380 381config DEBUG_OBJECTS_TIMERS 382 bool "Debug timer objects" 383 depends on DEBUG_OBJECTS 384 help 385 If you say Y here, additional code will be inserted into the 386 timer routines to track the life time of timer objects and 387 validate the timer operations. 388 389config DEBUG_OBJECTS_WORK 390 bool "Debug work objects" 391 depends on DEBUG_OBJECTS 392 help 393 If you say Y here, additional code will be inserted into the 394 work queue routines to track the life time of work objects and 395 validate the work operations. 396 397config DEBUG_OBJECTS_RCU_HEAD 398 bool "Debug RCU callbacks objects" 399 depends on DEBUG_OBJECTS 400 help 401 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 402 403config DEBUG_OBJECTS_PERCPU_COUNTER 404 bool "Debug percpu counter objects" 405 depends on DEBUG_OBJECTS 406 help 407 If you say Y here, additional code will be inserted into the 408 percpu counter routines to track the life time of percpu counter 409 objects and validate the percpu counter operations. 410 411config DEBUG_OBJECTS_ENABLE_DEFAULT 412 int "debug_objects bootup default value (0-1)" 413 range 0 1 414 default "1" 415 depends on DEBUG_OBJECTS 416 help 417 Debug objects boot parameter default value 418 419config DEBUG_SLAB 420 bool "Debug slab memory allocations" 421 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 422 help 423 Say Y here to have the kernel do limited verification on memory 424 allocation as well as poisoning memory on free to catch use of freed 425 memory. This can make kmalloc/kfree-intensive workloads much slower. 426 427config DEBUG_SLAB_LEAK 428 bool "Memory leak debugging" 429 depends on DEBUG_SLAB 430 431config SLUB_DEBUG_ON 432 bool "SLUB debugging on by default" 433 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 434 default n 435 help 436 Boot with debugging on by default. SLUB boots by default with 437 the runtime debug capabilities switched off. Enabling this is 438 equivalent to specifying the "slub_debug" parameter on boot. 439 There is no support for more fine grained debug control like 440 possible with slub_debug=xxx. SLUB debugging may be switched 441 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 442 "slub_debug=-". 443 444config SLUB_STATS 445 default n 446 bool "Enable SLUB performance statistics" 447 depends on SLUB && SYSFS 448 help 449 SLUB statistics are useful to debug SLUBs allocation behavior in 450 order find ways to optimize the allocator. This should never be 451 enabled for production use since keeping statistics slows down 452 the allocator by a few percentage points. The slabinfo command 453 supports the determination of the most active slabs to figure 454 out which slabs are relevant to a particular load. 455 Try running: slabinfo -DA 456 457config HAVE_DEBUG_KMEMLEAK 458 bool 459 460config DEBUG_KMEMLEAK 461 bool "Kernel memory leak detector" 462 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 463 select DEBUG_FS 464 select STACKTRACE if STACKTRACE_SUPPORT 465 select KALLSYMS 466 select CRC32 467 help 468 Say Y here if you want to enable the memory leak 469 detector. The memory allocation/freeing is traced in a way 470 similar to the Boehm's conservative garbage collector, the 471 difference being that the orphan objects are not freed but 472 only shown in /sys/kernel/debug/kmemleak. Enabling this 473 feature will introduce an overhead to memory 474 allocations. See Documentation/kmemleak.txt for more 475 details. 476 477 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 478 of finding leaks due to the slab objects poisoning. 479 480 In order to access the kmemleak file, debugfs needs to be 481 mounted (usually at /sys/kernel/debug). 482 483config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 484 int "Maximum kmemleak early log entries" 485 depends on DEBUG_KMEMLEAK 486 range 200 40000 487 default 400 488 help 489 Kmemleak must track all the memory allocations to avoid 490 reporting false positives. Since memory may be allocated or 491 freed before kmemleak is initialised, an early log buffer is 492 used to store these actions. If kmemleak reports "early log 493 buffer exceeded", please increase this value. 494 495config DEBUG_KMEMLEAK_TEST 496 tristate "Simple test for the kernel memory leak detector" 497 depends on DEBUG_KMEMLEAK && m 498 help 499 This option enables a module that explicitly leaks memory. 500 501 If unsure, say N. 502 503config DEBUG_KMEMLEAK_DEFAULT_OFF 504 bool "Default kmemleak to off" 505 depends on DEBUG_KMEMLEAK 506 help 507 Say Y here to disable kmemleak by default. It can then be enabled 508 on the command line via kmemleak=on. 509 510config DEBUG_STACK_USAGE 511 bool "Stack utilization instrumentation" 512 depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAG 513 help 514 Enables the display of the minimum amount of free stack which each 515 task has ever had available in the sysrq-T and sysrq-P debug output. 516 517 This option will slow down process creation somewhat. 518 519config DEBUG_VM 520 bool "Debug VM" 521 depends on DEBUG_KERNEL 522 help 523 Enable this to turn on extended checks in the virtual-memory system 524 that may impact performance. 525 526 If unsure, say N. 527 528config DEBUG_VM_VMACACHE 529 bool "Debug VMA caching" 530 depends on DEBUG_VM 531 help 532 Enable this to turn on VMA caching debug information. Doing so 533 can cause significant overhead, so only enable it in non-production 534 environments. 535 536 If unsure, say N. 537 538config DEBUG_VM_RB 539 bool "Debug VM red-black trees" 540 depends on DEBUG_VM 541 help 542 Enable VM red-black tree debugging information and extra validations. 543 544 If unsure, say N. 545 546config DEBUG_VIRTUAL 547 bool "Debug VM translations" 548 depends on DEBUG_KERNEL && X86 549 help 550 Enable some costly sanity checks in virtual to page code. This can 551 catch mistakes with virt_to_page() and friends. 552 553 If unsure, say N. 554 555config DEBUG_NOMMU_REGIONS 556 bool "Debug the global anon/private NOMMU mapping region tree" 557 depends on DEBUG_KERNEL && !MMU 558 help 559 This option causes the global tree of anonymous and private mapping 560 regions to be regularly checked for invalid topology. 561 562config DEBUG_MEMORY_INIT 563 bool "Debug memory initialisation" if EXPERT 564 default !EXPERT 565 help 566 Enable this for additional checks during memory initialisation. 567 The sanity checks verify aspects of the VM such as the memory model 568 and other information provided by the architecture. Verbose 569 information will be printed at KERN_DEBUG loglevel depending 570 on the mminit_loglevel= command-line option. 571 572 If unsure, say Y 573 574config MEMORY_NOTIFIER_ERROR_INJECT 575 tristate "Memory hotplug notifier error injection module" 576 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 577 help 578 This option provides the ability to inject artificial errors to 579 memory hotplug notifier chain callbacks. It is controlled through 580 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 581 582 If the notifier call chain should be failed with some events 583 notified, write the error code to "actions/<notifier event>/error". 584 585 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 586 587 # cd /sys/kernel/debug/notifier-error-inject/memory 588 # echo -12 > actions/MEM_GOING_OFFLINE/error 589 # echo offline > /sys/devices/system/memory/memoryXXX/state 590 bash: echo: write error: Cannot allocate memory 591 592 To compile this code as a module, choose M here: the module will 593 be called memory-notifier-error-inject. 594 595 If unsure, say N. 596 597config DEBUG_PER_CPU_MAPS 598 bool "Debug access to per_cpu maps" 599 depends on DEBUG_KERNEL 600 depends on SMP 601 help 602 Say Y to verify that the per_cpu map being accessed has 603 been set up. This adds a fair amount of code to kernel memory 604 and decreases performance. 605 606 Say N if unsure. 607 608config DEBUG_HIGHMEM 609 bool "Highmem debugging" 610 depends on DEBUG_KERNEL && HIGHMEM 611 help 612 This option enables additional error checking for high memory 613 systems. Disable for production systems. 614 615config HAVE_DEBUG_STACKOVERFLOW 616 bool 617 618config DEBUG_STACKOVERFLOW 619 bool "Check for stack overflows" 620 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 621 ---help--- 622 Say Y here if you want to check for overflows of kernel, IRQ 623 and exception stacks (if your archicture uses them). This 624 option will show detailed messages if free stack space drops 625 below a certain limit. 626 627 These kinds of bugs usually occur when call-chains in the 628 kernel get too deep, especially when interrupts are 629 involved. 630 631 Use this in cases where you see apparently random memory 632 corruption, especially if it appears in 'struct thread_info' 633 634 If in doubt, say "N". 635 636source "lib/Kconfig.kmemcheck" 637 638endmenu # "Memory Debugging" 639 640config DEBUG_SHIRQ 641 bool "Debug shared IRQ handlers" 642 depends on DEBUG_KERNEL 643 help 644 Enable this to generate a spurious interrupt as soon as a shared 645 interrupt handler is registered, and just before one is deregistered. 646 Drivers ought to be able to handle interrupts coming in at those 647 points; some don't and need to be caught. 648 649menu "Debug Lockups and Hangs" 650 651config LOCKUP_DETECTOR 652 bool "Detect Hard and Soft Lockups" 653 depends on DEBUG_KERNEL && !S390 654 help 655 Say Y here to enable the kernel to act as a watchdog to detect 656 hard and soft lockups. 657 658 Softlockups are bugs that cause the kernel to loop in kernel 659 mode for more than 20 seconds, without giving other tasks a 660 chance to run. The current stack trace is displayed upon 661 detection and the system will stay locked up. 662 663 Hardlockups are bugs that cause the CPU to loop in kernel mode 664 for more than 10 seconds, without letting other interrupts have a 665 chance to run. The current stack trace is displayed upon detection 666 and the system will stay locked up. 667 668 The overhead should be minimal. A periodic hrtimer runs to 669 generate interrupts and kick the watchdog task every 4 seconds. 670 An NMI is generated every 10 seconds or so to check for hardlockups. 671 672 The frequency of hrtimer and NMI events and the soft and hard lockup 673 thresholds can be controlled through the sysctl watchdog_thresh. 674 675config HARDLOCKUP_DETECTOR 676 def_bool y 677 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 678 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 679 680config BOOTPARAM_HARDLOCKUP_PANIC 681 bool "Panic (Reboot) On Hard Lockups" 682 depends on HARDLOCKUP_DETECTOR 683 help 684 Say Y here to enable the kernel to panic on "hard lockups", 685 which are bugs that cause the kernel to loop in kernel 686 mode with interrupts disabled for more than 10 seconds (configurable 687 using the watchdog_thresh sysctl). 688 689 Say N if unsure. 690 691config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 692 int 693 depends on HARDLOCKUP_DETECTOR 694 range 0 1 695 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 696 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 697 698config BOOTPARAM_SOFTLOCKUP_PANIC 699 bool "Panic (Reboot) On Soft Lockups" 700 depends on LOCKUP_DETECTOR 701 help 702 Say Y here to enable the kernel to panic on "soft lockups", 703 which are bugs that cause the kernel to loop in kernel 704 mode for more than 20 seconds (configurable using the watchdog_thresh 705 sysctl), without giving other tasks a chance to run. 706 707 The panic can be used in combination with panic_timeout, 708 to cause the system to reboot automatically after a 709 lockup has been detected. This feature is useful for 710 high-availability systems that have uptime guarantees and 711 where a lockup must be resolved ASAP. 712 713 Say N if unsure. 714 715config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 716 int 717 depends on LOCKUP_DETECTOR 718 range 0 1 719 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 720 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 721 722config DETECT_HUNG_TASK 723 bool "Detect Hung Tasks" 724 depends on DEBUG_KERNEL 725 default LOCKUP_DETECTOR 726 help 727 Say Y here to enable the kernel to detect "hung tasks", 728 which are bugs that cause the task to be stuck in 729 uninterruptible "D" state indefinitiley. 730 731 When a hung task is detected, the kernel will print the 732 current stack trace (which you should report), but the 733 task will stay in uninterruptible state. If lockdep is 734 enabled then all held locks will also be reported. This 735 feature has negligible overhead. 736 737config DEFAULT_HUNG_TASK_TIMEOUT 738 int "Default timeout for hung task detection (in seconds)" 739 depends on DETECT_HUNG_TASK 740 default 120 741 help 742 This option controls the default timeout (in seconds) used 743 to determine when a task has become non-responsive and should 744 be considered hung. 745 746 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 747 sysctl or by writing a value to 748 /proc/sys/kernel/hung_task_timeout_secs. 749 750 A timeout of 0 disables the check. The default is two minutes. 751 Keeping the default should be fine in most cases. 752 753config BOOTPARAM_HUNG_TASK_PANIC 754 bool "Panic (Reboot) On Hung Tasks" 755 depends on DETECT_HUNG_TASK 756 help 757 Say Y here to enable the kernel to panic on "hung tasks", 758 which are bugs that cause the kernel to leave a task stuck 759 in uninterruptible "D" state. 760 761 The panic can be used in combination with panic_timeout, 762 to cause the system to reboot automatically after a 763 hung task has been detected. This feature is useful for 764 high-availability systems that have uptime guarantees and 765 where a hung tasks must be resolved ASAP. 766 767 Say N if unsure. 768 769config BOOTPARAM_HUNG_TASK_PANIC_VALUE 770 int 771 depends on DETECT_HUNG_TASK 772 range 0 1 773 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 774 default 1 if BOOTPARAM_HUNG_TASK_PANIC 775 776endmenu # "Debug lockups and hangs" 777 778config PANIC_ON_OOPS 779 bool "Panic on Oops" 780 help 781 Say Y here to enable the kernel to panic when it oopses. This 782 has the same effect as setting oops=panic on the kernel command 783 line. 784 785 This feature is useful to ensure that the kernel does not do 786 anything erroneous after an oops which could result in data 787 corruption or other issues. 788 789 Say N if unsure. 790 791config PANIC_ON_OOPS_VALUE 792 int 793 range 0 1 794 default 0 if !PANIC_ON_OOPS 795 default 1 if PANIC_ON_OOPS 796 797config PANIC_TIMEOUT 798 int "panic timeout" 799 default 0 800 help 801 Set the timeout value (in seconds) until a reboot occurs when the 802 the kernel panics. If n = 0, then we wait forever. A timeout 803 value n > 0 will wait n seconds before rebooting, while a timeout 804 value n < 0 will reboot immediately. 805 806config SCHED_DEBUG 807 bool "Collect scheduler debugging info" 808 depends on DEBUG_KERNEL && PROC_FS 809 default y 810 help 811 If you say Y here, the /proc/sched_debug file will be provided 812 that can help debug the scheduler. The runtime overhead of this 813 option is minimal. 814 815config SCHEDSTATS 816 bool "Collect scheduler statistics" 817 depends on DEBUG_KERNEL && PROC_FS 818 help 819 If you say Y here, additional code will be inserted into the 820 scheduler and related routines to collect statistics about 821 scheduler behavior and provide them in /proc/schedstat. These 822 stats may be useful for both tuning and debugging the scheduler 823 If you aren't debugging the scheduler or trying to tune a specific 824 application, you can say N to avoid the very slight overhead 825 this adds. 826 827config TIMER_STATS 828 bool "Collect kernel timers statistics" 829 depends on DEBUG_KERNEL && PROC_FS 830 help 831 If you say Y here, additional code will be inserted into the 832 timer routines to collect statistics about kernel timers being 833 reprogrammed. The statistics can be read from /proc/timer_stats. 834 The statistics collection is started by writing 1 to /proc/timer_stats, 835 writing 0 stops it. This feature is useful to collect information 836 about timer usage patterns in kernel and userspace. This feature 837 is lightweight if enabled in the kernel config but not activated 838 (it defaults to deactivated on bootup and will only be activated 839 if some application like powertop activates it explicitly). 840 841config DEBUG_PREEMPT 842 bool "Debug preemptible kernel" 843 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 844 default y 845 help 846 If you say Y here then the kernel will use a debug variant of the 847 commonly used smp_processor_id() function and will print warnings 848 if kernel code uses it in a preemption-unsafe way. Also, the kernel 849 will detect preemption count underflows. 850 851menu "Lock Debugging (spinlocks, mutexes, etc...)" 852 853config DEBUG_RT_MUTEXES 854 bool "RT Mutex debugging, deadlock detection" 855 depends on DEBUG_KERNEL && RT_MUTEXES 856 help 857 This allows rt mutex semantics violations and rt mutex related 858 deadlocks (lockups) to be detected and reported automatically. 859 860config RT_MUTEX_TESTER 861 bool "Built-in scriptable tester for rt-mutexes" 862 depends on DEBUG_KERNEL && RT_MUTEXES && BROKEN 863 help 864 This option enables a rt-mutex tester. 865 866config DEBUG_SPINLOCK 867 bool "Spinlock and rw-lock debugging: basic checks" 868 depends on DEBUG_KERNEL 869 select UNINLINE_SPIN_UNLOCK 870 help 871 Say Y here and build SMP to catch missing spinlock initialization 872 and certain other kinds of spinlock errors commonly made. This is 873 best used in conjunction with the NMI watchdog so that spinlock 874 deadlocks are also debuggable. 875 876config DEBUG_MUTEXES 877 bool "Mutex debugging: basic checks" 878 depends on DEBUG_KERNEL 879 help 880 This feature allows mutex semantics violations to be detected and 881 reported. 882 883config DEBUG_WW_MUTEX_SLOWPATH 884 bool "Wait/wound mutex debugging: Slowpath testing" 885 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 886 select DEBUG_LOCK_ALLOC 887 select DEBUG_SPINLOCK 888 select DEBUG_MUTEXES 889 help 890 This feature enables slowpath testing for w/w mutex users by 891 injecting additional -EDEADLK wound/backoff cases. Together with 892 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 893 will test all possible w/w mutex interface abuse with the 894 exception of simply not acquiring all the required locks. 895 Note that this feature can introduce significant overhead, so 896 it really should not be enabled in a production or distro kernel, 897 even a debug kernel. If you are a driver writer, enable it. If 898 you are a distro, do not. 899 900config DEBUG_LOCK_ALLOC 901 bool "Lock debugging: detect incorrect freeing of live locks" 902 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 903 select DEBUG_SPINLOCK 904 select DEBUG_MUTEXES 905 select LOCKDEP 906 help 907 This feature will check whether any held lock (spinlock, rwlock, 908 mutex or rwsem) is incorrectly freed by the kernel, via any of the 909 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 910 vfree(), etc.), whether a live lock is incorrectly reinitialized via 911 spin_lock_init()/mutex_init()/etc., or whether there is any lock 912 held during task exit. 913 914config PROVE_LOCKING 915 bool "Lock debugging: prove locking correctness" 916 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 917 select LOCKDEP 918 select DEBUG_SPINLOCK 919 select DEBUG_MUTEXES 920 select DEBUG_LOCK_ALLOC 921 select TRACE_IRQFLAGS 922 default n 923 help 924 This feature enables the kernel to prove that all locking 925 that occurs in the kernel runtime is mathematically 926 correct: that under no circumstance could an arbitrary (and 927 not yet triggered) combination of observed locking 928 sequences (on an arbitrary number of CPUs, running an 929 arbitrary number of tasks and interrupt contexts) cause a 930 deadlock. 931 932 In short, this feature enables the kernel to report locking 933 related deadlocks before they actually occur. 934 935 The proof does not depend on how hard and complex a 936 deadlock scenario would be to trigger: how many 937 participant CPUs, tasks and irq-contexts would be needed 938 for it to trigger. The proof also does not depend on 939 timing: if a race and a resulting deadlock is possible 940 theoretically (no matter how unlikely the race scenario 941 is), it will be proven so and will immediately be 942 reported by the kernel (once the event is observed that 943 makes the deadlock theoretically possible). 944 945 If a deadlock is impossible (i.e. the locking rules, as 946 observed by the kernel, are mathematically correct), the 947 kernel reports nothing. 948 949 NOTE: this feature can also be enabled for rwlocks, mutexes 950 and rwsems - in which case all dependencies between these 951 different locking variants are observed and mapped too, and 952 the proof of observed correctness is also maintained for an 953 arbitrary combination of these separate locking variants. 954 955 For more details, see Documentation/lockdep-design.txt. 956 957config LOCKDEP 958 bool 959 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 960 select STACKTRACE 961 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE 962 select KALLSYMS 963 select KALLSYMS_ALL 964 965config LOCK_STAT 966 bool "Lock usage statistics" 967 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 968 select LOCKDEP 969 select DEBUG_SPINLOCK 970 select DEBUG_MUTEXES 971 select DEBUG_LOCK_ALLOC 972 default n 973 help 974 This feature enables tracking lock contention points 975 976 For more details, see Documentation/lockstat.txt 977 978 This also enables lock events required by "perf lock", 979 subcommand of perf. 980 If you want to use "perf lock", you also need to turn on 981 CONFIG_EVENT_TRACING. 982 983 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 984 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 985 986config DEBUG_LOCKDEP 987 bool "Lock dependency engine debugging" 988 depends on DEBUG_KERNEL && LOCKDEP 989 help 990 If you say Y here, the lock dependency engine will do 991 additional runtime checks to debug itself, at the price 992 of more runtime overhead. 993 994config DEBUG_ATOMIC_SLEEP 995 bool "Sleep inside atomic section checking" 996 select PREEMPT_COUNT 997 depends on DEBUG_KERNEL 998 help 999 If you say Y here, various routines which may sleep will become very 1000 noisy if they are called inside atomic sections: when a spinlock is 1001 held, inside an rcu read side critical section, inside preempt disabled 1002 sections, inside an interrupt, etc... 1003 1004config DEBUG_LOCKING_API_SELFTESTS 1005 bool "Locking API boot-time self-tests" 1006 depends on DEBUG_KERNEL 1007 help 1008 Say Y here if you want the kernel to run a short self-test during 1009 bootup. The self-test checks whether common types of locking bugs 1010 are detected by debugging mechanisms or not. (if you disable 1011 lock debugging then those bugs wont be detected of course.) 1012 The following locking APIs are covered: spinlocks, rwlocks, 1013 mutexes and rwsems. 1014 1015config LOCK_TORTURE_TEST 1016 tristate "torture tests for locking" 1017 depends on DEBUG_KERNEL 1018 select TORTURE_TEST 1019 default n 1020 help 1021 This option provides a kernel module that runs torture tests 1022 on kernel locking primitives. The kernel module may be built 1023 after the fact on the running kernel to be tested, if desired. 1024 1025 Say Y here if you want kernel locking-primitive torture tests 1026 to be built into the kernel. 1027 Say M if you want these torture tests to build as a module. 1028 Say N if you are unsure. 1029 1030endmenu # lock debugging 1031 1032config TRACE_IRQFLAGS 1033 bool 1034 help 1035 Enables hooks to interrupt enabling and disabling for 1036 either tracing or lock debugging. 1037 1038config STACKTRACE 1039 bool "Stack backtrace support" 1040 depends on STACKTRACE_SUPPORT 1041 help 1042 This option causes the kernel to create a /proc/pid/stack for 1043 every process, showing its current stack trace. 1044 It is also used by various kernel debugging features that require 1045 stack trace generation. 1046 1047config DEBUG_KOBJECT 1048 bool "kobject debugging" 1049 depends on DEBUG_KERNEL 1050 help 1051 If you say Y here, some extra kobject debugging messages will be sent 1052 to the syslog. 1053 1054config DEBUG_KOBJECT_RELEASE 1055 bool "kobject release debugging" 1056 depends on DEBUG_OBJECTS_TIMERS 1057 help 1058 kobjects are reference counted objects. This means that their 1059 last reference count put is not predictable, and the kobject can 1060 live on past the point at which a driver decides to drop it's 1061 initial reference to the kobject gained on allocation. An 1062 example of this would be a struct device which has just been 1063 unregistered. 1064 1065 However, some buggy drivers assume that after such an operation, 1066 the memory backing the kobject can be immediately freed. This 1067 goes completely against the principles of a refcounted object. 1068 1069 If you say Y here, the kernel will delay the release of kobjects 1070 on the last reference count to improve the visibility of this 1071 kind of kobject release bug. 1072 1073config HAVE_DEBUG_BUGVERBOSE 1074 bool 1075 1076config DEBUG_BUGVERBOSE 1077 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1078 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1079 default y 1080 help 1081 Say Y here to make BUG() panics output the file name and line number 1082 of the BUG call as well as the EIP and oops trace. This aids 1083 debugging but costs about 70-100K of memory. 1084 1085config DEBUG_LIST 1086 bool "Debug linked list manipulation" 1087 depends on DEBUG_KERNEL 1088 help 1089 Enable this to turn on extended checks in the linked-list 1090 walking routines. 1091 1092 If unsure, say N. 1093 1094config DEBUG_PI_LIST 1095 bool "Debug priority linked list manipulation" 1096 depends on DEBUG_KERNEL 1097 help 1098 Enable this to turn on extended checks in the priority-ordered 1099 linked-list (plist) walking routines. This checks the entire 1100 list multiple times during each manipulation. 1101 1102 If unsure, say N. 1103 1104config DEBUG_SG 1105 bool "Debug SG table operations" 1106 depends on DEBUG_KERNEL 1107 help 1108 Enable this to turn on checks on scatter-gather tables. This can 1109 help find problems with drivers that do not properly initialize 1110 their sg tables. 1111 1112 If unsure, say N. 1113 1114config DEBUG_NOTIFIERS 1115 bool "Debug notifier call chains" 1116 depends on DEBUG_KERNEL 1117 help 1118 Enable this to turn on sanity checking for notifier call chains. 1119 This is most useful for kernel developers to make sure that 1120 modules properly unregister themselves from notifier chains. 1121 This is a relatively cheap check but if you care about maximum 1122 performance, say N. 1123 1124config DEBUG_CREDENTIALS 1125 bool "Debug credential management" 1126 depends on DEBUG_KERNEL 1127 help 1128 Enable this to turn on some debug checking for credential 1129 management. The additional code keeps track of the number of 1130 pointers from task_structs to any given cred struct, and checks to 1131 see that this number never exceeds the usage count of the cred 1132 struct. 1133 1134 Furthermore, if SELinux is enabled, this also checks that the 1135 security pointer in the cred struct is never seen to be invalid. 1136 1137 If unsure, say N. 1138 1139menu "RCU Debugging" 1140 1141config PROVE_RCU 1142 bool "RCU debugging: prove RCU correctness" 1143 depends on PROVE_LOCKING 1144 default n 1145 help 1146 This feature enables lockdep extensions that check for correct 1147 use of RCU APIs. This is currently under development. Say Y 1148 if you want to debug RCU usage or help work on the PROVE_RCU 1149 feature. 1150 1151 Say N if you are unsure. 1152 1153config PROVE_RCU_REPEATEDLY 1154 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1155 depends on PROVE_RCU 1156 default n 1157 help 1158 By itself, PROVE_RCU will disable checking upon issuing the 1159 first warning (or "splat"). This feature prevents such 1160 disabling, allowing multiple RCU-lockdep warnings to be printed 1161 on a single reboot. 1162 1163 Say Y to allow multiple RCU-lockdep warnings per boot. 1164 1165 Say N if you are unsure. 1166 1167config SPARSE_RCU_POINTER 1168 bool "RCU debugging: sparse-based checks for pointer usage" 1169 default n 1170 help 1171 This feature enables the __rcu sparse annotation for 1172 RCU-protected pointers. This annotation will cause sparse 1173 to flag any non-RCU used of annotated pointers. This can be 1174 helpful when debugging RCU usage. Please note that this feature 1175 is not intended to enforce code cleanliness; it is instead merely 1176 a debugging aid. 1177 1178 Say Y to make sparse flag questionable use of RCU-protected pointers 1179 1180 Say N if you are unsure. 1181 1182config TORTURE_TEST 1183 tristate 1184 default n 1185 1186config RCU_TORTURE_TEST 1187 tristate "torture tests for RCU" 1188 depends on DEBUG_KERNEL 1189 select TORTURE_TEST 1190 default n 1191 help 1192 This option provides a kernel module that runs torture tests 1193 on the RCU infrastructure. The kernel module may be built 1194 after the fact on the running kernel to be tested, if desired. 1195 1196 Say Y here if you want RCU torture tests to be built into 1197 the kernel. 1198 Say M if you want the RCU torture tests to build as a module. 1199 Say N if you are unsure. 1200 1201config RCU_TORTURE_TEST_RUNNABLE 1202 bool "torture tests for RCU runnable by default" 1203 depends on RCU_TORTURE_TEST = y 1204 default n 1205 help 1206 This option provides a way to build the RCU torture tests 1207 directly into the kernel without them starting up at boot 1208 time. You can use /proc/sys/kernel/rcutorture_runnable 1209 to manually override this setting. This /proc file is 1210 available only when the RCU torture tests have been built 1211 into the kernel. 1212 1213 Say Y here if you want the RCU torture tests to start during 1214 boot (you probably don't). 1215 Say N here if you want the RCU torture tests to start only 1216 after being manually enabled via /proc. 1217 1218config RCU_CPU_STALL_TIMEOUT 1219 int "RCU CPU stall timeout in seconds" 1220 depends on RCU_STALL_COMMON 1221 range 3 300 1222 default 21 1223 help 1224 If a given RCU grace period extends more than the specified 1225 number of seconds, a CPU stall warning is printed. If the 1226 RCU grace period persists, additional CPU stall warnings are 1227 printed at more widely spaced intervals. 1228 1229config RCU_CPU_STALL_VERBOSE 1230 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" 1231 depends on TREE_PREEMPT_RCU 1232 default y 1233 help 1234 This option causes RCU to printk detailed per-task information 1235 for any tasks that are stalling the current RCU grace period. 1236 1237 Say N if you are unsure. 1238 1239 Say Y if you want to enable such checks. 1240 1241config RCU_CPU_STALL_INFO 1242 bool "Print additional diagnostics on RCU CPU stall" 1243 depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL 1244 default n 1245 help 1246 For each stalled CPU that is aware of the current RCU grace 1247 period, print out additional per-CPU diagnostic information 1248 regarding scheduling-clock ticks, idle state, and, 1249 for RCU_FAST_NO_HZ kernels, idle-entry state. 1250 1251 Say N if you are unsure. 1252 1253 Say Y if you want to enable such diagnostics. 1254 1255config RCU_TRACE 1256 bool "Enable tracing for RCU" 1257 depends on DEBUG_KERNEL 1258 select TRACE_CLOCK 1259 help 1260 This option provides tracing in RCU which presents stats 1261 in debugfs for debugging RCU implementation. 1262 1263 Say Y here if you want to enable RCU tracing 1264 Say N if you are unsure. 1265 1266endmenu # "RCU Debugging" 1267 1268config DEBUG_BLOCK_EXT_DEVT 1269 bool "Force extended block device numbers and spread them" 1270 depends on DEBUG_KERNEL 1271 depends on BLOCK 1272 default n 1273 help 1274 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1275 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1276 YOU ARE DOING. Distros, please enable this and fix whatever 1277 is broken. 1278 1279 Conventionally, block device numbers are allocated from 1280 predetermined contiguous area. However, extended block area 1281 may introduce non-contiguous block device numbers. This 1282 option forces most block device numbers to be allocated from 1283 the extended space and spreads them to discover kernel or 1284 userland code paths which assume predetermined contiguous 1285 device number allocation. 1286 1287 Note that turning on this debug option shuffles all the 1288 device numbers for all IDE and SCSI devices including libata 1289 ones, so root partition specified using device number 1290 directly (via rdev or root=MAJ:MIN) won't work anymore. 1291 Textual device names (root=/dev/sdXn) will continue to work. 1292 1293 Say N if you are unsure. 1294 1295config NOTIFIER_ERROR_INJECTION 1296 tristate "Notifier error injection" 1297 depends on DEBUG_KERNEL 1298 select DEBUG_FS 1299 help 1300 This option provides the ability to inject artificial errors to 1301 specified notifier chain callbacks. It is useful to test the error 1302 handling of notifier call chain failures. 1303 1304 Say N if unsure. 1305 1306config CPU_NOTIFIER_ERROR_INJECT 1307 tristate "CPU notifier error injection module" 1308 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1309 help 1310 This option provides a kernel module that can be used to test 1311 the error handling of the cpu notifiers by injecting artificial 1312 errors to CPU notifier chain callbacks. It is controlled through 1313 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1314 1315 If the notifier call chain should be failed with some events 1316 notified, write the error code to "actions/<notifier event>/error". 1317 1318 Example: Inject CPU offline error (-1 == -EPERM) 1319 1320 # cd /sys/kernel/debug/notifier-error-inject/cpu 1321 # echo -1 > actions/CPU_DOWN_PREPARE/error 1322 # echo 0 > /sys/devices/system/cpu/cpu1/online 1323 bash: echo: write error: Operation not permitted 1324 1325 To compile this code as a module, choose M here: the module will 1326 be called cpu-notifier-error-inject. 1327 1328 If unsure, say N. 1329 1330config PM_NOTIFIER_ERROR_INJECT 1331 tristate "PM notifier error injection module" 1332 depends on PM && NOTIFIER_ERROR_INJECTION 1333 default m if PM_DEBUG 1334 help 1335 This option provides the ability to inject artificial errors to 1336 PM notifier chain callbacks. It is controlled through debugfs 1337 interface /sys/kernel/debug/notifier-error-inject/pm 1338 1339 If the notifier call chain should be failed with some events 1340 notified, write the error code to "actions/<notifier event>/error". 1341 1342 Example: Inject PM suspend error (-12 = -ENOMEM) 1343 1344 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1345 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1346 # echo mem > /sys/power/state 1347 bash: echo: write error: Cannot allocate memory 1348 1349 To compile this code as a module, choose M here: the module will 1350 be called pm-notifier-error-inject. 1351 1352 If unsure, say N. 1353 1354config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1355 tristate "OF reconfig notifier error injection module" 1356 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1357 help 1358 This option provides the ability to inject artificial errors to 1359 OF reconfig notifier chain callbacks. It is controlled 1360 through debugfs interface under 1361 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1362 1363 If the notifier call chain should be failed with some events 1364 notified, write the error code to "actions/<notifier event>/error". 1365 1366 To compile this code as a module, choose M here: the module will 1367 be called of-reconfig-notifier-error-inject. 1368 1369 If unsure, say N. 1370 1371config FAULT_INJECTION 1372 bool "Fault-injection framework" 1373 depends on DEBUG_KERNEL 1374 help 1375 Provide fault-injection framework. 1376 For more details, see Documentation/fault-injection/. 1377 1378config FAILSLAB 1379 bool "Fault-injection capability for kmalloc" 1380 depends on FAULT_INJECTION 1381 depends on SLAB || SLUB 1382 help 1383 Provide fault-injection capability for kmalloc. 1384 1385config FAIL_PAGE_ALLOC 1386 bool "Fault-injection capabilitiy for alloc_pages()" 1387 depends on FAULT_INJECTION 1388 help 1389 Provide fault-injection capability for alloc_pages(). 1390 1391config FAIL_MAKE_REQUEST 1392 bool "Fault-injection capability for disk IO" 1393 depends on FAULT_INJECTION && BLOCK 1394 help 1395 Provide fault-injection capability for disk IO. 1396 1397config FAIL_IO_TIMEOUT 1398 bool "Fault-injection capability for faking disk interrupts" 1399 depends on FAULT_INJECTION && BLOCK 1400 help 1401 Provide fault-injection capability on end IO handling. This 1402 will make the block layer "forget" an interrupt as configured, 1403 thus exercising the error handling. 1404 1405 Only works with drivers that use the generic timeout handling, 1406 for others it wont do anything. 1407 1408config FAIL_MMC_REQUEST 1409 bool "Fault-injection capability for MMC IO" 1410 select DEBUG_FS 1411 depends on FAULT_INJECTION && MMC 1412 help 1413 Provide fault-injection capability for MMC IO. 1414 This will make the mmc core return data errors. This is 1415 useful to test the error handling in the mmc block device 1416 and to test how the mmc host driver handles retries from 1417 the block device. 1418 1419config FAULT_INJECTION_DEBUG_FS 1420 bool "Debugfs entries for fault-injection capabilities" 1421 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1422 help 1423 Enable configuration of fault-injection capabilities via debugfs. 1424 1425config FAULT_INJECTION_STACKTRACE_FILTER 1426 bool "stacktrace filter for fault-injection capabilities" 1427 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1428 depends on !X86_64 1429 select STACKTRACE 1430 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1431 help 1432 Provide stacktrace filter for fault-injection capabilities 1433 1434config LATENCYTOP 1435 bool "Latency measuring infrastructure" 1436 depends on HAVE_LATENCYTOP_SUPPORT 1437 depends on DEBUG_KERNEL 1438 depends on STACKTRACE_SUPPORT 1439 depends on PROC_FS 1440 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1441 select KALLSYMS 1442 select KALLSYMS_ALL 1443 select STACKTRACE 1444 select SCHEDSTATS 1445 select SCHED_DEBUG 1446 help 1447 Enable this option if you want to use the LatencyTOP tool 1448 to find out which userspace is blocking on what kernel operations. 1449 1450config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1451 bool 1452 1453config DEBUG_STRICT_USER_COPY_CHECKS 1454 bool "Strict user copy size checks" 1455 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1456 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING 1457 help 1458 Enabling this option turns a certain set of sanity checks for user 1459 copy operations into compile time failures. 1460 1461 The copy_from_user() etc checks are there to help test if there 1462 are sufficient security checks on the length argument of 1463 the copy operation, by having gcc prove that the argument is 1464 within bounds. 1465 1466 If unsure, say N. 1467 1468source kernel/trace/Kconfig 1469 1470menu "Runtime Testing" 1471 1472config LKDTM 1473 tristate "Linux Kernel Dump Test Tool Module" 1474 depends on DEBUG_FS 1475 depends on BLOCK 1476 default n 1477 help 1478 This module enables testing of the different dumping mechanisms by 1479 inducing system failures at predefined crash points. 1480 If you don't need it: say N 1481 Choose M here to compile this code as a module. The module will be 1482 called lkdtm. 1483 1484 Documentation on how to use the module can be found in 1485 Documentation/fault-injection/provoke-crashes.txt 1486 1487config TEST_LIST_SORT 1488 bool "Linked list sorting test" 1489 depends on DEBUG_KERNEL 1490 help 1491 Enable this to turn on 'list_sort()' function test. This test is 1492 executed only once during system boot, so affects only boot time. 1493 1494 If unsure, say N. 1495 1496config KPROBES_SANITY_TEST 1497 bool "Kprobes sanity tests" 1498 depends on DEBUG_KERNEL 1499 depends on KPROBES 1500 default n 1501 help 1502 This option provides for testing basic kprobes functionality on 1503 boot. A sample kprobe, jprobe and kretprobe are inserted and 1504 verified for functionality. 1505 1506 Say N if you are unsure. 1507 1508config BACKTRACE_SELF_TEST 1509 tristate "Self test for the backtrace code" 1510 depends on DEBUG_KERNEL 1511 default n 1512 help 1513 This option provides a kernel module that can be used to test 1514 the kernel stack backtrace code. This option is not useful 1515 for distributions or general kernels, but only for kernel 1516 developers working on architecture code. 1517 1518 Note that if you want to also test saved backtraces, you will 1519 have to enable STACKTRACE as well. 1520 1521 Say N if you are unsure. 1522 1523config RBTREE_TEST 1524 tristate "Red-Black tree test" 1525 depends on DEBUG_KERNEL 1526 help 1527 A benchmark measuring the performance of the rbtree library. 1528 Also includes rbtree invariant checks. 1529 1530config INTERVAL_TREE_TEST 1531 tristate "Interval tree test" 1532 depends on m && DEBUG_KERNEL 1533 select INTERVAL_TREE 1534 help 1535 A benchmark measuring the performance of the interval tree library 1536 1537config PERCPU_TEST 1538 tristate "Per cpu operations test" 1539 depends on m && DEBUG_KERNEL 1540 help 1541 Enable this option to build test module which validates per-cpu 1542 operations. 1543 1544 If unsure, say N. 1545 1546config ATOMIC64_SELFTEST 1547 bool "Perform an atomic64_t self-test at boot" 1548 help 1549 Enable this option to test the atomic64_t functions at boot. 1550 1551 If unsure, say N. 1552 1553config ASYNC_RAID6_TEST 1554 tristate "Self test for hardware accelerated raid6 recovery" 1555 depends on ASYNC_RAID6_RECOV 1556 select ASYNC_MEMCPY 1557 ---help--- 1558 This is a one-shot self test that permutes through the 1559 recovery of all the possible two disk failure scenarios for a 1560 N-disk array. Recovery is performed with the asynchronous 1561 raid6 recovery routines, and will optionally use an offload 1562 engine if one is available. 1563 1564 If unsure, say N. 1565 1566config TEST_STRING_HELPERS 1567 tristate "Test functions located in the string_helpers module at runtime" 1568 1569config TEST_KSTRTOX 1570 tristate "Test kstrto*() family of functions at runtime" 1571 1572config TEST_RHASHTABLE 1573 bool "Perform selftest on resizable hash table" 1574 default n 1575 help 1576 Enable this option to test the rhashtable functions at boot. 1577 1578 If unsure, say N. 1579 1580endmenu # runtime tests 1581 1582config PROVIDE_OHCI1394_DMA_INIT 1583 bool "Remote debugging over FireWire early on boot" 1584 depends on PCI && X86 1585 help 1586 If you want to debug problems which hang or crash the kernel early 1587 on boot and the crashing machine has a FireWire port, you can use 1588 this feature to remotely access the memory of the crashed machine 1589 over FireWire. This employs remote DMA as part of the OHCI1394 1590 specification which is now the standard for FireWire controllers. 1591 1592 With remote DMA, you can monitor the printk buffer remotely using 1593 firescope and access all memory below 4GB using fireproxy from gdb. 1594 Even controlling a kernel debugger is possible using remote DMA. 1595 1596 Usage: 1597 1598 If ohci1394_dma=early is used as boot parameter, it will initialize 1599 all OHCI1394 controllers which are found in the PCI config space. 1600 1601 As all changes to the FireWire bus such as enabling and disabling 1602 devices cause a bus reset and thereby disable remote DMA for all 1603 devices, be sure to have the cable plugged and FireWire enabled on 1604 the debugging host before booting the debug target for debugging. 1605 1606 This code (~1k) is freed after boot. By then, the firewire stack 1607 in charge of the OHCI-1394 controllers should be used instead. 1608 1609 See Documentation/debugging-via-ohci1394.txt for more information. 1610 1611config BUILD_DOCSRC 1612 bool "Build targets in Documentation/ tree" 1613 depends on HEADERS_CHECK 1614 help 1615 This option attempts to build objects from the source files in the 1616 kernel Documentation/ tree. 1617 1618 Say N if you are unsure. 1619 1620config DMA_API_DEBUG 1621 bool "Enable debugging of DMA-API usage" 1622 depends on HAVE_DMA_API_DEBUG 1623 help 1624 Enable this option to debug the use of the DMA API by device drivers. 1625 With this option you will be able to detect common bugs in device 1626 drivers like double-freeing of DMA mappings or freeing mappings that 1627 were never allocated. 1628 1629 This also attempts to catch cases where a page owned by DMA is 1630 accessed by the cpu in a way that could cause data corruption. For 1631 example, this enables cow_user_page() to check that the source page is 1632 not undergoing DMA. 1633 1634 This option causes a performance degradation. Use only if you want to 1635 debug device drivers and dma interactions. 1636 1637 If unsure, say N. 1638 1639config TEST_MODULE 1640 tristate "Test module loading with 'hello world' module" 1641 default n 1642 depends on m 1643 help 1644 This builds the "test_module" module that emits "Hello, world" 1645 on printk when loaded. It is designed to be used for basic 1646 evaluation of the module loading subsystem (for example when 1647 validating module verification). It lacks any extra dependencies, 1648 and will not normally be loaded by the system unless explicitly 1649 requested by name. 1650 1651 If unsure, say N. 1652 1653config TEST_USER_COPY 1654 tristate "Test user/kernel boundary protections" 1655 default n 1656 depends on m 1657 help 1658 This builds the "test_user_copy" module that runs sanity checks 1659 on the copy_to/from_user infrastructure, making sure basic 1660 user/kernel boundary testing is working. If it fails to load, 1661 a regression has been detected in the user/kernel memory boundary 1662 protections. 1663 1664 If unsure, say N. 1665 1666config TEST_BPF 1667 tristate "Test BPF filter functionality" 1668 default n 1669 depends on m && NET 1670 help 1671 This builds the "test_bpf" module that runs various test vectors 1672 against the BPF interpreter or BPF JIT compiler depending on the 1673 current setting. This is in particular useful for BPF JIT compiler 1674 development, but also to run regression tests against changes in 1675 the interpreter code. 1676 1677 If unsure, say N. 1678 1679config TEST_FIRMWARE 1680 tristate "Test firmware loading via userspace interface" 1681 default n 1682 depends on FW_LOADER 1683 help 1684 This builds the "test_firmware" module that creates a userspace 1685 interface for testing firmware loading. This can be used to 1686 control the triggering of firmware loading without needing an 1687 actual firmware-using device. The contents can be rechecked by 1688 userspace. 1689 1690 If unsure, say N. 1691 1692config TEST_UDELAY 1693 tristate "udelay test driver" 1694 default n 1695 help 1696 This builds the "udelay_test" module that helps to make sure 1697 that udelay() is working properly. 1698 1699 If unsure, say N. 1700 1701source "samples/Kconfig" 1702 1703source "lib/Kconfig.kgdb" 1704 1705