Use switch_root from util-linux

switch_root from busybox does not move /dev, /sys, /proc and /run.
If we do that manually there is a small window for a race condition
when /dev, /sys or /proc is still needed but already moved. switch_root
from util-linux will move these mounts on its own and will therefore
avoid any potential problems.

Signed-off-by: Thomas Deutschmann <whissi@gentoo.org>

3 files changed, 38 insertions, 44 deletions

diff --git a/defaults/linuxrc b/defaults/linuxrc
index 5c3b0ce..afb91d8 100644
--- a/defaults/linuxrc
+++ b/defaults/linuxrc
@@ -1335,34 +1335,6 @@ then
 	run pkill -9 udevd >/dev/null 2>&1
 fi
 
-# If devtmpfs is mounted, try move it to the new root
-# If that fails, try to unmount all possible mounts of
-# devtmpfs as stuff breaks otherwise
-for fs in /run /dev /sys /proc
-do
-	if grep -qs "${fs}" /proc/mounts
-	then
-		chroot_dir="${CHROOT}${fs}"
-		[ ! -d "${chroot_dir}" ] && run mkdir -p "${chroot_dir}"
-
-		if ! run mount -o move ${fs} "${CHROOT}"${fs}
-		then
-			run umount ${fs} || \
-			bad_msg "Failed to move and unmount the ramdisk ${fs}!"
-		fi
-
-		unset chroot_dir
-	fi
-done
-
-if [ ! -e "${CHROOT}/dev/console" ] || [ ! -e "${CHROOT}/dev/null" ]
-then
-	bad_msg "ERROR: your real /dev is missing console and null"
-elif [ -e /etc/initrd.splash -a ! -e "${CHROOT}/dev/tty1" ]
-then
-	bad_msg "ERROR: your real /dev is missing tty1, required for splash"
-fi
-
 # Run debug shell if requested
 rundebugshell "before entering switch_root"
 
@@ -1380,8 +1352,8 @@ elif [ $$ != 1 ]
 then
 	bad_msg "PID was not 1! switch_root would fail"
 else
-	good_msg "Switching to real root: switch_root -c /dev/console ${CHROOT} ${init} ${init_opts}"
-	exec switch_root -c "/dev/console" "${CHROOT}" "${init}" ${init_opts}
+	good_msg "Switching to real root: switch_root ${CHROOT} ${init} ${init_opts}"
+	exec switch_root "${CHROOT}" "${init}" ${init_opts}
 fi
 
 # If we get here, something bad has happened
diff --git a/gen_initramfs.sh b/gen_initramfs.sh
index 875068c..479e6a6 100755
--- a/gen_initramfs.sh
+++ b/gen_initramfs.sh
@@ -635,9 +635,9 @@ append_bcache() {
 	fi
 }
 
-append_blkid() {
-	local PN="util-linux"
-	local TDIR="${TEMP}/initramfs-blkid-temp"
+append_unionfs_fuse() {
+	local PN=unionfs-fuse
+	local TDIR="${TEMP}/initramfs-${PN}-temp"
 	if [ -d "${TDIR}" ]
 	then
 		rm -r "${TDIR}" || gen_die "Failed to clean out existing '${TDIR}'!"
@@ -650,13 +650,9 @@ append_blkid() {
 	unpack "$(get_gkpkg_binpkg "${PN}")" "${TDIR}"
 
 	cd "${TDIR}" || gen_die "Failed to chdir to '${TDIR}'!"
-
-	# Delete unneeded files
-	rm -rf usr/
-
 	log_future_cpio_content
 	find . -print0 | "${CPIO_COMMAND}" ${CPIO_ARGS} --append -F "${CPIO_ARCHIVE}" \
-		|| gen_die "Failed to append blkid to cpio!"
+		|| gen_die "Failed to append ${PN} to cpio!"
 
 	cd "${TEMP}" || die "Failed to chdir to '${TEMP}'!"
 	if isTrue "${CLEANUP}"
@@ -665,9 +661,9 @@ append_blkid() {
 	fi
 }
 
-append_unionfs_fuse() {
-	local PN=unionfs-fuse
-	local TDIR="${TEMP}/initramfs-${PN}-temp"
+append_util-linux() {
+	local PN="util-linux"
+	local TDIR="${TEMP}/initramfs-util-linux-temp"
 	if [ -d "${TDIR}" ]
 	then
 		rm -r "${TDIR}" || gen_die "Failed to clean out existing '${TDIR}'!"
@@ -680,6 +676,10 @@ append_unionfs_fuse() {
 	unpack "$(get_gkpkg_binpkg "${PN}")" "${TDIR}"
 
 	cd "${TDIR}" || gen_die "Failed to chdir to '${TDIR}'!"
+
+	# Delete unneeded files
+	rm -rf usr/
+
 	log_future_cpio_content
 	find . -print0 | "${CPIO_COMMAND}" ${CPIO_ARGS} --append -F "${CPIO_ARCHIVE}" \
 		|| gen_die "Failed to append ${PN} to cpio!"
@@ -1930,11 +1930,11 @@ create_initramfs() {
 	CPIO_ARCHIVE="${TMPDIR}/${GK_FILENAME_TEMP_INITRAMFS}"
 	append_data 'devices' # WARNING, must be first!
 	append_data 'base_layout'
+	append_data 'util-linux'
 	append_data 'eudev'
 	append_data 'devicemanager'
 	append_data 'auxilary' "${BUSYBOX}"
 	append_data 'busybox' "${BUSYBOX}"
-	append_data 'blkid' "${DISKLABEL}"
 	append_data 'b2sum' "${B2SUM}"
 	append_data 'btrfs' "${BTRFS}"
 	append_data 'dmraid' "${DMRAID}"
diff --git a/gkbuilds/util-linux.gkbuild b/gkbuilds/util-linux.gkbuild
index 81670c1..40ea1fb 100644
--- a/gkbuilds/util-linux.gkbuild
+++ b/gkbuilds/util-linux.gkbuild
@@ -1,6 +1,18 @@
 # Copyright 1999-2020 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
+src_prepare() {
+	default
+
+	# Build static switch_root
+	sed -i \
+		-e '/^switch_root_SOURCES =.*/a switch_root_LDFLAGS = -all-static' \
+		sys-utils/Makemodule.am \
+		|| die
+
+	gkautoreconf
+}
+
 src_configure() {
 	export ac_cv_header_security_pam_misc_h=no
 	export ac_cv_header_security_pam_appl_h=no
@@ -16,6 +28,7 @@ src_configure() {
 		--disable-widechar
 		--without-python
 		--disable-pylibmount
+		--enable-switch_root
 		--enable-static-programs=blkid
 	)
 
@@ -37,6 +50,15 @@ src_install() {
 	cp -a blkid.static "${D}"/sbin/blkid \
 		|| die "Failed to copy '${S}/blkid.static' to '${D}/sbin/blkid'!"
 
-	"${STRIP}" --strip-all "${D}"/sbin/blkid \
-		|| die "Failed to strip '${D}/sbin/blkid'!"
+	cp -a switch_root "${D}"/sbin/switch_root \
+		|| die "Failed to copy '${S}/switch_root' to '${D}/sbin/switch_root'!"
+
+	local sbin
+	for sbin in \
+		"${D}/sbin/blkid" \
+		"${D}/sbin/switch_root" \
+	; do
+		"${STRIP}" --strip-all "${sbin}" \
+			|| die "Failed to strip '${sbin}'!"
+	done
 }