question about data directives

flat assembler
Message board for the users of flat assembler.

Index > OS Construction > question about data directives

Author

Thread

jatos

Joined: 04 Nov 2006
Posts: 20

jatos 23 Apr 2008, 18:26

I just wondering with data directives, are there any trick I could use to put a data directive that is say bits 16-31 of a memory reference, for things like descriptors in the GDT and IDT

so say I had the label

int_1:

is there anyway I could put something after a dw directive that referenced bits 16-31 of memory location of int_1: label.

_________________
Jamie

23 Apr 2008, 18:26

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20333
Location: In your JS exploiting you and your system

revolution 23 Apr 2008, 18:52

Code:

int1:
...
dw int1 shr 16

But you need to state your file format, this won't work with some formats due to relocations etc.

Is that that what you are asking?

23 Apr 2008, 18:52

edfed

Joined: 20 Feb 2006
Posts: 4332
Location: Now

edfed 23 Apr 2008, 19:26

Code:

easy:
dd int_1
...
mov eax,[easy]
shr eax,16

23 Apr 2008, 19:26

rugxulo

Joined: 09 Aug 2005
Posts: 2341
Location: Usono (aka, USA)

rugxulo 23 Apr 2008, 19:37

Code:

easy:
dd int_1
...
mov ax,[easy+2]

23 Apr 2008, 19:37

jatos

Joined: 04 Nov 2006
Posts: 20

jatos 23 Apr 2008, 19:51

I will keeping this for flat binary files, currently with the org of 0x1600 (where a boot loads the binary file from)

For my text trick, the same for bits 0-15, should be easy enough.

23 Apr 2008, 19:51

< Last Thread | Next Thread >

Forum Rules:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum