From f7e077768fe47075130bfa774c88c331d2ad54ff Mon Sep 17 00:00:00 2001
From: "Wang, Jian J" <jian.j.wang@intel.com>
Date: Sat, 26 Aug 2017 09:08:10 +0800
Subject: [PATCH] MdeModulePkg/MdeModulePkg.dec,.uni: Add NULL pointer
 detection PCD

PCD PcdNullPointerDetectionPropertyMask is a bitmask used to control the
NULL address detection functionality in code for different phases.

If enabled, accessing NULL address in UEFI or SMM code can be caught
as a page fault exception.

    BIT0    - Enable NULL pointer detection for UEFI.
    BIT1    - Enable NULL pointer detection for SMM.
    BIT2..6 - Reserved for future uses.
    BIT7    - Disable NULL pointer detection just after EndOfDxe. This is a
              workaround for those unsolvable NULL access issues in
              OptionROM, boot loader, etc. It can also help to avoid
              unnecessary exception caused by legacy memory (0-4095) access
              after EndOfDxe, such as Windows 7 boot on Qemu.

Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Ayellet Wolman <ayellet.wolman@intel.com>
Suggested-by: Ayellet Wolman <ayellet.wolman@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
---
 MdeModulePkg/MdeModulePkg.dec | 13 +++++++++++++
 MdeModulePkg/MdeModulePkg.uni | 13 +++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/MdeModulePkg/MdeModulePkg.dec b/MdeModulePkg/MdeModulePkg.dec
index a3c0633ee1..9248d10da8 100644
--- a/MdeModulePkg/MdeModulePkg.dec
+++ b/MdeModulePkg/MdeModulePkg.dec
@@ -867,6 +867,19 @@
   # @ValidList  0x80000006 | 0x03058002
   gEfiMdeModulePkgTokenSpaceGuid.PcdErrorCodeSetVariable|0x03058002|UINT32|0x30001040
 
+  ## Mask to control the NULL address detection in code for different phases.
+  #  If enabled, accessing NULL address in UEFI or SMM code can be caught.<BR><BR>
+  #    BIT0    - Enable NULL pointer detection for UEFI.<BR>
+  #    BIT1    - Enable NULL pointer detection for SMM.<BR>
+  #    BIT2..6 - Reserved for future uses.<BR>
+  #    BIT7    - Disable NULL pointer detection just after EndOfDxe. <BR>
+  #              This is a workaround for those unsolvable NULL access issues in
+  #              OptionROM, boot loader, etc. It can also help to avoid unnecessary
+  #              exception caused by legacy memory (0-4095) access after EndOfDxe,
+  #              such as Windows 7 boot on Qemu.<BR>
+  # @Prompt Enable NULL address detection.
+  gEfiMdeModulePkgTokenSpaceGuid.PcdNullPointerDetectionPropertyMask|0x0|UINT8|0x30001050
+
 [PcdsFixedAtBuild, PcdsPatchableInModule]
   ## Dynamic type PCD can be registered callback function for Pcd setting action.
   #  PcdMaxPeiPcdCallBackNumberPerPcdEntry indicates the maximum number of callback function
diff --git a/MdeModulePkg/MdeModulePkg.uni b/MdeModulePkg/MdeModulePkg.uni
index d6015de75f..f8b31694ba 100644
--- a/MdeModulePkg/MdeModulePkg.uni
+++ b/MdeModulePkg/MdeModulePkg.uni
@@ -1127,3 +1127,16 @@
                                                                                                      "enabled on AMD processors supporting the Secure Encrypted Virtualization (SEV) feature.\n"
                                                                                                      "This mask should be applied when creating 1:1 virtual to physical mapping tables."
 
+#string STR_gEfiMdeModulePkgTokenSpaceGuid_PcdNullPointerDetectionPropertyMask_PROMPT  #language en-US "Enable NULL pointer detection"
+
+#string STR_gEfiMdeModulePkgTokenSpaceGuid_PcdNullPointerDetectionPropertyMask_HELP    #language en-US "Mask to control the NULL address detection in code for different phases.\n"
+                                                                                                       " If enabled, accessing NULL address in UEFI or SMM code can be caught.\n\n"
+                                                                                                       "   BIT0    - Enable NULL pointer detection for UEFI.\n"
+                                                                                                       "   BIT1    - Enable NULL pointer detection for SMM.\n"
+                                                                                                       "   BIT2..6 - Reserved for future uses.\n"
+                                                                                                       "   BIT7    - Disable NULL pointer detection just after EndOfDxe."
+                                                                                                       " This is a workaround for those unsolvable NULL access issues in"
+                                                                                                       " OptionROM, boot loader, etc. It can also help to avoid unnecessary"
+                                                                                                       " exception caused by legacy memory (0-4095) access after EndOfDxe,"
+                                                                                                       " such as Windows 7 boot on Qemu.\n"
+
-- 
2.39.2