An open extensible tool environment for Event-B

Abstract. We consider modelling indispensable for the development of complex systems. Modelling must be carried out in a formal notation to reason and make meaningful conjectures about a model. But formal modelling of complex systems is a difficult task. Even when theorem provers improve further and get more powerful, modelling will remain difficult. The reason for this that modelling is an exploratory activity that requires ingenuity in order to arrive at a meaningful model. We are aware that automated theorem provers can discharge most of the onerous trivial proof obligations that appear when modelling systems. In this article we present a modelling tool that seamlessly integrates modelling and proving similar to what is offered today in modern integrated development environments for programming. The tool is extensible and configurable so that it can be adapted more easily to different application domains and development methods.

MUNCH - Automated Reasoner for Sets and Multisets

This system description provides an overview of the MUNCH reasoner for sets and multisets. MUNCH takes as the input a formula in a logic that supports expressions about sets, multisets, and integers. Constraints over collections and integers are connected using the cardinality operator. Our logic is a fragment of logics of popular interactive theorem provers, and MUNCH is the first fully automated reasoner for this logic. MUNCH reduces input formulas to equisatisfiable linear integer arithmetic formulas. MUNCH reasoner is publicly available. It is implemented in the Scala programming language and currently uses the SMT solver Z3 to solve the generated integer linear arithmetic constraints

Qed. Computing what remains to be proved

International audienceWe propose a framework for manipulating in a efficient way terms and formulæ in classical logic modulo theories. Qed was initially designed for the generation of proof obligations of a weakest-precondition engine for C programs inside the Frama-C framework, but it has been implemented as an independent library. Key features of Qed include on-the-fly strong normalization with various theories and maximal sharing of terms in memory. Qed is also equipped with an extensible simplification engine. We illustrate the power of our framework by the implementation of non-trivial simplifications inside the Wp plug-in of Frama-C. These optimizations have been used to prove industrial, critical embedded softwares

Generating Optimised and Formally Checked Packet Parsing Code

Part 5: Software SecurityInternational audienceWhile implementing distributed applications, the parsing of binary packets is a very difficult and error-prone task the developer has to face. Moreover, these programming mistakes are often the source of distant vulnerabilities. In this paper we present a code-generation library, called Promiwag, for creating optimised and safe packet parsing code. Its input is concise human-readable descriptions of the protocols and the interests of the application in specific pieces of information. Promiwag follows a dependency-based algorithm, and uses high-level optimisation techniques to generate minimal parsing automatons. These automatons can be compiled into C or OCaml code for efficient execution, and to annotatedWhy code. This latter output is then used to automatically prove that for any possible input packet, the generated code cannot perform any illegal memory access, and that no infinite loop can be triggered. We have used our code generator to implement a pretty-printer for Internet protocols, and we provide experimental results on the performance of the generated code

Importing HOL Light into Coq

Abstract. We present a new scheme to translate mathematical developments from HOL Light to Coq, where they can be re-used and rechecked. By relying on a carefully chosen embedding of Higher-Order Logic into Type Theory, we try to avoid some pitfalls of inter-operation between proof systems. In particular, our translation keeps the mathematical statements intelligible. This translation has been implemented and allows the importation of the HOL Light basic library into Coq.

Precise Interprocedural Analysis in the Presence of Pointers to the Stack

International audienceIn a language with procedures calls and pointers as parameters, an instruction can modify memory locations anywhere in the call-stack. The presence of such side effects breaks most generic interprocedural analysis methods, which assume that only the top of the stack may be modified. We present a method that addresses this issue, based on the definition of an equivalent local semantics in which writing through pointers has a local effect on the stack. Our second contribution in this context is an adequate representation of summary functions that models the effect of a procedure, not only on the values of its scalar and pointer variables, but also on the values contained in pointed memory locations. Our implementation in the interprocedural analyser PInterproc results in a verification tool that infers relational properties on the value of Boolean, numerical and pointer variables

Validating the Translation of an Industrial Optimizing Compiler ∗

The paper presents an approach to the translation validation of an optimizing compiler which translates synchronous C programs into machine code programs. Being synchronous means that both source and target programs are loop free. This enables representation of each of these programs by a single state transformer, and verification of the translation correctness is based on comparison of the source and target state transformers. The approach has been implemented on a tool called MCVT which is also described.