Linux Kernel Module Cheat

Run one command, get into QEMU Buildroot BusyBox with several minimal Linux kernel 4.9 module example tutorials. Tested in Ubuntu 14.04.

Usage:

./run

First build will take a while (GCC, Linux kernel).

QEMU opens up, and you can run:

insmod /hello.ko
insmod /hello2.ko
rmmod hello
rmmod hello2

Each module comes from a C file under kernel_module/. For module usage do:

head *.c

We use Buildroot's default kernel version, you can confirm it after build with:

grep BR2_LINUX_KERNEL_VERSION buildroot/.config

We use printk a lot, and it shows on the QEMU terminal by default. If that annoys you (e.g. you want to see stdout separately), do:

dmesg -n 1

See also: https://superuser.com/questions/351387/how-to-stop-kernel-messages-from-flooding-my-console

When your kernel starts crashing, get the full trace with:

./run -n

1. Introduction
2. Build
3. kmod
4. Bibliography
5. Examples
   1. Host
   2. Buildroot
      1. hello
      2. hello2
      3. debugfs
      4. fops
      5. workqueue
      6. panic