| 1 | ; $Id: bs3-cmn-SwitchTo32Bit.asm 59863 2016-02-26 20:59:52Z vboxsync $
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| 2 | ;; @file
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| 3 | ; BS3Kit - Bs3SwitchTo32Bit
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| 4 | ;
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| 5 |
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| 6 | ;
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| 7 | ; Copyright (C) 2007-2015 Oracle Corporation
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| 8 | ;
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| 9 | ; This file is part of VirtualBox Open Source Edition (OSE), as
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| 10 | ; available from http://www.alldomusa.eu.org. This file is free software;
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| 11 | ; you can redistribute it and/or modify it under the terms of the GNU
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| 12 | ; General Public License (GPL) as published by the Free Software
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| 13 | ; Foundation, in version 2 as it comes in the "COPYING" file of the
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| 14 | ; VirtualBox OSE distribution. VirtualBox OSE is distributed in the
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| 15 | ; hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
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| 16 | ;
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| 17 | ; The contents of this file may alternatively be used under the terms
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| 18 | ; of the Common Development and Distribution License Version 1.0
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| 19 | ; (CDDL) only, as it comes in the "COPYING.CDDL" file of the
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| 20 | ; VirtualBox OSE distribution, in which case the provisions of the
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| 21 | ; CDDL are applicable instead of those of the GPL.
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| 22 | ;
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| 23 | ; You may elect to license modified versions of this file under the
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| 24 | ; terms and conditions of either the GPL or the CDDL or both.
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| 25 | ;
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| 26 |
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| 27 | %include "bs3kit-template-header.mac"
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| 28 |
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| 29 |
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| 30 | %if TMPL_BITS != 32
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| 31 | BS3_EXTERN_DATA16 g_bBs3CurrentMode
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| 32 | TMPL_BEGIN_TEXT
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| 33 | %endif
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| 34 |
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| 35 |
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| 36 | ;;
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| 37 | ; @cproto BS3_DECL(void) Bs3SwitchTo32Bit(void);
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| 38 | ;
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| 39 | ; @remarks Does not require 20h of parameter scratch space in 64-bit mode.
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| 40 | ;
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| 41 | BS3_PROC_BEGIN_CMN Bs3SwitchTo32Bit
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| 42 | %if TMPL_BITS == 32
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| 43 | ret
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| 44 | %else
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| 45 | %if TMPL_BITS == 16
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| 46 | push ax ; Reserve space for larger return value (adjusted in 32-bit code).
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| 47 | push eax
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| 48 | pushfd
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| 49 | %else
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| 50 | pushfq
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| 51 | mov [rsp + 4], eax
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| 52 | %endif
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| 53 | cli
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| 54 |
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| 55 | ; Calc ring addend.
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| 56 | mov ax, cs
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| 57 | and xAX, 3
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| 58 | shl xAX, BS3_SEL_RING_SHIFT
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| 59 | add xAX, BS3_SEL_R0_CS32
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| 60 |
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| 61 | ; Create far return for switching to 32-bit mode.
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| 62 | push sAX
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| 63 | %if TMPL_BITS == 16
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| 64 | push dword .thirty_two_bit wrt FLAT
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| 65 | o32 retf
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| 66 | %else
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| 67 | push .thirty_two_bit
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| 68 | o64 retf
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| 69 | %endif
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| 70 |
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| 71 | BS3_SET_BITS 32
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| 72 | .thirty_two_bit:
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| 73 | ; Load 32-bit segment registers.
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| 74 | add eax, BS3_SEL_R0_SS32 - BS3_SEL_R0_CS32
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| 75 | mov ss, ax
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| 76 |
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| 77 | add eax, BS3_SEL_R0_DS32 - BS3_SEL_R0_SS32
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| 78 | mov ds, ax
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| 79 | mov es, ax
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| 80 |
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| 81 | ; Update globals.
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| 82 | and byte [g_bBs3CurrentMode], ~BS3_MODE_CODE_MASK
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| 83 | or byte [g_bBs3CurrentMode], BS3_MODE_CODE_32
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| 84 |
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| 85 | %if TMPL_BITS == 16
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| 86 | ; Adjust the return address.
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| 87 | movsx eax, word [esp + 4*2 + 2]
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| 88 | add eax, BS3_ADDR_BS3TEXT16
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| 89 | mov [esp + 4*2], eax
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| 90 | %endif
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| 91 |
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| 92 | ; Restore and return.
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| 93 | popfd
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| 94 | pop eax
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| 95 | ret
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| 96 | %endif
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| 97 | BS3_PROC_END_CMN Bs3SwitchTo32Bit
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| 98 |
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