retroforth/source/interfaces/minimal-no-libc/fbsd.s

;  ___ ___ _____ ___  ___      __  ___            ___ ___ ___
; | _ \ __|_   _| _ \/ _ \    / / | __| _ ___ ___| _ ) __|   \
; |   / _|  | | |   / (_) |  / /  | _| '_/ -_) -_) _ \__ \ |) |
; |_|_\___| |_| |_|_\\___/  /_/   |_||_| \___\___|___/___/___/
;
; This is the minimal startup + I/O functionality needed to run
; RETRO on a FreeBSD 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
        push    dword 1
        push    dword buf
        push    dword 1
        mov     eax, 4
        call    kernel
        add     esp, 12
        ret

align 4
getchar:
        push    dword 1
        push    dword buf
        push    dword 0
        mov     eax, 3
        call    kernel
        add     esp, 12
        mov     eax, 0
        mov     eax, [buf]
        ret

align 4
kernel:
        int     80h
        ret

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