Add build-bpf-gcc action

.github/workflows/kernel-build.yml

@@ -117,6 +117,8 @@ jobs:
         env:
           MAX_MAKE_JOBS: 32
           RELEASE: ${{ inputs.release && '1' || '' }}
+          # GCC for building BPF selftests will be installed into BPF_GCC directory
+          BPF_GCC: ${{ github.workspace }}/bpf-gcc
         with:
           arch: ${{ inputs.arch }}
           kernel-root: ${{ env.KERNEL_ROOT }}

build-bpf-gcc/action.yml

@@ -0,0 +1,32 @@
+name: 'Build BPF GCC'
+description: 'Fetch latest GCC and binutils snapshots, bulid GCC and install into the target directory'
+inputs:
+  install-dir:
+    description: "Path to the GCC installation directory"
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+
+    - name: Determine latest snapshots
+      id: latest-snapshots
+      shell: bash
+      run: ${GITHUB_ACTION_PATH}/latest-snapshots.sh
+
+    - uses: actions/cache@v4
+      id: cache
+      with:
+        path: ${{ inputs.install-dir }}
+        key: BPF-GCC-${{ steps.latest-snapshots.outputs.GCC_BASENAME }}-${{ steps.latest-snapshots.outputs.BINUTILS_BASENAME }}
+
+    - if: steps.cache.outputs.cache-hit != 'true'
+      name: Build BPF GCC
+      env:
+        LOGFILE: /tmp/build-bpf-gcc.log
+      shell: bash
+      run: |
+        ${GITHUB_ACTION_PATH}/build-and-install.sh ${{ inputs.install-dir }} \
+          || { cat $LOGFILE; exit 1; }
+
+

build-bpf-gcc/build-and-install.sh

@@ -0,0 +1,42 @@
+#!/bin/bash
+set -euxo pipefail
+
+INSTALLDIR=$(realpath $1)
+LOGFILE=${LOGFILE:-build-bpf-gcc.log}
+
+source ${GITHUB_ACTION_PATH}/.env
+
+test -f $BINUTILS_TARBALL || {
+  echo -n "Fetching $BINUTILS_URL... ";
+  wget -o /dev/null $BINUTILS_URL || { echo -e "\nerror: could not fetch $BINUTILS_URL"; exit 1; };
+  echo done;
+}
+
+test -f $GCC_TARBALL || {
+  echo -n "Fetching $GCC_URL... ";
+  wget -o /dev/null $GCC_URL || { echo -e "\nerror: could not fetch $GCC_URL"; exit 1; };
+  echo done;
+}
+
+if [ ! -f  "${INSTALLDIR}/${BINUTILS_BASENAME}.built" ]; then
+  echo -n "Building and installing $BINUTILS_BASENAME... ";
+  (tar xJf $BINUTILS_TARBALL;
+  cd ${BINUTILS_BASENAME};
+   mkdir build-bpf;
+   cd build-bpf && ../configure --target=bpf-unknown-none --prefix=$INSTALLDIR && make -j $(nproc) && make install && touch ${INSTALLDIR}/${BINUTILS_BASENAME}.built;
+   ) >> $LOGFILE 2>&1 || { echo -e "\nerror: building $BINUTILS_TARBALL"; exit 1; }
+  echo done
+fi
+
+if [ ! -f  "${INSTALLDIR}/${GCC_BASENAME}.built" ]; then
+  echo -n "Building and installing $GCC_BASENAME... ";
+  (tar xJf $GCC_TARBALL;
+   cd ${GCC_BASENAME};
+   ./contrib/download_prerequisites
+   mkdir build-bpf;
+   cd build-bpf && ../configure --target=bpf-unknown-none --prefix=$INSTALLDIR && make -j $(nproc) && make install && touch ${INSTALLDIR}/${GCC_BASENAME}.built;
+   ) >> $LOGFILE 2>&1 || { echo -e "\nerror: building $GCC_TARBALL"; exit 1; }
+  echo done
+fi
+
+exit 0

build-bpf-gcc/latest-snapshots.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+set -euo pipefail
+
+BINUTILS_TARBALL=`wget https://snapshots.sourceware.org/binutils/trunk/latest/src/sha512.sum -O - -o /dev/null | grep -E 'binutils-[0-9a-f.-]+.tar.xz' | sed -e 's/.*\(binutils-[^<]*\).*/\1/'`
+GCC_TARBALL=`wget https://gcc.gnu.org/pub/gcc/snapshots/LATEST-15 -O - -o /dev/null | grep -E 'gcc-15-[0-9]+.tar.xz' | sed -e 's/.*\(gcc-15-[^<]*\).*/\1/'`
+
+BINUTILS_URL="https://snapshots.sourceware.org/binutils/trunk/latest/src/$BINUTILS_TARBALL"
+GCC_URL="https://gcc.gnu.org/pub/gcc/snapshots/LATEST-15/$GCC_TARBALL"
+
+BINUTILS_BASENAME=$(basename $BINUTILS_TARBALL .tar.xz)
+GCC_BASENAME=$(basename $GCC_TARBALL .tar.xz)
+
+cat > ${GITHUB_ACTION_PATH}/.env <<EOF
+BINUTILS_TARBALL=$BINUTILS_TARBALL
+GCC_TARBALL=$GCC_TARBALL
+BINUTILS_URL=$BINUTILS_URL
+GCC_URL=$GCC_URL
+BINUTILS_BASENAME=$BINUTILS_BASENAME
+GCC_BASENAME=$GCC_BASENAME
+EOF
+
+echo "BINUTILS_BASENAME=${BINUTILS_BASENAME}" >> "$GITHUB_OUTPUT"
+echo "GCC_BASENAME=${GCC_BASENAME}" >> "$GITHUB_OUTPUT"
+
+exit 0

build-selftests/action.yml

@@ -18,6 +18,12 @@ inputs:
 runs:
   using: "composite"
   steps:
+
+    - if: ${{ env.BPF_GCC }}
+      uses: ./build-bpf-gcc
+      with:
+        install-dir: ${{ env.BPF_GCC }}
+
     - name: build selftests
       shell: bash
       env:

build-selftests/build_selftests.sh

@@ -29,6 +29,7 @@ foldable start build_selftests "Building selftests with $TOOLCHAIN"
 
 MAKE_OPTS=$(cat <<EOF
 	ARCH=${ARCH}
+	BPF_GCC=${BPF_GCC:-}
 	CROSS_COMPILE=${CROSS_COMPILE}
 	CLANG=clang-${LLVM_VERSION}
 	LLC=llc-${LLVM_VERSION}