Category: Assembly Tutorials

Teaching Assembly with RAVM

Posted by endeavormac – June 29, 2011

This post is not a class on assembly. It is about a tool I use and hope others will find useful. An understanding of x86 assembly will help.

What is the RAVM, and why create it?

Learning how programs work at the assembly level is crucial towards gaining a holistic understanding of modern day computing. While studying Computer Science at the United States Military Academy, I was introduced to a fantastic piece of in-house developed software: the MARC and MARASM (available publicly here). The MARC is a virtual 16-bit CPU programmed in ADA. When paired with the MARASM, an assembler for the MARC, cadets can write, assemble, and run assembly programs with a simplistic toolchain.

The MARC is a perfect example of using simple applications geared towards education to teach concepts, not features. Students trying to learn new concepts need tools that just work. I wanted to borrow the concepts of the MARC and create a piece of software which could be used as a stepping stone towards x86 assembly. More specifically, I wanted:

  • A more comprehensive, but not complicated, instruction set which more closely mimicked an x86 instruction set.
  • 32-bit, little endian words.
  • A way to help students visualize what was happening in memory while their programs were running.
  • A code base programmed in C, making it more accessible for expansion and hacking by others.

With these goals in mind, I created the RAVM, the Rainbowsandpwnies Assembler and Virtual Machine. The RAVM comes with three parts: assembler, disassembler, and virtual machine. Here’s how you can grab a copy of the RAVM in Ubuntu:

sudo apt-get install git build-essential libncurses5-dev
git clone git://github.com/endeav0r/ravm.git
cd ravm
make

More→

x86 Assembly for C Programmers 1.1, Reddit Follow-up

Posted by endeavormac – October 24, 2009

I posted x86 Assembly for C Programmers 1 to reddit and got some great feedback. There were a few things that were brought up, and I’m taking a minute to address some of them (I’m not addressing everything).  Thanks to everyone out there who took the time to point out mistakes and make suggestions. More→

x86 Assembly for C Programmers 1

Posted by endeavormac – October 13, 2009

Introduction

I’m writing a series of tutorials on x86 assembly for C programmers who are already familiar with many of the basics of programming and computing. The assembly tutorials available online just aren’t doing it for me, and I need something organized the way I think, on the topics I’m interested in, presented in a way which make comprehensive understanding easy. I’ll do the work, go find the answers, and then drop everything here for you to enjoy.

Please note I do not claim to be an expert on the assembly language.

My interest in assembly is for both optimizing C applications, and the purpose of developing exploits for vulnerabilities in common applications, not write applications in assembly from scratch. I’m not interested in, “Good,” examples of assembly, I’m interested in real examples. This will affect the assembly we look at. More specifically, I write the code in C, compile it with gcc, and what comes out is what we’ll be dissecting.

For the purposes of these tutorials, 32-bit x86 assembly. Everything compiled/built/disassembled on the latest stable distro of Ubuntu. More→