flat assembler - Accessing BIOS - for real or just an emulation?

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StrenoJr

Joined: 13 Mar 2014
Posts: 22
Location: Slovakia

StrenoJr 09 Apr 2014, 20:11

Hi, I have a theoretical question.
When I try to access BIOS on Windows XP with this

Code:

org 0x0100 
use16

mov ah, 1
int 0x16

the program reacts only if it is focused (typing directly to the window).
This makes me think that I am not accessing the BIOS directly, only some layer of windows which passes the keystrokes to my window.
Is this really just an emulation? Could you send me some documents on this or say something more?
Is there any way to bypass Windows and control BIOS (probably a bad question)?
Thanks experts!

09 Apr 2014, 20:11

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20759
Location: In your JS exploiting you and your system

revolution 09 Apr 2014, 20:14

Look up NTVDM.

Protected OSes like XP won't give you real mode access. If it did then it wouldn't be a protected OS.

09 Apr 2014, 20:14

badc0de02

Joined: 25 Nov 2013
Posts: 214
Location: %x

badc0de02 09 Apr 2014, 21:51

so the real mode idt accesses only the bios functions there had windows set the idt for protected mode.
so in protected mode cant use windows the bios functions more.

idt=interrupt descriptor table

so ntvdm cant use the bios functions
and emulates a virtual bios.

ntvdm=Virtual DOS Machine

http://en.wikipedia.org/wiki/Virtual_DOS_machine

09 Apr 2014, 21:51

badc0de02

Joined: 25 Nov 2013
Posts: 214
Location: %x

badc0de02 09 Apr 2014, 22:21

if you want a way to access hardware somehow then write a driver for windows xp

09 Apr 2014, 22:21

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