postmarketos-initramfs: refactor cmdline parsing

Currently the initramfs is littered with various code snippets which
read /proc/cmdline. This is error prone and results in more complicated
code especially as we want to standardise all the pmos specific cmdline
arguments, and where some arguments have the same behaviour as
deviceinfo variables.

Let's do the parsing correctly, once, and set global variables to
enable/disable/configure parts of the initramfs. At the same time
introduce namespaced and standard versions of the remaining arguments
which haven't been standardised yet.

Now (for example) to check if the splash is disabled, rather than
grepping /proc/cmdline for PMOS_NOSPLASH AND checking if
deviceinfo_no_framebuffer is true, you can just check if "$nosplash" =
"y".

This will drastically simplify the process of adding additional
configuration options in the future.

Most of the code here was taken from the Arch Linux initramfs and
simplified/adjusted to better fix our use case.

Signed-off-by: Caleb Connolly <caleb@postmarketos.org>
Part-of: !6172

main/postmarketos-initramfs/init.sh

@@ -27,6 +27,7 @@ export PATH=/usr/bin:/bin:/usr/sbin:/sbin
 
 # Mount everything, set up logging, modules, mdev
 mount_proc_sys_dev
+parse_cmdline < /proc/cmdline
 setup_log
 echo "  ❬❬ PMOS STAGE 1 ❭❭"
 echo "initramfs version: $INITRAMFS_PKG_VERSION"

main/postmarketos-initramfs/init_2nd.sh

@@ -32,7 +32,7 @@ if [ "$IN_CI" = "true" ]; then
 	fail_halt_boot
 fi
 
-if grep -q "pmos.debug-shell" /proc/cmdline; then
+if [ "$debug_shell" = "y" ]; then
 	debug_shell
 fi
 
@@ -71,7 +71,7 @@ echo "Switching root"
 # were stashed
 if [ -e "/proc/1/fd/3" ]; then
 	exec 1>&3 2>&4
-elif ! grep -q "pmos.debug-shell" /proc/cmdline; then
+elif [ "$debug_shell" != "y" ]; then
 	echo "$LOG_PREFIX Disabling console output again (use 'pmos.debug-shell' to keep it enabled)"
 	exec >/dev/null 2>&1
 fi

main/postmarketos-initramfs/init_functions.sh

@@ -17,8 +17,180 @@ deviceinfo_getty="${deviceinfo_getty:-}"
 deviceinfo_name="${deviceinfo_name:-}"
 deviceinfo_codename="${deviceinfo_codename:-}"
 deviceinfo_create_initfs_extra="${deviceinfo_create_initfs_extra:-}"
+deviceinfo_no_framebuffer="${deviceinfo_no_framebuffer:-}"
 
-# Redirect stdout and stderr to logfile
+# Does word start with prefix?
+startswith() {
+	local word="$1" prefix="$2"
+
+	case "$word" in
+		$prefix*)
+			return 0
+			;;
+	esac
+
+	return 1
+}
+
+# Does word end with suffix?
+endswith() {
+	local word="$1" suffix="$2"
+
+	case "$word" in
+		*$suffix)
+			return 0
+			;;
+	esac
+
+	return 1
+}
+
+# Parse individual items from the cmdline and take appropriate
+# action (e.g. set variables).
+parse_cmdline_item() {
+	local key="$1" value="$2"
+
+	# For information on what each cmdline argument does, please refer
+	# to https://wiki.postmarketos.org/wiki/Initramfs#Kernel_cmdline
+	case "$key" in
+		pmos.boot | pmos_boot)
+			boot_path="$value"
+			;;
+		pmos.boot_uuid | pmos_boot_uuid)
+			boot_uuid="$value"
+			;;
+		pmos.bootchart2 | PMOS_BOOTCHART2)
+			bootchart2=y
+			;;
+		pmos.debug-shell)
+			# used by init_2nd.sh
+			# shellcheck disable=SC2034
+			debug_shell=y
+			;;
+		pmos.force-partition-resize | PMOS_FORCE_PARTITION_RESIZE)
+			# used by init_functions_2nd.sh which is sourced
+			# after this script.
+			# shellcheck disable=SC2034
+			force_partition_resize=y
+			;;
+		pmos.nosplash | PMOS_NOSPLASH)
+			nosplash=y
+			;;
+		pmos.root | pmos_root)
+			root_path="$value"
+			;;
+		pmos.root_uuid | pmos_root_uuid)
+			root_uuid="$value"
+			;;
+		pmos.rootfsopts | pmos_rootfsopts)
+			# Prepend a comma since this will be appended to
+			# "rw" when passed to mount
+			rootfsopts=",$value"
+			;;
+		pmos.stowaway)
+			stowaway=y
+			;;
+		pmos.usb-storage)
+			usb_storage="$value"
+			;;
+		[![:alpha:]_]* | [[:alpha:]_]*[![:alnum:]_]*)
+			# invalid shell variable, ignore it
+			;;
+		*)
+			# valid shell variable
+			# ignore these since we get all kinds of weird
+			# arguments from quirky bootloaders and we really
+			# don't want to deal with that here. Add options
+			# explicitly above instead.
+			;;
+	esac
+}
+
+process_cmdline_param() {
+	# $1: key (the cmdline parameter)
+	# $2: value (after the =)
+	local key="$1" value="$2"
+
+	# maybe unquote the value
+	# busybox ash supports string indexing
+	# shellcheck disable=SC3057
+	if startswith "$value" "[\"']" && endswith "$value" "${value:0:1}"; then
+		value="${value#?}" value="${value%?}"
+	fi
+
+	parse_cmdline_item "$key" "$value"
+}
+
+# Parse the kernel cmdline and configure the environment
+parse_cmdline() {
+	local cmdline word quoted key value
+
+	# Disable globbing so we don't accidentally expand
+	# cmdline options into paths
+	set -f
+	read -r cmdline
+	# shellcheck disable=SC2086
+	set -- $cmdline
+	set +f
+
+	# Walk over each cmdline argument
+	for word; do
+		# Handle quoted values
+		if [ -n "$quoted" ]; then
+			value="$value $word"
+		else
+			case "$word" in
+				# Easy case: key=value
+				*=*)
+					key="${word%%=*}"
+					value="${word#*=}"
+
+					if startswith "$value" "[\"']"; then
+						# busybox ash supports string indexing
+						# shellcheck disable=SC3057
+						quoted="${value:0:1}"
+					fi
+					;;
+				# A comment (only used for unit tests)
+				'#'*)
+					break
+					;;
+				# A key without a value
+				*)
+					key="$word"
+					;;
+			esac
+		fi
+
+		# If inside a quoted string, check if $value contains the closing quote
+		if [ -n "$quoted" ]; then
+			if endswith "$value" "$quoted"; then
+				unset quoted
+			else
+				# Otherwise continue reading words
+				continue
+			fi
+		fi
+
+		process_cmdline_param "$key" "$value"
+		unset key value
+	done
+
+	if [ -n "$key" ]; then
+		process_cmdline_param "$key" "$value"
+	fi
+
+	# Also set some options from deviceinfo variables
+
+	if [ "$deviceinfo_no_framebuffer" = "true" ]; then
+		nosplash=y
+	fi
+}
+
+# Redirect stdout/stderr to the log file, as well as to the kernel via
+# syslog. Additionally, if pmos.nosplash is set and there are no active
+# consoles, try to be helpful by logging to tty0 and the devices serial
+# port.
 setup_log() {
 	local console
 	local log_targets
@@ -363,7 +535,7 @@ mount_boot_partition() {
 	mount_opts="-o nodev,nosuid,noexec"
 
 	# We dont need to do this when using stowaways
-	if grep -q "pmos.stowaway" /proc/cmdline; then
+	if [ "$stowaway" = "y" ]; then
 		return
 	fi
 
@@ -478,14 +650,6 @@ mount_root_partition() {
 	local partition
 
 	partition="$(find_root_partition)"
-	rootfsopts=""
-
-	# shellcheck disable=SC2013
-	for x in $(cat /proc/cmdline); do
-		[ "$x" = "${x#pmos_rootfsopts=}" ] && continue
-		# Prepend a comma because this will be appended to "rw" below
-		rootfsopts=",${x#pmos_rootfsopts=}"
-	done
 
 	echo "Mount root partition ($partition) to /sysroot (read-write) with options ${rootfsopts#,}"
 	type="$(get_partition_type "$partition")"
@@ -835,13 +999,6 @@ debug_shell() {
 	Read the initramfs log with 'cat /pmOS_init.log'.
 	EOF
 
-	# Expose storage specified on cmdline on USB
-	local storage_dev=""
-	# shellcheck disable=SC2013
-	for x in $(cat /proc/cmdline); do
-		[ "$x" = "${x#pmos.usb-storage=}" ] || storage_dev="${x#pmos.usb-storage=}"
-	done
-
 	# Add pmos_logdump message only if relevant
 	if [ -n "$have_udc" ]; then
 		echo "Run 'pmos_logdump' to generate a log dump and expose it over USB." >> /README
@@ -851,8 +1008,8 @@ debug_shell() {
 		'setup_usb_storage_configfs /dev/DEVICE'
 		EOF
 
-		if [ -n "$storage_dev" ]; then
-			echo "$storage_dev is exposed over USB by default (pmos.usb-storage)" >> /README
+		if [ -n "$usb_storage" ]; then
+			echo "$usb_storage is exposed over USB by default (pmos.usb-storage)" >> /README
 		fi
 	fi
 
@@ -940,7 +1097,7 @@ debug_shell() {
 	telnetd -b "${HOST_IP}:23" -l /sbin/pmos_getty &
 
 	# Set up USB mass storage if pmos.usb-storage= was specified on cmdline
-	[ -z "$storage_dev" ] || setup_usb_storage_configfs "$storage_dev"
+	[ -z "$usb_storage" ] || setup_usb_storage_configfs "$usb_storage"
 
 	# wait until we get the signal to continue boot
 	while ! [ -e /tmp/continue_boot ]; do
@@ -988,15 +1145,7 @@ check_keys() {
 
 # $1: Message to show
 show_splash() {
-	# Skip for non-framebuffer devices
-	# shellcheck disable=SC2154
-	if [ "$deviceinfo_no_framebuffer" = "true" ]; then
-		echo "NOTE: Skipping framebuffer splashscreen (deviceinfo_no_framebuffer)"
-		return
-	fi
-
-	# Disable splash
-	if grep -q PMOS_NOSPLASH /proc/cmdline; then
+	if [ "$nosplash" = "y" ]; then
 		return
 	fi
 
@@ -1009,6 +1158,9 @@ show_splash() {
 }
 
 hide_splash() {
+	if [ "$nosplash" = "y" ]; then
+		return
+	fi
 	killall pbsplash 2>/dev/null
 
 	while pgrep pbsplash >/dev/null; do
@@ -1026,10 +1178,7 @@ set_framebuffer_mode() {
 }
 
 setup_framebuffer() {
-	# Skip for non-framebuffer devices
-	# shellcheck disable=SC2154
-	if [ "$deviceinfo_no_framebuffer" = "true" ]; then
-		echo "NOTE: Skipping framebuffer setup (deviceinfo_no_framebuffer)"
+	if [ "$nosplash" = "y" ]; then
 		return
 	fi
 
@@ -1049,7 +1198,7 @@ setup_framebuffer() {
 }
 
 setup_bootchart2() {
-	if grep -q PMOS_BOOTCHART2 /proc/cmdline; then
+	if [ "$bootchart2" = "y" ]; then
 		if [ -f "/sysroot/sbin/bootchartd" ]; then
 			# shellcheck disable=SC2034
 			init="/sbin/bootchartd"

main/postmarketos-initramfs/init_functions_2nd.sh

@@ -55,7 +55,7 @@ resize_root_partition() {
 	# this, except for QEMU devices and non-android devices (e.g.
 	# PinePhone). For them, it is fine to use the whole storage device and
 	# so we pass PMOS_FORCE_PARTITION_RESIZE as kernel parameter.
-	elif grep -q PMOS_FORCE_PARTITION_RESIZE /proc/cmdline; then
+	elif [ "$force_partition_resize" = "y" ]; then
 		partition_dev="$(echo "$partition" | sed -E 's/p?2$//')"
 		if has_unallocated_space "$partition_dev"; then
 			echo "Resize root partition ($partition)"