kernel: add build config for the experimental "split kernel"

The aim of the split kernel is to introduce a level of intra-kernel
protection into the kernel so that, amongst other things, it can
offer lifetime guarantees over kernel code and data integrity.

These patches only wire in the kernel build from a 4.11-rc3 snapshot.
The userspace tools will follow shortly.  Instructions came via
https://github.com/linux-okernel/linux-okernel (linux-okernel branch)
and via @edwards-n and @t-koulouris.

The build can be done via `cd projects/okernel && make`.

Signed-off-by: Anil Madhavapeddy <anil@docker.com>

projects/okernel/Dockerfile.okernel

@@ -0,0 +1,55 @@
+FROM mobylinux/alpine-build-kernel:0e893fbf6fa7638d2f23354de03ea11017bb8065@sha256:3ef3f9d11f0802b759dbd9c43a7706cf0ec37263c99ae90e2b10c29ea85739fa
+
+ARG KERNEL_PREFIX
+ARG KERNEL_VERSION
+ARG DEBUG=0
+
+ENV KERNEL_SOURCE=https://github.com/linux-okernel/linux-okernel/archive/ok-${KERNEL_VERSION}.tar.gz
+
+RUN curl -fsSL -o linux-${KERNEL_PREFIX}${KERNEL_VERSION}.tar.gz ${KERNEL_SOURCE}
+
+RUN cat linux-${KERNEL_PREFIX}${KERNEL_VERSION}.tar.gz | tar --absolute-names -xz &&  mv /linux-${KERNEL_PREFIX}${KERNEL_VERSION} /linux
+
+# NOTE: This currently re-uses the 4.9 kernel config with CONFIG_OKERNEL set
+COPY kernel_config.okernel /linux/arch/x86/configs/x86_64_defconfig
+#COPY kernel_config.debug /linux/debug_config
+
+RUN if [ $DEBUG -ne "0" ]; then \
+    sed -i 's/CONFIG_PANIC_ON_OOPS=y/# CONFIG_PANIC_ON_OOPS is not set/' /linux/arch/x86/configs/x86_64_defconfig; \
+    cat /linux/debug_config >> /linux/arch/x86/configs/x86_64_defconfig; \
+    fi
+
+# Apply local patches
+# COPY patches-4.10 /patches
+#RUN cd /linux && \
+#   set -e && for patch in /patches/*.patch; do \
+#        echo "Applying $patch"; \
+#        patch -p1 < "$patch"; \
+#    done
+
+RUN cd /linux && \
+    make defconfig && \
+    make oldconfig && \
+    make -j "$(getconf _NPROCESSORS_ONLN)" KCFLAGS="-fno-pie"
+RUN cd /linux && \
+    make INSTALL_MOD_PATH=/tmp/kernel-modules modules_install && \
+    ( DVER=$(basename $(find /tmp/kernel-modules/lib/modules/ -mindepth 1 -maxdepth 1)) && \
+      cd /tmp/kernel-modules/lib/modules/$DVER && \
+      rm build source && \
+      ln -s /usr/src/linux-headers-$DVER build ) && \
+    mkdir -p /tmp/kernel-headers/usr && \
+    make INSTALL_HDR_PATH=/tmp/kernel-headers/usr headers_install && \
+    ( cd /tmp/kernel-headers && tar cf /kernel-headers.tar usr ) && \
+    ( cd /tmp/kernel-modules && tar cf /kernel-modules.tar lib ) && \
+    cp vmlinux arch/x86_64/boot/bzImage /
+
+RUN DVER=$(basename $(find /tmp/kernel-modules/lib/modules/ -mindepth 1 -maxdepth 1)) && \
+    dir=/tmp/usr/src/linux-headers-$DVER && \
+    mkdir -p $dir && \
+    cp /linux/.config $dir && \
+    cd /linux && \
+    cp -a include "$dir" && \
+    mkdir -p "$dir"/arch/x86 && cp -a arch/x86/include "$dir"/arch/x86/ && \
+    ( cd /tmp && tar cf /kernel-dev.tar usr/src )
+
+RUN printf "KERNEL_SOURCE=${KERNEL_SOURCE}\n" > /kernel-source-info