compat: fs: Generic compat_sys_sendfile implementation

This function is used by sparc, powerpc and arm64 for compat support.
The patch adds a generic implementation which calls do_sendfile()
directly and avoids set_fs().

The sparc architecture has wrappers for the sign extensions while
powerpc relies on the compiler to do the this. The patch adds wrappers
for powerpc to handle the u32->int type conversion.

compat_sys_sendfile64() can be replaced by a sys_sendfile() call since
compat_loff_t has the same size as off_t on a 64-bit system.

On powerpc, the patch also changes the 64-bit sendfile call from
sys_sendile64 to sys_sendfile.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 26 insertions, 2 deletions

diff --git a/fs/compat.c b/fs/compat.c
index d72d51e19025..b7a24d0ca30d 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1792,3 +1792,25 @@ compat_sys_open_by_handle_at(int mountdirfd,
         return do_handle_open(mountdirfd, handle, flags);
 }
 #endif
+
+#ifdef __ARCH_WANT_COMPAT_SYS_SENDFILE
+asmlinkage long compat_sys_sendfile(int out_fd, int in_fd,
+                                    compat_off_t __user *offset, compat_size_t count)
+{
+        loff_t pos;
+        off_t off;
+        ssize_t ret;
+
+        if (offset) {
+                if (unlikely(get_user(off, offset)))
+                        return -EFAULT;
+                pos = off;
+                ret = do_sendfile(out_fd, in_fd, &pos, count, MAX_NON_LFS);
+                if (unlikely(put_user(pos, offset)))
+                        return -EFAULT;
+                return ret;
+        }
+
+        return do_sendfile(out_fd, in_fd, NULL, count, 0);
+}
+#endif /* __ARCH_WANT_COMPAT_SYS_SENDFILE */
diff --git a/fs/read_write.c b/fs/read_write.c
index 28b38279a219..d06534857e9e 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -862,8 +862,8 @@ SYSCALL_DEFINE5(pwritev, unsigned long, fd, const struct iovec __user *, vec,
         return ret;
 }
 
-static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
-                           size_t count, loff_t max)
+ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos, size_t count,
+                    loff_t max)
 {
         struct fd in, out;
         struct inode *in_inode, *out_inode;
diff --git a/fs/read_write.h b/fs/read_write.h
index d07b954c6e0c..d3e00ef67420 100644
--- a/fs/read_write.h
+++ b/fs/read_write.h
@@ -12,3 +12,5 @@ ssize_t do_sync_readv_writev(struct file *filp, const struct iovec *iov,
                 unsigned long nr_segs, size_t len, loff_t *ppos, iov_fn_t fn);
 ssize_t do_loop_readv_writev(struct file *filp, struct iovec *iov,
                 unsigned long nr_segs, loff_t *ppos, io_fn_t fn);
+ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos, size_t count,
+                    loff_t max);