classes: rootfs-postcommands: autologin root on serial-getty

when empty-root-password AND serial-autologin-root are part of the
IMAGE_FEATURES, save some of the developers time by not having to type
the (then still sole) 'root' username on the serial console after each
and every reboot

this is done by inserting '--autologin root' into the command line of
the responsible 'getty' service

(From OE-Core rev: 01b3cb46405f814e27cab5290118211786cd63a0)

Signed-off-by: Johannes Schneider <johannes.schneider@leica-geosystems.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes-recipe/core-image.bbclass

@@ -31,6 +31,7 @@
 #   - allow-empty-password
 #   - allow-root-login
 #   - post-install-logging
+# - serial-autologin-root - with 'empty-root-password': autologin 'root' on the serial console
 # - dev-pkgs            - development packages (headers, etc.) for all installed packages in the rootfs
 # - dbg-pkgs            - debug symbol packages for all installed packages in the rootfs
 # - lic-pkgs            - license packages for all installed pacakges in the rootfs, requires

meta/classes-recipe/image.bbclass

@@ -39,7 +39,7 @@ INHIBIT_DEFAULT_DEPS = "1"
 # IMAGE_FEATURES may contain any available package group
 IMAGE_FEATURES ?= ""
 IMAGE_FEATURES[type] = "list"
-IMAGE_FEATURES[validitems] += "debug-tweaks read-only-rootfs read-only-rootfs-delayed-postinsts stateless-rootfs empty-root-password allow-empty-password allow-root-login post-install-logging overlayfs-etc"
+IMAGE_FEATURES[validitems] += "debug-tweaks read-only-rootfs read-only-rootfs-delayed-postinsts stateless-rootfs empty-root-password allow-empty-password allow-root-login serial-autologin-root post-install-logging overlayfs-etc"
 
 # Generate companion debugfs?
 IMAGE_GEN_DEBUGFS ?= "0"

meta/classes-recipe/rootfs-postcommands.bbclass

@@ -13,6 +13,9 @@ ROOTFS_POSTPROCESS_COMMAND += '${@bb.utils.contains_any("IMAGE_FEATURES", [ 'deb
 # Allow dropbear/openssh to accept root logins if debug-tweaks or allow-root-login is enabled
 ROOTFS_POSTPROCESS_COMMAND += '${@bb.utils.contains_any("IMAGE_FEATURES", [ 'debug-tweaks', 'allow-root-login' ], "ssh_allow_root_login; ", "",d)}'
 
+# Autologin the root user on the serial console, if empty-root-password and serial-autologin-root are active
+ROOTFS_POSTPROCESS_COMMAND += '${@bb.utils.contains("IMAGE_FEATURES", [ 'empty-root-password', 'serial-autologin-root' ], "serial_autologin_root; ", "",d)}'
+
 # Enable postinst logging if debug-tweaks or post-install-logging is enabled
 ROOTFS_POSTPROCESS_COMMAND += '${@bb.utils.contains_any("IMAGE_FEATURES", [ 'debug-tweaks', 'post-install-logging' ], "postinst_enable_logging; ", "",d)}'
 
@@ -201,6 +204,23 @@ ssh_allow_root_login () {
 	fi
 }
 
+#
+# Autologin the 'root' user on the serial terminal,
+# if empty-root-password' AND 'serial-autologin-root are enabled
+#
+serial_autologin_root () {
+	if ${@bb.utils.contains("DISTRO_FEATURES", "sysvinit", "true", "false", d)}; then
+		# add autologin option to util-linux getty only
+		sed -i 's/options="/&--autologin root /' \
+			"${IMAGE_ROOTFS}${base_bindir}/start_getty"
+	elif ${@bb.utils.contains("DISTRO_FEATURES", "systemd", "true", "false", d)}; then
+		if [ -e ${IMAGE_ROOTFS}${systemd_system_unitdir}/serial-getty@.service ]; then
+			sed -i '/^\s*ExecStart\b/ s/getty /&--autologin root /' \
+				"${IMAGE_ROOTFS}${systemd_system_unitdir}/serial-getty@.service"
+		fi
+	fi
+}
+
 python sort_passwd () {
     import rootfspostcommands
     rootfspostcommands.sort_passwd(d.expand('${IMAGE_ROOTFS}${sysconfdir}'))

meta/recipes-core/sysvinit/sysvinit-inittab/start_getty

@@ -9,9 +9,10 @@ case $(readlink -f "${getty}") in
         if [ -x "/usr/bin/setsid" ] ; then
             setsid="/usr/bin/setsid"
         fi
+        options=""
         ;;
 esac
 
 if [ -e /sys/class/tty/$2 -a -c /dev/$2 ]; then
-	${setsid:-} ${getty} -L $1 $2 $3
+	${setsid:-} ${getty} ${options:-} -L $1 $2 $3
 fi