rust_example.rs

// SPDX-License-Identifier: GPL-2.0

#![no_std]
#![feature(allocator_api, global_asm)]

use alloc::boxed::Box;
use core::pin::Pin;
use kernel::prelude::*;
use kernel::{cstr, file_operations::FileOperations, miscdev};

module! {
    type: RustExample,
    name: b"rust_example",
    author: b"Rust for Linux Contributors",
    description: b"An example kernel module written in Rust",
    license: b"GPL v2",
    params: {
        my_bool: bool {
            default: true,
            permissions: 0,
            description: b"Example of bool",
        },
        my_i32: i32 {
            default: 42,
            permissions: 0o644,
            description: b"Example of i32",
        },
    },
}

struct RustFile;

impl FileOperations for RustFile {
    type Wrapper = Box<Self>;

    fn open() -> KernelResult<Self::Wrapper> {
        println!("rust file was opened!");
        Ok(Box::try_new(Self)?)
    }
}

struct RustExample {
    message: String,
    _dev: Pin<Box<miscdev::Registration>>,
}

impl KernelModule for RustExample {
    fn init() -> KernelResult<Self> {
        println!("Rust Example (init)");
        println!("Am I built-in? {}", !cfg!(MODULE));
        println!("Parameters:");
        println!("  my_bool:  {}", my_bool.read());
        println!("  my_i32:   {}", my_i32.read());

        // Including this large variable on the stack will trigger a call to
        // `compiler_builtins::probestack::__rust_probestack` on x86_64.
        // This will verify that we are able to link modules which call
        // `__rust_probestack`.
        let x: [u64; 1028] = [5; 1028];
        println!("Large array has length: {}", x.len());

        Ok(RustExample {
            message: "on the heap!".to_owned(),
            _dev: miscdev::Registration::new_pinned::<RustFile>(cstr!("rust_miscdev"), None)?,
        })
    }
}

impl Drop for RustExample {
    fn drop(&mut self) {
        println!("My message is {}", self.message);
        println!("Rust Example (exit)");
    }
}