Two implementations are given for Java's stackinspection access-control policy. Each implementation is obtained by generating an inlined reference monitor (IRM) for a different formulation of the policy. Performance of the implementations is evaluated, and one is found to be competitive with Java's less-flexible, JVM-resident implementation. The exercise illustrates the power of the IRM approach for enforcing security policies.

. This paper presents Soot, a framework for optimizing Java TM bytecode. The framework is implemented in Java and supports three intermediate representations for representing Java bytecode: Baf, a streamlined representation of Java's stack-based bytecode; Jimple, a typed three-address intermediate representation suitable for optimization; and Grimp, an aggregated version of Jimple. Our approach to class le optimization is to rst convert the stack-based bytecode into Jimple, a three-address form more amenable to traditional program optimization, and then convert the optimized Jimple back to bytecode. In order to demonstrate that our approach is feasible, we present experimental results showing the eects of processing class les through our framework. In particular, we study the techniques necessary to effectively translate Jimple back to bytecode, without losing performance. Finally, we demonstrate that class le optimization can be quite eective by showing the resul...

With the spread of the Internet the computing model on server systems is undergoing several important changes. Recent research ideas concerning dynamic operating system extensibility are finding their way into the commercial domain, resulting in designs of extensible databases and Web servers. In addition, both ordinary users and service providers must deal with untrusted downloadable executable code of unknown origin and intentions. Across the board, Java has emerged as the language of choice for Internet-oriented software. We argue that, in order to realize its full potential in applications dealing with untrusted code, Java needs a flexible resource accounting interface. The design and prototype implementation of such an interface --- JRes --- is presented in this paper. The interface allows to account for heap memory, CPU time, and network resources consumed by individual threads or groups of threads. JRes allows limits to be set on resources available to threads and it can invoke...

This paper presents Soot, a framework for optimizing Java bytecode. The framework is implemented in Java and supports three intermediate representations for representing Java bytecode: Baf, a streamlined representation of bytecode which is simple to manipulate; Jimple, a typed 3-address intermediate representation suitable for optimization; and Grimp, an aggregated version of Jimple suitable for decompilation. We describe the motivation for each representation, and the salient points in translating from one representation to another. In order to demonstrate the usefulness of the framework, we have implemented intraprocedural and whole program optimizations. To show that whole program bytecode optimization can give performance improvements, we provide experimental results for 12 large benchmarks, including 8 SPECjvm98 benchmarks running on JDK 1.2 for GNU/Linuxtm . These results show up to 8% improvement when the optimized bytecode is run using the interpreter and up to 21% when run...

Modern software must evolve in response to changing conditions. In the most widely used programming environments, code is static and cannot change at runtime. This poses problems for applications, that have limited down-time. More support is needed for dynamic evolution. In this paper we present an approach for supporting dynamic evolution of Java programs. In this approach, Java programs can evolve by changing their components, namely classes, during their execution. Changes in a class lead to changes in the its instances, thereby allowing evolution of both code and state. The approach promotes compatibility with existing Java applications, and maintains the security and type safety controls imposed by Java’s dynamic linking mechanism. Experimental analyses of our implementation indicate that the implementation imposes a moderate performance penalty relative to the unmodified virtual machine.

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When using Aspect Oriented Programming in the development of software components, a developer must understand the program units actually changed by weaving, how they behave, and possibly correct the aspects used. Support for rapid AOP prototyping and debugging is therefore crucial in such situations. Rapid prototyping is difficult with current aspect weaving tools because they do not support dynamic changes. This paper describes PROSE (PROgrammable extenSions of sErvices), a platform based on Java which addresses dynamic AOP. Aspects are expressed in the same source language as the application (Java), and PROSE allows aspects to be woven, unwoven, or replaced at run-time.

Several module and class testing techniques have been applied to object-oriented programs, but researchers have only recently begun developing test criteria that evaluate the use of key OO features such as inheritance, polymorphism, and encapsulation. Mutation testing is a powerful testing technique for generating software tests and evaluating the quality of software. However, the cost of mutation testing has traditionally been so high it cannot be applied without full automated tool support. This paper presents a method to reduce the execution cost of mutation testing for OO programs by using two key technologies, Mutant Schemata Generation (MSG) and bytecode translation. This method adapts the existing MSG method for mutants that change the program behavior and uses bytecode translation for mutants that change the program structure. A key advantage is in performance: only two compilations are required and both the compilation and execution time for each is greatly reduced. A mutation tool based on the MSG/bytecode translation method has been built and used to measure the speedup over the separate compilation approach. Experimental results show that the MSG/bytecode translation method is about five times faster than separate compilation.

The term “Java” is used to denote two different concepts: the language itself and the related execution environment, the Java Virtual Machine (JVM), which executes byte code instructions. Several research projects deal with byte code-generating compilers or the implementation of new features via byte code transformations. Examples are code optimization, the implementation of parameterized types for Java, or the adaptation of run-time behavior through load-time transformations. Many programmers are doing this by implementing their own specialized byte code manipulation tools, which are, however, restricted in the range of their reusability. Therefore, we have developed a general purpose framework for the static analysis and dynamic creation or transformation of byte code. In this paper we present its main features and possible application areas.

This paper describes the motivation, architecture and performance of a distributed virtual machine (DVM) for networked computers. DVMs rely on a distributed service architecture to meet the manageability, security and uniformity requirements of large, heterogeneous clusters of networked computers. In a DVM, system services, such as verification, security enforcement, compilation and optimization, are factored out of clients and located on powerful network servers. This partitioning of system functionality reduces resource requirements on network clients, improves site security through physical isolation and increases the manageability of a large and heterogeneous network without sacrificing performance. Our DVM implements the Java virtual machine, runs on x86 and DEC Alpha processors and supports existing Java-enabled clients.