UefiCpuPkg CpuDxe GDT init question?

[Andrew Fish <afish@apple.com>]

I'm trying to understand why gdtPtr.Base is casting to (UINT32)? 
1) gdtPtr.Base is a a UINTN
2) It is legal for AllocateRuntimePool() to return an address > 4GB

It seems like the code should just cast to (UINTN)?


https://github.com/tianocore/edk2/blob/master/UefiCpuPkg/CpuDxe/CpuGdt.c#L151



VOID
InitGlobalDescriptorTable (
  VOID
  )
{
  GDT_ENTRIES *gdt;
  IA32_DESCRIPTOR gdtPtr;

  //
  // Allocate Runtime Data for the GDT
  //
  gdt = AllocateRuntimePool (sizeof (GdtTemplate) + 8);
  ASSERT (gdt != NULL);
  gdt = ALIGN_POINTER (gdt, 8);

  //
  // Initialize all GDT entries
  //
  CopyMem (gdt, &GdtTemplate, sizeof (GdtTemplate));

  //
  // Write GDT register
  //
  gdtPtr.Base = (UINT32)(UINTN)(VOID*) gdt;
  gdtPtr.Limit = (UINT16) (sizeof (GdtTemplate) - 1);
  AsmWriteGdtr (&gdtPtr);

Thanks,

Andrew Fish