asm to print command line arguments

printargs.asm

section .data

EXIT_SUCCESS    equ 0  ; successful operation
SYS_exit        equ 60 ; call code for terminate
linefeed        db  10
stringRes       db  "Number of arguments: "

section .text
    global _start

%macro LF_macro 0
    mov rax, 1
    mov rdi, 1
    mov rsi, linefeed
    mov rdx, 1
    syscall
%endmacro

; print to stout a string located at rdi as pointer
_printstring:
    mov rsi, rdi
    call _strlen
    mov rdx, rax
    mov rax, 1
    mov rdi, 1
    syscall
    ret

_start:
    mov r8, [rsp]
    add r8, 48
    mov [stringRes + 20], r8
    mov rdi, stringRes
    call _printstring
    LF_macro

    pop rcx ; argc

_printloop:
    pop rdi     ; argv[0...argc]
    push rcx

    call _printstring
    LF_macro

    pop rcx
    loop _printloop

    ; Exit
    mov rax, SYS_exit
    mov rdi, EXIT_SUCCESS
    syscall

; input rdi as pointer to \0 terminated string
; return rax as length of string
_strlen:
    xor rax, rax
_strlenLoop:
    cmp byte [rdi], 0
    je _strlenRet
    inc rax
    inc rdi
    jmp _strlenLoop
_strlenRet:
    ret