[PATCH 4/5] ArmPkg/ArmMmuLib ARM: implement memory permission control routines

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

Now that we have the prerequisite functionality available in ArmMmuLib,
wire it up into ArmSetMemoryRegionNoExec, ArmClearMemoryRegionNoExec,
ArmSetMemoryRegionReadOnly and ArmClearMemoryRegionReadOnly. This is
used by the non-executable stack feature that is configured by DxeIpl.

NOTE: The current implementation will not combine RO and XP attributes,
      i.e., setting/clearing a region no-exec will unconditionally
      clear the read-only attribute, and vice versa. Currently, we
      only use ArmSetMemoryRegionNoExec(), so for now, we should be
      able to live with this.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 ArmPkg/Library/ArmMmuLib/Arm/ArmMmuLibCore.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/ArmPkg/Library/ArmMmuLib/Arm/ArmMmuLibCore.c b/ArmPkg/Library/ArmMmuLib/Arm/ArmMmuLibCore.c
index 1112660b434e..55601328d93e 100644
--- a/ArmPkg/Library/ArmMmuLib/Arm/ArmMmuLibCore.c
+++ b/ArmPkg/Library/ArmMmuLib/Arm/ArmMmuLibCore.c
@@ -761,40 +761,40 @@ ArmSetMemoryAttributes (
   return Status;
 }
 
-RETURN_STATUS
+EFI_STATUS
 ArmSetMemoryRegionNoExec (
   IN  EFI_PHYSICAL_ADDRESS      BaseAddress,
   IN  UINT64                    Length
   )
 {
-  return RETURN_UNSUPPORTED;
+  return ArmSetMemoryAttributes (BaseAddress, Length, EFI_MEMORY_XP);
 }
 
-RETURN_STATUS
+EFI_STATUS
 ArmClearMemoryRegionNoExec (
   IN  EFI_PHYSICAL_ADDRESS      BaseAddress,
   IN  UINT64                    Length
   )
 {
-  return RETURN_UNSUPPORTED;
+  return ArmSetMemoryAttributes (BaseAddress, Length, 0);
 }
 
-RETURN_STATUS
+EFI_STATUS
 ArmSetMemoryRegionReadOnly (
   IN  EFI_PHYSICAL_ADDRESS      BaseAddress,
   IN  UINT64                    Length
   )
 {
-  return RETURN_UNSUPPORTED;
+  return ArmSetMemoryAttributes (BaseAddress, Length, EFI_MEMORY_RO);
 }
 
-RETURN_STATUS
+EFI_STATUS
 ArmClearMemoryRegionReadOnly (
   IN  EFI_PHYSICAL_ADDRESS      BaseAddress,
   IN  UINT64                    Length
   )
 {
-  return RETURN_UNSUPPORTED;
+  return ArmSetMemoryAttributes (BaseAddress, Length, 0);
 }
 
 RETURN_STATUS
-- 
2.7.4