Architecture specifications notionally define the fundamental interface between hardware and software: the envelope of allowed behaviour for processor implementations, and the basic assumptions for software development and verification. But in practice, they are typically prose and pseudocode documents, not rigorous or executable artifacts, leaving software and verification on shaky ground.
In this paper, we present rigorous semantic models for the sequential behaviour of large parts of the mainstream ARMv8-A, RISC-V, and MIPS architectures, and the research CHERI-MIPS architecture, that are complete enough to boot operating systems, variously Linux, FreeBSD, or seL4. Our ARMv8-A models are automatically translated from authoritative ARM-internal definitions, and (in one variant) tested against the ARM Architecture Validation Suite.
We do this using a custom language for ISA semantics, Sail, with a lightweight dependent type system, that supports automatic generation of emulator code in C and OCaml, and automatic generation of proof-assistant definitions for Isabelle, HOL4, and (currently only for MIPS) Coq. We use the former for validation, and to assess specification coverage. To demonstrate the usability of the latter, we prove (in Isabelle) correctness of a purely functional characterisation of ARMv8-A address translation. We moreover integrate the RISC-V model into the RMEM tool for (user-mode) relaxed-memory concurrency exploration. We prove (on paper) the soundness of the core Sail type system.
We thereby take a big step towards making the architectural abstraction actually well-defined, establishing foundations for verification and reasoning.
Thu 17 Jan
|10:36 - 10:58|
Aleš BizjakAarhus University, Daniel Gratzer, Robbert KrebbersDelft University of Technology, Lars BirkedalAarhus UniversityLink to publication DOI Media Attached File Attached
|10:58 - 11:20|
José Fragoso SantosImperial College London, Petar MaksimovićImperial College London, UK and Mathematical Institute of the Serbian Academy of Sciences and Arts, Serbia, Gabriela SampaioImperial College London, UK, Philippa GardnerImperial College LondonLink to publication DOI Media Attached File Attached
|11:20 - 11:42|
Alasdair ArmstrongUniversity of Cambridge, Thomas BauereissUniversity of Cambridge, Brian CampbellUniversity of Edinburgh, Alastair ReidArm Ltd, Kathryn E. GrayUniversity of Cambridge, Robert M. NortonUniversity of Cambridge, Prashanth MundkurSRI International, Mark WassellUniversity of Cambridge, Jon FrenchUniversity of Cambridge, Christopher PulteUniversity of Cambridge, Shaked FlurUniversity of Cambridge, Ian StarkThe University of Edinburgh, Neelakantan R. KrishnaswamiComputer Laboratory, University of Cambridge, Peter SewellUniversity of CambridgeLink to publication DOI Media Attached File Attached
|11:42 - 12:04|
Kayvan MemarianUniversity of Cambridge, Victor B. F. GomesUniversity of Cambridge, UK, Brooks DavisSRI International, Stephen KellUniversity of Kent, Alexander RichardsonUniversity of Cambridge, Robert N. M. WatsonUniversity of Cambridge, Peter SewellUniversity of CambridgeLink to publication DOI Media Attached File Attached