Guide: Stack Operations

The stack_operations.asm file demonstrates various stack operations. The main focus is to show how to manipulate the stack by pushing and popping values, and how to “allocate” and “deallocate” memory on the stack.

Note: Notice how push and pop are just syntactic sugar for the simpler sub, add, and mov instructions.

For convenience, here’s the contents of the file. To play around with it, clone the repository locally.

%include "printf64.asm"

section .data
    var: dq ?

section .text

; rsp -> stack pointer
; rbp -> base pointer

extern printf
global main
main:
    push rbp
    mov rbp, rsp

    push qword 10  ;  same as:  sub rsp, 8   followed by:  mov [rsp], 10
    push qword 11  ;  same as:  sub rsp, 8   followed by:  mov [rsp], 11
    push qword 12  ;  same as:  sub rsp, 8   followed by:  mov [rsp], 12
    push qword 13  ;  same as:  sub rsp, 8   followed by:  mov [rsp], 13
    push qword 14  ;  same as:  sub rsp, 8   followed by:  mov [rsp], 13

    ; Version 1
    pop rax        ;  same as:  mov rax, [rsp]   followed by:  add rsp, 8
    pop rax        ;  same as:  mov rax, [rsp]   followed by:  add rsp, 8
    pop rax        ;  same as:  mov rax, [rsp]   followed by:  add rsp, 8
    pop rax        ;  same as:  mov rax, [rsp]   followed by:  add rsp, 8
    pop rax        ;  same as:  mov rax, [rsp]   followed by:  add rsp, 8

    ; Version 2
    ; add rsp, 40  ;  8 * number_of_push

    ; Version 3
    ; mov rsp, rbp

    ; sub rsp <-> add rsp -> use to allocate/deallocate memory

    ; Aloc 16 bytes <-> 2 long
    ; sub rsp, 16
    ; mov [rsp], 10
    ; mov [rsp + 8], 12

    ; Push/Pop from global variable

    mov qword [var], 1337

    push qword [var]
    pop qword [var]

    mov rax, [var]
    PRINTF64 `VAR: %d\n\x0`, rax


    leave
    ret