Kconfig.debug 66.9 KB
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menu "printk and dmesg options"
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config PRINTK_TIME
	bool "Show timing information on printks"
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	depends on PRINTK
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	help
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	  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
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	  parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst
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config CONSOLE_LOGLEVEL_DEFAULT
	int "Default console loglevel (1-15)"
	range 1 15
	default "7"
	help
	  Default loglevel to determine what will be printed on the console.

	  Setting a default here is equivalent to passing in loglevel=<x> in
	  the kernel bootargs. loglevel=<x> continues to override whatever
	  value is specified here as well.

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	  Note: This does not affect the log level of un-prefixed printk()
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	  usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
	  option.

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config MESSAGE_LOGLEVEL_DEFAULT
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	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.

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	  Note: This does not affect what message level gets printed on the console
	  by default. To change that, use loglevel=<x> in the kernel bootargs,
	  or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value.

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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

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	  See Documentation/admin-guide/dynamic-debug-howto.rst for additional
	  information.
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endmenu # "printk and dmesg options"

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menu "Compile-time checks and compiler options"

config DEBUG_INFO
	bool "Compile the kernel with debug info"
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	depends on DEBUG_KERNEL && !COMPILE_TEST
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	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.

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config DEBUG_INFO_SPLIT
	bool "Produce split debuginfo in .dwo files"
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	depends on DEBUG_INFO && !FRV
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	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.

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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.

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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
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	  instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
	  for further details.
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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.

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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.
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config FRAME_WARN
	int "Warn for stack frames larger than (needs gcc 4.4)"
	range 0 8192
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	default 3072 if KASAN_EXTRA
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	default 2048 if GCC_PLUGIN_LATENT_ENTROPY
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	default 1280 if (!64BIT && PARISC)
	default 1024 if (!64BIT && !PARISC)
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	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

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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.

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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.

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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.

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

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config DEBUG_FS
	bool "Debug Filesystem"
	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.

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

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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.
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	  During linktime or runtime, some sections are dropped;
	  any use of code/data previously in these sections would
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	  most likely result in an oops.
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	  In the code, functions and variables are annotated with
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	  __init,, etc. (see the full list in include/linux/init.h),
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	  which results in the code/data being placed in specific sections.
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	  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
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	    the analysis would not catch the illegal reference.
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	    This option tells gcc to inline less (but it does result in
	    a larger kernel).
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	  - Run the section mismatch analysis for each module/built-in.a file.
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	    When we run the section mismatch analysis on vmlinux.o, we
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	    lose valuable information about where the mismatch was
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	    introduced.
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	    Running the analysis for each module/built-in.a file
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	    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.
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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.

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

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	  This is also a prerequisite for generation of ORC unwind data, which
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	  is needed for CONFIG_UNWINDER_ORC.
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	  For more information, see
	  tools/objtool/Documentation/stack-validation.txt.

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config DEBUG_FORCE_WEAK_PER_CPU
	bool "Force weak per-cpu definitions"
	depends on DEBUG_KERNEL
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	help
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	  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.
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	  1. percpu symbols must be unique whether static or not
	  2. percpu variables can't be defined inside a function
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	  To ensure that generic code follows the above rules, this
	  option forces all percpu variables to be defined as weak.
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endmenu # "Compiler options"
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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
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	  keys are documented in <file:Documentation/admin-guide/sysrq.rst>.
	  Don't say Y unless you really know what this hack does.
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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
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	  to a bitmask as described in Documentation/admin-guide/sysrq.rst.
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config MAGIC_SYSRQ_SERIAL
	bool "Enable magic SysRq key over serial"
	depends on MAGIC_SYSRQ
	default y
	help
	  Many embedded boards have a disconnected TTL level serial which can
	  generate some garbage that can lead to spurious false sysrq detects.
	  This option allows you to decide whether you want to enable the
	  magic SysRq key.

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config DEBUG_KERNEL
	bool "Kernel debugging"
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	help
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	  Say Y here if you are developing drivers or trying to debug and
	  identify kernel problems.
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menu "Memory Debugging"
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source mm/Kconfig.debug
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config DEBUG_OBJECTS
	bool "Debug object operations"
	depends on DEBUG_KERNEL
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	help
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	  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.
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config DEBUG_OBJECTS_SELFTEST
	bool "Debug objects selftest"
	depends on DEBUG_OBJECTS
	help
	  This enables the selftest of the object debug code.
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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.
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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.

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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.

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config DEBUG_OBJECTS_RCU_HEAD
	bool "Debug RCU callbacks objects"
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	depends on DEBUG_OBJECTS
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	help
	  Enable this to turn on debugging of RCU list heads (call_rcu() usage).

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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.

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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

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config DEBUG_SLAB
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	bool "Debug slab memory allocations"
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	depends on DEBUG_KERNEL && SLAB
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	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.

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config DEBUG_SLAB_LEAK
	bool "Memory leak debugging"
	depends on DEBUG_SLAB

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config SLUB_DEBUG_ON
	bool "SLUB debugging on by default"
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	depends on SLUB && SLUB_DEBUG
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	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=-".

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config SLUB_STATS
	default n
	bool "Enable SLUB performance statistics"
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	depends on SLUB && SYSFS
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	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

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config HAVE_DEBUG_KMEMLEAK
	bool

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config DEBUG_KMEMLEAK
	bool "Kernel memory leak detector"
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	depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
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	select DEBUG_FS
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	select STACKTRACE if STACKTRACE_SUPPORT
	select KALLSYMS
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	select CRC32
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	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
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	  allocations. See Documentation/dev-tools/kmemleak.rst for more
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	  details.

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	  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"
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	depends on DEBUG_KERNEL && !IA64
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	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.

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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.

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config DEBUG_VM_RB
	bool "Debug VM red-black trees"
	depends on DEBUG_VM
	help
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	  Enable VM red-black tree debugging information and extra validations.
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	  If unsure, say N.

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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.

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config ARCH_HAS_DEBUG_VIRTUAL
	bool

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config DEBUG_VIRTUAL
	bool "Debug VM translations"
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	depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL
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	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
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	  This option enables additional error checking for high memory
	  systems.  Disable for production systems.
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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
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	  and exception stacks (if your architecture uses them). This
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	  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".

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source "lib/Kconfig.kasan"

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endmenu # "Memory Debugging"

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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
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	select GCC_PLUGINS if !COMPILE_TEST
	select GCC_PLUGIN_SANCOV if !COMPILE_TEST
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	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.

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	  For more details, see Documentation/dev-tools/kcov.rst.
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config KCOV_ENABLE_COMPARISONS
	bool "Enable comparison operands collection by KCOV"
	depends on KCOV
	default n
	help
	  KCOV also exposes operands of every comparison in the instrumented
	  code along with operand sizes and PCs of the comparison instructions.
	  These operands can be used by fuzzing engines to improve the quality
	  of fuzzing coverage.

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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.

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config DEBUG_SHIRQ
	bool "Debug shared IRQ handlers"
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	depends on DEBUG_KERNEL
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	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.

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menu "Debug Lockups and Hangs"

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config LOCKUP_DETECTOR
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	bool

config SOFTLOCKUP_DETECTOR
	bool "Detect Soft Lockups"
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	depends on DEBUG_KERNEL && !S390
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	select LOCKUP_DETECTOR
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	help
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	  Say Y here to enable the kernel to act as a watchdog to detect
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	  soft lockups.
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	  Softlockups are bugs that cause the kernel to loop in kernel
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	  mode for more than 20 seconds, without giving other tasks a
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	  chance to run.  The current stack trace is displayed upon
	  detection and the system will stay locked up.
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config HARDLOCKUP_DETECTOR_PERF
	bool
	select SOFTLOCKUP_DETECTOR

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#
# Enables a timestamp based low pass filter to compensate for perf based
# hard lockup detection which runs too fast due to turbo modes.
#
config HARDLOCKUP_CHECK_TIMESTAMP
	bool

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#
# arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
# lockup detector rather than the perf based detector.
#
config HARDLOCKUP_DETECTOR
	bool "Detect Hard Lockups"
	depends on DEBUG_KERNEL && !S390
	depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH
	select LOCKUP_DETECTOR
	select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF
	select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH
	help
	  Say Y here to enable the kernel to act as a watchdog to detect
	  hard lockups.

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	  Hardlockups are bugs that cause the CPU to loop in kernel mode
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	  for more than 10 seconds, without letting other interrupts have a
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	  chance to run.  The current stack trace is displayed upon detection
	  and the system will stay locked up.
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config BOOTPARAM_HARDLOCKUP_PANIC
	bool "Panic (Reboot) On Hard Lockups"
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	depends on HARDLOCKUP_DETECTOR
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	help
	  Say Y here to enable the kernel to panic on "hard lockups",
	  which are bugs that cause the kernel to loop in kernel
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	  mode with interrupts disabled for more than 10 seconds (configurable
	  using the watchdog_thresh sysctl).
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	  Say N if unsure.

config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
	int
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	depends on HARDLOCKUP_DETECTOR
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	range 0 1
	default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
	default 1 if BOOTPARAM_HARDLOCKUP_PANIC

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config BOOTPARAM_SOFTLOCKUP_PANIC
	bool "Panic (Reboot) On Soft Lockups"
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	depends on SOFTLOCKUP_DETECTOR
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	help
	  Say Y here to enable the kernel to panic on "soft lockups",
	  which are bugs that cause the kernel to loop in kernel
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	  mode for more than 20 seconds (configurable using the watchdog_thresh
	  sysctl), without giving other tasks a chance to run.
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	  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
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	depends on SOFTLOCKUP_DETECTOR
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	range 0 1
	default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
	default 1 if BOOTPARAM_SOFTLOCKUP_PANIC

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config DETECT_HUNG_TASK
	bool "Detect Hung Tasks"
	depends on DEBUG_KERNEL
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	default SOFTLOCKUP_DETECTOR
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	help
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	  Say Y here to enable the kernel to detect "hung tasks",
	  which are bugs that cause the task to be stuck in
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	  uninterruptible "D" state indefinitely.
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	  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.
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config DEFAULT_HUNG_TASK_TIMEOUT
	int "Default timeout for hung task detection (in seconds)"
	depends on DETECT_HUNG_TASK
	default 120
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	help
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	  This option controls the default timeout (in seconds) used
	  to determine when a task has become non-responsive and should
	  be considered hung.
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	  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.
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	  A timeout of 0 disables the check.  The default is two minutes.
	  Keeping the default should be fine in most cases.
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config BOOTPARAM_HUNG_TASK_PANIC
	bool "Panic (Reboot) On Hung Tasks"
	depends on DETECT_HUNG_TASK
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	help
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	  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.
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	  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.
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	  Say N if unsure.
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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
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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.

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endmenu # "Debug lockups and hangs"

config PANIC_ON_OOPS
	bool "Panic on Oops"
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	help
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	  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.
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	  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

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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.

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config SCHED_DEBUG
	bool "Collect scheduler debugging info"
	depends on DEBUG_KERNEL && PROC_FS
	default y
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	help
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	  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.
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config SCHED_INFO
	bool
	default n

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

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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.

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config DEBUG_PREEMPT
	bool "Debug preemptible kernel"
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	depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
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	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.

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

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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.

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config DEBUG_SPINLOCK
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	bool "Spinlock and rw-lock debugging: basic checks"
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	depends on DEBUG_KERNEL
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	select UNINLINE_SPIN_UNLOCK
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	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.

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

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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.
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	 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.
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config DEBUG_LOCK_ALLOC
	bool "Lock debugging: detect incorrect freeing of live locks"
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	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
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	select DEBUG_SPINLOCK
	select DEBUG_MUTEXES
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	select DEBUG_RT_MUTEXES if RT_MUTEXES
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	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"
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	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
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	select LOCKDEP
	select DEBUG_SPINLOCK
	select DEBUG_MUTEXES
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	select DEBUG_RT_MUTEXES if RT_MUTEXES
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	select DEBUG_LOCK_ALLOC
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	select TRACE_IRQFLAGS
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	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.

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	 For more details, see Documentation/locking/lockdep-design.txt.
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config LOCKDEP
	bool
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	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
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	select STACKTRACE
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	select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE && !X86
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	select KALLSYMS
	select KALLSYMS_ALL

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config LOCKDEP_SMALL
	bool

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config LOCK_STAT
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	bool "Lock usage statistics"
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	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
	select LOCKDEP
	select DEBUG_SPINLOCK
	select DEBUG_MUTEXES
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	select DEBUG_RT_MUTEXES if RT_MUTEXES
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	select DEBUG_LOCK_ALLOC
	default n
	help
	 This feature enables tracking lock contention points

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	 For more details, see Documentation/locking/lockstat.txt
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	 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.
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	 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
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	 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
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config DEBUG_LOCKDEP
	bool "Lock dependency engine debugging"
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	depends on DEBUG_KERNEL && LOCKDEP
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	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.

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config DEBUG_ATOMIC_SLEEP
	bool "Sleep inside atomic section checking"
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	select PREEMPT_COUNT
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	depends on DEBUG_KERNEL
	help
	  If you say Y here, various routines which may sleep will become very
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	  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...
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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.

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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.

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config WW_MUTEX_SELFTEST
	tristate "Wait/wound mutex selftests"
	help
	  This option provides a kernel module that runs tests on the
	  on the struct ww_mutex locking API.

	  It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
	  with this test harness.

	  Say M if you want these self tests to build as a module.
	  Say N if you are unsure.

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endmenu # lock debugging
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config TRACE_IRQFLAGS
	bool
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	help
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	  Enables hooks to interrupt enabling and disabling for
	  either tracing or lock debugging.
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config STACKTRACE
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	bool "Stack backtrace support"
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	depends on STACKTRACE_SUPPORT
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	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.
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config WARN_ALL_UNSEEDED_RANDOM
	bool "Warn for all uses of unseeded randomness"
	default n
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	help
	  Some parts of the kernel contain bugs relating to their use of
	  cryptographically secure random numbers before it's actually possible
	  to generate those numbers securely. This setting ensures that these
	  flaws don't go unnoticed, by enabling a message, should this ever
	  occur. This will allow people with obscure setups to know when things
	  are going wrong, so that they might contact developers about fixing
	  it.

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	  Unfortunately, on some models of some architectures getting
	  a fully seeded CRNG is extremely difficult, and so this can
	  result in dmesg getting spammed for a surprisingly long
	  time.  This is really bad from a security perspective, and
	  so architecture maintainers really need to do what they can
	  to get the CRNG seeded sooner after the system is booted.
	  However, since users can not do anything actionble to
	  address this, by default the kernel will issue only a single
	  warning for the first use of unseeded randomness.

	  Say Y here if you want to receive warnings for all uses of
	  unseeded randomness.  This will be of use primarily for
	  those developers interersted in improving the security of
	  Linux kernels running on their architecture (or
	  subarchitecture).
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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. 

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config DEBUG_KOBJECT_RELEASE
	bool "kobject release debugging"
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	depends on DEBUG_OBJECTS_TIMERS
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	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.

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config HAVE_DEBUG_BUGVERBOSE
	bool

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config DEBUG_BUGVERBOSE
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	bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
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	depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
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	default y
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	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.

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config DEBUG_LIST
	bool "Debug linked list manipulation"
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	depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
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	help
	  Enable this to turn on extended checks in the linked-list
	  walking routines.

	  If unsure, say N.

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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.

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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.

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