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 STACKDEPOT 248 select PAGE_EXTENSION 249 help 250 This keeps track of what call chain is the owner of a page, may 251 help to find bare alloc_page(s) leaks. Even if you include this 252 feature on your build, it is disabled in default. You should pass 253 "page_owner=on" to boot parameter in order to enable it. Eats 254 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 255 for user-space helper. 256 257 If unsure, say N. 258 259config DEBUG_FS 260 bool "Debug Filesystem" 261 select SRCU 262 help 263 debugfs is a virtual file system that kernel developers use to put 264 debugging files into. Enable this option to be able to read and 265 write to these files. 266 267 For detailed documentation on the debugfs API, see 268 Documentation/DocBook/filesystems. 269 270 If unsure, say N. 271 272config HEADERS_CHECK 273 bool "Run 'make headers_check' when building vmlinux" 274 depends on !UML 275 help 276 This option will extract the user-visible kernel headers whenever 277 building the kernel, and will run basic sanity checks on them to 278 ensure that exported files do not attempt to include files which 279 were not exported, etc. 280 281 If you're making modifications to header files which are 282 relevant for userspace, say 'Y', and check the headers 283 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 284 your build tree), to make sure they're suitable. 285 286config DEBUG_SECTION_MISMATCH 287 bool "Enable full Section mismatch analysis" 288 help 289 The section mismatch analysis checks if there are illegal 290 references from one section to another section. 291 During linktime or runtime, some sections are dropped; 292 any use of code/data previously in these sections would 293 most likely result in an oops. 294 In the code, functions and variables are annotated with 295 __init,, etc. (see the full list in include/linux/init.h), 296 which results in the code/data being placed in specific sections. 297 The section mismatch analysis is always performed after a full 298 kernel build, and enabling this option causes the following 299 additional steps to occur: 300 - Add the option -fno-inline-functions-called-once to gcc commands. 301 When inlining a function annotated with __init in a non-init 302 function, we would lose the section information and thus 303 the analysis would not catch the illegal reference. 304 This option tells gcc to inline less (but it does result in 305 a larger kernel). 306 - Run the section mismatch analysis for each module/built-in.o file. 307 When we run the section mismatch analysis on vmlinux.o, we 308 lose valueble information about where the mismatch was 309 introduced. 310 Running the analysis for each module/built-in.o file 311 tells where the mismatch happens much closer to the 312 source. The drawback is that the same mismatch is 313 reported at least twice. 314 - Enable verbose reporting from modpost in order to help resolve 315 the section mismatches that are reported. 316 317config SECTION_MISMATCH_WARN_ONLY 318 bool "Make section mismatch errors non-fatal" 319 default y 320 help 321 If you say N here, the build process will fail if there are any 322 section mismatch, instead of just throwing warnings. 323 324 If unsure, say Y. 325 326# 327# Select this config option from the architecture Kconfig, if it 328# is preferred to always offer frame pointers as a config 329# option on the architecture (regardless of KERNEL_DEBUG): 330# 331config ARCH_WANT_FRAME_POINTERS 332 bool 333 help 334 335config FRAME_POINTER 336 bool "Compile the kernel with frame pointers" 337 depends on DEBUG_KERNEL && \ 338 (CRIS || M68K || FRV || UML || \ 339 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \ 340 ARCH_WANT_FRAME_POINTERS 341 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 342 help 343 If you say Y here the resulting kernel image will be slightly 344 larger and slower, but it gives very useful debugging information 345 in case of kernel bugs. (precise oopses/stacktraces/warnings) 346 347config STACK_VALIDATION 348 bool "Compile-time stack metadata validation" 349 depends on HAVE_STACK_VALIDATION 350 default n 351 help 352 Add compile-time checks to validate stack metadata, including frame 353 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure 354 that runtime stack traces are more reliable. 355 356 For more information, see 357 tools/objtool/Documentation/stack-validation.txt. 358 359config DEBUG_FORCE_WEAK_PER_CPU 360 bool "Force weak per-cpu definitions" 361 depends on DEBUG_KERNEL 362 help 363 s390 and alpha require percpu variables in modules to be 364 defined weak to work around addressing range issue which 365 puts the following two restrictions on percpu variable 366 definitions. 367 368 1. percpu symbols must be unique whether static or not 369 2. percpu variables can't be defined inside a function 370 371 To ensure that generic code follows the above rules, this 372 option forces all percpu variables to be defined as weak. 373 374endmenu # "Compiler options" 375 376config MAGIC_SYSRQ 377 bool "Magic SysRq key" 378 depends on !UML 379 help 380 If you say Y here, you will have some control over the system even 381 if the system crashes for example during kernel debugging (e.g., you 382 will be able to flush the buffer cache to disk, reboot the system 383 immediately or dump some status information). This is accomplished 384 by pressing various keys while holding SysRq (Alt+PrintScreen). It 385 also works on a serial console (on PC hardware at least), if you 386 send a BREAK and then within 5 seconds a command keypress. The 387 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 388 unless you really know what this hack does. 389 390config MAGIC_SYSRQ_DEFAULT_ENABLE 391 hex "Enable magic SysRq key functions by default" 392 depends on MAGIC_SYSRQ 393 default 0x1 394 help 395 Specifies which SysRq key functions are enabled by default. 396 This may be set to 1 or 0 to enable or disable them all, or 397 to a bitmask as described in Documentation/sysrq.txt. 398 399config DEBUG_KERNEL 400 bool "Kernel debugging" 401 help 402 Say Y here if you are developing drivers or trying to debug and 403 identify kernel problems. 404 405menu "Memory Debugging" 406 407source mm/Kconfig.debug 408 409config DEBUG_OBJECTS 410 bool "Debug object operations" 411 depends on DEBUG_KERNEL 412 help 413 If you say Y here, additional code will be inserted into the 414 kernel to track the life time of various objects and validate 415 the operations on those objects. 416 417config DEBUG_OBJECTS_SELFTEST 418 bool "Debug objects selftest" 419 depends on DEBUG_OBJECTS 420 help 421 This enables the selftest of the object debug code. 422 423config DEBUG_OBJECTS_FREE 424 bool "Debug objects in freed memory" 425 depends on DEBUG_OBJECTS 426 help 427 This enables checks whether a k/v free operation frees an area 428 which contains an object which has not been deactivated 429 properly. This can make kmalloc/kfree-intensive workloads 430 much slower. 431 432config DEBUG_OBJECTS_TIMERS 433 bool "Debug timer objects" 434 depends on DEBUG_OBJECTS 435 help 436 If you say Y here, additional code will be inserted into the 437 timer routines to track the life time of timer objects and 438 validate the timer operations. 439 440config DEBUG_OBJECTS_WORK 441 bool "Debug work objects" 442 depends on DEBUG_OBJECTS 443 help 444 If you say Y here, additional code will be inserted into the 445 work queue routines to track the life time of work objects and 446 validate the work operations. 447 448config DEBUG_OBJECTS_RCU_HEAD 449 bool "Debug RCU callbacks objects" 450 depends on DEBUG_OBJECTS 451 help 452 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 453 454config DEBUG_OBJECTS_PERCPU_COUNTER 455 bool "Debug percpu counter objects" 456 depends on DEBUG_OBJECTS 457 help 458 If you say Y here, additional code will be inserted into the 459 percpu counter routines to track the life time of percpu counter 460 objects and validate the percpu counter operations. 461 462config DEBUG_OBJECTS_ENABLE_DEFAULT 463 int "debug_objects bootup default value (0-1)" 464 range 0 1 465 default "1" 466 depends on DEBUG_OBJECTS 467 help 468 Debug objects boot parameter default value 469 470config DEBUG_SLAB 471 bool "Debug slab memory allocations" 472 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 473 help 474 Say Y here to have the kernel do limited verification on memory 475 allocation as well as poisoning memory on free to catch use of freed 476 memory. This can make kmalloc/kfree-intensive workloads much slower. 477 478config DEBUG_SLAB_LEAK 479 bool "Memory leak debugging" 480 depends on DEBUG_SLAB 481 482config SLUB_DEBUG_ON 483 bool "SLUB debugging on by default" 484 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 485 default n 486 help 487 Boot with debugging on by default. SLUB boots by default with 488 the runtime debug capabilities switched off. Enabling this is 489 equivalent to specifying the "slub_debug" parameter on boot. 490 There is no support for more fine grained debug control like 491 possible with slub_debug=xxx. SLUB debugging may be switched 492 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 493 "slub_debug=-". 494 495config SLUB_STATS 496 default n 497 bool "Enable SLUB performance statistics" 498 depends on SLUB && SYSFS 499 help 500 SLUB statistics are useful to debug SLUBs allocation behavior in 501 order find ways to optimize the allocator. This should never be 502 enabled for production use since keeping statistics slows down 503 the allocator by a few percentage points. The slabinfo command 504 supports the determination of the most active slabs to figure 505 out which slabs are relevant to a particular load. 506 Try running: slabinfo -DA 507 508config HAVE_DEBUG_KMEMLEAK 509 bool 510 511config DEBUG_KMEMLEAK 512 bool "Kernel memory leak detector" 513 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 514 select DEBUG_FS 515 select STACKTRACE if STACKTRACE_SUPPORT 516 select KALLSYMS 517 select CRC32 518 help 519 Say Y here if you want to enable the memory leak 520 detector. The memory allocation/freeing is traced in a way 521 similar to the Boehm's conservative garbage collector, the 522 difference being that the orphan objects are not freed but 523 only shown in /sys/kernel/debug/kmemleak. Enabling this 524 feature will introduce an overhead to memory 525 allocations. See Documentation/kmemleak.txt for more 526 details. 527 528 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 529 of finding leaks due to the slab objects poisoning. 530 531 In order to access the kmemleak file, debugfs needs to be 532 mounted (usually at /sys/kernel/debug). 533 534config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 535 int "Maximum kmemleak early log entries" 536 depends on DEBUG_KMEMLEAK 537 range 200 40000 538 default 400 539 help 540 Kmemleak must track all the memory allocations to avoid 541 reporting false positives. Since memory may be allocated or 542 freed before kmemleak is initialised, an early log buffer is 543 used to store these actions. If kmemleak reports "early log 544 buffer exceeded", please increase this value. 545 546config DEBUG_KMEMLEAK_TEST 547 tristate "Simple test for the kernel memory leak detector" 548 depends on DEBUG_KMEMLEAK && m 549 help 550 This option enables a module that explicitly leaks memory. 551 552 If unsure, say N. 553 554config DEBUG_KMEMLEAK_DEFAULT_OFF 555 bool "Default kmemleak to off" 556 depends on DEBUG_KMEMLEAK 557 help 558 Say Y here to disable kmemleak by default. It can then be enabled 559 on the command line via kmemleak=on. 560 561config DEBUG_STACK_USAGE 562 bool "Stack utilization instrumentation" 563 depends on DEBUG_KERNEL && !IA64 564 help 565 Enables the display of the minimum amount of free stack which each 566 task has ever had available in the sysrq-T and sysrq-P debug output. 567 568 This option will slow down process creation somewhat. 569 570config DEBUG_VM 571 bool "Debug VM" 572 depends on DEBUG_KERNEL 573 help 574 Enable this to turn on extended checks in the virtual-memory system 575 that may impact performance. 576 577 If unsure, say N. 578 579config DEBUG_VM_VMACACHE 580 bool "Debug VMA caching" 581 depends on DEBUG_VM 582 help 583 Enable this to turn on VMA caching debug information. Doing so 584 can cause significant overhead, so only enable it in non-production 585 environments. 586 587 If unsure, say N. 588 589config DEBUG_VM_RB 590 bool "Debug VM red-black trees" 591 depends on DEBUG_VM 592 help 593 Enable VM red-black tree debugging information and extra validations. 594 595 If unsure, say N. 596 597config DEBUG_VM_PGFLAGS 598 bool "Debug page-flags operations" 599 depends on DEBUG_VM 600 help 601 Enables extra validation on page flags operations. 602 603 If unsure, say N. 604 605config DEBUG_VIRTUAL 606 bool "Debug VM translations" 607 depends on DEBUG_KERNEL && X86 608 help 609 Enable some costly sanity checks in virtual to page code. This can 610 catch mistakes with virt_to_page() and friends. 611 612 If unsure, say N. 613 614config DEBUG_NOMMU_REGIONS 615 bool "Debug the global anon/private NOMMU mapping region tree" 616 depends on DEBUG_KERNEL && !MMU 617 help 618 This option causes the global tree of anonymous and private mapping 619 regions to be regularly checked for invalid topology. 620 621config DEBUG_MEMORY_INIT 622 bool "Debug memory initialisation" if EXPERT 623 default !EXPERT 624 help 625 Enable this for additional checks during memory initialisation. 626 The sanity checks verify aspects of the VM such as the memory model 627 and other information provided by the architecture. Verbose 628 information will be printed at KERN_DEBUG loglevel depending 629 on the mminit_loglevel= command-line option. 630 631 If unsure, say Y 632 633config MEMORY_NOTIFIER_ERROR_INJECT 634 tristate "Memory hotplug notifier error injection module" 635 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 636 help 637 This option provides the ability to inject artificial errors to 638 memory hotplug notifier chain callbacks. It is controlled through 639 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 640 641 If the notifier call chain should be failed with some events 642 notified, write the error code to "actions/<notifier event>/error". 643 644 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 645 646 # cd /sys/kernel/debug/notifier-error-inject/memory 647 # echo -12 > actions/MEM_GOING_OFFLINE/error 648 # echo offline > /sys/devices/system/memory/memoryXXX/state 649 bash: echo: write error: Cannot allocate memory 650 651 To compile this code as a module, choose M here: the module will 652 be called memory-notifier-error-inject. 653 654 If unsure, say N. 655 656config DEBUG_PER_CPU_MAPS 657 bool "Debug access to per_cpu maps" 658 depends on DEBUG_KERNEL 659 depends on SMP 660 help 661 Say Y to verify that the per_cpu map being accessed has 662 been set up. This adds a fair amount of code to kernel memory 663 and decreases performance. 664 665 Say N if unsure. 666 667config DEBUG_HIGHMEM 668 bool "Highmem debugging" 669 depends on DEBUG_KERNEL && HIGHMEM 670 help 671 This option enables additional error checking for high memory 672 systems. Disable for production systems. 673 674config HAVE_DEBUG_STACKOVERFLOW 675 bool 676 677config DEBUG_STACKOVERFLOW 678 bool "Check for stack overflows" 679 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 680 ---help--- 681 Say Y here if you want to check for overflows of kernel, IRQ 682 and exception stacks (if your architecture uses them). This 683 option will show detailed messages if free stack space drops 684 below a certain limit. 685 686 These kinds of bugs usually occur when call-chains in the 687 kernel get too deep, especially when interrupts are 688 involved. 689 690 Use this in cases where you see apparently random memory 691 corruption, especially if it appears in 'struct thread_info' 692 693 If in doubt, say "N". 694 695source "lib/Kconfig.kmemcheck" 696 697source "lib/Kconfig.kasan" 698 699endmenu # "Memory Debugging" 700 701config ARCH_HAS_KCOV 702 bool 703 help 704 KCOV does not have any arch-specific code, but currently it is enabled 705 only for x86_64. KCOV requires testing on other archs, and most likely 706 disabling of instrumentation for some early boot code. 707 708config KCOV 709 bool "Code coverage for fuzzing" 710 depends on ARCH_HAS_KCOV 711 select DEBUG_FS 712 select GCC_PLUGINS if !COMPILE_TEST 713 select GCC_PLUGIN_SANCOV if !COMPILE_TEST 714 help 715 KCOV exposes kernel code coverage information in a form suitable 716 for coverage-guided fuzzing (randomized testing). 717 718 If RANDOMIZE_BASE is enabled, PC values will not be stable across 719 different machines and across reboots. If you need stable PC values, 720 disable RANDOMIZE_BASE. 721 722 For more details, see Documentation/kcov.txt. 723 724config KCOV_INSTRUMENT_ALL 725 bool "Instrument all code by default" 726 depends on KCOV 727 default y if KCOV 728 help 729 If you are doing generic system call fuzzing (like e.g. syzkaller), 730 then you will want to instrument the whole kernel and you should 731 say y here. If you are doing more targeted fuzzing (like e.g. 732 filesystem fuzzing with AFL) then you will want to enable coverage 733 for more specific subsets of files, and should say n here. 734 735config DEBUG_SHIRQ 736 bool "Debug shared IRQ handlers" 737 depends on DEBUG_KERNEL 738 help 739 Enable this to generate a spurious interrupt as soon as a shared 740 interrupt handler is registered, and just before one is deregistered. 741 Drivers ought to be able to handle interrupts coming in at those 742 points; some don't and need to be caught. 743 744menu "Debug Lockups and Hangs" 745 746config LOCKUP_DETECTOR 747 bool "Detect Hard and Soft Lockups" 748 depends on DEBUG_KERNEL && !S390 749 help 750 Say Y here to enable the kernel to act as a watchdog to detect 751 hard and soft lockups. 752 753 Softlockups are bugs that cause the kernel to loop in kernel 754 mode for more than 20 seconds, without giving other tasks a 755 chance to run. The current stack trace is displayed upon 756 detection and the system will stay locked up. 757 758 Hardlockups are bugs that cause the CPU to loop in kernel mode 759 for more than 10 seconds, without letting other interrupts have a 760 chance to run. The current stack trace is displayed upon detection 761 and the system will stay locked up. 762 763 The overhead should be minimal. A periodic hrtimer runs to 764 generate interrupts and kick the watchdog task every 4 seconds. 765 An NMI is generated every 10 seconds or so to check for hardlockups. 766 767 The frequency of hrtimer and NMI events and the soft and hard lockup 768 thresholds can be controlled through the sysctl watchdog_thresh. 769 770config HARDLOCKUP_DETECTOR 771 def_bool y 772 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 773 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 774 775config BOOTPARAM_HARDLOCKUP_PANIC 776 bool "Panic (Reboot) On Hard Lockups" 777 depends on HARDLOCKUP_DETECTOR 778 help 779 Say Y here to enable the kernel to panic on "hard lockups", 780 which are bugs that cause the kernel to loop in kernel 781 mode with interrupts disabled for more than 10 seconds (configurable 782 using the watchdog_thresh sysctl). 783 784 Say N if unsure. 785 786config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 787 int 788 depends on HARDLOCKUP_DETECTOR 789 range 0 1 790 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 791 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 792 793config BOOTPARAM_SOFTLOCKUP_PANIC 794 bool "Panic (Reboot) On Soft Lockups" 795 depends on LOCKUP_DETECTOR 796 help 797 Say Y here to enable the kernel to panic on "soft lockups", 798 which are bugs that cause the kernel to loop in kernel 799 mode for more than 20 seconds (configurable using the watchdog_thresh 800 sysctl), without giving other tasks a chance to run. 801 802 The panic can be used in combination with panic_timeout, 803 to cause the system to reboot automatically after a 804 lockup has been detected. This feature is useful for 805 high-availability systems that have uptime guarantees and 806 where a lockup must be resolved ASAP. 807 808 Say N if unsure. 809 810config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 811 int 812 depends on LOCKUP_DETECTOR 813 range 0 1 814 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 815 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 816 817config DETECT_HUNG_TASK 818 bool "Detect Hung Tasks" 819 depends on DEBUG_KERNEL 820 default LOCKUP_DETECTOR 821 help 822 Say Y here to enable the kernel to detect "hung tasks", 823 which are bugs that cause the task to be stuck in 824 uninterruptible "D" state indefinitely. 825 826 When a hung task is detected, the kernel will print the 827 current stack trace (which you should report), but the 828 task will stay in uninterruptible state. If lockdep is 829 enabled then all held locks will also be reported. This 830 feature has negligible overhead. 831 832config DEFAULT_HUNG_TASK_TIMEOUT 833 int "Default timeout for hung task detection (in seconds)" 834 depends on DETECT_HUNG_TASK 835 default 120 836 help 837 This option controls the default timeout (in seconds) used 838 to determine when a task has become non-responsive and should 839 be considered hung. 840 841 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 842 sysctl or by writing a value to 843 /proc/sys/kernel/hung_task_timeout_secs. 844 845 A timeout of 0 disables the check. The default is two minutes. 846 Keeping the default should be fine in most cases. 847 848config BOOTPARAM_HUNG_TASK_PANIC 849 bool "Panic (Reboot) On Hung Tasks" 850 depends on DETECT_HUNG_TASK 851 help 852 Say Y here to enable the kernel to panic on "hung tasks", 853 which are bugs that cause the kernel to leave a task stuck 854 in uninterruptible "D" state. 855 856 The panic can be used in combination with panic_timeout, 857 to cause the system to reboot automatically after a 858 hung task has been detected. This feature is useful for 859 high-availability systems that have uptime guarantees and 860 where a hung tasks must be resolved ASAP. 861 862 Say N if unsure. 863 864config BOOTPARAM_HUNG_TASK_PANIC_VALUE 865 int 866 depends on DETECT_HUNG_TASK 867 range 0 1 868 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 869 default 1 if BOOTPARAM_HUNG_TASK_PANIC 870 871config WQ_WATCHDOG 872 bool "Detect Workqueue Stalls" 873 depends on DEBUG_KERNEL 874 help 875 Say Y here to enable stall detection on workqueues. If a 876 worker pool doesn't make forward progress on a pending work 877 item for over a given amount of time, 30s by default, a 878 warning message is printed along with dump of workqueue 879 state. This can be configured through kernel parameter 880 "workqueue.watchdog_thresh" and its sysfs counterpart. 881 882endmenu # "Debug lockups and hangs" 883 884config PANIC_ON_OOPS 885 bool "Panic on Oops" 886 help 887 Say Y here to enable the kernel to panic when it oopses. This 888 has the same effect as setting oops=panic on the kernel command 889 line. 890 891 This feature is useful to ensure that the kernel does not do 892 anything erroneous after an oops which could result in data 893 corruption or other issues. 894 895 Say N if unsure. 896 897config PANIC_ON_OOPS_VALUE 898 int 899 range 0 1 900 default 0 if !PANIC_ON_OOPS 901 default 1 if PANIC_ON_OOPS 902 903config PANIC_TIMEOUT 904 int "panic timeout" 905 default 0 906 help 907 Set the timeout value (in seconds) until a reboot occurs when the 908 the kernel panics. If n = 0, then we wait forever. A timeout 909 value n > 0 will wait n seconds before rebooting, while a timeout 910 value n < 0 will reboot immediately. 911 912config SCHED_DEBUG 913 bool "Collect scheduler debugging info" 914 depends on DEBUG_KERNEL && PROC_FS 915 default y 916 help 917 If you say Y here, the /proc/sched_debug file will be provided 918 that can help debug the scheduler. The runtime overhead of this 919 option is minimal. 920 921config SCHED_INFO 922 bool 923 default n 924 925config SCHEDSTATS 926 bool "Collect scheduler statistics" 927 depends on DEBUG_KERNEL && PROC_FS 928 select SCHED_INFO 929 help 930 If you say Y here, additional code will be inserted into the 931 scheduler and related routines to collect statistics about 932 scheduler behavior and provide them in /proc/schedstat. These 933 stats may be useful for both tuning and debugging the scheduler 934 If you aren't debugging the scheduler or trying to tune a specific 935 application, you can say N to avoid the very slight overhead 936 this adds. 937 938config SCHED_STACK_END_CHECK 939 bool "Detect stack corruption on calls to schedule()" 940 depends on DEBUG_KERNEL 941 default n 942 help 943 This option checks for a stack overrun on calls to schedule(). 944 If the stack end location is found to be over written always panic as 945 the content of the corrupted region can no longer be trusted. 946 This is to ensure no erroneous behaviour occurs which could result in 947 data corruption or a sporadic crash at a later stage once the region 948 is examined. The runtime overhead introduced is minimal. 949 950config DEBUG_TIMEKEEPING 951 bool "Enable extra timekeeping sanity checking" 952 help 953 This option will enable additional timekeeping sanity checks 954 which may be helpful when diagnosing issues where timekeeping 955 problems are suspected. 956 957 This may include checks in the timekeeping hotpaths, so this 958 option may have a (very small) performance impact to some 959 workloads. 960 961 If unsure, say N. 962 963config TIMER_STATS 964 bool "Collect kernel timers statistics" 965 depends on DEBUG_KERNEL && PROC_FS 966 help 967 If you say Y here, additional code will be inserted into the 968 timer routines to collect statistics about kernel timers being 969 reprogrammed. The statistics can be read from /proc/timer_stats. 970 The statistics collection is started by writing 1 to /proc/timer_stats, 971 writing 0 stops it. This feature is useful to collect information 972 about timer usage patterns in kernel and userspace. This feature 973 is lightweight if enabled in the kernel config but not activated 974 (it defaults to deactivated on bootup and will only be activated 975 if some application like powertop activates it explicitly). 976 977config DEBUG_PREEMPT 978 bool "Debug preemptible kernel" 979 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 980 default y 981 help 982 If you say Y here then the kernel will use a debug variant of the 983 commonly used smp_processor_id() function and will print warnings 984 if kernel code uses it in a preemption-unsafe way. Also, the kernel 985 will detect preemption count underflows. 986 987menu "Lock Debugging (spinlocks, mutexes, etc...)" 988 989config DEBUG_RT_MUTEXES 990 bool "RT Mutex debugging, deadlock detection" 991 depends on DEBUG_KERNEL && RT_MUTEXES 992 help 993 This allows rt mutex semantics violations and rt mutex related 994 deadlocks (lockups) to be detected and reported automatically. 995 996config DEBUG_SPINLOCK 997 bool "Spinlock and rw-lock debugging: basic checks" 998 depends on DEBUG_KERNEL 999 select UNINLINE_SPIN_UNLOCK 1000 help 1001 Say Y here and build SMP to catch missing spinlock initialization 1002 and certain other kinds of spinlock errors commonly made. This is 1003 best used in conjunction with the NMI watchdog so that spinlock 1004 deadlocks are also debuggable. 1005 1006config DEBUG_MUTEXES 1007 bool "Mutex debugging: basic checks" 1008 depends on DEBUG_KERNEL 1009 help 1010 This feature allows mutex semantics violations to be detected and 1011 reported. 1012 1013config DEBUG_WW_MUTEX_SLOWPATH 1014 bool "Wait/wound mutex debugging: Slowpath testing" 1015 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1016 select DEBUG_LOCK_ALLOC 1017 select DEBUG_SPINLOCK 1018 select DEBUG_MUTEXES 1019 help 1020 This feature enables slowpath testing for w/w mutex users by 1021 injecting additional -EDEADLK wound/backoff cases. Together with 1022 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 1023 will test all possible w/w mutex interface abuse with the 1024 exception of simply not acquiring all the required locks. 1025 Note that this feature can introduce significant overhead, so 1026 it really should not be enabled in a production or distro kernel, 1027 even a debug kernel. If you are a driver writer, enable it. If 1028 you are a distro, do not. 1029 1030config DEBUG_LOCK_ALLOC 1031 bool "Lock debugging: detect incorrect freeing of live locks" 1032 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1033 select DEBUG_SPINLOCK 1034 select DEBUG_MUTEXES 1035 select LOCKDEP 1036 help 1037 This feature will check whether any held lock (spinlock, rwlock, 1038 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1039 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1040 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1041 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1042 held during task exit. 1043 1044config PROVE_LOCKING 1045 bool "Lock debugging: prove locking correctness" 1046 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1047 select LOCKDEP 1048 select DEBUG_SPINLOCK 1049 select DEBUG_MUTEXES 1050 select DEBUG_LOCK_ALLOC 1051 select TRACE_IRQFLAGS 1052 default n 1053 help 1054 This feature enables the kernel to prove that all locking 1055 that occurs in the kernel runtime is mathematically 1056 correct: that under no circumstance could an arbitrary (and 1057 not yet triggered) combination of observed locking 1058 sequences (on an arbitrary number of CPUs, running an 1059 arbitrary number of tasks and interrupt contexts) cause a 1060 deadlock. 1061 1062 In short, this feature enables the kernel to report locking 1063 related deadlocks before they actually occur. 1064 1065 The proof does not depend on how hard and complex a 1066 deadlock scenario would be to trigger: how many 1067 participant CPUs, tasks and irq-contexts would be needed 1068 for it to trigger. The proof also does not depend on 1069 timing: if a race and a resulting deadlock is possible 1070 theoretically (no matter how unlikely the race scenario 1071 is), it will be proven so and will immediately be 1072 reported by the kernel (once the event is observed that 1073 makes the deadlock theoretically possible). 1074 1075 If a deadlock is impossible (i.e. the locking rules, as 1076 observed by the kernel, are mathematically correct), the 1077 kernel reports nothing. 1078 1079 NOTE: this feature can also be enabled for rwlocks, mutexes 1080 and rwsems - in which case all dependencies between these 1081 different locking variants are observed and mapped too, and 1082 the proof of observed correctness is also maintained for an 1083 arbitrary combination of these separate locking variants. 1084 1085 For more details, see Documentation/locking/lockdep-design.txt. 1086 1087config LOCKDEP 1088 bool 1089 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1090 select STACKTRACE 1091 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE 1092 select KALLSYMS 1093 select KALLSYMS_ALL 1094 1095config LOCK_STAT 1096 bool "Lock usage statistics" 1097 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1098 select LOCKDEP 1099 select DEBUG_SPINLOCK 1100 select DEBUG_MUTEXES 1101 select DEBUG_LOCK_ALLOC 1102 default n 1103 help 1104 This feature enables tracking lock contention points 1105 1106 For more details, see Documentation/locking/lockstat.txt 1107 1108 This also enables lock events required by "perf lock", 1109 subcommand of perf. 1110 If you want to use "perf lock", you also need to turn on 1111 CONFIG_EVENT_TRACING. 1112 1113 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1114 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1115 1116config DEBUG_LOCKDEP 1117 bool "Lock dependency engine debugging" 1118 depends on DEBUG_KERNEL && LOCKDEP 1119 help 1120 If you say Y here, the lock dependency engine will do 1121 additional runtime checks to debug itself, at the price 1122 of more runtime overhead. 1123 1124config DEBUG_ATOMIC_SLEEP 1125 bool "Sleep inside atomic section checking" 1126 select PREEMPT_COUNT 1127 depends on DEBUG_KERNEL 1128 help 1129 If you say Y here, various routines which may sleep will become very 1130 noisy if they are called inside atomic sections: when a spinlock is 1131 held, inside an rcu read side critical section, inside preempt disabled 1132 sections, inside an interrupt, etc... 1133 1134config DEBUG_LOCKING_API_SELFTESTS 1135 bool "Locking API boot-time self-tests" 1136 depends on DEBUG_KERNEL 1137 help 1138 Say Y here if you want the kernel to run a short self-test during 1139 bootup. The self-test checks whether common types of locking bugs 1140 are detected by debugging mechanisms or not. (if you disable 1141 lock debugging then those bugs wont be detected of course.) 1142 The following locking APIs are covered: spinlocks, rwlocks, 1143 mutexes and rwsems. 1144 1145config LOCK_TORTURE_TEST 1146 tristate "torture tests for locking" 1147 depends on DEBUG_KERNEL 1148 select TORTURE_TEST 1149 default n 1150 help 1151 This option provides a kernel module that runs torture tests 1152 on kernel locking primitives. The kernel module may be built 1153 after the fact on the running kernel to be tested, if desired. 1154 1155 Say Y here if you want kernel locking-primitive torture tests 1156 to be built into the kernel. 1157 Say M if you want these torture tests to build as a module. 1158 Say N if you are unsure. 1159 1160endmenu # lock debugging 1161 1162config TRACE_IRQFLAGS 1163 bool 1164 help 1165 Enables hooks to interrupt enabling and disabling for 1166 either tracing or lock debugging. 1167 1168config STACKTRACE 1169 bool "Stack backtrace support" 1170 depends on STACKTRACE_SUPPORT 1171 help 1172 This option causes the kernel to create a /proc/pid/stack for 1173 every process, showing its current stack trace. 1174 It is also used by various kernel debugging features that require 1175 stack trace generation. 1176 1177config DEBUG_KOBJECT 1178 bool "kobject debugging" 1179 depends on DEBUG_KERNEL 1180 help 1181 If you say Y here, some extra kobject debugging messages will be sent 1182 to the syslog. 1183 1184config DEBUG_KOBJECT_RELEASE 1185 bool "kobject release debugging" 1186 depends on DEBUG_OBJECTS_TIMERS 1187 help 1188 kobjects are reference counted objects. This means that their 1189 last reference count put is not predictable, and the kobject can 1190 live on past the point at which a driver decides to drop it's 1191 initial reference to the kobject gained on allocation. An 1192 example of this would be a struct device which has just been 1193 unregistered. 1194 1195 However, some buggy drivers assume that after such an operation, 1196 the memory backing the kobject can be immediately freed. This 1197 goes completely against the principles of a refcounted object. 1198 1199 If you say Y here, the kernel will delay the release of kobjects 1200 on the last reference count to improve the visibility of this 1201 kind of kobject release bug. 1202 1203config HAVE_DEBUG_BUGVERBOSE 1204 bool 1205 1206config DEBUG_BUGVERBOSE 1207 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1208 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1209 default y 1210 help 1211 Say Y here to make BUG() panics output the file name and line number 1212 of the BUG call as well as the EIP and oops trace. This aids 1213 debugging but costs about 70-100K of memory. 1214 1215config DEBUG_LIST 1216 bool "Debug linked list manipulation" 1217 depends on DEBUG_KERNEL 1218 help 1219 Enable this to turn on extended checks in the linked-list 1220 walking routines. 1221 1222 If unsure, say N. 1223 1224config DEBUG_PI_LIST 1225 bool "Debug priority linked list manipulation" 1226 depends on DEBUG_KERNEL 1227 help 1228 Enable this to turn on extended checks in the priority-ordered 1229 linked-list (plist) walking routines. This checks the entire 1230 list multiple times during each manipulation. 1231 1232 If unsure, say N. 1233 1234config DEBUG_SG 1235 bool "Debug SG table operations" 1236 depends on DEBUG_KERNEL 1237 help 1238 Enable this to turn on checks on scatter-gather tables. This can 1239 help find problems with drivers that do not properly initialize 1240 their sg tables. 1241 1242 If unsure, say N. 1243 1244config DEBUG_NOTIFIERS 1245 bool "Debug notifier call chains" 1246 depends on DEBUG_KERNEL 1247 help 1248 Enable this to turn on sanity checking for notifier call chains. 1249 This is most useful for kernel developers to make sure that 1250 modules properly unregister themselves from notifier chains. 1251 This is a relatively cheap check but if you care about maximum 1252 performance, say N. 1253 1254config DEBUG_CREDENTIALS 1255 bool "Debug credential management" 1256 depends on DEBUG_KERNEL 1257 help 1258 Enable this to turn on some debug checking for credential 1259 management. The additional code keeps track of the number of 1260 pointers from task_structs to any given cred struct, and checks to 1261 see that this number never exceeds the usage count of the cred 1262 struct. 1263 1264 Furthermore, if SELinux is enabled, this also checks that the 1265 security pointer in the cred struct is never seen to be invalid. 1266 1267 If unsure, say N. 1268 1269menu "RCU Debugging" 1270 1271config PROVE_RCU 1272 def_bool PROVE_LOCKING 1273 1274config PROVE_RCU_REPEATEDLY 1275 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1276 depends on PROVE_RCU 1277 default n 1278 help 1279 By itself, PROVE_RCU will disable checking upon issuing the 1280 first warning (or "splat"). This feature prevents such 1281 disabling, allowing multiple RCU-lockdep warnings to be printed 1282 on a single reboot. 1283 1284 Say Y to allow multiple RCU-lockdep warnings per boot. 1285 1286 Say N if you are unsure. 1287 1288config SPARSE_RCU_POINTER 1289 bool "RCU debugging: sparse-based checks for pointer usage" 1290 default n 1291 help 1292 This feature enables the __rcu sparse annotation for 1293 RCU-protected pointers. This annotation will cause sparse 1294 to flag any non-RCU used of annotated pointers. This can be 1295 helpful when debugging RCU usage. Please note that this feature 1296 is not intended to enforce code cleanliness; it is instead merely 1297 a debugging aid. 1298 1299 Say Y to make sparse flag questionable use of RCU-protected pointers 1300 1301 Say N if you are unsure. 1302 1303config TORTURE_TEST 1304 tristate 1305 default n 1306 1307config RCU_PERF_TEST 1308 tristate "performance tests for RCU" 1309 depends on DEBUG_KERNEL 1310 select TORTURE_TEST 1311 select SRCU 1312 select TASKS_RCU 1313 default n 1314 help 1315 This option provides a kernel module that runs performance 1316 tests on the RCU infrastructure. The kernel module may be built 1317 after the fact on the running kernel to be tested, if desired. 1318 1319 Say Y here if you want RCU performance tests to be built into 1320 the kernel. 1321 Say M if you want the RCU performance tests to build as a module. 1322 Say N if you are unsure. 1323 1324config RCU_TORTURE_TEST 1325 tristate "torture tests for RCU" 1326 depends on DEBUG_KERNEL 1327 select TORTURE_TEST 1328 select SRCU 1329 select TASKS_RCU 1330 default n 1331 help 1332 This option provides a kernel module that runs torture tests 1333 on the RCU infrastructure. The kernel module may be built 1334 after the fact on the running kernel to be tested, if desired. 1335 1336 Say Y here if you want RCU torture tests to be built into 1337 the kernel. 1338 Say M if you want the RCU torture tests to build as a module. 1339 Say N if you are unsure. 1340 1341config RCU_TORTURE_TEST_SLOW_PREINIT 1342 bool "Slow down RCU grace-period pre-initialization to expose races" 1343 depends on RCU_TORTURE_TEST 1344 help 1345 This option delays grace-period pre-initialization (the 1346 propagation of CPU-hotplug changes up the rcu_node combining 1347 tree) for a few jiffies between initializing each pair of 1348 consecutive rcu_node structures. This helps to expose races 1349 involving grace-period pre-initialization, in other words, it 1350 makes your kernel less stable. It can also greatly increase 1351 grace-period latency, especially on systems with large numbers 1352 of CPUs. This is useful when torture-testing RCU, but in 1353 almost no other circumstance. 1354 1355 Say Y here if you want your system to crash and hang more often. 1356 Say N if you want a sane system. 1357 1358config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY 1359 int "How much to slow down RCU grace-period pre-initialization" 1360 range 0 5 1361 default 3 1362 depends on RCU_TORTURE_TEST_SLOW_PREINIT 1363 help 1364 This option specifies the number of jiffies to wait between 1365 each rcu_node structure pre-initialization step. 1366 1367config RCU_TORTURE_TEST_SLOW_INIT 1368 bool "Slow down RCU grace-period initialization to expose races" 1369 depends on RCU_TORTURE_TEST 1370 help 1371 This option delays grace-period initialization for a few 1372 jiffies between initializing each pair of consecutive 1373 rcu_node structures. This helps to expose races involving 1374 grace-period initialization, in other words, it makes your 1375 kernel less stable. It can also greatly increase grace-period 1376 latency, especially on systems with large numbers of CPUs. 1377 This is useful when torture-testing RCU, but in almost no 1378 other circumstance. 1379 1380 Say Y here if you want your system to crash and hang more often. 1381 Say N if you want a sane system. 1382 1383config RCU_TORTURE_TEST_SLOW_INIT_DELAY 1384 int "How much to slow down RCU grace-period initialization" 1385 range 0 5 1386 default 3 1387 depends on RCU_TORTURE_TEST_SLOW_INIT 1388 help 1389 This option specifies the number of jiffies to wait between 1390 each rcu_node structure initialization. 1391 1392config RCU_TORTURE_TEST_SLOW_CLEANUP 1393 bool "Slow down RCU grace-period cleanup to expose races" 1394 depends on RCU_TORTURE_TEST 1395 help 1396 This option delays grace-period cleanup for a few jiffies 1397 between cleaning up each pair of consecutive rcu_node 1398 structures. This helps to expose races involving grace-period 1399 cleanup, in other words, it makes your kernel less stable. 1400 It can also greatly increase grace-period latency, especially 1401 on systems with large numbers of CPUs. This is useful when 1402 torture-testing RCU, but in almost no other circumstance. 1403 1404 Say Y here if you want your system to crash and hang more often. 1405 Say N if you want a sane system. 1406 1407config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY 1408 int "How much to slow down RCU grace-period cleanup" 1409 range 0 5 1410 default 3 1411 depends on RCU_TORTURE_TEST_SLOW_CLEANUP 1412 help 1413 This option specifies the number of jiffies to wait between 1414 each rcu_node structure cleanup operation. 1415 1416config RCU_CPU_STALL_TIMEOUT 1417 int "RCU CPU stall timeout in seconds" 1418 depends on RCU_STALL_COMMON 1419 range 3 300 1420 default 21 1421 help 1422 If a given RCU grace period extends more than the specified 1423 number of seconds, a CPU stall warning is printed. If the 1424 RCU grace period persists, additional CPU stall warnings are 1425 printed at more widely spaced intervals. 1426 1427config RCU_TRACE 1428 bool "Enable tracing for RCU" 1429 depends on DEBUG_KERNEL 1430 select TRACE_CLOCK 1431 help 1432 This option provides tracing in RCU which presents stats 1433 in debugfs for debugging RCU implementation. 1434 1435 Say Y here if you want to enable RCU tracing 1436 Say N if you are unsure. 1437 1438config RCU_EQS_DEBUG 1439 bool "Provide debugging asserts for adding NO_HZ support to an arch" 1440 depends on DEBUG_KERNEL 1441 help 1442 This option provides consistency checks in RCU's handling of 1443 NO_HZ. These checks have proven quite helpful in detecting 1444 bugs in arch-specific NO_HZ code. 1445 1446 Say N here if you need ultimate kernel/user switch latencies 1447 Say Y if you are unsure 1448 1449endmenu # "RCU Debugging" 1450 1451config DEBUG_WQ_FORCE_RR_CPU 1452 bool "Force round-robin CPU selection for unbound work items" 1453 depends on DEBUG_KERNEL 1454 default n 1455 help 1456 Workqueue used to implicitly guarantee that work items queued 1457 without explicit CPU specified are put on the local CPU. This 1458 guarantee is no longer true and while local CPU is still 1459 preferred work items may be put on foreign CPUs. Kernel 1460 parameter "workqueue.debug_force_rr_cpu" is added to force 1461 round-robin CPU selection to flush out usages which depend on the 1462 now broken guarantee. This config option enables the debug 1463 feature by default. When enabled, memory and cache locality will 1464 be impacted. 1465 1466config DEBUG_BLOCK_EXT_DEVT 1467 bool "Force extended block device numbers and spread them" 1468 depends on DEBUG_KERNEL 1469 depends on BLOCK 1470 default n 1471 help 1472 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1473 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1474 YOU ARE DOING. Distros, please enable this and fix whatever 1475 is broken. 1476 1477 Conventionally, block device numbers are allocated from 1478 predetermined contiguous area. However, extended block area 1479 may introduce non-contiguous block device numbers. This 1480 option forces most block device numbers to be allocated from 1481 the extended space and spreads them to discover kernel or 1482 userland code paths which assume predetermined contiguous 1483 device number allocation. 1484 1485 Note that turning on this debug option shuffles all the 1486 device numbers for all IDE and SCSI devices including libata 1487 ones, so root partition specified using device number 1488 directly (via rdev or root=MAJ:MIN) won't work anymore. 1489 Textual device names (root=/dev/sdXn) will continue to work. 1490 1491 Say N if you are unsure. 1492 1493config CPU_HOTPLUG_STATE_CONTROL 1494 bool "Enable CPU hotplug state control" 1495 depends on DEBUG_KERNEL 1496 depends on HOTPLUG_CPU 1497 default n 1498 help 1499 Allows to write steps between "offline" and "online" to the CPUs 1500 sysfs target file so states can be stepped granular. This is a debug 1501 option for now as the hotplug machinery cannot be stopped and 1502 restarted at arbitrary points yet. 1503 1504 Say N if your are unsure. 1505 1506config NOTIFIER_ERROR_INJECTION 1507 tristate "Notifier error injection" 1508 depends on DEBUG_KERNEL 1509 select DEBUG_FS 1510 help 1511 This option provides the ability to inject artificial errors to 1512 specified notifier chain callbacks. It is useful to test the error 1513 handling of notifier call chain failures. 1514 1515 Say N if unsure. 1516 1517config CPU_NOTIFIER_ERROR_INJECT 1518 tristate "CPU notifier error injection module" 1519 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1520 help 1521 This option provides a kernel module that can be used to test 1522 the error handling of the cpu notifiers by injecting artificial 1523 errors to CPU notifier chain callbacks. It is controlled through 1524 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1525 1526 If the notifier call chain should be failed with some events 1527 notified, write the error code to "actions/<notifier event>/error". 1528 1529 Example: Inject CPU offline error (-1 == -EPERM) 1530 1531 # cd /sys/kernel/debug/notifier-error-inject/cpu 1532 # echo -1 > actions/CPU_DOWN_PREPARE/error 1533 # echo 0 > /sys/devices/system/cpu/cpu1/online 1534 bash: echo: write error: Operation not permitted 1535 1536 To compile this code as a module, choose M here: the module will 1537 be called cpu-notifier-error-inject. 1538 1539 If unsure, say N. 1540 1541config PM_NOTIFIER_ERROR_INJECT 1542 tristate "PM notifier error injection module" 1543 depends on PM && NOTIFIER_ERROR_INJECTION 1544 default m if PM_DEBUG 1545 help 1546 This option provides the ability to inject artificial errors to 1547 PM notifier chain callbacks. It is controlled through debugfs 1548 interface /sys/kernel/debug/notifier-error-inject/pm 1549 1550 If the notifier call chain should be failed with some events 1551 notified, write the error code to "actions/<notifier event>/error". 1552 1553 Example: Inject PM suspend error (-12 = -ENOMEM) 1554 1555 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1556 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1557 # echo mem > /sys/power/state 1558 bash: echo: write error: Cannot allocate memory 1559 1560 To compile this code as a module, choose M here: the module will 1561 be called pm-notifier-error-inject. 1562 1563 If unsure, say N. 1564 1565config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1566 tristate "OF reconfig notifier error injection module" 1567 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1568 help 1569 This option provides the ability to inject artificial errors to 1570 OF reconfig notifier chain callbacks. It is controlled 1571 through debugfs interface under 1572 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1573 1574 If the notifier call chain should be failed with some events 1575 notified, write the error code to "actions/<notifier event>/error". 1576 1577 To compile this code as a module, choose M here: the module will 1578 be called of-reconfig-notifier-error-inject. 1579 1580 If unsure, say N. 1581 1582config NETDEV_NOTIFIER_ERROR_INJECT 1583 tristate "Netdev notifier error injection module" 1584 depends on NET && NOTIFIER_ERROR_INJECTION 1585 help 1586 This option provides the ability to inject artificial errors to 1587 netdevice notifier chain callbacks. It is controlled through debugfs 1588 interface /sys/kernel/debug/notifier-error-inject/netdev 1589 1590 If the notifier call chain should be failed with some events 1591 notified, write the error code to "actions/<notifier event>/error". 1592 1593 Example: Inject netdevice mtu change error (-22 = -EINVAL) 1594 1595 # cd /sys/kernel/debug/notifier-error-inject/netdev 1596 # echo -22 > actions/NETDEV_CHANGEMTU/error 1597 # ip link set eth0 mtu 1024 1598 RTNETLINK answers: Invalid argument 1599 1600 To compile this code as a module, choose M here: the module will 1601 be called netdev-notifier-error-inject. 1602 1603 If unsure, say N. 1604 1605config FAULT_INJECTION 1606 bool "Fault-injection framework" 1607 depends on DEBUG_KERNEL 1608 help 1609 Provide fault-injection framework. 1610 For more details, see Documentation/fault-injection/. 1611 1612config FAILSLAB 1613 bool "Fault-injection capability for kmalloc" 1614 depends on FAULT_INJECTION 1615 depends on SLAB || SLUB 1616 help 1617 Provide fault-injection capability for kmalloc. 1618 1619config FAIL_PAGE_ALLOC 1620 bool "Fault-injection capabilitiy for alloc_pages()" 1621 depends on FAULT_INJECTION 1622 help 1623 Provide fault-injection capability for alloc_pages(). 1624 1625config FAIL_MAKE_REQUEST 1626 bool "Fault-injection capability for disk IO" 1627 depends on FAULT_INJECTION && BLOCK 1628 help 1629 Provide fault-injection capability for disk IO. 1630 1631config FAIL_IO_TIMEOUT 1632 bool "Fault-injection capability for faking disk interrupts" 1633 depends on FAULT_INJECTION && BLOCK 1634 help 1635 Provide fault-injection capability on end IO handling. This 1636 will make the block layer "forget" an interrupt as configured, 1637 thus exercising the error handling. 1638 1639 Only works with drivers that use the generic timeout handling, 1640 for others it wont do anything. 1641 1642config FAIL_MMC_REQUEST 1643 bool "Fault-injection capability for MMC IO" 1644 depends on FAULT_INJECTION_DEBUG_FS && MMC 1645 help 1646 Provide fault-injection capability for MMC IO. 1647 This will make the mmc core return data errors. This is 1648 useful to test the error handling in the mmc block device 1649 and to test how the mmc host driver handles retries from 1650 the block device. 1651 1652config FAIL_FUTEX 1653 bool "Fault-injection capability for futexes" 1654 select DEBUG_FS 1655 depends on FAULT_INJECTION && FUTEX 1656 help 1657 Provide fault-injection capability for futexes. 1658 1659config FAULT_INJECTION_DEBUG_FS 1660 bool "Debugfs entries for fault-injection capabilities" 1661 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1662 help 1663 Enable configuration of fault-injection capabilities via debugfs. 1664 1665config FAULT_INJECTION_STACKTRACE_FILTER 1666 bool "stacktrace filter for fault-injection capabilities" 1667 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1668 depends on !X86_64 1669 select STACKTRACE 1670 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1671 help 1672 Provide stacktrace filter for fault-injection capabilities 1673 1674config LATENCYTOP 1675 bool "Latency measuring infrastructure" 1676 depends on DEBUG_KERNEL 1677 depends on STACKTRACE_SUPPORT 1678 depends on PROC_FS 1679 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1680 select KALLSYMS 1681 select KALLSYMS_ALL 1682 select STACKTRACE 1683 select SCHEDSTATS 1684 select SCHED_DEBUG 1685 help 1686 Enable this option if you want to use the LatencyTOP tool 1687 to find out which userspace is blocking on what kernel operations. 1688 1689source kernel/trace/Kconfig 1690 1691menu "Runtime Testing" 1692 1693config LKDTM 1694 tristate "Linux Kernel Dump Test Tool Module" 1695 depends on DEBUG_FS 1696 depends on BLOCK 1697 default n 1698 help 1699 This module enables testing of the different dumping mechanisms by 1700 inducing system failures at predefined crash points. 1701 If you don't need it: say N 1702 Choose M here to compile this code as a module. The module will be 1703 called lkdtm. 1704 1705 Documentation on how to use the module can be found in 1706 Documentation/fault-injection/provoke-crashes.txt 1707 1708config TEST_LIST_SORT 1709 bool "Linked list sorting test" 1710 depends on DEBUG_KERNEL 1711 help 1712 Enable this to turn on 'list_sort()' function test. This test is 1713 executed only once during system boot, so affects only boot time. 1714 1715 If unsure, say N. 1716 1717config KPROBES_SANITY_TEST 1718 bool "Kprobes sanity tests" 1719 depends on DEBUG_KERNEL 1720 depends on KPROBES 1721 default n 1722 help 1723 This option provides for testing basic kprobes functionality on 1724 boot. A sample kprobe, jprobe and kretprobe are inserted and 1725 verified for functionality. 1726 1727 Say N if you are unsure. 1728 1729config BACKTRACE_SELF_TEST 1730 tristate "Self test for the backtrace code" 1731 depends on DEBUG_KERNEL 1732 default n 1733 help 1734 This option provides a kernel module that can be used to test 1735 the kernel stack backtrace code. This option is not useful 1736 for distributions or general kernels, but only for kernel 1737 developers working on architecture code. 1738 1739 Note that if you want to also test saved backtraces, you will 1740 have to enable STACKTRACE as well. 1741 1742 Say N if you are unsure. 1743 1744config RBTREE_TEST 1745 tristate "Red-Black tree test" 1746 depends on DEBUG_KERNEL 1747 help 1748 A benchmark measuring the performance of the rbtree library. 1749 Also includes rbtree invariant checks. 1750 1751config INTERVAL_TREE_TEST 1752 tristate "Interval tree test" 1753 depends on m && DEBUG_KERNEL 1754 select INTERVAL_TREE 1755 help 1756 A benchmark measuring the performance of the interval tree library 1757 1758config PERCPU_TEST 1759 tristate "Per cpu operations test" 1760 depends on m && DEBUG_KERNEL 1761 help 1762 Enable this option to build test module which validates per-cpu 1763 operations. 1764 1765 If unsure, say N. 1766 1767config ATOMIC64_SELFTEST 1768 bool "Perform an atomic64_t self-test at boot" 1769 help 1770 Enable this option to test the atomic64_t functions at boot. 1771 1772 If unsure, say N. 1773 1774config ASYNC_RAID6_TEST 1775 tristate "Self test for hardware accelerated raid6 recovery" 1776 depends on ASYNC_RAID6_RECOV 1777 select ASYNC_MEMCPY 1778 ---help--- 1779 This is a one-shot self test that permutes through the 1780 recovery of all the possible two disk failure scenarios for a 1781 N-disk array. Recovery is performed with the asynchronous 1782 raid6 recovery routines, and will optionally use an offload 1783 engine if one is available. 1784 1785 If unsure, say N. 1786 1787config TEST_HEXDUMP 1788 tristate "Test functions located in the hexdump module at runtime" 1789 1790config TEST_STRING_HELPERS 1791 tristate "Test functions located in the string_helpers module at runtime" 1792 1793config TEST_KSTRTOX 1794 tristate "Test kstrto*() family of functions at runtime" 1795 1796config TEST_PRINTF 1797 tristate "Test printf() family of functions at runtime" 1798 1799config TEST_BITMAP 1800 tristate "Test bitmap_*() family of functions at runtime" 1801 default n 1802 help 1803 Enable this option to test the bitmap functions at boot. 1804 1805 If unsure, say N. 1806 1807config TEST_UUID 1808 tristate "Test functions located in the uuid module at runtime" 1809 1810config TEST_RHASHTABLE 1811 tristate "Perform selftest on resizable hash table" 1812 default n 1813 help 1814 Enable this option to test the rhashtable functions at boot. 1815 1816 If unsure, say N. 1817 1818config TEST_HASH 1819 tristate "Perform selftest on hash functions" 1820 default n 1821 help 1822 Enable this option to test the kernel's integer (<linux/hash,h>) 1823 and string (<linux/stringhash.h>) hash functions on boot 1824 (or module load). 1825 1826 This is intended to help people writing architecture-specific 1827 optimized versions. If unsure, say N. 1828 1829endmenu # runtime tests 1830 1831config PROVIDE_OHCI1394_DMA_INIT 1832 bool "Remote debugging over FireWire early on boot" 1833 depends on PCI && X86 1834 help 1835 If you want to debug problems which hang or crash the kernel early 1836 on boot and the crashing machine has a FireWire port, you can use 1837 this feature to remotely access the memory of the crashed machine 1838 over FireWire. This employs remote DMA as part of the OHCI1394 1839 specification which is now the standard for FireWire controllers. 1840 1841 With remote DMA, you can monitor the printk buffer remotely using 1842 firescope and access all memory below 4GB using fireproxy from gdb. 1843 Even controlling a kernel debugger is possible using remote DMA. 1844 1845 Usage: 1846 1847 If ohci1394_dma=early is used as boot parameter, it will initialize 1848 all OHCI1394 controllers which are found in the PCI config space. 1849 1850 As all changes to the FireWire bus such as enabling and disabling 1851 devices cause a bus reset and thereby disable remote DMA for all 1852 devices, be sure to have the cable plugged and FireWire enabled on 1853 the debugging host before booting the debug target for debugging. 1854 1855 This code (~1k) is freed after boot. By then, the firewire stack 1856 in charge of the OHCI-1394 controllers should be used instead. 1857 1858 See Documentation/debugging-via-ohci1394.txt for more information. 1859 1860config BUILD_DOCSRC 1861 bool "Build targets in Documentation/ tree" 1862 depends on HEADERS_CHECK 1863 help 1864 This option attempts to build objects from the source files in the 1865 kernel Documentation/ tree. 1866 1867 Say N if you are unsure. 1868 1869config DMA_API_DEBUG 1870 bool "Enable debugging of DMA-API usage" 1871 depends on HAVE_DMA_API_DEBUG 1872 help 1873 Enable this option to debug the use of the DMA API by device drivers. 1874 With this option you will be able to detect common bugs in device 1875 drivers like double-freeing of DMA mappings or freeing mappings that 1876 were never allocated. 1877 1878 This also attempts to catch cases where a page owned by DMA is 1879 accessed by the cpu in a way that could cause data corruption. For 1880 example, this enables cow_user_page() to check that the source page is 1881 not undergoing DMA. 1882 1883 This option causes a performance degradation. Use only if you want to 1884 debug device drivers and dma interactions. 1885 1886 If unsure, say N. 1887 1888config TEST_LKM 1889 tristate "Test module loading with 'hello world' module" 1890 default n 1891 depends on m 1892 help 1893 This builds the "test_module" module that emits "Hello, world" 1894 on printk when loaded. It is designed to be used for basic 1895 evaluation of the module loading subsystem (for example when 1896 validating module verification). It lacks any extra dependencies, 1897 and will not normally be loaded by the system unless explicitly 1898 requested by name. 1899 1900 If unsure, say N. 1901 1902config TEST_USER_COPY 1903 tristate "Test user/kernel boundary protections" 1904 default n 1905 depends on m 1906 help 1907 This builds the "test_user_copy" module that runs sanity checks 1908 on the copy_to/from_user infrastructure, making sure basic 1909 user/kernel boundary testing is working. If it fails to load, 1910 a regression has been detected in the user/kernel memory boundary 1911 protections. 1912 1913 If unsure, say N. 1914 1915config TEST_BPF 1916 tristate "Test BPF filter functionality" 1917 default n 1918 depends on m && NET 1919 help 1920 This builds the "test_bpf" module that runs various test vectors 1921 against the BPF interpreter or BPF JIT compiler depending on the 1922 current setting. This is in particular useful for BPF JIT compiler 1923 development, but also to run regression tests against changes in 1924 the interpreter code. It also enables test stubs for eBPF maps and 1925 verifier used by user space verifier testsuite. 1926 1927 If unsure, say N. 1928 1929config TEST_FIRMWARE 1930 tristate "Test firmware loading via userspace interface" 1931 default n 1932 depends on FW_LOADER 1933 help 1934 This builds the "test_firmware" module that creates a userspace 1935 interface for testing firmware loading. This can be used to 1936 control the triggering of firmware loading without needing an 1937 actual firmware-using device. The contents can be rechecked by 1938 userspace. 1939 1940 If unsure, say N. 1941 1942config TEST_UDELAY 1943 tristate "udelay test driver" 1944 default n 1945 help 1946 This builds the "udelay_test" module that helps to make sure 1947 that udelay() is working properly. 1948 1949 If unsure, say N. 1950 1951config MEMTEST 1952 bool "Memtest" 1953 depends on HAVE_MEMBLOCK 1954 ---help--- 1955 This option adds a kernel parameter 'memtest', which allows memtest 1956 to be set. 1957 memtest=0, mean disabled; -- default 1958 memtest=1, mean do 1 test pattern; 1959 ... 1960 memtest=17, mean do 17 test patterns. 1961 If you are unsure how to answer this question, answer N. 1962 1963config TEST_STATIC_KEYS 1964 tristate "Test static keys" 1965 default n 1966 depends on m 1967 help 1968 Test the static key interfaces. 1969 1970 If unsure, say N. 1971 1972source "samples/Kconfig" 1973 1974source "lib/Kconfig.kgdb" 1975 1976source "lib/Kconfig.ubsan" 1977 1978config ARCH_HAS_DEVMEM_IS_ALLOWED 1979 bool 1980 1981config STRICT_DEVMEM 1982 bool "Filter access to /dev/mem" 1983 depends on MMU 1984 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 1985 default y if TILE || PPC 1986 ---help--- 1987 If this option is disabled, you allow userspace (root) access to all 1988 of memory, including kernel and userspace memory. Accidental 1989 access to this is obviously disastrous, but specific access can 1990 be used by people debugging the kernel. Note that with PAT support 1991 enabled, even in this case there are restrictions on /dev/mem 1992 use due to the cache aliasing requirements. 1993 1994 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 1995 file only allows userspace access to PCI space and the BIOS code and 1996 data regions. This is sufficient for dosemu and X and all common 1997 users of /dev/mem. 1998 1999 If in doubt, say Y. 2000 2001config IO_STRICT_DEVMEM 2002 bool "Filter I/O access to /dev/mem" 2003 depends on STRICT_DEVMEM 2004 ---help--- 2005 If this option is disabled, you allow userspace (root) access to all 2006 io-memory regardless of whether a driver is actively using that 2007 range. Accidental access to this is obviously disastrous, but 2008 specific access can be used by people debugging kernel drivers. 2009 2010 If this option is switched on, the /dev/mem file only allows 2011 userspace access to *idle* io-memory ranges (see /proc/iomem) This 2012 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 2013 if the driver using a given range cannot be disabled. 2014 2015 If in doubt, say Y. 2016