[aw1621107]

> Any non-free standing program running on a modern OS on modern hardware trying to access memory its not supposed to will be killed by the OS.

This seems like a rather strong statement to me. Do you mind elaborating further?

[1718627440]

I think bugs in the MMU hardware or the kernel accidentally configuring the MMU to allow access across processes that isn't supposed to be are quite rare.

[aw1621107]

Sure, but I think illegal interprocess memory accesses is a fairly narrow definition for "access[ing] memory its not supposed to". There's plenty of undesirable memory accesses that are possible without needing to cross process boundaries and I don't think the OS does that much to solve those outside of currently niche hardware.

[1718627440]

It might be undesirable to you, but you haven't specified this to the computer. Process-boundaries are one way how we specify what is allowed to touch and what not.

[aw1621107]

OK, sure, but there's no reason you can't extend that argument to in-process improper memory accesses either. free() is you specifying that a particular bit of memory isn't supposed to be touched any more, malloc() is you specifying that some amount of memory is legal to access, etc. Language runtimes, inserted/compile-time checks, etc. would be analogous to the OS/MMU here.

[1718627440]

Yes, but this is not across a trust boundary. Since these are in the same process/program. Rust "only" applies checks at compile time, it doesn't enforce security.

Not sure, if I'm clear. Rust is like cooperative multitasking, nice but not guaranteed. My claim here is, that we actually want preemptive multitasking.

[aw1621107]

I'm not quite sure I'm understanding your analogy here, but would that effectively mean each allocation lives in its own process?