[Patch V4 02/21] UefiCpuPkg/CpuPageTableLib: Add check for input Length

["duntan" <dun.tan@intel.com>]

Add check for input Length in PageTableMap (). Return
RETURN_SUCCESS when input Length is 0.

Signed-off-by: Dun Tan <dun.tan@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
---
 UefiCpuPkg/Include/Library/CpuPageTableLib.h         | 4 ++--
 UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c | 6 +++++-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/UefiCpuPkg/Include/Library/CpuPageTableLib.h b/UefiCpuPkg/Include/Library/CpuPageTableLib.h
index 2dc9b7d18e..5f44ece548 100644
--- a/UefiCpuPkg/Include/Library/CpuPageTableLib.h
+++ b/UefiCpuPkg/Include/Library/CpuPageTableLib.h
@@ -1,7 +1,7 @@
 /** @file
   Public include file for PageTableLib library.
 
-  Copyright (c) 2022, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2022 - 2023, Intel Corporation. All rights reserved.<BR>
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
 **/
@@ -81,7 +81,7 @@ typedef enum {
   @retval RETURN_BUFFER_TOO_SMALL   The buffer is too small for page table creation/updating.
                                     BufferSize is updated to indicate the expected buffer size.
                                     Caller may still get RETURN_BUFFER_TOO_SMALL with the new BufferSize.
-  @retval RETURN_SUCCESS            PageTable is created/updated successfully.
+  @retval RETURN_SUCCESS            PageTable is created/updated successfully or the input Length is 0.
 **/
 RETURN_STATUS
 EFIAPI
diff --git a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
index 52535e5a8d..218068a3e1 100644
--- a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
+++ b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
@@ -544,7 +544,7 @@ PageTableLibMapInLevel (
   @retval RETURN_BUFFER_TOO_SMALL   The buffer is too small for page table creation/updating.
                                     BufferSize is updated to indicate the expected buffer size.
                                     Caller may still get RETURN_BUFFER_TOO_SMALL with the new BufferSize.
-  @retval RETURN_SUCCESS            PageTable is created/updated successfully.
+  @retval RETURN_SUCCESS            PageTable is created/updated successfully or the input Length is 0.
 **/
 RETURN_STATUS
 EFIAPI
@@ -567,6 +567,10 @@ PageTableMap (
   IA32_PAGE_LEVEL     MaxLeafLevel;
   IA32_MAP_ATTRIBUTE  ParentAttribute;
 
+  if (Length == 0) {
+    return RETURN_SUCCESS;
+  }
+
   if ((PagingMode == Paging32bit) || (PagingMode == PagingPae) || (PagingMode >= PagingModeMax)) {
     //
     // 32bit paging is never supported.
-- 
2.31.1.windows.1