back trace issue

["nagaraju.m" <nagaraju dot m at redpinesignals dot com>]

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