overlord/BackstageInjection-Rust/build.rs

use std::time::{SystemTime, UNIX_EPOCH};

fn main() {
    let root_dir = std::env::var("CARGO_MANIFEST_DIR").unwrap();
    let mh_dir = std::path::Path::new(&root_dir).join("vendor/minhook");
    let mh_src = mh_dir.join("src");
    let target = std::env::var("TARGET").unwrap();
    let arch = target.splitn(4, '-').next().unwrap();

    let hde = if arch == "i686" {
        "hde/hde32.c"
    } else if arch == "x86_64" {
        "hde/hde64.c"
    } else {
        panic!("unsupported arch {arch}");
    };

    cc::Build::new()
        .flag("-ffunction-sections")
        .flag("-fdata-sections")
        .file(mh_src.join("buffer.c"))
        .file(mh_src.join("hook.c"))
        .file(mh_src.join("trampoline.c"))
        .file(mh_src.join(hde))
        .compile("libminhook.a");

    generate_loader_entry();

    println!("cargo:rerun-if-changed=vendor/minhook");
    println!("cargo:rerun-if-changed=build.rs");
}

fn generate_loader_entry() {
    // The loader export is always a per-build randomized `x<hex>` name. The
    // legacy fixed `ReflectiveLoader` export is no longer supported.
    let seed = std::env::var("BACKSTAGE_LOADER_SEED")
        .ok()
        .and_then(|value| value.parse::<u64>().ok())
        .unwrap_or_else(|| {
            SystemTime::now()
                .duration_since(UNIX_EPOCH)
                .unwrap()
                .as_nanos() as u64
                ^ (std::process::id() as u64).wrapping_mul(0x9E37_79B9_7F4A_7C15)
        });
    let name = format!("x{:06x}", seed & 0xFFFF_FF);

    let src = format!(
        "// Generated by build.rs — do not edit.\n\
         // Version-selected reflective loader export name.\n\
         pub(crate) const LOADER_EXPORT: &[u8] = b\"{name}\\0\";\n\
         \n\
         #[unsafe(no_mangle)]\n\
         pub extern \"system\" fn {name}(lpParameter: usize) -> usize {{\n\
         \x20   crate::reflective::loader_impl(lpParameter)\n\
         }}\n"
    );

    let out_dir = std::env::var("OUT_DIR").unwrap();
    std::fs::write(std::path::Path::new(&out_dir).join("loader_entry.rs"), src)
        .expect("failed to write loader_entry.rs");
    println!("cargo:rerun-if-env-changed=BACKSTAGE_LOADER_SEED");
}