README.md

Exercise 1: Hello world module in Rust

Overview

In this exercise you will inspect a "Hello world" kernel module written in Rust. It writes a message to the system log when it is loaded. You will extend it to also print a message when the module is unloaded.

Task 1: Connect to your lab VM

1. Connect to your VM using ssh.

Task 2: Setup tmux

Start tmux so that connection issues do not prevent you from being able to get back to your shell:

    tmux -u attach -d || tmux -u

Task 3: Build the module

Build the module with make:

    make

Inspect Makefile, the only difference from the C version is that we have LLVM=1 to use the LLVM toolchain instead of gcc.

Task 4: Load the module

Load the module using insmod:

    sudo insmod hello.ko

Task 5: Check for messages from the module

Check for messages from the module using dmesg:

    sudo dmesg

You should see a messages as follows:

[ 2736.667232] hello: Hello world

Task 6: Remove the module

Remove the module using rmmod:

    sudo rmmod hello

Task 7: Add a Drop implementation

Add the following code to hello.rs:

impl Drop for Hello {
    fn drop(&mut self) {
        pr_info!("Goodbye world!\n");
    }
}

Repeat steps 3 to 6 above. After step 6, check the log again:

    sudo dmesg

You should see a message as follows:

[ 2742.305703] hello: Goodbye world!

Summary

In this exercise, you got familiar with building kernel modules in Rust, loading and unloading them, and inspecting the system log for messages.