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 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 3072 if KASAN_EXTRA 221 default 2048 if GCC_PLUGIN_LATENT_ENTROPY 222 default 1280 if (!64BIT && PARISC) 223 default 1024 if (!64BIT && !PARISC) 224 default 2048 if 64BIT 225 help 226 Tell gcc to warn at build time for stack frames larger than this. 227 Setting this too low will cause a lot of warnings. 228 Setting it to 0 disables the warning. 229 Requires gcc 4.4 230 231config STRIP_ASM_SYMS 232 bool "Strip assembler-generated symbols during link" 233 default n 234 help 235 Strip internal assembler-generated symbols during a link (symbols 236 that look like '.Lxxx') so they don't pollute the output of 237 get_wchan() and suchlike. 238 239config READABLE_ASM 240 bool "Generate readable assembler code" 241 depends on DEBUG_KERNEL 242 help 243 Disable some compiler optimizations that tend to generate human unreadable 244 assembler output. This may make the kernel slightly slower, but it helps 245 to keep kernel developers who have to stare a lot at assembler listings 246 sane. 247 248config UNUSED_SYMBOLS 249 bool "Enable unused/obsolete exported symbols" 250 default y if X86 251 help 252 Unused but exported symbols make the kernel needlessly bigger. For 253 that reason most of these unused exports will soon be removed. This 254 option is provided temporarily to provide a transition period in case 255 some external kernel module needs one of these symbols anyway. If you 256 encounter such a case in your module, consider if you are actually 257 using the right API. (rationale: since nobody in the kernel is using 258 this in a module, there is a pretty good chance it's actually the 259 wrong interface to use). If you really need the symbol, please send a 260 mail to the linux kernel mailing list mentioning the symbol and why 261 you really need it, and what the merge plan to the mainline kernel for 262 your module is. 263 264config PAGE_OWNER 265 bool "Track page owner" 266 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 267 select DEBUG_FS 268 select STACKTRACE 269 select STACKDEPOT 270 select PAGE_EXTENSION 271 help 272 This keeps track of what call chain is the owner of a page, may 273 help to find bare alloc_page(s) leaks. Even if you include this 274 feature on your build, it is disabled in default. You should pass 275 "page_owner=on" to boot parameter in order to enable it. Eats 276 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 277 for user-space helper. 278 279 If unsure, say N. 280 281config DEBUG_FS 282 bool "Debug Filesystem" 283 help 284 debugfs is a virtual file system that kernel developers use to put 285 debugging files into. Enable this option to be able to read and 286 write to these files. 287 288 For detailed documentation on the debugfs API, see 289 Documentation/filesystems/. 290 291 If unsure, say N. 292 293config HEADERS_CHECK 294 bool "Run 'make headers_check' when building vmlinux" 295 depends on !UML 296 help 297 This option will extract the user-visible kernel headers whenever 298 building the kernel, and will run basic sanity checks on them to 299 ensure that exported files do not attempt to include files which 300 were not exported, etc. 301 302 If you're making modifications to header files which are 303 relevant for userspace, say 'Y', and check the headers 304 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 305 your build tree), to make sure they're suitable. 306 307config DEBUG_SECTION_MISMATCH 308 bool "Enable full Section mismatch analysis" 309 help 310 The section mismatch analysis checks if there are illegal 311 references from one section to another section. 312 During linktime or runtime, some sections are dropped; 313 any use of code/data previously in these sections would 314 most likely result in an oops. 315 In the code, functions and variables are annotated with 316 __init,, etc. (see the full list in include/linux/init.h), 317 which results in the code/data being placed in specific sections. 318 The section mismatch analysis is always performed after a full 319 kernel build, and enabling this option causes the following 320 additional steps to occur: 321 - Add the option -fno-inline-functions-called-once to gcc commands. 322 When inlining a function annotated with __init in a non-init 323 function, we would lose the section information and thus 324 the analysis would not catch the illegal reference. 325 This option tells gcc to inline less (but it does result in 326 a larger kernel). 327 - Run the section mismatch analysis for each module/built-in.a 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.a 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 355config FRAME_POINTER 356 bool "Compile the kernel with frame pointers" 357 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS 358 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 359 help 360 If you say Y here the resulting kernel image will be slightly 361 larger and slower, but it gives very useful debugging information 362 in case of kernel bugs. (precise oopses/stacktraces/warnings) 363 364config STACK_VALIDATION 365 bool "Compile-time stack metadata validation" 366 depends on HAVE_STACK_VALIDATION 367 default n 368 help 369 Add compile-time checks to validate stack metadata, including frame 370 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure 371 that runtime stack traces are more reliable. 372 373 This is also a prerequisite for generation of ORC unwind data, which 374 is needed for CONFIG_UNWINDER_ORC. 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/admin-guide/sysrq.rst>. 408 Don't say Y 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/admin-guide/sysrq.rst. 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 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 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 ARCH_HAS_DEBUG_VIRTUAL 636 bool 637 638config DEBUG_VIRTUAL 639 bool "Debug VM translations" 640 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL 641 help 642 Enable some costly sanity checks in virtual to page code. This can 643 catch mistakes with virt_to_page() and friends. 644 645 If unsure, say N. 646 647config DEBUG_NOMMU_REGIONS 648 bool "Debug the global anon/private NOMMU mapping region tree" 649 depends on DEBUG_KERNEL && !MMU 650 help 651 This option causes the global tree of anonymous and private mapping 652 regions to be regularly checked for invalid topology. 653 654config DEBUG_MEMORY_INIT 655 bool "Debug memory initialisation" if EXPERT 656 default !EXPERT 657 help 658 Enable this for additional checks during memory initialisation. 659 The sanity checks verify aspects of the VM such as the memory model 660 and other information provided by the architecture. Verbose 661 information will be printed at KERN_DEBUG loglevel depending 662 on the mminit_loglevel= command-line option. 663 664 If unsure, say Y 665 666config MEMORY_NOTIFIER_ERROR_INJECT 667 tristate "Memory hotplug notifier error injection module" 668 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 669 help 670 This option provides the ability to inject artificial errors to 671 memory hotplug notifier chain callbacks. It is controlled through 672 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 673 674 If the notifier call chain should be failed with some events 675 notified, write the error code to "actions/<notifier event>/error". 676 677 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 678 679 # cd /sys/kernel/debug/notifier-error-inject/memory 680 # echo -12 > actions/MEM_GOING_OFFLINE/error 681 # echo offline > /sys/devices/system/memory/memoryXXX/state 682 bash: echo: write error: Cannot allocate memory 683 684 To compile this code as a module, choose M here: the module will 685 be called memory-notifier-error-inject. 686 687 If unsure, say N. 688 689config DEBUG_PER_CPU_MAPS 690 bool "Debug access to per_cpu maps" 691 depends on DEBUG_KERNEL 692 depends on SMP 693 help 694 Say Y to verify that the per_cpu map being accessed has 695 been set up. This adds a fair amount of code to kernel memory 696 and decreases performance. 697 698 Say N if unsure. 699 700config DEBUG_HIGHMEM 701 bool "Highmem debugging" 702 depends on DEBUG_KERNEL && HIGHMEM 703 help 704 This option enables additional error checking for high memory 705 systems. Disable for production systems. 706 707config HAVE_DEBUG_STACKOVERFLOW 708 bool 709 710config DEBUG_STACKOVERFLOW 711 bool "Check for stack overflows" 712 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 713 ---help--- 714 Say Y here if you want to check for overflows of kernel, IRQ 715 and exception stacks (if your architecture uses them). This 716 option will show detailed messages if free stack space drops 717 below a certain limit. 718 719 These kinds of bugs usually occur when call-chains in the 720 kernel get too deep, especially when interrupts are 721 involved. 722 723 Use this in cases where you see apparently random memory 724 corruption, especially if it appears in 'struct thread_info' 725 726 If in doubt, say "N". 727 728source "lib/Kconfig.kasan" 729 730endmenu # "Memory Debugging" 731 732config ARCH_HAS_KCOV 733 bool 734 help 735 KCOV does not have any arch-specific code, but currently it is enabled 736 only for x86_64. KCOV requires testing on other archs, and most likely 737 disabling of instrumentation for some early boot code. 738 739config CC_HAS_SANCOV_TRACE_PC 740 def_bool $(cc-option,-fsanitize-coverage=trace-pc) 741 742config KCOV 743 bool "Code coverage for fuzzing" 744 depends on ARCH_HAS_KCOV 745 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS 746 select DEBUG_FS 747 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC 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_ENABLE_COMPARISONS 759 bool "Enable comparison operands collection by KCOV" 760 depends on KCOV 761 depends on $(cc-option,-fsanitize-coverage=trace-cmp) 762 help 763 KCOV also exposes operands of every comparison in the instrumented 764 code along with operand sizes and PCs of the comparison instructions. 765 These operands can be used by fuzzing engines to improve the quality 766 of fuzzing coverage. 767 768config KCOV_INSTRUMENT_ALL 769 bool "Instrument all code by default" 770 depends on KCOV 771 default y 772 help 773 If you are doing generic system call fuzzing (like e.g. syzkaller), 774 then you will want to instrument the whole kernel and you should 775 say y here. If you are doing more targeted fuzzing (like e.g. 776 filesystem fuzzing with AFL) then you will want to enable coverage 777 for more specific subsets of files, and should say n here. 778 779config DEBUG_SHIRQ 780 bool "Debug shared IRQ handlers" 781 depends on DEBUG_KERNEL 782 help 783 Enable this to generate a spurious interrupt as soon as a shared 784 interrupt handler is registered, and just before one is deregistered. 785 Drivers ought to be able to handle interrupts coming in at those 786 points; some don't and need to be caught. 787 788menu "Debug Lockups and Hangs" 789 790config LOCKUP_DETECTOR 791 bool 792 793config SOFTLOCKUP_DETECTOR 794 bool "Detect Soft Lockups" 795 depends on DEBUG_KERNEL && !S390 796 select LOCKUP_DETECTOR 797 help 798 Say Y here to enable the kernel to act as a watchdog to detect 799 soft lockups. 800 801 Softlockups are bugs that cause the kernel to loop in kernel 802 mode for more than 20 seconds, without giving other tasks a 803 chance to run. The current stack trace is displayed upon 804 detection and the system will stay locked up. 805 806config BOOTPARAM_SOFTLOCKUP_PANIC 807 bool "Panic (Reboot) On Soft Lockups" 808 depends on SOFTLOCKUP_DETECTOR 809 help 810 Say Y here to enable the kernel to panic on "soft lockups", 811 which are bugs that cause the kernel to loop in kernel 812 mode for more than 20 seconds (configurable using the watchdog_thresh 813 sysctl), without giving other tasks a chance to run. 814 815 The panic can be used in combination with panic_timeout, 816 to cause the system to reboot automatically after a 817 lockup has been detected. This feature is useful for 818 high-availability systems that have uptime guarantees and 819 where a lockup must be resolved ASAP. 820 821 Say N if unsure. 822 823config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 824 int 825 depends on SOFTLOCKUP_DETECTOR 826 range 0 1 827 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 828 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 829 830config HARDLOCKUP_DETECTOR_PERF 831 bool 832 select SOFTLOCKUP_DETECTOR 833 834# 835# Enables a timestamp based low pass filter to compensate for perf based 836# hard lockup detection which runs too fast due to turbo modes. 837# 838config HARDLOCKUP_CHECK_TIMESTAMP 839 bool 840 841# 842# arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard 843# lockup detector rather than the perf based detector. 844# 845config HARDLOCKUP_DETECTOR 846 bool "Detect Hard Lockups" 847 depends on DEBUG_KERNEL && !S390 848 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH 849 select LOCKUP_DETECTOR 850 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF 851 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH 852 help 853 Say Y here to enable the kernel to act as a watchdog to detect 854 hard lockups. 855 856 Hardlockups are bugs that cause the CPU to loop in kernel mode 857 for more than 10 seconds, without letting other interrupts have a 858 chance to run. The current stack trace is displayed upon detection 859 and the system will stay locked up. 860 861config BOOTPARAM_HARDLOCKUP_PANIC 862 bool "Panic (Reboot) On Hard Lockups" 863 depends on HARDLOCKUP_DETECTOR 864 help 865 Say Y here to enable the kernel to panic on "hard lockups", 866 which are bugs that cause the kernel to loop in kernel 867 mode with interrupts disabled for more than 10 seconds (configurable 868 using the watchdog_thresh sysctl). 869 870 Say N if unsure. 871 872config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 873 int 874 depends on HARDLOCKUP_DETECTOR 875 range 0 1 876 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 877 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 878 879config DETECT_HUNG_TASK 880 bool "Detect Hung Tasks" 881 depends on DEBUG_KERNEL 882 default SOFTLOCKUP_DETECTOR 883 help 884 Say Y here to enable the kernel to detect "hung tasks", 885 which are bugs that cause the task to be stuck in 886 uninterruptible "D" state indefinitely. 887 888 When a hung task is detected, the kernel will print the 889 current stack trace (which you should report), but the 890 task will stay in uninterruptible state. If lockdep is 891 enabled then all held locks will also be reported. This 892 feature has negligible overhead. 893 894config DEFAULT_HUNG_TASK_TIMEOUT 895 int "Default timeout for hung task detection (in seconds)" 896 depends on DETECT_HUNG_TASK 897 default 120 898 help 899 This option controls the default timeout (in seconds) used 900 to determine when a task has become non-responsive and should 901 be considered hung. 902 903 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 904 sysctl or by writing a value to 905 /proc/sys/kernel/hung_task_timeout_secs. 906 907 A timeout of 0 disables the check. The default is two minutes. 908 Keeping the default should be fine in most cases. 909 910config BOOTPARAM_HUNG_TASK_PANIC 911 bool "Panic (Reboot) On Hung Tasks" 912 depends on DETECT_HUNG_TASK 913 help 914 Say Y here to enable the kernel to panic on "hung tasks", 915 which are bugs that cause the kernel to leave a task stuck 916 in uninterruptible "D" state. 917 918 The panic can be used in combination with panic_timeout, 919 to cause the system to reboot automatically after a 920 hung task has been detected. This feature is useful for 921 high-availability systems that have uptime guarantees and 922 where a hung tasks must be resolved ASAP. 923 924 Say N if unsure. 925 926config BOOTPARAM_HUNG_TASK_PANIC_VALUE 927 int 928 depends on DETECT_HUNG_TASK 929 range 0 1 930 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 931 default 1 if BOOTPARAM_HUNG_TASK_PANIC 932 933config WQ_WATCHDOG 934 bool "Detect Workqueue Stalls" 935 depends on DEBUG_KERNEL 936 help 937 Say Y here to enable stall detection on workqueues. If a 938 worker pool doesn't make forward progress on a pending work 939 item for over a given amount of time, 30s by default, a 940 warning message is printed along with dump of workqueue 941 state. This can be configured through kernel parameter 942 "workqueue.watchdog_thresh" and its sysfs counterpart. 943 944endmenu # "Debug lockups and hangs" 945 946config PANIC_ON_OOPS 947 bool "Panic on Oops" 948 help 949 Say Y here to enable the kernel to panic when it oopses. This 950 has the same effect as setting oops=panic on the kernel command 951 line. 952 953 This feature is useful to ensure that the kernel does not do 954 anything erroneous after an oops which could result in data 955 corruption or other issues. 956 957 Say N if unsure. 958 959config PANIC_ON_OOPS_VALUE 960 int 961 range 0 1 962 default 0 if !PANIC_ON_OOPS 963 default 1 if PANIC_ON_OOPS 964 965config PANIC_TIMEOUT 966 int "panic timeout" 967 default 0 968 help 969 Set the timeout value (in seconds) until a reboot occurs when the 970 the kernel panics. If n = 0, then we wait forever. A timeout 971 value n > 0 will wait n seconds before rebooting, while a timeout 972 value n < 0 will reboot immediately. 973 974config SCHED_DEBUG 975 bool "Collect scheduler debugging info" 976 depends on DEBUG_KERNEL && PROC_FS 977 default y 978 help 979 If you say Y here, the /proc/sched_debug file will be provided 980 that can help debug the scheduler. The runtime overhead of this 981 option is minimal. 982 983config SCHED_INFO 984 bool 985 default n 986 987config SCHEDSTATS 988 bool "Collect scheduler statistics" 989 depends on DEBUG_KERNEL && PROC_FS 990 select SCHED_INFO 991 help 992 If you say Y here, additional code will be inserted into the 993 scheduler and related routines to collect statistics about 994 scheduler behavior and provide them in /proc/schedstat. These 995 stats may be useful for both tuning and debugging the scheduler 996 If you aren't debugging the scheduler or trying to tune a specific 997 application, you can say N to avoid the very slight overhead 998 this adds. 999 1000config SCHED_STACK_END_CHECK 1001 bool "Detect stack corruption on calls to schedule()" 1002 depends on DEBUG_KERNEL 1003 default n 1004 help 1005 This option checks for a stack overrun on calls to schedule(). 1006 If the stack end location is found to be over written always panic as 1007 the content of the corrupted region can no longer be trusted. 1008 This is to ensure no erroneous behaviour occurs which could result in 1009 data corruption or a sporadic crash at a later stage once the region 1010 is examined. The runtime overhead introduced is minimal. 1011 1012config DEBUG_TIMEKEEPING 1013 bool "Enable extra timekeeping sanity checking" 1014 help 1015 This option will enable additional timekeeping sanity checks 1016 which may be helpful when diagnosing issues where timekeeping 1017 problems are suspected. 1018 1019 This may include checks in the timekeeping hotpaths, so this 1020 option may have a (very small) performance impact to some 1021 workloads. 1022 1023 If unsure, say N. 1024 1025config DEBUG_PREEMPT 1026 bool "Debug preemptible kernel" 1027 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 1028 default y 1029 help 1030 If you say Y here then the kernel will use a debug variant of the 1031 commonly used smp_processor_id() function and will print warnings 1032 if kernel code uses it in a preemption-unsafe way. Also, the kernel 1033 will detect preemption count underflows. 1034 1035menu "Lock Debugging (spinlocks, mutexes, etc...)" 1036 1037config LOCK_DEBUGGING_SUPPORT 1038 bool 1039 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1040 default y 1041 1042config PROVE_LOCKING 1043 bool "Lock debugging: prove locking correctness" 1044 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1045 select LOCKDEP 1046 select DEBUG_SPINLOCK 1047 select DEBUG_MUTEXES 1048 select DEBUG_RT_MUTEXES if RT_MUTEXES 1049 select DEBUG_RWSEMS if RWSEM_SPIN_ON_OWNER 1050 select DEBUG_WW_MUTEX_SLOWPATH 1051 select DEBUG_LOCK_ALLOC 1052 select TRACE_IRQFLAGS 1053 default n 1054 help 1055 This feature enables the kernel to prove that all locking 1056 that occurs in the kernel runtime is mathematically 1057 correct: that under no circumstance could an arbitrary (and 1058 not yet triggered) combination of observed locking 1059 sequences (on an arbitrary number of CPUs, running an 1060 arbitrary number of tasks and interrupt contexts) cause a 1061 deadlock. 1062 1063 In short, this feature enables the kernel to report locking 1064 related deadlocks before they actually occur. 1065 1066 The proof does not depend on how hard and complex a 1067 deadlock scenario would be to trigger: how many 1068 participant CPUs, tasks and irq-contexts would be needed 1069 for it to trigger. The proof also does not depend on 1070 timing: if a race and a resulting deadlock is possible 1071 theoretically (no matter how unlikely the race scenario 1072 is), it will be proven so and will immediately be 1073 reported by the kernel (once the event is observed that 1074 makes the deadlock theoretically possible). 1075 1076 If a deadlock is impossible (i.e. the locking rules, as 1077 observed by the kernel, are mathematically correct), the 1078 kernel reports nothing. 1079 1080 NOTE: this feature can also be enabled for rwlocks, mutexes 1081 and rwsems - in which case all dependencies between these 1082 different locking variants are observed and mapped too, and 1083 the proof of observed correctness is also maintained for an 1084 arbitrary combination of these separate locking variants. 1085 1086 For more details, see Documentation/locking/lockdep-design.txt. 1087 1088config LOCK_STAT 1089 bool "Lock usage statistics" 1090 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1091 select LOCKDEP 1092 select DEBUG_SPINLOCK 1093 select DEBUG_MUTEXES 1094 select DEBUG_RT_MUTEXES if RT_MUTEXES 1095 select DEBUG_LOCK_ALLOC 1096 default n 1097 help 1098 This feature enables tracking lock contention points 1099 1100 For more details, see Documentation/locking/lockstat.txt 1101 1102 This also enables lock events required by "perf lock", 1103 subcommand of perf. 1104 If you want to use "perf lock", you also need to turn on 1105 CONFIG_EVENT_TRACING. 1106 1107 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1108 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1109 1110config DEBUG_RT_MUTEXES 1111 bool "RT Mutex debugging, deadlock detection" 1112 depends on DEBUG_KERNEL && RT_MUTEXES 1113 help 1114 This allows rt mutex semantics violations and rt mutex related 1115 deadlocks (lockups) to be detected and reported automatically. 1116 1117config DEBUG_SPINLOCK 1118 bool "Spinlock and rw-lock debugging: basic checks" 1119 depends on DEBUG_KERNEL 1120 select UNINLINE_SPIN_UNLOCK 1121 help 1122 Say Y here and build SMP to catch missing spinlock initialization 1123 and certain other kinds of spinlock errors commonly made. This is 1124 best used in conjunction with the NMI watchdog so that spinlock 1125 deadlocks are also debuggable. 1126 1127config DEBUG_MUTEXES 1128 bool "Mutex debugging: basic checks" 1129 depends on DEBUG_KERNEL 1130 help 1131 This feature allows mutex semantics violations to be detected and 1132 reported. 1133 1134config DEBUG_WW_MUTEX_SLOWPATH 1135 bool "Wait/wound mutex debugging: Slowpath testing" 1136 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1137 select DEBUG_LOCK_ALLOC 1138 select DEBUG_SPINLOCK 1139 select DEBUG_MUTEXES 1140 help 1141 This feature enables slowpath testing for w/w mutex users by 1142 injecting additional -EDEADLK wound/backoff cases. Together with 1143 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 1144 will test all possible w/w mutex interface abuse with the 1145 exception of simply not acquiring all the required locks. 1146 Note that this feature can introduce significant overhead, so 1147 it really should not be enabled in a production or distro kernel, 1148 even a debug kernel. If you are a driver writer, enable it. If 1149 you are a distro, do not. 1150 1151config DEBUG_RWSEMS 1152 bool "RW Semaphore debugging: basic checks" 1153 depends on DEBUG_KERNEL && RWSEM_SPIN_ON_OWNER 1154 help 1155 This debugging feature allows mismatched rw semaphore locks and unlocks 1156 to be detected and reported. 1157 1158config DEBUG_LOCK_ALLOC 1159 bool "Lock debugging: detect incorrect freeing of live locks" 1160 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1161 select DEBUG_SPINLOCK 1162 select DEBUG_MUTEXES 1163 select DEBUG_RT_MUTEXES if RT_MUTEXES 1164 select LOCKDEP 1165 help 1166 This feature will check whether any held lock (spinlock, rwlock, 1167 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1168 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1169 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1170 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1171 held during task exit. 1172 1173config LOCKDEP 1174 bool 1175 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1176 select STACKTRACE 1177 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !X86 1178 select KALLSYMS 1179 select KALLSYMS_ALL 1180 1181config LOCKDEP_SMALL 1182 bool 1183 1184config DEBUG_LOCKDEP 1185 bool "Lock dependency engine debugging" 1186 depends on DEBUG_KERNEL && LOCKDEP 1187 help 1188 If you say Y here, the lock dependency engine will do 1189 additional runtime checks to debug itself, at the price 1190 of more runtime overhead. 1191 1192config DEBUG_ATOMIC_SLEEP 1193 bool "Sleep inside atomic section checking" 1194 select PREEMPT_COUNT 1195 depends on DEBUG_KERNEL 1196 help 1197 If you say Y here, various routines which may sleep will become very 1198 noisy if they are called inside atomic sections: when a spinlock is 1199 held, inside an rcu read side critical section, inside preempt disabled 1200 sections, inside an interrupt, etc... 1201 1202config DEBUG_LOCKING_API_SELFTESTS 1203 bool "Locking API boot-time self-tests" 1204 depends on DEBUG_KERNEL 1205 help 1206 Say Y here if you want the kernel to run a short self-test during 1207 bootup. The self-test checks whether common types of locking bugs 1208 are detected by debugging mechanisms or not. (if you disable 1209 lock debugging then those bugs wont be detected of course.) 1210 The following locking APIs are covered: spinlocks, rwlocks, 1211 mutexes and rwsems. 1212 1213config LOCK_TORTURE_TEST 1214 tristate "torture tests for locking" 1215 depends on DEBUG_KERNEL 1216 select TORTURE_TEST 1217 default n 1218 help 1219 This option provides a kernel module that runs torture tests 1220 on kernel locking primitives. The kernel module may be built 1221 after the fact on the running kernel to be tested, if desired. 1222 1223 Say Y here if you want kernel locking-primitive torture tests 1224 to be built into the kernel. 1225 Say M if you want these torture tests to build as a module. 1226 Say N if you are unsure. 1227 1228config WW_MUTEX_SELFTEST 1229 tristate "Wait/wound mutex selftests" 1230 help 1231 This option provides a kernel module that runs tests on the 1232 on the struct ww_mutex locking API. 1233 1234 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction 1235 with this test harness. 1236 1237 Say M if you want these self tests to build as a module. 1238 Say N if you are unsure. 1239 1240endmenu # lock debugging 1241 1242config TRACE_IRQFLAGS 1243 bool 1244 help 1245 Enables hooks to interrupt enabling and disabling for 1246 either tracing or lock debugging. 1247 1248config STACKTRACE 1249 bool "Stack backtrace support" 1250 depends on STACKTRACE_SUPPORT 1251 help 1252 This option causes the kernel to create a /proc/pid/stack for 1253 every process, showing its current stack trace. 1254 It is also used by various kernel debugging features that require 1255 stack trace generation. 1256 1257config WARN_ALL_UNSEEDED_RANDOM 1258 bool "Warn for all uses of unseeded randomness" 1259 default n 1260 help 1261 Some parts of the kernel contain bugs relating to their use of 1262 cryptographically secure random numbers before it's actually possible 1263 to generate those numbers securely. This setting ensures that these 1264 flaws don't go unnoticed, by enabling a message, should this ever 1265 occur. This will allow people with obscure setups to know when things 1266 are going wrong, so that they might contact developers about fixing 1267 it. 1268 1269 Unfortunately, on some models of some architectures getting 1270 a fully seeded CRNG is extremely difficult, and so this can 1271 result in dmesg getting spammed for a surprisingly long 1272 time. This is really bad from a security perspective, and 1273 so architecture maintainers really need to do what they can 1274 to get the CRNG seeded sooner after the system is booted. 1275 However, since users can not do anything actionble to 1276 address this, by default the kernel will issue only a single 1277 warning for the first use of unseeded randomness. 1278 1279 Say Y here if you want to receive warnings for all uses of 1280 unseeded randomness. This will be of use primarily for 1281 those developers interersted in improving the security of 1282 Linux kernels running on their architecture (or 1283 subarchitecture). 1284 1285config DEBUG_KOBJECT 1286 bool "kobject debugging" 1287 depends on DEBUG_KERNEL 1288 help 1289 If you say Y here, some extra kobject debugging messages will be sent 1290 to the syslog. 1291 1292config DEBUG_KOBJECT_RELEASE 1293 bool "kobject release debugging" 1294 depends on DEBUG_OBJECTS_TIMERS 1295 help 1296 kobjects are reference counted objects. This means that their 1297 last reference count put is not predictable, and the kobject can 1298 live on past the point at which a driver decides to drop it's 1299 initial reference to the kobject gained on allocation. An 1300 example of this would be a struct device which has just been 1301 unregistered. 1302 1303 However, some buggy drivers assume that after such an operation, 1304 the memory backing the kobject can be immediately freed. This 1305 goes completely against the principles of a refcounted object. 1306 1307 If you say Y here, the kernel will delay the release of kobjects 1308 on the last reference count to improve the visibility of this 1309 kind of kobject release bug. 1310 1311config HAVE_DEBUG_BUGVERBOSE 1312 bool 1313 1314config DEBUG_BUGVERBOSE 1315 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1316 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1317 default y 1318 help 1319 Say Y here to make BUG() panics output the file name and line number 1320 of the BUG call as well as the EIP and oops trace. This aids 1321 debugging but costs about 70-100K of memory. 1322 1323config DEBUG_LIST 1324 bool "Debug linked list manipulation" 1325 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION 1326 help 1327 Enable this to turn on extended checks in the linked-list 1328 walking routines. 1329 1330 If unsure, say N. 1331 1332config DEBUG_PI_LIST 1333 bool "Debug priority linked list manipulation" 1334 depends on DEBUG_KERNEL 1335 help 1336 Enable this to turn on extended checks in the priority-ordered 1337 linked-list (plist) walking routines. This checks the entire 1338 list multiple times during each manipulation. 1339 1340 If unsure, say N. 1341 1342config DEBUG_SG 1343 bool "Debug SG table operations" 1344 depends on DEBUG_KERNEL 1345 help 1346 Enable this to turn on checks on scatter-gather tables. This can 1347 help find problems with drivers that do not properly initialize 1348 their sg tables. 1349 1350 If unsure, say N. 1351 1352config DEBUG_NOTIFIERS 1353 bool "Debug notifier call chains" 1354 depends on DEBUG_KERNEL 1355 help 1356 Enable this to turn on sanity checking for notifier call chains. 1357 This is most useful for kernel developers to make sure that 1358 modules properly unregister themselves from notifier chains. 1359 This is a relatively cheap check but if you care about maximum 1360 performance, say N. 1361 1362config DEBUG_CREDENTIALS 1363 bool "Debug credential management" 1364 depends on DEBUG_KERNEL 1365 help 1366 Enable this to turn on some debug checking for credential 1367 management. The additional code keeps track of the number of 1368 pointers from task_structs to any given cred struct, and checks to 1369 see that this number never exceeds the usage count of the cred 1370 struct. 1371 1372 Furthermore, if SELinux is enabled, this also checks that the 1373 security pointer in the cred struct is never seen to be invalid. 1374 1375 If unsure, say N. 1376 1377source "kernel/rcu/Kconfig.debug" 1378 1379config DEBUG_WQ_FORCE_RR_CPU 1380 bool "Force round-robin CPU selection for unbound work items" 1381 depends on DEBUG_KERNEL 1382 default n 1383 help 1384 Workqueue used to implicitly guarantee that work items queued 1385 without explicit CPU specified are put on the local CPU. This 1386 guarantee is no longer true and while local CPU is still 1387 preferred work items may be put on foreign CPUs. Kernel 1388 parameter "workqueue.debug_force_rr_cpu" is added to force 1389 round-robin CPU selection to flush out usages which depend on the 1390 now broken guarantee. This config option enables the debug 1391 feature by default. When enabled, memory and cache locality will 1392 be impacted. 1393 1394config DEBUG_BLOCK_EXT_DEVT 1395 bool "Force extended block device numbers and spread them" 1396 depends on DEBUG_KERNEL 1397 depends on BLOCK 1398 default n 1399 help 1400 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1401 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1402 YOU ARE DOING. Distros, please enable this and fix whatever 1403 is broken. 1404 1405 Conventionally, block device numbers are allocated from 1406 predetermined contiguous area. However, extended block area 1407 may introduce non-contiguous block device numbers. This 1408 option forces most block device numbers to be allocated from 1409 the extended space and spreads them to discover kernel or 1410 userland code paths which assume predetermined contiguous 1411 device number allocation. 1412 1413 Note that turning on this debug option shuffles all the 1414 device numbers for all IDE and SCSI devices including libata 1415 ones, so root partition specified using device number 1416 directly (via rdev or root=MAJ:MIN) won't work anymore. 1417 Textual device names (root=/dev/sdXn) will continue to work. 1418 1419 Say N if you are unsure. 1420 1421config CPU_HOTPLUG_STATE_CONTROL 1422 bool "Enable CPU hotplug state control" 1423 depends on DEBUG_KERNEL 1424 depends on HOTPLUG_CPU 1425 default n 1426 help 1427 Allows to write steps between "offline" and "online" to the CPUs 1428 sysfs target file so states can be stepped granular. This is a debug 1429 option for now as the hotplug machinery cannot be stopped and 1430 restarted at arbitrary points yet. 1431 1432 Say N if your are unsure. 1433 1434config NOTIFIER_ERROR_INJECTION 1435 tristate "Notifier error injection" 1436 depends on DEBUG_KERNEL 1437 select DEBUG_FS 1438 help 1439 This option provides the ability to inject artificial errors to 1440 specified notifier chain callbacks. It is useful to test the error 1441 handling of notifier call chain failures. 1442 1443 Say N if unsure. 1444 1445config PM_NOTIFIER_ERROR_INJECT 1446 tristate "PM notifier error injection module" 1447 depends on PM && NOTIFIER_ERROR_INJECTION 1448 default m if PM_DEBUG 1449 help 1450 This option provides the ability to inject artificial errors to 1451 PM notifier chain callbacks. It is controlled through debugfs 1452 interface /sys/kernel/debug/notifier-error-inject/pm 1453 1454 If the notifier call chain should be failed with some events 1455 notified, write the error code to "actions/<notifier event>/error". 1456 1457 Example: Inject PM suspend error (-12 = -ENOMEM) 1458 1459 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1460 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1461 # echo mem > /sys/power/state 1462 bash: echo: write error: Cannot allocate memory 1463 1464 To compile this code as a module, choose M here: the module will 1465 be called pm-notifier-error-inject. 1466 1467 If unsure, say N. 1468 1469config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1470 tristate "OF reconfig notifier error injection module" 1471 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1472 help 1473 This option provides the ability to inject artificial errors to 1474 OF reconfig notifier chain callbacks. It is controlled 1475 through debugfs interface under 1476 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1477 1478 If the notifier call chain should be failed with some events 1479 notified, write the error code to "actions/<notifier event>/error". 1480 1481 To compile this code as a module, choose M here: the module will 1482 be called of-reconfig-notifier-error-inject. 1483 1484 If unsure, say N. 1485 1486config NETDEV_NOTIFIER_ERROR_INJECT 1487 tristate "Netdev notifier error injection module" 1488 depends on NET && NOTIFIER_ERROR_INJECTION 1489 help 1490 This option provides the ability to inject artificial errors to 1491 netdevice notifier chain callbacks. It is controlled through debugfs 1492 interface /sys/kernel/debug/notifier-error-inject/netdev 1493 1494 If the notifier call chain should be failed with some events 1495 notified, write the error code to "actions/<notifier event>/error". 1496 1497 Example: Inject netdevice mtu change error (-22 = -EINVAL) 1498 1499 # cd /sys/kernel/debug/notifier-error-inject/netdev 1500 # echo -22 > actions/NETDEV_CHANGEMTU/error 1501 # ip link set eth0 mtu 1024 1502 RTNETLINK answers: Invalid argument 1503 1504 To compile this code as a module, choose M here: the module will 1505 be called netdev-notifier-error-inject. 1506 1507 If unsure, say N. 1508 1509config FUNCTION_ERROR_INJECTION 1510 def_bool y 1511 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES 1512 1513config FAULT_INJECTION 1514 bool "Fault-injection framework" 1515 depends on DEBUG_KERNEL 1516 help 1517 Provide fault-injection framework. 1518 For more details, see Documentation/fault-injection/. 1519 1520config FAILSLAB 1521 bool "Fault-injection capability for kmalloc" 1522 depends on FAULT_INJECTION 1523 depends on SLAB || SLUB 1524 help 1525 Provide fault-injection capability for kmalloc. 1526 1527config FAIL_PAGE_ALLOC 1528 bool "Fault-injection capabilitiy for alloc_pages()" 1529 depends on FAULT_INJECTION 1530 help 1531 Provide fault-injection capability for alloc_pages(). 1532 1533config FAIL_MAKE_REQUEST 1534 bool "Fault-injection capability for disk IO" 1535 depends on FAULT_INJECTION && BLOCK 1536 help 1537 Provide fault-injection capability for disk IO. 1538 1539config FAIL_IO_TIMEOUT 1540 bool "Fault-injection capability for faking disk interrupts" 1541 depends on FAULT_INJECTION && BLOCK 1542 help 1543 Provide fault-injection capability on end IO handling. This 1544 will make the block layer "forget" an interrupt as configured, 1545 thus exercising the error handling. 1546 1547 Only works with drivers that use the generic timeout handling, 1548 for others it wont do anything. 1549 1550config FAIL_FUTEX 1551 bool "Fault-injection capability for futexes" 1552 select DEBUG_FS 1553 depends on FAULT_INJECTION && FUTEX 1554 help 1555 Provide fault-injection capability for futexes. 1556 1557config FAULT_INJECTION_DEBUG_FS 1558 bool "Debugfs entries for fault-injection capabilities" 1559 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1560 help 1561 Enable configuration of fault-injection capabilities via debugfs. 1562 1563config FAIL_FUNCTION 1564 bool "Fault-injection capability for functions" 1565 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION 1566 help 1567 Provide function-based fault-injection capability. 1568 This will allow you to override a specific function with a return 1569 with given return value. As a result, function caller will see 1570 an error value and have to handle it. This is useful to test the 1571 error handling in various subsystems. 1572 1573config FAIL_MMC_REQUEST 1574 bool "Fault-injection capability for MMC IO" 1575 depends on FAULT_INJECTION_DEBUG_FS && MMC 1576 help 1577 Provide fault-injection capability for MMC IO. 1578 This will make the mmc core return data errors. This is 1579 useful to test the error handling in the mmc block device 1580 and to test how the mmc host driver handles retries from 1581 the block device. 1582 1583config FAULT_INJECTION_STACKTRACE_FILTER 1584 bool "stacktrace filter for fault-injection capabilities" 1585 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1586 depends on !X86_64 1587 select STACKTRACE 1588 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !X86 1589 help 1590 Provide stacktrace filter for fault-injection capabilities 1591 1592config LATENCYTOP 1593 bool "Latency measuring infrastructure" 1594 depends on DEBUG_KERNEL 1595 depends on STACKTRACE_SUPPORT 1596 depends on PROC_FS 1597 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !X86 1598 select KALLSYMS 1599 select KALLSYMS_ALL 1600 select STACKTRACE 1601 select SCHEDSTATS 1602 select SCHED_DEBUG 1603 help 1604 Enable this option if you want to use the LatencyTOP tool 1605 to find out which userspace is blocking on what kernel operations. 1606 1607source kernel/trace/Kconfig 1608 1609config PROVIDE_OHCI1394_DMA_INIT 1610 bool "Remote debugging over FireWire early on boot" 1611 depends on PCI && X86 1612 help 1613 If you want to debug problems which hang or crash the kernel early 1614 on boot and the crashing machine has a FireWire port, you can use 1615 this feature to remotely access the memory of the crashed machine 1616 over FireWire. This employs remote DMA as part of the OHCI1394 1617 specification which is now the standard for FireWire controllers. 1618 1619 With remote DMA, you can monitor the printk buffer remotely using 1620 firescope and access all memory below 4GB using fireproxy from gdb. 1621 Even controlling a kernel debugger is possible using remote DMA. 1622 1623 Usage: 1624 1625 If ohci1394_dma=early is used as boot parameter, it will initialize 1626 all OHCI1394 controllers which are found in the PCI config space. 1627 1628 As all changes to the FireWire bus such as enabling and disabling 1629 devices cause a bus reset and thereby disable remote DMA for all 1630 devices, be sure to have the cable plugged and FireWire enabled on 1631 the debugging host before booting the debug target for debugging. 1632 1633 This code (~1k) is freed after boot. By then, the firewire stack 1634 in charge of the OHCI-1394 controllers should be used instead. 1635 1636 See Documentation/debugging-via-ohci1394.txt for more information. 1637 1638config DMA_API_DEBUG 1639 bool "Enable debugging of DMA-API usage" 1640 select NEED_DMA_MAP_STATE 1641 help 1642 Enable this option to debug the use of the DMA API by device drivers. 1643 With this option you will be able to detect common bugs in device 1644 drivers like double-freeing of DMA mappings or freeing mappings that 1645 were never allocated. 1646 1647 This also attempts to catch cases where a page owned by DMA is 1648 accessed by the cpu in a way that could cause data corruption. For 1649 example, this enables cow_user_page() to check that the source page is 1650 not undergoing DMA. 1651 1652 This option causes a performance degradation. Use only if you want to 1653 debug device drivers and dma interactions. 1654 1655 If unsure, say N. 1656 1657config DMA_API_DEBUG_SG 1658 bool "Debug DMA scatter-gather usage" 1659 default y 1660 depends on DMA_API_DEBUG 1661 help 1662 Perform extra checking that callers of dma_map_sg() have respected the 1663 appropriate segment length/boundary limits for the given device when 1664 preparing DMA scatterlists. 1665 1666 This is particularly likely to have been overlooked in cases where the 1667 dma_map_sg() API is used for general bulk mapping of pages rather than 1668 preparing literal scatter-gather descriptors, where there is a risk of 1669 unexpected behaviour from DMA API implementations if the scatterlist 1670 is technically out-of-spec. 1671 1672 If unsure, say N. 1673 1674menuconfig RUNTIME_TESTING_MENU 1675 bool "Runtime Testing" 1676 def_bool y 1677 1678if RUNTIME_TESTING_MENU 1679 1680config LKDTM 1681 tristate "Linux Kernel Dump Test Tool Module" 1682 depends on DEBUG_FS 1683 depends on BLOCK 1684 default n 1685 help 1686 This module enables testing of the different dumping mechanisms by 1687 inducing system failures at predefined crash points. 1688 If you don't need it: say N 1689 Choose M here to compile this code as a module. The module will be 1690 called lkdtm. 1691 1692 Documentation on how to use the module can be found in 1693 Documentation/fault-injection/provoke-crashes.txt 1694 1695config TEST_LIST_SORT 1696 tristate "Linked list sorting test" 1697 depends on DEBUG_KERNEL || m 1698 help 1699 Enable this to turn on 'list_sort()' function test. This test is 1700 executed only once during system boot (so affects only boot time), 1701 or at module load time. 1702 1703 If unsure, say N. 1704 1705config TEST_SORT 1706 tristate "Array-based sort test" 1707 depends on DEBUG_KERNEL || m 1708 help 1709 This option enables the self-test function of 'sort()' at boot, 1710 or at module load time. 1711 1712 If unsure, say N. 1713 1714config KPROBES_SANITY_TEST 1715 bool "Kprobes sanity tests" 1716 depends on DEBUG_KERNEL 1717 depends on KPROBES 1718 default n 1719 help 1720 This option provides for testing basic kprobes functionality on 1721 boot. A sample kprobe, jprobe and kretprobe are inserted and 1722 verified for functionality. 1723 1724 Say N if you are unsure. 1725 1726config BACKTRACE_SELF_TEST 1727 tristate "Self test for the backtrace code" 1728 depends on DEBUG_KERNEL 1729 default n 1730 help 1731 This option provides a kernel module that can be used to test 1732 the kernel stack backtrace code. This option is not useful 1733 for distributions or general kernels, but only for kernel 1734 developers working on architecture code. 1735 1736 Note that if you want to also test saved backtraces, you will 1737 have to enable STACKTRACE as well. 1738 1739 Say N if you are unsure. 1740 1741config RBTREE_TEST 1742 tristate "Red-Black tree test" 1743 depends on DEBUG_KERNEL 1744 help 1745 A benchmark measuring the performance of the rbtree library. 1746 Also includes rbtree invariant checks. 1747 1748config INTERVAL_TREE_TEST 1749 tristate "Interval tree test" 1750 depends on DEBUG_KERNEL 1751 select INTERVAL_TREE 1752 help 1753 A benchmark measuring the performance of the interval tree library 1754 1755config PERCPU_TEST 1756 tristate "Per cpu operations test" 1757 depends on m && DEBUG_KERNEL 1758 help 1759 Enable this option to build test module which validates per-cpu 1760 operations. 1761 1762 If unsure, say N. 1763 1764config ATOMIC64_SELFTEST 1765 tristate "Perform an atomic64_t self-test" 1766 help 1767 Enable this option to test the atomic64_t functions at boot or 1768 at module load time. 1769 1770 If unsure, say N. 1771 1772config ASYNC_RAID6_TEST 1773 tristate "Self test for hardware accelerated raid6 recovery" 1774 depends on ASYNC_RAID6_RECOV 1775 select ASYNC_MEMCPY 1776 ---help--- 1777 This is a one-shot self test that permutes through the 1778 recovery of all the possible two disk failure scenarios for a 1779 N-disk array. Recovery is performed with the asynchronous 1780 raid6 recovery routines, and will optionally use an offload 1781 engine if one is available. 1782 1783 If unsure, say N. 1784 1785config TEST_HEXDUMP 1786 tristate "Test functions located in the hexdump module at runtime" 1787 1788config TEST_STRING_HELPERS 1789 tristate "Test functions located in the string_helpers module at runtime" 1790 1791config TEST_KSTRTOX 1792 tristate "Test kstrto*() family of functions at runtime" 1793 1794config TEST_PRINTF 1795 tristate "Test printf() family of functions at runtime" 1796 1797config TEST_BITMAP 1798 tristate "Test bitmap_*() family of functions at runtime" 1799 default n 1800 help 1801 Enable this option to test the bitmap functions at boot. 1802 1803 If unsure, say N. 1804 1805config TEST_UUID 1806 tristate "Test functions located in the uuid module at runtime" 1807 1808config TEST_OVERFLOW 1809 tristate "Test check_*_overflow() functions at runtime" 1810 1811config TEST_RHASHTABLE 1812 tristate "Perform selftest on resizable hash table" 1813 default n 1814 help 1815 Enable this option to test the rhashtable functions at boot. 1816 1817 If unsure, say N. 1818 1819config TEST_HASH 1820 tristate "Perform selftest on hash functions" 1821 default n 1822 help 1823 Enable this option to test the kernel's integer (<linux/hash.h>), 1824 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>) 1825 hash functions on boot (or module load). 1826 1827 This is intended to help people writing architecture-specific 1828 optimized versions. If unsure, say N. 1829 1830config TEST_PARMAN 1831 tristate "Perform selftest on priority array manager" 1832 default n 1833 depends on PARMAN 1834 help 1835 Enable this option to test priority array manager on boot 1836 (or module load). 1837 1838 If unsure, say N. 1839 1840config TEST_LKM 1841 tristate "Test module loading with 'hello world' module" 1842 default n 1843 depends on m 1844 help 1845 This builds the "test_module" module that emits "Hello, world" 1846 on printk when loaded. It is designed to be used for basic 1847 evaluation of the module loading subsystem (for example when 1848 validating module verification). It lacks any extra dependencies, 1849 and will not normally be loaded by the system unless explicitly 1850 requested by name. 1851 1852 If unsure, say N. 1853 1854config TEST_USER_COPY 1855 tristate "Test user/kernel boundary protections" 1856 default n 1857 depends on m 1858 help 1859 This builds the "test_user_copy" module that runs sanity checks 1860 on the copy_to/from_user infrastructure, making sure basic 1861 user/kernel boundary testing is working. If it fails to load, 1862 a regression has been detected in the user/kernel memory boundary 1863 protections. 1864 1865 If unsure, say N. 1866 1867config TEST_BPF 1868 tristate "Test BPF filter functionality" 1869 default n 1870 depends on m && NET 1871 help 1872 This builds the "test_bpf" module that runs various test vectors 1873 against the BPF interpreter or BPF JIT compiler depending on the 1874 current setting. This is in particular useful for BPF JIT compiler 1875 development, but also to run regression tests against changes in 1876 the interpreter code. It also enables test stubs for eBPF maps and 1877 verifier used by user space verifier testsuite. 1878 1879 If unsure, say N. 1880 1881config FIND_BIT_BENCHMARK 1882 tristate "Test find_bit functions" 1883 default n 1884 help 1885 This builds the "test_find_bit" module that measure find_*_bit() 1886 functions performance. 1887 1888 If unsure, say N. 1889 1890config TEST_FIRMWARE 1891 tristate "Test firmware loading via userspace interface" 1892 default n 1893 depends on FW_LOADER 1894 help 1895 This builds the "test_firmware" module that creates a userspace 1896 interface for testing firmware loading. This can be used to 1897 control the triggering of firmware loading without needing an 1898 actual firmware-using device. The contents can be rechecked by 1899 userspace. 1900 1901 If unsure, say N. 1902 1903config TEST_SYSCTL 1904 tristate "sysctl test driver" 1905 default n 1906 depends on PROC_SYSCTL 1907 help 1908 This builds the "test_sysctl" module. This driver enables to test the 1909 proc sysctl interfaces available to drivers safely without affecting 1910 production knobs which might alter system functionality. 1911 1912 If unsure, say N. 1913 1914config TEST_UDELAY 1915 tristate "udelay test driver" 1916 default n 1917 help 1918 This builds the "udelay_test" module that helps to make sure 1919 that udelay() is working properly. 1920 1921 If unsure, say N. 1922 1923config TEST_STATIC_KEYS 1924 tristate "Test static keys" 1925 default n 1926 depends on m 1927 help 1928 Test the static key interfaces. 1929 1930 If unsure, say N. 1931 1932config TEST_KMOD 1933 tristate "kmod stress tester" 1934 default n 1935 depends on m 1936 depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS 1937 depends on NETDEVICES && NET_CORE && INET # for TUN 1938 select TEST_LKM 1939 select XFS_FS 1940 select TUN 1941 select BTRFS_FS 1942 help 1943 Test the kernel's module loading mechanism: kmod. kmod implements 1944 support to load modules using the Linux kernel's usermode helper. 1945 This test provides a series of tests against kmod. 1946 1947 Although technically you can either build test_kmod as a module or 1948 into the kernel we disallow building it into the kernel since 1949 it stress tests request_module() and this will very likely cause 1950 some issues by taking over precious threads available from other 1951 module load requests, ultimately this could be fatal. 1952 1953 To run tests run: 1954 1955 tools/testing/selftests/kmod/kmod.sh --help 1956 1957 If unsure, say N. 1958 1959config TEST_DEBUG_VIRTUAL 1960 tristate "Test CONFIG_DEBUG_VIRTUAL feature" 1961 depends on DEBUG_VIRTUAL 1962 help 1963 Test the kernel's ability to detect incorrect calls to 1964 virt_to_phys() done against the non-linear part of the 1965 kernel's virtual address map. 1966 1967 If unsure, say N. 1968 1969endif # RUNTIME_TESTING_MENU 1970 1971config MEMTEST 1972 bool "Memtest" 1973 depends on HAVE_MEMBLOCK 1974 ---help--- 1975 This option adds a kernel parameter 'memtest', which allows memtest 1976 to be set. 1977 memtest=0, mean disabled; -- default 1978 memtest=1, mean do 1 test pattern; 1979 ... 1980 memtest=17, mean do 17 test patterns. 1981 If you are unsure how to answer this question, answer N. 1982 1983config BUG_ON_DATA_CORRUPTION 1984 bool "Trigger a BUG when data corruption is detected" 1985 select DEBUG_LIST 1986 help 1987 Select this option if the kernel should BUG when it encounters 1988 data corruption in kernel memory structures when they get checked 1989 for validity. 1990 1991 If unsure, say N. 1992 1993source "samples/Kconfig" 1994 1995source "lib/Kconfig.kgdb" 1996 1997source "lib/Kconfig.ubsan" 1998 1999config ARCH_HAS_DEVMEM_IS_ALLOWED 2000 bool 2001 2002config STRICT_DEVMEM 2003 bool "Filter access to /dev/mem" 2004 depends on MMU && DEVMEM 2005 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 2006 default y if PPC || X86 || ARM64 2007 ---help--- 2008 If this option is disabled, you allow userspace (root) access to all 2009 of memory, including kernel and userspace memory. Accidental 2010 access to this is obviously disastrous, but specific access can 2011 be used by people debugging the kernel. Note that with PAT support 2012 enabled, even in this case there are restrictions on /dev/mem 2013 use due to the cache aliasing requirements. 2014 2015 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 2016 file only allows userspace access to PCI space and the BIOS code and 2017 data regions. This is sufficient for dosemu and X and all common 2018 users of /dev/mem. 2019 2020 If in doubt, say Y. 2021 2022config IO_STRICT_DEVMEM 2023 bool "Filter I/O access to /dev/mem" 2024 depends on STRICT_DEVMEM 2025 ---help--- 2026 If this option is disabled, you allow userspace (root) access to all 2027 io-memory regardless of whether a driver is actively using that 2028 range. Accidental access to this is obviously disastrous, but 2029 specific access can be used by people debugging kernel drivers. 2030 2031 If this option is switched on, the /dev/mem file only allows 2032 userspace access to *idle* io-memory ranges (see /proc/iomem) This 2033 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 2034 if the driver using a given range cannot be disabled. 2035 2036 If in doubt, say Y. 2037