[PATCH] MdeModulePkg/Pcdpeim: Fixed PcdGetPtr() caused memory wasting.

["gaoliming" <gaoliming@byosoft.com.cn>]

From: zengzhi <zengzhi@byosoft.com.cn>

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=2964

GuidHob was added to cache the VariableGuid,VariableName,VariableData.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Dandan Bi <dandan.bi@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>

Signed-off-by: zengzhi <zengzhi@byosoft.com.cn>
---
 MdeModulePkg/Universal/PCD/Pei/Service.c | 55 ++++++++++++++++++++----
 1 file changed, 46 insertions(+), 9 deletions(-)

diff --git a/MdeModulePkg/Universal/PCD/Pei/Service.c b/MdeModulePkg/Universal/PCD/Pei/Service.c
index 5b037353ad..c13be25a31 100644
--- a/MdeModulePkg/Universal/PCD/Pei/Service.c
+++ b/MdeModulePkg/Universal/PCD/Pei/Service.c
@@ -452,6 +452,7 @@ BuildPcdDatabase (
   return Database;
 }
 
+EFI_GUID mGetVariableGuid = { 0x2f5a9b0e, 0xc338, 0x4f95, { 0xa8, 0x39, 0xf3, 0x8d, 0x27, 0xa2, 0x80, 0xc2 } };
 /**
   The function is provided by PCD PEIM and PCD DXE driver to
   do the work of reading a HII variable from variable service.
@@ -474,13 +475,36 @@ GetHiiVariable (
 {
   UINTN      Size;
   EFI_STATUS Status;
-  VOID       *Buffer;
+  UINTN      DataLength;
+  VOID       *HobData;
+  UINT8      *GetGuidHobData;
+  EFI_HOB_GUID_TYPE               *GuidHob;
   EFI_PEI_READ_ONLY_VARIABLE2_PPI *VariablePpi;
-
+  // Get the variable from the Guid Hob first, return it if found,
+  // and use the getVarible() function if not found.
+  GuidHob =  GetFirstGuidHob (&mGetVariableGuid);
+  while (GuidHob != NULL) {
+    GetGuidHobData = GET_GUID_HOB_DATA (GuidHob);
+    if (CompareGuid((EFI_GUID *) (GetGuidHobData + sizeof(UINT32)), VariableGuid) &&
+      StrnCmp((VOID *) (GetGuidHobData + sizeof(UINT32) + sizeof(EFI_GUID)), VariableName, StrLen(VariableName)) == 0){
+      //  If the variableGuid and variableName in the HOB are the same as
+      //  the input variableGuid and variableName, the VariableData and Size
+      //  in the HOB are returned as output values.
+      *VariableSize = *((UINT32 *) GetGuidHobData);
+      *VariableData = (VOID *) (GetGuidHobData + sizeof(UINT32) + sizeof(EFI_GUID) + StrSize(VariableName));
+      return EFI_SUCCESS;
+    } else {
+      GuidHob = GetNextGuidHob (&mGetVariableGuid, GET_NEXT_HOB (GuidHob));
+     }
+  }
+  // Load the PeiReadOnlyVariable2 PPI, which provides a service to read EFI Variable.
+  // If the load is unsuccessful, the function cannot be continued.
   Status = PeiServicesLocatePpi (&gEfiPeiReadOnlyVariable2PpiGuid, 0, NULL, (VOID **) &VariablePpi);
   ASSERT_EFI_ERROR (Status);
 
   Size = 0;
+  // EFI Variable is read with an empty Buffer, and if an EFI Variable exists,
+  // it returns the actual required Buffer size.
   Status = VariablePpi->GetVariable (
                           VariablePpi,
                           VariableName,
@@ -491,22 +515,35 @@ GetHiiVariable (
                           );
 
   if (Status == EFI_BUFFER_TOO_SMALL) {
-    Status = PeiServicesAllocatePool (Size, &Buffer);
-    ASSERT_EFI_ERROR (Status);
-
+    //  DataLength
+    //  -------------------------------------------------------------
+    //  | VariableSize | VariableGuid | VariableName | VariableData |
+    //  -------------------------------------------------------------
+    DataLength = sizeof(UINT32) + sizeof(EFI_GUID) + StrSize(VariableName) + Size;
+    HobData = BuildGuidHob(
+                 &mGetVariableGuid,
+                 DataLength
+                 );
+    // The VariableSize VariableGuid, VariableName, VariableData copy to GuidHob in turn.
+    CopyMem (HobData, (VOID *) &Size, sizeof(Size));
+    HobData = (VOID *) ((UINT8 *) HobData + sizeof(UINT32));
+    CopyMem (HobData, VariableGuid, sizeof(EFI_GUID));
+    HobData = (VOID *) ((UINT8 *) HobData + sizeof (EFI_GUID));
+    CopyMem (HobData, VariableName, StrSize(VariableName));
+    HobData = (VOID *) ((UINT8 *) HobData + StrSize(VariableName));
+    // Read EFI Variable into Guidhob. After a successful read,
+    // the read data is returned as the output value.
     Status = VariablePpi->GetVariable (
                               VariablePpi,
                               (UINT16 *) VariableName,
                               (EFI_GUID *) VariableGuid,
                               NULL,
                               &Size,
-                              Buffer
+                              HobData
                               );
     ASSERT_EFI_ERROR (Status);
-
     *VariableSize = Size;
-    *VariableData = Buffer;
-
+    *VariableData = HobData;
     return EFI_SUCCESS;
   }
 
-- 
2.26.2.windows.1