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Date:   Tue,  5 Oct 2021 12:58:54 +0200
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Subject: [PATCH -rcu/kcsan 12/23] kcsan: Ignore GCC 11+ warnings about TSan
 runtime support
From:   Marco Elver <elver@google.com>
To:     elver@google.com, "Paul E . McKenney" <paulmck@kernel.org>
Cc:     Alexander Potapenko <glider@google.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Borislav Petkov <bp@alien8.de>,
        Dmitry Vyukov <dvyukov@google.com>,
        Ingo Molnar <mingo@kernel.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Waiman Long <longman@redhat.com>,
        Will Deacon <will@kernel.org>, kasan-dev@googlegroups.com,
        linux-arch@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, x86@kernel.org
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GCC 11 has introduced a new warning option, -Wtsan [1], to warn about
unsupported operations in the TSan runtime. But KCSAN !=3D TSan runtime,
so none of the warnings apply.

[1] https://gcc.gnu.org/onlinedocs/gcc-11.1.0/gcc/Warning-Options.html

Ignore the warnings.

Currently the warning only fires in the test for __atomic_thread_fence():

kernel/kcsan/kcsan_test.c: In function =E2=80=98test_atomic_builtins=E2=80=
=99:
kernel/kcsan/kcsan_test.c:1234:17: warning: =E2=80=98atomic_thread_fence=E2=
=80=99 is not supported with =E2=80=98-fsanitize=3Dthread=E2=80=99 [-Wtsan]
 1234 |                 __atomic_thread_fence(__ATOMIC_SEQ_CST);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

which exists to ensure the KCSAN runtime keeps supporting the builtin
instrumentation.

Signed-off-by: Marco Elver <elver@google.com>
---
 scripts/Makefile.kcsan | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/scripts/Makefile.kcsan b/scripts/Makefile.kcsan
index 4c7f0d282e42..19f693b68a96 100644
--- a/scripts/Makefile.kcsan
+++ b/scripts/Makefile.kcsan
@@ -13,6 +13,12 @@ kcsan-cflags :=3D -fsanitize=3Dthread -fno-optimize-sibl=
ing-calls \
 	$(call cc-option,$(call cc-param,tsan-compound-read-before-write=3D1),$(c=
all cc-option,$(call cc-param,tsan-instrument-read-before-write=3D1))) \
 	$(call cc-param,tsan-distinguish-volatile=3D1)
=20
+ifdef CONFIG_CC_IS_GCC
+# GCC started warning about operations unsupported by the TSan runtime. Bu=
t
+# KCSAN !=3D TSan, so just ignore these warnings.
+kcsan-cflags +=3D -Wno-tsan
+endif
+
 ifndef CONFIG_KCSAN_WEAK_MEMORY
 kcsan-cflags +=3D $(call cc-option,$(call cc-param,tsan-instrument-func-en=
try-exit=3D0))
 endif
--=20
2.33.0.800.g4c38ced690-goog