BEST: a Binary Executable Slicing Tool

We describe the implementation of BEST, a tool for slicing binary code. We aim to integrate this tool in a WCET estimation framework based on model checking. In this approach, program slicing is used to abstract the program model in order to reduce the state space of the system. In this article, we also report on the results of an evaluation of the efficiency of the abstraction technique

Program Semantics in Model-Based WCET Analysis: A State of the Art Perspective

Advanced design techniques of safety-critical applications use specialized development model based methods. Under this setting, the application exists at several levels of description, as the result of a sequence of transformations. On the positive side, the application is developed in a systematic way, while on the negative side, its high-level semantics may be obfuscated when represented at the lower levels. The application should provide certain functional and non-functional guarantees. When the application is a hard real-time program, such guarantees could be deadlines, thus making the computation of worst-case execution time (WCET) bounds mandatory. This paper overviews, in the context of WCET analysis, what are the existing techniques to extract, express and exploit the program semantics along the model-based development workflow

Timed automata for modelling caches and pipelines

In this paper, we focus on modelling the timing aspects of binary programs running on architectures featuring caches and pipelines. The objective is to obtain a timed automaton model to compute tight bounds for the worst-case execution time (WCET) of the programs using model-checking tehcniques.Author gratefully acknowledges the funding from projects TEC2011-28666-C04-02, TEC2014-58036-C4-3-R and grant BES-2012-055572, awarded by the Spanish Ministry of Economy and Competitivity

A Formally Verified WCET Estimation Tool

The application of formal methods in the development of safety-critical embedded software is recommended in order to provide strong guarantees about the absence of software errors. In this context, WCET estimation tools constitute an important element to be formally verified. We present a formally verified WCET estimation tool, integrated to the formally verified CompCert C compiler. Our tool comes with a machine-checked proof which ensures that its WCET estimates are safe. Our tool operates over C programs and is composed of two main parts, a loop bound estimation and an Implicit Path Enumeration Technique (IPET)-based WCET calculation method. We evaluated the precision of the WCET estimates on a reference benchmark and obtained results which are competitive with state-of-the-art WCET estimation techniques

How to Compute Worst-Case Execution Time by Optimization Modulo Theory and a Clever Encoding of Program Semantics

International audienceIn systems with hard real-time constraints, it is necessary to compute upper bounds on the worst-case execution time (WCET) of programs; the closer the bound to the real WCET, the better. This is especially the case of synchronous reactive control loops with a fixed clock; the WCET of the loop body must not exceed the clock period. We compute the WCET (or at least a close upper bound thereof) as the solution of an optimization modulo theory problem that takes into account the semantics of the program, in contrast to other methods that compute the longest path whether or not it is feasible according to these semantics. Optimization modulo theory extends satisfiability modulo theory (SMT) to maximization problems. Immediate encodings of WCET problems into SMT yield formulas intractable for all current production-grade solvers; this is inherent to the DPLL(T) approach to SMT implemented in these solvers. By conjoining some appropriate "cuts" to these formulas, we considerably reduce the computation time of the SMT-solver. We experimented our approach on a variety of control programs, using the OTAWA analyzer both as baseline and as underlying microarchitectural analysis for our analysis, and show notable improvement on the WCET bound on a variety of benchmarks and control programs