global _start

section .data
  str: db "Please give me a string: " ; \n = 0xA

  strSize: equ $ - str
  ; $ = current assembler address.
  ; Since str is all that is above it must be the size

  stdin: equ 0 ; POSIX
  stdout: equ 1 ; POSIX

; Uninitialized space goes here, pretty much your heap of uninitialized bytes
; for all kinds of purposes
section .bss
  strBuffer: resb 64 ; reserve 64 bytes
  strBufferSize: equ 64 ; same as above

; This is where the code goes. Text. Makes sense, right?
section .text
_start:
  ; x64 has the syscall function, in contrast to int in x86 and ARM
  ; See /usr/include/asm/unistd_64.h for the numbers

  ; Clobbered registers
  ; rax rdi rsi rdx r10 r8 r9

  ; Write to stdout
  mov rax, 1
  mov rdi, stdout  ; fd to write to
  mov rsi, str     ; pointer
  mov rdx, strSize ; size
  syscall ; all arguments are specified above! (x86 = int 0x80)

  ; Read from stdin
  xor rax, rax ; 0
  mov rdi, stdin     ; fd to read from
  mov rsi, strBuffer ; where to store it
  mov rdx, strBufferSize ; maximum number of bytes
  syscall

  ; syscall return codes are always stored in register A
  ; The number of bytes read in was returned through this
	mov rdx, rax

	mov rax, 1
	mov rdi, stdout
	mov rsi, strBuffer
	syscall

  ; Exit routine
  mov rax, 60 ; 60 is the exit routine
  xor rdi, rdi ; our return code (0)
  syscall