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kasan: simplify and clarify Makefile

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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: Andrey Konovalov <andreyknvl@gmail.com>
Acked-by: Marco Elver <elver@google.com>
Link: https://lore.kernel.org/r/20240814161052.10374-1-andrey.konovalov@linux.dev
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Andrey Konovalov 2024-08-14 18:10:52 +02:00 committed by Miguel Ojeda
parent ca627e6365
commit cc1d98f9fe
1 changed files with 22 additions and 21 deletions
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31
scripts/Makefile.kasan
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@ -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