| 1 | ; $Id: bs3-cmn-SwitchToRingX.asm 82968 2020-02-04 10:35:17Z vboxsync $
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| 2 | ;; @file
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| 3 | ; BS3Kit - Bs3SwitchToRingX
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| 4 | ;
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| 5 |
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| 6 | ;
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| 7 | ; Copyright (C) 2007-2020 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.virtualbox.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 | BS3_EXTERN_CMN Bs3Syscall
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| 31 | %if TMPL_BITS == 16
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| 32 | BS3_EXTERN_DATA16 g_bBs3CurrentMode
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| 33 | %endif
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| 34 | TMPL_BEGIN_TEXT
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| 35 |
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| 36 |
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| 37 | ;;
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| 38 | ; @cproto BS3_DECL(void) Bs3SwitchToRingX(uint8_t bRing);
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| 39 | ;
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| 40 | ; @param bRing The target ring (0..3).
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| 41 | ; @remarks Does not require 20h of parameter scratch space in 64-bit mode.
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| 42 | ;
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| 43 | ; @uses No GPRs.
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| 44 | ;
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| 45 | BS3_PROC_BEGIN_CMN Bs3SwitchToRingX, BS3_PBC_HYBRID_SAFE
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| 46 | BS3_CALL_CONV_PROLOG 1
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| 47 | push xBP
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| 48 | mov xBP, xSP
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| 49 | push xAX
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| 50 |
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| 51 | %if TMPL_BITS == 16
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| 52 | ; Check the current mode.
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| 53 | mov al, [BS3_DATA16_WRT(g_bBs3CurrentMode)]
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| 54 |
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| 55 | ; If real mode: Nothing we can do, but we'll bitch if the request isn't for ring-0.
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| 56 | cmp al, BS3_MODE_RM
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| 57 | je .return_real_mode
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| 58 |
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| 59 | ; If V8086 mode: Always do syscall and add a lock prefix to make sure it gets to the VMM.
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| 60 | test al, BS3_MODE_CODE_V86
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| 61 | jnz .just_do_it
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| 62 | %endif
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| 63 |
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| 64 | ; In protected mode: Check the CPL we're currently at skip syscall if ring-0 already.
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| 65 | mov ax, cs
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| 66 | and al, 3
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| 67 | cmp al, byte [xBP + xCB + cbCurRetAddr]
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| 68 | je .return
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| 69 |
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| 70 | .just_do_it:
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| 71 | mov xAX, BS3_SYSCALL_TO_RING0
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| 72 | add al, [xBP + xCB + cbCurRetAddr]
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| 73 | call Bs3Syscall
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| 74 |
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| 75 | %ifndef BS3_STRICT
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| 76 | .return_real_mode:
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| 77 | %endif
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| 78 | .return:
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| 79 | pop xAX
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| 80 | pop xBP
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| 81 | BS3_CALL_CONV_EPILOG 1
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| 82 | BS3_HYBRID_RET
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| 83 |
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| 84 | %ifdef BS3_STRICT
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| 85 | ; In real mode, only ring-0 makes any sense.
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| 86 | .return_real_mode:
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| 87 | cmp byte [xBP + xCB + cbCurRetAddr], 0
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| 88 | je .return
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| 89 | int3
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| 90 | jmp .return
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| 91 | %endif
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| 92 | BS3_PROC_END_CMN Bs3SwitchToRingX
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| 93 |
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