[build] Allow for building EFI ISOs without syslinux

The isohybrid tool (that creates a partition table to describe the ESP
embedded within the ISO image) relies upon the existence of the
x86-only isolinux.bin file.  This file may not be available on non-x86
build hosts.

We already allow for the possibility that isohybrid may not be present
on the build host, in which case we fall back to creating a non-hybrid
ISO image.  Make a similar allowance for the possibility that the
isolinux.bin file may not be present: require its existence only if we
are attempting to build a BIOS-bootable image, or if we will be
attempting to use isohybrid to create a hybrid ISO image.

Reported-by: Xiaotian Wu <wuxiaotian@loongson.cn>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/util/genfsimg

@@ -4,7 +4,6 @@
 
 set -e
 set -u
-set -x
 
 # Print usage message
 #
@@ -18,58 +17,28 @@ help() {
     echo " -s SCRIPT  use executable script"
 }
 
-# Get big-endian hex value from binary file
-#
-get_be() {
-    local FILENAME
-    local OFFSET
-    local LEN
-
-    FILENAME="${1}"
-    OFFSET="${2}"
-    LEN="${3}"
-
-    od -j "${OFFSET}" -N "${LEN}" -A n -t x1 -- "${FILENAME}" | tr -d " "
-}
-
-# Get little-endian hex value from binary file
-#
-get_le() {
-    local FILENAME
-    local OFFSET
-    local LEN
-    local BYTE
-    local VALUE
-
-    FILENAME="${1}"
-    OFFSET="${2}"
-    LEN="${3}"
-
-    VALUE=""
-    while [ "${LEN}" -gt 0 ] ; do
-	LEN=$(( "${LEN}" - 1 ))
-	BYTE=$(get_be "${FILENAME}" $(( "${OFFSET}" + "${LEN}" )) 1)
-	VALUE="${VALUE}${BYTE}"
-    done
-    echo "${VALUE}"
-}
-
 # Get hex byte from binary file
 #
 get_byte() {
-    get_be "${1}" "${2}" 1
+    local FILENAME
+    local OFFSET
+
+    FILENAME="${1}"
+    OFFSET="${2}"
+
+    od -j "${OFFSET}" -N 1 -A n -t x1 -- "${FILENAME}" | tr -d " "
 }
 
-# Get little-endian hex word from binary file
+# Get hex word from binary file
 #
 get_word() {
-    get_le "${1}" "${2}" 2
-}
+    local FILENAME
+    local OFFSET
 
-# Get little-endian hex dword from binary file
-#
-get_dword() {
-    get_le "${1}" "${2}" 4
+    FILENAME="${1}"
+    OFFSET="${2}"
+
+    od -j "${OFFSET}" -N 2 -A n -t x1 -- "${FILENAME}" | tr -d " "
 }
 
 # Get appropriate EFI boot filename for CPU architecture
@@ -82,31 +51,31 @@ efi_boot_name() {
     FILENAME="${1}"
 
     MZSIG=$(get_word "${FILENAME}" 0)
-    if [ "${MZSIG}" != "5a4d" ] ; then
+    if [ "${MZSIG}" != "4d5a" ] ; then
 	echo "${FILENAME}: invalid MZ header" >&2
 	exit 1
     fi
     PEOFF=$(get_byte "${FILENAME}" 0x3c)
     PESIG=$(get_word "${FILENAME}" 0x${PEOFF})
-    if [ "${PESIG}" != "4550" ] ; then
+    if [ "${PESIG}" != "5045" ] ; then
 	echo "${FILENAME}: invalid PE header" >&2
 	exit 1
     fi
     ARCH=$(get_word "${FILENAME}" $(( 0x${PEOFF} + 4 )) )
     case "${ARCH}" in
-	"014c" )
+	"4c01" )
 	    echo "BOOTIA32.EFI"
 	    ;;
-	"8664" )
+	"6486" )
 	    echo "BOOTX64.EFI"
 	    ;;
-	"01c2" )
+	"c201" )
 	    echo "BOOTARM.EFI"
 	    ;;
-	"6264" )
+	"6462" )
 	    echo "BOOTLOONGARCH64.EFI"
 	    ;;
-	"aa64" )
+	"64aa" )
 	    echo "BOOTAA64.EFI"
 	    ;;
 	* )
@@ -148,28 +117,6 @@ copy_syslinux_file() {
     return 1
 }
 
-# Create EFI boot partition
-#
-create_esp() {
-    local FILENAME
-    local BOOTCAT
-    local PLATFORM
-    local START
-    local COUNT
-
-    FILENAME="${1}"
-
-    BOOTCAT=$(( 0x$(get_dword "${FILENAME}" 0x8847) * 0x800 ))
-    PLATFORM=$(get_byte "${FILENAME}" $(( ${BOOTCAT} + 0x01 )) )
-    if [ "${PLATFORM}" != "ef" ] ; then
-	echo "${FILENAME}: missing EFI boot catalog" >&2
-	exit 1
-    fi
-    START=$(( 0x$(get_dword "${FILENAME}" $(( ${BOOTCAT} + 0x28 )) ) * 4 ))
-    COUNT=$(( 0x$(get_word "${FILENAME}" $(( ${BOOTCAT} + 0x26 )) ) * 4 ))
-    echo "${START},${COUNT},0xef;" | sfdisk -f -w never "${FILENAME}"
-}
-
 # Parse command-line options
 #
 OUTFILE=
@@ -282,19 +229,24 @@ done
 
 # Configure ISO image, if applicable
 #
-# Note that the BIOS boot files are required even for an EFI-only ISO,
-# since isohybrid will refuse to work without them.
+# Note that the BIOS boot files are required even for an EFI-only
+# hybrid ISO, since isohybrid will refuse to work without them.
 #
 if [ -n "${ISOIMG}" ] ; then
     ISOARGS="-J -R -l"
-    if [ -n "${LKRN}" ] ; then
+    if isohybrid --version >/dev/null 2>&1 ; then
+	ISOHYBRID=isohybrid
+    else
+	ISOHYBRID=
+    fi
+    if [ -n "${LKRN}" -o -n "${ISOHYBRID}" ] ; then
 	copy_syslinux_file "isolinux.bin" "${ISODIR}"
 	copy_syslinux_file "ldlinux.c32" "${ISODIR}" 2>/dev/null || true
 	ISOARGS="${ISOARGS} -no-emul-boot -eltorito-boot isolinux.bin"
 	ISOARGS="${ISOARGS} -boot-load-size 4 -boot-info-table"
-    fi
-    if [ -n "${LKRN}" -a -n "${EFI}" ] ; then
-	ISOARGS="${ISOARGS} -eltorito-alt-boot"
+	if [ -n "${EFI}" ] ; then
+	    ISOARGS="${ISOARGS} -eltorito-alt-boot"
+	fi
     fi
     if [ -n "${EFI}" ] ; then
 	ISOARGS="${ISOARGS} -no-emul-boot -e esp.img"
@@ -367,8 +319,7 @@ if [ -n "${ISOIMG}" ] ; then
 	    -appid "iPXE - Open Source Network Boot Firmware" \
 	    -publisher "ipxe.org" -sysid "iPXE" -o "${ISOIMG}" \
 	    ${ISOARGS} "${ISODIR}"
-    create_esp "${ISOIMG}"
-    if isohybrid --version >/dev/null 2>&1 ; then
+    if [ -n "${ISOHYBRID}" ] ; then
 	ISOHYBRIDARGS=
 	if [ -n "${EFI}" ] ; then
 	    ISOHYBRIDARGS="${ISOHYBRIDARGS} --uefi"
@@ -376,7 +327,7 @@ if [ -n "${ISOIMG}" ] ; then
 	if [ -n "${SOURCE_DATE_EPOCH:-}" ] ; then
 	    ISOHYBRIDARGS="${ISOHYBRIDARGS} --id ${SOURCE_DATE_EPOCH}"
 	fi
-	isohybrid ${ISOHYBRIDARGS} "${ISOIMG}"
+	"${ISOHYBRID}" ${ISOHYBRIDARGS} "${ISOIMG}"
     fi
 fi