kdump: Rebuild default initrd for firmware assisted dump

The current kdump infrastructure builds a separate initrd which then
gets loaded into memory by kexec-tools for use by  kdump kernel. But
firmware  assisted dump (FADUMP) does not  use kexec-based approach.
After crash, firmware reboots  the  partition and  loads grub loader
like the normal  booting process does. Hence in the FADUMP approach,
the second kernel  (after crash) will always  use the default initrd
(OS built). So, to support FADUMP, change is required,  as in to add
dump capturing steps, in this initrd.

The  current kdumpctl script implementation  already has the code to
build initrd  using mkdumprd. This patch  uses  the new  '--rebuild'
option introduced, in  dracut, to incrementally build  the initramfs
image. Before rebuilding, we may need to  probe the initrd image for
fadump support, to avoid  rebuilding the initrd image multiple times
unnecessarily. This can be done using "lsinitrd" tool with the newly
proposed '--mod' option  & inspecting the presence of "kdumpbase" in
the list of modules of default initrd image. We rebuild the image if
only "kdumpbase" module is missing in the initrd image. Also, before
rebuilding, a backup of default initrd image is taken.

Kexec-tools package in rhel7 is now enhanced to insert a out-of-tree
kdump  module for  dracut,  which is responsible for  adding  vmcore
capture  steps into initrd,  if dracut is  invoked  with  "IN_KDUMP"
environment variable set to 1.  mkdumprd script exports "IN_KDUMP=1"
environment variable before  invoking  dracut to build kdump initrd.
This patch relies on this current mechanism of kdump init script.

Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Hari Bathini <hbathini@linux.vnet.ibm.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>

kdumpctl

@@ -9,6 +9,7 @@ MKDUMPRD="/sbin/mkdumprd -f"
 SAVE_PATH=/var/crash
 SSH_KEY_LOCATION="/root/.ssh/kdump_id_rsa"
 DUMP_TARGET=""
+TARGET_INITRD=""
 FADUMP_ENABLED_SYS_NODE="/sys/kernel/fadump_enabled"
 FADUMP_REGISTER_SYS_NODE="/sys/kernel/fadump_registered"
 #kdump shall be the default dump mode
@@ -143,13 +144,47 @@ save_core()
 	fi
 }
 
-rebuild_initrd()
+rebuild_fadump_initrd()
 {
-	$MKDUMPRD $kdump_initrd $kdump_kver
+	local target_initrd_tmp
+
+	# backup fadump initrd for reference before replacing it
+	backup_initrd
+
+	target_initrd_tmp="$TARGET_INITRD.tmp"
+	$MKDUMPRD $target_initrd_tmp --rebuild $TARGET_INITRD --kver $kdump_kver
+	if [ $? != 0 ]; then
+		echo "mkdumprd: failed to rebuild initrd with fadump support" >&2
+		return 1
+	fi
+
+	# updating fadump initrd
+	mv $target_initrd_tmp $TARGET_INITRD
+	sync
+
+	return 0
+}
+
+rebuild_kdump_initrd()
+{
+	$MKDUMPRD $TARGET_INITRD $kdump_kver
 	if [ $? != 0 ]; then
 		echo "mkdumprd: failed to make kdump initrd" >&2
 		return 1
 	fi
+
+	return 0
+}
+
+rebuild_initrd()
+{
+	if [ $DEFAULT_DUMP_MODE == "fadump" ]; then
+		rebuild_fadump_initrd
+	else
+		rebuild_kdump_initrd
+	fi
+
+	return $?
 }
 
 #$1: the files to be checked with IFS=' '
@@ -174,6 +209,18 @@ check_executable()
 	done
 }
 
+backup_initrd()
+{
+	local target_initrd_bak
+
+	# Check if backup initrd is already present.
+	target_initrd_bak="$TARGET_INITRD.bak"
+	if [ ! -e $target_initrd_bak ];then
+		echo "Backing up $TARGET_INITRD"
+		cp $TARGET_INITRD $target_initrd_bak
+	fi
+}
+
 check_config()
 {
 	local nr
@@ -240,10 +287,24 @@ get_pcs_cluster_modified_files()
 	echo $modified_files
 }
 
+setup_target_initrd()
+{
+	if [ $DEFAULT_DUMP_MODE == "fadump" ]; then
+		TARGET_INITRD="${KDUMP_BOOTDIR}/initramfs-${kdump_kver}.img"
+		if [ ! -s "$TARGET_INITRD" ]; then
+			echo "Error: No initrd found to rebuild!"
+			return 1
+		fi
+	else
+		TARGET_INITRD="${KDUMP_BOOTDIR}/initramfs-${kdump_kver}kdump.img"
+	fi
+}
+
 check_rebuild()
 {
 	local extra_modules modified_files=""
 	local _force_rebuild force_rebuild="0"
+	local initramfs_has_fadump
 
 	if [ -z "$KDUMP_KERNELVER" ]; then
 		kdump_kver=`uname -r`
@@ -252,7 +313,10 @@ check_rebuild()
 	fi
 
 	kdump_kernel="${KDUMP_BOOTDIR}/${KDUMP_IMG}-${kdump_kver}${KDUMP_IMG_EXT}"
-	kdump_initrd="${KDUMP_BOOTDIR}/initramfs-${kdump_kver}kdump.img"
+	setup_target_initrd
+	if [ $? -ne 0 ]; then
+		return 1
+	fi
 
 	_force_rebuild=`grep ^force_rebuild $KDUMP_CONFIG_FILE 2>/dev/null`
 	if [ $? -eq 0 ]; then
@@ -269,8 +333,8 @@ check_rebuild()
 
 	#check to see if dependent files has been modified
 	#since last build of the image file
-	if [ -f $kdump_initrd ]; then
+	if [ -f $TARGET_INITRD ]; then
-		image_time=`stat -c "%Y" $kdump_initrd 2>/dev/null`
+		image_time=`stat -c "%Y" $TARGET_INITRD 2>/dev/null`
 	else
 		image_time=0
 	fi
@@ -295,10 +359,15 @@ check_rebuild()
 		fi
 	done
 
+	#check if target initrd has fadump support
+	initramfs_has_fadump=`lsinitrd -m $TARGET_INITRD | grep ^kdumpbase$ | wc -l`
+
 	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 $kdump_initrd"; echo
+		echo -n "Force rebuild $TARGET_INITRD"; echo
 	elif [ -n "$modified_files" ]; then
 		echo "Detected change(s) in the following file(s):"
 		echo -n "  "; echo "$modified_files" | sed 's/\s/\n  /g'
@@ -306,7 +375,7 @@ check_rebuild()
 		return 0
 	fi
 
-	echo "Rebuilding $kdump_initrd"
+	echo "Rebuilding $TARGET_INITRD"
 	rebuild_initrd
 	return $?
 }
@@ -359,7 +428,7 @@ load_kdump()
 
 	$KEXEC $KEXEC_ARGS $standard_kexec_args \
 		--command-line="$KDUMP_COMMANDLINE" \
-		--initrd=$kdump_initrd $kdump_kernel 2>/dev/null
+		--initrd=$TARGET_INITRD $kdump_kernel 2>/dev/null
 	if [ $? == 0 ]; then
 		echo "kexec: loaded kdump kernel"
 		return 0