i386/boot1/nullboot1.s

   1 ; Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   2 ;
   3 ; @APPLE_LICENSE_HEADER_START@
   4 ;
   5 ; Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
   6 ; Reserved.  This file contains Original Code and/or Modifications of
   7 ; Original Code as defined in and that are subject to the Apple Public
   8 ; Source License Version 1.1 (the "License").  You may not use this file
   9 ; except in compliance with the License.  Please obtain a copy of the
  10 ; License at http://www.apple.com/publicsource and read it before using
  11 ; this file.
  12 ;
  13 ; The Original Code and all software distributed under the License are
  14 ; distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15 ; EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16 ; INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17 ; FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT.  Please see the
  18 ; License for the specific language governing rights and limitations
  19 ; under the License.
  20 ;
  21 ; @APPLE_LICENSE_HEADER_END@
  22 ;
  23 ; nullboot.s - boot1 written for nasm assembler, since gas only
  24 ; generates 32 bit code and this must run in real mode.
  25 ; To compile as floppy boot1f.not:
  26 ;       nasm -dBOOTDEV=FLOPPY nullboot1.s -o nullboot1
  27
  28 ;***********************************************************************
  29 ;       This is the code for the NeXT boot1 bootsector.
  30 ;***********************************************************************
  31
  32         SEGMENT .text
  33
  34         SDEBUG EQU 0
  35
  36 BOOTSEG         EQU     00h
  37 BOOTOFF         EQU     1000h
  38 BUFSZ           EQU     2000h   ; 8K disk transfer buffer
  39
  40 ; This code is a replacement for boot1.  It is loaded at 0x0:0x7c00
  41
  42 start:
  43         mov     ax,BOOTSEG
  44         cli                     ; interrupts off
  45         mov     ss,ax           ; set up stack seg
  46         mov     sp,0fff0h
  47         sti                     ; reenable interrupts
  48
  49         xor     ax,ax
  50         mov     es,ax
  51         mov     ds,ax
  52         mov     si,7C00h
  53         cld                     ; so pointers will get updated
  54         mov     di,0E000h       ; relocate boot program to 0xE000
  55         mov     cx,100h         ; copy 256x2 bytes
  56         repnz   movsw           ; move it
  57         jmp     0000:0E000h + (a1 - start)      ; jump to a1 in relocated place
  58
  59 a1:
  60         mov     ax,0E00h
  61         mov     ds,ax
  62         mov     ax,BOOTSEG
  63         mov     es,ax
  64
  65         mov     si, not_boot
  66         call    message         ; display intro message
  67
  68 halt:
  69         mov     ah, 00h
  70         int     16h
  71         jmp     short halt              ; get key and loop forever
  72
  73 message:                                ; write the error message in ds:esi
  74                                         ; to console
  75         push    es
  76         mov     ax,ds
  77         mov     es,ax
  78
  79         mov     bx, 1                   ; bh=0, bl=1 (blue)
  80         cld
  81
  82 nextb:
  83         lodsb                           ; load a byte into al
  84         cmp     al, 0
  85         je      done
  86         mov     ah, 0eh                 ; bios int 10, function 0xe
  87         int     10h                     ; bios display a byte in tty mode
  88         jmp     short nextb
  89 done:   pop     es
  90         ret
  91
  92 putchr:
  93         push    bx
  94         mov     bx, 1                   ; bh=0, bl=1 (blue)
  95         mov     ah, 0eh                 ; bios int 10, function 0xe
  96         int     10h                     ; bios display a byte in tty mode
  97         pop     bx
  98         ret
  99
 100
 101 not_boot:
 102         db      10,13
 103         db     'The disk in the floppy disk drive isn',39,'t a startup disk:'
 104         db      10,13
 105         db      'It doesn',39,'t contain '      ; 39 = a ' char
 106         db      'the system files required to start up the computer.'
 107         db      10,13
 108         db      'Please eject this disk and restart the computer'
 109         db      ' with a floppy disk,'
 110         db      10,13
 111         db      'hard disk, or CD-ROM that is a startup disk.'
 112         db      10,13
 113         db      0
 114
 115 ; the last 2 bytes in the sector contain the signature
 116 d1:
 117         a2 equ 510 - (d1 - start)
 118   times a2 db 0                         ; fill the rest with zeros
 119         dw 0AA55h
 120         ENDS
 121         END