Blue Fox

CHAPTER 1Introduction to Reverse Engineering

Introduction to Assembly

If you're reading this book, you've probably already heard about this thing called the Arm assembly language and know that understanding it is the key to analyzing binaries that run on Arm. But what is this language, and why does it exist? After all, programmers usually write code in high‐level languages such as C/C++, and hardly anyone programs in assembly directly. High‐level languages are, after all, far more convenient for programmers to program in.

Unfortunately, these high‐level languages are too complex for processors to interpret directly. Instead, programmers compile these high‐level programs down into the binary machine code that the processor can run.

This machine code is not quite the same as assembly language. If you were to look at it directly in a text editor, it would look unintelligible. Processors also don't run assembly language; they run only machine code. So, why is it so important in reverse engineering?

To understand the purpose of assembly, let's do a quick tour of the history of computing to see how we got to where we are and how everything connects.

Bits and Bytes

Back in the mists of time when it all started, people decided to create computers and have them perform simple tasks. Computers don't speak our human languages—they are just electronic devices after all—and so we needed a way to communicate with them electronically. At the lowest level, computers operate on electrical ...