compat: Create compat_sys_p{read,write}v64

For 32-bit ABIs which have real 64-bit registers, we don't want to
break the position argument into two.  However, we still need compat
support to deal with 32-bit pointers, so we can't just use
sys_p{read,write} directly.
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

fs/compat.c

@@ -1177,10 +1177,9 @@ compat_sys_readv(unsigned long fd, const struct compat_iovec __user *vec,
 }
 
 asmlinkage ssize_t
-compat_sys_preadv(unsigned long fd, const struct compat_iovec __user *vec,
-		  unsigned long vlen, u32 pos_low, u32 pos_high)
+compat_sys_preadv64(unsigned long fd, const struct compat_iovec __user *vec,
+		    unsigned long vlen, loff_t pos)
 {
-	loff_t pos = ((loff_t)pos_high << 32) | pos_low;
 	struct file *file;
 	int fput_needed;
 	ssize_t ret;
@@ -1197,6 +1196,14 @@ compat_sys_preadv(unsigned long fd, const struct compat_iovec __user *vec,
 	return ret;
 }
 
+asmlinkage ssize_t
+compat_sys_preadv(unsigned long fd, const struct compat_iovec __user *vec,
+		  unsigned long vlen, u32 pos_low, u32 pos_high)
+{
+	loff_t pos = ((loff_t)pos_high << 32) | pos_low;
+	return compat_sys_preadv64(fd, vec, vlen, pos);
+}
+
 static size_t compat_writev(struct file *file,
 			    const struct compat_iovec __user *vec,
 			    unsigned long vlen, loff_t *pos)
@@ -1236,10 +1243,9 @@ compat_sys_writev(unsigned long fd, const struct compat_iovec __user *vec,
 }
 
 asmlinkage ssize_t
-compat_sys_pwritev(unsigned long fd, const struct compat_iovec __user *vec,
-		   unsigned long vlen, u32 pos_low, u32 pos_high)
+compat_sys_pwritev64(unsigned long fd, const struct compat_iovec __user *vec,
+		     unsigned long vlen, loff_t pos)
 {
-	loff_t pos = ((loff_t)pos_high << 32) | pos_low;
 	struct file *file;
 	int fput_needed;
 	ssize_t ret;
@@ -1256,6 +1262,14 @@ compat_sys_pwritev(unsigned long fd, const struct compat_iovec __user *vec,
 	return ret;
 }
 
+asmlinkage ssize_t
+compat_sys_pwritev(unsigned long fd, const struct compat_iovec __user *vec,
+		   unsigned long vlen, u32 pos_low, u32 pos_high)
+{
+	loff_t pos = ((loff_t)pos_high << 32) | pos_low;
+	return compat_sys_pwritev64(fd, vec, vlen, pos);
+}
+
 asmlinkage long
 compat_sys_vmsplice(int fd, const struct compat_iovec __user *iov32,
 		    unsigned int nr_segs, unsigned int flags)