Re: [PATCH 2/2] MdeModulePkg/Core: Fix feature conflict between NX and Stack guard

["Zeng, Star" <star.zeng@intel.com>]

A quick minor comment.
GetHobList() could be used instead of EfiGetSystemConfigurationTable (&gEfiHobListGuid, &HobList).

Thanks,
Star
-----Original Message-----
From: Wu, Hao A 
Sent: Tuesday, March 6, 2018 8:11 PM
To: edk2-devel@lists.01.org
Cc: Wu, Hao A <hao.a.wu@intel.com>; Wang, Jian J <jian.j.wang@intel.com>; Zeng, Star <star.zeng@intel.com>; Dong, Eric <eric.dong@intel.com>; Yao, Jiewen <jiewen.yao@intel.com>; Ni, Ruiyu <ruiyu.ni@intel.com>
Subject: [PATCH 2/2] MdeModulePkg/Core: Fix feature conflict between NX and Stack guard

If enabled, NX memory protection feature will mark some types of active memory as NX (non-executable), which includes the first page of the stack.
This will overwrite the attributes of the first page of the stack if the stack guard feature is also enabled.

The solution is to override the attributes setting to the first page of the stack by adding back the 'EFI_MEMORY_RP' attribute when the stack guard feature is enabled.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
---
 MdeModulePkg/Core/Dxe/DxeMain.inf             |  4 +-
 MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c | 61 +++++++++++++++++++++++++++
 2 files changed, 64 insertions(+), 1 deletion(-)

diff --git a/MdeModulePkg/Core/Dxe/DxeMain.inf b/MdeModulePkg/Core/Dxe/DxeMain.inf
index 7334780326..d2e7360ed4 100644
--- a/MdeModulePkg/Core/Dxe/DxeMain.inf
+++ b/MdeModulePkg/Core/Dxe/DxeMain.inf
@@ -3,7 +3,7 @@
 #
 #  It provides an implementation of DXE Core that is compliant with DXE CIS.
 #
-#  Copyright (c) 2006 - 2017, Intel Corporation. All rights reserved.<BR>
+#  Copyright (c) 2006 - 2018, Intel Corporation. All rights 
+reserved.<BR>
 #  This program and the accompanying materials  #  are licensed and made available under the terms and conditions of the BSD License  #  which accompanies this distribution.  The full text of the license may be found at @@ -130,6 +130,7 @@
   gEfiPropertiesTableGuid                       ## SOMETIMES_PRODUCES   ## SystemTable
   gEfiMemoryAttributesTableGuid                 ## SOMETIMES_PRODUCES   ## SystemTable
   gEfiEndOfDxeEventGroupGuid                    ## SOMETIMES_CONSUMES   ## Event
+  gEfiHobMemoryAllocStackGuid                   ## SOMETIMES_CONSUMES   ## SystemTable
 
 [Ppis]
   gEfiVectorHandoffInfoPpiGuid                  ## UNDEFINED # HOB
@@ -198,6 +199,7 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdHeapGuardPageType                       ## CONSUMES
   gEfiMdeModulePkgTokenSpaceGuid.PcdHeapGuardPoolType                       ## CONSUMES
   gEfiMdeModulePkgTokenSpaceGuid.PcdHeapGuardPropertyMask                   ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdCpuStackGuard                           ## CONSUMES
 
 # [Hob]
 # RESOURCE_DESCRIPTOR   ## CONSUMES
diff --git a/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c b/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
index a2ea445eef..a6de22d3af 100644
--- a/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
+++ b/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
@@ -801,6 +801,11 @@ InitializeDxeNxMemoryProtectionPolicy (
   UINT64                            Attributes;
   LIST_ENTRY                        *Link;
   EFI_GCD_MAP_ENTRY                 *Entry;
+  VOID                              *HobList;
+  EFI_PEI_HOB_POINTERS              Hob;
+  EFI_HOB_MEMORY_ALLOCATION         *MemoryHob;
+  EFI_PHYSICAL_ADDRESS              StackBase;
+  BOOLEAN                           StackBaseFound;
 
   //
   // Get the EFI memory map.
@@ -832,6 +837,45 @@ InitializeDxeNxMemoryProtectionPolicy (
   } while (Status == EFI_BUFFER_TOO_SMALL);
   ASSERT_EFI_ERROR (Status);
 
+  StackBase = 0;
+  StackBaseFound = FALSE;
+  if (PcdGetBool (PcdCpuStackGuard)) {
+    //
+    // Get the base of stack from Hob.
+    //
+    Status = EfiGetSystemConfigurationTable (&gEfiHobListGuid, &HobList);
+    if (!EFI_ERROR (Status)) {
+      for (Hob.Raw = HobList; !END_OF_HOB_LIST (Hob); Hob.Raw = GET_NEXT_HOB (Hob)) {
+        if (GET_HOB_TYPE(Hob) == EFI_HOB_TYPE_MEMORY_ALLOCATION) {
+          MemoryHob = Hob.MemoryAllocation;
+          if (CompareGuid(&gEfiHobMemoryAllocStackGuid, &MemoryHob->AllocDescriptor.Name)) {
+            DEBUG ((
+              DEBUG_INFO,
+              "%a: StackBase = 0x%016lx  StackSize = 0x%016lx\n",
+              __FUNCTION__,
+              MemoryHob->AllocDescriptor.MemoryBaseAddress,
+              MemoryHob->AllocDescriptor.MemoryLength
+              ));
+
+            StackBase = MemoryHob->AllocDescriptor.MemoryBaseAddress;
+            //
+            // Ensure the base of the stack is page-size aligned.
+            //
+            ASSERT ((StackBase & EFI_PAGE_MASK) == 0);
+            StackBaseFound = TRUE;
+            break;
+          }
+        }
+      }
+    }
+
+    //
+    // Ensure the base of stack can be found from Hob when stack guard is
+    // enabled.
+    //
+    ASSERT (StackBaseFound);
+  }
+
   DEBUG ((
     DEBUG_INFO,
     "%a: applying strict permissions to active memory regions\n", @@ -864,6 +908,23 @@ InitializeDxeNxMemoryProtectionPolicy (
           EFI_PAGES_TO_SIZE (1),
           EFI_MEMORY_RP | Attributes);
       }
+
+      if (StackBaseFound &&
+          (StackBase >= MemoryMapEntry->PhysicalStart &&
+           StackBase <  MemoryMapEntry->PhysicalStart +
+                        LShiftU64 (MemoryMapEntry->NumberOfPages, EFI_PAGE_SHIFT)) &&
+          PcdGetBool (PcdCpuStackGuard)) {
+
+        //
+        // Add EFI_MEMORY_RP attribute for the first page of the stack if stack
+        // guard is enabled.
+        //
+        SetUefiImageMemoryAttributes (
+          StackBase,
+          EFI_PAGES_TO_SIZE (1),
+          EFI_MEMORY_RP | Attributes);
+      }
+
     }
     MemoryMapEntry = NEXT_MEMORY_DESCRIPTOR (MemoryMapEntry, DescriptorSize);
   }
--
2.12.0.windows.1