MdePkg: SmmMemLib: Added New Interface for Communicate Buffer Validation

Current MMI handlers would leverage SmmIsBufferOutsideSmmValid interface
to validate the incoming communicate buffer.

However, if/when SMM core would like to improve security level by copying
the communicate buffer into TSEG before dispatching, these handlers will
fail due to these changes.

This change added new interface for traditional MM handlers to validate
incoming communicate buffer, which should pave way for MM core to copy
incoming buffer into TSEG prior to handler dispatching. The current
implementation will remain to use SmmIsBufferOutsideSmmValid till Core
has such functionality.

The interface should be used and only used for validating communicate
buffer upon dispatching. For other memory region validity check, handlers
should still use SmmIsBufferOutsideSmmValid.

MdePkg/Include/Library/SmmMemLib.h

@@ -129,4 +129,20 @@ SmmSetMem (
   IN UINT8  Value
   );
 
+/**
+  This function should be used for MMI handlers to check if the communicate buffer is valid.
+
+  @param Buffer  The buffer start address to be checked.
+  @param Length  The buffer length to be checked.
+
+  @retval TRUE  This communicate buffer is valid per processor architecture.
+  @retval FALSE This communicate buffer is not valid per processor architecture.
+**/
+BOOLEAN
+EFIAPI
+SmmCommBufferValid (
+  IN EFI_PHYSICAL_ADDRESS  Buffer,
+  IN UINT64                Length
+  );
+
 #endif

MdePkg/Library/SmmMemLib/SmmMemLib.c

@@ -591,6 +591,25 @@ SmmLibInternalReadyToLockNotify (
   return EFI_SUCCESS;
 }
 
+/**
+  This function should be used for MMI handlers to check if the communicate buffer is valid.
+
+  @param Buffer  The buffer start address to be checked.
+  @param Length  The buffer length to be checked.
+
+  @retval TRUE  This communicate buffer is valid per processor architecture.
+  @retval FALSE This communicate buffer is not valid per processor architecture.
+**/
+BOOLEAN
+EFIAPI
+SmmCommBufferValid (
+  IN EFI_PHYSICAL_ADDRESS  Buffer,
+  IN UINT64                Length
+  )
+{
+  return SmmIsBufferOutsideSmmValid (Buffer, Length);
+}
+
 /**
   The constructor function initializes the Smm Mem library