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Christian Lidström

Publications and source records attributed to Christian Lidström.

5 recordsLinked to original sources

Verification of Configurable SRA Systems

Many digital systems are designed as collections of asynchronous processes orchestrated by a domain-specific scheduler. The verification of such scheduler-restricted asynchronous systems (SRA) is challenging due to process-process and process-scheduler interactions. In this paper, we tackle the problem of verifying configurable SRA. A configurable SRA describes an unbounded family of possible SRA, each resulting from an instantiation satisfying given configuration constraints; our goal is proving at once that every legal instantiation of a configurable SRA is correct. We propose a contract-based, deductive verification approach that combines (i) compositional proof rules that abstract the scheduler to prove top-level invariant properties, (ii) automatic summarizations of the methods invoked by the scheduler, (iii) simplification with respect to the nature of the space of configurations. The approach is grounded in (object-oriented) first order logic, requires reasoning over quantified statements, and leverages the Dafny software verifier as a backend. An experimental evaluation on industrial case studies demonstrates that the framework scales effectively and enables practical reasoning about complex parameterized behaviors.

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AutoDeduct: A Tool for Automated Deductive Verification of C Code

Deductive verification has become a mature paradigm for the verification of industrial software. Applying deductive verification, however, requires that every function in the code base is annotated with a function contract specifying its behaviour. This introduces a large overhead of manual work. To address this challenge, we introduce the AutoDeduct toolchain, built on top of the Frama-C framework. It implements a combination of techniques to automatically infer contracts for functions in C programs, in the syntax of ACSL, the specification language of Frama-C. Contract inference in AutoDecuct is implemented as two plugins for Frama-C, each inferring different types of annotations. We assume that programs have an entry-point function already equipped with a contract, which is used in conjunction with the program source code to infer contracts for the helper functions, so that the entry-point contract can be verified. The current release of AutoDeduct is the first public prototype, which we evaluate on an example adapted from industrial software.

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A Program Instrumentation Framework for Automatic Verification

In deductive verification and software model checking, dealing with certain specification language constructs can be problematic when the back-end solver is not sufficiently powerful or lacks the required theories. One way to deal with this is to transform, for verification purposes, the program to an equivalent one not using the problematic constructs, and to reason about this equivalent program instead. In this article, we propose program instrumentation as a unifying verification paradigm that subsumes various existing ad-hoc approaches, has a clear formal correctness criterion, can be applied automatically, and can transfer back witnesses and counterexamples. We illustrate our approach on the automated verification of programs that involve quantification and aggregation operations over arrays, such as the maximum value or sum of the elements in a given segment of the array, which are known to be difficult to reason about automatically. We implement our approach in the MonoCera tool, which is tailored to the verification of programs with aggregation, and evaluate it on example programs, including SV-COMP programs.

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Automatic Program Instrumentation for Automatic Verification (Extended Technical Report)

In deductive verification and software model checking, dealing with certain specification language constructs can be problematic when the back-end solver is not sufficiently powerful or lacks the required theories. One way to deal with this is to transform, for verification purposes, the program to an equivalent one not using the problematic constructs, and to reason about its correctness instead. In this paper, we propose instrumentation as a unifying verification paradigm that subsumes various existing ad-hoc approaches, has a clear formal correctness criterion, can be applied automatically, and can transfer back witnesses and counterexamples. We illustrate our approach on the automated verification of programs that involve quantification and aggregation operations over arrays, such as the maximum value or sum of the elements in a given segment of the array, which are known to be difficult to reason about automatically. We formalise array aggregation operations as monoid homomorphisms. We implement our approach in the MonoCera tool, which is tailored to the verification of programs with aggregation, and evaluate it on example programs, including SV-COMP programs.

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An Abstract Contract Theory for Programs with Procedures

When developing complex software and systems, contracts provide a means for controlling the complexity by dividing the responsibilities among the components of the system in a hierarchical fashion. In specific application areas, dedicated contract theories formalise the notion of contract and the operations on contracts in a manner that supports best the development of systems in that area. At the other end, contract meta-theories attempt to provide a systematic view on the various contract theories by axiomatising their desired properties. However, there exists a noticeable gap between the most well-known contract meta-theory of Benveniste et al., which focuses on the design of embedded and cyber-physical systems, and the established way of using contracts when developing general software, following Meyer's design-by-contract methodology. At the core of this gap appears to be the notion of procedure: while it is a central unit of composition in software development, the meta-theory does not suggest an obvious way of treating procedures as components. In this paper, we provide a first step towards a contract theory that takes procedures as the basic building block, and is at the same time an instantiation of the meta-theory. To this end, we propose an abstract contract theory for sequential programming languages with procedures, based on denotational semantics. We show that, on the one hand, the specification of contracts of procedures in Hoare logic, and their procedure-modular verification, can be cast naturally in the framework of our abstract contract theory. On the other hand, we also show our contract theory to fulfil the axioms of the meta-theory. In this way, we give further evidence for the utility of the meta-theory, and prepare the ground for combining our instantiation with other, already existing instantiations.

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