kernels: Create LinuKit kernel images from Ubuntu mainline

The Ubuntu mainline PPA has kernel.org based kernels for many
kernel releaseis.  This commit adds suport for downloading and
converting the 3.16.x long long term support kernel as well
as the current 4.x series.  The "mainline.sh" script only
downloads/processes kernels which have not yet been put on
Hub.

The kernels are stored under "linuxkit/kernel-mainline" and are
tagged with the kernel version.

Signed-off-by: Rolf Neugebauer <rolf.neugebauer@docker.com>

scripts/kernels/Dockerfile.deb

@@ -0,0 +1,24 @@
+FROM alpine:3.5 AS extract
+
+ARG DEB_URLS
+
+RUN apk add --no-cache curl dpkg tar && true
+WORKDIR /deb
+RUN mkdir extract
+RUN for url in ${DEB_URLS}; do \
+        echo "Extracting: $url"; \
+        curl -fsSL -o dl.deb $url && \
+        dpkg-deb -x dl.deb . ;\
+    done
+
+RUN mkdir /out
+RUN cp -a boot/vmlinuz-* /out/kernel
+RUN cp -a boot/config-* /out/kernel_config
+RUN tar cf /out/kernel.tar lib
+RUN tar cf /out/kernel-dev.tar usr
+
+FROM linuxkit/toybox-media:d7e82a7d19ccc84c9071fa7a88ecaa58ae958f7c@sha256:4c7d25f2be2429cd08417c36e04161cb924e46f3e419ee33a0aa9ff3a0942e02
+WORKDIR /
+ENTRYPOINT []
+CMD []
+COPY --from=extract /out/* /

scripts/kernels/mainline.sh

@@ -0,0 +1,49 @@
+#! /bin/sh
+
+REPO="linuxkit/kernel-mainline"
+BASE_URL=http://kernel.ubuntu.com/~kernel-ppa/mainline
+
+build_image() {
+    VERSION=$1
+    KDIR=$2
+    ARCH=amd64
+
+    LINKS=$(curl -s ${BASE_URL}/${KDIR}/ | \
+                sed -n 's/.*href="\([^"]*\).*/\1/p')
+
+    IMAGE=$(echo $LINKS | \
+            grep -o "linux-image[^ ]\+-generic[^ ]\+${ARCH}.deb" | head -1)
+    [ -z "${IMAGE}" ] && return 1
+    HDR_GEN=$(echo $LINKS | grep -o "linux-headers[^ ]\+_all.deb" | head -1)
+    [ -z "${HDR_GEN}" ] && return 1
+    HDR_ARCH=$(echo $LINKS | \
+               grep -o "linux-headers[^ ]\+-generic[^ ]\+${ARCH}.deb" | head -1)
+    [ -z "${HDR_ARCH}" ] && return 1
+
+    DEB_URL=${BASE_URL}/${KDIR}/${IMAGE}
+    HDR_GEN_URL=${BASE_URL}/${KDIR}/${HDR_GEN}
+    HDR_ARCH_URL=${BASE_URL}/${KDIR}/${HDR_ARCH}
+    echo "Trying to fetch ${VERSION} from ${DEB_URL}"
+
+    docker build -t ${REPO}:${VERSION} -f Dockerfile.deb --no-cache \
+           --build-arg DEB_URLS="${DEB_URL} ${HDR_GEN_URL} ${HDR_ARCH_URL}" .
+}
+
+LINKS=$(curl -s ${BASE_URL}/ | sed -n 's/.*href="\([^"]*\).*/\1/p')
+# Extract all kernel versions (drop RCs, ckt(?) and other links)
+VERSIONS=$(echo $LINKS | grep -o "v[0-9]\+\.[0-9]\+\.[0-9]\+[^ ]*" | \
+           grep -ve '-rc' | grep -ve '-ckt' | uniq)
+
+# Extract 3.16.x and 4.x.x
+THREES=$(echo $VERSIONS | grep -o "v3\.16\.[0-9]\+[^ ]*")
+FOURS=$(echo $VERSIONS | grep -o "v4\.[0-9]\+\.[0-9]\+[^ ]*")
+KDIRS="${THREES} ${FOURS}"
+
+for KDIR in $KDIRS; do
+    # Strip the Ubuntu release name for the tag and also the 'v' like with
+    # the other kernel packages
+    VERSION=$(echo $KDIR | grep -o "[0-9]\+\.[0-9]\+\.[0-9]\+")
+    DOCKER_CONTENT_TRUST=1 docker pull ${REPO}:${VERSION} && continue
+    build_image ${VERSION} ${KDIR} && \
+        DOCKER_CONTENT_TRUST=1 docker push ${REPO}:${VERSION}
+done