# A Linux kernel OCI artifact built from torvalds/linux at the v7.0 tag.
#
# An ordinary CONTAINER build (FROM a base image, not a kernel): every RUN
# executes in a container on the build-env's toolchain — there is no special
# "kernel mode". The output is a plain OCI image labelled `type=kernel`; a
# downstream *bootable* build consumes it via `FROM`, and `FROM` resolving to a
# `type=kernel` artifact is precisely what marks that build bootable.
FROM registry.bitswalk.net/examples/kernel-build-env:1.0

# Version knobs as ENV (not ARG): ENV values are present in each RUN's
# container environment and the shell expands $VAR. UMF does not substitute
# ARG into RUN, so ARG would not work here.
#
# The git *tag* is v7.0; the resulting kernel *release* (VERSION.PATCHLEVEL.
# SUBLEVEL) is 7.0.0 — the label and the on-disk vmlinuz/modules suffixes all
# use 7.0.0 and must agree.
ENV KERNEL_TAG="v7.0"
ENV KERNEL_RELEASE="7.0.0"

WORKDIR /usr/src

# Fetch exactly the tagged tree, shallow (no history), from upstream.
RUN git clone --depth 1 --branch "$KERNEL_TAG" \
        https://github.com/torvalds/linux.git linux

WORKDIR /usr/src/linux

# Configure. `defconfig` is the arch's sane default; for a curated kernel,
# `ADD ./config/myconfig .config` then `RUN make olddefconfig` instead.
RUN make defconfig

# Build the kernel image + modules. Empty LOCALVERSION keeps `make
# kernelrelease` exactly equal to $KERNEL_RELEASE so the install paths match.
RUN make -j"$(nproc)" LOCALVERSION= all

# Lay the artifact down in the layout the FROM-kernel resolver expects:
#   boot/vmlinuz-<release>   and   lib/modules/<release>/
RUN install -Dm644 "$(make -s image_name)" "/boot/vmlinuz-$KERNEL_RELEASE" \
 && make INSTALL_MOD_PATH=/ INSTALL_MOD_STRIP=1 modules_install

# `type=kernel` is what lets a downstream bootable build's `FROM` validate this
# artifact (L0 introspection); `kernel.release` MUST match the vmlinuz/modules
# suffix written above.
LABEL org.imagilux.umf.type=kernel
LABEL org.imagilux.umf.kernel.release="7.0.0"
LABEL org.imagilux.umf.kernel.config=defconfig