1menu "Kernel hacking" 2 3menu "printk and dmesg options" 4 5config PRINTK_TIME 6 bool "Show timing information on printks" 7 depends on PRINTK 8 help 9 Selecting this option causes time stamps of the printk() 10 messages to be added to the output of the syslog() system 11 call and at the console. 12 13 The timestamp is always recorded internally, and exported 14 to /dev/kmsg. This flag just specifies if the timestamp should 15 be included, not that the timestamp is recorded. 16 17 The behavior is also controlled by the kernel command line 18 parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst 19 20config CONSOLE_LOGLEVEL_DEFAULT 21 int "Default console loglevel (1-15)" 22 range 1 15 23 default "7" 24 help 25 Default loglevel to determine what will be printed on the console. 26 27 Setting a default here is equivalent to passing in loglevel=<x> in 28 the kernel bootargs. loglevel=<x> continues to override whatever 29 value is specified here as well. 30 31 Note: This does not affect the log level of un-prefixed printk() 32 usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT 33 option. 34 35config CONSOLE_LOGLEVEL_QUIET 36 int "quiet console loglevel (1-15)" 37 range 1 15 38 default "4" 39 help 40 loglevel to use when "quiet" is passed on the kernel commandline. 41 42 When "quiet" is passed on the kernel commandline this loglevel 43 will be used as the loglevel. IOW passing "quiet" will be the 44 equivalent of passing "loglevel=<CONSOLE_LOGLEVEL_QUIET>" 45 46config MESSAGE_LOGLEVEL_DEFAULT 47 int "Default message log level (1-7)" 48 range 1 7 49 default "4" 50 help 51 Default log level for printk statements with no specified priority. 52 53 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks 54 that are auditing their logs closely may want to set it to a lower 55 priority. 56 57 Note: This does not affect what message level gets printed on the console 58 by default. To change that, use loglevel=<x> in the kernel bootargs, 59 or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value. 60 61config BOOT_PRINTK_DELAY 62 bool "Delay each boot printk message by N milliseconds" 63 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 64 help 65 This build option allows you to read kernel boot messages 66 by inserting a short delay after each one. The delay is 67 specified in milliseconds on the kernel command line, 68 using "boot_delay=N". 69 70 It is likely that you would also need to use "lpj=M" to preset 71 the "loops per jiffie" value. 72 See a previous boot log for the "lpj" value to use for your 73 system, and then set "lpj=M" before setting "boot_delay=N". 74 NOTE: Using this option may adversely affect SMP systems. 75 I.e., processors other than the first one may not boot up. 76 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect 77 what it believes to be lockup conditions. 78 79config DYNAMIC_DEBUG 80 bool "Enable dynamic printk() support" 81 default n 82 depends on PRINTK 83 depends on DEBUG_FS 84 help 85 86 Compiles debug level messages into the kernel, which would not 87 otherwise be available at runtime. These messages can then be 88 enabled/disabled based on various levels of scope - per source file, 89 function, module, format string, and line number. This mechanism 90 implicitly compiles in all pr_debug() and dev_dbg() calls, which 91 enlarges the kernel text size by about 2%. 92 93 If a source file is compiled with DEBUG flag set, any 94 pr_debug() calls in it are enabled by default, but can be 95 disabled at runtime as below. Note that DEBUG flag is 96 turned on by many CONFIG_*DEBUG* options. 97 98 Usage: 99 100 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 101 which is contained in the 'debugfs' filesystem. Thus, the debugfs 102 filesystem must first be mounted before making use of this feature. 103 We refer the control file as: <debugfs>/dynamic_debug/control. This 104 file contains a list of the debug statements that can be enabled. The 105 format for each line of the file is: 106 107 filename:lineno [module]function flags format 108 109 filename : source file of the debug statement 110 lineno : line number of the debug statement 111 module : module that contains the debug statement 112 function : function that contains the debug statement 113 flags : '=p' means the line is turned 'on' for printing 114 format : the format used for the debug statement 115 116 From a live system: 117 118 nullarbor:~ # cat <debugfs>/dynamic_debug/control 119 # filename:lineno [module]function flags format 120 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012" 121 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012" 122 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012" 123 124 Example usage: 125 126 // enable the message at line 1603 of file svcsock.c 127 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 128 <debugfs>/dynamic_debug/control 129 130 // enable all the messages in file svcsock.c 131 nullarbor:~ # echo -n 'file svcsock.c +p' > 132 <debugfs>/dynamic_debug/control 133 134 // enable all the messages in the NFS server module 135 nullarbor:~ # echo -n 'module nfsd +p' > 136 <debugfs>/dynamic_debug/control 137 138 // enable all 12 messages in the function svc_process() 139 nullarbor:~ # echo -n 'func svc_process +p' > 140 <debugfs>/dynamic_debug/control 141 142 // disable all 12 messages in the function svc_process() 143 nullarbor:~ # echo -n 'func svc_process -p' > 144 <debugfs>/dynamic_debug/control 145 146 See Documentation/admin-guide/dynamic-debug-howto.rst for additional 147 information. 148 149endmenu # "printk and dmesg options" 150 151menu "Compile-time checks and compiler options" 152 153config DEBUG_INFO 154 bool "Compile the kernel with debug info" 155 depends on DEBUG_KERNEL && !COMPILE_TEST 156 help 157 If you say Y here the resulting kernel image will include 158 debugging info resulting in a larger kernel image. 159 This adds debug symbols to the kernel and modules (gcc -g), and 160 is needed if you intend to use kernel crashdump or binary object 161 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 162 Say Y here only if you plan to debug the kernel. 163 164 If unsure, say N. 165 166config DEBUG_INFO_REDUCED 167 bool "Reduce debugging information" 168 depends on DEBUG_INFO 169 help 170 If you say Y here gcc is instructed to generate less debugging 171 information for structure types. This means that tools that 172 need full debugging information (like kgdb or systemtap) won't 173 be happy. But if you merely need debugging information to 174 resolve line numbers there is no loss. Advantage is that 175 build directory object sizes shrink dramatically over a full 176 DEBUG_INFO build and compile times are reduced too. 177 Only works with newer gcc versions. 178 179config DEBUG_INFO_SPLIT 180 bool "Produce split debuginfo in .dwo files" 181 depends on DEBUG_INFO 182 help 183 Generate debug info into separate .dwo files. This significantly 184 reduces the build directory size for builds with DEBUG_INFO, 185 because it stores the information only once on disk in .dwo 186 files instead of multiple times in object files and executables. 187 In addition the debug information is also compressed. 188 189 Requires recent gcc (4.7+) and recent gdb/binutils. 190 Any tool that packages or reads debug information would need 191 to know about the .dwo files and include them. 192 Incompatible with older versions of ccache. 193 194config DEBUG_INFO_DWARF4 195 bool "Generate dwarf4 debuginfo" 196 depends on DEBUG_INFO 197 help 198 Generate dwarf4 debug info. This requires recent versions 199 of gcc and gdb. It makes the debug information larger. 200 But it significantly improves the success of resolving 201 variables in gdb on optimized code. 202 203config GDB_SCRIPTS 204 bool "Provide GDB scripts for kernel debugging" 205 depends on DEBUG_INFO 206 help 207 This creates the required links to GDB helper scripts in the 208 build directory. If you load vmlinux into gdb, the helper 209 scripts will be automatically imported by gdb as well, and 210 additional functions are available to analyze a Linux kernel 211 instance. See Documentation/dev-tools/gdb-kernel-debugging.rst 212 for further details. 213 214config ENABLE_MUST_CHECK 215 bool "Enable __must_check logic" 216 default y 217 help 218 Enable the __must_check logic in the kernel build. Disable this to 219 suppress the "warning: ignoring return value of 'foo', declared with 220 attribute warn_unused_result" messages. 221 222config FRAME_WARN 223 int "Warn for stack frames larger than (needs gcc 4.4)" 224 range 0 8192 225 default 3072 if KASAN_EXTRA 226 default 2048 if GCC_PLUGIN_LATENT_ENTROPY 227 default 1280 if (!64BIT && PARISC) 228 default 1024 if (!64BIT && !PARISC) 229 default 2048 if 64BIT 230 help 231 Tell gcc to warn at build time for stack frames larger than this. 232 Setting this too low will cause a lot of warnings. 233 Setting it to 0 disables the warning. 234 Requires gcc 4.4 235 236config STRIP_ASM_SYMS 237 bool "Strip assembler-generated symbols during link" 238 default n 239 help 240 Strip internal assembler-generated symbols during a link (symbols 241 that look like '.Lxxx') so they don't pollute the output of 242 get_wchan() and suchlike. 243 244config READABLE_ASM 245 bool "Generate readable assembler code" 246 depends on DEBUG_KERNEL 247 help 248 Disable some compiler optimizations that tend to generate human unreadable 249 assembler output. This may make the kernel slightly slower, but it helps 250 to keep kernel developers who have to stare a lot at assembler listings 251 sane. 252 253config UNUSED_SYMBOLS 254 bool "Enable unused/obsolete exported symbols" 255 default y if X86 256 help 257 Unused but exported symbols make the kernel needlessly bigger. For 258 that reason most of these unused exports will soon be removed. This 259 option is provided temporarily to provide a transition period in case 260 some external kernel module needs one of these symbols anyway. If you 261 encounter such a case in your module, consider if you are actually 262 using the right API. (rationale: since nobody in the kernel is using 263 this in a module, there is a pretty good chance it's actually the 264 wrong interface to use). If you really need the symbol, please send a 265 mail to the linux kernel mailing list mentioning the symbol and why 266 you really need it, and what the merge plan to the mainline kernel for 267 your module is. 268 269config PAGE_OWNER 270 bool "Track page owner" 271 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 272 select DEBUG_FS 273 select STACKTRACE 274 select STACKDEPOT 275 select PAGE_EXTENSION 276 help 277 This keeps track of what call chain is the owner of a page, may 278 help to find bare alloc_page(s) leaks. Even if you include this 279 feature on your build, it is disabled in default. You should pass 280 "page_owner=on" to boot parameter in order to enable it. Eats 281 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 282 for user-space helper. 283 284 If unsure, say N. 285 286config DEBUG_FS 287 bool "Debug Filesystem" 288 help 289 debugfs is a virtual file system that kernel developers use to put 290 debugging files into. Enable this option to be able to read and 291 write to these files. 292 293 For detailed documentation on the debugfs API, see 294 Documentation/filesystems/. 295 296 If unsure, say N. 297 298config HEADERS_CHECK 299 bool "Run 'make headers_check' when building vmlinux" 300 depends on !UML 301 help 302 This option will extract the user-visible kernel headers whenever 303 building the kernel, and will run basic sanity checks on them to 304 ensure that exported files do not attempt to include files which 305 were not exported, etc. 306 307 If you're making modifications to header files which are 308 relevant for userspace, say 'Y', and check the headers 309 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 310 your build tree), to make sure they're suitable. 311 312config DEBUG_SECTION_MISMATCH 313 bool "Enable full Section mismatch analysis" 314 help 315 The section mismatch analysis checks if there are illegal 316 references from one section to another section. 317 During linktime or runtime, some sections are dropped; 318 any use of code/data previously in these sections would 319 most likely result in an oops. 320 In the code, functions and variables are annotated with 321 __init,, etc. (see the full list in include/linux/init.h), 322 which results in the code/data being placed in specific sections. 323 The section mismatch analysis is always performed after a full 324 kernel build, and enabling this option causes the following 325 additional steps to occur: 326 - Add the option -fno-inline-functions-called-once to gcc commands. 327 When inlining a function annotated with __init in a non-init 328 function, we would lose the section information and thus 329 the analysis would not catch the illegal reference. 330 This option tells gcc to inline less (but it does result in 331 a larger kernel). 332 - Run the section mismatch analysis for each module/built-in.a file. 333 When we run the section mismatch analysis on vmlinux.o, we 334 lose valuable information about where the mismatch was 335 introduced. 336 Running the analysis for each module/built-in.a file 337 tells where the mismatch happens much closer to the 338 source. The drawback is that the same mismatch is 339 reported at least twice. 340 - Enable verbose reporting from modpost in order to help resolve 341 the section mismatches that are reported. 342 343config SECTION_MISMATCH_WARN_ONLY 344 bool "Make section mismatch errors non-fatal" 345 default y 346 help 347 If you say N here, the build process will fail if there are any 348 section mismatch, instead of just throwing warnings. 349 350 If unsure, say Y. 351 352# 353# Select this config option from the architecture Kconfig, if it 354# is preferred to always offer frame pointers as a config 355# option on the architecture (regardless of KERNEL_DEBUG): 356# 357config ARCH_WANT_FRAME_POINTERS 358 bool 359 360config FRAME_POINTER 361 bool "Compile the kernel with frame pointers" 362 depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS 363 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 364 help 365 If you say Y here the resulting kernel image will be slightly 366 larger and slower, but it gives very useful debugging information 367 in case of kernel bugs. (precise oopses/stacktraces/warnings) 368 369config STACK_VALIDATION 370 bool "Compile-time stack metadata validation" 371 depends on HAVE_STACK_VALIDATION 372 default n 373 help 374 Add compile-time checks to validate stack metadata, including frame 375 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure 376 that runtime stack traces are more reliable. 377 378 This is also a prerequisite for generation of ORC unwind data, which 379 is needed for CONFIG_UNWINDER_ORC. 380 381 For more information, see 382 tools/objtool/Documentation/stack-validation.txt. 383 384config DEBUG_FORCE_WEAK_PER_CPU 385 bool "Force weak per-cpu definitions" 386 depends on DEBUG_KERNEL 387 help 388 s390 and alpha require percpu variables in modules to be 389 defined weak to work around addressing range issue which 390 puts the following two restrictions on percpu variable 391 definitions. 392 393 1. percpu symbols must be unique whether static or not 394 2. percpu variables can't be defined inside a function 395 396 To ensure that generic code follows the above rules, this 397 option forces all percpu variables to be defined as weak. 398 399endmenu # "Compiler options" 400 401config MAGIC_SYSRQ 402 bool "Magic SysRq key" 403 depends on !UML 404 help 405 If you say Y here, you will have some control over the system even 406 if the system crashes for example during kernel debugging (e.g., you 407 will be able to flush the buffer cache to disk, reboot the system 408 immediately or dump some status information). This is accomplished 409 by pressing various keys while holding SysRq (Alt+PrintScreen). It 410 also works on a serial console (on PC hardware at least), if you 411 send a BREAK and then within 5 seconds a command keypress. The 412 keys are documented in <file:Documentation/admin-guide/sysrq.rst>. 413 Don't say Y unless you really know what this hack does. 414 415config MAGIC_SYSRQ_DEFAULT_ENABLE 416 hex "Enable magic SysRq key functions by default" 417 depends on MAGIC_SYSRQ 418 default 0x1 419 help 420 Specifies which SysRq key functions are enabled by default. 421 This may be set to 1 or 0 to enable or disable them all, or 422 to a bitmask as described in Documentation/admin-guide/sysrq.rst. 423 424config MAGIC_SYSRQ_SERIAL 425 bool "Enable magic SysRq key over serial" 426 depends on MAGIC_SYSRQ 427 default y 428 help 429 Many embedded boards have a disconnected TTL level serial which can 430 generate some garbage that can lead to spurious false sysrq detects. 431 This option allows you to decide whether you want to enable the 432 magic SysRq key. 433 434config DEBUG_KERNEL 435 bool "Kernel debugging" 436 help 437 Say Y here if you are developing drivers or trying to debug and 438 identify kernel problems. 439 440menu "Memory Debugging" 441 442source "mm/Kconfig.debug" 443 444config DEBUG_OBJECTS 445 bool "Debug object operations" 446 depends on DEBUG_KERNEL 447 help 448 If you say Y here, additional code will be inserted into the 449 kernel to track the life time of various objects and validate 450 the operations on those objects. 451 452config DEBUG_OBJECTS_SELFTEST 453 bool "Debug objects selftest" 454 depends on DEBUG_OBJECTS 455 help 456 This enables the selftest of the object debug code. 457 458config DEBUG_OBJECTS_FREE 459 bool "Debug objects in freed memory" 460 depends on DEBUG_OBJECTS 461 help 462 This enables checks whether a k/v free operation frees an area 463 which contains an object which has not been deactivated 464 properly. This can make kmalloc/kfree-intensive workloads 465 much slower. 466 467config DEBUG_OBJECTS_TIMERS 468 bool "Debug timer objects" 469 depends on DEBUG_OBJECTS 470 help 471 If you say Y here, additional code will be inserted into the 472 timer routines to track the life time of timer objects and 473 validate the timer operations. 474 475config DEBUG_OBJECTS_WORK 476 bool "Debug work objects" 477 depends on DEBUG_OBJECTS 478 help 479 If you say Y here, additional code will be inserted into the 480 work queue routines to track the life time of work objects and 481 validate the work operations. 482 483config DEBUG_OBJECTS_RCU_HEAD 484 bool "Debug RCU callbacks objects" 485 depends on DEBUG_OBJECTS 486 help 487 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 488 489config DEBUG_OBJECTS_PERCPU_COUNTER 490 bool "Debug percpu counter objects" 491 depends on DEBUG_OBJECTS 492 help 493 If you say Y here, additional code will be inserted into the 494 percpu counter routines to track the life time of percpu counter 495 objects and validate the percpu counter operations. 496 497config DEBUG_OBJECTS_ENABLE_DEFAULT 498 int "debug_objects bootup default value (0-1)" 499 range 0 1 500 default "1" 501 depends on DEBUG_OBJECTS 502 help 503 Debug objects boot parameter default value 504 505config DEBUG_SLAB 506 bool "Debug slab memory allocations" 507 depends on DEBUG_KERNEL && SLAB 508 help 509 Say Y here to have the kernel do limited verification on memory 510 allocation as well as poisoning memory on free to catch use of freed 511 memory. This can make kmalloc/kfree-intensive workloads much slower. 512 513config DEBUG_SLAB_LEAK 514 bool "Memory leak debugging" 515 depends on DEBUG_SLAB 516 517config SLUB_DEBUG_ON 518 bool "SLUB debugging on by default" 519 depends on SLUB && SLUB_DEBUG 520 default n 521 help 522 Boot with debugging on by default. SLUB boots by default with 523 the runtime debug capabilities switched off. Enabling this is 524 equivalent to specifying the "slub_debug" parameter on boot. 525 There is no support for more fine grained debug control like 526 possible with slub_debug=xxx. SLUB debugging may be switched 527 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 528 "slub_debug=-". 529 530config SLUB_STATS 531 default n 532 bool "Enable SLUB performance statistics" 533 depends on SLUB && SYSFS 534 help 535 SLUB statistics are useful to debug SLUBs allocation behavior in 536 order find ways to optimize the allocator. This should never be 537 enabled for production use since keeping statistics slows down 538 the allocator by a few percentage points. The slabinfo command 539 supports the determination of the most active slabs to figure 540 out which slabs are relevant to a particular load. 541 Try running: slabinfo -DA 542 543config HAVE_DEBUG_KMEMLEAK 544 bool 545 546config DEBUG_KMEMLEAK 547 bool "Kernel memory leak detector" 548 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 549 select DEBUG_FS 550 select STACKTRACE if STACKTRACE_SUPPORT 551 select KALLSYMS 552 select CRC32 553 help 554 Say Y here if you want to enable the memory leak 555 detector. The memory allocation/freeing is traced in a way 556 similar to the Boehm's conservative garbage collector, the 557 difference being that the orphan objects are not freed but 558 only shown in /sys/kernel/debug/kmemleak. Enabling this 559 feature will introduce an overhead to memory 560 allocations. See Documentation/dev-tools/kmemleak.rst for more 561 details. 562 563 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 564 of finding leaks due to the slab objects poisoning. 565 566 In order to access the kmemleak file, debugfs needs to be 567 mounted (usually at /sys/kernel/debug). 568 569config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 570 int "Maximum kmemleak early log entries" 571 depends on DEBUG_KMEMLEAK 572 range 200 40000 573 default 400 574 help 575 Kmemleak must track all the memory allocations to avoid 576 reporting false positives. Since memory may be allocated or 577 freed before kmemleak is initialised, an early log buffer is 578 used to store these actions. If kmemleak reports "early log 579 buffer exceeded", please increase this value. 580 581config DEBUG_KMEMLEAK_TEST 582 tristate "Simple test for the kernel memory leak detector" 583 depends on DEBUG_KMEMLEAK && m 584 help 585 This option enables a module that explicitly leaks memory. 586 587 If unsure, say N. 588 589config DEBUG_KMEMLEAK_DEFAULT_OFF 590 bool "Default kmemleak to off" 591 depends on DEBUG_KMEMLEAK 592 help 593 Say Y here to disable kmemleak by default. It can then be enabled 594 on the command line via kmemleak=on. 595 596config DEBUG_KMEMLEAK_AUTO_SCAN 597 bool "Enable kmemleak auto scan thread on boot up" 598 default y 599 depends on DEBUG_KMEMLEAK 600 help 601 Depending on the cpu, kmemleak scan may be cpu intensive and can 602 stall user tasks at times. This option enables/disables automatic 603 kmemleak scan at boot up. 604 605 Say N here to disable kmemleak auto scan thread to stop automatic 606 scanning. Disabling this option disables automatic reporting of 607 memory leaks. 608 609 If unsure, say Y. 610 611config DEBUG_STACK_USAGE 612 bool "Stack utilization instrumentation" 613 depends on DEBUG_KERNEL && !IA64 614 help 615 Enables the display of the minimum amount of free stack which each 616 task has ever had available in the sysrq-T and sysrq-P debug output. 617 618 This option will slow down process creation somewhat. 619 620config DEBUG_VM 621 bool "Debug VM" 622 depends on DEBUG_KERNEL 623 help 624 Enable this to turn on extended checks in the virtual-memory system 625 that may impact performance. 626 627 If unsure, say N. 628 629config DEBUG_VM_VMACACHE 630 bool "Debug VMA caching" 631 depends on DEBUG_VM 632 help 633 Enable this to turn on VMA caching debug information. Doing so 634 can cause significant overhead, so only enable it in non-production 635 environments. 636 637 If unsure, say N. 638 639config DEBUG_VM_RB 640 bool "Debug VM red-black trees" 641 depends on DEBUG_VM 642 help 643 Enable VM red-black tree debugging information and extra validations. 644 645 If unsure, say N. 646 647config DEBUG_VM_PGFLAGS 648 bool "Debug page-flags operations" 649 depends on DEBUG_VM 650 help 651 Enables extra validation on page flags operations. 652 653 If unsure, say N. 654 655config ARCH_HAS_DEBUG_VIRTUAL 656 bool 657 658config DEBUG_VIRTUAL 659 bool "Debug VM translations" 660 depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL 661 help 662 Enable some costly sanity checks in virtual to page code. This can 663 catch mistakes with virt_to_page() and friends. 664 665 If unsure, say N. 666 667config DEBUG_NOMMU_REGIONS 668 bool "Debug the global anon/private NOMMU mapping region tree" 669 depends on DEBUG_KERNEL && !MMU 670 help 671 This option causes the global tree of anonymous and private mapping 672 regions to be regularly checked for invalid topology. 673 674config DEBUG_MEMORY_INIT 675 bool "Debug memory initialisation" if EXPERT 676 default !EXPERT 677 help 678 Enable this for additional checks during memory initialisation. 679 The sanity checks verify aspects of the VM such as the memory model 680 and other information provided by the architecture. Verbose 681 information will be printed at KERN_DEBUG loglevel depending 682 on the mminit_loglevel= command-line option. 683 684 If unsure, say Y 685 686config MEMORY_NOTIFIER_ERROR_INJECT 687 tristate "Memory hotplug notifier error injection module" 688 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 689 help 690 This option provides the ability to inject artificial errors to 691 memory hotplug notifier chain callbacks. It is controlled through 692 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 693 694 If the notifier call chain should be failed with some events 695 notified, write the error code to "actions/<notifier event>/error". 696 697 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 698 699 # cd /sys/kernel/debug/notifier-error-inject/memory 700 # echo -12 > actions/MEM_GOING_OFFLINE/error 701 # echo offline > /sys/devices/system/memory/memoryXXX/state 702 bash: echo: write error: Cannot allocate memory 703 704 To compile this code as a module, choose M here: the module will 705 be called memory-notifier-error-inject. 706 707 If unsure, say N. 708 709config DEBUG_PER_CPU_MAPS 710 bool "Debug access to per_cpu maps" 711 depends on DEBUG_KERNEL 712 depends on SMP 713 help 714 Say Y to verify that the per_cpu map being accessed has 715 been set up. This adds a fair amount of code to kernel memory 716 and decreases performance. 717 718 Say N if unsure. 719 720config DEBUG_HIGHMEM 721 bool "Highmem debugging" 722 depends on DEBUG_KERNEL && HIGHMEM 723 help 724 This option enables additional error checking for high memory 725 systems. Disable for production systems. 726 727config HAVE_DEBUG_STACKOVERFLOW 728 bool 729 730config DEBUG_STACKOVERFLOW 731 bool "Check for stack overflows" 732 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 733 ---help--- 734 Say Y here if you want to check for overflows of kernel, IRQ 735 and exception stacks (if your architecture uses them). This 736 option will show detailed messages if free stack space drops 737 below a certain limit. 738 739 These kinds of bugs usually occur when call-chains in the 740 kernel get too deep, especially when interrupts are 741 involved. 742 743 Use this in cases where you see apparently random memory 744 corruption, especially if it appears in 'struct thread_info' 745 746 If in doubt, say "N". 747 748source "lib/Kconfig.kasan" 749 750endmenu # "Memory Debugging" 751 752config ARCH_HAS_KCOV 753 bool 754 help 755 KCOV does not have any arch-specific code, but currently it is enabled 756 only for x86_64. KCOV requires testing on other archs, and most likely 757 disabling of instrumentation for some early boot code. 758 759config CC_HAS_SANCOV_TRACE_PC 760 def_bool $(cc-option,-fsanitize-coverage=trace-pc) 761 762config KCOV 763 bool "Code coverage for fuzzing" 764 depends on ARCH_HAS_KCOV 765 depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS 766 select DEBUG_FS 767 select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC 768 help 769 KCOV exposes kernel code coverage information in a form suitable 770 for coverage-guided fuzzing (randomized testing). 771 772 If RANDOMIZE_BASE is enabled, PC values will not be stable across 773 different machines and across reboots. If you need stable PC values, 774 disable RANDOMIZE_BASE. 775 776 For more details, see Documentation/dev-tools/kcov.rst. 777 778config KCOV_ENABLE_COMPARISONS 779 bool "Enable comparison operands collection by KCOV" 780 depends on KCOV 781 depends on $(cc-option,-fsanitize-coverage=trace-cmp) 782 help 783 KCOV also exposes operands of every comparison in the instrumented 784 code along with operand sizes and PCs of the comparison instructions. 785 These operands can be used by fuzzing engines to improve the quality 786 of fuzzing coverage. 787 788config KCOV_INSTRUMENT_ALL 789 bool "Instrument all code by default" 790 depends on KCOV 791 default y 792 help 793 If you are doing generic system call fuzzing (like e.g. syzkaller), 794 then you will want to instrument the whole kernel and you should 795 say y here. If you are doing more targeted fuzzing (like e.g. 796 filesystem fuzzing with AFL) then you will want to enable coverage 797 for more specific subsets of files, and should say n here. 798 799config DEBUG_SHIRQ 800 bool "Debug shared IRQ handlers" 801 depends on DEBUG_KERNEL 802 help 803 Enable this to generate a spurious interrupt as soon as a shared 804 interrupt handler is registered, and just before one is deregistered. 805 Drivers ought to be able to handle interrupts coming in at those 806 points; some don't and need to be caught. 807 808menu "Debug Lockups and Hangs" 809 810config LOCKUP_DETECTOR 811 bool 812 813config SOFTLOCKUP_DETECTOR 814 bool "Detect Soft Lockups" 815 depends on DEBUG_KERNEL && !S390 816 select LOCKUP_DETECTOR 817 help 818 Say Y here to enable the kernel to act as a watchdog to detect 819 soft lockups. 820 821 Softlockups are bugs that cause the kernel to loop in kernel 822 mode for more than 20 seconds, without giving other tasks a 823 chance to run. The current stack trace is displayed upon 824 detection and the system will stay locked up. 825 826config BOOTPARAM_SOFTLOCKUP_PANIC 827 bool "Panic (Reboot) On Soft Lockups" 828 depends on SOFTLOCKUP_DETECTOR 829 help 830 Say Y here to enable the kernel to panic on "soft lockups", 831 which are bugs that cause the kernel to loop in kernel 832 mode for more than 20 seconds (configurable using the watchdog_thresh 833 sysctl), without giving other tasks a chance to run. 834 835 The panic can be used in combination with panic_timeout, 836 to cause the system to reboot automatically after a 837 lockup has been detected. This feature is useful for 838 high-availability systems that have uptime guarantees and 839 where a lockup must be resolved ASAP. 840 841 Say N if unsure. 842 843config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 844 int 845 depends on SOFTLOCKUP_DETECTOR 846 range 0 1 847 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 848 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 849 850config HARDLOCKUP_DETECTOR_PERF 851 bool 852 select SOFTLOCKUP_DETECTOR 853 854# 855# Enables a timestamp based low pass filter to compensate for perf based 856# hard lockup detection which runs too fast due to turbo modes. 857# 858config HARDLOCKUP_CHECK_TIMESTAMP 859 bool 860 861# 862# arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard 863# lockup detector rather than the perf based detector. 864# 865config HARDLOCKUP_DETECTOR 866 bool "Detect Hard Lockups" 867 depends on DEBUG_KERNEL && !S390 868 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH 869 select LOCKUP_DETECTOR 870 select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF 871 select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH 872 help 873 Say Y here to enable the kernel to act as a watchdog to detect 874 hard lockups. 875 876 Hardlockups are bugs that cause the CPU to loop in kernel mode 877 for more than 10 seconds, without letting other interrupts have a 878 chance to run. The current stack trace is displayed upon detection 879 and the system will stay locked up. 880 881config BOOTPARAM_HARDLOCKUP_PANIC 882 bool "Panic (Reboot) On Hard Lockups" 883 depends on HARDLOCKUP_DETECTOR 884 help 885 Say Y here to enable the kernel to panic on "hard lockups", 886 which are bugs that cause the kernel to loop in kernel 887 mode with interrupts disabled for more than 10 seconds (configurable 888 using the watchdog_thresh sysctl). 889 890 Say N if unsure. 891 892config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 893 int 894 depends on HARDLOCKUP_DETECTOR 895 range 0 1 896 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 897 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 898 899config DETECT_HUNG_TASK 900 bool "Detect Hung Tasks" 901 depends on DEBUG_KERNEL 902 default SOFTLOCKUP_DETECTOR 903 help 904 Say Y here to enable the kernel to detect "hung tasks", 905 which are bugs that cause the task to be stuck in 906 uninterruptible "D" state indefinitely. 907 908 When a hung task is detected, the kernel will print the 909 current stack trace (which you should report), but the 910 task will stay in uninterruptible state. If lockdep is 911 enabled then all held locks will also be reported. This 912 feature has negligible overhead. 913 914config DEFAULT_HUNG_TASK_TIMEOUT 915 int "Default timeout for hung task detection (in seconds)" 916 depends on DETECT_HUNG_TASK 917 default 120 918 help 919 This option controls the default timeout (in seconds) used 920 to determine when a task has become non-responsive and should 921 be considered hung. 922 923 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 924 sysctl or by writing a value to 925 /proc/sys/kernel/hung_task_timeout_secs. 926 927 A timeout of 0 disables the check. The default is two minutes. 928 Keeping the default should be fine in most cases. 929 930config BOOTPARAM_HUNG_TASK_PANIC 931 bool "Panic (Reboot) On Hung Tasks" 932 depends on DETECT_HUNG_TASK 933 help 934 Say Y here to enable the kernel to panic on "hung tasks", 935 which are bugs that cause the kernel to leave a task stuck 936 in uninterruptible "D" state. 937 938 The panic can be used in combination with panic_timeout, 939 to cause the system to reboot automatically after a 940 hung task has been detected. This feature is useful for 941 high-availability systems that have uptime guarantees and 942 where a hung tasks must be resolved ASAP. 943 944 Say N if unsure. 945 946config BOOTPARAM_HUNG_TASK_PANIC_VALUE 947 int 948 depends on DETECT_HUNG_TASK 949 range 0 1 950 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 951 default 1 if BOOTPARAM_HUNG_TASK_PANIC 952 953config WQ_WATCHDOG 954 bool "Detect Workqueue Stalls" 955 depends on DEBUG_KERNEL 956 help 957 Say Y here to enable stall detection on workqueues. If a 958 worker pool doesn't make forward progress on a pending work 959 item for over a given amount of time, 30s by default, a 960 warning message is printed along with dump of workqueue 961 state. This can be configured through kernel parameter 962 "workqueue.watchdog_thresh" and its sysfs counterpart. 963 964endmenu # "Debug lockups and hangs" 965 966config PANIC_ON_OOPS 967 bool "Panic on Oops" 968 help 969 Say Y here to enable the kernel to panic when it oopses. This 970 has the same effect as setting oops=panic on the kernel command 971 line. 972 973 This feature is useful to ensure that the kernel does not do 974 anything erroneous after an oops which could result in data 975 corruption or other issues. 976 977 Say N if unsure. 978 979config PANIC_ON_OOPS_VALUE 980 int 981 range 0 1 982 default 0 if !PANIC_ON_OOPS 983 default 1 if PANIC_ON_OOPS 984 985config PANIC_TIMEOUT 986 int "panic timeout" 987 default 0 988 help 989 Set the timeout value (in seconds) until a reboot occurs when the 990 the kernel panics. If n = 0, then we wait forever. A timeout 991 value n > 0 will wait n seconds before rebooting, while a timeout 992 value n < 0 will reboot immediately. 993 994config SCHED_DEBUG 995 bool "Collect scheduler debugging info" 996 depends on DEBUG_KERNEL && PROC_FS 997 default y 998 help 999 If you say Y here, the /proc/sched_debug file will be provided 1000 that can help debug the scheduler. The runtime overhead of this 1001 option is minimal. 1002 1003config SCHED_INFO 1004 bool 1005 default n 1006 1007config SCHEDSTATS 1008 bool "Collect scheduler statistics" 1009 depends on DEBUG_KERNEL && PROC_FS 1010 select SCHED_INFO 1011 help 1012 If you say Y here, additional code will be inserted into the 1013 scheduler and related routines to collect statistics about 1014 scheduler behavior and provide them in /proc/schedstat. These 1015 stats may be useful for both tuning and debugging the scheduler 1016 If you aren't debugging the scheduler or trying to tune a specific 1017 application, you can say N to avoid the very slight overhead 1018 this adds. 1019 1020config SCHED_STACK_END_CHECK 1021 bool "Detect stack corruption on calls to schedule()" 1022 depends on DEBUG_KERNEL 1023 default n 1024 help 1025 This option checks for a stack overrun on calls to schedule(). 1026 If the stack end location is found to be over written always panic as 1027 the content of the corrupted region can no longer be trusted. 1028 This is to ensure no erroneous behaviour occurs which could result in 1029 data corruption or a sporadic crash at a later stage once the region 1030 is examined. The runtime overhead introduced is minimal. 1031 1032config DEBUG_TIMEKEEPING 1033 bool "Enable extra timekeeping sanity checking" 1034 help 1035 This option will enable additional timekeeping sanity checks 1036 which may be helpful when diagnosing issues where timekeeping 1037 problems are suspected. 1038 1039 This may include checks in the timekeeping hotpaths, so this 1040 option may have a (very small) performance impact to some 1041 workloads. 1042 1043 If unsure, say N. 1044 1045config DEBUG_PREEMPT 1046 bool "Debug preemptible kernel" 1047 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 1048 default y 1049 help 1050 If you say Y here then the kernel will use a debug variant of the 1051 commonly used smp_processor_id() function and will print warnings 1052 if kernel code uses it in a preemption-unsafe way. Also, the kernel 1053 will detect preemption count underflows. 1054 1055menu "Lock Debugging (spinlocks, mutexes, etc...)" 1056 1057config LOCK_DEBUGGING_SUPPORT 1058 bool 1059 depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1060 default y 1061 1062config PROVE_LOCKING 1063 bool "Lock debugging: prove locking correctness" 1064 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1065 select LOCKDEP 1066 select DEBUG_SPINLOCK 1067 select DEBUG_MUTEXES 1068 select DEBUG_RT_MUTEXES if RT_MUTEXES 1069 select DEBUG_RWSEMS if RWSEM_SPIN_ON_OWNER 1070 select DEBUG_WW_MUTEX_SLOWPATH 1071 select DEBUG_LOCK_ALLOC 1072 select TRACE_IRQFLAGS 1073 default n 1074 help 1075 This feature enables the kernel to prove that all locking 1076 that occurs in the kernel runtime is mathematically 1077 correct: that under no circumstance could an arbitrary (and 1078 not yet triggered) combination of observed locking 1079 sequences (on an arbitrary number of CPUs, running an 1080 arbitrary number of tasks and interrupt contexts) cause a 1081 deadlock. 1082 1083 In short, this feature enables the kernel to report locking 1084 related deadlocks before they actually occur. 1085 1086 The proof does not depend on how hard and complex a 1087 deadlock scenario would be to trigger: how many 1088 participant CPUs, tasks and irq-contexts would be needed 1089 for it to trigger. The proof also does not depend on 1090 timing: if a race and a resulting deadlock is possible 1091 theoretically (no matter how unlikely the race scenario 1092 is), it will be proven so and will immediately be 1093 reported by the kernel (once the event is observed that 1094 makes the deadlock theoretically possible). 1095 1096 If a deadlock is impossible (i.e. the locking rules, as 1097 observed by the kernel, are mathematically correct), the 1098 kernel reports nothing. 1099 1100 NOTE: this feature can also be enabled for rwlocks, mutexes 1101 and rwsems - in which case all dependencies between these 1102 different locking variants are observed and mapped too, and 1103 the proof of observed correctness is also maintained for an 1104 arbitrary combination of these separate locking variants. 1105 1106 For more details, see Documentation/locking/lockdep-design.txt. 1107 1108config LOCK_STAT 1109 bool "Lock usage statistics" 1110 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1111 select LOCKDEP 1112 select DEBUG_SPINLOCK 1113 select DEBUG_MUTEXES 1114 select DEBUG_RT_MUTEXES if RT_MUTEXES 1115 select DEBUG_LOCK_ALLOC 1116 default n 1117 help 1118 This feature enables tracking lock contention points 1119 1120 For more details, see Documentation/locking/lockstat.txt 1121 1122 This also enables lock events required by "perf lock", 1123 subcommand of perf. 1124 If you want to use "perf lock", you also need to turn on 1125 CONFIG_EVENT_TRACING. 1126 1127 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1128 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1129 1130config DEBUG_RT_MUTEXES 1131 bool "RT Mutex debugging, deadlock detection" 1132 depends on DEBUG_KERNEL && RT_MUTEXES 1133 help 1134 This allows rt mutex semantics violations and rt mutex related 1135 deadlocks (lockups) to be detected and reported automatically. 1136 1137config DEBUG_SPINLOCK 1138 bool "Spinlock and rw-lock debugging: basic checks" 1139 depends on DEBUG_KERNEL 1140 select UNINLINE_SPIN_UNLOCK 1141 help 1142 Say Y here and build SMP to catch missing spinlock initialization 1143 and certain other kinds of spinlock errors commonly made. This is 1144 best used in conjunction with the NMI watchdog so that spinlock 1145 deadlocks are also debuggable. 1146 1147config DEBUG_MUTEXES 1148 bool "Mutex debugging: basic checks" 1149 depends on DEBUG_KERNEL 1150 help 1151 This feature allows mutex semantics violations to be detected and 1152 reported. 1153 1154config DEBUG_WW_MUTEX_SLOWPATH 1155 bool "Wait/wound mutex debugging: Slowpath testing" 1156 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1157 select DEBUG_LOCK_ALLOC 1158 select DEBUG_SPINLOCK 1159 select DEBUG_MUTEXES 1160 help 1161 This feature enables slowpath testing for w/w mutex users by 1162 injecting additional -EDEADLK wound/backoff cases. Together with 1163 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 1164 will test all possible w/w mutex interface abuse with the 1165 exception of simply not acquiring all the required locks. 1166 Note that this feature can introduce significant overhead, so 1167 it really should not be enabled in a production or distro kernel, 1168 even a debug kernel. If you are a driver writer, enable it. If 1169 you are a distro, do not. 1170 1171config DEBUG_RWSEMS 1172 bool "RW Semaphore debugging: basic checks" 1173 depends on DEBUG_KERNEL && RWSEM_SPIN_ON_OWNER 1174 help 1175 This debugging feature allows mismatched rw semaphore locks and unlocks 1176 to be detected and reported. 1177 1178config DEBUG_LOCK_ALLOC 1179 bool "Lock debugging: detect incorrect freeing of live locks" 1180 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1181 select DEBUG_SPINLOCK 1182 select DEBUG_MUTEXES 1183 select DEBUG_RT_MUTEXES if RT_MUTEXES 1184 select LOCKDEP 1185 help 1186 This feature will check whether any held lock (spinlock, rwlock, 1187 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1188 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1189 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1190 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1191 held during task exit. 1192 1193config LOCKDEP 1194 bool 1195 depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT 1196 select STACKTRACE 1197 select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86 1198 select KALLSYMS 1199 select KALLSYMS_ALL 1200 1201config LOCKDEP_SMALL 1202 bool 1203 1204config DEBUG_LOCKDEP 1205 bool "Lock dependency engine debugging" 1206 depends on DEBUG_KERNEL && LOCKDEP 1207 help 1208 If you say Y here, the lock dependency engine will do 1209 additional runtime checks to debug itself, at the price 1210 of more runtime overhead. 1211 1212config DEBUG_ATOMIC_SLEEP 1213 bool "Sleep inside atomic section checking" 1214 select PREEMPT_COUNT 1215 depends on DEBUG_KERNEL 1216 depends on !ARCH_NO_PREEMPT 1217 help 1218 If you say Y here, various routines which may sleep will become very 1219 noisy if they are called inside atomic sections: when a spinlock is 1220 held, inside an rcu read side critical section, inside preempt disabled 1221 sections, inside an interrupt, etc... 1222 1223config DEBUG_LOCKING_API_SELFTESTS 1224 bool "Locking API boot-time self-tests" 1225 depends on DEBUG_KERNEL 1226 help 1227 Say Y here if you want the kernel to run a short self-test during 1228 bootup. The self-test checks whether common types of locking bugs 1229 are detected by debugging mechanisms or not. (if you disable 1230 lock debugging then those bugs wont be detected of course.) 1231 The following locking APIs are covered: spinlocks, rwlocks, 1232 mutexes and rwsems. 1233 1234config LOCK_TORTURE_TEST 1235 tristate "torture tests for locking" 1236 depends on DEBUG_KERNEL 1237 select TORTURE_TEST 1238 help 1239 This option provides a kernel module that runs torture tests 1240 on kernel locking primitives. The kernel module may be built 1241 after the fact on the running kernel to be tested, if desired. 1242 1243 Say Y here if you want kernel locking-primitive torture tests 1244 to be built into the kernel. 1245 Say M if you want these torture tests to build as a module. 1246 Say N if you are unsure. 1247 1248config WW_MUTEX_SELFTEST 1249 tristate "Wait/wound mutex selftests" 1250 help 1251 This option provides a kernel module that runs tests on the 1252 on the struct ww_mutex locking API. 1253 1254 It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction 1255 with this test harness. 1256 1257 Say M if you want these self tests to build as a module. 1258 Say N if you are unsure. 1259 1260endmenu # lock debugging 1261 1262config TRACE_IRQFLAGS 1263 bool 1264 help 1265 Enables hooks to interrupt enabling and disabling for 1266 either tracing or lock debugging. 1267 1268config STACKTRACE 1269 bool "Stack backtrace support" 1270 depends on STACKTRACE_SUPPORT 1271 help 1272 This option causes the kernel to create a /proc/pid/stack for 1273 every process, showing its current stack trace. 1274 It is also used by various kernel debugging features that require 1275 stack trace generation. 1276 1277config WARN_ALL_UNSEEDED_RANDOM 1278 bool "Warn for all uses of unseeded randomness" 1279 default n 1280 help 1281 Some parts of the kernel contain bugs relating to their use of 1282 cryptographically secure random numbers before it's actually possible 1283 to generate those numbers securely. This setting ensures that these 1284 flaws don't go unnoticed, by enabling a message, should this ever 1285 occur. This will allow people with obscure setups to know when things 1286 are going wrong, so that they might contact developers about fixing 1287 it. 1288 1289 Unfortunately, on some models of some architectures getting 1290 a fully seeded CRNG is extremely difficult, and so this can 1291 result in dmesg getting spammed for a surprisingly long 1292 time. This is really bad from a security perspective, and 1293 so architecture maintainers really need to do what they can 1294 to get the CRNG seeded sooner after the system is booted. 1295 However, since users cannot do anything actionable to 1296 address this, by default the kernel will issue only a single 1297 warning for the first use of unseeded randomness. 1298 1299 Say Y here if you want to receive warnings for all uses of 1300 unseeded randomness. This will be of use primarily for 1301 those developers interested in improving the security of 1302 Linux kernels running on their architecture (or 1303 subarchitecture). 1304 1305config DEBUG_KOBJECT 1306 bool "kobject debugging" 1307 depends on DEBUG_KERNEL 1308 help 1309 If you say Y here, some extra kobject debugging messages will be sent 1310 to the syslog. 1311 1312config DEBUG_KOBJECT_RELEASE 1313 bool "kobject release debugging" 1314 depends on DEBUG_OBJECTS_TIMERS 1315 help 1316 kobjects are reference counted objects. This means that their 1317 last reference count put is not predictable, and the kobject can 1318 live on past the point at which a driver decides to drop it's 1319 initial reference to the kobject gained on allocation. An 1320 example of this would be a struct device which has just been 1321 unregistered. 1322 1323 However, some buggy drivers assume that after such an operation, 1324 the memory backing the kobject can be immediately freed. This 1325 goes completely against the principles of a refcounted object. 1326 1327 If you say Y here, the kernel will delay the release of kobjects 1328 on the last reference count to improve the visibility of this 1329 kind of kobject release bug. 1330 1331config HAVE_DEBUG_BUGVERBOSE 1332 bool 1333 1334config DEBUG_BUGVERBOSE 1335 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1336 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1337 default y 1338 help 1339 Say Y here to make BUG() panics output the file name and line number 1340 of the BUG call as well as the EIP and oops trace. This aids 1341 debugging but costs about 70-100K of memory. 1342 1343config DEBUG_LIST 1344 bool "Debug linked list manipulation" 1345 depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION 1346 help 1347 Enable this to turn on extended checks in the linked-list 1348 walking routines. 1349 1350 If unsure, say N. 1351 1352config DEBUG_PI_LIST 1353 bool "Debug priority linked list manipulation" 1354 depends on DEBUG_KERNEL 1355 help 1356 Enable this to turn on extended checks in the priority-ordered 1357 linked-list (plist) walking routines. This checks the entire 1358 list multiple times during each manipulation. 1359 1360 If unsure, say N. 1361 1362config DEBUG_SG 1363 bool "Debug SG table operations" 1364 depends on DEBUG_KERNEL 1365 help 1366 Enable this to turn on checks on scatter-gather tables. This can 1367 help find problems with drivers that do not properly initialize 1368 their sg tables. 1369 1370 If unsure, say N. 1371 1372config DEBUG_NOTIFIERS 1373 bool "Debug notifier call chains" 1374 depends on DEBUG_KERNEL 1375 help 1376 Enable this to turn on sanity checking for notifier call chains. 1377 This is most useful for kernel developers to make sure that 1378 modules properly unregister themselves from notifier chains. 1379 This is a relatively cheap check but if you care about maximum 1380 performance, say N. 1381 1382config DEBUG_CREDENTIALS 1383 bool "Debug credential management" 1384 depends on DEBUG_KERNEL 1385 help 1386 Enable this to turn on some debug checking for credential 1387 management. The additional code keeps track of the number of 1388 pointers from task_structs to any given cred struct, and checks to 1389 see that this number never exceeds the usage count of the cred 1390 struct. 1391 1392 Furthermore, if SELinux is enabled, this also checks that the 1393 security pointer in the cred struct is never seen to be invalid. 1394 1395 If unsure, say N. 1396 1397source "kernel/rcu/Kconfig.debug" 1398 1399config DEBUG_WQ_FORCE_RR_CPU 1400 bool "Force round-robin CPU selection for unbound work items" 1401 depends on DEBUG_KERNEL 1402 default n 1403 help 1404 Workqueue used to implicitly guarantee that work items queued 1405 without explicit CPU specified are put on the local CPU. This 1406 guarantee is no longer true and while local CPU is still 1407 preferred work items may be put on foreign CPUs. Kernel 1408 parameter "workqueue.debug_force_rr_cpu" is added to force 1409 round-robin CPU selection to flush out usages which depend on the 1410 now broken guarantee. This config option enables the debug 1411 feature by default. When enabled, memory and cache locality will 1412 be impacted. 1413 1414config DEBUG_BLOCK_EXT_DEVT 1415 bool "Force extended block device numbers and spread them" 1416 depends on DEBUG_KERNEL 1417 depends on BLOCK 1418 default n 1419 help 1420 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1421 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1422 YOU ARE DOING. Distros, please enable this and fix whatever 1423 is broken. 1424 1425 Conventionally, block device numbers are allocated from 1426 predetermined contiguous area. However, extended block area 1427 may introduce non-contiguous block device numbers. This 1428 option forces most block device numbers to be allocated from 1429 the extended space and spreads them to discover kernel or 1430 userland code paths which assume predetermined contiguous 1431 device number allocation. 1432 1433 Note that turning on this debug option shuffles all the 1434 device numbers for all IDE and SCSI devices including libata 1435 ones, so root partition specified using device number 1436 directly (via rdev or root=MAJ:MIN) won't work anymore. 1437 Textual device names (root=/dev/sdXn) will continue to work. 1438 1439 Say N if you are unsure. 1440 1441config CPU_HOTPLUG_STATE_CONTROL 1442 bool "Enable CPU hotplug state control" 1443 depends on DEBUG_KERNEL 1444 depends on HOTPLUG_CPU 1445 default n 1446 help 1447 Allows to write steps between "offline" and "online" to the CPUs 1448 sysfs target file so states can be stepped granular. This is a debug 1449 option for now as the hotplug machinery cannot be stopped and 1450 restarted at arbitrary points yet. 1451 1452 Say N if your are unsure. 1453 1454config NOTIFIER_ERROR_INJECTION 1455 tristate "Notifier error injection" 1456 depends on DEBUG_KERNEL 1457 select DEBUG_FS 1458 help 1459 This option provides the ability to inject artificial errors to 1460 specified notifier chain callbacks. It is useful to test the error 1461 handling of notifier call chain failures. 1462 1463 Say N if unsure. 1464 1465config PM_NOTIFIER_ERROR_INJECT 1466 tristate "PM notifier error injection module" 1467 depends on PM && NOTIFIER_ERROR_INJECTION 1468 default m if PM_DEBUG 1469 help 1470 This option provides the ability to inject artificial errors to 1471 PM notifier chain callbacks. It is controlled through debugfs 1472 interface /sys/kernel/debug/notifier-error-inject/pm 1473 1474 If the notifier call chain should be failed with some events 1475 notified, write the error code to "actions/<notifier event>/error". 1476 1477 Example: Inject PM suspend error (-12 = -ENOMEM) 1478 1479 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1480 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1481 # echo mem > /sys/power/state 1482 bash: echo: write error: Cannot allocate memory 1483 1484 To compile this code as a module, choose M here: the module will 1485 be called pm-notifier-error-inject. 1486 1487 If unsure, say N. 1488 1489config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1490 tristate "OF reconfig notifier error injection module" 1491 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1492 help 1493 This option provides the ability to inject artificial errors to 1494 OF reconfig notifier chain callbacks. It is controlled 1495 through debugfs interface under 1496 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1497 1498 If the notifier call chain should be failed with some events 1499 notified, write the error code to "actions/<notifier event>/error". 1500 1501 To compile this code as a module, choose M here: the module will 1502 be called of-reconfig-notifier-error-inject. 1503 1504 If unsure, say N. 1505 1506config NETDEV_NOTIFIER_ERROR_INJECT 1507 tristate "Netdev notifier error injection module" 1508 depends on NET && NOTIFIER_ERROR_INJECTION 1509 help 1510 This option provides the ability to inject artificial errors to 1511 netdevice notifier chain callbacks. It is controlled through debugfs 1512 interface /sys/kernel/debug/notifier-error-inject/netdev 1513 1514 If the notifier call chain should be failed with some events 1515 notified, write the error code to "actions/<notifier event>/error". 1516 1517 Example: Inject netdevice mtu change error (-22 = -EINVAL) 1518 1519 # cd /sys/kernel/debug/notifier-error-inject/netdev 1520 # echo -22 > actions/NETDEV_CHANGEMTU/error 1521 # ip link set eth0 mtu 1024 1522 RTNETLINK answers: Invalid argument 1523 1524 To compile this code as a module, choose M here: the module will 1525 be called netdev-notifier-error-inject. 1526 1527 If unsure, say N. 1528 1529config FUNCTION_ERROR_INJECTION 1530 def_bool y 1531 depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES 1532 1533config FAULT_INJECTION 1534 bool "Fault-injection framework" 1535 depends on DEBUG_KERNEL 1536 help 1537 Provide fault-injection framework. 1538 For more details, see Documentation/fault-injection/. 1539 1540config FAILSLAB 1541 bool "Fault-injection capability for kmalloc" 1542 depends on FAULT_INJECTION 1543 depends on SLAB || SLUB 1544 help 1545 Provide fault-injection capability for kmalloc. 1546 1547config FAIL_PAGE_ALLOC 1548 bool "Fault-injection capabilitiy for alloc_pages()" 1549 depends on FAULT_INJECTION 1550 help 1551 Provide fault-injection capability for alloc_pages(). 1552 1553config FAIL_MAKE_REQUEST 1554 bool "Fault-injection capability for disk IO" 1555 depends on FAULT_INJECTION && BLOCK 1556 help 1557 Provide fault-injection capability for disk IO. 1558 1559config FAIL_IO_TIMEOUT 1560 bool "Fault-injection capability for faking disk interrupts" 1561 depends on FAULT_INJECTION && BLOCK 1562 help 1563 Provide fault-injection capability on end IO handling. This 1564 will make the block layer "forget" an interrupt as configured, 1565 thus exercising the error handling. 1566 1567 Only works with drivers that use the generic timeout handling, 1568 for others it wont do anything. 1569 1570config FAIL_FUTEX 1571 bool "Fault-injection capability for futexes" 1572 select DEBUG_FS 1573 depends on FAULT_INJECTION && FUTEX 1574 help 1575 Provide fault-injection capability for futexes. 1576 1577config FAULT_INJECTION_DEBUG_FS 1578 bool "Debugfs entries for fault-injection capabilities" 1579 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1580 help 1581 Enable configuration of fault-injection capabilities via debugfs. 1582 1583config FAIL_FUNCTION 1584 bool "Fault-injection capability for functions" 1585 depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION 1586 help 1587 Provide function-based fault-injection capability. 1588 This will allow you to override a specific function with a return 1589 with given return value. As a result, function caller will see 1590 an error value and have to handle it. This is useful to test the 1591 error handling in various subsystems. 1592 1593config FAIL_MMC_REQUEST 1594 bool "Fault-injection capability for MMC IO" 1595 depends on FAULT_INJECTION_DEBUG_FS && MMC 1596 help 1597 Provide fault-injection capability for MMC IO. 1598 This will make the mmc core return data errors. This is 1599 useful to test the error handling in the mmc block device 1600 and to test how the mmc host driver handles retries from 1601 the block device. 1602 1603config FAULT_INJECTION_STACKTRACE_FILTER 1604 bool "stacktrace filter for fault-injection capabilities" 1605 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1606 depends on !X86_64 1607 select STACKTRACE 1608 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86 1609 help 1610 Provide stacktrace filter for fault-injection capabilities 1611 1612config LATENCYTOP 1613 bool "Latency measuring infrastructure" 1614 depends on DEBUG_KERNEL 1615 depends on STACKTRACE_SUPPORT 1616 depends on PROC_FS 1617 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86 1618 select KALLSYMS 1619 select KALLSYMS_ALL 1620 select STACKTRACE 1621 select SCHEDSTATS 1622 select SCHED_DEBUG 1623 help 1624 Enable this option if you want to use the LatencyTOP tool 1625 to find out which userspace is blocking on what kernel operations. 1626 1627source "kernel/trace/Kconfig" 1628 1629config PROVIDE_OHCI1394_DMA_INIT 1630 bool "Remote debugging over FireWire early on boot" 1631 depends on PCI && X86 1632 help 1633 If you want to debug problems which hang or crash the kernel early 1634 on boot and the crashing machine has a FireWire port, you can use 1635 this feature to remotely access the memory of the crashed machine 1636 over FireWire. This employs remote DMA as part of the OHCI1394 1637 specification which is now the standard for FireWire controllers. 1638 1639 With remote DMA, you can monitor the printk buffer remotely using 1640 firescope and access all memory below 4GB using fireproxy from gdb. 1641 Even controlling a kernel debugger is possible using remote DMA. 1642 1643 Usage: 1644 1645 If ohci1394_dma=early is used as boot parameter, it will initialize 1646 all OHCI1394 controllers which are found in the PCI config space. 1647 1648 As all changes to the FireWire bus such as enabling and disabling 1649 devices cause a bus reset and thereby disable remote DMA for all 1650 devices, be sure to have the cable plugged and FireWire enabled on 1651 the debugging host before booting the debug target for debugging. 1652 1653 This code (~1k) is freed after boot. By then, the firewire stack 1654 in charge of the OHCI-1394 controllers should be used instead. 1655 1656 See Documentation/debugging-via-ohci1394.txt for more information. 1657 1658config DMA_API_DEBUG 1659 bool "Enable debugging of DMA-API usage" 1660 select NEED_DMA_MAP_STATE 1661 help 1662 Enable this option to debug the use of the DMA API by device drivers. 1663 With this option you will be able to detect common bugs in device 1664 drivers like double-freeing of DMA mappings or freeing mappings that 1665 were never allocated. 1666 1667 This also attempts to catch cases where a page owned by DMA is 1668 accessed by the cpu in a way that could cause data corruption. For 1669 example, this enables cow_user_page() to check that the source page is 1670 not undergoing DMA. 1671 1672 This option causes a performance degradation. Use only if you want to 1673 debug device drivers and dma interactions. 1674 1675 If unsure, say N. 1676 1677config DMA_API_DEBUG_SG 1678 bool "Debug DMA scatter-gather usage" 1679 default y 1680 depends on DMA_API_DEBUG 1681 help 1682 Perform extra checking that callers of dma_map_sg() have respected the 1683 appropriate segment length/boundary limits for the given device when 1684 preparing DMA scatterlists. 1685 1686 This is particularly likely to have been overlooked in cases where the 1687 dma_map_sg() API is used for general bulk mapping of pages rather than 1688 preparing literal scatter-gather descriptors, where there is a risk of 1689 unexpected behaviour from DMA API implementations if the scatterlist 1690 is technically out-of-spec. 1691 1692 If unsure, say N. 1693 1694menuconfig RUNTIME_TESTING_MENU 1695 bool "Runtime Testing" 1696 def_bool y 1697 1698if RUNTIME_TESTING_MENU 1699 1700config LKDTM 1701 tristate "Linux Kernel Dump Test Tool Module" 1702 depends on DEBUG_FS 1703 depends on BLOCK 1704 help 1705 This module enables testing of the different dumping mechanisms by 1706 inducing system failures at predefined crash points. 1707 If you don't need it: say N 1708 Choose M here to compile this code as a module. The module will be 1709 called lkdtm. 1710 1711 Documentation on how to use the module can be found in 1712 Documentation/fault-injection/provoke-crashes.txt 1713 1714config TEST_LIST_SORT 1715 tristate "Linked list sorting test" 1716 depends on DEBUG_KERNEL || m 1717 help 1718 Enable this to turn on 'list_sort()' function test. This test is 1719 executed only once during system boot (so affects only boot time), 1720 or at module load time. 1721 1722 If unsure, say N. 1723 1724config TEST_SORT 1725 tristate "Array-based sort test" 1726 depends on DEBUG_KERNEL || m 1727 help 1728 This option enables the self-test function of 'sort()' at boot, 1729 or at module load time. 1730 1731 If unsure, say N. 1732 1733config KPROBES_SANITY_TEST 1734 bool "Kprobes sanity tests" 1735 depends on DEBUG_KERNEL 1736 depends on KPROBES 1737 help 1738 This option provides for testing basic kprobes functionality on 1739 boot. Samples of kprobe and kretprobe are inserted and 1740 verified for functionality. 1741 1742 Say N if you are unsure. 1743 1744config BACKTRACE_SELF_TEST 1745 tristate "Self test for the backtrace code" 1746 depends on DEBUG_KERNEL 1747 help 1748 This option provides a kernel module that can be used to test 1749 the kernel stack backtrace code. This option is not useful 1750 for distributions or general kernels, but only for kernel 1751 developers working on architecture code. 1752 1753 Note that if you want to also test saved backtraces, you will 1754 have to enable STACKTRACE as well. 1755 1756 Say N if you are unsure. 1757 1758config RBTREE_TEST 1759 tristate "Red-Black tree test" 1760 depends on DEBUG_KERNEL 1761 help 1762 A benchmark measuring the performance of the rbtree library. 1763 Also includes rbtree invariant checks. 1764 1765config INTERVAL_TREE_TEST 1766 tristate "Interval tree test" 1767 depends on DEBUG_KERNEL 1768 select INTERVAL_TREE 1769 help 1770 A benchmark measuring the performance of the interval tree library 1771 1772config PERCPU_TEST 1773 tristate "Per cpu operations test" 1774 depends on m && DEBUG_KERNEL 1775 help 1776 Enable this option to build test module which validates per-cpu 1777 operations. 1778 1779 If unsure, say N. 1780 1781config ATOMIC64_SELFTEST 1782 tristate "Perform an atomic64_t self-test" 1783 help 1784 Enable this option to test the atomic64_t functions at boot or 1785 at module load time. 1786 1787 If unsure, say N. 1788 1789config ASYNC_RAID6_TEST 1790 tristate "Self test for hardware accelerated raid6 recovery" 1791 depends on ASYNC_RAID6_RECOV 1792 select ASYNC_MEMCPY 1793 ---help--- 1794 This is a one-shot self test that permutes through the 1795 recovery of all the possible two disk failure scenarios for a 1796 N-disk array. Recovery is performed with the asynchronous 1797 raid6 recovery routines, and will optionally use an offload 1798 engine if one is available. 1799 1800 If unsure, say N. 1801 1802config TEST_HEXDUMP 1803 tristate "Test functions located in the hexdump module at runtime" 1804 1805config TEST_STRING_HELPERS 1806 tristate "Test functions located in the string_helpers module at runtime" 1807 1808config TEST_KSTRTOX 1809 tristate "Test kstrto*() family of functions at runtime" 1810 1811config TEST_PRINTF 1812 tristate "Test printf() family of functions at runtime" 1813 1814config TEST_BITMAP 1815 tristate "Test bitmap_*() family of functions at runtime" 1816 help 1817 Enable this option to test the bitmap functions at boot. 1818 1819 If unsure, say N. 1820 1821config TEST_BITFIELD 1822 tristate "Test bitfield functions at runtime" 1823 help 1824 Enable this option to test the bitfield functions at boot. 1825 1826 If unsure, say N. 1827 1828config TEST_UUID 1829 tristate "Test functions located in the uuid module at runtime" 1830 1831config TEST_XARRAY 1832 tristate "Test the XArray code at runtime" 1833 1834config TEST_OVERFLOW 1835 tristate "Test check_*_overflow() functions at runtime" 1836 1837config TEST_RHASHTABLE 1838 tristate "Perform selftest on resizable hash table" 1839 help 1840 Enable this option to test the rhashtable functions at boot. 1841 1842 If unsure, say N. 1843 1844config TEST_HASH 1845 tristate "Perform selftest on hash functions" 1846 help 1847 Enable this option to test the kernel's integer (<linux/hash.h>), 1848 string (<linux/stringhash.h>), and siphash (<linux/siphash.h>) 1849 hash functions on boot (or module load). 1850 1851 This is intended to help people writing architecture-specific 1852 optimized versions. If unsure, say N. 1853 1854config TEST_IDA 1855 tristate "Perform selftest on IDA functions" 1856 1857config TEST_PARMAN 1858 tristate "Perform selftest on priority array manager" 1859 depends on PARMAN 1860 help 1861 Enable this option to test priority array manager on boot 1862 (or module load). 1863 1864 If unsure, say N. 1865 1866config TEST_LKM 1867 tristate "Test module loading with 'hello world' module" 1868 depends on m 1869 help 1870 This builds the "test_module" module that emits "Hello, world" 1871 on printk when loaded. It is designed to be used for basic 1872 evaluation of the module loading subsystem (for example when 1873 validating module verification). It lacks any extra dependencies, 1874 and will not normally be loaded by the system unless explicitly 1875 requested by name. 1876 1877 If unsure, say N. 1878 1879config TEST_USER_COPY 1880 tristate "Test user/kernel boundary protections" 1881 depends on m 1882 help 1883 This builds the "test_user_copy" module that runs sanity checks 1884 on the copy_to/from_user infrastructure, making sure basic 1885 user/kernel boundary testing is working. If it fails to load, 1886 a regression has been detected in the user/kernel memory boundary 1887 protections. 1888 1889 If unsure, say N. 1890 1891config TEST_BPF 1892 tristate "Test BPF filter functionality" 1893 depends on m && NET 1894 help 1895 This builds the "test_bpf" module that runs various test vectors 1896 against the BPF interpreter or BPF JIT compiler depending on the 1897 current setting. This is in particular useful for BPF JIT compiler 1898 development, but also to run regression tests against changes in 1899 the interpreter code. It also enables test stubs for eBPF maps and 1900 verifier used by user space verifier testsuite. 1901 1902 If unsure, say N. 1903 1904config FIND_BIT_BENCHMARK 1905 tristate "Test find_bit functions" 1906 help 1907 This builds the "test_find_bit" module that measure find_*_bit() 1908 functions performance. 1909 1910 If unsure, say N. 1911 1912config TEST_FIRMWARE 1913 tristate "Test firmware loading via userspace interface" 1914 depends on FW_LOADER 1915 help 1916 This builds the "test_firmware" module that creates a userspace 1917 interface for testing firmware loading. This can be used to 1918 control the triggering of firmware loading without needing an 1919 actual firmware-using device. The contents can be rechecked by 1920 userspace. 1921 1922 If unsure, say N. 1923 1924config TEST_SYSCTL 1925 tristate "sysctl test driver" 1926 depends on PROC_SYSCTL 1927 help 1928 This builds the "test_sysctl" module. This driver enables to test the 1929 proc sysctl interfaces available to drivers safely without affecting 1930 production knobs which might alter system functionality. 1931 1932 If unsure, say N. 1933 1934config TEST_UDELAY 1935 tristate "udelay test driver" 1936 help 1937 This builds the "udelay_test" module that helps to make sure 1938 that udelay() is working properly. 1939 1940 If unsure, say N. 1941 1942config TEST_STATIC_KEYS 1943 tristate "Test static keys" 1944 depends on m 1945 help 1946 Test the static key interfaces. 1947 1948 If unsure, say N. 1949 1950config TEST_KMOD 1951 tristate "kmod stress tester" 1952 depends on m 1953 depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS 1954 depends on NETDEVICES && NET_CORE && INET # for TUN 1955 select TEST_LKM 1956 select XFS_FS 1957 select TUN 1958 select BTRFS_FS 1959 help 1960 Test the kernel's module loading mechanism: kmod. kmod implements 1961 support to load modules using the Linux kernel's usermode helper. 1962 This test provides a series of tests against kmod. 1963 1964 Although technically you can either build test_kmod as a module or 1965 into the kernel we disallow building it into the kernel since 1966 it stress tests request_module() and this will very likely cause 1967 some issues by taking over precious threads available from other 1968 module load requests, ultimately this could be fatal. 1969 1970 To run tests run: 1971 1972 tools/testing/selftests/kmod/kmod.sh --help 1973 1974 If unsure, say N. 1975 1976config TEST_DEBUG_VIRTUAL 1977 tristate "Test CONFIG_DEBUG_VIRTUAL feature" 1978 depends on DEBUG_VIRTUAL 1979 help 1980 Test the kernel's ability to detect incorrect calls to 1981 virt_to_phys() done against the non-linear part of the 1982 kernel's virtual address map. 1983 1984 If unsure, say N. 1985 1986config TEST_MEMCAT_P 1987 tristate "Test memcat_p() helper function" 1988 help 1989 Test the memcat_p() helper for correctly merging two 1990 pointer arrays together. 1991 1992 If unsure, say N. 1993 1994config TEST_OBJAGG 1995 tristate "Perform selftest on object aggreration manager" 1996 default n 1997 depends on OBJAGG 1998 help 1999 Enable this option to test object aggregation manager on boot 2000 (or module load). 2001 2002 If unsure, say N. 2003 2004endif # RUNTIME_TESTING_MENU 2005 2006config MEMTEST 2007 bool "Memtest" 2008 ---help--- 2009 This option adds a kernel parameter 'memtest', which allows memtest 2010 to be set. 2011 memtest=0, mean disabled; -- default 2012 memtest=1, mean do 1 test pattern; 2013 ... 2014 memtest=17, mean do 17 test patterns. 2015 If you are unsure how to answer this question, answer N. 2016 2017config BUG_ON_DATA_CORRUPTION 2018 bool "Trigger a BUG when data corruption is detected" 2019 select DEBUG_LIST 2020 help 2021 Select this option if the kernel should BUG when it encounters 2022 data corruption in kernel memory structures when they get checked 2023 for validity. 2024 2025 If unsure, say N. 2026 2027source "samples/Kconfig" 2028 2029source "lib/Kconfig.kgdb" 2030 2031source "lib/Kconfig.ubsan" 2032 2033config ARCH_HAS_DEVMEM_IS_ALLOWED 2034 bool 2035 2036config STRICT_DEVMEM 2037 bool "Filter access to /dev/mem" 2038 depends on MMU && DEVMEM 2039 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 2040 default y if PPC || X86 || ARM64 2041 ---help--- 2042 If this option is disabled, you allow userspace (root) access to all 2043 of memory, including kernel and userspace memory. Accidental 2044 access to this is obviously disastrous, but specific access can 2045 be used by people debugging the kernel. Note that with PAT support 2046 enabled, even in this case there are restrictions on /dev/mem 2047 use due to the cache aliasing requirements. 2048 2049 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 2050 file only allows userspace access to PCI space and the BIOS code and 2051 data regions. This is sufficient for dosemu and X and all common 2052 users of /dev/mem. 2053 2054 If in doubt, say Y. 2055 2056config IO_STRICT_DEVMEM 2057 bool "Filter I/O access to /dev/mem" 2058 depends on STRICT_DEVMEM 2059 ---help--- 2060 If this option is disabled, you allow userspace (root) access to all 2061 io-memory regardless of whether a driver is actively using that 2062 range. Accidental access to this is obviously disastrous, but 2063 specific access can be used by people debugging kernel drivers. 2064 2065 If this option is switched on, the /dev/mem file only allows 2066 userspace access to *idle* io-memory ranges (see /proc/iomem) This 2067 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 2068 if the driver using a given range cannot be disabled. 2069 2070 If in doubt, say Y. 2071 2072source "arch/$(SRCARCH)/Kconfig.debug" 2073 2074endmenu # Kernel hacking 2075