# Linux Kernel Module Cheat

#### 29.3.2. x86 PUSH and POP instructions

userland/arch/x86_64/push.S

`push %rax` is basically equivalent to:

    sub $8, %rsp
    mov %rax, (%rsp)

and `pop %rax`:

    mov (%rsp), %rax
    add $8, %rsp

Why do those instructions exist at all vs MOV / ADD / SUB: https://stackoverflow.com/questions/4584089/what-is-the-function-of-push-pop-registers-in-x86-assembly/33583134#33583134