X86-assembly/Instructions/push

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X86-assembly

Instructions

push[a|ad]

Description

• The push instruction is used to push values on the stack.
• The pusha instruction is used to push the 16-bit registers in the following order: AX, CX, DX, BX, SP, BP, SI, DI
• The pushad instruction is used to push the 32-bit registers in the following order: EAX, ECX, EDX, EBX, ESP, EBP, ESI, EDI

Syntax

push value
pusha
pushad

Examples

Example 1

push   0xdebf        ; push a value to the stack
pop    eax           ; eax is now 0xdebf

Example 2

; swap content of registers
push   eax
mov    eax, ebx
pop    ebx

Example 3

; push parameters of a function to the stack
push   6             ; protocol IPPROTO_TCP
push   1             ; type     SOCK_STREAM
push   2             ; af       AF_INET (IP v4)
call   ds:socket

Example 4

Following C code:

printf("x equals y.\n");

Can be disassembled as follows:

push   offset aXEqualsY ; "x equals y.\n"
call   printf