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copied!<p>I don't have all answers but I can explain what I know.</p> <p><code>ebp</code> is used by the function to store the initial state of <code>esp</code> during its flow, a reference to where are the arguments passed to the function and where are its own local variables. The first thing a function does is to save the status of the given <code>ebp</code> doing <code>pushl %ebp</code>, it is vital to the function that make the call, and than replaces it by its own current stack position <code>esp</code> doing <code>movl %esp, %ebp</code>. Zeroing the last 4 bits of <code>ebp</code> at this point is GCC specific, I don't know why this compiler does that. It would work without doing it. Now finally we go into business, <code>call ___main</code>, who is __main? I don't know either... maybe more GCC specific procedures, and finally the only thing your main() does, set return value as 0 with <code>movl $0, %eax</code> and <code>leave</code> which is the same as doing <code>movl %ebp, %esp; popl %ebp</code> to restore <code>ebp</code> state, then <code>ret</code> to finish. <code>ret</code> pops <code>eip</code> and continue thread flow from that point, wherever it is (as its the main(), this ret probably leads to some kernel procedure which handles the end of the program).</p> <p>Most of it is all about managing the stack. I wrote a detailed tutorial about how stack is used some time ago, it would be useful to explain why all those things are made. But its in portuguese...</p>

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