Question

To start off, I need to write a assembly (Intel IA-32) function that returns the contents of the caller’s frame pointer. I don’t think I’m doing it correctly, but what I came up with was

pushl %ebp
movl %esp, %ebp
movl %eax, 4(ebp)
leave
ret

However, I’m supposed to use that in a c function to count the number of frames on the stack, and I’m really not sure at all how that is supposed to work. Am I supposed to jump to the value in the old ebp, and then call the function again? Any guidance would be greatly appreciated.

Answer 1

No, you are not required to jump anywhere, but once you have copied the frame pointer to a local variable, you can treat it as a linked list.

 int mymagicfunction(int a, int b){

     int *c = asm_copy_ebp();
     int *d = c;
     while ( it_makes_sense ) {
           c=*c;
           dump_memory_between(c,d);
           d=c;
     }

Perhaps it makes sense only when the distance between c and d is small.