base-files: add support for staged sysupgrades from failsafe mode

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>

package/base-files/files/lib/preinit/40_run_failsafe_hook

@@ -5,8 +5,12 @@
 run_failsafe_hook() {
     [ "$pi_preinit_no_failsafe" = "y" ] && return
     if [ "$FAILSAFE" = "true" ]; then
+	lock /tmp/.failsafe
 	boot_run_hook failsafe
-	lock -w /tmp/.failsafe
+	while [ ! -e /tmp/sysupgrade ]; do
+	    lock -w /tmp/.failsafe
+	done
+	exit
     fi
 }
 

package/base-files/files/lib/preinit/99_10_failsafe_login

@@ -8,10 +8,13 @@ failsafe_netlogin () {
 }
 
 failsafe_shell() {
-	lock /tmp/.failsafe
-	ash --login
-	echo "Please reboot system when done with failsafe network logins"
-	while true; do sleep 1; done
+	local console="$(sed -e 's/ /\n/g' /proc/cmdline | grep '^console=' | head -1 | sed -e 's/^console=//' -e 's/,.*//')"
+	[ -n "$console" ] || console=console
+	[ -c "/dev/$console" ] || return 0
+	while true; do
+		ash --login <"/dev/$console" >"/dev/$console" 2>"/dev/$console"
+		sleep 1
+	done &
 }
 
 boot_hook_add failsafe failsafe_netlogin