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We introduce Wasm Logic, a sound program logic for first-order, encapsulated WebAssembly. We design a novel assertion syntax, tailored to WebAssembly’s stack-based semantics and the strong guarantees given by WebAssembly’s type system, and show how to adapt the standard separation logic triple and proof rules in a principled way to capture WebAssembly’s uncommon structured control flow. Using Wasm Logic, we specify and verify a simple WebAssembly B-tree library, giving abstract specifications independent of the underlying implementation. We mechanise Wasm Logic and its soundness proof in full in Isabelle/HOL. As part of the soundness proof, we formalise and fully mechanise a novel, big-step semantics of WebAssembly, which we prove equivalent, up to transitive closure, to the original WebAssembly small-step semantics. Wasm Logic is the first program logic for WebAssembly, and represents a first step towards the creation of static analysis tools for WebAssembly.
@InProceedings{watt_et_al:LIPIcs.ECOOP.2019.9,
author = {Watt, Conrad and Maksimovi\'{c}, Petar and Krishnaswami, Neelakantan R. and Gardner, Philippa},
title = {{A Program Logic for First-Order Encapsulated WebAssembly}},
booktitle = {33rd European Conference on Object-Oriented Programming (ECOOP 2019)},
pages = {9:1--9:30},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-111-5},
ISSN = {1868-8969},
year = {2019},
volume = {134},
editor = {Donaldson, Alastair F.},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2019.9},
URN = {urn:nbn:de:0030-drops-108011},
doi = {10.4230/LIPIcs.ECOOP.2019.9},
annote = {Keywords: WebAssembly, program logic, separation logic, soundness, mechanisation}
}