OvmfPkg/SmbiosPlatformDxe/X86Xen.c

   1 /** @file
   2   Detect Xen hvmloader SMBIOS data for usage by OVMF.
   3
   4   Copyright (c) 2011, Bei Guan <gbtju85@gmail.com>
   5   Copyright (c) 2011, Intel Corporation. All rights reserved.<BR>
   6
   7   SPDX-License-Identifier: BSD-2-Clause-Patent
   8
   9 **/
  10
  11 #include <Library/BaseLib.h> // AsciiStrnCmp()
  12 #include <Library/HobLib.h>  // GetFirstGuidHob()
  13 #include <Pi/PiHob.h>        // EFI_HOB_GUID_TYPE
  14
  15 #include "XenSmbiosPlatformDxe.h"
  16
  17 #define XEN_SMBIOS_PHYSICAL_ADDRESS  0x000EB000
  18 #define XEN_SMBIOS_PHYSICAL_END      0x000F0000
  19
  20 /**
  21   Validates the SMBIOS entry point structure
  22
  23   @param  EntryPointStructure  SMBIOS entry point structure
  24
  25   @retval TRUE   The entry point structure is valid
  26   @retval FALSE  The entry point structure is not valid
  27
  28 **/
  29 STATIC
  30 BOOLEAN
  31 IsEntryPointStructureValid (
  32   IN SMBIOS_TABLE_ENTRY_POINT  *EntryPointStructure
  33   )
  34 {
  35   UINTN  Index;
  36   UINT8  Length;
  37   UINT8  Checksum;
  38   UINT8  *BytePtr;
  39
  40   BytePtr  = (UINT8 *)EntryPointStructure;
  41   Length   = EntryPointStructure->EntryPointLength;
  42   Checksum = 0;
  43
  44   for (Index = 0; Index < Length; Index++) {
  45     Checksum = Checksum + (UINT8)BytePtr[Index];
  46   }
  47
  48   if (Checksum != 0) {
  49     return FALSE;
  50   } else {
  51     return TRUE;
  52   }
  53 }
  54
  55 /**
  56   Locates the Xen SMBIOS data if it exists
  57
  58   @return SMBIOS_TABLE_ENTRY_POINT   Address of Xen SMBIOS data
  59
  60 **/
  61 SMBIOS_TABLE_ENTRY_POINT *
  62 GetXenSmbiosTables (
  63   VOID
  64   )
  65 {
  66   UINT8                     *XenSmbiosPtr;
  67   SMBIOS_TABLE_ENTRY_POINT  *XenSmbiosEntryPointStructure;
  68   EFI_HOB_GUID_TYPE         *GuidHob;
  69
  70   //
  71   // See if a XenInfo HOB is available
  72   //
  73   GuidHob = GetFirstGuidHob (&gEfiXenInfoGuid);
  74   if (GuidHob == NULL) {
  75     return NULL;
  76   }
  77
  78   for (XenSmbiosPtr = (UINT8 *)(UINTN)XEN_SMBIOS_PHYSICAL_ADDRESS;
  79        XenSmbiosPtr < (UINT8 *)(UINTN)XEN_SMBIOS_PHYSICAL_END;
  80        XenSmbiosPtr += 0x10)
  81   {
  82     XenSmbiosEntryPointStructure = (SMBIOS_TABLE_ENTRY_POINT *)XenSmbiosPtr;
  83
  84     if (!AsciiStrnCmp ((CHAR8 *)XenSmbiosEntryPointStructure->AnchorString, "_SM_", 4) &&
  85         !AsciiStrnCmp ((CHAR8 *)XenSmbiosEntryPointStructure->IntermediateAnchorString, "_DMI_", 5) &&
  86         IsEntryPointStructureValid (XenSmbiosEntryPointStructure))
  87     {
  88       return XenSmbiosEntryPointStructure;
  89     }
  90   }
  91
  92   return NULL;
  93 }