ci: Use pre-release LLVM versions from tarballs

Instead of relying on Homebrew for macOS (which ships older LLVM
versions) and `apt.llvm.org` for Linux (which often has bugs at the
packaging level), we now use:

- The tarball from Rust CI to provide `libLLVM`. This ensures it always
  matches the version used by the latest Rust nightly.
- The tarball from https://github.com/llvm/llvm-project to provide
  `clang` and `llvm-objcopy`. In this case, an exact match with
  `libLLVM` in `rustc` is not necessary. Nevertheless, using the latest
  versions is preferred.

Fixing the build on macOS runners is the main motivation behind this
change.

Co-authored-by: tyrone-wu <wudevelops@gmail.com>

.github/workflows/ci.yml

@@ -14,7 +14,6 @@ on:
 
 env:
   CARGO_TERM_COLOR: always
-  LLVM_VERSION: 18
 
 jobs:
   lint:
@@ -183,14 +182,16 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        runner:
+        include:
           # macos-14 is arm64 per
           # https://github.com/actions/runner-images#available-images which
           # doesn't support nested virtualization per
           # https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners/about-github-hosted-runners#limitations-for-arm64-macos-runners
-          - macos-13
-          - ubuntu-22.04
-    runs-on: ${{ matrix.runner }}
+          - target: x86_64-apple-darwin
+            os: macos-13
+          - target: x86_64-unknown-linux-gnu
+            os: ubuntu-22.04
+    runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4
         with:
@@ -198,27 +199,29 @@ jobs:
 
       - name: Install prerequisites
         if: runner.os == 'Linux'
-        # ubuntu-22.04 comes with clang 14[0] which doesn't include support for signed and 64bit
-        # enum values which was added in clang 15[1].
-        #
         # gcc-multilib provides at least <asm/types.h> which is referenced by libbpf.
         #
-        # llvm provides llvm-objcopy which is used to build the BTF relocation tests.
+        # ubuntu-22.04 comes with clang 14[0] which doesn't include support for signed and 64bit
+        # enum values which was added in clang 15[1]. llvm-objcopy is used to build the BTF
+        # relocation tests. Use the latest LLVM release tarball to provide both dependencies.
         #
         # [0] https://github.com/actions/runner-images/blob/ubuntu22/20230724.1/images/linux/Ubuntu2204-Readme.md
         #
         # [1] https://github.com/llvm/llvm-project/commit/dc1c43d
         run: |
           set -euxo pipefail
-          wget -qO- https://apt.llvm.org/llvm-snapshot.gpg.key | sudo tee /etc/apt/trusted.gpg.d/apt.llvm.org.asc
-          echo deb http://apt.llvm.org/jammy/ llvm-toolchain-jammy-${{ env.LLVM_VERSION }} main | sudo tee /etc/apt/sources.list.d/llvm.list
           sudo apt update
-          sudo apt -y install clang-${{ env.LLVM_VERSION }} gcc-multilib llvm-${{ env.LLVM_VERSION }} locate qemu-system-{arm,x86}
-          echo /usr/lib/llvm-${{ env.LLVM_VERSION }}/bin >> $GITHUB_PATH
-
-      - name: bpf-linker
-        if: runner.os == 'Linux'
-        run: cargo install bpf-linker --git https://github.com/aya-rs/bpf-linker.git
+          sudo apt -y install gcc-multilib locate qemu-system-{arm,x86}
+
+          llvm_tarball_url=$(curl -s -H "Authorization: token ${{ secrets.GITHUB_TOKEN }}" \
+            https://api.github.com/repos/llvm/llvm-project/releases | jq -r \
+            'map(select(.prerelease)) | first | .assets |
+             map(select(.name | endswith("Linux-X64.tar.xz"))) | first |
+             .browser_download_url')
+          mkdir -p /tmp/llvm-upstream
+          wget -q -O - $llvm_tarball_url | tar -xJ --strip-components 1 \
+            -C /tmp/llvm-upstream
+          echo /tmp/llvm-upstream/bin >> $GITHUB_PATH
 
       - name: Install prerequisites
         if: runner.os == 'macOS'
@@ -227,8 +230,6 @@ jobs:
         # The tar shipped on macOS doesn't support --wildcards, so we need GNU tar.
         #
         # The clang shipped on macOS doesn't support BPF, so we need LLVM from brew.
-        #
-        # We also need LLVM for bpf-linker, see comment below.
         run: |
           set -euxo pipefail
           brew update
@@ -249,10 +250,31 @@ jobs:
 
       - uses: Swatinem/rust-cache@v2
 
+      - name: Install libLLVM
+        # Use LLVM tarball from Rust CI to make sure that the libLLVM version
+        # matches exactly the one used by the current Rust nightly.
+        run: |
+          set -euxo pipefail
+          # Get the partial SHA from Rust nightly.
+          rustc_sha=$(rustc +nightly --version | grep -oE '[a-f0-9]{7,40}')
+          # Get the full SHA from GitHub.
+          rustc_sha=$(curl -s https://api.github.com/repos/rust-lang/rust/commits/$rustc_sha \
+            --header 'authorization: Bearer ${{ secrets.GITHUB_TOKEN }}' \
+            --header 'content-type: application/json' \
+            | jq -r '.sha')
+          mkdir -p /tmp/rustc-llvm
+          wget -q -O - https://ci-artifacts.rust-lang.org/rustc-builds/$rustc_sha/rust-dev-nightly-${{ matrix.target }}.tar.xz | \
+            tar -xJ --strip-components 2 -C /tmp/rustc-llvm
+          echo /tmp/rustc-llvm/bin >> $GITHUB_PATH
+
+      - name: bpf-linker
+        if: runner.os == 'Linux'
+        run: cargo install bpf-linker --git https://github.com/aya-rs/bpf-linker.git
+
       - name: bpf-linker
         if: runner.os == 'macOS'
         # NB: rustc doesn't ship libLLVM.so on macOS, so disable proxying (default feature). We also
-        # --force so that bpf-linker gets always relinked against the latest LLVM installed by brew.
+        # --force so that bpf-linker gets always relinked against the latest LLVM downloaded above.
         run: cargo install --force bpf-linker --git https://github.com/aya-rs/bpf-linker.git --no-default-features
 
       - name: Download debian kernels

test/integration-ebpf/src/test.rs

@@ -3,8 +3,10 @@
 
 use aya_ebpf::{
     bindings::xdp_action,
+    bpf_printk,
     macros::{kprobe, kretprobe, tracepoint, uprobe, uretprobe, xdp},
     programs::{ProbeContext, RetProbeContext, TracePointContext, XdpContext},
+    EbpfContext,
 };
 
 #[xdp]
@@ -30,8 +32,20 @@ pub fn test_kretprobe(_ctx: RetProbeContext) -> u32 {
 }
 
 #[tracepoint]
-pub fn test_tracepoint(_ctx: TracePointContext) -> u32 {
-    0
+pub fn test_tracepoint(ctx: TracePointContext) -> u32 {
+    // Some arbitrary work, to make the program running for some time and have
+    // a real `run_time` in `test_program_info`.
+    let mut res = ctx.uid().wrapping_add(ctx.pid());
+    for _ in 0..10_000 {
+        res = res.wrapping_mul(123);
+        res ^= (ctx.pid() << 3) ^ (ctx.uid() << 4);
+        res = res.rotate_left(2);
+        res = res.reverse_bits();
+        res = res.swap_bytes();
+        res = res.count_ones();
+        unsafe { bpf_printk!(b"number %u", res) };
+    }
+    res
 }
 
 #[uprobe]

test/integration-test/src/tests/info.rs

@@ -214,6 +214,12 @@ fn test_prog_stats() {
         .unwrap();
     prog.load().unwrap();
     prog.attach("syscalls", "sys_enter_bpf").unwrap();
+
+    // Executing bpf syscalls to trigger `sys_enter_bpf`
+    for _ in 0..5 {
+        let _ = loaded_programs().collect::<Vec<_>>();
+    }
+
     let test_prog = prog.info().unwrap();
 
     kernel_assert!(