Enable building a toolchain for Linux

Leverage coreboot's buildgcc to build a suitable Linux toolchain if
needed.

Signed-off-by: David Hendricks <david.hendricks@gmail.com>

Author: dhendrix

Makefile.inc

@@ -120,7 +120,15 @@ endif
 # example "x86_64-linux-gnu-gcc-10".
 ifeq ($(CROSS_COMPILING), 1)
 INITRAMFS_BUILD_GOROOT ?= /usr/local/go
+ifeq ($(shell which $(LINUX_GCC_TUPLE)gcc),)
+BUILD_LINUX_WITH_COREBOOT_TOOLCHAIN = 1
+CROSS_COMPILE ?= $(COREBOOT_BUILD_DIR)/util/crossgcc/xgcc/bin/$(LINUX_GCC_TUPLE)
 else
+BUILD_LINUX_WITH_COREBOOT_TOOLCHAIN = 0
+CROSS_COMPILE ?= $(LINUX_GCC_TUPLE)
+endif
+else
+CROSS_COMPILE =
 # FIXME: Also need to fix behavior when we're not cross-compilng, but system's
 # go version doesn't match the version we're using to build the initramfs...
 #INITRAMFS_BUILD_GOROOT ?= $(INITRAMFS_BUILD_DIR)/go
@@ -201,8 +209,8 @@ $(COREBOOT_TOOLCHAIN_OUT)/bin/iasl: $(COREBOOT_DEPS_FLAG) $(COREBOOT_PATCH_FLAG)
 	  tar xf $(COREBOOT_TOOLCHAIN_CACHE) -C $(dir $(COREBOOT_TOOLCHAIN_OUT)); \
 	  touch $@; \
 	else \
-	  COREBOOT_BUILD_DIR=$(COREBOOT_BUILD_DIR) CPUS=$(NPROC) MAKE=$(MAKE) ARCH=$(ARCH) TOOLS_DIR=$(TOOLS_DIR) \
-	    $(TOOLS_DIR)/build_toolchain.sh; \
+	  COREBOOT_BUILD_DIR=$(COREBOOT_BUILD_DIR) CPUS=$(NPROC) MAKE=$(MAKE) ARCH=$(COREBOOT_TOOLCHAIN_ARCH) \
+	  TOOLS_DIR=$(TOOLS_DIR) $(TOOLS_DIR)/build_toolchain.sh coreboot; \
 	fi
 
 # Creates coreboot config file using the user-provided one and feeding it to make olddefconfig.
@@ -236,19 +244,28 @@ wipe-coreboot:
 # Top-level initramfs target, for use by humans.
 kernel: $(KERNEL_OUT)
 
+kernel_toolchain: $(COREBOOT_DEPS_FLAG) $(COREBOOT_PATCH_FLAG)
+ifeq "$(BUILD_LINUX_WITH_COREBOOT_TOOLCHAIN)" "1"
+	echo 'Building cross toolchain for Linux'
+	COREBOOT_BUILD_DIR=$(COREBOOT_BUILD_DIR) CPUS=$(NPROC) MAKE=$(MAKE) ARCH=$(LINUX_ARCH) \
+	 TOOLS_DIR=$(TOOLS_DIR) $(TOOLS_DIR)/build_toolchain.sh linux;
+else
+	echo 'Building Linux with toolchain tuple: $(CROSS_COMPILE)'
+endif
+
 # Kernel build target. Requires initrmafs image, config and patches.
 ifneq "$(INITRAMFS_IN)" ""
-$(KERNEL_OUT): $(INITRAMFS_IN) $(KERNEL_CONFIG_OUT) $(KERNEL_PATCH_FLAG)
+$(KERNEL_OUT): $(INITRAMFS_IN) $(KERNEL_CONFIG_OUT) $(KERNEL_PATCH_FLAG) kernel_toolchain
 else
-$(KERNEL_OUT): $(KERNEL_CONFIG_OUT) $(KERNEL_PATCH_FLAG)
+$(KERNEL_OUT): $(KERNEL_CONFIG_OUT) $(KERNEL_PATCH_FLAG) $(KERNEL_TOOLCHAIN) $(KERNEL_TOOLCHAIN)
 endif
 	@# If lzma(1) is not available, kernel build will fall back to gzip and we don't want that.
 	@if ! lzma -h > /dev/null 2>/dev/null; then \
 	  echo ' *** Please install the lzma CLI utility.' >&2; \
 	  echo ' *** In RedHat distros it`s provided by xz-lzma-compat, in Debian/Ubuntu it`s provided by xz-utils.' >&2; \
 	  exit 1; \
 	fi
-	MAKEFLAGS= $(MAKE) -C $(KERNEL_BUILD_DIR) -j$(NPROC) KCFLAGS=-pipe
+	ARCH=$(LINUX_ARCH) CROSS_COMPILE=$(CROSS_COMPILE) MAKEFLAGS= $(MAKE) -C $(KERNEL_BUILD_DIR) -j$(NPROC) KCFLAGS=-pipe
 	[ "$@" = "$(KERNEL_OUT_DEFAULT)" ] || cp -v "$(KERNEL_OUT_DEFAULT)" "$@"
 
 ifeq "$(ALWAYS_BUILD_KERNEL)" "1"
@@ -258,7 +275,7 @@ endif
 $(KERNEL_CONFIG_OUT): $(KERNEL_CONFIG) $(KERNEL_DEPS_FLAG)
 	cp $(KERNEL_CONFIG) $@
 	sed -i "s|CONFIG_INITRAMFS_SOURCE=.*|CONFIG_INITRAMFS_SOURCE=\"$(INITRAMFS_IN)\"|" $@
-	MAKEFLAGS= $(MAKE) -C $(KERNEL_BUILD_DIR) olddefconfig
+	ARCH=$(LINUX_ARCH) MAKEFLAGS= $(MAKE) -C $(KERNEL_BUILD_DIR) olddefconfig
 
 $(KERNEL_PATCH_FLAG): $(realpath $(wildcard $(PATCHES_DIR)/kernel-*))
 	$(call patch,$(KERNEL_BUILD_DIR),$^)

examples/qemu/Makefile

@@ -12,7 +12,9 @@ CROSS_COMPILING := 0
 endif
 
 ifeq ($(ARCH), x86_64)
+COREBOOT_TOOLCHAIN_ARCH := i386
 LINUX_ARCH := $(ARCH)
+LINUX_GCC_TUPLE := $(ARCH)-linux-
 LINUX_IMAGE_RELATIVE_PATH := arch/x86/boot/bzImage
 GOARCH := amd64
 PLATFORM := qemu-amd64

tools/build_toolchain.sh

@@ -19,26 +19,41 @@ cleanup
 # This will be used by the wget script to record external dependencies while fetching.
 export EXTERNAL_DEPS_FILE
 
-if [ -z "${ARCH##x86*}" ] || [ -z "${ARCH##amd64}" ]; then
-	ARCH=i386
-elif [ -z "${ARCH##ppc*}" ]; then
-	ARCH=ppc64
-fi
+if [ "$1" == "coreboot" ]; then
+	if [ -z "${ARCH##x86*}" ] || [ -z "${ARCH##amd64}" ]; then
+		ARCH=i386
+	elif [ -z "${ARCH##ppc*}" ]; then
+		ARCH=ppc64
+	fi
 
-if ! MAKEFLAGS="" PATH="${TOOLS_DIR}:${PATH}" "${MAKE}" -C "${COREBOOT_BUILD_DIR}" crossgcc-${ARCH} BUILD_LANGUAGES=c; then
-  {
-    echo
-    echo "=== Toolchain build failed"
-    if [ -f "${EXTERNAL_DEPS_FILE}" ]
-    then
-      echo
-      echo -n "One or more additional external dependencies are required for the build: "
-      cat "${EXTERNAL_DEPS_FILE}"
-      echo
-      echo "Please re-run build with USE_FWDPROXY=1 to collect all the required files."
-    fi
-  } >&2
-  exit 1
+	if ! MAKEFLAGS="" PATH="${TOOLS_DIR}:${PATH}" "${MAKE}" -C "${COREBOOT_BUILD_DIR}" crossgcc-${ARCH} BUILD_LANGUAGES=c; then
+	  {
+	    echo
+	    echo "=== Toolchain build failed"
+	    if [ -f "${EXTERNAL_DEPS_FILE}" ]
+	    then
+	      echo
+	      echo -n "One or more additional external dependencies are required for the build: "
+	      cat "${EXTERNAL_DEPS_FILE}"
+	      echo
+	      echo "Please re-run build with USE_FWDPROXY=1 to collect all the required files."
+	    fi
+	  } >&2
+	  exit 1
+	fi
+elif [ "$1" == "linux" ]; then
+	rc=0
+	pushd .
+	cd "${COREBOOT_BUILD_DIR}/util/crossgcc"
+	if ! ./buildgcc -p ${ARCH}-linux -j$(nproc --ignore=1); then
+	  {
+		echo
+		echo "=== Toolchain build failed"
+		rc=1
+	  } >&2
+	fi
+	popd
+	exit $rc
 fi
 
 if [ -f "${EXTERNAL_DEPS_FILE}" ]