utils: add copy_struct_from_client()

Which is our variant of copy_struct_from_user() that Aleksa and I added to the
kernel.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/src/lxc/utils.h b/src/lxc/utils.h
index dd51afdc4c8d2918f77b71828a78b424d2dcefac..f2b50e87b84a6af14117dc7c3be2f2224ed68b7d 100644 (file)
--- a/src/lxc/utils.h
+++ b/src/lxc/utils.h
@@ -245,4 +245,22 @@ __hidden extern int safe_mount_beneath_at(int beneat_fd, const char *src, const
                                          const char *fstype, unsigned int flags, const void *data);
 __hidden __lxc_unused int print_r(int fd, const char *path);
 
+static inline int copy_struct_from_client(__u32 server_size, void *dst,
+                                         __u32 client_size, const void *src)
+{
+       __u32 size = min(server_size, client_size);
+       __u32 rest = min(server_size, client_size) - size;
+
+       /* Deal with trailing bytes. */
+       if (client_size < server_size) {
+               memset(dst + size, 0, rest);
+       } else if (client_size > server_size) {
+               /* TODO: Actually come up with a nice way to test for 0. */
+               return 0;
+       }
+
+       memcpy(dst, src, size);
+       return 0;
+}
+
 #endif /* __LXC_UTILS_H */