Here are some simple conceptions that I summarized:

              1, %rsp    -----  top of the stack

　　　　2, %rbp    -----  base address

              3, The stack of function is upside down

                   So when we push a value, %rsp sub

　　　   4, We push parameters before we call a function. So the values of parameters are above the %rbp(base address).

　　　　　　　　　　　　                                                    And the values of local variables are under the %rbp.

              5, We must save the former base address before calling a new function.Because maybe we are calling a function from another function. the Nested Functions.

　　       6, after saving the value of former base address, the new base address should be pointed to the %rsp(top of the stack).

How to use the function of assembly.