scripts/gcc-plugins/Kconfig - linux - Git at Google

 preferred-plugin-hostcc := $(if-success,[ $(gcc-version) -ge 40800 ],$(HOSTCXX),$(HOSTCC))

 config PLUGIN_HOSTCC
 	string
 	default "$(shell,$(srctree)/scripts/gcc-plugin.sh "$(preferred-plugin-hostcc)" "$(HOSTCXX)" "$(CC)")" if CC_IS_GCC
 	help
 	  Host compiler used to build GCC plugins.  This can be $(HOSTCXX),
 	  $(HOSTCC), or a null string if GCC plugin is unsupported.

 config HAVE_GCC_PLUGINS
 	bool
 	help
 	  An arch should select this symbol if it supports building with
 	  GCC plugins.

 menuconfig GCC_PLUGINS
 	bool "GCC plugins"
 	depends on HAVE_GCC_PLUGINS
 	depends on PLUGIN_HOSTCC != ""
 	help
 	  GCC plugins are loadable modules that provide extra features to the
 	  compiler. They are useful for runtime instrumentation and static analysis.

 	  See Documentation/gcc-plugins.txt for details.

 if GCC_PLUGINS

 config GCC_PLUGIN_CYC_COMPLEXITY
 	bool "Compute the cyclomatic complexity of a function" if EXPERT
 	depends on !COMPILE_TEST	# too noisy
 	help
 	  The complexity M of a function's control flow graph is defined as:
 	   M = E - N + 2P
 	  where

 	  E = the number of edges
 	  N = the number of nodes
 	  P = the number of connected components (exit nodes).

 	  Enabling this plugin reports the complexity to stderr during the
 	  build. It mainly serves as a simple example of how to create a
 	  gcc plugin for the kernel.

 config GCC_PLUGIN_SANCOV
 	bool
 	help
 	  This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
 	  basic blocks. It supports all gcc versions with plugin support (from
 	  gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
 	  by Dmitry Vyukov <dvyukov@google.com>.

 config GCC_PLUGIN_LATENT_ENTROPY
 	bool "Generate some entropy during boot and runtime"
 	help
 	  By saying Y here the kernel will instrument some kernel code to
 	  extract some entropy from both original and artificially created
 	  program state.  This will help especially embedded systems where
 	  there is little 'natural' source of entropy normally.  The cost
 	  is some slowdown of the boot process (about 0.5%) and fork and
 	  irq processing.

 	  Note that entropy extracted this way is not cryptographically
 	  secure!

 	  This plugin was ported from grsecurity/PaX. More information at:
 	   * https://grsecurity.net/
 	   * https://pax.grsecurity.net/

 config GCC_PLUGIN_STRUCTLEAK
 	bool "Zero initialize stack variables"
 	help
 	  While the kernel is built with warnings enabled for any missed
 	  stack variable initializations, this warning is silenced for
 	  anything passed by reference to another function, under the
 	  occasionally misguided assumption that the function will do
 	  the initialization. As this regularly leads to exploitable
 	  flaws, this plugin is available to identify and zero-initialize
 	  such variables, depending on the chosen level of coverage.

 	  This plugin was originally ported from grsecurity/PaX. More
 	  information at:
 	   * https://grsecurity.net/
 	   * https://pax.grsecurity.net/

 choice
 	prompt "Coverage"
 	depends on GCC_PLUGIN_STRUCTLEAK
 	default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
 	help
 	  This chooses the level of coverage over classes of potentially
 	  uninitialized variables. The selected class will be
 	  zero-initialized before use.

 	config GCC_PLUGIN_STRUCTLEAK_USER
 		bool "structs marked for userspace"
 		help
 		  Zero-initialize any structures on the stack containing
 		  a __user attribute. This can prevent some classes of
 		  uninitialized stack variable exploits and information
 		  exposures, like CVE-2013-2141:
 		  https://git.kernel.org/linus/b9e146d8eb3b9eca

 	config GCC_PLUGIN_STRUCTLEAK_BYREF
 		bool "structs passed by reference"
 		help
 		  Zero-initialize any structures on the stack that may
 		  be passed by reference and had not already been
 		  explicitly initialized. This can prevent most classes
 		  of uninitialized stack variable exploits and information
 		  exposures, like CVE-2017-1000410:
 		  https://git.kernel.org/linus/06e7e776ca4d3654

 	config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
 		bool "anything passed by reference"
 		help
 		  Zero-initialize any stack variables that may be passed
 		  by reference and had not already been explicitly
 		  initialized. This is intended to eliminate all classes
 		  of uninitialized stack variable exploits and information
 		  exposures.

 endchoice

 config GCC_PLUGIN_STRUCTLEAK_VERBOSE
 	bool "Report forcefully initialized variables"
 	depends on GCC_PLUGIN_STRUCTLEAK
 	depends on !COMPILE_TEST	# too noisy
 	help
 	  This option will cause a warning to be printed each time the
 	  structleak plugin finds a variable it thinks needs to be
 	  initialized. Since not all existing initializers are detected
 	  by the plugin, this can produce false positive warnings.

 config GCC_PLUGIN_RANDSTRUCT
 	bool "Randomize layout of sensitive kernel structures"
 	select MODVERSIONS if MODULES
 	help
 	  If you say Y here, the layouts of structures that are entirely
 	  function pointers (and have not been manually annotated with
 	  __no_randomize_layout), or structures that have been explicitly
 	  marked with __randomize_layout, will be randomized at compile-time.
 	  This can introduce the requirement of an additional information
 	  exposure vulnerability for exploits targeting these structure
 	  types.

 	  Enabling this feature will introduce some performance impact,
 	  slightly increase memory usage, and prevent the use of forensic
 	  tools like Volatility against the system (unless the kernel
 	  source tree isn't cleaned after kernel installation).

 	  The seed used for compilation is located at
 	  scripts/gcc-plgins/randomize_layout_seed.h.  It remains after
 	  a make clean to allow for external modules to be compiled with
 	  the existing seed and will be removed by a make mrproper or
 	  make distclean.

 	  Note that the implementation requires gcc 4.7 or newer.

 	  This plugin was ported from grsecurity/PaX. More information at:
 	   * https://grsecurity.net/
 	   * https://pax.grsecurity.net/

 config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
 	bool "Use cacheline-aware structure randomization"
 	depends on GCC_PLUGIN_RANDSTRUCT
 	depends on !COMPILE_TEST	# do not reduce test coverage
 	help
 	  If you say Y here, the RANDSTRUCT randomization will make a
 	  best effort at restricting randomization to cacheline-sized
 	  groups of elements.  It will further not randomize bitfields
 	  in structures.  This reduces the performance hit of RANDSTRUCT
 	  at the cost of weakened randomization.

 config GCC_PLUGIN_STACKLEAK
 	bool "Erase the kernel stack before returning from syscalls"
 	depends on GCC_PLUGINS
 	depends on HAVE_ARCH_STACKLEAK
 	help
 	  This option makes the kernel erase the kernel stack before
 	  returning from system calls. That reduces the information which
 	  kernel stack leak bugs can reveal and blocks some uninitialized
 	  stack variable attacks.

 	  The tradeoff is the performance impact: on a single CPU system kernel
 	  compilation sees a 1% slowdown, other systems and workloads may vary
 	  and you are advised to test this feature on your expected workload
 	  before deploying it.

 	  This plugin was ported from grsecurity/PaX. More information at:
 	   * https://grsecurity.net/
 	   * https://pax.grsecurity.net/

 config STACKLEAK_TRACK_MIN_SIZE
 	int "Minimum stack frame size of functions tracked by STACKLEAK"
 	default 100
 	range 0 4096
 	depends on GCC_PLUGIN_STACKLEAK
 	help
 	  The STACKLEAK gcc plugin instruments the kernel code for tracking
 	  the lowest border of the kernel stack (and for some other purposes).
 	  It inserts the stackleak_track_stack() call for the functions with
 	  a stack frame size greater than or equal to this parameter.
 	  If unsure, leave the default value 100.

 config STACKLEAK_METRICS
 	bool "Show STACKLEAK metrics in the /proc file system"
 	depends on GCC_PLUGIN_STACKLEAK
 	depends on PROC_FS
 	help
 	  If this is set, STACKLEAK metrics for every task are available in
 	  the /proc file system. In particular, /proc/<pid>/stack_depth
 	  shows the maximum kernel stack consumption for the current and
 	  previous syscalls. Although this information is not precise, it
 	  can be useful for estimating the STACKLEAK performance impact for
 	  your workloads.

 config STACKLEAK_RUNTIME_DISABLE
 	bool "Allow runtime disabling of kernel stack erasing"
 	depends on GCC_PLUGIN_STACKLEAK
 	help
 	  This option provides 'stack_erasing' sysctl, which can be used in
 	  runtime to control kernel stack erasing for kernels built with
 	  CONFIG_GCC_PLUGIN_STACKLEAK.

 config GCC_PLUGIN_ARM_SSP_PER_TASK
 	bool
 	depends on GCC_PLUGINS && ARM

 endif
	preferred-plugin-hostcc := $(if-success,[ $(gcc-version) -ge 40800 ],$(HOSTCXX),$(HOSTCC))

	config PLUGIN_HOSTCC
	string
	default "$(shell,$(srctree)/scripts/gcc-plugin.sh "$(preferred-plugin-hostcc)" "$(HOSTCXX)" "$(CC)")" if CC_IS_GCC
	help
	Host compiler used to build GCC plugins. This can be $(HOSTCXX),
	$(HOSTCC), or a null string if GCC plugin is unsupported.

	config HAVE_GCC_PLUGINS
	bool
	help
	An arch should select this symbol if it supports building with
	GCC plugins.

	menuconfig GCC_PLUGINS
	bool "GCC plugins"
	depends on HAVE_GCC_PLUGINS
	depends on PLUGIN_HOSTCC != ""
	help
	GCC plugins are loadable modules that provide extra features to the
	compiler. They are useful for runtime instrumentation and static analysis.

	See Documentation/gcc-plugins.txt for details.

	if GCC_PLUGINS

	config GCC_PLUGIN_CYC_COMPLEXITY
	bool "Compute the cyclomatic complexity of a function" if EXPERT
	depends on !COMPILE_TEST # too noisy
	help
	The complexity M of a function's control flow graph is defined as:
	M = E - N + 2P
	where

	E = the number of edges
	N = the number of nodes
	P = the number of connected components (exit nodes).

	Enabling this plugin reports the complexity to stderr during the
	build. It mainly serves as a simple example of how to create a
	gcc plugin for the kernel.

	config GCC_PLUGIN_SANCOV
	bool
	help
	This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
	basic blocks. It supports all gcc versions with plugin support (from
	gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
	by Dmitry Vyukov <dvyukov@google.com>.

	config GCC_PLUGIN_LATENT_ENTROPY
	bool "Generate some entropy during boot and runtime"
	help
	By saying Y here the kernel will instrument some kernel code to
	extract some entropy from both original and artificially created
	program state. This will help especially embedded systems where
	there is little 'natural' source of entropy normally. The cost
	is some slowdown of the boot process (about 0.5%) and fork and
	irq processing.

	Note that entropy extracted this way is not cryptographically
	secure!

	This plugin was ported from grsecurity/PaX. More information at:
	* https://grsecurity.net/
	* https://pax.grsecurity.net/

	config GCC_PLUGIN_STRUCTLEAK
	bool "Zero initialize stack variables"
	help
	While the kernel is built with warnings enabled for any missed
	stack variable initializations, this warning is silenced for
	anything passed by reference to another function, under the
	occasionally misguided assumption that the function will do
	the initialization. As this regularly leads to exploitable
	flaws, this plugin is available to identify and zero-initialize
	such variables, depending on the chosen level of coverage.

	This plugin was originally ported from grsecurity/PaX. More
	information at:
	* https://grsecurity.net/
	* https://pax.grsecurity.net/

	choice
	prompt "Coverage"
	depends on GCC_PLUGIN_STRUCTLEAK
	default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
	help
	This chooses the level of coverage over classes of potentially
	uninitialized variables. The selected class will be
	zero-initialized before use.

	config GCC_PLUGIN_STRUCTLEAK_USER
	bool "structs marked for userspace"
	help
	Zero-initialize any structures on the stack containing
	a __user attribute. This can prevent some classes of
	uninitialized stack variable exploits and information
	exposures, like CVE-2013-2141:
	https://git.kernel.org/linus/b9e146d8eb3b9eca

	config GCC_PLUGIN_STRUCTLEAK_BYREF
	bool "structs passed by reference"
	help
	Zero-initialize any structures on the stack that may
	be passed by reference and had not already been
	explicitly initialized. This can prevent most classes
	of uninitialized stack variable exploits and information
	exposures, like CVE-2017-1000410:
	https://git.kernel.org/linus/06e7e776ca4d3654

	config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
	bool "anything passed by reference"
	help
	Zero-initialize any stack variables that may be passed
	by reference and had not already been explicitly
	initialized. This is intended to eliminate all classes
	of uninitialized stack variable exploits and information
	exposures.

	endchoice

	config GCC_PLUGIN_STRUCTLEAK_VERBOSE
	bool "Report forcefully initialized variables"
	depends on GCC_PLUGIN_STRUCTLEAK
	depends on !COMPILE_TEST # too noisy
	help
	This option will cause a warning to be printed each time the
	structleak plugin finds a variable it thinks needs to be
	initialized. Since not all existing initializers are detected
	by the plugin, this can produce false positive warnings.

	config GCC_PLUGIN_RANDSTRUCT
	bool "Randomize layout of sensitive kernel structures"
	select MODVERSIONS if MODULES
	help
	If you say Y here, the layouts of structures that are entirely
	function pointers (and have not been manually annotated with
	__no_randomize_layout), or structures that have been explicitly
	marked with __randomize_layout, will be randomized at compile-time.
	This can introduce the requirement of an additional information
	exposure vulnerability for exploits targeting these structure
	types.

	Enabling this feature will introduce some performance impact,
	slightly increase memory usage, and prevent the use of forensic
	tools like Volatility against the system (unless the kernel
	source tree isn't cleaned after kernel installation).

	The seed used for compilation is located at
	scripts/gcc-plgins/randomize_layout_seed.h. It remains after
	a make clean to allow for external modules to be compiled with
	the existing seed and will be removed by a make mrproper or
	make distclean.

	Note that the implementation requires gcc 4.7 or newer.

	This plugin was ported from grsecurity/PaX. More information at:
	* https://grsecurity.net/
	* https://pax.grsecurity.net/

	config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
	bool "Use cacheline-aware structure randomization"
	depends on GCC_PLUGIN_RANDSTRUCT
	depends on !COMPILE_TEST # do not reduce test coverage
	help
	If you say Y here, the RANDSTRUCT randomization will make a
	best effort at restricting randomization to cacheline-sized
	groups of elements. It will further not randomize bitfields
	in structures. This reduces the performance hit of RANDSTRUCT
	at the cost of weakened randomization.

	config GCC_PLUGIN_STACKLEAK
	bool "Erase the kernel stack before returning from syscalls"
	depends on GCC_PLUGINS
	depends on HAVE_ARCH_STACKLEAK
	help
	This option makes the kernel erase the kernel stack before
	returning from system calls. That reduces the information which
	kernel stack leak bugs can reveal and blocks some uninitialized
	stack variable attacks.

	The tradeoff is the performance impact: on a single CPU system kernel
	compilation sees a 1% slowdown, other systems and workloads may vary
	and you are advised to test this feature on your expected workload
	before deploying it.

	This plugin was ported from grsecurity/PaX. More information at:
	* https://grsecurity.net/
	* https://pax.grsecurity.net/

	config STACKLEAK_TRACK_MIN_SIZE
	int "Minimum stack frame size of functions tracked by STACKLEAK"
	default 100
	range 0 4096
	depends on GCC_PLUGIN_STACKLEAK
	help
	The STACKLEAK gcc plugin instruments the kernel code for tracking
	the lowest border of the kernel stack (and for some other purposes).
	It inserts the stackleak_track_stack() call for the functions with
	a stack frame size greater than or equal to this parameter.
	If unsure, leave the default value 100.

	config STACKLEAK_METRICS
	bool "Show STACKLEAK metrics in the /proc file system"
	depends on GCC_PLUGIN_STACKLEAK
	depends on PROC_FS
	help
	If this is set, STACKLEAK metrics for every task are available in
	the /proc file system. In particular, /proc/<pid>/stack_depth
	shows the maximum kernel stack consumption for the current and
	previous syscalls. Although this information is not precise, it
	can be useful for estimating the STACKLEAK performance impact for
	your workloads.

	config STACKLEAK_RUNTIME_DISABLE
	bool "Allow runtime disabling of kernel stack erasing"
	depends on GCC_PLUGIN_STACKLEAK
	help
	This option provides 'stack_erasing' sysctl, which can be used in
	runtime to control kernel stack erasing for kernels built with
	CONFIG_GCC_PLUGIN_STACKLEAK.

	config GCC_PLUGIN_ARM_SSP_PER_TASK
	bool
	depends on GCC_PLUGINS && ARM

	endif