Rust for Morello: Always-on memory safety, even in unsafe code (experience paper)

Memory safety issues are a serious concern in systems programming. Rust is a systems language that provides memory safety through a combination of a static checks embodied in the type system and ad hoc dynamic checks inserted where this analysis becomes impractical. The Morello prototype architecture from ARM uses capabilities, fat pointers augmented with object bounds information, to catch failures of memory safety. This paper presents a compiler from Rust to the Morello architecture, together with a comparison of the performance of Rust’s runtime safety checks and the hardware-supported checks of Morello. The cost of Morello’s always-on memory safety guarantees is 39% in our 19 benchmark suites from the Rust crates repository (comprising 870 total benchmarks). For this cost, Morello’s capabilities ensure that even unsafe Rust code benefits from memory safety guarantees.