[PATCH dwarves] CI: support building kernel with LLVM

Since LLVM true signature work will change function list, have
method to build kernel/compare functions for LLVM.

Example run here:

https://github.com/alan-maguire/dwarves/actions/runs/23435796365/job/68173414313

Signed-off-by: Alan Maguire <[email protected]>
---
 .github/scripts/build-kernel.sh      | 12 ++++++++++--
 .github/scripts/build-pahole.sh      |  2 ++
 .github/scripts/compare-functions.sh | 12 ++++++++++--
 .github/workflows/test.yml           |  9 +++++++++
 .github/workflows/vmtest.yml         | 16 +++++++++++++++-
 5 files changed, 46 insertions(+), 5 deletions(-)

diff --git a/.github/scripts/build-kernel.sh b/.github/scripts/build-kernel.sh
index 504c249..0a1fd3f 100755
--- a/.github/scripts/build-kernel.sh
+++ b/.github/scripts/build-kernel.sh
@@ -9,6 +9,8 @@ INPUTS_ARCH=${INPUTS_ARCH:-$(uname -m)}
 REPO=${REPO:-https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git}
 REPO_BRANCH=${REPO_BRANCH:-master}
 REPO_TARGET=${GITHUB_WORKSPACE}/.kernel
+CC=${CC:-gcc}
+LLVM_VERSION=${LLVM_VERSION:-18}
 
 export PATH=${GITHUB_WORKSPACE}/install/usr/local/bin:${PATH}
 export PAHOLE=${GITHUB_WORKSPACE}/install/usr/local/bin/pahole
@@ -22,13 +24,19 @@ fi
 cd $REPO_TARGET
 git checkout $REPO_BRANCH
 
+buildopts=
+if [[ "$CC" = "clang" ]]; then
+	buildopts="LLVM=-${LLVM_VERSION}"
+	echo "Building with $buildopts"
+fi
+
 cat tools/testing/selftests/bpf/config \
     tools/testing/selftests/bpf/config.${INPUTS_ARCH} > .config
 # this file might or might not exist depending on kernel version
 if [[ -f tools/testing/selftests/bpf/config.vm ]]; then
 	cat tools/testing/selftests/bpf/config.vm >> .config
 fi
-make olddefconfig && make prepare
+make $buildopts olddefconfig && make prepare
 cat .config
-make -j $((4*$(nproc))) all
+make -j $((4*$(nproc))) $buildopts all
 
diff --git a/.github/scripts/build-pahole.sh b/.github/scripts/build-pahole.sh
index 7a37771..4f4013f 100755
--- a/.github/scripts/build-pahole.sh
+++ b/.github/scripts/build-pahole.sh
@@ -11,6 +11,7 @@ function restore() {
 
 GITHUB_WORKSPACE=${GITHUB_WORKSPACE:-$(dirname $0)/../..}
 BASELINE=${BASELINE:-next}
+CC=${CC:-gcc}
 
 cd $GITHUB_WORKSPACE
 git log --oneline -1
@@ -19,6 +20,7 @@ git submodule update --init
 mkdir -p build
 cd build
 pwd
+
 cmake -DGIT_SUBMODULE=OFF -DBUILD_SHARED_LIBS=OFF ..
 make -j$((4*$(nproc))) all
 make DESTDIR=../install install
diff --git a/.github/scripts/compare-functions.sh b/.github/scripts/compare-functions.sh
index cbe6596..48fc086 100755
--- a/.github/scripts/compare-functions.sh
+++ b/.github/scripts/compare-functions.sh
@@ -9,10 +9,18 @@ REPO_TARGET=${GITHUB_WORKSPACE}/.kernel
 VMLINUX=${GITHUB_WORKSPACE}/.kernel/vmlinux
 BASELINE=${BASELINE:-next}
 GITHUB_STEP_SUMMARY=${GITHUB_STEP_SUMMARY:-/dev/null}
+CC=${CC:-gcc}
+LLVM_VERSION=${LLVM_VERSION:-18}
 
 export PATH=${GITHUB_WORKSPACE}/install/usr/local/bin:${PATH}
 which pahole
 pahole --version
+
+buildopts=
+if [[ "$CC" = "clang" ]]; then
+	buildopts="LLVM=-${LLVM_VERSION}"
+fi
+
 cd $REPO_TARGET
 pfunct --all --format_path=btf $VMLINUX > functions
 
@@ -23,8 +31,8 @@ export PATH=${GITHUB_WORKSPACE}/install.${BASELINE}/usr/local/bin:${PATH}
 export PAHOLE=${GITHUB_WORKSPACE}/install.${BASELINE}/usr/local/bin/pahole
 which pahole
 pahole --version
-make oldconfig
-make -j $((4*$(nproc))) all
+make $buildopts oldconfig
+make -j $((4*$(nproc))) $buildopts all
 pfunct --all --format_path=btf $VMLINUX > functions.${BASELINE}
 echo "### Compare vmlinux BTF functions generated with this change vs baseline (none means no differences)." | tee -a $GITHUB_STEP_SUMMARY
 diff functions.${BASELINE} functions | tee -a $GITHUB_STEP_SUMMARY
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index ac28e92..f47cc4a 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -21,11 +21,19 @@ jobs:
             arch: 'x86_64'
             llvm-version: '18'
             pahole: 'none'
+            cc: 'gcc'
+          - kernel: 'LATEST'
+            runs_on: 'ubuntu-24.04'
+            arch: 'x86_64'
+            llvm-version: '18'
+            pahole: 'none'
+            cc: 'clang'
           - kernel: 'LATEST'
             runs_on: 'ubuntu-24.04-arm'
             arch: 'aarch64'
             llvm-version: '18'
             pahole: 'none'
+            cc: 'gcc'
     name: Linux ${{ matrix.kernel }}
     uses: ./.github/workflows/vmtest.yml
     with:
@@ -34,3 +42,4 @@ jobs:
       arch: ${{ matrix.arch }}
       llvm-version: ${{ matrix.llvm-version }}
       pahole: ${{ matrix.pahole }}
+      cc: ${{ matrix.cc }}
diff --git a/.github/workflows/vmtest.yml b/.github/workflows/vmtest.yml
index 54bb92e..147b608 100644
--- a/.github/workflows/vmtest.yml
+++ b/.github/workflows/vmtest.yml
@@ -27,9 +27,14 @@ on:
         required: false
         default: '18'
         type: string
+      cc:
+        description: 'compiler'
+        required: true
+        type: string
+
 jobs:
   vmtest:
-    name: pahole@${{ inputs.arch }}
+    name: pahole-${{ inputs.cc }}@${{ inputs.arch }}
     runs-on: ${{ inputs.runs_on }}
     steps:
 
@@ -44,6 +49,9 @@ jobs:
 
       - name: Build,install current pahole
         shell: bash
+        env:
+          CC: ${{ inputs.cc }}
+          LLVM_VERSION: ${{ inputs.llvm-version}}
         run: .github/scripts/build-pahole.sh
 
       - name: Get kernel source
@@ -54,6 +62,9 @@ jobs:
 
       - name: Configure, build kernel with current pahole
         shell: bash
+        env:
+          CC: ${{ inputs.cc }}
+          LLVM_VERSION: ${{ inputs.llvm-version }}
         run: .github/scripts/build-kernel.sh
 
       - name: Run selftests
@@ -62,5 +73,8 @@ jobs:
 
       - name: Compare functions generated
         shell: bash
+        env:
+          CC: ${{ inputs.cc }}
+          LLVM_VERSION: ${{ inputs.llvm_version }}
         run: .github/scripts/compare-functions.sh
 
-- 
2.43.5