Copy-paste chromeos script

msm-cros-efs-loader.sh

 #!/bin/sh
-
-# For now this just creates empty files which is fine for non-LTE devices.
-# TODO: Implement parsing the actual EFS from /dev/mmcblk*boot0
-# See: https://chromium.googlesource.com/chromiumos/overlays/board-overlays/+/refs/heads/main/baseboard-trogdor/chromeos-base/chromeos-bsp-baseboard-trogdor/files/verify_fsg.sh
-
-directory="/var/lib/rmtfs"
-
-if [ ! -d "$directory" ]; then
-	mkdir -p "$directory"
-fi
-
-for i in fs1 fs2 fsg fsc; do
-	file="$directory/modem_$i"
-	if [ ! -f "$file" ]; then
-		dd if=/dev/zero bs=1M count=2 of="$file"
-	fi
-done
+# Based on https://chromium.googlesource.com/chromiumos/overlays/board-overlays/+/refs/heads/main/baseboard-trogdor/chromeos-base/chromeos-bsp-baseboard-trogdor/files/verify_fsg.sh
+# which is Copyright 2020 The ChromiumOS Authors
+JOB="verify_fsg.sh"
+RMTFS_DIR=/var/lib/rmtfs
+RMTFS_BOOT_DIR="${RMTFS_DIR}/boot"
+FSG_PATH="${RMTFS_BOOT_DIR}/modem_fsg"
+FSG_SOURCE="$(echo /dev/mmcblk*boot0)"
+# Logging messages go directly to /dev/kmsg because we run before
+# syslog is available.
+logit() {
+	echo "<6>${JOB}:" "$@" > /dev/kmsg
+}
+logwarn() {
+	echo "<4>${JOB}:" "$@" > /dev/kmsg
+}
+logerr() {
+	echo "<3>${JOB}:" "$@" > /dev/kmsg
+}
+# Read the FSG fuse hash, and store the result into
+# fsg_fuse_hash.
+read_fuses() {
+	fuse_path="$(realpath /sys/bus/nvmem/devices/qfprom*/nvmem)"
+	fsg_fuse_hash=
+	if [ ! -r "${fuse_path}" ]; then
+		logerr "Fuse driver does not appear to be loaded."
+		return 1
+	fi
+	fsg_fuse_hash="$(dd if="${fuse_path}" bs=1 skip=$((0x750)) count=32 \
+										 status=none | od -tx1 -vAn | tr -d ' \n')"
+}
+# Compare the FSG hash to what's in the fuses.
+check_fsg_hash() {
+	if [ ! -f "${FSG_PATH}" ]; then
+		return 1
+	fi
+	read_fuses
+	# If the fuses are unprogrammed, then return failure differently.
+	local z16="0000000000000000"
+	local unprogrammed="${z16}${z16}${z16}${z16}"
+	if [ -z "${fsg_fuse_hash}" ] || \
+		 [ "${fsg_fuse_hash}" = "${unprogrammed}" ]; then
+		return 2
+	fi
+	# Hash the FSG, and compare against what was burned into the fuses
+	# in the factory.
+	local fsg_hash
+	fsg_hash="$(sha256sum < "${FSG_PATH}" | awk '{print $1}')"
+	if [ "${fsg_hash}" != "${fsg_fuse_hash}" ]; then
+		return 1
+	fi
+	return 0
+}
+# See if this is an old style eMMC partition, and load the size if so.
+# Note: This function works by altering the fsg_size variable used by
+# reload_fsg().
+# TODO(evgreen): Delete this after the last P2A build.
+# There is only expected to be one more P2A build.
+load_old_fsg_size() {
+	# In the old style format, there's just a size at 0 and the FSG at 512.
+	fsg_size="$(dd if="${FSG_SOURCE}" bs=8 skip=0 count=1 status=none | \
+							tr -d '\n\0' | grep -a -E '^[0-9]{4,}$')"
+	: "${fsg_size:=0}"
+}
+# Read the FSG out of the eMMC boot partition.
+reload_fsg() {
+	local fsg_header
+	local fsg_size=0
+	local fsg_tmp_path="${FSG_PATH}.tmp"
+	# Get the 3 byte header, which is "FSG".
+	fsg_header="$(dd if="${FSG_SOURCE}" bs=3 skip=0 count=1 status=none)"
+	if [ "${fsg_header}" = "FSG" ]; then
+		fsg_size="$(dd if="${FSG_SOURCE}" bs=1 skip=4 count=8 status=none)"
+	# If the header area is just blank, save an extra read and just bail now.
+	elif [ -z "${fsg_header}" ]; then
+		logit "Blank eMMC boot partition."
+		return 1
+	else
+		# Ordinarily this would be the place to error out. For this next
+		# build, also check for an "old-style" FSG.
+		load_old_fsg_size
+	fi
+	# Wifi-only SKUs will land here the first time through.
+	if [ "${fsg_size}" -eq 0 ]; then
+		logit "No LTE FSG found."
+		return 1
+	fi
+	logit "Reloading FSG"
+	if [ "${fsg_size}" -gt 4193792 ]; then
+		logwarn "Warning: FSG size invalid. LTE will not work."
+	fi
+	mkdir -p "${RMTFS_BOOT_DIR}"
+	chmod 0700 "${RMTFS_BOOT_DIR}" "${RMTFS_DIR}"
+	rm -f "${FSG_PATH}" "${fsg_tmp_path}"
+	# Copy to a temporary file and rename to avoid ending up with a
+	# partially loaded file in case of power loss.
+	# Ensure the dd succeeded.
+	if ! dd if="${FSG_SOURCE}" of="${fsg_tmp_path}" bs=1M \
+				iflag=count_bytes,skip_bytes count="${fsg_size}" \
+				skip=512 status=none; then
+		logerr "Error: Failed to read FSG."
+		return 1
+	fi
+	# Sync to ensure the temporary file is fully written to disk. Then
+	# move the final file into place as an atomic op.
+	# This sync could be slow, but FSG reloading is also rare.
+	sync
+	mv "${fsg_tmp_path}" "${FSG_PATH}"
+	sync
+}
+verify_fsg() {
+	local retval
+	# Check the FSG hash against the fuses. Reload from the eMMC boot
+	# partition if it fails.
+	check_fsg_hash
+	retval=$?
+	if [ "${retval}" -eq 0 ]; then
+		return
+	elif [ "${retval}" -eq 2 ]; then
+		# For WiFi SKUs, the first factory run, or for certain pre-production
+		# devices), the FSG hash is not set. Allow it to continue with the FSG
+		# tarball pre-populated in the boot partition.
+		logit "Fuses are unprogrammed."
+		# If the FSG already exists no need to copy it again; bail out.
+		if [ -f "${FSG_PATH}" ]; then
+			return
+		fi
+	fi
+	if ! reload_fsg; then
+		# Perhaps this is a wifi-only SKU.
+		return
+	fi
+	check_fsg_hash
+	retval=$?
+	if [ "${retval}" -eq 0 ]; then
+		# Delete all EFS images in case they got corrupted and that
+		# causes the modem to crash or hang rather than turning to the FSG.
+		# Only do this if the hash now agrees, otherwise developers with
+		# unprogrammed fuses will be constantly fighting this deletion.
+		rm -f "${RMTFS_BOOT_DIR}"/modem_fs[c12]
+	elif [ "${retval}" -ne 2 ]; then
+		# Allow a hash mismatch in dev/test images.
+		if crossystem "cros_debug?1" ; then
+			logwarn "FSG hash check failed, forgiven in developer mode."
+		# For other errors, blank out the FSG in case the eMMC boot partition
+		# was compromised.
+		else
+			logerr "FSG hash check failed. LTE will not work"
+			rm -f "${FSG_PATH}"
+		fi
+	fi
+}
+main() {
+	if [ "$#" -ne 0 ]; then
+		logerr "$0: Expected no arguments."
+		exit 1
+	fi
+	verify_fsg
+}
+main "$@"