KernelSupport.c

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#include "BootCompatInternal.h"
 
#include <Guid/OcVariable.h>
#include <IndustryStandard/AppleHibernate.h>
 
#include <Library/BaseLib.h>
#include <Library/BaseMemoryLib.h>
#include <Library/DebugLib.h>
#include <Library/OcBootManagementLib.h>
#include <Library/OcDeviceTreeLib.h>
#include <Library/OcMachoLib.h>
#include <Library/OcMemoryLib.h>
#include <Library/OcMiscLib.h>
#include <Library/OcStringLib.h>
#include <Library/PrintLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include <Library/UefiLib.h>
#include <Library/UefiRuntimeServicesTableLib.h>
 
STATIC
VOID
ProtectRtMemoryFromRelocation (
  IN OUT RT_RELOC_PROTECT_DATA  *RtReloc,
  IN     UINTN                  MemoryMapSize,
  IN     UINTN                  DescriptorSize,
  IN OUT EFI_MEMORY_DESCRIPTOR  *MemoryMap,
  IN     EFI_PHYSICAL_ADDRESS   SysTableArea,
  IN     UINTN                  SysTableAreaSize
  )
{
  //
  // We protect RT data & code from relocation by marking them MemMapIO except EFI_SYSTEM_TABLE area.
  //
  // This fixes NVRAM issues on some boards where access to NVRAM after boot services is possible
  // only in SMM mode. RT driver passes data to SMM handler through previously negotiated buffer
  // and this buffer must not be relocated.
  // Explained and examined in detail by CodeRush and night199uk:
  // https://web.archive.org/web/20141025080709/http://www.projectosx.com/forum/lofiversion/index.php/t3298.html
  //
  // Starting with APTIO V for NVRAM to work not only RT data but RT code too can no longer be moved
  // due to the use of commbuffers. This, however, creates a memory protection issue, because
  // XNU maps RT data as RW and code as RX, and AMI appears use global variables in some RT drivers.
  // For this reason we shim (most?) affected RT services via wrapers that unset the WP bit during
  // the UEFI call and set it back on return in a separate driver.
  // Explained in detail by Download-Fritz and vit9696:
  // http://www.insanelymac.com/forum/topic/331381-aptiomemoryfix (first 2 links in particular).
  //
  // EFI_SYSTEM_TABLE is passed directly through kernel boot arguments, and thus goes through static
  // mapping (ml_static_ptovirt) in efi_set_tables_64 call. This mapping works as PHYS | CONST = VIRT.
  // To avoid kernel accessing unmapped virtual address we let boot.efi relocate the page with
  // EFI_SYSTEM_TABLE area. While technically it is possible to let the original page to be relocated,
  // we pick a safer root by using a private copy.
  //
  // The primary downside of this approach is that boot.efi will still reserve the contiguous memory
  // for runtime services after the kernel: efiRuntimeServicesPageCount pages starting from
  // efiRuntimeServicesPageStart within kaddr ~ ksize range. However, unlike Macs, which have reserved
  // gaps only for ACPI NVS, MemMapIO and similar regions, with this approach almost no physical memory
  // in efiRuntimeServicesPageStart area is used at all. This memory is never reclaimed by XNU, which
  // marks it as allocated in i386_vm_init. Expirements show that at least 85 MBs (Z170) are used for
  // this process. On server systems the issue is much worse due to many devices in place.
  // Ideally boot.efi should only count RT code and RT data pages, but it is not easy to change.
  //
 
  UINTN                  NumEntries;
  UINTN                  Index;
  EFI_MEMORY_DESCRIPTOR  *Desc;
  RT_RELOC_PROTECT_INFO  *RelocInfo;
 
  Desc                = MemoryMap;
  RtReloc->NumEntries = 0;
  RelocInfo           = &RtReloc->RelocInfo[0];
  NumEntries          = MemoryMapSize / DescriptorSize;
 
  for (Index = 0; Index < NumEntries; ++Index) {
    if (  ((Desc->Attribute & EFI_MEMORY_RUNTIME) != 0)
       && (Desc->NumberOfPages > 0)
       && ((Desc->Type == EfiRuntimeServicesCode) || (Desc->Type == EfiRuntimeServicesData))
       && !AREA_WITHIN_DESCRIPTOR (Desc, SysTableArea, SysTableAreaSize))
    {
      if (RtReloc->NumEntries == ARRAY_SIZE (RtReloc->RelocInfo)) {
        RUNTIME_DEBUG (
          (
           DEBUG_ERROR,
           "OCABC: Cannot save mem type for entry: %Lx (type 0x%x)\n",
           (UINT64)Desc->PhysicalStart,
           (UINT32)Desc->Type
          )
          );
        return;
      }
 
      RelocInfo->PhysicalStart = Desc->PhysicalStart;
      RelocInfo->PhysicalEnd   = LAST_DESCRIPTOR_ADDR (Desc);
      RelocInfo->Type          = Desc->Type;
      Desc->Type               = EfiMemoryMappedIO;
      ++RelocInfo;
      ++RtReloc->NumEntries;
    }
 
    Desc = NEXT_MEMORY_DESCRIPTOR (Desc, DescriptorSize);
  }
}
 
STATIC
EFI_STATUS
PerformRtMemoryVirtualMapping (
  IN OUT KERNEL_SUPPORT_STATE   *KernelState,
  IN     UINTN                  MemoryMapSize,
  IN     UINTN                  DescriptorSize,
  IN     UINT32                 DescriptorVersion,
  IN     EFI_MEMORY_DESCRIPTOR  *MemoryMap
  )
{
  //
  // About partial memmap:
  // Some UEFIs are converting pointers to virtual addresses even if they do not
  // point to regions with RT flag. This means that those UEFIs are using
  // Desc->VirtualStart even for non-RT regions. Linux had issues with this:
  // http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=7cb00b72876ea2451eb79d468da0e8fb9134aa8a
  // They are doing it Windows way now - copying RT descriptors to separate
  // mem map and passing that stripped map to SetVirtualAddressMap().
  // We'll do the same, although it seems that just assigning
  // VirtualStart = PhysicalStart for non-RT areas also does the job.
  //
  // About virtual to physical mappings:
  // Also adds virtual to physical address mappings for RT areas. This is needed since
  // SetVirtualAddressMap() does not work on my Aptio without that. Probably because some driver
  // has a bug and is trying to access new virtual addresses during the change.
  // Linux and Windows are doing the same thing and problem is
  // not visible there.
  //
 
  UINTN                           NumEntries;
  UINTN                           Index;
  EFI_MEMORY_DESCRIPTOR           *Desc;
  EFI_MEMORY_DESCRIPTOR           *VirtualDesc;
  EFI_STATUS                      Status;
  PAGE_MAP_AND_DIRECTORY_POINTER  *PageTable;
 
  Desc                       = MemoryMap;
  NumEntries                 = MemoryMapSize / DescriptorSize;
  VirtualDesc                = KernelState->VmMap;
  KernelState->VmMapSize     = 0;
  KernelState->VmMapDescSize = DescriptorSize;
 
  //
  // Get current VM page table.
  //
  PageTable = OcGetCurrentPageTable (NULL);
 
  for (Index = 0; Index < NumEntries; ++Index) {
    //
    // Legacy note. Some UEFIs end up with "reserved" area with EFI_MEMORY_RUNTIME flag set when
    // Intel HD3000 or HD4000 is used. For example, on GA-H81N-D2H there is a single 1 GB descriptor:
    // 000000009F800000-00000000DF9FFFFF 0000000000040200 8000000000000000
    //
    // Older EfiBoot (from 10.4.x) assigns virtual addresses to all descriptors containing
    // EFI_MEMORY_RUNTIME flag, including ones with EfiReservedMemoryType. Starting with 10.5
    // this is fixed, and virtual addresses are not assigned to reserved descriptors.
    // We might eventually need to add some workaround to prevent exceeding virtual address space
    // in EfiBoot from 10.4 by dropping the EFI_MEMORY_RUNTIME flag.
    //
    // The relevant discussion and the original fix can be found here:
    // http://web.archive.org/web/20141111124211/http://www.projectosx.com:80/forum/lofiversion/index.php/t2428-450.html
    // https://sourceforge.net/p/cloverefiboot/code/605/
    //
    // The correct approach is to properly handle EfiReservedMemoryType with EFI_MEMORY_RUNTIME
    // attribute set, and not mess with the memory map passed to boot.efi. As done here.
    //
    if ((Desc->Type != EfiReservedMemoryType) && ((Desc->Attribute & EFI_MEMORY_RUNTIME) != 0)) {
      //
      // Check if there is enough space in virtual map.
      //
      if (KernelState->VmMapSize + DescriptorSize > sizeof (KernelState->VmMap)) {
        RUNTIME_DEBUG ((DEBUG_ERROR, "OCABC: Too many RT entries to memory map\n"));
        return EFI_OUT_OF_RESOURCES;
      }
 
      //
      // Copy region with EFI_MEMORY_RUNTIME flag to virtual map.
      //
      CopyMem (VirtualDesc, Desc, DescriptorSize);
 
      //
      // Define virtual to physical mapping.
      //
      Status = VmMapVirtualPages (
                 &KernelState->VmContext,
                 PageTable,
                 Desc->VirtualStart,
                 Desc->NumberOfPages,
                 Desc->PhysicalStart
                 );
      if (EFI_ERROR (Status)) {
        RUNTIME_DEBUG ((DEBUG_ERROR, "OCABC: RT mapping failure - %r\n", Status));
        return EFI_OUT_OF_RESOURCES;
      }
 
      //
      // Proceed to next virtual map slot.
      //
      VirtualDesc             = NEXT_MEMORY_DESCRIPTOR (VirtualDesc, DescriptorSize);
      KernelState->VmMapSize += DescriptorSize;
    }
 
    //
    // Proceed to next original map slot.
    //
    Desc = NEXT_MEMORY_DESCRIPTOR (Desc, DescriptorSize);
  }
 
  VmFlushCaches ();
 
  Status = gRT->SetVirtualAddressMap (
                  KernelState->VmMapSize,
                  DescriptorSize,
                  DescriptorVersion,
                  KernelState->VmMap
                  );
 
  return Status;
}
 
STATIC
VOID
RestoreProtectedRtMemoryTypes (
  IN     RT_RELOC_PROTECT_DATA  *RtReloc,
  IN     UINTN                  MemoryMapSize,
  IN     UINTN                  DescriptorSize,
  IN OUT EFI_MEMORY_DESCRIPTOR  *MemoryMap
  )
{
  UINTN                  Index;
  UINTN                  Index2;
  UINTN                  NumEntriesLeft;
  UINTN                  NumEntries;
  EFI_PHYSICAL_ADDRESS   PhysicalStart;
  EFI_PHYSICAL_ADDRESS   PhysicalEnd;
  EFI_MEMORY_DESCRIPTOR  *Desc;
 
  NumEntriesLeft = RtReloc->NumEntries;
  NumEntries     = MemoryMapSize / DescriptorSize;
  Desc           = MemoryMap;
 
  for (Index = 0; Index < NumEntries && NumEntriesLeft > 0; ++Index) {
    PhysicalStart = Desc->PhysicalStart;
    PhysicalEnd   = LAST_DESCRIPTOR_ADDR (Desc);
 
    for (Index2 = 0; Index2 < RtReloc->NumEntries; ++Index2) {
      //
      // PhysicalStart match is enough, but just in case.
      // Some types of firmware, such as on the Lenovo ThinkPad X240, have unusual reserved areas.
      // For example, 0000000000000000-FFFFFFFFFFFFFFFF 0000000000000000 0000000000000000.
      // Execute exact comparisons as fuzzy matching often results in errors.
      //
      if (  (PhysicalStart == RtReloc->RelocInfo[Index2].PhysicalStart)
         && (PhysicalEnd == RtReloc->RelocInfo[Index2].PhysicalEnd))
      {
        Desc->Type = RtReloc->RelocInfo[Index2].Type;
        --NumEntriesLeft;
        break;
      }
    }
 
    Desc = NEXT_MEMORY_DESCRIPTOR (Desc, DescriptorSize);
  }
 
  if (NumEntriesLeft > 0) {
    RUNTIME_DEBUG (
      (
       DEBUG_ERROR,
       "OCABC: Failed to restore %u entries out of %u\n",
       (UINT32)NumEntriesLeft,
       (UINT32)RtReloc->NumEntries
      )
      );
  }
}
 
VOID
AppleMapPrepareForBooting (
  IN OUT BOOT_COMPAT_CONTEXT  *BootCompat,
  IN OUT VOID                 *BootArgs
  )
{
  EFI_STATUS             Status;
  DTEntry                Chosen;
  CHAR8                  *ArgsStr;
  UINT32                 ArgsSize;
  OC_BOOT_ARGUMENTS      BA;
  UINTN                  MemoryMapSize;
  EFI_MEMORY_DESCRIPTOR  *MemoryMap;
  UINTN                  DescriptorSize;
 
  OcParseBootArgs (&BA, BootArgs);
 
  if (BootCompat->Settings.ProvideCustomSlide) {
    //
    // Restore the variables we tampered with to support custom slides.
    //
    AppleSlideRestore (BootCompat, &BA);
  }
 
  if (BootCompat->Settings.DisableSingleUser) {
    //
    // First, there is a BootArgs entry for XNU.
    //
    OcRemoveArgumentFromCmd (BA.CommandLine, "-s");
  }
 
  if (  BootCompat->Settings.DisableSingleUser
     || BootCompat->Settings.ForceBooterSignature)
  {
    DTInit ((VOID *)(UINTN)*BA.DeviceTreeP, BA.DeviceTreeLength);
    Status = DTLookupEntry (NULL, "/chosen", &Chosen);
    if (!EFI_ERROR (Status)) {
      if (BootCompat->Settings.DisableSingleUser) {
        //
        // Second, there is a DT entry.
        //
        Status = DTGetProperty (Chosen, "boot-args", (VOID **)&ArgsStr, &ArgsSize);
        if (!EFI_ERROR (Status) && (ArgsSize > 0)) {
          OcRemoveArgumentFromCmd (ArgsStr, "-s");
        }
      }
 
      if (BootCompat->Settings.ForceBooterSignature) {
        Status = DTGetProperty (Chosen, "boot-signature", (VOID **)&ArgsStr, &ArgsSize);
        if (!EFI_ERROR (Status) && (ArgsSize == SHA1_DIGEST_SIZE)) {
          CopyMem (ArgsStr, BootCompat->Settings.BooterSignature, ArgsSize);
        }
      }
    }
  }
 
  if ((BootCompat->KernelState.RelocationBlock != 0) && !BootCompat->KernelState.RelocationBlockLegacy) {
    //
    // When using Relocation Block, EfiBoot on macOS 10.6 and newer will not virtualize the addresses
    // since they cannot be mapped 1:1 due to any region from the relocation block being outside
    // of static XNU vaddr to paddr mapping. This causes a clean early exit in their
    // SetVirtualAddressMap calling routine avoiding gRT->SetVirtualAddressMap.
    //
    // For this reason we need to perform it ourselves right here before we restored
    // runtime memory protections as we also need to defragment EFI_SYSTEM_TABLE memory
    // to be accessible from XNU.
    //
    AppleRelocationVirtualize (BootCompat, &BA);
  }
 
  if (BootCompat->Settings.AvoidRuntimeDefrag) {
    MemoryMapSize  = *BA.MemoryMapSize;
    MemoryMap      = (EFI_MEMORY_DESCRIPTOR *)(UINTN)(*BA.MemoryMap);
    DescriptorSize = *BA.MemoryMapDescriptorSize;
 
    //
    // We must restore EfiRuntimeServicesCode memory area types, because otherwise
    // RuntimeServices won't be mapped.
    //
    RestoreProtectedRtMemoryTypes (
      &BootCompat->RtReloc,
      MemoryMapSize,
      DescriptorSize,
      MemoryMap
      );
 
    //
    // On native Macs due to EfiBoot defragmentation it is guaranteed that
    // VADDR % BASE_1GB == PADDR. macOS 11 started to rely on this in
    // acpi_count_enabled_logical_processors, which needs to access MADT (APIC)
    // ACPI table, and does that through ConfigurationTables.
    //
    // The simplest approach is to just copy the table, so that it is accessible
    // at both actual mapping and 1:1 defragmented mapping. This should be safe,
    // as the memory for 1:1 defragmented mapping is reserved by EfiBoot in the
    // first place and is otherwise stolen anyway.
    //
    if (BootCompat->KernelState.ConfigurationTable != NULL) {
      CopyMem (
        (VOID *)((UINTN)BA.SystemTable->ConfigurationTable & (BASE_1GB - 1)),
        BootCompat->KernelState.ConfigurationTable,
        sizeof (*BootCompat->KernelState.ConfigurationTable) * BA.SystemTable->NumberOfTableEntries
        );
    }
  }
 
  if (BootCompat->KernelState.RelocationBlock != 0) {
    AppleRelocationRebase (BootCompat, &BA);
  }
}
 
VOID
AppleMapPrepareForHibernateWake (
  IN OUT BOOT_COMPAT_CONTEXT  *BootCompat,
  IN     UINTN                ImageHeaderPage
  )
{
  IOHibernateImageHeader  *ImageHeader;
  IOHibernateHandoff      *Handoff;
 
  ImageHeader = (IOHibernateImageHeader *)EFI_PAGES_TO_SIZE (ImageHeaderPage);
 
  //
  // Legacy note. In legacy implementations systemTableOffset was unconditionally overwritten
  // with a wrong address due to ImageHeader->runtimePages not being converted from pages to bytes.
  // Fortunately systemTableOffset was unused when kIOHibernateHandoffTypeMemoryMap is unspecified.
  // systemTableOffset is calculated properly by boot.efi itself starting from 10.6.8 at least,
  // and thus this assignment was useless in the first place.
  //
 
  //
  // At this step we have two routes.
  //
  // 1. Remove newly generated memory map from hibernate image to let XNU use the original mapping.
  //    This is known to work well on most systems primarily because Windows requires UEFI firmware
  //    to preserve physical memory consistency at S4 wake. "On a UEFI platform, firmware runtime memory
  //    must be consistent across S4 sleep state transitions, in both size and location.", see:
  //    https://docs.microsoft.com/en-us/windows-hardware/design/device-experiences/oem-uefi#hibernation-state-s4-transition-requirements
  // 2. Recover memory map just as we do for normal booting. This created issues on some types of firmware
  //    resulting in unusual memory maps after S4 wake. In other cases, this should not immediately
  //    break things. XNU will entirely remove efiRuntimeServicesPageStart/efiRuntimeServicesPageSize
  //    mapping and our new memory map entries will unconditionally overwrite previous ones. In case
  //    no physical memory changes happened, this should work fine.
  //
  Handoff = (IOHibernateHandoff *)EFI_PAGES_TO_SIZE ((UINTN)ImageHeader->handoffPages);
  while (Handoff->type != kIOHibernateHandoffTypeEnd) {
    if (Handoff->type == kIOHibernateHandoffTypeMemoryMap) {
      if (BootCompat->Settings.DiscardHibernateMap) {
        //
        // Route 1. Discard the new memory map here, and let XNU use what it had.
        // It is unknown whether there are still examples of firmware that need this.
        //
        Handoff->type = kIOHibernateHandoffType;
      } else {
        //
        // Route 2. Recovery memory protection types just as normal boot.
        //
 
        if (BootCompat->KernelState.VmMapDescSize == 0) {
          RUNTIME_DEBUG ((DEBUG_ERROR, "OCABC: Saved descriptor size cannot be 0\n"));
          return;
        }
 
        //
        // TODO: If we try to work on hibernation support with relocation block
        // We will need to add a call similar to AppleRelocationVirtualize here.
        //
 
        if (BootCompat->Settings.AvoidRuntimeDefrag) {
          //
          // I think we should not be there, but ideally all quirks are relatively independent.
          //
          RestoreProtectedRtMemoryTypes (
            &BootCompat->RtReloc,
            Handoff->bytecount,
            BootCompat->KernelState.VmMapDescSize,
            (EFI_MEMORY_DESCRIPTOR *)(UINTN)Handoff->data
            );
        }
      }
 
      break;
    }
 
    Handoff = (IOHibernateHandoff *)((UINTN)Handoff + sizeof (Handoff) + Handoff->bytecount);
  }
 
  //
  // TODO: To support hibernation with relocation block we will need to add a call similar
  // to AppleRelocationRebase here.
  //
}
 
VOID
AppleMapPrepareMemoryPool (
  IN OUT BOOT_COMPAT_CONTEXT  *BootCompat
  )
{
  EFI_STATUS  Status;
 
  if (  !BootCompat->Settings.SetupVirtualMap
     || (BootCompat->KernelState.VmContext.MemoryPool != NULL))
  {
    return;
  }
 
  Status = VmAllocateMemoryPool (
             &BootCompat->KernelState.VmContext,
             OC_DEFAULT_VMEM_PAGE_COUNT,
             BootCompat->ServicePtrs.GetMemoryMap
             );
 
  if (EFI_ERROR (Status)) {
    DEBUG ((DEBUG_ERROR, "OCABC: Memory pool allocation failure - %r\n", Status));
  }
}
 
VOID
AppleMapPrepareBooterState (
  IN OUT BOOT_COMPAT_CONTEXT  *BootCompat,
  IN OUT EFI_LOADED_IMAGE     *LoadedImage,
  IN     EFI_GET_MEMORY_MAP   GetMemoryMap  OPTIONAL
  )
{
  EFI_STATUS  Status;
 
  //
  // Allocate memory pool if needed.
  //
  AppleMapPrepareMemoryPool (
    BootCompat
    );
 
  if (BootCompat->Settings.AvoidRuntimeDefrag) {
    if (BootCompat->KernelState.SysTableRtArea == 0) {
      //
      // Allocate RT data pages for copy of UEFI system table for kernel.
      // This one also has to be 32-bit due to XNU BootArgs structure.
      // The reason for this allocation to be required is because XNU uses static
      // mapping for directly passed pointers (see ProtectRtMemoryFromRelocation).
      //
      BootCompat->KernelState.SysTableRtArea     = BASE_4GB;
      BootCompat->KernelState.SysTableRtAreaSize = gST->Hdr.HeaderSize;
      Status                                     = OcAllocatePagesFromTop (
                                                     EfiRuntimeServicesData,
                                                     EFI_SIZE_TO_PAGES (gST->Hdr.HeaderSize),
                                                     &BootCompat->KernelState.SysTableRtArea,
                                                     GetMemoryMap,
                                                     NULL,
                                                     NULL
                                                     );
      if (EFI_ERROR (Status)) {
        DEBUG ((
          DEBUG_ERROR,
          "OCABC: Failed to allocate system table memory - %r\n",
          Status
          ));
        BootCompat->KernelState.SysTableRtArea = 0;
        return;
      }
 
      DEBUG ((DEBUG_VERBOSE, "OCABC: Allocated SysTableRtArea %p\n", BootCompat->KernelState.SysTableRtArea));
 
      //
      // Copy UEFI system table to the new location.
      //
      CopyMem (
        (VOID *)(UINTN)BootCompat->KernelState.SysTableRtArea,
        gST,
        gST->Hdr.HeaderSize
        );
      //
      // Remember physical configuration table location.
      //
      BootCompat->KernelState.ConfigurationTable = gST->ConfigurationTable;
    }
 
    //
    // Assign loaded image with custom system table.
    //
    LoadedImage->SystemTable =
      (EFI_SYSTEM_TABLE *)(UINTN)BootCompat->KernelState.SysTableRtArea;
  }
}
 
EFI_STATUS
AppleMapPrepareMemState (
  IN OUT BOOT_COMPAT_CONTEXT    *BootCompat,
  IN     UINTN                  MemoryMapSize,
  IN     UINTN                  DescriptorSize,
  IN     UINT32                 DescriptorVersion,
  IN     EFI_MEMORY_DESCRIPTOR  *MemoryMap
  )
{
  EFI_STATUS             Status;
  UINTN                  NumEntries;
  UINTN                  Index;
  EFI_MEMORY_DESCRIPTOR  *Desc;
 
  //
  // Protect RT areas from relocation by marking then MemMapIO.
  //
  if (BootCompat->Settings.AvoidRuntimeDefrag) {
    ProtectRtMemoryFromRelocation (
      &BootCompat->RtReloc,
      MemoryMapSize,
      DescriptorSize,
      MemoryMap,
      BootCompat->KernelState.SysTableRtArea,
      BootCompat->KernelState.SysTableRtAreaSize
      );
  }
 
  //
  // macOS 10.4 and 10.5 always call SetVirtualAddressMap, even when using a relocation block.
  // Perform adjustment of virtual addresses here to their final positions.
  //
  if (BootCompat->KernelState.RelocationBlockLegacy) {
    Desc       = MemoryMap;
    NumEntries = MemoryMapSize / DescriptorSize;
 
    for (Index = 0; Index < NumEntries; ++Index) {
      if (  (Desc->VirtualStart >= BootCompat->KernelState.RelocationBlock + BootCompat->KernelState.RelocationBlockUsed)
         && (Desc->VirtualStart < BootCompat->KernelState.RelocationBlock + ESTIMATED_KERNEL_SIZE))
      {
        Desc->VirtualStart -= BootCompat->KernelState.RelocationBlock - KERNEL_BASE_PADDR;
      }
 
      Desc = NEXT_MEMORY_DESCRIPTOR (Desc, DescriptorSize);
    }
  }
 
  //
  // Virtualize RT services with all needed fixes.
  //
  if (BootCompat->Settings.SetupVirtualMap) {
    Status = PerformRtMemoryVirtualMapping (
               &BootCompat->KernelState,
               MemoryMapSize,
               DescriptorSize,
               DescriptorVersion,
               MemoryMap
               );
  } else {
    Status = gRT->SetVirtualAddressMap (
                    MemoryMapSize,
                    DescriptorSize,
                    DescriptorVersion,
                    MemoryMap
                    );
  }
 
  //
  // Copy now virtualized UEFI system table for boot.efi to hand it to the kernel.
  //
  if (BootCompat->Settings.AvoidRuntimeDefrag) {
    CopyMem (
      (VOID *)(UINTN)BootCompat->KernelState.SysTableRtArea,
      gST,
      gST->Hdr.HeaderSize
      );
  }
 
  return Status;
}