The following commit has been merged into the locking/kcsan branch of tip: Commit-ID: 52dfbb97a90fbf6a9826f15a71fca37861330a13 Gitweb: https://git.kernel.org/tip/52dfbb97a90fbf6a9826f15a71fca37861330a13 Author: Marco Elver <elver@xxxxxxxxxx> AuthorDate: Thu, 21 May 2020 16:20:40 +02:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Fri, 22 May 2020 14:57:39 +02:00 kcsan: Pass option tsan-instrument-read-before-write to Clang Clang (unlike GCC) removes reads before writes with matching addresses in the same basic block. This is an optimization for TSAN, since writes will always cause conflict if the preceding read would have. However, for KCSAN we cannot rely on this option, because we apply several special rules to writes, in particular when the KCSAN_ASSUME_PLAIN_WRITES_ATOMIC option is selected. To avoid missing potential data races, pass the -tsan-instrument-read-before-write option to Clang if it is available [1]. [1] https://github.com/llvm/llvm-project/commit/151ed6aa38a3ec6c01973b35f684586b6e1c0f7e Signed-off-by: Marco Elver <elver@xxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Acked-by: Will Deacon <will@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20200521142047.169334-5-elver@xxxxxxxxxx --- scripts/Makefile.kcsan | 1 + 1 file changed, 1 insertion(+) diff --git a/scripts/Makefile.kcsan b/scripts/Makefile.kcsan index 75d2942..bd4da1a 100644 --- a/scripts/Makefile.kcsan +++ b/scripts/Makefile.kcsan @@ -13,6 +13,7 @@ endif # of some options does not break KCSAN nor causes false positive reports. CFLAGS_KCSAN := -fsanitize=thread \ $(call cc-option,$(call cc-param,tsan-instrument-func-entry-exit=0) -fno-optimize-sibling-calls) \ + $(call cc-option,$(call cc-param,tsan-instrument-read-before-write=1)) \ $(call cc-param,tsan-distinguish-volatile=1) endif # CONFIG_KCSAN
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