feat: Autogenerate all eBPF feature combinations

* Add `bpf-features` crate which contains only the `BpfFeatures` struct
  with a static method `all_combinations`, which is then used both by
  `bpf-builder` (to build programs with all feature combinations) and
  and `bpf-common` (to pick the correct program based on detected
  features).
* Add `bpf-feature-autodetect` crate and move feature probes there.
* Add `bpf-features-macros` crate for with the `ebpf_programs_map`
  macro which autogenerates mapping of features to program bytes. The
  program bytes (for all feature sets) are still embedded in the final
  binary.

Cargo.toml

@@ -34,9 +34,12 @@ env_logger = { workspace = true }
 futures-util = { workspace = true }
 log = { workspace = true }
 nix = { workspace = true }
+quote = "1.0"
+proc-macro2 = "1.0"
 rust-ini = { workspace = true }
 serde = { workspace = true }
 semver = { workspace = true, features = ["serde"] }
+syn = { version = "1.0", features = ["full"] }
 tokio = { workspace = true, features = ["full"] }
 
 [features]
@@ -65,6 +68,9 @@ members = [
     "crates/engine-api",
     "crates/validatron",
     "crates/bpf-filtering",
+    "crates/bpf-features",
+    "crates/bpf-feature-autodetect",
+    "crates/bpf-features-macros",
     "xtask",
     "test-suite",
 ]
@@ -82,6 +88,9 @@ bpf-common = { path = "crates/bpf-common", features = [
     "test-utils",
     "test-suite",
 ] }
+bpf-features = { path = "crates/bpf-features" }
+bpf-feature-autodetect = { path = "crates/bpf-feature-autodetect" }
+bpf-features-macros = { path = "crates/bpf-features-macros" }
 bpf-filtering = { path = "crates/bpf-filtering", features = ["test-suite"] }
 engine-api = { path = "crates/engine-api" }
 pulsar-core = { path = "crates/pulsar-core" }

crates/bpf-builder/Cargo.toml

@@ -7,3 +7,4 @@ repository.workspace = true
 
 [dependencies]
 anyhow = { workspace = true }
+bpf-features = { workspace = true }

crates/bpf-builder/src/lib.rs

@@ -6,6 +6,7 @@ use std::{
 };
 
 use anyhow::{bail, Context};
+use bpf_features::BpfFeatures;
 
 static CLANG_DEFAULT: &str = "clang";
 static LLVM_STRIP: &str = "llvm-strip";
@@ -24,35 +25,14 @@ pub fn build(name: &str, source: &str) -> Result<(), Box<dyn std::error::Error>>
     println!("cargo:rerun-if-changed={INCLUDE_PATH}/get_path.bpf.h");
     println!("cargo:rerun-if-changed={INCLUDE_PATH}/task.bpf.h");
 
-    let features = [
-        ("FEATURE_ATOMICS", "a"),
-        ("FEATURE_CGROUP_TASK_BTF", "c"),
-        ("FEATURE_FN_POINTERS", "f"),
-        ("FEATURE_LSM", "l"),
-    ];
-
     let out_dir = env::var("OUT_DIR").context("OUT_DIR not set")?;
     let out_path = Path::new(&out_dir).join(name);
 
-    for bits in 0..(1 << features.len()) {
-        let mut feature_args = Vec::new();
-        let mut suffix = String::new();
-
-        for (i, (feature, code)) in features.iter().enumerate() {
-            if bits & (1 << i) != 0 {
-                feature_args.push(format!("-D{}", feature));
-                suffix.push_str(code);
-            }
-        }
-
-        if suffix.is_empty() {
-            suffix.push_str("none");
-        }
-
-        let filename = format!("{}.{}.bpf.o", name, suffix);
+    for (_, (bpf_objfile_suffix, build_args)) in BpfFeatures::all_combinations() {
+        let filename = format!("{name}.{bpf_objfile_suffix}");
         let full_path = out_path.with_file_name(filename);
-        compile(source, full_path, &feature_args)
-            .context("Error compiling programs with features: {feature_args:?}")?;
+        compile(source, full_path, &build_args)
+            .context("Error compiling programs with features: {build_args:?}")?;
     }
 
     Ok(())

crates/bpf-common/Cargo.toml

@@ -13,8 +13,9 @@ sqlite3-vendored = ["libsqlite3-sys/bundled"]
 
 [dependencies]
 aya = { workspace = true, features = ["async_tokio"] }
-aya-ebpf-bindings = { workspace = true }
-aya-obj = { workspace = true }
+bpf-features = { workspace = true }
+bpf-feature-autodetect = { workspace = true }
+bpf-features-macros = { workspace = true }
 bytes = { workspace = true }
 thiserror = { workspace = true }
 tokio = { workspace = true, features = ["full"] }

crates/bpf-common/src/lib.rs

@@ -1,6 +1,5 @@
 mod bpf_sender;
 pub mod containers;
-pub mod insn;
 pub mod program;
 #[cfg(feature = "test-utils")]
 pub mod test_runner;
@@ -14,16 +13,16 @@ mod bump_memlock_rlimit;
 pub mod parsing;
 pub mod time;
 
+pub use bpf_feature_autodetect;
+pub use bpf_features::BpfFeatures;
+pub use bpf_features_macros::ebpf_programs_map;
 pub use bpf_sender::{BpfSender, BpfSenderWrapper};
 pub use bump_memlock_rlimit::bump_memlock_rlimit;
 pub use program::{Program, ProgramBuilder, ProgramError};
 
 pub use aya;
 
-pub use aya_obj::generated::bpf_prog_type as BpfProgType;
-
 pub mod bpf_fs;
-pub mod feature_autodetect;
 
 /// Utility function to pretty print an error with its sources.
 ///