genkernel: add simple udev support, include udev into initramfs if --udev

defaults/initrd.defaults

@@ -55,6 +55,8 @@ ROOT_LINKS='bin sbin lib lib32 lib64 boot usr opt emul'
 ROOT_TREES='etc root home var'
 KSUFF='.ko'
 
+UDEVD='/sbin/udevd'
+MDEVD='/sbin/mdev'
 REAL_ROOT=''
 CONSOLE='/dev/console'
 NEW_ROOT='/newroot'

defaults/initrd.scripts

@@ -344,6 +344,19 @@ fs_type_in_use() {
 	cut -d ' ' -f 3 < /proc/mounts | fgrep -q "${fs_type}"
 }
 
+is_udev() {
+	[ -x "${UDEVD}" ] && [ -z "${USE_MDEV}" ] && return 0
+	return 1
+}
+
+is_mdev() {
+	if [ ! -x "${UDEVD}" ] || [ -n "${USE_MDEV}" ]
+	then
+		return 0
+	fi
+	return 1
+}
+
 mount_devfs () {
 	# Use devtmpfs if enabled in kernel,
 	# else tmpfs. Always run mdev just in case
@@ -736,6 +749,8 @@ startVolumes() {
 			fi
 		fi
 	fi
+
+	is_udev && udevadm settle
 }
 
 startiscsi() {

defaults/linuxrc

@@ -22,6 +22,7 @@ fi
 
 mount -t proc -o noexec,nosuid,nodev proc /proc >/dev/null 2>&1
 mount -o remount,rw / >/dev/null 2>&1
+mount -t tmpfs -o rw,nosuid,nodev,relatime,mode=755 none /run 2>&1
 
 # Set up symlinks
 /bin/busybox --install -s
@@ -87,6 +88,9 @@ do
 		isoboot=*)
 			ISOBOOT=${x#*=}
 		;;
+		domdev)
+			USE_MDEV=1
+		;;
 		# Start Volume manager options
 		dolvm)
 			USE_LVM_NORMAL=1
@@ -327,14 +331,18 @@ mount_devfs
 # Mount sysfs
 mount_sysfs
 
-# Initialize mdev
-good_msg 'Activating mdev'
-
-# Serialize hotplug events
-touch /dev/mdev.seq
-
 # Setup hotplugging for firmware loading
-echo /sbin/mdev > /proc/sys/kernel/hotplug
+if is_udev
+then
+	good_msg 'Activating udev'
+	echo "${UDEVD}" > /proc/sys/kernel/hotplug
+	echo "" > /sys/kernel/uevent_helper
+else
+	good_msg 'Activating mdev'
+	# Serialize hotplug events
+	touch /dev/mdev.seq
+	echo "${MDEVD}" > /proc/sys/kernel/hotplug
+fi
 
 # Load modules listed in MY_HWOPTS if /lib/modules exists for the running kernel
 if [ -z "${DO_modules}" ]
@@ -357,8 +365,19 @@ else
 	good_msg 'Skipping module load; no modules in the ramdisk!'
 fi
 
-# Ensure that device nodes are properly configured
+if is_udev
-mdev -s || bad_msg "mdev -s failed"
+then
+	# Initialize udev
+	"${UDEVD}" --daemon --resolve-names=never && \
+		udevadm trigger --action=add && \
+		udevadm settle || bad_msg "udevd failed to run"
+elif is_mdev
+then
+	# Ensure that device nodes are properly configured
+	"${MDEVD}" -s || bad_msg "mdev -s failed"
+else
+	bad_msg "Cannot find either udev or mdev"
+fi
 
 # Apply scan delay if specified
 sdelay
@@ -375,7 +394,7 @@ fi
 setup_btrfsctl
 
 # Setup md device nodes if they dont exist
-setup_md_device
+is_mdev && setup_md_device
 
 # Scan volumes
 startVolumes
@@ -914,10 +933,16 @@ good_msg "Booting (initramfs)"
 cd "${CHROOT}"
 mkdir "${CHROOT}/proc" "${CHROOT}/sys" "${CHROOT}/run" 2>/dev/null
 
+is_udev && udevadm settle
+
+if is_udev
+then
+	udevadm control --exit || bad_msg "Unable to terminate udevd"
+fi
+
 # If devtmpfs is mounted, try move it to the new root
-# If that fails, try to unmount all possible mounts of
+# If that fails, try to unmount all possible mounts of devtmpfs as stuff breaks otherwise
-# devtmpfs as stuff breaks otherwise
+for fs in /run /dev /sys /proc
-for fs in /dev /sys /proc
 do
 	if grep -qs "$fs" /proc/mounts
 	then

doc/genkernel.8.txt

@@ -247,6 +247,10 @@ INITIALIZATION
 *--*[*no-*]*keymap*::
     Enables or disables keymap selection at boot.
 
+*--*[*no-*]*udev*::
+        Adds or exclude in udev support from static binaries if they exist on
+        the system.
+
 *--*[*no-*]*lvm*::
 	Adds or skips in LVM support from static binaries if they exist on the
 	system,  or compile static LVM binaries if static ones do not exist.

gen_cmdline.sh

@@ -86,6 +86,8 @@ longusage() {
   echo "	--do-keymap-auto	Forces keymap selection at boot"
   echo "	--keymap		Enables keymap selection support"
   echo "	--no-keymap		Disables keymap selection support"
+  echo "	--udev			Include udev and use it instead of mdev"
+  echo "	--no-udev		Exclude udev and use it instead of mdev"
   echo "	--lvm			Include LVM support"
   echo "	--no-lvm		Exclude LVM support"
   echo "	--mdadm			Include MDADM/MDMON support"
@@ -270,6 +272,10 @@ parse_cmdline() {
 			CMD_KEYMAP=`parse_optbool "$*"`
 			print_info 2 "CMD_KEYMAP: ${CMD_KEYMAP}"
 			;;
+		--udev|--no-udev)
+			CMD_UDEV=`parse_optbool "$*"`
+			print_info 2 "CMD_UDEV: ${CMD_UDEV}"
+			;;
 		--lvm|--no-lvm)
 			CMD_LVM=`parse_optbool "$*"`
 			print_info 2 "CMD_LVM: ${CMD_LVM}"

gen_determineargs.sh

@@ -111,6 +111,7 @@ determine_real_args() {
 	set_config_with_override BOOL   SYMLINK              CMD_SYMLINK
 	set_config_with_override STRING INSTALL_MOD_PATH     CMD_INSTALL_MOD_PATH
 	set_config_with_override BOOL   OLDCONFIG            CMD_OLDCONFIG
+	set_config_with_override BOOL   UDEV                 CMD_UDEV
 	set_config_with_override BOOL   LVM                  CMD_LVM
 	set_config_with_override BOOL   DMRAID               CMD_DMRAID
 	set_config_with_override BOOL   ISCSI                CMD_ISCSI

gen_initramfs.sh

@@ -563,6 +563,39 @@ append_gpg() {
 	rm -rf "${TEMP}/initramfs-gpg-temp" > /dev/null
 }
 
+append_udev() {
+	if [ -d "${TEMP}/initramfs-udev-temp" ]
+	then
+		rm -r "${TEMP}/initramfs-udev-temp"
+	fi
+
+	udev_files="
+		/lib/udev/rules.d/50-udev-default.rules
+		/lib/udev/rules.d/60-persistent-storage.rules
+		/lib/udev/rules.d/80-drivers.rules
+		/lib/udev/rules.d/99-systemd.rules
+		/etc/udev/udev.conf
+	"
+	for f in ${udev_files}; do
+		mkdir -p "${TEMP}/initramfs-udev-temp"/$(dirname "${f}") || \
+			gen_die "cannot create rules.d directory"
+		cp "${f}" "${TEMP}/initramfs-udev-temp/${f}" || \
+			gen_die "cannot copy ${f} from system"
+	done
+
+	# Copy binaries
+	copy_binaries "${TEMP}/initramfs-udev-temp" \
+		/sbin/udevd /bin/udevadm /lib/udev/scsi_id \
+		/lib/udev/ata_id /lib/udev/mtd_probe
+
+	cd "${TEMP}/initramfs-udev-temp/"
+	log_future_cpio_content
+	find . -print | cpio ${CPIO_ARGS} --append -F "${CPIO}" \
+			|| gen_die "compressing udev cpio"
+	cd "${TEMP}"
+	rm -rf "${TEMP}/initramfs-udev-temp" > /dev/null
+}
+
 print_list()
 {
 	local x
@@ -773,6 +806,7 @@ create_initramfs() {
 		|| gen_die "Could not create empty cpio at ${CPIO}"
 
 	append_data 'base_layout'
+	append_data 'udev' "${UDEV}"
 	append_data 'auxilary' "${BUSYBOX}"
 	append_data 'busybox' "${BUSYBOX}"
 	isTrue "${CMD_E2FSPROGS}" && append_data 'e2fsprogs'