From 7572ec0727663d4491323fc1719b71951826fa41 Mon Sep 17 00:00:00 2001
From: Chris Fernald <chfernal@microsoft.com>
Date: Wed, 19 Jun 2024 15:09:54 -0700
Subject: [PATCH] Do not treat RP memory as valid for access (#40)

## Description

When accessing memory, treat read protected memory the same as
non-resident VAs. There shouldn't be a need to read or write to these
addresses and if so in the future they should be sup[ported through
physical read/write instructions.

- [x] Impacts functionality?
- [ ] Impacts security?
- [ ] Breaking change?
- [ ] Includes tests?
- [ ] Includes documentation?

## How This Was Tested

Tested in SBSA

## Integration Instructions

N/A
---
 .../Library/DebugAgent/DebugAgentDxe.c        | 19 ++++++-------------
 1 file changed, 6 insertions(+), 13 deletions(-)

diff --git a/DebuggerFeaturePkg/Library/DebugAgent/DebugAgentDxe.c b/DebuggerFeaturePkg/Library/DebugAgent/DebugAgentDxe.c
index 11e1a8d..89fd09e 100644
--- a/DebuggerFeaturePkg/Library/DebugAgent/DebugAgentDxe.c
+++ b/DebuggerFeaturePkg/Library/DebugAgent/DebugAgentDxe.c
@@ -459,24 +459,17 @@ AccessMemory (
         return FALSE;
       }
 
-      if (Write && (Attributes & EFI_MEMORY_RO)) {
-        Status = mMemoryAttributeProtocol->ClearMemoryAttributes (
-                                             mMemoryAttributeProtocol,
-                                             Address & ~EFI_PAGE_MASK,
-                                             EFI_PAGE_SIZE,
-                                             EFI_MEMORY_RO | EFI_MEMORY_RP
-                                             );
-        if (EFI_ERROR (Status)) {
-          return FALSE;
-        }
+      if (Attributes & EFI_MEMORY_RP) {
+        // Treat RP memory as non-valid.
+        return FALSE;
+      }
 
-        AttributesChanged = TRUE;
-      } else if (Attributes & EFI_MEMORY_RP) {
+      if (Write && (Attributes & EFI_MEMORY_RO)) {
         Status = mMemoryAttributeProtocol->ClearMemoryAttributes (
                                              mMemoryAttributeProtocol,
                                              Address & ~EFI_PAGE_MASK,
                                              EFI_PAGE_SIZE,
-                                             EFI_MEMORY_RP
+                                             EFI_MEMORY_RO
                                              );
         if (EFI_ERROR (Status)) {
           return FALSE;