[RFC PATCH 09/10] MdeModulePkg/DxeIpl: Use memory attribute PPI to remap the stack NX

["Ard Biesheuvel" <ardb@kernel.org>]

If the associated PCD is set to TRUE, use the memory attribute PPI to
remap the stack non-executable. This provides a generic method for doing
so, which will be used by ARM and AArch64 as well once they move to the
generic DxeIpl handoff implementation.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 MdeModulePkg/Core/DxeIplPeim/DxeHandoff.c | 29 ++++++++++++++++++--
 MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf   |  5 +++-
 2 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/MdeModulePkg/Core/DxeIplPeim/DxeHandoff.c b/MdeModulePkg/Core/DxeIplPeim/DxeHandoff.c
index a0f85ebea56e6cba..22caabb02840ba88 100644
--- a/MdeModulePkg/Core/DxeIplPeim/DxeHandoff.c
+++ b/MdeModulePkg/Core/DxeIplPeim/DxeHandoff.c
@@ -2,12 +2,15 @@
   Generic version of arch-specific functionality for DxeLoad.
 
 Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2023, Google, LLC. All rights reserved.<BR>
 SPDX-License-Identifier: BSD-2-Clause-Patent
 
 **/
 
 #include "DxeIpl.h"
 
+#include <Ppi/MemoryAttribute.h>
+
 /**
    Transfers control to DxeCore.
 
@@ -25,9 +28,10 @@ HandOffToDxeCore (
   IN EFI_PEI_HOB_POINTERS  HobList
   )
 {
-  VOID        *BaseOfStack;
-  VOID        *TopOfStack;
-  EFI_STATUS  Status;
+  VOID                        *BaseOfStack;
+  VOID                        *TopOfStack;
+  EFI_STATUS                  Status;
+  EDKII_MEMORY_ATTRIBUTE_PPI  *MemoryPpi;
 
   //
   // Allocate 128KB for the Stack
@@ -35,6 +39,25 @@ HandOffToDxeCore (
   BaseOfStack = AllocatePages (EFI_SIZE_TO_PAGES (STACK_SIZE));
   ASSERT (BaseOfStack != NULL);
 
+  if (PcdGetBool (PcdSetNxForStack)) {
+    Status = PeiServicesLocatePpi (
+               &gEdkiiMemoryAttributePpiGuid,
+               0,
+               NULL,
+               (VOID **)&MemoryPpi
+               );
+    ASSERT_EFI_ERROR (Status);
+
+    Status = MemoryPpi->SetPermissions (
+                          MemoryPpi,
+                          (UINTN)BaseOfStack,
+                          STACK_SIZE,
+                          EFI_MEMORY_XP,
+                          0
+                          );
+    ASSERT_EFI_ERROR (Status);
+  }
+
   //
   // Compute the top of the stack we were allocated. Pre-allocate a UINTN
   // for safety.
diff --git a/MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf b/MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf
index 60c998be6c1bad01..7126a96d8378d1f8 100644
--- a/MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf
+++ b/MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf
@@ -91,6 +91,7 @@ [Ppis]
   gEfiPeiMemoryDiscoveredPpiGuid         ## SOMETIMES_CONSUMES
   gEdkiiPeiBootInCapsuleOnDiskModePpiGuid  ## SOMETIMES_CONSUMES
   gEdkiiPeiCapsuleOnDiskPpiGuid            ## SOMETIMES_CONSUMES # Consumed on firmware update boot path
+  gEdkiiMemoryAttributePpiGuid             ## SOMETIMES_CONSUMES
 
 [Guids]
   ## SOMETIMES_CONSUMES ## Variable:L"MemoryTypeInformation"
@@ -117,10 +118,12 @@ [Pcd.IA32,Pcd.X64]
   gEfiMdeModulePkgTokenSpaceGuid.PcdGhcbSize                            ## CONSUMES
 
 [Pcd.IA32,Pcd.X64,Pcd.ARM,Pcd.AARCH64]
-  gEfiMdeModulePkgTokenSpaceGuid.PcdSetNxForStack               ## SOMETIMES_CONSUMES
   gEfiMdeModulePkgTokenSpaceGuid.PcdDxeNxMemoryProtectionPolicy ## SOMETIMES_CONSUMES
   gEfiMdeModulePkgTokenSpaceGuid.PcdImageProtectionPolicy       ## SOMETIMES_CONSUMES
 
+[Pcd]
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSetNxForStack               ## SOMETIMES_CONSUMES
+
 [Depex]
   gEfiPeiLoadFilePpiGuid AND gEfiPeiMasterBootModePpiGuid
 
-- 
2.39.2