reactos/boot/freeldr/freeldr/arch/i386/boot.S

   1 /*
   2  *  FreeLoader
   3  *  Copyright (C) 1998-2002  Brian Palmer  <brianp@sginet.com>
   4  *
   5  *  This program is free software; you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation; either version 2 of the License, or
   8  *  (at your option) any later version.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License along
  16  *  with this program; if not, write to the Free Software Foundation, Inc.,
  17  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18  */
  19
  20         .text
  21         .code16
  22
  23 #define ASM
  24 #include <arch.h>
  25
  26
  27 EXTERN(_ChainLoadBiosBootSectorCode)
  28         .code32
  29
  30         call    switch_to_real
  31         .code16
  32
  33         /* Set the boot drive */
  34         movb    (_BootDrive),%dl
  35
  36         /* Load segment registers */
  37         cli
  38         movw    $0x0000,%bx
  39         movw    %bx,%ds
  40         movw    %bx,%es
  41         movw    %bx,%fs
  42         movw    %bx,%gs
  43         movw    %bx,%ss
  44         movw    $0x7C00,%sp
  45
  46         ljmpl   $0x0000,$0x7C00
  47
  48 EXTERN(_SoftReboot)
  49         .code32
  50
  51         call    switch_to_real
  52         .code16
  53
  54         movw    $0x40,%ax
  55         movw    %ax,%ds
  56         movw    $0x72,%si
  57
  58         // Set the word at location 40:72 to 1234h
  59         movw    $0x1234,(%si)
  60
  61         // and jump to location FFFF:0 in ROM
  62         ljmpl   $0xFFFF,$0x0000