#!/bin/bash
#
# QEMU trick to dive user in his own hoe environment
# as root in a virualized shadow of his own system
#
# (C) 2013 Pavel Pisa <pisa@cmp.felk.cvut.cz>
#
# THE TSCRIPT IS PROVIDED “AS IS” WITHOUT WARRANTY
# OF ANY KIND, EITHER EXPRESSED OR IMPLIED.
#
# There is no limitation of scrip use, modification
# and distribution or relicensing.
#
# Some used ideas are documented at CTU FEE A4M35OSP
# excercises pages
#   http://support.dce.felk.cvut.cz/osp/cviceni/2/
#   http://support.dce.felk.cvut.cz/osp/cviceni/2-en/
#
# and Departemnt Of Control Engineering IT Wiki
#   https://support.dce.felk.cvut.cz/
#

QEMU=qemu-system-x86_64
BUSYBOX=$(which busybox)
RESIZE=$(which resize)
KERNEL_VERSION=$(uname -r)
KERNEL_IMAGE=/boot/vmlinuz-${KERNEL_VERSION}
RAMDISK_ARCHIVE=ramdisk.cpio
#GEN_INIT_CPIO=$(dirname $0)/gen_init_cpio
INITRD_DIR=initrd_content
MODULES_LIST="virtio virtio_ring virtio_pci virtio_net virtio_net fscache 9pnet 9pnet_virtio 9p aufs overlay"
QEMU_MEMORY="-m 1024"
QEMU_KVM_ENABLE="-enable-kvm"
#QEMU_OUTPUT="-vga cirrus -serial null"
QEMU_OUTPUT="-nographic -append console=ttyS0"

INITRD_DIR_ABS=$(readlink -f ${INITRD_DIR})

function libraries_for_binary()
{
  ldd $1 | sed -n -e 's#^\t\(/[^ ]*\) .*$#\1#p' -e 's#^\t\([^ ]*\) => \([^ ]\+\) .*$#\2#p'
}

function deep_copy()
{
  src=$1
  tgt_dir=$2

  while true ; do
    mkdir -p ${tgt_dir}/$(dirname ${src}) || return 1
    cp -av ${src} ${tgt_dir}/${src#/} || return 1

    l=$(readlink ${src})
    if [ -z "$l" ] ; then
      return 0
    fi
    if [ ${l:0:1} != '/' ] ; then
      l=$(dirname ${src})/${l}
    fi
    src=${l}
  done
}

function setup_initrd_content()
{
  mkdir -p ${INITRD_DIR_ABS}
  mkdir -p ${INITRD_DIR_ABS}/bin
  mkdir -p ${INITRD_DIR_ABS}/etc/init.d

  LIBS=$(libraries_for_binary ${BUSYBOX})
  if [ -n "${RESIZE}" ] ; then
    LIBS+=" "$(libraries_for_binary ${RESIZE})
  fi

  LIBS="$(for i in ${LIBS} ; do echo $i ; done | sort -u)"

  for i in ${LIBS}; do
    deep_copy ${i} ${INITRD_DIR_ABS}
  done

  cp -a ${BUSYBOX} ${INITRD_DIR_ABS}/bin
  ( cd ${INITRD_DIR_ABS}/bin && ln -s busybox sh )

  if [ -n "${RESIZE}" ] ; then
    cp -a ${RESIZE} ${INITRD_DIR_ABS}/bin
  fi


  for m in ${MODULES_LIST} ; do
    mf=$(find /lib/modules/${KERNEL_VERSION} -name ${m}.ko )
    if [ -n "${mf}" ] ; then
      mkdir -p "${INITRD_DIR_ABS}/$(dirname ${mf})"
      cp -a "${mf}" "${INITRD_DIR_ABS}/${mf#/}"
    else
      echo "Module ${m} not found"
    fi
  done

  rootmnt=/mnt/root
  init=/sbin/init
  root_dir_list="/proc /sys /dev /mnt /mnt/root /mnt/rootbase /mnt/overlay /tmp"

  (
    echo '#!/bin/sh'
    for d in $root_dir_list ; do
       echo "mkdir -p $d"
    done

    cat <<EOF
echo "Starting QEMU trick"
mount -t proc none /proc
mount -t sysfs none /sys
mount -t tmpfs none /dev
depmod
EOF
    for m in ${MODULES_LIST} ; do
      echo modprobe $m
    done
    cat <<EOF
mdev -s
if [ -e /bin/resize ] ; then
  mv /dev/tty /dev/tty-backup
  ln -s /dev/console /dev/tty
  /bin/resize >/tmp/term-size
  . /tmp/term-size
  stty cols \$COLUMNS rows \$LINES
  rm -f /dev/tty
  mv /dev/tty-backup /dev/tty
fi
mount -t 9p -o ro,trans=virtio root /mnt/rootbase
mount -t tmpfs overlay /mnt/overlay
mkdir -p /mnt/overlay/data

if grep -q aufs /proc/filesystems ; then
  echo "Using aufs to remap root"
  mount -n -t aufs -o dirs=/mnt/overlay/data=rw:/mnt/rootbase=ro unionfs ${rootmnt}
else
  echo "Using overlay to remap root"
  mkdir -p /mnt/overlay/work
  mount -n -t overlay -o upperdir=/mnt/overlay/data,workdir=/mnt/overlay/work,lowerdir=/mnt/rootbase overlay ${rootmnt}
fi

mount -n -o move /dev ${rootmnt}/dev
mount -n -o move /sys ${rootmnt}/sys
mount -n -o move /proc ${rootmnt}/proc
mount -t 9p -o trans=virtio home ${rootmnt}/home
mount -t tmpfs none ${rootmnt}/root
mount -t tmpfs none ${rootmnt}/tmp
mount -t tmpfs none ${rootmnt}/run
mount -t tmpfs none ${rootmnt}/var/log
mount -t tmpfs none ${rootmnt}/var/tmp

rm ${rootmnt}/var/lib/urandom/random-seed 
rm -rf ${rootmnt}/etc/shadow
echo >${rootmnt}/etc/shadow
rm -rf ${rootmnt}/etc/ssh
mkdir ${rootmnt}/etc/ssh

rm -f ${rootmnt}/etc/rc2.d/* ${rootmnt}/etc/rc3.d/* ${rootmnt}/etc/rc4.d/* ${rootmnt}/etc/rc5.d/*

rm -rf ${rootmnt}/etc/fstab.d ${rootmnt}/etc/fstab
echo >${rootmnt}/etc/fstab

rm -rf ${rootmnt}/var/lib/dpkg/lock ${rootmnt}/var/lib/apt/lists/lock ${rootmnt}/var/cache/apt/archives/lock
rm -rf ${rootmnt}/etc/apt/apt.conf.d/*etckeeper ${rootmnt}/var/lib/dpkg/triggers/Lock

rm -rf ${rootmnt}/etc/network/interfaces.d ${rootmnt}/etc/network/interfaces
echo "auto lo eth0" >${rootmnt}/etc/network/interfaces
echo "iface lo inet loopback" >>${rootmnt}/etc/network/interfaces
echo "iface eth0 inet dhcp" >>${rootmnt}/etc/network/interfaces

if  [ -e ${rootmnt}/bin/bash ] ; then
  shell=/bin/bash
else
  shell=/bin/sh
fi

mv ${rootmnt}/etc/inittab ${rootmnt}/etc/inittab.orig
cp ${rootmnt}/etc/inittab.orig ${rootmnt}/etc/inittab
sed -i -e '/\/sbin\/.*getty/d' ${rootmnt}/etc/inittab
#echo "1:2345:respawn:/bin/sh" >>${rootmnt}/etc/inittab
#echo "T0:1234:respawn:/bin/sh" >>${rootmnt}/etc/inittab

echo "1:2345:respawn:/sbin/agetty -n -l \${shell} -o '-l' tty1 38400 linux" >>${rootmnt}/etc/inittab
echo "2:23:respawn:/sbin/agetty -n -l \${shell} -o '-l' tty2 38400 linux" >>${rootmnt}/etc/inittab
echo "T0:23:respawn:/sbin/agetty -n -l \${shell} -o '-l' -L ttyS0 9600 xterm" >>${rootmnt}/etc/inittab

exec switch_root ${rootmnt} /sbin/init
EOF

  ) >${INITRD_DIR_ABS}/init

  chmod 755 ${INITRD_DIR_ABS}/init

  return 0
}

function build_initrd_gen_init_cpio()
{

  (
    cat <<EOF
dir /dev 755 0 0
nod /dev/tty0 644 0 0 c 4 0
nod /dev/tty1 644 0 0 c 4 1
nod /dev/tty2 644 0 0 c 4 2
nod /dev/tty3 644 0 0 c 4 3
nod /dev/tty4 644 0 0 c 4 4
#slink /init bin/busybox 700 0 0
dir /proc 755 0 0
dir /sys 755 0 0
dir /mnt 755 0 0
dir /mnt/root 755 0 0
dir /mnt/rootbase 755 0 0
dir /mnt/overlay 755 0 0
EOF
    find ${INITRD_DIR} -mindepth 1 -type d -printf "dir /%P %m 0 0\n"
    find ${INITRD_DIR} -type f -printf "file /%P %p %m 0 0\n"
    find ${INITRD_DIR} -type l -printf "slink /%P %l %m 0 0\n"
  ) > filelist

  $GEN_INIT_CPIO filelist | gzip > ${RAMDISK_ARCHIVE}

  return 0
}

function build_initrd_cpio()
{
  ( cd ${INITRD_DIR_ABS} && find . | cpio --quiet -H newc -o  ) | gzip -9 > ${RAMDISK_ARCHIVE}
}

function run_virt_system()
{
  $QEMU -enable-kvm -kernel ${KERNEL_IMAGE} \
        -initrd ${RAMDISK_ARCHIVE} ${QEMU_MEMORY} \
        -virtfs local,path=/,security_model=none,mount_tag=root \
        -virtfs local,path=/home,security_model=none,mount_tag=home \
        -net nic,macaddr=be:be:be:10:00:01,model=virtio,vlan=0 \
        -net user,vlan=0 \
        ${QEMU_KVM_ENABLE} ${QEMU_OUTPUT}

#     -chardev can,id=canbus0,port=can0
#     -device pci-can,chardev=canbus0,model=SJA1000
#     -device apohw -vga cirrus
#     -device mf624,port=55555

  return $?
}

function clean_setup()
{
  rm -rf ${RAMDISK_ARCHIVE} filelist ${INITRD_DIR_ABS}
}

if [ "$(whoami)" == "root" ] ; then
  echo "$0: !!! TOO DANGEROUS TO RUN AS ROOT !!!"
  exit 1;
fi

clean_setup || exit 1
echo "=== setup_initrd_content ==="
setup_initrd_content || exit 1
echo "=== build_initrd ==="
if [ -n "${GEN_INIT_CPIO}" ] ; then
  build_initrd_gen_init_cpio || exit 1
else
  build_initrd_cpio || exit 1
fi
echo "=== run_virt_system ==="
run_virt_system || exit 1