WASM?

Posted Jun 8, 2024 2:25 UTC (Sat) by Cyberax (✭ supporter ✭, #52523)
In reply to: WASM? by roc
Parent article: Modernizing BPF for the next 10 years

WASM and BPF instructions and registers are equally typed. And access to memory is equally untyped: https://www.kernel.org/doc/html/latest/bpf/standardizatio...

At this point there's no conceptual between WASM and eBPF. The eBPF runtime tries to be more resilient to timing attacks (via constant blinding), but that's a property of runtime. It can be added to WASM runtimes.

WASM?

Posted Jun 10, 2024 7:31 UTC (Mon) by roc (subscriber, #30627) [Link] (1 responses)

The eBPF verifier does type propagation and checking and prevents pointer arithmetic. https://docs.kernel.org/6.1/bpf/verifier.html#register-va...
It's not well documented and all very ad-hoc, but this is not the usual WASM array-of-bytes model.

I think the closest WASM equivalent of this is reference types, which are pretty new. I don't see instructions for doing field load/stores via references yet.

WASM?

Posted Jun 10, 2024 17:11 UTC (Mon) by Cyberax (✭ supporter ✭, #52523) [Link]

I doubt that this tracking adds any real value. For practical reasons, it's likely that just adding range-checking accessors should be enough for practical reasons.

I'm also going to bet, that eBPF will grow pointer arithmetic that can re-interpret types in the future.