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/DocBook/filesystems. 290 291 If unsure, say N. 292 293config HEADERS_CHECK 294 bool "Run 'make headers_check' when building vmlinux" 295 depends on !UML 296 help 297 This option will extract the user-visible kernel headers whenever 298 building the kernel, and will run basic sanity checks on them to 299 ensure that exported files do not attempt to include files which 300 were not exported, etc. 301 302 If you're making modifications to header files which are 303 relevant for userspace, say 'Y', and check the headers 304 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 305 your build tree), to make sure they're suitable. 306 307config DEBUG_SECTION_MISMATCH 308 bool "Enable full Section mismatch analysis" 309 help 310 The section mismatch analysis checks if there are illegal 311 references from one section to another section. 312 During linktime or runtime, some sections are dropped; 313 any use of code/data previously in these sections would 314 most likely result in an oops. 315 In the code, functions and variables are annotated with 316 __init,, etc. (see the full list in include/linux/init.h), 317 which results in the code/data being placed in specific sections. 318 The section mismatch analysis is always performed after a full 319 kernel build, and enabling this option causes the following 320 additional steps to occur: 321 - Add the option -fno-inline-functions-called-once to gcc commands. 322 When inlining a function annotated with __init in a non-init 323 function, we would lose the section information and thus 324 the analysis would not catch the illegal reference. 325 This option tells gcc to inline less (but it does result in 326 a larger kernel). 327 - Run the section mismatch analysis for each module/built-in.o file. 328 When we run the section mismatch analysis on vmlinux.o, we 329 lose valuable information about where the mismatch was 330 introduced. 331 Running the analysis for each module/built-in.o file 332 tells where the mismatch happens much closer to the 333 source. The drawback is that the same mismatch is 334 reported at least twice. 335 - Enable verbose reporting from modpost in order to help resolve 336 the section mismatches that are reported. 337 338config SECTION_MISMATCH_WARN_ONLY 339 bool "Make section mismatch errors non-fatal" 340 default y 341 help 342 If you say N here, the build process will fail if there are any 343 section mismatch, instead of just throwing warnings. 344 345 If unsure, say Y. 346 347# 348# Select this config option from the architecture Kconfig, if it 349# is preferred to always offer frame pointers as a config 350# option on the architecture (regardless of KERNEL_DEBUG): 351# 352config ARCH_WANT_FRAME_POINTERS 353 bool 354 help 355 356config FRAME_POINTER 357 bool "Compile the kernel with frame pointers" 358 depends on DEBUG_KERNEL && \ 359 (CRIS || M68K || FRV || UML || \ 360 SUPERH || BLACKFIN || MN10300 || METAG) || \ 361 ARCH_WANT_FRAME_POINTERS 362 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 363 help 364 If you say Y here the resulting kernel image will be slightly 365 larger and slower, but it gives very useful debugging information 366 in case of kernel bugs. (precise oopses/stacktraces/warnings) 367 368config STACK_VALIDATION 369 bool "Compile-time stack metadata validation" 370 depends on HAVE_STACK_VALIDATION 371 default n 372 help 373 Add compile-time checks to validate stack metadata, including frame 374 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure 375 that runtime stack traces are more reliable. 376 377 For more information, see 378 tools/objtool/Documentation/stack-validation.txt. 379 380config DEBUG_FORCE_WEAK_PER_CPU 381 bool "Force weak per-cpu definitions" 382 depends on DEBUG_KERNEL 383 help 384 s390 and alpha require percpu variables in modules to be 385 defined weak to work around addressing range issue which 386 puts the following two restrictions on percpu variable 387 definitions. 388 389 1. percpu symbols must be unique whether static or not 390 2. percpu variables can't be defined inside a function 391 392 To ensure that generic code follows the above rules, this 393 option forces all percpu variables to be defined as weak. 394 395endmenu # "Compiler options" 396 397config MAGIC_SYSRQ 398 bool "Magic SysRq key" 399 depends on !UML 400 help 401 If you say Y here, you will have some control over the system even 402 if the system crashes for example during kernel debugging (e.g., you 403 will be able to flush the buffer cache to disk, reboot the system 404 immediately or dump some status information). This is accomplished 405 by pressing various keys while holding SysRq (Alt+PrintScreen). It 406 also works on a serial console (on PC hardware at least), if you 407 send a BREAK and then within 5 seconds a command keypress. The 408 keys are documented in <file:Documentation/admin-guide/sysrq.rst>. 409 Don't say Y unless you really know what this hack does. 410 411config MAGIC_SYSRQ_DEFAULT_ENABLE 412 hex "Enable magic SysRq key functions by default" 413 depends on MAGIC_SYSRQ 414 default 0x1 415 help 416 Specifies which SysRq key functions are enabled by default. 417 This may be set to 1 or 0 to enable or disable them all, or 418 to a bitmask as described in Documentation/admin-guide/sysrq.rst. 419 420config MAGIC_SYSRQ_SERIAL 421 bool "Enable magic SysRq key over serial" 422 depends on MAGIC_SYSRQ 423 default y 424 help 425 Many embedded boards have a disconnected TTL level serial which can 426 generate some garbage that can lead to spurious false sysrq detects. 427 This option allows you to decide whether you want to enable the 428 magic SysRq key. 429 430config DEBUG_KERNEL 431 bool "Kernel debugging" 432 help 433 Say Y here if you are developing drivers or trying to debug and 434 identify kernel problems. 435 436menu "Memory Debugging" 437 438source mm/Kconfig.debug 439 440config DEBUG_OBJECTS 441 bool "Debug object operations" 442 depends on DEBUG_KERNEL 443 help 444 If you say Y here, additional code will be inserted into the 445 kernel to track the life time of various objects and validate 446 the operations on those objects. 447 448config DEBUG_OBJECTS_SELFTEST 449 bool "Debug objects selftest" 450 depends on DEBUG_OBJECTS 451 help 452 This enables the selftest of the object debug code. 453 454config DEBUG_OBJECTS_FREE 455 bool "Debug objects in freed memory" 456 depends on DEBUG_OBJECTS 457 help 458 This enables checks whether a k/v free operation frees an area 459 which contains an object which has not been deactivated 460 properly. This can make kmalloc/kfree-intensive workloads 461 much slower. 462 463config DEBUG_OBJECTS_TIMERS 464 bool "Debug timer objects" 465 depends on DEBUG_OBJECTS 466 help 467 If you say Y here, additional code will be inserted into the 468 timer routines to track the life time of timer objects and 469 validate the timer operations. 470 471config DEBUG_OBJECTS_WORK 472 bool "Debug work objects" 473 depends on DEBUG_OBJECTS 474 help 475 If you say Y here, additional code will be inserted into the 476 work queue routines to track the life time of work objects and 477 validate the work operations. 478 479config DEBUG_OBJECTS_RCU_HEAD 480 bool "Debug RCU callbacks objects" 481 depends on DEBUG_OBJECTS 482 help 483 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 484 485config DEBUG_OBJECTS_PERCPU_COUNTER 486 bool "Debug percpu counter objects" 487 depends on DEBUG_OBJECTS 488 help 489 If you say Y here, additional code will be inserted into the 490 percpu counter routines to track the life time of percpu counter 491 objects and validate the percpu counter operations. 492 493config DEBUG_OBJECTS_ENABLE_DEFAULT 494 int "debug_objects bootup default value (0-1)" 495 range 0 1 496 default "1" 497 depends on DEBUG_OBJECTS 498 help 499 Debug objects boot parameter default value 500 501config DEBUG_SLAB 502 bool "Debug slab memory allocations" 503 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 504 help 505 Say Y here to have the kernel do limited verification on memory 506 allocation as well as poisoning memory on free to catch use of freed 507 memory. This can make kmalloc/kfree-intensive workloads much slower. 508 509config DEBUG_SLAB_LEAK 510 bool "Memory leak debugging" 511 depends on DEBUG_SLAB 512 513config SLUB_DEBUG_ON 514 bool "SLUB debugging on by default" 515 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 516 default n 517 help 518 Boot with debugging on by default. SLUB boots by default with 519 the runtime debug capabilities switched off. Enabling this is 520 equivalent to specifying the "slub_debug" parameter on boot. 521 There is no support for more fine grained debug control like 522 possible with slub_debug=xxx. SLUB debugging may be switched 523 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 524 "slub_debug=-". 525 526config SLUB_STATS 527 default n 528 bool "Enable SLUB performance statistics" 529 depends on SLUB && SYSFS 530 help 531 SLUB statistics are useful to debug SLUBs allocation behavior in 532 order find ways to optimize the allocator. This should never be 533 enabled for production use since keeping statistics slows down 534 the allocator by a few percentage points. The slabinfo command 535 supports the determination of the most active slabs to figure 536 out which slabs are relevant to a particular load. 537 Try running: slabinfo -DA 538 539config HAVE_DEBUG_KMEMLEAK 540 bool 541 542config DEBUG_KMEMLEAK 543 bool "Kernel memory leak detector" 544 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 545 select DEBUG_FS 546 select STACKTRACE if STACKTRACE_SUPPORT 547 select KALLSYMS 548 select CRC32 549 help 550 Say Y here if you want to enable the memory leak 551 detector. The memory allocation/freeing is traced in a way 552 similar to the Boehm's conservative garbage collector, the 553 difference being that the orphan objects are not freed but 554 only shown in /sys/kernel/debug/kmemleak. Enabling this 555 feature will introduce an overhead to memory 556 allocations. See Documentation/dev-tools/kmemleak.rst for more 557 details. 558 559 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 560 of finding leaks due to the slab objects poisoning. 561 562 In order to access the kmemleak file, debugfs needs to be 563 mounted (usually at /sys/kernel/debug). 564 565config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 566 int "Maximum kmemleak early log entries" 567 depends on DEBUG_KMEMLEAK 568 range 200 40000 569 default 400 570 help 571 Kmemleak must track all the memory allocations to avoid 572 reporting false positives. Since memory may be allocated or 573 freed before kmemleak is initialised, an early log buffer is 574 used to store these actions. If kmemleak reports "early log 575 buffer exceeded", please increase this value. 576 577config DEBUG_KMEMLEAK_TEST 578 tristate "Simple test for the kernel memory leak detector" 579 depends on DEBUG_KMEMLEAK && m 580 help 581 This option enables a module that explicitly leaks memory. 582 583 If unsure, say N. 584 585config DEBUG_KMEMLEAK_DEFAULT_OFF 586 bool "Default kmemleak to off" 587 depends on DEBUG_KMEMLEAK 588 help 589 Say Y here to disable kmemleak by default. It can then be enabled 590 on the command line via kmemleak=on. 591 592config DEBUG_STACK_USAGE 593 bool "Stack utilization instrumentation" 594 depends on DEBUG_KERNEL && !IA64 595 help 596 Enables the display of the minimum amount of free stack which each 597 task has ever had available in the sysrq-T and sysrq-P debug output. 598 599 This option will slow down process creation somewhat. 600 601config DEBUG_VM 602 bool "Debug VM" 603 depends on DEBUG_KERNEL 604 help 605 Enable this to turn on extended checks in the virtual-memory system 606 that may impact performance. 607 608 If unsure, say N. 609 610config DEBUG_VM_VMACACHE 611 bool "Debug VMA caching" 612 depends on DEBUG_VM 613 help 614 Enable this to turn on VMA caching debug information. Doing so 615 can cause significant overhead, so only enable it in non-production 616 environments. 617 618 If unsure, say N. 619 620config DEBUG_VM_RB 621 bool "Debug VM red-black trees" 622 depends on DEBUG_VM 623 help 624 Enable VM red-black tree debugging information and extra validations. 625 626 If unsure, say N. 627 628config DEBUG_VM_PGFLAGS 629 bool "Debug page-flags operations" 630 depends on DEBUG_VM 631 help 632 Enables extra validation on page flags operations. 633 634 If unsure, say N. 635 636config ARCH_HAS_DEBUG_VIRTUAL 637 bool 638 639config DEBUG_VIRTUAL 640 bool "Debug VM translations" 641 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL 642 help 643 Enable some costly sanity checks in virtual to page code. This can 644 catch mistakes with virt_to_page() and friends. 645 646 If unsure, say N. 647 648config DEBUG_NOMMU_REGIONS 649 bool "Debug the global anon/private NOMMU mapping region tree" 650 depends on DEBUG_KERNEL && !MMU 651 help 652 This option causes the global tree of anonymous and private mapping 653 regions to be regularly checked for invalid topology. 654 655config DEBUG_MEMORY_INIT 656 bool "Debug memory initialisation" if EXPERT 657 default !EXPERT 658 help 659 Enable this for additional checks during memory initialisation. 660 The sanity checks verify aspects of the VM such as the memory model 661 and other information provided by the architecture. Verbose 662 information will be printed at KERN_DEBUG loglevel depending 663 on the mminit_loglevel= command-line option. 664 665 If unsure, say Y 666 667config MEMORY_NOTIFIER_ERROR_INJECT 668 tristate "Memory hotplug notifier error injection module" 669 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 670 help 671 This option provides the ability to inject artificial errors to 672 memory hotplug notifier chain callbacks. It is controlled through 673 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 674 675 If the notifier call chain should be failed with some events 676 notified, write the error code to "actions/<notifier event>/error". 677 678 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 679 680 # cd /sys/kernel/debug/notifier-error-inject/memory 681 # echo -12 > actions/MEM_GOING_OFFLINE/error 682 # echo offline > /sys/devices/system/memory/memoryXXX/state 683 bash: echo: write error: Cannot allocate memory 684 685 To compile this code as a module, choose M here: the module will 686 be called memory-notifier-error-inject. 687 688 If unsure, say N. 689 690config DEBUG_PER_CPU_MAPS 691 bool "Debug access to per_cpu maps" 692 depends on DEBUG_KERNEL 693 depends on SMP 694 help 695 Say Y to verify that the per_cpu map being accessed has 696 been set up. This adds a fair amount of code to kernel memory 697 and decreases performance. 698 699 Say N if unsure. 700 701config DEBUG_HIGHMEM 702 bool "Highmem debugging" 703 depends on DEBUG_KERNEL && HIGHMEM 704 help 705 This option enables additional error checking for high memory 706 systems. Disable for production systems. 707 708config HAVE_DEBUG_STACKOVERFLOW 709 bool 710 711config DEBUG_STACKOVERFLOW 712 bool "Check for stack overflows" 713 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 714 ---help--- 715 Say Y here if you want to check for overflows of kernel, IRQ 716 and exception stacks (if your architecture uses them). This 717 option will show detailed messages if free stack space drops 718 below a certain limit. 719 720 These kinds of bugs usually occur when call-chains in the 721 kernel get too deep, especially when interrupts are 722 involved. 723 724 Use this in cases where you see apparently random memory 725 corruption, especially if it appears in 'struct thread_info' 726 727 If in doubt, say "N". 728 729source "lib/Kconfig.kmemcheck" 730 731source "lib/Kconfig.kasan" 732 733endmenu # "Memory Debugging" 734 735config ARCH_HAS_KCOV 736 bool 737 help 738 KCOV does not have any arch-specific code, but currently it is enabled 739 only for x86_64. KCOV requires testing on other archs, and most likely 740 disabling of instrumentation for some early boot code. 741 742config KCOV 743 bool "Code coverage for fuzzing" 744 depends on ARCH_HAS_KCOV 745 select DEBUG_FS 746 select GCC_PLUGINS if !COMPILE_TEST 747 select GCC_PLUGIN_SANCOV if !COMPILE_TEST 748 help 749 KCOV exposes kernel code coverage information in a form suitable 750 for coverage-guided fuzzing (randomized testing). 751 752 If RANDOMIZE_BASE is enabled, PC values will not be stable across 753 different machines and across reboots. If you need stable PC values, 754 disable RANDOMIZE_BASE. 755 756 For more details, see Documentation/dev-tools/kcov.rst. 757 758config KCOV_INSTRUMENT_ALL 759 bool "Instrument all code by default" 760 depends on KCOV 761 default y if KCOV 762 help 763 If you are doing generic system call fuzzing (like e.g. syzkaller), 764 then you will want to instrument the whole kernel and you should 765 say y here. If you are doing more targeted fuzzing (like e.g. 766 filesystem fuzzing with AFL) then you will want to enable coverage 767 for more specific subsets of files, and should say n here. 768 769config DEBUG_SHIRQ 770 bool "Debug shared IRQ handlers" 771 depends on DEBUG_KERNEL 772 help 773 Enable this to generate a spurious interrupt as soon as a shared 774 interrupt handler is registered, and just before one is deregistered. 775 Drivers ought to be able to handle interrupts coming in at those 776 points; some don't and need to be caught. 777 778menu "Debug Lockups and Hangs" 779 780config LOCKUP_DETECTOR 781 bool "Detect Hard and Soft Lockups" 782 depends on DEBUG_KERNEL && !S390 783 help 784 Say Y here to enable the kernel to act as a watchdog to detect 785 hard and soft lockups. 786 787 Softlockups are bugs that cause the kernel to loop in kernel 788 mode for more than 20 seconds, without giving other tasks a 789 chance to run. The current stack trace is displayed upon 790 detection and the system will stay locked up. 791 792 Hardlockups are bugs that cause the CPU to loop in kernel mode 793 for more than 10 seconds, without letting other interrupts have a 794 chance to run. The current stack trace is displayed upon detection 795 and the system will stay locked up. 796 797 The overhead should be minimal. A periodic hrtimer runs to 798 generate interrupts and kick the watchdog task every 4 seconds. 799 An NMI is generated every 10 seconds or so to check for hardlockups. 800 801 The frequency of hrtimer and NMI events and the soft and hard lockup 802 thresholds can be controlled through the sysctl watchdog_thresh. 803 804config HARDLOCKUP_DETECTOR 805 def_bool y 806 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 807 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 808 809config BOOTPARAM_HARDLOCKUP_PANIC 810 bool "Panic (Reboot) On Hard Lockups" 811 depends on HARDLOCKUP_DETECTOR 812 help 813 Say Y here to enable the kernel to panic on "hard lockups", 814 which are bugs that cause the kernel to loop in kernel 815 mode with interrupts disabled for more than 10 seconds (configurable 816 using the watchdog_thresh sysctl). 817 818 Say N if unsure. 819 820config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 821 int 822 depends on HARDLOCKUP_DETECTOR 823 range 0 1 824 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 825 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 826 827config BOOTPARAM_SOFTLOCKUP_PANIC 828 bool "Panic (Reboot) On Soft Lockups" 829 depends on LOCKUP_DETECTOR 830 help 831 Say Y here to enable the kernel to panic on "soft lockups", 832 which are bugs that cause the kernel to loop in kernel 833 mode for more than 20 seconds (configurable using the watchdog_thresh 834 sysctl), without giving other tasks a chance to run. 835 836 The panic can be used in combination with panic_timeout, 837 to cause the system to reboot automatically after a 838 lockup has been detected. This feature is useful for 839 high-availability systems that have uptime guarantees and 840 where a lockup must be resolved ASAP. 841 842 Say N if unsure. 843 844config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 845 int 846 depends on LOCKUP_DETECTOR 847 range 0 1 848 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 849 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 850 851config DETECT_HUNG_TASK 852 bool "Detect Hung Tasks" 853 depends on DEBUG_KERNEL 854 default LOCKUP_DETECTOR 855 help 856 Say Y here to enable the kernel to detect "hung tasks", 857 which are bugs that cause the task to be stuck in 858 uninterruptible "D" state indefinitely. 859 860 When a hung task is detected, the kernel will print the 861 current stack trace (which you should report), but the 862 task will stay in uninterruptible state. If lockdep is 863 enabled then all held locks will also be reported. This 864 feature has negligible overhead. 865 866config DEFAULT_HUNG_TASK_TIMEOUT 867 int "Default timeout for hung task detection (in seconds)" 868 depends on DETECT_HUNG_TASK 869 default 120 870 help 871 This option controls the default timeout (in seconds) used 872 to determine when a task has become non-responsive and should 873 be considered hung. 874 875 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 876 sysctl or by writing a value to 877 /proc/sys/kernel/hung_task_timeout_secs. 878 879 A timeout of 0 disables the check. The default is two minutes. 880 Keeping the default should be fine in most cases. 881 882config BOOTPARAM_HUNG_TASK_PANIC 883 bool "Panic (Reboot) On Hung Tasks" 884 depends on DETECT_HUNG_TASK 885 help 886 Say Y here to enable the kernel to panic on "hung tasks", 887 which are bugs that cause the kernel to leave a task stuck 888 in uninterruptible "D" state. 889 890 The panic can be used in combination with panic_timeout, 891 to cause the system to reboot automatically after a 892 hung task has been detected. This feature is useful for 893 high-availability systems that have uptime guarantees and 894 where a hung tasks must be resolved ASAP. 895 896 Say N if unsure. 897 898config BOOTPARAM_HUNG_TASK_PANIC_VALUE 899 int 900 depends on DETECT_HUNG_TASK 901 range 0 1 902 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 903 default 1 if BOOTPARAM_HUNG_TASK_PANIC 904 905config WQ_WATCHDOG 906 bool "Detect Workqueue Stalls" 907 depends on DEBUG_KERNEL 908 help 909 Say Y here to enable stall detection on workqueues. If a 910 worker pool doesn't make forward progress on a pending work 911 item for over a given amount of time, 30s by default, a 912 warning message is printed along with dump of workqueue 913 state. This can be configured through kernel parameter 914 "workqueue.watchdog_thresh" and its sysfs counterpart. 915 916endmenu # "Debug lockups and hangs" 917 918config PANIC_ON_OOPS 919 bool "Panic on Oops" 920 help 921 Say Y here to enable the kernel to panic when it oopses. This 922 has the same effect as setting oops=panic on the kernel command 923 line. 924 925 This feature is useful to ensure that the kernel does not do 926 anything erroneous after an oops which could result in data 927 corruption or other issues. 928 929 Say N if unsure. 930 931config PANIC_ON_OOPS_VALUE 932 int 933 range 0 1 934 default 0 if !PANIC_ON_OOPS 935 default 1 if PANIC_ON_OOPS 936 937config PANIC_TIMEOUT 938 int "panic timeout" 939 default 0 940 help 941 Set the timeout value (in seconds) until a reboot occurs when the 942 the kernel panics. If n = 0, then we wait forever. A timeout 943 value n > 0 will wait n seconds before rebooting, while a timeout 944 value n < 0 will reboot immediately. 945 946config SCHED_DEBUG 947 bool "Collect scheduler debugging info" 948 depends on DEBUG_KERNEL && PROC_FS 949 default y 950 help 951 If you say Y here, the /proc/sched_debug file will be provided 952 that can help debug the scheduler. The runtime overhead of this 953 option is minimal. 954 955config SCHED_INFO 956 bool 957 default n 958 959config SCHEDSTATS 960 bool "Collect scheduler statistics" 961 depends on DEBUG_KERNEL && PROC_FS 962 select SCHED_INFO 963 help 964 If you say Y here, additional code will be inserted into the 965 scheduler and related routines to collect statistics about 966 scheduler behavior and provide them in /proc/schedstat. These 967 stats may be useful for both tuning and debugging the scheduler 968 If you aren't debugging the scheduler or trying to tune a specific 969 application, you can say N to avoid the very slight overhead 970 this adds. 971 972config SCHED_STACK_END_CHECK 973 bool "Detect stack corruption on calls to schedule()" 974 depends on DEBUG_KERNEL 975 default n 976 help 977 This option checks for a stack overrun on calls to schedule(). 978 If the stack end location is found to be over written always panic as 979 the content of the corrupted region can no longer be trusted. 980 This is to ensure no erroneous behaviour occurs which could result in 981 data corruption or a sporadic crash at a later stage once the region 982 is examined. The runtime overhead introduced is minimal. 983 984config DEBUG_TIMEKEEPING 985 bool "Enable extra timekeeping sanity checking" 986 help 987 This option will enable additional timekeeping sanity checks 988 which may be helpful when diagnosing issues where timekeeping 989 problems are suspected. 990 991 This may include checks in the timekeeping hotpaths, so this 992 option may have a (very small) performance impact to some 993 workloads. 994 995 If unsure, say N. 996 997config DEBUG_PREEMPT 998 bool "Debug preemptible kernel" 999 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 1000 default y 1001 help 1002 If you say Y here then the kernel will use a debug variant of the 1003 commonly used smp_processor_id() function and will print warnings 1004 if kernel code uses it in a preemption-unsafe way. Also, the kernel 1005 will detect preemption count underflows. 1006 1007menu "Lock Debugging (spinlocks, mutexes, etc...)" 1008 1009config DEBUG_RT_MUTEXES 1010 bool "RT Mutex debugging, deadlock detection" 1011 depends on DEBUG_KERNEL && RT_MUTEXES 1012 help 1013 This allows rt mutex semantics violations and rt mutex related 1014 deadlocks (lockups) to be detected and reported automatically. 1015 1016config DEBUG_SPINLOCK 1017 bool "Spinlock and rw-lock debugging: basic checks" 1018 depends on DEBUG_KERNEL 1019 select UNINLINE_SPIN_UNLOCK 1020 help 1021 Say Y here and build SMP to catch missing spinlock initialization 1022 and certain other kinds of spinlock errors commonly made. This is 1023 best used in conjunction with the NMI watchdog so that spinlock 1024 deadlocks are also debuggable. 1025 1026config DEBUG_MUTEXES 1027 bool "Mutex debugging: basic checks" 1028 depends on DEBUG_KERNEL 1029 help 1030 This feature allows mutex semantics violations to be detected and 1031 reported. 1032 1033config DEBUG_WW_MUTEX_SLOWPATH 1034 bool "Wait/wound mutex debugging: Slowpath testing" 1035 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1036 select DEBUG_LOCK_ALLOC 1037 select DEBUG_SPINLOCK 1038 select DEBUG_MUTEXES 1039 help 1040 This feature enables slowpath testing for w/w mutex users by 1041 injecting additional -EDEADLK wound/backoff cases. Together with 1042 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 1043 will test all possible w/w mutex interface abuse with the 1044 exception of simply not acquiring all the required locks. 1045 Note that this feature can introduce significant overhead, so 1046 it really should not be enabled in a production or distro kernel, 1047 even a debug kernel. If you are a driver writer, enable it. If 1048 you are a distro, do not. 1049 1050config DEBUG_LOCK_ALLOC 1051 bool "Lock debugging: detect incorrect freeing of live locks" 1052 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1053 select DEBUG_SPINLOCK 1054 select DEBUG_MUTEXES 1055 select LOCKDEP 1056 help 1057 This feature will check whether any held lock (spinlock, rwlock, 1058 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1059 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1060 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1061 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1062 held during task exit. 1063 1064config PROVE_LOCKING 1065 bool "Lock debugging: prove locking correctness" 1066 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1067 select LOCKDEP 1068 select DEBUG_SPINLOCK 1069 select DEBUG_MUTEXES 1070 select DEBUG_LOCK_ALLOC 1071 select TRACE_IRQFLAGS 1072 default n 1073 help 1074 This feature enables the kernel to prove that all locking 1075 that occurs in the kernel runtime is mathematically 1076 correct: that under no circumstance could an arbitrary (and 1077 not yet triggered) combination of observed locking 1078 sequences (on an arbitrary number of CPUs, running an 1079 arbitrary number of tasks and interrupt contexts) cause a 1080 deadlock. 1081 1082 In short, this feature enables the kernel to report locking 1083 related deadlocks before they actually occur. 1084 1085 The proof does not depend on how hard and complex a 1086 deadlock scenario would be to trigger: how many 1087 participant CPUs, tasks and irq-contexts would be needed 1088 for it to trigger. The proof also does not depend on 1089 timing: if a race and a resulting deadlock is possible 1090 theoretically (no matter how unlikely the race scenario 1091 is), it will be proven so and will immediately be 1092 reported by the kernel (once the event is observed that 1093 makes the deadlock theoretically possible). 1094 1095 If a deadlock is impossible (i.e. the locking rules, as 1096 observed by the kernel, are mathematically correct), the 1097 kernel reports nothing. 1098 1099 NOTE: this feature can also be enabled for rwlocks, mutexes 1100 and rwsems - in which case all dependencies between these 1101 different locking variants are observed and mapped too, and 1102 the proof of observed correctness is also maintained for an 1103 arbitrary combination of these separate locking variants. 1104 1105 For more details, see Documentation/locking/lockdep-design.txt. 1106 1107config LOCKDEP 1108 bool 1109 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1110 select STACKTRACE 1111 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE 1112 select KALLSYMS 1113 select KALLSYMS_ALL 1114 1115config LOCKDEP_SMALL 1116 bool 1117 1118config LOCK_STAT 1119 bool "Lock usage statistics" 1120 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1121 select LOCKDEP 1122 select DEBUG_SPINLOCK 1123 select DEBUG_MUTEXES 1124 select DEBUG_LOCK_ALLOC 1125 default n 1126 help 1127 This feature enables tracking lock contention points 1128 1129 For more details, see Documentation/locking/lockstat.txt 1130 1131 This also enables lock events required by "perf lock", 1132 subcommand of perf. 1133 If you want to use "perf lock", you also need to turn on 1134 CONFIG_EVENT_TRACING. 1135 1136 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1137 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1138 1139config DEBUG_LOCKDEP 1140 bool "Lock dependency engine debugging" 1141 depends on DEBUG_KERNEL && LOCKDEP 1142 help 1143 If you say Y here, the lock dependency engine will do 1144 additional runtime checks to debug itself, at the price 1145 of more runtime overhead. 1146 1147config DEBUG_ATOMIC_SLEEP 1148 bool "Sleep inside atomic section checking" 1149 select PREEMPT_COUNT 1150 depends on DEBUG_KERNEL 1151 help 1152 If you say Y here, various routines which may sleep will become very 1153 noisy if they are called inside atomic sections: when a spinlock is 1154 held, inside an rcu read side critical section, inside preempt disabled 1155 sections, inside an interrupt, etc... 1156 1157config DEBUG_LOCKING_API_SELFTESTS 1158 bool "Locking API boot-time self-tests" 1159 depends on DEBUG_KERNEL 1160 help 1161 Say Y here if you want the kernel to run a short self-test during 1162 bootup. The self-test checks whether common types of locking bugs 1163 are detected by debugging mechanisms or not. (if you disable 1164 lock debugging then those bugs wont be detected of course.) 1165 The following locking APIs are covered: spinlocks, rwlocks, 1166 mutexes and rwsems. 1167 1168config LOCK_TORTURE_TEST 1169 tristate "torture tests for locking" 1170 depends on DEBUG_KERNEL 1171 select TORTURE_TEST 1172 default n 1173 help 1174 This option provides a kernel module that runs torture tests 1175 on kernel locking primitives. The kernel module may be built 1176 after the fact on the running kernel to be tested, if desired. 1177 1178 Say Y here if you want kernel locking-primitive torture tests 1179 to be built into the kernel. 1180 Say M if you want these torture tests to build as a module. 1181 Say N if you are unsure. 1182 1183config WW_MUTEX_SELFTEST 1184 tristate "Wait/wound mutex selftests" 1185 help 1186 This option provides a kernel module that runs tests on the 1187 on the struct ww_mutex locking API. 1188 1189 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction 1190 with this test harness. 1191 1192 Say M if you want these self tests to build as a module. 1193 Say N if you are unsure. 1194 1195endmenu # lock debugging 1196 1197config TRACE_IRQFLAGS 1198 bool 1199 help 1200 Enables hooks to interrupt enabling and disabling for 1201 either tracing or lock debugging. 1202 1203config STACKTRACE 1204 bool "Stack backtrace support" 1205 depends on STACKTRACE_SUPPORT 1206 help 1207 This option causes the kernel to create a /proc/pid/stack for 1208 every process, showing its current stack trace. 1209 It is also used by various kernel debugging features that require 1210 stack trace generation. 1211 1212config DEBUG_KOBJECT 1213 bool "kobject debugging" 1214 depends on DEBUG_KERNEL 1215 help 1216 If you say Y here, some extra kobject debugging messages will be sent 1217 to the syslog. 1218 1219config DEBUG_KOBJECT_RELEASE 1220 bool "kobject release debugging" 1221 depends on DEBUG_OBJECTS_TIMERS 1222 help 1223 kobjects are reference counted objects. This means that their 1224 last reference count put is not predictable, and the kobject can 1225 live on past the point at which a driver decides to drop it's 1226 initial reference to the kobject gained on allocation. An 1227 example of this would be a struct device which has just been 1228 unregistered. 1229 1230 However, some buggy drivers assume that after such an operation, 1231 the memory backing the kobject can be immediately freed. This 1232 goes completely against the principles of a refcounted object. 1233 1234 If you say Y here, the kernel will delay the release of kobjects 1235 on the last reference count to improve the visibility of this 1236 kind of kobject release bug. 1237 1238config HAVE_DEBUG_BUGVERBOSE 1239 bool 1240 1241config DEBUG_BUGVERBOSE 1242 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1243 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1244 default y 1245 help 1246 Say Y here to make BUG() panics output the file name and line number 1247 of the BUG call as well as the EIP and oops trace. This aids 1248 debugging but costs about 70-100K of memory. 1249 1250config DEBUG_LIST 1251 bool "Debug linked list manipulation" 1252 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION 1253 help 1254 Enable this to turn on extended checks in the linked-list 1255 walking routines. 1256 1257 If unsure, say N. 1258 1259config DEBUG_PI_LIST 1260 bool "Debug priority linked list manipulation" 1261 depends on DEBUG_KERNEL 1262 help 1263 Enable this to turn on extended checks in the priority-ordered 1264 linked-list (plist) walking routines. This checks the entire 1265 list multiple times during each manipulation. 1266 1267 If unsure, say N. 1268 1269config DEBUG_SG 1270 bool "Debug SG table operations" 1271 depends on DEBUG_KERNEL 1272 help 1273 Enable this to turn on checks on scatter-gather tables. This can 1274 help find problems with drivers that do not properly initialize 1275 their sg tables. 1276 1277 If unsure, say N. 1278 1279config DEBUG_NOTIFIERS 1280 bool "Debug notifier call chains" 1281 depends on DEBUG_KERNEL 1282 help 1283 Enable this to turn on sanity checking for notifier call chains. 1284 This is most useful for kernel developers to make sure that 1285 modules properly unregister themselves from notifier chains. 1286 This is a relatively cheap check but if you care about maximum 1287 performance, say N. 1288 1289config DEBUG_CREDENTIALS 1290 bool "Debug credential management" 1291 depends on DEBUG_KERNEL 1292 help 1293 Enable this to turn on some debug checking for credential 1294 management. The additional code keeps track of the number of 1295 pointers from task_structs to any given cred struct, and checks to 1296 see that this number never exceeds the usage count of the cred 1297 struct. 1298 1299 Furthermore, if SELinux is enabled, this also checks that the 1300 security pointer in the cred struct is never seen to be invalid. 1301 1302 If unsure, say N. 1303 1304menu "RCU Debugging" 1305 1306config PROVE_RCU 1307 def_bool PROVE_LOCKING 1308 1309config PROVE_RCU_REPEATEDLY 1310 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1311 depends on PROVE_RCU 1312 default n 1313 help 1314 By itself, PROVE_RCU will disable checking upon issuing the 1315 first warning (or "splat"). This feature prevents such 1316 disabling, allowing multiple RCU-lockdep warnings to be printed 1317 on a single reboot. 1318 1319 Say Y to allow multiple RCU-lockdep warnings per boot. 1320 1321 Say N if you are unsure. 1322 1323config SPARSE_RCU_POINTER 1324 bool "RCU debugging: sparse-based checks for pointer usage" 1325 default n 1326 help 1327 This feature enables the __rcu sparse annotation for 1328 RCU-protected pointers. This annotation will cause sparse 1329 to flag any non-RCU used of annotated pointers. This can be 1330 helpful when debugging RCU usage. Please note that this feature 1331 is not intended to enforce code cleanliness; it is instead merely 1332 a debugging aid. 1333 1334 Say Y to make sparse flag questionable use of RCU-protected pointers 1335 1336 Say N if you are unsure. 1337 1338config TORTURE_TEST 1339 tristate 1340 default n 1341 1342config RCU_PERF_TEST 1343 tristate "performance tests for RCU" 1344 depends on DEBUG_KERNEL 1345 select TORTURE_TEST 1346 select SRCU 1347 select TASKS_RCU 1348 default n 1349 help 1350 This option provides a kernel module that runs performance 1351 tests on the RCU infrastructure. The kernel module may be built 1352 after the fact on the running kernel to be tested, if desired. 1353 1354 Say Y here if you want RCU performance tests to be built into 1355 the kernel. 1356 Say M if you want the RCU performance tests to build as a module. 1357 Say N if you are unsure. 1358 1359config RCU_TORTURE_TEST 1360 tristate "torture tests for RCU" 1361 depends on DEBUG_KERNEL 1362 select TORTURE_TEST 1363 select SRCU 1364 select TASKS_RCU 1365 default n 1366 help 1367 This option provides a kernel module that runs torture tests 1368 on the RCU infrastructure. The kernel module may be built 1369 after the fact on the running kernel to be tested, if desired. 1370 1371 Say Y here if you want RCU torture tests to be built into 1372 the kernel. 1373 Say M if you want the RCU torture tests to build as a module. 1374 Say N if you are unsure. 1375 1376config RCU_TORTURE_TEST_SLOW_PREINIT 1377 bool "Slow down RCU grace-period pre-initialization to expose races" 1378 depends on RCU_TORTURE_TEST 1379 help 1380 This option delays grace-period pre-initialization (the 1381 propagation of CPU-hotplug changes up the rcu_node combining 1382 tree) for a few jiffies between initializing each pair of 1383 consecutive rcu_node structures. This helps to expose races 1384 involving grace-period pre-initialization, in other words, it 1385 makes your kernel less stable. It can also greatly increase 1386 grace-period latency, especially on systems with large numbers 1387 of CPUs. This is useful when torture-testing RCU, but in 1388 almost no other circumstance. 1389 1390 Say Y here if you want your system to crash and hang more often. 1391 Say N if you want a sane system. 1392 1393config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY 1394 int "How much to slow down RCU grace-period pre-initialization" 1395 range 0 5 1396 default 3 1397 depends on RCU_TORTURE_TEST_SLOW_PREINIT 1398 help 1399 This option specifies the number of jiffies to wait between 1400 each rcu_node structure pre-initialization step. 1401 1402config RCU_TORTURE_TEST_SLOW_INIT 1403 bool "Slow down RCU grace-period initialization to expose races" 1404 depends on RCU_TORTURE_TEST 1405 help 1406 This option delays grace-period initialization for a few 1407 jiffies between initializing each pair of consecutive 1408 rcu_node structures. This helps to expose races involving 1409 grace-period initialization, in other words, it makes your 1410 kernel less stable. It can also greatly increase grace-period 1411 latency, especially on systems with large numbers of CPUs. 1412 This is useful when torture-testing RCU, but in almost no 1413 other circumstance. 1414 1415 Say Y here if you want your system to crash and hang more often. 1416 Say N if you want a sane system. 1417 1418config RCU_TORTURE_TEST_SLOW_INIT_DELAY 1419 int "How much to slow down RCU grace-period initialization" 1420 range 0 5 1421 default 3 1422 depends on RCU_TORTURE_TEST_SLOW_INIT 1423 help 1424 This option specifies the number of jiffies to wait between 1425 each rcu_node structure initialization. 1426 1427config RCU_TORTURE_TEST_SLOW_CLEANUP 1428 bool "Slow down RCU grace-period cleanup to expose races" 1429 depends on RCU_TORTURE_TEST 1430 help 1431 This option delays grace-period cleanup for a few jiffies 1432 between cleaning up each pair of consecutive rcu_node 1433 structures. This helps to expose races involving grace-period 1434 cleanup, in other words, it makes your kernel less stable. 1435 It can also greatly increase grace-period latency, especially 1436 on systems with large numbers of CPUs. This is useful when 1437 torture-testing RCU, but in almost no other circumstance. 1438 1439 Say Y here if you want your system to crash and hang more often. 1440 Say N if you want a sane system. 1441 1442config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY 1443 int "How much to slow down RCU grace-period cleanup" 1444 range 0 5 1445 default 3 1446 depends on RCU_TORTURE_TEST_SLOW_CLEANUP 1447 help 1448 This option specifies the number of jiffies to wait between 1449 each rcu_node structure cleanup operation. 1450 1451config RCU_CPU_STALL_TIMEOUT 1452 int "RCU CPU stall timeout in seconds" 1453 depends on RCU_STALL_COMMON 1454 range 3 300 1455 default 21 1456 help 1457 If a given RCU grace period extends more than the specified 1458 number of seconds, a CPU stall warning is printed. If the 1459 RCU grace period persists, additional CPU stall warnings are 1460 printed at more widely spaced intervals. 1461 1462config RCU_TRACE 1463 bool "Enable tracing for RCU" 1464 depends on DEBUG_KERNEL 1465 default y if TREE_RCU 1466 select TRACE_CLOCK 1467 help 1468 This option provides tracing in RCU which presents stats 1469 in debugfs for debugging RCU implementation. It also enables 1470 additional tracepoints for ftrace-style event tracing. 1471 1472 Say Y here if you want to enable RCU tracing 1473 Say N if you are unsure. 1474 1475config RCU_EQS_DEBUG 1476 bool "Provide debugging asserts for adding NO_HZ support to an arch" 1477 depends on DEBUG_KERNEL 1478 help 1479 This option provides consistency checks in RCU's handling of 1480 NO_HZ. These checks have proven quite helpful in detecting 1481 bugs in arch-specific NO_HZ code. 1482 1483 Say N here if you need ultimate kernel/user switch latencies 1484 Say Y if you are unsure 1485 1486endmenu # "RCU Debugging" 1487 1488config DEBUG_WQ_FORCE_RR_CPU 1489 bool "Force round-robin CPU selection for unbound work items" 1490 depends on DEBUG_KERNEL 1491 default n 1492 help 1493 Workqueue used to implicitly guarantee that work items queued 1494 without explicit CPU specified are put on the local CPU. This 1495 guarantee is no longer true and while local CPU is still 1496 preferred work items may be put on foreign CPUs. Kernel 1497 parameter "workqueue.debug_force_rr_cpu" is added to force 1498 round-robin CPU selection to flush out usages which depend on the 1499 now broken guarantee. This config option enables the debug 1500 feature by default. When enabled, memory and cache locality will 1501 be impacted. 1502 1503config DEBUG_BLOCK_EXT_DEVT 1504 bool "Force extended block device numbers and spread them" 1505 depends on DEBUG_KERNEL 1506 depends on BLOCK 1507 default n 1508 help 1509 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1510 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1511 YOU ARE DOING. Distros, please enable this and fix whatever 1512 is broken. 1513 1514 Conventionally, block device numbers are allocated from 1515 predetermined contiguous area. However, extended block area 1516 may introduce non-contiguous block device numbers. This 1517 option forces most block device numbers to be allocated from 1518 the extended space and spreads them to discover kernel or 1519 userland code paths which assume predetermined contiguous 1520 device number allocation. 1521 1522 Note that turning on this debug option shuffles all the 1523 device numbers for all IDE and SCSI devices including libata 1524 ones, so root partition specified using device number 1525 directly (via rdev or root=MAJ:MIN) won't work anymore. 1526 Textual device names (root=/dev/sdXn) will continue to work. 1527 1528 Say N if you are unsure. 1529 1530config CPU_HOTPLUG_STATE_CONTROL 1531 bool "Enable CPU hotplug state control" 1532 depends on DEBUG_KERNEL 1533 depends on HOTPLUG_CPU 1534 default n 1535 help 1536 Allows to write steps between "offline" and "online" to the CPUs 1537 sysfs target file so states can be stepped granular. This is a debug 1538 option for now as the hotplug machinery cannot be stopped and 1539 restarted at arbitrary points yet. 1540 1541 Say N if your are unsure. 1542 1543config NOTIFIER_ERROR_INJECTION 1544 tristate "Notifier error injection" 1545 depends on DEBUG_KERNEL 1546 select DEBUG_FS 1547 help 1548 This option provides the ability to inject artificial errors to 1549 specified notifier chain callbacks. It is useful to test the error 1550 handling of notifier call chain failures. 1551 1552 Say N if unsure. 1553 1554config PM_NOTIFIER_ERROR_INJECT 1555 tristate "PM notifier error injection module" 1556 depends on PM && NOTIFIER_ERROR_INJECTION 1557 default m if PM_DEBUG 1558 help 1559 This option provides the ability to inject artificial errors to 1560 PM notifier chain callbacks. It is controlled through debugfs 1561 interface /sys/kernel/debug/notifier-error-inject/pm 1562 1563 If the notifier call chain should be failed with some events 1564 notified, write the error code to "actions/<notifier event>/error". 1565 1566 Example: Inject PM suspend error (-12 = -ENOMEM) 1567 1568 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1569 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1570 # echo mem > /sys/power/state 1571 bash: echo: write error: Cannot allocate memory 1572 1573 To compile this code as a module, choose M here: the module will 1574 be called pm-notifier-error-inject. 1575 1576 If unsure, say N. 1577 1578config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1579 tristate "OF reconfig notifier error injection module" 1580 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1581 help 1582 This option provides the ability to inject artificial errors to 1583 OF reconfig notifier chain callbacks. It is controlled 1584 through debugfs interface under 1585 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1586 1587 If the notifier call chain should be failed with some events 1588 notified, write the error code to "actions/<notifier event>/error". 1589 1590 To compile this code as a module, choose M here: the module will 1591 be called of-reconfig-notifier-error-inject. 1592 1593 If unsure, say N. 1594 1595config NETDEV_NOTIFIER_ERROR_INJECT 1596 tristate "Netdev notifier error injection module" 1597 depends on NET && NOTIFIER_ERROR_INJECTION 1598 help 1599 This option provides the ability to inject artificial errors to 1600 netdevice notifier chain callbacks. It is controlled through debugfs 1601 interface /sys/kernel/debug/notifier-error-inject/netdev 1602 1603 If the notifier call chain should be failed with some events 1604 notified, write the error code to "actions/<notifier event>/error". 1605 1606 Example: Inject netdevice mtu change error (-22 = -EINVAL) 1607 1608 # cd /sys/kernel/debug/notifier-error-inject/netdev 1609 # echo -22 > actions/NETDEV_CHANGEMTU/error 1610 # ip link set eth0 mtu 1024 1611 RTNETLINK answers: Invalid argument 1612 1613 To compile this code as a module, choose M here: the module will 1614 be called netdev-notifier-error-inject. 1615 1616 If unsure, say N. 1617 1618config FAULT_INJECTION 1619 bool "Fault-injection framework" 1620 depends on DEBUG_KERNEL 1621 help 1622 Provide fault-injection framework. 1623 For more details, see Documentation/fault-injection/. 1624 1625config FAILSLAB 1626 bool "Fault-injection capability for kmalloc" 1627 depends on FAULT_INJECTION 1628 depends on SLAB || SLUB 1629 help 1630 Provide fault-injection capability for kmalloc. 1631 1632config FAIL_PAGE_ALLOC 1633 bool "Fault-injection capabilitiy for alloc_pages()" 1634 depends on FAULT_INJECTION 1635 help 1636 Provide fault-injection capability for alloc_pages(). 1637 1638config FAIL_MAKE_REQUEST 1639 bool "Fault-injection capability for disk IO" 1640 depends on FAULT_INJECTION && BLOCK 1641 help 1642 Provide fault-injection capability for disk IO. 1643 1644config FAIL_IO_TIMEOUT 1645 bool "Fault-injection capability for faking disk interrupts" 1646 depends on FAULT_INJECTION && BLOCK 1647 help 1648 Provide fault-injection capability on end IO handling. This 1649 will make the block layer "forget" an interrupt as configured, 1650 thus exercising the error handling. 1651 1652 Only works with drivers that use the generic timeout handling, 1653 for others it wont do anything. 1654 1655config FAIL_MMC_REQUEST 1656 bool "Fault-injection capability for MMC IO" 1657 depends on FAULT_INJECTION_DEBUG_FS && MMC 1658 help 1659 Provide fault-injection capability for MMC IO. 1660 This will make the mmc core return data errors. This is 1661 useful to test the error handling in the mmc block device 1662 and to test how the mmc host driver handles retries from 1663 the block device. 1664 1665config FAIL_FUTEX 1666 bool "Fault-injection capability for futexes" 1667 select DEBUG_FS 1668 depends on FAULT_INJECTION && FUTEX 1669 help 1670 Provide fault-injection capability for futexes. 1671 1672config FAULT_INJECTION_DEBUG_FS 1673 bool "Debugfs entries for fault-injection capabilities" 1674 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1675 help 1676 Enable configuration of fault-injection capabilities via debugfs. 1677 1678config FAULT_INJECTION_STACKTRACE_FILTER 1679 bool "stacktrace filter for fault-injection capabilities" 1680 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1681 depends on !X86_64 1682 select STACKTRACE 1683 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1684 help 1685 Provide stacktrace filter for fault-injection capabilities 1686 1687config LATENCYTOP 1688 bool "Latency measuring infrastructure" 1689 depends on DEBUG_KERNEL 1690 depends on STACKTRACE_SUPPORT 1691 depends on PROC_FS 1692 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1693 select KALLSYMS 1694 select KALLSYMS_ALL 1695 select STACKTRACE 1696 select SCHEDSTATS 1697 select SCHED_DEBUG 1698 help 1699 Enable this option if you want to use the LatencyTOP tool 1700 to find out which userspace is blocking on what kernel operations. 1701 1702source kernel/trace/Kconfig 1703 1704menu "Runtime Testing" 1705 1706config LKDTM 1707 tristate "Linux Kernel Dump Test Tool Module" 1708 depends on DEBUG_FS 1709 depends on BLOCK 1710 default n 1711 help 1712 This module enables testing of the different dumping mechanisms by 1713 inducing system failures at predefined crash points. 1714 If you don't need it: say N 1715 Choose M here to compile this code as a module. The module will be 1716 called lkdtm. 1717 1718 Documentation on how to use the module can be found in 1719 Documentation/fault-injection/provoke-crashes.txt 1720 1721config TEST_LIST_SORT 1722 tristate "Linked list sorting test" 1723 depends on DEBUG_KERNEL || m 1724 help 1725 Enable this to turn on 'list_sort()' function test. This test is 1726 executed only once during system boot (so affects only boot time), 1727 or at module load time. 1728 1729 If unsure, say N. 1730 1731config TEST_SORT 1732 tristate "Array-based sort test" 1733 depends on DEBUG_KERNEL || m 1734 help 1735 This option enables the self-test function of 'sort()' at boot, 1736 or at module load time. 1737 1738 If unsure, say N. 1739 1740config KPROBES_SANITY_TEST 1741 bool "Kprobes sanity tests" 1742 depends on DEBUG_KERNEL 1743 depends on KPROBES 1744 default n 1745 help 1746 This option provides for testing basic kprobes functionality on 1747 boot. A sample kprobe, jprobe and kretprobe are inserted and 1748 verified for functionality. 1749 1750 Say N if you are unsure. 1751 1752config BACKTRACE_SELF_TEST 1753 tristate "Self test for the backtrace code" 1754 depends on DEBUG_KERNEL 1755 default n 1756 help 1757 This option provides a kernel module that can be used to test 1758 the kernel stack backtrace code. This option is not useful 1759 for distributions or general kernels, but only for kernel 1760 developers working on architecture code. 1761 1762 Note that if you want to also test saved backtraces, you will 1763 have to enable STACKTRACE as well. 1764 1765 Say N if you are unsure. 1766 1767config RBTREE_TEST 1768 tristate "Red-Black tree test" 1769 depends on DEBUG_KERNEL 1770 help 1771 A benchmark measuring the performance of the rbtree library. 1772 Also includes rbtree invariant checks. 1773 1774config INTERVAL_TREE_TEST 1775 tristate "Interval tree test" 1776 depends on m && DEBUG_KERNEL 1777 select INTERVAL_TREE 1778 help 1779 A benchmark measuring the performance of the interval tree library 1780 1781config PERCPU_TEST 1782 tristate "Per cpu operations test" 1783 depends on m && DEBUG_KERNEL 1784 help 1785 Enable this option to build test module which validates per-cpu 1786 operations. 1787 1788 If unsure, say N. 1789 1790config ATOMIC64_SELFTEST 1791 tristate "Perform an atomic64_t self-test" 1792 help 1793 Enable this option to test the atomic64_t functions at boot or 1794 at module load time. 1795 1796 If unsure, say N. 1797 1798config ASYNC_RAID6_TEST 1799 tristate "Self test for hardware accelerated raid6 recovery" 1800 depends on ASYNC_RAID6_RECOV 1801 select ASYNC_MEMCPY 1802 ---help--- 1803 This is a one-shot self test that permutes through the 1804 recovery of all the possible two disk failure scenarios for a 1805 N-disk array. Recovery is performed with the asynchronous 1806 raid6 recovery routines, and will optionally use an offload 1807 engine if one is available. 1808 1809 If unsure, say N. 1810 1811config TEST_HEXDUMP 1812 tristate "Test functions located in the hexdump module at runtime" 1813 1814config TEST_STRING_HELPERS 1815 tristate "Test functions located in the string_helpers module at runtime" 1816 1817config TEST_KSTRTOX 1818 tristate "Test kstrto*() family of functions at runtime" 1819 1820config TEST_PRINTF 1821 tristate "Test printf() family of functions at runtime" 1822 1823config TEST_BITMAP 1824 tristate "Test bitmap_*() family of functions at runtime" 1825 default n 1826 help 1827 Enable this option to test the bitmap functions at boot. 1828 1829 If unsure, say N. 1830 1831config TEST_UUID 1832 tristate "Test functions located in the uuid module at runtime" 1833 1834config TEST_RHASHTABLE 1835 tristate "Perform selftest on resizable hash table" 1836 default n 1837 help 1838 Enable this option to test the rhashtable functions at boot. 1839 1840 If unsure, say N. 1841 1842config TEST_HASH 1843 tristate "Perform selftest on hash functions" 1844 default n 1845 help 1846 Enable this option to test the kernel's integer (<linux/hash.h>), 1847 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>) 1848 hash functions on boot (or module load). 1849 1850 This is intended to help people writing architecture-specific 1851 optimized versions. If unsure, say N. 1852 1853config TEST_PARMAN 1854 tristate "Perform selftest on priority array manager" 1855 default n 1856 depends on PARMAN 1857 help 1858 Enable this option to test priority array manager on boot 1859 (or module load). 1860 1861 If unsure, say N. 1862 1863endmenu # runtime tests 1864 1865config PROVIDE_OHCI1394_DMA_INIT 1866 bool "Remote debugging over FireWire early on boot" 1867 depends on PCI && X86 1868 help 1869 If you want to debug problems which hang or crash the kernel early 1870 on boot and the crashing machine has a FireWire port, you can use 1871 this feature to remotely access the memory of the crashed machine 1872 over FireWire. This employs remote DMA as part of the OHCI1394 1873 specification which is now the standard for FireWire controllers. 1874 1875 With remote DMA, you can monitor the printk buffer remotely using 1876 firescope and access all memory below 4GB using fireproxy from gdb. 1877 Even controlling a kernel debugger is possible using remote DMA. 1878 1879 Usage: 1880 1881 If ohci1394_dma=early is used as boot parameter, it will initialize 1882 all OHCI1394 controllers which are found in the PCI config space. 1883 1884 As all changes to the FireWire bus such as enabling and disabling 1885 devices cause a bus reset and thereby disable remote DMA for all 1886 devices, be sure to have the cable plugged and FireWire enabled on 1887 the debugging host before booting the debug target for debugging. 1888 1889 This code (~1k) is freed after boot. By then, the firewire stack 1890 in charge of the OHCI-1394 controllers should be used instead. 1891 1892 See Documentation/debugging-via-ohci1394.txt for more information. 1893 1894config DMA_API_DEBUG 1895 bool "Enable debugging of DMA-API usage" 1896 depends on HAVE_DMA_API_DEBUG 1897 help 1898 Enable this option to debug the use of the DMA API by device drivers. 1899 With this option you will be able to detect common bugs in device 1900 drivers like double-freeing of DMA mappings or freeing mappings that 1901 were never allocated. 1902 1903 This also attempts to catch cases where a page owned by DMA is 1904 accessed by the cpu in a way that could cause data corruption. For 1905 example, this enables cow_user_page() to check that the source page is 1906 not undergoing DMA. 1907 1908 This option causes a performance degradation. Use only if you want to 1909 debug device drivers and dma interactions. 1910 1911 If unsure, say N. 1912 1913config TEST_LKM 1914 tristate "Test module loading with 'hello world' module" 1915 default n 1916 depends on m 1917 help 1918 This builds the "test_module" module that emits "Hello, world" 1919 on printk when loaded. It is designed to be used for basic 1920 evaluation of the module loading subsystem (for example when 1921 validating module verification). It lacks any extra dependencies, 1922 and will not normally be loaded by the system unless explicitly 1923 requested by name. 1924 1925 If unsure, say N. 1926 1927config TEST_USER_COPY 1928 tristate "Test user/kernel boundary protections" 1929 default n 1930 depends on m 1931 help 1932 This builds the "test_user_copy" module that runs sanity checks 1933 on the copy_to/from_user infrastructure, making sure basic 1934 user/kernel boundary testing is working. If it fails to load, 1935 a regression has been detected in the user/kernel memory boundary 1936 protections. 1937 1938 If unsure, say N. 1939 1940config TEST_BPF 1941 tristate "Test BPF filter functionality" 1942 default n 1943 depends on m && NET 1944 help 1945 This builds the "test_bpf" module that runs various test vectors 1946 against the BPF interpreter or BPF JIT compiler depending on the 1947 current setting. This is in particular useful for BPF JIT compiler 1948 development, but also to run regression tests against changes in 1949 the interpreter code. It also enables test stubs for eBPF maps and 1950 verifier used by user space verifier testsuite. 1951 1952 If unsure, say N. 1953 1954config TEST_FIRMWARE 1955 tristate "Test firmware loading via userspace interface" 1956 default n 1957 depends on FW_LOADER 1958 help 1959 This builds the "test_firmware" module that creates a userspace 1960 interface for testing firmware loading. This can be used to 1961 control the triggering of firmware loading without needing an 1962 actual firmware-using device. The contents can be rechecked by 1963 userspace. 1964 1965 If unsure, say N. 1966 1967config TEST_UDELAY 1968 tristate "udelay test driver" 1969 default n 1970 help 1971 This builds the "udelay_test" module that helps to make sure 1972 that udelay() is working properly. 1973 1974 If unsure, say N. 1975 1976config MEMTEST 1977 bool "Memtest" 1978 depends on HAVE_MEMBLOCK 1979 ---help--- 1980 This option adds a kernel parameter 'memtest', which allows memtest 1981 to be set. 1982 memtest=0, mean disabled; -- default 1983 memtest=1, mean do 1 test pattern; 1984 ... 1985 memtest=17, mean do 17 test patterns. 1986 If you are unsure how to answer this question, answer N. 1987 1988config TEST_STATIC_KEYS 1989 tristate "Test static keys" 1990 default n 1991 depends on m 1992 help 1993 Test the static key interfaces. 1994 1995 If unsure, say N. 1996 1997config BUG_ON_DATA_CORRUPTION 1998 bool "Trigger a BUG when data corruption is detected" 1999 select DEBUG_LIST 2000 help 2001 Select this option if the kernel should BUG when it encounters 2002 data corruption in kernel memory structures when they get checked 2003 for validity. 2004 2005 If unsure, say N. 2006 2007source "samples/Kconfig" 2008 2009source "lib/Kconfig.kgdb" 2010 2011source "lib/Kconfig.ubsan" 2012 2013config ARCH_HAS_DEVMEM_IS_ALLOWED 2014 bool 2015 2016config STRICT_DEVMEM 2017 bool "Filter access to /dev/mem" 2018 depends on MMU && DEVMEM 2019 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 2020 default y if TILE || PPC 2021 ---help--- 2022 If this option is disabled, you allow userspace (root) access to all 2023 of memory, including kernel and userspace memory. Accidental 2024 access to this is obviously disastrous, but specific access can 2025 be used by people debugging the kernel. Note that with PAT support 2026 enabled, even in this case there are restrictions on /dev/mem 2027 use due to the cache aliasing requirements. 2028 2029 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 2030 file only allows userspace access to PCI space and the BIOS code and 2031 data regions. This is sufficient for dosemu and X and all common 2032 users of /dev/mem. 2033 2034 If in doubt, say Y. 2035 2036config IO_STRICT_DEVMEM 2037 bool "Filter I/O access to /dev/mem" 2038 depends on STRICT_DEVMEM 2039 ---help--- 2040 If this option is disabled, you allow userspace (root) access to all 2041 io-memory regardless of whether a driver is actively using that 2042 range. Accidental access to this is obviously disastrous, but 2043 specific access can be used by people debugging kernel drivers. 2044 2045 If this option is switched on, the /dev/mem file only allows 2046 userspace access to *idle* io-memory ranges (see /proc/iomem) This 2047 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 2048 if the driver using a given range cannot be disabled. 2049 2050 If in doubt, say Y. 2051