ArmPkg/ArmMmuLib ARM: Clear individual permission bits

Currently, the MMU code that is supposed to clear the RO or XP
attributes from a region just clears both unconditionally. This
approximates the desired behavior to some extent, but it does mean that
setting the RO bit first on a code region, and then clearing the XP bit
results both RO and XP being cleared, and we end up with writable code,
and avoiding that is the point of all these protections.

Once we introduce RP support, this will only get worse, so let's fix
this up, by reshuffling the attribute update code to take the entry mask
from the caller, and use the mask to preserve other attributes when
clearing RO or XP.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Leif Lindholm <quic_llindhol@quicinc.com>

0 files changed, 0 insertions, 0 deletions