diff --git a/cmds/installd/installd.h b/cmds/installd/installd.h
index 9ca2f86..cab5cb7 100644
--- a/cmds/installd/installd.h
+++ b/cmds/installd/installd.h
@@ -75,6 +75,9 @@
 
 #define UPDATE_COMMANDS_DIR_PREFIX  "/system/etc/updatecmds/"
 
+#define IDMAP_PREFIX           "/data/resource-cache/"
+#define IDMAP_SUFFIX           "@idmap"
+
 #define PKG_NAME_MAX  128   /* largest allowed package name */
 #define PKG_PATH_MAX  256   /* max size of any path we use */
 
@@ -207,3 +210,4 @@
 int dexopt(const char *apk_path, uid_t uid, int is_public);
 int movefiles();
 int linklib(const char* target, const char* source, int userId);
+int idmap(const char *target_path, const char *overlay_path, uid_t uid);