this paper is structured in the following way: a thorough description of the structure of a decompiler, followed by the description of our implementation of an # An idiom is a sequence of instruction that forms a logical entity and has a meaning that cannot be derived by considering the primary meanings of the individual instructions # # # # HLL program (language dependent) Back-end (analysis) UDM (machine dependent) Front-end binary program Figure 1. Decompiler modules automatic decompiling system, and conclusions. The paper is followed by the definitions of graph theoretical concepts used throughout the paper (Appendix I), and sample output from different phases of the decompilation of a program (Appendix II)

Reverse engineering of software systems has traditionally centered upon the generation of high-level abstractions or specifications from high-level code or databases. In this paper we report on a reverse engineering environment for low-level executable code: a reverse compilation or decompilation environment that aids in the understanding of the underlying executable program. The reverse compilation process recovers high-level code from executable programs at a higher representation level than that produced by disassemblers; in fact, disassembly is part of the first stage in this process. Several tools aid in the process of reverse compilation, these are: loaders, signature generators, library prototype generators, disassemblers, library bindings, and language to language translators. The integration of these tools in the whole process is presented in this paper. The results obtained by the prototype reverse compilation system dcc are encouraging: high-level code is regenerated with c...