noe-ba-project

Bachelor project 2023 at DCSL @ EPFL

Linux drivers inside kernel 6.2.x

Setup a dev VM

1. install qemu and qemu-system

2. download a debian iso (https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/debian-11.6.0-amd64-netinst.iso) (update DEBIAN_IMG in the following Makefile to be the path of the iso)

3. do commands:

   1. make disk-img it will create a disk.img file of size 20Go
   2. make install-debian and proceed to installation of debian (with ssh-server if you don't want to use the vm in graphical mode but via ssh connection)

Launch (and connect) to dev VM

1. launch vm: make boot-dev-vm or make boot-dev-vm-nographical for non graphical mode

2. (in non graphical mode) ssh into vm: make connect-vm

Setting up  the toolchain

Rust in kernel intro explains all the required components: https://www.kernel.org/doc/html/latest/rust/quick-start.html

rustc

for the moment, the kernel depends on some unstable Rust features

Rust standard library source

The Rust standard library source is required because the build system will cross-compile core and alloc.

libclang

Use of LLVM for understand C code in the kernel:

libclang (part of LLVM) is used by bindgen to understand the C code in the kernel, which means LLVM needs to be installed; like when the kernel is compiled with CC=clang or LLVM=1.

bindgen

The bindings to the C side of the kernel are generated at build time using the bindgen tool.

Building

Building a kernel with a complete LLVM toolchain is the best supported setup at the moment.

Inside the dev VM: build and install the kernel

1. Install dependencies for compiling the kernel apt install git build-essential fakeroot libncurses5-dev libssl-dev flex bison libelf-dev

2. Install Rust: https://www.rust-lang.org/tools/install and setup the tools chain as described in previous section

3. Download the linux kernel: (works the Rust-for-linux kernel too) git clone --depth=1 --branch=v6.2 http://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

4. Go inside the linux-6.2.2 folder: cd linux

5. Check if rust is available in the config make LLVM=1 rustavailable

6. Activate rust support in the kernel, the option will be visible if a compatible toolchain is available make menuconfig

   General setup --->
      L[*] Rust support

7. Compile the kernel (~20min) it will produce a linux-image-6.2.0_6.2.0-6_amd64.deb image make bindeb-pkg ARCH=x86_64 CC=clang

8. Install the kernel sudo apt install ./linux-image-6.2.0_6.2.0-6_amd64.deb

9. verify the installation, it must match the image version: uname -a

Write, build and insert a rust kernel out-of-tree

Sample of rust drivers can be found in the folder rust-drivers

Build the module with command:

make KDIR=<PATH_TO_LINUX> CC=clang

The following commands are useful to manage modules:

sudo insmod hello_world.ko    	# insert the module in the kernel 
sudo rmmod hello_world        	# delete module
sudo modinfo hello_world.ko   	# print info about a module file
sudo lsmod			# list all installed modules
dmesg  				# print the kernel logs

IOCLT in a Rust driver

Kernel documentation reference: https://www.kernel.org/doc/html/latest/driver-api/ioctl.html

IOCTL can't be implemented now in the official linux kernel version. But we can use the version of the Rust-for-Linux project in order to use a more rust-friendly version of the kernel.