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/kernel-parameters.txt 17 18config MESSAGE_LOGLEVEL_DEFAULT 19 int "Default message log level (1-7)" 20 range 1 7 21 default "4" 22 help 23 Default log level for printk statements with no specified priority. 24 25 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks 26 that are auditing their logs closely may want to set it to a lower 27 priority. 28 29config BOOT_PRINTK_DELAY 30 bool "Delay each boot printk message by N milliseconds" 31 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 32 help 33 This build option allows you to read kernel boot messages 34 by inserting a short delay after each one. The delay is 35 specified in milliseconds on the kernel command line, 36 using "boot_delay=N". 37 38 It is likely that you would also need to use "lpj=M" to preset 39 the "loops per jiffie" value. 40 See a previous boot log for the "lpj" value to use for your 41 system, and then set "lpj=M" before setting "boot_delay=N". 42 NOTE: Using this option may adversely affect SMP systems. 43 I.e., processors other than the first one may not boot up. 44 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect 45 what it believes to be lockup conditions. 46 47config DYNAMIC_DEBUG 48 bool "Enable dynamic printk() support" 49 default n 50 depends on PRINTK 51 depends on DEBUG_FS 52 help 53 54 Compiles debug level messages into the kernel, which would not 55 otherwise be available at runtime. These messages can then be 56 enabled/disabled based on various levels of scope - per source file, 57 function, module, format string, and line number. This mechanism 58 implicitly compiles in all pr_debug() and dev_dbg() calls, which 59 enlarges the kernel text size by about 2%. 60 61 If a source file is compiled with DEBUG flag set, any 62 pr_debug() calls in it are enabled by default, but can be 63 disabled at runtime as below. Note that DEBUG flag is 64 turned on by many CONFIG_*DEBUG* options. 65 66 Usage: 67 68 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 69 which is contained in the 'debugfs' filesystem. Thus, the debugfs 70 filesystem must first be mounted before making use of this feature. 71 We refer the control file as: <debugfs>/dynamic_debug/control. This 72 file contains a list of the debug statements that can be enabled. The 73 format for each line of the file is: 74 75 filename:lineno [module]function flags format 76 77 filename : source file of the debug statement 78 lineno : line number of the debug statement 79 module : module that contains the debug statement 80 function : function that contains the debug statement 81 flags : '=p' means the line is turned 'on' for printing 82 format : the format used for the debug statement 83 84 From a live system: 85 86 nullarbor:~ # cat <debugfs>/dynamic_debug/control 87 # filename:lineno [module]function flags format 88 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012" 89 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012" 90 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012" 91 92 Example usage: 93 94 // enable the message at line 1603 of file svcsock.c 95 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 96 <debugfs>/dynamic_debug/control 97 98 // enable all the messages in file svcsock.c 99 nullarbor:~ # echo -n 'file svcsock.c +p' > 100 <debugfs>/dynamic_debug/control 101 102 // enable all the messages in the NFS server module 103 nullarbor:~ # echo -n 'module nfsd +p' > 104 <debugfs>/dynamic_debug/control 105 106 // enable all 12 messages in the function svc_process() 107 nullarbor:~ # echo -n 'func svc_process +p' > 108 <debugfs>/dynamic_debug/control 109 110 // disable all 12 messages in the function svc_process() 111 nullarbor:~ # echo -n 'func svc_process -p' > 112 <debugfs>/dynamic_debug/control 113 114 See Documentation/dynamic-debug-howto.txt for additional information. 115 116endmenu # "printk and dmesg options" 117 118menu "Compile-time checks and compiler options" 119 120config DEBUG_INFO 121 bool "Compile the kernel with debug info" 122 depends on DEBUG_KERNEL && !COMPILE_TEST 123 help 124 If you say Y here the resulting kernel image will include 125 debugging info resulting in a larger kernel image. 126 This adds debug symbols to the kernel and modules (gcc -g), and 127 is needed if you intend to use kernel crashdump or binary object 128 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 129 Say Y here only if you plan to debug the kernel. 130 131 If unsure, say N. 132 133config DEBUG_INFO_REDUCED 134 bool "Reduce debugging information" 135 depends on DEBUG_INFO 136 help 137 If you say Y here gcc is instructed to generate less debugging 138 information for structure types. This means that tools that 139 need full debugging information (like kgdb or systemtap) won't 140 be happy. But if you merely need debugging information to 141 resolve line numbers there is no loss. Advantage is that 142 build directory object sizes shrink dramatically over a full 143 DEBUG_INFO build and compile times are reduced too. 144 Only works with newer gcc versions. 145 146config DEBUG_INFO_SPLIT 147 bool "Produce split debuginfo in .dwo files" 148 depends on DEBUG_INFO 149 help 150 Generate debug info into separate .dwo files. This significantly 151 reduces the build directory size for builds with DEBUG_INFO, 152 because it stores the information only once on disk in .dwo 153 files instead of multiple times in object files and executables. 154 In addition the debug information is also compressed. 155 156 Requires recent gcc (4.7+) and recent gdb/binutils. 157 Any tool that packages or reads debug information would need 158 to know about the .dwo files and include them. 159 Incompatible with older versions of ccache. 160 161config DEBUG_INFO_DWARF4 162 bool "Generate dwarf4 debuginfo" 163 depends on DEBUG_INFO 164 help 165 Generate dwarf4 debug info. This requires recent versions 166 of gcc and gdb. It makes the debug information larger. 167 But it significantly improves the success of resolving 168 variables in gdb on optimized code. 169 170config GDB_SCRIPTS 171 bool "Provide GDB scripts for kernel debugging" 172 depends on DEBUG_INFO 173 help 174 This creates the required links to GDB helper scripts in the 175 build directory. If you load vmlinux into gdb, the helper 176 scripts will be automatically imported by gdb as well, and 177 additional functions are available to analyze a Linux kernel 178 instance. See Documentation/gdb-kernel-debugging.txt for further 179 details. 180 181config ENABLE_WARN_DEPRECATED 182 bool "Enable __deprecated logic" 183 default y 184 help 185 Enable the __deprecated logic in the kernel build. 186 Disable this to suppress the "warning: 'foo' is deprecated 187 (declared at kernel/power/somefile.c:1234)" messages. 188 189config ENABLE_MUST_CHECK 190 bool "Enable __must_check logic" 191 default y 192 help 193 Enable the __must_check logic in the kernel build. Disable this to 194 suppress the "warning: ignoring return value of 'foo', declared with 195 attribute warn_unused_result" messages. 196 197config FRAME_WARN 198 int "Warn for stack frames larger than (needs gcc 4.4)" 199 range 0 8192 200 default 0 if KASAN 201 default 1024 if !64BIT 202 default 2048 if 64BIT 203 help 204 Tell gcc to warn at build time for stack frames larger than this. 205 Setting this too low will cause a lot of warnings. 206 Setting it to 0 disables the warning. 207 Requires gcc 4.4 208 209config STRIP_ASM_SYMS 210 bool "Strip assembler-generated symbols during link" 211 default n 212 help 213 Strip internal assembler-generated symbols during a link (symbols 214 that look like '.Lxxx') so they don't pollute the output of 215 get_wchan() and suchlike. 216 217config READABLE_ASM 218 bool "Generate readable assembler code" 219 depends on DEBUG_KERNEL 220 help 221 Disable some compiler optimizations that tend to generate human unreadable 222 assembler output. This may make the kernel slightly slower, but it helps 223 to keep kernel developers who have to stare a lot at assembler listings 224 sane. 225 226config UNUSED_SYMBOLS 227 bool "Enable unused/obsolete exported symbols" 228 default y if X86 229 help 230 Unused but exported symbols make the kernel needlessly bigger. For 231 that reason most of these unused exports will soon be removed. This 232 option is provided temporarily to provide a transition period in case 233 some external kernel module needs one of these symbols anyway. If you 234 encounter such a case in your module, consider if you are actually 235 using the right API. (rationale: since nobody in the kernel is using 236 this in a module, there is a pretty good chance it's actually the 237 wrong interface to use). If you really need the symbol, please send a 238 mail to the linux kernel mailing list mentioning the symbol and why 239 you really need it, and what the merge plan to the mainline kernel for 240 your module is. 241 242config PAGE_OWNER 243 bool "Track page owner" 244 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 245 select DEBUG_FS 246 select STACKTRACE 247 select PAGE_EXTENSION 248 help 249 This keeps track of what call chain is the owner of a page, may 250 help to find bare alloc_page(s) leaks. Even if you include this 251 feature on your build, it is disabled in default. You should pass 252 "page_owner=on" to boot parameter in order to enable it. Eats 253 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 254 for user-space helper. 255 256 If unsure, say N. 257 258config DEBUG_FS 259 bool "Debug Filesystem" 260 help 261 debugfs is a virtual file system that kernel developers use to put 262 debugging files into. Enable this option to be able to read and 263 write to these files. 264 265 For detailed documentation on the debugfs API, see 266 Documentation/DocBook/filesystems. 267 268 If unsure, say N. 269 270config HEADERS_CHECK 271 bool "Run 'make headers_check' when building vmlinux" 272 depends on !UML 273 help 274 This option will extract the user-visible kernel headers whenever 275 building the kernel, and will run basic sanity checks on them to 276 ensure that exported files do not attempt to include files which 277 were not exported, etc. 278 279 If you're making modifications to header files which are 280 relevant for userspace, say 'Y', and check the headers 281 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 282 your build tree), to make sure they're suitable. 283 284config DEBUG_SECTION_MISMATCH 285 bool "Enable full Section mismatch analysis" 286 help 287 The section mismatch analysis checks if there are illegal 288 references from one section to another section. 289 During linktime or runtime, some sections are dropped; 290 any use of code/data previously in these sections would 291 most likely result in an oops. 292 In the code, functions and variables are annotated with 293 __init,, etc. (see the full list in include/linux/init.h), 294 which results in the code/data being placed in specific sections. 295 The section mismatch analysis is always performed after a full 296 kernel build, and enabling this option causes the following 297 additional steps to occur: 298 - Add the option -fno-inline-functions-called-once to gcc commands. 299 When inlining a function annotated with __init in a non-init 300 function, we would lose the section information and thus 301 the analysis would not catch the illegal reference. 302 This option tells gcc to inline less (but it does result in 303 a larger kernel). 304 - Run the section mismatch analysis for each module/built-in.o file. 305 When we run the section mismatch analysis on vmlinux.o, we 306 lose valueble information about where the mismatch was 307 introduced. 308 Running the analysis for each module/built-in.o file 309 tells where the mismatch happens much closer to the 310 source. The drawback is that the same mismatch is 311 reported at least twice. 312 - Enable verbose reporting from modpost in order to help resolve 313 the section mismatches that are reported. 314 315config SECTION_MISMATCH_WARN_ONLY 316 bool "Make section mismatch errors non-fatal" 317 default y 318 help 319 If you say N here, the build process will fail if there are any 320 section mismatch, instead of just throwing warnings. 321 322 If unsure, say Y. 323 324# 325# Select this config option from the architecture Kconfig, if it 326# is preferred to always offer frame pointers as a config 327# option on the architecture (regardless of KERNEL_DEBUG): 328# 329config ARCH_WANT_FRAME_POINTERS 330 bool 331 help 332 333config FRAME_POINTER 334 bool "Compile the kernel with frame pointers" 335 depends on DEBUG_KERNEL && \ 336 (CRIS || M68K || FRV || UML || \ 337 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \ 338 ARCH_WANT_FRAME_POINTERS 339 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 340 help 341 If you say Y here the resulting kernel image will be slightly 342 larger and slower, but it gives very useful debugging information 343 in case of kernel bugs. (precise oopses/stacktraces/warnings) 344 345config STACK_VALIDATION 346 bool "Compile-time stack metadata validation" 347 depends on HAVE_STACK_VALIDATION 348 default n 349 help 350 Add compile-time checks to validate stack metadata, including frame 351 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure 352 that runtime stack traces are more reliable. 353 354 For more information, see 355 tools/objtool/Documentation/stack-validation.txt. 356 357config DEBUG_FORCE_WEAK_PER_CPU 358 bool "Force weak per-cpu definitions" 359 depends on DEBUG_KERNEL 360 help 361 s390 and alpha require percpu variables in modules to be 362 defined weak to work around addressing range issue which 363 puts the following two restrictions on percpu variable 364 definitions. 365 366 1. percpu symbols must be unique whether static or not 367 2. percpu variables can't be defined inside a function 368 369 To ensure that generic code follows the above rules, this 370 option forces all percpu variables to be defined as weak. 371 372endmenu # "Compiler options" 373 374config MAGIC_SYSRQ 375 bool "Magic SysRq key" 376 depends on !UML 377 help 378 If you say Y here, you will have some control over the system even 379 if the system crashes for example during kernel debugging (e.g., you 380 will be able to flush the buffer cache to disk, reboot the system 381 immediately or dump some status information). This is accomplished 382 by pressing various keys while holding SysRq (Alt+PrintScreen). It 383 also works on a serial console (on PC hardware at least), if you 384 send a BREAK and then within 5 seconds a command keypress. The 385 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 386 unless you really know what this hack does. 387 388config MAGIC_SYSRQ_DEFAULT_ENABLE 389 hex "Enable magic SysRq key functions by default" 390 depends on MAGIC_SYSRQ 391 default 0x1 392 help 393 Specifies which SysRq key functions are enabled by default. 394 This may be set to 1 or 0 to enable or disable them all, or 395 to a bitmask as described in Documentation/sysrq.txt. 396 397config DEBUG_KERNEL 398 bool "Kernel debugging" 399 help 400 Say Y here if you are developing drivers or trying to debug and 401 identify kernel problems. 402 403menu "Memory Debugging" 404 405source mm/Kconfig.debug 406 407config DEBUG_OBJECTS 408 bool "Debug object operations" 409 depends on DEBUG_KERNEL 410 help 411 If you say Y here, additional code will be inserted into the 412 kernel to track the life time of various objects and validate 413 the operations on those objects. 414 415config DEBUG_OBJECTS_SELFTEST 416 bool "Debug objects selftest" 417 depends on DEBUG_OBJECTS 418 help 419 This enables the selftest of the object debug code. 420 421config DEBUG_OBJECTS_FREE 422 bool "Debug objects in freed memory" 423 depends on DEBUG_OBJECTS 424 help 425 This enables checks whether a k/v free operation frees an area 426 which contains an object which has not been deactivated 427 properly. This can make kmalloc/kfree-intensive workloads 428 much slower. 429 430config DEBUG_OBJECTS_TIMERS 431 bool "Debug timer objects" 432 depends on DEBUG_OBJECTS 433 help 434 If you say Y here, additional code will be inserted into the 435 timer routines to track the life time of timer objects and 436 validate the timer operations. 437 438config DEBUG_OBJECTS_WORK 439 bool "Debug work objects" 440 depends on DEBUG_OBJECTS 441 help 442 If you say Y here, additional code will be inserted into the 443 work queue routines to track the life time of work objects and 444 validate the work operations. 445 446config DEBUG_OBJECTS_RCU_HEAD 447 bool "Debug RCU callbacks objects" 448 depends on DEBUG_OBJECTS 449 help 450 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 451 452config DEBUG_OBJECTS_PERCPU_COUNTER 453 bool "Debug percpu counter objects" 454 depends on DEBUG_OBJECTS 455 help 456 If you say Y here, additional code will be inserted into the 457 percpu counter routines to track the life time of percpu counter 458 objects and validate the percpu counter operations. 459 460config DEBUG_OBJECTS_ENABLE_DEFAULT 461 int "debug_objects bootup default value (0-1)" 462 range 0 1 463 default "1" 464 depends on DEBUG_OBJECTS 465 help 466 Debug objects boot parameter default value 467 468config DEBUG_SLAB 469 bool "Debug slab memory allocations" 470 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 471 help 472 Say Y here to have the kernel do limited verification on memory 473 allocation as well as poisoning memory on free to catch use of freed 474 memory. This can make kmalloc/kfree-intensive workloads much slower. 475 476config DEBUG_SLAB_LEAK 477 bool "Memory leak debugging" 478 depends on DEBUG_SLAB 479 480config SLUB_DEBUG_ON 481 bool "SLUB debugging on by default" 482 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 483 default n 484 help 485 Boot with debugging on by default. SLUB boots by default with 486 the runtime debug capabilities switched off. Enabling this is 487 equivalent to specifying the "slub_debug" parameter on boot. 488 There is no support for more fine grained debug control like 489 possible with slub_debug=xxx. SLUB debugging may be switched 490 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 491 "slub_debug=-". 492 493config SLUB_STATS 494 default n 495 bool "Enable SLUB performance statistics" 496 depends on SLUB && SYSFS 497 help 498 SLUB statistics are useful to debug SLUBs allocation behavior in 499 order find ways to optimize the allocator. This should never be 500 enabled for production use since keeping statistics slows down 501 the allocator by a few percentage points. The slabinfo command 502 supports the determination of the most active slabs to figure 503 out which slabs are relevant to a particular load. 504 Try running: slabinfo -DA 505 506config HAVE_DEBUG_KMEMLEAK 507 bool 508 509config DEBUG_KMEMLEAK 510 bool "Kernel memory leak detector" 511 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 512 select DEBUG_FS 513 select STACKTRACE if STACKTRACE_SUPPORT 514 select KALLSYMS 515 select CRC32 516 help 517 Say Y here if you want to enable the memory leak 518 detector. The memory allocation/freeing is traced in a way 519 similar to the Boehm's conservative garbage collector, the 520 difference being that the orphan objects are not freed but 521 only shown in /sys/kernel/debug/kmemleak. Enabling this 522 feature will introduce an overhead to memory 523 allocations. See Documentation/kmemleak.txt for more 524 details. 525 526 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 527 of finding leaks due to the slab objects poisoning. 528 529 In order to access the kmemleak file, debugfs needs to be 530 mounted (usually at /sys/kernel/debug). 531 532config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 533 int "Maximum kmemleak early log entries" 534 depends on DEBUG_KMEMLEAK 535 range 200 40000 536 default 400 537 help 538 Kmemleak must track all the memory allocations to avoid 539 reporting false positives. Since memory may be allocated or 540 freed before kmemleak is initialised, an early log buffer is 541 used to store these actions. If kmemleak reports "early log 542 buffer exceeded", please increase this value. 543 544config DEBUG_KMEMLEAK_TEST 545 tristate "Simple test for the kernel memory leak detector" 546 depends on DEBUG_KMEMLEAK && m 547 help 548 This option enables a module that explicitly leaks memory. 549 550 If unsure, say N. 551 552config DEBUG_KMEMLEAK_DEFAULT_OFF 553 bool "Default kmemleak to off" 554 depends on DEBUG_KMEMLEAK 555 help 556 Say Y here to disable kmemleak by default. It can then be enabled 557 on the command line via kmemleak=on. 558 559config DEBUG_STACK_USAGE 560 bool "Stack utilization instrumentation" 561 depends on DEBUG_KERNEL && !IA64 562 help 563 Enables the display of the minimum amount of free stack which each 564 task has ever had available in the sysrq-T and sysrq-P debug output. 565 566 This option will slow down process creation somewhat. 567 568config DEBUG_VM 569 bool "Debug VM" 570 depends on DEBUG_KERNEL 571 help 572 Enable this to turn on extended checks in the virtual-memory system 573 that may impact performance. 574 575 If unsure, say N. 576 577config DEBUG_VM_VMACACHE 578 bool "Debug VMA caching" 579 depends on DEBUG_VM 580 help 581 Enable this to turn on VMA caching debug information. Doing so 582 can cause significant overhead, so only enable it in non-production 583 environments. 584 585 If unsure, say N. 586 587config DEBUG_VM_RB 588 bool "Debug VM red-black trees" 589 depends on DEBUG_VM 590 help 591 Enable VM red-black tree debugging information and extra validations. 592 593 If unsure, say N. 594 595config DEBUG_VM_PGFLAGS 596 bool "Debug page-flags operations" 597 depends on DEBUG_VM 598 help 599 Enables extra validation on page flags operations. 600 601 If unsure, say N. 602 603config DEBUG_VIRTUAL 604 bool "Debug VM translations" 605 depends on DEBUG_KERNEL && X86 606 help 607 Enable some costly sanity checks in virtual to page code. This can 608 catch mistakes with virt_to_page() and friends. 609 610 If unsure, say N. 611 612config DEBUG_NOMMU_REGIONS 613 bool "Debug the global anon/private NOMMU mapping region tree" 614 depends on DEBUG_KERNEL && !MMU 615 help 616 This option causes the global tree of anonymous and private mapping 617 regions to be regularly checked for invalid topology. 618 619config DEBUG_MEMORY_INIT 620 bool "Debug memory initialisation" if EXPERT 621 default !EXPERT 622 help 623 Enable this for additional checks during memory initialisation. 624 The sanity checks verify aspects of the VM such as the memory model 625 and other information provided by the architecture. Verbose 626 information will be printed at KERN_DEBUG loglevel depending 627 on the mminit_loglevel= command-line option. 628 629 If unsure, say Y 630 631config MEMORY_NOTIFIER_ERROR_INJECT 632 tristate "Memory hotplug notifier error injection module" 633 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 634 help 635 This option provides the ability to inject artificial errors to 636 memory hotplug notifier chain callbacks. It is controlled through 637 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 638 639 If the notifier call chain should be failed with some events 640 notified, write the error code to "actions/<notifier event>/error". 641 642 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 643 644 # cd /sys/kernel/debug/notifier-error-inject/memory 645 # echo -12 > actions/MEM_GOING_OFFLINE/error 646 # echo offline > /sys/devices/system/memory/memoryXXX/state 647 bash: echo: write error: Cannot allocate memory 648 649 To compile this code as a module, choose M here: the module will 650 be called memory-notifier-error-inject. 651 652 If unsure, say N. 653 654config DEBUG_PER_CPU_MAPS 655 bool "Debug access to per_cpu maps" 656 depends on DEBUG_KERNEL 657 depends on SMP 658 help 659 Say Y to verify that the per_cpu map being accessed has 660 been set up. This adds a fair amount of code to kernel memory 661 and decreases performance. 662 663 Say N if unsure. 664 665config DEBUG_HIGHMEM 666 bool "Highmem debugging" 667 depends on DEBUG_KERNEL && HIGHMEM 668 help 669 This option enables additional error checking for high memory 670 systems. Disable for production systems. 671 672config HAVE_DEBUG_STACKOVERFLOW 673 bool 674 675config DEBUG_STACKOVERFLOW 676 bool "Check for stack overflows" 677 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 678 ---help--- 679 Say Y here if you want to check for overflows of kernel, IRQ 680 and exception stacks (if your architecture uses them). This 681 option will show detailed messages if free stack space drops 682 below a certain limit. 683 684 These kinds of bugs usually occur when call-chains in the 685 kernel get too deep, especially when interrupts are 686 involved. 687 688 Use this in cases where you see apparently random memory 689 corruption, especially if it appears in 'struct thread_info' 690 691 If in doubt, say "N". 692 693source "lib/Kconfig.kmemcheck" 694 695source "lib/Kconfig.kasan" 696 697endmenu # "Memory Debugging" 698 699config ARCH_HAS_KCOV 700 bool 701 help 702 KCOV does not have any arch-specific code, but currently it is enabled 703 only for x86_64. KCOV requires testing on other archs, and most likely 704 disabling of instrumentation for some early boot code. 705 706config KCOV 707 bool "Code coverage for fuzzing" 708 depends on ARCH_HAS_KCOV 709 select DEBUG_FS 710 help 711 KCOV exposes kernel code coverage information in a form suitable 712 for coverage-guided fuzzing (randomized testing). 713 714 If RANDOMIZE_BASE is enabled, PC values will not be stable across 715 different machines and across reboots. If you need stable PC values, 716 disable RANDOMIZE_BASE. 717 718 For more details, see Documentation/kcov.txt. 719 720config DEBUG_SHIRQ 721 bool "Debug shared IRQ handlers" 722 depends on DEBUG_KERNEL 723 help 724 Enable this to generate a spurious interrupt as soon as a shared 725 interrupt handler is registered, and just before one is deregistered. 726 Drivers ought to be able to handle interrupts coming in at those 727 points; some don't and need to be caught. 728 729menu "Debug Lockups and Hangs" 730 731config LOCKUP_DETECTOR 732 bool "Detect Hard and Soft Lockups" 733 depends on DEBUG_KERNEL && !S390 734 help 735 Say Y here to enable the kernel to act as a watchdog to detect 736 hard and soft lockups. 737 738 Softlockups are bugs that cause the kernel to loop in kernel 739 mode for more than 20 seconds, without giving other tasks a 740 chance to run. The current stack trace is displayed upon 741 detection and the system will stay locked up. 742 743 Hardlockups are bugs that cause the CPU to loop in kernel mode 744 for more than 10 seconds, without letting other interrupts have a 745 chance to run. The current stack trace is displayed upon detection 746 and the system will stay locked up. 747 748 The overhead should be minimal. A periodic hrtimer runs to 749 generate interrupts and kick the watchdog task every 4 seconds. 750 An NMI is generated every 10 seconds or so to check for hardlockups. 751 752 The frequency of hrtimer and NMI events and the soft and hard lockup 753 thresholds can be controlled through the sysctl watchdog_thresh. 754 755config HARDLOCKUP_DETECTOR 756 def_bool y 757 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 758 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 759 760config BOOTPARAM_HARDLOCKUP_PANIC 761 bool "Panic (Reboot) On Hard Lockups" 762 depends on HARDLOCKUP_DETECTOR 763 help 764 Say Y here to enable the kernel to panic on "hard lockups", 765 which are bugs that cause the kernel to loop in kernel 766 mode with interrupts disabled for more than 10 seconds (configurable 767 using the watchdog_thresh sysctl). 768 769 Say N if unsure. 770 771config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 772 int 773 depends on HARDLOCKUP_DETECTOR 774 range 0 1 775 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 776 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 777 778config BOOTPARAM_SOFTLOCKUP_PANIC 779 bool "Panic (Reboot) On Soft Lockups" 780 depends on LOCKUP_DETECTOR 781 help 782 Say Y here to enable the kernel to panic on "soft lockups", 783 which are bugs that cause the kernel to loop in kernel 784 mode for more than 20 seconds (configurable using the watchdog_thresh 785 sysctl), without giving other tasks a chance to run. 786 787 The panic can be used in combination with panic_timeout, 788 to cause the system to reboot automatically after a 789 lockup has been detected. This feature is useful for 790 high-availability systems that have uptime guarantees and 791 where a lockup must be resolved ASAP. 792 793 Say N if unsure. 794 795config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 796 int 797 depends on LOCKUP_DETECTOR 798 range 0 1 799 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 800 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 801 802config DETECT_HUNG_TASK 803 bool "Detect Hung Tasks" 804 depends on DEBUG_KERNEL 805 default LOCKUP_DETECTOR 806 help 807 Say Y here to enable the kernel to detect "hung tasks", 808 which are bugs that cause the task to be stuck in 809 uninterruptible "D" state indefinitiley. 810 811 When a hung task is detected, the kernel will print the 812 current stack trace (which you should report), but the 813 task will stay in uninterruptible state. If lockdep is 814 enabled then all held locks will also be reported. This 815 feature has negligible overhead. 816 817config DEFAULT_HUNG_TASK_TIMEOUT 818 int "Default timeout for hung task detection (in seconds)" 819 depends on DETECT_HUNG_TASK 820 default 120 821 help 822 This option controls the default timeout (in seconds) used 823 to determine when a task has become non-responsive and should 824 be considered hung. 825 826 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 827 sysctl or by writing a value to 828 /proc/sys/kernel/hung_task_timeout_secs. 829 830 A timeout of 0 disables the check. The default is two minutes. 831 Keeping the default should be fine in most cases. 832 833config BOOTPARAM_HUNG_TASK_PANIC 834 bool "Panic (Reboot) On Hung Tasks" 835 depends on DETECT_HUNG_TASK 836 help 837 Say Y here to enable the kernel to panic on "hung tasks", 838 which are bugs that cause the kernel to leave a task stuck 839 in uninterruptible "D" state. 840 841 The panic can be used in combination with panic_timeout, 842 to cause the system to reboot automatically after a 843 hung task has been detected. This feature is useful for 844 high-availability systems that have uptime guarantees and 845 where a hung tasks must be resolved ASAP. 846 847 Say N if unsure. 848 849config BOOTPARAM_HUNG_TASK_PANIC_VALUE 850 int 851 depends on DETECT_HUNG_TASK 852 range 0 1 853 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 854 default 1 if BOOTPARAM_HUNG_TASK_PANIC 855 856config WQ_WATCHDOG 857 bool "Detect Workqueue Stalls" 858 depends on DEBUG_KERNEL 859 help 860 Say Y here to enable stall detection on workqueues. If a 861 worker pool doesn't make forward progress on a pending work 862 item for over a given amount of time, 30s by default, a 863 warning message is printed along with dump of workqueue 864 state. This can be configured through kernel parameter 865 "workqueue.watchdog_thresh" and its sysfs counterpart. 866 867endmenu # "Debug lockups and hangs" 868 869config PANIC_ON_OOPS 870 bool "Panic on Oops" 871 help 872 Say Y here to enable the kernel to panic when it oopses. This 873 has the same effect as setting oops=panic on the kernel command 874 line. 875 876 This feature is useful to ensure that the kernel does not do 877 anything erroneous after an oops which could result in data 878 corruption or other issues. 879 880 Say N if unsure. 881 882config PANIC_ON_OOPS_VALUE 883 int 884 range 0 1 885 default 0 if !PANIC_ON_OOPS 886 default 1 if PANIC_ON_OOPS 887 888config PANIC_TIMEOUT 889 int "panic timeout" 890 default 0 891 help 892 Set the timeout value (in seconds) until a reboot occurs when the 893 the kernel panics. If n = 0, then we wait forever. A timeout 894 value n > 0 will wait n seconds before rebooting, while a timeout 895 value n < 0 will reboot immediately. 896 897config SCHED_DEBUG 898 bool "Collect scheduler debugging info" 899 depends on DEBUG_KERNEL && PROC_FS 900 default y 901 help 902 If you say Y here, the /proc/sched_debug file will be provided 903 that can help debug the scheduler. The runtime overhead of this 904 option is minimal. 905 906config SCHED_INFO 907 bool 908 default n 909 910config SCHEDSTATS 911 bool "Collect scheduler statistics" 912 depends on DEBUG_KERNEL && PROC_FS 913 select SCHED_INFO 914 help 915 If you say Y here, additional code will be inserted into the 916 scheduler and related routines to collect statistics about 917 scheduler behavior and provide them in /proc/schedstat. These 918 stats may be useful for both tuning and debugging the scheduler 919 If you aren't debugging the scheduler or trying to tune a specific 920 application, you can say N to avoid the very slight overhead 921 this adds. 922 923config SCHED_STACK_END_CHECK 924 bool "Detect stack corruption on calls to schedule()" 925 depends on DEBUG_KERNEL 926 default n 927 help 928 This option checks for a stack overrun on calls to schedule(). 929 If the stack end location is found to be over written always panic as 930 the content of the corrupted region can no longer be trusted. 931 This is to ensure no erroneous behaviour occurs which could result in 932 data corruption or a sporadic crash at a later stage once the region 933 is examined. The runtime overhead introduced is minimal. 934 935config DEBUG_TIMEKEEPING 936 bool "Enable extra timekeeping sanity checking" 937 help 938 This option will enable additional timekeeping sanity checks 939 which may be helpful when diagnosing issues where timekeeping 940 problems are suspected. 941 942 This may include checks in the timekeeping hotpaths, so this 943 option may have a (very small) performance impact to some 944 workloads. 945 946 If unsure, say N. 947 948config TIMER_STATS 949 bool "Collect kernel timers statistics" 950 depends on DEBUG_KERNEL && PROC_FS 951 help 952 If you say Y here, additional code will be inserted into the 953 timer routines to collect statistics about kernel timers being 954 reprogrammed. The statistics can be read from /proc/timer_stats. 955 The statistics collection is started by writing 1 to /proc/timer_stats, 956 writing 0 stops it. This feature is useful to collect information 957 about timer usage patterns in kernel and userspace. This feature 958 is lightweight if enabled in the kernel config but not activated 959 (it defaults to deactivated on bootup and will only be activated 960 if some application like powertop activates it explicitly). 961 962config DEBUG_PREEMPT 963 bool "Debug preemptible kernel" 964 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 965 default y 966 help 967 If you say Y here then the kernel will use a debug variant of the 968 commonly used smp_processor_id() function and will print warnings 969 if kernel code uses it in a preemption-unsafe way. Also, the kernel 970 will detect preemption count underflows. 971 972menu "Lock Debugging (spinlocks, mutexes, etc...)" 973 974config DEBUG_RT_MUTEXES 975 bool "RT Mutex debugging, deadlock detection" 976 depends on DEBUG_KERNEL && RT_MUTEXES 977 help 978 This allows rt mutex semantics violations and rt mutex related 979 deadlocks (lockups) to be detected and reported automatically. 980 981config DEBUG_SPINLOCK 982 bool "Spinlock and rw-lock debugging: basic checks" 983 depends on DEBUG_KERNEL 984 select UNINLINE_SPIN_UNLOCK 985 help 986 Say Y here and build SMP to catch missing spinlock initialization 987 and certain other kinds of spinlock errors commonly made. This is 988 best used in conjunction with the NMI watchdog so that spinlock 989 deadlocks are also debuggable. 990 991config DEBUG_MUTEXES 992 bool "Mutex debugging: basic checks" 993 depends on DEBUG_KERNEL 994 help 995 This feature allows mutex semantics violations to be detected and 996 reported. 997 998config DEBUG_WW_MUTEX_SLOWPATH 999 bool "Wait/wound mutex debugging: Slowpath testing" 1000 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
1001 select DEBUG_LOCK_ALLOC 1002 select DEBUG_SPINLOCK 1003 select DEBUG_MUTEXES 1004 help 1005 This feature enables slowpath testing for w/w mutex users by 1006 injecting additional -EDEADLK wound/backoff cases. Together with 1007 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 1008 will test all possible w/w mutex interface abuse with the 1009 exception of simply not acquiring all the required locks. 1010 Note that this feature can introduce significant overhead, so 1011 it really should not be enabled in a production or distro kernel, 1012 even a debug kernel. If you are a driver writer, enable it. If 1013 you are a distro, do not. 1014 1015config DEBUG_LOCK_ALLOC 1016 bool "Lock debugging: detect incorrect freeing of live locks" 1017 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1018 select DEBUG_SPINLOCK 1019 select DEBUG_MUTEXES 1020 select LOCKDEP 1021 help 1022 This feature will check whether any held lock (spinlock, rwlock, 1023 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1024 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1025 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1026 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1027 held during task exit. 1028 1029config PROVE_LOCKING 1030 bool "Lock debugging: prove locking correctness" 1031 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1032 select LOCKDEP 1033 select DEBUG_SPINLOCK 1034 select DEBUG_MUTEXES 1035 select DEBUG_LOCK_ALLOC 1036 select TRACE_IRQFLAGS 1037 default n 1038 help 1039 This feature enables the kernel to prove that all locking 1040 that occurs in the kernel runtime is mathematically 1041 correct: that under no circumstance could an arbitrary (and 1042 not yet triggered) combination of observed locking 1043 sequences (on an arbitrary number of CPUs, running an 1044 arbitrary number of tasks and interrupt contexts) cause a 1045 deadlock. 1046 1047 In short, this feature enables the kernel to report locking 1048 related deadlocks before they actually occur. 1049 1050 The proof does not depend on how hard and complex a 1051 deadlock scenario would be to trigger: how many 1052 participant CPUs, tasks and irq-contexts would be needed 1053 for it to trigger. The proof also does not depend on 1054 timing: if a race and a resulting deadlock is possible 1055 theoretically (no matter how unlikely the race scenario 1056 is), it will be proven so and will immediately be 1057 reported by the kernel (once the event is observed that 1058 makes the deadlock theoretically possible). 1059 1060 If a deadlock is impossible (i.e. the locking rules, as 1061 observed by the kernel, are mathematically correct), the 1062 kernel reports nothing. 1063 1064 NOTE: this feature can also be enabled for rwlocks, mutexes 1065 and rwsems - in which case all dependencies between these 1066 different locking variants are observed and mapped too, and 1067 the proof of observed correctness is also maintained for an 1068 arbitrary combination of these separate locking variants. 1069 1070 For more details, see Documentation/locking/lockdep-design.txt. 1071 1072config LOCKDEP 1073 bool 1074 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1075 select STACKTRACE 1076 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE 1077 select KALLSYMS 1078 select KALLSYMS_ALL 1079 1080config LOCK_STAT 1081 bool "Lock usage statistics" 1082 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1083 select LOCKDEP 1084 select DEBUG_SPINLOCK 1085 select DEBUG_MUTEXES 1086 select DEBUG_LOCK_ALLOC 1087 default n 1088 help 1089 This feature enables tracking lock contention points 1090 1091 For more details, see Documentation/locking/lockstat.txt 1092 1093 This also enables lock events required by "perf lock", 1094 subcommand of perf. 1095 If you want to use "perf lock", you also need to turn on 1096 CONFIG_EVENT_TRACING. 1097 1098 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1099 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1100 1101config DEBUG_LOCKDEP 1102 bool "Lock dependency engine debugging" 1103 depends on DEBUG_KERNEL && LOCKDEP 1104 help 1105 If you say Y here, the lock dependency engine will do 1106 additional runtime checks to debug itself, at the price 1107 of more runtime overhead. 1108 1109config DEBUG_ATOMIC_SLEEP 1110 bool "Sleep inside atomic section checking" 1111 select PREEMPT_COUNT 1112 depends on DEBUG_KERNEL 1113 help 1114 If you say Y here, various routines which may sleep will become very 1115 noisy if they are called inside atomic sections: when a spinlock is 1116 held, inside an rcu read side critical section, inside preempt disabled 1117 sections, inside an interrupt, etc... 1118 1119config DEBUG_LOCKING_API_SELFTESTS 1120 bool "Locking API boot-time self-tests" 1121 depends on DEBUG_KERNEL 1122 help 1123 Say Y here if you want the kernel to run a short self-test during 1124 bootup. The self-test checks whether common types of locking bugs 1125 are detected by debugging mechanisms or not. (if you disable 1126 lock debugging then those bugs wont be detected of course.) 1127 The following locking APIs are covered: spinlocks, rwlocks, 1128 mutexes and rwsems. 1129 1130config LOCK_TORTURE_TEST 1131 tristate "torture tests for locking" 1132 depends on DEBUG_KERNEL 1133 select TORTURE_TEST 1134 default n 1135 help 1136 This option provides a kernel module that runs torture tests 1137 on kernel locking primitives. The kernel module may be built 1138 after the fact on the running kernel to be tested, if desired. 1139 1140 Say Y here if you want kernel locking-primitive torture tests 1141 to be built into the kernel. 1142 Say M if you want these torture tests to build as a module. 1143 Say N if you are unsure. 1144 1145endmenu # lock debugging 1146 1147config TRACE_IRQFLAGS 1148 bool 1149 help 1150 Enables hooks to interrupt enabling and disabling for 1151 either tracing or lock debugging. 1152 1153config STACKTRACE 1154 bool "Stack backtrace support" 1155 depends on STACKTRACE_SUPPORT 1156 help 1157 This option causes the kernel to create a /proc/pid/stack for 1158 every process, showing its current stack trace. 1159 It is also used by various kernel debugging features that require 1160 stack trace generation. 1161 1162config DEBUG_KOBJECT 1163 bool "kobject debugging" 1164 depends on DEBUG_KERNEL 1165 help 1166 If you say Y here, some extra kobject debugging messages will be sent 1167 to the syslog. 1168 1169config DEBUG_KOBJECT_RELEASE 1170 bool "kobject release debugging" 1171 depends on DEBUG_OBJECTS_TIMERS 1172 help 1173 kobjects are reference counted objects. This means that their 1174 last reference count put is not predictable, and the kobject can 1175 live on past the point at which a driver decides to drop it's 1176 initial reference to the kobject gained on allocation. An 1177 example of this would be a struct device which has just been 1178 unregistered. 1179 1180 However, some buggy drivers assume that after such an operation, 1181 the memory backing the kobject can be immediately freed. This 1182 goes completely against the principles of a refcounted object. 1183 1184 If you say Y here, the kernel will delay the release of kobjects 1185 on the last reference count to improve the visibility of this 1186 kind of kobject release bug. 1187 1188config HAVE_DEBUG_BUGVERBOSE 1189 bool 1190 1191config DEBUG_BUGVERBOSE 1192 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1193 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1194 default y 1195 help 1196 Say Y here to make BUG() panics output the file name and line number 1197 of the BUG call as well as the EIP and oops trace. This aids 1198 debugging but costs about 70-100K of memory. 1199 1200config DEBUG_LIST 1201 bool "Debug linked list manipulation" 1202 depends on DEBUG_KERNEL 1203 help 1204 Enable this to turn on extended checks in the linked-list 1205 walking routines. 1206 1207 If unsure, say N. 1208 1209config DEBUG_PI_LIST 1210 bool "Debug priority linked list manipulation" 1211 depends on DEBUG_KERNEL 1212 help 1213 Enable this to turn on extended checks in the priority-ordered 1214 linked-list (plist) walking routines. This checks the entire 1215 list multiple times during each manipulation. 1216 1217 If unsure, say N. 1218 1219config DEBUG_SG 1220 bool "Debug SG table operations" 1221 depends on DEBUG_KERNEL 1222 help 1223 Enable this to turn on checks on scatter-gather tables. This can 1224 help find problems with drivers that do not properly initialize 1225 their sg tables. 1226 1227 If unsure, say N. 1228 1229config DEBUG_NOTIFIERS 1230 bool "Debug notifier call chains" 1231 depends on DEBUG_KERNEL 1232 help 1233 Enable this to turn on sanity checking for notifier call chains. 1234 This is most useful for kernel developers to make sure that 1235 modules properly unregister themselves from notifier chains. 1236 This is a relatively cheap check but if you care about maximum 1237 performance, say N. 1238 1239config DEBUG_CREDENTIALS 1240 bool "Debug credential management" 1241 depends on DEBUG_KERNEL 1242 help 1243 Enable this to turn on some debug checking for credential 1244 management. The additional code keeps track of the number of 1245 pointers from task_structs to any given cred struct, and checks to 1246 see that this number never exceeds the usage count of the cred 1247 struct. 1248 1249 Furthermore, if SELinux is enabled, this also checks that the 1250 security pointer in the cred struct is never seen to be invalid. 1251 1252 If unsure, say N. 1253 1254menu "RCU Debugging" 1255 1256config PROVE_RCU 1257 def_bool PROVE_LOCKING 1258 1259config PROVE_RCU_REPEATEDLY 1260 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1261 depends on PROVE_RCU 1262 default n 1263 help 1264 By itself, PROVE_RCU will disable checking upon issuing the 1265 first warning (or "splat"). This feature prevents such 1266 disabling, allowing multiple RCU-lockdep warnings to be printed 1267 on a single reboot. 1268 1269 Say Y to allow multiple RCU-lockdep warnings per boot. 1270 1271 Say N if you are unsure. 1272 1273config SPARSE_RCU_POINTER 1274 bool "RCU debugging: sparse-based checks for pointer usage" 1275 default n 1276 help 1277 This feature enables the __rcu sparse annotation for 1278 RCU-protected pointers. This annotation will cause sparse 1279 to flag any non-RCU used of annotated pointers. This can be 1280 helpful when debugging RCU usage. Please note that this feature 1281 is not intended to enforce code cleanliness; it is instead merely 1282 a debugging aid. 1283 1284 Say Y to make sparse flag questionable use of RCU-protected pointers 1285 1286 Say N if you are unsure. 1287 1288config TORTURE_TEST 1289 tristate 1290 default n 1291 1292config RCU_TORTURE_TEST 1293 tristate "torture tests for RCU" 1294 depends on DEBUG_KERNEL 1295 select TORTURE_TEST 1296 select SRCU 1297 select TASKS_RCU 1298 default n 1299 help 1300 This option provides a kernel module that runs torture tests 1301 on the RCU infrastructure. The kernel module may be built 1302 after the fact on the running kernel to be tested, if desired. 1303 1304 Say Y here if you want RCU torture tests to be built into 1305 the kernel. 1306 Say M if you want the RCU torture tests to build as a module. 1307 Say N if you are unsure. 1308 1309config RCU_TORTURE_TEST_RUNNABLE 1310 bool "torture tests for RCU runnable by default" 1311 depends on RCU_TORTURE_TEST = y 1312 default n 1313 help 1314 This option provides a way to build the RCU torture tests 1315 directly into the kernel without them starting up at boot 1316 time. You can use /proc/sys/kernel/rcutorture_runnable 1317 to manually override this setting. This /proc file is 1318 available only when the RCU torture tests have been built 1319 into the kernel. 1320 1321 Say Y here if you want the RCU torture tests to start during 1322 boot (you probably don't). 1323 Say N here if you want the RCU torture tests to start only 1324 after being manually enabled via /proc. 1325 1326config RCU_TORTURE_TEST_SLOW_PREINIT 1327 bool "Slow down RCU grace-period pre-initialization to expose races" 1328 depends on RCU_TORTURE_TEST 1329 help 1330 This option delays grace-period pre-initialization (the 1331 propagation of CPU-hotplug changes up the rcu_node combining 1332 tree) for a few jiffies between initializing each pair of 1333 consecutive rcu_node structures. This helps to expose races 1334 involving grace-period pre-initialization, in other words, it 1335 makes your kernel less stable. It can also greatly increase 1336 grace-period latency, especially on systems with large numbers 1337 of CPUs. This is useful when torture-testing RCU, but in 1338 almost no other circumstance. 1339 1340 Say Y here if you want your system to crash and hang more often. 1341 Say N if you want a sane system. 1342 1343config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY 1344 int "How much to slow down RCU grace-period pre-initialization" 1345 range 0 5 1346 default 3 1347 depends on RCU_TORTURE_TEST_SLOW_PREINIT 1348 help 1349 This option specifies the number of jiffies to wait between 1350 each rcu_node structure pre-initialization step. 1351 1352config RCU_TORTURE_TEST_SLOW_INIT 1353 bool "Slow down RCU grace-period initialization to expose races" 1354 depends on RCU_TORTURE_TEST 1355 help 1356 This option delays grace-period initialization for a few 1357 jiffies between initializing each pair of consecutive 1358 rcu_node structures. This helps to expose races involving 1359 grace-period initialization, in other words, it makes your 1360 kernel less stable. It can also greatly increase grace-period 1361 latency, especially on systems with large numbers of CPUs. 1362 This is useful when torture-testing RCU, but in almost no 1363 other circumstance. 1364 1365 Say Y here if you want your system to crash and hang more often. 1366 Say N if you want a sane system. 1367 1368config RCU_TORTURE_TEST_SLOW_INIT_DELAY 1369 int "How much to slow down RCU grace-period initialization" 1370 range 0 5 1371 default 3 1372 depends on RCU_TORTURE_TEST_SLOW_INIT 1373 help 1374 This option specifies the number of jiffies to wait between 1375 each rcu_node structure initialization. 1376 1377config RCU_TORTURE_TEST_SLOW_CLEANUP 1378 bool "Slow down RCU grace-period cleanup to expose races" 1379 depends on RCU_TORTURE_TEST 1380 help 1381 This option delays grace-period cleanup for a few jiffies 1382 between cleaning up each pair of consecutive rcu_node 1383 structures. This helps to expose races involving grace-period 1384 cleanup, in other words, it makes your kernel less stable. 1385 It can also greatly increase grace-period latency, especially 1386 on systems with large numbers of CPUs. This is useful when 1387 torture-testing RCU, but in almost no other circumstance. 1388 1389 Say Y here if you want your system to crash and hang more often. 1390 Say N if you want a sane system. 1391 1392config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY 1393 int "How much to slow down RCU grace-period cleanup" 1394 range 0 5 1395 default 3 1396 depends on RCU_TORTURE_TEST_SLOW_CLEANUP 1397 help 1398 This option specifies the number of jiffies to wait between 1399 each rcu_node structure cleanup operation. 1400 1401config RCU_CPU_STALL_TIMEOUT 1402 int "RCU CPU stall timeout in seconds" 1403 depends on RCU_STALL_COMMON 1404 range 3 300 1405 default 21 1406 help 1407 If a given RCU grace period extends more than the specified 1408 number of seconds, a CPU stall warning is printed. If the 1409 RCU grace period persists, additional CPU stall warnings are 1410 printed at more widely spaced intervals. 1411 1412config RCU_TRACE 1413 bool "Enable tracing for RCU" 1414 depends on DEBUG_KERNEL 1415 select TRACE_CLOCK 1416 help 1417 This option provides tracing in RCU which presents stats 1418 in debugfs for debugging RCU implementation. 1419 1420 Say Y here if you want to enable RCU tracing 1421 Say N if you are unsure. 1422 1423config RCU_EQS_DEBUG 1424 bool "Provide debugging asserts for adding NO_HZ support to an arch" 1425 depends on DEBUG_KERNEL 1426 help 1427 This option provides consistency checks in RCU's handling of 1428 NO_HZ. These checks have proven quite helpful in detecting 1429 bugs in arch-specific NO_HZ code. 1430 1431 Say N here if you need ultimate kernel/user switch latencies 1432 Say Y if you are unsure 1433 1434endmenu # "RCU Debugging" 1435 1436config DEBUG_WQ_FORCE_RR_CPU 1437 bool "Force round-robin CPU selection for unbound work items" 1438 depends on DEBUG_KERNEL 1439 default n 1440 help 1441 Workqueue used to implicitly guarantee that work items queued 1442 without explicit CPU specified are put on the local CPU. This 1443 guarantee is no longer true and while local CPU is still 1444 preferred work items may be put on foreign CPUs. Kernel 1445 parameter "workqueue.debug_force_rr_cpu" is added to force 1446 round-robin CPU selection to flush out usages which depend on the 1447 now broken guarantee. This config option enables the debug 1448 feature by default. When enabled, memory and cache locality will 1449 be impacted. 1450 1451config DEBUG_BLOCK_EXT_DEVT 1452 bool "Force extended block device numbers and spread them" 1453 depends on DEBUG_KERNEL 1454 depends on BLOCK 1455 default n 1456 help 1457 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1458 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1459 YOU ARE DOING. Distros, please enable this and fix whatever 1460 is broken. 1461 1462 Conventionally, block device numbers are allocated from 1463 predetermined contiguous area. However, extended block area 1464 may introduce non-contiguous block device numbers. This 1465 option forces most block device numbers to be allocated from 1466 the extended space and spreads them to discover kernel or 1467 userland code paths which assume predetermined contiguous 1468 device number allocation. 1469 1470 Note that turning on this debug option shuffles all the 1471 device numbers for all IDE and SCSI devices including libata 1472 ones, so root partition specified using device number 1473 directly (via rdev or root=MAJ:MIN) won't work anymore. 1474 Textual device names (root=/dev/sdXn) will continue to work. 1475 1476 Say N if you are unsure. 1477 1478config CPU_HOTPLUG_STATE_CONTROL 1479 bool "Enable CPU hotplug state control" 1480 depends on DEBUG_KERNEL 1481 depends on HOTPLUG_CPU 1482 default n 1483 help 1484 Allows to write steps between "offline" and "online" to the CPUs 1485 sysfs target file so states can be stepped granular. This is a debug 1486 option for now as the hotplug machinery cannot be stopped and 1487 restarted at arbitrary points yet. 1488 1489 Say N if your are unsure. 1490 1491config NOTIFIER_ERROR_INJECTION 1492 tristate "Notifier error injection" 1493 depends on DEBUG_KERNEL 1494 select DEBUG_FS 1495 help 1496 This option provides the ability to inject artificial errors to 1497 specified notifier chain callbacks. It is useful to test the error 1498 handling of notifier call chain failures. 1499 1500 Say N if unsure. 1501 1502config CPU_NOTIFIER_ERROR_INJECT 1503 tristate "CPU notifier error injection module" 1504 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1505 help 1506 This option provides a kernel module that can be used to test 1507 the error handling of the cpu notifiers by injecting artificial 1508 errors to CPU notifier chain callbacks. It is controlled through 1509 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1510 1511 If the notifier call chain should be failed with some events 1512 notified, write the error code to "actions/<notifier event>/error". 1513 1514 Example: Inject CPU offline error (-1 == -EPERM) 1515 1516 # cd /sys/kernel/debug/notifier-error-inject/cpu 1517 # echo -1 > actions/CPU_DOWN_PREPARE/error 1518 # echo 0 > /sys/devices/system/cpu/cpu1/online 1519 bash: echo: write error: Operation not permitted 1520 1521 To compile this code as a module, choose M here: the module will 1522 be called cpu-notifier-error-inject. 1523 1524 If unsure, say N. 1525 1526config PM_NOTIFIER_ERROR_INJECT 1527 tristate "PM notifier error injection module" 1528 depends on PM && NOTIFIER_ERROR_INJECTION 1529 default m if PM_DEBUG 1530 help 1531 This option provides the ability to inject artificial errors to 1532 PM notifier chain callbacks. It is controlled through debugfs 1533 interface /sys/kernel/debug/notifier-error-inject/pm 1534 1535 If the notifier call chain should be failed with some events 1536 notified, write the error code to "actions/<notifier event>/error". 1537 1538 Example: Inject PM suspend error (-12 = -ENOMEM) 1539 1540 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1541 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1542 # echo mem > /sys/power/state 1543 bash: echo: write error: Cannot allocate memory 1544 1545 To compile this code as a module, choose M here: the module will 1546 be called pm-notifier-error-inject. 1547 1548 If unsure, say N. 1549 1550config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1551 tristate "OF reconfig notifier error injection module" 1552 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1553 help 1554 This option provides the ability to inject artificial errors to 1555 OF reconfig notifier chain callbacks. It is controlled 1556 through debugfs interface under 1557 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1558 1559 If the notifier call chain should be failed with some events 1560 notified, write the error code to "actions/<notifier event>/error". 1561 1562 To compile this code as a module, choose M here: the module will 1563 be called of-reconfig-notifier-error-inject. 1564 1565 If unsure, say N. 1566 1567config NETDEV_NOTIFIER_ERROR_INJECT 1568 tristate "Netdev notifier error injection module" 1569 depends on NET && NOTIFIER_ERROR_INJECTION 1570 help 1571 This option provides the ability to inject artificial errors to 1572 netdevice notifier chain callbacks. It is controlled through debugfs 1573 interface /sys/kernel/debug/notifier-error-inject/netdev 1574 1575 If the notifier call chain should be failed with some events 1576 notified, write the error code to "actions/<notifier event>/error". 1577 1578 Example: Inject netdevice mtu change error (-22 = -EINVAL) 1579 1580 # cd /sys/kernel/debug/notifier-error-inject/netdev 1581 # echo -22 > actions/NETDEV_CHANGEMTU/error 1582 # ip link set eth0 mtu 1024 1583 RTNETLINK answers: Invalid argument 1584 1585 To compile this code as a module, choose M here: the module will 1586 be called netdev-notifier-error-inject. 1587 1588 If unsure, say N. 1589 1590config FAULT_INJECTION 1591 bool "Fault-injection framework" 1592 depends on DEBUG_KERNEL 1593 help 1594 Provide fault-injection framework. 1595 For more details, see Documentation/fault-injection/. 1596 1597config FAILSLAB 1598 bool "Fault-injection capability for kmalloc" 1599 depends on FAULT_INJECTION 1600 depends on SLAB || SLUB 1601 help 1602 Provide fault-injection capability for kmalloc. 1603 1604config FAIL_PAGE_ALLOC 1605 bool "Fault-injection capabilitiy for alloc_pages()" 1606 depends on FAULT_INJECTION 1607 help 1608 Provide fault-injection capability for alloc_pages(). 1609 1610config FAIL_MAKE_REQUEST 1611 bool "Fault-injection capability for disk IO" 1612 depends on FAULT_INJECTION && BLOCK 1613 help 1614 Provide fault-injection capability for disk IO. 1615 1616config FAIL_IO_TIMEOUT 1617 bool "Fault-injection capability for faking disk interrupts" 1618 depends on FAULT_INJECTION && BLOCK 1619 help 1620 Provide fault-injection capability on end IO handling. This 1621 will make the block layer "forget" an interrupt as configured, 1622 thus exercising the error handling. 1623 1624 Only works with drivers that use the generic timeout handling, 1625 for others it wont do anything. 1626 1627config FAIL_MMC_REQUEST 1628 bool "Fault-injection capability for MMC IO" 1629 depends on FAULT_INJECTION_DEBUG_FS && MMC 1630 help 1631 Provide fault-injection capability for MMC IO. 1632 This will make the mmc core return data errors. This is 1633 useful to test the error handling in the mmc block device 1634 and to test how the mmc host driver handles retries from 1635 the block device. 1636 1637config FAIL_FUTEX 1638 bool "Fault-injection capability for futexes" 1639 select DEBUG_FS 1640 depends on FAULT_INJECTION && FUTEX 1641 help 1642 Provide fault-injection capability for futexes. 1643 1644config FAULT_INJECTION_DEBUG_FS 1645 bool "Debugfs entries for fault-injection capabilities" 1646 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1647 help 1648 Enable configuration of fault-injection capabilities via debugfs. 1649 1650config FAULT_INJECTION_STACKTRACE_FILTER 1651 bool "stacktrace filter for fault-injection capabilities" 1652 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1653 depends on !X86_64 1654 select STACKTRACE 1655 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1656 help 1657 Provide stacktrace filter for fault-injection capabilities 1658 1659config LATENCYTOP 1660 bool "Latency measuring infrastructure" 1661 depends on DEBUG_KERNEL 1662 depends on STACKTRACE_SUPPORT 1663 depends on PROC_FS 1664 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1665 select KALLSYMS 1666 select KALLSYMS_ALL 1667 select STACKTRACE 1668 select SCHEDSTATS 1669 select SCHED_DEBUG 1670 help 1671 Enable this option if you want to use the LatencyTOP tool 1672 to find out which userspace is blocking on what kernel operations. 1673 1674config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1675 bool 1676 1677config DEBUG_STRICT_USER_COPY_CHECKS 1678 bool "Strict user copy size checks" 1679 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1680 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING 1681 help 1682 Enabling this option turns a certain set of sanity checks for user 1683 copy operations into compile time failures. 1684 1685 The copy_from_user() etc checks are there to help test if there 1686 are sufficient security checks on the length argument of 1687 the copy operation, by having gcc prove that the argument is 1688 within bounds. 1689 1690 If unsure, say N. 1691 1692source kernel/trace/Kconfig 1693 1694menu "Runtime Testing" 1695 1696config LKDTM 1697 tristate "Linux Kernel Dump Test Tool Module" 1698 depends on DEBUG_FS 1699 depends on BLOCK 1700 default n 1701 help 1702 This module enables testing of the different dumping mechanisms by 1703 inducing system failures at predefined crash points. 1704 If you don't need it: say N 1705 Choose M here to compile this code as a module. The module will be 1706 called lkdtm. 1707 1708 Documentation on how to use the module can be found in 1709 Documentation/fault-injection/provoke-crashes.txt 1710 1711config TEST_LIST_SORT 1712 bool "Linked list sorting test" 1713 depends on DEBUG_KERNEL 1714 help 1715 Enable this to turn on 'list_sort()' function test. This test is 1716 executed only once during system boot, so affects only boot time. 1717 1718 If unsure, say N. 1719 1720config KPROBES_SANITY_TEST 1721 bool "Kprobes sanity tests" 1722 depends on DEBUG_KERNEL 1723 depends on KPROBES 1724 default n 1725 help 1726 This option provides for testing basic kprobes functionality on 1727 boot. A sample kprobe, jprobe and kretprobe are inserted and 1728 verified for functionality. 1729 1730 Say N if you are unsure. 1731 1732config BACKTRACE_SELF_TEST 1733 tristate "Self test for the backtrace code" 1734 depends on DEBUG_KERNEL 1735 default n 1736 help 1737 This option provides a kernel module that can be used to test 1738 the kernel stack backtrace code. This option is not useful 1739 for distributions or general kernels, but only for kernel 1740 developers working on architecture code. 1741 1742 Note that if you want to also test saved backtraces, you will 1743 have to enable STACKTRACE as well. 1744 1745 Say N if you are unsure. 1746 1747config RBTREE_TEST 1748 tristate "Red-Black tree test" 1749 depends on DEBUG_KERNEL 1750 help 1751 A benchmark measuring the performance of the rbtree library. 1752 Also includes rbtree invariant checks. 1753 1754config INTERVAL_TREE_TEST 1755 tristate "Interval tree test" 1756 depends on m && DEBUG_KERNEL 1757 select INTERVAL_TREE 1758 help 1759 A benchmark measuring the performance of the interval tree library 1760 1761config PERCPU_TEST 1762 tristate "Per cpu operations test" 1763 depends on m && DEBUG_KERNEL 1764 help 1765 Enable this option to build test module which validates per-cpu 1766 operations. 1767 1768 If unsure, say N. 1769 1770config ATOMIC64_SELFTEST 1771 bool "Perform an atomic64_t self-test at boot" 1772 help 1773 Enable this option to test the atomic64_t functions at boot. 1774 1775 If unsure, say N. 1776 1777config ASYNC_RAID6_TEST 1778 tristate "Self test for hardware accelerated raid6 recovery" 1779 depends on ASYNC_RAID6_RECOV 1780 select ASYNC_MEMCPY 1781 ---help--- 1782 This is a one-shot self test that permutes through the 1783 recovery of all the possible two disk failure scenarios for a 1784 N-disk array. Recovery is performed with the asynchronous 1785 raid6 recovery routines, and will optionally use an offload 1786 engine if one is available. 1787 1788 If unsure, say N. 1789 1790config TEST_HEXDUMP 1791 tristate "Test functions located in the hexdump module at runtime" 1792 1793config TEST_STRING_HELPERS 1794 tristate "Test functions located in the string_helpers module at runtime" 1795 1796config TEST_KSTRTOX 1797 tristate "Test kstrto*() family of functions at runtime" 1798 1799config TEST_PRINTF 1800 tristate "Test printf() family of functions at runtime" 1801 1802config TEST_BITMAP 1803 tristate "Test bitmap_*() family of functions at runtime" 1804 default n 1805 help 1806 Enable this option to test the bitmap functions at boot. 1807 1808 If unsure, say N. 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 1818endmenu # runtime tests 1819 1820config PROVIDE_OHCI1394_DMA_INIT 1821 bool "Remote debugging over FireWire early on boot" 1822 depends on PCI && X86 1823 help 1824 If you want to debug problems which hang or crash the kernel early 1825 on boot and the crashing machine has a FireWire port, you can use 1826 this feature to remotely access the memory of the crashed machine 1827 over FireWire. This employs remote DMA as part of the OHCI1394 1828 specification which is now the standard for FireWire controllers. 1829 1830 With remote DMA, you can monitor the printk buffer remotely using 1831 firescope and access all memory below 4GB using fireproxy from gdb. 1832 Even controlling a kernel debugger is possible using remote DMA. 1833 1834 Usage: 1835 1836 If ohci1394_dma=early is used as boot parameter, it will initialize 1837 all OHCI1394 controllers which are found in the PCI config space. 1838 1839 As all changes to the FireWire bus such as enabling and disabling 1840 devices cause a bus reset and thereby disable remote DMA for all 1841 devices, be sure to have the cable plugged and FireWire enabled on 1842 the debugging host before booting the debug target for debugging. 1843 1844 This code (~1k) is freed after boot. By then, the firewire stack 1845 in charge of the OHCI-1394 controllers should be used instead. 1846 1847 See Documentation/debugging-via-ohci1394.txt for more information. 1848 1849config BUILD_DOCSRC 1850 bool "Build targets in Documentation/ tree" 1851 depends on HEADERS_CHECK 1852 help 1853 This option attempts to build objects from the source files in the 1854 kernel Documentation/ tree. 1855 1856 Say N if you are unsure. 1857 1858config DMA_API_DEBUG 1859 bool "Enable debugging of DMA-API usage" 1860 depends on HAVE_DMA_API_DEBUG 1861 help 1862 Enable this option to debug the use of the DMA API by device drivers. 1863 With this option you will be able to detect common bugs in device 1864 drivers like double-freeing of DMA mappings or freeing mappings that 1865 were never allocated. 1866 1867 This also attempts to catch cases where a page owned by DMA is 1868 accessed by the cpu in a way that could cause data corruption. For 1869 example, this enables cow_user_page() to check that the source page is 1870 not undergoing DMA. 1871 1872 This option causes a performance degradation. Use only if you want to 1873 debug device drivers and dma interactions. 1874 1875 If unsure, say N. 1876 1877config TEST_LKM 1878 tristate "Test module loading with 'hello world' module" 1879 default n 1880 depends on m 1881 help 1882 This builds the "test_module" module that emits "Hello, world" 1883 on printk when loaded. It is designed to be used for basic 1884 evaluation of the module loading subsystem (for example when 1885 validating module verification). It lacks any extra dependencies, 1886 and will not normally be loaded by the system unless explicitly 1887 requested by name. 1888 1889 If unsure, say N. 1890 1891config TEST_USER_COPY 1892 tristate "Test user/kernel boundary protections" 1893 default n 1894 depends on m 1895 help 1896 This builds the "test_user_copy" module that runs sanity checks 1897 on the copy_to/from_user infrastructure, making sure basic 1898 user/kernel boundary testing is working. If it fails to load, 1899 a regression has been detected in the user/kernel memory boundary 1900 protections. 1901 1902 If unsure, say N. 1903 1904config TEST_BPF 1905 tristate "Test BPF filter functionality" 1906 default n 1907 depends on m && NET 1908 help 1909 This builds the "test_bpf" module that runs various test vectors 1910 against the BPF interpreter or BPF JIT compiler depending on the 1911 current setting. This is in particular useful for BPF JIT compiler 1912 development, but also to run regression tests against changes in 1913 the interpreter code. It also enables test stubs for eBPF maps and 1914 verifier used by user space verifier testsuite. 1915 1916 If unsure, say N. 1917 1918config TEST_FIRMWARE 1919 tristate "Test firmware loading via userspace interface" 1920 default n 1921 depends on FW_LOADER 1922 help 1923 This builds the "test_firmware" module that creates a userspace 1924 interface for testing firmware loading. This can be used to 1925 control the triggering of firmware loading without needing an 1926 actual firmware-using device. The contents can be rechecked by 1927 userspace. 1928 1929 If unsure, say N. 1930 1931config TEST_UDELAY 1932 tristate "udelay test driver" 1933 default n 1934 help 1935 This builds the "udelay_test" module that helps to make sure 1936 that udelay() is working properly. 1937 1938 If unsure, say N. 1939 1940config MEMTEST 1941 bool "Memtest" 1942 depends on HAVE_MEMBLOCK 1943 ---help--- 1944 This option adds a kernel parameter 'memtest', which allows memtest 1945 to be set. 1946 memtest=0, mean disabled; -- default 1947 memtest=1, mean do 1 test pattern; 1948 ... 1949 memtest=17, mean do 17 test patterns. 1950 If you are unsure how to answer this question, answer N. 1951 1952config TEST_STATIC_KEYS 1953 tristate "Test static keys" 1954 default n 1955 depends on m 1956 help 1957 Test the static key interfaces. 1958 1959 If unsure, say N. 1960 1961source "samples/Kconfig" 1962 1963source "lib/Kconfig.kgdb" 1964 1965source "lib/Kconfig.ubsan" 1966 1967config ARCH_HAS_DEVMEM_IS_ALLOWED 1968 bool 1969 1970config STRICT_DEVMEM 1971 bool "Filter access to /dev/mem" 1972 depends on MMU 1973 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 1974 default y if TILE || PPC 1975 ---help--- 1976 If this option is disabled, you allow userspace (root) access to all 1977 of memory, including kernel and userspace memory. Accidental 1978 access to this is obviously disastrous, but specific access can 1979 be used by people debugging the kernel. Note that with PAT support 1980 enabled, even in this case there are restrictions on /dev/mem 1981 use due to the cache aliasing requirements. 1982 1983 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 1984 file only allows userspace access to PCI space and the BIOS code and 1985 data regions. This is sufficient for dosemu and X and all common 1986 users of /dev/mem. 1987 1988 If in doubt, say Y. 1989 1990config IO_STRICT_DEVMEM 1991 bool "Filter I/O access to /dev/mem" 1992 depends on STRICT_DEVMEM 1993 ---help--- 1994 If this option is disabled, you allow userspace (root) access to all 1995 io-memory regardless of whether a driver is actively using that 1996 range. Accidental access to this is obviously disastrous, but 1997 specific access can be used by people debugging kernel drivers. 1998 1999 If this option is switched on, the /dev/mem file only allows 2000 userspace access to *idle* io-memory ranges (see /proc/iomem) This
2001 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 2002 if the driver using a given range cannot be disabled. 2003 2004 If in doubt, say Y. 2005