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 2048 if GCC_PLUGIN_LATENT_ENTROPY 202 default 1024 if !64BIT 203 default 2048 if 64BIT 204 help 205 Tell gcc to warn at build time for stack frames larger than this. 206 Setting this too low will cause a lot of warnings. 207 Setting it to 0 disables the warning. 208 Requires gcc 4.4 209 210config STRIP_ASM_SYMS 211 bool "Strip assembler-generated symbols during link" 212 default n 213 help 214 Strip internal assembler-generated symbols during a link (symbols 215 that look like '.Lxxx') so they don't pollute the output of 216 get_wchan() and suchlike. 217 218config READABLE_ASM 219 bool "Generate readable assembler code" 220 depends on DEBUG_KERNEL 221 help 222 Disable some compiler optimizations that tend to generate human unreadable 223 assembler output. This may make the kernel slightly slower, but it helps 224 to keep kernel developers who have to stare a lot at assembler listings 225 sane. 226 227config UNUSED_SYMBOLS 228 bool "Enable unused/obsolete exported symbols" 229 default y if X86 230 help 231 Unused but exported symbols make the kernel needlessly bigger. For 232 that reason most of these unused exports will soon be removed. This 233 option is provided temporarily to provide a transition period in case 234 some external kernel module needs one of these symbols anyway. If you 235 encounter such a case in your module, consider if you are actually 236 using the right API. (rationale: since nobody in the kernel is using 237 this in a module, there is a pretty good chance it's actually the 238 wrong interface to use). If you really need the symbol, please send a 239 mail to the linux kernel mailing list mentioning the symbol and why 240 you really need it, and what the merge plan to the mainline kernel for 241 your module is. 242 243config PAGE_OWNER 244 bool "Track page owner" 245 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 246 select DEBUG_FS 247 select STACKTRACE 248 select STACKDEPOT 249 select PAGE_EXTENSION 250 help 251 This keeps track of what call chain is the owner of a page, may 252 help to find bare alloc_page(s) leaks. Even if you include this 253 feature on your build, it is disabled in default. You should pass 254 "page_owner=on" to boot parameter in order to enable it. Eats 255 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 256 for user-space helper. 257 258 If unsure, say N. 259 260config DEBUG_FS 261 bool "Debug Filesystem" 262 select SRCU 263 help 264 debugfs is a virtual file system that kernel developers use to put 265 debugging files into. Enable this option to be able to read and 266 write to these files. 267 268 For detailed documentation on the debugfs API, see 269 Documentation/DocBook/filesystems. 270 271 If unsure, say N. 272 273config HEADERS_CHECK 274 bool "Run 'make headers_check' when building vmlinux" 275 depends on !UML 276 help 277 This option will extract the user-visible kernel headers whenever 278 building the kernel, and will run basic sanity checks on them to 279 ensure that exported files do not attempt to include files which 280 were not exported, etc. 281 282 If you're making modifications to header files which are 283 relevant for userspace, say 'Y', and check the headers 284 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 285 your build tree), to make sure they're suitable. 286 287config DEBUG_SECTION_MISMATCH 288 bool "Enable full Section mismatch analysis" 289 help 290 The section mismatch analysis checks if there are illegal 291 references from one section to another section. 292 During linktime or runtime, some sections are dropped; 293 any use of code/data previously in these sections would 294 most likely result in an oops. 295 In the code, functions and variables are annotated with 296 __init,, etc. (see the full list in include/linux/init.h), 297 which results in the code/data being placed in specific sections. 298 The section mismatch analysis is always performed after a full 299 kernel build, and enabling this option causes the following 300 additional steps to occur: 301 - Add the option -fno-inline-functions-called-once to gcc commands. 302 When inlining a function annotated with __init in a non-init 303 function, we would lose the section information and thus 304 the analysis would not catch the illegal reference. 305 This option tells gcc to inline less (but it does result in 306 a larger kernel). 307 - Run the section mismatch analysis for each module/built-in.o file. 308 When we run the section mismatch analysis on vmlinux.o, we 309 lose valuable information about where the mismatch was 310 introduced. 311 Running the analysis for each module/built-in.o file 312 tells where the mismatch happens much closer to the 313 source. The drawback is that the same mismatch is 314 reported at least twice. 315 - Enable verbose reporting from modpost in order to help resolve 316 the section mismatches that are reported. 317 318config SECTION_MISMATCH_WARN_ONLY 319 bool "Make section mismatch errors non-fatal" 320 default y 321 help 322 If you say N here, the build process will fail if there are any 323 section mismatch, instead of just throwing warnings. 324 325 If unsure, say Y. 326 327# 328# Select this config option from the architecture Kconfig, if it 329# is preferred to always offer frame pointers as a config 330# option on the architecture (regardless of KERNEL_DEBUG): 331# 332config ARCH_WANT_FRAME_POINTERS 333 bool 334 help 335 336config FRAME_POINTER 337 bool "Compile the kernel with frame pointers" 338 depends on DEBUG_KERNEL && \ 339 (CRIS || M68K || FRV || UML || \ 340 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \ 341 ARCH_WANT_FRAME_POINTERS 342 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 343 help 344 If you say Y here the resulting kernel image will be slightly 345 larger and slower, but it gives very useful debugging information 346 in case of kernel bugs. (precise oopses/stacktraces/warnings) 347 348config STACK_VALIDATION 349 bool "Compile-time stack metadata validation" 350 depends on HAVE_STACK_VALIDATION 351 default n 352 help 353 Add compile-time checks to validate stack metadata, including frame 354 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure 355 that runtime stack traces are more reliable. 356 357 For more information, see 358 tools/objtool/Documentation/stack-validation.txt. 359 360config DEBUG_FORCE_WEAK_PER_CPU 361 bool "Force weak per-cpu definitions" 362 depends on DEBUG_KERNEL 363 help 364 s390 and alpha require percpu variables in modules to be 365 defined weak to work around addressing range issue which 366 puts the following two restrictions on percpu variable 367 definitions. 368 369 1. percpu symbols must be unique whether static or not 370 2. percpu variables can't be defined inside a function 371 372 To ensure that generic code follows the above rules, this 373 option forces all percpu variables to be defined as weak. 374 375endmenu # "Compiler options" 376 377config MAGIC_SYSRQ 378 bool "Magic SysRq key" 379 depends on !UML 380 help 381 If you say Y here, you will have some control over the system even 382 if the system crashes for example during kernel debugging (e.g., you 383 will be able to flush the buffer cache to disk, reboot the system 384 immediately or dump some status information). This is accomplished 385 by pressing various keys while holding SysRq (Alt+PrintScreen). It 386 also works on a serial console (on PC hardware at least), if you 387 send a BREAK and then within 5 seconds a command keypress. The 388 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 389 unless you really know what this hack does. 390 391config MAGIC_SYSRQ_DEFAULT_ENABLE 392 hex "Enable magic SysRq key functions by default" 393 depends on MAGIC_SYSRQ 394 default 0x1 395 help 396 Specifies which SysRq key functions are enabled by default. 397 This may be set to 1 or 0 to enable or disable them all, or 398 to a bitmask as described in Documentation/sysrq.txt. 399 400config DEBUG_KERNEL 401 bool "Kernel debugging" 402 help 403 Say Y here if you are developing drivers or trying to debug and 404 identify kernel problems. 405 406menu "Memory Debugging" 407 408source mm/Kconfig.debug 409 410config DEBUG_OBJECTS 411 bool "Debug object operations" 412 depends on DEBUG_KERNEL 413 help 414 If you say Y here, additional code will be inserted into the 415 kernel to track the life time of various objects and validate 416 the operations on those objects. 417 418config DEBUG_OBJECTS_SELFTEST 419 bool "Debug objects selftest" 420 depends on DEBUG_OBJECTS 421 help 422 This enables the selftest of the object debug code. 423 424config DEBUG_OBJECTS_FREE 425 bool "Debug objects in freed memory" 426 depends on DEBUG_OBJECTS 427 help 428 This enables checks whether a k/v free operation frees an area 429 which contains an object which has not been deactivated 430 properly. This can make kmalloc/kfree-intensive workloads 431 much slower. 432 433config DEBUG_OBJECTS_TIMERS 434 bool "Debug timer objects" 435 depends on DEBUG_OBJECTS 436 help 437 If you say Y here, additional code will be inserted into the 438 timer routines to track the life time of timer objects and 439 validate the timer operations. 440 441config DEBUG_OBJECTS_WORK 442 bool "Debug work objects" 443 depends on DEBUG_OBJECTS 444 help 445 If you say Y here, additional code will be inserted into the 446 work queue routines to track the life time of work objects and 447 validate the work operations. 448 449config DEBUG_OBJECTS_RCU_HEAD 450 bool "Debug RCU callbacks objects" 451 depends on DEBUG_OBJECTS 452 help 453 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 454 455config DEBUG_OBJECTS_PERCPU_COUNTER 456 bool "Debug percpu counter objects" 457 depends on DEBUG_OBJECTS 458 help 459 If you say Y here, additional code will be inserted into the 460 percpu counter routines to track the life time of percpu counter 461 objects and validate the percpu counter operations. 462 463config DEBUG_OBJECTS_ENABLE_DEFAULT 464 int "debug_objects bootup default value (0-1)" 465 range 0 1 466 default "1" 467 depends on DEBUG_OBJECTS 468 help 469 Debug objects boot parameter default value 470 471config DEBUG_SLAB 472 bool "Debug slab memory allocations" 473 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 474 help 475 Say Y here to have the kernel do limited verification on memory 476 allocation as well as poisoning memory on free to catch use of freed 477 memory. This can make kmalloc/kfree-intensive workloads much slower. 478 479config DEBUG_SLAB_LEAK 480 bool "Memory leak debugging" 481 depends on DEBUG_SLAB 482 483config SLUB_DEBUG_ON 484 bool "SLUB debugging on by default" 485 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 486 default n 487 help 488 Boot with debugging on by default. SLUB boots by default with 489 the runtime debug capabilities switched off. Enabling this is 490 equivalent to specifying the "slub_debug" parameter on boot. 491 There is no support for more fine grained debug control like 492 possible with slub_debug=xxx. SLUB debugging may be switched 493 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 494 "slub_debug=-". 495 496config SLUB_STATS 497 default n 498 bool "Enable SLUB performance statistics" 499 depends on SLUB && SYSFS 500 help 501 SLUB statistics are useful to debug SLUBs allocation behavior in 502 order find ways to optimize the allocator. This should never be 503 enabled for production use since keeping statistics slows down 504 the allocator by a few percentage points. The slabinfo command 505 supports the determination of the most active slabs to figure 506 out which slabs are relevant to a particular load. 507 Try running: slabinfo -DA 508 509config HAVE_DEBUG_KMEMLEAK 510 bool 511 512config DEBUG_KMEMLEAK 513 bool "Kernel memory leak detector" 514 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 515 select DEBUG_FS 516 select STACKTRACE if STACKTRACE_SUPPORT 517 select KALLSYMS 518 select CRC32 519 help 520 Say Y here if you want to enable the memory leak 521 detector. The memory allocation/freeing is traced in a way 522 similar to the Boehm's conservative garbage collector, the 523 difference being that the orphan objects are not freed but 524 only shown in /sys/kernel/debug/kmemleak. Enabling this 525 feature will introduce an overhead to memory 526 allocations. See Documentation/kmemleak.txt for more 527 details. 528 529 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 530 of finding leaks due to the slab objects poisoning. 531 532 In order to access the kmemleak file, debugfs needs to be 533 mounted (usually at /sys/kernel/debug). 534 535config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 536 int "Maximum kmemleak early log entries" 537 depends on DEBUG_KMEMLEAK 538 range 200 40000 539 default 400 540 help 541 Kmemleak must track all the memory allocations to avoid 542 reporting false positives. Since memory may be allocated or 543 freed before kmemleak is initialised, an early log buffer is 544 used to store these actions. If kmemleak reports "early log 545 buffer exceeded", please increase this value. 546 547config DEBUG_KMEMLEAK_TEST 548 tristate "Simple test for the kernel memory leak detector" 549 depends on DEBUG_KMEMLEAK && m 550 help 551 This option enables a module that explicitly leaks memory. 552 553 If unsure, say N. 554 555config DEBUG_KMEMLEAK_DEFAULT_OFF 556 bool "Default kmemleak to off" 557 depends on DEBUG_KMEMLEAK 558 help 559 Say Y here to disable kmemleak by default. It can then be enabled 560 on the command line via kmemleak=on. 561 562config DEBUG_STACK_USAGE 563 bool "Stack utilization instrumentation" 564 depends on DEBUG_KERNEL && !IA64 565 help 566 Enables the display of the minimum amount of free stack which each 567 task has ever had available in the sysrq-T and sysrq-P debug output. 568 569 This option will slow down process creation somewhat. 570 571config DEBUG_VM 572 bool "Debug VM" 573 depends on DEBUG_KERNEL 574 help 575 Enable this to turn on extended checks in the virtual-memory system 576 that may impact performance. 577 578 If unsure, say N. 579 580config DEBUG_VM_VMACACHE 581 bool "Debug VMA caching" 582 depends on DEBUG_VM 583 help 584 Enable this to turn on VMA caching debug information. Doing so 585 can cause significant overhead, so only enable it in non-production 586 environments. 587 588 If unsure, say N. 589 590config DEBUG_VM_RB 591 bool "Debug VM red-black trees" 592 depends on DEBUG_VM 593 help 594 Enable VM red-black tree debugging information and extra validations. 595 596 If unsure, say N. 597 598config DEBUG_VM_PGFLAGS 599 bool "Debug page-flags operations" 600 depends on DEBUG_VM 601 help 602 Enables extra validation on page flags operations. 603 604 If unsure, say N. 605 606config DEBUG_VIRTUAL 607 bool "Debug VM translations" 608 depends on DEBUG_KERNEL && X86 609 help 610 Enable some costly sanity checks in virtual to page code. This can 611 catch mistakes with virt_to_page() and friends. 612 613 If unsure, say N. 614 615config DEBUG_NOMMU_REGIONS 616 bool "Debug the global anon/private NOMMU mapping region tree" 617 depends on DEBUG_KERNEL && !MMU 618 help 619 This option causes the global tree of anonymous and private mapping 620 regions to be regularly checked for invalid topology. 621 622config DEBUG_MEMORY_INIT 623 bool "Debug memory initialisation" if EXPERT 624 default !EXPERT 625 help 626 Enable this for additional checks during memory initialisation. 627 The sanity checks verify aspects of the VM such as the memory model 628 and other information provided by the architecture. Verbose 629 information will be printed at KERN_DEBUG loglevel depending 630 on the mminit_loglevel= command-line option. 631 632 If unsure, say Y 633 634config MEMORY_NOTIFIER_ERROR_INJECT 635 tristate "Memory hotplug notifier error injection module" 636 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 637 help 638 This option provides the ability to inject artificial errors to 639 memory hotplug notifier chain callbacks. It is controlled through 640 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 641 642 If the notifier call chain should be failed with some events 643 notified, write the error code to "actions/<notifier event>/error". 644 645 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 646 647 # cd /sys/kernel/debug/notifier-error-inject/memory 648 # echo -12 > actions/MEM_GOING_OFFLINE/error 649 # echo offline > /sys/devices/system/memory/memoryXXX/state 650 bash: echo: write error: Cannot allocate memory 651 652 To compile this code as a module, choose M here: the module will 653 be called memory-notifier-error-inject. 654 655 If unsure, say N. 656 657config DEBUG_PER_CPU_MAPS 658 bool "Debug access to per_cpu maps" 659 depends on DEBUG_KERNEL 660 depends on SMP 661 help 662 Say Y to verify that the per_cpu map being accessed has 663 been set up. This adds a fair amount of code to kernel memory 664 and decreases performance. 665 666 Say N if unsure. 667 668config DEBUG_HIGHMEM 669 bool "Highmem debugging" 670 depends on DEBUG_KERNEL && HIGHMEM 671 help 672 This option enables additional error checking for high memory 673 systems. Disable for production systems. 674 675config HAVE_DEBUG_STACKOVERFLOW 676 bool 677 678config DEBUG_STACKOVERFLOW 679 bool "Check for stack overflows" 680 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 681 ---help--- 682 Say Y here if you want to check for overflows of kernel, IRQ 683 and exception stacks (if your architecture uses them). This 684 option will show detailed messages if free stack space drops 685 below a certain limit. 686 687 These kinds of bugs usually occur when call-chains in the 688 kernel get too deep, especially when interrupts are 689 involved. 690 691 Use this in cases where you see apparently random memory 692 corruption, especially if it appears in 'struct thread_info' 693 694 If in doubt, say "N". 695 696source "lib/Kconfig.kmemcheck" 697 698source "lib/Kconfig.kasan" 699 700endmenu # "Memory Debugging" 701 702config ARCH_HAS_KCOV 703 bool 704 help 705 KCOV does not have any arch-specific code, but currently it is enabled 706 only for x86_64. KCOV requires testing on other archs, and most likely 707 disabling of instrumentation for some early boot code. 708 709config KCOV 710 bool "Code coverage for fuzzing" 711 depends on ARCH_HAS_KCOV 712 select DEBUG_FS 713 select GCC_PLUGINS if !COMPILE_TEST 714 select GCC_PLUGIN_SANCOV if !COMPILE_TEST 715 help 716 KCOV exposes kernel code coverage information in a form suitable 717 for coverage-guided fuzzing (randomized testing). 718 719 If RANDOMIZE_BASE is enabled, PC values will not be stable across 720 different machines and across reboots. If you need stable PC values, 721 disable RANDOMIZE_BASE. 722 723 For more details, see Documentation/kcov.txt. 724 725config KCOV_INSTRUMENT_ALL 726 bool "Instrument all code by default" 727 depends on KCOV 728 default y if KCOV 729 help 730 If you are doing generic system call fuzzing (like e.g. syzkaller), 731 then you will want to instrument the whole kernel and you should 732 say y here. If you are doing more targeted fuzzing (like e.g. 733 filesystem fuzzing with AFL) then you will want to enable coverage 734 for more specific subsets of files, and should say n here. 735 736config DEBUG_SHIRQ 737 bool "Debug shared IRQ handlers" 738 depends on DEBUG_KERNEL 739 help 740 Enable this to generate a spurious interrupt as soon as a shared 741 interrupt handler is registered, and just before one is deregistered. 742 Drivers ought to be able to handle interrupts coming in at those 743 points; some don't and need to be caught. 744 745menu "Debug Lockups and Hangs" 746 747config LOCKUP_DETECTOR 748 bool "Detect Hard and Soft Lockups" 749 depends on DEBUG_KERNEL && !S390 750 help 751 Say Y here to enable the kernel to act as a watchdog to detect 752 hard and soft lockups. 753 754 Softlockups are bugs that cause the kernel to loop in kernel 755 mode for more than 20 seconds, without giving other tasks a 756 chance to run. The current stack trace is displayed upon 757 detection and the system will stay locked up. 758 759 Hardlockups are bugs that cause the CPU to loop in kernel mode 760 for more than 10 seconds, without letting other interrupts have a 761 chance to run. The current stack trace is displayed upon detection 762 and the system will stay locked up. 763 764 The overhead should be minimal. A periodic hrtimer runs to 765 generate interrupts and kick the watchdog task every 4 seconds. 766 An NMI is generated every 10 seconds or so to check for hardlockups. 767 768 The frequency of hrtimer and NMI events and the soft and hard lockup 769 thresholds can be controlled through the sysctl watchdog_thresh. 770 771config HARDLOCKUP_DETECTOR 772 def_bool y 773 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 774 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 775 776config BOOTPARAM_HARDLOCKUP_PANIC 777 bool "Panic (Reboot) On Hard Lockups" 778 depends on HARDLOCKUP_DETECTOR 779 help 780 Say Y here to enable the kernel to panic on "hard lockups", 781 which are bugs that cause the kernel to loop in kernel 782 mode with interrupts disabled for more than 10 seconds (configurable 783 using the watchdog_thresh sysctl). 784 785 Say N if unsure. 786 787config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 788 int 789 depends on HARDLOCKUP_DETECTOR 790 range 0 1 791 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 792 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 793 794config BOOTPARAM_SOFTLOCKUP_PANIC 795 bool "Panic (Reboot) On Soft Lockups" 796 depends on LOCKUP_DETECTOR 797 help 798 Say Y here to enable the kernel to panic on "soft lockups", 799 which are bugs that cause the kernel to loop in kernel 800 mode for more than 20 seconds (configurable using the watchdog_thresh 801 sysctl), without giving other tasks a chance to run. 802 803 The panic can be used in combination with panic_timeout, 804 to cause the system to reboot automatically after a 805 lockup has been detected. This feature is useful for 806 high-availability systems that have uptime guarantees and 807 where a lockup must be resolved ASAP. 808 809 Say N if unsure. 810 811config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 812 int 813 depends on LOCKUP_DETECTOR 814 range 0 1 815 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 816 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 817 818config DETECT_HUNG_TASK 819 bool "Detect Hung Tasks" 820 depends on DEBUG_KERNEL 821 default LOCKUP_DETECTOR 822 help 823 Say Y here to enable the kernel to detect "hung tasks", 824 which are bugs that cause the task to be stuck in 825 uninterruptible "D" state indefinitely. 826 827 When a hung task is detected, the kernel will print the 828 current stack trace (which you should report), but the 829 task will stay in uninterruptible state. If lockdep is 830 enabled then all held locks will also be reported. This 831 feature has negligible overhead. 832 833config DEFAULT_HUNG_TASK_TIMEOUT 834 int "Default timeout for hung task detection (in seconds)" 835 depends on DETECT_HUNG_TASK 836 default 120 837 help 838 This option controls the default timeout (in seconds) used 839 to determine when a task has become non-responsive and should 840 be considered hung. 841 842 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 843 sysctl or by writing a value to 844 /proc/sys/kernel/hung_task_timeout_secs. 845 846 A timeout of 0 disables the check. The default is two minutes. 847 Keeping the default should be fine in most cases. 848 849config BOOTPARAM_HUNG_TASK_PANIC 850 bool "Panic (Reboot) On Hung Tasks" 851 depends on DETECT_HUNG_TASK 852 help 853 Say Y here to enable the kernel to panic on "hung tasks", 854 which are bugs that cause the kernel to leave a task stuck 855 in uninterruptible "D" state. 856 857 The panic can be used in combination with panic_timeout, 858 to cause the system to reboot automatically after a 859 hung task has been detected. This feature is useful for 860 high-availability systems that have uptime guarantees and 861 where a hung tasks must be resolved ASAP. 862 863 Say N if unsure. 864 865config BOOTPARAM_HUNG_TASK_PANIC_VALUE 866 int 867 depends on DETECT_HUNG_TASK 868 range 0 1 869 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 870 default 1 if BOOTPARAM_HUNG_TASK_PANIC 871 872config WQ_WATCHDOG 873 bool "Detect Workqueue Stalls" 874 depends on DEBUG_KERNEL 875 help 876 Say Y here to enable stall detection on workqueues. If a 877 worker pool doesn't make forward progress on a pending work 878 item for over a given amount of time, 30s by default, a 879 warning message is printed along with dump of workqueue 880 state. This can be configured through kernel parameter 881 "workqueue.watchdog_thresh" and its sysfs counterpart. 882 883endmenu # "Debug lockups and hangs" 884 885config PANIC_ON_OOPS 886 bool "Panic on Oops" 887 help 888 Say Y here to enable the kernel to panic when it oopses. This 889 has the same effect as setting oops=panic on the kernel command 890 line. 891 892 This feature is useful to ensure that the kernel does not do 893 anything erroneous after an oops which could result in data 894 corruption or other issues. 895 896 Say N if unsure. 897 898config PANIC_ON_OOPS_VALUE 899 int 900 range 0 1 901 default 0 if !PANIC_ON_OOPS 902 default 1 if PANIC_ON_OOPS 903 904config PANIC_TIMEOUT 905 int "panic timeout" 906 default 0 907 help 908 Set the timeout value (in seconds) until a reboot occurs when the 909 the kernel panics. If n = 0, then we wait forever. A timeout 910 value n > 0 will wait n seconds before rebooting, while a timeout 911 value n < 0 will reboot immediately. 912 913config SCHED_DEBUG 914 bool "Collect scheduler debugging info" 915 depends on DEBUG_KERNEL && PROC_FS 916 default y 917 help 918 If you say Y here, the /proc/sched_debug file will be provided 919 that can help debug the scheduler. The runtime overhead of this 920 option is minimal. 921 922config SCHED_INFO 923 bool 924 default n 925 926config SCHEDSTATS 927 bool "Collect scheduler statistics" 928 depends on DEBUG_KERNEL && PROC_FS 929 select SCHED_INFO 930 help 931 If you say Y here, additional code will be inserted into the 932 scheduler and related routines to collect statistics about 933 scheduler behavior and provide them in /proc/schedstat. These 934 stats may be useful for both tuning and debugging the scheduler 935 If you aren't debugging the scheduler or trying to tune a specific 936 application, you can say N to avoid the very slight overhead 937 this adds. 938 939config SCHED_STACK_END_CHECK 940 bool "Detect stack corruption on calls to schedule()" 941 depends on DEBUG_KERNEL 942 default n 943 help 944 This option checks for a stack overrun on calls to schedule(). 945 If the stack end location is found to be over written always panic as 946 the content of the corrupted region can no longer be trusted. 947 This is to ensure no erroneous behaviour occurs which could result in 948 data corruption or a sporadic crash at a later stage once the region 949 is examined. The runtime overhead introduced is minimal. 950 951config DEBUG_TIMEKEEPING 952 bool "Enable extra timekeeping sanity checking" 953 help 954 This option will enable additional timekeeping sanity checks 955 which may be helpful when diagnosing issues where timekeeping 956 problems are suspected. 957 958 This may include checks in the timekeeping hotpaths, so this 959 option may have a (very small) performance impact to some 960 workloads. 961 962 If unsure, say N. 963 964config TIMER_STATS 965 bool "Collect kernel timers statistics" 966 depends on DEBUG_KERNEL && PROC_FS 967 help 968 If you say Y here, additional code will be inserted into the 969 timer routines to collect statistics about kernel timers being 970 reprogrammed. The statistics can be read from /proc/timer_stats. 971 The statistics collection is started by writing 1 to /proc/timer_stats, 972 writing 0 stops it. This feature is useful to collect information 973 about timer usage patterns in kernel and userspace. This feature 974 is lightweight if enabled in the kernel config but not activated 975 (it defaults to deactivated on bootup and will only be activated 976 if some application like powertop activates it explicitly). 977 978config DEBUG_PREEMPT 979 bool "Debug preemptible kernel" 980 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 981 default y 982 help 983 If you say Y here then the kernel will use a debug variant of the 984 commonly used smp_processor_id() function and will print warnings 985 if kernel code uses it in a preemption-unsafe way. Also, the kernel 986 will detect preemption count underflows. 987 988menu "Lock Debugging (spinlocks, mutexes, etc...)" 989 990config DEBUG_RT_MUTEXES 991 bool "RT Mutex debugging, deadlock detection" 992 depends on DEBUG_KERNEL && RT_MUTEXES 993 help 994 This allows rt mutex semantics violations and rt mutex related 995 deadlocks (lockups) to be detected and reported automatically. 996 997config DEBUG_SPINLOCK 998 bool "Spinlock and rw-lock debugging: basic checks" 999 depends on DEBUG_KERNEL 1000 select UNINLINE_SPIN_UNLOCK 1001 help 1002 Say Y here and build SMP to catch missing spinlock initialization 1003 and certain other kinds of spinlock errors commonly made. This is 1004 best used in conjunction with the NMI watchdog so that spinlock 1005 deadlocks are also debuggable. 1006 1007config DEBUG_MUTEXES 1008 bool "Mutex debugging: basic checks" 1009 depends on DEBUG_KERNEL 1010 help 1011 This feature allows mutex semantics violations to be detected and 1012 reported. 1013 1014config DEBUG_WW_MUTEX_SLOWPATH 1015 bool "Wait/wound mutex debugging: Slowpath testing" 1016 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1017 select DEBUG_LOCK_ALLOC 1018 select DEBUG_SPINLOCK 1019 select DEBUG_MUTEXES 1020 help 1021 This feature enables slowpath testing for w/w mutex users by 1022 injecting additional -EDEADLK wound/backoff cases. Together with 1023 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 1024 will test all possible w/w mutex interface abuse with the 1025 exception of simply not acquiring all the required locks. 1026 Note that this feature can introduce significant overhead, so 1027 it really should not be enabled in a production or distro kernel, 1028 even a debug kernel. If you are a driver writer, enable it. If 1029 you are a distro, do not. 1030 1031config DEBUG_LOCK_ALLOC 1032 bool "Lock debugging: detect incorrect freeing of live locks" 1033 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1034 select DEBUG_SPINLOCK 1035 select DEBUG_MUTEXES 1036 select LOCKDEP 1037 help 1038 This feature will check whether any held lock (spinlock, rwlock, 1039 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1040 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1041 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1042 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1043 held during task exit. 1044 1045config PROVE_LOCKING 1046 bool "Lock debugging: prove locking correctness" 1047 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1048 select LOCKDEP 1049 select DEBUG_SPINLOCK 1050 select DEBUG_MUTEXES 1051 select DEBUG_LOCK_ALLOC 1052 select TRACE_IRQFLAGS 1053 default n 1054 help 1055 This feature enables the kernel to prove that all locking 1056 that occurs in the kernel runtime is mathematically 1057 correct: that under no circumstance could an arbitrary (and 1058 not yet triggered) combination of observed locking 1059 sequences (on an arbitrary number of CPUs, running an 1060 arbitrary number of tasks and interrupt contexts) cause a 1061 deadlock. 1062 1063 In short, this feature enables the kernel to report locking 1064 related deadlocks before they actually occur. 1065 1066 The proof does not depend on how hard and complex a 1067 deadlock scenario would be to trigger: how many 1068 participant CPUs, tasks and irq-contexts would be needed 1069 for it to trigger. The proof also does not depend on 1070 timing: if a race and a resulting deadlock is possible 1071 theoretically (no matter how unlikely the race scenario 1072 is), it will be proven so and will immediately be 1073 reported by the kernel (once the event is observed that 1074 makes the deadlock theoretically possible). 1075 1076 If a deadlock is impossible (i.e. the locking rules, as 1077 observed by the kernel, are mathematically correct), the 1078 kernel reports nothing. 1079 1080 NOTE: this feature can also be enabled for rwlocks, mutexes 1081 and rwsems - in which case all dependencies between these 1082 different locking variants are observed and mapped too, and 1083 the proof of observed correctness is also maintained for an 1084 arbitrary combination of these separate locking variants. 1085 1086 For more details, see Documentation/locking/lockdep-design.txt. 1087 1088config LOCKDEP 1089 bool 1090 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1091 select STACKTRACE 1092 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE 1093 select KALLSYMS 1094 select KALLSYMS_ALL 1095 1096config LOCK_STAT 1097 bool "Lock usage statistics" 1098 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1099 select LOCKDEP 1100 select DEBUG_SPINLOCK 1101 select DEBUG_MUTEXES 1102 select DEBUG_LOCK_ALLOC 1103 default n 1104 help 1105 This feature enables tracking lock contention points 1106 1107 For more details, see Documentation/locking/lockstat.txt 1108 1109 This also enables lock events required by "perf lock", 1110 subcommand of perf. 1111 If you want to use "perf lock", you also need to turn on 1112 CONFIG_EVENT_TRACING. 1113 1114 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1115 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1116 1117config DEBUG_LOCKDEP 1118 bool "Lock dependency engine debugging" 1119 depends on DEBUG_KERNEL && LOCKDEP 1120 help 1121 If you say Y here, the lock dependency engine will do 1122 additional runtime checks to debug itself, at the price 1123 of more runtime overhead. 1124 1125config DEBUG_ATOMIC_SLEEP 1126 bool "Sleep inside atomic section checking" 1127 select PREEMPT_COUNT 1128 depends on DEBUG_KERNEL 1129 help 1130 If you say Y here, various routines which may sleep will become very 1131 noisy if they are called inside atomic sections: when a spinlock is 1132 held, inside an rcu read side critical section, inside preempt disabled 1133 sections, inside an interrupt, etc... 1134 1135config DEBUG_LOCKING_API_SELFTESTS 1136 bool "Locking API boot-time self-tests" 1137 depends on DEBUG_KERNEL 1138 help 1139 Say Y here if you want the kernel to run a short self-test during 1140 bootup. The self-test checks whether common types of locking bugs 1141 are detected by debugging mechanisms or not. (if you disable 1142 lock debugging then those bugs wont be detected of course.) 1143 The following locking APIs are covered: spinlocks, rwlocks, 1144 mutexes and rwsems. 1145 1146config LOCK_TORTURE_TEST 1147 tristate "torture tests for locking" 1148 depends on DEBUG_KERNEL 1149 select TORTURE_TEST 1150 default n 1151 help 1152 This option provides a kernel module that runs torture tests 1153 on kernel locking primitives. The kernel module may be built 1154 after the fact on the running kernel to be tested, if desired. 1155 1156 Say Y here if you want kernel locking-primitive torture tests 1157 to be built into the kernel. 1158 Say M if you want these torture tests to build as a module. 1159 Say N if you are unsure. 1160 1161endmenu # lock debugging 1162 1163config TRACE_IRQFLAGS 1164 bool 1165 help 1166 Enables hooks to interrupt enabling and disabling for 1167 either tracing or lock debugging. 1168 1169config STACKTRACE 1170 bool "Stack backtrace support" 1171 depends on STACKTRACE_SUPPORT 1172 help 1173 This option causes the kernel to create a /proc/pid/stack for 1174 every process, showing its current stack trace. 1175 It is also used by various kernel debugging features that require 1176 stack trace generation. 1177 1178config DEBUG_KOBJECT 1179 bool "kobject debugging" 1180 depends on DEBUG_KERNEL 1181 help 1182 If you say Y here, some extra kobject debugging messages will be sent 1183 to the syslog. 1184 1185config DEBUG_KOBJECT_RELEASE 1186 bool "kobject release debugging" 1187 depends on DEBUG_OBJECTS_TIMERS 1188 help 1189 kobjects are reference counted objects. This means that their 1190 last reference count put is not predictable, and the kobject can 1191 live on past the point at which a driver decides to drop it's 1192 initial reference to the kobject gained on allocation. An 1193 example of this would be a struct device which has just been 1194 unregistered. 1195 1196 However, some buggy drivers assume that after such an operation, 1197 the memory backing the kobject can be immediately freed. This 1198 goes completely against the principles of a refcounted object. 1199 1200 If you say Y here, the kernel will delay the release of kobjects 1201 on the last reference count to improve the visibility of this 1202 kind of kobject release bug. 1203 1204config HAVE_DEBUG_BUGVERBOSE 1205 bool 1206 1207config DEBUG_BUGVERBOSE 1208 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1209 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1210 default y 1211 help 1212 Say Y here to make BUG() panics output the file name and line number 1213 of the BUG call as well as the EIP and oops trace. This aids 1214 debugging but costs about 70-100K of memory. 1215 1216config DEBUG_LIST 1217 bool "Debug linked list manipulation" 1218 depends on DEBUG_KERNEL 1219 help 1220 Enable this to turn on extended checks in the linked-list 1221 walking routines. 1222 1223 If unsure, say N. 1224 1225config DEBUG_PI_LIST 1226 bool "Debug priority linked list manipulation" 1227 depends on DEBUG_KERNEL 1228 help 1229 Enable this to turn on extended checks in the priority-ordered 1230 linked-list (plist) walking routines. This checks the entire 1231 list multiple times during each manipulation. 1232 1233 If unsure, say N. 1234 1235config DEBUG_SG 1236 bool "Debug SG table operations" 1237 depends on DEBUG_KERNEL 1238 help 1239 Enable this to turn on checks on scatter-gather tables. This can 1240 help find problems with drivers that do not properly initialize 1241 their sg tables. 1242 1243 If unsure, say N. 1244 1245config DEBUG_NOTIFIERS 1246 bool "Debug notifier call chains" 1247 depends on DEBUG_KERNEL 1248 help 1249 Enable this to turn on sanity checking for notifier call chains. 1250 This is most useful for kernel developers to make sure that 1251 modules properly unregister themselves from notifier chains. 1252 This is a relatively cheap check but if you care about maximum 1253 performance, say N. 1254 1255config DEBUG_CREDENTIALS 1256 bool "Debug credential management" 1257 depends on DEBUG_KERNEL 1258 help 1259 Enable this to turn on some debug checking for credential 1260 management. The additional code keeps track of the number of 1261 pointers from task_structs to any given cred struct, and checks to 1262 see that this number never exceeds the usage count of the cred 1263 struct. 1264 1265 Furthermore, if SELinux is enabled, this also checks that the 1266 security pointer in the cred struct is never seen to be invalid. 1267 1268 If unsure, say N. 1269 1270menu "RCU Debugging" 1271 1272config PROVE_RCU 1273 def_bool PROVE_LOCKING 1274 1275config PROVE_RCU_REPEATEDLY 1276 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1277 depends on PROVE_RCU 1278 default n 1279 help 1280 By itself, PROVE_RCU will disable checking upon issuing the 1281 first warning (or "splat"). This feature prevents such 1282 disabling, allowing multiple RCU-lockdep warnings to be printed 1283 on a single reboot. 1284 1285 Say Y to allow multiple RCU-lockdep warnings per boot. 1286 1287 Say N if you are unsure. 1288 1289config SPARSE_RCU_POINTER 1290 bool "RCU debugging: sparse-based checks for pointer usage" 1291 default n 1292 help 1293 This feature enables the __rcu sparse annotation for 1294 RCU-protected pointers. This annotation will cause sparse 1295 to flag any non-RCU used of annotated pointers. This can be 1296 helpful when debugging RCU usage. Please note that this feature 1297 is not intended to enforce code cleanliness; it is instead merely 1298 a debugging aid. 1299 1300 Say Y to make sparse flag questionable use of RCU-protected pointers 1301 1302 Say N if you are unsure. 1303 1304config TORTURE_TEST 1305 tristate 1306 default n 1307 1308config RCU_PERF_TEST 1309 tristate "performance tests for RCU" 1310 depends on DEBUG_KERNEL 1311 select TORTURE_TEST 1312 select SRCU 1313 select TASKS_RCU 1314 default n 1315 help 1316 This option provides a kernel module that runs performance 1317 tests on the RCU infrastructure. The kernel module may be built 1318 after the fact on the running kernel to be tested, if desired. 1319 1320 Say Y here if you want RCU performance tests to be built into 1321 the kernel. 1322 Say M if you want the RCU performance tests to build as a module. 1323 Say N if you are unsure. 1324 1325config RCU_TORTURE_TEST 1326 tristate "torture tests for RCU" 1327 depends on DEBUG_KERNEL 1328 select TORTURE_TEST 1329 select SRCU 1330 select TASKS_RCU 1331 default n 1332 help 1333 This option provides a kernel module that runs torture tests 1334 on the RCU infrastructure. The kernel module may be built 1335 after the fact on the running kernel to be tested, if desired. 1336 1337 Say Y here if you want RCU torture tests to be built into 1338 the kernel. 1339 Say M if you want the RCU torture tests to build as a module. 1340 Say N if you are unsure. 1341 1342config RCU_TORTURE_TEST_SLOW_PREINIT 1343 bool "Slow down RCU grace-period pre-initialization to expose races" 1344 depends on RCU_TORTURE_TEST 1345 help 1346 This option delays grace-period pre-initialization (the 1347 propagation of CPU-hotplug changes up the rcu_node combining 1348 tree) for a few jiffies between initializing each pair of 1349 consecutive rcu_node structures. This helps to expose races 1350 involving grace-period pre-initialization, in other words, it 1351 makes your kernel less stable. It can also greatly increase 1352 grace-period latency, especially on systems with large numbers 1353 of CPUs. This is useful when torture-testing RCU, but in 1354 almost no other circumstance. 1355 1356 Say Y here if you want your system to crash and hang more often. 1357 Say N if you want a sane system. 1358 1359config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY 1360 int "How much to slow down RCU grace-period pre-initialization" 1361 range 0 5 1362 default 3 1363 depends on RCU_TORTURE_TEST_SLOW_PREINIT 1364 help 1365 This option specifies the number of jiffies to wait between 1366 each rcu_node structure pre-initialization step. 1367 1368config RCU_TORTURE_TEST_SLOW_INIT 1369 bool "Slow down RCU grace-period initialization to expose races" 1370 depends on RCU_TORTURE_TEST 1371 help 1372 This option delays grace-period initialization for a few 1373 jiffies between initializing each pair of consecutive 1374 rcu_node structures. This helps to expose races involving 1375 grace-period initialization, in other words, it makes your 1376 kernel less stable. It can also greatly increase grace-period 1377 latency, especially on systems with large numbers of CPUs. 1378 This is useful when torture-testing RCU, but in almost no 1379 other circumstance. 1380 1381 Say Y here if you want your system to crash and hang more often. 1382 Say N if you want a sane system. 1383 1384config RCU_TORTURE_TEST_SLOW_INIT_DELAY 1385 int "How much to slow down RCU grace-period initialization" 1386 range 0 5 1387 default 3 1388 depends on RCU_TORTURE_TEST_SLOW_INIT 1389 help 1390 This option specifies the number of jiffies to wait between 1391 each rcu_node structure initialization. 1392 1393config RCU_TORTURE_TEST_SLOW_CLEANUP 1394 bool "Slow down RCU grace-period cleanup to expose races" 1395 depends on RCU_TORTURE_TEST 1396 help 1397 This option delays grace-period cleanup for a few jiffies 1398 between cleaning up each pair of consecutive rcu_node 1399 structures. This helps to expose races involving grace-period 1400 cleanup, in other words, it makes your kernel less stable. 1401 It can also greatly increase grace-period latency, especially 1402 on systems with large numbers of CPUs. This is useful when 1403 torture-testing RCU, but in almost no other circumstance. 1404 1405 Say Y here if you want your system to crash and hang more often. 1406 Say N if you want a sane system. 1407 1408config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY 1409 int "How much to slow down RCU grace-period cleanup" 1410 range 0 5 1411 default 3 1412 depends on RCU_TORTURE_TEST_SLOW_CLEANUP 1413 help 1414 This option specifies the number of jiffies to wait between 1415 each rcu_node structure cleanup operation. 1416 1417config RCU_CPU_STALL_TIMEOUT 1418 int "RCU CPU stall timeout in seconds" 1419 depends on RCU_STALL_COMMON 1420 range 3 300 1421 default 21 1422 help 1423 If a given RCU grace period extends more than the specified 1424 number of seconds, a CPU stall warning is printed. If the 1425 RCU grace period persists, additional CPU stall warnings are 1426 printed at more widely spaced intervals. 1427 1428config RCU_TRACE 1429 bool "Enable tracing for RCU" 1430 depends on DEBUG_KERNEL 1431 select TRACE_CLOCK 1432 help 1433 This option provides tracing in RCU which presents stats 1434 in debugfs for debugging RCU implementation. 1435 1436 Say Y here if you want to enable RCU tracing 1437 Say N if you are unsure. 1438 1439config RCU_EQS_DEBUG 1440 bool "Provide debugging asserts for adding NO_HZ support to an arch" 1441 depends on DEBUG_KERNEL 1442 help 1443 This option provides consistency checks in RCU's handling of 1444 NO_HZ. These checks have proven quite helpful in detecting 1445 bugs in arch-specific NO_HZ code. 1446 1447 Say N here if you need ultimate kernel/user switch latencies 1448 Say Y if you are unsure 1449 1450endmenu # "RCU Debugging" 1451 1452config DEBUG_WQ_FORCE_RR_CPU 1453 bool "Force round-robin CPU selection for unbound work items" 1454 depends on DEBUG_KERNEL 1455 default n 1456 help 1457 Workqueue used to implicitly guarantee that work items queued 1458 without explicit CPU specified are put on the local CPU. This 1459 guarantee is no longer true and while local CPU is still 1460 preferred work items may be put on foreign CPUs. Kernel 1461 parameter "workqueue.debug_force_rr_cpu" is added to force 1462 round-robin CPU selection to flush out usages which depend on the 1463 now broken guarantee. This config option enables the debug 1464 feature by default. When enabled, memory and cache locality will 1465 be impacted. 1466 1467config DEBUG_BLOCK_EXT_DEVT 1468 bool "Force extended block device numbers and spread them" 1469 depends on DEBUG_KERNEL 1470 depends on BLOCK 1471 default n 1472 help 1473 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1474 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1475 YOU ARE DOING. Distros, please enable this and fix whatever 1476 is broken. 1477 1478 Conventionally, block device numbers are allocated from 1479 predetermined contiguous area. However, extended block area 1480 may introduce non-contiguous block device numbers. This 1481 option forces most block device numbers to be allocated from 1482 the extended space and spreads them to discover kernel or 1483 userland code paths which assume predetermined contiguous 1484 device number allocation. 1485 1486 Note that turning on this debug option shuffles all the 1487 device numbers for all IDE and SCSI devices including libata 1488 ones, so root partition specified using device number 1489 directly (via rdev or root=MAJ:MIN) won't work anymore. 1490 Textual device names (root=/dev/sdXn) will continue to work. 1491 1492 Say N if you are unsure. 1493 1494config CPU_HOTPLUG_STATE_CONTROL 1495 bool "Enable CPU hotplug state control" 1496 depends on DEBUG_KERNEL 1497 depends on HOTPLUG_CPU 1498 default n 1499 help 1500 Allows to write steps between "offline" and "online" to the CPUs 1501 sysfs target file so states can be stepped granular. This is a debug 1502 option for now as the hotplug machinery cannot be stopped and 1503 restarted at arbitrary points yet. 1504 1505 Say N if your are unsure. 1506 1507config NOTIFIER_ERROR_INJECTION 1508 tristate "Notifier error injection" 1509 depends on DEBUG_KERNEL 1510 select DEBUG_FS 1511 help 1512 This option provides the ability to inject artificial errors to 1513 specified notifier chain callbacks. It is useful to test the error 1514 handling of notifier call chain failures. 1515 1516 Say N if unsure. 1517 1518config CPU_NOTIFIER_ERROR_INJECT 1519 tristate "CPU notifier error injection module" 1520 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1521 help 1522 This option provides a kernel module that can be used to test 1523 the error handling of the cpu notifiers by injecting artificial 1524 errors to CPU notifier chain callbacks. It is controlled through 1525 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1526 1527 If the notifier call chain should be failed with some events 1528 notified, write the error code to "actions/<notifier event>/error". 1529 1530 Example: Inject CPU offline error (-1 == -EPERM) 1531 1532 # cd /sys/kernel/debug/notifier-error-inject/cpu 1533 # echo -1 > actions/CPU_DOWN_PREPARE/error 1534 # echo 0 > /sys/devices/system/cpu/cpu1/online 1535 bash: echo: write error: Operation not permitted 1536 1537 To compile this code as a module, choose M here: the module will 1538 be called cpu-notifier-error-inject. 1539 1540 If unsure, say N. 1541 1542config PM_NOTIFIER_ERROR_INJECT 1543 tristate "PM notifier error injection module" 1544 depends on PM && NOTIFIER_ERROR_INJECTION 1545 default m if PM_DEBUG 1546 help 1547 This option provides the ability to inject artificial errors to 1548 PM notifier chain callbacks. It is controlled through debugfs 1549 interface /sys/kernel/debug/notifier-error-inject/pm 1550 1551 If the notifier call chain should be failed with some events 1552 notified, write the error code to "actions/<notifier event>/error". 1553 1554 Example: Inject PM suspend error (-12 = -ENOMEM) 1555 1556 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1557 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1558 # echo mem > /sys/power/state 1559 bash: echo: write error: Cannot allocate memory 1560 1561 To compile this code as a module, choose M here: the module will 1562 be called pm-notifier-error-inject. 1563 1564 If unsure, say N. 1565 1566config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1567 tristate "OF reconfig notifier error injection module" 1568 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1569 help 1570 This option provides the ability to inject artificial errors to 1571 OF reconfig notifier chain callbacks. It is controlled 1572 through debugfs interface under 1573 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 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 To compile this code as a module, choose M here: the module will 1579 be called of-reconfig-notifier-error-inject. 1580 1581 If unsure, say N. 1582 1583config NETDEV_NOTIFIER_ERROR_INJECT 1584 tristate "Netdev notifier error injection module" 1585 depends on NET && NOTIFIER_ERROR_INJECTION 1586 help 1587 This option provides the ability to inject artificial errors to 1588 netdevice notifier chain callbacks. It is controlled through debugfs 1589 interface /sys/kernel/debug/notifier-error-inject/netdev 1590 1591 If the notifier call chain should be failed with some events 1592 notified, write the error code to "actions/<notifier event>/error". 1593 1594 Example: Inject netdevice mtu change error (-22 = -EINVAL) 1595 1596 # cd /sys/kernel/debug/notifier-error-inject/netdev 1597 # echo -22 > actions/NETDEV_CHANGEMTU/error 1598 # ip link set eth0 mtu 1024 1599 RTNETLINK answers: Invalid argument 1600 1601 To compile this code as a module, choose M here: the module will 1602 be called netdev-notifier-error-inject. 1603 1604 If unsure, say N. 1605 1606config FAULT_INJECTION 1607 bool "Fault-injection framework" 1608 depends on DEBUG_KERNEL 1609 help 1610 Provide fault-injection framework. 1611 For more details, see Documentation/fault-injection/. 1612 1613config FAILSLAB 1614 bool "Fault-injection capability for kmalloc" 1615 depends on FAULT_INJECTION 1616 depends on SLAB || SLUB 1617 help 1618 Provide fault-injection capability for kmalloc. 1619 1620config FAIL_PAGE_ALLOC 1621 bool "Fault-injection capabilitiy for alloc_pages()" 1622 depends on FAULT_INJECTION 1623 help 1624 Provide fault-injection capability for alloc_pages(). 1625 1626config FAIL_MAKE_REQUEST 1627 bool "Fault-injection capability for disk IO" 1628 depends on FAULT_INJECTION && BLOCK 1629 help 1630 Provide fault-injection capability for disk IO. 1631 1632config FAIL_IO_TIMEOUT 1633 bool "Fault-injection capability for faking disk interrupts" 1634 depends on FAULT_INJECTION && BLOCK 1635 help 1636 Provide fault-injection capability on end IO handling. This 1637 will make the block layer "forget" an interrupt as configured, 1638 thus exercising the error handling. 1639 1640 Only works with drivers that use the generic timeout handling, 1641 for others it wont do anything. 1642 1643config FAIL_MMC_REQUEST 1644 bool "Fault-injection capability for MMC IO" 1645 depends on FAULT_INJECTION_DEBUG_FS && MMC 1646 help 1647 Provide fault-injection capability for MMC IO. 1648 This will make the mmc core return data errors. This is 1649 useful to test the error handling in the mmc block device 1650 and to test how the mmc host driver handles retries from 1651 the block device. 1652 1653config FAIL_FUTEX 1654 bool "Fault-injection capability for futexes" 1655 select DEBUG_FS 1656 depends on FAULT_INJECTION && FUTEX 1657 help 1658 Provide fault-injection capability for futexes. 1659 1660config FAULT_INJECTION_DEBUG_FS 1661 bool "Debugfs entries for fault-injection capabilities" 1662 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1663 help 1664 Enable configuration of fault-injection capabilities via debugfs. 1665 1666config FAULT_INJECTION_STACKTRACE_FILTER 1667 bool "stacktrace filter for fault-injection capabilities" 1668 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1669 depends on !X86_64 1670 select STACKTRACE 1671 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1672 help 1673 Provide stacktrace filter for fault-injection capabilities 1674 1675config LATENCYTOP 1676 bool "Latency measuring infrastructure" 1677 depends on DEBUG_KERNEL 1678 depends on STACKTRACE_SUPPORT 1679 depends on PROC_FS 1680 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1681 select KALLSYMS 1682 select KALLSYMS_ALL 1683 select STACKTRACE 1684 select SCHEDSTATS 1685 select SCHED_DEBUG 1686 help 1687 Enable this option if you want to use the LatencyTOP tool 1688 to find out which userspace is blocking on what kernel operations. 1689 1690source kernel/trace/Kconfig 1691 1692menu "Runtime Testing" 1693 1694config LKDTM 1695 tristate "Linux Kernel Dump Test Tool Module" 1696 depends on DEBUG_FS 1697 depends on BLOCK 1698 default n 1699 help 1700 This module enables testing of the different dumping mechanisms by 1701 inducing system failures at predefined crash points. 1702 If you don't need it: say N 1703 Choose M here to compile this code as a module. The module will be 1704 called lkdtm. 1705 1706 Documentation on how to use the module can be found in 1707 Documentation/fault-injection/provoke-crashes.txt 1708 1709config TEST_LIST_SORT 1710 bool "Linked list sorting test" 1711 depends on DEBUG_KERNEL 1712 help 1713 Enable this to turn on 'list_sort()' function test. This test is 1714 executed only once during system boot, so affects only boot time. 1715 1716 If unsure, say N. 1717 1718config KPROBES_SANITY_TEST 1719 bool "Kprobes sanity tests" 1720 depends on DEBUG_KERNEL 1721 depends on KPROBES 1722 default n 1723 help 1724 This option provides for testing basic kprobes functionality on 1725 boot. A sample kprobe, jprobe and kretprobe are inserted and 1726 verified for functionality. 1727 1728 Say N if you are unsure. 1729 1730config BACKTRACE_SELF_TEST 1731 tristate "Self test for the backtrace code" 1732 depends on DEBUG_KERNEL 1733 default n 1734 help 1735 This option provides a kernel module that can be used to test 1736 the kernel stack backtrace code. This option is not useful 1737 for distributions or general kernels, but only for kernel 1738 developers working on architecture code. 1739 1740 Note that if you want to also test saved backtraces, you will 1741 have to enable STACKTRACE as well. 1742 1743 Say N if you are unsure. 1744 1745config RBTREE_TEST 1746 tristate "Red-Black tree test" 1747 depends on DEBUG_KERNEL 1748 help 1749 A benchmark measuring the performance of the rbtree library. 1750 Also includes rbtree invariant checks. 1751 1752config INTERVAL_TREE_TEST 1753 tristate "Interval tree test" 1754 depends on m && DEBUG_KERNEL 1755 select INTERVAL_TREE 1756 help 1757 A benchmark measuring the performance of the interval tree library 1758 1759config PERCPU_TEST 1760 tristate "Per cpu operations test" 1761 depends on m && DEBUG_KERNEL 1762 help 1763 Enable this option to build test module which validates per-cpu 1764 operations. 1765 1766 If unsure, say N. 1767 1768config ATOMIC64_SELFTEST 1769 bool "Perform an atomic64_t self-test at boot" 1770 help 1771 Enable this option to test the atomic64_t functions at boot. 1772 1773 If unsure, say N. 1774 1775config ASYNC_RAID6_TEST 1776 tristate "Self test for hardware accelerated raid6 recovery" 1777 depends on ASYNC_RAID6_RECOV 1778 select ASYNC_MEMCPY 1779 ---help--- 1780 This is a one-shot self test that permutes through the 1781 recovery of all the possible two disk failure scenarios for a 1782 N-disk array. Recovery is performed with the asynchronous 1783 raid6 recovery routines, and will optionally use an offload 1784 engine if one is available. 1785 1786 If unsure, say N. 1787 1788config TEST_HEXDUMP 1789 tristate "Test functions located in the hexdump module at runtime" 1790 1791config TEST_STRING_HELPERS 1792 tristate "Test functions located in the string_helpers module at runtime" 1793 1794config TEST_KSTRTOX 1795 tristate "Test kstrto*() family of functions at runtime" 1796 1797config TEST_PRINTF 1798 tristate "Test printf() family of functions at runtime" 1799 1800config TEST_BITMAP 1801 tristate "Test bitmap_*() family of functions at runtime" 1802 default n 1803 help 1804 Enable this option to test the bitmap functions at boot. 1805 1806 If unsure, say N. 1807 1808config TEST_UUID 1809 tristate "Test functions located in the uuid module at runtime" 1810 1811config TEST_RHASHTABLE 1812 tristate "Perform selftest on resizable hash table" 1813 default n 1814 help 1815 Enable this option to test the rhashtable functions at boot. 1816 1817 If unsure, say N. 1818 1819config TEST_HASH 1820 tristate "Perform selftest on hash functions" 1821 default n 1822 help 1823 Enable this option to test the kernel's integer (<linux/hash,h>) 1824 and string (<linux/stringhash.h>) hash functions on boot 1825 (or module load). 1826 1827 This is intended to help people writing architecture-specific 1828 optimized versions. If unsure, say N. 1829 1830endmenu # runtime tests 1831 1832config PROVIDE_OHCI1394_DMA_INIT 1833 bool "Remote debugging over FireWire early on boot" 1834 depends on PCI && X86 1835 help 1836 If you want to debug problems which hang or crash the kernel early 1837 on boot and the crashing machine has a FireWire port, you can use 1838 this feature to remotely access the memory of the crashed machine 1839 over FireWire. This employs remote DMA as part of the OHCI1394 1840 specification which is now the standard for FireWire controllers. 1841 1842 With remote DMA, you can monitor the printk buffer remotely using 1843 firescope and access all memory below 4GB using fireproxy from gdb. 1844 Even controlling a kernel debugger is possible using remote DMA. 1845 1846 Usage: 1847 1848 If ohci1394_dma=early is used as boot parameter, it will initialize 1849 all OHCI1394 controllers which are found in the PCI config space. 1850 1851 As all changes to the FireWire bus such as enabling and disabling 1852 devices cause a bus reset and thereby disable remote DMA for all 1853 devices, be sure to have the cable plugged and FireWire enabled on 1854 the debugging host before booting the debug target for debugging. 1855 1856 This code (~1k) is freed after boot. By then, the firewire stack 1857 in charge of the OHCI-1394 controllers should be used instead. 1858 1859 See Documentation/debugging-via-ohci1394.txt for more information. 1860 1861config DMA_API_DEBUG 1862 bool "Enable debugging of DMA-API usage" 1863 depends on HAVE_DMA_API_DEBUG 1864 help 1865 Enable this option to debug the use of the DMA API by device drivers. 1866 With this option you will be able to detect common bugs in device 1867 drivers like double-freeing of DMA mappings or freeing mappings that 1868 were never allocated. 1869 1870 This also attempts to catch cases where a page owned by DMA is 1871 accessed by the cpu in a way that could cause data corruption. For 1872 example, this enables cow_user_page() to check that the source page is 1873 not undergoing DMA. 1874 1875 This option causes a performance degradation. Use only if you want to 1876 debug device drivers and dma interactions. 1877 1878 If unsure, say N. 1879 1880config TEST_LKM 1881 tristate "Test module loading with 'hello world' module" 1882 default n 1883 depends on m 1884 help 1885 This builds the "test_module" module that emits "Hello, world" 1886 on printk when loaded. It is designed to be used for basic 1887 evaluation of the module loading subsystem (for example when 1888 validating module verification). It lacks any extra dependencies, 1889 and will not normally be loaded by the system unless explicitly 1890 requested by name. 1891 1892 If unsure, say N. 1893 1894config TEST_USER_COPY 1895 tristate "Test user/kernel boundary protections" 1896 default n 1897 depends on m 1898 help 1899 This builds the "test_user_copy" module that runs sanity checks 1900 on the copy_to/from_user infrastructure, making sure basic 1901 user/kernel boundary testing is working. If it fails to load, 1902 a regression has been detected in the user/kernel memory boundary 1903 protections. 1904 1905 If unsure, say N. 1906 1907config TEST_BPF 1908 tristate "Test BPF filter functionality" 1909 default n 1910 depends on m && NET 1911 help 1912 This builds the "test_bpf" module that runs various test vectors 1913 against the BPF interpreter or BPF JIT compiler depending on the 1914 current setting. This is in particular useful for BPF JIT compiler 1915 development, but also to run regression tests against changes in 1916 the interpreter code. It also enables test stubs for eBPF maps and 1917 verifier used by user space verifier testsuite. 1918 1919 If unsure, say N. 1920 1921config TEST_FIRMWARE 1922 tristate "Test firmware loading via userspace interface" 1923 default n 1924 depends on FW_LOADER 1925 help 1926 This builds the "test_firmware" module that creates a userspace 1927 interface for testing firmware loading. This can be used to 1928 control the triggering of firmware loading without needing an 1929 actual firmware-using device. The contents can be rechecked by 1930 userspace. 1931 1932 If unsure, say N. 1933 1934config TEST_UDELAY 1935 tristate "udelay test driver" 1936 default n 1937 help 1938 This builds the "udelay_test" module that helps to make sure 1939 that udelay() is working properly. 1940 1941 If unsure, say N. 1942 1943config MEMTEST 1944 bool "Memtest" 1945 depends on HAVE_MEMBLOCK 1946 ---help--- 1947 This option adds a kernel parameter 'memtest', which allows memtest 1948 to be set. 1949 memtest=0, mean disabled; -- default 1950 memtest=1, mean do 1 test pattern; 1951 ... 1952 memtest=17, mean do 17 test patterns. 1953 If you are unsure how to answer this question, answer N. 1954 1955config TEST_STATIC_KEYS 1956 tristate "Test static keys" 1957 default n 1958 depends on m 1959 help 1960 Test the static key interfaces. 1961 1962 If unsure, say N. 1963 1964source "samples/Kconfig" 1965 1966source "lib/Kconfig.kgdb" 1967 1968source "lib/Kconfig.ubsan" 1969 1970config ARCH_HAS_DEVMEM_IS_ALLOWED 1971 bool 1972 1973config STRICT_DEVMEM 1974 bool "Filter access to /dev/mem" 1975 depends on MMU 1976 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 1977 default y if TILE || PPC 1978 ---help--- 1979 If this option is disabled, you allow userspace (root) access to all 1980 of memory, including kernel and userspace memory. Accidental 1981 access to this is obviously disastrous, but specific access can 1982 be used by people debugging the kernel. Note that with PAT support 1983 enabled, even in this case there are restrictions on /dev/mem 1984 use due to the cache aliasing requirements. 1985 1986 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 1987 file only allows userspace access to PCI space and the BIOS code and 1988 data regions. This is sufficient for dosemu and X and all common 1989 users of /dev/mem. 1990 1991 If in doubt, say Y. 1992 1993config IO_STRICT_DEVMEM 1994 bool "Filter I/O access to /dev/mem" 1995 depends on STRICT_DEVMEM 1996 ---help--- 1997 If this option is disabled, you allow userspace (root) access to all 1998 io-memory regardless of whether a driver is actively using that 1999 range. Accidental access to this is obviously disastrous, but 2000 specific access can be used by people debugging kernel drivers. 2001 2002 If this option is switched on, the /dev/mem file only allows 2003 userspace access to *idle* io-memory ranges (see /proc/iomem) This 2004 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 2005 if the driver using a given range cannot be disabled. 2006 2007 If in doubt, say Y. 2008