This post is a collection of reports on the tutorials provided for the MAC5856 class for Open Source Development. As such, this post will be continuously edited to account for my latest experiences with the tutorials.

More specifically, the tutoral pages provide a guide on how to setup a development environment for building and developing the Linux kernel.

After years of being an Arch Linux user, I've opted for going with a Fedora installation for a change. This required some small changes with respect to the tutorials - all of them are documented below.

Tutorial 1 - QEMU and Libvirt Setup

This first tutorial focuses on the creation of the basis for the development setup, such as the installation of all necessary packages for virtualisation.

  • Although the tutorial uses the libvirt-qemu user for the directory ownership, I had to go with the qemu user in Fedora.

  • To avoid having to use sudo every time I use virsh, I opted for creating a tiny wrapper virshh in the activate.sh script that solves this:

    function virshh() {
    virsh --connect "qemu:///system" $@
}
export -f virshh

    Now instead of using virsh I use virshh and it's working flawlessly so far.

  • As many other students reported, I also had to install the openssh-server package in the VM:

    apt update && apt install openssh-server
    systemctl enable ssh && systemctl start ssh && systemctl status ssh

Tutorial 2 - Building and Booting The Kernel

  • I wasn't able to use rsync to fetch the vm_mod_list we created in the last tutorial. For that I had to install rsync in the VM first.

  • I had a very annoyoing problem when creating the new VM: the system would never completely boot. Instead virt-install would halt very early and never finish the creation of the VM itself. After many attempts, this version worked:

    export img_file="${VM_DIR}/arm64_img.qcow2"
export root_vda="/dev/vda2"
export kernel_file="${IIO_TREE}/arch/arm64/boot/Image"
export initrd_file="${BOOT_DIR}/initrd.img-6.1.0-44-arm64"
export vm_name="arm64"

function create-vm-virsh() {
    sudo virt-install \
        --name ${vm_name} \
        --memory 2048 \
        --arch aarch64 \
        --machine virt \
        --osinfo detect=on,require=off \
        --import \
        --features acpi=off \
        --disk path=${img_file},bus=virtio,format=qcow2 \
        --boot kernel=${kernel_file},initrd=${initrd_file},kernel_args="loglevel=8 root=${root_vda} rootwait" \
        --network bridge:virbr0 \
        --graphics none
}

    The problem seems to be that the device mapping was not going as expected but adding the bus=virtio,format=qcow2 did the job.

Tutorial 3 - Modules and Build Config

Pretty much uneventful tutorial, very easy to follow. For some reason I had to restart the VM network system with

systemctl restart systemd-networkd

Because virsh net-dhcp-leases default was failing to find any open connections even though its networking capabilities were on.

Tutorial 4 - Device Characters

My only trouble in this tutorial was cross-compiling the host programs. Fedora doesn't ship a complete aarch64-compliant toolchain like Debian, so the easiest way around it (without manually installing an arm64-sysroot) was to use the Zig cross-compiler - which is honestly a shame for C/C++ compilers as it should've been easier with them anyway... Here is the simple command that made it work:

zig cc -target aarch64-linux-gnu read_prog.c -o read_prog