.intel_syntax noprefix

    .globl _start

    .text


# String-copying routine.
# Commented-out lines would also return the starting address of the destination address.
strcpy:
#    push rsi
.loop:
    movb r10b, [rdi]
    cmpb r10b, 0
    je .end
    movb [rsi], r10b
    inc rdi
    inc rsi
    jmp .loop
.end:
#    pop rax
    ret

_start:

    mov rdi, offset str2
    mov rsi, offset str1
    call strcpy
    # mov rsi, rax  -- would copy the string start address to rsi

    mov rax, 1
    mov rdi, 1
    mov rsi, offset str1
    mov rdx, 14
    syscall

    # exit
    mov rax, 60
    mov rdi, 0
    syscall

    .bss
str1:
    .skip 30

    .data
str2:
    .string "Hello, world!\n"