Architest

Architest is a collection of scripts and configurations for making it easier to test software across a wide range of Linux kernels and architectures.

Our use-case is running a test-suite of eBPF programs over multiple machines for quickly spotting regressions.

Getting started with pre-compiled machines

Download a ready to use virtual machine from our release page.

wget https://github.com/Exein-io/architest/releases/download/0.2/aarch64_6.0.tar.gz
tar -xzf aarch64_6.0.tar.gz
cd build/aarch64_6.0/images/
./start-qemu.sh

The machine can then be reached over SSH.

ssh root@localhost -p 3366

If you want to download all of them, you can use Github CLI:

gh release download -R Exein-io/architest -D release -p "*.tar.gz"
cd release
for file in *.tar.gz; do tar -xzf $file --one-top-level && rm $file; done
ls

Building new machines

If you need some sort of customization or the machine you need lacks a prebuilt binary, you'll have to clone the project and build from source. This repository is just a collection of configuration files for buildroot, you'll probably need to consult its documentation.

git clone --recurse-submodules git@github.com:Exein-io/architest.git

After cloning it you can setup a build folder. make will compile the kernel and the root file system. Finally, the generated start-qemu.sh script will make it easy to start qemy-system with the right settings.

$ ./scripts/bootstrap.sh x86_64 5.15
...
$ cd build/x86_64_5.15/
$ make
...
$ ./images/start-qemu.sh
...

How to use

Fragments folder and the bootstrap script

The fragments/ folder contains the partial configurations:

• fragments/common.frag contains shared configurations
• fragments/linux/ contains kernel specific configurations
• fragments/arch/ contains architecture specific configurations

The bootstrap script will merge them together to produce a working configuration. That script is extremely simple, it's just a convenience for cancatenating the three files.

$ ./scripts/bootstrap.sh 
Usage: ./scripts/bootstrap.sh <architecture> <linux_version>

Available architectures:
- x86_64
- aarch64
- riscv64
- mips

Available linux versions:
- 5.5
- 5.10
- 5.13
- 5.15
- 6.0

Build directories

All the build artifacts will go in the build directory. Each target will have its own build/<arch>_<kernel>/ folder.

To save space and time, all the targets will share the downloaded files in build/download.

In order to have multiple output directories, we use the buildroot "build out of tree" feature. For more details, see https://buildroot.org/downloads/manual/manual.html#_building_out_of_tree

Advanced topics

Trying a custom kernel

Whether to test a particular commit or a local change, we may want to compile a custom kernel.

Bootstrap a architest build directory as usual. Then edit local.mk and make it point to your local clone:

LINUX_OVERRIDE_SRCDIR=/home/dev/projects/linux/

Note: local.mk is the default makefile override file, as specified by BR2_PACKAGE_OVERRIDE_FILE. Configurations for kernels up to 5.15 do override that settings to work-around a compilation issue with pahole.

Building a release

The ./scripts/release.sh script can be used to automate the creation of of multiple machines. For each architecture/kernel combination in that file, the script will call ./scripts/bootstrap.sh $ARCH $KERNEL, run make and pack the results into ./build/release/$ARCH_$KERNEL.tar.gz.

Customizations

Buildroot linking

We include buildroot as a submodule. Than we include architest configurations by using the BR2_EXTERNAL variable. See https://buildroot.org/downloads/manual/manual.html#outside-br-custom

Networking

The guest networking is started in user-mode, with the SSH port forwarding to the host port 3366. This is very unsecure, be aware that anyone with access to local port 3366 will have root access to the qemu virtual machine.

We use user networking to avoid the need for root access when starting up qemu.

-nic user,model=virtio-net-pci,hostfwd=tcp:127.0.0.1:3366-10.0.2.14:22

You can connect with ssh qemu after adding this alias to your ~/.ssh/config:

Host qemu
  Hostname localhost
  User root
  port 3366
  StrictHostKeyChecking no
  UserKnownHostsFile /dev/null
  LogLevel QUIET

BPF support

We've enabled most kernel flags for eBPF support.

We've setup the fstab file to auto-mount BPF related folders:

• /sys/fs/bpf
• /sys/kernel/debug
• /sys/kernel/tracing
• /sys/kernel/security