improve: allow using bpftool for stripping

Also skip stripping if failed.

Add env EINAT_BPF_STRIP_CMD to force stripping command used.

README.md

@@ -22,15 +22,15 @@ For implementation details, see documentations under [reference](./docs/referenc
 -   Linux kernel >= 5.15 (compiled with BPF and BTF support) on target machine
 -   Rust toolchain (`cargo` etc.)
 -   `clang` for compiling BPF C code
--   `llvm-strip` for stripping compiled BPF object
+-   `bpftool` or `llvm-strip` for stripping compiled BPF object
 -   `libbpf` headers
 -   (optional) `pkg-config` to locate `libbpf` headers
 
 Additional dependencies for `"libbpf"` loader:
 
 -   `rustfmt` for formatting generated code
 -   `clang` libs for bindgen
--   `libelf` from elfutils and  `zlib` on target platform
+-   `libelf` from elfutils and `zlib` on target platform
 
 Currently we support `"aya"`, `"libbpf"` and `"libbpf-skel"` eBPF loaders, only the `"aya"` is enabled by default as it requires no native dependencies on target platform except libc.
 
@@ -65,10 +65,11 @@ See also [cross-compilation guide](./docs/guide/cross.md) for cross-compilation
 
 ### Build Environment Variables
 
-| Name                   | Example Value              | Note                                            |
-| ---------------------- | -------------------------- | ----------------------------------------------- |
-| `EINAT_BPF_CFLAGS`     | `-I/usr/include/<triplet>` | Specify extra CFLAGS for BPF object compilation |
-| `LIBBPF_NO_PKG_CONFIG` | `1`                        | Disable [pkg_config lookup] of libbpf.          |
+| Name                   | Example Value              | Note                                                                        |
+| ---------------------- | -------------------------- | --------------------------------------------------------------------------- |
+| `EINAT_BPF_CFLAGS`     | `-I/usr/include/<triplet>` | Specify extra CFLAGS for BPF object compilation                             |
+| `EINAT_BPF_STRIP_CMD`  | `llvm-strip -g -o`         | BPF object stripping command, would followed by target path and source path |
+| `LIBBPF_NO_PKG_CONFIG` | `1`                        | Disable [pkg_config lookup] of libbpf.                                      |
 
 [pkg_config lookup]: https://docs.rs/pkg-config/0.3.31/pkg_config/index.html#environment-variables
 

build.rs

@@ -33,8 +33,10 @@ fn c_args() -> Vec<String> {
 
 #[cfg(any(feature = "aya", feature = "libbpf"))]
 fn einat_obj_build() {
+    use std::ffi::OsStr;
     use std::process::Command;
 
+    let bpf_obj_tmp = &out_path("einat.bpf.tmp.o");
     let bpf_obj = &out_path("einat.bpf.o");
 
     // compile BPF C code
@@ -79,22 +81,60 @@ fn einat_obj_build() {
         .arg("-c")
         .arg(SRC)
         .arg("-o")
-        .arg(bpf_obj)
+        .arg(bpf_obj_tmp)
         .status()
         .expect("compile BPF object failed");
     if !res.success() {
         panic!("{}", res);
     }
 
-    // strip the DWARF debug information
-    let res = Command::new("llvm-strip")
-        .arg("--strip-debug")
-        .arg(bpf_obj)
-        .status()
-        .expect("llvm-strip BPF object file failed");
-    if !res.success() {
-        panic!("{}", res);
+    fn strip_obj<S: AsRef<OsStr>>(strip_cmd: &str, target: S, source: S) -> Result<(), String> {
+        let mut args = strip_cmd.split_ascii_whitespace();
+        let cmd = args.next().unwrap();
+        let res = Command::new(cmd)
+            .args(args)
+            .arg(target)
+            .arg(source)
+            .status();
+
+        match res {
+            Ok(res) => {
+                if res.success() {
+                    return Ok(());
+                }
+                Err(format!("{}: {}", strip_cmd, res))
+            }
+            Err(err) => Err(format!("{}: {}", strip_cmd, err)),
+        }
     }
+
+    // strip the DWARF debug information
+    let strip_bpf_obj = || -> Result<(), String> {
+        if let Some(strip_cmd) = option_env!("EINAT_BPF_STRIP_CMD") {
+            return strip_obj(strip_cmd, bpf_obj, bpf_obj_tmp);
+        }
+
+        let res = strip_obj("bpftool gen object", bpf_obj, bpf_obj_tmp);
+        if res.is_ok() {
+            return res;
+        }
+        eprintln!("strip with bpftool failed, fallback to llvm-strip");
+
+        let res = strip_obj("llvm-strip -g -o", bpf_obj, bpf_obj_tmp);
+        if res.is_ok() {
+            return res;
+        }
+        eprintln!("strip with llvm-strip failed, skip stripping");
+
+        std::fs::rename(bpf_obj_tmp, bpf_obj).unwrap();
+
+        Ok(())
+    };
+
+    strip_bpf_obj().expect("strip BPF object file failed");
+
+    println!("cargo:rerun-if-env-changed=EINAT_BPF_CFLAGS");
+    println!("cargo:rerun-if-env-changed=EINAT_BPF_STRIP_CMD");
 }
 
 #[cfg(feature = "libbpf-skel")]
@@ -120,4 +160,6 @@ fn main() {
 
     println!("cargo:rerun-if-changed={}", SRC_DIR);
     println!("cargo:rerun-if-changed=build.rs");
+
+    println!("cargo:rerun-if-changed=/null");
 }

docs/guide/cross.md

@@ -10,7 +10,11 @@ To enable only the "libbpf" loader, specify Cargo flags `--no-default-features -
 Install `gcc-aarch64-linux-gnu` for cross linking. Install `clang` for bindgen and compile eBPF C code in this project.
 
 ```
-apt install gcc-aarch64-linux-gnu clang llvm
+apt install gcc-aarch64-linux-gnu clang
+# bpftool for BPF object stripping
+apt install linux-tools-common
+# Or use llvm-strip
+apt install llvm
 ```
 
 Install `rustup` to get Rust>=1.74, see https://www.rust-lang.org/tools/install. Also make sure `rustfmt` is installed as it's used by `libbpf-cargo`.
@@ -47,6 +51,7 @@ export CFLAGS_aarch64_unknown_linux_gnu="-I /usr/include/aarch64-linux-gnu -L /u
 ```
 
 Specify `EINAT_BPF_CFLAGS` if einat build script failed to locate libbpf headers.
+
 ```
 export EINAT_BPF_CFLAGS="-I /usr/include/aarch64-linux-gnu"
 ```