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 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 STACK_VALIDATION 346 bool "Compile-time stack metadata validation" 347 depends on HAVE_STACK_VALIDATION 348 default n 349 help 350 Add compile-time checks to validate stack metadata, including frame 351 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure 352 that runtime stack traces are more reliable. 353 354 For more information, see 355 tools/objtool/Documentation/stack-validation.txt. 356 357config DEBUG_FORCE_WEAK_PER_CPU 358 bool "Force weak per-cpu definitions" 359 depends on DEBUG_KERNEL 360 help 361 s390 and alpha require percpu variables in modules to be 362 defined weak to work around addressing range issue which 363 puts the following two restrictions on percpu variable 364 definitions. 365 366 1. percpu symbols must be unique whether static or not 367 2. percpu variables can't be defined inside a function 368 369 To ensure that generic code follows the above rules, this 370 option forces all percpu variables to be defined as weak. 371 372endmenu # "Compiler options" 373 374config MAGIC_SYSRQ 375 bool "Magic SysRq key" 376 depends on !UML 377 help 378 If you say Y here, you will have some control over the system even 379 if the system crashes for example during kernel debugging (e.g., you 380 will be able to flush the buffer cache to disk, reboot the system 381 immediately or dump some status information). This is accomplished 382 by pressing various keys while holding SysRq (Alt+PrintScreen). It 383 also works on a serial console (on PC hardware at least), if you 384 send a BREAK and then within 5 seconds a command keypress. The 385 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 386 unless you really know what this hack does. 387 388config MAGIC_SYSRQ_DEFAULT_ENABLE 389 hex "Enable magic SysRq key functions by default" 390 depends on MAGIC_SYSRQ 391 default 0x1 392 help 393 Specifies which SysRq key functions are enabled by default. 394 This may be set to 1 or 0 to enable or disable them all, or 395 to a bitmask as described in Documentation/sysrq.txt. 396 397config DEBUG_KERNEL 398 bool "Kernel debugging" 399 help 400 Say Y here if you are developing drivers or trying to debug and 401 identify kernel problems. 402 403menu "Memory Debugging" 404 405source mm/Kconfig.debug 406 407config DEBUG_OBJECTS 408 bool "Debug object operations" 409 depends on DEBUG_KERNEL 410 help 411 If you say Y here, additional code will be inserted into the 412 kernel to track the life time of various objects and validate 413 the operations on those objects. 414 415config DEBUG_OBJECTS_SELFTEST 416 bool "Debug objects selftest" 417 depends on DEBUG_OBJECTS 418 help 419 This enables the selftest of the object debug code. 420 421config DEBUG_OBJECTS_FREE 422 bool "Debug objects in freed memory" 423 depends on DEBUG_OBJECTS 424 help 425 This enables checks whether a k/v free operation frees an area 426 which contains an object which has not been deactivated 427 properly. This can make kmalloc/kfree-intensive workloads 428 much slower. 429 430config DEBUG_OBJECTS_TIMERS 431 bool "Debug timer objects" 432 depends on DEBUG_OBJECTS 433 help 434 If you say Y here, additional code will be inserted into the 435 timer routines to track the life time of timer objects and 436 validate the timer operations. 437 438config DEBUG_OBJECTS_WORK 439 bool "Debug work objects" 440 depends on DEBUG_OBJECTS 441 help 442 If you say Y here, additional code will be inserted into the 443 work queue routines to track the life time of work objects and 444 validate the work operations. 445 446config DEBUG_OBJECTS_RCU_HEAD 447 bool "Debug RCU callbacks objects" 448 depends on DEBUG_OBJECTS 449 help 450 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 451 452config DEBUG_OBJECTS_PERCPU_COUNTER 453 bool "Debug percpu counter objects" 454 depends on DEBUG_OBJECTS 455 help 456 If you say Y here, additional code will be inserted into the 457 percpu counter routines to track the life time of percpu counter 458 objects and validate the percpu counter operations. 459 460config DEBUG_OBJECTS_ENABLE_DEFAULT 461 int "debug_objects bootup default value (0-1)" 462 range 0 1 463 default "1" 464 depends on DEBUG_OBJECTS 465 help 466 Debug objects boot parameter default value 467 468config DEBUG_SLAB 469 bool "Debug slab memory allocations" 470 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 471 help 472 Say Y here to have the kernel do limited verification on memory 473 allocation as well as poisoning memory on free to catch use of freed 474 memory. This can make kmalloc/kfree-intensive workloads much slower. 475 476config DEBUG_SLAB_LEAK 477 bool "Memory leak debugging" 478 depends on DEBUG_SLAB 479 480config SLUB_DEBUG_ON 481 bool "SLUB debugging on by default" 482 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 483 default n 484 help 485 Boot with debugging on by default. SLUB boots by default with 486 the runtime debug capabilities switched off. Enabling this is 487 equivalent to specifying the "slub_debug" parameter on boot. 488 There is no support for more fine grained debug control like 489 possible with slub_debug=xxx. SLUB debugging may be switched 490 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 491 "slub_debug=-". 492 493config SLUB_STATS 494 default n 495 bool "Enable SLUB performance statistics" 496 depends on SLUB && SYSFS 497 help 498 SLUB statistics are useful to debug SLUBs allocation behavior in 499 order find ways to optimize the allocator. This should never be 500 enabled for production use since keeping statistics slows down 501 the allocator by a few percentage points. The slabinfo command 502 supports the determination of the most active slabs to figure 503 out which slabs are relevant to a particular load. 504 Try running: slabinfo -DA 505 506config HAVE_DEBUG_KMEMLEAK 507 bool 508 509config DEBUG_KMEMLEAK 510 bool "Kernel memory leak detector" 511 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 512 select DEBUG_FS 513 select STACKTRACE if STACKTRACE_SUPPORT 514 select KALLSYMS 515 select CRC32 516 help 517 Say Y here if you want to enable the memory leak 518 detector. The memory allocation/freeing is traced in a way 519 similar to the Boehm's conservative garbage collector, the 520 difference being that the orphan objects are not freed but 521 only shown in /sys/kernel/debug/kmemleak. Enabling this 522 feature will introduce an overhead to memory 523 allocations. See Documentation/kmemleak.txt for more 524 details. 525 526 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 527 of finding leaks due to the slab objects poisoning. 528 529 In order to access the kmemleak file, debugfs needs to be 530 mounted (usually at /sys/kernel/debug). 531 532config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 533 int "Maximum kmemleak early log entries" 534 depends on DEBUG_KMEMLEAK 535 range 200 40000 536 default 400 537 help 538 Kmemleak must track all the memory allocations to avoid 539 reporting false positives. Since memory may be allocated or 540 freed before kmemleak is initialised, an early log buffer is 541 used to store these actions. If kmemleak reports "early log 542 buffer exceeded", please increase this value. 543 544config DEBUG_KMEMLEAK_TEST 545 tristate "Simple test for the kernel memory leak detector" 546 depends on DEBUG_KMEMLEAK && m 547 help 548 This option enables a module that explicitly leaks memory. 549 550 If unsure, say N. 551 552config DEBUG_KMEMLEAK_DEFAULT_OFF 553 bool "Default kmemleak to off" 554 depends on DEBUG_KMEMLEAK 555 help 556 Say Y here to disable kmemleak by default. It can then be enabled 557 on the command line via kmemleak=on. 558 559config DEBUG_STACK_USAGE 560 bool "Stack utilization instrumentation" 561 depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAG 562 help 563 Enables the display of the minimum amount of free stack which each 564 task has ever had available in the sysrq-T and sysrq-P debug output. 565 566 This option will slow down process creation somewhat. 567 568config DEBUG_VM 569 bool "Debug VM" 570 depends on DEBUG_KERNEL 571 help 572 Enable this to turn on extended checks in the virtual-memory system 573 that may impact performance. 574 575 If unsure, say N. 576 577config DEBUG_VM_VMACACHE 578 bool "Debug VMA caching" 579 depends on DEBUG_VM 580 help 581 Enable this to turn on VMA caching debug information. Doing so 582 can cause significant overhead, so only enable it in non-production 583 environments. 584 585 If unsure, say N. 586 587config DEBUG_VM_RB 588 bool "Debug VM red-black trees" 589 depends on DEBUG_VM 590 help 591 Enable VM red-black tree debugging information and extra validations. 592 593 If unsure, say N. 594 595config DEBUG_VM_PGFLAGS 596 bool "Debug page-flags operations" 597 depends on DEBUG_VM 598 help 599 Enables extra validation on page flags operations. 600 601 If unsure, say N. 602 603config DEBUG_VIRTUAL 604 bool "Debug VM translations" 605 depends on DEBUG_KERNEL && X86 606 help 607 Enable some costly sanity checks in virtual to page code. This can 608 catch mistakes with virt_to_page() and friends. 609 610 If unsure, say N. 611 612config DEBUG_NOMMU_REGIONS 613 bool "Debug the global anon/private NOMMU mapping region tree" 614 depends on DEBUG_KERNEL && !MMU 615 help 616 This option causes the global tree of anonymous and private mapping 617 regions to be regularly checked for invalid topology. 618 619config DEBUG_MEMORY_INIT 620 bool "Debug memory initialisation" if EXPERT 621 default !EXPERT 622 help 623 Enable this for additional checks during memory initialisation. 624 The sanity checks verify aspects of the VM such as the memory model 625 and other information provided by the architecture. Verbose 626 information will be printed at KERN_DEBUG loglevel depending 627 on the mminit_loglevel= command-line option. 628 629 If unsure, say Y 630 631config MEMORY_NOTIFIER_ERROR_INJECT 632 tristate "Memory hotplug notifier error injection module" 633 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 634 help 635 This option provides the ability to inject artificial errors to 636 memory hotplug notifier chain callbacks. It is controlled through 637 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 638 639 If the notifier call chain should be failed with some events 640 notified, write the error code to "actions/<notifier event>/error". 641 642 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 643 644 # cd /sys/kernel/debug/notifier-error-inject/memory 645 # echo -12 > actions/MEM_GOING_OFFLINE/error 646 # echo offline > /sys/devices/system/memory/memoryXXX/state 647 bash: echo: write error: Cannot allocate memory 648 649 To compile this code as a module, choose M here: the module will 650 be called memory-notifier-error-inject. 651 652 If unsure, say N. 653 654config DEBUG_PER_CPU_MAPS 655 bool "Debug access to per_cpu maps" 656 depends on DEBUG_KERNEL 657 depends on SMP 658 help 659 Say Y to verify that the per_cpu map being accessed has 660 been set up. This adds a fair amount of code to kernel memory 661 and decreases performance. 662 663 Say N if unsure. 664 665config DEBUG_HIGHMEM 666 bool "Highmem debugging" 667 depends on DEBUG_KERNEL && HIGHMEM 668 help 669 This option enables additional error checking for high memory 670 systems. Disable for production systems. 671 672config HAVE_DEBUG_STACKOVERFLOW 673 bool 674 675config DEBUG_STACKOVERFLOW 676 bool "Check for stack overflows" 677 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 678 ---help--- 679 Say Y here if you want to check for overflows of kernel, IRQ 680 and exception stacks (if your architecture uses them). This 681 option will show detailed messages if free stack space drops 682 below a certain limit. 683 684 These kinds of bugs usually occur when call-chains in the 685 kernel get too deep, especially when interrupts are 686 involved. 687 688 Use this in cases where you see apparently random memory 689 corruption, especially if it appears in 'struct thread_info' 690 691 If in doubt, say "N". 692 693source "lib/Kconfig.kmemcheck" 694 695source "lib/Kconfig.kasan" 696 697endmenu # "Memory Debugging" 698 699config DEBUG_SHIRQ 700 bool "Debug shared IRQ handlers" 701 depends on DEBUG_KERNEL 702 help 703 Enable this to generate a spurious interrupt as soon as a shared 704 interrupt handler is registered, and just before one is deregistered. 705 Drivers ought to be able to handle interrupts coming in at those 706 points; some don't and need to be caught. 707 708menu "Debug Lockups and Hangs" 709 710config LOCKUP_DETECTOR 711 bool "Detect Hard and Soft Lockups" 712 depends on DEBUG_KERNEL && !S390 713 help 714 Say Y here to enable the kernel to act as a watchdog to detect 715 hard and soft lockups. 716 717 Softlockups are bugs that cause the kernel to loop in kernel 718 mode for more than 20 seconds, without giving other tasks a 719 chance to run. The current stack trace is displayed upon 720 detection and the system will stay locked up. 721 722 Hardlockups are bugs that cause the CPU to loop in kernel mode 723 for more than 10 seconds, without letting other interrupts have a 724 chance to run. The current stack trace is displayed upon detection 725 and the system will stay locked up. 726 727 The overhead should be minimal. A periodic hrtimer runs to 728 generate interrupts and kick the watchdog task every 4 seconds. 729 An NMI is generated every 10 seconds or so to check for hardlockups. 730 731 The frequency of hrtimer and NMI events and the soft and hard lockup 732 thresholds can be controlled through the sysctl watchdog_thresh. 733 734config HARDLOCKUP_DETECTOR 735 def_bool y 736 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 737 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 738 739config BOOTPARAM_HARDLOCKUP_PANIC 740 bool "Panic (Reboot) On Hard Lockups" 741 depends on HARDLOCKUP_DETECTOR 742 help 743 Say Y here to enable the kernel to panic on "hard lockups", 744 which are bugs that cause the kernel to loop in kernel 745 mode with interrupts disabled for more than 10 seconds (configurable 746 using the watchdog_thresh sysctl). 747 748 Say N if unsure. 749 750config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 751 int 752 depends on HARDLOCKUP_DETECTOR 753 range 0 1 754 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 755 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 756 757config BOOTPARAM_SOFTLOCKUP_PANIC 758 bool "Panic (Reboot) On Soft Lockups" 759 depends on LOCKUP_DETECTOR 760 help 761 Say Y here to enable the kernel to panic on "soft lockups", 762 which are bugs that cause the kernel to loop in kernel 763 mode for more than 20 seconds (configurable using the watchdog_thresh 764 sysctl), without giving other tasks a chance to run. 765 766 The panic can be used in combination with panic_timeout, 767 to cause the system to reboot automatically after a 768 lockup has been detected. This feature is useful for 769 high-availability systems that have uptime guarantees and 770 where a lockup must be resolved ASAP. 771 772 Say N if unsure. 773 774config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 775 int 776 depends on LOCKUP_DETECTOR 777 range 0 1 778 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 779 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 780 781config DETECT_HUNG_TASK 782 bool "Detect Hung Tasks" 783 depends on DEBUG_KERNEL 784 default LOCKUP_DETECTOR 785 help 786 Say Y here to enable the kernel to detect "hung tasks", 787 which are bugs that cause the task to be stuck in 788 uninterruptible "D" state indefinitiley. 789 790 When a hung task is detected, the kernel will print the 791 current stack trace (which you should report), but the 792 task will stay in uninterruptible state. If lockdep is 793 enabled then all held locks will also be reported. This 794 feature has negligible overhead. 795 796config DEFAULT_HUNG_TASK_TIMEOUT 797 int "Default timeout for hung task detection (in seconds)" 798 depends on DETECT_HUNG_TASK 799 default 120 800 help 801 This option controls the default timeout (in seconds) used 802 to determine when a task has become non-responsive and should 803 be considered hung. 804 805 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 806 sysctl or by writing a value to 807 /proc/sys/kernel/hung_task_timeout_secs. 808 809 A timeout of 0 disables the check. The default is two minutes. 810 Keeping the default should be fine in most cases. 811 812config BOOTPARAM_HUNG_TASK_PANIC 813 bool "Panic (Reboot) On Hung Tasks" 814 depends on DETECT_HUNG_TASK 815 help 816 Say Y here to enable the kernel to panic on "hung tasks", 817 which are bugs that cause the kernel to leave a task stuck 818 in uninterruptible "D" state. 819 820 The panic can be used in combination with panic_timeout, 821 to cause the system to reboot automatically after a 822 hung task has been detected. This feature is useful for 823 high-availability systems that have uptime guarantees and 824 where a hung tasks must be resolved ASAP. 825 826 Say N if unsure. 827 828config BOOTPARAM_HUNG_TASK_PANIC_VALUE 829 int 830 depends on DETECT_HUNG_TASK 831 range 0 1 832 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 833 default 1 if BOOTPARAM_HUNG_TASK_PANIC 834 835config WQ_WATCHDOG 836 bool "Detect Workqueue Stalls" 837 depends on DEBUG_KERNEL 838 help 839 Say Y here to enable stall detection on workqueues. If a 840 worker pool doesn't make forward progress on a pending work 841 item for over a given amount of time, 30s by default, a 842 warning message is printed along with dump of workqueue 843 state. This can be configured through kernel parameter 844 "workqueue.watchdog_thresh" and its sysfs counterpart. 845 846endmenu # "Debug lockups and hangs" 847 848config PANIC_ON_OOPS 849 bool "Panic on Oops" 850 help 851 Say Y here to enable the kernel to panic when it oopses. This 852 has the same effect as setting oops=panic on the kernel command 853 line. 854 855 This feature is useful to ensure that the kernel does not do 856 anything erroneous after an oops which could result in data 857 corruption or other issues. 858 859 Say N if unsure. 860 861config PANIC_ON_OOPS_VALUE 862 int 863 range 0 1 864 default 0 if !PANIC_ON_OOPS 865 default 1 if PANIC_ON_OOPS 866 867config PANIC_TIMEOUT 868 int "panic timeout" 869 default 0 870 help 871 Set the timeout value (in seconds) until a reboot occurs when the 872 the kernel panics. If n = 0, then we wait forever. A timeout 873 value n > 0 will wait n seconds before rebooting, while a timeout 874 value n < 0 will reboot immediately. 875 876config SCHED_DEBUG 877 bool "Collect scheduler debugging info" 878 depends on DEBUG_KERNEL && PROC_FS 879 default y 880 help 881 If you say Y here, the /proc/sched_debug file will be provided 882 that can help debug the scheduler. The runtime overhead of this 883 option is minimal. 884 885config SCHED_INFO 886 bool 887 default n 888 889config SCHEDSTATS 890 bool "Collect scheduler statistics" 891 depends on DEBUG_KERNEL && PROC_FS 892 select SCHED_INFO 893 help 894 If you say Y here, additional code will be inserted into the 895 scheduler and related routines to collect statistics about 896 scheduler behavior and provide them in /proc/schedstat. These 897 stats may be useful for both tuning and debugging the scheduler 898 If you aren't debugging the scheduler or trying to tune a specific 899 application, you can say N to avoid the very slight overhead 900 this adds. 901 902config SCHED_STACK_END_CHECK 903 bool "Detect stack corruption on calls to schedule()" 904 depends on DEBUG_KERNEL 905 default n 906 help 907 This option checks for a stack overrun on calls to schedule(). 908 If the stack end location is found to be over written always panic as 909 the content of the corrupted region can no longer be trusted. 910 This is to ensure no erroneous behaviour occurs which could result in 911 data corruption or a sporadic crash at a later stage once the region 912 is examined. The runtime overhead introduced is minimal. 913 914config DEBUG_TIMEKEEPING 915 bool "Enable extra timekeeping sanity checking" 916 help 917 This option will enable additional timekeeping sanity checks 918 which may be helpful when diagnosing issues where timekeeping 919 problems are suspected. 920 921 This may include checks in the timekeeping hotpaths, so this 922 option may have a (very small) performance impact to some 923 workloads. 924 925 If unsure, say N. 926 927config TIMER_STATS 928 bool "Collect kernel timers statistics" 929 depends on DEBUG_KERNEL && PROC_FS 930 help 931 If you say Y here, additional code will be inserted into the 932 timer routines to collect statistics about kernel timers being 933 reprogrammed. The statistics can be read from /proc/timer_stats. 934 The statistics collection is started by writing 1 to /proc/timer_stats, 935 writing 0 stops it. This feature is useful to collect information 936 about timer usage patterns in kernel and userspace. This feature 937 is lightweight if enabled in the kernel config but not activated 938 (it defaults to deactivated on bootup and will only be activated 939 if some application like powertop activates it explicitly). 940 941config DEBUG_PREEMPT 942 bool "Debug preemptible kernel" 943 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 944 default y 945 help 946 If you say Y here then the kernel will use a debug variant of the 947 commonly used smp_processor_id() function and will print warnings 948 if kernel code uses it in a preemption-unsafe way. Also, the kernel 949 will detect preemption count underflows. 950 951menu "Lock Debugging (spinlocks, mutexes, etc...)" 952 953config DEBUG_RT_MUTEXES 954 bool "RT Mutex debugging, deadlock detection" 955 depends on DEBUG_KERNEL && RT_MUTEXES 956 help 957 This allows rt mutex semantics violations and rt mutex related 958 deadlocks (lockups) to be detected and reported automatically. 959 960config DEBUG_SPINLOCK 961 bool "Spinlock and rw-lock debugging: basic checks" 962 depends on DEBUG_KERNEL 963 select UNINLINE_SPIN_UNLOCK 964 help 965 Say Y here and build SMP to catch missing spinlock initialization 966 and certain other kinds of spinlock errors commonly made. This is 967 best used in conjunction with the NMI watchdog so that spinlock 968 deadlocks are also debuggable. 969 970config DEBUG_MUTEXES 971 bool "Mutex debugging: basic checks" 972 depends on DEBUG_KERNEL 973 help 974 This feature allows mutex semantics violations to be detected and 975 reported. 976 977config DEBUG_WW_MUTEX_SLOWPATH 978 bool "Wait/wound mutex debugging: Slowpath testing" 979 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 980 select DEBUG_LOCK_ALLOC 981 select DEBUG_SPINLOCK 982 select DEBUG_MUTEXES 983 help 984 This feature enables slowpath testing for w/w mutex users by 985 injecting additional -EDEADLK wound/backoff cases. Together with 986 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 987 will test all possible w/w mutex interface abuse with the 988 exception of simply not acquiring all the required locks. 989 Note that this feature can introduce significant overhead, so 990 it really should not be enabled in a production or distro kernel, 991 even a debug kernel. If you are a driver writer, enable it. If 992 you are a distro, do not. 993 994config DEBUG_LOCK_ALLOC 995 bool "Lock debugging: detect incorrect freeing of live locks" 996 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 997 select DEBUG_SPINLOCK 998 select DEBUG_MUTEXES 999 select LOCKDEP 1000 help 1001 This feature will check whether any held lock (spinlock, rwlock, 1002 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1003 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1004 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1005 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1006 held during task exit. 1007 1008config PROVE_LOCKING 1009 bool "Lock debugging: prove locking correctness" 1010 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1011 select LOCKDEP 1012 select DEBUG_SPINLOCK 1013 select DEBUG_MUTEXES 1014 select DEBUG_LOCK_ALLOC 1015 select TRACE_IRQFLAGS 1016 default n 1017 help 1018 This feature enables the kernel to prove that all locking 1019 that occurs in the kernel runtime is mathematically 1020 correct: that under no circumstance could an arbitrary (and 1021 not yet triggered) combination of observed locking 1022 sequences (on an arbitrary number of CPUs, running an 1023 arbitrary number of tasks and interrupt contexts) cause a 1024 deadlock. 1025 1026 In short, this feature enables the kernel to report locking 1027 related deadlocks before they actually occur. 1028 1029 The proof does not depend on how hard and complex a 1030 deadlock scenario would be to trigger: how many 1031 participant CPUs, tasks and irq-contexts would be needed 1032 for it to trigger. The proof also does not depend on 1033 timing: if a race and a resulting deadlock is possible 1034 theoretically (no matter how unlikely the race scenario 1035 is), it will be proven so and will immediately be 1036 reported by the kernel (once the event is observed that 1037 makes the deadlock theoretically possible). 1038 1039 If a deadlock is impossible (i.e. the locking rules, as 1040 observed by the kernel, are mathematically correct), the 1041 kernel reports nothing. 1042 1043 NOTE: this feature can also be enabled for rwlocks, mutexes 1044 and rwsems - in which case all dependencies between these 1045 different locking variants are observed and mapped too, and 1046 the proof of observed correctness is also maintained for an 1047 arbitrary combination of these separate locking variants. 1048 1049 For more details, see Documentation/locking/lockdep-design.txt. 1050 1051config LOCKDEP 1052 bool 1053 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1054 select STACKTRACE 1055 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE 1056 select KALLSYMS 1057 select KALLSYMS_ALL 1058 1059config LOCK_STAT 1060 bool "Lock usage statistics" 1061 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1062 select LOCKDEP 1063 select DEBUG_SPINLOCK 1064 select DEBUG_MUTEXES 1065 select DEBUG_LOCK_ALLOC 1066 default n 1067 help 1068 This feature enables tracking lock contention points 1069 1070 For more details, see Documentation/locking/lockstat.txt 1071 1072 This also enables lock events required by "perf lock", 1073 subcommand of perf. 1074 If you want to use "perf lock", you also need to turn on 1075 CONFIG_EVENT_TRACING. 1076 1077 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1078 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1079 1080config DEBUG_LOCKDEP 1081 bool "Lock dependency engine debugging" 1082 depends on DEBUG_KERNEL && LOCKDEP 1083 help 1084 If you say Y here, the lock dependency engine will do 1085 additional runtime checks to debug itself, at the price 1086 of more runtime overhead. 1087 1088config DEBUG_ATOMIC_SLEEP 1089 bool "Sleep inside atomic section checking" 1090 select PREEMPT_COUNT 1091 depends on DEBUG_KERNEL 1092 help 1093 If you say Y here, various routines which may sleep will become very 1094 noisy if they are called inside atomic sections: when a spinlock is 1095 held, inside an rcu read side critical section, inside preempt disabled 1096 sections, inside an interrupt, etc... 1097 1098config DEBUG_LOCKING_API_SELFTESTS 1099 bool "Locking API boot-time self-tests" 1100 depends on DEBUG_KERNEL 1101 help 1102 Say Y here if you want the kernel to run a short self-test during 1103 bootup. The self-test checks whether common types of locking bugs 1104 are detected by debugging mechanisms or not. (if you disable 1105 lock debugging then those bugs wont be detected of course.) 1106 The following locking APIs are covered: spinlocks, rwlocks, 1107 mutexes and rwsems. 1108 1109config LOCK_TORTURE_TEST 1110 tristate "torture tests for locking" 1111 depends on DEBUG_KERNEL 1112 select TORTURE_TEST 1113 default n 1114 help 1115 This option provides a kernel module that runs torture tests 1116 on kernel locking primitives. The kernel module may be built 1117 after the fact on the running kernel to be tested, if desired. 1118 1119 Say Y here if you want kernel locking-primitive torture tests 1120 to be built into the kernel. 1121 Say M if you want these torture tests to build as a module. 1122 Say N if you are unsure. 1123 1124endmenu # lock debugging 1125 1126config TRACE_IRQFLAGS 1127 bool 1128 help 1129 Enables hooks to interrupt enabling and disabling for 1130 either tracing or lock debugging. 1131 1132config STACKTRACE 1133 bool "Stack backtrace support" 1134 depends on STACKTRACE_SUPPORT 1135 help 1136 This option causes the kernel to create a /proc/pid/stack for 1137 every process, showing its current stack trace. 1138 It is also used by various kernel debugging features that require 1139 stack trace generation. 1140 1141config DEBUG_KOBJECT 1142 bool "kobject debugging" 1143 depends on DEBUG_KERNEL 1144 help 1145 If you say Y here, some extra kobject debugging messages will be sent 1146 to the syslog. 1147 1148config DEBUG_KOBJECT_RELEASE 1149 bool "kobject release debugging" 1150 depends on DEBUG_OBJECTS_TIMERS 1151 help 1152 kobjects are reference counted objects. This means that their 1153 last reference count put is not predictable, and the kobject can 1154 live on past the point at which a driver decides to drop it's 1155 initial reference to the kobject gained on allocation. An 1156 example of this would be a struct device which has just been 1157 unregistered. 1158 1159 However, some buggy drivers assume that after such an operation, 1160 the memory backing the kobject can be immediately freed. This 1161 goes completely against the principles of a refcounted object. 1162 1163 If you say Y here, the kernel will delay the release of kobjects 1164 on the last reference count to improve the visibility of this 1165 kind of kobject release bug. 1166 1167config HAVE_DEBUG_BUGVERBOSE 1168 bool 1169 1170config DEBUG_BUGVERBOSE 1171 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1172 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1173 default y 1174 help 1175 Say Y here to make BUG() panics output the file name and line number 1176 of the BUG call as well as the EIP and oops trace. This aids 1177 debugging but costs about 70-100K of memory. 1178 1179config DEBUG_LIST 1180 bool "Debug linked list manipulation" 1181 depends on DEBUG_KERNEL 1182 help 1183 Enable this to turn on extended checks in the linked-list 1184 walking routines. 1185 1186 If unsure, say N. 1187 1188config DEBUG_PI_LIST 1189 bool "Debug priority linked list manipulation" 1190 depends on DEBUG_KERNEL 1191 help 1192 Enable this to turn on extended checks in the priority-ordered 1193 linked-list (plist) walking routines. This checks the entire 1194 list multiple times during each manipulation. 1195 1196 If unsure, say N. 1197 1198config DEBUG_SG 1199 bool "Debug SG table operations" 1200 depends on DEBUG_KERNEL 1201 help 1202 Enable this to turn on checks on scatter-gather tables. This can 1203 help find problems with drivers that do not properly initialize 1204 their sg tables. 1205 1206 If unsure, say N. 1207 1208config DEBUG_NOTIFIERS 1209 bool "Debug notifier call chains" 1210 depends on DEBUG_KERNEL 1211 help 1212 Enable this to turn on sanity checking for notifier call chains. 1213 This is most useful for kernel developers to make sure that 1214 modules properly unregister themselves from notifier chains. 1215 This is a relatively cheap check but if you care about maximum 1216 performance, say N. 1217 1218config DEBUG_CREDENTIALS 1219 bool "Debug credential management" 1220 depends on DEBUG_KERNEL 1221 help 1222 Enable this to turn on some debug checking for credential 1223 management. The additional code keeps track of the number of 1224 pointers from task_structs to any given cred struct, and checks to 1225 see that this number never exceeds the usage count of the cred 1226 struct. 1227 1228 Furthermore, if SELinux is enabled, this also checks that the 1229 security pointer in the cred struct is never seen to be invalid. 1230 1231 If unsure, say N. 1232 1233menu "RCU Debugging" 1234 1235config PROVE_RCU 1236 def_bool PROVE_LOCKING 1237 1238config PROVE_RCU_REPEATEDLY 1239 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1240 depends on PROVE_RCU 1241 default n 1242 help 1243 By itself, PROVE_RCU will disable checking upon issuing the 1244 first warning (or "splat"). This feature prevents such 1245 disabling, allowing multiple RCU-lockdep warnings to be printed 1246 on a single reboot. 1247 1248 Say Y to allow multiple RCU-lockdep warnings per boot. 1249 1250 Say N if you are unsure. 1251 1252config SPARSE_RCU_POINTER 1253 bool "RCU debugging: sparse-based checks for pointer usage" 1254 default n 1255 help 1256 This feature enables the __rcu sparse annotation for 1257 RCU-protected pointers. This annotation will cause sparse 1258 to flag any non-RCU used of annotated pointers. This can be 1259 helpful when debugging RCU usage. Please note that this feature 1260 is not intended to enforce code cleanliness; it is instead merely 1261 a debugging aid. 1262 1263 Say Y to make sparse flag questionable use of RCU-protected pointers 1264 1265 Say N if you are unsure. 1266 1267config TORTURE_TEST 1268 tristate 1269 default n 1270 1271config RCU_TORTURE_TEST 1272 tristate "torture tests for RCU" 1273 depends on DEBUG_KERNEL 1274 select TORTURE_TEST 1275 select SRCU 1276 select TASKS_RCU 1277 default n 1278 help 1279 This option provides a kernel module that runs torture tests 1280 on the RCU infrastructure. The kernel module may be built 1281 after the fact on the running kernel to be tested, if desired. 1282 1283 Say Y here if you want RCU torture tests to be built into 1284 the kernel. 1285 Say M if you want the RCU torture tests to build as a module. 1286 Say N if you are unsure. 1287 1288config RCU_TORTURE_TEST_RUNNABLE 1289 bool "torture tests for RCU runnable by default" 1290 depends on RCU_TORTURE_TEST = y 1291 default n 1292 help 1293 This option provides a way to build the RCU torture tests 1294 directly into the kernel without them starting up at boot 1295 time. You can use /proc/sys/kernel/rcutorture_runnable 1296 to manually override this setting. This /proc file is 1297 available only when the RCU torture tests have been built 1298 into the kernel. 1299 1300 Say Y here if you want the RCU torture tests to start during 1301 boot (you probably don't). 1302 Say N here if you want the RCU torture tests to start only 1303 after being manually enabled via /proc. 1304 1305config RCU_TORTURE_TEST_SLOW_PREINIT 1306 bool "Slow down RCU grace-period pre-initialization to expose races" 1307 depends on RCU_TORTURE_TEST 1308 help 1309 This option delays grace-period pre-initialization (the 1310 propagation of CPU-hotplug changes up the rcu_node combining 1311 tree) for a few jiffies between initializing each pair of 1312 consecutive rcu_node structures. This helps to expose races 1313 involving grace-period pre-initialization, in other words, it 1314 makes your kernel less stable. It can also greatly increase 1315 grace-period latency, especially on systems with large numbers 1316 of CPUs. This is useful when torture-testing RCU, but in 1317 almost no other circumstance. 1318 1319 Say Y here if you want your system to crash and hang more often. 1320 Say N if you want a sane system. 1321 1322config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY 1323 int "How much to slow down RCU grace-period pre-initialization" 1324 range 0 5 1325 default 3 1326 depends on RCU_TORTURE_TEST_SLOW_PREINIT 1327 help 1328 This option specifies the number of jiffies to wait between 1329 each rcu_node structure pre-initialization step. 1330 1331config RCU_TORTURE_TEST_SLOW_INIT 1332 bool "Slow down RCU grace-period initialization to expose races" 1333 depends on RCU_TORTURE_TEST 1334 help 1335 This option delays grace-period initialization for a few 1336 jiffies between initializing each pair of consecutive 1337 rcu_node structures. This helps to expose races involving 1338 grace-period initialization, in other words, it makes your 1339 kernel less stable. It can also greatly increase grace-period 1340 latency, especially on systems with large numbers of CPUs. 1341 This is useful when torture-testing RCU, but in almost no 1342 other circumstance. 1343 1344 Say Y here if you want your system to crash and hang more often. 1345 Say N if you want a sane system. 1346 1347config RCU_TORTURE_TEST_SLOW_INIT_DELAY 1348 int "How much to slow down RCU grace-period initialization" 1349 range 0 5 1350 default 3 1351 depends on RCU_TORTURE_TEST_SLOW_INIT 1352 help 1353 This option specifies the number of jiffies to wait between 1354 each rcu_node structure initialization. 1355 1356config RCU_TORTURE_TEST_SLOW_CLEANUP 1357 bool "Slow down RCU grace-period cleanup to expose races" 1358 depends on RCU_TORTURE_TEST 1359 help 1360 This option delays grace-period cleanup for a few jiffies 1361 between cleaning up each pair of consecutive rcu_node 1362 structures. This helps to expose races involving grace-period 1363 cleanup, in other words, it makes your kernel less stable. 1364 It can also greatly increase grace-period latency, especially 1365 on systems with large numbers of CPUs. This is useful when 1366 torture-testing RCU, but in almost no other circumstance. 1367 1368 Say Y here if you want your system to crash and hang more often. 1369 Say N if you want a sane system. 1370 1371config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY 1372 int "How much to slow down RCU grace-period cleanup" 1373 range 0 5 1374 default 3 1375 depends on RCU_TORTURE_TEST_SLOW_CLEANUP 1376 help 1377 This option specifies the number of jiffies to wait between 1378 each rcu_node structure cleanup operation. 1379 1380config RCU_CPU_STALL_TIMEOUT 1381 int "RCU CPU stall timeout in seconds" 1382 depends on RCU_STALL_COMMON 1383 range 3 300 1384 default 21 1385 help 1386 If a given RCU grace period extends more than the specified 1387 number of seconds, a CPU stall warning is printed. If the 1388 RCU grace period persists, additional CPU stall warnings are 1389 printed at more widely spaced intervals. 1390 1391config RCU_TRACE 1392 bool "Enable tracing for RCU" 1393 depends on DEBUG_KERNEL 1394 select TRACE_CLOCK 1395 help 1396 This option provides tracing in RCU which presents stats 1397 in debugfs for debugging RCU implementation. 1398 1399 Say Y here if you want to enable RCU tracing 1400 Say N if you are unsure. 1401 1402config RCU_EQS_DEBUG 1403 bool "Provide debugging asserts for adding NO_HZ support to an arch" 1404 depends on DEBUG_KERNEL 1405 help 1406 This option provides consistency checks in RCU's handling of 1407 NO_HZ. These checks have proven quite helpful in detecting 1408 bugs in arch-specific NO_HZ code. 1409 1410 Say N here if you need ultimate kernel/user switch latencies 1411 Say Y if you are unsure 1412 1413endmenu # "RCU Debugging" 1414 1415config DEBUG_WQ_FORCE_RR_CPU 1416 bool "Force round-robin CPU selection for unbound work items" 1417 depends on DEBUG_KERNEL 1418 default n 1419 help 1420 Workqueue used to implicitly guarantee that work items queued 1421 without explicit CPU specified are put on the local CPU. This 1422 guarantee is no longer true and while local CPU is still 1423 preferred work items may be put on foreign CPUs. Kernel 1424 parameter "workqueue.debug_force_rr_cpu" is added to force 1425 round-robin CPU selection to flush out usages which depend on the 1426 now broken guarantee. This config option enables the debug 1427 feature by default. When enabled, memory and cache locality will 1428 be impacted. 1429 1430config DEBUG_BLOCK_EXT_DEVT 1431 bool "Force extended block device numbers and spread them" 1432 depends on DEBUG_KERNEL 1433 depends on BLOCK 1434 default n 1435 help 1436 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1437 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1438 YOU ARE DOING. Distros, please enable this and fix whatever 1439 is broken. 1440 1441 Conventionally, block device numbers are allocated from 1442 predetermined contiguous area. However, extended block area 1443 may introduce non-contiguous block device numbers. This 1444 option forces most block device numbers to be allocated from 1445 the extended space and spreads them to discover kernel or 1446 userland code paths which assume predetermined contiguous 1447 device number allocation. 1448 1449 Note that turning on this debug option shuffles all the 1450 device numbers for all IDE and SCSI devices including libata 1451 ones, so root partition specified using device number 1452 directly (via rdev or root=MAJ:MIN) won't work anymore. 1453 Textual device names (root=/dev/sdXn) will continue to work. 1454 1455 Say N if you are unsure. 1456 1457config NOTIFIER_ERROR_INJECTION 1458 tristate "Notifier error injection" 1459 depends on DEBUG_KERNEL 1460 select DEBUG_FS 1461 help 1462 This option provides the ability to inject artificial errors to 1463 specified notifier chain callbacks. It is useful to test the error 1464 handling of notifier call chain failures. 1465 1466 Say N if unsure. 1467 1468config CPU_NOTIFIER_ERROR_INJECT 1469 tristate "CPU notifier error injection module" 1470 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1471 help 1472 This option provides a kernel module that can be used to test 1473 the error handling of the cpu notifiers by injecting artificial 1474 errors to CPU notifier chain callbacks. It is controlled through 1475 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1476 1477 If the notifier call chain should be failed with some events 1478 notified, write the error code to "actions/<notifier event>/error". 1479 1480 Example: Inject CPU offline error (-1 == -EPERM) 1481 1482 # cd /sys/kernel/debug/notifier-error-inject/cpu 1483 # echo -1 > actions/CPU_DOWN_PREPARE/error 1484 # echo 0 > /sys/devices/system/cpu/cpu1/online 1485 bash: echo: write error: Operation not permitted 1486 1487 To compile this code as a module, choose M here: the module will 1488 be called cpu-notifier-error-inject. 1489 1490 If unsure, say N. 1491 1492config PM_NOTIFIER_ERROR_INJECT 1493 tristate "PM notifier error injection module" 1494 depends on PM && NOTIFIER_ERROR_INJECTION 1495 default m if PM_DEBUG 1496 help 1497 This option provides the ability to inject artificial errors to 1498 PM notifier chain callbacks. It is controlled through debugfs 1499 interface /sys/kernel/debug/notifier-error-inject/pm 1500 1501 If the notifier call chain should be failed with some events 1502 notified, write the error code to "actions/<notifier event>/error". 1503 1504 Example: Inject PM suspend error (-12 = -ENOMEM) 1505 1506 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1507 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1508 # echo mem > /sys/power/state 1509 bash: echo: write error: Cannot allocate memory 1510 1511 To compile this code as a module, choose M here: the module will 1512 be called pm-notifier-error-inject. 1513 1514 If unsure, say N. 1515 1516config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1517 tristate "OF reconfig notifier error injection module" 1518 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1519 help 1520 This option provides the ability to inject artificial errors to 1521 OF reconfig notifier chain callbacks. It is controlled 1522 through debugfs interface under 1523 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1524 1525 If the notifier call chain should be failed with some events 1526 notified, write the error code to "actions/<notifier event>/error". 1527 1528 To compile this code as a module, choose M here: the module will 1529 be called of-reconfig-notifier-error-inject. 1530 1531 If unsure, say N. 1532 1533config NETDEV_NOTIFIER_ERROR_INJECT 1534 tristate "Netdev notifier error injection module" 1535 depends on NET && NOTIFIER_ERROR_INJECTION 1536 help 1537 This option provides the ability to inject artificial errors to 1538 netdevice notifier chain callbacks. It is controlled through debugfs 1539 interface /sys/kernel/debug/notifier-error-inject/netdev 1540 1541 If the notifier call chain should be failed with some events 1542 notified, write the error code to "actions/<notifier event>/error". 1543 1544 Example: Inject netdevice mtu change error (-22 = -EINVAL) 1545 1546 # cd /sys/kernel/debug/notifier-error-inject/netdev 1547 # echo -22 > actions/NETDEV_CHANGEMTU/error 1548 # ip link set eth0 mtu 1024 1549 RTNETLINK answers: Invalid argument 1550 1551 To compile this code as a module, choose M here: the module will 1552 be called netdev-notifier-error-inject. 1553 1554 If unsure, say N. 1555 1556config FAULT_INJECTION 1557 bool "Fault-injection framework" 1558 depends on DEBUG_KERNEL 1559 help 1560 Provide fault-injection framework. 1561 For more details, see Documentation/fault-injection/. 1562 1563config FAILSLAB 1564 bool "Fault-injection capability for kmalloc" 1565 depends on FAULT_INJECTION 1566 depends on SLAB || SLUB 1567 help 1568 Provide fault-injection capability for kmalloc. 1569 1570config FAIL_PAGE_ALLOC 1571 bool "Fault-injection capabilitiy for alloc_pages()" 1572 depends on FAULT_INJECTION 1573 help 1574 Provide fault-injection capability for alloc_pages(). 1575 1576config FAIL_MAKE_REQUEST 1577 bool "Fault-injection capability for disk IO" 1578 depends on FAULT_INJECTION && BLOCK 1579 help 1580 Provide fault-injection capability for disk IO. 1581 1582config FAIL_IO_TIMEOUT 1583 bool "Fault-injection capability for faking disk interrupts" 1584 depends on FAULT_INJECTION && BLOCK 1585 help 1586 Provide fault-injection capability on end IO handling. This 1587 will make the block layer "forget" an interrupt as configured, 1588 thus exercising the error handling. 1589 1590 Only works with drivers that use the generic timeout handling, 1591 for others it wont do anything. 1592 1593config FAIL_MMC_REQUEST 1594 bool "Fault-injection capability for MMC IO" 1595 depends on FAULT_INJECTION_DEBUG_FS && MMC 1596 help 1597 Provide fault-injection capability for MMC IO. 1598 This will make the mmc core return data errors. This is 1599 useful to test the error handling in the mmc block device 1600 and to test how the mmc host driver handles retries from 1601 the block device. 1602 1603config FAIL_FUTEX 1604 bool "Fault-injection capability for futexes" 1605 select DEBUG_FS 1606 depends on FAULT_INJECTION && FUTEX 1607 help 1608 Provide fault-injection capability for futexes. 1609 1610config FAULT_INJECTION_DEBUG_FS 1611 bool "Debugfs entries for fault-injection capabilities" 1612 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1613 help 1614 Enable configuration of fault-injection capabilities via debugfs. 1615 1616config FAULT_INJECTION_STACKTRACE_FILTER 1617 bool "stacktrace filter for fault-injection capabilities" 1618 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1619 depends on !X86_64 1620 select STACKTRACE 1621 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1622 help 1623 Provide stacktrace filter for fault-injection capabilities 1624 1625config LATENCYTOP 1626 bool "Latency measuring infrastructure" 1627 depends on DEBUG_KERNEL 1628 depends on STACKTRACE_SUPPORT 1629 depends on PROC_FS 1630 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1631 select KALLSYMS 1632 select KALLSYMS_ALL 1633 select STACKTRACE 1634 select SCHEDSTATS 1635 select SCHED_DEBUG 1636 help 1637 Enable this option if you want to use the LatencyTOP tool 1638 to find out which userspace is blocking on what kernel operations. 1639 1640config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1641 bool 1642 1643config DEBUG_STRICT_USER_COPY_CHECKS 1644 bool "Strict user copy size checks" 1645 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1646 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING 1647 help 1648 Enabling this option turns a certain set of sanity checks for user 1649 copy operations into compile time failures. 1650 1651 The copy_from_user() etc checks are there to help test if there 1652 are sufficient security checks on the length argument of 1653 the copy operation, by having gcc prove that the argument is 1654 within bounds. 1655 1656 If unsure, say N. 1657 1658source kernel/trace/Kconfig 1659 1660menu "Runtime Testing" 1661 1662config LKDTM 1663 tristate "Linux Kernel Dump Test Tool Module" 1664 depends on DEBUG_FS 1665 depends on BLOCK 1666 default n 1667 help 1668 This module enables testing of the different dumping mechanisms by 1669 inducing system failures at predefined crash points. 1670 If you don't need it: say N 1671 Choose M here to compile this code as a module. The module will be 1672 called lkdtm. 1673 1674 Documentation on how to use the module can be found in 1675 Documentation/fault-injection/provoke-crashes.txt 1676 1677config TEST_LIST_SORT 1678 bool "Linked list sorting test" 1679 depends on DEBUG_KERNEL 1680 help 1681 Enable this to turn on 'list_sort()' function test. This test is 1682 executed only once during system boot, so affects only boot time. 1683 1684 If unsure, say N. 1685 1686config KPROBES_SANITY_TEST 1687 bool "Kprobes sanity tests" 1688 depends on DEBUG_KERNEL 1689 depends on KPROBES 1690 default n 1691 help 1692 This option provides for testing basic kprobes functionality on 1693 boot. A sample kprobe, jprobe and kretprobe are inserted and 1694 verified for functionality. 1695 1696 Say N if you are unsure. 1697 1698config BACKTRACE_SELF_TEST 1699 tristate "Self test for the backtrace code" 1700 depends on DEBUG_KERNEL 1701 default n 1702 help 1703 This option provides a kernel module that can be used to test 1704 the kernel stack backtrace code. This option is not useful 1705 for distributions or general kernels, but only for kernel 1706 developers working on architecture code. 1707 1708 Note that if you want to also test saved backtraces, you will 1709 have to enable STACKTRACE as well. 1710 1711 Say N if you are unsure. 1712 1713config RBTREE_TEST 1714 tristate "Red-Black tree test" 1715 depends on DEBUG_KERNEL 1716 help 1717 A benchmark measuring the performance of the rbtree library. 1718 Also includes rbtree invariant checks. 1719 1720config INTERVAL_TREE_TEST 1721 tristate "Interval tree test" 1722 depends on m && DEBUG_KERNEL 1723 select INTERVAL_TREE 1724 help 1725 A benchmark measuring the performance of the interval tree library 1726 1727config PERCPU_TEST 1728 tristate "Per cpu operations test" 1729 depends on m && DEBUG_KERNEL 1730 help 1731 Enable this option to build test module which validates per-cpu 1732 operations. 1733 1734 If unsure, say N. 1735 1736config ATOMIC64_SELFTEST 1737 bool "Perform an atomic64_t self-test at boot" 1738 help 1739 Enable this option to test the atomic64_t functions at boot. 1740 1741 If unsure, say N. 1742 1743config ASYNC_RAID6_TEST 1744 tristate "Self test for hardware accelerated raid6 recovery" 1745 depends on ASYNC_RAID6_RECOV 1746 select ASYNC_MEMCPY 1747 ---help--- 1748 This is a one-shot self test that permutes through the 1749 recovery of all the possible two disk failure scenarios for a 1750 N-disk array. Recovery is performed with the asynchronous 1751 raid6 recovery routines, and will optionally use an offload 1752 engine if one is available. 1753 1754 If unsure, say N. 1755 1756config TEST_HEXDUMP 1757 tristate "Test functions located in the hexdump module at runtime" 1758 1759config TEST_STRING_HELPERS 1760 tristate "Test functions located in the string_helpers module at runtime" 1761 1762config TEST_KSTRTOX 1763 tristate "Test kstrto*() family of functions at runtime" 1764 1765config TEST_PRINTF 1766 tristate "Test printf() family of functions at runtime" 1767 1768config TEST_RHASHTABLE 1769 tristate "Perform selftest on resizable hash table" 1770 default n 1771 help 1772 Enable this option to test the rhashtable functions at boot. 1773 1774 If unsure, say N. 1775 1776endmenu # runtime tests 1777 1778config PROVIDE_OHCI1394_DMA_INIT 1779 bool "Remote debugging over FireWire early on boot" 1780 depends on PCI && X86 1781 help 1782 If you want to debug problems which hang or crash the kernel early 1783 on boot and the crashing machine has a FireWire port, you can use 1784 this feature to remotely access the memory of the crashed machine 1785 over FireWire. This employs remote DMA as part of the OHCI1394 1786 specification which is now the standard for FireWire controllers. 1787 1788 With remote DMA, you can monitor the printk buffer remotely using 1789 firescope and access all memory below 4GB using fireproxy from gdb. 1790 Even controlling a kernel debugger is possible using remote DMA. 1791 1792 Usage: 1793 1794 If ohci1394_dma=early is used as boot parameter, it will initialize 1795 all OHCI1394 controllers which are found in the PCI config space. 1796 1797 As all changes to the FireWire bus such as enabling and disabling 1798 devices cause a bus reset and thereby disable remote DMA for all 1799 devices, be sure to have the cable plugged and FireWire enabled on 1800 the debugging host before booting the debug target for debugging. 1801 1802 This code (~1k) is freed after boot. By then, the firewire stack 1803 in charge of the OHCI-1394 controllers should be used instead. 1804 1805 See Documentation/debugging-via-ohci1394.txt for more information. 1806 1807config BUILD_DOCSRC 1808 bool "Build targets in Documentation/ tree" 1809 depends on HEADERS_CHECK 1810 help 1811 This option attempts to build objects from the source files in the 1812 kernel Documentation/ tree. 1813 1814 Say N if you are unsure. 1815 1816config DMA_API_DEBUG 1817 bool "Enable debugging of DMA-API usage" 1818 depends on HAVE_DMA_API_DEBUG 1819 help 1820 Enable this option to debug the use of the DMA API by device drivers. 1821 With this option you will be able to detect common bugs in device 1822 drivers like double-freeing of DMA mappings or freeing mappings that 1823 were never allocated. 1824 1825 This also attempts to catch cases where a page owned by DMA is 1826 accessed by the cpu in a way that could cause data corruption. For 1827 example, this enables cow_user_page() to check that the source page is 1828 not undergoing DMA. 1829 1830 This option causes a performance degradation. Use only if you want to 1831 debug device drivers and dma interactions. 1832 1833 If unsure, say N. 1834 1835config TEST_LKM 1836 tristate "Test module loading with 'hello world' module" 1837 default n 1838 depends on m 1839 help 1840 This builds the "test_module" module that emits "Hello, world" 1841 on printk when loaded. It is designed to be used for basic 1842 evaluation of the module loading subsystem (for example when 1843 validating module verification). It lacks any extra dependencies, 1844 and will not normally be loaded by the system unless explicitly 1845 requested by name. 1846 1847 If unsure, say N. 1848 1849config TEST_USER_COPY 1850 tristate "Test user/kernel boundary protections" 1851 default n 1852 depends on m 1853 help 1854 This builds the "test_user_copy" module that runs sanity checks 1855 on the copy_to/from_user infrastructure, making sure basic 1856 user/kernel boundary testing is working. If it fails to load, 1857 a regression has been detected in the user/kernel memory boundary 1858 protections. 1859 1860 If unsure, say N. 1861 1862config TEST_BPF 1863 tristate "Test BPF filter functionality" 1864 default n 1865 depends on m && NET 1866 help 1867 This builds the "test_bpf" module that runs various test vectors 1868 against the BPF interpreter or BPF JIT compiler depending on the 1869 current setting. This is in particular useful for BPF JIT compiler 1870 development, but also to run regression tests against changes in 1871 the interpreter code. It also enables test stubs for eBPF maps and 1872 verifier used by user space verifier testsuite. 1873 1874 If unsure, say N. 1875 1876config TEST_FIRMWARE 1877 tristate "Test firmware loading via userspace interface" 1878 default n 1879 depends on FW_LOADER 1880 help 1881 This builds the "test_firmware" module that creates a userspace 1882 interface for testing firmware loading. This can be used to 1883 control the triggering of firmware loading without needing an 1884 actual firmware-using device. The contents can be rechecked by 1885 userspace. 1886 1887 If unsure, say N. 1888 1889config TEST_UDELAY 1890 tristate "udelay test driver" 1891 default n 1892 help 1893 This builds the "udelay_test" module that helps to make sure 1894 that udelay() is working properly. 1895 1896 If unsure, say N. 1897 1898config MEMTEST 1899 bool "Memtest" 1900 depends on HAVE_MEMBLOCK 1901 ---help--- 1902 This option adds a kernel parameter 'memtest', which allows memtest 1903 to be set. 1904 memtest=0, mean disabled; -- default 1905 memtest=1, mean do 1 test pattern; 1906 ... 1907 memtest=17, mean do 17 test patterns. 1908 If you are unsure how to answer this question, answer N. 1909 1910config TEST_STATIC_KEYS 1911 tristate "Test static keys" 1912 default n 1913 depends on m 1914 help 1915 Test the static key interfaces. 1916 1917 If unsure, say N. 1918 1919source "samples/Kconfig" 1920 1921source "lib/Kconfig.kgdb" 1922 1923source "lib/Kconfig.ubsan" 1924 1925config ARCH_HAS_DEVMEM_IS_ALLOWED 1926 bool 1927 1928config STRICT_DEVMEM 1929 bool "Filter access to /dev/mem" 1930 depends on MMU 1931 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 1932 default y if TILE || PPC 1933 ---help--- 1934 If this option is disabled, you allow userspace (root) access to all 1935 of memory, including kernel and userspace memory. Accidental 1936 access to this is obviously disastrous, but specific access can 1937 be used by people debugging the kernel. Note that with PAT support 1938 enabled, even in this case there are restrictions on /dev/mem 1939 use due to the cache aliasing requirements. 1940 1941 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 1942 file only allows userspace access to PCI space and the BIOS code and 1943 data regions. This is sufficient for dosemu and X and all common 1944 users of /dev/mem. 1945 1946 If in doubt, say Y. 1947 1948config IO_STRICT_DEVMEM 1949 bool "Filter I/O access to /dev/mem" 1950 depends on STRICT_DEVMEM 1951 ---help--- 1952 If this option is disabled, you allow userspace (root) access to all 1953 io-memory regardless of whether a driver is actively using that 1954 range. Accidental access to this is obviously disastrous, but 1955 specific access can be used by people debugging kernel drivers. 1956 1957 If this option is switched on, the /dev/mem file only allows 1958 userspace access to *idle* io-memory ranges (see /proc/iomem) This 1959 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 1960 if the driver using a given range cannot be disabled. 1961 1962 If in doubt, say Y. 1963