#!/bin/sh

# This script generates the dummy FAT filesystem used for the EFI boot
# blocks. It uses newfs_msdos to generate a template filesystem with the
# relevant interesting files. These are then found by grep, and the offsets
# written to a Makefile snippet.
#
# Because it requires root, and because it is overkill, we do not
# do this as part of the normal build. If makefs(8) grows workable FAT
# support, this should be revisited.

# $FreeBSD$

FAT_SIZE=1600 			#Size in 512-byte blocks of the produced image

BOOT1_OFFSET=2d
BOOT1_SIZE=384k

if [ $(id -u) != 0 ]; then
	echo "${0##*/}: must run as root" >&2
	exit 1
fi

# Record maximum boot1 size in bytes
case $BOOT1_SIZE in
*k)
	BOOT1_MAXSIZE=$(expr ${BOOT1_SIZE%k} '*' 1024)
	;;
*)
	BOOT1_MAXSIZE=$BOOT1_SIZE
	;;
esac

echo '# This file autogenerated by generate-fat.sh - DO NOT EDIT' > Makefile.fat
echo "# \$FreeBSD\$" >> Makefile.fat
echo "BOOT1_OFFSET=0x$BOOT1_OFFSET" >> Makefile.fat
echo "BOOT1_MAXSIZE=$BOOT1_MAXSIZE" >> Makefile.fat

while read ARCH FILENAME; do
	# Generate 800K FAT image
	OUTPUT_FILE=fat-${ARCH}.tmpl

	dd if=/dev/zero of=$OUTPUT_FILE bs=512 count=$FAT_SIZE
	DEVICE=`mdconfig -a -f $OUTPUT_FILE`
	newfs_msdos -F 12 -L EFISYS $DEVICE
	mkdir stub
	mount -t msdosfs /dev/$DEVICE stub

	# Create and bless a directory for the boot loader
	mkdir -p stub/efi/boot

	# Make a dummy file for boot1
	echo 'Boot1 START' | dd of=stub/efi/boot/$FILENAME cbs=$BOOT1_SIZE count=1 conv=block
	# Provide a fallback startup.nsh
	echo $FILENAME > stub/efi/boot/startup.nsh

	umount stub
	mdconfig -d -u $DEVICE
	rmdir stub

	# Locate the offset of the fake file
	OFFSET=$(hd $OUTPUT_FILE | grep 'Boot1 START' | cut -f 1 -d ' ')

	# Convert to number of blocks
	OFFSET=$(echo 0x$OFFSET | awk '{printf("%x\n",$1/512);}')

	# Validate the offset
	if [ $OFFSET != $BOOT1_OFFSET ]; then
		echo "Incorrect offset $OFFSET != $BOOT1_OFFSET" >&2
		exit 1
	fi

	xz -f $OUTPUT_FILE
done <<EOF
	amd64	BOOTx64.efi
	arm64	BOOTaa64.efi
	arm	BOOTarm.efi
	i386	BOOTia32.efi
EOF