Introduce compat_u64 and compat_s64 types

One common problem with 32 bit system call and ioctl emulation is the
different alignment rules between i386 and 64 bit machines.  A number of
drivers work around this by marking the compat structures as
'attribute((packed))', which is not the right solution because it breaks
all the non-x86 architectures that want to use the same compat code.

Hopefully, this patch improves the situation, it introduces two new types,
compat_u64 and compat_s64.  These are defined on all architectures to have
the same size and alignment as the 32 bit version of u64 and s64.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Andi Kleen <ak@suse.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Vasily Tarasov <vtaras@openvz.org>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/asm-x86_64/compat.h b/include/asm-x86_64/compat.h
index b37ab82..53cb96b 100644
--- a/include/asm-x86_64/compat.h
+++ b/include/asm-x86_64/compat.h
@@ -33,8 +33,10 @@ typedef s32		compat_key_t;
 
 typedef s32		compat_int_t;
 typedef s32		compat_long_t;
+typedef s64 __attribute__((aligned(4))) compat_s64;
 typedef u32		compat_uint_t;
 typedef u32		compat_ulong_t;
+typedef u64 __attribute__((aligned(4))) compat_u64;
 
 struct compat_timespec {
 	compat_time_t	tv_sec;