#!/bin/sh
# Copyright 2023 Johannes Schauer Marin Rodrigues <josch@debian.org>
# Copyright 2023 Helmut Grohne <helmut@subdivi.de>
# SPDX-License-Identifier: MIT

# We generally use single quotes to avoid variable expansion:
# shellcheck disable=SC2016

# Replacement for autopkgtest-build-qemu and vmdb2 for all architectures
# supporting EFI booting (amd64, arm64, armhf, i386, riscv64).
# For use as replacement for autopkgtest-build-qemu and vmdb2 on ppc64el which
# neither supports extlinux nor efi booting there is an unmaintained script
# which uses grub instead to boot:
#
#     https://gitlab.mister-muffin.de/josch/mmdebstrap/src/commit/
#     e523741610a4ed8579642bfc755956f64c847ef3/mmdebstrap-autopkgtest-build-qemu

: <<'POD2MAN'
=head1 NAME

mmdebstrap-autopkgtest-build-qemu - autopkgtest-build-qemu without vmdb2 but mmdebstrap and EFI boot

=head1 SYNOPSIS

B<mmdebstrap-autopkgtest-build-qemu> [I<OPTIONS>] B<--boot>=B<efi> I<RELEASE> I<IMAGE>

=head1 DESCRIPTION

B<mmdebstrap-autopkgtest-build-qemu> is a mostly compatible drop-in replacement
for L<autopkgtest-build-qemu(1)> with two main differences: Firstly, it uses
L<mmdebstrap(1)> instead of L<vmdb2(1)> and thus is able to create QEMU disk
images without requiring superuser privileges.  Secondly, it uses
L<systemd-boot(7)> and thus only supports booting via EFI.

=head1 POSITIONAL PARAMETERS

=over 8

=item I<RELEASE>

The release to download from the I<MIRROR>.  This parameter is required.

=item I<IMAGE>

The file to write, in raw format. This parameter is required.

=back

=head1 OPTIONS

=over 8

=item B<--mirror>=I<MIRROR>

Specify  which  distribution  to install.  It defaults to
http://deb.debian.org/debian (i.e. Debian), but you can pass a mirror of any
Debian derivative.

=item B<--architecture>=I<ARCHITECTURE>

Set the architecture for the virtual machine image, specified as a L<dpkg(1)>
architecture.  If  omitted, the host architecture is assumed.

B<--arch>=I<ARCH> is an alias for this option.

=item B<--script>=I<SCRIPT>

Specifies a user script that will be called with the root filesystem of the
image as its first parameter. This script can them make any necesssary
modifications to the root filesystem.

The script must be a POSIX shell script, and should not depend on bash-specific
features. This  script will be executed inside a L<chroot(1)> call in the
virtual machine root filesystem.

=item B<--size>=I<SIZE>

Specifies the image size for the virtual machine, defaulting to 25G.

=item B<--apt-proxy>=I<PROXY>

Specify  an  apt proxy to use in the virtual machine.  By default, if you have
an apt proxy configured on the host, the virtual machine will automatically use
this, otherwise there is no default.

=item B<--boot>=B<efi>, B<--efi>

Select the way the generated image will expect to be booted. Unless you
explicitly select --boot=efi, operation will fail.

=item B<--keyring>=I<KEYRING>

Passes an additional B<--keyring> parameter to B<mmdebstrap>.

=back

=head1 EXAMPLES

    $ mmdebstrap-autopkgtest-build-qemu --boot=efi stable /path/to/debian-stable-i386.img i386

    $ mmdebstrap-autopkgtest-build-qemu --boot=efi unstable /path/to/debian-unstable.img

=head1 SEE ALSO

L<autopkgtest-build-qemu(1)>, L<autopkgtest-virt-qemu(1)>, L<mmdebstrap(1)>, L<autopkgtest(1)>

=cut
POD2MAN

set -eu

die() {
	echo "$*" 1>&2
	exit 1
}
usage() {
	die "usage: $0 [--architecture=|--apt-proxy=|--keyring=|--mirror=|--script=|--size=] --boot=efi <RELEASE> <IMAGE>"
}
usage_error() {
	echo "error: $*" 1>&2
	usage
}

BOOT=auto
ARCHITECTURE=$(dpkg --print-architecture)
IMAGE=
MIRROR=
KEYRING=
RELEASE=
SIZE=25G
SCRIPT=

# consumed by setup-testbed
export AUTOPKGTEST_BUILD_QEMU=1

opt_boot() {
	BOOT="$1"
}
opt_architecture() {
	ARCHITECTURE="$1"
}
opt_arch() {
	ARCHITECTURE="$1"
}
opt_apt_proxy() {
	# consumed by setup-testbed
	export AUTOPKGTEST_APT_PROXY="$1"
	# consumed by mmdebstrap
	if test "$1" = DIRECT; then
		unset http_proxy
	else
		export http_proxy="$1"
	fi
}
opt_keyring() {
	KEYRING="$1"
}
opt_mirror() {
	# consumed by setup-testbed
	export MIRROR="$1"
}
opt_script() {
	test -f "$1" || die "passed script '$1' does not refer to a file"
	SCRIPT="$1"
}
opt_size() {
	SIZE="$1"
}

positional=1
positional_1() {
	# consumed by setup-testbed
	export RELEASE="$1"
}
positional_2() {
	IMAGE="$1"
}
positional_3() { opt_mirror "$@"; }
positional_4() { opt_architecture "$@"; }
positional_5() { opt_script "$@"; }
positional_6() { opt_size "$@"; }
positional_7() {
	die "too many positional options"
}

while test "$#" -gt 0; do
	case "$1" in
		--architecture=*|--arch=*|--boot=*|--keyring=*|--mirror=*|--script=*|--size=*)
			optname="${1%%=*}"
			"opt_${optname#--}" "${1#*=}"
		;;
		--apt-proxy=*)
			opt_apt_proxy "${1#*=}"
		;;
		--architecture|--arch|--boot|--keyring|--mirror|--script|--size)
			test "$#" -ge 2 || usage_error "missing argument for $1"
			"opt_${1#--}" "$2"
			shift
		;;
		--apt-proxy)
			test "$#" -ge 2 || usage_error "missing argument for $1"
			opt_apt_proxy "$2"
			shift
		;;
		--efi)
			opt_boot efi
		;;
		--*)
			usage_error "unrecognized argument $1"
		;;
		*)
			"positional_$positional" "$1"
			positional=$((positional + 1))
		;;
	esac
	shift
done

test -z "$RELEASE" -o -z "$IMAGE" && usage_error "missing positional arguments"
test "$BOOT" = efi ||
	die "this tool does not support boot modes other than efi"

case "$ARCHITECTURE" in
	amd64)
		EFIIMG=bootx64.efi
	;;
	arm64)
		EFIIMG=bootaa64.efi
	;;
	armhf)
		EFIIMG=bootarm.efi
	;;
	i386)
		EFIIMG=bootia32.efi
	;;
	riscv64)
		EFIIMG=bootriscv64.efi
	;;
	*)
		die "unsupported architecture"
	;;
esac

if test "$(dpkg-query -f '${db:Status-Status}' -W binutils-multiarch)" = installed; then
	GNU_PREFIX=
else
	GNU_ARCHITECTURE="$(dpkg-architecture "-a$ARCHITECTURE" -qDEB_HOST_GNU_TYPE)"
	GNU_PREFIX="$GNU_ARCHITECTURE-"
	GNU_SUFFIX="-$(echo "$GNU_ARCHITECTURE" | tr _ -)"
	test "$(dpkg-query -f '${db:Status-Status}' -W "binutils$GNU_SUFFIX")" = installed ||
		die "please install binutils$GNU_SUFFIX or binutils-multiarch"
fi
for pkg in autopkgtest dosfstools e2fsprogs fdisk mount mtools passwd "systemd-boot-efi:$ARCHITECTURE" uidmap; do
	test "$(dpkg-query -f '${db:Status-Status}' -W "$pkg")" = installed ||
		die "please install $pkg"
done

BOOTSTUB="/usr/lib/systemd/boot/efi/linux${EFIIMG#boot}.stub"

WORKDIR=

cleanup() {
	test -n "$WORKDIR" && rm -Rf "$WORKDIR"
}

trap cleanup EXIT INT TERM QUIT

WORKDIR=$(mktemp -d)

FAT_OFFSET_SECTORS=$((1024*2))
FAT_SIZE_SECTORS=$((1024*254))

# Make the image writeable to the first subgid. mmdebstrap will map this gid to
# the root group. unshare instead will map the current gid to 0 and the first
# subgid to 1. Therefore mmdebstrap will be able to write to the image.
rm -f "$IMAGE"
: >"$IMAGE"
unshare -U -r --map-groups=auto chown 0:1 "$IMAGE"
chmod 0660 "$IMAGE"

set -- \
	--mode=unshare \
	--variant=important \
	--architecture="$ARCHITECTURE"

test "$RELEASE" = jessie &&
	set -- "$@" --hook-dir=/usr/share/mmdebstrap/hooks/jessie-or-older

set -- "$@" \
	"--include=init,linux-image-$ARCHITECTURE,python3" \
	'--customize-hook=echo autopkgtestvm >"$1/etc/hostname"' \
	'--customize-hook=echo 127.0.0.1 localhost autopkgtestvm >"$1/etc/hosts"' \
	'--customize-hook=passwd --root "$1" --delete root' \
	'--customize-hook=useradd --root "$1" --home-dir /home/user --create-home user' \
	'--customize-hook=passwd --root "$1" --delete user' \
	'--customize-hook=/usr/share/autopkgtest/setup-commands/setup-testbed'

if test -n "$SCRIPT"; then
	set -- "$@" \
		"--customize-hook=upload '$SCRIPT' /userscript" \
		"--chrooted-customize-hook=sh /userscript" \
		'--customize-hook=rm -f "$1/userscript"'
fi

EXT4_OFFSET_BYTES=$(( (FAT_OFFSET_SECTORS + FAT_SIZE_SECTORS) * 512))
EXT4_OPTIONS="offset=$EXT4_OFFSET_BYTES,assume_storage_prezeroed=1"
set -- "$@" \
	"--customize-hook=download vmlinuz '$WORKDIR/kernel'" \
	"--customize-hook=download initrd.img '$WORKDIR/initrd'" \
	'--customize-hook=mount --bind "$1" "$1/mnt"' \
	'--customize-hook=mount --bind "$1/mnt/mnt" "$1/mnt/dev"' \
	'--customize-hook=/sbin/mkfs.ext4 -d "$1/mnt" -L autopkgtestvm -E '"'$EXT4_OPTIONS' '$IMAGE' '$SIZE'" \
	'--customize-hook=umount --lazy "$1/mnt"' \
	"$RELEASE" \
	/dev/null

test -n "$MIRROR" && set -- "$@" "$MIRROR"
test -n "$KEYRING" && set -- "$@" "--keyring=$KEYRING"

echo "mmdebstrap $*"
mmdebstrap "$@" || die "mmdebstrap failed"

unshare -U -r --map-groups=auto chown 0:0 "$IMAGE"
chmod "$(printf %o "$(( 0666 - 0$(umask) ))")" "$IMAGE"

echo "root=LABEL=autopkgtestvm rw console=ttyS0" > "$WORKDIR/cmdline"

align_size() {
	echo "$(( ($1) + ($2) - 1 - (($1) + ($2) - 1) % ($2) ))"
}

alignment=$("${GNU_PREFIX}objdump" -p "$BOOTSTUB" | sed 's/^SectionAlignment\s\+\([0-9]\)/0x/;t;d')
test -z "$alignment" && die "failed to discover the alignment of the efi stub"
echo "determined efi vma alignment as $alignment"
test "$RELEASE" = jessie -a "$((alignment))" -lt "$((1024*1024))" && {
	echo "increasing efi vma alignment for jessie"
	alignment=$((1024*1024))
}
lastoffset=0
# shellcheck disable=SC2034  # unused variables serve documentation
lastoffset="$("${GNU_PREFIX}objdump" -h "$BOOTSTUB" |
	while read -r idx name size vma lma fileoff algn behind; do
		test -z "$behind" -a "${algn#"2**"}" != "$algn" || continue
		offset=$(( 0x$vma + 0x$size ))
		test "$offset" -gt "$lastoffset" || continue
		lastoffset="$offset"
		echo "$lastoffset"
	done | tail -n1)"
lastoffset=$(align_size "$lastoffset" "$alignment")
echo "determined minimum efi vma offset as $lastoffset"

cmdline_size="$(stat -Lc%s "$WORKDIR/cmdline")"
cmdline_size="$(align_size "$cmdline_size" "$alignment")"
linux_size="$(stat -Lc%s "$WORKDIR/kernel")"
linux_size="$(align_size "$linux_size" "$alignment")"
cmdline_offset="$lastoffset"
linux_offset=$((cmdline_offset + cmdline_size))
initrd_offset=$((linux_offset + linux_size))

SOURCE_DATE_EPOCH=0 \
	"${GNU_PREFIX}objcopy" \
	--enable-deterministic-archives \
	--add-section .cmdline="$WORKDIR/cmdline" \
	--change-section-vma .cmdline="$(printf 0x%x "$cmdline_offset")" \
	--add-section .linux="$WORKDIR/kernel" \
	--change-section-vma .linux="$(printf 0x%x "$linux_offset")" \
	--add-section .initrd="$WORKDIR/initrd" \
	--change-section-vma .initrd="$(printf 0x%x "$initrd_offset")" \
	"$BOOTSTUB" "$WORKDIR/efiimg"

rm -f "$WORKDIR/kernel" "$WORKDIR/initrd"

truncate -s "$((FAT_SIZE_SECTORS * 512))" "$WORKDIR/fat"
/sbin/mkfs.fat -F 32 --invariant "$WORKDIR/fat"
mmd -i "$WORKDIR/fat" EFI EFI/BOOT
mcopy -i "$WORKDIR/fat" "$WORKDIR/efiimg" "::EFI/BOOT/$EFIIMG"

rm -f "$WORKDIR/efiimg"

truncate --size="+$((34*512))" "$IMAGE"
/sbin/sfdisk "$IMAGE" <<EOF
label: gpt
unit: sectors

start=$FAT_OFFSET_SECTORS, size=$FAT_SIZE_SECTORS, type=C12A7328-F81F-11D2-BA4B-00A0C93EC93B
start=$((FAT_OFFSET_SECTORS + FAT_SIZE_SECTORS)), type=0FC63DAF-8483-4772-8E79-3D69D8477DE4
EOF

dd if="$WORKDIR/fat" of="$IMAGE" conv=notrunc,sparse bs=512 "seek=$FAT_OFFSET_SECTORS" status=none