ArmPlatformPkg/PrePeiCore: Reserve some memory on the top of the stack for Global Variables in XIP code

The size of this memory is controlled by a PCD. The Global Variable in this regsion are defined by their offset.

This memory region can be use to store the PEI Services Table Pointer.
Update the PeiServicesTablePointerLib to use this region instead of PcdPeiServicePtrAddr.



git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11803 6f19259b-4bc3-4df7-8a09-765794883524

ArmPlatformPkg/PrePeiCore/PrePeiCoreEntryPoint.S

@@ -1,22 +1,21 @@
 //
 //  Copyright (c) 2011, ARM Limited. All rights reserved.
 //  
-# 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.             
-#
-#
+//  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 <AsmMacroIoLib.h>
 #include <Base.h>
 #include <Library/PcdLib.h>
 #include <AutoGen.h>
 
-#start of the code section
 .text
 .align 3
 
@@ -45,9 +44,17 @@ _SetupStack:
   add     r3,r3,r2,LSR #1   @ r3 = stack_offset + (stack_size/2)   <-- the top half is for the heap
   mov     sp, r3
 
-  # lr points to area in reset vector block containing PEI core address. lr needs to
-  # be saved from the beginning as the _ModuleEntryPoint could call helper functions
-  # that will overwrite 'lr'
+  # Only allocate memory in top of the primary core stack
+  cmp   r0, #0
+  bne   _PrepareArguments
+
+_AllocateGlobalPeiVariables:
+  # Reserve top of the stack for Global PEI Variables (eg: PeiServicesTablePointer)
+  LoadConstantToReg (FixedPcdGet32(PcdPeiGlobalVariableSize), r1)
+  sub   sp, sp, r1
+
+_PrepareArguments:
+  # The PEI Core Entry Point has been computed by GenFV and stored in the second entry of the Reset Vector
   LoadConstantToReg (FixedPcdGet32(PcdNormalFdBaseAddress), r2)
   add   r2, r2, #4
   ldr   r1, [r2]