1menu "Kernel hacking" 2 3menu "printk and dmesg options" 4 5config PRINTK_TIME 6 bool "Show timing information on printks" 7 depends on PRINTK 8 help 9 Selecting this option causes time stamps of the printk() 10 messages to be added to the output of the syslog() system 11 call and at the console. 12 13 The timestamp is always recorded internally, and exported 14 to /dev/kmsg. This flag just specifies if the timestamp should 15 be included, not that the timestamp is recorded. 16 17 The behavior is also controlled by the kernel command line 18 parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst 19 20config CONSOLE_LOGLEVEL_DEFAULT 21 int "Default console loglevel (1-15)" 22 range 1 15 23 default "7" 24 help 25 Default loglevel to determine what will be printed on the console. 26 27 Setting a default here is equivalent to passing in loglevel=<x> in 28 the kernel bootargs. loglevel=<x> continues to override whatever 29 value is specified here as well. 30 31 Note: This does not affect the log level of un-prefixed printk() 32 usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT 33 option. 34 35config CONSOLE_LOGLEVEL_QUIET 36 int "quiet console loglevel (1-15)" 37 range 1 15 38 default "4" 39 help 40 loglevel to use when "quiet" is passed on the kernel commandline. 41 42 When "quiet" is passed on the kernel commandline this loglevel 43 will be used as the loglevel. IOW passing "quiet" will be the 44 equivalent of passing "loglevel=<CONSOLE_LOGLEVEL_QUIET>" 45 46config MESSAGE_LOGLEVEL_DEFAULT 47 int "Default message log level (1-7)" 48 range 1 7 49 default "4" 50 help 51 Default log level for printk statements with no specified priority. 52 53 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks 54 that are auditing their logs closely may want to set it to a lower 55 priority. 56 57 Note: This does not affect what message level gets printed on the console 58 by default. To change that, use loglevel=<x> in the kernel bootargs, 59 or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value. 60 61config BOOT_PRINTK_DELAY 62 bool "Delay each boot printk message by N milliseconds" 63 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 64 help 65 This build option allows you to read kernel boot messages 66 by inserting a short delay after each one. The delay is 67 specified in milliseconds on the kernel command line, 68 using "boot_delay=N". 69 70 It is likely that you would also need to use "lpj=M" to preset 71 the "loops per jiffie" value. 72 See a previous boot log for the "lpj" value to use for your 73 system, and then set "lpj=M" before setting "boot_delay=N". 74 NOTE: Using this option may adversely affect SMP systems. 75 I.e., processors other than the first one may not boot up. 76 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect 77 what it believes to be lockup conditions. 78 79config DYNAMIC_DEBUG 80 bool "Enable dynamic printk() support" 81 default n 82 depends on PRINTK 83 depends on DEBUG_FS 84 help 85 86 Compiles debug level messages into the kernel, which would not 87 otherwise be available at runtime. These messages can then be 88 enabled/disabled based on various levels of scope - per source file, 89 function, module, format string, and line number. This mechanism 90 implicitly compiles in all pr_debug() and dev_dbg() calls, which 91 enlarges the kernel text size by about 2%. 92 93 If a source file is compiled with DEBUG flag set, any 94 pr_debug() calls in it are enabled by default, but can be 95 disabled at runtime as below. Note that DEBUG flag is 96 turned on by many CONFIG_*DEBUG* options. 97 98 Usage: 99 100 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 101 which is contained in the 'debugfs' filesystem. Thus, the debugfs 102 filesystem must first be mounted before making use of this feature. 103 We refer the control file as: <debugfs>/dynamic_debug/control. This 104 file contains a list of the debug statements that can be enabled. The 105 format for each line of the file is: 106 107 filename:lineno [module]function flags format 108 109 filename : source file of the debug statement 110 lineno : line number of the debug statement 111 module : module that contains the debug statement 112 function : function that contains the debug statement 113 flags : '=p' means the line is turned 'on' for printing 114 format : the format used for the debug statement 115 116 From a live system: 117 118 nullarbor:~ # cat <debugfs>/dynamic_debug/control 119 # filename:lineno [module]function flags format 120 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012" 121 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012" 122 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012" 123 124 Example usage: 125 126 // enable the message at line 1603 of file svcsock.c 127 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 128 <debugfs>/dynamic_debug/control 129 130 // enable all the messages in file svcsock.c 131 nullarbor:~ # echo -n 'file svcsock.c +p' > 132 <debugfs>/dynamic_debug/control 133 134 // enable all the messages in the NFS server module 135 nullarbor:~ # echo -n 'module nfsd +p' > 136 <debugfs>/dynamic_debug/control 137 138 // enable all 12 messages in the function svc_process() 139 nullarbor:~ # echo -n 'func svc_process +p' > 140 <debugfs>/dynamic_debug/control 141 142 // disable all 12 messages in the function svc_process() 143 nullarbor:~ # echo -n 'func svc_process -p' > 144 <debugfs>/dynamic_debug/control 145 146 See Documentation/admin-guide/dynamic-debug-howto.rst for additional 147 information. 148 149endmenu # "printk and dmesg options" 150 151menu "Compile-time checks and compiler options" 152 153config DEBUG_INFO 154 bool "Compile the kernel with debug info" 155 depends on DEBUG_KERNEL && !COMPILE_TEST 156 help 157 If you say Y here the resulting kernel image will include 158 debugging info resulting in a larger kernel image. 159 This adds debug symbols to the kernel and modules (gcc -g), and 160 is needed if you intend to use kernel crashdump or binary object 161 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 162 Say Y here only if you plan to debug the kernel. 163 164 If unsure, say N. 165 166config DEBUG_INFO_REDUCED 167 bool "Reduce debugging information" 168 depends on DEBUG_INFO 169 help 170 If you say Y here gcc is instructed to generate less debugging 171 information for structure types. This means that tools that 172 need full debugging information (like kgdb or systemtap) won't 173 be happy. But if you merely need debugging information to 174 resolve line numbers there is no loss. Advantage is that 175 build directory object sizes shrink dramatically over a full 176 DEBUG_INFO build and compile times are reduced too. 177 Only works with newer gcc versions. 178 179config DEBUG_INFO_SPLIT 180 bool "Produce split debuginfo in .dwo files" 181 depends on DEBUG_INFO 182 help 183 Generate debug info into separate .dwo files. This significantly 184 reduces the build directory size for builds with DEBUG_INFO, 185 because it stores the information only once on disk in .dwo 186 files instead of multiple times in object files and executables. 187 In addition the debug information is also compressed. 188 189 Requires recent gcc (4.7+) and recent gdb/binutils. 190 Any tool that packages or reads debug information would need 191 to know about the .dwo files and include them. 192 Incompatible with older versions of ccache. 193 194config DEBUG_INFO_DWARF4 195 bool "Generate dwarf4 debuginfo" 196 depends on DEBUG_INFO 197 help 198 Generate dwarf4 debug info. This requires recent versions 199 of gcc and gdb. It makes the debug information larger. 200 But it significantly improves the success of resolving 201 variables in gdb on optimized code. 202 203config GDB_SCRIPTS 204 bool "Provide GDB scripts for kernel debugging" 205 depends on DEBUG_INFO 206 help 207 This creates the required links to GDB helper scripts in the 208 build directory. If you load vmlinux into gdb, the helper 209 scripts will be automatically imported by gdb as well, and 210 additional functions are available to analyze a Linux kernel 211 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst 212 for further details. 213 214config ENABLE_MUST_CHECK 215 bool "Enable __must_check logic" 216 default y 217 help 218 Enable the __must_check logic in the kernel build. Disable this to 219 suppress the "warning: ignoring return value of 'foo', declared with 220 attribute warn_unused_result" messages. 221 222config FRAME_WARN 223 int "Warn for stack frames larger than (needs gcc 4.4)" 224 range 0 8192 225 default 3072 if KASAN_EXTRA 226 default 2048 if GCC_PLUGIN_LATENT_ENTROPY 227 default 1280 if (!64BIT && PARISC) 228 default 1024 if (!64BIT && !PARISC) 229 default 2048 if 64BIT 230 help 231 Tell gcc to warn at build time for stack frames larger than this. 232 Setting this too low will cause a lot of warnings. 233 Setting it to 0 disables the warning. 234 Requires gcc 4.4 235 236config STRIP_ASM_SYMS 237 bool "Strip assembler-generated symbols during link" 238 default n 239 help 240 Strip internal assembler-generated symbols during a link (symbols 241 that look like '.Lxxx') so they don't pollute the output of 242 get_wchan() and suchlike. 243 244config READABLE_ASM 245 bool "Generate readable assembler code" 246 depends on DEBUG_KERNEL 247 help 248 Disable some compiler optimizations that tend to generate human unreadable 249 assembler output. This may make the kernel slightly slower, but it helps 250 to keep kernel developers who have to stare a lot at assembler listings 251 sane. 252 253config UNUSED_SYMBOLS 254 bool "Enable unused/obsolete exported symbols" 255 default y if X86 256 help 257 Unused but exported symbols make the kernel needlessly bigger. For 258 that reason most of these unused exports will soon be removed. This 259 option is provided temporarily to provide a transition period in case 260 some external kernel module needs one of these symbols anyway. If you 261 encounter such a case in your module, consider if you are actually 262 using the right API. (rationale: since nobody in the kernel is using 263 this in a module, there is a pretty good chance it's actually the 264 wrong interface to use). If you really need the symbol, please send a 265 mail to the linux kernel mailing list mentioning the symbol and why 266 you really need it, and what the merge plan to the mainline kernel for 267 your module is. 268 269config PAGE_OWNER 270 bool "Track page owner" 271 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 272 select DEBUG_FS 273 select STACKTRACE 274 select STACKDEPOT 275 select PAGE_EXTENSION 276 help 277 This keeps track of what call chain is the owner of a page, may 278 help to find bare alloc_page(s) leaks. Even if you include this 279 feature on your build, it is disabled in default. You should pass 280 "page_owner=on" to boot parameter in order to enable it. Eats 281 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 282 for user-space helper. 283 284 If unsure, say N. 285 286config DEBUG_FS 287 bool "Debug Filesystem" 288 help 289 debugfs is a virtual file system that kernel developers use to put 290 debugging files into. Enable this option to be able to read and 291 write to these files. 292 293 For detailed documentation on the debugfs API, see 294 Documentation/filesystems/. 295 296 If unsure, say N. 297 298config HEADERS_CHECK 299 bool "Run 'make headers_check' when building vmlinux" 300 depends on !UML 301 help 302 This option will extract the user-visible kernel headers whenever 303 building the kernel, and will run basic sanity checks on them to 304 ensure that exported files do not attempt to include files which 305 were not exported, etc. 306 307 If you're making modifications to header files which are 308 relevant for userspace, say 'Y', and check the headers 309 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 310 your build tree), to make sure they're suitable. 311 312config DEBUG_SECTION_MISMATCH 313 bool "Enable full Section mismatch analysis" 314 help 315 The section mismatch analysis checks if there are illegal 316 references from one section to another section. 317 During linktime or runtime, some sections are dropped; 318 any use of code/data previously in these sections would 319 most likely result in an oops. 320 In the code, functions and variables are annotated with 321 __init,, etc. (see the full list in include/linux/init.h), 322 which results in the code/data being placed in specific sections. 323 The section mismatch analysis is always performed after a full 324 kernel build, and enabling this option causes the following 325 additional steps to occur: 326 - Add the option -fno-inline-functions-called-once to gcc commands. 327 When inlining a function annotated with __init in a non-init 328 function, we would lose the section information and thus 329 the analysis would not catch the illegal reference. 330 This option tells gcc to inline less (but it does result in 331 a larger kernel). 332 - Run the section mismatch analysis for each module/built-in.a file. 333 When we run the section mismatch analysis on vmlinux.o, we 334 lose valuable information about where the mismatch was 335 introduced. 336 Running the analysis for each module/built-in.a file 337 tells where the mismatch happens much closer to the 338 source. The drawback is that the same mismatch is 339 reported at least twice. 340 - Enable verbose reporting from modpost in order to help resolve 341 the section mismatches that are reported. 342 343config SECTION_MISMATCH_WARN_ONLY 344 bool "Make section mismatch errors non-fatal" 345 default y 346 help 347 If you say N here, the build process will fail if there are any 348 section mismatch, instead of just throwing warnings. 349 350 If unsure, say Y. 351 352# 353# Select this config option from the architecture Kconfig, if it 354# is preferred to always offer frame pointers as a config 355# option on the architecture (regardless of KERNEL_DEBUG): 356# 357config ARCH_WANT_FRAME_POINTERS 358 bool 359 360config FRAME_POINTER 361 bool "Compile the kernel with frame pointers" 362 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS 363 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 364 help 365 If you say Y here the resulting kernel image will be slightly 366 larger and slower, but it gives very useful debugging information 367 in case of kernel bugs. (precise oopses/stacktraces/warnings) 368 369config STACK_VALIDATION 370 bool "Compile-time stack metadata validation" 371 depends on HAVE_STACK_VALIDATION 372 default n 373 help 374 Add compile-time checks to validate stack metadata, including frame 375 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure 376 that runtime stack traces are more reliable. 377 378 This is also a prerequisite for generation of ORC unwind data, which 379 is needed for CONFIG_UNWINDER_ORC. 380 381 For more information, see 382 tools/objtool/Documentation/stack-validation.txt. 383 384config DEBUG_FORCE_WEAK_PER_CPU 385 bool "Force weak per-cpu definitions" 386 depends on DEBUG_KERNEL 387 help 388 s390 and alpha require percpu variables in modules to be 389 defined weak to work around addressing range issue which 390 puts the following two restrictions on percpu variable 391 definitions. 392 393 1. percpu symbols must be unique whether static or not 394 2. percpu variables can't be defined inside a function 395 396 To ensure that generic code follows the above rules, this 397 option forces all percpu variables to be defined as weak. 398 399endmenu # "Compiler options" 400 401config MAGIC_SYSRQ 402 bool "Magic SysRq key" 403 depends on !UML 404 help 405 If you say Y here, you will have some control over the system even 406 if the system crashes for example during kernel debugging (e.g., you 407 will be able to flush the buffer cache to disk, reboot the system 408 immediately or dump some status information). This is accomplished 409 by pressing various keys while holding SysRq (Alt+PrintScreen). It 410 also works on a serial console (on PC hardware at least), if you 411 send a BREAK and then within 5 seconds a command keypress. The 412 keys are documented in <file:Documentation/admin-guide/sysrq.rst>. 413 Don't say Y unless you really know what this hack does. 414 415config MAGIC_SYSRQ_DEFAULT_ENABLE 416 hex "Enable magic SysRq key functions by default" 417 depends on MAGIC_SYSRQ 418 default 0x1 419 help 420 Specifies which SysRq key functions are enabled by default. 421 This may be set to 1 or 0 to enable or disable them all, or 422 to a bitmask as described in Documentation/admin-guide/sysrq.rst. 423 424config MAGIC_SYSRQ_SERIAL 425 bool "Enable magic SysRq key over serial" 426 depends on MAGIC_SYSRQ 427 default y 428 help 429 Many embedded boards have a disconnected TTL level serial which can 430 generate some garbage that can lead to spurious false sysrq detects. 431 This option allows you to decide whether you want to enable the 432 magic SysRq key. 433 434config DEBUG_KERNEL 435 bool "Kernel debugging" 436 help 437 Say Y here if you are developing drivers or trying to debug and 438 identify kernel problems. 439 440menu "Memory Debugging" 441 442source mm/Kconfig.debug 443 444config DEBUG_OBJECTS 445 bool "Debug object operations" 446 depends on DEBUG_KERNEL 447 help 448 If you say Y here, additional code will be inserted into the 449 kernel to track the life time of various objects and validate 450 the operations on those objects. 451 452config DEBUG_OBJECTS_SELFTEST 453 bool "Debug objects selftest" 454 depends on DEBUG_OBJECTS 455 help 456 This enables the selftest of the object debug code. 457 458config DEBUG_OBJECTS_FREE 459 bool "Debug objects in freed memory" 460 depends on DEBUG_OBJECTS 461 help 462 This enables checks whether a k/v free operation frees an area 463 which contains an object which has not been deactivated 464 properly. This can make kmalloc/kfree-intensive workloads 465 much slower. 466 467config DEBUG_OBJECTS_TIMERS 468 bool "Debug timer objects" 469 depends on DEBUG_OBJECTS 470 help 471 If you say Y here, additional code will be inserted into the 472 timer routines to track the life time of timer objects and 473 validate the timer operations. 474 475config DEBUG_OBJECTS_WORK 476 bool "Debug work objects" 477 depends on DEBUG_OBJECTS 478 help 479 If you say Y here, additional code will be inserted into the 480 work queue routines to track the life time of work objects and 481 validate the work operations. 482 483config DEBUG_OBJECTS_RCU_HEAD 484 bool "Debug RCU callbacks objects" 485 depends on DEBUG_OBJECTS 486 help 487 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 488 489config DEBUG_OBJECTS_PERCPU_COUNTER 490 bool "Debug percpu counter objects" 491 depends on DEBUG_OBJECTS 492 help 493 If you say Y here, additional code will be inserted into the 494 percpu counter routines to track the life time of percpu counter 495 objects and validate the percpu counter operations. 496 497config DEBUG_OBJECTS_ENABLE_DEFAULT 498 int "debug_objects bootup default value (0-1)" 499 range 0 1 500 default "1" 501 depends on DEBUG_OBJECTS 502 help 503 Debug objects boot parameter default value 504 505config DEBUG_SLAB 506 bool "Debug slab memory allocations" 507 depends on DEBUG_KERNEL && SLAB 508 help 509 Say Y here to have the kernel do limited verification on memory 510 allocation as well as poisoning memory on free to catch use of freed 511 memory. This can make kmalloc/kfree-intensive workloads much slower. 512 513config DEBUG_SLAB_LEAK 514 bool "Memory leak debugging" 515 depends on DEBUG_SLAB 516 517config SLUB_DEBUG_ON 518 bool "SLUB debugging on by default" 519 depends on SLUB && SLUB_DEBUG 520 default n 521 help 522 Boot with debugging on by default. SLUB boots by default with 523 the runtime debug capabilities switched off. Enabling this is 524 equivalent to specifying the "slub_debug" parameter on boot. 525 There is no support for more fine grained debug control like 526 possible with slub_debug=xxx. SLUB debugging may be switched 527 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 528 "slub_debug=-". 529 530config SLUB_STATS 531 default n 532 bool "Enable SLUB performance statistics" 533 depends on SLUB && SYSFS 534 help 535 SLUB statistics are useful to debug SLUBs allocation behavior in 536 order find ways to optimize the allocator. This should never be 537 enabled for production use since keeping statistics slows down 538 the allocator by a few percentage points. The slabinfo command 539 supports the determination of the most active slabs to figure 540 out which slabs are relevant to a particular load. 541 Try running: slabinfo -DA 542 543config HAVE_DEBUG_KMEMLEAK 544 bool 545 546config DEBUG_KMEMLEAK 547 bool "Kernel memory leak detector" 548 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 549 select DEBUG_FS 550 select STACKTRACE if STACKTRACE_SUPPORT 551 select KALLSYMS 552 select CRC32 553 help 554 Say Y here if you want to enable the memory leak 555 detector. The memory allocation/freeing is traced in a way 556 similar to the Boehm's conservative garbage collector, the 557 difference being that the orphan objects are not freed but 558 only shown in /sys/kernel/debug/kmemleak. Enabling this 559 feature will introduce an overhead to memory 560 allocations. See Documentation/dev-tools/kmemleak.rst for more 561 details. 562 563 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 564 of finding leaks due to the slab objects poisoning. 565 566 In order to access the kmemleak file, debugfs needs to be 567 mounted (usually at /sys/kernel/debug). 568 569config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 570 int "Maximum kmemleak early log entries" 571 depends on DEBUG_KMEMLEAK 572 range 200 40000 573 default 400 574 help 575 Kmemleak must track all the memory allocations to avoid 576 reporting false positives. Since memory may be allocated or 577 freed before kmemleak is initialised, an early log buffer is 578 used to store these actions. If kmemleak reports "early log 579 buffer exceeded", please increase this value. 580 581config DEBUG_KMEMLEAK_TEST 582 tristate "Simple test for the kernel memory leak detector" 583 depends on DEBUG_KMEMLEAK && m 584 help 585 This option enables a module that explicitly leaks memory. 586 587 If unsure, say N. 588 589config DEBUG_KMEMLEAK_DEFAULT_OFF 590 bool "Default kmemleak to off" 591 depends on DEBUG_KMEMLEAK 592 help 593 Say Y here to disable kmemleak by default. It can then be enabled 594 on the command line via kmemleak=on. 595 596config DEBUG_STACK_USAGE 597 bool "Stack utilization instrumentation" 598 depends on DEBUG_KERNEL && !IA64 599 help 600 Enables the display of the minimum amount of free stack which each 601 task has ever had available in the sysrq-T and sysrq-P debug output. 602 603 This option will slow down process creation somewhat. 604 605config DEBUG_VM 606 bool "Debug VM" 607 depends on DEBUG_KERNEL 608 help 609 Enable this to turn on extended checks in the virtual-memory system 610 that may impact performance. 611 612 If unsure, say N. 613 614config DEBUG_VM_VMACACHE 615 bool "Debug VMA caching" 616 depends on DEBUG_VM 617 help 618 Enable this to turn on VMA caching debug information. Doing so 619 can cause significant overhead, so only enable it in non-production 620 environments. 621 622 If unsure, say N. 623 624config DEBUG_VM_RB 625 bool "Debug VM red-black trees" 626 depends on DEBUG_VM 627 help 628 Enable VM red-black tree debugging information and extra validations. 629 630 If unsure, say N. 631 632config DEBUG_VM_PGFLAGS 633 bool "Debug page-flags operations" 634 depends on DEBUG_VM 635 help 636 Enables extra validation on page flags operations. 637 638 If unsure, say N. 639 640config ARCH_HAS_DEBUG_VIRTUAL 641 bool 642 643config DEBUG_VIRTUAL 644 bool "Debug VM translations" 645 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL 646 help 647 Enable some costly sanity checks in virtual to page code. This can 648 catch mistakes with virt_to_page() and friends. 649 650 If unsure, say N. 651 652config DEBUG_NOMMU_REGIONS 653 bool "Debug the global anon/private NOMMU mapping region tree" 654 depends on DEBUG_KERNEL && !MMU 655 help 656 This option causes the global tree of anonymous and private mapping 657 regions to be regularly checked for invalid topology. 658 659config DEBUG_MEMORY_INIT 660 bool "Debug memory initialisation" if EXPERT 661 default !EXPERT 662 help 663 Enable this for additional checks during memory initialisation. 664 The sanity checks verify aspects of the VM such as the memory model 665 and other information provided by the architecture. Verbose 666 information will be printed at KERN_DEBUG loglevel depending 667 on the mminit_loglevel= command-line option. 668 669 If unsure, say Y 670 671config MEMORY_NOTIFIER_ERROR_INJECT 672 tristate "Memory hotplug notifier error injection module" 673 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 674 help 675 This option provides the ability to inject artificial errors to 676 memory hotplug notifier chain callbacks. It is controlled through 677 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 678 679 If the notifier call chain should be failed with some events 680 notified, write the error code to "actions/<notifier event>/error". 681 682 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 683 684 # cd /sys/kernel/debug/notifier-error-inject/memory 685 # echo -12 > actions/MEM_GOING_OFFLINE/error 686 # echo offline > /sys/devices/system/memory/memoryXXX/state 687 bash: echo: write error: Cannot allocate memory 688 689 To compile this code as a module, choose M here: the module will 690 be called memory-notifier-error-inject. 691 692 If unsure, say N. 693 694config DEBUG_PER_CPU_MAPS 695 bool "Debug access to per_cpu maps" 696 depends on DEBUG_KERNEL 697 depends on SMP 698 help 699 Say Y to verify that the per_cpu map being accessed has 700 been set up. This adds a fair amount of code to kernel memory 701 and decreases performance. 702 703 Say N if unsure. 704 705config DEBUG_HIGHMEM 706 bool "Highmem debugging" 707 depends on DEBUG_KERNEL && HIGHMEM 708 help 709 This option enables additional error checking for high memory 710 systems. Disable for production systems. 711 712config HAVE_DEBUG_STACKOVERFLOW 713 bool 714 715config DEBUG_STACKOVERFLOW 716 bool "Check for stack overflows" 717 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 718 ---help--- 719 Say Y here if you want to check for overflows of kernel, IRQ 720 and exception stacks (if your architecture uses them). This 721 option will show detailed messages if free stack space drops 722 below a certain limit. 723 724 These kinds of bugs usually occur when call-chains in the 725 kernel get too deep, especially when interrupts are 726 involved. 727 728 Use this in cases where you see apparently random memory 729 corruption, especially if it appears in 'struct thread_info' 730 731 If in doubt, say "N". 732 733source "lib/Kconfig.kasan" 734 735endmenu # "Memory Debugging" 736 737config ARCH_HAS_KCOV 738 bool 739 help 740 KCOV does not have any arch-specific code, but currently it is enabled 741 only for x86_64. KCOV requires testing on other archs, and most likely 742 disabling of instrumentation for some early boot code. 743 744config CC_HAS_SANCOV_TRACE_PC 745 def_bool $(cc-option,-fsanitize-coverage=trace-pc) 746 747config KCOV 748 bool "Code coverage for fuzzing" 749 depends on ARCH_HAS_KCOV 750 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS 751 select DEBUG_FS 752 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC 753 help 754 KCOV exposes kernel code coverage information in a form suitable 755 for coverage-guided fuzzing (randomized testing). 756 757 If RANDOMIZE_BASE is enabled, PC values will not be stable across 758 different machines and across reboots. If you need stable PC values, 759 disable RANDOMIZE_BASE. 760 761 For more details, see Documentation/dev-tools/kcov.rst. 762 763config KCOV_ENABLE_COMPARISONS 764 bool "Enable comparison operands collection by KCOV" 765 depends on KCOV 766 depends on $(cc-option,-fsanitize-coverage=trace-cmp) 767 help 768 KCOV also exposes operands of every comparison in the instrumented 769 code along with operand sizes and PCs of the comparison instructions. 770 These operands can be used by fuzzing engines to improve the quality 771 of fuzzing coverage. 772 773config KCOV_INSTRUMENT_ALL 774 bool "Instrument all code by default" 775 depends on KCOV 776 default y 777 help 778 If you are doing generic system call fuzzing (like e.g. syzkaller), 779 then you will want to instrument the whole kernel and you should 780 say y here. If you are doing more targeted fuzzing (like e.g. 781 filesystem fuzzing with AFL) then you will want to enable coverage 782 for more specific subsets of files, and should say n here. 783 784config DEBUG_SHIRQ 785 bool "Debug shared IRQ handlers" 786 depends on DEBUG_KERNEL 787 help 788 Enable this to generate a spurious interrupt as soon as a shared 789 interrupt handler is registered, and just before one is deregistered. 790 Drivers ought to be able to handle interrupts coming in at those 791 points; some don't and need to be caught. 792 793menu "Debug Lockups and Hangs" 794 795config LOCKUP_DETECTOR 796 bool 797 798config SOFTLOCKUP_DETECTOR 799 bool "Detect Soft Lockups" 800 depends on DEBUG_KERNEL && !S390 801 select LOCKUP_DETECTOR 802 help 803 Say Y here to enable the kernel to act as a watchdog to detect 804 soft lockups. 805 806 Softlockups are bugs that cause the kernel to loop in kernel 807 mode for more than 20 seconds, without giving other tasks a 808 chance to run. The current stack trace is displayed upon 809 detection and the system will stay locked up. 810 811config BOOTPARAM_SOFTLOCKUP_PANIC 812 bool "Panic (Reboot) On Soft Lockups" 813 depends on SOFTLOCKUP_DETECTOR 814 help 815 Say Y here to enable the kernel to panic on "soft lockups", 816 which are bugs that cause the kernel to loop in kernel 817 mode for more than 20 seconds (configurable using the watchdog_thresh 818 sysctl), without giving other tasks a chance to run. 819 820 The panic can be used in combination with panic_timeout, 821 to cause the system to reboot automatically after a 822 lockup has been detected. This feature is useful for 823 high-availability systems that have uptime guarantees and 824 where a lockup must be resolved ASAP. 825 826 Say N if unsure. 827 828config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 829 int 830 depends on SOFTLOCKUP_DETECTOR 831 range 0 1 832 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 833 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 834 835config HARDLOCKUP_DETECTOR_PERF 836 bool 837 select SOFTLOCKUP_DETECTOR 838 839# 840# Enables a timestamp based low pass filter to compensate for perf based 841# hard lockup detection which runs too fast due to turbo modes. 842# 843config HARDLOCKUP_CHECK_TIMESTAMP 844 bool 845 846# 847# arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard 848# lockup detector rather than the perf based detector. 849# 850config HARDLOCKUP_DETECTOR 851 bool "Detect Hard Lockups" 852 depends on DEBUG_KERNEL && !S390 853 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH 854 select LOCKUP_DETECTOR 855 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF 856 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH 857 help 858 Say Y here to enable the kernel to act as a watchdog to detect 859 hard lockups. 860 861 Hardlockups are bugs that cause the CPU to loop in kernel mode 862 for more than 10 seconds, without letting other interrupts have a 863 chance to run. The current stack trace is displayed upon detection 864 and the system will stay locked up. 865 866config BOOTPARAM_HARDLOCKUP_PANIC 867 bool "Panic (Reboot) On Hard Lockups" 868 depends on HARDLOCKUP_DETECTOR 869 help 870 Say Y here to enable the kernel to panic on "hard lockups", 871 which are bugs that cause the kernel to loop in kernel 872 mode with interrupts disabled for more than 10 seconds (configurable 873 using the watchdog_thresh sysctl). 874 875 Say N if unsure. 876 877config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 878 int 879 depends on HARDLOCKUP_DETECTOR 880 range 0 1 881 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 882 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 883 884config DETECT_HUNG_TASK 885 bool "Detect Hung Tasks" 886 depends on DEBUG_KERNEL 887 default SOFTLOCKUP_DETECTOR 888 help 889 Say Y here to enable the kernel to detect "hung tasks", 890 which are bugs that cause the task to be stuck in 891 uninterruptible "D" state indefinitely. 892 893 When a hung task is detected, the kernel will print the 894 current stack trace (which you should report), but the 895 task will stay in uninterruptible state. If lockdep is 896 enabled then all held locks will also be reported. This 897 feature has negligible overhead. 898 899config DEFAULT_HUNG_TASK_TIMEOUT 900 int "Default timeout for hung task detection (in seconds)" 901 depends on DETECT_HUNG_TASK 902 default 120 903 help 904 This option controls the default timeout (in seconds) used 905 to determine when a task has become non-responsive and should 906 be considered hung. 907 908 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 909 sysctl or by writing a value to 910 /proc/sys/kernel/hung_task_timeout_secs. 911 912 A timeout of 0 disables the check. The default is two minutes. 913 Keeping the default should be fine in most cases. 914 915config BOOTPARAM_HUNG_TASK_PANIC 916 bool "Panic (Reboot) On Hung Tasks" 917 depends on DETECT_HUNG_TASK 918 help 919 Say Y here to enable the kernel to panic on "hung tasks", 920 which are bugs that cause the kernel to leave a task stuck 921 in uninterruptible "D" state. 922 923 The panic can be used in combination with panic_timeout, 924 to cause the system to reboot automatically after a 925 hung task has been detected. This feature is useful for 926 high-availability systems that have uptime guarantees and 927 where a hung tasks must be resolved ASAP. 928 929 Say N if unsure. 930 931config BOOTPARAM_HUNG_TASK_PANIC_VALUE 932 int 933 depends on DETECT_HUNG_TASK 934 range 0 1 935 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 936 default 1 if BOOTPARAM_HUNG_TASK_PANIC 937 938config WQ_WATCHDOG 939 bool "Detect Workqueue Stalls" 940 depends on DEBUG_KERNEL 941 help 942 Say Y here to enable stall detection on workqueues. If a 943 worker pool doesn't make forward progress on a pending work 944 item for over a given amount of time, 30s by default, a 945 warning message is printed along with dump of workqueue 946 state. This can be configured through kernel parameter 947 "workqueue.watchdog_thresh" and its sysfs counterpart. 948 949endmenu # "Debug lockups and hangs" 950 951config PANIC_ON_OOPS 952 bool "Panic on Oops" 953 help 954 Say Y here to enable the kernel to panic when it oopses. This 955 has the same effect as setting oops=panic on the kernel command 956 line. 957 958 This feature is useful to ensure that the kernel does not do 959 anything erroneous after an oops which could result in data 960 corruption or other issues. 961 962 Say N if unsure. 963 964config PANIC_ON_OOPS_VALUE 965 int 966 range 0 1 967 default 0 if !PANIC_ON_OOPS 968 default 1 if PANIC_ON_OOPS 969 970config PANIC_TIMEOUT 971 int "panic timeout" 972 default 0 973 help 974 Set the timeout value (in seconds) until a reboot occurs when the 975 the kernel panics. If n = 0, then we wait forever. A timeout 976 value n > 0 will wait n seconds before rebooting, while a timeout 977 value n < 0 will reboot immediately. 978 979config SCHED_DEBUG 980 bool "Collect scheduler debugging info" 981 depends on DEBUG_KERNEL && PROC_FS 982 default y 983 help 984 If you say Y here, the /proc/sched_debug file will be provided 985 that can help debug the scheduler. The runtime overhead of this 986 option is minimal. 987 988config SCHED_INFO 989 bool 990 default n 991 992config SCHEDSTATS 993 bool "Collect scheduler statistics" 994 depends on DEBUG_KERNEL && PROC_FS 995 select SCHED_INFO 996 help 997 If you say Y here, additional code will be inserted into the 998 scheduler and related routines to collect statistics about 999 scheduler behavior and provide them in /proc/schedstat. These 1000 stats may be useful for both tuning and debugging the scheduler 1001 If you aren't debugging the scheduler or trying to tune a specific 1002 application, you can say N to avoid the very slight overhead 1003 this adds. 1004 1005config SCHED_STACK_END_CHECK 1006 bool "Detect stack corruption on calls to schedule()" 1007 depends on DEBUG_KERNEL 1008 default n 1009 help 1010 This option checks for a stack overrun on calls to schedule(). 1011 If the stack end location is found to be over written always panic as 1012 the content of the corrupted region can no longer be trusted. 1013 This is to ensure no erroneous behaviour occurs which could result in 1014 data corruption or a sporadic crash at a later stage once the region 1015 is examined. The runtime overhead introduced is minimal. 1016 1017config DEBUG_TIMEKEEPING 1018 bool "Enable extra timekeeping sanity checking" 1019 help 1020 This option will enable additional timekeeping sanity checks 1021 which may be helpful when diagnosing issues where timekeeping 1022 problems are suspected. 1023 1024 This may include checks in the timekeeping hotpaths, so this 1025 option may have a (very small) performance impact to some 1026 workloads. 1027 1028 If unsure, say N. 1029 1030config DEBUG_PREEMPT 1031 bool "Debug preemptible kernel" 1032 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 1033 default y 1034 help 1035 If you say Y here then the kernel will use a debug variant of the 1036 commonly used smp_processor_id() function and will print warnings 1037 if kernel code uses it in a preemption-unsafe way. Also, the kernel 1038 will detect preemption count underflows. 1039 1040menu "Lock Debugging (spinlocks, mutexes, etc...)" 1041 1042config LOCK_DEBUGGING_SUPPORT 1043 bool 1044 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1045 default y 1046 1047config PROVE_LOCKING 1048 bool "Lock debugging: prove locking correctness" 1049 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1050 select LOCKDEP 1051 select DEBUG_SPINLOCK 1052 select DEBUG_MUTEXES 1053 select DEBUG_RT_MUTEXES if RT_MUTEXES 1054 select DEBUG_RWSEMS if RWSEM_SPIN_ON_OWNER 1055 select DEBUG_WW_MUTEX_SLOWPATH 1056 select DEBUG_LOCK_ALLOC 1057 select TRACE_IRQFLAGS 1058 default n 1059 help 1060 This feature enables the kernel to prove that all locking 1061 that occurs in the kernel runtime is mathematically 1062 correct: that under no circumstance could an arbitrary (and 1063 not yet triggered) combination of observed locking 1064 sequences (on an arbitrary number of CPUs, running an 1065 arbitrary number of tasks and interrupt contexts) cause a 1066 deadlock. 1067 1068 In short, this feature enables the kernel to report locking 1069 related deadlocks before they actually occur. 1070 1071 The proof does not depend on how hard and complex a 1072 deadlock scenario would be to trigger: how many 1073 participant CPUs, tasks and irq-contexts would be needed 1074 for it to trigger. The proof also does not depend on 1075 timing: if a race and a resulting deadlock is possible 1076 theoretically (no matter how unlikely the race scenario 1077 is), it will be proven so and will immediately be 1078 reported by the kernel (once the event is observed that 1079 makes the deadlock theoretically possible). 1080 1081 If a deadlock is impossible (i.e. the locking rules, as 1082 observed by the kernel, are mathematically correct), the 1083 kernel reports nothing. 1084 1085 NOTE: this feature can also be enabled for rwlocks, mutexes 1086 and rwsems - in which case all dependencies between these 1087 different locking variants are observed and mapped too, and 1088 the proof of observed correctness is also maintained for an 1089 arbitrary combination of these separate locking variants. 1090 1091 For more details, see Documentation/locking/lockdep-design.txt. 1092 1093config LOCK_STAT 1094 bool "Lock usage statistics" 1095 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1096 select LOCKDEP 1097 select DEBUG_SPINLOCK 1098 select DEBUG_MUTEXES 1099 select DEBUG_RT_MUTEXES if RT_MUTEXES 1100 select DEBUG_LOCK_ALLOC 1101 default n 1102 help 1103 This feature enables tracking lock contention points 1104 1105 For more details, see Documentation/locking/lockstat.txt 1106 1107 This also enables lock events required by "perf lock", 1108 subcommand of perf. 1109 If you want to use "perf lock", you also need to turn on 1110 CONFIG_EVENT_TRACING. 1111 1112 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1113 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1114 1115config DEBUG_RT_MUTEXES 1116 bool "RT Mutex debugging, deadlock detection" 1117 depends on DEBUG_KERNEL && RT_MUTEXES 1118 help 1119 This allows rt mutex semantics violations and rt mutex related 1120 deadlocks (lockups) to be detected and reported automatically. 1121 1122config DEBUG_SPINLOCK 1123 bool "Spinlock and rw-lock debugging: basic checks" 1124 depends on DEBUG_KERNEL 1125 select UNINLINE_SPIN_UNLOCK 1126 help 1127 Say Y here and build SMP to catch missing spinlock initialization 1128 and certain other kinds of spinlock errors commonly made. This is 1129 best used in conjunction with the NMI watchdog so that spinlock 1130 deadlocks are also debuggable. 1131 1132config DEBUG_MUTEXES 1133 bool "Mutex debugging: basic checks" 1134 depends on DEBUG_KERNEL 1135 help 1136 This feature allows mutex semantics violations to be detected and 1137 reported. 1138 1139config DEBUG_WW_MUTEX_SLOWPATH 1140 bool "Wait/wound mutex debugging: Slowpath testing" 1141 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1142 select DEBUG_LOCK_ALLOC 1143 select DEBUG_SPINLOCK 1144 select DEBUG_MUTEXES 1145 help 1146 This feature enables slowpath testing for w/w mutex users by 1147 injecting additional -EDEADLK wound/backoff cases. Together with 1148 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 1149 will test all possible w/w mutex interface abuse with the 1150 exception of simply not acquiring all the required locks. 1151 Note that this feature can introduce significant overhead, so 1152 it really should not be enabled in a production or distro kernel, 1153 even a debug kernel. If you are a driver writer, enable it. If 1154 you are a distro, do not. 1155 1156config DEBUG_RWSEMS 1157 bool "RW Semaphore debugging: basic checks" 1158 depends on DEBUG_KERNEL && RWSEM_SPIN_ON_OWNER 1159 help 1160 This debugging feature allows mismatched rw semaphore locks and unlocks 1161 to be detected and reported. 1162 1163config DEBUG_LOCK_ALLOC 1164 bool "Lock debugging: detect incorrect freeing of live locks" 1165 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1166 select DEBUG_SPINLOCK 1167 select DEBUG_MUTEXES 1168 select DEBUG_RT_MUTEXES if RT_MUTEXES 1169 select LOCKDEP 1170 help 1171 This feature will check whether any held lock (spinlock, rwlock, 1172 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1173 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1174 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1175 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1176 held during task exit. 1177 1178config LOCKDEP 1179 bool 1180 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1181 select STACKTRACE 1182 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !X86 1183 select KALLSYMS 1184 select KALLSYMS_ALL 1185 1186config LOCKDEP_SMALL 1187 bool 1188 1189config DEBUG_LOCKDEP 1190 bool "Lock dependency engine debugging" 1191 depends on DEBUG_KERNEL && LOCKDEP 1192 help 1193 If you say Y here, the lock dependency engine will do 1194 additional runtime checks to debug itself, at the price 1195 of more runtime overhead. 1196 1197config DEBUG_ATOMIC_SLEEP 1198 bool "Sleep inside atomic section checking" 1199 select PREEMPT_COUNT 1200 depends on DEBUG_KERNEL 1201 depends on !ARCH_NO_PREEMPT 1202 help 1203 If you say Y here, various routines which may sleep will become very 1204 noisy if they are called inside atomic sections: when a spinlock is 1205 held, inside an rcu read side critical section, inside preempt disabled 1206 sections, inside an interrupt, etc... 1207 1208config DEBUG_LOCKING_API_SELFTESTS 1209 bool "Locking API boot-time self-tests" 1210 depends on DEBUG_KERNEL 1211 help 1212 Say Y here if you want the kernel to run a short self-test during 1213 bootup. The self-test checks whether common types of locking bugs 1214 are detected by debugging mechanisms or not. (if you disable 1215 lock debugging then those bugs wont be detected of course.) 1216 The following locking APIs are covered: spinlocks, rwlocks, 1217 mutexes and rwsems. 1218 1219config LOCK_TORTURE_TEST 1220 tristate "torture tests for locking" 1221 depends on DEBUG_KERNEL 1222 select TORTURE_TEST 1223 help 1224 This option provides a kernel module that runs torture tests 1225 on kernel locking primitives. The kernel module may be built 1226 after the fact on the running kernel to be tested, if desired. 1227 1228 Say Y here if you want kernel locking-primitive torture tests 1229 to be built into the kernel. 1230 Say M if you want these torture tests to build as a module. 1231 Say N if you are unsure. 1232 1233config WW_MUTEX_SELFTEST 1234 tristate "Wait/wound mutex selftests" 1235 help 1236 This option provides a kernel module that runs tests on the 1237 on the struct ww_mutex locking API. 1238 1239 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction 1240 with this test harness. 1241 1242 Say M if you want these self tests to build as a module. 1243 Say N if you are unsure. 1244 1245endmenu # lock debugging 1246 1247config TRACE_IRQFLAGS 1248 bool 1249 help 1250 Enables hooks to interrupt enabling and disabling for 1251 either tracing or lock debugging. 1252 1253config STACKTRACE 1254 bool "Stack backtrace support" 1255 depends on STACKTRACE_SUPPORT 1256 help 1257 This option causes the kernel to create a /proc/pid/stack for 1258 every process, showing its current stack trace. 1259 It is also used by various kernel debugging features that require 1260 stack trace generation. 1261 1262config WARN_ALL_UNSEEDED_RANDOM 1263 bool "Warn for all uses of unseeded randomness" 1264 default n 1265 help 1266 Some parts of the kernel contain bugs relating to their use of 1267 cryptographically secure random numbers before it's actually possible 1268 to generate those numbers securely. This setting ensures that these 1269 flaws don't go unnoticed, by enabling a message, should this ever 1270 occur. This will allow people with obscure setups to know when things 1271 are going wrong, so that they might contact developers about fixing 1272 it. 1273 1274 Unfortunately, on some models of some architectures getting 1275 a fully seeded CRNG is extremely difficult, and so this can 1276 result in dmesg getting spammed for a surprisingly long 1277 time. This is really bad from a security perspective, and 1278 so architecture maintainers really need to do what they can 1279 to get the CRNG seeded sooner after the system is booted. 1280 However, since users cannot do anything actionable to 1281 address this, by default the kernel will issue only a single 1282 warning for the first use of unseeded randomness. 1283 1284 Say Y here if you want to receive warnings for all uses of 1285 unseeded randomness. This will be of use primarily for 1286 those developers interested in improving the security of 1287 Linux kernels running on their architecture (or 1288 subarchitecture). 1289 1290config DEBUG_KOBJECT 1291 bool "kobject debugging" 1292 depends on DEBUG_KERNEL 1293 help 1294 If you say Y here, some extra kobject debugging messages will be sent 1295 to the syslog. 1296 1297config DEBUG_KOBJECT_RELEASE 1298 bool "kobject release debugging" 1299 depends on DEBUG_OBJECTS_TIMERS 1300 help 1301 kobjects are reference counted objects. This means that their 1302 last reference count put is not predictable, and the kobject can 1303 live on past the point at which a driver decides to drop it's 1304 initial reference to the kobject gained on allocation. An 1305 example of this would be a struct device which has just been 1306 unregistered. 1307 1308 However, some buggy drivers assume that after such an operation, 1309 the memory backing the kobject can be immediately freed. This 1310 goes completely against the principles of a refcounted object. 1311 1312 If you say Y here, the kernel will delay the release of kobjects 1313 on the last reference count to improve the visibility of this 1314 kind of kobject release bug. 1315 1316config HAVE_DEBUG_BUGVERBOSE 1317 bool 1318 1319config DEBUG_BUGVERBOSE 1320 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1321 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1322 default y 1323 help 1324 Say Y here to make BUG() panics output the file name and line number 1325 of the BUG call as well as the EIP and oops trace. This aids 1326 debugging but costs about 70-100K of memory. 1327 1328config DEBUG_LIST 1329 bool "Debug linked list manipulation" 1330 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION 1331 help 1332 Enable this to turn on extended checks in the linked-list 1333 walking routines. 1334 1335 If unsure, say N. 1336 1337config DEBUG_PI_LIST 1338 bool "Debug priority linked list manipulation" 1339 depends on DEBUG_KERNEL 1340 help 1341 Enable this to turn on extended checks in the priority-ordered 1342 linked-list (plist) walking routines. This checks the entire 1343 list multiple times during each manipulation. 1344 1345 If unsure, say N. 1346 1347config DEBUG_SG 1348 bool "Debug SG table operations" 1349 depends on DEBUG_KERNEL 1350 help 1351 Enable this to turn on checks on scatter-gather tables. This can 1352 help find problems with drivers that do not properly initialize 1353 their sg tables. 1354 1355 If unsure, say N. 1356 1357config DEBUG_NOTIFIERS 1358 bool "Debug notifier call chains" 1359 depends on DEBUG_KERNEL 1360 help 1361 Enable this to turn on sanity checking for notifier call chains. 1362 This is most useful for kernel developers to make sure that 1363 modules properly unregister themselves from notifier chains. 1364 This is a relatively cheap check but if you care about maximum 1365 performance, say N. 1366 1367config DEBUG_CREDENTIALS 1368 bool "Debug credential management" 1369 depends on DEBUG_KERNEL 1370 help 1371 Enable this to turn on some debug checking for credential 1372 management. The additional code keeps track of the number of 1373 pointers from task_structs to any given cred struct, and checks to 1374 see that this number never exceeds the usage count of the cred 1375 struct. 1376 1377 Furthermore, if SELinux is enabled, this also checks that the 1378 security pointer in the cred struct is never seen to be invalid. 1379 1380 If unsure, say N. 1381 1382source "kernel/rcu/Kconfig.debug" 1383 1384config DEBUG_WQ_FORCE_RR_CPU 1385 bool "Force round-robin CPU selection for unbound work items" 1386 depends on DEBUG_KERNEL 1387 default n 1388 help 1389 Workqueue used to implicitly guarantee that work items queued 1390 without explicit CPU specified are put on the local CPU. This 1391 guarantee is no longer true and while local CPU is still 1392 preferred work items may be put on foreign CPUs. Kernel 1393 parameter "workqueue.debug_force_rr_cpu" is added to force 1394 round-robin CPU selection to flush out usages which depend on the 1395 now broken guarantee. This config option enables the debug 1396 feature by default. When enabled, memory and cache locality will 1397 be impacted. 1398 1399config DEBUG_BLOCK_EXT_DEVT 1400 bool "Force extended block device numbers and spread them" 1401 depends on DEBUG_KERNEL 1402 depends on BLOCK 1403 default n 1404 help 1405 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1406 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1407 YOU ARE DOING. Distros, please enable this and fix whatever 1408 is broken. 1409 1410 Conventionally, block device numbers are allocated from 1411 predetermined contiguous area. However, extended block area 1412 may introduce non-contiguous block device numbers. This 1413 option forces most block device numbers to be allocated from 1414 the extended space and spreads them to discover kernel or 1415 userland code paths which assume predetermined contiguous 1416 device number allocation. 1417 1418 Note that turning on this debug option shuffles all the 1419 device numbers for all IDE and SCSI devices including libata 1420 ones, so root partition specified using device number 1421 directly (via rdev or root=MAJ:MIN) won't work anymore. 1422 Textual device names (root=/dev/sdXn) will continue to work. 1423 1424 Say N if you are unsure. 1425 1426config CPU_HOTPLUG_STATE_CONTROL 1427 bool "Enable CPU hotplug state control" 1428 depends on DEBUG_KERNEL 1429 depends on HOTPLUG_CPU 1430 default n 1431 help 1432 Allows to write steps between "offline" and "online" to the CPUs 1433 sysfs target file so states can be stepped granular. This is a debug 1434 option for now as the hotplug machinery cannot be stopped and 1435 restarted at arbitrary points yet. 1436 1437 Say N if your are unsure. 1438 1439config NOTIFIER_ERROR_INJECTION 1440 tristate "Notifier error injection" 1441 depends on DEBUG_KERNEL 1442 select DEBUG_FS 1443 help 1444 This option provides the ability to inject artificial errors to 1445 specified notifier chain callbacks. It is useful to test the error 1446 handling of notifier call chain failures. 1447 1448 Say N if unsure. 1449 1450config PM_NOTIFIER_ERROR_INJECT 1451 tristate "PM notifier error injection module" 1452 depends on PM && NOTIFIER_ERROR_INJECTION 1453 default m if PM_DEBUG 1454 help 1455 This option provides the ability to inject artificial errors to 1456 PM notifier chain callbacks. It is controlled through debugfs 1457 interface /sys/kernel/debug/notifier-error-inject/pm 1458 1459 If the notifier call chain should be failed with some events 1460 notified, write the error code to "actions/<notifier event>/error". 1461 1462 Example: Inject PM suspend error (-12 = -ENOMEM) 1463 1464 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1465 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1466 # echo mem > /sys/power/state 1467 bash: echo: write error: Cannot allocate memory 1468 1469 To compile this code as a module, choose M here: the module will 1470 be called pm-notifier-error-inject. 1471 1472 If unsure, say N. 1473 1474config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1475 tristate "OF reconfig notifier error injection module" 1476 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1477 help 1478 This option provides the ability to inject artificial errors to 1479 OF reconfig notifier chain callbacks. It is controlled 1480 through debugfs interface under 1481 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1482 1483 If the notifier call chain should be failed with some events 1484 notified, write the error code to "actions/<notifier event>/error". 1485 1486 To compile this code as a module, choose M here: the module will 1487 be called of-reconfig-notifier-error-inject. 1488 1489 If unsure, say N. 1490 1491config NETDEV_NOTIFIER_ERROR_INJECT 1492 tristate "Netdev notifier error injection module" 1493 depends on NET && NOTIFIER_ERROR_INJECTION 1494 help 1495 This option provides the ability to inject artificial errors to 1496 netdevice notifier chain callbacks. It is controlled through debugfs 1497 interface /sys/kernel/debug/notifier-error-inject/netdev 1498 1499 If the notifier call chain should be failed with some events 1500 notified, write the error code to "actions/<notifier event>/error". 1501 1502 Example: Inject netdevice mtu change error (-22 = -EINVAL) 1503 1504 # cd /sys/kernel/debug/notifier-error-inject/netdev 1505 # echo -22 > actions/NETDEV_CHANGEMTU/error 1506 # ip link set eth0 mtu 1024 1507 RTNETLINK answers: Invalid argument 1508 1509 To compile this code as a module, choose M here: the module will 1510 be called netdev-notifier-error-inject. 1511 1512 If unsure, say N. 1513 1514config FUNCTION_ERROR_INJECTION 1515 def_bool y 1516 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES 1517 1518config FAULT_INJECTION 1519 bool "Fault-injection framework" 1520 depends on DEBUG_KERNEL 1521 help 1522 Provide fault-injection framework. 1523 For more details, see Documentation/fault-injection/. 1524 1525config FAILSLAB 1526 bool "Fault-injection capability for kmalloc" 1527 depends on FAULT_INJECTION 1528 depends on SLAB || SLUB 1529 help 1530 Provide fault-injection capability for kmalloc. 1531 1532config FAIL_PAGE_ALLOC 1533 bool "Fault-injection capabilitiy for alloc_pages()" 1534 depends on FAULT_INJECTION 1535 help 1536 Provide fault-injection capability for alloc_pages(). 1537 1538config FAIL_MAKE_REQUEST 1539 bool "Fault-injection capability for disk IO" 1540 depends on FAULT_INJECTION && BLOCK 1541 help 1542 Provide fault-injection capability for disk IO. 1543 1544config FAIL_IO_TIMEOUT 1545 bool "Fault-injection capability for faking disk interrupts" 1546 depends on FAULT_INJECTION && BLOCK 1547 help 1548 Provide fault-injection capability on end IO handling. This 1549 will make the block layer "forget" an interrupt as configured, 1550 thus exercising the error handling. 1551 1552 Only works with drivers that use the generic timeout handling, 1553 for others it wont do anything. 1554 1555config FAIL_FUTEX 1556 bool "Fault-injection capability for futexes" 1557 select DEBUG_FS 1558 depends on FAULT_INJECTION && FUTEX 1559 help 1560 Provide fault-injection capability for futexes. 1561 1562config FAULT_INJECTION_DEBUG_FS 1563 bool "Debugfs entries for fault-injection capabilities" 1564 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1565 help 1566 Enable configuration of fault-injection capabilities via debugfs. 1567 1568config FAIL_FUNCTION 1569 bool "Fault-injection capability for functions" 1570 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION 1571 help 1572 Provide function-based fault-injection capability. 1573 This will allow you to override a specific function with a return 1574 with given return value. As a result, function caller will see 1575 an error value and have to handle it. This is useful to test the 1576 error handling in various subsystems. 1577 1578config FAIL_MMC_REQUEST 1579 bool "Fault-injection capability for MMC IO" 1580 depends on FAULT_INJECTION_DEBUG_FS && MMC 1581 help 1582 Provide fault-injection capability for MMC IO. 1583 This will make the mmc core return data errors. This is 1584 useful to test the error handling in the mmc block device 1585 and to test how the mmc host driver handles retries from 1586 the block device. 1587 1588config FAULT_INJECTION_STACKTRACE_FILTER 1589 bool "stacktrace filter for fault-injection capabilities" 1590 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1591 depends on !X86_64 1592 select STACKTRACE 1593 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !X86 1594 help 1595 Provide stacktrace filter for fault-injection capabilities 1596 1597config LATENCYTOP 1598 bool "Latency measuring infrastructure" 1599 depends on DEBUG_KERNEL 1600 depends on STACKTRACE_SUPPORT 1601 depends on PROC_FS 1602 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !X86 1603 select KALLSYMS 1604 select KALLSYMS_ALL 1605 select STACKTRACE 1606 select SCHEDSTATS 1607 select SCHED_DEBUG 1608 help 1609 Enable this option if you want to use the LatencyTOP tool 1610 to find out which userspace is blocking on what kernel operations. 1611 1612source kernel/trace/Kconfig 1613 1614config PROVIDE_OHCI1394_DMA_INIT 1615 bool "Remote debugging over FireWire early on boot" 1616 depends on PCI && X86 1617 help 1618 If you want to debug problems which hang or crash the kernel early 1619 on boot and the crashing machine has a FireWire port, you can use 1620 this feature to remotely access the memory of the crashed machine 1621 over FireWire. This employs remote DMA as part of the OHCI1394 1622 specification which is now the standard for FireWire controllers. 1623 1624 With remote DMA, you can monitor the printk buffer remotely using 1625 firescope and access all memory below 4GB using fireproxy from gdb. 1626 Even controlling a kernel debugger is possible using remote DMA. 1627 1628 Usage: 1629 1630 If ohci1394_dma=early is used as boot parameter, it will initialize 1631 all OHCI1394 controllers which are found in the PCI config space. 1632 1633 As all changes to the FireWire bus such as enabling and disabling 1634 devices cause a bus reset and thereby disable remote DMA for all 1635 devices, be sure to have the cable plugged and FireWire enabled on 1636 the debugging host before booting the debug target for debugging. 1637 1638 This code (~1k) is freed after boot. By then, the firewire stack 1639 in charge of the OHCI-1394 controllers should be used instead. 1640 1641 See Documentation/debugging-via-ohci1394.txt for more information. 1642 1643config DMA_API_DEBUG 1644 bool "Enable debugging of DMA-API usage" 1645 select NEED_DMA_MAP_STATE 1646 help 1647 Enable this option to debug the use of the DMA API by device drivers. 1648 With this option you will be able to detect common bugs in device 1649 drivers like double-freeing of DMA mappings or freeing mappings that 1650 were never allocated. 1651 1652 This also attempts to catch cases where a page owned by DMA is 1653 accessed by the cpu in a way that could cause data corruption. For 1654 example, this enables cow_user_page() to check that the source page is 1655 not undergoing DMA. 1656 1657 This option causes a performance degradation. Use only if you want to 1658 debug device drivers and dma interactions. 1659 1660 If unsure, say N. 1661 1662config DMA_API_DEBUG_SG 1663 bool "Debug DMA scatter-gather usage" 1664 default y 1665 depends on DMA_API_DEBUG 1666 help 1667 Perform extra checking that callers of dma_map_sg() have respected the 1668 appropriate segment length/boundary limits for the given device when 1669 preparing DMA scatterlists. 1670 1671 This is particularly likely to have been overlooked in cases where the 1672 dma_map_sg() API is used for general bulk mapping of pages rather than 1673 preparing literal scatter-gather descriptors, where there is a risk of 1674 unexpected behaviour from DMA API implementations if the scatterlist 1675 is technically out-of-spec. 1676 1677 If unsure, say N. 1678 1679menuconfig RUNTIME_TESTING_MENU 1680 bool "Runtime Testing" 1681 def_bool y 1682 1683if RUNTIME_TESTING_MENU 1684 1685config LKDTM 1686 tristate "Linux Kernel Dump Test Tool Module" 1687 depends on DEBUG_FS 1688 depends on BLOCK 1689 help 1690 This module enables testing of the different dumping mechanisms by 1691 inducing system failures at predefined crash points. 1692 If you don't need it: say N 1693 Choose M here to compile this code as a module. The module will be 1694 called lkdtm. 1695 1696 Documentation on how to use the module can be found in 1697 Documentation/fault-injection/provoke-crashes.txt 1698 1699config TEST_LIST_SORT 1700 tristate "Linked list sorting test" 1701 depends on DEBUG_KERNEL || m 1702 help 1703 Enable this to turn on 'list_sort()' function test. This test is 1704 executed only once during system boot (so affects only boot time), 1705 or at module load time. 1706 1707 If unsure, say N. 1708 1709config TEST_SORT 1710 tristate "Array-based sort test" 1711 depends on DEBUG_KERNEL || m 1712 help 1713 This option enables the self-test function of 'sort()' at boot, 1714 or at module load time. 1715 1716 If unsure, say N. 1717 1718config KPROBES_SANITY_TEST 1719 bool "Kprobes sanity tests" 1720 depends on DEBUG_KERNEL 1721 depends on KPROBES 1722 help 1723 This option provides for testing basic kprobes functionality on 1724 boot. Samples of kprobe and kretprobe are inserted and 1725 verified for functionality. 1726 1727 Say N if you are unsure. 1728 1729config BACKTRACE_SELF_TEST 1730 tristate "Self test for the backtrace code" 1731 depends on DEBUG_KERNEL 1732 help 1733 This option provides a kernel module that can be used to test 1734 the kernel stack backtrace code. This option is not useful 1735 for distributions or general kernels, but only for kernel 1736 developers working on architecture code. 1737 1738 Note that if you want to also test saved backtraces, you will 1739 have to enable STACKTRACE as well. 1740 1741 Say N if you are unsure. 1742 1743config RBTREE_TEST 1744 tristate "Red-Black tree test" 1745 depends on DEBUG_KERNEL 1746 help 1747 A benchmark measuring the performance of the rbtree library. 1748 Also includes rbtree invariant checks. 1749 1750config INTERVAL_TREE_TEST 1751 tristate "Interval tree test" 1752 depends on DEBUG_KERNEL 1753 select INTERVAL_TREE 1754 help 1755 A benchmark measuring the performance of the interval tree library 1756 1757config PERCPU_TEST 1758 tristate "Per cpu operations test" 1759 depends on m && DEBUG_KERNEL 1760 help 1761 Enable this option to build test module which validates per-cpu 1762 operations. 1763 1764 If unsure, say N. 1765 1766config ATOMIC64_SELFTEST 1767 tristate "Perform an atomic64_t self-test" 1768 help 1769 Enable this option to test the atomic64_t functions at boot or 1770 at module load time. 1771 1772 If unsure, say N. 1773 1774config ASYNC_RAID6_TEST 1775 tristate "Self test for hardware accelerated raid6 recovery" 1776 depends on ASYNC_RAID6_RECOV 1777 select ASYNC_MEMCPY 1778 ---help--- 1779 This is a one-shot self test that permutes through the 1780 recovery of all the possible two disk failure scenarios for a 1781 N-disk array. Recovery is performed with the asynchronous 1782 raid6 recovery routines, and will optionally use an offload 1783 engine if one is available. 1784 1785 If unsure, say N. 1786 1787config TEST_HEXDUMP 1788 tristate "Test functions located in the hexdump module at runtime" 1789 1790config TEST_STRING_HELPERS 1791 tristate "Test functions located in the string_helpers module at runtime" 1792 1793config TEST_KSTRTOX 1794 tristate "Test kstrto*() family of functions at runtime" 1795 1796config TEST_PRINTF 1797 tristate "Test printf() family of functions at runtime" 1798 1799config TEST_BITMAP 1800 tristate "Test bitmap_*() family of functions at runtime" 1801 help 1802 Enable this option to test the bitmap functions at boot. 1803 1804 If unsure, say N. 1805 1806config TEST_BITFIELD 1807 tristate "Test bitfield functions at runtime" 1808 help 1809 Enable this option to test the bitfield functions at boot. 1810 1811 If unsure, say N. 1812 1813config TEST_UUID 1814 tristate "Test functions located in the uuid module at runtime" 1815 1816config TEST_OVERFLOW 1817 tristate "Test check_*_overflow() functions at runtime" 1818 1819config TEST_RHASHTABLE 1820 tristate "Perform selftest on resizable hash table" 1821 help 1822 Enable this option to test the rhashtable functions at boot. 1823 1824 If unsure, say N. 1825 1826config TEST_HASH 1827 tristate "Perform selftest on hash functions" 1828 help 1829 Enable this option to test the kernel's integer (<linux/hash.h>), 1830 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>) 1831 hash functions on boot (or module load). 1832 1833 This is intended to help people writing architecture-specific 1834 optimized versions. If unsure, say N. 1835 1836config TEST_IDA 1837 tristate "Perform selftest on IDA functions" 1838 1839config TEST_PARMAN 1840 tristate "Perform selftest on priority array manager" 1841 depends on PARMAN 1842 help 1843 Enable this option to test priority array manager on boot 1844 (or module load). 1845 1846 If unsure, say N. 1847 1848config TEST_LKM 1849 tristate "Test module loading with 'hello world' module" 1850 depends on m 1851 help 1852 This builds the "test_module" module that emits "Hello, world" 1853 on printk when loaded. It is designed to be used for basic 1854 evaluation of the module loading subsystem (for example when 1855 validating module verification). It lacks any extra dependencies, 1856 and will not normally be loaded by the system unless explicitly 1857 requested by name. 1858 1859 If unsure, say N. 1860 1861config TEST_USER_COPY 1862 tristate "Test user/kernel boundary protections" 1863 depends on m 1864 help 1865 This builds the "test_user_copy" module that runs sanity checks 1866 on the copy_to/from_user infrastructure, making sure basic 1867 user/kernel boundary testing is working. If it fails to load, 1868 a regression has been detected in the user/kernel memory boundary 1869 protections. 1870 1871 If unsure, say N. 1872 1873config TEST_BPF 1874 tristate "Test BPF filter functionality" 1875 depends on m && NET 1876 help 1877 This builds the "test_bpf" module that runs various test vectors 1878 against the BPF interpreter or BPF JIT compiler depending on the 1879 current setting. This is in particular useful for BPF JIT compiler 1880 development, but also to run regression tests against changes in 1881 the interpreter code. It also enables test stubs for eBPF maps and 1882 verifier used by user space verifier testsuite. 1883 1884 If unsure, say N. 1885 1886config FIND_BIT_BENCHMARK 1887 tristate "Test find_bit functions" 1888 help 1889 This builds the "test_find_bit" module that measure find_*_bit() 1890 functions performance. 1891 1892 If unsure, say N. 1893 1894config TEST_FIRMWARE 1895 tristate "Test firmware loading via userspace interface" 1896 depends on FW_LOADER 1897 help 1898 This builds the "test_firmware" module that creates a userspace 1899 interface for testing firmware loading. This can be used to 1900 control the triggering of firmware loading without needing an 1901 actual firmware-using device. The contents can be rechecked by 1902 userspace. 1903 1904 If unsure, say N. 1905 1906config TEST_SYSCTL 1907 tristate "sysctl test driver" 1908 depends on PROC_SYSCTL 1909 help 1910 This builds the "test_sysctl" module. This driver enables to test the 1911 proc sysctl interfaces available to drivers safely without affecting 1912 production knobs which might alter system functionality. 1913 1914 If unsure, say N. 1915 1916config TEST_UDELAY 1917 tristate "udelay test driver" 1918 help 1919 This builds the "udelay_test" module that helps to make sure 1920 that udelay() is working properly. 1921 1922 If unsure, say N. 1923 1924config TEST_STATIC_KEYS 1925 tristate "Test static keys" 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 depends on m 1935 depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS 1936 depends on NETDEVICES && NET_CORE && INET # for TUN 1937 select TEST_LKM 1938 select XFS_FS 1939 select TUN 1940 select BTRFS_FS 1941 help 1942 Test the kernel's module loading mechanism: kmod. kmod implements 1943 support to load modules using the Linux kernel's usermode helper. 1944 This test provides a series of tests against kmod. 1945 1946 Although technically you can either build test_kmod as a module or 1947 into the kernel we disallow building it into the kernel since 1948 it stress tests request_module() and this will very likely cause 1949 some issues by taking over precious threads available from other 1950 module load requests, ultimately this could be fatal. 1951 1952 To run tests run: 1953 1954 tools/testing/selftests/kmod/kmod.sh --help 1955 1956 If unsure, say N. 1957 1958config TEST_DEBUG_VIRTUAL 1959 tristate "Test CONFIG_DEBUG_VIRTUAL feature" 1960 depends on DEBUG_VIRTUAL 1961 help 1962 Test the kernel's ability to detect incorrect calls to 1963 virt_to_phys() done against the non-linear part of the 1964 kernel's virtual address map. 1965 1966 If unsure, say N. 1967 1968endif # RUNTIME_TESTING_MENU 1969 1970config MEMTEST 1971 bool "Memtest" 1972 depends on HAVE_MEMBLOCK 1973 ---help--- 1974 This option adds a kernel parameter 'memtest', which allows memtest 1975 to be set. 1976 memtest=0, mean disabled; -- default 1977 memtest=1, mean do 1 test pattern; 1978 ... 1979 memtest=17, mean do 17 test patterns. 1980 If you are unsure how to answer this question, answer N. 1981 1982config BUG_ON_DATA_CORRUPTION 1983 bool "Trigger a BUG when data corruption is detected" 1984 select DEBUG_LIST 1985 help 1986 Select this option if the kernel should BUG when it encounters 1987 data corruption in kernel memory structures when they get checked 1988 for validity. 1989 1990 If unsure, say N. 1991 1992source "samples/Kconfig" 1993 1994source "lib/Kconfig.kgdb" 1995 1996source "lib/Kconfig.ubsan" 1997 1998config ARCH_HAS_DEVMEM_IS_ALLOWED 1999 bool 2000 2001config STRICT_DEVMEM 2002 bool "Filter access to /dev/mem" 2003 depends on MMU && DEVMEM 2004 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 2005 default y if PPC || X86 || ARM64 2006 ---help--- 2007 If this option is disabled, you allow userspace (root) access to all 2008 of memory, including kernel and userspace memory. Accidental 2009 access to this is obviously disastrous, but specific access can 2010 be used by people debugging the kernel. Note that with PAT support 2011 enabled, even in this case there are restrictions on /dev/mem 2012 use due to the cache aliasing requirements. 2013 2014 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 2015 file only allows userspace access to PCI space and the BIOS code and 2016 data regions. This is sufficient for dosemu and X and all common 2017 users of /dev/mem. 2018 2019 If in doubt, say Y. 2020 2021config IO_STRICT_DEVMEM 2022 bool "Filter I/O access to /dev/mem" 2023 depends on STRICT_DEVMEM 2024 ---help--- 2025 If this option is disabled, you allow userspace (root) access to all 2026 io-memory regardless of whether a driver is actively using that 2027 range. Accidental access to this is obviously disastrous, but 2028 specific access can be used by people debugging kernel drivers. 2029 2030 If this option is switched on, the /dev/mem file only allows 2031 userspace access to *idle* io-memory ranges (see /proc/iomem) This 2032 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 2033 if the driver using a given range cannot be disabled. 2034 2035 If in doubt, say Y. 2036 2037source "arch/$(SRCARCH)/Kconfig.debug" 2038 2039endmenu # Kernel hacking 2040
