KernelTLV Linux Hacking Environment

Purpose

This project is a way to bring up a Linux kernel development environment quickly and easily, without using tools like QEMU or building a toolchain and cross-compiling. This is done by building a kernel from the Debian-supplied package and using it with the Debian distribution.

The project also includes khack, a utility for taking some guesswork out of the process of hacking on the kernel as well as serving as a guide for newcomers, as an alternative for reading a lot of material online and attempting to learn by trial and error.

Requirements

1. Vagrant
2. VirtualBox
3. The vagrant-vbguest plugin (Run vagrant plugin install vagrant-vbguest).
4. ~15GB of free space.

Usage

Run vagrant up where you cloned the repo (where Vagrantfile is) to create a shiny new VM with everything you need.

This will take a while.

Once it's done, run vagrant ssh to enter the machine and from there, depending on your level of familiarity with kernel development, either:

• Newcomer - run khack for an explanation of what you can do here (WIP),
• Experienced developer - run khack --help for a list of useful scripts,

or just ignore khack entirely and do your own thing.

Details

Inside the VM home directory, there will be:

• linux-source: Linux kernel sources ready to be compiled with the minimal configuration from linux-config.
• khack: The khack utility.
• module: Scaffold code for a kernel module.
• linux-config: Premade kernel configs.
• system-config: Configuration files for different system-related programs, there's usually no need to touch this.
• boot-backup: A backup of /boot, just in case.

khack, module and linux-config are set up to be shared with the host operating system, so you can use your favorite editor to edit files in them.
To edit the kernel source, see below. Everything else can be done the traditional way (compile and install the kernel, etc) or using khack for convenience.

Editing from host

We reveal the source via SMB/CIFS, to avoid issues with building the kernel on a VirtualBox shared directory. To mount:

Ubuntu

Via terminal:

sudo apt install cifs-utils
sudo mount -t cifs //localhost/kernel-source WHERE_TO_MOUNT -o port=10139,username=vagrant,password=vagrant,uid=$USER,gid=$USER

Via Nautilus:

smb://vagrant:vagrant@localhost:10139/kernel-source/

macOS

Via terminal:

sudo mount -t smbfs '//vagrant:vagrant@localhost:10139/kernel-source' WHERE_TO_MOUNT

Via Finder:

Use Connect to Server (cmd+K) with the URL smb://vagrant:vagrant@localhost:10139/.

khack

khack is meant to simplify hacking on the kernel and teach newcomers which commands actually work by, you know, showing that they actually work, saving learners from the frustration of trying to adjust incantations from an online tutorial written ten years ago.

Its source is available under khack and it can be used as simply khack within the VM as it is symlinked into the right place (see setup_vm.sh).

For example:

• khack kernel make will build the kernel in ~\linux-source.
• khack kernel install will install the built kernel so that it will run when the VM is restarted.
• khack kernel running will report if the latest compiled kernel is actually running.

Experiment and have fun,

KernelTLV Team