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 GDB_SCRIPTS 171 bool "Provide GDB scripts for kernel debugging" 172 depends on DEBUG_INFO 173 help 174 This creates the required links to GDB helper scripts in the 175 build directory. If you load vmlinux into gdb, the helper 176 scripts will be automatically imported by gdb as well, and 177 additional functions are available to analyze a Linux kernel 178 instance. See Documentation/gdb-kernel-debugging.txt for further 179 details. 180 181config ENABLE_WARN_DEPRECATED 182 bool "Enable __deprecated logic" 183 default y 184 help 185 Enable the __deprecated logic in the kernel build. 186 Disable this to suppress the "warning: 'foo' is deprecated 187 (declared at kernel/power/somefile.c:1234)" messages. 188 189config ENABLE_MUST_CHECK 190 bool "Enable __must_check logic" 191 default y 192 help 193 Enable the __must_check logic in the kernel build. Disable this to 194 suppress the "warning: ignoring return value of 'foo', declared with 195 attribute warn_unused_result" messages. 196 197config FRAME_WARN 198 int "Warn for stack frames larger than (needs gcc 4.4)" 199 range 0 8192 200 default 1024 if !64BIT 201 default 2048 if 64BIT 202 help 203 Tell gcc to warn at build time for stack frames larger than this. 204 Setting this too low will cause a lot of warnings. 205 Setting it to 0 disables the warning. 206 Requires gcc 4.4 207 208config STRIP_ASM_SYMS 209 bool "Strip assembler-generated symbols during link" 210 default n 211 help 212 Strip internal assembler-generated symbols during a link (symbols 213 that look like '.Lxxx') so they don't pollute the output of 214 get_wchan() and suchlike. 215 216config READABLE_ASM 217 bool "Generate readable assembler code" 218 depends on DEBUG_KERNEL 219 help 220 Disable some compiler optimizations that tend to generate human unreadable 221 assembler output. This may make the kernel slightly slower, but it helps 222 to keep kernel developers who have to stare a lot at assembler listings 223 sane. 224 225config UNUSED_SYMBOLS 226 bool "Enable unused/obsolete exported symbols" 227 default y if X86 228 help 229 Unused but exported symbols make the kernel needlessly bigger. For 230 that reason most of these unused exports will soon be removed. This 231 option is provided temporarily to provide a transition period in case 232 some external kernel module needs one of these symbols anyway. If you 233 encounter such a case in your module, consider if you are actually 234 using the right API. (rationale: since nobody in the kernel is using 235 this in a module, there is a pretty good chance it's actually the 236 wrong interface to use). If you really need the symbol, please send a 237 mail to the linux kernel mailing list mentioning the symbol and why 238 you really need it, and what the merge plan to the mainline kernel for 239 your module is. 240 241config PAGE_OWNER 242 bool "Track page owner" 243 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 244 select DEBUG_FS 245 select STACKTRACE 246 select PAGE_EXTENSION 247 help 248 This keeps track of what call chain is the owner of a page, may 249 help to find bare alloc_page(s) leaks. Even if you include this 250 feature on your build, it is disabled in default. You should pass 251 "page_owner=on" to boot parameter in order to enable it. Eats 252 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 253 for user-space helper. 254 255 If unsure, say N. 256 257config DEBUG_FS 258 bool "Debug Filesystem" 259 help 260 debugfs is a virtual file system that kernel developers use to put 261 debugging files into. Enable this option to be able to read and 262 write to these files. 263 264 For detailed documentation on the debugfs API, see 265 Documentation/DocBook/filesystems. 266 267 If unsure, say N. 268 269config HEADERS_CHECK 270 bool "Run 'make headers_check' when building vmlinux" 271 depends on !UML 272 help 273 This option will extract the user-visible kernel headers whenever 274 building the kernel, and will run basic sanity checks on them to 275 ensure that exported files do not attempt to include files which 276 were not exported, etc. 277 278 If you're making modifications to header files which are 279 relevant for userspace, say 'Y', and check the headers 280 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 281 your build tree), to make sure they're suitable. 282 283config DEBUG_SECTION_MISMATCH 284 bool "Enable full Section mismatch analysis" 285 help 286 The section mismatch analysis checks if there are illegal 287 references from one section to another section. 288 During linktime or runtime, some sections are dropped; 289 any use of code/data previously in these sections would 290 most likely result in an oops. 291 In the code, functions and variables are annotated with 292 __init,, etc. (see the full list in include/linux/init.h), 293 which results in the code/data being placed in specific sections. 294 The section mismatch analysis is always performed after a full 295 kernel build, and enabling this option causes the following 296 additional steps to occur: 297 - Add the option -fno-inline-functions-called-once to gcc commands. 298 When inlining a function annotated with __init in a non-init 299 function, we would lose the section information and thus 300 the analysis would not catch the illegal reference. 301 This option tells gcc to inline less (but it does result in 302 a larger kernel). 303 - Run the section mismatch analysis for each module/built-in.o file. 304 When we run the section mismatch analysis on vmlinux.o, we 305 lose valueble information about where the mismatch was 306 introduced. 307 Running the analysis for each module/built-in.o file 308 tells where the mismatch happens much closer to the 309 source. The drawback is that the same mismatch is 310 reported at least twice. 311 - Enable verbose reporting from modpost in order to help resolve 312 the section mismatches that are reported. 313 314# 315# Select this config option from the architecture Kconfig, if it 316# is preferred to always offer frame pointers as a config 317# option on the architecture (regardless of KERNEL_DEBUG): 318# 319config ARCH_WANT_FRAME_POINTERS 320 bool 321 help 322 323config FRAME_POINTER 324 bool "Compile the kernel with frame pointers" 325 depends on DEBUG_KERNEL && \ 326 (CRIS || M68K || FRV || UML || \ 327 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \ 328 ARCH_WANT_FRAME_POINTERS 329 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 330 help 331 If you say Y here the resulting kernel image will be slightly 332 larger and slower, but it gives very useful debugging information 333 in case of kernel bugs. (precise oopses/stacktraces/warnings) 334 335config DEBUG_FORCE_WEAK_PER_CPU 336 bool "Force weak per-cpu definitions" 337 depends on DEBUG_KERNEL 338 help 339 s390 and alpha require percpu variables in modules to be 340 defined weak to work around addressing range issue which 341 puts the following two restrictions on percpu variable 342 definitions. 343 344 1. percpu symbols must be unique whether static or not 345 2. percpu variables can't be defined inside a function 346 347 To ensure that generic code follows the above rules, this 348 option forces all percpu variables to be defined as weak. 349 350endmenu # "Compiler options" 351 352config MAGIC_SYSRQ 353 bool "Magic SysRq key" 354 depends on !UML 355 help 356 If you say Y here, you will have some control over the system even 357 if the system crashes for example during kernel debugging (e.g., you 358 will be able to flush the buffer cache to disk, reboot the system 359 immediately or dump some status information). This is accomplished 360 by pressing various keys while holding SysRq (Alt+PrintScreen). It 361 also works on a serial console (on PC hardware at least), if you 362 send a BREAK and then within 5 seconds a command keypress. The 363 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 364 unless you really know what this hack does. 365 366config MAGIC_SYSRQ_DEFAULT_ENABLE 367 hex "Enable magic SysRq key functions by default" 368 depends on MAGIC_SYSRQ 369 default 0x1 370 help 371 Specifies which SysRq key functions are enabled by default. 372 This may be set to 1 or 0 to enable or disable them all, or 373 to a bitmask as described in Documentation/sysrq.txt. 374 375config DEBUG_KERNEL 376 bool "Kernel debugging" 377 help 378 Say Y here if you are developing drivers or trying to debug and 379 identify kernel problems. 380 381menu "Memory Debugging" 382 383source mm/Kconfig.debug 384 385config DEBUG_OBJECTS 386 bool "Debug object operations" 387 depends on DEBUG_KERNEL 388 help 389 If you say Y here, additional code will be inserted into the 390 kernel to track the life time of various objects and validate 391 the operations on those objects. 392 393config DEBUG_OBJECTS_SELFTEST 394 bool "Debug objects selftest" 395 depends on DEBUG_OBJECTS 396 help 397 This enables the selftest of the object debug code. 398 399config DEBUG_OBJECTS_FREE 400 bool "Debug objects in freed memory" 401 depends on DEBUG_OBJECTS 402 help 403 This enables checks whether a k/v free operation frees an area 404 which contains an object which has not been deactivated 405 properly. This can make kmalloc/kfree-intensive workloads 406 much slower. 407 408config DEBUG_OBJECTS_TIMERS 409 bool "Debug timer objects" 410 depends on DEBUG_OBJECTS 411 help 412 If you say Y here, additional code will be inserted into the 413 timer routines to track the life time of timer objects and 414 validate the timer operations. 415 416config DEBUG_OBJECTS_WORK 417 bool "Debug work objects" 418 depends on DEBUG_OBJECTS 419 help 420 If you say Y here, additional code will be inserted into the 421 work queue routines to track the life time of work objects and 422 validate the work operations. 423 424config DEBUG_OBJECTS_RCU_HEAD 425 bool "Debug RCU callbacks objects" 426 depends on DEBUG_OBJECTS 427 help 428 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 429 430config DEBUG_OBJECTS_PERCPU_COUNTER 431 bool "Debug percpu counter objects" 432 depends on DEBUG_OBJECTS 433 help 434 If you say Y here, additional code will be inserted into the 435 percpu counter routines to track the life time of percpu counter 436 objects and validate the percpu counter operations. 437 438config DEBUG_OBJECTS_ENABLE_DEFAULT 439 int "debug_objects bootup default value (0-1)" 440 range 0 1 441 default "1" 442 depends on DEBUG_OBJECTS 443 help 444 Debug objects boot parameter default value 445 446config DEBUG_SLAB 447 bool "Debug slab memory allocations" 448 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 449 help 450 Say Y here to have the kernel do limited verification on memory 451 allocation as well as poisoning memory on free to catch use of freed 452 memory. This can make kmalloc/kfree-intensive workloads much slower. 453 454config DEBUG_SLAB_LEAK 455 bool "Memory leak debugging" 456 depends on DEBUG_SLAB 457 458config SLUB_DEBUG_ON 459 bool "SLUB debugging on by default" 460 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 461 default n 462 help 463 Boot with debugging on by default. SLUB boots by default with 464 the runtime debug capabilities switched off. Enabling this is 465 equivalent to specifying the "slub_debug" parameter on boot. 466 There is no support for more fine grained debug control like 467 possible with slub_debug=xxx. SLUB debugging may be switched 468 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 469 "slub_debug=-". 470 471config SLUB_STATS 472 default n 473 bool "Enable SLUB performance statistics" 474 depends on SLUB && SYSFS 475 help 476 SLUB statistics are useful to debug SLUBs allocation behavior in 477 order find ways to optimize the allocator. This should never be 478 enabled for production use since keeping statistics slows down 479 the allocator by a few percentage points. The slabinfo command 480 supports the determination of the most active slabs to figure 481 out which slabs are relevant to a particular load. 482 Try running: slabinfo -DA 483 484config HAVE_DEBUG_KMEMLEAK 485 bool 486 487config DEBUG_KMEMLEAK 488 bool "Kernel memory leak detector" 489 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 490 select DEBUG_FS 491 select STACKTRACE if STACKTRACE_SUPPORT 492 select KALLSYMS 493 select CRC32 494 help 495 Say Y here if you want to enable the memory leak 496 detector. The memory allocation/freeing is traced in a way 497 similar to the Boehm's conservative garbage collector, the 498 difference being that the orphan objects are not freed but 499 only shown in /sys/kernel/debug/kmemleak. Enabling this 500 feature will introduce an overhead to memory 501 allocations. See Documentation/kmemleak.txt for more 502 details. 503 504 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 505 of finding leaks due to the slab objects poisoning. 506 507 In order to access the kmemleak file, debugfs needs to be 508 mounted (usually at /sys/kernel/debug). 509 510config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 511 int "Maximum kmemleak early log entries" 512 depends on DEBUG_KMEMLEAK 513 range 200 40000 514 default 400 515 help 516 Kmemleak must track all the memory allocations to avoid 517 reporting false positives. Since memory may be allocated or 518 freed before kmemleak is initialised, an early log buffer is 519 used to store these actions. If kmemleak reports "early log 520 buffer exceeded", please increase this value. 521 522config DEBUG_KMEMLEAK_TEST 523 tristate "Simple test for the kernel memory leak detector" 524 depends on DEBUG_KMEMLEAK && m 525 help 526 This option enables a module that explicitly leaks memory. 527 528 If unsure, say N. 529 530config DEBUG_KMEMLEAK_DEFAULT_OFF 531 bool "Default kmemleak to off" 532 depends on DEBUG_KMEMLEAK 533 help 534 Say Y here to disable kmemleak by default. It can then be enabled 535 on the command line via kmemleak=on. 536 537config DEBUG_STACK_USAGE 538 bool "Stack utilization instrumentation" 539 depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAG 540 help 541 Enables the display of the minimum amount of free stack which each 542 task has ever had available in the sysrq-T and sysrq-P debug output. 543 544 This option will slow down process creation somewhat. 545 546config DEBUG_VM 547 bool "Debug VM" 548 depends on DEBUG_KERNEL 549 help 550 Enable this to turn on extended checks in the virtual-memory system 551 that may impact performance. 552 553 If unsure, say N. 554 555config DEBUG_VM_VMACACHE 556 bool "Debug VMA caching" 557 depends on DEBUG_VM 558 help 559 Enable this to turn on VMA caching debug information. Doing so 560 can cause significant overhead, so only enable it in non-production 561 environments. 562 563 If unsure, say N. 564 565config DEBUG_VM_RB 566 bool "Debug VM red-black trees" 567 depends on DEBUG_VM 568 help 569 Enable VM red-black tree debugging information and extra validations. 570 571 If unsure, say N. 572 573config DEBUG_VIRTUAL 574 bool "Debug VM translations" 575 depends on DEBUG_KERNEL && X86 576 help 577 Enable some costly sanity checks in virtual to page code. This can 578 catch mistakes with virt_to_page() and friends. 579 580 If unsure, say N. 581 582config DEBUG_NOMMU_REGIONS 583 bool "Debug the global anon/private NOMMU mapping region tree" 584 depends on DEBUG_KERNEL && !MMU 585 help 586 This option causes the global tree of anonymous and private mapping 587 regions to be regularly checked for invalid topology. 588 589config DEBUG_MEMORY_INIT 590 bool "Debug memory initialisation" if EXPERT 591 default !EXPERT 592 help 593 Enable this for additional checks during memory initialisation. 594 The sanity checks verify aspects of the VM such as the memory model 595 and other information provided by the architecture. Verbose 596 information will be printed at KERN_DEBUG loglevel depending 597 on the mminit_loglevel= command-line option. 598 599 If unsure, say Y 600 601config MEMORY_NOTIFIER_ERROR_INJECT 602 tristate "Memory hotplug notifier error injection module" 603 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 604 help 605 This option provides the ability to inject artificial errors to 606 memory hotplug notifier chain callbacks. It is controlled through 607 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 608 609 If the notifier call chain should be failed with some events 610 notified, write the error code to "actions/<notifier event>/error". 611 612 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 613 614 # cd /sys/kernel/debug/notifier-error-inject/memory 615 # echo -12 > actions/MEM_GOING_OFFLINE/error 616 # echo offline > /sys/devices/system/memory/memoryXXX/state 617 bash: echo: write error: Cannot allocate memory 618 619 To compile this code as a module, choose M here: the module will 620 be called memory-notifier-error-inject. 621 622 If unsure, say N. 623 624config DEBUG_PER_CPU_MAPS 625 bool "Debug access to per_cpu maps" 626 depends on DEBUG_KERNEL 627 depends on SMP 628 help 629 Say Y to verify that the per_cpu map being accessed has 630 been set up. This adds a fair amount of code to kernel memory 631 and decreases performance. 632 633 Say N if unsure. 634 635config DEBUG_HIGHMEM 636 bool "Highmem debugging" 637 depends on DEBUG_KERNEL && HIGHMEM 638 help 639 This option enables additional error checking for high memory 640 systems. Disable for production systems. 641 642config HAVE_DEBUG_STACKOVERFLOW 643 bool 644 645config DEBUG_STACKOVERFLOW 646 bool "Check for stack overflows" 647 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 648 ---help--- 649 Say Y here if you want to check for overflows of kernel, IRQ 650 and exception stacks (if your architecture uses them). This 651 option will show detailed messages if free stack space drops 652 below a certain limit. 653 654 These kinds of bugs usually occur when call-chains in the 655 kernel get too deep, especially when interrupts are 656 involved. 657 658 Use this in cases where you see apparently random memory 659 corruption, especially if it appears in 'struct thread_info' 660 661 If in doubt, say "N". 662 663source "lib/Kconfig.kmemcheck" 664 665source "lib/Kconfig.kasan" 666 667endmenu # "Memory Debugging" 668 669config DEBUG_SHIRQ 670 bool "Debug shared IRQ handlers" 671 depends on DEBUG_KERNEL 672 help 673 Enable this to generate a spurious interrupt as soon as a shared 674 interrupt handler is registered, and just before one is deregistered. 675 Drivers ought to be able to handle interrupts coming in at those 676 points; some don't and need to be caught. 677 678menu "Debug Lockups and Hangs" 679 680config LOCKUP_DETECTOR 681 bool "Detect Hard and Soft Lockups" 682 depends on DEBUG_KERNEL && !S390 683 help 684 Say Y here to enable the kernel to act as a watchdog to detect 685 hard and soft lockups. 686 687 Softlockups are bugs that cause the kernel to loop in kernel 688 mode for more than 20 seconds, without giving other tasks a 689 chance to run. The current stack trace is displayed upon 690 detection and the system will stay locked up. 691 692 Hardlockups are bugs that cause the CPU to loop in kernel mode 693 for more than 10 seconds, without letting other interrupts have a 694 chance to run. The current stack trace is displayed upon detection 695 and the system will stay locked up. 696 697 The overhead should be minimal. A periodic hrtimer runs to 698 generate interrupts and kick the watchdog task every 4 seconds. 699 An NMI is generated every 10 seconds or so to check for hardlockups. 700 701 The frequency of hrtimer and NMI events and the soft and hard lockup 702 thresholds can be controlled through the sysctl watchdog_thresh. 703 704config HARDLOCKUP_DETECTOR 705 def_bool y 706 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 707 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 708 709config BOOTPARAM_HARDLOCKUP_PANIC 710 bool "Panic (Reboot) On Hard Lockups" 711 depends on HARDLOCKUP_DETECTOR 712 help 713 Say Y here to enable the kernel to panic on "hard lockups", 714 which are bugs that cause the kernel to loop in kernel 715 mode with interrupts disabled for more than 10 seconds (configurable 716 using the watchdog_thresh sysctl). 717 718 Say N if unsure. 719 720config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 721 int 722 depends on HARDLOCKUP_DETECTOR 723 range 0 1 724 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 725 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 726 727config BOOTPARAM_SOFTLOCKUP_PANIC 728 bool "Panic (Reboot) On Soft Lockups" 729 depends on LOCKUP_DETECTOR 730 help 731 Say Y here to enable the kernel to panic on "soft lockups", 732 which are bugs that cause the kernel to loop in kernel 733 mode for more than 20 seconds (configurable using the watchdog_thresh 734 sysctl), without giving other tasks a chance to run. 735 736 The panic can be used in combination with panic_timeout, 737 to cause the system to reboot automatically after a 738 lockup has been detected. This feature is useful for 739 high-availability systems that have uptime guarantees and 740 where a lockup must be resolved ASAP. 741 742 Say N if unsure. 743 744config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 745 int 746 depends on LOCKUP_DETECTOR 747 range 0 1 748 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 749 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 750 751config DETECT_HUNG_TASK 752 bool "Detect Hung Tasks" 753 depends on DEBUG_KERNEL 754 default LOCKUP_DETECTOR 755 help 756 Say Y here to enable the kernel to detect "hung tasks", 757 which are bugs that cause the task to be stuck in 758 uninterruptible "D" state indefinitiley. 759 760 When a hung task is detected, the kernel will print the 761 current stack trace (which you should report), but the 762 task will stay in uninterruptible state. If lockdep is 763 enabled then all held locks will also be reported. This 764 feature has negligible overhead. 765 766config DEFAULT_HUNG_TASK_TIMEOUT 767 int "Default timeout for hung task detection (in seconds)" 768 depends on DETECT_HUNG_TASK 769 default 120 770 help 771 This option controls the default timeout (in seconds) used 772 to determine when a task has become non-responsive and should 773 be considered hung. 774 775 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 776 sysctl or by writing a value to 777 /proc/sys/kernel/hung_task_timeout_secs. 778 779 A timeout of 0 disables the check. The default is two minutes. 780 Keeping the default should be fine in most cases. 781 782config BOOTPARAM_HUNG_TASK_PANIC 783 bool "Panic (Reboot) On Hung Tasks" 784 depends on DETECT_HUNG_TASK 785 help 786 Say Y here to enable the kernel to panic on "hung tasks", 787 which are bugs that cause the kernel to leave a task stuck 788 in uninterruptible "D" state. 789 790 The panic can be used in combination with panic_timeout, 791 to cause the system to reboot automatically after a 792 hung task has been detected. This feature is useful for 793 high-availability systems that have uptime guarantees and 794 where a hung tasks must be resolved ASAP. 795 796 Say N if unsure. 797 798config BOOTPARAM_HUNG_TASK_PANIC_VALUE 799 int 800 depends on DETECT_HUNG_TASK 801 range 0 1 802 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 803 default 1 if BOOTPARAM_HUNG_TASK_PANIC 804 805endmenu # "Debug lockups and hangs" 806 807config PANIC_ON_OOPS 808 bool "Panic on Oops" 809 help 810 Say Y here to enable the kernel to panic when it oopses. This 811 has the same effect as setting oops=panic on the kernel command 812 line. 813 814 This feature is useful to ensure that the kernel does not do 815 anything erroneous after an oops which could result in data 816 corruption or other issues. 817 818 Say N if unsure. 819 820config PANIC_ON_OOPS_VALUE 821 int 822 range 0 1 823 default 0 if !PANIC_ON_OOPS 824 default 1 if PANIC_ON_OOPS 825 826config PANIC_TIMEOUT 827 int "panic timeout" 828 default 0 829 help 830 Set the timeout value (in seconds) until a reboot occurs when the 831 the kernel panics. If n = 0, then we wait forever. A timeout 832 value n > 0 will wait n seconds before rebooting, while a timeout 833 value n < 0 will reboot immediately. 834 835config SCHED_DEBUG 836 bool "Collect scheduler debugging info" 837 depends on DEBUG_KERNEL && PROC_FS 838 default y 839 help 840 If you say Y here, the /proc/sched_debug file will be provided 841 that can help debug the scheduler. The runtime overhead of this 842 option is minimal. 843 844config SCHEDSTATS 845 bool "Collect scheduler statistics" 846 depends on DEBUG_KERNEL && PROC_FS 847 help 848 If you say Y here, additional code will be inserted into the 849 scheduler and related routines to collect statistics about 850 scheduler behavior and provide them in /proc/schedstat. These 851 stats may be useful for both tuning and debugging the scheduler 852 If you aren't debugging the scheduler or trying to tune a specific 853 application, you can say N to avoid the very slight overhead 854 this adds. 855 856config SCHED_STACK_END_CHECK 857 bool "Detect stack corruption on calls to schedule()" 858 depends on DEBUG_KERNEL 859 default n 860 help 861 This option checks for a stack overrun on calls to schedule(). 862 If the stack end location is found to be over written always panic as 863 the content of the corrupted region can no longer be trusted. 864 This is to ensure no erroneous behaviour occurs which could result in 865 data corruption or a sporadic crash at a later stage once the region 866 is examined. The runtime overhead introduced is minimal. 867 868config DEBUG_TIMEKEEPING 869 bool "Enable extra timekeeping sanity checking" 870 help 871 This option will enable additional timekeeping sanity checks 872 which may be helpful when diagnosing issues where timekeeping 873 problems are suspected. 874 875 This may include checks in the timekeeping hotpaths, so this 876 option may have a (very small) performance impact to some 877 workloads. 878 879 If unsure, say N. 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 def_bool PROVE_LOCKING 1197 1198config PROVE_RCU_REPEATEDLY 1199 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1200 depends on PROVE_RCU 1201 default n 1202 help 1203 By itself, PROVE_RCU will disable checking upon issuing the 1204 first warning (or "splat"). This feature prevents such 1205 disabling, allowing multiple RCU-lockdep warnings to be printed 1206 on a single reboot. 1207 1208 Say Y to allow multiple RCU-lockdep warnings per boot. 1209 1210 Say N if you are unsure. 1211 1212config SPARSE_RCU_POINTER 1213 bool "RCU debugging: sparse-based checks for pointer usage" 1214 default n 1215 help 1216 This feature enables the __rcu sparse annotation for 1217 RCU-protected pointers. This annotation will cause sparse 1218 to flag any non-RCU used of annotated pointers. This can be 1219 helpful when debugging RCU usage. Please note that this feature 1220 is not intended to enforce code cleanliness; it is instead merely 1221 a debugging aid. 1222 1223 Say Y to make sparse flag questionable use of RCU-protected pointers 1224 1225 Say N if you are unsure. 1226 1227config TORTURE_TEST 1228 tristate 1229 default n 1230 1231config RCU_TORTURE_TEST 1232 tristate "torture tests for RCU" 1233 depends on DEBUG_KERNEL 1234 select TORTURE_TEST 1235 select SRCU 1236 default n 1237 help 1238 This option provides a kernel module that runs torture tests 1239 on the RCU infrastructure. The kernel module may be built 1240 after the fact on the running kernel to be tested, if desired. 1241 1242 Say Y here if you want RCU torture tests to be built into 1243 the kernel. 1244 Say M if you want the RCU torture tests to build as a module. 1245 Say N if you are unsure. 1246 1247config RCU_TORTURE_TEST_RUNNABLE 1248 bool "torture tests for RCU runnable by default" 1249 depends on RCU_TORTURE_TEST = y 1250 default n 1251 help 1252 This option provides a way to build the RCU torture tests 1253 directly into the kernel without them starting up at boot 1254 time. You can use /proc/sys/kernel/rcutorture_runnable 1255 to manually override this setting. This /proc file is 1256 available only when the RCU torture tests have been built 1257 into the kernel. 1258 1259 Say Y here if you want the RCU torture tests to start during 1260 boot (you probably don't). 1261 Say N here if you want the RCU torture tests to start only 1262 after being manually enabled via /proc. 1263 1264config RCU_TORTURE_TEST_SLOW_INIT 1265 bool "Slow down RCU grace-period initialization to expose races" 1266 depends on RCU_TORTURE_TEST 1267 help 1268 This option makes grace-period initialization block for a 1269 few jiffies between initializing each pair of consecutive 1270 rcu_node structures. This helps to expose races involving 1271 grace-period initialization, in other words, it makes your 1272 kernel less stable. It can also greatly increase grace-period 1273 latency, especially on systems with large numbers of CPUs. 1274 This is useful when torture-testing RCU, but in almost no 1275 other circumstance. 1276 1277 Say Y here if you want your system to crash and hang more often. 1278 Say N if you want a sane system. 1279 1280config RCU_TORTURE_TEST_SLOW_INIT_DELAY 1281 int "How much to slow down RCU grace-period initialization" 1282 range 0 5 1283 default 3 1284 help 1285 This option specifies the number of jiffies to wait between 1286 each rcu_node structure initialization. 1287 1288config RCU_CPU_STALL_TIMEOUT 1289 int "RCU CPU stall timeout in seconds" 1290 depends on RCU_STALL_COMMON 1291 range 3 300 1292 default 21 1293 help 1294 If a given RCU grace period extends more than the specified 1295 number of seconds, a CPU stall warning is printed. If the 1296 RCU grace period persists, additional CPU stall warnings are 1297 printed at more widely spaced intervals. 1298 1299config RCU_CPU_STALL_INFO 1300 bool "Print additional diagnostics on RCU CPU stall" 1301 depends on (TREE_RCU || PREEMPT_RCU) && DEBUG_KERNEL 1302 default y 1303 help 1304 For each stalled CPU that is aware of the current RCU grace 1305 period, print out additional per-CPU diagnostic information 1306 regarding scheduling-clock ticks, idle state, and, 1307 for RCU_FAST_NO_HZ kernels, idle-entry state. 1308 1309 Say N if you are unsure. 1310 1311 Say Y if you want to enable such diagnostics. 1312 1313config RCU_TRACE 1314 bool "Enable tracing for RCU" 1315 depends on DEBUG_KERNEL 1316 select TRACE_CLOCK 1317 help 1318 This option provides tracing in RCU which presents stats 1319 in debugfs for debugging RCU implementation. 1320 1321 Say Y here if you want to enable RCU tracing 1322 Say N if you are unsure. 1323 1324endmenu # "RCU Debugging" 1325 1326config DEBUG_BLOCK_EXT_DEVT 1327 bool "Force extended block device numbers and spread them" 1328 depends on DEBUG_KERNEL 1329 depends on BLOCK 1330 default n 1331 help 1332 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1333 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1334 YOU ARE DOING. Distros, please enable this and fix whatever 1335 is broken. 1336 1337 Conventionally, block device numbers are allocated from 1338 predetermined contiguous area. However, extended block area 1339 may introduce non-contiguous block device numbers. This 1340 option forces most block device numbers to be allocated from 1341 the extended space and spreads them to discover kernel or 1342 userland code paths which assume predetermined contiguous 1343 device number allocation. 1344 1345 Note that turning on this debug option shuffles all the 1346 device numbers for all IDE and SCSI devices including libata 1347 ones, so root partition specified using device number 1348 directly (via rdev or root=MAJ:MIN) won't work anymore. 1349 Textual device names (root=/dev/sdXn) will continue to work. 1350 1351 Say N if you are unsure. 1352 1353config NOTIFIER_ERROR_INJECTION 1354 tristate "Notifier error injection" 1355 depends on DEBUG_KERNEL 1356 select DEBUG_FS 1357 help 1358 This option provides the ability to inject artificial errors to 1359 specified notifier chain callbacks. It is useful to test the error 1360 handling of notifier call chain failures. 1361 1362 Say N if unsure. 1363 1364config CPU_NOTIFIER_ERROR_INJECT 1365 tristate "CPU notifier error injection module" 1366 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1367 help 1368 This option provides a kernel module that can be used to test 1369 the error handling of the cpu notifiers by injecting artificial 1370 errors to CPU notifier chain callbacks. It is controlled through 1371 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1372 1373 If the notifier call chain should be failed with some events 1374 notified, write the error code to "actions/<notifier event>/error". 1375 1376 Example: Inject CPU offline error (-1 == -EPERM) 1377 1378 # cd /sys/kernel/debug/notifier-error-inject/cpu 1379 # echo -1 > actions/CPU_DOWN_PREPARE/error 1380 # echo 0 > /sys/devices/system/cpu/cpu1/online 1381 bash: echo: write error: Operation not permitted 1382 1383 To compile this code as a module, choose M here: the module will 1384 be called cpu-notifier-error-inject. 1385 1386 If unsure, say N. 1387 1388config PM_NOTIFIER_ERROR_INJECT 1389 tristate "PM notifier error injection module" 1390 depends on PM && NOTIFIER_ERROR_INJECTION 1391 default m if PM_DEBUG 1392 help 1393 This option provides the ability to inject artificial errors to 1394 PM notifier chain callbacks. It is controlled through debugfs 1395 interface /sys/kernel/debug/notifier-error-inject/pm 1396 1397 If the notifier call chain should be failed with some events 1398 notified, write the error code to "actions/<notifier event>/error". 1399 1400 Example: Inject PM suspend error (-12 = -ENOMEM) 1401 1402 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1403 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1404 # echo mem > /sys/power/state 1405 bash: echo: write error: Cannot allocate memory 1406 1407 To compile this code as a module, choose M here: the module will 1408 be called pm-notifier-error-inject. 1409 1410 If unsure, say N. 1411 1412config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1413 tristate "OF reconfig notifier error injection module" 1414 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1415 help 1416 This option provides the ability to inject artificial errors to 1417 OF reconfig notifier chain callbacks. It is controlled 1418 through debugfs interface under 1419 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1420 1421 If the notifier call chain should be failed with some events 1422 notified, write the error code to "actions/<notifier event>/error". 1423 1424 To compile this code as a module, choose M here: the module will 1425 be called of-reconfig-notifier-error-inject. 1426 1427 If unsure, say N. 1428 1429config FAULT_INJECTION 1430 bool "Fault-injection framework" 1431 depends on DEBUG_KERNEL 1432 help 1433 Provide fault-injection framework. 1434 For more details, see Documentation/fault-injection/. 1435 1436config FAILSLAB 1437 bool "Fault-injection capability for kmalloc" 1438 depends on FAULT_INJECTION 1439 depends on SLAB || SLUB 1440 help 1441 Provide fault-injection capability for kmalloc. 1442 1443config FAIL_PAGE_ALLOC 1444 bool "Fault-injection capabilitiy for alloc_pages()" 1445 depends on FAULT_INJECTION 1446 help 1447 Provide fault-injection capability for alloc_pages(). 1448 1449config FAIL_MAKE_REQUEST 1450 bool "Fault-injection capability for disk IO" 1451 depends on FAULT_INJECTION && BLOCK 1452 help 1453 Provide fault-injection capability for disk IO. 1454 1455config FAIL_IO_TIMEOUT 1456 bool "Fault-injection capability for faking disk interrupts" 1457 depends on FAULT_INJECTION && BLOCK 1458 help 1459 Provide fault-injection capability on end IO handling. This 1460 will make the block layer "forget" an interrupt as configured, 1461 thus exercising the error handling. 1462 1463 Only works with drivers that use the generic timeout handling, 1464 for others it wont do anything. 1465 1466config FAIL_MMC_REQUEST 1467 bool "Fault-injection capability for MMC IO" 1468 select DEBUG_FS 1469 depends on FAULT_INJECTION && MMC 1470 help 1471 Provide fault-injection capability for MMC IO. 1472 This will make the mmc core return data errors. This is 1473 useful to test the error handling in the mmc block device 1474 and to test how the mmc host driver handles retries from 1475 the block device. 1476 1477config FAULT_INJECTION_DEBUG_FS 1478 bool "Debugfs entries for fault-injection capabilities" 1479 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1480 help 1481 Enable configuration of fault-injection capabilities via debugfs. 1482 1483config FAULT_INJECTION_STACKTRACE_FILTER 1484 bool "stacktrace filter for fault-injection capabilities" 1485 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1486 depends on !X86_64 1487 select STACKTRACE 1488 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1489 help 1490 Provide stacktrace filter for fault-injection capabilities 1491 1492config LATENCYTOP 1493 bool "Latency measuring infrastructure" 1494 depends on HAVE_LATENCYTOP_SUPPORT 1495 depends on DEBUG_KERNEL 1496 depends on STACKTRACE_SUPPORT 1497 depends on PROC_FS 1498 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1499 select KALLSYMS 1500 select KALLSYMS_ALL 1501 select STACKTRACE 1502 select SCHEDSTATS 1503 select SCHED_DEBUG 1504 help 1505 Enable this option if you want to use the LatencyTOP tool 1506 to find out which userspace is blocking on what kernel operations. 1507 1508config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1509 bool 1510 1511config DEBUG_STRICT_USER_COPY_CHECKS 1512 bool "Strict user copy size checks" 1513 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1514 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING 1515 help 1516 Enabling this option turns a certain set of sanity checks for user 1517 copy operations into compile time failures. 1518 1519 The copy_from_user() etc checks are there to help test if there 1520 are sufficient security checks on the length argument of 1521 the copy operation, by having gcc prove that the argument is 1522 within bounds. 1523 1524 If unsure, say N. 1525 1526source kernel/trace/Kconfig 1527 1528menu "Runtime Testing" 1529 1530config LKDTM 1531 tristate "Linux Kernel Dump Test Tool Module" 1532 depends on DEBUG_FS 1533 depends on BLOCK 1534 default n 1535 help 1536 This module enables testing of the different dumping mechanisms by 1537 inducing system failures at predefined crash points. 1538 If you don't need it: say N 1539 Choose M here to compile this code as a module. The module will be 1540 called lkdtm. 1541 1542 Documentation on how to use the module can be found in 1543 Documentation/fault-injection/provoke-crashes.txt 1544 1545config TEST_LIST_SORT 1546 bool "Linked list sorting test" 1547 depends on DEBUG_KERNEL 1548 help 1549 Enable this to turn on 'list_sort()' function test. This test is 1550 executed only once during system boot, so affects only boot time. 1551 1552 If unsure, say N. 1553 1554config KPROBES_SANITY_TEST 1555 bool "Kprobes sanity tests" 1556 depends on DEBUG_KERNEL 1557 depends on KPROBES 1558 default n 1559 help 1560 This option provides for testing basic kprobes functionality on 1561 boot. A sample kprobe, jprobe and kretprobe are inserted and 1562 verified for functionality. 1563 1564 Say N if you are unsure. 1565 1566config BACKTRACE_SELF_TEST 1567 tristate "Self test for the backtrace code" 1568 depends on DEBUG_KERNEL 1569 default n 1570 help 1571 This option provides a kernel module that can be used to test 1572 the kernel stack backtrace code. This option is not useful 1573 for distributions or general kernels, but only for kernel 1574 developers working on architecture code. 1575 1576 Note that if you want to also test saved backtraces, you will 1577 have to enable STACKTRACE as well. 1578 1579 Say N if you are unsure. 1580 1581config RBTREE_TEST 1582 tristate "Red-Black tree test" 1583 depends on DEBUG_KERNEL 1584 help 1585 A benchmark measuring the performance of the rbtree library. 1586 Also includes rbtree invariant checks. 1587 1588config INTERVAL_TREE_TEST 1589 tristate "Interval tree test" 1590 depends on m && DEBUG_KERNEL 1591 select INTERVAL_TREE 1592 help 1593 A benchmark measuring the performance of the interval tree library 1594 1595config PERCPU_TEST 1596 tristate "Per cpu operations test" 1597 depends on m && DEBUG_KERNEL 1598 help 1599 Enable this option to build test module which validates per-cpu 1600 operations. 1601 1602 If unsure, say N. 1603 1604config ATOMIC64_SELFTEST 1605 bool "Perform an atomic64_t self-test at boot" 1606 help 1607 Enable this option to test the atomic64_t functions at boot. 1608 1609 If unsure, say N. 1610 1611config ASYNC_RAID6_TEST 1612 tristate "Self test for hardware accelerated raid6 recovery" 1613 depends on ASYNC_RAID6_RECOV 1614 select ASYNC_MEMCPY 1615 ---help--- 1616 This is a one-shot self test that permutes through the 1617 recovery of all the possible two disk failure scenarios for a 1618 N-disk array. Recovery is performed with the asynchronous 1619 raid6 recovery routines, and will optionally use an offload 1620 engine if one is available. 1621 1622 If unsure, say N. 1623 1624config TEST_HEXDUMP 1625 tristate "Test functions located in the hexdump module at runtime" 1626 1627config TEST_STRING_HELPERS 1628 tristate "Test functions located in the string_helpers module at runtime" 1629 1630config TEST_KSTRTOX 1631 tristate "Test kstrto*() family of functions at runtime" 1632 1633config TEST_RHASHTABLE 1634 tristate "Perform selftest on resizable hash table" 1635 default n 1636 help 1637 Enable this option to test the rhashtable functions at boot. 1638 1639 If unsure, say N. 1640 1641endmenu # runtime tests 1642 1643config PROVIDE_OHCI1394_DMA_INIT 1644 bool "Remote debugging over FireWire early on boot" 1645 depends on PCI && X86 1646 help 1647 If you want to debug problems which hang or crash the kernel early 1648 on boot and the crashing machine has a FireWire port, you can use 1649 this feature to remotely access the memory of the crashed machine 1650 over FireWire. This employs remote DMA as part of the OHCI1394 1651 specification which is now the standard for FireWire controllers. 1652 1653 With remote DMA, you can monitor the printk buffer remotely using 1654 firescope and access all memory below 4GB using fireproxy from gdb. 1655 Even controlling a kernel debugger is possible using remote DMA. 1656 1657 Usage: 1658 1659 If ohci1394_dma=early is used as boot parameter, it will initialize 1660 all OHCI1394 controllers which are found in the PCI config space. 1661 1662 As all changes to the FireWire bus such as enabling and disabling 1663 devices cause a bus reset and thereby disable remote DMA for all 1664 devices, be sure to have the cable plugged and FireWire enabled on 1665 the debugging host before booting the debug target for debugging. 1666 1667 This code (~1k) is freed after boot. By then, the firewire stack 1668 in charge of the OHCI-1394 controllers should be used instead. 1669 1670 See Documentation/debugging-via-ohci1394.txt for more information. 1671 1672config BUILD_DOCSRC 1673 bool "Build targets in Documentation/ tree" 1674 depends on HEADERS_CHECK 1675 help 1676 This option attempts to build objects from the source files in the 1677 kernel Documentation/ tree. 1678 1679 Say N if you are unsure. 1680 1681config DMA_API_DEBUG 1682 bool "Enable debugging of DMA-API usage" 1683 depends on HAVE_DMA_API_DEBUG 1684 help 1685 Enable this option to debug the use of the DMA API by device drivers. 1686 With this option you will be able to detect common bugs in device 1687 drivers like double-freeing of DMA mappings or freeing mappings that 1688 were never allocated. 1689 1690 This also attempts to catch cases where a page owned by DMA is 1691 accessed by the cpu in a way that could cause data corruption. For 1692 example, this enables cow_user_page() to check that the source page is 1693 not undergoing DMA. 1694 1695 This option causes a performance degradation. Use only if you want to 1696 debug device drivers and dma interactions. 1697 1698 If unsure, say N. 1699 1700config TEST_LKM 1701 tristate "Test module loading with 'hello world' module" 1702 default n 1703 depends on m 1704 help 1705 This builds the "test_module" module that emits "Hello, world" 1706 on printk when loaded. It is designed to be used for basic 1707 evaluation of the module loading subsystem (for example when 1708 validating module verification). It lacks any extra dependencies, 1709 and will not normally be loaded by the system unless explicitly 1710 requested by name. 1711 1712 If unsure, say N. 1713 1714config TEST_USER_COPY 1715 tristate "Test user/kernel boundary protections" 1716 default n 1717 depends on m 1718 help 1719 This builds the "test_user_copy" module that runs sanity checks 1720 on the copy_to/from_user infrastructure, making sure basic 1721 user/kernel boundary testing is working. If it fails to load, 1722 a regression has been detected in the user/kernel memory boundary 1723 protections. 1724 1725 If unsure, say N. 1726 1727config TEST_BPF 1728 tristate "Test BPF filter functionality" 1729 default n 1730 depends on m && NET 1731 help 1732 This builds the "test_bpf" module that runs various test vectors 1733 against the BPF interpreter or BPF JIT compiler depending on the 1734 current setting. This is in particular useful for BPF JIT compiler 1735 development, but also to run regression tests against changes in 1736 the interpreter code. It also enables test stubs for eBPF maps and 1737 verifier used by user space verifier testsuite. 1738 1739 If unsure, say N. 1740 1741config TEST_FIRMWARE 1742 tristate "Test firmware loading via userspace interface" 1743 default n 1744 depends on FW_LOADER 1745 help 1746 This builds the "test_firmware" module that creates a userspace 1747 interface for testing firmware loading. This can be used to 1748 control the triggering of firmware loading without needing an 1749 actual firmware-using device. The contents can be rechecked by 1750 userspace. 1751 1752 If unsure, say N. 1753 1754config TEST_UDELAY 1755 tristate "udelay test driver" 1756 default n 1757 help 1758 This builds the "udelay_test" module that helps to make sure 1759 that udelay() is working properly. 1760 1761 If unsure, say N. 1762 1763config MEMTEST 1764 bool "Memtest" 1765 depends on HAVE_MEMBLOCK 1766 ---help--- 1767 This option adds a kernel parameter 'memtest', which allows memtest 1768 to be set. 1769 memtest=0, mean disabled; -- default 1770 memtest=1, mean do 1 test pattern; 1771 ... 1772 memtest=17, mean do 17 test patterns. 1773 If you are unsure how to answer this question, answer N. 1774 1775source "samples/Kconfig" 1776 1777source "lib/Kconfig.kgdb" 1778 1779