Static Analysis of Code Binaries for Safe Software Reuse

In this paper we consider reusability of software component binaries. Reuse of code at the binary level is important because usually only the machine code for system components is available; vendors do not want to share their source code for proprietary reasons. We develop necessary and sufficient conditions for ensuring that software binaries are reusable and relate them to the coding standards that have been developed in the industry to ensure binary code reusability. These coding standards, in essence, discourage the (i) use of hard-coded pointers, and (ii) writing of nonreentrant code. Checking that binary code satisfies these standards/conditions, however, is undecidable, in general. We thus develop static analysis based methods for checking if a software binary satisfies these conditions. This static analysis rests on the abstract interpretation framework. We illustrate our approach by showing how we statically analyze the presence of hard coded pointer variables in assembly code obtained from binaries of digital signal processing applications. The analyzer we have developed takes the binary to be checked for reuse as input, disassembles it, builds the flow graph, and statically analyzes the flow graph to check for the presence of code that will hinder its reuse. The construction of this analyzer is described and its performance results reported.