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CHAPTER

This appendix discusses the most common logical and control flow constructs

used in high-level languages and demonstrates how they are implemented in

IA-32 assembly language. The idea is to provide a sort of dictionary for typical

assembly language sequences you are likely to run into while reversing IA-32

assembly language code.

This appendix starts off with a detailed explanation of how logic is imple-

mented in IA-32, including how operands are compared and the various con-

ditional codes used by the conditional branch instructions. This is followed by

a detailed examination of every popular control flow construct and how it is

implemented in assembly language, including loops and a variety of condi-

tional blocks. The next section discusses branchless logic, and demonstrates

the most common branchless logic sequences. Finally, I’ve included a brief dis-

cussion on the impact of working-set tuning on the reversing process for Win-

dows applications.

Understanding Low-Level Logic

The most basic element in software that distinguishes your average pocket cal-

culator from a full-blown computer is the ability to execute a sequence of log-

ical and conditional instructions. The following sections demonstrate the most

common types of low-level logical constructs frequently encountered while

Deciphering Code Structures

APPENDIX

A

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