1menu "printk and dmesg options" 2 3config PRINTK_TIME 4 bool "Show timing information on printks" 5 depends on PRINTK 6 help 7 Selecting this option causes time stamps of the printk() 8 messages to be added to the output of the syslog() system 9 call and at the console. 10 11 The timestamp is always recorded internally, and exported 12 to /dev/kmsg. This flag just specifies if the timestamp should 13 be included, not that the timestamp is recorded. 14 15 The behavior is also controlled by the kernel command line 16 parameter printk.time=1. See Documentation/kernel-parameters.txt 17 18config MESSAGE_LOGLEVEL_DEFAULT 19 int "Default message log level (1-7)" 20 range 1 7 21 default "4" 22 help 23 Default log level for printk statements with no specified priority. 24 25 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks 26 that are auditing their logs closely may want to set it to a lower 27 priority. 28 29config BOOT_PRINTK_DELAY 30 bool "Delay each boot printk message by N milliseconds" 31 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 32 help 33 This build option allows you to read kernel boot messages 34 by inserting a short delay after each one. The delay is 35 specified in milliseconds on the kernel command line, 36 using "boot_delay=N". 37 38 It is likely that you would also need to use "lpj=M" to preset 39 the "loops per jiffie" value. 40 See a previous boot log for the "lpj" value to use for your 41 system, and then set "lpj=M" before setting "boot_delay=N". 42 NOTE: Using this option may adversely affect SMP systems. 43 I.e., processors other than the first one may not boot up. 44 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect 45 what it believes to be lockup conditions. 46 47config DYNAMIC_DEBUG 48 bool "Enable dynamic printk() support" 49 default n 50 depends on PRINTK 51 depends on DEBUG_FS 52 help 53 54 Compiles debug level messages into the kernel, which would not 55 otherwise be available at runtime. These messages can then be 56 enabled/disabled based on various levels of scope - per source file, 57 function, module, format string, and line number. This mechanism 58 implicitly compiles in all pr_debug() and dev_dbg() calls, which 59 enlarges the kernel text size by about 2%. 60 61 If a source file is compiled with DEBUG flag set, any 62 pr_debug() calls in it are enabled by default, but can be 63 disabled at runtime as below. Note that DEBUG flag is 64 turned on by many CONFIG_*DEBUG* options. 65 66 Usage: 67 68 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 69 which is contained in the 'debugfs' filesystem. Thus, the debugfs 70 filesystem must first be mounted before making use of this feature. 71 We refer the control file as: <debugfs>/dynamic_debug/control. This 72 file contains a list of the debug statements that can be enabled. The 73 format for each line of the file is: 74 75 filename:lineno [module]function flags format 76 77 filename : source file of the debug statement 78 lineno : line number of the debug statement 79 module : module that contains the debug statement 80 function : function that contains the debug statement 81 flags : '=p' means the line is turned 'on' for printing 82 format : the format used for the debug statement 83 84 From a live system: 85 86 nullarbor:~ # cat <debugfs>/dynamic_debug/control 87 # filename:lineno [module]function flags format 88 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012" 89 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012" 90 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012" 91 92 Example usage: 93 94 // enable the message at line 1603 of file svcsock.c 95 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 96 <debugfs>/dynamic_debug/control 97 98 // enable all the messages in file svcsock.c 99 nullarbor:~ # echo -n 'file svcsock.c +p' > 100 <debugfs>/dynamic_debug/control 101 102 // enable all the messages in the NFS server module 103 nullarbor:~ # echo -n 'module nfsd +p' > 104 <debugfs>/dynamic_debug/control 105 106 // enable all 12 messages in the function svc_process() 107 nullarbor:~ # echo -n 'func svc_process +p' > 108 <debugfs>/dynamic_debug/control 109 110 // disable all 12 messages in the function svc_process() 111 nullarbor:~ # echo -n 'func svc_process -p' > 112 <debugfs>/dynamic_debug/control 113 114 See Documentation/dynamic-debug-howto.txt for additional information. 115 116endmenu # "printk and dmesg options" 117 118menu "Compile-time checks and compiler options" 119 120config DEBUG_INFO 121 bool "Compile the kernel with debug info" 122 depends on DEBUG_KERNEL && !COMPILE_TEST 123 help 124 If you say Y here the resulting kernel image will include 125 debugging info resulting in a larger kernel image. 126 This adds debug symbols to the kernel and modules (gcc -g), and 127 is needed if you intend to use kernel crashdump or binary object 128 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 129 Say Y here only if you plan to debug the kernel. 130 131 If unsure, say N. 132 133config DEBUG_INFO_REDUCED 134 bool "Reduce debugging information" 135 depends on DEBUG_INFO 136 help 137 If you say Y here gcc is instructed to generate less debugging 138 information for structure types. This means that tools that 139 need full debugging information (like kgdb or systemtap) won't 140 be happy. But if you merely need debugging information to 141 resolve line numbers there is no loss. Advantage is that 142 build directory object sizes shrink dramatically over a full 143 DEBUG_INFO build and compile times are reduced too. 144 Only works with newer gcc versions. 145 146config DEBUG_INFO_SPLIT 147 bool "Produce split debuginfo in .dwo files" 148 depends on DEBUG_INFO && !FRV 149 help 150 Generate debug info into separate .dwo files. This significantly 151 reduces the build directory size for builds with DEBUG_INFO, 152 because it stores the information only once on disk in .dwo 153 files instead of multiple times in object files and executables. 154 In addition the debug information is also compressed. 155 156 Requires recent gcc (4.7+) and recent gdb/binutils. 157 Any tool that packages or reads debug information would need 158 to know about the .dwo files and include them. 159 Incompatible with older versions of ccache. 160 161config DEBUG_INFO_DWARF4 162 bool "Generate dwarf4 debuginfo" 163 depends on DEBUG_INFO 164 help 165 Generate dwarf4 debug info. This requires recent versions 166 of gcc and gdb. It makes the debug information larger. 167 But it significantly improves the success of resolving 168 variables in gdb on optimized code. 169 170config 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 2048 if GCC_PLUGIN_LATENT_ENTROPY 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 315config SECTION_MISMATCH_WARN_ONLY 316 bool "Make section mismatch errors non-fatal" 317 default y 318 help 319 If you say N here, the build process will fail if there are any 320 section mismatch, instead of just throwing warnings. 321 322 If unsure, say Y. 323 324# 325# Select this config option from the architecture Kconfig, if it 326# is preferred to always offer frame pointers as a config 327# option on the architecture (regardless of KERNEL_DEBUG): 328# 329config ARCH_WANT_FRAME_POINTERS 330 bool 331 help 332 333config FRAME_POINTER 334 bool "Compile the kernel with frame pointers" 335 depends on DEBUG_KERNEL && \ 336 (CRIS || M68K || FRV || UML || \ 337 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \ 338 ARCH_WANT_FRAME_POINTERS 339 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 340 help 341 If you say Y here the resulting kernel image will be slightly 342 larger and slower, but it gives very useful debugging information 343 in case of kernel bugs. (precise oopses/stacktraces/warnings) 344 345config DEBUG_FORCE_WEAK_PER_CPU 346 bool "Force weak per-cpu definitions" 347 depends on DEBUG_KERNEL 348 help 349 s390 and alpha require percpu variables in modules to be 350 defined weak to work around addressing range issue which 351 puts the following two restrictions on percpu variable 352 definitions. 353 354 1. percpu symbols must be unique whether static or not 355 2. percpu variables can't be defined inside a function 356 357 To ensure that generic code follows the above rules, this 358 option forces all percpu variables to be defined as weak. 359 360endmenu # "Compiler options" 361 362config MAGIC_SYSRQ 363 bool "Magic SysRq key" 364 depends on !UML 365 help 366 If you say Y here, you will have some control over the system even 367 if the system crashes for example during kernel debugging (e.g., you 368 will be able to flush the buffer cache to disk, reboot the system 369 immediately or dump some status information). This is accomplished 370 by pressing various keys while holding SysRq (Alt+PrintScreen). It 371 also works on a serial console (on PC hardware at least), if you 372 send a BREAK and then within 5 seconds a command keypress. The 373 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 374 unless you really know what this hack does. 375 376config MAGIC_SYSRQ_DEFAULT_ENABLE 377 hex "Enable magic SysRq key functions by default" 378 depends on MAGIC_SYSRQ 379 default 0x1 380 help 381 Specifies which SysRq key functions are enabled by default. 382 This may be set to 1 or 0 to enable or disable them all, or 383 to a bitmask as described in Documentation/sysrq.txt. 384 385config DEBUG_KERNEL 386 bool "Kernel debugging" 387 help 388 Say Y here if you are developing drivers or trying to debug and 389 identify kernel problems. 390 391menu "Memory Debugging" 392 393source mm/Kconfig.debug 394 395config DEBUG_OBJECTS 396 bool "Debug object operations" 397 depends on DEBUG_KERNEL 398 help 399 If you say Y here, additional code will be inserted into the 400 kernel to track the life time of various objects and validate 401 the operations on those objects. 402 403config DEBUG_OBJECTS_SELFTEST 404 bool "Debug objects selftest" 405 depends on DEBUG_OBJECTS 406 help 407 This enables the selftest of the object debug code. 408 409config DEBUG_OBJECTS_FREE 410 bool "Debug objects in freed memory" 411 depends on DEBUG_OBJECTS 412 help 413 This enables checks whether a k/v free operation frees an area 414 which contains an object which has not been deactivated 415 properly. This can make kmalloc/kfree-intensive workloads 416 much slower. 417 418config DEBUG_OBJECTS_TIMERS 419 bool "Debug timer objects" 420 depends on DEBUG_OBJECTS 421 help 422 If you say Y here, additional code will be inserted into the 423 timer routines to track the life time of timer objects and 424 validate the timer operations. 425 426config DEBUG_OBJECTS_WORK 427 bool "Debug work objects" 428 depends on DEBUG_OBJECTS 429 help 430 If you say Y here, additional code will be inserted into the 431 work queue routines to track the life time of work objects and 432 validate the work operations. 433 434config DEBUG_OBJECTS_RCU_HEAD 435 bool "Debug RCU callbacks objects" 436 depends on DEBUG_OBJECTS 437 help 438 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 439 440config DEBUG_OBJECTS_PERCPU_COUNTER 441 bool "Debug percpu counter objects" 442 depends on DEBUG_OBJECTS 443 help 444 If you say Y here, additional code will be inserted into the 445 percpu counter routines to track the life time of percpu counter 446 objects and validate the percpu counter operations. 447 448config DEBUG_OBJECTS_ENABLE_DEFAULT 449 int "debug_objects bootup default value (0-1)" 450 range 0 1 451 default "1" 452 depends on DEBUG_OBJECTS 453 help 454 Debug objects boot parameter default value 455 456config DEBUG_SLAB 457 bool "Debug slab memory allocations" 458 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 459 help 460 Say Y here to have the kernel do limited verification on memory 461 allocation as well as poisoning memory on free to catch use of freed 462 memory. This can make kmalloc/kfree-intensive workloads much slower. 463 464config DEBUG_SLAB_LEAK 465 bool "Memory leak debugging" 466 depends on DEBUG_SLAB 467 468config SLUB_DEBUG_ON 469 bool "SLUB debugging on by default" 470 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 471 default n 472 help 473 Boot with debugging on by default. SLUB boots by default with 474 the runtime debug capabilities switched off. Enabling this is 475 equivalent to specifying the "slub_debug" parameter on boot. 476 There is no support for more fine grained debug control like 477 possible with slub_debug=xxx. SLUB debugging may be switched 478 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 479 "slub_debug=-". 480 481config SLUB_STATS 482 default n 483 bool "Enable SLUB performance statistics" 484 depends on SLUB && SYSFS 485 help 486 SLUB statistics are useful to debug SLUBs allocation behavior in 487 order find ways to optimize the allocator. This should never be 488 enabled for production use since keeping statistics slows down 489 the allocator by a few percentage points. The slabinfo command 490 supports the determination of the most active slabs to figure 491 out which slabs are relevant to a particular load. 492 Try running: slabinfo -DA 493 494config HAVE_DEBUG_KMEMLEAK 495 bool 496 497config DEBUG_KMEMLEAK 498 bool "Kernel memory leak detector" 499 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 500 select DEBUG_FS 501 select STACKTRACE if STACKTRACE_SUPPORT 502 select KALLSYMS 503 select CRC32 504 help 505 Say Y here if you want to enable the memory leak 506 detector. The memory allocation/freeing is traced in a way 507 similar to the Boehm's conservative garbage collector, the 508 difference being that the orphan objects are not freed but 509 only shown in /sys/kernel/debug/kmemleak. Enabling this 510 feature will introduce an overhead to memory 511 allocations. See Documentation/kmemleak.txt for more 512 details. 513 514 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 515 of finding leaks due to the slab objects poisoning. 516 517 In order to access the kmemleak file, debugfs needs to be 518 mounted (usually at /sys/kernel/debug). 519 520config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 521 int "Maximum kmemleak early log entries" 522 depends on DEBUG_KMEMLEAK 523 range 200 40000 524 default 16000 525 help 526 Kmemleak must track all the memory allocations to avoid 527 reporting false positives. Since memory may be allocated or 528 freed before kmemleak is initialised, an early log buffer is 529 used to store these actions. If kmemleak reports "early log 530 buffer exceeded", please increase this value. 531 532config DEBUG_KMEMLEAK_TEST 533 tristate "Simple test for the kernel memory leak detector" 534 depends on DEBUG_KMEMLEAK && m 535 help 536 This option enables a module that explicitly leaks memory. 537 538 If unsure, say N. 539 540config DEBUG_KMEMLEAK_DEFAULT_OFF 541 bool "Default kmemleak to off" 542 depends on DEBUG_KMEMLEAK 543 help 544 Say Y here to disable kmemleak by default. It can then be enabled 545 on the command line via kmemleak=on. 546 547config DEBUG_STACK_USAGE 548 bool "Stack utilization instrumentation" 549 depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAG 550 help 551 Enables the display of the minimum amount of free stack which each 552 task has ever had available in the sysrq-T and sysrq-P debug output. 553 554 This option will slow down process creation somewhat. 555 556config DEBUG_VM 557 bool "Debug VM" 558 depends on DEBUG_KERNEL 559 help 560 Enable this to turn on extended checks in the virtual-memory system 561 that may impact performance. 562 563 If unsure, say N. 564 565config DEBUG_VM_VMACACHE 566 bool "Debug VMA caching" 567 depends on DEBUG_VM 568 help 569 Enable this to turn on VMA caching debug information. Doing so 570 can cause significant overhead, so only enable it in non-production 571 environments. 572 573 If unsure, say N. 574 575config DEBUG_VM_RB 576 bool "Debug VM red-black trees" 577 depends on DEBUG_VM 578 help 579 Enable VM red-black tree debugging information and extra validations. 580 581 If unsure, say N. 582 583config DEBUG_VIRTUAL 584 bool "Debug VM translations" 585 depends on DEBUG_KERNEL && X86 586 help 587 Enable some costly sanity checks in virtual to page code. This can 588 catch mistakes with virt_to_page() and friends. 589 590 If unsure, say N. 591 592config DEBUG_NOMMU_REGIONS 593 bool "Debug the global anon/private NOMMU mapping region tree" 594 depends on DEBUG_KERNEL && !MMU 595 help 596 This option causes the global tree of anonymous and private mapping 597 regions to be regularly checked for invalid topology. 598 599config DEBUG_MEMORY_INIT 600 bool "Debug memory initialisation" if EXPERT 601 default !EXPERT 602 help 603 Enable this for additional checks during memory initialisation. 604 The sanity checks verify aspects of the VM such as the memory model 605 and other information provided by the architecture. Verbose 606 information will be printed at KERN_DEBUG loglevel depending 607 on the mminit_loglevel= command-line option. 608 609 If unsure, say Y 610 611config MEMORY_NOTIFIER_ERROR_INJECT 612 tristate "Memory hotplug notifier error injection module" 613 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 614 help 615 This option provides the ability to inject artificial errors to 616 memory hotplug notifier chain callbacks. It is controlled through 617 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 618 619 If the notifier call chain should be failed with some events 620 notified, write the error code to "actions/<notifier event>/error". 621 622 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 623 624 # cd /sys/kernel/debug/notifier-error-inject/memory 625 # echo -12 > actions/MEM_GOING_OFFLINE/error 626 # echo offline > /sys/devices/system/memory/memoryXXX/state 627 bash: echo: write error: Cannot allocate memory 628 629 To compile this code as a module, choose M here: the module will 630 be called memory-notifier-error-inject. 631 632 If unsure, say N. 633 634config DEBUG_PER_CPU_MAPS 635 bool "Debug access to per_cpu maps" 636 depends on DEBUG_KERNEL 637 depends on SMP 638 help 639 Say Y to verify that the per_cpu map being accessed has 640 been set up. This adds a fair amount of code to kernel memory 641 and decreases performance. 642 643 Say N if unsure. 644 645config DEBUG_HIGHMEM 646 bool "Highmem debugging" 647 depends on DEBUG_KERNEL && HIGHMEM 648 help 649 This option enables additional error checking for high memory 650 systems. Disable for production systems. 651 652config HAVE_DEBUG_STACKOVERFLOW 653 bool 654 655config DEBUG_STACKOVERFLOW 656 bool "Check for stack overflows" 657 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 658 ---help--- 659 Say Y here if you want to check for overflows of kernel, IRQ 660 and exception stacks (if your architecture uses them). This 661 option will show detailed messages if free stack space drops 662 below a certain limit. 663 664 These kinds of bugs usually occur when call-chains in the 665 kernel get too deep, especially when interrupts are 666 involved. 667 668 Use this in cases where you see apparently random memory 669 corruption, especially if it appears in 'struct thread_info' 670 671 If in doubt, say "N". 672 673source "lib/Kconfig.kmemcheck" 674 675source "lib/Kconfig.kasan" 676 677endmenu # "Memory Debugging" 678 679config ARCH_HAS_KCOV 680 bool 681 help 682 KCOV does not have any arch-specific code, but currently it is enabled 683 only for x86_64. KCOV requires testing on other archs, and most likely 684 disabling of instrumentation for some early boot code. 685 686config KCOV 687 bool "Code coverage for fuzzing" 688 depends on ARCH_HAS_KCOV 689 select DEBUG_FS 690 help 691 KCOV exposes kernel code coverage information in a form suitable 692 for coverage-guided fuzzing (randomized testing). 693 694 If RANDOMIZE_BASE is enabled, PC values will not be stable across 695 different machines and across reboots. If you need stable PC values, 696 disable RANDOMIZE_BASE. 697 698 For more details, see Documentation/kcov.txt. 699 700config DEBUG_SHIRQ 701 bool "Debug shared IRQ handlers" 702 depends on DEBUG_KERNEL 703 help 704 Enable this to generate a spurious interrupt as soon as a shared 705 interrupt handler is registered, and just before one is deregistered. 706 Drivers ought to be able to handle interrupts coming in at those 707 points; some don't and need to be caught. 708 709menu "Debug Lockups and Hangs" 710 711config LOCKUP_DETECTOR 712 bool "Detect Hard and Soft Lockups" 713 depends on DEBUG_KERNEL && !S390 714 help 715 Say Y here to enable the kernel to act as a watchdog to detect 716 hard and soft lockups. 717 718 Softlockups are bugs that cause the kernel to loop in kernel 719 mode for more than 20 seconds, without giving other tasks a 720 chance to run. The current stack trace is displayed upon 721 detection and the system will stay locked up. 722 723 Hardlockups are bugs that cause the CPU to loop in kernel mode 724 for more than 10 seconds, without letting other interrupts have a 725 chance to run. The current stack trace is displayed upon detection 726 and the system will stay locked up. 727 728 The overhead should be minimal. A periodic hrtimer runs to 729 generate interrupts and kick the watchdog task every 4 seconds. 730 An NMI is generated every 10 seconds or so to check for hardlockups. 731 If NMIs are not available on the platform, every 12 seconds the 732 hrtimer interrupt on one cpu will be used to check for hardlockups 733 on the next cpu. 734 735 The frequency of hrtimer and NMI events and the soft and hard lockup 736 thresholds can be controlled through the sysctl watchdog_thresh. 737 738config HARDLOCKUP_DETECTOR_NMI 739 def_bool y 740 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 741 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 742 743config HARDLOCKUP_DETECTOR_OTHER_CPU 744 def_bool y 745 depends on LOCKUP_DETECTOR && SMP 746 depends on !HARDLOCKUP_DETECTOR_NMI && !HAVE_NMI_WATCHDOG 747 748config HARDLOCKUP_DETECTOR 749 def_bool y 750 depends on HARDLOCKUP_DETECTOR_NMI || HARDLOCKUP_DETECTOR_OTHER_CPU 751 752config BOOTPARAM_HARDLOCKUP_PANIC 753 bool "Panic (Reboot) On Hard Lockups" 754 depends on HARDLOCKUP_DETECTOR 755 help 756 Say Y here to enable the kernel to panic on "hard lockups", 757 which are bugs that cause the kernel to loop in kernel 758 mode with interrupts disabled for more than 10 seconds (configurable 759 using the watchdog_thresh sysctl). 760 761 Say N if unsure. 762 763config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 764 int 765 depends on HARDLOCKUP_DETECTOR 766 range 0 1 767 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 768 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 769 770config BOOTPARAM_SOFTLOCKUP_PANIC 771 bool "Panic (Reboot) On Soft Lockups" 772 depends on LOCKUP_DETECTOR 773 help 774 Say Y here to enable the kernel to panic on "soft lockups", 775 which are bugs that cause the kernel to loop in kernel 776 mode for more than 20 seconds (configurable using the watchdog_thresh 777 sysctl), without giving other tasks a chance to run. 778 779 The panic can be used in combination with panic_timeout, 780 to cause the system to reboot automatically after a 781 lockup has been detected. This feature is useful for 782 high-availability systems that have uptime guarantees and 783 where a lockup must be resolved ASAP. 784 785 Say N if unsure. 786 787config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 788 int 789 depends on LOCKUP_DETECTOR 790 range 0 1 791 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 792 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 793 794config DETECT_HUNG_TASK 795 bool "Detect Hung Tasks" 796 depends on DEBUG_KERNEL 797 default LOCKUP_DETECTOR 798 help 799 Say Y here to enable the kernel to detect "hung tasks", 800 which are bugs that cause the task to be stuck in 801 uninterruptible "D" state indefinitiley. 802 803 When a hung task is detected, the kernel will print the 804 current stack trace (which you should report), but the 805 task will stay in uninterruptible state. If lockdep is 806 enabled then all held locks will also be reported. This 807 feature has negligible overhead. 808 809config DEFAULT_HUNG_TASK_TIMEOUT 810 int "Default timeout for hung task detection (in seconds)" 811 depends on DETECT_HUNG_TASK 812 default 120 813 help 814 This option controls the default timeout (in seconds) used 815 to determine when a task has become non-responsive and should 816 be considered hung. 817 818 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 819 sysctl or by writing a value to 820 /proc/sys/kernel/hung_task_timeout_secs. 821 822 A timeout of 0 disables the check. The default is two minutes. 823 Keeping the default should be fine in most cases. 824 825config BOOTPARAM_HUNG_TASK_PANIC 826 bool "Panic (Reboot) On Hung Tasks" 827 depends on DETECT_HUNG_TASK 828 help 829 Say Y here to enable the kernel to panic on "hung tasks", 830 which are bugs that cause the kernel to leave a task stuck 831 in uninterruptible "D" state. 832 833 The panic can be used in combination with panic_timeout, 834 to cause the system to reboot automatically after a 835 hung task has been detected. This feature is useful for 836 high-availability systems that have uptime guarantees and 837 where a hung tasks must be resolved ASAP. 838 839 Say N if unsure. 840 841config BOOTPARAM_HUNG_TASK_PANIC_VALUE 842 int 843 depends on DETECT_HUNG_TASK 844 range 0 1 845 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 846 default 1 if BOOTPARAM_HUNG_TASK_PANIC 847 848endmenu # "Debug lockups and hangs" 849 850config PANIC_ON_OOPS 851 bool "Panic on Oops" 852 help 853 Say Y here to enable the kernel to panic when it oopses. This 854 has the same effect as setting oops=panic on the kernel command 855 line. 856 857 This feature is useful to ensure that the kernel does not do 858 anything erroneous after an oops which could result in data 859 corruption or other issues. 860 861 Say N if unsure. 862 863config PANIC_ON_OOPS_VALUE 864 int 865 range 0 1 866 default 0 if !PANIC_ON_OOPS 867 default 1 if PANIC_ON_OOPS 868 869config PANIC_TIMEOUT 870 int "panic timeout" 871 default 0 872 help 873 Set the timeout value (in seconds) until a reboot occurs when the 874 the kernel panics. If n = 0, then we wait forever. A timeout 875 value n > 0 will wait n seconds before rebooting, while a timeout 876 value n < 0 will reboot immediately. 877 878config SCHED_DEBUG 879 bool "Collect scheduler debugging info" 880 depends on DEBUG_KERNEL && PROC_FS 881 default y 882 help 883 If you say Y here, the /proc/sched_debug file will be provided 884 that can help debug the scheduler. The runtime overhead of this 885 option is minimal. 886 887config SCHED_INFO 888 bool 889 default n 890 891config PANIC_ON_RT_THROTTLING 892 bool "Panic on RT throttling" 893 help 894 Say Y here to enable the kernel to panic when a realtime 895 runqueue is throttled. This may be useful for detecting 896 and debugging RT throttling issues. 897 898 Say N if unsure. 899 900config SCHEDSTATS 901 bool "Collect scheduler statistics" 902 depends on DEBUG_KERNEL && PROC_FS 903 select SCHED_INFO 904 help 905 If you say Y here, additional code will be inserted into the 906 scheduler and related routines to collect statistics about 907 scheduler behavior and provide them in /proc/schedstat. These 908 stats may be useful for both tuning and debugging the scheduler 909 If you aren't debugging the scheduler or trying to tune a specific 910 application, you can say N to avoid the very slight overhead 911 this adds. 912 913config SCHED_STACK_END_CHECK 914 bool "Detect stack corruption on calls to schedule()" 915 depends on DEBUG_KERNEL 916 default n 917 help 918 This option checks for a stack overrun on calls to schedule(). 919 If the stack end location is found to be over written always panic as 920 the content of the corrupted region can no longer be trusted. 921 This is to ensure no erroneous behaviour occurs which could result in 922 data corruption or a sporadic crash at a later stage once the region 923 is examined. The runtime overhead introduced is minimal. 924 925config DEBUG_TIMEKEEPING 926 bool "Enable extra timekeeping sanity checking" 927 help 928 This option will enable additional timekeeping sanity checks 929 which may be helpful when diagnosing issues where timekeeping 930 problems are suspected. 931 932 This may include checks in the timekeeping hotpaths, so this 933 option may have a (very small) performance impact to some 934 workloads. 935 936 If unsure, say N. 937 938config TIMER_STATS 939 bool "Collect kernel timers statistics" 940 depends on DEBUG_KERNEL && PROC_FS 941 help 942 If you say Y here, additional code will be inserted into the 943 timer routines to collect statistics about kernel timers being 944 reprogrammed. The statistics can be read from /proc/timer_stats. 945 The statistics collection is started by writing 1 to /proc/timer_stats, 946 writing 0 stops it. This feature is useful to collect information 947 about timer usage patterns in kernel and userspace. This feature 948 is lightweight if enabled in the kernel config but not activated 949 (it defaults to deactivated on bootup and will only be activated 950 if some application like powertop activates it explicitly). 951 952config DEBUG_PREEMPT 953 bool "Debug preemptible kernel" 954 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 955 default y 956 help 957 If you say Y here then the kernel will use a debug variant of the 958 commonly used smp_processor_id() function and will print warnings 959 if kernel code uses it in a preemption-unsafe way. Also, the kernel 960 will detect preemption count underflows. 961 962menu "Lock Debugging (spinlocks, mutexes, etc...)" 963 964config DEBUG_RT_MUTEXES 965 bool "RT Mutex debugging, deadlock detection" 966 depends on DEBUG_KERNEL && RT_MUTEXES 967 help 968 This allows rt mutex semantics violations and rt mutex related 969 deadlocks (lockups) to be detected and reported automatically. 970 971config DEBUG_SPINLOCK 972 bool "Spinlock and rw-lock debugging: basic checks" 973 depends on DEBUG_KERNEL 974 select UNINLINE_SPIN_UNLOCK 975 help 976 Say Y here and build SMP to catch missing spinlock initialization 977 and certain other kinds of spinlock errors commonly made. This is 978 best used in conjunction with the NMI watchdog so that spinlock 979 deadlocks are also debuggable. 980 981config DEBUG_MUTEXES 982 bool "Mutex debugging: basic checks" 983 depends on DEBUG_KERNEL 984 help 985 This feature allows mutex semantics violations to be detected and 986 reported. 987 988config DEBUG_WW_MUTEX_SLOWPATH 989 bool "Wait/wound mutex debugging: Slowpath testing" 990 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 991 select DEBUG_LOCK_ALLOC 992 select DEBUG_SPINLOCK 993 select DEBUG_MUTEXES 994 help 995 This feature enables slowpath testing for w/w mutex users by 996 injecting additional -EDEADLK wound/backoff cases. Together with 997 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 998 will test all possible w/w mutex interface abuse with the 999 exception of simply not acquiring all the required locks. 1000 Note that this feature can introduce significant overhead, so 1001 it really should not be enabled in a production or distro kernel, 1002 even a debug kernel. If you are a driver writer, enable it. If 1003 you are a distro, do not. 1004 1005config DEBUG_LOCK_ALLOC 1006 bool "Lock debugging: detect incorrect freeing of live locks" 1007 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1008 select DEBUG_SPINLOCK 1009 select DEBUG_MUTEXES 1010 select LOCKDEP 1011 help 1012 This feature will check whether any held lock (spinlock, rwlock, 1013 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1014 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1015 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1016 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1017 held during task exit. 1018 1019config PROVE_LOCKING 1020 bool "Lock debugging: prove locking correctness" 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 select TRACE_IRQFLAGS 1027 default n 1028 help 1029 This feature enables the kernel to prove that all locking 1030 that occurs in the kernel runtime is mathematically 1031 correct: that under no circumstance could an arbitrary (and 1032 not yet triggered) combination of observed locking 1033 sequences (on an arbitrary number of CPUs, running an 1034 arbitrary number of tasks and interrupt contexts) cause a 1035 deadlock. 1036 1037 In short, this feature enables the kernel to report locking 1038 related deadlocks before they actually occur. 1039 1040 The proof does not depend on how hard and complex a 1041 deadlock scenario would be to trigger: how many 1042 participant CPUs, tasks and irq-contexts would be needed 1043 for it to trigger. The proof also does not depend on 1044 timing: if a race and a resulting deadlock is possible 1045 theoretically (no matter how unlikely the race scenario 1046 is), it will be proven so and will immediately be 1047 reported by the kernel (once the event is observed that 1048 makes the deadlock theoretically possible). 1049 1050 If a deadlock is impossible (i.e. the locking rules, as 1051 observed by the kernel, are mathematically correct), the 1052 kernel reports nothing. 1053 1054 NOTE: this feature can also be enabled for rwlocks, mutexes 1055 and rwsems - in which case all dependencies between these 1056 different locking variants are observed and mapped too, and 1057 the proof of observed correctness is also maintained for an 1058 arbitrary combination of these separate locking variants. 1059 1060 For more details, see Documentation/locking/lockdep-design.txt. 1061 1062config LOCKDEP 1063 bool 1064 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1065 select STACKTRACE 1066 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE 1067 select KALLSYMS 1068 select KALLSYMS_ALL 1069 1070config LOCK_STAT 1071 bool "Lock usage statistics" 1072 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1073 select LOCKDEP 1074 select DEBUG_SPINLOCK 1075 select DEBUG_MUTEXES 1076 select DEBUG_LOCK_ALLOC 1077 default n 1078 help 1079 This feature enables tracking lock contention points 1080 1081 For more details, see Documentation/locking/lockstat.txt 1082 1083 This also enables lock events required by "perf lock", 1084 subcommand of perf. 1085 If you want to use "perf lock", you also need to turn on 1086 CONFIG_EVENT_TRACING. 1087 1088 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1089 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1090 1091config DEBUG_LOCKDEP 1092 bool "Lock dependency engine debugging" 1093 depends on DEBUG_KERNEL && LOCKDEP 1094 help 1095 If you say Y here, the lock dependency engine will do 1096 additional runtime checks to debug itself, at the price 1097 of more runtime overhead. 1098 1099config DEBUG_ATOMIC_SLEEP 1100 bool "Sleep inside atomic section checking" 1101 select PREEMPT_COUNT 1102 depends on DEBUG_KERNEL 1103 help 1104 If you say Y here, various routines which may sleep will become very 1105 noisy if they are called inside atomic sections: when a spinlock is 1106 held, inside an rcu read side critical section, inside preempt disabled 1107 sections, inside an interrupt, etc... 1108 1109config DEBUG_LOCKING_API_SELFTESTS 1110 bool "Locking API boot-time self-tests" 1111 depends on DEBUG_KERNEL 1112 help 1113 Say Y here if you want the kernel to run a short self-test during 1114 bootup. The self-test checks whether common types of locking bugs 1115 are detected by debugging mechanisms or not. (if you disable 1116 lock debugging then those bugs wont be detected of course.) 1117 The following locking APIs are covered: spinlocks, rwlocks, 1118 mutexes and rwsems. 1119 1120config LOCK_TORTURE_TEST 1121 tristate "torture tests for locking" 1122 depends on DEBUG_KERNEL 1123 select TORTURE_TEST 1124 default n 1125 help 1126 This option provides a kernel module that runs torture tests 1127 on kernel locking primitives. The kernel module may be built 1128 after the fact on the running kernel to be tested, if desired. 1129 1130 Say Y here if you want kernel locking-primitive torture tests 1131 to be built into the kernel. 1132 Say M if you want these torture tests to build as a module. 1133 Say N if you are unsure. 1134 1135endmenu # lock debugging 1136 1137config TRACE_IRQFLAGS 1138 bool 1139 help 1140 Enables hooks to interrupt enabling and disabling for 1141 either tracing or lock debugging. 1142 1143config STACKTRACE 1144 bool "Stack backtrace support" 1145 depends on STACKTRACE_SUPPORT 1146 help 1147 This option causes the kernel to create a /proc/pid/stack for 1148 every process, showing its current stack trace. 1149 It is also used by various kernel debugging features that require 1150 stack trace generation. 1151 1152config DEBUG_KOBJECT 1153 bool "kobject debugging" 1154 depends on DEBUG_KERNEL 1155 help 1156 If you say Y here, some extra kobject debugging messages will be sent 1157 to the syslog. 1158 1159config DEBUG_KOBJECT_RELEASE 1160 bool "kobject release debugging" 1161 depends on DEBUG_OBJECTS_TIMERS 1162 help 1163 kobjects are reference counted objects. This means that their 1164 last reference count put is not predictable, and the kobject can 1165 live on past the point at which a driver decides to drop it's 1166 initial reference to the kobject gained on allocation. An 1167 example of this would be a struct device which has just been 1168 unregistered. 1169 1170 However, some buggy drivers assume that after such an operation, 1171 the memory backing the kobject can be immediately freed. This 1172 goes completely against the principles of a refcounted object. 1173 1174 If you say Y here, the kernel will delay the release of kobjects 1175 on the last reference count to improve the visibility of this 1176 kind of kobject release bug. 1177 1178config HAVE_DEBUG_BUGVERBOSE 1179 bool 1180 1181config DEBUG_BUGVERBOSE 1182 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1183 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1184 default y 1185 help 1186 Say Y here to make BUG() panics output the file name and line number 1187 of the BUG call as well as the EIP and oops trace. This aids 1188 debugging but costs about 70-100K of memory. 1189 1190config DEBUG_LIST 1191 bool "Debug linked list manipulation" 1192 depends on DEBUG_KERNEL 1193 help 1194 Enable this to turn on extended checks in the linked-list 1195 walking routines. 1196 1197 If unsure, say N. 1198 1199config DEBUG_PI_LIST 1200 bool "Debug priority linked list manipulation" 1201 depends on DEBUG_KERNEL 1202 help 1203 Enable this to turn on extended checks in the priority-ordered 1204 linked-list (plist) walking routines. This checks the entire 1205 list multiple times during each manipulation. 1206 1207 If unsure, say N. 1208 1209config DEBUG_SG 1210 bool "Debug SG table operations" 1211 depends on DEBUG_KERNEL 1212 help 1213 Enable this to turn on checks on scatter-gather tables. This can 1214 help find problems with drivers that do not properly initialize 1215 their sg tables. 1216 1217 If unsure, say N. 1218 1219config DEBUG_NOTIFIERS 1220 bool "Debug notifier call chains" 1221 depends on DEBUG_KERNEL 1222 help 1223 Enable this to turn on sanity checking for notifier call chains. 1224 This is most useful for kernel developers to make sure that 1225 modules properly unregister themselves from notifier chains. 1226 This is a relatively cheap check but if you care about maximum 1227 performance, say N. 1228 1229config DEBUG_CREDENTIALS 1230 bool "Debug credential management" 1231 depends on DEBUG_KERNEL 1232 help 1233 Enable this to turn on some debug checking for credential 1234 management. The additional code keeps track of the number of 1235 pointers from task_structs to any given cred struct, and checks to 1236 see that this number never exceeds the usage count of the cred 1237 struct. 1238 1239 Furthermore, if SELinux is enabled, this also checks that the 1240 security pointer in the cred struct is never seen to be invalid. 1241 1242 If unsure, say N. 1243 1244menu "RCU Debugging" 1245 1246config PROVE_RCU 1247 def_bool PROVE_LOCKING 1248 1249config PROVE_RCU_REPEATEDLY 1250 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1251 depends on PROVE_RCU 1252 default n 1253 help 1254 By itself, PROVE_RCU will disable checking upon issuing the 1255 first warning (or "splat"). This feature prevents such 1256 disabling, allowing multiple RCU-lockdep warnings to be printed 1257 on a single reboot. 1258 1259 Say Y to allow multiple RCU-lockdep warnings per boot. 1260 1261 Say N if you are unsure. 1262 1263config SPARSE_RCU_POINTER 1264 bool "RCU debugging: sparse-based checks for pointer usage" 1265 default n 1266 help 1267 This feature enables the __rcu sparse annotation for 1268 RCU-protected pointers. This annotation will cause sparse 1269 to flag any non-RCU used of annotated pointers. This can be 1270 helpful when debugging RCU usage. Please note that this feature 1271 is not intended to enforce code cleanliness; it is instead merely 1272 a debugging aid. 1273 1274 Say Y to make sparse flag questionable use of RCU-protected pointers 1275 1276 Say N if you are unsure. 1277 1278config TORTURE_TEST 1279 tristate 1280 default n 1281 1282config RCU_TORTURE_TEST 1283 tristate "torture tests for RCU" 1284 depends on DEBUG_KERNEL 1285 select TORTURE_TEST 1286 select SRCU 1287 select TASKS_RCU 1288 default n 1289 help 1290 This option provides a kernel module that runs torture tests 1291 on the RCU infrastructure. The kernel module may be built 1292 after the fact on the running kernel to be tested, if desired. 1293 1294 Say Y here if you want RCU torture tests to be built into 1295 the kernel. 1296 Say M if you want the RCU torture tests to build as a module. 1297 Say N if you are unsure. 1298 1299config RCU_TORTURE_TEST_RUNNABLE 1300 bool "torture tests for RCU runnable by default" 1301 depends on RCU_TORTURE_TEST = y 1302 default n 1303 help 1304 This option provides a way to build the RCU torture tests 1305 directly into the kernel without them starting up at boot 1306 time. You can use /proc/sys/kernel/rcutorture_runnable 1307 to manually override this setting. This /proc file is 1308 available only when the RCU torture tests have been built 1309 into the kernel. 1310 1311 Say Y here if you want the RCU torture tests to start during 1312 boot (you probably don't). 1313 Say N here if you want the RCU torture tests to start only 1314 after being manually enabled via /proc. 1315 1316config RCU_TORTURE_TEST_SLOW_PREINIT 1317 bool "Slow down RCU grace-period pre-initialization to expose races" 1318 depends on RCU_TORTURE_TEST 1319 help 1320 This option delays grace-period pre-initialization (the 1321 propagation of CPU-hotplug changes up the rcu_node combining 1322 tree) for a few jiffies between initializing each pair of 1323 consecutive rcu_node structures. This helps to expose races 1324 involving grace-period pre-initialization, in other words, it 1325 makes your kernel less stable. It can also greatly increase 1326 grace-period latency, especially on systems with large numbers 1327 of CPUs. This is useful when torture-testing RCU, but in 1328 almost no other circumstance. 1329 1330 Say Y here if you want your system to crash and hang more often. 1331 Say N if you want a sane system. 1332 1333config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY 1334 int "How much to slow down RCU grace-period pre-initialization" 1335 range 0 5 1336 default 3 1337 depends on RCU_TORTURE_TEST_SLOW_PREINIT 1338 help 1339 This option specifies the number of jiffies to wait between 1340 each rcu_node structure pre-initialization step. 1341 1342config RCU_TORTURE_TEST_SLOW_INIT 1343 bool "Slow down RCU grace-period initialization to expose races" 1344 depends on RCU_TORTURE_TEST 1345 help 1346 This option delays grace-period initialization for a few 1347 jiffies between initializing each pair of consecutive 1348 rcu_node structures. This helps to expose races involving 1349 grace-period initialization, in other words, it makes your 1350 kernel less stable. It can also greatly increase grace-period 1351 latency, especially on systems with large numbers of CPUs. 1352 This is useful when torture-testing RCU, but in almost no 1353 other circumstance. 1354 1355 Say Y here if you want your system to crash and hang more often. 1356 Say N if you want a sane system. 1357 1358config RCU_TORTURE_TEST_SLOW_INIT_DELAY 1359 int "How much to slow down RCU grace-period initialization" 1360 range 0 5 1361 default 3 1362 depends on RCU_TORTURE_TEST_SLOW_INIT 1363 help 1364 This option specifies the number of jiffies to wait between 1365 each rcu_node structure initialization. 1366 1367config RCU_TORTURE_TEST_SLOW_CLEANUP 1368 bool "Slow down RCU grace-period cleanup to expose races" 1369 depends on RCU_TORTURE_TEST 1370 help 1371 This option delays grace-period cleanup for a few jiffies 1372 between cleaning up each pair of consecutive rcu_node 1373 structures. This helps to expose races involving grace-period 1374 cleanup, in other words, it makes your kernel less stable. 1375 It can also greatly increase grace-period latency, especially 1376 on systems with large numbers of CPUs. This is useful when 1377 torture-testing RCU, but in almost no other circumstance. 1378 1379 Say Y here if you want your system to crash and hang more often. 1380 Say N if you want a sane system. 1381 1382config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY 1383 int "How much to slow down RCU grace-period cleanup" 1384 range 0 5 1385 default 3 1386 depends on RCU_TORTURE_TEST_SLOW_CLEANUP 1387 help 1388 This option specifies the number of jiffies to wait between 1389 each rcu_node structure cleanup operation. 1390 1391config RCU_CPU_STALL_TIMEOUT 1392 int "RCU CPU stall timeout in seconds" 1393 depends on RCU_STALL_COMMON 1394 range 3 300 1395 default 21 1396 help 1397 If a given RCU grace period extends more than the specified 1398 number of seconds, a CPU stall warning is printed. If the 1399 RCU grace period persists, additional CPU stall warnings are 1400 printed at more widely spaced intervals. 1401 1402config RCU_TRACE 1403 bool "Enable tracing for RCU" 1404 depends on DEBUG_KERNEL 1405 select TRACE_CLOCK 1406 help 1407 This option provides tracing in RCU which presents stats 1408 in debugfs for debugging RCU implementation. 1409 1410 Say Y here if you want to enable RCU tracing 1411 Say N if you are unsure. 1412 1413config RCU_EQS_DEBUG 1414 bool "Provide debugging asserts for adding NO_HZ support to an arch" 1415 depends on DEBUG_KERNEL 1416 help 1417 This option provides consistency checks in RCU's handling of 1418 NO_HZ. These checks have proven quite helpful in detecting 1419 bugs in arch-specific NO_HZ code. 1420 1421 Say N here if you need ultimate kernel/user switch latencies 1422 Say Y if you are unsure 1423 1424endmenu # "RCU Debugging" 1425 1426config DEBUG_BLOCK_EXT_DEVT 1427 bool "Force extended block device numbers and spread them" 1428 depends on DEBUG_KERNEL 1429 depends on BLOCK 1430 default n 1431 help 1432 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1433 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1434 YOU ARE DOING. Distros, please enable this and fix whatever 1435 is broken. 1436 1437 Conventionally, block device numbers are allocated from 1438 predetermined contiguous area. However, extended block area 1439 may introduce non-contiguous block device numbers. This 1440 option forces most block device numbers to be allocated from 1441 the extended space and spreads them to discover kernel or 1442 userland code paths which assume predetermined contiguous 1443 device number allocation. 1444 1445 Note that turning on this debug option shuffles all the 1446 device numbers for all IDE and SCSI devices including libata 1447 ones, so root partition specified using device number 1448 directly (via rdev or root=MAJ:MIN) won't work anymore. 1449 Textual device names (root=/dev/sdXn) will continue to work. 1450 1451 Say N if you are unsure. 1452 1453config NOTIFIER_ERROR_INJECTION 1454 tristate "Notifier error injection" 1455 depends on DEBUG_KERNEL 1456 select DEBUG_FS 1457 help 1458 This option provides the ability to inject artificial errors to 1459 specified notifier chain callbacks. It is useful to test the error 1460 handling of notifier call chain failures. 1461 1462 Say N if unsure. 1463 1464config CPU_NOTIFIER_ERROR_INJECT 1465 tristate "CPU notifier error injection module" 1466 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1467 help 1468 This option provides a kernel module that can be used to test 1469 the error handling of the cpu notifiers by injecting artificial 1470 errors to CPU notifier chain callbacks. It is controlled through 1471 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1472 1473 If the notifier call chain should be failed with some events 1474 notified, write the error code to "actions/<notifier event>/error". 1475 1476 Example: Inject CPU offline error (-1 == -EPERM) 1477 1478 # cd /sys/kernel/debug/notifier-error-inject/cpu 1479 # echo -1 > actions/CPU_DOWN_PREPARE/error 1480 # echo 0 > /sys/devices/system/cpu/cpu1/online 1481 bash: echo: write error: Operation not permitted 1482 1483 To compile this code as a module, choose M here: the module will 1484 be called cpu-notifier-error-inject. 1485 1486 If unsure, say N. 1487 1488config PM_NOTIFIER_ERROR_INJECT 1489 tristate "PM notifier error injection module" 1490 depends on PM && NOTIFIER_ERROR_INJECTION 1491 default m if PM_DEBUG 1492 help 1493 This option provides the ability to inject artificial errors to 1494 PM notifier chain callbacks. It is controlled through debugfs 1495 interface /sys/kernel/debug/notifier-error-inject/pm 1496 1497 If the notifier call chain should be failed with some events 1498 notified, write the error code to "actions/<notifier event>/error". 1499 1500 Example: Inject PM suspend error (-12 = -ENOMEM) 1501 1502 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1503 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1504 # echo mem > /sys/power/state 1505 bash: echo: write error: Cannot allocate memory 1506 1507 To compile this code as a module, choose M here: the module will 1508 be called pm-notifier-error-inject. 1509 1510 If unsure, say N. 1511 1512config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1513 tristate "OF reconfig notifier error injection module" 1514 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1515 help 1516 This option provides the ability to inject artificial errors to 1517 OF reconfig notifier chain callbacks. It is controlled 1518 through debugfs interface under 1519 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1520 1521 If the notifier call chain should be failed with some events 1522 notified, write the error code to "actions/<notifier event>/error". 1523 1524 To compile this code as a module, choose M here: the module will 1525 be called of-reconfig-notifier-error-inject. 1526 1527 If unsure, say N. 1528 1529config FAULT_INJECTION 1530 bool "Fault-injection framework" 1531 depends on DEBUG_KERNEL 1532 help 1533 Provide fault-injection framework. 1534 For more details, see Documentation/fault-injection/. 1535 1536config FAILSLAB 1537 bool "Fault-injection capability for kmalloc" 1538 depends on FAULT_INJECTION 1539 depends on SLAB || SLUB 1540 help 1541 Provide fault-injection capability for kmalloc. 1542 1543config FAIL_PAGE_ALLOC 1544 bool "Fault-injection capabilitiy for alloc_pages()" 1545 depends on FAULT_INJECTION 1546 help 1547 Provide fault-injection capability for alloc_pages(). 1548 1549config FAIL_MAKE_REQUEST 1550 bool "Fault-injection capability for disk IO" 1551 depends on FAULT_INJECTION && BLOCK 1552 help 1553 Provide fault-injection capability for disk IO. 1554 1555config FAIL_IO_TIMEOUT 1556 bool "Fault-injection capability for faking disk interrupts" 1557 depends on FAULT_INJECTION && BLOCK 1558 help 1559 Provide fault-injection capability on end IO handling. This 1560 will make the block layer "forget" an interrupt as configured, 1561 thus exercising the error handling. 1562 1563 Only works with drivers that use the generic timeout handling, 1564 for others it wont do anything. 1565 1566config FAIL_MMC_REQUEST 1567 bool "Fault-injection capability for MMC IO" 1568 select DEBUG_FS 1569 depends on FAULT_INJECTION && MMC 1570 help 1571 Provide fault-injection capability for MMC IO. 1572 This will make the mmc core return data errors. This is 1573 useful to test the error handling in the mmc block device 1574 and to test how the mmc host driver handles retries from 1575 the block device. 1576 1577config FAIL_FUTEX 1578 bool "Fault-injection capability for futexes" 1579 select DEBUG_FS 1580 depends on FAULT_INJECTION && FUTEX 1581 help 1582 Provide fault-injection capability for futexes. 1583 1584config FAULT_INJECTION_DEBUG_FS 1585 bool "Debugfs entries for fault-injection capabilities" 1586 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1587 help 1588 Enable configuration of fault-injection capabilities via debugfs. 1589 1590config FAULT_INJECTION_STACKTRACE_FILTER 1591 bool "stacktrace filter for fault-injection capabilities" 1592 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1593 depends on !X86_64 1594 select STACKTRACE 1595 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1596 help 1597 Provide stacktrace filter for fault-injection capabilities 1598 1599config LATENCYTOP 1600 bool "Latency measuring infrastructure" 1601 depends on HAVE_LATENCYTOP_SUPPORT 1602 depends on DEBUG_KERNEL 1603 depends on STACKTRACE_SUPPORT 1604 depends on PROC_FS 1605 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1606 select KALLSYMS 1607 select KALLSYMS_ALL 1608 select STACKTRACE 1609 select SCHEDSTATS 1610 select SCHED_DEBUG 1611 help 1612 Enable this option if you want to use the LatencyTOP tool 1613 to find out which userspace is blocking on what kernel operations. 1614 1615config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1616 bool 1617 1618config DEBUG_STRICT_USER_COPY_CHECKS 1619 bool "Strict user copy size checks" 1620 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1621 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING 1622 help 1623 Enabling this option turns a certain set of sanity checks for user 1624 copy operations into compile time failures. 1625 1626 The copy_from_user() etc checks are there to help test if there 1627 are sufficient security checks on the length argument of 1628 the copy operation, by having gcc prove that the argument is 1629 within bounds. 1630 1631 If unsure, say N. 1632 1633source kernel/trace/Kconfig 1634 1635menu "Runtime Testing" 1636 1637config LKDTM 1638 tristate "Linux Kernel Dump Test Tool Module" 1639 depends on DEBUG_FS 1640 depends on BLOCK 1641 default n 1642 help 1643 This module enables testing of the different dumping mechanisms by 1644 inducing system failures at predefined crash points. 1645 If you don't need it: say N 1646 Choose M here to compile this code as a module. The module will be 1647 called lkdtm. 1648 1649 Documentation on how to use the module can be found in 1650 Documentation/fault-injection/provoke-crashes.txt 1651 1652config TEST_LIST_SORT 1653 bool "Linked list sorting test" 1654 depends on DEBUG_KERNEL 1655 help 1656 Enable this to turn on 'list_sort()' function test. This test is 1657 executed only once during system boot, so affects only boot time. 1658 1659 If unsure, say N. 1660 1661config KPROBES_SANITY_TEST 1662 bool "Kprobes sanity tests" 1663 depends on DEBUG_KERNEL 1664 depends on KPROBES 1665 default n 1666 help 1667 This option provides for testing basic kprobes functionality on 1668 boot. A sample kprobe, jprobe and kretprobe are inserted and 1669 verified for functionality. 1670 1671 Say N if you are unsure. 1672 1673config BACKTRACE_SELF_TEST 1674 tristate "Self test for the backtrace code" 1675 depends on DEBUG_KERNEL 1676 default n 1677 help 1678 This option provides a kernel module that can be used to test 1679 the kernel stack backtrace code. This option is not useful 1680 for distributions or general kernels, but only for kernel 1681 developers working on architecture code. 1682 1683 Note that if you want to also test saved backtraces, you will 1684 have to enable STACKTRACE as well. 1685 1686 Say N if you are unsure. 1687 1688config RBTREE_TEST 1689 tristate "Red-Black tree test" 1690 depends on DEBUG_KERNEL 1691 help 1692 A benchmark measuring the performance of the rbtree library. 1693 Also includes rbtree invariant checks. 1694 1695config INTERVAL_TREE_TEST 1696 tristate "Interval tree test" 1697 depends on m && DEBUG_KERNEL 1698 select INTERVAL_TREE 1699 help 1700 A benchmark measuring the performance of the interval tree library 1701 1702config PERCPU_TEST 1703 tristate "Per cpu operations test" 1704 depends on m && DEBUG_KERNEL 1705 help 1706 Enable this option to build test module which validates per-cpu 1707 operations. 1708 1709 If unsure, say N. 1710 1711config ATOMIC64_SELFTEST 1712 bool "Perform an atomic64_t self-test at boot" 1713 help 1714 Enable this option to test the atomic64_t functions at boot. 1715 1716 If unsure, say N. 1717 1718config ASYNC_RAID6_TEST 1719 tristate "Self test for hardware accelerated raid6 recovery" 1720 depends on ASYNC_RAID6_RECOV 1721 select ASYNC_MEMCPY 1722 ---help--- 1723 This is a one-shot self test that permutes through the 1724 recovery of all the possible two disk failure scenarios for a 1725 N-disk array. Recovery is performed with the asynchronous 1726 raid6 recovery routines, and will optionally use an offload 1727 engine if one is available. 1728 1729 If unsure, say N. 1730 1731config TEST_HEXDUMP 1732 tristate "Test functions located in the hexdump module at runtime" 1733 1734config TEST_STRING_HELPERS 1735 tristate "Test functions located in the string_helpers module at runtime" 1736 1737config TEST_KSTRTOX 1738 tristate "Test kstrto*() family of functions at runtime" 1739 1740config TEST_PRINTF 1741 tristate "Test printf() family of functions at runtime" 1742 1743config TEST_RHASHTABLE 1744 tristate "Perform selftest on resizable hash table" 1745 default n 1746 help 1747 Enable this option to test the rhashtable functions at boot. 1748 1749 If unsure, say N. 1750 1751config TEST_HASH 1752 tristate "Perform selftest on hash functions" 1753 default n 1754 help 1755 Enable this option to test the kernel's siphash (<linux/siphash.h>) 1756 hash functions on boot (or module load). 1757 1758 This is intended to help people writing architecture-specific 1759 optimized versions. If unsure, say N. 1760 1761endmenu # runtime tests 1762 1763config PROVIDE_OHCI1394_DMA_INIT 1764 bool "Remote debugging over FireWire early on boot" 1765 depends on PCI && X86 1766 help 1767 If you want to debug problems which hang or crash the kernel early 1768 on boot and the crashing machine has a FireWire port, you can use 1769 this feature to remotely access the memory of the crashed machine 1770 over FireWire. This employs remote DMA as part of the OHCI1394 1771 specification which is now the standard for FireWire controllers. 1772 1773 With remote DMA, you can monitor the printk buffer remotely using 1774 firescope and access all memory below 4GB using fireproxy from gdb. 1775 Even controlling a kernel debugger is possible using remote DMA. 1776 1777 Usage: 1778 1779 If ohci1394_dma=early is used as boot parameter, it will initialize 1780 all OHCI1394 controllers which are found in the PCI config space. 1781 1782 As all changes to the FireWire bus such as enabling and disabling 1783 devices cause a bus reset and thereby disable remote DMA for all 1784 devices, be sure to have the cable plugged and FireWire enabled on 1785 the debugging host before booting the debug target for debugging. 1786 1787 This code (~1k) is freed after boot. By then, the firewire stack 1788 in charge of the OHCI-1394 controllers should be used instead. 1789 1790 See Documentation/debugging-via-ohci1394.txt for more information. 1791 1792config BUILD_DOCSRC 1793 bool "Build targets in Documentation/ tree" 1794 depends on HEADERS_CHECK 1795 help 1796 This option attempts to build objects from the source files in the 1797 kernel Documentation/ tree. 1798 1799 Say N if you are unsure. 1800 1801config DMA_API_DEBUG 1802 bool "Enable debugging of DMA-API usage" 1803 depends on HAVE_DMA_API_DEBUG 1804 help 1805 Enable this option to debug the use of the DMA API by device drivers. 1806 With this option you will be able to detect common bugs in device 1807 drivers like double-freeing of DMA mappings or freeing mappings that 1808 were never allocated. 1809 1810 This also attempts to catch cases where a page owned by DMA is 1811 accessed by the cpu in a way that could cause data corruption. For 1812 example, this enables cow_user_page() to check that the source page is 1813 not undergoing DMA. 1814 1815 This option causes a performance degradation. Use only if you want to 1816 debug device drivers and dma interactions. 1817 1818 If unsure, say N. 1819 1820config TEST_LKM 1821 tristate "Test module loading with 'hello world' module" 1822 default n 1823 depends on m 1824 help 1825 This builds the "test_module" module that emits "Hello, world" 1826 on printk when loaded. It is designed to be used for basic 1827 evaluation of the module loading subsystem (for example when 1828 validating module verification). It lacks any extra dependencies, 1829 and will not normally be loaded by the system unless explicitly 1830 requested by name. 1831 1832 If unsure, say N. 1833 1834config TEST_USER_COPY 1835 tristate "Test user/kernel boundary protections" 1836 default n 1837 depends on m 1838 help 1839 This builds the "test_user_copy" module that runs sanity checks 1840 on the copy_to/from_user infrastructure, making sure basic 1841 user/kernel boundary testing is working. If it fails to load, 1842 a regression has been detected in the user/kernel memory boundary 1843 protections. 1844 1845 If unsure, say N. 1846 1847config TEST_BPF 1848 tristate "Test BPF filter functionality" 1849 default n 1850 depends on m && NET 1851 help 1852 This builds the "test_bpf" module that runs various test vectors 1853 against the BPF interpreter or BPF JIT compiler depending on the 1854 current setting. This is in particular useful for BPF JIT compiler 1855 development, but also to run regression tests against changes in 1856 the interpreter code. It also enables test stubs for eBPF maps and 1857 verifier used by user space verifier testsuite. 1858 1859 If unsure, say N. 1860 1861config TEST_FIRMWARE 1862 tristate "Test firmware loading via userspace interface" 1863 default n 1864 depends on FW_LOADER 1865 help 1866 This builds the "test_firmware" module that creates a userspace 1867 interface for testing firmware loading. This can be used to 1868 control the triggering of firmware loading without needing an 1869 actual firmware-using device. The contents can be rechecked by 1870 userspace. 1871 1872 If unsure, say N. 1873 1874config TEST_UDELAY 1875 tristate "udelay test driver" 1876 default n 1877 help 1878 This builds the "udelay_test" module that helps to make sure 1879 that udelay() is working properly. 1880 1881 If unsure, say N. 1882 1883config MEMTEST 1884 bool "Memtest" 1885 depends on HAVE_MEMBLOCK 1886 ---help--- 1887 This option adds a kernel parameter 'memtest', which allows memtest 1888 to be set. 1889 memtest=0, mean disabled; -- default 1890 memtest=1, mean do 1 test pattern; 1891 ... 1892 memtest=17, mean do 17 test patterns. 1893 If you are unsure how to answer this question, answer N. 1894 1895config TEST_STATIC_KEYS 1896 tristate "Test static keys" 1897 default n 1898 depends on m 1899 help 1900 Test the static key interfaces. 1901 1902 If unsure, say N. 1903 1904source "samples/Kconfig" 1905 1906source "lib/Kconfig.kgdb" 1907 1908