diff --git a/core/jni/android_util_AssetManager.cpp b/core/jni/android_util_AssetManager.cpp
index c2800e7..373bda9 100644
--- a/core/jni/android_util_AssetManager.cpp
+++ b/core/jni/android_util_AssetManager.cpp
@@ -119,6 +119,96 @@
     return block;
 }
 
+// This is called by zygote (running as user root) as part of preloadResources.
+static void verifySystemIdmaps()
+{
+    pid_t pid;
+    char system_id[10];
+
+    snprintf(system_id, sizeof(system_id), "%d", AID_SYSTEM);
+
+    switch (pid = fork()) {
+        case -1:
+            ALOGE("failed to fork for idmap: %s", strerror(errno));
+            break;
+        case 0: // child
+            {
+                struct __user_cap_header_struct capheader;
+                struct __user_cap_data_struct capdata;
+
+                memset(&capheader, 0, sizeof(capheader));
+                memset(&capdata, 0, sizeof(capdata));
+
+                capheader.version = _LINUX_CAPABILITY_VERSION;
+                capheader.pid = 0;
+
+                if (capget(&capheader, &capdata) != 0) {
+                    ALOGE("capget: %s\n", strerror(errno));
+                    exit(1);
+                }
+
+                capdata.effective = capdata.permitted;
+                if (capset(&capheader, &capdata) != 0) {
+                    ALOGE("capset: %s\n", strerror(errno));
+                    exit(1);
+                }
+
+                if (setgid(AID_SYSTEM) != 0) {
+                    ALOGE("setgid: %s\n", strerror(errno));
+                    exit(1);
+                }
+
+                if (setuid(AID_SYSTEM) != 0) {
+                    ALOGE("setuid: %s\n", strerror(errno));
+                    exit(1);
+                }
+
+                // Generic idmap parameters
+                const char* argv[8];
+                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: if OVERLAY_THEME_DIR_PROPERTY is defined,
+                // use OVERLAY_DIR/<value of OVERLAY_THEME_DIR_PROPERTY> in addition to OVERLAY_DIR.
+                char subdir[PROP_VALUE_MAX];
+                int len = __system_property_get(AssetManager::OVERLAY_THEME_DIR_PERSIST_PROPERTY,
+                        subdir);
+                if (len == 0) {
+                    len = __system_property_get(AssetManager::OVERLAY_THEME_DIR_PROPERTY, subdir);
+                }
+                if (len > 0) {
+                    String8 overlayPath = String8(AssetManager::OVERLAY_DIR) + "/" + subdir;
+                    if (stat(overlayPath.string(), &st) == 0) {
+                        argv[argc++] = overlayPath.string();
+                    }
+                }
+                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 execv for idmap: %s", strerror(errno));
+                    exit(1); // should never get here
+                } else {
+                    exit(0);
+                }
+            }
+            break;
+        default: // parent
+            waitpid(pid, NULL, 0);
+            break;
+    }
+}
+
 // ----------------------------------------------------------------------------
 
 // this guy is exported to other jni routines
@@ -1507,6 +1597,9 @@
 
 static void android_content_AssetManager_init(JNIEnv* env, jobject clazz, jboolean isSystem)
 {
+    if (isSystem) {
+        verifySystemIdmaps();
+    }
     AssetManager* am = new AssetManager();
     if (am == NULL) {
         jniThrowException(env, "java/lang/OutOfMemoryError", "");