• Prepare the environment: Install the source package and xargo.

rustup add component rust-src
cargo install xargo

• Specify the OpenWRT gcc environment: Copy the toolchain to the designated directory, or leave it in the source directory, and edit the specified toolchain’s bin directory in the bash script ~/.bashrc for xargo to use.
• Edit build.rs to specify the lib libraries needed during linking, as follows:

use std::env;

fn main() {
    let staging_dir = env::var("STAGING_DIR").unwrap();
    println!(
        r"cargo:rustc-link-search={}/target-mipsel_24kec+dsp_uClibc-0.9.33.2/usr/lib",
        staging_dir
    );
}

• Specify the target in .cargo/config

[build]
target = "mipsel-unknown-linux-gnu"

[target.mipsel-unknown-linux-gnu]
linker = "mipsel-openwrt-linux-uclibc-gcc"
rustflags = ["-C", "embed-bitcode"]
#rustflags = ["-C", "embed-bitcode", "-C", "prefer-dynamic"]

• Download the GitHub code and place it in a directory under OpenWRT’s package.

https://github.com/likon/hello-rust