posix_acl: uapi header split

Export the base definitions and the xattr representation of POSIX ACLs
to user space.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/uapi/linux/posix_acl_xattr.h

@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2002 Andreas Gruenbacher <a.gruenbacher@computer.org>
+ * Copyright (C) 2016 Red Hat, Inc.
+ *
+ * This file is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This file is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ */
+
+#ifndef __UAPI_POSIX_ACL_XATTR_H
+#define __UAPI_POSIX_ACL_XATTR_H
+
+#include <linux/types.h>
+
+/* Supported ACL a_version fields */
+#define POSIX_ACL_XATTR_VERSION	0x0002
+
+/* An undefined entry e_id value */
+#define ACL_UNDEFINED_ID	(-1)
+
+struct posix_acl_xattr_entry {
+	__le16			e_tag;
+	__le16			e_perm;
+	__le32			e_id;
+};
+
+struct posix_acl_xattr_header {
+	__le32			a_version;
+};
+
+#endif	/* __UAPI_POSIX_ACL_XATTR_H */