From 61ece967cb59509608aa747fc9424c619646fc9d Mon Sep 17 00:00:00 2001
From: rsun3 <rsun3@6f19259b-4bc3-4df7-8a09-765794883524>
Date: Fri, 11 Jun 2010 03:22:15 +0000
Subject: Skip restoration of DRx registers to support in-circuit emualators or
 debuggers set breakpoint in interrupt/exception context.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@10573 6f19259b-4bc3-4df7-8a09-765794883524
---
 UefiCpuPkg/CpuDxe/Ia32/CpuAsm.S | 25 ++++---------------------
 1 file changed, 4 insertions(+), 21 deletions(-)

(limited to 'UefiCpuPkg/CpuDxe/Ia32/CpuAsm.S')

diff --git a/UefiCpuPkg/CpuDxe/Ia32/CpuAsm.S b/UefiCpuPkg/CpuDxe/Ia32/CpuAsm.S
index 04896578f7..d3e1dee624 100644
--- a/UefiCpuPkg/CpuDxe/Ia32/CpuAsm.S
+++ b/UefiCpuPkg/CpuDxe/Ia32/CpuAsm.S
@@ -1,6 +1,6 @@
 #------------------------------------------------------------------------------
 #*
-#*   Copyright (c) 2006 - 2009, Intel Corporation. All rights reserved.<BR>
+#*   Copyright (c) 2006 - 2010, 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
@@ -258,16 +258,8 @@ ErrorCodeAndVectorOnStack:
 #; UINT32  Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
     movl    %dr7, %eax
     pushl   %eax
-#; clear Dr7 while executing debugger itself
-    xorl    %eax, %eax
-    movl    %eax, %dr7
-
     movl    %dr6, %eax
     pushl   %eax
-#; insure all status bits in dr6 are clear...
-    xorl    %eax, %eax
-    movl    %eax, %dr6
-
     movl    %dr3, %eax
     pushl   %eax
     movl    %dr2, %eax
@@ -319,18 +311,9 @@ nullExternalExceptionHandler:
     addl    $512, %esp
 
 #; UINT32  Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
-    popl    %eax
-    movl    %eax, %dr0
-    popl    %eax
-    movl    %eax, %dr1
-    popl    %eax
-    movl    %eax, %dr2
-    popl    %eax
-    movl    %eax, %dr3
-#; skip restore of dr6.  We cleared dr6 during the context save.
-    addl    $4, %esp
-    popl    %eax
-    movl    %eax, %dr7
+#; Skip restoration of DRx registers to support in-circuit emualators
+#; or debuggers set breakpoint in interrupt/exception context
+    addl    $24, %esp
 
 #; UINT32  Cr0, Cr1, Cr2, Cr3, Cr4;
     popl    %eax
-- 
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