[PATCH] Fix copying of unaligned data across user/kernel boundary

32 bit compatibility code sometimes needs to copy unaligned data across
kernel/user boundary and currently there is no architecture independent API
to do it.

(1) Introduce new APIs __{get,put}_user_unaligned. These APIs are
    necessary because the optimal way to copy unaligned data across
    kernel/user boundary is different on different architectures.
    Some architectures don't even care about alignment.
    On some __put_user is faster than __copy_to_user for small sizes.
(2) Optimize __{get,put}_user_unaligned for ia64, x86-64, s390, ppc64.
(3) Fix compat_filldir64() which is broken on big-endian machines

Thanks to Arnd Bergmann <arnd@arndb.de> for his help.
Signed-off-by: Gordon Jin <gordon.jin@intel.com>
Signed-off-by: Arun Sharma <arun.sharma@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/compat.c

@@ -981,19 +981,14 @@ static int compat_filldir64(void * __buf, const char * name, int namlen, loff_t
 	dirent = buf->previous;
 
 	if (dirent) {
-		if (__put_user(offset, (u32 __user *)&dirent->d_off))
-			goto efault;
-		if (__put_user(offset >> 32,
-				((u32 __user *)&dirent->d_off) + 1))
+		if (__put_user_unaligned(offset, &dirent->d_off))
 			goto efault;
 	}
 	dirent = buf->current_dir;
-	if ((__put_user(ino, (u32 __user *)&dirent->d_ino))
-	 || (__put_user(ino >> 32, ((u32 __user *)&dirent->d_ino) + 1)))
+	if (__put_user_unaligned(ino, &dirent->d_ino))
 		goto efault;
 	off = 0;
-	if ((__put_user(off, (u32 __user *)&dirent->d_off))
-	 || (__put_user(off >> 32, ((u32 __user *)&dirent->d_off) + 1)))
+	if (__put_user_unaligned(off, &dirent->d_off))
 		goto efault;
 	if (__put_user(reclen, &dirent->d_reclen))
 		goto efault;
@@ -1042,8 +1037,7 @@ asmlinkage long compat_sys_getdents64(unsigned int fd,
 	lastdirent = buf.previous;
 	if (lastdirent) {
 		typeof(lastdirent->d_off) d_off = file->f_pos;
-		__put_user(d_off, (u32 __user *)&lastdirent->d_off);
-		__put_user(d_off >> 32, ((u32 __user *)&lastdirent->d_off) + 1);
+		__put_user_unaligned(d_off, &lastdirent->d_off);
 		error = count - buf.count;
 	}
 

include/asm-generic/uaccess.h

+#ifndef _ASM_GENERIC_UACCESS_H_
+#define _ASM_GENERIC_UACCESS_H_
+
+/*
+ * This macro should be used instead of __get_user() when accessing
+ * values at locations that are not known to be aligned.
+ */
+#define __get_user_unaligned(x, ptr)					\
+({									\
+	__typeof__ (*(ptr)) __x;					\
+	__copy_from_user(&__x, (ptr), sizeof(*(ptr))) ? -EFAULT : 0;	\
+	(x) = _x;							\
+})
+
+
+/*
+ * This macro should be used instead of __put_user() when accessing
+ * values at locations that are not known to be aligned.
+ */
+#define __put_user_unaligned(x, ptr)					\
+({									\
+	__typeof__ (*(ptr)) __x = (x);					\
+	__copy_to_user((ptr), &__x, sizeof(*(ptr))) ? -EFAULT : 0;	\
+})
+
+#endif /* _ASM_GENERIC_UACCESS_H */

include/asm-ia64/uaccess.h

@@ -91,6 +91,42 @@ verify_area (int type, const void *addr, unsigned long size)
 #define __put_user(x, ptr)	__put_user_nocheck((__typeof__(*(ptr))) (x), (ptr), sizeof(*(ptr)))
 #define __get_user(x, ptr)	__get_user_nocheck((x), (ptr), sizeof(*(ptr)))
 
+extern long __put_user_unaligned_unknown (void);
+
+#define __put_user_unaligned(x, ptr)								\
+({												\
+	long __ret;										\
+	switch (sizeof(*(ptr))) {								\
+		case 1: __ret = __put_user((x), (ptr)); break;					\
+		case 2: __ret = (__put_user((x), (u8 __user *)(ptr)))				\
+			| (__put_user((x) >> 8, ((u8 __user *)(ptr) + 1))); break;		\
+		case 4: __ret = (__put_user((x), (u16 __user *)(ptr)))				\
+			| (__put_user((x) >> 16, ((u16 __user *)(ptr) + 1))); break;		\
+		case 8: __ret = (__put_user((x), (u32 __user *)(ptr)))				\
+			| (__put_user((x) >> 32, ((u32 __user *)(ptr) + 1))); break;		\
+		default: __ret = __put_user_unaligned_unknown();				\
+	}											\
+	__ret;											\
+})
+
+extern long __get_user_unaligned_unknown (void);
+
+#define __get_user_unaligned(x, ptr)								\
+({												\
+	long __ret;										\
+	switch (sizeof(*(ptr))) {								\
+		case 1: __ret = __get_user((x), (ptr)); break;					\
+		case 2: __ret = (__get_user((x), (u8 __user *)(ptr)))				\
+			| (__get_user((x) >> 8, ((u8 __user *)(ptr) + 1))); break;		\
+		case 4: __ret = (__get_user((x), (u16 __user *)(ptr)))				\
+			| (__get_user((x) >> 16, ((u16 __user *)(ptr) + 1))); break;		\
+		case 8: __ret = (__get_user((x), (u32 __user *)(ptr)))				\
+			| (__get_user((x) >> 32, ((u32 __user *)(ptr) + 1))); break;		\
+		default: __ret = __get_user_unaligned_unknown();				\
+	}											\
+	__ret;											\
+})
+
 #ifdef ASM_SUPPORTED
   struct __large_struct { unsigned long buf[100]; };
 # define __m(x) (*(struct __large_struct *)(x))

include/asm-mips/uaccess.h

@@ -13,6 +13,7 @@
 #include <linux/compiler.h>
 #include <linux/errno.h>
 #include <linux/thread_info.h>
+#include <asm-generic/uaccess.h>
 
 /*
  * The fs value determines whether argument validity checking should be

include/asm-ppc64/uaccess.h

@@ -111,6 +111,9 @@ extern unsigned long search_exception_table(unsigned long);
 #define __put_user(x,ptr) \
   __put_user_nocheck((__typeof__(*(ptr)))(x),(ptr),sizeof(*(ptr)))
 
+#define __get_user_unaligned __get_user
+#define __put_user_unaligned __put_user
+
 extern long __put_user_bad(void);
 
 #define __put_user_nocheck(x,ptr,size)				\

include/asm-s390/uaccess.h

@@ -250,6 +250,9 @@ extern int __put_user_bad(void);
 
 extern int __get_user_bad(void);
 
+#define __put_user_unaligned __put_user
+#define __get_user_unaligned __get_user
+
 extern long __copy_to_user_asm(const void *from, long n, void __user *to);
 
 /**

include/asm-sparc64/uaccess.h

@@ -14,6 +14,7 @@
 #include <asm/asi.h>
 #include <asm/system.h>
 #include <asm/spitfire.h>
+#include <asm-generic/uaccess.h>
 #endif
 
 #ifndef __ASSEMBLY__

include/asm-x86_64/uaccess.h

@@ -137,6 +137,9 @@ extern void __put_user_bad(void);
 #define __put_user(x,ptr) \
   __put_user_nocheck((__typeof__(*(ptr)))(x),(ptr),sizeof(*(ptr)))
 
+#define __get_user_unaligned __get_user
+#define __put_user_unaligned __put_user
+
 #define __put_user_nocheck(x,ptr,size)			\
 ({							\
 	int __pu_err;					\