diff options
Diffstat (limited to 'src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-SelFlatCodeToRealMode.asm')
| -rw-r--r-- | src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-SelFlatCodeToRealMode.asm | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-SelFlatCodeToRealMode.asm b/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-SelFlatCodeToRealMode.asm new file mode 100644 index 00000000..13cbcfdc --- /dev/null +++ b/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-SelFlatCodeToRealMode.asm @@ -0,0 +1,153 @@ +; $Id: bs3-cmn-SelFlatCodeToRealMode.asm $ +;; @file +; BS3Kit - Bs3SelFlatCodeToRealMode. +; + +; +; Copyright (C) 2007-2019 Oracle Corporation +; +; This file is part of VirtualBox Open Source Edition (OSE), as +; available from http://www.virtualbox.org. This file is free software; +; you can redistribute it and/or modify it under the terms of the GNU +; General Public License (GPL) as published by the Free Software +; Foundation, in version 2 as it comes in the "COPYING" file of the +; VirtualBox OSE distribution. VirtualBox OSE is distributed in the +; hope that it will be useful, but WITHOUT ANY WARRANTY of any kind. +; +; The contents of this file may alternatively be used under the terms +; of the Common Development and Distribution License Version 1.0 +; (CDDL) only, as it comes in the "COPYING.CDDL" file of the +; VirtualBox OSE distribution, in which case the provisions of the +; CDDL are applicable instead of those of the GPL. +; +; You may elect to license modified versions of this file under the +; terms and conditions of either the GPL or the CDDL or both. +; + + +;********************************************************************************************************************************* +;* Header Files * +;********************************************************************************************************************************* +%include "bs3kit-template-header.mac" + + +;********************************************************************************************************************************* +;* Global Variables * +;********************************************************************************************************************************* +BS3_EXTERN_DATA16 Bs3RmText16_EndOfSegment +BS3_EXTERN_DATA16 Bs3X0Text16_EndOfSegment +BS3_EXTERN_DATA16 Bs3X1Text16_EndOfSegment + + +; +; Make sure we can get at all the segments. +; +BS3_BEGIN_TEXT16 +BS3_BEGIN_RMTEXT16 +BS3_BEGIN_X0TEXT16 +BS3_BEGIN_X1TEXT16 +TMPL_BEGIN_TEXT + + +;; +; @cproto BS3_CMN_PROTO(uint32_t, Bs3SelRealModeCodeToProtMode,(uint32_t uFlatAddr), false); +; +; @uses Only return registers (ax:dx, eax, eax) +; +BS3_PROC_BEGIN_CMN Bs3SelFlatCodeToRealMode, BS3_PBC_NEAR + BS3_CALL_CONV_PROLOG 1 + push xBP + mov xBP, xSP + push xCX + push xBX +%if TMPL_BITS != 16 + push xDX +%endif + + ; + ; Load the real mode frame number into DX so we can compare with the + ; segment frame numbers fixed up by the linker. + ; + ; Imagine: FlatAddr = 0x054321 + ; + mov dx, [xBP + xCB + cbCurRetAddr + 1] ; dx = 0x0543 + mov al, [xBP + xCB + cbCurRetAddr + 0] ; al = 0x21 + mov cl,4 + shl dx, 4 ; dx = 0x5430 + shr al, 4 ; al = 0x02 + or dl, al ; dx = 0x5432 + + mov ax, dx + sub ax, CGROUP16 + cmp ax, 1000h + jb .bs3text16 + + mov ax, dx + sub ax, BS3GROUPRMTEXT16 + mov bx, Bs3RmText16_EndOfSegment wrt BS3GROUPRMTEXT16 + add bx, 15 + shr bx, cl + cmp ax, bx + jb .bs3rmtext16 + + mov ax, dx + sub ax, BS3GROUPX0TEXT16 + mov bx, Bs3X0Text16_EndOfSegment wrt BS3GROUPX0TEXT16 + add bx, 15 + shr bx, cl + cmp ax, bx + jb .bs3x0text16 + + mov ax, dx + sub ax, BS3GROUPX1TEXT16 + mov bx, Bs3X1Text16_EndOfSegment wrt BS3GROUPX1TEXT16 + add bx, 15 + shr bx, cl + cmp ax, bx + jb .bs3x1text16 + + extern BS3_CMN_NM(Bs3Panic) + call BS3_CMN_NM(Bs3Panic) + + ; + ; Load the real-mode frame into DX and calc the offset in AX. + ; +.bs3x1text16: + mov dx, BS3GROUPX1TEXT16 + jmp .calc_return +.bs3x0text16: + mov dx, BS3GROUPX0TEXT16 + jmp .calc_return +.bs3rmtext16: + mov dx, BS3GROUPRMTEXT16 + jmp .calc_return +.bs3text16: + mov dx, CGROUP16 +.calc_return: + ; Convert the real-mode frame into the low 16-bit base (BX). + mov bx, dx + shl bx, cl + ; Subtract the 16-bit base from the flat address. (No need to consider + ; the top half on either side.) + mov ax, [xBP + xCB + cbCurRetAddr + 0] + sub ax, bx +%if TMPL_BITS != 16 + ; Got a single 32-bit return register here. + shl edx, 16 + mov dx, ax + mov eax, edx + pop xDX +%endif + pop xBX + pop xCX + pop xBP + BS3_CALL_CONV_EPILOG 1 + BS3_HYBRID_RET +BS3_PROC_END_CMN Bs3SelFlatCodeToRealMode + +; +; We may be using the near code in some critical code paths, so don't +; penalize it. +; +BS3_CMN_FAR_STUB Bs3SelFlatCodeToRealMode, 4 + |