ref: Create separate kernel and module images

This commit moves the kernel image out of the flintlock/ subdir and
splits the kernel image into two: one containing just the binary, the
other just the module.

The sequence works like so:
- `builder` creates a starting point image from Ubuntu, installing
  packages etc.
- `base` uses builder, pulls and compiles the kernel, then saves the
  modules and the binary in a `scratch` image. I have kept this image
  under the old `flintlock-kernel` name with modules and the binary to
  maintain backwards compatibility.
- `modules` and `bin` use `base` and simply copy the things they need
  into a `scratch` image.

The images produced are:
- `kernel-builder`
- `flintlock-kernel` (kept the same for backwards compatibility)
- `kernel-bin`
- `kernel-modules`

.github/workflows/flintlock-ubuntu-perftest.yml

@@ -1,14 +1,14 @@
 name: Ubuntu Perf Test - Build and release
 
-on:
-  pull_request:
-    paths:
-      - 'flintlock/perf-test/**'
-    branches: [main]
-  push:
-    paths:
-      - 'flintlock/perf-test/**'
-    branches: [main]
+on: {}
+  # pull_request:
+  #   paths:
+  #     - 'flintlock/perf-test/**'
+  #   branches: [main]
+  # push:
+  #   paths:
+  #     - 'flintlock/perf-test/**'
+  #   branches: [main]
 
 defaults:
   run:
@@ -41,4 +41,4 @@ jobs:
       - name: Build and push
         run: |
           make
-          make push
+          make push

.github/workflows/kernel-images-manual.yml

@@ -6,7 +6,7 @@ on:
 
 defaults:
   run:
-    working-directory: flintlock/kernel
+    working-directory: kernel
 
 jobs:
   release:
@@ -30,5 +30,6 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
       - name: Build and push
         run: |
+          make builder
           make
-          make push
+          make push

.github/workflows/kernel-images.yml

@@ -3,16 +3,16 @@ name: Kernel - Build and release
 on:
   pull_request:
     paths:
-      - 'flintlock/kernel/**'
+      - 'kernel/**'
     branches: [main]
   push:
     paths:
-      - 'flintlock/kernel/**'
+      - 'kernel/**'
     branches: [main]
 
 defaults:
   run:
-    working-directory: flintlock/kernel
+    working-directory: kernel
 
 jobs:
   build:
@@ -27,7 +27,9 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Build kernel
-        run: make
+        run: |
+          make builder
+          make
   release:
     if: github.event_name != 'pull_request'
     runs-on: ubuntu-latest
@@ -50,5 +52,6 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
       - name: Build and push
         run: |
+          make builder
           make
-          make push
+          make push

kernel/Makefile

@@ -0,0 +1,41 @@
+DOCKER := docker
+
+REGISTRY?=ghcr.io/weaveworks-liquidmetal
+
+BUILDER_IMAGE_NAME?=kernel-builder
+BASE_IMAGE_NAME?=flintlock-kernel
+BIN_IMAGE_NAME?=kernel-bin
+MOD_IMAGE_NAME?=kernel-modules
+
+KERNEL_VERSIONS ?= 4.19.215 5.10.77 # If you update this list, please remember to update the matrix in the kernel-images.yml github action!
+
+all: build
+
+builder:
+	$(DOCKER) build -t $(BUILDER_IMAGE_NAME):dev \
+		-f builder/Dockerfile .
+
+build: $(addprefix build-,$(KERNEL_VERSIONS))
+build-%: builder
+	$(MAKE) base-$*
+	$(MAKE) binary-$*
+	$(MAKE) modules-$*
+base-%:
+	$(DOCKER) build -t $(BASE_IMAGE_NAME):$* \
+		--build-arg KERNEL_VERSION=$* \
+		--build-arg IMAGE_NAME=$(BUILDER_IMAGE_NAME) \
+		-f base/Dockerfile .
+binary-%:
+	$(DOCKER) build -t $(BIN_IMAGE_NAME):$* \
+		--build-arg IMAGE_NAME=$(BASE_IMAGE_NAME):$* \
+		-f bin/Dockerfile .
+modules-%:
+	$(DOCKER) build -t $(MOD_IMAGE_NAME):$* \
+		--build-arg IMAGE_NAME=$(BASE_IMAGE_NAME):$* \
+		-f modules/Dockerfile .
+
+push: $(addprefix push-,$(KERNEL_VERSIONS))
+push-%:
+	$(DOCKER) push $(REGISTRY)/$(BASE_IMAGE_NAME):$*
+	$(DOCKER) push $(REGISTRY)/$(BIN_IMAGE_NAME):$*
+	$(DOCKER) push $(REGISTRY)/$(MOD_IMAGE_NAME):$*

kernel/bin/Dockerfile

@@ -0,0 +1,5 @@
+ARG IMAGE_NAME
+FROM ${IMAGE_NAME} AS builder
+FROM scratch
+
+COPY --from=builder /boot /boot

kernel/modules/Dockerfile

@@ -0,0 +1,5 @@
+ARG IMAGE_NAME
+FROM ${IMAGE_NAME} AS builder
+FROM scratch
+
+COPY --from=builder /lib/modules /lib/modules