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