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

[Willy Tarreau]

From: Gavin Shan <gwshan@xxxxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
[wt: backported only for ipv6 out-of-bounds fix]

Signed-off-by: Willy Tarreau <w@xxxxxx>
---
 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