Some interesting rare choices there (some of which would be applicable to normal userlands or even to language VMs):
* Memory access is protected, but addresses are not virtually mapped. The lack of paging of course ties strongly to the inability to dynamically add tasks.
* They wish they could have read-only shared libraries (viable since there's only one address space) so they could truly be shared, but the current ecosystem assumes mutability is possible (even though in Rust mutable globals are rare).
https://oxidecomputer.github.io/hubris/reference/