1menu "printk and dmesg options" 2 3config PRINTK_TIME 4 bool "Show timing information on printks" 5 depends on PRINTK 6 help 7 Selecting this option causes time stamps of the printk() 8 messages to be added to the output of the syslog() system 9 call and at the console. 10 11 The timestamp is always recorded internally, and exported 12 to /dev/kmsg. This flag just specifies if the timestamp should 13 be included, not that the timestamp is recorded. 14 15 The behavior is also controlled by the kernel command line 16 parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst 17 18config CONSOLE_LOGLEVEL_DEFAULT 19 int "Default console loglevel (1-15)" 20 range 1 15 21 default "7" 22 help 23 Default loglevel to determine what will be printed on the console. 24 25 Setting a default here is equivalent to passing in loglevel=<x> in 26 the kernel bootargs. loglevel=<x> continues to override whatever 27 value is specified here as well. 28 29 Note: This does not affect the log level of un-prefixed printk() 30 usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT 31 option. 32 33config MESSAGE_LOGLEVEL_DEFAULT 34 int "Default message log level (1-7)" 35 range 1 7 36 default "4" 37 help 38 Default log level for printk statements with no specified priority. 39 40 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks 41 that are auditing their logs closely may want to set it to a lower 42 priority. 43 44 Note: This does not affect what message level gets printed on the console 45 by default. To change that, use loglevel=<x> in the kernel bootargs, 46 or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value. 47 48config BOOT_PRINTK_DELAY 49 bool "Delay each boot printk message by N milliseconds" 50 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 51 help 52 This build option allows you to read kernel boot messages 53 by inserting a short delay after each one. The delay is 54 specified in milliseconds on the kernel command line, 55 using "boot_delay=N". 56 57 It is likely that you would also need to use "lpj=M" to preset 58 the "loops per jiffie" value. 59 See a previous boot log for the "lpj" value to use for your 60 system, and then set "lpj=M" before setting "boot_delay=N". 61 NOTE: Using this option may adversely affect SMP systems. 62 I.e., processors other than the first one may not boot up. 63 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect 64 what it believes to be lockup conditions. 65 66config DYNAMIC_DEBUG 67 bool "Enable dynamic printk() support" 68 default n 69 depends on PRINTK 70 depends on DEBUG_FS 71 help 72 73 Compiles debug level messages into the kernel, which would not 74 otherwise be available at runtime. These messages can then be 75 enabled/disabled based on various levels of scope - per source file, 76 function, module, format string, and line number. This mechanism 77 implicitly compiles in all pr_debug() and dev_dbg() calls, which 78 enlarges the kernel text size by about 2%. 79 80 If a source file is compiled with DEBUG flag set, any 81 pr_debug() calls in it are enabled by default, but can be 82 disabled at runtime as below. Note that DEBUG flag is 83 turned on by many CONFIG_*DEBUG* options. 84 85 Usage: 86 87 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 88 which is contained in the 'debugfs' filesystem. Thus, the debugfs 89 filesystem must first be mounted before making use of this feature. 90 We refer the control file as: <debugfs>/dynamic_debug/control. This 91 file contains a list of the debug statements that can be enabled. The 92 format for each line of the file is: 93 94 filename:lineno [module]function flags format 95 96 filename : source file of the debug statement 97 lineno : line number of the debug statement 98 module : module that contains the debug statement 99 function : function that contains the debug statement 100 flags : '=p' means the line is turned 'on' for printing 101 format : the format used for the debug statement 102 103 From a live system: 104 105 nullarbor:~ # cat <debugfs>/dynamic_debug/control 106 # filename:lineno [module]function flags format 107 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012" 108 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012" 109 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012" 110 111 Example usage: 112 113 // enable the message at line 1603 of file svcsock.c 114 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 115 <debugfs>/dynamic_debug/control 116 117 // enable all the messages in file svcsock.c 118 nullarbor:~ # echo -n 'file svcsock.c +p' > 119 <debugfs>/dynamic_debug/control 120 121 // enable all the messages in the NFS server module 122 nullarbor:~ # echo -n 'module nfsd +p' > 123 <debugfs>/dynamic_debug/control 124 125 // enable all 12 messages in the function svc_process() 126 nullarbor:~ # echo -n 'func svc_process +p' > 127 <debugfs>/dynamic_debug/control 128 129 // disable all 12 messages in the function svc_process() 130 nullarbor:~ # echo -n 'func svc_process -p' > 131 <debugfs>/dynamic_debug/control 132 133 See Documentation/dynamic-debug-howto.txt for additional information. 134 135endmenu # "printk and dmesg options" 136 137menu "Compile-time checks and compiler options" 138 139config DEBUG_INFO 140 bool "Compile the kernel with debug info" 141 depends on DEBUG_KERNEL && !COMPILE_TEST 142 help 143 If you say Y here the resulting kernel image will include 144 debugging info resulting in a larger kernel image. 145 This adds debug symbols to the kernel and modules (gcc -g), and 146 is needed if you intend to use kernel crashdump or binary object 147 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 148 Say Y here only if you plan to debug the kernel. 149 150 If unsure, say N. 151 152config DEBUG_INFO_REDUCED 153 bool "Reduce debugging information" 154 depends on DEBUG_INFO 155 help 156 If you say Y here gcc is instructed to generate less debugging 157 information for structure types. This means that tools that 158 need full debugging information (like kgdb or systemtap) won't 159 be happy. But if you merely need debugging information to 160 resolve line numbers there is no loss. Advantage is that 161 build directory object sizes shrink dramatically over a full 162 DEBUG_INFO build and compile times are reduced too. 163 Only works with newer gcc versions. 164 165config DEBUG_INFO_SPLIT 166 bool "Produce split debuginfo in .dwo files" 167 depends on DEBUG_INFO 168 help 169 Generate debug info into separate .dwo files. This significantly 170 reduces the build directory size for builds with DEBUG_INFO, 171 because it stores the information only once on disk in .dwo 172 files instead of multiple times in object files and executables. 173 In addition the debug information is also compressed. 174 175 Requires recent gcc (4.7+) and recent gdb/binutils. 176 Any tool that packages or reads debug information would need 177 to know about the .dwo files and include them. 178 Incompatible with older versions of ccache. 179 180config DEBUG_INFO_DWARF4 181 bool "Generate dwarf4 debuginfo" 182 depends on DEBUG_INFO 183 help 184 Generate dwarf4 debug info. This requires recent versions 185 of gcc and gdb. It makes the debug information larger. 186 But it significantly improves the success of resolving 187 variables in gdb on optimized code. 188 189config GDB_SCRIPTS 190 bool "Provide GDB scripts for kernel debugging" 191 depends on DEBUG_INFO 192 help 193 This creates the required links to GDB helper scripts in the 194 build directory. If you load vmlinux into gdb, the helper 195 scripts will be automatically imported by gdb as well, and 196 additional functions are available to analyze a Linux kernel 197 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst 198 for further details. 199 200config ENABLE_WARN_DEPRECATED 201 bool "Enable __deprecated logic" 202 default y 203 help 204 Enable the __deprecated logic in the kernel build. 205 Disable this to suppress the "warning: 'foo' is deprecated 206 (declared at kernel/power/somefile.c:1234)" messages. 207 208config ENABLE_MUST_CHECK 209 bool "Enable __must_check logic" 210 default y 211 help 212 Enable the __must_check logic in the kernel build. Disable this to 213 suppress the "warning: ignoring return value of 'foo', declared with 214 attribute warn_unused_result" messages. 215 216config FRAME_WARN 217 int "Warn for stack frames larger than (needs gcc 4.4)" 218 range 0 8192 219 default 0 if KASAN 220 default 2048 if GCC_PLUGIN_LATENT_ENTROPY 221 default 1024 if !64BIT 222 default 2048 if 64BIT 223 help 224 Tell gcc to warn at build time for stack frames larger than this. 225 Setting this too low will cause a lot of warnings. 226 Setting it to 0 disables the warning. 227 Requires gcc 4.4 228 229config STRIP_ASM_SYMS 230 bool "Strip assembler-generated symbols during link" 231 default n 232 help 233 Strip internal assembler-generated symbols during a link (symbols 234 that look like '.Lxxx') so they don't pollute the output of 235 get_wchan() and suchlike. 236 237config READABLE_ASM 238 bool "Generate readable assembler code" 239 depends on DEBUG_KERNEL 240 help 241 Disable some compiler optimizations that tend to generate human unreadable 242 assembler output. This may make the kernel slightly slower, but it helps 243 to keep kernel developers who have to stare a lot at assembler listings 244 sane. 245 246config UNUSED_SYMBOLS 247 bool "Enable unused/obsolete exported symbols" 248 default y if X86 249 help 250 Unused but exported symbols make the kernel needlessly bigger. For 251 that reason most of these unused exports will soon be removed. This 252 option is provided temporarily to provide a transition period in case 253 some external kernel module needs one of these symbols anyway. If you 254 encounter such a case in your module, consider if you are actually 255 using the right API. (rationale: since nobody in the kernel is using 256 this in a module, there is a pretty good chance it's actually the 257 wrong interface to use). If you really need the symbol, please send a 258 mail to the linux kernel mailing list mentioning the symbol and why 259 you really need it, and what the merge plan to the mainline kernel for 260 your module is. 261 262config PAGE_OWNER 263 bool "Track page owner" 264 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 265 select DEBUG_FS 266 select STACKTRACE 267 select STACKDEPOT 268 select PAGE_EXTENSION 269 help 270 This keeps track of what call chain is the owner of a page, may 271 help to find bare alloc_page(s) leaks. Even if you include this 272 feature on your build, it is disabled in default. You should pass 273 "page_owner=on" to boot parameter in order to enable it. Eats 274 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 275 for user-space helper. 276 277 If unsure, say N. 278 279config DEBUG_FS 280 bool "Debug Filesystem" 281 select SRCU 282 help 283 debugfs is a virtual file system that kernel developers use to put 284 debugging files into. Enable this option to be able to read and 285 write to these files. 286 287 For detailed documentation on the debugfs API, see 288 Documentation/DocBook/filesystems. 289 290 If unsure, say N. 291 292config HEADERS_CHECK 293 bool "Run 'make headers_check' when building vmlinux" 294 depends on !UML 295 help 296 This option will extract the user-visible kernel headers whenever 297 building the kernel, and will run basic sanity checks on them to 298 ensure that exported files do not attempt to include files which 299 were not exported, etc. 300 301 If you're making modifications to header files which are 302 relevant for userspace, say 'Y', and check the headers 303 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 304 your build tree), to make sure they're suitable. 305 306config DEBUG_SECTION_MISMATCH 307 bool "Enable full Section mismatch analysis" 308 help 309 The section mismatch analysis checks if there are illegal 310 references from one section to another section. 311 During linktime or runtime, some sections are dropped; 312 any use of code/data previously in these sections would 313 most likely result in an oops. 314 In the code, functions and variables are annotated with 315 __init,, etc. (see the full list in include/linux/init.h), 316 which results in the code/data being placed in specific sections. 317 The section mismatch analysis is always performed after a full 318 kernel build, and enabling this option causes the following 319 additional steps to occur: 320 - Add the option -fno-inline-functions-called-once to gcc commands. 321 When inlining a function annotated with __init in a non-init 322 function, we would lose the section information and thus 323 the analysis would not catch the illegal reference. 324 This option tells gcc to inline less (but it does result in 325 a larger kernel). 326 - Run the section mismatch analysis for each module/built-in.o file. 327 When we run the section mismatch analysis on vmlinux.o, we 328 lose valuable information about where the mismatch was 329 introduced. 330 Running the analysis for each module/built-in.o file 331 tells where the mismatch happens much closer to the 332 source. The drawback is that the same mismatch is 333 reported at least twice. 334 - Enable verbose reporting from modpost in order to help resolve 335 the section mismatches that are reported. 336 337config SECTION_MISMATCH_WARN_ONLY 338 bool "Make section mismatch errors non-fatal" 339 default y 340 help 341 If you say N here, the build process will fail if there are any 342 section mismatch, instead of just throwing warnings. 343 344 If unsure, say Y. 345 346# 347# Select this config option from the architecture Kconfig, if it 348# is preferred to always offer frame pointers as a config 349# option on the architecture (regardless of KERNEL_DEBUG): 350# 351config ARCH_WANT_FRAME_POINTERS 352 bool 353 help 354 355config FRAME_POINTER 356 bool "Compile the kernel with frame pointers" 357 depends on DEBUG_KERNEL && \ 358 (CRIS || M68K || FRV || UML || \ 359 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \ 360 ARCH_WANT_FRAME_POINTERS 361 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 362 help 363 If you say Y here the resulting kernel image will be slightly 364 larger and slower, but it gives very useful debugging information 365 in case of kernel bugs. (precise oopses/stacktraces/warnings) 366 367config STACK_VALIDATION 368 bool "Compile-time stack metadata validation" 369 depends on HAVE_STACK_VALIDATION 370 default n 371 help 372 Add compile-time checks to validate stack metadata, including frame 373 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure 374 that runtime stack traces are more reliable. 375 376 For more information, see 377 tools/objtool/Documentation/stack-validation.txt. 378 379config DEBUG_FORCE_WEAK_PER_CPU 380 bool "Force weak per-cpu definitions" 381 depends on DEBUG_KERNEL 382 help 383 s390 and alpha require percpu variables in modules to be 384 defined weak to work around addressing range issue which 385 puts the following two restrictions on percpu variable 386 definitions. 387 388 1. percpu symbols must be unique whether static or not 389 2. percpu variables can't be defined inside a function 390 391 To ensure that generic code follows the above rules, this 392 option forces all percpu variables to be defined as weak. 393 394endmenu # "Compiler options" 395 396config MAGIC_SYSRQ 397 bool "Magic SysRq key" 398 depends on !UML 399 help 400 If you say Y here, you will have some control over the system even 401 if the system crashes for example during kernel debugging (e.g., you 402 will be able to flush the buffer cache to disk, reboot the system 403 immediately or dump some status information). This is accomplished 404 by pressing various keys while holding SysRq (Alt+PrintScreen). It 405 also works on a serial console (on PC hardware at least), if you 406 send a BREAK and then within 5 seconds a command keypress. The 407 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 408 unless you really know what this hack does. 409 410config MAGIC_SYSRQ_DEFAULT_ENABLE 411 hex "Enable magic SysRq key functions by default" 412 depends on MAGIC_SYSRQ 413 default 0x1 414 help 415 Specifies which SysRq key functions are enabled by default. 416 This may be set to 1 or 0 to enable or disable them all, or 417 to a bitmask as described in Documentation/sysrq.txt. 418 419config DEBUG_KERNEL 420 bool "Kernel debugging" 421 help 422 Say Y here if you are developing drivers or trying to debug and 423 identify kernel problems. 424 425menu "Memory Debugging" 426 427source mm/Kconfig.debug 428 429config DEBUG_OBJECTS 430 bool "Debug object operations" 431 depends on DEBUG_KERNEL 432 help 433 If you say Y here, additional code will be inserted into the 434 kernel to track the life time of various objects and validate 435 the operations on those objects. 436 437config DEBUG_OBJECTS_SELFTEST 438 bool "Debug objects selftest" 439 depends on DEBUG_OBJECTS 440 help 441 This enables the selftest of the object debug code. 442 443config DEBUG_OBJECTS_FREE 444 bool "Debug objects in freed memory" 445 depends on DEBUG_OBJECTS 446 help 447 This enables checks whether a k/v free operation frees an area 448 which contains an object which has not been deactivated 449 properly. This can make kmalloc/kfree-intensive workloads 450 much slower. 451 452config DEBUG_OBJECTS_TIMERS 453 bool "Debug timer objects" 454 depends on DEBUG_OBJECTS 455 help 456 If you say Y here, additional code will be inserted into the 457 timer routines to track the life time of timer objects and 458 validate the timer operations. 459 460config DEBUG_OBJECTS_WORK 461 bool "Debug work objects" 462 depends on DEBUG_OBJECTS 463 help 464 If you say Y here, additional code will be inserted into the 465 work queue routines to track the life time of work objects and 466 validate the work operations. 467 468config DEBUG_OBJECTS_RCU_HEAD 469 bool "Debug RCU callbacks objects" 470 depends on DEBUG_OBJECTS 471 help 472 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 473 474config DEBUG_OBJECTS_PERCPU_COUNTER 475 bool "Debug percpu counter objects" 476 depends on DEBUG_OBJECTS 477 help 478 If you say Y here, additional code will be inserted into the 479 percpu counter routines to track the life time of percpu counter 480 objects and validate the percpu counter operations. 481 482config DEBUG_OBJECTS_ENABLE_DEFAULT 483 int "debug_objects bootup default value (0-1)" 484 range 0 1 485 default "1" 486 depends on DEBUG_OBJECTS 487 help 488 Debug objects boot parameter default value 489 490config DEBUG_SLAB 491 bool "Debug slab memory allocations" 492 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 493 help 494 Say Y here to have the kernel do limited verification on memory 495 allocation as well as poisoning memory on free to catch use of freed 496 memory. This can make kmalloc/kfree-intensive workloads much slower. 497 498config DEBUG_SLAB_LEAK 499 bool "Memory leak debugging" 500 depends on DEBUG_SLAB 501 502config SLUB_DEBUG_ON 503 bool "SLUB debugging on by default" 504 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 505 default n 506 help 507 Boot with debugging on by default. SLUB boots by default with 508 the runtime debug capabilities switched off. Enabling this is 509 equivalent to specifying the "slub_debug" parameter on boot. 510 There is no support for more fine grained debug control like 511 possible with slub_debug=xxx. SLUB debugging may be switched 512 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 513 "slub_debug=-". 514 515config SLUB_STATS 516 default n 517 bool "Enable SLUB performance statistics" 518 depends on SLUB && SYSFS 519 help 520 SLUB statistics are useful to debug SLUBs allocation behavior in 521 order find ways to optimize the allocator. This should never be 522 enabled for production use since keeping statistics slows down 523 the allocator by a few percentage points. The slabinfo command 524 supports the determination of the most active slabs to figure 525 out which slabs are relevant to a particular load. 526 Try running: slabinfo -DA 527 528config HAVE_DEBUG_KMEMLEAK 529 bool 530 531config DEBUG_KMEMLEAK 532 bool "Kernel memory leak detector" 533 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 534 select DEBUG_FS 535 select STACKTRACE if STACKTRACE_SUPPORT 536 select KALLSYMS 537 select CRC32 538 help 539 Say Y here if you want to enable the memory leak 540 detector. The memory allocation/freeing is traced in a way 541 similar to the Boehm's conservative garbage collector, the 542 difference being that the orphan objects are not freed but 543 only shown in /sys/kernel/debug/kmemleak. Enabling this 544 feature will introduce an overhead to memory 545 allocations. See Documentation/dev-tools/kmemleak.rst for more 546 details. 547 548 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 549 of finding leaks due to the slab objects poisoning. 550 551 In order to access the kmemleak file, debugfs needs to be 552 mounted (usually at /sys/kernel/debug). 553 554config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 555 int "Maximum kmemleak early log entries" 556 depends on DEBUG_KMEMLEAK 557 range 200 40000 558 default 400 559 help 560 Kmemleak must track all the memory allocations to avoid 561 reporting false positives. Since memory may be allocated or 562 freed before kmemleak is initialised, an early log buffer is 563 used to store these actions. If kmemleak reports "early log 564 buffer exceeded", please increase this value. 565 566config DEBUG_KMEMLEAK_TEST 567 tristate "Simple test for the kernel memory leak detector" 568 depends on DEBUG_KMEMLEAK && m 569 help 570 This option enables a module that explicitly leaks memory. 571 572 If unsure, say N. 573 574config DEBUG_KMEMLEAK_DEFAULT_OFF 575 bool "Default kmemleak to off" 576 depends on DEBUG_KMEMLEAK 577 help 578 Say Y here to disable kmemleak by default. It can then be enabled 579 on the command line via kmemleak=on. 580 581config DEBUG_STACK_USAGE 582 bool "Stack utilization instrumentation" 583 depends on DEBUG_KERNEL && !IA64 584 help 585 Enables the display of the minimum amount of free stack which each 586 task has ever had available in the sysrq-T and sysrq-P debug output. 587 588 This option will slow down process creation somewhat. 589 590config DEBUG_VM 591 bool "Debug VM" 592 depends on DEBUG_KERNEL 593 help 594 Enable this to turn on extended checks in the virtual-memory system 595 that may impact performance. 596 597 If unsure, say N. 598 599config DEBUG_VM_VMACACHE 600 bool "Debug VMA caching" 601 depends on DEBUG_VM 602 help 603 Enable this to turn on VMA caching debug information. Doing so 604 can cause significant overhead, so only enable it in non-production 605 environments. 606 607 If unsure, say N. 608 609config DEBUG_VM_RB 610 bool "Debug VM red-black trees" 611 depends on DEBUG_VM 612 help 613 Enable VM red-black tree debugging information and extra validations. 614 615 If unsure, say N. 616 617config DEBUG_VM_PGFLAGS 618 bool "Debug page-flags operations" 619 depends on DEBUG_VM 620 help 621 Enables extra validation on page flags operations. 622 623 If unsure, say N. 624 625config DEBUG_VIRTUAL 626 bool "Debug VM translations" 627 depends on DEBUG_KERNEL && X86 628 help 629 Enable some costly sanity checks in virtual to page code. This can 630 catch mistakes with virt_to_page() and friends. 631 632 If unsure, say N. 633 634config DEBUG_NOMMU_REGIONS 635 bool "Debug the global anon/private NOMMU mapping region tree" 636 depends on DEBUG_KERNEL && !MMU 637 help 638 This option causes the global tree of anonymous and private mapping 639 regions to be regularly checked for invalid topology. 640 641config DEBUG_MEMORY_INIT 642 bool "Debug memory initialisation" if EXPERT 643 default !EXPERT 644 help 645 Enable this for additional checks during memory initialisation. 646 The sanity checks verify aspects of the VM such as the memory model 647 and other information provided by the architecture. Verbose 648 information will be printed at KERN_DEBUG loglevel depending 649 on the mminit_loglevel= command-line option. 650 651 If unsure, say Y 652 653config MEMORY_NOTIFIER_ERROR_INJECT 654 tristate "Memory hotplug notifier error injection module" 655 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 656 help 657 This option provides the ability to inject artificial errors to 658 memory hotplug notifier chain callbacks. It is controlled through 659 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 660 661 If the notifier call chain should be failed with some events 662 notified, write the error code to "actions/<notifier event>/error". 663 664 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 665 666 # cd /sys/kernel/debug/notifier-error-inject/memory 667 # echo -12 > actions/MEM_GOING_OFFLINE/error 668 # echo offline > /sys/devices/system/memory/memoryXXX/state 669 bash: echo: write error: Cannot allocate memory 670 671 To compile this code as a module, choose M here: the module will 672 be called memory-notifier-error-inject. 673 674 If unsure, say N. 675 676config DEBUG_PER_CPU_MAPS 677 bool "Debug access to per_cpu maps" 678 depends on DEBUG_KERNEL 679 depends on SMP 680 help 681 Say Y to verify that the per_cpu map being accessed has 682 been set up. This adds a fair amount of code to kernel memory 683 and decreases performance. 684 685 Say N if unsure. 686 687config DEBUG_HIGHMEM 688 bool "Highmem debugging" 689 depends on DEBUG_KERNEL && HIGHMEM 690 help 691 This option enables additional error checking for high memory 692 systems. Disable for production systems. 693 694config HAVE_DEBUG_STACKOVERFLOW 695 bool 696 697config DEBUG_STACKOVERFLOW 698 bool "Check for stack overflows" 699 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 700 ---help--- 701 Say Y here if you want to check for overflows of kernel, IRQ 702 and exception stacks (if your architecture uses them). This 703 option will show detailed messages if free stack space drops 704 below a certain limit. 705 706 These kinds of bugs usually occur when call-chains in the 707 kernel get too deep, especially when interrupts are 708 involved. 709 710 Use this in cases where you see apparently random memory 711 corruption, especially if it appears in 'struct thread_info' 712 713 If in doubt, say "N". 714 715source "lib/Kconfig.kmemcheck" 716 717source "lib/Kconfig.kasan" 718 719endmenu # "Memory Debugging" 720 721config ARCH_HAS_KCOV 722 bool 723 help 724 KCOV does not have any arch-specific code, but currently it is enabled 725 only for x86_64. KCOV requires testing on other archs, and most likely 726 disabling of instrumentation for some early boot code. 727 728config KCOV 729 bool "Code coverage for fuzzing" 730 depends on ARCH_HAS_KCOV 731 select DEBUG_FS 732 select GCC_PLUGINS if !COMPILE_TEST 733 select GCC_PLUGIN_SANCOV if !COMPILE_TEST 734 help 735 KCOV exposes kernel code coverage information in a form suitable 736 for coverage-guided fuzzing (randomized testing). 737 738 If RANDOMIZE_BASE is enabled, PC values will not be stable across 739 different machines and across reboots. If you need stable PC values, 740 disable RANDOMIZE_BASE. 741 742 For more details, see Documentation/dev-tools/kcov.rst. 743 744config KCOV_INSTRUMENT_ALL 745 bool "Instrument all code by default" 746 depends on KCOV 747 default y if KCOV 748 help 749 If you are doing generic system call fuzzing (like e.g. syzkaller), 750 then you will want to instrument the whole kernel and you should 751 say y here. If you are doing more targeted fuzzing (like e.g. 752 filesystem fuzzing with AFL) then you will want to enable coverage 753 for more specific subsets of files, and should say n here. 754 755config DEBUG_SHIRQ 756 bool "Debug shared IRQ handlers" 757 depends on DEBUG_KERNEL 758 help 759 Enable this to generate a spurious interrupt as soon as a shared 760 interrupt handler is registered, and just before one is deregistered. 761 Drivers ought to be able to handle interrupts coming in at those 762 points; some don't and need to be caught. 763 764menu "Debug Lockups and Hangs" 765 766config LOCKUP_DETECTOR 767 bool "Detect Hard and Soft Lockups" 768 depends on DEBUG_KERNEL && !S390 769 help 770 Say Y here to enable the kernel to act as a watchdog to detect 771 hard and soft lockups. 772 773 Softlockups are bugs that cause the kernel to loop in kernel 774 mode for more than 20 seconds, without giving other tasks a 775 chance to run. The current stack trace is displayed upon 776 detection and the system will stay locked up. 777 778 Hardlockups are bugs that cause the CPU to loop in kernel mode 779 for more than 10 seconds, without letting other interrupts have a 780 chance to run. The current stack trace is displayed upon detection 781 and the system will stay locked up. 782 783 The overhead should be minimal. A periodic hrtimer runs to 784 generate interrupts and kick the watchdog task every 4 seconds. 785 An NMI is generated every 10 seconds or so to check for hardlockups. 786 787 The frequency of hrtimer and NMI events and the soft and hard lockup 788 thresholds can be controlled through the sysctl watchdog_thresh. 789 790config HARDLOCKUP_DETECTOR 791 def_bool y 792 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 793 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 794 795config BOOTPARAM_HARDLOCKUP_PANIC 796 bool "Panic (Reboot) On Hard Lockups" 797 depends on HARDLOCKUP_DETECTOR 798 help 799 Say Y here to enable the kernel to panic on "hard lockups", 800 which are bugs that cause the kernel to loop in kernel 801 mode with interrupts disabled for more than 10 seconds (configurable 802 using the watchdog_thresh sysctl). 803 804 Say N if unsure. 805 806config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 807 int 808 depends on HARDLOCKUP_DETECTOR 809 range 0 1 810 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 811 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 812 813config BOOTPARAM_SOFTLOCKUP_PANIC 814 bool "Panic (Reboot) On Soft Lockups" 815 depends on LOCKUP_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 LOCKUP_DETECTOR 833 range 0 1 834 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 835 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 836 837config DETECT_HUNG_TASK 838 bool "Detect Hung Tasks" 839 depends on DEBUG_KERNEL 840 default LOCKUP_DETECTOR 841 help 842 Say Y here to enable the kernel to detect "hung tasks", 843 which are bugs that cause the task to be stuck in 844 uninterruptible "D" state indefinitely. 845 846 When a hung task is detected, the kernel will print the 847 current stack trace (which you should report), but the 848 task will stay in uninterruptible state. If lockdep is 849 enabled then all held locks will also be reported. This 850 feature has negligible overhead. 851 852config DEFAULT_HUNG_TASK_TIMEOUT 853 int "Default timeout for hung task detection (in seconds)" 854 depends on DETECT_HUNG_TASK 855 default 120 856 help 857 This option controls the default timeout (in seconds) used 858 to determine when a task has become non-responsive and should 859 be considered hung. 860 861 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 862 sysctl or by writing a value to 863 /proc/sys/kernel/hung_task_timeout_secs. 864 865 A timeout of 0 disables the check. The default is two minutes. 866 Keeping the default should be fine in most cases. 867 868config BOOTPARAM_HUNG_TASK_PANIC 869 bool "Panic (Reboot) On Hung Tasks" 870 depends on DETECT_HUNG_TASK 871 help 872 Say Y here to enable the kernel to panic on "hung tasks", 873 which are bugs that cause the kernel to leave a task stuck 874 in uninterruptible "D" state. 875 876 The panic can be used in combination with panic_timeout, 877 to cause the system to reboot automatically after a 878 hung task has been detected. This feature is useful for 879 high-availability systems that have uptime guarantees and 880 where a hung tasks must be resolved ASAP. 881 882 Say N if unsure. 883 884config BOOTPARAM_HUNG_TASK_PANIC_VALUE 885 int 886 depends on DETECT_HUNG_TASK 887 range 0 1 888 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 889 default 1 if BOOTPARAM_HUNG_TASK_PANIC 890 891config WQ_WATCHDOG 892 bool "Detect Workqueue Stalls" 893 depends on DEBUG_KERNEL 894 help 895 Say Y here to enable stall detection on workqueues. If a 896 worker pool doesn't make forward progress on a pending work 897 item for over a given amount of time, 30s by default, a 898 warning message is printed along with dump of workqueue 899 state. This can be configured through kernel parameter 900 "workqueue.watchdog_thresh" and its sysfs counterpart. 901 902endmenu # "Debug lockups and hangs" 903 904config PANIC_ON_OOPS 905 bool "Panic on Oops" 906 help 907 Say Y here to enable the kernel to panic when it oopses. This 908 has the same effect as setting oops=panic on the kernel command 909 line. 910 911 This feature is useful to ensure that the kernel does not do 912 anything erroneous after an oops which could result in data 913 corruption or other issues. 914 915 Say N if unsure. 916 917config PANIC_ON_OOPS_VALUE 918 int 919 range 0 1 920 default 0 if !PANIC_ON_OOPS 921 default 1 if PANIC_ON_OOPS 922 923config PANIC_TIMEOUT 924 int "panic timeout" 925 default 0 926 help 927 Set the timeout value (in seconds) until a reboot occurs when the 928 the kernel panics. If n = 0, then we wait forever. A timeout 929 value n > 0 will wait n seconds before rebooting, while a timeout 930 value n < 0 will reboot immediately. 931 932config SCHED_DEBUG 933 bool "Collect scheduler debugging info" 934 depends on DEBUG_KERNEL && PROC_FS 935 default y 936 help 937 If you say Y here, the /proc/sched_debug file will be provided 938 that can help debug the scheduler. The runtime overhead of this 939 option is minimal. 940 941config SCHED_INFO 942 bool 943 default n 944 945config SCHEDSTATS 946 bool "Collect scheduler statistics" 947 depends on DEBUG_KERNEL && PROC_FS 948 select SCHED_INFO 949 help 950 If you say Y here, additional code will be inserted into the 951 scheduler and related routines to collect statistics about 952 scheduler behavior and provide them in /proc/schedstat. These 953 stats may be useful for both tuning and debugging the scheduler 954 If you aren't debugging the scheduler or trying to tune a specific 955 application, you can say N to avoid the very slight overhead 956 this adds. 957 958config SCHED_STACK_END_CHECK 959 bool "Detect stack corruption on calls to schedule()" 960 depends on DEBUG_KERNEL 961 default n 962 help 963 This option checks for a stack overrun on calls to schedule(). 964 If the stack end location is found to be over written always panic as 965 the content of the corrupted region can no longer be trusted. 966 This is to ensure no erroneous behaviour occurs which could result in 967 data corruption or a sporadic crash at a later stage once the region 968 is examined. The runtime overhead introduced is minimal. 969 970config DEBUG_TIMEKEEPING 971 bool "Enable extra timekeeping sanity checking" 972 help 973 This option will enable additional timekeeping sanity checks 974 which may be helpful when diagnosing issues where timekeeping 975 problems are suspected. 976 977 This may include checks in the timekeeping hotpaths, so this 978 option may have a (very small) performance impact to some 979 workloads. 980 981 If unsure, say N. 982 983config TIMER_STATS 984 bool "Collect kernel timers statistics" 985 depends on DEBUG_KERNEL && PROC_FS 986 help 987 If you say Y here, additional code will be inserted into the 988 timer routines to collect statistics about kernel timers being 989 reprogrammed. The statistics can be read from /proc/timer_stats. 990 The statistics collection is started by writing 1 to /proc/timer_stats, 991 writing 0 stops it. This feature is useful to collect information 992 about timer usage patterns in kernel and userspace. This feature 993 is lightweight if enabled in the kernel config but not activated 994 (it defaults to deactivated on bootup and will only be activated 995 if some application like powertop activates it explicitly). 996 997config DEBUG_PREEMPT 998 bool "Debug preemptible kernel" 999 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 1000 default y 1001 help 1002 If you say Y here then the kernel will use a debug variant of the 1003 commonly used smp_processor_id() function and will print warnings 1004 if kernel code uses it in a preemption-unsafe way. Also, the kernel 1005 will detect preemption count underflows. 1006 1007menu "Lock Debugging (spinlocks, mutexes, etc...)" 1008 1009config DEBUG_RT_MUTEXES 1010 bool "RT Mutex debugging, deadlock detection" 1011 depends on DEBUG_KERNEL && RT_MUTEXES 1012 help 1013 This allows rt mutex semantics violations and rt mutex related 1014 deadlocks (lockups) to be detected and reported automatically. 1015 1016config DEBUG_SPINLOCK 1017 bool "Spinlock and rw-lock debugging: basic checks" 1018 depends on DEBUG_KERNEL 1019 select UNINLINE_SPIN_UNLOCK 1020 help 1021 Say Y here and build SMP to catch missing spinlock initialization 1022 and certain other kinds of spinlock errors commonly made. This is 1023 best used in conjunction with the NMI watchdog so that spinlock 1024 deadlocks are also debuggable. 1025 1026config DEBUG_MUTEXES 1027 bool "Mutex debugging: basic checks" 1028 depends on DEBUG_KERNEL 1029 help 1030 This feature allows mutex semantics violations to be detected and 1031 reported. 1032 1033config DEBUG_WW_MUTEX_SLOWPATH 1034 bool "Wait/wound mutex debugging: Slowpath testing" 1035 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1036 select DEBUG_LOCK_ALLOC 1037 select DEBUG_SPINLOCK 1038 select DEBUG_MUTEXES 1039 help 1040 This feature enables slowpath testing for w/w mutex users by 1041 injecting additional -EDEADLK wound/backoff cases. Together with 1042 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 1043 will test all possible w/w mutex interface abuse with the 1044 exception of simply not acquiring all the required locks. 1045 Note that this feature can introduce significant overhead, so 1046 it really should not be enabled in a production or distro kernel, 1047 even a debug kernel. If you are a driver writer, enable it. If 1048 you are a distro, do not. 1049 1050config DEBUG_LOCK_ALLOC 1051 bool "Lock debugging: detect incorrect freeing of live locks" 1052 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1053 select DEBUG_SPINLOCK 1054 select DEBUG_MUTEXES 1055 select LOCKDEP 1056 help 1057 This feature will check whether any held lock (spinlock, rwlock, 1058 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1059 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1060 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1061 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1062 held during task exit. 1063 1064config PROVE_LOCKING 1065 bool "Lock debugging: prove locking correctness" 1066 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1067 select LOCKDEP 1068 select DEBUG_SPINLOCK 1069 select DEBUG_MUTEXES 1070 select DEBUG_LOCK_ALLOC 1071 select TRACE_IRQFLAGS 1072 default n 1073 help 1074 This feature enables the kernel to prove that all locking 1075 that occurs in the kernel runtime is mathematically 1076 correct: that under no circumstance could an arbitrary (and 1077 not yet triggered) combination of observed locking 1078 sequences (on an arbitrary number of CPUs, running an 1079 arbitrary number of tasks and interrupt contexts) cause a 1080 deadlock. 1081 1082 In short, this feature enables the kernel to report locking 1083 related deadlocks before they actually occur. 1084 1085 The proof does not depend on how hard and complex a 1086 deadlock scenario would be to trigger: how many 1087 participant CPUs, tasks and irq-contexts would be needed 1088 for it to trigger. The proof also does not depend on 1089 timing: if a race and a resulting deadlock is possible 1090 theoretically (no matter how unlikely the race scenario 1091 is), it will be proven so and will immediately be 1092 reported by the kernel (once the event is observed that 1093 makes the deadlock theoretically possible). 1094 1095 If a deadlock is impossible (i.e. the locking rules, as 1096 observed by the kernel, are mathematically correct), the 1097 kernel reports nothing. 1098 1099 NOTE: this feature can also be enabled for rwlocks, mutexes 1100 and rwsems - in which case all dependencies between these 1101 different locking variants are observed and mapped too, and 1102 the proof of observed correctness is also maintained for an 1103 arbitrary combination of these separate locking variants. 1104 1105 For more details, see Documentation/locking/lockdep-design.txt. 1106 1107config PROVE_LOCKING_SMALL 1108 bool 1109 1110config LOCKDEP 1111 bool 1112 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1113 select STACKTRACE 1114 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE 1115 select KALLSYMS 1116 select KALLSYMS_ALL 1117 1118config LOCK_STAT 1119 bool "Lock usage statistics" 1120 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1121 select LOCKDEP 1122 select DEBUG_SPINLOCK 1123 select DEBUG_MUTEXES 1124 select DEBUG_LOCK_ALLOC 1125 default n 1126 help 1127 This feature enables tracking lock contention points 1128 1129 For more details, see Documentation/locking/lockstat.txt 1130 1131 This also enables lock events required by "perf lock", 1132 subcommand of perf. 1133 If you want to use "perf lock", you also need to turn on 1134 CONFIG_EVENT_TRACING. 1135 1136 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1137 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1138 1139config DEBUG_LOCKDEP 1140 bool "Lock dependency engine debugging" 1141 depends on DEBUG_KERNEL && LOCKDEP 1142 help 1143 If you say Y here, the lock dependency engine will do 1144 additional runtime checks to debug itself, at the price 1145 of more runtime overhead. 1146 1147config DEBUG_ATOMIC_SLEEP 1148 bool "Sleep inside atomic section checking" 1149 select PREEMPT_COUNT 1150 depends on DEBUG_KERNEL 1151 help 1152 If you say Y here, various routines which may sleep will become very 1153 noisy if they are called inside atomic sections: when a spinlock is 1154 held, inside an rcu read side critical section, inside preempt disabled 1155 sections, inside an interrupt, etc... 1156 1157config DEBUG_LOCKING_API_SELFTESTS 1158 bool "Locking API boot-time self-tests" 1159 depends on DEBUG_KERNEL 1160 help 1161 Say Y here if you want the kernel to run a short self-test during 1162 bootup. The self-test checks whether common types of locking bugs 1163 are detected by debugging mechanisms or not. (if you disable 1164 lock debugging then those bugs wont be detected of course.) 1165 The following locking APIs are covered: spinlocks, rwlocks, 1166 mutexes and rwsems. 1167 1168config LOCK_TORTURE_TEST 1169 tristate "torture tests for locking" 1170 depends on DEBUG_KERNEL 1171 select TORTURE_TEST 1172 default n 1173 help 1174 This option provides a kernel module that runs torture tests 1175 on kernel locking primitives. The kernel module may be built 1176 after the fact on the running kernel to be tested, if desired. 1177 1178 Say Y here if you want kernel locking-primitive torture tests 1179 to be built into the kernel. 1180 Say M if you want these torture tests to build as a module. 1181 Say N if you are unsure. 1182 1183endmenu # lock debugging 1184 1185config TRACE_IRQFLAGS 1186 bool 1187 help 1188 Enables hooks to interrupt enabling and disabling for 1189 either tracing or lock debugging. 1190 1191config STACKTRACE 1192 bool "Stack backtrace support" 1193 depends on STACKTRACE_SUPPORT 1194 help 1195 This option causes the kernel to create a /proc/pid/stack for 1196 every process, showing its current stack trace. 1197 It is also used by various kernel debugging features that require 1198 stack trace generation. 1199 1200config DEBUG_KOBJECT 1201 bool "kobject debugging" 1202 depends on DEBUG_KERNEL 1203 help 1204 If you say Y here, some extra kobject debugging messages will be sent 1205 to the syslog. 1206 1207config DEBUG_KOBJECT_RELEASE 1208 bool "kobject release debugging" 1209 depends on DEBUG_OBJECTS_TIMERS 1210 help 1211 kobjects are reference counted objects. This means that their 1212 last reference count put is not predictable, and the kobject can 1213 live on past the point at which a driver decides to drop it's 1214 initial reference to the kobject gained on allocation. An 1215 example of this would be a struct device which has just been 1216 unregistered. 1217 1218 However, some buggy drivers assume that after such an operation, 1219 the memory backing the kobject can be immediately freed. This 1220 goes completely against the principles of a refcounted object. 1221 1222 If you say Y here, the kernel will delay the release of kobjects 1223 on the last reference count to improve the visibility of this 1224 kind of kobject release bug. 1225 1226config HAVE_DEBUG_BUGVERBOSE 1227 bool 1228 1229config DEBUG_BUGVERBOSE 1230 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1231 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1232 default y 1233 help 1234 Say Y here to make BUG() panics output the file name and line number 1235 of the BUG call as well as the EIP and oops trace. This aids 1236 debugging but costs about 70-100K of memory. 1237 1238config DEBUG_LIST 1239 bool "Debug linked list manipulation" 1240 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION 1241 help 1242 Enable this to turn on extended checks in the linked-list 1243 walking routines. 1244 1245 If unsure, say N. 1246 1247config DEBUG_PI_LIST 1248 bool "Debug priority linked list manipulation" 1249 depends on DEBUG_KERNEL 1250 help 1251 Enable this to turn on extended checks in the priority-ordered 1252 linked-list (plist) walking routines. This checks the entire 1253 list multiple times during each manipulation. 1254 1255 If unsure, say N. 1256 1257config DEBUG_SG 1258 bool "Debug SG table operations" 1259 depends on DEBUG_KERNEL 1260 help 1261 Enable this to turn on checks on scatter-gather tables. This can 1262 help find problems with drivers that do not properly initialize 1263 their sg tables. 1264 1265 If unsure, say N. 1266 1267config DEBUG_NOTIFIERS 1268 bool "Debug notifier call chains" 1269 depends on DEBUG_KERNEL 1270 help 1271 Enable this to turn on sanity checking for notifier call chains. 1272 This is most useful for kernel developers to make sure that 1273 modules properly unregister themselves from notifier chains. 1274 This is a relatively cheap check but if you care about maximum 1275 performance, say N. 1276 1277config DEBUG_CREDENTIALS 1278 bool "Debug credential management" 1279 depends on DEBUG_KERNEL 1280 help 1281 Enable this to turn on some debug checking for credential 1282 management. The additional code keeps track of the number of 1283 pointers from task_structs to any given cred struct, and checks to 1284 see that this number never exceeds the usage count of the cred 1285 struct. 1286 1287 Furthermore, if SELinux is enabled, this also checks that the 1288 security pointer in the cred struct is never seen to be invalid. 1289 1290 If unsure, say N. 1291 1292menu "RCU Debugging" 1293 1294config PROVE_RCU 1295 def_bool PROVE_LOCKING 1296 1297config PROVE_RCU_REPEATEDLY 1298 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1299 depends on PROVE_RCU 1300 default n 1301 help 1302 By itself, PROVE_RCU will disable checking upon issuing the 1303 first warning (or "splat"). This feature prevents such 1304 disabling, allowing multiple RCU-lockdep warnings to be printed 1305 on a single reboot. 1306 1307 Say Y to allow multiple RCU-lockdep warnings per boot. 1308 1309 Say N if you are unsure. 1310 1311config SPARSE_RCU_POINTER 1312 bool "RCU debugging: sparse-based checks for pointer usage" 1313 default n 1314 help 1315 This feature enables the __rcu sparse annotation for 1316 RCU-protected pointers. This annotation will cause sparse 1317 to flag any non-RCU used of annotated pointers. This can be 1318 helpful when debugging RCU usage. Please note that this feature 1319 is not intended to enforce code cleanliness; it is instead merely 1320 a debugging aid. 1321 1322 Say Y to make sparse flag questionable use of RCU-protected pointers 1323 1324 Say N if you are unsure. 1325 1326config TORTURE_TEST 1327 tristate 1328 default n 1329 1330config RCU_PERF_TEST 1331 tristate "performance tests for RCU" 1332 depends on DEBUG_KERNEL 1333 select TORTURE_TEST 1334 select SRCU 1335 select TASKS_RCU 1336 default n 1337 help 1338 This option provides a kernel module that runs performance 1339 tests on the RCU infrastructure. The kernel module may be built 1340 after the fact on the running kernel to be tested, if desired. 1341 1342 Say Y here if you want RCU performance tests to be built into 1343 the kernel. 1344 Say M if you want the RCU performance tests to build as a module. 1345 Say N if you are unsure. 1346 1347config RCU_TORTURE_TEST 1348 tristate "torture tests for RCU" 1349 depends on DEBUG_KERNEL 1350 select TORTURE_TEST 1351 select SRCU 1352 select TASKS_RCU 1353 default n 1354 help 1355 This option provides a kernel module that runs torture tests 1356 on the RCU infrastructure. The kernel module may be built 1357 after the fact on the running kernel to be tested, if desired. 1358 1359 Say Y here if you want RCU torture tests to be built into 1360 the kernel. 1361 Say M if you want the RCU torture tests to build as a module. 1362 Say N if you are unsure. 1363 1364config RCU_TORTURE_TEST_SLOW_PREINIT 1365 bool "Slow down RCU grace-period pre-initialization to expose races" 1366 depends on RCU_TORTURE_TEST 1367 help 1368 This option delays grace-period pre-initialization (the 1369 propagation of CPU-hotplug changes up the rcu_node combining 1370 tree) for a few jiffies between initializing each pair of 1371 consecutive rcu_node structures. This helps to expose races 1372 involving grace-period pre-initialization, in other words, it 1373 makes your kernel less stable. It can also greatly increase 1374 grace-period latency, especially on systems with large numbers 1375 of CPUs. This is useful when torture-testing RCU, but in 1376 almost no other circumstance. 1377 1378 Say Y here if you want your system to crash and hang more often. 1379 Say N if you want a sane system. 1380 1381config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY 1382 int "How much to slow down RCU grace-period pre-initialization" 1383 range 0 5 1384 default 3 1385 depends on RCU_TORTURE_TEST_SLOW_PREINIT 1386 help 1387 This option specifies the number of jiffies to wait between 1388 each rcu_node structure pre-initialization step. 1389 1390config RCU_TORTURE_TEST_SLOW_INIT 1391 bool "Slow down RCU grace-period initialization to expose races" 1392 depends on RCU_TORTURE_TEST 1393 help 1394 This option delays grace-period initialization for a few 1395 jiffies between initializing each pair of consecutive 1396 rcu_node structures. This helps to expose races involving 1397 grace-period initialization, in other words, it makes your 1398 kernel less stable. It can also greatly increase grace-period 1399 latency, especially on systems with large numbers of CPUs. 1400 This is useful when torture-testing RCU, but in almost no 1401 other circumstance. 1402 1403 Say Y here if you want your system to crash and hang more often. 1404 Say N if you want a sane system. 1405 1406config RCU_TORTURE_TEST_SLOW_INIT_DELAY 1407 int "How much to slow down RCU grace-period initialization" 1408 range 0 5 1409 default 3 1410 depends on RCU_TORTURE_TEST_SLOW_INIT 1411 help 1412 This option specifies the number of jiffies to wait between 1413 each rcu_node structure initialization. 1414 1415config RCU_TORTURE_TEST_SLOW_CLEANUP 1416 bool "Slow down RCU grace-period cleanup to expose races" 1417 depends on RCU_TORTURE_TEST 1418 help 1419 This option delays grace-period cleanup for a few jiffies 1420 between cleaning up each pair of consecutive rcu_node 1421 structures. This helps to expose races involving grace-period 1422 cleanup, in other words, it makes your kernel less stable. 1423 It can also greatly increase grace-period latency, especially 1424 on systems with large numbers of CPUs. This is useful when 1425 torture-testing RCU, but in almost no other circumstance. 1426 1427 Say Y here if you want your system to crash and hang more often. 1428 Say N if you want a sane system. 1429 1430config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY 1431 int "How much to slow down RCU grace-period cleanup" 1432 range 0 5 1433 default 3 1434 depends on RCU_TORTURE_TEST_SLOW_CLEANUP 1435 help 1436 This option specifies the number of jiffies to wait between 1437 each rcu_node structure cleanup operation. 1438 1439config RCU_CPU_STALL_TIMEOUT 1440 int "RCU CPU stall timeout in seconds" 1441 depends on RCU_STALL_COMMON 1442 range 3 300 1443 default 21 1444 help 1445 If a given RCU grace period extends more than the specified 1446 number of seconds, a CPU stall warning is printed. If the 1447 RCU grace period persists, additional CPU stall warnings are 1448 printed at more widely spaced intervals. 1449 1450config RCU_TRACE 1451 bool "Enable tracing for RCU" 1452 depends on DEBUG_KERNEL 1453 select TRACE_CLOCK 1454 help 1455 This option provides tracing in RCU which presents stats 1456 in debugfs for debugging RCU implementation. It also enables 1457 additional tracepoints for ftrace-style event tracing. 1458 1459 Say Y here if you want to enable RCU tracing 1460 Say N if you are unsure. 1461 1462config RCU_EQS_DEBUG 1463 bool "Provide debugging asserts for adding NO_HZ support to an arch" 1464 depends on DEBUG_KERNEL 1465 help 1466 This option provides consistency checks in RCU's handling of 1467 NO_HZ. These checks have proven quite helpful in detecting 1468 bugs in arch-specific NO_HZ code. 1469 1470 Say N here if you need ultimate kernel/user switch latencies 1471 Say Y if you are unsure 1472 1473endmenu # "RCU Debugging" 1474 1475config DEBUG_WQ_FORCE_RR_CPU 1476 bool "Force round-robin CPU selection for unbound work items" 1477 depends on DEBUG_KERNEL 1478 default n 1479 help 1480 Workqueue used to implicitly guarantee that work items queued 1481 without explicit CPU specified are put on the local CPU. This 1482 guarantee is no longer true and while local CPU is still 1483 preferred work items may be put on foreign CPUs. Kernel 1484 parameter "workqueue.debug_force_rr_cpu" is added to force 1485 round-robin CPU selection to flush out usages which depend on the 1486 now broken guarantee. This config option enables the debug 1487 feature by default. When enabled, memory and cache locality will 1488 be impacted. 1489 1490config DEBUG_BLOCK_EXT_DEVT 1491 bool "Force extended block device numbers and spread them" 1492 depends on DEBUG_KERNEL 1493 depends on BLOCK 1494 default n 1495 help 1496 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1497 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1498 YOU ARE DOING. Distros, please enable this and fix whatever 1499 is broken. 1500 1501 Conventionally, block device numbers are allocated from 1502 predetermined contiguous area. However, extended block area 1503 may introduce non-contiguous block device numbers. This 1504 option forces most block device numbers to be allocated from 1505 the extended space and spreads them to discover kernel or 1506 userland code paths which assume predetermined contiguous 1507 device number allocation. 1508 1509 Note that turning on this debug option shuffles all the 1510 device numbers for all IDE and SCSI devices including libata 1511 ones, so root partition specified using device number 1512 directly (via rdev or root=MAJ:MIN) won't work anymore. 1513 Textual device names (root=/dev/sdXn) will continue to work. 1514 1515 Say N if you are unsure. 1516 1517config CPU_HOTPLUG_STATE_CONTROL 1518 bool "Enable CPU hotplug state control" 1519 depends on DEBUG_KERNEL 1520 depends on HOTPLUG_CPU 1521 default n 1522 help 1523 Allows to write steps between "offline" and "online" to the CPUs 1524 sysfs target file so states can be stepped granular. This is a debug 1525 option for now as the hotplug machinery cannot be stopped and 1526 restarted at arbitrary points yet. 1527 1528 Say N if your are unsure. 1529 1530config NOTIFIER_ERROR_INJECTION 1531 tristate "Notifier error injection" 1532 depends on DEBUG_KERNEL 1533 select DEBUG_FS 1534 help 1535 This option provides the ability to inject artificial errors to 1536 specified notifier chain callbacks. It is useful to test the error 1537 handling of notifier call chain failures. 1538 1539 Say N if unsure. 1540 1541config PM_NOTIFIER_ERROR_INJECT 1542 tristate "PM notifier error injection module" 1543 depends on PM && NOTIFIER_ERROR_INJECTION 1544 default m if PM_DEBUG 1545 help 1546 This option provides the ability to inject artificial errors to 1547 PM notifier chain callbacks. It is controlled through debugfs 1548 interface /sys/kernel/debug/notifier-error-inject/pm 1549 1550 If the notifier call chain should be failed with some events 1551 notified, write the error code to "actions/<notifier event>/error". 1552 1553 Example: Inject PM suspend error (-12 = -ENOMEM) 1554 1555 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1556 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1557 # echo mem > /sys/power/state 1558 bash: echo: write error: Cannot allocate memory 1559 1560 To compile this code as a module, choose M here: the module will 1561 be called pm-notifier-error-inject. 1562 1563 If unsure, say N. 1564 1565config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1566 tristate "OF reconfig notifier error injection module" 1567 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1568 help 1569 This option provides the ability to inject artificial errors to 1570 OF reconfig notifier chain callbacks. It is controlled 1571 through debugfs interface under 1572 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1573 1574 If the notifier call chain should be failed with some events 1575 notified, write the error code to "actions/<notifier event>/error". 1576 1577 To compile this code as a module, choose M here: the module will 1578 be called of-reconfig-notifier-error-inject. 1579 1580 If unsure, say N. 1581 1582config NETDEV_NOTIFIER_ERROR_INJECT 1583 tristate "Netdev notifier error injection module" 1584 depends on NET && NOTIFIER_ERROR_INJECTION 1585 help 1586 This option provides the ability to inject artificial errors to 1587 netdevice notifier chain callbacks. It is controlled through debugfs 1588 interface /sys/kernel/debug/notifier-error-inject/netdev 1589 1590 If the notifier call chain should be failed with some events 1591 notified, write the error code to "actions/<notifier event>/error". 1592 1593 Example: Inject netdevice mtu change error (-22 = -EINVAL) 1594 1595 # cd /sys/kernel/debug/notifier-error-inject/netdev 1596 # echo -22 > actions/NETDEV_CHANGEMTU/error 1597 # ip link set eth0 mtu 1024 1598 RTNETLINK answers: Invalid argument 1599 1600 To compile this code as a module, choose M here: the module will 1601 be called netdev-notifier-error-inject. 1602 1603 If unsure, say N. 1604 1605config FAULT_INJECTION 1606 bool "Fault-injection framework" 1607 depends on DEBUG_KERNEL 1608 help 1609 Provide fault-injection framework. 1610 For more details, see Documentation/fault-injection/. 1611 1612config FAILSLAB 1613 bool "Fault-injection capability for kmalloc" 1614 depends on FAULT_INJECTION 1615 depends on SLAB || SLUB 1616 help 1617 Provide fault-injection capability for kmalloc. 1618 1619config FAIL_PAGE_ALLOC 1620 bool "Fault-injection capabilitiy for alloc_pages()" 1621 depends on FAULT_INJECTION 1622 help 1623 Provide fault-injection capability for alloc_pages(). 1624 1625config FAIL_MAKE_REQUEST 1626 bool "Fault-injection capability for disk IO" 1627 depends on FAULT_INJECTION && BLOCK 1628 help 1629 Provide fault-injection capability for disk IO. 1630 1631config FAIL_IO_TIMEOUT 1632 bool "Fault-injection capability for faking disk interrupts" 1633 depends on FAULT_INJECTION && BLOCK 1634 help 1635 Provide fault-injection capability on end IO handling. This 1636 will make the block layer "forget" an interrupt as configured, 1637 thus exercising the error handling. 1638 1639 Only works with drivers that use the generic timeout handling, 1640 for others it wont do anything. 1641 1642config FAIL_MMC_REQUEST 1643 bool "Fault-injection capability for MMC IO" 1644 depends on FAULT_INJECTION_DEBUG_FS && MMC 1645 help 1646 Provide fault-injection capability for MMC IO. 1647 This will make the mmc core return data errors. This is 1648 useful to test the error handling in the mmc block device 1649 and to test how the mmc host driver handles retries from 1650 the block device. 1651 1652config FAIL_FUTEX 1653 bool "Fault-injection capability for futexes" 1654 select DEBUG_FS 1655 depends on FAULT_INJECTION && FUTEX 1656 help 1657 Provide fault-injection capability for futexes. 1658 1659config FAULT_INJECTION_DEBUG_FS 1660 bool "Debugfs entries for fault-injection capabilities" 1661 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1662 help 1663 Enable configuration of fault-injection capabilities via debugfs. 1664 1665config FAULT_INJECTION_STACKTRACE_FILTER 1666 bool "stacktrace filter for fault-injection capabilities" 1667 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1668 depends on !X86_64 1669 select STACKTRACE 1670 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1671 help 1672 Provide stacktrace filter for fault-injection capabilities 1673 1674config LATENCYTOP 1675 bool "Latency measuring infrastructure" 1676 depends on DEBUG_KERNEL 1677 depends on STACKTRACE_SUPPORT 1678 depends on PROC_FS 1679 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1680 select KALLSYMS 1681 select KALLSYMS_ALL 1682 select STACKTRACE 1683 select SCHEDSTATS 1684 select SCHED_DEBUG 1685 help 1686 Enable this option if you want to use the LatencyTOP tool 1687 to find out which userspace is blocking on what kernel operations. 1688 1689source kernel/trace/Kconfig 1690 1691menu "Runtime Testing" 1692 1693config LKDTM 1694 tristate "Linux Kernel Dump Test Tool Module" 1695 depends on DEBUG_FS 1696 depends on BLOCK 1697 default n 1698 help 1699 This module enables testing of the different dumping mechanisms by 1700 inducing system failures at predefined crash points. 1701 If you don't need it: say N 1702 Choose M here to compile this code as a module. The module will be 1703 called lkdtm. 1704 1705 Documentation on how to use the module can be found in 1706 Documentation/fault-injection/provoke-crashes.txt 1707 1708config TEST_LIST_SORT 1709 bool "Linked list sorting test" 1710 depends on DEBUG_KERNEL 1711 help 1712 Enable this to turn on 'list_sort()' function test. This test is 1713 executed only once during system boot, so affects only boot time. 1714 1715 If unsure, say N. 1716 1717config KPROBES_SANITY_TEST 1718 bool "Kprobes sanity tests" 1719 depends on DEBUG_KERNEL 1720 depends on KPROBES 1721 default n 1722 help 1723 This option provides for testing basic kprobes functionality on 1724 boot. A sample kprobe, jprobe 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 default n 1733 help 1734 This option provides a kernel module that can be used to test 1735 the kernel stack backtrace code. This option is not useful 1736 for distributions or general kernels, but only for kernel 1737 developers working on architecture code. 1738 1739 Note that if you want to also test saved backtraces, you will 1740 have to enable STACKTRACE as well. 1741 1742 Say N if you are unsure. 1743 1744config RBTREE_TEST 1745 tristate "Red-Black tree test" 1746 depends on DEBUG_KERNEL 1747 help 1748 A benchmark measuring the performance of the rbtree library. 1749 Also includes rbtree invariant checks. 1750 1751config INTERVAL_TREE_TEST 1752 tristate "Interval tree test" 1753 depends on m && DEBUG_KERNEL 1754 select INTERVAL_TREE 1755 help 1756 A benchmark measuring the performance of the interval tree library 1757 1758config PERCPU_TEST 1759 tristate "Per cpu operations test" 1760 depends on m && DEBUG_KERNEL 1761 help 1762 Enable this option to build test module which validates per-cpu 1763 operations. 1764 1765 If unsure, say N. 1766 1767config ATOMIC64_SELFTEST 1768 bool "Perform an atomic64_t self-test at boot" 1769 help 1770 Enable this option to test the atomic64_t functions at boot. 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 default n 1802 help 1803 Enable this option to test the bitmap functions at boot. 1804 1805 If unsure, say N. 1806 1807config TEST_UUID 1808 tristate "Test functions located in the uuid module at runtime" 1809 1810config TEST_RHASHTABLE 1811 tristate "Perform selftest on resizable hash table" 1812 default n 1813 help 1814 Enable this option to test the rhashtable functions at boot. 1815 1816 If unsure, say N. 1817 1818config TEST_HASH 1819 tristate "Perform selftest on hash functions" 1820 default n 1821 help 1822 Enable this option to test the kernel's integer (<linux/hash,h>) 1823 and string (<linux/stringhash.h>) hash functions on boot 1824 (or module load). 1825 1826 This is intended to help people writing architecture-specific 1827 optimized versions. If unsure, say N. 1828 1829endmenu # runtime tests 1830 1831config PROVIDE_OHCI1394_DMA_INIT 1832 bool "Remote debugging over FireWire early on boot" 1833 depends on PCI && X86 1834 help 1835 If you want to debug problems which hang or crash the kernel early 1836 on boot and the crashing machine has a FireWire port, you can use 1837 this feature to remotely access the memory of the crashed machine 1838 over FireWire. This employs remote DMA as part of the OHCI1394 1839 specification which is now the standard for FireWire controllers. 1840 1841 With remote DMA, you can monitor the printk buffer remotely using 1842 firescope and access all memory below 4GB using fireproxy from gdb. 1843 Even controlling a kernel debugger is possible using remote DMA. 1844 1845 Usage: 1846 1847 If ohci1394_dma=early is used as boot parameter, it will initialize 1848 all OHCI1394 controllers which are found in the PCI config space. 1849 1850 As all changes to the FireWire bus such as enabling and disabling 1851 devices cause a bus reset and thereby disable remote DMA for all 1852 devices, be sure to have the cable plugged and FireWire enabled on 1853 the debugging host before booting the debug target for debugging. 1854 1855 This code (~1k) is freed after boot. By then, the firewire stack 1856 in charge of the OHCI-1394 controllers should be used instead. 1857 1858 See Documentation/debugging-via-ohci1394.txt for more information. 1859 1860config DMA_API_DEBUG 1861 bool "Enable debugging of DMA-API usage" 1862 depends on HAVE_DMA_API_DEBUG 1863 help 1864 Enable this option to debug the use of the DMA API by device drivers. 1865 With this option you will be able to detect common bugs in device 1866 drivers like double-freeing of DMA mappings or freeing mappings that 1867 were never allocated. 1868 1869 This also attempts to catch cases where a page owned by DMA is 1870 accessed by the cpu in a way that could cause data corruption. For 1871 example, this enables cow_user_page() to check that the source page is 1872 not undergoing DMA. 1873 1874 This option causes a performance degradation. Use only if you want to 1875 debug device drivers and dma interactions. 1876 1877 If unsure, say N. 1878 1879config TEST_LKM 1880 tristate "Test module loading with 'hello world' module" 1881 default n 1882 depends on m 1883 help 1884 This builds the "test_module" module that emits "Hello, world" 1885 on printk when loaded. It is designed to be used for basic 1886 evaluation of the module loading subsystem (for example when 1887 validating module verification). It lacks any extra dependencies, 1888 and will not normally be loaded by the system unless explicitly 1889 requested by name. 1890 1891 If unsure, say N. 1892 1893config TEST_USER_COPY 1894 tristate "Test user/kernel boundary protections" 1895 default n 1896 depends on m 1897 help 1898 This builds the "test_user_copy" module that runs sanity checks 1899 on the copy_to/from_user infrastructure, making sure basic 1900 user/kernel boundary testing is working. If it fails to load, 1901 a regression has been detected in the user/kernel memory boundary 1902 protections. 1903 1904 If unsure, say N. 1905 1906config TEST_BPF 1907 tristate "Test BPF filter functionality" 1908 default n 1909 depends on m && NET 1910 help 1911 This builds the "test_bpf" module that runs various test vectors 1912 against the BPF interpreter or BPF JIT compiler depending on the 1913 current setting. This is in particular useful for BPF JIT compiler 1914 development, but also to run regression tests against changes in 1915 the interpreter code. It also enables test stubs for eBPF maps and 1916 verifier used by user space verifier testsuite. 1917 1918 If unsure, say N. 1919 1920config TEST_FIRMWARE 1921 tristate "Test firmware loading via userspace interface" 1922 default n 1923 depends on FW_LOADER 1924 help 1925 This builds the "test_firmware" module that creates a userspace 1926 interface for testing firmware loading. This can be used to 1927 control the triggering of firmware loading without needing an 1928 actual firmware-using device. The contents can be rechecked by 1929 userspace. 1930 1931 If unsure, say N. 1932 1933config TEST_UDELAY 1934 tristate "udelay test driver" 1935 default n 1936 help 1937 This builds the "udelay_test" module that helps to make sure 1938 that udelay() is working properly. 1939 1940 If unsure, say N. 1941 1942config MEMTEST 1943 bool "Memtest" 1944 depends on HAVE_MEMBLOCK 1945 ---help--- 1946 This option adds a kernel parameter 'memtest', which allows memtest 1947 to be set. 1948 memtest=0, mean disabled; -- default 1949 memtest=1, mean do 1 test pattern; 1950 ... 1951 memtest=17, mean do 17 test patterns. 1952 If you are unsure how to answer this question, answer N. 1953 1954config TEST_STATIC_KEYS 1955 tristate "Test static keys" 1956 default n 1957 depends on m 1958 help 1959 Test the static key interfaces. 1960 1961 If unsure, say N. 1962 1963config BUG_ON_DATA_CORRUPTION 1964 bool "Trigger a BUG when data corruption is detected" 1965 select DEBUG_LIST 1966 help 1967 Select this option if the kernel should BUG when it encounters 1968 data corruption in kernel memory structures when they get checked 1969 for validity. 1970 1971 If unsure, say N. 1972 1973source "samples/Kconfig" 1974 1975source "lib/Kconfig.kgdb" 1976 1977source "lib/Kconfig.ubsan" 1978 1979config ARCH_HAS_DEVMEM_IS_ALLOWED 1980 bool 1981 1982config STRICT_DEVMEM 1983 bool "Filter access to /dev/mem" 1984 depends on MMU && DEVMEM 1985 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 1986 default y if TILE || PPC 1987 ---help--- 1988 If this option is disabled, you allow userspace (root) access to all 1989 of memory, including kernel and userspace memory. Accidental 1990 access to this is obviously disastrous, but specific access can 1991 be used by people debugging the kernel. Note that with PAT support 1992 enabled, even in this case there are restrictions on /dev/mem 1993 use due to the cache aliasing requirements. 1994 1995 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 1996 file only allows userspace access to PCI space and the BIOS code and 1997 data regions. This is sufficient for dosemu and X and all common 1998 users of /dev/mem. 1999 2000 If in doubt, say Y. 2001 2002config IO_STRICT_DEVMEM 2003 bool "Filter I/O access to /dev/mem" 2004 depends on STRICT_DEVMEM 2005 ---help--- 2006 If this option is disabled, you allow userspace (root) access to all 2007 io-memory regardless of whether a driver is actively using that 2008 range. Accidental access to this is obviously disastrous, but 2009 specific access can be used by people debugging kernel drivers. 2010 2011 If this option is switched on, the /dev/mem file only allows 2012 userspace access to *idle* io-memory ranges (see /proc/iomem) This 2013 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 2014 if the driver using a given range cannot be disabled. 2015 2016 If in doubt, say Y. 2017