linux-kernel - [PATCH v3 15/25] locking/barriers, kcsan: Support generic instrumentation

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Message-Id: <20211130114433.2580590-16-elver@google.com>
Date:   Tue, 30 Nov 2021 12:44:23 +0100
From:   Marco Elver <elver@...gle.com>
To:     elver@...gle.com, "Paul E. McKenney" <paulmck@...nel.org>
Cc:     Alexander Potapenko <glider@...gle.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Waiman Long <longman@...hat.com>,
        Will Deacon <will@...nel.org>, kasan-dev@...glegroups.com,
        linux-arch@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, llvm@...ts.linux.dev, x86@...nel.org
Subject: [PATCH v3 15/25] locking/barriers, kcsan: Support generic instrumentation

Thus far only smp_*() barriers had been defined by asm-generic/barrier.h
based on __smp_*() barriers, because the !SMP case is usually generic.

With the introduction of instrumentation, it also makes sense to have
asm-generic/barrier.h assist in the definition of instrumented versions
of mb(), rmb(), wmb(), dma_rmb(), and dma_wmb().

Because there is no requirement to distinguish the !SMP case, the
definition can be simpler: we can avoid also providing fallbacks for the
__ prefixed cases, and only check if `defined(__<barrier>)`, to finally
define the KCSAN-instrumented versions.

This also allows for the compiler to complain if an architecture
accidentally defines both the normal and __ prefixed variant.

Signed-off-by: Marco Elver <elver@...gle.com>
---
 include/asm-generic/barrier.h | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h
index 27a9c9edfef6..02c4339c8eeb 100644
--- a/include/asm-generic/barrier.h
+++ b/include/asm-generic/barrier.h
@@ -21,6 +21,31 @@
 #define nop()	asm volatile ("nop")
 #endif
 
+/*
+ * Architectures that want generic instrumentation can define __ prefixed
+ * variants of all barriers.
+ */
+
+#ifdef __mb
+#define mb()	do { kcsan_mb(); __mb(); } while (0)
+#endif
+
+#ifdef __rmb
+#define rmb()	do { kcsan_rmb(); __rmb(); } while (0)
+#endif
+
+#ifdef __wmb
+#define wmb()	do { kcsan_wmb(); __wmb(); } while (0)
+#endif
+
+#ifdef __dma_rmb
+#define dma_rmb()	do { kcsan_rmb(); __dma_rmb(); } while (0)
+#endif
+
+#ifdef __dma_wmb
+#define dma_wmb()	do { kcsan_wmb(); __dma_wmb(); } while (0)
+#endif
+
 /*
  * Force strict CPU ordering. And yes, this is required on UP too when we're
  * talking to devices.
-- 
2.34.0.rc2.393.gf8c9666880-goog