1menu "printk and dmesg options" 2 3config PRINTK_TIME 4 bool "Show timing information on printks" 5 depends on PRINTK 6 help 7 Selecting this option causes time stamps of the printk() 8 messages to be added to the output of the syslog() system 9 call and at the console. 10 11 The timestamp is always recorded internally, and exported 12 to /dev/kmsg. This flag just specifies if the timestamp should 13 be included, not that the timestamp is recorded. 14 15 The behavior is also controlled by the kernel command line 16 parameter printk.time=1. See Documentation/kernel-parameters.txt 17 18config MESSAGE_LOGLEVEL_DEFAULT 19 int "Default message log level (1-7)" 20 range 1 7 21 default "4" 22 help 23 Default log level for printk statements with no specified priority. 24 25 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks 26 that are auditing their logs closely may want to set it to a lower 27 priority. 28 29config BOOT_PRINTK_DELAY 30 bool "Delay each boot printk message by N milliseconds" 31 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 32 help 33 This build option allows you to read kernel boot messages 34 by inserting a short delay after each one. The delay is 35 specified in milliseconds on the kernel command line, 36 using "boot_delay=N". 37 38 It is likely that you would also need to use "lpj=M" to preset 39 the "loops per jiffie" value. 40 See a previous boot log for the "lpj" value to use for your 41 system, and then set "lpj=M" before setting "boot_delay=N". 42 NOTE: Using this option may adversely affect SMP systems. 43 I.e., processors other than the first one may not boot up. 44 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect 45 what it believes to be lockup conditions. 46 47config DYNAMIC_DEBUG 48 bool "Enable dynamic printk() support" 49 default n 50 depends on PRINTK 51 depends on DEBUG_FS 52 help 53 54 Compiles debug level messages into the kernel, which would not 55 otherwise be available at runtime. These messages can then be 56 enabled/disabled based on various levels of scope - per source file, 57 function, module, format string, and line number. This mechanism 58 implicitly compiles in all pr_debug() and dev_dbg() calls, which 59 enlarges the kernel text size by about 2%. 60 61 If a source file is compiled with DEBUG flag set, any 62 pr_debug() calls in it are enabled by default, but can be 63 disabled at runtime as below. Note that DEBUG flag is 64 turned on by many CONFIG_*DEBUG* options. 65 66 Usage: 67 68 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 69 which is contained in the 'debugfs' filesystem. Thus, the debugfs 70 filesystem must first be mounted before making use of this feature. 71 We refer the control file as: <debugfs>/dynamic_debug/control. This 72 file contains a list of the debug statements that can be enabled. The 73 format for each line of the file is: 74 75 filename:lineno [module]function flags format 76 77 filename : source file of the debug statement 78 lineno : line number of the debug statement 79 module : module that contains the debug statement 80 function : function that contains the debug statement 81 flags : '=p' means the line is turned 'on' for printing 82 format : the format used for the debug statement 83 84 From a live system: 85 86 nullarbor:~ # cat <debugfs>/dynamic_debug/control 87 # filename:lineno [module]function flags format 88 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012" 89 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012" 90 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012" 91 92 Example usage: 93 94 // enable the message at line 1603 of file svcsock.c 95 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 96 <debugfs>/dynamic_debug/control 97 98 // enable all the messages in file svcsock.c 99 nullarbor:~ # echo -n 'file svcsock.c +p' > 100 <debugfs>/dynamic_debug/control 101 102 // enable all the messages in the NFS server module 103 nullarbor:~ # echo -n 'module nfsd +p' > 104 <debugfs>/dynamic_debug/control 105 106 // enable all 12 messages in the function svc_process() 107 nullarbor:~ # echo -n 'func svc_process +p' > 108 <debugfs>/dynamic_debug/control 109 110 // disable all 12 messages in the function svc_process() 111 nullarbor:~ # echo -n 'func svc_process -p' > 112 <debugfs>/dynamic_debug/control 113 114 See Documentation/dynamic-debug-howto.txt for additional information. 115 116endmenu # "printk and dmesg options" 117 118menu "Compile-time checks and compiler options" 119 120config DEBUG_INFO 121 bool "Compile the kernel with debug info" 122 depends on DEBUG_KERNEL && !COMPILE_TEST 123 help 124 If you say Y here the resulting kernel image will include 125 debugging info resulting in a larger kernel image. 126 This adds debug symbols to the kernel and modules (gcc -g), and 127 is needed if you intend to use kernel crashdump or binary object 128 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 129 Say Y here only if you plan to debug the kernel. 130 131 If unsure, say N. 132 133config DEBUG_INFO_REDUCED 134 bool "Reduce debugging information" 135 depends on DEBUG_INFO 136 help 137 If you say Y here gcc is instructed to generate less debugging 138 information for structure types. This means that tools that 139 need full debugging information (like kgdb or systemtap) won't 140 be happy. But if you merely need debugging information to 141 resolve line numbers there is no loss. Advantage is that 142 build directory object sizes shrink dramatically over a full 143 DEBUG_INFO build and compile times are reduced too. 144 Only works with newer gcc versions. 145 146config DEBUG_INFO_SPLIT 147 bool "Produce split debuginfo in .dwo files" 148 depends on DEBUG_INFO 149 help 150 Generate debug info into separate .dwo files. This significantly 151 reduces the build directory size for builds with DEBUG_INFO, 152 because it stores the information only once on disk in .dwo 153 files instead of multiple times in object files and executables. 154 In addition the debug information is also compressed. 155 156 Requires recent gcc (4.7+) and recent gdb/binutils. 157 Any tool that packages or reads debug information would need 158 to know about the .dwo files and include them. 159 Incompatible with older versions of ccache. 160 161config DEBUG_INFO_DWARF4 162 bool "Generate dwarf4 debuginfo" 163 depends on DEBUG_INFO 164 help 165 Generate dwarf4 debug info. This requires recent versions 166 of gcc and gdb. It makes the debug information larger. 167 But it significantly improves the success of resolving 168 variables in gdb on optimized code. 169 170config GDB_SCRIPTS 171 bool "Provide GDB scripts for kernel debugging" 172 depends on DEBUG_INFO 173 help 174 This creates the required links to GDB helper scripts in the 175 build directory. If you load vmlinux into gdb, the helper 176 scripts will be automatically imported by gdb as well, and 177 additional functions are available to analyze a Linux kernel 178 instance. See Documentation/gdb-kernel-debugging.txt for further 179 details. 180 181config ENABLE_WARN_DEPRECATED 182 bool "Enable __deprecated logic" 183 default y 184 help 185 Enable the __deprecated logic in the kernel build. 186 Disable this to suppress the "warning: 'foo' is deprecated 187 (declared at kernel/power/somefile.c:1234)" messages. 188 189config ENABLE_MUST_CHECK 190 bool "Enable __must_check logic" 191 default y 192 help 193 Enable the __must_check logic in the kernel build. Disable this to 194 suppress the "warning: ignoring return value of 'foo', declared with 195 attribute warn_unused_result" messages. 196 197config FRAME_WARN 198 int "Warn for stack frames larger than (needs gcc 4.4)" 199 range 0 8192 200 default 0 if KASAN 201 default 1024 if !64BIT 202 default 2048 if 64BIT 203 help 204 Tell gcc to warn at build time for stack frames larger than this. 205 Setting this too low will cause a lot of warnings. 206 Setting it to 0 disables the warning. 207 Requires gcc 4.4 208 209config STRIP_ASM_SYMS 210 bool "Strip assembler-generated symbols during link" 211 default n 212 help 213 Strip internal assembler-generated symbols during a link (symbols 214 that look like '.Lxxx') so they don't pollute the output of 215 get_wchan() and suchlike. 216 217config READABLE_ASM 218 bool "Generate readable assembler code" 219 depends on DEBUG_KERNEL 220 help 221 Disable some compiler optimizations that tend to generate human unreadable 222 assembler output. This may make the kernel slightly slower, but it helps 223 to keep kernel developers who have to stare a lot at assembler listings 224 sane. 225 226config UNUSED_SYMBOLS 227 bool "Enable unused/obsolete exported symbols" 228 default y if X86 229 help 230 Unused but exported symbols make the kernel needlessly bigger. For 231 that reason most of these unused exports will soon be removed. This 232 option is provided temporarily to provide a transition period in case 233 some external kernel module needs one of these symbols anyway. If you 234 encounter such a case in your module, consider if you are actually 235 using the right API. (rationale: since nobody in the kernel is using 236 this in a module, there is a pretty good chance it's actually the 237 wrong interface to use). If you really need the symbol, please send a 238 mail to the linux kernel mailing list mentioning the symbol and why 239 you really need it, and what the merge plan to the mainline kernel for 240 your module is. 241 242config PAGE_OWNER 243 bool "Track page owner" 244 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 245 select DEBUG_FS 246 select STACKTRACE 247 select PAGE_EXTENSION 248 help 249 This keeps track of what call chain is the owner of a page, may 250 help to find bare alloc_page(s) leaks. Even if you include this 251 feature on your build, it is disabled in default. You should pass 252 "page_owner=on" to boot parameter in order to enable it. Eats 253 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 254 for user-space helper. 255 256 If unsure, say N. 257 258config DEBUG_FS 259 bool "Debug Filesystem" 260 select SRCU 261 help 262 debugfs is a virtual file system that kernel developers use to put 263 debugging files into. Enable this option to be able to read and 264 write to these files. 265 266 For detailed documentation on the debugfs API, see 267 Documentation/DocBook/filesystems. 268 269 If unsure, say N. 270 271config HEADERS_CHECK 272 bool "Run 'make headers_check' when building vmlinux" 273 depends on !UML 274 help 275 This option will extract the user-visible kernel headers whenever 276 building the kernel, and will run basic sanity checks on them to 277 ensure that exported files do not attempt to include files which 278 were not exported, etc. 279 280 If you're making modifications to header files which are 281 relevant for userspace, say 'Y', and check the headers 282 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 283 your build tree), to make sure they're suitable. 284 285config DEBUG_SECTION_MISMATCH 286 bool "Enable full Section mismatch analysis" 287 help 288 The section mismatch analysis checks if there are illegal 289 references from one section to another section. 290 During linktime or runtime, some sections are dropped; 291 any use of code/data previously in these sections would 292 most likely result in an oops. 293 In the code, functions and variables are annotated with 294 __init,, etc. (see the full list in include/linux/init.h), 295 which results in the code/data being placed in specific sections. 296 The section mismatch analysis is always performed after a full 297 kernel build, and enabling this option causes the following 298 additional steps to occur: 299 - Add the option -fno-inline-functions-called-once to gcc commands. 300 When inlining a function annotated with __init in a non-init 301 function, we would lose the section information and thus 302 the analysis would not catch the illegal reference. 303 This option tells gcc to inline less (but it does result in 304 a larger kernel). 305 - Run the section mismatch analysis for each module/built-in.o file. 306 When we run the section mismatch analysis on vmlinux.o, we 307 lose valueble information about where the mismatch was 308 introduced. 309 Running the analysis for each module/built-in.o file 310 tells where the mismatch happens much closer to the 311 source. The drawback is that the same mismatch is 312 reported at least twice. 313 - Enable verbose reporting from modpost in order to help resolve 314 the section mismatches that are reported. 315 316config SECTION_MISMATCH_WARN_ONLY 317 bool "Make section mismatch errors non-fatal" 318 default y 319 help 320 If you say N here, the build process will fail if there are any 321 section mismatch, instead of just throwing warnings. 322 323 If unsure, say Y. 324 325# 326# Select this config option from the architecture Kconfig, if it 327# is preferred to always offer frame pointers as a config 328# option on the architecture (regardless of KERNEL_DEBUG): 329# 330config ARCH_WANT_FRAME_POINTERS 331 bool 332 help 333 334config FRAME_POINTER 335 bool "Compile the kernel with frame pointers" 336 depends on DEBUG_KERNEL && \ 337 (CRIS || M68K || FRV || UML || \ 338 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \ 339 ARCH_WANT_FRAME_POINTERS 340 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 341 help 342 If you say Y here the resulting kernel image will be slightly 343 larger and slower, but it gives very useful debugging information 344 in case of kernel bugs. (precise oopses/stacktraces/warnings) 345 346config STACK_VALIDATION 347 bool "Compile-time stack metadata validation" 348 depends on HAVE_STACK_VALIDATION 349 default n 350 help 351 Add compile-time checks to validate stack metadata, including frame 352 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure 353 that runtime stack traces are more reliable. 354 355 For more information, see 356 tools/objtool/Documentation/stack-validation.txt. 357 358config DEBUG_FORCE_WEAK_PER_CPU 359 bool "Force weak per-cpu definitions" 360 depends on DEBUG_KERNEL 361 help 362 s390 and alpha require percpu variables in modules to be 363 defined weak to work around addressing range issue which 364 puts the following two restrictions on percpu variable 365 definitions. 366 367 1. percpu symbols must be unique whether static or not 368 2. percpu variables can't be defined inside a function 369 370 To ensure that generic code follows the above rules, this 371 option forces all percpu variables to be defined as weak. 372 373endmenu # "Compiler options" 374 375config MAGIC_SYSRQ 376 bool "Magic SysRq key" 377 depends on !UML 378 help 379 If you say Y here, you will have some control over the system even 380 if the system crashes for example during kernel debugging (e.g., you 381 will be able to flush the buffer cache to disk, reboot the system 382 immediately or dump some status information). This is accomplished 383 by pressing various keys while holding SysRq (Alt+PrintScreen). It 384 also works on a serial console (on PC hardware at least), if you 385 send a BREAK and then within 5 seconds a command keypress. The 386 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 387 unless you really know what this hack does. 388 389config MAGIC_SYSRQ_DEFAULT_ENABLE 390 hex "Enable magic SysRq key functions by default" 391 depends on MAGIC_SYSRQ 392 default 0x1 393 help 394 Specifies which SysRq key functions are enabled by default. 395 This may be set to 1 or 0 to enable or disable them all, or 396 to a bitmask as described in Documentation/sysrq.txt. 397 398config DEBUG_KERNEL 399 bool "Kernel debugging" 400 help 401 Say Y here if you are developing drivers or trying to debug and 402 identify kernel problems. 403 404menu "Memory Debugging" 405 406source mm/Kconfig.debug 407 408config DEBUG_OBJECTS 409 bool "Debug object operations" 410 depends on DEBUG_KERNEL 411 help 412 If you say Y here, additional code will be inserted into the 413 kernel to track the life time of various objects and validate 414 the operations on those objects. 415 416config DEBUG_OBJECTS_SELFTEST 417 bool "Debug objects selftest" 418 depends on DEBUG_OBJECTS 419 help 420 This enables the selftest of the object debug code. 421 422config DEBUG_OBJECTS_FREE 423 bool "Debug objects in freed memory" 424 depends on DEBUG_OBJECTS 425 help 426 This enables checks whether a k/v free operation frees an area 427 which contains an object which has not been deactivated 428 properly. This can make kmalloc/kfree-intensive workloads 429 much slower. 430 431config DEBUG_OBJECTS_TIMERS 432 bool "Debug timer objects" 433 depends on DEBUG_OBJECTS 434 help 435 If you say Y here, additional code will be inserted into the 436 timer routines to track the life time of timer objects and 437 validate the timer operations. 438 439config DEBUG_OBJECTS_WORK 440 bool "Debug work objects" 441 depends on DEBUG_OBJECTS 442 help 443 If you say Y here, additional code will be inserted into the 444 work queue routines to track the life time of work objects and 445 validate the work operations. 446 447config DEBUG_OBJECTS_RCU_HEAD 448 bool "Debug RCU callbacks objects" 449 depends on DEBUG_OBJECTS 450 help 451 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 452 453config DEBUG_OBJECTS_PERCPU_COUNTER 454 bool "Debug percpu counter objects" 455 depends on DEBUG_OBJECTS 456 help 457 If you say Y here, additional code will be inserted into the 458 percpu counter routines to track the life time of percpu counter 459 objects and validate the percpu counter operations. 460 461config DEBUG_OBJECTS_ENABLE_DEFAULT 462 int "debug_objects bootup default value (0-1)" 463 range 0 1 464 default "1" 465 depends on DEBUG_OBJECTS 466 help 467 Debug objects boot parameter default value 468 469config DEBUG_SLAB 470 bool "Debug slab memory allocations" 471 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 472 help 473 Say Y here to have the kernel do limited verification on memory 474 allocation as well as poisoning memory on free to catch use of freed 475 memory. This can make kmalloc/kfree-intensive workloads much slower. 476 477config DEBUG_SLAB_LEAK 478 bool "Memory leak debugging" 479 depends on DEBUG_SLAB 480 481config SLUB_DEBUG_ON 482 bool "SLUB debugging on by default" 483 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 484 default n 485 help 486 Boot with debugging on by default. SLUB boots by default with 487 the runtime debug capabilities switched off. Enabling this is 488 equivalent to specifying the "slub_debug" parameter on boot. 489 There is no support for more fine grained debug control like 490 possible with slub_debug=xxx. SLUB debugging may be switched 491 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 492 "slub_debug=-". 493 494config SLUB_STATS 495 default n 496 bool "Enable SLUB performance statistics" 497 depends on SLUB && SYSFS 498 help 499 SLUB statistics are useful to debug SLUBs allocation behavior in 500 order find ways to optimize the allocator. This should never be 501 enabled for production use since keeping statistics slows down 502 the allocator by a few percentage points. The slabinfo command 503 supports the determination of the most active slabs to figure 504 out which slabs are relevant to a particular load. 505 Try running: slabinfo -DA 506 507config HAVE_DEBUG_KMEMLEAK 508 bool 509 510config DEBUG_KMEMLEAK 511 bool "Kernel memory leak detector" 512 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 513 select DEBUG_FS 514 select STACKTRACE if STACKTRACE_SUPPORT 515 select KALLSYMS 516 select CRC32 517 help 518 Say Y here if you want to enable the memory leak 519 detector. The memory allocation/freeing is traced in a way 520 similar to the Boehm's conservative garbage collector, the 521 difference being that the orphan objects are not freed but 522 only shown in /sys/kernel/debug/kmemleak. Enabling this 523 feature will introduce an overhead to memory 524 allocations. See Documentation/kmemleak.txt for more 525 details. 526 527 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 528 of finding leaks due to the slab objects poisoning. 529 530 In order to access the kmemleak file, debugfs needs to be 531 mounted (usually at /sys/kernel/debug). 532 533config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 534 int "Maximum kmemleak early log entries" 535 depends on DEBUG_KMEMLEAK 536 range 200 40000 537 default 400 538 help 539 Kmemleak must track all the memory allocations to avoid 540 reporting false positives. Since memory may be allocated or 541 freed before kmemleak is initialised, an early log buffer is 542 used to store these actions. If kmemleak reports "early log 543 buffer exceeded", please increase this value. 544 545config DEBUG_KMEMLEAK_TEST 546 tristate "Simple test for the kernel memory leak detector" 547 depends on DEBUG_KMEMLEAK && m 548 help 549 This option enables a module that explicitly leaks memory. 550 551 If unsure, say N. 552 553config DEBUG_KMEMLEAK_DEFAULT_OFF 554 bool "Default kmemleak to off" 555 depends on DEBUG_KMEMLEAK 556 help 557 Say Y here to disable kmemleak by default. It can then be enabled 558 on the command line via kmemleak=on. 559 560config DEBUG_STACK_USAGE 561 bool "Stack utilization instrumentation" 562 depends on DEBUG_KERNEL && !IA64 563 help 564 Enables the display of the minimum amount of free stack which each 565 task has ever had available in the sysrq-T and sysrq-P debug output. 566 567 This option will slow down process creation somewhat. 568 569config DEBUG_VM 570 bool "Debug VM" 571 depends on DEBUG_KERNEL 572 help 573 Enable this to turn on extended checks in the virtual-memory system 574 that may impact performance. 575 576 If unsure, say N. 577 578config DEBUG_VM_VMACACHE 579 bool "Debug VMA caching" 580 depends on DEBUG_VM 581 help 582 Enable this to turn on VMA caching debug information. Doing so 583 can cause significant overhead, so only enable it in non-production 584 environments. 585 586 If unsure, say N. 587 588config DEBUG_VM_RB 589 bool "Debug VM red-black trees" 590 depends on DEBUG_VM 591 help 592 Enable VM red-black tree debugging information and extra validations. 593 594 If unsure, say N. 595 596config DEBUG_VM_PGFLAGS 597 bool "Debug page-flags operations" 598 depends on DEBUG_VM 599 help 600 Enables extra validation on page flags operations. 601 602 If unsure, say N. 603 604config DEBUG_VIRTUAL 605 bool "Debug VM translations" 606 depends on DEBUG_KERNEL && X86 607 help 608 Enable some costly sanity checks in virtual to page code. This can 609 catch mistakes with virt_to_page() and friends. 610 611 If unsure, say N. 612 613config DEBUG_NOMMU_REGIONS 614 bool "Debug the global anon/private NOMMU mapping region tree" 615 depends on DEBUG_KERNEL && !MMU 616 help 617 This option causes the global tree of anonymous and private mapping 618 regions to be regularly checked for invalid topology. 619 620config DEBUG_MEMORY_INIT 621 bool "Debug memory initialisation" if EXPERT 622 default !EXPERT 623 help 624 Enable this for additional checks during memory initialisation. 625 The sanity checks verify aspects of the VM such as the memory model 626 and other information provided by the architecture. Verbose 627 information will be printed at KERN_DEBUG loglevel depending 628 on the mminit_loglevel= command-line option. 629 630 If unsure, say Y 631 632config MEMORY_NOTIFIER_ERROR_INJECT 633 tristate "Memory hotplug notifier error injection module" 634 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 635 help 636 This option provides the ability to inject artificial errors to 637 memory hotplug notifier chain callbacks. It is controlled through 638 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 639 640 If the notifier call chain should be failed with some events 641 notified, write the error code to "actions/<notifier event>/error". 642 643 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 644 645 # cd /sys/kernel/debug/notifier-error-inject/memory 646 # echo -12 > actions/MEM_GOING_OFFLINE/error 647 # echo offline > /sys/devices/system/memory/memoryXXX/state 648 bash: echo: write error: Cannot allocate memory 649 650 To compile this code as a module, choose M here: the module will 651 be called memory-notifier-error-inject. 652 653 If unsure, say N. 654 655config DEBUG_PER_CPU_MAPS 656 bool "Debug access to per_cpu maps" 657 depends on DEBUG_KERNEL 658 depends on SMP 659 help 660 Say Y to verify that the per_cpu map being accessed has 661 been set up. This adds a fair amount of code to kernel memory 662 and decreases performance. 663 664 Say N if unsure. 665 666config DEBUG_HIGHMEM 667 bool "Highmem debugging" 668 depends on DEBUG_KERNEL && HIGHMEM 669 help 670 This option enables additional error checking for high memory 671 systems. Disable for production systems. 672 673config HAVE_DEBUG_STACKOVERFLOW 674 bool 675 676config DEBUG_STACKOVERFLOW 677 bool "Check for stack overflows" 678 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 679 ---help--- 680 Say Y here if you want to check for overflows of kernel, IRQ 681 and exception stacks (if your architecture uses them). This 682 option will show detailed messages if free stack space drops 683 below a certain limit. 684 685 These kinds of bugs usually occur when call-chains in the 686 kernel get too deep, especially when interrupts are 687 involved. 688 689 Use this in cases where you see apparently random memory 690 corruption, especially if it appears in 'struct thread_info' 691 692 If in doubt, say "N". 693 694source "lib/Kconfig.kmemcheck" 695 696source "lib/Kconfig.kasan" 697 698endmenu # "Memory Debugging" 699 700config ARCH_HAS_KCOV 701 bool 702 help 703 KCOV does not have any arch-specific code, but currently it is enabled 704 only for x86_64. KCOV requires testing on other archs, and most likely 705 disabling of instrumentation for some early boot code. 706 707config KCOV 708 bool "Code coverage for fuzzing" 709 depends on ARCH_HAS_KCOV 710 select DEBUG_FS 711 select GCC_PLUGINS 712 select GCC_PLUGIN_SANCOV 713 help 714 KCOV exposes kernel code coverage information in a form suitable 715 for coverage-guided fuzzing (randomized testing). 716 717 If RANDOMIZE_BASE is enabled, PC values will not be stable across 718 different machines and across reboots. If you need stable PC values, 719 disable RANDOMIZE_BASE. 720 721 For more details, see Documentation/kcov.txt. 722 723config DEBUG_SHIRQ 724 bool "Debug shared IRQ handlers" 725 depends on DEBUG_KERNEL 726 help 727 Enable this to generate a spurious interrupt as soon as a shared 728 interrupt handler is registered, and just before one is deregistered. 729 Drivers ought to be able to handle interrupts coming in at those 730 points; some don't and need to be caught. 731 732menu "Debug Lockups and Hangs" 733 734config LOCKUP_DETECTOR 735 bool "Detect Hard and Soft Lockups" 736 depends on DEBUG_KERNEL && !S390 737 help 738 Say Y here to enable the kernel to act as a watchdog to detect 739 hard and soft lockups. 740 741 Softlockups are bugs that cause the kernel to loop in kernel 742 mode for more than 20 seconds, without giving other tasks a 743 chance to run. The current stack trace is displayed upon 744 detection and the system will stay locked up. 745 746 Hardlockups are bugs that cause the CPU to loop in kernel mode 747 for more than 10 seconds, without letting other interrupts have a 748 chance to run. The current stack trace is displayed upon detection 749 and the system will stay locked up. 750 751 The overhead should be minimal. A periodic hrtimer runs to 752 generate interrupts and kick the watchdog task every 4 seconds. 753 An NMI is generated every 10 seconds or so to check for hardlockups. 754 755 The frequency of hrtimer and NMI events and the soft and hard lockup 756 thresholds can be controlled through the sysctl watchdog_thresh. 757 758config HARDLOCKUP_DETECTOR 759 def_bool y 760 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 761 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 762 763config BOOTPARAM_HARDLOCKUP_PANIC 764 bool "Panic (Reboot) On Hard Lockups" 765 depends on HARDLOCKUP_DETECTOR 766 help 767 Say Y here to enable the kernel to panic on "hard lockups", 768 which are bugs that cause the kernel to loop in kernel 769 mode with interrupts disabled for more than 10 seconds (configurable 770 using the watchdog_thresh sysctl). 771 772 Say N if unsure. 773 774config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 775 int 776 depends on HARDLOCKUP_DETECTOR 777 range 0 1 778 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 779 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 780 781config BOOTPARAM_SOFTLOCKUP_PANIC 782 bool "Panic (Reboot) On Soft Lockups" 783 depends on LOCKUP_DETECTOR 784 help 785 Say Y here to enable the kernel to panic on "soft lockups", 786 which are bugs that cause the kernel to loop in kernel 787 mode for more than 20 seconds (configurable using the watchdog_thresh 788 sysctl), without giving other tasks a chance to run. 789 790 The panic can be used in combination with panic_timeout, 791 to cause the system to reboot automatically after a 792 lockup has been detected. This feature is useful for 793 high-availability systems that have uptime guarantees and 794 where a lockup must be resolved ASAP. 795 796 Say N if unsure. 797 798config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 799 int 800 depends on LOCKUP_DETECTOR 801 range 0 1 802 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 803 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 804 805config DETECT_HUNG_TASK 806 bool "Detect Hung Tasks" 807 depends on DEBUG_KERNEL 808 default LOCKUP_DETECTOR 809 help 810 Say Y here to enable the kernel to detect "hung tasks", 811 which are bugs that cause the task to be stuck in 812 uninterruptible "D" state indefinitiley. 813 814 When a hung task is detected, the kernel will print the 815 current stack trace (which you should report), but the 816 task will stay in uninterruptible state. If lockdep is 817 enabled then all held locks will also be reported. This 818 feature has negligible overhead. 819 820config DEFAULT_HUNG_TASK_TIMEOUT 821 int "Default timeout for hung task detection (in seconds)" 822 depends on DETECT_HUNG_TASK 823 default 120 824 help 825 This option controls the default timeout (in seconds) used 826 to determine when a task has become non-responsive and should 827 be considered hung. 828 829 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 830 sysctl or by writing a value to 831 /proc/sys/kernel/hung_task_timeout_secs. 832 833 A timeout of 0 disables the check. The default is two minutes. 834 Keeping the default should be fine in most cases. 835 836config BOOTPARAM_HUNG_TASK_PANIC 837 bool "Panic (Reboot) On Hung Tasks" 838 depends on DETECT_HUNG_TASK 839 help 840 Say Y here to enable the kernel to panic on "hung tasks", 841 which are bugs that cause the kernel to leave a task stuck 842 in uninterruptible "D" state. 843 844 The panic can be used in combination with panic_timeout, 845 to cause the system to reboot automatically after a 846 hung task has been detected. This feature is useful for 847 high-availability systems that have uptime guarantees and 848 where a hung tasks must be resolved ASAP. 849 850 Say N if unsure. 851 852config BOOTPARAM_HUNG_TASK_PANIC_VALUE 853 int 854 depends on DETECT_HUNG_TASK 855 range 0 1 856 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 857 default 1 if BOOTPARAM_HUNG_TASK_PANIC 858 859config WQ_WATCHDOG 860 bool "Detect Workqueue Stalls" 861 depends on DEBUG_KERNEL 862 help 863 Say Y here to enable stall detection on workqueues. If a 864 worker pool doesn't make forward progress on a pending work 865 item for over a given amount of time, 30s by default, a 866 warning message is printed along with dump of workqueue 867 state. This can be configured through kernel parameter 868 "workqueue.watchdog_thresh" and its sysfs counterpart. 869 870endmenu # "Debug lockups and hangs" 871 872config PANIC_ON_OOPS 873 bool "Panic on Oops" 874 help 875 Say Y here to enable the kernel to panic when it oopses. This 876 has the same effect as setting oops=panic on the kernel command 877 line. 878 879 This feature is useful to ensure that the kernel does not do 880 anything erroneous after an oops which could result in data 881 corruption or other issues. 882 883 Say N if unsure. 884 885config PANIC_ON_OOPS_VALUE 886 int 887 range 0 1 888 default 0 if !PANIC_ON_OOPS 889 default 1 if PANIC_ON_OOPS 890 891config PANIC_TIMEOUT 892 int "panic timeout" 893 default 0 894 help 895 Set the timeout value (in seconds) until a reboot occurs when the 896 the kernel panics. If n = 0, then we wait forever. A timeout 897 value n > 0 will wait n seconds before rebooting, while a timeout 898 value n < 0 will reboot immediately. 899 900config SCHED_DEBUG 901 bool "Collect scheduler debugging info" 902 depends on DEBUG_KERNEL && PROC_FS 903 default y 904 help 905 If you say Y here, the /proc/sched_debug file will be provided 906 that can help debug the scheduler. The runtime overhead of this 907 option is minimal. 908 909config SCHED_INFO 910 bool 911 default n 912 913config SCHEDSTATS 914 bool "Collect scheduler statistics" 915 depends on DEBUG_KERNEL && PROC_FS 916 select SCHED_INFO 917 help 918 If you say Y here, additional code will be inserted into the 919 scheduler and related routines to collect statistics about 920 scheduler behavior and provide them in /proc/schedstat. These 921 stats may be useful for both tuning and debugging the scheduler 922 If you aren't debugging the scheduler or trying to tune a specific 923 application, you can say N to avoid the very slight overhead 924 this adds. 925 926config SCHED_STACK_END_CHECK 927 bool "Detect stack corruption on calls to schedule()" 928 depends on DEBUG_KERNEL 929 default n 930 help 931 This option checks for a stack overrun on calls to schedule(). 932 If the stack end location is found to be over written always panic as 933 the content of the corrupted region can no longer be trusted. 934 This is to ensure no erroneous behaviour occurs which could result in 935 data corruption or a sporadic crash at a later stage once the region 936 is examined. The runtime overhead introduced is minimal. 937 938config DEBUG_TIMEKEEPING 939 bool "Enable extra timekeeping sanity checking" 940 help 941 This option will enable additional timekeeping sanity checks 942 which may be helpful when diagnosing issues where timekeeping 943 problems are suspected. 944 945 This may include checks in the timekeeping hotpaths, so this 946 option may have a (very small) performance impact to some 947 workloads. 948 949 If unsure, say N. 950 951config TIMER_STATS 952 bool "Collect kernel timers statistics" 953 depends on DEBUG_KERNEL && PROC_FS 954 help 955 If you say Y here, additional code will be inserted into the 956 timer routines to collect statistics about kernel timers being 957 reprogrammed. The statistics can be read from /proc/timer_stats. 958 The statistics collection is started by writing 1 to /proc/timer_stats, 959 writing 0 stops it. This feature is useful to collect information 960 about timer usage patterns in kernel and userspace. This feature 961 is lightweight if enabled in the kernel config but not activated 962 (it defaults to deactivated on bootup and will only be activated 963 if some application like powertop activates it explicitly). 964 965config DEBUG_PREEMPT 966 bool "Debug preemptible kernel" 967 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 968 default y 969 help 970 If you say Y here then the kernel will use a debug variant of the 971 commonly used smp_processor_id() function and will print warnings 972 if kernel code uses it in a preemption-unsafe way. Also, the kernel 973 will detect preemption count underflows. 974 975menu "Lock Debugging (spinlocks, mutexes, etc...)" 976 977config DEBUG_RT_MUTEXES 978 bool "RT Mutex debugging, deadlock detection" 979 depends on DEBUG_KERNEL && RT_MUTEXES 980 help 981 This allows rt mutex semantics violations and rt mutex related 982 deadlocks (lockups) to be detected and reported automatically. 983 984config DEBUG_SPINLOCK 985 bool "Spinlock and rw-lock debugging: basic checks" 986 depends on DEBUG_KERNEL 987 select UNINLINE_SPIN_UNLOCK 988 help 989 Say Y here and build SMP to catch missing spinlock initialization 990 and certain other kinds of spinlock errors commonly made. This is 991 best used in conjunction with the NMI watchdog so that spinlock 992 deadlocks are also debuggable. 993 994config DEBUG_MUTEXES 995 bool "Mutex debugging: basic checks" 996 depends on DEBUG_KERNEL 997 help 998 This feature allows mutex semantics violations to be detected and 999 reported. 1000 1001config DEBUG_WW_MUTEX_SLOWPATH 1002 bool "Wait/wound mutex debugging: Slowpath testing" 1003 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1004 select DEBUG_LOCK_ALLOC 1005 select DEBUG_SPINLOCK 1006 select DEBUG_MUTEXES 1007 help 1008 This feature enables slowpath testing for w/w mutex users by 1009 injecting additional -EDEADLK wound/backoff cases. Together with 1010 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 1011 will test all possible w/w mutex interface abuse with the 1012 exception of simply not acquiring all the required locks. 1013 Note that this feature can introduce significant overhead, so 1014 it really should not be enabled in a production or distro kernel, 1015 even a debug kernel. If you are a driver writer, enable it. If 1016 you are a distro, do not. 1017 1018config DEBUG_LOCK_ALLOC 1019 bool "Lock debugging: detect incorrect freeing of live locks" 1020 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1021 select DEBUG_SPINLOCK 1022 select DEBUG_MUTEXES 1023 select LOCKDEP 1024 help 1025 This feature will check whether any held lock (spinlock, rwlock, 1026 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1027 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1028 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1029 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1030 held during task exit. 1031 1032config PROVE_LOCKING 1033 bool "Lock debugging: prove locking correctness" 1034 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1035 select LOCKDEP 1036 select DEBUG_SPINLOCK 1037 select DEBUG_MUTEXES 1038 select DEBUG_LOCK_ALLOC 1039 select TRACE_IRQFLAGS 1040 default n 1041 help 1042 This feature enables the kernel to prove that all locking 1043 that occurs in the kernel runtime is mathematically 1044 correct: that under no circumstance could an arbitrary (and 1045 not yet triggered) combination of observed locking 1046 sequences (on an arbitrary number of CPUs, running an 1047 arbitrary number of tasks and interrupt contexts) cause a 1048 deadlock. 1049 1050 In short, this feature enables the kernel to report locking 1051 related deadlocks before they actually occur. 1052 1053 The proof does not depend on how hard and complex a 1054 deadlock scenario would be to trigger: how many 1055 participant CPUs, tasks and irq-contexts would be needed 1056 for it to trigger. The proof also does not depend on 1057 timing: if a race and a resulting deadlock is possible 1058 theoretically (no matter how unlikely the race scenario 1059 is), it will be proven so and will immediately be 1060 reported by the kernel (once the event is observed that 1061 makes the deadlock theoretically possible). 1062 1063 If a deadlock is impossible (i.e. the locking rules, as 1064 observed by the kernel, are mathematically correct), the 1065 kernel reports nothing. 1066 1067 NOTE: this feature can also be enabled for rwlocks, mutexes 1068 and rwsems - in which case all dependencies between these 1069 different locking variants are observed and mapped too, and 1070 the proof of observed correctness is also maintained for an 1071 arbitrary combination of these separate locking variants. 1072 1073 For more details, see Documentation/locking/lockdep-design.txt. 1074 1075config LOCKDEP 1076 bool 1077 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1078 select STACKTRACE 1079 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE 1080 select KALLSYMS 1081 select KALLSYMS_ALL 1082 1083config LOCK_STAT 1084 bool "Lock usage statistics" 1085 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1086 select LOCKDEP 1087 select DEBUG_SPINLOCK 1088 select DEBUG_MUTEXES 1089 select DEBUG_LOCK_ALLOC 1090 default n 1091 help 1092 This feature enables tracking lock contention points 1093 1094 For more details, see Documentation/locking/lockstat.txt 1095 1096 This also enables lock events required by "perf lock", 1097 subcommand of perf. 1098 If you want to use "perf lock", you also need to turn on 1099 CONFIG_EVENT_TRACING. 1100 1101 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1102 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1103 1104config DEBUG_LOCKDEP 1105 bool "Lock dependency engine debugging" 1106 depends on DEBUG_KERNEL && LOCKDEP 1107 help 1108 If you say Y here, the lock dependency engine will do 1109 additional runtime checks to debug itself, at the price 1110 of more runtime overhead. 1111 1112config DEBUG_ATOMIC_SLEEP 1113 bool "Sleep inside atomic section checking" 1114 select PREEMPT_COUNT 1115 depends on DEBUG_KERNEL 1116 help 1117 If you say Y here, various routines which may sleep will become very 1118 noisy if they are called inside atomic sections: when a spinlock is 1119 held, inside an rcu read side critical section, inside preempt disabled 1120 sections, inside an interrupt, etc... 1121 1122config DEBUG_LOCKING_API_SELFTESTS 1123 bool "Locking API boot-time self-tests" 1124 depends on DEBUG_KERNEL 1125 help 1126 Say Y here if you want the kernel to run a short self-test during 1127 bootup. The self-test checks whether common types of locking bugs 1128 are detected by debugging mechanisms or not. (if you disable 1129 lock debugging then those bugs wont be detected of course.) 1130 The following locking APIs are covered: spinlocks, rwlocks, 1131 mutexes and rwsems. 1132 1133config LOCK_TORTURE_TEST 1134 tristate "torture tests for locking" 1135 depends on DEBUG_KERNEL 1136 select TORTURE_TEST 1137 default n 1138 help 1139 This option provides a kernel module that runs torture tests 1140 on kernel locking primitives. The kernel module may be built 1141 after the fact on the running kernel to be tested, if desired. 1142 1143 Say Y here if you want kernel locking-primitive torture tests 1144 to be built into the kernel. 1145 Say M if you want these torture tests to build as a module. 1146 Say N if you are unsure. 1147 1148endmenu # lock debugging 1149 1150config TRACE_IRQFLAGS 1151 bool 1152 help 1153 Enables hooks to interrupt enabling and disabling for 1154 either tracing or lock debugging. 1155 1156config STACKTRACE 1157 bool "Stack backtrace support" 1158 depends on STACKTRACE_SUPPORT 1159 help 1160 This option causes the kernel to create a /proc/pid/stack for 1161 every process, showing its current stack trace. 1162 It is also used by various kernel debugging features that require 1163 stack trace generation. 1164 1165config DEBUG_KOBJECT 1166 bool "kobject debugging" 1167 depends on DEBUG_KERNEL 1168 help 1169 If you say Y here, some extra kobject debugging messages will be sent 1170 to the syslog. 1171 1172config DEBUG_KOBJECT_RELEASE 1173 bool "kobject release debugging" 1174 depends on DEBUG_OBJECTS_TIMERS 1175 help 1176 kobjects are reference counted objects. This means that their 1177 last reference count put is not predictable, and the kobject can 1178 live on past the point at which a driver decides to drop it's 1179 initial reference to the kobject gained on allocation. An 1180 example of this would be a struct device which has just been 1181 unregistered. 1182 1183 However, some buggy drivers assume that after such an operation, 1184 the memory backing the kobject can be immediately freed. This 1185 goes completely against the principles of a refcounted object. 1186 1187 If you say Y here, the kernel will delay the release of kobjects 1188 on the last reference count to improve the visibility of this 1189 kind of kobject release bug. 1190 1191config HAVE_DEBUG_BUGVERBOSE 1192 bool 1193 1194config DEBUG_BUGVERBOSE 1195 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1196 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1197 default y 1198 help 1199 Say Y here to make BUG() panics output the file name and line number 1200 of the BUG call as well as the EIP and oops trace. This aids 1201 debugging but costs about 70-100K of memory. 1202 1203config DEBUG_LIST 1204 bool "Debug linked list manipulation" 1205 depends on DEBUG_KERNEL 1206 help 1207 Enable this to turn on extended checks in the linked-list 1208 walking routines. 1209 1210 If unsure, say N. 1211 1212config DEBUG_PI_LIST 1213 bool "Debug priority linked list manipulation" 1214 depends on DEBUG_KERNEL 1215 help 1216 Enable this to turn on extended checks in the priority-ordered 1217 linked-list (plist) walking routines. This checks the entire 1218 list multiple times during each manipulation. 1219 1220 If unsure, say N. 1221 1222config DEBUG_SG 1223 bool "Debug SG table operations" 1224 depends on DEBUG_KERNEL 1225 help 1226 Enable this to turn on checks on scatter-gather tables. This can 1227 help find problems with drivers that do not properly initialize 1228 their sg tables. 1229 1230 If unsure, say N. 1231 1232config DEBUG_NOTIFIERS 1233 bool "Debug notifier call chains" 1234 depends on DEBUG_KERNEL 1235 help 1236 Enable this to turn on sanity checking for notifier call chains. 1237 This is most useful for kernel developers to make sure that 1238 modules properly unregister themselves from notifier chains. 1239 This is a relatively cheap check but if you care about maximum 1240 performance, say N. 1241 1242config DEBUG_CREDENTIALS 1243 bool "Debug credential management" 1244 depends on DEBUG_KERNEL 1245 help 1246 Enable this to turn on some debug checking for credential 1247 management. The additional code keeps track of the number of 1248 pointers from task_structs to any given cred struct, and checks to 1249 see that this number never exceeds the usage count of the cred 1250 struct. 1251 1252 Furthermore, if SELinux is enabled, this also checks that the 1253 security pointer in the cred struct is never seen to be invalid. 1254 1255 If unsure, say N. 1256 1257menu "RCU Debugging" 1258 1259config PROVE_RCU 1260 def_bool PROVE_LOCKING 1261 1262config PROVE_RCU_REPEATEDLY 1263 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1264 depends on PROVE_RCU 1265 default n 1266 help 1267 By itself, PROVE_RCU will disable checking upon issuing the 1268 first warning (or "splat"). This feature prevents such 1269 disabling, allowing multiple RCU-lockdep warnings to be printed 1270 on a single reboot. 1271 1272 Say Y to allow multiple RCU-lockdep warnings per boot. 1273 1274 Say N if you are unsure. 1275 1276config SPARSE_RCU_POINTER 1277 bool "RCU debugging: sparse-based checks for pointer usage" 1278 default n 1279 help 1280 This feature enables the __rcu sparse annotation for 1281 RCU-protected pointers. This annotation will cause sparse 1282 to flag any non-RCU used of annotated pointers. This can be 1283 helpful when debugging RCU usage. Please note that this feature 1284 is not intended to enforce code cleanliness; it is instead merely 1285 a debugging aid. 1286 1287 Say Y to make sparse flag questionable use of RCU-protected pointers 1288 1289 Say N if you are unsure. 1290 1291config TORTURE_TEST 1292 tristate 1293 default n 1294 1295config RCU_PERF_TEST 1296 tristate "performance tests for RCU" 1297 depends on DEBUG_KERNEL 1298 select TORTURE_TEST 1299 select SRCU 1300 select TASKS_RCU 1301 default n 1302 help 1303 This option provides a kernel module that runs performance 1304 tests on the RCU infrastructure. The kernel module may be built 1305 after the fact on the running kernel to be tested, if desired. 1306 1307 Say Y here if you want RCU performance tests to be built into 1308 the kernel. 1309 Say M if you want the RCU performance tests to build as a module. 1310 Say N if you are unsure. 1311 1312config RCU_PERF_TEST_RUNNABLE 1313 bool "performance tests for RCU runnable by default" 1314 depends on RCU_PERF_TEST = y 1315 default n 1316 help 1317 This option provides a way to build the RCU performance tests 1318 directly into the kernel without them starting up at boot time. 1319 You can use /sys/module to manually override this setting. 1320 This /proc file is available only when the RCU performance 1321 tests have been built into the kernel. 1322 1323 Say Y here if you want the RCU performance tests to start during 1324 boot (you probably don't). 1325 Say N here if you want the RCU performance tests to start only 1326 after being manually enabled via /sys/module. 1327 1328config RCU_TORTURE_TEST 1329 tristate "torture tests for RCU" 1330 depends on DEBUG_KERNEL 1331 select TORTURE_TEST 1332 select SRCU 1333 select TASKS_RCU 1334 default n 1335 help 1336 This option provides a kernel module that runs torture tests 1337 on the RCU infrastructure. The kernel module may be built 1338 after the fact on the running kernel to be tested, if desired. 1339 1340 Say Y here if you want RCU torture tests to be built into 1341 the kernel. 1342 Say M if you want the RCU torture tests to build as a module. 1343 Say N if you are unsure. 1344 1345config RCU_TORTURE_TEST_RUNNABLE 1346 bool "torture tests for RCU runnable by default" 1347 depends on RCU_TORTURE_TEST = y 1348 default n 1349 help 1350 This option provides a way to build the RCU torture tests 1351 directly into the kernel without them starting up at boot 1352 time. You can use /proc/sys/kernel/rcutorture_runnable 1353 to manually override this setting. This /proc file is 1354 available only when the RCU torture tests have been built 1355 into the kernel. 1356 1357 Say Y here if you want the RCU torture tests to start during 1358 boot (you probably don't). 1359 Say N here if you want the RCU torture tests to start only 1360 after being manually enabled via /proc. 1361 1362config RCU_TORTURE_TEST_SLOW_PREINIT 1363 bool "Slow down RCU grace-period pre-initialization to expose races" 1364 depends on RCU_TORTURE_TEST 1365 help 1366 This option delays grace-period pre-initialization (the 1367 propagation of CPU-hotplug changes up the rcu_node combining 1368 tree) for a few jiffies between initializing each pair of 1369 consecutive rcu_node structures. This helps to expose races 1370 involving grace-period pre-initialization, in other words, it 1371 makes your kernel less stable. It can also greatly increase 1372 grace-period latency, especially on systems with large numbers 1373 of CPUs. This is useful when torture-testing RCU, but in 1374 almost no other circumstance. 1375 1376 Say Y here if you want your system to crash and hang more often. 1377 Say N if you want a sane system. 1378 1379config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY 1380 int "How much to slow down RCU grace-period pre-initialization" 1381 range 0 5 1382 default 3 1383 depends on RCU_TORTURE_TEST_SLOW_PREINIT 1384 help 1385 This option specifies the number of jiffies to wait between 1386 each rcu_node structure pre-initialization step. 1387 1388config RCU_TORTURE_TEST_SLOW_INIT 1389 bool "Slow down RCU grace-period initialization to expose races" 1390 depends on RCU_TORTURE_TEST 1391 help 1392 This option delays grace-period initialization for a few 1393 jiffies between initializing each pair of consecutive 1394 rcu_node structures. This helps to expose races involving 1395 grace-period initialization, in other words, it makes your 1396 kernel less stable. It can also greatly increase grace-period 1397 latency, especially on systems with large numbers of CPUs. 1398 This is useful when torture-testing RCU, but in almost no 1399 other circumstance. 1400 1401 Say Y here if you want your system to crash and hang more often. 1402 Say N if you want a sane system. 1403 1404config RCU_TORTURE_TEST_SLOW_INIT_DELAY 1405 int "How much to slow down RCU grace-period initialization" 1406 range 0 5 1407 default 3 1408 depends on RCU_TORTURE_TEST_SLOW_INIT 1409 help 1410 This option specifies the number of jiffies to wait between 1411 each rcu_node structure initialization. 1412 1413config RCU_TORTURE_TEST_SLOW_CLEANUP 1414 bool "Slow down RCU grace-period cleanup to expose races" 1415 depends on RCU_TORTURE_TEST 1416 help 1417 This option delays grace-period cleanup for a few jiffies 1418 between cleaning up each pair of consecutive rcu_node 1419 structures. This helps to expose races involving grace-period 1420 cleanup, in other words, it makes your kernel less stable. 1421 It can also greatly increase grace-period latency, especially 1422 on systems with large numbers of CPUs. This is useful when 1423 torture-testing RCU, but in almost no other circumstance. 1424 1425 Say Y here if you want your system to crash and hang more often. 1426 Say N if you want a sane system. 1427 1428config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY 1429 int "How much to slow down RCU grace-period cleanup" 1430 range 0 5 1431 default 3 1432 depends on RCU_TORTURE_TEST_SLOW_CLEANUP 1433 help 1434 This option specifies the number of jiffies to wait between 1435 each rcu_node structure cleanup operation. 1436 1437config RCU_CPU_STALL_TIMEOUT 1438 int "RCU CPU stall timeout in seconds" 1439 depends on RCU_STALL_COMMON 1440 range 3 300 1441 default 21 1442 help 1443 If a given RCU grace period extends more than the specified 1444 number of seconds, a CPU stall warning is printed. If the 1445 RCU grace period persists, additional CPU stall warnings are 1446 printed at more widely spaced intervals. 1447 1448config RCU_TRACE 1449 bool "Enable tracing for RCU" 1450 depends on DEBUG_KERNEL 1451 select TRACE_CLOCK 1452 help 1453 This option provides tracing in RCU which presents stats 1454 in debugfs for debugging RCU implementation. 1455 1456 Say Y here if you want to enable RCU tracing 1457 Say N if you are unsure. 1458 1459config RCU_EQS_DEBUG 1460 bool "Provide debugging asserts for adding NO_HZ support to an arch" 1461 depends on DEBUG_KERNEL 1462 help 1463 This option provides consistency checks in RCU's handling of 1464 NO_HZ. These checks have proven quite helpful in detecting 1465 bugs in arch-specific NO_HZ code. 1466 1467 Say N here if you need ultimate kernel/user switch latencies 1468 Say Y if you are unsure 1469 1470endmenu # "RCU Debugging" 1471 1472config DEBUG_WQ_FORCE_RR_CPU 1473 bool "Force round-robin CPU selection for unbound work items" 1474 depends on DEBUG_KERNEL 1475 default n 1476 help 1477 Workqueue used to implicitly guarantee that work items queued 1478 without explicit CPU specified are put on the local CPU. This 1479 guarantee is no longer true and while local CPU is still 1480 preferred work items may be put on foreign CPUs. Kernel 1481 parameter "workqueue.debug_force_rr_cpu" is added to force 1482 round-robin CPU selection to flush out usages which depend on the 1483 now broken guarantee. This config option enables the debug 1484 feature by default. When enabled, memory and cache locality will 1485 be impacted. 1486 1487config DEBUG_BLOCK_EXT_DEVT 1488 bool "Force extended block device numbers and spread them" 1489 depends on DEBUG_KERNEL 1490 depends on BLOCK 1491 default n 1492 help 1493 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1494 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1495 YOU ARE DOING. Distros, please enable this and fix whatever 1496 is broken. 1497 1498 Conventionally, block device numbers are allocated from 1499 predetermined contiguous area. However, extended block area 1500 may introduce non-contiguous block device numbers. This 1501 option forces most block device numbers to be allocated from 1502 the extended space and spreads them to discover kernel or 1503 userland code paths which assume predetermined contiguous 1504 device number allocation. 1505 1506 Note that turning on this debug option shuffles all the 1507 device numbers for all IDE and SCSI devices including libata 1508 ones, so root partition specified using device number 1509 directly (via rdev or root=MAJ:MIN) won't work anymore. 1510 Textual device names (root=/dev/sdXn) will continue to work. 1511 1512 Say N if you are unsure. 1513 1514config CPU_HOTPLUG_STATE_CONTROL 1515 bool "Enable CPU hotplug state control" 1516 depends on DEBUG_KERNEL 1517 depends on HOTPLUG_CPU 1518 default n 1519 help 1520 Allows to write steps between "offline" and "online" to the CPUs 1521 sysfs target file so states can be stepped granular. This is a debug 1522 option for now as the hotplug machinery cannot be stopped and 1523 restarted at arbitrary points yet. 1524 1525 Say N if your are unsure. 1526 1527config NOTIFIER_ERROR_INJECTION 1528 tristate "Notifier error injection" 1529 depends on DEBUG_KERNEL 1530 select DEBUG_FS 1531 help 1532 This option provides the ability to inject artificial errors to 1533 specified notifier chain callbacks. It is useful to test the error 1534 handling of notifier call chain failures. 1535 1536 Say N if unsure. 1537 1538config CPU_NOTIFIER_ERROR_INJECT 1539 tristate "CPU notifier error injection module" 1540 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1541 help 1542 This option provides a kernel module that can be used to test 1543 the error handling of the cpu notifiers by injecting artificial 1544 errors to CPU notifier chain callbacks. It is controlled through 1545 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1546 1547 If the notifier call chain should be failed with some events 1548 notified, write the error code to "actions/<notifier event>/error". 1549 1550 Example: Inject CPU offline error (-1 == -EPERM) 1551 1552 # cd /sys/kernel/debug/notifier-error-inject/cpu 1553 # echo -1 > actions/CPU_DOWN_PREPARE/error 1554 # echo 0 > /sys/devices/system/cpu/cpu1/online 1555 bash: echo: write error: Operation not permitted 1556 1557 To compile this code as a module, choose M here: the module will 1558 be called cpu-notifier-error-inject. 1559 1560 If unsure, say N. 1561 1562config PM_NOTIFIER_ERROR_INJECT 1563 tristate "PM notifier error injection module" 1564 depends on PM && NOTIFIER_ERROR_INJECTION 1565 default m if PM_DEBUG 1566 help 1567 This option provides the ability to inject artificial errors to 1568 PM notifier chain callbacks. It is controlled through debugfs 1569 interface /sys/kernel/debug/notifier-error-inject/pm 1570 1571 If the notifier call chain should be failed with some events 1572 notified, write the error code to "actions/<notifier event>/error". 1573 1574 Example: Inject PM suspend error (-12 = -ENOMEM) 1575 1576 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1577 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1578 # echo mem > /sys/power/state 1579 bash: echo: write error: Cannot allocate memory 1580 1581 To compile this code as a module, choose M here: the module will 1582 be called pm-notifier-error-inject. 1583 1584 If unsure, say N. 1585 1586config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1587 tristate "OF reconfig notifier error injection module" 1588 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1589 help 1590 This option provides the ability to inject artificial errors to 1591 OF reconfig notifier chain callbacks. It is controlled 1592 through debugfs interface under 1593 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1594 1595 If the notifier call chain should be failed with some events 1596 notified, write the error code to "actions/<notifier event>/error". 1597 1598 To compile this code as a module, choose M here: the module will 1599 be called of-reconfig-notifier-error-inject. 1600 1601 If unsure, say N. 1602 1603config NETDEV_NOTIFIER_ERROR_INJECT 1604 tristate "Netdev notifier error injection module" 1605 depends on NET && NOTIFIER_ERROR_INJECTION 1606 help 1607 This option provides the ability to inject artificial errors to 1608 netdevice notifier chain callbacks. It is controlled through debugfs 1609 interface /sys/kernel/debug/notifier-error-inject/netdev 1610 1611 If the notifier call chain should be failed with some events 1612 notified, write the error code to "actions/<notifier event>/error". 1613 1614 Example: Inject netdevice mtu change error (-22 = -EINVAL) 1615 1616 # cd /sys/kernel/debug/notifier-error-inject/netdev 1617 # echo -22 > actions/NETDEV_CHANGEMTU/error 1618 # ip link set eth0 mtu 1024 1619 RTNETLINK answers: Invalid argument 1620 1621 To compile this code as a module, choose M here: the module will 1622 be called netdev-notifier-error-inject. 1623 1624 If unsure, say N. 1625 1626config FAULT_INJECTION 1627 bool "Fault-injection framework" 1628 depends on DEBUG_KERNEL 1629 help 1630 Provide fault-injection framework. 1631 For more details, see Documentation/fault-injection/. 1632 1633config FAILSLAB 1634 bool "Fault-injection capability for kmalloc" 1635 depends on FAULT_INJECTION 1636 depends on SLAB || SLUB 1637 help 1638 Provide fault-injection capability for kmalloc. 1639 1640config FAIL_PAGE_ALLOC 1641 bool "Fault-injection capabilitiy for alloc_pages()" 1642 depends on FAULT_INJECTION 1643 help 1644 Provide fault-injection capability for alloc_pages(). 1645 1646config FAIL_MAKE_REQUEST 1647 bool "Fault-injection capability for disk IO" 1648 depends on FAULT_INJECTION && BLOCK 1649 help 1650 Provide fault-injection capability for disk IO. 1651 1652config FAIL_IO_TIMEOUT 1653 bool "Fault-injection capability for faking disk interrupts" 1654 depends on FAULT_INJECTION && BLOCK 1655 help 1656 Provide fault-injection capability on end IO handling. This 1657 will make the block layer "forget" an interrupt as configured, 1658 thus exercising the error handling. 1659 1660 Only works with drivers that use the generic timeout handling, 1661 for others it wont do anything. 1662 1663config FAIL_MMC_REQUEST 1664 bool "Fault-injection capability for MMC IO" 1665 depends on FAULT_INJECTION_DEBUG_FS && MMC 1666 help 1667 Provide fault-injection capability for MMC IO. 1668 This will make the mmc core return data errors. This is 1669 useful to test the error handling in the mmc block device 1670 and to test how the mmc host driver handles retries from 1671 the block device. 1672 1673config FAIL_FUTEX 1674 bool "Fault-injection capability for futexes" 1675 select DEBUG_FS 1676 depends on FAULT_INJECTION && FUTEX 1677 help 1678 Provide fault-injection capability for futexes. 1679 1680config FAULT_INJECTION_DEBUG_FS 1681 bool "Debugfs entries for fault-injection capabilities" 1682 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1683 help 1684 Enable configuration of fault-injection capabilities via debugfs. 1685 1686config FAULT_INJECTION_STACKTRACE_FILTER 1687 bool "stacktrace filter for fault-injection capabilities" 1688 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1689 depends on !X86_64 1690 select STACKTRACE 1691 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1692 help 1693 Provide stacktrace filter for fault-injection capabilities 1694 1695config LATENCYTOP 1696 bool "Latency measuring infrastructure" 1697 depends on DEBUG_KERNEL 1698 depends on STACKTRACE_SUPPORT 1699 depends on PROC_FS 1700 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1701 select KALLSYMS 1702 select KALLSYMS_ALL 1703 select STACKTRACE 1704 select SCHEDSTATS 1705 select SCHED_DEBUG 1706 help 1707 Enable this option if you want to use the LatencyTOP tool 1708 to find out which userspace is blocking on what kernel operations. 1709 1710config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1711 bool 1712 1713config DEBUG_STRICT_USER_COPY_CHECKS 1714 bool "Strict user copy size checks" 1715 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1716 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING 1717 help 1718 Enabling this option turns a certain set of sanity checks for user 1719 copy operations into compile time failures. 1720 1721 The copy_from_user() etc checks are there to help test if there 1722 are sufficient security checks on the length argument of 1723 the copy operation, by having gcc prove that the argument is 1724 within bounds. 1725 1726 If unsure, say N. 1727 1728source kernel/trace/Kconfig 1729 1730menu "Runtime Testing" 1731 1732config LKDTM 1733 tristate "Linux Kernel Dump Test Tool Module" 1734 depends on DEBUG_FS 1735 depends on BLOCK 1736 default n 1737 help 1738 This module enables testing of the different dumping mechanisms by 1739 inducing system failures at predefined crash points. 1740 If you don't need it: say N 1741 Choose M here to compile this code as a module. The module will be 1742 called lkdtm. 1743 1744 Documentation on how to use the module can be found in 1745 Documentation/fault-injection/provoke-crashes.txt 1746 1747config TEST_LIST_SORT 1748 bool "Linked list sorting test" 1749 depends on DEBUG_KERNEL 1750 help 1751 Enable this to turn on 'list_sort()' function test. This test is 1752 executed only once during system boot, so affects only boot time. 1753 1754 If unsure, say N. 1755 1756config KPROBES_SANITY_TEST 1757 bool "Kprobes sanity tests" 1758 depends on DEBUG_KERNEL 1759 depends on KPROBES 1760 default n 1761 help 1762 This option provides for testing basic kprobes functionality on 1763 boot. A sample kprobe, jprobe and kretprobe are inserted and 1764 verified for functionality. 1765 1766 Say N if you are unsure. 1767 1768config BACKTRACE_SELF_TEST 1769 tristate "Self test for the backtrace code" 1770 depends on DEBUG_KERNEL 1771 default n 1772 help 1773 This option provides a kernel module that can be used to test 1774 the kernel stack backtrace code. This option is not useful 1775 for distributions or general kernels, but only for kernel 1776 developers working on architecture code. 1777 1778 Note that if you want to also test saved backtraces, you will 1779 have to enable STACKTRACE as well. 1780 1781 Say N if you are unsure. 1782 1783config RBTREE_TEST 1784 tristate "Red-Black tree test" 1785 depends on DEBUG_KERNEL 1786 help 1787 A benchmark measuring the performance of the rbtree library. 1788 Also includes rbtree invariant checks. 1789 1790config INTERVAL_TREE_TEST 1791 tristate "Interval tree test" 1792 depends on m && DEBUG_KERNEL 1793 select INTERVAL_TREE 1794 help 1795 A benchmark measuring the performance of the interval tree library 1796 1797config PERCPU_TEST 1798 tristate "Per cpu operations test" 1799 depends on m && DEBUG_KERNEL 1800 help 1801 Enable this option to build test module which validates per-cpu 1802 operations. 1803 1804 If unsure, say N. 1805 1806config ATOMIC64_SELFTEST 1807 bool "Perform an atomic64_t self-test at boot" 1808 help 1809 Enable this option to test the atomic64_t functions at boot. 1810 1811 If unsure, say N. 1812 1813config ASYNC_RAID6_TEST 1814 tristate "Self test for hardware accelerated raid6 recovery" 1815 depends on ASYNC_RAID6_RECOV 1816 select ASYNC_MEMCPY 1817 ---help--- 1818 This is a one-shot self test that permutes through the 1819 recovery of all the possible two disk failure scenarios for a 1820 N-disk array. Recovery is performed with the asynchronous 1821 raid6 recovery routines, and will optionally use an offload 1822 engine if one is available. 1823 1824 If unsure, say N. 1825 1826config TEST_HEXDUMP 1827 tristate "Test functions located in the hexdump module at runtime" 1828 1829config TEST_STRING_HELPERS 1830 tristate "Test functions located in the string_helpers module at runtime" 1831 1832config TEST_KSTRTOX 1833 tristate "Test kstrto*() family of functions at runtime" 1834 1835config TEST_PRINTF 1836 tristate "Test printf() family of functions at runtime" 1837 1838config TEST_BITMAP 1839 tristate "Test bitmap_*() family of functions at runtime" 1840 default n 1841 help 1842 Enable this option to test the bitmap functions at boot. 1843 1844 If unsure, say N. 1845 1846config TEST_RHASHTABLE 1847 tristate "Perform selftest on resizable hash table" 1848 default n 1849 help 1850 Enable this option to test the rhashtable functions at boot. 1851 1852 If unsure, say N. 1853 1854config TEST_HASH 1855 tristate "Perform selftest on hash functions" 1856 default n 1857 help 1858 Enable this option to test the kernel's integer (<linux/hash,h>) 1859 and string (<linux/stringhash.h>) hash functions on boot 1860 (or module load). 1861 1862 This is intended to help people writing architecture-specific 1863 optimized versions. If unsure, say N. 1864 1865endmenu # runtime tests 1866 1867config PROVIDE_OHCI1394_DMA_INIT 1868 bool "Remote debugging over FireWire early on boot" 1869 depends on PCI && X86 1870 help 1871 If you want to debug problems which hang or crash the kernel early 1872 on boot and the crashing machine has a FireWire port, you can use 1873 this feature to remotely access the memory of the crashed machine 1874 over FireWire. This employs remote DMA as part of the OHCI1394 1875 specification which is now the standard for FireWire controllers. 1876 1877 With remote DMA, you can monitor the printk buffer remotely using 1878 firescope and access all memory below 4GB using fireproxy from gdb. 1879 Even controlling a kernel debugger is possible using remote DMA. 1880 1881 Usage: 1882 1883 If ohci1394_dma=early is used as boot parameter, it will initialize 1884 all OHCI1394 controllers which are found in the PCI config space. 1885 1886 As all changes to the FireWire bus such as enabling and disabling 1887 devices cause a bus reset and thereby disable remote DMA for all 1888 devices, be sure to have the cable plugged and FireWire enabled on 1889 the debugging host before booting the debug target for debugging. 1890 1891 This code (~1k) is freed after boot. By then, the firewire stack 1892 in charge of the OHCI-1394 controllers should be used instead. 1893 1894 See Documentation/debugging-via-ohci1394.txt for more information. 1895 1896config BUILD_DOCSRC 1897 bool "Build targets in Documentation/ tree" 1898 depends on HEADERS_CHECK 1899 help 1900 This option attempts to build objects from the source files in the 1901 kernel Documentation/ tree. 1902 1903 Say N if you are unsure. 1904 1905config DMA_API_DEBUG 1906 bool "Enable debugging of DMA-API usage" 1907 depends on HAVE_DMA_API_DEBUG 1908 help 1909 Enable this option to debug the use of the DMA API by device drivers. 1910 With this option you will be able to detect common bugs in device 1911 drivers like double-freeing of DMA mappings or freeing mappings that 1912 were never allocated. 1913 1914 This also attempts to catch cases where a page owned by DMA is 1915 accessed by the cpu in a way that could cause data corruption. For 1916 example, this enables cow_user_page() to check that the source page is 1917 not undergoing DMA. 1918 1919 This option causes a performance degradation. Use only if you want to 1920 debug device drivers and dma interactions. 1921 1922 If unsure, say N. 1923 1924config TEST_LKM 1925 tristate "Test module loading with 'hello world' module" 1926 default n 1927 depends on m 1928 help 1929 This builds the "test_module" module that emits "Hello, world" 1930 on printk when loaded. It is designed to be used for basic 1931 evaluation of the module loading subsystem (for example when 1932 validating module verification). It lacks any extra dependencies, 1933 and will not normally be loaded by the system unless explicitly 1934 requested by name. 1935 1936 If unsure, say N. 1937 1938config TEST_USER_COPY 1939 tristate "Test user/kernel boundary protections" 1940 default n 1941 depends on m 1942 help 1943 This builds the "test_user_copy" module that runs sanity checks 1944 on the copy_to/from_user infrastructure, making sure basic 1945 user/kernel boundary testing is working. If it fails to load, 1946 a regression has been detected in the user/kernel memory boundary 1947 protections. 1948 1949 If unsure, say N. 1950 1951config TEST_BPF 1952 tristate "Test BPF filter functionality" 1953 default n 1954 depends on m && NET 1955 help 1956 This builds the "test_bpf" module that runs various test vectors 1957 against the BPF interpreter or BPF JIT compiler depending on the 1958 current setting. This is in particular useful for BPF JIT compiler 1959 development, but also to run regression tests against changes in 1960 the interpreter code. It also enables test stubs for eBPF maps and 1961 verifier used by user space verifier testsuite. 1962 1963 If unsure, say N. 1964 1965config TEST_FIRMWARE 1966 tristate "Test firmware loading via userspace interface" 1967 default n 1968 depends on FW_LOADER 1969 help 1970 This builds the "test_firmware" module that creates a userspace 1971 interface for testing firmware loading. This can be used to 1972 control the triggering of firmware loading without needing an 1973 actual firmware-using device. The contents can be rechecked by 1974 userspace. 1975 1976 If unsure, say N. 1977 1978config TEST_UDELAY 1979 tristate "udelay test driver" 1980 default n 1981 help 1982 This builds the "udelay_test" module that helps to make sure 1983 that udelay() is working properly. 1984 1985 If unsure, say N. 1986 1987config MEMTEST 1988 bool "Memtest" 1989 depends on HAVE_MEMBLOCK 1990 ---help--- 1991 This option adds a kernel parameter 'memtest', which allows memtest 1992 to be set. 1993 memtest=0, mean disabled; -- default 1994 memtest=1, mean do 1 test pattern; 1995 ... 1996 memtest=17, mean do 17 test patterns. 1997 If you are unsure how to answer this question, answer N. 1998 1999config TEST_STATIC_KEYS 2000 tristate "Test static keys" 2001 default n 2002 depends on m 2003 help 2004 Test the static key interfaces. 2005 2006 If unsure, say N. 2007 2008source "samples/Kconfig" 2009 2010source "lib/Kconfig.kgdb" 2011 2012source "lib/Kconfig.ubsan" 2013 2014config ARCH_HAS_DEVMEM_IS_ALLOWED 2015 bool 2016 2017config STRICT_DEVMEM 2018 bool "Filter access to /dev/mem" 2019 depends on MMU 2020 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 2021 default y if TILE || PPC 2022 ---help--- 2023 If this option is disabled, you allow userspace (root) access to all 2024 of memory, including kernel and userspace memory. Accidental 2025 access to this is obviously disastrous, but specific access can 2026 be used by people debugging the kernel. Note that with PAT support 2027 enabled, even in this case there are restrictions on /dev/mem 2028 use due to the cache aliasing requirements. 2029 2030 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 2031 file only allows userspace access to PCI space and the BIOS code and 2032 data regions. This is sufficient for dosemu and X and all common 2033 users of /dev/mem. 2034 2035 If in doubt, say Y. 2036 2037config IO_STRICT_DEVMEM 2038 bool "Filter I/O access to /dev/mem" 2039 depends on STRICT_DEVMEM 2040 ---help--- 2041 If this option is disabled, you allow userspace (root) access to all 2042 io-memory regardless of whether a driver is actively using that 2043 range. Accidental access to this is obviously disastrous, but 2044 specific access can be used by people debugging kernel drivers. 2045 2046 If this option is switched on, the /dev/mem file only allows 2047 userspace access to *idle* io-memory ranges (see /proc/iomem) This 2048 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 2049 if the driver using a given range cannot be disabled. 2050 2051 If in doubt, say Y. 2052