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

Far pointers

It may be relatively safe to say that far pointers belong to the past when it comes to the application development level; however, it would not be right not to mention them here, as, after all, there are a few useful things we can do with it. Putting it simply, a far pointer combines a segment selector and an offset into the segment. Originating in the era of 16-bit modes of operation, surviving the 32-bit protected mode, far pointers have made it to the long mode, although they are hardly relevant, as, especially in long mode, all memory is considered to be a flat array and we are hardly going to use them.

The instructions used (some are obsolete) for loading a far pointer into the segment register: general-purpose register pairs are as follows:

  • LDS: This loads the selector part of the far pointer into the DS
  • LSS: This loads the selector part of the far pointer...