Add ArmPlatformPkg from ARM Ltd. patch.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11291 6f19259b-4bc3-4df7-8a09-765794883524

ArmPlatformPkg/PrePeiCore/SwitchStack.asm

@@ -0,0 +1,38 @@
+;------------------------------------------------------------------------------ 
+;
+; Copyright (c) 2006 - 2009, Intel Corporation. All rights reserved.<BR>
+; Portions copyright (c) 2008 - 2009, Apple Inc. 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.
+;
+;------------------------------------------------------------------------------
+  
+    EXPORT SecSwitchStack
+            
+    AREA   Switch_Stack, CODE, READONLY
+  
+;/**
+;  This allows the caller to switch the stack and return
+;
+; @param      StackDelta     Signed amount by which to modify the stack pointer
+;
+; @return     Nothing. Goes to the Entry Point passing in the new parameters
+;
+;**/
+;VOID
+;EFIAPI
+;SecSwitchStack (
+;  VOID  *StackDelta
+;  );
+;
+SecSwitchStack   
+    MOV   R1, SP
+    ADD   R1, R0, R1
+    MOV   SP, R1
+    BX    LR
+    END