common.sh, ...: add support for ext2-ro/rw hack

scripts/image_signing/sign_official_build.sh

 #!/bin/bash
 
 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Sign the final build image using the "official" keys.
 #
 # Prerequisite tools needed in the system path:
 #
@@ skipping 120 matching lines @@
     mount_image_partition "${image}" 3 "${rootfs_dir}"
     sudo rm -f "${rootfs_dir}/${TAG_NEEDS_TO_BE_SIGNED}"
   fi
   sudo umount -d "${rootfs_dir}"
 
   local rootfs_image=$(make_temp_file)
   extract_image_partition ${image} 3 ${rootfs_image}
   local kernel_config=$(grab_kernel_config "${image}")
   local hash_image=$(make_temp_file)
 
+  # Disable rw mount support prior to hashing.
+  disable_rw_mount "${rootfs_image}"
+
   local new_kernel_config=$(calculate_rootfs_hash "${rootfs_image}" \
     "${kernel_config}" "${hash_image}")
 
   local rootfs_blocks=$(sudo dumpe2fs "${rootfs_image}" 2> /dev/null |
     grep "Block count" |
     tr -d ' ' |
     cut -f2 -d:)
   local rootfs_sectors=$((rootfs_blocks * 8))
 
   # Overwrite the appended hashes in the rootfs
@@ skipping 214 matching lines @@
 elif [ "${TYPE}" == "install" ]; then
   resign_firmware_payload ${INPUT_IMAGE}
   update_rootfs_hash ${INPUT_IMAGE} \
     ${KEY_DIR}/installer_kernel.keyblock \
     ${KEY_DIR}/recovery_kernel_data_key.vbprivk
   sign_for_factory_install
 else
   echo "Invalid type ${TYPE}"
   exit 1
 fi