Book Image

Mastering Assembly Programming

By : Alexey Lyashko
3 (1)
Book Image

Mastering Assembly Programming

3 (1)
By: Alexey Lyashko

Overview of this book

The Assembly language is the lowest level human readable programming language on any platform. Knowing the way things are on the Assembly level will help developers design their code in a much more elegant and efficient way. It may be produced by compiling source code from a high-level programming language (such as C/C++) but can also be written from scratch. Assembly code can be converted to machine code using an assembler. The first section of the book starts with setting up the development environment on Windows and Linux, mentioning most common toolchains. The reader is led through the basic structure of CPU and memory, and is presented the most important Assembly instructions through examples for both Windows and Linux, 32 and 64 bits. Then the reader would understand how high level languages are translated into Assembly and then compiled into object code. Finally we will cover patching existing code, either legacy code without sources or a running code in same or remote process.
Table of Contents (12 chapters)
Free Chapter
1
Intel Architecture

Arrays

By now, we have come a long way, dealing primarily with basic data types ranging from bytes to quad words, preparing ourselves for more complex data-related concepts. Let's continue by looking into arrays, which may be characterized as the sequential storage of data of the same type. Theoretically, there is no limitation to the size of array members, but practically we are limited to, for example, the size of a register. However, workarounds exist and we will see that later in this chapter.

Simple byte arrays

A good example of a widely used, yet simple, array would be a forward substitution table and/or a reverse substitution table used with the AES algorithm:

aes_sbox:
db 0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f...