syslinux: build with the target toolchain

Until now, the host toolchain was used to build syslinux, as it was
not possible to build a 32-bit syslinux with a x86-64 toolchain.

However, syslinux requires gnu-efi, and gnu-efi is built using the
target toolchain. Mixing different toolchains doesn't work well, so
this commit changes the syslinux package to use the target toolchain
for syslinux as well. This is made possible by patches
0003-Fix-ldlinux.elf-Not-enough-room-for-program-headers-.patch and
0004-memdisk-Force-ld-output-format-to-32-bits.patch.

Since syslinux also contains some utilities that have to run on the
host, those have to continue being built with the host toolchain,
which requires patch 0005-utils-Use-the-host-toolchain-to-build.patch.

Patch 0006-lzo-Use-the-host-toolchain-for-prepcore.patch is about
building prepcore, another utility with the host toolchain as it is
required at build-time.

This was tested using a Buildroot's built x86_64 toolchain, and
checked that the output binaries are 32-bits. It was tested as well if
they actually boot on hardware.

Signed-off-by: Benoît Allard <benoit.allard@greenbone.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

1 files changed, 22 insertions, 7 deletions

diff --git a/boot/syslinux/syslinux.mk b/boot/syslinux/syslinux.mk
index 5b7906cffd..2b3b9a75f4 100644
--- a/boot/syslinux/syslinux.mk
+++ b/boot/syslinux/syslinux.mk
@@ -13,7 +13,7 @@ SYSLINUX_LICENSE_FILES = COPYING
 
 SYSLINUX_INSTALL_IMAGES = YES
 
-SYSLINUX_DEPENDENCIES = host-nasm host-util-linux host-upx
+SYSLINUX_DEPENDENCIES = host-nasm host-upx util-linux
 
 ifeq ($(BR2_TARGET_SYSLINUX_LEGACY_BIOS),y)
 SYSLINUX_TARGET += bios
@@ -51,21 +51,36 @@ SYSLINUX_POST_PATCH_HOOKS += SYSLINUX_CLEANUP
 # and the internal zlib should take precedence so -I shouldn't
 # be used.
 define SYSLINUX_BUILD_CMDS
-	$(TARGET_MAKE_ENV) $(MAKE1) CC="$(HOSTCC) -idirafter $(HOST_DIR)/usr/include $(HOST_LDFLAGS)" \
-		AR="$(HOSTAR)" $(SYSLINUX_EFI_ARGS) -C $(@D) $(SYSLINUX_TARGET)
+	$(TARGET_MAKE_ENV) $(MAKE1) \
+		CC="$(TARGET_CC)" \
+		LD="$(TARGET_LD)" \
+		NASM="$(HOST_DIR)/usr/bin/nasm" \
+		CC_FOR_BUILD="$(HOSTCC)" \
+		CFLAGS_FOR_BUILD="$(HOST_CFLAGS)" \
+		LDFLAGS_FOR_BUILD="$(HOST_LDFLAGS)" \
+            $(SYSLINUX_EFI_ARGS) -C $(@D) $(SYSLINUX_TARGET)
 endef
 
 # While the actual bootloader is compiled for the target, several
 # utilities for installing the bootloader are meant for the host.
 # Repeat the target, otherwise syslinux will try to build everything
-# Repeat CC and AR, since syslinux really wants to check them at
-# install time
+# Repeat LD (and CC) as it happens that some binaries are linked at
+# install-time.
 define SYSLINUX_INSTALL_TARGET_CMDS
-	$(TARGET_MAKE_ENV) $(MAKE1) CC="$(HOSTCC) -idirafter $(HOST_DIR)/usr/include $(HOST_LDFLAGS)" \
-		AR="$(HOSTAR)" $(SYSLINUX_EFI_ARGS) INSTALLROOT=$(HOST_DIR) \
+	$(TARGET_MAKE_ENV) $(MAKE1) $(SYSLINUX_EFI_ARGS) INSTALLROOT=$(HOST_DIR) \
+		CC="$(TARGET_CC)" \
+		LD="$(TARGET_LD)" \
 		-C $(@D) $(SYSLINUX_TARGET) install
 endef
 
+# That 'syslinux' binary is an installer actually built for the target.
+# However, buildroot makes no usage of it, so better delete it than have it
+# installed at the wrong place
+define SYSLINUX_POST_INSTALL_CLEANUP
+	rm -rf $(HOST_DIR)/usr/bin/syslinux
+endef
+SYSLINUX_POST_INSTALL_TARGET_HOOKS += SYSLINUX_POST_INSTALL_CLEANUP
+
 SYSLINUX_IMAGES-$(BR2_TARGET_SYSLINUX_ISOLINUX) += bios/core/isolinux.bin
 SYSLINUX_IMAGES-$(BR2_TARGET_SYSLINUX_PXELINUX) += bios/core/pxelinux.bin
 SYSLINUX_IMAGES-$(BR2_TARGET_SYSLINUX_MBR) += bios/mbr/mbr.bin