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

The issue

Whether we try to run our executables on Windows or on Linux, we would hardly notice any problem, as the program asks for our name and then prints it back. This will keep working in a stable manner as long as the program does not encounter a name longer than 127 ASCII characters (the 128th character is the terminating NULL value) and such names exist. Let's try to run this executable (we are referring to the one built for Windows, but the same idea applies to the Linux executable too) and feed it with a long line of text, much longer than 127 characters. This is what will happen:

The reason for this message is the gets() function. If C is not your language of choice, you may be unaware of the fact that this function does not check the length of the input, which may lead to stack corruption in the best case (just like what caused the preceding message to appear...