tag kernel with builder version; simplify Makefile

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

test/cases/020_kernel/111_kmod_5.4.x/Dockerfile

@@ -6,7 +6,7 @@
 FROM linuxkit/kernel:5.4.116 AS ksrc
 
 # Extract headers and compile module
-FROM linuxkit/alpine:2be490394653b7967c250e86fd42cef88de428ba AS build
+FROM linuxkit/kernel:5.4.116-builder AS build
 RUN apk add build-base elfutils-dev
 
 COPY --from=ksrc /kernel-dev.tar /

test/cases/020_kernel/113_kmod_5.10.x/Dockerfile

@@ -6,7 +6,7 @@
 FROM linuxkit/kernel:5.10.34 AS ksrc
 
 # Extract headers and compile module
-FROM linuxkit/alpine:2be490394653b7967c250e86fd42cef88de428ba AS build
+FROM linuxkit/kernel:5.10.34-builder AS build
 RUN apk add build-base elfutils-dev
 
 COPY --from=ksrc /kernel-dev.tar /

test/cases/020_kernel/114_kmod_5.11.x/Dockerfile

@@ -6,7 +6,7 @@
 FROM linuxkit/kernel:5.11.18 AS ksrc
 
 # Extract headers and compile module
-FROM linuxkit/alpine:2be490394653b7967c250e86fd42cef88de428ba AS build
+FROM linuxkit/kernel:5.11.18-builder AS build
 RUN apk add build-base elfutils-dev
 
 COPY --from=ksrc /kernel-dev.tar /

test/cases/020_kernel/211_tags_5.4.x/test.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+# SUMMARY: Test existence and correctness of kernel builder tag, label and file
+# LABELS:
+# REPEAT:
+
+set -e
+
+KERNEL=linuxkit/kernel:5.4.116
+
+# just include the common test
+. ../tags.sh

test/cases/020_kernel/213_tags_5.10.x/test.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+# SUMMARY: Test existence and correctness of kernel builder tag, label and file
+# LABELS:
+# REPEAT:
+
+set -e
+
+KERNEL=linuxkit/kernel:5.10.34
+
+# just include the common test
+. ../tags.sh

test/cases/020_kernel/214_tags_5.11.x/test.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+# SUMMARY: Test existence and correctness of kernel builder tag, label and file
+# LABELS:
+# REPEAT:
+
+set -e
+
+KERNEL=linuxkit/kernel:5.11.18
+
+# just include the common test
+. ../tags.sh

test/cases/020_kernel/tags.sh

@@ -0,0 +1,66 @@
+#!/bin/sh
+
+# common tags tests
+
+#!/bin/sh
+# SUMMARY: Test existence and correctness of kernel builder tag, label and file
+# LABELS:
+# REPEAT:
+
+set -e
+
+# Source libraries. Uncomment if needed/defined
+#. "${RT_LIB}"
+. "${RT_PROJECT_ROOT}/_lib/lib.sh"
+
+if [ -z "${KERNEL}" ]; then
+	echo "KERNEL env var must be set"
+	exit 1
+fi
+
+NAME=tags
+
+clean_up() {
+	docker rm ${ctrid}
+	/bin/rm -f ${BUILDERFILE}
+}
+trap clean_up EXIT
+
+# check the kernel images for tags, labels, files
+BUILDER=${KERNEL}-builder
+BUILDERFILE=/tmp/kernel-builder-$$
+
+docker pull ${KERNEL}
+docker pull ${BUILDER}
+BUILDERLABEL=$(docker inspect -f '{{index .Config.Labels "org.mobyproject.linuxkit.kernel.buildimage"}}'  ${KERNEL})
+# create the container; /bin/sh does not exist, but that does not prevent us from indicating what the command
+#   *would* be. Indeed, you *must* have a command for `docker create` to work
+ctrid=$(docker create $KERNEL /bin/sh)
+docker cp ${ctrid}:/etc/kernel-builder ${BUILDERFILE}
+FILECONTENTS=$(cat ${BUILDERFILE})
+
+# get the manifests for the referenced tag and for the referenced builder.
+# these are not guaranated to be identical, since the orders can change. So we need to account for that.
+sumtag=$(docker manifest inspect ${BUILDER} | jq  -c '.manifests | sort_by(.digest)' | sha256sum | awk '{print $1}')
+sumlabel=$(docker manifest inspect ${BUILDERLABEL} | jq  -c '.manifests | sort_by(.digest)' | sha256sum | awk '{print $1}')
+
+# these two files should be identical
+echo "builder label: ${BUILDERLABEL}"
+echo "builder file: ${FILECONTENTS}"
+echo "builder tag: ${BUILDER}"
+echo "builder tag sha256: ${sumtag}"
+echo "builder label sha256: ${sumlabel}"
+
+# check that the label and file contents match
+if [ "${BUILDERLABEL}" != "${FILECONTENTS}" ]; then
+	echo "label vs file contents mismatch"
+	exit 1
+fi
+# check that the tag actually points to the manifest
+if [ "${sumtag}" != "${sumlabel}" ]; then
+	echo "tag ${BUILDER} and label ${BUILDERLABEL} have mismatched contents"
+	exit 1
+fi
+
+
+exit 0