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 0 if KASAN 201 default 1024 if !64BIT 202 default 2048 if 64BIT 203 help 204 Tell gcc to warn at build time for stack frames larger than this. 205 Setting this too low will cause a lot of warnings. 206 Setting it to 0 disables the warning. 207 Requires gcc 4.4 208 209config STRIP_ASM_SYMS 210 bool "Strip assembler-generated symbols during link" 211 default n 212 help 213 Strip internal assembler-generated symbols during a link (symbols 214 that look like '.Lxxx') so they don't pollute the output of 215 get_wchan() and suchlike. 216 217config READABLE_ASM 218 bool "Generate readable assembler code" 219 depends on DEBUG_KERNEL 220 help 221 Disable some compiler optimizations that tend to generate human unreadable 222 assembler output. This may make the kernel slightly slower, but it helps 223 to keep kernel developers who have to stare a lot at assembler listings 224 sane. 225 226config UNUSED_SYMBOLS 227 bool "Enable unused/obsolete exported symbols" 228 default y if X86 229 help 230 Unused but exported symbols make the kernel needlessly bigger. For 231 that reason most of these unused exports will soon be removed. This 232 option is provided temporarily to provide a transition period in case 233 some external kernel module needs one of these symbols anyway. If you 234 encounter such a case in your module, consider if you are actually 235 using the right API. (rationale: since nobody in the kernel is using 236 this in a module, there is a pretty good chance it's actually the 237 wrong interface to use). If you really need the symbol, please send a 238 mail to the linux kernel mailing list mentioning the symbol and why 239 you really need it, and what the merge plan to the mainline kernel for 240 your module is. 241 242config PAGE_OWNER 243 bool "Track page owner" 244 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 245 select DEBUG_FS 246 select STACKTRACE 247 select PAGE_EXTENSION 248 help 249 This keeps track of what call chain is the owner of a page, may 250 help to find bare alloc_page(s) leaks. Even if you include this 251 feature on your build, it is disabled in default. You should pass 252 "page_owner=on" to boot parameter in order to enable it. Eats 253 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 254 for user-space helper. 255 256 If unsure, say N. 257 258config DEBUG_FS 259 bool "Debug Filesystem" 260 help 261 debugfs is a virtual file system that kernel developers use to put 262 debugging files into. Enable this option to be able to read and 263 write to these files. 264 265 For detailed documentation on the debugfs API, see 266 Documentation/DocBook/filesystems. 267 268 If unsure, say N. 269 270config HEADERS_CHECK 271 bool "Run 'make headers_check' when building vmlinux" 272 depends on !UML 273 help 274 This option will extract the user-visible kernel headers whenever 275 building the kernel, and will run basic sanity checks on them to 276 ensure that exported files do not attempt to include files which 277 were not exported, etc. 278 279 If you're making modifications to header files which are 280 relevant for userspace, say 'Y', and check the headers 281 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 282 your build tree), to make sure they're suitable. 283 284config DEBUG_SECTION_MISMATCH 285 bool "Enable full Section mismatch analysis" 286 help 287 The section mismatch analysis checks if there are illegal 288 references from one section to another section. 289 During linktime or runtime, some sections are dropped; 290 any use of code/data previously in these sections would 291 most likely result in an oops. 292 In the code, functions and variables are annotated with 293 __init,, etc. (see the full list in include/linux/init.h), 294 which results in the code/data being placed in specific sections. 295 The section mismatch analysis is always performed after a full 296 kernel build, and enabling this option causes the following 297 additional steps to occur: 298 - Add the option -fno-inline-functions-called-once to gcc commands. 299 When inlining a function annotated with __init in a non-init 300 function, we would lose the section information and thus 301 the analysis would not catch the illegal reference. 302 This option tells gcc to inline less (but it does result in 303 a larger kernel). 304 - Run the section mismatch analysis for each module/built-in.o file. 305 When we run the section mismatch analysis on vmlinux.o, we 306 lose valueble information about where the mismatch was 307 introduced. 308 Running the analysis for each module/built-in.o file 309 tells where the mismatch happens much closer to the 310 source. The drawback is that the same mismatch is 311 reported at least twice. 312 - Enable verbose reporting from modpost in order to help resolve 313 the section mismatches that are reported. 314 315# 316# Select this config option from the architecture Kconfig, if it 317# is preferred to always offer frame pointers as a config 318# option on the architecture (regardless of KERNEL_DEBUG): 319# 320config ARCH_WANT_FRAME_POINTERS 321 bool 322 help 323 324config FRAME_POINTER 325 bool "Compile the kernel with frame pointers" 326 depends on DEBUG_KERNEL && \ 327 (CRIS || M68K || FRV || UML || \ 328 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \ 329 ARCH_WANT_FRAME_POINTERS 330 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 331 help 332 If you say Y here the resulting kernel image will be slightly 333 larger and slower, but it gives very useful debugging information 334 in case of kernel bugs. (precise oopses/stacktraces/warnings) 335 336config DEBUG_FORCE_WEAK_PER_CPU 337 bool "Force weak per-cpu definitions" 338 depends on DEBUG_KERNEL 339 help 340 s390 and alpha require percpu variables in modules to be 341 defined weak to work around addressing range issue which 342 puts the following two restrictions on percpu variable 343 definitions. 344 345 1. percpu symbols must be unique whether static or not 346 2. percpu variables can't be defined inside a function 347 348 To ensure that generic code follows the above rules, this 349 option forces all percpu variables to be defined as weak. 350 351endmenu # "Compiler options" 352 353config MAGIC_SYSRQ 354 bool "Magic SysRq key" 355 depends on !UML 356 help 357 If you say Y here, you will have some control over the system even 358 if the system crashes for example during kernel debugging (e.g., you 359 will be able to flush the buffer cache to disk, reboot the system 360 immediately or dump some status information). This is accomplished 361 by pressing various keys while holding SysRq (Alt+PrintScreen). It 362 also works on a serial console (on PC hardware at least), if you 363 send a BREAK and then within 5 seconds a command keypress. The 364 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 365 unless you really know what this hack does. 366 367config MAGIC_SYSRQ_DEFAULT_ENABLE 368 hex "Enable magic SysRq key functions by default" 369 depends on MAGIC_SYSRQ 370 default 0x1 371 help 372 Specifies which SysRq key functions are enabled by default. 373 This may be set to 1 or 0 to enable or disable them all, or 374 to a bitmask as described in Documentation/sysrq.txt. 375 376config DEBUG_KERNEL 377 bool "Kernel debugging" 378 help 379 Say Y here if you are developing drivers or trying to debug and 380 identify kernel problems. 381 382menu "Memory Debugging" 383 384source mm/Kconfig.debug 385 386config DEBUG_OBJECTS 387 bool "Debug object operations" 388 depends on DEBUG_KERNEL 389 help 390 If you say Y here, additional code will be inserted into the 391 kernel to track the life time of various objects and validate 392 the operations on those objects. 393 394config DEBUG_OBJECTS_SELFTEST 395 bool "Debug objects selftest" 396 depends on DEBUG_OBJECTS 397 help 398 This enables the selftest of the object debug code. 399 400config DEBUG_OBJECTS_FREE 401 bool "Debug objects in freed memory" 402 depends on DEBUG_OBJECTS 403 help 404 This enables checks whether a k/v free operation frees an area 405 which contains an object which has not been deactivated 406 properly. This can make kmalloc/kfree-intensive workloads 407 much slower. 408 409config DEBUG_OBJECTS_TIMERS 410 bool "Debug timer objects" 411 depends on DEBUG_OBJECTS 412 help 413 If you say Y here, additional code will be inserted into the 414 timer routines to track the life time of timer objects and 415 validate the timer operations. 416 417config DEBUG_OBJECTS_WORK 418 bool "Debug work objects" 419 depends on DEBUG_OBJECTS 420 help 421 If you say Y here, additional code will be inserted into the 422 work queue routines to track the life time of work objects and 423 validate the work operations. 424 425config DEBUG_OBJECTS_RCU_HEAD 426 bool "Debug RCU callbacks objects" 427 depends on DEBUG_OBJECTS 428 help 429 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 430 431config DEBUG_OBJECTS_PERCPU_COUNTER 432 bool "Debug percpu counter objects" 433 depends on DEBUG_OBJECTS 434 help 435 If you say Y here, additional code will be inserted into the 436 percpu counter routines to track the life time of percpu counter 437 objects and validate the percpu counter operations. 438 439config DEBUG_OBJECTS_ENABLE_DEFAULT 440 int "debug_objects bootup default value (0-1)" 441 range 0 1 442 default "1" 443 depends on DEBUG_OBJECTS 444 help 445 Debug objects boot parameter default value 446 447config DEBUG_SLAB 448 bool "Debug slab memory allocations" 449 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 450 help 451 Say Y here to have the kernel do limited verification on memory 452 allocation as well as poisoning memory on free to catch use of freed 453 memory. This can make kmalloc/kfree-intensive workloads much slower. 454 455config DEBUG_SLAB_LEAK 456 bool "Memory leak debugging" 457 depends on DEBUG_SLAB 458 459config SLUB_DEBUG_ON 460 bool "SLUB debugging on by default" 461 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 462 default n 463 help 464 Boot with debugging on by default. SLUB boots by default with 465 the runtime debug capabilities switched off. Enabling this is 466 equivalent to specifying the "slub_debug" parameter on boot. 467 There is no support for more fine grained debug control like 468 possible with slub_debug=xxx. SLUB debugging may be switched 469 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 470 "slub_debug=-". 471 472config SLUB_STATS 473 default n 474 bool "Enable SLUB performance statistics" 475 depends on SLUB && SYSFS 476 help 477 SLUB statistics are useful to debug SLUBs allocation behavior in 478 order find ways to optimize the allocator. This should never be 479 enabled for production use since keeping statistics slows down 480 the allocator by a few percentage points. The slabinfo command 481 supports the determination of the most active slabs to figure 482 out which slabs are relevant to a particular load. 483 Try running: slabinfo -DA 484 485config HAVE_DEBUG_KMEMLEAK 486 bool 487 488config DEBUG_KMEMLEAK 489 bool "Kernel memory leak detector" 490 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 491 select DEBUG_FS 492 select STACKTRACE if STACKTRACE_SUPPORT 493 select KALLSYMS 494 select CRC32 495 help 496 Say Y here if you want to enable the memory leak 497 detector. The memory allocation/freeing is traced in a way 498 similar to the Boehm's conservative garbage collector, the 499 difference being that the orphan objects are not freed but 500 only shown in /sys/kernel/debug/kmemleak. Enabling this 501 feature will introduce an overhead to memory 502 allocations. See Documentation/kmemleak.txt for more 503 details. 504 505 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 506 of finding leaks due to the slab objects poisoning. 507 508 In order to access the kmemleak file, debugfs needs to be 509 mounted (usually at /sys/kernel/debug). 510 511config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 512 int "Maximum kmemleak early log entries" 513 depends on DEBUG_KMEMLEAK 514 range 200 40000 515 default 400 516 help 517 Kmemleak must track all the memory allocations to avoid 518 reporting false positives. Since memory may be allocated or 519 freed before kmemleak is initialised, an early log buffer is 520 used to store these actions. If kmemleak reports "early log 521 buffer exceeded", please increase this value. 522 523config DEBUG_KMEMLEAK_TEST 524 tristate "Simple test for the kernel memory leak detector" 525 depends on DEBUG_KMEMLEAK && m 526 help 527 This option enables a module that explicitly leaks memory. 528 529 If unsure, say N. 530 531config DEBUG_KMEMLEAK_DEFAULT_OFF 532 bool "Default kmemleak to off" 533 depends on DEBUG_KMEMLEAK 534 help 535 Say Y here to disable kmemleak by default. It can then be enabled 536 on the command line via kmemleak=on. 537 538config DEBUG_STACK_USAGE 539 bool "Stack utilization instrumentation" 540 depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAG 541 help 542 Enables the display of the minimum amount of free stack which each 543 task has ever had available in the sysrq-T and sysrq-P debug output. 544 545 This option will slow down process creation somewhat. 546 547config DEBUG_VM 548 bool "Debug VM" 549 depends on DEBUG_KERNEL 550 help 551 Enable this to turn on extended checks in the virtual-memory system 552 that may impact performance. 553 554 If unsure, say N. 555 556config DEBUG_VM_VMACACHE 557 bool "Debug VMA caching" 558 depends on DEBUG_VM 559 help 560 Enable this to turn on VMA caching debug information. Doing so 561 can cause significant overhead, so only enable it in non-production 562 environments. 563 564 If unsure, say N. 565 566config DEBUG_VM_RB 567 bool "Debug VM red-black trees" 568 depends on DEBUG_VM 569 help 570 Enable VM red-black tree debugging information and extra validations. 571 572 If unsure, say N. 573 574config DEBUG_VIRTUAL 575 bool "Debug VM translations" 576 depends on DEBUG_KERNEL && X86 577 help 578 Enable some costly sanity checks in virtual to page code. This can 579 catch mistakes with virt_to_page() and friends. 580 581 If unsure, say N. 582 583config DEBUG_NOMMU_REGIONS 584 bool "Debug the global anon/private NOMMU mapping region tree" 585 depends on DEBUG_KERNEL && !MMU 586 help 587 This option causes the global tree of anonymous and private mapping 588 regions to be regularly checked for invalid topology. 589 590config DEBUG_MEMORY_INIT 591 bool "Debug memory initialisation" if EXPERT 592 default !EXPERT 593 help 594 Enable this for additional checks during memory initialisation. 595 The sanity checks verify aspects of the VM such as the memory model 596 and other information provided by the architecture. Verbose 597 information will be printed at KERN_DEBUG loglevel depending 598 on the mminit_loglevel= command-line option. 599 600 If unsure, say Y 601 602config MEMORY_NOTIFIER_ERROR_INJECT 603 tristate "Memory hotplug notifier error injection module" 604 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 605 help 606 This option provides the ability to inject artificial errors to 607 memory hotplug notifier chain callbacks. It is controlled through 608 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 609 610 If the notifier call chain should be failed with some events 611 notified, write the error code to "actions/<notifier event>/error". 612 613 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 614 615 # cd /sys/kernel/debug/notifier-error-inject/memory 616 # echo -12 > actions/MEM_GOING_OFFLINE/error 617 # echo offline > /sys/devices/system/memory/memoryXXX/state 618 bash: echo: write error: Cannot allocate memory 619 620 To compile this code as a module, choose M here: the module will 621 be called memory-notifier-error-inject. 622 623 If unsure, say N. 624 625config DEBUG_PER_CPU_MAPS 626 bool "Debug access to per_cpu maps" 627 depends on DEBUG_KERNEL 628 depends on SMP 629 help 630 Say Y to verify that the per_cpu map being accessed has 631 been set up. This adds a fair amount of code to kernel memory 632 and decreases performance. 633 634 Say N if unsure. 635 636config DEBUG_HIGHMEM 637 bool "Highmem debugging" 638 depends on DEBUG_KERNEL && HIGHMEM 639 help 640 This option enables additional error checking for high memory 641 systems. Disable for production systems. 642 643config HAVE_DEBUG_STACKOVERFLOW 644 bool 645 646config DEBUG_STACKOVERFLOW 647 bool "Check for stack overflows" 648 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 649 ---help--- 650 Say Y here if you want to check for overflows of kernel, IRQ 651 and exception stacks (if your architecture uses them). This 652 option will show detailed messages if free stack space drops 653 below a certain limit. 654 655 These kinds of bugs usually occur when call-chains in the 656 kernel get too deep, especially when interrupts are 657 involved. 658 659 Use this in cases where you see apparently random memory 660 corruption, especially if it appears in 'struct thread_info' 661 662 If in doubt, say "N". 663 664source "lib/Kconfig.kmemcheck" 665 666source "lib/Kconfig.kasan" 667 668endmenu # "Memory Debugging" 669 670config DEBUG_SHIRQ 671 bool "Debug shared IRQ handlers" 672 depends on DEBUG_KERNEL 673 help 674 Enable this to generate a spurious interrupt as soon as a shared 675 interrupt handler is registered, and just before one is deregistered. 676 Drivers ought to be able to handle interrupts coming in at those 677 points; some don't and need to be caught. 678 679menu "Debug Lockups and Hangs" 680 681config LOCKUP_DETECTOR 682 bool "Detect Hard and Soft Lockups" 683 depends on DEBUG_KERNEL && !S390 684 help 685 Say Y here to enable the kernel to act as a watchdog to detect 686 hard and soft lockups. 687 688 Softlockups are bugs that cause the kernel to loop in kernel 689 mode for more than 20 seconds, without giving other tasks a 690 chance to run. The current stack trace is displayed upon 691 detection and the system will stay locked up. 692 693 Hardlockups are bugs that cause the CPU to loop in kernel mode 694 for more than 10 seconds, without letting other interrupts have a 695 chance to run. The current stack trace is displayed upon detection 696 and the system will stay locked up. 697 698 The overhead should be minimal. A periodic hrtimer runs to 699 generate interrupts and kick the watchdog task every 4 seconds. 700 An NMI is generated every 10 seconds or so to check for hardlockups. 701 702 The frequency of hrtimer and NMI events and the soft and hard lockup 703 thresholds can be controlled through the sysctl watchdog_thresh. 704 705config HARDLOCKUP_DETECTOR 706 def_bool y 707 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 708 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 709 710config BOOTPARAM_HARDLOCKUP_PANIC 711 bool "Panic (Reboot) On Hard Lockups" 712 depends on HARDLOCKUP_DETECTOR 713 help 714 Say Y here to enable the kernel to panic on "hard lockups", 715 which are bugs that cause the kernel to loop in kernel 716 mode with interrupts disabled for more than 10 seconds (configurable 717 using the watchdog_thresh sysctl). 718 719 Say N if unsure. 720 721config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 722 int 723 depends on HARDLOCKUP_DETECTOR 724 range 0 1 725 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 726 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 727 728config BOOTPARAM_SOFTLOCKUP_PANIC 729 bool "Panic (Reboot) On Soft Lockups" 730 depends on LOCKUP_DETECTOR 731 help 732 Say Y here to enable the kernel to panic on "soft lockups", 733 which are bugs that cause the kernel to loop in kernel 734 mode for more than 20 seconds (configurable using the watchdog_thresh 735 sysctl), without giving other tasks a chance to run. 736 737 The panic can be used in combination with panic_timeout, 738 to cause the system to reboot automatically after a 739 lockup has been detected. This feature is useful for 740 high-availability systems that have uptime guarantees and 741 where a lockup must be resolved ASAP. 742 743 Say N if unsure. 744 745config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 746 int 747 depends on LOCKUP_DETECTOR 748 range 0 1 749 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 750 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 751 752config DETECT_HUNG_TASK 753 bool "Detect Hung Tasks" 754 depends on DEBUG_KERNEL 755 default LOCKUP_DETECTOR 756 help 757 Say Y here to enable the kernel to detect "hung tasks", 758 which are bugs that cause the task to be stuck in 759 uninterruptible "D" state indefinitiley. 760 761 When a hung task is detected, the kernel will print the 762 current stack trace (which you should report), but the 763 task will stay in uninterruptible state. If lockdep is 764 enabled then all held locks will also be reported. This 765 feature has negligible overhead. 766 767config DEFAULT_HUNG_TASK_TIMEOUT 768 int "Default timeout for hung task detection (in seconds)" 769 depends on DETECT_HUNG_TASK 770 default 120 771 help 772 This option controls the default timeout (in seconds) used 773 to determine when a task has become non-responsive and should 774 be considered hung. 775 776 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 777 sysctl or by writing a value to 778 /proc/sys/kernel/hung_task_timeout_secs. 779 780 A timeout of 0 disables the check. The default is two minutes. 781 Keeping the default should be fine in most cases. 782 783config BOOTPARAM_HUNG_TASK_PANIC 784 bool "Panic (Reboot) On Hung Tasks" 785 depends on DETECT_HUNG_TASK 786 help 787 Say Y here to enable the kernel to panic on "hung tasks", 788 which are bugs that cause the kernel to leave a task stuck 789 in uninterruptible "D" state. 790 791 The panic can be used in combination with panic_timeout, 792 to cause the system to reboot automatically after a 793 hung task has been detected. This feature is useful for 794 high-availability systems that have uptime guarantees and 795 where a hung tasks must be resolved ASAP. 796 797 Say N if unsure. 798 799config BOOTPARAM_HUNG_TASK_PANIC_VALUE 800 int 801 depends on DETECT_HUNG_TASK 802 range 0 1 803 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 804 default 1 if BOOTPARAM_HUNG_TASK_PANIC 805 806endmenu # "Debug lockups and hangs" 807 808config PANIC_ON_OOPS 809 bool "Panic on Oops" 810 help 811 Say Y here to enable the kernel to panic when it oopses. This 812 has the same effect as setting oops=panic on the kernel command 813 line. 814 815 This feature is useful to ensure that the kernel does not do 816 anything erroneous after an oops which could result in data 817 corruption or other issues. 818 819 Say N if unsure. 820 821config PANIC_ON_OOPS_VALUE 822 int 823 range 0 1 824 default 0 if !PANIC_ON_OOPS 825 default 1 if PANIC_ON_OOPS 826 827config PANIC_TIMEOUT 828 int "panic timeout" 829 default 0 830 help 831 Set the timeout value (in seconds) until a reboot occurs when the 832 the kernel panics. If n = 0, then we wait forever. A timeout 833 value n > 0 will wait n seconds before rebooting, while a timeout 834 value n < 0 will reboot immediately. 835 836config SCHED_DEBUG 837 bool "Collect scheduler debugging info" 838 depends on DEBUG_KERNEL && PROC_FS 839 default y 840 help 841 If you say Y here, the /proc/sched_debug file will be provided 842 that can help debug the scheduler. The runtime overhead of this 843 option is minimal. 844 845config SCHED_INFO 846 bool 847 default n 848 849config SCHEDSTATS 850 bool "Collect scheduler statistics" 851 depends on DEBUG_KERNEL && PROC_FS 852 select SCHED_INFO 853 help 854 If you say Y here, additional code will be inserted into the 855 scheduler and related routines to collect statistics about 856 scheduler behavior and provide them in /proc/schedstat. These 857 stats may be useful for both tuning and debugging the scheduler 858 If you aren't debugging the scheduler or trying to tune a specific 859 application, you can say N to avoid the very slight overhead 860 this adds. 861 862config SCHED_STACK_END_CHECK 863 bool "Detect stack corruption on calls to schedule()" 864 depends on DEBUG_KERNEL 865 default n 866 help 867 This option checks for a stack overrun on calls to schedule(). 868 If the stack end location is found to be over written always panic as 869 the content of the corrupted region can no longer be trusted. 870 This is to ensure no erroneous behaviour occurs which could result in 871 data corruption or a sporadic crash at a later stage once the region 872 is examined. The runtime overhead introduced is minimal. 873 874config DEBUG_TIMEKEEPING 875 bool "Enable extra timekeeping sanity checking" 876 help 877 This option will enable additional timekeeping sanity checks 878 which may be helpful when diagnosing issues where timekeeping 879 problems are suspected. 880 881 This may include checks in the timekeeping hotpaths, so this 882 option may have a (very small) performance impact to some 883 workloads. 884 885 If unsure, say N. 886 887config TIMER_STATS 888 bool "Collect kernel timers statistics" 889 depends on DEBUG_KERNEL && PROC_FS 890 help 891 If you say Y here, additional code will be inserted into the 892 timer routines to collect statistics about kernel timers being 893 reprogrammed. The statistics can be read from /proc/timer_stats. 894 The statistics collection is started by writing 1 to /proc/timer_stats, 895 writing 0 stops it. This feature is useful to collect information 896 about timer usage patterns in kernel and userspace. This feature 897 is lightweight if enabled in the kernel config but not activated 898 (it defaults to deactivated on bootup and will only be activated 899 if some application like powertop activates it explicitly). 900 901config DEBUG_PREEMPT 902 bool "Debug preemptible kernel" 903 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 904 default y 905 help 906 If you say Y here then the kernel will use a debug variant of the 907 commonly used smp_processor_id() function and will print warnings 908 if kernel code uses it in a preemption-unsafe way. Also, the kernel 909 will detect preemption count underflows. 910 911menu "Lock Debugging (spinlocks, mutexes, etc...)" 912 913config DEBUG_RT_MUTEXES 914 bool "RT Mutex debugging, deadlock detection" 915 depends on DEBUG_KERNEL && RT_MUTEXES 916 help 917 This allows rt mutex semantics violations and rt mutex related 918 deadlocks (lockups) to be detected and reported automatically. 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 select TASKS_RCU 1237 default n 1238 help 1239 This option provides a kernel module that runs torture tests 1240 on the RCU infrastructure. The kernel module may be built 1241 after the fact on the running kernel to be tested, if desired. 1242 1243 Say Y here if you want RCU torture tests to be built into 1244 the kernel. 1245 Say M if you want the RCU torture tests to build as a module. 1246 Say N if you are unsure. 1247 1248config RCU_TORTURE_TEST_RUNNABLE 1249 bool "torture tests for RCU runnable by default" 1250 depends on RCU_TORTURE_TEST = y 1251 default n 1252 help 1253 This option provides a way to build the RCU torture tests 1254 directly into the kernel without them starting up at boot 1255 time. You can use /proc/sys/kernel/rcutorture_runnable 1256 to manually override this setting. This /proc file is 1257 available only when the RCU torture tests have been built 1258 into the kernel. 1259 1260 Say Y here if you want the RCU torture tests to start during 1261 boot (you probably don't). 1262 Say N here if you want the RCU torture tests to start only 1263 after being manually enabled via /proc. 1264 1265config RCU_TORTURE_TEST_SLOW_PREINIT 1266 bool "Slow down RCU grace-period pre-initialization to expose races" 1267 depends on RCU_TORTURE_TEST 1268 help 1269 This option delays grace-period pre-initialization (the 1270 propagation of CPU-hotplug changes up the rcu_node combining 1271 tree) for a few jiffies between initializing each pair of 1272 consecutive rcu_node structures. This helps to expose races 1273 involving grace-period pre-initialization, in other words, it 1274 makes your kernel less stable. It can also greatly increase 1275 grace-period latency, especially on systems with large numbers 1276 of CPUs. This is useful when torture-testing RCU, but in 1277 almost no other circumstance. 1278 1279 Say Y here if you want your system to crash and hang more often. 1280 Say N if you want a sane system. 1281 1282config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY 1283 int "How much to slow down RCU grace-period pre-initialization" 1284 range 0 5 1285 default 3 1286 depends on RCU_TORTURE_TEST_SLOW_PREINIT 1287 help 1288 This option specifies the number of jiffies to wait between 1289 each rcu_node structure pre-initialization step. 1290 1291config RCU_TORTURE_TEST_SLOW_INIT 1292 bool "Slow down RCU grace-period initialization to expose races" 1293 depends on RCU_TORTURE_TEST 1294 help 1295 This option delays grace-period initialization for a few 1296 jiffies between initializing each pair of consecutive 1297 rcu_node structures. This helps to expose races involving 1298 grace-period initialization, in other words, it makes your 1299 kernel less stable. It can also greatly increase grace-period 1300 latency, especially on systems with large numbers of CPUs. 1301 This is useful when torture-testing RCU, but in almost no 1302 other circumstance. 1303 1304 Say Y here if you want your system to crash and hang more often. 1305 Say N if you want a sane system. 1306 1307config RCU_TORTURE_TEST_SLOW_INIT_DELAY 1308 int "How much to slow down RCU grace-period initialization" 1309 range 0 5 1310 default 3 1311 depends on RCU_TORTURE_TEST_SLOW_INIT 1312 help 1313 This option specifies the number of jiffies to wait between 1314 each rcu_node structure initialization. 1315 1316config RCU_TORTURE_TEST_SLOW_CLEANUP 1317 bool "Slow down RCU grace-period cleanup to expose races" 1318 depends on RCU_TORTURE_TEST 1319 help 1320 This option delays grace-period cleanup for a few jiffies 1321 between cleaning up each pair of consecutive rcu_node 1322 structures. This helps to expose races involving grace-period 1323 cleanup, in other words, it makes your kernel less stable. 1324 It can also greatly increase grace-period latency, especially 1325 on systems with large numbers of CPUs. This is useful when 1326 torture-testing RCU, but in almost no other circumstance. 1327 1328 Say Y here if you want your system to crash and hang more often. 1329 Say N if you want a sane system. 1330 1331config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY 1332 int "How much to slow down RCU grace-period cleanup" 1333 range 0 5 1334 default 3 1335 depends on RCU_TORTURE_TEST_SLOW_CLEANUP 1336 help 1337 This option specifies the number of jiffies to wait between 1338 each rcu_node structure cleanup operation. 1339 1340config RCU_CPU_STALL_TIMEOUT 1341 int "RCU CPU stall timeout in seconds" 1342 depends on RCU_STALL_COMMON 1343 range 3 300 1344 default 21 1345 help 1346 If a given RCU grace period extends more than the specified 1347 number of seconds, a CPU stall warning is printed. If the 1348 RCU grace period persists, additional CPU stall warnings are 1349 printed at more widely spaced intervals. 1350 1351config RCU_TRACE 1352 bool "Enable tracing for RCU" 1353 depends on DEBUG_KERNEL 1354 select TRACE_CLOCK 1355 help 1356 This option provides tracing in RCU which presents stats 1357 in debugfs for debugging RCU implementation. 1358 1359 Say Y here if you want to enable RCU tracing 1360 Say N if you are unsure. 1361 1362config RCU_EQS_DEBUG 1363 bool "Provide debugging asserts for adding NO_HZ support to an arch" 1364 depends on DEBUG_KERNEL 1365 help 1366 This option provides consistency checks in RCU's handling of 1367 NO_HZ. These checks have proven quite helpful in detecting 1368 bugs in arch-specific NO_HZ code. 1369 1370 Say N here if you need ultimate kernel/user switch latencies 1371 Say Y if you are unsure 1372 1373endmenu # "RCU Debugging" 1374 1375config DEBUG_BLOCK_EXT_DEVT 1376 bool "Force extended block device numbers and spread them" 1377 depends on DEBUG_KERNEL 1378 depends on BLOCK 1379 default n 1380 help 1381 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1382 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1383 YOU ARE DOING. Distros, please enable this and fix whatever 1384 is broken. 1385 1386 Conventionally, block device numbers are allocated from 1387 predetermined contiguous area. However, extended block area 1388 may introduce non-contiguous block device numbers. This 1389 option forces most block device numbers to be allocated from 1390 the extended space and spreads them to discover kernel or 1391 userland code paths which assume predetermined contiguous 1392 device number allocation. 1393 1394 Note that turning on this debug option shuffles all the 1395 device numbers for all IDE and SCSI devices including libata 1396 ones, so root partition specified using device number 1397 directly (via rdev or root=MAJ:MIN) won't work anymore. 1398 Textual device names (root=/dev/sdXn) will continue to work. 1399 1400 Say N if you are unsure. 1401 1402config NOTIFIER_ERROR_INJECTION 1403 tristate "Notifier error injection" 1404 depends on DEBUG_KERNEL 1405 select DEBUG_FS 1406 help 1407 This option provides the ability to inject artificial errors to 1408 specified notifier chain callbacks. It is useful to test the error 1409 handling of notifier call chain failures. 1410 1411 Say N if unsure. 1412 1413config CPU_NOTIFIER_ERROR_INJECT 1414 tristate "CPU notifier error injection module" 1415 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1416 help 1417 This option provides a kernel module that can be used to test 1418 the error handling of the cpu notifiers by injecting artificial 1419 errors to CPU notifier chain callbacks. It is controlled through 1420 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1421 1422 If the notifier call chain should be failed with some events 1423 notified, write the error code to "actions/<notifier event>/error". 1424 1425 Example: Inject CPU offline error (-1 == -EPERM) 1426 1427 # cd /sys/kernel/debug/notifier-error-inject/cpu 1428 # echo -1 > actions/CPU_DOWN_PREPARE/error 1429 # echo 0 > /sys/devices/system/cpu/cpu1/online 1430 bash: echo: write error: Operation not permitted 1431 1432 To compile this code as a module, choose M here: the module will 1433 be called cpu-notifier-error-inject. 1434 1435 If unsure, say N. 1436 1437config PM_NOTIFIER_ERROR_INJECT 1438 tristate "PM notifier error injection module" 1439 depends on PM && NOTIFIER_ERROR_INJECTION 1440 default m if PM_DEBUG 1441 help 1442 This option provides the ability to inject artificial errors to 1443 PM notifier chain callbacks. It is controlled through debugfs 1444 interface /sys/kernel/debug/notifier-error-inject/pm 1445 1446 If the notifier call chain should be failed with some events 1447 notified, write the error code to "actions/<notifier event>/error". 1448 1449 Example: Inject PM suspend error (-12 = -ENOMEM) 1450 1451 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1452 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1453 # echo mem > /sys/power/state 1454 bash: echo: write error: Cannot allocate memory 1455 1456 To compile this code as a module, choose M here: the module will 1457 be called pm-notifier-error-inject. 1458 1459 If unsure, say N. 1460 1461config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1462 tristate "OF reconfig notifier error injection module" 1463 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1464 help 1465 This option provides the ability to inject artificial errors to 1466 OF reconfig notifier chain callbacks. It is controlled 1467 through debugfs interface under 1468 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1469 1470 If the notifier call chain should be failed with some events 1471 notified, write the error code to "actions/<notifier event>/error". 1472 1473 To compile this code as a module, choose M here: the module will 1474 be called of-reconfig-notifier-error-inject. 1475 1476 If unsure, say N. 1477 1478config FAULT_INJECTION 1479 bool "Fault-injection framework" 1480 depends on DEBUG_KERNEL 1481 help 1482 Provide fault-injection framework. 1483 For more details, see Documentation/fault-injection/. 1484 1485config FAILSLAB 1486 bool "Fault-injection capability for kmalloc" 1487 depends on FAULT_INJECTION 1488 depends on SLAB || SLUB 1489 help 1490 Provide fault-injection capability for kmalloc. 1491 1492config FAIL_PAGE_ALLOC 1493 bool "Fault-injection capabilitiy for alloc_pages()" 1494 depends on FAULT_INJECTION 1495 help 1496 Provide fault-injection capability for alloc_pages(). 1497 1498config FAIL_MAKE_REQUEST 1499 bool "Fault-injection capability for disk IO" 1500 depends on FAULT_INJECTION && BLOCK 1501 help 1502 Provide fault-injection capability for disk IO. 1503 1504config FAIL_IO_TIMEOUT 1505 bool "Fault-injection capability for faking disk interrupts" 1506 depends on FAULT_INJECTION && BLOCK 1507 help 1508 Provide fault-injection capability on end IO handling. This 1509 will make the block layer "forget" an interrupt as configured, 1510 thus exercising the error handling. 1511 1512 Only works with drivers that use the generic timeout handling, 1513 for others it wont do anything. 1514 1515config FAIL_MMC_REQUEST 1516 bool "Fault-injection capability for MMC IO" 1517 select DEBUG_FS 1518 depends on FAULT_INJECTION && MMC 1519 help 1520 Provide fault-injection capability for MMC IO. 1521 This will make the mmc core return data errors. This is 1522 useful to test the error handling in the mmc block device 1523 and to test how the mmc host driver handles retries from 1524 the block device. 1525 1526config FAIL_FUTEX 1527 bool "Fault-injection capability for futexes" 1528 select DEBUG_FS 1529 depends on FAULT_INJECTION && FUTEX 1530 help 1531 Provide fault-injection capability for futexes. 1532 1533config FAULT_INJECTION_DEBUG_FS 1534 bool "Debugfs entries for fault-injection capabilities" 1535 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1536 help 1537 Enable configuration of fault-injection capabilities via debugfs. 1538 1539config FAULT_INJECTION_STACKTRACE_FILTER 1540 bool "stacktrace filter for fault-injection capabilities" 1541 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1542 depends on !X86_64 1543 select STACKTRACE 1544 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1545 help 1546 Provide stacktrace filter for fault-injection capabilities 1547 1548config LATENCYTOP 1549 bool "Latency measuring infrastructure" 1550 depends on HAVE_LATENCYTOP_SUPPORT 1551 depends on DEBUG_KERNEL 1552 depends on STACKTRACE_SUPPORT 1553 depends on PROC_FS 1554 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1555 select KALLSYMS 1556 select KALLSYMS_ALL 1557 select STACKTRACE 1558 select SCHEDSTATS 1559 select SCHED_DEBUG 1560 help 1561 Enable this option if you want to use the LatencyTOP tool 1562 to find out which userspace is blocking on what kernel operations. 1563 1564config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1565 bool 1566 1567config DEBUG_STRICT_USER_COPY_CHECKS 1568 bool "Strict user copy size checks" 1569 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1570 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING 1571 help 1572 Enabling this option turns a certain set of sanity checks for user 1573 copy operations into compile time failures. 1574 1575 The copy_from_user() etc checks are there to help test if there 1576 are sufficient security checks on the length argument of 1577 the copy operation, by having gcc prove that the argument is 1578 within bounds. 1579 1580 If unsure, say N. 1581 1582source kernel/trace/Kconfig 1583 1584menu "Runtime Testing" 1585 1586config LKDTM 1587 tristate "Linux Kernel Dump Test Tool Module" 1588 depends on DEBUG_FS 1589 depends on BLOCK 1590 default n 1591 help 1592 This module enables testing of the different dumping mechanisms by 1593 inducing system failures at predefined crash points. 1594 If you don't need it: say N 1595 Choose M here to compile this code as a module. The module will be 1596 called lkdtm. 1597 1598 Documentation on how to use the module can be found in 1599 Documentation/fault-injection/provoke-crashes.txt 1600 1601config TEST_LIST_SORT 1602 bool "Linked list sorting test" 1603 depends on DEBUG_KERNEL 1604 help 1605 Enable this to turn on 'list_sort()' function test. This test is 1606 executed only once during system boot, so affects only boot time. 1607 1608 If unsure, say N. 1609 1610config KPROBES_SANITY_TEST 1611 bool "Kprobes sanity tests" 1612 depends on DEBUG_KERNEL 1613 depends on KPROBES 1614 default n 1615 help 1616 This option provides for testing basic kprobes functionality on 1617 boot. A sample kprobe, jprobe and kretprobe are inserted and 1618 verified for functionality. 1619 1620 Say N if you are unsure. 1621 1622config BACKTRACE_SELF_TEST 1623 tristate "Self test for the backtrace code" 1624 depends on DEBUG_KERNEL 1625 default n 1626 help 1627 This option provides a kernel module that can be used to test 1628 the kernel stack backtrace code. This option is not useful 1629 for distributions or general kernels, but only for kernel 1630 developers working on architecture code. 1631 1632 Note that if you want to also test saved backtraces, you will 1633 have to enable STACKTRACE as well. 1634 1635 Say N if you are unsure. 1636 1637config RBTREE_TEST 1638 tristate "Red-Black tree test" 1639 depends on DEBUG_KERNEL 1640 help 1641 A benchmark measuring the performance of the rbtree library. 1642 Also includes rbtree invariant checks. 1643 1644config INTERVAL_TREE_TEST 1645 tristate "Interval tree test" 1646 depends on m && DEBUG_KERNEL 1647 select INTERVAL_TREE 1648 help 1649 A benchmark measuring the performance of the interval tree library 1650 1651config PERCPU_TEST 1652 tristate "Per cpu operations test" 1653 depends on m && DEBUG_KERNEL 1654 help 1655 Enable this option to build test module which validates per-cpu 1656 operations. 1657 1658 If unsure, say N. 1659 1660config ATOMIC64_SELFTEST 1661 bool "Perform an atomic64_t self-test at boot" 1662 help 1663 Enable this option to test the atomic64_t functions at boot. 1664 1665 If unsure, say N. 1666 1667config ASYNC_RAID6_TEST 1668 tristate "Self test for hardware accelerated raid6 recovery" 1669 depends on ASYNC_RAID6_RECOV 1670 select ASYNC_MEMCPY 1671 ---help--- 1672 This is a one-shot self test that permutes through the 1673 recovery of all the possible two disk failure scenarios for a 1674 N-disk array. Recovery is performed with the asynchronous 1675 raid6 recovery routines, and will optionally use an offload 1676 engine if one is available. 1677 1678 If unsure, say N. 1679 1680config TEST_HEXDUMP 1681 tristate "Test functions located in the hexdump module at runtime" 1682 1683config TEST_STRING_HELPERS 1684 tristate "Test functions located in the string_helpers module at runtime" 1685 1686config TEST_KSTRTOX 1687 tristate "Test kstrto*() family of functions at runtime" 1688 1689config TEST_RHASHTABLE 1690 tristate "Perform selftest on resizable hash table" 1691 default n 1692 help 1693 Enable this option to test the rhashtable functions at boot. 1694 1695 If unsure, say N. 1696 1697endmenu # runtime tests 1698 1699config PROVIDE_OHCI1394_DMA_INIT 1700 bool "Remote debugging over FireWire early on boot" 1701 depends on PCI && X86 1702 help 1703 If you want to debug problems which hang or crash the kernel early 1704 on boot and the crashing machine has a FireWire port, you can use 1705 this feature to remotely access the memory of the crashed machine 1706 over FireWire. This employs remote DMA as part of the OHCI1394 1707 specification which is now the standard for FireWire controllers. 1708 1709 With remote DMA, you can monitor the printk buffer remotely using 1710 firescope and access all memory below 4GB using fireproxy from gdb. 1711 Even controlling a kernel debugger is possible using remote DMA. 1712 1713 Usage: 1714 1715 If ohci1394_dma=early is used as boot parameter, it will initialize 1716 all OHCI1394 controllers which are found in the PCI config space. 1717 1718 As all changes to the FireWire bus such as enabling and disabling 1719 devices cause a bus reset and thereby disable remote DMA for all 1720 devices, be sure to have the cable plugged and FireWire enabled on 1721 the debugging host before booting the debug target for debugging. 1722 1723 This code (~1k) is freed after boot. By then, the firewire stack 1724 in charge of the OHCI-1394 controllers should be used instead. 1725 1726 See Documentation/debugging-via-ohci1394.txt for more information. 1727 1728config BUILD_DOCSRC 1729 bool "Build targets in Documentation/ tree" 1730 depends on HEADERS_CHECK 1731 help 1732 This option attempts to build objects from the source files in the 1733 kernel Documentation/ tree. 1734 1735 Say N if you are unsure. 1736 1737config DMA_API_DEBUG 1738 bool "Enable debugging of DMA-API usage" 1739 depends on HAVE_DMA_API_DEBUG 1740 help 1741 Enable this option to debug the use of the DMA API by device drivers. 1742 With this option you will be able to detect common bugs in device 1743 drivers like double-freeing of DMA mappings or freeing mappings that 1744 were never allocated. 1745 1746 This also attempts to catch cases where a page owned by DMA is 1747 accessed by the cpu in a way that could cause data corruption. For 1748 example, this enables cow_user_page() to check that the source page is 1749 not undergoing DMA. 1750 1751 This option causes a performance degradation. Use only if you want to 1752 debug device drivers and dma interactions. 1753 1754 If unsure, say N. 1755 1756config TEST_LKM 1757 tristate "Test module loading with 'hello world' module" 1758 default n 1759 depends on m 1760 help 1761 This builds the "test_module" module that emits "Hello, world" 1762 on printk when loaded. It is designed to be used for basic 1763 evaluation of the module loading subsystem (for example when 1764 validating module verification). It lacks any extra dependencies, 1765 and will not normally be loaded by the system unless explicitly 1766 requested by name. 1767 1768 If unsure, say N. 1769 1770config TEST_USER_COPY 1771 tristate "Test user/kernel boundary protections" 1772 default n 1773 depends on m 1774 help 1775 This builds the "test_user_copy" module that runs sanity checks 1776 on the copy_to/from_user infrastructure, making sure basic 1777 user/kernel boundary testing is working. If it fails to load, 1778 a regression has been detected in the user/kernel memory boundary 1779 protections. 1780 1781 If unsure, say N. 1782 1783config TEST_BPF 1784 tristate "Test BPF filter functionality" 1785 default n 1786 depends on m && NET 1787 help 1788 This builds the "test_bpf" module that runs various test vectors 1789 against the BPF interpreter or BPF JIT compiler depending on the 1790 current setting. This is in particular useful for BPF JIT compiler 1791 development, but also to run regression tests against changes in 1792 the interpreter code. It also enables test stubs for eBPF maps and 1793 verifier used by user space verifier testsuite. 1794 1795 If unsure, say N. 1796 1797config TEST_FIRMWARE 1798 tristate "Test firmware loading via userspace interface" 1799 default n 1800 depends on FW_LOADER 1801 help 1802 This builds the "test_firmware" module that creates a userspace 1803 interface for testing firmware loading. This can be used to 1804 control the triggering of firmware loading without needing an 1805 actual firmware-using device. The contents can be rechecked by 1806 userspace. 1807 1808 If unsure, say N. 1809 1810config TEST_UDELAY 1811 tristate "udelay test driver" 1812 default n 1813 help 1814 This builds the "udelay_test" module that helps to make sure 1815 that udelay() is working properly. 1816 1817 If unsure, say N. 1818 1819config MEMTEST 1820 bool "Memtest" 1821 depends on HAVE_MEMBLOCK 1822 ---help--- 1823 This option adds a kernel parameter 'memtest', which allows memtest 1824 to be set. 1825 memtest=0, mean disabled; -- default 1826 memtest=1, mean do 1 test pattern; 1827 ... 1828 memtest=17, mean do 17 test patterns. 1829 If you are unsure how to answer this question, answer N. 1830 1831config TEST_STATIC_KEYS 1832 tristate "Test static keys" 1833 default n 1834 depends on m 1835 help 1836 Test the static key interfaces. 1837 1838 If unsure, say N. 1839 1840source "samples/Kconfig" 1841 1842source "lib/Kconfig.kgdb" 1843 1844