MdePkg/Library/BaseLib/Ia32/InternalSwitchStack.S

#------------------------------------------------------------------------------
#
# Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
# Portions copyright (c) 2011, 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
# 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