1 files changed, 18 insertions, 10 deletions

diff --git a/arch/x86/include/asm/shmbuf.h b/arch/x86/include/asm/shmbuf.h
index b51413b74971..5768fa60ac82 100644
--- a/arch/x86/include/asm/shmbuf.h
+++ b/arch/x86/include/asm/shmbuf.h
@@ -1,32 +1,40 @@
-#ifndef _ASM_X86_SHMBUF_H
-#define _ASM_X86_SHMBUF_H
+#ifndef __ASM_GENERIC_SHMBUF_H
+#define __ASM_GENERIC_SHMBUF_H
+
+#include <asm/bitsperlong.h>
 
 /*
  * The shmid64_ds structure for x86 architecture.
  * Note extra padding because this structure is passed back and forth
  * between kernel and user space.
  *
- * Pad space on 32 bit is left for:
+ * shmid64_ds was originally meant to be architecture specific, but
+ * everyone just ended up making identical copies without specific
+ * optimizations, so we may just as well all use the same one.
+ *
+ * 64 bit architectures typically define a 64 bit __kernel_time_t,
+ * so they do not need the first two padding words.
+ * On big-endian systems, the padding is in the wrong place.
+ *
+ *
+ * Pad space is left for:
  * - 64-bit time_t to solve y2038 problem
  * - 2 miscellaneous 32-bit values
- *
- * Pad space on 64 bit is left for:
- * - 2 miscellaneous 64-bit values
  */
 
 struct shmid64_ds {
         struct ipc64_perm       shm_perm;       /* operation perms */
         size_t                  shm_segsz;      /* size of segment (bytes) */
         __kernel_time_t         shm_atime;      /* last attach time */
-#ifdef __i386__
+#if __BITS_PER_LONG != 64
         unsigned long           __unused1;
 #endif
         __kernel_time_t         shm_dtime;      /* last detach time */
-#ifdef __i386__
+#if __BITS_PER_LONG != 64
         unsigned long           __unused2;
 #endif
         __kernel_time_t         shm_ctime;      /* last change time */
-#ifdef __i386__
+#if __BITS_PER_LONG != 64
         unsigned long           __unused3;
 #endif
         __kernel_pid_t          shm_cpid;       /* pid of creator */
@@ -48,4 +56,4 @@ struct shminfo64 {
         unsigned long   __unused4;
 };
 
-#endif /* _ASM_X86_SHMBUF_H */
+#endif /* __ASM_GENERIC_SHMBUF_H */