Kernel Module Developement

A collection of resources and such as I learn how to write kernel modules.

Resources

• https://docs.kernel.org/
• https://kernelnewbies.org/
• https://elixir.bootlin.com/linux/v7.0.1/source
• https://wiki.qemu.org/Documentation/9psetup

Steps to create the kernel

Follow https://github.com/bluedragon1221/minlinux2

Build kernel with for console output

CONFIG_SERIAL_8250=y
CONFIG_SERIAL_8250_CONSOLE=y

Also enable virtio for P9

Generating the RAMFS for QEMU

Add this to fstab: hostmods /host 9p trans=virtio,version=9p2000.L 0 0

Set this instead of the default login in inittab: console::respawn:/bin/sh

Create a host directory to live mount modules

Running

Mv the kernel image to the test directory. Generate the cpio file with

pushd initfiles
find . | cpio -o -H newc --owner=+0:+0 > ../init.cpio
popd

Run with qemu. Outputs directly to the terminal.

qemu-system-x86_64 \
  -kernel bzImage \
  -initrd init.cpio \
  -nographic \
  -append "console=ttyS0" \
  -virtfs local,mount_tag="hostmods",path="PATH_HERE",security_model=none