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 help 713 KCOV exposes kernel code coverage information in a form suitable 714 for coverage-guided fuzzing (randomized testing). 715 716 If RANDOMIZE_BASE is enabled, PC values will not be stable across 717 different machines and across reboots. If you need stable PC values, 718 disable RANDOMIZE_BASE. 719 720 For more details, see Documentation/kcov.txt. 721 722config DEBUG_SHIRQ 723 bool "Debug shared IRQ handlers" 724 depends on DEBUG_KERNEL 725 help 726 Enable this to generate a spurious interrupt as soon as a shared 727 interrupt handler is registered, and just before one is deregistered. 728 Drivers ought to be able to handle interrupts coming in at those 729 points; some don't and need to be caught. 730 731menu "Debug Lockups and Hangs" 732 733config LOCKUP_DETECTOR 734 bool "Detect Hard and Soft Lockups" 735 depends on DEBUG_KERNEL && !S390 736 help 737 Say Y here to enable the kernel to act as a watchdog to detect 738 hard and soft lockups. 739 740 Softlockups are bugs that cause the kernel to loop in kernel 741 mode for more than 20 seconds, without giving other tasks a 742 chance to run. The current stack trace is displayed upon 743 detection and the system will stay locked up. 744 745 Hardlockups are bugs that cause the CPU to loop in kernel mode 746 for more than 10 seconds, without letting other interrupts have a 747 chance to run. The current stack trace is displayed upon detection 748 and the system will stay locked up. 749 750 The overhead should be minimal. A periodic hrtimer runs to 751 generate interrupts and kick the watchdog task every 4 seconds. 752 An NMI is generated every 10 seconds or so to check for hardlockups. 753 754 The frequency of hrtimer and NMI events and the soft and hard lockup 755 thresholds can be controlled through the sysctl watchdog_thresh. 756 757config HARDLOCKUP_DETECTOR 758 def_bool y 759 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 760 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 761 762config BOOTPARAM_HARDLOCKUP_PANIC 763 bool "Panic (Reboot) On Hard Lockups" 764 depends on HARDLOCKUP_DETECTOR 765 help 766 Say Y here to enable the kernel to panic on "hard lockups", 767 which are bugs that cause the kernel to loop in kernel 768 mode with interrupts disabled for more than 10 seconds (configurable 769 using the watchdog_thresh sysctl). 770 771 Say N if unsure. 772 773config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 774 int 775 depends on HARDLOCKUP_DETECTOR 776 range 0 1 777 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 778 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 779 780config BOOTPARAM_SOFTLOCKUP_PANIC 781 bool "Panic (Reboot) On Soft Lockups" 782 depends on LOCKUP_DETECTOR 783 help 784 Say Y here to enable the kernel to panic on "soft lockups", 785 which are bugs that cause the kernel to loop in kernel 786 mode for more than 20 seconds (configurable using the watchdog_thresh 787 sysctl), without giving other tasks a chance to run. 788 789 The panic can be used in combination with panic_timeout, 790 to cause the system to reboot automatically after a 791 lockup has been detected. This feature is useful for 792 high-availability systems that have uptime guarantees and 793 where a lockup must be resolved ASAP. 794 795 Say N if unsure. 796 797config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 798 int 799 depends on LOCKUP_DETECTOR 800 range 0 1 801 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 802 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 803 804config DETECT_HUNG_TASK 805 bool "Detect Hung Tasks" 806 depends on DEBUG_KERNEL 807 default LOCKUP_DETECTOR 808 help 809 Say Y here to enable the kernel to detect "hung tasks", 810 which are bugs that cause the task to be stuck in 811 uninterruptible "D" state indefinitiley. 812 813 When a hung task is detected, the kernel will print the 814 current stack trace (which you should report), but the 815 task will stay in uninterruptible state. If lockdep is 816 enabled then all held locks will also be reported. This 817 feature has negligible overhead. 818 819config DEFAULT_HUNG_TASK_TIMEOUT 820 int "Default timeout for hung task detection (in seconds)" 821 depends on DETECT_HUNG_TASK 822 default 120 823 help 824 This option controls the default timeout (in seconds) used 825 to determine when a task has become non-responsive and should 826 be considered hung. 827 828 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 829 sysctl or by writing a value to 830 /proc/sys/kernel/hung_task_timeout_secs. 831 832 A timeout of 0 disables the check. The default is two minutes. 833 Keeping the default should be fine in most cases. 834 835config BOOTPARAM_HUNG_TASK_PANIC 836 bool "Panic (Reboot) On Hung Tasks" 837 depends on DETECT_HUNG_TASK 838 help 839 Say Y here to enable the kernel to panic on "hung tasks", 840 which are bugs that cause the kernel to leave a task stuck 841 in uninterruptible "D" state. 842 843 The panic can be used in combination with panic_timeout, 844 to cause the system to reboot automatically after a 845 hung task has been detected. This feature is useful for 846 high-availability systems that have uptime guarantees and 847 where a hung tasks must be resolved ASAP. 848 849 Say N if unsure. 850 851config BOOTPARAM_HUNG_TASK_PANIC_VALUE 852 int 853 depends on DETECT_HUNG_TASK 854 range 0 1 855 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 856 default 1 if BOOTPARAM_HUNG_TASK_PANIC 857 858config WQ_WATCHDOG 859 bool "Detect Workqueue Stalls" 860 depends on DEBUG_KERNEL 861 help 862 Say Y here to enable stall detection on workqueues. If a 863 worker pool doesn't make forward progress on a pending work 864 item for over a given amount of time, 30s by default, a 865 warning message is printed along with dump of workqueue 866 state. This can be configured through kernel parameter 867 "workqueue.watchdog_thresh" and its sysfs counterpart. 868 869endmenu # "Debug lockups and hangs" 870 871config PANIC_ON_OOPS 872 bool "Panic on Oops" 873 help 874 Say Y here to enable the kernel to panic when it oopses. This 875 has the same effect as setting oops=panic on the kernel command 876 line. 877 878 This feature is useful to ensure that the kernel does not do 879 anything erroneous after an oops which could result in data 880 corruption or other issues. 881 882 Say N if unsure. 883 884config PANIC_ON_OOPS_VALUE 885 int 886 range 0 1 887 default 0 if !PANIC_ON_OOPS 888 default 1 if PANIC_ON_OOPS 889 890config PANIC_TIMEOUT 891 int "panic timeout" 892 default 0 893 help 894 Set the timeout value (in seconds) until a reboot occurs when the 895 the kernel panics. If n = 0, then we wait forever. A timeout 896 value n > 0 will wait n seconds before rebooting, while a timeout 897 value n < 0 will reboot immediately. 898 899config SCHED_DEBUG 900 bool "Collect scheduler debugging info" 901 depends on DEBUG_KERNEL && PROC_FS 902 default y 903 help 904 If you say Y here, the /proc/sched_debug file will be provided 905 that can help debug the scheduler. The runtime overhead of this 906 option is minimal. 907 908config SCHED_INFO 909 bool 910 default n 911 912config SCHEDSTATS 913 bool "Collect scheduler statistics" 914 depends on DEBUG_KERNEL && PROC_FS 915 select SCHED_INFO 916 help 917 If you say Y here, additional code will be inserted into the 918 scheduler and related routines to collect statistics about 919 scheduler behavior and provide them in /proc/schedstat. These 920 stats may be useful for both tuning and debugging the scheduler 921 If you aren't debugging the scheduler or trying to tune a specific 922 application, you can say N to avoid the very slight overhead 923 this adds. 924 925config SCHED_STACK_END_CHECK 926 bool "Detect stack corruption on calls to schedule()" 927 depends on DEBUG_KERNEL 928 default n 929 help 930 This option checks for a stack overrun on calls to schedule(). 931 If the stack end location is found to be over written always panic as 932 the content of the corrupted region can no longer be trusted. 933 This is to ensure no erroneous behaviour occurs which could result in 934 data corruption or a sporadic crash at a later stage once the region 935 is examined. The runtime overhead introduced is minimal. 936 937config DEBUG_TIMEKEEPING 938 bool "Enable extra timekeeping sanity checking" 939 help 940 This option will enable additional timekeeping sanity checks 941 which may be helpful when diagnosing issues where timekeeping 942 problems are suspected. 943 944 This may include checks in the timekeeping hotpaths, so this 945 option may have a (very small) performance impact to some 946 workloads. 947 948 If unsure, say N. 949 950config TIMER_STATS 951 bool "Collect kernel timers statistics" 952 depends on DEBUG_KERNEL && PROC_FS 953 help 954 If you say Y here, additional code will be inserted into the 955 timer routines to collect statistics about kernel timers being 956 reprogrammed. The statistics can be read from /proc/timer_stats. 957 The statistics collection is started by writing 1 to /proc/timer_stats, 958 writing 0 stops it. This feature is useful to collect information 959 about timer usage patterns in kernel and userspace. This feature 960 is lightweight if enabled in the kernel config but not activated 961 (it defaults to deactivated on bootup and will only be activated 962 if some application like powertop activates it explicitly). 963 964config DEBUG_PREEMPT 965 bool "Debug preemptible kernel" 966 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 967 default y 968 help 969 If you say Y here then the kernel will use a debug variant of the 970 commonly used smp_processor_id() function and will print warnings 971 if kernel code uses it in a preemption-unsafe way. Also, the kernel 972 will detect preemption count underflows. 973 974menu "Lock Debugging (spinlocks, mutexes, etc...)" 975 976config DEBUG_RT_MUTEXES 977 bool "RT Mutex debugging, deadlock detection" 978 depends on DEBUG_KERNEL && RT_MUTEXES 979 help 980 This allows rt mutex semantics violations and rt mutex related 981 deadlocks (lockups) to be detected and reported automatically. 982 983config DEBUG_SPINLOCK 984 bool "Spinlock and rw-lock debugging: basic checks" 985 depends on DEBUG_KERNEL 986 select UNINLINE_SPIN_UNLOCK 987 help 988 Say Y here and build SMP to catch missing spinlock initialization 989 and certain other kinds of spinlock errors commonly made. This is 990 best used in conjunction with the NMI watchdog so that spinlock 991 deadlocks are also debuggable. 992 993config DEBUG_MUTEXES 994 bool "Mutex debugging: basic checks" 995 depends on DEBUG_KERNEL 996 help 997 This feature allows mutex semantics violations to be detected and 998 reported. 999 1000config DEBUG_WW_MUTEX_SLOWPATH 1001 bool "Wait/wound mutex debugging: Slowpath testing" 1002 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1003 select DEBUG_LOCK_ALLOC 1004 select DEBUG_SPINLOCK 1005 select DEBUG_MUTEXES 1006 help 1007 This feature enables slowpath testing for w/w mutex users by 1008 injecting additional -EDEADLK wound/backoff cases. Together with 1009 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 1010 will test all possible w/w mutex interface abuse with the 1011 exception of simply not acquiring all the required locks. 1012 Note that this feature can introduce significant overhead, so 1013 it really should not be enabled in a production or distro kernel, 1014 even a debug kernel. If you are a driver writer, enable it. If 1015 you are a distro, do not. 1016 1017config DEBUG_LOCK_ALLOC 1018 bool "Lock debugging: detect incorrect freeing of live locks" 1019 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1020 select DEBUG_SPINLOCK 1021 select DEBUG_MUTEXES 1022 select LOCKDEP 1023 help 1024 This feature will check whether any held lock (spinlock, rwlock, 1025 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1026 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1027 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1028 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1029 held during task exit. 1030 1031config PROVE_LOCKING 1032 bool "Lock debugging: prove locking correctness" 1033 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1034 select LOCKDEP 1035 select DEBUG_SPINLOCK 1036 select DEBUG_MUTEXES 1037 select DEBUG_LOCK_ALLOC 1038 select TRACE_IRQFLAGS 1039 default n 1040 help 1041 This feature enables the kernel to prove that all locking 1042 that occurs in the kernel runtime is mathematically 1043 correct: that under no circumstance could an arbitrary (and 1044 not yet triggered) combination of observed locking 1045 sequences (on an arbitrary number of CPUs, running an 1046 arbitrary number of tasks and interrupt contexts) cause a 1047 deadlock. 1048 1049 In short, this feature enables the kernel to report locking 1050 related deadlocks before they actually occur. 1051 1052 The proof does not depend on how hard and complex a 1053 deadlock scenario would be to trigger: how many 1054 participant CPUs, tasks and irq-contexts would be needed 1055 for it to trigger. The proof also does not depend on 1056 timing: if a race and a resulting deadlock is possible 1057 theoretically (no matter how unlikely the race scenario 1058 is), it will be proven so and will immediately be 1059 reported by the kernel (once the event is observed that 1060 makes the deadlock theoretically possible). 1061 1062 If a deadlock is impossible (i.e. the locking rules, as 1063 observed by the kernel, are mathematically correct), the 1064 kernel reports nothing. 1065 1066 NOTE: this feature can also be enabled for rwlocks, mutexes 1067 and rwsems - in which case all dependencies between these 1068 different locking variants are observed and mapped too, and 1069 the proof of observed correctness is also maintained for an 1070 arbitrary combination of these separate locking variants. 1071 1072 For more details, see Documentation/locking/lockdep-design.txt. 1073 1074config LOCKDEP 1075 bool 1076 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1077 select STACKTRACE 1078 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE 1079 select KALLSYMS 1080 select KALLSYMS_ALL 1081 1082config LOCK_STAT 1083 bool "Lock usage statistics" 1084 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1085 select LOCKDEP 1086 select DEBUG_SPINLOCK 1087 select DEBUG_MUTEXES 1088 select DEBUG_LOCK_ALLOC 1089 default n 1090 help 1091 This feature enables tracking lock contention points 1092 1093 For more details, see Documentation/locking/lockstat.txt 1094 1095 This also enables lock events required by "perf lock", 1096 subcommand of perf. 1097 If you want to use "perf lock", you also need to turn on 1098 CONFIG_EVENT_TRACING. 1099 1100 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1101 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1102 1103config DEBUG_LOCKDEP 1104 bool "Lock dependency engine debugging" 1105 depends on DEBUG_KERNEL && LOCKDEP 1106 help 1107 If you say Y here, the lock dependency engine will do 1108 additional runtime checks to debug itself, at the price 1109 of more runtime overhead. 1110 1111config DEBUG_ATOMIC_SLEEP 1112 bool "Sleep inside atomic section checking" 1113 select PREEMPT_COUNT 1114 depends on DEBUG_KERNEL 1115 help 1116 If you say Y here, various routines which may sleep will become very 1117 noisy if they are called inside atomic sections: when a spinlock is 1118 held, inside an rcu read side critical section, inside preempt disabled 1119 sections, inside an interrupt, etc... 1120 1121config DEBUG_LOCKING_API_SELFTESTS 1122 bool "Locking API boot-time self-tests" 1123 depends on DEBUG_KERNEL 1124 help 1125 Say Y here if you want the kernel to run a short self-test during 1126 bootup. The self-test checks whether common types of locking bugs 1127 are detected by debugging mechanisms or not. (if you disable 1128 lock debugging then those bugs wont be detected of course.) 1129 The following locking APIs are covered: spinlocks, rwlocks, 1130 mutexes and rwsems. 1131 1132config LOCK_TORTURE_TEST 1133 tristate "torture tests for locking" 1134 depends on DEBUG_KERNEL 1135 select TORTURE_TEST 1136 default n 1137 help 1138 This option provides a kernel module that runs torture tests 1139 on kernel locking primitives. The kernel module may be built 1140 after the fact on the running kernel to be tested, if desired. 1141 1142 Say Y here if you want kernel locking-primitive torture tests 1143 to be built into the kernel. 1144 Say M if you want these torture tests to build as a module. 1145 Say N if you are unsure. 1146 1147endmenu # lock debugging 1148 1149config TRACE_IRQFLAGS 1150 bool 1151 help 1152 Enables hooks to interrupt enabling and disabling for 1153 either tracing or lock debugging. 1154 1155config STACKTRACE 1156 bool "Stack backtrace support" 1157 depends on STACKTRACE_SUPPORT 1158 help 1159 This option causes the kernel to create a /proc/pid/stack for 1160 every process, showing its current stack trace. 1161 It is also used by various kernel debugging features that require 1162 stack trace generation. 1163 1164config DEBUG_KOBJECT 1165 bool "kobject debugging" 1166 depends on DEBUG_KERNEL 1167 help 1168 If you say Y here, some extra kobject debugging messages will be sent 1169 to the syslog. 1170 1171config DEBUG_KOBJECT_RELEASE 1172 bool "kobject release debugging" 1173 depends on DEBUG_OBJECTS_TIMERS 1174 help 1175 kobjects are reference counted objects. This means that their 1176 last reference count put is not predictable, and the kobject can 1177 live on past the point at which a driver decides to drop it's 1178 initial reference to the kobject gained on allocation. An 1179 example of this would be a struct device which has just been 1180 unregistered. 1181 1182 However, some buggy drivers assume that after such an operation, 1183 the memory backing the kobject can be immediately freed. This 1184 goes completely against the principles of a refcounted object. 1185 1186 If you say Y here, the kernel will delay the release of kobjects 1187 on the last reference count to improve the visibility of this 1188 kind of kobject release bug. 1189 1190config HAVE_DEBUG_BUGVERBOSE 1191 bool 1192 1193config DEBUG_BUGVERBOSE 1194 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1195 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1196 default y 1197 help 1198 Say Y here to make BUG() panics output the file name and line number 1199 of the BUG call as well as the EIP and oops trace. This aids 1200 debugging but costs about 70-100K of memory. 1201 1202config DEBUG_LIST 1203 bool "Debug linked list manipulation" 1204 depends on DEBUG_KERNEL 1205 help 1206 Enable this to turn on extended checks in the linked-list 1207 walking routines. 1208 1209 If unsure, say N. 1210 1211config DEBUG_PI_LIST 1212 bool "Debug priority linked list manipulation" 1213 depends on DEBUG_KERNEL 1214 help 1215 Enable this to turn on extended checks in the priority-ordered 1216 linked-list (plist) walking routines. This checks the entire 1217 list multiple times during each manipulation. 1218 1219 If unsure, say N. 1220 1221config DEBUG_SG 1222 bool "Debug SG table operations" 1223 depends on DEBUG_KERNEL 1224 help 1225 Enable this to turn on checks on scatter-gather tables. This can 1226 help find problems with drivers that do not properly initialize 1227 their sg tables. 1228 1229 If unsure, say N. 1230 1231config DEBUG_NOTIFIERS 1232 bool "Debug notifier call chains" 1233 depends on DEBUG_KERNEL 1234 help 1235 Enable this to turn on sanity checking for notifier call chains. 1236 This is most useful for kernel developers to make sure that 1237 modules properly unregister themselves from notifier chains. 1238 This is a relatively cheap check but if you care about maximum 1239 performance, say N. 1240 1241config DEBUG_CREDENTIALS 1242 bool "Debug credential management" 1243 depends on DEBUG_KERNEL 1244 help 1245 Enable this to turn on some debug checking for credential 1246 management. The additional code keeps track of the number of 1247 pointers from task_structs to any given cred struct, and checks to 1248 see that this number never exceeds the usage count of the cred 1249 struct. 1250 1251 Furthermore, if SELinux is enabled, this also checks that the 1252 security pointer in the cred struct is never seen to be invalid. 1253 1254 If unsure, say N. 1255 1256menu "RCU Debugging" 1257 1258config PROVE_RCU 1259 def_bool PROVE_LOCKING 1260 1261config PROVE_RCU_REPEATEDLY 1262 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1263 depends on PROVE_RCU 1264 default n 1265 help 1266 By itself, PROVE_RCU will disable checking upon issuing the 1267 first warning (or "splat"). This feature prevents such 1268 disabling, allowing multiple RCU-lockdep warnings to be printed 1269 on a single reboot. 1270 1271 Say Y to allow multiple RCU-lockdep warnings per boot. 1272 1273 Say N if you are unsure. 1274 1275config SPARSE_RCU_POINTER 1276 bool "RCU debugging: sparse-based checks for pointer usage" 1277 default n 1278 help 1279 This feature enables the __rcu sparse annotation for 1280 RCU-protected pointers. This annotation will cause sparse 1281 to flag any non-RCU used of annotated pointers. This can be 1282 helpful when debugging RCU usage. Please note that this feature 1283 is not intended to enforce code cleanliness; it is instead merely 1284 a debugging aid. 1285 1286 Say Y to make sparse flag questionable use of RCU-protected pointers 1287 1288 Say N if you are unsure. 1289 1290config TORTURE_TEST 1291 tristate 1292 default n 1293 1294config RCU_PERF_TEST 1295 tristate "performance tests for RCU" 1296 depends on DEBUG_KERNEL 1297 select TORTURE_TEST 1298 select SRCU 1299 select TASKS_RCU 1300 default n 1301 help 1302 This option provides a kernel module that runs performance 1303 tests on the RCU infrastructure. The kernel module may be built 1304 after the fact on the running kernel to be tested, if desired. 1305 1306 Say Y here if you want RCU performance tests to be built into 1307 the kernel. 1308 Say M if you want the RCU performance tests to build as a module. 1309 Say N if you are unsure. 1310 1311config RCU_TORTURE_TEST 1312 tristate "torture tests for RCU" 1313 depends on DEBUG_KERNEL 1314 select TORTURE_TEST 1315 select SRCU 1316 select TASKS_RCU 1317 default n 1318 help 1319 This option provides a kernel module that runs torture tests 1320 on the RCU infrastructure. The kernel module may be built 1321 after the fact on the running kernel to be tested, if desired. 1322 1323 Say Y here if you want RCU torture tests to be built into 1324 the kernel. 1325 Say M if you want the RCU torture tests to build as a module. 1326 Say N if you are unsure. 1327 1328config RCU_TORTURE_TEST_SLOW_PREINIT 1329 bool "Slow down RCU grace-period pre-initialization to expose races" 1330 depends on RCU_TORTURE_TEST 1331 help 1332 This option delays grace-period pre-initialization (the 1333 propagation of CPU-hotplug changes up the rcu_node combining 1334 tree) for a few jiffies between initializing each pair of 1335 consecutive rcu_node structures. This helps to expose races 1336 involving grace-period pre-initialization, in other words, it 1337 makes your kernel less stable. It can also greatly increase 1338 grace-period latency, especially on systems with large numbers 1339 of CPUs. This is useful when torture-testing RCU, but in 1340 almost no other circumstance. 1341 1342 Say Y here if you want your system to crash and hang more often. 1343 Say N if you want a sane system. 1344 1345config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY 1346 int "How much to slow down RCU grace-period pre-initialization" 1347 range 0 5 1348 default 3 1349 depends on RCU_TORTURE_TEST_SLOW_PREINIT 1350 help 1351 This option specifies the number of jiffies to wait between 1352 each rcu_node structure pre-initialization step. 1353 1354config RCU_TORTURE_TEST_SLOW_INIT 1355 bool "Slow down RCU grace-period initialization to expose races" 1356 depends on RCU_TORTURE_TEST 1357 help 1358 This option delays grace-period initialization for a few 1359 jiffies between initializing each pair of consecutive 1360 rcu_node structures. This helps to expose races involving 1361 grace-period initialization, in other words, it makes your 1362 kernel less stable. It can also greatly increase grace-period 1363 latency, especially on systems with large numbers of CPUs. 1364 This is useful when torture-testing RCU, but in almost no 1365 other circumstance. 1366 1367 Say Y here if you want your system to crash and hang more often. 1368 Say N if you want a sane system. 1369 1370config RCU_TORTURE_TEST_SLOW_INIT_DELAY 1371 int "How much to slow down RCU grace-period initialization" 1372 range 0 5 1373 default 3 1374 depends on RCU_TORTURE_TEST_SLOW_INIT 1375 help 1376 This option specifies the number of jiffies to wait between 1377 each rcu_node structure initialization. 1378 1379config RCU_TORTURE_TEST_SLOW_CLEANUP 1380 bool "Slow down RCU grace-period cleanup to expose races" 1381 depends on RCU_TORTURE_TEST 1382 help 1383 This option delays grace-period cleanup for a few jiffies 1384 between cleaning up each pair of consecutive rcu_node 1385 structures. This helps to expose races involving grace-period 1386 cleanup, in other words, it makes your kernel less stable. 1387 It can also greatly increase grace-period latency, especially 1388 on systems with large numbers of CPUs. This is useful when 1389 torture-testing RCU, but in almost no other circumstance. 1390 1391 Say Y here if you want your system to crash and hang more often. 1392 Say N if you want a sane system. 1393 1394config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY 1395 int "How much to slow down RCU grace-period cleanup" 1396 range 0 5 1397 default 3 1398 depends on RCU_TORTURE_TEST_SLOW_CLEANUP 1399 help 1400 This option specifies the number of jiffies to wait between 1401 each rcu_node structure cleanup operation. 1402 1403config RCU_CPU_STALL_TIMEOUT 1404 int "RCU CPU stall timeout in seconds" 1405 depends on RCU_STALL_COMMON 1406 range 3 300 1407 default 21 1408 help 1409 If a given RCU grace period extends more than the specified 1410 number of seconds, a CPU stall warning is printed. If the 1411 RCU grace period persists, additional CPU stall warnings are 1412 printed at more widely spaced intervals. 1413 1414config RCU_TRACE 1415 bool "Enable tracing for RCU" 1416 depends on DEBUG_KERNEL 1417 select TRACE_CLOCK 1418 help 1419 This option provides tracing in RCU which presents stats 1420 in debugfs for debugging RCU implementation. 1421 1422 Say Y here if you want to enable RCU tracing 1423 Say N if you are unsure. 1424 1425config RCU_EQS_DEBUG 1426 bool "Provide debugging asserts for adding NO_HZ support to an arch" 1427 depends on DEBUG_KERNEL 1428 help 1429 This option provides consistency checks in RCU's handling of 1430 NO_HZ. These checks have proven quite helpful in detecting 1431 bugs in arch-specific NO_HZ code. 1432 1433 Say N here if you need ultimate kernel/user switch latencies 1434 Say Y if you are unsure 1435 1436endmenu # "RCU Debugging" 1437 1438config DEBUG_WQ_FORCE_RR_CPU 1439 bool "Force round-robin CPU selection for unbound work items" 1440 depends on DEBUG_KERNEL 1441 default n 1442 help 1443 Workqueue used to implicitly guarantee that work items queued 1444 without explicit CPU specified are put on the local CPU. This 1445 guarantee is no longer true and while local CPU is still 1446 preferred work items may be put on foreign CPUs. Kernel 1447 parameter "workqueue.debug_force_rr_cpu" is added to force 1448 round-robin CPU selection to flush out usages which depend on the 1449 now broken guarantee. This config option enables the debug 1450 feature by default. When enabled, memory and cache locality will 1451 be impacted. 1452 1453config DEBUG_BLOCK_EXT_DEVT 1454 bool "Force extended block device numbers and spread them" 1455 depends on DEBUG_KERNEL 1456 depends on BLOCK 1457 default n 1458 help 1459 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1460 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1461 YOU ARE DOING. Distros, please enable this and fix whatever 1462 is broken. 1463 1464 Conventionally, block device numbers are allocated from 1465 predetermined contiguous area. However, extended block area 1466 may introduce non-contiguous block device numbers. This 1467 option forces most block device numbers to be allocated from 1468 the extended space and spreads them to discover kernel or 1469 userland code paths which assume predetermined contiguous 1470 device number allocation. 1471 1472 Note that turning on this debug option shuffles all the 1473 device numbers for all IDE and SCSI devices including libata 1474 ones, so root partition specified using device number 1475 directly (via rdev or root=MAJ:MIN) won't work anymore. 1476 Textual device names (root=/dev/sdXn) will continue to work. 1477 1478 Say N if you are unsure. 1479 1480config CPU_HOTPLUG_STATE_CONTROL 1481 bool "Enable CPU hotplug state control" 1482 depends on DEBUG_KERNEL 1483 depends on HOTPLUG_CPU 1484 default n 1485 help 1486 Allows to write steps between "offline" and "online" to the CPUs 1487 sysfs target file so states can be stepped granular. This is a debug 1488 option for now as the hotplug machinery cannot be stopped and 1489 restarted at arbitrary points yet. 1490 1491 Say N if your are unsure. 1492 1493config NOTIFIER_ERROR_INJECTION 1494 tristate "Notifier error injection" 1495 depends on DEBUG_KERNEL 1496 select DEBUG_FS 1497 help 1498 This option provides the ability to inject artificial errors to 1499 specified notifier chain callbacks. It is useful to test the error 1500 handling of notifier call chain failures. 1501 1502 Say N if unsure. 1503 1504config CPU_NOTIFIER_ERROR_INJECT 1505 tristate "CPU notifier error injection module" 1506 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1507 help 1508 This option provides a kernel module that can be used to test 1509 the error handling of the cpu notifiers by injecting artificial 1510 errors to CPU notifier chain callbacks. It is controlled through 1511 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1512 1513 If the notifier call chain should be failed with some events 1514 notified, write the error code to "actions/<notifier event>/error". 1515 1516 Example: Inject CPU offline error (-1 == -EPERM) 1517 1518 # cd /sys/kernel/debug/notifier-error-inject/cpu 1519 # echo -1 > actions/CPU_DOWN_PREPARE/error 1520 # echo 0 > /sys/devices/system/cpu/cpu1/online 1521 bash: echo: write error: Operation not permitted 1522 1523 To compile this code as a module, choose M here: the module will 1524 be called cpu-notifier-error-inject. 1525 1526 If unsure, say N. 1527 1528config PM_NOTIFIER_ERROR_INJECT 1529 tristate "PM notifier error injection module" 1530 depends on PM && NOTIFIER_ERROR_INJECTION 1531 default m if PM_DEBUG 1532 help 1533 This option provides the ability to inject artificial errors to 1534 PM notifier chain callbacks. It is controlled through debugfs 1535 interface /sys/kernel/debug/notifier-error-inject/pm 1536 1537 If the notifier call chain should be failed with some events 1538 notified, write the error code to "actions/<notifier event>/error". 1539 1540 Example: Inject PM suspend error (-12 = -ENOMEM) 1541 1542 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1543 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1544 # echo mem > /sys/power/state 1545 bash: echo: write error: Cannot allocate memory 1546 1547 To compile this code as a module, choose M here: the module will 1548 be called pm-notifier-error-inject. 1549 1550 If unsure, say N. 1551 1552config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1553 tristate "OF reconfig notifier error injection module" 1554 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1555 help 1556 This option provides the ability to inject artificial errors to 1557 OF reconfig notifier chain callbacks. It is controlled 1558 through debugfs interface under 1559 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1560 1561 If the notifier call chain should be failed with some events 1562 notified, write the error code to "actions/<notifier event>/error". 1563 1564 To compile this code as a module, choose M here: the module will 1565 be called of-reconfig-notifier-error-inject. 1566 1567 If unsure, say N. 1568 1569config NETDEV_NOTIFIER_ERROR_INJECT 1570 tristate "Netdev notifier error injection module" 1571 depends on NET && NOTIFIER_ERROR_INJECTION 1572 help 1573 This option provides the ability to inject artificial errors to 1574 netdevice notifier chain callbacks. It is controlled through debugfs 1575 interface /sys/kernel/debug/notifier-error-inject/netdev 1576 1577 If the notifier call chain should be failed with some events 1578 notified, write the error code to "actions/<notifier event>/error". 1579 1580 Example: Inject netdevice mtu change error (-22 = -EINVAL) 1581 1582 # cd /sys/kernel/debug/notifier-error-inject/netdev 1583 # echo -22 > actions/NETDEV_CHANGEMTU/error 1584 # ip link set eth0 mtu 1024 1585 RTNETLINK answers: Invalid argument 1586 1587 To compile this code as a module, choose M here: the module will 1588 be called netdev-notifier-error-inject. 1589 1590 If unsure, say N. 1591 1592config FAULT_INJECTION 1593 bool "Fault-injection framework" 1594 depends on DEBUG_KERNEL 1595 help 1596 Provide fault-injection framework. 1597 For more details, see Documentation/fault-injection/. 1598 1599config FAILSLAB 1600 bool "Fault-injection capability for kmalloc" 1601 depends on FAULT_INJECTION 1602 depends on SLAB || SLUB 1603 help 1604 Provide fault-injection capability for kmalloc. 1605 1606config FAIL_PAGE_ALLOC 1607 bool "Fault-injection capabilitiy for alloc_pages()" 1608 depends on FAULT_INJECTION 1609 help 1610 Provide fault-injection capability for alloc_pages(). 1611 1612config FAIL_MAKE_REQUEST 1613 bool "Fault-injection capability for disk IO" 1614 depends on FAULT_INJECTION && BLOCK 1615 help 1616 Provide fault-injection capability for disk IO. 1617 1618config FAIL_IO_TIMEOUT 1619 bool "Fault-injection capability for faking disk interrupts" 1620 depends on FAULT_INJECTION && BLOCK 1621 help 1622 Provide fault-injection capability on end IO handling. This 1623 will make the block layer "forget" an interrupt as configured, 1624 thus exercising the error handling. 1625 1626 Only works with drivers that use the generic timeout handling, 1627 for others it wont do anything. 1628 1629config FAIL_MMC_REQUEST 1630 bool "Fault-injection capability for MMC IO" 1631 depends on FAULT_INJECTION_DEBUG_FS && MMC 1632 help 1633 Provide fault-injection capability for MMC IO. 1634 This will make the mmc core return data errors. This is 1635 useful to test the error handling in the mmc block device 1636 and to test how the mmc host driver handles retries from 1637 the block device. 1638 1639config FAIL_FUTEX 1640 bool "Fault-injection capability for futexes" 1641 select DEBUG_FS 1642 depends on FAULT_INJECTION && FUTEX 1643 help 1644 Provide fault-injection capability for futexes. 1645 1646config FAULT_INJECTION_DEBUG_FS 1647 bool "Debugfs entries for fault-injection capabilities" 1648 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1649 help 1650 Enable configuration of fault-injection capabilities via debugfs. 1651 1652config FAULT_INJECTION_STACKTRACE_FILTER 1653 bool "stacktrace filter for fault-injection capabilities" 1654 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1655 depends on !X86_64 1656 select STACKTRACE 1657 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1658 help 1659 Provide stacktrace filter for fault-injection capabilities 1660 1661config LATENCYTOP 1662 bool "Latency measuring infrastructure" 1663 depends on DEBUG_KERNEL 1664 depends on STACKTRACE_SUPPORT 1665 depends on PROC_FS 1666 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1667 select KALLSYMS 1668 select KALLSYMS_ALL 1669 select STACKTRACE 1670 select SCHEDSTATS 1671 select SCHED_DEBUG 1672 help 1673 Enable this option if you want to use the LatencyTOP tool 1674 to find out which userspace is blocking on what kernel operations. 1675 1676config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1677 bool 1678 1679config DEBUG_STRICT_USER_COPY_CHECKS 1680 bool "Strict user copy size checks" 1681 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1682 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING 1683 help 1684 Enabling this option turns a certain set of sanity checks for user 1685 copy operations into compile time failures. 1686 1687 The copy_from_user() etc checks are there to help test if there 1688 are sufficient security checks on the length argument of 1689 the copy operation, by having gcc prove that the argument is 1690 within bounds. 1691 1692 If unsure, say N. 1693 1694source kernel/trace/Kconfig 1695 1696menu "Runtime Testing" 1697 1698config LKDTM 1699 tristate "Linux Kernel Dump Test Tool Module" 1700 depends on DEBUG_FS 1701 depends on BLOCK 1702 default n 1703 help 1704 This module enables testing of the different dumping mechanisms by 1705 inducing system failures at predefined crash points. 1706 If you don't need it: say N 1707 Choose M here to compile this code as a module. The module will be 1708 called lkdtm. 1709 1710 Documentation on how to use the module can be found in 1711 Documentation/fault-injection/provoke-crashes.txt 1712 1713config TEST_LIST_SORT 1714 bool "Linked list sorting test" 1715 depends on DEBUG_KERNEL 1716 help 1717 Enable this to turn on 'list_sort()' function test. This test is 1718 executed only once during system boot, so affects only boot time. 1719 1720 If unsure, say N. 1721 1722config KPROBES_SANITY_TEST 1723 bool "Kprobes sanity tests" 1724 depends on DEBUG_KERNEL 1725 depends on KPROBES 1726 default n 1727 help 1728 This option provides for testing basic kprobes functionality on 1729 boot. A sample kprobe, jprobe and kretprobe are inserted and 1730 verified for functionality. 1731 1732 Say N if you are unsure. 1733 1734config BACKTRACE_SELF_TEST 1735 tristate "Self test for the backtrace code" 1736 depends on DEBUG_KERNEL 1737 default n 1738 help 1739 This option provides a kernel module that can be used to test 1740 the kernel stack backtrace code. This option is not useful 1741 for distributions or general kernels, but only for kernel 1742 developers working on architecture code. 1743 1744 Note that if you want to also test saved backtraces, you will 1745 have to enable STACKTRACE as well. 1746 1747 Say N if you are unsure. 1748 1749config RBTREE_TEST 1750 tristate "Red-Black tree test" 1751 depends on DEBUG_KERNEL 1752 help 1753 A benchmark measuring the performance of the rbtree library. 1754 Also includes rbtree invariant checks. 1755 1756config INTERVAL_TREE_TEST 1757 tristate "Interval tree test" 1758 depends on m && DEBUG_KERNEL 1759 select INTERVAL_TREE 1760 help 1761 A benchmark measuring the performance of the interval tree library 1762 1763config PERCPU_TEST 1764 tristate "Per cpu operations test" 1765 depends on m && DEBUG_KERNEL 1766 help 1767 Enable this option to build test module which validates per-cpu 1768 operations. 1769 1770 If unsure, say N. 1771 1772config ATOMIC64_SELFTEST 1773 bool "Perform an atomic64_t self-test at boot" 1774 help 1775 Enable this option to test the atomic64_t functions at boot. 1776 1777 If unsure, say N. 1778 1779config ASYNC_RAID6_TEST 1780 tristate "Self test for hardware accelerated raid6 recovery" 1781 depends on ASYNC_RAID6_RECOV 1782 select ASYNC_MEMCPY 1783 ---help--- 1784 This is a one-shot self test that permutes through the 1785 recovery of all the possible two disk failure scenarios for a 1786 N-disk array. Recovery is performed with the asynchronous 1787 raid6 recovery routines, and will optionally use an offload 1788 engine if one is available. 1789 1790 If unsure, say N. 1791 1792config TEST_HEXDUMP 1793 tristate "Test functions located in the hexdump module at runtime" 1794 1795config TEST_STRING_HELPERS 1796 tristate "Test functions located in the string_helpers module at runtime" 1797 1798config TEST_KSTRTOX 1799 tristate "Test kstrto*() family of functions at runtime" 1800 1801config TEST_PRINTF 1802 tristate "Test printf() family of functions at runtime" 1803 1804config TEST_BITMAP 1805 tristate "Test bitmap_*() family of functions at runtime" 1806 default n 1807 help 1808 Enable this option to test the bitmap functions at boot. 1809 1810 If unsure, say N. 1811 1812config TEST_UUID 1813 tristate "Test functions located in the uuid module at runtime" 1814 1815config TEST_RHASHTABLE 1816 tristate "Perform selftest on resizable hash table" 1817 default n 1818 help 1819 Enable this option to test the rhashtable functions at boot. 1820 1821 If unsure, say N. 1822 1823config TEST_HASH 1824 tristate "Perform selftest on hash functions" 1825 default n 1826 help 1827 Enable this option to test the kernel's integer (<linux/hash,h>) 1828 and string (<linux/stringhash.h>) hash functions on boot 1829 (or module load). 1830 1831 This is intended to help people writing architecture-specific 1832 optimized versions. If unsure, say N. 1833 1834endmenu # runtime tests 1835 1836config PROVIDE_OHCI1394_DMA_INIT 1837 bool "Remote debugging over FireWire early on boot" 1838 depends on PCI && X86 1839 help 1840 If you want to debug problems which hang or crash the kernel early 1841 on boot and the crashing machine has a FireWire port, you can use 1842 this feature to remotely access the memory of the crashed machine 1843 over FireWire. This employs remote DMA as part of the OHCI1394 1844 specification which is now the standard for FireWire controllers. 1845 1846 With remote DMA, you can monitor the printk buffer remotely using 1847 firescope and access all memory below 4GB using fireproxy from gdb. 1848 Even controlling a kernel debugger is possible using remote DMA. 1849 1850 Usage: 1851 1852 If ohci1394_dma=early is used as boot parameter, it will initialize 1853 all OHCI1394 controllers which are found in the PCI config space. 1854 1855 As all changes to the FireWire bus such as enabling and disabling 1856 devices cause a bus reset and thereby disable remote DMA for all 1857 devices, be sure to have the cable plugged and FireWire enabled on 1858 the debugging host before booting the debug target for debugging. 1859 1860 This code (~1k) is freed after boot. By then, the firewire stack 1861 in charge of the OHCI-1394 controllers should be used instead. 1862 1863 See Documentation/debugging-via-ohci1394.txt for more information. 1864 1865config BUILD_DOCSRC 1866 bool "Build targets in Documentation/ tree" 1867 depends on HEADERS_CHECK 1868 help 1869 This option attempts to build objects from the source files in the 1870 kernel Documentation/ tree. 1871 1872 Say N if you are unsure. 1873 1874config DMA_API_DEBUG 1875 bool "Enable debugging of DMA-API usage" 1876 depends on HAVE_DMA_API_DEBUG 1877 help 1878 Enable this option to debug the use of the DMA API by device drivers. 1879 With this option you will be able to detect common bugs in device 1880 drivers like double-freeing of DMA mappings or freeing mappings that 1881 were never allocated. 1882 1883 This also attempts to catch cases where a page owned by DMA is 1884 accessed by the cpu in a way that could cause data corruption. For 1885 example, this enables cow_user_page() to check that the source page is 1886 not undergoing DMA. 1887 1888 This option causes a performance degradation. Use only if you want to 1889 debug device drivers and dma interactions. 1890 1891 If unsure, say N. 1892 1893config TEST_LKM 1894 tristate "Test module loading with 'hello world' module" 1895 default n 1896 depends on m 1897 help 1898 This builds the "test_module" module that emits "Hello, world" 1899 on printk when loaded. It is designed to be used for basic 1900 evaluation of the module loading subsystem (for example when 1901 validating module verification). It lacks any extra dependencies, 1902 and will not normally be loaded by the system unless explicitly 1903 requested by name. 1904 1905 If unsure, say N. 1906 1907config TEST_USER_COPY 1908 tristate "Test user/kernel boundary protections" 1909 default n 1910 depends on m 1911 help 1912 This builds the "test_user_copy" module that runs sanity checks 1913 on the copy_to/from_user infrastructure, making sure basic 1914 user/kernel boundary testing is working. If it fails to load, 1915 a regression has been detected in the user/kernel memory boundary 1916 protections. 1917 1918 If unsure, say N. 1919 1920config TEST_BPF 1921 tristate "Test BPF filter functionality" 1922 default n 1923 depends on m && NET 1924 help 1925 This builds the "test_bpf" module that runs various test vectors 1926 against the BPF interpreter or BPF JIT compiler depending on the 1927 current setting. This is in particular useful for BPF JIT compiler 1928 development, but also to run regression tests against changes in 1929 the interpreter code. It also enables test stubs for eBPF maps and 1930 verifier used by user space verifier testsuite. 1931 1932 If unsure, say N. 1933 1934config TEST_FIRMWARE 1935 tristate "Test firmware loading via userspace interface" 1936 default n 1937 depends on FW_LOADER 1938 help 1939 This builds the "test_firmware" module that creates a userspace 1940 interface for testing firmware loading. This can be used to 1941 control the triggering of firmware loading without needing an 1942 actual firmware-using device. The contents can be rechecked by 1943 userspace. 1944 1945 If unsure, say N. 1946 1947config TEST_UDELAY 1948 tristate "udelay test driver" 1949 default n 1950 help 1951 This builds the "udelay_test" module that helps to make sure 1952 that udelay() is working properly. 1953 1954 If unsure, say N. 1955 1956config MEMTEST 1957 bool "Memtest" 1958 depends on HAVE_MEMBLOCK 1959 ---help--- 1960 This option adds a kernel parameter 'memtest', which allows memtest 1961 to be set. 1962 memtest=0, mean disabled; -- default 1963 memtest=1, mean do 1 test pattern; 1964 ... 1965 memtest=17, mean do 17 test patterns. 1966 If you are unsure how to answer this question, answer N. 1967 1968config TEST_STATIC_KEYS 1969 tristate "Test static keys" 1970 default n 1971 depends on m 1972 help 1973 Test the static key interfaces. 1974 1975 If unsure, say N. 1976 1977source "samples/Kconfig" 1978 1979source "lib/Kconfig.kgdb" 1980 1981source "lib/Kconfig.ubsan" 1982 1983config ARCH_HAS_DEVMEM_IS_ALLOWED 1984 bool 1985 1986config STRICT_DEVMEM 1987 bool "Filter access to /dev/mem" 1988 depends on MMU 1989 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 1990 default y if TILE || PPC 1991 ---help--- 1992 If this option is disabled, you allow userspace (root) access to all 1993 of memory, including kernel and userspace memory. Accidental 1994 access to this is obviously disastrous, but specific access can 1995 be used by people debugging the kernel. Note that with PAT support 1996 enabled, even in this case there are restrictions on /dev/mem 1997 use due to the cache aliasing requirements. 1998 1999 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 2000 file only allows userspace access to PCI space and the BIOS code and 2001 data regions. This is sufficient for dosemu and X and all common 2002 users of /dev/mem. 2003 2004 If in doubt, say Y. 2005 2006config IO_STRICT_DEVMEM 2007 bool "Filter I/O access to /dev/mem" 2008 depends on STRICT_DEVMEM 2009 ---help--- 2010 If this option is disabled, you allow userspace (root) access to all 2011 io-memory regardless of whether a driver is actively using that 2012 range. Accidental access to this is obviously disastrous, but 2013 specific access can be used by people debugging kernel drivers. 2014 2015 If this option is switched on, the /dev/mem file only allows 2016 userspace access to *idle* io-memory ranges (see /proc/iomem) This 2017 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 2018 if the driver using a given range cannot be disabled. 2019 2020 If in doubt, say Y. 2021