machine

#!/usr/bin/env bash
# Basic script to start a qemu machine

UBOOT="uboot"
SD="sdcard.img"

MNT="mnt"
MNT_ROOT_FS="$MNT/rootfs"
MNT_BOOT="$MNT/boot"
MNT_LODEV="$MNT/lodev"

EXAMPLES="examples"

# check if qemu-system-arm is installed otherwise exit
command -v qemu-system-arm &> /dev/null || {
  echo "Please install qemu-system-arm!"
  exit 1
}

# check if parted is installed otherwise exit
command -v parted &> /dev/null || {
  echo "Please install parted!"
  exit 1
}

# run command as root
function run_as_root {
  if [ "$(id -u)" -eq 0 ]; then
    "$@"
  else
    sudo "$@"
  fi
}

# boot the system using qemu-system-arm
function boot {
  # check if sdcard is mounted
  [ -d "$MNT" ] && {
    echo "Looks like $SD is already mounted at $MNT/"
    echo "If you think it is not, please remove $MNT/ first!"
    exit 1
  }

  # start the qemu machine
  qemu-system-arm -M vexpress-a9 -m 128M -nographic -kernel "$UBOOT" \
    -sd "$SD"
}

# mount the sdcard
function mount_sdcard {
  [ -d "$MNT" ] && {
    echo "Looks like $SD is already mounted at $MNT/"
    echo "If you think it is not, please remove $MNT/ first!"
    exit 1
  }

  # setup loop device for the sdcard
  dev="$(run_as_root losetup -f --show --partscan $SD)"
  echo "Loop Device: $dev"

  [ -z "$dev" ] && {
    echo "Failed to setup loop device!"
    exit 1
  }

  # create mountpoints
  mkdir -p "$MNT_BOOT" "$MNT_ROOT_FS"
  # change  owner
  for f in "$MNT_BOOT" "$MNT_ROOT_FS"; do run_as_root chown 0:0 "$f"; done

  # mount
  run_as_root mount -o rw "$dev"p1 "$MNT_BOOT"
  run_as_root mount -o rw "$dev"p2 "$MNT_ROOT_FS"

  # set the lock file `lodev`
  echo "$dev" > "$MNT_LODEV"
  run_as_root chown 0:0 "$MNT_LODEV"
  run_as_root chmod 644 "$MNT_LODEV"
}

# unmount the sdcard
function umount_sdcard {
  if [ ! -d "$MNT" ] || [ ! -f "$MNT_LODEV" ]; then
    echo "$SD is not mounted!"
    exit 1
  fi

  for f in "$MNT_BOOT" "$MNT_ROOT_FS"; do run_as_root umount -f "$f"; done
  run_as_root losetup -d "$(cat $MNT_LODEV)"
  run_as_root rm -rf "$MNT"
}

# generate a basic sdcard image
function generate {
  # check if sdcard is mounted
  [ -d "$MNT" ] && {
    echo "Looks like $SD is already mounted at $MNT/"
    echo "If you think it is not, please remove $MNT/ first!"
    exit 1
  }

  # check if sdcard is found
  [ -f "$SD" ] && {
    echo "SDCard $SD was found!"
    read -rs -n1 -p "Press a key to remove and regenerate it!"
    echo
    rm -f "$SD"
  }

  clear

  echo "Create empty image of size 1GB -> $SD"
  echo
  dd if=/dev/zero of="$SD" bs=1M count=1024 status=progress

  echo
  echo "Create a new partition table of label msdos on $SD"
  echo
  parted "$SD" mktable msdos

  echo "Create boot partition of type fat16 and size 10MiB"
  echo
  parted "$SD" mkpart primary fat16 1MiB 10MiB

  echo "Create rootfs partition of type ext4 that takes the rest of the image"
  echo
  parted "$SD" mkpart primary ext4 10MiB 100%

  echo
  echo "Attach $SD to loop device"
  LODEV="$(run_as_root losetup -f --show --partscan $SD)"
  echo "Loop Device: $LODEV"
  echo

  [ -z "$LODEV" ] && {
    echo "Failed to setup loop device!"
    exit 1
  }

  echo "Make FATfs on the boot partition on ${LODEV}p1"
  echo
  run_as_root mkfs.fat -F16 -n BOOT "$LODEV"p1

  echo
  echo "Make ext4fs on the rootfs partition on ${LODEV}p2"
  echo
  run_as_root mkfs.ext4 "$LODEV"p2

  echo
  echo "Deattach loop device: $LODEV"
  echo
  run_as_root losetup -d "$LODEV"

  echo
  echo "Mount and copy example files"
  echo
  mount_sdcard

  run_as_root mkdir -v "$MNT_ROOT_FS/etc"
  run_as_root mkdir -v "$MNT_ROOT_FS/dev"
  run_as_root mkdir -v "$MNT_ROOT_FS/root"

  [ -d "$EXAMPLES/boot" ] && {
    echo
    echo "Coping boot example files to the root partition"
    echo "$EXAMPLES/boot -> $MNT"
    echo
    run_as_root chmod -v o+w "$MNT_BOOT"
    run_as_root cp -rvf "$EXAMPLES/boot/"* "$MNT/boot"
    run_as_root chmod -v o-w "$MNT_BOOT"
  }

  [ -d "$EXAMPLES/rootfs" ] && {
    echo
    echo "Coping rootfs example files to the rootfs partition"
    echo "$EXAMPLES/rootfs -> $MNT"
    echo
    run_as_root chmod -v o+w "$MNT_ROOT_FS"
    run_as_root cp -rvf "$EXAMPLES/rootfs/"* "$MNT/rootfs"
    run_as_root chmod -v o-w "$MNT_ROOT_FS"
  }

  echo
  echo "Set owner to root:root"
  run_as_root chown -v -R 0:0 "$MNT"

  echo
  echo "$SD is ready for use!"
  echo "Copy the necessary kernel files into the sdcard:"
  echo
  echo "uboot -> ./"
  echo
  echo "zImage -> mnt/boot/"
  echo "vexpress-v2p-ca9.dtb -> mnt/boot/"
  echo
  echo "busybox_output -> mnt/rootfs/"
  echo "toolchain_sysroot -> mnt/rootfs/"
  echo
  echo "After coping required resources execute:"
  echo "$ $0 umount  # to unmount the sdcard"
  echo
  echo "Then"
  echo "$ $0 boot  # to start booting the qemu machine"
}

case "$1" in
  "boot") boot;;
  "mount") mount_sdcard;;
  "umount") umount_sdcard;;
  "generate") generate;;
  *)
    echo "Usage: $0 {boot|mount|umount|generate}"
    echo "Check the README.md file for more information."
    exit 1
  ;;
esac