ERL-294: run_qemu.sh: use semi-persistent EFI variable storage

Instead of recreating the EFI variable storage with each invocation, the
default behaviour is to persist the EFI variable storage for a given VM
image in /tmp. Files in /tmp should be cleaned up by the system
automatically at reboot, so this shouldn't pollute the host.

This is useful for allowing pstore to make use of the EFI variable
storage for saving crash dumps.

Additionally, add an option for reverting to the previous behaviour of
always creating a temporary file for the EFI variables (-e), and another
option for overwriting any existing variable files (-o).

Signed-off-by: Isaac True <isaac.true@canonical.com>

run_qemu.sh

@@ -12,12 +12,14 @@ TELNET_PORT=""
 SSH_PORT="10022"
 DAEMONISE=""
 PID_FILE=""
+NO_EFI_STORAGE_PERSIST=""
+OVERWRITE_EFI=""
 
 function print_usage {
 	echo "$(basename "${0}"): run an EFI-based NemOS image using QEMU"
 	echo "Made by the NemOS Team <nemos-team@lists.launchpad.net>"
 	echo ""
-	echo "Usage: $(basename "${0}") [-h][-?] -f <path> [-a arch] [-m memory] [-c cpus] [-s port] [-t port] [-p pid] [-d]"
+	echo "Usage: $(basename "${0}") [-h][-?] -f <path> [-a arch] [-m memory] [-c cpus] [-s port] [-t port] [-p pid] [-d] [-e] [-o]"
 	echo ""
 	echo "  -h/-?: Print this help message"
 	echo "  -f:    Path to VM image (required)"
@@ -28,9 +30,11 @@ function print_usage {
 	echo "  -t:    Enable telnet console access on the given port number"
 	echo "  -p:    Write the process PID to the given file"
 	echo "  -d:    Daemonise the VM process"
+	echo "  -e:    Do not use persistent EFI storage (normally it will be saved to /tmp/<VM image file name>.efivars)"
+	echo "  -o:    Overwrite any existing EFI variable storage"
 }
 
-while getopts "h?a:f:c:m:s:t:p:d" opt; do
+while getopts "h?a:f:c:m:s:t:p:deo" opt; do
 	case "${opt}" in
 	h | \?)
 		print_usage
@@ -60,6 +64,12 @@ while getopts "h?a:f:c:m:s:t:p:d" opt; do
 	d)
 		DAEMONISE="1"
 		;;
+	e)
+		NO_EFI_STORAGE_PERSIST="1"
+		;;
+	o)
+		OVERWRITE_EFI="1"
+		;;
 	esac
 done
 
@@ -116,8 +126,18 @@ else
 	QEMU_ARGS="--cpu ${QEMU_CPU}"
 fi
 
-NVRAM=$(mktemp)
-cp "${NVRAM_PATH}" "${NVRAM}"
+if [ -n "${NO_EFI_STORAGE_PERSIST}" ]; then
+	NVRAM=$(mktemp)
+	echo "Using temporary EFI variable storage"
+else
+	NVRAM="/tmp/$(basename "${VM_IMAGE}").efivars"
+	echo "Using semi-persistent EFI variable storage (${NVRAM})"
+fi
+
+if [ ! -f "${NVRAM}" ] || [ -n "${OVERWRITE_EFI}" ]; then
+	echo "Copying EFI NVRAM base (${NVRAM_PATH}) to ${NVRAM}"
+	cp "${NVRAM_PATH}" "${NVRAM}"
+fi
 
 if [ -z "${TELNET_PORT}" ]; then
 	QEMU_ARGS="${QEMU_ARGS}
@@ -170,7 +190,10 @@ ${QEMU_CMD} \
 	-drive file="${VM_IMAGE}",if=virtio \
 	-device i6300esb,id=watchdog0 -watchdog-action reset
 
-rm "${NVRAM}"
+if [ -n "${NO_EFI_STORAGE_PERSIST}" ]; then
+	rm "${NVRAM}"
+fi
+
 if [ -n "${SWTPM_DIR}" ]; then
 	rm -rf "${SWTPM_DIR}"
 fi