OvmfPkg/Csm/LegacyBiosDxe/LegacyBda.c

   1 /** @file
   2   This code fills in BDA (0x400) and EBDA (pointed to by 0x4xx)
   3   information. There is support for doing initializeation before
   4   Legacy16 is loaded and before a legacy boot is attempted.
   5
   6 Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
   7
   8 SPDX-License-Identifier: BSD-2-Clause-Patent
   9
  10 **/
  11
  12 #include "LegacyBiosInterface.h"
  13
  14 /**
  15   Fill in the standard BDA and EBDA stuff before Legacy16 load
  16
  17   @param  Private     Legacy BIOS Instance data
  18
  19   @retval EFI_SUCCESS It should always work.
  20
  21 **/
  22 EFI_STATUS
  23 LegacyBiosInitBda (
  24   IN  LEGACY_BIOS_INSTANCE  *Private
  25   )
  26 {
  27   BDA_STRUC  *Bda;
  28   UINT8      *Ebda;
  29
  30   Bda  = (BDA_STRUC *)((UINTN)0x400);
  31   Ebda = (UINT8 *)((UINTN)0x9fc00);
  32
  33   ACCESS_PAGE0_CODE (
  34     ZeroMem (Bda, 0x100);
  35     //
  36     // 640k-1k for EBDA
  37     //
  38     Bda->MemSize       = 0x27f;
  39     Bda->KeyHead       = 0x1e;
  40     Bda->KeyTail       = 0x1e;
  41     Bda->FloppyData    = 0x00;
  42     Bda->FloppyTimeout = 0xff;
  43
  44     Bda->KeyStart       = 0x001E;
  45     Bda->KeyEnd         = 0x003E;
  46     Bda->KeyboardStatus = 0x10;
  47     Bda->Ebda           = 0x9fc0;
  48
  49     //
  50     // Move LPT time out here and zero out LPT4 since some SCSI OPROMS
  51     // use this as scratch pad (LPT4 is Reserved)
  52     //
  53     Bda->Lpt1_2Timeout = 0x1414;
  54     Bda->Lpt3_4Timeout = 0x1400;
  55
  56     );
  57
  58   ZeroMem (Ebda, 0x400);
  59   *Ebda = 0x01;
  60
  61   return EFI_SUCCESS;
  62 }