Solved

How to interpret opcode documentation

Posted on 2009-05-03
1
714 Views
Last Modified: 2013-12-13
Hi!
I'm trying to write some code using the opcode I found in the x86 processor opcode documentation I found on Intels homepage (link: http://developer.intel.com/design/PentiumII/manuals/243191.htm) and the opcode reference found in the masm32 install package. I have succesfuly made some simple stuff like this: B801000000C3H which stores 01H in eax and then returns.

However I don't understand how to read most of the documentation for the different opcodes. For example I would like to implement the CALLF instruktion.

The documentation in masm32 says:
9A cp CALL ptr16:32 Call far, absolute, address given in operand

So I thought that to call a function at address 00C40000H would be
9A0000C400H however that crashes.

Anyone know how it should be?

Thanks.
0
Comment
Question by:monoceres
1 Comment
 

Accepted Solution

by:
monoceres earned 0 total points
ID: 24291676
I guess this one can be closed early. I found info on this site:
http://coding.derkeiler.com/Archive/Assembler/comp.lang.asm.x86/2006-11/msg00207.html
That said that the 9A instruction couldn't be used, so the E8 instruction should be used instead.
So I calculated the difference between my function pointer and the next byte to be executed and voíla.
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

This is an explanation of a simple data model to help parse a JSON feed
Since upgrading to Office 2013 or higher installing the Smart Indenter addin will fail. This article will explain how to install it so it will work regardless of the Office version installed.
In this fourth video of the Xpdf series, we discuss and demonstrate the PDFinfo utility, which retrieves the contents of a PDF's Info Dictionary, as well as some other information, including the page count. We show how to isolate the page count in a…
In this seventh video of the Xpdf series, we discuss and demonstrate the PDFfonts utility, which lists all the fonts used in a PDF file. It does this via a command line interface, making it suitable for use in programs, scripts, batch files — any pl…

863 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

27 Experts available now in Live!

Get 1:1 Help Now