Simple asm

easy.asm

; Me dicking around with 64bit nasm. Depending on the number of arguments given
; we print a number of dots. Does not do much, but should help the asm 
; beginner just as it did me.
;
; author: Simon Symeonidis

section .data
    message:  db ". ", 0
    nl:       db 0xA
    counter:  dd 0

section .bss

section .text

    global _start

_start:
    pop rax ; get argc
    mov [counter], rax

.countdown:
    call print_dot

    ;; Decrease the counter
    mov eax, [counter]
    dec eax
    mov [counter], eax

    ;; check to see if done
    cmp eax, 0
    jge .countdown

    call newline

    ; syscall - exit, ret 0
    mov rax, 60
    mov rdi, 0
    syscall

print_dot:
    mov eax, 4
    mov ebx, 1
    mov ecx, message
    mov edx, 3
    int 80h
    ret

newline:
    mov rax, 4  ;syscall - write
    mov rdi, 1  ;stdout
    mov ecx, nl ;message address
    mov edx, 1  ;length
    syscall
    ret