package/dracut: new host package

Dracut is the tool used by desktop distributions to build initrds.

In the embedded world, it can be very useful, too, for instance when
wanting to create an initramfs for a system recovery mode.
Whereas it is definitively possible to achieve this with buildroot, the
process is to have a dedicated buildroot configuration for that, and
perform a full build. Instead of doing that, dracut can pick the needed
binaries/shared libraries, configuration files, or kernel modules from
the 'target' directory.
The advantage is to save build time, and also to have a consistency
between the packages versions taken for the recovery and the production
filesystem.

The principle of dracut is based on the so-called 'dracut modules'. The
modules determine what will be included in the initramfs. For example,
one of dracut's modules checks the kernel modules that are included and
also includes the corresponding firmware blobs.
On the host, they are on host/lib/dracut/modules.d
Each directory as a prefix number for the order of execution, and
at least a "module-setup.sh" script.

Dracut sources all of them, and typically calls the "check()" function,
which is the placeholder for required binaries (that are aimed to be
polulated in the initrd), then the "depends()" function, that lists
other modules to depend on, and the "install()" function, that makes
the actual work.

Dracut was initially thought to work with systems using systemd,
but it can also work without it. Do to so, every "systemd-xxx"
module must be disabled in the dracut configuration file. For
convenience, the 05busybox-init module is provided, to support
busybox init system. Note that this module should *not* be enabled when
using systemd init. It is therefore only installed if busybox init is
selected.

Musl and uClibc make assumptions about the existence of some symlinks
that are not discoverable with readelf. Therefore, another module
05libc-links is provided that creates those links. The module is
installed regardless of which libc is used - the script itself discovers
if the links need to be installed based on which libc is found.

Signed-off-by: Thierry Bultel <thierry.bultel@linatsea.fr>
[arnout@mind.be: many changes]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Cc: Adam Duskett <aduskett@gmail.com>
[yann.morin.1998@free.fr: some additional fixups]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

DEVELOPERS

@@ -225,6 +225,7 @@ F:	package/espeak/
 N:	Arnout Vandecappelle <arnout@mind.be>
 F:	package/arp-scan/
 F:	package/dehydrated/
+F:	package/dracut/
 F:	package/freescale-imx/firmware-imx/
 F:	package/freescale-imx/imx-lib/
 F:	package/libpagekite/
@@ -2796,6 +2797,7 @@ F:	configs/beagleboardx15_defconfig
 F:	package/pugixml/
 
 N:	Thierry Bultel <tbultel@free.fr>
+F:	package/dracut/
 F:	package/mpd-mpc/
 
 N:	Thijs Vermeir <thijsvermeir@gmail.com>

package/Config.in.host

@@ -19,6 +19,7 @@ menu "Host utilities"
 	source "package/dos2unix/Config.in.host"
 	source "package/dosfstools/Config.in.host"
 	source "package/doxygen/Config.in.host"
+	source "package/dracut/Config.in.host"
 	source "package/dtc/Config.in.host"
 	source "package/e2fsprogs/Config.in.host"
 	source "package/e2tools/Config.in.host"

package/dracut/0001-dracut.sh-don-t-unset-LD_PRELOAD.patch

@@ -0,0 +1,31 @@
+From bb12f15856911d8532b569116da7dab4cbf107be Mon Sep 17 00:00:00 2001
+From: Thierry Bultel <thierry.bultel@linatsea.fr>
+Date: Mon, 10 Jan 2022 09:09:43 +0100
+Subject: [PATCH] dracut.sh: don't unset LD_PRELOAD
+
+LD_PRELOAD and LD_LIBRARY_PATH are needed to run under fakeroot.
+
+Signed-off-by: Thierry Bultel <thierry.bultel@linatsea.fr>
+Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
+[yann.morin.1998@free.fr: commit log also mentions LD_LIBRARY_PATH]
+Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
+---
+ dracut.sh | 2 --
+ 1 file changed, 2 deletions(-)
+
+diff --git a/dracut.sh b/dracut.sh
+index 60ac46f4..37f25b38 100755
+--- a/dracut.sh
++++ b/dracut.sh
+@@ -868,8 +868,6 @@ export LC_ALL=C
+ export LANG=C
+ unset LC_MESSAGES
+ unset LC_CTYPE
+-unset LD_LIBRARY_PATH
+-unset LD_PRELOAD
+ unset GREP_OPTIONS
+ 
+ export DRACUT_LOG_LEVEL=warning
+-- 
+2.37.1
+

package/dracut/Config.in.host

@@ -0,0 +1,9 @@
+config BR2_PACKAGE_HOST_DRACUT
+	bool
+	select BR2_PACKAGE_HOST_KMOD
+	help
+	  dracut is used to create an initramfs image by
+	  copying tools and files from an installed system
+	  and combining it with the dracut framework.
+
+	  https://dracut.wiki.kernel.org

package/dracut/busybox-init-module-setup.sh

@@ -0,0 +1,59 @@
+#!/bin/bash
+
+check() {
+	require_binaries busybox || return 1
+	return 0
+}
+
+depends() {
+	return 0
+}
+
+install_busybox_links() {
+	dir="${1}"
+	linkname="${2}"
+
+	(cd "${dracutsysrootdir?}${dir}" &&
+	for x in *; do
+		if [ "$(readlink "${x}")" = "${linkname}" ]; then
+			ln -sf "${linkname}" "${initdir?}/${dir}/${x}"
+		fi
+	done
+	)
+}
+
+install() {
+	inst_multiple /bin/busybox
+
+	# wrapper script for early console; will launch /sbin/init
+	# after having mounted devtmpfs
+	inst_multiple /init
+
+	if [ -e "${dracutsysrootdir?}/lib64" ]; then
+		ln -sf lib "${initdir?}/lib64"
+		ln -sf lib "${initdir?}/usr/lib64"
+	fi
+
+	if [ -e "${dracutsysrootdir?}/lib32" ]; then
+		ln -sf lib "${initdir?}/lib32"
+		ln -sf lib "${initdir?}/usr/lib32"
+	fi
+
+	install_busybox_links "/bin" "busybox"
+	install_busybox_links "/sbin" "../bin/busybox"
+	if [ ! -L "${dracutsysrootdir?}/bin" ]; then
+		install_busybox_links "/usr/bin" "../../bin/busybox"
+		install_busybox_links "/usr/sbin" "../../bin/busybox"
+	fi
+
+	inst_multiple \
+		/etc/inittab	\
+		/etc/init.d/rcS \
+		/etc/init.d/rcK \
+		/etc/issue	\
+		/etc/fstab	\
+		/etc/group	\
+		/etc/passwd	\
+		/etc/shadow	\
+		/etc/hostname
+}

package/dracut/dracut.hash

@@ -0,0 +1,3 @@
+# Locally computed
+sha256  4baa08206cceeb124dbf1075a0daf774b5a8f144ce2e01d82a144af3020fd65b  dracut-055.tar.xz
+sha256  8177f97513213526df2cf6184d8ff986c675afb514d4e68a404010521b880643  COPYING

package/dracut/dracut.mk

@@ -0,0 +1,48 @@
+################################################################################
+#
+# dracut
+#
+################################################################################
+
+DRACUT_VERSION = 055
+DRACUT_SOURCE = dracut-$(DRACUT_VERSION).tar.xz
+DRACUT_SITE = $(BR2_KERNEL_MIRROR)/linux/utils/boot/dracut
+DRACUT_LICENSE = GPL-2.0
+DRACUT_LICENSE_FILES = COPYING
+
+HOST_DRACUT_DEPENDENCIES = host-pkgconf host-kmod host-prelink-cross
+
+define HOST_DRACUT_POST_INSTALL_WRAPPER_SCRIPT
+	mv $(HOST_DIR)/bin/dracut $(HOST_DIR)/bin/dracut.real
+	install -D -m 0755 $(HOST_DRACUT_PKGDIR)/dracut_wrapper \
+		$(HOST_DIR)/bin/dracut
+endef
+HOST_DRACUT_POST_INSTALL_HOOKS += HOST_DRACUT_POST_INSTALL_WRAPPER_SCRIPT
+
+# When using uClibc or musl, there must be "ld-uClibc.so.1" or
+# "ld-musl-x.so" symlinks, respectively - else the init process cannot
+# start
+define HOST_DRACUT_POST_INSTALL_LIBC_LINKS_MODULE
+	$(INSTALL) -D -m 0755 package/dracut/libc-links-module-setup.sh \
+		$(HOST_DIR)/lib/dracut/modules.d/05libc-links/module-setup.sh
+endef
+HOST_DRACUT_POST_INSTALL_HOOKS += HOST_DRACUT_POST_INSTALL_LIBC_LINKS_MODULE
+
+ifeq ($(BR2_INIT_BUSYBOX),y)
+# Dracut does not support busybox init (systemd init is assumed to work
+# out of the box, though). It provides a busybox module, that does not
+# use the same paths as buildroot, and is not meant to be used as an init
+# system.
+# So it is simpler for users to disable the standard 'busybox' module in
+# the configuration file, and enable the "busybox-init' module instead.
+# Note that setting the script as executable (0755) is not mandatory,
+# but this is what dracut does on all its modules, so lets just conform
+# to it.
+define HOST_DRACUT_POST_INSTALL_BUSYBOX_INIT_MODULE
+	$(INSTALL) -D -m 0755 package/dracut/busybox-init-module-setup.sh \
+		$(HOST_DIR)/lib/dracut/modules.d/05busybox-init/module-setup.sh
+endef
+HOST_DRACUT_POST_INSTALL_HOOKS += HOST_DRACUT_POST_INSTALL_BUSYBOX_INIT_MODULE
+endif
+
+$(eval $(host-autotools-package))

package/dracut/dracut_wrapper

@@ -0,0 +1,38 @@
+#!/bin/bash
+set -e
+
+# Find the --sysroot argument
+sysroot=
+next_arg=false
+for arg; do
+	if ${next_arg}; then
+		next_arg=false
+		sysroot="${arg}"
+		continue  # not break, in case there are more than one
+	fi
+	case "${arg}" in
+	(--sysroot|-r)
+		next_arg=true
+		continue
+		;;
+	(--sysroot=*)
+		sysroot="${arg#*=}"
+		continue  # not break, in case there are more than one
+		;;
+	(-r?*)
+		sysroot="${arg#-r}"
+		continue  # not break, in case there are more than one
+		;;
+	esac
+done
+if [ -z "${sysroot}" ]; then
+	echo "${0}: --sysroot argument must be given." 1>&2
+	exit 1
+fi
+
+topdir="$(dirname "$(realpath "$(dirname "${0}")")")"
+export DRACUT_LDD="${topdir}/sbin/prelink-rtld --root='${sysroot}'"
+export DRACUT_INSTALL="${topdir}/lib/dracut/dracut-install"
+export DRACUT_LDCONFIG=/bin/true
+export dracutbasedir="${topdir}/lib/dracut"
+exec "${topdir}/bin/dracut.real" "${@}"

package/dracut/libc-links-module-setup.sh

@@ -0,0 +1,27 @@
+#!/bin/bash
+
+# Adds the missing links for uClibc or musl, if needed
+
+check() {
+	return 0
+}
+
+depends() {
+	return 0
+}
+
+install() {
+	# Despite of the fact that the listed dependency (reported by readelf -d)
+	# is purely /lib/libc.so, the musl symlink is needed anyway.
+	musl_link="$(find "${dracutsysrootdir?}/lib/" -name "ld-musl-*.so*")"
+	if [ -n "${musl_link}" ] ; then
+		ln -s libc.so "${initdir?}/lib/${musl_link##*/}"
+	fi
+
+	# Same for uClibc, the listed dependency
+	# is ld-uClibc.so.1, the loader needs the ld-uClibc.so.0, too
+	uclibc_link="$(find "${dracutsysrootdir?}/lib/" -name "ld-uClibc-*.so*")"
+	if [ -n "$uclibc_link" ] ; then
+		ln -s ld-uClibc.so.1 "${initdir?}/lib/ld-uClibc.so.0"
+	fi
+}