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hyperzap



Joined: 22 Apr 2011
Posts: 4
hyperzap
Hi all,

I am writing small binary stub functions (which need to be runnable from any position in memory) which reference only themselves and the stack(offsets from EBP). I was wondering if there is a way to force FASM to output code that uses purely relative addresses for all jmp (and similar) operations? Is this the default behaviour?

Thanks,

Hyperzap
Post 15 May 2012, 12:40
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17281
Location: In your JS exploiting you and your system
revolution
Immediate near jumps and calls are always relative. This is part of the x86 design.
Post 15 May 2012, 13:09
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Madis731



Joined: 25 Sep 2003
Posts: 2141
Location: Estonia
Madis731
I think one can craft a FASM macro which catches the longer jumps and calls and emits an warning/error. Then there is no need to force FASM to do anything. It just tells you the places where to look for too long jumps and you can rearrange your code.
Post 16 May 2012, 09:50
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