Pitfalls in VM Implementation on CHERI: Lessons from Porting CRuby

CHERI (Capability Hardware Enhanced RISC Instructions) replaces traditional pointers with hardware capabilities to enforce memory safety. Porting virtual machines to CHERI is non-trivial because many VM implementation techniques rely on C undefined behaviors that are valid on conventional architectures but break under CHERI's stricter model. Researchers ported CRuby to CHERI as a case study, categorized the VM-specific pitfalls encountered, and documented workarounds with their trade-offs. The findings are validated against the CRuby port and prior VM porting case studies, providing a practical guide for developers building or porting VMs to CHERI.