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