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 && !FRV 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 ARCH_HAS_KCOV 641 bool 642 help 643 KCOV does not have any arch-specific code, but currently it is enabled 644 only for x86_64. KCOV requires testing on other archs, and most likely 645 disabling of instrumentation for some early boot code. 646 647config KCOV 648 bool "Code coverage for fuzzing" 649 depends on ARCH_HAS_KCOV 650 select DEBUG_FS 651 help 652 KCOV exposes kernel code coverage information in a form suitable 653 for coverage-guided fuzzing (randomized testing). 654 655 If RANDOMIZE_BASE is enabled, PC values will not be stable across 656 different machines and across reboots. If you need stable PC values, 657 disable RANDOMIZE_BASE. 658 659 For more details, see Documentation/kcov.txt. 660 661config DEBUG_SHIRQ 662 bool "Debug shared IRQ handlers" 663 depends on DEBUG_KERNEL 664 help 665 Enable this to generate a spurious interrupt as soon as a shared 666 interrupt handler is registered, and just before one is deregistered. 667 Drivers ought to be able to handle interrupts coming in at those 668 points; some don't and need to be caught. 669 670menu "Debug Lockups and Hangs" 671 672config LOCKUP_DETECTOR 673 bool "Detect Hard and Soft Lockups" 674 depends on DEBUG_KERNEL && !S390 675 help 676 Say Y here to enable the kernel to act as a watchdog to detect 677 hard and soft lockups. 678 679 Softlockups are bugs that cause the kernel to loop in kernel 680 mode for more than 20 seconds, without giving other tasks a 681 chance to run. The current stack trace is displayed upon 682 detection and the system will stay locked up. 683 684 Hardlockups are bugs that cause the CPU to loop in kernel mode 685 for more than 10 seconds, without letting other interrupts have a 686 chance to run. The current stack trace is displayed upon detection 687 and the system will stay locked up. 688 689 The overhead should be minimal. A periodic hrtimer runs to 690 generate interrupts and kick the watchdog task every 4 seconds. 691 An NMI is generated every 10 seconds or so to check for hardlockups. 692 If NMIs are not available on the platform, every 12 seconds the 693 hrtimer interrupt on one cpu will be used to check for hardlockups 694 on the next cpu. 695 696 The frequency of hrtimer and NMI events and the soft and hard lockup 697 thresholds can be controlled through the sysctl watchdog_thresh. 698 699config HARDLOCKUP_DETECTOR_NMI 700 def_bool y 701 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 702 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 703 704config HARDLOCKUP_DETECTOR_OTHER_CPU 705 def_bool y 706 depends on LOCKUP_DETECTOR && SMP 707 depends on !HARDLOCKUP_DETECTOR_NMI && !HAVE_NMI_WATCHDOG 708 709config HARDLOCKUP_DETECTOR 710 def_bool y 711 depends on HARDLOCKUP_DETECTOR_NMI || HARDLOCKUP_DETECTOR_OTHER_CPU 712 713config BOOTPARAM_HARDLOCKUP_PANIC 714 bool "Panic (Reboot) On Hard Lockups" 715 depends on HARDLOCKUP_DETECTOR 716 help 717 Say Y here to enable the kernel to panic on "hard lockups", 718 which are bugs that cause the kernel to loop in kernel 719 mode with interrupts disabled for more than 10 seconds (configurable 720 using the watchdog_thresh sysctl). 721 722 Say N if unsure. 723 724config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 725 int 726 depends on HARDLOCKUP_DETECTOR 727 range 0 1 728 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 729 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 730 731config BOOTPARAM_SOFTLOCKUP_PANIC 732 bool "Panic (Reboot) On Soft Lockups" 733 depends on LOCKUP_DETECTOR 734 help 735 Say Y here to enable the kernel to panic on "soft lockups", 736 which are bugs that cause the kernel to loop in kernel 737 mode for more than 20 seconds (configurable using the watchdog_thresh 738 sysctl), without giving other tasks a chance to run. 739 740 The panic can be used in combination with panic_timeout, 741 to cause the system to reboot automatically after a 742 lockup has been detected. This feature is useful for 743 high-availability systems that have uptime guarantees and 744 where a lockup must be resolved ASAP. 745 746 Say N if unsure. 747 748config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 749 int 750 depends on LOCKUP_DETECTOR 751 range 0 1 752 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 753 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 754 755config DETECT_HUNG_TASK 756 bool "Detect Hung Tasks" 757 depends on DEBUG_KERNEL 758 default LOCKUP_DETECTOR 759 help 760 Say Y here to enable the kernel to detect "hung tasks", 761 which are bugs that cause the task to be stuck in 762 uninterruptible "D" state indefinitiley. 763 764 When a hung task is detected, the kernel will print the 765 current stack trace (which you should report), but the 766 task will stay in uninterruptible state. If lockdep is 767 enabled then all held locks will also be reported. This 768 feature has negligible overhead. 769 770config DEFAULT_HUNG_TASK_TIMEOUT 771 int "Default timeout for hung task detection (in seconds)" 772 depends on DETECT_HUNG_TASK 773 default 120 774 help 775 This option controls the default timeout (in seconds) used 776 to determine when a task has become non-responsive and should 777 be considered hung. 778 779 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 780 sysctl or by writing a value to 781 /proc/sys/kernel/hung_task_timeout_secs. 782 783 A timeout of 0 disables the check. The default is two minutes. 784 Keeping the default should be fine in most cases. 785 786config BOOTPARAM_HUNG_TASK_PANIC 787 bool "Panic (Reboot) On Hung Tasks" 788 depends on DETECT_HUNG_TASK 789 help 790 Say Y here to enable the kernel to panic on "hung tasks", 791 which are bugs that cause the kernel to leave a task stuck 792 in uninterruptible "D" state. 793 794 The panic can be used in combination with panic_timeout, 795 to cause the system to reboot automatically after a 796 hung task has been detected. This feature is useful for 797 high-availability systems that have uptime guarantees and 798 where a hung tasks must be resolved ASAP. 799 800 Say N if unsure. 801 802config BOOTPARAM_HUNG_TASK_PANIC_VALUE 803 int 804 depends on DETECT_HUNG_TASK 805 range 0 1 806 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 807 default 1 if BOOTPARAM_HUNG_TASK_PANIC 808 809endmenu # "Debug lockups and hangs" 810 811config PANIC_ON_OOPS 812 bool "Panic on Oops" 813 help 814 Say Y here to enable the kernel to panic when it oopses. This 815 has the same effect as setting oops=panic on the kernel command 816 line. 817 818 This feature is useful to ensure that the kernel does not do 819 anything erroneous after an oops which could result in data 820 corruption or other issues. 821 822 Say N if unsure. 823 824config PANIC_ON_OOPS_VALUE 825 int 826 range 0 1 827 default 0 if !PANIC_ON_OOPS 828 default 1 if PANIC_ON_OOPS 829 830config PANIC_TIMEOUT 831 int "panic timeout" 832 default 0 833 help 834 Set the timeout value (in seconds) until a reboot occurs when the 835 the kernel panics. If n = 0, then we wait forever. A timeout 836 value n > 0 will wait n seconds before rebooting, while a timeout 837 value n < 0 will reboot immediately. 838 839config SCHED_DEBUG 840 bool "Collect scheduler debugging info" 841 depends on DEBUG_KERNEL && PROC_FS 842 default y 843 help 844 If you say Y here, the /proc/sched_debug file will be provided 845 that can help debug the scheduler. The runtime overhead of this 846 option is minimal. 847 848config PANIC_ON_RT_THROTTLING 849 bool "Panic on RT throttling" 850 help 851 Say Y here to enable the kernel to panic when a realtime 852 runqueue is throttled. This may be useful for detecting 853 and debugging RT throttling issues. 854 855 Say N if unsure. 856 857config SCHEDSTATS 858 bool "Collect scheduler statistics" 859 depends on DEBUG_KERNEL && PROC_FS 860 help 861 If you say Y here, additional code will be inserted into the 862 scheduler and related routines to collect statistics about 863 scheduler behavior and provide them in /proc/schedstat. These 864 stats may be useful for both tuning and debugging the scheduler 865 If you aren't debugging the scheduler or trying to tune a specific 866 application, you can say N to avoid the very slight overhead 867 this adds. 868 869config SCHED_STACK_END_CHECK 870 bool "Detect stack corruption on calls to schedule()" 871 depends on DEBUG_KERNEL 872 default n 873 help 874 This option checks for a stack overrun on calls to schedule(). 875 If the stack end location is found to be over written always panic as 876 the content of the corrupted region can no longer be trusted. 877 This is to ensure no erroneous behaviour occurs which could result in 878 data corruption or a sporadic crash at a later stage once the region 879 is examined. The runtime overhead introduced is minimal. 880 881config TIMER_STATS 882 bool "Collect kernel timers statistics" 883 depends on DEBUG_KERNEL && PROC_FS 884 help 885 If you say Y here, additional code will be inserted into the 886 timer routines to collect statistics about kernel timers being 887 reprogrammed. The statistics can be read from /proc/timer_stats. 888 The statistics collection is started by writing 1 to /proc/timer_stats, 889 writing 0 stops it. This feature is useful to collect information 890 about timer usage patterns in kernel and userspace. This feature 891 is lightweight if enabled in the kernel config but not activated 892 (it defaults to deactivated on bootup and will only be activated 893 if some application like powertop activates it explicitly). 894 895config DEBUG_PREEMPT 896 bool "Debug preemptible kernel" 897 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 898 default y 899 help 900 If you say Y here then the kernel will use a debug variant of the 901 commonly used smp_processor_id() function and will print warnings 902 if kernel code uses it in a preemption-unsafe way. Also, the kernel 903 will detect preemption count underflows. 904 905menu "Lock Debugging (spinlocks, mutexes, etc...)" 906 907config DEBUG_RT_MUTEXES 908 bool "RT Mutex debugging, deadlock detection" 909 depends on DEBUG_KERNEL && RT_MUTEXES 910 help 911 This allows rt mutex semantics violations and rt mutex related 912 deadlocks (lockups) to be detected and reported automatically. 913 914config RT_MUTEX_TESTER 915 bool "Built-in scriptable tester for rt-mutexes" 916 depends on DEBUG_KERNEL && RT_MUTEXES && BROKEN 917 help 918 This option enables a rt-mutex tester. 919 920config DEBUG_SPINLOCK 921 bool "Spinlock and rw-lock debugging: basic checks" 922 depends on DEBUG_KERNEL 923 select UNINLINE_SPIN_UNLOCK 924 help 925 Say Y here and build SMP to catch missing spinlock initialization 926 and certain other kinds of spinlock errors commonly made. This is 927 best used in conjunction with the NMI watchdog so that spinlock 928 deadlocks are also debuggable. 929 930config DEBUG_MUTEXES 931 bool "Mutex debugging: basic checks" 932 depends on DEBUG_KERNEL 933 help 934 This feature allows mutex semantics violations to be detected and 935 reported. 936 937config DEBUG_WW_MUTEX_SLOWPATH 938 bool "Wait/wound mutex debugging: Slowpath testing" 939 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 940 select DEBUG_LOCK_ALLOC 941 select DEBUG_SPINLOCK 942 select DEBUG_MUTEXES 943 help 944 This feature enables slowpath testing for w/w mutex users by 945 injecting additional -EDEADLK wound/backoff cases. Together with 946 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 947 will test all possible w/w mutex interface abuse with the 948 exception of simply not acquiring all the required locks. 949 Note that this feature can introduce significant overhead, so 950 it really should not be enabled in a production or distro kernel, 951 even a debug kernel. If you are a driver writer, enable it. If 952 you are a distro, do not. 953 954config DEBUG_LOCK_ALLOC 955 bool "Lock debugging: detect incorrect freeing of live locks" 956 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 957 select DEBUG_SPINLOCK 958 select DEBUG_MUTEXES 959 select LOCKDEP 960 help 961 This feature will check whether any held lock (spinlock, rwlock, 962 mutex or rwsem) is incorrectly freed by the kernel, via any of the 963 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 964 vfree(), etc.), whether a live lock is incorrectly reinitialized via 965 spin_lock_init()/mutex_init()/etc., or whether there is any lock 966 held during task exit. 967 968config PROVE_LOCKING 969 bool "Lock debugging: prove locking correctness" 970 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 971 select LOCKDEP 972 select DEBUG_SPINLOCK 973 select DEBUG_MUTEXES 974 select DEBUG_LOCK_ALLOC 975 select TRACE_IRQFLAGS 976 default n 977 help 978 This feature enables the kernel to prove that all locking 979 that occurs in the kernel runtime is mathematically 980 correct: that under no circumstance could an arbitrary (and 981 not yet triggered) combination of observed locking 982 sequences (on an arbitrary number of CPUs, running an 983 arbitrary number of tasks and interrupt contexts) cause a 984 deadlock. 985 986 In short, this feature enables the kernel to report locking 987 related deadlocks before they actually occur. 988 989 The proof does not depend on how hard and complex a 990 deadlock scenario would be to trigger: how many 991 participant CPUs, tasks and irq-contexts would be needed 992 for it to trigger. The proof also does not depend on 993 timing: if a race and a resulting deadlock is possible 994 theoretically (no matter how unlikely the race scenario 995 is), it will be proven so and will immediately be 996 reported by the kernel (once the event is observed that 997 makes the deadlock theoretically possible). 998 999 If a deadlock is impossible (i.e. the locking rules, as 1000 observed by the kernel, are mathematically correct), the 1001 kernel reports nothing. 1002 1003 NOTE: this feature can also be enabled for rwlocks, mutexes 1004 and rwsems - in which case all dependencies between these 1005 different locking variants are observed and mapped too, and 1006 the proof of observed correctness is also maintained for an 1007 arbitrary combination of these separate locking variants. 1008 1009 For more details, see Documentation/locking/lockdep-design.txt. 1010 1011config LOCKDEP 1012 bool 1013 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1014 select STACKTRACE 1015 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE 1016 select KALLSYMS 1017 select KALLSYMS_ALL 1018 1019config LOCK_STAT 1020 bool "Lock usage statistics" 1021 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1022 select LOCKDEP 1023 select DEBUG_SPINLOCK 1024 select DEBUG_MUTEXES 1025 select DEBUG_LOCK_ALLOC 1026 default n 1027 help 1028 This feature enables tracking lock contention points 1029 1030 For more details, see Documentation/locking/lockstat.txt 1031 1032 This also enables lock events required by "perf lock", 1033 subcommand of perf. 1034 If you want to use "perf lock", you also need to turn on 1035 CONFIG_EVENT_TRACING. 1036 1037 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1038 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1039 1040config DEBUG_LOCKDEP 1041 bool "Lock dependency engine debugging" 1042 depends on DEBUG_KERNEL && LOCKDEP 1043 help 1044 If you say Y here, the lock dependency engine will do 1045 additional runtime checks to debug itself, at the price 1046 of more runtime overhead. 1047 1048config DEBUG_ATOMIC_SLEEP 1049 bool "Sleep inside atomic section checking" 1050 select PREEMPT_COUNT 1051 depends on DEBUG_KERNEL 1052 help 1053 If you say Y here, various routines which may sleep will become very 1054 noisy if they are called inside atomic sections: when a spinlock is 1055 held, inside an rcu read side critical section, inside preempt disabled 1056 sections, inside an interrupt, etc... 1057 1058config DEBUG_LOCKING_API_SELFTESTS 1059 bool "Locking API boot-time self-tests" 1060 depends on DEBUG_KERNEL 1061 help 1062 Say Y here if you want the kernel to run a short self-test during 1063 bootup. The self-test checks whether common types of locking bugs 1064 are detected by debugging mechanisms or not. (if you disable 1065 lock debugging then those bugs wont be detected of course.) 1066 The following locking APIs are covered: spinlocks, rwlocks, 1067 mutexes and rwsems. 1068 1069config LOCK_TORTURE_TEST 1070 tristate "torture tests for locking" 1071 depends on DEBUG_KERNEL 1072 select TORTURE_TEST 1073 default n 1074 help 1075 This option provides a kernel module that runs torture tests 1076 on kernel locking primitives. The kernel module may be built 1077 after the fact on the running kernel to be tested, if desired. 1078 1079 Say Y here if you want kernel locking-primitive torture tests 1080 to be built into the kernel. 1081 Say M if you want these torture tests to build as a module. 1082 Say N if you are unsure. 1083 1084endmenu # lock debugging 1085 1086config TRACE_IRQFLAGS 1087 bool 1088 help 1089 Enables hooks to interrupt enabling and disabling for 1090 either tracing or lock debugging. 1091 1092config STACKTRACE 1093 bool "Stack backtrace support" 1094 depends on STACKTRACE_SUPPORT 1095 help 1096 This option causes the kernel to create a /proc/pid/stack for 1097 every process, showing its current stack trace. 1098 It is also used by various kernel debugging features that require 1099 stack trace generation. 1100 1101config DEBUG_KOBJECT 1102 bool "kobject debugging" 1103 depends on DEBUG_KERNEL 1104 help 1105 If you say Y here, some extra kobject debugging messages will be sent 1106 to the syslog. 1107 1108config DEBUG_KOBJECT_RELEASE 1109 bool "kobject release debugging" 1110 depends on DEBUG_OBJECTS_TIMERS 1111 help 1112 kobjects are reference counted objects. This means that their 1113 last reference count put is not predictable, and the kobject can 1114 live on past the point at which a driver decides to drop it's 1115 initial reference to the kobject gained on allocation. An 1116 example of this would be a struct device which has just been 1117 unregistered. 1118 1119 However, some buggy drivers assume that after such an operation, 1120 the memory backing the kobject can be immediately freed. This 1121 goes completely against the principles of a refcounted object. 1122 1123 If you say Y here, the kernel will delay the release of kobjects 1124 on the last reference count to improve the visibility of this 1125 kind of kobject release bug. 1126 1127config HAVE_DEBUG_BUGVERBOSE 1128 bool 1129 1130config DEBUG_BUGVERBOSE 1131 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1132 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1133 default y 1134 help 1135 Say Y here to make BUG() panics output the file name and line number 1136 of the BUG call as well as the EIP and oops trace. This aids 1137 debugging but costs about 70-100K of memory. 1138 1139config DEBUG_LIST 1140 bool "Debug linked list manipulation" 1141 depends on DEBUG_KERNEL 1142 help 1143 Enable this to turn on extended checks in the linked-list 1144 walking routines. 1145 1146 If unsure, say N. 1147 1148config DEBUG_PI_LIST 1149 bool "Debug priority linked list manipulation" 1150 depends on DEBUG_KERNEL 1151 help 1152 Enable this to turn on extended checks in the priority-ordered 1153 linked-list (plist) walking routines. This checks the entire 1154 list multiple times during each manipulation. 1155 1156 If unsure, say N. 1157 1158config DEBUG_SG 1159 bool "Debug SG table operations" 1160 depends on DEBUG_KERNEL 1161 help 1162 Enable this to turn on checks on scatter-gather tables. This can 1163 help find problems with drivers that do not properly initialize 1164 their sg tables. 1165 1166 If unsure, say N. 1167 1168config DEBUG_NOTIFIERS 1169 bool "Debug notifier call chains" 1170 depends on DEBUG_KERNEL 1171 help 1172 Enable this to turn on sanity checking for notifier call chains. 1173 This is most useful for kernel developers to make sure that 1174 modules properly unregister themselves from notifier chains. 1175 This is a relatively cheap check but if you care about maximum 1176 performance, say N. 1177 1178config DEBUG_CREDENTIALS 1179 bool "Debug credential management" 1180 depends on DEBUG_KERNEL 1181 help 1182 Enable this to turn on some debug checking for credential 1183 management. The additional code keeps track of the number of 1184 pointers from task_structs to any given cred struct, and checks to 1185 see that this number never exceeds the usage count of the cred 1186 struct. 1187 1188 Furthermore, if SELinux is enabled, this also checks that the 1189 security pointer in the cred struct is never seen to be invalid. 1190 1191 If unsure, say N. 1192 1193menu "RCU Debugging" 1194 1195config PROVE_RCU 1196 bool "RCU debugging: prove RCU correctness" 1197 depends on PROVE_LOCKING 1198 default n 1199 help 1200 This feature enables lockdep extensions that check for correct 1201 use of RCU APIs. This is currently under development. Say Y 1202 if you want to debug RCU usage or help work on the PROVE_RCU 1203 feature. 1204 1205 Say N if you are unsure. 1206 1207config PROVE_RCU_REPEATEDLY 1208 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1209 depends on PROVE_RCU 1210 default n 1211 help 1212 By itself, PROVE_RCU will disable checking upon issuing the 1213 first warning (or "splat"). This feature prevents such 1214 disabling, allowing multiple RCU-lockdep warnings to be printed 1215 on a single reboot. 1216 1217 Say Y to allow multiple RCU-lockdep warnings per boot. 1218 1219 Say N if you are unsure. 1220 1221config SPARSE_RCU_POINTER 1222 bool "RCU debugging: sparse-based checks for pointer usage" 1223 default n 1224 help 1225 This feature enables the __rcu sparse annotation for 1226 RCU-protected pointers. This annotation will cause sparse 1227 to flag any non-RCU used of annotated pointers. This can be 1228 helpful when debugging RCU usage. Please note that this feature 1229 is not intended to enforce code cleanliness; it is instead merely 1230 a debugging aid. 1231 1232 Say Y to make sparse flag questionable use of RCU-protected pointers 1233 1234 Say N if you are unsure. 1235 1236config TORTURE_TEST 1237 tristate 1238 default n 1239 1240config RCU_TORTURE_TEST 1241 tristate "torture tests for RCU" 1242 depends on DEBUG_KERNEL 1243 select TORTURE_TEST 1244 default n 1245 help 1246 This option provides a kernel module that runs torture tests 1247 on the RCU infrastructure. The kernel module may be built 1248 after the fact on the running kernel to be tested, if desired. 1249 1250 Say Y here if you want RCU torture tests to be built into 1251 the kernel. 1252 Say M if you want the RCU torture tests to build as a module. 1253 Say N if you are unsure. 1254 1255config RCU_TORTURE_TEST_RUNNABLE 1256 bool "torture tests for RCU runnable by default" 1257 depends on RCU_TORTURE_TEST = y 1258 default n 1259 help 1260 This option provides a way to build the RCU torture tests 1261 directly into the kernel without them starting up at boot 1262 time. You can use /proc/sys/kernel/rcutorture_runnable 1263 to manually override this setting. This /proc file is 1264 available only when the RCU torture tests have been built 1265 into the kernel. 1266 1267 Say Y here if you want the RCU torture tests to start during 1268 boot (you probably don't). 1269 Say N here if you want the RCU torture tests to start only 1270 after being manually enabled via /proc. 1271 1272config RCU_CPU_STALL_TIMEOUT 1273 int "RCU CPU stall timeout in seconds" 1274 depends on RCU_STALL_COMMON 1275 range 3 300 1276 default 21 1277 help 1278 If a given RCU grace period extends more than the specified 1279 number of seconds, a CPU stall warning is printed. If the 1280 RCU grace period persists, additional CPU stall warnings are 1281 printed at more widely spaced intervals. 1282 1283config RCU_CPU_STALL_VERBOSE 1284 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" 1285 depends on TREE_PREEMPT_RCU 1286 default y 1287 help 1288 This option causes RCU to printk detailed per-task information 1289 for any tasks that are stalling the current RCU grace period. 1290 1291 Say N if you are unsure. 1292 1293 Say Y if you want to enable such checks. 1294 1295config RCU_CPU_STALL_INFO 1296 bool "Print additional diagnostics on RCU CPU stall" 1297 depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL 1298 default n 1299 help 1300 For each stalled CPU that is aware of the current RCU grace 1301 period, print out additional per-CPU diagnostic information 1302 regarding scheduling-clock ticks, idle state, and, 1303 for RCU_FAST_NO_HZ kernels, idle-entry state. 1304 1305 Say N if you are unsure. 1306 1307 Say Y if you want to enable such diagnostics. 1308 1309config RCU_TRACE 1310 bool "Enable tracing for RCU" 1311 depends on DEBUG_KERNEL 1312 select TRACE_CLOCK 1313 help 1314 This option provides tracing in RCU which presents stats 1315 in debugfs for debugging RCU implementation. 1316 1317 Say Y here if you want to enable RCU tracing 1318 Say N if you are unsure. 1319 1320endmenu # "RCU Debugging" 1321 1322config DEBUG_BLOCK_EXT_DEVT 1323 bool "Force extended block device numbers and spread them" 1324 depends on DEBUG_KERNEL 1325 depends on BLOCK 1326 default n 1327 help 1328 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1329 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1330 YOU ARE DOING. Distros, please enable this and fix whatever 1331 is broken. 1332 1333 Conventionally, block device numbers are allocated from 1334 predetermined contiguous area. However, extended block area 1335 may introduce non-contiguous block device numbers. This 1336 option forces most block device numbers to be allocated from 1337 the extended space and spreads them to discover kernel or 1338 userland code paths which assume predetermined contiguous 1339 device number allocation. 1340 1341 Note that turning on this debug option shuffles all the 1342 device numbers for all IDE and SCSI devices including libata 1343 ones, so root partition specified using device number 1344 directly (via rdev or root=MAJ:MIN) won't work anymore. 1345 Textual device names (root=/dev/sdXn) will continue to work. 1346 1347 Say N if you are unsure. 1348 1349config NOTIFIER_ERROR_INJECTION 1350 tristate "Notifier error injection" 1351 depends on DEBUG_KERNEL 1352 select DEBUG_FS 1353 help 1354 This option provides the ability to inject artificial errors to 1355 specified notifier chain callbacks. It is useful to test the error 1356 handling of notifier call chain failures. 1357 1358 Say N if unsure. 1359 1360config CPU_NOTIFIER_ERROR_INJECT 1361 tristate "CPU notifier error injection module" 1362 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1363 help 1364 This option provides a kernel module that can be used to test 1365 the error handling of the cpu notifiers by injecting artificial 1366 errors to CPU notifier chain callbacks. It is controlled through 1367 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1368 1369 If the notifier call chain should be failed with some events 1370 notified, write the error code to "actions/<notifier event>/error". 1371 1372 Example: Inject CPU offline error (-1 == -EPERM) 1373 1374 # cd /sys/kernel/debug/notifier-error-inject/cpu 1375 # echo -1 > actions/CPU_DOWN_PREPARE/error 1376 # echo 0 > /sys/devices/system/cpu/cpu1/online 1377 bash: echo: write error: Operation not permitted 1378 1379 To compile this code as a module, choose M here: the module will 1380 be called cpu-notifier-error-inject. 1381 1382 If unsure, say N. 1383 1384config PM_NOTIFIER_ERROR_INJECT 1385 tristate "PM notifier error injection module" 1386 depends on PM && NOTIFIER_ERROR_INJECTION 1387 default m if PM_DEBUG 1388 help 1389 This option provides the ability to inject artificial errors to 1390 PM notifier chain callbacks. It is controlled through debugfs 1391 interface /sys/kernel/debug/notifier-error-inject/pm 1392 1393 If the notifier call chain should be failed with some events 1394 notified, write the error code to "actions/<notifier event>/error". 1395 1396 Example: Inject PM suspend error (-12 = -ENOMEM) 1397 1398 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1399 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1400 # echo mem > /sys/power/state 1401 bash: echo: write error: Cannot allocate memory 1402 1403 To compile this code as a module, choose M here: the module will 1404 be called pm-notifier-error-inject. 1405 1406 If unsure, say N. 1407 1408config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1409 tristate "OF reconfig notifier error injection module" 1410 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1411 help 1412 This option provides the ability to inject artificial errors to 1413 OF reconfig notifier chain callbacks. It is controlled 1414 through debugfs interface under 1415 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1416 1417 If the notifier call chain should be failed with some events 1418 notified, write the error code to "actions/<notifier event>/error". 1419 1420 To compile this code as a module, choose M here: the module will 1421 be called of-reconfig-notifier-error-inject. 1422 1423 If unsure, say N. 1424 1425config FAULT_INJECTION 1426 bool "Fault-injection framework" 1427 depends on DEBUG_KERNEL 1428 help 1429 Provide fault-injection framework. 1430 For more details, see Documentation/fault-injection/. 1431 1432config FAILSLAB 1433 bool "Fault-injection capability for kmalloc" 1434 depends on FAULT_INJECTION 1435 depends on SLAB || SLUB 1436 help 1437 Provide fault-injection capability for kmalloc. 1438 1439config FAIL_PAGE_ALLOC 1440 bool "Fault-injection capabilitiy for alloc_pages()" 1441 depends on FAULT_INJECTION 1442 help 1443 Provide fault-injection capability for alloc_pages(). 1444 1445config FAIL_MAKE_REQUEST 1446 bool "Fault-injection capability for disk IO" 1447 depends on FAULT_INJECTION && BLOCK 1448 help 1449 Provide fault-injection capability for disk IO. 1450 1451config FAIL_IO_TIMEOUT 1452 bool "Fault-injection capability for faking disk interrupts" 1453 depends on FAULT_INJECTION && BLOCK 1454 help 1455 Provide fault-injection capability on end IO handling. This 1456 will make the block layer "forget" an interrupt as configured, 1457 thus exercising the error handling. 1458 1459 Only works with drivers that use the generic timeout handling, 1460 for others it wont do anything. 1461 1462config FAIL_MMC_REQUEST 1463 bool "Fault-injection capability for MMC IO" 1464 select DEBUG_FS 1465 depends on FAULT_INJECTION && MMC 1466 help 1467 Provide fault-injection capability for MMC IO. 1468 This will make the mmc core return data errors. This is 1469 useful to test the error handling in the mmc block device 1470 and to test how the mmc host driver handles retries from 1471 the block device. 1472 1473config FAULT_INJECTION_DEBUG_FS 1474 bool "Debugfs entries for fault-injection capabilities" 1475 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1476 help 1477 Enable configuration of fault-injection capabilities via debugfs. 1478 1479config FAULT_INJECTION_STACKTRACE_FILTER 1480 bool "stacktrace filter for fault-injection capabilities" 1481 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1482 depends on !X86_64 1483 select STACKTRACE 1484 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1485 help 1486 Provide stacktrace filter for fault-injection capabilities 1487 1488config LATENCYTOP 1489 bool "Latency measuring infrastructure" 1490 depends on HAVE_LATENCYTOP_SUPPORT 1491 depends on DEBUG_KERNEL 1492 depends on STACKTRACE_SUPPORT 1493 depends on PROC_FS 1494 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1495 select KALLSYMS 1496 select KALLSYMS_ALL 1497 select STACKTRACE 1498 select SCHEDSTATS 1499 select SCHED_DEBUG 1500 help 1501 Enable this option if you want to use the LatencyTOP tool 1502 to find out which userspace is blocking on what kernel operations. 1503 1504config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1505 bool 1506 1507config DEBUG_STRICT_USER_COPY_CHECKS 1508 bool "Strict user copy size checks" 1509 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1510 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING 1511 help 1512 Enabling this option turns a certain set of sanity checks for user 1513 copy operations into compile time failures. 1514 1515 The copy_from_user() etc checks are there to help test if there 1516 are sufficient security checks on the length argument of 1517 the copy operation, by having gcc prove that the argument is 1518 within bounds. 1519 1520 If unsure, say N. 1521 1522source kernel/trace/Kconfig 1523 1524menu "Runtime Testing" 1525 1526config LKDTM 1527 tristate "Linux Kernel Dump Test Tool Module" 1528 depends on DEBUG_FS 1529 depends on BLOCK 1530 default n 1531 help 1532 This module enables testing of the different dumping mechanisms by 1533 inducing system failures at predefined crash points. 1534 If you don't need it: say N 1535 Choose M here to compile this code as a module. The module will be 1536 called lkdtm. 1537 1538 Documentation on how to use the module can be found in 1539 Documentation/fault-injection/provoke-crashes.txt 1540 1541config TEST_LIST_SORT 1542 bool "Linked list sorting test" 1543 depends on DEBUG_KERNEL 1544 help 1545 Enable this to turn on 'list_sort()' function test. This test is 1546 executed only once during system boot, so affects only boot time. 1547 1548 If unsure, say N. 1549 1550config KPROBES_SANITY_TEST 1551 bool "Kprobes sanity tests" 1552 depends on DEBUG_KERNEL 1553 depends on KPROBES 1554 default n 1555 help 1556 This option provides for testing basic kprobes functionality on 1557 boot. A sample kprobe, jprobe and kretprobe are inserted and 1558 verified for functionality. 1559 1560 Say N if you are unsure. 1561 1562config BACKTRACE_SELF_TEST 1563 tristate "Self test for the backtrace code" 1564 depends on DEBUG_KERNEL 1565 default n 1566 help 1567 This option provides a kernel module that can be used to test 1568 the kernel stack backtrace code. This option is not useful 1569 for distributions or general kernels, but only for kernel 1570 developers working on architecture code. 1571 1572 Note that if you want to also test saved backtraces, you will 1573 have to enable STACKTRACE as well. 1574 1575 Say N if you are unsure. 1576 1577config RBTREE_TEST 1578 tristate "Red-Black tree test" 1579 depends on DEBUG_KERNEL 1580 help 1581 A benchmark measuring the performance of the rbtree library. 1582 Also includes rbtree invariant checks. 1583 1584config INTERVAL_TREE_TEST 1585 tristate "Interval tree test" 1586 depends on m && DEBUG_KERNEL 1587 select INTERVAL_TREE 1588 help 1589 A benchmark measuring the performance of the interval tree library 1590 1591config PERCPU_TEST 1592 tristate "Per cpu operations test" 1593 depends on m && DEBUG_KERNEL 1594 help 1595 Enable this option to build test module which validates per-cpu 1596 operations. 1597 1598 If unsure, say N. 1599 1600config ATOMIC64_SELFTEST 1601 bool "Perform an atomic64_t self-test at boot" 1602 help 1603 Enable this option to test the atomic64_t functions at boot. 1604 1605 If unsure, say N. 1606 1607config ASYNC_RAID6_TEST 1608 tristate "Self test for hardware accelerated raid6 recovery" 1609 depends on ASYNC_RAID6_RECOV 1610 select ASYNC_MEMCPY 1611 ---help--- 1612 This is a one-shot self test that permutes through the 1613 recovery of all the possible two disk failure scenarios for a 1614 N-disk array. Recovery is performed with the asynchronous 1615 raid6 recovery routines, and will optionally use an offload 1616 engine if one is available. 1617 1618 If unsure, say N. 1619 1620config TEST_STRING_HELPERS 1621 tristate "Test functions located in the string_helpers module at runtime" 1622 1623config TEST_KSTRTOX 1624 tristate "Test kstrto*() family of functions at runtime" 1625 1626config TEST_RHASHTABLE 1627 bool "Perform selftest on resizable hash table" 1628 default n 1629 help 1630 Enable this option to test the rhashtable functions at boot. 1631 1632 If unsure, say N. 1633 1634endmenu # runtime tests 1635 1636config PROVIDE_OHCI1394_DMA_INIT 1637 bool "Remote debugging over FireWire early on boot" 1638 depends on PCI && X86 1639 help 1640 If you want to debug problems which hang or crash the kernel early 1641 on boot and the crashing machine has a FireWire port, you can use 1642 this feature to remotely access the memory of the crashed machine 1643 over FireWire. This employs remote DMA as part of the OHCI1394 1644 specification which is now the standard for FireWire controllers. 1645 1646 With remote DMA, you can monitor the printk buffer remotely using 1647 firescope and access all memory below 4GB using fireproxy from gdb. 1648 Even controlling a kernel debugger is possible using remote DMA. 1649 1650 Usage: 1651 1652 If ohci1394_dma=early is used as boot parameter, it will initialize 1653 all OHCI1394 controllers which are found in the PCI config space. 1654 1655 As all changes to the FireWire bus such as enabling and disabling 1656 devices cause a bus reset and thereby disable remote DMA for all 1657 devices, be sure to have the cable plugged and FireWire enabled on 1658 the debugging host before booting the debug target for debugging. 1659 1660 This code (~1k) is freed after boot. By then, the firewire stack 1661 in charge of the OHCI-1394 controllers should be used instead. 1662 1663 See Documentation/debugging-via-ohci1394.txt for more information. 1664 1665config BUILD_DOCSRC 1666 bool "Build targets in Documentation/ tree" 1667 depends on HEADERS_CHECK 1668 help 1669 This option attempts to build objects from the source files in the 1670 kernel Documentation/ tree. 1671 1672 Say N if you are unsure. 1673 1674config DMA_API_DEBUG 1675 bool "Enable debugging of DMA-API usage" 1676 depends on HAVE_DMA_API_DEBUG 1677 help 1678 Enable this option to debug the use of the DMA API by device drivers. 1679 With this option you will be able to detect common bugs in device 1680 drivers like double-freeing of DMA mappings or freeing mappings that 1681 were never allocated. 1682 1683 This also attempts to catch cases where a page owned by DMA is 1684 accessed by the cpu in a way that could cause data corruption. For 1685 example, this enables cow_user_page() to check that the source page is 1686 not undergoing DMA. 1687 1688 This option causes a performance degradation. Use only if you want to 1689 debug device drivers and dma interactions. 1690 1691 If unsure, say N. 1692 1693config TEST_LKM 1694 tristate "Test module loading with 'hello world' module" 1695 default n 1696 depends on m 1697 help 1698 This builds the "test_module" module that emits "Hello, world" 1699 on printk when loaded. It is designed to be used for basic 1700 evaluation of the module loading subsystem (for example when 1701 validating module verification). It lacks any extra dependencies, 1702 and will not normally be loaded by the system unless explicitly 1703 requested by name. 1704 1705 If unsure, say N. 1706 1707config TEST_USER_COPY 1708 tristate "Test user/kernel boundary protections" 1709 default n 1710 depends on m 1711 help 1712 This builds the "test_user_copy" module that runs sanity checks 1713 on the copy_to/from_user infrastructure, making sure basic 1714 user/kernel boundary testing is working. If it fails to load, 1715 a regression has been detected in the user/kernel memory boundary 1716 protections. 1717 1718 If unsure, say N. 1719 1720config TEST_BPF 1721 tristate "Test BPF filter functionality" 1722 default n 1723 depends on m && NET 1724 help 1725 This builds the "test_bpf" module that runs various test vectors 1726 against the BPF interpreter or BPF JIT compiler depending on the 1727 current setting. This is in particular useful for BPF JIT compiler 1728 development, but also to run regression tests against changes in 1729 the interpreter code. It also enables test stubs for eBPF maps and 1730 verifier used by user space verifier testsuite. 1731 1732 If unsure, say N. 1733 1734config TEST_FIRMWARE 1735 tristate "Test firmware loading via userspace interface" 1736 default n 1737 depends on FW_LOADER 1738 help 1739 This builds the "test_firmware" module that creates a userspace 1740 interface for testing firmware loading. This can be used to 1741 control the triggering of firmware loading without needing an 1742 actual firmware-using device. The contents can be rechecked by 1743 userspace. 1744 1745 If unsure, say N. 1746 1747config TEST_UDELAY 1748 tristate "udelay test driver" 1749 default n 1750 help 1751 This builds the "udelay_test" module that helps to make sure 1752 that udelay() is working properly. 1753 1754 If unsure, say N. 1755 1756source "samples/Kconfig" 1757 1758source "lib/Kconfig.kgdb" 1759 1760