Improved Memory-Access Analysis for x86 Executables

Thomas Reps and Gogul Balakrishnan

Over the last seven years, we have developed static-analysis methods to recover a good approximation to the variables and dynamically allocated memory objects of a stripped executable, and to track the flow of values through them. It is relatively easy to track the effects of an instruction operand that refers to a global address (i.e., an access to a global variable) or that uses a stack-frame offset (i.e., an access to a local scalar variable via the frame pointer or stack pointer). In our work, our algorithms are able to provide useful information for close to 100% of such ``direct'' uses and defs.

It is much harder for a static-analysis algorithm to track the effects of an instruction operand that uses a non-stack-frame register. These ``indirect'' uses and defs correspond to accesses to an array or a dynamically allocated memory object. In one study, our approach recovered useful information for only 29% of indirect uses and 33% of indirect defs. However, using the technique described in this paper, the algorithm recovered useful information for 81% of indirect uses and 90% of indirect defs.

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