mirror of https://github.com/acidanthera/audk.git
128 lines
4.0 KiB
C
128 lines
4.0 KiB
C
/** @file
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Real Mode Thunk Functions for IA32 and X64.
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Copyright (c) 2006, Intel Corporation<BR>
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All rights reserved. This program and the accompanying materials
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are licensed and made available under the terms and conditions of the BSD License
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which accompanies this distribution. The full text of the license may be found at
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http://opensource.org/licenses/bsd-license.php
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THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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Module Name: x86Thunk.c
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**/
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/**
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Invokes 16-bit code in big real mode and returns the updated register set.
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This function transfers control to the 16-bit code specified by CS:EIP using
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the stack specified by SS:ESP in RegisterSet. The updated registers are saved
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on the real mode stack and the starting address of the save area is returned.
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@param RegisterSet Values of registers before invocation of 16-bit code.
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@param Patch Pointer to the area following the 16-bit code.
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@return The pointer to a IA32_REGISTER_SET structure containing the updated
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register values.
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**/
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IA32_REGISTER_SET *
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InternalAsmThunk16 (
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IN IA32_REGISTER_SET *RegisterSet,
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IN OUT VOID *Patch
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);
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/**
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Prepares all structures a code required to use AsmThunk16().
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Prepares all structures and code required to use AsmThunk16().
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If ThunkContext is NULL, then ASSERT().
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@param ThunkContext A pointer to the context structure that describes the
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16-bit real mode code to call.
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**/
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VOID
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EFIAPI
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AsmPrepareThunk16 (
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OUT THUNK_CONTEXT *ThunkContext
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)
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{
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ASSERT (ThunkContext != NULL);
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}
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/**
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Transfers control to a 16-bit real mode entry point and returns the results.
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Transfers control to a 16-bit real mode entry point and returns the results.
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AsmPrepareThunk16() must be called with ThunkContext before this function is
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used. This function must be called with interrupts disabled.
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If ThunkContext is NULL, then ASSERT().
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If AsmPrepareThunk16() was not previously called with ThunkContext, then ASSERT().
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@param ThunkContext A pointer to the context structure that describes the
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16-bit real mode code to call.
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**/
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VOID
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EFIAPI
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AsmThunk16 (
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IN OUT THUNK_CONTEXT *ThunkContext
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)
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{
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UINT16 *Patch;
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ASSERT (ThunkContext != NULL);
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Patch = (UINT16*)(
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(UINTN)ThunkContext->RealModeCode +
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ThunkContext->RealModeCodeSize
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);
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//
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// 0x9a66 is the OpCode of far call with an operand size override.
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//
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*Patch = 0x9a66;
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//
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// CopyMem() here copies the updated register values back to RealModeState
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//
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CopyMem (
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&ThunkContext->RealModeState,
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InternalAsmThunk16 (&ThunkContext->RealModeState, Patch + 1),
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sizeof (ThunkContext->RealModeState)
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);
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}
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/**
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Prepares all structures and code for a 16-bit real mode thunk, transfers
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control to a 16-bit real mode entry point, and returns the results.
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Prepares all structures and code for a 16-bit real mode thunk, transfers
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control to a 16-bit real mode entry point, and returns the results. If the
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caller only need to perform a single 16-bit real mode thunk, then this
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service should be used. If the caller intends to make more than one 16-bit
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real mode thunk, then it is more efficient if AsmPrepareThunk16() is called
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once and AsmThunk16() can be called for each 16-bit real mode thunk. This
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function must be called with interrupts disabled.
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If ThunkContext is NULL, then ASSERT().
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@param ThunkContext A pointer to the context structure that describes the
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16-bit real mode code to call.
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**/
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VOID
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EFIAPI
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AsmPrepareAndThunk16 (
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IN OUT THUNK_CONTEXT *ThunkContext
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)
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{
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AsmPrepareThunk16 (ThunkContext);
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AsmThunk16 (ThunkContext);
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}
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