Assembly Integration (Unsigned Integer Multiplication)

Hi, can you help with a C programming assignment?
So a small part of the course covers writing/compiling assembler code as well, & I'm having some trouble figuring it out:

Basically it deals with unsigned integer multiplication (specifically in dealing with 32-bit int overflow), using two files: big_mult.c, and mull.s.
So far, I have written the big_mult.c, which contains two methods: int main, & void mull (mull.s).

Code:

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#include <stdio.h>
void mull(unsigned int x, unsigned int y, unsigned int* low, unsigned int* high);

int main(char *argv[]) {
  unsigned x, y;
  unsigned low = high = 0;
  sscanf(argv[1],"%x",&x);
  sscanf(argv[2],"%x",&y);
  mull(x,y,&low,&high);
  return 0;
}

---

Now mull.s function is to be written manually, and will be linked to the final program after compile: $ gcc -Wall -std=c99 -o big_mult.exe big_mult.c mull.s
This is the part I am lost at...
All I really know is that it starts out something like this:

Code:

---

_mull:
  pushl %ebp                | save stack pointer
  movl %esp, %ebp        | new stack pointer
  movl 8(%ebp), %eax        | get x
  movl 12(%ebp), %edx        | get y
  movl 16(%ebp), (%?)        | get *low
  movl 20(%ebp), (%?)        | get *high
  ...
  ...
  pop %ebp
  ret

---

Here is the sample output:

Code:

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$ ./big_mult 2f432f43 629b03cb
2f432f43 x 629b03cb = 12345678 87654321

---

* Using Cygwin Bash Shell


Can you please help?
Thank you! Thank you!