Re: Smashing the Stack?

[tide <tide () thunderchick com>]

That article is from 1996. About that time 16bit machines were state of
the art. Nowadays, we work on 32bit systems. Along with doubling the
bits, the alignment of variables in memory changed too. From 4Byte to
8...

At least that's what I'd think it is... Correct me if I'm wrong.
(last messed with c/asm a year ago :-) )


Am Mit, 2002-07-17 um 17.46 schrieb Jeremy Junginger:
> In "Smashing the Stack for Fun and Profit" by Aleph One, There is a nice
> example program called example1.c.  It looks like this:
>
> void function(int a, int b, int c) {
>       char buffer1[5];
>       char buffer2[10];
>
> void main() {
>       function(1,2,3);
> }
>
> Then, we go through how to generate assembley code output, how the
> values are pushed onto the stack in reverse order, then the function
> call, then moves the Frame Pointer onto the stack and copies the current
> Stack Pointer into EBP.  That part is groovy.  Then when we look at the
> function, in the example, he discusses how memory buffers are allocated
> in "word" (4 byte) increments.   That makes sense; however, when I
> generate the assembly code with the exact same code, I see that it is
> subtracting 40 rather than the expected 20
> (bufger1(5bytes=2words=8bytes+10bytes=3words=12bytes).  This part looks
> crucial to understanding the rest of the concepts in the paper, so I'm
> hesitant to continue without understanding this descrepancy.  Any input
> would be very much appreciated.