Stack frame

Every function call will maintain a stack frame （stack frame）, Stack frame is mainly used to pass parameters 、 Save return address 、 Save local variables, etc . First go directly to the previous one 《 Deep understanding of computer systems 》 Original image on .

among ,%rsp Point to the top of the stack ,%rbp Point to the bottom of the stack . And the stack grows from high address to address .

The layout of local variables is determined by the compiler , It may be from a high address to a low address , It may also change from low address to high address .

Before the called function 6 Parameters will be passed in by registers , exceed 6 The part of will be passed through the stack . What needs to be noted here is , In order to get the address of the input parameter in the called function , The called function will be before 6 Parameters are pushed into the stack of the called function .

Function call procedure ：

1. Parameter stack . In a certain order, the parameters will exceed 6 Stack the parameters after .
2. Return the address to the stack . Push an instruction address of the current code onto the stack , Function returns to continue execution .
3. Jump into the address of the called function .
4. EBP Push , Save the current stack frame state value .
5. ESP Value is assigned to EBP.
6. Allocate the current stack frame .

Function return procedure ：

1. Save the return value of the called function to EAX In the register .
2. recovery ESP.
3. The calling function stack frame saved at the bottom of the called function EBP Value pop in EBP register , Recover the calling function stack frame .
4. Pop up the current stack top element , Get the return address from the stack .

Here is an example to verify the next stack frame layout ：

Enter the first main Functional func Function call point ：

%rbp The value is 0x7fffffffe110,%rsp The value of is 0x7fffffffe0f0. The address of the next instruction can be obtained from disassembly 0x4008f4. Based on this information, we can deduce main Functions and func The stack frame of the function is as follows ：

The above stack frame information can dgb Print verification during debugging ：

Reference resources ：

• Deep understanding of computer systems