MdeModulePkg/DxeCore: implement memory protection policy

This implements a DXE memory protection policy that ensures that regions
that don't require executable permissions are mapped with the non-exec
attribute set.

First of all, it iterates over all entries in the UEFI memory map, and
removes executable permissions according to the configured DXE memory
protection policy, as recorded in PcdDxeNxMemoryProtectionPolicy.

Secondly, it sets or clears the non-executable attribute when allocating
or freeing pages, both for page based or pool based allocations.

Note that this complements the image protection facility, which applies
strict permissions to BootServicesCode/RuntimeServicesCode regions when
the section alignment allows it. The memory protection configured by this
patch operates on non-code regions only.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

MdeModulePkg/Core/Dxe/DxeMain.h

@@ -2949,4 +2949,28 @@ MemoryProtectionExitBootServicesCallback (
   VOID
   );
 
+/**
+  Manage memory permission attributes on a memory range, according to the
+  configured DXE memory protection policy.
+
+  @param  OldType           The old memory type of the range
+  @param  NewType           The new memory type of the range
+  @param  Memory            The base address of the range
+  @param  Length            The size of the range (in bytes)
+
+  @return EFI_SUCCESS       If the the CPU arch protocol is not installed yet
+  @return EFI_SUCCESS       If no DXE memory protection policy has been configured
+  @return EFI_SUCCESS       If OldType and NewType use the same permission attributes
+  @return other             Return value of gCpu->SetMemoryAttributes()
+
+**/
+EFI_STATUS
+EFIAPI
+ApplyMemoryProtectionPolicy (
+  IN  EFI_MEMORY_TYPE       OldType,
+  IN  EFI_MEMORY_TYPE       NewType,
+  IN  EFI_PHYSICAL_ADDRESS  Memory,
+  IN  UINT64                Length
+  );
+
 #endif