When getsx is called by getbuf, the stack frames look like this:

                 +-------------+
           esp ->|             |
                 |             |
                 |             |   getsx's stack frame
                 |             |
           ebp ->|getbuf's ebp |
                 +-------------+
                 |ret addr     |
                 +-------------+
                 |   parameter |   passed to getsx 
                 +-------------+
                 |             |
                 |             |
                 |             |   getbuf's stack frame
                 | main's ebp  |
                 +-------------+
                 |ret addr     |
                 +-------------+
                 |             |
                 |             |
                 |             |   main's stack frame
                 |             |
                 |             |
                 +-------------+