[Buildroot] [PATCH next v5 1/3] package/dracut: new host package

* [Buildroot] [PATCH next v5 1/3] package/dracut: new host package
@ 2022-08-15 11:17 Arnout Vandecappelle (Essensium/Mind)
  2022-08-15 11:17 ` [Buildroot] [PATCH next v5 2/3] fs/cpio: new option to use dracut tool Arnout Vandecappelle (Essensium/Mind)
                   ` (3 more replies)
  0 siblings, 4 replies; 10+ messages in thread
From: Arnout Vandecappelle (Essensium/Mind) @ 2022-08-15 11:17 UTC (permalink / raw)
  To: buildroot; +Cc: Thierry Bultel, Adam Duskett

From: Thierry Bultel <thierry.bultel@linatsea.fr>

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>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Cc: Adam Duskett <aduskett@gmail.com>
---
Changes v1 -> v2 (all suggested by Arnout)
  - added a wrapper script
Changes v2 -> v3
  - added modules for:
     - supporting busybox system init type
     - fixing a missing symlink for uClibc
Changes v3 -> v4
  - some explanations on the dracut modules in the commit log
  - fixed a bug on the 'require_binary' line in busybox module
  - expanded variables with double quotes and curly braces
  - removed commented out code
  - fixes for 'fakeroot' and 'uclibc' and 'musl' as patches
  - musl and uclibc dynamic fix
  - renamed dracut wrapper
  - disabled when using another init system than systemd or busybox
Changes v4 -> v5
  - add hash file;
  - add DEVELOPERS entries;
  - replace patch 0001 with an intree file and copy in post-install;
  - properly format patch 0000, add signoff, rename to 0001;
  - rename busybox-buildroot to busybox-init;
  - correct the symlink creation for musl and uclibc;
  - remove directory part from the extra modules;
  - remove unused dracut script (identical to dracut_wrapper);
  - switch to prelink-cross instead of cross-ldd;
  - make dracut_wrapper script relocatable;
  - don't set sysroot in wrapper script, expect it to be passed as
    --sysroot argument;
  - call the wrapper script bin/dracut instead of sbin/dracut, and
    rename the original to dracut.real;
  - fix shellcheck warnings in the module scripts.
---
 DEVELOPERS                                    |  2 +
 package/Config.in.host                        |  1 +
 ...001-dracut.sh-don-t-unset-LD_PRELOAD.patch | 29 +++++++++
 package/dracut/Config.in.host                 |  9 +++
 package/dracut/busybox-init-module-setup.sh   | 62 +++++++++++++++++++
 package/dracut/dracut.hash                    |  3 +
 package/dracut/dracut.mk                      | 47 ++++++++++++++
 package/dracut/dracut_wrapper.sh              | 33 ++++++++++
 package/dracut/libc-links-module-setup.sh     | 27 ++++++++
 9 files changed, 213 insertions(+)
 create mode 100644 package/dracut/0001-dracut.sh-don-t-unset-LD_PRELOAD.patch
 create mode 100644 package/dracut/Config.in.host
 create mode 100644 package/dracut/busybox-init-module-setup.sh
 create mode 100644 package/dracut/dracut.hash
 create mode 100644 package/dracut/dracut.mk
 create mode 100644 package/dracut/dracut_wrapper.sh
 create mode 100755 package/dracut/libc-links-module-setup.sh

diff --git a/DEVELOPERS b/DEVELOPERS
index d2bd0d809a..4287fd9cf7 100644
--- a/DEVELOPERS
+++ b/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>
diff --git a/package/Config.in.host b/package/Config.in.host
index 99edeafece..f437ef680c 100644
--- a/package/Config.in.host
+++ b/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"
diff --git a/package/dracut/0001-dracut.sh-don-t-unset-LD_PRELOAD.patch b/package/dracut/0001-dracut.sh-don-t-unset-LD_PRELOAD.patch
new file mode 100644
index 0000000000..87083d2cef
--- /dev/null
+++ b/package/dracut/0001-dracut.sh-don-t-unset-LD_PRELOAD.patch
@@ -0,0 +1,29 @@
+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 is needed to run under fakeroot.
+
+Signed-off-by: Thierry Bultel <thierry.bultel@linatsea.fr>
+Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
+---
+ 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
+
diff --git a/package/dracut/Config.in.host b/package/dracut/Config.in.host
new file mode 100644
index 0000000000..18f562b310
--- /dev/null
+++ b/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
diff --git a/package/dracut/busybox-init-module-setup.sh b/package/dracut/busybox-init-module-setup.sh
new file mode 100644
index 0000000000..2667f866d1
--- /dev/null
+++ b/package/dracut/busybox-init-module-setup.sh
@@ -0,0 +1,62 @@
+#!/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
+
+	ln -s ../bin/busybox "${initdir?}"/sbin/init
+
+	if [ -e "${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 "${initdir?}/usr/lib32"
+	fi
+
+	install_busybox_links "/bin" "busybox"
+	install_busybox_links "/sbin" "../bin/busybox"
+	if [ ! -L /bin ]; then
+		install_busybox_links "/usr/bin" "../../bin/busybox"
+		install_busybox_links "/usr/sbin" "../../bin/busybox"
+	fi
+
+	inst_multiple \
+		/etc/inittab	\
+		/etc/init.d/rcS \
+		/etc/init.d/rcK \
+		/etc/issue	\
+		/etc/fstab	\
+		/etc/group	\
+		/etc/passwd	\
+		/etc/shadow	\
+		/etc/hostname
+}
+
diff --git a/package/dracut/dracut.hash b/package/dracut/dracut.hash
new file mode 100644
index 0000000000..3cda736856
--- /dev/null
+++ b/package/dracut/dracut.hash
@@ -0,0 +1,3 @@
+# Locally computed
+sha256  4baa08206cceeb124dbf1075a0daf774b5a8f144ce2e01d82a144af3020fd65b  dracut-055.tar.xz
+sha256  8177f97513213526df2cf6184d8ff986c675afb514d4e68a404010521b880643  COPYING
diff --git a/package/dracut/dracut.mk b/package/dracut/dracut.mk
new file mode 100644
index 0000000000..7afec80c0e
--- /dev/null
+++ b/package/dracut/dracut.mk
@@ -0,0 +1,47 @@
+################################################################################
+#
+# dracut
+#
+################################################################################
+
+DRACUT_VERSION = 055
+DRACUT_SOURCE = dracut-$(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.sh $(HOST_DIR)/bin/dracut
+endef
+HOST_DRACUT_POST_INSTALL_HOOKS += HOST_DRACUT_POST_INSTALL_WRAPPER_SCRIPT
+
+# When using uClibc or musl, there must be "ls-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 $(host-autotools-package))
diff --git a/package/dracut/dracut_wrapper.sh b/package/dracut/dracut_wrapper.sh
new file mode 100644
index 0000000000..3f58b0907e
--- /dev/null
+++ b/package/dracut/dracut_wrapper.sh
@@ -0,0 +1,33 @@
+#!/bin/bash
+set -e
+
+# Find the --sysroot argument
+sysroot=
+next_arg=
+for arg; do
+	if [ "$next_arg" = 1 ]; then
+		next_arg=
+		sysroot="$arg"
+		continue
+	fi
+
+	case "$arg" in
+	--sysroot=*)
+		sysroot="${arg#*=}"
+		;;
+	--sysroot)
+		next_arg=1
+		;;
+	esac
+done
+if [ -z "$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" "$@"
diff --git a/package/dracut/libc-links-module-setup.sh b/package/dracut/libc-links-module-setup.sh
new file mode 100755
index 0000000000..e15b216e6e
--- /dev/null
+++ b/package/dracut/libc-links-module-setup.sh
@@ -0,0 +1,27 @@
+#!/bin/bash
+
+# Adds the missing links for uClibc or musl, if needed
+
+check() {
+	return 0
+}
+
+depends() {
+	return 0
+}
+
+install() {
+	# Despite of the fact that the listed dependency (reported by readelf -d)
+	# is purely /lib/libc.so, the musl symlink is needed anyway.
+	musl_link="$(find "${dracutsysrootdir?}/lib" -name "ld-musl-*.so*")"
+	if [ -n "$musl_link" ] ; then
+		ln -s libc.so "${initdir?}/lib/$(basename "${musl_link}")"
+	fi
+
+	# Same for uClibc, the listed dependency
+	# is ld-uClibc.so.1, the loader needs the ld-uClibc.so.0, too
+	uclibc_link="$(find "${dracutsysrootdir?}/lib" -name "ld-uClibc-*.so*")"
+	if [ -n "$uclibc_link" ] ; then
+		ln -s ld-uClibc.so.1 "${initdir?s}/lib/ld-uClibc.so.0"
+	fi
+}
-- 
2.37.1

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