MdePkg: Fix X64 clang compile issues.

Fixed issues with X64 clang, and also make StackSwitch push a zero on the new stack to prevent a stack unwind into memory that is no longer valid.

signed-off-by: andrewfish
reviewed-by: lgao4
reviewed-by: mdkinney



git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@12007 6f19259b-4bc3-4df7-8a09-765794883524

MdePkg/Library/BaseLib/Ia32/InternalSwitchStack.S

@@ -0,0 +1,48 @@
+#------------------------------------------------------------------------------
+#
+# Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
+# Portions copyright (c) 2011, Apple Inc. 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.
+#
+# Module Name:
+#
+#   InternalSwitchStack.S
+#
+# Abstract:
+#
+#   Implementation of a stack switch on IA-32.
+#
+#------------------------------------------------------------------------------
+
+ASM_GLOBAL ASM_PFX(InternalSwitchStack)
+
+#------------------------------------------------------------------------------
+# VOID
+# EFIAPI
+# InternalSwitchStack (
+#   IN      SWITCH_STACK_ENTRY_POINT  EntryPoint,
+#   IN      VOID                      *Context1,   OPTIONAL
+#   IN      VOID                      *Context2,   OPTIONAL
+#   IN      VOID                      *NewStack
+#   );
+#------------------------------------------------------------------------------
+ASM_PFX(InternalSwitchStack):
+  pushl %ebp
+	movl	%esp, %ebp
+
+	movl	20(%ebp), %esp      # switch stack
+	subl	$8, %esp
+
+	movl	16(%ebp), %eax
+	movl	%eax, 4(%esp)
+	movl	12(%ebp), %eax
+	movl	%eax, (%esp)
+	pushl $0                  # keeps gdb from unwinding stack
+	jmp   *8(%ebp)            # call and never return 
+