#![no_std]
// no_std用于表示没有std库，即freestanding环境
extern crate alloc;
use alloc::borrow::ToOwned;
use alloc::string::String;
// 我们以printk为底层，提供了println
use linux_kernel_module::println;
// 这个struct代表内核模块
struct HelloWorldModule {
    message: String,
}
// 实现内核模块初始化方法
impl linux_kernel_module::KernelModule for HelloWorldModule {
    fn init() -> linux_kernel_module::KernelResult<Self> {
        println!("Hello kernel module from rust!");
        Ok(HelloWorldModule {
            message: "on the heap!".to_owned(),
        })
    }
}
// 提供内核模块卸载方法
impl Drop for HelloWorldModule {
    fn drop(&mut self) {
        println!("My message is {}", self.message);
        println!("Goodbye kernel module from rust!");
    }
}
// 通过kernel_module宏，export了内核模块的相关信息
linux_kernel_module::kernel_module!(
    HelloWorldModule,
    author: b"Fish in a Barrel Contributors",
    description: b"An extremely simple kernel module",
    license: b"GPL"
);

$ cd linux-kernel-module-rust/hello-world
$ RUST_TARGET_PATH=$(pwd)/.. cargo +nightly xbuild --target x86_64-linux-kernel-module
$ make
$ insmod helloworld.ko
$ rmmod helloworld
$ dmesg | tail -n 3
[521088.916091] Hello kernel module from rust!
[521174.204889] My message is on the heap!
[521174.204891] Goodbye kernel module from rust!

{
    "rust-analyzer.cargo.extraEnv": {
        "RUST_TARGET_PATH": "/root/linux-kernel-module-rust"
    },
    "rust-analyzer.cargo.target": "x86_64-linux-kernel-module",
    "rust-analyzer.server.extraEnv": {
        "RA_LOG": "lsp_server=debug",
        "RUST_TARGET_PATH": "/root/linux-kernel-module-rust"
    },
    "rust-analyzer.trace.server": "verbose",
    "rust-analyzer.linkedProjects": [
        "hello-world/Cargo.toml",
        "Cargo.toml"
    ],
}