Rewrite the image builder in Golang

Author: sprat

Dockerfile

@@ -24,33 +24,27 @@ RUN \
 --mount=type=cache,target=/root/.cache/go-build \
 CGO_ENABLED=0 go build -o /go/bin/init -v --ldflags '-s -w -extldflags=-static'
 
+# =========================================================
+FROM golang:1.24.5-alpine AS imager-build
+WORKDIR /go/src
+# COPY imager/go.mod imager/go.sum ./
+# RUN go mod download
+COPY imager .
+#COPY --from=init /go/bin/init /usr/share/claylinux/init
+RUN \
+--mount=type=cache,target=/root/.cache/go-build \
+go generate -v ./... && \
+CGO_ENABLED=0 go build -o /go/bin/imager -v --ldflags '-s -w -extldflags=-static'
+
 # =========================================================
 FROM alpine:3.22.1 AS alpine-base
 
 # =========================================================
 FROM alpine-base AS imager
-SHELL ["/bin/ash", "-euxo", "pipefail", "-c"]
-RUN \
-echo "@edge-community https://dl-cdn.alpinelinux.org/alpine/edge/community" >>/etc/apk/repositories && \
-apk add --no-cache \
-bash \
-binutils \
-coreutils \
-cpio \
-dosfstools \
-findutils \
-mtools \
-pigz \
-qemu-img \
-sfdisk \
-xorriso \
-zstd \
-xz \
-systemd-efistub@edge-community
-COPY --from=init /go/bin/init /usr/share/claylinux/init
-COPY build-image.sh /usr/bin/build-image
+RUN apk add --no-cache binutils systemd-efistub
+COPY --from=imager-build /go/bin/imager /bin/imager
 WORKDIR /out
-ENTRYPOINT ["build-image"]
+ENTRYPOINT ["/bin/imager"]
 
 # =========================================================
 FROM alpine-base AS bootable-alpine-rootfs
@@ -110,7 +104,7 @@ RUN if [ "$UCODE" != "none" ]; then apk add --no-cache "${UCODE}-ucode"; fi
 # hadolint ignore=DL3006
 FROM imager AS test
 ARG FORMAT=efi
-RUN --mount=from=test-rootfs,target=/system build-image --format "$FORMAT"
+RUN --mount=from=test-rootfs,target=/system /bin/imager --format "$FORMAT"
 
 # =========================================================
 # Generate a qemu image running our custom OS image

build-image.sh imager/build.shbuild-image.sh renamed to imager/build.sh

@@ -1,135 +1,6 @@
 #!/bin/bash
 set -euo pipefail
 
-# exit with an error message
-die() {
-	echo "Error: $*" >&2
-	exit 1
-}
-
-# get the size of the file in bytes
-get_size() {
-	stat -c %s "$1"
-}
-
-# convert a number of bytes into MiB (i.e. 1024 * 1024 bytes), rounded to the next value
-in_mib() {
-	echo $(( ($1 + (1<<20) - 1) >> 20 ))
-}
-
-# get the size of the file in mibytes
-get_size_mib() {
-	in_mib "$(get_size "$1")"
-}
-
-# round the value given in $1 to the next multiple of the value given in $2
-# e.g. align 9 4 -> 12, align 8 4 -> 8
-align() {
-	echo "$(( ($1 + $2 - 1) / $2 * $2 ))"
-}
-
-# build the EFI executable
-build_efi() {
-	local size kernel
-
-	pushd "$build_dir" >/dev/null
-
-	echo "Building the EFI executable"
-	build_initramfs
-	size=$(get_size_mib initramfs)
-	echo "The size of the initramfs is: $size MiB"
-	kernel=$(find /system/boot -name 'vmlinu*' -print)
-	space_separated </system/boot/cmdline >cmdline
-	basename /system/lib/modules/* >kernel-release
-
-	# build the EFI UKI file
-	# TODO: add .dtb section on ARM?
-	build_uki <<-EOF
-	.osrel /system/etc/os-release
-	.uname kernel-release
-	.cmdline cmdline
-	.initrd initramfs
-	.linux $kernel
-	EOF
-
-	# delete all the temporary files
-	find . ! -name '*.efi' -delete
-
-	popd >/dev/null
-}
-
-# build the initramfs
-build_initramfs() {
-	mkdir initramfs_files
-
-	# copy the init script
-	cp /usr/share/claylinux/init initramfs_files
-
-	# copy /etc/hosts.target as /etc/hosts
-	if [[ -f /system/etc/hosts.target ]]; then
-		mkdir -p initramfs_files/etc
-		cp /system/etc/hosts.target initramfs_files/etc/hosts
-	fi
-
-	# copy etc/resolv.conf.target as etc/resolv.conf
-	if [[ -f /system/etc/resolv.conf.target ]]; then
-		mkdir -p initramfs_files/etc
-		cp /system/etc/resolv.conf.target initramfs_files/etc/resolv.conf
-	fi
-
-	# create an initramfs with these files
-	find initramfs_files -mindepth 1 -printf '%P\0' \
-	| cpio --quiet -o0H newc -D initramfs_files -F initramfs.img
-
-	# append the system files into the initramfs image, except /boot, /etc/hosts.target and /etc/resolv.conf.target
-	find /system \
-	-path /system/boot -prune -o \
-	! -path /system/init \
-	! -path /system/etc/hosts.target \
-	! -path /system/etc/resolv.conf.target \
-	-mindepth 1 -printf '%P\0' \
-	| cpio --quiet -o0AH newc -D /system -F initramfs.img
-
-	# compress the initramfs
-	compress initramfs.img
-
-	# build the final initramfs by concatenating the ucode images & our compressed initramfs image
-	# see https://docs.kernel.org/arch/x86/microcode.html
-	echo "$(find /system/boot/ -name '*-ucode.img') initramfs.img" | xargs cat >initramfs
-
-	# remove the temporary files
-	find . ! -name initramfs -delete
-}
-
-# create a Unified Kernel Image from the sections passed in the standard input
-build_uki() {
-	# the sections addresses should be aligned to PAGE_ALIGN(), i.e. 2<<12 == 4096 bytes
-	local args=() alignment=4096 size offset
-
-	# compute the start offset of the new sections
-	offset="$(objdump -h -w "$efi_stub" | awk 'END { offset=("0x"$4)+0; size=("0x"$3)+0; print offset + size }')"
-	offset=$(align "$offset" $alignment)
-
-	# compute the objcopy arguments
-	while read -r section file
-	do
-		# add the section to the parameters
-		args+=(
-			--add-section
-			"$section=$file"
-			--change-section-vma
-			"$section=$offset"
-		)
-
-		# compute the offset for the next section
-		size="$(get_size "$file")"
-		size=$(align "$size" $alignment)
-		offset=$(( offset + size ))
-	done
-
-	objcopy "${args[@]}" "$efi_stub" "$efi_file"
-}
-
 # detect the current EFI architecture
 get_efi_arch() {
 	local machine_arch
@@ -153,34 +24,6 @@ get_efi_arch() {
 	esac
 }
 
-# convert a multi-line input into a space separated list
-space_separated() {
-	paste -d' ' -s
-}
-
-# compress the initramfs with the specified scheme
-compress() {
-	case "$compression" in
-		none)
-			;;
-		gz)
-			pigz -9 "$1"
-			mv "$1".gz "$1"
-			;;
-		xz)
-			xz -C crc32 -9 -T0 "$1"
-			mv "$1".xz "$1"
-			;;
-		zstd)
-			zstd -19 -T0 --rm "$1"
-			mv "$1".zstd "$1"
-			;;
-		*)
-			die "invalid compression scheme '$compression'"
-			;;
-	esac
-}
-
 # just copy the build files to the output directory
 generate_efi() {
 	echo "Copying the OS files to the output directory"
@@ -312,7 +155,6 @@ format=raw
 volume=CLAYLINUX
 compression=gz
 efi_arch=$(get_efi_arch)
-efi_stub="/usr/lib/systemd/boot/efi/linux${efi_arch}.efi.stub"
 
 usage=$(cat <<-EOF
 	Usage: $(basename "$0") [OPTIONS ...]
@@ -373,7 +215,7 @@ done
 build_dir=$(mktemp -d)
 efi_file="$build_dir"/claylinux.efi
 esp_file="$build_dir"/claylinux.esp
-build_efi
+imager "$build_dir"
 mkdir -p "$(dirname "$output")"
 generate_"$format"
 rmdir "$build_dir"

imager/efi/arch_386.go

@@ -0,0 +1,5 @@
+//go:build 386
+
+package efi
+
+const Arch = "IA32"

imager/efi/arch_amd64.go

@@ -0,0 +1,5 @@
+//go:build amd64
+
+package efi
+
+const Arch = "X64"

imager/efi/arch_arm.go

@@ -0,0 +1,5 @@
+//go:build arm
+
+package efi
+
+const Arch = "ARM"

imager/efi/arch_arm64.go

@@ -0,0 +1,5 @@
+//go:build arm64
+
+package efi
+
+const Arch = "AA64"

imager/efi/constants.go

@@ -0,0 +1,3 @@
+package efi
+
+const Extension = ".efi"

imager/efi/initramfs.go

@@ -0,0 +1,78 @@
+package efi
+
+import (
+	"bytes"
+	"log"
+
+	"github.com/cavaliergopher/cpio"
+	//"github.com/u-root/u-root/pkg/cpio"
+)
+
+func BuildInitramfs(rootfsDir string, buildDir string) {
+	// Create a buffer to write our archive to.
+	buf := new(bytes.Buffer)
+
+	// Create a new cpio archive.
+	w := cpio.NewWriter(buf)
+
+	// Add some files to the archive.
+	var files = []struct {
+		Name, Body string
+	}{
+		{"readme.txt", "This archive contains some text files."},
+		{"gopher.txt", "Gopher names:\nGeorge\nGeoffrey\nGonzo"},
+		{"todo.txt", "Get animal handling license."},
+	}
+	for _, file := range files {
+		hdr := &cpio.Header{
+			Name: file.Name,
+			Mode: 0600,
+			Size: int64(len(file.Body)),
+		}
+		if err := w.WriteHeader(hdr); err != nil {
+			log.Fatalln(err)
+		}
+		if _, err := w.Write([]byte(file.Body)); err != nil {
+			log.Fatalln(err)
+		}
+	}
+
+	// Make sure to check the error on Close.
+	if err := w.Close(); err != nil {
+		log.Fatalln(err)
+	}
+
+	/*
+	os.Mkdir("initramfs_files", 0755)
+	run("cp", "/usr/share/claylinux/init", "initramfs_files")
+
+	if fileExists("/system/etc/hosts.target") {
+		os.MkdirAll("initramfs_files/etc", 0755)
+		run("cp", "/system/etc/hosts.target", "initramfs_files/etc/hosts")
+	}
+	if fileExists("/system/etc/resolv.conf.target") {
+		os.MkdirAll("initramfs_files/etc", 0755)
+		run("cp", "/system/etc/resolv.conf.target", "initramfs_files/etc/resolv.conf")
+	}
+	// cpio for initramfs_files
+	run("sh", "-c", `find initramfs_files -mindepth 1 -printf '%P\0' | cpio --quiet -o0H newc -D initramfs_files -F initramfs.img`)
+	// Add system files except boot, hosts.target, resolv.conf.target
+	run("sh", "-c", `find /system -path /system/boot -prune -o ! -path /system/init ! -path /system/etc/hosts.target ! -path /system/etc/resolv.conf.target -mindepth 1 -printf '%P\0' | cpio --quiet -o0AH newc -D /system -F initramfs.img`)
+	compress("initramfs.img")
+
+	ucode := runOutput("find", "/system/boot/", "-name", "*-ucode.img")
+	imgs := "initramfs.img"
+	if ucode != "" {
+		imgs = ucode + " " + imgs
+	}
+	run("sh", "-c", fmt.Sprintf("cat %s >initramfs", imgs))
+	run("find", ".", "!", "-name", "initramfs", "-delete")
+	*/
+}
+
+/*
+func compress(filename string) {
+	"none", "gz", "xz", "zstd"
+	"invalid compression scheme: " + compression
+}
+*/