Registers

[Lonewolff]

Hi Guys,

Which registers do not need to be preserved?

Thanks in advance 

[jj2007]

Eax, ecx, edx

[Lonewolff]

Cool! Thanks for that.

Why is it that the other registers require preservation? What happens with them to make them different?

[jj2007]

The Windows APIs rely on their values, that's all. Take the WndProc, for example: It gets called a Million times by Windows itself, and Windows uses esi edi ebx ebp for various purposes. So the message is "use them if you like, but on return I want my pointers to xyz exactly as they were on entry!".

[Lonewolff]

Awesome explanation  :t

[hutch--]

If you look in the help file "asmintro.chm" you will find a section in the file called "Register Preservation Convention" which explains in detail how the Intel Application Binary Interface works.