1 files changed, 20 insertions, 7 deletions
diff --git a/ArmPlatformPkg/PrePi/AArch64/ModuleEntryPoint.S b/ArmPlatformPkg/PrePi/AArch64/ModuleEntryPoint.S
index fcea9496cb..2c4a7e5324 100644
--- a/ArmPlatformPkg/PrePi/AArch64/ModuleEntryPoint.S
+++ b/ArmPlatformPkg/PrePi/AArch64/ModuleEntryPoint.S
@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2011-2013, ARM Limited. All rights reserved.
+//  Copyright (c) 2011-2015, 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
@@ -24,8 +24,10 @@ GCC_ASM_IMPORT(ArmReadMpidr)
 GCC_ASM_IMPORT(ArmPlatformPeiBootAction)
 GCC_ASM_IMPORT(ArmPlatformStackSet)
 GCC_ASM_EXPORT(_ModuleEntryPoint)
+GCC_ASM_EXPORT(mSystemMemoryEnd)
 
-StartupAddr:        .8byte ASM_PFX(CEntryPoint)
+StartupAddr:       .8byte ASM_PFX(CEntryPoint)
+mSystemMemoryEnd:  .8byte 0
 
 ASM_PFX(_ModuleEntryPoint):
   // Do early platform specific actions
@@ -40,12 +42,23 @@ _SetSVCMode:
 // Check if we can install the stack at the top of the System Memory or if we need
 // to install the stacks at the bottom of the Firmware Device (case the FD is located
 // at the top of the DRAM)
-_SetupStackPosition:
-  // Compute Top of System Memory
-  LoadConstantToReg (FixedPcdGet64 (PcdSystemMemoryBase), x1)
-  LoadConstantToReg (FixedPcdGet64 (PcdSystemMemorySize), x2)
+_SystemMemoryEndInit:
+  ldr   x1, mSystemMemoryEnd
+
+  // Is mSystemMemoryEnd initialized?
+  cmp   x1, #0
+  bne   _SetupStackPosition
+
+  LoadConstantToReg (FixedPcdGet32(PcdSystemMemoryBase), x1)
+  LoadConstantToReg (FixedPcdGet32(PcdSystemMemorySize), x2)
   sub   x2, x2, #1
-  add   x1, x1, x2      // x1 = SystemMemoryTop = PcdSystemMemoryBase + PcdSystemMemorySize
+  add   x1, x1, x2
+  // Update the global variable
+  adr   x2, mSystemMemoryEnd
+  str   x1, [x2]
+
+_SetupStackPosition:
+  // r1 = SystemMemoryTop
 
   // Calculate Top of the Firmware Device
   LoadConstantToReg (FixedPcdGet32(PcdFdBaseAddress), x2)