The list of locked variables is traversed at runtime, hence we must

convert the list when transferring from physical to virtual mode.

Contributed-under: TianoCore Contribution Agreement 1.0

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@14403 6f19259b-4bc3-4df7-8a09-765794883524

1 files changed, 502 insertions, 479 deletions

diff --git a/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableDxe.c b/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableDxe.c
index 3cb2c6bcf3..2aa2946904 100644
--- a/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableDxe.c
+++ b/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableDxe.c
@@ -1,479 +1,502 @@
-/** @file

-

-  Implement all four UEFI Runtime Variable services for the nonvolatile

-  and volatile storage space and install variable architecture protocol.

-  

-Copyright (c) 2006 - 2013, Intel Corporation. All rights reserved.<BR>

-This program and the accompanying materials                          

-are licensed and made available under the terms and conditions of the BSD License         

-which accompanies this distribution.  The full text of the license may be found at        

-http://opensource.org/licenses/bsd-license.php                                            

-

-THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,                     

-WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.             

-

-**/

-

-#include "Variable.h"

-

-extern VARIABLE_STORE_HEADER   *mNvVariableCache;

-extern VARIABLE_INFO_ENTRY     *gVariableInfo;

-EFI_HANDLE                     mHandle                    = NULL;

-EFI_EVENT                      mVirtualAddressChangeEvent = NULL;

-EFI_EVENT                      mFtwRegistration           = NULL;

-extern BOOLEAN                 mEndOfDxe;

-EDKII_VARIABLE_LOCK_PROTOCOL   mVariableLock              = { VariableLockRequestToLock };

-

-/**

-  Return TRUE if ExitBootServices () has been called.

-  

-  @retval TRUE If ExitBootServices () has been called.

-**/

-BOOLEAN

-AtRuntime (

-  VOID

-  )

-{

-  return EfiAtRuntime ();

-}

-

-

-/**

-  Initializes a basic mutual exclusion lock.

-

-  This function initializes a basic mutual exclusion lock to the released state 

-  and returns the lock.  Each lock provides mutual exclusion access at its task 

-  priority level.  Since there is no preemption or multiprocessor support in EFI,

-  acquiring the lock only consists of raising to the locks TPL.

-  If Lock is NULL, then ASSERT().

-  If Priority is not a valid TPL value, then ASSERT().

-

-  @param  Lock       A pointer to the lock data structure to initialize.

-  @param  Priority   EFI TPL is associated with the lock.

-

-  @return The lock.

-

-**/

-EFI_LOCK *

-InitializeLock (

-  IN OUT EFI_LOCK                         *Lock,

-  IN     EFI_TPL                          Priority

-  )

-{

-  return EfiInitializeLock (Lock, Priority);

-}

-

-

-/**

-  Acquires lock only at boot time. Simply returns at runtime.

-

-  This is a temperary function that will be removed when

-  EfiAcquireLock() in UefiLib can handle the call in UEFI

-  Runtimer driver in RT phase.

-  It calls EfiAcquireLock() at boot time, and simply returns

-  at runtime.

-

-  @param  Lock         A pointer to the lock to acquire.

-

-**/

-VOID

-AcquireLockOnlyAtBootTime (

-  IN EFI_LOCK                             *Lock

-  )

-{

-  if (!AtRuntime ()) {

-    EfiAcquireLock (Lock);

-  }

-}

-

-

-/**

-  Releases lock only at boot time. Simply returns at runtime.

-

-  This is a temperary function which will be removed when

-  EfiReleaseLock() in UefiLib can handle the call in UEFI

-  Runtimer driver in RT phase.

-  It calls EfiReleaseLock() at boot time and simply returns

-  at runtime.

-

-  @param  Lock         A pointer to the lock to release.

-

-**/

-VOID

-ReleaseLockOnlyAtBootTime (

-  IN EFI_LOCK                             *Lock

-  )

-{

-  if (!AtRuntime ()) {

-    EfiReleaseLock (Lock);

-  }

-}

-

-/**

-  Retrive the Fault Tolerent Write protocol interface.

-

-  @param[out] FtwProtocol       The interface of Ftw protocol

-

-  @retval EFI_SUCCESS           The FTW protocol instance was found and returned in FtwProtocol.

-  @retval EFI_NOT_FOUND         The FTW protocol instance was not found.

-  @retval EFI_INVALID_PARAMETER SarProtocol is NULL.

-

-**/

-EFI_STATUS

-GetFtwProtocol (

-  OUT VOID                                **FtwProtocol

-  )

-{

-  EFI_STATUS                              Status;

-

-  //

-  // Locate Fault Tolerent Write protocol

-  //

-  Status = gBS->LocateProtocol (

-                  &gEfiFaultTolerantWriteProtocolGuid,

-                  NULL,

-                  FtwProtocol

-                  );                    

-  return Status;

-}

-

-/**

-  Retrive the FVB protocol interface by HANDLE.

-

-  @param[in]  FvBlockHandle     The handle of FVB protocol that provides services for

-                                reading, writing, and erasing the target block.

-  @param[out] FvBlock           The interface of FVB protocol

-

-  @retval EFI_SUCCESS           The interface information for the specified protocol was returned.

-  @retval EFI_UNSUPPORTED       The device does not support the FVB protocol.

-  @retval EFI_INVALID_PARAMETER FvBlockHandle is not a valid EFI_HANDLE or FvBlock is NULL.

-  

-**/

-EFI_STATUS

-GetFvbByHandle (

-  IN  EFI_HANDLE                          FvBlockHandle,

-  OUT EFI_FIRMWARE_VOLUME_BLOCK_PROTOCOL  **FvBlock

-  )

-{

-  //

-  // To get the FVB protocol interface on the handle

-  //

-  return gBS->HandleProtocol (

-                FvBlockHandle,

-                &gEfiFirmwareVolumeBlockProtocolGuid,

-                (VOID **) FvBlock

-                );

-}

-

-

-/**

-  Function returns an array of handles that support the FVB protocol

-  in a buffer allocated from pool. 

-

-  @param[out]  NumberHandles    The number of handles returned in Buffer.

-  @param[out]  Buffer           A pointer to the buffer to return the requested

-                                array of  handles that support FVB protocol.

-

-  @retval EFI_SUCCESS           The array of handles was returned in Buffer, and the number of

-                                handles in Buffer was returned in NumberHandles.

-  @retval EFI_NOT_FOUND         No FVB handle was found.

-  @retval EFI_OUT_OF_RESOURCES  There is not enough pool memory to store the matching results.

-  @retval EFI_INVALID_PARAMETER NumberHandles is NULL or Buffer is NULL.

-  

-**/

-EFI_STATUS

-GetFvbCountAndBuffer (

-  OUT UINTN                               *NumberHandles,

-  OUT EFI_HANDLE                          **Buffer

-  )

-{

-  EFI_STATUS                              Status;

-

-  //

-  // Locate all handles of Fvb protocol

-  //

-  Status = gBS->LocateHandleBuffer (

-                  ByProtocol,

-                  &gEfiFirmwareVolumeBlockProtocolGuid,

-                  NULL,

-                  NumberHandles,

-                  Buffer

-                  );

-  return Status;

-}

-

-

-/**

-  Notification function of EVT_SIGNAL_VIRTUAL_ADDRESS_CHANGE.

-

-  This is a notification function registered on EVT_SIGNAL_VIRTUAL_ADDRESS_CHANGE event.

-  It convers pointer to new virtual address.

-

-  @param  Event        Event whose notification function is being invoked.

-  @param  Context      Pointer to the notification function's context.

-

-**/

-VOID

-EFIAPI

-VariableClassAddressChangeEvent (

-  IN EFI_EVENT                            Event,

-  IN VOID                                 *Context

-  )

-{

-  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->FvbInstance->GetBlockSize);

-  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->FvbInstance->GetPhysicalAddress);

-  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->FvbInstance->GetAttributes);

-  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->FvbInstance->SetAttributes);

-  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->FvbInstance->Read);

-  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->FvbInstance->Write);

-  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->FvbInstance->EraseBlocks);

-  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->FvbInstance);

-  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->PlatformLangCodes);

-  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->LangCodes);

-  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->PlatformLang);

-  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->VariableGlobal.NonVolatileVariableBase);

-  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->VariableGlobal.VolatileVariableBase);

-  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->VariableGlobal.HobVariableBase);

-  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal);

-  EfiConvertPointer (0x0, (VOID **) &mNvVariableCache);  

-}

-

-

-/**

-  Notification function of EVT_GROUP_READY_TO_BOOT event group.

-

-  This is a notification function registered on EVT_GROUP_READY_TO_BOOT event group.

-  When the Boot Manager is about to load and execute a boot option, it reclaims variable

-  storage if free size is below the threshold.

-

-  @param  Event        Event whose notification function is being invoked.

-  @param  Context      Pointer to the notification function's context.

-

-**/

-VOID

-EFIAPI

-OnReadyToBoot (

-  EFI_EVENT                               Event,

-  VOID                                    *Context

-  )

-{

-  //

-  // Set the End Of DXE bit in case the EFI_END_OF_DXE_EVENT_GROUP_GUID event is not signaled.

-  //

-  mEndOfDxe = TRUE;

-  ReclaimForOS ();

-  if (FeaturePcdGet (PcdVariableCollectStatistics)) {

-    gBS->InstallConfigurationTable (&gEfiVariableGuid, gVariableInfo);

-  }

-}

-

-/**

-  Notification function of EFI_END_OF_DXE_EVENT_GROUP_GUID event group.

-

-  This is a notification function registered on EFI_END_OF_DXE_EVENT_GROUP_GUID event group.

-

-  @param  Event        Event whose notification function is being invoked.

-  @param  Context      Pointer to the notification function's context.

-

-**/

-VOID

-EFIAPI

-OnEndOfDxe (

-  EFI_EVENT                               Event,

-  VOID                                    *Context

-  )

-{

-  mEndOfDxe = TRUE;

-}

-

-/**

-  Fault Tolerant Write protocol notification event handler.

-

-  Non-Volatile variable write may needs FTW protocol to reclaim when 

-  writting variable.

-

-  @param[in] Event    Event whose notification function is being invoked.

-  @param[in] Context  Pointer to the notification function's context.

-  

-**/

-VOID

-EFIAPI

-FtwNotificationEvent (

-  IN  EFI_EVENT                           Event,

-  IN  VOID                                *Context

-  )

-{

-  EFI_STATUS                              Status;

-  EFI_FIRMWARE_VOLUME_BLOCK_PROTOCOL      *FvbProtocol;

-  EFI_FAULT_TOLERANT_WRITE_PROTOCOL       *FtwProtocol;

-  EFI_PHYSICAL_ADDRESS                    NvStorageVariableBase;

-  EFI_GCD_MEMORY_SPACE_DESCRIPTOR         GcdDescriptor;

-  EFI_PHYSICAL_ADDRESS                    BaseAddress;

-  UINT64                                  Length;

-  EFI_PHYSICAL_ADDRESS                    VariableStoreBase;

-  UINT64                                  VariableStoreLength;

-

-  //

-  // Ensure FTW protocol is installed.

-  //

-  Status = GetFtwProtocol ((VOID**) &FtwProtocol);

-  if (EFI_ERROR (Status)) {

-    return ;

-  }

-  

-  //

-  // Find the proper FVB protocol for variable.

-  //

-  NvStorageVariableBase = (EFI_PHYSICAL_ADDRESS) PcdGet64 (PcdFlashNvStorageVariableBase64);

-  if (NvStorageVariableBase == 0) {

-    NvStorageVariableBase = (EFI_PHYSICAL_ADDRESS) PcdGet32 (PcdFlashNvStorageVariableBase);

-  }

-  Status = GetFvbInfoByAddress (NvStorageVariableBase, NULL, &FvbProtocol);

-  if (EFI_ERROR (Status)) {

-    return ;

-  }

-  mVariableModuleGlobal->FvbInstance = FvbProtocol;

-

-  //

-  // Mark the variable storage region of the FLASH as RUNTIME.

-  //

-  VariableStoreBase   = mVariableModuleGlobal->VariableGlobal.NonVolatileVariableBase;

-  VariableStoreLength = ((VARIABLE_STORE_HEADER *)(UINTN)VariableStoreBase)->Size;

-  BaseAddress = VariableStoreBase & (~EFI_PAGE_MASK);

-  Length      = VariableStoreLength + (VariableStoreBase - BaseAddress);

-  Length      = (Length + EFI_PAGE_SIZE - 1) & (~EFI_PAGE_MASK);

-

-  Status      = gDS->GetMemorySpaceDescriptor (BaseAddress, &GcdDescriptor);

-  if (EFI_ERROR (Status)) {

-    DEBUG ((DEBUG_WARN, "Variable driver failed to add EFI_MEMORY_RUNTIME attribute to Flash.\n"));

-  } else {

-    Status = gDS->SetMemorySpaceAttributes (

-                    BaseAddress,

-                    Length,

-                    GcdDescriptor.Attributes | EFI_MEMORY_RUNTIME

-                    );

-    if (EFI_ERROR (Status)) {

-      DEBUG ((DEBUG_WARN, "Variable driver failed to add EFI_MEMORY_RUNTIME attribute to Flash.\n"));

-    }

-  }

-  

-  Status = VariableWriteServiceInitialize ();

-  ASSERT_EFI_ERROR (Status);

- 

-  //

-  // Install the Variable Write Architectural protocol.

-  //

-  Status = gBS->InstallProtocolInterface (

-                  &mHandle,

-                  &gEfiVariableWriteArchProtocolGuid, 

-                  EFI_NATIVE_INTERFACE,

-                  NULL

-                  );

-  ASSERT_EFI_ERROR (Status);

-  

-  //

-  // Close the notify event to avoid install gEfiVariableWriteArchProtocolGuid again.

-  //

-  gBS->CloseEvent (Event);

-

-}

-

-

-/**

-  Variable Driver main entry point. The Variable driver places the 4 EFI

-  runtime services in the EFI System Table and installs arch protocols 

-  for variable read and write services being availible. It also registers

-  a notification function for an EVT_SIGNAL_VIRTUAL_ADDRESS_CHANGE event.

-

-  @param[in] ImageHandle    The firmware allocated handle for the EFI image.  

-  @param[in] SystemTable    A pointer to the EFI System Table.

-  

-  @retval EFI_SUCCESS       Variable service successfully initialized.

-

-**/

-EFI_STATUS

-EFIAPI

-VariableServiceInitialize (

-  IN EFI_HANDLE                         ImageHandle,

-  IN EFI_SYSTEM_TABLE                   *SystemTable

-  )

-{

-  EFI_STATUS                            Status;

-  EFI_EVENT                             ReadyToBootEvent;

-  EFI_EVENT                             EndOfDxeEvent;

-

-  Status = VariableCommonInitialize ();

-  ASSERT_EFI_ERROR (Status);

-

-  Status = gBS->InstallMultipleProtocolInterfaces (

-                  &mHandle,

-                  &gEdkiiVariableLockProtocolGuid,

-                  &mVariableLock,

-                  NULL

-                  );

-  ASSERT_EFI_ERROR (Status);

-

-  SystemTable->RuntimeServices->GetVariable         = VariableServiceGetVariable;

-  SystemTable->RuntimeServices->GetNextVariableName = VariableServiceGetNextVariableName;

-  SystemTable->RuntimeServices->SetVariable         = VariableServiceSetVariable;

-  SystemTable->RuntimeServices->QueryVariableInfo   = VariableServiceQueryVariableInfo;

-    

-  //

-  // Now install the Variable Runtime Architectural protocol on a new handle.

-  //

-  Status = gBS->InstallProtocolInterface (

-                  &mHandle,

-                  &gEfiVariableArchProtocolGuid, 

-                  EFI_NATIVE_INTERFACE,

-                  NULL

-                  );

-  ASSERT_EFI_ERROR (Status);

-

-  //

-  // Register FtwNotificationEvent () notify function.

-  // 

-  EfiCreateProtocolNotifyEvent (

-    &gEfiFaultTolerantWriteProtocolGuid,

-    TPL_CALLBACK,

-    FtwNotificationEvent,

-    (VOID *)SystemTable,

-    &mFtwRegistration

-    );

-

-  Status = gBS->CreateEventEx (

-                  EVT_NOTIFY_SIGNAL,

-                  TPL_NOTIFY,

-                  VariableClassAddressChangeEvent,

-                  NULL,

-                  &gEfiEventVirtualAddressChangeGuid,

-                  &mVirtualAddressChangeEvent

-                  );

-  ASSERT_EFI_ERROR (Status);

-

-  //

-  // Register the event handling function to reclaim variable for OS usage.

-  //

-  Status = EfiCreateEventReadyToBootEx (

-             TPL_NOTIFY, 

-             OnReadyToBoot, 

-             NULL, 

-             &ReadyToBootEvent

-             );

-  ASSERT_EFI_ERROR (Status);

-

-  //

-  // Register the event handling function to set the End Of DXE flag.

-  //

-  Status = gBS->CreateEventEx (

-                  EVT_NOTIFY_SIGNAL,

-                  TPL_NOTIFY,

-                  OnEndOfDxe,

-                  NULL,

-                  &gEfiEndOfDxeEventGroupGuid,

-                  &EndOfDxeEvent

-                  );

-  ASSERT_EFI_ERROR (Status);

-

-  return EFI_SUCCESS;

-}

-

+/** @file
+
+  Implement all four UEFI Runtime Variable services for the nonvolatile
+  and volatile storage space and install variable architecture protocol.
+  
+Copyright (C) 2013, Red Hat, Inc.
+Copyright (c) 2006 - 2013, Intel Corporation. All rights reserved.<BR>
+This program and the accompanying materials                          
+are licensed and made available under the terms and conditions of the BSD License         
+which accompanies this distribution.  The full text of the license may be found at        
+http://opensource.org/licenses/bsd-license.php                                            
+
+THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,                     
+WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.             
+
+**/
+
+#include "Variable.h"
+
+extern VARIABLE_STORE_HEADER   *mNvVariableCache;
+extern VARIABLE_INFO_ENTRY     *gVariableInfo;
+EFI_HANDLE                     mHandle                    = NULL;
+EFI_EVENT                      mVirtualAddressChangeEvent = NULL;
+EFI_EVENT                      mFtwRegistration           = NULL;
+extern LIST_ENTRY              mLockedVariableList;
+extern BOOLEAN                 mEndOfDxe;
+EDKII_VARIABLE_LOCK_PROTOCOL   mVariableLock              = { VariableLockRequestToLock };
+
+/**
+  Return TRUE if ExitBootServices () has been called.
+  
+  @retval TRUE If ExitBootServices () has been called.
+**/
+BOOLEAN
+AtRuntime (
+  VOID
+  )
+{
+  return EfiAtRuntime ();
+}
+
+
+/**
+  Initializes a basic mutual exclusion lock.
+
+  This function initializes a basic mutual exclusion lock to the released state 
+  and returns the lock.  Each lock provides mutual exclusion access at its task 
+  priority level.  Since there is no preemption or multiprocessor support in EFI,
+  acquiring the lock only consists of raising to the locks TPL.
+  If Lock is NULL, then ASSERT().
+  If Priority is not a valid TPL value, then ASSERT().
+
+  @param  Lock       A pointer to the lock data structure to initialize.
+  @param  Priority   EFI TPL is associated with the lock.
+
+  @return The lock.
+
+**/
+EFI_LOCK *
+InitializeLock (
+  IN OUT EFI_LOCK                         *Lock,
+  IN     EFI_TPL                          Priority
+  )
+{
+  return EfiInitializeLock (Lock, Priority);
+}
+
+
+/**
+  Acquires lock only at boot time. Simply returns at runtime.
+
+  This is a temperary function that will be removed when
+  EfiAcquireLock() in UefiLib can handle the call in UEFI
+  Runtimer driver in RT phase.
+  It calls EfiAcquireLock() at boot time, and simply returns
+  at runtime.
+
+  @param  Lock         A pointer to the lock to acquire.
+
+**/
+VOID
+AcquireLockOnlyAtBootTime (
+  IN EFI_LOCK                             *Lock
+  )
+{
+  if (!AtRuntime ()) {
+    EfiAcquireLock (Lock);
+  }
+}
+
+
+/**
+  Releases lock only at boot time. Simply returns at runtime.
+
+  This is a temperary function which will be removed when
+  EfiReleaseLock() in UefiLib can handle the call in UEFI
+  Runtimer driver in RT phase.
+  It calls EfiReleaseLock() at boot time and simply returns
+  at runtime.
+
+  @param  Lock         A pointer to the lock to release.
+
+**/
+VOID
+ReleaseLockOnlyAtBootTime (
+  IN EFI_LOCK                             *Lock
+  )
+{
+  if (!AtRuntime ()) {
+    EfiReleaseLock (Lock);
+  }
+}
+
+/**
+  Retrive the Fault Tolerent Write protocol interface.
+
+  @param[out] FtwProtocol       The interface of Ftw protocol
+
+  @retval EFI_SUCCESS           The FTW protocol instance was found and returned in FtwProtocol.
+  @retval EFI_NOT_FOUND         The FTW protocol instance was not found.
+  @retval EFI_INVALID_PARAMETER SarProtocol is NULL.
+
+**/
+EFI_STATUS
+GetFtwProtocol (
+  OUT VOID                                **FtwProtocol
+  )
+{
+  EFI_STATUS                              Status;
+
+  //
+  // Locate Fault Tolerent Write protocol
+  //
+  Status = gBS->LocateProtocol (
+                  &gEfiFaultTolerantWriteProtocolGuid,
+                  NULL,
+                  FtwProtocol
+                  );                    
+  return Status;
+}
+
+/**
+  Retrive the FVB protocol interface by HANDLE.
+
+  @param[in]  FvBlockHandle     The handle of FVB protocol that provides services for
+                                reading, writing, and erasing the target block.
+  @param[out] FvBlock           The interface of FVB protocol
+
+  @retval EFI_SUCCESS           The interface information for the specified protocol was returned.
+  @retval EFI_UNSUPPORTED       The device does not support the FVB protocol.
+  @retval EFI_INVALID_PARAMETER FvBlockHandle is not a valid EFI_HANDLE or FvBlock is NULL.
+  
+**/
+EFI_STATUS
+GetFvbByHandle (
+  IN  EFI_HANDLE                          FvBlockHandle,
+  OUT EFI_FIRMWARE_VOLUME_BLOCK_PROTOCOL  **FvBlock
+  )
+{
+  //
+  // To get the FVB protocol interface on the handle
+  //
+  return gBS->HandleProtocol (
+                FvBlockHandle,
+                &gEfiFirmwareVolumeBlockProtocolGuid,
+                (VOID **) FvBlock
+                );
+}
+
+
+/**
+  Function returns an array of handles that support the FVB protocol
+  in a buffer allocated from pool. 
+
+  @param[out]  NumberHandles    The number of handles returned in Buffer.
+  @param[out]  Buffer           A pointer to the buffer to return the requested
+                                array of  handles that support FVB protocol.
+
+  @retval EFI_SUCCESS           The array of handles was returned in Buffer, and the number of
+                                handles in Buffer was returned in NumberHandles.
+  @retval EFI_NOT_FOUND         No FVB handle was found.
+  @retval EFI_OUT_OF_RESOURCES  There is not enough pool memory to store the matching results.
+  @retval EFI_INVALID_PARAMETER NumberHandles is NULL or Buffer is NULL.
+  
+**/
+EFI_STATUS
+GetFvbCountAndBuffer (
+  OUT UINTN                               *NumberHandles,
+  OUT EFI_HANDLE                          **Buffer
+  )
+{
+  EFI_STATUS                              Status;
+
+  //
+  // Locate all handles of Fvb protocol
+  //
+  Status = gBS->LocateHandleBuffer (
+                  ByProtocol,
+                  &gEfiFirmwareVolumeBlockProtocolGuid,
+                  NULL,
+                  NumberHandles,
+                  Buffer
+                  );
+  return Status;
+}
+
+
+/**
+  Notification function of EVT_SIGNAL_VIRTUAL_ADDRESS_CHANGE.
+
+  This is a notification function registered on EVT_SIGNAL_VIRTUAL_ADDRESS_CHANGE event.
+  It convers pointer to new virtual address.
+
+  @param  Event        Event whose notification function is being invoked.
+  @param  Context      Pointer to the notification function's context.
+
+**/
+VOID
+EFIAPI
+VariableClassAddressChangeEvent (
+  IN EFI_EVENT                            Event,
+  IN VOID                                 *Context
+  )
+{
+  LIST_ENTRY     *Link;
+  VARIABLE_ENTRY *Entry;
+  EFI_STATUS     Status;
+
+  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->FvbInstance->GetBlockSize);
+  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->FvbInstance->GetPhysicalAddress);
+  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->FvbInstance->GetAttributes);
+  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->FvbInstance->SetAttributes);
+  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->FvbInstance->Read);
+  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->FvbInstance->Write);
+  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->FvbInstance->EraseBlocks);
+  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->FvbInstance);
+  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->PlatformLangCodes);
+  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->LangCodes);
+  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->PlatformLang);
+  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->VariableGlobal.NonVolatileVariableBase);
+  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->VariableGlobal.VolatileVariableBase);
+  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal->VariableGlobal.HobVariableBase);
+  EfiConvertPointer (0x0, (VOID **) &mVariableModuleGlobal);
+  EfiConvertPointer (0x0, (VOID **) &mNvVariableCache);  
+
+  //
+  // in the list of locked variables, convert the name pointers first
+  //
+  for ( Link = GetFirstNode (&mLockedVariableList)
+      ; !IsNull (&mLockedVariableList, Link)
+      ; Link = GetNextNode (&mLockedVariableList, Link)
+      ) {
+    Entry = BASE_CR (Link, VARIABLE_ENTRY, Link);
+    Status = EfiConvertPointer (0x0, (VOID **) &Entry->Name);
+    ASSERT_EFI_ERROR (Status);
+  }
+  //
+  // second, convert the list itself using UefiRuntimeLib
+  //
+  Status = EfiConvertList (0x0, &mLockedVariableList);
+  ASSERT_EFI_ERROR (Status);
+}
+
+
+/**
+  Notification function of EVT_GROUP_READY_TO_BOOT event group.
+
+  This is a notification function registered on EVT_GROUP_READY_TO_BOOT event group.
+  When the Boot Manager is about to load and execute a boot option, it reclaims variable
+  storage if free size is below the threshold.
+
+  @param  Event        Event whose notification function is being invoked.
+  @param  Context      Pointer to the notification function's context.
+
+**/
+VOID
+EFIAPI
+OnReadyToBoot (
+  EFI_EVENT                               Event,
+  VOID                                    *Context
+  )
+{
+  //
+  // Set the End Of DXE bit in case the EFI_END_OF_DXE_EVENT_GROUP_GUID event is not signaled.
+  //
+  mEndOfDxe = TRUE;
+  ReclaimForOS ();
+  if (FeaturePcdGet (PcdVariableCollectStatistics)) {
+    gBS->InstallConfigurationTable (&gEfiVariableGuid, gVariableInfo);
+  }
+}
+
+/**
+  Notification function of EFI_END_OF_DXE_EVENT_GROUP_GUID event group.
+
+  This is a notification function registered on EFI_END_OF_DXE_EVENT_GROUP_GUID event group.
+
+  @param  Event        Event whose notification function is being invoked.
+  @param  Context      Pointer to the notification function's context.
+
+**/
+VOID
+EFIAPI
+OnEndOfDxe (
+  EFI_EVENT                               Event,
+  VOID                                    *Context
+  )
+{
+  mEndOfDxe = TRUE;
+}
+
+/**
+  Fault Tolerant Write protocol notification event handler.
+
+  Non-Volatile variable write may needs FTW protocol to reclaim when 
+  writting variable.
+
+  @param[in] Event    Event whose notification function is being invoked.
+  @param[in] Context  Pointer to the notification function's context.
+  
+**/
+VOID
+EFIAPI
+FtwNotificationEvent (
+  IN  EFI_EVENT                           Event,
+  IN  VOID                                *Context
+  )
+{
+  EFI_STATUS                              Status;
+  EFI_FIRMWARE_VOLUME_BLOCK_PROTOCOL      *FvbProtocol;
+  EFI_FAULT_TOLERANT_WRITE_PROTOCOL       *FtwProtocol;
+  EFI_PHYSICAL_ADDRESS                    NvStorageVariableBase;
+  EFI_GCD_MEMORY_SPACE_DESCRIPTOR         GcdDescriptor;
+  EFI_PHYSICAL_ADDRESS                    BaseAddress;
+  UINT64                                  Length;
+  EFI_PHYSICAL_ADDRESS                    VariableStoreBase;
+  UINT64                                  VariableStoreLength;
+
+  //
+  // Ensure FTW protocol is installed.
+  //
+  Status = GetFtwProtocol ((VOID**) &FtwProtocol);
+  if (EFI_ERROR (Status)) {
+    return ;
+  }
+  
+  //
+  // Find the proper FVB protocol for variable.
+  //
+  NvStorageVariableBase = (EFI_PHYSICAL_ADDRESS) PcdGet64 (PcdFlashNvStorageVariableBase64);
+  if (NvStorageVariableBase == 0) {
+    NvStorageVariableBase = (EFI_PHYSICAL_ADDRESS) PcdGet32 (PcdFlashNvStorageVariableBase);
+  }
+  Status = GetFvbInfoByAddress (NvStorageVariableBase, NULL, &FvbProtocol);
+  if (EFI_ERROR (Status)) {
+    return ;
+  }
+  mVariableModuleGlobal->FvbInstance = FvbProtocol;
+
+  //
+  // Mark the variable storage region of the FLASH as RUNTIME.
+  //
+  VariableStoreBase   = mVariableModuleGlobal->VariableGlobal.NonVolatileVariableBase;
+  VariableStoreLength = ((VARIABLE_STORE_HEADER *)(UINTN)VariableStoreBase)->Size;
+  BaseAddress = VariableStoreBase & (~EFI_PAGE_MASK);
+  Length      = VariableStoreLength + (VariableStoreBase - BaseAddress);
+  Length      = (Length + EFI_PAGE_SIZE - 1) & (~EFI_PAGE_MASK);
+
+  Status      = gDS->GetMemorySpaceDescriptor (BaseAddress, &GcdDescriptor);
+  if (EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_WARN, "Variable driver failed to add EFI_MEMORY_RUNTIME attribute to Flash.\n"));
+  } else {
+    Status = gDS->SetMemorySpaceAttributes (
+                    BaseAddress,
+                    Length,
+                    GcdDescriptor.Attributes | EFI_MEMORY_RUNTIME
+                    );
+    if (EFI_ERROR (Status)) {
+      DEBUG ((DEBUG_WARN, "Variable driver failed to add EFI_MEMORY_RUNTIME attribute to Flash.\n"));
+    }
+  }
+  
+  Status = VariableWriteServiceInitialize ();
+  ASSERT_EFI_ERROR (Status);
+ 
+  //
+  // Install the Variable Write Architectural protocol.
+  //
+  Status = gBS->InstallProtocolInterface (
+                  &mHandle,
+                  &gEfiVariableWriteArchProtocolGuid, 
+                  EFI_NATIVE_INTERFACE,
+                  NULL
+                  );
+  ASSERT_EFI_ERROR (Status);
+  
+  //
+  // Close the notify event to avoid install gEfiVariableWriteArchProtocolGuid again.
+  //
+  gBS->CloseEvent (Event);
+
+}
+
+
+/**
+  Variable Driver main entry point. The Variable driver places the 4 EFI
+  runtime services in the EFI System Table and installs arch protocols 
+  for variable read and write services being availible. It also registers
+  a notification function for an EVT_SIGNAL_VIRTUAL_ADDRESS_CHANGE event.
+
+  @param[in] ImageHandle    The firmware allocated handle for the EFI image.  
+  @param[in] SystemTable    A pointer to the EFI System Table.
+  
+  @retval EFI_SUCCESS       Variable service successfully initialized.
+
+**/
+EFI_STATUS
+EFIAPI
+VariableServiceInitialize (
+  IN EFI_HANDLE                         ImageHandle,
+  IN EFI_SYSTEM_TABLE                   *SystemTable
+  )
+{
+  EFI_STATUS                            Status;
+  EFI_EVENT                             ReadyToBootEvent;
+  EFI_EVENT                             EndOfDxeEvent;
+
+  Status = VariableCommonInitialize ();
+  ASSERT_EFI_ERROR (Status);
+
+  Status = gBS->InstallMultipleProtocolInterfaces (
+                  &mHandle,
+                  &gEdkiiVariableLockProtocolGuid,
+                  &mVariableLock,
+                  NULL
+                  );
+  ASSERT_EFI_ERROR (Status);
+
+  SystemTable->RuntimeServices->GetVariable         = VariableServiceGetVariable;
+  SystemTable->RuntimeServices->GetNextVariableName = VariableServiceGetNextVariableName;
+  SystemTable->RuntimeServices->SetVariable         = VariableServiceSetVariable;
+  SystemTable->RuntimeServices->QueryVariableInfo   = VariableServiceQueryVariableInfo;
+    
+  //
+  // Now install the Variable Runtime Architectural protocol on a new handle.
+  //
+  Status = gBS->InstallProtocolInterface (
+                  &mHandle,
+                  &gEfiVariableArchProtocolGuid, 
+                  EFI_NATIVE_INTERFACE,
+                  NULL
+                  );
+  ASSERT_EFI_ERROR (Status);
+
+  //
+  // Register FtwNotificationEvent () notify function.
+  // 
+  EfiCreateProtocolNotifyEvent (
+    &gEfiFaultTolerantWriteProtocolGuid,
+    TPL_CALLBACK,
+    FtwNotificationEvent,
+    (VOID *)SystemTable,
+    &mFtwRegistration
+    );
+
+  Status = gBS->CreateEventEx (
+                  EVT_NOTIFY_SIGNAL,
+                  TPL_NOTIFY,
+                  VariableClassAddressChangeEvent,
+                  NULL,
+                  &gEfiEventVirtualAddressChangeGuid,
+                  &mVirtualAddressChangeEvent
+                  );
+  ASSERT_EFI_ERROR (Status);
+
+  //
+  // Register the event handling function to reclaim variable for OS usage.
+  //
+  Status = EfiCreateEventReadyToBootEx (
+             TPL_NOTIFY, 
+             OnReadyToBoot, 
+             NULL, 
+             &ReadyToBootEvent
+             );
+  ASSERT_EFI_ERROR (Status);
+
+  //
+  // Register the event handling function to set the End Of DXE flag.
+  //
+  Status = gBS->CreateEventEx (
+                  EVT_NOTIFY_SIGNAL,
+                  TPL_NOTIFY,
+                  OnEndOfDxe,
+                  NULL,
+                  &gEfiEndOfDxeEventGroupGuid,
+                  &EndOfDxeEvent
+                  );
+  ASSERT_EFI_ERROR (Status);
+
+  return EFI_SUCCESS;
+}
+