menu "printk and dmesg options"

  
  config PRINTK_TIME
  	bool "Show timing information on printks"

  	depends on PRINTK

  	help

  	  Selecting this option causes time stamps of the printk()
  	  messages to be added to the output of the syslog() system
  	  call and at the console.
  
  	  The timestamp is always recorded internally, and exported
  	  to /dev/kmsg. This flag just specifies if the timestamp should
  	  be included, not that the timestamp is recorded.
  
  	  The behavior is also controlled by the kernel command line
  	  parameter printk.time=1. See Documentation/kernel-parameters.txt

  config MESSAGE_LOGLEVEL_DEFAULT

  	int "Default message log level (1-7)"
  	range 1 7
  	default "4"
  	help
  	  Default log level for printk statements with no specified priority.
  
  	  This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
  	  that are auditing their logs closely may want to set it to a lower
  	  priority.

  config BOOT_PRINTK_DELAY
  	bool "Delay each boot printk message by N milliseconds"
  	depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
  	help
  	  This build option allows you to read kernel boot messages
  	  by inserting a short delay after each one.  The delay is
  	  specified in milliseconds on the kernel command line,
  	  using "boot_delay=N".
  
  	  It is likely that you would also need to use "lpj=M" to preset
  	  the "loops per jiffie" value.
  	  See a previous boot log for the "lpj" value to use for your
  	  system, and then set "lpj=M" before setting "boot_delay=N".
  	  NOTE:  Using this option may adversely affect SMP systems.
  	  I.e., processors other than the first one may not boot up.
  	  BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
  	  what it believes to be lockup conditions.
  
  config DYNAMIC_DEBUG
  	bool "Enable dynamic printk() support"
  	default n
  	depends on PRINTK
  	depends on DEBUG_FS
  	help
  
  	  Compiles debug level messages into the kernel, which would not
  	  otherwise be available at runtime. These messages can then be
  	  enabled/disabled based on various levels of scope - per source file,
  	  function, module, format string, and line number. This mechanism
  	  implicitly compiles in all pr_debug() and dev_dbg() calls, which
  	  enlarges the kernel text size by about 2%.
  
  	  If a source file is compiled with DEBUG flag set, any
  	  pr_debug() calls in it are enabled by default, but can be
  	  disabled at runtime as below.  Note that DEBUG flag is
  	  turned on by many CONFIG_*DEBUG* options.
  
  	  Usage:
  
  	  Dynamic debugging is controlled via the 'dynamic_debug/control' file,
  	  which is contained in the 'debugfs' filesystem. Thus, the debugfs
  	  filesystem must first be mounted before making use of this feature.
  	  We refer the control file as: <debugfs>/dynamic_debug/control. This
  	  file contains a list of the debug statements that can be enabled. The
  	  format for each line of the file is:
  
  		filename:lineno [module]function flags format
  
  	  filename : source file of the debug statement
  	  lineno : line number of the debug statement
  	  module : module that contains the debug statement
  	  function : function that contains the debug statement
            flags : '=p' means the line is turned 'on' for printing
            format : the format used for the debug statement
  
  	  From a live system:
  
  		nullarbor:~ # cat <debugfs>/dynamic_debug/control
  		# filename:lineno [module]function flags format
  		fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
  		fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
  		fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
  
  	  Example usage:
  
  		// enable the message at line 1603 of file svcsock.c
  		nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
  						<debugfs>/dynamic_debug/control
  
  		// enable all the messages in file svcsock.c
  		nullarbor:~ # echo -n 'file svcsock.c +p' >
  						<debugfs>/dynamic_debug/control
  
  		// enable all the messages in the NFS server module
  		nullarbor:~ # echo -n 'module nfsd +p' >
  						<debugfs>/dynamic_debug/control
  
  		// enable all 12 messages in the function svc_process()
  		nullarbor:~ # echo -n 'func svc_process +p' >
  						<debugfs>/dynamic_debug/control
  
  		// disable all 12 messages in the function svc_process()
  		nullarbor:~ # echo -n 'func svc_process -p' >
  						<debugfs>/dynamic_debug/control
  
  	  See Documentation/dynamic-debug-howto.txt for additional information.
  
  endmenu # "printk and dmesg options"

  menu "Compile-time checks and compiler options"
  
  config DEBUG_INFO
  	bool "Compile the kernel with debug info"

  	depends on DEBUG_KERNEL && !COMPILE_TEST

  	help
            If you say Y here the resulting kernel image will include
  	  debugging info resulting in a larger kernel image.
  	  This adds debug symbols to the kernel and modules (gcc -g), and
  	  is needed if you intend to use kernel crashdump or binary object
  	  tools like crash, kgdb, LKCD, gdb, etc on the kernel.
  	  Say Y here only if you plan to debug the kernel.
  
  	  If unsure, say N.
  
  config DEBUG_INFO_REDUCED
  	bool "Reduce debugging information"
  	depends on DEBUG_INFO
  	help
  	  If you say Y here gcc is instructed to generate less debugging
  	  information for structure types. This means that tools that
  	  need full debugging information (like kgdb or systemtap) won't
  	  be happy. But if you merely need debugging information to
  	  resolve line numbers there is no loss. Advantage is that
  	  build directory object sizes shrink dramatically over a full
  	  DEBUG_INFO build and compile times are reduced too.
  	  Only works with newer gcc versions.

  config DEBUG_INFO_SPLIT
  	bool "Produce split debuginfo in .dwo files"
  	depends on DEBUG_INFO
  	help
  	  Generate debug info into separate .dwo files. This significantly
  	  reduces the build directory size for builds with DEBUG_INFO,
  	  because it stores the information only once on disk in .dwo
  	  files instead of multiple times in object files and executables.
  	  In addition the debug information is also compressed.
  
  	  Requires recent gcc (4.7+) and recent gdb/binutils.
  	  Any tool that packages or reads debug information would need
  	  to know about the .dwo files and include them.
  	  Incompatible with older versions of ccache.

  config DEBUG_INFO_DWARF4
  	bool "Generate dwarf4 debuginfo"
  	depends on DEBUG_INFO
  	help
  	  Generate dwarf4 debug info. This requires recent versions
  	  of gcc and gdb. It makes the debug information larger.
  	  But it significantly improves the success of resolving
  	  variables in gdb on optimized code.

  config GDB_SCRIPTS
  	bool "Provide GDB scripts for kernel debugging"
  	depends on DEBUG_INFO
  	help
  	  This creates the required links to GDB helper scripts in the
  	  build directory. If you load vmlinux into gdb, the helper
  	  scripts will be automatically imported by gdb as well, and
  	  additional functions are available to analyze a Linux kernel
  	  instance. See Documentation/gdb-kernel-debugging.txt for further
  	  details.

  config ENABLE_WARN_DEPRECATED
  	bool "Enable __deprecated logic"
  	default y
  	help
  	  Enable the __deprecated logic in the kernel build.
  	  Disable this to suppress the "warning: 'foo' is deprecated
  	  (declared at kernel/power/somefile.c:1234)" messages.

  config ENABLE_MUST_CHECK
  	bool "Enable __must_check logic"
  	default y
  	help
  	  Enable the __must_check logic in the kernel build.  Disable this to
  	  suppress the "warning: ignoring return value of 'foo', declared with
  	  attribute warn_unused_result" messages.

  config FRAME_WARN
  	int "Warn for stack frames larger than (needs gcc 4.4)"
  	range 0 8192

  	default 0 if KASAN

  	default 2048 if GCC_PLUGIN_LATENT_ENTROPY

  	default 1024 if !64BIT
  	default 2048 if 64BIT
  	help
  	  Tell gcc to warn at build time for stack frames larger than this.
  	  Setting this too low will cause a lot of warnings.
  	  Setting it to 0 disables the warning.
  	  Requires gcc 4.4

  config STRIP_ASM_SYMS
  	bool "Strip assembler-generated symbols during link"
  	default n
  	help
  	  Strip internal assembler-generated symbols during a link (symbols
  	  that look like '.Lxxx') so they don't pollute the output of
  	  get_wchan() and suchlike.

  config READABLE_ASM
          bool "Generate readable assembler code"
          depends on DEBUG_KERNEL
          help
            Disable some compiler optimizations that tend to generate human unreadable
            assembler output. This may make the kernel slightly slower, but it helps
            to keep kernel developers who have to stare a lot at assembler listings
            sane.

  config UNUSED_SYMBOLS
  	bool "Enable unused/obsolete exported symbols"
  	default y if X86
  	help
  	  Unused but exported symbols make the kernel needlessly bigger.  For
  	  that reason most of these unused exports will soon be removed.  This
  	  option is provided temporarily to provide a transition period in case
  	  some external kernel module needs one of these symbols anyway. If you
  	  encounter such a case in your module, consider if you are actually
  	  using the right API.  (rationale: since nobody in the kernel is using
  	  this in a module, there is a pretty good chance it's actually the
  	  wrong interface to use).  If you really need the symbol, please send a
  	  mail to the linux kernel mailing list mentioning the symbol and why
  	  you really need it, and what the merge plan to the mainline kernel for
  	  your module is.

  config PAGE_OWNER
  	bool "Track page owner"
  	depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
  	select DEBUG_FS
  	select STACKTRACE

  	select STACKDEPOT

  	select PAGE_EXTENSION
  	help
  	  This keeps track of what call chain is the owner of a page, may
  	  help to find bare alloc_page(s) leaks. Even if you include this
  	  feature on your build, it is disabled in default. You should pass
  	  "page_owner=on" to boot parameter in order to enable it. Eats
  	  a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
  	  for user-space helper.
  
  	  If unsure, say N.

  config DEBUG_FS
  	bool "Debug Filesystem"

  	select SRCU

  	help
  	  debugfs is a virtual file system that kernel developers use to put
  	  debugging files into.  Enable this option to be able to read and
  	  write to these files.

  	  For detailed documentation on the debugfs API, see
  	  Documentation/DocBook/filesystems.

  	  If unsure, say N.
  
  config HEADERS_CHECK
  	bool "Run 'make headers_check' when building vmlinux"
  	depends on !UML
  	help
  	  This option will extract the user-visible kernel headers whenever
  	  building the kernel, and will run basic sanity checks on them to
  	  ensure that exported files do not attempt to include files which
  	  were not exported, etc.
  
  	  If you're making modifications to header files which are
  	  relevant for userspace, say 'Y', and check the headers
  	  exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
  	  your build tree), to make sure they're suitable.

  config DEBUG_SECTION_MISMATCH
  	bool "Enable full Section mismatch analysis"

  	help
  	  The section mismatch analysis checks if there are illegal
  	  references from one section to another section.

  	  During linktime or runtime, some sections are dropped;
  	  any use of code/data previously in these sections would

  	  most likely result in an oops.

  	  In the code, functions and variables are annotated with

  	  __init,, etc. (see the full list in include/linux/init.h),

  	  which results in the code/data being placed in specific sections.

  	  The section mismatch analysis is always performed after a full
  	  kernel build, and enabling this option causes the following
  	  additional steps to occur:
  	  - Add the option -fno-inline-functions-called-once to gcc commands.
  	    When inlining a function annotated with __init in a non-init
  	    function, we would lose the section information and thus

  	    the analysis would not catch the illegal reference.

  	    This option tells gcc to inline less (but it does result in
  	    a larger kernel).
  	  - Run the section mismatch analysis for each module/built-in.o file.
  	    When we run the section mismatch analysis on vmlinux.o, we

  	    lose valuable information about where the mismatch was

  	    introduced.
  	    Running the analysis for each module/built-in.o file

  	    tells where the mismatch happens much closer to the
  	    source. The drawback is that the same mismatch is
  	    reported at least twice.
  	  - Enable verbose reporting from modpost in order to help resolve
  	    the section mismatches that are reported.

  config SECTION_MISMATCH_WARN_ONLY
  	bool "Make section mismatch errors non-fatal"
  	default y
  	help
  	  If you say N here, the build process will fail if there are any
  	  section mismatch, instead of just throwing warnings.
  
  	  If unsure, say Y.

  #
  # Select this config option from the architecture Kconfig, if it
  # is preferred to always offer frame pointers as a config
  # option on the architecture (regardless of KERNEL_DEBUG):
  #
  config ARCH_WANT_FRAME_POINTERS
  	bool

  	help

  config FRAME_POINTER
  	bool "Compile the kernel with frame pointers"
  	depends on DEBUG_KERNEL && \
  		(CRIS || M68K || FRV || UML || \
  		 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \
  		ARCH_WANT_FRAME_POINTERS
  	default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS

  	help

  	  If you say Y here the resulting kernel image will be slightly
  	  larger and slower, but it gives very useful debugging information
  	  in case of kernel bugs. (precise oopses/stacktraces/warnings)

  config STACK_VALIDATION
  	bool "Compile-time stack metadata validation"
  	depends on HAVE_STACK_VALIDATION
  	default n
  	help
  	  Add compile-time checks to validate stack metadata, including frame
  	  pointers (if CONFIG_FRAME_POINTER is enabled).  This helps ensure
  	  that runtime stack traces are more reliable.
  
  	  For more information, see
  	  tools/objtool/Documentation/stack-validation.txt.

  config DEBUG_FORCE_WEAK_PER_CPU
  	bool "Force weak per-cpu definitions"
  	depends on DEBUG_KERNEL

  	help

  	  s390 and alpha require percpu variables in modules to be
  	  defined weak to work around addressing range issue which
  	  puts the following two restrictions on percpu variable
  	  definitions.

  	  1. percpu symbols must be unique whether static or not
  	  2. percpu variables can't be defined inside a function

  	  To ensure that generic code follows the above rules, this
  	  option forces all percpu variables to be defined as weak.

  endmenu # "Compiler options"

  config MAGIC_SYSRQ
  	bool "Magic SysRq key"
  	depends on !UML
  	help
  	  If you say Y here, you will have some control over the system even
  	  if the system crashes for example during kernel debugging (e.g., you
  	  will be able to flush the buffer cache to disk, reboot the system
  	  immediately or dump some status information). This is accomplished
  	  by pressing various keys while holding SysRq (Alt+PrintScreen). It
  	  also works on a serial console (on PC hardware at least), if you
  	  send a BREAK and then within 5 seconds a command keypress. The
  	  keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
  	  unless you really know what this hack does.

  config MAGIC_SYSRQ_DEFAULT_ENABLE
  	hex "Enable magic SysRq key functions by default"
  	depends on MAGIC_SYSRQ
  	default 0x1
  	help
  	  Specifies which SysRq key functions are enabled by default.
  	  This may be set to 1 or 0 to enable or disable them all, or
  	  to a bitmask as described in Documentation/sysrq.txt.

  config DEBUG_KERNEL
  	bool "Kernel debugging"

  	help

  	  Say Y here if you are developing drivers or trying to debug and
  	  identify kernel problems.

  menu "Memory Debugging"

  source mm/Kconfig.debug

  config DEBUG_OBJECTS
  	bool "Debug object operations"
  	depends on DEBUG_KERNEL

  	help

  	  If you say Y here, additional code will be inserted into the
  	  kernel to track the life time of various objects and validate
  	  the operations on those objects.

  config DEBUG_OBJECTS_SELFTEST
  	bool "Debug objects selftest"
  	depends on DEBUG_OBJECTS
  	help
  	  This enables the selftest of the object debug code.

  config DEBUG_OBJECTS_FREE
  	bool "Debug objects in freed memory"
  	depends on DEBUG_OBJECTS
  	help
  	  This enables checks whether a k/v free operation frees an area
  	  which contains an object which has not been deactivated
  	  properly. This can make kmalloc/kfree-intensive workloads
  	  much slower.

  config DEBUG_OBJECTS_TIMERS
  	bool "Debug timer objects"
  	depends on DEBUG_OBJECTS
  	help
  	  If you say Y here, additional code will be inserted into the
  	  timer routines to track the life time of timer objects and
  	  validate the timer operations.

  config DEBUG_OBJECTS_WORK
  	bool "Debug work objects"
  	depends on DEBUG_OBJECTS
  	help
  	  If you say Y here, additional code will be inserted into the
  	  work queue routines to track the life time of work objects and
  	  validate the work operations.

  config DEBUG_OBJECTS_RCU_HEAD
  	bool "Debug RCU callbacks objects"

  	depends on DEBUG_OBJECTS

  	help
  	  Enable this to turn on debugging of RCU list heads (call_rcu() usage).

  config DEBUG_OBJECTS_PERCPU_COUNTER
  	bool "Debug percpu counter objects"
  	depends on DEBUG_OBJECTS
  	help
  	  If you say Y here, additional code will be inserted into the
  	  percpu counter routines to track the life time of percpu counter
  	  objects and validate the percpu counter operations.

  config DEBUG_OBJECTS_ENABLE_DEFAULT
  	int "debug_objects bootup default value (0-1)"
          range 0 1
          default "1"
          depends on DEBUG_OBJECTS
          help
            Debug objects boot parameter default value

  config DEBUG_SLAB

  	bool "Debug slab memory allocations"

  	depends on DEBUG_KERNEL && SLAB && !KMEMCHECK

  	help
  	  Say Y here to have the kernel do limited verification on memory
  	  allocation as well as poisoning memory on free to catch use of freed
  	  memory. This can make kmalloc/kfree-intensive workloads much slower.

  config DEBUG_SLAB_LEAK
  	bool "Memory leak debugging"
  	depends on DEBUG_SLAB

  config SLUB_DEBUG_ON
  	bool "SLUB debugging on by default"

  	depends on SLUB && SLUB_DEBUG && !KMEMCHECK

  	default n
  	help
  	  Boot with debugging on by default. SLUB boots by default with
  	  the runtime debug capabilities switched off. Enabling this is
  	  equivalent to specifying the "slub_debug" parameter on boot.
  	  There is no support for more fine grained debug control like
  	  possible with slub_debug=xxx. SLUB debugging may be switched
  	  off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
  	  "slub_debug=-".

  config SLUB_STATS
  	default n
  	bool "Enable SLUB performance statistics"

  	depends on SLUB && SYSFS

  	help
  	  SLUB statistics are useful to debug SLUBs allocation behavior in
  	  order find ways to optimize the allocator. This should never be
  	  enabled for production use since keeping statistics slows down
  	  the allocator by a few percentage points. The slabinfo command
  	  supports the determination of the most active slabs to figure
  	  out which slabs are relevant to a particular load.
  	  Try running: slabinfo -DA

  config HAVE_DEBUG_KMEMLEAK
  	bool

  config DEBUG_KMEMLEAK
  	bool "Kernel memory leak detector"

  	depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK

  	select DEBUG_FS

  	select STACKTRACE if STACKTRACE_SUPPORT
  	select KALLSYMS

  	select CRC32

  	help
  	  Say Y here if you want to enable the memory leak
  	  detector. The memory allocation/freeing is traced in a way
  	  similar to the Boehm's conservative garbage collector, the
  	  difference being that the orphan objects are not freed but
  	  only shown in /sys/kernel/debug/kmemleak. Enabling this
  	  feature will introduce an overhead to memory
  	  allocations. See Documentation/kmemleak.txt for more
  	  details.

  	  Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
  	  of finding leaks due to the slab objects poisoning.
  
  	  In order to access the kmemleak file, debugfs needs to be
  	  mounted (usually at /sys/kernel/debug).
  
  config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
  	int "Maximum kmemleak early log entries"
  	depends on DEBUG_KMEMLEAK
  	range 200 40000
  	default 400
  	help
  	  Kmemleak must track all the memory allocations to avoid
  	  reporting false positives. Since memory may be allocated or
  	  freed before kmemleak is initialised, an early log buffer is
  	  used to store these actions. If kmemleak reports "early log
  	  buffer exceeded", please increase this value.
  
  config DEBUG_KMEMLEAK_TEST
  	tristate "Simple test for the kernel memory leak detector"
  	depends on DEBUG_KMEMLEAK && m
  	help
  	  This option enables a module that explicitly leaks memory.
  
  	  If unsure, say N.
  
  config DEBUG_KMEMLEAK_DEFAULT_OFF
  	bool "Default kmemleak to off"
  	depends on DEBUG_KMEMLEAK
  	help
  	  Say Y here to disable kmemleak by default. It can then be enabled
  	  on the command line via kmemleak=on.
  
  config DEBUG_STACK_USAGE
  	bool "Stack utilization instrumentation"

  	depends on DEBUG_KERNEL && !IA64

  	help
  	  Enables the display of the minimum amount of free stack which each
  	  task has ever had available in the sysrq-T and sysrq-P debug output.
  
  	  This option will slow down process creation somewhat.
  
  config DEBUG_VM
  	bool "Debug VM"
  	depends on DEBUG_KERNEL
  	help
  	  Enable this to turn on extended checks in the virtual-memory system
            that may impact performance.
  
  	  If unsure, say N.

  config DEBUG_VM_VMACACHE
  	bool "Debug VMA caching"
  	depends on DEBUG_VM
  	help
  	  Enable this to turn on VMA caching debug information. Doing so
  	  can cause significant overhead, so only enable it in non-production
  	  environments.
  
  	  If unsure, say N.

  config DEBUG_VM_RB
  	bool "Debug VM red-black trees"
  	depends on DEBUG_VM
  	help

  	  Enable VM red-black tree debugging information and extra validations.

  
  	  If unsure, say N.

  config DEBUG_VM_PGFLAGS
  	bool "Debug page-flags operations"
  	depends on DEBUG_VM
  	help
  	  Enables extra validation on page flags operations.
  
  	  If unsure, say N.

  config DEBUG_VIRTUAL
  	bool "Debug VM translations"
  	depends on DEBUG_KERNEL && X86
  	help
  	  Enable some costly sanity checks in virtual to page code. This can
  	  catch mistakes with virt_to_page() and friends.
  
  	  If unsure, say N.
  
  config DEBUG_NOMMU_REGIONS
  	bool "Debug the global anon/private NOMMU mapping region tree"
  	depends on DEBUG_KERNEL && !MMU
  	help
  	  This option causes the global tree of anonymous and private mapping
  	  regions to be regularly checked for invalid topology.
  
  config DEBUG_MEMORY_INIT
  	bool "Debug memory initialisation" if EXPERT
  	default !EXPERT
  	help
  	  Enable this for additional checks during memory initialisation.
  	  The sanity checks verify aspects of the VM such as the memory model
  	  and other information provided by the architecture. Verbose
  	  information will be printed at KERN_DEBUG loglevel depending
  	  on the mminit_loglevel= command-line option.
  
  	  If unsure, say Y
  
  config MEMORY_NOTIFIER_ERROR_INJECT
  	tristate "Memory hotplug notifier error injection module"
  	depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
  	help
  	  This option provides the ability to inject artificial errors to
  	  memory hotplug notifier chain callbacks.  It is controlled through
  	  debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
  
  	  If the notifier call chain should be failed with some events
  	  notified, write the error code to "actions/<notifier event>/error".
  
  	  Example: Inject memory hotplug offline error (-12 == -ENOMEM)
  
  	  # cd /sys/kernel/debug/notifier-error-inject/memory
  	  # echo -12 > actions/MEM_GOING_OFFLINE/error
  	  # echo offline > /sys/devices/system/memory/memoryXXX/state
  	  bash: echo: write error: Cannot allocate memory
  
  	  To compile this code as a module, choose M here: the module will
  	  be called memory-notifier-error-inject.
  
  	  If unsure, say N.
  
  config DEBUG_PER_CPU_MAPS
  	bool "Debug access to per_cpu maps"
  	depends on DEBUG_KERNEL
  	depends on SMP
  	help
  	  Say Y to verify that the per_cpu map being accessed has
  	  been set up. This adds a fair amount of code to kernel memory
  	  and decreases performance.
  
  	  Say N if unsure.
  
  config DEBUG_HIGHMEM
  	bool "Highmem debugging"
  	depends on DEBUG_KERNEL && HIGHMEM
  	help

  	  This option enables additional error checking for high memory
  	  systems.  Disable for production systems.

  
  config HAVE_DEBUG_STACKOVERFLOW
  	bool
  
  config DEBUG_STACKOVERFLOW
  	bool "Check for stack overflows"
  	depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
  	---help---
  	  Say Y here if you want to check for overflows of kernel, IRQ

  	  and exception stacks (if your architecture uses them). This

  	  option will show detailed messages if free stack space drops
  	  below a certain limit.
  
  	  These kinds of bugs usually occur when call-chains in the
  	  kernel get too deep, especially when interrupts are
  	  involved.
  
  	  Use this in cases where you see apparently random memory
  	  corruption, especially if it appears in 'struct thread_info'
  
  	  If in doubt, say "N".
  
  source "lib/Kconfig.kmemcheck"

  source "lib/Kconfig.kasan"

  endmenu # "Memory Debugging"

  config ARCH_HAS_KCOV
  	bool
  	help
  	  KCOV does not have any arch-specific code, but currently it is enabled
  	  only for x86_64. KCOV requires testing on other archs, and most likely
  	  disabling of instrumentation for some early boot code.
  
  config KCOV
  	bool "Code coverage for fuzzing"
  	depends on ARCH_HAS_KCOV
  	select DEBUG_FS

  	select GCC_PLUGINS if !COMPILE_TEST
  	select GCC_PLUGIN_SANCOV if !COMPILE_TEST

  	help
  	  KCOV exposes kernel code coverage information in a form suitable
  	  for coverage-guided fuzzing (randomized testing).
  
  	  If RANDOMIZE_BASE is enabled, PC values will not be stable across
  	  different machines and across reboots. If you need stable PC values,
  	  disable RANDOMIZE_BASE.
  
  	  For more details, see Documentation/kcov.txt.

  config KCOV_INSTRUMENT_ALL
  	bool "Instrument all code by default"
  	depends on KCOV
  	default y if KCOV
  	help
  	  If you are doing generic system call fuzzing (like e.g. syzkaller),
  	  then you will want to instrument the whole kernel and you should
  	  say y here. If you are doing more targeted fuzzing (like e.g.
  	  filesystem fuzzing with AFL) then you will want to enable coverage
  	  for more specific subsets of files, and should say n here.

  config DEBUG_SHIRQ
  	bool "Debug shared IRQ handlers"

  	depends on DEBUG_KERNEL

  	help
  	  Enable this to generate a spurious interrupt as soon as a shared
  	  interrupt handler is registered, and just before one is deregistered.
  	  Drivers ought to be able to handle interrupts coming in at those
  	  points; some don't and need to be caught.

  menu "Debug Lockups and Hangs"

  config LOCKUP_DETECTOR
  	bool "Detect Hard and Soft Lockups"

  	depends on DEBUG_KERNEL && !S390

  	help

  	  Say Y here to enable the kernel to act as a watchdog to detect
  	  hard and soft lockups.
  
  	  Softlockups are bugs that cause the kernel to loop in kernel

  	  mode for more than 20 seconds, without giving other tasks a

  	  chance to run.  The current stack trace is displayed upon
  	  detection and the system will stay locked up.

  	  Hardlockups are bugs that cause the CPU to loop in kernel mode

  	  for more than 10 seconds, without letting other interrupts have a

  	  chance to run.  The current stack trace is displayed upon detection
  	  and the system will stay locked up.

  	  The overhead should be minimal.  A periodic hrtimer runs to

  	  generate interrupts and kick the watchdog task every 4 seconds.
  	  An NMI is generated every 10 seconds or so to check for hardlockups.
  
  	  The frequency of hrtimer and NMI events and the soft and hard lockup
  	  thresholds can be controlled through the sysctl watchdog_thresh.

  config HARDLOCKUP_DETECTOR

  	def_bool y
  	depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
  	depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI

  config BOOTPARAM_HARDLOCKUP_PANIC
  	bool "Panic (Reboot) On Hard Lockups"

  	depends on HARDLOCKUP_DETECTOR

  	help
  	  Say Y here to enable the kernel to panic on "hard lockups",
  	  which are bugs that cause the kernel to loop in kernel

  	  mode with interrupts disabled for more than 10 seconds (configurable
  	  using the watchdog_thresh sysctl).

  
  	  Say N if unsure.
  
  config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
  	int

  	depends on HARDLOCKUP_DETECTOR

  	range 0 1
  	default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
  	default 1 if BOOTPARAM_HARDLOCKUP_PANIC

  config BOOTPARAM_SOFTLOCKUP_PANIC
  	bool "Panic (Reboot) On Soft Lockups"

  	depends on LOCKUP_DETECTOR

  	help
  	  Say Y here to enable the kernel to panic on "soft lockups",
  	  which are bugs that cause the kernel to loop in kernel

  	  mode for more than 20 seconds (configurable using the watchdog_thresh
  	  sysctl), without giving other tasks a chance to run.

  
  	  The panic can be used in combination with panic_timeout,
  	  to cause the system to reboot automatically after a
  	  lockup has been detected. This feature is useful for
  	  high-availability systems that have uptime guarantees and
  	  where a lockup must be resolved ASAP.
  
  	  Say N if unsure.
  
  config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
  	int

  	depends on LOCKUP_DETECTOR

  	range 0 1
  	default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
  	default 1 if BOOTPARAM_SOFTLOCKUP_PANIC

  config DETECT_HUNG_TASK
  	bool "Detect Hung Tasks"
  	depends on DEBUG_KERNEL

  	default LOCKUP_DETECTOR

  	help

  	  Say Y here to enable the kernel to detect "hung tasks",
  	  which are bugs that cause the task to be stuck in

  	  uninterruptible "D" state indefinitely.

  	  When a hung task is detected, the kernel will print the
  	  current stack trace (which you should report), but the
  	  task will stay in uninterruptible state. If lockdep is
  	  enabled then all held locks will also be reported. This
  	  feature has negligible overhead.

  config DEFAULT_HUNG_TASK_TIMEOUT
  	int "Default timeout for hung task detection (in seconds)"
  	depends on DETECT_HUNG_TASK
  	default 120

  	help

  	  This option controls the default timeout (in seconds) used
  	  to determine when a task has become non-responsive and should
  	  be considered hung.

  	  It can be adjusted at runtime via the kernel.hung_task_timeout_secs
  	  sysctl or by writing a value to
  	  /proc/sys/kernel/hung_task_timeout_secs.

  	  A timeout of 0 disables the check.  The default is two minutes.
  	  Keeping the default should be fine in most cases.

  config BOOTPARAM_HUNG_TASK_PANIC
  	bool "Panic (Reboot) On Hung Tasks"
  	depends on DETECT_HUNG_TASK

  	help

  	  Say Y here to enable the kernel to panic on "hung tasks",
  	  which are bugs that cause the kernel to leave a task stuck
  	  in uninterruptible "D" state.

  	  The panic can be used in combination with panic_timeout,
  	  to cause the system to reboot automatically after a
  	  hung task has been detected. This feature is useful for
  	  high-availability systems that have uptime guarantees and
  	  where a hung tasks must be resolved ASAP.

  	  Say N if unsure.

  config BOOTPARAM_HUNG_TASK_PANIC_VALUE
  	int
  	depends on DETECT_HUNG_TASK
  	range 0 1
  	default 0 if !BOOTPARAM_HUNG_TASK_PANIC
  	default 1 if BOOTPARAM_HUNG_TASK_PANIC

  config WQ_WATCHDOG
  	bool "Detect Workqueue Stalls"
  	depends on DEBUG_KERNEL
  	help
  	  Say Y here to enable stall detection on workqueues.  If a
  	  worker pool doesn't make forward progress on a pending work
  	  item for over a given amount of time, 30s by default, a
  	  warning message is printed along with dump of workqueue
  	  state.  This can be configured through kernel parameter
  	  "workqueue.watchdog_thresh" and its sysfs counterpart.

  endmenu # "Debug lockups and hangs"
  
  config PANIC_ON_OOPS
  	bool "Panic on Oops"

  	help

  	  Say Y here to enable the kernel to panic when it oopses. This
  	  has the same effect as setting oops=panic on the kernel command
  	  line.

  	  This feature is useful to ensure that the kernel does not do
  	  anything erroneous after an oops which could result in data
  	  corruption or other issues.
  
  	  Say N if unsure.
  
  config PANIC_ON_OOPS_VALUE
  	int
  	range 0 1
  	default 0 if !PANIC_ON_OOPS
  	default 1 if PANIC_ON_OOPS

  config PANIC_TIMEOUT
  	int "panic timeout"
  	default 0
  	help
  	  Set the timeout value (in seconds) until a reboot occurs when the
  	  the kernel panics. If n = 0, then we wait forever. A timeout
  	  value n > 0 will wait n seconds before rebooting, while a timeout
  	  value n < 0 will reboot immediately.

  config SCHED_DEBUG
  	bool "Collect scheduler debugging info"
  	depends on DEBUG_KERNEL && PROC_FS
  	default y

  	help

  	  If you say Y here, the /proc/sched_debug file will be provided
  	  that can help debug the scheduler. The runtime overhead of this
  	  option is minimal.

  config SCHED_INFO
  	bool
  	default n

  config SCHEDSTATS
  	bool "Collect scheduler statistics"
  	depends on DEBUG_KERNEL && PROC_FS

  	select SCHED_INFO

  	help
  	  If you say Y here, additional code will be inserted into the
  	  scheduler and related routines to collect statistics about
  	  scheduler behavior and provide them in /proc/schedstat.  These
  	  stats may be useful for both tuning and debugging the scheduler
  	  If you aren't debugging the scheduler or trying to tune a specific
  	  application, you can say N to avoid the very slight overhead
  	  this adds.

  config SCHED_STACK_END_CHECK
  	bool "Detect stack corruption on calls to schedule()"
  	depends on DEBUG_KERNEL
  	default n
  	help
  	  This option checks for a stack overrun on calls to schedule().
  	  If the stack end location is found to be over written always panic as
  	  the content of the corrupted region can no longer be trusted.
  	  This is to ensure no erroneous behaviour occurs which could result in
  	  data corruption or a sporadic crash at a later stage once the region
  	  is examined. The runtime overhead introduced is minimal.

  config DEBUG_TIMEKEEPING
  	bool "Enable extra timekeeping sanity checking"
  	help
  	  This option will enable additional timekeeping sanity checks
  	  which may be helpful when diagnosing issues where timekeeping
  	  problems are suspected.
  
  	  This may include checks in the timekeeping hotpaths, so this
  	  option may have a (very small) performance impact to some
  	  workloads.
  
  	  If unsure, say N.

  config TIMER_STATS
  	bool "Collect kernel timers statistics"
  	depends on DEBUG_KERNEL && PROC_FS

  	help

  	  If you say Y here, additional code will be inserted into the
  	  timer routines to collect statistics about kernel timers being
  	  reprogrammed. The statistics can be read from /proc/timer_stats.
  	  The statistics collection is started by writing 1 to /proc/timer_stats,
  	  writing 0 stops it. This feature is useful to collect information
  	  about timer usage patterns in kernel and userspace. This feature
  	  is lightweight if enabled in the kernel config but not activated
  	  (it defaults to deactivated on bootup and will only be activated
  	  if some application like powertop activates it explicitly).

  config DEBUG_PREEMPT
  	bool "Debug preemptible kernel"

  	depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT

  	default y
  	help
  	  If you say Y here then the kernel will use a debug variant of the
  	  commonly used smp_processor_id() function and will print warnings
  	  if kernel code uses it in a preemption-unsafe way. Also, the kernel
  	  will detect preemption count underflows.

  menu "Lock Debugging (spinlocks, mutexes, etc...)"

  config DEBUG_RT_MUTEXES
  	bool "RT Mutex debugging, deadlock detection"

  	depends on DEBUG_KERNEL && RT_MUTEXES
  	help
  	 This allows rt mutex semantics violations and rt mutex related
  	 deadlocks (lockups) to be detected and reported automatically.

  config DEBUG_SPINLOCK

  	bool "Spinlock and rw-lock debugging: basic checks"

  	depends on DEBUG_KERNEL

  	select UNINLINE_SPIN_UNLOCK

  	help
  	  Say Y here and build SMP to catch missing spinlock initialization
  	  and certain other kinds of spinlock errors commonly made.  This is
  	  best used in conjunction with the NMI watchdog so that spinlock
  	  deadlocks are also debuggable.

  config DEBUG_MUTEXES
  	bool "Mutex debugging: basic checks"
  	depends on DEBUG_KERNEL
  	help
  	 This feature allows mutex semantics violations to be detected and
  	 reported.

  config DEBUG_WW_MUTEX_SLOWPATH
  	bool "Wait/wound mutex debugging: Slowpath testing"
  	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
  	select DEBUG_LOCK_ALLOC
  	select DEBUG_SPINLOCK
  	select DEBUG_MUTEXES
  	help
  	 This feature enables slowpath testing for w/w mutex users by
  	 injecting additional -EDEADLK wound/backoff cases. Together with
  	 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
  	 will test all possible w/w mutex interface abuse with the
  	 exception of simply not acquiring all the required locks.

  	 Note that this feature can introduce significant overhead, so
  	 it really should not be enabled in a production or distro kernel,
  	 even a debug kernel.  If you are a driver writer, enable it.  If
  	 you are a distro, do not.

  config DEBUG_LOCK_ALLOC
  	bool "Lock debugging: detect incorrect freeing of live locks"

  	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT

  	select DEBUG_SPINLOCK
  	select DEBUG_MUTEXES

  	select LOCKDEP
  	help
  	 This feature will check whether any held lock (spinlock, rwlock,
  	 mutex or rwsem) is incorrectly freed by the kernel, via any of the
  	 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
  	 vfree(), etc.), whether a live lock is incorrectly reinitialized via
  	 spin_lock_init()/mutex_init()/etc., or whether there is any lock
  	 held during task exit.
  
  config PROVE_LOCKING
  	bool "Lock debugging: prove locking correctness"

  	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT

  	select LOCKDEP
  	select DEBUG_SPINLOCK
  	select DEBUG_MUTEXES

  	select DEBUG_LOCK_ALLOC

  	select TRACE_IRQFLAGS

  	default n
  	help
  	 This feature enables the kernel to prove that all locking
  	 that occurs in the kernel runtime is mathematically
  	 correct: that under no circumstance could an arbitrary (and
  	 not yet triggered) combination of observed locking
  	 sequences (on an arbitrary number of CPUs, running an
  	 arbitrary number of tasks and interrupt contexts) cause a
  	 deadlock.
  
  	 In short, this feature enables the kernel to report locking
  	 related deadlocks before they actually occur.
  
  	 The proof does not depend on how hard and complex a
  	 deadlock scenario would be to trigger: how many
  	 participant CPUs, tasks and irq-contexts would be needed
  	 for it to trigger. The proof also does not depend on
  	 timing: if a race and a resulting deadlock is possible
  	 theoretically (no matter how unlikely the race scenario
  	 is), it will be proven so and will immediately be
  	 reported by the kernel (once the event is observed that
  	 makes the deadlock theoretically possible).
  
  	 If a deadlock is impossible (i.e. the locking rules, as
  	 observed by the kernel, are mathematically correct), the
  	 kernel reports nothing.
  
  	 NOTE: this feature can also be enabled for rwlocks, mutexes
  	 and rwsems - in which case all dependencies between these
  	 different locking variants are observed and mapped too, and
  	 the proof of observed correctness is also maintained for an
  	 arbitrary combination of these separate locking variants.

  	 For more details, see Documentation/locking/lockdep-design.txt.

  config PROVE_LOCKING_SMALL
  	bool

  config LOCKDEP
  	bool

  	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT

  	select STACKTRACE

  	select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE

  	select KALLSYMS
  	select KALLSYMS_ALL

  config LOCK_STAT

  	bool "Lock usage statistics"

  	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
  	select LOCKDEP
  	select DEBUG_SPINLOCK
  	select DEBUG_MUTEXES
  	select DEBUG_LOCK_ALLOC
  	default n
  	help
  	 This feature enables tracking lock contention points

  	 For more details, see Documentation/locking/lockstat.txt

  	 This also enables lock events required by "perf lock",
  	 subcommand of perf.
  	 If you want to use "perf lock", you also need to turn on
  	 CONFIG_EVENT_TRACING.

  
  	 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.

  	 (CONFIG_LOCKDEP defines "acquire" and "release" events.)

  config DEBUG_LOCKDEP
  	bool "Lock dependency engine debugging"

  	depends on DEBUG_KERNEL && LOCKDEP

  	help
  	  If you say Y here, the lock dependency engine will do
  	  additional runtime checks to debug itself, at the price
  	  of more runtime overhead.

  config DEBUG_ATOMIC_SLEEP
  	bool "Sleep inside atomic section checking"

  	select PREEMPT_COUNT

  	depends on DEBUG_KERNEL
  	help
  	  If you say Y here, various routines which may sleep will become very

  	  noisy if they are called inside atomic sections: when a spinlock is
  	  held, inside an rcu read side critical section, inside preempt disabled
  	  sections, inside an interrupt, etc...

  config DEBUG_LOCKING_API_SELFTESTS
  	bool "Locking API boot-time self-tests"
  	depends on DEBUG_KERNEL
  	help
  	  Say Y here if you want the kernel to run a short self-test during
  	  bootup. The self-test checks whether common types of locking bugs
  	  are detected by debugging mechanisms or not. (if you disable
  	  lock debugging then those bugs wont be detected of course.)
  	  The following locking APIs are covered: spinlocks, rwlocks,
  	  mutexes and rwsems.

  config LOCK_TORTURE_TEST
  	tristate "torture tests for locking"
  	depends on DEBUG_KERNEL
  	select TORTURE_TEST
  	default n
  	help
  	  This option provides a kernel module that runs torture tests
  	  on kernel locking primitives.  The kernel module may be built
  	  after the fact on the running kernel to be tested, if desired.
  
  	  Say Y here if you want kernel locking-primitive torture tests
  	  to be built into the kernel.
  	  Say M if you want these torture tests to build as a module.
  	  Say N if you are unsure.

  endmenu # lock debugging

  config TRACE_IRQFLAGS
  	bool

  	help

  	  Enables hooks to interrupt enabling and disabling for
  	  either tracing or lock debugging.

  config STACKTRACE

  	bool "Stack backtrace support"

  	depends on STACKTRACE_SUPPORT

  	help
  	  This option causes the kernel to create a /proc/pid/stack for
  	  every process, showing its current stack trace.
  	  It is also used by various kernel debugging features that require
  	  stack trace generation.

  config DEBUG_KOBJECT
  	bool "kobject debugging"
  	depends on DEBUG_KERNEL
  	help
  	  If you say Y here, some extra kobject debugging messages will be sent
  	  to the syslog. 

  config DEBUG_KOBJECT_RELEASE
  	bool "kobject release debugging"

  	depends on DEBUG_OBJECTS_TIMERS

  	help
  	  kobjects are reference counted objects.  This means that their
  	  last reference count put is not predictable, and the kobject can
  	  live on past the point at which a driver decides to drop it's
  	  initial reference to the kobject gained on allocation.  An
  	  example of this would be a struct device which has just been
  	  unregistered.
  
  	  However, some buggy drivers assume that after such an operation,
  	  the memory backing the kobject can be immediately freed.  This
  	  goes completely against the principles of a refcounted object.
  
  	  If you say Y here, the kernel will delay the release of kobjects
  	  on the last reference count to improve the visibility of this
  	  kind of kobject release bug.

  config HAVE_DEBUG_BUGVERBOSE
  	bool

  config DEBUG_BUGVERBOSE

  	bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT

  	depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)

  	default y

  	help
  	  Say Y here to make BUG() panics output the file name and line number
  	  of the BUG call as well as the EIP and oops trace.  This aids
  	  debugging but costs about 70-100K of memory.

  config DEBUG_LIST
  	bool "Debug linked list manipulation"
  	depends on DEBUG_KERNEL
  	help
  	  Enable this to turn on extended checks in the linked-list
  	  walking routines.
  
  	  If unsure, say N.

  config DEBUG_PI_LIST
  	bool "Debug priority linked list manipulation"
  	depends on DEBUG_KERNEL
  	help
  	  Enable this to turn on extended checks in the priority-ordered
  	  linked-list (plist) walking routines.  This checks the entire
  	  list multiple times during each manipulation.
  
  	  If unsure, say N.

  config DEBUG_SG
  	bool "Debug SG table operations"
  	depends on DEBUG_KERNEL
  	help
  	  Enable this to turn on checks on scatter-gather tables. This can
  	  help find problems with drivers that do not properly initialize
  	  their sg tables.
  
  	  If unsure, say N.

  config DEBUG_NOTIFIERS
  	bool "Debug notifier call chains"
  	depends on DEBUG_KERNEL
  	help
  	  Enable this to turn on sanity checking for notifier call chains.
  	  This is most useful for kernel developers to make sure that
  	  modules properly unregister themselves from notifier chains.
  	  This is a relatively cheap check but if you care about maximum
  	  performance, say N.

  config DEBUG_CREDENTIALS
  	bool "Debug credential management"
  	depends on DEBUG_KERNEL
  	help
  	  Enable this to turn on some debug checking for credential
  	  management.  The additional code keeps track of the number of
  	  pointers from task_structs to any given cred struct, and checks to
  	  see that this number never exceeds the usage count of the cred
  	  struct.
  
  	  Furthermore, if SELinux is enabled, this also checks that the
  	  security pointer in the cred struct is never seen to be invalid.
  
  	  If unsure, say N.

  menu "RCU Debugging"
  
  config PROVE_RCU

  	def_bool PROVE_LOCKING

  
  config PROVE_RCU_REPEATEDLY
  	bool "RCU debugging: don't disable PROVE_RCU on first splat"
  	depends on PROVE_RCU
  	default n
  	help
  	 By itself, PROVE_RCU will disable checking upon issuing the
  	 first warning (or "splat").  This feature prevents such
  	 disabling, allowing multiple RCU-lockdep warnings to be printed
  	 on a single reboot.
  
  	 Say Y to allow multiple RCU-lockdep warnings per boot.
  
  	 Say N if you are unsure.

  config SPARSE_RCU_POINTER
  	bool "RCU debugging: sparse-based checks for pointer usage"
  	default n
  	help
  	 This feature enables the __rcu sparse annotation for
  	 RCU-protected pointers.  This annotation will cause sparse
  	 to flag any non-RCU used of annotated pointers.  This can be
  	 helpful when debugging RCU usage.  Please note that this feature
  	 is not intended to enforce code cleanliness; it is instead merely
  	 a debugging aid.
  
  	 Say Y to make sparse flag questionable use of RCU-protected pointers
  
  	 Say N if you are unsure.

  config TORTURE_TEST
  	tristate
  	default n

  config RCU_PERF_TEST
  	tristate "performance tests for RCU"
  	depends on DEBUG_KERNEL
  	select TORTURE_TEST
  	select SRCU
  	select TASKS_RCU
  	default n
  	help
  	  This option provides a kernel module that runs performance
  	  tests on the RCU infrastructure.  The kernel module may be built
  	  after the fact on the running kernel to be tested, if desired.
  
  	  Say Y here if you want RCU performance tests to be built into
  	  the kernel.
  	  Say M if you want the RCU performance tests to build as a module.
  	  Say N if you are unsure.

  config RCU_TORTURE_TEST
  	tristate "torture tests for RCU"
  	depends on DEBUG_KERNEL

  	select TORTURE_TEST

  	select SRCU

  	select TASKS_RCU

  	default n
  	help
  	  This option provides a kernel module that runs torture tests
  	  on the RCU infrastructure.  The kernel module may be built
  	  after the fact on the running kernel to be tested, if desired.

  	  Say Y here if you want RCU torture tests to be built into
  	  the kernel.

  	  Say M if you want the RCU torture tests to build as a module.
  	  Say N if you are unsure.

  config RCU_TORTURE_TEST_SLOW_PREINIT
  	bool "Slow down RCU grace-period pre-initialization to expose races"
  	depends on RCU_TORTURE_TEST
  	help
  	  This option delays grace-period pre-initialization (the
  	  propagation of CPU-hotplug changes up the rcu_node combining
  	  tree) for a few jiffies between initializing each pair of
  	  consecutive rcu_node structures.  This helps to expose races
  	  involving grace-period pre-initialization, in other words, it
  	  makes your kernel less stable.  It can also greatly increase
  	  grace-period latency, especially on systems with large numbers
  	  of CPUs.  This is useful when torture-testing RCU, but in
  	  almost no other circumstance.
  
  	  Say Y here if you want your system to crash and hang more often.
  	  Say N if you want a sane system.
  
  config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
  	int "How much to slow down RCU grace-period pre-initialization"
  	range 0 5
  	default 3
  	depends on RCU_TORTURE_TEST_SLOW_PREINIT
  	help
  	  This option specifies the number of jiffies to wait between
  	  each rcu_node structure pre-initialization step.

  config RCU_TORTURE_TEST_SLOW_INIT
  	bool "Slow down RCU grace-period initialization to expose races"
  	depends on RCU_TORTURE_TEST
  	help

  	  This option delays grace-period initialization for a few
  	  jiffies between initializing each pair of consecutive

  	  rcu_node structures.	This helps to expose races involving
  	  grace-period initialization, in other words, it makes your
  	  kernel less stable.  It can also greatly increase grace-period
  	  latency, especially on systems with large numbers of CPUs.
  	  This is useful when torture-testing RCU, but in almost no
  	  other circumstance.
  
  	  Say Y here if you want your system to crash and hang more often.
  	  Say N if you want a sane system.
  
  config RCU_TORTURE_TEST_SLOW_INIT_DELAY
  	int "How much to slow down RCU grace-period initialization"
  	range 0 5

  	default 3

  	depends on RCU_TORTURE_TEST_SLOW_INIT

  	help
  	  This option specifies the number of jiffies to wait between
  	  each rcu_node structure initialization.

  config RCU_TORTURE_TEST_SLOW_CLEANUP
  	bool "Slow down RCU grace-period cleanup to expose races"
  	depends on RCU_TORTURE_TEST
  	help
  	  This option delays grace-period cleanup for a few jiffies
  	  between cleaning up each pair of consecutive rcu_node
  	  structures.  This helps to expose races involving grace-period
  	  cleanup, in other words, it makes your kernel less stable.
  	  It can also greatly increase grace-period latency, especially
  	  on systems with large numbers of CPUs.  This is useful when
  	  torture-testing RCU, but in almost no other circumstance.
  
  	  Say Y here if you want your system to crash and hang more often.
  	  Say N if you want a sane system.
  
  config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
  	int "How much to slow down RCU grace-period cleanup"
  	range 0 5
  	default 3
  	depends on RCU_TORTURE_TEST_SLOW_CLEANUP
  	help
  	  This option specifies the number of jiffies to wait between
  	  each rcu_node structure cleanup operation.

  config RCU_CPU_STALL_TIMEOUT
  	int "RCU CPU stall timeout in seconds"

  	depends on RCU_STALL_COMMON

  	range 3 300

  	default 21

  	help
  	  If a given RCU grace period extends more than the specified
  	  number of seconds, a CPU stall warning is printed.  If the
  	  RCU grace period persists, additional CPU stall warnings are
  	  printed at more widely spaced intervals.

  config RCU_TRACE
  	bool "Enable tracing for RCU"

  	depends on DEBUG_KERNEL

  	select TRACE_CLOCK

  	help

  	  This option provides tracing in RCU which presents stats
  	  in debugfs for debugging RCU implementation.

  	  Say Y here if you want to enable RCU tracing

  	  Say N if you are unsure.

  config RCU_EQS_DEBUG

  	bool "Provide debugging asserts for adding NO_HZ support to an arch"

  	depends on DEBUG_KERNEL
  	help
  	  This option provides consistency checks in RCU's handling of
  	  NO_HZ.  These checks have proven quite helpful in detecting
  	  bugs in arch-specific NO_HZ code.
  
  	  Say N here if you need ultimate kernel/user switch latencies
  	  Say Y if you are unsure

  endmenu # "RCU Debugging"

  config DEBUG_WQ_FORCE_RR_CPU
  	bool "Force round-robin CPU selection for unbound work items"
  	depends on DEBUG_KERNEL
  	default n
  	help
  	  Workqueue used to implicitly guarantee that work items queued
  	  without explicit CPU specified are put on the local CPU.  This
  	  guarantee is no longer true and while local CPU is still
  	  preferred work items may be put on foreign CPUs.  Kernel
  	  parameter "workqueue.debug_force_rr_cpu" is added to force
  	  round-robin CPU selection to flush out usages which depend on the
  	  now broken guarantee.  This config option enables the debug
  	  feature by default.  When enabled, memory and cache locality will
  	  be impacted.

  config DEBUG_BLOCK_EXT_DEVT
          bool "Force extended block device numbers and spread them"
  	depends on DEBUG_KERNEL
  	depends on BLOCK

  	default n

  	help

  	  BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
  	  SOME DISTRIBUTIONS.  DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
  	  YOU ARE DOING.  Distros, please enable this and fix whatever
  	  is broken.

  	  Conventionally, block device numbers are allocated from
  	  predetermined contiguous area.  However, extended block area
  	  may introduce non-contiguous block device numbers.  This
  	  option forces most block device numbers to be allocated from
  	  the extended space and spreads them to discover kernel or
  	  userland code paths which assume predetermined contiguous
  	  device number allocation.

  	  Note that turning on this debug option shuffles all the
  	  device numbers for all IDE and SCSI devices including libata
  	  ones, so root partition specified using device number
  	  directly (via rdev or root=MAJ:MIN) won't work anymore.
  	  Textual device names (root=/dev/sdXn) will continue to work.

  	  Say N if you are unsure.

  config CPU_HOTPLUG_STATE_CONTROL
  	bool "Enable CPU hotplug state control"
  	depends on DEBUG_KERNEL
  	depends on HOTPLUG_CPU
  	default n
  	help
  	  Allows to write steps between "offline" and "online" to the CPUs
  	  sysfs target file so states can be stepped granular. This is a debug
  	  option for now as the hotplug machinery cannot be stopped and
  	  restarted at arbitrary points yet.
  
  	  Say N if your are unsure.

  config NOTIFIER_ERROR_INJECTION
  	tristate "Notifier error injection"
  	depends on DEBUG_KERNEL
  	select DEBUG_FS
  	help

  	  This option provides the ability to inject artificial errors to

  	  specified notifier chain callbacks. It is useful to test the error
  	  handling of notifier call chain failures.
  
  	  Say N if unsure.

  config CPU_NOTIFIER_ERROR_INJECT
  	tristate "CPU notifier error injection module"

  	depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION

  	help
  	  This option provides a kernel module that can be used to test

  	  the error handling of the cpu notifiers by injecting artificial

  	  errors to CPU notifier chain callbacks.  It is controlled through
  	  debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu
  
  	  If the notifier call chain should be failed with some events
  	  notified, write the error code to "actions/<notifier event>/error".
  
  	  Example: Inject CPU offline error (-1 == -EPERM)
  
  	  # cd /sys/kernel/debug/notifier-error-inject/cpu
  	  # echo -1 > actions/CPU_DOWN_PREPARE/error
  	  # echo 0 > /sys/devices/system/cpu/cpu1/online
  	  bash: echo: write error: Operation not permitted

  
  	  To compile this code as a module, choose M here: the module will
  	  be called cpu-notifier-error-inject.
  
  	  If unsure, say N.

  config PM_NOTIFIER_ERROR_INJECT
  	tristate "PM notifier error injection module"
  	depends on PM && NOTIFIER_ERROR_INJECTION
  	default m if PM_DEBUG
  	help

  	  This option provides the ability to inject artificial errors to

  	  PM notifier chain callbacks.  It is controlled through debugfs
  	  interface /sys/kernel/debug/notifier-error-inject/pm
  
  	  If the notifier call chain should be failed with some events
  	  notified, write the error code to "actions/<notifier event>/error".
  
  	  Example: Inject PM suspend error (-12 = -ENOMEM)
  
  	  # cd /sys/kernel/debug/notifier-error-inject/pm/
  	  # echo -12 > actions/PM_SUSPEND_PREPARE/error
  	  # echo mem > /sys/power/state
  	  bash: echo: write error: Cannot allocate memory
  
  	  To compile this code as a module, choose M here: the module will
  	  be called pm-notifier-error-inject.
  
  	  If unsure, say N.

  config OF_RECONFIG_NOTIFIER_ERROR_INJECT
  	tristate "OF reconfig notifier error injection module"
  	depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION

  	help

  	  This option provides the ability to inject artificial errors to

  	  OF reconfig notifier chain callbacks.  It is controlled

  	  through debugfs interface under

  	  /sys/kernel/debug/notifier-error-inject/OF-reconfig/

  
  	  If the notifier call chain should be failed with some events
  	  notified, write the error code to "actions/<notifier event>/error".
  
  	  To compile this code as a module, choose M here: the module will

  	  be called of-reconfig-notifier-error-inject.

  
  	  If unsure, say N.

  config NETDEV_NOTIFIER_ERROR_INJECT
  	tristate "Netdev notifier error injection module"
  	depends on NET && NOTIFIER_ERROR_INJECTION
  	help
  	  This option provides the ability to inject artificial errors to
  	  netdevice notifier chain callbacks.  It is controlled through debugfs
  	  interface /sys/kernel/debug/notifier-error-inject/netdev
  
  	  If the notifier call chain should be failed with some events
  	  notified, write the error code to "actions/<notifier event>/error".
  
  	  Example: Inject netdevice mtu change error (-22 = -EINVAL)
  
  	  # cd /sys/kernel/debug/notifier-error-inject/netdev
  	  # echo -22 > actions/NETDEV_CHANGEMTU/error
  	  # ip link set eth0 mtu 1024
  	  RTNETLINK answers: Invalid argument
  
  	  To compile this code as a module, choose M here: the module will
  	  be called netdev-notifier-error-inject.
  
  	  If unsure, say N.

  config FAULT_INJECTION

  	bool "Fault-injection framework"
  	depends on DEBUG_KERNEL

  	help
  	  Provide fault-injection framework.
  	  For more details, see Documentation/fault-injection/.

  config FAILSLAB

  	bool "Fault-injection capability for kmalloc"
  	depends on FAULT_INJECTION

  	depends on SLAB || SLUB

  	help

  	  Provide fault-injection capability for kmalloc.

  config FAIL_PAGE_ALLOC
  	bool "Fault-injection capabilitiy for alloc_pages()"

  	depends on FAULT_INJECTION

  	help

  	  Provide fault-injection capability for alloc_pages().

  config FAIL_MAKE_REQUEST

  	bool "Fault-injection capability for disk IO"

  	depends on FAULT_INJECTION && BLOCK

  	help

  	  Provide fault-injection capability for disk IO.

  config FAIL_IO_TIMEOUT

  	bool "Fault-injection capability for faking disk interrupts"

  	depends on FAULT_INJECTION && BLOCK
  	help
  	  Provide fault-injection capability on end IO handling. This
  	  will make the block layer "forget" an interrupt as configured,
  	  thus exercising the error handling.
  
  	  Only works with drivers that use the generic timeout handling,
  	  for others it wont do anything.

  config FAIL_MMC_REQUEST
  	bool "Fault-injection capability for MMC IO"

  	depends on FAULT_INJECTION_DEBUG_FS && MMC

  	help
  	  Provide fault-injection capability for MMC IO.
  	  This will make the mmc core return data errors. This is
  	  useful to test the error handling in the mmc block device
  	  and to test how the mmc host driver handles retries from
  	  the block device.

  config FAIL_FUTEX
  	bool "Fault-injection capability for futexes"
  	select DEBUG_FS
  	depends on FAULT_INJECTION && FUTEX
  	help
  	  Provide fault-injection capability for futexes.

  config FAULT_INJECTION_DEBUG_FS
  	bool "Debugfs entries for fault-injection capabilities"

  	depends on FAULT_INJECTION && SYSFS && DEBUG_FS

  	help

  	  Enable configuration of fault-injection capabilities via debugfs.

  
  config FAULT_INJECTION_STACKTRACE_FILTER
  	bool "stacktrace filter for fault-injection capabilities"
  	depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT

  	depends on !X86_64

  	select STACKTRACE

  	select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE

  	help
  	  Provide stacktrace filter for fault-injection capabilities

  config LATENCYTOP
  	bool "Latency measuring infrastructure"

  	depends on DEBUG_KERNEL
  	depends on STACKTRACE_SUPPORT
  	depends on PROC_FS

  	select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC

  	select KALLSYMS
  	select KALLSYMS_ALL
  	select STACKTRACE
  	select SCHEDSTATS
  	select SCHED_DEBUG

  	help
  	  Enable this option if you want to use the LatencyTOP tool
  	  to find out which userspace is blocking on what kernel operations.

  source kernel/trace/Kconfig

  menu "Runtime Testing"
  
  config LKDTM
  	tristate "Linux Kernel Dump Test Tool Module"
  	depends on DEBUG_FS
  	depends on BLOCK
  	default n
  	help
  	This module enables testing of the different dumping mechanisms by
  	inducing system failures at predefined crash points.
  	If you don't need it: say N
  	Choose M here to compile this code as a module. The module will be
  	called lkdtm.
  
  	Documentation on how to use the module can be found in
  	Documentation/fault-injection/provoke-crashes.txt
  
  config TEST_LIST_SORT
  	bool "Linked list sorting test"
  	depends on DEBUG_KERNEL
  	help
  	  Enable this to turn on 'list_sort()' function test. This test is
  	  executed only once during system boot, so affects only boot time.
  
  	  If unsure, say N.
  
  config KPROBES_SANITY_TEST
  	bool "Kprobes sanity tests"
  	depends on DEBUG_KERNEL
  	depends on KPROBES
  	default n
  	help
  	  This option provides for testing basic kprobes functionality on
  	  boot. A sample kprobe, jprobe and kretprobe are inserted and
  	  verified for functionality.
  
  	  Say N if you are unsure.
  
  config BACKTRACE_SELF_TEST
  	tristate "Self test for the backtrace code"
  	depends on DEBUG_KERNEL
  	default n
  	help
  	  This option provides a kernel module that can be used to test
  	  the kernel stack backtrace code. This option is not useful
  	  for distributions or general kernels, but only for kernel
  	  developers working on architecture code.
  
  	  Note that if you want to also test saved backtraces, you will
  	  have to enable STACKTRACE as well.
  
  	  Say N if you are unsure.

  config RBTREE_TEST
  	tristate "Red-Black tree test"

  	depends on DEBUG_KERNEL

  	help
  	  A benchmark measuring the performance of the rbtree library.
  	  Also includes rbtree invariant checks.

  config INTERVAL_TREE_TEST
  	tristate "Interval tree test"
  	depends on m && DEBUG_KERNEL

  	select INTERVAL_TREE

  	help
  	  A benchmark measuring the performance of the interval tree library

  config PERCPU_TEST
  	tristate "Per cpu operations test"
  	depends on m && DEBUG_KERNEL
  	help
  	  Enable this option to build test module which validates per-cpu
  	  operations.
  
  	  If unsure, say N.

  config ATOMIC64_SELFTEST
  	bool "Perform an atomic64_t self-test at boot"
  	help
  	  Enable this option to test the atomic64_t functions at boot.
  
  	  If unsure, say N.
  
  config ASYNC_RAID6_TEST
  	tristate "Self test for hardware accelerated raid6 recovery"
  	depends on ASYNC_RAID6_RECOV
  	select ASYNC_MEMCPY
  	---help---
  	  This is a one-shot self test that permutes through the
  	  recovery of all the possible two disk failure scenarios for a
  	  N-disk array.  Recovery is performed with the asynchronous
  	  raid6 recovery routines, and will optionally use an offload
  	  engine if one is available.
  
  	  If unsure, say N.

  config TEST_HEXDUMP
  	tristate "Test functions located in the hexdump module at runtime"

  config TEST_STRING_HELPERS
  	tristate "Test functions located in the string_helpers module at runtime"
  
  config TEST_KSTRTOX
  	tristate "Test kstrto*() family of functions at runtime"

  config TEST_PRINTF
  	tristate "Test printf() family of functions at runtime"

  config TEST_BITMAP
  	tristate "Test bitmap_*() family of functions at runtime"
  	default n
  	help
  	  Enable this option to test the bitmap functions at boot.
  
  	  If unsure, say N.

  config TEST_UUID
  	tristate "Test functions located in the uuid module at runtime"

  config TEST_RHASHTABLE

  	tristate "Perform selftest on resizable hash table"

  	default n
  	help
  	  Enable this option to test the rhashtable functions at boot.
  
  	  If unsure, say N.

  config TEST_HASH
  	tristate "Perform selftest on hash functions"
  	default n
  	help
  	  Enable this option to test the kernel's integer (<linux/hash,h>)
  	  and string (<linux/stringhash.h>) hash functions on boot
  	  (or module load).
  
  	  This is intended to help people writing architecture-specific
  	  optimized versions.  If unsure, say N.

  endmenu # runtime tests

  config PROVIDE_OHCI1394_DMA_INIT

  	bool "Remote debugging over FireWire early on boot"

  	depends on PCI && X86
  	help
  	  If you want to debug problems which hang or crash the kernel early
  	  on boot and the crashing machine has a FireWire port, you can use
  	  this feature to remotely access the memory of the crashed machine
  	  over FireWire. This employs remote DMA as part of the OHCI1394
  	  specification which is now the standard for FireWire controllers.
  
  	  With remote DMA, you can monitor the printk buffer remotely using
  	  firescope and access all memory below 4GB using fireproxy from gdb.
  	  Even controlling a kernel debugger is possible using remote DMA.
  
  	  Usage:
  
  	  If ohci1394_dma=early is used as boot parameter, it will initialize
  	  all OHCI1394 controllers which are found in the PCI config space.
  
  	  As all changes to the FireWire bus such as enabling and disabling
  	  devices cause a bus reset and thereby disable remote DMA for all
  	  devices, be sure to have the cable plugged and FireWire enabled on
  	  the debugging host before booting the debug target for debugging.
  
  	  This code (~1k) is freed after boot. By then, the firewire stack
  	  in charge of the OHCI-1394 controllers should be used instead.
  
  	  See Documentation/debugging-via-ohci1394.txt for more information.

  config DMA_API_DEBUG
  	bool "Enable debugging of DMA-API usage"
  	depends on HAVE_DMA_API_DEBUG
  	help
  	  Enable this option to debug the use of the DMA API by device drivers.
  	  With this option you will be able to detect common bugs in device
  	  drivers like double-freeing of DMA mappings or freeing mappings that
  	  were never allocated.

  
  	  This also attempts to catch cases where a page owned by DMA is
  	  accessed by the cpu in a way that could cause data corruption.  For
  	  example, this enables cow_user_page() to check that the source page is
  	  not undergoing DMA.
  
  	  This option causes a performance degradation.  Use only if you want to
  	  debug device drivers and dma interactions.
  
  	  If unsure, say N.

  config TEST_LKM

  	tristate "Test module loading with 'hello world' module"
  	default n
  	depends on m
  	help
  	  This builds the "test_module" module that emits "Hello, world"
  	  on printk when loaded. It is designed to be used for basic
  	  evaluation of the module loading subsystem (for example when
  	  validating module verification). It lacks any extra dependencies,
  	  and will not normally be loaded by the system unless explicitly
  	  requested by name.
  
  	  If unsure, say N.

  config TEST_USER_COPY
  	tristate "Test user/kernel boundary protections"
  	default n
  	depends on m
  	help
  	  This builds the "test_user_copy" module that runs sanity checks
  	  on the copy_to/from_user infrastructure, making sure basic
  	  user/kernel boundary testing is working. If it fails to load,
  	  a regression has been detected in the user/kernel memory boundary
  	  protections.
  
  	  If unsure, say N.

  config TEST_BPF
  	tristate "Test BPF filter functionality"
  	default n

  	depends on m && NET

  	help
  	  This builds the "test_bpf" module that runs various test vectors
  	  against the BPF interpreter or BPF JIT compiler depending on the
  	  current setting. This is in particular useful for BPF JIT compiler
  	  development, but also to run regression tests against changes in

  	  the interpreter code. It also enables test stubs for eBPF maps and
  	  verifier used by user space verifier testsuite.

  
  	  If unsure, say N.

  config TEST_FIRMWARE
  	tristate "Test firmware loading via userspace interface"
  	default n
  	depends on FW_LOADER
  	help
  	  This builds the "test_firmware" module that creates a userspace
  	  interface for testing firmware loading. This can be used to
  	  control the triggering of firmware loading without needing an
  	  actual firmware-using device. The contents can be rechecked by
  	  userspace.
  
  	  If unsure, say N.

  config TEST_UDELAY
  	tristate "udelay test driver"
  	default n
  	help
  	  This builds the "udelay_test" module that helps to make sure
  	  that udelay() is working properly.
  
  	  If unsure, say N.

  config MEMTEST
  	bool "Memtest"
  	depends on HAVE_MEMBLOCK
  	---help---
  	  This option adds a kernel parameter 'memtest', which allows memtest
  	  to be set.
  	        memtest=0, mean disabled; -- default
  	        memtest=1, mean do 1 test pattern;
  	        ...

  	        memtest=17, mean do 17 test patterns.

  	  If you are unsure how to answer this question, answer N.

  config TEST_STATIC_KEYS
  	tristate "Test static keys"

  	default n
  	depends on m
  	help

  	  Test the static key interfaces.

  
  	  If unsure, say N.

  source "samples/Kconfig"

  
  source "lib/Kconfig.kgdb"

  source "lib/Kconfig.ubsan"

  config ARCH_HAS_DEVMEM_IS_ALLOWED
  	bool
  
  config STRICT_DEVMEM
  	bool "Filter access to /dev/mem"
  	depends on MMU
  	depends on ARCH_HAS_DEVMEM_IS_ALLOWED
  	default y if TILE || PPC
  	---help---
  	  If this option is disabled, you allow userspace (root) access to all
  	  of memory, including kernel and userspace memory. Accidental
  	  access to this is obviously disastrous, but specific access can
  	  be used by people debugging the kernel. Note that with PAT support
  	  enabled, even in this case there are restrictions on /dev/mem
  	  use due to the cache aliasing requirements.

  	  If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
  	  file only allows userspace access to PCI space and the BIOS code and
  	  data regions.  This is sufficient for dosemu and X and all common
  	  users of /dev/mem.
  
  	  If in doubt, say Y.
  
  config IO_STRICT_DEVMEM
  	bool "Filter I/O access to /dev/mem"
  	depends on STRICT_DEVMEM

  	---help---
  	  If this option is disabled, you allow userspace (root) access to all
  	  io-memory regardless of whether a driver is actively using that
  	  range.  Accidental access to this is obviously disastrous, but
  	  specific access can be used by people debugging kernel drivers.

  	  If this option is switched on, the /dev/mem file only allows

  	  userspace access to *idle* io-memory ranges (see /proc/iomem) This
  	  may break traditional users of /dev/mem (dosemu, legacy X, etc...)
  	  if the driver using a given range cannot be disabled.

  
  	  If in doubt, say Y.