audk/OvmfPkg/SmbiosPlatformDxe/X86Xen.c

/** @file
  Detect Xen hvmloader SMBIOS data for usage by OVMF.

  Copyright (c) 2011, Bei Guan <gbtju85@gmail.com>
  Copyright (c) 2011, Intel Corporation. All rights reserved.<BR>

  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include "SmbiosPlatformDxe.h"
#include <Library/HobLib.h>
#include <Guid/XenInfo.h>

#define XEN_SMBIOS_PHYSICAL_ADDRESS       0x000EB000
#define XEN_SMBIOS_PHYSICAL_END           0x000F0000

/**
  Validates the SMBIOS entry point structure

  @param  EntryPointStructure  SMBIOS entry point structure

  @retval TRUE   The entry point structure is valid
  @retval FALSE  The entry point structure is not valid

**/
STATIC
BOOLEAN
IsEntryPointStructureValid (
  IN SMBIOS_TABLE_ENTRY_POINT  *EntryPointStructure
  )
{
  UINTN                     Index;
  UINT8                     Length;
  UINT8                     Checksum;
  UINT8                     *BytePtr;

  BytePtr = (UINT8*) EntryPointStructure;
  Length = EntryPointStructure->EntryPointLength;
  Checksum = 0;

  for (Index = 0; Index < Length; Index++) {
    Checksum = Checksum + (UINT8) BytePtr[Index];
  }

  if (Checksum != 0) {
    return FALSE;
  } else {
    return TRUE;
  }
}

/**
  Locates the Xen SMBIOS data if it exists

  @return SMBIOS_TABLE_ENTRY_POINT   Address of Xen SMBIOS data

**/
SMBIOS_TABLE_ENTRY_POINT *
GetXenSmbiosTables (
  VOID
  )
{
  UINT8                     *XenSmbiosPtr;
  SMBIOS_TABLE_ENTRY_POINT  *XenSmbiosEntryPointStructure;
  EFI_HOB_GUID_TYPE         *GuidHob;

  //
  // See if a XenInfo HOB is available
  //
  GuidHob = GetFirstGuidHob (&gEfiXenInfoGuid);
  if (GuidHob == NULL) {
    return NULL;
  }

  for (XenSmbiosPtr = (UINT8*)(UINTN) XEN_SMBIOS_PHYSICAL_ADDRESS;
       XenSmbiosPtr < (UINT8*)(UINTN) XEN_SMBIOS_PHYSICAL_END;
       XenSmbiosPtr += 0x10) {

    XenSmbiosEntryPointStructure = (SMBIOS_TABLE_ENTRY_POINT *) XenSmbiosPtr;

    if (!AsciiStrnCmp ((CHAR8 *) XenSmbiosEntryPointStructure->AnchorString, "_SM_", 4) &&
        !AsciiStrnCmp ((CHAR8 *) XenSmbiosEntryPointStructure->IntermediateAnchorString, "_DMI_", 5) &&
        IsEntryPointStructureValid (XenSmbiosEntryPointStructure)) {

      return XenSmbiosEntryPointStructure;

    }
  }

  return NULL;
}