lib/Kconfig.debug

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 && !FRV
	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 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 PAGE_OWNER_ENABLE_DEFAULT
	bool "Enable Track page owner by default"
	depends on PAGE_OWNER
	---help---
	  This keeps track of what call chain is the owner of a page, may
	  help to find bare alloc_page(s) leaks. If you include this
	  feature on your build, it is enabled by default. You should pass
	  "page_owner=off" to boot parameter in order to disable it. Eats
	  a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
	  for user-space helper.

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"

config DEBUG_REFCOUNT
	bool "Verbose refcount checks"
	help
	  Say Y here if you want reference counters (refcount_t and kref) to
	  generate WARNs on dubious usage. Without this refcount_t will still
	  be a saturating counter and avoid Use-After-Free by turning it into
	  a resource leak Denial-Of-Service.

	  Use of this option will increase kernel text size but will alert the
	  admin of potential abuse.

	  If in doubt, say "N".

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

config HARDLOCKUP_DETECTOR_OTHER_CPU
       def_bool y
       depends on LOCKUP_DETECTOR && SMP
       depends on !HARDLOCKUP_DETECTOR_NMI && !HAVE_NMI_WATCHDOG

config HARDLOCKUP_DETECTOR
       def_bool y
       depends on HARDLOCKUP_DETECTOR_NMI || HARDLOCKUP_DETECTOR_OTHER_CPU

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 PANIC_ON_RECURSIVE_FAULT
	bool "Panic on recursive faults during task exit"
	help
	  Panic upon the detection of a recursive fault during task exit,
	  rather than putting the task into an uninterruptible sleep.
	  This is particularly useful for debugging system hangs in
	  scenarios where the task experiencing the fault is critical
	  for system operation, rendering the system inoperable.

	  Say N if unsure.

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 PANIC_ON_SCHED_BUG
	bool "Panic on all bugs encountered by the scheduler"
	help
	  Say Y here to panic on all 'BUG:' conditions encountered by the
	  scheduler, even potentially-recoverable ones such as scheduling
	  while atomic, sleeping from invalid context, and detection of
	  broken arch topologies.

	  Say N if unsure.

config PANIC_ON_RT_THROTTLING
	bool "Panic on RT throttling"
	help
	  Say Y here to enable the kernel to panic when a realtime
	  runqueue is throttled. This may be useful for detecting
	  and debugging RT throttling issues.

	  Say N if unsure.

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 DEBUG_TASK_STACK_SCAN_OFF
	bool "Disable kmemleak task stack scan by default"
	depends on DEBUG_KMEMLEAK
	help
	  Say Y here to disable kmemleak task stack scan by default
	  at compile time. It can be enabled later if required by
	  writing to the debugfs entry :
	  echo "stack=on" > /sys/kernel/debug/kmemleak.

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.
choice
        prompt "Perform Action on spinlock bug"
        depends on DEBUG_SPINLOCK

        default DEBUG_SPINLOCK_BITE_ON_BUG

        config DEBUG_SPINLOCK_BITE_ON_BUG
                bool "Cause a Watchdog Bite on Spinlock bug"
                depends on QCOM_WATCHDOG_V2
                help
                  On a spinlock bug, cause a watchdog bite so that we can get
                  the precise state of the system captured at the time of spin
                  dump. This is mutually exclusive with the below
                  DEBUG_SPINLOCK_PANIC_ON_BUG config.

        config DEBUG_SPINLOCK_PANIC_ON_BUG
                bool "Cause a Kernel Panic on Spinlock bug"
                help
                  On a spinlock bug, cause a kernel panic so that we can get the complete
                  information about the system at the time of spin dump in the dmesg.
                  This is mutually exclusive with the above DEBUG_SPINLOCK_BITE_ON_BUG.
endchoice

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_PANIC_ON_STALL
	int "Panic on RCU Stalls"
	range 0 1
	default 0
	depends on RCU_STALL_COMMON
	help
	  Panic if a given RCU grace period extends more than the specified
	  number of seconds instead of just printing a CPU stall warning.
	  This helps to collect cpu context as part of ramdumps for post
	  mortem analysis.


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 UFS_FAULT_INJECTION
	bool "Fault-injection capability for UFS IO"
	select DEBUG_FS
	depends on FAULT_INJECTION && SCSI_UFSHCD
	help
	 Provide fault-injection capability for UFS IO.
	 This will make the UFS host controller driver to randomly
	 abort ongoing commands in the host controller, update OCS
	 field according to the injected fatal error and can also
	 forcefully hang the command indefinitely till upper layer
	 timeout occurs. This is useful to test error handling in
	 the UFS contoller driver and test how the driver handles
	 the retries from block/SCSI mid layer.

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 MEMTEST_ENABLE_DEFAULT
	int "Enable Memtest pattern test by default? (0-17)"
	range 0 17
	default "0"
	depends on MEMTEST
	help
	  This option helps to select Memtest to be enabled through
	  kernel defconfig options. Alternatively it can be enabled
	  using memtest=<patterns> kernel command line.

	  Default value is kept as "0" so that it is kept as disabled.
	  To enable enter any value between 1-17 range.

config TEST_STATIC_KEYS
	tristate "Test static keys"
	default n
	depends on m
	help
	  Test the static key interfaces.

	  If unsure, say N.

config PANIC_ON_DATA_CORRUPTION
	bool "Cause a Kernel Panic When Data Corruption is detected"
	help
	 Select this option to upgrade warnings for potentially
	 recoverable data corruption scenarios to system-halting panics,
	 for easier detection and debug.

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.