linux-kernel - [PATCH 3.10 216/319] drivers/vfio: Rework offsetofend()

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Message-Id: <1486322541-8206-117-git-send-email-w@1wt.eu>
Date:   Sun,  5 Feb 2017 20:20:38 +0100
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Gavin Shan <gwshan@...ux.vnet.ibm.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 216/319] drivers/vfio: Rework offsetofend()

From: Gavin Shan <gwshan@...ux.vnet.ibm.com>

commit b13460b92093b29347e99d6c3242e350052b62cd upstream.

The macro offsetofend() introduces unnecessary temporary variable
"tmp". The patch avoids that and saves a bit memory in stack.

Signed-off-by: Gavin Shan <gwshan@...ux.vnet.ibm.com>
Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
[wt: backported only for ipv6 out-of-bounds fix]

Signed-off-by: Willy Tarreau <w@....eu>
---
 include/linux/vfio.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index ac8d488..1a7f0ac 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -86,8 +86,7 @@ extern void vfio_unregister_iommu_driver(
  * from user space.  This allows us to easily determine if the provided
  * structure is sized to include various fields.
  */
-#define offsetofend(TYPE, MEMBER) ({				\
-	TYPE tmp;						\
-	offsetof(TYPE, MEMBER) + sizeof(tmp.MEMBER); })		\
+#define offsetofend(TYPE, MEMBER) \
+	(offsetof(TYPE, MEMBER)	+ sizeof(((TYPE *)0)->MEMBER))
 
 #endif /* VFIO_H */
-- 
2.8.0.rc2.1.gbe9624a