diff --git a/cmds/idmap/idmap.cpp b/cmds/idmap/idmap.cpp
index 90cfa2c..3ab1915 100644
--- a/cmds/idmap/idmap.cpp
+++ b/cmds/idmap/idmap.cpp
@@ -13,7 +13,8 @@
       idmap --help \n\
       idmap --fd target overlay fd \n\
       idmap --path target overlay idmap \n\
-      idmap --scan dir-to-scan target-to-look-for target dir-to-hold-idmaps \n\
+      idmap --scan target-package-name-to-look-for path-to-target-apk dir-to-hold-idmaps \\\
+                   dir-to-scan [additional-dir-to-scan [additional-dir-to-scan [...]]]\n\
       idmap --inspect idmap \n\
 \n\
 DESCRIPTION \n\
@@ -49,9 +50,9 @@
               'overlay' (path to apk); write results to 'idmap' (path). \n\
 \n\
       --scan: non-recursively search directory 'dir-to-scan' (path) for overlay packages with \n\
-              target package 'target-to-look-for' (package name) present at 'target' (path to \n\
-              apk). For each overlay package found, create an idmap file in 'dir-to-hold-idmaps' \n\
-              (path). \n\
+              target package 'target-package-name-to-look-for' (package name) present at\n\
+              'path-to-target-apk' (path to apk). For each overlay package found, create an\n\
+              idmap file in 'dir-to-hold-idmaps' (path). \n\
 \n\
       --inspect: decode the binary format of 'idmap' (path) and display the contents in a \n\
                  debug-friendly format. \n\
@@ -166,19 +167,14 @@
         return idmap_create_path(target_apk_path, overlay_apk_path, idmap_path);
     }
 
-    int maybe_scan(const char *overlay_dir, const char *target_package_name,
-            const char *target_apk_path, const char *idmap_dir)
+    int maybe_scan(const char *target_package_name, const char *target_apk_path,
+            const char *idmap_dir, const android::Vector<const char *> *overlay_dirs)
     {
         if (!verify_root_or_system()) {
             fprintf(stderr, "error: permission denied: not user root or user system\n");
             return -1;
         }
 
-        if (!verify_directory_readable(overlay_dir)) {
-            ALOGD("error: no read access to %s: %s\n", overlay_dir, strerror(errno));
-            return -1;
-        }
-
         if (!verify_file_readable(target_apk_path)) {
             ALOGD("error: failed to read apk %s: %s\n", target_apk_path, strerror(errno));
             return -1;
@@ -189,7 +185,16 @@
             return -1;
         }
 
-        return idmap_scan(overlay_dir, target_package_name, target_apk_path, idmap_dir);
+        const size_t N = overlay_dirs->size();
+        for (size_t i = 0; i < N; i++) {
+            const char *dir = overlay_dirs->itemAt(i);
+            if (!verify_directory_readable(dir)) {
+                ALOGD("error: no read access to %s: %s\n", dir, strerror(errno));
+                return -1;
+            }
+        }
+
+        return idmap_scan(target_package_name, target_apk_path, idmap_dir, overlay_dirs);
     }
 
     int maybe_inspect(const char *idmap_path)
@@ -230,8 +235,12 @@
         return maybe_create_path(argv[2], argv[3], argv[4]);
     }
 
-    if (argc == 6 && !strcmp(argv[1], "--scan")) {
-        return maybe_scan(argv[2], argv[3], argv[4], argv[5]);
+    if (argc >= 6 && !strcmp(argv[1], "--scan")) {
+        android::Vector<const char *> v;
+        for (int i = 5; i < argc; i++) {
+            v.push(argv[i]);
+        }
+        return maybe_scan(argv[2], argv[3], argv[4], &v);
     }
 
     if (argc == 3 && !strcmp(argv[1], "--inspect")) {
diff --git a/cmds/idmap/idmap.h b/cmds/idmap/idmap.h
index f507dd8..8d4210b 100644
--- a/cmds/idmap/idmap.h
+++ b/cmds/idmap/idmap.h
@@ -1,9 +1,11 @@
+
 #ifndef _IDMAP_H_
 #define _IDMAP_H_
 
 #define LOG_TAG "idmap"
 
 #include <utils/Log.h>
+#include <utils/Vector.h>
 
 #include <errno.h>
 #include <stdio.h>
@@ -26,8 +28,8 @@
 // Regarding target_package_name: the idmap_scan implementation should
 // be able to extract this from the manifest in target_apk_path,
 // simplifying the external API.
-int idmap_scan(const char *overlay_dir, const char *target_package_name,
-        const char *target_apk_path, const char *idmap_dir);
+int idmap_scan(const char *target_package_name, const char *target_apk_path,
+        const char *idmap_dir, const android::Vector<const char *> *overlay_dirs);
 
 int idmap_inspect(const char *idmap_path);
 
diff --git a/cmds/idmap/scan.cpp b/cmds/idmap/scan.cpp
index 612a7eb..a33c403 100644
--- a/cmds/idmap/scan.cpp
+++ b/cmds/idmap/scan.cpp
@@ -167,8 +167,8 @@
     }
 }
 
-int idmap_scan(const char *overlay_dir, const char *target_package_name,
-        const char *target_apk_path, const char *idmap_dir)
+int idmap_scan(const char *target_package_name, const char *target_apk_path,
+        const char *idmap_dir, const android::Vector<const char *> *overlay_dirs)
 {
     String8 filename = String8(idmap_dir);
     filename.appendPath("overlays.list");
@@ -176,45 +176,49 @@
         return EXIT_FAILURE;
     }
 
-    DIR *dir = opendir(overlay_dir);
-    if (dir == NULL) {
-        return EXIT_FAILURE;
-    }
-
     SortedVector<Overlay> overlayVector;
-    struct dirent *dirent;
-    while ((dirent = readdir(dir)) != NULL) {
-        struct stat st;
-        char overlay_apk_path[PATH_MAX + 1];
-        snprintf(overlay_apk_path, PATH_MAX, "%s/%s", overlay_dir, dirent->d_name);
-        if (stat(overlay_apk_path, &st) < 0) {
-            continue;
-        }
-        if (!S_ISREG(st.st_mode)) {
-            continue;
+    const size_t N = overlay_dirs->size();
+    for (size_t i = 0; i < N; ++i) {
+        const char *overlay_dir = overlay_dirs->itemAt(i);
+        DIR *dir = opendir(overlay_dir);
+        if (dir == NULL) {
+            return EXIT_FAILURE;
         }
 
-        int priority = parse_apk(overlay_apk_path, target_package_name);
-        if (priority < 0) {
-            continue;
+        struct dirent *dirent;
+        while ((dirent = readdir(dir)) != NULL) {
+            struct stat st;
+            char overlay_apk_path[PATH_MAX + 1];
+            snprintf(overlay_apk_path, PATH_MAX, "%s/%s", overlay_dir, dirent->d_name);
+            if (stat(overlay_apk_path, &st) < 0) {
+                continue;
+            }
+            if (!S_ISREG(st.st_mode)) {
+                continue;
+            }
+
+            int priority = parse_apk(overlay_apk_path, target_package_name);
+            if (priority < 0) {
+                continue;
+            }
+
+            String8 idmap_path(idmap_dir);
+            idmap_path.appendPath(flatten_path(overlay_apk_path + 1));
+            idmap_path.append("@idmap");
+
+            if (idmap_create_path(target_apk_path, overlay_apk_path, idmap_path.string()) != 0) {
+                ALOGE("error: failed to create idmap for target=%s overlay=%s idmap=%s\n",
+                        target_apk_path, overlay_apk_path, idmap_path.string());
+                continue;
+            }
+
+            Overlay overlay(String8(overlay_apk_path), idmap_path, priority);
+            overlayVector.add(overlay);
         }
 
-        String8 idmap_path(idmap_dir);
-        idmap_path.appendPath(flatten_path(overlay_apk_path + 1));
-        idmap_path.append("@idmap");
-
-        if (idmap_create_path(target_apk_path, overlay_apk_path, idmap_path.string()) != 0) {
-            ALOGE("error: failed to create idmap for target=%s overlay=%s idmap=%s\n",
-                    target_apk_path, overlay_apk_path, idmap_path.string());
-            continue;
-        }
-
-        Overlay overlay(String8(overlay_apk_path), idmap_path, priority);
-        overlayVector.add(overlay);
+        closedir(dir);
     }
 
-    closedir(dir);
-
     if (!writePackagesList(filename.string(), overlayVector)) {
         return EXIT_FAILURE;
     }
diff --git a/core/jni/android_util_AssetManager.cpp b/core/jni/android_util_AssetManager.cpp
index 614e82f..c94bc64 100644
--- a/core/jni/android_util_AssetManager.cpp
+++ b/core/jni/android_util_AssetManager.cpp
@@ -24,6 +24,7 @@
 #include <stdio.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <sys/stat.h>
 
 #include <private/android_filesystem_config.h> // for AID_SYSTEM
 
@@ -171,11 +172,32 @@
                     exit(1);
                 }
 
-                execl(AssetManager::IDMAP_BIN, AssetManager::IDMAP_BIN, "--scan",
-                        AssetManager::OVERLAY_DIR, AssetManager::TARGET_PACKAGE_NAME,
-                        AssetManager::TARGET_APK_PATH, AssetManager::IDMAP_DIR, (char*)NULL);
-                ALOGE("failed to execl for idmap: %s", strerror(errno));
-                exit(1); // should never get here
+                // Generic idmap parameters
+                const char* argv[7];
+                int argc = 0;
+                struct stat st;
+
+                memset(argv, NULL, sizeof(argv));
+                argv[argc++] = AssetManager::IDMAP_BIN;
+                argv[argc++] = "--scan";
+                argv[argc++] = AssetManager::TARGET_PACKAGE_NAME;
+                argv[argc++] = AssetManager::TARGET_APK_PATH;
+                argv[argc++] = AssetManager::IDMAP_DIR;
+
+                // Directories to scan for overlays
+                // /vendor/overlay
+                if (stat(AssetManager::OVERLAY_DIR, &st) == 0) {
+                    argv[argc++] = AssetManager::OVERLAY_DIR;
+                 }
+
+                // Finally, invoke idmap (if any overlay directory exists)
+                if (argc > 5) {
+                    execv(AssetManager::IDMAP_BIN, (char* const*)argv);
+                    ALOGE("failed to execl for idmap: %s", strerror(errno));
+                    exit(1); // should never get here
+                } else {
+                    exit(0);
+                }
             }
             break;
         default: // parent