Set Up Kernel Module Dev Environment

2026-05-06, Wed

Exmaple code in the venerable book Linux Device Drivers, Third Edition¹^,² could not run in current kernel kernel versions, hence this post for setting up a proper environment for module development.

1. Preparation

First, we need to install the kernel headers files needed

sudo dnf install kernel-devel

Then create a sample project directory and create file .clangd³ with following content:

# ref: ~/Workspace/SampleProject/.clangd
# The content format is YAML
CompileFlags:
  Add:
    - "-I/usr/src/kernels/6.8.9-100.fc38.aarch64/include"

This file is used for LSP Server clangd to recognize additional header files. The actual include path is /usr/src/kernel/$(uname -r)/include.

2. The Code

Now it's time to write down our first module:

// ref: hello_module.c
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("MEC");
MODULE_DESCRIPTION("A simple hello world module");


static int __init hello_init(void) {
  printk(KERN_INFO "Hello, kernel world!\n");
  return 0; // Success
}

static void __exit hello_exit(void) {
  printk(KERN_INFO "Goodbye, kernel world!\n");
}
module_init(hello_init);
module_exit(hello_exit);

along with the Makefile:

obj-m += hello_module.o

all:
        make -C /lib/modules/$(shell uname -r)/build M=${PWD} modules

clean:
        make -C /lib/modules/$(shell uname -r)/build M=${PWD} clean

To build this custom external module, run make.

3. The Module

Before we do anything further with this module, run sudo dmesg -w to see live update of message output from printk from code. Now try

sudo insmod hello_module.ko to install the module, and
lsmod | grep hello_module to see its current status, and
sudo rmmod hello_module to remove the module from kernel

4. References

See these docs for more info:

Kernel Documentation: Building External Modules https://docs.kernel.org/kbuild/modules.html

Footnotes:

LWN.net: Linux Device Drivers, Third Edition https://lwn.net/Kernel/LDD3/

O'Reilly: Linux Deivce Drivers https://www.oreilly.com/openbook/linuxdrive3/book/

clangd doc: Configuration -> Files https://clangd.llvm.org/config.html#files