UefiCpuPkg/CpuMpPei: Add GDT migration support (CVE-2019-11098)

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=1614

Moves the GDT to permanent memory in a memory discovered
callback. This is done to ensure the GDT authenticated in
pre-memory is not fetched from outside a verified location
after the permanent memory transition.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Signed-off-by: Michael Kubacki <michael.a.kubacki@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

UefiCpuPkg/CpuMpPei/CpuMpPei.c

@@ -429,6 +429,43 @@ GetGdtr (
   AsmReadGdtr ((IA32_DESCRIPTOR *)Buffer);
 }
 
+/**
+  Migrates the Global Descriptor Table (GDT) to permanent memory.
+
+  @retval   EFI_SUCCESS           The GDT was migrated successfully.
+  @retval   EFI_OUT_OF_RESOURCES  The GDT could not be migrated due to lack of available memory.
+
+**/
+EFI_STATUS
+MigrateGdt (
+  VOID
+  )
+{
+  EFI_STATUS          Status;
+  UINTN               GdtBufferSize;
+  IA32_DESCRIPTOR     Gdtr;
+  VOID                *GdtBuffer;
+
+  AsmReadGdtr ((IA32_DESCRIPTOR *) &Gdtr);
+  GdtBufferSize = sizeof (IA32_SEGMENT_DESCRIPTOR) -1 + Gdtr.Limit + 1;
+
+  Status =  PeiServicesAllocatePool (
+              GdtBufferSize,
+              &GdtBuffer
+              );
+  ASSERT (GdtBuffer != NULL);
+  if (EFI_ERROR (Status)) {
+    return EFI_OUT_OF_RESOURCES;
+  }
+
+  GdtBuffer = ALIGN_POINTER (GdtBuffer, sizeof (IA32_SEGMENT_DESCRIPTOR));
+  CopyMem (GdtBuffer, (VOID *) Gdtr.Base, Gdtr.Limit + 1);
+  Gdtr.Base = (UINTN) GdtBuffer;
+  AsmWriteGdtr (&Gdtr);
+
+  return EFI_SUCCESS;
+}
+
 /**
   Initializes CPU exceptions handlers for the sake of stack switch requirement.