build_image: Merge x86 and ARM where possible.

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)"
+  "Path to esp image (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)"
 DEFINE_string kernel_partition_sectors "0" \
   "Kernel partition sectors (Default: 0)"
 DEFINE_string usb_disk /dev/sdb3 \
-  "Path syslinux should use to do a usb (or arm!) boot. Default: /dev/sdb3"
+  "Path syslinux should use to do a usb boot. Default: /dev/sdb3"
 
 # Parse flags
 FLAGS "$@" || exit 1
 eval set -- "${FLAGS_ARGV}"
 set -e
 
 # If not provided by chromeos-common.sh, this will update all of the
 # boot loader files (both A and B) with the data pulled
 # from the kernel_partition.  The default boot target should
 # be set when the rootfs is stuffed.
@@ skipping 42 matching lines @@
     # and replace HDROOTA and HDROOTB with the correct /dev/sd%D%P.
   }
 fi
 
 ESP_DEV=
 if [[ ! -e "${FLAGS_to}" ]]; then
   error "The ESP doesn't exist"
   # This shouldn't happen.
   info "Creating a new esp image at ${FLAGS_to}" anyway.
   # Create EFI System Partition to boot stock EFI BIOS (but not ChromeOS EFI
-  # BIOS). We only need this for x86, but it's simpler and safer to keep the
-  # disk images the same for both x86 and ARM.
+  # BIOS).  ARM uses this space to determine which partition is bootable.
   # NOTE: The size argument for mkfs.vfat is in 1024-byte blocks.
   # We'll hard-code it to 16M for now.
   ESP_BLOCKS=16384
   /usr/sbin/mkfs.vfat -C "${FLAGS_to}" ${ESP_BLOCKS}
   ESP_DEV=$(sudo losetup -f)
   if [ -z "${ESP_DEV}" ]; then
     die "No free loop devices."
   fi
   sudo losetup "${ESP_DEV}" "${FLAGS_to}"
 else
@@ skipping 68 matching lines @@
 elif [[ "${FLAGS_arch}" = "arm" ]]; then
   # Copy u-boot script to ESP partition
   if [ -r "${FLAGS_from}/boot-A.scr.uimg" ]; then
     sudo mkdir -p "${ESP_FS_DIR}/u-boot"
     sudo cp "${FLAGS_from}/boot-A.scr.uimg" \
       "${ESP_FS_DIR}/u-boot/boot.scr.uimg"
   fi
 fi
 
 set +e