i386/boot1/nullboot1.s

   1 ; Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   2 ;
   3 ; @APPLE_LICENSE_HEADER_START@
   4 ;
   5 ; Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   6 ;
   7 ; This file contains Original Code and/or Modifications of Original Code
   8 ; as defined in and that are subject to the Apple Public Source License
   9 ; Version 2.0 (the 'License'). You may not use this file except in
  10 ; compliance with the License. Please obtain a copy of the License at
  11 ; http://www.opensource.apple.com/apsl/ and read it before using this
  12 ; file.
  13 ;
  14 ; The Original Code and all software distributed under the License are
  15 ; distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  16 ; EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  17 ; INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  18 ; FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  19 ; Please see the License for the specific language governing rights and
  20 ; limitations under the License.
  21 ;
  22 ; @APPLE_LICENSE_HEADER_END@
  23 ;
  24 ; nullboot.s - boot1 written for nasm assembler, since gas only
  25 ; generates 32 bit code and this must run in real mode.
  26 ; To compile as floppy boot1f.not:
  27 ;       nasm -dBOOTDEV=FLOPPY nullboot1.s -o nullboot1
  28
  29 ;***********************************************************************
  30 ;       This is the code for the NeXT boot1 bootsector.
  31 ;***********************************************************************
  32
  33         SEGMENT .text
  34
  35         SDEBUG EQU 0
  36
  37 BOOTSEG         EQU     00h
  38 BOOTOFF         EQU     1000h
  39 BUFSZ           EQU     2000h   ; 8K disk transfer buffer
  40
  41 ; This code is a replacement for boot1.  It is loaded at 0x0:0x7c00
  42
  43 start:
  44         mov     ax,BOOTSEG
  45         cli                     ; interrupts off
  46         mov     ss,ax           ; set up stack seg
  47         mov     sp,0fff0h
  48         sti                     ; reenable interrupts
  49
  50         xor     ax,ax
  51         mov     es,ax
  52         mov     ds,ax
  53         mov     si,7C00h
  54         cld                     ; so pointers will get updated
  55         mov     di,0E000h       ; relocate boot program to 0xE000
  56         mov     cx,100h         ; copy 256x2 bytes
  57         repnz   movsw           ; move it
  58         jmp     0000:0E000h + (a1 - start)      ; jump to a1 in relocated place
  59
  60 a1:
  61         mov     ax,0E00h
  62         mov     ds,ax
  63         mov     ax,BOOTSEG
  64         mov     es,ax
  65
  66         mov     si, not_boot
  67         call    message         ; display intro message
  68
  69 halt:
  70         mov     ah, 00h
  71         int     16h
  72         jmp     short halt              ; get key and loop forever
  73
  74 message:                                ; write the error message in ds:esi
  75                                         ; to console
  76         push    es
  77         mov     ax,ds
  78         mov     es,ax
  79
  80         mov     bx, 1                   ; bh=0, bl=1 (blue)
  81         cld
  82
  83 nextb:
  84         lodsb                           ; load a byte into al
  85         cmp     al, 0
  86         je      done
  87         mov     ah, 0eh                 ; bios int 10, function 0xe
  88         int     10h                     ; bios display a byte in tty mode
  89         jmp     short nextb
  90 done:   pop     es
  91         ret
  92
  93 putchr:
  94         push    bx
  95         mov     bx, 1                   ; bh=0, bl=1 (blue)
  96         mov     ah, 0eh                 ; bios int 10, function 0xe
  97         int     10h                     ; bios display a byte in tty mode
  98         pop     bx
  99         ret
 100
 101
 102 not_boot:
 103         db      10,13
 104         db     'The disk in the floppy disk drive isn',39,'t a startup disk:'
 105         db      10,13
 106         db      'It doesn',39,'t contain '      ; 39 = a ' char
 107         db      'the system files required to start up the computer.'
 108         db      10,13
 109         db      'Please eject this disk and restart the computer'
 110         db      ' with a floppy disk,'
 111         db      10,13
 112         db      'hard disk, or CD-ROM that is a startup disk.'
 113         db      10,13
 114         db      0
 115
 116 ; the last 2 bytes in the sector contain the signature
 117 d1:
 118         a2 equ 510 - (d1 - start)
 119   times a2 db 0                         ; fill the rest with zeros
 120         dw 0AA55h
 121         ENDS
 122         END