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/** @file
Real Mode Thunk Functions for IA32 and X64.
Copyright (c) 2006, Intel Corporation<BR>
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: x86Thunk.c
**/
/**
Invokes 16-bit code in big real mode and returns the updated register set.
This function transfers control to the 16-bit code specified by CS:EIP using
the stack specified by SS:ESP in RegisterSet. The updated registers are saved
on the real mode stack and the starting address of the save area is returned.
@param RegisterSet Values of registers before invocation of 16-bit code.
@param Patch Pointer to the area following the 16-bit code.
@return The pointer to a IA32_REGISTER_SET structure containing the updated
register values.
**/
IA32_REGISTER_SET *
InternalAsmThunk16 (
IN IA32_REGISTER_SET *RegisterSet,
IN OUT VOID *Patch
);
/**
Prepares all structures a code required to use AsmThunk16().
Prepares all structures and code required to use AsmThunk16().
If ThunkContext is NULL, then ASSERT().
@param ThunkContext A pointer to the context structure that describes the
16-bit real mode code to call.
**/
VOID
EFIAPI
AsmPrepareThunk16 (
OUT THUNK_CONTEXT *ThunkContext
)
{
ASSERT (ThunkContext != NULL);
}
/**
Transfers control to a 16-bit real mode entry point and returns the results.
Transfers control to a 16-bit real mode entry point and returns the results.
AsmPrepareThunk16() must be called with ThunkContext before this function is
used. This function must be called with interrupts disabled.
If ThunkContext is NULL, then ASSERT().
If AsmPrepareThunk16() was not previously called with ThunkContext, then ASSERT().
@param ThunkContext A pointer to the context structure that describes the
16-bit real mode code to call.
**/
VOID
EFIAPI
AsmThunk16 (
IN OUT THUNK_CONTEXT *ThunkContext
)
{
UINT16 *Patch;
ASSERT (ThunkContext != NULL);
Patch = (UINT16*)(
(UINTN)ThunkContext->RealModeCode +
ThunkContext->RealModeCodeSize
);
//
// 0x9a66 is the OpCode of far call with an operand size override.
//
*Patch = 0x9a66;
//
// CopyMem() here copies the updated register values back to RealModeState
//
CopyMem (
&ThunkContext->RealModeState,
InternalAsmThunk16 (&ThunkContext->RealModeState, Patch + 1),
sizeof (ThunkContext->RealModeState)
);
}
/**
Prepares all structures and code for a 16-bit real mode thunk, transfers
control to a 16-bit real mode entry point, and returns the results.
Prepares all structures and code for a 16-bit real mode thunk, transfers
control to a 16-bit real mode entry point, and returns the results. If the
caller only need to perform a single 16-bit real mode thunk, then this
service should be used. If the caller intends to make more than one 16-bit
real mode thunk, then it is more efficient if AsmPrepareThunk16() is called
once and AsmThunk16() can be called for each 16-bit real mode thunk. This
function must be called with interrupts disabled.
If ThunkContext is NULL, then ASSERT().
@param ThunkContext A pointer to the context structure that describes the
16-bit real mode code to call.
**/
VOID
EFIAPI
AsmPrepareAndThunk16 (
IN OUT THUNK_CONTEXT *ThunkContext
)
{
AsmPrepareThunk16 (ThunkContext);
AsmThunk16 (ThunkContext);
}
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