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Rice University Department of Computer Science presents Algis Rudys Master of Science Thesis Defense Termination and Rollback in Language-Based Systems Abstract Language run-time systems are routinely used to host potentially buggy or malicious codelets --- software modules, agents, applets, etc. --- in a secure environment. A number of techniques exist for managing access control to system services, but most language run-time systems have little or no support for managing system resources. For this thesis, we took a single aspect of the resource-management problem, that of code termination, and addressed it. We seek to solve not just the direct problem of how to terminate code, but also the related issue of restarting previously terminated code. Since portability is particularly important in language-based systems, where a single program is expected to run unmodified on different implementations of the run-time system, we base our designs on code-to-code transformations. Our goal is to provide a mechanism based on code-to-code transformations with semantics similar to those provided by operation systems for managing codelets in a run-time system. We wish to use two analysis techniques in developing these mechanisms. First, we desire a formal analysis and discussion of our mechanisms. We prove our termination system correct for an idealized language, and we discuss the ACID semantics of our transactional rollback system. Second, we implemented our systems in Java using bytecode rewriting to perform performance analyses. The results ranged from relatively modest (3 to 25% overhead for soft termination), to very heavy, although perhaps unavoidable (6 to 23X overhead for transactional rollback). Finally, we examined the technique of bytecode rewriting, and discuss some lessons we have learned that may apply to other systems developed with bytecode rewriting. Tuesday, October 22, 2002 at 3pm in Duncan Hall 3076 Copyright 2000 Rice University site problems: www@cs.rice.edu --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ---