Factor out tar-artifacts action (#148)

Rework tar-artifact.sh script, making it suitable for use as an
independent github action.

Use tar -rf (append) to accumulate files of interest before
compressing with zstd.

Control groups of artifacts to include (e.g. selftests/bpf,
selftests/sched_ext) with environment variables.

.github/workflows/kernel-build.yml

@@ -45,17 +45,17 @@ jobs:
     runs-on: ${{ fromJSON(inputs.runs_on) }}
     timeout-minutes: 100
     env:
-        ARCHIVE_MAKE_HELPERS: ${{ github.repository != 'kernel-patches/bpf' && 'true' || '' }}
-        KERNEL: ${{ inputs.kernel }}
-        REPO_ROOT: ${{ github.workspace }}
-        REPO_PATH: ""
-        KBUILD_OUTPUT: ${{ github.workspace }}/kbuild-output
+        ARTIFACTS_ARCHIVE: "vmlinux-${{ inputs.arch }}-${{ inputs.toolchain_full }}.tar.zst"
         BASE_BRANCH: >-
           ${{ github.event_name == 'push' && github.ref_name
               || github.base_ref
               || 'bpf-next'
           }}
         BUILD_SCHED_EXT_SELFTESTS: ${{ inputs.arch == 'x86_64' || inputs.arch == 'aarch64' && 'true' || '' }}
+        KBUILD_OUTPUT: ${{ github.workspace }}/kbuild-output
+        KERNEL: ${{ inputs.kernel }}
+        REPO_PATH: ""
+        REPO_ROOT: ${{ github.workspace }}
     steps:
       - uses: actions/checkout@v4
         # We fetch an actual bit of history here to facilitate incremental
@@ -140,9 +140,17 @@ jobs:
           max-make-jobs: 32
           llvm-version: ${{ inputs.llvm-version }}
       - name: Tar artifacts
-        working-directory: ${{ env.REPO_ROOT }}
-        run: |
-          bash .github/scripts/tar-artifact.sh ${{ inputs.arch }} ${{ inputs.toolchain_full }}
+        id: tar-artifacts
+        uses: ./tar-artifacts
+        env:
+          ARCHIVE_BPF_SELFTESTS: 'true'
+          ARCHIVE_MAKE_HELPERS: ${{ github.repository != 'kernel-patches/bpf' && 'true' || '' }}
+          ARCHIVE_SCHED_EXT_SELFTESTS: ${{ env.BUILD_SCHED_EXT_SELFTESTS }}
+        with:
+          arch: ${{ inputs.arch }}
+          archive: ${{ env.ARTIFACTS_ARCHIVE }}
+          kbuild-output: ${{ env.KBUILD_OUTPUT }}
+          repo-root: ${{ env.REPO_ROOT }}
       - if: ${{ github.event_name != 'push' }}
         name: Remove KBUILD_OUTPUT content
         shell: bash
@@ -155,4 +163,4 @@ jobs:
         with:
           name: vmlinux-${{ inputs.arch }}-${{ inputs.toolchain_full }}${{ inputs.release && '-release' || '' }}
           if-no-files-found: error
-          path: vmlinux-${{ inputs.arch }}-${{ inputs.toolchain_full }}.tar.zst
+          path: ${{ env.ARTIFACTS_ARCHIVE }}

tar-artifacts/README.md

@@ -0,0 +1,34 @@
+# Tar build artifacts
+
+This action creates a tarball with kbuild-output and other build
+artifacts necessary to run the selftests.
+
+The action is expected to be executed by a workflow with access to the
+Linux kernel repository.
+
+## Required inputs
+
+* `arch` - Kernel build architecture, required to find image_name
+* `archive` - path to the produced .zst archive
+* `kbuild-output` - Path to the kernel build output
+* `repo-root` - Path to the root of the Linux kernel repository
+
+# Archive options
+
+Essential content of the directory passed via `kbuild-output` input is
+always included in the tarball.
+
+For selftests artifacts the script checks environment variables to
+determine what to include. These are handled as bash flags:
+emptystring means false, any other value means true.
+
+* `ARCHIVE_BPF_SELFTESTS` - add `tools/testing/selftests/bpf` binaries
+  under `selftests/bpf` in the tarball
+* `ARCHIVE_MAKE_HELPERS` - add all the Linux repo makefiles and other
+  scripts
+* `ARCHIVE_SCHED_EXT_SELFTESTS` - add
+  `tools/testing/selftests/sched_ext` binaries under
+  `selftests/sched_ext` in the tarball
+
+
+

tar-artifacts/action.yml

@@ -0,0 +1,26 @@
+name: 'Tar build artifacts'
+inputs:
+  arch:
+    description: 'Target arch of the kernel, required for finding the image'
+    required: true
+  archive:
+    description: 'Path to the output archive'
+    required: true
+  kbuild-output:
+    description: 'Path to the kernel build output for archiving'
+    required: true
+  repo-root:
+    description: "Path to the root of the kernel repository"
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - name: Run tar-artifacts.sh
+      env:
+        KBUILD_OUTPUT: ${{ inputs.kbuild-output }}
+        REPO_ROOT: ${{ inputs.repo-root }}
+        ARCH: ${{ inputs.arch }}
+      shell: bash
+      run:
+        ${GITHUB_ACTION_PATH}/tar-artifacts.sh ${{ inputs.archive }}

tar-artifacts/tar-artifacts.sh

@@ -0,0 +1,79 @@
+#!/bin/bash
+
+set -eux -o pipefail
+
+if [ ! -d "${REPO_ROOT:-}" ]; then
+  echo "REPO_ROOT must be a directory: ${REPO_ROOT}"
+  exit 1
+fi
+
+if [ ! -d "${KBUILD_OUTPUT:-}" ]; then
+  echo "KBUILD_OUTPUT must be a directory: ${KBUILD_OUTPUT}"
+  exit 1
+fi
+
+zst_tarball="$1"
+arch="${ARCH}"
+
+ARCHIVE_BPF_SELFTESTS="${ARCHIVE_BPF_SELFTESTS:-true}"
+ARCHIVE_MAKE_HELPERS="${ARCHIVE_MAKE_HELPERS:-}"
+ARCHIVE_SCHED_EXT_SELFTESTS="${ARCHIVE_SCHED_EXT_SELFTESTS:-}"
+
+tarball=$(mktemp ./artifacts.XXXXXXXX.tar)
+
+source "${GITHUB_ACTION_PATH}/../helpers.sh"
+
+# Strip debug information, which is excessively large (consuming
+# bandwidth) while not actually being used (the kernel does not use
+# DWARF to symbolize stacktraces).
+"${arch}"-linux-gnu-strip --strip-debug "${KBUILD_OUTPUT}"/vmlinux
+
+image_name=$(make -C ${REPO_ROOT} ARCH="$(platform_to_kernel_arch "${arch}")" -s image_name)
+kbuild_output_file_list=(
+  ".config"
+  "${image_name}"
+  "include/config/auto.conf"
+  "include/generated/autoconf.h"
+  "vmlinux"
+)
+
+tar -rf "${tarball}" -C "${KBUILD_OUTPUT}" \
+    --transform "s,^,kbuild-output/,"      \
+    "${kbuild_output_file_list[@]}"
+
+# In case artifacts are restored not to the kernel repo root,
+# package up a bunch of additional infrastructure to support running
+# 'make kernelrelease' and bpf tool checks later on.
+if [[ -n "${ARCHIVE_MAKE_HELPERS}" ]]; then
+  find "${REPO_ROOT}" -iname Makefile -printf '%P\n' \
+    | tar -rf "${tarball}" -C "${REPO_ROOT}" -T -
+  tar -rf "${tarball}" -C "${REPO_ROOT}" \
+    --exclude '*.o'                      \
+    --exclude '*.d'                      \
+    "scripts/"                           \
+    "tools/testing/selftests/bpf/"       \
+    "tools/include/"                     \
+    "tools/bpf/bpftool/"
+fi
+
+if [[ -n "${ARCHIVE_BPF_SELFTESTS}" ]]; then
+  # add .bpf.o files
+    find "${REPO_ROOT}/tools/testing/selftests/bpf"   \
+         -name "*.bpf.o" -printf 'selftests/bpf/%P\n' \
+      | tar -rf "${tarball}" -C "${REPO_ROOT}/tools/testing" -T -
+  # add other relevant files
+  tar -rf "${tarball}" -C "${REPO_ROOT}/tools/testing" \
+      --exclude '*.cmd'    \
+      --exclude '*.d'      \
+      --exclude '*.h'      \
+      --exclude '*.o'      \
+      --exclude '*.output' \
+      selftests/bpf/
+fi
+
+if [[ -n "${ARCHIVE_SCHED_EXT_SELFTESTS}" ]]; then
+  tar -rf "${tarball}" -C "${REPO_ROOT}/tools/testing" selftests/sched_ext/
+fi
+
+zstd -T0 -19 -i "${tarball}" -o "${zst_tarball}"
+