ArmPkg/ArmMmuLib ARM: handle unmapped sections when updating permissions

The ARM ArmMmuLib code currently does not take into account that
setting permissions on a region should take into account that a
region may not be mapped yet to begin with.

So when updating a section descriptor whose old value is zero,
pass in the address explicitly.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/ArmPkg/Library/ArmMmuLib/Arm/ArmMmuLibCore.c b/ArmPkg/Library/ArmMmuLib/Arm/ArmMmuLibCore.c
index ec51e072ab..889b22867d 100644
--- a/ArmPkg/Library/ArmMmuLib/Arm/ArmMmuLibCore.c
+++ b/ArmPkg/Library/ArmMmuLib/Arm/ArmMmuLibCore.c
@@ -695,8 +695,12 @@ UpdateSectionEntries (
     } else {

       // still a section entry

 

-      // mask off appropriate fields

-      Descriptor = CurrentDescriptor & ~EntryMask;

+      if (CurrentDescriptor != 0) {

+        // mask off appropriate fields

+        Descriptor = CurrentDescriptor & ~EntryMask;

+      } else {

+        Descriptor = ((UINTN)FirstLevelIdx + i) << TT_DESCRIPTOR_SECTION_BASE_SHIFT;

+      }

 

       // mask in new attributes and/or permissions

       Descriptor |= EntryValue;