lib/Kconfig.ubsan

# SPDX-License-Identifier: GPL-2.0-only
config ARCH_HAS_UBSAN_SANITIZE_ALL
	bool

menuconfig UBSAN
	bool "Undefined behaviour sanity checker"
	help
	  This option enables the Undefined Behaviour sanity checker.
	  Compile-time instrumentation is used to detect various undefined
	  behaviours at runtime. For more details, see:
	  Documentation/dev-tools/ubsan.rst

if UBSAN

config UBSAN_TRAP
	bool "On Sanitizer warnings, abort the running kernel code"
	depends on !COMPILE_TEST
	depends on $(cc-option, -fsanitize-undefined-trap-on-error)
	help
	  Building kernels with Sanitizer features enabled tends to grow
	  the kernel size by around 5%, due to adding all the debugging
	  text on failure paths. To avoid this, Sanitizer instrumentation
	  can just issue a trap. This reduces the kernel size overhead but
	  turns all warnings (including potentially harmless conditions)
	  into full exceptions that abort the running kernel code
	  (regardless of context, locks held, etc), which may destabilize
	  the system. For some system builders this is an acceptable
	  trade-off.

config UBSAN_KCOV_BROKEN
	def_bool KCOV && CC_HAS_SANCOV_TRACE_PC
	depends on CC_IS_CLANG
	depends on !$(cc-option,-Werror=unused-command-line-argument -fsanitize=bounds -fsanitize-coverage=trace-pc)
	help
	  Some versions of clang support either UBSAN or KCOV but not the
	  combination of the two.
	  See https://bugs.llvm.org/show_bug.cgi?id=45831 for the status
	  in newer releases.

config CC_HAS_UBSAN_BOUNDS
	def_bool $(cc-option,-fsanitize=bounds)

config CC_HAS_UBSAN_ARRAY_BOUNDS
	def_bool $(cc-option,-fsanitize=array-bounds)

config UBSAN_BOUNDS
	bool "Perform array index bounds checking"
	default UBSAN
	depends on !UBSAN_KCOV_BROKEN
	depends on CC_HAS_UBSAN_ARRAY_BOUNDS || CC_HAS_UBSAN_BOUNDS
	help
	  This option enables detection of directly indexed out of bounds
	  array accesses, where the array size is known at compile time.
	  Note that this does not protect array overflows via bad calls
	  to the {str,mem}*cpy() family of functions (that is addressed
	  by CONFIG_FORTIFY_SOURCE).

config UBSAN_ONLY_BOUNDS
	def_bool CC_HAS_UBSAN_BOUNDS && !CC_HAS_UBSAN_ARRAY_BOUNDS
	depends on UBSAN_BOUNDS
	help
	  This is a weird case: Clang's -fsanitize=bounds includes
	  -fsanitize=local-bounds, but it's trapping-only, so for
	  Clang, we must use -fsanitize=array-bounds when we want
	  traditional array bounds checking enabled. For GCC, we
	  want -fsanitize=bounds.

config UBSAN_ARRAY_BOUNDS
	def_bool CC_HAS_UBSAN_ARRAY_BOUNDS
	depends on UBSAN_BOUNDS

config UBSAN_LOCAL_BOUNDS
	bool "Perform array local bounds checking"
	depends on UBSAN_TRAP
	depends on !UBSAN_KCOV_BROKEN
	depends on $(cc-option,-fsanitize=local-bounds)
	help
	  This option enables -fsanitize=local-bounds which traps when an
	  exception/error is detected. Therefore, it may only be enabled
	  with CONFIG_UBSAN_TRAP.

	  Enabling this option detects errors due to accesses through a
	  pointer that is derived from an object of a statically-known size,
	  where an added offset (which may not be known statically) is
	  out-of-bounds.

config UBSAN_SHIFT
	bool "Perform checking for bit-shift overflows"
	default UBSAN
	depends on $(cc-option,-fsanitize=shift)
	help
	  This option enables -fsanitize=shift which checks for bit-shift
	  operations that overflow to the left or go switch to negative
	  for signed types.

config UBSAN_DIV_ZERO
	bool "Perform checking for integer divide-by-zero"
	depends on $(cc-option,-fsanitize=integer-divide-by-zero)
	help
	  This option enables -fsanitize=integer-divide-by-zero which checks
	  for integer division by zero. This is effectively redundant with the
	  kernel's existing exception handling, though it can provide greater
	  debugging information under CONFIG_UBSAN_REPORT_FULL.

config UBSAN_UNREACHABLE
	bool "Perform checking for unreachable code"
	# objtool already handles unreachable checking and gets angry about
	# seeing UBSan instrumentation located in unreachable places.
	depends on !STACK_VALIDATION
	depends on $(cc-option,-fsanitize=unreachable)
	help
	  This option enables -fsanitize=unreachable which checks for control
	  flow reaching an expected-to-be-unreachable position.

config UBSAN_OBJECT_SIZE
	bool "Perform checking for accesses beyond the end of objects"
	default UBSAN
	# gcc hugely expands stack usage with -fsanitize=object-size
	# https://lore.kernel.org/lkml/CAHk-=wjPasyJrDuwDnpHJS2TuQfExwe=px-SzLeN8GFMAQJPmQ@mail.gmail.com/
	depends on !CC_IS_GCC
	depends on $(cc-option,-fsanitize=object-size)
	help
	  This option enables -fsanitize=object-size which checks for accesses
	  beyond the end of objects where the optimizer can determine both the
	  object being operated on and its size, usually seen with bad downcasts,
	  or access to struct members from NULL pointers.

config UBSAN_BOOL
	bool "Perform checking for non-boolean values used as boolean"
	default UBSAN
	depends on $(cc-option,-fsanitize=bool)
	help
	  This option enables -fsanitize=bool which checks for boolean values being
	  loaded that are neither 0 nor 1.

config UBSAN_ENUM
	bool "Perform checking for out of bounds enum values"
	default UBSAN
	depends on $(cc-option,-fsanitize=enum)
	help
	  This option enables -fsanitize=enum which checks for values being loaded
	  into an enum that are outside the range of given values for the given enum.

config UBSAN_ALIGNMENT
	bool "Perform checking for misaligned pointer usage"
	default !HAVE_EFFICIENT_UNALIGNED_ACCESS
	depends on !UBSAN_TRAP && !COMPILE_TEST
	depends on $(cc-option,-fsanitize=alignment)
	help
	  This option enables the check of unaligned memory accesses.
	  Enabling this option on architectures that support unaligned
	  accesses may produce a lot of false positives.

config UBSAN_SANITIZE_ALL
	bool "Enable instrumentation for the entire kernel"
	depends on ARCH_HAS_UBSAN_SANITIZE_ALL
	default y
	help
	  This option activates instrumentation for the entire kernel.
	  If you don't enable this option, you have to explicitly specify
	  UBSAN_SANITIZE := y for the files/directories you want to check for UB.
	  Enabling this option will get kernel image size increased
	  significantly.

config TEST_UBSAN
	tristate "Module for testing for undefined behavior detection"
	depends on m
	help
	  This is a test module for UBSAN.
	  It triggers various undefined behavior, and detect it.

endif	# if UBSAN