Re: [PATCH v2 dwarves 2/2] github CI: Add comparison of generated BTF functions between baseline, change

[Ihor Solodrai <ihor.solodrai@linux.dev>]

On 6/30/25 3:15 AM, Alan Maguire wrote:
> Sometimes changes can be introduced that modify the set of functions
> encoded in BTF, or change aspects of that encoding.  Add a non-fatal
> comparison job to compare between the change and the base branch,
> by default the "next" branch.
> 
> Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
> ---
>   .github/scripts/compare-functions.sh | 30 ++++++++++++++++++++++++++++
>   .github/workflows/vmtest.yml         |  4 ++++
>   2 files changed, 34 insertions(+)
>   create mode 100755 .github/scripts/compare-functions.sh
> 

Hi Alan. That's a good addition. See a couple of comments below.

> diff --git a/.github/scripts/compare-functions.sh b/.github/scripts/compare-functions.sh
> new file mode 100755
> index 0000000..062f15c
> --- /dev/null
> +++ b/.github/scripts/compare-functions.sh
> @@ -0,0 +1,30 @@
> +#!/usr/bin/bash
> +# SPDX-License-Identifier: GPL-2.0-only
> +#
> +# Copyright (c) 2025, Oracle and/or its affiliates.
> +#
> +
> +GITHUB_WORKSPACE=${GITHUB_WORKSPACE:-$(pwd)}
> +REPO_TARGET=${GITHUB_WORKSPACE}/.kernel
> +VMLINUX=${GITHUB_WORKSPACE}/.kernel/vmlinux
> +SELFTESTS=${GITHUB_WORKSPACE}/tests

nit: SELFTESTS isn't used

> +export PATH=${GITHUB_WORKSPACE}/install/usr/local/bin:${PATH}
> +which pahole
> +pahole --version
> +cd $REPO_TARGET
> +pfunct --all --format_path=btf $VMLINUX > functions_latest
> +# now use baseline pahole for comparison
> +export PAHOLE=/usr/local/bin/pahole

So we assume that the baseline is installed at this path?
And that would be an installation done by
libbpf/ci/setup-build-env action?

I would not rely on that behavior.  I think a better approach is to
build and use master (or whatever is the baseline) explicitly.

> +rm -f vmlinux vmlinux.o
> +export PATH=/usr/local/bin:${PATH}
> +make oldconfig
> +make -j $((4*$(nproc))) all
> +pfunct --all --format_path=btf $VMLINUX > functions_base
> +echo "Comparing vmlinux BTF functions generated with this change vs baseline."
> +echo "Differences are non-fatal to the workflow, but should be examined for correctness."

You might find it useful to dump a formatted diff to
$GITHUB_STEP_SUMMARY, to get a rendered output in github UI.

See here: 
https://docs.github.com/en/actions/reference/workflow-commands-for-github-actions?versionId=free-pro-team%40latest&productId=actions#adding-a-job-summary 


> +set +e
> +diff functions_base functions_latest
> +if [[ $? -eq 0 ]]; then
> +	echo "Function lists are identical."
> +fi
> +set -e
> diff --git a/.github/workflows/vmtest.yml b/.github/workflows/vmtest.yml
> index 0f66eed..54bb92e 100644
> --- a/.github/workflows/vmtest.yml
> +++ b/.github/workflows/vmtest.yml
> @@ -60,3 +60,7 @@ jobs:
>           shell: bash
>           run: .github/scripts/run-selftests.sh
>   
> +      - name: Compare functions generated
> +        shell: bash
> +        run: .github/scripts/compare-functions.sh
> +