boot/freeldr/freeldr/arch/i386/linux.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         .code32
  28 EXTERN(_BootNewLinuxKernel)
  29         call    switch_to_real
  30         .code16
  31
  32         /* Set the boot drive */
  33         movb    (_BootDrive),%dl
  34
  35         /* Load segment registers */
  36         cli
  37         movw    $0x9000,%bx
  38         movw    %bx,%ds
  39         movw    %bx,%es
  40         movw    %bx,%fs
  41         movw    %bx,%gs
  42         movw    %bx,%ss
  43         movw    $0x9000,%sp
  44
  45         ljmpl   $0x9020,$0x0000
  46
  47
  48         .code32
  49 /*
  50  *  VOID BootOldLinuxKernel(ULONG KernelSize);
  51  */
  52 EXTERN(_BootOldLinuxKernel)
  53
  54         /* First we have to copy the kernel down from 0x100000 to 0x10000 */
  55         /* The reason we can overwrite low memory is because this code */
  56         /* executes between 0000:8000 and 0000:FFFF. That leaves space for */
  57         /* 32k of code before we start interfering with Linux kernel address space. */
  58
  59         /* Get KernelSize in ECX and move the kernel down */
  60         movl    0x04(%esp),%ecx
  61         movl    $0x100000,%esi
  62         movl    $0x10000,%edi
  63         rep movsb
  64
  65         call    switch_to_real
  66         .code16
  67
  68         /* Set the boot drive */
  69         movb    (_BootDrive),%dl
  70
  71         /* Load segment registers */
  72         cli
  73         movw    $0x9000,%bx
  74         movw    %bx,%ds
  75         movw    %bx,%es
  76         movw    %bx,%fs
  77         movw    %bx,%gs
  78         movw    %bx,%ss
  79         movw    $0x9000,%sp
  80
  81         ljmpl   $0x9020,$0x0000