1 files changed, 44 insertions, 0 deletions
diff --git a/MdePkg/Library/MmUnblockMemoryLib/MmUnblockMemoryLibNull.c b/MdePkg/Library/MmUnblockMemoryLib/MmUnblockMemoryLibNull.c
new file mode 100644
index 000000000000..fa1d3ae3e623
--- /dev/null
+++ b/MdePkg/Library/MmUnblockMemoryLib/MmUnblockMemoryLibNull.c
@@ -0,0 +1,44 @@
+/** @file
+  Null instance of MM Unblock Page Library.
+
+  This library provides an interface to request non-MMRAM pages to be mapped/unblocked
+  from inside MM environment.
+
+  For MM modules that need to access regions outside of MMRAMs, the agents that set up
+  these regions are responsible for invoking this API in order for these memory areas
+  to be accessed from inside MM.
+
+  Copyright (c) Microsoft Corporation.
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Base.h>
+
+/**
+  This API provides a way to unblock certain data pages to be accessible inside MM environment.
+
+  @param  UnblockAddress              The address of buffer caller requests to unblock, the address
+                                      has to be page aligned.
+  @param  NumberOfPages               The number of pages requested to be unblocked from MM
+                                      environment.
+
+  @retval RETURN_SUCCESS              The request goes through successfully.
+  @retval RETURN_NOT_AVAILABLE_YET    The requested functionality is not produced yet.
+  @retval RETURN_UNSUPPORTED          The requested functionality is not supported on current platform.
+  @retval RETURN_SECURITY_VIOLATION   The requested address failed to pass security check for
+                                      unblocking.
+  @retval RETURN_INVALID_PARAMETER    Input address either NULL pointer or not page aligned.
+  @retval RETURN_ACCESS_DENIED        The request is rejected due to system has passed certain boot
+                                      phase.
+
+**/
+RETURN_STATUS
+EFIAPI
+MmUnblockMemoryRequest (
+  IN PHYSICAL_ADDRESS  UnblockAddress,
+  IN UINT64            NumberOfPages
+  )
+{
+  return RETURN_UNSUPPORTED;
+}