146 lines
2.6 KiB
NASM
146 lines
2.6 KiB
NASM
;++
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;
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; Copyright (c) Microsoft Corporation
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;
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; Module Name:
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;
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; bllegacy.asm
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;
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; Abstract:
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;
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; This module implements legacy call support.
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;
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; Environment:
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;
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; Boot loader.
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;
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;--
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include bl.inc
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.686p
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.model flat
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.code
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assume ds:flat
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assume es:flat
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assume ss:flat
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assume fs:flat
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.code
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;
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; Legacy call frame.
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;
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LegacyCallFrame struct
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_eax dq ?
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_ebx dq ?
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_ecx dq ?
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_edx dq ?
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_ebp dq ?
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_esi dq ?
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_edi dq ?
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_idtr df ?
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LegacyCallFrame ends
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BlLegacyReturnStackPointer dd 0
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;++
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;
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; VOID
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; FASTCALL
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; BlReturnToLegacyMode(
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; VOID
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; )
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;
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; Routine Description:
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;
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; This function returns to legacy mode to process a legacy request.
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;
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;--
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?BlReturnToLegacyMode@@YIXXZ proc
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;
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; Save all registers.
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;
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sub esp, (sizeof LegacyCallFrame)
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mov dword ptr [esp].LegacyCallFrame._eax, eax
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mov dword ptr [esp].LegacyCallFrame._ebx, ebx
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mov dword ptr [esp].LegacyCallFrame._ecx, ecx
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mov dword ptr [esp].LegacyCallFrame._edx, edx
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mov dword ptr [esp].LegacyCallFrame._ebp, ebp
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mov dword ptr [esp].LegacyCallFrame._esi, esi
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mov dword ptr [esp].LegacyCallFrame._edi, edi
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;
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; Save IDTR
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;
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sidt fword ptr [esp].LegacyCallFrame._idtr
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;
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; Save stack pointer.
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;
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mov BlLegacyReturnStackPointer, esp
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;
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; Set return address in BEB.
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;
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mov eax, BEB_BASE
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lea ecx, @f
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mov dword ptr [eax].BEB.LegacyReturnAddress, ecx
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;
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; Get legacy call stub address from BEB.
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;
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mov ecx, dword ptr [eax].BEB.LegacyCallAddress
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;
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; Return to legacy mode.
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;
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call ecx
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@@:
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;
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; Restore stack pointer.
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;
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mov esp, BlLegacyReturnStackPointer
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;
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; Restore all registers.
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;
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mov eax, dword ptr [esp].LegacyCallFrame._eax
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mov ebx, dword ptr [esp].LegacyCallFrame._ebx
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mov ecx, dword ptr [esp].LegacyCallFrame._ecx
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mov edx, dword ptr [esp].LegacyCallFrame._edx
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mov ebp, dword ptr [esp].LegacyCallFrame._ebp
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mov esi, dword ptr [esp].LegacyCallFrame._esi
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mov edi, dword ptr [esp].LegacyCallFrame._edi
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;
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; Restore IDT
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;
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lidt fword ptr [esp].LegacyCallFrame._idtr
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add esp, (sizeof LegacyCallFrame)
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ret
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?BlReturnToLegacyMode@@YIXXZ endp
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public ?BlReturnToLegacyMode@@YIXXZ
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end
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