kernel cmdline: add dm_verity.dev_wait=1

create_legacy_bootloader_templates.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 signed kernel image
 
 . "$(dirname "$0")/common.sh"
 
@@ skipping 17 matching lines @@
   "Verified boot error behavior [0: I/O errors, 1: reboot, 2: nothing] \
 (Default: 2)"
 DEFINE_integer verity_max_ios 1024 \
   "Optional number of outstanding I/O operations. (Default: 1024)"
 
 # Parse flags
 FLAGS "$@" || exit 1
 eval set -- "${FLAGS_ARGV}"
 set -e
 
+# Only let dm-verity block if rootfs verification is configured.
+dev_wait=0
+if [[ ${FLAGS_enable_rootfs_verification} -eq ${FLAGS_TRUE} ]]; then
+  dev_wait=1
+fi
+
 # Common kernel command-line args
 common_args="quiet console=tty2 init=/sbin/init boot=local rootwait ro noresume"
 common_args="${common_args} noswap loglevel=1 ${FLAGS_boot_args}"
 
 # Common verified boot command-line args
 verity_common="dm_verity.error_behavior=${FLAGS_verity_error_behavior}"
 verity_common="${verity_common} dm_verity.max_bios=${FLAGS_verity_max_ios}"
+# Ensure that dm-verity waits for its device.
+# TODO(wad) should add a timeout that display a useful message
+verity_common="${verity_common} dm_verity.dev_wait=${dev_wait}"
 
 # Populate the x86 rootfs to support legacy and EFI bios config templates.
 # The templates are used by the installer to populate partition 12 with
 # the correct bootloader configuration.
 # While we transition to that model, extlinux.conf will still be used
 # on the root filesystem.
 if [[ "${FLAGS_arch}" == "x86" ]]; then
   # Setup extlinux configuration.
   # TODO: For some reason the /dev/disk/by-uuid is not being generated by udev
   # in the initramfs. When we figure that out, switch to root=UUID=${UUID}.
@@ skipping 141 matching lines @@
 EOF
   if [[ ${FLAGS_enable_rootfs_verification} -eq ${FLAGS_TRUE} ]]; then
     sudo sed -i -e 's/^set default=.*/set default=2/' \
        "${FLAGS_to}/efi/boot/grub.cfg"
   fi
   info "Emitted ${FLAGS_to}/efi/boot/grub.cfg"
   exit 0
 fi
 
 info "The target platform does not use bootloader templates."