ArmPkg:CpuDxe: Use the Memory Protection HOB

Description

Project Mu doesn't used the memory protection fixed at build PCDs.

- [x] Impacts functionality?
  - **Functionality** - Does the change ultimately impact how firmware functions?
  - Examples: Add a new library, publish a new PPI, update an algorithm, ...
- [ ] Impacts security?
  - **Security** - Does the change have a direct security impact on an application,
    flow, or firmware?
  - Examples: Crypto algorithm change, buffer overflow fix, parameter
    validation improvement, ...
- [ ] Breaking change?
  - **Breaking change** - Will anyone consuming this change experience a break
    in build or boot behavior?
  - Examples: Add a new library class, move a module to a different repo, call
    a function in a new library class in a pre-existing module, ...
- [ ] Includes tests?
  - **Tests** - Does the change include any explicit test code?
  - Examples: Unit tests, integration tests, robot tests, ...
- [ ] Includes documentation?
  - **Documentation** - Does the change contain explicit documentation additions
    outside direct code modifications (and comments)?
  - Examples: Update readme file, add feature readme file, link to documentation
    on an a separate Web page, ...

How This Was Tested

Running QemuSbsaPkg

Integration Instructions

N/A

Author: TaylorBeebe

ArmPkg/ArmPkg.dsc

@@ -96,6 +96,7 @@
   ArmSvcLib|ArmPkg/Library/ArmSvcLib/ArmSvcLib.inf              # MU_CHANGE
   SafeIntLib|MdePkg/Library/BaseSafeIntLib/BaseSafeIntLib.inf   # MU_CHANGE
   NULL|MdePkg/Library/StackCheckLibNull/StackCheckLibNull.inf # MU_CHANGE: /GS and -fstack-protector support
+  DxeMemoryProtectionHobLib|MdeModulePkg/Library/MemoryProtectionHobLibNull/DxeMemoryProtectionHobLibNull.inf # MU_CHANGE
 
 [LibraryClasses.common.PEIM]
   HobLib|MdePkg/Library/PeiHobLib/PeiHobLib.inf

ArmPkg/Drivers/CpuDxe/CpuDxe.c

@@ -12,6 +12,7 @@
 #include <Guid/IdleLoopEvent.h>
 
 #include <Library/MemoryAllocationLib.h>
+#include <Library/DxeMemoryProtectionHobLib.h> // MU_CHANGE
 
 BOOLEAN  mIsFlushingGCD;
 
@@ -252,7 +253,10 @@ RemapUnusedMemoryNx (
   EFI_STATUS             Status;
 
   TestBit = LShiftU64 (1, EfiBootServicesData);
-  if ((PcdGet64 (PcdDxeNxMemoryProtectionPolicy) & TestBit) == 0) {
+  // MU_CHANGE START: Use memory protection HOB instead of PCD
+  // if ((PcdGet64 (PcdDxeNxMemoryProtectionPolicy) & TestBit) == 0) {
+  if (gDxeMps.NxProtectionPolicy.Fields.EfiConventionalMemory == 0) {
+    // MU_CHANGE END
     return;
   }
 

ArmPkg/Drivers/CpuDxe/CpuDxe.inf

@@ -52,6 +52,7 @@
   PeCoffGetEntryPointLib
   UefiDriverEntryPoint
   UefiLib
+  DxeMemoryProtectionHobLib # MU_CHANGE
 
 [Protocols]
   gEfiCpuArchProtocolGuid
@@ -65,7 +66,7 @@
 
 [Pcd.common]
   gArmTokenSpaceGuid.PcdVFPEnabled
-  gEfiMdeModulePkgTokenSpaceGuid.PcdDxeNxMemoryProtectionPolicy
+  # gEfiMdeModulePkgTokenSpaceGuid.PcdDxeNxMemoryProtectionPolicy # MU_CHANGE
 
 [FeaturePcd.common]
   gArmTokenSpaceGuid.PcdDebuggerExceptionSupport