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75d75b7a4d
In the kernel, the "volatile" keyword is used in various concurrent
contexts, whether in low-level synchronization primitives or for
legacy reasons. If supported by the compiler, it will be assumed
that aligned volatile accesses up to sizeof(long long) (matching
compiletime_assert_rwonce_type()) are atomic.
Recent versions of Clang [1] (GCC tentative [2]) can instrument
volatile accesses differently. Add the option (required) to enable the
instrumentation, and provide the necessary runtime functions. None of
the updated compilers are widely available yet (Clang 11 will be the
first release to support the feature).
[1] 5a2c31116f
[2] https://gcc.gnu.org/pipermail/gcc-patches/2020-April/544452.html
This change allows removing of any explicit checks in primitives such as
READ_ONCE() and WRITE_ONCE().
[ bp: Massage commit message a bit. ]
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200521142047.169334-4-elver@google.com
18 lines
632 B
Makefile
18 lines
632 B
Makefile
# SPDX-License-Identifier: GPL-2.0
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ifdef CONFIG_KCSAN
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# GCC and Clang accept backend options differently. Do not wrap in cc-option,
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# because Clang accepts "--param" even if it is unused.
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ifdef CONFIG_CC_IS_CLANG
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cc-param = -mllvm -$(1)
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else
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cc-param = --param -$(1)
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endif
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# Keep most options here optional, to allow enabling more compilers if absence
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# of some options does not break KCSAN nor causes false positive reports.
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CFLAGS_KCSAN := -fsanitize=thread \
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$(call cc-option,$(call cc-param,tsan-instrument-func-entry-exit=0) -fno-optimize-sibling-calls) \
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$(call cc-param,tsan-distinguish-volatile=1)
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endif # CONFIG_KCSAN
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