package/petitboot: run script when exiting to shell

When the user selects the shell escape option from the petitboot menu,
reset the terminal so output is raw rather than being confined to the
ncurses window set up for the petitboot menu, and print some helpful
text before running the shell.

To do this, override the default HOST_PROG_SH (/bin/sh) with a small
script. Doing so also enables someone to customize this behavior by
overlaying a different script.

Signed-off-by: Reza Arbab <arbab@linux.ibm.com>
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>

package/petitboot/pb-shell

@@ -0,0 +1,10 @@
+#!/bin/sh
+
+reset
+
+cat <<EOM
+Exiting petitboot. Type 'exit' to return.
+You may run 'pb-sos' to gather diagnostic data.
+EOM
+
+exec /bin/sh

package/petitboot/petitboot.mk

@@ -30,6 +30,7 @@ PETITBOOT_CONF_OPTS = \
 	--without-twin-x11 \
 	$(if $(BR2_PACKAGE_BUSYBOX),--enable-busybox,--disable-busybox) \
 	HOST_PROG_KEXEC=/usr/sbin/kexec \
+	HOST_PROG_SH=/usr/libexec/petitboot/pb-shell \
 	HOST_PROG_SHUTDOWN=/usr/libexec/petitboot/kexec-restart
 
 # HPA and Busybox tftp are supported. HPA tftp is part of Buildroot's tftpd
@@ -94,6 +95,8 @@ define PETITBOOT_POST_INSTALL
 		$(TARGET_DIR)/etc/init.d/S15pb-discover
 	$(INSTALL) -D -m 0755 $(PETITBOOT_PKGDIR)/pb-console \
 		$(TARGET_DIR)/etc/init.d/pb-console
+	$(INSTALL) -D -m 0755 $(PETITBOOT_PKGDIR)/pb-shell \
+		$(TARGET_DIR)/usr/libexec/petitboot/pb-shell
 
 	mkdir -p $(TARGET_DIR)/etc/udev/rules.d
 	for port in $(PETITBOOT_GETTY_PORT); do \