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 This is also a prerequisite for generation of ORC unwind data, which 378 is needed for CONFIG_ORC_UNWINDER. 379 380 For more information, see 381 tools/objtool/Documentation/stack-validation.txt. 382 383config DEBUG_FORCE_WEAK_PER_CPU 384 bool "Force weak per-cpu definitions" 385 depends on DEBUG_KERNEL 386 help 387 s390 and alpha require percpu variables in modules to be 388 defined weak to work around addressing range issue which 389 puts the following two restrictions on percpu variable 390 definitions. 391 392 1. percpu symbols must be unique whether static or not 393 2. percpu variables can't be defined inside a function 394 395 To ensure that generic code follows the above rules, this 396 option forces all percpu variables to be defined as weak. 397 398endmenu # "Compiler options" 399 400config MAGIC_SYSRQ 401 bool "Magic SysRq key" 402 depends on !UML 403 help 404 If you say Y here, you will have some control over the system even 405 if the system crashes for example during kernel debugging (e.g., you 406 will be able to flush the buffer cache to disk, reboot the system 407 immediately or dump some status information). This is accomplished 408 by pressing various keys while holding SysRq (Alt+PrintScreen). It 409 also works on a serial console (on PC hardware at least), if you 410 send a BREAK and then within 5 seconds a command keypress. The 411 keys are documented in <file:Documentation/admin-guide/sysrq.rst>. 412 Don't say Y unless you really know what this hack does. 413 414config MAGIC_SYSRQ_DEFAULT_ENABLE 415 hex "Enable magic SysRq key functions by default" 416 depends on MAGIC_SYSRQ 417 default 0x1 418 help 419 Specifies which SysRq key functions are enabled by default. 420 This may be set to 1 or 0 to enable or disable them all, or 421 to a bitmask as described in Documentation/admin-guide/sysrq.rst. 422 423config MAGIC_SYSRQ_SERIAL 424 bool "Enable magic SysRq key over serial" 425 depends on MAGIC_SYSRQ 426 default y 427 help 428 Many embedded boards have a disconnected TTL level serial which can 429 generate some garbage that can lead to spurious false sysrq detects. 430 This option allows you to decide whether you want to enable the 431 magic SysRq key. 432 433config DEBUG_KERNEL 434 bool "Kernel debugging" 435 help 436 Say Y here if you are developing drivers or trying to debug and 437 identify kernel problems. 438 439menu "Memory Debugging" 440 441source mm/Kconfig.debug 442 443config DEBUG_OBJECTS 444 bool "Debug object operations" 445 depends on DEBUG_KERNEL 446 help 447 If you say Y here, additional code will be inserted into the 448 kernel to track the life time of various objects and validate 449 the operations on those objects. 450 451config DEBUG_OBJECTS_SELFTEST 452 bool "Debug objects selftest" 453 depends on DEBUG_OBJECTS 454 help 455 This enables the selftest of the object debug code. 456 457config DEBUG_OBJECTS_FREE 458 bool "Debug objects in freed memory" 459 depends on DEBUG_OBJECTS 460 help 461 This enables checks whether a k/v free operation frees an area 462 which contains an object which has not been deactivated 463 properly. This can make kmalloc/kfree-intensive workloads 464 much slower. 465 466config DEBUG_OBJECTS_TIMERS 467 bool "Debug timer objects" 468 depends on DEBUG_OBJECTS 469 help 470 If you say Y here, additional code will be inserted into the 471 timer routines to track the life time of timer objects and 472 validate the timer operations. 473 474config DEBUG_OBJECTS_WORK 475 bool "Debug work objects" 476 depends on DEBUG_OBJECTS 477 help 478 If you say Y here, additional code will be inserted into the 479 work queue routines to track the life time of work objects and 480 validate the work operations. 481 482config DEBUG_OBJECTS_RCU_HEAD 483 bool "Debug RCU callbacks objects" 484 depends on DEBUG_OBJECTS 485 help 486 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 487 488config DEBUG_OBJECTS_PERCPU_COUNTER 489 bool "Debug percpu counter objects" 490 depends on DEBUG_OBJECTS 491 help 492 If you say Y here, additional code will be inserted into the 493 percpu counter routines to track the life time of percpu counter 494 objects and validate the percpu counter operations. 495 496config DEBUG_OBJECTS_ENABLE_DEFAULT 497 int "debug_objects bootup default value (0-1)" 498 range 0 1 499 default "1" 500 depends on DEBUG_OBJECTS 501 help 502 Debug objects boot parameter default value 503 504config DEBUG_SLAB 505 bool "Debug slab memory allocations" 506 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 507 help 508 Say Y here to have the kernel do limited verification on memory 509 allocation as well as poisoning memory on free to catch use of freed 510 memory. This can make kmalloc/kfree-intensive workloads much slower. 511 512config DEBUG_SLAB_LEAK 513 bool "Memory leak debugging" 514 depends on DEBUG_SLAB 515 516config SLUB_DEBUG_ON 517 bool "SLUB debugging on by default" 518 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 519 default n 520 help 521 Boot with debugging on by default. SLUB boots by default with 522 the runtime debug capabilities switched off. Enabling this is 523 equivalent to specifying the "slub_debug" parameter on boot. 524 There is no support for more fine grained debug control like 525 possible with slub_debug=xxx. SLUB debugging may be switched 526 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 527 "slub_debug=-". 528 529config SLUB_STATS 530 default n 531 bool "Enable SLUB performance statistics" 532 depends on SLUB && SYSFS 533 help 534 SLUB statistics are useful to debug SLUBs allocation behavior in 535 order find ways to optimize the allocator. This should never be 536 enabled for production use since keeping statistics slows down 537 the allocator by a few percentage points. The slabinfo command 538 supports the determination of the most active slabs to figure 539 out which slabs are relevant to a particular load. 540 Try running: slabinfo -DA 541 542config HAVE_DEBUG_KMEMLEAK 543 bool 544 545config DEBUG_KMEMLEAK 546 bool "Kernel memory leak detector" 547 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 548 select DEBUG_FS 549 select STACKTRACE if STACKTRACE_SUPPORT 550 select KALLSYMS 551 select CRC32 552 help 553 Say Y here if you want to enable the memory leak 554 detector. The memory allocation/freeing is traced in a way 555 similar to the Boehm's conservative garbage collector, the 556 difference being that the orphan objects are not freed but 557 only shown in /sys/kernel/debug/kmemleak. Enabling this 558 feature will introduce an overhead to memory 559 allocations. See Documentation/dev-tools/kmemleak.rst for more 560 details. 561 562 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 563 of finding leaks due to the slab objects poisoning. 564 565 In order to access the kmemleak file, debugfs needs to be 566 mounted (usually at /sys/kernel/debug). 567 568config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 569 int "Maximum kmemleak early log entries" 570 depends on DEBUG_KMEMLEAK 571 range 200 40000 572 default 400 573 help 574 Kmemleak must track all the memory allocations to avoid 575 reporting false positives. Since memory may be allocated or 576 freed before kmemleak is initialised, an early log buffer is 577 used to store these actions. If kmemleak reports "early log 578 buffer exceeded", please increase this value. 579 580config DEBUG_KMEMLEAK_TEST 581 tristate "Simple test for the kernel memory leak detector" 582 depends on DEBUG_KMEMLEAK && m 583 help 584 This option enables a module that explicitly leaks memory. 585 586 If unsure, say N. 587 588config DEBUG_KMEMLEAK_DEFAULT_OFF 589 bool "Default kmemleak to off" 590 depends on DEBUG_KMEMLEAK 591 help 592 Say Y here to disable kmemleak by default. It can then be enabled 593 on the command line via kmemleak=on. 594 595config DEBUG_STACK_USAGE 596 bool "Stack utilization instrumentation" 597 depends on DEBUG_KERNEL && !IA64 598 help 599 Enables the display of the minimum amount of free stack which each 600 task has ever had available in the sysrq-T and sysrq-P debug output. 601 602 This option will slow down process creation somewhat. 603 604config DEBUG_VM 605 bool "Debug VM" 606 depends on DEBUG_KERNEL 607 help 608 Enable this to turn on extended checks in the virtual-memory system 609 that may impact performance. 610 611 If unsure, say N. 612 613config DEBUG_VM_VMACACHE 614 bool "Debug VMA caching" 615 depends on DEBUG_VM 616 help 617 Enable this to turn on VMA caching debug information. Doing so 618 can cause significant overhead, so only enable it in non-production 619 environments. 620 621 If unsure, say N. 622 623config DEBUG_VM_RB 624 bool "Debug VM red-black trees" 625 depends on DEBUG_VM 626 help 627 Enable VM red-black tree debugging information and extra validations. 628 629 If unsure, say N. 630 631config DEBUG_VM_PGFLAGS 632 bool "Debug page-flags operations" 633 depends on DEBUG_VM 634 help 635 Enables extra validation on page flags operations. 636 637 If unsure, say N. 638 639config ARCH_HAS_DEBUG_VIRTUAL 640 bool 641 642config DEBUG_VIRTUAL 643 bool "Debug VM translations" 644 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL 645 help 646 Enable some costly sanity checks in virtual to page code. This can 647 catch mistakes with virt_to_page() and friends. 648 649 If unsure, say N. 650 651config DEBUG_NOMMU_REGIONS 652 bool "Debug the global anon/private NOMMU mapping region tree" 653 depends on DEBUG_KERNEL && !MMU 654 help 655 This option causes the global tree of anonymous and private mapping 656 regions to be regularly checked for invalid topology. 657 658config DEBUG_MEMORY_INIT 659 bool "Debug memory initialisation" if EXPERT 660 default !EXPERT 661 help 662 Enable this for additional checks during memory initialisation. 663 The sanity checks verify aspects of the VM such as the memory model 664 and other information provided by the architecture. Verbose 665 information will be printed at KERN_DEBUG loglevel depending 666 on the mminit_loglevel= command-line option. 667 668 If unsure, say Y 669 670config MEMORY_NOTIFIER_ERROR_INJECT 671 tristate "Memory hotplug notifier error injection module" 672 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 673 help 674 This option provides the ability to inject artificial errors to 675 memory hotplug notifier chain callbacks. It is controlled through 676 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 677 678 If the notifier call chain should be failed with some events 679 notified, write the error code to "actions/<notifier event>/error". 680 681 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 682 683 # cd /sys/kernel/debug/notifier-error-inject/memory 684 # echo -12 > actions/MEM_GOING_OFFLINE/error 685 # echo offline > /sys/devices/system/memory/memoryXXX/state 686 bash: echo: write error: Cannot allocate memory 687 688 To compile this code as a module, choose M here: the module will 689 be called memory-notifier-error-inject. 690 691 If unsure, say N. 692 693config DEBUG_PER_CPU_MAPS 694 bool "Debug access to per_cpu maps" 695 depends on DEBUG_KERNEL 696 depends on SMP 697 help 698 Say Y to verify that the per_cpu map being accessed has 699 been set up. This adds a fair amount of code to kernel memory 700 and decreases performance. 701 702 Say N if unsure. 703 704config DEBUG_HIGHMEM 705 bool "Highmem debugging" 706 depends on DEBUG_KERNEL && HIGHMEM 707 help 708 This option enables additional error checking for high memory 709 systems. Disable for production systems. 710 711config HAVE_DEBUG_STACKOVERFLOW 712 bool 713 714config DEBUG_STACKOVERFLOW 715 bool "Check for stack overflows" 716 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 717 ---help--- 718 Say Y here if you want to check for overflows of kernel, IRQ 719 and exception stacks (if your architecture uses them). This 720 option will show detailed messages if free stack space drops 721 below a certain limit. 722 723 These kinds of bugs usually occur when call-chains in the 724 kernel get too deep, especially when interrupts are 725 involved. 726 727 Use this in cases where you see apparently random memory 728 corruption, especially if it appears in 'struct thread_info' 729 730 If in doubt, say "N". 731 732source "lib/Kconfig.kmemcheck" 733 734source "lib/Kconfig.kasan" 735 736endmenu # "Memory Debugging" 737 738config ARCH_HAS_KCOV 739 bool 740 help 741 KCOV does not have any arch-specific code, but currently it is enabled 742 only for x86_64. KCOV requires testing on other archs, and most likely 743 disabling of instrumentation for some early boot code. 744 745config KCOV 746 bool "Code coverage for fuzzing" 747 depends on ARCH_HAS_KCOV 748 select DEBUG_FS 749 select GCC_PLUGINS if !COMPILE_TEST 750 select GCC_PLUGIN_SANCOV if !COMPILE_TEST 751 help 752 KCOV exposes kernel code coverage information in a form suitable 753 for coverage-guided fuzzing (randomized testing). 754 755 If RANDOMIZE_BASE is enabled, PC values will not be stable across 756 different machines and across reboots. If you need stable PC values, 757 disable RANDOMIZE_BASE. 758 759 For more details, see Documentation/dev-tools/kcov.rst. 760 761config KCOV_INSTRUMENT_ALL 762 bool "Instrument all code by default" 763 depends on KCOV 764 default y if KCOV 765 help 766 If you are doing generic system call fuzzing (like e.g. syzkaller), 767 then you will want to instrument the whole kernel and you should 768 say y here. If you are doing more targeted fuzzing (like e.g. 769 filesystem fuzzing with AFL) then you will want to enable coverage 770 for more specific subsets of files, and should say n here. 771 772config DEBUG_SHIRQ 773 bool "Debug shared IRQ handlers" 774 depends on DEBUG_KERNEL 775 help 776 Enable this to generate a spurious interrupt as soon as a shared 777 interrupt handler is registered, and just before one is deregistered. 778 Drivers ought to be able to handle interrupts coming in at those 779 points; some don't and need to be caught. 780 781menu "Debug Lockups and Hangs" 782 783config LOCKUP_DETECTOR 784 bool 785 786config SOFTLOCKUP_DETECTOR 787 bool "Detect Soft Lockups" 788 depends on DEBUG_KERNEL && !S390 789 select LOCKUP_DETECTOR 790 help 791 Say Y here to enable the kernel to act as a watchdog to detect 792 soft lockups. 793 794 Softlockups are bugs that cause the kernel to loop in kernel 795 mode for more than 20 seconds, without giving other tasks a 796 chance to run. The current stack trace is displayed upon 797 detection and the system will stay locked up. 798 799config HARDLOCKUP_DETECTOR_PERF 800 bool 801 select SOFTLOCKUP_DETECTOR 802 803# 804# arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard 805# lockup detector rather than the perf based detector. 806# 807config HARDLOCKUP_DETECTOR 808 bool "Detect Hard Lockups" 809 depends on DEBUG_KERNEL && !S390 810 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH 811 select LOCKUP_DETECTOR 812 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF 813 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH 814 help 815 Say Y here to enable the kernel to act as a watchdog to detect 816 hard lockups. 817 818 Hardlockups are bugs that cause the CPU to loop in kernel mode 819 for more than 10 seconds, without letting other interrupts have a 820 chance to run. The current stack trace is displayed upon detection 821 and the system will stay locked up. 822 823config BOOTPARAM_HARDLOCKUP_PANIC 824 bool "Panic (Reboot) On Hard Lockups" 825 depends on HARDLOCKUP_DETECTOR 826 help 827 Say Y here to enable the kernel to panic on "hard lockups", 828 which are bugs that cause the kernel to loop in kernel 829 mode with interrupts disabled for more than 10 seconds (configurable 830 using the watchdog_thresh sysctl). 831 832 Say N if unsure. 833 834config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 835 int 836 depends on HARDLOCKUP_DETECTOR 837 range 0 1 838 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 839 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 840 841config BOOTPARAM_SOFTLOCKUP_PANIC 842 bool "Panic (Reboot) On Soft Lockups" 843 depends on SOFTLOCKUP_DETECTOR 844 help 845 Say Y here to enable the kernel to panic on "soft lockups", 846 which are bugs that cause the kernel to loop in kernel 847 mode for more than 20 seconds (configurable using the watchdog_thresh 848 sysctl), without giving other tasks a chance to run. 849 850 The panic can be used in combination with panic_timeout, 851 to cause the system to reboot automatically after a 852 lockup has been detected. This feature is useful for 853 high-availability systems that have uptime guarantees and 854 where a lockup must be resolved ASAP. 855 856 Say N if unsure. 857 858config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 859 int 860 depends on SOFTLOCKUP_DETECTOR 861 range 0 1 862 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 863 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 864 865config DETECT_HUNG_TASK 866 bool "Detect Hung Tasks" 867 depends on DEBUG_KERNEL 868 default SOFTLOCKUP_DETECTOR 869 help 870 Say Y here to enable the kernel to detect "hung tasks", 871 which are bugs that cause the task to be stuck in 872 uninterruptible "D" state indefinitely. 873 874 When a hung task is detected, the kernel will print the 875 current stack trace (which you should report), but the 876 task will stay in uninterruptible state. If lockdep is 877 enabled then all held locks will also be reported. This 878 feature has negligible overhead. 879 880config DEFAULT_HUNG_TASK_TIMEOUT 881 int "Default timeout for hung task detection (in seconds)" 882 depends on DETECT_HUNG_TASK 883 default 120 884 help 885 This option controls the default timeout (in seconds) used 886 to determine when a task has become non-responsive and should 887 be considered hung. 888 889 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 890 sysctl or by writing a value to 891 /proc/sys/kernel/hung_task_timeout_secs. 892 893 A timeout of 0 disables the check. The default is two minutes. 894 Keeping the default should be fine in most cases. 895 896config BOOTPARAM_HUNG_TASK_PANIC 897 bool "Panic (Reboot) On Hung Tasks" 898 depends on DETECT_HUNG_TASK 899 help 900 Say Y here to enable the kernel to panic on "hung tasks", 901 which are bugs that cause the kernel to leave a task stuck 902 in uninterruptible "D" state. 903 904 The panic can be used in combination with panic_timeout, 905 to cause the system to reboot automatically after a 906 hung task has been detected. This feature is useful for 907 high-availability systems that have uptime guarantees and 908 where a hung tasks must be resolved ASAP. 909 910 Say N if unsure. 911 912config BOOTPARAM_HUNG_TASK_PANIC_VALUE 913 int 914 depends on DETECT_HUNG_TASK 915 range 0 1 916 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 917 default 1 if BOOTPARAM_HUNG_TASK_PANIC 918 919config WQ_WATCHDOG 920 bool "Detect Workqueue Stalls" 921 depends on DEBUG_KERNEL 922 help 923 Say Y here to enable stall detection on workqueues. If a 924 worker pool doesn't make forward progress on a pending work 925 item for over a given amount of time, 30s by default, a 926 warning message is printed along with dump of workqueue 927 state. This can be configured through kernel parameter 928 "workqueue.watchdog_thresh" and its sysfs counterpart. 929 930endmenu # "Debug lockups and hangs" 931 932config PANIC_ON_OOPS 933 bool "Panic on Oops" 934 help 935 Say Y here to enable the kernel to panic when it oopses. This 936 has the same effect as setting oops=panic on the kernel command 937 line. 938 939 This feature is useful to ensure that the kernel does not do 940 anything erroneous after an oops which could result in data 941 corruption or other issues. 942 943 Say N if unsure. 944 945config PANIC_ON_OOPS_VALUE 946 int 947 range 0 1 948 default 0 if !PANIC_ON_OOPS 949 default 1 if PANIC_ON_OOPS 950 951config PANIC_TIMEOUT 952 int "panic timeout" 953 default 0 954 help 955 Set the timeout value (in seconds) until a reboot occurs when the 956 the kernel panics. If n = 0, then we wait forever. A timeout 957 value n > 0 will wait n seconds before rebooting, while a timeout 958 value n < 0 will reboot immediately. 959 960config SCHED_DEBUG 961 bool "Collect scheduler debugging info" 962 depends on DEBUG_KERNEL && PROC_FS 963 default y 964 help 965 If you say Y here, the /proc/sched_debug file will be provided 966 that can help debug the scheduler. The runtime overhead of this 967 option is minimal. 968 969config SCHED_INFO 970 bool 971 default n 972 973config SCHEDSTATS 974 bool "Collect scheduler statistics" 975 depends on DEBUG_KERNEL && PROC_FS 976 select SCHED_INFO 977 help 978 If you say Y here, additional code will be inserted into the 979 scheduler and related routines to collect statistics about 980 scheduler behavior and provide them in /proc/schedstat. These 981 stats may be useful for both tuning and debugging the scheduler 982 If you aren't debugging the scheduler or trying to tune a specific 983 application, you can say N to avoid the very slight overhead 984 this adds. 985 986config SCHED_STACK_END_CHECK 987 bool "Detect stack corruption on calls to schedule()" 988 depends on DEBUG_KERNEL 989 default n 990 help 991 This option checks for a stack overrun on calls to schedule(). 992 If the stack end location is found to be over written always panic as 993 the content of the corrupted region can no longer be trusted. 994 This is to ensure no erroneous behaviour occurs which could result in 995 data corruption or a sporadic crash at a later stage once the region 996 is examined. The runtime overhead introduced is minimal. 997 998config DEBUG_TIMEKEEPING 999 bool "Enable extra timekeeping sanity checking" 1000 help 1001 This option will enable additional timekeeping sanity checks 1002 which may be helpful when diagnosing issues where timekeeping 1003 problems are suspected. 1004 1005 This may include checks in the timekeeping hotpaths, so this 1006 option may have a (very small) performance impact to some 1007 workloads. 1008 1009 If unsure, say N. 1010 1011config DEBUG_PREEMPT 1012 bool "Debug preemptible kernel" 1013 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 1014 default y 1015 help 1016 If you say Y here then the kernel will use a debug variant of the 1017 commonly used smp_processor_id() function and will print warnings 1018 if kernel code uses it in a preemption-unsafe way. Also, the kernel 1019 will detect preemption count underflows. 1020 1021menu "Lock Debugging (spinlocks, mutexes, etc...)" 1022 1023config DEBUG_RT_MUTEXES 1024 bool "RT Mutex debugging, deadlock detection" 1025 depends on DEBUG_KERNEL && RT_MUTEXES 1026 help 1027 This allows rt mutex semantics violations and rt mutex related 1028 deadlocks (lockups) to be detected and reported automatically. 1029 1030config DEBUG_SPINLOCK 1031 bool "Spinlock and rw-lock debugging: basic checks" 1032 depends on DEBUG_KERNEL 1033 select UNINLINE_SPIN_UNLOCK 1034 help 1035 Say Y here and build SMP to catch missing spinlock initialization 1036 and certain other kinds of spinlock errors commonly made. This is 1037 best used in conjunction with the NMI watchdog so that spinlock 1038 deadlocks are also debuggable. 1039 1040config DEBUG_MUTEXES 1041 bool "Mutex debugging: basic checks" 1042 depends on DEBUG_KERNEL 1043 help 1044 This feature allows mutex semantics violations to be detected and 1045 reported. 1046 1047config DEBUG_WW_MUTEX_SLOWPATH 1048 bool "Wait/wound mutex debugging: Slowpath testing" 1049 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1050 select DEBUG_LOCK_ALLOC 1051 select DEBUG_SPINLOCK 1052 select DEBUG_MUTEXES 1053 help 1054 This feature enables slowpath testing for w/w mutex users by 1055 injecting additional -EDEADLK wound/backoff cases. Together with 1056 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 1057 will test all possible w/w mutex interface abuse with the 1058 exception of simply not acquiring all the required locks. 1059 Note that this feature can introduce significant overhead, so 1060 it really should not be enabled in a production or distro kernel, 1061 even a debug kernel. If you are a driver writer, enable it. If 1062 you are a distro, do not. 1063 1064config DEBUG_LOCK_ALLOC 1065 bool "Lock debugging: detect incorrect freeing of live locks" 1066 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1067 select DEBUG_SPINLOCK 1068 select DEBUG_MUTEXES 1069 select DEBUG_RT_MUTEXES if RT_MUTEXES 1070 select LOCKDEP 1071 help 1072 This feature will check whether any held lock (spinlock, rwlock, 1073 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1074 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1075 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1076 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1077 held during task exit. 1078 1079config PROVE_LOCKING 1080 bool "Lock debugging: prove locking correctness" 1081 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1082 select LOCKDEP 1083 select DEBUG_SPINLOCK 1084 select DEBUG_MUTEXES 1085 select DEBUG_RT_MUTEXES if RT_MUTEXES 1086 select DEBUG_LOCK_ALLOC 1087 select TRACE_IRQFLAGS 1088 default n 1089 help 1090 This feature enables the kernel to prove that all locking 1091 that occurs in the kernel runtime is mathematically 1092 correct: that under no circumstance could an arbitrary (and 1093 not yet triggered) combination of observed locking 1094 sequences (on an arbitrary number of CPUs, running an 1095 arbitrary number of tasks and interrupt contexts) cause a 1096 deadlock. 1097 1098 In short, this feature enables the kernel to report locking 1099 related deadlocks before they actually occur. 1100 1101 The proof does not depend on how hard and complex a 1102 deadlock scenario would be to trigger: how many 1103 participant CPUs, tasks and irq-contexts would be needed 1104 for it to trigger. The proof also does not depend on 1105 timing: if a race and a resulting deadlock is possible 1106 theoretically (no matter how unlikely the race scenario 1107 is), it will be proven so and will immediately be 1108 reported by the kernel (once the event is observed that 1109 makes the deadlock theoretically possible). 1110 1111 If a deadlock is impossible (i.e. the locking rules, as 1112 observed by the kernel, are mathematically correct), the 1113 kernel reports nothing. 1114 1115 NOTE: this feature can also be enabled for rwlocks, mutexes 1116 and rwsems - in which case all dependencies between these 1117 different locking variants are observed and mapped too, and 1118 the proof of observed correctness is also maintained for an 1119 arbitrary combination of these separate locking variants. 1120 1121 For more details, see Documentation/locking/lockdep-design.txt. 1122 1123config LOCKDEP 1124 bool 1125 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1126 select STACKTRACE 1127 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE 1128 select KALLSYMS 1129 select KALLSYMS_ALL 1130 1131config LOCKDEP_SMALL 1132 bool 1133 1134config LOCK_STAT 1135 bool "Lock usage statistics" 1136 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1137 select LOCKDEP 1138 select DEBUG_SPINLOCK 1139 select DEBUG_MUTEXES 1140 select DEBUG_RT_MUTEXES if RT_MUTEXES 1141 select DEBUG_LOCK_ALLOC 1142 default n 1143 help 1144 This feature enables tracking lock contention points 1145 1146 For more details, see Documentation/locking/lockstat.txt 1147 1148 This also enables lock events required by "perf lock", 1149 subcommand of perf. 1150 If you want to use "perf lock", you also need to turn on 1151 CONFIG_EVENT_TRACING. 1152 1153 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1154 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1155 1156config DEBUG_LOCKDEP 1157 bool "Lock dependency engine debugging" 1158 depends on DEBUG_KERNEL && LOCKDEP 1159 help 1160 If you say Y here, the lock dependency engine will do 1161 additional runtime checks to debug itself, at the price 1162 of more runtime overhead. 1163 1164config DEBUG_ATOMIC_SLEEP 1165 bool "Sleep inside atomic section checking" 1166 select PREEMPT_COUNT 1167 depends on DEBUG_KERNEL 1168 help 1169 If you say Y here, various routines which may sleep will become very 1170 noisy if they are called inside atomic sections: when a spinlock is 1171 held, inside an rcu read side critical section, inside preempt disabled 1172 sections, inside an interrupt, etc... 1173 1174config DEBUG_LOCKING_API_SELFTESTS 1175 bool "Locking API boot-time self-tests" 1176 depends on DEBUG_KERNEL 1177 help 1178 Say Y here if you want the kernel to run a short self-test during 1179 bootup. The self-test checks whether common types of locking bugs 1180 are detected by debugging mechanisms or not. (if you disable 1181 lock debugging then those bugs wont be detected of course.) 1182 The following locking APIs are covered: spinlocks, rwlocks, 1183 mutexes and rwsems. 1184 1185config LOCK_TORTURE_TEST 1186 tristate "torture tests for locking" 1187 depends on DEBUG_KERNEL 1188 select TORTURE_TEST 1189 default n 1190 help 1191 This option provides a kernel module that runs torture tests 1192 on kernel locking primitives. The kernel module may be built 1193 after the fact on the running kernel to be tested, if desired. 1194 1195 Say Y here if you want kernel locking-primitive torture tests 1196 to be built into the kernel. 1197 Say M if you want these torture tests to build as a module. 1198 Say N if you are unsure. 1199 1200config WW_MUTEX_SELFTEST 1201 tristate "Wait/wound mutex selftests" 1202 help 1203 This option provides a kernel module that runs tests on the 1204 on the struct ww_mutex locking API. 1205 1206 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction 1207 with this test harness. 1208 1209 Say M if you want these self tests to build as a module. 1210 Say N if you are unsure. 1211 1212endmenu # lock debugging 1213 1214config TRACE_IRQFLAGS 1215 bool 1216 help 1217 Enables hooks to interrupt enabling and disabling for 1218 either tracing or lock debugging. 1219 1220config STACKTRACE 1221 bool "Stack backtrace support" 1222 depends on STACKTRACE_SUPPORT 1223 help 1224 This option causes the kernel to create a /proc/pid/stack for 1225 every process, showing its current stack trace. 1226 It is also used by various kernel debugging features that require 1227 stack trace generation. 1228 1229config WARN_ALL_UNSEEDED_RANDOM 1230 bool "Warn for all uses of unseeded randomness" 1231 default n 1232 help 1233 Some parts of the kernel contain bugs relating to their use of 1234 cryptographically secure random numbers before it's actually possible 1235 to generate those numbers securely. This setting ensures that these 1236 flaws don't go unnoticed, by enabling a message, should this ever 1237 occur. This will allow people with obscure setups to know when things 1238 are going wrong, so that they might contact developers about fixing 1239 it. 1240 1241 Unfortunately, on some models of some architectures getting 1242 a fully seeded CRNG is extremely difficult, and so this can 1243 result in dmesg getting spammed for a surprisingly long 1244 time. This is really bad from a security perspective, and 1245 so architecture maintainers really need to do what they can 1246 to get the CRNG seeded sooner after the system is booted. 1247 However, since users can not do anything actionble to 1248 address this, by default the kernel will issue only a single 1249 warning for the first use of unseeded randomness. 1250 1251 Say Y here if you want to receive warnings for all uses of 1252 unseeded randomness. This will be of use primarily for 1253 those developers interersted in improving the security of 1254 Linux kernels running on their architecture (or 1255 subarchitecture). 1256 1257config DEBUG_KOBJECT 1258 bool "kobject debugging" 1259 depends on DEBUG_KERNEL 1260 help 1261 If you say Y here, some extra kobject debugging messages will be sent 1262 to the syslog. 1263 1264config DEBUG_KOBJECT_RELEASE 1265 bool "kobject release debugging" 1266 depends on DEBUG_OBJECTS_TIMERS 1267 help 1268 kobjects are reference counted objects. This means that their 1269 last reference count put is not predictable, and the kobject can 1270 live on past the point at which a driver decides to drop it's 1271 initial reference to the kobject gained on allocation. An 1272 example of this would be a struct device which has just been 1273 unregistered. 1274 1275 However, some buggy drivers assume that after such an operation, 1276 the memory backing the kobject can be immediately freed. This 1277 goes completely against the principles of a refcounted object. 1278 1279 If you say Y here, the kernel will delay the release of kobjects 1280 on the last reference count to improve the visibility of this 1281 kind of kobject release bug. 1282 1283config HAVE_DEBUG_BUGVERBOSE 1284 bool 1285 1286config DEBUG_BUGVERBOSE 1287 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1288 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1289 default y 1290 help 1291 Say Y here to make BUG() panics output the file name and line number 1292 of the BUG call as well as the EIP and oops trace. This aids 1293 debugging but costs about 70-100K of memory. 1294 1295config DEBUG_LIST 1296 bool "Debug linked list manipulation" 1297 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION 1298 help 1299 Enable this to turn on extended checks in the linked-list 1300 walking routines. 1301 1302 If unsure, say N. 1303 1304config DEBUG_PI_LIST 1305 bool "Debug priority linked list manipulation" 1306 depends on DEBUG_KERNEL 1307 help 1308 Enable this to turn on extended checks in the priority-ordered 1309 linked-list (plist) walking routines. This checks the entire 1310 list multiple times during each manipulation. 1311 1312 If unsure, say N. 1313 1314config DEBUG_SG 1315 bool "Debug SG table operations" 1316 depends on DEBUG_KERNEL 1317 help 1318 Enable this to turn on checks on scatter-gather tables. This can 1319 help find problems with drivers that do not properly initialize 1320 their sg tables. 1321 1322 If unsure, say N. 1323 1324config DEBUG_NOTIFIERS 1325 bool "Debug notifier call chains" 1326 depends on DEBUG_KERNEL 1327 help 1328 Enable this to turn on sanity checking for notifier call chains. 1329 This is most useful for kernel developers to make sure that 1330 modules properly unregister themselves from notifier chains. 1331 This is a relatively cheap check but if you care about maximum 1332 performance, say N. 1333 1334config DEBUG_CREDENTIALS 1335 bool "Debug credential management" 1336 depends on DEBUG_KERNEL 1337 help 1338 Enable this to turn on some debug checking for credential 1339 management. The additional code keeps track of the number of 1340 pointers from task_structs to any given cred struct, and checks to 1341 see that this number never exceeds the usage count of the cred 1342 struct. 1343 1344 Furthermore, if SELinux is enabled, this also checks that the 1345 security pointer in the cred struct is never seen to be invalid. 1346 1347 If unsure, say N. 1348 1349source "kernel/rcu/Kconfig.debug" 1350 1351config DEBUG_WQ_FORCE_RR_CPU 1352 bool "Force round-robin CPU selection for unbound work items" 1353 depends on DEBUG_KERNEL 1354 default n 1355 help 1356 Workqueue used to implicitly guarantee that work items queued 1357 without explicit CPU specified are put on the local CPU. This 1358 guarantee is no longer true and while local CPU is still 1359 preferred work items may be put on foreign CPUs. Kernel 1360 parameter "workqueue.debug_force_rr_cpu" is added to force 1361 round-robin CPU selection to flush out usages which depend on the 1362 now broken guarantee. This config option enables the debug 1363 feature by default. When enabled, memory and cache locality will 1364 be impacted. 1365 1366config DEBUG_BLOCK_EXT_DEVT 1367 bool "Force extended block device numbers and spread them" 1368 depends on DEBUG_KERNEL 1369 depends on BLOCK 1370 default n 1371 help 1372 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1373 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1374 YOU ARE DOING. Distros, please enable this and fix whatever 1375 is broken. 1376 1377 Conventionally, block device numbers are allocated from 1378 predetermined contiguous area. However, extended block area 1379 may introduce non-contiguous block device numbers. This 1380 option forces most block device numbers to be allocated from 1381 the extended space and spreads them to discover kernel or 1382 userland code paths which assume predetermined contiguous 1383 device number allocation. 1384 1385 Note that turning on this debug option shuffles all the 1386 device numbers for all IDE and SCSI devices including libata 1387 ones, so root partition specified using device number 1388 directly (via rdev or root=MAJ:MIN) won't work anymore. 1389 Textual device names (root=/dev/sdXn) will continue to work. 1390 1391 Say N if you are unsure. 1392 1393config CPU_HOTPLUG_STATE_CONTROL 1394 bool "Enable CPU hotplug state control" 1395 depends on DEBUG_KERNEL 1396 depends on HOTPLUG_CPU 1397 default n 1398 help 1399 Allows to write steps between "offline" and "online" to the CPUs 1400 sysfs target file so states can be stepped granular. This is a debug 1401 option for now as the hotplug machinery cannot be stopped and 1402 restarted at arbitrary points yet. 1403 1404 Say N if your are unsure. 1405 1406config NOTIFIER_ERROR_INJECTION 1407 tristate "Notifier error injection" 1408 depends on DEBUG_KERNEL 1409 select DEBUG_FS 1410 help 1411 This option provides the ability to inject artificial errors to 1412 specified notifier chain callbacks. It is useful to test the error 1413 handling of notifier call chain failures. 1414 1415 Say N if unsure. 1416 1417config PM_NOTIFIER_ERROR_INJECT 1418 tristate "PM notifier error injection module" 1419 depends on PM && NOTIFIER_ERROR_INJECTION 1420 default m if PM_DEBUG 1421 help 1422 This option provides the ability to inject artificial errors to 1423 PM notifier chain callbacks. It is controlled through debugfs 1424 interface /sys/kernel/debug/notifier-error-inject/pm 1425 1426 If the notifier call chain should be failed with some events 1427 notified, write the error code to "actions/<notifier event>/error". 1428 1429 Example: Inject PM suspend error (-12 = -ENOMEM) 1430 1431 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1432 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1433 # echo mem > /sys/power/state 1434 bash: echo: write error: Cannot allocate memory 1435 1436 To compile this code as a module, choose M here: the module will 1437 be called pm-notifier-error-inject. 1438 1439 If unsure, say N. 1440 1441config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1442 tristate "OF reconfig notifier error injection module" 1443 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1444 help 1445 This option provides the ability to inject artificial errors to 1446 OF reconfig notifier chain callbacks. It is controlled 1447 through debugfs interface under 1448 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1449 1450 If the notifier call chain should be failed with some events 1451 notified, write the error code to "actions/<notifier event>/error". 1452 1453 To compile this code as a module, choose M here: the module will 1454 be called of-reconfig-notifier-error-inject. 1455 1456 If unsure, say N. 1457 1458config NETDEV_NOTIFIER_ERROR_INJECT 1459 tristate "Netdev notifier error injection module" 1460 depends on NET && NOTIFIER_ERROR_INJECTION 1461 help 1462 This option provides the ability to inject artificial errors to 1463 netdevice notifier chain callbacks. It is controlled through debugfs 1464 interface /sys/kernel/debug/notifier-error-inject/netdev 1465 1466 If the notifier call chain should be failed with some events 1467 notified, write the error code to "actions/<notifier event>/error". 1468 1469 Example: Inject netdevice mtu change error (-22 = -EINVAL) 1470 1471 # cd /sys/kernel/debug/notifier-error-inject/netdev 1472 # echo -22 > actions/NETDEV_CHANGEMTU/error 1473 # ip link set eth0 mtu 1024 1474 RTNETLINK answers: Invalid argument 1475 1476 To compile this code as a module, choose M here: the module will 1477 be called netdev-notifier-error-inject. 1478 1479 If unsure, say N. 1480 1481config FAULT_INJECTION 1482 bool "Fault-injection framework" 1483 depends on DEBUG_KERNEL 1484 help 1485 Provide fault-injection framework. 1486 For more details, see Documentation/fault-injection/. 1487 1488config FAILSLAB 1489 bool "Fault-injection capability for kmalloc" 1490 depends on FAULT_INJECTION 1491 depends on SLAB || SLUB 1492 help 1493 Provide fault-injection capability for kmalloc. 1494 1495config FAIL_PAGE_ALLOC 1496 bool "Fault-injection capabilitiy for alloc_pages()" 1497 depends on FAULT_INJECTION 1498 help 1499 Provide fault-injection capability for alloc_pages(). 1500 1501config FAIL_MAKE_REQUEST 1502 bool "Fault-injection capability for disk IO" 1503 depends on FAULT_INJECTION && BLOCK 1504 help 1505 Provide fault-injection capability for disk IO. 1506 1507config FAIL_IO_TIMEOUT 1508 bool "Fault-injection capability for faking disk interrupts" 1509 depends on FAULT_INJECTION && BLOCK 1510 help 1511 Provide fault-injection capability on end IO handling. This 1512 will make the block layer "forget" an interrupt as configured, 1513 thus exercising the error handling. 1514 1515 Only works with drivers that use the generic timeout handling, 1516 for others it wont do anything. 1517 1518config FAIL_MMC_REQUEST 1519 bool "Fault-injection capability for MMC IO" 1520 depends on FAULT_INJECTION_DEBUG_FS && MMC 1521 help 1522 Provide fault-injection capability for MMC IO. 1523 This will make the mmc core return data errors. This is 1524 useful to test the error handling in the mmc block device 1525 and to test how the mmc host driver handles retries from 1526 the block device. 1527 1528config FAIL_FUTEX 1529 bool "Fault-injection capability for futexes" 1530 select DEBUG_FS 1531 depends on FAULT_INJECTION && FUTEX 1532 help 1533 Provide fault-injection capability for futexes. 1534 1535config FAULT_INJECTION_DEBUG_FS 1536 bool "Debugfs entries for fault-injection capabilities" 1537 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1538 help 1539 Enable configuration of fault-injection capabilities via debugfs. 1540 1541config FAULT_INJECTION_STACKTRACE_FILTER 1542 bool "stacktrace filter for fault-injection capabilities" 1543 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1544 depends on !X86_64 1545 select STACKTRACE 1546 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1547 help 1548 Provide stacktrace filter for fault-injection capabilities 1549 1550config LATENCYTOP 1551 bool "Latency measuring infrastructure" 1552 depends on DEBUG_KERNEL 1553 depends on STACKTRACE_SUPPORT 1554 depends on PROC_FS 1555 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1556 select KALLSYMS 1557 select KALLSYMS_ALL 1558 select STACKTRACE 1559 select SCHEDSTATS 1560 select SCHED_DEBUG 1561 help 1562 Enable this option if you want to use the LatencyTOP tool 1563 to find out which userspace is blocking on what kernel operations. 1564 1565source kernel/trace/Kconfig 1566 1567menu "Runtime Testing" 1568 1569config LKDTM 1570 tristate "Linux Kernel Dump Test Tool Module" 1571 depends on DEBUG_FS 1572 depends on BLOCK 1573 default n 1574 help 1575 This module enables testing of the different dumping mechanisms by 1576 inducing system failures at predefined crash points. 1577 If you don't need it: say N 1578 Choose M here to compile this code as a module. The module will be 1579 called lkdtm. 1580 1581 Documentation on how to use the module can be found in 1582 Documentation/fault-injection/provoke-crashes.txt 1583 1584config TEST_LIST_SORT 1585 tristate "Linked list sorting test" 1586 depends on DEBUG_KERNEL || m 1587 help 1588 Enable this to turn on 'list_sort()' function test. This test is 1589 executed only once during system boot (so affects only boot time), 1590 or at module load time. 1591 1592 If unsure, say N. 1593 1594config TEST_SORT 1595 tristate "Array-based sort test" 1596 depends on DEBUG_KERNEL || m 1597 help 1598 This option enables the self-test function of 'sort()' at boot, 1599 or at module load time. 1600 1601 If unsure, say N. 1602 1603config KPROBES_SANITY_TEST 1604 bool "Kprobes sanity tests" 1605 depends on DEBUG_KERNEL 1606 depends on KPROBES 1607 default n 1608 help 1609 This option provides for testing basic kprobes functionality on 1610 boot. A sample kprobe, jprobe and kretprobe are inserted and 1611 verified for functionality. 1612 1613 Say N if you are unsure. 1614 1615config BACKTRACE_SELF_TEST 1616 tristate "Self test for the backtrace code" 1617 depends on DEBUG_KERNEL 1618 default n 1619 help 1620 This option provides a kernel module that can be used to test 1621 the kernel stack backtrace code. This option is not useful 1622 for distributions or general kernels, but only for kernel 1623 developers working on architecture code. 1624 1625 Note that if you want to also test saved backtraces, you will 1626 have to enable STACKTRACE as well. 1627 1628 Say N if you are unsure. 1629 1630config RBTREE_TEST 1631 tristate "Red-Black tree test" 1632 depends on DEBUG_KERNEL 1633 help 1634 A benchmark measuring the performance of the rbtree library. 1635 Also includes rbtree invariant checks. 1636 1637config INTERVAL_TREE_TEST 1638 tristate "Interval tree test" 1639 depends on DEBUG_KERNEL 1640 select INTERVAL_TREE 1641 help 1642 A benchmark measuring the performance of the interval tree library 1643 1644config PERCPU_TEST 1645 tristate "Per cpu operations test" 1646 depends on m && DEBUG_KERNEL 1647 help 1648 Enable this option to build test module which validates per-cpu 1649 operations. 1650 1651 If unsure, say N. 1652 1653config ATOMIC64_SELFTEST 1654 tristate "Perform an atomic64_t self-test" 1655 help 1656 Enable this option to test the atomic64_t functions at boot or 1657 at module load time. 1658 1659 If unsure, say N. 1660 1661config ASYNC_RAID6_TEST 1662 tristate "Self test for hardware accelerated raid6 recovery" 1663 depends on ASYNC_RAID6_RECOV 1664 select ASYNC_MEMCPY 1665 ---help--- 1666 This is a one-shot self test that permutes through the 1667 recovery of all the possible two disk failure scenarios for a 1668 N-disk array. Recovery is performed with the asynchronous 1669 raid6 recovery routines, and will optionally use an offload 1670 engine if one is available. 1671 1672 If unsure, say N. 1673 1674config TEST_HEXDUMP 1675 tristate "Test functions located in the hexdump module at runtime" 1676 1677config TEST_STRING_HELPERS 1678 tristate "Test functions located in the string_helpers module at runtime" 1679 1680config TEST_KSTRTOX 1681 tristate "Test kstrto*() family of functions at runtime" 1682 1683config TEST_PRINTF 1684 tristate "Test printf() family of functions at runtime" 1685 1686config TEST_BITMAP 1687 tristate "Test bitmap_*() family of functions at runtime" 1688 default n 1689 help 1690 Enable this option to test the bitmap functions at boot. 1691 1692 If unsure, say N. 1693 1694config TEST_UUID 1695 tristate "Test functions located in the uuid module at runtime" 1696 1697config TEST_RHASHTABLE 1698 tristate "Perform selftest on resizable hash table" 1699 default n 1700 help 1701 Enable this option to test the rhashtable functions at boot. 1702 1703 If unsure, say N. 1704 1705config TEST_HASH 1706 tristate "Perform selftest on hash functions" 1707 default n 1708 help 1709 Enable this option to test the kernel's integer (<linux/hash.h>), 1710 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>) 1711 hash functions on boot (or module load). 1712 1713 This is intended to help people writing architecture-specific 1714 optimized versions. If unsure, say N. 1715 1716config TEST_PARMAN 1717 tristate "Perform selftest on priority array manager" 1718 default n 1719 depends on PARMAN 1720 help 1721 Enable this option to test priority array manager on boot 1722 (or module load). 1723 1724 If unsure, say N. 1725 1726endmenu # runtime tests 1727 1728config PROVIDE_OHCI1394_DMA_INIT 1729 bool "Remote debugging over FireWire early on boot" 1730 depends on PCI && X86 1731 help 1732 If you want to debug problems which hang or crash the kernel early 1733 on boot and the crashing machine has a FireWire port, you can use 1734 this feature to remotely access the memory of the crashed machine 1735 over FireWire. This employs remote DMA as part of the OHCI1394 1736 specification which is now the standard for FireWire controllers. 1737 1738 With remote DMA, you can monitor the printk buffer remotely using 1739 firescope and access all memory below 4GB using fireproxy from gdb. 1740 Even controlling a kernel debugger is possible using remote DMA. 1741 1742 Usage: 1743 1744 If ohci1394_dma=early is used as boot parameter, it will initialize 1745 all OHCI1394 controllers which are found in the PCI config space. 1746 1747 As all changes to the FireWire bus such as enabling and disabling 1748 devices cause a bus reset and thereby disable remote DMA for all 1749 devices, be sure to have the cable plugged and FireWire enabled on 1750 the debugging host before booting the debug target for debugging. 1751 1752 This code (~1k) is freed after boot. By then, the firewire stack 1753 in charge of the OHCI-1394 controllers should be used instead. 1754 1755 See Documentation/debugging-via-ohci1394.txt for more information. 1756 1757config DMA_API_DEBUG 1758 bool "Enable debugging of DMA-API usage" 1759 depends on HAVE_DMA_API_DEBUG 1760 help 1761 Enable this option to debug the use of the DMA API by device drivers. 1762 With this option you will be able to detect common bugs in device 1763 drivers like double-freeing of DMA mappings or freeing mappings that 1764 were never allocated. 1765 1766 This also attempts to catch cases where a page owned by DMA is 1767 accessed by the cpu in a way that could cause data corruption. For 1768 example, this enables cow_user_page() to check that the source page is 1769 not undergoing DMA. 1770 1771 This option causes a performance degradation. Use only if you want to 1772 debug device drivers and dma interactions. 1773 1774 If unsure, say N. 1775 1776config TEST_LKM 1777 tristate "Test module loading with 'hello world' module" 1778 default n 1779 depends on m 1780 help 1781 This builds the "test_module" module that emits "Hello, world" 1782 on printk when loaded. It is designed to be used for basic 1783 evaluation of the module loading subsystem (for example when 1784 validating module verification). It lacks any extra dependencies, 1785 and will not normally be loaded by the system unless explicitly 1786 requested by name. 1787 1788 If unsure, say N. 1789 1790config TEST_USER_COPY 1791 tristate "Test user/kernel boundary protections" 1792 default n 1793 depends on m 1794 help 1795 This builds the "test_user_copy" module that runs sanity checks 1796 on the copy_to/from_user infrastructure, making sure basic 1797 user/kernel boundary testing is working. If it fails to load, 1798 a regression has been detected in the user/kernel memory boundary 1799 protections. 1800 1801 If unsure, say N. 1802 1803config TEST_BPF 1804 tristate "Test BPF filter functionality" 1805 default n 1806 depends on m && NET 1807 help 1808 This builds the "test_bpf" module that runs various test vectors 1809 against the BPF interpreter or BPF JIT compiler depending on the 1810 current setting. This is in particular useful for BPF JIT compiler 1811 development, but also to run regression tests against changes in 1812 the interpreter code. It also enables test stubs for eBPF maps and 1813 verifier used by user space verifier testsuite. 1814 1815 If unsure, say N. 1816 1817config TEST_FIRMWARE 1818 tristate "Test firmware loading via userspace interface" 1819 default n 1820 depends on FW_LOADER 1821 help 1822 This builds the "test_firmware" module that creates a userspace 1823 interface for testing firmware loading. This can be used to 1824 control the triggering of firmware loading without needing an 1825 actual firmware-using device. The contents can be rechecked by 1826 userspace. 1827 1828 If unsure, say N. 1829 1830config TEST_SYSCTL 1831 tristate "sysctl test driver" 1832 default n 1833 depends on PROC_SYSCTL 1834 help 1835 This builds the "test_sysctl" module. This driver enables to test the 1836 proc sysctl interfaces available to drivers safely without affecting 1837 production knobs which might alter system functionality. 1838 1839 If unsure, say N. 1840 1841config TEST_UDELAY 1842 tristate "udelay test driver" 1843 default n 1844 help 1845 This builds the "udelay_test" module that helps to make sure 1846 that udelay() is working properly. 1847 1848 If unsure, say N. 1849 1850config MEMTEST 1851 bool "Memtest" 1852 depends on HAVE_MEMBLOCK 1853 ---help--- 1854 This option adds a kernel parameter 'memtest', which allows memtest 1855 to be set. 1856 memtest=0, mean disabled; -- default 1857 memtest=1, mean do 1 test pattern; 1858 ... 1859 memtest=17, mean do 17 test patterns. 1860 If you are unsure how to answer this question, answer N. 1861 1862config TEST_STATIC_KEYS 1863 tristate "Test static keys" 1864 default n 1865 depends on m 1866 help 1867 Test the static key interfaces. 1868 1869 If unsure, say N. 1870 1871config BUG_ON_DATA_CORRUPTION 1872 bool "Trigger a BUG when data corruption is detected" 1873 select DEBUG_LIST 1874 help 1875 Select this option if the kernel should BUG when it encounters 1876 data corruption in kernel memory structures when they get checked 1877 for validity. 1878 1879 If unsure, say N. 1880 1881config TEST_KMOD 1882 tristate "kmod stress tester" 1883 default n 1884 depends on m 1885 depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS 1886 depends on NETDEVICES && NET_CORE && INET # for TUN 1887 select TEST_LKM 1888 select XFS_FS 1889 select TUN 1890 select BTRFS_FS 1891 help 1892 Test the kernel's module loading mechanism: kmod. kmod implements 1893 support to load modules using the Linux kernel's usermode helper. 1894 This test provides a series of tests against kmod. 1895 1896 Although technically you can either build test_kmod as a module or 1897 into the kernel we disallow building it into the kernel since 1898 it stress tests request_module() and this will very likely cause 1899 some issues by taking over precious threads available from other 1900 module load requests, ultimately this could be fatal. 1901 1902 To run tests run: 1903 1904 tools/testing/selftests/kmod/kmod.sh --help 1905 1906 If unsure, say N. 1907 1908source "samples/Kconfig" 1909 1910source "lib/Kconfig.kgdb" 1911 1912source "lib/Kconfig.ubsan" 1913 1914config ARCH_HAS_DEVMEM_IS_ALLOWED 1915 bool 1916 1917config STRICT_DEVMEM 1918 bool "Filter access to /dev/mem" 1919 depends on MMU && DEVMEM 1920 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 1921 default y if TILE || PPC 1922 ---help--- 1923 If this option is disabled, you allow userspace (root) access to all 1924 of memory, including kernel and userspace memory. Accidental 1925 access to this is obviously disastrous, but specific access can 1926 be used by people debugging the kernel. Note that with PAT support 1927 enabled, even in this case there are restrictions on /dev/mem 1928 use due to the cache aliasing requirements. 1929 1930 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 1931 file only allows userspace access to PCI space and the BIOS code and 1932 data regions. This is sufficient for dosemu and X and all common 1933 users of /dev/mem. 1934 1935 If in doubt, say Y. 1936 1937config IO_STRICT_DEVMEM 1938 bool "Filter I/O access to /dev/mem" 1939 depends on STRICT_DEVMEM 1940 ---help--- 1941 If this option is disabled, you allow userspace (root) access to all 1942 io-memory regardless of whether a driver is actively using that 1943 range. Accidental access to this is obviously disastrous, but 1944 specific access can be used by people debugging kernel drivers. 1945 1946 If this option is switched on, the /dev/mem file only allows 1947 userspace access to *idle* io-memory ranges (see /proc/iomem) This 1948 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 1949 if the driver using a given range cannot be disabled. 1950 1951 If in doubt, say Y. 1952