Assembly stack while calling subroutines

Question

So if I would have something like this

rout:
pop eax
pop ecx
add ecx,2
push ecx
ret

Then just

push 3
call rout

I've noticed that the first time to pop isn't going to give me the value 3 as I thought it would, instead I get it after the first pop.

My question is, what is the last value pushed to the stack while I'm calling it? (In register eax in this example)

gusbro · Accepted Answer · 2012-09-12 17:10:41Z

1

Assuming your are working with 80x86 architecture:

It's the return address of the proc (if its a near call). The next POP would give you your value (3) if it was a NEAR call, or the segment of the return address in case it was a FAR call.

Check this site for pseudocode of what actually happens when you issue a CALL.

answered Sep 12, 2012 at 17:10

gusbro

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