Execution replay of virtual machines is a technique which has many important applications, including debugging, fault-tolerance, and security. Execution replay for single processor virtual machines is well-understood, and available commercially. With the advancement of multi-core architectures, however, multiprocessor virtual machines are becoming more important. Our system, SMP-ReVirt, is the first system to log and replay a multiprocessor virtual machine on commodity hardware. We use hardware page protection to detect and accurately replay sharing between virtual cpus of a multi-cpu virtual machine, allowing us to replay the entire operating system and all applications. We have tested our system on a variety of workloads, and find that although sharing under SMP-ReVirt is expensive, for many workloads and applications, including debugging, the overhead is acceptable.

Many software attacks are based on injecting malicious code into a target host. This paper demonstrates the use of a well-known technique, data tainting, to track data received from the network as it propagates through a system and to prevent its execution. Unlike past approaches to taint tracking, which track tainted data by running the system completely in an emulator or simulator, resulting in considerable execution overhead, our work demonstrates the ability to dynamically switch a running system between virtualized and emulated execution. Using this technique, we are able to explore hardware support for taint-based protection that is deployable in real-world situations, as emulation is only used when tainted data is being processed by the CPU. By modifying the CPU, memory, and I/O devices to support taint tracking and protection, we guarantee that data received from the network may not be executed, even if it is written to, and later read from disk. We demonstrate near native speeds for workloads where little taint data is present.