Commit cc1d98f9 authored by Andrey Konovalov's avatar Andrey Konovalov Committed by Miguel Ojeda
Browse files

kasan: simplify and clarify Makefile 



When KASAN support was being added to the Linux kernel, GCC did not yet
support all of the KASAN-related compiler options. Thus, the KASAN
Makefile had to probe the compiler for supported options.

Nowadays, the Linux kernel GCC version requirement is 5.1+, and thus we
don't need the probing of the -fasan-shadow-offset parameter: it exists in
all 5.1+ GCCs.

Simplify the KASAN Makefile to drop CFLAGS_KASAN_MINIMAL.

Also add a few more comments and unify the indentation.

Signed-off-by: default avatarAndrey Konovalov <andreyknvl@gmail.com>
Acked-by: default avatarMarco Elver <elver@google.com>
Link: https://lore.kernel.org/r/20240814161052.10374-1-andrey.konovalov@linux.dev


Signed-off-by: default avatarMiguel Ojeda <ojeda@kernel.org>
parent ca627e63

scripts/Makefile.kasan

+23 −22
Original line number Diff line number Diff line
@@ -22,30 +22,31 @@ 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



CFLAGS_KASAN_MINIMAL := -fsanitize=kernel-address



# -fasan-shadow-offset fails without -fsanitize

CFLAGS_KASAN_SHADOW := $(call cc-option, -fsanitize=kernel-address \

# 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)))



ifeq ($(strip $(CFLAGS_KASAN_SHADOW)),)

	CFLAGS_KASAN := $(CFLAGS_KASAN_MINIMAL)

else

	# Now add all the compiler specific options that are valid standalone

	CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \

	 $(call cc-param,asan-globals=1) \

	 $(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \

	 $(call cc-param,asan-instrument-allocas=1)

endif



CFLAGS_KASAN += $(call cc-param,asan-stack=$(stack_enable))

# Now, add other parameters enabled similarly in both GCC and Clang.

# As some of them are not supported by older compilers, use cc-param.

CFLAGS_KASAN += $(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \

		$(call cc-param,asan-stack=$(stack_enable)) \

		$(call cc-param,asan-instrument-allocas=1) \

		$(call cc-param,asan-globals=1)



# Instrument memcpy/memset/memmove calls by using instrumented __asan_mem*()

# instead. With compilers that don't support this option, compiler-inserted