gen_mod_headers

#!/bin/bash
set -e; set -o pipefail

# Heavily based on PKGBUILD from
# https://www.archlinux.org/packages/core/x86_64/linux/

function error()
{
	echo $(basename $0): $@ >&2
}

function fatal()
{
	error $@
	exit 1
}

function usage()
{
	echo "usage: $(basename $0) [target dir] [linux source dir] [objects dir] <arch> <x-compile-prefix> <customcc>">&2

	exit 1
}

# See http://stackoverflow.com/a/4774063
function get_full_path()
{
	echo "$( cd "$1" ; pwd -P )"
}

function push()
{
	pushd $@ >/dev/null
}

function push_linux()
{
	push $linux_dir
}

function pop()
{
	popd >/dev/null
}

function copy_dir()
{
	from="$1"
	to="$2"

	if [[ -d "$from" ]]; then
		cp -a "$from" "$to"
	fi
}

function copy_mkdir()
{
	local target_dir="$1"
	local rel_path="$2"

	mkdir -p "$target_dir/$(dirname $rel_path)"
	cp "$rel_path" "$target_dir/$rel_path"
}

[[ $# -ge 3 ]] || usage

# Generate target dir if doesn't exist.
install -dm755 $1

target_dir=$(get_full_path $1)
linux_dir=$(get_full_path $2)
# The directory containing .config and Module.symvers.
obj_dir=$(get_full_path $3)
karch=${4:-x86}
prefix=$5
hostcc="${6:-${prefix}gcc}"

# FIXME: We assume host arch == x86.
if [[ "$karch" != "x86" ]]; then
	[[ -n $prefix ]] || fatal "Non-x86 arch but no prefix specified."
fi

build_opts=""
# Regardless of target arch, if a prefix is specified we are cross-compiling.
[[ -z "$prefix" ]] || build_opts="ARCH=$karch CROSS_COMPILE=$prefix"

karch_dir="arch/$karch"
target_karch_dir="$target_dir/$karch_dir"

[[ -f "${obj_dir}/.config" ]] || fatal "Missing kernel configuration."
[[ -f "${obj_dir}/Module.symvers" ]] || fatal "Missing Module.symvers."

# Copy in .config and Module.symvers so we can specify O=$target_dir.
cp "${obj_dir}/.config" "${obj_dir}/Module.symvers" "$target_dir"

extra_header_dirs="drivers/md net/mac80211 drivers/media/dvb-core include/config/dvb \
drivers/media/dvb-frontends drivers/media/usb/dvb-usb drivers/media/tuners"

extra_asm_dirs="arch/arm64/kernel/vdso"

push_linux
trap pop EXIT

[[ -d "$karch_dir" ]] || fatal "Unrecognised karch: $karch"

echo Running modules_prepare...
make O="$target_dir" $build_opts modules_prepare

echo Copying required files...

if [[ -n "$prefix" ]]; then
	# Move host arch script binaries so we can fix them up later. We don't want to
	# keep host binaries in place when we copy in source, we'll compile target arch
	# versions later.
	mv "$target_dir"/scripts "$target_dir"/xscripts
fi

for f in Makefile kernel/Makefile Documentation/DocBook/Makefile; do
	install -D -m644 "$f" "$target_dir/$f"
done

# Arch Linux copies only specific directories, however the difference is 31M
# vs. 37M (~168k compressed) so for future-proofing I think it's not much more
# of a cost to just copy everything.
find include -mindepth 1 -maxdepth 1 -type d | \
    xargs -I {} cp -a "{}" "$target_dir/include"

for d in include $extra_header_dirs $extra_asm_dirs; do
	[ -d "$d" ] && mkdir -p "$target_dir/$d"
done

# Configure arch/<arch> directory.
mkdir -p "$target_karch_dir"
copy_dir "$karch_dir/include" "$target_karch_dir"
copy_dir "$karch_dir/tools" "$target_karch_dir"
for f in $(find $karch_dir -iname '*.h' -o -name 'Makefile' -o -iname '*.tbl' -o -iname '*.sh'); do
	copy_mkdir "$target_dir" "$f"
done

for f in $(find security -iname '*.h'); do
	copy_mkdir "$target_dir" "$f"
done

# Copy over tools include as some builds require this.
mkdir -p "$target_dir/tools"
copy_dir tools/include "$target_dir/tools"

copy_dir scripts "$target_dir"
# Don't strip binaries as only makes 200kb difference...

mkdir -p "$target_karch_dir/kernel"
cp "$karch_dir/Makefile" "$target_karch_dir"

# May as well always copy these if available.
for f in Makefile_32.cpu kernel/asm-offsets.s; do
	p="$karch_dir/$f"
	[ -f $p ] && cp "$p" "$target_karch_dir/$f"
done

# Copy in extra headers. Directories already created above.
for d in $extra_header_dirs; do
	[ -d "$d" ] && (cp $d/*.h "$target_dir/$d" || true)
done

# Copy in extra assember. Directories already created above.
for d in $extra_asm_dirs; do
	[ -d "$d" ] && (cp $d/*.S "$target_dir/$d" || true)
done

# Specific required files.

if [[ -e drivers/media/i2c/msp3400-driver.h ]]; then
	mkdir -p "$target_dir/drivers/media/i2c/"
	cp drivers/media/i2c/msp3400-driver.h "$target_dir/drivers/media/i2c/"
fi

# Copy in Kconfig files.
for f in $(find . -name "Kconfig*"); do
	copy_mkdir "$target_dir" "$f"
done

if [[ -n "$prefix" ]]; then
	echo Fixing up script binaries...

	push "$target_dir"

	# Make some backups so we can restore sanity after we're done.
	cp scripts/basic/Makefile .backup.basic.Makefile
	cp scripts/Kbuild.include .backup.kbuild.Makefile.include
	cp scripts/Makefile.build .backup.Makefile.build
	cp scripts/mod/Makefile .backup.mod.Makefile
	cp scripts/kconfig/Makefile .backup.kconfig.Makefile

	# Fixup Makefile's so they reference our host arch binaries in xscripts.
	# We only need a few fixups since we're only building scripts here.
	sed -i 's|$(obj)/fixdep|x$(obj)/fixdep|' scripts/basic/Makefile
	sed -i 's|scripts/basic/fixdep|xscripts/basic/fixdep|' scripts/Kbuild.include
	sed -i 's|scripts/basic/fixdep|xscripts/basic/fixdep|' scripts/Makefile.build
	sed -i 's|$(obj)/mk_elfconfig|x$(obj)/mk_elfconfig|' scripts/mod/Makefile
	sed -i 's|$(obj)/conf|x$(obj)/conf|' scripts/kconfig/Makefile

	echo Building script binaries for target arch...

	make HOSTCC="$hostcc" $build_opts scripts/

	echo Cleaning up directory...

	# Reinstate pristine Makefile's.
	mv .backup.basic.Makefile scripts/basic/Makefile
	mv .backup.kbuild.Makefile.include scripts/Kbuild.include
	mv .backup.Makefile.build scripts/Makefile.build
	mv .backup.mod.Makefile scripts/mod/Makefile
	mv .backup.kconfig.Makefile scripts/kconfig/Makefile

	# Clean up host script bins.
	rm -rf xscripts

	pop
fi

echo Done!