sonic-buildimage/files/initramfs-tools/union-mount.j2

#!/bin/sh -e

PREREQS="varlog"

prereqs() { echo "$PREREQS"; }

case $1 in
  prereqs)
  prereqs
    exit 0
    ;;
esac

docker_inram=false
logs_inram=false
secureboot=false
bootloader=generic

# Extract kernel parameters
for x in $(cat /proc/cmdline); do
    case "$x" in
        Aboot=*)
            bootloader=aboot
            ;;
        docker_inram=on)
            docker_inram=true
            ;;
        logs_inram=on)
            logs_inram=true
            ;;
        secure_boot_enable=[y1])
            secureboot=true
            docker_inram=true
            ;;
        platform=*)
            platform_flag="${x#platform=}"
            ;;
    esac
done

set_tmpfs_log_partition_size()
{
  varlogsize=128

  # set varlogsize to existing var-log.ext4 size
  if [ -f ${rootmnt}/host/disk-img/var-log.ext4 ]; then
    varlogsize=$(ls -l ${rootmnt}/host/disk-img/var-log.ext4 | awk '{print $5}')
    varlogsize=$(($varlogsize/1024/1024))
  fi

  # make sure varlogsize is between 5% to 10% of total memory size
  memkb=$(grep MemTotal /proc/meminfo | awk '{print $2}')
  memmb=$(($memkb/1024))
  minsize=$(($memmb*5/100))
  maxsize=$(($memmb*10/100))

  [ $minsize -ge $varlogsize ] && varlogsize=$minsize
  [ $maxsize -le $varlogsize ] && varlogsize=$maxsize
}

remove_not_in_allowlist_files()
{
    local allowlist_file="$1"
    local targeted_dir="$2"
    local allowlist_pattern_file=/tmp/allowlist_paths.pattern

    # Return if the allowlist file does not exist
    if ! test -f "${allowlist_file}"; then
        echo "The file ${allowlist_file} is missing, failed to mount rw folder." 1>&2
        exit 1
    fi

    # Set the grep pattern file, remove the blank line in config file
    awk -v rw_dir="$targeted_dir" 'NF {print rw_dir"/"$0"$"}' ${allowlist_file} > $allowlist_pattern_file

    # Find the files in the rw folder, and remove the files not in the allowlist
    find ${targeted_dir} -type f | grep -v -f $allowlist_pattern_file | xargs /bin/rm -f
    rm -f $allowlist_pattern_file
}

## Mount the overlay file system: rw layer over squashfs
image_dir=$(cat /proc/cmdline | sed -e 's/.*loop=\(\S*\)\/.*/\1/')
rw_dir=${rootmnt}/host/$image_dir/rw
work_dir=${rootmnt}/host/$image_dir/work
mkdir -p "$rw_dir"
mkdir -p "$work_dir"

## Remove the files not in allowlist in the rw folder
if $secureboot; then
    if [ "$bootloader" = "aboot" ]; then
        swi_path="${rootmnt}/host/$(sed -E 's/.*loop=([^ ]+).*/\1/' /proc/cmdline)"
        unzip -q "$swi_path" allowlist_paths.conf -d /tmp
        allowlist_file=/tmp/allowlist_paths.conf
    else
        allowlist_file=${rootmnt}/host/$image_dir/allowlist_paths.conf
    fi
    remove_not_in_allowlist_files "$allowlist_file" "$rw_dir"
fi

## Remove the executable permission for all the files in rw folder except home folder
find ${rw_dir} -type f -not -path ${rw_dir}/home -exec chmod a-x {} +

mount -n -o lowerdir=${rootmnt},upperdir=${rw_dir},workdir=${work_dir} -t overlay root-overlay ${rootmnt}

## Check if the root block device is still there
[ -b ${ROOT} ] || mdev -s
case "${ROOT}" in
    ubi*)
        mtd=$(cat /proc/cmdline | sed -e 's/.*ubi.mtd=\([0-9]\) .*/\1/')
        if [ ! -f /dev/${ROOT}_0 ]; then
            ubiattach /dev/ubi_ctrl -m $mtd || true
        fi
        mount -t ubifs /dev/${ROOT}_0 ${rootmnt}/host
        ;;
    *)
        ## Mount the raw partition again
        mount ${ROOT} ${rootmnt}/host
        ;;
esac

mkdir -p ${rootmnt}/var/lib/docker
if $secureboot; then
    mount -t tmpfs -o rw,nodev,size={{ DOCKER_RAMFS_SIZE }} tmpfs ${rootmnt}/var/lib/docker
    if [ "$bootloader" = "aboot" ]; then
        unzip -qp "$swi_path" dockerfs.tar.gz | tar xz --numeric-owner -C ${rootmnt}/var/lib/docker
        ## Boot folder is not extracted during secureboot since content would inherently become unsafe
        mkdir -p ${rootmnt}/host/$image_dir/boot
    else
        echo "secureboot unsupported for bootloader $bootloader" 1>&2
        exit 1
    fi
elif [ -f ${rootmnt}/host/$image_dir/{{ FILESYSTEM_DOCKERFS }} ]; then
    ## mount tmpfs and extract docker into it
    mount -t tmpfs -o rw,nodev,size={{ DOCKER_RAMFS_SIZE }} tmpfs ${rootmnt}/var/lib/docker
    tar xz --numeric-owner -f ${rootmnt}/host/$image_dir/{{ FILESYSTEM_DOCKERFS }} -C ${rootmnt}/var/lib/docker
else
    ## Mount the working directory of docker engine in the raw partition, bypass the overlay
    mount --bind ${rootmnt}/host/$image_dir/{{ DOCKERFS_DIR }} ${rootmnt}/var/lib/docker
fi

## Mount the boot directory in the raw partition, bypass the overlay
mkdir -p ${rootmnt}/boot
mount --bind ${rootmnt}/host/$image_dir/boot ${rootmnt}/boot

## Mount loop device or tmpfs for /var/log
if $logs_inram; then
  # NOTE: some platforms, when reaching initramfs stage, have a small
  #       limit of mounting tmpfs partition, potentially due to amount
  #       of RAM available in this stage. e.g. Arista 7050-qx32[s] and 7060-cx32s
  set_tmpfs_log_partition_size
  mount -t tmpfs -o rw,nosuid,nodev,size=${varlogsize}M tmpfs ${rootmnt}/var/log
  [ -f ${rootmnt}/host/disk-img/var-log.ext4 ] && rm -rf ${rootmnt}/host/disk-img/var-log.ext4
else
  [ -f ${rootmnt}/host/disk-img/var-log.ext4 ] && fsck.ext4 -v -p ${rootmnt}/host/disk-img/var-log.ext4 2>&1 \
                                                  | gzip -c >> /tmp/fsck.log.gz
  [ -f ${rootmnt}/host/disk-img/var-log.ext4 ] && mount -t ext4 -o loop,rw ${rootmnt}/host/disk-img/var-log.ext4 ${rootmnt}/var/log
fi

## fscklog file: /tmp will be lost when overlayfs is mounted
if [ -f /tmp/fsck.log.gz ]; then
    mv /tmp/fsck.log.gz ${rootmnt}/var/log
fi