truncate -s 200m /tmp/efiboot.img
$MDDEV=$(mdconfig -a -t vnode -f /tmp/efiboot.img)
newfs_msdos -L EFISYS -F 32 -c 1 /dev/$MDDEV
mkdir /tmp/makefs
mount -t msdosfs /dev/$MDDEV /tmp/makefs
mkdir -p "/tmp/makefs/EFI/BOOT"
cp "${DESTDIR}/boot/loader.efi" "/tmp/makefs/EFI/BOOT/BOOTX64.efi"
umount /tmp/makefs
mdconfig -d -u $MDDEV
dd if=/tmp/efiboot.img of=/dev/ada0p1 bs=1m