path: root/UefiCpuPkg/PiSmmCpuDxeSmm/NonMmramMapDxeSmm.c

/** @file

Copyright (c) 2016 - 2024, Intel Corporation. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include "PiSmmCpuCommon.h"
#include <Library/DxeServicesTableLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include <Library/UefiRuntimeServicesTableLib.h>

//
// attributes for reserved memory before it is promoted to system memory
//
#define EFI_MEMORY_PRESENT      0x0100000000000000ULL
#define EFI_MEMORY_INITIALIZED  0x0200000000000000ULL
#define EFI_MEMORY_TESTED       0x0400000000000000ULL

#define PREVIOUS_MEMORY_DESCRIPTOR(MemoryDescriptor, Size) \
  ((EFI_MEMORY_DESCRIPTOR *)((UINT8 *)(MemoryDescriptor) - (Size)))

EFI_MEMORY_DESCRIPTOR  *mUefiMemoryMap;
UINTN                  mUefiMemoryMapSize;
UINTN                  mUefiDescriptorSize;

EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *mGcdMemSpace       = NULL;
UINTN                            mGcdMemNumberOfDesc = 0;

EFI_MEMORY_ATTRIBUTES_TABLE  *mUefiMemoryAttributesTable = NULL;

/**
  Sort memory map entries based upon PhysicalStart, from low to high.

  @param  MemoryMap              A pointer to the buffer in which firmware places
                                 the current memory map.
  @param  MemoryMapSize          Size, in bytes, of the MemoryMap buffer.
  @param  DescriptorSize         Size, in bytes, of an individual EFI_MEMORY_DESCRIPTOR.
**/
STATIC
VOID
SortMemoryMap (
  IN OUT EFI_MEMORY_DESCRIPTOR  *MemoryMap,
  IN UINTN                      MemoryMapSize,
  IN UINTN                      DescriptorSize
  )
{
  EFI_MEMORY_DESCRIPTOR  *MemoryMapEntry;
  EFI_MEMORY_DESCRIPTOR  *NextMemoryMapEntry;
  EFI_MEMORY_DESCRIPTOR  *MemoryMapEnd;
  EFI_MEMORY_DESCRIPTOR  TempMemoryMap;

  MemoryMapEntry     = MemoryMap;
  NextMemoryMapEntry = NEXT_MEMORY_DESCRIPTOR (MemoryMapEntry, DescriptorSize);
  MemoryMapEnd       = (EFI_MEMORY_DESCRIPTOR *)((UINT8 *)MemoryMap + MemoryMapSize);
  while (MemoryMapEntry < MemoryMapEnd) {
    while (NextMemoryMapEntry < MemoryMapEnd) {
      if (MemoryMapEntry->PhysicalStart > NextMemoryMapEntry->PhysicalStart) {
        CopyMem (&TempMemoryMap, MemoryMapEntry, sizeof (EFI_MEMORY_DESCRIPTOR));
        CopyMem (MemoryMapEntry, NextMemoryMapEntry, sizeof (EFI_MEMORY_DESCRIPTOR));
        CopyMem (NextMemoryMapEntry, &TempMemoryMap, sizeof (EFI_MEMORY_DESCRIPTOR));
      }

      NextMemoryMapEntry = NEXT_MEMORY_DESCRIPTOR (NextMemoryMapEntry, DescriptorSize);
    }

    MemoryMapEntry     = NEXT_MEMORY_DESCRIPTOR (MemoryMapEntry, DescriptorSize);
    NextMemoryMapEntry = NEXT_MEMORY_DESCRIPTOR (MemoryMapEntry, DescriptorSize);
  }
}

/**
  Return if a UEFI memory page should be marked as not present in SMM page table.
  If the memory map entries type is
  EfiLoaderCode/Data, EfiBootServicesCode/Data, EfiConventionalMemory,
  EfiUnusableMemory, EfiACPIReclaimMemory, return TRUE.
  Or return FALSE.

  @param[in]  MemoryMap              A pointer to the memory descriptor.

  @return TRUE  The memory described will be marked as not present in SMM page table.
  @return FALSE The memory described will not be marked as not present in SMM page table.
**/
BOOLEAN
IsUefiPageNotPresent (
  IN EFI_MEMORY_DESCRIPTOR  *MemoryMap
  )
{
  switch (MemoryMap->Type) {
    case EfiLoaderCode:
    case EfiLoaderData:
    case EfiBootServicesCode:
    case EfiBootServicesData:
    case EfiConventionalMemory:
    case EfiUnusableMemory:
    case EfiACPIReclaimMemory:
      return TRUE;
    default:
      return FALSE;
  }
}

/**
  Merge continuous memory map entries whose type is
  EfiLoaderCode/Data, EfiBootServicesCode/Data, EfiConventionalMemory,
  EfiUnusableMemory, EfiACPIReclaimMemory, because the memory described by
  these entries will be set as NOT present in SMM page table.

  @param[in, out]  MemoryMap              A pointer to the buffer in which firmware places
                                          the current memory map.
  @param[in, out]  MemoryMapSize          A pointer to the size, in bytes, of the
                                          MemoryMap buffer. On input, this is the size of
                                          the current memory map.  On output,
                                          it is the size of new memory map after merge.
  @param[in]       DescriptorSize         Size, in bytes, of an individual EFI_MEMORY_DESCRIPTOR.
**/
STATIC
VOID
MergeMemoryMapForNotPresentEntry (
  IN OUT EFI_MEMORY_DESCRIPTOR  *MemoryMap,
  IN OUT UINTN                  *MemoryMapSize,
  IN UINTN                      DescriptorSize
  )
{
  EFI_MEMORY_DESCRIPTOR  *MemoryMapEntry;
  EFI_MEMORY_DESCRIPTOR  *MemoryMapEnd;
  UINT64                 MemoryBlockLength;
  EFI_MEMORY_DESCRIPTOR  *NewMemoryMapEntry;
  EFI_MEMORY_DESCRIPTOR  *NextMemoryMapEntry;

  MemoryMapEntry    = MemoryMap;
  NewMemoryMapEntry = MemoryMap;
  MemoryMapEnd      = (EFI_MEMORY_DESCRIPTOR *)((UINT8 *)MemoryMap + *MemoryMapSize);
  while ((UINTN)MemoryMapEntry < (UINTN)MemoryMapEnd) {
    CopyMem (NewMemoryMapEntry, MemoryMapEntry, sizeof (EFI_MEMORY_DESCRIPTOR));
    NextMemoryMapEntry = NEXT_MEMORY_DESCRIPTOR (MemoryMapEntry, DescriptorSize);

    do {
      MemoryBlockLength = (UINT64)(EFI_PAGES_TO_SIZE ((UINTN)MemoryMapEntry->NumberOfPages));
      if (((UINTN)NextMemoryMapEntry < (UINTN)MemoryMapEnd) &&
          IsUefiPageNotPresent (MemoryMapEntry) && IsUefiPageNotPresent (NextMemoryMapEntry) &&
          ((MemoryMapEntry->PhysicalStart + MemoryBlockLength) == NextMemoryMapEntry->PhysicalStart))
      {
        MemoryMapEntry->NumberOfPages += NextMemoryMapEntry->NumberOfPages;
        if (NewMemoryMapEntry != MemoryMapEntry) {
          NewMemoryMapEntry->NumberOfPages += NextMemoryMapEntry->NumberOfPages;
        }

        NextMemoryMapEntry = NEXT_MEMORY_DESCRIPTOR (NextMemoryMapEntry, DescriptorSize);
        continue;
      } else {
        MemoryMapEntry = PREVIOUS_MEMORY_DESCRIPTOR (NextMemoryMapEntry, DescriptorSize);
        break;
      }
    } while (TRUE);

    MemoryMapEntry    = NEXT_MEMORY_DESCRIPTOR (MemoryMapEntry, DescriptorSize);
    NewMemoryMapEntry = NEXT_MEMORY_DESCRIPTOR (NewMemoryMapEntry, DescriptorSize);
  }

  *MemoryMapSize = (UINTN)NewMemoryMapEntry - (UINTN)MemoryMap;

  return;
}

/**
  This function caches the GCD memory map information.
**/
VOID
GetGcdMemoryMap (
  VOID
  )
{
  UINTN                            NumberOfDescriptors;
  EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *MemSpaceMap;
  EFI_STATUS                       Status;
  UINTN                            Index;

  Status = gDS->GetMemorySpaceMap (&NumberOfDescriptors, &MemSpaceMap);
  if (EFI_ERROR (Status)) {
    return;
  }

  mGcdMemNumberOfDesc = 0;
  for (Index = 0; Index < NumberOfDescriptors; Index++) {
    if ((MemSpaceMap[Index].GcdMemoryType == EfiGcdMemoryTypeReserved) &&
        ((MemSpaceMap[Index].Capabilities & (EFI_MEMORY_PRESENT | EFI_MEMORY_INITIALIZED | EFI_MEMORY_TESTED)) ==
         (EFI_MEMORY_PRESENT | EFI_MEMORY_INITIALIZED))
        )
    {
      mGcdMemNumberOfDesc++;
    }
  }

  mGcdMemSpace = AllocateZeroPool (mGcdMemNumberOfDesc * sizeof (EFI_GCD_MEMORY_SPACE_DESCRIPTOR));
  ASSERT (mGcdMemSpace != NULL);
  if (mGcdMemSpace == NULL) {
    mGcdMemNumberOfDesc = 0;
    gBS->FreePool (MemSpaceMap);
    return;
  }

  mGcdMemNumberOfDesc = 0;
  for (Index = 0; Index < NumberOfDescriptors; Index++) {
    if ((MemSpaceMap[Index].GcdMemoryType == EfiGcdMemoryTypeReserved) &&
        ((MemSpaceMap[Index].Capabilities & (EFI_MEMORY_PRESENT | EFI_MEMORY_INITIALIZED | EFI_MEMORY_TESTED)) ==
         (EFI_MEMORY_PRESENT | EFI_MEMORY_INITIALIZED))
        )
    {
      CopyMem (
        &mGcdMemSpace[mGcdMemNumberOfDesc],
        &MemSpaceMap[Index],
        sizeof (EFI_GCD_MEMORY_SPACE_DESCRIPTOR)
        );
      mGcdMemNumberOfDesc++;
    }
  }

  gBS->FreePool (MemSpaceMap);
}

/**
  Get UEFI MemoryAttributesTable.
**/
VOID
GetUefiMemoryAttributesTable (
  VOID
  )
{
  EFI_STATUS                   Status;
  EFI_MEMORY_ATTRIBUTES_TABLE  *MemoryAttributesTable;
  UINTN                        MemoryAttributesTableSize;

  Status = EfiGetSystemConfigurationTable (&gEfiMemoryAttributesTableGuid, (VOID **)&MemoryAttributesTable);
  if (!EFI_ERROR (Status) && (MemoryAttributesTable != NULL)) {
    MemoryAttributesTableSize  = sizeof (EFI_MEMORY_ATTRIBUTES_TABLE) + MemoryAttributesTable->DescriptorSize * MemoryAttributesTable->NumberOfEntries;
    mUefiMemoryAttributesTable = AllocateCopyPool (MemoryAttributesTableSize, MemoryAttributesTable);
    ASSERT (mUefiMemoryAttributesTable != NULL);
  }
}

/**
  This function caches the UEFI memory map information.
**/
VOID
GetUefiMemoryMap (
  VOID
  )
{
  EFI_STATUS             Status;
  UINTN                  MapKey;
  UINT32                 DescriptorVersion;
  EFI_MEMORY_DESCRIPTOR  *MemoryMap;
  UINTN                  UefiMemoryMapSize;

  DEBUG ((DEBUG_INFO, "GetUefiMemoryMap\n"));

  UefiMemoryMapSize = 0;
  MemoryMap         = NULL;
  Status            = gBS->GetMemoryMap (
                             &UefiMemoryMapSize,
                             MemoryMap,
                             &MapKey,
                             &mUefiDescriptorSize,
                             &DescriptorVersion
                             );
  ASSERT (Status == EFI_BUFFER_TOO_SMALL);

  do {
    Status = gBS->AllocatePool (EfiBootServicesData, UefiMemoryMapSize, (VOID **)&MemoryMap);
    ASSERT (MemoryMap != NULL);
    if (MemoryMap == NULL) {
      return;
    }

    Status = gBS->GetMemoryMap (
                    &UefiMemoryMapSize,
                    MemoryMap,
                    &MapKey,
                    &mUefiDescriptorSize,
                    &DescriptorVersion
                    );
    if (EFI_ERROR (Status)) {
      gBS->FreePool (MemoryMap);
      MemoryMap = NULL;
    }
  } while (Status == EFI_BUFFER_TOO_SMALL);

  if (MemoryMap == NULL) {
    return;
  }

  SortMemoryMap (MemoryMap, UefiMemoryMapSize, mUefiDescriptorSize);
  MergeMemoryMapForNotPresentEntry (MemoryMap, &UefiMemoryMapSize, mUefiDescriptorSize);

  mUefiMemoryMapSize = UefiMemoryMapSize;
  mUefiMemoryMap     = AllocateCopyPool (UefiMemoryMapSize, MemoryMap);
  ASSERT (mUefiMemoryMap != NULL);

  gBS->FreePool (MemoryMap);

  //
  // Get additional information from GCD memory map.
  //
  GetGcdMemoryMap ();

  //
  // Get UEFI memory attributes table.
  //
  GetUefiMemoryAttributesTable ();
}

/**
  This function updates UEFI memory attribute according to UEFI memory map.

**/
VOID
UpdateUefiMemMapAttributes (
  VOID
  )
{
  BOOLEAN                WriteProtect;
  BOOLEAN                CetEnabled;
  EFI_STATUS             Status;
  UINTN                  Index;
  UINT64                 Limit;
  UINT64                 PreviousAddress;
  UINTN                  PageTable;
  UINT64                 Base;
  EFI_MEMORY_DESCRIPTOR  *MemoryMap;
  UINTN                  MemoryMapEntryCount;
  EFI_MEMORY_DESCRIPTOR  *Entry;

  DEBUG ((DEBUG_INFO, "UpdateUefiMemMapAttributes Start...\n"));

  WRITE_UNPROTECT_RO_PAGES (WriteProtect, CetEnabled);

  PageTable = AsmReadCr3 ();
  Limit     = LShiftU64 (1, mPhysicalAddressBits);

  //
  // [0, 4k] may be non-present.
  //
  PreviousAddress = ((FixedPcdGet8 (PcdNullPointerDetectionPropertyMask) & BIT1) != 0) ? BASE_4KB : 0;

  //
  // NonMmram shall be non-executable after the SmmReadyToLock event occurs, regardless of whether
  // RestrictedMemoryAccess is enabled, since all MM drivers located in NonMmram have already been dispatched and executed.
  //
  for (Index = 0; Index < mSmmCpuSmramRangeCount; Index++) {
    Base = mSmmCpuSmramRanges[Index].CpuStart;
    if (Base > PreviousAddress) {
      Status = ConvertMemoryPageAttributes (PageTable, mPagingMode, PreviousAddress, Base - PreviousAddress, EFI_MEMORY_XP, TRUE, NULL);
      ASSERT_RETURN_ERROR (Status);
    }

    PreviousAddress = mSmmCpuSmramRanges[Index].CpuStart + mSmmCpuSmramRanges[Index].PhysicalSize;
  }

  if (PreviousAddress < Limit) {
    Status = ConvertMemoryPageAttributes (PageTable, mPagingMode, PreviousAddress, Limit - PreviousAddress, EFI_MEMORY_XP, TRUE, NULL);
    ASSERT_RETURN_ERROR (Status);
  }

  //
  // Set NonMmram to not-present by excluding "RT, Reserved and NVS" memory type when RestrictedMemoryAccess is enabled.
  //
  if (IsRestrictedMemoryAccess ()) {
    if (mUefiMemoryMap != NULL) {
      MemoryMapEntryCount = mUefiMemoryMapSize/mUefiDescriptorSize;
      MemoryMap           = mUefiMemoryMap;
      for (Index = 0; Index < MemoryMapEntryCount; Index++) {
        if (IsUefiPageNotPresent (MemoryMap)) {
          Status = ConvertMemoryPageAttributes (
                     PageTable,
                     mPagingMode,
                     MemoryMap->PhysicalStart,
                     EFI_PAGES_TO_SIZE ((UINTN)MemoryMap->NumberOfPages),
                     EFI_MEMORY_RP,
                     TRUE,
                     NULL
                     );
          DEBUG ((
            DEBUG_INFO,
            "UefiMemory protection: 0x%lx - 0x%lx %r\n",
            MemoryMap->PhysicalStart,
            MemoryMap->PhysicalStart + (UINT64)EFI_PAGES_TO_SIZE ((UINTN)MemoryMap->NumberOfPages),
            Status
            ));
        }

        MemoryMap = NEXT_MEMORY_DESCRIPTOR (MemoryMap, mUefiDescriptorSize);
      }
    }

    //
    // Do not free mUefiMemoryMap, it will be checked in IsSmmCommBufferForbiddenAddress().
    //

    //
    // Set untested NonMmram memory as not present.
    //
    if (mGcdMemSpace != NULL) {
      for (Index = 0; Index < mGcdMemNumberOfDesc; Index++) {
        Status = ConvertMemoryPageAttributes (
                   PageTable,
                   mPagingMode,
                   mGcdMemSpace[Index].BaseAddress,
                   mGcdMemSpace[Index].Length,
                   EFI_MEMORY_RP,
                   TRUE,
                   NULL
                   );
        DEBUG ((
          DEBUG_INFO,
          "GcdMemory protection: 0x%lx - 0x%lx %r\n",
          mGcdMemSpace[Index].BaseAddress,
          mGcdMemSpace[Index].BaseAddress + mGcdMemSpace[Index].Length,
          Status
          ));
      }
    }

    //
    // Do not free mGcdMemSpace, it will be checked in IsSmmCommBufferForbiddenAddress().
    //

    //
    // Above logic sets the whole RT memory as present.
    // Below logic is to set the RT code as not present.
    //
    if (mUefiMemoryAttributesTable != NULL) {
      Entry = (EFI_MEMORY_DESCRIPTOR *)(mUefiMemoryAttributesTable + 1);
      for (Index = 0; Index < mUefiMemoryAttributesTable->NumberOfEntries; Index++) {
        if ((Entry->Type == EfiRuntimeServicesCode) || (Entry->Type == EfiRuntimeServicesData)) {
          if ((Entry->Attribute & EFI_MEMORY_RO) != 0) {
            Status = ConvertMemoryPageAttributes (
                       PageTable,
                       mPagingMode,
                       Entry->PhysicalStart,
                       EFI_PAGES_TO_SIZE ((UINTN)Entry->NumberOfPages),
                       EFI_MEMORY_RP,
                       TRUE,
                       NULL
                       );
            DEBUG ((
              DEBUG_INFO,
              "UefiMemoryAttribute protection: 0x%lx - 0x%lx %r\n",
              Entry->PhysicalStart,
              Entry->PhysicalStart + (UINT64)EFI_PAGES_TO_SIZE ((UINTN)Entry->NumberOfPages),
              Status
              ));
          }
        }

        Entry = NEXT_MEMORY_DESCRIPTOR (Entry, mUefiMemoryAttributesTable->DescriptorSize);
      }
    }

    //
    // Do not free mUefiMemoryAttributesTable, it will be checked in IsSmmCommBufferForbiddenAddress().
    //
  }

  //
  // Flush TLB
  //
  CpuFlushTlb ();

  //
  // Set execute-disable flag
  //
  mXdEnabled = TRUE;

  WRITE_PROTECT_RO_PAGES (WriteProtect, CetEnabled);

  DEBUG ((DEBUG_INFO, "UpdateUefiMemMapAttributes Done.\n"));
}

/**
  Get SmmProfileData.

  @param[in, out]     Size     Return Size of SmmProfileData.

  @return Address of SmmProfileData

**/
EFI_PHYSICAL_ADDRESS
GetSmmProfileData (
  IN OUT  UINT64  *Size
  )
{
  EFI_STATUS            Status;
  EFI_PHYSICAL_ADDRESS  Base;

  ASSERT (Size != NULL);

  *Size = PcdGet32 (PcdCpuSmmProfileSize);

  Base   = 0xFFFFFFFF;
  Status = gBS->AllocatePages (
                  AllocateMaxAddress,
                  EfiReservedMemoryType,
                  (UINTN)EFI_SIZE_TO_PAGES (*Size),
                  &Base
                  );
  ASSERT_EFI_ERROR (Status);
  ZeroMem ((VOID *)(UINTN)Base, (UINTN)*Size);

  return Base;
}

/**
  Return if the Address is the NonMmram logging Address.

  @param[in] Address the address to be checked

  @return TRUE  The address is the NonMmram logging Address.
  @return FALSE The address is not the NonMmram logging Address.
**/
BOOLEAN
IsNonMmramLoggingAddress (
  IN UINT64  Address
  )
{
  ASSERT (FALSE);

  return TRUE;
}

/**
  Return if the Address is forbidden as SMM communication buffer.

  @param[in] Address the address to be checked

  @return TRUE  The address is forbidden as SMM communication buffer.
  @return FALSE The address is allowed as SMM communication buffer.
**/
BOOLEAN
IsSmmCommBufferForbiddenAddress (
  IN UINT64  Address
  )
{
  EFI_MEMORY_DESCRIPTOR  *MemoryMap;
  UINTN                  MemoryMapEntryCount;
  UINTN                  Index;
  EFI_MEMORY_DESCRIPTOR  *Entry;

  if (!IsRestrictedMemoryAccess ()) {
    return FALSE;
  }

  if (mUefiMemoryMap != NULL) {
    MemoryMap           = mUefiMemoryMap;
    MemoryMapEntryCount = mUefiMemoryMapSize/mUefiDescriptorSize;
    for (Index = 0; Index < MemoryMapEntryCount; Index++) {
      if (IsUefiPageNotPresent (MemoryMap)) {
        if ((Address >= MemoryMap->PhysicalStart) &&
            (Address < MemoryMap->PhysicalStart + EFI_PAGES_TO_SIZE ((UINTN)MemoryMap->NumberOfPages)))
        {
          return TRUE;
        }
      }

      MemoryMap = NEXT_MEMORY_DESCRIPTOR (MemoryMap, mUefiDescriptorSize);
    }
  }

  if (mGcdMemSpace != NULL) {
    for (Index = 0; Index < mGcdMemNumberOfDesc; Index++) {
      if ((Address >= mGcdMemSpace[Index].BaseAddress) &&
          (Address < mGcdMemSpace[Index].BaseAddress + mGcdMemSpace[Index].Length))
      {
        return TRUE;
      }
    }
  }

  if (mUefiMemoryAttributesTable != NULL) {
    Entry = (EFI_MEMORY_DESCRIPTOR *)(mUefiMemoryAttributesTable + 1);
    for (Index = 0; Index < mUefiMemoryAttributesTable->NumberOfEntries; Index++) {
      if ((Entry->Type == EfiRuntimeServicesCode) || (Entry->Type == EfiRuntimeServicesData)) {
        if ((Entry->Attribute & EFI_MEMORY_RO) != 0) {
          if ((Address >= Entry->PhysicalStart) &&
              (Address < Entry->PhysicalStart + LShiftU64 (Entry->NumberOfPages, EFI_PAGE_SHIFT)))
          {
            return TRUE;
          }

          Entry = NEXT_MEMORY_DESCRIPTOR (Entry, mUefiMemoryAttributesTable->DescriptorSize);
        }
      }
    }
  }

  return FALSE;
}

/**
  Create extended protection MemoryRegion.
  Return all MMIO ranges that are reported in GCD service at EndOfDxe.

  The caller is responsible for freeing MemoryRegion via FreePool().

  @param[out]     MemoryRegion         Returned Non-Mmram Memory regions.
  @param[out]     MemoryRegionCount    A pointer to the number of Memory regions.
**/
VOID
CreateExtendedProtectionRange (
  OUT MM_CPU_MEMORY_REGION  **MemoryRegion,
  OUT UINTN                 *MemoryRegionCount
  )
{
  UINTN                            Index;
  EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *MemorySpaceMap;
  UINTN                            NumberOfSpaceDescriptors;
  UINTN                            MemoryRegionIndex;
  UINTN                            Count;

  MemorySpaceMap           = NULL;
  NumberOfSpaceDescriptors = 0;
  Count                    = 0;

  ASSERT (MemoryRegion != NULL && MemoryRegionCount != NULL);

  *MemoryRegion      = NULL;
  *MemoryRegionCount = 0;

  //
  // Get MMIO ranges from GCD.
  //
  gDS->GetMemorySpaceMap (
         &NumberOfSpaceDescriptors,
         &MemorySpaceMap
         );
  for (Index = 0; Index < NumberOfSpaceDescriptors; Index++) {
    if (MemorySpaceMap[Index].GcdMemoryType == EfiGcdMemoryTypeMemoryMappedIo) {
      if (ADDRESS_IS_ALIGNED (MemorySpaceMap[Index].BaseAddress, SIZE_4KB) &&
          (MemorySpaceMap[Index].Length % SIZE_4KB == 0))
      {
        Count++;
      } else {
        //
        // Skip the MMIO range that BaseAddress and Length are not 4k aligned since
        // the minimum granularity of the page table is 4k
        //
        DEBUG ((
          DEBUG_WARN,
          "MMIO range [0x%lx, 0x%lx] is skipped since it is not 4k aligned.\n",
          MemorySpaceMap[Index].BaseAddress,
          MemorySpaceMap[Index].BaseAddress + MemorySpaceMap[Index].Length
          ));
      }
    }
  }

  *MemoryRegionCount = Count;

  *MemoryRegion = (MM_CPU_MEMORY_REGION *)AllocateZeroPool (sizeof (MM_CPU_MEMORY_REGION) * Count);
  ASSERT (*MemoryRegion != NULL);

  MemoryRegionIndex = 0;
  for (Index = 0; Index < NumberOfSpaceDescriptors; Index++) {
    if ((MemorySpaceMap[Index].GcdMemoryType == EfiGcdMemoryTypeMemoryMappedIo) &&
        ADDRESS_IS_ALIGNED (MemorySpaceMap[Index].BaseAddress, SIZE_4KB) &&
        (MemorySpaceMap[Index].Length % SIZE_4KB == 0))
    {
      (*MemoryRegion)[MemoryRegionIndex].Base   = MemorySpaceMap[Index].BaseAddress;
      (*MemoryRegion)[MemoryRegionIndex].Length = MemorySpaceMap[Index].Length;
      MemoryRegionIndex++;
    }
  }

  return;
}

/**
  Create the Non-Mmram Memory Region.
  Build MemoryRegion to cover [0, 2^PhysicalAddressBits) by excluding all Smram range.
  The memory attribute is all-allowed (read/write/executable).

  The caller is responsible for freeing MemoryRegion via FreePool().

  @param[in]      PhysicalAddressBits  The bits of physical address to map.
  @param[out]     MemoryRegion         Returned Non-Mmram Memory regions.
  @param[out]     MemoryRegionCount    A pointer to the number of Memory regions.
**/
VOID
CreateNonMmramMemMap (
  IN  UINT8                 PhysicalAddressBits,
  OUT MM_CPU_MEMORY_REGION  **MemoryRegion,
  OUT UINTN                 *MemoryRegionCount
  )
{
  UINT64  MaxLength;
  UINTN   Count;
  UINTN   Index;
  UINT64  PreviousAddress;
  UINT64  Base;
  UINT64  Length;

  ASSERT (MemoryRegion != NULL && MemoryRegionCount != NULL);

  *MemoryRegion      = NULL;
  *MemoryRegionCount = 0;

  MaxLength = LShiftU64 (1, PhysicalAddressBits);

  //
  // Build MemoryRegion to cover [0, 2^PhysicalAddressBits) by excluding all Smram range
  //
  Count = mSmmCpuSmramRangeCount + 1;

  *MemoryRegionCount = Count;

  *MemoryRegion = (MM_CPU_MEMORY_REGION *)AllocateZeroPool (sizeof (MM_CPU_MEMORY_REGION) * Count);
  ASSERT (*MemoryRegion != NULL);

  PreviousAddress = 0;
  for (Index = 0; Index < mSmmCpuSmramRangeCount; Index++) {
    Base   = mSmmCpuSmramRanges[Index].CpuStart;
    Length = mSmmCpuSmramRanges[Index].PhysicalSize;

    ASSERT (MaxLength > Base +  Length);

    if (Base > PreviousAddress) {
      (*MemoryRegion)[Index].Base      = PreviousAddress;
      (*MemoryRegion)[Index].Length    = Base - PreviousAddress;
      (*MemoryRegion)[Index].Attribute = 0;
    }

    PreviousAddress = Base + Length;
  }

  //
  // Set the last remaining range
  //
  if (PreviousAddress < MaxLength) {
    (*MemoryRegion)[Index].Base   = PreviousAddress;
    (*MemoryRegion)[Index].Length = MaxLength - PreviousAddress;
  }
}