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From: Marco Elver <elver@google.com>
To: elver@google.com
Cc: paulmck@kernel.org, dvyukov@google.com, glider@google.com,
	andreyknvl@google.com, kasan-dev@googlegroups.com,
	linux-kernel@vger.kernel.org, tglx@linutronix.de,
	mingo@kernel.org, peterz@infradead.org, will@kernel.org,
	clang-built-linux@googlegroups.com
Subject: [PATCH -tip 04/10] kcsan: Pass option tsan-instrument-read-before-write to Clang
Date: Fri, 15 May 2020 17:03:32 +0200	[thread overview]
Message-ID: <20200515150338.190344-5-elver@google.com> (raw)
In-Reply-To: <20200515150338.190344-1-elver@google.com>

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@google.com>
---
 scripts/Makefile.kcsan | 1 +
 1 file changed, 1 insertion(+)

diff --git a/scripts/Makefile.kcsan b/scripts/Makefile.kcsan
index c02662b30a7c..ea4a6301633e 100644
--- a/scripts/Makefile.kcsan
+++ b/scripts/Makefile.kcsan
@@ -13,6 +13,7 @@ endif
 # if the absence of some options still allows us to use KCSAN in most cases.
 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
-- 
2.26.2.761.g0e0b3e54be-goog


  parent reply	other threads:[~2020-05-15 15:04 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-15 15:03 [PATCH -tip 00/10] Fix KCSAN for new ONCE (require Clang 11) Marco Elver
2020-05-15 15:03 ` [PATCH -tip 01/10] ubsan, kcsan: don't combine sanitizer with kcov on clang Marco Elver
2020-05-15 15:03 ` [PATCH -tip 02/10] kcsan: Avoid inserting __tsan_func_entry/exit if possible Marco Elver
2020-05-15 15:03 ` [PATCH -tip 03/10] kcsan: Support distinguishing volatile accesses Marco Elver
2020-05-15 15:03 ` Marco Elver [this message]
2020-05-15 15:03 ` [PATCH -tip 05/10] kcsan: Remove 'noinline' from __no_kcsan_or_inline Marco Elver
2020-05-15 15:03 ` [PATCH -tip 06/10] kcsan: Restrict supported compilers Marco Elver
2020-05-15 15:03 ` [PATCH -tip 07/10] kcsan: Update Documentation to change " Marco Elver
2020-05-15 15:03 ` [PATCH -tip 08/10] READ_ONCE, WRITE_ONCE: Remove data_race() wrapping Marco Elver
2020-05-21  9:47   ` Marco Elver
2020-05-21 10:18     ` Marco Elver
2020-05-21 10:22       ` Will Deacon
2020-05-15 15:03 ` [PATCH -tip 09/10] compiler.h: Move function attributes to compiler_types.h Marco Elver
2020-05-15 15:03 ` [PATCH -tip 10/10] compiler_types.h, kasan: Use __SANITIZE_ADDRESS__ instead of CONFIG_KASAN to decide inlining Marco Elver
2020-05-21 11:11 ` [PATCH -tip 00/10] Fix KCSAN for new ONCE (require Clang 11) Marco Elver

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