nomicon VS seL4

it’s even written by the same person that wrote the Nomicon (the guide to the dark arts of unsafe)

If you want to dive deeper you can always have other options but now there are concrete cases, if you want to do low level thing https://doc.rust-lang.org/nomicon/ while if you want multi thread/concurrency stuff https://marabos.nl/atomics/ . There are many many books so you will have to point yourself to what you want

Nonononono. SeqCst is the most error prone memory order: https://github.com/rust-lang/nomicon/issues/166

Hope this helps. For more details, see the Rustonomicon. I referenced the subtyping chapter here extensively.

Nice video! Glad I could help out. This stuff is hard, and I'm still learning a lot about it myself even years later. The Rustonomicon is a great read if you haven't already.

Have you got a moment to read through the good book , after reading through this perhaps try the Rustonomicon.

That is not what UB means. Undefined Behaviour is behaviour that the compiler is allowed to assume will never happen, and which can consequently cause miscompilations due to optimisation passes gone wrong if it does in fact occur in the source code.

It's true that Rust does not have a written specification that clearly delineates what is and isn't UB in a single place. But:

1. UB is impossible in safe code (modulo bugs in unsafe code)

2. There are resources such as the Rustinomicon (https://doc.rust-lang.org/nomicon/) that provide a detailed guide on what is and isn't allowed in unsafe code.

In practice, it's much easier to avoid UB in Rust than it is in C++.

However, this is a wide topic out of scope for a Reddit comment, so maybe just read the Rustonomicon. It explains everything about data handling in Rust.

The ownership model & borrow checker makes rust a bit of an awkward language in which to write complex data structures like trees and graphs. It can be done - since you can always use raw pointers & unsafe code when you absolutely need to to treat rust like C. But the language fights you, and the community can get a bit moralistic about this sort of thing. The rust nomicon is a fantastic resource for learning the limits of the borrow checker, and where and how to use unsafe code correctly. You will need unsafe less than you think you will, but sometimes you will have no choice.

> People like to snob Unix but the fact is: the world runs on Unix.

The world you are aware of runs on it.

> Can we really do that much better or is it just hubris?

Yes. Have a look at seL4[1] and Barrelfish too[2], even though that's no longer active. seL4 in particular is powering a lot of highly secure computing systems. There is a surprisingly large sphere outside of Unix/POSIX.

[1] https://sel4.systems/

[2] https://barrelfish.org/

There are also RTOS-capable microkernels such as seL4[0], with few but extremely fast syscalls[1]. Note times are in cycles, not usec.

0. https://sel4.systems/

1. https://sel4.systems/About/Performance/

https://sel4.systems

Working on a number of platforms, verified on some. Multicore support is an ongoing effort afaict.

On OS built on this kernel is still subject to some assumptions (like, hardware working correctly, bootloader doing its job, etc). But mostly those assumptions are less of a problem / easier to prove than the properties of a complex software system.

As I understand it, guarantees that seL4 does provide, go well beyond anything else currently out there.

Take a look at this: https://sel4.systems/

It's probably have to be seL4 (https://sel4.systems), running on some fully OSS hardware.

There are question marks over much of available RISC-V chips due to chinese producers, so maybe OpenPower based hardware?

Plus, the entire system (motherboard, etc) would need to be manufactured using a good supply chain.

Hmmm, this has probably all been thought through in depth before by others. :)

You can use it to (mostly) validate small snippets are the same. See Alive2 for the application of Z3/formalization of programs as SMT for that [1]. As far as I'm aware there are some problems scaling up to arbitrarily sized programs due to a lack of formalization in higher level languages in addition to computational constraints. With a lot of time and effort it can be done though [2].

1. https://github.com/AliveToolkit/alive2

2. https://sel4.systems/

Formal methods. This is not in most general-purpose programming languages and probably never will be (maybe we'll see formal methods to verify unsafe code in Rust...) because it's a ton of boilerplate (you have to help the compiler type-check your code) and also extremely complicated. However, formal methods is very important for proving code secure, such as sel4 (microkernel formally verified to not have bugs or be exploitable) which has just received the ACM Software Systems Award 3 days ago.

Today we'd look at seL4.