armbian-build/lib/functions/compilation/kernel-debs.sh

#!/usr/bin/env bash
#
# SPDX-License-Identifier: GPL-2.0
#
# Copyright (c) 2013-2023 Igor Pecovnik, igor@armbian.com
#
# This file is a part of the Armbian Build Framework
# https://github.com/armbian/build/

# This is a re-imagining of mkdebian and builddeb from the kernel tree.

# We wanna produce Debian/Ubuntu compatible packages so we're able to use their standard tools, like
# `u-boot-menu`, `grub2`, and others, so we gotta stick to their conventions.

# The main difference is that this is NOT invoked from KBUILD's Makefile, but instead
# directly by Armbian, with references to the dirs where KBUILD's
# `make install dtbs_install modules_install headers_install` have already successfully been run.

# This will create a SET of packages. It should always create these:
# image package: vmlinuz and such, config, modules, and dtbs (if exist) in /usr/lib/xxx
# linux-headers package: "just" the kernel headers, for building out-of-tree modules, dkms, etc.
# linux-dtbs package: only dtbs, if they exist. in /boot/

# So this will handle
# - Creating .deb package skeleton dir (mktemp)
# - Moving/copying around of KBUILD installed stuff for Debian/Ubuntu/Armbian standard locations, in the correct packages
# - Fixing the symlinks to stuff so they fit a target system.
# - building the .debs.

is_enabled() {
	grep -q "^$1=y" include/config/auto.conf
}

if_enabled_echo() {
	if is_enabled "$1"; then
		echo -n "$2"
	elif [ $# -ge 3 ]; then
		echo -n "$3"
	fi
}

function prepare_kernel_packaging_debs() {
	: "${artifact_version:?artifact_version is not set}"

	declare kernel_work_dir="${1}"
	declare kernel_dest_install_dir="${2}"
	declare kernel_version="${3}"
	declare -n tmp_kernel_install_dirs="${4}" # nameref to 	declare -n kernel_install_dirs dictionary
	declare debs_target_dir="${kernel_work_dir}/.."

	# Some variables and settings used throughout the script
	declare kernel_version_family="${kernel_version}-${BRANCH}-${LINUXFAMILY}"

	# Package version. Affects users upgrading from repo!
	display_alert "Kernel .deb package version" "${artifact_version}" "info"

	# show incoming tree
	#display_alert "Kernel install dir" "incoming from KBUILD make" "debug"
	#run_host_command_logged tree -C --du -h "${kernel_dest_install_dir}" "| grep --line-buffered -v -e '\.ko' -e '\.h' "

	# display_alert "tmp_kernel_install_dirs INSTALL_PATH:" "${tmp_kernel_install_dirs[INSTALL_PATH]}" "debug"
	# display_alert "tmp_kernel_install_dirs INSTALL_MOD_PATH:" "${tmp_kernel_install_dirs[INSTALL_MOD_PATH]}" "debug"
	# display_alert "tmp_kernel_install_dirs INSTALL_HDR_PATH:" "${tmp_kernel_install_dirs[INSTALL_HDR_PATH]}" "debug"
	# display_alert "tmp_kernel_install_dirs INSTALL_DTBS_PATH:" "${tmp_kernel_install_dirs[INSTALL_DTBS_PATH]}" "debug"

	# Due to we call `make install` twice, we will get some `.old` files
	run_host_command_logged rm -rf "${tmp_kernel_install_dirs[INSTALL_PATH]}/*.old" || true

	if [[ "${KERNEL_DTB_ONLY}" != "yes" ]]; then
		# package the linux-image (image, modules, dtbs (if present))
		display_alert "Packaging linux-image" "${LINUXFAMILY} ${LINUXCONFIG}" "info"
		create_kernel_deb "linux-image-${BRANCH}-${LINUXFAMILY}" "${debs_target_dir}" kernel_package_callback_linux_image "linux-image"
	fi

	# if dtbs present, package those too separately, for u-boot usage.
	if [[ -d "${tmp_kernel_install_dirs[INSTALL_DTBS_PATH]}" ]]; then
		display_alert "Packaging linux-dtb" "${LINUXFAMILY} ${LINUXCONFIG}" "info"
		create_kernel_deb "linux-dtb-${BRANCH}-${LINUXFAMILY}" "${debs_target_dir}" kernel_package_callback_linux_dtb "linux-dtb"
	fi

	if [[ "${KERNEL_DTB_ONLY}" != "yes" ]]; then
		if [[ "${KERNEL_HAS_WORKING_HEADERS}" == "yes" ]]; then
			display_alert "Packaging linux-headers" "${LINUXFAMILY} ${LINUXCONFIG}" "info"
			create_kernel_deb "linux-headers-${BRANCH}-${LINUXFAMILY}" "${debs_target_dir}" kernel_package_callback_linux_headers "linux-headers"
		else
			display_alert "Skipping linux-headers package" "for ${KERNEL_MAJOR_MINOR} kernel version" "info"
		fi

		display_alert "Packaging linux-libc-dev" "${LINUXFAMILY} ${LINUXCONFIG}" "info"
		create_kernel_deb "linux-libc-dev-${BRANCH}-${LINUXFAMILY}" "${debs_target_dir}" kernel_package_callback_linux_libc_dev "linux-libc-dev"
	fi

	return 0
}

function create_kernel_deb() {
	declare package_name="${1}"
	declare deb_output_dir="${2}"
	declare callback_function="${3}"
	declare artifact_deb_id="${4}"

	declare cleanup_id="" package_directory=""
	prepare_temp_dir_in_workdir_and_schedule_cleanup "deb-k-${package_name}" cleanup_id package_directory # namerefs

	declare package_DEBIAN_dir="${package_directory}/DEBIAN" # DEBIAN dir
	mkdir -p "${package_DEBIAN_dir}"                         # maintainer scripts et al

	# Generate copyright file
	mkdir -p "${package_directory}/usr/share/doc/${package_name}"
	cat <<- COPYRIGHT > "${package_directory}/usr/share/doc/${package_name}/copyright"
		This is a packaged Armbian patched version of the Linux kernel.

		The sources may be found at most Linux archive sites, including:
		https://www.kernel.org/pub/linux/kernel

		Copyright: 1991 - 2018 Linus Torvalds and others.

		The git repository for mainline kernel development is at:
		git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

		    This program is free software; you can redistribute it and/or modify
		    it under the terms of the GNU General Public License as published by
		    the Free Software Foundation; version 2 dated June, 1991.

		On Debian GNU/Linux systems, the complete text of the GNU General Public
		License version 2 can be found in \`/usr/share/common-licenses/GPL-2'.
	COPYRIGHT

	# Run the callback.
	# display_alert "Running callback" "callback: ${callback_function}" "debug"
	"${callback_function}" "${@}"

	run_host_command_logged chown -R root:root "${package_directory}" # Fix ownership and permissions
	run_host_command_logged chmod -R go-w "${package_directory}"      # Fix ownership and permissions
	run_host_command_logged chmod -R a+rX "${package_directory}"      # in case we are in a restrictive umask environment like 0077
	run_host_command_logged chmod -R ug-s "${package_directory}"      # in case we build in a setuid/setgid directory

	cd "${package_directory}" || exit_with_error "major failure 774 for ${package_name}"

	# create md5sums file
	# sh -c "cd '${package_directory}'; find . -type f ! -path './DEBIAN/*' -printf '%P\0' | xargs -r0 md5sum > DEBIAN/md5sums"

	declare unpacked_size
	unpacked_size="$(du -h -s "${package_directory}" | awk '{print $1}')"
	display_alert "Unpacked ${package_name} tree" "${unpacked_size}" "debug"

	# Show it
	#display_alert "Package dir" "for package ${package_name}" "debug"
	#run_host_command_logged tree -C -h -d --du "${package_directory}"

	dpkg_deb_build "${package_directory}" "${artifact_deb_id}"

	done_with_temp_dir "${cleanup_id}" # changes cwd to "${SRC}" and fires the cleanup function early
}

function kernel_package_hook_helper() {
	declare script="${1}"
	declare contents="${2}"

	cat >> "${package_DEBIAN_dir}/${script}" <<- EOT
		#!/bin/bash
		echo "Armbian '${package_name}' for '${kernel_version_family}': '${script}' starting."
		set -e # Error control

		function is_boot_dev_vfat() {
			# When installing these packages during image build, /boot is not mounted, and will most definitely not be vfat.
			# Use an environment variable to signal that it _will_ be a fat32, so symlinks are not created.
			# This is passed by install_deb_chroot() explicitly via the runners.
			if [[ "\${ARMBIAN_IMAGE_BUILD_BOOTFS_TYPE:-"unknown"}" == "fat" ]]; then
				echo "Armbian: ARMBIAN_IMAGE_BUILD_BOOTFS_TYPE: '\${ARMBIAN_IMAGE_BUILD_BOOTFS_TYPE:-"not set"}'"
				return 0
			fi
			if ! mountpoint -q /boot; then
				return 1
			fi
			local boot_partition bootfstype
			boot_partition=\$(findmnt --nofsroot -n -o SOURCE /boot)
			bootfstype=\$(blkid -s TYPE -o value \$boot_partition)
			if [[ "\$bootfstype" == "vfat" ]]; then
				return 0
			fi
			return 1
		}

		#set -x # Debugging

		$(cat "${contents}")

		set +x # Disable debugging
		echo "Armbian '${package_name}' for '${kernel_version_family}': '${script}' finishing."
		true
	EOT
	chmod 775 "${package_DEBIAN_dir}/${script}"

	# produce log asset for script
	LOG_ASSET="deb-${package_name}-${script}.sh" do_with_log_asset run_host_command_logged cat "${package_DEBIAN_dir}/${script}"

}

function kernel_package_callback_linux_image() {
	display_alert "linux-image deb packaging" "${package_directory}" "debug"

	# @TODO: we expect _all_ kernels to produce this, which is... not true.
	declare kernel_pre_package_path="${tmp_kernel_install_dirs[INSTALL_PATH]}"
	declare kernel_image_pre_package_path="${kernel_pre_package_path}/vmlinuz-${kernel_version_family}"
	declare installed_image_path="boot/vmlinuz-${kernel_version_family}" # using old mkdebian terminology here for compatibility

	display_alert "Showing contents of Kbuild produced /boot" "linux-image" "debug"
	run_host_command_logged tree -C --du -h "${tmp_kernel_install_dirs[INSTALL_PATH]}"

	display_alert "Kernel-built image filetype" "vmlinuz-${kernel_version_family}: $(file --brief "${kernel_image_pre_package_path}")" "info"

	declare image_name="Image" # "Image" for arm64. or, "zImage" for arm, or "vmlinuz" for others. 'image_name' is for easy mkdebian compat
	# If NAME_KERNEL is set (usually in arch config file), warn and use that instead.
	if [[ -n "${NAME_KERNEL}" ]]; then
		display_alert "NAME_KERNEL is set" "using '${NAME_KERNEL}' instead of '${image_name}'" "debug"
		image_name="${NAME_KERNEL}"
	fi

	# allow hook to do stuff here. Some (legacy/vendor/weird) kernels spit out a vmlinuz that needs manual conversion to uImage, etc.
	run_host_command_logged ls -la "${kernel_pre_package_path}" "${kernel_image_pre_package_path}"

	call_extension_method "pre_package_kernel_image" <<- 'PRE_PACKAGE_KERNEL_IMAGE'
		*fix Image/uImage/zImage before packaging kernel*
		Some (legacy/vendor) kernels need preprocessing of the produced Image/uImage/zImage before packaging.
		Use this hook to do that, by modifying the file in place, in `${kernel_pre_package_path}` directory.
		The final file that will be used is stored in `${kernel_image_pre_package_path}` -- which you shouldn't change.
	PRE_PACKAGE_KERNEL_IMAGE

	display_alert "Kernel image filetype after pre_package_kernel_image" "vmlinuz-${kernel_version_family}: $(file --brief "${kernel_image_pre_package_path}")" "info"

	unset kernel_pre_package_path       # be done with var after hook
	unset kernel_image_pre_package_path # be done with var after hook

	run_host_command_logged cp -rp "${tmp_kernel_install_dirs[INSTALL_PATH]}" "${package_directory}/"         # /boot stuff
	run_host_command_logged cp -rp "${tmp_kernel_install_dirs[INSTALL_MOD_PATH]}/lib" "${package_directory}/" # so "lib" stuff sits at the root

	# Clean up symlinks in lib/modules/${kernel_version_family}/build and lib/modules/${kernel_version_family}/source; will be in the headers package
	run_host_command_logged rm -v -f "${package_directory}/lib/modules/${kernel_version_family}/build" "${package_directory}/lib/modules/${kernel_version_family}/source"

	if [[ -d "${package_directory}/lib/modules/${kernel_version_family}/kernel" ]]; then
		display_alert "Showing contents of Kbuild produced modules" "linux-image" "debug"
		run_host_command_logged tree -C --du -h -d -L 1 "${package_directory}/lib/modules/${kernel_version_family}/kernel" "|| true" # do not fail
	fi

	if [[ -d "${tmp_kernel_install_dirs[INSTALL_DTBS_PATH]}" ]]; then
		# /usr/lib/linux-image-${kernel_version_family} is wanted by u-boot-menu, and other standard Debian/Ubuntu utilities

		display_alert "DTBs present on kernel output" "DTBs ${package_name}: /usr/lib/linux-image-${kernel_version_family}" "debug"
		mkdir -p "${package_directory}/usr/lib"
		run_host_command_logged cp -rp "${tmp_kernel_install_dirs[INSTALL_DTBS_PATH]}" "${package_directory}/usr/lib/linux-image-${kernel_version_family}"
	fi

	# Generate a control file
	cat <<- CONTROL_FILE > "${package_DEBIAN_dir}/control"
		Package: ${package_name}
		Version: ${artifact_version}
		Source: linux-${kernel_version}
		Armbian-Kernel-Version: ${kernel_version}
		Armbian-Kernel-Version-Family: ${kernel_version_family}
		Architecture: ${ARCH}
		Maintainer: ${MAINTAINER} <${MAINTAINERMAIL}>
		Section: kernel
		Priority: optional
		Provides: linux-image, linux-image-armbian, armbian-$BRANCH
		Description: Armbian Linux $BRANCH kernel image $kernel_version_family
		 This package contains the Linux kernel, modules and corresponding other files.
		 ${artifact_version_reason:-"${kernel_version_family}"}
	CONTROL_FILE

	# Install the maintainer scripts
	# Note: hook scripts under /etc/kernel are also executed by official Debian
	# kernel packages, as well as kernel packages built using make-kpkg.
	# make-kpkg sets $INITRD to indicate whether an initramfs is wanted, and
	# so do we; recent versions of dracut and initramfs-tools will obey this.
	declare debian_kernel_hook_dir="/etc/kernel"
	for script in "postinst" "postrm" "preinst" "prerm"; do
		mkdir -p "${package_directory}${debian_kernel_hook_dir}/${script}.d" # create kernel hook dir, make sure.

		kernel_package_hook_helper "${script}" <(
			# Common for all of postinst/postrm/preinst/prerm
			cat <<- KERNEL_HOOK_DELEGATION # Reference: linux-image-6.1.0-7-amd64.postinst from Debian
				export DEB_MAINT_PARAMS="\$*" # Pass maintainer script parameters to hook scripts
				export INITRD=$(if_enabled_echo CONFIG_BLK_DEV_INITRD Yes No) # Tell initramfs builder whether it's wanted
				# Run the same hooks Debian/Ubuntu would for their kernel packages.
				test -d ${debian_kernel_hook_dir}/${script}.d && run-parts --arg="${kernel_version_family}" --arg="/${installed_image_path}" ${debian_kernel_hook_dir}/${script}.d
			KERNEL_HOOK_DELEGATION

			if [[ "${script}" == "preinst" ]]; then
				cat <<- HOOK_FOR_REMOVE_VFAT_BOOT_FILES
					if is_boot_dev_vfat; then
						rm -f /boot/System.map* /boot/config* /boot/vmlinuz* /boot/$image_name /boot/uImage
					fi
				HOOK_FOR_REMOVE_VFAT_BOOT_FILES
			fi

			# @TODO: only if u-boot, only for postinst. Gotta find a hook scheme for these...
			if [[ "${script}" == "postinst" ]]; then
				cat <<- HOOK_FOR_LINK_TO_LAST_INSTALLED_KERNEL # image_name="${NAME_KERNEL}", above
					touch /boot/.next
					if is_boot_dev_vfat; then
						echo "Armbian: FAT32 /boot: move last-installed kernel to '$image_name'..."
						mv -v /${installed_image_path} /boot/${image_name}
					else
						echo "Armbian: update last-installed kernel symlink to '$image_name'..."
						ln -sfv $(basename "${installed_image_path}") /boot/$image_name
					fi
				HOOK_FOR_LINK_TO_LAST_INSTALLED_KERNEL

				# Reference: linux-image-6.1.0-7-amd64.postinst from Debian
				cat <<- HOOK_FOR_DEBIAN_COMPAT_SYMLINK
					# call debian helper, for compatibility. this symlinks things according to /etc/kernel-img.conf
					# "install" or "upgrade" are decided in a very contrived way by Debian (".fresh-install" file)
					# do NOT do this if /boot is a vfat, though.
					if ! is_boot_dev_vfat; then
						echo "Armbian: Debian compat: linux-update-symlinks install ${kernel_version_family} ${installed_image_path}"
						linux-update-symlinks install "${kernel_version_family}" "${installed_image_path}" || true
					fi
				HOOK_FOR_DEBIAN_COMPAT_SYMLINK
			fi
		)
	done
}

function kernel_package_callback_linux_dtb() {
	display_alert "linux-dtb packaging" "${package_directory}" "debug"

	display_alert "Showing tree of Kbuild produced DTBs" "linux-dtb" "debug"
	run_host_command_logged tree -C --du -h -L 3 "${tmp_kernel_install_dirs[INSTALL_DTBS_PATH]}"

	mkdir -p "${package_directory}/boot/"
	run_host_command_logged cp -rp "${tmp_kernel_install_dirs[INSTALL_DTBS_PATH]}" "${package_directory}/boot/dtb-${kernel_version_family}"

	# Generate a control file
	cat <<- CONTROL_FILE > "${package_DEBIAN_dir}/control"
		Version: ${artifact_version}
		Maintainer: ${MAINTAINER} <${MAINTAINERMAIL}>
		Section: kernel
		Package: ${package_name}
		Architecture: ${ARCH}
		Priority: optional
		Provides: linux-dtb, linux-dtb-armbian, armbian-$BRANCH
		Description: Armbian Linux $BRANCH DTBs in /boot/dtb-${kernel_version_family}
		 This package contains device tree blobs from the Linux kernel, version ${kernel_version_family}
		 ${artifact_version_reason:-"${kernel_version_family}"}
	CONTROL_FILE

	kernel_package_hook_helper "preinst" <(
		cat <<- EOT
			rm -rf /boot/dtb
			rm -rf /boot/dtb-${kernel_version_family}
		EOT
	)

	kernel_package_hook_helper "postinst" <(
		cat <<- EOT
			cd /boot
			if ! is_boot_dev_vfat; then
				echo "Armbian: DTB: symlinking /boot/dtb to /boot/dtb-${kernel_version_family}..."
				ln -sfTv "dtb-${kernel_version_family}" dtb
			else
				echo "Armbian: DTB: FAT32: moving /boot/dtb-${kernel_version_family} to /boot/dtb ..."
				mv -v "dtb-${kernel_version_family}" dtb
			fi
		EOT
	)

}

function kernel_package_callback_linux_headers() {
	display_alert "linux-headers packaging" "${package_directory}" "debug"

	# targets.
	local headers_target_dir="${package_directory}/usr/src/linux-headers-${kernel_version_family}" # headers/tools etc
	local modules_target_dir="${package_directory}/lib/modules/${kernel_version_family}"           # symlink to above later

	mkdir -p "${headers_target_dir}" "${modules_target_dir}"                                                         # create both dirs
	run_host_command_logged ln -v -s "/usr/src/linux-headers-${kernel_version_family}" "${modules_target_dir}/build" # Symlink in modules so builds find the headers
	run_host_command_logged cp -vp "${kernel_work_dir}"/.config "${headers_target_dir}"/.config                      # copy .config manually to be where it's expected to be

	# gather stuff from the linux source tree: ${kernel_work_dir} (NOT the make install destination)
	# those can be source files or object (binary/compiled) stuff
	# how to get SRCARCH? only from the makefile itself. ARCH=amd64 then SRCARCH=x86. How to we know? @TODO
	local SRC_ARCH="${ARCH}"
	[[ "${SRC_ARCH}" == "amd64" ]] && SRC_ARCH="x86"
	[[ "${SRC_ARCH}" == "armhf" ]] && SRC_ARCH="arm"
	[[ "${SRC_ARCH}" == "riscv64" ]] && SRC_ARCH="riscv"
	[[ "${SRC_ARCH}" == "loong64" ]] && SRC_ARCH="loongarch"
	# @TODO: added KERNEL_SRC_ARCH to each arch'es .config file; let's make sure they're sane. Just use KERNEL_SRC_ARCH after confirmed.
	# Lets check and warn if it isn't. If warns don't popup over time we remove and just use ARCHITECTURE later.
	if [[ "${SRC_ARCH}" != "${KERNEL_SRC_ARCH}" ]]; then
		display_alert "WARNING: KERNEL_SRC_ARCH and SRC_ARCH don't match during kernel build." "KERNEL_SRC_ARCH=${ARCHITECTURE} SRC_ARCH=${SRC_ARCH}" "wrn"
	fi

	# Create a list of files to include, path-relative to the kernel tree
	local temp_file_list="${WORKDIR}/tmp_file_list_${kernel_version_family}.kernel.headers"

	# Find the files we want to include in the package. Those will be later cleaned, etc.
	(
		cd "${kernel_work_dir}" || exit 2
		find . -name Makefile\* -o -name Kconfig\* -o -name \*.pl

		find arch/*/include include scripts -type f -o -type l

		find security/*/include -type f
		[[ -d "arch/${SRC_ARCH}" ]] && {
			find "arch/${SRC_ARCH}" -name module.lds -o -name Kbuild.platforms -o -name Platform
			# shellcheck disable=SC2046 # I need to expand. Thanks.
			find $(find "arch/${SRC_ARCH}" -name include -o -name scripts -type d) -type f
			find arch/${SRC_ARCH}/include -type f
		}
		find Module.symvers include scripts -type f
		find . -name "bitsperlong.h" -type f

		# tools/include/tools has the byteshift utilities shared between kernel proper and the build scripts/tools.
		# This replaces 'headers-debian-byteshift.patch' which was used for years in Armbian.
		find tools -type f       # all tools; will trim a bit later
		find arch/x86/lib/insn.c # required by objtool stuff...

		if is_enabled CONFIG_GCC_PLUGINS; then
			find scripts/gcc-plugins -name gcc-common.h # @TODO something else here too?
		fi
	) > "${temp_file_list}"

	# Now include/copy those, using tar as intermediary. Just like builddeb does it.
	tar -c -f - -C "${kernel_work_dir}" -T "${temp_file_list}" | tar -xf - -C "${headers_target_dir}"

	# ${temp_file_list} is left at WORKDIR for later debugging, will be removed by WORKDIR cleanup trap

	# Small detour: in v6.3-rc1, in commit https://github.com/torvalds/linux/commit/799fb82aa132fa3a3886b7872997a5a84e820062,
	#               the tools/vm dir was renamed to tools/mm. Unfortunately tools/Makefile still expects it to exist,
	#               and "make clean" in the "/tools" dir fails. Drop in a fake Makefile there to work around this.
	if [[ ! -f "${headers_target_dir}/tools/vm/Makefile" ]]; then
		display_alert "Creating fake tools/vm/Makefile" "6.3+ hackfix" "debug"
		run_host_command_logged mkdir -p "${headers_target_dir}/tools/vm"
		echo -e "clean:\n\techo fake clean for tools/vm" > "${headers_target_dir}/tools/vm/Makefile"
	fi

	# Small detour: in v6.14-rc1, in commit https://github.com/torvalds/linux/commit/e19bde2269ca,
	#               the tools/pci dir was renamed to tools/testing/selftests/pci_endpoint.
	#               Unfortunately tools/Makefile still expects it to exist,
	#               and "make clean" in the "/tools" dir fails. Drop in a fake Makefile there to work around this.
	if [[ ! -f "${headers_target_dir}/tools/pci/Makefile" ]] && [[ "${KERNEL_MAJOR_MINOR}" == "6.14" ]]; then
		display_alert "Creating fake tools/pci/Makefile" "6.14 hackfix" "debug"
		run_host_command_logged mkdir -p "${headers_target_dir}/tools/pci"
		echo -e "clean:\n\techo fake clean for tools/pci" > "${headers_target_dir}/tools/pci/Makefile"
	fi

	# Hack for 6.5-rc1: create include/linux dir so the 'clean' step below doesn't fail. I've reported upstream...
	display_alert "Creating fake counter/include/linux" "6.5-rc1 hackfix" "debug"
	run_host_command_logged mkdir -p "${headers_target_dir}/tools/counter/include/linux"

	# Now, make the script dirs clean.
	# This is run in our _target_ dir, NOT the source tree, so we're free to make clean as we wish without invalidating the next build's cache.
	# Understand: I'm sending the logs of this to the bitbucket ON PURPOSE: "clean" tries to use clang, ALSA, etc, which are not available.
	#             The logs produced during this step throw off developers casually looking at the logs.
	#             Important: if the steps _fail_ here, you'll have to enable DEBUG=yes to see what's going on.
	#
	# In order for the cleanup to be correct  for tools, we need to pass the VMLINUX_BTF variable,
	# which contains the real path to the newly compiled vmlinux file.
	declare make_bitbucket="&> /dev/null"
	run_host_command_logged cd "${headers_target_dir}" "&&" make "ARCH=${SRC_ARCH}" "M=scripts" clean "${make_bitbucket}" "||" make "ARCH=${SRC_ARCH}" "M=scripts" clean
	run_host_command_logged cd "${headers_target_dir}/tools" "&&" make "ARCH=${SRC_ARCH}" "VMLINUX_BTF=${kernel_work_dir}/vmlinux" clean "${make_bitbucket}" "||" make "ARCH=${SRC_ARCH}" "VMLINUX_BTF=${kernel_work_dir}/vmlinux" clean

	# Trim down on the tools dir a bit after cleaning.
	rm -rf "${headers_target_dir}/tools/perf" "${headers_target_dir}/tools/testing"

	# Hack: after cleaning, copy over the scripts/module.lds file from the source tree. It will only exist on 5.10+
	# See https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1906131
	[[ -f "${kernel_work_dir}/scripts/module.lds" ]] &&
		run_host_command_logged cp -v "${kernel_work_dir}/scripts/module.lds" "${headers_target_dir}/scripts/module.lds"

	if [[ "${DEBUG}" == "yes" ]]; then
		# Check that no binaries are included by now. Expensive... @TODO: remove after me make sure.
		display_alert "Checking for binaries in kernel headers" "${headers_target_dir}" "debug"
		(
			cd "${headers_target_dir}" || exit 33
			find . -type f | grep -v -e "include/config/" -e "\.h$" -e ".c$" -e "Makefile$" -e "Kconfig$" -e "Kbuild$" -e "\.cocci$" | xargs file | grep -v -e "ASCII" -e "script text" -e "empty" -e "Unicode text" -e "symbolic link" -e "CSV text" -e "SAS 7+" || true
		)
	fi

	call_extension_method "pre_package_kernel_headers" <<- 'PRE_PACKAGE_KERNEL_HEADERS'
		*fix kernel headers before packaging*
		Some (legacy/vendor) kernels need preprocessing of the produced kernel headers before packaging.
		Use this hook to do that, by modifying the file in place, in `${headers_target_dir}` directory.
		The kernel sources can be found in `${kernel_work_dir}`.
	PRE_PACKAGE_KERNEL_HEADERS

	# Generate a control file
	# TODO: libssl-dev is only required if we're signing modules, which is a kernel .config option.
	cat <<- CONTROL_FILE > "${package_DEBIAN_dir}/control"
		Version: ${artifact_version}
		Maintainer: ${MAINTAINER} <${MAINTAINERMAIL}>
		Section: devel
		Package: ${package_name}
		Architecture: ${ARCH}
		Priority: optional
		Provides: linux-headers, linux-headers-armbian, armbian-$BRANCH
		Depends: make, gcc, libc6-dev, bison, flex, libssl-dev, libelf-dev
		Description: Armbian Linux $BRANCH headers ${kernel_version_family}
		 This package provides kernel header files for ${kernel_version_family}
		 .
		 This is useful for DKMS and building of external modules.
		 ${artifact_version_reason:-"${kernel_version_family}"}
	CONTROL_FILE

	# Make sure the target dir is clean/not-existing before installing.
	kernel_package_hook_helper "preinst" <(
		cat <<- EOT_PREINST
			if [[ -d "/usr/src/linux-headers-${kernel_version_family}" ]]; then
				echo "Cleaning pre-existing directory /usr/src/linux-headers-${kernel_version_family} ..."
				rm -rf "/usr/src/linux-headers-${kernel_version_family}"
			fi
		EOT_PREINST
	)

	# Make sure the target dir is removed before removing the package; that way we don't leave eventual compilation artifacts over there.
	kernel_package_hook_helper "prerm" <(
		cat <<- EOT_PRERM
			if [[ -d "/usr/src/linux-headers-${kernel_version_family}" ]]; then
				echo "Cleaning directory /usr/src/linux-headers-${kernel_version_family} ..."
				rm -rf "/usr/src/linux-headers-${kernel_version_family}"
			fi
		EOT_PRERM
	)

	kernel_package_hook_helper "postinst" <(
		cat <<- EOT_POSTINST
			cd "/usr/src/linux-headers-${kernel_version_family}"
			NCPU=\$(grep -c 'processor' /proc/cpuinfo)
			echo "Configuring kernel-headers (${kernel_version_family}) - please wait ..."
			make ARCH="${SRC_ARCH}" olddefconfig

			echo "Compiling kernel-headers scripts (${kernel_version_family}) using \$NCPU CPUs - please wait ..."
			make ARCH="${SRC_ARCH}" -j\$NCPU scripts

			echo "Compiling kernel-headers scripts/mod (${kernel_version_family}) using \$NCPU CPUs - please wait ..."
			make ARCH="${SRC_ARCH}" -j\$NCPU M=scripts/mod/

			# make ARCH="${SRC_ARCH}" -j\$NCPU modules_prepare # depends on too much other stuff.
			echo "Done compiling kernel-headers (${kernel_version_family})."
		EOT_POSTINST

		if [[ "${ARCH}" == "amd64" ]]; then # This really only works on x86/amd64; @TODO revisit later
			cat <<- EOT_POSTINST_OBJTOOL
				echo "Compiling kernel-header objtool (${kernel_version_family})."
				make ARCH="${SRC_ARCH}" -j\$NCPU tools/objtool
				echo "Done compiling kernel-header objtool (${kernel_version_family})."
			EOT_POSTINST_OBJTOOL
		fi

		cat <<- EOT_POSTINST_FINISH
			echo "Done compiling kernel-headers tools (${kernel_version_family})."
		EOT_POSTINST_FINISH
	)
}

function kernel_package_callback_linux_libc_dev() {
	display_alert "linux-libc-dev packaging" "${package_directory}" "debug"

	mkdir -p "${package_directory}/usr"
	run_host_command_logged cp -rp "${tmp_kernel_install_dirs[INSTALL_HDR_PATH]}/include" "${package_directory}/usr"
	HOST_ARCH=$(dpkg-architecture -a${ARCH} -q"DEB_HOST_MULTIARCH")
	run_host_command_logged mkdir "${package_directory}/usr/include/${HOST_ARCH}"
	run_host_command_logged mv "${package_directory}/usr/include/asm" "${package_directory}/usr/include/${HOST_ARCH}"

	# Generate a control file
	cat <<- CONTROL_FILE > "${package_DEBIAN_dir}/control"
		Version: ${artifact_version}
		Maintainer: ${MAINTAINER} <${MAINTAINERMAIL}>
		Package: ${package_name}
		Section: devel
		Priority: optional
		Provides: linux-libc-dev
		Conflicts: linux-libc-dev
		Architecture: ${ARCH}
		Description: Armbian Linux support headers for userspace development
		 This package provides userspaces headers from the Linux kernel.  These headers
		 are used by the installed headers for GNU glibc and other system libraries.
		Multi-Arch: same
	CONTROL_FILE
}