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 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 400 525 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 DEBUG_SHIRQ 680 bool "Debug shared IRQ handlers" 681 depends on DEBUG_KERNEL 682 help 683 Enable this to generate a spurious interrupt as soon as a shared 684 interrupt handler is registered, and just before one is deregistered. 685 Drivers ought to be able to handle interrupts coming in at those 686 points; some don't and need to be caught. 687 688menu "Debug Lockups and Hangs" 689 690config LOCKUP_DETECTOR 691 bool "Detect Hard and Soft Lockups" 692 depends on DEBUG_KERNEL && !S390 693 help 694 Say Y here to enable the kernel to act as a watchdog to detect 695 hard and soft lockups. 696 697 Softlockups are bugs that cause the kernel to loop in kernel 698 mode for more than 20 seconds, without giving other tasks a 699 chance to run. The current stack trace is displayed upon 700 detection and the system will stay locked up. 701 702 Hardlockups are bugs that cause the CPU to loop in kernel mode 703 for more than 10 seconds, without letting other interrupts have a 704 chance to run. The current stack trace is displayed upon detection 705 and the system will stay locked up. 706 707 The overhead should be minimal. A periodic hrtimer runs to 708 generate interrupts and kick the watchdog task every 4 seconds. 709 An NMI is generated every 10 seconds or so to check for hardlockups. 710 711 The frequency of hrtimer and NMI events and the soft and hard lockup 712 thresholds can be controlled through the sysctl watchdog_thresh. 713 714config HARDLOCKUP_DETECTOR 715 def_bool y 716 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 717 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 718 719config BOOTPARAM_HARDLOCKUP_PANIC 720 bool "Panic (Reboot) On Hard Lockups" 721 depends on HARDLOCKUP_DETECTOR 722 help 723 Say Y here to enable the kernel to panic on "hard lockups", 724 which are bugs that cause the kernel to loop in kernel 725 mode with interrupts disabled for more than 10 seconds (configurable 726 using the watchdog_thresh sysctl). 727 728 Say N if unsure. 729 730config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 731 int 732 depends on HARDLOCKUP_DETECTOR 733 range 0 1 734 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 735 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 736 737config BOOTPARAM_SOFTLOCKUP_PANIC 738 bool "Panic (Reboot) On Soft Lockups" 739 depends on LOCKUP_DETECTOR 740 help 741 Say Y here to enable the kernel to panic on "soft lockups", 742 which are bugs that cause the kernel to loop in kernel 743 mode for more than 20 seconds (configurable using the watchdog_thresh 744 sysctl), without giving other tasks a chance to run. 745 746 The panic can be used in combination with panic_timeout, 747 to cause the system to reboot automatically after a 748 lockup has been detected. This feature is useful for 749 high-availability systems that have uptime guarantees and 750 where a lockup must be resolved ASAP. 751 752 Say N if unsure. 753 754config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 755 int 756 depends on LOCKUP_DETECTOR 757 range 0 1 758 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 759 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 760 761config DETECT_HUNG_TASK 762 bool "Detect Hung Tasks" 763 depends on DEBUG_KERNEL 764 default LOCKUP_DETECTOR 765 help 766 Say Y here to enable the kernel to detect "hung tasks", 767 which are bugs that cause the task to be stuck in 768 uninterruptible "D" state indefinitiley. 769 770 When a hung task is detected, the kernel will print the 771 current stack trace (which you should report), but the 772 task will stay in uninterruptible state. If lockdep is 773 enabled then all held locks will also be reported. This 774 feature has negligible overhead. 775 776config DEFAULT_HUNG_TASK_TIMEOUT 777 int "Default timeout for hung task detection (in seconds)" 778 depends on DETECT_HUNG_TASK 779 default 120 780 help 781 This option controls the default timeout (in seconds) used 782 to determine when a task has become non-responsive and should 783 be considered hung. 784 785 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 786 sysctl or by writing a value to 787 /proc/sys/kernel/hung_task_timeout_secs. 788 789 A timeout of 0 disables the check. The default is two minutes. 790 Keeping the default should be fine in most cases. 791 792config BOOTPARAM_HUNG_TASK_PANIC 793 bool "Panic (Reboot) On Hung Tasks" 794 depends on DETECT_HUNG_TASK 795 help 796 Say Y here to enable the kernel to panic on "hung tasks", 797 which are bugs that cause the kernel to leave a task stuck 798 in uninterruptible "D" state. 799 800 The panic can be used in combination with panic_timeout, 801 to cause the system to reboot automatically after a 802 hung task has been detected. This feature is useful for 803 high-availability systems that have uptime guarantees and 804 where a hung tasks must be resolved ASAP. 805 806 Say N if unsure. 807 808config BOOTPARAM_HUNG_TASK_PANIC_VALUE 809 int 810 depends on DETECT_HUNG_TASK 811 range 0 1 812 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 813 default 1 if BOOTPARAM_HUNG_TASK_PANIC 814 815endmenu # "Debug lockups and hangs" 816 817config PANIC_ON_OOPS 818 bool "Panic on Oops" 819 help 820 Say Y here to enable the kernel to panic when it oopses. This 821 has the same effect as setting oops=panic on the kernel command 822 line. 823 824 This feature is useful to ensure that the kernel does not do 825 anything erroneous after an oops which could result in data 826 corruption or other issues. 827 828 Say N if unsure. 829 830config PANIC_ON_OOPS_VALUE 831 int 832 range 0 1 833 default 0 if !PANIC_ON_OOPS 834 default 1 if PANIC_ON_OOPS 835 836config PANIC_TIMEOUT 837 int "panic timeout" 838 default 0 839 help 840 Set the timeout value (in seconds) until a reboot occurs when the 841 the kernel panics. If n = 0, then we wait forever. A timeout 842 value n > 0 will wait n seconds before rebooting, while a timeout 843 value n < 0 will reboot immediately. 844 845config SCHED_DEBUG 846 bool "Collect scheduler debugging info" 847 depends on DEBUG_KERNEL && PROC_FS 848 default y 849 help 850 If you say Y here, the /proc/sched_debug file will be provided 851 that can help debug the scheduler. The runtime overhead of this 852 option is minimal. 853 854config SCHED_INFO 855 bool 856 default n 857 858config SCHEDSTATS 859 bool "Collect scheduler statistics" 860 depends on DEBUG_KERNEL && PROC_FS 861 select SCHED_INFO 862 help 863 If you say Y here, additional code will be inserted into the 864 scheduler and related routines to collect statistics about 865 scheduler behavior and provide them in /proc/schedstat. These 866 stats may be useful for both tuning and debugging the scheduler 867 If you aren't debugging the scheduler or trying to tune a specific 868 application, you can say N to avoid the very slight overhead 869 this adds. 870 871config SCHED_STACK_END_CHECK 872 bool "Detect stack corruption on calls to schedule()" 873 depends on DEBUG_KERNEL 874 default n 875 help 876 This option checks for a stack overrun on calls to schedule(). 877 If the stack end location is found to be over written always panic as 878 the content of the corrupted region can no longer be trusted. 879 This is to ensure no erroneous behaviour occurs which could result in 880 data corruption or a sporadic crash at a later stage once the region 881 is examined. The runtime overhead introduced is minimal. 882 883config DEBUG_TIMEKEEPING 884 bool "Enable extra timekeeping sanity checking" 885 help 886 This option will enable additional timekeeping sanity checks 887 which may be helpful when diagnosing issues where timekeeping 888 problems are suspected. 889 890 This may include checks in the timekeeping hotpaths, so this 891 option may have a (very small) performance impact to some 892 workloads. 893 894 If unsure, say N. 895 896config TIMER_STATS 897 bool "Collect kernel timers statistics" 898 depends on DEBUG_KERNEL && PROC_FS 899 help 900 If you say Y here, additional code will be inserted into the 901 timer routines to collect statistics about kernel timers being 902 reprogrammed. The statistics can be read from /proc/timer_stats. 903 The statistics collection is started by writing 1 to /proc/timer_stats, 904 writing 0 stops it. This feature is useful to collect information 905 about timer usage patterns in kernel and userspace. This feature 906 is lightweight if enabled in the kernel config but not activated 907 (it defaults to deactivated on bootup and will only be activated 908 if some application like powertop activates it explicitly). 909 910config DEBUG_PREEMPT 911 bool "Debug preemptible kernel" 912 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 913 default y 914 help 915 If you say Y here then the kernel will use a debug variant of the 916 commonly used smp_processor_id() function and will print warnings 917 if kernel code uses it in a preemption-unsafe way. Also, the kernel 918 will detect preemption count underflows. 919 920menu "Lock Debugging (spinlocks, mutexes, etc...)" 921 922config DEBUG_RT_MUTEXES 923 bool "RT Mutex debugging, deadlock detection" 924 depends on DEBUG_KERNEL && RT_MUTEXES 925 help 926 This allows rt mutex semantics violations and rt mutex related 927 deadlocks (lockups) to be detected and reported automatically. 928 929config DEBUG_SPINLOCK 930 bool "Spinlock and rw-lock debugging: basic checks" 931 depends on DEBUG_KERNEL 932 select UNINLINE_SPIN_UNLOCK 933 help 934 Say Y here and build SMP to catch missing spinlock initialization 935 and certain other kinds of spinlock errors commonly made. This is 936 best used in conjunction with the NMI watchdog so that spinlock 937 deadlocks are also debuggable. 938 939config DEBUG_MUTEXES 940 bool "Mutex debugging: basic checks" 941 depends on DEBUG_KERNEL 942 help 943 This feature allows mutex semantics violations to be detected and 944 reported. 945 946config DEBUG_WW_MUTEX_SLOWPATH 947 bool "Wait/wound mutex debugging: Slowpath testing" 948 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 949 select DEBUG_LOCK_ALLOC 950 select DEBUG_SPINLOCK 951 select DEBUG_MUTEXES 952 help 953 This feature enables slowpath testing for w/w mutex users by 954 injecting additional -EDEADLK wound/backoff cases. Together with 955 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 956 will test all possible w/w mutex interface abuse with the 957 exception of simply not acquiring all the required locks. 958 Note that this feature can introduce significant overhead, so 959 it really should not be enabled in a production or distro kernel, 960 even a debug kernel. If you are a driver writer, enable it. If 961 you are a distro, do not. 962 963config DEBUG_LOCK_ALLOC 964 bool "Lock debugging: detect incorrect freeing of live locks" 965 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 966 select DEBUG_SPINLOCK 967 select DEBUG_MUTEXES 968 select LOCKDEP 969 help 970 This feature will check whether any held lock (spinlock, rwlock, 971 mutex or rwsem) is incorrectly freed by the kernel, via any of the 972 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 973 vfree(), etc.), whether a live lock is incorrectly reinitialized via 974 spin_lock_init()/mutex_init()/etc., or whether there is any lock 975 held during task exit. 976 977config PROVE_LOCKING 978 bool "Lock debugging: prove locking correctness" 979 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 980 select LOCKDEP 981 select DEBUG_SPINLOCK 982 select DEBUG_MUTEXES 983 select DEBUG_LOCK_ALLOC 984 select TRACE_IRQFLAGS 985 default n 986 help 987 This feature enables the kernel to prove that all locking 988 that occurs in the kernel runtime is mathematically 989 correct: that under no circumstance could an arbitrary (and 990 not yet triggered) combination of observed locking 991 sequences (on an arbitrary number of CPUs, running an 992 arbitrary number of tasks and interrupt contexts) cause a 993 deadlock. 994 995 In short, this feature enables the kernel to report locking 996 related deadlocks before they actually occur. 997 998 The proof does not depend on how hard and complex a 999 deadlock scenario would be to trigger: how many 1000 participant CPUs, tasks and irq-contexts would be needed 1001 for it to trigger. The proof also does not depend on 1002 timing: if a race and a resulting deadlock is possible 1003 theoretically (no matter how unlikely the race scenario 1004 is), it will be proven so and will immediately be 1005 reported by the kernel (once the event is observed that 1006 makes the deadlock theoretically possible). 1007 1008 If a deadlock is impossible (i.e. the locking rules, as 1009 observed by the kernel, are mathematically correct), the 1010 kernel reports nothing. 1011 1012 NOTE: this feature can also be enabled for rwlocks, mutexes 1013 and rwsems - in which case all dependencies between these 1014 different locking variants are observed and mapped too, and 1015 the proof of observed correctness is also maintained for an 1016 arbitrary combination of these separate locking variants. 1017 1018 For more details, see Documentation/locking/lockdep-design.txt. 1019 1020config LOCKDEP 1021 bool 1022 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1023 select STACKTRACE 1024 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE 1025 select KALLSYMS 1026 select KALLSYMS_ALL 1027 1028config LOCK_STAT 1029 bool "Lock usage statistics" 1030 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1031 select LOCKDEP 1032 select DEBUG_SPINLOCK 1033 select DEBUG_MUTEXES 1034 select DEBUG_LOCK_ALLOC 1035 default n 1036 help 1037 This feature enables tracking lock contention points 1038 1039 For more details, see Documentation/locking/lockstat.txt 1040 1041 This also enables lock events required by "perf lock", 1042 subcommand of perf. 1043 If you want to use "perf lock", you also need to turn on 1044 CONFIG_EVENT_TRACING. 1045 1046 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1047 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1048 1049config DEBUG_LOCKDEP 1050 bool "Lock dependency engine debugging" 1051 depends on DEBUG_KERNEL && LOCKDEP 1052 help 1053 If you say Y here, the lock dependency engine will do 1054 additional runtime checks to debug itself, at the price 1055 of more runtime overhead. 1056 1057config DEBUG_ATOMIC_SLEEP 1058 bool "Sleep inside atomic section checking" 1059 select PREEMPT_COUNT 1060 depends on DEBUG_KERNEL 1061 help 1062 If you say Y here, various routines which may sleep will become very 1063 noisy if they are called inside atomic sections: when a spinlock is 1064 held, inside an rcu read side critical section, inside preempt disabled 1065 sections, inside an interrupt, etc... 1066 1067config DEBUG_LOCKING_API_SELFTESTS 1068 bool "Locking API boot-time self-tests" 1069 depends on DEBUG_KERNEL 1070 help 1071 Say Y here if you want the kernel to run a short self-test during 1072 bootup. The self-test checks whether common types of locking bugs 1073 are detected by debugging mechanisms or not. (if you disable 1074 lock debugging then those bugs wont be detected of course.) 1075 The following locking APIs are covered: spinlocks, rwlocks, 1076 mutexes and rwsems. 1077 1078config LOCK_TORTURE_TEST 1079 tristate "torture tests for locking" 1080 depends on DEBUG_KERNEL 1081 select TORTURE_TEST 1082 default n 1083 help 1084 This option provides a kernel module that runs torture tests 1085 on kernel locking primitives. The kernel module may be built 1086 after the fact on the running kernel to be tested, if desired. 1087 1088 Say Y here if you want kernel locking-primitive torture tests 1089 to be built into the kernel. 1090 Say M if you want these torture tests to build as a module. 1091 Say N if you are unsure. 1092 1093endmenu # lock debugging 1094 1095config TRACE_IRQFLAGS 1096 bool 1097 help 1098 Enables hooks to interrupt enabling and disabling for 1099 either tracing or lock debugging. 1100 1101config STACKTRACE 1102 bool "Stack backtrace support" 1103 depends on STACKTRACE_SUPPORT 1104 help 1105 This option causes the kernel to create a /proc/pid/stack for 1106 every process, showing its current stack trace. 1107 It is also used by various kernel debugging features that require 1108 stack trace generation. 1109 1110config DEBUG_KOBJECT 1111 bool "kobject debugging" 1112 depends on DEBUG_KERNEL 1113 help 1114 If you say Y here, some extra kobject debugging messages will be sent 1115 to the syslog. 1116 1117config DEBUG_KOBJECT_RELEASE 1118 bool "kobject release debugging" 1119 depends on DEBUG_OBJECTS_TIMERS 1120 help 1121 kobjects are reference counted objects. This means that their 1122 last reference count put is not predictable, and the kobject can 1123 live on past the point at which a driver decides to drop it's 1124 initial reference to the kobject gained on allocation. An 1125 example of this would be a struct device which has just been 1126 unregistered. 1127 1128 However, some buggy drivers assume that after such an operation, 1129 the memory backing the kobject can be immediately freed. This 1130 goes completely against the principles of a refcounted object. 1131 1132 If you say Y here, the kernel will delay the release of kobjects 1133 on the last reference count to improve the visibility of this 1134 kind of kobject release bug. 1135 1136config HAVE_DEBUG_BUGVERBOSE 1137 bool 1138 1139config DEBUG_BUGVERBOSE 1140 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1141 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1142 default y 1143 help 1144 Say Y here to make BUG() panics output the file name and line number 1145 of the BUG call as well as the EIP and oops trace. This aids 1146 debugging but costs about 70-100K of memory. 1147 1148config DEBUG_LIST 1149 bool "Debug linked list manipulation" 1150 depends on DEBUG_KERNEL 1151 help 1152 Enable this to turn on extended checks in the linked-list 1153 walking routines. 1154 1155 If unsure, say N. 1156 1157config DEBUG_PI_LIST 1158 bool "Debug priority linked list manipulation" 1159 depends on DEBUG_KERNEL 1160 help 1161 Enable this to turn on extended checks in the priority-ordered 1162 linked-list (plist) walking routines. This checks the entire 1163 list multiple times during each manipulation. 1164 1165 If unsure, say N. 1166 1167config DEBUG_SG 1168 bool "Debug SG table operations" 1169 depends on DEBUG_KERNEL 1170 help 1171 Enable this to turn on checks on scatter-gather tables. This can 1172 help find problems with drivers that do not properly initialize 1173 their sg tables. 1174 1175 If unsure, say N. 1176 1177config DEBUG_NOTIFIERS 1178 bool "Debug notifier call chains" 1179 depends on DEBUG_KERNEL 1180 help 1181 Enable this to turn on sanity checking for notifier call chains. 1182 This is most useful for kernel developers to make sure that 1183 modules properly unregister themselves from notifier chains. 1184 This is a relatively cheap check but if you care about maximum 1185 performance, say N. 1186 1187config DEBUG_CREDENTIALS 1188 bool "Debug credential management" 1189 depends on DEBUG_KERNEL 1190 help 1191 Enable this to turn on some debug checking for credential 1192 management. The additional code keeps track of the number of 1193 pointers from task_structs to any given cred struct, and checks to 1194 see that this number never exceeds the usage count of the cred 1195 struct. 1196 1197 Furthermore, if SELinux is enabled, this also checks that the 1198 security pointer in the cred struct is never seen to be invalid. 1199 1200 If unsure, say N. 1201 1202menu "RCU Debugging" 1203 1204config PROVE_RCU 1205 def_bool PROVE_LOCKING 1206 1207config PROVE_RCU_REPEATEDLY 1208 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1209 depends on PROVE_RCU 1210 default n 1211 help 1212 By itself, PROVE_RCU will disable checking upon issuing the 1213 first warning (or "splat"). This feature prevents such 1214 disabling, allowing multiple RCU-lockdep warnings to be printed 1215 on a single reboot. 1216 1217 Say Y to allow multiple RCU-lockdep warnings per boot. 1218 1219 Say N if you are unsure. 1220 1221config SPARSE_RCU_POINTER 1222 bool "RCU debugging: sparse-based checks for pointer usage" 1223 default n 1224 help 1225 This feature enables the __rcu sparse annotation for 1226 RCU-protected pointers. This annotation will cause sparse 1227 to flag any non-RCU used of annotated pointers. This can be 1228 helpful when debugging RCU usage. Please note that this feature 1229 is not intended to enforce code cleanliness; it is instead merely 1230 a debugging aid. 1231 1232 Say Y to make sparse flag questionable use of RCU-protected pointers 1233 1234 Say N if you are unsure. 1235 1236config TORTURE_TEST 1237 tristate 1238 default n 1239 1240config RCU_TORTURE_TEST 1241 tristate "torture tests for RCU" 1242 depends on DEBUG_KERNEL 1243 select TORTURE_TEST 1244 select SRCU 1245 select TASKS_RCU 1246 default n 1247 help 1248 This option provides a kernel module that runs torture tests 1249 on the RCU infrastructure. The kernel module may be built 1250 after the fact on the running kernel to be tested, if desired. 1251 1252 Say Y here if you want RCU torture tests to be built into 1253 the kernel. 1254 Say M if you want the RCU torture tests to build as a module. 1255 Say N if you are unsure. 1256 1257config RCU_TORTURE_TEST_RUNNABLE 1258 bool "torture tests for RCU runnable by default" 1259 depends on RCU_TORTURE_TEST = y 1260 default n 1261 help 1262 This option provides a way to build the RCU torture tests 1263 directly into the kernel without them starting up at boot 1264 time. You can use /proc/sys/kernel/rcutorture_runnable 1265 to manually override this setting. This /proc file is 1266 available only when the RCU torture tests have been built 1267 into the kernel. 1268 1269 Say Y here if you want the RCU torture tests to start during 1270 boot (you probably don't). 1271 Say N here if you want the RCU torture tests to start only 1272 after being manually enabled via /proc. 1273 1274config RCU_TORTURE_TEST_SLOW_PREINIT 1275 bool "Slow down RCU grace-period pre-initialization to expose races" 1276 depends on RCU_TORTURE_TEST 1277 help 1278 This option delays grace-period pre-initialization (the 1279 propagation of CPU-hotplug changes up the rcu_node combining 1280 tree) for a few jiffies between initializing each pair of 1281 consecutive rcu_node structures. This helps to expose races 1282 involving grace-period pre-initialization, in other words, it 1283 makes your kernel less stable. It can also greatly increase 1284 grace-period latency, especially on systems with large numbers 1285 of CPUs. This is useful when torture-testing RCU, but in 1286 almost no other circumstance. 1287 1288 Say Y here if you want your system to crash and hang more often. 1289 Say N if you want a sane system. 1290 1291config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY 1292 int "How much to slow down RCU grace-period pre-initialization" 1293 range 0 5 1294 default 3 1295 depends on RCU_TORTURE_TEST_SLOW_PREINIT 1296 help 1297 This option specifies the number of jiffies to wait between 1298 each rcu_node structure pre-initialization step. 1299 1300config RCU_TORTURE_TEST_SLOW_INIT 1301 bool "Slow down RCU grace-period initialization to expose races" 1302 depends on RCU_TORTURE_TEST 1303 help 1304 This option delays grace-period initialization for a few 1305 jiffies between initializing each pair of consecutive 1306 rcu_node structures. This helps to expose races involving 1307 grace-period initialization, in other words, it makes your 1308 kernel less stable. It can also greatly increase grace-period 1309 latency, especially on systems with large numbers of CPUs. 1310 This is useful when torture-testing RCU, but in almost no 1311 other circumstance. 1312 1313 Say Y here if you want your system to crash and hang more often. 1314 Say N if you want a sane system. 1315 1316config RCU_TORTURE_TEST_SLOW_INIT_DELAY 1317 int "How much to slow down RCU grace-period initialization" 1318 range 0 5 1319 default 3 1320 depends on RCU_TORTURE_TEST_SLOW_INIT 1321 help 1322 This option specifies the number of jiffies to wait between 1323 each rcu_node structure initialization. 1324 1325config RCU_TORTURE_TEST_SLOW_CLEANUP 1326 bool "Slow down RCU grace-period cleanup to expose races" 1327 depends on RCU_TORTURE_TEST 1328 help 1329 This option delays grace-period cleanup for a few jiffies 1330 between cleaning up each pair of consecutive rcu_node 1331 structures. This helps to expose races involving grace-period 1332 cleanup, in other words, it makes your kernel less stable. 1333 It can also greatly increase grace-period latency, especially 1334 on systems with large numbers of CPUs. This is useful when 1335 torture-testing RCU, but in almost no other circumstance. 1336 1337 Say Y here if you want your system to crash and hang more often. 1338 Say N if you want a sane system. 1339 1340config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY 1341 int "How much to slow down RCU grace-period cleanup" 1342 range 0 5 1343 default 3 1344 depends on RCU_TORTURE_TEST_SLOW_CLEANUP 1345 help 1346 This option specifies the number of jiffies to wait between 1347 each rcu_node structure cleanup operation. 1348 1349config RCU_CPU_STALL_TIMEOUT 1350 int "RCU CPU stall timeout in seconds" 1351 depends on RCU_STALL_COMMON 1352 range 3 300 1353 default 21 1354 help 1355 If a given RCU grace period extends more than the specified 1356 number of seconds, a CPU stall warning is printed. If the 1357 RCU grace period persists, additional CPU stall warnings are 1358 printed at more widely spaced intervals. 1359 1360config RCU_TRACE 1361 bool "Enable tracing for RCU" 1362 depends on DEBUG_KERNEL 1363 select TRACE_CLOCK 1364 help 1365 This option provides tracing in RCU which presents stats 1366 in debugfs for debugging RCU implementation. 1367 1368 Say Y here if you want to enable RCU tracing 1369 Say N if you are unsure. 1370 1371config RCU_EQS_DEBUG 1372 bool "Provide debugging asserts for adding NO_HZ support to an arch" 1373 depends on DEBUG_KERNEL 1374 help 1375 This option provides consistency checks in RCU's handling of 1376 NO_HZ. These checks have proven quite helpful in detecting 1377 bugs in arch-specific NO_HZ code. 1378 1379 Say N here if you need ultimate kernel/user switch latencies 1380 Say Y if you are unsure 1381 1382endmenu # "RCU Debugging" 1383 1384config DEBUG_BLOCK_EXT_DEVT 1385 bool "Force extended block device numbers and spread them" 1386 depends on DEBUG_KERNEL 1387 depends on BLOCK 1388 default n 1389 help 1390 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1391 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1392 YOU ARE DOING. Distros, please enable this and fix whatever 1393 is broken. 1394 1395 Conventionally, block device numbers are allocated from 1396 predetermined contiguous area. However, extended block area 1397 may introduce non-contiguous block device numbers. This 1398 option forces most block device numbers to be allocated from 1399 the extended space and spreads them to discover kernel or 1400 userland code paths which assume predetermined contiguous 1401 device number allocation. 1402 1403 Note that turning on this debug option shuffles all the 1404 device numbers for all IDE and SCSI devices including libata 1405 ones, so root partition specified using device number 1406 directly (via rdev or root=MAJ:MIN) won't work anymore. 1407 Textual device names (root=/dev/sdXn) will continue to work. 1408 1409 Say N if you are unsure. 1410 1411config NOTIFIER_ERROR_INJECTION 1412 tristate "Notifier error injection" 1413 depends on DEBUG_KERNEL 1414 select DEBUG_FS 1415 help 1416 This option provides the ability to inject artificial errors to 1417 specified notifier chain callbacks. It is useful to test the error 1418 handling of notifier call chain failures. 1419 1420 Say N if unsure. 1421 1422config CPU_NOTIFIER_ERROR_INJECT 1423 tristate "CPU notifier error injection module" 1424 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1425 help 1426 This option provides a kernel module that can be used to test 1427 the error handling of the cpu notifiers by injecting artificial 1428 errors to CPU notifier chain callbacks. It is controlled through 1429 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1430 1431 If the notifier call chain should be failed with some events 1432 notified, write the error code to "actions/<notifier event>/error". 1433 1434 Example: Inject CPU offline error (-1 == -EPERM) 1435 1436 # cd /sys/kernel/debug/notifier-error-inject/cpu 1437 # echo -1 > actions/CPU_DOWN_PREPARE/error 1438 # echo 0 > /sys/devices/system/cpu/cpu1/online 1439 bash: echo: write error: Operation not permitted 1440 1441 To compile this code as a module, choose M here: the module will 1442 be called cpu-notifier-error-inject. 1443 1444 If unsure, say N. 1445 1446config PM_NOTIFIER_ERROR_INJECT 1447 tristate "PM notifier error injection module" 1448 depends on PM && NOTIFIER_ERROR_INJECTION 1449 default m if PM_DEBUG 1450 help 1451 This option provides the ability to inject artificial errors to 1452 PM notifier chain callbacks. It is controlled through debugfs 1453 interface /sys/kernel/debug/notifier-error-inject/pm 1454 1455 If the notifier call chain should be failed with some events 1456 notified, write the error code to "actions/<notifier event>/error". 1457 1458 Example: Inject PM suspend error (-12 = -ENOMEM) 1459 1460 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1461 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1462 # echo mem > /sys/power/state 1463 bash: echo: write error: Cannot allocate memory 1464 1465 To compile this code as a module, choose M here: the module will 1466 be called pm-notifier-error-inject. 1467 1468 If unsure, say N. 1469 1470config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1471 tristate "OF reconfig notifier error injection module" 1472 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1473 help 1474 This option provides the ability to inject artificial errors to 1475 OF reconfig notifier chain callbacks. It is controlled 1476 through debugfs interface under 1477 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1478 1479 If the notifier call chain should be failed with some events 1480 notified, write the error code to "actions/<notifier event>/error". 1481 1482 To compile this code as a module, choose M here: the module will 1483 be called of-reconfig-notifier-error-inject. 1484 1485 If unsure, say N. 1486 1487config FAULT_INJECTION 1488 bool "Fault-injection framework" 1489 depends on DEBUG_KERNEL 1490 help 1491 Provide fault-injection framework. 1492 For more details, see Documentation/fault-injection/. 1493 1494config FAILSLAB 1495 bool "Fault-injection capability for kmalloc" 1496 depends on FAULT_INJECTION 1497 depends on SLAB || SLUB 1498 help 1499 Provide fault-injection capability for kmalloc. 1500 1501config FAIL_PAGE_ALLOC 1502 bool "Fault-injection capabilitiy for alloc_pages()" 1503 depends on FAULT_INJECTION 1504 help 1505 Provide fault-injection capability for alloc_pages(). 1506 1507config FAIL_MAKE_REQUEST 1508 bool "Fault-injection capability for disk IO" 1509 depends on FAULT_INJECTION && BLOCK 1510 help 1511 Provide fault-injection capability for disk IO. 1512 1513config FAIL_IO_TIMEOUT 1514 bool "Fault-injection capability for faking disk interrupts" 1515 depends on FAULT_INJECTION && BLOCK 1516 help 1517 Provide fault-injection capability on end IO handling. This 1518 will make the block layer "forget" an interrupt as configured, 1519 thus exercising the error handling. 1520 1521 Only works with drivers that use the generic timeout handling, 1522 for others it wont do anything. 1523 1524config FAIL_MMC_REQUEST 1525 bool "Fault-injection capability for MMC IO" 1526 select DEBUG_FS 1527 depends on FAULT_INJECTION && MMC 1528 help 1529 Provide fault-injection capability for MMC IO. 1530 This will make the mmc core return data errors. This is 1531 useful to test the error handling in the mmc block device 1532 and to test how the mmc host driver handles retries from 1533 the block device. 1534 1535config FAIL_FUTEX 1536 bool "Fault-injection capability for futexes" 1537 select DEBUG_FS 1538 depends on FAULT_INJECTION && FUTEX 1539 help 1540 Provide fault-injection capability for futexes. 1541 1542config FAULT_INJECTION_DEBUG_FS 1543 bool "Debugfs entries for fault-injection capabilities" 1544 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1545 help 1546 Enable configuration of fault-injection capabilities via debugfs. 1547 1548config FAULT_INJECTION_STACKTRACE_FILTER 1549 bool "stacktrace filter for fault-injection capabilities" 1550 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1551 depends on !X86_64 1552 select STACKTRACE 1553 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1554 help 1555 Provide stacktrace filter for fault-injection capabilities 1556 1557config LATENCYTOP 1558 bool "Latency measuring infrastructure" 1559 depends on HAVE_LATENCYTOP_SUPPORT 1560 depends on DEBUG_KERNEL 1561 depends on STACKTRACE_SUPPORT 1562 depends on PROC_FS 1563 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1564 select KALLSYMS 1565 select KALLSYMS_ALL 1566 select STACKTRACE 1567 select SCHEDSTATS 1568 select SCHED_DEBUG 1569 help 1570 Enable this option if you want to use the LatencyTOP tool 1571 to find out which userspace is blocking on what kernel operations. 1572 1573config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1574 bool 1575 1576config DEBUG_STRICT_USER_COPY_CHECKS 1577 bool "Strict user copy size checks" 1578 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1579 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING 1580 help 1581 Enabling this option turns a certain set of sanity checks for user 1582 copy operations into compile time failures. 1583 1584 The copy_from_user() etc checks are there to help test if there 1585 are sufficient security checks on the length argument of 1586 the copy operation, by having gcc prove that the argument is 1587 within bounds. 1588 1589 If unsure, say N. 1590 1591source kernel/trace/Kconfig 1592 1593menu "Runtime Testing" 1594 1595config LKDTM 1596 tristate "Linux Kernel Dump Test Tool Module" 1597 depends on DEBUG_FS 1598 depends on BLOCK 1599 default n 1600 help 1601 This module enables testing of the different dumping mechanisms by 1602 inducing system failures at predefined crash points. 1603 If you don't need it: say N 1604 Choose M here to compile this code as a module. The module will be 1605 called lkdtm. 1606 1607 Documentation on how to use the module can be found in 1608 Documentation/fault-injection/provoke-crashes.txt 1609 1610config TEST_LIST_SORT 1611 bool "Linked list sorting test" 1612 depends on DEBUG_KERNEL 1613 help 1614 Enable this to turn on 'list_sort()' function test. This test is 1615 executed only once during system boot, so affects only boot time. 1616 1617 If unsure, say N. 1618 1619config KPROBES_SANITY_TEST 1620 bool "Kprobes sanity tests" 1621 depends on DEBUG_KERNEL 1622 depends on KPROBES 1623 default n 1624 help 1625 This option provides for testing basic kprobes functionality on 1626 boot. A sample kprobe, jprobe and kretprobe are inserted and 1627 verified for functionality. 1628 1629 Say N if you are unsure. 1630 1631config BACKTRACE_SELF_TEST 1632 tristate "Self test for the backtrace code" 1633 depends on DEBUG_KERNEL 1634 default n 1635 help 1636 This option provides a kernel module that can be used to test 1637 the kernel stack backtrace code. This option is not useful 1638 for distributions or general kernels, but only for kernel 1639 developers working on architecture code. 1640 1641 Note that if you want to also test saved backtraces, you will 1642 have to enable STACKTRACE as well. 1643 1644 Say N if you are unsure. 1645 1646config RBTREE_TEST 1647 tristate "Red-Black tree test" 1648 depends on DEBUG_KERNEL 1649 help 1650 A benchmark measuring the performance of the rbtree library. 1651 Also includes rbtree invariant checks. 1652 1653config INTERVAL_TREE_TEST 1654 tristate "Interval tree test" 1655 depends on m && DEBUG_KERNEL 1656 select INTERVAL_TREE 1657 help 1658 A benchmark measuring the performance of the interval tree library 1659 1660config PERCPU_TEST 1661 tristate "Per cpu operations test" 1662 depends on m && DEBUG_KERNEL 1663 help 1664 Enable this option to build test module which validates per-cpu 1665 operations. 1666 1667 If unsure, say N. 1668 1669config ATOMIC64_SELFTEST 1670 bool "Perform an atomic64_t self-test at boot" 1671 help 1672 Enable this option to test the atomic64_t functions at boot. 1673 1674 If unsure, say N. 1675 1676config ASYNC_RAID6_TEST 1677 tristate "Self test for hardware accelerated raid6 recovery" 1678 depends on ASYNC_RAID6_RECOV 1679 select ASYNC_MEMCPY 1680 ---help--- 1681 This is a one-shot self test that permutes through the 1682 recovery of all the possible two disk failure scenarios for a 1683 N-disk array. Recovery is performed with the asynchronous 1684 raid6 recovery routines, and will optionally use an offload 1685 engine if one is available. 1686 1687 If unsure, say N. 1688 1689config TEST_HEXDUMP 1690 tristate "Test functions located in the hexdump module at runtime" 1691 1692config TEST_STRING_HELPERS 1693 tristate "Test functions located in the string_helpers module at runtime" 1694 1695config TEST_KSTRTOX 1696 tristate "Test kstrto*() family of functions at runtime" 1697 1698config TEST_PRINTF 1699 tristate "Test printf() family of functions at runtime" 1700 1701config TEST_RHASHTABLE 1702 tristate "Perform selftest on resizable hash table" 1703 default n 1704 help 1705 Enable this option to test the rhashtable functions at boot. 1706 1707 If unsure, say N. 1708 1709endmenu # runtime tests 1710 1711config PROVIDE_OHCI1394_DMA_INIT 1712 bool "Remote debugging over FireWire early on boot" 1713 depends on PCI && X86 1714 help 1715 If you want to debug problems which hang or crash the kernel early 1716 on boot and the crashing machine has a FireWire port, you can use 1717 this feature to remotely access the memory of the crashed machine 1718 over FireWire. This employs remote DMA as part of the OHCI1394 1719 specification which is now the standard for FireWire controllers. 1720 1721 With remote DMA, you can monitor the printk buffer remotely using 1722 firescope and access all memory below 4GB using fireproxy from gdb. 1723 Even controlling a kernel debugger is possible using remote DMA. 1724 1725 Usage: 1726 1727 If ohci1394_dma=early is used as boot parameter, it will initialize 1728 all OHCI1394 controllers which are found in the PCI config space. 1729 1730 As all changes to the FireWire bus such as enabling and disabling 1731 devices cause a bus reset and thereby disable remote DMA for all 1732 devices, be sure to have the cable plugged and FireWire enabled on 1733 the debugging host before booting the debug target for debugging. 1734 1735 This code (~1k) is freed after boot. By then, the firewire stack 1736 in charge of the OHCI-1394 controllers should be used instead. 1737 1738 See Documentation/debugging-via-ohci1394.txt for more information. 1739 1740config BUILD_DOCSRC 1741 bool "Build targets in Documentation/ tree" 1742 depends on HEADERS_CHECK 1743 help 1744 This option attempts to build objects from the source files in the 1745 kernel Documentation/ tree. 1746 1747 Say N if you are unsure. 1748 1749config DMA_API_DEBUG 1750 bool "Enable debugging of DMA-API usage" 1751 depends on HAVE_DMA_API_DEBUG 1752 help 1753 Enable this option to debug the use of the DMA API by device drivers. 1754 With this option you will be able to detect common bugs in device 1755 drivers like double-freeing of DMA mappings or freeing mappings that 1756 were never allocated. 1757 1758 This also attempts to catch cases where a page owned by DMA is 1759 accessed by the cpu in a way that could cause data corruption. For 1760 example, this enables cow_user_page() to check that the source page is 1761 not undergoing DMA. 1762 1763 This option causes a performance degradation. Use only if you want to 1764 debug device drivers and dma interactions. 1765 1766 If unsure, say N. 1767 1768config TEST_LKM 1769 tristate "Test module loading with 'hello world' module" 1770 default n 1771 depends on m 1772 help 1773 This builds the "test_module" module that emits "Hello, world" 1774 on printk when loaded. It is designed to be used for basic 1775 evaluation of the module loading subsystem (for example when 1776 validating module verification). It lacks any extra dependencies, 1777 and will not normally be loaded by the system unless explicitly 1778 requested by name. 1779 1780 If unsure, say N. 1781 1782config TEST_USER_COPY 1783 tristate "Test user/kernel boundary protections" 1784 default n 1785 depends on m 1786 help 1787 This builds the "test_user_copy" module that runs sanity checks 1788 on the copy_to/from_user infrastructure, making sure basic 1789 user/kernel boundary testing is working. If it fails to load, 1790 a regression has been detected in the user/kernel memory boundary 1791 protections. 1792 1793 If unsure, say N. 1794 1795config TEST_BPF 1796 tristate "Test BPF filter functionality" 1797 default n 1798 depends on m && NET 1799 help 1800 This builds the "test_bpf" module that runs various test vectors 1801 against the BPF interpreter or BPF JIT compiler depending on the 1802 current setting. This is in particular useful for BPF JIT compiler 1803 development, but also to run regression tests against changes in 1804 the interpreter code. It also enables test stubs for eBPF maps and 1805 verifier used by user space verifier testsuite. 1806 1807 If unsure, say N. 1808 1809config TEST_FIRMWARE 1810 tristate "Test firmware loading via userspace interface" 1811 default n 1812 depends on FW_LOADER 1813 help 1814 This builds the "test_firmware" module that creates a userspace 1815 interface for testing firmware loading. This can be used to 1816 control the triggering of firmware loading without needing an 1817 actual firmware-using device. The contents can be rechecked by 1818 userspace. 1819 1820 If unsure, say N. 1821 1822config TEST_UDELAY 1823 tristate "udelay test driver" 1824 default n 1825 help 1826 This builds the "udelay_test" module that helps to make sure 1827 that udelay() is working properly. 1828 1829 If unsure, say N. 1830 1831config MEMTEST 1832 bool "Memtest" 1833 depends on HAVE_MEMBLOCK 1834 ---help--- 1835 This option adds a kernel parameter 'memtest', which allows memtest 1836 to be set. 1837 memtest=0, mean disabled; -- default 1838 memtest=1, mean do 1 test pattern; 1839 ... 1840 memtest=17, mean do 17 test patterns. 1841 If you are unsure how to answer this question, answer N. 1842 1843config TEST_STATIC_KEYS 1844 tristate "Test static keys" 1845 default n 1846 depends on m 1847 help 1848 Test the static key interfaces. 1849 1850 If unsure, say N. 1851 1852source "samples/Kconfig" 1853 1854source "lib/Kconfig.kgdb" 1855 1856