retroforth/experimental/linux.s

;  ___ ___ _____ ___  ___      __  _    _
; | _ \ __|_   _| _ \/ _ \    / / | |  (_)_ _ _  ___ __
; |   / _|  | | |   / (_) |  / /  | |__| | ' \ || \ \ /
; |_|_\___| |_| |_|_\\___/  /_/   |____|_|_||_\_,_/_\_\
;
; This is the minimal startup + I/O functionality needed to run
; RETRO on a Linux x86 system.
; =============================================================

bits 32

section .text
global putchar
global getchar
global _start
extern main

align 4

_start:
        call    main
        jmp     $

align 4
putchar:
        mov     eax, [esp+4]
        mov     [buf], eax
        mov     edx, 1
        mov     ecx, buf
        mov     ebx, 1
        mov     eax, 4
        int     0x80
        ret

align 4
getchar:
        mov     edx, 1
        mov     ecx, buf
        mov     ebx, 0
        mov     eax, 3
        int     0x80
        mov     eax, 0
        mov     eax, [buf]
        ret

section .data
buf:
        dd 0
        dd 0
        dd 0
        dd 0