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Jesper Amilon

Publications and source records attributed to Jesper Amilon.

5 recordsLinked to original sources

Contract Based Verification of Non-functional Requirements for Embedded Automotive C Code

Code contracts provide a robust way to specify functional requirements of safety-critical software in embedded systems. For example, the ANSI/ISO C Specification Language (ACSL) can be used to specify the functional behavior of C code that is then formally verified by the Frama-C framework's Wp plugin. However, non-functional requirements, such as restrictions on control flow and data flow, are also important for embedded systems safety. Untrusted code developed by subcontractors, junior developers, or generated by large language models, can be verified by Wp but may nevertheless call unsafe functions or use uninitialized program variables. To address this problem, we constructed a set of general rules concerning non-functional requirements of C code in safety-critical embedded systems. Our rules are orthogonal to popular C rulesets such as MISRA-C and center on modules and their interaction through interfaces. To enable checking our rules, we propose an interface specification contract language for C modules. We implemented a checker for our rules as a Frama-C plugin, which takes as input a C module and its contract and checks control flow and data flow properties, ensuring, e.g., that only permitted functions are called by the module. We integrated our checker in a toolchain to enable specification and verification of module contracts and ACSL contracts for untrusted code. We report on two case studies on safety-critical C code using software in Scania trucks, where we defined module contracts and ACSL function contracts based on informal system requirements and verified them using our toolchain.

cs.PL

Contract Based Program Models for Software Model Checking

Model checking temporal properties of software is algorithmically hard. To be practically feasible, it usually requires the creation of simpler, abstract models of the software, over which the properties are checked. However, creating suitable abstractions is another difficult problem. We argue that such abstract models can be obtained with little effort, when the state transformation properties of the software components have already been deductively verified. As a concrete, language-independent representation of such abstractions we propose the use of \emph{flow graphs}, a formalism previously developed for the purposes of compositional model checking. In this paper, we describe how we envisage the work flow and tool chain to support the proposed verification approach in the context of embedded, safety-critical software written in~C.

cs.FL

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.

cs.LO

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.

cs.LO

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.

cs.SE