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Index > Windows > Registers usage by Windows API

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barmentalisk



Joined: 06 Sep 2005
Posts: 36
barmentalisk
Is there any document with description which registers does each API use?
I'm interested in APIs in WinXP.
Or the one way to find it - is decompilation of each function ?
Post 01 Oct 2008, 11:49
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17715
Location: In your JS exploiting you and your system
revolution
All Windows APIs can/might/will use EAX, ECX and EDX at anytime. All other registers are preserved.
Post 01 Oct 2008, 11:56
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barmentalisk



Joined: 06 Sep 2005
Posts: 36
barmentalisk
Thank you. But that I already know.
I'd like to know if some API, for example, does not use EDX, how can I find it without decompillation of every API? Is anywhere such information?
Post 01 Oct 2008, 12:18
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17715
Location: In your JS exploiting you and your system
revolution
I've never seen any official documentation and I doubt I ever will. The OS is written in HLL and the compiler generally doesn't tell you what functions are not using particular registers.

But, be that as it may, what you propose is risky. Your code can break at any time with a new security patch or service patch or upgrade or whatever. And what you might gain, if anything, is of dubious value.
Post 01 Oct 2008, 12:24
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barmentalisk



Joined: 06 Sep 2005
Posts: 36
barmentalisk
Thank you very much. Now I've got the idea Wink
You are a real brother-in-asm =).
Post 01 Oct 2008, 13:09
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