erofs output (#4162)

* add erofs as output option

Signed-off-by: Avi Deitcher <avi@deitcher.net>

* unify nearly identical functions

Signed-off-by: Avi Deitcher <avi@deitcher.net>

---------

Signed-off-by: Avi Deitcher <avi@deitcher.net>

src/cmd/linuxkit/moby/build/images.yaml

@@ -5,6 +5,7 @@
  raw-bios:       linuxkit/mkimage-raw-bios:42706053b66824d430e59edd7c195ee9b66493f4
  raw-efi:        linuxkit/mkimage-raw-efi:eac58d3efbfe1324fc9dbdd836e44fd6cd48f93c
  squashfs:       linuxkit/mkimage-squashfs:6908664b03dc38a5ad4381a2451c7a55ae32210f
+ erofs:          linuxkit/mkimage-erofs:cb41abbb3684773b14f51ab6649b2050d1241747
  gcp:            linuxkit/mkimage-gcp:7f220881aed6336708b62afea9820e436b573cea
  qcow2-efi:      linuxkit/mkimage-qcow2-efi:dbabe68ec09490b5ac44bd26962d848a33e0777d
  vhd:            linuxkit/mkimage-vhd:c6f7696575081986bdda9a6b48ead70498e2aeee

src/cmd/linuxkit/moby/build/output.go

@@ -102,6 +102,13 @@ var outFuns = map[string]func(base string, ir io.Reader, size int, arch string)
 		}
 		return nil
 	},
+	"kernel+erofs": func(base string, image io.Reader, size int, arch string) error {
+		err := outputKernelEroFS(outputImages["erofs"], base, image, arch)
+		if err != nil {
+			return fmt.Errorf("error writing kernel+erofs output: %v", err)
+		}
+		return nil
+	},
 	"kernel+iso": func(base string, image io.Reader, size int, arch string) error {
 		err := outputKernelISO(outputImages["iso"], base, image, arch)
 		if err != nil {
@@ -503,9 +510,10 @@ func outputKernelInitrdTarball(base string, kernel []byte, initrd []byte, cmdlin
 	return tw.Close()
 }
 
-func outputKernelSquashFS(image, base string, filesystem io.Reader, arch string) error {
+// outputKernelImage is a unified function for ISO, SquashFS, and EroFS kernel image outputs
-	log.Debugf("output kernel/squashfs: %s %s", image, base)
+func outputKernelImage(image, base, format, outfile string, filesystem io.Reader, arch string) error {
-	log.Infof("  %s-squashfs.img", base)
+	log.Debugf("output kernel/%s: %s %s", format, image, base)
+	log.Infof("  %s", outfile)
 
 	tr := tar.NewReader(filesystem)
 	buf := new(bytes.Buffer)
@@ -549,7 +557,7 @@ func outputKernelSquashFS(image, base string, filesystem io.Reader, arch string)
 	}
 	_ = rootfs.Close()
 
-	output, err := os.Create(base + "-squashfs.img")
+	output, err := os.Create(outfile)
 	if err != nil {
 		return err
 	}
@@ -562,61 +570,14 @@ func outputKernelSquashFS(image, base string, filesystem io.Reader, arch string)
 	return dockerRun(buf, output, image, []string{fmt.Sprintf("TARGETARCH=%s", march)})
 }
 
+func outputKernelSquashFS(image, base string, filesystem io.Reader, arch string) error {
+	return outputKernelImage(image, base, "squashfs", base+"-squashfs.img", filesystem, arch)
+}
+
+func outputKernelEroFS(image, base string, filesystem io.Reader, arch string) error {
+	return outputKernelImage(image, base, "erofs", base+"-erofs.img", filesystem, arch)
+}
+
 func outputKernelISO(image, base string, filesystem io.Reader, arch string) error {
-	log.Debugf("output kernel/iso: %s %s", image, base)
+	return outputKernelImage(image, base, "iso", base+".iso", filesystem, arch)
-	log.Infof("  %s.iso", base)
-
-	tr := tar.NewReader(filesystem)
-	buf := new(bytes.Buffer)
-	rootfs := tar.NewWriter(buf)
-
-	for {
-		var thdr *tar.Header
-		thdr, err := tr.Next()
-		if err == io.EOF {
-			break
-		}
-		if err != nil {
-			return err
-		}
-		thdr.Format = tar.FormatPAX
-		switch {
-		case thdr.Name == "boot/kernel":
-			kernel, err := io.ReadAll(tr)
-			if err != nil {
-				return err
-			}
-			if err := os.WriteFile(base+"-kernel", kernel, os.FileMode(0644)); err != nil {
-				return err
-			}
-		case thdr.Name == "boot/cmdline":
-			cmdline, err := io.ReadAll(tr)
-			if err != nil {
-				return err
-			}
-			if err := os.WriteFile(base+"-cmdline", cmdline, os.FileMode(0644)); err != nil {
-				return err
-			}
-		case strings.HasPrefix(thdr.Name, "boot/"):
-			// skip the rest of boot/
-		default:
-			_ = rootfs.WriteHeader(thdr)
-			if _, err := io.Copy(rootfs, tr); err != nil {
-				return err
-			}
-		}
-	}
-	_ = rootfs.Close()
-
-	output, err := os.Create(base + ".iso")
-	if err != nil {
-		return err
-	}
-	defer func() { _ = output.Close() }()
-
-	march, err := util.MArch(arch)
-	if err != nil {
-		return err
-	}
-	return dockerRun(buf, output, image, []string{fmt.Sprintf("TARGETARCH=%s", march)})
 }

test/cases/000_build/000_formats/014_kernel+erofs/test.sh

@@ -0,0 +1,24 @@
+#!/bin/sh
+# SUMMARY: Check that kernel+squashfs output format is generated
+# LABELS:
+
+set -e
+
+# Source libraries. Uncomment if needed/defined
+#. "${RT_LIB}"
+. "${RT_PROJECT_ROOT}/_lib/lib.sh"
+
+NAME=check
+
+clean_up() {
+	rm -f ${NAME}*
+}
+
+trap clean_up EXIT
+
+linuxkit build --format kernel+erofs --name "${NAME}" ../test.yml
+[ -f "${NAME}-kernel" ] || exit 1
+[ -f "${NAME}-erofs.img" ] || exit 1
+[ -f "${NAME}-cmdline" ] || exit 1
+
+exit 0

tools/mkimage-erofs/Dockerfile

@@ -0,0 +1,15 @@
+FROM linuxkit/alpine:6090baae063eb5023c9601966e88df831f789a70 AS mirror
+RUN mkdir -p /out/etc/apk && cp -r /etc/apk/* /out/etc/apk/
+RUN apk add --no-cache --initdb -p /out \
+  alpine-baselayout \
+  busybox \
+  libarchive-tools \
+  erofs-utils \
+  && true
+RUN mv /out/etc/apk/repositories.upstream /out/etc/apk/repositories
+
+FROM scratch
+WORKDIR /
+COPY --from=mirror /out/ /
+COPY . .
+ENTRYPOINT [ "/make-erofs" ]

tools/mkimage-erofs/build.yml

@@ -0,0 +1 @@
+image: mkimage-erofs

tools/mkimage-erofs/make-erofs

@@ -0,0 +1,22 @@
+#!/bin/sh
+
+set -e
+
+mkdir -p /tmp/rootfs
+cd /tmp/rootfs
+
+# input is a tarball of filesystem on stdin with the root filesytem
+# output is a squashfs image on stdout
+
+# extract. BSD tar auto recognises compression, unlike GNU tar
+# only if stdin is a tty, if so need files volume mounted...
+[ -t 0 ] || bsdtar xzf -
+cd /tmp
+
+# we want everything except the final result to stderr
+(
+    exec 1>&2;
+
+    mkfs.erofs ./rootfs.img rootfs
+)
+cat rootfs.img