linux-kernel-module
===================

Sample out-of-tree linux kernel module.

Author:  Giovanni Santini
Mail:    giovanni.santini@proton.me
License: GPLv2


Usage
-----

To build and load the kernel module, you first need the kernel
sources. In addition to building the module, we will also build the
kernel and an image to boot it with qemu for development. This is
adviced since kernel panics in your module may crash the system.

Download a kernel version:

    wget https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.17.6.tar.xz
    tar -xvf linux-6.17.6 && mv linux-6.17.6 linux
    cd linux
    make defconfig && make -j$(nproc)
    cd ..

Build the module:

    make KVERSION=6.17.6

Clean the build:

    make clean

Create an image, copy the module, and boot with qemu:

    make img
    make copy
    make qemu

Inside the image, you will find the module in the /root directory. You
can load it with `insmod`

    insmod ./hello.ko

Check messages in `dmeg`:

    dmesg

List loaded modules:

    lsmod | grep hello

Remove it with:

    rmmod -f hello


Debugging
---------

Follow this guide to debug kernel modules with gdb:

    https://www.kernel.org/doc/html/v6.17/process/debugging/gdb-kernel-debugging.html