[PATCH RFC v3 12/36] kmsan: define READ_ONCE_NOCHECK()

From: glider@google.com
To: Mark Rutland <mark.rutland@arm.com>,
	Vegard Nossum <vegard.nossum@oracle.com>,
	 Dmitry Vyukov <dvyukov@google.com>,
	linux-mm@kvack.org
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Subject: [PATCH RFC v3 12/36] kmsan: define READ_ONCE_NOCHECK()
Date: Fri, 22 Nov 2019 12:25:57 +0100
Message-ID: <20191122112621.204798-13-glider@google.com> (raw)
In-Reply-To: <20191122112621.204798-1-glider@google.com>

READ_ONCE_NOCHECK() is already used by KASAN to ignore memory accesses
from e.g. stack unwinders.
Define READ_ONCE_NOCHECK() for KMSAN so that it returns initialized
values. This helps defeat false positives from leftover stack contents.

Signed-off-by: Alexander Potapenko <glider@google.com>
To: Alexander Potapenko <glider@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: linux-mm@kvack.org
---
v3:
 - removed unnecessary #ifdef as requested by Mark Rutland

Change-Id: Ib38369ba038ab3b581d8e45b81036c3304fb79cb
---
 include/linux/compiler.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 5e88e7e33abe..99d40f31a2c3 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -270,9 +270,9 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
 
 /*
  * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
- * to hide memory access from KASAN.
+ * to hide memory access from KASAN or KMSAN.
  */
-#define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
+#define READ_ONCE_NOCHECK(x) KMSAN_INIT_VALUE(__READ_ONCE(x, 0))
 
 static __no_kasan_or_inline
 unsigned long read_word_at_a_time(const void *addr)
-- 
2.24.0.432.g9d3f5f5b63-goog


