integration-ebpf: artifact dependency bpf-linker

- integration-ebpf: add artifact dependency on bpf-linker.
- integration-ebpf: remove manual rerun-if-changed=bpf-linker.
- integration-ebpf: make bpf-linker availble to rustc in build.rs.
- xtask: filter for test binaries now that the build also produces the
  bpf-linker binary.
- github: remove `cargo install bpf-linker`.
- integration-test: remove bpf-linker installation instructions.

Blockers:
- https://github.com/rust-lang/cargo/issues/12385 (artifact = "bin"
  makes entire workspace nightly-only).

.cargo/config.toml

@@ -9,3 +9,9 @@ linker = "arm-linux-gnueabihf-gcc"
 
 [target.aarch64-unknown-linux-musl]
 linker = "aarch64-linux-musl-gcc"
+
+# See https://github.com/rust-lang/rust-analyzer/issues/14510.
+#
+# Turns out this affects all cargo invocations in the project, not just rust-analyzer.
+[unstable]
+bindeps = true

.github/workflows/ci.yml

@@ -131,9 +131,6 @@ jobs:
 
       - uses: Swatinem/rust-cache@v2
 
-      - name: bpf-linker
-        run: cargo install bpf-linker --git https://github.com/aya-rs/bpf-linker.git
-
       - uses: taiki-e/install-action@cargo-hack
       - name: Build
         env:
@@ -185,10 +182,6 @@ jobs:
           sudo apt update
           sudo apt -y install clang gcc-multilib llvm locate qemu-system-{arm,x86}
 
-      - name: bpf-linker
-        if: runner.os == 'Linux'
-        run: cargo install bpf-linker --git https://github.com/aya-rs/bpf-linker.git
-
       - name: Install prerequisites
         if: runner.os == 'macOS'
         # The xargs shipped on macOS always exits 0 with -P0, so we need GNU findutils.
@@ -211,11 +204,6 @@ jobs:
           # https://github.com/Homebrew/homebrew-core/issues/140244
           codesign --verify $(which qemu-system-x86_64) || brew reinstall qemu --build-from-source
 
-      - name: bpf-linker
-        if: runner.os == 'macOS'
-        # NB: rustc doesn't ship libLLVM.so on macOS, so disable proxying (default feature).
-        run: cargo install bpf-linker --git https://github.com/aya-rs/bpf-linker.git --no-default-features
-
       - name: Download debian kernels
         if: runner.arch == 'ARM64'
         run: |

Cargo.toml

@@ -59,6 +59,7 @@ aya-obj = { path = "aya-obj", version = "0.1.0", default-features = false }
 aya-tool = { path = "aya-tool", default-features = false }
 bindgen = { version = "0.69", default-features = false }
 bitflags = { version = "2.2.1", default-features = false }
+bpf-linker = { version = "0.9.10", artifact = "bin" }
 bytes = { version = "1", default-features = false }
 cargo_metadata = { version = "0.18.0", default-features = false }
 clap = { version = "4", default-features = false }
@@ -95,7 +96,6 @@ test-log = { version = "0.2.13", default-features = false }
 testing_logger = { version = "0.1.1", default-features = false }
 thiserror = { version = "1", default-features = false }
 tokio = { version = "1.24.0", default-features = false }
-which = { version = "5.0.0", default-features = false }
 xtask = { path = "xtask", default-features = false }
 
 [profile.dev]
@@ -107,3 +107,6 @@ panic = "abort"
 [profile.release.package.integration-ebpf]
 debug = 2
 codegen-units = 1
+
+[patch.crates-io]
+bpf-linker = { git = "https://github.com/aya-rs/bpf-linker.git", artifact = "bin" }

test/README.md

@@ -10,7 +10,6 @@ You'll need:
 
 1. `rustup toolchain install nightly`
 1. `rustup target add {aarch64,x86_64}-unknown-linux-musl`
-1. `cargo install bpf-linker`
 1. (virtualized only) `qemu`
 
 ## Usage

test/integration-ebpf/Cargo.toml

@@ -9,8 +9,8 @@ aya-bpf = { path = "../../bpf/aya-bpf" }
 aya-log-ebpf = { path = "../../bpf/aya-log-ebpf" }
 
 [build-dependencies]
-which = { workspace = true }
 xtask = { path = "../../xtask" }
+bpf-linker = { workspace = true }
 
 [[bin]]
 name = "log"

test/integration-ebpf/build.rs

@@ -1,6 +1,4 @@
 use std::env;
-
-use which::which;
 use xtask::AYA_BUILD_INTEGRATION_BPF;
 
 /// Building this crate has an undeclared dependency on the `bpf-linker` binary. This would be
@@ -25,7 +23,31 @@ fn main() {
         .unwrap_or_default();
 
     if build_integration_bpf {
-        let bpf_linker = which("bpf-linker").unwrap();
-        println!("cargo:rerun-if-changed={}", bpf_linker.to_str().unwrap());
+        let out_dir = env::var_os("OUT_DIR").unwrap();
+        let out_dir = std::path::PathBuf::from(out_dir);
+
+        let bpf_linker = env::var("CARGO_BIN_FILE_BPF_LINKER").unwrap();
+
+        // There seems to be no way to pass `-Clinker={}` to rustc from here.
+        //
+        // We assume rustc is going to look for `bpf-linker` on the PATH, so we can create a symlink
+        // and put it on the PATH.
+        let bin_dir = out_dir.join("bin");
+        std::fs::create_dir_all(&bin_dir).unwrap();
+        let bpf_linker_symlink = bin_dir.join("bpf-linker");
+        match std::fs::remove_file(&bpf_linker_symlink) {
+            Ok(()) => {}
+            Err(err) => {
+                if err.kind() != std::io::ErrorKind::NotFound {
+                    panic!("failed to remove symlink: {err}")
+                }
+            }
+        }
+        std::os::unix::fs::symlink(bpf_linker, bpf_linker_symlink).unwrap();
+        let path = env::var_os("PATH");
+        let path = path.as_ref();
+        let paths = std::iter::once(bin_dir).chain(path.into_iter().flat_map(env::split_paths));
+        let path = env::join_paths(paths).unwrap();
+        println!("cargo:rustc-env=PATH={}", path.to_str().unwrap());
     }
 }

xtask/Cargo.toml

@@ -20,4 +20,3 @@ rustdoc-json = { workspace = true }
 rustup-toolchain = { workspace = true }
 syn = { workspace = true }
 tempfile = { workspace = true }
-which = { workspace = true }

xtask/src/run.rs

@@ -11,7 +11,7 @@ use std::{
 };
 
 use anyhow::{anyhow, bail, Context as _, Result};
-use cargo_metadata::{Artifact, CompilerMessage, Message, Target};
+use cargo_metadata::{Artifact, ArtifactProfile, CompilerMessage, Message, Target};
 use clap::Parser;
 use xtask::{exec, Errors, AYA_BUILD_INTEGRATION_BPF};
 
@@ -79,12 +79,15 @@ where
             Message::CompilerArtifact(Artifact {
                 executable,
                 target: Target { name, .. },
+                profile: ArtifactProfile { test, .. },
                 ..
             }) => {
+                if test {
                     if let Some(executable) = executable {
                         executables.push((name, executable.into()));
                     }
                 }
+            }
             Message::CompilerMessage(CompilerMessage { message, .. }) => {
                 println!("{message}");
             }