In practice, few security bugs found in source code are urgent, but quickly identifying which ones are is hard.We describe the application of bounded model checking to triaging reported issues quickly at the cloud service provider Amazon Web Services (AWS).We focus on the job of reactive security experts who need to determine the severity of bugs found in the Xen hypervisor.We show that, using our publicly available extensions to the model checker CBMC, a security expert can obtain traces to construct security tests and estimate the severity of the reported finding within 15 minutes.We believe that the changes made to the model checker, as well as the methodology for using tools in this scenario, will generalise to other organisations and environments.

AMD's Advanced Synchronization Facility (ASF) is an x86 instruction set extension proposal intended to simplify and speed up the synchronization of concurrent programs. In this paper, we report our experiences using ASF for implementing transactional memory. We have extended a C/C++ compiler to support language-level transactions and generate code that takes advantage of ASF. We use a software fallback mechanism for transactions that cannot be committed within ASF (e.g., because of hardware capacity limitations). Our evaluation uses a cycle-accurate x86 simulator that we have extended with ASF support. Building a complete ASF-based software stack allows us to evaluate the performance gains that a user-level program can obtain from ASF. Our measurements on a wide range of benchmarks indicate that the overheads traditionally associated with software transactional memories can be significantly reduced with the help of ASF.

Advanced Synchronization Facility (ASF) is an AMD64 hardware extension for lock-free data structures and transactional memory. It provides a speculative region that atomically executes speculative accesses in the region. Five new instructions are added to demarcate the region, use speculative accesses selectively, and control the speculative hardware context. Programmers can use speculative regions to build flexible multi-word atomic primitives with no additional software support by relying on the minimum guarantee of available ASF hardware resources for lock-free programming. Transactional programs with high-level TM language constructs can either be compiled directly to the ASF code or be linked to software TM systems that use ASF to accelerate transactional execution. In this paper we develop an out-of-order hardware design to implement ASF on a future AMD processor and evaluate it with an in-house simulator. The experimental results show that the combined use of the L1 cache and the LS unit is very helpful for the performance robustness of ASF-based lock free data structures, and that the selective use of speculative accesses enables transactional programs to scale with limited ASF hardware resources.

In this paper, we present a method to predict per-frame decoding times of modern video decoder algorithms. By examining especially the MPEG-1, MPEG-2, and MPEG-4 pt. 2 algorithms, we developed a generic model for these decoders, which also applies to a wide range of other decoders. From this model, we derived a method to predict decoding times with an up-to-now unmatched accuracy while keeping the overhead low. We show the effectiveness of this method with an example implementation and compare the resulting predictions with the actual decoding times using video material from commercial DVDs

Component-based applications require runtime support to be able to guarantee non-functional properties. This paper proposes an architecture for a real-time-capable, component-based runtime environment, which allows to separate non-functional and functional concerns in component-based software development. The architecture is presented with particular focus on the real-time-non-real-time split of the runtime environment and the communication issues of respective component types and container parts.

Scheduling disk requests with service guarantees has to bring the demand to meet guarantees in line with the need to optimize disk utilization. This paper presents the design, implementation, and experimental evaluation of a disk-scheduling framework which optimizes the disk utilization under the constraints of both hard and statistical service guarantees. The framework is based on two principles: 1) upon each scheduling decision, the calculation of a subset of the outstanding disk requests such that all service guarantees can be enforced under worst-case assumptions; and 2) the scheduling of this subset based on the rotational position of requests in order to improve the disk utilization. Results are presented through an implementation of the scheduling framework in DROPS, the Dresden real-time operating system.