Non-CHERI mechanism to fault on pointer loads for CoPA

Identify hardware or software mechanisms, other than CHERI capability load faults, that can reliably trigger faults specifically on loads of absolute memory references (pointers) in order to enable the Copy-on-Pointer-Access (CoPA) optimization for relocating pointers during fork in single-address-space operating system implementations.

Background

The paper proposes a single-address-space fork design that relies on identifying and relocating absolute memory references so the child process’s pointers refer to its own memory region. To reduce copying overhead, the authors introduce Copy-on-Pointer-Access (CoPA), which shares pages until the child loads an absolute pointer; at that point, the page is copied and the pointer is relocated.

Implementing CoPA requires the ability to fault precisely on loads of absolute memory references. CHERI provides this via a capability-load fault mechanism, but the authors explicitly state they are not aware of any other mechanism that can deliver the same behavior. Finding non-CHERI alternatives would broaden the applicability of CoPA to other architectures and systems.