#!/bin/bash
# Build a bootable UEFI rescue shell image
# Copyright 2014 TJ <hacker@iam.tj>
# Licensed on the terms of the GNU General Public License version 3
#
# Creates an image file named "UEFI-GPT-recovery-shell.img" with a default
# size of 64MB containing a bootable UEFI image that starts the 
# Tianocore Shell v2, and also contains GRUB EFI boot-manager and supporting files
#
set +x

ARCH=$(uname -m)
ARCH_U=${ARCH^^}

# Default values (can be set in the environment prior to executing this script)
SIZE=${SIZE:-64}
IMG=${IMG:-UEFI-GPT-recovery-shell.img}
URL_UEFI_SHELL=${UEL_UEFI_SHELL:-https://svn.code.sf.net/p/edk2/code/trunk/edk2/ShellBinPkg/UefiShell/X64/Shell.efi}
GRUB_EFI=${GRUB_EFI:-/usr/lib/grub/${ARCH}-efi/}
GRUB_EFI_SIGNED=${GRUB_EFI_SIGNED:-/usr/lib/grub/${ARCH}-efi-signed/}
SUDO=""

if [ $(id -u) -ne 0 ]; then
  SUDO="sudo"
  echo "warning: sudo privileges will be required for some operations"
fi


dd if=/dev/zero bs=1M "count=$SIZE" "of=$IMG" || exit 1
DEV=$($SUDO losetup --show -f "$IMG") || exit 2
PART=${DEV}p1
$SUDO parted -s $DEV "unit s mklabel gpt mkpart primary fat32 2048s -34s set 1 boot on print" || exit 3
$SUDO mkfs.fat -F 32 -M 0xF8 -n 'EFI.ESP' ${PART} || exit 4

MOUNTPOINT="/mnt/uefi-$RANDOM"
MP_BOOT=${MOUNTPOINT}/EFI/BOOT
MP_GRUB=${MOUNTPOINT}/EFI/GRUB

$SUDO mkdir -p $MOUNTPOINT || exit 5
$SUDO mount -t msdos $PART $MOUNTPOINT || exit 6
$SUDO mkdir -p ${MP_BOOT} ${MP_GRUB} || exit 7
$SUDO wget $URL_UEFI_SHELL -O ${MP_BOOT}/BOOTx64.EFI || exit 8

if [ -d "$GRUB_EFI" ]; then
  $SUDO grub-install --no-nvram --bootloader-id=grub "--target=${ARCH}-efi" --uefi-secure-boot --efi-directory=${MOUNTPOINT} --boot-directory=${MP_GRUB%/*} $DEV || exit 9
fi

$SUDO parted $DEV unit s print
echo "info: UEFI System Partition with FAT32 file-system contains these UEFI boot managers:"
find ${MOUNTPOINT} -type f -name '*.efi' | sed "s,^${MOUNTPOINT}\(.*\),\1,"

sync
$SUDO umount ${MOUNTPOINT}
$SUDO rmdir ${MOUNTPOINT}
$SUDO losetup -d $DEV

echo "info: Successfully created UEFI bootable Shell in $IMG"
exit 0