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/dynamic-debug-howto.txt for additional information. 134 135endmenu # "printk and dmesg options" 136 137menu "Compile-time checks and compiler options" 138 139config DEBUG_INFO 140 bool "Compile the kernel with debug info" 141 depends on DEBUG_KERNEL && !COMPILE_TEST 142 help 143 If you say Y here the resulting kernel image will include 144 debugging info resulting in a larger kernel image. 145 This adds debug symbols to the kernel and modules (gcc -g), and 146 is needed if you intend to use kernel crashdump or binary object 147 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 148 Say Y here only if you plan to debug the kernel. 149 150 If unsure, say N. 151 152config DEBUG_INFO_REDUCED 153 bool "Reduce debugging information" 154 depends on DEBUG_INFO 155 help 156 If you say Y here gcc is instructed to generate less debugging 157 information for structure types. This means that tools that 158 need full debugging information (like kgdb or systemtap) won't 159 be happy. But if you merely need debugging information to 160 resolve line numbers there is no loss. Advantage is that 161 build directory object sizes shrink dramatically over a full 162 DEBUG_INFO build and compile times are reduced too. 163 Only works with newer gcc versions. 164 165config DEBUG_INFO_SPLIT 166 bool "Produce split debuginfo in .dwo files" 167 depends on DEBUG_INFO && !FRV 168 help 169 Generate debug info into separate .dwo files. This significantly 170 reduces the build directory size for builds with DEBUG_INFO, 171 because it stores the information only once on disk in .dwo 172 files instead of multiple times in object files and executables. 173 In addition the debug information is also compressed. 174 175 Requires recent gcc (4.7+) and recent gdb/binutils. 176 Any tool that packages or reads debug information would need 177 to know about the .dwo files and include them. 178 Incompatible with older versions of ccache. 179 180config DEBUG_INFO_DWARF4 181 bool "Generate dwarf4 debuginfo" 182 depends on DEBUG_INFO 183 help 184 Generate dwarf4 debug info. This requires recent versions 185 of gcc and gdb. It makes the debug information larger. 186 But it significantly improves the success of resolving 187 variables in gdb on optimized code. 188 189config GDB_SCRIPTS 190 bool "Provide GDB scripts for kernel debugging" 191 depends on DEBUG_INFO 192 help 193 This creates the required links to GDB helper scripts in the 194 build directory. If you load vmlinux into gdb, the helper 195 scripts will be automatically imported by gdb as well, and 196 additional functions are available to analyze a Linux kernel 197 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst 198 for further details. 199 200config ENABLE_WARN_DEPRECATED 201 bool "Enable __deprecated logic" 202 default y 203 help 204 Enable the __deprecated logic in the kernel build. 205 Disable this to suppress the "warning: 'foo' is deprecated 206 (declared at kernel/power/somefile.c:1234)" messages. 207 208config ENABLE_MUST_CHECK 209 bool "Enable __must_check logic" 210 default y 211 help 212 Enable the __must_check logic in the kernel build. Disable this to 213 suppress the "warning: ignoring return value of 'foo', declared with 214 attribute warn_unused_result" messages. 215 216config FRAME_WARN 217 int "Warn for stack frames larger than (needs gcc 4.4)" 218 range 0 8192 219 default 0 if KASAN 220 default 2048 if GCC_PLUGIN_LATENT_ENTROPY 221 default 1024 if !64BIT 222 default 2048 if 64BIT 223 help 224 Tell gcc to warn at build time for stack frames larger than this. 225 Setting this too low will cause a lot of warnings. 226 Setting it to 0 disables the warning. 227 Requires gcc 4.4 228 229config STRIP_ASM_SYMS 230 bool "Strip assembler-generated symbols during link" 231 default n 232 help 233 Strip internal assembler-generated symbols during a link (symbols 234 that look like '.Lxxx') so they don't pollute the output of 235 get_wchan() and suchlike. 236 237config READABLE_ASM 238 bool "Generate readable assembler code" 239 depends on DEBUG_KERNEL 240 help 241 Disable some compiler optimizations that tend to generate human unreadable 242 assembler output. This may make the kernel slightly slower, but it helps 243 to keep kernel developers who have to stare a lot at assembler listings 244 sane. 245 246config UNUSED_SYMBOLS 247 bool "Enable unused/obsolete exported symbols" 248 default y if X86 249 help 250 Unused but exported symbols make the kernel needlessly bigger. For 251 that reason most of these unused exports will soon be removed. This 252 option is provided temporarily to provide a transition period in case 253 some external kernel module needs one of these symbols anyway. If you 254 encounter such a case in your module, consider if you are actually 255 using the right API. (rationale: since nobody in the kernel is using 256 this in a module, there is a pretty good chance it's actually the 257 wrong interface to use). If you really need the symbol, please send a 258 mail to the linux kernel mailing list mentioning the symbol and why 259 you really need it, and what the merge plan to the mainline kernel for 260 your module is. 261 262config PAGE_OWNER 263 bool "Track page owner" 264 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 265 select DEBUG_FS 266 select STACKTRACE 267 select STACKDEPOT 268 select PAGE_EXTENSION 269 help 270 This keeps track of what call chain is the owner of a page, may 271 help to find bare alloc_page(s) leaks. Even if you include this 272 feature on your build, it is disabled in default. You should pass 273 "page_owner=on" to boot parameter in order to enable it. Eats 274 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 275 for user-space helper. 276 277 If unsure, say N. 278 279config DEBUG_FS 280 bool "Debug Filesystem" 281 select SRCU 282 help 283 debugfs is a virtual file system that kernel developers use to put 284 debugging files into. Enable this option to be able to read and 285 write to these files. 286 287 For detailed documentation on the debugfs API, see 288 Documentation/DocBook/filesystems. 289 290 If unsure, say N. 291 292config HEADERS_CHECK 293 bool "Run 'make headers_check' when building vmlinux" 294 depends on !UML 295 help 296 This option will extract the user-visible kernel headers whenever 297 building the kernel, and will run basic sanity checks on them to 298 ensure that exported files do not attempt to include files which 299 were not exported, etc. 300 301 If you're making modifications to header files which are 302 relevant for userspace, say 'Y', and check the headers 303 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 304 your build tree), to make sure they're suitable. 305 306config DEBUG_SECTION_MISMATCH 307 bool "Enable full Section mismatch analysis" 308 help 309 The section mismatch analysis checks if there are illegal 310 references from one section to another section. 311 During linktime or runtime, some sections are dropped; 312 any use of code/data previously in these sections would 313 most likely result in an oops. 314 In the code, functions and variables are annotated with 315 __init,, etc. (see the full list in include/linux/init.h), 316 which results in the code/data being placed in specific sections. 317 The section mismatch analysis is always performed after a full 318 kernel build, and enabling this option causes the following 319 additional steps to occur: 320 - Add the option -fno-inline-functions-called-once to gcc commands. 321 When inlining a function annotated with __init in a non-init 322 function, we would lose the section information and thus 323 the analysis would not catch the illegal reference. 324 This option tells gcc to inline less (but it does result in 325 a larger kernel). 326 - Run the section mismatch analysis for each module/built-in.o file. 327 When we run the section mismatch analysis on vmlinux.o, we 328 lose valuable information about where the mismatch was 329 introduced. 330 Running the analysis for each module/built-in.o file 331 tells where the mismatch happens much closer to the 332 source. The drawback is that the same mismatch is 333 reported at least twice. 334 - Enable verbose reporting from modpost in order to help resolve 335 the section mismatches that are reported. 336 337config SECTION_MISMATCH_WARN_ONLY 338 bool "Make section mismatch errors non-fatal" 339 default y 340 help 341 If you say N here, the build process will fail if there are any 342 section mismatch, instead of just throwing warnings. 343 344 If unsure, say Y. 345 346# 347# Select this config option from the architecture Kconfig, if it 348# is preferred to always offer frame pointers as a config 349# option on the architecture (regardless of KERNEL_DEBUG): 350# 351config ARCH_WANT_FRAME_POINTERS 352 bool 353 help 354 355config FRAME_POINTER 356 bool "Compile the kernel with frame pointers" 357 depends on DEBUG_KERNEL && \ 358 (CRIS || M68K || FRV || UML || \ 359 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \ 360 ARCH_WANT_FRAME_POINTERS 361 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 362 help 363 If you say Y here the resulting kernel image will be slightly 364 larger and slower, but it gives very useful debugging information 365 in case of kernel bugs. (precise oopses/stacktraces/warnings) 366 367config STACK_VALIDATION 368 bool "Compile-time stack metadata validation" 369 depends on HAVE_STACK_VALIDATION 370 default n 371 help 372 Add compile-time checks to validate stack metadata, including frame 373 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure 374 that runtime stack traces are more reliable. 375 376 For more information, see 377 tools/objtool/Documentation/stack-validation.txt. 378 379config DEBUG_FORCE_WEAK_PER_CPU 380 bool "Force weak per-cpu definitions" 381 depends on DEBUG_KERNEL 382 help 383 s390 and alpha require percpu variables in modules to be 384 defined weak to work around addressing range issue which 385 puts the following two restrictions on percpu variable 386 definitions. 387 388 1. percpu symbols must be unique whether static or not 389 2. percpu variables can't be defined inside a function 390 391 To ensure that generic code follows the above rules, this 392 option forces all percpu variables to be defined as weak. 393 394endmenu # "Compiler options" 395 396config MAGIC_SYSRQ 397 bool "Magic SysRq key" 398 depends on !UML 399 help 400 If you say Y here, you will have some control over the system even 401 if the system crashes for example during kernel debugging (e.g., you 402 will be able to flush the buffer cache to disk, reboot the system 403 immediately or dump some status information). This is accomplished 404 by pressing various keys while holding SysRq (Alt+PrintScreen). It 405 also works on a serial console (on PC hardware at least), if you 406 send a BREAK and then within 5 seconds a command keypress. The 407 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 408 unless you really know what this hack does. 409 410config MAGIC_SYSRQ_DEFAULT_ENABLE 411 hex "Enable magic SysRq key functions by default" 412 depends on MAGIC_SYSRQ 413 default 0x1 414 help 415 Specifies which SysRq key functions are enabled by default. 416 This may be set to 1 or 0 to enable or disable them all, or 417 to a bitmask as described in Documentation/sysrq.txt. 418 419config MAGIC_SYSRQ_SERIAL 420 bool "Enable magic SysRq key over serial" 421 depends on MAGIC_SYSRQ 422 default y 423 help 424 Many embedded boards have a disconnected TTL level serial which can 425 generate some garbage that can lead to spurious false sysrq detects. 426 This option allows you to decide whether you want to enable the 427 magic SysRq key. 428 429config DEBUG_KERNEL 430 bool "Kernel debugging" 431 help 432 Say Y here if you are developing drivers or trying to debug and 433 identify kernel problems. 434 435menu "Memory Debugging" 436 437source mm/Kconfig.debug 438 439config DEBUG_OBJECTS 440 bool "Debug object operations" 441 depends on DEBUG_KERNEL 442 help 443 If you say Y here, additional code will be inserted into the 444 kernel to track the life time of various objects and validate 445 the operations on those objects. 446 447config DEBUG_OBJECTS_SELFTEST 448 bool "Debug objects selftest" 449 depends on DEBUG_OBJECTS 450 help 451 This enables the selftest of the object debug code. 452 453config DEBUG_OBJECTS_FREE 454 bool "Debug objects in freed memory" 455 depends on DEBUG_OBJECTS 456 help 457 This enables checks whether a k/v free operation frees an area 458 which contains an object which has not been deactivated 459 properly. This can make kmalloc/kfree-intensive workloads 460 much slower. 461 462config DEBUG_OBJECTS_TIMERS 463 bool "Debug timer objects" 464 depends on DEBUG_OBJECTS 465 help 466 If you say Y here, additional code will be inserted into the 467 timer routines to track the life time of timer objects and 468 validate the timer operations. 469 470config DEBUG_OBJECTS_WORK 471 bool "Debug work objects" 472 depends on DEBUG_OBJECTS 473 help 474 If you say Y here, additional code will be inserted into the 475 work queue routines to track the life time of work objects and 476 validate the work operations. 477 478config DEBUG_OBJECTS_RCU_HEAD 479 bool "Debug RCU callbacks objects" 480 depends on DEBUG_OBJECTS 481 help 482 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 483 484config DEBUG_OBJECTS_PERCPU_COUNTER 485 bool "Debug percpu counter objects" 486 depends on DEBUG_OBJECTS 487 help 488 If you say Y here, additional code will be inserted into the 489 percpu counter routines to track the life time of percpu counter 490 objects and validate the percpu counter operations. 491 492config DEBUG_OBJECTS_ENABLE_DEFAULT 493 int "debug_objects bootup default value (0-1)" 494 range 0 1 495 default "1" 496 depends on DEBUG_OBJECTS 497 help 498 Debug objects boot parameter default value 499 500config DEBUG_SLAB 501 bool "Debug slab memory allocations" 502 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 503 help 504 Say Y here to have the kernel do limited verification on memory 505 allocation as well as poisoning memory on free to catch use of freed 506 memory. This can make kmalloc/kfree-intensive workloads much slower. 507 508config DEBUG_SLAB_LEAK 509 bool "Memory leak debugging" 510 depends on DEBUG_SLAB 511 512config SLUB_DEBUG_ON 513 bool "SLUB debugging on by default" 514 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 515 default n 516 help 517 Boot with debugging on by default. SLUB boots by default with 518 the runtime debug capabilities switched off. Enabling this is 519 equivalent to specifying the "slub_debug" parameter on boot. 520 There is no support for more fine grained debug control like 521 possible with slub_debug=xxx. SLUB debugging may be switched 522 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 523 "slub_debug=-". 524 525config SLUB_STATS 526 default n 527 bool "Enable SLUB performance statistics" 528 depends on SLUB && SYSFS 529 help 530 SLUB statistics are useful to debug SLUBs allocation behavior in 531 order find ways to optimize the allocator. This should never be 532 enabled for production use since keeping statistics slows down 533 the allocator by a few percentage points. The slabinfo command 534 supports the determination of the most active slabs to figure 535 out which slabs are relevant to a particular load. 536 Try running: slabinfo -DA 537 538config HAVE_DEBUG_KMEMLEAK 539 bool 540 541config DEBUG_KMEMLEAK 542 bool "Kernel memory leak detector" 543 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 544 select DEBUG_FS 545 select STACKTRACE if STACKTRACE_SUPPORT 546 select KALLSYMS 547 select CRC32 548 help 549 Say Y here if you want to enable the memory leak 550 detector. The memory allocation/freeing is traced in a way 551 similar to the Boehm's conservative garbage collector, the 552 difference being that the orphan objects are not freed but 553 only shown in /sys/kernel/debug/kmemleak. Enabling this 554 feature will introduce an overhead to memory 555 allocations. See Documentation/dev-tools/kmemleak.rst for more 556 details. 557 558 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 559 of finding leaks due to the slab objects poisoning. 560 561 In order to access the kmemleak file, debugfs needs to be 562 mounted (usually at /sys/kernel/debug). 563 564config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 565 int "Maximum kmemleak early log entries" 566 depends on DEBUG_KMEMLEAK 567 range 200 40000 568 default 400 569 help 570 Kmemleak must track all the memory allocations to avoid 571 reporting false positives. Since memory may be allocated or 572 freed before kmemleak is initialised, an early log buffer is 573 used to store these actions. If kmemleak reports "early log 574 buffer exceeded", please increase this value. 575 576config DEBUG_KMEMLEAK_TEST 577 tristate "Simple test for the kernel memory leak detector" 578 depends on DEBUG_KMEMLEAK && m 579 help 580 This option enables a module that explicitly leaks memory. 581 582 If unsure, say N. 583 584config DEBUG_KMEMLEAK_DEFAULT_OFF 585 bool "Default kmemleak to off" 586 depends on DEBUG_KMEMLEAK 587 help 588 Say Y here to disable kmemleak by default. It can then be enabled 589 on the command line via kmemleak=on. 590 591config DEBUG_STACK_USAGE 592 bool "Stack utilization instrumentation" 593 depends on DEBUG_KERNEL && !IA64 594 help 595 Enables the display of the minimum amount of free stack which each 596 task has ever had available in the sysrq-T and sysrq-P debug output. 597 598 This option will slow down process creation somewhat. 599 600config DEBUG_VM 601 bool "Debug VM" 602 depends on DEBUG_KERNEL 603 help 604 Enable this to turn on extended checks in the virtual-memory system 605 that may impact performance. 606 607 If unsure, say N. 608 609config DEBUG_VM_VMACACHE 610 bool "Debug VMA caching" 611 depends on DEBUG_VM 612 help 613 Enable this to turn on VMA caching debug information. Doing so 614 can cause significant overhead, so only enable it in non-production 615 environments. 616 617 If unsure, say N. 618 619config DEBUG_VM_RB 620 bool "Debug VM red-black trees" 621 depends on DEBUG_VM 622 help 623 Enable VM red-black tree debugging information and extra validations. 624 625 If unsure, say N. 626 627config DEBUG_VM_PGFLAGS 628 bool "Debug page-flags operations" 629 depends on DEBUG_VM 630 help 631 Enables extra validation on page flags operations. 632 633 If unsure, say N. 634 635config DEBUG_VIRTUAL 636 bool "Debug VM translations" 637 depends on DEBUG_KERNEL && X86 638 help 639 Enable some costly sanity checks in virtual to page code. This can 640 catch mistakes with virt_to_page() and friends. 641 642 If unsure, say N. 643 644config DEBUG_NOMMU_REGIONS 645 bool "Debug the global anon/private NOMMU mapping region tree" 646 depends on DEBUG_KERNEL && !MMU 647 help 648 This option causes the global tree of anonymous and private mapping 649 regions to be regularly checked for invalid topology. 650 651config DEBUG_MEMORY_INIT 652 bool "Debug memory initialisation" if EXPERT 653 default !EXPERT 654 help 655 Enable this for additional checks during memory initialisation. 656 The sanity checks verify aspects of the VM such as the memory model 657 and other information provided by the architecture. Verbose 658 information will be printed at KERN_DEBUG loglevel depending 659 on the mminit_loglevel= command-line option. 660 661 If unsure, say Y 662 663config MEMORY_NOTIFIER_ERROR_INJECT 664 tristate "Memory hotplug notifier error injection module" 665 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 666 help 667 This option provides the ability to inject artificial errors to 668 memory hotplug notifier chain callbacks. It is controlled through 669 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 670 671 If the notifier call chain should be failed with some events 672 notified, write the error code to "actions/<notifier event>/error". 673 674 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 675 676 # cd /sys/kernel/debug/notifier-error-inject/memory 677 # echo -12 > actions/MEM_GOING_OFFLINE/error 678 # echo offline > /sys/devices/system/memory/memoryXXX/state 679 bash: echo: write error: Cannot allocate memory 680 681 To compile this code as a module, choose M here: the module will 682 be called memory-notifier-error-inject. 683 684 If unsure, say N. 685 686config DEBUG_PER_CPU_MAPS 687 bool "Debug access to per_cpu maps" 688 depends on DEBUG_KERNEL 689 depends on SMP 690 help 691 Say Y to verify that the per_cpu map being accessed has 692 been set up. This adds a fair amount of code to kernel memory 693 and decreases performance. 694 695 Say N if unsure. 696 697config DEBUG_HIGHMEM 698 bool "Highmem debugging" 699 depends on DEBUG_KERNEL && HIGHMEM 700 help 701 This option enables additional error checking for high memory 702 systems. Disable for production systems. 703 704config HAVE_DEBUG_STACKOVERFLOW 705 bool 706 707config DEBUG_STACKOVERFLOW 708 bool "Check for stack overflows" 709 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 710 ---help--- 711 Say Y here if you want to check for overflows of kernel, IRQ 712 and exception stacks (if your architecture uses them). This 713 option will show detailed messages if free stack space drops 714 below a certain limit. 715 716 These kinds of bugs usually occur when call-chains in the 717 kernel get too deep, especially when interrupts are 718 involved. 719 720 Use this in cases where you see apparently random memory 721 corruption, especially if it appears in 'struct thread_info' 722 723 If in doubt, say "N". 724 725source "lib/Kconfig.kmemcheck" 726 727source "lib/Kconfig.kasan" 728 729endmenu # "Memory Debugging" 730 731config ARCH_HAS_KCOV 732 bool 733 help 734 KCOV does not have any arch-specific code, but currently it is enabled 735 only for x86_64. KCOV requires testing on other archs, and most likely 736 disabling of instrumentation for some early boot code. 737 738config KCOV 739 bool "Code coverage for fuzzing" 740 depends on ARCH_HAS_KCOV 741 select DEBUG_FS 742 select GCC_PLUGINS if !COMPILE_TEST 743 select GCC_PLUGIN_SANCOV if !COMPILE_TEST 744 help 745 KCOV exposes kernel code coverage information in a form suitable 746 for coverage-guided fuzzing (randomized testing). 747 748 If RANDOMIZE_BASE is enabled, PC values will not be stable across 749 different machines and across reboots. If you need stable PC values, 750 disable RANDOMIZE_BASE. 751 752 For more details, see Documentation/dev-tools/kcov.rst. 753 754config KCOV_INSTRUMENT_ALL 755 bool "Instrument all code by default" 756 depends on KCOV 757 default y if KCOV 758 help 759 If you are doing generic system call fuzzing (like e.g. syzkaller), 760 then you will want to instrument the whole kernel and you should 761 say y here. If you are doing more targeted fuzzing (like e.g. 762 filesystem fuzzing with AFL) then you will want to enable coverage 763 for more specific subsets of files, and should say n here. 764 765config DEBUG_SHIRQ 766 bool "Debug shared IRQ handlers" 767 depends on DEBUG_KERNEL 768 help 769 Enable this to generate a spurious interrupt as soon as a shared 770 interrupt handler is registered, and just before one is deregistered. 771 Drivers ought to be able to handle interrupts coming in at those 772 points; some don't and need to be caught. 773 774menu "Debug Lockups and Hangs" 775 776config LOCKUP_DETECTOR 777 bool "Detect Hard and Soft Lockups" 778 depends on DEBUG_KERNEL && !S390 779 help 780 Say Y here to enable the kernel to act as a watchdog to detect 781 hard and soft lockups. 782 783 Softlockups are bugs that cause the kernel to loop in kernel 784 mode for more than 20 seconds, without giving other tasks a 785 chance to run. The current stack trace is displayed upon 786 detection and the system will stay locked up. 787 788 Hardlockups are bugs that cause the CPU to loop in kernel mode 789 for more than 10 seconds, without letting other interrupts have a 790 chance to run. The current stack trace is displayed upon detection 791 and the system will stay locked up. 792 793 The overhead should be minimal. A periodic hrtimer runs to 794 generate interrupts and kick the watchdog task every 4 seconds. 795 An NMI is generated every 10 seconds or so to check for hardlockups. 796 797 The frequency of hrtimer and NMI events and the soft and hard lockup 798 thresholds can be controlled through the sysctl watchdog_thresh. 799 800config HARDLOCKUP_DETECTOR 801 def_bool y 802 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 803 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 804 805config BOOTPARAM_HARDLOCKUP_PANIC 806 bool "Panic (Reboot) On Hard Lockups" 807 depends on HARDLOCKUP_DETECTOR 808 help 809 Say Y here to enable the kernel to panic on "hard lockups", 810 which are bugs that cause the kernel to loop in kernel 811 mode with interrupts disabled for more than 10 seconds (configurable 812 using the watchdog_thresh sysctl). 813 814 Say N if unsure. 815 816config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 817 int 818 depends on HARDLOCKUP_DETECTOR 819 range 0 1 820 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 821 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 822 823config BOOTPARAM_SOFTLOCKUP_PANIC 824 bool "Panic (Reboot) On Soft Lockups" 825 depends on LOCKUP_DETECTOR 826 help 827 Say Y here to enable the kernel to panic on "soft lockups", 828 which are bugs that cause the kernel to loop in kernel 829 mode for more than 20 seconds (configurable using the watchdog_thresh 830 sysctl), without giving other tasks a chance to run. 831 832 The panic can be used in combination with panic_timeout, 833 to cause the system to reboot automatically after a 834 lockup has been detected. This feature is useful for 835 high-availability systems that have uptime guarantees and 836 where a lockup must be resolved ASAP. 837 838 Say N if unsure. 839 840config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 841 int 842 depends on LOCKUP_DETECTOR 843 range 0 1 844 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 845 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 846 847config DETECT_HUNG_TASK 848 bool "Detect Hung Tasks" 849 depends on DEBUG_KERNEL 850 default LOCKUP_DETECTOR 851 help 852 Say Y here to enable the kernel to detect "hung tasks", 853 which are bugs that cause the task to be stuck in 854 uninterruptible "D" state indefinitely. 855 856 When a hung task is detected, the kernel will print the 857 current stack trace (which you should report), but the 858 task will stay in uninterruptible state. If lockdep is 859 enabled then all held locks will also be reported. This 860 feature has negligible overhead. 861 862config DEFAULT_HUNG_TASK_TIMEOUT 863 int "Default timeout for hung task detection (in seconds)" 864 depends on DETECT_HUNG_TASK 865 default 120 866 help 867 This option controls the default timeout (in seconds) used 868 to determine when a task has become non-responsive and should 869 be considered hung. 870 871 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 872 sysctl or by writing a value to 873 /proc/sys/kernel/hung_task_timeout_secs. 874 875 A timeout of 0 disables the check. The default is two minutes. 876 Keeping the default should be fine in most cases. 877 878config BOOTPARAM_HUNG_TASK_PANIC 879 bool "Panic (Reboot) On Hung Tasks" 880 depends on DETECT_HUNG_TASK 881 help 882 Say Y here to enable the kernel to panic on "hung tasks", 883 which are bugs that cause the kernel to leave a task stuck 884 in uninterruptible "D" state. 885 886 The panic can be used in combination with panic_timeout, 887 to cause the system to reboot automatically after a 888 hung task has been detected. This feature is useful for 889 high-availability systems that have uptime guarantees and 890 where a hung tasks must be resolved ASAP. 891 892 Say N if unsure. 893 894config BOOTPARAM_HUNG_TASK_PANIC_VALUE 895 int 896 depends on DETECT_HUNG_TASK 897 range 0 1 898 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 899 default 1 if BOOTPARAM_HUNG_TASK_PANIC 900 901config WQ_WATCHDOG 902 bool "Detect Workqueue Stalls" 903 depends on DEBUG_KERNEL 904 help 905 Say Y here to enable stall detection on workqueues. If a 906 worker pool doesn't make forward progress on a pending work 907 item for over a given amount of time, 30s by default, a 908 warning message is printed along with dump of workqueue 909 state. This can be configured through kernel parameter 910 "workqueue.watchdog_thresh" and its sysfs counterpart. 911 912endmenu # "Debug lockups and hangs" 913 914config PANIC_ON_OOPS 915 bool "Panic on Oops" 916 help 917 Say Y here to enable the kernel to panic when it oopses. This 918 has the same effect as setting oops=panic on the kernel command 919 line. 920 921 This feature is useful to ensure that the kernel does not do 922 anything erroneous after an oops which could result in data 923 corruption or other issues. 924 925 Say N if unsure. 926 927config PANIC_ON_OOPS_VALUE 928 int 929 range 0 1 930 default 0 if !PANIC_ON_OOPS 931 default 1 if PANIC_ON_OOPS 932 933config PANIC_TIMEOUT 934 int "panic timeout" 935 default 0 936 help 937 Set the timeout value (in seconds) until a reboot occurs when the 938 the kernel panics. If n = 0, then we wait forever. A timeout 939 value n > 0 will wait n seconds before rebooting, while a timeout 940 value n < 0 will reboot immediately. 941 942config SCHED_DEBUG 943 bool "Collect scheduler debugging info" 944 depends on DEBUG_KERNEL && PROC_FS 945 default y 946 help 947 If you say Y here, the /proc/sched_debug file will be provided 948 that can help debug the scheduler. The runtime overhead of this 949 option is minimal. 950 951config SCHED_INFO 952 bool 953 default n 954 955config SCHEDSTATS 956 bool "Collect scheduler statistics" 957 depends on DEBUG_KERNEL && PROC_FS 958 select SCHED_INFO 959 help 960 If you say Y here, additional code will be inserted into the 961 scheduler and related routines to collect statistics about 962 scheduler behavior and provide them in /proc/schedstat. These 963 stats may be useful for both tuning and debugging the scheduler 964 If you aren't debugging the scheduler or trying to tune a specific 965 application, you can say N to avoid the very slight overhead 966 this adds. 967 968config SCHED_STACK_END_CHECK 969 bool "Detect stack corruption on calls to schedule()" 970 depends on DEBUG_KERNEL 971 default n 972 help 973 This option checks for a stack overrun on calls to schedule(). 974 If the stack end location is found to be over written always panic as 975 the content of the corrupted region can no longer be trusted. 976 This is to ensure no erroneous behaviour occurs which could result in 977 data corruption or a sporadic crash at a later stage once the region 978 is examined. The runtime overhead introduced is minimal. 979 980config DEBUG_TIMEKEEPING 981 bool "Enable extra timekeeping sanity checking" 982 help 983 This option will enable additional timekeeping sanity checks 984 which may be helpful when diagnosing issues where timekeeping 985 problems are suspected. 986 987 This may include checks in the timekeeping hotpaths, so this 988 option may have a (very small) performance impact to some 989 workloads. 990 991 If unsure, say N. 992 993config TIMER_STATS 994 bool "Collect kernel timers statistics" 995 depends on DEBUG_KERNEL && PROC_FS 996 help 997 If you say Y here, additional code will be inserted into the 998 timer routines to collect statistics about kernel timers being 999 reprogrammed. The statistics can be read from /proc/timer_stats. 1000 The statistics collection is started by writing 1 to /proc/timer_stats, 1001 writing 0 stops it. This feature is useful to collect information 1002 about timer usage patterns in kernel and userspace. This feature 1003 is lightweight if enabled in the kernel config but not activated 1004 (it defaults to deactivated on bootup and will only be activated 1005 if some application like powertop activates it explicitly). 1006 1007config DEBUG_PREEMPT 1008 bool "Debug preemptible kernel" 1009 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 1010 default y 1011 help 1012 If you say Y here then the kernel will use a debug variant of the 1013 commonly used smp_processor_id() function and will print warnings 1014 if kernel code uses it in a preemption-unsafe way. Also, the kernel 1015 will detect preemption count underflows. 1016 1017menu "Lock Debugging (spinlocks, mutexes, etc...)" 1018 1019config DEBUG_RT_MUTEXES 1020 bool "RT Mutex debugging, deadlock detection" 1021 depends on DEBUG_KERNEL && RT_MUTEXES 1022 help 1023 This allows rt mutex semantics violations and rt mutex related 1024 deadlocks (lockups) to be detected and reported automatically. 1025 1026config DEBUG_SPINLOCK 1027 bool "Spinlock and rw-lock debugging: basic checks" 1028 depends on DEBUG_KERNEL 1029 select UNINLINE_SPIN_UNLOCK 1030 help 1031 Say Y here and build SMP to catch missing spinlock initialization 1032 and certain other kinds of spinlock errors commonly made. This is 1033 best used in conjunction with the NMI watchdog so that spinlock 1034 deadlocks are also debuggable. 1035 1036config DEBUG_MUTEXES 1037 bool "Mutex debugging: basic checks" 1038 depends on DEBUG_KERNEL 1039 help 1040 This feature allows mutex semantics violations to be detected and 1041 reported. 1042 1043config DEBUG_WW_MUTEX_SLOWPATH 1044 bool "Wait/wound mutex debugging: Slowpath testing" 1045 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1046 select DEBUG_LOCK_ALLOC 1047 select DEBUG_SPINLOCK 1048 select DEBUG_MUTEXES 1049 help 1050 This feature enables slowpath testing for w/w mutex users by 1051 injecting additional -EDEADLK wound/backoff cases. Together with 1052 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 1053 will test all possible w/w mutex interface abuse with the 1054 exception of simply not acquiring all the required locks. 1055 Note that this feature can introduce significant overhead, so 1056 it really should not be enabled in a production or distro kernel, 1057 even a debug kernel. If you are a driver writer, enable it. If 1058 you are a distro, do not. 1059 1060config DEBUG_LOCK_ALLOC 1061 bool "Lock debugging: detect incorrect freeing of live locks" 1062 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1063 select DEBUG_SPINLOCK 1064 select DEBUG_MUTEXES 1065 select LOCKDEP 1066 help 1067 This feature will check whether any held lock (spinlock, rwlock, 1068 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1069 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1070 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1071 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1072 held during task exit. 1073 1074config PROVE_LOCKING 1075 bool "Lock debugging: prove locking correctness" 1076 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1077 select LOCKDEP 1078 select DEBUG_SPINLOCK 1079 select DEBUG_MUTEXES 1080 select DEBUG_LOCK_ALLOC 1081 select TRACE_IRQFLAGS 1082 default n 1083 help 1084 This feature enables the kernel to prove that all locking 1085 that occurs in the kernel runtime is mathematically 1086 correct: that under no circumstance could an arbitrary (and 1087 not yet triggered) combination of observed locking 1088 sequences (on an arbitrary number of CPUs, running an 1089 arbitrary number of tasks and interrupt contexts) cause a 1090 deadlock. 1091 1092 In short, this feature enables the kernel to report locking 1093 related deadlocks before they actually occur. 1094 1095 The proof does not depend on how hard and complex a 1096 deadlock scenario would be to trigger: how many 1097 participant CPUs, tasks and irq-contexts would be needed 1098 for it to trigger. The proof also does not depend on 1099 timing: if a race and a resulting deadlock is possible 1100 theoretically (no matter how unlikely the race scenario 1101 is), it will be proven so and will immediately be 1102 reported by the kernel (once the event is observed that 1103 makes the deadlock theoretically possible). 1104 1105 If a deadlock is impossible (i.e. the locking rules, as 1106 observed by the kernel, are mathematically correct), the 1107 kernel reports nothing. 1108 1109 NOTE: this feature can also be enabled for rwlocks, mutexes 1110 and rwsems - in which case all dependencies between these 1111 different locking variants are observed and mapped too, and 1112 the proof of observed correctness is also maintained for an 1113 arbitrary combination of these separate locking variants. 1114 1115 For more details, see Documentation/locking/lockdep-design.txt. 1116 1117config PROVE_LOCKING_SMALL 1118 bool 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 LOCK_STAT 1129 bool "Lock usage statistics" 1130 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1131 select LOCKDEP 1132 select DEBUG_SPINLOCK 1133 select DEBUG_MUTEXES 1134 select DEBUG_LOCK_ALLOC 1135 default n 1136 help 1137 This feature enables tracking lock contention points 1138 1139 For more details, see Documentation/locking/lockstat.txt 1140 1141 This also enables lock events required by "perf lock", 1142 subcommand of perf. 1143 If you want to use "perf lock", you also need to turn on 1144 CONFIG_EVENT_TRACING. 1145 1146 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1147 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1148 1149config DEBUG_LOCKDEP 1150 bool "Lock dependency engine debugging" 1151 depends on DEBUG_KERNEL && LOCKDEP 1152 help 1153 If you say Y here, the lock dependency engine will do 1154 additional runtime checks to debug itself, at the price 1155 of more runtime overhead. 1156 1157config DEBUG_ATOMIC_SLEEP 1158 bool "Sleep inside atomic section checking" 1159 select PREEMPT_COUNT 1160 depends on DEBUG_KERNEL 1161 help 1162 If you say Y here, various routines which may sleep will become very 1163 noisy if they are called inside atomic sections: when a spinlock is 1164 held, inside an rcu read side critical section, inside preempt disabled 1165 sections, inside an interrupt, etc... 1166 1167config DEBUG_LOCKING_API_SELFTESTS 1168 bool "Locking API boot-time self-tests" 1169 depends on DEBUG_KERNEL 1170 help 1171 Say Y here if you want the kernel to run a short self-test during 1172 bootup. The self-test checks whether common types of locking bugs 1173 are detected by debugging mechanisms or not. (if you disable 1174 lock debugging then those bugs wont be detected of course.) 1175 The following locking APIs are covered: spinlocks, rwlocks, 1176 mutexes and rwsems. 1177 1178config LOCK_TORTURE_TEST 1179 tristate "torture tests for locking" 1180 depends on DEBUG_KERNEL 1181 select TORTURE_TEST 1182 default n 1183 help 1184 This option provides a kernel module that runs torture tests 1185 on kernel locking primitives. The kernel module may be built 1186 after the fact on the running kernel to be tested, if desired. 1187 1188 Say Y here if you want kernel locking-primitive torture tests 1189 to be built into the kernel. 1190 Say M if you want these torture tests to build as a module. 1191 Say N if you are unsure. 1192 1193endmenu # lock debugging 1194 1195config TRACE_IRQFLAGS 1196 bool 1197 help 1198 Enables hooks to interrupt enabling and disabling for 1199 either tracing or lock debugging. 1200 1201config STACKTRACE 1202 bool "Stack backtrace support" 1203 depends on STACKTRACE_SUPPORT 1204 help 1205 This option causes the kernel to create a /proc/pid/stack for 1206 every process, showing its current stack trace. 1207 It is also used by various kernel debugging features that require 1208 stack trace generation. 1209 1210config DEBUG_KOBJECT 1211 bool "kobject debugging" 1212 depends on DEBUG_KERNEL 1213 help 1214 If you say Y here, some extra kobject debugging messages will be sent 1215 to the syslog. 1216 1217config DEBUG_KOBJECT_RELEASE 1218 bool "kobject release debugging" 1219 depends on DEBUG_OBJECTS_TIMERS 1220 help 1221 kobjects are reference counted objects. This means that their 1222 last reference count put is not predictable, and the kobject can 1223 live on past the point at which a driver decides to drop it's 1224 initial reference to the kobject gained on allocation. An 1225 example of this would be a struct device which has just been 1226 unregistered. 1227 1228 However, some buggy drivers assume that after such an operation, 1229 the memory backing the kobject can be immediately freed. This 1230 goes completely against the principles of a refcounted object. 1231 1232 If you say Y here, the kernel will delay the release of kobjects 1233 on the last reference count to improve the visibility of this 1234 kind of kobject release bug. 1235 1236config HAVE_DEBUG_BUGVERBOSE 1237 bool 1238 1239config DEBUG_BUGVERBOSE 1240 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1241 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1242 default y 1243 help 1244 Say Y here to make BUG() panics output the file name and line number 1245 of the BUG call as well as the EIP and oops trace. This aids 1246 debugging but costs about 70-100K of memory. 1247 1248config DEBUG_LIST 1249 bool "Debug linked list manipulation" 1250 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION 1251 help 1252 Enable this to turn on extended checks in the linked-list 1253 walking routines. 1254 1255 If unsure, say N. 1256 1257config DEBUG_PI_LIST 1258 bool "Debug priority linked list manipulation" 1259 depends on DEBUG_KERNEL 1260 help 1261 Enable this to turn on extended checks in the priority-ordered 1262 linked-list (plist) walking routines. This checks the entire 1263 list multiple times during each manipulation. 1264 1265 If unsure, say N. 1266 1267config DEBUG_SG 1268 bool "Debug SG table operations" 1269 depends on DEBUG_KERNEL 1270 help 1271 Enable this to turn on checks on scatter-gather tables. This can 1272 help find problems with drivers that do not properly initialize 1273 their sg tables. 1274 1275 If unsure, say N. 1276 1277config DEBUG_NOTIFIERS 1278 bool "Debug notifier call chains" 1279 depends on DEBUG_KERNEL 1280 help 1281 Enable this to turn on sanity checking for notifier call chains. 1282 This is most useful for kernel developers to make sure that 1283 modules properly unregister themselves from notifier chains. 1284 This is a relatively cheap check but if you care about maximum 1285 performance, say N. 1286 1287config DEBUG_CREDENTIALS 1288 bool "Debug credential management" 1289 depends on DEBUG_KERNEL 1290 help 1291 Enable this to turn on some debug checking for credential 1292 management. The additional code keeps track of the number of 1293 pointers from task_structs to any given cred struct, and checks to 1294 see that this number never exceeds the usage count of the cred 1295 struct. 1296 1297 Furthermore, if SELinux is enabled, this also checks that the 1298 security pointer in the cred struct is never seen to be invalid. 1299 1300 If unsure, say N. 1301 1302menu "RCU Debugging" 1303 1304config PROVE_RCU 1305 def_bool PROVE_LOCKING 1306 1307config PROVE_RCU_REPEATEDLY 1308 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1309 depends on PROVE_RCU 1310 default n 1311 help 1312 By itself, PROVE_RCU will disable checking upon issuing the 1313 first warning (or "splat"). This feature prevents such 1314 disabling, allowing multiple RCU-lockdep warnings to be printed 1315 on a single reboot. 1316 1317 Say Y to allow multiple RCU-lockdep warnings per boot. 1318 1319 Say N if you are unsure. 1320 1321config SPARSE_RCU_POINTER 1322 bool "RCU debugging: sparse-based checks for pointer usage" 1323 default n 1324 help 1325 This feature enables the __rcu sparse annotation for 1326 RCU-protected pointers. This annotation will cause sparse 1327 to flag any non-RCU used of annotated pointers. This can be 1328 helpful when debugging RCU usage. Please note that this feature 1329 is not intended to enforce code cleanliness; it is instead merely 1330 a debugging aid. 1331 1332 Say Y to make sparse flag questionable use of RCU-protected pointers 1333 1334 Say N if you are unsure. 1335 1336config TORTURE_TEST 1337 tristate 1338 default n 1339 1340config RCU_PERF_TEST 1341 tristate "performance tests for RCU" 1342 depends on DEBUG_KERNEL 1343 select TORTURE_TEST 1344 select SRCU 1345 select TASKS_RCU 1346 default n 1347 help 1348 This option provides a kernel module that runs performance 1349 tests on the RCU infrastructure. The kernel module may be built 1350 after the fact on the running kernel to be tested, if desired. 1351 1352 Say Y here if you want RCU performance tests to be built into 1353 the kernel. 1354 Say M if you want the RCU performance tests to build as a module. 1355 Say N if you are unsure. 1356 1357config RCU_TORTURE_TEST 1358 tristate "torture tests for RCU" 1359 depends on DEBUG_KERNEL 1360 select TORTURE_TEST 1361 select SRCU 1362 select TASKS_RCU 1363 default n 1364 help 1365 This option provides a kernel module that runs torture tests 1366 on the RCU infrastructure. The kernel module may be built 1367 after the fact on the running kernel to be tested, if desired. 1368 1369 Say Y here if you want RCU torture tests to be built into 1370 the kernel. 1371 Say M if you want the RCU torture tests to build as a module. 1372 Say N if you are unsure. 1373 1374config RCU_TORTURE_TEST_SLOW_PREINIT 1375 bool "Slow down RCU grace-period pre-initialization to expose races" 1376 depends on RCU_TORTURE_TEST 1377 help 1378 This option delays grace-period pre-initialization (the 1379 propagation of CPU-hotplug changes up the rcu_node combining 1380 tree) for a few jiffies between initializing each pair of 1381 consecutive rcu_node structures. This helps to expose races 1382 involving grace-period pre-initialization, in other words, it 1383 makes your kernel less stable. It can also greatly increase 1384 grace-period latency, especially on systems with large numbers 1385 of CPUs. This is useful when torture-testing RCU, but in 1386 almost no other circumstance. 1387 1388 Say Y here if you want your system to crash and hang more often. 1389 Say N if you want a sane system. 1390 1391config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY 1392 int "How much to slow down RCU grace-period pre-initialization" 1393 range 0 5 1394 default 3 1395 depends on RCU_TORTURE_TEST_SLOW_PREINIT 1396 help 1397 This option specifies the number of jiffies to wait between 1398 each rcu_node structure pre-initialization step. 1399 1400config RCU_TORTURE_TEST_SLOW_INIT 1401 bool "Slow down RCU grace-period initialization to expose races" 1402 depends on RCU_TORTURE_TEST 1403 help 1404 This option delays grace-period initialization for a few 1405 jiffies between initializing each pair of consecutive 1406 rcu_node structures. This helps to expose races involving 1407 grace-period initialization, in other words, it makes your 1408 kernel less stable. It can also greatly increase grace-period 1409 latency, especially on systems with large numbers of CPUs. 1410 This is useful when torture-testing RCU, but in almost no 1411 other circumstance. 1412 1413 Say Y here if you want your system to crash and hang more often. 1414 Say N if you want a sane system. 1415 1416config RCU_TORTURE_TEST_SLOW_INIT_DELAY 1417 int "How much to slow down RCU grace-period initialization" 1418 range 0 5 1419 default 3 1420 depends on RCU_TORTURE_TEST_SLOW_INIT 1421 help 1422 This option specifies the number of jiffies to wait between 1423 each rcu_node structure initialization. 1424 1425config RCU_TORTURE_TEST_SLOW_CLEANUP 1426 bool "Slow down RCU grace-period cleanup to expose races" 1427 depends on RCU_TORTURE_TEST 1428 help 1429 This option delays grace-period cleanup for a few jiffies 1430 between cleaning up each pair of consecutive rcu_node 1431 structures. This helps to expose races involving grace-period 1432 cleanup, in other words, it makes your kernel less stable. 1433 It can also greatly increase grace-period latency, especially 1434 on systems with large numbers of CPUs. This is useful when 1435 torture-testing RCU, but in almost no other circumstance. 1436 1437 Say Y here if you want your system to crash and hang more often. 1438 Say N if you want a sane system. 1439 1440config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY 1441 int "How much to slow down RCU grace-period cleanup" 1442 range 0 5 1443 default 3 1444 depends on RCU_TORTURE_TEST_SLOW_CLEANUP 1445 help 1446 This option specifies the number of jiffies to wait between 1447 each rcu_node structure cleanup operation. 1448 1449config RCU_CPU_STALL_TIMEOUT 1450 int "RCU CPU stall timeout in seconds" 1451 depends on RCU_STALL_COMMON 1452 range 3 300 1453 default 21 1454 help 1455 If a given RCU grace period extends more than the specified 1456 number of seconds, a CPU stall warning is printed. If the 1457 RCU grace period persists, additional CPU stall warnings are 1458 printed at more widely spaced intervals. 1459 1460config RCU_TRACE 1461 bool "Enable tracing for RCU" 1462 depends on DEBUG_KERNEL 1463 select TRACE_CLOCK 1464 help 1465 This option provides tracing in RCU which presents stats 1466 in debugfs for debugging RCU implementation. It also enables 1467 additional tracepoints for ftrace-style event tracing. 1468 1469 Say Y here if you want to enable RCU tracing 1470 Say N if you are unsure. 1471 1472config RCU_EQS_DEBUG 1473 bool "Provide debugging asserts for adding NO_HZ support to an arch" 1474 depends on DEBUG_KERNEL 1475 help 1476 This option provides consistency checks in RCU's handling of 1477 NO_HZ. These checks have proven quite helpful in detecting 1478 bugs in arch-specific NO_HZ code. 1479 1480 Say N here if you need ultimate kernel/user switch latencies 1481 Say Y if you are unsure 1482 1483endmenu # "RCU Debugging" 1484 1485config DEBUG_WQ_FORCE_RR_CPU 1486 bool "Force round-robin CPU selection for unbound work items" 1487 depends on DEBUG_KERNEL 1488 default n 1489 help 1490 Workqueue used to implicitly guarantee that work items queued 1491 without explicit CPU specified are put on the local CPU. This 1492 guarantee is no longer true and while local CPU is still 1493 preferred work items may be put on foreign CPUs. Kernel 1494 parameter "workqueue.debug_force_rr_cpu" is added to force 1495 round-robin CPU selection to flush out usages which depend on the 1496 now broken guarantee. This config option enables the debug 1497 feature by default. When enabled, memory and cache locality will 1498 be impacted. 1499 1500config DEBUG_BLOCK_EXT_DEVT 1501 bool "Force extended block device numbers and spread them" 1502 depends on DEBUG_KERNEL 1503 depends on BLOCK 1504 default n 1505 help 1506 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1507 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1508 YOU ARE DOING. Distros, please enable this and fix whatever 1509 is broken. 1510 1511 Conventionally, block device numbers are allocated from 1512 predetermined contiguous area. However, extended block area 1513 may introduce non-contiguous block device numbers. This 1514 option forces most block device numbers to be allocated from 1515 the extended space and spreads them to discover kernel or 1516 userland code paths which assume predetermined contiguous 1517 device number allocation. 1518 1519 Note that turning on this debug option shuffles all the 1520 device numbers for all IDE and SCSI devices including libata 1521 ones, so root partition specified using device number 1522 directly (via rdev or root=MAJ:MIN) won't work anymore. 1523 Textual device names (root=/dev/sdXn) will continue to work. 1524 1525 Say N if you are unsure. 1526 1527config CPU_HOTPLUG_STATE_CONTROL 1528 bool "Enable CPU hotplug state control" 1529 depends on DEBUG_KERNEL 1530 depends on HOTPLUG_CPU 1531 default n 1532 help 1533 Allows to write steps between "offline" and "online" to the CPUs 1534 sysfs target file so states can be stepped granular. This is a debug 1535 option for now as the hotplug machinery cannot be stopped and 1536 restarted at arbitrary points yet. 1537 1538 Say N if your are unsure. 1539 1540config NOTIFIER_ERROR_INJECTION 1541 tristate "Notifier error injection" 1542 depends on DEBUG_KERNEL 1543 select DEBUG_FS 1544 help 1545 This option provides the ability to inject artificial errors to 1546 specified notifier chain callbacks. It is useful to test the error 1547 handling of notifier call chain failures. 1548 1549 Say N if unsure. 1550 1551config PM_NOTIFIER_ERROR_INJECT 1552 tristate "PM notifier error injection module" 1553 depends on PM && NOTIFIER_ERROR_INJECTION 1554 default m if PM_DEBUG 1555 help 1556 This option provides the ability to inject artificial errors to 1557 PM notifier chain callbacks. It is controlled through debugfs 1558 interface /sys/kernel/debug/notifier-error-inject/pm 1559 1560 If the notifier call chain should be failed with some events 1561 notified, write the error code to "actions/<notifier event>/error". 1562 1563 Example: Inject PM suspend error (-12 = -ENOMEM) 1564 1565 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1566 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1567 # echo mem > /sys/power/state 1568 bash: echo: write error: Cannot allocate memory 1569 1570 To compile this code as a module, choose M here: the module will 1571 be called pm-notifier-error-inject. 1572 1573 If unsure, say N. 1574 1575config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1576 tristate "OF reconfig notifier error injection module" 1577 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1578 help 1579 This option provides the ability to inject artificial errors to 1580 OF reconfig notifier chain callbacks. It is controlled 1581 through debugfs interface under 1582 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1583 1584 If the notifier call chain should be failed with some events 1585 notified, write the error code to "actions/<notifier event>/error". 1586 1587 To compile this code as a module, choose M here: the module will 1588 be called of-reconfig-notifier-error-inject. 1589 1590 If unsure, say N. 1591 1592config NETDEV_NOTIFIER_ERROR_INJECT 1593 tristate "Netdev notifier error injection module" 1594 depends on NET && NOTIFIER_ERROR_INJECTION 1595 help 1596 This option provides the ability to inject artificial errors to 1597 netdevice notifier chain callbacks. It is controlled through debugfs 1598 interface /sys/kernel/debug/notifier-error-inject/netdev 1599 1600 If the notifier call chain should be failed with some events 1601 notified, write the error code to "actions/<notifier event>/error". 1602 1603 Example: Inject netdevice mtu change error (-22 = -EINVAL) 1604 1605 # cd /sys/kernel/debug/notifier-error-inject/netdev 1606 # echo -22 > actions/NETDEV_CHANGEMTU/error 1607 # ip link set eth0 mtu 1024 1608 RTNETLINK answers: Invalid argument 1609 1610 To compile this code as a module, choose M here: the module will 1611 be called netdev-notifier-error-inject. 1612 1613 If unsure, say N. 1614 1615config FAULT_INJECTION 1616 bool "Fault-injection framework" 1617 depends on DEBUG_KERNEL 1618 help 1619 Provide fault-injection framework. 1620 For more details, see Documentation/fault-injection/. 1621 1622config FAILSLAB 1623 bool "Fault-injection capability for kmalloc" 1624 depends on FAULT_INJECTION 1625 depends on SLAB || SLUB 1626 help 1627 Provide fault-injection capability for kmalloc. 1628 1629config FAIL_PAGE_ALLOC 1630 bool "Fault-injection capabilitiy for alloc_pages()" 1631 depends on FAULT_INJECTION 1632 help 1633 Provide fault-injection capability for alloc_pages(). 1634 1635config FAIL_MAKE_REQUEST 1636 bool "Fault-injection capability for disk IO" 1637 depends on FAULT_INJECTION && BLOCK 1638 help 1639 Provide fault-injection capability for disk IO. 1640 1641config FAIL_IO_TIMEOUT 1642 bool "Fault-injection capability for faking disk interrupts" 1643 depends on FAULT_INJECTION && BLOCK 1644 help 1645 Provide fault-injection capability on end IO handling. This 1646 will make the block layer "forget" an interrupt as configured, 1647 thus exercising the error handling. 1648 1649 Only works with drivers that use the generic timeout handling, 1650 for others it wont do anything. 1651 1652config FAIL_MMC_REQUEST 1653 bool "Fault-injection capability for MMC IO" 1654 depends on FAULT_INJECTION_DEBUG_FS && MMC 1655 help 1656 Provide fault-injection capability for MMC IO. 1657 This will make the mmc core return data errors. This is 1658 useful to test the error handling in the mmc block device 1659 and to test how the mmc host driver handles retries from 1660 the block device. 1661 1662config FAIL_FUTEX 1663 bool "Fault-injection capability for futexes" 1664 select DEBUG_FS 1665 depends on FAULT_INJECTION && FUTEX 1666 help 1667 Provide fault-injection capability for futexes. 1668 1669config FAULT_INJECTION_DEBUG_FS 1670 bool "Debugfs entries for fault-injection capabilities" 1671 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1672 help 1673 Enable configuration of fault-injection capabilities via debugfs. 1674 1675config FAULT_INJECTION_STACKTRACE_FILTER 1676 bool "stacktrace filter for fault-injection capabilities" 1677 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1678 depends on !X86_64 1679 select STACKTRACE 1680 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1681 help 1682 Provide stacktrace filter for fault-injection capabilities 1683 1684config LATENCYTOP 1685 bool "Latency measuring infrastructure" 1686 depends on DEBUG_KERNEL 1687 depends on STACKTRACE_SUPPORT 1688 depends on PROC_FS 1689 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1690 select KALLSYMS 1691 select KALLSYMS_ALL 1692 select STACKTRACE 1693 select SCHEDSTATS 1694 select SCHED_DEBUG 1695 help 1696 Enable this option if you want to use the LatencyTOP tool 1697 to find out which userspace is blocking on what kernel operations. 1698 1699source kernel/trace/Kconfig 1700 1701menu "Runtime Testing" 1702 1703config LKDTM 1704 tristate "Linux Kernel Dump Test Tool Module" 1705 depends on DEBUG_FS 1706 depends on BLOCK 1707 default n 1708 help 1709 This module enables testing of the different dumping mechanisms by 1710 inducing system failures at predefined crash points. 1711 If you don't need it: say N 1712 Choose M here to compile this code as a module. The module will be 1713 called lkdtm. 1714 1715 Documentation on how to use the module can be found in 1716 Documentation/fault-injection/provoke-crashes.txt 1717 1718config TEST_LIST_SORT 1719 bool "Linked list sorting test" 1720 depends on DEBUG_KERNEL 1721 help 1722 Enable this to turn on 'list_sort()' function test. This test is 1723 executed only once during system boot, so affects only boot time. 1724 1725 If unsure, say N. 1726 1727config KPROBES_SANITY_TEST 1728 bool "Kprobes sanity tests" 1729 depends on DEBUG_KERNEL 1730 depends on KPROBES 1731 default n 1732 help 1733 This option provides for testing basic kprobes functionality on 1734 boot. A sample kprobe, jprobe and kretprobe are inserted and 1735 verified for functionality. 1736 1737 Say N if you are unsure. 1738 1739config BACKTRACE_SELF_TEST 1740 tristate "Self test for the backtrace code" 1741 depends on DEBUG_KERNEL 1742 default n 1743 help 1744 This option provides a kernel module that can be used to test 1745 the kernel stack backtrace code. This option is not useful 1746 for distributions or general kernels, but only for kernel 1747 developers working on architecture code. 1748 1749 Note that if you want to also test saved backtraces, you will 1750 have to enable STACKTRACE as well. 1751 1752 Say N if you are unsure. 1753 1754config RBTREE_TEST 1755 tristate "Red-Black tree test" 1756 depends on DEBUG_KERNEL 1757 help 1758 A benchmark measuring the performance of the rbtree library. 1759 Also includes rbtree invariant checks. 1760 1761config INTERVAL_TREE_TEST 1762 tristate "Interval tree test" 1763 depends on m && DEBUG_KERNEL 1764 select INTERVAL_TREE 1765 help 1766 A benchmark measuring the performance of the interval tree library 1767 1768config PERCPU_TEST 1769 tristate "Per cpu operations test" 1770 depends on m && DEBUG_KERNEL 1771 help 1772 Enable this option to build test module which validates per-cpu 1773 operations. 1774 1775 If unsure, say N. 1776 1777config ATOMIC64_SELFTEST 1778 bool "Perform an atomic64_t self-test at boot" 1779 help 1780 Enable this option to test the atomic64_t functions at boot. 1781 1782 If unsure, say N. 1783 1784config ASYNC_RAID6_TEST 1785 tristate "Self test for hardware accelerated raid6 recovery" 1786 depends on ASYNC_RAID6_RECOV 1787 select ASYNC_MEMCPY 1788 ---help--- 1789 This is a one-shot self test that permutes through the 1790 recovery of all the possible two disk failure scenarios for a 1791 N-disk array. Recovery is performed with the asynchronous 1792 raid6 recovery routines, and will optionally use an offload 1793 engine if one is available. 1794 1795 If unsure, say N. 1796 1797config TEST_HEXDUMP 1798 tristate "Test functions located in the hexdump module at runtime" 1799 1800config TEST_STRING_HELPERS 1801 tristate "Test functions located in the string_helpers module at runtime" 1802 1803config TEST_KSTRTOX 1804 tristate "Test kstrto*() family of functions at runtime" 1805 1806config TEST_PRINTF 1807 tristate "Test printf() family of functions at runtime" 1808 1809config TEST_BITMAP 1810 tristate "Test bitmap_*() family of functions at runtime" 1811 default n 1812 help 1813 Enable this option to test the bitmap functions at boot. 1814 1815 If unsure, say N. 1816 1817config TEST_UUID 1818 tristate "Test functions located in the uuid module at runtime" 1819 1820config TEST_RHASHTABLE 1821 tristate "Perform selftest on resizable hash table" 1822 default n 1823 help 1824 Enable this option to test the rhashtable functions at boot. 1825 1826 If unsure, say N. 1827 1828config TEST_HASH 1829 tristate "Perform selftest on hash functions" 1830 default n 1831 help 1832 Enable this option to test the kernel's integer (<linux/hash,h>) 1833 and string (<linux/stringhash.h>) hash functions on boot 1834 (or module load). 1835 1836 This is intended to help people writing architecture-specific 1837 optimized versions. If unsure, say N. 1838 1839endmenu # runtime tests 1840 1841config PROVIDE_OHCI1394_DMA_INIT 1842 bool "Remote debugging over FireWire early on boot" 1843 depends on PCI && X86 1844 help 1845 If you want to debug problems which hang or crash the kernel early 1846 on boot and the crashing machine has a FireWire port, you can use 1847 this feature to remotely access the memory of the crashed machine 1848 over FireWire. This employs remote DMA as part of the OHCI1394 1849 specification which is now the standard for FireWire controllers. 1850 1851 With remote DMA, you can monitor the printk buffer remotely using 1852 firescope and access all memory below 4GB using fireproxy from gdb. 1853 Even controlling a kernel debugger is possible using remote DMA. 1854 1855 Usage: 1856 1857 If ohci1394_dma=early is used as boot parameter, it will initialize 1858 all OHCI1394 controllers which are found in the PCI config space. 1859 1860 As all changes to the FireWire bus such as enabling and disabling 1861 devices cause a bus reset and thereby disable remote DMA for all 1862 devices, be sure to have the cable plugged and FireWire enabled on 1863 the debugging host before booting the debug target for debugging. 1864 1865 This code (~1k) is freed after boot. By then, the firewire stack 1866 in charge of the OHCI-1394 controllers should be used instead. 1867 1868 See Documentation/debugging-via-ohci1394.txt for more information. 1869 1870config DMA_API_DEBUG 1871 bool "Enable debugging of DMA-API usage" 1872 depends on HAVE_DMA_API_DEBUG 1873 help 1874 Enable this option to debug the use of the DMA API by device drivers. 1875 With this option you will be able to detect common bugs in device 1876 drivers like double-freeing of DMA mappings or freeing mappings that 1877 were never allocated. 1878 1879 This also attempts to catch cases where a page owned by DMA is 1880 accessed by the cpu in a way that could cause data corruption. For 1881 example, this enables cow_user_page() to check that the source page is 1882 not undergoing DMA. 1883 1884 This option causes a performance degradation. Use only if you want to 1885 debug device drivers and dma interactions. 1886 1887 If unsure, say N. 1888 1889config TEST_LKM 1890 tristate "Test module loading with 'hello world' module" 1891 default n 1892 depends on m 1893 help 1894 This builds the "test_module" module that emits "Hello, world" 1895 on printk when loaded. It is designed to be used for basic 1896 evaluation of the module loading subsystem (for example when 1897 validating module verification). It lacks any extra dependencies, 1898 and will not normally be loaded by the system unless explicitly 1899 requested by name. 1900 1901 If unsure, say N. 1902 1903config TEST_USER_COPY 1904 tristate "Test user/kernel boundary protections" 1905 default n 1906 depends on m 1907 help 1908 This builds the "test_user_copy" module that runs sanity checks 1909 on the copy_to/from_user infrastructure, making sure basic 1910 user/kernel boundary testing is working. If it fails to load, 1911 a regression has been detected in the user/kernel memory boundary 1912 protections. 1913 1914 If unsure, say N. 1915 1916config TEST_BPF 1917 tristate "Test BPF filter functionality" 1918 default n 1919 depends on m && NET 1920 help 1921 This builds the "test_bpf" module that runs various test vectors 1922 against the BPF interpreter or BPF JIT compiler depending on the 1923 current setting. This is in particular useful for BPF JIT compiler 1924 development, but also to run regression tests against changes in 1925 the interpreter code. It also enables test stubs for eBPF maps and 1926 verifier used by user space verifier testsuite. 1927 1928 If unsure, say N. 1929 1930config TEST_FIRMWARE 1931 tristate "Test firmware loading via userspace interface" 1932 default n 1933 depends on FW_LOADER 1934 help 1935 This builds the "test_firmware" module that creates a userspace 1936 interface for testing firmware loading. This can be used to 1937 control the triggering of firmware loading without needing an 1938 actual firmware-using device. The contents can be rechecked by 1939 userspace. 1940 1941 If unsure, say N. 1942 1943config TEST_UDELAY 1944 tristate "udelay test driver" 1945 default n 1946 help 1947 This builds the "udelay_test" module that helps to make sure 1948 that udelay() is working properly. 1949 1950 If unsure, say N. 1951 1952config MEMTEST 1953 bool "Memtest" 1954 depends on HAVE_MEMBLOCK 1955 ---help--- 1956 This option adds a kernel parameter 'memtest', which allows memtest 1957 to be set. 1958 memtest=0, mean disabled; -- default 1959 memtest=1, mean do 1 test pattern; 1960 ... 1961 memtest=17, mean do 17 test patterns. 1962 If you are unsure how to answer this question, answer N. 1963 1964config TEST_STATIC_KEYS 1965 tristate "Test static keys" 1966 default n 1967 depends on m 1968 help 1969 Test the static key interfaces. 1970 1971 If unsure, say N. 1972 1973config BUG_ON_DATA_CORRUPTION 1974 bool "Trigger a BUG when data corruption is detected" 1975 select DEBUG_LIST 1976 help 1977 Select this option if the kernel should BUG when it encounters 1978 data corruption in kernel memory structures when they get checked 1979 for validity. 1980 1981 If unsure, say N. 1982 1983source "samples/Kconfig" 1984 1985source "lib/Kconfig.kgdb" 1986 1987source "lib/Kconfig.ubsan" 1988 1989config ARCH_HAS_DEVMEM_IS_ALLOWED 1990 bool 1991 1992config STRICT_DEVMEM 1993 bool "Filter access to /dev/mem" 1994 depends on MMU && DEVMEM 1995 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 1996 default y if TILE || PPC 1997 ---help--- 1998 If this option is disabled, you allow userspace (root) access to all 1999 of memory, including kernel and userspace memory. Accidental 2000 access to this is obviously disastrous, but specific access can 2001 be used by people debugging the kernel. Note that with PAT support 2002 enabled, even in this case there are restrictions on /dev/mem 2003 use due to the cache aliasing requirements. 2004 2005 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 2006 file only allows userspace access to PCI space and the BIOS code and 2007 data regions. This is sufficient for dosemu and X and all common 2008 users of /dev/mem. 2009 2010 If in doubt, say Y. 2011 2012config IO_STRICT_DEVMEM 2013 bool "Filter I/O access to /dev/mem" 2014 depends on STRICT_DEVMEM 2015 ---help--- 2016 If this option is disabled, you allow userspace (root) access to all 2017 io-memory regardless of whether a driver is actively using that 2018 range. Accidental access to this is obviously disastrous, but 2019 specific access can be used by people debugging kernel drivers. 2020 2021 If this option is switched on, the /dev/mem file only allows 2022 userspace access to *idle* io-memory ranges (see /proc/iomem) This 2023 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 2024 if the driver using a given range cannot be disabled. 2025 2026 If in doubt, say Y. 2027