Update grub configuration to handle ESP kernels, build it into grub

The grub configuration needs some updates to handle dealing with booting
the kernel from the ESP rather than from inside the image. We also want to
be able to avoid dealing with signing the config file, so build it into the
binary. Finally, rather than having to cope with signing grub modules, build
the ones we need to boot into the grub image.

build_library/grub.cfg

@@ -1,5 +1,8 @@
 # Main GRUB config
 
+# Set the prefix back to the correct value after we're done with memdisk
+set prefix=($root)/coreos/grub
+
 # Load any and all video drivers.
 # Required under UEFI to boot Linux with a working console.
 insmod all_video
@@ -37,38 +40,30 @@ if [ -z "$linux_console" ]; then
     fi
 fi
 
-
-# Load a kernel and boot! $root must point at USR-A or USR-B
-function load_coreos {
-    # UEFI uses linuxefi/initrdefi instead of linux/initrd
-    if [ "$grub_platform" = efi ]; then
-        set suf="efi"
-    else
-        set suf=""
-    fi
-
-    echo "Loading ($root)/boot/vmlinuz"
-    linux$suf /boot/vmlinuz $linux_console $linux_root "$@" $linux_append
-
-    if [ -f /boot/initrd ]; then
-        echo "Loading ($root)/boot/initrd"
-        initrd$suf /boot/initrd
-    fi
-
-    echo "Booting CoreOS!"
-}
+# UEFI uses linuxefi/initrdefi instead of linux/initrd
+if [ "$grub_platform" = efi ]; then
+    set suf="efi"
+else
+    set suf=""
+fi
 
 menuentry "CoreOS default" --id=coreos {
-    gptprio.next -d root -u usr_uuid
-    load_coreos mount.usr=PARTUUID=$usr_uuid
+    gptprio.next -d usr -u usr_uuid
+    if [ "$usr_uuid" = "7130c94a-213a-4e5a-8e26-6cce9662f132" ]; then
+       linux$suf /coreos/vmlinuz-a $linux_console $linux_root \
+            mount.usr=PARTUUID=$usr_uuid $linux_append
+    else
+       linux$suf /coreos/vmlinuz-b $linux_console $linux_root \
+            mount.usr=PARTUUID=$usr_uuid $linux_append
+    fi
 }
 
 menuentry "CoreOS USR-A" --id=coreos-a {
-    search --no-floppy --set root --part-label USR-A --hint "$root"
-    load_coreos mount.usr=PARTLABEL=USR-A
+    linux$suf /coreos/vmlinuz-a $linux_console $linux_root \
+         mount.usr=PARTLABEL=USR-A $linux_append
 }
 
 menuentry "CoreOS USR-B" --id=coreos-b {
-    search --no-floppy --set root --part-label USR-B --hint "$root"
-    load_coreos mount.usr=PARTLABEL=USR-B
+    linux$suf /coreos/vmlinuz-b $linux_console $linux_root \
+         mount.usr=PARTLABEL=USR-B $linux_append
 }

build_library/grub_install.sh

@@ -29,18 +29,19 @@ switch_to_strict_mode
 # Our GRUB lives under coreos/grub so new pygrub versions cannot find grub.cfg
 GRUB_DIR="coreos/grub/${FLAGS_target}"
 
-# Modules required to find and read everything else from ESP
-CORE_MODULES=( fat part_gpt search_fs_uuid gzio )
+# Modules required to boot a standard CoreOS configuration
+CORE_MODULES=( normal search test fat part_gpt search_fs_uuid gzio search_part_label terminal gptprio configfile memdisk tar echo )
 
 # Name of the core image, depends on target
 CORE_NAME=
 
 case "${FLAGS_target}" in
     i386-pc)
-        CORE_MODULES+=( biosdisk )
+        CORE_MODULES+=( biosdisk serial )
         CORE_NAME="core.img"
         ;;
     x86_64-efi)
+	CORE_MODULES+=( serial linuxefi efi_gop )
         CORE_NAME="core.efi"
         ;;
     x86_64-xen)
@@ -111,25 +112,26 @@ info "Generating ${GRUB_DIR}/load.cfg"
 ESP_FSID=$(sudo grub-probe -t fs_uuid -d "${LOOP_DEV}p1")
 sudo_clobber "${ESP_DIR}/${GRUB_DIR}/load.cfg" <<EOF
 search.fs_uuid ${ESP_FSID} root \$root
-set prefix=(\$root)/coreos/grub
+set prefix=(memdisk)
 set
 EOF
 
+if [[ ! -f "${ESP_DIR}/coreos/grub/grub.cfg.tar" ]]; then
+    info "Generating grub.cfg memdisk"
+    sudo tar cf "${ESP_DIR}/coreos/grub/grub.cfg.tar" \
+	 -C "${BUILD_LIBRARY_DIR}" "grub.cfg"
+fi
+
 info "Generating ${GRUB_DIR}/${CORE_NAME}"
 sudo grub-mkimage \
     --compression=auto \
     --format "${FLAGS_target}" \
     --prefix "(,gpt1)/coreos/grub" \
     --config "${ESP_DIR}/${GRUB_DIR}/load.cfg" \
+    --memdisk "${ESP_DIR}/coreos/grub/grub.cfg.tar" \
     --output "${ESP_DIR}/${GRUB_DIR}/${CORE_NAME}" \
     "${CORE_MODULES[@]}"
 
-# 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)