Software experiments such as BLAST are hard to reproduce even if identical hardware is available because external data sets could have changed, software used in the original experiment may be unavailable, or the input parameters for the experiment may not be documented. This paper presents Rex, a toolset that allows one to record an experiment and archive its apparatus, replay an experiment, conduct new experiments on a recorded apparatus, and compare differences between experiments. The execution time overhead of recording experiments is on average about 2%; the space overhead of an archive ranges from 8 MB to 5 GB.

General-purpose operating systems, such as Linux, are increasingly being used in embedded systems. Computational resources are usually limited, and embedded processors often have a limited amount of memory. This makes code size especially important. This paper describes techniques for automatically reducing the memory footprint of general-purpose operating systems on embedded platforms. The problem is complicated by the fact that kernel code tends to be quite different from ordinary application code, including the presence of a significant amount of hand-written assembly code, multiple entry points, implicit control flow paths involving interrupt handlers, and frequent indirect control flow via function pointers. We use a novel "approximate decompilation" technique to apply source-level program analysis to hand-written assembly code. A prototype implementation of our ideas on an Intel x86 platform, applied to a Linux kernel that has been configured to exclude unnecessary code, obtains a code size reduction of close to 24%