Re: [MirageOS-devel] Rust unikernels

[Thomas Leonard <talex5@xxxxxxxxx>]

On 24 July 2015 at 13:00, Geoffroy Couprie <contact@xxxxxxxxxxxxxxxxxxx> wrote:
> Hello!
>
> A chat on Twitter showed some interest in unikernels developed in
> Rust, and I was pointed here for further discussion.
>
> First, I want to acknowledge the amazing work done on MirageOS by
> everybody here. I have followed it from afar for some time, and there
> has been great progress to make it available and usable.
>
> Second, I know making a unikernel system means years of work and a
> team of developers and testers. I am not planning to attempt it alone.
> What I want is to sort out the skills needed, the big pitfalls, the
> important milestones, and know about the unknown unknowns. Then push
> for that project in the Rust community.
>
> From the beginning, people experimented with OS development in Rust
> (cf https://github.com/ryanra/RustOS
> https://github.com/thepowersgang/rust-barebones-kernel or
> https://github.com/charliesome/rustboot ). There is also a very active
> IRC channel, #rust-osdev on irc.mozilla.org
>
> From what I understand, the bare minimum to experiment would be an OS
> booting and communicating with a network card, scheduling and task
> switching, remote debugging, a network stack. Also, tools to help in
> building, deploying and testing applications.
> The ryanra/RustOS project seems well advanced, but it could use a network 
> stack.

Hi Geoffroy,

Have you thought about running Mirage on top of a minimal Rust OS
kernel to start with? Then you could implement new drivers in Rust
alongside existing Mirage code. As a garbage-collected language, OCaml
can't be used to implement the very lowest levels of Mirage (e.g.
malloc) and we currently use (my branch of) Mini-OS [1] for running as
a unikernel on Xen. A common question is whether we could replace this
C code with Rust. I'd be interested to help out if so - I've been
meaning to take another look at Rust now it's stable.

> A rough plan could be to take that project and:
> - strenghten the rtl8139 driver

If you target running under Xen, you only need to provide a simple Xen
network driver, whatever the physical hardware is. Likewise for
storage. This makes it easier to get started, and you'll support EC2,
etc.

> - write parsers and serializers for ARP, IP, TCP (it looks like
> MirageOS does not even need DHCP, since the IP address is passed at
> compilation time, is that right?).

Mirage can use DHCP or static addresses.

> This is something I am already
> pushing for a parser combinators project I launched (
> https://github.com/Geal/nom )
> - building the API above that network stack
> - the system can be monotask at first, but preemtive threading should
> happen at some point

If you have promises (and make all your low-level APIs non-blocking)
then you can get a very long way without preemptive threading,
although it would be good to have it eventually.

> - a part of Rust standard library is already available, I do not know
> how much is needed to support the use case of a HTTP server
> - building monitoring tools inside the kernel

When running under Xen, we share a trace buffer with dom0. This allows
you to see what the system is doing, even if it is hung or crashed.
See: https://mirage.io/wiki/profiling

> - building a testing infrastructure
>
> These steps look quite naive, but as I said, that's a very rough plan
> for something that could take years. As for the skills needed:
> - writing drivers and schedulers
> - developing network stacks (there are projects like
> https://github.com/libpnet/libpnet which could be integrated)
> - implementing Rust libstd APIs
> - testing and tooling industrialization
>
> What would you think of this project? What would increase its chances
> of success? Which steps will be very difficult?
>
> It could really benefit from Mirage's experience :)
>
> Cheers,
>
> Geoffroy Couprie

[1] https://github.com/talex5/mini-os


-- 
Dr Thomas Leonard        http://roscidus.com/blog/
GPG: DA98 25AE CAD0 8975 7CDA  BD8E 0713 3F96 CA74 D8BA

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