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POWhat is exactly the base pointer and stack pointer? To what do they point?
 

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  1. POWhat is exactly the base pointer and stack pointer? To what do they point?
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    <p>Using <a href="http://en.wikipedia.org/wiki/Call_stack" rel="noreferrer">this example</a> coming from wikipedia, in which DrawSquare() calls DrawLine(),</p> <p><img src="https://upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Call_stack_layout.svg/342px-Call_stack_layout.svg.png" alt="alt text"></p> <p>(Note that this diagram has high addresses at the bottom and low addresses at the top.)</p> <p>Could anyone explain me what <code>ebp</code> and <code>esp</code> are in this context?</p> <p>From what I see, I'd say the stack pointer points always to the top of the stack, and the base pointer to the beginning of the the current function? Or what?</p> <hr> <p>edit: I mean this in the context of windows programs</p> <p><strong>edit2: And how does <code>eip</code> work, too?</strong></p> <p><strong>edit3:</strong> I have the following code from MSVC++:</p> <pre><code>var_C= dword ptr -0Ch var_8= dword ptr -8 var_4= dword ptr -4 hInstance= dword ptr 8 hPrevInstance= dword ptr 0Ch lpCmdLine= dword ptr 10h nShowCmd= dword ptr 14h </code></pre> <p>All of them seem to be dwords, thus taking 4 bytes each. So I can see there is a gap from hInstance to var_4 of 4 bytes. What are they? I assume it is the return address, as can be seen in wikipedia's picture?</p> <hr> <p>(editor's note: removed a long quote from Michael's answer, which doesn't belong in the question, but a followup question was edited in):</p> <p>This is because the flow of the function call is:</p> <pre><code>* Push parameters (hInstance, etc.) * Call function, which pushes return address * Push ebp * Allocate space for locals </code></pre> <p><strong>My question (last, i hope!) now is, what is exactly what happens from the instant I pop the arguments of the function i want to call up to the end of the prolog? I want to know how the ebp, esp evolve during those moments(I already understood how the prolog works, I just want to know what is happening after i pushed the arguments on the stack and before the prolog).</strong></p>
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    1. COOne important thing to note is that the stack grows "downwards" in memory. This means that to move the stack pointer upward you decrease its value.
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    2. COOne hint to differentiate what EBP/ESP and EIP are doing: EBP & ESP deal with data, while EIP deals with code.
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    3. COYou mean that if I called a new function named for example DrawPixel(), appearing on the top of the current stack, ESP would decrease, is that it? And after the function returned it would increase again(so the picture would look just like it is right now)?
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