config: improve BIOS/EFI bootloader selection handling

the design choice from when EFI support was introduced was to change
`--bootloader` to `--bootloaders`, with users specifying their selection
of BIOS and EFI bootloaders together. at this time there were not even any
decent validation checks being performed, and invalid combinations could
cause some chaos.

since then proper validation was put in place, including checking that
only a single instance of each of BIOS and EFI bootloaders exists in the
selection.

here we tweak things such that we stick with the same option, but we split
the selection up such that we store the BIOS and EFI selections separately
within the saved config file, and offer it up to scripts to help simplify
those scripts.

we must however retain support for splitting from the combined option,
both because we still use it in the combined option, and for backwards
compatibility with older saved configs.

Gbp-Dch: Short

functions/configuration.sh

@@ -287,24 +287,33 @@ Prepare_config ()
 			;;
 	esac
 
-	if [ -z "${LB_BOOTLOADERS}" ]
-	then
-		case "${LB_ARCHITECTURE}" in
-			amd64|i386)
-				case "${LB_IMAGE_TYPE}" in
-					hdd|netboot)
-						LB_BOOTLOADERS="syslinux"
-						;;
-					*)
-						LB_BOOTLOADERS="syslinux,grub-efi"
-						;;
-				esac
-				;;
-		esac
+	case "${LB_ARCHITECTURE}" in
+		amd64|i386)
+			LB_BOOTLOADER_BIOS="${LB_BOOTLOADER_BIOS:-syslinux}"
+			if ! In_list "${LB_IMAGE_TYPE}" hdd netboot; then
+				LB_BOOTLOADER_EFI="${LB_BOOTLOADER_EFI:-grub-efi}"
+			fi
+			;;
+	esac
+	# Command line option combines BIOS and EFI selection in one.
+	# Also, need to support old config files that held `LB_BOOTLOADERS`.
+	# Note that this function does not perform validation, so none is done here.
+	if [ -n "${LB_BOOTLOADERS}" ]; then
+		LB_BOOTLOADERS="$(echo "${LB_BOOTLOADERS}" | tr "," " ")"
+		unset LB_BOOTLOADER_BIOS
+		unset LB_BOOTLOADER_EFI
+		local BOOTLOADER
+		for BOOTLOADER in $LB_BOOTLOADERS; do
+			case "${BOOTLOADER}" in
+				grub-legacy|grub-pc|syslinux)
+					LB_BOOTLOADER_BIOS="${BOOTLOADER}"
+					;;
+				grub-efi)
+					LB_BOOTLOADER_EFI="${BOOTLOADER}"
+					;;
+			esac
+		done
 	fi
-	LB_BOOTLOADERS="$(echo "${LB_BOOTLOADERS}" | tr "," " ")"
-
-	LB_FIRST_BOOTLOADER=$(echo "${LB_BOOTLOADERS}" | awk '{ print $1 }')
 
 	LB_CHECKSUMS="${LB_CHECKSUMS:-sha256}"
 
@@ -572,9 +581,18 @@ Validate_config_permitted_values ()
 		exit 1
 	fi
 
-	if [ -z "${LB_BOOTLOADERS}" ]; then
+	if [ -z "${LB_BOOTLOADER_BIOS}" ] && [ -z "${LB_BOOTLOADER_EFI}" ]; then
 		Echo_warning "You have specified no bootloaders; I predict that you will experience some problems!"
-	else
+	fi
+	if [ -n "${LB_BOOTLOADER_BIOS}" ] && ! In_list "${LB_BOOTLOADER_BIOS}" grub-legacy grub-pc syslinux; then
+		Echo_error "You have specified an invalid BIOS bootloader."
+		exit 1
+	fi
+	if [ -n "${LB_BOOTLOADER_EFI}" ] && ! In_list "${LB_BOOTLOADER_EFI}" grub-efi; then
+		Echo_error "You have specified an invalid EFI bootloader."
+		exit 1
+	fi
+	if [ -n "${LB_BOOTLOADERS}" ]; then
 		local BOOTLOADER
 		local BOOTLOADERS_BIOS=0
 		local BOOTLOADERS_EFI=0

scripts/build/binary_grub-efi

@@ -21,7 +21,7 @@ USAGE="${PROGRAM} [--force]"
 # Processing arguments and configuration files
 Init_config_data "${@}"
 
-if ! In_list "grub-efi" $LB_BOOTLOADERS; then
+if [ "${LB_BOOTLOADER_EFI}" != "grub-efi" ]; then
 	exit 0
 fi
 

scripts/build/binary_grub-legacy

@@ -21,7 +21,7 @@ USAGE="${PROGRAM} [--force]"
 # Processing arguments and configuration files
 Init_config_data "${@}"
 
-if ! In_list "grub-legacy" $LB_BOOTLOADERS; then
+if [ "${LB_BOOTLOADER_BIOS}" != "grub-legacy" ]; then
 	exit 0
 fi
 

scripts/build/binary_grub-pc

@@ -21,7 +21,7 @@ USAGE="${PROGRAM} [--force]"
 # Processing arguments and configuration files
 Init_config_data "${@}"
 
-if ! In_list "grub-pc" $LB_BOOTLOADERS; then
+if [ "${LB_BOOTLOADER_BIOS}" != "grub-pc" ]; then
 	exit 0
 fi
 

scripts/build/binary_hdd

@@ -52,15 +52,11 @@ Check_package chroot /sbin/parted parted
 Check_package host /sbin/fdisk fdisk
 Check_package host /sbin/losetup mount
 
-for BOOTLOADER in ${LB_BOOTLOADERS}; do
-	case "${BOOTLOADER}" in
-		grub-legacy)
-			Check_package chroot /usr/sbin/grub grub
-			;;
-	esac
-done
+case "${LB_BOOTLOADER_BIOS}" in
+	grub-legacy)
+		Check_package chroot /usr/sbin/grub grub
+		;;
 
-case ${LB_FIRST_BOOTLOADER} in
 	syslinux)
 		case ${LB_BINARY_FILESYSTEM} in
 			fat*|ntfs)
@@ -189,8 +185,7 @@ case "${LB_BUILD_WITH_CHROOT}" in
 		Chroot chroot "parted -s ${FREELO} set 1 boot on" || true
 		Chroot chroot "parted -s ${FREELO} set 1 lba off" || true
 
-		if [ "${LB_FIRST_BOOTLOADER}" = "syslinux" ]
-		then
+		if [ "${LB_BOOTLOADER_BIOS}" = "syslinux" ]; then
 			dd if=chroot/usr/lib/$(echo ${_BOOTLOADER} | tr [a-z] [A-Z])/mbr.bin of=${FREELO} bs=440 count=1
 		fi
 		;;
@@ -209,8 +204,7 @@ case "${LB_BUILD_WITH_CHROOT}" in
 		parted -s "${FREELO}" set 1 boot on || true
 		parted -s "${FREELO}" set 1 lba off || true
 
-		if [ "${LB_FIRST_BOOTLOADER}" = "syslinux" ]
-		then
+		if [ "${LB_BOOTLOADER_BIOS}" = "syslinux" ]; then
 			dd if=/usr/lib/$(echo ${_BOOTLOADER} | tr [a-z] [A-Z])/mbr.bin of=${FREELO} bs=440 count=1
 		fi
 		;;
@@ -275,8 +269,7 @@ cp -T ${CP_OPTIONS} binary/ chroot/binary.tmp
 
 FIXME()
 {
-if [ "${LB_FIRST_BOOTLOADER}" = "grub-legacy" ]
-then
+if [ "${LB_BOOTLOADER_BIOS}" = "grub-legacy" ]; then
 
 cat > chroot/grub.sh << EOF
 #!/bin/sh

scripts/build/binary_syslinux

@@ -21,7 +21,7 @@ USAGE="${PROGRAM} [--force]"
 # Processing arguments and configuration files
 Init_config_data "${@}"
 
-if ! In_list "syslinux" $LB_BOOTLOADERS; then
+if [ "${LB_BOOTLOADER_BIOS}" != "syslinux" ]; then
 	exit 0
 fi
 

scripts/build/config

@@ -364,6 +364,7 @@ Local_arguments ()
 				;;
 
 			--bootloaders|--bootloader)
+				# This will be split up into BIOS and EFI selections by `Prepare_config()`
 				LB_BOOTLOADERS="${2}"
 				shift 2
 				;;
@@ -1182,8 +1183,11 @@ LB_BOOTAPPEND_INSTALL="${LB_BOOTAPPEND_INSTALL}"
 # Set boot parameters
 LB_BOOTAPPEND_LIVE_FAILSAFE="${LB_BOOTAPPEND_LIVE_FAILSAFE}"
 
-# Set bootloaders
-LB_BOOTLOADERS="${LB_BOOTLOADERS}"
+# Set BIOS bootloader
+LB_BOOTLOADER_BIOS="${LB_BOOTLOADER_BIOS}"
+
+# Set EFI bootloader
+LB_BOOTLOADER_EFI="${LB_BOOTLOADER_EFI}"
 
 # Set checksums
 LB_CHECKSUMS="${LB_CHECKSUMS}"

scripts/build/source_debian

@@ -54,9 +54,12 @@ Chroot chroot "sh source-selection.sh"
 rm -f chroot/source-selection.sh
 mv chroot/source-selection.txt ./
 
-for BOOTLOADER in ${LB_BOOTLOADERS}; do
-	echo "${BOOTLOADER}" >> source-selection.txt
-done
+if [ -n "${LB_BOOTLOADER_BIOS}" ]; then
+	echo "${LB_BOOTLOADER_BIOS}" >> source-selection.txt
+fi
+if [ -n "${LB_BOOTLOADER_EFI}" ]; then
+	echo "${LB_BOOTLOADER_EFI}" >> source-selection.txt
+fi
 
 echo "live-build" >> source-selection.txt