back trace issue

[nagaraju.m]

Hi,
    I am new to gdb. I am using  ported gdb to a specific target.
    when i am using back trace it is giving only the top most frame.

example:
    int add(int x,int y)
{
 int z;
 z=min(x,y);
 return z;
 }
int min(int p,int q)
{
 int r;
 r=max(p,q);
 return r;
 }
int max(int d,int e)
{
 return (d+e);
 }


int main()
{
int a, b, c,i;
a = 10;
b =20;
for(i=0;i<10;i++)
c = add(a,b);
return 0;
}

suppose if the control is in max function
(gdb) bt
#0  max (d=10, e=20) at abc.c:15
#1  0x20010348 in ?? ()

can you please  suggest me where to provide the information  to gdb so 
that "back trace" works properly.....

Thanks in advance,
Nagaraju