scripts/Makefile.kasan

# SPDX-License-Identifier: GPL-2.0

ifdef CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX
# Safe for compiler to generate meminstrinsic calls in uninstrumented files.
CFLAGS_KASAN_NOSANITIZE :=
else
# Don't let compiler generate memintrinsic calls in uninstrumented files
# because they are instrumented.
CFLAGS_KASAN_NOSANITIZE := -fno-builtin
endif

KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)

cc-param = $(call cc-option, -mllvm -$(1), $(call cc-option, --param $(1)))
rustc-param = $(call rustc-option, -Cllvm-args=-$(1),)

check-args = $(foreach arg,$(2),$(call $(1),$(arg)))

kasan_params :=

ifdef CONFIG_KASAN_STACK
	stack_enable := 1
else
	stack_enable := 0
endif

ifdef CONFIG_KASAN_GENERIC

ifdef CONFIG_KASAN_INLINE
	# When the number of memory accesses in a function is less than this
	# call threshold number, the compiler will use inline instrumentation.
	# 10000 is chosen offhand as a sufficiently large number to make all
	# kernel functions to be instrumented inline.
	call_threshold := 10000
else
	call_threshold := 0
endif

# First, enable -fsanitize=kernel-address together with providing the shadow
# mapping offset, as for GCC, -fasan-shadow-offset fails without -fsanitize
# (GCC accepts the shadow mapping offset via -fasan-shadow-offset instead of
# a --param like the other KASAN parameters).
# Instead of ifdef-checking the compiler, rely on cc-option.
CFLAGS_KASAN := $(call cc-option, -fsanitize=kernel-address \
		-fasan-shadow-offset=$(KASAN_SHADOW_OFFSET), \
		$(call cc-option, -fsanitize=kernel-address \
		-mllvm -asan-mapping-offset=$(KASAN_SHADOW_OFFSET)))

# The minimum supported `rustc` version has a minimum supported LLVM
# version late enough that we can assume support for -asan-mapping-offset.
RUSTFLAGS_KASAN := -Zsanitizer=kernel-address \
		   -Zsanitizer-recover=kernel-address \
		   -Cllvm-args=-asan-mapping-offset=$(KASAN_SHADOW_OFFSET)

# Now, add other parameters enabled similarly in GCC, Clang, and rustc.
# As some of them are not supported by older compilers, these will be filtered
# through `cc-param` or `rust-param` as applicable.
kasan_params += asan-instrumentation-with-call-threshold=$(call_threshold) \
		asan-stack=$(stack_enable) \
		asan-instrument-allocas=1 \
		asan-globals=1

# Instrument memcpy/memset/memmove calls by using instrumented __asan_mem*()
# instead. With compilers that don't support this option, compiler-inserted
# memintrinsics won't be checked by KASAN on GENERIC_ENTRY architectures.
kasan_params += asan-kernel-mem-intrinsic-prefix=1

endif # CONFIG_KASAN_GENERIC

ifdef CONFIG_KASAN_SW_TAGS

CFLAGS_KASAN := -fsanitize=kernel-hwaddress

RUSTFLAGS_KASAN := -Zsanitizer=kernel-hwaddress \
		   -Zsanitizer-recover=kernel-hwaddress

ifdef CONFIG_KASAN_INLINE
	kasan_params += hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET)
else
	kasan_params += hwasan-instrument-with-calls=1
endif

kasan_params += hwasan-instrument-stack=$(stack_enable) \
		hwasan-use-short-granules=0 \
		hwasan-inline-all-checks=0

# Instrument memcpy/memset/memmove calls by using instrumented __(hw)asan_mem*().
ifdef CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX
	ifdef CONFIG_CC_IS_GCC
		kasan_params += asan-kernel-mem-intrinsic-prefix=1
	else
		kasan_params += hwasan-kernel-mem-intrinsic-prefix=1
	endif
endif # CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX

endif # CONFIG_KASAN_SW_TAGS

# Add all as-supported KASAN LLVM parameters requested by the configuration.
CFLAGS_KASAN += $(call check-args, cc-param, $(kasan_params))

ifdef CONFIG_RUST
	# Avoid calling `rustc-param` unless Rust is enabled.
	RUSTFLAGS_KASAN += $(call check-args, rustc-param, $(kasan_params))
endif # CONFIG_RUST

export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE RUSTFLAGS_KASAN