fadump: restore default initrd when fadump mode is disabled

When fadump mode is enabled, the default initrd is rebuilt with kdump
dracut module. As the default initrd is altered, the original default
initrd is backed up. But we are not restoring it when fadump mode is
disabled. This patch tries to restore the backed up default initrd on
disabling fadump mode.

Signed-off-by: Hari Bathini <hbathini@linux.vnet.ibm.com>
Acked-by: Dave Young <dyoung@redhat.com>

kdumpctl

@@ -8,7 +8,10 @@ KDUMP_CONFIG_FILE="/etc/kdump.conf"
 MKDUMPRD="/sbin/mkdumprd -f"
 SAVE_PATH=/var/crash
 SSH_KEY_LOCATION="/root/.ssh/kdump_id_rsa"
+INITRD_CHECKSUM_LOCATION="/boot/.fadump_initrd_checksum"
 DUMP_TARGET=""
+DEFAULT_INITRD=""
+DEFAULT_INITRD_BAK=""
 TARGET_INITRD=""
 FADUMP_ENABLED_SYS_NODE="/sys/kernel/fadump_enabled"
 FADUMP_REGISTER_SYS_NODE="/sys/kernel/fadump_registered"
@@ -158,9 +161,6 @@ rebuild_fadump_initrd()
 {
 	local target_initrd_tmp
 
-	# backup fadump initrd for reference before replacing it
-	backup_initrd
-
 	# this file tells the initrd is fadump enabled
 	touch /tmp/fadump.initramfs
 	target_initrd_tmp="$TARGET_INITRD.tmp"
@@ -224,15 +224,39 @@ check_executable()
 	done
 }
 
-backup_initrd()
+backup_default_initrd()
 {
-	local target_initrd_bak
+	if [ ! -e $DEFAULT_INITRD_BAK ]; then
+		echo "Backing up $DEFAULT_INITRD before rebuild."
+		# save checksum to verify before restoring
+		sha1sum $DEFAULT_INITRD > $INITRD_CHECKSUM_LOCATION
+		cp $DEFAULT_INITRD $DEFAULT_INITRD_BAK
+		if [ $? -ne 0 ]; then
+			echo "WARNING: failed to backup $DEFAULT_INITRD."
+			rm -f $DEFAULT_INITRD_BAK
+		fi
+	fi
+}
 
-	# Check if backup initrd is already present.
+restore_default_initrd()
-	target_initrd_bak="$TARGET_INITRD.bak"
+{
-	if [ ! -e $target_initrd_bak ];then
+	# If a backup initrd exists, we must be switching back from
-		echo "Backing up $TARGET_INITRD"
+	# fadump to kdump. Restore the original default initrd.
-		cp $TARGET_INITRD $target_initrd_bak
+	if [ -f $DEFAULT_INITRD_BAK ] && [ -f $INITRD_CHECKSUM_LOCATION ]; then
+		# verify checksum before restoring
+		backup_checksum=`sha1sum $DEFAULT_INITRD_BAK | awk '{ print $1 }'`
+		default_checksum=`cat $INITRD_CHECKSUM_LOCATION | awk '{ print $1 }'`
+		if [ "$default_checksum" != "$backup_checksum" ]; then
+			echo "WARNING: checksum mismatch! Can't restore original initrd.."
+		else
+			rm -f $INITRD_CHECKSUM_LOCATION
+			mv $DEFAULT_INITRD_BAK $DEFAULT_INITRD
+			if [[ $? -eq 0 ]]; then
+				echo -n "Restoring original initrd as fadump mode "
+				echo "is disabled."
+				sync
+			fi
+		fi
 	fi
 }
 
@@ -324,10 +348,12 @@ check_boot_dir()
 	fi
 }
 
-setup_target_initrd()
+setup_initrd()
 {
+	DEFAULT_INITRD="${KDUMP_BOOTDIR}/initramfs-`uname -r`.img"
+	DEFAULT_INITRD_BAK="${KDUMP_BOOTDIR}/.initramfs-`uname -r`.img.default"
 	if [ $DEFAULT_DUMP_MODE == "fadump" ]; then
-		TARGET_INITRD="${KDUMP_BOOTDIR}/initramfs-${kdump_kver}.img"
+		TARGET_INITRD="$DEFAULT_INITRD"
 		if [ ! -s "$TARGET_INITRD" ]; then
 			echo "Error: No initrd found to rebuild!"
 			return 1
@@ -508,7 +534,6 @@ check_rebuild()
 	local extra_modules
 	local _force_rebuild force_rebuild="0"
 	local ret system_modified="0"
-	local initramfs_has_fadump
 
 	check_boot_dir
 
@@ -519,7 +544,7 @@ check_rebuild()
 	fi
 
 	kdump_kernel="${KDUMP_BOOTDIR}/${KDUMP_IMG}-${kdump_kver}${KDUMP_IMG_EXT}"
-	setup_target_initrd
+	setup_initrd
 	if [ $? -ne 0 ]; then
 		return 1
 	fi
@@ -551,15 +576,11 @@ check_rebuild()
 		system_modified="1"
 	fi
 
-	#check if target initrd has fadump support
+	if is_mode_switched; then
-	if [ "$DEFAULT_DUMP_MODE" = "fadump" ] && [ -f "$TARGET_INITRD" ]; then
+		echo -n "Dump mode changed from last boot."; echo
-		initramfs_has_fadump=`lsinitrd -m $TARGET_INITRD | grep ^kdumpbase$ | wc -l`
+		handle_mode_switch
-	fi
+	elif [ $image_time -eq 0 ]; then
-
-	if [ $image_time -eq 0 ]; then
 		echo  -n "No kdump initial ramdisk found."; echo
-	elif [ $DEFAULT_DUMP_MODE == "fadump" ] && [ "$initramfs_has_fadump" -eq "0" ]; then
-		echo "$TARGET_INITRD has no fadump support"
 	elif [ "$force_rebuild" != "0" ]; then
 		echo -n "Force rebuild $TARGET_INITRD"; echo
 	elif [ "$system_modified" != "0" ]; then
@@ -718,6 +739,46 @@ propagate_ssh_key()
 	fi
 }
 
+is_mode_switched()
+{
+	local _mod_included
+
+	if [ ! -f $DEFAULT_INITRD ]; then
+		return 1
+	fi
+
+	# find if default initrd has kdumpbase module included.
+	_mod_included=`lsinitrd -m $DEFAULT_INITRD | grep ^kdumpbase$ | wc -l`
+
+	if [ "$DEFAULT_DUMP_MODE" != "fadump" ]; then
+		# If kdumpbase module is included in default initrd,
+		# we must have just switched from fadump mode.
+		if [ "$_mod_included" -eq "1" ]; then
+			return 0
+		fi
+	elif [ "$_mod_included" -eq "0" ]; then
+		# If kdumpbase module is missing in default initrd,
+		# we must have just switched from kdump mode.
+		return 0
+	fi
+
+	return 1
+}
+
+handle_mode_switch()
+{
+	if [ "$DEFAULT_DUMP_MODE" == "fadump" ]; then
+		# backup initrd for reference before replacing it
+		# with fadump aware initrd
+		backup_default_initrd
+	else
+		# check if a backup of default initrd exists. If yes,
+		# it signifies a switch from fadump mode. So, restore
+		# the backed up default initrd.
+		restore_default_initrd
+	fi
+}
+
 is_fadump_capable()
 {
 	# Check if firmware-assisted dump is enabled