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/admin-guide/kernel-parameters.rst 17 18config CONSOLE_LOGLEVEL_DEFAULT 19 int "Default console loglevel (1-15)" 20 range 1 15 21 default "7" 22 help 23 Default loglevel to determine what will be printed on the console. 24 25 Setting a default here is equivalent to passing in loglevel=<x> in 26 the kernel bootargs. loglevel=<x> continues to override whatever 27 value is specified here as well. 28 29 Note: This does not affect the log level of un-prefixed printk() 30 usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT 31 option. 32 33config MESSAGE_LOGLEVEL_DEFAULT 34 int "Default message log level (1-7)" 35 range 1 7 36 default "4" 37 help 38 Default log level for printk statements with no specified priority. 39 40 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks 41 that are auditing their logs closely may want to set it to a lower 42 priority. 43 44 Note: This does not affect what message level gets printed on the console 45 by default. To change that, use loglevel=<x> in the kernel bootargs, 46 or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value. 47 48config BOOT_PRINTK_DELAY 49 bool "Delay each boot printk message by N milliseconds" 50 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 51 help 52 This build option allows you to read kernel boot messages 53 by inserting a short delay after each one. The delay is 54 specified in milliseconds on the kernel command line, 55 using "boot_delay=N". 56 57 It is likely that you would also need to use "lpj=M" to preset 58 the "loops per jiffie" value. 59 See a previous boot log for the "lpj" value to use for your 60 system, and then set "lpj=M" before setting "boot_delay=N". 61 NOTE: Using this option may adversely affect SMP systems. 62 I.e., processors other than the first one may not boot up. 63 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect 64 what it believes to be lockup conditions. 65 66config DYNAMIC_DEBUG 67 bool "Enable dynamic printk() support" 68 default n 69 depends on PRINTK 70 depends on DEBUG_FS 71 help 72 73 Compiles debug level messages into the kernel, which would not 74 otherwise be available at runtime. These messages can then be 75 enabled/disabled based on various levels of scope - per source file, 76 function, module, format string, and line number. This mechanism 77 implicitly compiles in all pr_debug() and dev_dbg() calls, which 78 enlarges the kernel text size by about 2%. 79 80 If a source file is compiled with DEBUG flag set, any 81 pr_debug() calls in it are enabled by default, but can be 82 disabled at runtime as below. Note that DEBUG flag is 83 turned on by many CONFIG_*DEBUG* options. 84 85 Usage: 86 87 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 88 which is contained in the 'debugfs' filesystem. Thus, the debugfs 89 filesystem must first be mounted before making use of this feature. 90 We refer the control file as: <debugfs>/dynamic_debug/control. This 91 file contains a list of the debug statements that can be enabled. The 92 format for each line of the file is: 93 94 filename:lineno [module]function flags format 95 96 filename : source file of the debug statement 97 lineno : line number of the debug statement 98 module : module that contains the debug statement 99 function : function that contains the debug statement 100 flags : '=p' means the line is turned 'on' for printing 101 format : the format used for the debug statement 102 103 From a live system: 104 105 nullarbor:~ # cat <debugfs>/dynamic_debug/control 106 # filename:lineno [module]function flags format 107 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012" 108 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012" 109 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012" 110 111 Example usage: 112 113 // enable the message at line 1603 of file svcsock.c 114 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 115 <debugfs>/dynamic_debug/control 116 117 // enable all the messages in file svcsock.c 118 nullarbor:~ # echo -n 'file svcsock.c +p' > 119 <debugfs>/dynamic_debug/control 120 121 // enable all the messages in the NFS server module 122 nullarbor:~ # echo -n 'module nfsd +p' > 123 <debugfs>/dynamic_debug/control 124 125 // enable all 12 messages in the function svc_process() 126 nullarbor:~ # echo -n 'func svc_process +p' > 127 <debugfs>/dynamic_debug/control 128 129 // disable all 12 messages in the function svc_process() 130 nullarbor:~ # echo -n 'func svc_process -p' > 131 <debugfs>/dynamic_debug/control 132 133 See Documentation/admin-guide/dynamic-debug-howto.rst for additional 134 information. 135 136endmenu # "printk and dmesg options" 137 138menu "Compile-time checks and compiler options" 139 140config DEBUG_INFO 141 bool "Compile the kernel with debug info" 142 depends on DEBUG_KERNEL && !COMPILE_TEST 143 help 144 If you say Y here the resulting kernel image will include 145 debugging info resulting in a larger kernel image. 146 This adds debug symbols to the kernel and modules (gcc -g), and 147 is needed if you intend to use kernel crashdump or binary object 148 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 149 Say Y here only if you plan to debug the kernel. 150 151 If unsure, say N. 152 153config DEBUG_INFO_REDUCED 154 bool "Reduce debugging information" 155 depends on DEBUG_INFO 156 help 157 If you say Y here gcc is instructed to generate less debugging 158 information for structure types. This means that tools that 159 need full debugging information (like kgdb or systemtap) won't 160 be happy. But if you merely need debugging information to 161 resolve line numbers there is no loss. Advantage is that 162 build directory object sizes shrink dramatically over a full 163 DEBUG_INFO build and compile times are reduced too. 164 Only works with newer gcc versions. 165 166config DEBUG_INFO_SPLIT 167 bool "Produce split debuginfo in .dwo files" 168 depends on DEBUG_INFO && !FRV 169 help 170 Generate debug info into separate .dwo files. This significantly 171 reduces the build directory size for builds with DEBUG_INFO, 172 because it stores the information only once on disk in .dwo 173 files instead of multiple times in object files and executables. 174 In addition the debug information is also compressed. 175 176 Requires recent gcc (4.7+) and recent gdb/binutils. 177 Any tool that packages or reads debug information would need 178 to know about the .dwo files and include them. 179 Incompatible with older versions of ccache. 180 181config DEBUG_INFO_DWARF4 182 bool "Generate dwarf4 debuginfo" 183 depends on DEBUG_INFO 184 help 185 Generate dwarf4 debug info. This requires recent versions 186 of gcc and gdb. It makes the debug information larger. 187 But it significantly improves the success of resolving 188 variables in gdb on optimized code. 189 190config GDB_SCRIPTS 191 bool "Provide GDB scripts for kernel debugging" 192 depends on DEBUG_INFO 193 help 194 This creates the required links to GDB helper scripts in the 195 build directory. If you load vmlinux into gdb, the helper 196 scripts will be automatically imported by gdb as well, and 197 additional functions are available to analyze a Linux kernel 198 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst 199 for further details. 200 201config ENABLE_WARN_DEPRECATED 202 bool "Enable __deprecated logic" 203 default y 204 help 205 Enable the __deprecated logic in the kernel build. 206 Disable this to suppress the "warning: 'foo' is deprecated 207 (declared at kernel/power/somefile.c:1234)" messages. 208 209config ENABLE_MUST_CHECK 210 bool "Enable __must_check logic" 211 default y 212 help 213 Enable the __must_check logic in the kernel build. Disable this to 214 suppress the "warning: ignoring return value of 'foo', declared with 215 attribute warn_unused_result" messages. 216 217config FRAME_WARN 218 int "Warn for stack frames larger than (needs gcc 4.4)" 219 range 0 8192 220 default 0 if KASAN 221 default 2048 if GCC_PLUGIN_LATENT_ENTROPY 222 default 1024 if !64BIT 223 default 2048 if 64BIT 224 help 225 Tell gcc to warn at build time for stack frames larger than this. 226 Setting this too low will cause a lot of warnings. 227 Setting it to 0 disables the warning. 228 Requires gcc 4.4 229 230config STRIP_ASM_SYMS 231 bool "Strip assembler-generated symbols during link" 232 default n 233 help 234 Strip internal assembler-generated symbols during a link (symbols 235 that look like '.Lxxx') so they don't pollute the output of 236 get_wchan() and suchlike. 237 238config READABLE_ASM 239 bool "Generate readable assembler code" 240 depends on DEBUG_KERNEL 241 help 242 Disable some compiler optimizations that tend to generate human unreadable 243 assembler output. This may make the kernel slightly slower, but it helps 244 to keep kernel developers who have to stare a lot at assembler listings 245 sane. 246 247config UNUSED_SYMBOLS 248 bool "Enable unused/obsolete exported symbols" 249 default y if X86 250 help 251 Unused but exported symbols make the kernel needlessly bigger. For 252 that reason most of these unused exports will soon be removed. This 253 option is provided temporarily to provide a transition period in case 254 some external kernel module needs one of these symbols anyway. If you 255 encounter such a case in your module, consider if you are actually 256 using the right API. (rationale: since nobody in the kernel is using 257 this in a module, there is a pretty good chance it's actually the 258 wrong interface to use). If you really need the symbol, please send a 259 mail to the linux kernel mailing list mentioning the symbol and why 260 you really need it, and what the merge plan to the mainline kernel for 261 your module is. 262 263config PAGE_OWNER 264 bool "Track page owner" 265 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 266 select DEBUG_FS 267 select STACKTRACE 268 select STACKDEPOT 269 select PAGE_EXTENSION 270 help 271 This keeps track of what call chain is the owner of a page, may 272 help to find bare alloc_page(s) leaks. Even if you include this 273 feature on your build, it is disabled in default. You should pass 274 "page_owner=on" to boot parameter in order to enable it. Eats 275 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 276 for user-space helper. 277 278 If unsure, say N. 279 280config DEBUG_FS 281 bool "Debug Filesystem" 282 select SRCU 283 help 284 debugfs is a virtual file system that kernel developers use to put 285 debugging files into. Enable this option to be able to read and 286 write to these files. 287 288 For detailed documentation on the debugfs API, see 289 Documentation/filesystems/. 290 291 If unsure, say N. 292 293config HEADERS_CHECK 294 bool "Run 'make headers_check' when building vmlinux" 295 depends on !UML 296 help 297 This option will extract the user-visible kernel headers whenever 298 building the kernel, and will run basic sanity checks on them to 299 ensure that exported files do not attempt to include files which 300 were not exported, etc. 301 302 If you're making modifications to header files which are 303 relevant for userspace, say 'Y', and check the headers 304 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 305 your build tree), to make sure they're suitable. 306 307config DEBUG_SECTION_MISMATCH 308 bool "Enable full Section mismatch analysis" 309 help 310 The section mismatch analysis checks if there are illegal 311 references from one section to another section. 312 During linktime or runtime, some sections are dropped; 313 any use of code/data previously in these sections would 314 most likely result in an oops. 315 In the code, functions and variables are annotated with 316 __init,, etc. (see the full list in include/linux/init.h), 317 which results in the code/data being placed in specific sections. 318 The section mismatch analysis is always performed after a full 319 kernel build, and enabling this option causes the following 320 additional steps to occur: 321 - Add the option -fno-inline-functions-called-once to gcc commands. 322 When inlining a function annotated with __init in a non-init 323 function, we would lose the section information and thus 324 the analysis would not catch the illegal reference. 325 This option tells gcc to inline less (but it does result in 326 a larger kernel). 327 - Run the section mismatch analysis for each module/built-in.o file. 328 When we run the section mismatch analysis on vmlinux.o, we 329 lose valuable information about where the mismatch was 330 introduced. 331 Running the analysis for each module/built-in.o file 332 tells where the mismatch happens much closer to the 333 source. The drawback is that the same mismatch is 334 reported at least twice. 335 - Enable verbose reporting from modpost in order to help resolve 336 the section mismatches that are reported. 337 338config SECTION_MISMATCH_WARN_ONLY 339 bool "Make section mismatch errors non-fatal" 340 default y 341 help 342 If you say N here, the build process will fail if there are any 343 section mismatch, instead of just throwing warnings. 344 345 If unsure, say Y. 346 347# 348# Select this config option from the architecture Kconfig, if it 349# is preferred to always offer frame pointers as a config 350# option on the architecture (regardless of KERNEL_DEBUG): 351# 352config ARCH_WANT_FRAME_POINTERS 353 bool 354 help 355 356config FRAME_POINTER 357 bool "Compile the kernel with frame pointers" 358 depends on DEBUG_KERNEL && \ 359 (CRIS || M68K || FRV || UML || \ 360 SUPERH || BLACKFIN || MN10300 || METAG) || \ 361 ARCH_WANT_FRAME_POINTERS 362 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 363 help 364 If you say Y here the resulting kernel image will be slightly 365 larger and slower, but it gives very useful debugging information 366 in case of kernel bugs. (precise oopses/stacktraces/warnings) 367 368config STACK_VALIDATION 369 bool "Compile-time stack metadata validation" 370 depends on HAVE_STACK_VALIDATION 371 default n 372 help 373 Add compile-time checks to validate stack metadata, including frame 374 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure 375 that runtime stack traces are more reliable. 376 377 For more information, see 378 tools/objtool/Documentation/stack-validation.txt. 379 380config DEBUG_FORCE_WEAK_PER_CPU 381 bool "Force weak per-cpu definitions" 382 depends on DEBUG_KERNEL 383 help 384 s390 and alpha require percpu variables in modules to be 385 defined weak to work around addressing range issue which 386 puts the following two restrictions on percpu variable 387 definitions. 388 389 1. percpu symbols must be unique whether static or not 390 2. percpu variables can't be defined inside a function 391 392 To ensure that generic code follows the above rules, this 393 option forces all percpu variables to be defined as weak. 394 395endmenu # "Compiler options" 396 397config MAGIC_SYSRQ 398 bool "Magic SysRq key" 399 depends on !UML 400 help 401 If you say Y here, you will have some control over the system even 402 if the system crashes for example during kernel debugging (e.g., you 403 will be able to flush the buffer cache to disk, reboot the system 404 immediately or dump some status information). This is accomplished 405 by pressing various keys while holding SysRq (Alt+PrintScreen). It 406 also works on a serial console (on PC hardware at least), if you 407 send a BREAK and then within 5 seconds a command keypress. The 408 keys are documented in <file:Documentation/admin-guide/sysrq.rst>. 409 Don't say Y unless you really know what this hack does. 410 411config MAGIC_SYSRQ_DEFAULT_ENABLE 412 hex "Enable magic SysRq key functions by default" 413 depends on MAGIC_SYSRQ 414 default 0x1 415 help 416 Specifies which SysRq key functions are enabled by default. 417 This may be set to 1 or 0 to enable or disable them all, or 418 to a bitmask as described in Documentation/admin-guide/sysrq.rst. 419 420config MAGIC_SYSRQ_SERIAL 421 bool "Enable magic SysRq key over serial" 422 depends on MAGIC_SYSRQ 423 default y 424 help 425 Many embedded boards have a disconnected TTL level serial which can 426 generate some garbage that can lead to spurious false sysrq detects. 427 This option allows you to decide whether you want to enable the 428 magic SysRq key. 429 430config DEBUG_KERNEL 431 bool "Kernel debugging" 432 help 433 Say Y here if you are developing drivers or trying to debug and 434 identify kernel problems. 435 436menu "Memory Debugging" 437 438source mm/Kconfig.debug 439 440config DEBUG_OBJECTS 441 bool "Debug object operations" 442 depends on DEBUG_KERNEL 443 help 444 If you say Y here, additional code will be inserted into the 445 kernel to track the life time of various objects and validate 446 the operations on those objects. 447 448config DEBUG_OBJECTS_SELFTEST 449 bool "Debug objects selftest" 450 depends on DEBUG_OBJECTS 451 help 452 This enables the selftest of the object debug code. 453 454config DEBUG_OBJECTS_FREE 455 bool "Debug objects in freed memory" 456 depends on DEBUG_OBJECTS 457 help 458 This enables checks whether a k/v free operation frees an area 459 which contains an object which has not been deactivated 460 properly. This can make kmalloc/kfree-intensive workloads 461 much slower. 462 463config DEBUG_OBJECTS_TIMERS 464 bool "Debug timer objects" 465 depends on DEBUG_OBJECTS 466 help 467 If you say Y here, additional code will be inserted into the 468 timer routines to track the life time of timer objects and 469 validate the timer operations. 470 471config DEBUG_OBJECTS_WORK 472 bool "Debug work objects" 473 depends on DEBUG_OBJECTS 474 help 475 If you say Y here, additional code will be inserted into the 476 work queue routines to track the life time of work objects and 477 validate the work operations. 478 479config DEBUG_OBJECTS_RCU_HEAD 480 bool "Debug RCU callbacks objects" 481 depends on DEBUG_OBJECTS 482 help 483 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 484 485config DEBUG_OBJECTS_PERCPU_COUNTER 486 bool "Debug percpu counter objects" 487 depends on DEBUG_OBJECTS 488 help 489 If you say Y here, additional code will be inserted into the 490 percpu counter routines to track the life time of percpu counter 491 objects and validate the percpu counter operations. 492 493config DEBUG_OBJECTS_ENABLE_DEFAULT 494 int "debug_objects bootup default value (0-1)" 495 range 0 1 496 default "1" 497 depends on DEBUG_OBJECTS 498 help 499 Debug objects boot parameter default value 500 501config DEBUG_SLAB 502 bool "Debug slab memory allocations" 503 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 504 help 505 Say Y here to have the kernel do limited verification on memory 506 allocation as well as poisoning memory on free to catch use of freed 507 memory. This can make kmalloc/kfree-intensive workloads much slower. 508 509config DEBUG_SLAB_LEAK 510 bool "Memory leak debugging" 511 depends on DEBUG_SLAB 512 513config SLUB_DEBUG_ON 514 bool "SLUB debugging on by default" 515 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 516 default n 517 help 518 Boot with debugging on by default. SLUB boots by default with 519 the runtime debug capabilities switched off. Enabling this is 520 equivalent to specifying the "slub_debug" parameter on boot. 521 There is no support for more fine grained debug control like 522 possible with slub_debug=xxx. SLUB debugging may be switched 523 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 524 "slub_debug=-". 525 526config SLUB_STATS 527 default n 528 bool "Enable SLUB performance statistics" 529 depends on SLUB && SYSFS 530 help 531 SLUB statistics are useful to debug SLUBs allocation behavior in 532 order find ways to optimize the allocator. This should never be 533 enabled for production use since keeping statistics slows down 534 the allocator by a few percentage points. The slabinfo command 535 supports the determination of the most active slabs to figure 536 out which slabs are relevant to a particular load. 537 Try running: slabinfo -DA 538 539config HAVE_DEBUG_KMEMLEAK 540 bool 541 542config DEBUG_KMEMLEAK 543 bool "Kernel memory leak detector" 544 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 545 select DEBUG_FS 546 select STACKTRACE if STACKTRACE_SUPPORT 547 select KALLSYMS 548 select CRC32 549 help 550 Say Y here if you want to enable the memory leak 551 detector. The memory allocation/freeing is traced in a way 552 similar to the Boehm's conservative garbage collector, the 553 difference being that the orphan objects are not freed but 554 only shown in /sys/kernel/debug/kmemleak. Enabling this 555 feature will introduce an overhead to memory 556 allocations. See Documentation/dev-tools/kmemleak.rst for more 557 details. 558 559 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 560 of finding leaks due to the slab objects poisoning. 561 562 In order to access the kmemleak file, debugfs needs to be 563 mounted (usually at /sys/kernel/debug). 564 565config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 566 int "Maximum kmemleak early log entries" 567 depends on DEBUG_KMEMLEAK 568 range 200 40000 569 default 400 570 help 571 Kmemleak must track all the memory allocations to avoid 572 reporting false positives. Since memory may be allocated or 573 freed before kmemleak is initialised, an early log buffer is 574 used to store these actions. If kmemleak reports "early log 575 buffer exceeded", please increase this value. 576 577config DEBUG_KMEMLEAK_TEST 578 tristate "Simple test for the kernel memory leak detector" 579 depends on DEBUG_KMEMLEAK && m 580 help 581 This option enables a module that explicitly leaks memory. 582 583 If unsure, say N. 584 585config DEBUG_KMEMLEAK_DEFAULT_OFF 586 bool "Default kmemleak to off" 587 depends on DEBUG_KMEMLEAK 588 help 589 Say Y here to disable kmemleak by default. It can then be enabled 590 on the command line via kmemleak=on. 591 592config DEBUG_STACK_USAGE 593 bool "Stack utilization instrumentation" 594 depends on DEBUG_KERNEL && !IA64 595 help 596 Enables the display of the minimum amount of free stack which each 597 task has ever had available in the sysrq-T and sysrq-P debug output. 598 599 This option will slow down process creation somewhat. 600 601config DEBUG_VM 602 bool "Debug VM" 603 depends on DEBUG_KERNEL 604 help 605 Enable this to turn on extended checks in the virtual-memory system 606 that may impact performance. 607 608 If unsure, say N. 609 610config DEBUG_VM_VMACACHE 611 bool "Debug VMA caching" 612 depends on DEBUG_VM 613 help 614 Enable this to turn on VMA caching debug information. Doing so 615 can cause significant overhead, so only enable it in non-production 616 environments. 617 618 If unsure, say N. 619 620config DEBUG_VM_RB 621 bool "Debug VM red-black trees" 622 depends on DEBUG_VM 623 help 624 Enable VM red-black tree debugging information and extra validations. 625 626 If unsure, say N. 627 628config DEBUG_VM_PGFLAGS 629 bool "Debug page-flags operations" 630 depends on DEBUG_VM 631 help 632 Enables extra validation on page flags operations. 633 634 If unsure, say N. 635 636config ARCH_HAS_DEBUG_VIRTUAL 637 bool 638 639config DEBUG_VIRTUAL 640 bool "Debug VM translations" 641 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL 642 help 643 Enable some costly sanity checks in virtual to page code. This can 644 catch mistakes with virt_to_page() and friends. 645 646 If unsure, say N. 647 648config DEBUG_NOMMU_REGIONS 649 bool "Debug the global anon/private NOMMU mapping region tree" 650 depends on DEBUG_KERNEL && !MMU 651 help 652 This option causes the global tree of anonymous and private mapping 653 regions to be regularly checked for invalid topology. 654 655config DEBUG_MEMORY_INIT 656 bool "Debug memory initialisation" if EXPERT 657 default !EXPERT 658 help 659 Enable this for additional checks during memory initialisation. 660 The sanity checks verify aspects of the VM such as the memory model 661 and other information provided by the architecture. Verbose 662 information will be printed at KERN_DEBUG loglevel depending 663 on the mminit_loglevel= command-line option. 664 665 If unsure, say Y 666 667config MEMORY_NOTIFIER_ERROR_INJECT 668 tristate "Memory hotplug notifier error injection module" 669 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 670 help 671 This option provides the ability to inject artificial errors to 672 memory hotplug notifier chain callbacks. It is controlled through 673 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 674 675 If the notifier call chain should be failed with some events 676 notified, write the error code to "actions/<notifier event>/error". 677 678 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 679 680 # cd /sys/kernel/debug/notifier-error-inject/memory 681 # echo -12 > actions/MEM_GOING_OFFLINE/error 682 # echo offline > /sys/devices/system/memory/memoryXXX/state 683 bash: echo: write error: Cannot allocate memory 684 685 To compile this code as a module, choose M here: the module will 686 be called memory-notifier-error-inject. 687 688 If unsure, say N. 689 690config DEBUG_PER_CPU_MAPS 691 bool "Debug access to per_cpu maps" 692 depends on DEBUG_KERNEL 693 depends on SMP 694 help 695 Say Y to verify that the per_cpu map being accessed has 696 been set up. This adds a fair amount of code to kernel memory 697 and decreases performance. 698 699 Say N if unsure. 700 701config DEBUG_HIGHMEM 702 bool "Highmem debugging" 703 depends on DEBUG_KERNEL && HIGHMEM 704 help 705 This option enables additional error checking for high memory 706 systems. Disable for production systems. 707 708config HAVE_DEBUG_STACKOVERFLOW 709 bool 710 711config DEBUG_STACKOVERFLOW 712 bool "Check for stack overflows" 713 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 714 ---help--- 715 Say Y here if you want to check for overflows of kernel, IRQ 716 and exception stacks (if your architecture uses them). This 717 option will show detailed messages if free stack space drops 718 below a certain limit. 719 720 These kinds of bugs usually occur when call-chains in the 721 kernel get too deep, especially when interrupts are 722 involved. 723 724 Use this in cases where you see apparently random memory 725 corruption, especially if it appears in 'struct thread_info' 726 727 If in doubt, say "N". 728 729source "lib/Kconfig.kmemcheck" 730 731source "lib/Kconfig.kasan" 732 733endmenu # "Memory Debugging" 734 735config ARCH_HAS_KCOV 736 bool 737 help 738 KCOV does not have any arch-specific code, but currently it is enabled 739 only for x86_64. KCOV requires testing on other archs, and most likely 740 disabling of instrumentation for some early boot code. 741 742config KCOV 743 bool "Code coverage for fuzzing" 744 depends on ARCH_HAS_KCOV 745 select DEBUG_FS 746 select GCC_PLUGINS if !COMPILE_TEST 747 select GCC_PLUGIN_SANCOV if !COMPILE_TEST 748 help 749 KCOV exposes kernel code coverage information in a form suitable 750 for coverage-guided fuzzing (randomized testing). 751 752 If RANDOMIZE_BASE is enabled, PC values will not be stable across 753 different machines and across reboots. If you need stable PC values, 754 disable RANDOMIZE_BASE. 755 756 For more details, see Documentation/dev-tools/kcov.rst. 757 758config KCOV_INSTRUMENT_ALL 759 bool "Instrument all code by default" 760 depends on KCOV 761 default y if KCOV 762 help 763 If you are doing generic system call fuzzing (like e.g. syzkaller), 764 then you will want to instrument the whole kernel and you should 765 say y here. If you are doing more targeted fuzzing (like e.g. 766 filesystem fuzzing with AFL) then you will want to enable coverage 767 for more specific subsets of files, and should say n here. 768 769config DEBUG_SHIRQ 770 bool "Debug shared IRQ handlers" 771 depends on DEBUG_KERNEL 772 help 773 Enable this to generate a spurious interrupt as soon as a shared 774 interrupt handler is registered, and just before one is deregistered. 775 Drivers ought to be able to handle interrupts coming in at those 776 points; some don't and need to be caught. 777 778menu "Debug Lockups and Hangs" 779 780config LOCKUP_DETECTOR 781 bool 782 783config SOFTLOCKUP_DETECTOR 784 bool "Detect Soft Lockups" 785 depends on DEBUG_KERNEL && !S390 786 select LOCKUP_DETECTOR 787 help 788 Say Y here to enable the kernel to act as a watchdog to detect 789 soft lockups. 790 791 Softlockups are bugs that cause the kernel to loop in kernel 792 mode for more than 20 seconds, without giving other tasks a 793 chance to run. The current stack trace is displayed upon 794 detection and the system will stay locked up. 795 796config HARDLOCKUP_DETECTOR_PERF 797 bool 798 select SOFTLOCKUP_DETECTOR 799 800# 801# arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard 802# lockup detector rather than the perf based detector. 803# 804config HARDLOCKUP_DETECTOR 805 bool "Detect Hard Lockups" 806 depends on DEBUG_KERNEL && !S390 807 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH 808 select LOCKUP_DETECTOR 809 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF 810 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH 811 help 812 Say Y here to enable the kernel to act as a watchdog to detect 813 hard lockups. 814 815 Hardlockups are bugs that cause the CPU to loop in kernel mode 816 for more than 10 seconds, without letting other interrupts have a 817 chance to run. The current stack trace is displayed upon detection 818 and the system will stay locked up. 819 820config BOOTPARAM_HARDLOCKUP_PANIC 821 bool "Panic (Reboot) On Hard Lockups" 822 depends on HARDLOCKUP_DETECTOR 823 help 824 Say Y here to enable the kernel to panic on "hard lockups", 825 which are bugs that cause the kernel to loop in kernel 826 mode with interrupts disabled for more than 10 seconds (configurable 827 using the watchdog_thresh sysctl). 828 829 Say N if unsure. 830 831config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 832 int 833 depends on HARDLOCKUP_DETECTOR 834 range 0 1 835 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 836 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 837 838config BOOTPARAM_SOFTLOCKUP_PANIC 839 bool "Panic (Reboot) On Soft Lockups" 840 depends on SOFTLOCKUP_DETECTOR 841 help 842 Say Y here to enable the kernel to panic on "soft lockups", 843 which are bugs that cause the kernel to loop in kernel 844 mode for more than 20 seconds (configurable using the watchdog_thresh 845 sysctl), without giving other tasks a chance to run. 846 847 The panic can be used in combination with panic_timeout, 848 to cause the system to reboot automatically after a 849 lockup has been detected. This feature is useful for 850 high-availability systems that have uptime guarantees and 851 where a lockup must be resolved ASAP. 852 853 Say N if unsure. 854 855config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 856 int 857 depends on SOFTLOCKUP_DETECTOR 858 range 0 1 859 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 860 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 861 862config DETECT_HUNG_TASK 863 bool "Detect Hung Tasks" 864 depends on DEBUG_KERNEL 865 default SOFTLOCKUP_DETECTOR 866 help 867 Say Y here to enable the kernel to detect "hung tasks", 868 which are bugs that cause the task to be stuck in 869 uninterruptible "D" state indefinitely. 870 871 When a hung task is detected, the kernel will print the 872 current stack trace (which you should report), but the 873 task will stay in uninterruptible state. If lockdep is 874 enabled then all held locks will also be reported. This 875 feature has negligible overhead. 876 877config DEFAULT_HUNG_TASK_TIMEOUT 878 int "Default timeout for hung task detection (in seconds)" 879 depends on DETECT_HUNG_TASK 880 default 120 881 help 882 This option controls the default timeout (in seconds) used 883 to determine when a task has become non-responsive and should 884 be considered hung. 885 886 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 887 sysctl or by writing a value to 888 /proc/sys/kernel/hung_task_timeout_secs. 889 890 A timeout of 0 disables the check. The default is two minutes. 891 Keeping the default should be fine in most cases. 892 893config BOOTPARAM_HUNG_TASK_PANIC 894 bool "Panic (Reboot) On Hung Tasks" 895 depends on DETECT_HUNG_TASK 896 help 897 Say Y here to enable the kernel to panic on "hung tasks", 898 which are bugs that cause the kernel to leave a task stuck 899 in uninterruptible "D" state. 900 901 The panic can be used in combination with panic_timeout, 902 to cause the system to reboot automatically after a 903 hung task has been detected. This feature is useful for 904 high-availability systems that have uptime guarantees and 905 where a hung tasks must be resolved ASAP. 906 907 Say N if unsure. 908 909config BOOTPARAM_HUNG_TASK_PANIC_VALUE 910 int 911 depends on DETECT_HUNG_TASK 912 range 0 1 913 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 914 default 1 if BOOTPARAM_HUNG_TASK_PANIC 915 916config WQ_WATCHDOG 917 bool "Detect Workqueue Stalls" 918 depends on DEBUG_KERNEL 919 help 920 Say Y here to enable stall detection on workqueues. If a 921 worker pool doesn't make forward progress on a pending work 922 item for over a given amount of time, 30s by default, a 923 warning message is printed along with dump of workqueue 924 state. This can be configured through kernel parameter 925 "workqueue.watchdog_thresh" and its sysfs counterpart. 926 927endmenu # "Debug lockups and hangs" 928 929config PANIC_ON_OOPS 930 bool "Panic on Oops" 931 help 932 Say Y here to enable the kernel to panic when it oopses. This 933 has the same effect as setting oops=panic on the kernel command 934 line. 935 936 This feature is useful to ensure that the kernel does not do 937 anything erroneous after an oops which could result in data 938 corruption or other issues. 939 940 Say N if unsure. 941 942config PANIC_ON_OOPS_VALUE 943 int 944 range 0 1 945 default 0 if !PANIC_ON_OOPS 946 default 1 if PANIC_ON_OOPS 947 948config PANIC_TIMEOUT 949 int "panic timeout" 950 default 0 951 help 952 Set the timeout value (in seconds) until a reboot occurs when the 953 the kernel panics. If n = 0, then we wait forever. A timeout 954 value n > 0 will wait n seconds before rebooting, while a timeout 955 value n < 0 will reboot immediately. 956 957config SCHED_DEBUG 958 bool "Collect scheduler debugging info" 959 depends on DEBUG_KERNEL && PROC_FS 960 default y 961 help 962 If you say Y here, the /proc/sched_debug file will be provided 963 that can help debug the scheduler. The runtime overhead of this 964 option is minimal. 965 966config SCHED_INFO 967 bool 968 default n 969 970config SCHEDSTATS 971 bool "Collect scheduler statistics" 972 depends on DEBUG_KERNEL && PROC_FS 973 select SCHED_INFO 974 help 975 If you say Y here, additional code will be inserted into the 976 scheduler and related routines to collect statistics about 977 scheduler behavior and provide them in /proc/schedstat. These 978 stats may be useful for both tuning and debugging the scheduler 979 If you aren't debugging the scheduler or trying to tune a specific 980 application, you can say N to avoid the very slight overhead 981 this adds. 982 983config SCHED_STACK_END_CHECK 984 bool "Detect stack corruption on calls to schedule()" 985 depends on DEBUG_KERNEL 986 default n 987 help 988 This option checks for a stack overrun on calls to schedule(). 989 If the stack end location is found to be over written always panic as 990 the content of the corrupted region can no longer be trusted. 991 This is to ensure no erroneous behaviour occurs which could result in 992 data corruption or a sporadic crash at a later stage once the region 993 is examined. The runtime overhead introduced is minimal. 994 995config DEBUG_TIMEKEEPING 996 bool "Enable extra timekeeping sanity checking" 997 help 998 This option will enable additional timekeeping sanity checks 999 which may be helpful when diagnosing issues where timekeeping 1000 problems are suspected. 1001 1002 This may include checks in the timekeeping hotpaths, so this 1003 option may have a (very small) performance impact to some 1004 workloads. 1005 1006 If unsure, say N. 1007 1008config DEBUG_PREEMPT 1009 bool "Debug preemptible kernel" 1010 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 1011 default y 1012 help 1013 If you say Y here then the kernel will use a debug variant of the 1014 commonly used smp_processor_id() function and will print warnings 1015 if kernel code uses it in a preemption-unsafe way. Also, the kernel 1016 will detect preemption count underflows. 1017 1018menu "Lock Debugging (spinlocks, mutexes, etc...)" 1019 1020config DEBUG_RT_MUTEXES 1021 bool "RT Mutex debugging, deadlock detection" 1022 depends on DEBUG_KERNEL && RT_MUTEXES 1023 help 1024 This allows rt mutex semantics violations and rt mutex related 1025 deadlocks (lockups) to be detected and reported automatically. 1026 1027config DEBUG_SPINLOCK 1028 bool "Spinlock and rw-lock debugging: basic checks" 1029 depends on DEBUG_KERNEL 1030 select UNINLINE_SPIN_UNLOCK 1031 help 1032 Say Y here and build SMP to catch missing spinlock initialization 1033 and certain other kinds of spinlock errors commonly made. This is 1034 best used in conjunction with the NMI watchdog so that spinlock 1035 deadlocks are also debuggable. 1036 1037config DEBUG_MUTEXES 1038 bool "Mutex debugging: basic checks" 1039 depends on DEBUG_KERNEL 1040 help 1041 This feature allows mutex semantics violations to be detected and 1042 reported. 1043 1044config DEBUG_WW_MUTEX_SLOWPATH 1045 bool "Wait/wound mutex debugging: Slowpath testing" 1046 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1047 select DEBUG_LOCK_ALLOC 1048 select DEBUG_SPINLOCK 1049 select DEBUG_MUTEXES 1050 help 1051 This feature enables slowpath testing for w/w mutex users by 1052 injecting additional -EDEADLK wound/backoff cases. Together with 1053 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 1054 will test all possible w/w mutex interface abuse with the 1055 exception of simply not acquiring all the required locks. 1056 Note that this feature can introduce significant overhead, so 1057 it really should not be enabled in a production or distro kernel, 1058 even a debug kernel. If you are a driver writer, enable it. If 1059 you are a distro, do not. 1060 1061config DEBUG_LOCK_ALLOC 1062 bool "Lock debugging: detect incorrect freeing of live locks" 1063 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1064 select DEBUG_SPINLOCK 1065 select DEBUG_MUTEXES 1066 select DEBUG_RT_MUTEXES if RT_MUTEXES 1067 select LOCKDEP 1068 help 1069 This feature will check whether any held lock (spinlock, rwlock, 1070 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1071 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1072 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1073 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1074 held during task exit. 1075 1076config PROVE_LOCKING 1077 bool "Lock debugging: prove locking correctness" 1078 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1079 select LOCKDEP 1080 select DEBUG_SPINLOCK 1081 select DEBUG_MUTEXES 1082 select DEBUG_RT_MUTEXES if RT_MUTEXES 1083 select DEBUG_LOCK_ALLOC 1084 select TRACE_IRQFLAGS 1085 default n 1086 help 1087 This feature enables the kernel to prove that all locking 1088 that occurs in the kernel runtime is mathematically 1089 correct: that under no circumstance could an arbitrary (and 1090 not yet triggered) combination of observed locking 1091 sequences (on an arbitrary number of CPUs, running an 1092 arbitrary number of tasks and interrupt contexts) cause a 1093 deadlock. 1094 1095 In short, this feature enables the kernel to report locking 1096 related deadlocks before they actually occur. 1097 1098 The proof does not depend on how hard and complex a 1099 deadlock scenario would be to trigger: how many 1100 participant CPUs, tasks and irq-contexts would be needed 1101 for it to trigger. The proof also does not depend on 1102 timing: if a race and a resulting deadlock is possible 1103 theoretically (no matter how unlikely the race scenario 1104 is), it will be proven so and will immediately be 1105 reported by the kernel (once the event is observed that 1106 makes the deadlock theoretically possible). 1107 1108 If a deadlock is impossible (i.e. the locking rules, as 1109 observed by the kernel, are mathematically correct), the 1110 kernel reports nothing. 1111 1112 NOTE: this feature can also be enabled for rwlocks, mutexes 1113 and rwsems - in which case all dependencies between these 1114 different locking variants are observed and mapped too, and 1115 the proof of observed correctness is also maintained for an 1116 arbitrary combination of these separate locking variants. 1117 1118 For more details, see Documentation/locking/lockdep-design.txt. 1119 1120config LOCKDEP 1121 bool 1122 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1123 select STACKTRACE 1124 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE 1125 select KALLSYMS 1126 select KALLSYMS_ALL 1127 1128config LOCKDEP_SMALL 1129 bool 1130 1131config LOCK_STAT 1132 bool "Lock usage statistics" 1133 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1134 select LOCKDEP 1135 select DEBUG_SPINLOCK 1136 select DEBUG_MUTEXES 1137 select DEBUG_RT_MUTEXES if RT_MUTEXES 1138 select DEBUG_LOCK_ALLOC 1139 default n 1140 help 1141 This feature enables tracking lock contention points 1142 1143 For more details, see Documentation/locking/lockstat.txt 1144 1145 This also enables lock events required by "perf lock", 1146 subcommand of perf. 1147 If you want to use "perf lock", you also need to turn on 1148 CONFIG_EVENT_TRACING. 1149 1150 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1151 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1152 1153config DEBUG_LOCKDEP 1154 bool "Lock dependency engine debugging" 1155 depends on DEBUG_KERNEL && LOCKDEP 1156 help 1157 If you say Y here, the lock dependency engine will do 1158 additional runtime checks to debug itself, at the price 1159 of more runtime overhead. 1160 1161config DEBUG_ATOMIC_SLEEP 1162 bool "Sleep inside atomic section checking" 1163 select PREEMPT_COUNT 1164 depends on DEBUG_KERNEL 1165 help 1166 If you say Y here, various routines which may sleep will become very 1167 noisy if they are called inside atomic sections: when a spinlock is 1168 held, inside an rcu read side critical section, inside preempt disabled 1169 sections, inside an interrupt, etc... 1170 1171config DEBUG_LOCKING_API_SELFTESTS 1172 bool "Locking API boot-time self-tests" 1173 depends on DEBUG_KERNEL 1174 help 1175 Say Y here if you want the kernel to run a short self-test during 1176 bootup. The self-test checks whether common types of locking bugs 1177 are detected by debugging mechanisms or not. (if you disable 1178 lock debugging then those bugs wont be detected of course.) 1179 The following locking APIs are covered: spinlocks, rwlocks, 1180 mutexes and rwsems. 1181 1182config LOCK_TORTURE_TEST 1183 tristate "torture tests for locking" 1184 depends on DEBUG_KERNEL 1185 select TORTURE_TEST 1186 default n 1187 help 1188 This option provides a kernel module that runs torture tests 1189 on kernel locking primitives. The kernel module may be built 1190 after the fact on the running kernel to be tested, if desired. 1191 1192 Say Y here if you want kernel locking-primitive torture tests 1193 to be built into the kernel. 1194 Say M if you want these torture tests to build as a module. 1195 Say N if you are unsure. 1196 1197config WW_MUTEX_SELFTEST 1198 tristate "Wait/wound mutex selftests" 1199 help 1200 This option provides a kernel module that runs tests on the 1201 on the struct ww_mutex locking API. 1202 1203 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction 1204 with this test harness. 1205 1206 Say M if you want these self tests to build as a module. 1207 Say N if you are unsure. 1208 1209endmenu # lock debugging 1210 1211config TRACE_IRQFLAGS 1212 bool 1213 help 1214 Enables hooks to interrupt enabling and disabling for 1215 either tracing or lock debugging. 1216 1217config STACKTRACE 1218 bool "Stack backtrace support" 1219 depends on STACKTRACE_SUPPORT 1220 help 1221 This option causes the kernel to create a /proc/pid/stack for 1222 every process, showing its current stack trace. 1223 It is also used by various kernel debugging features that require 1224 stack trace generation. 1225 1226config DEBUG_KOBJECT 1227 bool "kobject debugging" 1228 depends on DEBUG_KERNEL 1229 help 1230 If you say Y here, some extra kobject debugging messages will be sent 1231 to the syslog. 1232 1233config DEBUG_KOBJECT_RELEASE 1234 bool "kobject release debugging" 1235 depends on DEBUG_OBJECTS_TIMERS 1236 help 1237 kobjects are reference counted objects. This means that their 1238 last reference count put is not predictable, and the kobject can 1239 live on past the point at which a driver decides to drop it's 1240 initial reference to the kobject gained on allocation. An 1241 example of this would be a struct device which has just been 1242 unregistered. 1243 1244 However, some buggy drivers assume that after such an operation, 1245 the memory backing the kobject can be immediately freed. This 1246 goes completely against the principles of a refcounted object. 1247 1248 If you say Y here, the kernel will delay the release of kobjects 1249 on the last reference count to improve the visibility of this 1250 kind of kobject release bug. 1251 1252config HAVE_DEBUG_BUGVERBOSE 1253 bool 1254 1255config DEBUG_BUGVERBOSE 1256 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1257 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1258 default y 1259 help 1260 Say Y here to make BUG() panics output the file name and line number 1261 of the BUG call as well as the EIP and oops trace. This aids 1262 debugging but costs about 70-100K of memory. 1263 1264config DEBUG_LIST 1265 bool "Debug linked list manipulation" 1266 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION 1267 help 1268 Enable this to turn on extended checks in the linked-list 1269 walking routines. 1270 1271 If unsure, say N. 1272 1273config DEBUG_PI_LIST 1274 bool "Debug priority linked list manipulation" 1275 depends on DEBUG_KERNEL 1276 help 1277 Enable this to turn on extended checks in the priority-ordered 1278 linked-list (plist) walking routines. This checks the entire 1279 list multiple times during each manipulation. 1280 1281 If unsure, say N. 1282 1283config DEBUG_SG 1284 bool "Debug SG table operations" 1285 depends on DEBUG_KERNEL 1286 help 1287 Enable this to turn on checks on scatter-gather tables. This can 1288 help find problems with drivers that do not properly initialize 1289 their sg tables. 1290 1291 If unsure, say N. 1292 1293config DEBUG_NOTIFIERS 1294 bool "Debug notifier call chains" 1295 depends on DEBUG_KERNEL 1296 help 1297 Enable this to turn on sanity checking for notifier call chains. 1298 This is most useful for kernel developers to make sure that 1299 modules properly unregister themselves from notifier chains. 1300 This is a relatively cheap check but if you care about maximum 1301 performance, say N. 1302 1303config DEBUG_CREDENTIALS 1304 bool "Debug credential management" 1305 depends on DEBUG_KERNEL 1306 help 1307 Enable this to turn on some debug checking for credential 1308 management. The additional code keeps track of the number of 1309 pointers from task_structs to any given cred struct, and checks to 1310 see that this number never exceeds the usage count of the cred 1311 struct. 1312 1313 Furthermore, if SELinux is enabled, this also checks that the 1314 security pointer in the cred struct is never seen to be invalid. 1315 1316 If unsure, say N. 1317 1318source "kernel/rcu/Kconfig.debug" 1319 1320config DEBUG_WQ_FORCE_RR_CPU 1321 bool "Force round-robin CPU selection for unbound work items" 1322 depends on DEBUG_KERNEL 1323 default n 1324 help 1325 Workqueue used to implicitly guarantee that work items queued 1326 without explicit CPU specified are put on the local CPU. This 1327 guarantee is no longer true and while local CPU is still 1328 preferred work items may be put on foreign CPUs. Kernel 1329 parameter "workqueue.debug_force_rr_cpu" is added to force 1330 round-robin CPU selection to flush out usages which depend on the 1331 now broken guarantee. This config option enables the debug 1332 feature by default. When enabled, memory and cache locality will 1333 be impacted. 1334 1335config DEBUG_BLOCK_EXT_DEVT 1336 bool "Force extended block device numbers and spread them" 1337 depends on DEBUG_KERNEL 1338 depends on BLOCK 1339 default n 1340 help 1341 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1342 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1343 YOU ARE DOING. Distros, please enable this and fix whatever 1344 is broken. 1345 1346 Conventionally, block device numbers are allocated from 1347 predetermined contiguous area. However, extended block area 1348 may introduce non-contiguous block device numbers. This 1349 option forces most block device numbers to be allocated from 1350 the extended space and spreads them to discover kernel or 1351 userland code paths which assume predetermined contiguous 1352 device number allocation. 1353 1354 Note that turning on this debug option shuffles all the 1355 device numbers for all IDE and SCSI devices including libata 1356 ones, so root partition specified using device number 1357 directly (via rdev or root=MAJ:MIN) won't work anymore. 1358 Textual device names (root=/dev/sdXn) will continue to work. 1359 1360 Say N if you are unsure. 1361 1362config CPU_HOTPLUG_STATE_CONTROL 1363 bool "Enable CPU hotplug state control" 1364 depends on DEBUG_KERNEL 1365 depends on HOTPLUG_CPU 1366 default n 1367 help 1368 Allows to write steps between "offline" and "online" to the CPUs 1369 sysfs target file so states can be stepped granular. This is a debug 1370 option for now as the hotplug machinery cannot be stopped and 1371 restarted at arbitrary points yet. 1372 1373 Say N if your are unsure. 1374 1375config NOTIFIER_ERROR_INJECTION 1376 tristate "Notifier error injection" 1377 depends on DEBUG_KERNEL 1378 select DEBUG_FS 1379 help 1380 This option provides the ability to inject artificial errors to 1381 specified notifier chain callbacks. It is useful to test the error 1382 handling of notifier call chain failures. 1383 1384 Say N if unsure. 1385 1386config PM_NOTIFIER_ERROR_INJECT 1387 tristate "PM notifier error injection module" 1388 depends on PM && NOTIFIER_ERROR_INJECTION 1389 default m if PM_DEBUG 1390 help 1391 This option provides the ability to inject artificial errors to 1392 PM notifier chain callbacks. It is controlled through debugfs 1393 interface /sys/kernel/debug/notifier-error-inject/pm 1394 1395 If the notifier call chain should be failed with some events 1396 notified, write the error code to "actions/<notifier event>/error". 1397 1398 Example: Inject PM suspend error (-12 = -ENOMEM) 1399 1400 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1401 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1402 # echo mem > /sys/power/state 1403 bash: echo: write error: Cannot allocate memory 1404 1405 To compile this code as a module, choose M here: the module will 1406 be called pm-notifier-error-inject. 1407 1408 If unsure, say N. 1409 1410config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1411 tristate "OF reconfig notifier error injection module" 1412 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1413 help 1414 This option provides the ability to inject artificial errors to 1415 OF reconfig notifier chain callbacks. It is controlled 1416 through debugfs interface under 1417 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1418 1419 If the notifier call chain should be failed with some events 1420 notified, write the error code to "actions/<notifier event>/error". 1421 1422 To compile this code as a module, choose M here: the module will 1423 be called of-reconfig-notifier-error-inject. 1424 1425 If unsure, say N. 1426 1427config NETDEV_NOTIFIER_ERROR_INJECT 1428 tristate "Netdev notifier error injection module" 1429 depends on NET && NOTIFIER_ERROR_INJECTION 1430 help 1431 This option provides the ability to inject artificial errors to 1432 netdevice notifier chain callbacks. It is controlled through debugfs 1433 interface /sys/kernel/debug/notifier-error-inject/netdev 1434 1435 If the notifier call chain should be failed with some events 1436 notified, write the error code to "actions/<notifier event>/error". 1437 1438 Example: Inject netdevice mtu change error (-22 = -EINVAL) 1439 1440 # cd /sys/kernel/debug/notifier-error-inject/netdev 1441 # echo -22 > actions/NETDEV_CHANGEMTU/error 1442 # ip link set eth0 mtu 1024 1443 RTNETLINK answers: Invalid argument 1444 1445 To compile this code as a module, choose M here: the module will 1446 be called netdev-notifier-error-inject. 1447 1448 If unsure, say N. 1449 1450config FAULT_INJECTION 1451 bool "Fault-injection framework" 1452 depends on DEBUG_KERNEL 1453 help 1454 Provide fault-injection framework. 1455 For more details, see Documentation/fault-injection/. 1456 1457config FAILSLAB 1458 bool "Fault-injection capability for kmalloc" 1459 depends on FAULT_INJECTION 1460 depends on SLAB || SLUB 1461 help 1462 Provide fault-injection capability for kmalloc. 1463 1464config FAIL_PAGE_ALLOC 1465 bool "Fault-injection capabilitiy for alloc_pages()" 1466 depends on FAULT_INJECTION 1467 help 1468 Provide fault-injection capability for alloc_pages(). 1469 1470config FAIL_MAKE_REQUEST 1471 bool "Fault-injection capability for disk IO" 1472 depends on FAULT_INJECTION && BLOCK 1473 help 1474 Provide fault-injection capability for disk IO. 1475 1476config FAIL_IO_TIMEOUT 1477 bool "Fault-injection capability for faking disk interrupts" 1478 depends on FAULT_INJECTION && BLOCK 1479 help 1480 Provide fault-injection capability on end IO handling. This 1481 will make the block layer "forget" an interrupt as configured, 1482 thus exercising the error handling. 1483 1484 Only works with drivers that use the generic timeout handling, 1485 for others it wont do anything. 1486 1487config FAIL_MMC_REQUEST 1488 bool "Fault-injection capability for MMC IO" 1489 depends on FAULT_INJECTION_DEBUG_FS && MMC 1490 help 1491 Provide fault-injection capability for MMC IO. 1492 This will make the mmc core return data errors. This is 1493 useful to test the error handling in the mmc block device 1494 and to test how the mmc host driver handles retries from 1495 the block device. 1496 1497config FAIL_FUTEX 1498 bool "Fault-injection capability for futexes" 1499 select DEBUG_FS 1500 depends on FAULT_INJECTION && FUTEX 1501 help 1502 Provide fault-injection capability for futexes. 1503 1504config FAULT_INJECTION_DEBUG_FS 1505 bool "Debugfs entries for fault-injection capabilities" 1506 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1507 help 1508 Enable configuration of fault-injection capabilities via debugfs. 1509 1510config FAULT_INJECTION_STACKTRACE_FILTER 1511 bool "stacktrace filter for fault-injection capabilities" 1512 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1513 depends on !X86_64 1514 select STACKTRACE 1515 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1516 help 1517 Provide stacktrace filter for fault-injection capabilities 1518 1519config LATENCYTOP 1520 bool "Latency measuring infrastructure" 1521 depends on DEBUG_KERNEL 1522 depends on STACKTRACE_SUPPORT 1523 depends on PROC_FS 1524 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1525 select KALLSYMS 1526 select KALLSYMS_ALL 1527 select STACKTRACE 1528 select SCHEDSTATS 1529 select SCHED_DEBUG 1530 help 1531 Enable this option if you want to use the LatencyTOP tool 1532 to find out which userspace is blocking on what kernel operations. 1533 1534source kernel/trace/Kconfig 1535 1536menu "Runtime Testing" 1537 1538config LKDTM 1539 tristate "Linux Kernel Dump Test Tool Module" 1540 depends on DEBUG_FS 1541 depends on BLOCK 1542 default n 1543 help 1544 This module enables testing of the different dumping mechanisms by 1545 inducing system failures at predefined crash points. 1546 If you don't need it: say N 1547 Choose M here to compile this code as a module. The module will be 1548 called lkdtm. 1549 1550 Documentation on how to use the module can be found in 1551 Documentation/fault-injection/provoke-crashes.txt 1552 1553config TEST_LIST_SORT 1554 tristate "Linked list sorting test" 1555 depends on DEBUG_KERNEL || m 1556 help 1557 Enable this to turn on 'list_sort()' function test. This test is 1558 executed only once during system boot (so affects only boot time), 1559 or at module load time. 1560 1561 If unsure, say N. 1562 1563config TEST_SORT 1564 tristate "Array-based sort test" 1565 depends on DEBUG_KERNEL || m 1566 help 1567 This option enables the self-test function of 'sort()' at boot, 1568 or at module load time. 1569 1570 If unsure, say N. 1571 1572config KPROBES_SANITY_TEST 1573 bool "Kprobes sanity tests" 1574 depends on DEBUG_KERNEL 1575 depends on KPROBES 1576 default n 1577 help 1578 This option provides for testing basic kprobes functionality on 1579 boot. A sample kprobe, jprobe and kretprobe are inserted and 1580 verified for functionality. 1581 1582 Say N if you are unsure. 1583 1584config BACKTRACE_SELF_TEST 1585 tristate "Self test for the backtrace code" 1586 depends on DEBUG_KERNEL 1587 default n 1588 help 1589 This option provides a kernel module that can be used to test 1590 the kernel stack backtrace code. This option is not useful 1591 for distributions or general kernels, but only for kernel 1592 developers working on architecture code. 1593 1594 Note that if you want to also test saved backtraces, you will 1595 have to enable STACKTRACE as well. 1596 1597 Say N if you are unsure. 1598 1599config RBTREE_TEST 1600 tristate "Red-Black tree test" 1601 depends on DEBUG_KERNEL 1602 help 1603 A benchmark measuring the performance of the rbtree library. 1604 Also includes rbtree invariant checks. 1605 1606config INTERVAL_TREE_TEST 1607 tristate "Interval tree test" 1608 depends on DEBUG_KERNEL 1609 select INTERVAL_TREE 1610 help 1611 A benchmark measuring the performance of the interval tree library 1612 1613config PERCPU_TEST 1614 tristate "Per cpu operations test" 1615 depends on m && DEBUG_KERNEL 1616 help 1617 Enable this option to build test module which validates per-cpu 1618 operations. 1619 1620 If unsure, say N. 1621 1622config ATOMIC64_SELFTEST 1623 tristate "Perform an atomic64_t self-test" 1624 help 1625 Enable this option to test the atomic64_t functions at boot or 1626 at module load time. 1627 1628 If unsure, say N. 1629 1630config ASYNC_RAID6_TEST 1631 tristate "Self test for hardware accelerated raid6 recovery" 1632 depends on ASYNC_RAID6_RECOV 1633 select ASYNC_MEMCPY 1634 ---help--- 1635 This is a one-shot self test that permutes through the 1636 recovery of all the possible two disk failure scenarios for a 1637 N-disk array. Recovery is performed with the asynchronous 1638 raid6 recovery routines, and will optionally use an offload 1639 engine if one is available. 1640 1641 If unsure, say N. 1642 1643config TEST_HEXDUMP 1644 tristate "Test functions located in the hexdump module at runtime" 1645 1646config TEST_STRING_HELPERS 1647 tristate "Test functions located in the string_helpers module at runtime" 1648 1649config TEST_KSTRTOX 1650 tristate "Test kstrto*() family of functions at runtime" 1651 1652config TEST_PRINTF 1653 tristate "Test printf() family of functions at runtime" 1654 1655config TEST_BITMAP 1656 tristate "Test bitmap_*() family of functions at runtime" 1657 default n 1658 help 1659 Enable this option to test the bitmap functions at boot. 1660 1661 If unsure, say N. 1662 1663config TEST_UUID 1664 tristate "Test functions located in the uuid module at runtime" 1665 1666config TEST_RHASHTABLE 1667 tristate "Perform selftest on resizable hash table" 1668 default n 1669 help 1670 Enable this option to test the rhashtable functions at boot. 1671 1672 If unsure, say N. 1673 1674config TEST_HASH 1675 tristate "Perform selftest on hash functions" 1676 default n 1677 help 1678 Enable this option to test the kernel's integer (<linux/hash.h>), 1679 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>) 1680 hash functions on boot (or module load). 1681 1682 This is intended to help people writing architecture-specific 1683 optimized versions. If unsure, say N. 1684 1685config TEST_PARMAN 1686 tristate "Perform selftest on priority array manager" 1687 default n 1688 depends on PARMAN 1689 help 1690 Enable this option to test priority array manager on boot 1691 (or module load). 1692 1693 If unsure, say N. 1694 1695endmenu # runtime tests 1696 1697config PROVIDE_OHCI1394_DMA_INIT 1698 bool "Remote debugging over FireWire early on boot" 1699 depends on PCI && X86 1700 help 1701 If you want to debug problems which hang or crash the kernel early 1702 on boot and the crashing machine has a FireWire port, you can use 1703 this feature to remotely access the memory of the crashed machine 1704 over FireWire. This employs remote DMA as part of the OHCI1394 1705 specification which is now the standard for FireWire controllers. 1706 1707 With remote DMA, you can monitor the printk buffer remotely using 1708 firescope and access all memory below 4GB using fireproxy from gdb. 1709 Even controlling a kernel debugger is possible using remote DMA. 1710 1711 Usage: 1712 1713 If ohci1394_dma=early is used as boot parameter, it will initialize 1714 all OHCI1394 controllers which are found in the PCI config space. 1715 1716 As all changes to the FireWire bus such as enabling and disabling 1717 devices cause a bus reset and thereby disable remote DMA for all 1718 devices, be sure to have the cable plugged and FireWire enabled on 1719 the debugging host before booting the debug target for debugging. 1720 1721 This code (~1k) is freed after boot. By then, the firewire stack 1722 in charge of the OHCI-1394 controllers should be used instead. 1723 1724 See Documentation/debugging-via-ohci1394.txt for more information. 1725 1726config DMA_API_DEBUG 1727 bool "Enable debugging of DMA-API usage" 1728 depends on HAVE_DMA_API_DEBUG 1729 help 1730 Enable this option to debug the use of the DMA API by device drivers. 1731 With this option you will be able to detect common bugs in device 1732 drivers like double-freeing of DMA mappings or freeing mappings that 1733 were never allocated. 1734 1735 This also attempts to catch cases where a page owned by DMA is 1736 accessed by the cpu in a way that could cause data corruption. For 1737 example, this enables cow_user_page() to check that the source page is 1738 not undergoing DMA. 1739 1740 This option causes a performance degradation. Use only if you want to 1741 debug device drivers and dma interactions. 1742 1743 If unsure, say N. 1744 1745config TEST_LKM 1746 tristate "Test module loading with 'hello world' module" 1747 default n 1748 depends on m 1749 help 1750 This builds the "test_module" module that emits "Hello, world" 1751 on printk when loaded. It is designed to be used for basic 1752 evaluation of the module loading subsystem (for example when 1753 validating module verification). It lacks any extra dependencies, 1754 and will not normally be loaded by the system unless explicitly 1755 requested by name. 1756 1757 If unsure, say N. 1758 1759config TEST_USER_COPY 1760 tristate "Test user/kernel boundary protections" 1761 default n 1762 depends on m 1763 help 1764 This builds the "test_user_copy" module that runs sanity checks 1765 on the copy_to/from_user infrastructure, making sure basic 1766 user/kernel boundary testing is working. If it fails to load, 1767 a regression has been detected in the user/kernel memory boundary 1768 protections. 1769 1770 If unsure, say N. 1771 1772config TEST_BPF 1773 tristate "Test BPF filter functionality" 1774 default n 1775 depends on m && NET 1776 help 1777 This builds the "test_bpf" module that runs various test vectors 1778 against the BPF interpreter or BPF JIT compiler depending on the 1779 current setting. This is in particular useful for BPF JIT compiler 1780 development, but also to run regression tests against changes in 1781 the interpreter code. It also enables test stubs for eBPF maps and 1782 verifier used by user space verifier testsuite. 1783 1784 If unsure, say N. 1785 1786config TEST_FIRMWARE 1787 tristate "Test firmware loading via userspace interface" 1788 default n 1789 depends on FW_LOADER 1790 help 1791 This builds the "test_firmware" module that creates a userspace 1792 interface for testing firmware loading. This can be used to 1793 control the triggering of firmware loading without needing an 1794 actual firmware-using device. The contents can be rechecked by 1795 userspace. 1796 1797 If unsure, say N. 1798 1799config TEST_SYSCTL 1800 tristate "sysctl test driver" 1801 default n 1802 depends on PROC_SYSCTL 1803 help 1804 This builds the "test_sysctl" module. This driver enables to test the 1805 proc sysctl interfaces available to drivers safely without affecting 1806 production knobs which might alter system functionality. 1807 1808 If unsure, say N. 1809 1810config TEST_UDELAY 1811 tristate "udelay test driver" 1812 default n 1813 help 1814 This builds the "udelay_test" module that helps to make sure 1815 that udelay() is working properly. 1816 1817 If unsure, say N. 1818 1819config MEMTEST 1820 bool "Memtest" 1821 depends on HAVE_MEMBLOCK 1822 ---help--- 1823 This option adds a kernel parameter 'memtest', which allows memtest 1824 to be set. 1825 memtest=0, mean disabled; -- default 1826 memtest=1, mean do 1 test pattern; 1827 ... 1828 memtest=17, mean do 17 test patterns. 1829 If you are unsure how to answer this question, answer N. 1830 1831config TEST_STATIC_KEYS 1832 tristate "Test static keys" 1833 default n 1834 depends on m 1835 help 1836 Test the static key interfaces. 1837 1838 If unsure, say N. 1839 1840config BUG_ON_DATA_CORRUPTION 1841 bool "Trigger a BUG when data corruption is detected" 1842 select DEBUG_LIST 1843 help 1844 Select this option if the kernel should BUG when it encounters 1845 data corruption in kernel memory structures when they get checked 1846 for validity. 1847 1848 If unsure, say N. 1849 1850config TEST_KMOD 1851 tristate "kmod stress tester" 1852 default n 1853 depends on m 1854 depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS 1855 depends on NETDEVICES && NET_CORE && INET # for TUN 1856 select TEST_LKM 1857 select XFS_FS 1858 select TUN 1859 select BTRFS_FS 1860 help 1861 Test the kernel's module loading mechanism: kmod. kmod implements 1862 support to load modules using the Linux kernel's usermode helper. 1863 This test provides a series of tests against kmod. 1864 1865 Although technically you can either build test_kmod as a module or 1866 into the kernel we disallow building it into the kernel since 1867 it stress tests request_module() and this will very likely cause 1868 some issues by taking over precious threads available from other 1869 module load requests, ultimately this could be fatal. 1870 1871 To run tests run: 1872 1873 tools/testing/selftests/kmod/kmod.sh --help 1874 1875 If unsure, say N. 1876 1877source "samples/Kconfig" 1878 1879source "lib/Kconfig.kgdb" 1880 1881source "lib/Kconfig.ubsan" 1882 1883config ARCH_HAS_DEVMEM_IS_ALLOWED 1884 bool 1885 1886config STRICT_DEVMEM 1887 bool "Filter access to /dev/mem" 1888 depends on MMU && DEVMEM 1889 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 1890 default y if TILE || PPC 1891 ---help--- 1892 If this option is disabled, you allow userspace (root) access to all 1893 of memory, including kernel and userspace memory. Accidental 1894 access to this is obviously disastrous, but specific access can 1895 be used by people debugging the kernel. Note that with PAT support 1896 enabled, even in this case there are restrictions on /dev/mem 1897 use due to the cache aliasing requirements. 1898 1899 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 1900 file only allows userspace access to PCI space and the BIOS code and 1901 data regions. This is sufficient for dosemu and X and all common 1902 users of /dev/mem. 1903 1904 If in doubt, say Y. 1905 1906config IO_STRICT_DEVMEM 1907 bool "Filter I/O access to /dev/mem" 1908 depends on STRICT_DEVMEM 1909 ---help--- 1910 If this option is disabled, you allow userspace (root) access to all 1911 io-memory regardless of whether a driver is actively using that 1912 range. Accidental access to this is obviously disastrous, but 1913 specific access can be used by people debugging kernel drivers. 1914 1915 If this option is switched on, the /dev/mem file only allows 1916 userspace access to *idle* io-memory ranges (see /proc/iomem) This 1917 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 1918 if the driver using a given range cannot be disabled. 1919 1920 If in doubt, say Y. 1921