Functions and stack frame, C/C++ Programming

Each function has its own stack frame between %fp and %sp. Let Caller calls Callee. Then Caller's %sp becomes callee's %fp, and callee's %sp set to be a new value (a smaller one because stack grows from large address to small address). You can think that Callee's stack frame is on top of Caller's stack frame.

In Caller: put arguments in %o0 to %o5 registers or if number of arguments more than 6, prepare values in call linkage of the current stack frame. Then "call" address_of_callee; %o7 stored the returned address. (This %o7 will becomes %i7 in callee after the callee executes save instruction.)

In Callee: it executes "save" instruction:

  • 0. Caller's %i (input registers) and %l (local registers) are reserved in its own stack frame. They are put in the top portion of the caller's stack frame. Implication: the return address of Caller (NOT CALLEE), %i7, is stored there.
  • 1. set callee's %i (input registers) by callers %o (output registers). The implication: pass parameters and return address now is in %i7. And now callee's fp (%i6) <-- caller's sp (%o6).
  • 2. Allocate space for new frame pointers. Caller's sp (%o6) is now set to be the new value.

So at this point in callee, %i6 (%fp was caller's %o6) is set, and %o6 (%sp is set to be a new value). Question: where is the old %fp? It is stored somewhere in the top portion of the previous stack frame (see step 0.) The return address of Callee is stored in %i7. Is it possible to write a program to overflow this %i7? What return address that you really can overflow? Question: how to access that return address.

The "restore" instruction is the inverse function of save. Then the "ret" instruction should branch to %i7+8. The normal address should be %i7+4 as the next instruction address after call. The extra 4 is because sparc has a "branch delay" instruction that is executed BEFORE the call is made even it is put just after CALL. Is it strange. Not really. This is because modern CPU is a pipeline machine. It loads instruction every clock cycle, and branch (or jump or call) somewhat cannot be really done until the later stage the pipeline. And then it is already too late because the one JUST after this branch has already been executed. If you want to know more, you should take a look at computer architecture textbook which I think every graduate should know.

You should be very clear what return address in server.c is overflowed? Is it the return address of main() or the return address of copy()?

Posted Date: 2/19/2013 1:02:55 AM | Location : United States







Related Discussions:- Functions and stack frame, Assignment Help, Ask Question on Functions and stack frame, Get Answer, Expert's Help, Functions and stack frame Discussions

Write discussion on Functions and stack frame
Your posts are moderated
Related Questions
how would land elevation have changed if Coronado had traveled 150 miles due west from what is today Arizona instead of east toward New Mexico

Spider webs have two types of silk, sticky silk and strength silk, spiders do not move on the sticky silken threads only on the strength threads. Assume one type of spider creates

Consider the following algorithm to generate a sequence of numbers. Start with an integer n. If n is even, divide by 2. If n is odd, multiply by 3 and add 1. Repeat this process wi

A: BinarySearchTree.h ---------------------- #ifndef BINARY_SEARCH_TREE_H_ #define BINARY_SEARCH_TREE_H_ #include "dsexceptions.h" #include // For NULL // Binary

Should I explicitly call a destructor on a local variable? Explain it.

program for compiler design in c

THIS PROGRAM IS TO COMPARE THE TWO DATES GIVEN BY THE USER #include #include #include struct date  {   int dd;   int mm;   int yy;  }; date compare(date d1,date d2)  {

Smugglers are becoming very smart day by day. Now they have developed a new technique of sending their messages from one smuggler to another. In their new technology, they are send

A palindrome is a string that reads the same from both the ends. Given a string S convert it to a palindrome by doing character replacement. Your task is to convert S to palindrome

Raj is a newbie to the programming and while learning the programming language he came to know the following rules: · Each program must start with ''{'' and end with ''}''