# Copyright 2020 Gentoo Authors
# Distributed under the terms of the GNU General Public License v2

# @ECLASS: kernel-build.eclass
# @MAINTAINER:
# Distribution Kernel Project <dist-kernel@gentoo.org>
# @AUTHOR:
# Michał Górny <mgorny@gentoo.org>
# @SUPPORTED_EAPIS: 7
# @BLURB: Build mechanics for Distribution Kernels
# @DESCRIPTION:
# This eclass provides the logic to build a Distribution Kernel from
# source and install it.  Post-install and test logic is inherited
# from kernel-install.eclass.
#
# The ebuild must take care of unpacking the kernel sources, copying
# an appropriate .config into them (e.g. in src_prepare()) and setting
# correct S.  The eclass takes care of respecting savedconfig, building
# the kernel and installing it along with its modules and subset
# of sources needed to build external modules.

if [[ ! ${_KERNEL_BUILD_ECLASS} ]]; then

case "${EAPI:-0}" in
	0|1|2|3|4|5|6)
		die "Unsupported EAPI=${EAPI:-0} (too old) for ${ECLASS}"
		;;
	7)
		;;
	*)
		die "Unsupported EAPI=${EAPI} (unknown) for ${ECLASS}"
		;;
esac

inherit savedconfig toolchain-funcs kernel-install

BDEPEND="
	sys-devel/bc
	virtual/libelf"

# @FUNCTION: kernel-build_src_configure
# @DESCRIPTION:
# Prepare the toolchain for building the kernel, get the default .config
# or restore savedconfig, and get build tree configured for modprep.
kernel-build_src_configure() {
	debug-print-function ${FUNCNAME} "${@}"

	# force ld.bfd if we can find it easily
	local LD="$(tc-getLD)"
	if type -P "${LD}.bfd" &>/dev/null; then
		LD+=.bfd
	fi

	tc-export_build_env
	MAKEARGS=(
		V=1

		HOSTCC="$(tc-getBUILD_CC)"
		HOSTCXX="$(tc-getBUILD_CXX)"
		HOSTCFLAGS="${BUILD_CFLAGS}"
		HOSTLDFLAGS="${BUILD_LDFLAGS}"

		CROSS_COMPILE=${CHOST}-
		AS="$(tc-getAS)"
		CC="$(tc-getCC)"
		LD="${LD}"
		AR="$(tc-getAR)"
		NM="$(tc-getNM)"
		STRIP=":"
		OBJCOPY="$(tc-getOBJCOPY)"
		OBJDUMP="$(tc-getOBJDUMP)"

		# we need to pass it to override colliding Gentoo envvar
		ARCH=$(tc-arch-kernel)
	)

	[[ -f .config ]] || die "Ebuild error: please copy default config into .config"
	restore_config .config

	mkdir -p "${WORKDIR}"/modprep || die
	mv .config "${WORKDIR}"/modprep/ || die
	emake O="${WORKDIR}"/modprep "${MAKEARGS[@]}" olddefconfig
	emake O="${WORKDIR}"/modprep "${MAKEARGS[@]}" modules_prepare
	cp -pR "${WORKDIR}"/modprep "${WORKDIR}"/build || die
}

# @FUNCTION: kernel-build_src_compile
# @DESCRIPTION:
# Compile the kernel sources.
kernel-build_src_compile() {
	debug-print-function ${FUNCNAME} "${@}"

	emake O="${WORKDIR}"/build "${MAKEARGS[@]}" all
}

# @FUNCTION: kernel-build_src_test
# @DESCRIPTION:
# Test the built kernel via qemu.  This just wraps the logic
# from kernel-install.eclass with the correct paths.
kernel-build_src_test() {
	debug-print-function ${FUNCNAME} "${@}"

	emake O="${WORKDIR}"/build "${MAKEARGS[@]}" \
		INSTALL_MOD_PATH="${T}" modules_install

	kernel-install_test "${PV}" \
		"${WORKDIR}/build/$(kernel-install_get_image_path)" \
		"${T}/lib/modules/${PV}"
}

# @FUNCTION: kernel-build_src_install
# @DESCRIPTION:
# Install the built kernel along with subset of sources
# into /usr/src/linux-${PV}.  Install the modules.  Save the config.
kernel-build_src_install() {
	debug-print-function ${FUNCNAME} "${@}"

	# do not use 'make install' as it behaves differently based
	# on what kind of installkernel is installed
	emake O="${WORKDIR}"/build "${MAKEARGS[@]}" \
		INSTALL_MOD_PATH="${ED}" modules_install

	# note: we're using mv rather than doins to save space and time
	# install main and arch-specific headers first, and scripts
	local kern_arch=$(tc-arch-kernel)
	dodir "/usr/src/linux-${PV}/arch/${kern_arch}"
	mv include scripts "${ED}/usr/src/linux-${PV}/" || die
	mv "arch/${kern_arch}/include" \
		"${ED}/usr/src/linux-${PV}/arch/${kern_arch}/" || die

	# remove everything but Makefile* and Kconfig*
	find -type f '!' '(' -name 'Makefile*' -o -name 'Kconfig*' ')' \
		-delete || die
	find -type l -delete || die
	cp -p -R * "${ED}/usr/src/linux-${PV}/" || die

	cd "${WORKDIR}" || die
	# strip out-of-source build stuffs from modprep
	# and then copy built files as well
	find modprep -type f '(' \
			-name Makefile -o \
			-name '*.[ao]' -o \
			'(' -name '.*' -a -not -name '.config' ')' \
		')' -delete || die
	rm modprep/source || die
	cp -p -R modprep/. "${ED}/usr/src/linux-${PV}"/ || die

	# install the kernel and files needed for module builds
	insinto "/usr/src/linux-${PV}"
	doins build/{System.map,Module.symvers}
	local image_path=$(kernel-install_get_image_path)
	cp -p "build/${image_path}" "${ED}/usr/src/linux-${PV}/${image_path}" || die

	# strip empty directories
	find "${D}" -type d -empty -exec rmdir {} + || die

	# fix source tree and build dir symlinks
	dosym ../../../usr/src/linux-${PV} /lib/modules/${PV}/build
	dosym ../../../usr/src/linux-${PV} /lib/modules/${PV}/source

	save_config build/.config
}

# @FUNCTION: kernel-build_pkg_postinst
# @DESCRIPTION:
# Combine postinst from kernel-install and savedconfig eclasses.
kernel-build_pkg_postinst() {
	kernel-install_pkg_postinst
	savedconfig_pkg_postinst
}

_KERNEL_BUILD_ECLASS=1
fi

EXPORT_FUNCTIONS src_configure src_compile src_test src_install pkg_postinst