scx_rustland_core: introduce RustLandBuilder()

Introduce a wrapper to scx_utils::BpfBuilder that can be used to build
the BPF component provided by scx_rustland_core.

The source of the BPF components (main.bpf.c) is included in the crate
as an array of bytes, the content is then unpacked in a temporary file
to perform the build.

The RustLandBuilder() helper is also used to generate bpf.rs (that
implements the low-level user-space Rust connector to the BPF
commponent).

Schedulers based on scx_rustland_core can simply use RustLandBuilder(),
to build the backend provided by scx_rustland_core.

Signed-off-by: Andrea Righi <andrea.righi@canonical.com>

rust/scx_rustland_core/Cargo.toml

@@ -7,26 +7,20 @@ license = "GPL-2.0-only"
 repository = "https://github.com/sched-ext/scx"
 description = "Framework to implement sched_ext schedulers running in user space"
 
+include = [
+    "src/bpf/intf.h",
+    "src/bpf/main.bpf.c",
+]
+
 [dependencies]
 anyhow = "1.0"
-bitvec = { version = "1.0", features = ["serde"] }
-# FIXME - We need to allow both 0.68 and 0.69 to accommodate fedora. See the
-# comment in BpfBuilder::bindgen_bpf_intf() for details.
-bindgen = ">=0.68, <0.70"
-glob = "0.3"
-hex = "0.4.3"
-lazy_static = "1.4"
-libbpf-cargo = "0.22"
 libbpf-rs = "0.22.0"
 libc = "0.2.137"
 buddy-alloc = "0.5.1"
-log = "0.4.17"
-regex = "1.10"
-sscanf = "0.4"
-tar = "0.4"
-version-compare = "0.1"
+tempfile = "3.10.1"
+scx_utils = { path = "../scx_utils", version = "0.6" }
 
 [build-dependencies]
-bindgen = ">=0.68, <0.70"
 tar = "0.4"
 walkdir = "2.4"
+scx_utils = { path = "../scx_utils", version = "0.6" }

rust/scx_rustland_core/src/lib.rs

@@ -2,3 +2,6 @@ mod bindings;
 
 mod alloc;
 pub use alloc::ALLOCATOR;
+
+mod rustland_builder;
+pub use rustland_builder::RustLandBuilder;

rust/scx_rustland_core/src/rustland_builder.rs

@@ -0,0 +1,67 @@
+// Copyright (c) Andrea Righi <andrea.righi@canonical.com>
+
+// This software may be used and distributed according to the terms of the
+// GNU General Public License version 2.
+
+use anyhow::Result;
+
+use std::error::Error;
+use std::fs::File;
+use std::io::Write;
+use std::path::{Path, PathBuf};
+
+use tempfile::tempdir;
+
+use scx_utils::BpfBuilder;
+
+pub struct RustLandBuilder {
+    inner_builder: BpfBuilder,
+    temp_dir: tempfile::TempDir,
+}
+
+impl RustLandBuilder {
+    pub fn new() -> Result<Self> {
+        Ok(Self {
+            inner_builder: BpfBuilder::new()?,
+            temp_dir: tempdir()?,
+        })
+    }
+
+    fn create_temp_file(
+        &mut self,
+        file_name: &str,
+        content: &[u8],
+    ) -> Result<PathBuf, Box<dyn Error>> {
+        let mut temp_file = self.temp_dir.as_ref().to_path_buf();
+        temp_file.push(file_name);
+        let mut file = File::create(&temp_file)?;
+        file.write_all(content)?;
+
+        Ok(temp_file)
+    }
+
+    fn get_bpf_rs_content(&self) -> &'static str {
+        include_str!("bpf.rs")
+    }
+
+    pub fn build(&mut self) -> Result<()> {
+        // Embed the BPF source files in the crate.
+        let intf = include_bytes!(concat!(env!("CARGO_MANIFEST_DIR"), "/src/bpf/intf.h"));
+        let skel = include_bytes!(concat!(env!("CARGO_MANIFEST_DIR"), "/src/bpf/main.bpf.c"));
+
+        let intf_path = self.create_temp_file("intf.h", intf).unwrap();
+        let skel_path = self.create_temp_file("main.bpf.c", skel).unwrap();
+
+        self.inner_builder
+            .enable_intf(intf_path.to_str().unwrap(), "bpf_intf.rs");
+        self.inner_builder
+            .enable_skel(skel_path.to_str().unwrap(), "bpf");
+
+        let content = self.get_bpf_rs_content();
+        let path = Path::new("src/bpf.rs");
+        let mut file = File::create(&path).expect("Unable to create file");
+        file.write_all(content.as_bytes()).expect("Unable to write to file");
+
+        self.inner_builder.build()
+    }
+}

scheds/rust/scx_rlfifo/.gitignore

@@ -1,3 +1,4 @@
 src/bpf/.output
+bpf.rs
 Cargo.lock
 target

scheds/rust/scx_rlfifo/Cargo.toml

@@ -9,7 +9,6 @@ license = "GPL-2.0-only"
 [dependencies]
 anyhow = "1.0.65"
 ctrlc = { version = "3.1", features = ["termination"] }
-hex = "0.4.3"
 libbpf-rs = "0.22.0"
 libc = "0.2.137"
 scx_utils = { path = "../../../rust/scx_utils", version = "0.6" }
@@ -17,6 +16,7 @@ scx_rustland_core = { path = "../../../rust/scx_rustland_core", version = "0.1"
 
 [build-dependencies]
 scx_utils = { path = "../../../rust/scx_utils", version = "0.6" }
+scx_rustland_core = { path = "../../../rust/scx_rustland_core", version = "0.1" }
 
 [features]
 enable_backtrace = []

scheds/rust/scx_rlfifo/build.rs

@@ -2,10 +2,8 @@
 // GNU General Public License version 2.
 
 fn main() {
-    scx_utils::BpfBuilder::new()
+    scx_rustland_core::RustLandBuilder::new()
         .unwrap()
-        .enable_intf("../../../rust/scx_rustland_core/src/bpf/intf.h", "bpf_intf.rs")
-        .enable_skel("../../../rust/scx_rustland_core/src/bpf/main.bpf.c", "bpf")
         .build()
         .unwrap();
 }

scheds/rust/scx_rlfifo/src/bpf.rs

@@ -1,4 +0,0 @@
-// This software may be used and distributed according to the terms of the
-// GNU General Public License version 2.
-
-include!("../../../../rust/scx_rustland_core/src/bpf.rs");

scheds/rust/scx_rustland/.gitignore

@@ -1,3 +1,4 @@
 src/bpf/.output
+bpf.rs
 Cargo.lock
 target

scheds/rust/scx_rustland/Cargo.toml

@@ -8,11 +8,9 @@ license = "GPL-2.0-only"
 
 [dependencies]
 anyhow = "1.0.65"
-bitvec = { version = "1.0", features = ["serde"] }
 clap = { version = "4.1", features = ["derive", "env", "unicode", "wrap_help"] }
 ctrlc = { version = "3.1", features = ["termination"] }
 fb_procfs = "0.7.0"
-hex = "0.4.3"
 libbpf-rs = "0.22.0"
 libc = "0.2.137"
 log = "0.4.17"
@@ -23,6 +21,7 @@ simplelog = "0.12.0"
 
 [build-dependencies]
 scx_utils = { path = "../../../rust/scx_utils", version = "0.6" }
+scx_rustland_core = { path = "../../../rust/scx_rustland_core", version = "0.1" }
 
 [features]
 enable_backtrace = []

scheds/rust/scx_rustland/build.rs

@@ -2,10 +2,8 @@
 // GNU General Public License version 2.
 
 fn main() {
-    scx_utils::BpfBuilder::new()
+    scx_rustland_core::RustLandBuilder::new()
         .unwrap()
-        .enable_intf("../../../rust/scx_rustland_core/src/bpf/intf.h", "bpf_intf.rs")
-        .enable_skel("../../../rust/scx_rustland_core/src/bpf/main.bpf.c", "bpf")
         .build()
         .unwrap();
 }

scheds/rust/scx_rustland/src/bpf.rs

@@ -1,4 +0,0 @@
-// This software may be used and distributed according to the terms of the
-// GNU General Public License version 2.
-
-include!("../../../../rust/scx_rustland_core/src/bpf.rs");