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 2048 if PARISC 228 default 1536 if (!64BIT && XTENSA) 229 default 1280 if KASAN && !64BIT 230 default 1024 if !64BIT 231 default 2048 if 64BIT 232 help 233 Tell gcc to warn at build time for stack frames larger than this. 234 Setting this too low will cause a lot of warnings. 235 Setting it to 0 disables the warning. 236 Requires gcc 4.4 237 238config STRIP_ASM_SYMS 239 bool "Strip assembler-generated symbols during link" 240 default n 241 help 242 Strip internal assembler-generated symbols during a link (symbols 243 that look like '.Lxxx') so they don't pollute the output of 244 get_wchan() and suchlike. 245 246config READABLE_ASM 247 bool "Generate readable assembler code" 248 depends on DEBUG_KERNEL 249 help 250 Disable some compiler optimizations that tend to generate human unreadable 251 assembler output. This may make the kernel slightly slower, but it helps 252 to keep kernel developers who have to stare a lot at assembler listings 253 sane. 254 255config UNUSED_SYMBOLS 256 bool "Enable unused/obsolete exported symbols" 257 default y if X86 258 help 259 Unused but exported symbols make the kernel needlessly bigger. For 260 that reason most of these unused exports will soon be removed. This 261 option is provided temporarily to provide a transition period in case 262 some external kernel module needs one of these symbols anyway. If you 263 encounter such a case in your module, consider if you are actually 264 using the right API. (rationale: since nobody in the kernel is using 265 this in a module, there is a pretty good chance it's actually the 266 wrong interface to use). If you really need the symbol, please send a 267 mail to the linux kernel mailing list mentioning the symbol and why 268 you really need it, and what the merge plan to the mainline kernel for 269 your module is. 270 271config PAGE_OWNER 272 bool "Track page owner" 273 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 274 select DEBUG_FS 275 select STACKTRACE 276 select STACKDEPOT 277 select PAGE_EXTENSION 278 help 279 This keeps track of what call chain is the owner of a page, may 280 help to find bare alloc_page(s) leaks. Even if you include this 281 feature on your build, it is disabled in default. You should pass 282 "page_owner=on" to boot parameter in order to enable it. Eats 283 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 284 for user-space helper. 285 286 If unsure, say N. 287 288config DEBUG_FS 289 bool "Debug Filesystem" 290 help 291 debugfs is a virtual file system that kernel developers use to put 292 debugging files into. Enable this option to be able to read and 293 write to these files. 294 295 For detailed documentation on the debugfs API, see 296 Documentation/filesystems/. 297 298 If unsure, say N. 299 300config HEADERS_CHECK 301 bool "Run 'make headers_check' when building vmlinux" 302 depends on !UML 303 help 304 This option will extract the user-visible kernel headers whenever 305 building the kernel, and will run basic sanity checks on them to 306 ensure that exported files do not attempt to include files which 307 were not exported, etc. 308 309 If you're making modifications to header files which are 310 relevant for userspace, say 'Y', and check the headers 311 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 312 your build tree), to make sure they're suitable. 313 314config DEBUG_SECTION_MISMATCH 315 bool "Enable full Section mismatch analysis" 316 help 317 The section mismatch analysis checks if there are illegal 318 references from one section to another section. 319 During linktime or runtime, some sections are dropped; 320 any use of code/data previously in these sections would 321 most likely result in an oops. 322 In the code, functions and variables are annotated with 323 __init,, etc. (see the full list in include/linux/init.h), 324 which results in the code/data being placed in specific sections. 325 The section mismatch analysis is always performed after a full 326 kernel build, and enabling this option causes the following 327 additional steps to occur: 328 - Add the option -fno-inline-functions-called-once to gcc commands. 329 When inlining a function annotated with __init in a non-init 330 function, we would lose the section information and thus 331 the analysis would not catch the illegal reference. 332 This option tells gcc to inline less (but it does result in 333 a larger kernel). 334 - Run the section mismatch analysis for each module/built-in.a file. 335 When we run the section mismatch analysis on vmlinux.o, we 336 lose valuable information about where the mismatch was 337 introduced. 338 Running the analysis for each module/built-in.a file 339 tells where the mismatch happens much closer to the 340 source. The drawback is that the same mismatch is 341 reported at least twice. 342 - Enable verbose reporting from modpost in order to help resolve 343 the section mismatches that are reported. 344 345config SECTION_MISMATCH_WARN_ONLY 346 bool "Make section mismatch errors non-fatal" 347 default y 348 help 349 If you say N here, the build process will fail if there are any 350 section mismatch, instead of just throwing warnings. 351 352 If unsure, say Y. 353 354# 355# Select this config option from the architecture Kconfig, if it 356# is preferred to always offer frame pointers as a config 357# option on the architecture (regardless of KERNEL_DEBUG): 358# 359config ARCH_WANT_FRAME_POINTERS 360 bool 361 362config FRAME_POINTER 363 bool "Compile the kernel with frame pointers" 364 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS 365 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 366 help 367 If you say Y here the resulting kernel image will be slightly 368 larger and slower, but it gives very useful debugging information 369 in case of kernel bugs. (precise oopses/stacktraces/warnings) 370 371config STACK_VALIDATION 372 bool "Compile-time stack metadata validation" 373 depends on HAVE_STACK_VALIDATION 374 default n 375 help 376 Add compile-time checks to validate stack metadata, including frame 377 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure 378 that runtime stack traces are more reliable. 379 380 This is also a prerequisite for generation of ORC unwind data, which 381 is needed for CONFIG_UNWINDER_ORC. 382 383 For more information, see 384 tools/objtool/Documentation/stack-validation.txt. 385 386config DEBUG_FORCE_WEAK_PER_CPU 387 bool "Force weak per-cpu definitions" 388 depends on DEBUG_KERNEL 389 help 390 s390 and alpha require percpu variables in modules to be 391 defined weak to work around addressing range issue which 392 puts the following two restrictions on percpu variable 393 definitions. 394 395 1. percpu symbols must be unique whether static or not 396 2. percpu variables can't be defined inside a function 397 398 To ensure that generic code follows the above rules, this 399 option forces all percpu variables to be defined as weak. 400 401endmenu # "Compiler options" 402 403config MAGIC_SYSRQ 404 bool "Magic SysRq key" 405 depends on !UML 406 help 407 If you say Y here, you will have some control over the system even 408 if the system crashes for example during kernel debugging (e.g., you 409 will be able to flush the buffer cache to disk, reboot the system 410 immediately or dump some status information). This is accomplished 411 by pressing various keys while holding SysRq (Alt+PrintScreen). It 412 also works on a serial console (on PC hardware at least), if you 413 send a BREAK and then within 5 seconds a command keypress. The 414 keys are documented in <file:Documentation/admin-guide/sysrq.rst>. 415 Don't say Y unless you really know what this hack does. 416 417config MAGIC_SYSRQ_DEFAULT_ENABLE 418 hex "Enable magic SysRq key functions by default" 419 depends on MAGIC_SYSRQ 420 default 0x1 421 help 422 Specifies which SysRq key functions are enabled by default. 423 This may be set to 1 or 0 to enable or disable them all, or 424 to a bitmask as described in Documentation/admin-guide/sysrq.rst. 425 426config MAGIC_SYSRQ_SERIAL 427 bool "Enable magic SysRq key over serial" 428 depends on MAGIC_SYSRQ 429 default y 430 help 431 Many embedded boards have a disconnected TTL level serial which can 432 generate some garbage that can lead to spurious false sysrq detects. 433 This option allows you to decide whether you want to enable the 434 magic SysRq key. 435 436config DEBUG_KERNEL 437 bool "Kernel debugging" 438 help 439 Say Y here if you are developing drivers or trying to debug and 440 identify kernel problems. 441 442menu "Memory Debugging" 443 444source mm/Kconfig.debug 445 446config DEBUG_OBJECTS 447 bool "Debug object operations" 448 depends on DEBUG_KERNEL 449 help 450 If you say Y here, additional code will be inserted into the 451 kernel to track the life time of various objects and validate 452 the operations on those objects. 453 454config DEBUG_OBJECTS_SELFTEST 455 bool "Debug objects selftest" 456 depends on DEBUG_OBJECTS 457 help 458 This enables the selftest of the object debug code. 459 460config DEBUG_OBJECTS_FREE 461 bool "Debug objects in freed memory" 462 depends on DEBUG_OBJECTS 463 help 464 This enables checks whether a k/v free operation frees an area 465 which contains an object which has not been deactivated 466 properly. This can make kmalloc/kfree-intensive workloads 467 much slower. 468 469config DEBUG_OBJECTS_TIMERS 470 bool "Debug timer objects" 471 depends on DEBUG_OBJECTS 472 help 473 If you say Y here, additional code will be inserted into the 474 timer routines to track the life time of timer objects and 475 validate the timer operations. 476 477config DEBUG_OBJECTS_WORK 478 bool "Debug work objects" 479 depends on DEBUG_OBJECTS 480 help 481 If you say Y here, additional code will be inserted into the 482 work queue routines to track the life time of work objects and 483 validate the work operations. 484 485config DEBUG_OBJECTS_RCU_HEAD 486 bool "Debug RCU callbacks objects" 487 depends on DEBUG_OBJECTS 488 help 489 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 490 491config DEBUG_OBJECTS_PERCPU_COUNTER 492 bool "Debug percpu counter objects" 493 depends on DEBUG_OBJECTS 494 help 495 If you say Y here, additional code will be inserted into the 496 percpu counter routines to track the life time of percpu counter 497 objects and validate the percpu counter operations. 498 499config DEBUG_OBJECTS_ENABLE_DEFAULT 500 int "debug_objects bootup default value (0-1)" 501 range 0 1 502 default "1" 503 depends on DEBUG_OBJECTS 504 help 505 Debug objects boot parameter default value 506 507config DEBUG_SLAB 508 bool "Debug slab memory allocations" 509 depends on DEBUG_KERNEL && SLAB 510 help 511 Say Y here to have the kernel do limited verification on memory 512 allocation as well as poisoning memory on free to catch use of freed 513 memory. This can make kmalloc/kfree-intensive workloads much slower. 514 515config DEBUG_SLAB_LEAK 516 bool "Memory leak debugging" 517 depends on DEBUG_SLAB 518 519config SLUB_DEBUG_ON 520 bool "SLUB debugging on by default" 521 depends on SLUB && SLUB_DEBUG 522 default n 523 help 524 Boot with debugging on by default. SLUB boots by default with 525 the runtime debug capabilities switched off. Enabling this is 526 equivalent to specifying the "slub_debug" parameter on boot. 527 There is no support for more fine grained debug control like 528 possible with slub_debug=xxx. SLUB debugging may be switched 529 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 530 "slub_debug=-". 531 532config SLUB_STATS 533 default n 534 bool "Enable SLUB performance statistics" 535 depends on SLUB && SYSFS 536 help 537 SLUB statistics are useful to debug SLUBs allocation behavior in 538 order find ways to optimize the allocator. This should never be 539 enabled for production use since keeping statistics slows down 540 the allocator by a few percentage points. The slabinfo command 541 supports the determination of the most active slabs to figure 542 out which slabs are relevant to a particular load. 543 Try running: slabinfo -DA 544 545config HAVE_DEBUG_KMEMLEAK 546 bool 547 548config DEBUG_KMEMLEAK 549 bool "Kernel memory leak detector" 550 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 551 select DEBUG_FS 552 select STACKTRACE if STACKTRACE_SUPPORT 553 select KALLSYMS 554 select CRC32 555 help 556 Say Y here if you want to enable the memory leak 557 detector. The memory allocation/freeing is traced in a way 558 similar to the Boehm's conservative garbage collector, the 559 difference being that the orphan objects are not freed but 560 only shown in /sys/kernel/debug/kmemleak. Enabling this 561 feature will introduce an overhead to memory 562 allocations. See Documentation/dev-tools/kmemleak.rst for more 563 details. 564 565 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 566 of finding leaks due to the slab objects poisoning. 567 568 In order to access the kmemleak file, debugfs needs to be 569 mounted (usually at /sys/kernel/debug). 570 571config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 572 int "Maximum kmemleak early log entries" 573 depends on DEBUG_KMEMLEAK 574 range 200 40000 575 default 16000 576 help 577 Kmemleak must track all the memory allocations to avoid 578 reporting false positives. Since memory may be allocated or 579 freed before kmemleak is initialised, an early log buffer is 580 used to store these actions. If kmemleak reports "early log 581 buffer exceeded", please increase this value. 582 583config DEBUG_KMEMLEAK_TEST 584 tristate "Simple test for the kernel memory leak detector" 585 depends on DEBUG_KMEMLEAK && m 586 help 587 This option enables a module that explicitly leaks memory. 588 589 If unsure, say N. 590 591config DEBUG_KMEMLEAK_DEFAULT_OFF 592 bool "Default kmemleak to off" 593 depends on DEBUG_KMEMLEAK 594 help 595 Say Y here to disable kmemleak by default. It can then be enabled 596 on the command line via kmemleak=on. 597 598config DEBUG_STACK_USAGE 599 bool "Stack utilization instrumentation" 600 depends on DEBUG_KERNEL && !IA64 601 help 602 Enables the display of the minimum amount of free stack which each 603 task has ever had available in the sysrq-T and sysrq-P debug output. 604 605 This option will slow down process creation somewhat. 606 607config DEBUG_VM 608 bool "Debug VM" 609 depends on DEBUG_KERNEL 610 help 611 Enable this to turn on extended checks in the virtual-memory system 612 that may impact performance. 613 614 If unsure, say N. 615 616config DEBUG_VM_VMACACHE 617 bool "Debug VMA caching" 618 depends on DEBUG_VM 619 help 620 Enable this to turn on VMA caching debug information. Doing so 621 can cause significant overhead, so only enable it in non-production 622 environments. 623 624 If unsure, say N. 625 626config DEBUG_VM_RB 627 bool "Debug VM red-black trees" 628 depends on DEBUG_VM 629 help 630 Enable VM red-black tree debugging information and extra validations. 631 632 If unsure, say N. 633 634config DEBUG_VM_PGFLAGS 635 bool "Debug page-flags operations" 636 depends on DEBUG_VM 637 help 638 Enables extra validation on page flags operations. 639 640 If unsure, say N. 641 642config ARCH_HAS_DEBUG_VIRTUAL 643 bool 644 645config DEBUG_VIRTUAL 646 bool "Debug VM translations" 647 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL 648 help 649 Enable some costly sanity checks in virtual to page code. This can 650 catch mistakes with virt_to_page() and friends. 651 652 If unsure, say N. 653 654config DEBUG_NOMMU_REGIONS 655 bool "Debug the global anon/private NOMMU mapping region tree" 656 depends on DEBUG_KERNEL && !MMU 657 help 658 This option causes the global tree of anonymous and private mapping 659 regions to be regularly checked for invalid topology. 660 661config DEBUG_MEMORY_INIT 662 bool "Debug memory initialisation" if EXPERT 663 default !EXPERT 664 help 665 Enable this for additional checks during memory initialisation. 666 The sanity checks verify aspects of the VM such as the memory model 667 and other information provided by the architecture. Verbose 668 information will be printed at KERN_DEBUG loglevel depending 669 on the mminit_loglevel= command-line option. 670 671 If unsure, say Y 672 673config MEMORY_NOTIFIER_ERROR_INJECT 674 tristate "Memory hotplug notifier error injection module" 675 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 676 help 677 This option provides the ability to inject artificial errors to 678 memory hotplug notifier chain callbacks. It is controlled through 679 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 680 681 If the notifier call chain should be failed with some events 682 notified, write the error code to "actions/<notifier event>/error". 683 684 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 685 686 # cd /sys/kernel/debug/notifier-error-inject/memory 687 # echo -12 > actions/MEM_GOING_OFFLINE/error 688 # echo offline > /sys/devices/system/memory/memoryXXX/state 689 bash: echo: write error: Cannot allocate memory 690 691 To compile this code as a module, choose M here: the module will 692 be called memory-notifier-error-inject. 693 694 If unsure, say N. 695 696config DEBUG_PER_CPU_MAPS 697 bool "Debug access to per_cpu maps" 698 depends on DEBUG_KERNEL 699 depends on SMP 700 help 701 Say Y to verify that the per_cpu map being accessed has 702 been set up. This adds a fair amount of code to kernel memory 703 and decreases performance. 704 705 Say N if unsure. 706 707config DEBUG_HIGHMEM 708 bool "Highmem debugging" 709 depends on DEBUG_KERNEL && HIGHMEM 710 help 711 This option enables additional error checking for high memory 712 systems. Disable for production systems. 713 714config HAVE_DEBUG_STACKOVERFLOW 715 bool 716 717config DEBUG_STACKOVERFLOW 718 bool "Check for stack overflows" 719 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 720 ---help--- 721 Say Y here if you want to check for overflows of kernel, IRQ 722 and exception stacks (if your architecture uses them). This 723 option will show detailed messages if free stack space drops 724 below a certain limit. 725 726 These kinds of bugs usually occur when call-chains in the 727 kernel get too deep, especially when interrupts are 728 involved. 729 730 Use this in cases where you see apparently random memory 731 corruption, especially if it appears in 'struct thread_info' 732 733 If in doubt, say "N". 734 735source "lib/Kconfig.kasan" 736 737endmenu # "Memory Debugging" 738 739config ARCH_HAS_KCOV 740 bool 741 help 742 KCOV does not have any arch-specific code, but currently it is enabled 743 only for x86_64. KCOV requires testing on other archs, and most likely 744 disabling of instrumentation for some early boot code. 745 746config CC_HAS_SANCOV_TRACE_PC 747 def_bool $(cc-option,-fsanitize-coverage=trace-pc) 748 749config KCOV 750 bool "Code coverage for fuzzing" 751 depends on ARCH_HAS_KCOV 752 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS 753 select DEBUG_FS 754 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC 755 help 756 KCOV exposes kernel code coverage information in a form suitable 757 for coverage-guided fuzzing (randomized testing). 758 759 If RANDOMIZE_BASE is enabled, PC values will not be stable across 760 different machines and across reboots. If you need stable PC values, 761 disable RANDOMIZE_BASE. 762 763 For more details, see Documentation/dev-tools/kcov.rst. 764 765config KCOV_ENABLE_COMPARISONS 766 bool "Enable comparison operands collection by KCOV" 767 depends on KCOV 768 depends on $(cc-option,-fsanitize-coverage=trace-cmp) 769 help 770 KCOV also exposes operands of every comparison in the instrumented 771 code along with operand sizes and PCs of the comparison instructions. 772 These operands can be used by fuzzing engines to improve the quality 773 of fuzzing coverage. 774 775config KCOV_INSTRUMENT_ALL 776 bool "Instrument all code by default" 777 depends on KCOV 778 default y 779 help 780 If you are doing generic system call fuzzing (like e.g. syzkaller), 781 then you will want to instrument the whole kernel and you should 782 say y here. If you are doing more targeted fuzzing (like e.g. 783 filesystem fuzzing with AFL) then you will want to enable coverage 784 for more specific subsets of files, and should say n here. 785 786config DEBUG_SHIRQ 787 bool "Debug shared IRQ handlers" 788 depends on DEBUG_KERNEL 789 help 790 Enable this to generate a spurious interrupt as soon as a shared 791 interrupt handler is registered, and just before one is deregistered. 792 Drivers ought to be able to handle interrupts coming in at those 793 points; some don't and need to be caught. 794 795menu "Debug Lockups and Hangs" 796 797config LOCKUP_DETECTOR 798 bool 799 800config SOFTLOCKUP_DETECTOR 801 bool "Detect Soft Lockups" 802 depends on DEBUG_KERNEL && !S390 803 select LOCKUP_DETECTOR 804 help 805 Say Y here to enable the kernel to act as a watchdog to detect 806 soft lockups. 807 808 Softlockups are bugs that cause the kernel to loop in kernel 809 mode for more than 20 seconds, without giving other tasks a 810 chance to run. The current stack trace is displayed upon 811 detection and the system will stay locked up. 812 813config BOOTPARAM_SOFTLOCKUP_PANIC 814 bool "Panic (Reboot) On Soft Lockups" 815 depends on SOFTLOCKUP_DETECTOR 816 help 817 Say Y here to enable the kernel to panic on "soft lockups", 818 which are bugs that cause the kernel to loop in kernel 819 mode for more than 20 seconds (configurable using the watchdog_thresh 820 sysctl), without giving other tasks a chance to run. 821 822 The panic can be used in combination with panic_timeout, 823 to cause the system to reboot automatically after a 824 lockup has been detected. This feature is useful for 825 high-availability systems that have uptime guarantees and 826 where a lockup must be resolved ASAP. 827 828 Say N if unsure. 829 830config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 831 int 832 depends on SOFTLOCKUP_DETECTOR 833 range 0 1 834 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 835 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 836 837config HARDLOCKUP_DETECTOR_PERF 838 bool 839 select SOFTLOCKUP_DETECTOR 840 841# 842# Enables a timestamp based low pass filter to compensate for perf based 843# hard lockup detection which runs too fast due to turbo modes. 844# 845config HARDLOCKUP_CHECK_TIMESTAMP 846 bool 847 848# 849# arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard 850# lockup detector rather than the perf based detector. 851# 852config HARDLOCKUP_DETECTOR 853 bool "Detect Hard Lockups" 854 depends on DEBUG_KERNEL && !S390 855 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH 856 select LOCKUP_DETECTOR 857 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF 858 help 859 Say Y here to enable the kernel to act as a watchdog to detect 860 hard lockups. 861 862 Hardlockups are bugs that cause the CPU to loop in kernel mode 863 for more than 10 seconds, without letting other interrupts have a 864 chance to run. The current stack trace is displayed upon detection 865 and the system will stay locked up. 866 867config BOOTPARAM_HARDLOCKUP_PANIC 868 bool "Panic (Reboot) On Hard Lockups" 869 depends on HARDLOCKUP_DETECTOR 870 help 871 Say Y here to enable the kernel to panic on "hard lockups", 872 which are bugs that cause the kernel to loop in kernel 873 mode with interrupts disabled for more than 10 seconds (configurable 874 using the watchdog_thresh sysctl). 875 876 Say N if unsure. 877 878config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 879 int 880 depends on HARDLOCKUP_DETECTOR 881 range 0 1 882 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 883 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 884 885config DETECT_HUNG_TASK 886 bool "Detect Hung Tasks" 887 depends on DEBUG_KERNEL 888 default SOFTLOCKUP_DETECTOR 889 help 890 Say Y here to enable the kernel to detect "hung tasks", 891 which are bugs that cause the task to be stuck in 892 uninterruptible "D" state indefinitely. 893 894 When a hung task is detected, the kernel will print the 895 current stack trace (which you should report), but the 896 task will stay in uninterruptible state. If lockdep is 897 enabled then all held locks will also be reported. This 898 feature has negligible overhead. 899 900config DEFAULT_HUNG_TASK_TIMEOUT 901 int "Default timeout for hung task detection (in seconds)" 902 depends on DETECT_HUNG_TASK 903 default 120 904 help 905 This option controls the default timeout (in seconds) used 906 to determine when a task has become non-responsive and should 907 be considered hung. 908 909 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 910 sysctl or by writing a value to 911 /proc/sys/kernel/hung_task_timeout_secs. 912 913 A timeout of 0 disables the check. The default is two minutes. 914 Keeping the default should be fine in most cases. 915 916config BOOTPARAM_HUNG_TASK_PANIC 917 bool "Panic (Reboot) On Hung Tasks" 918 depends on DETECT_HUNG_TASK 919 help 920 Say Y here to enable the kernel to panic on "hung tasks", 921 which are bugs that cause the kernel to leave a task stuck 922 in uninterruptible "D" state. 923 924 The panic can be used in combination with panic_timeout, 925 to cause the system to reboot automatically after a 926 hung task has been detected. This feature is useful for 927 high-availability systems that have uptime guarantees and 928 where a hung tasks must be resolved ASAP. 929 930 Say N if unsure. 931 932config BOOTPARAM_HUNG_TASK_PANIC_VALUE 933 int 934 depends on DETECT_HUNG_TASK 935 range 0 1 936 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 937 default 1 if BOOTPARAM_HUNG_TASK_PANIC 938 939config WQ_WATCHDOG 940 bool "Detect Workqueue Stalls" 941 depends on DEBUG_KERNEL 942 help 943 Say Y here to enable stall detection on workqueues. If a 944 worker pool doesn't make forward progress on a pending work 945 item for over a given amount of time, 30s by default, a 946 warning message is printed along with dump of workqueue 947 state. This can be configured through kernel parameter 948 "workqueue.watchdog_thresh" and its sysfs counterpart. 949 950endmenu # "Debug lockups and hangs" 951 952config PANIC_ON_OOPS 953 bool "Panic on Oops" 954 help 955 Say Y here to enable the kernel to panic when it oopses. This 956 has the same effect as setting oops=panic on the kernel command 957 line. 958 959 This feature is useful to ensure that the kernel does not do 960 anything erroneous after an oops which could result in data 961 corruption or other issues. 962 963 Say N if unsure. 964 965config PANIC_ON_OOPS_VALUE 966 int 967 range 0 1 968 default 0 if !PANIC_ON_OOPS 969 default 1 if PANIC_ON_OOPS 970 971config PANIC_TIMEOUT 972 int "panic timeout" 973 default 0 974 help 975 Set the timeout value (in seconds) until a reboot occurs when the 976 the kernel panics. If n = 0, then we wait forever. A timeout 977 value n > 0 will wait n seconds before rebooting, while a timeout 978 value n < 0 will reboot immediately. 979 980config SCHED_DEBUG 981 bool "Collect scheduler debugging info" 982 depends on DEBUG_KERNEL && PROC_FS 983 default y 984 help 985 If you say Y here, the /proc/sched_debug file will be provided 986 that can help debug the scheduler. The runtime overhead of this 987 option is minimal. 988 989config SCHED_INFO 990 bool 991 default n 992 993config SCHEDSTATS 994 bool "Collect scheduler statistics" 995 depends on DEBUG_KERNEL && PROC_FS 996 select SCHED_INFO 997 help 998 If you say Y here, additional code will be inserted into the 999 scheduler and related routines to collect statistics about 1000 scheduler behavior and provide them in /proc/schedstat. These 1001 stats may be useful for both tuning and debugging the scheduler 1002 If you aren't debugging the scheduler or trying to tune a specific 1003 application, you can say N to avoid the very slight overhead 1004 this adds. 1005 1006config SCHED_STACK_END_CHECK 1007 bool "Detect stack corruption on calls to schedule()" 1008 depends on DEBUG_KERNEL 1009 default n 1010 help 1011 This option checks for a stack overrun on calls to schedule(). 1012 If the stack end location is found to be over written always panic as 1013 the content of the corrupted region can no longer be trusted. 1014 This is to ensure no erroneous behaviour occurs which could result in 1015 data corruption or a sporadic crash at a later stage once the region 1016 is examined. The runtime overhead introduced is minimal. 1017 1018config DEBUG_TIMEKEEPING 1019 bool "Enable extra timekeeping sanity checking" 1020 help 1021 This option will enable additional timekeeping sanity checks 1022 which may be helpful when diagnosing issues where timekeeping 1023 problems are suspected. 1024 1025 This may include checks in the timekeeping hotpaths, so this 1026 option may have a (very small) performance impact to some 1027 workloads. 1028 1029 If unsure, say N. 1030 1031config DEBUG_PREEMPT 1032 bool "Debug preemptible kernel" 1033 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 1034 default y 1035 help 1036 If you say Y here then the kernel will use a debug variant of the 1037 commonly used smp_processor_id() function and will print warnings 1038 if kernel code uses it in a preemption-unsafe way. Also, the kernel 1039 will detect preemption count underflows. 1040 1041menu "Lock Debugging (spinlocks, mutexes, etc...)" 1042 1043config LOCK_DEBUGGING_SUPPORT 1044 bool 1045 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1046 default y 1047 1048config PROVE_LOCKING 1049 bool "Lock debugging: prove locking correctness" 1050 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1051 select LOCKDEP 1052 select DEBUG_SPINLOCK 1053 select DEBUG_MUTEXES 1054 select DEBUG_RT_MUTEXES if RT_MUTEXES 1055 select DEBUG_RWSEMS if RWSEM_SPIN_ON_OWNER 1056 select DEBUG_WW_MUTEX_SLOWPATH 1057 select DEBUG_LOCK_ALLOC 1058 select TRACE_IRQFLAGS 1059 default n 1060 help 1061 This feature enables the kernel to prove that all locking 1062 that occurs in the kernel runtime is mathematically 1063 correct: that under no circumstance could an arbitrary (and 1064 not yet triggered) combination of observed locking 1065 sequences (on an arbitrary number of CPUs, running an 1066 arbitrary number of tasks and interrupt contexts) cause a 1067 deadlock. 1068 1069 In short, this feature enables the kernel to report locking 1070 related deadlocks before they actually occur. 1071 1072 The proof does not depend on how hard and complex a 1073 deadlock scenario would be to trigger: how many 1074 participant CPUs, tasks and irq-contexts would be needed 1075 for it to trigger. The proof also does not depend on 1076 timing: if a race and a resulting deadlock is possible 1077 theoretically (no matter how unlikely the race scenario 1078 is), it will be proven so and will immediately be 1079 reported by the kernel (once the event is observed that 1080 makes the deadlock theoretically possible). 1081 1082 If a deadlock is impossible (i.e. the locking rules, as 1083 observed by the kernel, are mathematically correct), the 1084 kernel reports nothing. 1085 1086 NOTE: this feature can also be enabled for rwlocks, mutexes 1087 and rwsems - in which case all dependencies between these 1088 different locking variants are observed and mapped too, and 1089 the proof of observed correctness is also maintained for an 1090 arbitrary combination of these separate locking variants. 1091 1092 For more details, see Documentation/locking/lockdep-design.txt. 1093 1094config LOCK_STAT 1095 bool "Lock usage statistics" 1096 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1097 select LOCKDEP 1098 select DEBUG_SPINLOCK 1099 select DEBUG_MUTEXES 1100 select DEBUG_RT_MUTEXES if RT_MUTEXES 1101 select DEBUG_LOCK_ALLOC 1102 default n 1103 help 1104 This feature enables tracking lock contention points 1105 1106 For more details, see Documentation/locking/lockstat.txt 1107 1108 This also enables lock events required by "perf lock", 1109 subcommand of perf. 1110 If you want to use "perf lock", you also need to turn on 1111 CONFIG_EVENT_TRACING. 1112 1113 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1114 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1115 1116config DEBUG_RT_MUTEXES 1117 bool "RT Mutex debugging, deadlock detection" 1118 depends on DEBUG_KERNEL && RT_MUTEXES 1119 help 1120 This allows rt mutex semantics violations and rt mutex related 1121 deadlocks (lockups) to be detected and reported automatically. 1122 1123config DEBUG_SPINLOCK 1124 bool "Spinlock and rw-lock debugging: basic checks" 1125 depends on DEBUG_KERNEL 1126 select UNINLINE_SPIN_UNLOCK 1127 help 1128 Say Y here and build SMP to catch missing spinlock initialization 1129 and certain other kinds of spinlock errors commonly made. This is 1130 best used in conjunction with the NMI watchdog so that spinlock 1131 deadlocks are also debuggable. 1132 1133config DEBUG_MUTEXES 1134 bool "Mutex debugging: basic checks" 1135 depends on DEBUG_KERNEL 1136 help 1137 This feature allows mutex semantics violations to be detected and 1138 reported. 1139 1140config DEBUG_WW_MUTEX_SLOWPATH 1141 bool "Wait/wound mutex debugging: Slowpath testing" 1142 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1143 select DEBUG_LOCK_ALLOC 1144 select DEBUG_SPINLOCK 1145 select DEBUG_MUTEXES 1146 help 1147 This feature enables slowpath testing for w/w mutex users by 1148 injecting additional -EDEADLK wound/backoff cases. Together with 1149 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 1150 will test all possible w/w mutex interface abuse with the 1151 exception of simply not acquiring all the required locks. 1152 Note that this feature can introduce significant overhead, so 1153 it really should not be enabled in a production or distro kernel, 1154 even a debug kernel. If you are a driver writer, enable it. If 1155 you are a distro, do not. 1156 1157config DEBUG_RWSEMS 1158 bool "RW Semaphore debugging: basic checks" 1159 depends on DEBUG_KERNEL && RWSEM_SPIN_ON_OWNER 1160 help 1161 This debugging feature allows mismatched rw semaphore locks and unlocks 1162 to be detected and reported. 1163 1164config DEBUG_LOCK_ALLOC 1165 bool "Lock debugging: detect incorrect freeing of live locks" 1166 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1167 select DEBUG_SPINLOCK 1168 select DEBUG_MUTEXES 1169 select DEBUG_RT_MUTEXES if RT_MUTEXES 1170 select LOCKDEP 1171 help 1172 This feature will check whether any held lock (spinlock, rwlock, 1173 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1174 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1175 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1176 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1177 held during task exit. 1178 1179config LOCKDEP 1180 bool 1181 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1182 select STACKTRACE 1183 select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86 1184 select KALLSYMS 1185 select KALLSYMS_ALL 1186 1187config LOCKDEP_SMALL 1188 bool 1189 1190config DEBUG_LOCKDEP 1191 bool "Lock dependency engine debugging" 1192 depends on DEBUG_KERNEL && LOCKDEP 1193 help 1194 If you say Y here, the lock dependency engine will do 1195 additional runtime checks to debug itself, at the price 1196 of more runtime overhead. 1197 1198config DEBUG_ATOMIC_SLEEP 1199 bool "Sleep inside atomic section checking" 1200 select PREEMPT_COUNT 1201 depends on DEBUG_KERNEL 1202 depends on !ARCH_NO_PREEMPT 1203 help 1204 If you say Y here, various routines which may sleep will become very 1205 noisy if they are called inside atomic sections: when a spinlock is 1206 held, inside an rcu read side critical section, inside preempt disabled 1207 sections, inside an interrupt, etc... 1208 1209config DEBUG_LOCKING_API_SELFTESTS 1210 bool "Locking API boot-time self-tests" 1211 depends on DEBUG_KERNEL 1212 help 1213 Say Y here if you want the kernel to run a short self-test during 1214 bootup. The self-test checks whether common types of locking bugs 1215 are detected by debugging mechanisms or not. (if you disable 1216 lock debugging then those bugs wont be detected of course.) 1217 The following locking APIs are covered: spinlocks, rwlocks, 1218 mutexes and rwsems. 1219 1220config LOCK_TORTURE_TEST 1221 tristate "torture tests for locking" 1222 depends on DEBUG_KERNEL 1223 select TORTURE_TEST 1224 help 1225 This option provides a kernel module that runs torture tests 1226 on kernel locking primitives. The kernel module may be built 1227 after the fact on the running kernel to be tested, if desired. 1228 1229 Say Y here if you want kernel locking-primitive torture tests 1230 to be built into the kernel. 1231 Say M if you want these torture tests to build as a module. 1232 Say N if you are unsure. 1233 1234config WW_MUTEX_SELFTEST 1235 tristate "Wait/wound mutex selftests" 1236 help 1237 This option provides a kernel module that runs tests on the 1238 on the struct ww_mutex locking API. 1239 1240 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction 1241 with this test harness. 1242 1243 Say M if you want these self tests to build as a module. 1244 Say N if you are unsure. 1245 1246endmenu # lock debugging 1247 1248config TRACE_IRQFLAGS 1249 bool 1250 help 1251 Enables hooks to interrupt enabling and disabling for 1252 either tracing or lock debugging. 1253 1254config STACKTRACE 1255 bool "Stack backtrace support" 1256 depends on STACKTRACE_SUPPORT 1257 help 1258 This option causes the kernel to create a /proc/pid/stack for 1259 every process, showing its current stack trace. 1260 It is also used by various kernel debugging features that require 1261 stack trace generation. 1262 1263config WARN_ALL_UNSEEDED_RANDOM 1264 bool "Warn for all uses of unseeded randomness" 1265 default n 1266 help 1267 Some parts of the kernel contain bugs relating to their use of 1268 cryptographically secure random numbers before it's actually possible 1269 to generate those numbers securely. This setting ensures that these 1270 flaws don't go unnoticed, by enabling a message, should this ever 1271 occur. This will allow people with obscure setups to know when things 1272 are going wrong, so that they might contact developers about fixing 1273 it. 1274 1275 Unfortunately, on some models of some architectures getting 1276 a fully seeded CRNG is extremely difficult, and so this can 1277 result in dmesg getting spammed for a surprisingly long 1278 time. This is really bad from a security perspective, and 1279 so architecture maintainers really need to do what they can 1280 to get the CRNG seeded sooner after the system is booted. 1281 However, since users cannot do anything actionable to 1282 address this, by default this option is disabled. 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 bool "Fault-injections of functions" 1516 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES 1517 help 1518 Add fault injections into various functions that are annotated with 1519 ALLOW_ERROR_INJECTION() in the kernel. BPF may also modify the return 1520 value of theses functions. This is useful to test error paths of code. 1521 1522 If unsure, say N 1523 1524config FAULT_INJECTION 1525 bool "Fault-injection framework" 1526 depends on DEBUG_KERNEL 1527 help 1528 Provide fault-injection framework. 1529 For more details, see Documentation/fault-injection/. 1530 1531config FAILSLAB 1532 bool "Fault-injection capability for kmalloc" 1533 depends on FAULT_INJECTION 1534 depends on SLAB || SLUB 1535 help 1536 Provide fault-injection capability for kmalloc. 1537 1538config FAIL_PAGE_ALLOC 1539 bool "Fault-injection capabilitiy for alloc_pages()" 1540 depends on FAULT_INJECTION 1541 help 1542 Provide fault-injection capability for alloc_pages(). 1543 1544config FAIL_MAKE_REQUEST 1545 bool "Fault-injection capability for disk IO" 1546 depends on FAULT_INJECTION && BLOCK 1547 help 1548 Provide fault-injection capability for disk IO. 1549 1550config FAIL_IO_TIMEOUT 1551 bool "Fault-injection capability for faking disk interrupts" 1552 depends on FAULT_INJECTION && BLOCK 1553 help 1554 Provide fault-injection capability on end IO handling. This 1555 will make the block layer "forget" an interrupt as configured, 1556 thus exercising the error handling. 1557 1558 Only works with drivers that use the generic timeout handling, 1559 for others it wont do anything. 1560 1561config FAIL_FUTEX 1562 bool "Fault-injection capability for futexes" 1563 select DEBUG_FS 1564 depends on FAULT_INJECTION && FUTEX 1565 help 1566 Provide fault-injection capability for futexes. 1567 1568config FAULT_INJECTION_DEBUG_FS 1569 bool "Debugfs entries for fault-injection capabilities" 1570 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1571 help 1572 Enable configuration of fault-injection capabilities via debugfs. 1573 1574config FAIL_FUNCTION 1575 bool "Fault-injection capability for functions" 1576 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION 1577 help 1578 Provide function-based fault-injection capability. 1579 This will allow you to override a specific function with a return 1580 with given return value. As a result, function caller will see 1581 an error value and have to handle it. This is useful to test the 1582 error handling in various subsystems. 1583 1584config FAIL_MMC_REQUEST 1585 bool "Fault-injection capability for MMC IO" 1586 depends on FAULT_INJECTION_DEBUG_FS && MMC 1587 help 1588 Provide fault-injection capability for MMC IO. 1589 This will make the mmc core return data errors. This is 1590 useful to test the error handling in the mmc block device 1591 and to test how the mmc host driver handles retries from 1592 the block device. 1593 1594config FAULT_INJECTION_STACKTRACE_FILTER 1595 bool "stacktrace filter for fault-injection capabilities" 1596 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1597 depends on !X86_64 1598 select STACKTRACE 1599 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86 1600 help 1601 Provide stacktrace filter for fault-injection capabilities 1602 1603config LATENCYTOP 1604 bool "Latency measuring infrastructure" 1605 depends on DEBUG_KERNEL 1606 depends on STACKTRACE_SUPPORT 1607 depends on PROC_FS 1608 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86 1609 select KALLSYMS 1610 select KALLSYMS_ALL 1611 select STACKTRACE 1612 select SCHEDSTATS 1613 select SCHED_DEBUG 1614 help 1615 Enable this option if you want to use the LatencyTOP tool 1616 to find out which userspace is blocking on what kernel operations. 1617 1618source kernel/trace/Kconfig 1619 1620config PROVIDE_OHCI1394_DMA_INIT 1621 bool "Remote debugging over FireWire early on boot" 1622 depends on PCI && X86 1623 help 1624 If you want to debug problems which hang or crash the kernel early 1625 on boot and the crashing machine has a FireWire port, you can use 1626 this feature to remotely access the memory of the crashed machine 1627 over FireWire. This employs remote DMA as part of the OHCI1394 1628 specification which is now the standard for FireWire controllers. 1629 1630 With remote DMA, you can monitor the printk buffer remotely using 1631 firescope and access all memory below 4GB using fireproxy from gdb. 1632 Even controlling a kernel debugger is possible using remote DMA. 1633 1634 Usage: 1635 1636 If ohci1394_dma=early is used as boot parameter, it will initialize 1637 all OHCI1394 controllers which are found in the PCI config space. 1638 1639 As all changes to the FireWire bus such as enabling and disabling 1640 devices cause a bus reset and thereby disable remote DMA for all 1641 devices, be sure to have the cable plugged and FireWire enabled on 1642 the debugging host before booting the debug target for debugging. 1643 1644 This code (~1k) is freed after boot. By then, the firewire stack 1645 in charge of the OHCI-1394 controllers should be used instead. 1646 1647 See Documentation/debugging-via-ohci1394.txt for more information. 1648 1649config DMA_API_DEBUG 1650 bool "Enable debugging of DMA-API usage" 1651 select NEED_DMA_MAP_STATE 1652 help 1653 Enable this option to debug the use of the DMA API by device drivers. 1654 With this option you will be able to detect common bugs in device 1655 drivers like double-freeing of DMA mappings or freeing mappings that 1656 were never allocated. 1657 1658 This also attempts to catch cases where a page owned by DMA is 1659 accessed by the cpu in a way that could cause data corruption. For 1660 example, this enables cow_user_page() to check that the source page is 1661 not undergoing DMA. 1662 1663 This option causes a performance degradation. Use only if you want to 1664 debug device drivers and dma interactions. 1665 1666 If unsure, say N. 1667 1668config DMA_API_DEBUG_SG 1669 bool "Debug DMA scatter-gather usage" 1670 default y 1671 depends on DMA_API_DEBUG 1672 help 1673 Perform extra checking that callers of dma_map_sg() have respected the 1674 appropriate segment length/boundary limits for the given device when 1675 preparing DMA scatterlists. 1676 1677 This is particularly likely to have been overlooked in cases where the 1678 dma_map_sg() API is used for general bulk mapping of pages rather than 1679 preparing literal scatter-gather descriptors, where there is a risk of 1680 unexpected behaviour from DMA API implementations if the scatterlist 1681 is technically out-of-spec. 1682 1683 If unsure, say N. 1684 1685menuconfig RUNTIME_TESTING_MENU 1686 bool "Runtime Testing" 1687 def_bool y 1688 1689if RUNTIME_TESTING_MENU 1690 1691config LKDTM 1692 tristate "Linux Kernel Dump Test Tool Module" 1693 depends on DEBUG_FS 1694 depends on BLOCK 1695 help 1696 This module enables testing of the different dumping mechanisms by 1697 inducing system failures at predefined crash points. 1698 If you don't need it: say N 1699 Choose M here to compile this code as a module. The module will be 1700 called lkdtm. 1701 1702 Documentation on how to use the module can be found in 1703 Documentation/fault-injection/provoke-crashes.txt 1704 1705config TEST_LIST_SORT 1706 tristate "Linked list sorting test" 1707 depends on DEBUG_KERNEL || m 1708 help 1709 Enable this to turn on 'list_sort()' function test. This test is 1710 executed only once during system boot (so affects only boot time), 1711 or at module load time. 1712 1713 If unsure, say N. 1714 1715config TEST_SORT 1716 tristate "Array-based sort test" 1717 depends on DEBUG_KERNEL || m 1718 help 1719 This option enables the self-test function of 'sort()' at boot, 1720 or at module load time. 1721 1722 If unsure, say N. 1723 1724config KPROBES_SANITY_TEST 1725 bool "Kprobes sanity tests" 1726 depends on DEBUG_KERNEL 1727 depends on KPROBES 1728 help 1729 This option provides for testing basic kprobes functionality on 1730 boot. Samples of kprobe and kretprobe are inserted and 1731 verified for functionality. 1732 1733 Say N if you are unsure. 1734 1735config BACKTRACE_SELF_TEST 1736 tristate "Self test for the backtrace code" 1737 depends on DEBUG_KERNEL 1738 help 1739 This option provides a kernel module that can be used to test 1740 the kernel stack backtrace code. This option is not useful 1741 for distributions or general kernels, but only for kernel 1742 developers working on architecture code. 1743 1744 Note that if you want to also test saved backtraces, you will 1745 have to enable STACKTRACE as well. 1746 1747 Say N if you are unsure. 1748 1749config RBTREE_TEST 1750 tristate "Red-Black tree test" 1751 depends on DEBUG_KERNEL 1752 help 1753 A benchmark measuring the performance of the rbtree library. 1754 Also includes rbtree invariant checks. 1755 1756config INTERVAL_TREE_TEST 1757 tristate "Interval tree test" 1758 depends on DEBUG_KERNEL 1759 select INTERVAL_TREE 1760 help 1761 A benchmark measuring the performance of the interval tree library 1762 1763config PERCPU_TEST 1764 tristate "Per cpu operations test" 1765 depends on m && DEBUG_KERNEL 1766 help 1767 Enable this option to build test module which validates per-cpu 1768 operations. 1769 1770 If unsure, say N. 1771 1772config ATOMIC64_SELFTEST 1773 tristate "Perform an atomic64_t self-test" 1774 help 1775 Enable this option to test the atomic64_t functions at boot or 1776 at module load time. 1777 1778 If unsure, say N. 1779 1780config ASYNC_RAID6_TEST 1781 tristate "Self test for hardware accelerated raid6 recovery" 1782 depends on ASYNC_RAID6_RECOV 1783 select ASYNC_MEMCPY 1784 ---help--- 1785 This is a one-shot self test that permutes through the 1786 recovery of all the possible two disk failure scenarios for a 1787 N-disk array. Recovery is performed with the asynchronous 1788 raid6 recovery routines, and will optionally use an offload 1789 engine if one is available. 1790 1791 If unsure, say N. 1792 1793config TEST_HEXDUMP 1794 tristate "Test functions located in the hexdump module at runtime" 1795 1796config TEST_STRING_HELPERS 1797 tristate "Test functions located in the string_helpers module at runtime" 1798 1799config TEST_KSTRTOX 1800 tristate "Test kstrto*() family of functions at runtime" 1801 1802config TEST_PRINTF 1803 tristate "Test printf() family of functions at runtime" 1804 1805config TEST_BITMAP 1806 tristate "Test bitmap_*() family of functions at runtime" 1807 help 1808 Enable this option to test the bitmap functions at boot. 1809 1810 If unsure, say N. 1811 1812config TEST_BITFIELD 1813 tristate "Test bitfield functions at runtime" 1814 help 1815 Enable this option to test the bitfield functions at boot. 1816 1817 If unsure, say N. 1818 1819config TEST_UUID 1820 tristate "Test functions located in the uuid module at runtime" 1821 1822config TEST_OVERFLOW 1823 tristate "Test check_*_overflow() functions at runtime" 1824 1825config TEST_RHASHTABLE 1826 tristate "Perform selftest on resizable hash table" 1827 help 1828 Enable this option to test the rhashtable functions at boot. 1829 1830 If unsure, say N. 1831 1832config TEST_HASH 1833 tristate "Perform selftest on hash functions" 1834 help 1835 Enable this option to test the kernel's integer (<linux/hash.h>), 1836 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>) 1837 hash functions on boot (or module load). 1838 1839 This is intended to help people writing architecture-specific 1840 optimized versions. If unsure, say N. 1841 1842config TEST_IDA 1843 tristate "Perform selftest on IDA functions" 1844 1845config TEST_PARMAN 1846 tristate "Perform selftest on priority array manager" 1847 depends on PARMAN 1848 help 1849 Enable this option to test priority array manager on boot 1850 (or module load). 1851 1852 If unsure, say N. 1853 1854config TEST_LKM 1855 tristate "Test module loading with 'hello world' module" 1856 depends on m 1857 help 1858 This builds the "test_module" module that emits "Hello, world" 1859 on printk when loaded. It is designed to be used for basic 1860 evaluation of the module loading subsystem (for example when 1861 validating module verification). It lacks any extra dependencies, 1862 and will not normally be loaded by the system unless explicitly 1863 requested by name. 1864 1865 If unsure, say N. 1866 1867config TEST_USER_COPY 1868 tristate "Test user/kernel boundary protections" 1869 depends on m 1870 help 1871 This builds the "test_user_copy" module that runs sanity checks 1872 on the copy_to/from_user infrastructure, making sure basic 1873 user/kernel boundary testing is working. If it fails to load, 1874 a regression has been detected in the user/kernel memory boundary 1875 protections. 1876 1877 If unsure, say N. 1878 1879config TEST_BPF 1880 tristate "Test BPF filter functionality" 1881 depends on m && NET 1882 help 1883 This builds the "test_bpf" module that runs various test vectors 1884 against the BPF interpreter or BPF JIT compiler depending on the 1885 current setting. This is in particular useful for BPF JIT compiler 1886 development, but also to run regression tests against changes in 1887 the interpreter code. It also enables test stubs for eBPF maps and 1888 verifier used by user space verifier testsuite. 1889 1890 If unsure, say N. 1891 1892config FIND_BIT_BENCHMARK 1893 tristate "Test find_bit functions" 1894 help 1895 This builds the "test_find_bit" module that measure find_*_bit() 1896 functions performance. 1897 1898 If unsure, say N. 1899 1900config TEST_FIRMWARE 1901 tristate "Test firmware loading via userspace interface" 1902 depends on FW_LOADER 1903 help 1904 This builds the "test_firmware" module that creates a userspace 1905 interface for testing firmware loading. This can be used to 1906 control the triggering of firmware loading without needing an 1907 actual firmware-using device. The contents can be rechecked by 1908 userspace. 1909 1910 If unsure, say N. 1911 1912config TEST_SYSCTL 1913 tristate "sysctl test driver" 1914 depends on PROC_SYSCTL 1915 help 1916 This builds the "test_sysctl" module. This driver enables to test the 1917 proc sysctl interfaces available to drivers safely without affecting 1918 production knobs which might alter system functionality. 1919 1920 If unsure, say N. 1921 1922config TEST_UDELAY 1923 tristate "udelay test driver" 1924 help 1925 This builds the "udelay_test" module that helps to make sure 1926 that udelay() is working properly. 1927 1928 If unsure, say N. 1929 1930config TEST_STATIC_KEYS 1931 tristate "Test static keys" 1932 depends on m 1933 help 1934 Test the static key interfaces. 1935 1936 If unsure, say N. 1937 1938config TEST_KMOD 1939 tristate "kmod stress tester" 1940 depends on m 1941 depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS 1942 depends on NETDEVICES && NET_CORE && INET # for TUN 1943 depends on BLOCK 1944 select TEST_LKM 1945 select XFS_FS 1946 select TUN 1947 select BTRFS_FS 1948 help 1949 Test the kernel's module loading mechanism: kmod. kmod implements 1950 support to load modules using the Linux kernel's usermode helper. 1951 This test provides a series of tests against kmod. 1952 1953 Although technically you can either build test_kmod as a module or 1954 into the kernel we disallow building it into the kernel since 1955 it stress tests request_module() and this will very likely cause 1956 some issues by taking over precious threads available from other 1957 module load requests, ultimately this could be fatal. 1958 1959 To run tests run: 1960 1961 tools/testing/selftests/kmod/kmod.sh --help 1962 1963 If unsure, say N. 1964 1965config TEST_DEBUG_VIRTUAL 1966 tristate "Test CONFIG_DEBUG_VIRTUAL feature" 1967 depends on DEBUG_VIRTUAL 1968 help 1969 Test the kernel's ability to detect incorrect calls to 1970 virt_to_phys() done against the non-linear part of the 1971 kernel's virtual address map. 1972 1973 If unsure, say N. 1974 1975endif # RUNTIME_TESTING_MENU 1976 1977config MEMTEST 1978 bool "Memtest" 1979 depends on HAVE_MEMBLOCK 1980 ---help--- 1981 This option adds a kernel parameter 'memtest', which allows memtest 1982 to be set. 1983 memtest=0, mean disabled; -- default 1984 memtest=1, mean do 1 test pattern; 1985 ... 1986 memtest=17, mean do 17 test patterns. 1987 If you are unsure how to answer this question, answer N. 1988 1989config BUG_ON_DATA_CORRUPTION 1990 bool "Trigger a BUG when data corruption is detected" 1991 select DEBUG_LIST 1992 help 1993 Select this option if the kernel should BUG when it encounters 1994 data corruption in kernel memory structures when they get checked 1995 for validity. 1996 1997 If unsure, say N. 1998 1999source "samples/Kconfig" 2000 2001source "lib/Kconfig.kgdb" 2002 2003source "lib/Kconfig.ubsan" 2004 2005config ARCH_HAS_DEVMEM_IS_ALLOWED 2006 bool 2007 2008config STRICT_DEVMEM 2009 bool "Filter access to /dev/mem" 2010 depends on MMU && DEVMEM 2011 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 2012 default y if PPC || X86 || ARM64 2013 ---help--- 2014 If this option is disabled, you allow userspace (root) access to all 2015 of memory, including kernel and userspace memory. Accidental 2016 access to this is obviously disastrous, but specific access can 2017 be used by people debugging the kernel. Note that with PAT support 2018 enabled, even in this case there are restrictions on /dev/mem 2019 use due to the cache aliasing requirements. 2020 2021 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 2022 file only allows userspace access to PCI space and the BIOS code and 2023 data regions. This is sufficient for dosemu and X and all common 2024 users of /dev/mem. 2025 2026 If in doubt, say Y. 2027 2028config IO_STRICT_DEVMEM 2029 bool "Filter I/O access to /dev/mem" 2030 depends on STRICT_DEVMEM 2031 ---help--- 2032 If this option is disabled, you allow userspace (root) access to all 2033 io-memory regardless of whether a driver is actively using that 2034 range. Accidental access to this is obviously disastrous, but 2035 specific access can be used by people debugging kernel drivers. 2036 2037 If this option is switched on, the /dev/mem file only allows 2038 userspace access to *idle* io-memory ranges (see /proc/iomem) This 2039 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 2040 if the driver using a given range cannot be disabled. 2041 2042 If in doubt, say Y. 2043 2044source "arch/$(SRCARCH)/Kconfig.debug" 2045 2046endmenu # Kernel hacking 2047