Ben Breech

Electron and proton heating by solar wind turbulence

[1] Previous formulations of heating and transport associated with strong magnetohydrodynamic (MHD) turbulence are generalized to incorporate separate internal energy equations for electrons and protons. Electron heat conduction is included. Energy is supplied by turbulent heating that affects both electrons and protons and is exchanged between them via collisions. Comparison to available Ulysses data shows that a reasonable accounting for the data is provided when (1) the energy exchange timescale is very long and (2) the deposition of heat due to turbulence is divided, with 60% going to proton heating and 40% into electron heating. Heat conduction, determined here by an empirical fit, plays a major role in describing the electron data.

Online impact analysis via dynamic compilation technology

Dynamic impact analysis based on whole path profiling of method calls and returns has been shown to provide more useful predictions of software change impacts than method-level static slicing and to avoid the overhead of expensive dependency analysis needed for dynamic slicing-based impact analysis. This work presents the design, implementation, and evaluation of an online approach to dynamic impact analysis as an extension to the DynamoRIO binary code modification system and to the Jikes Research Virtual Machine. Storage and postmortem analysis of program traces, even compressed, are avoided.

Kinetic driven turbulence: Structure in space and time

The structure in space and time of a driven turbulent magnetoplasma is analyzed using kinetic simulations. For a two dimensional case with a strong uniform out-of-plane magnetic field, large scale driving produces a turbulent state that spans fluid scales to kinetic proton scales. There are fluid electrons in this hybrid representation. In near steady conditions, spectral analysis shows an almost complete absence of discrete point spectral features that would be associated with a dispersion relation and wave activity. While there is indication of a low level of wave activity, the results show that the dynamics are dominated by nonlinear activity. Implications for understanding plasma cascade, dissipation, and heating are discussed.

A comparison of online and dynamic impact analysis algorithms

Impact analysis is the process of determining the effect, or impact, of a change to a software system. Dynamic impact analysis uses data obtained from executing a program to perform analysis after program termination for determining impacts more in line with how a program is used. Online impact analysis has the same goal, but is performed concurrently with program execution. While some of the tradeoffs between dynamic algorithms have been studied, no such study has been performed for online algorithms. In this paper, we present such a study by comparing two online algorithms and two previously published dynamic algorithms in terms of their space overhead, time for computation, computed impact sets, and scalability. Our results indicate that performing impact analysis online can be more scalable than the dynamic counterparts.

Integrating Influence Mechanisms into Impact Analysis for Increased Precision

Software change impact analysis is the process of determining the potential effects, or impacts, of a change to a program. Strategies for impact analysis vary in their approach toward the opposing goals of high precision and low analysis time. Fine-grained techniques, such as slicing, can be used to gain very precise knowledge of a changes impact, but may be prohibitively expensive. Coarse-grained techniques such as method-level impact analyses sacrifice precision for faster analysis. In this paper, we present static and dynamic method-level impact analysis algorithms that utilize value propagation information from the source code to increase precision and keep analysis times low. We experimentally compare the results of our analyses with common static and dynamic impact analysis techniques. Our results show that the precision of the common method-level analyses can be improved with very little added overhead

Region Formation Analysis with Demand-Driven Inlining for Region-Based Optimization

Region-based compilation repartitions a program into more desirable compilation units for optimization and scheduling, particularly beneficial for ILP architectures. With region-based compilation, the compiler can control problem size and complexity by controlling region size and contents, expose interprocedural scheduling and optimisation opportunities without interprocedural analysis or large function bodies, and create compilation units for program analysis that more accurately reflect the dynamic behavior of the program. This paper presents a region formation algorithm that eliminates the high compile-time memory costs due to an aggressive inlining prepass. Individual subregions are inlined in a demand-driven way during interprocedural region formation. Our experimental results on a subset of the SPEC benchmarks demonstrate a significant reduction in compile-time memory requirements with comparable runtime performance.

A framework for testing security mechanisms for program-based attacks

Program vulnerabilities leave organizations open to malicious attacks that can result in severe damage to company finances, resources, consumer privacy, and data. Engineering applications and systems so that vulnerabilities do not exist would be the best solution, but this strategy may be impractical due to fiscal constraints or inadequate knowledge. Therefore, a variety of program and system-based solutions have been proposed to deal with vulnerabilities in a manageable way. Unfortunately, proposed strategies are often poorly tested, because current testing techniques focus on the common case whereas vulnerabilities are often exploited by uncommon inputs.In this paper, we present the design of a testing framework that enables the efficient, automatic and systematic testing of security mechanisms designed to prevent program-based attacks. The key insight of the framework is that dynamic compilation technology allows us to insert and simulate attacks during program execution. Thus, a security mechanism can be tested using any program, not only those with known vulnerabilities.

An Attack Simulator for Systematically Testing Program-based Security Mechanisms

The use of insecure programming practices has led to a large number of vulnerable programs that can be exploited for malicious purposes. These vulnerabilities are often difficult to find during traditional software testing. In response to these difficulties, various program-based security mechanisms have been proposed to help protect potentially vulnerable programs. Testing these security mechanisms, however, also can be difficult and is currently rather ad hoc. In this paper, we describe the design, implementation, and evaluation of an attack simulator that enables the systematic and semi-automatic testing and evaluation of the effectiveness of current and future security mechanisms by automatically providing numerous contexts for testing the reliability of the mechanisms. Capable of automatically creating attacks on running programs by dynamically adding code (but not modifying existing code), the attack simulator can run in different modes and simulate attacks at various program points systematically. Through a case study, we demonstrate how our tool can be used to test two well-known security mechanisms for stack smashing attacks in several different testing modes

Heating of the solar wind with electron and proton effects

We examine the effects of including effects of both protons and electrons on the heating of the fast solar wind through two different approaches. In the first approach, we incorporate the electron temperature in an MHD turbulence transport model for the solar wind. In the second approach, we adopt more empirically based methods by analyzing the measured proton and electron temperatures to calculate the heat deposition rates. Overall, we conclude that incorporating separate proton and electron temperatures and heat conduction effects provides an improved and more complete model of the heating of the solar wind.

RUGRAT: Runtime Test Case Generation Using Dynamic Compilers

The testing of error handling and dynamic security mechanisms often depends on reproducing specific conditions outside the realm of an applications normal program state. We present RUGRAT, a novel technique to automatically generate tests for these challenging test situations. RUGRAT uses a dynamic compiler to add instructions to the program during execution, and thus dynamically generates tests to exercise code designed to handle uncommon situations during program execution. The RUGRAT testing approach is independent of the source language, requires no modification to the source orbinary program under test and generates runtime tests automatically based on a simple test specification. We demonstrate RUGRATs capabilities by targeting two particular uncommon situations: handling errors from system and application calls, and testing security mechanisms that protect a program against attacks on function pointers. Both code coverage and failure detection results indicate that RUGRAT is a cost effective approach that reduces the number of required test inputs and need for vulnerable programs.