4 files changed, 16 insertions, 4 deletions
diff --git a/MdeModulePkg/Universal/DebugSupportDxe/Ia32/AsmFuncs.S b/MdeModulePkg/Universal/DebugSupportDxe/Ia32/AsmFuncs.S
index b6108227bd..fd1a96b76f 100644
--- a/MdeModulePkg/Universal/DebugSupportDxe/Ia32/AsmFuncs.S
+++ b/MdeModulePkg/Universal/DebugSupportDxe/Ia32/AsmFuncs.S
@@ -1,7 +1,7 @@
 #/**@file
 # Low leve IA32 specific debug support functions.
 #
-# Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
+# Copyright (c) 2006 - 2011, Intel Corporation. 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
@@ -276,6 +276,9 @@ ASM_PFX(CommonIdtEntry):
         # They MUST be.  If they are not, a GP fault will occur.
         fxsave (%edi)
 
+## UEFI calling convention for IA32 requires that Direction flag in EFLAGs is clear
+        cld
+                
 ## UINT32  ExceptionData;
         mov    0x0,%eax
         push   %eax
diff --git a/MdeModulePkg/Universal/DebugSupportDxe/X64/AsmFuncs.S b/MdeModulePkg/Universal/DebugSupportDxe/X64/AsmFuncs.S
index 6fb92e4350..e6a40e8dad 100644
--- a/MdeModulePkg/Universal/DebugSupportDxe/X64/AsmFuncs.S
+++ b/MdeModulePkg/Universal/DebugSupportDxe/X64/AsmFuncs.S
@@ -1,7 +1,7 @@
 ///**@file
 // Low leve x64 specific debug support functions.
 //
-// Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
+// Copyright (c) 2006 - 2011, 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
@@ -357,6 +357,9 @@ ExtraPushDone:
                 #     FXSTOR_RDI
                 fxsave      (%rdi)
 
+// UEFI calling convention for x64 requires that Direction flag in EFLAGs is clear
+                cld
+                
 // UINT64  ExceptionData;
                 movq    ASM_PFX(ExceptData)(%rip),  %rax
                 pushq   %rax
diff --git a/UefiCpuPkg/CpuDxe/Ia32/CpuAsm.S b/UefiCpuPkg/CpuDxe/Ia32/CpuAsm.S
index d3e1dee624..38f46ab335 100644
--- a/UefiCpuPkg/CpuDxe/Ia32/CpuAsm.S
+++ b/UefiCpuPkg/CpuDxe/Ia32/CpuAsm.S
@@ -1,6 +1,6 @@
 #------------------------------------------------------------------------------
 #*
-#*   Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
+#*   Copyright (c) 2006 - 2011, Intel Corporation. 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
@@ -274,6 +274,9 @@ ErrorCodeAndVectorOnStack:
     movl    %esp, %edi
     .byte      0x0f, 0x0ae, 0x07 #fxsave [edi]
 
+#; UEFI calling convention for IA32 requires that Direction flag in EFLAGs is clear
+    cld
+
 #; UINT32  ExceptionData;
     pushl   8(%ebp)
 
diff --git a/UefiCpuPkg/CpuDxe/X64/CpuAsm.S b/UefiCpuPkg/CpuDxe/X64/CpuAsm.S
index 8f191320a8..f1481d85d6 100644
--- a/UefiCpuPkg/CpuDxe/X64/CpuAsm.S
+++ b/UefiCpuPkg/CpuDxe/X64/CpuAsm.S
@@ -2,7 +2,7 @@
 
 #------------------------------------------------------------------------------
 #*
-#*   Copyright (c) 2008 - 2010, Intel Corporation. All rights reserved.<BR>
+#*   Copyright (c) 2008 - 2011, Intel Corporation. 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
@@ -234,6 +234,9 @@ CommonInterruptEntry_al_0000:
     movq    %rsp, %rdi
     .byte 0x0f, 0x0ae, 0x07 #fxsave [rdi]
 
+#; UEFI calling convention for x64 requires that Direction flag in EFLAGs is clear
+    cld
+
 #; UINT32  ExceptionData;
     pushq   16(%rbp)