build_image,update_bootloaders: directly update the built image

update_bootloaders.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.
 
 # Helper script that generates the legacy/efi bootloader partitions.
 # It does not populate the templates, but can update a loop device.
 
 . "$(dirname "$0")/common.sh"
 . "$(dirname "$0")/chromeos-common.sh"  # installer
 
 get_default_board
 
 # Flags.
 DEFINE_string arch "x86" \
   "The boot architecture: arm or x86. (Default: x86)"
 # TODO(wad) once extlinux is dead, we can remove this.
 DEFINE_boolean install_syslinux ${FLAGS_FALSE} \
   "Controls whether syslinux is run on 'to'. (Default: false)"
 DEFINE_string from "/tmp/boot" \
   "Path the legacy bootloader templates are copied from. (Default /tmp/boot)"
 DEFINE_string to "/tmp/esp.img" \
   "Path to esp image or ARM output MBR (Default: /tmp/esp.img)"
+DEFINE_integer to_offset 0 \
+  "Offset in bytes into 'to' if it is a file (Default: 0)"
+DEFINE_integer to_size -1 \
+  "Size in bytes of 'to' to use if it is a file. -1 is ignored. (Default: -1)"
 DEFINE_string vmlinuz "/tmp/vmlinuz" \
   "Path to the vmlinuz file to use (Default: /tmp/vmlinuz)"
 # The kernel_partition and the kernel_cmdline each are used to supply
 # verified boot configuration: dm="".
 DEFINE_string kernel_partition "/tmp/vmlinuz.image" \
   "Path to the signed kernel image. (Default: /tmp/vmlinuz.image)"
 DEFINE_string kernel_cmdline "" \
   "Kernel commandline if no kernel_partition given. (Default: '')"
 DEFINE_string kernel_partition_offset "0" \
   "Offset to the kernel partition [KERN-A] (Default: 0)"
@@ skipping 64 matching lines @@
   # This shouldn't happen.
   info "Creating a new esp image at ${FLAGS_to}" anyway.
   # Create EFI System Partition to boot stock EFI BIOS (but not ChromeOS EFI
   # BIOS). We only need this for x86, but it's simpler and safer to keep the
   # disk images the same for both x86 and ARM.
   # NOTE: The size argument for mkfs.vfat is in 1024-byte blocks.
   # We'll hard-code it to 16M for now.
   ESP_BLOCKS=16384
   /usr/sbin/mkfs.vfat -C "${FLAGS_to}" ${ESP_BLOCKS}
   ESP_DEV=$(sudo losetup -f)
-  test -z "${ESP_DEV}" && error "No free loop devices."
+  if [ -z "${ESP_DEV}" ]; then
+    die "No free loop devices."
+  fi
   sudo losetup "${ESP_DEV}" "${FLAGS_to}"
 else
   if [[ -f "${FLAGS_to}" ]]; then
     ESP_DEV=$(sudo losetup -f)
-    test -z "${ESP_DEV}" && error "No free loop devices."
-    sudo losetup "${ESP_DEV}" "${FLAGS_to}"
+    if [ -z "${ESP_DEV}" ]; then
+      die "No free loop devices."
+    fi
+
+    esp_offset="--offset ${FLAGS_to_offset}"
+    esp_size="--sizelimit ${FLAGS_to_size}"
+    if [ ${FLAGS_to_size} -lt 0 ]; then
+      esp_size=
+    fi
+    sudo losetup ${esp_offset} ${esp_size} "${ESP_DEV}" "${FLAGS_to}"
   else
     # If it is a block device or something else, try to mount it anyway.
     ESP_DEV="${FLAGS_to}"
   fi
 fi
 
 ESP_FS_DIR=$(mktemp -d /tmp/esp.XXXXXX)
 cleanup() {
   set +e
   sudo umount "${ESP_FS_DIR}"
@@ skipping 34 matching lines @@
   fi
   update_x86_bootloaders "${old_root}" \
                          "${kernel_cfg}" \
                          "${ESP_FS_DIR}" \
                          "${FLAGS_from}"
 
   # Install the syslinux loader on the ESP image (part 12) so it is ready when
   # we cut over from rootfs booting (extlinux).
   if [[ ${FLAGS_install_syslinux} -eq ${FLAGS_TRUE} ]]; then
     sudo umount "${ESP_FS_DIR}"
-    sudo syslinux -d /syslinux "${FLAGS_to}"
+    sudo syslinux -d /syslinux "${ESP_DEV}"
   fi
 elif [[ "${FLAGS_arch}" = "arm" ]]; then
   # Extract kernel flags
   kernel_cfg=
   old_root="sd%D%P"
   if [[ -n "${FLAGS_kernel_cmdline}" ]]; then
     info "Using supplied kernel_cmdline to update templates."
     kernel_cfg="${FLAGS_kernel_cmdline}"
   elif [[ -n "${FLAGS_kernel_partition}" ]]; then
     info "Extracting the kernel command line from ${FLAGS_kernel_partition}"
@@ skipping 17 matching lines @@
     ${FLAGS_kernel_partition_offset} \
     ${FLAGS_kernel_partition_sectors} \
     ${device} \
     "'dm=\"${dm_table}\"'")
   sudo dd bs=1 count=`stat --printf="%s" ${MBR_SCRIPT_UIMG}` \
      if="$MBR_SCRIPT_UIMG" of=${FLAGS_to}
   info "Emitted new ARM MBR to ${FLAGS_to}"
 fi
 
 set +e