Integrated Java Bytecode Verification

AbstractExisting Java verifiers perform an iterative data-flow analysis to discover the unambiguous type of values stored on the stack or in registers. Our novel verification algorithm uses abstract interpretation to obtain definition/use information for each register and stack location in the program, which in turn is used to transform the program into Static Single Assignment form. In SSA, verification is reduced to simple type compatibility checking between the definition type of each SSA variable and the type of each of its uses. Inter-adjacent transitions of a value through stack and registers are no longer verified explicitly. This integrated approach is more efficient than traditional bytecode verification but still as safe as strict verification, as overall program correctness can be induced once the data flow from each definition to all associated uses is known to be type-safe

Computing stack maps with interfaces

International audienceLightweight bytecode verification uses stack maps to annotate Java bytecode programs with type information in order to reduce the verification to type checking. This paper describes an improved bytecode analyser together with algorithms for optimizing the stack maps generated. The analyser is simplified in its treatment of base values (keeping only the necessary information to ensure memory safety) and enriched in its representation of interface types, using the Dedekind-MacNeille completion technique. The computed interface information allows to remove the dynamic checks at interface method invocations. We prove the memory safety property guaranteed by the bytecode verifier using an operational semantics whose distinguishing feature is the use of un-tagged 32-bit values. For bytecode typable without sets of types we show how to prune the fix-point to obtain a stack map that can be checked without computing with sets of interfaces i.e., lightweight verification is not made more complex or costly. Experiments on three substantial test suites show that stack maps can be computed and correctly pruned by an optimized (but incomplete) pruning algorithm

Programmiersprachen und Rechenkonzepte

Seit 1984 veranstaltet die GI--Fachgruppe 2.1.4 "Programmiersprachen und Rechenkonzepte", die aus den ehemaligen Fachgruppen 2.1.3 "Implementierung von Programmiersprachen" und 2.1.4 "Alternative Konzepte für Sprachen und Rechner" hervorgegangen ist, regelmäßi g im Frühjahr einen Workshop im Physikzentrum Bad Honnef. Das Treffen dient in erster Linie dem gegenseitigen Kennenlernen, dem Erfahrungsaustausch, der Diskussion und der Vertiefung gegenseitiger Kontakte

Increasing the Performance and Predictability of the Code Execution on an Embedded Java Platform

This thesis explores the execution of object-oriented code on an embedded Java platform. It presents established and derives new approaches for the implementation of high-level object-oriented functionality and commonly expected system services. The goal of the developed techniques is the provision of the architectural base for an efficient and predictable code execution. The research vehicle of this thesis is the Java-programmed SHAP platform. It consists of its platform tool chain and the highly-customizable SHAP bytecode processor. SHAP offers a fully operational embedded CLDC environment, in which the proposed techniques have been implemented, verified, and evaluated. Two strands are followed to achieve the goal of this thesis. First of all, the sequential execution of bytecode is optimized through a joint effort of an optimizing offline linker and an on-chip application loader. Additionally, SHAP pioneers a reference coloring mechanism, which enables a constant-time interface method dispatch that need not be backed a large sparse dispatch table. Secondly, this thesis explores the implementation of essential system services within designated concurrent hardware modules. This effort is necessary to decouple the computational progress of the user application from the interference induced by time-sharing software implementations of these services. The concrete contributions comprise a spill-free, on-chip stack; a predictable method cache; and a concurrent garbage collection. Each approached means is described and evaluated after the relevant state of the art has been reviewed. This review is not limited to preceding small embedded approaches but also includes techniques that have proven successful on larger-scale platforms. The other way around, the chances that these platforms may benefit from the techniques developed for SHAP are discussed

Modélisation par contraintes de programmes en bytecode Java pour la génération automatique de tests

Program verification is essential to maintain a certain level of quality and reliability. Testing is to date the most used software verification mean in industry. Constraint programming is seen as an effective way to automate test data generation. In this thesis we propose a constraint modeling of the Java bytecode semantics, and a method, based on this modeling, to automatically generate test data. Our constraint model of the semantics of a Java bytecode program allows effective deductions, including in the presence of complex data structures or inheritance. In particular, the use of type variables can take into account inheritance and polymorphic method calls. Our method of test data generation uses the constraint model to cover specific instructions of the program under test. It uses a backward progression in the control flow graph to enumerate paths leading to the target instructions. This method suits particularly to cover instructions that are not reached by other methods of test data generation. Finally this method is implemented in a prototype named JAUT (Java Automatic Unit Testing). The experiments show that the prototype can increase the statements coverage obtained with the other available tools.La vérification des programmes est indispensable pour maintenir un certain niveau de qualité et de fiabilité. Le test est à ce jour le moyen de vérification des logiciels le plus utilisé dans l¤industrie. La programmation par contraintes est vue comme un moyen efficace pour automatiser la génération de données de test. Dans cette thèse nous proposons une modélisation par contraintes de la sémantique du bytecode Java, ainsi qu¤une méthode, basée sur cette modélisation, pour générer automatiquement des données de test. Notre modèle à contraintes de la sémantique d¤un programme en bytecode Java permet de faire des déductions efficaces, y compris en présence de structures de données complexes ou d¤héritage. En particulier, l¤utilisation de variables de type permet de prendre en compte l¤héritage et les appels de méthodes polymorphes. Notre méthode de génération de données de test exploite le modèle à contraintes pour couvrir des instructions particulières du programme sous test. Elle se base sur un parcours en arrière du graphe de flot de contrôle pour énumérer des chemins menant aux instructions cibles. Elle est en particulier adaptée à la couverture d¤instructions non couvertes par les autres méthodes de génération de données de test. Enfin cette méthode est mise en application dans un prototype, JAUT (Java Automatic Unit Testing). Les expériences montrent que le prototype permet d¤augmenter la couverture des instructions obtenue avec les autres outils disponibles