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

[mirror_edk2.git] / UefiCpuPkg / CpuMpPei / CpuMpPei.c

diff --git a/UefiCpuPkg/CpuMpPei/CpuMpPei.c b/UefiCpuPkg/CpuMpPei/CpuMpPei.c
index 07ccbe7c6a91febda2ce9169eac46db57d9c8f73..d07540cf747126b6ae32e32a15021135ac1146c0 100644 (file)
--- a/UefiCpuPkg/CpuMpPei/CpuMpPei.c
+++ b/UefiCpuPkg/CpuMpPei/CpuMpPei.c
@@ -429,6 +429,43 @@ GetGdtr (
   AsmReadGdtr ((IA32_DESCRIPTOR *)Buffer);\r
 }\r
 \r
+/**\r
+  Migrates the Global Descriptor Table (GDT) to permanent memory.\r
+\r
+  @retval   EFI_SUCCESS           The GDT was migrated successfully.\r
+  @retval   EFI_OUT_OF_RESOURCES  The GDT could not be migrated due to lack of available memory.\r
+\r
+**/\r
+EFI_STATUS\r
+MigrateGdt (\r
+  VOID\r
+  )\r
+{\r
+  EFI_STATUS          Status;\r
+  UINTN               GdtBufferSize;\r
+  IA32_DESCRIPTOR     Gdtr;\r
+  VOID                *GdtBuffer;\r
+\r
+  AsmReadGdtr ((IA32_DESCRIPTOR *) &Gdtr);\r
+  GdtBufferSize = sizeof (IA32_SEGMENT_DESCRIPTOR) -1 + Gdtr.Limit + 1;\r
+\r
+  Status =  PeiServicesAllocatePool (\r
+              GdtBufferSize,\r
+              &GdtBuffer\r
+              );\r
+  ASSERT (GdtBuffer != NULL);\r
+  if (EFI_ERROR (Status)) {\r
+    return EFI_OUT_OF_RESOURCES;\r
+  }\r
+\r
+  GdtBuffer = ALIGN_POINTER (GdtBuffer, sizeof (IA32_SEGMENT_DESCRIPTOR));\r
+  CopyMem (GdtBuffer, (VOID *) Gdtr.Base, Gdtr.Limit + 1);\r
+  Gdtr.Base = (UINTN) GdtBuffer;\r
+  AsmWriteGdtr (&Gdtr);\r
+\r
+  return EFI_SUCCESS;\r
+}\r
+\r
 /**\r
   Initializes CPU exceptions handlers for the sake of stack switch requirement.\r
 \r