asm 서브루틴

section .data
text db "Hello, World!",10,0
text2 db "World?",10,0

Section .text
global _start

_start:
mov rax, text
call _print

mov rax, text2
call _print

mov rax, 60
mov rdi, 0
syscall

;input: rax as pointer to string
;output: print string at rax
_print:
push rax
mov rbx, 0
_printLoop:
inc rax
inc rbx
mov cl,  [rax]
cmp cl, 0
jne _printLoop

mov rax, 1
mov rdi, 1
pop rsi
mov rdx, rbx
syscall

ret

; nasm -f elf64 05_SubRoutine.asm -o 05_SubRoutine.o
; ld 05_SubRoutine.o -o 05_SubRoutine
; ./05_SubRoutine