grub_install: new install script for grub, add UEFI bootloader

This script replaces the standard grub-install tool to give us some more
control over what is going and ensure grub-install's auto-detection
magic doesn't make any incorrect choices. Also this script sets up a
loopback device and mounts the EFI partition in just the right way for
grub-bios-setup's auto-detection magic to work correctly.

I've chosen not to adapt disk_util to use partitioned loop devices to
make grub happy because ensuring loop devices get cleaned up properly
for the general case gets tricky and less robust.

build_library/grub.cfg

@@ -1,4 +1,8 @@
-# Use both default console and ttyS0
+# Load any and all video drivers.
+# Required under UEFI to boot Linux with a working console.
+insmod all_video
+
+# Use both default text console and ttyS0
 serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
 terminal_input console serial
 terminal_output console serial
@@ -6,4 +10,4 @@ terminal_output console serial
 # Re-use the existing syslinux configuration
 echo "Loading SYSLINUX configuration..."
 insmod syslinuxcfg
-syslinux_configfile -s /syslinux/syslinux.cfg
+syslinux_source -s /syslinux/syslinux.cfg

build_library/grub_install.sh

@@ -0,0 +1,127 @@
+#!/bin/bash
+
+# Copyright (c) 2014 The CoreOS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Replacement script for 'grub-install' which does not detect drives
+# properly when partitions are mounted via individual loopback devices.
+
+SCRIPT_ROOT=$(readlink -f $(dirname "$0")/..)
+. "${SCRIPT_ROOT}/common.sh" || exit 1
+
+# We're invoked only by build_image, which runs in the chroot
+assert_inside_chroot
+
+# Flags.
+DEFINE_string target "" \
+  "The GRUB target to install such as i386-pc or x86_64-efi"
+DEFINE_string esp_dir "" \
+  "Path to EFI System partition mount point."
+DEFINE_string disk_image "" \
+  "The disk image containing the EFI System partition."
+
+# Parse flags
+FLAGS "$@" || exit 1
+eval set -- "${FLAGS_ARGV}"
+switch_to_strict_mode
+
+# Our GRUB lives under coreos/grub so new pygrub versions cannot find grub.cfg
+GRUB_DIR="coreos/grub/${FLAGS_target}"
+
+# Assumes the ESP is the first partition, GRUB cannot search for it by type.
+GRUB_PREFIX="(,gpt1)/coreos/grub"
+
+# Modules required to find and read everything else from ESP
+CORE_MODULES=( fat part_gpt gzio )
+
+# Name of the core image, depends on target
+CORE_NAME=
+
+case "${FLAGS_target}" in
+    i386-pc)
+        CORE_MODULES+=( biosdisk )
+        CORE_NAME="core.img"
+        ;;
+    x86_64-efi)
+        CORE_NAME="core.efi"
+        ;;
+    *)
+        die_notrace "Unknown GRUB target ${FLAGS_target}"
+        ;;
+esac
+
+# In order for grub-setup-bios to properly detect the layout of the disk
+# image it expects a normal partitioned block device. For most of the build
+# disk_util maps individual loop devices to each partition in the image so
+# the kernel can automatically detach the loop devices on unmount. When
+# using a single loop device with partitions there is no such cleanup.
+# That's the story of why this script has all this goo for loop and mount.
+STAGE_DIR=
+ESP_DIR=
+LOOP_DEV=
+
+cleanup() {
+    if [[ -d "${STAGE_DIR}" ]]; then
+        rm -rf "${STAGE_DIR}"
+    fi
+    if [[ -d "${ESP_DIR}" ]]; then
+        if mountpoint -q "${ESP_DIR}"; then
+            sudo umount "${ESP_DIR}"
+        fi
+        rm -rf "${ESP_DIR}"
+    fi
+    if [[ -b "${LOOP_DEV}" ]]; then
+        sudo losetup --detach "${LOOP_DEV}"
+    fi
+}
+trap cleanup EXIT
+
+STAGE_DIR=$(mktemp --directory)
+mkdir -p "${STAGE_DIR}/${GRUB_DIR}"
+
+info "Compressing modules in ${GRUB_DIR}"
+for file in "/usr/lib/grub/${FLAGS_target}"/*{.lst,.mod}; do
+    out="${STAGE_DIR}/${GRUB_DIR}/${file##*/}"
+    gzip --best --stdout "${file}" > "${out}"
+done
+
+info "Generating ${GRUB_DIR}/${CORE_NAME}"
+grub-mkimage \
+    --compression=auto \
+    --format "${FLAGS_target}" \
+    --prefix "${GRUB_PREFIX}" \
+    --output "${STAGE_DIR}/${GRUB_DIR}/${CORE_NAME}" \
+    "${CORE_MODULES[@]}"
+
+info "Installing GRUB ${FLAGS_target} to ${FLAGS_disk_image##*/}"
+LOOP_DEV=$(sudo losetup --find --show --partscan "${FLAGS_disk_image}")
+ESP_DIR=$(mktemp --directory)
+sudo mount -t vfat "${LOOP_DEV}p1" "${ESP_DIR}"
+sudo cp -r "${STAGE_DIR}/." "${ESP_DIR}/."
+
+# This script will get called a few times, no need to re-copy grub.cfg
+if [[ ! -f "${ESP_DIR}/coreos/grub/grub.cfg" ]]; then
+    info "Installing grub.cfg"
+    sudo cp "${BUILD_LIBRARY_DIR}/grub.cfg" "${ESP_DIR}/coreos/grub/grub.cfg"
+fi
+
+# Now target specific steps to make the system bootable
+case "${FLAGS_target}" in
+    i386-pc)
+        info "Installing MBR and the BIOS Boot partition."
+        sudo cp "/usr/lib/grub/i386-pc/boot.img" "${ESP_DIR}/${GRUB_DIR}"
+        sudo grub-bios-setup --device-map=/dev/null \
+            --directory="${ESP_DIR}/${GRUB_DIR}" "${LOOP_DEV}"
+        ;;
+    x86_64-efi)
+        info "Installing default x86_64 UEFI bootloader."
+        sudo mkdir -p "${ESP_DIR}/EFI/boot"
+        sudo cp "${STAGE_DIR}/${GRUB_DIR}/${CORE_NAME}" \
+            "${ESP_DIR}/EFI/boot/bootx64.efi"
+        ;;
+esac
+
+cleanup
+trap - EXIT
+command_completed