fw_fallback.sh

#!/bin/sh
# SPDX-License-Identifier: GPL-2.0
# This validates that the kernel will fall back to using the fallback mechanism
# to load firmware it can't find on disk itself. We must request a firmware
# that the kernel won't find, and any installed helper (e.g. udev) also
# won't find so that we can do the load ourself manually.
set -e

modprobe test_firmware

DIR=/sys/devices/virtual/misc/test_firmware

# CONFIG_FW_LOADER_USER_HELPER has a sysfs class under /sys/class/firmware/
# These days no one enables CONFIG_FW_LOADER_USER_HELPER so check for that
# as an indicator for CONFIG_FW_LOADER_USER_HELPER.
HAS_FW_LOADER_USER_HELPER=$(if [ -d /sys/class/firmware/ ]; then echo yes; else echo no; fi)

if [ "$HAS_FW_LOADER_USER_HELPER" = "yes" ]; then
       OLD_TIMEOUT=$(cat /sys/class/firmware/timeout)
else
	echo "usermode helper disabled so ignoring test"
	exit 0
fi

FWPATH=$(mktemp -d)
FW="$FWPATH/test-firmware.bin"

test_finish()
{
	echo "$OLD_TIMEOUT" >/sys/class/firmware/timeout
	rm -f "$FW"
	rmdir "$FWPATH"
}

load_fw()
{
	local name="$1"
	local file="$2"

	# This will block until our load (below) has finished.
	echo -n "$name" >"$DIR"/trigger_request &

	# Give kernel a chance to react.
	local timeout=10
	while [ ! -e "$DIR"/"$name"/loading ]; do
		sleep 0.1
		timeout=$(( $timeout - 1 ))
		if [ "$timeout" -eq 0 ]; then
			echo "$0: firmware interface never appeared" >&2
			exit 1
		fi
	done

	echo 1 >"$DIR"/"$name"/loading
	cat "$file" >"$DIR"/"$name"/data
	echo 0 >"$DIR"/"$name"/loading

	# Wait for request to finish.
	wait
}

load_fw_cancel()
{
	local name="$1"
	local file="$2"

	# This will block until our load (below) has finished.
	echo -n "$name" >"$DIR"/trigger_request 2>/dev/null &

	# Give kernel a chance to react.
	local timeout=10
	while [ ! -e "$DIR"/"$name"/loading ]; do
		sleep 0.1
		timeout=$(( $timeout - 1 ))
		if [ "$timeout" -eq 0 ]; then
			echo "$0: firmware interface never appeared" >&2
			exit 1
		fi
	done

	echo -1 >"$DIR"/"$name"/loading

	# Wait for request to finish.
	wait
}

load_fw_custom()
{
	if [ ! -e "$DIR"/trigger_custom_fallback ]; then
		echo "$0: custom fallback trigger not present, ignoring test" >&2
		return 1
	fi

	local name="$1"
	local file="$2"

	echo -n "$name" >"$DIR"/trigger_custom_fallback 2>/dev/null &

	# Give kernel a chance to react.
	local timeout=10
	while [ ! -e "$DIR"/"$name"/loading ]; do
		sleep 0.1
		timeout=$(( $timeout - 1 ))
		if [ "$timeout" -eq 0 ]; then
			echo "$0: firmware interface never appeared" >&2
			exit 1
		fi
	done

	echo 1 >"$DIR"/"$name"/loading
	cat "$file" >"$DIR"/"$name"/data
	echo 0 >"$DIR"/"$name"/loading

	# Wait for request to finish.
	wait
	return 0
}


load_fw_custom_cancel()
{
	if [ ! -e "$DIR"/trigger_custom_fallback ]; then
		echo "$0: canceling custom fallback trigger not present, ignoring test" >&2
		return 1
	fi

	local name="$1"
	local file="$2"

	echo -n "$name" >"$DIR"/trigger_custom_fallback 2>/dev/null &

	# Give kernel a chance to react.
	local timeout=10
	while [ ! -e "$DIR"/"$name"/loading ]; do
		sleep 0.1
		timeout=$(( $timeout - 1 ))
		if [ "$timeout" -eq 0 ]; then
			echo "$0: firmware interface never appeared" >&2
			exit 1
		fi
	done

	echo -1 >"$DIR"/"$name"/loading

	# Wait for request to finish.
	wait
	return 0
}

load_fw_fallback_with_child()
{
	local name="$1"
	local file="$2"

	# This is the value already set but we want to be explicit
	echo 4 >/sys/class/firmware/timeout

	sleep 1 &
	SECONDS_BEFORE=$(date +%s)
	echo -n "$name" >"$DIR"/trigger_request 2>/dev/null
	SECONDS_AFTER=$(date +%s)
	SECONDS_DELTA=$(($SECONDS_AFTER - $SECONDS_BEFORE))
	if [ "$SECONDS_DELTA" -lt 4 ]; then
		RET=1
	else
		RET=0
	fi
	wait
	return $RET
}

trap "test_finish" EXIT

# This is an unlikely real-world firmware content. :)
echo "ABCD0123" >"$FW"
NAME=$(basename "$FW")

test_syfs_timeout()
{
	DEVPATH="$DIR"/"nope-$NAME"/loading

	# Test failure when doing nothing (timeout works).
	echo -n 2 >/sys/class/firmware/timeout
	echo -n "nope-$NAME" >"$DIR"/trigger_request 2>/dev/null &

	# Give the kernel some time to load the loading file, must be less
	# than the timeout above.
	sleep 1
	if [ ! -f $DEVPATH ]; then
		echo "$0: fallback mechanism immediately cancelled"
		echo ""
		echo "The file never appeared: $DEVPATH"
		echo ""
		echo "This might be a distribution udev rule setup by your distribution"
		echo "to immediately cancel all fallback requests, this must be"
		echo "removed before running these tests. To confirm look for"
		echo "a firmware rule like /lib/udev/rules.d/50-firmware.rules"
		echo "and see if you have something like this:"
		echo ""
		echo "SUBSYSTEM==\"firmware\", ACTION==\"add\", ATTR{loading}=\"-1\""
		echo ""
		echo "If you do remove this file or comment out this line before"
		echo "proceeding with these tests."
		exit 1
	fi

	if diff -q "$FW" /dev/test_firmware >/dev/null ; then
		echo "$0: firmware was not expected to match" >&2
		exit 1
	else
		echo "$0: timeout works"
	fi
}

test_syfs_timeout

# Put timeout high enough for us to do work but not so long that failures
# slow down this test too much.
echo 4 >/sys/class/firmware/timeout

# Load this script instead of the desired firmware.
load_fw "$NAME" "$0"
if diff -q "$FW" /dev/test_firmware >/dev/null ; then
	echo "$0: firmware was not expected to match" >&2
	exit 1
else
	echo "$0: firmware comparison works"
fi

# Do a proper load, which should work correctly.
load_fw "$NAME" "$FW"
if ! diff -q "$FW" /dev/test_firmware >/dev/null ; then
	echo "$0: firmware was not loaded" >&2
	exit 1
else
	echo "$0: fallback mechanism works"
fi

load_fw_cancel "nope-$NAME" "$FW"
if diff -q "$FW" /dev/test_firmware >/dev/null ; then
	echo "$0: firmware was expected to be cancelled" >&2
	exit 1
else
	echo "$0: cancelling fallback mechanism works"
fi

if load_fw_custom "$NAME" "$FW" ; then
	if ! diff -q "$FW" /dev/test_firmware >/dev/null ; then
		echo "$0: firmware was not loaded" >&2
		exit 1
	else
		echo "$0: custom fallback loading mechanism works"
	fi
fi

if load_fw_custom_cancel "nope-$NAME" "$FW" ; then
	if diff -q "$FW" /dev/test_firmware >/dev/null ; then
		echo "$0: firmware was expected to be cancelled" >&2
		exit 1
	else
		echo "$0: cancelling custom fallback mechanism works"
	fi
fi

set +e
load_fw_fallback_with_child "nope-signal-$NAME" "$FW"
if [ "$?" -eq 0 ]; then
	echo "$0: SIGCHLD on sync ignored as expected" >&2
else
	echo "$0: error - sync firmware request cancelled due to SIGCHLD" >&2
	exit 1
fi
set -e

exit 0