Compile the UML kernel and download it in Github Actions

Add a build job, prerequisite of the existing job, to compile the UML
kernel and upload it and the signing key to a cache. Github configuration
should have two variables: LINUX_URL, the full URL of the kernel
repository; LINUX_BRANCH, the branch to check out as fallback if the kernel
repository does not have the same branch name as the one being pushed for
ima-evm-utils. See:

https://docs.github.com/en/actions/learn-github-actions/variables

for directions on how to define those variables.

If the two variables are not defined, the default values are:

LINUX_URL=https://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity.git
LINUX_BRANCH=next-integrity

If there is a cache hit (same kernel commit and same kernel configuration),
next time the UML kernel will not be rebuilt. To use the cache, it is
necessary to install zstd in the container. Add this dependency to
ci/fedora.sh.

The cache can be managed at the following URL:

https://github.com/<username>/ima-evm-utils/actions/caches

The page also offers the possibility to clean the cache, to force
rebuilding the kernel.

Add a new entry in the testing matrix, for the fedora-latest container
image, to run the tests with the UML kernel. The entry differs from the
others for the new environment variable TST_ENV, set to 'um', and
TST_KERNEL set to '../linux', as the tests will be executed from the
tests/ directory in ima-evm-utils.

Add a new volume to the container, /dev/shm from the host, as it is
required for running the UML kernel.

Extend the existing job with steps to download the UML kernel and signing
key from the cache. The new steps are executed only if the matrix entry has
TST_ENV set.

Finally, pass TST_ENV and TST_KERNEL to the tests. A test should also
propagate these variables to the new environment, by passing them to the
kernel command line.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

.github/workflows/ci.yml

@@ -3,7 +3,79 @@ name: "distros"
 on: [push, pull_request]
 
 jobs:
+  build:
+    runs-on: ubuntu-latest
+    outputs:
+      LINUX_SHA: ${{ steps.last-commit.outputs.LINUX_SHA }}
+    name: build
+    timeout-minutes: 100
+    strategy:
+      fail-fast: false
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Determine last kernel commit
+        id: last-commit
+        shell: bash
+        run: |
+          mkdir linux-integrity
+          pushd linux-integrity
+          git init
+          LINUX_URL=${{ vars.LINUX_URL }}
+          if [ -z "$LINUX_URL" ]; then
+              LINUX_URL=https://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity.git
+          fi
+          LINUX_BRANCH=${{ vars.LINUX_BRANCH }}
+          if [ -z "$LINUX_BRANCH" ]; then
+              LINUX_BRANCH=next-integrity
+          fi
+          git remote add origin $LINUX_URL
+          LINUX_SHA=$(git ls-remote origin $GITHUB_REF_NAME | awk '{print $1}')
+          [ -z "$LINUX_SHA" ] && LINUX_SHA=$(git ls-remote origin $LINUX_BRANCH | awk '{print $1}')
+          echo "LINUX_SHA=$LINUX_SHA" >> $GITHUB_OUTPUT
+          popd
+
+      - name: Cache UML kernel
+        id: cache-linux
+        uses: actions/cache@v3
+        with:
+          path: linux
+          key: linux-${{ steps.last-commit.outputs.LINUX_SHA }}-${{ hashFiles('**/kernel-configs/*') }}
+
+      - name: Cache signing key
+        id: cache-key
+        uses: actions/cache@v3
+        with:
+          path: signing_key.pem
+          key: signing_key.pem-${{ steps.last-commit.outputs.LINUX_SHA }}-${{ hashFiles('**/kernel-configs/*') }}
+
+      - name: Compile UML kernel
+        if: steps.cache-linux.outputs.cache-hit != 'true' || steps.cache-key.outputs.cache-hit != 'true'
+        shell: bash
+        run: |
+          if [ "$DEVTOOLSET" = "yes" ]; then
+                  source /opt/rh/devtoolset-10/enable
+          fi
+          if [ "$ARCH" = "i386" ]; then
+                  CROSS_COMPILE_OPT="CROSS_COMPILE=i686-linux-gnu-"
+          fi
+          pushd linux-integrity
+          git pull --depth 1 origin ${{ steps.last-commit.outputs.LINUX_SHA }}
+          make ARCH=um defconfig
+          ./scripts/kconfig/merge_config.sh -m .config $(ls ../kernel-configs/*)
+          # Update manually, to specify ARCH=um
+          make ARCH=um olddefconfig
+          # Make everything built-in
+          make ARCH=um localyesconfig
+          make ARCH=um $CROSS_COMPILE_OPT -j$(nproc)
+          chmod +x linux
+          cp linux ..
+          cp certs/signing_key.pem ..
+          popd
+
   job:
+    needs: build
     runs-on: ubuntu-latest
 
     strategy:
@@ -75,6 +147,13 @@ jobs:
               CC: clang
               TSS: ibmtss
 
+          - container: "fedora:latest"
+            env:
+              CC: clang
+              TSS: ibmtss
+              TST_ENV: um
+              TST_KERNEL: ../linux
+
           - container: "centos:7"
             env:
               CC: gcc
@@ -98,7 +177,7 @@ jobs:
     container:
       image: ${{ matrix.container }}
       env: ${{ matrix.env }}
-      options: --privileged --device /dev/loop-control
+      options: --privileged --device /dev/loop-control -v /dev/shm:/dev/shm
 
     steps:
     - name: Show OS
@@ -125,8 +204,24 @@ jobs:
             fi
         fi
 
+    - name: Retrieve UML kernel
+      if: ${{ matrix.env.TST_ENV }}
+      uses: actions/cache@v3
+      continue-on-error: false
+      with:
+        path: linux
+        key: linux-${{ needs.build.outputs.LINUX_SHA }}-${{ hashFiles('**/kernel-configs/*') }}
+
+    - name: Retrieve signing key
+      if: ${{ matrix.env.TST_ENV }}
+      continue-on-error: false
+      uses: actions/cache@v3
+      with:
+        path: signing_key.pem
+        key: signing_key.pem-${{ needs.build.outputs.LINUX_SHA }}-${{ hashFiles('**/kernel-configs/*') }}
+
     - name: Compiler version
       run: $CC --version
 
     - name: Compile
-      run: CC="$CC" VARIANT="$VARIANT" COMPILE_SSL="$COMPILE_SSL" ./build.sh
+      run: CC="$CC" VARIANT="$VARIANT" COMPILE_SSL="$COMPILE_SSL" TST_ENV="$TST_ENV" TST_KERNEL="$TST_KERNEL" ./build.sh

ci/fedora.sh

@@ -44,7 +44,8 @@ yum -y install \
 	util-linux \
 	vim-common \
 	wget \
-	which
+	which \
+	zstd
 
 yum -y install docbook5-style-xsl || true
 yum -y install swtpm || true