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

Structures

As a developer, I believe you would agree that most of the time we are not working with arrays of uniform data (I am definitely not underestimating the power of a regular array). Since data may be anything, starting with 8-bit numbers and ending with complex structures, we need a way to describe such data for the assembler, and the term structure is the key. Flat Assembler, just as any other assembler, lets us declare structures and treat them as additional types of data (similar to the typedef struct in C).

Let's declare a simple structure, an entry of a string table, and then see what is what:

struc strtabentry [s]
{
.length dw .pad - .string ; Length of the string
.string db s, 0 ; Bytes of the string
.pad rb 30 - (.pad - .string) ; Padding to fill 30 bytes
.size = $ - .length ; Size of the structure (valid...