Section: Software

Binary files decompiler

Our research on efficient memory profiling has lead us to develop a sophisticated decompiler. This tool analyzes x86-64 binary programs and libraries, and extracts various structured representations of the code. It works on a routine per routine basis, and first builds a loop hierarchy to characterize the overall structure of the algorithm. It then puts the code into Static Single Assignment (SSA) form to highlight the fine-grain data-flow between registers and memory. Building on these, it performs the following analyzes:

• All memory addresses are expressed as symbolic expressions involving specific versions of register contents, as well as loop counters. Loop counter definitions are recovered by resolving linearly incremented registers and memory cells, i.e., registers that act as induction variables.

• Most conditional branches are also expressed symbolically (with registers, memory contents, and loop counters). This captures the control-flow of the program, but also helps in defining what amounts to loop “trip-counts”, even though our model is slightly more general, because it can represent any kind of iterative structure.

This tool embodies several passes that, as far as we know, do not exist in any existing similar tool. For instance, it is able to track data-flow through stack slots in most cases. It has been specially designed to extract a representation that can be useful in looking for parallel (or parallelizable) loops  [48] . It is the basis of several of our studies.

Because binary program decompilation is especially useful to reduce the cost of memory profiling, our current implementation is based on the Pin binary instrumenter. It uses Pin's API to analyze binary code, and directly interfaces with the upper layers we have developed (e.g., program skeletonization, or minimal profiling). However, we have been careful to clearly decouple the various layers, and to not use any specific mechanism in designing the binary analysis component. Therefore, we believe that it could be ported with minimal effort, by using a binary file format extractor and a suitable binary code parser. It is also designed to abstract away the detailed instruction set, and should be easy to port (even though we have no practical experience in doing so).

We feel that such a tool could be useful to other researchers, because it makes binary code available under abstractions that have been traditionally available for source code only. If sufficient interest emerges, e.g., from the embedded systems community, or from researchers working on WCET, or from teams working on software security, we are willing to distribute and/or to help make it available under other environments.